Association of cellular adhesion molecules and oxidative stress with endothelial function in obstructive sleep apnea

Evaluation of Blood Intercellular Adhesion Molecule-1 (ICAM-1) Level in Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis

Background and objective: Intercellular adhesion molecule-1 (ICAM-1) appears to be an active and important biomarker for decreasing the risk of cardiovascular issues among individuals with obstructive sleep apnea (OSA). Herein, a systematic review and meta-analysis was designed to probe whether plasma/serum ICAM-1levels are different in adults with OSA compared to adults with no OSA, as well as adults with severe OSA compared to adults with mild/moderate OSA. Materials and methods: A thorough and systematic literature search was performed in four databases (PubMed/Medline, Web of Science, Scopus, and Cochrane Library) until 17 July 2022, without any age and sample size restrictions to retrieve the relevant articles. The standardized mean difference (SMD) along with a 95% confidence interval (CI) of plasma/serum of ICAM-1 levels was reported. Analyses, including sensitivity analysis, subgroup analysis, trial sequential analysis, meta-regression, and a funnel plot analysis, were performed in the pooled analysis. Results: A total of 414 records were identified in the databases, and 17 articles including 22 studies were entered into the meta-analysis. The pooled SMD of serum/plasma ICAM-1 levels in adults with OSA compared to controls was 2.00 (95%CI: 1.41, 2.59; p < 0.00001). The pooled SMD of serum/plasma ICAM-1 levels in adults with severe compared to mild/moderate OSA was 3.62 (95%CI: 1.74, 5.51; p = 0.0002). Higher serum/plasma ICAM-1 levels were associated with a higher mean age of controls, higher scores for the apnea-hypopnea index, and with a lower mean age of adults with OSA and with smaller sample sizes. Conclusions: Th results of the present meta-analysis showed that serum/plasma ICAM-1 levels in adults with OSA was higher than serum/plasma ICAM-1 levels in controls. Similarly, serum/plasma ICAM-1 levels in adults with severe OSA were higher compared to serum/plasma ICAM-1 levels of adults with mild or moderate OSA. Therefore, ICAM-1 may be used as an additional diagnostic and therapeutic biomarker in adults with OSA.

Retinal and Choroidal Effects of Continuous Positive Airway Pressure as Treatment for Sleep Apnea: Results at 12 Months

BACKGROUND

To determine the impacts of continuous positive airway pressure (CPAP) treatment on retinal and choroidal thickness measurement in individuals with obstructive sleep apnea (OSA).

METHODS

Participants were 28 patients with OSA treated with CPAP who were enrolled immediately after diagnosis and graded according to the apnea hypopnea index (AHI) determined in an overnight polysomnography. Inclusion criteria were a new diagnosis of OSA and an indication for CPAP. Participants underwent a full ophthalmologic examination including standard automated perimetry (SAP) and optical coherence tomography (OCT) at the levels peripapillary, macular, and choroidal before CPAP onset, and after three and twelve months of CPAP. The data compared before and after treatment were intraocular pressure, SAP, and the thicknesses peripapillary retinal nerve fiber layer (pRNFL), total retinal (TR), retinal ganglion cell layer (RGCL), inner plexiform layer (IPL), photoreceptor layer (PL), and choroidal.

RESULTS

After 3 months of CPAP, we observed thickening of the pRNFL (in 5/6 subfields) (p < 0.004) and TR (in 5/9 subfields) (p < 0.010). At 12 months, thickening persisted in these layers, this time affecting 2/6 and 2/9 subfields, respectively (p < 0.012 and p < 0.001, respectively). Choroidal thinning was observed at the temporal level at both 3 and 12 months compared to measurements before starting CPAP treatment (p = 0.014 and p = 0.038, respectively). SAP remained unchanged. Intraocular pressure was higher at 12 months than at 3 months (p = 0.001).

CONCLUSIONS

12 months of CPAP avoids retinal thinning and normalizes choroidal thickness in OSA patients.

Increasing circulating ESM-1 and adhesion molecules are associated with earlystage atherosclerosis in OSA patients:A cross-sectional study

BACKGROUND

There are increasing evidences for a direct relationship between the vascular system and obstructive sleep apnea (OSA). The aim of this study was to investigate the relationship between circulating endothelial cell specific molecule-1 (ESM-1), adhesion molecules and subclinical atherosclerosis in patients with OSA.

