Biomarkers to improve diagnosis and monitoring of obstructive sleep apnea syndrome: current status and future perspectives

Sex-specific differences in overnight nitrate levels in persons with obstructive sleep apnea and type 2 diabetes

STUDY OBJECTIVES

Sex-specific differences in OSA-associated symptoms and polysomnographic findings are well recognized. However, sex differences in intermediate pathways potentially linking OSA and cardiometabolic outcomes are limited. OSA is known to be associated with decreased nitric oxide (NO)-related vasodilation and endothelial dysfunction. The current study sought to characterize the independent association between OSA severity and overnight NO metabolites (i.e. markers of oxidative stress) and determine if there were differences by sex in persons with type 2 diabetes mellitus (T2DM).

METHODS

Adults with T2DM and undiagnosed OSA were recruited from the community. Demographic information, an overnight polysomnogram, and pre- and post-sleep plasma samples were collected. The association between OSA and nitrite and nitrate levels were examined using multivariable linear regression. Analyses were done for the entire sample and stratified by sex.

RESULTS

The sample included 83 participants with 52 % men. Stratified, fully adjusted models showed that compared to women with mild OSA, women with moderate or severe OSA did not exhibit the expected decline in overnight nitrate levels: 4.84 μM (-12.3, 2.7: p = 0.09) and 5.82 μM (-4.7, 16.3: p < 0.01) for moderate and severe OSA, respectively. Overnight nitrate levels decreased in males regardless of OSA severity, without significant differences across severity categories. An interaction between OSA severity and sex was seen for post-sleep nitrates in women with severe OSA.

CONCLUSION

The association between OSA and overnight nitrates varies by sex and OSA severity. Women with severe OSA did not have a decline in overnight nitrate levels whereas men did, suggesting they have higher overnight oxidative stress.

Integrative analysis of candidate MicroRNAs and gene targets for OSA management using in silico and in-vitro approach

MicroRNAs (miRNAs) have been implicated in the pathogenesis of human diseases including sleep disorders. The aim of this study is to address the involvement of miRNAs (miR-21 and miR-29) in the pathophysiology of obstructive sleep apnea (OSA). In this study we have done integrated analysis of miRNAs with their potential gene targets as a strategy for management of OSA.

Methods

miRNA expression levels were quantified in healthy control group and obese vs. Non-obese OSA subjects by Quantitative real-time PCR. In-silico analysis of interplay of miRNAs with potential gene targets was done using Schrödinger Release 2023-1.

Results

The real time expression analysis revealed a differential expression pattern in miRNAs indicating down-regulation of miR-21 in obese OSA while miR-29 showed upregulation as compared to non-obese OSA and healthy subjects with p values of ≤0.01 and <0.0001respectively. A trend was observed where target genes TGFBR2, NAMPT, and NPPB were significantly increased with p-value of ≤0.0001 and TGFBR3 and INSIG2 showed decreasing trend with p-value of ≤0.0001 between obese and non-obese OSA respectively. MD simulation analysis provided valuable information regarding the stability, flexibility, compactness and solvent exposure of the complexes over time.

Conclusion

miR-21 and miR-29 possesses differential expressions in obese OSA subject and exihbits strong molecular interactions with potential target genes, such as TGFBR2, NPPB, NAMPT and INSIG2. Identifying the miRNAs, genes and pathways associated with OSA can help to expand our understanding of the risk factors for the disease as well as provide new avenues for potential treatment.

Oxidative Stress in the Pathogenesis of Oral Cancer

Oxidative stress, arising from an imbalance between reactive oxygen species (ROS) and antioxidants, contributes significantly to oral cancer such as oral squamous cell carcinoma (OSCC) initiation, promotion, and progression. ROS, generated both internally and externally, induce cellular damage including DNA mutations and lipid peroxidation, fostering oncogene activation and carcinogenesis. The objective of this review was to cover and analyze the interplay between ROS and antioxidants, influencing the key processes such as cell proliferation, apoptosis, and angiogenesis, shaping the trajectory of OSCC development. Despite the promise of antioxidants to halt cancer progression and mitigate oxidative damage, their therapeutic efficacy remains debated. The conducted literature search highlighted potential biomarkers that indicate levels of oxidative stress, showing promise for the early detection and monitoring of OSCC. Furthermore, melatonin has emerged as a promising adjunct therapy for OSCC, exerting antioxidant and oncostatic effects by modulating tumor-associated neutrophils and inhibiting cancer cell survival and migration. In addition, this review aims to shed light on developing personalized therapeutic strategies for patients with OSCC such as melatonin therapy, which will be discussed. Research is needed to elucidate the underlying mechanisms and clinical implications of oxidative stress modulation in the context of oral cancer.

Impact of Intermittent Hypoxia Related to Obstructive Sleep Apnoea Syndrome on Low-Grade Inflammation in Hypertensive Patients: Potential Implications for Cardiovascular Risk

There is evidence for a particular relationship between low-grade inflammation (LGI) and intermittent hypoxia (IH) related to obstructive sleep apnoea syndrome (OSAS). However, despite the potential deleterious cardiovascular consequences associated with this LGI in hypertensive patients, few studies have investigated the impact of IH related to OSAS on CRP levels in this subpopulation. In total, 1404 hypertensive patients were selected retrospectively from the Sleep Laboratory database. CRP levels ≥3 mg/L but <10 mg/L were used as cut-offs to identify hypertensive patients with LGI. Logistic regressions were conducted to examine the risk of LGI associated with IH related to OSAS in hypertensive patients. LGI was frequent (33.8%) in hypertensive patients. After adjustment for confounders, multivariate logistic regressions revealed that only moderate to severe OSAS (apnoea-hypopnoea index ≥ 15/h) with high IH (oxygen desaturation index ≥ 15/h) [OR 1.51 (95% CI 1.06-2.14)] was significantly associated with LGI in hypertensive patients (p-value = 0.045). Consistent with our hypothesis, our results demonstrated the existence of a particular subtype of hypertensive patients at high cardiovascular risk characterised by the presence of LGI induced by IH hypoxia related to moderate to severe OSAS, which justifies the establishment of adequate management of this pathology to allow better cardiovascular prevention in this subpopulation.

