The effects of running exercise on oxidative capacity and PGC-1α mRNA levels in the soleus muscle of rats with metabolic syndrome

Skeletal muscles in animals with metabolic syndrome exhibit reduced oxidative capacity. We investigated the effects of running exercise on fiber characteristics, oxidative capacity, and mRNA levels in the soleus muscles of rats with metabolic syndrome [SHR/NDmcr-cp (cp/cp); CP]. We divided 5-week-old CP rats into non-exercise (CP) and exercise (CP-Ex) groups. Wistar-Kyoto rats (WKY) were used as the control group. CP-Ex rats were permitted voluntary exercise on running wheels for 10 weeks. Triglyceride levels were higher and adiponectin levels lower in the CP and CP-Ex groups than in the WKY group. However, triglyceride levels were lower and adiponectin levels higher in the CP-Ex group than in the CP group. The soleus muscles in CP-Ex rats contained only high-oxidative type I fibers, whereas those in WKY and CP rats contained type I, IIA, and IIC fibers. Muscle succinate dehydrogenase (SDH) activity was higher in the CP-Ex group than in the CP group; there was no difference in SDH activity between the WKY and CP-Ex groups. Muscle proliferator-activated receptor γ coactivator-1α (PGC-1α) mRNA levels were higher in the CP-Ex group than in the CP group; there was no difference in PGC-1α mRNA levels between the WKY and CP-Ex groups. In CP-Ex rats, longer running distance was associated with increased muscle SDH activity and PGC-1α mRNA levels. We concluded that running exercise restored decreased muscle oxidative capacity and PGC-1α mRNA levels and improved hypertriglyceridemia in rats with metabolic syndrome.     

Calcineurin A and CaMKIV transactivate PGC-1α promoter, but differentially regulate cytochrome c promoter in rat skeletal muscle

In skeletal muscle, slow-twitch fibers are highly dependent on mitochondrial oxidative metabolism suggesting the existence of common regulatory pathways in the control of slow muscle-specific protein expression and mitochondrial biogenesis. In this study, we determined whether peroxisome proliferator-activated receptor γ co-activator-1α (PGC-1α) could transactivate promoters of nuclear-encoded mitochondrial protein (cytochrome c) and muscle-specific proteins (fast troponin I, MyoD). We also investigated if calcineurin A (CnA) and calcium/calmodulin kinase IV (CaMKIV) were involved in the regulation of PGC-1α and cytochrome c promoter. For this purpose, we took advantage of the gene electrotransfer technique, which allows acute expression of a gene of interest. Electrotransfer of a PGC-1α expression vector into rat Tibialis anterior muscle induced a strong transactivation of cytochrome c promoter (P < 0.001) independent of nuclear respiratory factor 1. PGC-1α gene electrotransfer did not transactivate fast troponin I promoter, whereas it did transactivate MyoD promoter (P < 0.05). Finally, whereas electrotransfers of CnA or CaMKIV expression vectors transactivated PGC-1α promoter (P < 0.001), gene electrotransfer of CaMKIV was only able to transactivate cytochrome c promoter. Taken together, these data suggest that CnA triggers PGC-1α promoter transactivation to drive the expression of non-mitochondrial proteins.     

Living at high altitude in combination with sea-level sprint training increases hematological parameters but does not improve performance in rats

The regimen of aerobic training at sea level with recovery at high altitude has been used by athletes to improve performance. However, little is known about the effects of hypoxia when combined with sprint interval training on performance. The aim of the present study was to determine the effect of a “living high-sprint training low” strategy on hemoglobin, hematocrit and erythropoietin levels in rats. We also wanted to test whether the addition of a hypoxic stress to the program of daily treadmill running at high speeds induces expressional adaptations in skeletal muscle and affects performance. The protein content of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), cytochrome C, pyruvate dehydrogenase kinase (PDK1), heat shock protein 70 (HSP70), manganese superoxide dismutase (MnSOD) and citrate synthase activity were determined in different muscle fiber types in our animals (red and white gastrocnemius muscle). We also determined the maximal aerobic velocity (MAV) before and after the training period. A total of 24 male Wistar rats (3 month old) were randomly divided into four experimental groups: the normoxic control group (n = 6), the normoxic trained group (n = 6), the hypoxic control group (12 h pO₂ 12%/12 h pO₂ 21%) (n = 6) and the hypoxic trained group (12 h pO₂ 12%/12 h pO₂ 21%). Living in normobaric hypoxia condition for 21 days significantly increased hemoglobin, hematocrit and erythropoietin levels in both the rest and the trained groups. The trained animals (normoxia and hypoxia) significantly increased their maximal aerobic velocity. No changes were found in the skeletal muscle in PGC-1α, cytochrome C, PDK1, HSP70, MnSOD protein content and in the citrate synthase activity in any experimental group. Regardless of whether it is combined with sprint interval training or not, after 21 days of living at high altitude we found a significant increase in the hematological values determined in our study. However, contrary to our starting hypothesis, the combination of normobaric hypoxia and sprint training did not improve MAV in our animals.     

