FNDC5 and type 2 diabetes mellitus: In addition, we measured the plasma level of irisin in the study population and found a significantly higher increase in the irisin level in T2D (623.01 ± 21.82 ng/mL) as compared to non-diabetic individuals (508.23 ± 15.38 ng/mL) with p < 0.001 (Figure 3A).