Skip to main content
NCBI home page
NIHPA Author Manuscripts logoLink to NIHPA Author Manuscripts
. Author manuscript; available in PMC: 2011 Sep 1.
Published in final edited form as: Bone. 2010 Jun 19;47(3):631–635. doi: 10.1016/j.bone.2010.06.010

Moderate Weight Gain Does Not Influence Bone Metabolism in Skeletally Mature Female Rats

RT Turner 1, UT Iwaniec 1,*
PMCID: PMC2926277  NIHMSID: NIHMS216497  PMID: 20601291

Abstract

Bone mass is correlated with body weight during growth. However, it is unclear how bone mass is influenced by weight gain following skeletal maturity. The purpose of this study was to determine the effects of weight maintenance and two rates of weight gain on bone metabolism using skeletally mature female rats. Eight-month-old female rats were fed one of 3 diets for 13 weeks: Lieber DeCarli liquid diet ad libitum (control diet), the same diet with caloric restriction to maintain initial body weight (calorie-restricted diet), and the same diet fed ad lib with the exception that appetite was enhanced (calorie-increased diet) by replacing a small quantity of maltose-dextran isolcalorically with ethanol (0.5% caloric intake). Compared to baseline, rats fed the calorie-restricted, control, and calorie-increased diets changed in weight by −1 ± 2% (mean ± SE), 10 ± 3%, and 21 ± 2%, respectively. Weight gain was associated with a significant increase in serum leptin, a putative regulator of bone formation. In contrast, significant differences in tibial bone mineral content and density were not detected among treatments groups following dietary intervention or between treatment groups and the baseline group. Similarly, indices of cancellous bone architecture (area, trabecular number, thickness, and separation) and bone turnover (mineralizing perimeter, mineral apposition rate, and bone formation rate) did not differ among groups following dietary intervention. Our findings suggest that neither weight gain nor increased serum leptin levels, over the range evaluated, influence bone metabolism in skeletally mature female rats.

Keywords: Bone turnover, caloric restriction, osteoporosis, obesity, leptin

Introduction

The peak prevalence of obesity in adults is reached between 50 and 60 years of age [1, 2]. Excessive weight gain in this population is associated with a variety of chronic diseases and increased mortality. Obese individuals are at increased risk for heart disease, chronic obstructive pulmonary disease, type 2 diabetes, osteoarthritis, and certain cancers [3–5].

Not all health effects correlated with excessive weight gain are detrimental. Obesity in humans is often associated with increased bone mass and reduced risk for osteoporosis [6, 7]. Bone mass is also correlated with body weight in growing mice fed a normal diet [8]. The mechanisms for the positive relationship between body weight and bone mass are under investigation. Increased skeletal loading may be a contributing factor but obese individuals often have increased bone mass at non-weight bearing as well as weight bearing sites [9]. Also, ob/ob mice, in spite of being morbidly obese due to inability to produce the adipokine leptin, have smaller bones with locally increased trabecular density then their lean wild type counterparts [10–13]. Thus, the specific contributions of body weight, energy intake compared to expenditure, and circulating levels of adipokines on bone balance remain unclear.

Female rats increase in body weight following skeletal maturity, providing an opportunity to investigate the effects of weight gain on the non-growing skeleton [14, 15]. In rats, longitudinal growth ceases as a result of formation of bone bridges that penetrate and cross the growth plate. This occurs by 8 months of age in tibia of female Sprague Dawley rats [14]. As in adult humans, radial bone growth in rats continues at a very slow rate following cessation of longitudinal bone growth [14, 15]. Also, in rats, as in humans, cancellous bone remodeling continues throughout adult life [16].

The goal of the present study was to determine whether increases in weight have an effect on bone mass, architecture, and turnover in skeletally mature 8-month-old female rats. This goal was accomplished by comparing the skeletal effects of 13 weeks of treatment using 3 dietary interventions: rats were caloric restricted to prevent further weight gain, fed the same diet ad lib to monitor normal weight gain, or fed the same diet slightly modified by isocaloric replacement of a small amount (0.5 % caloric intake) of maltose/dextran with alcohol to stimulate appetite and increase food consumption. Additionally, we evaluated accompanying changes in serum leptin levels as a potential mechanism for the anticipated effects of weight gain on bone metabolism.

