Exercise gluconeogenesis during

The mechanism that produces increased amino acid oxidation during exercise is unknown. White and Brooks (29) demonstrated a relationship of amino acid oxidation to use oT blood glucose. Concomitant with increases in the intensity of exercise and leucine oxidation, the oxidation of glucose and alanine increased. These data in combination with the earlier reports of increased flux of leucine to skeletal muscles and alanine from muscles to the liver suggest that the oxidation of amino acids may be linked to the need for glucose and to generation of substrates for gluconeogenesis. 

The different fuels used by exercising muscle are discussed in subsequent sections. These fuels may be arranged in the following "hierarchy," where the order of appearance approximates relative importance during exercise (1) creatine phosphate, (2) muscle and liver glycogen, (3) gluconeogenesis, and (4) fatty acids. 

Net breakdown of muscle can occur with either exercise or prolonged fasting. The mechanisms that control the breakdown of the various types of protein found in muscle are not well understood. It has, however, been established that while the branched-chain amino acids (BCAAs) released tend to be oxidized for energy in the muscle cell, other released amino acids enter the bloodstream for catabolism, and perhaps gluconeogenesis, in the liver Examination of the amino acids released from skeletal muscle reveals an apparent anomaly alanine accounts for or ly about 6% of the amino acids of muscle, but for about 35% of the amino acids released from muscle during exerdse. 

Gluconeogenesis occurs primarily in the liver. It can also occur in the kidney, but this contribution is relatively small. The carbon skeletons used for glucose synthesis can be derived from lactate, glycerol, or amino acids. During exercise, the lactate produced and released by fermentative muscle is taken up by the liver and... 

Wasserman, D. H., Williams, P. E., Lacy, D. B., Green, D. R., and Cherrington, A. D. (1988). Importance of intrahepatic mechanisms to gluconeogenesis from alanine during exercise and recovery. Am. J. Physiol. 254, E518-E525. 

During exercise, blood glucose is also maintained by liver glycogenolysis and gluconeogenesis. 

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