Obstructive sleep apnea is associated with lower adiponectin and higher cholesterol levels independently of traditional factors and other sleep disorders in middle-aged adults: the ELSA-Brasil cohort

Gender Modulated the Association of Sleep Apnea and Sleep Duration with Arterial Stiffness: The ELSA-Brasil Study

Increased arterial stiffness is independently associated with cardiovascular risk. Obstructive sleep apnea (OSA) and sleep duration (SDUR) may contribute to increased arterial stiffness, but it is unclear whether this association is modulated by gender. We aimed to evaluate the potential impact of gender in modulating the association of OSA and SDUR with arterial stiffness. Participants from the ELSA-Brasil study performed sleep assessments with portable polygraph to define OSA severity and SDUR by 1-week wrist actigraphy. Pulse wave velocity (PWV) was measured using a standard technique without access to the sleep data. We studied 1863 participants (42.2% male, age: 49±8 years, respiratory disturbance index (RDI): 9.9 (4.5-19.4) events/h, SDUR: 6.5 (5.9-7.1) hours, mean PWV: 7.3 ± 1.2 m/s). We found that men had higher PWV, higher frequency of diabetes, and higher blood pressure when compared to women. The regression analysis showed an independent association between increased RDI and PWV in men (ß: 0.007; 95% CI: 0.001-0.012), but not in women. In contrast, an independent association between SDUR and increased arterial stiffness was observed only in women (ß: 0.068; 95% CI: 0.002-0.134). In conclusion, the association of sleep disorders with arterial stiffness showed a distinct gender pattern depending on the sleep variable studied.

Chronic intermittent hypoxia triggers cardiac fibrosis: Role of epididymal white adipose tissue senescent remodeling?

AIM

Obstructive sleep apnea (OSA) is a growing health problem affecting nearly 1 billion people worldwide. The landmark feature of OSA is chronic intermittent hypoxia (CIH), accounting for multiple organ damage, including heart disease. CIH profoundly alters both visceral white adipose tissue (WAT) and heart structure and function, but little is known regarding inter-organ interaction in the context of CIH. We recently showed that visceral WAT senescence drives myocardial alterations in aged mice without CIH. Here, we aimed at investigating whether CIH induces a premature visceral WAT senescent phenotype, triggering subsequent cardiac remodeling.

METHODS

In a first experiment, 10-week-old C57bl6J male mice (n = 10/group) were exposed to 14 days of CIH (8 h daily, 5%-21% cyclic inspired oxygen fraction, 60 s per cycle). In a second series, mice were submitted to either epididymal WAT surgical lipectomy or sham surgery before CIH exposure. Finally, we used p53 deficient mice or Wild-type (WT) littermates, also exposed to the same CIH protocol. Epididymal WAT was assessed for fibrosis, DNA damages, oxidative stress, markers of senescence (p16, p21, and p53), and inflammation by RT-qPCR and histology, and myocardium was assessed for fibrosis and cardiomyocyte hypertrophy.

RESULTS

CIH-induced epididymal WAT remodeling characterized by increased fibrosis, oxidative stress, DNA damage response, inflammation, and increased expression of senescent markers. CIH-induced epididymal WAT remodeling was associated with subtle and early myocardial interstitial fibrosis. Both epididymal WAT surgical lipectomy and p53 deletion prevented CIH-induced myocardial fibrosis.

CONCLUSION

Short-term exposure to CIH induces epididymal WAT senescent remodeling and cardiac interstitial fibrosis, the latter being prevented by lipectomy. This finding strongly suggests visceral WAT senescence as a new target to mitigate OSA-related cardiac disorders.

Association between hepatic steatosis and lipoprotein(a) levels in non-alcoholic patients: A systematic review

BACKGROUND AND OBJECTIVES

It is well known that lipid abnormalities exist in the context of non-alcoholic fatty liver disease (NAFLD). The association between lipoprotein(a) [Lp(a)] levels and NAFLD is poorly understood. The main objective of the present study was to assess the association between Lp(a) levels and NAFLD.

METHODS

This systematic review was performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO CRD42023392526). A literature search was performed to detect studies that evaluated the association between Lp(a) levels, NAFLD and steatohepatitis (NASH).

