The role of exosomal circular RNA ZNF292 in intermittent hypoxia-induced AC16 cardiomyocytes injury.

BACKGROUND: Exosomes are involved in cell-to-cell communication in numerous diseases including cardiovascular diseases, neurological diseases. Little attention has been dedicated to exosomal circular RNAs in obstructive sleep apnea (OSA)-related cardiovascular diseases. The aim of this study was to explore the role of exosomal circular RNA ZNF292 (circZNF292) on AC16 cells exposure to intermittent hypoxia (IH). METHODS: Exosome release inhibitor GW4869 was used to examine the effect of exosomes on IH-induced AC16 cells apoptosis. The expression of exosomal circZNF292 was detected by qRT-PCR in AC16 cells exposure to IH, and a luciferase reporter assay was conducted to confirm the connection between circZNF292 and miR-146a-5p. Exosomal circZNF292 was stably transfected with short hairpin RNAs (shRNAs) against circZNF292 and co-cultured with AC16 cells. The expression of miR-146a-5p and apoptosis-related protein was then measured to evaluate the effect of exosomal circZNF292. RESULTS: We found that IH contributed to the AC16 cells apoptosis, and the administration of GW4869 increased the apoptosis of cardiomyocytes when exposed to IH. The expression of exosomal circZNF292 decreased and miR-146a-5p increased significantly in AC16 cells exposed to IH compared to normoxic conditions. Bioinformatics analysis predicted a circZNF292/miR-146a-5p axis in IH-induced cardiomyocytes apoptosis. The dual-luciferase reporter system validated the direct interaction of circZNF292 and miR-146a-5p. Knockdown of circZNF292 increased the expressions of miR-146a-5p and accelerated the AC16 cardiomyocytes apoptosis. CONCLUSIONS: The findings of this study suggested a novel mechanism by which exosomes transmit intrinsic regulatory signals to the myocardium through the exosomal circZNF292/miR-146a-5p axis. This finding highlights the potential of targeting this pathway as a therapeutic approach for treating cardiovascular diseases associated with OSA.

LncRNA XR_595552 inhibition alleviates intermittent hypoxia-induced cardiomyocyte damage via activating the PI3K/AKT pathway.

BACKGROUND: Although the long noncoding RNAs (lncRNAs) expression profiles have been observed in previous study, the biological functions and underlying mechanisms of lncRNAs in OSA-related cardiac injury have not been elucidated. In the present study, we investigated a novel lncRNA, lncRNA XR_595552, and evaluated its role in intermittent hypoxia (IH)-induced damage in H9c2 cardiomyocytes. METHODS: H9c2 cells were exposed to IH condition. Real-time quantitative polymerase chain reaction (RT-qPCR) was conducted to measure the expression changes of lncRNA XR_595552 in H9c2 cells stimulated by IH. H9c2 cells were subjected to IH after transfection. CCK-8 was used to evaluate cell viability, and apoptosis was analyzed by Western blotting. Additionally, the regulatory relationship between lncRNA XR_595552 and PI3K/AKT was tested by RT-qPCR and Western blot. RESULTS: IH significantly induced injury in H9c2 cells (inhibited cell viability and promoted cell apoptosis). lncRNA XR_595552 was upregulated in a cell model of IH. Inhibition of lncRNA XR_595552 protected H9c2 cells against IH-induced damage, as the viability was increased, Bax, Caspase-9, and Caspase-3 were downregulated, and Bcl-2 was upregulated. More interestingly, lncRNA XR_595552 downregulation activated the PI3K/AKT pathway. Blocking the PI3K/AKT signal pathway by the use of LY294002 eliminated the myocardioprotective effects of lncRNA XR_595552 in H9c2 cells under IH condition. CONCLUSIONS: The results show that lncRNA XR_595552, a novel lncRNA, may play a protective role in attenuating IH-induced injury in cardiomyocytes via a regulating PI3K/AKT pathway. The findings suggest that this lncRNA could serve as a therapeutic target to treat OSA-related cardiovascular disorders.

The role of ferroptosis and endoplasmic reticulum stress in intermittent hypoxia-induced myocardial injury.

