The role of the gut-liver axis in modulating non-alcoholic fatty liver disease through dietary patterns and microecological agents

Non-alcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease, closely associated with dyslipidemia, obesity, and diabetes. The gut-liver axis (GLA) plays a pivotal role in the pathogenesis of NAFLD, with dietary factors acting as key regulators that shape gut microbiota and mediate GLA, consequently impacting NAFLD and host health. While reviews on specific dietary patterns or components and their relationship with NAFLD have been published in the past five years, a comprehensive summary of these dietary factors and their effects on NAFLD via the GLA mechanism is lacking. This review aims to provide a comprehensive overview of this mechanism by analyzing GLA-dependent metabolites, including bile acids, short-chain fatty acids, choline, trimethylamine-N-oxide, endotoxin, ammonia, and amino acids. Additionally, the review summarizes the various dietary factors that influence NAFLD through the GLA, encompassing dietary patterns such as western-style diet, Mediterranean diet, methionine-restricted diet, calorie-restricted diet, and protein-restricted diet, as well as oral microecological agents such as probiotics, prebiotics, synbiotics, and postbiotics. The majority of these dietary interventions, except for the western-style diet and long-term protein-restricted diet, demonstrate positive effects on improving NAFLD. Furthermore, synbiotics and postbiotics have emerged as promising agents for ameliorating NAFLD-associated liver inflammation and lipid accumulation. In conclusion, this review provides a detailed understanding of the GLA mechanism and presents multiple possibilities for the nutritional treatment of NAFLD.