Substrate use and biochemical response to a 3,211-km bicycle tour in trained cyclists

The purpose of this study was to assess the physiological adaptations in physically fit individuals to a period of intensified training. Ten trained males cycled outdoors ~170 km day⁻¹ on 19 out of 21 days. Expired gas was collected on days 1 and 21 during maximal graded exercise and used for the determination of gross efficiency and whole body substrate use. Muscle biopsies were obtained before and after exercise on days 2 and 22 for the determination of mtDNA/gDNA ratio, gene expression, metabolic enzyme activity and glycogen use. Muscle glycogen before and after exercise, fat oxidation, and gross efficiency increased, carbohydrate oxidation decreased (p < 0.05), and VO_2max did not change over the 21 days of training. Citrate synthase (CS), β-hydroxyacyl CoA dehydrogenase (β-HAD) and cytochrome c oxidase (COX) enzyme activity did not change with training. CS and β-HAD mRNA did not change with acute exercise or training. COX (subunit IV) mRNA increased with acute exercise (p < 0.05) but did not change over the 21 days. PGC-1α mRNA increased with acute exercise, but did not increase to the same degree on day 22 as it did on day 2 (p < 0.05). UCP3 mRNA decreased with training (p < 0.05). Acute exercise caused an increase in mitofusin2 (MFN2) mRNA (p < 0.05) and a trend for an increase in mtDNA/gDNA ratio (p = 0.057). However, training did not affect MFN2 mRNA or mtDNA/gDNA ratio. In response to 3,211 km of cycling, changes in substrate use and gross efficiency appear to be more profound than mitochondrial adaptations in trained individuals.     

SIRT1, AMP-activated protein kinase phosphorylation and downstream kinases in response to a single bout of sprint exercise: influence of glucose ingestion

This study was designed to examine potential in vivo mechanisms of AMP-activated protein kinase (AMPK) phosphorylation inhibition and its downstream signaling consequences during the recovery period after a single bout of sprint exercise. Sprint exercise induces Thr¹⁷²-AMPK phosphorylation and increased PGC-1α mRNA, by an unknown mechanism. Muscle biopsies were obtained in 15 young healthy men in response to a 30-s sprint exercise (Wingate test) randomly distributed into two groups: the fasting (n = 7, C) and the glucose group (n = 8, G), who ingested 75 g of glucose 1 h before exercising to inhibit AMPKα phosphorylation. Exercise elicited different patterns of Ser²²¹-ACCβ, Ser⁴⁷³-Akt and Thr⁶⁴²-AS160 phosphorylation, during the recovery period after glucose ingestion. Thirty minutes after the control sprint, Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2 phosphorylation was reduced by 33% coinciding with increased Thr¹⁷²-AMPKα phosphorylation (both, P < 0.05). Glucose abolished the 30-min Thr¹⁷²-AMPKα phosphorylation. Ser²²¹-ACCβ phosphorylation was elevated immediately following and 30 min after exercise in C and G, implying a dissociation between Thr¹⁷²-AMPKα and Ser²²¹-ACCβ phosphorylation. Two hours after the sprint, PGC-1α protein expression remained unchanged while SIRT1 (its upstream deacetylase) was increased. Glucose ingestion abolished the SIRT1 response without any significant effect on PGC-1α protein expression. In conclusion, glucose ingestion prior to a sprint exercise profoundly affects Thr¹⁷²-AMPKα phosphorylation and its downstream signaling during the recovery period.     

Eccentric endurance training in subjects with coronary artery disease: a novel exercise paradigm in cardiac rehabilitation?

