Exercise training alleviates MCT1 and MCT4 reductions in heart and skeletal muscles of STZ-induced diabetic rats.

We compared the changes in monocarboxylate transporter 1 (MCT1) and 4 (MCT4) proteins in heart and skeletal muscles in sedentary control and streptozotocin (STZ)-induced diabetic rats (3 wk) and in trained (3 wk) control and STZ-induced diabetic animals. In nondiabetic animals, training increased MCT1 in the plantaris (+51%; P < 0.01) but not in the soleus (+9%) or the heart (+14%). MCT4 was increased in the plantaris (+48%; P < 0.01) but not in the soleus muscles of trained nondiabetic animals. In sedentary diabetic animals, MCT1 was reduced in the heart (-30%), and in the plantaris (-31%; P < 0.01) and soleus (-26%) muscles. MCT4 content was also reduced in sedentary diabetic animals in the plantaris (-52%; P < 0.01) and soleus (-25%) muscles. In contrast, in trained diabetic animals, MCT1 and MCT4 in heart and/or muscle were similar to those of sedentary, nondiabetic animals (P > 0.05) but were markedly greater than in the sedentary diabetic animals [MCT1: plantaris +63%, soleus +51%, heart +51% (P > 0.05); MCT4: plantaris +107%, soleus +17% (P > 0.05)]. These studies have shown that 1) with STZ-induced diabetes, MCT1 and MCT4 are reduced in skeletal muscle and/or the heart and 2) exercise training alleviated these diabetes-induced reductions.     

Influence of estrogen on pulmonary arterial hypertension: role of oxidative stress

Pulmonary arterial hypertension (PAH) is a disease that increases the pulmonary vascular resistance, causing hypertrophy and subsequent right heart failure. Oxidative stress is involved in the pathogenesis of PAH, and estrogen is considered an antioxidant. Thus, the aim of this study was to test the hypothesis that estrogen could attenuate PAH by modulating oxidative stress. Female Wistar rats were ovariectomized or suffered the surgery simulation (sham). After 7 days, subcutaneous pellets with 17β‐estradiol or sunflower oil were implanted. At this time, PAH was induced by means of a single dose of monocrotaline (MCT) (60 mg·kg^‐1 i.p.). The experimental groups were as follows: (1) sham, (2) sham + MCT, (3) ovariectomy (O), (4) ovariectomy + MCT (OM), (5) ovariectomy + estrogen replacement + MCT (ORM). Hemodynamic measurements were performed 21 days after MCT or saline. Nonovariectomized animals were assessed in the stage of diestrus. Afterwards, the rats were killed to collect the heart, the lung and the liver to evaluate morphometry. Samples of the right ventricle were used to analyse the reduced glutathione : oxidized glutathione ratio. Lung congestion in the OM group, which was decreased in the ORM group, was observed. Right ventricle end‐diastolic pressure was increased in the OM and the ORM groups. The glutathione ratio decreased in the groups O, OM and ORM. The data suggest that estrogen can exert great influence on the cellular redox balance. The maintenance of physiological estrogen levels may help to avoid the appearance of pulmonary oedema, characteristic of this model of PAH, and right ventricular failure. Copyright © 2011 John Wiley & Sons, Ltd.     

Reversal of MicroRNA Dysregulation in an Animal Model of Pulmonary Hypertension

Background

Animals models have played an important role in enhancing our understanding of the pathogenesis of pulmonary arterial hypertension (PAH). Dysregulation of the profile of microRNAs (miRNAs) has been demonstrated in human tissues from PAH patients and in animal models. In this study, we measured miRNA levels in the monocrotaline (MCT) rat model of PAH and examined whether blocking a specific dysregulated miRNA not previously reported in this model, attenuated PAH. We also evaluated changes in miRNA expression in lung specimens from MCT PAH rats overexpressing human prostacyclin synthase, which has been shown to attenuate MCT PAH.

