Myostatin信号通路在4周离心耐力运动改善2型糖尿病大鼠骨骼肌萎缩中的作用

目的：观察4周离心耐力运动对2型糖尿病大鼠代谢障碍及肌萎缩的影响,探讨myostatin/Smad3/atrogin-1信号通路在肌萎缩中的作用。方法：9周高脂饲养联合STZ注射建立2型糖尿病大鼠模型。将普通饲料组大鼠随机分为对照组（C,n=6）和运动组（E,n=9;将2型糖尿病模型组大鼠随机分为糖尿病对照组（D,n=8）和糖尿病运动组（DE,n=12）。运动方案：坡度-5°,跑速16 m/min,每次60 min、每日一次,每周训练5 d,连续4周。最后一次运动后禁食12 h,测定空腹血糖（FBG）、空腹胰岛素（FINS）,计算稳态模式胰岛素抵抗指数（HOMA-IR）和胰岛素敏感指数（ISI）,进行葡萄糖耐量试验。取比目鱼肌观察肌萎缩现象并检测myostatin、Smad3、p-Smad3和atrogin-1表达情况。结果：①与对照组相比,糖尿病组大鼠体重、比目鱼肌质量/胫骨长和肌纤维平均横截面积、FINS和ISI显著降低（P<0.01）,FBG、HOMA-IR和血糖曲线下面积（AUC_BG）以及myostatin、Smad3、p-Smad3、atrogin-1表达均显著升高（P<0.01）。②4周离心运动后,与糖尿病组相比,糖尿病运动组大鼠肌纤维平均横截面积显著升高（P<0.01）,AUC_BG、HOMA-IR及myostatin、p-Smad3、atrogin-1表达显著降低（P<0.05,P<0.01）。结论：myostatin/Smad3/atrogin-1信号通路上调是导致2型糖尿病肌萎缩的重要原因,4周离心耐力运动可能通过下调myostatin、p-Smad3和atrogin-1表达抑制肌萎缩,进而改善2型糖尿病代谢障碍,提高胰岛素敏感性。     

Vanadium increases GLUT4 in diabetic rat skeletal muscle

The effect of vanadium in lowering blood glucose in diabetic animals is well established; however, the exact mechanism of action of vanadium still eludes us. There are several reports from in vitro studies indicating that vanadium increases enzyme activity in insulin signalling pathways, however these findings have not been duplicated in vivo. Glucose transporters (GLUT) have a major role to play in any glucoregulatory effects. Insulin dependent GLUT4 is a major glucose transporter present in skeletal muscle, adipocytes and heart. In the present study we found that the plasma glucose in streptozotocin (STZ) diabetic animals was restored to normal following treatment with a single dose of BMOV, an organic vanadium compound, given by oral gavage (0.6 mmol/kg), similar to the response with chronic BMOV treatment. The response to BMOV by oral gavage was rapid and the animals were normoglycemic within 24 h of treatment and still demonstrated a significant effect even after 72 h. Using a specific antibody against GLUT4 we found an overall reduction in the GLUT4 in the total membrane fraction in skeletal muscle of diabetic animals. However, with a single dose of BMOV the GLUT4 level was restored to normal. This is the first report that establishes a direct effect of vanadium on the regulation of GLUT4 expression in diabetic animals in vivo, and may at least partially explain the glucoregulatory effects of vanadium.     

Interleukin-6 gene expression is increased in insulin-resistant rat skeletal muscle following insulin stimulation