RESULTS

Ten observational studies, including 40,045 patients, were identified and considered eligible for this systematic review. There were 9266 subjects in the NAFLD groups and 30,779 individuals in the respective control groups. Five studies evaluated patients with NAFLD (hepatic steatosis was associated with lower Lp(a) levels in four studies, while the remaining showed opposite results). Two studies evaluating NASH patients showed that Lp(a) levels were not different compared to controls. However, the increment of Lp(a) levels was correlated with liver fibrosis in one of them. In addition, one study analyzed simultaneously patients with NAFLD and NASH, showing a neutral result in NAFLD patients and a positive relationship in NASH patients. Two studies that included patients with the new definition of metabolic-associated fatty liver disease (MAFLD) also showed neutral results.

CONCLUSION

Although there could be an association between Lp(a) levels and hepatic steatosis, the results of the studies published to date are contradictory and not definitive.

Genetic study of the causal effect of lipid profiles on insomnia risk: a Mendelian randomization trial

OBJECTIVES

In response to the controversy surrounding observational studies of the association between lipid profiles and the risk of insomnia, the aim of this study was to analyze lipid profiles, including triglycerides (TG), apolipoprotein A-1 (ApoA-1), apolipoprotein B (ApoB) and lipoprotein A (LPA), in a European population to further assess the causal relationship between these lipid types and insomnia.

MATERIALS AND METHODS

This study explores the causal effect of lipid profiles on insomnia based on a genome-wide association study (GWAS)-derived public dataset using two-sample and multivariate Mendelian randomization (MVMR) analysis. The main MR analyses used inverse variance weighting (IVW) odds ratio (OR), and the sensitivity analyses included weighted median (WM) and MR‒Egger.

RESULTS

Both MR and MVMR showed that lowering ApoA-1 and LPA levels had causal effects on the risk of insomnia [MR: per 10 units, ApoA-1: OR: 0.7546, 95% CI: 0.6075-0.9372, P = 0.011; LPA: OR: 0.8392, 95% CI: 0.7202-0.9778, P = 0.025; MVMR: per 10 units, ApoA-1: OR: 0.7600, 95% CI: 0.6362-0.9079, P = 0.002; LPA, OR: 0.903, 95% CI: 0.8283-0.9845, P = 0.021]. There were no causal effects of TG or ApoB on insomnia (all P > 0.05). The MR‒Egger intercept test, funnel plot, and IVW methods all suggested an absence of strong directional pleiotropy, and leave-one-out permutation analysis did not detect any single single-nucleotide polymorphism that had a strong influence on the results.

CONCLUSION

Elevated levels of ApoA-1 and LPA were independently and causally associated with the risk of insomnia, suggesting that elevated ApoA-1 and LPA levels may contribute to a reduced risk of insomnia.

Interleukin-10 is not associated with obstructive sleep apnea hypopnea syndrome: A meta-analysis and meta-regression

BACKGROUND

This study was conducted to explore the potential relationship between interleukin-10 (IL-10) and obstructive sleep apnea hypopnea syndrome (OSAHS).

METHODS

All the related research articles published before October 2022 were retrieved through the online database (EMBASE, VIP, Wan Fang, Web of Science, PubMed, and CNKI). Stata 11.0 software was used to calculate the standard mean difference (SMD) of the continuous variable and 95% confidence interval (CI). Expression profiles GSE38792 and GSE135917 were acquired from Gene Expression Omnibus (GEO) database, respectively. The expression of IL-10 mRNA in subcutaneous adipose tissue and visceral adipose tissue of OSAHS patients and healthy subjects was extracted by R software to verify the difference in IL-10 between the 2 groups.

RESULTS

The IL-10 level in the plasma of people with and without OSAHS (STD Mean Difference (SMD) = -0.68, 95% CI = -1.58 to 0.21, I2 = 94.3%, P = .136) was the same. There was also no difference in IL-10 levels in serum between people with and without OSAHS (SMD = -0.12, 95% CI = -0.55 to 0.32, I2 = 94.4%, P = .591). In addition, the subjects were divided into different subgroups for meta-analysis according to race, body mass index, age, study type, and disease severity. Based on the outcomes, no notable difference was observed in the plasma/serum IL-10 level between the OSAHS subgroups and the control group. The results of bioinformatics analysis indicated that there was no significant difference in the expression of IL-10 mRNA in subcutaneous adipose tissue and visceral adipose tissue between patients with OSAHS and those in the control group.