Methods

Expression levels of a panel of miRNAs were measured in MCT-PAH rats as compared to naïve (saline) control rats. Subsequently, MCT PAH rats were injected with a specific inhibitor (antagomiR) for miR-223 (A223) or a nonspecific control oligonucleotide (A-control) 4 days after MCT administration, then weekly. Three weeks later, RV systolic pressure and RV mass were measured. Total RNA, isolated from the lungs, microdissected pulmonary arteries, and right ventricle, was reverse transcribed and real-time quantitative PCR was performed. MiRNA levels were also measured in RNA isolated from paraffin sections of MCT-PAH rats overexpressing prostacyclin synthase.

Results

MiRs 17, 21, and 223 were consistently upregulated, whereas miRs 126, 145, 150, 204, 424, and 503 were downregulated in MCT PAH as compared to vehicle control. A223 significantly reduced levels of miR-223 in PA and lungs of MCT PAH rats as compared to levels measured in A-control or control MCT PAH rats, but A223 did not attenuate MCT PAH. Right ventricular mass and right ventricular systolic pressure in rats treated with A223 were not different from values in A-control or MCT PAH rats. In contrast, analysis of total RNA from lung specimens of MCT PAH rats overexpressing human prostacyclin synthase (hPGIS) demonstrated reversal of MCT-induced upregulation of miRs 17, 21, and 223 and an increase in levels of miR-424 and miR-503. Reduction in bone morphogenetic receptor 2 (BMPR2) messenger (m)RNA expression was not altered by A223, whereas human prostacyclin synthase overexpression restored BMPR2 mRNA to levels in MCT PAH to levels measured in naive controls.

Conclusions

Inhibition of miR-223 did not attenuate MCT PAH, whereas human prostacyclin synthase overexpression restored miRNA levels in MCT PAH to levels detected in naïve rats. These data may establish a paradigm linking attenuation of PAH to restoration of BMPR2 signaling.     

Cryptotanshinone inhibits endothelin-1 expression and stimulates nitric oxide production in human vascular endothelial cells

The Chinese herb Salvia miltiorrhiza (SM) has been found to have beneficial effects on the circulatory system. In the present study, we investigated the effects of cryptotanshinone (derived from SM) on endothelin-1 (ET-1) expression in human umbilical vein endothelial cells (HUVECs). The effect of cryptotanshinone on nitric oxide (NO) in HUVECs was also examined. We found that cryptotanshinone inhibited basal and tumor necrosis factor-alpha (TNF-alpha) stimulated ET-1 secretion in a concentration-dependent manner. Cryptotanshinone also induced a concentration-dependent decrease in ET-1 mRNA expression. Cryptotanshinone increased basal and TNF-alpha-attenuated NO production in a dose-dependent fashion. Cryptotanshinone induced a concentration-dependent increase in endothelial nitric oxide synthase (eNOS) expression without significantly changing neuronal nitric oxide synthase (nNOS) expression in HUVECs in the presence or absence of TNF-alpha. NOS activities in the HUVECs were also induced by cryptotanshinone. Furthermore, decreased ET-1 expression in response to cryptotanshinone was not antagonized by the NOS inhibitor l-NAME. A gel shift assay further showed that TNF-alpha-induced Nuclear Factor-kappaB (NF-kappaB) activity was significantly reduced by cryptotanshinone. These data suggest that cryptotanshinone inhibits ET-1 production, at least in part, through a mechanism that involves NF-kappaB but not NO production.     

野百合碱诱导大鼠肺动脉高压及肺源性心脏病的病理生理特征

目的:探讨野百合碱诱发肺动脉高压及肺源性心脏病模型的建立机制。方法:雄性Wistar大鼠20只,随机分为两组(n=10):正常组,模型组。模型组大鼠腹腔一次性注射野百合碱50 mg/kg,对照组注射同剂量的溶媒,28 d后测定大鼠血流动力学参数,硝酸盐还原酶法测定血清和肺组织中一氧化氮的含量;放射免疫法测定血浆中内皮素、脑钠素和肺组织中肿瘤坏死因子、内皮素的含量。结果:与对照组比较,右心室压力上升、心率和平均动脉压下降,血液和肺组织中肿瘤坏死因子、一氧化氮、内皮素-1、脑钠素含量上升,具有统计学意义。结论:野百合碱通过诱发肺血管和组织炎性损伤,升高体内肿瘤坏死因子、一氧化氮、内皮素-1的含量,建立肺动脉高压及肺源性心脏病模型。     