METHODS

This was a cross-sectional study in which 161 patients with OSA and 56 controls were recruited. Demographic data, biochemical and polysomnography parameters were collected. We used a powerful high-throughput Multiplex Immunobead Assay technique to simultaneously test plasm levels of ESM-1, P-selectin, E-selectin, L-selectin, inter-cellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). Carotid intima-media thickness (CIMT) were measured as parameters of vascular endothelial dysfunction and early atherosclerosis.

RESULTS

Increasing circulating levels of ESM-1, P-selectin, E-selectin, L-selectin, ICAM-1 and VCAM-1 were found increased in patients with OSA (all P &lt; 0.001). Furthermore, OSA patients exhibited increased CIMT than controls (P &lt; 0.05). Multivariate linear analysis indicated that elevated ESM-1, P-Selectin, E-selectin, and L-selectin levels were associated with AHI (all P &lt; 0.05). Moreover, multivariate analysis showed that increasing ESM-1, VCAM-1, P-Selectin, and L-selectin were significantly associated with thick CIMT in OSA patients (all P &lt; 0.05).

CONCLUSIONS

Increased circulating ESM-1 and adhesion molecules associated with thick CIMT in OSA, which is a marker of subclinical atherosclerosis. Strict attention to monitor circulating ESM-1 and adhesion molecules is necessary for early detection of subclinical atherosclerosis in OSA patients.

Retinal and choroidal thickness measurements in obstructive sleep apnea: impacts of continuous positive airway pressure treatment

PURPOSE

To examine retinal and choroidal thicknesses in individuals with obstructive sleep apnea (OSA) and determine the impacts of continuous positive airway pressure (CPAP) treatment.

METHODS

Prospective follow-up study conducted at a university hospital. 40 patients with OSA, 28 treated with CPAP, and 12 untreated, were enrolled immediately after diagnosis and graded according to the apnea hypopnea index (AHI) determined in an overnight polysomnography. Inclusion criteria were a new diagnosis of OSA and CPAP indicated. Participants underwent a full ophthalmologic examination including optical coherence tomography (OCT) at the peripapillary, macular, and choroidal levels and the same examination 3 months later. Outcome measures were peripapillary retinal nerve fiber layer (RNFL), total retinal (TRT), retinal ganglion cell layer (RGCL), inner plexiform layer (IPL), photoreceptor layer (PL), and choroidal thicknesses.

RESULTS

At 3 months, RGCL thickness was reduced at the inner nasal macula segment in the no-CPAP group (P = 0.016). In + CPAP, increases were produced in RNFL thickness (5/6 segments) and TRT (7/ 9 segments), while choroidal thinning was observed temporally (P = 0.003). At baseline, positive correlation was detected between choroidal thickness and AHI (r = 0.352, P = 0.005) and between IPL thickness (7/9 segments) and AHI (r = 0.414, P < 0.001).

CONCLUSIONS

Initial retinal and choroidal thickening was followed by RGCL thinning over 3 months. In patients receiving CPAP, we observed no thinning of any retinal layer and normalization of choroidal thickness.

Soluble P-selectin levels in patients with obstructive sleep apnea: a systematic review and meta-analysis

PURPOSE

Obstructive sleep apnea (OSA) patients are at increased risk for cardiovascular disease, stroke, atherosclerosis, hypertension, and venous thromboembolism. Elevated soluble P-selectin (sP-selectin) levels are also associated with increased risk of above diseases. But whether sP-selectin levels in OSA patients are higher than their counterparts remain unclear, since previous studies yielded inconsistent results. Therefore, a meta-analysis is warranted.

METHODS

PubMed, Embase, Cochrane Library, and Web of Science databases were searched for eligible studies. Studies were included if they reported sP-selectin levels of both OSA patients and non-OSA controls. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to determine the effect sizes.

RESULTS

Nine eligible studies were finally evaluated. When all the studies were pooled, sP-selectin levels in OSA patients were significantly higher than that in controls (SMD = 0.54, 95% CI 0.29-0.78, I² = 66%, p < 0.0001). In the subgroup analysis based on BMI matched groups, sP-selectin levels were significantly higher in OSA patients than that in controls (SMD = 0.52, 95% CI 0.27-0.76, I² = 23%, p < 0.0001). In the subgroup analysis stratified by blood source, either serum sP-selectin levels or plasma sP-selectin levels in OSA patients were higher than that in controls. Moderate-to-severe OSA patients had significant higher sP-selectin levels (SMD = 0.80, 95% CI 0.45-1.15, I² = 67%, p < 0.00001), while mild OSA patients showed no significant difference with controls.

