Nevertheless, studies had revealed that serum FGF21 levels are significantly higher in obese patients with MetS components than that in healthy controls, progressively elevated with worsening dysglycemia from normal glucose tolerance to prediabetes and diabetes, and prominently increased in human cardiometabolic diseases such as obesity, MetS, T2DM, coronary artery disease, and nonalcoholic fatty liver disease [9, 10, 23, 25]. This evidence concerns the gene FGF21 and type 2 diabetes mellitus.