High intensity exercise training-induced metabolic alterations in respiratory muscles.

Limited information exists concerning the effects of high intensity interval exercise training (HIET) on metabolic alterations in both inspiratory and expiratory muscles. To test the hypothesis that HIET will improve the oxidative capacity of the diaphragm and major expiratory muscles, we examined Krebs cycle and beta oxidation enzyme activities in the diaphragm and three groups of expiratory (abdominal) muscles in rats subjected to 12 weeks (5 days.wk-1) of treadmill exercise. Two groups of female Sprague-Dawley rats (age ca 120 days) were studied: (1) HIET group (n = 10; animals performed 6 x ca 5-min running intervals.day-1 at ca 90-95% VO2max); (2) sedentary control group (n = 7). When compared to controls, HIET resulted in significantly elevated (P less than 0.05) activities of 3-hydroxy-acyl-Co-A dehydrogenase (HADH) and citrate synthase (CS) in the costal diaphragm, rectus abdominus, external obliques, and the plantaris muscles. In contrast, training did not increase (P greater than 0.05) the activities of CS or HADH in the crural diaphragm or the internal obliques/transversus abdominus muscles. By comparison, the training-induced increases in oxidative capacity (e.g., CS activity) in the costal diaphragm, rectus abdominus, and external obliques were relatively small (ca 23, 10, 12%, respectively) when contrasted to the exercise-induced increase in CS activity in the plantaris muscle (ca 47%). We conclude that HIET results in small but significant improvements in the oxidative and beta oxidation capacities of the costal diaphragm and at least two abdominal expiratory muscles.     

Influence of exercise training on the oxidative capacity of rat abdominal muscles.

Our purpose was to determine if endurance exercise training would increase the oxidative capacity of the abdominal expiratory muscles of the rat. Accordingly, 9 male rats were subjected to an endurance training protocol (1 h/day, 6 days/week, 9 weeks) and 9 litter-mates served as controls. Citrate synthase (CS) activity was used as an index of oxidative capacity, and was determined in the following muscles: soleus, plantaris, costal diaphragm, crural diaphragm, and in all four abdominal muscles: rectus abdominis, transversus abdominis, external oblique, and internal oblique. Compared to their non-trained litter-mates, the trained rats had higher peak whole body oxygen consumption rates (+ 16%) and CS activities in plantaris (+34%) and soleus (+36%) muscles. Thus, the training program caused substantial systemic and locomotor muscle adaptations. The CS activity of costal diaphragm was 20% greater in the trained animals, but no difference was observed in crural diaphragm. The CS activity in the abdominal muscles was less than one-half of that in locomotor and diaphragm muscles, and there were no significant changes with training except in the rectus abdominis where a 26% increase was observed. The increase in rectus abdominis CS activity may reflect its role in postural support and/or locomotion, as none of the primary expiratory pumping muscles adapted to the training protocol. The relatively low levels of CS activity in the abdominal muscles suggests that they are not recruited frequently at rest, and the lack of an increase with training indicates that these muscles do not contribute significantly to the increased ventilatory activity accompanying exercise in the rat.     

Endurance exercise increases the SIRT1 and peroxisome proliferator-activated receptor gamma coactivator-1alpha protein expressions in rat skeletal muscle

Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) is considered to play a pivotal role in the exercise-induced metabolic adaptation of skeletal muscle. Although the oxidized form of nicotinamide adenine dinucloetide (NAD(+))-dependent histone deacetylase SIRT1 has been shown to mediate PGC-1alpha-induced metabolic adaptation, the effect of endurance exercise on the SIRT1 protein remains to be elucidated. The purposes of this study were (1) to investigate the distribution of SIRT1 and PGC-1alpha proteins in skeletal muscle and (2) to examine the effects of acute endurance exercise and low- or high-intensity exercise training on SIRT1 and PGC-1alpha protein expressions and on the metabolic components in rat skeletal muscle. Both the SIRT1 and PGC-1alpha proteins preferentially accumulate in red oxidative muscles. Acute endurance exercise on a motor-driven treadmill (20 m/min, 18.5% incline, 45 minutes) increases the PGC-1alpha protein expression at 18 hours after exercise and the SIRT1 protein expression at 2 hours after exercise in the soleus muscle. In the training experiment, the rats were divided into control, low-intensity (20 m/min, 18.5% incline, 90 min/d), and high-intensity (30 m/min, 18.5% incline, 60 min/d) training groups. After 14 days of training, the SIRT1 and PGC-1alpha proteins, hexokinase activity, mitochondrial proteins and enzyme activities, and glucose transporter 4 protein in the soleus muscle were increased by both trainings. In the plantaris muscle, SIRT1, hexokinase activity, mitochondrial proteins and enzyme activities, and glucose transporter 4 were increased by high-intensity training whereas the PGC-1alpha was not. These results suggest that endurance exercise increases the skeletal muscle SIRT1 protein content. In addition, the findings also raise the possibility that the SIRT1 protein expression may play a potentially important role in such adaptations, whereas an increase in the PGC-1alpha protein expression is not necessary for such adaptations.     

Preserved response of mitochondrial function to short-term endurance training in skeletal muscle of heart transplant recipients

OBJECTIVES: We sought to determine whether intrinsic mitochondrial function and regulation were altered in heart transplant recipients (HTRs) and to investigate the response of mitochondrial function to six-week endurance training in these patients. BACKGROUND: Despite the normalization of central oxygen transport during exercise, HTRs are still characterized by limited exercise capacity, which is thought to result from skeletal muscle metabolic abnormalities. METHODS: Twenty HTRS agreed to have vastus lateralis biopsies and exercise testing: before and after training for 12 of them and before and after the same control period for eight subjects unwilling to train. Mitochondrial respiration was evaluated on saponin-permeabilized muscle fibers in the absence or presence (maximum respiration rate [V(max)]) of saturating adenosine diphosphate. RESULTS: Mitochondrial function was preserved at the level of sedentary subjects in untrained HTRs, although they showed 28 +/- 5% functional aerobic impairment (FAI). After training, V(max), citrate synthase, cytochrome c oxidase, and mitochondrial creatine kinase (CK) activities were significantly increased by 48%, 40%, 67%, and 53%, respectively (p < 0.05), whereas FAI decreased to 12 +/- 5% (p < 0.01). The control of mitochondrial respiration by creatine and mitochondrial CK was also improved (p < 0.01), suggesting that phosphocreatine synthesis and transfer by the mitochondrial CK become coupled to oxidative phosphorylation, as shown in trained, healthy subjects. CONCLUSIONS: In HTRs, the mitochondrial properties of skeletal muscle were preserved and responded well to training, reaching values of physically active, healthy subjects. This suggests that, in HTRs, immunosuppressive drugs do not alter the intrinsic muscle oxidative capacities and that the patients' physical handicap results from nonmitochondrial mechanisms.     

Effect of 3,3'-diiodothyronine and 3,5-diiodothyronine on rat liver oxidative capacity.

We report that 3,5,3'-triiodothyronine (T3) as well as two other iodothyronines (3,3'-diiodothyronine and 3,5-diiodothyronine (T2s)) stimulate rat liver oxidative capacity (measured as cytochrome oxidase activity (COX)). In hypothyroid rats COX activity and mitochondrial protein content are significantly lower than in normal control animals. The administration of both T3 and T2s to hypothyroid rats significantly enhances hepatic COX activity with T3 having the greatest effect (+60%); moreover, T3 restores the mitochondrial protein content whereas the T2s are ineffective. Administration of T2s results in a faster stimulation (already significant 1 h after the injection) of hepatic COX activity than T3 injection. Our results suggest that T3 acts on the protein synthesis mechanism involved in the regulation of the mitochondrial mass while T2s would act directly at the mitochondrial level.     