This study evaluated the effects of 8 weeks of eccentric endurance training (EET) in male subjects (age range 42–66 years) with coronary artery disease (CAD). EET was compared to concentric endurance training (CET) carried out at the same metabolic exercise intensity, three times per week for half an hour. CET (n=6) was done on a conventional cycle ergometer and EET (n=6) on a custom-built motor-driven ergometer. During the first 5 weeks of the training program the metabolic load was progressively increased to 60% of peak oxygen uptake in both groups. At this metabolic load, mechanical work rate achieved was 97 (8) W [mean (SE)] for CET and 338 (34) W for EET, respectively. Leg muscle mass was determined by dual-energy X-ray absorptiometry, quadriceps strength with an isokinetic dynamometer and muscle fibre composition of the vastus lateralis muscle with morphometry. The leg muscle mass increased significantly in both groups by some 3%. Strength parameters of knee extensors improved in EET only. Significant changes of +11 (4.9)%, +15 (3.2)% and +9 (2.5)% were reached for peak isometric torque and peak concentric torques at 60° s^–1 and 120° s^–1, respectively. Fibre size increased significantly by 19% in CET only. In conclusion, the present investigation showed that EET is feasible in middle-aged CAD patients and has functional advantages over CET by increasing muscle strength. Muscle mass increased similarly in both groups whereas muscle structural composition was differently affected by the respective training protocols. Potential limitations of this study are the cautiously chosen conditioning protocol and the restricted number of subjects.     

Chronic low frequency/low volume resistance training reduces pro-inflammatory cytokine protein levels and TLR4 mRNA in rat skeletal muscle

Skeletal muscle is the source of pro- and anti-inflammatory cytokines, and recently, it has been recognized as an important source of interleukin 6 (IL-6), a cytokine that exerts inhibitory effects on several pro-inflammatory cytokines. Although dynamic chronic resistance training has been shown to produce the known “repeated bout effect”, which abolishes the acute muscle damage, performing of high-intensity resistance training has been regarded highly advisable, at least from the hypertrophy perspective. On the other hand, a more therapeutic, “non-damaging” resistance training program, mainly composed of concentric forces, low frequency/low volume of training, and the same exercise, could theoretically benefit the muscle when the main issue is to avoid muscle inflammation (as in the treatment of several “low-grade” inflammatory diseases) because the acute effect of each resistance exercise session could be diminished/avoided, at the same time that the muscle is still being overloaded in a concentric manner. However, the benefits of such “less demanding” resistance training schedule on the muscle inflammatory profile have never been investigated. Therefore, we assessed the protein expression of IL-6, TNF-α, IL-10, IL-10/TNF-α ratio, and HSP70 levels and mRNA expression of SCF^β-TrCP, IL-15, and TLR-4 in the skeletal muscle of rats submitted to resistance training. Briefly, animals were randomly assigned to either a control group (S, n = 8) or a resistance-trained group (T, n = 7). Trained rats were exercised over a duration of 12 weeks (two times per day, two times per week). Detection of IL-6, TNF-α, IL-10, and HSP70 protein expression was carried out by western blotting and SCF^β-TrCP (SKP Cullin F-Box Protein Ligases), a class of enzymes involved in the ubiquitination of protein substrates to proteasomal degradation, IL-15, and TLR-4 by RT-PCR. Our results show a decreased expression of TNF-α and TLR4 mRNA (40 and 60%, respectively; p < 0.05) in the plantar muscle from trained, when compared with control rats. In conclusion, exercise training induced decreased TNF-α and TLR-4 expressions, resulting in a modified IL-10/TNF-α ratio in the skeletal muscle. These data show that, in healthy rats, 12-week resistance training, predominantly composed of concentric stimuli and low frequency/low volume schedule, down regulates skeletal muscle production of cytokines involved in the onset, maintenance, and regulation of inflammation.     

The Involvement of the CD40-CD40L Pathway in Activated Platelet-Induced Changes in HUVEC COX-2 and PPARα Expression

We aim to determine the extent of the CD40-CD40L pathway involvement in activated platelet-induced changes in human umbilical endothelial cells (HUVECs). Activated platelets were co-incubated with HUVECs in the presence or absence of CD40LmAb. HUVECs were also directly stimulated with rhCD40L. HUVEC endothelial cyclooxygenase 2 (COX-2) and peroxisome proliferator-activated receptor alpha (PPARα) expression was then assessed. To estimate COX-2 activity, PGE2 concentration was determined. PPARα activity was assessed using a nuclear factor activity kit. Co-incubation with activated platelets increased HUVEC COX-2 and PPARα mRNA expression (P < 0.01). The addition of CD40L mAb significantly attenuated these increases in mRNA and protein (both P < 0.01). Direct stimulation by rhCD40L increased HUVEC COX-2 mRNA and protein (P < 0.05) but did not significantly change the expression of PPARα mRNA and protein. CD40LmAb significantly decreased (P < 0.05) and rhCD40L significantly (P < 0.01) increased COX-2 enzymatic activity, but had almost no effects on PPARα binding activity. Activated platelets may increase HUVEC COX-2 expression and activity partly through the CD40-CD40L pathway.     

