Table 1.
Preclinical studies (rodent models) addressing the effects of different single-strain probiotics on diet-induced NAFLD.
| Reference | Animal Model | Experimental Conditions | Probiotic Treatment | Effects on Liver | Mechanisms of Action |
|---|---|---|---|---|---|
| [32] | Female C57BL/J6 mice 6-week-old |
STD diet with 30% fructose in drinking water. |
L. rhamnosus GG—LGG Daily administration Dose: 5.2 × 107 CFU/bw g/d. Diluted in drinking water Treatment length: 8 w. |
↓ Liver fat accumulation ↓ Liver TG content ↓ Serum ALT levels ↓ Liver inflammation |
Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Acc, Fas and Chrebp. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Il-1β, Il-8R, Tnfα and Il-12. Decreased portal levels of LPS. Up-regulation of markers of intestinal mucosa integrity: ↑ Protein expression of Occludin-1 and Claudin-1. |
| [16] | Male C57BL/6 mice 4-week-old |
HFD (60% energy from fat). |
L. rhamnosus GG—LGG Oral daily administration Dose: 1 × 108 CFU/day Treatment length: 13 w. |
↓ Liver weight ↓ Liver fat accumulation ↓ Liver inflammation |
Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Srebp-1 and Ppar-γ. Down-regulation of genes related to long-chain fatty acid uptake and lipoprotein synthesis: ↓ Gene expression of Cd36 and ApoB100. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Il-6, Il-12, F4/80 and Cd11b. Modulation of gut microbiota composition: ↑ Proportion of Bacteroidetes. |
| [17] | Male C57BL/6 mice 4-week-old |
HFD. |
L. paracasei N1115 Oral daily administration Dose: 2.2 × 109 CFU/mL diluted in normal saline (0.5 mL/day). Treatment length: 16 w. |
↓ Liver fat accumulation ↓ Liver inflammation ↓ Liver fibrosis |
Decreased content of hepatic inflammatory mediators (Tnfα and IL-1β). Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Nf-κB, Tlr-4 and Lps. Decreased serum levels of liver fibrosis markers (MAO). Up-regulation of markers of intestinal mucosa integrity: ↑ Protein expression of Occludin-1 and Claudin-1. |
| [33] | Female C57BL/6N mice 6–8-week-old |
STD diet with 30% fructose in drinking water. |
L. rhamnosus Oral daily gavage Dose:1 × 109 CFU/day. Treatment length: 5 or 12 w. |
↓ Liver fat accumulation ↓ Liver TG, TC and VLDL content ↓ Liver inflammation ↓ Liver apoptotic cells |
Down-regulation of liver injury protection markers: ↑ Gene expression of Fgf21. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Tnfα and Cxcl10. Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Fas, Srebp1c and Scd1. ↓ Protein expression of SREBP1c and ChREBP. Up-regulation of fatty acid oxidation markers in the liver: ↑ Gene expression of CPT1 and PPARα. Down-regulation of markers involved in hepatic ceramide content: ↓ Methylation of PP2AC. |
| [34] | Male C57BL/6N mice 8-week-old |
HFD/F (65% energy from fat and 30% fructose solution). |
L. plantarum NA136 group Oral daily administration Dose: 1 × 109 CFU/day. Treatment length: 16 w. |
↓ Liver fat accumulation ↓ Liver FFA content ↓ Liver inflammation ↓ Liver ALT and AST levels |
Down-regulation of lipogenic markers in the liver: ↓ Protein expression of FAS and SREBP-1. ↑ Phosphorylation of ACC. Up-regulation of energy yielding pathways in the liver: ↑ Phosphorylation of AMPK. Down-regulation of oxidative stress in the liver: ↓ Content of MDA. ↑ Protein expression of HO-1 andNrf2. ↑ Content of CAT. ↑ Activity of SOD. |
| [18] | Male SPF C57BL/6J mice 6-week-old |
Normal or Western diet (42% energy from fat). |
L. bulgaricus L. casei L. helveticus P. pentosaceus KID7 Daily administration Dose: 1 × 109 CFU/g suspended in distilled water. Treatment length: 8 w. |