A Systematic Review and Meta-Analysis of Mean Platelet Volume and Platelet Distribution Width in Patients with Obstructive Sleep Apnoea Syndrome

Obstructive sleep apnoea syndrome (OSAS) is a highly prevalent yet underestimated disorder caused by the complete or partial obstruction of the upper airways. Although polysomnography is the gold standard for OSAS diagnosis, there is an active search for easily accessible biomarkers of disease presence and severity, particularly those reflecting morphological changes in specific blood cells. We investigated the associations between the presence and severity of OSAS, continuous positive airway pressure (CPAP) treatment, mean platelet volume (MPV), and platelet distribution width (PDW), routinely assessed as part of the complete blood count. From 262 retrieved records from PubMed, the Web of Science, Scopus, and Google Scholar, 31 manuscripts were selected for a final analysis, 30 investigating MPV and 15 investigating PDW. MPV was not statistically different between OSAS patients and healthy controls; however, it progressively increased with disease severity. By contrast, OSAS patients had significantly higher PDW values than controls (SMD = 0.40, 95% CI: 0.25 to 0.56; p ˂ 0.001), and the difference increased with disease severity. In a univariate meta-regression, there were significant associations between the MPV and publication year, the apnoea-hypopnea index, and diabetes mellitus, while no associations were observed with the PDW. No significant between-group differences were observed in the subgroup analyses. These data suggest that PDW, and to a lesser extent, MPV, are potential biomarkers of OSAS and require further research to ascertain their pathophysiological significance (PROSPERO, CRD42023459413).

Salivary biomarker C-reactive protein levels in children with sleep problems and Class II malocclusion before and after twin-block therapy

Context

Disturbances in sleep affects the overall quality of a child's life, with several short- and long-lasting consequences. Hence, early diagnosis and monitoring is crucial in the management of sleep disorders in children.

Aims

The aim of this study was to evaluate salivary C-reactive protein (CRP) levels in a group of children with Class II malocclusion and sleep problems before and after twin-block appliance therapy.

Settings and Design

The study was a prospective clinical study with a 9-month follow-up period.

Subjects and Methods

Eleven children aged 8-12 years with skeletal Class II malocclusion and at least one sleep disorder were enrolled in the study. All children were subjected to a recording of their sleep history and a clinical as well as radiographic examination. Pretreatment levels of salivary CRP were recorded. A twin-block appliance was custom made and delivered to every child. At the end of 9-month follow-up, all children were recalled for a re-evaluation of salivary biomarker levels.

Statistical Analysis

Pretreatment and posttreatment changes in biomarker levels were assessed statistically using the students paired t-test.

Results

Levels of salivary biomarker CRP were significantly decreased in children following myofunctional therapy using a twin-block appliance (P < 0.001). There was a considerable improvement in the clinical symptoms such as a decrease in snoring and noisy breathing in most children post-twin-block therapy.

Conclusion

The measurement of salivary biomarker CRP could be used as an alternative and noninvasive method to evaluate prognosis of oral myofunctional therapy for children with sleep disordered breathing.

Autoantibodies of inflammatory cytokines as serum biomarkers in OSA patients

As many as 90% of patients with obstructive sleep apnea (OSA) may be undiagnosed. It is necessary to explore the potential value of autoantibodies against CRP, IL-6, IL-8 and TNF-α in the diagnosis of OSA. ELISA was performed to detect the level of autoantibodies against CRP, IL-6, IL-8 and TNF-α in sera from 264 OSA patients and 231 normal controls (NCs). The expression level of autoantibodies against CRP, IL-6 and IL-8 in OSA were significantly higher than that in NC while the level of anti-TNF-α was lower in OSA than that in NC. The per SD increment of anti-CRP, anti-IL-6 and anti-IL-8 autoantibodies were significantly associated with a 430%, 100% and 31% higher risk for OSA, respectively. The AUC of anti-CRP was 0.808 (95% CI: 0.771-0.845) when comparing OSA with NC, while the AUC increased to 0.876 (95% CI: 0.846-0.906) combining four autoantibodies. For discrimination of severe OSA versus NC and non-severe OSA versus NC, the AUC for four autoantibodies combination was 0.885 (95% CI: 0.851-0.918) and 0.876 (95% CI: 0.842-0.913). This study revealed the association between autoantibodies against inflammatory factors and OSA, and the combination of autoantibodies against CRP, IL-6, IL-8 and TNF-α may function as novel biomarker for monitoring the presence of OSA.

Association between Red Blood Cell Distribution Width and Obstructive Sleep Apnea Syndrome: A Systematic Review and Meta-Analysis

Although polysomnography is the gold standard method to diagnose obstructive sleep apnea syndrome (OSAS), there is an ongoing quest for simpler and relatively inexpensive biomarkers of disease presence and severity. To address this issue, we conducted a systematic review of the potential diagnostic role of the red blood cell distribution width (RDW), a routine hematological parameter of red blood cell volume variability, in OSAS. A total of 1478 articles were initially identified in the databases PubMed, Web of Science, Scopus, Embase, and Google Scholar, from their inception to February 2023, and 20 were selected for final analysis. The RDW was significantly higher in OSAS than in non-OSAS subjects (SMD = 0.44, 95% CI 0.20 to 0.67, p < 0.001; low certainty of evidence). In univariate meta-regression, the mean oxygen saturation (SpO₂) was significantly associated with the effect size. No significant between-group differences were observed in subgroup analyses. Notably, in OSAS subjects, the RDW SMD progressively increased with disease severity. In conclusion, these results suggest that the RDW is a promising biomarker of OSAS (PROSPERO registration number: CRD42023398047).

