Features Of Obstructive Sleep Apnea Research Articles

In-depth proteomics and Phosphoproteomics reveal biomarkers and molecular pathways of chronic intermittent hypoxia in mice

Obstructive sleep apnea (OSA) syndrome is characterized by Chronic Intermittent Hypoxia (CIH). In this study, we employed Data-independent acquisition (DIA) Mass Spectrometry to conduct comprehensive proteomic and phosphoproteomic profiling of a murine model subjected to Chronic Intermittent Hypoxia (CIH), a model we had previously established. Utilizing three CIH and three normal control genioglossus samples, we gathered valuable insights into the molecular alterations associated with CIH. Our analyses identified a total of 4576 protein groups and 13,867 phosphosites. Differential analysis of the proteomic data highlighted a significant upregulation of Ras signaling (Egf, Ngf, and Fyb1) and calcium signaling (Tnn, Thbs4, and Ppp2r2d) in CIH samples, contrasting with a notable decrease in oxidative phosphorylation (Atp5mf, Atp5me, and Atp5mg). Additionally, we observed a substantial increase in the phosphorylation of PI3K-AKT signaling (Ptk2_Y861, Mapk3_T203, and Eif4b_S230) and HIF-1 signaling (Gapdh_S208, Eno3_T229, and Camk2b_T382) in CIH samples. These findings prompted a deeper investigation into the association of the characterized proteins and phosphoproteins with Obstructive Sleep Apnea (OSA). The comprehensive profiling revealed molecular signatures that may serve as valuable insights into the pathophysiology of chronic intermittent hypoxia and its link to obstructive sleep apnea. Our observations provide a foundation for future research endeavors, offering potential avenues for advancing our understanding and treatment strategies for these conditions. SignificanceThe significance of this study lies in its comprehensive exploration of the molecular mechanisms underpinning Chronic Intermittent Hypoxia (CIH), a key feature of Obstructive Sleep Apnea (OSA). By employing Data-independent acquisition (DIA) Mass Spectrometry, this research provides an in-depth proteomic and phosphoproteomic analysis, uncovering critical signaling pathways and molecular alterations associated with CIH. The identification of significant changes in Ras and calcium signaling pathways, along with increased phosphorylation in PI3K-AKT and HIF-1 signaling, offers novel insights into the pathophysiological processes involved in CIH and OSA. These findings not only enhance our understanding of the molecular basis of OSA but also pave the way for the development of targeted therapeutic strategies, ultimately contributing to better management and treatment of OSA and related conditions.

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

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. 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. 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. 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.

Preserved ratio impaired spirometry and severity of obstructive sleep apnea: An observational cross-sectional study

Background and objectiveLung function abnormality of obstructive sleep apnea (OSA) has not been explored well. Preserved ratio impaired spirometry (PRISm) is known for its association with obesity and cardiovascular morbidity, which are also characteristic features of OSA. This study aims to investigate whether the prevalence of PRISm increases according to apnea–hypopnea index levels among subjects with OSA. MethodsConducted as an observational cross-sectional study, the study included 372 patients ≥40 years of age with definitive diagnoses of OSA and pulmonary function assessment from 2000 to 2004. Study subjects were classified based on OSA severity (mild/moderate versus severe). The prevalence of PRISm was estimated and compared between mild/moderate and severe OSA groups. ResultsThe prevalence of PRISm was 9.4 % in study subjects, with a higher prevalence in the severe OSA group than the mild/moderate group (12.9 % and 6.2 %, respectively, P = 0.04). The positive association between severe OSA and PRISm remained robust after multivariable adjustment for age, gender, and obesity (multivariable-adjusted odds ratio 2.29 (95 % confidence intervals 1.08–4.86), P = 0.03). ConclusionSevere OSA is an independent risk factor for PRISm, highlighting the need for comprehensive management of OSA that addresses the potential risk of PRISm.

Sex-specific differences in presenting symptoms of obstructive sleep apnea.

