The effect of training and detraining on lactate dehydrogenase isoenzymes in the horse

In the horse, total LDH activity increased with training and the H and M subunit activity parallelled this increase. It is suggested that these increases are in response to a stimulus from the type of training program utilised. The first half of a detraining program decreased the activity of the H and M subunits as might be expected. A sharp rise in the total LDH and the M subunit activity occurred during the latter half of the detraining program. This unexpected increase may be due to relatively more hypoxic conditions prevailing in the muscle during the detraining period.     

Adaptation of mitochondrial ATP production in human skeletal muscle to endurance training and detraining.

The adaptation of mitochondrial ATP production rate (MAPR) to training and detraining was evaluated in nine healthy men. Muscle samples (approximately 60 mg) were obtained before and after 6 wk of endurance training and after 3 wk of detraining. MAPR was measured in isolated mitochondria by a bioluminometric method. In addition, the activities of mitochondrial and glycolytic enzymes were determined in skeletal muscle. In response to training, MAPR increased by 70%, with a substrate combination of pyruvate + palmitoyl-L-carnitine + alpha-ketoglutarate + malate, by 50% with only pyruvate + malate, and by 92% with palmitoyl-L-carnitine + malate. With detraining MAPR decreased by 12-28% from the posttraining rate (although not significantly for all substrates). No differences were found when MAPR was related to the protein content in the mitochondrial fraction. The largest increase in mitochondrial enzyme activities induced by training was observed for cytochrome-c oxidase (78%), whereas succinate cytochrome c reductase showed only an 18% increase. The activity of citrate synthase increased by 40% and of glutamate dehydrogenase by 45%. Corresponding changes in maximal O2 uptake were a 9.6% increase by training and a 6.0% reversion after detraining. In conclusion, both MAPR and mitochondrial enzyme activities are shown to increase with endurance training and to decrease with detraining.     

Effect of training and detraining on skeletal muscle glucose transporter (GLUT4) content in rats.

The aim of the present study was to examine the effects of treadmill exercise training and detraining on the skeletal muscle fiber type specific expression of the insulin-regulated glucose transporter protein (GLUT4) in rats. GLUT4 protein content was determined by Western and dot-blot analysis, using a polyclonal antibody raised against the carboxy-terminal peptide. Rats were sacrificed 24 h after the last training session. There were no significant changes in muscle GLUT4 after 1 day or 1 week of training. Six weeks of training increased GLUT4 protein content 1.4- to 1.7-fold (p < 0.05) over controls in the soleus and red vastus lateralis, whereas no significant change was evident in the white vastus lateralis muscle. GLUT4 protein content in both soleus and red vastus lateralis muscle returned to near control values after 7 days of detraining. Similar to GLUT4, citrate synthase activity showed no change after 1 day or 1 week of training, increased 1.8-fold over controls after 6 weeks of training, but returned to control values after 7 days detraining. These findings demonstrate that muscle GLUT4 protein is increased in rats with as little as 6 weeks of treadmill exercise training but that the adaptation is lost within 1 week of detraining. It is suggested that expression of the GLUT4 protein is coordinated with the well-documented adaptations in oxidative enzyme activity with endurance training and detraining.     

Effects of iron deficiency and training on mitochondrial enzymes in skeletal muscle

We measured mitochondrial enzyme activities in skeletal muscle under conditions of iron deficiency and endurance training to assess the effects of these interventions on the contents and proportions of non-iron-containing and iron-dependent enzymes and proteins. Male Sprague-Dawley rats, 21 days of age, received a diet containing either 6 (iron deficient) or 50 mg iron/kg diet (iron sufficient). At 35 days of age animals were subdivided into sedentary and endurance training groups (running at 0.7 mph, 0% grade, 45 min/day, 6 days/wk). By 70 days of age, iron deficiency had decreased gastrocnemius muscle cytochrome c by 62% in sedentary animals. In contrast, the activities of tricarboxylic acid cycle enzymes were increased, remained unchanged or were slightly decreased, indicating that iron deficiency markedly altered mitochondrial composition. Endurance training increased cytochrome c (35%), tricarboxylic acid cycle enzymes (approximately 15%), and manganese superoxide dismutase (33%) in iron-deficient rats, whereas the same exercise regimen had no effect on the skeletal muscle of iron-sufficient animals. The interactive effect of dietary iron deficiency and mild exercise on mitochondrial enzymes suggests that adaptation to a training stimulus is, to some extent, geared to the relationship between the energy demand of exercise and the capacity for O2 transport and utilization.     

