Lipid metabolism mRNA expression and cellularity of intramuscular adipocytes within the Longissimus muscle of Angus- and Wagyu-sired cattle fed for a similar days on feed or body weight endpoint

J R Jaborek; F L Fluharty; Kichoon Lee; Henry N Zerby; A E Relling

doi:10.1093/jas/skac371

. 2023 Feb 8;101:skac371. doi: 10.1093/jas/skac371

Lipid metabolism mRNA expression and cellularity of intramuscular adipocytes within the Longissimus muscle of Angus- and Wagyu-sired cattle fed for a similar days on feed or body weight endpoint

J R Jaborek ^1,², F L Fluharty ³, Kichoon Lee ⁴, Henry N Zerby ⁵, A E Relling ^6,^✉

PMCID: PMC9907753 PMID: 36753534

Abstract

This study investigates intramuscular (IM) adipocyte development in the Longissimus muscle (LM) between Wagyu- and Angus-sired steers compared at a similar age and days on feed (D) endpoint or similar body weight (B) endpoint by measuring IM adipocyte cell area and lipid metabolism mRNA expression. Angus-sired steers (AN, n = 6) were compared with steers from two different Wagyu sires (WA), selected for either growth (G) or marbling (M), to be compared at a similar days on feed (DOF; 258 ± 26.7 d; WA-GD, n = 5 and WA-MD, n = 5) in Exp. 1 or body weight (BW; 613 ± 18.0 kg; WA-GB, n = 4 and WA-MB, n = 5) in Exp. 2, respectively. In Exp. 1, WA-MD steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GD steers. In Exp. 2, WA-MB steers had a greater (P ≤ 0.01) percentage of IM fat in the LM compared with AN and WA-GB steers. The distribution of IM adipocyte area was unimodal at all biopsy collections, with IM adipocyte area becoming progressively larger as cattle age (P ≤ 0.01) and BW increased (P ≤ 0.01). Peroxisome proliferator activated receptor delta (PPARd) was upregulated earlier for WA-MD and WA-MB cattle compared with other steers at a similar DOF and BW (P ≤ 0.02; treatment × biopsy interaction). Peroxisome proliferator activated receptor gamma was upregulated (PPARg) at a lesser BW for WA-MB steers (P = 0.09; treatment × biopsy interaction), while WA-MD steers had a greater (P ≤ 0.04) overall mean PPARg mRNA expression compared with other steers. Glycerol-3-phosphate acyltransferase, lipin 1, and hormone sensitive lipase demonstrated mRNA expression patterns similar to PPARg and PPARd or CCAAT enhancer binding protein beta, which emphasizes their importance in marbling development and growth. Additionally, WA-MD and WA-MB steers often had a greater early mRNA expression of fatty acid transporters (fatty acid transport protein 1; P < 0.02; treatment × biopsy interaction) and binding proteins (fatty acid binding protein 4) compared with other steers. Cattle with a greater marbling propensity appear to upregulate adipogenesis at a younger chronological and physiological maturity through PPARd, PPARg, and possibly adipogenic regulating compounds, lysophosphatidic acid, and diacylglycerol. These genes and compounds could be used as potential markers for marbling propensity of cattle in the future.

Keywords: age, body weight, cellularity, lipid metabolism, Wagyu

Intramuscular adipocyte size and mRNA expression of lipid metabolism related genes from Wagyu-sired steers selected for either growth or marbling potential were compared with Angus-sired steers over time. Wagyu-sired steers selected for marbling potential had a greater percentage of intramuscular fat in the Longissimus muscle and had either an earlier or a greater upregulation of adipogenic genes responsible for fatty acid transport and triglyceride synthesis.

Introduction

Marbling, also known as intramuscular (IM) fat, can be visually recognized as the deposition of fat between the muscle fibers within the muscle bundles of the muscle. Marbling has been reported to have a positive impact on the three sensory characteristics of tenderness, juiciness, and flavor resulting in improved beef eating quality and consumer acceptability (May et al., 1992; Platter et al., 2003; Killinger et al., 2004). As an indication of eating quality and value, marbling score is extremely influential in determining beef carcass USDA quality grade. Therefore, considerable interest has been directed towards expanding the knowledge focused on IM fat development and growth.

Intramuscular adipocytes develop from mesenchymal progenitor cells in a process known as adipogenesis (Ailhaud et al., 1992; Smas and Sul, 1995; Campos et al., 2016). Adipogenesis begins with the commitment or determination of mesenchymal stem cells to the adipose tissue lineage and formation of fibro/adipogenic progenitor cells, also known as pre-adipocytes. A cell signaling cascade allows pre-adipocytes to proliferate, followed by pre-adipocytes differentiating into mature adipocytes through the incorporation and storage of triglycerides (Aihaud et al., 1992; Farmer, 2006).

Cattle of varying breed or genetic background can result in significant differences in marbling deposition. Wagyu cattle are known for their ability to deposit large amounts of IM fat in Japan (Gotoh et al., 2009; Albrecht et al., 2011), even when compared with the Angus breed that is well recognized for its marbling ability in the United States (Lunt et al., 1993, 2005). Previous research results from Wang et al. (2009) indicated a critical time period when pre-adipocytes undergo proliferation in cattle at approximately 7 months of age, with differentiation occurring around 12 months of age, followed by increased IM adipocyte hypertrophy.

The objective of the present study was to increase the understanding of the cellular signaling pathways responsible for marbling differences in cattle with different genotypes over time at a similar age endpoint, with a similar number of days consuming a finishing diet, or at a similar body weight endpoint. Genes analyzed in the present study are representative of adipogenesis, angiogenesis, fatty acid synthesis and transport, triglyceride synthesis, and lipolysis signaling pathways. We hypothesized that the mRNA expression of genes responsible for marbling accumulation would display different patterns of IM adipogenesis between Angus- and Wagyu-sired steers. Determining the distribution of IM adipocyte size in combination with measuring the mRNA expression of genes associated with different stages of adipogenesis should provide further information on the mechanisms regulating adipogenesis in cattle.

Materials and Methods

Animal procedures and husbandry practices were approved by the Institutional Animal Care and Use Committee (IACUC; protocol number 2015A00000093) of The Ohio State University and followed the guidelines recommended in the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching (FASS, 2010).

Experiment 1 treatments (constant DOF comparison)

Experiment 1 was designed to compare similarly aged Angus- and Wagyu-sired steers, produced from SimAngus dams, when fed for a similar number of days (D). Angus-sired steers (AN, n = 6) were sired by GAR Sunrise (registration #: 16933958), which ranked in the top 15% for yearling weight and top and 4% for marbling within the Angus breed. Wagyu-sired steers (n = 5) selected for growth (G) potential were sired by LMR Fukutsuru 729T (WA-GD; registration #: FB7480. Wagyu-sired steers (n = 5) selected for marbling (M) potential were sired by OW Yasufuku 24K 229Y (WA-MD; registration #: FB13141). Angus-sired steers, WA-GD, and WA-MD steers were blocked (n = 6) by receiving BW to maintain a similar number of DOF (258 ± 26.7 d). Once the AN steer in the blocking criteria reached the target body weight (BW) endpoint of 612 kg (599 ± 34.1 kg) the block of steers was removed for slaughter.

Experiment 2 treatments (constant BW comparison)

Angus-sired steers from Exp. 1 were also used in the comparison with Wagyu-sired cattle at a similar targeted BW endpoint (612 kg). Wagyu-sired steers selected for growth potential were sired by LMR Fukutsuru 729T (WA-GB,n = 4) and Wagyu-sired steers selected for marbling potential were sired by OW Yasufuku 24K 229Y (WA-MB,n = 5) from SimAngus dams. Individual Angus- and Wagyu-sired steers were removed from the feedlot for slaughter after reaching the target BW endpoint of 612 kg (613 ± 18.0 kg).

Management, feeding, and biopsy collection

Steers were born from SimAngus dams at the Jackson Agricultural Research Station (JARS; Jackson, OH) in March of 2017. Calves were weighed and weaned at seven months of age (204 ± 7.77 d of age [DOA]). Calves were backgrounded for 49 d with free choice hay and a concentrate pellet (consisting of approximately 54% ground corn, 21%, corn gluten feed, 18% low-fat dried distillers grain, 3% soybean meal, 3% animal-vegetable fat blend, and the remainder consisting of Amaferm ([BioZyme, St. Joseph, MO], vitamins, and minerals) before being transported to the Ohio Agricultural Research and Development Center (OARDC; Wooster, OH) feedlot. Upon receiving at the OARDC feedlot, calves were weighed, ear-tagged, and administered Inforce 3 (Zoetis, Parsippany, NJ) and Vetmetric pour-on (MWI veterinary supply; Northern Ireland). Calves were placed into individual pens (2.6 × 1.5 m) consisting of concrete slatted floors, with a 1.5 m long concrete feed bunk, and ad libitum access to clean, fresh water. No growth-promoting implants were administered to prevent their potential interference with marbling development and growth (Chung et al., 2012; Smith et al., 2017).

Diets were formulated to meet the nutrient requirements of growing and finishing beef cattle (NASEM, 2016; Table 1), with the exception of excluding vitamin A from the supplement. Steers were offered a growing diet for approximately 4 months (119 d) before making a three-week transition to the finishing diet, which they consumed until removal for slaughter. Weaning BW was collected at weaning, receiving BW was collected at the OARDC feedlot upon arrival, and off-test BW was collected at the OARDC feedlot before being transported to the Ohio State University abattoir (Columbus, OH). Feedlot performance, carcass data, and fatty acid composition results were reported previously by Jaborek et al. (2023). A thin slice of the LM at the 12th rib interface (~20 g), free of subcutaneous (SC) fat and connective tissue, was collected and frozen to determine LM IMF percentage by ether extraction (AOAC, 2005).

Table 1.

Composition (%) of diets offered during the experiment on a dry matter basis

	Growing	Finishing
Ingredient
Whole shelled corn	17.50	55.00
DDGS	17.50	10.00
Corn silage	55.00	25.00
Supplement	10.00	10.00
Ground corn	1.12	1.51
Soybean meal	5.00	5.00
Digest more¹	0.78	0.39
Limestone	1.10	1.10
White salt	1.00	1.00
Urea	0.50	0.50
Vit. A, 30,000 IU/g	0.00	0.00
Vit. D, 3,000 IU/g	0.01	0.01
Vit. E, 44 IU/g	0.02	0.02
Selenium, 201 ppm	0.14	0.14
Potassium chloride	0.30	0.30
Copper sulfate	0.01	0.01
Zinc sulfate	0.02	0.02
Magnesium sulfate	0.01	0.01
Analyzed composition
Crude protein, %	14.22	12.90
NDF, %	28.18	17.09
Fat, %	3.71	3.59
Ca, %	0.52	0.45
P, %	0.35	0.33
NEm, Mcal/kg	2.01	2.21
NEg, Mcal/kg	1.35	1.52

Open in a new tab

¹Amaferm (BioZyme, St. Joseph, MO).

In Exp. 1, individual steers were biopsied on the same day, five different times, at a similar age, with an average age of 205, 268, 331, 422, and 513 d. Steers in Exp. 2 were biopsied on the same day as a treatment, when the average weight of the three treatments was similar, when steers weighed 241 ± 18.4, 296 ± 24.3, 400 ± 33.9, 531 ± 33.3, and 613 ± 18.0 kg. Exp. 2 steers were 205 ± 9.5, 280 ± 10.0, 352 ± 16.3, 458 ± 31.9, and 546 ± 50.1 DOA when biopsies were collected. The longissimus muscle (LM) on the left side of the body was biopsied beginning at the 13th rib for the first biopsy collection. Subsequent biopsies were collected approximately 2.54 cm posterior from the previous biopsy site. Prior to surgery, the biopsy site was clipped to remove the hair, scrubbed 3 times with betadine surgical scrub, and followed by 3 scrubs with rubbing alcohol (70% isopropyl). Administration of 5 mL of lidocaine was administered prior to making a 2.54 cm incision to place the biopsy needle. A 10-mm muscle biopsy cannula (Millennium Surgical Corporation; Narberth, PA) was used to collect approximately 1 g of LM tissue. The biopsy incision site was closed with staples and sprayed with a water-resistant aerosol bandage (Aluspray; Neogen Corporation; Lexington, KY). Biopsies samples were snap frozen in liquid nitrogen and stored at −80 °C or in histology cassettes in 10% neutral buffered formalin. The slaughter (5th/final) LM biopsy was collected from the LM of the carcass immediately after hide removal with a knife, snap frozen in liquid nitrogen, and stored at −80 °C.

Cellularity analysis

Histological slides were prepared by The Ohio State University Comparative Pathology and Mouse Phenotyping and Histology/Immunohistochemistry (CPMPSR) laboratory. Briefly, formalin-fixed biopsy samples were embedded in paraffin, cut into 5 µm sections, and stained with hematoxylin and eosin. Intramuscular adipocytes appeared white with a blue membrane, while myocytes were stained pink. Multiple pictures were collected from each histology slide to identify all IM adipocytes using a Thermo Fisher EVOS XL Core Cell Imaging System (Thermo Fisher Scientific, Waltham, MA). The circumference of all traceable IM adipocytes was traced using ImageJ (NIH, Bethesda, MD) to determine the area of each IM adipocyte.

RNA extraction and analysis

Extraction of RNA was performed using RNAzol RT (Molecular Research Center; Cincinnati, OH) according to the manufacturer’s instructions. Briefly, 1 mL of RNAzol RT and 0.15 g of 0.1 mm zirconium beads were placed into a 2 mL micro-centrifuge tube, along with 0.1 g of biopsied LM tissue, and chilled on ice. Samples were homogenized for 1 min with a bead beater, chilled on ice for 1 min, and repeated. RNase-free water (0.4 mL) was added, samples were vortexed for 15 s, and allowed to incubate for 15 min at room temperature. Next, samples were centrifuged at 12,000 × g for 5 min at 4 °C. After, 0.6 mL of supernatant was pipetted into 2 new micro-centrifuge tubes, containing 0.4 mL of isopropanol, vortexed for 2 s, and allowed to incubate for 10 min at room temperature, before centrifuging at 12,000 × g for 10 min at 4 °C. Supernatant was discarded; 0.4 mL of 75% ethanol was pipetted into each tube, and centrifuged at 4,000 × g for 3 min at 20 °C. After repeating the last step, the RNA pellet was allowed to dry and 10 µl of RNase-free water was pipetted into each tube to resuspend the RNA pellet. The 2 centrifuge tubes containing RNA were combined and frozen at −80 °C until analysis.

Extracted RNA was quantified using UV spectroscopy (NanoDrop Technologies; Wilmington, DE) and RNA integrity was assessed using a BioAnalyzer 2100 and RNA NanoChip assay (Agilent Technologies; Santa Clara, CA). Expression of mRNA was determined using a NanoString nCounter XT Assay (NanoString Technologies; Seattle, WA). A custom bovine panel was created with genes involved in lipid metabolism. The NanoString nCounter XT Assay followed the procedures previously described by Coleman et al. (2018). The nSolver Analysis Software 3.0 (NanoString Technologies, Seattle, WA) was used to analyze nCounter data. Data were normalized to the geometric mean of the reference genes: actin-beta, cyclophilin A, and hypoxanthine phosphoribosyltransferase 1 (Table 2), and results are shown in Figure 4 through 8. A relative mRNA expression of 20 was the limit of detection.

Table 2.

List of genes analyzed from longissimus muscle tissue of Angus- and Wagyu-sired steers

Gene abbreviation	Gene name	Accession number
ACACA	acetyl-CoA carboxylase alpha	NM_174224.2
ACACB	acetyl-CoA carboxylase beta	NM_001205333.1
ACADVL	acyl-CoA dehydrogenase very long chain	NM_174494.2
ACLY	ATP citrate lyase	NM_001037457.1
AGPAT1	1-acylglycerol-3-phosphate O-acyltransferase 1	NM_177518.1
ANGPT1	angiopoietin 1	NM_001076797.1
ANGPT2	angiopoietin 2	NM_001098855.1
CD36	cd36 molecule (thrombospondin receptor)	NM_174010.2
CEBPA	CCAAT enhancer binding protein alpha	NM_176784.2
CEBPB	CCAAT enhancer binding protein beta	NM_176788.1
CPAT1A	carnitine palmitoyltransferase 1A	NM_001304989.2
CREB1	cAMP responsive element binding protein 1	NM_174285.1
DBI	diazepam binding inhibitor	NM_001113321.1
DGAT1	diacylglycerol O-acyltransferase 1	NM_174693.2
DLK1	delta like non-canonical notch ligand 1	NM_174037.2
ELOVL6	fatty acid elongase 6	NM_001102155.1
FABP4	fatty acid binding protein 4	NM_174314.2
FASN	fatty acid synthase	NM_001012669.1
FBLN1	fibulin 1	NM_001098029.1
GPAM	glycerol-3-phosphate acyltransferase	NM_001012282.1
GPD1	glycerol-3-phosphate dehydrogenase 1	NM_001035354.1
LDLR	low density lipoprotein receptor	NM_001166530.1
LIPE	lipase E, hormone sensitive type	NM_001080220.1
LPIN1	lipin 1	NM_001206156.2
LPL	lipoprotein lipase	NM_001075120.1
MGL	monoglyceride lipase	NM_001206681.1
OLR1	oxidized low density lipoprotein receptor 1	NM_174132.2
PDGFRA	platelet-derived growth factor receptor alpha	NM_001192345.1
PDGFRB	platelet-derived growth factor receptor beta	NM_001075896.2
PNPLA2	patatin like phospholipase domain containing 2	NM_001046005.2
PPARA	peroxisome proliferator activated receptor alpha	NM_001034036.1
PPARD	peroxisome proliferator activated receptor delta	NM_001083636.1
PPARG	peroxisome proliferator activated receptor gamma	NM_181024.2
PPARGC1A	PPARG coactivator 1 alpha	NM_177945.3
PTGIS	prostaglandin I2 synthase	NM_174444.1
PTGS1	prostaglandin-endoperoxide synthase 1	NM_001105323.1
PTGS2	prostaglandin-endoperoxide synthase 2	NM_174445.2
SCARB1	scavenger receptor class B member 1	NM_174597.2
SCD	stearoyl-CoA desaturase	NM_173959.4
SLC27A1	solute carrier family 27 member 1	NM_001033625.2
SREBF1	sterol regulatory element binding transcription factor 1	NM_001113302.1
VEGFA	vascular endothelial growth factor A	NM_174216.2
ZFP423	zinc finger protein 423	NM_001101893.1
ACTB	actin beta	NM_173979.3
EEF1A2	eukaryotic translation elongation factor 1 alpha 2	NM_001037464.1
HPRT1	hypoxanthine phosphoribosyltransferase 1	NM_001034035.1
PPIA	peptidylprolyl isomerase A	NM_178320.2
PPP1CA	protein phosphatase 1 catalytic subunit alpha	NM_001035316.2
SDHA	succinate dehydrogenase complex flavoprotein subunit A	NM_174178.2

Open in a new tab

Figure 4. — Treatment × Biopsy collection interactions for mRNA expression of adipogenic genes (cAMP responsive element binding protein 1 [CREB1], CCAAT enhancer binding protein beta [CEBPB], peroxisome proliferator activated receptor delta [PPARD], peroxisome proliferator activated receptor gamma [PPARG]) for Angus- and Wagyu-sired steers. Treatment × Biopsy Collection lsmean estimates are designated as AN (■), WA-GD (●), and WA-MD (○) for days on feed (DOF) at 205, 268, 331, and 513 d of age in Exp. 1. Treatment × Biopsy collection lsmean estimates are designated as AN (■), WA-GB (●), and WA-MB (○) for body weight (BW) at 241, 296, 400, and 613 kg in Exp. 2. Biopsy collections with significant treatment differences are identified by an (*).

