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Glucoregulation during and after intense exercise: effects of beta-blockade
R J Sigal1, C Purdon, D Bilinski
1McGill Nutrition and Food Science Center, Royal Victoria Hospital, Montreal, Quebec, Canada.
The Journal of Clinical Endocrinology and Metabolism
|February 1, 1994
Summary
Beta-adrenergic blockade during intense exercise revealed an unmasked alpha-adrenergic effect on glucose production and highlighted beta-adrenergic restraint on glucose uptake. This study clarifies adrenergic receptor roles in exercise metabolism.
Area of Science:
- Exercise Physiology
- Endocrinology
- Adrenergic Receptor Signaling
Background:
- Adrenergic receptors, specifically beta- and alpha-adrenergic receptors, play crucial roles in regulating physiological responses during intense physical activity.
- Understanding their distinct contributions to glucose metabolism during maximal exercise is essential for comprehending exercise physiology and metabolic control.
Purpose of the Study:
- To elucidate the specific roles of beta- and alpha-adrenergic receptors in modulating glucose kinetics during high-intensity exercise.
- To investigate the impact of beta-adrenergic blockade on glucose appearance and disappearance rates, and hormonal responses.
Main Methods:
- Seventeen healthy young males performed cycle ergometer exercise at maximal oxygen uptake (MAX), 87% VO2max with intravenous propranolol (P; beta-blocker), and 87% VO2max as controls (C).
- Measurements included plasma glucose, insulin, glucagon, norepinephrine, and epinephrine levels.
- Calculations of the rates of glucose appearance (Ra) and disappearance (Rd) were performed.
Main Results:
- Plasma glucose and the rate of glucose appearance (Ra) increased significantly during MAX and P exercise compared to controls (C).
- The rate of glucose disappearance (Rd) was significantly elevated in the P group compared to controls, suggesting a role for beta-adrenergic receptors in limiting glucose uptake.
- Propranolol treatment altered the insulin and glucagon responses and was associated with higher peak norepinephrine and epinephrine levels.
Conclusions:
- Beta-adrenergic blockade unmasked an alpha-adrenergic contribution to increased glucose production during intense exercise, potentially mediated by the glucagon/insulin ratio.
- Beta-adrenergic receptors play a significant role in restraining glucose disappearance during high-intensity exercise.