Methods

Animal experiment

Eight-month-old, virgin, female Sprague-Dawley rats weighing 279 ± 3 g (mean ± SE) were obtained from Harlan Sprague-Dawley, Inc. (Indianapolis, IN, USA). The rats were housed individually in a temperature- and humidity-controlled animal facility on a 12-h light/dark cycle. All animal care and experimental procedures were approved by the Institutional Animal Care and Use Committee in accordance with the National Institutes of Health (NIH) Guide for the Care and Use of Laboratory Animals.

During the first week of the study, all animals were acclimated to a modified Lieber-DeCarli liquid diet (BioServe, Frenchtown, NJ), the use of which facilitated administration of alcohol and measurement of food consumption. The diet contained 1.3 g/liter calcium and 1.7 g/liter phosphorous. Protein, fat, and carbohydrates contributed 18, 35, and 47% of caloric intake, respectively.

Following acclimation, the rats were randomized by weight into four groups (n = 10/group); 1) a group sacrificed at treatment initiation (baseline), 2) a group fed the diet ad lib (control), 3) a group in which the amount of diet was restricted to prevent weight gain (calorie-restricted), and 4) a group fed the diet ad lib in which ethanol contributed 0.5% of caloric intake to induce increased food consumption (calorie-increased) [17]. In the calorie-increased group, alcohol isocalorically replaced maltose/dextran. The volume of food offered to the rats in the calorie-restricted group was adjusted daily to minimize changes in body weight. The rats consumed their respective diets for 13 weeks. All but baseline control rats were injected (20 mg/kg body weight) with the fluorochromes calcein (Sigma, St. Louis, MO) and demeclocycline (Sigma) 9 and 2 days before sacrifice, respectively, to label mineralizing bone.

For tissue collection, the rats were anesthetized using ketamine and xylazine, weighed, and decapitated. Trunk blood was collected for measurement of serum leptin and tibiae were harvested and fixed in 70% ethanol for bone dual energy absorptiometry (DXA) and histomorphometry.

Serum Leptin

Serum leptin was measured as a biochemical marker of fat mass by immunoassay as recommended by the manufacturer (R&D Systems, Minneapolis, MN).

DXA

Whole tibiae with attached fibulae were scanned ex vivo using DXA (PIXIMUS, Lunar Corporation, Madison, WI) to determine bone mineral content (BMC, mg), apparent tissue area of the bone and marrow, and bone mineral density (BMD, mg/cm2).

Histomorphometry

For histomorphometric evaluation of cancellous bone, proximal tibiae were dehydrated in a graded series of ethanol and xylene, and embedded undecalcified in modified methyl methacrylate. Longitudinal sections (5 μm thick) were cut with a vertical bed microtome (Leica 2065) and affixed to slides. One section/animal was used for determining bone area and fluorochrome-based measurements of bone formation.

Histomorphometric data were collected at 10x within the proximal tibial metaphysis using the OsteoMeasure System (OsteoMetrics, Inc., Atlanta, GA) as described [18]. The region of interest (2.9 mm2) included cancellous bone only. Static cancellous bone measurements included: 1) cancellous bone area/tissue area (area of total tissue evaluated that is occupied by cancellous bone, %), 2) trabecular thickness (μm), 3) trabecular number (1/mm), and 4) trabecular separation (μm). Fluorochrome-based indices of bone formation included: 1) mineralizing perimeter/bone perimeter (percentage of cancellous bone perimeter covered with double fluorochrome label, %), 2) mineral apposition rate (distance between two fluorochrome labels that comprise a double label divided by the number of days between label administration, μm/day), and bone formation rate (calculated using a perimeter referent (μm2/μm/day) as well as a bone area referent (%/year) as described [19]. All bone histomorphometric data are reported using standard nomenclature [20].

Statistics

Differences among treatment groups were determined using one-way ANOVA (SPSS 17.0, SPSS Inc., Chicago, IL). When significant treatment effects were detected, a Bonferroni post-hoc test was used to evaluate pair-wise differences. If ANOVA assumptions of homogeneity of variance were not met, a Kruskal-Walis test followed by a Tamhane post-hoc test was applied. A paired t-test was used to compare baseline and terminal body weight within a treatment group. Differences were considered significant at P < 0.05. All data are reported as mean ± SE.