CONCLUSION

The current meta-analysis highlighted that IL-10 levels between patients with OSAHS and healthy people had no difference.

The potential of tRF-21-U0EZY9X1B plasmatic level as a biomarker of children with obstructive sleep apnea-hypopnea syndrome

PURPOSE

We investigated changes in plasma transfer RNA related fragments (tRF) in children with obstructive sleep apnea-hypopnea syndrome (OSAHS) and the potential value as a disease marker.

METHODS

Firstly, we randomly selected five plasma samples from the case group and the control group for high-throughput RNA sequencing. Secondly, we screened one tRF with different expression between the two groups, amplified it by quantitative reverse transcription-PCR (qRT-PCR) and sequenced the amplified product. After confirming that the qRT-PCR results were consistent with the sequencing results and the sequence of the amplified product contained the original sequence of the tRF, we performed qRT-PCR on all samples. Then we analyzed the diagnostic value of the tRF and its correlation with some clinical data.

RESULTS

A total of 50 OSAHS children and 38 control children were included in this study. There were significant differences in height, serum creatinine (SCR) and total cholesterol (TC) between the two groups. The plasma expression levels of tRF-21-U0EZY9X1B (tRF-21) were significantly different between the two groups. Receiver operating characteristic curve (ROC) showed that it had valuable diagnostic index, with area under the curve (AUC) of 0.773, 86.71% and 63.16% sensitivity and specificity.

CONCLUSIONS

The expression levels of tRF-21 in the plasma of OSAHS children decreased significantly which were closely related to hemoglobin, mean corpuscular hemoglobin, triglyceride and creatine kinase-MB, may become novel biomarkers for the diagnosis of pediatric OSAHS.

The Modulation of Adipokines, Adipomyokines, and Sleep Disorders on Carcinogenesis

Obesity and sarcopenia, i.e., decreased skeletal muscle mass and function, are global health challenges. Moreover, people with obesity and sedentary lifestyles often have sleep disorders. Despite the potential associations, metabolic disturbances linking obesity, sarcopenia, and sleep disorders with cancer are neither well-defined nor understood fully. Abnormal levels of adipokines and adipomyokines originating from both adipose tissue and skeletal muscles are observed in some patients with obesity, sarcopenia and sleep disorders, as well as in cancer patients. This warrants investigation with respect to carcinogenesis. Adipokines and adipomyokines may exert either pro-carcinogenic or anti-carcinogenic effects. These factors, acting independently or together, may significantly modulate the incidence and progression of cancer. This review indicates that one of the possible pathways influencing the development of cancer may be the mutual relationship between obesity and/or sarcopenia, sleep quantity and quality, and adipokines/adipomyokines excretion. Taking into account the high proportion of persons with obesity and sedentary lifestyles, as well as the associations of these conditions with sleep disturbances, more attention should be paid to the individual and combined effects on cancer pathophysiology.

Sleep irregularity and the association with hypertension and blood pressure levels: the ELSA-Brasil study

OBJECTIVE

To evaluate the associations of sleep irregularity with hypertension (HTN) and blood pressure (BP) levels.

METHODS

Adult participants from the ELSA-Brasil performed a clinical evaluation including objective sleep duration (actigraphy), insomnia, and a sleep study for defining obstructive sleep apnoea (OSA). To quantify sleep irregularity, we used two parameters obtained through actigraphy: 7-day standard deviation (SD) of sleep duration and 7-day SD of sleep-onset timing. A multivariate analysis was used to determine the independent associations of sleep irregularity with HTN and SBP/DBP values.

RESULTS

We studied 1720 participants (age 49 ± 8 years; 43.4% men) and 27% fulfilled the HTN diagnosis. After adjustments for age, gender, race, BMI, excessive alcohol consumption, physical activity intensity, urinary sodium excretion, insomnia, objective sleep duration and OSA (apnoea-hypopnoea index ≥15 events/h), we found that the continuous analysis of 7-day SD of sleep duration was modestly associated with prevalent HTN. However, 7-day SD of sleep duration more than 90 min was independently associated with SBP [ β : 1.55; 95% confidence interval (CI) 0.23-2.88] and DBP ( β : 1.07; 95% CI 0.12-2.01). Stratification analysis excluding participants with OSA revealed that a 7-day SD of sleep duration greater than 90 min was associated with a 48% higher chance of having HTN (OR: 1.48; 95% CI: 1.05-2.07). No significant associations were observed for the SD of sleep-onset timing.

