Review article: emerging role of the gut microbiome in the progression of nonalcoholic fatty liver disease and potential therapeutic implications

Background Nonalcoholic fatty liver disease (NAFLD) is a prevalent disorder associated with obesity and diabetes. Few treatment options are effective for patients with NAFLD, but connections between the gut microbiome and NAFLD and NAFLD-associated conditions suggest that modulation of the gut microbiota could be a novel therapeutic option. Aim To examine the effect of the gut microbiota on pathophysiologic causes of NAFLD and assess the potential of microbiota-targeting therapies for NAFLD. Methods A PubMed search of the literature was performed; relevant articles were included. Results The composition of bacteria in the gastrointestinal tract can enhance fat deposition, modulate energy metabolism and alter inflammatory processes. Emerging evidence suggests a role for the gut microbiome in obesity and metabolic syndrome. NAFLD is often considered the hepatic manifestation of metabolic syndrome, and there has been tremendous progress in understanding the association of gut microbiome composition with NAFLD disease severity. We discuss the role of the gut microbiome in NAFLD pathophysiology and whether the microbiome composition can differentiate the two categories of NAFLD: nonalcoholic fatty liver (NAFL, the non-progressive form) vs nonalcoholic steatohepatitis (NASH, the progressive form). The association between gut microbiome and fibrosis progression in NAFLD is also discussed. Finally, we review whether modulation of the gut microbiome plays a role in improving treatment outcomes for patients with NAFLD. Conclusions Multiple pathophysiologic pathways connect the gut microbiome with the pathophysiology of NAFLD. Therefore, therapeutics that effectively target the gut microbiome may be beneficial for the treatment of patients with NAFLD.