Serum cholic acid and cecal Faecalibaculum increase in a male-specific manner in a murine hepatocellular carcinoma model

Hepatocellular carcinoma (HCC) has a higher incidence in males and is a leading cause of cancer-related deaths, which lacks effective therapies and surveillance markers. Using a murine model of bile acid excess (farnesoid X receptor and small heterodimer partner double knockout, DKO), which phenocopies many aspects of HCC, including sex differences, we investigated the links between sex, bile acid metabolism, and microbial composition. Unexpectedly, the increase in the ratios of carcinogenic deoxycholic acid (DCA) was similar between DKO males with HCC and cancer-resistant DKO females. However, both taurine-conjugated and free cholic acid (CA) sharply increased in the serum of DKO males, with free-CA comprising 65% of the bile acid pool, whereas DKO female serum was mostly comprised of conjugated bile acids. Unlike such sex differences in DKO serum composition, conjugated bile acids were predominant in the hepatic BA pool irrespective of the sex or genotype, as expected. Fecal and cecal microbiota-many of which harbor bile acid transformation/deconjugation capacity-were altered in DKO mice in a sex-specific manner. Untargeted fecal metabolite analysis showed differences in bile acids, phospholipids, and oxidized fatty acids between the genotypes, with DKO females excreting more sulphated and oxidized CA than tumor-bearing DKO males. Further analysis revealed a direct correlation between unconjugated CA levels with the abundance of the microbial genus Faecalibaculum in the DKO HCC model. These findings suggest distinct sex-specific changes in cecal and fecal microbiota, and BA composition may be leveraged in combination as a potential tool for HCC surveillance.