The fifth study conducted by Liu et al. firstly reported that circulating irisin is lower in T2DM compared with non-diabetic controls; in the non-diabetic subjects, irisin was positively correlated with several markers of cardiometabolic risks, including fasting glucose, BMI, LDL-cholesterol, total triglycerides, total cholesterol, and diastolic blood pressure [21]. This evidence concerns the gene FNDC5 and type 2 diabetes mellitus.