Glucocorticoid-Induced Insulin Resistance in Vitro: Evidence for Both Receptor and Postreceptor Defects*

Abstract

Glucocorticoid excess in vivo has been shown to cause decreases in insulin sensitivity and insulin receptor binding in target tissues. It has not been previously possible to produce all of these changes in vitro because of limitations of the isolated rat adipocyte as an experimental model. We have studied the effects of glucocorticoid hormones on insulin binding and insulin action in differentiated mouse 3T3-L1 fatty fibroblasts, in an attempt to develop a complete in vitro model of the insulin resistance associated with glucocorticoid excess. Exposure of 3T3-L1 cells to dexamethasone, a synthetic glucocorticoid, resulted in decreased binding of insulin to its receptor and decreased insulin stimulation of 2-deoxyglucose uptake. Although some effect of dexamethasone on these parameters was observed after 24 h, more than 3 days were required for maximal inhibition of both binding and biological response. The magnitude of these changes was concentration dependent over a range of 0.1-100 nM dexamethasone. Exposure to hydrocortisone produced similar changes, although higher concentrations were required. Cortexolone and deoxycorticosterone, compounds which weakly interact with the glucocorticoid receptor, caused partial inhibition of insulin action. Estradiol, testosterone, and methyl testosterone were inactive.When analyzed by Scatchard plots, the defect in insulin binding was identical to that seen when rodents were treated in vivo with glucocorticoids, namely a decrease in the affinity of the receptor for insulin, with little change in receptor concentration. A marked decrease in the sensitivity of dexamethasonetreated cells to insulin was seen, as well as a reduction in the ability of insulin to maximally stimulate 2-deoxyglucose uptake. When the binding and biological activity data were compared, the decreased affinity of the insulin receptor appeared to account for much, but not all, of the decrease in insulin sensitivity. Some postreceptor changes must also occur to account for the decrease in both maximal responsiveness and insulin sensitivity. In summary, we have been able to demonstrate in cultured cells each of the components of glucocorticoid-induced insulin resistance seen in vivo. Since the effects of glucocorticoid hormones in these cells are first seen within physiological concentrations, these changes may help explain the derangements in glucose metabolism seen in both hypo-and hyperadrenocortical states. (Endocrinology 109: 1723 , 1981) G LUCOCORTICOID excess results in insulin resistance as well as glucose intolerance in man and experimental animals (1-6). This insulin resistance is manifested by hyperglycemia in the face of hyperinsulinemia (2, 3) and decreased response to exogenous insulin (4, 5). Similarly, insulin sensitivity is increased in adrenal insufficiency (4, 6).

Effects of glucocorticoid excess on the sensitivity of glucose transport and metabolism to insulin in rat skeletal muscle

“…Studies using blood cells, fibroblasts and adipocytes have shown that glucocorticoids decrease the insulin-stimulated rate of glucose transport and the binding of insulin to its receptors [5][6][7][8][9][10]. Although muscle is quantitatively most important for glucose disposal in response to insulin [11], there are very few reports on the effects of glucocorticoids on this tissue.…”

Prednisone Increases the Number of Insulin Receptors in Erythrocytes from Children

“…Accordingly, there usually exists an inverse relationship between insulin binding and fasting plasma insulin levels in hyperinsulinemic states ( 9 , which was not found to be the case in the present study where insulin binding increased despite fasting hyperinsulinemia. In human and animal studies, other glucocorticoids such as cortisone and dexamethasone have been shown to cause insulin resistance by interfering at both receptor and postreceptor steps (10,21). Insofar as insulin receptors on erythrocytes reflect the status of insulin receptors on major target tissues like muscle, liver, and fat, our results suggest that prednisone-induced insulin resistance results from postreceptor defects.…”

“…Animal and in vitro studies have led to conflicting results: the effects of glucocorticoids on insulin binding to its receptor were variable, depending on the type of glucocorticoid tested, the cellular model used and the duration of its exposure to steroid (7,10,21,23,31,32). The investigation of insulin binding after glucocorticoid administration to human subjects has also provided ambiguous results (3,11,15,29,38).…”

Dexamethasone‐dependent expression of β1–24 corticotropin stimulated adenylate cyclase during adipose conversion of 3T3‐F442A cells

“…In these differentiating 3T3-L1 cells dexamethasone has been already shown to elicit a/5'1 to ~'2 switch of ~-adrenergic receptor subtypes [25] and to mimic some aspects of insulin resistance including both receptor and postreceptor defects [26]. From our studies, it is probable that the appearance of ACTH receptors, evidenced in 3T3-LI adipocytes by Grunfeld et al [27], is linked to the presence of dexamethasone in the differentiation protocol used by these authors.…”