Adaptation of muscle to exercise. Increase in levels of palmityl Coa synthetase, carnitine palmityltransferase, and palmityl Coa dehydrogenase, and in the capacity to oxidize fatty acids

Cytochrome c oxidase activity and fatty acid oxidation in various types of human muscle

Cytochrome c oxidase activity, carnitine concentration and oxidation rates of pyruvate and palmitate were determined in homogenates of various types of human skeletal muscle. Cytochrome c oxidase activity appeared to be closely related to the pyruvate oxidation rate, but its correlation with palmitate oxidation was less distinct. Trunk muscles oxidize less palmitate and have a lower cytochrome c oxidase activity per mg homogenate protein than leg muscles; soleus muscle biopsies showed higher activities than those of other leg muscles. Based on cytochrome c oxidase activity no large differences are found in palmitate oxidation rate between various types of human muscle. Cytochrome c oxidase activity and palmitate oxidation rate of muscles do not show an age dependency. The carnitine concentration is similar in all kinds of human skeletal muscle.

Effect of inflammatory and noninflammatory stress on plasma ketone bodies and free fatty acids and on glucagon and insulin in peripheral and portal blood

Inflammatory stress as characterized by infection with Streptococcus pneumoniae, administration of endotoxin, or the induction of a turpentine abscess is characterized by the inhibition of the ketosis assoicated with fasting and a decline in the level of free fatty acids in the plasma. Moreover, rats subjectd to these inflammatory stresses demonstrate a significant rise in peripheral and portal insulin and glucagon. Rats subjected to noninflammatory stresses, screen-restraint, or noninvasive femoral fracture did not demonstrate the inhibition of ketosis but did show a decrease in plasma free fatty acids. The noninflammatroy stresses did not show an abnormal elevation of plasma or portal insulin or glucagon.

Metabolic response to heavy physical exercise before and after a 3-month training period

Twenty healthy athletes performed a heavy physical exercise before and after a controlled training period of 3 months. As a result of physical training there was a reduction in lactate concentration during and after exercise. Plasma free fatty acids and triglyceride levels were lower at rest as well as during and after exercise. Insulin concentrations decreased during exercise before the training period whereas they remained constant afterwards. The composition of individual free fatty acids changed in the same way during exercise before and after training: fatty acids with shorter hydrocarbon chains increased, those with longer chains decreased. Comparing the pattern of individual free fatty acids before and after training a higher percentage of saturated and a lower percentage of mono-unsaturated fatty acids was observed. It is concluded that changes in the plasma free fatty acid profile during heavy exercise reflect a preferential uptake and oxidation of certain individual free fatty acids. The significance of training-induced changes in the plasma free fatty acid pattern is discussed.

Activities of malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase and fructose-1,6-diphosphatase with regard to metabolic subpopulations of fast- and slow-twitch fibres in rabbit muscles

Activities of malate dehydrogenase (MDH), 3-hydroxyacyl-CoA dehydrogenase (HAD) and fructose-1,6-diphosphatase (FDPase) were determined in single fibres dissected from freeze-dried rabbit psoas and soleus muscles. Slow-twitch fibres as determined by qualitative ATPase reaction represent a rather uniform population with regard to HAD and MDH activities. In these fibres the two enzymes are in constant proportions. FDPase is found at extremely low activities in slow-twitch fibres and because of its relatively high activity in fast-twitch fibres of soleus and psoas muscle it might be used as a marker enzyme. Fast-twitch fibres in psoas muscle represent a heterogeneous population with regard to activities of MDH as well as of HAD. The two enzyme activities are not proportional in fast-twitch psoas fibres. These findings suggest the existence of metabolic subpopulations of fast-twitch fibres having a wide range of aerobic oxidative capacities and having differences in their capacity to oxidizing fatty acids.

The effect of training and detraining on several enzymes in horse skeletal muscle

Training and detraining had little effect on the activity of glycogen synthase, hexokinase, glycerol 3-phosphate dehydrogenase or total protein. The activity of 3-hydroxyacyl-CoA dehydrogenase increased markedly during training. After 5 weeks of detraining, the activity of 3-hydroxyacyl-CoA dehydrogenase was returning to pre-training values, whilst by 10-week detraining, the levels were increasing again.

