Detection of Autonomic Dysfunction in Hemodialysis Patients Using the Exercise Treadmill Test: The Role of the Chronotropic Index,Heart Rate Recovery,and R-R Variability

Autonomic dysfunction is highly prevalent in hemodialysis patients and has been implicated in their increased risk of cardiovascular mortality.

Objective

To evaluate the ability of different parameters of exercise treadmill test to detect autonomic dysfunction in hemodialysis patients.

Methods

Cross-sectional study involving hemodialysis patients and a control group. Clinical examination, blood sampling, echocardiogram, 24-hour Holter, and exercise treadmill test were performed. A ramp treadmill protocol symptom-limited with active recovery was employed.

Results

Forty-one hemodialysis patients and 41 controls concluded the study. There was significant difference between hemodialysis patients and controls in autonomic function parameters in 24h-Holter and exercise treadmill test. Probability of having autonomic dysfunction in hemodialysis patients compared to controls was 29.7 at the exercise treadmill test and 13.0 in the 24-hour Holter. Chronotropic index, heart rate recovery at the 1st min, and SDNN at exercise were used to develop an autonomic dysfunction score to grade autonomic dysfunction, in which, 83% of hemodialysis patients reached a scoring ≥2 in contrast to 20% of controls. Hemodialysis was independently associated with either altered chronotropic index or autonomic dysfunction scoring ≥2 in every tested model (OR=50.1, P=0.003; and OR=270.9, P=0.002, respectively, model 5).

Conclusion

The exercise treadmill test was feasible and useful to diagnose of the autonomic dysfunction in hemodialysis patients. Chronotropic index and autonomic dysfunction scoring ≥2 were the most effective parameters to differentiate between hemodialysis patients and controls suggesting that these variables portrays the best ability to detect autonomic dysfunction in this setting.     

中等强度跑台运动预防去卵巢大鼠骨质疏松

目的观察中等强度跑台运动对去卵巢大鼠骨质疏松的预防作用。方法将30只3月龄未经产雌性SD大鼠随机分为假手术、去卵巢静止和去卵巢运动三个组。去卵巢运动组每周进行4次时间45min、速度18m/min、坡度5°的跑台训练。实验结束时,检测血清雌二醇（E2）、碱性磷酸酶（ALP）、抗酒石酸酸性磷酸酶（TRAP）和骨钙素（BGP）水平以及右侧游离股骨和胫骨的骨密度（BMD）和骨矿物含量（BMC）;同时观察左侧股骨远端和胫骨近端组织形态学变化。结果与假手术组比较,去卵巢静止组大鼠血清ALP活性和BGP含量显著升高,血清TRAP活性和E2含量显著下降,股骨近段和远端以及胫骨近端BMD和BMC显著下降,股骨远端和胫骨近端骨小梁断裂增加、数目减少;与去卵巢静止组比较,去卵巢运动组大鼠血清E2和BGP含量显著上升,股骨三个部位以及胫骨近端BMD和BMC显著增加,股骨远端和胫骨近端骨小梁断裂减少、数目增加。结论中等强度跑台运动能增加去卵巢大鼠血清E2和BGP含量,改善去卵巢大鼠骨组织学结构。     

Increased Expression of Neurotrophin 4 Following Focal Cerebral Ischemia in Adult Rat Brain with Treadmill Exercise

Neurotrophin 4 (NT-4) belongs to the family of neurotrophic factors, and it interacts with the tyrosine kinase B (trkB) receptor. NT-4 has neuroprotective effects following cerebral ischemia. Its role might be similar to brain-derived neurotrophic factor (BDNF), because both interact with trkB. Exercise also improves neural function by increasing neurotrophic factors. However, expression profiles of NT-4 in the brain during exercise are unknown. Here, we assessed the expressions of NT-4 and its receptor, trkB, following cerebral ischemia and hypothesized that exercise changes the expressions of NT-4 and trkB. Results showed that in a permanent middle cerebral artery occlusion rat model, ischemia decreased NT-4 and trkB expression. Immunohistochemistry showed their immunoreactivities around the region of the ischemic area. Treadmill exercise changed the expression of NT-4, which increased in the contralateral hemisphere in rats with ischemic injury. TrkB also showed similar patterns to its neurotophins. The change in NT-4 suggested that exercise might have primed NT4 production so that further injury causes slightly greater increases in NT4 compared with non-exercise controls.     

