The sex-dependence of gut microbiota characteristics and keystone species identification of lipid metabolism in dyslipidemia

High-fat diet (HFD) induced comparable hepatic steatosis and inflammation in both sexes. However, male mice exhibited earlier body weight gain and impaired intestinal barrier integrity (downregulated ZO-1/Occludin). Metabolomics analysis revealed distinct sex-specific bile acid metabolic signatures, with females showing increased levels of several bile acids and enrichment of ascorbate and aldarate metabolism, while males exhibited reduced primary bile acids together with enrichement of bile acid biosynthesis and secretion pathways. Male-specific Lactobacillus johnsonii depletion in clinical and HFD mice correlated with keystone taxa (Lactobacillus) and with lipid, inflammation, and bile acid markers. Moreover, the isolated L. johnsonii DM2420 strain demonstrated cholesterol-lowering activity, BSH activity, multiple genes associated with stress adaptation, and supernatant metabolomics confirming bile acid remodeling and anti-inflammatory potential in vitro. Collectively, males are more susceptible than females to HFD-induced dyslipidemia, closely linked to male-selective depletion of the keystone taxon L. johnsonii and to sex-divergent bile acid metabolic reprogramming, with the isolated strain of L. johnsonii DM2420 exhibiting a multifunctional profile that underscores its probiotic potential.