CONCLUSION

The pooled results reveal that OSA patients have higher sP-selectin levels than non-OSA controls. This conclusion remains unaltered in all subgroups other than the subgroup of mild OSA patients. Additional studies are warranted to better identify the role of sP-selectin as a potential biomarker in OSA patients.

The Assessment of Endothelial Dysfunction among OSA Patients after CPAP Treatment

Background and Objectives: Microcirculation dysfunction is present in patients with obstructive sleep apnea (OSA). Intermittent hypoxia generates “oxidative stress”, which contributes to chronic inflammation. The secretion of nitric oxide (NO), which is responsible for adequate regulation of the endothelium, is impaired due to a decrease in endothelial nitric oxide synthetase (eNOS) expression and an increase in endogenous eNOS inhibitors. Furthermore, nocturnal awakenings lead to the dysregulation of cortisol release and increased stimulation of the sympathetic nervous system. The non-invasive method of choice in OSA treatment is continuous positive airway pressure (CPAP). Materials and Methods: PubMed, Scopus, and Google Scholar databases were searched, and only papers published in the last 15 years were subsequently analyzed. For this purpose, we searched for keywords in article titles or contents such as “obstructive sleep apnea”, “microcirculation”, and “CPAP”. In our review, we only studied English articles that reported systemic reviews and meta-analyses, clinical studies, and case reports. Results: Endothelial dysfunction can be assessed by methods based on reactive hyperemia, such as flow-mediated dilation (FMD) measured by ultrasonography, laser-Doppler flowmetry (LDF), or capillaroscopy. In invasive techniques, intravenous administration of vasodilator substances takes place. Some surveys detected impaired microcirculation in OSA patients compared with healthy individuals. The level of dysfunction depended on the severity of OSA. CPAP treatment significantly improved endothelial function and microvascular blood flow and lowered the inflammatory mediator level. Conclusions: The first-choice treatment—CPAP—reduces the number of apneas and hypopneas during the night, induces the reversal of hypopnea and the chronic inflammatory state, and enhances activation of the sympathetic nervous system. Changes are visible as improved blood flow in both macro- and microcirculation, increased arterial elasticity, and decreased stiffness. Thus, early implementation of adequate treatment could be essential to reduce high cardiovascular risk in patients with OSA.

Increased the circulating levels of malondialdehyde in patients with obstructive sleep apnea: a systematic review and meta-analysis

PURPOSE

Obstructive sleep apnea (OSA) is a prevalent sleep disorder associated with increased risk of cardiovascular disease. Several studies have demonstrated elevated oxidative stress in patients with OSA. This oxidative stress is a direct inducer of lipid peroxidation. Malondialdehyde (MDA), a robust marker of lipid peroxidation, has been evaluated in patients with OSA but results have been inconsistent. The present systematic review and meta-analysis was performed to quantify the circulating levels of MDA in patients with OSA compared to controls.

METHODS

Search was performed in data bases of PubMed, Scopus, EMBASE, Web of Science, and Cochrane library, to find out those studies that measured MDA in patients with OSA compared to controls.

RESULTS

The search produced 563 records and after removing duplicates, 383 records remained. Screening by title and abstract and the evaluation of the full text resulted in the selection of 14 articles, which were included in the meta-analysis. Pooled analysis demonstrated higher levels of MDA in the patients compared to the controls (SMD (95% CI): 1.18 (0.68, 1.68), p < 0.0001).

CONCLUSION

The results of this meta-analysis demonstrated considerable elevation of MDA in patients with OSA compared to controls. The meta-analysis also indicated a positive association of MDA levels with the degree of severity of OSA. These results suggest a state of increased lipid peroxidation in patients with OSA.

Obstructive Sleep Apnea Severity, Body Mass Index, and Circulating Levels of Cellular Adhesion Molecules

PURPOSE

To investigate the relationship between obstructive sleep apnea (OSA) severity, body mass index (BMI), and circulating levels of inflammatory adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin).

METHODS

A cross-sectional clinical cohort study on all consecutive adults referred to the University of British Columbia (UBC) Sleep Laboratory for a polysomnogram (PSG) for suspected OSA provided a morning blood sample. Samples were analyzed with multiplex immune assay (MilliporeSigma, CA) to assess the levels of adhesion molecules.

