Evaluation of MIh Scoring System in Diagnosis of Obstructive Sleep Apnea Syndrome

Predictors and markers of the cardiovascular impact of obstructive sleep apnoea

PURPOSE OF REVIEW

Obstructive sleep apnoea (OSA) is the most common form of sleep-disordered breathing and has been linked to cardiovascular health. However, some of the findings supporting this are controversial. These discrepancies might be a result of heterogeneity among OSA patients, and thus, additional information would be required to better stratify OSA patients according to cardiovascular risk. In this review, we aim to discuss the potential of biomarkers to fulfil this role.

RECENT FINDINGS

Randomized controlled trials have been unable to confirm whether OSA treatment with continuous positive airway pressure (CPAP) has a positive effect on cardiovascular outcomes. Emerging physiology-based metrics of OSA seem to be more suitable for identifying patients at higher risk of cardiovascular disease and predicting the effects of CPAP outcomes on cardiovascular health. Similarly, blood-based molecular markers have gained attention in this context over the last few years.

SUMMARY

Accurate cardiovascular risk stratification and appropriate treatment allocation for OSA patients remain challenging. However, significant efforts are being made to develop novel tools to address these important issues.

The effects of disease severity and comorbidity on oxidative stress biomarkers in obstructive sleep apnea

PURPOSE

Ischemia-modified albumin (IMA), total oxidant status (TOS), and total antioxidant status (TAS) are biomarkers used to evaluate oxidative stress status in various diseases including obstructive sleep apnea (OSA). In this study, we investigated the effects of disease severity and comorbidity on IMA, TOS and TAS levels in OSA.

METHODS

Patients with severe OSA (no-comorbidity, one comorbidity, and multiple comorbidities) and mild-moderate OSA (no-comorbidity, one and multiple comorbidities), and healthy controls were included in the study. Polysomnography was applied to all cases and blood samples were taken from each participant at the same time of day. ELISA was used to measure IMA levels in serum samples and colorimetric commercial kits were used to perform TOS and TAS analyses. In addition, routine biochemical analyses were performed on all serum samples.

RESULTS

A total of 74 patients and 14 healthy controls were enrolled. There was no statistically significant difference between the disease groups according to gender, smoking status, age, body mass index (BMI), HDL, T3, T4, TSH, and B12 (p > 0.05). As the severity of OSA and comorbidities increased, IMA, TOS, apnea-hypopnea index (AHI), desaturation index (T90), cholesterol, LDL, triglyceride, AST, and CRP values increased significantly (p < 0.05). On the other hand, TAS, minimum desaturation, and mean desaturation values decreased significantly (p < 0.05).

CONCLUSIONS

We concluded that IMA, TOS, and TAS levels may indicate OSA-related oxidative stress, but as the severity of OSA increases and with the presence of comorbidity, IMA and TOS levels may increase and TAS levels decrease. These findings suggest that disease severity and presence/absence of comorbidity should be considered in studies on OSA.

Identification of novel proteins for sleep apnea by integrating genome-wide association data and human brain proteomes

BACKGROUND

Sleep apnea is regarded as a significant global public health issue. The relationship between sleep apnea and nervous system diseases is intricate, yet the precise mechanism remains unclear.

METHODS

In this study, we conducted a comprehensive analysis integrating the human brain proteome and transcriptome with sleep apnea genome-wide association study (GWAS), employing genome-wide association study (PWAS), transcriptome-wide association study (TWAS), Mendelian randomization (MR), and colocalization analysis to identify brain proteins associated with sleep apnea.

RESULTS

The discovery PWAS identified six genes (CNNM2, XRCC6, C3orf18, CSDC2, SQRDL, and DGUOK) whose altered protein abundances in the brain were found to be associated with sleep apnea. The independent confirmatory PWAS successfully replicated four out of these six genes (CNNM2, C3orf18, CSDC2, and SQRDL). The transcriptome level TWAS analysis further confirmed two out of the four genes (C3orf18 and CSDC2). The subsequent two-sample Mendelian randomization provided compelling causal evidence supporting the association of C3orf18, CSDC2, CNNM2, and SQRDL with sleep apnea. The co-localization analysis further supported the association between CSDC2 and sleep apnea (posterior probability of hypothesis 4 = 0.75).

CONCLUSIONS

In summary, the integration of brain proteomic and transcriptomic data provided multifaceted evidence supporting causal relationships between four specific brain proteins (CSDC2, C3orf18, CNNM2, and SQRDL) and sleep apnea. Our findings provide new insights into the molecular basis of sleep apnea in the brain, promising to advance understanding of its pathogenesis in future research.

