CPT2 and diabetes mellitus: However, key enzymes for FAO, including carnitine palmitoyltransferase 1A (CPT1a) and carnitine palmitoyltransferase 2 (CPT2), were downregulated, and peroxisome proliferator–activated receptor-α, a master regulator for FAO, was also reduced in the kidneys of patients with diabetes, all of whose levels were inversely correlated with kidney fibrosis (13).