Low-intensity interval exercise training attenuates coronary vascular dysfunction and preserves Ca²⁺-sensitive K⁺ current in miniature swine with LV hypertrophy

Coronary vascular dysfunction has been observed in several models of heart failure (HF). Recent evidence indicates that exercise training is beneficial for patients with HF, but the precise intensity and underlying mechanisms are unknown. Left ventricular (LV) hypertrophy can play a significant role in the development of HF; therefore, the purpose of this study was to assess the effects of low-intensity interval exercise training on coronary vascular function in sedentary (HF) and exercise trained (HF-TR) aortic-banded miniature swine displaying LV hypertrophy. Six months postsurgery, in vivo coronary vascular responses to endothelin-1 (ET-1) and adenosine were measured in the left anterior descending coronary artery. Baseline and maximal coronary vascular conductance were similar between all groups. ET-1-induced reductions in coronary vascular conductance (P < 0.05) were greater in HF vs. sedentary control and HF-TR groups. Pretreatment with the ET type A (ET(A)) receptor blocker BQ-123 prevented ET-1 hypersensitivity in HF animals. Whole cell voltage clamp was used to characterize composite K(+) currents (I(K(+))) in coronary smooth muscle cells. Raising internal Ca(2+) from 200 to 500 nM increased Ca(2+)-sensitive K(+) current in HF-TR and control, but not HF animals. In conclusion, an ET(A)-receptor-mediated hypersensitivity to ET-1, elevated resting LV wall tension, and decreased coronary smooth muscle cell Ca(2+)-sensitive I(K(+)) was found in sedentary animals with LV hypertrophy. Low-intensity interval exercise training preserved normal coronary vascular function and smooth muscle cell Ca(2+)-sensitive I(K(+)), illustrating a potential mechanism underlying coronary vascular dysfunction in a large-animal model of LV hypertrophy. Our results demonstrate the potential clinical impact of exercise on coronary vascular function in HF patients displaying pathological LV hypertrophy.     

Effect of tetrahydrobiopterin and exercise training on endothelium-dependent vasorelaxation in SHR

We examined whether the improvement of impaired NO-dependent vasorelaxation by exercise training could be mediated through a BH₄-dependent mechanism. Male spontaneously hypertensive rats (SHR, n?=?20) and Wistar-Kyoto rats (WKY, n?=?20) were trained (Tr) for 9 weeks on a treadmill and compared to age-matched sedentary animals (Sed). Endothelium-dependent vasorelaxation (EDV) was assessed with acetylcholine by measuring isometric tension in rings of femoral artery precontracted with 10^?5?M phenylephrine. EDV was impaired in SHR-Sed as compared to WKY-Sed (p?=?0.02). Training alone improved EDV in both WKY (p?=?0.01) and SHR (p?=?0.0001). Moreover, EDV was not different in trained SHR than in trained WKY (p?=?0.934). Pretreatment of rings with L-NAME (50 μM) cancelled the difference in ACh-induced relaxation between all groups, suggesting that NO pathway is involved in these differences. The presence of 10^?5?M BH₄ in the organ bath significantly improved EDV for sedentary SHR (p?=?0.030) but not WKY group (p?=?0.815). Exercise training turned the beneficial effect of BH₄ on SHR to impairment of ACh-induced vasorelaxation in both SHR-Tr (p?=?0.01) and WKY-Tr groups (p?=?0.04). These results suggest that beneficial effect of exercise training on endothelial function is due partly to a BH₄-dependent mechanism in established hypertension.     