IL-6 expression in skeletal muscle is stimulated by contractions. We sought to examine whether hyperinsulinaemia increases IL-6 mRNA in skeletal muscle and whether any increase is modified in insulin resistant muscle. We hypothesized that intramuscular IL-6 mRNA would be increased in response to insulin, but such an affect would be unaffected by insulin resistance because the primary insulin sensitive signalling protein responsible for activating IL-6 functions normally in insulin resistant muscle. Transgenic rats over-expressing the gluconeogenic regulatory enzyme phosphoenolpyruvate carboxykinase (PEPCK) were studied. White gastrocnemius muscle samples were obtained under hyperinsulinaemic, euglycaemic clamp (4 mU kg(-1)min(-1) insulin, plasma glucose concentration 4-6 mmol L(-1)) and basal conditions in both PEPCK (basal n=4; insulin n=5) and wild-type (CON) (basal n=5; insulin n=4) rats, which were previously injected with a bolus of 2-[1-14C]deoxyglucose (2-DG) into the carotid artery. Muscle samples were assayed for 2-DG uptake and IL-6 mRNA. No differences in 2-DG uptake or IL-6 mRNA were observed when comparing groups under basal conditions. Under clamp conditions, 2-DG uptake was lower (P<0.05) in PEPCK compared with CON. Insulin stimulation in CON did not change IL-6 mRNA compared with basal levels. In contrast, there was an approximately 8-fold increase (P<0.05) in IL-6 mRNA in insulin-stimulated PEPCK compared with CON basal levels. Insulin stimulation increases IL-6 gene expression in insulin resistant, but not healthy, skeletal muscle, suggesting that IL-6 expression in skeletal muscle is sensitive to changes in insulin in circumstances of insulin resistance. It is likely that the differences observed when comparing healthy with insulin resistant muscle are due to the differential activation of insulin sensitive signalling proteins responsible for activating IL-6.     

有氧运动对2型糖尿病大鼠骨骼肌ERK1/2活性的影响

目的：观察有氧运动对2型糖尿病大鼠骨骼肌细胞外信号调节激酶（ERK1/2）活性的影响,探讨有氧运动对2型糖尿病的预防和调控机制。方法：将75只SD大鼠随机分为正常对照组（CON）、糖尿病对照1组（DC1）、糖尿病运动1组（DE1）、糖尿病对照2组（DC2）、糖尿病运动2组（DE2）5组（n=15）。正常对照组用普通饲料喂养,糖尿病组用高脂高糖配方饲料喂养。经过8周高脂高糖喂养后,糖尿病2组大鼠腹腔内注射链脲佐菌素（STZ）,诱发2型糖尿病;糖尿病运动1组游泳的最后1周初和糖尿病对照1组同时注射STZ,注射剂量为35 mg/kg,3 d后尾部取血测血糖≥ 16.7 mmol/L为造模成功。运动干预8周后,测定大鼠血清胰岛素、骨骼肌中ERK1/2蛋白表达等指标。结果：①与正常对照组比较,糖尿病各对照组血液中总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白（LDL-C）、游离脂肪酸（FFA）显著升高（P<0.05,P<0.01）,空腹血糖（FBG）、胰岛素（FIN）含量和胰岛素抵抗指数（HOMA-IR）显著升高（P<0.01）,ERK1/2磷酸化的蛋白表达显著下降（P<0.05）,糖尿病对照2组ERK1/2蛋白含量显著下降（P<0.05）;②8周游泳运动后,与糖尿病对照组比较,糖尿病运动组血液中TC、TG、FFA、LDL-C显著下降（P<0.05）,FBG、FIN、HOMA-IR显著下降（P<0.05,P<0.01）,ERK1/2磷酸化蛋白表达显著升高（P<0.05）。结论：长时间有氧运动,增加了骨骼肌ERK1/2磷酸化水平,改善了2型糖尿病大鼠胰岛素抵抗的状况,降低血糖。这可能是改善糖代谢紊乱,提高胰岛素敏感性的机制之一。     