Substrate oxidation specificity in different types of mammalian muscle

The maximal capacity of homogenates prepared from cardiac, fast-oxidative-glycogenolytic (FOG) vastus lateralis, fast-glycogenolytic (FG) vastus lateralis, and slow-oxidative (SO) soleus muscle to oxidize pyruvate, palmitate, alpha-glycerophosphate, and acetoacetate was assessed by measuring oxygen consumption under conditions of nonlimiting substrate and cofactors. Pyruvate oxidation varied eight-fold among the muscle types and was highest in cardiac, followed by FOG, SO, and FG muscle. Palmitate was oxidized at 97%, 85%, 77%, and 57% of the relative rate for pyruvate in cardiac, FOG, SO, and FG muscle, respectively. In contrast, alpha-glycerophosphate oxidation rates were highest in FG muscle, followed by cardiac, FOG, and SO muscle. Although cardiac muscle possessed the highest absolute rate for acetoacetate oxidation, it had the lowest capacity relative to pyruvate (19%), whereas SO muscle possessed the highest (61%). FOG and FG muscle had similar relative capacities for this substrate (30%). These results provide further evidence to suggest that mammalian muscle types are differentiated in terms of both mitochondrial mass and substrate oxidation specificity.

Lipoprotein lipase activity in adipose tissue and skeletal muscle of runners: relation to serum lipoproteins

Physically well-trained people generally have lower VLDL-triglyceride and higher HDL-cholesterol levels than sedentary subjects. To examine the underlying mechanisms of this lipoprotein pattern, we measured the lipoprotein lipase (LPL) activity in needle biopsy specimens of adipose tissue and skeletal muscle of competitive runners and of body weight-matched, physically less-active controls. The active sportsmen were either sprinters, whose training program consisted mainly of athletics of short duration or long distance runners undergoing a strenuous endurance exercise program. In sprinters (all males) the serum lipid and lipoprotein concentrations did not differ significantly from those of controls and the mean LPL activities in muscle and adipose tissue were also similar in these two groups. The long distance runners (both sexes), on the other hand, had higher means levels of HDL-cholesterol than the respective controls. The LPL-activity of both adipose tissue (p less than 0.05) and skeletal muscle (p less than 0.01) was significantly higher in male long distance runners than in control males. Female runners had higher muscle LPL activity than controls (p less than 0.01) but in adipose tissue the difference in LPL activity was not significant. Rough estimates calculated for LPL activity present in whole body adipose tissue and skeletal muscle indicated that total LPL activity was 2.3 times higher in male long distance runners and 1.5 times higher in female long distance runners than in the respective controls. In combined groups of male runners and controls, there was a highly significant positive correlation between the serum HDL-cholesterol level and the LPL activity of adipose tissue expressed per tissue weight (r = +0.72, p less than 0.001) or per whole body fat (r = +0.62, p less than 0.001). The group means of HDL-cholesterol and adipose tissue LPL activity in the five cohorts studied (male sprinters, distance runners and controls and female distance runners and controls) were also positively correlated (r = +0.94). It is concluded that endurance training is associated with an adaptive increase of LPL activity not only in skeletal muscle but also in adipose tissue. These changes are not observed in sprinters who are trained by exercises of shorter duration. The high HDL-cholesterol levels of physically well-trained people are probably accounted for, at least partly, by the increased LPL activity and the concomitant rapid turnover or triglyceride-rich lipoproteins.

Physical exercise and the prevention of atherosclerosis and cholesterol gall stones

There is accumulating evidence in man and experimental animals that even mild exercise, if regularly repeated, may alter the metabolism of lipids. Exercise has been reported as decreasing peripheral tissue cholesterol in red blood cells, working muscle, lungs and the liver. During physical activity, the output of cholesterol and bile acids into the bile increases. This probably leads to higher faecal losses of sterols which may lead to lower cholesterol levels in the peripheral tissues and in the bile, when exercise is repeated regularly. Preferential release of unsaturated fatty acids from the adipose tissue during exercise and the linoleic acid-dependent LCAT enzyme (transporting plasma cholesterol) may be partly responsible for this effect of exercise. The experimental data reviewed provide supportive basis for epidemiological studies reporting on the beneficial effect of regular exercise.

Physical activity is an important factor in the phylogeny of all animal species, secondary only to food intake and reproduction. Exercise is readily available to all population groups. There is good evidence that the amount of exercise required for a protective effect is easily accessible for time-pressured and older individuals. Short bursts of activity repeated several times a day may be equally or more beneficial than prolonged exhaustive exercise. Modified exercise is also beneficial for patients with coronary heart disease and for elderly patients, provided this is done under strict medical supervision. To be effective, physical exercise should be regular and continuous throughout life.

