AJP - Endocrinology and Metabolism, Vol 244, Issue 3 203-E208, Copyright © 1983 by American Physiological Society
Significance of hyperinsulinemia in ventromedial hypothalamus-lesioned rats
F. M. Hansen, P. Nilsson, B. E. Hustvedt, P. Nilsson-Ehle and A. Lovo
The significance of the hyperinsulinemia on the altered metabolism in
ventromedial hypothalamus (VMH)-lesioned rats was tested. VMH lesions
induced increases in fatty acid synthesis, lipoprotein lipase (LPL)
activity, and plasma urea levels, and a decrease in plasma triglyceride
concentrations. Similarly, in normal rats treated with pharmacological
doses of insulin (14 U X rat-1 X day-1), fatty acid synthesis and LPL
activity in fat tissue and the plasma urea were considerably elevated and
plasma triglyceride was lowered compared with untreated controls. When
endogenous insulin production was abolished by streptozotocin treatment,
the four metabolic variables in the VMH-lesioned rats did not differ from
those in diabetic controls. Substitution with 2 U of insulin X rat-1 X
day-1, however, restored the differences in metabolism between VMH-lesioned
diabetic and control diabetic rats. Substitution with 3 or 4 U insulin X
rat-1 X day-1 showed the same differences. In VMH-lesioned rats the insulin
level increased significantly from the 10th to the 70th day
postoperatively; however, the rate of fatty acid synthesis, LPL activity,
and plasma urea levels decreased, whereas plasma triglyceride
concentrations increased. The results strongly suggest that the metabolic
changes occurring after VMH lesions are only in part explained by the
hyperinsulinemia associated with the VMH syndrome and indicate that other
hormonal and/or nervous factors are involved.