Purinergic receptors expressed in human skeletal muscle fibres

Purinergic receptors are present in most tissues and thought to be involved in various signalling pathways, including neural signalling, cell metabolism and local regulation of the microcirculation in skeletal muscles. The present study aims to determine the distribution and intracellular content of purinergic receptors in skeletal muscle fibres in patients with type 2 diabetes and age-matched controls. Muscle biopsies from vastus lateralis were obtained from six type 2 diabetic patients and seven age-matched controls. Purinergic receptors were analysed using light and confocal microscopy in immunolabelled transverse sections of muscle biopsies. The receptors P2Y(4), P2Y(11) and likely P2X(1) were present intracellularly or in the plasma membrane of muscle fibres and were thus selected for further detailed morphological analysis. P2X(1) receptors were expressed in intracellular vesicles and sarcolemma. P2Y(4) receptors were present in sarcolemma. P2Y(11) receptors were abundantly and diffusely expressed intracellularly and were more explicitly expressed in type I than in type II fibres, whereas P2X(1) and P2Y(4) showed no fibre-type specificity. Both diabetic patients and healthy controls showed similar distribution of receptors. The current study demonstrates that purinergic receptors are located intracellularly in human skeletal muscle fibres. The similar cellular localization of receptors in healthy and diabetic subjects suggests that diabetes is not associated with an altered distribution of purinergic receptors in skeletal muscle fibres. We speculate that the intracellular localization of purinergic receptors may reflect a role in regulation of muscle metabolism; further studies are nevertheless needed to determine the function of the purinergic system in skeletal muscle cells.     

Human skeletal muscle CD90+ fibro-adipogenic progenitors are associated with muscle degeneration in type 2 diabetic patients

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不同运动方式对2型糖尿病大鼠骨骼肌Rab5蛋白及糖代谢的影响*

目的: 探讨持续运动和间歇负重运动对2型糖尿病(T2DM)骨骼肌组织细胞形态、骨骼肌Rab5 mRNA及蛋白表达、骨骼肌糖代谢的影响。方法: SD大鼠选取8只为空白对照组(CR),其他采用高脂高糖饲料喂养6周后,腹腔注射STZ(35 mg/kg)构建T2DM模型。选取24只T2DM分3组(n=8),分别为:T2DM模型组(DRM)、持续运动组(DCRE)、间歇负重运动组(DWRE)。持续运动方案:为前1～2 周准备活动15 m/min(10 min)、运动20 m/min(40 min)、整理活动15 m/min(10 min),后3～8周为 18 m/min(10 min)、25 m/min(40 min)、15 m/min(10 min);间歇负重运动方案:采用负荷重量为15%(1～2周)、30%(3～4周)、45%(5～8周),运动均为15 m/min(5 min),共12组,组间休息3 min。8周后,通过HE观察骨骼肌病理形态变化,qRT-PCR检测骨骼肌Rab5、葡萄糖转运酶4(GLUT4)的mRNA表达,免疫荧光组化技术及Western blot检测骨骼肌Rab5的蛋白表达,ELISA检测血浆Rab5和糖化血红蛋白(GHb)浓度。结果: 相比CR,DRM存在骨骼肌病理损伤,骨骼肌Rab5mRNA及蛋白表达、GLUT4 mRNA表达均降低(P＜0.01),血浆Rab5和GHb均显著升高(P＜0.01);与DRM比较, DCRE、DWRE骨骼肌病理损伤均显著减轻,骨骼肌Rab5 mRNA及蛋白表达、GLUT4 mRNA表达均升高(P＜0.05,P＜0.01),血浆Rab5和GHb降低(P＜0.01);DCRE与DWRE组间均无统计学差异(P＞0.05)。结论: 2种运动方式均能改善2型糖尿病大鼠骨骼肌病理损伤,并可通过提高骨骼肌Rab5基因和蛋白表达从而增强 GLUT4转运能力,缓解骨骼肌糖代谢稳态失衡,但2种运动方式对骨骼肌Rab5蛋白和糖代谢的影响无明显差异性。     

Downregulation of the skeletal muscle pyruvate dehydrogenase complex in the Otsuka Long-Evans Tokushima Fatty rat both before and after the onset of diabetes mellitus

The pyruvate dehydrogenase complex (PDC) catalyzes the irreversible oxidative decarboxylation of pyruvate in mitochondria. The PDC activity is regulated by a phosphorylation/dephosphorylation cycle catalyzed by specific kinases (PDK) and phosphatases (PDP). In this study, the regulatory mechanisms of PDC were examined in skeletal muscle of the spontaneously diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rat before and after the onset of diabetes. The Long-Evans Tokushima Otsuka (LETO) rat was used as control. Plasma glucose and insulin concentrations were at normal levels in both groups at 8 weeks of age but were significantly higher in OLETF than in LETO rats at 25 weeks of age (1.2-fold for glucose and 15-fold for insulin), indicating development of diabetes in the former. Plasma free fatty acids were 1.6-fold concentrated and the skeletal muscle PDC activity state was significantly lower in OLETF than in LETO rats at both ages, suggesting suppression of pyruvate oxidation in OLETF rats even before the onset of diabetes. The PDK activity and the abundance of the PDK isoform 4 protein as well as mRNA were greater in OLETF rats at both ages. Conversely, the abundance of the PDP isoform 1 protein and mRNA was less in OLETF than in LETO rats at both ages. These results suggest that concomitant greater PDK4 and less PDP1 expression in skeletal muscle of OLETF rats before the onset of diabetes are responsible for the lowering of the PDC activity and may be related with the development of diabetes mellitus.     

