title: Regular exercise prevents the development of hyperglucocorticoidemia via adaptations in the brain and adrenal glands in male Zucker diabetic fatty rats.
abstract: We determined the effects of voluntary wheel running on the hypothalamic-pituitary-adrenal (HPA) axis, and the peripheral determinants of glucocorticoids action, in male Zucker diabetic fatty (ZDF) rats. Six-week-old euglycemic ZDF rats were divided into Basal, Sedentary, and Exercise groups (n = 8-9 per group). Basal animals were immediately killed, whereas Sedentary and Exercising rats were monitored for 10 wk. Basal (i.e., approximately 0900 AM in the resting state) glucocorticoid levels increased 2.3-fold by week 3 in Sedentary rats where they remained elevated for the duration of the study. After an initial elevation in basal glucocorticoid levels at week 1, Exercise rats maintained low glucocorticoid levels from week 3 through week 10. Hyperglycemia was evident in Sedentary animals by week 7, whereas Exercising animals maintained euglycemia throughout. At the time of death, the Sedentary group had approximately 40% lower glucocorticoid receptor (GR) content in the hippocampus, compared with the Basal and Exercise groups (P < 0.05), suggesting that the former group had impaired negative feedback regulation of the HPA axis. Both Sedentary and Exercise groups had elevated ACTH compared with Basal rats, indicating that central drive of the axis was similar between groups. However, Sedentary, but not Exercise, animals had elevated adrenal ACTH receptor and steroidogenic acute regulatory protein content compared with the Basal animals, suggesting that regular exercise protects against elevations in glucocorticoids by a downregulation of adrenal sensitivity to ACTH. GR and 11beta-hydroxysteroid dehydrogenase type 1 content in skeletal muscle and liver were similar between groups, however, GR content in adipose tissue was elevated in the Sedentary groups compared with the Basal and Exercise (P < 0.05) groups. Thus, the gradual elevations in glucocorticoid levels associated with the development of insulin resistance in male ZDF rats can be prevented with regular exercise, likely because of adaptations that occur primarily in the adrenal glands.
authors.affiliation: School of Kinesiology and Health Science, Faculty of Health, Muscle Health Research Centre, York University, Canada.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Campbell
authors.forename: Michael A
authors.initials: MA
authors.lastname: Király
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Atkinson
authors.forename: Anna M
authors.initials: AM
authors.lastname: D'souza
authors.forename: Mladen
authors.initials: M
authors.lastname: Vranic
authors.forename: Michael C
authors.initials: MC
authors.lastname: Riddell
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000378:metabolism; D042842:11-beta-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000222:Adaptation, Physiological; D000273:Adipose Tissue / Q000378:metabolism; D000311:Adrenal Glands / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003920:Diabetes Mellitus; D005938:Glucocorticoids / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D007333:Insulin Resistance; D008099:Liver / Q000378:metabolism; D008297:Male; D009043:Motor Activity; D018482:Muscle, Skeletal / Q000502:physiology; D010805:Physical Conditioning, Animal; D051381:Rats; D011924:Rats, Zucker; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D012420:Running
chemical_list: D005938:Glucocorticoids; C497713:NR3C1 protein, human; D011965:Receptors, Glucocorticoid; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; D042842:11-beta-Hydroxysteroid Dehydrogenases