Effects of two high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performance

The purpose of this study was to investigate the effects of repeated high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performances. First, nineteen subjects were submitted to a 15-week cycle ergometer training program which involved both continuous and high-intensity interval work patterns. Among these 19 subjects, six participated in a second 15-week training program after 7 weeks of detraining. Subjects were tested before and after each training program for maximal aerobic power and maximal short-term ergocycle performances of 10 and 90s. Muscle biopsy from the vastus lateralis before and after both training programs served for the determination of creatine kinase (CK), hexokinase, phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH) activities. The first training program induced significant increases in all performances and enzyme activities but not in CK. Seven weeks of detraining provoked significant decreases in maximal aerobic power and maximal 90s ergocycle performance. While the interruption of training had no effect on glycolytic enzyme markers (PFK and LDH), oxidative enzyme activities (HADH and OGDH) declined. These results suggest that a fairly long interruption in training has negligeable effects on glycolytic enzymes while a persistent training stimulus is required to maintain high oxidative enzyme levels in human skeletal muscle. The degree of adaptation observed after the second training program confirms that the magnitude of the adaptive response to exercise-training is limited.     

Divergent response of metabolite transport proteins in human skeletal muscle after sprint interval training and detraining

Skeletal muscle primarily relies on carbohydrate (CHO) for energy provision during high-intensity exercise. We hypothesized that sprint interval training (SIT), or repeated sessions of high-intensity exercise, would induce rapid changes in transport proteins associated with CHO metabolism, whereas changes in skeletal muscle fatty acid transporters would occur more slowly. Eight active men (22 +/- 1 yr; peak oxygen uptake = 50 +/- 2 ml.kg(-1).min(-1)) performed 4-6 x 30 s all-out cycling efforts with 4-min recovery, 3 days/wk for 6 wk. Needle muscle biopsy samples (vastus lateralis) were obtained before training (Pre), after 1 and 6 wk of SIT, and after 1 and 6 wk of detraining. Muscle oxidative capacity, as reflected by the protein content of cytochrome c oxidase subunit 4 (COX4), increased by approximately 35% after 1 wk of SIT and remained higher compared with Pre, even after 6 wk of detraining (P < 0.05). Muscle GLUT4 content increased after 1 wk of SIT and remained approximately 20% higher compared with baseline during detraining (P < 0.05). The monocarboxylate tranporter (MCT) 4 was higher after 1 and 6 wk of SIT compared with Pre, whereas MCT1 increased after 6 wk of training and remained higher after 1 wk of detraining (P < 0.05). There was no effect of training or detraining on the muscle content of fatty acid translocase (FAT/CD36) or plasma membrane associated fatty acid binding protein (FABPpm) (P > 0.05). We conclude that short-term SIT induces rapid increases in skeletal muscle oxidative capacity but has divergent effects on proteins associated with glucose, lactate, and fatty acid transport.     

Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining.

