CYP27B1 and Obesity: CYP27B1 is the sole 1α‐hydroxylase of 25‐OH‐D that produces the full active form of vitamin D, 1α,25(OH)2D. The kidney is the main site of CYP27B1 expression; however, some recent studies have reported expression also in extrarenal tissues, for example, in immune cells.(26) Therefore, it was of interest to determine if HFD‐induced obesity could affect CYP27B1 expression in the kidney and other tissues.