A Review of the Gut Microbiome and Its Role in Non-alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a common metabolic disorder connected to the gut microbiome. Increasingly, the influence of the microbiome on intestinal permeability, systemic inflammation and hepatic lipid metabolism has been regarded as crucial to the pathogenesis and progression of NAFLD. Several therapeutic approaches have been tried targeting the gut microbiota to reduce the severity of the disease. This review was done in accordance with the PRISMA guidelines. Data extracted from the studies focused on microbial composition, functional pathways, diagnostic methods and treatment interventions on both host metabolic parameters and microbial markers are synthesised and analysed. The results showed that there was a consistent change in gut microbiota in NAFLD patients, with a decrease in beneficial taxa, such as Bifidobacterium, and an increase in pathogenic strains. Interventions on the microbiome, including dietary changes, probiotics, synbiotics and faecal microbiota transplantation (FMT), showed mixed effects on hepatic steatosis and inflammatory markers. Dietary interventions reduced hepatic steatosis by up to 40%, whereas resistant starch supplementation reduced intrahepatic triglycerides by 9.08%. Synbiotics and FMT normalised gut dysbiosis and hepatic parameters, although probiotics were not very effective. The diagnostic methodologies for NAFLD were different, and there were considerable differences in outcome measures across interventions. Gut microbiome modulation emerged as a promising avenue for the management of NAFLD. However, the heterogeneity in efficacy among interventions indicated the complexity of the interactions between the microbiota and host and necessitated personalised therapeutic approaches.