Exhaustive exercise causes an anti-inflammatory effect in skeletal muscle and a pro-inflammatory effect in adipose tissue in rats

It is well known that exhaustive exercise increases serum and skeletal muscle IL-6 concentrations. However, the effect of exhaustive exercise on the concentrations of other cytokines in the muscle and in the adipose tissue is controversial. The purpose of this study was to evaluate the effect of exhaustive exercise on mRNA and protein expression of IL-10, TNF-α and IL-6 in different types of skeletal muscle (EDL, soleus) and in two different depots of white adipose tissue (mesenteric–MEAT and retroperitoneal–RPAT). Rats were killed by decapitation immediately (E0 group, n = 6), 2 (E2 group, n = 6) and 6 (E6 group, n = 6) hours after the exhaustion protocol, which consisted of running on a treadmill (approximately 70% VO_2max for 50 min and then subsequently at an elevated rate that increased at 1 m/min every minute, until exhaustion). The control group (C group, n = 6) was not subjected to exercise. Cytokine protein expression increased in EDL, soleus, MEAT and RPAT from all exercised groups, as detected by ELISA. EDL IL-10 and TNF-α expression was higher than that of the soleus. The IL-10/TNF-α ratio was increased in the skeletal muscle, especially in EDL, but it was found to be decreased in the adipose tissue. These results show that exhaustive exercise presents a different effect depending on the tissue which is analysed: in the muscle, it induces an anti-inflammatory effect, especially in type 2 fibres, while the pro-inflammatory effect prevails in adipose tissue, possibly contributing to increased lipolysis to provide energy for the exercising muscle.     

Exercise and adrenaline increase PGC-1α mRNA expression in rat adipose tissue

The purpose of the present investigation was to explore the effects of exercise and adrenaline on the mRNA expression of PGC-1α, a master regulator of mitochondrial biogenesis, in rat abdominal adipose tissue. We hypothesized that (1) exercise training would increase PGC-1α mRNA expression in association with increases in mitochondrial marker enzymes, (2) adrenaline would increase PGC-1α mRNA expression and (3) the effect of exercise on PGC-1α mRNA expression in white adipose tissue would be attenuated by a β-blocker. Two hours of daily swim training for 4 weeks led to increases in mitochondrial marker proteins and PGC-1α mRNA expression in epididymal and retroperitoneal fat depots. Additionally, a single 2 h bout of exercise led to increases in PGC-1α mRNA expression immediately following exercise cessation. Adrenaline treatment of adipose tissue organ cultures led to dose-dependent increases in PGC-1α mRNA expression. A supra-physiological concentration of adrenaline increased PGC-1α mRNA expression in epididymal but not retroperitoneal adipose tissue. β-Blockade attenuated the effects of an acute bout of exercise on PGC-1α mRNA expression in epididymal but not retroperitoneal fat pads. In summary, this is the first investigation to demonstrate that exercise training, an acute bout of exercise and adrenaline all increase PGC-1α mRNA expression in rat white adipose tissue. Furthermore it would appear that increases in circulating catecholamine levels may be one potential mechanism mediating exercise induced increases in PGC-1α mRNA expression in rat abdominal adipose tissue.     

The Role of Inflammation and COX-Derived Prostanoids in the Effects of Bradykinin on Isolated Rat Aorta and Urinary Bladder