Scant data from India are available on the gender differences in presenting features of Obstructive Sleep Apnea (OSA) in India. This study aims to compare male and female patients with OSA for general characteristics and presenting symptoms. Retrospective study was done in OSA patients diagnosed in our sleep lab. History, biochemical reports, and polysomnography variables were retrieved from the sleep registry and were compared between males and females. Out of 514 patients of OSA (367 males; 147 females). Females were older (55.97 ± 9.73 v/s 50.2 + 12.70 years, P<0.001) and more obese (BMI 35.26 ± 7.17 v/s 29.58 ± 5.49 Kg/m2; P<0.001). Waist and hip circumference were significantly higher in the female patients (P = 0.009 and <0.001 respectively). Morning headache, nocturia, fatigability (P < 0.001), and depression (P = 0.005) was more common in females (P = 0.036). Hypersomnia was more commonly seen in males (P < 0.001). Mean diastolic blood pressure was significantly higher in males, although no difference was seen in Systolic BP. Females had higher mean Fasting Blood glucose (FBS) (P = 0.02). Apnea hypopnea index was significantly higher in females {P = 0.01}. Women with OSA are more obese, elderly, and with higher fasting blood glucose than males at the time of diagnosis. Females have a higher prevalence of symptoms like fatigability, depression, nocturia and early morning headache and had more severe AHI than males.

Correlation of morning dry mouth with clinical features of OSA in a community population: a cross-sectional study

ABSTRACT Objectives Morning dry mouth, commonly seen in Obstructive Sleep Apnea (OSA) patients, is absent in current OSA screening tools. This study evaluated the link between morning dry mouth and OSA’s clinical symptoms and complications, aiming to determine its viability as a screening indicator. Methods This research analyses baseline data from a prospective cohort study (the PIFCOPD study). Demographic information, medical history, and the presence of morning dry mouth symptoms were collected. The STOP-Bang questionnaire was performed for OSA screening. Logistic regression analyses were employed to establish the correlations between morning dry mouth and the clinical symptoms and comorbidities of OSA. Result 1291 participants (62.1±7.5 years; 501 males, 790 females) were included, of which 416 reported morning dry mouth (32.2%). 42.6% in the high-risk OSA group and 22.1% in the low-risk group reported morning dry mouth. Individuals with morning dry mouth also showed higher STOP-Bang scores (3.3±1.6 vs. 2.3±1.4, P<0.01). Significant associations were found between morning dry mouth and loud snoring, observed sleep apnea, daytime fatigue, and hyperlipidemia (P<0.01), but not with alcohol consumption, tea consumption, diabetes, or hypertension. Conclusion Morning dry mouth is associated with increased OSA risk and its clinical signs, suggesting its potential as an OSA screening symptom. Clinical trial registration This study has been registered at www.ClinicalTrials.gov (registration identifier: NCT03532893) on 21 May 2018.

Airway Collapsibility during Drug-Induced Sleep Endoscopy Relates with Clinical Features of Obstructive Sleep Apnea.

Increased pharyngeal collapsibility leads to obstructive sleep apnea (OSA). Positive airway pressure titration during drug-induced sleep endoscopy (DISE-PAP) provides objective collapsibility metrics, the pharyngeal opening pressure (PhOP), and active pharyngeal critical pressure (PcritA ). We examined the interrelationships between risk factors of OSA, airway collapsibility measures, and clinical manifestations of the disease. This is a cross-sectional analysis of consecutive OSA patients undergoing DISE-PAP. Nasal PAP was increased stepwise until inspiratory flow limitation was abolished, signifying PhOP. PcritA was derived from the resulting titration pressure-flow relationships. Clinical data including demographics, anthropometrics, sleep studies, and patient-symptom questionnaires were obtained from the electronic medical record. Multivariate regression was used to evaluate the relationship between risk factors, airway collapsibility, and clinical data. On average, the 164 patients meeting inclusion criteria were middle-aged (54.2 ± 14.7 years), overweight/obese (BMI 29.9 ± 4.5 kg/m2 ), male (72.6%), White (79.3%) and had severe OSA (AHI 32.0 ± 20.5 events/hour). Mean PhOP was 7.5 ± 3.3 cm H2 O and mean PcritA was 0.80 ± 3.70 cm H2 O. Younger age (Standardized β = -0.191, p = 0.015) and higher BMI (Standardized β = 0.176, p = 0.028) were associated with higher PhOP, but not PcritA . PhOP and PcritA were both associated with AHI, supine AHI, and SpO2 nadir. Higher PhOP was associated with higher snoring scores (Standardized β = 0.246, p = 0.008), but not other patient-reported outcomes. Objective assessment of passive and active airway mechanics during DISE relates with clinical risk factors for OSA. Quantitative measures of collapsibility provide accessible and meaningful data, enhancing the standard sleep surgery evaluation. 4 Laryngoscope, 134:1978-1985, 2024.