Results

The effect of dietary interventions on body weight as a function of time is shown in Figure 1A. Caloric restriction was effective in preventing body weight gain. Compared to initial values, rats in the calorie-restricted group did not change significantly in body weight (−1 ± 2%) during the 13 week duration of study. In contrast, rats in the control group increased in weight by 10 ± 3% (P < 0.006) and those in the calorie-increased group increased in weight by 21 ± 2% (P<0.001) compared to initial values. At the end of the dietary intervention, the rats in the calorie-increased group were 15% (P< 0.001) heavier than rats fed the control diet.

Figure 1.

Figure 1

Open in a new tab

Effect of diet on body weight (A) and food consumption (B) as a function of time in 8-month-old female rats. The inset in Figure 1B represents total food consumed over the 13-week duration of study. Groups with different letters are different (P < 0.05) from one another. *Different from baseline, P<0.05. Values are mean ± SE.

Food intake as a function of time for the 3 treatment groups is shown in Figure 1B. The quantity of food required to maintain stable body weight in the calorie-restricted group was 19.8 ± 1.5% (P<0.001) less than that consumed by the control group. Rats fed a diet containing a small amount of alcohol (calorie-increased) consumed 20.4 ± 1.8% (P<0.001) more diet than rats in the control group. The total volume of diet consumed during the 13 week intervention by the calorie-restricted, control, and calorie-increased groups was 4,927 ± 89, 5,903 ± 105, and 7,109 ± 106 ml, respectively.

The effect of dietary intervention on serum leptin levels is shown in Figure 2. Compared to baseline, leptin levels were not significantly changed in the calorie-restricted group, and significantly higher in the control diet and calorie-increased diet groups by 183 ± 46% (P<0.028) and 607 ± 77% (P<0.002), respectively. At the end of the dietary intervention, the rats in the calorie-increased diet group had serum leptin levels that were 150 ± 27% (P<0.008) greater than the rats fed the control diet.

Figure 2.

Figure 2

Open in a new tab

Effect of diet on serum leptin levels at baseline and following 13 weeks of dietary intervention. Groups with same letter are not different (P > 0.05) from one another. Values are mean ± SE.

The effect of intervention on total tibia BMC and BMD is shown in Table 1. Tibial BMC and BMD in control rats sacrificed at baseline did not differ from the treatment groups sacrificed following the 13 weeks of dietary intervention. Furthermore, differences in BMC or BMD among treatment groups were not detected following dietary intervention.

Table 1.

Effect of body weight on tibial BMC and BMD.

Diet
Endpoint Baseline Control Calorie-restricted Calorie-increased ANOVA (P<)
Bone mineral content (mg) 0.34 ± 0.01 0.32 ± 0.01 0.33 ± 0.01 0.32 ± 0.01 NS
Bone mineral density (mg/cm2) 0.16 ± 0.01 0.15 ± 0.01 0.16 ± 0.01 0.16 ± 0.01 NS
Open in a new tab

Data are mean ± SE

The effects of treatments on static and dynamic bone histomorphometry of the proximal tibial metaphysis are shown in Table 2. Significant differences among treatment groups were not detected for cancellous bone area/tissue area, trabecular number, trabecular thickness, trabecular separation, mineralizing perimeter/bone perimeter, mineral apposition rate, or bone formation rates expressed relative to either bone perimeter or bone area referents.

Table 2.

Effect of body weight on bone histomorphometry in the proximal tibial metaphysis.

Diet
Control Calorie-restricted Calorie-increased ANOVA (P<)
Static Endpoints
 Bone area/Tissue area (%) 16.3 ± 2.5 17.1 ± 1.6 14.6 ± 2.5 NS
 Trabecular number (1/mm) 2.7 ± 0.2 3.0 ± 0.1 2.6 ± 0.2 NS
 Trabecular thickness (μm) 57 ± 6 55 ± 3 55 ± 4 NS
 Trabecular separation (μm) 343 ± 58 282 ± 20 341 ± 34 NS
Dynamic Endpoints
 Mineralizing perimeter/Bone perimeter (%) 8.2 ± 1.3 6.7 ±0.7 6.4 ± 1.2 NS
 Mineral apposition rate (μm/day) 0.76 ± 0.06 0.75 ± 0.03 0.72 ±0.04 NS
 Bone formation rate/Bone perimeter (μm2/μm/day) 0.062 ± 0.010 0.052 ± 0.006 0.046 ± 0.009 NS
 Bone formation rate/Bone area (%/day) 0.22 ± 0.03 0.19 ± 0.02 0.19 ± 0.05 NS
Open in a new tab

Data are mean ± SE

NS, Not significant

Discussion

Compared to ad lib feeding the standard diet, weight gain was prevented by caloric restriction and enhanced by increasing food intake through the addition of a small amount of alcohol in the diet. Body weight of the rats in the calorie-restricted, control, and calorie-increased groups changed compared to initial values by −1 ± 2%, 10 ± 3% and 21 ± 2%, respectively. A similar pattern among groups was observed for energy intake and serum leptin levels. In spite of the large differences in energy consumption and weight gain among treatment groups, significant intergroup differences were not detected in indices of bone mass, architecture, or dynamic histomorphometry.

