Salivary markers of oxidative stress in patients with obstructive sleep apnea treated with continuous positive airway pressure

The effect of continuous positive airway pressure on total antioxidant capacity in obstructive sleep apnea: a systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA), a sleep-related disorder with high prevalence, is associated with an imbalance in oxidative stress and is linked to cardiovascular disease. There are conflicting reports regarding the effectiveness of continuous positive airway pressure (CPAP) therapy on oxidative stress/antioxidant markers in patients with OSA. This review was performed to evaluate the influence of therapy with CPAP on serum/plasma total antioxidant capacity (TAC) in patients with OSA.

METHODS

The Cochrane Library, Web of Science, Scopus, Embase, and PubMed were searched through June 2022 to obtain studies evaluating CPAP treatment on TAC in patients with OSA. Overall results were tested using standardized mean difference (SMD) with a 95% confidence interval (CI). Comprehensive Meta-Analysis V2 software was employed to perform analyses.

RESULTS

Ten studies with 12 effect sizes were eligible for inclusion in this analysis. The overall SMD revealed that CPAP therapy significantly increased TAC [SMD 0.497; 95% CI: 0.21 to 0.77; p: 0.00] in OSA. Analyses based on subgroups showed that the effect of CPAP therapy was significant in all subgroups according to therapy duration, age, BMI, and AHI. Whereas the meta-regression results indicated that the impact of therapy with CPAP on TAC is associated with AHI, BMI, and age in patients with OSA.

CONCLUSIONS

The finding of this meta-analysis demonstrated a favorable impact of CPAP therapy on TAC levels in patients suffering from OSA.

Oxidative Stress and Inflammation Biomarker Expression in Obstructive Sleep Apnea Patients

Obstructive Sleep Apnea Syndrome (OSAS) is a respiratory sleep disorder characterised by repeated episodes of partial or complete obstruction of the upper airway during the night. This obstruction usually occurs with a reduction (hypopnea) or complete cessation (apnea) of the airflow in the upper airways with the persistence of thoracic-diaphragmatic respiratory movements. During the hypopnea/apnea events, poor alveolar ventilation reduces the oxygen saturation in the arterial blood (SaO₂) and a gradual increase in the partial arterial pressure of carbon dioxide (PaCO₂). The direct consequence of the intermittent hypoxia is an oxidative imbalance, with reactive oxygen species production and the inflammatory cascade’s activation with pro and anti-inflammatory cytokines growth. Tumour necrosis factors, inflammatory cytokines (IL2, IL4, IL6), lipid peroxidation, and cell-free DNA have been found to increase in OSAS patients. However, even though different risk-related markers have been described and analysed in the literature, it has not yet been clarified whether specified inflammatory bio-markers better correlates with OSAS diagnosis and its clinical evolution/comorbidities. We perform a scientific literature review to discuss inflammatory and oxidative stress biomarkers currently tested in OSAS patients and their correlation with the disease’s severity and treatment.

Oxidative stress and inflammatory profiles in obstructive sleep apnea: are short-term CPAP or aerobic exercise therapies effective?

PURPOSE

The effects of medium to long-term continuous positive airway pressure (CPAP) or physical activity in decreasing oxidative stress, inflammatory, and cell-free DNA markers in obstructive sleep apnea (OSA) have been explored. Here we evaluate oxidative stress markers (TBARS, AOPP, SOD), proinflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8), anti-inflammatory cytokines (IL-4, IL-10), and cell-free DNA levels before and after 8-week CPAP treatment or moderate-intensity aerobic training in moderate to severe OSA.

METHODS

Thirty-nine patients diagnosed with OSA were randomly divided into CPAP (N = 18), with or without humidifier, and exercise groups (N = 21). Excessive daytime sleepiness and sleep quality were assessed by the Epworth Sleepiness Scale and the Pittsburgh questionnaire, respectively. Biomarkers for lipid and protein oxidation, pro and anti-inflammatory cytokines, and cell-free DNA were quantified in blood samples, before and after 8 weeks of both treatments.

RESULTS

After 8 weeks of either CPAP or exercise, no significant differences were observed in the levels of cell-free DNA, oxidative stress, and inflammation markers, except for an increase in AOPP and IL-17A levels in individuals who went through CPAP, which were higher when the CPAP device was used without the humidifier. We have also observed that CPAP significantly decreased the Pittsburgh scores and improved sleep efficiency and hours of sleep, while ESS scores remained unaffected.

