Activities of muscle energy supplying enzymes after 5 days complete fasting in young men.
The effect of 5 days' complete fasting on the activity of 7 enzymes of energy supplying metabolism was studied in the vastus lateralis muscles of 9 healthy male volunteers. There was a significant decrease of lactate dehydrogenase (by 66%), triosephosphate dehydrogenase (by 61%), malate:NAD dehydrogenase (by 48%), hexokinase (by 40%), 3-hydroxyacyl-CoA-dehydrogenase (by 40%), triosephosphate dehydrogenase/3-hydroxyacyl-CoA-dehydrogenase (by 35%), citrate synthase (by 33%). Glycerolphosphate:NAD dehydrogenase activity did not decrease significantly. These findings suggest a) that utilization of the major energy substrates decreases; b) that the decrease mainly concerns the catabolism of carbohydrates, that of fatty acids to a lesser extent; c) that the decreased capacity of carbohydrate catabolism is partly compensated for by the predominance of the more economic aerobic-oxidative pathway; d) that the reducing equivalents formed in the cytosol may be transported via the glycerolphosphate shuttle into the respiratory chain to a greater extent, so that a greater portion is not lost by the reduction of pyruvate to lactate.
D000328:Adult; D004734:Energy Metabolism; D005215:Fasting; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008297:Male; D009132:Muscles / Q000201:enzymology*; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid
D005227:Fatty Acids; D011773:Pyruvates; D019289:Pyruvic Acid; D005947:Glucose