The utility of proinflammatory markers in patients with obstructive sleep apnea

Inhibiting the CB1 receptor in CIH-induced animal model alleviates colon injury

Obstructive sleep apnea (OSA) can lead to intestinal injury, endotoxemia, and disturbance of intestinal flora. Additionally, as a crucial component of the endocannabinoid system, some studies have demonstrated that cannabinoid 1 (CB1) receptors are closely linked to the multiple organ dysfunction triggered by OSA. However, the role of the CB1 receptor in alleviating OSA-induced colon injury remains unclear. Here, through the construction of the OSA classic model, we found that the colon tissue of chronic intermittent hypoxia (CIH)-induced mice exhibited an overexpression of the CB1 receptor. The results of hematoxylin-eosin staining and transmission electron microscopy revealed that inhibition of the CB1 receptor could decrease the gap between the mucosa and muscularis mucosae, alleviate mitochondrial swelling, reduce microvilli shedding, and promote the recovery of tight junctions of CIH-induced mice. Furthermore, CB1 receptor inhibition reduced the levels of metabolic endotoxemia and inflammatory responses, exhibiting significant protective effects on the colon injury caused by CIH. At the molecular level, through western blotting and real-time polymerase chain reaction techniques, we found that inhibiting the CB1 receptor can significantly increase the expression of ZO-1 and Occludin proteins, which are closely related to the maintenance of intestinal mucosal barrier function. Through 16S rRNA high-throughput sequencing and short-chain fatty acid (SCFA) determination, we found that inhibition of the CB1 receptor increased the diversity of the microbial flora and controlled the makeup of intestinal flora. Moreover, butyric acid concentration and the amount of SCFA-producing bacteria, such as Ruminococcaceae and Lachnospiraceae, were both markedly elevated by CB1 receptor inhibition. The results of the spearman correlation study indicated that Lachnospiraceae showed a positive association with both ZO-1 and Occludin but was negatively correlated with the colon CB1 receptor, IL-1β, and TNF-α. According to this study, we found that inhibiting CB1 receptor can improve CIH-induced colon injury by regulating gut microbiota, reducing mucosal damage and promoting tight junction recovery. KEY POINTS: •CIH leads to overexpression of CB1 receptor in colon tissue. •CIH causes intestinal flora disorder, intestinal mucosal damage, and disruption of tight junctions. •Inhibition of CB1 receptor can alleviate the colon injury caused by CIH through regulating the gut microbiota, reducing mucosal injury, and promoting tight junction recovery.

Biomarkers for the severity of periodontal disease in patients with obstructive sleep apnea:IL-1 β, IL-6, IL-17A, and IL-33

Objective

This study aims to compare the salivary and gingival crevicular fluid (GCF) concentrations of five cytokines: IL-1β, IL-6, IL-17A, IL-33, and Tumor Necrosis Factor-alpha (TNF-α) in patients with OSA and their association with periodontitis.

Methods

Samples of saliva and GCF were obtained from 84 patients classified into four groups according to periodontal and OSA diagnosis: G1(H) healthy patients, G2(P) periodontitis and non-OSA patients, G3(OSA) OSA and non-periodontitis patients, and G4(P-OSA) periodontitis and OSA patients. The cytokines in the samples were quantified using multiplexed bead immunoassays. Data were analyzed with the Kruskal-Wallis test, Dunn's multiple comparisons test, and the Spearman correlation test.

Results

Stage III periodontitis was the highest in patients with severe OSA (69%; p=0.0142). Similar levels of IL-1β and IL-6 in saliva were noted in G2(P) and G4(P-OSA). The IL-6, IL-17A and IL-33 levels were higher in the GCF of G4(P-OSA). There was a significant positive correlation between IL-33 in saliva and stage IV periodontitis in G4(P-OSA) (r _s  = 0.531). The cytokine profile of the patients in G4(P-OSA) with Candida spp. had an increase of the cytokine's levels compared to patients who did not have the yeast.

Conclusions

OSA may increase the risk of developing periodontitis due to increase of IL-1β and IL-6 in saliva and IL-6, IL-17A and IL-33 in GCF that share the activation of the osteoclastogenesis. Those cytokines may be considered as biomarkers of OSA and periodontitis.