The present studies evaluated BMC and BMD of whole tibia and cancellous bone mass, architecture and turnover in proximal tibial metaphysis of skeletally mature rats. The tibia is a weight bearing bone and can adapt to changes in mechanical loading. However, the effects of loading on bone are non-linear. Consistent with the mechanostat theory, bone responds to changes in muscle forces once a threshold level of loading is crossed [21, 22]. Large reductions in skeletal loading during disuse (e.g., spaceflight or immobilization) decrease bone formation and increase bone resorption [23, 24]. This uncoupling between formation and resorption results in rapid bone loss [25, 26]. However, increasing loads on the skeleton by up to 65% using weighted backpacks had no effect on cortical or cancellous bone histomorphometry or bone biomechanical properties in 12-month-old female rats [27]. This lack of an effect in normal rats was likely due to the failure to increase loads sufficient to induce an adaptive response. In comparison, simple jumps in humans generate ground reaction forces 3–5 times resting body weight, and 45 minutes of such activity/day results in rates of force that are 500 times greater than body weight [28]. Thus, based on the magnitude of the changes in body weight observed in the present study, it is not entirely surprising that bone mass did not differ among treatment groups.

There is discussion in the literature as to whether bone mass should be adjusted to body weight and if so whether it should be adjusted to total or lean mass [29–31]. In the present study, the amount of bone mass per unit body weight decreased in the two ad lib fed groups compared to the calorie-restricted group by an amount proportional to the increase in body weight. Adjustment of bone mass to body weight implies that there is a consistent causal relationship between the two endpoints. However, the weight of evidence does not support a tight relationship. BMC and BMD typically increase with bodyweight up to skeletal maturity, but the present study suggests that the relationship is much less pronounced in adults. Even in growing animals, the relationship between bone mass and body weight is neither linear nor constant among skeletal sites. In inbred mice fed a normal diet, differences in body weight explain 35–75% of the variation in bone mass. Furthermore, the precise relationship between body weight and bone mass depends upon the individual bone (e.g., femur versus 3rd lumbar vertebra) and region (diaphysis versus metaphysis) measured [8]. These observations argue strongly against indiscriminant normalization of bone mass to body weight as an index of bone health.

Increased weight gain in the present study was associated with increased serum leptin levels. The adipokine leptin is produced in proportion to fat mass and serum levels of the hormone reflect energy stored in fat [32]. Leptin plays a key role in energy homeostasis by influencing food consumption and non-shivering thermogenesis [33, 34]. However, the rise in leptin levels observed in the present studies had no clear cut effect on food consumption or weight gain.

There is evidence that bone metabolism is coupled to energy homeostasis through leptin signaling [35, 36]. In support of a critical role for leptin signaling, leptin-deficient ob/ob mice have multiple skeletal abnormalities which are corrected by systemic or central leptin administration or by hypothalamic leptin gene therapy [12]. ob/ob mice and leptin receptor-deficient mice (db/db) and rats (Zucker fa/fa) are morbidly obese but, even without adjusting for the increase in body weight, have low bone mass compared to lean littermates [8, 36, 37]. These findings in leptin signaling-deficient rodents suggest that leptin may play a role in mediating the increase in bone mass associated with excessive weight gain. However, studies performed in lean wild type and ob/ob mice fed normal and high fat diets illustrate that body weight gain has both independent, as well as leptin-dependent, effects on bone mass and architecture [8].

Although leptin is essential for normal bone growth and turnover, similar to its action on reproduction [38], the hormone may act on the skeleton as a permissive off/on factor. Whereas administration of leptin to leptin-deficient ob/ob mice has a profound effect on bone metabolism, there is a notable lack of an effect in leptin-replete animals [39, 40]. The results of the present study further support the conclusion that the skeletal actions of leptin are largely permissive because substantial increases in body weight with correspondingly large increases in serum leptin levels within the physiological range had no effect on bone mass, architecture, or turnover in skeletally mature female rats.