Expression of the skeletal muscle dystrophin-dystroglycan complex and syntrophin-nitric oxide synthase complex is severely affected in the type 2 diabetic Goto-Kakizaki rat

The inability of insulin to stimulate glucose metabolism in skeletal muscle fibres is a classic characteristic of type 2 diabetes. Using the non-obese Goto-Kakizaki rat as an established animal model of this type of diabetes, sucrose gradient centrifugation studies were performed and confirmed the abnormal subcellular location of the glucose transporter GLUT4. In addition, this analysis revealed an unexpected drastic reduction in the surface membrane marker beta-dystroglycan, a dystrophin-associated glycoprotein. Based on this finding, a comprehensive immunoblotting survey was conducted which showed a dramatic decrease in the Dp427 isoform of dystrophin and the alpha/beta-dystroglycan subcomplex, but not in laminin, sarcoglycans, dystrobrevin, and excitation-contraction-relaxation cycle elements. Thus, the backbone of the trans-sarcolemmal linkage between the extracellular matrix and the actin membrane cytoskeleton might be structurally impaired in diabetic fibres. Immunohistochemical studies revealed that the reduction in the dystrophin-dystroglycan complex does not induce obvious signs of muscle pathology, and is neither universal in all fibres, nor fibre-type specific. Most importantly, the expression of alpha-syntrophin and the syntrophin-associated neuronal isoform of nitric oxide synthase, nNOS, was demonstrated to be severely reduced in diabetic fibres. The loss of the dystrophin-dystroglycan complex and the syntrophin-nNOS complex in selected fibres suggests a weakening of the sarcolemma, abnormal signalling and probably a decreased cytoprotective mechanism in diabetes. Impaired anchoring of the cortical actin cytoskeleton via dystrophin might interfere with the proper recruitment of the glucose transporter to the surface membrane, following stimulation by insulin or muscle contraction. This may, at least partially, be responsible for the insulin resistance in diabetic skeletal muscles.     

Vitamin E supplementation modifies adaptive responses to training in rat skeletal muscle

Abstract

Aim of the present study was to test, by vitamin E treatment, the hypothesis that muscle adaptive responses to training are mediated by free radicals produced during the single exercise sessions. Therefore, we determined aerobic capacity of tissue homogenates and mitochondrial fractions, tissue content of mitochondrial proteins and expression of factors (PGC-1, NRF-1, and NRF-2) involved in mitochondrial biogenesis. Moreover, we determined the oxidative damage extent, antioxidant enzyme activities, and glutathione content in both tissue preparations, mitochondrial ROS production rate. Finally we tested mitochondrial ROS production rate and muscle susceptibility to oxidative stress. The metabolic adaptations to training, consisting in increased muscle oxidative capacity coupled with the proliferation of a mitochondrial population with decreased oxidative capacity, were generally prevented by antioxidant supplementation. Accordingly, the expression of the factors involved in mitochondrial biogenesis, which were increased by training, was restored to the control level by the antioxidant treatment. Even the training-induced increase in antioxidant enzyme activities, glutathione level and tissue capacity to oppose to an oxidative attach were prevented by vitamin E treatment. Our results support the idea that the stimulus for training-induced adaptive responses derives from the increased production, during the training sessions, of reactive oxygen species that stimulates the expression of PGC-1, which is involved in mitochondrial biogenesis and antioxidant enzymes expression. On the other hand, the observation that changes induced by training in some parameters are only attenuated by vitamin E treatment suggests that other signaling pathways, which are activated during exercise and impinge on PGC-1, can modify the response to the antioxidant integration.     