↓ Liver steatosis grade (all treated groups) ↓ Liver inflammation (all treated groups except animals receiving L. casei) ↓ Liver/bw ratio (groups treated with L. bulgaricus, L. helveticus and P. pentosaceus) ↓ Liver AST levels (groups treated with L. bulgaricus and L. helveticus) ↓ Liver ALT levels (group treated with L. bulgaricus) ↓ NAS (groups treated with L. bulgaricus, L. helveticus and P. pentosaceus) |
Down-regulation of macrophage markers in the liver: ↓ Expression of Cd68 (groups treated with L. bulgaricus, L. helveticus, L. casei and P. pentosaceus). Modulation of gut microbiota composition: ↓ F/B ratio (groups treated with L. bulgaricus, L. helveticus, P. pentosaceus and L. casei). ↑ Content of A. muciniphila (groups treated with L. bulgaricus, L. helveticus and L. casei). Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Tnfα Il-6 and Il-1β (in all the treated groups). |
| [19] | Male Swiss mice 4-week-old |
HFD (61% energy from fat). |
B. longum Daily oral gavage Dose: 5 × 109 CFU/kg bw/d Treatment length: 4 w. |
↓ Liver lipid droplet size | Up-regulation of RAS related genes in the liver: ↑ Gene expression of Ace2 and Masr. |
| [20] | Male C57BL/6N mice 6-week-old |
HFD. Animals also received a 10% fructose solution. |
L. fermentum—CQPC06 L. delbrueckii subsp. Bulgaricus—LDSB Daily oral gavage Dose of 1 × 109 CFU/kg bw/d (L. fermentum—CQPC06) or 1 × 1010 CFU/kg bw/d (L. fermentum—CQPC06 and L. delbrueckii subsp. Bulgaricus—LDSB) suspended in sterile saline. Treatment length: 8 w. |
↓ Liver weight and index ↓ Liver TG ↓ Serum and liver AST and ALT levels ↓ Serum and liver AKP levels |
Decreased ROS levels in the livers of animals receiving L. fermentum—CQPC06 (at both doses) and L. delbrueckii subsp. Bulgaricus—LDSB. Up-regulation of fatty acid oxidation markers in the liver (L. fermentum—CQPC06 (at both doses)): ↑ Gene expression of Cpt1 and Ppar-α. ↑ Protein expression of CPT1 and PPAR-α. Down-regulation of lipogenic markers in the liver (L. fermentum—CQPC06 (at both doses)): ↓ Gene expression of C/ebp-α and Ppar-γ. ↓ Protein expression of C/EBP-α and PPAR-γ. Up-regulation of markers of intestinal mucosa integrity (L. fermentum—CQPC06 (at both doses)): ↑ Protein expression of ZO-1, Occludin and Claudin-1. Modulation of gut microbiota composition (L. fermentum—CQPC06 (at both doses) and L. delbrueckii subsp. Bulgaricus—LDSB): ↓ F/B ratio. ↑ Content of Akkermansia. |
| [21] | Female C57BL/6 mice |
WSD (40% energy from fat). |
L. rhamnosus GG ATCC 53103 L. lactis subsp. cremoris ATCC 19257 Oral gavage Thrice weekly Dose: 1 × 109 CFU Treatment length: 16 w. |
↓ Liver weight (group treated with L. cremoris) ↓ Liver PC, PS, TG and TG content (group treated with L. cremoris) ↓ Liver lipid droplet area (group treated with L. cremoris) ↓ Liver inflammation (group treated with L. cremoris) |
Down-regulation of hepatic content of lipids related to pro-inflammatory response: ↓ Levels of ARA containing lipids (group treated with L. cremoris). Down-regulation of inflammation associated metabolites in the liver: ↓ Levels of Resolvin E1, 9-HETE and 9HpODE (group treated with L. cremoris). |
| [22] | Male C57BL/6J mice 6-week-old |
HFD (45% energy from fat). |
L. reuteri 6475 L. reuteri VPL3461 Daily oral gavage (in a volume of 100 μL) Dose of 1 × 109 CFU/mL Treatment length: 8 w. |
↓ Liver TG content (all groups) | Not specified. |
| [23] | Male C57BL/6N mice 3–4-weeks-old |
HFD (42% energy from fat). |
L. rhamnosus GG Daily administration Dose: 1 × 108 CFU/day mixed in the experimental diet. Treatment length: 17 w. |
↓ Liver weight ↓ Liver TG content |
Modulation of SCFA levels in the cecum: ↑ Acetate levels. Modulation of SCFA in the liver: ↑ Acetate levels. Modulation of anti-inflammatory lipid mediator levels: ↓ ώ6/ώ 3 PUFA ratio. |