Increases in body weight can be induced in rodents by feeding them energy dense high fat diets. Bone compartment-specific increases and decreases in bone mass have been reported in growing mice fed high fat diets [8, 41]. A limitation of comparing high and normal fat diets is that it is difficult to distinguish between the effects of weight gain and those caused by differences in composition of the diets. In the present study, the major cause for the differences in weight gain among treatment groups was the volume of food consumed. The diet of the calorie-increased group contained ethanol, which in total contributed only 0.5% of caloric intake. Alcohol stimulates appetite in humans [42, 43]. Whereas high concentrations of alcohol suppress appetite in rats [19], the small amount used in the present study significantly increased the volume of food consumed and facilitated body weight gain. This finding was anticipated because we had noted increased food consumption with low levels of alcohol consumption in dose-response studies in rats [17].

Alcohol itself has potent effects on bone metabolism. In adult female rats, dose-response studies revealed that levels of alcohol consumed by moderate drinkers (3 and 6% caloric intake) reduced bone turnover without impacting bone mass [17]. However, we found that alcohol consumption of 1 or 2% caloric intake had no significant effect on bone histomorphometry (unpublished results). Thus, it is unlikely that the even lower level of alcohol used to stimulate appetite in the current study had independent effects on bone metabolism.

Dietary restriction, resulting in reduced weight gain during growth [44], or a reduction in body weight in adults loss [45–49], is accompanied by decreased bone formation and/or increased bone resorption. Since bone formation requires energy, it is not surprising that reduced bone formation occurs when energy is severely restricted. Although there were marked differences in food intake, serum leptin levels, and body weight among treatment groups in the current study, even the calorie-restricted group was fed sufficient energy to maintain body weight. Thus, the present study demonstrates that weight gain, over the range studied, in skeletally mature female rats had neither beneficial nor detrimental effects on bone mass, architecture, or turnover. Furthermore, the results do not support a role for serum leptin, over the range evaluated, in regulating bone metabolism in skeletally mature female rats.

Acknowledgments

These studies were supported by NIH grants AA 011140 (to R.T. Turner) and AR 054609 (to U.T. Iwaniec).

Footnotes

Conflict of Interest: The authors have no conflict of interest.

Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

References Cited

  • 1.Hjartaker A, Langseth H, Weiderpass E. Obesity and diabetes epidemics: cancer repercussions. Adv Exp Med Biol. 2008;630:72–93. doi: 10.1007/978-0-387-78818-0_6. [DOI] [PubMed] [Google Scholar]
  • 2.Low S, Chin MC, Deurenberg-Yap M. Review on epidemic of obesity. Ann Acad Med Singapore. 2009;38:57–9. [PubMed] [Google Scholar]
  • 3.Franssen FM, O’Donnell DE, Goossens GH, Blaak EE, Schols AM. Obesity and the lung: 5. Obesity and COPD. Thorax. 2008;63:1110–7. doi: 10.1136/thx.2007.086827. [DOI] [PubMed] [Google Scholar]
  • 4.Magliano M. Obesity and arthritis. Menopause Int. 2008;14:149–54. doi: 10.1258/mi.2008.008018. [DOI] [PubMed] [Google Scholar]
  • 5.Misra A, Khurana L. Obesity and the metabolic syndrome in developing countries. J Clin Endocrinol Metab. 2008;93:S9–30. doi: 10.1210/jc.2008-1595. [DOI] [PubMed] [Google Scholar]
  • 6.De Laet C, Kanis JA, Oden A, Johanson H, Johnell O, Delmas P, Eisman JA, Kroger H, Fujiwara S, Garnero P, McCloskey EV, Mellstrom D, Melton LJ, 3rd, Meunier PJ, Pols HA, Reeve J, Silman A, Tenenhouse A. Body mass index as a predictor of fracture risk: a meta-analysis. Osteoporos Int. 2005;16:1330–8. doi: 10.1007/s00198-005-1863-y. [DOI] [PubMed] [Google Scholar]
  • 7.El Hage R, Jacob C, Moussa E, Benhamou CL, Jaffre C. Total body, lumbar spine and hip bone mineral density in overweight adolescent girls: decreased or increased? J Bone Miner Metab. 2009;27:629–33. doi: 10.1007/s00774-009-0074-6. [DOI] [PubMed] [Google Scholar]
  • 8.Iwaniec UT, Dube MG, Boghossian S, Song H, Helferich WG, Turner RT, Kalra SP. Body mass influences cortical bone mass independent of leptin signaling. Bone. 2009;44:404–12. doi: 10.1016/j.bone.2008.10.058. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Kuwahata A, Kawamura Y, Yonehara Y, Matsuo T, Iwamoto I, Douchi T. Non-weight-bearing effect of trunk and peripheral fat mass on bone mineral density in pre- and post-menopausal women. Maturitas. 2008;60:244–7. doi: 10.1016/j.maturitas.2008.07.005. [DOI] [PubMed] [Google Scholar]
  • 10.Gat-Yablonski G, Phillip M. Leptin and regulation of linear growth. Curr Opin Clin Nutr Metab Care. 2008;11:303–8. doi: 10.1097/MCO.0b013e3282f795cf. [DOI] [PubMed] [Google Scholar]
  • 11.Hamrick MW, Pennington C, Newton D, Xie D, Isales C. Leptin deficiency produces contrasting phenotypes in bones of the limb and spine. Bone. 2004;34:376–83. doi: 10.1016/j.bone.2003.11.020. [DOI] [PubMed] [Google Scholar]
  • 12.Iwaniec UT, Boghossian S, Lapke PD, Turner RT, Kalra SP. Central leptin gene therapy corrects skeletal abnormalities in leptin-deficient ob/ob mice. Peptides. 2007;28:1012–9. doi: 10.1016/j.peptides.2007.02.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13.Steppan CM, Crawford DT, Chidsey-Frink KL, Ke H, Swick AG. Leptin is a potent stimulator of bone growth in ob/ob mice. Regul Pept. 2000;92:73–8. doi: 10.1016/s0167-0115(00)00152-x. [DOI] [PubMed] [Google Scholar]
  • 14.Martin EA, Ritman EL, Turner RT. Time course of epiphyseal growth plate fusion in rat tibiae. Bone. 2003;32:261–7. doi: 10.1016/s8756-3282(02)00983-3. [DOI] [PubMed] [Google Scholar]
  • 15.Turner RT, Spelsberg TC. Correlation between mRNA levels for bone cell proteins and bone formation in long bones of maturing rats. Am J Physiol. 1991;261:E348–53. doi: 10.1152/ajpendo.1991.261.3.E348. [DOI] [PubMed] [Google Scholar]
  • 16.Iwaniec UT, Turner RT. Animal models for osteoporosis. In: Marcus R, Feldman D, Nelson DA, Rosen CJ, editors. Osteoporosis. 3. Boston: Elsevier; 2008. pp. 985–1009. [Google Scholar]
  • 17.Turner RT, Kidder LS, Kennedy A, Evans GL, Sibonga JD. Moderate alcohol consumption suppresses bone turnover in adult female rats. J Bone Miner Res. 2001;16:589–94. doi: 10.1359/jbmr.2001.16.3.589. [DOI] [PubMed] [Google Scholar]
