Hyperinsulinemia in rats with ventromedial hypothalamic lesions: role of hyperphagia

The relation of hyperinsulinemia to hyperphagia was examined in rats with lesions of the ventromedial hypothalamus (VMH). Plasma insulin and glucose levels were assayed after a 4-hr fast and 17 min after the initiation of a meal (6 ml of sweetened milk in 7 min) in animals with sham lesions, VMH animals maintained at preoperative body weight by food restriction, and VMH animals fed ad lib. Both VMH groups displayed basal and postabsorptive hyperinsulinemia, compared with the sham-operated control group, but insulin levels were greatest under the ad lib feeding condition. It is suggested that VMH hyperinsulinemia is due both to a primary effect of the lesion and to hyperphagia and that marked obesity can result in the absence of basal hyperinsulinemia as a result of hyperphagia with consequent postabsorptive hyperinsulinemia.