Incident Coronary Calcium Score in Patients With OSA With and Without Excessive Sleepiness: Brazilian Longitudinal Study of Adult Health

Uncertainty exists about the impact of OSA and its phenotypes on cardiovascular disease. Are OSA and clinical features such as daytime sleepiness associated with incident subclinical coronary atherosclerosis? In this prospective community-based cohort study, we administered a sleepiness questionnaire, actigraphy, and home sleep studies at baseline. Coronary artery calcium (CAC; 64-slice multidetector CT scan imaging) was measured at two different time points throughout the study (baseline, between 2010 and 2014, and follow-up, between 2016 and 2018). Incidence of subclinical atherosclerosis was defined as baseline CAC of 0 followed by CAC of > 0 at a 5-year follow-up visit. The association of incident CAC outcome was assessed using logistic regression. Stratified analyses based on excessive daytime sleepiness (EDS) were performed. We analyzed 1,956 participants with available CAC scores at baseline (mean age, 49 ± 8 years; 57.9%female; 32.4%with OSA). In covariate-adjusted analyses (n= 1,247; mean follow-up, 5.1 ± 0.9 years), we found a significant association between OSA and incidence of subclinical atherosclerosis (OR, 1.26; 95%CI, 1.06-1.48), with stronger effects among those reporting EDS (OR, 1.66; 95%CI, 1.30-2.12; P= .028 for interaction). Interestingly, EDS per se was not associated with any CAC outcome. An exploratory analysis of the square root of CAC progression (baseline CAC > 0 followed by a numerical increase in scores at follow-up; n= 319) showed a positive association for both OSA (β= 1.084; 95%CI, 0.032-2.136; P= .043) and OSA with EDS (β= 1.651; 95%CI, 0.208-3.094; P= .025). OSA, particularly with EDS, predicts the incidence and progression of CAC. These results support biological plausibility for the increased cardiovascular risk observed among patients with OSA with excessive sleepiness.

Mechanisms of Atrial Fibrillation in Obstructive Sleep Apnoea.

Obstructive sleep apnoea (OSA) is a strong independent risk factor for atrial fibrillation (AF). Emerging clinical data cite adverse effects of OSA on AF induction, maintenance, disease severity, and responsiveness to treatment. Prevention using continuous positive airway pressure (CPAP) is effective in some groups but is limited by its poor compliance. Thus, an improved understanding of the underlying arrhythmogenic mechanisms will facilitate the development of novel therapies and/or better selection of those currently available to complement CPAP in alleviating the burden of AF in OSA. Arrhythmogenesis in OSA is a multifactorial process characterised by a combination of acute atrial stimulation on a background of chronic electrical, structural, and autonomic remodelling. Chronic intermittent hypoxia (CIH), a key feature of OSA, is associated with long-term adaptive changes in myocyte ion channel currents, sensitising the atria to episodic bursts of autonomic reflex activity. CIH is also a potent driver of inflammatory and hypoxic stress, leading to fibrosis, connexin downregulation, and conduction slowing. Atrial stretch is brought about by negative thoracic pressure (NTP) swings during apnoea, promoting further chronic structural remodelling, as well as acutely dysregulating calcium handling and electrical function. Here, we provide an up-to-date review of these topical mechanistic insights and their roles in arrhythmia.