Bradykinin, a vasoactive peptide, increases during inflammation and induces the formation of prostaglandins through specific receptor activation. Two types of receptors mediate the biological effects of bradykinin, B₁ and B₂ receptors. Although B₂ receptors are present in most tissues, B₁ receptors are expressed after inflammatory stimuli or tissue injury. Bradykinin has a high affinity for B₂ and a low affinity for B₁ receptors, whereas the opposite occurs for des-Arg⁹-bradykinin. Recently, it has been reported that nonsteroidal anti-inflammatory drugs have different inhibitory activities on cyclooxygenase isozymes, COX-1, COX-2, and COX-3. In the present study, we have investigated the contributions of different COX isozyme inhibitions and inflammation on bradykinin-induced effects of isolated rat aorta and urinary bladder smooth muscle contractions. Male Sprague–Dawley rats weighing 200–250 g were used in the study. The vasodilatory responses to bradykinin (1 nM–1 μM) were studied on isolated rat aorta rings contracted with norepinephrine (0.1 μM) following incubation with dipyrone (100, 700, and 2,000 μM). The relaxant responses of dipyrone (100, 700, and 2,000 μM) were also compared on the isolated rat urinary bladder contracted with bradykinin (n = 8). A bacterial lipopolysaccharide was used for the induction of inflammation (n = 8). The levels of PGE₂, PGF_1α, TXB₂, nitric oxide synthase (NOS), IL-10, and TNF-α were all determined in both the plasma and the perfusate of the aorta preparations (n = 5). The vasodilatory activities of bradykinin and des-Arg9-bradykinin were significantly increased upon the inhibition of COX-3 (dipyrone at 100 μM). These effects disappeared in the inflamed group. PGE₂, PGF1α, and TXB₂ were significantly high, but NOS activity was low in the aorta perfusate after the inhibition of COX-3. Dipyrone showed the relaxant activity of the urinary bladder contracted with bradykinin. The vasodilatory activity of des-Arg⁹-bradykinin was in the inflamed group but not in the non-inflamed group. Bradykinin did not contract urinary bladder in inflamed group. The results suggest that COX-induced products may play an important role in the bradykinin-induced rat aortic smooth muscle relaxations.     

运动性过氧化物酶体增殖物受体γ共激活因子1α的变化机制

背景：研究发现,过氧化物酶体增殖物受体γ共激活因子1α可能在运动诱导骨骼肌的适应机制起着重要的作用,参与调节运动诱导多种生物学反应过程。 目的：综述过氧化物酶体增殖物受体γ共激活因子1α与运动性骨骼肌的适应机制相关方面的研究。 方法：以PGC1α,skeletal muscle,exercise,mitochondrial biogenesis,adaptations为检索词,检索Pubmed数据库(1995年1月至2010年10月)。文献检索语种限制为英文。纳入过氧化物酶体增殖物受体γ共激活因子1α与运动性骨骼肌适应的相关的内容,排除重复性研究。计算机初检得到59篇文献,根据纳入排除标准,对37篇进行分析。 结果与结论：耐力训练可增加骨骼肌膜的转运蛋白的表达、线粒体代谢酶的活性和毛细血管的密度等,从而增加骨骼肌氧化能力,提高碳水化合物和脂肪酸的氧化能力。氧化物酶体增殖物受体γ共激活因子1α基因敲除或过表达转基因小鼠研究表明在维持骨骼肌线粒体代谢和抗氧化酶表达,氧化物酶体增殖物受体γ共激活因子1α起着重要的作用。氧化物酶体增殖物受体γ共激活因子1α影响运动性线粒体蛋白的适应。但是,氧化物酶体增殖物受体γ共激活因子1α不是惟一的因素,其他的一些因素同样涉及到基础的表达和运动性骨骼肌的适应机制。运动诱导氧化物酶体增殖物受体γ共激活因子1α表达和活性的提高可能是运动性线粒体的适应一个机制,合理体力活动可获得健康的效果。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Comparison of cyclooxygenase-2 and CD44 mRNA expression in colorectal cancer and its relevance for prognosis

This study evaluated CD44 and COX-2 expression in colorectal cancer (CRC) and analyzed its relationship with the clinicopathological characteristics. The prognostic impact on patient survival was compared between the two proteins. CD44 and COX-2 mRNA levels in 42 primary CRCs were analyzed using quantitative real-time PCR, with normalization relative to GAPDH. The cycle threshold (Ct) values were measured, and results are expressed as the Ct ratios of CD44 or COX-2 to GAPDH. The COX-2 Ct ratio was much lower in cases of lymphovascular invasion by the tumor than for no invasion (P = 0.004). During follow-up for a median of 40 months, there was no significant difference in the median CD44 Ct ratio between survivors and non-survivors (P = 0.362), whereas the COX-2 Ct ratio was significantly associated with survival at the time of data analysis (P = 0.042). The survival of colorectal cancer patients with a high COX-2 Ct ratio was significantly longer than that of patients with a low COX-2 Ct ratio (P = 0.048). This study suggests that COX-2 expression has a more significant impact than CD44 expression on the survival of CRC patients. Further studies are needed to resolve these issues with a large sample size.