In other studies, in mice with obesity or diabetes, levels of cardiac extracellular signal-regulated protein kinase 5 (ERK5) were found to be reduced; experiments to test the potential impact of this observation employed cardiomyocyte-specific deletion of Erk5 in mice fed a high-fat diet; this resulted in reduction in cardiac contractility and increased mitochondrial damage with reductions in fuel oxidation and increased oxidative damage [63]. The gene discussed is MAPK7; the disease is obesity due to melanocortin 4 receptor deficiency.