壳寡糖对运动大鼠心肌组织保护作用的研究

目的: 研究壳寡糖(COS)对大负荷运动大鼠心肌组织的保护作用。方法: 将36只3月龄SPF级SD雄性大鼠随机分为正常对照组、耐力运动组和壳寡糖组,每组12只。耐力运动组和COS治疗组进行6周的跑台训练。24 h后处死大鼠,迅速取出心脏,在光镜和透射电镜下分别观察大鼠心肌组织的形态结构。测定心肌组织和血清超氧化物歧化酶(SOD)和丙二醛(MDA)的水平,SOD活性采用黄嘌呤氧化酶法测定,MDA含量采用TBA缩合比色法测定。结果: COS组大鼠心肌SOD活性（246.38±0.79）较运动组（138.61±1.17）显著增高（P<0.05）,而血清SOD活性（67.92±18.47）较运动组（98.79±16.10）显著降低（P<0.05）;心肌和血清MDA含量（3.64±0.19和4.50±0.74）均较运动组（6.87±0.34和7.86±0.46）显著降低（P<0.05）。COS治疗组大鼠心肌组织和血清中SOD的活性及MDA的含量与正常对照组比较差异无显著性。光镜下观察,运动组大鼠心肌细胞出现不同程度的水肿、变性和坏死;电镜下观察,耐力运动组大鼠心肌细胞损伤明显,肌原纤维模糊、断裂甚至坏死,线粒体肿胀等有形态学改变。COS治疗组大鼠心肌损伤的程度与耐力运动组比较明显减轻,而与正常对照组比较心肌组织的形态结构无明显变化。结论: 大负荷运动可导致大鼠心肌组织、血清抗氧化功能指标改变,心肌组织损伤。COS可提高大负荷运动大鼠心肌组织的抗氧化功能,维持心肌组织的正常形态结构。     

The influence of age on steroidogenic enzyme activities of the rat adrenal gland: enhanced expression of cholesterol side-chain cleavage activity

The ability of isolated adrenocortical cells to secrete corticosterone in response to ACTH challenge declines as rats age, but the site or mechanism(s) of this impairment is still unknown. To test the functionality of steroidogenic capacity per se, we measured the key enzyme activities involved in corticosterone biosynthesis. We also measured the mitochondrial cytochrome P-450 content and nonsteroidogenic enzymes specific for subcellular fractions. Mitochondria and microsomal fractions were isolated from the adrenals of 2-, 12-, and 18-month-old animals and used for various enzyme measurements. Mitochondrial side-chain cleavage enzyme activity (nanomoles per min mg protein-1) increased from a mean of 0.43 +/- 0.06 in 2-month-old rats to 1.26 +/- 0.11 and 1.51 +/- 0.06 in 12- and 18-month old rats, respectively. After incubation with 5-cholesten-3 beta,25-diol (25-hydroxycholesterol; 25 micrograms/ml) side-chain cleave activity rose to 5.0 +/- 0.6, 12.4 +/- 1.2, and 16 +/- 1.4 nmol min-1 mg protein-1 in adrenal mitochondrial fractions from 2-, 12-, and 18-month-old rats, respectively. In contrast, mitochondrial cytochrome P-450 content did not vary with advancing age. Microsomal delta 5-3 beta-hydroxysteroid dehydrogenase-delta 5-delta 4-isomerase activities were similar in 2- and 12-month-old rats, but 21-hydroxylase (nanomoles per min mg protein-1) activity was significantly increased in 12-month-old rats (2-month-old, 5.2 +/- 0.2; 12-month-old, 7.7 +/- 0.5). Finally, mitochondrial 11 beta-hydroxylase was comparable in both age groups. In addition, activities of mitochondrial nonsteroidogenic enzymes, such as monoamine oxidase, amytal insensitive NADH cytochrome c reductase, cytochrome c oxidase, succinate dehydrogenase, and malate dehydrogenase, did not change with age. It appears from the evidence presented that the activities of the steroidogenic enzymes are not responsible for the diminished capacity in corticosterone production seen with aging in the rat.     