Statistical analysis

Statistical analyses were performed using PROC MIXED in SAS (SAS Inst. Inc., Cary, NC). Experiments 1 and 2 used a completely randomized design with animal as the experimental unit. Prior to cellularity analysis, PROC UNIVARIATE was used to determine the percentage of IM adipocytes traced that had an area within 500 µm² intervals ranging from zero to greater than 13,000 µm². The statistical model used for cellularity and mRNA expression analyses was: Y_ij = μ + T_i + B_j + TB_ij + e_ij, where T_i = treatment, B_j = biopsy collection, TB_ij is the interaction as a fixed effect, and e_ij = random error. The REPEATED statement was used to determine the effect of time (biopsy collection) on mRNA expression, and the covariance structure with the lowest BIC was used. The LSMEANS, PDIFF, and SLICE statements were used to record treatment least square mean estimates, standard error of the mean (SEM), and distinguish differences between the treatment levels. A significance of fixed effects was established at P ≤ 0.05 and tendencies are discussed at 0.05 < P≤ 0.15.

Results

In Exp. 1, 12th rib LM IM fat percentage, tended (P = 0.15) to be greater for WA-MD steers compared with AN and WA-GD steers (12.7 vs. 9.9, 8.8%, respectively). In Exp. 2, 12th rib LM IM fat percentage, was greater (P < 0.01) for WA-MB steers compared with AN and WA-GB steers (14.7, 10.0, and 8.5%, respectively), while AN and WA-GB steers were not different (P = 0.39). Overall, WA steers selected for high marbling potential had a greater percentage of IM fat at slaughter compared with AN steers high marbling potential, and WA steers selected for growth potential regardless of slaughter endpoint (Jaborek et al., 2023).

Intramuscular adipocyte cellularity

The distribution of IM adipocytes from steers slaughtered at a similar age and DOF in Exp. 1 and similar BW in Exp. 2, exhibited unimodal distributions with a positive skew (Figure 1). In Exp. 1, AN steers had a greater (P < 0.04) proportion of IM adipocytes with an area between 1,500 and 2,000 µm² at 205 DOA compared with WA-MD steers (treatment × biopsy collection interaction; Figure 2A). The WA-GD and WA-MD steers had a greater (P < 0.02) proportion of IM adipocytes with an area between 12,500 and 13,000 µm² at 513 DOA compared with AN steers, while WA-GD tended (P = 0.07) to have a greater proportion of IM adipocytes with an area between 11,500 and 12,000 µm² at 513 DOA compared with AN steers (Figure 2D). Among the different treatments, AN steers tended to have a lesser proportion of IM adipocytes with an area between 6,500 and 7,000 µm² (P = 0.14), 7,000 and 7,500 µm² (P = 0.06), 8,500 and 9,000 µm² (P = 0.15), 9,500 and 10,000 µm² (P = 0.15) compared with WA-MD steers, and 10,000 and 10,500 µm² (P = 0.11), 12,500 and 13,000 µm² (P = 0.07), and larger than 13,000 µm² (P = 0.11) compared with WA-GD steers. Over time, animal age affected (P ≤ 0.04) the proportion of IM adipocytes in each 500 µm² interval, except between 2,000 and 2,500 µm² (P = 0.33; Figure 1A). In general, at 205, 268, and 331 DOA there was a greater proportion of IM adipocytes between 0 and 2,000 µm² and at 531 DOA there was a greater proportion of IM adipocytes between 4,500 and greater than 13,000 µm².

Figure 1. — Distribution of intramuscular (IM) adipocyte area in the longissimus muscle of steers compared (A) at a similar number of days on feed (DOF) and age (205, 268, 331, 422, 513 d of age) in Exp. 1 or (B) at a similar body weight (BW; 241, 296, 400, 531, 613 kg) in Exp. 2. Biopsy collection lsmean estimates are designated: 1 (▲), 2 (■), 3 (●), and 5 (Ж).

Figure 2. — Distribution of intramuscular adipocyte area in the longissimus muscle of steers compared at a similar number of days on feed (DOF) and age in Exp. 1: (A) 205, (B) 268, (C) 331, and (D) 513 d of age, for biopsy collections 1, 2, 3, and 5, respectively. Treatment lsmean estimates are designated as AN (●), WA-GD/WA-GB (■), and WA-MD/WA-MB (▲).

In Exp. 2, WA-GB and WA-MB steers had a greater (P < 0.03) proportion of IM adipocytes with an area between 12,500 and 13,000 µm² at 613 kg compared with AN steers, and a tendency for WA-GB steers to have the greatest proportion of IM adipocytes with an area between 5,500 and 6,000 µm² (P = 0.12) and 9,500 and 10,000 µm² (P = 0.12) at 613 kg (treatment × time interaction; Figure 3D). Likewise, WA-MB steers tended to have a greater proportion of IM adipocytes with an area between 5,500 and 6,000 µm² (P = 0.12) compared with AN steers at 296 kg (Figure 3B). Among the different treatments, AN steers tended to have a lesser proportion of IM adipocytes with an area between 4,000 and 4,500 µm² (P = 0.11), 4,500 and 5,000 µm² (P = 0.08), 6,500 and 7,000 µm² (P = 0.14), 7,000 and 7,500 µm² (P = 0.10), 8,000 and 8,500 µm² (P = 0.13) compared with WA-GB steers. Angus-sire steers had a lesser proportion of IM adipocytes with an area 8,500 to 9,000 µm² (P < 0.02, P < 0.04), 9,500 to 10,000 µm² (P < 0.01, P < 0.01) compared with WA-GB and WA-MB steers, respectively. In addition, AN steers tended to have a lesser proportion of IM adipocytes with an area 10,000 to 10,500 µm² (P = 0.06), and larger than 13,000 µm² (P = 0.07) compared with WA-MB steers. Over time, the proportion of IM adipocytes in each 500 µm² interval was different (P ≤ 0.02) when steers were compared at a similar BW (Figure 1B). In general, when steers weighed 241, 296, and 400 kg there was a greater proportion of IM adipocytes between 0 to 2,000 µm² and when steers weighed 613 kg there was a greater proportion of IM adipocytes between 4,500 and greater than 13,000 µm².

Sample size was relatively small in this study and resulted in a greater variability than expected for the IM adipocyte cellularity results. As a result of discovering fewer significant treatment × time interactions than what was hypothesized, additional discussion will be given to the IM adipocyte cellularity treatment × time distributions. In Exp. 1, at 205 DOA (Figure 2A), WA-MD steers had IM adipocytes that were less mature compared with AN and WA-GD steers, which is illustrated by a greater proportion (+8%) of small IM adipocytes (0 to 500 µm²) and a lesser proportion of larger IM adipocytes (1,000 to 2,000 µm²). At the second biopsy time point (268 DOA; Figure 2B), WA-GD steers developed a greater proportion (+10%) of small IM adipocytes (0 to 500 µm²) relative to AN and WA-MD steers. A greater proportion of smaller IM adipocytes for WA-MD and WA-GD steers at 205 and 268 DOA, respectively, may indicate the proliferation of new smaller IM adipocytes. At 331 DOA (Figure 2C), WA-GD and WA-MD steers shift to a greater proportion of larger IM adipocytes (1,500 to 3,000 µm²), but interestingly AN steers retained a portion of smaller IM adipocytes (1,000 to 1,500 µm²) while increasing the proportion of larger IM adipocytes (2,000 to 6,500 µm²). At slaughter (513 DOA; Figure 2D), the distribution of IM adipocyte area was very similar between steers in different treatments, indicating that marbling differences between the treatments at slaughter were likely due to IM adipocyte number rather than IM adipocyte size.

In Exp. 2, the distribution of IM adipocytes from the first biopsy (241 kg; Figure 3A) is very similar to Exp. 1, as steers were biopsied on the same day to initiate the present study. However, at the second biopsy (246 kg Figure 3B), IM adipocytes from WA-GB steers began to shift towards a greater proportion of larger IM adipocytes with an area between 1,000 to 2,000 µm² when compared with AN and WA-MB steers. At 400 kg (Figure 3C) WA-GB and WA-MB steers continued to demonstrate a shift towards a greater proportion of larger IM adipocytes (2,500 to 4,000 µm²) compared with AN steers, while AN steers still had a greater proportion of smaller IM adipocytes (1,000 to 1,500 µm²). At slaughter (613 kg; Figure 3D), the distribution of IM adipocyte area would indicate that WA-GB steers had a slightly larger IM adipocyte area on average due to the distribution being shifted slightly towards the right.

Expression of mRNA for adipogenic genes

Expression of mRNA for adipogenic genes measured at a similar age and DOF are shown in Table 3 and Figure 4. In Exp. 1, zinc finger protein 423 (ZFP423) mRNA expression increased over time (P ≤ 0.01), with an upregulation at 331 and 442 DOA, with no differences (P = 0.73) observed among steers in different treatments. Expression of mRNA for delta like noncanonical notch ligand 1 (DLK1), also known as preadipocyte factor 1, was not different among the three treatments (P = 0.99) and tended (P = 0.14) to be greater at the fifth biopsy collection relative to the other four biopsy collection time points. Similarly, fibulin 1 (FBLN1) mRNA expression was greater (P ≤ 0.01) at 513 DOA for steers in the present study. The mRNA expression of prostaglandin I₂ synthase (PTGIS) was greater (P ≤ 0.01) at 205 and 513 DOA than at 331 and 422 DOA, with no differences (P = 0.37) observed among steers in different treatments. There was a greater (P ≤ 0.02) cAMP responsive element binding protein 1 (CREB1) mRNA expression at 422 DOA and up to 513 DOA, but there also tended to be a treatment × biopsy interaction (P = 0.10; Figure 4A) where AN steers tended to have a greater CREB1 mRNA expression at 422 DOA compared with WA-MD steers. The mRNA expression of CCAAT enhancer binding protein beta (CEBPB) (P ≤ 0.01; Figure 4B) and peroxisome proliferator activated receptor delta (PPARD) (P ≤ 0.02; Figure 4C) had significant treatment × biopsy interactions. At 268 DOA, PPARD mRNA expression was sustained at a greater level by WA-MD steers compared with AN (P < 0.02) and WA-GD (P < 0.03) steers. Additionally, AN steers had a greater PPARD mRNA expression compared with WA-GD (P < 0.01) and WA-MD (P < 0.01) steers at 422 DOA and WA-GD (P < 0.01) steers at 513 DOA. The AN steers also exhibited a greater CEBPB mRNA expression at 422 DOA compared with WA-GD (P < 0.01) and WA-MD (P < 0.01) steers. The mRNA expression of CCAAT enhancer binding protein alpha (CEBPA) was near the limit of detection in the present study, but demonstrated a slight upregulation (P ≤ 0.01) at 422 and 513 DOA, and tended(P = 0.15) to be greater for WA-MD steers compared with WA-GD steers. The mRNA expression for peroxisome proliferator activated receptor gamma 2 (PPARG) was greater (P ≤ 0.01) at 422 and 513 DOA; while WA-MD steers had a greater (P < 0.04; P < 0.02) PPARGmRNA expression when compared with AN and WA-GD steers, respectively.

Table 3.

Exp. 1 – RNA expression of adipogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar number of days on feed and age

Item	Treatment¹			SEM²	Biopsy collection (age, d)					SEM²	P-values³
Item	AN	WA-GD	WA-MD		205	268	331	422	513	SEM²	TRT	BC	T × B
ZFP423	163.4	154.3	160.9	7.88	133.4e	129.4^e	157.0^d	187.9^c	189.8^c	9.12	0.70	0.01	0.78
DLK1	65.2	64.8	64.2	6.80	63.4	57.3	67.5	57.5	77.9	8.77	1.00	0.14	0.41
FBLN1	142.2	158.4	157.9	9.42	106^e	115^d,e	148^d	127^d,e	268^c	11.7	0.37	0.01	0.98
PTGIS	54.3	60.3	64.3	5.07	75.4^c	62.3^c,d	46.5^d,e	39.8^e	74.1^c	8.94	0.37	0.01	0.44
CREB1	84.9	82.3	78.1	3.83	73.8^e	80.0^d,e	77.7^d,e	82.6^c,d	94.7^c	6.57	0.43	0.01	0.10
PPARD	49.0	40.5	45.6	2.72	59.6^c	51.9^cd	28.4^f	36.4^e	48.9^d	3.67	0.09	0.01	0.01
CEBPB	744	679	740	54.1	729^d	504^f	634^e	667^d,e	1,070^c	88.4	0.64	0.01	0.01
CEBPA	22.8	21.5	24.5	1.08	21.9^d	21.1^d,e	20.1^e	26.7^c	24.9^c,d	2.03	0.15	0.01	0.36
PPARG	40.9^b	38.5^b	56.4^a	5.11	38.9^de	30.4^e	34.6^de	53.3^cd	69.2^c	6.72	0.03	0.01	0.46

Open in a new tab

¹AN, Angus-sired steers selected for a combination of growth and marbling potential, WA-GB, Wagyu-sired steers selected for growth potential, WA-MB, Wagyu-sired steers selected for marbling potential.

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 4).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for adipogenic genes measured at a similar BW are shown in Table 4 and Figure 4. In Exp. 2, ZFP423 mRNA expression was greater (P ≤ 0.01) at the fourth and fifth biopsy collection when steer body weight was 531 and 613 kg. The mRNA expression for DLK1 was not different among treatments (P = 0.29) or biopsy collections (P = 0.26). The mRNA expression of FBLN1 was greatest (P ≤ 0.01) at slaughter (613 kg), intermediate when steers weighed 400 kg and 531 kg, and least at 296 and 241 kg, with WA-MB steers tending (P = 0.07) to have a greater FBLN1 mRNA expression compared with AN steers. The mRNA expression of PTGIS (P ≤ 0.01) was down regulated at 276 kg, but was upregulated again at 613 kg. Expression of mRNA for CREB1 exhibited a treatment × biopsy interaction (P ≤ 0.02), where AN steers had a greater mRNA expression at 531 kg compared with WA-GB (P < 0.01) and WA-MB (P < 0.02) steers, and AN steers also tended (P = 0.06) to have a greater CREB1 mRNA expression at 400 kg compared with WA-MB steers (Figure 4D). There was a treatment × biopsy interaction for PPARD mRNA expression (P ≤ 0.01), where WA-MB steers exhibited approximately 2 times greater PPARD mRNA expression at 400 kg compared with AN (P < 0.01) and WA-GB (P < 0.01) steers, while AN steers had a slightly greater PPARD mRNA expression than WA-GB (P < 0.01) and WA-MB (P < 0.01) steers at 531 kg (Figure 4F). The mRNA expression of CEBPB was upregulated (P ≤ 0.01) at 613 kg. However, CEBPB tended to exhibit a treatment × biopsy interaction (P = 0.15; Figure 4E), where AN steers tended to have a greater mRNA expression at 531 kg compared with WA-MB steers, WA-GD and WA-MD steers tended to have a greater CEBPB mRNA expression at 296 kg compared with AN steers, and WA-MD steers tended to have a greater mRNA expression at 400 kg compared with AN steers. The mRNA expression of CEBPA was not different due to treatment or time, likely due to the low expression (close to the detection limit for this gene). The mRNA expression of PPARG tended to display a treatment × biopsy interaction (P = 0.09), where WA-MB steers tended to have a greater PPARG mRNA expression at 400 kg compared with AN and WA-GB steers (Figure 4G). Additionally, PPARG mRNA expression was greater (P ≤ 0.01) at 531 and 613 kg, and tended (P = 0.09) to be greater on average for WA-MB steers compared with AN and WA-GB steers.

Table 4.

Exp. 2 – RNA expression of adipogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar body weight

Item	Treatment¹			SEM²	Biopsy Collection (BW, kg)					SEM²	P-values³
Item	AN	WA-GB	WA-MB		241	296	400	531	613		TRT	BC	T × B
ZFP423	162	156	177	12.5	133^e	158^d	156^d	188^c	190^c	12.5	0.42	0.01	0.21
DLK1	65.4	68.7	56.0	6.30	63.4	53.2	62.3	66.1	71.9	6.57	0.28	0.26	0.38
FBLN1	144	156	174	10.2	106^e	115^e	152^d	152^d	266^c	11.5	0.07	0.01	0.40
PTGIS	53.5	63.2	53.9	4.56	75.4^c	43.0^d	49.3^d	43.8^d	72.9^c	5.82	0.22	0.01	0.20
CREB1	85.6	77.9	76.2	3.54	73.8	82.7	77.3	78.2	87.6	6.73	0.05	0.10	0.02
PPARD	48.5	45.1	47.0	3.25	59.6^c	35.2^d	44.0^cd	38.9^d	56.6^c	5.43	0.73	0.01	0.01
CEBPB	736	779	783	52.4	729.1^d	668^d	649^d	724^d	1,061^c	61.0	0.72	0.01	0.15
CEBPA	22.8	21.1	22.0	1.06	21.9	20.4	20.6	24.5	22.2	1.97	0.45	0.18	0.80
PPARG	40.9	38.3	52.7	5.34	38.9^d	25.4^e	33.0^d	59.1^c	63.4^c	8.25	0.09	0.01	0.09

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 4).

