Abstract Body: Hypercholesterolemia is a major contributor to atherosclerosis development in adults. Cholesterol is catabolized in the liver through the production of bile acids, which then facilitate the absorption of cholesterol and other lipids in the intestine. Individual bile acids differ in efficiency for solubilizing dietary lipid and signaling as ligands. Understanding how these nuances impact cholesterol metabolism will provide a new understanding in the importance of bile acids in human cardiometabolic diseases.

The human bile acid pool is primarily comprised of chenodeoxycholic acid (CDCA) and cholic acid (CA), which is converted by intestinal microbiota to deoxycholic acid (DCA). In contrast, mice have low levels of CDCA due to the presence of CYP2C70, a rodent-specific enzyme which converts CDCA to muricholic acids (MCAs). To generate a more human-like bile acid pool and increase the amount of CDCA, we used AAV-CRISPR to disrupt hepatic Cyp2c70 in mice. Loss of CYP2C70 increased CDCA levels, and we assessed hepatic lipid metabolism, lipid absorption, gut barrier function, and microbial metabolites. We observed mild hepatic fibrosis as well as impaired gut barrier function that was exacerbated with time. Interestingly, the most significantly increased microbial metabolite we observed was trimethylamine N-oxide (TMAO).

Because bile acids are associated with both cholesterol and cardiovascular disease, and TMAO is also linked to cardiovascular disease, we next examined whether Cyp2c70 disruption altered atherosclerosis. We co-disrupted Cyp2c70 with Low density lipoprotein receptor (Ldlr) to induce hypercholesterolemia and atherosclerosis. We observed increased atherosclerosis at 14 weeks following loss of CYP2C70. Cyp2c70/Ldlr CRISPR mice exhibited greatly increased plasma cholesterol levels as early as two weeks after AAV-CRISPR injection, suggesting bile acid-mediated changes in cholesterol metabolism. Finally, loss of CYP2C70 enlarged the abdominal aortae in a subset of mice, potentially linking bile acids to aneurism risk via TMAO. Taken together, our data suggest that a humanized bile acid profile is proatherogenic via regulation of cholesterol and TMAO.