Baoyuan Chen

Endothelial mechanisms of endothelial dysfunction in patients with obstructive sleep apnea

BackgroundObstructive sleep apnea (OSA) occurs in 2% of middle-aged women and 4% of middle-aged men in the general population and the prevalence is much higher in specific patient groups. Intermittent hypoxia (IH, oxygen desaturation and re-oxygenation) cycle, a major pathophysiologic character of OSA, and the physiological responses this evokes are thought to be responsible for its association with increased cardiovascular morbidity and mortality. Endothelial dysfunction, resulting from IH and as a key early event in atherosclerosis, was demonstrated repeatedly in patients with OSA and in animal models of IH, providing an important mechanistic link between the acute cyclical IH during sleep and the increased prevalence of chronic vascular diseases.ConclusionsFrom this work, we conclude that IH from OSA may result in endothelial dysfunction, as a potential promoter of atherosclerosis, through nitric oxide unavailability, oxidative stress and inflammation, cell apoptosis, the crosstalk between endothelial cells and circulating inflammatory cells, microparticles, and damage repairing process. Though effective continuous positive airway pressure (CPAP) may specifically improve endothelial function, more controlled larger interventional trials that will include multiple centers and randomized allocation of CPAP therapy are needed to see if such changes are reversible before cause and effect can be implied finally, while further studies on cellular and animal level are also needed to elucidate molecular biologic/pathologic pathways.

An experimental research on chronic intermittent hypoxia leading to liver injury

PurposeSleep apnea–hypopnea syndrome and its chronic intermittent hypoxia component may cause multi-system-targeted injury. The latest finding shows that liver is one of the injured organs. The purpose of the study is to observe the dynamic process of the influence that chronic intermittent hypoxia plays on rat liver enzyme, hepatic histology, and ultrastructure based on lipid disorders.MethodsA total of 72 male Wistar rats were randomly divided into three groups. The control group was fed with a regular chow diet, the high fat group with a high fat diet, and the high fat plus intermittent hypoxia group with a high fat diet with a 7-h/day intermittent hypoxia treatment. Changes were observed in rat liver enzyme, hepatic histology, and ultrastructure of the three groups on the third, sixth, and ninth weeks, respectively. The liver paraffin sections were detected with myeloperoxidase.ResultsThe liver function and structure of the control group were found to be normal; the liver enzyme level of the high fat group was significantly higher than that of the control group on the sixth and ninth weeks; and the liver enzyme level of the high fat plus intermittent hypoxia group was significantly higher than that of the control group and the high fat group on the third, sixth, and ninth weeks (all P < 0.01). Observed by a light microscope and a transmission electron microscope, the high fat group and the high fat plus intermittent hypoxia group were all characterized by nonalcoholic fatty liver disease: the high fat group was characterized by simple fatty liver on the third and sixth weeks and by steatohepatitis on the ninth week; the damage of the high fat plus intermittent hypoxia group was significantly more severe than that of the high fat group in all the monitoring points, characterized by steatohepatitis on the sixth week and by obvious liver fibrosis on the ninth week; the myeloperoxidase level of the high fat plus intermittent hypoxia group was significantly higher than that of the control group and the high fat group (all P < 0.01).ConclusionsUnder the conditions of high fat and intermittent hypoxia, the injury to the liver function, hepatic histology, and ultrastructure is more severe than that of the high fat group. The injury mainly was characterized by nonalcoholic fatty liver disease and becomes more severe with increased exposure time. Oxidative stress may play an important role in the mechanism.

Is automatic CPAP titration as effective as manual CPAP titration in OSAHS patients? A meta-analysis

PurposeIt is costly and time-consuming to conduct the standard manual titration to identify an effective pressure before continuous positive airway pressure (CPAP) treatment for obstructive sleep apnea (OSA) patients. Automatic titration is cheaper and more easily available than manual titration. The purpose of this systematic review was to evaluate the effect of automatic titration in identifying a pressure and on the improvement of apnea/hyponea index (AHI) and somnolence, the change of sleep quality, and the acceptance and compliance of CPAP treatment, compared with the manual titration.MethodsA systematic search was made of the PubMed, EMBASE, Cochrane Library, SCI, China Academic Journals Full-text Databases, Chinese Biomedical Literature Database, Chinese Scientific Journals Databases and Chinese Medical Association Journals. Randomized controlled trials comparing automatic titration and manual titration were reviewed. Studies were pooled to yield odds ratios (OR) or mean differences (MD) with 95% confidence intervals (CI).ResultsTen trials involving 849 patients met the inclusion criteria. It is hard to identify a trend in the pressures determined by either automatic or manual titration. Automatic titration can improve the AHI (MD = 0.03/h, 95% CI = −4.48 to 4.53) and Epworth sleepiness scale (SMD = −0.02, 95% CI = −0.34 to 0.31,) as effectively as the manual titration. There is no difference between sleep architecture under automatic titration or manual titration. The acceptance of CPAP treatment (OR = 0.96, 95% CI = 0.60 to 1.55) and the compliance with treatment (MD = −0.04, 95% CI = −0.17 to 0.10) after automatic titration is not different from manual titration.ConclusionAutomatic titration is as effective as standard manual titration in improving AHI, somnolence while maintaining sleep quality similar to the standard method. In addition, automatic titration has the same effect on the acceptance and compliance of CPAP treatment as manual titration. With the potential advantage of time and cost savings, automatic titration was recommended to be applied in identifying a proper pressure for CPAP treatment instead of manual titration in clinical practice.

