Interplay between obesity and aging on myocardial geometry and function: Role of leptin-STAT3-stress signaling

BACKGROUND: Uncorrected obesity facilitates premature aging and cardiovascular anomalies. This study examined the interaction between obesity and aging on cardiac remodeling and contractile function. METHODS: Cardiac echocardiographic geometry, function, morphology, intracellular Ca²⁺ handling, oxidative stress (DHE fluorescence), STAT3 and stress signaling were evaluated in young (3-mo) and old (12- and 18-mo) lean and leptin deficient ob/ob obese mice. Cardiomyocytes from young and old lean and ob/ob mice were treated with leptin (1 nM) for 4 h in vitro prior to assessment of mechanical and biochemical properties. High fat diet (45% calorie from fat) and the leptin receptor mutant db/db obese mice at young and old age were evaluated for comparison. RESULTS: Our results displayed reduced survival in ob/ob mice. Obesity but less likely older age dampened echocardiographic, geometric, cardiomyocyte function and intracellular Ca²⁺ properties, elevated O₂⁻ and p47phox NADPH oxidase levels with a more pronounced geometric change at older age. Immunoblot analysis revealed elevated p47phox NADPH oxidase and dampened phosphorylation of STAT3, with a more pronounced response in old ob/ob mice, the effects were restored by leptin. Obesity and aging inhibited phosphorylation of Akt, eNOS, AMPK, and p38 while promoting phosphorylation of JNK and IκB. Leptin reconciled cardiomyocyte dysfunction, O₂⁻ yield, p47phox upregulation, STAT3 dephosphorylation and stress signaling in ob/ob mice although its action on stress signaling cascades were lost at old age. High fat diet-induced and db/db obesity displayed aging-associated cardiomyocyte anomalies reminiscent of ob/ob model albeit lost leptin response. CONCLUSIONS: Our data suggest disparate age-associated obesity response in cardiac remodeling and contractile dysfunction due to phosphorylation of Akt, eNOS and stress signaling-related oxidative stress.