title: Prolonged exendin-4 administration stimulates pituitary-adrenocortical axis of normal and streptozotocin-induced diabetic rats.
abstract: Evidence is available that exendin-4 (EX4), a glucagon-like peptide-1 receptor (GLP-1R) agonist acutely stimulates hypothalamo-pituitary-adrenal (HPA) axis in the rat. EX4 is a potent insulinotropic agent, which is currently under clinical trial for treatment of type 2 diabetes. Since diabetes is known to affect adrenal function, we investigated the effects of the prolonged administration of EX4 and/or the GLP-1R antagonist EX4(9-39) (EX4-A) (daily subcutaneous injections of 1 nmol/kg EX4 and/or EX4-A, for 7 days) on the HPA axis of normoglycemic and streptozotocin (STZ)-induced diabetic rats. In STZ-untreated rats, chronic EX4 treatment did not change the blood level of ACTH. In contrast, it evoked a marked rise in the plasma concentrations of aldosterone and corticosterone, these effects being reversed by EX4-A. In STZ-induced diabetic rats, prolonged EX4 administration increased the plasma levels of ACTH, aldosterone and corticosterone. EX4-A did not prevent the first two effects of EX4, and annulled the latter one. These findings allow us to draw the following conclusions: i) EX4 prolonged exposure desensitizes hypothalamo-hypophyseal GLP-1R in normal rats, and exerts an ACTH-independent GLP-1R-mediated aldosterone and corticosterone secretagogue effect; and ii) experimental diabetes induces the expression of EX4 receptors other than the classic GLP-1R, whose activation mediate the ACTH and aldosterone, but not corticosterone, secretagogue effects. Our study provides evidence that metabolic dysregulations occurring in STZ-induced diabetic rats are able to profoundly affect the response of the HPA axis to GLP-1.
authors.affiliation: Department of Histology and Embryology, Karol Marcinkowski University of Medical Sciences, PL-60781 Poznan, Poland.
authors.forename: Ludwik K
authors.initials: LK
authors.lastname: Malendowicz
authors.forename: Giuliano
authors.initials: G
authors.lastname: Neri
authors.forename: Gastone G
authors.initials: GG
authors.lastname: Nussdorfer
authors.forename: Krzysztof W
authors.initials: KW
authors.lastname: Nowak
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Zyterska
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Ziolkowska
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000450:Aldosterone / Q000097:blood; D000818:Animals; D003345:Corticosterone / Q000097:blood; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy; D000077270:Exenatide; D005260:Female; D000067757:Glucagon-Like Peptide-1 Receptor; D010455:Peptides / Q000008:administration & dosage* / Q000737:chemistry; D010913:Pituitary-Adrenal System; D051381:Rats; D017208:Rats, Wistar; D018027:Receptors, Glucagon / Q000819:agonists; D013311:Streptozocin / Q000494:pharmacology; D013997:Time Factors; D014688:Venoms / Q000008:administration & dosage*
chemical_list: C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D010455:Peptides; D018027:Receptors, Glucagon; D014688:Venoms; D000450:Aldosterone; D013311:Streptozocin; D000324:Adrenocorticotropic Hormone; D000077270:Exenatide; D003345:Corticosterone