Validation of NoSAS score for the screening of obstructive sleep apnea

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder (SBD) characterized by the repetitive collapse of the upper airway during sleep. The aim of the present study was to validate the Neck circumference, Obesity, Snoring, Age, Sex (NoSAS) score in a sample population and to compare its validity for OSA screening, with that of the Berlin questionnaire, STOP-BANG questionnaire and Epworth Sleepiness Scale (ESS). A retrospective analysis was conducted on individuals, aged 18 to 80 years, who reported symptoms indicating SBD and were examined with full-night polysomnography (PSG) at a sleep center. Demographics, anthropometric parameters, comorbidities, ESS, STOP-BANG questionnaire, Berlin questionnaire and PSG data were obtained from the recorded data of the patients. The NoSAS score was determined using the recorded data. A total of 347 participants were enrolled in the study. The NoSAS scores identified individuals with OSA, with an area under the curve (AUC) of 0.774. The NoSAS score performed significantly better than the Berlin questionnaire (AUC 0.617) and the ESS (AUC 0.642), and similarly to STOP-BANG (AUC 0.777) for OSA screening. Using a NoSAS score >7 to predict OSA, the sensitivity and specificity were 85.6 and 50%, respectively; using the STOP-BANG questionnaire, for a score >2, the values were 98.32 and 22% respectively; using the Berlin questionnaire for >1 positive categories, the values were 93.6 and 20%, and using the ESS, for a score >10, the values were 30.3% and 72%, respectively. On the whole, the present study demonstrates that the NoSAS score is a simple, efficient and easy method for screening OSA in the clinical setting. The NoSAS score performs significantly more efficiently than the Berlin questionnaire and ESS, and similarly to STOP-BANG questionnaire for OSA screening.

Changes in Left Heart Geometry, Function, and Blood Serum Biomarkers in Patients with Obstructive Sleep Apnea after Treatment with Continuous Positive Airway Pressure

Background: Cardiovascular remodeling is essential in patients with obstructive sleep apnea (OSA), and continuous positive airway pressure (CPAP) therapy could improve these processes. Two-dimensional (2D) speckle-tracking (ST) echocardiography is a useful method for subclinical biventricular dysfunction diagnosis and thus might help as an earlier treatment for OSA patients. It is still not clear which blood serum biomarkers could be used to assess CPAP treatment efficacy. Objectives: To evaluate left heart geometry, function, deformation parameters, and blood serum biomarker (galectin-3, sST2, endothelin-1) levels in patients with OSA, as well as to assess changes after short-term CPAP treatment. Materials and Methods: Thirty-four patients diagnosed with moderate or severe OSA, as well as thirteen patients as a control group, were included in the study. All the subjects were obese (body mass index (BMI) > 30 kg/m2). Transthoracic 2D ST echocardiography was performed before and after 3 months of treatment with CPAP; for the control group, at baseline only. Peripheral blood samples for the testing of biomarkers were collected at the time of study enrolment before the initiation of CPAP therapy and after 3 months of CPAP treatment (blood samples were taken just for OSA group patients). Results: The left ventricle (LV) end-diastolic diameter and volume, as well as LV ejection fraction (EF), did not differ between groups, but an increased LV end-systolic volume and a reduced LV global longitudinal strain (GLS) were found in the OSA group patients (p = 0.015 and p = 0.035, respectively). Indexed by height, higher LV MMi in OSA patients (p = 0.007) and a higher prevalence of LV diastolic dysfunction (p = 0.023) were found in this group of patients. Although left atrium (LA) volume did not differ between groups, OSA group patients had significantly lower LA reservoir strain (p < 0.001). Conventional RV longitudinal and global function parameters (S′, fractional area change (FAC)) did not differ between groups; however, RV GLS was reduced in OSA patients (p = 0.026). OSA patients had a significantly higher right atrium (RA) diameter and mean pulmonary artery pressure (PAP) (p < 0.05). Galectin-3 and sST2 concentrations significantly decreased after 3 months of CPAP treatment. Conclusions: OSA is associated with the left heart remodeling process—increased LV myocardial mass index, LV diastolic dysfunction, reduced LV and RV longitudinal strain, and reduced LA reservoir function. A short-term, 3-months CPAP treatment improves LV global longitudinal strain and LA reservoir function and positively affects blood serum biomarkers. This new indexing system for LV myocardial mass by height helps to identify myocardial structural changes in obese patients with OSA.

Inflammatory Biomarkers for Children with Sleep Disorders: A Review

Introduction Obstructive sleep apnea (OSA) syndrome is a highly prevalent problem in children. Unfortunately sleep disorders in children remain largely unreported and underdiagnosed due to various reasons. Overnight in-laboratory polysomnography (PSG) is the gold standard diagnostic method for OSA; however, it has several drawbacks. Hence there is a need for simple alternative diagnostic methods, such as biomarkers. Children with OSA seem to have an inflammatory aspect to its pathophysiology; thus the rationale for evaluating inflammatory biomarkers.

Objective This narrative review aimed to evaluate the existing knowledge regarding inflammatory biomarkers for children with sleep disorders.

Materials and Methods An extensive search of all literature linked to the topic was performed in PubMed, Medline, EBSCOhost, Cochrane library database CENTRAL, and Google Scholar search engine. Keywords used in the search included combinations of the following: inflammation, sleep disorders, children, and biomarkers. Studies in the list of references of relevant literature were also included. A total of 155 articles published in the period from 1997 to 2021 were initially included in this review. Selected articles comprised original research, meta-analysis, and systematic reviews.