The therapeutic effect of aerobic exercise with resistance training in elderly men with type 2 diabetes mellitus

Objective: This study was conducted to examine the effects of aerobic exercise alone and aerobic exercise with resistance training on the quality of life in men over the age of 55 years with type 2 diabetes mellitus. Methods: A total of 54 participants were divided into the following three groups so that there were no significant differences in blood chemistry or physical ability indexes among the three groups: control, aerobic exercise, and aerobic exercise with resistance training. The latter two groups exercised for 24 weeks, while the control group performed no exercise. Blood chemistry levels and measures of physical ability in each group members were examined one day before and one day after the exercise regimens. Results: Compared with those before the study, blood glucose, glycated hemoglobin, triglycerides, cholesterol, and low-density lipoprotein levels as well as vital capacity, reaction time, sit-and-reach ability, and balancing while standing on one leg with closed eyes were significantly improved in the aerobic exercise only group(P 0.05). All these measures as well as high-density lipoprotein levels and grip, back, and leg strength were significantly improved in the combined aerobic and resistance training group(P 0.05). By contrast, no significant differences before and after the experiment were found in any measure for the control group(P 0.05). Conclusion: Although both aerobic exercise and aerobic exercise combined with resistance training for 24 weeks effectively improved the quality of life in patients with type 2 diabetes, the effect of the combined training was better than that of aerobic exercise alone. These results suggest that resistance training may be safely added to the rehabilitation training regimen of patients with type 2 diabetes mellitus.     

Effects of isokinetic training of the knee extensors on high-intensity exercise performance and skeletal muscle buffering

Twenty-three subjects isokinetically trained the right and left quadriceps femoris, three times per week for 16 weeks; one group (n=13) trained at an angular velocity of 4.19 rad · s^–1 and a second group (n=10), at 1.05 rad · s^–1. A control group (n=10) performed no training. Isometric endurance time at 60% quadriceps maximum voluntary contraction (MVC), mean power output and work done (W) during all-out cycling, and the muscle buffer value (B) and carnosine concentration of biopsy samples from the vastus lateralis, were all assessed before and after training. The two training groups did not differ significantly from each other in their training response to any of these variables (P < 0.05). No significant difference in either 60% MVC endurance time or impulse [(endurance time × force) at 60% MVC] was observed for any group after the 16 week period (P > 0.05). However, the post-training increase (9%) in W during high-intensity cycling was greater in the training group than in the control group (P=0.04). NeitherB nor carnosine concentration showed any significant change following training (P=0.56 andP=0.37, respectively). It is concluded that 16 weeks of isokinetic training of the knee extensors enables subjects to do more work during high-intensity cycling. Although the precise adaptations responsible for the improved performance have yet to be identified, they are unlikely to include an increase inB.     

Different metabolic adaptation of heart and skeletal muscles to moderate-intensity treadmill training in the rat

The effect was investigated of treadmill training of moderate intensity on the fatty acid-binding protein (FABP) content in relation to parameters of oxidative and glycolytic metabolism. To this end, the cytoplasmic FABP content and the activity of beta-hydroxyacyl-coenzyme A dehydrogenase (HAD), citrate synthase (CS), and 6-phosphofructokinase (PFK) were measured in heart, fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus muscles (SOL) of male Wistar rats. To investigate the influence of the amount of training (defined as the product of exercise duration, intensity and frequency), two training groups were created that differed in training frequency (HF, high frequency 5 days x week(-1), n = 9; LF, low frequency 2 days x week(-1), n = 9; the exercise being 20 m x min(-1) for 2 h with no gradient, over 6 weeks) and compared with SC, sedentary controls (n = 7). In heart muscle, the cytoplasmic FABP content was 34% higher in HF than in SC but was the same as in LF. The CS and HAD activities were no different in the three groups, suggesting that the capacity to oxidize fatty acids (FA) was not affected by training. The PFK activity was higher (43%) in HF, suggesting a shift towards carbohydrate utilization. The FABP content and HAD activity did not change in SOL and EDL after training whereas the CS activity increased (27%) in SOL and decreased (21%) in EDL in both training groups. In addition, PFK activity in EDL was much higher (113%) in the HF than in SC group. The HF training was associated with a fine-tuning of FA availability and use in heart muscle, and with a more efficient energy production. It is suggested therefore that cytoplasmic FABP could be an early marker of muscle adaptation to training in heart but not in skeletal muscle. The training reinforced the metabolic profile of the skeletal muscles, in particular that of the fast-twitch glycolytic muscle. We concluded that a large amount of training is needed when the effect on both oxidative and glycolytic parameters is to be studied.     