PURPOSE: Obstructive sleep apnea (OSA) is related to increased risk of cardiovascular disease. Ferroptosis is a form of programmed cell death characterized by iron overload and plays critical roles in myocardial injury. This study aimed to investigate the role of ferroptosis in intermittent hypoxia (IH)-induced myocardial injury involving endoplasmic reticulum stress (ERS). METHODS: AC16 human cardiomyocytes were exposed to IH or normoxia conditions. Mice were randomly grouped as follows: normal control (NC), IH, ferrostatin-1 + IH (FIH), and N-acetylcysteine + IH (AIH). The mRNA levels of GPX4, xCT, FTH1, and FACL4 in AC16 cells were detected by qRT-PCR. The protein levels of GPX4, xCT, NOX4, ATF4, CHOP, Bcl-2, and Bax in myocardial tissue were detected by Western blot analysis. RESULTS: The mRNA expression levels of GPX4 and xCT in AC16 cells were significantly lower in IH group than that of NC group. In IH mice, myocardial tissues were injured accompanied by increased level of ferroptosis and ERS. Inhibition of ferroptosis and treatment of N-acetylcysteine reduced ERS and myocardial injury in mice exposed to IH. In addition, compared to ferrostatin-1, N-acetylcysteine exerted a greater effect in relieving IH-induced myocardial damage and ERS. CONCLUSIONS: Ferroptosis was involved in IH-related myocardial injury accompanied by the activation of ERS. Inhibition of ferroptosis and acetylcysteine treatment alleviated IH-related myocardial injury, which may be a potential target for therapeutic approaches to OSA-induced myocardial injury.

Nrf2 plays protective role during intermittent hypoxia-induced ferroptosis in rat liver (BRL-3A) cells.

PURPOSE: Ferroptosis is reported to be involved in the chronic intermittent hypoxia (CIH)-related liver damage in vivo. Nuclear factor E2-related factor 2 (Nrf2) has an essential role in the regulation of ferroptosis. This study tested the hypothesis that intermittent hypoxia (IH) could lead to hepatocyte ferroptosis in vitro and the function of Nrf2 in IH-induced hepatocyte ferroptosis. METHODS: BRL-3A cells (rat liver cells) were exposed to normoxia or IH. The protocol of IH consisted of 32 cycles of 60-min hypoxic exposure with 30-min reoxygenation phase (nadir of 1% oxygen to peak of 20% oxygen). Ferroptosis was evaluated by cell viability, iron concentration, lipid reactive oxygen species (ROS), protein content of ferritin heavy chain (FTH1), and glutathione peroxidase 4 (GPX4). Both ferrostatin-1 (a ferroptosis inhibitor) and Nrf2 interfering RNA were applied to treat BRL-3A cells, respectively. RESULTS: IH exposure induced ferroptosis in BRL-3A cells with decreased cell viability and increased total iron content and lipid ROS levels. The protein contents of GPX4 and FTH1 in IH group were markedly lower than that in normoxic control. Ferroptosis inhibitor ferrostatin-1 alleviated IH-induced ferroptosis in BRL-3A cells. IH treatment enhanced expression of Nrf2, and Nrf2 knockdown augmented IH-induced ferroptosis in BRL-3A cells. CONCLUSIONS: The results revealed that Nrf2 played a protective role during IH-induced ferroptosis in BRL-3A cells. The finding provides a therapeutic target for obstructive sleep apnea-related liver injury.

MiR-210-3p enhances intermittent hypoxia-induced tumor progression via inhibition of E2F3.