Results Studies have mainly centered their investigations on serum inflammatory biomarkers, namely interleukin-6, tumor necrosis factor-α, and C-reactive protein. Very few studies investigated salivary inflammatory biomarkers in children.

Conclusion Evidence suggests that children with sleep disorders have elevated levels of salivary as well as serum inflammatory biomarkers in comparison to normal healthy children. Also increased levels of these biomarkers correlate with disease severity. However, more studies are needed to determine the sensitivity and specificity of salivary inflammatory biomarkers for children with sleep disorders.

Current and future strategies for diagnostic and management of obstructive sleep apnea

INTRODUCTION

Obstructive sleep apnea (OSA) is a common sleep disorder with multiple comorbidities including hypertension, diabetes, and cardiovascular disorders. Detected based on an overnight sleep study is called polysomnography (PSG); OSA still remains undiagnosed in majority of the population mainly attributed to lack of awareness. To overcome the limitations posed by PSG such as patient discomfort and overnight hospitalization, newer technologies are being explored. In addition, challenges associated with current management of OSA using continuous positive airway pressure (CPAP), etc. presents several pitfalls.

AREAS COVERED

Conventional and modern detection/management techniques including PSG, CPAP, smart wearable/pillows, bio-motion sensors, etc., have both pros and cons. To fulfill the limitations in OSA diagnostics, there is an imperative need for new technology for screening of symptomatic and more importantly asymptomatic OSA patients to reduce the risk of several associated life-threatening comorbidities. In this line, molecular marker-based diagnostics have shown great promises.

EXPERT OPINION

A detailed overview is presented on the OSA management and diagnostic approaches and recent advances in the molecular screening methods. The potentials of biomarker-based detection and its limitations are also portrayed and a comparison between the standard, current modern approaches, and promising futuristic technologies for OSA diagnostics and management is set forth.ABBREVIATIONS AHI: Apnea hypopnea index; AI: artificial intelligence; CAM: Cell adhesion molecules; CPAP: Continuous Positive Airway Pressure; COVID-19: Coronavirus Disease 2019; CVD: Cardiovascular disease; ELISA: Enzyme linked immunosorbent assay; HSAT: Home sleep apnea testing; IR-UWB: Impulse radio-ultra wideband; MMA: maxillomandibular advancement; PSG: Polysomnography; OSA: Obstructive sleep apnea; SOD: Superoxide dismutase; QD: Quantum dot.

Cardiovascular Disease in Patients with Chronic Obstructive Pulmonary Disease, Obstructive Sleep Apnoea Syndrome and Overlap Syndrome

Chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea syndrome (OSAS) are among the most prevalent chronic respiratory disorders. Accumulating data suggest that there is a significant burden of cardiovascular disease (CVD) in patients with COPD and OSAS, affecting negatively patients' quality of life and survival. Overlap syndrome (OS), i.e. the co-existence of both COPD and OSAS in the same patient, has an additional impact on the cardiovascular system multiplying the risk of morbidity and mortality. The underlying mechanisms for the development of CVD in patients with either OSAS or COPD and OS are not entirely elucidated. Several mechanisms, in addition to smoking and obesity, may be implicated, including systemic inflammation, increased sympathetic activity, oxidative stress and endothelial dysfunction. Early diagnosis and proper management of these patients might reduce cardiovascular risk and improve patients' survival. In this review, we summarize the current knowledge regarding epidemiological aspects, pathophysiological mechanisms and present point-to-point specific associations between COPD, OSAS, OS and components of CVD, namely, pulmonary hypertension, coronary artery disease, peripheral arterial disease and stroke.

Sex-Specific Differential Responses of Circulating Biomarkers in Obstructive Sleep Apnea Treatment. A Post Hoc Analysis of a Randomized Controlled Trial

Rationale: Knowledge of sex-specific changes of cardiovascular biomarkers in response to continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA) is limited.Objectives: We hypothesized a differential sex-specific cardiovascular biomarker response with CPAP therapy for OSA.Methods: Participants with moderate-severe OSA (apnea-hypopnea index, 15 events/h) were randomized to CPAP versus sham and completed polysomnography and collection of biomarkers of inflammation (myeloperoxidase, fibrinogen, paraoxonase, interleukin [IL]-6, IL-6 soluble receptor, aryl esterase, oxidized low-density lipoprotein, lipoprotein A, plasminogen activator inhibitor 1, and F₂-isoprostane urine/creatinine ratio) and vascular measures at baseline and 8 weeks of therapy with either CPAP (n = 72) or sham treatment (n = 70). Post hoc secondary analyses of sex-study arm interaction relative to change in inflammatory biomarkers were evaluated via linear regression with adjustment for baseline biomarker value, age, race, body mass, index, waist circumference, and CPAP adherence. Interactions were further evaluated via sex-stratified analyses.Results: The study sample comprised a total of 149 participants aged 50.8 ± 11.7 years; 55% were male, and 55% were white. Participants had a median apnea-hypopnea index of 26.3 events per hour (interquartile range, 13-37). There were substantial interactions between study arm and sex for myeloperoxidase, paraoxonase, and fibrinogen (P = 0.03, P = 0.03, and P = 0.08, respectively). No significant interactions were found for the vascular measures. Estimates were similar but with decreased power in sex-stratified analyses, with decreased biomarkers in women and increased biomarkers in men.Conclusions: Differential sex-specific responses to CPAP therapy for OSA were observed for circulating inflammatory biomarkers, which persisted after adjustment for confounders. These findings set the stage for validation studies and, if confirmed, biochemical pathway elucidation to inform sex-specific personalized treatment approaches.Clinical trial registered with www.clinicaltrials.gov (NCT00607893).