RESULTS

488 patients were studied; the majority were male (68%) with a mean age of 50 yrs, mean AHI of 23 events/hour, and mean BMI of 32 kg/m². In multivariable linear regression models, all three adhesion molecules were significantly associated with BMI (E-selectin p < 0.0001; ICAM-1 p = 0.0007; VCAM-1 p = 0.0003). However, only E-selectin was independently associated with AHI (p = 0.02); there was no significant interaction between AHI and BMI for E-selectin (p = 0.33).

CONCLUSIONS

Although all three adhesion molecules were associated with BMI, only E-selectin was independently associated with OSA severity. Future studies are needed to determine the clinical significance of the relationship between E-selectin and OSA.

The impact of OSA and CPAP treatment on cell adhesion molecules' night-morning variation

PURPOSE

Obstructive sleep apnea (OSA) has been related to vascular inflammation and production of endothelial cell adhesion molecules (CAMs). We aimed to determine night-morning variation of CAMs in patients with OSA compared to controls and the effect of one-night continuous positive airway pressure (CPAP) treatment on them.

METHODS

Nonsmoking men went through a full-attended polysomnography (PSG) study. Participants with moderate to severe OSA went through another PSG study while being treated with CPAP. Participants who did not have OSA composed the control group. Serum levels of intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and E-selectin were measured before and after sleep on both nights.

RESULTS

Of 30 men, 20 had moderate to severe OSA while 10 did not. Night and morning ICAM-1 levels of patients with OSA were significantly higher than controls (p = 0.002 and p < 0.0001 respectively), while both night and morning VCAM-1 and E-selectin levels were not. Morning ICAM-1 levels of controls were significantly lower than night levels (p = 0.031), while morning ICAM-1, VCAM-1, and E-selectin levels of patients with OSA and morning VCAM-1 and E-selectin levels of controls were not. After CPAP treatment, the morning ICAM-1 levels, but not VCAM-1 levels, of patients with OSA were significantly lower than night levels (p = 0.006) and E-selectin levels showed a tendency for reduction (p = 0.06).

CONCLUSIONS

OSA is associated with elevated night and morning ICAM-1 levels in adult men with OSA. Even one night of CPAP treatment restores the normal night-morning variation of ICAM-1 levels and may have an effect on E-selectin levels, as well.

Circulating P-Selectin Glycoprotein Ligand 1 and P-Selectin Levels in Obstructive Sleep Apnea Patients

Purpose

Obstructive sleep apnea (OSA) is characterized by chronic intermittent hypoxia which induces inflammation in blood vessels leading to the development of cardiovascular comorbidities. Several studies implicated the role of P-selectin in vascular inflammation of OSA. P-selectin glycoprotein ligand 1 (PSGL-1) is the main activator for P-selectin and is involved in immune cell trafficking. However, PSGL-1 has not been analyzed in OSA. The aim of the study was to investigate plasma PSGL-1 and P-selectin levels to have a deeper understanding on their interaction in obstructive sleep apnea.

Methods

Fifty-one untreated patients with OSA and 42 non-OSA controls were recruited. Plasma PSGL-1 levels were determined in evening and morning samples, P-selectin levels were analyzed in morning samples using commercially available ELISA kits. Polysomnography was performed in all participants. OSA was defined by an apnea–hypopnea index ≥ 5/h.

Results

PSGL-1 levels did not differ between controls and OSA patients either in the evening or in the morning. Although, there was no difference between controls (16.9/6.8–40.8 ng/ml) and patients with OSA (19.6/8.4–56.8, p = 0.24), patients with severe OSA had increased plasma P-selectin levels (25.6/8.4–56.8 ng/ml) compared to mild OSA patients (14.1/8.5–35.3 ng/ml, p = 0.006) and controls (p = 0.03).

Conclusions

P-selectin expression relates to disease severity suggesting a pathophysiological role in endothelial cell activation. PSGL-1 levels are unaltered in OSA, suggesting an alternative activation pathway for P-selectin in OSA.

