2005). Reduced Pgc1 levels and impaired mitochondrial function occur in diabetes mellitus, the metabolic syndrome, ageing and heart failure (Garnier et al. 2003; Leone & Kelly, 2011). Despite normal baseline function, Pgc1β‐deficient mice demonstrate compromised heart rate responses with adrenergic stimulation (Lelliott et al. 2006). Their ex vivo Langendorff‐perfused hearts show ventricular arrhythmic tendencies, abnormal diastolic Ca2+ transients and altered ion channel expression (Gurung et al. 2011). Here, PPARGC1B is linked to diabetes mellitus.