Effect of vagotomy on hyperinsulinemia in obese rats with hypothalamic lesions

With the purpose of investigating the pathogenesis of obesity and hyperinsulinemia in rats with hypothalamic lesions (HTL), HTL were made in vagotomized rats, and the development of obesity was serially followed up to 15 weeks as well as the changes of plasma triglyceride and immunoreactive insulin (IRI) levels. Even in vagotomized rats, obesity developed after HTL and plasma triglyceride and IRI levels increased significantly. However, obesity was slightly less in grade and occurred later as compared with sham-vagotomy-HTL rats. Plasma IRI levels in vagotomized rats significantly correlated with the body weight, Lee's index, the weight of adipose tissue and plasma triglyceride level. Similar results were also obtained in rats with HTL which were pair-fed following vagotomy. These results suggest that the hyperinsulinemia in obese rats with HTL may be involved not only by hypersecretion of insulin mediated by hypothalamo-vagal nerve system but also by some insulin-antagonistic factors such as increases of adipose tissues and plasma lipids.