Circulating P-Selectin and Its Glycoprotein Ligand in Nondiabetic Obstructive Sleep Apnea Patients

Selectins and their ligands play an important role in atherosclerosis. The role of these adhesion molecules in the pathogenesis of obstructive sleep apnea (OSA) may be of clinical relevance. Therefore, the aim of this study was to assess the serum content of platelet P-selectin (P-SEL) and P-selectin glycoprotein ligand 1 (PSGL-1) in different OSA stages. The study was performed in nondiabetic patients, aged 32-71, in whom OSA was verified by polysomnography. The apnea/hypopnea index (AHI) was used to stratify OSA stages: AHI <5, no sleep pathology (OSA-0); AHI 5-15, (OSA-1); AHI 16-30, (OSA-2); and AHI >30, (OSA-3). There were 16 patients in each group. P-SEL and PSGL-1 were assessed by ELISA kits. There were no appreciable differences in the patients' glucose or high-specificity C-reactive protein content. We found that P-SEL and PSGL-1 significantly increased from OSA-0 to OSA-3. There were the following positive associations in all OSA patients: P-SEL vs. AHI, PSGL-1 vs. AHI, and P-SEL vs. PSGL-1. In addition, the adhesion molecules are associated with the anthropometric parameters, oxygen saturation, and sleep architecture in the OSA-1 group. We conclude that the adhesion molecules consistently increase in the blood of nondiabetic OSA patients, along with progression of disorder severity.

Mechanisms of vascular endothelial cell injury in response to intermittent and/or continuous hypoxia exposure and protective effects of anti-inflammatory and anti-oxidant agents

BACKGROUND

Hypoxia induces vascular endothelial injuries; however, the mechanisms involved and effects of interventions remain unclear.

OBJECTIVE

Investigate the inflammatory response and oxidative stress in co-cultured neutrophils and vascular endothelial cells, apoptotic changes in endothelial cells, and effects of the antioxidant, Tempol, or the NF-êB inflammatory channel blocker, pyrrolidine dithiocarbamate (PDTC), upon endothelial cells under conditions of intermittent and/or continuous hypoxic exposure.

METHODS

Polymorphonuclear neutrophils co-cultured with human umbilical vein endothelial cells were subjected to the following conditions: intermittent normoxia (IN), intermittent hypoxia (IH), continuous hypoxia (CH), intermittent with continuous hypoxia (OS), OS+Tempol (OS+T), or OS+PDTC (OS+P) for 2, 5, or 8 h. Inflammatory factors, TNF-α and IL-6, the adhesion molecule, ICAM-1, CAT activity, and MDA concentrations in supernatants from the co-culture as well as pro- (Bak) and anti- (Bcl-xl) apoptotic gene expression levels in the endothelial cells were determined.

RESULTS

Inflammatory factors, adhesion molecules, oxidative stress, and apoptosis genes in all groups showed significant, time-dependent increases as compared with the IN group. TNF-α, IL-6, ICAM-1, and MDA levels in the OS group were increased, while CAT was decreased as compared with that observed in the IH, CH, OS+T, and OS+P groups. Bcl-x1 expression and Bcl-x1/BAK ratios were decreased and BAX increased in the OS versus IH, CH, OS+T, or OS+P groups. Both pro- and anti-apoptotic proteins showed time-dependent increases, while the Bcl-x1/BAK ratio decreased over these times. Tempol and PDTC partially prevented these effects.

CONCLUSION

Inflammation, oxidative stress, and apoptosis are all involved in vascular endothelial injury induced by OS. Anti-inflammatory and anti-oxidative interventions can partially improve effects of OS.

Adhesion molecule gene variants and plasma protein levels in patients with suspected obstructive sleep apnea

Study objectives

Untreated obstructive sleep apnea (OSA) patients have an increased risk of cardiovascular disease (CVD). Adhesion molecules, including soluble E-selectin (sE-selectin), intercellular adhesion molecule-1 (ICAM-1), and vascular adhesion molecule-1 (VCAM-1), are associated with incident CVD. We hypothesized that specific genetic variants will be associated with plasma levels of adhesion molecules in suspected OSA patients. We also hypothesized that there may be an interaction between these variants and OSA.

Methods

We measured levels of sE-selectin, sICAM-1 and sVCAM-1 in 491 patients with suspected OSA and genotyped them for 20 polymorphisms.

Results

The most significant association was between the ABO rs579459 polymorphism and sE-selectin levels (P = 7×10⁻²¹), with the major allele T associated with higher levels. The direction of effect and proportion of the variance in sE-selectin levels accounted for by rs579459 (16%) was consistent with estimates from non-OSA cohorts. In a multivariate regression analysis, addition of rs579459 improved the model performance in predicting sE-selectin levels. Three polymorphisms were nominally associated with sICAM-1 levels but none with sVCAM-1 levels. The combination of severe OSA and two rs579459 T alleles identified a group of patients with high sE-selectin levels; however, the increase in sE-selectin levels associated with severe OSA was greater in patients without two T alleles (P = 0.05 test for interaction).

