PPARα suppresses the activity of cholesterol 7α-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1), the rate-limiting enzymes in bile acid synthesis (Post et al., 2001; Ghonem et al., 2015), leading to a decrease in bile acid production and the likely development of biliary tract–related adverse effects, including cholelithiasis (Post et al., 2001). The gene discussed is CYP27A1; the disease is cholelithiasis.