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Changes in basal hypothalamo-pituitary-adrenal activity during exercise training are centrally mediated
Edward Park1, Owen Chan, Qifu Li
1School of Kinesiology and Health Science, York University, 4700 Keele St., Toronto, Ontario, Canada M3J 1P3.
Summary
Exercise training helps regulate the hypothalamo-pituitary-adrenal (HPA) axis by altering gene expression in the brain and pituitary, preventing elevated stress responses. Sham exercise, however, may increase basal HPA activity.
Area of Science:
- Endocrinology
- Neuroscience
- Exercise Physiology
Background:
- The impact of exercise training on hypothalamo-pituitary-adrenal (HPA) axis function remains incompletely understood.
- Adaptation of the pituitary-adrenal system during exercise may involve changes in brain and pituitary gene expression for neuropeptides and corticosteroid receptors.
Purpose of the Study:
- To investigate if pituitary-adrenal adaptation during exercise training is mediated by alterations in neuropeptide and corticosteroid receptor gene expression.
- To examine the effects of progressive exercise intensity on HPA axis response and gene expression.
Main Methods:
- Sprague-Dawley rats underwent daily swimming (DS) or sham exercise (SE) for 2, 4, or 6 weeks.
- Plasma ACTH and corticosterone (Cort) levels were measured.
- Gene expression of glucocorticoid receptor (GR) and corticotrophin-releasing hormone (CRH) in the paraventricular nucleus (PVN) and pituitary, and mineralocorticoid receptor (MR) in the hippocampus were analyzed.
Main Results:
- HPA axis response to exercise (Cort and catecholamines) was more robust at 6 weeks compared to 2 and 4 weeks in the DS group.
- Basal plasma ACTH and Cort increased from 2 to 4 weeks and plateaued at 6 weeks in DS rats.
- Exercise training led to transient decreases in GR mRNA in the PVN and pituitary and transient increases in CRH mRNA in DS rats. In contrast, SE resulted in decreased hippocampal MR and PVN GR mRNA expression by 6 weeks.
Conclusions:
- Exercise training appears to prevent elevated basal pituitary-adrenal activity by transiently modulating gene expression of GR and CRH, thereby suppressing central HPA axis drive.
- Repeated sham exercise may lead to increased basal pituitary-adrenal activity, potentially linked to reduced hippocampal MR and PVN GR mRNA expression.