Autophagy and hippocampal neuronal injury

BackgroundAutophagy is a specific universal biological phenomenon in eukaryotic cells, which is characterized by cytoplasmic vacuoles in the process of degrading cellular contents in lysosomes. The hippocampus plays an important role in higher nervous activities such as emotional integration, cognition, and memory. As an area closely related to learning and memory functions of the brain, the hippocampus is particularly sensitive to injuries caused by various reasons.PurposeAutophagy has certain links with a variety of causes of hippocampal neuronal injury. This short review discusses and summarizes this correlation with a focus on the possible role of autophagy and mechanisms in it.ConclusionThe current correlation between autophagy and hippocampal neuronal injury has not been completely determined by the general public alike. Further studies are needed to determine special effects of autophagy on hippocampal neuronal injury, which might accelerate the development of therapeutic interventions in hippocampal neuronal injury in many neurological disorders.

Prevalence of hypertension and circadian blood pressure variations in patients with obstructive sleep apnoea–hypopnoea syndrome

Objective To investigate the prevalence of hypertension and circadian blood pressure (BP) variations in patients with obstructive sleep apnoea–hypopnoea syndrome (OSAHS). Methods Patients referred to a sleep clinic underwent polysomnography with measurement of BP at four time points. They were classified into four groups (control, and mild, moderate or severe sleep apnoea) using the apnoea–hypopnoea index (AHI). Circadian variation was assessed using night-time to daytime mean BP (RN/D) and morning to evening mean BP (RM/E) ratios. Results Hypertension was significantly more common in patients with OSAHS (50.5%) than in controls (30.4%). AHI was positively correlated with hypertension after controlling for related confounders. Mean BP values at all four time points rose with increasing AHI. The increase in night-time and morning values was more pronounced than the increase in daytime and evening values in patients with OSAHS, resulting in loss of the normal BP diurnal rhythm. The RN/D and RM/E ratios increased with increasing AHI. Daytime BP was significantly correlated with AHI and the lowest oxygen saturation value. Conclusion OSAHS was shown to be an independent risk factor for hypertension. It was also associated with loss of the normal BP diurnal rhythm.

Inflammation induced by increased frequency of intermittent hypoxia is attenuated by tempol administration

The levels of serum inflammatory cytokines and the activation of nuclear factor kappa B (NF-κB) and hypoxia inducible factor-1α (HIF-1α) in heart tissues in response to different frequencies of intermittent hypoxia (IH) and the antioxidant tempol were evaluated. Wistar rats (64 males, 200-220 g) were randomly divided into 6 experimental groups and 2 control groups. Four groups were exposed to IH 10, 20, 30, or 40 times/h. The other 2 experimental groups were challenged with IH (30 times/h) plus tempol, either beginning on day 0 (IH30T0) or on day 29 (IH30T29). After 6 weeks of challenge, serum levels of tumor necrosis factor (TNF)-α, intracellular adhesion molecule (ICAM)-1, and interleukin-10 were measured, and western blot analysis was used to detect NF-κB p65 and HIF-1α in myocardial tissues. Serum levels of TNF-α and ICAM-1 and myocardial expression of NF-κB p65 and HIF-1α were all significantly higher in IH rats than in controls (P<0.001). Increased IH frequency resulted in more significant changes. Administration of tempol in IH rats significantly reduced levels of TNF-α, ICAM-1, NF-κB and HIF-1α compared with the non-tempol-treated group (F=16.936, P<0.001). IH induced an inflammatory response in a frequency-dependent manner. Additionally, HIF-1α and NF-κB were increased following IH administration. Importantly, tempol treatment attenuated this effect.

Noninvasive ventilation with complex critical care ventilator in the treatment of acute exacerbation of chronic obstructive pulmonary disease

Objective To compare the clinical effect of noninvasive positive-pressure ventilation (NIPPV), delivered via critical care ventilator or miniventilator, in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Methods Prospective comparison study. Patients with AECOPD underwent NIPPV via: miniventilator with BiLevel positive airway pressure (BiPAP; Group A); critical care ventilator with pressure support ventilation and positive end expiratory pressure (PSV + PEEP; Group B); critical care ventilator with pressure-synchronized intermittent mandatory ventilation (P-SIMV)+PSV + PEEP (Group C). Physiological parameters were recorded before, during and after ventilation. Results Patients in Group C (n = 21) showed significantly better improvements in physiological parameters (compared with pretreatment values) than those in Group B (n = 20) or Group A (n = 22). Conclusion NIPPV delivered via critical care ventilator has a better treatment effect than miniventilator NIPPV in patients with AECOPD. The use of P-SIMV + PSV + PEEP mode provides a significantly better treatment effect than PSV + PEEP alone.

Inhibition of iNOS to Protect Intermittent Hypoxia-Induced Hippocampal Neurons Impairment by Astragalus Extract in Rat

The aim of this paper is to research the protective effect of Astragalus against intermittent hypoxia-induced hippocampal neurons impairment in rat and lay the theoretical foundation for sleep apnea improvement in cognitive function by Astragalus. Male Wistar rats were divided into four groups: (1) blank control group; (2) normoxia group; (3) intermittent hypoxia group; (4) Astragalus treated intermittent hypoxia group. After 6-week treatment, the expression of iNOS was detected by real-time reverse transcription polymerase chain reaction (RT-PCR) at mRNA level as well as by immunohistochemistry (IHC) and western blot at protein level. As a result, Astragalus reduced the expression of iNOS at mRNA and protein levels in hippocampus compared with non-treated groups (P < 0.05). In conclusion, Astragalus could protect intermittent hypoxia-induced hippocampal neurons impairment in rat.