Analysis of the Ischemia-Modified Albumin as a Potential Biomarker for Cardiovascular Damage in Obstructive Sleep Apnea Patients with Acute Coronary Syndrome

Obstructive sleep apnea (OSA) has been identified as a cardiovascular (CV) risk factor. The potential of OSA promoting the synthesis of CV biomarkers in acute coronary syndrome (ACS) is unknown. Ischemia-modified albumin (IMA) has been identified as a specific CV biomarker. The aim of this study was to evaluate the role of IMA as a potential biomarker for determining the impact of OSA in ACS patients. A total of 925 patients (15.5% women, age: 59 years, body mass index: 28.8 kg/m²) from the ISAACC study (NCT01335087) were included. During hospitalization for ACS, a sleep study for OSA diagnosis was performed and blood samples extraction for IMA determination were obtained. IMA values were significantly higher in severe OSA (median (IQR), 33.7 (17.2-60.3) U/L) and moderate (32.8 (16.9-58.8) U/L) than in mild/no OSA (27.7 (11.8-48.6) U/L) (p = 0.002). IMA levels were very weakly related to apnea-hypopnea index (AHI) as well as hospital and intensive care unit stay, although they only maintained a significant relationship with days of hospital stay after adjusting for sex, age and BMI (ß = 0.410, p = 0.013). The results of the present study would suggest a potentially weaker role of OSA in the synthesis of the CV risk biomarker IMA in patients with ACS than in primary prevention.

Serum Magnesium Levels in Patients with Obstructive Sleep Apnoea: A Systematic Review and Meta-Analysis

Aims: Obstructive sleep apnoea (OSA) affects patients’ quality of life and health. Magnesium (Mg) is an essential mineral and a potent antioxidant. Mg deficiency can worsen oxidative stress caused by sleep deprivation or disorders. The impact of OSA on serum Mg levels and its health consequences remain unclear. Data Synthesis: This study systematically reviewed clinical studies investigating the serum Mg levels of OSA patients and the potential relationships with other biomarkers. Six articles were included for qualitative synthesis and quantitative analysis. Two out of four studies that compared OSA patients to healthy controls found them to have significantly lower serum Mg levels. Our meta-analysis with three studies shows that patients with OSA had significantly lower serum Mg with an effect size of −1.22 (95% CI: −2.24, −0.21). However, the mean serum Mg level of OSA patients (n = 251) pooled from five studies (1.90 mg/dL, 95% CI: 1.77, 2.04) does not differ significantly from the normal range between 1.82 to 2.30 mg/dL. OSA severity appears to affect serum Mg negatively. Serum Mg levels generally improve after treatment, coinciding with the improvement of OSA severity. Low serum Mg levels correlate with the worsening of cardiovascular risk biomarkers of C-reactive protein, ischaemia-modified albumin, and carotid intima-media thickness. The serum Mg levels also potentially correlate with biomarkers for lipid profile, glucose metabolism, calcium, and heavy metals. Conclusions: Sleep deprivation appears to deplete Mg levels of OSA patients, making them at risk of Mg deficiency, which potentially increases systemic inflammation and the risk of cardiovascular and metabolic diseases.

Evaluation of Blood Levels of C-Reactive Protein Marker in Obstructive Sleep Apnea: A Systematic Review, Meta-Analysis and Meta-Regression

