FNDC5 and type 2 diabetes mellitus: Irisin is thought to influence glucose homeostasis, based on the finding of decreased serum irisin in a cohort of drug-naive patients with new-onset T2DM compared to controls with normal glucose tolerance (NGT) matched for age, sex and body mass index (BMI)[12] and on the observation of lower circulating irisin in T2DM patients with the drug intervention compared with nondiabetic controls[13].