CONCLUSIONS

Short-term treatment for OSA, be it CPAP therapy or moderate-intensity aerobic exercise, was not sufficient to alter either the oxidative stress and inflammatory profiles or the cell-free DNA levels of moderate to severe OSA patients. Short-term CPAP did, however, improve self-reported sleep quality.

Investigation of Urinary Sestrin2 in Patients with Obstructive Sleep Apnea

Background

Obstructive sleep apnea (OSA) is a disease seriously threatening individual health, which results in serious complications such as hypertension and stroke. These complications are associated with oxidative stress triggered by intermittent hypoxia in OSA. Sestrin2 is a crucial factor involved in oxidative stress. The goal of this study was to investigate if a relationship exists between OSA and Sestrin2.

Methods

We prospectively enrolled 71 subjects, and 16 patients of them with severe OSA completed 4 weeks of nasal continuous positive airway pressure (nCPAP) therapy. We measured and compared the concentration of Sestrin2 in the urine of all subjects, as well as the changes between before and after nCPAP treatment. Additionally, the correlation between Sestrin2 and sleep parameters was analyzed, and the multiple linear regression analysis with stepwise selection was performed to explore the relationship between Sestrin2 and various factors.

Results

A total of 71 subjects were enrolled and divided into two groups: OSA group (n = 41), control group (n = 30). The level of urinary Sestrin2 in OSA patients was significantly higher than that of the control group, and increased with the severity of OSA, while it reduced after nCPAP treatment. Additionally, Sestrin2 was positively correlated with apnea/hypopnea index (AHI), oxygen desaturation index, oxygen saturation < 90% percentage of recording time spent (PRTS) and high-density lipoprotein (HDL), while negatively correlated with the lowest oxygen saturation. Importantly, Sestrin2 was independently associated with AHI, oxygen saturation < 90% PRTS and HDL.

Conclusions

Urinary Sestrin2 is involved in OSA, and is a paramount marker of OSA severity.

Short-term effects of continuous positive airway pressure on oxidative stress in severe sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) is associated with oxidative stress that is involved in the pathogenesis of cardiovascular and metabolic complications. The concentrations of salivary markers of oxidative stress in patients with OSA increase considerably during the night. The dynamics is not affected by continuous positive airway pressure (CPAP) in mild to moderate OSA. The aim of this study was to analyze the short-term effects of CPAP on salivary oxidative stress markers in patients with severe OSA.

METHODS

Salivary samples were collected from 24 patients with apnea-hypopnea index higher than 30 during the first (diagnostic) night, who were treated by CPAP during the second (therapeutic) night.

RESULTS

The salivary markers of oxidative stress (TBARS, AGEs, and AOPP) were higher in the morning after the diagnostic night when compared to the evening concentrations (p < 0.01 for TBARS and p < 0.05 for AGEs and AOPP). Treatment by CPAP significantly decreased the morning concentrations of TBARS, AOPP (p < 0.01 for both), and AGEs (p < 0.05). Also, TBARS and AGEs positively correlated with apnea-hypopnea index (r = 0.48 and 0.49, respectively; p < 0.05). Antioxidant statuss was not affected.

CONCLUSION

Severe OSA is associated with increased levels of saliva markers for lipid peroxidation, protein oxidative damage, and carbonyl damage. Even short-term CPAP partially prevents oxidative and carbonyl stress during the night and this can be monitored non-invasively using saliva.

Parafoveal and optic disc vessel density in patients with obstructive sleep apnea syndrome: an optical coherence tomography angiography study

AIMS

To compare optic disc perfusion, radial peripapillary capillaries (RPC) and macular vascular density, between normal subjects and subjects with obstructive sleep apnea syndrome (OSAS) using spectral-domain OCT angiography (OCTA).

METHODS

Sixteen eyes of patients with mild OSAS, 17 eyes with moderate OSAS, 20 eyes with severe OSAS on polygraphy and 28 controls were evaluated with OCTA RT XR Avanti (AngioVue software, Optovue Inc., Fremont, CA). Optic nerve head (ONH), RPC and macular vessel density were measured. Clinical data, visual field parameters, and Spectral Domain OCT evaluation (retinal nerve fiber layer (RNFL) thickness and ganglion cell complex (GCC) thickness) were recorded for all patients.