The Discovery, Validation, and Function of Hypoxia-Related Gene Biomarkers for Obstructive Sleep Apnea

While there is emerging evidence that hypoxia critically contributes to the pathobiology of obstructive sleep apnea (OSA), the diagnostic value of measuring hypoxia or its surrogates in OSA remains unclear. Here we investigated the diagnostic value of hypoxia-related genes and explored their potential molecular mechanisms of action in OSA. Expression data from OSA and control subjects were downloaded from the Gene Expression Omnibus database. Differentially-expressed genes (DEGs) between OSA and control subjects were identified using the limma R package and their biological functions investigated with the clusterProfiler R package. Hypoxia-related DEGs in OSA were obtained by overlapping DEGs with hypoxia-related genes. The diagnostic value of hypoxia-related DEGs in OSA was evaluated by receiver operating curve (ROC) analysis. Random forest (RF) and lasso machine learning algorithms were used to construct diagnostic models to distinguish OSA from control. Geneset enrichment analysis (GSEA) was performed to explore pathways related to key hypoxia-related genes in OSA. Sixty-three genes associated with hypoxia, transcriptional regulation, and inflammation were identified as differentially expressed between OSA and control samples. By intersecting these with known hypoxia-related genes, 17 hypoxia-related DEGs related to OSA were identified. Protein-protein interaction network analysis showed that 16 hypoxia-related genes interacted, and their diagnostic value was further explored. The 16 hypoxia-related genes accurately predicted OSA with AUCs >0.7. A lasso model constructed using AREG, ATF3, ZFP36, and DUSP1 had a better performance and accuracy in classifying OSA and control samples compared with an RF model as assessed by multiple metrics. Moreover, GSEA revealed that AREG, ATF3, ZFP36, and DUSP1 may regulate OSA via inflammation and contribute to OSA-related cancer risk. Here we constructed a reliable diagnostic model for OSA based on hypoxia-related genes. Furthermore, these transcriptional changes may contribute to the etiology, pathogenesis, and sequelae of OSA.

Putative associations between inflammatory biomarkers, obesity, and obstructive sleep apnea

BACKGROUND:

Previous studies have reported increased levels of inflammatory mediators in patients with obstructive sleep apnea (OSA), but their relation with the severity of OSA is controversial.

OBJECTIVE:

To address potential relationships between OSA-related inflammatory markers, namely, C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and fibrinogen, with different oxygenation parameters and with BMI.

METHODS:

All eligible patients with suspected OSA newly referred to the Sleep Medicine Research Center at King Abdulaziz University Hospital, Jeddah, were evaluated demographically and anthropometrically, and underwent overnight polysomnography. Fasting morning blood samples were collected to measure serum levels of CRP, fibrinogen, TNF-α, and IL-6. Potential correlations between these inflammatory mediators and severity measures of OSA and body mass index (BMI) were explored.

RESULTS:

Sixty-four patients completed the study (40 with OSA and 24 without OSA). Significantly increased levels of CRP, fibrinogen, IL-6, and TNF-α emerged in patients with OSA compared to non-OSA. Significant associations between log CRP and log fibrinogen levels emerged with increasing BMI. However, there was no significant association between any of the inflammatory markers and the severity of OSA based on the apnea/hypopnea index or oxyhemoglobin saturation-derived parameters.

CONCLUSIONS:

OSA patients exhibit increased levels of inflammatory mediators that do not appear to be associated with polysomnographic measures, but exhibit positive correlation with the degree of adiposity.

The effect of chronic intermittent hypoxia in cardiovascular gene expression is modulated by age in a mice model of sleep apnea

STUDY OBJECTIVES

Chronic intermittent hypoxia (CIH) is a major determinant in obstructive sleep apnea cardiovascular morbidity and this effect is influenced by age. The objective of the present study was to assess the differential molecular mechanisms at gene-level expression involved in the cardiovascular remodeling induced by CIH according to chronological age.

METHODS

Two- and 18-month-old mice (N = 8 each) were subjected to CIH or normoxia for 8 weeks. Total messenger RNA (mRNA) was extracted from left ventricle myocardium and aortic arch, and gene expression of 46 intermediaries of aging, oxidative stress, and inflammation was measured by quantitative real-time polymerase chain reaction.