| [37] | Male C57BL/6N mice 8-week-old |
HFD/F (65% energy from fat and 30% dietary volume provided as fructose solution). |
L. plantarum NA136 Daily oral administration daily Dose: 1 × 109 CFU/day. Treatment length: 16 w. |
↓ Liver lipid content | Modulation of gut microbiota composition: ↑ Bacterial richness and diversity. Up-regulation of intestinal mucosa integrity markers: ↑ Protein expression of tight-junction markers (ZO-1, Occludin, Claudin-1). ↓ Protein expression mucosal dysfunction markers (HIF-1α). Decreased serum levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) and LPS. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Protein expression of NF-κB. ↓ Phosphorylation of p38. |
| [24] | Male SPF C57BL/6J mice 6-week-old |
WSD (42% energy from fat). |
L. acidophilus L. fermentum L. paracasei L. plantarum Daily administration Dose: 1 × 109 CFU suspended in drinking water. Treatment length: 8 w. |
↓ Liver steatosis score (groups treated with L. paracasei, L. plantarum and L. acidophilus) ↓ Liver TG content (groups treated with L. acidophilus, L. fermentum and L. paracasei) |
Modulation of microbiota composition: ↑ Bacteroidetes content (group treated with L. paracasei). ↓ Firmicutes content (group treated with L. paracasei). |
| [25] | Male Sprague-Dawley rats |
HFD |
L. acidophilus CGMCC 2106. B. longum CGMCC 2107. Daily administration Dose: 1 × 1010 CFU/mL suspended in drinking water. Treatment length: 12 w. |
↓ Liver fat accumulation (group treated with B. longum) | Modulation of fecal microbiota composition: ↑ Bifidobacterium content (group treated with B. longum). ↑ Lactobacillus content (group treated with L. acidophilus). |
| [36] | Male Fischer 344 rats | CDAA diet (30% energy from fat). Animals were fed ad libitum and had free access to drinking water during the whole experiment. |
C. butyricum Daily administration Dose: 8.5 × 109 CFU/g mixed in the diet. Treatment length: 42 w. |
↓ Liver total lipid and TG content ↓ Liver inflammation ↓ NAFLD progression (fibrosis) ↓ Serum ALT levels ↓ Liver lipid peroxidation ↓ Oxidative stress |
Up-regulation of energy yielding pathways in the liver: ↑ Phosphorylation of AMPK. Up-regulation of fatty acid oxidation markers in the liver: ↑ Protein expression of PPARα. Down-regulation of lipogenic markers in the liver: ↓ Protein expression of SREBP-1c and PPAR-γ. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Protein expression of NF-kB and TNF-α. Down-regulation of lipid peroxidation markers in the liver: ↓ Content of 4-HNE and MDA. Up-regulation of antioxidant markers in the liver: ↑ Protein expression of Nrf2 and HO-1. Up-regulation of markers of intestinal mucosa integrity: ↑ Protein expression of ZO1 and Ocln. |
| [26] | Male Sprague-Dawley rats |
HFD. |
L. plantarum NCU116-L L. plantarum NCU116-H Daily administration Dose: 1 × 108 CFU/mL (L. plantarum NCU116-L) or 1 × 109 CFU/mL (L. plantarum NCU116-H) suspended in a sterile saline solution. Treatment length: 5 w. |
↓ Liver AST levels (group treated with L. plantarum NCU116-H) ↓ Liver oxidative stress ↓ Liver TC and TG content ↓ Liver inflammation |
Down-regulation of oxidative stress markers in liver: ↓ MDA content (group treated with L. plantarum NCU116-H). Up-regulation of antioxidant markers in the liver: ↑ Activity of SOD and GPx (all groups). ↑ Activity of CAT (group treated with L. plantarum NCU116-H). ↑ T-AOC (all groups). Down-regulation of serum pro-inflammatory cytokines: ↓ Levels of LPS and IL-6 (all groups). ↓ Levels of TNFα (L. plantarum NCU116-H). Up-regulation of fatty acid oxidation and lipolysis markers in the liver: ↑ Gene expression of Pparα, Pparγ, Pparδ, Pgc1α and Cpt1α (all groups). Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Fas, Acc and Scd1 (all groups). Modulation of colonic microbiota composition: ↓ Gene expression of Bacteroides (all groups). ↑ Gene expression of Lactobacillus spp. and Bifidobacterium spp. (all groups). |
