Genistein Alleviates Diet-Induced Hypercholesterolemia via the Gut Microbiota–Bile Acid–SCFA Axis in Mice

Hypercholesterolemia is a major risk factor for cardiovascular diseases. Genistein, a major bioactive isoflavone, has shown cholesterol-lowering potential, but the mechanisms underlying this effect remain unclear. In this study, genistein was purified from fermented soybean meal, and ICR mice fed a high-cholesterol diet were treated with genistein (40 mg/kg body weight/day) from fermented soybean meal for eight weeks. Genistein reduced body weight gain without affecting food intake, and decreased serum total cholesterol and low-density lipoprotein cholesterol. Genistein increased fecal total bile acid excretion and decreased serum total bile acids, accompanied by elevated fecal ursodeoxycholic acid and muricholic acid derivatives. Gut microbiota analysis showed restored alpha diversity, a decreased Firmicutes/Bacteroidetes ratio, and enriched Akkermansia, Parabacteroides and norank_f__Muribaculaceae. Fecal short-chain fatty acids (SCFAs) were increased, especially butyrate and valerate, and propionate was restored to levels comparable to normal controls. At the mRNA level, genistein treatment reduced intestinal farnesoid X receptor and fibroblast growth factor 15 expression and increased hepatic cholesterol 7α-hydroxylase expression, accompanied by altered expression of genes involved in cholesterol synthesis and efflux. Correlation analysis linked genistein-enriched taxa with improved cholesterol, bile acid, and SCFA profiles. In conclusion, purified genistein may alleviate diet-induced hypercholesterolemia by affecting the bile acid pool, gut microbiota, and SCFA production. These findings provide mechanistic insights into the cholesterol-lowering effects of genistein and may offer a scientific basis for the future development of genistein-based functional ingredients from soybean-derived materials.