CONCLUSION

Objective measurement of sleep irregularity, evaluated by SD of sleep duration for 1 week, was associated with HTN and higher BP levels, especially in participants without OSA.

Association between glycolipids and risk of obstructive sleep apnea: A population-based study

Background

This study aimed to investigate the associations between multiple glycolipid biomarkers and the risk of obstructive sleep apnea (OSA).

Methods

Participants (10,286) aged from 35 to 74 years old were included in this cross-sectional study from the baseline survey of the Guangzhou Heart Study. OSA was ascertained using both Berlin Questionnaire and STOP-BANG Questionnaire. Fasting blood samples were collected from each participant; fasting blood glucose (FBG) and serum concentrations of high-density lipoprotein cholesterol (HDL-CH), low-density lipoprotein cholesterol (LDL-CH), total cholesterol (TC), and triglyceride (TG) were determined. Odds ratio (OR) with 95% confidence interval (CI) was calculated using the multivariate logistic regression model after adjustment for covariates.

Results

Of the participants included, 15.56% were categorized into the pre-OSA group, and 8.22% into the OSA group. When comparing the highest with the lowest quartiles, HDL-HC was associated with a 22% (OR: 0.78, 95% CI: 0.65–0.94) and 41% (OR: 0.59, 95% CI: 0.45–0.78) reduced risk of pre-OSA and OSA, triglyceride was associated with a 32% (OR 1.32, 95% CI 1.08–1.60) and a 56% (OR 1.56, 95% CI 1.18–2.07) increased risk of pre-OSA and OSA, and FBG was associated with a 1.37-fold (95% CI 1.13–1.67) risk of pre-OSA and 1.38-fold (95% CI 1.03–1.85) risk of OSA. A significant exposure-response trend was observed for HDL-HC, TG, and FBG with both OSA and Pre-OSA (all p < 0.05). No significant association of LDL-CH and TC with the risk of both pre-OSA and OSA was observed.

Conclusion

The findings suggest that serum HDL-CH was inversely associated with OSA risk, while elevated serum TG and FBG could increase the risk of OSA. Healthy glycolipid metabolism warrants more attention in the field of OSA prevention.

Excessive daytime sleepiness, but not sleep apnea, sleep duration or insomnia, was associated with poor adherence to anti-hypertensive treatment: The ELSA-Brasil study

Hypertension is the leading risk factor for cardiovascular mortality. Poor adherence may partially explain this scenario. Beyond traditional factors, it is conceivable that sleep conditions such as Obstructive Sleep Apnea (OSA), Sleep Duration (SDUR), sleepiness and insomnia may contribute to impair adherence but the evidence is scanty. Consecutive participants with hypertension from the ELSA-Brasil study performed a home sleep monitoring and 7-days actigraphy to determine OSA (apnea-hypopnea index ≥15 events/hour) and SDUR, respectively. Excessive daytime sleepiness (EDS) and insomnia were evaluated by Epworth Sleepiness Scale (ESS) and Clinical Interview Scheduled Revised (CIS-R), respectively. The 4-itens Morisky questionnaire was used to evaluate adherence to anti-hypertensive therapy. A total of 411 patients were including in the analysis (mean age: 54 ± 8 years, 47% men). Medium/low adherence to anti-hypertensive therapy was observed in 62%. Compared to the high adherence group, the participants with medium/low adherence had lower frequencies of Whites (64.1 vs. 47.8%), high-degree education (50.6 vs. 40%), and monthly per-capita income ($1021.90 vs. $805.20). In contrast, we observed higher frequency of EDS (35.9 vs. 46.1%). No differences were observed for OSA, short SDUR (<6 h) and insomnia. Logistic regression analysis showed that race other than White (OR: 1.80; 95% IC:1.15-2.82), lower monthly income (OR: 1.74; 95% IC:1.01-3.0) and EDS (OR: 1.63; 95% IC:1.05-2.53) were independently associated with medium/low adherence to the anti-hypertensive treatment. Interestingly, EDS mediated the abdominal obesity-adherence outcome. In conclusion, among sleep-related parameters, EDS, but not OSA, short SDUR or insomnia, were associated to impaired adherence to anti-hypertensive therapy.