^{a, b} Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f} Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for lipogenic genes

Expression of mRNA for lipogenic genes measured at a similar age and DOF are shown in Table 5 and Figure 5. In Exp. 1, sterol regulatory element binding transcription factor 1 (SREBF1) mRNA expression (P ≤ 0.01) was greater at the first, fourth, and fifth biopsies, corresponding to 205, 422, and 513 DOA for steers, respectively. The mRNA expression of SREBF1 tended to exhibit a treatment × biopsy interaction (P = 0.051; Figure 5A), where AN steers had a numerically greater SREBF1 mRNA expression at 422 DOA compared with WA-GD and WA-MD steers. The mRNA expression of ATP citrate lyase (ACLY; P ≤ 0.01), acetyl-CoA carboxylase alpha (ACACA; P ≤ 0.01), and fatty acid synthase (FASN; P ≤ 0.01) similarly mirrored SREBF1 mRNA expression and peaked at 422 DOA or the fourth biopsy. The mRNA expression of ACACA tended (P = 0.09) to be greater for WA-MD steers compared with AN and WA-GD steers, which was driven by its numerically greater mRNA expression at 422 DOA. Expression of mRNA for acetyl-CoA carboxylase beta (ACACB) was greatest (P ≤ 0.01) at 513 DOA and exhibited a treatment × biopsy interaction (P ≤ 0.04; Figure 5B), where AN steers had a greater mRNA expression compared with WA-GD (P < 0.03) and WA-MD (P < 0.01) steers at 422 DOA, and WA-GD steers had a greater ACACB mRNA expression compared with WA-MD (P < 0.01) steers at 422 DOA. The mRNA expression of fatty acid elongase 6 (ELOVL6; P ≤ 0.01) and stearoyl-CoA desaturase (SCD; P ≤ 0.01) were upregulated at 422 DOA and ELOVL6 (P = 0.06) and SCD (P = 0.08) mRNA expression tended to be greater for WA-MD steers compared with AN and WA-GD steers. The mRNA expression of glycerol-3-phosphate dehydrogenase 1 (GPD1) was greater (P ≤ 0.01) at 268, 331, and 422 DOA in steers, while GPD1 became downregulated at 513 DOA. The mRNA expression of glycerol-3-phosphate acyltransferase (GPAM) exhibited a treatment × biopsy interaction (P ≤ 0.04; Figure 5C), where mRNA expression at 331 DOA was greater for WA-GD (P < 0.01) and tended to be greater for WA-MD (P = 0.10) steers compared with AN steers, and WA-MD steers tended to have a greater GPAM mRNA expression compared with AN (P = 0.09) and WA-GD (P = 0.06) steers at 422 DOA. The mRNA expression of 1-acylglycerol-3-phosphate O-acyltransferase 1 (AGPAT1) was slightly greater (P ≤ 0.02) at 205 and 513 DOA, but there were no treatment differences (P = 0.47). A treatment × biopsy interaction (P ≤ 0.02; Figure 5D) for phosphatidic acid phosphatase, also known as lipin 1 (LPIN1), resulted from WA-MD steers having greater (P < 0.03) mRNA expression at 268 DOA compared with AN steers, while AN steers had a greater mRNA expression at 422 DOA compared with WA-GD (P < 0.01) and WA-MD (P < 0.01) steers. Diacylglycerol O-acyltransferase 1 (DGAT1) mRNA expression was relatively constant with the greatest mRNA expression tending (P = 0.07) to be at 513 DOA.

Table 5.

Exp. 1 – RNA expression of lipogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar number of days on feed and age

Item	Treatment¹			SEM²	Biopsy Collection (Age, d)					SEM²	P-values³
Item	AN	WA-GD	WA-MD		205	268	331	422	513	SEM²	TRT	BC	T × B
SREBF1	60.3	54.2	56.3	4.42	66.9^c	42.8^d	38.6^d	72.6^c	63.8^c	4.53	0.60	0.01	0.05
ACLY	71	58	89	11.5	39^e	50^d,e	67^d	146^c	61^d	28.8	0.18	0.01	0.79
ACACA	71.7	69.5	96.5	9.51	54^e	55^e	74^d,e	125^c	87^c,d	20.4	0.09	0.01	0.63
ACACB	347	357	364	25.1	294^d,e	352^d	263^e	294^d,e	576^c	62.7	0.89	0.01	0.04
FASN	694	598	927	131	351^e	497^d,e	682^d	1,309^c	859^c,d	263	0.19	0.01	0.87
ELOVL6	101	87	172	26.5	42^e	62^d,e	100^d	273^c	126^d	62.7	0.05	0.01	0.54
SCD	1,550	1,483	2,277	273	886^e	981^e	1,551^d,e	3,109^c	2,323^c,d	359	0.08	0.01	0.40
GPD1	3,388	3,496	3,370	172	3,213^d	3,568^c	3,611^c	3,925^c	2,775^e	172	0.85	0.01	0.36
GPAM	150^b	172^a,b	196^a	12.5	143^e	137^e	161^de	205^c,d	217^c	21.9	0.03	0.01	0.03
AGPAT1	41.1	38.1	41.4	2.06	44.0^c	39.0^c,d	35.6^d	37.6^d	44.8^c	2.28	0.47	0.01	0.86
LPIN1	1,550	1,339	2,002	300	1,233^e	1,812^d	921^f	962^f	3,224^c	714	0.28	0.01	0.01
DGAT1	29.1	29.9	32.9	1.54	32.5	27.3	28.2	30.5	34.7	2.03	0.18	0.06	0.91

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 5).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for lipogenic genes measured at a similar BW are shown in Table 6 and Figure 5. In Exp. 2, SREBF1 mRNA expression exhibited a treatment × biopsy interaction (P ≤ 0.01), with WA-GB and WA-MB steers having a greater mRNA expression at the third biopsy, at 400 kg, but AN steers had a greater mRNA expression than WA-GB and WA-MB steers at the fourth biopsy when steers weighed 531 kg (Figure 5E). Similar to Exp. 1, steers in Exp. 2 had a greater mRNA expression of ACLY (P ≤ 0.01), ACACA (P ≤ 0.01), FASN (P ≤ 0.01), ELOVL6 (P ≤ 0.01), and SCD (P ≤ 0.01) at the fourth biopsy collection or 531 kg. Expression of mRNA for ACACB was greatest (P ≤ 0.01) at 513 DOA and exhibited a treatment × biopsy interaction (P ≤ 0.01), where WA-MB steers had a greater mRNA expression at 400 kg compared with AN and WA-GB steers, and AN steers had a greater mRNA expression at 531 kg compared with WA-GB and WA-MB steers (Figure 5F). The mRNA expression pattern of GPD1 was similar to Exp. 1, where GPD1 mRNA expression was greater (P ≤ 0.01) at the second, third, and fourth biopsies. Expression of mRNA for GPAM exhibited a treatment × biopsy interaction (P ≤ 0.02), with a greater mRNA expression for WA-MB steers at 400 and 613 kg compared with AN and WA-GB steers (Figure 5G). The mRNA expression pattern of AGPAT1 was also similar to Exp. 1, where AGPAT1 mRNA expression was greater (P ≤ 0.01) at the first and fifth biopsies, or 241 and 613 kg. Lipin 1 exhibited a similar pattern of mRNA expression as PPARD, with a greater mRNA expression for WA-MB steers at 400 kg compared with AN and WA-GD steers, and AN steers having a greater mRNA expression at 531 kg compared with WA-GB and WA-MB steers (treatment × biopsy interaction, P ≤ 0.01; Figure 5H). The mRNA expression of DGAT1 tended (P = 0.07) to be greater for WA-GB and WA-MB steers compared with AN steers.

Table 6.

Exp. 2 – RNA expression of lipogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar body weight

Item	Treatment¹			SEM²	Biopsy Collection (BW, kg)					SEM²	P-values³
Item	AN	WA-GB	WA-MB	SEM²	241	296	400	531	613	SEM²	TRT	BC	T × B
SREBF1	59.8	57.7	56.9	4.71	66.9^c	42.4^e	51.2^d	68.2^c	61.8^c	6.67	0.89	0.01	0.01
ACLY	72	68	67	13.4	39^f	50^e	72^c,d	125^c	58^d,e	28.2	0.96	0.01	0.96
ACACA	72.3	72.9	85.6	9.08	55^e	50^e	71^d	128^c	82^c,d	19.7	0.43	0.01	0.65
ACACB	345	362	354	25.2	294^d	335^d	287^d	276^d	575^c	52.1	0.85	0.01	0.01
FASN	707	586	815	140	351^d	410^d	740^c	1,180^c	833^c	255	0.48	0.01	0.86
ELOVL6	104	84	139	23.0	42^e	46^e	104^d	227^c	127^c,d	52.0	0.19	0.01	0.62
SCD	1,586	1,531	2,268	398	886^e	772^e	1,820^d	3,190^c	2,308^c,d	595	0.28	0.01	0.59
GPD1	3,390	3,542	3,670	159	3,213^d	4,010^c	3,632^c	4,022^c	2,793^e	166	0.38	0.01	0.27
GPAM	149^b	155^b	194^a	13.3	143^d	119^e	146^d	198^c	224^c	22.9	0.02	0.01	0.02
AGPAT1	40.9	39.6	40.4	1.90	44.0^c,d	37.2^e	36.2^e	38.6^d,e	45.6^c	2.43	0.87	0.01	0.59
LPIN1	1,545	1,478	1,489	155	1,233^d	1,181^d	1,308^d	1,055^d	2,744^c	333	0.93	0.01	0.01
DGAT1	29.3	34.1	34.4	1.92	32.5	29.1	30.8	35.4	35.1	2.17	0.07	0.13	0.83

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 5).

^{a, b} Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f} Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for angiogenicgenes

Angiogenic mRNA expression from AN and WA steers measured at a similar age and DOF are shown in Table 7. In Exp. 1, vascular endothelial growth factor A (VEGFA) mRNA expression was greater (P ≤ 0.01) at 205 and 268 DOA for steers. The mRNA expression of angiopoietin 1 (ANGPT1) was relatively constant from 205 DOA to 422 DOA, but decreased (P ≤ 0.04) afterwards. The opposite mRNA expression pattern was exhibited for angiopoietin 2 (ANGPT2), where mRNA expression increased (P ≤ 0.01) from 205 DOA until 331 DOA and remained relatively constant thereafter. The mRNA expression of platelet-derived growth factor receptor alpha (PDGFRA) was greater (P ≤ 0.01) at the third and fifth biopsy, 331 and 513 DOA, respectively. The mRNA expression for PDGF receptor beta (PDGFRB) was greatest (P ≤ 0.01) at slaughter or 513 DOA.

Table 7.

Exp. 1 – RNA expression of angiogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar number of days on feed and age

Item	Treatment¹			SEM²	Biopsy Collection (Age, d)					SEM²	P-values³
Item	AN	WA-GD	WA-MD	SEM²	205	268	331	422	513	SEM²	TRT	BC	T × B
VEGFA	280	302	307	16.5	354^c,d	370^c	231^f	294^d,e	233^e,f	34.8	0.46	0.01	0.62
ANGPT1	37.5	38.8	41.6	3.04	37.3^c,d	41.1^c,d	42.7^c	44.3^c	31.1^d	4.39	0.61	0.04	0.40
ANGPT2	27.2	28.9	28.9	1.63	21.3^e	26.4^d	29.9^c,d	33.0^c	31.3^c,d	2.71	0.68	0.01	0.38
PDGFRA	183.2	188.8	192.3	8.13	170^e	176^d,e	200^c,d	173^d,e	221^c	10.7	0.72	0.01	0.79
PDGFRB	214.6	216.2	203.3	6.67	206.2^d	191.4^d	206.4^d	209.0^d	243.8^c	8.77	0.33	0.01	0.52

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction.

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Experiment 2 demonstrated many of the same mRNA expression patterns as Exp. 1 for the angiogenic genes (Table 8 and Figure 6). The mRNA expression of VEGFA tended (P = 0.07) to be greatest at weaning; and tended to exhibit a treatment × biopsy interaction (P = 0.15) with AN and WA-MB steers tending to have a greater VEGFA mRNA expression at 531 kg compared with WA-GB steers. Expression of mRNA for ANGPT1 exhibited a treatment × biopsy interaction (P ≤ 0.02; Figure 6), where ANGPT1 mRNA expression was nearly two times greater for AN (P < 0.01) and WA-GB (P < 0.01) steers compared with WA-MB steers at 400 kg. Steers had a lesser (P ≤ 0.01) mRNA expression of ANGPT2 at weaning relative to other biopsy collections. In addition to the greater (P ≤ 0.02) mRNA expression of PDGFRA at 613 kg, WA-GB steers had a greater PDGFRA mRNA expression compared with AN (P < 0.02) and WA-MB (P < 0.01) steers. No treatment (P = 0.47) or biopsy collections timepoint (P = 0.19) differences were detected for PDGFRB mRNA expression for steers in Exp. 2.

Table 8.

Exp. 2 – RNA expression of angiogenic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar body weight

Item	Treatment¹			SEM²	Biopsy Collection (BW, kg)					SEM²	P-values³
Item	AN	WA-GB	WA-MB	SEM²	241	296	400	531	613	SEM²	TRT	BC	T × B
VEGFA	278	265	293	19.4	354	275	268	259	238	35.0	0.57	0.07	0.15
ANGPT1	37.7	41.4	35.8	2.75	37.3^d,e	45.3^c,d	35.7^e	46.4^c	26.7^f	3.75	0.32	0.01	0.02
ANGPT2	27.4	29.5	29.9	2.09	21.3^d	28.6^c	31.0^c	30.6^c	33.3^c	2.70	0.56	0.01	0.42
PDGFRA	184.9^b	209.7^a	172.5^b	7.84	170^d	188^d	191^c,d	181^d	216^c	10.0	0.01	0.01	0.31
PDGFRB	213.2	223.2	212.7	7.09	206.2	208.5	212.3	225.8	229.0	9.05	0.47	0.19	0.54

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 6).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Figure 6. — Treatment × Biopsy collection interactions for mRNA expression of angiogenic genes (angiopoietin 1 [ANGPT1]) for Angus- and Wagyu-sired steers. Treatment × Biopsy collection lsmean estimates are designated as AN (■), WA-GB (●), and WA-MB (○) for body weight (BW) at 241, 296, 400, and 613 kg in Exp. 2. Biopsy collections with significant treatment differences are identified by an (*).

Expression of mRNA for fatty acids uptake and transport genes

Expression of mRNA for FA uptake and transport genes measured at a similar age and DOF are shown in Table 9 and Figure 7. In Exp. 1, lipoprotein lipase (LPL) mRNA expression was greater (P ≤ 0.01) at 205 and 513 DOA for steers. The mRNA expression of low density lipoprotein receptor (LDLR) demonstrated a treatment × biopsy interaction (P ≤ 0.01; Figure 7A) with WA-MD steers having a greater mRNA expression at 422 DOA compared with AN (P < 0.01) and WA-GD (P < 0.01) steers. On average, WA-MD steers tended (P = 0.08) to have a greater LDLR expression compared with AN and WA-GD steers. Expression of mRNA for scavenger receptor class B member 1 (SCARB1) was greater (P ≤ 0.01) at 205, 268, and 331 DOA, and decreased afterwards, with AN steers tending (P = 0.07) to have a greater SCARB1 mRNA expression compared with WA-GD and WA-MD steers. The mRNA expression of cd36 molecule (CD36) was greater (P ≤ 0.01) at 513 DOA, while WA-MD steers tended (P = 0.11) to have a greater CD36 mRNA expression than AN steers. The mRNA expression of solute carrier family 27 member 1, also known as fatty acid transport protein 1 (FATP1), had a treatment × biopsy interaction (P ≤ 0.01; Figure 7B) with AN steers having a greater mRNA expression at 422 DOA compared with WA-GD (P < 0.04) and WA-MD (P < 0.01) steers. The mRNA expression of FATP1 was greater (P < 0.03) for WA-MD steers compared with AN steers at 513 DOA, and WA-GD steers tended (P = 0.09) to have greater FATP1 mRNA expression compared with AN steers at 513 DOA. Expression of mRNA for fatty acid binding protein 4 (FABP4) was greater (P ≤ 0.01) at 422 and 513 DOA, and tended (P = 0.07) to be greater for WA-MD steers compared with AN and WA-GD steers. The mRNA expression of diazepam binding inhibitor, also known as acyl-CoA binding protein (ACBP), became upregulated (P ≤ 0.01) after 205 DOA, with the greatest mRNA expression at 268 and 513 DOA.

Table 9.

Exp. 1 – RNA expression of fatty acid transporter genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar number of days on feed and age

Item	Treatment¹			SEM²	Biopsy Collection (Age, d)					SEM²	P-values³
Item	AN	WA-GD	WA-MD	SEM²	205	268	331	422	513	SEM²	TRT	BC	T × B
LPL	850	792	942	60.2	1,025^c	663^d	720^d	823^d	1,076^c	74.4	0.21	0.01	0.22
LDLR	29.3	30.1	38.5	3.26	32.1^d,e	29.5^d,e	35.2^c,d	41.8^c	24.6^e	3.73	0.07	0.01	0.01
SCARB1	63.6	56.0	55.0	2.83	61.5^c,d	66.9^c	62.0^c,d	56.2^d	44.5^e	3.71	0.06	0.01	0.30
CD36	1,915	2,126	2,207	99.4	1,818^d	1,692^d	1,734^d	1,787^d	3,384^c	171	0.11	0.01	0.35
FATP1	147.2	160.4	158.3	9.20	164^c	132^d	138^d	179^c	163^c	11.0	0.55	0.01	0.01
FABP4	1,155	959	1,709	233	1,064^d	570^d	809^d	1,671^c	2,256^c	415	0.07	0.01	0.43
ACBP	2,606	2,669	2,850	132	1,617^f	3,140^c,d	2,751^e	2,866^d,e	3,169^c	122	0.40	0.01	0.47

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 7).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for FA uptake and transport genes measured at a similar BW are shown in Table 10 and Figure 7. In Exp. 2, LPL mRNA expression was greater (P ≤ 0.01) at 241 and 613 kg, while AN steers tended (P = 0.13) to have a greater LPL mRNA expression compared with WA-GB steers. Low density lipoprotein receptor mRNA expression was greater for WA-GB (P < 0.03) and WA-MB (P < 0.05) steers at 296 kg compared with AN steers, and WA-GB steers had a greater mRNA expression at 400 kg compared with AN (P < 0.01) and WA-MB (P < 0.01) steers (treatment × biopsy interaction, P ≤ 0.01; Figure 7C). The mRNA expression of SCARB1 was greatest (P ≤ 0.01) at 296 kg and decreased thereafter, with AN steers tending (P = 0.06) to have a greater mRNA expression compared with WA-MB steers. The CD36 mRNA expression was greatest (P ≤ 0.01) at the fifth biopsy collection (613 kg), and WA-MB steers had a greater (P < 0.01) CD36 mRNA expression compared with AN steers, while WA-GB steers were intermediate to WA-MB (P = 0.30) and AN (P = 0.17) steers. AN steers had a greater mRNA expression of FATP1 at the fourth biopsy collection (531 kg) compared with WA-GB (P < 0.02) and WA-MB (P < 0.04) steers (treatment × biopsy interaction, P ≤ 0.02; Figure 7D). In addition, WA-GB (P < 0.05) and WA-MB (P < 0.01) steers had a greater mRNA expression of FATP1 at the second biopsy collection (276 kg) compared with AN steers. Expression of mRNA for FABP4 was greatest (P ≤ 0.01) at 531 and 613 kg. The mRNA expression of ACBP exhibited a treatment × biopsy interaction (P ≤ 0.05; Figure 7E), where WA-GB steers had a greater mRNA expression at 276 kg compared with AN (P < 0.01) and WA-MB (P < 0.01) steers.