RESULTS

ONH vascular flow (p = 0,396), RPC vascular density (automatized data "whole" p = 0,913, "peripapillary" p = 0,539, and segmented analysis with a topographic grid) and macular vascular density (foveal p = 0,484, parafoveal p = 0,491) were not significantly different between the four groups. FDT-Matrix™ and Humphrey 24/2 mean deviation were significantly lower in eyes with severe OSAS and were correlated to the apnea-hypopnea index. Retinal nerve fiber layer (RNFL) thickness, Cup/Disc ratio, rim area, and ganglion cell complex (GCC) were not significantly modified.

CONCLUSIONS

OCTA did not detect reduced ONH, RPC, neither macular blood vessel density in eyes with OSAS. The precise mechanisms that link OSAS with optic nerve pathologies remain unclear: our study was not able to demonstrate a vascular impact by OCTA examination.

Chronic intermittent hypoxia induces hormonal and male sexual behavioral changes: Hypoxia as an advancer of aging

Sleep apnea is a common sleep disorder characterized by intermittent periods of low blood oxygen levels. The risk for sleep apnea increases with age and is more prevalent in men than women. A common comorbidity of sleep apnea includes male sexual dysfunction, but it is not clear if a causal relationship exists between sleep apnea and sexual dysfunction. Possible mechanisms that link these two disorders include oxidative stress and testosterone. Oxidative stress is elevated in clinical patients with sleep apnea and in rodents exposed to chronic intermittent hypoxia (CIH), an animal model for apnea-induced hypopnea. Further, oxidative stress levels increase with age. Therefore, age may play a role in sleep apnea-induced sexual dysfunction and oxidative stress generation. To investigate this relationship, we exposed gonadally intact 3 (young) and 12 (middle-aged) month old male F344/BN F1 hybrid male rats to 8 days of CIH, and then examined male sexual function. Plasma was used to assess circulating oxidative stress and hormone levels. Middle-aged male rats had lower testosterone levels with increased sexual dysfunction and oxidative stress, independent of CIH. However, CIH decreased testosterone levels and increased sexual dysfunction and oxidative stress only in young gonadally intact male rats, but not in gonadectomized young rats with physiological testosterone replacement. In sum, CIH had a greater impact on younger gonadally intact animals, with respect to sexual behaviors, testosterone, and oxidative stress. Our data indicate CIH mimics the effects of aging on male sexual behavior in young gonadally intact male rats.

Oxidative and carbonyl stress in pregnant women with obstructive sleep apnea

PURPOSE

Pregnant women are particularly susceptible to sleep-disordered breathing. Obstructive sleep apnea (OSA) in pregnancy is associated with poor pregnancy and fetal outcomes. Oxidative stress caused by intermittent hypoxemia and reoxygenation may impact pregnancy health. We hypothesize that pregnant women with OSA have a pronounced oxidative stress profile.

METHODS

A case-control study was performed to study oxidative stress markers in the serum of pregnant women with or without OSA. Patients with OSA were identified between 2003 and 2009. Contemporaneous controls were pregnant subjects without apnea, gasping, or snoring around the time of delivery. Serum markers of oxidative and carbonyl stress were measured by spectrophotometric/fluorometric methods. Multiple linear regression analysis was used with a model including age, body mass index at delivery, history of diabetes, and gestational age.

RESULTS

Serum samples from 23 OSA cases and 41 controls were identified. Advanced oxidation protein products, a marker for oxidative stress, and advanced glycation end products (AGEs), a marker for carbonyl stress, were significantly lower in women with OSA than in controls (p value <0.0001). Total antioxidant capacity was higher in women with OSA in comparison to controls (p value <0.0001). The difference in AGEs remained significant even after adjusting for confounders.

CONCLUSION

Contrary to our hypothesis, the results of this study suggest that pregnant women with OSA have higher antioxidant capacity and lower oxidative and carbonyl stress markers compared to controls, suggesting a possible protective effect of intermittent hypoxia. Whether OSA in pregnancy impacts oxidative stress differently than OSA in the general population remains to be confirmed.

Role of Oxidative Stress in the Neurocognitive Dysfunction of Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) is characterized by chronic nocturnal intermittent hypoxia and sleep fragmentations. Neurocognitive dysfunction, a significant and extraordinary complication of OSAS, influences patients' career, family, and social life and reduces quality of life to some extent. Previous researches revealed that repetitive hypoxia and reoxygenation caused mitochondria and endoplasmic reticulum dysfunction, overactivated NADPH oxidase, xanthine oxidase, and uncoupling nitric oxide synthase, induced an imbalance between prooxidants and antioxidants, and then got rise to a series of oxidative stress (OS) responses, such as protein oxidation, lipid peroxidation, and DNA oxidation along with inflammatory reaction. OS in brain could trigger neuron injury especially in the hippocampus and cerebral cortex regions. Those two regions are fairly susceptible to hypoxia and oxidative stress production which could consequently result in cognitive dysfunction. Apart from continuous positive airway pressure (CPAP), antioxidant may be a promising therapeutic method to improve partially reversible neurocognitive function. Understanding the role that OS played in the cognitive deficits is crucial for future research and therapeutic strategy development. In this paper, recent important literature concerning the relationship between oxidative stress and cognitive impairment in OSAS will be summarized and the results can provide a rewarding overview for future breakthrough in this field.

