FNDC5 and diabetes mellitus: Interestingly, decreased serum irisin levels were observed to be asignificant predictor of HFpEF patients with type 2 diabetes mellitus (T2DM), butnot in HF patients with mid-range ejection fraction (HfmrEF) and HFrEF, which canpotentially make way for a new approach for stratifying HF risk among T2DMpatients [41].