Table 10.

Exp. 2 – RNA expression of fatty acid transporter genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar body weight

Item	Treatment¹			SEM²	Biopsy Collection (BW, kg)					SEM²	P-values³
Item	AN	WA-GB	WA-MB	SEM²	241	296	400	531	613	SEM²	TRT	BC	T × B
LPL	853	676	795	64.8	1,025^c	622^e	606^e	760^d,e	861^c,d	93.8	0.13	0.01	0.68
LDLR	29.4^b	50.3^a	37.7^b	3.89	32.1^d	45.6^c	54.8^c	41.0^c,d	22.3^e	6.69	0.01	0.01	0.01
SCARB1	64.2	57.4	51.5	4.08	61.5^d	74.7^c	60.8^d	50.4^d,e	41.1^e	4.20	0.06	0.01	0.16
CD36	1,929^b	2,110^a,b	2,250^a	103	1,818^d	1,855^d	1,795^d	1,869^d	3,145^c	217	0.03	0.01	0.68
FATP1	146.2	162.6	160.1	7.59	164	157	139	172	150	9.68	0.19	0.12	0.01
FABP4	1,158	937	1,248	210	1,064^d,e	335^f	696^e	1,538^c,d	1,936^c	340	0.53	0.01	0.85
ACBP	2,636	2,999	2,741	114	1,617^e	3,459^c	2,921^d	2,873^d	3,090^d	131	0.06	0.01	0.04

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 7).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Expression of mRNA for lipolyticgenes

The mRNA expression of lipolytic genes measured at a similar age and DOF are shown in Table 11 and Figure 8. The mRNA expression of peroxisome proliferator activated receptor alpha (PPARA) tended (P = 0.08) to be greater at 205 DOA compared with 331 DOA for steers in Exp. 1. The mRNA expression of PPARG coactivator 1 alpha (PPARGC1A) closely resembled PPARA mRNA expression, such that PPARGC1A mRNA expression decreased (P ≤ 0.01) from 205 to 331 DOA. Expression of mRNA for patatin like phospholipase domain containing 2, also known as adipose triglyceride lipase (ATGL) was upregulated (P ≤ 0.01) at 205 and 513 DOA for steers. The mRNA expression of lipase E, also known as hormone sensitive lipase (HSL), was greater (P ≤ 0.01) at 513 DOA, with WA-MD steers having a greater (P ≤ 0.04) overall mean HSL mRNA expression compared with AN and WA-GD steers. Expression of mRNA for monoglyceride lipase (MGL) was greatest (P ≤ 0.01) at 513 DOA, and WA-MD steers tended (P = 0.10) to have a greater MGL mRNA expression at 422 DOA compared with AN and WA-GD steers (treatment × biopsy interaction; Figure 8A). Expression of mRNA for carnitine palmitoyltransferase 1A (CPT1; P ≤ 0.01) and ACAD very long chain (ACADVL; P ≤ 0.01) were greater at 205 DOA compared with 268, 331, and 442 DOA, with the greatest mRNA expression for CPT1 and ACADVL at 513 DOA.

Table 11.

Exp. 1 – RNA expression of lipolytic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar number of days on feed and age

Item	Treatment¹			SEM²	Biopsy Collection (Age, d)					SEM²	P-values³
Item	AN	WA-GD	WA-MD	SEM²	205	268	331	422	513	SEM²	TRT	BC	T × B
PPARA	571	581	548	21.9	622	565	525	549	573	43.5	0.53	0.07	0.97
PPARGC1A	187	168	174	16.7	257^c	191^d	129^f	131^e,f	174^d,e	27.8	0.71	0.01	0.36
ATGL	943	920	989	61.0	1,124^c	732^d,e	685^e	838^d	1,373^c	133	0.72	0.01	0.71
HSL	39.9^b	36.5^b	53.1^a	4.73	43.4^d	32.1^d,e	23.9^e	38.6^d	77.8^c	7.95	0.04	0.01	0.64
MGL	23.1	24.6	25.2	1.37	23.0^d	20.4^e	21.4^d,e	22.0^d	35.0^c	3.49	0.51	0.01	0.09
CPT1	28.3	28.5	29.2	1.85	29.7^d	22.9^e	20.5^e	20.7^e	49.5^c	4.30	0.93	0.01	0.67
ACADVL	614	646	667	32.6	707^d	531^e,f	476^f	572^e	926^c	71.4	0.50	0.01	0.16

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 8).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

The mRNA expression of lipolytic genes measured at a similar BW is shown in Table 12 and Figure 8. In Exp. 2, PPARA mRNA expression was greater (P ≤ 0.03) for steers at 241, 276, and 613 kg, and tended to be greater (P = 0.10) for WA-GB steers compared with AN and WA-MB steers. Expression of mRNA for PPARGC1A was greatest (P ≤ 0.01) when steers weighed 241 kg and decreased thereafter. The mRNA expression of ATGL (P ≤ 0.01) was greater at the first and fifth biopsy collections, when steers weighed 241 and 613 kg. The mRNA expression of HSL exhibited a treatment × biopsy interaction (P ≤ 0.05; Figure 8C) with a greater mRNA expression for WA-MB steers at 400 kg compared with AN (P < 0.01) and WA-GB (P < 0.01) steers. Expression of mRNA for MGL (P ≤ 0.01) was greatest at the fifth biopsy when cattle weighed 613 kg. Additionally, WA-MB steers tended (P = 0.07) to have a greater MGL mRNA expression compared with AN and WA-GB steers. Expression of mRNA for CTP1 was greater (P ≤ 0.01) when steers weighed 613 kg, while WA-MB steers tended (treatment × biopsy interaction, P = 0.11; Figure 8B) to have a greater mRNA expression of CPT1 at 400 kg compared with AN and WA-GB steers. The mRNA expression of ACADVL tended to have a treatment × biopsy interaction (P = 0.07; Figure 8D) with a greater mRNA expression for WA-MB steers compared with AN and WA-GB steers at 400 kg, and for AN steers at 531 kg compared with WA-GB steers. Additionally, WA-MB steers had a greater ACADVL mRNA expression compared with AN (P < 0.01) and tended (P = 0.08) to have greater mRNA expression compared with WA-GB steers.

Table 12.

Exp. 2 – RNA expression of lipolytic genes in the longissimus of Angus- and Wagyu-sired steers when compared at a similar body weight

Item	Treatment¹			SEM²	Biopsy Collection (BW, kg)					SEM²	P-values³
Item	AN	WA-GB	WA-MB	SEM²	241	296	400	531	613	SEM²	TRT	BC	T × B
PPARA	573	624	549	26.4	622^c	608^c	538^d	540^d	602^c,d	50.2	0.10	0.03	0.63
PPARGC1A	182	171	176	20.8	257^c	193^c,d	156^d,e	127^f	149^e	29.4	0.93	0.01	0.35
ATGL	930	921	1,064	71.4	1,124^c	817^d	710^e	855^d	1,350^c	148.6	0.18	0.01	0.19
HSL	40.1	36.3	47.2	4.19	43.4^d	23.4^f	30.2^e	35.8^d	73.1^c	6.56	0.13	0.01	0.05
MGL	23.1	23.0	26.3	1.26	23.0^d	20.0^d	21.0	21.6	35.1^c	1.61	0.07	0.01	0.53
CPT1	28.2	28.4	30.5	2.05	29.7^d	21.4^e	22.2^e	21.3^e	50.7^c	4.26	0.57	0.01	0.10
ACADVL	610^b	636^a,b	715^a	33.1	707^d	551^e	518^e	576^e	916^c	62.7	0.03	0.01	0.06

Open in a new tab

²The reported standard error of the mean is the greatest between the different treatments.

³TRT, Treatment, BC, Biopsy collection timepoint, T × B, Treatment × Biopsy collection timepoint interaction (Figure 8).

^{a, b}Treatment lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

^{c, d, e, f}Biopsy Collection lsmean estimates within a row, without a common superscript differ (P ≤ 0.05).

Discussion

Two techniques are commonly used to determine adipocyte cellularity: 1) IM adipocytes are measured within the muscle tissue or 2) IM adipocytes are dissected and extracted from the muscle and subsequently measured. Due to the irregular shape of IM adipocytes found within the muscle tissue, IM adipocyte size is reported by adipocyte area in the present study, which makes comparisons to reports of adipocyte diameter somewhat difficult. Regardless, many of the IM adipocyte distributions that are reported (Schiavetta et al., 1990; Albrecht, et al., 2011; Yamada and Nakanishi, 2012) have a greater proportion of medium-sized IM adipocytes with a normal distribution. When IM adipocyte distributions from the present study are presented by diameter rather than area, they also show a greater proportion of medium-sized IM adipocytes with a normal distribution. Albrecht et al. (2011) reported a 10 to 20 µm smaller size difference in IM adipocyte diameter between intact and dissected IM adipocyte measurements, which may explain the smaller IM adipocyte size observed in the present study. Interestingly, others (Hood and Allen, 1973; Schoonmaker et al., 2004; Gorocica-Buenfil et al., 2007; Pickworth et al., 2011, 2012) reported bimodal IM adipocyte distributions, in addition to the larger proportion of medium-sized adipocytes, a new cluster of small adipocytes were recruited from pre-adipocytes. Robelin (1981) and Schoonmaker et al. (2004) proposed that a new wave of pre-adipocytes are recruited to form a new cluster of small-sized adipocytes once the average adipocyte diameter reaches approximately 90 µm. However, when the mean IM adipocyte diameter is compared between the study reported by Schoonmaker et al. (2004) and others (Gorocica-Buenfil et al., 2007; Pickworth et al., 2011, 2012), mean IM adipocyte diameter was smaller than 90 µm, but IM adipocytes already exhibited a bimodal distribution. This may be due to the breed of cattle used in the study, as Schoonmaker et al. (2004) used Holsteins and the other studies (Gorocica-Buenfil et al., 2007; Pickworth et al., 2011, 2012) used SimAngus crossbred cattle. Additionally, the LM lipid content was lesser for Holstein steers reported by Schoonmaker et al. (2004) when compared with the other studies (Gorocica-Buenfil et al., 2007; Pickworth et al., 2011, 2012), indicating major differences in IM adipocyte number contributing to the differences in lipid content deposited in the LM. When comparing IM adipocyte size between Wagyu and Holstein steers, both breeds demonstrate hypertrophy with increasing IM adipocyte size from 10 to 18 months of age, but IM adipocytes remained at a similar size from 18 to 26 months of age (Albrecht et al., 2011). Results from the present study are in agreement, as IM adipocyte size continued to increase from 205 DOA until slaughter (513, 536, and 591 DOA for AN steers, WA-GB steers, and WA-MB steers, respectively). Unique IM adipocyte distributions have been reported in older cattle by May et al. (1994; 34 and 26 months of age) and Kruk et al. (2018; 22 months of age), where a very large proportion of new small IM adipocytes were recruited to produce an IM adipocyte distribution with a very strong positive skew. May et al. (1994) reported a greater proportion of smaller IM adipocytes (from 20 to 40 µm) for crossbred Wagyu steers, which had a greater marbling score at slaughter, compared with Angus steers (53 vs. 47%, respectively). Kruk et al. (2018) reported 46% of IM adipocytes with a diameter ranging from 10 to 30 µm. Based on the lack of a bimodal distribution indicating pre-adipocyte recruitment for the formation of a cluster of small-sized IM adipocytes in the present study, we believe that an influx of small-sized IM adipocytes was forthcoming if steers had remained on feed longer.

The process of determination, proliferation, and the differentiation of preadipocytes into mature adipocytes, also known as adipogenesis, is regulated by a complex signaling cascade of genes (Ailhaud et al., 1992; Smas and Sul, 1995). It was hypothesized that the mRNA expression of genes associated with adipogenesis over time would be different between the treatments in each experiment and provide support to the expected differences in marbling deposition. Zinc finger protein 423 (Gupta et al., 2010; Huang et al., 2012) and DLK1 (Hudak and Sul, 2013) have been recognized as preadipocyte markers. No differences in ZFP423 and DLK1 mRNA expression were observed between steers in the different treatments over time in Exp. 1 and 2. In disagreement, Wagyu steers were reported to have a greater mRNA expression of ZFP423 in the sternomandibularis muscle and a greater percentage of IM fat compared with Angus steers at 24 mo of age (Duarte et al., 2013), while a greater mRNA expression of ZFP423 has been reported in the biceps femoris muscle of Angus heifers compared with Wagyu heifers at 12 mo of age (Fu et al., 2017). Albrecht et al. (2015) believe they were able to properly identify preadipocytes by using DLK1 as a marker in the LM of a 6-mo-old bovine fetus and LM tissue from 26-mo-old Holstein and Wagyu steers. A greater number of DLK1 positive cells were identified in Holstein steers compared with Wagyu steers at 26 months of age, and Holstein steers had a greater overall mean DLK1 mRNA expression compared with Wagyu steers across all biopsy collections (10, 14, 18, 22, and 26 months of age; Albrecht et al., 2015). In agreement with our results, Pickworth et al. (2011) reported no difference in DLK1 mRNA expression at slaughter between high and low marbling steers. The mRNA expression of DLK1 has been reported in skeletal muscle, particularly satellite cells, and promotes myogenic differentiation for muscle regeneration and hypertrophy (Waddell et al., 2010). Therefore, it is impossible to determine the contribution of DLK1 as a preadipocyte marker due to the combined presence of preadipocytes and satellite cells within the muscle samples collected in the present study, which may partially explain the lack of differences. Fibulin 1, a glycoprotein associated with the extracellular matrix, and PTGIS could also be potential IM preadipocyte markers in muscle (Kichoon Lee, personal communication). Neither FBLN1 nor PTGIS exhibited any treatment × time interactions in Exp. 1 and 2 and the mRNA expression of PTGS1/2, also called cyclooxygenase 1/2, genes responsible for creating prostacyclin from arachidonic acid, were near or below the expressoion of detection in the present study. However, prostacyclin from preadipocytes or mature adipocytes can impose an autocrine or paracrine effect to initiate adipocyte differentiation (Darimont et al., 1994; Rahman et al., 2014; Rahman, 2019). Observing a greater PTGIS mRNA expression at the first and fifth biopsy in both Exp. 1 and 2 may suggest a cluster of preadipocytes were beginning to initiate differentiation through autocrine signaling at the time of the first biopsy, while at the fifth biopsy, mature adipocytes were paracrine signaling to preadipocytes to begin differentiation again to form a new cluster of small adipocytes. This second wave of small adipocytes may have been too small to identify in the cellularity analysis, which provides further support for the lack of bimodal distribution observed with the IM adipocyte cellularity results.

Upregulation of CREB1, via cAMP, protein kinase A, and extracellular signal-regulated kinase, is needed for the upregulation of early differentiation transcription factors, such as CEBPB and CEBPD (Aubert et al., 2000; Belmonte et al., 2001). However, CREB1 mRNA expression can be transient for its upregulation of CEBP (Reusch et al., 2000), which may explain the unique treatment × time mRNA expression patterns of CEBPB and PPARD where Angus-sired steers typically had a greater mRNA expression at the fourth biopsy (approximately 13.8 months of age) compared with Wagyu-sired steers. Meanwhile, CEBPB and PPARD mRNA expression demonstrated an upregulation at times coinciding with the second and third biopsy collections for Wagyu-sired steers, particularly those selected for marbling potential, when compared with Angus-sired steers. Upregulation of early differentiation markers, such as PPARD, that are known to promote mitotic expansion of preadipocytes, help facilitate fatty acid transport and uptake for beta-oxidation in the LM, and assist with the subsequent upregulation of PPARG (Bastie et al., 1999; Hansen et al., 2001; Holst et al., 2003); which may have lead to a greater mRNA expression of the master regulator of adipogenesis, PPARG, by Wagyu-sired steers selected for marbling potential compared with Angus- and Wagyu-sired steers selected for growth shortly after being transitioned to the finishing diet at 377 DOA (12.4 months of age). In support of these findings, Duarte et al. (2013) and Fu et al. (2017) reported a greater PPARG mRNA expression in the muscle of Wagyu cattle compared with Angus cattle. Additionally, Wang et al. (2009) reported a much greater PPARG mRNA expression for Wagyu-sired heifers compared with Piedmontese-sired heifers just prior to being transitioned to a finishing diet at 25 months of age. The upregulation of PPARG can upregulate CEBPA to activate insulin-dependent signaling, where the two transcription factors can work synergistically to advance terminal differentiation and the upregulation of other genes associated with lipogenesis (Wu, et al., 1996; Tang et al., 2003). The mRNA expression of CEBPA was near the limit of detection in both Exp. 1 and 2, but tended to be greater for Wagyu-sired steers selected for marbling ability compared with Angus- and Wagyu-sired steers selected for growth. Interestingly, Moisa et al. (2014) reported that early weaned steers (4.6 mo of age) fed a finishing diet did not upregulate early differentiation markers, CEBPB and CEBPD, but did upregulate late differentiation markers, PPARG and CEBPA; while normal weaned, creep-fed steers (7 mo of age) upregulated early differentiation markers, CEBPB and CEBPD, at 10 mo of age, but did not upregulate late differentiation markers, PPARG and CEBPA, before being slaughtered at approximately 12 mo of age. Early weaned steers had a numerically greater marbling score compared with normal weaned, creep-fed steers (Moisa et al., 2014), which was likely due to the upregulation of late differentiation markers that subsequently upregulated other lipogenic genes in response to earlier exposure of the finishing diet. Overall, Wagyu-sired steers that were selected for and had greater marbling deposition demonstrated an upregulation of early and late differentiation markers which were likely responsible for their greater deposition of IM fat compared with steers that had less IM fat.