Exercise training and muscle microvascular oxygenation: functional role of nitric oxide

Exercise training induces multiple adaptations within skeletal muscle that may improve local O(2) delivery-utilization matching (i.e., Po(2)mv). We tested the hypothesis that increased nitric oxide (NO) function is intrinsic to improved muscle Po(2)mv kinetics from rest to contractions after exercise training. Healthy young Sprague-Dawley rats were assigned to sedentary (n = 18) or progressive treadmill exercise training (n = 10; 5 days/wk, 6-8 wk, final workload of 60 min/day at 35 m/min, -14% grade) groups. Po(2)mv was measured via phosphorescence quenching in the spinotrapezius muscle at rest and during 1-Hz twitch contractions under control (Krebs-Henseleit solution), sodium nitroprusside (SNP, NO donor; 300 μM), and N(G)-nitro-l-arginine methyl ester (l-NAME, nonspecific NO synthase blockade; 1.5 mM) superfusion conditions. Exercise-trained rats had greater peak oxygen uptake (Vo(2peak)) than their sedentary counterparts (81 ± 1 vs. 72 ± 2 ml·kg(-1)·min(-1), respectively; P < 0.05). Exercise-trained rats had significantly slower Po(2)mv fall throughout contractions (τ(1); time constant for the first component) during control (sedentary: 8.1 ± 0.6; trained: 15.2 ± 2.8 s). Compared with control, SNP slowed τ(1) to a greater extent in sedentary rats (sedentary: 38.7 ± 5.6; trained: 26.8 ± 4.1 s; P > 0.05) whereas l-NAME abolished the differences in τ(1) between sedentary and trained rats (sedentary: 12.0 ± 1.7; trained: 11.2 ± 1.4 s; P < 0.05). Our results indicate that endurance exercise training leads to greater muscle microvascular oxygenation across the metabolic transient following the onset of contractions (i.e., slower Po(2)mv kinetics) partly via increased NO-mediated function, which likely constitutes an important mechanism for training-induced metabolic adaptations.     

Attenuation of exercise-induced heat shock protein 72 expression blunts improvements in whole-body insulin resistance in rats with type 2 diabetes

Heat shock proteins (HSPs) play an important role in insulin resistance and improve the cellular stress response via HSP induction by exercise to treat type 2 diabetes. In this study, the effects of exercise-induced HSP72 expression levels on whole-body insulin resistance in type 2 diabetic rats were investigated. Male 25-week-old Otsuka Long-Evans Tokushima Fatty rats were divided into three groups: sedentary (Sed), trained in a thermal-neutral environment (NTr: 25 °C), and trained in a cold environment (CTr: 4 °C). Exercise training was conducted 5 days/week for 10 weeks. Rectal temperature was measured following each bout of exercise. An intraperitoneal glucose tolerance test (IPGTT) was performed after the training sessions. The serum, gastrocnemius muscle, and liver were sampled 48 h after the final exercise session. HSP72 and heat shock cognate protein 73 expression levels were analyzed by Western blot, and serum total cholesterol, triglyceride (TG), and free fatty acid (FFA) levels were measured. NTr animals exhibited significantly higher body temperatures following exercise, whereas, CTr animals did not. Exercise training increased HSP72 levels in the gastrocnemius muscle and liver, whereas, HSP72 expression was significantly lower in the CTr group than that in the NTr group (p < 0.05). Glucose tolerance improved equally in both trained animals; however, insulin levels during the IPGTT were higher in CTr animals than those in NTr animals (p < 0.05). In addition, the TG and FFA levels decreased significantly only in NTr animals compared with those in Sed animals. These results suggest that attenuation of exercise-induced HSP72 expression partially blunts improvement in whole-body insulin resistance and lipid metabolism in type 2 diabetic rats.     

Sildenafil improves long-term effect of endothelial progenitor cell-based treatment for monocrotaline-induced rat pulmonary arterial hypertension