Six women who had participated in a previous 20-wk strength training study for the lower limb detrained for 30-32 wk and subsequently retrained for 6 wk. Seven untrained women also participated in the 6-wk "retraining" phase. In addition, four women from each group volunteered to continue training an additional 7 wk. The initial 20-wk training program caused an increase in maximal dynamic strength, hypertrophy of all three major fiber types, and a decrease in the percentage of type IIb fibers. Detraining had relatively little effect on fiber cross-sectional area but resulted in an increased percentage of type IIb fibers with a concomitant decrease in IIa fibers. Maximal dynamic strength decreased but not to pretraining levels. Retraining for 6 wk resulted in significant increases in the cross-sectional areas of both fast fiber types (IIa and IIab + IIb) compared with detraining values and a decrease in the percentage of type IIb fibers. The 7-wk extension accentuated these trends such that cross-sectional areas continued to increase (nonsignificant) and no IIb fibers could be found. Similar results were found for the nonpreviously trained women. These data suggest that rapid muscular adaptations occur as a result of strength training in previously trained as well as non-previously trained women. Some adaptations (fiber area and maximal dynamic strength) may be retained for long periods during detraining and may contribute to a rapid return to "competitive" form.     

NADH shuttle enzymes and cytochrome b5 reductase in human skeletal muscle: effect of strength training

The main aim of this study was to investigate whether enzyme levels of the malate-aspartate and alpha-glycerophosphate shuttles and of cytochrome b5 reductase in human skeletal muscle are affected by strength training. Muscle biopsy samples from the deltoid muscle of the nondominant arm in untrained (n = 12) and strength-trained (n = 12) subjects were compared. The strength-trained muscles were characterized by a tendency to a higher percentage of type I fibers (67 vs. 59%), a lower percentage of type IIb fibers (12 vs. 18%), 34% larger mean fiber areas, and 19% more capillaries per fiber (P less than 0.1). No difference was noted in levels of enzymes representing the citric acid cycle, fatty acid oxidation, and glycolysis, nor in the number of capillaries per square millimeter. Neither did the levels of malate-aspartate and alpha-glycerophosphate shuttle enzymes nor cytochrome b5 reductase differ. Levels of cytochrome b5 reductase correlated (r = 0.59, P less than 0.01) with levels of the mitochondrial marker enzyme citrate synthase. It is concluded that strength training does not appear to result in increased levels of NADH shuttle enzymes and cytochrome b5 reductase.     

The effect of exercise training and water extract from propolis intake on the antioxidant enzymes activity of skeletal muscle and liver in rat

[Purpose]

In this study, the authors have intended to investigate the effects that the exercise training and the intake of the water extract from propolis have on the activity of antioxidant enzymes.

[Methods]

For this purpose, the exercise training (70% VO₂max treadmill running exercise for 60min)of 5 times per week for six weeks and the intake (50mg/kg/day) of the water extract from propolis were performed by separating the experimental animals (SD rats, n=32) into CON(n=8) group, CON+Ex(n=8), PA(n=8), and PA+Ex(n=8).

[Results]

As a result, the following conclusions were obtained: The concentration of the blood glucose and insulin of the CON+Ex group and PA+Ex group which are the exercise parallel group were significantly decreased in comparison with the control group, whereas if comparing the glycogen concentration in skeletal muscle and liver tissue between the exercise parallel group and the CON group, the former showed significantly high value in comparison with the latter (p < .05). In the case of the activity of the antioxidant enzyme in the skeletal muscle and the liver tissue, the activities of SOD, GPX and CAT in the gastrocnemius muscle tissue of the experimental animals showed significantly high value in PA+Ex group in comparison with other experimental groups (p < .05). In addition, the SOD activity in the liver tissue showed that only PA+Ex group was significantly increased, whereas GDX activity showed significantly higher value in CON+Ex group and PA group than CON group (p < .05). However, the activity of CAT in the liver tissue showed that there is no difference between the experimental groups. As a result that measured the concentration of MDA in order to evaluate the damage level of the tissue by oxygen free radicals, the difference between the groups in the liver tissue was not shown, while it was shown that only PA+Ex group in the skeletal muscle tissue was significantly decreased in comparison with other experimental groups (p < .05).

[Conclusion]

Taken together the above findings, it is considered that the parallel treatment of the exercise training and the water extract from propolis can not only increase the use of glycogen of the skeletal muscle and liver tissue, but also it can give the effect to suppress the creation of active oxygen by inducing the activity of the antioxidant enzyme in the body, and in the future, the possibility as the exercise supplements and the antioxidant of the water-soluble propolis are expected.     

