Consequences of hypoxia-reoxygenation phenomena in patients with obstructive sleep apnea syndrome

Is there a relationship between hematological parameters and duration of respiratory events in severe OSA

Aim: The aim of this study was to compare hematological parameters with the mean obstructive apnea duration (MOAD), mean mixed apnea duration (MMAD), mean central apnea duration (MCAD), mean total apnea duration (MTAD) and mean hypopnea duration (MHD), and blood oxygenation, other polysomnographic sleep parameters in patients with severe OSA.Material and methods: A retrospective study included 120 patients with severe OSA. The correlations between the hematological parameters with MOAD, MMAD, MCAD, MTAD, MHD, and blood oxygenation, other polysomnographic sleep parameters were analyzed.Results: There was a positive correlation between hgb with MOAD, MMAD, MTAD MCAD, MHD; mean oxygen desaturation, and the number of desaturation (≥5%). Also, hgb associated negatively with N1 sleep, WASO (wake time after sleep onset) and positively with REM, N2 sleep, total sleep time, and sleep efficiency. RDW and MOAD, MTAD, MHD were negatively related. Also, RDW related positively with sleep latency, WASO, and N1 sleep; negatively with sleep efficiency and REM sleep. There was no relationship between duration of respiratory events with NLR, PRL, and MPV.Conclusions: Hematological parameters, especially hgb and RDW, can be used to assess the severity of the disease in severe OSA patients in addition to AHI.

Effects of continuous positive airway pressure on exhaled transforming growth factor-β and vascular endothelial growth factor in patients with obstructive sleep apnea

Background

Both transforming growth factor β (TGF-β) and vascular endothelial growth factor (VEGF) are master regulators of airway remodeling; however, their pathological roles in obstructive sleep apnea (OSA) remain unclear. The aim of the present study was to evaluate the expression of TGF-β and VEGF protein in the serum and exhaled breath condensate (EBC) before and after continuous positive airway pressure (CPAP) treatment in OSA patients.

Methods

Forty patients with moderate to severe OSA requiring CPAP and 20 healthy subjects were prospectively recruited. The concentrations of TGF-β and VEGF protein in the serum and EBC were evaluated by enzyme-linked immunosorbent assay. All OSA patients underwent a sleep study that was repeated 3 months after receiving CPAP therapy.

Results

Protein concentrations of TGF-β and VEGF in the serum did not differ between healthy controls and OSA patients before CPAP treatment. There was also no difference in the serum protein concentrations of TGF-β and VEGF of the OSA patients before and after CPAP treatment. However, both the TGF-β and VEGF protein concentrations in the EBC were higher in the OSA patients than those in control subjects, and recovered to normal levels after CPAP.

Conclusions

Successful treatment of OSA by CPAP can restore the TGF-β and VEGF protein concentrations in the EBC.

Impact of continuous positive airway pressure on vascular endothelial growth factor in patients with obstructive sleep apnea: a meta-analysis

PURPOSE

Cumulative evidence supports the clear relationship of obstructive sleep apnea (OSA) with cardiovascular disease (CVD). And, adherence to continuous positive airway pressure (CPAP) treatment alleviates the risk of CVD in subjects with OSA. Vascular endothelial growth factor (VEGF), a potent angiogenic cytokine regulated by hypoxia-inducible factor, stimulates the progression of CVD. Thus, whether treatment with CPAP can actually decrease VEGF in patients with OSA remains inconclusive. The purpose of the present study was to quantitatively evaluate the impact of CPAP therapy on VEGF levels in OSA patients.

METHODS

We systematically searched Web of Science, Cochrane Library, PubMed, and Embase databases that examined the impact of CPAP on VEGF levels in OSA patients prior to May 1, 2017. Related searching terms were "sleep apnea, obstructive," "sleep disordered breathing," "continuous positive airway pressure," "positive airway pressure," and "vascular endothelial growth factor." We used standardized mean difference (SMD) to analyze the summary estimates for CPAP therapy.

RESULTS

Six studies involving 392 patients were eligible for the meta-analysis. Meta-analysis of the pooled effect showed that levels of VEGF were significantly decreased in patients with OSA before and after CPAP treatment (SMD = - 0.440, 95% confidence interval (CI) = - 0.684 to - 0.196, z = 3.53, p = 0.000). Further, results demonstrated that differences in age, body mass index, apnea-hypopnea index, CPAP therapy duration, sample size, and racial differences also affected CPAP efficacy.

CONCLUSIONS

Improved endothelial function measured by VEGF may be associated with CPAP therapy in OSA patients. The use of VEGF levels may be clinically important in evaluating CVD for OSA patients. Further large-scale, well-designed long-term interventional investigations are needed to clarify this issue.

Matrix Metalloproteinase-9 Is a Predictive Factor for Systematic Hypertension and Heart Dysfunction in Patients with Obstructive Sleep Apnea Syndrome

Patients with obstructive sleep apnea syndrome (OSAS) showed higher prevalence in cardiovascular diseases due to aberrant hypoxia and oxidative stress. However, not all OSAS patients end up with cardiovascular disorders, and identification of novel biomarker will be invaluable for differentiating patients at risk. Here we tested the serum matrix metalloproteinase-9 (MMP-9) levels in 47 untreated OSAS patients and found that the MMP-9 level was positively correlated with severity of OSAS, which was consistent with hypoxia degree and duration. Besides, the MMP-9 level was higher in patients complicated with systematic hypertension (P < 0.001). Furthermore, we selected those OSAS patients without any cardiovascular dysfunction (n = 35) and followed up for up to five years. By the end of follow-up, 12 patients had hypertension onset and 3 patients had left ventricular hypertrophy. By analyzing the clinical outcomes with MMP-9 expression, we demonstrated that high serum MMP-9 in OSAS patients was a risk factor for occurrence of cardiovascular diseases. In addition, we cultured the vascular endothelial cells (VEC) from rat aorta in hypoxia condition to investigate whether MMP-9 was elevated due to hypoxia in OSAS patients. Cellular results revealed that the expression, secretion, and activity of MMP-9 were all upregulated by hypoxia and can cleave the beta2-adrenergic receptor (β2AR) on VEC surface. Our results not only determined MMP-9 as a risk factor for cardiovascular diseases in OSAS patients, but also showed the possible involvement of hypoxia-MMP-9-β2AR signaling axis.

