FNDC5 and heart failure: Bosanack et al. took advantage of fifty-two patients with heart failure with preserved ejection fraction and arterial fibrillation and analyzed the serum levels of irisin, leptin, adiponectin, insulin-like growth factor 1 (IGF-1), and malondialdehyde, and observed that irisin, leptin, and malondialdehyde were significantly lower in these patients [48].