Table 2.
Preclinical studies (rodent models) addressing the effects of different probiotic mixtures in diet-induced NAFLD.
| Reference | Animal Model | Experimental Conditions | Probiotic Treatment | Effects in Liver | Mechanisms of Action |
|---|---|---|---|---|---|
| [44] | Male C57BL/6J mice 5-week-old |
HFD (60% energy from fat). |
Probiotic mixtures: Bacillus mixture: B. sonorensis JJY12–3, B. paralicheniformis JJY12–8, B. sonorensis JJY13–1, B. sonorensis JJY 13–3 and B. sonorensis JJY 13–8. VSL#3: L. acidophilus, L. plantarum, L. casei, L. delbrueckii subspecies bulgaricus, B. breve, B. longum, B. infantis and S. salivarius subspecies thermophilus Daily administration Dose of 1 × 108 CFU/day Treatment length: 13 w. |
↓ Liver weight (group treated with Bacillus mixture) ↓ Liver fat accumulation (group treated with Bacillus mixture) ↓ Liver TG content (group treated with Bacillus mixture) ↓ Liver inflammation (group treated with Bacillus mixture) |
Up-regulation of markers related to fatty acid oxidation in the liver (group treated with Bacillus mixture): ↑ Gene expression of Acox1 and Cpt1. ↑ Protein expression of PCG1α. Down-regulation of pro-inflammatory markers and mediators in the liver (group treated with Bacillus mixture): ↓ Gene expression of Tnfα, Infγ, Mcp-1 and Il-12. Up-regulation of markers of intestinal mucosa integrity (group treated with Bacillus mixture): ↑ Gene expression of Zo1 and Ocln. ↑ Protein expression of Occludin. Modulation of cecum SCFA content and hepatic receptors: ↓ Cecum acetate levels (group treated with Bacillus mixture). ↓ Gene expression of acetate receptor Gpr43 (group treated with Bacillus mixture). |
| [45] | Male C57BL/6 mice 6-week-old |
HFD (60% energy from fat). |
Probiotic mixture: L. plantarum LC27 B. longum LC67 Daily oral gavage 3:1 proportion (0.75 × 109 CFU of L. plantarum and 0.25 × 109 CFU of B. longum) Treatment length: 4 w. |
↓ Liver weight ↓ Liver lipid accumulation ↓ Liver TG content (group treated with L. plantarum LC27) ↓ NAS (all groups) ↓ Serum AST and ALT levels |
Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Levels of TNFα. ↓ Activity of MPO. ↓ Protein expression of iNOS and COX-2. ↓ Protein expression of p65. ↓ Phosphorylation of p65. ↑ Protein expression of Iκβα. ↓ Phosphorylation of Iκβα. Up-regulation of energy yielding pathways in the liver: ↑ Phosphorylation of AMPK. Down-regulation of periportal fibrogenesis markers in the liver: ↓ Protein expression of α-SMA. ↓ Phosphorylation of α-SMA. Up-regulation of markers of intestinal mucosa integrity: ↑ Protein expression of Occludin-1 and Claudin-1. Modulation of gut microbiota composition: ↓ Proportion of Firmicutes, Bacteroidetes, Proteobacteria, Deferribacteria. ↓ F/B ratio. ↓ P/B ratio. ↑ Proportion of Actinobacteria. ↓ Gut content of LPS. |
| [46] | Male C57BL/6N mice >78-week-old |
HFD (60% energy from fat). |
Human origin probiotic mixture: 5 strains of Lactobacillus 5 strains of Enterococcus Daily administration Dose: 1 × 109 CFU/mL suspended in the drinking water. Treatment length: 10 w. |
↓ Liver fat accumulation ↓ Liver inflammation |
Enhanced microbial diversity enriched in beneficial commensal bacteria. Up-regulation of markers of intestinal mucosa integrity: ↑ Gene expression of Zo1 and Ocln. Modulation of microbial metabolites in the gut: ↑ Abundance of butyrate and propionate. |
| [18] | Male SPF C57BL/6J mice 6-week-old |
Normal or a Western diet (42% energy from fat). |
Probiotic mixtures: Mix 1: L. casei + L. helveticus Mix 2: L. casei + L. helveticus + P. pentosaceus KID7 Mix 3: L. casei + L. helveticus + L. bulgaricus Daily administration Dose of 1 × 109 CFU/g suspended in distilled water. Treatment length: 8 w. |
↓ Liver steatosis grade (all groups) ↓ Liver inflammation (all groups) ↓ Liver/bw ratio (groups treated with Mix 1 and Mix 2) ↓ NAS (all groups) |
Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ Gene expression of Tnfα (all groups). ↓ Gene expression of Il-6 (groups treated with Mix 2 and Mix 3). ↓ Gene expression of Il-1β (group treated with Mix 3). |
| [47] | Male SPF C57BL/6J mice 3–4-week-old |
HFD (60% energy from fat). |
Probiotic mixture: L. plantarum KLDS1.0344 L. plantarum KLDS1.0386 Daily oral gavage Dose: 108 CFU Treatment length: 8 w. |
↓ Serum ALT and AST levels ↓ Liver TG content |
