CNS-periphery relationships and body weight homeostasis: influence of the glucocorticoid status.

The obesity-like effects produced by the chronic intracerebroventricular (i.c.v.) neuropeptide Y (NPY) infusion in normal rats require the presence of glucocorticoids, as none of them occurs when NPY is similarly infused in adrenalectomized rats. NPY effects are present again when i.c.v. NPY is infused together with i.c.v. dexamethasone in adrenalectomized animals. The inhibitory effect of leptin on food intake and body weight observed when the hormone is i.c.v. administered to normal rats is markedly enhanced and longer lasting when the same dose of leptin is i.c.v. administered to adrenalectomized rats. Glucocorticoid administration to adrenalectomized rats dose-dependently reduces, then abolishes, this potent effect of leptin. Thus, glucocorticoids limit leptin-induced effects. The chronic i.c.v. infusion of glucocorticoids (dexamethasone) to normal rats produces an obesity syndrome with its several abnormalities. This appears to be due to glucocorticoid-elicited increases in hypothalamic NPY levels together with decreases in those of CRH. Thus, the status of the hypothalamo-pituitary-adrenal axis and related glucocorticoid output is a relevant facet of body weight homeostasis. It may be a deleterious environmental factor responsible for the development of obesity, insulin as well as leptin resistance, and type 2 diabetes.