有氧运动联合褪黑素对Ⅱ型糖尿病大鼠骨质疏松的影响

目的：观察有氧运动和褪黑素对Ⅱ型糖尿病大鼠骨质疏松的影响。方法：6周龄的成年雌性SD大鼠60只,随机分为安静对照组（N组）10只和Ⅱ型糖尿病模型组50只,N组大鼠不加任何干预,Ⅱ型糖尿病模型组大鼠一次性腹腔注射35 mg/kg链脲佐菌素（STZ）,1周后检测大鼠血糖大于16.7 mmol/L为Ⅱ型糖尿病造模成功,将40只成模大鼠随机分为糖尿病对照组（D）、糖尿病+有氧运动组（DE）、糖尿病+褪黑素组（DM）、糖尿病+有氧运动+褪黑素组（DEM）,每组10只;DE组和DEM组大鼠采用20 min的递增负荷的方式进行跑台有氧运动,训练持续6周,DM组和DEM组大鼠每天灌胃40 mg/kg褪黑素,观察各组大鼠体重、脊椎骨以及左右股骨骨密度（BMD）、观察大鼠血糖、血清丙二醛（MDA）、超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）、血清总钙（Ca）、无机磷（P）和甲状旁腺素（PTH）的变化。结果：与N组相比,D组大鼠体重、血清SOD、GSH-Px水平、血Ca、腰椎和左右股骨BMD显著降低（P < 0.05,P < 0.01）,血糖、血清MDA和血PTH水平显著升高（P < 0.01）,血P无明显变化（P > 0.05）;与D组比较,DE组、DM组大鼠大鼠体重、血清SOD、GSH-Px水平、血Ca、腰椎和左右股骨BMD显著升高（P < 0.05,P <0.01）,血糖、血清MDA和血PTH水平显著降低（P < 0.05,P < 0.01）,血P无明显变化（P > 0.05）,有氧运动和褪黑素同时干预效果更好。结论：有氧运动和褪黑素均能改善糖尿病骨质疏松,且两者联合干预的效果更加显著,其可能与通过提高糖尿病大鼠的抗氧化应激能力,调节糖的代谢从而有效地降低血钙和PTH,改善BMD来缓解骨质疏松有关。     

抗阻训练对增龄大鼠骨骼肌线粒体功能的影响*

目的: 从线粒体动力学的角度,探讨抗阻运动对增龄大鼠骨骼肌线粒体功能的影响。方法: 40只雄性SD大鼠随机分为4组:2月龄安静对照组(C1组)、2月龄抗阻运动训练组(R1组)、6月龄安静对照组(C2组)、6月龄抗阻运动训练组(R2组),每组10只。C1、C2组正常喂养,R1、R2组大鼠进行跑台坡度为35°,速度为15 m/min的抗阻运动,一次跑动15 s,间歇30 s,4次为一组,组间间歇3 min,3组为一次循环,一天为2个循环,循环间歇10 min,每周6 d,共8周。采用Western blot法测定各组大鼠股四头肌线粒体融合蛋白2(Mfn2)、GTP酶1(DRP1) 蛋白含量,使用流式细胞仪测定各组大鼠股四头肌线粒体膜电位(ΔΨm)、活性氧(ROS)和游离钙(Ca²⁺)水平。结果: ① 与C1组相比,R1组大鼠DRP1蛋白升高(P＜0.01)、Mfn2蛋白无显著变化,C2组大鼠DRP1、Mfn2蛋白均降低(P均＜0.01);与C2组相比,R2组大鼠DRP1、Mfn2蛋白均升高(P＜0.01,P＜0.05);与R1组相比,R2组DRP1、Mfn2蛋白均降低(P＜0.01,P＜0.05)。② 与C1组相比,R1组Ca²⁺含量降低(P＜0.01)、C2组Ca²⁺含量升高(P＜0.01);与C2组相比,R2组Ca²⁺含量降低(P＜0.01);与R1组相比,R2组Ca²⁺含量升高(P＜0.01)。③ 与C1组相比,R1组ROS含量有所上升,但无显著性差异,C2组ROS含量升高(P＜0.01);与C2组相比,R2组ROS含量降低(P＜0.01);与R1组相比,R2组ROS含量升高(P＜0.01)。④ 与C1组相比,C2组ΔΨm降低(P＜0.01);与C2组相比,R2组ΔΨm升高(P＜0.01);与R1组相比,R2组ΔΨm有所降低,但无统计学差异。结论: 大鼠增龄过程中股四头肌线粒体出现Ca²⁺堆积、活性氧增多、线粒体膜电位下降、融合蛋白减少等现象,抗阻训练可有效改善这些变化。     