Salivary biomarkers associated with obstructive sleep apnea: a systematic review

Introduction: This study aimed to define and characterize current literature describing salivary biomarker changes with the goal of improving diagnosis and treatment outcomes for sleep apnea.Area Covered: A search of six databases yielded 401 peer-reviewed articles published through October 2019 corresponded to 221 unique references following deduplication. Twenty studies were selected. The sample size ranged from 17 to 99. The samples were mostly whole saliva and selected glandular areas.Expert Opinion: Most targeted studies focused on the level of salivary cortisol and ɑ-amylase. One study used RNA transcriptome analysis of 96 genes. Only two explored novel targets using mass spectrometry. ɑ-amylase, myeloperoxidase, and IL-6 were among those biomarkers found associated with OSA. Cytokeratin, CystatinB, calgranulin A, and alpha-2-HS-glycoprotein are upregulated in OSA patients based on non-targeting mass spectrometry. Salivary cortisol and ɑ-amylase and others appeared to be associated with severity of OSA and OSA treatment. There were inconsistencies in saliva collection and processing protocols. More studies are needed in exploring novel biomarkers to examine if these biomarkers are capable of diagnosing and monitoring OSA through proteomics or transcriptomics. Salivary biomarkers have a potential to be a noninvasive measure for the disease diagnosis and treatment outcome monitoring for sleep apnea.

Technologic advances in the assessment and management of obstructive sleep apnoea beyond the apnoea-hypopnoea index: a narrative review

Obstructive sleep apnoea (OSA) is a growing and serious worldwide health problem with significant health and socioeconomic consequences. Current diagnostic testing strategies are limited by cost, access to resources and over reliance on one measure, namely the apnoea-hypopnoea frequency per hour (AHI). Recent evidence supports moving away from the AHI as the principle measure of OSA severity towards a more personalised approach to OSA diagnosis and treatment that includes phenotypic and biological traits. Novel advances in technology include the use of signals such as heart rate variability (HRV), oximetry and peripheral arterial tonometry (PAT) as alternative or additional measures. Ubiquitous use of smartphones and developments in wearable technology have also led to increased availability of applications and devices to facilitate home screening of at-risk populations, although current evidence indicates relatively poor accuracy in comparison with the traditional gold standard polysomnography (PSG). In this review, we evaluate the current strategies for diagnosing OSA in the context of their limitations, potential physiological targets as alternatives to AHI and the role of novel technology in OSA. We also evaluate the current evidence for using newer technologies in OSA diagnosis, the physiological targets such as smartphone applications and wearable technology. Future developments in OSA diagnosis and assessment will likely focus increasingly on systemic effects of sleep disordered breathing (SDB) such as changes in nocturnal oxygen and blood pressure (BP); and may also include other factors such as circulating biomarkers. These developments will likely require a re-evaluation of the diagnostic and grading criteria for clinically significant OSA.

Ahmad WMA, Ahmed Asif J, Khoo SP, Husein A, Ab-Ghani Z, Kassim NK. Biomarkers for Temporomandibular Disorders: Current Status and Future Directions

Numerous studies have been conducted in the previous years with an objective to determine the ideal biomarker or set of biomarkers in temporomandibular disorders (TMDs). It was recorded that tumour necrosis factor (TNF), interleukin 8 (IL-8), IL-6, and IL-1 were the most common biomarkers of TMDs. As of recently, although the research on TMDs biomarkers still aims to find more diagnostic agents, no recent study employs the biomarker as a targeting point of pharmacotherapy to suppress the inflammatory responses. This article represents an explicit review on the biomarkers of TMDs that have been discovered so far and provides possible future directions towards further research on these biomarkers. The potential implementation of the interactions of TNF with its receptor 2 (TNFR2) in the inflammatory process has been interpreted, and thus, this review presents a new hypothesis towards suppression of the inflammatory response using TNFR2-agonist. Subsequently, this hypothesis could be explored as a potential pain elimination approach in patients with TMDs.

Advances and challenges in pursuing biomarkers for obstructive sleep apnea: Implications for the cardiovascular risk

Obstructive sleep apnea (OSA) is a common clinical condition associated with increased cardiovascular morbidity and mortality. Recent evidence from clinical studies and animal models suggest that OSA can promote cardiovascular disease by inducing autonomic, hemodynamic, inflammatory and metabolic dysregulation. However, most of the evidence addressing hard endpoints in humans is derived from observational studies. Several challenges have been noted in the pursuit of a comprehensive knowledge base about the impact of OSA including: 1) the precise mechanisms by which OSA causes metabolic and cardiovascular consequences are not clear, which limits our current ability to address potential targets in OSA; 2) several patients with OSA, even with severe forms, present with no or mild daytime symptoms. Beyond the obvious challenges for obtaining good adherence for conventional OSA treatments, there is evidence that symptomatic vs. asymptomatic patients with OSA do not necessarily have the same metabolic and cardiovascular outcomes; and 3) the cardiovascular response to OSA treatment may vary even in those patients with good adherence. In this scenario, there is an obvious need to develop biomarkers in the OSA research area. This review focuses on describing the advances that have occurred so far in exploring potential OSA biomarkers with clear emphasis for the cardiovascular risk. Particular attention will be devoted to discuss molecular biomarkers including the potential role of microRNAs, proteomics and metabolomics. We also discuss the major challenges and perspectives in this growing research field.

The role of vitamin D in obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome (OSAS) is a common disorder of multifactorial pathogenesis and is associated with obesity, diabetes and cardiovascular disease. Vitamin D is a fat-soluble vitamin with an important function in calcium absorption and homeostasis, which is also implicated in several nonskeletal conditions. The prevalence of vitamin D deficiency is increasing worldwide and is associated with similar metabolic disturbances to OSAS. Moreover, recent data suggest that in OSAS patients serum levels of vitamin D are lower compared with non-apnoeic subjects. However, the mechanisms linking vitamin D deficiency and OSAS are not completely understood and several hypotheses have been advanced. To date, a limited number of studies have assessed the association between lower serum concentrations of vitamin D and OSAS, and have reported inconsistent results. Similarly, contradictory results have been produced by studies which evaluated the effect of continuous positive airway pressure treatment on serum vitamin D levels. The aim of this review is to summarise current knowledge on the association between OSAS and vitamin D levels.