PURPOSE: Intermittent hypoxia (IH) is a hallmark of obstructive sleep apnea (OSA), which is related to tumorigenesis and progression. Although micro-ribonucleic acid-210-3p (miR-210-3p) is correlated with hypoxia-induced tumor development, its role in the relationship between IH and tumor function remains poorly understood. The present work focused on elucidating the molecular mechanism through which miR-210-3p drives tumor progression under IH. METHODS: MiR-210-3p levels were quantified within tumor samples from patients with lung adenocarcinoma who had or did not have OSA. Correlations between miR-210-3p and polysomnographic variables were analyzed. For in vitro experiments, miR-210-3p was inhibited or overexpressed via transfection under IH conditions. Cell viability, growth, invasion and migration assays were carried out. For in vivo modeling of IH using mouse xenografts, a miR-210-3p antagomir was intratumorally injected, tumor biological behaviors were evaluated, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunohistochemistry and western blot were carried out for detecting miR-210-3p and E2F transcription factor 3 (E2F3) expression. RESULTS: For patients with lung adenocarcinoma and OSA, high miR-210-3p levels showed positive relation to polysomnographic variables, such as oxygen desaturation index, apnea-hypopnea index, and proportion of total sleep time with oxygen saturation in arterial blood < 90%. IH enhanced tumor viability, proliferation, migration, and invasion, downregulated E2F3 expression, and increased miR-210-3-p levels. miR-210-3p overexpression induced similar changes. These changes were reversed by miR-210-3p inhibition in vitro or miR-210-3p antagomir through intratumoral injection in vivo. CONCLUSIONS: IH-induced tumor development is driven through miR-210-3p by E2F3 suppression. MiR-210-3p represents a potential therapeutic target among patients with concomitant cancer and OSA.

The association between obstructive sleep apnea and lung nodule, carcinoembryonic antigen.

PURPOSE: The association between obstructive sleep apnea (OSA) and cancer risks gaining more and more attention. Data on the association between OSA and lung cancer risk are limited. This study is to investigate whether a link exists between low-dose computed tomography (LDCT) scanning of the chest findings, carcinoembryonic antigen (CEA) and OSA in patients suspected of OSA. METHODS: The cross-sectional study included patients aged 18 years or older who underwent continuous nocturnal polysomnography at our sleep center between February 2019 and November 2020. All subjects underwent chest LDCT and CEA. Patients with an apnea-hypopnea index (AHI) of ≥ 15/h were classified as clinically significant OSA group, whereas patients with an AHI < 15/h were classified as control group. RESULTS: A total of 277 patients were enrolled in the study. 176 patients were categorized into the OSA group, while 101 patients were categorized into the control group. There is no relationship between any OSA-related parameter and presence of lung nodule or presence of ≥ 6 mm lung nodule in the binary logistic regression analysis. OSA group demonstrated a significant higher value of CEA than control group. Stepwise multiple linear regression analysis showed that lowest O2 saturation (ß = - 0.256, p < 0.001), smoking status (ß = 0.156, p = 0.007) and age (ß = 0.153, p = 0.008) were independent predictors of elevated CEA. CONCLUSIONS: OSA was independently related to the elevated of serum CEA level, but not with presence of pulmonary nodule or ≥ 6 mm pulmonary nodule in LDCT. Further well-designed longitudinal studies with pathology available are needed to identify the association between OSA and risk of lung cancer.

Long non-coding RNA MALAT1 affects intermittent hypoxia-induced endothelial injury by regulating miR-142-3p/HMGB1.

BACKGROUND: Obstructive sleep apnea (OSA) is a risk factor for atherosclerosis. Long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is strongly linked to endothelial cell functions. However, the function of MALAT1 in intermittent hypoxia (IH) associated vascular endothelial injury has not been explored yet. The current study makes great attempts to investigate the function of MALAT1 in IH-induced endothelial injury and its latent control network. METHODS: To mimic the effect of OSA, we cultured the human umbilical vein endothelial cells (HUVECs) under intermittent hypoxia. Western blot was applied to measure the expression level of associated proteins including capase-3, Bax, Bcl-2 while qRT-PCR was used in measurement of MALAT1 and miR-142-3p. Cell Counting Kit-8 (CCK-8) was carried out in assessing cell viability. Dual-luciferase reporter assay was applied to verify the relationships among high mobility group box (HMGB)1 and MALAT1, miR-142-3p. RESULTS: IH treatment significantly reduced cell viability but enhanced cell apoptosis in HUVECs. Concomitantly, MALAT1 was significantly upregulated in IH-treated HUVECs. Further experiment showed that MALAT1 knockdown augmented IH-induced injury of HUVECs. In addition, it was confirmed by dual-luciferase reporter assay that MALAT1 interacted with miR-142-3p directly. Besides, inhibition of miR-142-3p alleviated damage induced by MALAT1 knockdown in IH-treated HUVECs. Finally, miR-142-3p interacted with HMGB1 directly and inhibition of HMGB1 protein expression mediated by MALAT1 knockdown was reversed by miR-142-3p inhibitor. CONCLUSIONS: IH resulted in increased expression of MALAT1 in HUVECs. MALAT1 knockdown augmented IH-induced injury of HUVECs. MALAT1 exerted its effects on IH-treated HUVECs via miR-142-3p/HMGB1.