Biochemical and physiologic consequences of carnitine palmityltransferase deficiency

A patient with a long history of exercise-unduced pain developed myoglobinuria and respiratory failure following extensive exercise (football). Although muscle histochemistry was normal, tissue oxidation of 14C-labeled palmitate was decreased, and muscle carnitine palmityltransferase (CPT) activity was one-tenth of normal. During fasting, his creatine kinase (CK) rose from 127 mu/ml to 278 mu/ml and blood ketones failed to exhibit a normal rise. Triglycerides were normal, as was fatty-acid mobilization. Prolonged exercise resulted in an inordinately increased CK with only moderate elevations in lactate. Treatment with medium-chain triglycerides did not alter his symptoms or improve exercise performance. Pain on exercise is a common complaint, but the occurrence of myoglobinuria points to a defect of energy metabolism; Screening for defects of fat utilization may be accomplished by the prolonged-exercise test, invitro oxidation of 14C-labeled substrates, and prolonged fasting.

Low intensity training, inactivity and resumed training in sedentary men

The effects of a low intensity training regimen, consisting of two 7-week periods with an interspersed 8-week inactivity period were investigated in 16 sedentary men. A follow-up was made on 7 subjects after 38 additional weeks' training. Systemic as well as local effects were studied using exercise tests and leg muscle biopsies. The two 7-week training periods both resulted in a 6% increase in Vo2 max and a lowered heart rate during submaximal work. No persisting training effects were detected by exercise tests after inactivity. In skeletal muscle, however, striking differences in enzyme activity pattern and ultrastructure were observed between the two periods, indicating that some training effect of importance for muscle metabolic adaptation might have persisted during inactivity. It is suggested that such an effect might be associated with the local oxygen supply. During the 38-week training period there was a large increase in muscle metabolic capacity, but no change in maximal oxygen uptake. This separation of systemic and local training effects indicates a lack of a direct causal relationship between muscle metabolic potential and max imal oxygen uptake. It is suggested that the elevated muscle oxidative capacity is of importance for an increased endurance capacity.

The effect of training and detraining on muscle composition in the horse

1. Percutaneous needle biopsies were obtained from six limb muscles in six horses before and during a training programme of 10 or 15 weeks designed to involve both aerobic and anaerobic work. In a subsequent detraining period, biopsies were also taken after 5 and 10 weeks. 2. Samples were analysed biochemically for enzyme activity of lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aldolase (ALD), citrate synthase (CS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) and for glycogen content. Fibre typing was carried out histochemically before and 10 weeks after commencement of training. 3. There was a significant increase in the percentage of high myosin ATPase activity pH 9-4/high oxidative (FTH) fibres with a corresponding decrease in high myosin ATPase activity pH 9-4/low oxidative (FT) fibres and low myosin ATPase activity pH 9-4/high oxidative (ST) fibres after 10 weeks training. 4. During training, enzyme activities increased progressively but at different rates with an approximate twofold increase in all of the enzymes except CPK by the end of the training period. Changes in all the muscles studied were similar. Glycogen content increased by approximately 33% which was significant when all the muscles were considered together. 5. A decrease in enzyme activity occurred after 5 weeks detraining. However at 10 weeks a consistent but inexplicable increase in all enzyme levels, except CS again occurred. 6. It is concluded that training increased greatly the activity of enzymes involved in both aerobic and anaerobic metabolism.

The effect of long-term stimulation of fast muscles on their blood flow, metabolism and ability to withstand fatigue

Chronic stimulation of fast rabbit muscles (tibialis anterior, extensor digitorum longus and the peroneal muscle group) at a frequency naturally occurring in nerves to slow muscles increased their ability to withstand fatigue. Isometric tension decreased during a 10-min period of contractions at 4 Hz by 75% in control muscles, but only 55% in muscles chronically stimulated for 4 days, and 23% in muscles stimulated for 28 days. Chronic stimulation had little effect on resting blood flow, oxygen or glucose consumption. The output or consumption of lactate and free fatty acids (FFA) at rest were also unaffected. The glycogen content was regularly increased, and was apparent after only 2 days of stimulation. The activity of fatty acid activating enzyme was increased after 28 days. During a 10-min period of isometric contractions at 4 Hz, there was a markedly greater increase in blood flow and oxygen consumption in muscles stimulated for 14-28 days than in control muscles; lactic acid output was lower in muscles stimulated for 28 days, and the uptake of FFA was significantly higher. It is therefore suggested that muscles chronically stimulated for 14-28 days use fats as the main source of energy during isometric contractions. The predominantly oxidative metabolism is probably facilitated by the higher density of capillaries. The latter also enables more efficient delivery of oxygen, and therefore smaller fatiguability, already after 4 days of chronic stimulation.

