FNDC5 and type 2 diabetes mellitus: It has been reported that circulating irisin levels are positively associated with endothelium-dependent vasodilation (EDV) in newly diagnosed type 2 diabetic patients without clinical angiopathy, indicating that circulating lower irisin levels are tightly associated with endothelial dysfunction and could be a marker for early stage atherosclerosis in type 2 diabetes [13].