Background aimsWe hypothesized that the long-term therapeutic effect of combined sildenafil and bone marrow-derived endothelial progenitor cells (BMDEPCs) on monocrotaline (MCT)-induced rat pulmonary arterial hypertension (PAH) is superior to either treatment alone.MethodsMale Sprague-Dawley rats (n = 40) were equally divided into normal controls, MCT (65 mg/kg, subcutaneously) only, MCT + sildenafil (25 mg/kg/day, orally), MCT + BMDEPCs (2.0 × 10⁶ autologous cells, intravenously) and MCT + sildenafil+ BMDEPCs. BMDEPCs and sildenafil were given on day 21 after MCT administration. Animals were sacrificed by day 90 after MCT administration.ResultsThe apoptotic (caspase 3, Bax) and inflammatory (tumor necrosis factor-α, matrix metalloproteinase-9) biomarkers in right ventricle and lung and pulmonary expressions of fibrotic biomarkers (transforming growth factor-β, p-Smad3) and connexin 43 protein were lower in monotherapy groups (i.e., MCT + sildenafil and MCT + BMDEPCs) and further decreased in normal controls and combined treatment groups (i.e., MCT + sildenafil + BMDEPCs) compared with untreated animals (i.e., MCT only) (all P < 0.01). Expressions of anti-fibrotic biomarkers (bone morphogenetic protein-2, p-Smad1/5) and numbers of alveolar sacs and arterioles in lung were higher in monotherapy groups and further increased in normal controls and combined treatment groups compared with untreated animals (all P < 0.005). In right ventricle, connexin 43 and α-myosin heavy chain (MHC) expressions were higher in the monotherapy groups and further elevated in normal controls and combined treatment groups compared with untreated animals, whereas β-MHC exhibited the opposite pattern (all P < 0.01). Right ventricular systolic pressure and weight were lower in the monotherapy animals and further reduced in normal controls and combined treatment groups compared with untreated animals (all P < 0.0001).ConclusionsCombined therapy with BMDEPCs and sildenafil was superior to either treatment alone in attenuating rodent MCT-induced PAH.     

Improvement in symptoms and pulmonary function of asthmatic patients due to their treatment according to the Global Strategy for Asthma Management (GINA)

Background

Endothelin-1 (ET-1) and Nitric Oxide (NO) are crucial mediators for establishing pulmonary artery hypertension (PAH). We tested the hypothesis that their imbalance might also occur in COPD patients with PAH.

Methods

The aims of the study were to measure exhaled breath condensate (EBC) and circulating levels of ET-1, as well as exhaled NO (FENO) levels by, respectively, a specific enzyme immunoassay kit, and by chemiluminescence analysis in 3 groups of subjects: COPD with PAH (12), COPD only (36), and healthy individuals (15). In order to evaluate pulmonary-artery systolic pressure (PaPs), all COPD patients underwent Echo-Doppler assessment.

Results

Significantly increased exhaled and circulating levels of ET-1 were found in COPD with PAH compared to both COPD (p < 0.0001) only, and healthy controls (p < 0.0001). In COPD with PAH, linear regression analysis showed good correlation between ET-1 in EBC and PaPs (r = 0.621; p = 0.031), and between arterial levels of ET-1 and PaPs (r = 0.648; p = 0.022), while arterial levels of ET-1 inversely correlated with FEV₁%, (r = -0.59, p = 0.043), and PaPs negatively correlated to PaO₂ (r = -0.618; p = 0.032). Significantly reduced levels of FENO were found in COPD associated with PAH, compared to COPD only (22.92 ± 11.38 vs.35.07 ± 17.53 ppb; p = 0.03). Thus, we observed an imbalanced output in the breath between ET-1 and NO, as expression of pulmonary endothelium and epithelium impairment, in COPD with PAH compared to COPD only. Whether this imbalance is an early cause or result of PAH due to COPD is still unknown and deserves further investigations.     

Effects of training on biochemical and functional properties of rodent neonatal heart

This study was undertaken to determine biochemical and functional (in vivo) adaptations of the rodent neonatal heart in response to a training program of endurance running. Ten day-old rats were progressively trained on a treadmill (final intensity, 21 m/min, 30% grade, 1 h/day) until 75 days of age. The training program induced 14, 57, and 24% increases in relative heart mass, skeletal muscle citrate synthase activity, and whole-body maximal O2 uptake, respectively (P less than 0.05). Cardiac myosin (ATPase) and Ca2+-regulated myofibril ATPase were both reduced by approximately 15% in trained vs. sedentary animals (P less than 0.05). In the majority of trained hearts examined, the myosin isozyme profile reflected an estimated 14 +/- 3% shift toward the V3 or low ATPase isozyme. Left ventricular functional indices during submaximal exercise, derived from a fluid-filled indwelling cannula, indicated that the trained animals maintained similar left ventricular (LV) systolic pressure, LV + the time derivative of pressure, and systemic arterial mean blood pressure compared with their sedentary counterparts. These functional parameters were maintained even though the trained animals performed with lower submaximal exercise heart rate. These findings suggest that maximal exercise capacity can be enhanced in neonatal rats even though the biochemical potential for ATP degradation in the cardiac contractile system is lowered. We speculate that the trend to maintain the myosin isozyme pattern further in the direction of the V3 isozyme in the trained neonatal rat heart may reflect a means to economize cross-bridge cycling while maintaining normal levels of ventricle performance at a given submaximal work load.     

