Exercise and training in mitochondrial myopathies

The intriguing concept of exercise training as therapy for mitochondrial disease is currently unsettled: in the unique setting of mitochondrial heteroplasmy, what are the effects of chronic exercise on skeletal muscle containing a mixture of mutated and wild-type mitochondrial DNA (mtDNA)? Furthermore, what are the consequences of habitual physical inactivity on mitochondrial heteroplasmy? In patients with mtDNA defects, deleterious effects of limited physical activity likely magnify the mitochondrial oxidative impairment contributing to varying degrees of exercise intolerance. Normal adaptive responses to endurance training offer the potential to increase levels of functional mitochondria, improving exercise tolerance. The few clinical studies assessing such training effects in patients with mtDNA defects have unequivocally demonstrated physiologic and biochemical adaptations that improve exercise tolerance and quality of life. Uncertain, however, is the training effect on mitochondrial heteroplasmy. To determine therapeutic advisability of endurance training, it remains imperative to establish whether: reported increases in mutant mtDNA levels can be offset by increases in absolute wild-type mtDNA levels; and chronic physical inactivity leads to a selective down-regulation of wild-type mtDNA. Resistance exercise training offers an alternate, innovative therapeutic approach in patients with sporadic mtDNA mutations; exercise-induced transfer of normal mtDNA templates from muscle satellite cells to mature myofibers, thereby lowering mutation load (increasing functional mitochondrial load). Efficacy and safety of this approach needs to be replicated in a larger group of patients. Currently, appropriate recommendation (either in support or against) exercise training in mitochondrial disease is lacking, which is frustrating for physicians and disheartening for patients. Although considerable progress has been made, an immediate urgency exists to resolve the effects of chronic exercise on skeletal muscle in patients with heteroplasmic mtDNA mutations.     

The role of exercise in the treatment of cardiovascular disease associated with type 2 diabetes mellitus

The role of exercise training in the prevention and treatment of type 2 diabetes mellitus has been studied extensively over the past two decades. Although the primary treatment aim for patients with type 2 diabetes is metabolic control, the morbidity and mortality associated with the disease is more a function of cardiovascular disease. As exercise is associated with favourable reductions in the risk for cardiovascular disease in other high-risk populations, here we explore the role of exercise in the treatment of cardiovascular maladaptations associated with type 2 diabetes.The cardiovascular adaptation to type 2 diabetes is characterised by hypertrophy, stiffening and loss of functional reserve. Clinically, the cardiovascular adaptations to the diabetic state are associated with an increased risk for cardiovascular disease. Functionally, these adaptations have been shown to contribute to a reduced exercise capacity, which may explain the reduced cardiovascular fitness observed in this population.Exercise training is associated with improved exercise capacity in various populations, including type 2 diabetes. Several structural and functional adaptations within the cardiovascular system following exercise training could explain these findings, such as reductions in ventricular and vascular structural hypertrophy and compliance coupled with increased functional reserve. Although these cardiovascular adaptations to aerobic exercise training have been well documented in older populations with similar decrements in cardiovascular fitness and function, they have yet to be examined in patients with type 2 diabetes. For this reason, we contend that exercise training may be an excellent therapeutic adjunct in the treatment of diabetic cardiovascular disease.     