Alterations of the mitochondrial respiratory chain in human dilated cardiomyopathy

The defects underlying the impairment of systolic pump function in human dilated cardiomyopathy (DCM) are not known. We isolated mitochondrial particles from 10 hearts of transplant recipients with DCM and from nine normal hearts not used for transplantation. Yield was similar in both groups (2.77 vs 2.81 mg mitochondrial protein per gram heart). Cytochrome content (difference spectrophotometry) was found reduced in DCM mitochondria, e.g. cytochrome c was 0.295 +/- 0.06 in the DCM group and 0.371 +/- 0.04 mumol g-1 in the control group (P less than 0.05). Enzymatic activity of the cytochrome-containing complexes III (3.77 +/- 0.82 vs 4.95 +/- 1.15 mumol min-1.mg-1) and IV (2.63 +/- 0.96 vs 3.65 +/- 0.6 mumol min-1.mg-1) of the respiratory chain was reduced in the DCM group (P less than 0.05). Complex IV, the cytochrome c oxidase, in the DCM group showed impaired activity also in whole heart homogenates (0.173 +/- 0.04 vs 0.258 +/- 0.8 mumol min-1.mg-1). Subunit composition of the cytochrome c oxidase on sodium dodecyl sulphate-gel electrophoresis did not differ between DCM and normal hearts. Activity of complexes II and V of the respiratory chain, not containing cytochromes, was unchanged in DCM mitochondria compared with the control group. The present data show a decrease in cytochrome content and in cytochrome-dependent enzyme activity in human dilated cardiomyopathy. Further studies are necessary to clarify whether these findings are specific for dilated cardiomyopathy or whether they are epiphenomena of failing hearts.     

Age-related changes in enzyme activity in the rat diaphragm

Limited data exist concerning the effect of growth and aging on the metabolic properties of the diaphragm. Therefore, we investigated age-related changes in protein concentration and glycolytic and Krebs cycle enzyme activity in the diaphragm as well as the plantaris muscle of female Sprague-Dawley rats ranging in age from 1 to 12 months. Samples from the costal and crural diaphragm and the plantaris muscle were obtained from 38 animals in the following age groups: (1) 1 month old (N = 7); (2) 4 month old (N = 6) (3) 6 month old (N = 13); and (4) 12-month-old (N = 12). Body weight and diaphragm weight increased rapidly by a factor of 6 and in parallel during 1-4 months postpartum before reaching a plateau at 6 months of age. No significant difference (P greater than 0.05) existed in the ratio of diaphragm weight to body weight among age groups. Protein concentration was significantly higher (P less than 0.05) in the costal diaphragm and plantaris at 4 and 6 months when compared to 1 and 12 months of age. In the crural diaphragm, protein concentration was significantly lower (P less than 0.05) at 1 month postpartum when compared to all other age groups. Succinate dehydrogenase (SDH) activity was significantly higher (P less than 0.05) at 1 month of age in the plantaris, the costal diaphragm and the crural diaphragm when compared to older animals. In contrast, the activity of lactate dehydrogenase (LDH) in the plantaris, the costal diaphragm and the crural diaphragm was significantly lower (P less than 0.05) in the 1-month-old animals when compared to all other ages.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diaphragmatic fiber type specific adaptation to endurance exercise.

