Sympathetic Nervous System and Cardiovascular Alterations Due to Food Restrictions

Abstract

Excessive food intake over a prolonged period is known to result in obesity, a risk factor for heart disease, associated with derangements of myocardial metabolism. Furthermore, food restriction has been shown to reduce obesity, attenuate metabolic changes in the myocardium and improve hemodynamic performance. This article is therefore intended to discuss the impact of food restriction on cardiovascular performance and sympathetic activity to understand the mechanisms for its beneficial effects. Feeding rats 25% of ad libitum diet (severe food restriction) increased blood pressure and left ventricular function during 2 to 7 days but decreased these parameters as well as heart rate during 10 to 14 days. Both plasma and cardiac norepinephrine levels were increased during 2 to 14 days whereas plasma epinephrine levels were elevated during 2 to 7 days and cardiac epinephrine content was increased during 10 to 14 days of feeding 25% of ad libitum diet. Restriction of food (25% ad libitum) for 14 days also attenuated the epinephrine-induced inotropic effect as well as different types of arrhythmias; this was associated with reduction of β-adrenoceptor density in the myocardium. An increase in sympathetic activity was also seen due to starvation of animals for 4 days. Feeding (50% ad libitum) diet (moderate food restriction) for 14 and 28 days showed depression in different parameters of cardiovascular function as well as increased cardiac norepinephrine and epinephrine content whereas plasma norepinephrine levels were increased at 14 days and decreased at 28 days without any changes in plasma epinephrine levels. These studies indicate that augmentation of sympathetic activity is associated with enhanced cardiovascular performance at initial stages followed by depression in