Telomere length is independently associated with age,oxidative biomarkers,and sport training in skeletal muscle of healthy adult males

In skeletal muscle, which mainly contains postmitotic myonuclei, it has been suggested that telomere length remains roughly constant throughout adult life, or shortens in response to physiopathological conditions in muscle diseases or in the elderly. However, telomere length results from both the replicative history of a specific tissue and the exposure to environmental, DNA damage-related factors, therefore the predictive biological significance of telomere measures should combine the analysis of the various interactive factors. In the present study, we analysed any relationship between telomere length [mean and minimum terminal restriction fragment (TRF) length] chronological age, oxidative damage (4-HNE, protein carbonyls), catalase activity, and heat shock proteins expression (αB-crystallin, Hsp27, Hsp90) in semitendinous muscle biopsies of 26 healthy adult males between 20 and 50 years of age, also exploring the influence of regular exercise participation. The multiple linear regression analysis identified age, 4-HNE, catalase, and training status as significant independent variables associated with telomere length and jointly accounting for ～30–36% of interindividual variation in mean and/or minimum TRF length. No association has been identified between telomere length and protein carbonyl, αB-crystallin, Hsp27, and Hsp90, as well as between age and the variables related to stress response. Our results showed that skeletal muscle from healthy adults displays an age-dependent telomere attrition and that oxidised environment plays an age-independent contribution, partially influenced by exercise training.     

Effects of long-term resistance exercise training on autophagy in rat skeletal muscle of chloroquine-induced sporadic inclusion body myositis

Purpose

We examined whether resistance exercise training restores impaired autophagy functions caused by Chloroquine (CQ)-induced Sporadic Inclusion Body Myositis (sIBM) in rat skeletal muscle.

Methods

Male wistar rats were randomly assigned into three groups: Sham (n = 6), CQ (n = 6), and CQ + Exercise (CE, n = 6). To create a rat model of sIBM, rats in the CQ and CE group were intraperitoneally injected with CQ 5 days a week for 16 weeks. Rats in the CE group performed resistance exercise training 3 times a week for 8 weeks in conjunction with CQ starting from week 9 to week 16. During the training period, maximal carrying load, body weight, muscle weight, and relative muscle weight were measured. Autophagy responses were examined by measuring specific markers.

Results

While maximal carrying capacity for resistance exercise training was dramatically increased in the CE group, no significant changes occurred in the skeletal muscle weight as well as in the relative muscle weight of CE compared to the other groups. CQ treatment caused significant increases in the levels of Beclin-1 and p62, and decreases in the levels of LAMP-2 proteins. Interestingly, no significant differences in the LC3-II/I ratio or the LC3-II protein levels were observed. Although CQ-treatment groups suppressed the levels of the potent autophagy inducer, BNIP3, p62 levels were decreased in only the CE group.

Conclusion

Our findings demonstrate that sIBM induced by CQ treatment results in muscle degeneration via impaired autophagy and that resistance exercise training improves movable loading activity. Finally, regular exercise training may provide protection against sIBM by enhancing the autophagy flux through p62 protein.     

