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Carbohydrate metabolism during exercise: influence of circulating fat availability
D P Bracy1, B A Zinker, J C Jacobs
1Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 1, 1995
Summary
Circulating fat influences carbohydrate metabolism during exercise. Suppressing fat availability (lipolysis) increased glucagon and lactate, but did not alter glucose or insulin levels significantly.
Area of Science:
- Exercise Physiology
- Metabolic Regulation
- Nutritional Biochemistry
Background:
- Circulating free fatty acids (FFAs) are a key energy substrate during exercise.
- The precise role of FFAs in regulating carbohydrate metabolism during physical activity remains under investigation.
Purpose of the Study:
- To investigate the impact of suppressed lipolysis on carbohydrate metabolism during rest and exercise in dogs.
- To determine how circulating fat availability affects glucose production, utilization, and hormonal responses.
Main Methods:
- Utilized isotopic and hindlimb arteriovenous techniques in dogs.
- Compared metabolic responses during rest and treadmill exercise with and without Intralipid infusion to manipulate lipolysis.
- Measured plasma glucose, insulin, glucagon, catecholamines, cortisol, FFAs, and lactate.
Main Results:
- Plasma glucose and hormonal differences (insulin, catecholamines, cortisol) were insignificant between groups.
- Suppressed lipolysis led to higher glucagon and arterial blood lactate levels.
- Despite altered FFA availability, glucose production and utilization showed significant differences, while limb glucose uptake remained similar.
Conclusions:
- Circulating fat plays a role in modulating carbohydrate metabolism during exercise, influencing glucagon and lactate.
- While FFAs impact glucose flux, their direct effect on glucose utilization by muscles may be less pronounced under these conditions.