Obstructive sleep apnea and the risk of mortality in patients with lung cancer: a meta-analysis.

PURPOSE: Prior reports have examined the relationship between obstructive sleep apnea (OSA) and the mortality rate of lung cancer. However, the findings remain controversial. The present meta-analysis was performed to assess the relationship between OSA and increased risk of mortality in patients with lung cancer. METHODS: PubMed, Web of Science, and Embase were systematically searched for the correlative studies. Data were analyzed and pooled to evaluate odds ratios (ORs) of lung cancer mortality related to OSA. RESULTS: From 249 identified studies, 3 met inclusion criteria and were analyzed, including 67 patients with lung cancer and comorbid OSA and 45 patients with lung cancer and no OSA. The meta-analysis indicated that OSA was not significantly correlated with mortality rate in lung cancer (OR = 2.005, 95% CI = 0.703 to 5.715, z = 1.30, p = 0.193). There was no significant publication bias according to Begg's tests (p = 0.296) and Egger's tests (p = 0.097). CONCLUSION: This meta-analysis suggests that OSA is not significantly correlated with the mortality rate in lung cancer.

Associations between comorbidities and annual incidence plus frequency of asthma exacerbation hospitalisation during the past year: data from CARN study.

PURPOSE: While asthma comorbidities are associated with higher health care utilisation, lower quality of life and poorer asthma control, the impact of asthma comorbidities on hospitalisation for asthma exacerbation (H-AX) remains less recognised. We aim to analyse the impact of asthma comorbidities on H-AX. METHODS: Based on a national survey on asthma control and disease perception (CARN 2015 study), we analysed the impact of comorbidities on annual incidence and frequency of H-AX in China. Information on demographic characteristics, asthma comorbidities and annual incidence and frequency of H-AX were presented in this study. RESULTS: Among 3875 ambulatory asthma patients, 75.9% (2941/3875) had comorbidities, and 26.4% (1017/3858) experienced H-AX during past year. After adjusting for confounding factors such as demographic data, smoking status and asthma control, COPD [OR = 2.189, 95% CI (1.673, 2.863)] and coronary heart disease [OR = 1.387, 95% CI (1.032, 1.864)] were associated with higher annual incidence, while allergic rhinitis [OR = 0.692, 95% CI (0.588, 0.815)] was associated with lower annual incidence, of H-AX. In terms of frequency, allergic rhinitis [OR = 1.630, 95% CI (1.214, 2.187)], COPD [OR = 1.472, 95% CI (1.021, 2.122)] and anxiety [OR = 2.609, 95% CI (1.051, 6.477)] showed statistically significant correlation with frequent H-AX. CONCLUSIONS: COPD and coronary heart disease were associated with higher annual incidence, while allergic rhinitis was associated with lower annual incidence of H-AX. Allergic rhinitis, COPD and anxiety were associated with frequent H-AX. Comorbidities may have an important role in the risk and frequency of annual hospitalisations due to asthma exacerbation. The goal of asthma control should rely on a multi-disciplinary treatment protocol.

Decreased expression of PPARγ is associated with aortic endothelial cell apoptosis in intermittently hypoxic rats.