NOCTURNAL HYPOXIA INDEXES ARE ASSOCIATED WITH LEFT VENTRICULAR REMODELING AND DIASTOLIC DYSFUNCTION IN OBSTRUCTIVE SLEEP APNEA PATIENTS

Objective: Echocardiography features of obstructive sleep apnea (OSA) are heart derangements as higher left ventricular mass index (LVMI) and left ventricular end-diastolic diameter, lower left ventricular ejection fraction (LVEF), and impaired diastolic function. The apnea/hypopnea index (AHI), the parameter currently used to define diagnosis and severity of OSA, poorly predicts cardiovascular damage, cardiovascular events, and mortality. Thus, we aimed to assess, if, in addition to AHI, other polygraphic indices of OSA presence and severity might serve as better predictors of echocardiographic cardiac remodeling. Design and method: We enrolled two cohorts of subjects referred for suspected OSA to the outpatient facilities of the IRCCS Istituto Auxologico Italiano, Milano, and of the Clinica Medica 3, Padova. All patients underwent home sleep apnea testing and echocardiography. Based on the AHI the cohort was divided into no-OSA (AHI&lt;15 events/hour) and moderate-severe OSA (AHI&gt; = 15 events/hour). A stepwise multiple regression analysis was used to identify the covariates among age, gender, body mass index, past medical history, and polygrapic variables, independently associated to four echocardiographic variables, e.g., LVMI, LVEF, left ventricular end-diastolic volume (LVEDV), early and late ventricular filling velocity ratio (E/A). Results: We recruited 162 patients and found that compared to patients with no-OSA, those with moderate-severe OSA showed higher LV remodeling [LVEDV 48.4±11.5 ml/m2 vs. 54.1±14.0 ml/m2, respectively, p = 0.005] and lower LVEF (65.3±5.8 % vs. 61.6±7.8%, respectively, p = 0.002), whereas we could not find any difference in LVMI and E/A. At multivariate linear regression analysis, the only polygraphic independent predictor of LVEDV was the percentage of time with SatO2 &lt; 90% (↓ = 0.262), whereas, the independent predictors of E/A were AHI (↓ = -0.379) and oxygen desaturation index (↓ = -0.422). None of the polygraphic variables was associated to LVMI and LVEF at multivariate linear regression analysis. Conclusions: Our study shows that nocturnal hypoxia-related indexes were associated with left ventricular remodeling and diastolic dysfunction in OSA patients. If confirmed in future studies with a wider sample of patients included, these results support the adoption of hypoxia indexes in the evaluation of OSA patients, particularly those at a greater cardiovascular risk.

Obstructive sleep apnea in a mouse model is associated with tissue-specific transcriptomic changes in circadian rhythmicity and mean 24-hour gene expression.

Intermittent hypoxia (IH) is a major clinical feature of obstructive sleep apnea (OSA). The mechanisms that become dysregulated after periods of exposure to IH are unclear, particularly in the early stages of disease. The circadian clock governs a wide array of biological functions and is intimately associated with stabilization of hypoxia-inducible factors (HIFs) under hypoxic conditions. In patients, IH occurs during the sleep phase of the 24-hour sleep-wake cycle, potentially affecting their circadian rhythms. Alterations in the circadian clock have the potential to accelerate pathological processes, including other comorbid conditions that can be associated with chronic, untreated OSA. We hypothesized that changes in the circadian clock would manifest differently in those organs and systems known to be impacted by OSA. Using an IH model to represent OSA, we evaluated circadian rhythmicity and mean 24-hour expression of the transcriptome in 6 different mouse tissues, including the liver, lung, kidney, muscle, heart, and cerebellum, after a 7-day exposure to IH. We found that transcriptomic changes within cardiopulmonary tissues were more affected by IH than other tissues. Also, IH exposure resulted in an overall increase in core body temperature. Our findings demonstrate a relationship between early exposure to IH and changes in specific physiological outcomes. This study provides insight into the early pathophysiological mechanisms associated with IH.

