α2-AMPK activity is not essential for an increase in fatty acid oxidation during low-intensity exercise

Oct 23, 2008American journal of physiology. Endocrinology and metabolism

Alpha2-AMPK is not needed for increased fat burning during light exercise

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Abstract

Alpha(1)-AMPK-DN mice exhibited a 50% reduction in alpha(1)-AMPK activity compared to wild-type mice.

A single bout of exercise enhances glucose uptake and fatty acid oxidation in skeletal muscle.
The exercise-induced increase in glucose uptake is partly linked to the activation of AMPK.
Alpha(1)-AMPK-DN mice could not perform high-intensity treadmill exercise, unlike wild-type mice.
There were no significant differences in oxygen consumption or respiratory quotient during low-intensity exercise between the two groups.
Increased fatty acid oxidation during low-intensity exercise was unaffected in alpha(1)-AMPK-DN mice, indicating a similar utilization of fatty acids to wild-type mice.

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A single bout of exercise increases glucose uptake and fatty acid oxidation in skeletal muscle, with a corresponding activation of AMP-activated protein kinase (AMPK). While the exercise-induced increase in glucose uptake is partly due to activation of AMPK, it is unclear whether the increase of fatty acid oxidation is dependent on activation of AMPK. To examine this, transgenic mice were produced expressing a dominant-negative (DN) mutant of alpha(1)-AMPK (alpha(1)-AMPK-DN) in skeletal muscle and subjected to treadmill running. alpha(1)-AMPK-DN mice exhibited a 50% reduction in alpha(1)-AMPK activity and almost complete loss of alpha(2)-AMPK activity in skeletal muscle compared with wild-type littermates (WT). The fasting-induced decrease in respiratory quotient (RQ) ratio and reduced body weight were similar in both groups. In contrast with WT mice, alpha(1)-AMPK-DN mice could not perform high-intensity (30 m/min) treadmill exercise, although their response to low-intensity (10 m/min) treadmill exercise was not compromised. Changes in oxygen consumption and the RQ ratio during sedentary and low-intensity exercise were not different between alpha(1)-AMPK-DN and WT. Importantly, at low-intensity exercise, increased fatty acid oxidation in response to exercise in soleus (type I, slow twitch muscle) or extensor digitorum longus muscle (type II, fast twitch muscle) was not impaired in alpha(1)-AMPK-DN mice, indicating that alpha(1)-AMPK-DN mice utilize fatty acid in the same manner as WT mice during low-intensity exercise. These findings suggest that an increased alpha(2)-AMPK activity is not essential for increased skeletal muscle fatty acid oxidation during endurance exercise.

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α2-AMPK activity is not essential for an increase in fatty acid oxidation during low-intensity exercise

Abstract

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