Sterol regulatory element binding transcription factor 1 regulates fatty acid synthesis by transcribing ACLY, ACAC, and FASN as well as others (Shimano, 2001). The transcription of SREBF1 is regulated initially by CEBPB and CEBPD, and eventually CEBPA (Payne et al., 2010), which explains the upregulation of lipogenic genes at the fourth and fifth biopsy collections when steers were approximately 13.8 to 19.4 months of age. This pattern of SREBF1 expression was also reported by Moisa et al. (2014) where early-weaned steers had a greater SREBF1 mRNA expression at 10.1 and 11.9 months of age compared with normal-weaned steers that were creep-fed. The greater mRNA expression of SREBF1 for Angus-sired steers at the fourth biopsy did not result in a greater mRNA expression of ACLY, ACACA, FASN, ELOVL6, or SCD for Angus-sired steers compared with Wagyu-sired steers. Likewise, in Exp. 2, Wagyu-sired steers demonstrated a greater SREBF1 mRNA expression at the third biopsy or 400 kg, but this didn’t necessarily translate to any noticeable improvements in lipogenic mRNA expression relative to Angus-sired steers. Interestingly, the pattern of mRNA expression for ACLY, FASN, ELOVL6, SCD, LPL, FABP4, and DGAT2 reported by Moisa et al. (2014) appeared to proceed the upregulation of SREBF1 and more closely resembled PPARG expression for steers. Peroxisome proliferator activated receptor gamma can assist SREBF1 with the regulation of genes, such as GPAM, involved in triglyceride synthesis (Coleman and Lee, 2004). The mRNA expression pattern of GPAM was similar to PPARG, where Wagyu-sired steers selected for marbling had a greater GPAM mRNA expression compared with other steers from 10.9 months of age until slaughter (16.3 to 19.4 months of age). Additionally, the mRNA expression of LPIN1 closely resembled the mRNA expression pattern of PPARD or CEBPB, where Wagyu-sired steers selected for marbling had a greater mRNA expression at either the second or third biopsy collection in Exp. 1 or 2, respectively. In support, De Jager et al. (2013) reported a greater GPAM mRNA expression by Wagyu-sired heifers compared with Piedmontese-sired heifers at 25 months of age. Genes involved in triglyceride synthesis (GPAM, AGPAT1, DGAT1, and DGAT2) have been reported to be positively correlated with IM fat percentage in the LM of Korean steers. This correlation between GPAM, LIPN1, and IM fat percentage highlights the importance of these genes and their products, lysophosphatidic acid and diacylglycerol, respectively, in the development and accumulation of marbling in cattle. Lysophosphatidic acid is produced by the enzymatic activity of GPAM, can directly activate PPARG (McIntyre et al., 2003). Meanwhile, phosphatidic acid can inhibit PPARG activation, but LPIN1 is able to restore PPARG activation and its downstream genes by converting phosphatidic acid into diacylglycerol (Zhang et al., 2012). Future research is needed to quantify these intermediate products of triglyceride synthesis in cattle to further assess their ability as potential indicators of marbling potential.

Adipose tissue development, particularly IM fat development, appears to be spatially related to capillary proximity, which has been reported by others (Blumer et al., 1962; Moody and Cassens, 1968; Crandall et al., 1997) and was observed while conducting IM adipocyte cellularity analysis in the present study. A link between angiogenesis and adipogenesis is not surprising considering the circulatory system transports energy substrate to the peripheral tissues (Hausman and Richardson, 2004). Yamada et al. (2010) reported that the angiogenic mRNA expression was closely related to adipocyte size, which was largely dependent on fat depot location. Forage-based compared with grain-based diets can also influence the angiogenic mRNA expression in the various fat depots, with forage-based diets increasing angiogenic expression in the mesenteric and intermuscular fat depots compared with grain-based diets, while SC and IM fat depots had similar angiogenic mRNA expression between the different diets. The present study did not observe any differences between Angus- and Wagyu-sired steers of varying marbling potential for the expression of angiogenic genes in the LM. Similarly, Lancaster et al. (2014) and Roberts et al. (2015) reported in steers with different growth rates very few treatment differences for angiogenic mRNA expression. The change in VEGFA mRNA expression over time would indicate that blood vessel development in the LM was occurring when steers were younger (6.7 to 8.7 mo of age), while vascular branching and remodeling were relatively constant. Platelet derived growth factors helps regulate the proliferation and mitogenic expansion of mesenchymal progenitor cells, and therefore, can inhibit the terminal differentiation of adipocytes (Kim et al., 2015). In addition, Uezumi et al. (2010) reported that PDGFRA was a cell surface marker that could be used for identifying mesenchymal progenitor cells determined to the adipogenic lineage. The mRNA expression of PDGFR alpha and beta did not differ between Angus- and Wagyu-sired steers, which is in support of the adipocyte cellularity results that failed to demonstrate the recruitment of new preadipocytes for the maturation of small adipocytes sometime before slaughter.

Fatty acids derived from dietary feedstuffs or created via de novo fatty acid synthesis in the liver can be transported in the form of triglycerides by chylomicrons and lipoproteins throughout the circulatory system to supply peripheral tissues such as the skeletal muscle and adipose tissue with energy for use and storage. Lipoprotein lipase mRNA expression demonstrated a greater fatty acid uptake within the LM when steers were approximately 6.7 and 16.8 to 19.4 months of age. The expression pattern of LPL may be a partial indication of a greater dietary fatty acid supply from consuming milk at 6.7 months of age and an increasingly greater intake of the finishing diet as steers grew. Results of LPL mRNA expression from Wang et al. (2009) are in support, while LPL mRNA expression results reported by Moisa et al. (2014) do not agree, as LPL mRNA expression closely followed other lipogenic genes for early-weaned steers. Wagyu-sired steers selected for marbling had a greater LDLR mRNA expression from 9.4 to 13.8 months of age compared with Angus-sired steers, and Wagyu-sired steers selected for growth had a greater LDLR mRNA expression relative to Angus-sired steers at 9.2 and 11.6 months of age. Saturated fatty acids (SFA) can decrease, and polyunsaturated fatty acids (PUFA) can increase the mRNA expression of LDLR (Woollett et al., 1992). In agreement, Wagyu-sired steers selected for marbling potential had a greater PUFA:SFA compared with other steers in the present study; however, in disagreement, Wagyu-sired steers selected for growth did not have a greater PUFA:SFA compared with Angus-sired steers (Jaborek et al., 2023). A greater LDLR mRNA expression may indicate a greater role of receptor-mediated triglyceride hydrolysis for Wagyu-sired steers, while Angus-sired steers tended to have a greater mRNA expression of LPL, where triglyceride hydrolysis is not receptor-mediated. The mRNA expression of oxidized low density lipoprotein receptor 1 (OLR1) was below the limit of detection in the present study which likely indicates its lack of involvement in marbling deposition in the LM of cattle. Scavenger receptor class B member 1 mediates cholesterol transfer from high density lipoproteins, which was greatest at the second biopsy in steers and decreased thereafter. Angus-sired steers tended to have a greater mRNA expression of SCARB1 compared with Wagyu-sired steers. Previous studies have not reported cholesterol differences due to cattle breed in the dissected LM (Rule et al., 1997; Chung et al., 2006) or intact LM (Wheeler et al., 1987; Brugiapaglia et al., 2014). Rhee et al. (1982)reported that cholesterol content of the LM is not related to marbling score or the percentage of IM fat. However, on a percent lipid basis, LM muscle with lesser marbling scores had a greater cholesterol content (r = −0.66; Rhee et al., 1982), indicating that a large proportion of cholesterol in beef LM is present in the structural lipids of the cell membrane.

The transport of FA into the cell can be mediated by CD36 and FATP1. Wagyu-steers selected for marbling tended to have a greater mRNA expression of CD36 compared with Angus-sired steers. The upregulation of CD36 did not occur until approximately 16.8 to 19.4 months of age or the time of slaughter. Therefore, fatty acid uptake could have been occurring via another transport protein such as FATP1. Wagyu-sired steers demonstrated a relatively constant mRNA expression of FATP1, while Angus-sired steers had lesser mRNA expression prior to peak mRNA expression for FATP1 at approximately 13.8 months of age. Along with CD36, Jeong et al. (2012) reported that FATP1 was positively correlated with the percentage of IM fat in the LM of Korean steers. These differences between Angus- and Wagyu-sired steers for fatty acid transport may represent differences in energy substrate needed for energy metabolism within the muscle. Previous research has reported that muscle fiber type can change over time as the animal grows, including a shift in skeletal muscle energy metabolism (Gotoh, 2003). Intramuscular fat percentage has been positively correlated with the percentage of type I muscle fibers (Gotoh, 2003; Hwang et al., 2010; Joo et al., 2017) and negatively correlated with the percentage of type II muscle fibers (Calkins et al., 1981; Ozawa et al., 2000; Gotoh, 2003; Hwang et al., 2010) in the skeletal muscle of cattle (Underwood et al., 2007).

Fatty acid binding protein 4 mRNA expression closely resembled PPARG mRNA expression, with a large increase in mRNA expression after 13.8 months of age and a tendency for a greater FABP4 mRNA expression by Wagyu-sired steers selected for marbling in Exp. 1. In agreement with the present study, Wang et al. (2009) and Moisa et al. (2014) reported that FABP4 mRNA expression closely mirrored PPARG mRNA expression in cattle. The similar pattern of mRNA expression between PPARG and FABP4 is likely due to the regulation of FABP4 by PPARG (Tontonoz et al., 1994). Previous reports indicate FABP4 is positively correlated with the percentage of IM fat in the LM (Moore et al., 1991; Jurie et al., 2007). Duarte et al. (2013) reported a greater number of FABP4 positive cells in the LM of Wagyu steers compared with Angus steers. Additionally, Albrecht et al. (2011) reported that FABP4 mRNA expression increased from 10 until 22 months of age, before mRNA expression became downregulated at 26 months of age in Japanese Black Wagyu and Holstein steers. Interestingly, greater expression of FABP4 has been reported to trigger proteasomal degradation of PPARG and inhibit adipogenesis in a negative feedback loop to inhibit preadipocyte differentiation (Garin-Shkolnik et al., 2014). Therefore, FABP4 mRNA expression may need to become downregulated before another wave of preadipocytes is allowed to differentiate into mature adipocytes. The mRNA expression of another intracellular fatty acid transporter, ACBP, demonstrated a dramatic increase in mRNA expression at the second biopsy collection or after cattle arrived at the feedlot at 8.8 months of age. This upregulation of ACBP coincides with the diet change steer calves experienced as they transitioned from milk to dry feedstuffs.

The mRNA expression of PPARA was quadratic with a greater expression at the first and fifth biopsy collections, which was 6.7 months of age and 16.8 to 19.4 months of age. Having a greater mRNA expression at the first biopsy collection and decreasing until the third biopsy collection, PPARGC1A mRNA expression could indicate a greater energy metabolism and greater beta-oxidation of fatty acids at 6.7 months of age. Other lipolytic genes, such as CPT1, ACADVL, ATGL, HSL, and MGL became upregulated after the fourth biopsy collection or before slaughter. It is possible the stress of fasting and transportation to the abattoir upregulated the lipogenic genes needed to breakdown triglycerides and fatty acids for energy in the steers in the present study. Interestingly, Moisa et al. (2014) reported a breed × time interaction, where SimAngus steers exhibited peak ATGL mRNA expression before Angus steers, with ATGL mRNA expression decreasing at slaughter. Jeong et al. (2012) reported negative correlations for the percentage of IM fat in the LM with CPT1, ACADVL, ATGL, and MGL, but a positive correlation with HSL, as did Kazala et al. (2003) believe HSL and DGAT enzyme activities within the LM may be related to maturity status of the IM fat depot and could be used as potential indicators of marbling status, because a greater percentage of IM fat in the muscle is associated with a lesser DGAT and greater HSL activity. Interestingly, this is a similar hypothesis to the one proposed earlier with the regulation of triglyceride synthesis by GPAM and LPIN1 for the production of adipogenic regulatory compounds in lysophosphatidic acid and diacylglycerol. In agreement, the Wagyu-sired steers selected ssfor marbling potential had a greater percentage of IM fat and overall mRNA expression of HSL compared with other steers in the present study. The mRNA expression of MGL and CTP1 was greater at times for Wagyu-sired steers selected for marbling compared with other steers. However, mRNA expression of MGL and CTP1 were near the limit of detection at the second, third, and fourth biopsy collections.

In conclusion, Wagyu-sired steers selected for marbling potential had a greater percentage of IM fat in the LM compared with Angus-sired steers selected for marbling and Wagyu-sired steers selected for growth potential. The mRNA expression of lipid metabolism related genes during the feeding period was quite similar between Angus- and Wagyu-sired steers. The upregulated mRNA expression of PPARD likely led to the upregulation of fatty acid transport proteins, as well as an earlier and overall greater mRNA expression of PPARG by the Wagyu-sired steers selected for marbling potential. As a result, Wagyu-sired steers selected for marbling potential had a greater mRNA expression of GPAM, LPIN1, and HSL, which may assist in upregulating and sustaining adipogenesis by producing adipogenic regulatory compounds in lysophosphatidic acid and diacylglycerol. Furthermore, the combination of IM adipocyte cellularity analysis and mRNA expression results would indicate that there could be periods of IM adipocyte proliferation prior to the initiation of differentiation occurring around the time of weaning and slaughter, at approximately 6.7 months of age and 16.8 to 19.4 months of age for steers in the present study. In addition to genetics, the consumption of excess calories during the finishing period appears to directly influence the timing and accumulation of IM fat in the LM. Future feeding strategies may be developed to optimize energy availability during critical times of IM adipocyte development to reduce overall feed costs while maximizing marbling deposition during the finishing period for cattle feeding operations.

Acknowledgments

The authors would like to acknowledge the farm staff from the Ohio Agricultural Research and Developmental Center (OARDC) feedlot for their help caring for the animals, staff from the Ohio State University (OSU) Meat Science Laboratory for their help with slaughtering the cattle, and the Comparative Pathology & Mouse Phenotyping Shared Resource (CPMPSR) Laboratory for preparing the histology slides for adipocyte cellularity analysis.

Glossary

Abbreviations

ACACA: acetyl-CoA carboxylase alpha
ACABA: acetyl-CoA carboxylase beta
ACADVL: acyl-CoA dehydrogenase very long chain
ACLY: ATP citrate lyase
ACTB: actin beta
AGPAT1: 1-acylglycerol-3-phosphate O-acyltransferase 1
AN: Angus-sired steers
ANGPT1: angiopoietin 1
ANGPT2: angiopoietin 2
BW: body weight
CD36: cd36 molecule (thrombospondin receptor)
CEBPA: CCAAT enhancer binding protein alpha
CEBPB: CCAAT enhancer binding protein beta
CPAT1A: carnitine palmitoyltransferase 1A
CREB1: cAMP responsive element binding protein 1
DBI: diazepam binding inhibitor
DGAT1: diacylglycerol O-acyltransferase 1
DLK1: delta like non-canonical notch ligand 1
DOA: days of age
DOF: days on feed
EEF1A2: eukaryotic translation elongation factor 1 alpha 2
ELOVL6: fatty acid elongase 6
FABP4: fatty acid binding protein 4
FASN: fatty acid synthase
FBLN1: fibulin 1
GPAM: glycerol-3-phosphate acyltransferase
GPD1: glycerol-3-phosphate dehydrogenase 1
HPRT1: hypoxanthine phosphoribosyltransferase 1
IM: intramuscular
LDLR: low density lipoprotein receptor
LIPE: lipase E, hormone sensitive type
LM: longissimus muscle
LPIN1: lipin 1
LPL: lipoprotein lipase
MGL: monoglyceride lipase
OLR1: oxidized low density lipoprotein receptor 1
PDGFRA: platelet-derived growth factor receptor alpha
PDGFRB: platelet-derived growth factor receptor beta
PNPLA2: patatin like phospholipase domain containing 2
PPARA: peroxisome proliferator activated receptor alpha
PPARD: peroxisome proliferator activated receptor delta
PPARG: peroxisome proliferator activated receptor gamma 2
PPARGC1A: PPARG coactivator 1 alpha
PPIA: peptidylprolyl isomerase A
PPP1CA: protein phosphatase 1 catalytic subunit alpha
PTGIS: prostaglandin I2 synthase
SCARB1: scavenger receptor class B member 1
SCD: stearoyl-CoA desaturase
SDHA: succinate dehydrogenase complex flavoprotein subunit A
SEM: standard error of the mean
SLC27A1: solute carrier family 27 member 1
SREBF1: sterol regulatory element binding transcription factor 1
VEGFA: vascular endothelial growth factor A
WA-GB: Wagyu sires selected for growth compared at a similar BW
WA-GD: Wagyu sires selected for growth compared at a similar age and DOF
WA-MB: Wagyu sires selected for marbling compared at a similar BW
WA-MD: Wagyu sires selected for marbling compared at a similar age and DOF
ZFP423: zinc finger protein 423

Contributor Information

J R Jaborek, Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA; Michigan State University Extension – Sanilac County, Sandusky, MI 48471, USA.

F L Fluharty, Department of Animal and Dairy Science, University of Georgia, Athens, GA 30602, USA.

Kichoon Lee, Department of Animal Sciences, The Ohio State University, Columbus, OH 43210, USA.

Henry N Zerby, Quality Supply Chain Co-op., Dublin, OH 43017, USA.

A E Relling, Department of Animal Sciences, The Ohio State University, Wooster, OH 44691, USA.

Conflict of Interest Statement

The authors declare no conflict of interest for the present research.