| [24] | Male Wistar rats |
HFD (60% energy from fat). |
L. paracasei Jlus66 Daily oral administration Doses: 1, 2 or 4 × 1010 CFU/d. Treatment length: 20 w. |
↓ Liver weight ↓ Liver fat accumulation ↓ Liver inflammation ↓ Serum ALT levels (high dose) |
Not specified. |
| [35] | Male Sprague-Dawley Rats 42-day-old |
STD plus 20% fructose in drinking water. |
L. acidophilus B. coagulans L. casei L. reuteri Daily administration Dose: 1 × 109 CFU/mL suspended in drinking water. Treatment length: 16 w. |
↓ Liver TG content (groups treated with L. acidophilus and L. reuteri) ↓ Serum ALT levels (all groups) ↓ Liver oxidative stress (all groups) |
Up-regulation of antioxidant response in the liver: ↑ Content of glutathione (groups treated with L. acidophilus and L. casei). ↓ Liver ROS formation (groups treated with L. acidophilus, L. casei and B. coagulans). ↓ Liver protein-carbonylation (all groups). ↓ Liver lipid peroxidation (all groups). |
| [28] | Sprague-Dawley rats 8-week-old |
HFD 54% energy from fat). Animals were injected with 600 mg/kg/day of D-galactose daily. |
L. fermentum DR9 L. plantarum DR7 L. reuteri 8513d Daily administration Dose: 1 × 1010 CFU/day dissolved in 100 μL of saline and mixed into 1 g of experimental diet. Treatment length: 12 w. |
↓ Liver lipid content (groups treated with L. fermentum DR9, L. plantarum DR7 and L. reuteri 8513d) ↓ Liver inflammation (groups treated with L. fermentum DR9, L. plantarum DR7 and L. reuteri 8513d) ↓ Liver ALP content (groups treated with L. fermentum DR9 and L. plantarum DR7) |
Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Scd1 gene expression (groups treated with L. fermentum DR9 and L. plantarum DR7). Decreased liver content of pro-inflammatory cytokines: ↓ IL-4 levels (groups treated with L. fermentum DR9 and L. plantarum DR7). Up-regulation of energy yielding pathways in the liver: ↑ Gene expression of Ampkα1 (groups treated with L. fermentum DR9 and L. plantarum DR7) and Ampkα2 gene expression (group treated with L. plantarum DR7). |
| [16] | Male Wistar Rats 6-week-old |
HFD (45% of energy from fat). Animals also received 10% fructose in drinking water. |
L. Plantarum strain ATG-K2 L. Plantarum strain ATG-K6 Daily oral gavage Dose: 5 × 108 CFU/d. Treatment length: 8 w. |
↓ Liver TG and TC content ↓ Serum AST and ALT levels (all groups) ↓ Serum ALP levels (all groups) ↓ Liver lipid peroxidation |
Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Srebp-1c and Fas (all groups). ↓ Protein expression of SREBP-1c (group treated with L. Plantarum strain ATG-K6). ↓ Protein expression of FAS (all groups). ↓ Protein expression of C/EBP (group treated with L. Plantarum strain ATG-K2). ↑ Phosphorylation of ACC (group treated with L. Plantarum strain ATG-K2). Up-regulation of energy yielding pathways in the liver: ↑ Phosphorylation of AMPK (group treated with L. Plantarum strain ATG-K2). Up-regulation of fatty acid oxidation markers in the liver: ↑ Protein expression of CPT-1 (group treated with L. Plantarum strain ATG-K2). Decreased liver MDA content. Modulation of gut microbiota composition: ↓ Relative abundance of Firmicutes (all groups). ↑ Relative abundance of Bacteroidetes (all groups). |
| [30] | Male Wistar rats | HFD (60% energy from fat). |
B. animalis subsp. Lactis
V9 Daily oral gavage Dose: 1 × 109 CFU/mL. Treatment length: 4 w. |