Effect of sprint cycle training on activities of antioxidant enzymes in human skeletal muscle

Hellsten, Ylva, Fred S. Apple, and Bertil Sjödin.Effect of sprint cycle training on activities of antioxidantenzymes in human skeletal muscle. J. Appl.Physiol. 81(4): 1484-1487, 1996.The effect ofintermittent sprint cycle training on the level of muscle antioxidantenzyme protection was investigated. Resting muscle biopsies, obtainedbefore and after 6 wk of training and 3, 24, and 72 h after the finalsession of an additional 1 wk of more frequent training, were analyzedfor activities of the antioxidant enzymes glutathione peroxidase (GPX),glutathione reductase (GR), and superoxide dismutase (SOD). Activitiesof several muscle metabolic enzymes were determined to assess the effectiveness of the training. After the first 6-wk training period, nochange in GPX, GR, or SOD was observed, but after the 7th week oftraining there was an increase in GPX from 120 ± 12 (SE) to 164 ± 24 µmol ^· min^{1 ·} gdry wt¹(P < 0.05) and in GR from 10.8 ± 0.8 to 16.8 ± 2.4 µmol ^· min^{1 ·} gdry wt¹(P < 0.05). There was no significantchange in SOD. Sprint cycle training induced a significant(P < 0.05) elevation in the activity of phosphofructokinase and creatine kinase, implying an enhanced anaerobic capacity in the trained muscle. The present studydemonstrates that intermittent sprint cycle training that induces anenhanced capacity for anaerobic energy generation also improves thelevel of antioxidant protection in the muscle.

     

Effects of physical training on several glycolytic enzymes in rat heart.

In response to a program of daily swimming for 16 weeks, the activities of pyruvate kinase and lactate dehydrogenase increased significantly in the hearts of young male rats. The isozyme composition in M of cardial lactate dehydrogenase increased from 28.5 to 32.7% in the trained animals. Phosphofructokinase activity and glycogen content were unchanged. The hearts of the exercising animals were 28% heavier than those of sedentary paired weight controls.     

The effect of several diphosphonates on acid phosphohydrolases and other lysosomal enzymes.

Diphosphonates are known to inhibit bone resorption in tissue culture and in experimental animals. This effect may be due to their ability to inhibit the dissolution of hydroxyapatite crystals, but other mechanisms may be important. Since lysosomal enzymes have implicated in the process of bone resorption, we have examined the effect of several phosphonates and of a polyphosphate (P20,2) on lysosomal hydrolases derived from rat liver and rat bone. Dichloromethylene diphosphonate strongly inhibited acid beta-glycerophosphatase (EC 3.1.3.2) and acid p-nitrophenyl phosphatase (EC 3.1.3.2) and to a lesser degree (in descending order) acid pyrophosphatase (EC 3.1.3.-), arylsulfatase A (EC 3.1.6.1), deoxyribonuclease II(EC 3.1.4.6) and phosphoprotein phosphatase (EC 3.1.3.16) of rat liver. Inhibition of acid p-nitrophenyl phosphatase and arylsulfatase A was competitive. Ethane-1-hydroxy-1, 1-diphosphonate did not inhibit any of these enzymes, except at high concentrations. Neither dichloromethylene diphosphonate nor ethane-1-hydroxy-1, 1-diphosphonate had any effect on beta-glucuronidase (EC 3.2.1.31), arylesterase (EC 3.1.1.2) and cathepsin D (EC 3.4.23.5). Of several other phosphonates tested only undec-10-ene-1-hydroxy-1, 1-diphosphonic acid inhibited acid p-nitrophenyl phosphatase strongly, the polyphosphate (P20, I) had little effect. Acid p-nitrophenyl phosphatase in rat calvaria extract behaved in the same way as the liver enzyme and was also strongly inhibited by dichloromethylene diphosphonate, but not by ethane-1-hydroxy-1, 1-diphosphonate. It is suggested that the inhibition of bone resorption by dichloromethylene diphosphonate might be due in part to a direct effect of this diphosphonate on lysosomal hydrolases.     