0040 Leptin Signaling in the Dorsomedial Hypothalamus Couples Metabolism and Breathing in Obesity

Abstract Introduction Individuals with obesity hypoventilation syndrome (OHS) are unable to increase ventilation to match increased CO2 production (VCO2). Obstructive sleep apnea (OSA), defined by the closure of the upper airway during sleep, is present in 90% of OHS patients. Leptin, an adipocyte-produced hormone, acts in leptin receptor (LEPRb) positive neurons and was implicated in the pathophysiology of OSA and OHS. Diet-induced obese (DIO) C57BL/6J mice shows features of OHS and OSA. Leptin-mediated neural pathways may link metabolism and breathing in obesity. We hypothesized that LEPRb-positive neurons in the dorsomedial hypothalamus (DMH) are necessary and sufficient to match control of breathing to VCO2 and that the stimulation of these neurons relieves OHS in DIO mice. Methods We expressed designer receptors exclusively activated by designer drugs (DREADDs) in DMH of DIO Leprb-Cre mice and measured breathing during sleep, the hypercapnic ventilatory response (HCVR), VCO2, and O2 consumption (VO2). Results Activation of LEPRb-positive DMH neurons increased inspiratory flow and minute ventilation during REM sleep, without affecting sleep architecture. The effect was pronounced during inspiratory flow limitation, suggeting that upper airway obstruction during REM sleep was relieved. Activation of these neurons increased the HCVR and this response was blunted by a serotonin receptor antagonist, methysergide. Activation of these neurons augmented VCO2, VO2, and VE/VCO2, suggesting that breathing was stimulated out of proportion to increases in metabolism. In vitro experiments revealed that LEPRb-positive DMH neurons project to 5-HT neurons in the dorsal raphe (DR) and that optogenetic stimulation of these neurons evoked excitatory postsynaptic currents in 5-HT neurons of the DR. Administration of retrograde Cre-dependent AAV harboring caspase to the DR in Leprb-Cre mice deleted LEPRb-positive DMH neurons and abolished respiratory and metabolic effects of chemogenetic stimulation. Apoptosis of LEPRb-positive DMH neurons projecting to the DR also prevented the increase in ventilation during REM sleep induced by intranasal leptin. Conclusion Leptin increases the HCVR, improves upper airway patency during sleep, and increases VCO2 acting on LEPRb-positive DMH neurons projecting to the DR. We conclude that LEPRb-positive DMH neurons projecting to the DR couple metabolism and breathing in obesity. Support (if any) NIH (R01 HL128970, R01 HL133100, and R01 HL138932), AHA (#915167).

0796 Safety and efficacy of the combination of atomoxetine and oxybutynin for OSA treatment in children with Down Syndrome

Abstract Introduction Children with Down syndrome (DS) are at very high risk for obstructive sleep apnea (OSA), with a prevalence of OSA of 50-79%. Current OSA treatments for children with DS have limited effectiveness, as positive airway pressure therapy is poorly tolerated and adenotonsillectomy is not curative in most children with DS. The combination of atomoxetine and oxybutynin (ato-oxy) is a promising OSA treatment in adults. Ato-oxy has been shown to improve upper airway hypotonia, a key feature of OSA in children with DS, thus it may be particularly effective for OSA in children with DS. Methods We performed a randomized, double-blind, crossover pilot trial examining the short-term efficacy of ato-oxy in 15 children aged 6 to 17 years with DS and OSA. Participants received 4 weeks of low dose (0.5 mg/kg atomoxetine and 5 mg oxybutynin) as well as 4 weeks of high dose (1.2 mg/kg atomoxetine and 5 mg oxybutynin) in random order. Participants underwent polysomnography as well as parent-reported health-related quality of life assessment using the OSA-18 at baseline and at the end of each dosing period. The primary study endpoint was reduction in obstructive apnea-hypopnea index (oAHI) from baseline. Paired t-tests were used to compare baseline to low and high dose ato-oxy. Results 15 participants qualified for randomization and 11 participants had complete data at all points. Baseline oAHI was 7.4 ± 3.7 (mean ± standard deviation), oAHI with low dose ato-oxy was 3.6 ± 3.3 (p=0.001 vs baseline) and oAHI with high dose ato-oxy was 3.9 ± 2.8 (p=0.003 vs baseline). There were no differences in sleep architecture or sleep efficiency between baseline and either dose of ato-oxy. OSA-18 total score was 51.5 ± 18.5 at baseline; improved to 44.6 ± 17.0 (p=0.09) at the end of 4-weeks of low dose ato-oxy; and improved to 45.5 ± 15.7 (p=0.37) at the end of high-dose ato-oxy therapy. The most common adverse effects were irritability and fatigue, and these were generally mild. Conclusion Ato-oxy is a promising treatment for OSA in children with DS. Support (if any) Funding provided by NIH (HL151254 and HD109777) as well as the Lumind-IDSC foundation.