Effects of Treadmill Exercise on Motor and Cognitive Function Recovery of MCAO Mice Through the Caveolin-1/VEGF Signaling Pathway in Ischemic Penumbra

Exercise has been regarded as an effective rehabilitation strategy to facilitate motor and cognitive functional recovery after stroke, even though the complex effects associated with exercise-induced repair of cerebral ischemic injury are not fully elucidated. The enhancement of angiogenesis and neurogenesis, and the improvement of synaptic plasticity following moderate exercise are conducive to functional recovery after ischemic damage. Our previous studies have confirmed the angiogenesis and neurogenesis through the caveolin-1/VEGF pathway in MCAO rats. As an essential neurotrophic factor, BDNF has multiple effects on ischemic injury. In this study, we attempted to determine an additional mechanism of treadmill exercise-mediated motor and cognitive functional recovery through the caveolin-1/VEGF pathway associated with BDNF in the ischemic penumbra of MCAO mice. We found that mice exposed to treadmill exercise after the MCAO operation showed a significant up-regulation in expression of caveolin-1, VEGF, BDNF, synapsin I and CYFIP1 proteins, numbers of cells positive for BrdU/CD34, BDNF, BrdU/NeuN, BrdU/Synapsin I and CYFIP1 expression were increased, which support the reduction in neurological deficit and infarction volume, as well as improved synaptic morphology and spatial learning abilities, compared with the non-exercise mice. However, the caveolin-1 inhibitor, daidzein, resulted in increase in neurological deficit and infarction volume. The selective VEGFR2 inhibitor, PD173074, significantly induced larger infarction volume and neurological injury, and decreased the expression of BDNF in the ischemic penumbra. These findings indicate that exercise improves angiogenesis, neurogenesis and synaptic plasticity to ameliorate motor and cognitive impairment after stroke partially through the caveolin-1/VEGF pathway, which is associated with the coregulator factor, BDNF.

     

The Recovery of Repeated-Sprint Exercise Is Associated with PCr Resynthesis,while Muscle pH and EMG Amplitude Remain Depressed

The physiological equivalents of power output maintenance and recovery during repeated-sprint exercise (RSE) remain to be fully elucidated. In an attempt to improve our understanding of the determinants of RSE performance we therefore aimed to determine its recovery following exhaustive exercise (which affected intramuscular and neural factors) concomitantly with those of intramuscular concentrations of adenosine triphosphate [ATP], phosphocreatine [PCr] and pH values and electromyography (EMG) activity (a proxy for net motor unit activity) changes. Eight young men performed 10, 6-s all-out sprints on a cycle ergometer, interspersed with 30 s of recovery, followed, after 6 min of passive recovery, by five 6-s sprints, again interspersed by 30 s of passive recovery. Biopsies of the vastus lateralis were obtained at rest, immediately after the first 10 sprints and after 6 min of recovery. EMG activity of the vastus lateralis was obtained from surface electrodes throughout exercise. Total work (TW), [ATP], [PCr], pH and EMG amplitude decreased significantly throughout the first ten sprints (P<0.05). After 6 min of recovery, TW during sprint 11 recovered to 86.3±7.7% of sprint 1. ATP and PCr were resynthesized to 92.6±6.0% and 85.3±10.3% of the resting value, respectively, but muscle pH and EMG amplitude remained depressed. PCr resynthesis was correlated with TW done in sprint 11 (r = 0.79, P<0.05) and TW done during sprints 11 to 15 (r = 0.67, P<0.05). There was a ∼2-fold greater decrease in the TW/EMG ratio in the last five sprints (sprint 11 to 15) than in the first five sprints (sprint 1 to 5) resulting in a disproportionate decrease in mechanical power (i.e., TW) in relation to EMG. Thus, we conclude that the inability to produce power output during repeated sprints is mostly mediated by intramuscular fatigue signals probably related with the control of PCr metabolism.     

