Consistent with other reports [31], STZ-treated mice had impaired cardiac function, which was ameliorated (LVEF and LVFS) (Fig. 2A1, 2A2, and A3) or normalized (LVIDd and LVIDs) (Fig. 2A4 and 5) by irisin (10 μg/kg body weight/day), intraperitoneally injected daily for 4 weeks, although irisin did not affect the body weights or blood glucose levels of T1DM mice (Additional file 1: Figures S1A and B). The gene discussed is FNDC5; the disease is type 1 diabetes mellitus.