Carotid body contribution to the physio-pathological consequences of intermittent hypoxia: role of nitro-oxidative stress and inflammation.

Obstructive sleep apnoea (OSA), characterized by chronic intermittent hypoxia (CIH), is considered to be an independent risk for hypertension. The pathological cardiorespiratory consequences of OSA have been attributed to systemic oxidative stress, inflammation and sympathetic overflow induced by CIH, but an emerging body of evidence indicates that a nitro-oxidative and pro-inflammatory milieu within the carotid body (CB) is involved in the potentiation of CB chemosensory responses to hypoxia, which contribute to enhance the sympathetic activity. Accordingly, autonomic and cardiovascular alterations induced by CIH are critically dependent on an abnormally heightened CB chemosensory input to the nucleus of tractus solitarius (NTS), where second-order neurons project onto the rostral ventrolateral medulla (RVLM), activating pre-sympathetic neurons that control pre-ganglionic sympathetic neurons. CIH produces oxidative stress and neuroinflammation in the NTS and RVLM, which may contribute to the long-term irreversibility of the CIH-induced alterations. This brief review is mainly focused on the contribution of nitro-oxidative stress and pro-inflammatory molecules on the hyperactivation of the hypoxic chemoreflex pathway including the CB and the brainstem centres, and whether the persistence of autonomic and cardiorespiratory alterations may depend on the glial-related neuroinflammation induced by the enhanced CB chemosensory afferent input.

Leptin signaling in the dorsomedial hypothalamus couples metabolism and breathing in obesity

Individuals with obesity hypoventilation syndrome (OHS) are unable to increase ventilation to match increased CO 2 production (VCO 2 ). Obstructive sleep apnea (OSA), defined by the closure of the upper airway during sleep, is present in 90% of OHS patients. Leptin, an adipocyte-produced hormone, acts in leptin receptor (LEPR b ) positive neurons and was implicated in the pathophysiology of OSA and OHS. Diet-induced obese (DIO) C57BL/6J mice shows features of OHS and OSA. Leptin-mediated neural pathways may link metabolism and breathing in obesity. We hypothesized that LEPR b -positive neurons in the dorsomedial hypothalamus (DMH) are necessary and sufficient to match control of breathing to VCO 2 and that the stimulation of these neurons relieves OHS in DIO mice. We examined our hypothesis using in vivo and in vitro studies. We expressed designer receptors exclusively activated by designer drugs (DREADDs) in DMH of DIO Lepr b -Cre mice and measured breathing during sleep, the hypercapnic ventilatory response (HCVR), VCO 2 , and O 2 consumption (VO 2 ). Activation of LEPR b -positive DMH neurons increased inspiratory flow and minute ventilation during REM sleep, without affecting sleep architecture. The effect was pronounced during inspiratory flow limitation, suggesting that upper airway obstruction during REM sleep was relieved. Activation of these neurons increased the HCVR and this response was blunted by a serotonin receptor antagonist, methysergide. Activation of these neurons augmented VCO 2 , VO 2 , and VE/VCO 2 , suggesting that breathing was stimulated out of proportion to increases in metabolism. In vitro experiments revealed that LEPR b -positive DMH neurons project to 5-HT neurons in the dorsal raphe (DR) and that optogenetic stimulation of these neurons evoked excitatory postsynaptic currents in 5-HT neurons of the DR. Administration of retrograde Cre-dependent AAV harboring caspase to the DR in Lepr b -Cre mice deleted LEPR b -positive DMH neurons and abolished respiratory and metabolic effects of chemogenetic stimulation. Apoptosis of LEPR b -positive DMH neurons projecting to the DR also prevented the increase in ventilation during REM sleep induced by intranasal leptin. Leptin increases the HCVR, improves upper airway patency during sleep, and increases VCO 2 acting on LEPR b -positive DMH neurons projecting to the DR. We conclude that LEPR b -positive DMH neurons projecting to the DR couple metabolism and breathing in obesity. NIH (R01 HL128970, R01 HL133100, and R01 HL138932), AHA (#915167). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Intermittent hypoxia induces fibroblast activation: An in vitro approach in NIH/3T3 cells