  • 18.Westerlind KC, Wronski TJ, Ritman EL, Luo ZP, An KN, Bell NH, Turner RT. Estrogen regulates the rate of bone turnover but bone balance in ovariectomized rats is modulated by prevailing mechanical strain. Proc Natl Acad Sci U S A. 1997;94:4199–204. doi: 10.1073/pnas.94.8.4199. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19.Maddalozzo GF, Turner RT, Edwards CH, Howe KS, Widrick JJ, Rosen CJ, Iwaniec UT. Alcohol alters whole body composition, inhibits bone formation, and increases bone marrow adiposity in rats. Osteoporos Int. 2009;20:1529–1538. doi: 10.1007/s00198-009-0836-y. [DOI] [PubMed] [Google Scholar]
  • 20.Parfitt AM, Drezner MK, Glorieux FH, Kanis JA, Malluche H, Meunier PJ, Ott SM, Recker RR. Bone histomorphometry: standardization of nomenclature, symbols, and units. Report of the ASBMR Histomorphometry Nomenclature Committee. J Bone Miner Res. 1987;2:595–610. doi: 10.1002/jbmr.5650020617. [DOI] [PubMed] [Google Scholar]
  • 21.Ferretti JL, Capozza RF, Cointry GR, Capiglioni R, Roldan EJ, Zanchetta JR. Densitometric and tomographic analyses of musculoskeletal interactions in humans. J Musculoskelet Neuronal Interact. 2000;1:31–4. [PubMed] [Google Scholar]
  • 22.Petit MA, Beck TJ, Shults J, Zemel BS, Foster BJ, Leonard MB. Proximal femur bone geometry is appropriately adapted to lean mass in overweight children and adolescents. Bone. 2005;36:568–76. doi: 10.1016/j.bone.2004.12.003. [DOI] [PubMed] [Google Scholar]
  • 23.Hefferan TE, Evans GL, Lotinun S, Zhang M, Morey-Holton E, Turner RT. Effect of gender on bone turnover in adult rats during simulated weightlessness. J Appl Physiol. 2003;95:1775–80. doi: 10.1152/japplphysiol.00455.2002. [DOI] [PubMed] [Google Scholar]
  • 24.Turner RT. Invited review: what do we know about the effects of spaceflight on bone? J Appl Physiol. 2000;89:840–7. doi: 10.1152/jappl.2000.89.2.840. [DOI] [PubMed] [Google Scholar]
  • 25.Bikle DD, Halloran BP. The response of bone to unloading. J Bone Miner Metab. 1999;17:233–44. doi: 10.1007/s007740050090. [DOI] [PubMed] [Google Scholar]
  • 26.Turner CH, Pavalko FM. Mechanotransduction and functional response of the skeleton to physical stress: the mechanisms and mechanics of bone adaptation. J Orthop Sci. 1998;3:346–55. doi: 10.1007/s007760050064. [DOI] [PubMed] [Google Scholar]
  • 27.Buhl KM, Jacobs CR, Turner RT, Evans GL, Farrell PA, Donahue HJ. Aged bone displays an increased responsiveness to low-intensity resistance exercise. J Appl Physiol. 2001;90:1359–64. doi: 10.1152/jappl.2001.90.4.1359. [DOI] [PubMed] [Google Scholar]
  • 28.McKay H, Tsang G, Heinonen A, MacKelvie K, Sanderson D, Khan KM. Ground reaction forces associated with an effective elementary school based jumping intervention. Br J Sports Med. 2005;39:10–14. doi: 10.1136/bjsm.2003.008615. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 29.Crepaldi G, Romanato G, Tonin P, Maggi S. Osteoporosis and body composition. J Endocrinol Invest. 2007;30:42–7. [PubMed] [Google Scholar]
  • 30.Reid IR. Relationships between fat and bone. Osteoporos Int. 2008;19:595–606. doi: 10.1007/s00198-007-0492-z. [DOI] [PubMed] [Google Scholar]
  • 31.Zhao LJ, Jiang H, Papasian CJ, Maulik D, Drees B, Hamilton J, Deng HW. Correlation of obesity and osteoporosis: effect of fat mass on the determination of osteoporosis. J Bone Miner Res. 2008;23:17–29. doi: 10.1359/JBMR.070813. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Fried SK, Ricci MR, Russell CD, Laferrere B. Regulation of leptin production in humans. J Nutr. 2000;130:3127S–3131S. doi: 10.1093/jn/130.12.3127S. [DOI] [PubMed] [Google Scholar]
  • 33.Bates SH, Dundon TA, Seifert M, Carlson M, Maratos-Flier E, Myers MG., Jr LRb-STAT3 signaling is required for the neuroendocrine regulation of energy expenditure by leptin. Diabetes. 2004;53:3067–73. doi: 10.2337/diabetes.53.12.3067. [DOI] [PubMed] [Google Scholar]