Conclusions

These genetic polymorphisms may help to identify patients at greatest risk of incident CVD and may help in developing a more precision-based approach to OSA care.

Obstructive Sleep Apnea and Vascular Diseases

Obstructive sleep apnea (OSA) affects a large proportion of adults, and is as an independent risk factor for cerebrovascular and cardiovascular disease. The repetitive airway obstruction that characterizes OSA results in intermittent hypoxia, intrathoracic pressure swings, and sleep fragmentation, which in turn lead to sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. This review outlines the associations between OSA and vascular diseases and describes basic mechanisms that may be responsible for this association, in both the micro- and macrocirculation. It also reports on interventional studies that aim to ameliorate OSA and thereby reduce vascular disease burden. © 2016 American Physiological Society. Compr Physiol 6:1519-1528, 2016.

Adenotonsillectomy Complications: A Meta-analysis

BACKGROUND AND OBJECTIVE

Complications after adenotonsillectomy (AT) in children have been extensively studied, but differences between children with and without obstructive sleep apnea (OSA) have not been systematically reported. Our objective was to identify the most frequent complications after AT, and evaluate if differences between children with and without OSA exist.

METHODS

Several electronic databases were searched. A partial gray literature search was undertaken by using Google Scholar. Experts were consulted to identify any missing publications. Studies assessing complications after AT in otherwise healthy children were included. One author collected the required information from the selected articles. A second author crosschecked the collected information and confirmed its accuracy. Most of the selected studies collected information from medical charts.

RESULTS

A total of 1254 studies were initially identified. Only 23 articles remained after a 2-step selection process. The most frequent complication was respiratory compromise (9.4%), followed by secondary hemorrhage (2.6%). Four studies compared postoperative complications in children with and without OSA, and revealed that children with OSA have nearly 5 times more respiratory complications after AT than children without OSA (odds ratio = 4.90; 95% confidence interval: 2.38-10.10). In contrast, children with OSA are less likely to have postoperative bleeding when compared with children without OSA (odds ratio = 0.41; 95% confidence interval: 0.23-0.74).

CONCLUSIONS

The most frequent early complications after AT are respiratory compromise and secondary hemorrhage. Based on the current limited evidence, children with OSA appear to have more respiratory complications. Conversely, hemorrhage appears to be more frequent in children without OSA.

Biomarkers associated with obstructive sleep apnea: A scoping review

The overall validity of biomarkers in the diagnosis of obstructive sleep apnea (OSA) remains unclear. We conducted a scoping review to provide assessments of biomarkers characteristics in the context of obstructive sleep apnea (OSA) and to identify gaps in the literature. A scoping review of studies in humans without age restriction that evaluated the potential diagnostic value of biological markers (blood, exhaled breath condensate, salivary, and urinary) in the OSA diagnosis was undertaken. Retained articles were those focused on the identification of biomarkers in subjects with OSA, the latter being confirmed with a full overnight or home-based polysomnography (PSG). Search strategies for six different databases were developed. The methodology of selected studies was classified using an adaptation of the evidence quality criteria from the American Academy of Pediatrics. Additionally the biomarkers were classified according to their potential clinical application. We identified 572 relevant studies, of which 117 met the inclusion criteria. Eighty-two studies were conducted in adults, 34 studies involved children, and one study had a sample composed of both adults and children. Most of the studies evaluated blood biomarkers. Potential diagnostic biomarkers were found in nine pediatric studies and in 58 adults studies. Only nine studies reported sensitivity and specificity, which varied substantially from 43% to 100%, and from 45% to 100%, respectively. Studies in adults have focused on the investigation of IL-6, TNF-α and hsCRP. There was no specific biomarker that was tested by a majority of authors in pediatric studies, and combinatorial urine biomarker approaches have shown preliminary promising results. In adults IL-6 and IL-10 seem to have a favorable potential to become a good biomarker to identify OSA.

Reduction in oxidative stress biomarkers after adenotonsillectomy

OBJECTIVES

A number of otolaryngic conditions such as chronic tonsillitis, adenoid hypertrophy, and obstructive sleep apnea are associated with oxidative stress and elevated levels of serum oxidants. The objective of this study is to measure changes in urine biomarkers of oxidative stress in children after adenotonsillectomy.