Adipocytokines in obstructive sleep apnea: A systematic review and meta-analysis

BACKGROUND AND AIM

Adipocytokines play an important role in obstructive sleep apnea (OSA) by mediating inflammatory responses. Previous studies have reported that OSA is related to a change in the serum levels of adipocytokines; however, the results are still controversial. This meta-analysis aimed to assess the relationship between OSA and circulating level of adipocytokines in adults and children.

METHODS

A comprehensive search was conducted in databases of Medline/PubMed and Scopus for pertinent articles published since their inception to July 2022. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were used to assess the strength of the relationship between the concentrations of adipocytokines with OSA.

RESULTS

In the overall analysis, contrary to IL-10, which showed a significant reduction, IL-1β, IL-4, IL-8, IL-17, and IFN- gamma showed higher levels in OSA patients in comparison with control groups (p <0.05). For adults, IL-1β, IL-8, IL-17, IL-18, vaspin, visfatin, and chemerin were linked to a greater serum levels in patients with OSA, while, IL-5 and IL-10 were detected significantly lower in adults with OSA in comparison with healthy adults (p <0.05). In children with OSA, the serum levels of IL-4, IL-8, IL-12, IL-17, IL-23, and IFN-gamma were significantly higher than healthy children (p <0.05).

CONCLUSION

The levels of inflammatory markers were found to be higher in OSA patients compared with control individuals, suggesting that adipocytokines may contribute to the pathology of OSA.

Alterations of cholesterol synthesis and absorption in obstructive sleep apnea: Influence of obesity and disease severity

BACKGROUND AND AIMS

Obstructive sleep apnea (OSA) is closely linked to obesity and related adverse metabolic changes, including dyslipidemia. However, it is not clear whether OSA is an independent contributing factor to dyslipidemia, or the observed association is a reflection of a concomitant presence of obesity. Additionally, dyslipidemia is usually evaluated through measurement of parameters of routine lipid status, while more precise evaluation of lipid homeostasis is rarely performed in OSA. In this study, we analyzed markers of cholesterol synthesis and absorption in patients with OSA with respect to the presence of obesity and the disease severity.

METHODS AND RESULTS

This study enrolled 116 OSA patients. Concentrations of non-cholesterol sterols (NCS), measured by LC-MS/MS, were used as markers of cholesterol synthesis and absorption. Apnea-hypopnea index (AHI) and oxygen saturation (SaO₂) were utilized as markers of OSA severity. Serum lipid status parameters were determined by routine enzymatic methods. Markers of cholesterol synthesis were increased (P = 0.005), whilst markers of cholesterol absorption decreased (P = 0.001) in obese OSA patients. Cholesterol synthesis/absorption ratio was elevated in obese subjects (P < 0.001). Concentration of cholesterol synthesis marker lathosterol was significantly higher in subjects with severe OSA (P = 0.014) and we observed a trend of decreased cholesterol absorption in these patients. AHI was revealed as an independent determinant of lathosterol concentration (P = 0.022).

CONCLUSIONS

Our results suggest that the presence of obesity and severe forms of OSA is characterized by elevated endogenous cholesterol synthesis. AHI was singled out as an independent determinant of the serum level of cholesterol synthesis marker lathosterol.

Association of Blood MCP-1 Levels with Risk of Obstructive Sleep Apnea: A Systematic Review and Meta-Analysis

