In biopsy samples of the lateral part of the quadriceps femoris muscle of 6 obese diabetic male patients and of 11 obese males with a normal glucose tolerance, the activities of 7 enzymes of energy metabolism were estimated: hexokinase, cytoplasmic glycerol-3-phosphate: NAD dehydrogenase, triosephosphate dehydrogenase, lactate dehydrogenase, citrate synthase, malate dehydrogenase and 3-hydroxyacyl-CoA dehydrogenase. The obese diabetic male patients exhibited decreased activities of enzymes of carbohydrate breakdown and cytoplasmic NAD regeneration. Enzymes connected functionally with aerobic metabolism were less affected. The unchanged activity of 3-hydroxyacyl-CoA dehydrogenase points to an increased role of fatty acid catabolism in the muscle.
1. In 3 groups of men, differing as to the amount and intensity of physical training loads, increasing in the order "sedentary": "sporting": "athletic", enzyme activities were estimated in biopsy samples of m. quadriceps femoris (vastus lateralis). The enzymes were: Hexokinase (HK), NAD: glycerol-3-phosphate dehydrogenase (GPDH), triosephosphate dehydrogenase (TPDH), lactate dehydrogenase (LDH), citrate synthase (CS), NAD: malate dehydrogenase (MDH), and 3-hydroxyacyl-CoA dehydrogenase (HOADH). Indicators of laboratory performance and whole-body metabolic capacities (maximal oxygen consumption etc.) were estimated in the "sporting" and "athletic" groups. 2. In the 2 latter groups, distinguished by greater physical activity, the atypical enzyme activity pattern, remarkable by a low activity of LDH and high relative activities of GPDH and HK, as reported earlier in a sedentary group (Bass et al., 1975a), disappeared. The possibility of the atypical low LDH enzyme activity pattern as resulting from lack of bodily exertion is discussed. 3. The moderately trained "sporting" group distinguishes itself from the "sedentary" one mainly by a higher activity of LDH and by lower activities of GPDH and MDH. In the intensively trained "athletic" group, enzymes connected to aerobic oxidation (MDH, CS, HOADH) and GPDH also show higher activities than in the "sporting" group. The difference between the two more active groups is further borne out by a higher maximum oxygen uptake and carbon dioxide release of the well-trained "athletic" group. This difference of enzyme activity pattern may not be confined to the quadriceps femoris muscle.
In the quadriceps femoris muscle of obese women the glycogen concentration was significantly lower than in the control group, while protein and DNA values showed no significant differences. After 37 days of intermittent fasting, which consisted of repeated 5-day fasts alternating with 3-day intervals on 500 kcal/day with 60 g protein, in a group of 21 obese women a significant decline of the hexokinase activity in skeletal muscle was found. Other enzymes: triosophosphate dehydrogenase, lactate dehydrogenase, glycerol-3-phosphate dehydrogenase, citrate synthase, malate dehydrogenase and hydroxyacyl-CoA dehydrogenase showed no significant changes. There was a significant fall in concentration of DNA and glycogen, but the protein concentration did not change.
1. The following enzyme activities were estimated in needle-biopsy samples of the lateral part of the human quadriceps femoris muscle: triosephosphate dehydrogenase (TPDH), lactate dehydrogenase (LDH), NAD : glycerol-3-phosphate dehydrogenase (GPDH), hexokinase (HK), NAD: malate dehydrogenase (MDH), citrate synthase (CS) and hydroxyacyl-CoA dehydrogenase. 2. Although the enzyme activities in muscles of women were lesser than in those of men, no difference was found in the calculated enzyme activity ratios. There is thus no sex-dependent metabolic type-differentiation in this muscle. 3. The human quadriceps femoris is a low-activity muscle, in comparison with muscles of homoiotherm laboratory animals. The enzyme activity ratio of TPDH to CS, characterizing the glycolytic pyruvate formation to aerobic oxidative capacities, shows this muscle to be of an intermediate type in this respect, similarly as the extensor digitorum longus of the rat. The relatively very high capacity of glucose phosphorylation (HK), the high aerobic regeneration of cytoplasmic dehydrogenated NAD (GPDH) and the very low anaerobic regeneration (LDH), show the unusually high proportion of carbohydrates (glucose) which can be broken down aerobically.
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