Effect of exhaustive ultra-endurance exercise in muscular glycogen and both Alpha1 and Alpha2 Ampk protein expression in trained rats

Glycogen is the main store of readily energy in skeletal muscle and plays a key role in muscle function, demonstrated by the inability to sustain prolonged high-intensity exercise upon depletion of these glycogen stores. With prolonged exercise, glycogen depletion occurs and 5′-AMP-activated protein kinase (AMPK), a potent regulator of muscle metabolism and gene expression, is activated promoting molecular signalling that increases glucose uptake by muscular skeletal cells. The aim of this study was primarily to determine the effect of ultra-endurance exercise on muscle glycogen reserves and secondly to verify the influence of this type of exercise on AMPK protein expression. Twenty-four male Wistar rats, 60 days old, were divided into four experimental groups: sedentary, sedentary exhausted (SE), endurance trained (T) and endurance trained exhausted (TE). The animals ran for 10 to 90 min/day, 5 days/week, for 12 weeks to attain trained status. Rats were killed immediately after the exhaustion protocol, which consisted of running on a treadmill (at approximately 60 % V _max until exhaustion). Optical density of periodic acid-Schiff was detected and glycogen depletion observed predominantly in type I muscle fibres of the TE group and in both type I and II muscle fibres in the SE group. Plasma glucose decreased only in the TE group. Hepatic glycogen was increased in T group and significantly depleted in TE group. AMPK protein expression was significantly elevated in TE and T groups. In conclusion, acute exhaustive ultra-endurance exercise promoted muscle glycogen depletion. It seems that total AMPK protein and gene expression is more influenced by status training.     

Endurance training increases lactate transport in male Zucker fa/fa rats

The purpose of this study was to investigate the effect of endurance training (10 weeks) on previously reported alterations of lactate exchange in obese Zucker fa/fa rats. We used sarcolemmal vesicles to measure lactate transport capacity in control sedentary rats, Zucker (fa/fa), and endurance trained Zucker (fa/fa) rats. Monocarboxylate transporter (MCT) 1 and 4 content was measured in sarcolemmal vesicles and skeletal muscle. Training increased citrate synthase activity in soleus and in red tibialis anterior, and improved insulin sensitivity measured by intraperitoneal glucose tolerance test. Endurance training increased lactate influx in sarcolemmal vesicles at 1 mM of external lactate concentration and increased MCT1 expression on sarcolemmal vesicles. Furthermore, muscular lactate level was significantly decreased after training in red tibialis anterior and extensor digitorum longus. This study shows that endurance training improves impairment of lactate transport capacity that is found in insulin resistance state like obesity and type 2 diabetes.     

Diurnal variations of postural stability and attentional capacities in 5–6-year-old tennis players