Background and objective: Among the broad variety of chemokines, monocyte chemoattractant protein-1 (MCP-1) is considered to be one of the most important chemokines. Among others, MCP-1 activates monocytes and other immune cells highly involved in inflammation. In the present systematic review and meta-analysis, we evaluated the relationship between serum/plasma MCP-1 levels and the risk of obstructive sleep apnea (OSA) in adults as a disease related to inflammation. Materials and methods: Four databases were systematically investigated until 12 July 2022. We used the Review Manager 5.3 software (Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark) to extract and calculate the standardized mean difference (SMD) and its 95% confidence interval (CI) of plasma/serum levels of MCP-1 between adults with and without OSA. Results: Eight articles including eleven studies in adults were entered into the meta-analysis. The serum/plasma MCP-1 levels in adults with OSA were higher than that in the controls (SMD = 0.81; p = 0.0007) and as well as for adults with severe OSA compared to those with mild and moderate OSA (SMD = 0.42; p < 0.0001). The subgroup analysis showed that ethnicity was an effective factor in the pooled analysis of blood MCP-1 levels in adults with OSA compared to the controls (Asians: (p < 0.0001), mixed ethnicity: (p = 0.04), and Caucasians: (p = 0.89)). The meta-regression showed increasing serum/plasma MCP-1 levels in adults with OSA versus the controls, publication year, age of controls, body mass index (BMI) of controls, and sample size reduced, and also BMI and the apnea−hypopnea index of adults with OSA increased. Conclusions: The meta-analysis showed that compared to the controls, serum/plasma levels of MCP-1 in adults with OSA were significantly more, as well as adults with severe OSA having more serum/plasma MCP-1 levels compared to the adults with mild to moderate OSA. Therefore, MCP-1 can be used as a diagnostic and therapeutic factor in adults with OSA.

Associations between abdominal obesity and the risk of stroke in Chinese older patients with obstructive sleep apnea: Is there an obesity paradox?

Background and purpose

Abdominal obesity (AO) is a well-known independent risk factor for stroke in the general population although it remains unclear in the case of the elderly, especially in Chinese older patients with obstructive sleep apnea (OSA), considering the obesity paradox. This study aimed to investigate the association between AO and stroke among Chinese older patients with OSA.

Methods

Data were collected from January 2015 to October 2017, and 1,290 older patients (age 60–96 years) with OSA (apnea–hypopnea index ≥ 5 events/h on polysomnography) were consecutively enrolled from sleep centers at six hospitals, evaluated for AO defined as waist circumference (WC) using the standardized criteria for the Chinese population, and followed up prospectively for a median period of 42 months. Logistic regression and Cox regression analyses were used to determine the cross-sectional and longitudinal associations between AO and stroke risk in these participants and different groups of the severity of OSA.

Results

Participants with AO had a higher prevalence of stroke at baseline. A higher incidence of stroke during a median follow-up period of 42 months in participants with AO than in participants without AO (12.4% vs. 6.8% and 8.3% vs. 2.4%, respectively; both P &lt; 0.05) was predicted. Cross-sectional analysis revealed an association between AO and stroke (odds ratio [OR]1.96, 95% confidence interval [CI] 1.31–2.91), which was stronger among participants with moderate OSA only (OR 2.16, 95%CI 1.05–4.43). Cox regression analysis showed that, compared to participants without AO, participants with AO had a higher cumulative incidence of stroke (hazard ratio [HR] 2.16, 95% CI 1.12–4.04) during a median follow-up of 42 months, and this association was observed in patients with severe OSA only (HR 3.67, 95% CI 1.41–9.87) but not for individuals with mild OSA (HR = 1.84, 95% CI 0.43–6.23) and moderate OSA (HR = 1.98, 95% CI 0.73–6.45).

Conclusion

The risk of stroke is associated with AO among Chinese older patients who have OSA, both at baseline and during follow-up, and the strength of the association varied by OSA severity. Active surveillance for early detection of AO could facilitate the implementation of stroke-preventive interventions in the Chinese older OSA population.

Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance

The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.

Obesity and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is characterized by upper airway collapse during sleep. Chronic intermittent hypoxia, sleep fragmentation, and inflammatory activation are the main pathophysiological mechanisms of OSA. OSA is highly prevalent in obese patients and may contribute to cardiometabolic risk by exerting detrimental effects on adipose tissue metabolism and potentiating the adipose tissue dysfunction typically found in obesity. This chapter will provide an update on: (a) the epidemiological studies linking obesity and OSA; (b) the studies exploring the effects of intermittent hypoxia and sleep fragmentation on the adipose tissue; (c) the effects of OSA treatment with continuous positive airway pressure (CPAP) on metabolic derangements; and (d) current research on new anti-diabetic drugs that could be useful in the treatment of obese OSA patients.