MAPK8 and obesity due to melanocortin 4 receptor deficiency: The major findings of our current study revealed that increased age mimickedleptin-deficient ob/ob obesity-induced changes in cardiomyocytecontractile function, intracellular Ca2+ homeostasis, NADPHoxidase expression, O2− accumulation, Akt/eNOS andstress signaling (p38, JNK and NFκB).