Introduction:
Sedentary lifestyle and excessive calorie intake are risk factors for CVD. We have demonstrated the cardioprotective effect of exercise in aged mice and the critical role of visceral adiposity and its profibrotic secretome in increasing cardiovascular risks in obesity and aging. The association between exercise, lowered plasma leptin and reduced inflammatory leukocytes has been recently shown in patients with atherosclerosis. It remains unclear whether elevated plasma leptin can preserve or alter cardiovascular function in obesity.
Methods:
We analyzed the effect of high fat diet (HFD) in C57BL/6J male mice on the heart in terms of function, structure, histology and key molecular markers. Two interventions were used: 1) active fat mass loss via exercise (daily swimming) during HFD; 2) passive fat mass loss via surgical removal of the visceral adipose tissue (VAT lipectomy) followed by HFD.
Results:
HFD increased body weight and adiposity, leading to higher plasma leptin, glucose and insulin levels, compared to control diet (CD) mice. HFD impaired left ventricle (LV) structure (hypertrophy, interstitial fibrosis) and cardiac function (echocardiography,
in vivo
hemodynamics). Atria of HFD mice had enhanced pro-inflammatory protein production. Exercise reduced circulating leptin levels in HFD mice by 50%, in line with fat mass loss. In contrast, lipectomy reduced visceral fat mass, but body weight, adiposity and plasma leptin did not change. Both exercise and VAT lipectomy improved cardiac contractility, reversed collagen deposition and oxidative stress in HFD mice. Both interventions downregulated LV pro-inflammatory markers. We proved the role of leptin in cardiac remodeling
in vitro
by incubating primary cardiac fibroblasts with hyperleptinemic plasma from HFD mice. Remarkably, plasma from HFD-EX (exercise) suppressed the fibro-proliferative and pro-inflammatory responses of cardiac fibroblasts.
Conclusions:
Leptin directly contribute to cardiac fibrosis in obesity via activation and proliferation of cardiac fibroblasts. Understanding how leptin signals to the heart might have implications in a wide range of CVD, potentially helping early stratification and personalized care.
The impact of weight and fat mass loss and increased physical activity on physical function in overweight, postmenopausal women
