The link between metabolic dysfunction-associated steatotic liver disease and gut microbiota in the elderly

Background:Metabolic dysfunction-associated steatotic liver disease (MASLD) is a newly proposed concept that describes hepatic steatosis in the presence of cardiometabolic risk factors. While the gut-liver axis has been implicated in liver disease, specific gut microbiota features of MASLD remain poorly understood.Methods:We conducted a cross-sectional study involving 786 older adults (age 65 or older) in Kyotango, Japan, a region known for healthy longevity. MASLD was defined by a fatty liver index (FLI) of 60 or higher and at least one cardiometabolic risk factor. Propensity score matching (1:2) identified 59 MASLD cases and 118 matched healthy controls. Gut microbiota was profiled using 16S rRNA gene sequencing. Frailty was evaluated using a deficit accumulation model. Dietary intake was assessed via a brief self-administered diet history questionnaire.Results:MASLD was significantly associated with a higher prevalence of frailty (15.1% vs. 2.1%). The MASLD group exhibited lower alpha diversity (Shannon index, P = 0.0069) and distinct beta diversity (P < 0.01). Compared to controls, MASLD participants had reduced levels of butyrate-producing genera such as Faecalibacterium, Blautia, and Christensenellaceae R-7, and increased levels of pro-inflammatory genera including [Ruminococcus] gnavus, Fusobacterium, and Lachnoclostridium. Higher dietary fiber intake was linked to greater abundance of health-associated bacteria, while lower intake correlated with MASLD-associated bacteria.Conclusion:Elderly individuals with MASLD demonstrate distinct gut microbiota profiles, marked by reduced butyrate producers and increased pro-inflammatory taxa. These findings suggest that gut microbial alterations may play a role in MASLD and offer potential targets for dietary or microbiome-based interventions in aging populations.