Salivary and Urinary Total Antioxidant Capacity as Biomarkers of Oxidative Stress in Humans

Total Antioxidant Capacity (TAC) is a biomarker often used in order to investigate oxidative stress in many pathological conditions. Saliva and urine can be collected noninvasively and represent attractive diagnostic fluids for detecting biomarkers of various pathological conditions. The reviewed case-control and intervention studies that measured salivary or urinary TAC revealed that diseases, antioxidant foods, or supplements and age, gender, and lifestyle factors influenced salivary or urinary TAC. Salivary and urinary TAC were particularly affected by oral or renal status, respectively, as well as by infection; therefore these factors must be taken into account in both case-control and intervention studies. Furthermore, some considerations on sample collection and normalization strategies could be made. In particular, unstimulated saliva could be the better approach to measure salivary TAC, whereas 24 h or spontaneous urine collection should be chosen on the basis of the study outcome and of the creatinine clearance. Finally, the uric acid-independent TAC could be the better approach to evaluate red-ox status of body, in particular after nutritional interventions and in diseases associated with hyperuricaemia.

Association between glaucoma and obstructive sleep apnea syndrome: a meta-analysis and systematic review

Background

Obstructive sleep apnea syndrome (OSAS) is a common disease that increases the risk of diabetes, heart disease, and stroke. However, studies of an association between OSAS and glaucoma neuropathy have reported controversial findings.

Objective

The main purpose of this study was to evaluate whether a significant association exists between OSAS and glaucoma by performing a meta-analysis of previous studies.

Methods

A comprehensive literature search using the PubMed and Embase databases was performed to identify cross-sectional, case-control, and cohort studies related to the topic. We estimated a pooled odds ratio (OR) for the association between OSAS and glaucoma, by a fixed- or random-effects model.

Results

In total, 16 studies with 2,278,832 participants met the inclusion criteria: one retrospective cohort study reported an adjusted hazard ratio of glaucoma of 1.67 (95% CI = 1.30–2.17). Using a fixed-effects model, the pooled OR of six case-control studies was 1.96 (95% CI = 1.37 2.80). A significant association was also identified in a meta-analysis of nine cross-sectional studies using a random-effects model, which showed a pooled OR of 1.41 (95% CI = 1.11 1.79). However, the reported pooled estimates for case control studies and cross-sectional studies were based on unadjusted ORs.

Conclusions

Our results suggest that OSAS is associated with the prevalence of glaucoma. However, this result was based only on unadjusted estimates. Prospective cohort studies designed to take into consideration potential confounders, or examination of data from interventional trials to determine whether a reduction in OSAS status is associated with a reduced incidence of glaucoma, are needed to clarify whether OSAS is an independent risk factor for glaucoma.

Metabolic dysfunction in obstructive sleep apnea: A critical examination of underlying mechanisms

It has recently become clear that obstructive sleep apnea (OSA) is an independent risk factor for the development of metabolic syndrome, a disorder of defective energy storage and use. Several mechanisms have been proposed to explain this finding, drawing upon the characteristics that define OSA. In particular, intermittent hypoxia, sleep fragmentation, elevated sympathetic tone, and oxidative stress - all consequences of OSA - have been implicated in the progression of poor metabolic outcomes in OSA. In this review we examine the evidence to support each of these disease manifestations of OSA as a unique risk for metabolic dysfunction. Tissue hypoxia and sleep fragmentation are each directly connected to insulin resistance and hypertension, and each of these also may increase sympathetic tone, resulting in defective glucose homeostasis, excessive lipolysis, and elevated blood pressure. Oxidative stress further worsens insulin resistance and in turn, metabolic dysfunction also increases oxidative stress. However, despite many studies linking each of these individual components of OSA to the development of metabolic syndrome, there are very few reports that actually provide a coherent narrative about the mechanism underlying metabolic dysfunction in OSA.