不同训练负荷对大鼠骨骼肌超微结构及线粒体功能的影响

 目的 研究不同训练负荷下,大鼠骨骼肌超微结构及线粒体呼吸链酶复合体Ⅰ、Ⅱ、Ⅲ、Ⅳ和总超氧化物歧化酶(total superoxide dismutase, T-SOD)、锰超氧化物歧化酶(manganese superoxide dismutase, Mn-SOD)和铜锌超氧化物歧化酶(copper zincsuperoxide dismutase, CuZn-SOD)的变化。方法 建立SD大鼠跑台训练模型,将24只大鼠随机分为正常对照组、有氧训练组、无氧训练组,每组8只,正常对照组大鼠笼内正常生活,其他两组分别进行有氧和无氧训练4周,有氧训练时采用递增负荷训练,无氧训练时采用高速训练。采用透射电镜观察骨骼肌形态及线粒体变化。用可见分光光度计检测大鼠骨骼肌线粒体呼吸链酶复合体Ⅰ、Ⅱ、Ⅲ、Ⅳ,以及T-SOD、Mn-SOD和CuZn-SOD活性。结果 相比正常对照组,电镜下有氧训练组线粒体数量增多,三联体结构明显。无氧训练组中可见大量发生肿胀的线粒体,电子密度较正常染色体低;明带与暗带界限不清,粗细肌丝排列紊乱。相比正常对照组,有氧训练组大鼠骨骼肌线粒体呼吸链酶复合体Ⅰ、Ⅱ、Ⅲ、Ⅳ,以及T-SOD、Mn-SOD和CuZn-SOD活性均显著上升(P<0.05);无氧训练组线粒体呼吸链酶复合体Ⅰ、Ⅱ、Ⅲ、Ⅳ以及T-SOD和Mn-SOD活性显著下降(P< 0.05),CuZn-SOD活性[(2.68±0.61)×10³ nkat/mgprot]与正常对照组活性值[(3.73±1.24)×10³ nkat/mgprot]相比,差异无统计学意义(P> 0.05)。结论 不同训练负荷可以改变大鼠骨骼肌线粒体功能,导致抗氧化功能发生相应变化,从而对骨骼肌形态产生较大影响。有氧训练可以改善骨骼肌形态结构和线粒体功能,减轻机体疲劳。     

"解偶联蛋白库"参与急性运动中骨骼肌线粒体解偶联蛋白3的迅速表达

目的研究急性运动中和运动后,骨骼肌线粒体活性氧(ROS)生成与解偶联蛋白3(UCP3)表达的相互关系,探讨骨骼肌胞浆中解偶联蛋白库的作用.方法采用修正的SD大鼠三级递增负荷跑台运动模型,分别选取安静态、运动45、90、120、150min和运动后3、6、12、24h为实验观察点(time course),荧光法测定骨骼肌线粒体ROS生成;荧光定量PCR测定UCP3 mRNA;蛋白印迹法测定骨骼肌和线粒体UCP3蛋白表达;免疫荧光分析检测骨骼肌线粒体外是否存在UCP3蛋白.结果(1)急性运动中及运动后UCP3 mRNA含量和线粒体UCP3蛋白水平均呈先上升后下降的变化趋势UCP3 mRNA含量在运动45min时显著高于安静态(P＜0.01),并持续增高到150min时.虽然在运动后明显下降,但仍显著高于安静态(P＜0.05);线粒体UCP3蛋白含量在运动120min和150min时显著高于安静态(P＜0.001),而骨骼肌UCP3蛋白含量各时间点均未见显著性差异(P＞0.05);(2)免疫荧光分析显示,安静态胞浆内存在大量UCP3蛋白,运动120分钟时明显减少;(3)急性运动中及运动后骨骼肌线粒体ROS生成呈先上升后下降的变化趋势运动45min开始显著升高(P＜0.05),并持续升高至运动120min(P＜0.001),150min时有所下降,但仍显著高于安静态(P＜0.01);运动后3、6、12、24hROS生成均高于安静态,12、24h显著高于安静态(P＜0.05).结论骨骼肌细胞胞浆内存在"UCP3蛋白库",可在运动应激条件下快速动员装载入线粒体,发挥运动抗氧化的快速应答效应.     

Non‐invasive ventilation abolishes the IL‐6 response to exercise in muscle‐wasted COPD patients: A pilot study

Systemic inflammation in patients with chronic obstructive pulmonary disease (COPD) has been related to the development of comorbidities. The level of systemic inflammatory mediators is aggravated as a response to exercise in these patients. The aim of this study was to investigate whether unloading of the respiratory muscles attenuates the inflammatory response to exercise in COPD patients. In a cross‐over design, eight muscle‐wasted stable COPD patients performed 40 W constant work‐rate cycle exercise with and without non‐invasive ventilation support (NIV vs control). Patients exercised until symptom limitation for maximally 20 min. Blood samples were taken at rest and at isotime or immediately after exercise. Duration of control and NIV‐supported exercise was similar, both 12.9 ± 2.8 min. Interleukin‐ 6 (IL‐6) plasma levels increased significantly by 25 ± 9% in response to control exercise, but not in response to NIV‐supported exercise. Leukocyte concentrations increased similarly after control and NIV‐supported exercise by ～15%. Plasma concentrations of C‐reactive protein, carbonylated proteins, and production of reactive oxygen species by blood cells were not affected by both exercise modes. This study demonstrates that NIV abolishes the IL‐6 response to exercise in muscle‐wasted patients with COPD. These data suggest that the respiratory muscles contribute to exercise‐induced IL‐6 release in these patients.     