Gfat1基因在2型糖尿病大鼠肺组织中的表达

观察2型糖尿病大鼠不同时期肺组织谷氨酰胺果糖转移酶1(Gfat1)的表达情况.方法 SD大鼠随机分为正常对照组和模型组,对照组18只,模型组28只.模型组高脂饲料喂养2个月后,腹腔注射链脲佐菌素(STZ 15mg/kg)复制糖尿病模型,统计体重变化及空腹血糖值.RT-PCR方法检测造模成功后2周、4周和6周肺组织Gfat1 mRNA表达.结果 模型组大鼠体重增长较快,造模开始第28天,第42天,第56天和第70天高脂模型组与对照组体重差异有显著性(P＜0.05).注射STZ的高脂模型组空腹血糖值较高(FBG≥10.0),和对照组比较,FBG差异有极显著性(P＜0.01).糖尿病大鼠造模成功后2周,模型组肺组织Gfat1的表达低于对照组,与对照组比较差异无显著性(P＞0.05),4周模型组Gfat1的表达高于对照组,模型组与对照组比较差异有显著性(P＜0.05).6周模型组Gfat1的表达高于对照组,但模型组与对照组比较差异无显著性(P＞0.05).结论 大鼠饲喂高脂饲料结合腹腔注射STZ可成功建立2型糖尿病大鼠模型;在不同时期2型糖尿病大鼠肺组织中,Gfat1表达水平发生改变.     

不同训练方式对大鼠骨骼肌纤维类型转化和CaMK II/MEF2传导途径的影响*

目的: 探讨间歇速度训练和耐力训练对大鼠骨骼肌纤维类型转化及钙调蛋白激酶/肌细胞增强因子2(CaMK II/MEF2)信号传导通路的影响。方法: 成年雄性SD大鼠(8周龄)18只,随机分成间歇速度训练组(IST),耐力训练组(ET),设空白组(C),每组6只,IST组采用75 m/min×1 min、20 m/min×1 min的交替训练6次,跑台坡度15,持续时间12 min/d;ET组采用速度30 m/ min、跑台坡度7、持续时间90 min/d的耐力训练。干预8周后,分别取小鼠右侧胫骨前肌、比目鱼肌,酶联免疫吸附法检测骨骼肌琥珀酸脱氢酶(SDH)、乳酸脱氢酶(LDH)活性,ATP酶染色法观察I、Ⅱ型肌纤维面密度、数密度变化情况,SDS-PAGE凝胶电泳技术观察骨骼肌MHC亚型百分比含量、骨骼肌mRNA表达谱测序分析及qRT-PCR技术检测CaN、CaMKII、MEF2水平。结果: 相比C组,ET组SDH活性显著上升,LDH活性降低(P＜0.05);IST组胫骨前肌中LDH活性值升高(P＜0.01)。ET组胫骨前肌MHCIIa%升高,MHCIIb%降低(P＜0.05),比目鱼肌MHCI% 和MHCIIa%升高,MHCIIb%均降低(P＜0.05)。相比IST组,ET组胫骨前肌MHCIIx%升高(P＜0.05)。相比C组,ET组胫骨前肌 I、II 型纤维纤维密度上升,IST组II型纤维纤维密度提高,IST组、ET组比目鱼肌I型纤维纤维密度上升(P＜0.05)。相比C组,ET组骨骼肌CaN、CaMKII、MEF2 mRNA表达水平增高,IST组CaN、CaMKII、MEF2 mRNA表达水平下降(P＜0.01)。Illumina高通量测序筛选骨骼肌纤维转化相关因子及关联分析,运动干预促使骨骼肌纤维转化相关因子表达变化富集于TGF-β/Smad3、CaN/MEF2、AdipoQ等信号通路,而耐力训练显著提高骨骼肌纤维转化、干细胞功能相关信号通路的富集。结论: 耐力训练促进向氧化型肌纤维转化(慢肌),而间歇速度训练向酵解型肌纤维转化(快肌),并伴随着CaMK II/MEF2传导途径中CaN、CaMKII、MEF2基因的高表达。