  • 34.Ueno N, Inui A, Kalra PS, Kalra SP. Leptin transgene expression in the hypothalamus enforces euglycemia in diabetic, insulin-deficient nonobese Akita mice and leptin-deficient obese ob/ob mice. Peptides. 2006;27:2332–42. doi: 10.1016/j.peptides.2006.03.006. [DOI] [PubMed] [Google Scholar]
  • 35.Hamrick MW, Ding KH, Ponnala S, Ferrari SL, Isales CM. Caloric restriction decreases cortical bone mass but spares trabecular bone in the mouse skeleton: implications for the regulation of bone mass by body weight. J Bone Miner Res. 2008;23:870–8. doi: 10.1359/jbmr.080213. [DOI] [PubMed] [Google Scholar]
  • 36.Hamrick MW, Ferrari SL. Leptin and the sympathetic connection of fat to bone. Osteoporos Int. 2008;19:905–12. doi: 10.1007/s00198-007-0487-9. [DOI] [PubMed] [Google Scholar]
  • 37.Tamasi JA, Arey BJ, Bertolini DR, Feyen JH. Characterization of bone structure in leptin receptor-deficient Zucker (fa/fa) rats. J Bone Miner Res. 2003;18:1605–11. doi: 10.1359/jbmr.2003.18.9.1605. [DOI] [PubMed] [Google Scholar]
  • 38.Moschos S, Chan JL, Mantzoros CS. Leptin and reproduction: a review. Fertil Steril. 2002;77:433–44. doi: 10.1016/s0015-0282(01)03010-2. [DOI] [PubMed] [Google Scholar]
  • 39.Duan J, Choi YH, Hartzell D, Della-Fera MA, Hamrick M, Baile CA. Effects of subcutaneous leptin injections on hypothalamic gene profiles in lean and ob/ob mice. Obesity (Silver Spring) 2007;15:2624–33. doi: 10.1038/oby.2007.314. [DOI] [PubMed] [Google Scholar]
  • 40.Hamrick MW, Della-Fera MA, Choi YH, Pennington C, Hartzell D, Baile CA. Leptin treatment induces loss of bone marrow adipocytes and increases bone formation in leptin-deficient ob/ob mice. J Bone Miner Res. 2005;20:994–1001. doi: 10.1359/JBMR.050103. [DOI] [PubMed] [Google Scholar]
  • 41.Cao JJ, Gregoire BR, Gao H. High-fat diet decreases cancellous bone mass but has no effect on cortical bone mass in the tibia in mice. Bone. 2009;44:1097–104. doi: 10.1016/j.bone.2009.02.017. [DOI] [PubMed] [Google Scholar]
  • 42.Caton SJ, Ball M, Ahern A, Hetherington MM. Dose-dependent effects of alcohol on appetite and food intake. Physiol Behav. 2004;81:51–8. doi: 10.1016/j.physbeh.2003.12.017. [DOI] [PubMed] [Google Scholar]
  • 43.Yeomans MR. Effects of alcohol on food and energy intake in human subjects: evidence for passive and active over-consumption of energy. Br J Nutr. 2004;92 (Suppl 1):S31–4. doi: 10.1079/bjn20041139. [DOI] [PubMed] [Google Scholar]
  • 44.Devlin M, Cloutier A, Thomas N, Panus D, Lotinun S, Pinz I, Baron R, Rosen C, Bouxsein M. Caloric restriction leads to high marrow adiposity and low bone mass in growing mice. J Bone Miner Res. doi: 10.1002/jbmr.82. In Press. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45.Meyer HE, Tverdal A, Selmer R. Weight variability, weight change and the incidence of hip fracture: a prospective study of 39,000 middle-aged Norwegians. Osteoporos Int. 1998;8:373–8. doi: 10.1007/s001980050077. [DOI] [PubMed] [Google Scholar]
  • 46.Park HA, Lee JS, Kuller LH, Cauley JA. Effects of weight control during the menopausal transition on bone mineral density. J Clin Endocrinol Metab. 2007;92:3809–15. doi: 10.1210/jc.2007-1040. [DOI] [PubMed] [Google Scholar]
  • 47.Prouteau S, Benhamou L, Courteix D. Relationships between serum leptin and bone markers during stable weight, weight reduction and weight regain in male and female judoists. Eur J Endocrinol. 2006;154:389–95. doi: 10.1530/eje.1.02103. [DOI] [PubMed] [Google Scholar]
  • 48.Sogaard AJ, Meyer HE, Tonstad S, Haheim LL, Holme I. Weight cycling and risk of forearm fractures: a 28-year follow-up of men in the Oslo Study. Am J Epidemiol. 2008;167:1005–13. doi: 10.1093/aje/kwm384. [DOI] [PubMed] [Google Scholar]
  • 49.Wucher H, Ciangura C, Poitou C, Czernichow S. Effects of weight loss on bone status after bariatric surgery: association between adipokines and bone markers. Obes Surg. 2008;18:58–65. doi: 10.1007/s11695-007-9258-0. [DOI] [PubMed] [Google Scholar]

RESOURCES