METHODS

Twenty-two children with sleep disordered breathing (SDB) with tonsil and adenoid hypertrophy were enrolled prior to adenotonsillectomy. Controls consisted of 20 healthy children. Urine samples were collected from all patients. Levels of three urinary biomarkers for oxidative status, 8-hydroxy-2-deoxyguanosine (8-OxodG), F(2)-isoprostane, and malondialdehyde (MDA) were measured using high performance liquid chromatography. For the study group, urine samples were repeated 3 weeks after surgery.

RESULTS

In the study group, preoperative urinary levels of 8-OxodG were higher than in controls (p=0.015). Levels decreased after surgery compared to preoperative levels (p=0.002), and reached control levels (p=0.167) at 3 weeks. Levels of urinary F(2)-isoprostane were similar in both groups (p=0.252), but decreased significantly after surgery (p=0.020).

CONCLUSIONS

Children with SDB have elevated levels of urinary 8-OxodG, a marker of oxidative stress. Adenotonsillectomy results in decreased 8-OxodG and F(2)-isoprostane. These findings suggest that urine analysis may represent a valuable tool for the measurement of oxidative stress.

Diagnostic capability of biological markers in assessment of obstructive sleep apnea: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review is to evaluate the diagnostic value of biological markers (exhaled breath condensate, blood, salivary and urinary) in the diagnosis of OSA in comparison to the gold standard of nocturnal PSG.

METHODS

Studies that differentiated OSA from controls based on PSG results, without age restriction, were eligible for inclusion. The sample of selected studies could include studies in obese patients and with known cardiac disease. A detailed individual search strategy for each of the following bibliographic databases was developed: Cochrane, EMBASE, MEDLINE, PubMed, and LILACS. The references cited in these articles were also crosschecked and a partial grey literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies.

RESULTS

After a two-step selection process, nine articles were identified and subjected to qualitative and quantitative analyses. Among them, only one study conducted in children and one in adults found biomarkers that exhibit sufficiently satisfactory diagnostic accuracy that enables application as a diagnostic method for OSA.

CONCLUSION

Kallikrein-1, uromodulin, urocotin-3, and orosomucoid-1 when combined have enough accuracy to be an OSA diagnostic test in children. IL-6 and IL-10 plasma levels have potential to be good biomarkers in identifying or excluding the presence of OSA in adults.

Association between obstructive sleep apnea and deep vein thrombosis / pulmonary embolism: a population-based retrospective cohort study

BACKGROUND

Obstructive sleep apnea (OSA) is a major contributor to cardiovascular disease, and may cause severe morbidity and mortality. Recent studies have indicated that OSA patients exhibited elevated platelet activity, fibrinogen levels, and platelet aggregation.

OBJECTIVES

We investigated the risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) in patients diagnosed with OSA compared with age- and sex-matched unaffected people.

PATIENTS/METHODS

This longitudinal, nationwide, population-based cohort study was conducted using data from Taiwan National Health Insurance Research Database (NHIRD) recorded between January 2000 and December 2011. The study consisted of 3511 patients with OSA and 35110 matched comparison individuals. A Cox proportional hazard regression was used to compute the risk of DVT and PE in patients with OSA compared with those without OSA.

RESULTS

The DVT and PE risks were 3.50- and 3.97-fold higher (95% CI=1.83-6.69 and 1.85-8.51) respectively, in the OSA cohort than in the reference cohort after we adjusted for age, sex, and comorbidities.

CONCLUSION

This nationwide population-based cohort study indicates that patients with OSA exhibit a higher risk of subsequent DVT and PE.

Association between obstructive sleep apnea severity and endothelial dysfunction in an increased background of cardiovascular burden

The objective of this study is to examine whether increasing obstructive sleep apnea (OSA) severity is associated with worsening endothelial function. The design is a cross-sectional examination of the baseline assessment of a multi-centre randomized controlled clinical trial examining the effects of oxygen, continuous positive airway pressure (CPAP) therapy or lifestyle modifications on cardiovascular biomarkers. Participants were recruited from cardiology clinics at four sites. Participants with an apnea-hypopnea index (AHI) of 15-50 and known cardio/cerebrovascular disease (CVD) or CVD risk factors were included. OSA severity indices [oxygen desaturation index (ODI), AHI and percentage of sleep time below 90% oxygen saturation (total sleep time <90)] and a measure of endothelium-mediated vasodilatation [Framingham reactive hyperaemia index (F-RHI) derived from peripheral arterial tonometry (PAT)] were assessed. The sample included 267 individuals with a mean AHI of 25.0 ± 8.5 SD and mean F-RHI 0.44 ± 0.38. In adjusted models, the slope of the relationship between ODI and F-RHI differed above and below an ODI of 24.6 (P = 0.04), such that above an ODI of 24.6 there was a marginally significant decline in the geometric mean of the PAT ratio by 3% [95% confidence interval (CI): 0%, 5%; P = 0.05], while below this point, there was a marginally significant incline in the geometric mean of the PAT ratio by 13% (95% CI: 0%, 27%; P = 0.05) per 5-unit increase in ODI. A similar pattern was observed between AHI and F-RHI. No relation was noted with total sleep time <90 and F-RHI. There was evidence of a graded decline in endothelial function in association with higher levels of intermittent hypoxaemia.