Physical training in man. Skeletal muscle metabolism in relation to muscle morphology and running ability

The metabolic and morphologic adaptation to physical training in skeletal muscle tissue of eleven middle-aged, physically untrained men was studied. Muscle biopsies were taken from the vastus lateralis before, after 8 weeks and after 6 months of physical training for analysis of metabolic and morphologic variables. Glucose tolerance test indicated increased insulin sensitivity after 6 months of physical training. The activities of glycogen phosphorylase, hexokinase and glucose-6-P-dehydrogenase were increased but other enzymes involved in glycogen turnover and glycolysis were unchanged after 6 months of physical traning. The activities of citrate synthase and cytochrome-c-oxidase, representing the oxidative capacity were significantly increased already after 8 weeks of physical training. The incorporation rate of palmitate-carbon into CO2 and triglycerides increased, and the incorporation rate of leucine-carbon into CO2 decreased with 6 months of physical training. The fiber diameter of both Type 1- and Type 2-fibers increased, while the mitochondrial volume increased predominantly in Type 2-fibers. Significant correlations were found between metabolic, physiologic and morphologic variables before and after physical training. The results indicate an increased oxidative capacity, mainly located to Type 2-fibers, and an increased utilization of fatty acids in response to this type of physical training.

A comparative histochemical study of the masseter muscle of the cattle, sheep, swine, dog, guinea pig, and rat

The masseter muscles of different mammals were studied by means of hisotchemical reactions: NADH: Nitro BT oxidoreductase (NADHOX), 3-hydroxybutyrate: NAD+ oxidoreductase (HBOX), glycerol-3-phosphate: menadione oxidoreductase (GPOX), and acid-stable and alkali-stable myosin adenosine triphosphatase (ATPase). The masseter mucles of cattle and sheep consisted only of the fibres that reacted moderately for GPOX and strongly for NADHOX, HBOX, and the acid-stable ATPase. The masseter fibres of rats and guinea pigs reacted uniformly and strongly for GPOX and the alkali-stable ATPase. The fibres of the rats showed a weak to strong reaction for NADHOX and mostly a negative reaction for HBOX, whereas those of the guinea pigs reacted uniformly and strongly for NADHOX and HBOX.The masseter fibres of swine and dogs showed a weak or strong reaction for the alkali-stable and a negative or weak reation for HBOX. The fibres of the swine were weak to strong in NADHOX activity and those of the dogs uniformly strong; the fibres of the two species gave a moderate to strong reaction for GPOX. The masseter fibres of the ruminant differed from those of the other species in histochemical properties, and appeared to have the histochemical characteristics that meed functional demands for slow, long-term exercise.

Carnitine concentration in relation to enzyme activities and substrate utilization in human skeletal muscles

The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, beta-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.

Effects of physical training on ventilatory equivalent and respiratory exchange ratio during weight supported, steady-state exercise

Thirty-three college men participated in a 9-week endurance training program. An equal number of subjects served as controls. Pre- and post-test metabolic measurements were made during 10 min of submaximal exercise (1080 kpm/min at 60 rpm) and 15 min of recovery. Measurements included oxygen consumption, CO2 production, ventilatory equivalent (Ve/VO2 ratio) and respiratory exchange ratio (R). A three factor design variance analysis was used to analyze the effects of training on min-by-min exercise and recovery Ve/VO2 ratio and R. For the experimental group training resulted in a significant improvement in ventilatory efficiency during exercise, as well as a significant decrease in R. During recovery, Ve/VO2 and R decreased significantly for both groups although the magnitude of change was greater for the group that trained. Apparently, there was a significant habituation effect due to test procedures for the control group. The results are discussed in terms of lactate production and substrate utilization during exercise.