Caractéristiques du vieillissement musculaire et effets préventifs de l'exercice régulier

AimsThis paper was aimed to present the current knowledge concerning the clinical aspects of sarcopenia, its mechanisms, as well as the role played by regular exercise on the potential health problems such as impairments in mobility and activities of daily living.Current knowledgeMuscle ageing is associated with a marked decrease in muscle mass, muscular performances, and with an increase in muscle fatigability. The mechanisms of sarcopenia remain largely unknown; the decrease in muscle mass appears to be related to an alteration of protein metabolism with a decrease in protein synthesis which mainly affects contractile proteins and the fast myosin isoforms. This alteration in protein metabolism directly affects the myofiber size. An age-related loss of myofibers also contributes to explain muscle wasting, especially related to an impairment of the control of satellite cell activation and proliferation. These alterations may participate in the accumulation of repeated episodes of incomplete repair and regeneration, thus contributing to the loss of skeletal muscle mass and function with aging. A reduction in mitochondrial number and activity might account for muscle fatigability. Deletions, rearrangements, or DNA damage accumulated over time contribute to explain reduced mitochondrial protein synthesis and oxidative enzyme activity. Both regular strength and endurance exercises have provided some of the most promising data for prevention of muscle loss and fatigability. Physical exercise programs have been shown to increase muscle protein synthesis rate, and enhance oxygen diffusion and use by peripheral tissue.Future prospectsFuture studies are needed to examine the specific effects of several kinds of exercise programs on muscle mass, structure and function.     

Exercise attenuates diabetes-induced ultrastructural changes in rat cardiac tissue

INTRODUCTION/PURPOSE: Exercise is an effective nonpharmacological treatment in the prevention of mortality and morbidity due to cardiovascular disease in Type I diabetes. This study sought to explore the effects of endurance exercise on the ultrastructural changes seen in diabetic cardiomyopathy. METHODS: Seven-week-old rats were divided into three groups consisting of sedentary nondiabetic control, sedentary diabetic, and exercised diabetic animals. Diabetes was induced using streptozotocin injection, and the exercised animals were run daily on a treadmill for 9 wk. Changes in heart ultrastructure were analyzed using transmission electron microscopy. RESULTS: Ultrastructural changes in the left ventricle produced by diabetes included changes in myofibrillar arrangements, disrupted mitochondria, and increased cytoplasmic area with an increase in lipid amounts and an increase in individual collagen fiber cross-sectional surface area. Also, an increase in heterochromatin lining the nuclear envelope and an increase in invaginations of the nuclear membrane were observed in cardiomyocytes from diabetic rats when compared with the nuclei from nondiabetic cells. Exercise was found to significantly attenuate the diabetes-induced changes in collagen fibrils, cytoplasmic area, and level of mitochondrial disruption. In contrast, exercise did not appear to significantly influence myofibril volume density, lipid accumulation, or nuclear deformities. CONCLUSION: These findings indicate that exercise restores specific ultrastructural characteristics of diabetic cardiomyopathy returning them toward nondiabetic phenotypes, particularly in the mitochondria and extracellular matrix proteins.     