Literature Cited

Ailhaud, G., Grimaldi P., and Négrel R... 1992. Cellular and molecular aspects of adipose tissue development. Annu. Rev. Nutr. 12:207–233. doi: 10.1146/annurev.nu.12.070192.001231 [DOI] [PubMed] [Google Scholar]
Albrecht, E., Gotoh T., Ebara F., Xu J. X., Viergutz T., Nürnberg G., Maak S., and Wegner J... 2011. Cellular conditions for intramuscular fat deposition in Japanese Black and Holstein steers. Meat Sci. 891:13–20. doi: 10.1016/j.meatsci.2011.03.012. [DOI] [PubMed] [Google Scholar]
Albrecht, E., Kuzinski J., Komolka K., Gotoh T., and Maak S... 2015. Localization and abundance of early markers of fat cell differentiation in the skeletal muscle of cattle during growth - are DLK1-positive cells the origin of marbling flecks? Meat Sci. 100:237–245. doi: 10.1016/j.meatsci.2014.10.012 [DOI] [PubMed] [Google Scholar]
AOAC. 2005. Official methods of analysis. 17th ed. Washington, DC, USA: Association of Official Analytical Chemists. [Google Scholar]
Aubert, J., Saint-Marc P., Belmonte N., Dani C., Négrel R., and Ailhaud G... 2000. Prostacyclin IP receptor up-regulates the early expression of C/EBPβ and C/EBPδ in preadipose cells. Mol. Cell. Endocr. 160:149–156. doi: 10.1016/S0303-7207(99)00210-5 [DOI] [PubMed] [Google Scholar]
Bastie, C., Holst D., Gaillard D., Jehl-Pietri C., and Grimaldi P. A... 1999. Expression of peroxisome proliferator-activated receptor PPARδ promotes induction of PPARγ and adipocyte differentiation in 3WA-MDC2 fibroblasts. J. Biol. Chem. 274:21920–21925. doi: 10.1074/jbc.274.31.21920 [DOI] [PubMed] [Google Scholar]
Belmonte, N., Phillips B. W., Massiera F., Villageois P., Wdziekonski B., Saint-Marc P., Nichols J., Aubert J., Saeki K., Yuo A.,. et al. 2001. Activation of extracellular signal-regulated kinases and CREB/ATF-1 mediate the expression of CCAAT/enhancer binding proteins β and-δ in preadipocytes. Mol. Cell. Endocr. 15:2037–2049. doi: 10.1210/mend.15.11.0721 [DOI] [PubMed] [Google Scholar]
Blumer, T. N., Craig H. B., Pierce E. A., W. W. G.Smart, Jr., and Wise M. B... 1962. Nature and variability of marbling deposits in Longissimus dorsi muscle of beef carcasses. J. Anim. Sci. 21: 935–942. doi: 10.2527/jas1962.214935x [DOI] [Google Scholar]
Brugiapaglia, A., Lussiana C., and Destefanis G... 2014. Fatty acid profile and cholesterol content of beef at retail of Piemontese, Limousin and Friesian breeds. Meat Sci. 96:568–573. doi: 10.1016/j.meatsci.2013.08.012 [DOI] [PubMed] [Google Scholar]
Campos, C. F., Duarte M. S., Guimarães S. E. F., Verardo L. L., Wei S., Du M., Jiang Z., Bergen W. G., Hausman G. J., Fernyhough-Culver M.,. et al. 2016. Review: animal model and the current understanding of molecule dynamics of adipogenesis. Animal. 10:927–932. doi: 10.1017/S1751731115002992 [DOI] [PubMed] [Google Scholar]
Calkins, C. R., Dutson T. R., Smith G. C., Carpenter Z. L., and Davis G. W... 1981. Relationship of fiber type composition to marbling and tenderness of bovine muscle. J. Food Sci. 46:708–710. doi: 10.1111/j.1365-2621.1981.tb15331.x [DOI] [Google Scholar]
Chung, K. Y., Baxa T. J., Parr S. L., Luqué L. D., and Johnson B. J... 2012. Administration of estradiol, trenbolone acetate, and trenbolone acetate/estradiol implants alters adipogenic and myogenic gene expression in bovine skeletal muscle. J. Anim. Sci. 90:1421–1427. doi: 10.2527/jas.2011-3496 [DOI] [PubMed] [Google Scholar]
Chung, K. Y., Lunt D. K., Choi C. B., Chae S. H., Rhoades R. D., Adams T. H., Booren B., and Smith S. B... 2006. Lipid characteristics of subcutaneous adipose tissue and M. longissimus thoracis of Angus and Wagyu steers fed to US and Japanese endpoints. Meat Sci. 73:432–441. doi: 10.1016/j.meatsci.2006.01.002 [DOI] [PubMed] [Google Scholar]
Coleman, R. A., and Lee D. P... 2004. Enzymes of triacylglycerol synthesis and their regulation. Prog. Lipid Res. 43:134–176. doi: 10.1016/s0163-7827(03)00051-1 [DOI] [PubMed] [Google Scholar]
Coleman, D. N., Murphy K. D., and Relling A. E... 2018. Prepartum fatty acid supplementation in sheep. II. Supplementation of eicosapentaenoic acid and docosahexaenoic acid during late gestation alters the fatty acid profile of plasma, colostrum, milk and adipose tissue, and increases lipogenic gene expression of adipose tissue. J. Anim. Sci. 96:1181–1204. doi: 10.1093/jas/skx013 [DOI] [PMC free article] [PubMed] [Google Scholar]
Crandall, D. L., Hausman G. J., and Kral J. G... 1997. A review of the microcirculation of adipose tissue: anatomic, metabolic, and angiogenic perspectives. Microcirculation. 4:211–232. doi: 10.3109/10739689709146786 [DOI] [PubMed] [Google Scholar]
Darimont, C., Vassaux G., Ailhaud G., and Negrel R... 1994. Differentiation of preadipose cells: paracrine role of prostacyclin upon stimulation of adipose cells by angiotensin-II. Endocrinology. 135:2030–2036. doi: 10.1210/endo.135.5.7956925 [DOI] [PubMed] [Google Scholar]
De Jager, N., Hudson N. J., Reverter A., Barnard R., Cafe L. M., Greenwood P. L., and Dalrymple B. P... 2013. Gene expression phenotypes for lipid metabolism and intramuscular fat in skeletal muscle of cattle. J. Anim. Sci. 91:1112–1128. doi: 10.2527/jas.2012-5409 [DOI] [PubMed] [Google Scholar]
Duarte, M. S., Paulino P. V. R., Das A. K., Wei S., Serao N. V. L., Fu X., Harris S. M., Dodson M. V., and Du M... 2013. Enhancement of adipogenesis and fibrogenesis in skeletal muscle of Wagyu compared with Angus cattle. J. Anim. Sci. 91:2938–2946. doi: 10.2527/jas.2012-5892 [DOI] [PubMed] [Google Scholar]
Farmer, S. R. 2006. Transcriptional control of adipocyte formation. Cell Metab. 4:263–273. doi: 10.1016/j.cmet.2006.07.001 [DOI] [PMC free article] [PubMed] [Google Scholar]
FASS. 2010. Guide for the care and use of agricultural animals in agricultural research and teaching. 3rd revised edition. Champaign, IL: Fed. Anim. Sci. Soc. [Google Scholar]
Fu, X., Yang Q., Wang B., Zhao J., Zhu M., Parish S. M., and Du M... 2017. Reduced satellite cell density and myogenesis in Wagyu compared with Angus cattle as a possible explanation of its high marbling. Animal. 12:990–997. doi: 10.1017/S1751731117002403 [DOI] [PubMed] [Google Scholar]
Garin-Shkolnik, T., Rudich A., Hotamisligil G. S., and Rubinstein M... 2014. FABP4 attenuates PPARγ and adipogenesis and is inversely correlated with PPARγ in adipose tissues. Diabetes. 63:900–911. doi: 10.2337/db13-0436 [DOI] [PubMed] [Google Scholar]
Gorocica-Buenfil, M. A., Fluharty F. L., Reynolds C. K., and Loerch S. C... 2007. Effect of dietary vitamin A concentration and roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef. J. Anim. Sci. 85:2230–2242. doi: 10.2527/jas.2006-780 [DOI] [PubMed] [Google Scholar]
Gotoh, T. 2003. Histochemical properties of skeletal muscles in Japanese cattle and their meat production ability. Anim. Sci. J. 74:339–354. doi: 10.1046/j.1344-3941.2003.00125.x [DOI] [Google Scholar]
Gotoh, T., Albrecht E., Teuscher F., Kawabata K., Sakashita K., Iwamoto H., and Wegner J... 2009. Differences in muscle and fat accretion in Japanese Black and European cattle. Meat Sci. 82:300–308. doi: 10.1016/j.meatsci.2009.01.026 [DOI] [PubMed] [Google Scholar]
Gupta, R. K., Arany Z., Seale P., Mepani R. J., Ye L., Conroe H. M., Roby Y. A., Kulaga H., Reed R. R., and Spiegelman B. M... 2010. Transcriptional control of preadipocyte determination by Zfp423. Nature. 464:619–623. doi: 10.1038/nature08816 [DOI] [PMC free article] [PubMed] [Google Scholar]
Hausman, G. J., and Richardson R. L... 2004. Adipose tissue angiogenesis. J. Anim. Sci. 82:925–934. doi: 10.2527/2004.823925x [DOI] [PubMed] [Google Scholar]
Hansen, J. B., Zhang H., Rasmussen T. H., Petersen R. K., Flindt E. N., and Kristiansen K... 2001. Peroxisome proliferator-activated receptor δ (PPARδ)-mediated regulation of preadipocyte proliferation and gene expression is dependent on cAMP signaling. J. Biol. Chem. 276:3175–3182. doi: 10.1074/jbc.M005567200 [DOI] [PubMed] [Google Scholar]
Holst, D., Luquet S., Nogueira V., Kristiansen K., Leverve X., and Grimaldi P. A... 2003. Nutritional regulation and role of peroxisome proliferator-activated receptor δ in fatty acid catabolism in skeletal muscle. Biochim. Biophys. Acta, Mol. Cell. Biol. Lipids. 1633:43–50. doi: 10.1016/S1388-1981(03)00071-4 [DOI] [PubMed] [Google Scholar]
Hood, R., and Allen C. E... 1973. Cellularity of bovine adipose tissue. J. Lipid Res. 14:605–610. doi: 10.1016/S0022-2275(20)36840-1 [DOI] [PubMed] [Google Scholar]
Huang, Y., Das A. K., Yang Q. Y., Zhu M. J., and Du M... 2012. Zfp423 promotes adipogenic differentiation of bovine stromal vascular cells. PLoS One. 7:e47496. doi: 10.1371/journal.pone.0047496 [DOI] [PMC free article] [PubMed] [Google Scholar]
Hudak, C. S., and Sul H. S... 2013. Pref-1, a gatekeeper of adipogenesis. Front. Endocr. 4: 1–6. doi: 10.3389/fendo.2013.00079 [DOI] [PMC free article] [PubMed] [Google Scholar]
Hwang, Y. H., Kim G. D., Jeong J. Y., Hur S. J., and Joo S. T... 2010. The relationship between muscle fiber characteristics and meat quality traits of highly marbled Hanwoo (Korean native cattle) steers. Meat Sci. 86:456–461. doi: 10.1016/j.meatsci.2010.05.034 [DOI] [PubMed] [Google Scholar]
Jaborek, J. R., Fluharty F. L., Zerby H. N., and Relling A. E... 2023. Angus- and Wagyu-sired cattle raised to a similar days on feed or body weight endpoint I: comparison of feedlot performance, carcass characteristics, and fatty acid composition. J. Anim. Sci. XX:XX–XX. doi: 10.1093/jas/skac343 [DOI] [PMC free article] [PubMed] [Google Scholar]
Jeong, J., Kwon E. G., Im S. K., Seo K. S., and Baik M... 2012. Expression of fat deposition and fat removal genes is associated with intramuscular fat content in longissimus dorsi muscle of Korean cattle steers. J. Anim. Sci. 90:2044–2053. doi: 10.2527/jas.2011-4753 [DOI] [PubMed] [Google Scholar]
Joo, S. T., Lee K. W., Hwang Y. H., and Joo S. H... 2017. The relationships between muscle fiber characteristics, intramuscular fat content, and fatty acid compositions in M. longissimus lumborum of Hanwoo steers. Korean J. Food Sci. Anim. Resour. 37:716–725. doi: 10.5851/kosfa.2017.37.5.780 [DOI] [PMC free article] [PubMed] [Google Scholar]
Jurie, C., Cassar-Malek I., Bonnet M., Leroux C., Bauchart D., Boulesteix P., Pethick D. W., and Hocquette J. F... 2007. Adipocyte fatty acid-binding protein and mitochondrial enzyme activities in muscles as relevant indicators of marbling in cattle. J. Anim. Sci. 85:2660–2669. doi: 10.2527/jas.2006-837 [DOI] [PubMed] [Google Scholar]
Kazala, E. C., Petrak J. L., Lozeman F. J., Mir P. S., Laroche A., Deng J., and Weselake R. J... 2003. Hormone-sensitive lipase activity in relation to fat content of muscle in Wagyu hybrid cattle. Livest. Prod. Sci. 79:87–96. doi: 10.1016/S0301-6226(02)00141-0 [DOI] [Google Scholar]
Killinger, K. M., Calkins C. R., Umberger W. J., Feuz D. M., and Eskridge K. M... 2004. Consumer sensory acceptance and value for beef steaks of similar tenderness, but differing in marbling level. J. Anim. Sci. 82:3294–3301. doi: 10.2527/2004.82113294x [DOI] [PubMed] [Google Scholar]
Kim, W. S., Park H. S., and Sung J. H... 2015. The pivotal role of PDGF and its receptor isoforms in adipose-derived stem cells. Histol. Histopathol. 30:793–799. doi: 10.14670/HH-11-598 [DOI] [PubMed] [Google Scholar]
Kruk, Z. A., Bottema M. J., Reyes-Veliz L., Forder R. E. A., Pitchford W. S., and Bottema C. D... 2018. Vitamin A and marbling attributes: Intramuscular fat hyperplasia effects in cattle. Meat Sci. 137:139–146. doi: 10.1016/j.meatsci.2017.11.024 [DOI] [PubMed] [Google Scholar]
Lancaster, P. A., Sharman E. D., Horn G. W., Krehbiel C. R., and Starkey J. D... 2014. Effect of rate of weight gain of steers during the stocker phase. III. Gene expression of adipose tissues and skeletal muscle in growing–finishing beef cattle. J. Anim. Sci. 92: 1462-72. doi: 10.2527/jas.2013-6976 [DOI] [PubMed] [Google Scholar]
Lunt, D. K., Chung K. Y., Choi C. B., and Smith S. B... 2005. Production characteristics and carcass quality of Angus and Wagyu steers fed to US and Japanese endpoints. J. Anim. Vet. Adv. 4:949–953. doi:javaa.2005.949.953 [Google Scholar]
Lunt, D. K., Riley R. R., and Smith S. B... 1993. Growth and carcass characteristics of Angus and American Wagyu steers. Meat Sci. 34:327–334. doi: 10.1016/0309-1740(93)90081-R [DOI] [PubMed] [Google Scholar]
May, S. G., Dolezal H. G., Gill D. R., Ray F. K., and Buchanan D. S... 1992. Effect of days fed, carcass grade traits, and subcutaneous fat removal on postmortem muscle characteristics and beef palatability. J. Anim. Sci. 70:444–453. doi: 10.2527/1992.702444x [DOI] [PubMed] [Google Scholar]
May, S. G., Savell J. W., Lunt D. K., Wilson J. J., Laurenz J. C., and Smith S. B... 1994. Evidence for preadipocyte proliferation during culture of subcutaneous and intramuscular adipose tissues from Angus and Wagyu crossbred steers. J. Anim. Sci. 72:3110–3117. doi: 10.2527/1994.72123110x [DOI] [PubMed] [Google Scholar]
McIntyre, T. M., Pontsler A. V., Silva A. R., Hilaire A. S., Xu Y., Hinshaw J. C., Zimmerman G. A., Hama K., Aoki J., Ara H.,. et al. 2003. Identification of an intracellular receptor for lysophosphatidic acid (LPA): LPA is a transcellular PPARγ agonist. Proc. Nat. Acad. Sci. 100: 131-136. 10.1073/pnas.0135855100. [DOI] [PMC free article] [PubMed] [Google Scholar]
Moisá, S. J., Shike D. W., Faulkner D. B., Meteer W. T., Keisler D., and Loor J. J... 2014. Central role of the PPARγ gene network in coordinating beef cattle intramuscular adipogenesis in response to weaning age and nutrition. Gene Reg. Sys. Biol. 8: 17–32. 10.4137/GRSB.S11782 [DOI] [PMC free article] [PubMed] [Google Scholar]
Moody, W. G., and Cassens R. G... 1968. A quantitative and morphological study of bovine Longissimus fat cells. Food Sci. 33:47–52. doi: 10.1111/j.1365-2621.1968.tb00882.x [DOI] [Google Scholar]
Moore, K. K., Ekeren P. A., Lunt D. K., and Smith S. B... 1991. Relationship between fatty acid-binding protein activity and marbling scores in bovine longissimus muscle. J. Anim. Sci. 69:1515–1521. doi: 10.2527/1991.6941515x [DOI] [PubMed] [Google Scholar]
NASEM (National Academies of Sciences, Engineering, and Medicine). 2016. Nutrient requirements of beef cattle. 8th rev. ed. Washington, DC: Natl. Acad. Press. doi: 10.17226/19014 [DOI] [Google Scholar]
Ozawa, S., Mitsuhashi T., Mitsumoto M., Matsumoto S., Itoh N., Itagaki K., Kohno Y., and Dohgo T... 2000. The characteristics of muscle fiber types of longissimus thoracis muscle and their influences on the quantity and quality of meat from Japanese Black steers. Meat Sci. 54:65–70. doi: 10.1016/s0309-1740(99)00072-8 [DOI] [PubMed] [Google Scholar]
Payne, V. A., Au W. S., Lowe C. E., Rahman S. M., Friedman J. E., O’Rahilly S., and Rochford J. J... 2010. C/EBP transcription factors regulate SREBP1c gene expression during adipogenesis. Biochem. J. 425:215–224. doi: 10.1042/BJ20091112 [DOI] [PMC free article] [PubMed] [Google Scholar]
Pickworth, C. L., Loerch S. C., and Fluharty F. L... 2012. Restriction of vitamin A and D in beef cattle finishing diets on feedlot performance and adipose accretion. J. Anim. Sci. 90:1866–1878. doi: 10.2527/jas.2010-3590 [DOI] [PubMed] [Google Scholar]
Pickworth, C. L., Loerch S. C., Velleman S. G., Pate J. L., Poole D. H., and Fluharty F. L... 2011. Adipogenic differentiation state-specific gene expression as related to bovine carcass adiposity. J. Anim. Sci. 89:355–366. doi: 10.2527/jas.2010-3229 [DOI] [PubMed] [Google Scholar]
Platter, W. J., Tatum J. D., Belk K. E., Chapman P. L., Scanga J. A., and Smith G. C... 2003. Relationships of consumer sensory ratings, marbling score, and shear force value to consumer acceptance of beef strip loin steaks. J. Anim. Sci. 81:2741–2750. doi: 10.2527/2003.81112741x [DOI] [PubMed] [Google Scholar]
Rahman, M. S. 2019. Prostacyclin: a major prostaglandin in the regulation of adipose tissue development. J. Cell. Phys. 234: 3254–3262. doi: 10.1002/jcp.26932 [DOI] [PubMed] [Google Scholar]
Rahman, M. S., Khan F., Syeda P. K., Nishimura K., Jisaka M., Nagaya T., Shono F., and Yokota K... 2014. Endogenous synthesis of prostacyclin was positively regulated during the maturation phase of cultured adipocytes. Cytotechnology. 66:635–646. doi: 10.1007/s10616-013-9616-9 [DOI] [PMC free article] [PubMed] [Google Scholar]
Reusch, J. E., Colton L. A., and Klemm D. J... 2000. CREB activation induces adipogenesis in 3WA-MD-L1 cells. Mol. Cell. Biol. 20: 1008–1020. doi: 10.1128/MCB.20.3.1008-1020.2000 [DOI] [PMC free article] [PubMed] [Google Scholar]
Rhee, K. S., Dutson T. R., Smith G. C., Hostetler R. L., and Reiser R... 1982. Cholesterol content of raw and cooked beef longissimus muscles with different degrees of marbling. J. Food Sci. 47:716–719. doi: 10.1111/j.1365-2621.1982.tb12698.x [DOI] [Google Scholar]
Robelin, J. 1981. Cellularity of bovine adipose tissues: developmental changes from 15 to 65 percent mature weight. J. Lipid Res. 22:452–457. doi: 10.1016/S0022-2275(20)34959-2 [DOI] [PubMed] [Google Scholar]
Roberts, S. L., Lancaster P. A., DeSilva U., Horn G. W., and Krehbiel C. R... 2015. Coordinated gene expression between skeletal muscle and intramuscular adipose tissue in growing beef cattle. J. Anim. Sci. 93:4302–4311. doi: 10.2527/jas.2015-8886 [DOI] [PubMed] [Google Scholar]
Rule, D. C., MacNeil M. D., and Short R. E... 1997. Influence of sire growth potential, time on feed, and growing-finishing strategy on cholesterol and fatty acids of the ground carcass and longissimus muscle of beef steers. J. Anim. Sci. 75:1525–1533. doi: 10.2527/1997.7561525x [DOI] [PubMed] [Google Scholar]
Schiavetta, A. M., Miller M. F., Lunt D. K., Davis S. K., and Smith S. B... 1990. Adipose tissue cellularity and muscle growth in young steers fed the beta-adrenergic agonist clenbuterol for 50 days and after 78 days of withdrawal. J. Anim. Sci. 68:3614–3623. doi: 10.2527/1990.68113614x [DOI] [PubMed] [Google Scholar]
Schoonmaker, J. P., Fluharty F. L., and Loerch S. C... 2004. Effect of source and amount of energy and rate of growth in the growing phase on adipocyte cellularity and lipogenic enzyme activity in the intramuscular and subcutaneous fat depots of Holstein steers. J. Anim. Sci. 82:137–148. doi: 10.2527/2004.821137x [DOI] [PubMed] [Google Scholar]
Shimano, H. 2001. Sterol regulatory element-binding proteins (SREBPs): transcriptional regulators of lipid synthetic genes. Prog. Lipid Res. 40:439–452. doi: 10.1016/s0163-7827(01)00010-8 [DOI] [PubMed] [Google Scholar]
Smas, C. M., and Sul H. S... 1995. Control of adipocyte differentiation. Biochem. J. 309:697–710. doi: 10.1042/bj3090697 [DOI] [PMC free article] [PubMed] [Google Scholar]
Smith, Z. K., Chung K. Y., Parr S. L., and Johnson B. J... 2017. Anabolic payout of terminal implant alters adipogenic gene expression of the longissimus muscle in beef steers. J. Anim. Sci. 95:1197–1204. doi: 10.2527/jas.2016.0630 [DOI] [PubMed] [Google Scholar]
Tang, Q. Q., Otto T. C., and Lane M. D... 2003. CCAAT/enhancer-binding protein β is required for mitotic clonal expansion during adipogenesis. Proc. Nat. Acad. Sci. 100:850–855. doi: 10.1073/pnas.0337434100 [DOI] [PMC free article] [PubMed] [Google Scholar]
Tontonoz, P., Hu E., Graves R. A., Budavari A. I., and Spiegelman B. M... 1994. mPPAR gamma 2: tissue-specific regulator of an adipocyte enhancer. Genes Dev. 8: 1224–1234. doi: 10.1101/gad.8.10.1224 [DOI] [PubMed] [Google Scholar]
Uezumi, A., Fukada S. I., Yamamoto N., Takeda S. I., and Tsuchida K... 2010. Mesenchymal progenitors distinct from satellite cells contribute to ectopic fat cell formation in skeletal muscle. Nat. Cell Biol. 12:143–153. doi: 10.1038/ncb2014 [DOI] [PubMed] [Google Scholar]
Underwood, K. R., Tong J., Zhu M. J., Shen Q. W., Means W. J., Ford S. P., Paisley S. I., Hess B. W., and Du M... 2007. Relationship between kinase phosphorylation, muscle fiber typing, and glycogen accumulation in longissimus muscle of beef cattle with high and low intramuscular fat. J. Agric. Food Chem. 55:9698–9703. doi: 10.1021/jf071573z [DOI] [PubMed] [Google Scholar]
Waddell, J. N., Zhang P., Wen Y., Gupta S. K., Yevtodiyenko A., Schmidt J. V., Bidwell C. A., Kumar A., and Kuang S... 2010. Dlk1 is necessary for proper skeletal muscle development and regeneration. PLoS One. 5:e15055. doi: 10.1371/journal.pone.0015055 [DOI] [PMC free article] [PubMed] [Google Scholar]
Wang, Y. H., Bower B. L., Reverter A., Tan S. H., De Jager N., Wang R., McWilliam S. M., Cafe L. M., Greenwood P. L., and Lehnert S. A... 2009. Gene expression patterns during intramuscular fat development in cattle. J. Anim. Sci. 87:119–130. doi: 10.2527/jas.2008-1082 [DOI] [PubMed] [Google Scholar]
Wheeler, T. L., Davis G. W., Stoecker B. J., and Harmon C. J... 1987. Cholesterol concentration of longissimus muscle, subcutaneous fat and serum of two beef cattle breed types. J. Anim. Sci. 65:1531–1537. doi: 10.2527/jas1987.6561531x [DOI] [PubMed] [Google Scholar]
Woollett, L. A., Spady D. K., and Dietschy J. M... 1992. Saturated and unsaturated fatty acids independently regulate low density lipoprotein receptor activity and production rate. J. Lipid Res. 33:77–88. doi: 10.1016/S0022-2275(20)41885-1 [DOI] [PubMed] [Google Scholar]
Wu, Z., Bucher N. L., and Farmer S. R... 1996. Induction of peroxisome proliferator-activated receptor gamma during the conversion of 3T3 fibroblasts into adipocytes is mediated by C/EBPbeta, C/EBPdelta, and glucocorticoids. Mol. Cell. Biol. 16:4128–4136. doi: 10.1128/MCB.16.8.4128 [DOI] [PMC free article] [PubMed] [Google Scholar]
Yamada, T., and Nakanishi N... 2012. Effects of the roughage/concentrate ratio on the expression of angiogenic growth factors in adipose tissue of fattening Wagyu steers. Meat Sci. 90:807–813. doi: 10.1016/j.meatsci.2011.11.019 [DOI] [PubMed] [Google Scholar]
Yamada, T., Kawakami S., and Nakanishi N... 2010. Fat depot-specific differences in angiogenic growth factor gene expression and its relation to adipocyte size in cattle. J. Vet. Med. Sci. 72:991–997. doi: 10.1292/jvms.10-0031 [DOI] [PubMed] [Google Scholar]
Zhang, P., Takeuchi K., Csaki L. S., and Reue K... 2012. Lipin-1 phosphatidic phosphatase activity modulates phosphatidate levels to promote peroxisome proliferator-activated receptor γ (PPARγ) gene expression during adipogenesis. J. Biol. Chem. 287:3485–3494. doi: 10.1074/jbc.M111.296681 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0001] Ailhaud, G., Grimaldi P., and Négrel R... 1992. Cellular and molecular aspects of adipose tissue development. Annu. Rev. Nutr. 12:207–233. doi: 10.1146/annurev.nu.12.070192.001231 [DOI] [PubMed] [Google Scholar]

