Muscles glucose transport during exercise

Glucose Transport into Muscle during Exercise A Contradiction ... 

Muscle GLUT4 transporters also can be induced by AMP levels (see Chapter 47), through the actions of the AMP-activated protein kinase. Thus, if energy levels are very low, and AMP levels increase, glucose can still be transported from the circulation into the muscle to provide energy. This most often occurs during exercise. 

Glucose transport into muscle cells can be stimulated during exercise because of the activity of the AMP-activated protein kinase Fatty acid uptake into exercising muscle is dependent on the levels of circulating fatty acids, which are increased by epinephrine release. 

Glucose is formed from pyruvate, which in turn can he obtained from lactate that accumulates in muscle during exercise. This process, called glu-coneogenesis, takes place in the liver after lactate is transported there hy the blood. The newly formed glucose is transported back to the muscles by the blood. 

Once the fatty acids are in the cytoplasm of the muscle cells, they are transported across the mitochondrial membrane by carnitine palmityol transferases I and II for P-oxidation and energy production. During exercise, total fat oxidation rates can increase more than ten-fold during the transition from rest to moderate-intensity exercise. The availability of glucose, rather than that of fatty acids, controls the rate of fatty acid oxidation because glucose can decrease the oxidation of long-chain fatty acids by inhibiting their transport into the mitochondria. 

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