Erythropoietin levels in patients with sleep apnea: a meta-analysis

Currently available data regarding the blood levels of erythropoietin (EPO) in sleep apnea (SA) patients are contradictory. The aim of the present meta-analysis was to evaluate the EPO levels in SA patients via quantitative analysis. A systematic search of Pubmed, Embase, and Web of Science were performed. EPO levels in SA group and control group were extracted from each eligible study. Weight mean difference (WMD) or Standard mean difference (SMD) with 95% confidence interval (CI) was calculated by using fixed-effects or random effect model analysis according to the degree of heterogeneity between studies. A total of 9 studies involving 407 participants were enrolled. The results indicated that EPO levels in SA group were significantly higher than that in control group (SMD 0.61, 95% CI 0.11–1.11, p = 0.016). Significantly higher EPO levels were found in patients with body mass index <30 kg/m², and cardiovascular complications in the subsequent subgroup analysis (both p < 0.05). High blood EPO levels were found in SA patients in the present meta-analysis.

Vascular endothelial growth factor levels in patients with obstructive sleep apnea: a meta-analysis

Published articles regarding the blood levels of vascular endothelial growth factor (VEGF) in obstructive sleep apnea (OSA) patients are contradictory. The objective of this study was to explore whether VEGF levels is high or not in OSA subjects via quantitatively statistical analysis. The electronic databases of Pubmed, Web of Science, EMBASE were systematic searched. The VEGF levels and clinical characteristics of participants between OSA group and control group were extracted for analysis. Weighted mean difference (WMD) or standard mean difference (SMD) with 95 % confidence interval (CI) was calculated by fixed effects or random effects model. Appropriate statistical software was employed for data synthesis. Totaling 15 articles with 697 participants were included in this study. Pooled meta-analysis showed that blood VEGF concentrations were significantly higher in OSA patients than in control subjects (SMD 1.89, 95 % CI 0.92-2.87, p = 0.000). Subgroup analysis demonstrated that when compared with control group, OSA patients with age ≥50 years (SMD 2.54, 95 % CI 1.28-3.80, p = 0.000), apnea hypopnea index ≥30 events/h (SMD 2.47, 95 % CI 1.20-3.73, p = 0.000) had higher VEGF levels. Compared with control subjects, OSA patients had an elevated VEGF in serum (SMD 3.55, 95 % CI 1.82-5.28, p = 0.000) rather than in plasma. High blood VEGF concentrations were observed in OSA patients, particularly in the older and more serious patients.

Vascular endothelial growth factor genotypes and haplotypes contribute to the susceptibility of obstructive sleep apnea syndrome

Background

To investigate whether VEGF polymorphisms (-460T/C, +405G/C, and +936C/T)/haplotypes influence the susceptibility of obstructive sleep apnea (OSA).

Method

A prospective case-control study was conducted to evaluate the genetic effects of VEGF polymorphisms on the development of OSA. 150 patients and 225 healthy controls were recruited for this study and their genotypes were determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP). The odds ratios (OR) and 95% confidence intervals (CI) were calculated by logistic regression analysis.

Result

Our study showed that the -460C allele (C vs. T: OR = 1.95, 95% CI = 1.38–2.76) and +936T allele (T vs. C: OR = 1.48, 95% CI = 1.02–2.15) were associated with an increased OSA risk, whereas +405C allele was associated with a decreased susceptibility to OSA (C vs. G: OR = 0.61, 95% CI = 0.45–0.83). Compared with the most common haplotype CCT, CGC (OR = 2.22, 95% CI = 1.19–4.13) and TGC (OR = 3.83, 95% CI = 1.56–9.40) were associated with a significantly increased risk of OSA.

Conclusion

These observations implied that VEGF gene polymorphisms might be associated with the susceptibility to OSA. These results need to be validated by other independent studies, especially in diverse ethnic populations.

Obstructive sleep apnea and cognitive impairment: addressing the blood-brain barrier

Increasing data support a connection between obstructive sleep apnea (OSA) and cognitive impairment but a causal link has yet to be established. Although neuronal loss has been linked to cognitive impairment, emerging theories propose that changes in synaptic plasticity can cause cognitive impairment. Studies demonstrate that disruption to the blood-brain barrier (BBB), which is uniquely structured to tightly maintain homeostasis inside the brain, leads to changes in the brain's microenvironment and affects synaptic plasticity. Cyclical intermittent hypoxia is a stressor that could disrupt the BBB via molecular responses already known to occur in either OSA patients or animal models of intermittent hypoxia. However, we do not yet know if or how intermittent hypoxia can cause cognitive impairment by mechanisms operating at the BBB. Therefore, we propose that initially, adaptive homeostatic responses at the BBB occur in response to increased oxygen and nutrient demand, specifically through regulation of influx and efflux BBB transporters that alter microvessel permeability. We further hypothesize that although these responses are initially adaptive, these changes in BBB transporters can have long-term consequences that disrupt the brain's microenvironment and alter synaptic plasticity leading to cognitive impairment.