PURPOSE: Increasing medical researche shows that endothelial dysfunction is one of the important causes of various cardiovascular diseases related to chronic intermittent hypoxia (CIH). This study aimed to identify target proteins in CIH-related vascular dysfunction. METHODS: A comparative proteomics analysis was conducted in aortic samples of rats treated with CIH and controls with normoxia. Bioinformatics analyses were performed to determine the potential roles of major proteins. The expressions of target proteins were measured by western blotting. Cell apoptotic ratio was detected by flow cytometer. RESULTS: A total of 3,593 proteins in aortic tissues of rats were quantified. Ninety-two upregulated proteins and 468 downregulated proteins were identified when the cutoff of fold change was set at 1.5 (CIH vs. normoxia). The results of bioinformatics analysis revealed that the differentially expressed proteins were enriched in the processes of energy metabolism and lipid metabolism. The reduced expression level of peroxisome proliferator-activated receptor γ (PPARγ) protein was identified in thoracic aortic tissues of rats with CIH by proteomics analysis and western blotting. In intermittent hypoxia-treated rat aortic endothelial cells, PPARγ protein levels were reduced, and the apoptosis rate and caspase-3 and Bax protein levels were markedly elevated. Importantly, forced expression of PPARγ by rosiglitazone in intermittent hypoxia-treated rat aortic endothelial cells not only attenuated caspase-3 and Bax protein levels but also reduced the rate of apoptosis. CONCLUSION: PPARγ is critical in endothelial dysfunction of rats with CIH. Additional studies on these differentially expressed proteins associated with CIH-related endothelial dysfunction are necessary.

Impact of CPAP treatment for obstructive sleep apnea on visceral adipose tissue: a meta-analysis of randomized controlled trials.

BACKGROUND: It is still controversial if the continuous positive airway pressure (CPAP) treatment for patients with obstructive sleep apnea (OSA) can markedly influence an effect on visceral adipose tissue (VAT). The current study aimed to assess the efficacy of CPAP interventions in reducing VAT in OSA patients. METHODS: The Web of Science, PubMed, Embase, and Cochrane Library (up to December, 2019) were searched for randomized trials that assessed the effect of CPAP therapy in decreasing VAT in OSA patients. Information on the study, pre- and post-CPAP treatment of VAT, and patient characteristics were extracted for analysis. The standardized mean difference (SMD) was applied to measure the summary estimates. The analysis was conducted with STATA 13.0 and RevMan v.5.3. RESULTS: Five studies (6 cohorts) that involved 169 patients were enrolled in the meta-analysis. There was no significant change of VAT in patients with OSA before and after CPAP treatment (SMD = - 0.00, 95% CI = - 0.21 to 0.21, z = 0.01, p = 0.99). Subgroup analyses further demonstrated that the results were not influenced by CPAP therapy duration, patient age, sample size, or baseline body mass index. CONCLUSIONS: Among the patients with OSA, our meta-analysis revealed that treatment with CPAP does not significantly lead to a reduction of VAT. High-quality randomized controlled trials may provide further clarifying information.

Resveratrol Attenuates Intermittent Hypoxia-Induced Lung Injury by Activating the Nrf2/ARE Pathway.

PURPOSE: Obstructive sleep apnea (OSA) is associated with lung injury. As a novel pathophysiological hallmark of OSA, chronic intermittent hypoxia (CIH) enhances apoptosis. The present study aims to evaluate the effect of resveratrol (Res) on CIH-induced lung apoptosis and inflammation in a rat model of CIH. METHODS: Rats were randomly allocated to normoxia (control), CIH, and CIH + Res groups (n = 10 in each group). The CIH exposure duration was 12 weeks. Rats in the CIH + Res group were additionally administered Res (50 mg kg-1 d-1). Inflammatory cytokine levels were detected by enzyme-linked immunosorbent assays (ELISAs). A terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay was conducted to evaluate the apoptosis rate. Bax, cleaved caspase-3, Nrf2 and HO-1 protein levels were detected by western blotting. RESULTS: The IL-6 and TNF-α levels in the serum and alveolar lavage fluid in the CIH group were markedly higher than those in the control group. The percentage of apoptotic cells in the CIH group was higher than that in the control group. Bax and cleaved caspase-3 protein levels were increased in the CIH group compared with those in the control group. Nrf2 and HO-1 protein levels were decreased in the CIH group compared with those in the control group (p < 0.05). Compared with the CIH group, rats in the CIH + Res group had lower percentages of apoptotic cells, lower IL-6, TNF-α, Bax and cleaved caspase-3 protein levels, and higher Nrf2 and HO-1 protein levels (p < 0.05). CONCLUSION: Res attenuates CIH-related inflammatory reactions and apoptosis in lung tissue by activating the Nrf2/ARE pathway.

