AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 2 203-R208, Copyright © 1985 by American Physiological Society
Insulin and central regulation of spontaneous fattening and weight loss
R. B. Melnyk and J. M. Martin
Insulin binding to receptors in a partially purified hypothalamic membrane
preparation is altered by prolonged starvation. To define further the
relationship between hypothalamic insulin binding and energy balance, we
studied the Richardson's ground squirrel, a hibernator that exhibits
spontaneous 6- to 8-mo body weight cycles when kept in constant conditions.
Isolated pancreatic islets from squirrels killed during the weight gain
phase had greater glucose-stimulated insulin secretion than those from
weight loss phase animals, and adipocytes showed significantly greater
glucose incorporation into total lipid in response to insulin. Differences
in lipogenesis were not attributable to changes in insulin-binding
capacity. Hypothalamic tissue from weight gain phase animals bound more
insulin than that from weight loss phase animals. Maximal binding was
correlated with pancreatic islet responsiveness and maximal
insulin-stimulated lipogenesis. The strong positive correlation between
peripheral metabolic events associated with spontaneous alterations in
energy balance and the binding kinetics of hypothalamic insulin receptors
suggests that insulin may play an important role in the central regulation
of body weight.
