REFEEDING HYPERTENSION IN OBESE SPONTANEOUSLY HYPERTENSIVE RATS

Very-low-calorie diets lower blood pressure acutely in obese humans and rats. However, refeeding after dietary restriction produces mild hypertension in rats. Refeeding hypertension was characterized in genetically obese spontaneously hypertensive rats (obese SHR, Koletsky rat), a model of genetic obesity and hypertension. Obese SHR were fed a restricted diet (Optifast) for 12 days, refed ad libitum for 28 days, dieted again for 12 days, and then refed 4 days and killed. Control obese SHR and lean SHR littermates were fed ad libitum continuously. Dietary restriction led to rapid weight loss followed by prompt regain to baseline weight after return, to unrestricted food intake. Heart rate fell with institution of the low-calorie diet and returned to baseline on refeeding. Blood pressure became elevated during refeeding in dieted obese SHR relative to ad libitum fed obese SHR controls. The fall in blood pressure after ganglionic blockade with chlorisondamine was exaggerated in refed obese SHR, and cardiac beta-adrenergic receptors were downregulated. Both of these findings imply increased sympathetic tone. The left ventricular wall was thicker in the refed obese SHR than in the ad libitum fed obese SHR. Shorter cycles of weight loss and regain in lean SHR led to transient increases in blood pressure and heart rate. Cycles of dietary restriction and refeeding in obese SHR elicit sustained blood pressure elevation via sympathetic activation and exacerbate cardiac hypertrophy, Drastic fluctuations in nutrient intake may not be advantageous in hypertension.