↓ Liver TG and FFA content ↓ Serum AST and ALT levels ↓ Liver inflammation ↓ Progression to NASH |
Down-regulation of lipogenic markers in the liver: ↓ Gene expression of Srebp-1c and Fas. Up-regulation of fatty acid oxidation markers in the liver: ↑ Gene expression of Pparα. Up-regulation of energy yielding pathways in the liver: ↑ Phosphorylation of AMPK. Down-regulation of NASH progression markers in the liver: ↓ Gene expression of Nlrp3, Asc, Tlr-4 and Tlr-9. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Tnfα, IL-1β and IL-6. ↓ Phosphorylation of JNK, NF-kB, ERK and AKT. |
| [31] | Male Sprague-Dawley rats |
HFD (45% energy from fat). |
Eosinophil-Lactobacillus Daily oral gavage (312 mg/kg). Dose: 1 × 107 CFU/g. Treatment length: 8 w. |
↓ Liver lipid content ↓ Liver inflammation ↓ Serum and liver ALT and AST levels |
Modulation of gut microbiota composition: ↑ Bacterial diversity. ↓ Pathogenic bacteria content. Up-regulation of liver lipogenesis inhibitors: ↑ Protein expression of FGF15. |
ACC: acetyl-CoA carboxylase; ACE2: angiotensin-converting enzyme 2; Akt: protein kinase B; ALP: alkaline phosphatase; ALT: alanine transaminase; AMPK: AMP-activated protein kinase; ApoB100: apolipoprotein B100; ARA: arachidonic acid; ASC: Apoptosis-associated speck-like protein containing a caspase recruitment domain; AST: aspartate transaminase; bw: body weight; d: day; CAT: catalase; CD36: cluster of differentiation 36; CD11b: cluster of differentiation molecule 11B; CD68: cluster of differentiation 68; CDAA: choline-deficient/L-amino acid-defined; C/EBP-α: CCAAT/enhancer binding protein α; CFU: colony-forming unit; ChREBP: carbohydrate-responsive element-binding protein; CPT1: carnitine palmitoyltransferase 1; CXCL10: C-X-C Motif Chemokine Ligand 10; ERK: extracellular-signal-regulated kinase; F4/80: EGF-like module-containing mucin-like hormone receptor-like 1; FAS: fatty acid synthase; F/B: Firmicutes/Bacteroidetes; FGF15: fibroblast growth factor-15; FGF21: fibroblast growth factor-21; GPx: glutathione peroxidase; HFD: high-fat diet; HFD/F: high-fat and fructose diet; HIF-1α: hypoxia Inducible factor 1 Subunit α; HO-1: heme oxygenase 1; IL-1β: interleukin 1β; IL-4: interleukin 4; IL-6: interleukin 6; IL-8R: interleukin 8 receptor; IL-12: interleukin 12; JNK: janus kinase; LDL-c: LDL cholesterol; LPS: lipopolysaccharide; MAO: monoamino oxidase; MASR: Mas receptor; MDA: malondialdehyde; NAS: NAFLD activity score; NASH: non-alcoholic steatohepatitis; NF-κB: nuclear factor kappa B; NLRP3: nod-like receptor protein 3; Nrf2: nuclear factor erythroid 2–related factor 2; Ocln: Occludin; p38: p38 MAP kinase; PBS: phosphate buffered saline; PGC1α: peroxisome proliferator-activated receptor gamma coactivator 1-α; PP2AC: protein phosphatase 2 catalytic subunit α; PPAR-α: peroxisome proliferator-activated receptor α; PPAR-γ: peroxisome proliferator-activated receptor γ; PPAR-δ: peroxisome proliferator-activated receptor δ; PUFA: polyunsaturated fatty acids; RAS: renin–angiotensin system; ROS: reactive oxygen species; SCD1: stearoyl-CoA desaturase; SCFA: short-chain fatty acids; SOD: superoxide dismutase; SPF: specific pathogen-free; SREBP-1: Sterol regulatory element-binding protein 1; STD: standard; T-AOC: total antioxidant capacity; TC: total cholesterol; TG: triglycerides; TLR-4: toll-like receptor 4; TLR-9: toll-like receptor 9; Tnfα: tumor necrosis factor α; w: weeks; WSD: western-style diet; ZO1: Zonula Occludens 1; 4-HNE: 4-hydroxynonenal; 9-HETE: 9-hydroxy-5Z,7E,11Z,14Z-eicosatetraenoic acid; 9HpODE: 9-hydroperoxy-10E,12Z-octadecadienoic acid; ↓: significant reduction; ↑: significant increase.