Steatotic Liver Disease in Younger Adults is Associated With Altered Gut Microbiology

Background and Aims: Steatotic liver disease (SLD) is a leading cause of chronic liver disease worldwide. As SLD pathogenesis has been linked to gut microbiome alterations, we aimed to identify SLD-associated gut microbiome features early in SLD development by utilising a highly characterised cohort of community-dwelling younger adults. Methods and Results: At age 27 years, 588 participants of the Raine Study Generation 2 underwent cross-sectional assessment. Hepatic steatosis was quantified using a validated magnetic resonance imaging (MRI) volumetric liver fat fraction (VLFF) equation (HepaFat). Of the 588 participants, 488 (83%) were classified as having ‘no SLD’ (VLFF ≤ 3.55%), 76 (12.9%) with ‘mild–moderate’ SLD (VLFF: 3.56%–13.4%) and 24 (4.10%) with ‘severe’ SLD (VLFF > 13.4%). Stool microbiome profiling identified an association between severe SLD and lower microbiota alpha diversity (observed features [p = 0.015], Pielou evenness [p = 0.001] and Shannon diversity [p = 0.002]) compared to no SLD. Faecal microbiota composition differed significantly between no SLD and both mild–moderate (p = 0.004) and severe SLD groups (p = 0.001). There was no significant difference in microbiota dispersion between SLD groups. Reduced relative abundance of short-chain fatty acid producing bacteria, and higher levels of proinflammatory bacterial taxa, were both significantly associated with severe SLD (q < 0.05). Conclusions: SLD in younger adults is associated with reduced intestinal microbial diversity and a pattern of bacterial taxa depletion that is consistent with other chronic inflammatory conditions. Our characterisation of gut microbiome characteristics in early SLD development provides a potential basis for risk identification and reduction.