title: Glucocorticoid-deficient corticotropin-releasing hormone knockout mice maintain glucose requirements but not autonomic responses during repeated hypoglycemia.
abstract: Glucocorticoids have been implicated in hypoglycemia-induced autonomic failure but also contribute to normal counterregulation. To determine the influence of normal and hypoglycemia-induced levels of glucocorticoids on counterregulatory responses to acute and repeated hypoglycemia, we compared plasma catecholamines, corticosterone, glucagon, and glucose requirements in male wild-type (WT) and glucocorticoid-deficient, corticotropin-releasing hormone knockout (CRH KO) mice. Conscious, chronically cannulated, unrestrained WT and CRH KO mice underwent a euglycemic (Prior Eu) or hypoglycemic clamp (Prior Hypo) on day 1 followed by a hypoglycemic clamp on day 2 (blood glucose both days, 65 +/- 1 mg/dl). Baseline epinephrine and glucagon were similar, and norepinephrine was elevated, in CRH KO vs. WT mice. CRH KO corticosterone was almost undetectable (<1.5 microg/dl) and unresponsive to hypoglycemia. CRH KO glucose requirements were significantly higher during day 1 hypoglycemia despite epinephrine and glucagon responses that were comparable to or greater than those in WT. Hyperinsulinemic euglycemia did not increase hormones or glucose requirements above baseline. On day 2, Prior Hypo WT had significantly higher glucose requirements and significantly lower corticosterone and glucagon responses. Prior Hypo and Prior Eu CRH KO mice had similar day 2 glucose requirements. However, Prior Hypo CRH KO mice had significantly lower day 2 epinephrine and norepinephrine vs. Prior Eu CRH KO and tended to have lower glucagon than on day 1. We conclude that glucocorticoid insufficiency in CRH KO mice correlates with 1) impaired counterregulation during acute hypoglycemia and 2) complex effects after repeated hypoglycemia, neither preventing decreased hormone responses nor worsening glucose requirements.
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, MC-136, Albany, NY 12208, USA. JACOBSL@mail.amc.edu
authors.forename: Lauren
authors.initials: L
authors.lastname: Jacobson
authors.forename: Tasneem
authors.initials: T
authors.lastname: Ansari
authors.forename: Jessica
authors.initials: J
authors.lastname: Potts
authors.forename: Owen P
authors.initials: OP
authors.lastname: McGuinness
mesh_terms: D000313:Adrenal Medulla / Q000378:metabolism / Q000503:physiopathology; D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001786:Blood Glucose / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000172:deficiency* / Q000378:metabolism; D004837:Epinephrine / Q000097:blood; D005934:Glucagon / Q000097:blood; D005938:Glucocorticoids / Q000172:deficiency* / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D007003:Hypoglycemia / Q000378:metabolism* / Q000503:physiopathology; D007328:Insulin / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009638:Norepinephrine / Q000097:blood
chemical_list: D001786:Blood Glucose; D005938:Glucocorticoids; D007328:Insulin; D005934:Glucagon; D003346:Corticotropin-Releasing Hormone; D005947:Glucose; D003345:Corticosterone; D009638:Norepinephrine; D004837:Epinephrine