CYP7A1 and CYP8B1 are key enzymes in bile acid synthesis with the former as the rate-limiting enzyme and the latter as a crucial regulator that determines the ratio of 12-OH bile acids to non-12-OH bile acids.24 Accumulating studies have reported that the increased 12-OH bile acid ratio or upregulation of CYP8B1 leads to human diseases, such as NAFLD, obesity, and inflammatory bowel disease (IBD),25–27 which makes CYP8B1 a viable therapeutic target for metabolic diseases. The gene discussed is CYP8B1; the disease is obesity due to melanocortin 4 receptor deficiency.