AJP - Endocrinology and Metabolism, Vol 262, Issue 2 E161-E166, Copyright © 1992 by American Physiological Society
Insulin receptor kinase activity in muscles and white adipose tissue during course of VMH obesity
A. Pujol, B. Cousin, A. F. Burnol, M. Loizeau, L. Picon, J. Girard and L. Penicaud
Laboratoire de Physiopathologie de la Nutrition, Centre National de la Recherche Scientifique Unite de Recherche Associee 307, Universite Paris VII, France.
Early after lesion of the ventromedial hypothalamus nuclei (VMH),
insulin-induced glucose utilization is increased in white adipose tissue
(WAT), whereas oxidative and glycolytic muscles are, respectively,
normoresponsive or resistant to insulin. Five weeks later, all of the
muscles are resistant, whereas WAT returns to normal responsiveness. The
aim of this study was to characterize the insulin receptor kinase activity
in WAT and muscles 1 and 6 wk after lesion. The number and affinity of
insulin receptors were not modified in any of the tissues studied.
Autophosphorylation and phosphorylation of an exogenous substrate were
similar in oxidative and glycolytic muscles of VMH and control rats both 1
and 6 wk after the lesion. Insulin receptors from WAT of 1-wk VMH rats
exhibited a 2.5-fold increase in insulin-stimulated autophosphorylation and
phosphorylation. Six weeks after the lesion, both autophosphorylation and
phosphorylation returned to normal values. This suggests that insulin
receptor tyrosine kinase activity does not play a significant role in the
insulin resistance of skeletal muscles but has a crucial role in mediating
the variations of insulin action on WAT observed during the development of
VMH obesity.