[CIT0002] Albrecht, E., Gotoh T., Ebara F., Xu J. X., Viergutz T., Nürnberg G., Maak S., and Wegner J... 2011. Cellular conditions for intramuscular fat deposition in Japanese Black and Holstein steers. Meat Sci. 891:13–20. doi: 10.1016/j.meatsci.2011.03.012. [DOI] [PubMed] [Google Scholar]

[CIT0003] Albrecht, E., Kuzinski J., Komolka K., Gotoh T., and Maak S... 2015. Localization and abundance of early markers of fat cell differentiation in the skeletal muscle of cattle during growth - are DLK1-positive cells the origin of marbling flecks? Meat Sci. 100:237–245. doi: 10.1016/j.meatsci.2014.10.012 [DOI] [PubMed] [Google Scholar]

[CIT0004] AOAC. 2005. Official methods of analysis. 17th ed. Washington, DC, USA: Association of Official Analytical Chemists. [Google Scholar]

[CIT0005] Aubert, J., Saint-Marc P., Belmonte N., Dani C., Négrel R., and Ailhaud G... 2000. Prostacyclin IP receptor up-regulates the early expression of C/EBPβ and C/EBPδ in preadipose cells. Mol. Cell. Endocr. 160:149–156. doi: 10.1016/S0303-7207(99)00210-5 [DOI] [PubMed] [Google Scholar]

[CIT0006] Bastie, C., Holst D., Gaillard D., Jehl-Pietri C., and Grimaldi P. A... 1999. Expression of peroxisome proliferator-activated receptor PPARδ promotes induction of PPARγ and adipocyte differentiation in 3WA-MDC2 fibroblasts. J. Biol. Chem. 274:21920–21925. doi: 10.1074/jbc.274.31.21920 [DOI] [PubMed] [Google Scholar]

[CIT0007] Belmonte, N., Phillips B. W., Massiera F., Villageois P., Wdziekonski B., Saint-Marc P., Nichols J., Aubert J., Saeki K., Yuo A.,. et al. 2001. Activation of extracellular signal-regulated kinases and CREB/ATF-1 mediate the expression of CCAAT/enhancer binding proteins β and-δ in preadipocytes. Mol. Cell. Endocr. 15:2037–2049. doi: 10.1210/mend.15.11.0721 [DOI] [PubMed] [Google Scholar]

[CIT0008] Blumer, T. N., Craig H. B., Pierce E. A., W. W. G.Smart, Jr., and Wise M. B... 1962. Nature and variability of marbling deposits in Longissimus dorsi muscle of beef carcasses. J. Anim. Sci. 21: 935–942. doi: 10.2527/jas1962.214935x [DOI] [Google Scholar]

[CIT0009] Brugiapaglia, A., Lussiana C., and Destefanis G... 2014. Fatty acid profile and cholesterol content of beef at retail of Piemontese, Limousin and Friesian breeds. Meat Sci. 96:568–573. doi: 10.1016/j.meatsci.2013.08.012 [DOI] [PubMed] [Google Scholar]

[CIT0010] Campos, C. F., Duarte M. S., Guimarães S. E. F., Verardo L. L., Wei S., Du M., Jiang Z., Bergen W. G., Hausman G. J., Fernyhough-Culver M.,. et al. 2016. Review: animal model and the current understanding of molecule dynamics of adipogenesis. Animal. 10:927–932. doi: 10.1017/S1751731115002992 [DOI] [PubMed] [Google Scholar]

[CIT0011] Calkins, C. R., Dutson T. R., Smith G. C., Carpenter Z. L., and Davis G. W... 1981. Relationship of fiber type composition to marbling and tenderness of bovine muscle. J. Food Sci. 46:708–710. doi: 10.1111/j.1365-2621.1981.tb15331.x [DOI] [Google Scholar]

[CIT0012] Chung, K. Y., Baxa T. J., Parr S. L., Luqué L. D., and Johnson B. J... 2012. Administration of estradiol, trenbolone acetate, and trenbolone acetate/estradiol implants alters adipogenic and myogenic gene expression in bovine skeletal muscle. J. Anim. Sci. 90:1421–1427. doi: 10.2527/jas.2011-3496 [DOI] [PubMed] [Google Scholar]

[CIT0013] Chung, K. Y., Lunt D. K., Choi C. B., Chae S. H., Rhoades R. D., Adams T. H., Booren B., and Smith S. B... 2006. Lipid characteristics of subcutaneous adipose tissue and M. longissimus thoracis of Angus and Wagyu steers fed to US and Japanese endpoints. Meat Sci. 73:432–441. doi: 10.1016/j.meatsci.2006.01.002 [DOI] [PubMed] [Google Scholar]

[CIT0014] Coleman, R. A., and Lee D. P... 2004. Enzymes of triacylglycerol synthesis and their regulation. Prog. Lipid Res. 43:134–176. doi: 10.1016/s0163-7827(03)00051-1 [DOI] [PubMed] [Google Scholar]

[CIT0015] Coleman, D. N., Murphy K. D., and Relling A. E... 2018. Prepartum fatty acid supplementation in sheep. II. Supplementation of eicosapentaenoic acid and docosahexaenoic acid during late gestation alters the fatty acid profile of plasma, colostrum, milk and adipose tissue, and increases lipogenic gene expression of adipose tissue. J. Anim. Sci. 96:1181–1204. doi: 10.1093/jas/skx013 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0016] Crandall, D. L., Hausman G. J., and Kral J. G... 1997. A review of the microcirculation of adipose tissue: anatomic, metabolic, and angiogenic perspectives. Microcirculation. 4:211–232. doi: 10.3109/10739689709146786 [DOI] [PubMed] [Google Scholar]

[CIT0017] Darimont, C., Vassaux G., Ailhaud G., and Negrel R... 1994. Differentiation of preadipose cells: paracrine role of prostacyclin upon stimulation of adipose cells by angiotensin-II. Endocrinology. 135:2030–2036. doi: 10.1210/endo.135.5.7956925 [DOI] [PubMed] [Google Scholar]

[CIT0018] De Jager, N., Hudson N. J., Reverter A., Barnard R., Cafe L. M., Greenwood P. L., and Dalrymple B. P... 2013. Gene expression phenotypes for lipid metabolism and intramuscular fat in skeletal muscle of cattle. J. Anim. Sci. 91:1112–1128. doi: 10.2527/jas.2012-5409 [DOI] [PubMed] [Google Scholar]

[CIT0019] Duarte, M. S., Paulino P. V. R., Das A. K., Wei S., Serao N. V. L., Fu X., Harris S. M., Dodson M. V., and Du M... 2013. Enhancement of adipogenesis and fibrogenesis in skeletal muscle of Wagyu compared with Angus cattle. J. Anim. Sci. 91:2938–2946. doi: 10.2527/jas.2012-5892 [DOI] [PubMed] [Google Scholar]

[CIT0020] Farmer, S. R. 2006. Transcriptional control of adipocyte formation. Cell Metab. 4:263–273. doi: 10.1016/j.cmet.2006.07.001 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0021] FASS. 2010. Guide for the care and use of agricultural animals in agricultural research and teaching. 3rd revised edition. Champaign, IL: Fed. Anim. Sci. Soc. [Google Scholar]

[CIT0022] Fu, X., Yang Q., Wang B., Zhao J., Zhu M., Parish S. M., and Du M... 2017. Reduced satellite cell density and myogenesis in Wagyu compared with Angus cattle as a possible explanation of its high marbling. Animal. 12:990–997. doi: 10.1017/S1751731117002403 [DOI] [PubMed] [Google Scholar]

[CIT0023] Garin-Shkolnik, T., Rudich A., Hotamisligil G. S., and Rubinstein M... 2014. FABP4 attenuates PPARγ and adipogenesis and is inversely correlated with PPARγ in adipose tissues. Diabetes. 63:900–911. doi: 10.2337/db13-0436 [DOI] [PubMed] [Google Scholar]

[CIT0024] Gorocica-Buenfil, M. A., Fluharty F. L., Reynolds C. K., and Loerch S. C... 2007. Effect of dietary vitamin A concentration and roasted soybean inclusion on marbling, adipose cellularity, and fatty acid composition of beef. J. Anim. Sci. 85:2230–2242. doi: 10.2527/jas.2006-780 [DOI] [PubMed] [Google Scholar]

[CIT0025] Gotoh, T. 2003. Histochemical properties of skeletal muscles in Japanese cattle and their meat production ability. Anim. Sci. J. 74:339–354. doi: 10.1046/j.1344-3941.2003.00125.x [DOI] [Google Scholar]

[CIT0026] Gotoh, T., Albrecht E., Teuscher F., Kawabata K., Sakashita K., Iwamoto H., and Wegner J... 2009. Differences in muscle and fat accretion in Japanese Black and European cattle. Meat Sci. 82:300–308. doi: 10.1016/j.meatsci.2009.01.026 [DOI] [PubMed] [Google Scholar]

[CIT0027] Gupta, R. K., Arany Z., Seale P., Mepani R. J., Ye L., Conroe H. M., Roby Y. A., Kulaga H., Reed R. R., and Spiegelman B. M... 2010. Transcriptional control of preadipocyte determination by Zfp423. Nature. 464:619–623. doi: 10.1038/nature08816 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0028] Hausman, G. J., and Richardson R. L... 2004. Adipose tissue angiogenesis. J. Anim. Sci. 82:925–934. doi: 10.2527/2004.823925x [DOI] [PubMed] [Google Scholar]

[CIT0029] Hansen, J. B., Zhang H., Rasmussen T. H., Petersen R. K., Flindt E. N., and Kristiansen K... 2001. Peroxisome proliferator-activated receptor δ (PPARδ)-mediated regulation of preadipocyte proliferation and gene expression is dependent on cAMP signaling. J. Biol. Chem. 276:3175–3182. doi: 10.1074/jbc.M005567200 [DOI] [PubMed] [Google Scholar]

[CIT0030] Holst, D., Luquet S., Nogueira V., Kristiansen K., Leverve X., and Grimaldi P. A... 2003. Nutritional regulation and role of peroxisome proliferator-activated receptor δ in fatty acid catabolism in skeletal muscle. Biochim. Biophys. Acta, Mol. Cell. Biol. Lipids. 1633:43–50. doi: 10.1016/S1388-1981(03)00071-4 [DOI] [PubMed] [Google Scholar]

[CIT0031] Hood, R., and Allen C. E... 1973. Cellularity of bovine adipose tissue. J. Lipid Res. 14:605–610. doi: 10.1016/S0022-2275(20)36840-1 [DOI] [PubMed] [Google Scholar]