The present study aimed to investigate the diurnal variation of postural stability, attentional capacities, and oral temperature in 5–6-year-old tennis players. A total of 24 young children were divided into two groups: Twelve tennis players with 2 years of training experience and twelve sedentary children without previous experience in any type of sport. They were asked to maintain an upright bipedal stance on a static force platform with eyes open (EO) and eyes closed (EC) at 07:00, 10:00, 14:00, and 18:00 h. Postural stability was evaluated by the center of pressure (CoP), surface area (CoP_Area), CoP mean velocity (CoP_Vm), and Romberg’s index (RI). Oral temperature and simple reaction time (SRT) were also recorded at the beginning of each test session. Postural stability in 5–6-year-old tennis players was low at 07:00 h and improved at 10:00 h (p < 0.001); then, it worsened at 14:00 h (p < 0.001) and improved again at 18:00 h (p < 0.001) as found in sedentary children. This rhythm was also close to that of SRT in both groups. Body temperature increased significantly (p < 0.001) from the morning to the afternoon in both groups. However, the peak of postural performance, the peak of attentional capacities, and the greatest vision contribution to maintain balance observed at 18:00 h were only found in the trained group. Moreover, young tennis players were more stable (p < 0.001) and more attentive (p < 0.01) than sedentary ones at 18:00 h. The amplitude of the diurnal rhythm of CoP parameters was significantly larger (p < 0.01) in trained children compared to sedentary ones (43.1 ± 8.5 vs 31.7 ± 8.3 for the CoP_Area; 27.5 ± 7.4 vs 17.7 ± 8.2 for the CoP_Vm). Therefore, time-of-day has a significant effect on static postural stability and attentional capacities in young tennis players with better performances in the late afternoon (habitual hour of training). Thus, we recommend planning some training sessions at 07:00 and/or 14:00 h to optimize postural stability at the time of its batyphase and to reduce the incidence of fall-related injury risks during this critical age in athletic environments.     

Disease severity–related alterations of cardiac microRNAs in experimental pulmonary hypertension

Right ventricular (RV) failure is the primary cause of death in pulmonary arterial hypertension (PAH). We hypothesized that heart‐relevant microRNAs, that is myomiRs (miR‐1, miR‐133a, miR‐208, miR‐499) and miR‐214, can have a role in the right ventricle in the development of PAH. To mimic PAH, male Wistar rats were injected with monocrotaline (MCT, 60 mg/kg, s.c.); control group received vehicle. MCT rats were divided into two groups, based on the clinical presentation: MCT group terminated 4 weeks after MCT administration and prematurely terminated group (ptMCT) displaying signs of terminal disease. Myocardial damage genes and candidate microRNAs expressions were determined by RT‐qPCR. Reduced blood oxygen saturation, breathing disturbances, RV enlargement as well as elevated levels of markers of myocardial damage confirmed PH in MCT animals and were more pronounced in ptMCT. MyomiRs (miR‐1/miR‐133a/miR‐208a/miR‐499) were decreased and the expression of miR‐214 was increased only in ptMCT group (P < 0.05). The myomiRs negatively correlated with Fulton index as a measure of RV hypertrophy in MCT group (P < 0.05), whereas miR‐214 showed a positive correlation (P < 0.05). We conclude that the expression of determined microRNAs mirrored the disease severity and targeting their pathways might represent potential future therapeutic approach in PAH.     

Increased in vivo mitochondrial oxygenation with right ventricular failure induced by pulmonary arterial hypertension: mitochondrial inhibition as driver of cardiac failure?

Background

The leading cause of mortality due to pulmonary arterial hypertension (PAH) is failure of the cardiac right ventricle. It has long been hypothesized that during the development of chronic cardiac failure the heart becomes energy deprived, possibly due to shortage of oxygen at the level of cardiomyocyte mitochondria. However, direct evaluation of oxygen tension levels within the in vivo right ventricle during PAH is currently lacking. Here we directly evaluated this hypothesis by using a recently reported technique of oxygen-dependent quenching of delayed fluorescence of mitochondrial protoprophyrin IX, to determine the distribution of mitochondrial oxygen tension (mitoPO₂) within the right ventricle (RV) subjected to progressive PAH.

Methods

PAH was induced through a single injection of monocrotaline (MCT). Control (saline-injected), compensated RV hypertrophy (30 mg/kg MCT; MCT30), and RV failure (60 mg/kg MCT; MCT60) rats were compared 4 wk after treatment. The distribution of mitoPO₂ within the RV was determined in mechanically-ventilated, anaesthetized animals, applying different inspired oxygen (FiO₂) levels and two increment dosages of dobutamine.

