Beyond biomarkers of lipid and sugar metabolism, our analyses also uncovered interesting covariation between gut microbial families (especially Peptostreptococcaceae, but also Christensenellaceae and Marinifilaceae) and metabolic indicators of liver damage, i.e., ALT and AST, which are biomarkers of non-alcoholic fatty liver disease (NAFLD). This evidence concerns the gene GPT and metabolic dysfunction-associated steatotic liver disease.