运动性疲劳状态下线粒体膜生物学特征的研究-Ⅲ:递增负荷力竭性运动后大鼠肝线粒体膜NADH-CoQ还原酶及肝组织NAD~(+)的变化

以５０大鼠三级递增负荷跑台跑为力竭性运动模型，分别测定了运动后即刻肝线粒体内膜ＭＭＤＨ－ＣｏＱ还原酶（复合体１）活性的变化；肝组织内ＮＡＤ含量及线粒体膜脂质过氧化水平（ＭＤＡ含量）的变化。发现：一次力竭性运动后，大鼠肝线粒体膜复合体１活性及肝组织当中ＭＤ”含量显著性下降，ＭＤＡ含量显著增加。研究提示，递增负荷力竭性运动中线粒体内膜复合体１损害，肝组织呼吸链底物堆积，线粒体氧利用能力下降，可能是运动性线粒体膜损害及疲劳的重要膜分子机制之一。     

运动性疲劳的线粒体膜分子机制研究.Ⅰ.急性力竭运动中线粒体电子漏引起质子漏增加及其相互作用

以大鼠渐增负荷力竭性跑台跑为运动性疲劳模型，观察了运动后大鼠骨骼肌线粒体电子漏和质子漏的变化。测定线粒体超氧阴离子生成量和脂质过氧化水平。分别测定线粒体以苹果酸＋谷氨酸和以琥珀酸为底物的态4呼吸、态3呼吸、呼吸控制比及磷氧比。结果表明，运动性疲劳状态下大鼠骨骼肌线粒体超氧阴离子生成增加，脂质过氧化水平也显著增加；以苹果酸十谷氨酸或以琥珀酸为底物的态4呼吸速率明显加快，呼吸控制比、磷氧比显著下降。结果提示，力竭性运动后下大鼠骨骼肌线粒体电子漏导致线粒体质子漏增多，是运动性疲劳状态下线粒体氧化磷酸化偶联程度下降的重要因素。实验结果支持电子漏引起质子漏的假说。     

Resistance exercise training in patients with heart failure

The utility, safety and physiological adaptations of resistance exercise training in patients with chronic heart failure (CHF) are reviewed and recommendations based on current research are presented. Patients with CHF have a poor clinical status and impaired exercise capacity due to both cardiac limitations and peripheral maladaptations of the skeletal musculature. Because muscle atrophy has been demonstrated to be a hallmark of CHF, the main principle of exercise programmes in such patients is to train the peripheral muscles effectively without producing great cardiovascular stress. For this reason, new modes of training as well as new training methods have been applied. Dynamic resistance training, based on the principles of interval training, has recently been established as a safe and effective mode of exercise in patients with CHF. Patients perform dynamic strength exercises slowly, on specific machines at an intensity usually in the range of 50-60% of one repetition maximum; work phases are of short duration (< or =60 seconds) and should be followed by an adequate recovery period (work/recovery ratio >1 : 2). Patients with a low cardiac reserve can use small free weights (0.5, 1 or 3 kg), elastic bands with 8-10 repetitions, or they can perform resistance exercises in a segmental fashion. Based on recent scientific evidence, the application of specific resistance exercise programmes is safe and induces significant histochemical, metabolic and functional adaptations in skeletal muscles, contributing to the treatment of muscle weakness and specific myopathy occurring in the majority of CHF patients. Increased exercise tolerance and peak oxygen consumption (V-dotO(2peak)), changes in muscle composition, increases in muscle mass, alterations in skeletal muscle metabolism, improvement in muscular strength and endurance have also been reported in the literature after resistance exercise alone or in combination with aerobic exercise. According to new scientific evidence, appropriate dynamic resistance exercise should be recommended as a safe and effective alternative training mode (supplementary to conventional aerobic exercise) in order to counteract peripheral maladaptation and improve muscle strength, which is necessary for recreational and daily living activities, and thus quality of life, of patients with stable, CHF.     