Poor Prognosis with In Vitro Fertilization in Indian Women Compared to Caucasian Women Despite Similar Embryo Quality

Background

Disease prevalence and response to medical therapy may differ among patients of diverse ethnicities. Poor outcomes with in vitro fertilization (IVF) treatment have been previously shown in Indian women compared to Caucasian women, and some evidence suggests that poor embryo quality may be a cause for the discrepancy. In our center, only patients with the highest quality cleavage stage embryos are considered eligible for extending embryo culture to the blastocyst stage. We compared live birth rates (LBR) between Indian and Caucasian women after blastocyst transfer to investigate whether differences in IVF outcomes between these ethnicities would persist in patients who transferred similar quality embryos.

Methodology/Principal Findings

In this retrospective cohort analysis, we compared IVF outcome between 145 Caucasians and 80 Indians who had a blastocyst transfer between January 1, 2005 and June 31, 2007 in our university center. Indians were younger than Caucasians by 2.7 years (34.03 vs. 36.71, P = 0.03), were more likely to have an agonist down regulation protocol (68% vs. 43%, P<0.01), and were more likely to have polycystic ovarian syndrome (PCOS), although not significant, (24% vs. 14%, P = 0.06). Sixty eight percent of Indian patients had the highest quality embryos (4AB blastocyst or better) transferred compared to 71% of the Caucasians (P = 0.2). LBR was significantly lower in the Indians compared to the Caucasians (24% vs. 41%, P<0.01) with an odds ratio of 0.63, (95%CI 0.46–0.86). Controlling for age, stimulation protocol and PCOS showed persistently lower LBR with an adjusted odds ratio of 0.56, (95%CI 0.40–0.79) in the multivariate analysis.

Conclusions/Significance

Despite younger age and similar embryo quality, Indians had a significantly lower LBR than Caucasians. In this preliminary study, poor prognosis after IVF for Indian ethnicity persisted despite limiting analysis to patients with high quality embryos transferred. Further investigation into explanations for ethnic differences in reproduction is needed.     

Effects of Treadmill Exercise Combined with MK 801 Treatment on Neuroblast Differentiation in the Dentate Gyrus in Rats

N-methyl-d-aspartate receptor (NR) is involved in activity-dependent synaptic plasticity, such as associative long-term potentiation, and in related central functions, such as learning and memory. In this study, we observed effects of treadmill exercise on NR1 and doublecortin (DCX, a marker for neuroblast differentiation) in the subgranular zone of the dentate gyrus (DG). At 6 weeks of age, rats were put on a treadmill with or without running for 1 h/day for 5 consecutive days at 22 m/min for 5 weeks. Exercise increased NR1 immunoreactivity and protein level in the hippocampus. To identify the correlations between NR and neuroblasts, we intraperitoneally administered a NR antagonist, MK-801, to the exercised rats. MK-801 treatment reduced NR1 protein level in the hippocampus of the exercised rats. In addition, in the MK-801-treated group, the number of DCX cells was significantly decreased in the subgranular zone of the DG. These results suggest that NR may be one of the important factors that modulate neuroblast differentiation during exercise in rats.     

Ritonavir-Boosted Darunavir Is Rarely Associated with Nephrolithiasis Compared with Ritonavir-Boosted Atazanavir in HIV-Infected Patients

Background

Although ritonavir-boosted atazanavir (ATV/r) is known to be associated with nephrolithiasis, little is known about the incidence of nephrolithiasis in patients treated with ritonavir-boosted Darunavir (DRV/r), the other preferred protease inhibitor.