Effects of CPAP therapy on subcutaneous adipose tissue in patients with obstructive sleep apnea: a meta-analysis.

PURPOSE: Continuous positive airway pressure (CPAP) is an effective treatment for obstructive sleep apnea (OSA). However, studies provide conflicting results on the effects of CPAP on subcutaneous adipose tissue (SAT) in patients with OSA. We therefore performed a meta-analysis to evaluate whether or not CPAP has an effect on SAT in patients with OSA. METHODS: Studies were retrieved by searching the Cochrane Library, Web of Science, Embase, and Pubmed. Information on study and patient characteristics, study design, and SAT pre- and post-CPAP treatment was extracted for analysis. Different methods for measurement of SAT were also notated. Standardized mean difference (SMD) and 95% confidence interval (CI) were measured to estimate the change in SAT before and after CPAP treatment. Meta-analysis was performed using the RevMan v.5.3 and Stata 14.0. RESULTS: A total of 10 studies met inclusion criteria encompassing 309 patients in the final analysis. The pooled estimate showed that CPAP treatment resulted in no significant change in SAT (SMD = - 0.014, 95% CI = - 0.161 to 0.133, p = 0.896). Meta-regression analyses revealed no predictor, including methods of measuring SAT, that influenced the CPAP effect on SAT. CONCLUSION: Our meta-analysis demonstrated that after CPAP therapy, there was no significant change in SAT in patients with OSA.

Effects of CPAP on visceral adipose tissue in patients with obstructive sleep apnea: a meta-analysis.

PURPOSE: The efficacy of obstructive sleep apnea (OSA) treatment with continuous positive airway pressure (CPAP) on visceral adipose tissue (VAT) yielded conflicting results. This meta-analysis was performed to assess whether OSA treatment with CPAP could reduce VAT. METHODS: The PubMed, Cochrane Library, Embase, and Web of Science were searched before April 2019. Information on characteristics of study participants, pre- and post-CPAP treatment of VAT, and study design was utilized for analysis. Standardized mean difference (SMD) and 95% confidence interval (CI) were used to fully analyze the overall effects. Eleven studies were obtained and the meta-analysis was performed using RevMan v.5.2 and STATA 12.0. RESULTS: A total of 11 studies (16 cohorts) were pooled into meta-analysis, which included 398 patients. The value of VAT before and after CPAP treatment showed no change in OSA patients (SMD = - 0.02, 95% CI - 0.16 to 0.12, z = 0.24, p = 0.81). Subgroup analyses were further conducted, which revealed that age, gender distribution, baseline body mass index, daily duration, CPAP therapy duration, measure, sample size, and study design did not affect the results. CONCLUSIONS: This meta-analysis revealed that CPAP therapy has no effect on VAT in OSA patients. Further large-scale, well-designed randomized controlled trials are required to address this issue.

The role of ferroptosis in chronic intermittent hypoxia-induced liver injury in rats.

PURPOSE: Obstructive sleep apnea (OSA) has been related to an increased risk of liver injury. Ferroptosis is a form of programmed cell death implicated in multiple physiological and pathological processes. This study aimed to explore the role of ferroptosis in chronic intermittent hypoxia (CIH)-induced liver injury as well as to uncover the underlying mechanisms using a CIH rat model. METHODS: Fourteen male Sprague-Dawley rats were randomly allocated to either the normal control (NC) (n = 7) or the CIH group (n = 7). Rats were exposed to intermittent hypoxia for 8 weeks in CIH group. Liver function, histological changes, and markers of oxidative stress were evaluated. The protein levels of hypoxia-inducible factor-1α, nuclear factor E2-related factor 2 (Nrf2), Acyl-CoA synthetase long-chain family member 4 (ACSL4), and glutathione peroxidase 4 (GPX4) in liver were examined by Western blot analysis. RESULTS: CIH treatment caused significant increase of serum alanine aminotransferase, aspartate aminotransferase, and malondialdehyde (MDA). Liver MDA was significantly higher in CIH group than that in NC group. Histology showed that CIH treatment induced discernible swelled, disordered hepatocytes, necrosis, and infiltrated inflammatory cells. CIH treatment significantly reduced the expression of GPX4, while markedly up-regulated expression of ACSL4, indicating elevation in hepatic ferroptosis. In addition, the protein expression of Nrf2 in CIH group was significantly lower than that in NC group. CONCLUSIONS: Ferroptosis played a crucial role in CIH-induced liver injury. The hepatic ferroptosis in CIH rat model might be mediated by the dysregulation of Nrf2. This highlights a potential therapeutic target for the treatment of OSA-related liver injury.