Suppressed heat shock protein response in the kidney of exercise‐trained diabetic rats

Impaired expression of heat shock proteins (HSP s) and increased oxidative stress may contribute to the pathophysiology of diabetes by disrupted tissue protection. Acute exercise induces oxidative stress, whereas exercise training up‐regulates endogenous antioxidant defenses and HSP expression. Although diabetic nephropathy is a major contributor to diabetic morbidity, information regarding the effect of HSP s on kidney protection is limited. This study evaluated the effects of eight‐week exercise training on kidney HSP expression and markers of oxidative stress at rest and after acute exercise in rats with or without streptozotocin‐induced diabetes. Induction of diabetes increased DNA ‐binding activity of heat shock factor‐1, but decreased the expression of HSP 72, HSP 60, and HSP 90. The inflammatory markers IL ‐6 and TNF ‐alpha were increased in the kidney tissue of diabetic animals. Both exercise training and acute exercise increased HSP 72 and HSP 90 protein levels only in non‐diabetic rats. On the other hand, exercise training appeared to reverse the diabetes‐induced histological changes together with decreased expression of TGF ‐beta as a key inducer of glomerulosclerosis, and decreased levels of IL ‐6 and TNF ‐alpha. Notably, HSP 72 and TGF ‐beta were negatively correlated. In conclusion, impaired HSP defense seems to contribute to kidney injury vulnerability in diabetes and exercise training does not up‐regulate kidney HSP expression despite the improvements in histopathological and inflammatory markers.     

Adaptation of skeletal muscle to endurance exercise.

Skeletal muscle adapts to endurance excerise, such as long distance running, with an increase in the capacity for aerobic metabolism. This is reflected in an increased capacity of whole homogenates and of the mitochondrial fraction of muscle to oxidize pyruvate and long chain fatty acids. Underlying this increase in the ability to obtain energy by respiration is an increase in the levels of a number of mitochondrial enzymes. These include the enzymes involved in fatty acid oxidation, the enzymes of the citric acid cycle, the components of the respiratory chain that link the oxidation of succinate and NADH to oxygen, and coupling factor 1. These increases in mitochondrial enzyme activity appear to be due to an increase in enzyme protein as evidenced by a doubling of the concentration of cytochrome c and a 60% increase in the protein content of the mitochondrial fraction skeletal muscle. Electronmicroscopic studies suggest that increases in both the size and number of mitochondria are responsible for the increase in mitochondrial protein. An alteration in mitochondrial composition also occurs, with some mitochondrial enzymes increasing 2-fold, others increasing only 35% to 60%, while others, including mitochondrial alpha-glycerophosphate dehydrogenase, creatine phosphokinase and adenylate kinase do not increase at all. As a result of these and other exercise induced biochemical adaptations skeletal muscle tends to become more like heart muscle in its enzyme pattern.     

线粒体移动相关基因miro1在急性运动中的表达特征

目的:探讨在急性运动中骨骼肌线粒体能量代谢与线粒体移动相关基因miro1的表达变化特征。方法:以C57 BL/6小鼠一次中等强度负荷跑台运动(0°,13m/min)为实验模型,将小鼠随机分为5组:安静对照组、运动30min、60min、90min、120min组,分别测定骨骼肌线粒体呼吸控制比(RCR),ATP合成酶活性、骨骼肌H2O2生成量,并观察运动中骨骼肌miro1 mRNA表达变化。结果:(1)120分钟急性运动过程中miro1mRNA表达均较安静组显著升高,其中E30、E60、E90、E120组分别较安静组增高32.8%、107.6%、63.8%及44.8%;(2)运动中各时间点骨骼肌H2O2均较安静组显著升高,E30～E120组分别较安静组升高22.1%、26.7%、37.6%、33.7%;(3)E30组ATP合成酶活性与安静组比较明显增加,其余各组无明显变化;整个运动过程中线粒体呼吸控制比无显著变化。结论:急性运动中骨骼肌miro1 mRNA表达较安静时显著增加,可能利于促进线粒体呼吸和ATP合成,以应对细胞能量需求。     