Recent evidence suggests that exercise training results in a significant improvement in the oxidative capacity of the mammalian diaphragm; however, limited data exist concerning which diaphragmatic fiber types are metabolically altered due to training. To test the hypothesis that exercise training increases the oxidative capacity of diaphragmatic type I and IIa fibers only, we examined the effects of endurance training on the fiber type specific changes in oxidative capacity, cross-sectional area, and capillarity of the costal diaphragm. Female Fischer-344 rats (age ca 180 days) were divided into either sedentary control group (n = 6) or an exercise training group (n = 6). The trained animals exercised for 10 wks on a motor-driven treadmill (60 min.day-1; 5 days.wk-1) at a work rate equal to ca 55-65% VO2max. Capillaries were identified histologically and fiber types determined using ATPase histochemistry. Fiber cross-sectional area (CSA) and succinate dehydrogenase (SDH) activity in individual fibers were measured using a computerized image analysis system. Compared to control animals, training did not increase the capillary to fiber ratio in any diaphragm fiber type (P greater than 0.05); however, training increased capillary density (capillary No./CSA) in type IIa fibers due to a reduction in cell CSA (P less than 0.05). Further, training resulted in significant (P less than 0.05) increases in total diaphragmatic SDH activity (delta increase = 17.5%) and an increase in SDH activity in both type I (delta increase = 14%) and IIa fibers (delta increase = 17.4%). In contrast, training did not alter (P greater than 0.05) SDH activity in type IIb fibers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Skeletal muscle aging in F344BN F1-hybrid rats: I. Mitochondrial dysfunction contributes to the age-associated reduction in VO2max

Although mitochondrial DNA damage accumulates in aging skeletal muscles, how this relates to the decline in muscle mass-specific skeletal muscle aerobic function is unknown. We used a pump-perfused rat hind-limb model to examine maximal aerobic performance (VO(2max)) in young adult (YA; 8-9-month-old), late middle aged (LMA; 28-30-month-old) and senescent (SEN; 36-month-old) Fischer 344 x Brown Norway F1-hybrid rats at matched rates of convective O(2) delivery (QO(2)). Despite similar muscle QO(2) during a 4-minute contraction bout, muscle mass-specific VO(2max) was reduced in LMA (15%) and SEN (52%) versus YA. In plantaris muscle homogenates, nested polymerase chain reaction revealed an increased frequency of mitochondrial DNA deletions in the older animals. A greater reduction in the flux through electron transport chain complexes I-III than citrate synthase activity in the older animals suggests mitochondrial dysfunction consequent to mitochondrial DNA damage with aging. These results support the hypothesis that a reduced oxidative capacity, due in part to age-related mitochondrial dysfunction, contributes to the decline in aerobic performance in aging skeletal muscles.     

Cytochrome oxidase status in protein-energy-deficient rats

Effects of changes in dietary protein have been investigated on three mitochondrial enzymes, succinate dehydrogenase, isocitrate dehydrogenase and cytochrome oxidase. Weanling rats (21 days old) were fed for 30 days on (a) a commercially produced diet (CPD) containing 21.0% dietary protein and (b) a low protein-high carbohydrate diet (LPD) containing 3.47% dietary protein. Signs of protein-energy malnutrition developed in the animals having the low protein diet. The mitochondrial enzymes were assayed. Some of the experimental rats were repleted by feeding them on a protein-rich diet for 3 weeks, and the same mitochondrial enzymes were assayed. The activity of mitochondrial cytochrome oxidase, which fell to 24% of the control values during the period of deficiency, rose to 91% of the values for control rats during rehabilitation. The activities of succinate dehydrogenase and NAD+-isocitrate dehydrogenase fell to 75 and 73% of the control values, respectively, during depletion and rose to 83 and 88% during repletion in line with the general rate of recovery of the malnourished rats as reflected by the changes in the body weights during repletion. These results show that mitochondrial cytochrome oxidase is very sensitive to changes in dietary protein. Its activity drops sharply with reduction in dietary protein intake and rises rapidly, outstripping the rate of general recovery on reverting to a protein-rich diet.     

NADPH oxidase hyperactivity induces plantaris atrophy in heart failure rats

Background

Skeletal muscle wasting is associated with poor prognosis and increased mortality in heart failure (HF) patients. Glycolytic muscles are more susceptible to catabolic wasting than oxidative ones. This is particularly important in HF since glycolytic muscle wasting is associated with increased levels of reactive oxygen species (ROS). However, the main ROS sources involved in muscle redox imbalance in HF have not been characterized. Therefore, we hypothesized that NADPH oxidases would be hyperactivated in the plantaris muscle of infarcted rats, contributing to oxidative stress and hyperactivation of the ubiquitin-proteasome system (UPS), ultimately leading to atrophy.