Due to multiple confounding factors, vitamin D deficiency is common among sleep apnoea patients; thus, screening should be performed when clinically indicatedhttp://ow.ly/L3ow30krmol

Mean Platelet Volume and Platelet Distribution Width in Patients With Obstructive Sleep Apnea Syndrome and Concurrent Chronic Obstructive Pulmonary Disease

Evidence suggests that there is platelet activation in obstructive sleep apnea syndrome (OSAS) and chronic obstructive pulmonary disease (COPD). Our objective is to evaluate mean platelet volume (MPV) and platelet distribution width (PDW) in patients with overlap syndrome (OS), that is, concurrent COPD with OSAS. Mean platelet volume and PDW were assessed in consecutive patients who had undergone polysomnography and pulmonary function testing. They were divided into the following groups: controls (apnea-hypopnea index [AHI] <5/hour, and forced expiratory volume in 1st second [FEV₁]/forced vital capacity [FVC] >70%), OSAS group (AHI ≥5/hour and FEV₁/FVC >70%), and OS group (AHI ≥5/hour and FEV₁/FVC <70%). A total of 485 patients (360 males and 125 females) were included. Mean platelet volume in controls was lower compared with the other groups: 10 ± 0.9 fL for controls versus 10.3 ± 1.2 fL for OSAS ( P = .006), versus 10.7 ± 1 fL for OS ( P < .001). Additionally, MPV was higher in OS group than OSAS: 10.7 ± 1 fL versus 10.3 ± 1.2 fL, respectively ( P = .002). Platelet distribution width was lower in controls compared with the other groups: 12.9 ± 2 fL for controls versus 13.6 ± 1.9 fL for OSAS ( P = .007), versus 13.8 ± 2.3 fL for OS ( P = .008), while there was no difference between OS and OSAS groups. Mean platelet volume and PDW are increased in patients with OS compared with healthy controls, with respiratory function being the major contributor in platelet activation in this series.

C-reactive protein improves the ability to detect cardiometabolic risk in mild-to-moderate obstructive sleep apnea

Obstructive sleep apnea (OSA), particularly in the mild‐to‐moderate range, affects up to 40% of the adult general population. While it is clear that treatment should be pursued in severe cases of OSA, when and how to best treat OSA in the mild‐to‐moderate range remains complicated, despite its high prevalence. The aim of this study was to compare the relative utility of apnea/hypopnea index (AHI) versus a biomarker of inflammation, C‐reactive protein (CRP), in identifying the presence and severity of hypertension and hyperglycemia. Middle‐aged (n = 60) adults with mild‐to‐moderate OSA (AHI between 5 and 29 events per hour) underwent 8‐h polysomnography, a physical examination including measures of blood pressure and body mass index, and a fasting morning blood draw for glucose and CRP. CRP levels were associated with greater odds for having hypertension and hyperglycemia compared to AHI. Receiver‐operating characteristics (ROC) curves revealed that adding CRP to standard clinical factors (age, sex, and BMI) yielded moderately good to strong risk models for the disorders (AUC = 0.721 and AUC = 0.813, respectively). These preliminary findings suggest that including a measure of CRP improves the ability for clinicians to detect cases of mild‐to‐moderate OSA with true cardiometabolic risk, with implications in improving prognosis and treatment within this clinically gray area.

A multicenter matched case-control analysis on seven polymorphisms from HMGB1 and RAGE genes in predicting hepatocellular carcinoma risk

Based on 540 hepatocellular carcinoma patients and 540 age- and gender-matched controls, we tested the hypothesis that high mobility group protein box1 (HMGB1) and the receptor for advanced glycation end products (RAGE) genes are two potential candidate susceptibility genes for hepatocellular carcinoma in a multicenter hospital-based case-control analysis. The genotypes of seven widely-studied polymorphisms were determined, and their distributions respected the Hardy-Weinberg equilibrium. The mutant alleles of two polymorphisms, rs1045411 in HMGB1 gene and rs2070600 in RAGE gene, had significantly higher frequencies in patients than in controls (P < 0.001), with the power to detect this significance of being over 99.9%. Moreover, the above two polymorphisms increased the risk of developing hepatocellular carcinoma significantly, particularly for rs2070600 under the additive (odds ratio [OR] = 1.77; 95% confidence interval [CI]: 1.34-2.32; P < 0.001) and dominant (OR = 1.75; 95% CI: 1.23-2.50; P = 0.002) models after adjusting for body mass index, smoking and drinking. Haplotype analysis showed that the T-C-T haplotype (rs1045411-rs2249825-rs1415125) in HMGB1 gene was associated with a 2.47-fold (95% CI: 1.41-4.34; P = 0.002) increased risk of hepatocellular carcinoma compared with the commonest C-C-T haplotype after adjustment. In RAGE gene, the T-T-A-G (rs1800625-rs1800624-rs2070600-rs184003) (adjusted OR; 95% CI; P: 1.75; 1.02-3.03; 0.045) and T-T-A-T (adjusted OR; 95% CI; P: 1.95; 1.01-3.76; 0.048) haplotypes were associated with a marginally increased risk of hepatocellular carcinoma compared with the commonest T-T-G-G haplotype. In summary, we identified two risk-associated polymorphisms (rs1045411 and rs2070600), and more importantly a joint impact of seven polymorphisms from the HMGB1/RAGE axis in susceptibility to hepatocellular carcinoma.