The effect of continuous positive airway pressure on circulating malondialdehyde among obstructive sleep apnea patients: a meta-analysis.

BACKGROUND: Obstructive sleep apnea (OSA) has been demonstrated to be associated with an increase of oxidative stress. However, whether circulating malondialdehyde (MDA), a widely used biomarker of oxidative stress, could be reduced by the treatment of OSA by continuous positive airway pressure (CPAP) is debated. The present meta-analysis was performed to determine the effect of CPAP treatment on circulating MDA among patients with OSA. METHODS: A systematic search of PubMed, Embase, and Web of Science was performed for literature covering the period between 1967 and August 2019. Standardized mean difference (SMD) was calculated to estimate the treatment effects of pre- and post-CPAP therapy. RESULTS: A total of 10 studies with 220 patients were included in this meta-analysis. A significant decrease in circulating MDA was observed after CPAP treatment (SMD = 1.164, 95% CI = 0.443 to 1.885, z = 3.16, p = 0.002) in OSA patients. Subgroup analyses revealed that CPAP therapy was associated with a significant decrease of circulating MDA in elder (SMD = 1.629, 95% CI = 0.265 to 2.994, z = 2.34, p = 0.019), more obese patients (SMD = 0.954, 95% CI = 0.435 to 1.473, z = 3.61, p = 0.000), more severe OSA patients (SMD = 0.879, 95% CI = 0.421 to 1.336, z = 3.76, p = 0.000), patients with therapeutic duration ≥ 3 months (SMD = 1.867, 95% CI = 0.563 to 3.172, z = 2.80, p = 0.005), and patients with good compliance (SMD = 1.004, 95% CI = 0.703 to 1.305, z = 6.54, p = 0.000). CONCLUSIONS: This meta-analysis suggested that CPAP therapy exerted significant lowering effects on circulating MDA, especially in elder, more obese, and more severe OSA patients and patients with good compliance as well as longer duration of CPAP application.

Effect of chronic intermittent hypoxia on gene expression profiles of rat liver: a better understanding of OSA-related liver disease.

PURPOSE: Obstructive sleep apnea (OSA) and OSA-associated chronic intermittent hypoxia (CIH) have been suggested to be associated with increased risk of liver disease. Little is known about the biological pathophysiology and underlying molecular mechanisms. Here we use whole-genome expression profiling to explore the transcriptomic changes induced by CIH in rat liver. METHODS: Rats (n = 3) were exposed to CIH for 8 weeks and were compared with rats exposed to normoxia (n = 3). Illumina HiSeq 4000 platform was used to examine differentially expressed genes (DEGs) in the liver between control group and CIH rat model. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to validate DEGs. Biological functions of DEGs were determined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. RESULTS: Compared with control group, 318 genes were identified to be dysregulated in the liver of CIH rat model, with 211genes upregulated and 107 genes downregulated. Bioinformatics analysis showed that these genes were extensively related to various physiologic processes such as hepatic metabolism, apoptotic process, and oxidative stress. 10 genes with 5 upregulated and 5 downregulated were selected and further verified by qRT-PCR. CONCLUSIONS: CIH resulted in altered gene expression patterns in the liver of rat. The DEGs were related to various physiological and pathological processes in CIH rat liver. These data provide a better understanding of the mechanisms and underlying molecular changes of OSA-related liver disease.

Endothelial cell autophagy in chronic intermittent hypoxia is impaired by miRNA-30a-mediated translational control of Beclin-1.

