Early Effects of Feeding upon Hormonal and Metabolic Alterations in Adult Rats with Ventromedial (VMH) Lesions

Abstract

The importance of the nutritional state for the development of metabolic alterations after ventromedial hypothalamic (VMH) destructions has been investigated. In the first experiment, groups of fed and 12 hours fasted animals were operated, given an intraperitoneal injection of ³H₂O (1mCi), and left without food until sacrificed 12 hours postoperatively. The lipogenesis in liver and adipose tissue, and the plasma levels of insulin, glucose, urea, free fatty acids (FFA) and triglycerides (TG) were measured. Animals operated in the fed state had increased lipogenesis in parametrial adipose tissue and hypoglycemia compared to their controls, whereas we found no differences between the groups which had been fasted 12 hours before surgery.

In the second experiment, animals were deprived of food for 12 hours before being lesioned or sham-operated, and for 12 more hours postoperatively. They were then given one meal by stomach tube, and groups were killed 2, 4, 8 and 12 hours later. The following differences between groups were observed: 2 hours after feeding, the lesioned animals had increased plasma TG levels, but decreased liver lipogenesis. 4 hours after feeding, animals with lesions were hypoglycemic, and had lower plasma levels of FFA and TG than the controls. Hypoglycemia in lesioned animals was found also 8 hours after feeding, together with increased plasma TG levels. 12 hours after feeding, increased liver lipogenesis in lesioned animals was the only difference observed between the groups.

The third and last experiment investigated the effect of three meals given 12, 18 and 24 hours postoperatively. Lesioned animals sacrificed 4 hours after the third meal had hypoglycemia, increased plasma TG levels and increased lipogenesis, both in liver and adipose tissue. The metabolic differences between lesioned and sham-operated animals persisted also 8 hours after the last meal, except for the lipogenesis in adipose tissue.

No differences in plasma insulin levels between animals with lesions or sham-operations were observed in these experiments.

Key words

Hypothalamic Lesions - Insulin Secretion - Metabolism - Lipogenesis