Metabolic Syndrome and Vitamin D Levels in Patients with Obstructive Sleep Apnea Syndrome

BACKGROUND

Numerous studies have indicated that obstructive sleep apnea syndrome (OSAS), may contribute to the development of metabolic syndrome (MetS) and diabetes. Moreover, OSAS has been associated with lowered vitamin D (Vit D) levels, but reports are inconclusive. Aim of the study was to compare Vit D levels according to the presence of MetS and its components in OSAS patients.

METHODS

The presence of MetS was evaluated and serum 25-hydroxy vitamin D [25(OH)D] levels were measured in consecutive newly diagnosed, by polysomnography, subjects with OSAS.

RESULTS

A total of 107 subjects (88 men) with OSAS were included in the study. Patients were divided into group A (OSAS with MetS group: 55 subjects) and group B (OSAS without MetS: 52 subjects). There were no differences between the two groups in terms of age, body mass index, and sleep parameters. Patients in group A exhibited higher levels of daytime sleepiness, as expressed by Epworth Sleepiness Scale score (12 ± 5.5 vs. 9.3 ± 4.8 for groups A vs. B, p = 0.008). Serum 25(OH)D levels were significantly decreased in group A, as compared with group B (18 ± 8.6 ng/mL vs. 23.9 ± 14.1 ng/mL, respectively, p = 0.012). Group A was then subdivided in two smaller groups, according to patients' metabolic index: OSAS patients with metabolic score = 3 and OSAS patients with metabolic score >3. Serum 25(OH)D levels were higher in OSAS patients with metabolic score = 3 compared with OSAS patients with metabolic score >3 (19.8 ± 8.9 ng/mL vs. 15.1 ± 7.3 ng/mL respectively, p = 0.038).

CONCLUSIONS

OSAS patients with concurrent MetS exhibit lower serum Vit D levels, as compared with those without MetS.

Impairment of vascular strain in patients with obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is an independent risk factor for the development of cardiovascular diseases. Aim of this present study was to evaluate and extend recent research on the influence of obstructive sleep apnea on vascular strain.

Methods

A total number of 98 patients were integrated in the study. Patients were grouped according to the Apnea-Hypopnea-Index (AHI) in patients with mild-to-moderate OSA (5/h ≤ AHI < 30/h), severe OSA (AHI ≥ 30/h) and controls (AHI < 5/h). Groups were matched in age, body-mass-index and cardiovascular risks. Vascular strain of common carotid arteries was assessed by ultrasound speckle-tracking. A minor group of 30 patients and controls further underwent assessment of vascular strain of brachial and femoral arteries. Additionally, all patients underwent blood testing to reveal potential influences of inflammatory markers on arterial stiffness. In additional analysis we examined the effect of statin therapy on vascular strain.

Results

Patients with OSA showed significantly reduced values of vascular strain of common carotid arteries. Radial and circumferential strains were significantly lower in both patients with mild-to-moderate (p = .05) and patients with severe OSA (p = .001) compared to control. Vascular strain parameters of brachial and femoral arteries showed no consistent results. There were no significant correlations of inflammatory markers with vascular strain parameters. No significant differences in vascular strain were detected between statin and non-statin groups.

Conclusion

Patients with OSA show significantly reduced vascular strain assessed by ultrasound-based speckle-tracking. Vascular stiffness increases with the severity of the disease. Target vessels to assess vascular strain in patients with OSA are common carotid arteries, whereas other sites of the arterial tree are not reliable. No significant impact of current statin therapy on vascular strain was found. Further studies are needed to evaluate potential benefit of statins in secondary prevention of atherosclerosis in OSA.

Erythrocyte deformability, plasma lipid peroxidation and plasma protein oxidation in a group of OSAS subjects

Considering that obstructive sleep apnea syndrome (OSAS) is usually associated with endothelial dysfunction, atherosclerosis and cardiovascular disorders, our aim was to examine the erythrocyte deformability and the oxidative status in a group of OSAS subjects. We consecutively enrolled 48 subjects with OSAS defined after a 1-night cardiorespiratory sleep study, subsequently subdivided according to the apnea/hypopnea index (AHI) value in two subgroups: Low (L = 21 subjects with AHI<30) and High (H = 27 subjects with AHI>30). We evaluated the erythrocyte deformability, expressed as elongation index (EI) and the parameters of the oxidative status, such as lipid peroxidation (expressed as thiobarbituric acid-reactive substances - TBARS) and protein oxidation (measured as carbonyl groups - PC). In the entire group and in the two subgroups of OSAS subjects we found a decreased erytrocyte deformability at all shear stresses, not correlated with the plasmatic oxidative stress nor with the polysomnographic parameters. Lipid peroxidation was increased in the whole group and in the H subgroup of OSAS while protein oxidation showed a different trend. As in OSAS the osmotic fragility and the metabolism of the red cells seem to be not impaired, the oxidative damage to the red cell membrane proteins might be responsible for the reduced erythrocyte deformability. This rheological alteration, in addition to the increase in whole blood and plasma viscosity and to the erythrocyte hyperaggregation, could influence the microcircolatory profile in OSAS subjects.

