Non-Alcoholic Fatty Liver Disease, Gut Microbiota and Synbiotics: A Review of the Experimental and Clinical Evidence

Background: Non-alcoholic fatty liver disease (NAFLD) is a multi-cause disease. Several factors are involved in the pathogenesis of NAFLD. Recently, the role of gut microbiota in the pathogenesis of NAFLD has attracted the attention of researchers. This study was performed to review the role of gut microbiota in the pathogenesis of NAFLD. In addition, the mechanisms and clinical effects of synbiotics on NAFLD were reviewed. Methods: A narrative review of the most recent advances was conducted regarding the role of dysbiosis in the pathogenesis of NAFLD. In addition, the mechanisms and clinical results obtained from experimental and clinical studies investigating the effects of synbiotics on features of NAFLD were reviewed. Relevant studies published after 2010 were selected. Results: Dysbiosis induces hepatic steatosis through stimulating obesity via harvesting energy, inflammation, altering dietary choline and bile acid metabolism, endogenous ethanol production, insulin resistance and increasing gut permeability. Synbiotics can improve levels of liver enzymes and hepatic steatosis. However, the effect of synbiotic on hepatic fibrosis is unclear, and the results are inconsistent. Studies with higher intervention duration showed beneficial effect of synbiotics on hepatic fibrosis. Conclusions: Dysbiosis through various mechanisms is linked to the pathogenesis of NAFLD. Synbiotics can improve liver enzymes levels and hepatic steatosis. Investigating the effect of synbiotics on fibrosis can be the main objective of the future investigations in this field.