Methods

Rats were submitted to myocardial infarction (MI) or Sham surgery. Four weeks after surgery, MI and Sham groups underwent eight weeks of treatment with apocynin, a NADPH oxidase inhibitor, or placebo. NADPH oxidase activity, oxidative stress markers, NF-κB activity, p38 MAPK phosphorylation, mRNA and sarcolemmal protein levels of NADPH oxidase components, UPS activation and fiber cross-sectional area were assessed in the plantaris muscle.

Results

The plantaris of MI rats displayed atrophy associated with increased Nox2 mRNA and sarcolemmal protein levels, NADPH oxidase activity, ROS production, lipid hydroperoxides levels, NF-κB activity, p38 MAPK phosphorylation and UPS activation. NADPH oxidase inhibition by apocynin prevented MI-induced skeletal muscle atrophy by reducing ROS production, NF-κB hyperactivation, p38 MAPK phosphorylation and proteasomal hyperactivity.

Conclusion

Our data provide evidence for NADPH oxidase hyperactivation as an important source of ROS production leading to plantaris atrophy in heart failure rats, suggesting that this enzyme complex plays key role in skeletal muscle wasting in HF.     

Oxidative capacity of muscle and mitochondria: correlation of physiological, biochemical, and morphometric characteristics.

The oxidative capacity of cat skeletal muscles (soleus, gracilis, and gracilis chronically stimulated for 28 days) was derived from the total mitochondrial content in the muscle, the surface area of mitochondrial inner membranes, and respiratory activities of isolated mitochondria. Mitochondrial content was estimated by standard morphometry. The surface area of mitochondrial inner membranes per unit volume of mitochondria was estimated by a stereological method. The respiratory activities of isolated mitochondria were measured biochemically, using pyruvate/malate, glutamate/malate, succinate, or cytochrome c as substrate. Structurally and functionally, mitochondria from the three muscle types showed nearly identical characteristics. Oxidative activity was dependent on substrate; with succinate, 5.8 ml of O2 per min per ml of mitochondria was the rate most likely to represent physiological conditions. Oxidative activities of 3.1 ml.min-1.ml-1 with pyruvate/malate and 14.5 ml.min-1.ml-1 with cytochrome c as substrates were theoretical lower and upper bounds. The oxidative capacity of each of the three muscles was thus in direct proportion to the total volume of mitochondria in the muscle. The respiratory capacity of isolated mitochondria was very near to the maximal oxygen uptake rate of mitochondria that is commonly estimated in intact muscles of a wide variety of animals.     

Mitochondrial function in diaphragm of emphysematous hamsters after treatment with nandrolone

Respiratory failure in patients with COPD may be caused by insufficient force production or insufficient endurance capacity of the respiratory muscles. Anabolic steroids may improve respiratory muscle function in COPD. The effect of anabolic steroids on mitochondrial function in the diaphragm in emphysema is unknown. In an emphysematous male hamster model, we investigated whether administration of the anabolic steroid nandrolone decanoate (ND) altered the activity of mitochondrial respiratory chain complexes in the diaphragm. The bodyweight of hamsters treated with ND was decreased after treatment compared with initial values, and serum testosterone levels were significantly lower in hamsters treated with ND than in control hamsters. No difference in the activity of mitochondrial respiratory chain complexes in the diaphragm between normal and emphysematous hamsters was observed. Treatment with ND did not change the activity of mitochondrial respiratory chain complexes in the diaphragm of both normal and emphysematous hamsters. In emphysematous hamsters, administration of ND decreased the activity of succinate:cytochrome c oxidoreductase compared with ND treatment in normal hamsters. We conclude that anabolic steroids have negative effects on the activity of succinate:cytochrome c oxidoreductase and anabolic status in this emphysematous hamster model.     

Stereological and functional analysis of liver mitochondria from rats with secondary biliary cirrhosis: impaired mitochondrial metabolism and increased mitochondrial content per hepatocyte.