(1) Introduction: High sensitivity C-reactive protein (hs-CRP) and CRP are inflammatory biomarkers associated with several inflammatory diseases. In both pediatric and adult individuals with Obstructive Sleep Apnea (OSA) higher hs-CRP and CRP were observed, compared to controls. With the present systematic review, meta-analysis and meta-regression we expand upon previous meta-analyses in four ways: (1) We included 109 studies (96 in adults and 13 in children); (2) we reported subgroup and meta-regression analyses in adults with OSA compared to controls on the serum and plasma levels of hs-CRP; (3) we reported subgroup and meta-regression analyses in adults with OSA compared to controls on the serum and plasma levels of CRP; (4) we reported serum and plasma levels of both hs-CRP and CRP in children with OSA, always compared to controls. (2) Materials and Methods: The PubMed/Medline, Scopus, Cochrane Library, and Web of Science databases were searched to retrieve articles published until 31 May 2020, with no restrictions. The data included basic information involving the first author, publication year, country of study, ethnicity of participants in each study, age, BMI, and AHI of both groups, and mean and standard deviation (SD) of plasma and serum levels of CRP and hs-CRP. (3) Results: A total of 1046 records were retrieved from the databases, and 109 studies were selected for the analysis (96 studies reporting the blood levels of hs-CRP/CRP in adults and 13 studies in children). For adults, 11 studies reported plasma hs-CRP, 44 serum hs-CRP, 9 plasma CRP, and 32 serum CRP levels. For children, 6 studies reported plasma hs-CRP, 4 serum hs-CRP, 1 plasma CRP, and 2 serum CRP levels. Compared to controls, the pooled MD of plasma hs-CRP levels in adults with OSA was 0.11 mg/dL (p < 0.00001). Compared to controls, the pooled MD of serum hs-CRP levels in adults with OSA was 0.09 mg/dL (p < 0.00001). Compared to controls, the pooled MD of plasma CRP levels in adults with OSA was 0.06 mg/dL (p = 0.72). Compared to controls, the pooled MD of serum CRP levels in adults with OSA was 0.36 mg/dL (p < 0.00001). Compared to controls, the pooled MD of plasma hs-CRP, serum hs-CRP, plasma hs-CRP, and serum hs-CRP in children with OSA was 1.17 mg/dL (p = 0.005), 0.18 mg/dL (p = 0.05), 0.08 mg/dL (p = 0.10), and 0.04 mg/dL (p = 0.33), respectively. The meta-regression showed that with a greater apnea-hypapnea index (AHI), serum hs-CRP levels were significantly higher. (4) Conclusions: The results of the present systematic review, meta-analysis and meta-regression showed that compared to healthy controls plasma and serum levels of hs-CRP and serum CRP level were higher in adults with OSA; for children, and compared to controls, just plasma hs-CRP levels in children with OSA were higher.

Astragaloside IV ameliorates intermittent hypoxia-induced inflammatory dysfunction by suppressing MAPK/NF-κB signalling pathways in Beas-2B cells

PURPOSE

Intermittent hypoxia is a characteristic pathological change in obstructive sleep apnoea (OSA) that can initiate oxidative stress reaction and pro-inflammatory cytokine release. The purpose of this study was to assess the effect and protective mechanism of Astragaloside IV (AS-IV) in intermittent hypoxia-induced human lung epithelial Beas-2B cells.

METHODS

Human lung epithelial Beas-2B cells were exposed to intermittent hypoxia or normoxia in the absence or presence of AS-IV. MTT assay was performed to determine the cell viability. The levels of reactive oxygen species (ROS), lactate dehydrogenase (LDH), malonaldehyde (MDA), and superoxide dismutase (SOD) were measured to evaluate oxidative stress. The levels of cytokines interleukin (IL)-8, IL-1β, and IL-6 were evaluated by enzyme-linked immunosorbent assay and real-time PCR. The expression of Toll-like receptor 4 (TLR4), mitogen-activated protein kinase (MAPK), and nuclear transcription factor-kappa B (NF-κB) signalling pathways was analysed by western blot.

RESULTS

The results showed that AS-IV significantly reduced the levels of ROS, LDH, MDA, IL-8, IL-1β, and IL-6, and increased the level of SOD in intermittent hypoxia-induced Beas-2B cells. It also suppressed the phosphorylation of MAPKs, including P38, c-Jun N-terminal kinase and extracellular signal-regulated kinase, and inhibited the activation of the NF-κB signalling pathway by reducing the phosphorylation of IκBα and p65.

CONCLUSIONS

AS-IV attenuates inflammation and oxidative stress by inhibiting TLR4-mediated MAPK/NF-κB signalling pathways in intermittent hypoxia-induced Beas-2B cells.

Does ischemia-modified albumin level predict severity of obstructive sleep apnea?

OBJECTIVE AND AIM

Ischemia-modified albumin (IMA) is a newly recognized marker of chronic inflammation used to evaluate oxidative stress status in patients with various diseases. We explored the possible relationship between IMA levels and obstructive sleep apnea (OSA).

METHODS

In this retrospective study, 169 of 216 sequential patients being evaluated for suspicion of OSAS met inclusion criteria. Polysomnography confirmed OSA in 86 patients (51%) while 81 patients (49%) without OSA were categorized as control subjects. All study participants were tested for blood IMA level, neutrophil/lymphocyte ratio (NLR), C-reactive protein (CRP) level, and red blood cell distribution width (RDW).