Methods

In a single-center cohort, the incidence of nephrolithiasis was compared between HIV-infected patients who commenced DRV/r-containing antiretroviral therapy and those on ATV/r. The effects of ATV/r use over DRV/r were estimated by univariate and multivariate Cox hazards models.

Results

Renal stones were diagnosed in only one patient (0.86 per 1000 person-years) of the DRV/r group (n=540) and 37 (20.2 per 1000 person-years) of the ATV/r group (n=517). The median [interquartile (IQR)] observation period in the DRV/r group was 27.1 months (IQR 18.1-38.4 months), and 40.6 months (IQR 17.5-42.7) for the ATV/r group. The total observation period was 1,163.6 person-years and 1,829.6 person-years for the DRV/r group and for the ATV/r group, respectively. In the 37 patients on ATV/r who developed nephrolithiasis, the median time from commencement of ATV/r to diagnosis was 28.1 months (IQR 18.4–42.7), whereas nephrolithiasis in the single patient of the DRV/r group occurred 11.2 month after the introduction of DRV/r. ATV/r use over DRV/r was significantly associated with nephrolithiasis by uni- and multivariate analyses (HR=26.01; 95% CI, 3.541–191.0; p=0.001) (adjusted HR=21.47; 95% CI, 2.879–160.2; p=0.003).

Conclusion

The incidence of nephrolithiasis was substantially lower in patients on DRV/r than those on ATV/r. The results suggest that DRV/r should be selected for treatment of HIV-infected patients at risk of chronic kidney disease.     

Comparative Effect of Treadmill Exercise on Mature BDNF Production in Control versus Stroke Rats

Physical exercise constitutes an innovative strategy to treat deficits associated with stroke through the promotion of BDNF-dependent neuroplasticity. However, there is no consensus on the optimal intensity/duration of exercise. In addition, whether previous stroke changes the effect of exercise on the brain is not known. Therefore, the present study compared the effects of a clinically-relevant form of exercise on cerebral BDNF levels and localization in control versus stroke rats. For this purpose, treadmill exercise (0.3 m/s, 30 min/day, for 7 consecutive days) was started in rats with a cortical ischemic stroke after complete maturation of the lesion or in control rats. Sedentary rats were run in parallel. Mature and proBDNF levels were measured on the day following the last boot of exercise using Western blotting analysis. Total BDNF levels were simultaneously measured using ELISA tests. As compared to the striatum and the hippocampus, the cortex was the most responsive region to exercise. In this region, exercise resulted in a comparable increase in the production of mature BDNF in intact and stroke rats but increased proBDNF levels only in intact rats. Importantly, levels of mature BDNF and synaptophysin were strongly correlated. These changes in BDNF metabolism coincided with the appearance of intense BDNF labeling in the endothelium of cortical vessels. Notably, ELISA tests failed to detect changes in BDNF forms. Our results suggest that control beings can be used to find conditions of exercise that will result in increased mBDNF levels in stroke beings. They also suggest cerebral endothelium as a potential source of BDNF after exercise and highlight the importance to specifically measure the mature form of BDNF to assess BDNF-dependent plasticity in relation with exercise.     

Polysomnographic comparison between Chinese and Caucasian patients with obstructive sleep apnea

Sleep and Biological Rhythms - The Chinese population has a comparable prevalence of obstructive sleep apnea (OSA) compared to their Caucasian counterparts, but are notably less obese. Given this...     

Heart Rate Variability Is Associated with Exercise Capacity in Patients with Cardiac Syndrome X

