A cohort study of physical activity, gut microbiota, serum metabolites, and the risk of steatotic liver disease.

INTRODUCTION AND OBJECTIVES: Prospective evidence on the association between physical activity (PA) and steatotic liver disease (SLD) risk is limited. Gut microbiota profiles and metabolites associated with PA remain unclear. PATIENTS AND METHODS: We investigated the association between PA and SLD risk in a cohort of 2,942 free-living adults, where PA and SLD were measured using a validated self-reported questionnaire and transient elastography, respectively. We further identified 1-year gut microbial changes and serum metabolites related to moderate-to-vigorous PA (MVPA), and examined their associations with SLD in a subset of the cohort (n=754), where fecal samples for 16S rRNA sequencing were collected twice (1-year apart), species-level microbial profiles were generated using shotgun metagenomics, targeted metabolomics was performed using baseline serum samples, and PA was assessed by accelerometer. RESULTS: From 2020 to 2025, 565 SLD cases were newly diagnosed. MVPA levels were inversely associated with SLD risk (HRT3vs.T1=0.78, 95% CI: 0.63-0.98), while sedentary hours were positively associated with SLD (HRT3vs.T1=1.26, 95% CI: 1.00-1.58). Twelve genera showed longitudinal changes in relation to MVPA (pFDR<0.05). Proteus was positively associated with SLD risk (OR=1.32, 95% CI: 1.01-1.72), supported by species-level shotgun metagenomics for Proteus cibarius. L-valine concentrations were inversely correlated with MVPA (β=-0.23, pFDR=0.031), while demonstrating a positive association with SLD risk (OR=1.78, 95% CI: 1.22-2.63). L-valine was also correlated with the MVPA-associated genus Synergistes. CONCLUSIONS: MVPA is associated with changes in the gut microbiota and microbiota-related metabolites that are linked to a more favorable SLD profile, whereas sedentary behavior is associated with higher SLD risk.