Postabsorptive hyperinsulinemia in rats with subdiaphragmatic vagotomy

Abstract

The effects of bilateral subdiaphragmatic vagotomy and of lateral hypothalamic lesions on the acute plasma glucose and insulin responses to liquid and solid meals were studied in female rats. Following recovery of an initial postoperative weight loss, vagotomized rats exhibited an exaggeration of plasma glucose and insulin responses compared to sham-vagotomized animals 17 min after the initiation of a liquid meal (6 ml sweetened milk in 7 min). Vagotomy did not alter basal glucose and insulin levels. The exaggerated postabsorptive response to oral liquid glucose in vagotomized rats was not observed after the consumption of an isocaloric solid meal (1.86 g sucrose pellets in 7 min). Rats with lateral hypothalamic lesions had significantly lower basal glucose and insulin levels, but both the preabsorptive and postabsorptive responses to oral glucose were unaffected by the lesion. The results in vagotomized animals were attributed to enhanced gastric emptying of liquid loads leading to a more rapid absorption of glucose from the intestine, which in turn resulted in an increased insulin response. In humans this is followed by rapid-onset hypoglycemia, and it is hypothesized that the abnormal postabsorptive glucose and insulin responses account in part for the pattern of small, frequent meals observed with vagotomized animals on liquid diets.