[CIT0032] Huang, Y., Das A. K., Yang Q. Y., Zhu M. J., and Du M... 2012. Zfp423 promotes adipogenic differentiation of bovine stromal vascular cells. PLoS One. 7:e47496. doi: 10.1371/journal.pone.0047496 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0033] Hudak, C. S., and Sul H. S... 2013. Pref-1, a gatekeeper of adipogenesis. Front. Endocr. 4: 1–6. doi: 10.3389/fendo.2013.00079 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0034] Hwang, Y. H., Kim G. D., Jeong J. Y., Hur S. J., and Joo S. T... 2010. The relationship between muscle fiber characteristics and meat quality traits of highly marbled Hanwoo (Korean native cattle) steers. Meat Sci. 86:456–461. doi: 10.1016/j.meatsci.2010.05.034 [DOI] [PubMed] [Google Scholar]

[CIT0035] Jaborek, J. R., Fluharty F. L., Zerby H. N., and Relling A. E... 2023. Angus- and Wagyu-sired cattle raised to a similar days on feed or body weight endpoint I: comparison of feedlot performance, carcass characteristics, and fatty acid composition. J. Anim. Sci. XX:XX–XX. doi: 10.1093/jas/skac343 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0036] Jeong, J., Kwon E. G., Im S. K., Seo K. S., and Baik M... 2012. Expression of fat deposition and fat removal genes is associated with intramuscular fat content in longissimus dorsi muscle of Korean cattle steers. J. Anim. Sci. 90:2044–2053. doi: 10.2527/jas.2011-4753 [DOI] [PubMed] [Google Scholar]

[CIT0037] Joo, S. T., Lee K. W., Hwang Y. H., and Joo S. H... 2017. The relationships between muscle fiber characteristics, intramuscular fat content, and fatty acid compositions in M. longissimus lumborum of Hanwoo steers. Korean J. Food Sci. Anim. Resour. 37:716–725. doi: 10.5851/kosfa.2017.37.5.780 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0038] Jurie, C., Cassar-Malek I., Bonnet M., Leroux C., Bauchart D., Boulesteix P., Pethick D. W., and Hocquette J. F... 2007. Adipocyte fatty acid-binding protein and mitochondrial enzyme activities in muscles as relevant indicators of marbling in cattle. J. Anim. Sci. 85:2660–2669. doi: 10.2527/jas.2006-837 [DOI] [PubMed] [Google Scholar]

[CIT0039] Kazala, E. C., Petrak J. L., Lozeman F. J., Mir P. S., Laroche A., Deng J., and Weselake R. J... 2003. Hormone-sensitive lipase activity in relation to fat content of muscle in Wagyu hybrid cattle. Livest. Prod. Sci. 79:87–96. doi: 10.1016/S0301-6226(02)00141-0 [DOI] [Google Scholar]

[CIT0040] Killinger, K. M., Calkins C. R., Umberger W. J., Feuz D. M., and Eskridge K. M... 2004. Consumer sensory acceptance and value for beef steaks of similar tenderness, but differing in marbling level. J. Anim. Sci. 82:3294–3301. doi: 10.2527/2004.82113294x [DOI] [PubMed] [Google Scholar]

[CIT0041] Kim, W. S., Park H. S., and Sung J. H... 2015. The pivotal role of PDGF and its receptor isoforms in adipose-derived stem cells. Histol. Histopathol. 30:793–799. doi: 10.14670/HH-11-598 [DOI] [PubMed] [Google Scholar]

[CIT0042] Kruk, Z. A., Bottema M. J., Reyes-Veliz L., Forder R. E. A., Pitchford W. S., and Bottema C. D... 2018. Vitamin A and marbling attributes: Intramuscular fat hyperplasia effects in cattle. Meat Sci. 137:139–146. doi: 10.1016/j.meatsci.2017.11.024 [DOI] [PubMed] [Google Scholar]

[CIT0043] Lancaster, P. A., Sharman E. D., Horn G. W., Krehbiel C. R., and Starkey J. D... 2014. Effect of rate of weight gain of steers during the stocker phase. III. Gene expression of adipose tissues and skeletal muscle in growing–finishing beef cattle. J. Anim. Sci. 92: 1462-72. doi: 10.2527/jas.2013-6976 [DOI] [PubMed] [Google Scholar]

[CIT0044] Lunt, D. K., Chung K. Y., Choi C. B., and Smith S. B... 2005. Production characteristics and carcass quality of Angus and Wagyu steers fed to US and Japanese endpoints. J. Anim. Vet. Adv. 4:949–953. doi:javaa.2005.949.953 [Google Scholar]

[CIT0045] Lunt, D. K., Riley R. R., and Smith S. B... 1993. Growth and carcass characteristics of Angus and American Wagyu steers. Meat Sci. 34:327–334. doi: 10.1016/0309-1740(93)90081-R [DOI] [PubMed] [Google Scholar]

[CIT0046] May, S. G., Dolezal H. G., Gill D. R., Ray F. K., and Buchanan D. S... 1992. Effect of days fed, carcass grade traits, and subcutaneous fat removal on postmortem muscle characteristics and beef palatability. J. Anim. Sci. 70:444–453. doi: 10.2527/1992.702444x [DOI] [PubMed] [Google Scholar]

[CIT0047] May, S. G., Savell J. W., Lunt D. K., Wilson J. J., Laurenz J. C., and Smith S. B... 1994. Evidence for preadipocyte proliferation during culture of subcutaneous and intramuscular adipose tissues from Angus and Wagyu crossbred steers. J. Anim. Sci. 72:3110–3117. doi: 10.2527/1994.72123110x [DOI] [PubMed] [Google Scholar]

[CIT0048] McIntyre, T. M., Pontsler A. V., Silva A. R., Hilaire A. S., Xu Y., Hinshaw J. C., Zimmerman G. A., Hama K., Aoki J., Ara H.,. et al. 2003. Identification of an intracellular receptor for lysophosphatidic acid (LPA): LPA is a transcellular PPARγ agonist. Proc. Nat. Acad. Sci. 100: 131-136. 10.1073/pnas.0135855100. [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0049] Moisá, S. J., Shike D. W., Faulkner D. B., Meteer W. T., Keisler D., and Loor J. J... 2014. Central role of the PPARγ gene network in coordinating beef cattle intramuscular adipogenesis in response to weaning age and nutrition. Gene Reg. Sys. Biol. 8: 17–32. 10.4137/GRSB.S11782 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0050] Moody, W. G., and Cassens R. G... 1968. A quantitative and morphological study of bovine Longissimus fat cells. Food Sci. 33:47–52. doi: 10.1111/j.1365-2621.1968.tb00882.x [DOI] [Google Scholar]

[CIT0051] Moore, K. K., Ekeren P. A., Lunt D. K., and Smith S. B... 1991. Relationship between fatty acid-binding protein activity and marbling scores in bovine longissimus muscle. J. Anim. Sci. 69:1515–1521. doi: 10.2527/1991.6941515x [DOI] [PubMed] [Google Scholar]

[CIT0052] NASEM (National Academies of Sciences, Engineering, and Medicine). 2016. Nutrient requirements of beef cattle. 8th rev. ed. Washington, DC: Natl. Acad. Press. doi: 10.17226/19014 [DOI] [Google Scholar]

[CIT0053] Ozawa, S., Mitsuhashi T., Mitsumoto M., Matsumoto S., Itoh N., Itagaki K., Kohno Y., and Dohgo T... 2000. The characteristics of muscle fiber types of longissimus thoracis muscle and their influences on the quantity and quality of meat from Japanese Black steers. Meat Sci. 54:65–70. doi: 10.1016/s0309-1740(99)00072-8 [DOI] [PubMed] [Google Scholar]

[CIT0054] Payne, V. A., Au W. S., Lowe C. E., Rahman S. M., Friedman J. E., O’Rahilly S., and Rochford J. J... 2010. C/EBP transcription factors regulate SREBP1c gene expression during adipogenesis. Biochem. J. 425:215–224. doi: 10.1042/BJ20091112 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0055] Pickworth, C. L., Loerch S. C., and Fluharty F. L... 2012. Restriction of vitamin A and D in beef cattle finishing diets on feedlot performance and adipose accretion. J. Anim. Sci. 90:1866–1878. doi: 10.2527/jas.2010-3590 [DOI] [PubMed] [Google Scholar]

[CIT0056] Pickworth, C. L., Loerch S. C., Velleman S. G., Pate J. L., Poole D. H., and Fluharty F. L... 2011. Adipogenic differentiation state-specific gene expression as related to bovine carcass adiposity. J. Anim. Sci. 89:355–366. doi: 10.2527/jas.2010-3229 [DOI] [PubMed] [Google Scholar]

[CIT0057] Platter, W. J., Tatum J. D., Belk K. E., Chapman P. L., Scanga J. A., and Smith G. C... 2003. Relationships of consumer sensory ratings, marbling score, and shear force value to consumer acceptance of beef strip loin steaks. J. Anim. Sci. 81:2741–2750. doi: 10.2527/2003.81112741x [DOI] [PubMed] [Google Scholar]

[CIT0058] Rahman, M. S. 2019. Prostacyclin: a major prostaglandin in the regulation of adipose tissue development. J. Cell. Phys. 234: 3254–3262. doi: 10.1002/jcp.26932 [DOI] [PubMed] [Google Scholar]

[CIT0059] Rahman, M. S., Khan F., Syeda P. K., Nishimura K., Jisaka M., Nagaya T., Shono F., and Yokota K... 2014. Endogenous synthesis of prostacyclin was positively regulated during the maturation phase of cultured adipocytes. Cytotechnology. 66:635–646. doi: 10.1007/s10616-013-9616-9 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0060] Reusch, J. E., Colton L. A., and Klemm D. J... 2000. CREB activation induces adipogenesis in 3WA-MD-L1 cells. Mol. Cell. Biol. 20: 1008–1020. doi: 10.1128/MCB.20.3.1008-1020.2000 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0061] Rhee, K. S., Dutson T. R., Smith G. C., Hostetler R. L., and Reiser R... 1982. Cholesterol content of raw and cooked beef longissimus muscles with different degrees of marbling. J. Food Sci. 47:716–719. doi: 10.1111/j.1365-2621.1982.tb12698.x [DOI] [Google Scholar]

[CIT0062] Robelin, J. 1981. Cellularity of bovine adipose tissues: developmental changes from 15 to 65 percent mature weight. J. Lipid Res. 22:452–457. doi: 10.1016/S0022-2275(20)34959-2 [DOI] [PubMed] [Google Scholar]

[CIT0063] Roberts, S. L., Lancaster P. A., DeSilva U., Horn G. W., and Krehbiel C. R... 2015. Coordinated gene expression between skeletal muscle and intramuscular adipose tissue in growing beef cattle. J. Anim. Sci. 93:4302–4311. doi: 10.2527/jas.2015-8886 [DOI] [PubMed] [Google Scholar]

[CIT0064] Rule, D. C., MacNeil M. D., and Short R. E... 1997. Influence of sire growth potential, time on feed, and growing-finishing strategy on cholesterol and fatty acids of the ground carcass and longissimus muscle of beef steers. J. Anim. Sci. 75:1525–1533. doi: 10.2527/1997.7561525x [DOI] [PubMed] [Google Scholar]

[CIT0065] Schiavetta, A. M., Miller M. F., Lunt D. K., Davis S. K., and Smith S. B... 1990. Adipose tissue cellularity and muscle growth in young steers fed the beta-adrenergic agonist clenbuterol for 50 days and after 78 days of withdrawal. J. Anim. Sci. 68:3614–3623. doi: 10.2527/1990.68113614x [DOI] [PubMed] [Google Scholar]

[CIT0066] Schoonmaker, J. P., Fluharty F. L., and Loerch S. C... 2004. Effect of source and amount of energy and rate of growth in the growing phase on adipocyte cellularity and lipogenic enzyme activity in the intramuscular and subcutaneous fat depots of Holstein steers. J. Anim. Sci. 82:137–148. doi: 10.2527/2004.821137x [DOI] [PubMed] [Google Scholar]

[CIT0067] Shimano, H. 2001. Sterol regulatory element-binding proteins (SREBPs): transcriptional regulators of lipid synthetic genes. Prog. Lipid Res. 40:439–452. doi: 10.1016/s0163-7827(01)00010-8 [DOI] [PubMed] [Google Scholar]

[CIT0068] Smas, C. M., and Sul H. S... 1995. Control of adipocyte differentiation. Biochem. J. 309:697–710. doi: 10.1042/bj3090697 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0069] Smith, Z. K., Chung K. Y., Parr S. L., and Johnson B. J... 2017. Anabolic payout of terminal implant alters adipogenic gene expression of the longissimus muscle in beef steers. J. Anim. Sci. 95:1197–1204. doi: 10.2527/jas.2016.0630 [DOI] [PubMed] [Google Scholar]

[CIT0070] Tang, Q. Q., Otto T. C., and Lane M. D... 2003. CCAAT/enhancer-binding protein β is required for mitotic clonal expansion during adipogenesis. Proc. Nat. Acad. Sci. 100:850–855. doi: 10.1073/pnas.0337434100 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0071] Tontonoz, P., Hu E., Graves R. A., Budavari A. I., and Spiegelman B. M... 1994. mPPAR gamma 2: tissue-specific regulator of an adipocyte enhancer. Genes Dev. 8: 1224–1234. doi: 10.1101/gad.8.10.1224 [DOI] [PubMed] [Google Scholar]

[CIT0072] Uezumi, A., Fukada S. I., Yamamoto N., Takeda S. I., and Tsuchida K... 2010. Mesenchymal progenitors distinct from satellite cells contribute to ectopic fat cell formation in skeletal muscle. Nat. Cell Biol. 12:143–153. doi: 10.1038/ncb2014 [DOI] [PubMed] [Google Scholar]

[CIT0073] Underwood, K. R., Tong J., Zhu M. J., Shen Q. W., Means W. J., Ford S. P., Paisley S. I., Hess B. W., and Du M... 2007. Relationship between kinase phosphorylation, muscle fiber typing, and glycogen accumulation in longissimus muscle of beef cattle with high and low intramuscular fat. J. Agric. Food Chem. 55:9698–9703. doi: 10.1021/jf071573z [DOI] [PubMed] [Google Scholar]

[CIT0074] Waddell, J. N., Zhang P., Wen Y., Gupta S. K., Yevtodiyenko A., Schmidt J. V., Bidwell C. A., Kumar A., and Kuang S... 2010. Dlk1 is necessary for proper skeletal muscle development and regeneration. PLoS One. 5:e15055. doi: 10.1371/journal.pone.0015055 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0075] Wang, Y. H., Bower B. L., Reverter A., Tan S. H., De Jager N., Wang R., McWilliam S. M., Cafe L. M., Greenwood P. L., and Lehnert S. A... 2009. Gene expression patterns during intramuscular fat development in cattle. J. Anim. Sci. 87:119–130. doi: 10.2527/jas.2008-1082 [DOI] [PubMed] [Google Scholar]

[CIT0076] Wheeler, T. L., Davis G. W., Stoecker B. J., and Harmon C. J... 1987. Cholesterol concentration of longissimus muscle, subcutaneous fat and serum of two beef cattle breed types. J. Anim. Sci. 65:1531–1537. doi: 10.2527/jas1987.6561531x [DOI] [PubMed] [Google Scholar]

[CIT0077] Woollett, L. A., Spady D. K., and Dietschy J. M... 1992. Saturated and unsaturated fatty acids independently regulate low density lipoprotein receptor activity and production rate. J. Lipid Res. 33:77–88. doi: 10.1016/S0022-2275(20)41885-1 [DOI] [PubMed] [Google Scholar]

[CIT0078] Wu, Z., Bucher N. L., and Farmer S. R... 1996. Induction of peroxisome proliferator-activated receptor gamma during the conversion of 3T3 fibroblasts into adipocytes is mediated by C/EBPbeta, C/EBPdelta, and glucocorticoids. Mol. Cell. Biol. 16:4128–4136. doi: 10.1128/MCB.16.8.4128 [DOI] [PMC free article] [PubMed] [Google Scholar]

[CIT0079] Yamada, T., and Nakanishi N... 2012. Effects of the roughage/concentrate ratio on the expression of angiogenic growth factors in adipose tissue of fattening Wagyu steers. Meat Sci. 90:807–813. doi: 10.1016/j.meatsci.2011.11.019 [DOI] [PubMed] [Google Scholar]

[CIT0080] Yamada, T., Kawakami S., and Nakanishi N... 2010. Fat depot-specific differences in angiogenic growth factor gene expression and its relation to adipocyte size in cattle. J. Vet. Med. Sci. 72:991–997. doi: 10.1292/jvms.10-0031 [DOI] [PubMed] [Google Scholar]

[CIT0081] Zhang, P., Takeuchi K., Csaki L. S., and Reue K... 2012. Lipin-1 phosphatidic phosphatase activity modulates phosphatidate levels to promote peroxisome proliferator-activated receptor γ (PPARγ) gene expression during adipogenesis. J. Biol. Chem. 287:3485–3494. doi: 10.1074/jbc.M111.296681 [DOI] [PMC free article] [PubMed] [Google Scholar]

PERMALINK

Lipid metabolism mRNA expression and cellularity of intramuscular adipocytes within the Longissimus muscle of Angus- and Wagyu-sired cattle fed for a similar days on feed or body weight endpoint

J R Jaborek

F L Fluharty

Kichoon Lee

Henry N Zerby

A E Relling

Abstract

Introduction

Materials and Methods

Experiment 1 treatments (constant DOF comparison)

Experiment 2 treatments (constant BW comparison)

Management, feeding, and biopsy collection

Table 1.

Cellularity analysis

RNA extraction and analysis

Table 2.

Figure 4.

Statistical analysis

Results

Intramuscular adipocyte cellularity

Figure 1.

Figure 2.

Figure 3.

Expression of mRNA for adipogenic genes

Table 3.

Table 4.

Expression of mRNA for lipogenic genes

Table 5.

Figure 5.

Table 6.

Expression of mRNA for angiogenicgenes

Table 7.

Table 8.

Figure 6.

Expression of mRNA for fatty acids uptake and transport genes

Table 9.

Figure 7.

Table 10.

Expression of mRNA for lipolyticgenes

Table 11.

Figure 8.

Table 12.

Discussion

Acknowledgments

Glossary

Abbreviations

Contributor Information

Conflict of Interest Statement

Literature Cited

ACTIONS

PERMALINK

RESOURCES

Similar articles

Cited by other articles

Links to NCBI Databases