Adipose tissue cellularity and lipolysis. Response to exercise and cortisol treatment

Male rats a 5 wk of age were subjected to 13 wk of intensive treadmill running to study the effect of exercise on adipose tissue cellularity and lipolysis. Untrained controls of the same age remained sedentary in their cages for the duration of the experiment. Adipocyte numbers were similar in eqidiymal fat pads from trained and untrained rats (12.7 plus or minus 1.3 X 10(6) vs. 15.3 plus or minus 1.3 X 10(6) cells/pad), however trained rats had smaller fat pads containing smaller cells (0.09 plus of minus 0.01 vs. 0.20 plus or minus 0.04 mug triglyceride/cell). Adipocytes from trained rats possessed greater epinephrine-sensitive lipase activity than sedentary rats on a per cell, per milligram protein, per gram adipose tissue, or per fat pad basis. Although the smaller cells of the trained rats had greater epinephrine-sensitive lipase activity than the larger cells of the untrained rats, lipolysis was positively correlated with cell size within both treatment groups. Cortisol treatment of intact animals did not significantly affect in vitro adipose tissue lipolysis. The results of this study indicate that exercise training increased the potential of adipose tissue cells to release free fatty acids in response to epinephrine stimulation. Exercise training initiated at 5 wk of age had only a small effect on adipose tissue cell numbers but significantly decreased cell size.

Response of lipogenesis and fatty acid synthetase to physical training and exhaustive exercise in rats

The effect of physical training and exhaustive exercise on fatty acid synthesis in rat liver and adipose tissue has been investigated. Exercise training (treadmill running) significantly (p less than 0.05) decreased body wt, eipdidymal fat pad wt, adipocyte size, and hepatic fatty acid synthetase activity. Training did not significantly affect adipose tissue cell number, lipogenesis from glucose-U-14C, or fatty acid synthetase. Exercise to exhaustion immediately prior to sacrifice significantly (p less than 0.05) decreased lipogenesis from glucose-U-14C and fatty acid synthetase in adipose tissue from trained but not untrained rats. Liver fatty acid synthetase was not significantly influenced by exhaustive exercise. The results of this study indicate that rats may adapt to physical training by decreasing adipose tissue lipogenesis during exhaustive exercise. This adaptation in energy metabolism may facilitate physically trained animals in conserving blood glucose during exhaustive exercise, thereby prolonging endurance.

Depletion of muscle and liver glycogen during exercise. Protective effect of training

Carbohydrate depletion during exercise was measured in the liver, in the three different types of skeletal muscle, and in the blood of exercise-trained and untrained rats. The acute exercise test consisted of 45 min of treadmill running of progressively increasing intensity. The training program consisted of 6 hrs of swimming per day, 5 days per week for 14 weeks; the training induced an increase of approximately 35 percent in the respiratory capacity of gastrocnemius muscle, and a 14 percent incrase in heart weight. Glycogen stores in fast-twitch red, fast-twitch white, and slow-twitch red types of skeletal muscle, were depleted significantly more slowly in the trained than in the untrained animals during the treadmill exercise test. Resting glycogen stores in the liver were higher and were depleted more slowly during exercise in the trained than the untrained animals. Blood lactate concentration was significantly lower in the trained than in the untrained rats at the end of the exercise test. These results provide evidence that endurance exercise training induces adaptation which protect against the depletion of glycogen from the liver and from the tree types of skeletal muscle during prolonged exercise.

Free fatty acid metabolism of leg muscles during exercise in patients with obliterative iliac and femoral artery disease before and after reconstructive surgery

The free fatty acid (FFA) uptake and oxidation and the carbohydrate substrate exchange of leg muscles were studied during exercise in 14 patients with occlusive disease of the iliac or femoral arteries before and 3-6 months after reconstructive vascular surgery and in 5 healthy subjects. (14)C-labeled oleic acid was infused continuously at rest and during exercise at work loads of 150-400 kg-m/min. The arterial concentration of FFA was similar both at rest and during exercise in patients and controls. The patients showed a smaller increase in the fractional turnover of FFA during exercise. Leg uptake and release of FFA in terms of micromoles per liter plasma did not differ significantly either at rest or during exercise between patients and controls. FFA oxidation could not be measured at rest but exercise data showed a lower fractional oxidation of FFA (P < 0.001) in the patient group (53+/-6%) compared with the controls (84+/-2%). For the entire material, fractional oxidation of FFA showed a significant negative regression on the lactate/pyruvate ratio in femoral venous blood. The ventilatory respiratory quotient (RQ) and the leg muscle exchange of glucose and lactate in the patients exceeded that of the controls. When six patients were studied after reconstructive surgery, fractional oxidation of FFA had risen from a preoperative value of 47+/-8 to 90+/-10%, other data for leg muscle FFA metabolism being unchanged. IT IS CONCLUDED: (a) that substrate catabolism by the leg muscles during exercise in these patients proceeds in excess of the simultaneous capacity to oxidize acetyl-CoA in the tricarboxylic acid cycle, and (b) oxidation of FFA by contracting muscle is related to the muscle cell redox state.