Cardiovascular protection afforded by caloric restriction: essential role of nitric oxide synthase

Caloric restriction is an established intervention, of which anti-aging effects are scientifically proven. It has pleiotropic effects on the cardiovascular system: vascular protection, improvement of myocardial ischemic tolerance and retardation of cardiac senescence. First, increasing evidence from both experimental and clinical studies supports the concept that "a man is as old as his arteries". Caloric restriction could prevent the progression of atherosclerosis and vascular aging through direct and indirect mechanisms. Second, the hearts of senescent animals are more susceptible to ischemia than those of young animals. We demonstrated that short-term and prolonged caloric restriction confers cardioprotection against ischemia/reperfusion injury in young and aged rodents. Furthermore, we showed that the increase in circulating adiponectin levels and subsequent activation of adenosine monophosphate-activated protein kinase are necessary for the cardioprotection afforded by short-term caloric restriction. In contrast, the mechanisms by which prolonged caloric restriction confers cardioprotection seem more complicated. Adiponectin, nitric oxide synthase and sirtuin may form a network of cardiovascular protection during caloric restriction. Recently, by using genetically engineered mice, we found that, in addition to endothelial nitric oxide synthase, neuronal nitric oxide synthase plays an essential role in the development of cardioprotection afforded by prolonged caloric restriction. Third, long-term caloric restriction has cardiac-specific effects that attenuate the age-associated impairment seen in left ventricular diastolic function. It is possible that long-term caloric restriction partially retards cardiac senescence by attenuating oxidative damage in the aged heart. Overall, we strongly believe that caloric restriction could reduce morbidity and mortality of cardiovascular events in humans.