Results

MCT60 resulted in RV failure (increased mortality, weight loss, increased lung weight), MCT30 resulted in compensated RV hypertrophy. At 30% or 40% FiO₂, necessary to obtain physiological arterial PO₂ in the diseased animals, RV failure rats had significantly less mitochondria (15% of total mitochondria) in the 0-20 mmHg mitoPO₂ range than hypertrophied RV rats (48%) or control rats (54%). Only when oxygen supply was reduced to 21% FiO_2, resulting in low arterial PO₂ for the MCT60 animals, or when oxygen demand increased with high dose dobutamine, the number of failing RV mitochondria with low oxygen became similar to control RV. In addition, metabolic enzyme analysis revealed similar mitochondrial mass, increased glycolytic hexokinase activity following MCT, with increased lactate dehydrogenase activity only in compensated hypertrophied RV.

Conclusions

Our novel observation of increased mitochondrial oxygenation suggests down-regulation of in vivo mitochondrial oxygen consumption, in the absence of hypoxia, with transition towards right ventricular failure induced by pulmonary arterial hypertension.     

Papillary mechanics and cardiac morphology of infarcted rat hearts after training

Infarction of the left ventricle was induced by ligation of the coronary artery in male Sprague-Dawley rats under ketamine-xylazine anesthesia. Three weeks after surgery, animals were assigned to a trained (n = 21; running at 20 m/min, 10% grade, 1 h/day, 5 days/wk) or nontrained group (n = 23) for an additional 8 wk. A third, sham-operated control group (n = 16) remained cage sedentary for 11 wk. Ventricular mass was greater in the trained and nontrained infarct groups [1,335 +/- 57.3 and 1,414 +/- 56.1 mg, respectively (mean +/- SE)] compared with the control group (1,155 +/- 50.9 mg) (P less than or equal to 0.05). The diameter of septal fibers was 13% greater in the trained and 17% greater in the nontrained infarct groups compared with control. The specific peak developed force and maximum rate of force development of left ventricular papillary muscle in vitro were 75 and 62% greater in both infarcted groups compared with the control group; these variables were unaffected by training. Myofibrillar adenosine triphosphatase activity of septum was 20% lower in both infarct groups compared with sham-operated animals. We conclude that exercise training did not alter the magnitude of morphological and physiological adaptations to infarction.     

Exercise training changes autonomic cardiovascular balance in mice.

Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary (n = 8) and trained mice (n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 +/- 9 vs. 612 +/- 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 +/- 2 vs. 108 +/- 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 +/- 0.97 vs. 1.6 +/- 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 +/- 12 vs. 40 +/- 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 +/- 11 vs. 97 +/- 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.     

Hyperpalatable Diet and Physical Exercise Modulate the Expression of the Glial Monocarboxylate Transporters MCT1 and 4

Hyperpalatable diets (HP) impair brain metabolism, and regular physical exercise has an apparent opposite effect. Here, we combined a prior long-term exposure to HP diet followed by physical exercise and evaluated the impact on some neuroenergetic components and on cognitive performance. We assessed the extracellular lactate concentration, expression of monocarboxylate transporters (MCTs), pyruvate dehydrogenase (PDH), and mitochondrial function in the hippocampus. Male C57BL/6J mice were fed 4 months with HP or a control diet. Subsequently, they were divided in the following groups: control diet sedentary (CDS), control diet exercise (CDE), HP diet sedentary (HPS), and HP diet exercise (HPE) (n = 15 per group) and were engaged for an additional 30-day period of voluntary exercise and HP diet. Relative to the control situation, exercise increased MCT1, MCT4, and PDH protein levels, while the HP diet increased MCT1 and MCT4 protein levels. The production of hydrogen peroxide (H₂O₂) and the mitochondrial membrane potential (??_m) stimulated by succinate in hippocampal homogenates were not significantly different between groups. ADP phosphorylation and the maximal respiratory rate induced by FCCP showed similar responses between groups, implying a normal mitochondrial function. Also, extracellular brain lactate levels were increased in the HPE group compared to other groups soon after performing the Y-maze task. However, such enhanced lactate levels were not associated with improved memory performance. In summary, hippocampal protein expression levels of MCT1 and 4 were increased by physical exercise and HP diet, whereas PDH was only increased by exercise. These observations indicate that a hippocampal metabolic reprogramming takes place in response to these environmental factors.