RESULTS

The serum IMA level was significantly higher in patients with OSAS than controls (p = 0.008). The serum IMA level increased significantly as OSAS severity increased (r = 0.50, p < 0.001) and was positively correlated with the AHI (r = 0.41, p < 0.001), CRP level (r = 0.31, p = 0.004), body mass index (r = 0.24, p = 0.022), RDW (r = 0.31, p = 0.03), oxygen desaturation index (ODI) (r = 0.22, p = 0.02), and negatively correlated with the hemoglobin concentration (r = - 0.28, p = 0.04) and minimum hemoglobin oxygen saturation (SpO2) (r = - 0.25, p = 0.02). Receiver operator curve (ROC) analysis showed that the optimal serum IMA, CRP, RDW, and NLR values were not different for predicting OSAS diagnosis (areas under the curves (AUC) = 0.62, 0.59, 0.60, and 0.43, respectively). However, the serum IMA level was superior in reflecting OSAS severity (AUC = 0.78) compared to CRP, RDW, and NLR values (AUC = 0.61, 0.53, and 0.51, respectively) (all p < 0.001).

CONCLUSION

Like other markers of inflammation, blood IMA levels were significantly elevated in patients with OSA. However, blood IMA level was a better predictor of disease severity than the other markers.

Toll-Like Receptor 4 (TLR-4) Pathway Promotes Pulmonary Inflammation in Chronic Intermittent Hypoxia-Induced Obstructive Sleep Apnea

Background

Studies have shown that intermittent hypoxia mimics obstructive sleep apnea in causing pulmonary inflammation, but the mechanism is not yet clear.TLR-4 is a recognized proinflammatory factor, so the purpose of this study was to assess the function of TLR-4 in pulmonary inflammation induced by chronic intermittent hypoxia simulating obstructive sleep apnea.

Material/Methods

Healthy male Wistar rats were divided into 3 groups (8 in each group): the normoxia control group (CG), the intermittent hypoxia group (IH), and the TLR4 antagonist TAK242 treatment group (3 mg/kg, daily), with exposure durations of 12 weeks and 16 weeks (HI). The morphological changes of lung tissue were determined with hematoxylin-eosin (HE) staining. The expressions of the TLR-4 pathway in lung tissue were tested by Western blotting and RT-PCR. The levels of IL-6 and TNF-α in serum and lung tissue were detected by enzyme-linked immunosorbent assay (ELISA). The levels of SOD and MDA in lung tissue were detected by use of SOD and MDA kits, respectively.

Results

After TAK242 treatment, damage to lung tissue was increased, and the expressions of TLR-4, MYD88, P65, IL-6, TNF-α, MDA, and SOD were decreased. Intermittent hypoxic exposure caused alveolar expansion, thickening of alveolar septum, and fusion of adjacent alveoli into larger cysts under intermittent hypoxia in a time-dependent manner. Compared with the CG and HI groups, the mean lining interval (MLI) become more thickened and the alveolar destruction index (DI) increased significantly in the IH group.

Conclusions

Chronic intermittent hypoxia causes pulmonary inflammatory response and the inflammatory pathway involved in TLR4 receptor may be one of the mechanisms that trigger lung inflammation.

Ischemia-modified albumin: Crosstalk between fatty acid and cobalt binding

Myocardial ischemia is difficult to diagnose effectively with still few well-defined biochemical markers for identification in advance, or in the absence of myocardial necrosis. "Ischemia-modified albumin" (IMA), a form of albumin displaying reduced cobalt-binding affinity, is significantly elevated in ischemic patients, and the albumin cobalt-binding (ACB) assay can measure its level indirectly. Elucidating the molecular mechanism underlying the identity of IMA and the ACB assay hinges on understanding metal-binding properties of albumin. Albumin binds most metal ions and harbours four primary metal binding sites: site A, site B, the N-terminal site (NTS), and the free thiol at Cys34. Previous efforts to clarify the identity of IMA and the causes for its reduced cobalt-binding capacity were focused on the NTS site, but the degree of N-terminal modification could not be correlated to the presence of ischemia. More recent work suggested that Co2+ ions as used in the ACB assay bind preferentially to site B, then to site A, and finally to the NTS. This insight paved the way for a new consistent molecular basis of the ACB assay: albumin is also the main plasma carrier for free fatty acids (FFAs), and binding of a fatty acid to the high-affinity site FA2 results in conformational changes in albumin which prevent metal binding at site A and partially at site B. Thus, this review advances the hypothesis that high IMA levels in myocardial ischemia and many other conditions originate from high plasma FFA levels hampering the binding of Co2+ to sites A and/or B. This is supported by biophysical studies and the co-association of a range of pathological conditions with positive ACB assays and high plasma FFA levels.