Protein metabolism during exercise

Layman, D.K. (2002). Role of leucine in protein metabolism during exercise and recovery. Can J Appl Physiol 27 646-663. 

Protein and Amino Acid Metabolism During Exercise... 

Bowtell, J.L., Leese, G.P., Smith, K. et al.. Modulation of whole body protein metabolism, during and after exercise, by variation of dietary protein, J Appl Physiol, 85,... 

The second study concerns the enzyme that catalyzes the synthesis of "2-6," fructase-6-phosphate 2-kinase. The liver is composed of several types of cells. The major cell, the hepatocyte, constitutes about S0% of the cell population and contains about 99% of the protein, Hepatocytes carry out most of the metabolic functions of the liver, Castenodd. (1979) added glucagon to hepatocytes in culture and found that fructo e-6-phosphate 2-kinase decreased within the first minute of addition of the hormone. Addition of the hormone was intended to simulate, in part, hormonal changes that occur in the body during exercise. The observed decrease in enzyme activity is consistent with the dramatic drop in "2-6" that occurred in the running rat experiment. The work described thus far shows that "2-6" levels in the liver Increase or decrease under certain conditions. These facts, though interesting, do not directly indicate a function for "2-6,"... 

Gillingham MB, et al. Metabolic control during exercise with and without medium-chain triglycerides (MCT) in children with long-chain 3-hydroxy acyl-CoA dehydrogenase (LCHAD) or trifunctional protein (TFP) deficiency. Mol Genet Metab. 2006 89(l-2) 58-63. 

Rennie, M.J. and Tipton, K.D., Protein and amino acid metabolism during and after exercise and the effects of nutrition, Anna Rev Nutr, 20, 457, 2000. 

Tipton ICD, Cocke TL, Wolf SE, Wolfe RR. Response of muscle protein metabolism to resistance training and acute resistance exercise during hyperaminoacidemia. Am J Physiol 2006 in press. 

One of the metabolic reactions to majot ttauma, such as a burn, a broken limb, or surgery, is an increase in the net catabolism of tissue proteins. As much as 6-7% of the total body protein may be lost ovet 10 days. Prolonged bed rest results in considetable loss of protein because of atrophy of muscles. Protein is catabohzed as normal, but without the stimulus of exercise it is not completely replaced. Lost protein is replaced during convalescence, when there is positive nittogen balance. A normal diet is adequate to petmit this replacement. 

The calorific capacity of amino acids is comparable to that of carbohydrates so despite their prime importance in maintaining structural integrity of cells as proteins, amino acids may be used as fuels especially during times when carbohydrate metabolism is compromised, for example, starvation or prolonged vigorous exercise. Muscle and liver are particularly important in the metabolism of amino acids as both have transaminase enzymes (see Figures 6.2 and 6.3 and Section 6.4.2) which convert the carbon skeletons of several different amino acids into intermediates of glycolysis (e.g. pyruvate) or the TCA cycle (e.g. oxaloacetate). Not all amino acids are catabolized to the same extent... 

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