Leucine oxidation, effect exercise

The work by Wolfe et al. (31,32) serves to emphasize some of these problems. They utilized a mild bicycle exercise and examined the effects on leucine oxidation and urea production. 

Preliminary work in our laboratory suggests that the effect of exercise on leucine oxidation is not just a transient effect of beginning an exercise program, and that the magnitude of the effect is dependent on the duration of the exercise (Fig. 2). 

In contrast to endurance exercise, acute whole-body resistance exercise does not alter leucine oxidation. In this same study we also did not find an effect of acute resistance exercise on whole-body protein synthesis, either during exerdse or for up to 2 h post-exerdse. We hypothesized that since muscle protein synthesis (MPS) accounted for only 25% of whole-body synthesis, changes in MPS either may be not measurable or would be negated by a redprocal change in the synthesis of another protein, such as one in the gastrointestinal tract. 

Gaine, FC., Viesselman, C.T., Pikosky, M.A. et al.. Aerobic exercise training decreases leucine oxidation at rest in healthy adults, J Nutr, 135, 1088, 2005. Campbell, W.W., Crim, M.C., Young, V.R., Joseph, L.J., and Evans, W.J., Effects of resistance training and dietary protein intake on protein metabolism in older adults. Am J Physiol, 268, El 143, 1995. 

Four untrained men were exercised for 105 minutes on a bicycle ergometer at an intensity designed to maintain a heart rate of 110 beats/minute (approximately 30% V02niax Comparing a pre-exercise rest period to immediately post-exercise, they found a 2- to 3-fold increase in the production of CO2 from leucine, but they found no Increase in urea production. They also determined that while mild exercise Increased oxidation of leucine, there was no effect on the catabolism of another essential amino... 

Aerobic exercise usually increases the percentage of muscle mass due to a decrease in body fat, but produces no absolute change in the amount of muscle. Aerobic exercise has been shown to alter protein metabolism including increases in amino acid oxidation with specific effects on the branched-chain amino acid leucine, increased urinary urea, and increased sweat nitrogen. 

Hogg, S.A., Morse, E.L. Adibi, S.A. (1982) Effect of exercise on rates of oxidation, turnover, and plasma clearance of leucine in human subjects. Amer. J. Physiol. 242, E407-E410. 

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