Heart rate variability (HRV) reflects the healthiness of autonomic nervous system, which is associated with exercise capacity. We therefore investigated whether HRV could predict the exercise capacity in the adults with cardiac syndrome X (CSX). A total of 238 subjects (57±12 years, 67.8% men), who were diagnosed as CSX by the positive exercise stress test and nearly normal coronary angiogram were enrolled. Power spectrum from the 24-hour recording of heart rate was analyzed in frequency domain using total power (TP) and spectral components of the very low frequency (VLF), low frequency (LF) and high frequency (HF) ranges. Among the study population, 129 subjects with impaired exercise capacity during the treadmill test had significantly lower HRV indices than those with preserved exercise capacity (≥90% of the age predicted maximal heart rate). After accounting for age, sex, and baseline SBP and heart rate, VLF (odds ratio per 1SD and 95% CI: 2.02, 1.19–3.42), LF (1.67, 1.10–2.55), and TP (1.82, 1.17–2.83) remained significantly associated with preserved exercise capacity. In addition, increased HRV indices were also associated with increased exercise duration, rate-pressure product, and heart rate recovery, independent of age, body mass index, and baseline SBP and heart rate. In subgroup analysis, HRV indices demonstrated similar predictive values related to exercise capacity across various subpopulations, especially in the young. In patients with CSX, HRV was independently associated with exercise capacity, especially in young subjects. The healthiness of autonomic nervous system may have a role in modulating the exercise capacity in patients with CSX.     

平板运动试验对冠心病的诊断意义

目的:探讨平板运动试验(TET)对诊断冠状动脉粥样硬化性心脏病(冠心病)的临床意义。方法:对比分析217例疑诊或临床诊断冠心病患者的平板运动试验和选择性冠状动脉造影(CAG)结果。结果:以选择性冠状动脉造影为标准,平板运动试验敏感性为68.4%,特异性为88.4%,阳性预测值为77.1%,阴性预测值为82.9%。结论:简便、易行及无创的平板运动试验是诊断冠心病的重要手段。     

Acute Moderate Exercise Does Not Further Alter the Autonomic Nervous System Activity in Patients with Sickle Cell Anemia

A decreased global autonomic nervous system (ANS) activity and increased sympathetic activation in patients with sickle cell anemia (SCA) seem to worsen the clinical severity and could play a role in the pathophysiology of the disease, notably by triggering vaso-occlusive crises. Because exercise challenges the ANS activity in the general population, we sought to determine whether a short (<15 min) and progressive moderate exercise session conducted until the first ventilatory threshold had an effect on the ANS activity of a group of SCA patients and a group of healthy individuals (CONT group). Temporal and spectral analyses of the nocturnal heart rate variability were performed before and on the 3 nights following the exercise session. Standard deviation of all normal RR intervals (SDNN), total power, low frequencies (LF) and high frequencies powers (HF) were lower but LF/HF was higher in SCA patients than in the CONT group. Moderate exercise did not modify ANS activity in both groups. In addition, no adverse clinical events occurred during the entire protocol. These results imply that this kind of short and moderate exercise is not detrimental for SCA patients.     

跑台训练与强制性运动对脑梗死大鼠神经功能恢复的对比性研究

目的:探讨跑台训练与强制性运动康复训练对脑梗死大鼠神经功能恢复的差异。方法:将50只SD雄性大鼠随机分为正常组、假手术组、模型组、跑台训练组(T组)、强制性运动训练组(C组),每组10只,T组及C组于造模后24 h分别进行跑台训练及强制性运动训练,其他各组正常饲养。于术后14天、21天及28天分别进行神经功能缺损评分(NSS评分),随后取脑采用免疫组织化学方法观察脑梗死灶周围巢蛋白(Nestin)、半胱氨酸天冬氨酸蛋白酶-3(Caspase-3)、神经胶质酸性蛋白(GFAP)的表达。结果:各亚组同一时间NSS评分组间比较:C组、T组评分高于正常组及假手术组,但明显低于模型组(P0.05);C组评分明显低于T组(P0.05);各组内比较差异无统计学意义(P0.05)。C组、T组Caspase-3的表达明显低于正常组、假手术组及模型组(P0.05),而Nestin、GFAP的表达高于正常组、假手术组及模型组(P0.05)。T组Caspase-3的表达明显高于C组(P0.05),Nestin、GFAP的表达低于C组(P0.05)。结论:跑台训练与强制性运动康复训练2种方法对脑梗死大鼠神经功能恢复均有效;强制性运动的效果优于跑台训练。