Cystatin C Levels in Middle-Aged Patients with Obstructive Sleep Apnea Syndrome

Background. Obstructive sleep apnea syndrome (OSAS) is associated with systemic inflammation and increased risk of cardiovascular and chronic kidney disease. Cystatin C (Cyst C) is a novel biomarker of both latent renal damage and cardiovascular disease. Aim of the study was to measure serum levels of Cyst C, as well as IL-8 and CRP, in otherwise healthy OSAS patients. Methods. 84 individuals examined with polysomnography for OSAS symptoms without known comorbidities were prospectively recruited. Results. According to apnea hypopnea index (AHI) subjects were divided in two groups: OSAS group (AHI > 5/hour, n = 64) and controls (AHI < 5/hour, n = 20), which were age- and BMI-matched. Cyst C levels were higher in OSAS patients versus controls (1176.13 ± 351.33 versus 938.60 ± 245.83 ng/mL, resp.; p = 0.017) while serum IL-8 and CRP levels did not differ significantly. Positive correlation was found between Cyst C levels and respiratory disturbance index (RDI) (r = 0.240, p = 0.039) and percentage of time with oxygen saturation <90% (r = 0.290, p = 0.02) and negative correlation was found between Cyst C levels and average oxygen saturation during sleep (r = -0.291, p = 0.012). After adjustment for age and BMI, RDI was the only independent predictor of Cyst C levels (β = 0.256, p = 0.039). Conclusion. Cyst C serum levels are increased in OSAS patients without comorbidities, suggesting an increased renal and cardiovascular disease risk.

Chromatography/Mass Spectrometry-Based Biomarkers in the Field of Obstructive Sleep Apnea

Biomarker assessment is based on quantifying several proteins and metabolites. Recent developments in proteomics and metabolomics have enabled detection of these small molecules in biological samples and exploration of the underlying disease mechanisms in obstructive sleep apnea (OSA). This systemic review was performed to identify biomarkers, which were only detected by chromatography and/or mass spectrometry (MS) and to discuss the role of these biomarkers in the field of OSA. We systemically reviewed relevant articles from PubMed and EMBASE referring to proteins and metabolite profiles of biological samples in patients with OSA. The analytical platforms in this review were focused on chromatography and/or MS. In total, 30 studies evaluating biomarkers in patients with OSA using chromatography and/or MS methods were included. Numerous proteins and metabolites, including lipid profiles, adrenergic/dopaminergic biomarkers and derivatives, amino acids, oxidative stress biomarkers, and other micromolecules were identified in patients with OSA. Applying chromatography and/or MS methods to detect biomarkers helps develop an understanding of OSA mechanisms. More proteomic and metabolomic studies are warranted to develop potential diagnostic and clinical monitoring methods for OSA.

Copeptin: a new predictor for severe obstructive sleep apnea

INTRODUCTION

Copeptin which is the C-terminal fragment of antidiuretic hormone (ADH), is a biomarker that has been reported to be increased in various cardiovascular disorders, cerebrovascular diseases and associated with prognosis. Patients with obstructive sleep apnea syndrome (OSAS) have a tendency to develop coronary and cerebral atherosclerotic diseases.

OBJECTIVES

The aim of the present study was to study copeptin levels in patients with obstructive sleep apnea and in a control group in order to determine whether copeptin could be used as a biomarker predicting the severity of OSAS and possible complications in this group.

METHODS

A total of 116 patients with OSAS, diagnosed by polysomnography, and 27 controls were included in the study. Blood samples were collected after overnight fasting, and copeptin levels were measured with enzyme-linked immunosorbent assay.

RESULTS

Copeptin levels were significantly higher in the OSAS group compared to control group (2,156±502; 1,845±500 pg/mL, respectively, P=0.004). Mean copeptin level of the patients having apnea-hypopnea index (AHI) ≥30 was significantly higher than that of the patients having AHI <30 (2,392±415; 2,017±500 pg/mL, respectively, P<0.001). A multivariate regression analysis showed that copeptin level, (hazard ratio: 1.58; 95% confidence interval: 1.09-2.30) was a predictor of severe OSAS (P=0.016). Copeptin levels showed significant positive correlation with AHI (r=0.32; P<0.001), desaturation index (r=0.23; P=0.012), arousal index (r=0.24; P=0.010) and CRP (r=0.26; P=0.011) respectively.

CONCLUSION

Copeptin levels are high in OSAS patients and copeptin is a potential marker for identifying patients with a high risk of early cardiovascular complications of OSAS. Copeptin has modest sensitivity (84%) for discriminating severe OSAS patients who are candidates for severe cardiovascular complications.

Copeptin: a new predictor for severe obstructive sleep apnea

INTRODUCTION

Copeptin which is the C-terminal fragment of antidiuretic hormone (ADH), is a biomarker that has been reported to be increased in various cardiovascular disorders, cerebrovascular diseases and associated with prognosis. Patients with obstructive sleep apnea syndrome (OSAS) have a tendency to develop coronary and cerebral atherosclerotic diseases.

OBJECTIVES

The aim of the present study was to study copeptin levels in patients with obstructive sleep apnea and in a control group in order to determine whether copeptin could be used as a biomarker predicting the severity of OSAS and possible complications in this group.

METHODS

A total of 116 patients with OSAS, diagnosed by polysomnography, and 27 controls were included in the study. Blood samples were collected after overnight fasting, and copeptin levels were measured with enzyme-linked immunosorbent assay.

RESULTS

Copeptin levels were significantly higher in the OSAS group compared to control group (2,156±502; 1,845±500 pg/mL, respectively, P=0.004). Mean copeptin level of the patients having apnea-hypopnea index (AHI) ≥30 was significantly higher than that of the patients having AHI <30 (2,392±415; 2,017±500 pg/mL, respectively, P<0.001). A multivariate regression analysis showed that copeptin level, (hazard ratio: 1.58; 95% confidence interval: 1.09-2.30) was a predictor of severe OSAS (P=0.016). Copeptin levels showed significant positive correlation with AHI (r=0.32; P<0.001), desaturation index (r=0.23; P=0.012), arousal index (r=0.24; P=0.010) and CRP (r=0.26; P=0.011) respectively.

CONCLUSION

Copeptin levels are high in OSAS patients and copeptin is a potential marker for identifying patients with a high risk of early cardiovascular complications of OSAS. Copeptin has modest sensitivity (84%) for discriminating severe OSAS patients who are candidates for severe cardiovascular complications.