Down-regulation of oxidative stress markers in the liver: ↓ Content of MDA. ↑ Content of GSH-Px. ↑ Content of CAT. ↑ Content of SOD. Modulation of gut microbiota composition: - Relative abundance of Parabacteroides, Eubacterium xylanophilum group, GCA-900066575, Lachnoclostridium, Lachnospiraceae UCG-006 and Rombustia. ↑ Richness of Lachnospiraceae NK4A136 group and Bacteroides. Modulation of gut SCFA production: ↑ Levels of acetic and butyric acids. |
| [48] | Male C57BL/6J mice 5-week-old |
HFD (60% energy from fat). |
Probiotic mixture: B. subtilis (1.4 × 109 CFU) E. faecium (1.55 × 1010 CFU) Daily oral gavage. Treatment length: 16 w. |
↓ Liver index ↓ Serum ALT and AST levels ↓ Liver lipid accumulation |
Up-regulation of fatty acid oxidation markers in the liver: ↑ Protein expression of CPT1 and PPARα. Down-regulation of pro-inflammatory markers and mediators in the liver: ↓ LPS levels. ↓ Gene expression of Il-1β, Il-6 and Tnf-α. ↓ Protein expression of TLR-4 and NF-κβ. Up-regulation of markers of intestinal mucosa integrity: ↑ Protein expression of Occludin-1 and Claudin-1. Modulation of gut microbiota composition: ↓ F/B ratio. ↓ Relative abundance of Firmicutes. ↑ Relative abundance of Bacteroidetes, Verrucomicrobia, Akkermansia and Oscillibacter. |
| [49] | Male Zucker-Leprfa/fa rats | Chow diet. | Probiotic mixture: L. paracasei CNCM I-4034 B. breve CNCM I-4035 Daily oral gavage Dose: 1010 CFU. Treatment length: 30 days. |
↓ Liver TG content | Decreased serum levels of pro-inflammatory markers cytokines and mediators: ↓ Levels of TNF-α. ↓ Levels of LPS. |
| [50] | Male albino rats 6-week-old |
HFSD (59% energy from fat). |
Probiotic mixture: L. acidophilus (10 × 108 CFU/g). L. plantarum (9.8 × 107 CFU/g). B. bifidum (2 × 106 CFU/g). B. subtilis fermentation extract (50 g per kg of product). A. oryzae fermentation extract (50 g per kg of product). Daily administration Dose: 1 g of probiotic mixture/kg diet Treatment length: 4 w. |
↓ Serum ALT levels ↓ NAS ↓ Liver inflammation |
Not specified. |
| [51] | Male Sprague-Dawley rats 7-week-old |
HCD (15% energy from fat). |
Probiotic mixture: B. longum CBG-C11 B. lactis CBG-C10 B. breve CBG-C2 L. reuteri CBG-C15 L. plantarum CBG-C21 Daily by oral gavage Doses: Low dose (1.65 × 109 CFU/kg/d) Medium dose (5.5 × 109 CFU/kg/d) High dose (1.65 × 1010 CFU/kg/d) Treatment length: 8 w. |
↓ Hepatic steatosis score (group treated with the high dose) ↓ Liver TG and TC content (all groups) ↓ Liver AST and ALT levels (all groups) |
Down-regulation of lipogenic markers in the liver: ↓ Protein expression of FAS, ACC and SREBP-1 (all doses). |
| [35] | Male Sprague-Dawley rats 42-day-old |
STD + 20% fructose in drinking water. | Probiotic mixture: 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 ↓ Serum ALT levels ↓ Liver oxidative stress |
Up-regulation of antioxidant response in the liver: ↑ Content of glutathione. ↓ Liver ROS formation. ↑ Liver total antioxidant level. ↓ Liver protein-carbonylation. ↓ Liver lipid peroxidation. |
ACC: acyl-CoA-carboxylase; Acox 1: acyl-CoA oxidase 1; ALT: alanine transaminase; AMPK: AMP-activated protein kinase; α-SMA: smooth muscle alpha-actin; bw: body weight; CAT: catalase; CFU: colony-forming unit; COX-2: cyclooxygenase-2; CPT1: carnitine palmitoyltransferase 1; FAS: fatty acid synthase; F/B: Firmicutes/Bacteroidetes ratio; GPR-43: G-protein coupled receptor 43; GSH-Px: plasma glutathione peroxidase; HCD: high-cholesterol diet; HFD: high-fat diet; HFSD: high-fat sucrose diet; Iκβα: NF-κβ inhibitor; IL-1β: interleukin 1β; IL-2: interleukin 2; IL-6: interleukin 6; IL-12: interleukin 12; INFγ: interferon γ; iNOS: inducible nitric oxide synthase; LPS: lipopolysaccharides; MCP-1: monocyte chemoattractant protein-1; MDA: malonaldehyde; MPO: myeloperoxidase; NAS: NAFLD activity score; NF-κβ: nuclear factor kappa-light-chain-enhancer of activated B cells; Ocln: Occludin; PBS: phosphate buffered saline; P/B: Proteobacteria/Bacteroidetes ratio; PCG1α: peroxisome proliferator-activated receptor gamma coactivator 1-α; PPARα: peroxisome proliferator-activated receptor alpha; ROS: reactive oxygen species; SCFA: short-chain fatty acids; SOD: superoxide dismutase; SPF: specific pathogen-free; SREBP-1: sterol regulatory element-binding transcription factor-1; STD: standard; TG: triglycerides; TLR-4: toll-like receptor 4; Tnfα: tumor necrosis factor α; w: weeks; ZO-1: Zonula Occludens; ↓: significant reduction; ↑: significant increase.