Chronic intermittent hypoxia (CIH) in obstructive sleep apnea causes damage of aortic endothelial cells, which predisposes the development of many cardiovascular diseases. Recently, both altered expression of microRNAs (miRNAs) and impaired autophagy were found to be associated with endothelial cell dysfunction in CIH. However, the exact molecular regulatory pathway has not been determined. Here, we address this question. In a mouse model of CIH, we detected significant upregulation of miR-30a, a miRNA that targets 3'-untranslated region of autophagy-associated protein 6 (Beclin-1) messenger RNA (mRNA) for suppressing the protein translation, which subsequently attenuated the endothelial cell autophagy against cell death. Indeed, unlike Beclin-1 mRNA, the Beclin-1 protein in endothelial cells did not increase after CIH. Suppression of miR-30a by expression of antisense of miR-30a significantly increased Beclin-1 levels to enhance endothelial cell autophagy in vitro and in vivo, which improved endothelial cell survival against CIH. Together, these data suggest that endothelial cell autophagy in CIH may be attenuated by miR-30a-mediated translational control of Beclin-1 as an important cause of endothelial cell dysfunction and damage.

Expression profile of long non-coding RNAs in rat models of OSA-induced cardiovascular disease: new insight into pathogenesis.

PURPOSE: Long non-coding RNAs (lncRNAs) are a recently identified class of regulatory molecules involved in the regulation of numerous biological processes, but their functions in a rat model of chronic intermittent hypoxia (CIH) remain largely unknown. Therefore, for further investigation, we aimed to explore lncRNA expression profiles and reveal their potential functional roles in rat models of CIH. METHODS: We used a well-established CIH rat model and conducted lncRNA microarray experiments on the heart samples of rats with CIH and under normoxia control. Differentially expressed lncRNAs and mRNAs were identified via fold-change filtering and verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Bioinformatics analyses were applied to reveal the potential roles of key lncRNAs. Co-expression analysis was conducted to determine the transcriptional regulatory relationship of lncRNAs and mRNAs between the two groups. RESULTS: Our data indicated that 157 lncRNAs and 319 mRNAs were upregulated, while 132 lncRNAs and 428 mRNAs were downregulated in the rat model of CIH compared with sham control. Pathway analyses showed that 31 pathways involved in upregulated transcripts and 28 pathways involved in downregulated transcripts. Co-expression networks were also constructed to explore the potential roles of differentially expressed lncRNAs on mRNAs. LncRNAs, namely, XR_596701, XR_344474, XR_600374, ENSRNOT00000065561, XR_590196, and XR_597099, were validated by the use of qRT-PCR. CONCLUSIONS: The present study first revealed lncRNAs expression profiles in a rat model of CIH, providing new insight into the pathogenesis of obstructive sleep apnea-induced cardiovascular disease.

The association between glycometabolism and nonalcoholic fatty liver disease in patients with obstructive sleep apnea.

PURPOSE: Growing evidence has revealed that nonalcoholic fatty liver disease (NAFLD) is associated with type 2 diabetes. This study aimed to assess the association between glycometabolism and NAFLD in patients with obstructive sleep apnea (OSA). METHODS: Patients with suspected OSA were enrolled consecutively and then underwent polysomnography, liver ultrasound, and biochemical measurements. Logistic regressions were used to identify factors associated with NAFLD. RESULTS: In total, 415 patients were included. The prevalence of NAFLD in the non-OSA, mild OSA, moderate OSA, and severe OSA groups was 37.21%, 69.09%, 68.34%, and 78.08%, respectively. Stepwise logistic regression suggested that percentage of total sleep time spent with oxygen saturation of < 90% (TS90), lowest oxygen saturation (LaSO2), and homeostatic model assessment of insulin resistance (HOMA-IR) were independently associated with NAFLD in all subjects, after adjusting for confounders (odds ratio [OR] = 1.037, p = 0.014; OR = 1.056, p = 0.004; OR = 0.732, p = 0.009; respectively). TS90, LaSO2, and HOMA-IR were also independent predictors for NAFLD in patients with mild and moderate OSA, whereas TS90, LaSO2, and ODI were independent predictors for NAFLD in patients with severe OSA. CONCLUSIONS: There is a relationship between OSA and NAFLD, and the combination of disordered glycometabolism and intermittent hypoxia may act as a "two hit" mechanism to promote the development of NAFLD. Furthermore, intermittent hypoxia alone was an independent predictor for NAFLD in severe OSA patients.