FGF21 and type 2 diabetes mellitus: FGF21 plasma levels are increased in type 2 diabetes, obesity, nonalcoholic fatty liver disease (NAFLD) and dyslipidemia (35, 36, 37, 38, 39), but injection of FGF21 in animal models of insulin resistance has been shown to improve this condition (9, 10, 11, 13, 14).