Reductions in Glucocorticoid Inhibition of Glucose Oxidation and Presumptive Glucocorticoid Receptor Content in Rat Adipocytes During Aging

Abstract

Exposure of adipocytes to glucocorticoid hormones in vitro inhibits glucose transport and metabolism. Maximal inhibition of glucose oxidation is reduced from 42-50 to 22-25 to 5-8% in young, mature and senescent rat adipocytes, respectively. Percent values reflect absolute reduction, since basal levels of glucose oxidation per cell are constant at all ages. Adipocytes of CD strain rats continue to increase in size throughout their lifespan, while cell size remains constant during the latter 80% of the Wistar adipocyte lifespan. Cellular age, and possibly size, seems to be associated with these changes, since they occur in adipocytes of both strains. Concentrations and absolute numbers of presumptive glucocorticoid receptors per cell are progressively reduced during maturation and aging of adipocytes in both rat strains. Glucocorticoid effects require about 2 h and can be blocked by various antimetabolites during this period, reminiscent of classical steroid receptor-mediated responses. Gradual loss of glucocorticoid receptors from adipocytes during maturation and aging may be related to progressively decreased glucocorticoid responsiveness.