线粒体移动相关基因mirol在急性运动中的表达特征

目的:探讨在急性运动中骨骼肌线粒体能量代谢与线粒体移动相关基因mirol的表达变化特征.方法:以C57 BL/6小鼠一次中等强度负荷跑台运动(0°,13m/min)为实验模型,将小鼠随机分为5组:安静对照组、运动30min、60min、90min、120min组,分别测定骨骼肌线粒体呼吸控制比(RCR),ATP合成酶活性、骨骼肌H_2O_2生成量,并观察运动中骨骼肌mirol mRNA表达变化.结果:(1)120分钟急性运动过程中mirolmRNA表达均较安静组显著升高,其中E30、E60、E90、E120组分别较安静组增高32.8%、107.6%、63.8%及44.8%;(2)运动中各时间点骨骼肌H_2O_2均较安静组显著升高,E30～E120组分别较安静组升高22.1%、26.7%、37.6%、33.7%;(3)E30组ATP合成酶活性与安静组比较明显增加,其余各组无明显变化;整个运动过程中线粒体呼吸控制比无显著变化.结论:急性运动中骨骼肌mirol mRNA表达较安静时显著增加,可能利于促进线粒体呼吸和ATP合成,以应对细胞能量需求.     

The role of calcium in the control of respiration by muscle mitochondria

In muscle, energy supply is finely tuned to energy demand. Ca2+-activated ATP hydrolysis in the cytosol provides ADP to the mitochondrion to stimulate oxidative phosphorylation by acceptor control of mitochondrial respiration. Although mitochondria are responsive to increased concentrations of ADP in vitro, oxygen extraction in cardiac muscle may increase independently of any significant alterations in cellular ADP levels or of dramatic changes in cellular phosphate metabolites as determined by P-31 NMR. Alterations in ATP/ADP ratios in skeletal muscle with aerobic exercise may be dependent on fiber type, with maintained ATP levels seen in oxidative fibers during muscle work. These data are consistent with increased rates of NADH generation by mitochondrial dehydrogenases, so that ATP production keeps pace with ATP hydrolysis in the cytosol. The mechanism of increased ATP synthesis in muscle mitochondria is termed "stimulus-response-metabolism coupling." Ca2+ ion increases in the muscle cytosol enhance contractility and glycogen breakdown. The Ca2+ signal is then transmitted to the mitochondria to provide matrix Ca2+ concentrations, which activate Ca2+-sensitive dehydrogenase activities, leading to accelerated rates of NAD reduction and oxidative phosphorylation. Thus, Ca2+ signaling to the mitochondria may explain the lack of dramatic fluctuations in the cytosolic phosphorylation potential over a large range of contractile activities in cardiac muscle.     

有氧运动改善高脂膳食诱导的胰岛素抵抗:增强骨骼肌线粒体融合与分裂及功能

目的:研究高脂膳食诱导胰岛素抵抗(IR)发生中骨骼肌线粒体融合与分裂的改变和长期耐力训练对其影响,为深入探讨IR发生的分子病理学机制以及运动防治IR的机制提供依据。方法:雄性C57BL/6小鼠通过8周高脂膳食诱导IR,再分别将正常和IR小鼠分为安静组和运动组,即正常膳食对照组(NS)、正常膳食运动组(NE)、高脂膳食对照组(HS)、高脂膳食运动组(HE),各运动组进行8周有氧运动训练。检测空腹血糖、胰岛素。提取骨骼肌线粒体测定呼吸功能和ATP合成酶活力。实时荧光定量PCR和Western blot分别测定骨骼肌Mfn2、Opa1、Drp1、Fis1的mRNA和蛋白表达。结果:(1)HS组小鼠空腹血糖、胰岛素和胰岛素抵抗指数均显著高于NS组(P<0.01);骨骼肌线粒体态3呼吸速率、呼吸控制比和ATP酶合成活力均显著低于NS组(P<0.01);Mfn2蛋白显著低于NS组(P<0.01),Drp1和Fis1显著高于NS组(P<0.01)。(2)HE组小鼠空腹血糖、胰岛素和胰岛素抵抗指数均显著高于HS组(P<0.01);骨骼肌线粒体态3呼吸速率、RCR和ATP酶合成活力均显著高于HS组(P<0.01);Mfn2、Opa1和Drp1蛋白显著高于HS组(P<0.01,P<0.05,P<0.01)。结论:高脂膳食诱导IR的小鼠骨骼肌线粒体趋于分裂,呼吸功能和ATP合成能力下降,可能是高脂膳食诱导IR的机制之一。长期有氧运动训练使正常和IR小鼠骨骼肌线粒体融合和分裂均增强,促进线粒体呼吸功能和ATP合成能力,有利于预防和改善IR。