Mitochondrial and cytosolic functions were studied in vivo and in perfused livers from rats with secondary biliary cirrhosis induced by bile duct ligation for 5 wk and in sham-operated controls. The livers were stereologically analyzed, and mitochondrial and cytosolic functions were related to liver structure. Oxygen consumption by perfused livers expressed per stereologically determined mitochondrial volume was decreased by 49% in bile duct-ligated rats compared with control rats. Glucose production (expressed per mitochondrial volume) was reduced by more than 90% in bile duct ligation, whereas urea production was not affected. Lactate production, a cytosolic function, was increased fivefold in bile duct ligation, and both the lactate/pyruvate and the beta-hydroxybutyrate/aceto-acetate ratios were increased in the liver perfusate of bile duct-ligated rats. In comparison with control rats, the stereologically determined mitochondrial volume fraction per hepatocyte was increased by 28% in bile duct-ligated rats. Activities of mitochondrial enzymes expressed per area of mitochondrial membrane or per mitochondrial volume were either unchanged (ATPase, cytochrome c oxidase and glutamate dehydrogenase) or decreased (monoamine oxidase) in bile duct ligation. Thus in comparison with control rats, mitochondrial metabolism is impaired in perfused livers from bile duct-ligated rats; increased mitochondrial volume per hepatocyte may represent a strategy to maintain hepatic energy metabolism in rats with secondary biliary cirrhosis.     

Age-dependent decrease in the cytochrome c oxidase activity and changes in phospholipids in rat-heart mitochondria

The effect of aging on the kinetic characteristics of cytochrome c oxidase in rat heart mitochondria was investigated. Mitochondria from young and aged rats had equivalent Km values for cytochrome c, while the maximal activity of the oxidase was significantly reduced in mitochondria from aged rats. The cytochrome aa3 content was the same in both these two types of mitochondria. The Arrhenius plot characteristics differ for cytochrome oxidase activity in mitochondria from aged rats as compared with young rats in that the breakpoint of the biphasic plot was shifted to a higher temperature. Cardiolipin content was markedly decreased in mitochondrial membrane from aged rats. No alterations were found in the patterns of the phospholipid fatty acid distribution of mitochondrial membranes from young and aged rats. The results support the conclusion that the reduced mitochondrial cytochrome c oxidase activity in aged animals is due to a specific decrease in the cardiolipin content.     

Exercise training in chronic heart failure: correlation between reduced local inflammation and improved oxidative capacity in the skeletal muscle.

BACKGROUND: Chronic heart failure (CHF) is accompanied by an inflammatory activation which occurs both systemically and in the skeletal muscle. Exercise training has been shown to reduce the local expression of cytokines and inducible nitric oxide synthase (iNOS) in muscle biopsies of CHF patients. INOS-derived NO can inhibit oxidative phosphorylation and contribute to skeletal muscle dysfunction in CHF. DESIGN: To investigate the correlation between changes in local iNOS expression associated with regular exercise and changes in aerobic enzyme activities in the skeletal muscle of patients with CHF. Twenty male CHF patients [ejection fraction 25% (SE 2), age 54 (SE 2) years] were randomized to a training (n=10) or a control group (C, n=10). METHODS: At baseline and after 6 months skeletal muscle iNOS expression was measured by real-time polymerase chain reaction. INOS protein and protein nitrosylation were assessed by immunohistochemistry. Cytochrome c oxidase (COX) activity was quantified electrochemically using the Clark oxygen electrode. RESULTS: Exercise training led to a 27% increase in cytochrome c oxidase activity [from 21.8 (SE 3.2) to 27.7 (SE 3.5) nmol O2/mg per min, P=0.02 versus baseline]. Changes in iNOS expression and iNOS protein content were inversely correlated with changes in COX-activity (r=-0.60, P=0.01; r=-0.71, P<0.001). CONCLUSIONS: The inverse correlation between iNOS expression/iNOS protein content and COX-activity indicates that local anti-inflammatory effects may contribute to improved muscular oxidative metabolism.