Therefore, the present study aims to demonstrate the association of circulating betatrophin and irisin levels with pancreatic β-cell function, assessed by the gold standard measure of β-cell function, the area under the curve (AUC) of C-peptide [11], and the possible correlation between betatrophin and irisin levels in previously diagnosed T2DM patients. Here, FNDC5 is linked to type 2 diabetes mellitus.