RESULTS

Cardiac gene expression of Nrf2 (2.05-fold increase, p < 0.001), Sod2 (1.9-fold increase, p = 0.035), Igf1r (1.4-fold increase, p = 0.028), Mtor (1.8-fold increase, p = 0.06), Foxo3 (1.5-fold increase, p = 0.020), Sirt4, Sirt6, and Sirt7 (1.3-fold increase, p = 0.012; 1.1-fold change, p = 0.031; 1.3-fold change, p = 0.029) was increased after CIH in young mice, but not in old mice. In aortic tissue, endothelial isoform of nitric oxide synthase was reduced in young mice (p < 0.001), Nrf2 was reduced in 80% (p < 0.001) in young mice and 45% (p = 0.07) in old mice, as its downstream antioxidant target Sod2 (82% reduced, p < 0.001). IL33.

CONCLUSIONS

CIH effect in gene expression is organ-dependent, and is modulated by age. CIH increased transcriptional expression of genes involved in cardioprotection and cell survival in young, but not in old mice. In aortic tissue, CIH reduced gene expression related to an antioxidant response in both young and old mice, suggesting vascular oxidative stress and a proaging process.

A community study of the risk for obstructive sleep apnea and respiratory inflammation in an adult Chinese population

Objectives: We aimed to investigate the relationship between obstructive sleep apnea (OSA) risk and respiratory inflammation evaluated by the exhaled breath condensate (EBC) interleukin-6 (IL-6) and plasma surfactant protein-D (SP-D), based on the Berlin questionnaire (BQ) screening values in an adult, urban community in Beijing, China.Methods: Volunteers aged >40 years were recruited from the Shichahai community of central Beijing (Registration number: NCT04832711). Their general information and disease history were recorded. OSA risk was assessed using the BQ. IL-6 in EBC and plasma SP-D were d etected by enzyme-linked immunoassay through specimens collected while fasting. The differences in IL-6 and SP-D values between high-risk and low-risk groups for OSA were compared, and the factors affecting their values were analyzed.Results: Among 1,239 participants, 18.8% of participants were in the high-risk group. There were more participants with higher body mass index, chronic hypertension, coronary heart disease, and diabetes in the high-risk group than in the low-risk group (P < 0.05). There were no significant differences in EBC IL-6 and plasma SP-D between the high- and low-OSA risk groups (p > 0.05). After adjustment for age, sex and chronic comorbidities, multivariate logistic regression showed that there was no correlation between risk of OSA and IL-6 in EBC. However, the risk of OSA (odds ratio [OR] [95% CI]: 1.69 [1.15,2.48]; β = 0.522) and BMI (OR [95%CI]: 0.94 [0.91,0.98]; β = -0.061) were independently associated with plasma SP-D level (p < 0.05 for both). Stratification analysis showed that OSA risk were independently associated with plasma SP-D levels in participants <65 years, or men, or participants with BMI<25.Conclusion: This study showed that plasma SP-D, an inflammation biomarker, was associated with risk of OSA and BMI in a Chinese central urban community.The relationship between the risk of OSA and respiratory inflammation in community populations needs to be further evaluated.

The gut microbiome as a target for adjuvant therapy in obstructive sleep apnea

Introduction: Gut dysbiosis is assumed to play a role in obstructive sleep apnea (OSA)-associated morbidities. Pre- and probiotics, short chain fatty acids (SCFA) and fecal matter transplantation (FMT) may offer potential as novel therapeutic strategies that target this gut dysbiosis. As more mechanisms of OSA-induced dysbiosis are being elucidated, these novel approaches are being tested in preclinical and clinical development. Areas covered: We examined the evidence linking OSA to gut dysbiosis and discuss the effects of pre- and probiotics on associated cardiometabolic, neurobehavioral and gastrointestinal disorders. The therapeutic potential of SCFA and FMT are also discussed. We reviewed the National Center for Biotechnology Information database, including PubMed and PubMed Central between 2000 - 2020. Expert opinion: To date, there are no clinical trials and only limited evidence from animal studies describing the beneficial effects of pre- and probiotic supplementation on OSA-mediated dysbiosis. Thus, more work is necessary to assess whether prebiotics, probiotics and SCFA are promising future novel strategies for targeting OSA-mediated dysbiosis.