Changes in the human muscle force-velocity relationship in response to resistance training and subsequent detraining.

Previous studies show that cessation of resistance training, commonly known as "detraining," is associated with strength loss, decreased neural drive, and muscular atrophy. Detraining may also increase the expression of fast muscle myosin heavy chain (MHC) isoforms. The present study examined the effect of detraining subsequent to resistance training on contractile performance during slow-to-medium velocity isokinetic muscle contraction vs. performance of maximal velocity "unloaded" limb movement (i.e., no external loading of the limb). Maximal knee extensor strength was measured in an isokinetic dynamometer at 30 and 240 degrees/s, and performance of maximal velocity limb movement was measured with a goniometer during maximal unloaded knee extension. Muscle cross-sectional area was determined with MRI. Electromyographic signals were measured in the quadriceps and hamstring muscles. Twitch contractions were evoked in the passive vastus lateralis muscle. MHC isoform composition was determined with SDS-PAGE. Isokinetic muscle strength increased 18% (P < 0.01) and 10% (P < 0.05) at slow and medium velocities, respectively, along with gains in muscle cross-sectional area and increased electromyogram in response to 3 mo of resistance training. After 3 mo of detraining these gains were lost, whereas in contrast maximal unloaded knee extension velocity and power increased 14% (P < 0.05) and 44% (P < 0.05), respectively. Additionally, faster muscle twitch contractile properties along with an increased and decreased amount of MHC type II and MHC type I isoforms, respectively, were observed. In conclusion, detraining subsequent to resistance training increases maximal unloaded movement speed and power in previously untrained subjects. A phenotypic shift toward faster muscle MHC isoforms (I --> IIA --> IIX) and faster electrically evoked muscle contractile properties in response to detraining may explain the present results.     

Changes in the characteristics of several carbohydrate metabolism enzymes during differentiation of loach skeletal muscle]

The gradual change of enzymes of glycogen metabolism proceeds during the skeletal muscle differentiation in the loach. The portion of the muscle type phosphorylase in the skeletal muscles of the embryo at the stage of the beginning of movement amounts to 30% and that at the stage of hatching to slightly over 50%. At the stage of yolk resorption, the skeletal muscles contain the muscle type phosphorylase only. At the same time the value of KM(UDPG) for glycogen synthetase gradually increases from 0,1 X 10(-3) up to 0,57 X 10(-3) M. The activity of alpha-glycerophosphate dehydrogenase increases more than 70 times.     

The enzymes of adenine nucleotide metabolism in developing skeletal muscle

1. During late foetal and early post-natal development of rabbit skeletal muscle the total protein increased more rapidly than the non-protein nitrogen content per g. wet wt. 2. AMP-deaminase activity of rabbit leg muscles increased rapidly over the period 5-15 days after birth. In diaphragm muscle from the same animal the rapid increase to the adult enzymic activity took place at about the time of birth. 3. The rapid increase in AMP-deaminase activity of leg muscle occurred earlier in animals born relatively mature, such as the chick and guinea pig, than in animals less well developed at birth, such as the rabbit and rat. 4. The pattern of enzymic activity shown by AMP deaminase during development in diaphragm, leg and cardiac muscles in a given species was closely paralleled by those of adenylate kinase and creatine phosphokinase. 5. When young rabbits were encouraged to become active at an earlier stage than is normal, the rise in creatine-phosphokinase activity occurred at an earlier age than in the control animals. 6. The results suggest that the activity pattern of the muscle is an important factor in determining the time at which the activities of the enzymes of special significance for muscle rise sharply to the adult values. 7. Development in rabbit leg muscle also involved an increase in aldolase activity. The pattern of change was similar to that obtained with other enzymes studied.