Molecular biomarkers of vascular dysfunction in obstructive sleep apnea

Untreated and long-lasting obstructive sleep apnea (OSA) may lead to important vascular abnormalities, including endothelial cell (EC) dysfunction, hypertension, and atherosclerosis. We observed a correlation between microcirculatory reactivity and endothelium-dependent release of nitric oxide in OSA patients. Therefore, we hypothesized that OSA affects (micro)vasculature and we aimed to identify vascular gene targets of OSA that could possibly serve as reliable biomarkers of severity of the disease and possibly of vascular risk. Using quantitative RT-PCR, we evaluated gene expression in skin biopsies of OSA patients, mouse aortas from animals exposed to 4-week intermittent hypoxia (IH; rapid oscillations in oxygen desaturation and reoxygenation), and human dermal microvascular (HMVEC) and coronary artery endothelial cells (HCAEC) cultured under IH. We demonstrate a significant upregulation of endothelial nitric oxide synthase (eNOS), tumor necrosis factor-alpha-induced protein 3 (TNFAIP3; A20), hypoxia-inducible factor 1 alpha (HIF-1α?? and vascular endothelial growth factor (VEGF) expression in skin biopsies obtained from OSA patients with severe nocturnal hypoxemia (nadir saturated oxygen levels [SaO2]<75%) compared to mildly hypoxemic OSA patients (SaO2 75%-90%) and a significant upregulation of vascular cell adhesion molecule 1 (VCAM-1) expression compared to control subjects. Gene expression profile in aortas of mice exposed to IH demonstrated a significant upregulation of eNOS and VEGF. In an in vitro model of OSA, IH increased expression of A20 and decreased eNOS and HIF-1α expression in HMVEC, while increased A20, VCAM-1 and HIF-1αexpression in HCAEC, indicating that EC in culture originating from distinct vascular beds respond differently to IH stress. We conclude that gene expression profiles in skin of OSA patients may correlate with disease severity and, if validated by further studies, could possibly predict vascular risk in OSA patients.

Influence of obstructive sleep apnea on serum butyrylcholinesterase activity and ischemia-modified albumin levels

OBJECTIVE

To investigate the effect of obstructive sleep apnea and continuous positive airway pressure treatment on serum butyrylcholinesterase activity and ischemia-modified albumin levels.

METHODS

Thirty-two patients with obstructive sleep apnea and 30 age- and sex-matched controls were enrolled and underwent a diagnostic polysomnogram. The serum butyrylcholinesterase activity, ischemia-modified albumin levels, metabolic parameters, and polysomnography scores were detected and evaluated. Nine patients were studied before and after treatment with continuous positive airway pressure.

RESULTS

The serum ischemia-modified albumin levels were significantly higher and the butyrylcholinesterase activity was significantly lower in patients with obstructive sleep apnea than in the controls (p<0.001). The continuous positive airway pressure treatment decreased the modified albumin levels and elevated the buthrylcholinesterase activity (p=0.019 and p=0.023, respectively). The modified albumin levels were positively correlated with the apnea-hypopnea index (r=0.462, p=0.008) at baseline. Elevated ischemia-modified albumin levels can be more accurate than butyrylcholinesterase activity at reflecting the presence of obstructive sleep apnea. Receiver operating characteristic curves revealed a significant difference between the areas under the curve 0.916 for ischemia-modified albumin and 0.777 for butyrylcholinesterase (z=2.154, p=0.031).

CONCLUSION

The elevated ischemia-modified albumin level was significantly associated with obstructive sleep apnea and was more sensitive than butyrylcholinesterase activity in reflecting obstructive sleep apnea. The continuous positive airway pressure treatment helped to ameliorate the imbalance.