Expression of pituitary glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase 1 in obese diabetic rats

Diabetic rat model was induced by high fat diet combined with streptozotocin (STZ). After the model was established, blood samples were taken from jugular veins to examine plasma adrenocorticotropic hormone (ACTH) and corticosterone, and hypothalamus and pituitary were removed for real-time PCR. There were no significant differences in basal plasma ACTH and corticosterone level among control, obese, and obese diabetic rats (P=0.07). The corticosterone rhythm in obese and obese diabetic rats was impaired. Hypothalamus glucocorticoid receptors (GR) mRNA expressions yielded similar results in the groups, but 11β-HSD1 mRNA expression in obese diabetic rats was up-regulated ( vs control rats, P<0.05 ). The expressions of GR and 11β-HSD1 in pituitary of obese diabetic and obese rats were significantly down-regulated (both P<0.05). In the obese diabetic rats, the impaired glucocorticoid negative feedback was partly due to down-regulation of 11 β-HSD1 and GR expressions in pituitary. Key words: Diabetes mellitus, type 2; Pituitary; Negative feedback; 11β-hydroxysteroid dehydrogenase type 1; Glucocorticoid receptors