FNDC5 and type 2 diabetes mellitus: Notably, circulating betatrophin levels were significantly elevated (592.1 ± 37.5 versus 291.1 ± 37.3 pg/mL), while irisin levels were significantly decreased (3.4 ± 0.1 versus 4.7 ± 0.1 ng/mL), in patients with T2DM compared with NGT subjects.