Obstructive sleep apnea (OSA) is recognized as an independent cardiovascular (CV) risk factor. Intermittent hypoxia (IH), the landmark feature of OSA, represents the major detrimental factor triggering CV complications. In rodent models, IH contributes to cardiac remodeling, mainly characterized by early interstitial fibrosis. However, the direct effect of IH on cardiac fibrosis, as well as involved mechanisms are unclear. The aim of this study is to investigate in vitro whether IH induces fibroblast activation. NIH/3T3 murine fibroblasts were exposed to normoxic condition (N) or fast IH cycles, including 5-min normoxia (16% O2) followed by 5-min hypoxia (2% O2), in the presence or not of 10 ng/ml transforming growth factor (Tgf-∝). Cell proliferation was assessed after 48 h N or IH exposure by MTT assay; cell migration was evaluated during 12 h epxosure by scratch assay; mRNA expression of several markers of fibrosis was evaluated after 6 h exposure. Fibroblast differentiation was evaluated through α Smooth Muscle Actin (Acta2) mRNA expression and fibrosis through expression of Collagen 1 (Col1a1), lysyl oxidase (Lox), Tgf∝ and Tgf∝ receptor (Tgf-∝R). Data were analyzed by 2-ways Anova (Impact of IH and Tgf-β), followed by a Tukey post-hoc test. Our results confirm the well-known role of Tgf-∝ on fibroblast activation, characterized by increased proliferation (P = 0.004) and mRNA expression of Acta2 (P = 0.002), Col1a1 (P = 0.008) and Lox (P = 0.04). Independently of Tgf-β, IH does not increase cell proliferation, tends to increase fibroblasts migration (P = 0.1) and significantly increases mRNA expression of Acta2 (P = 0.002) and Col1a1 (P = 0.05), whereas increases in Lox and Tgf-β expression do not reach significance (P = 0.06 and P = 0.08). Interestingly, concomitant stimulation with Tgf-β and IH does not potentiate cell proliferation and migration, but synergistically increases Acta2, Col1a1 and Lox mRNA expression. Our in vitro results shows that IH induces fibroblast activation, promoting migration, differentiation into myofibroblast and expression of fibrotic markers. Furthermore, IH and Tgf-∝ seem to exert synergistic effects on fibrosis. Further studies are needed to understand specific mechanisms involved in IH-induced fibrosis.

Impact of IH-induced sympathetic hyperactivity and metabolic dysfunctions on ischemic cardiomyopathy progression

Patients with obstructive sleep apnea (OSA) exhibit poor prognosis after myocardial infarction (MI). Intermittent hypoxia (IH), the hallmark feature of OSA, promotes sympathetic hyperactivity and systemic insulin resistance, and has been identified as a major contributor to post-MI cardiac remodeling and contractile dysfunction. We hypothesize that sympathetic hyperactivity and metabolic alterations induced by IH promote desensitization of cardiac adrenergic and insulin pathways via activation of G protein-coupled receptors (GRK2), and subsequently participate in the aggravation of ischemic cardiomyopathy. MI is induced in C57bl6 mice by permanent ligation of the left coronary artery (MI). Mice are then randomized to IH (21–5% FiO2, 60 s cycle, 8 h/day) or normoxia for up to 6 weeks. After two weeks, mice are treated with a GRK2 inhibitor, Paroxetine (5 mg/kg/d), or 25% DMSO (Alzet® pumps). Longitudinal follow-up of mice includes evaluation of sympathetic activity (spectral analysis of heart rate variability (HRV), systemic insulin sensitivity (dynamic insulin tolerance test) and determination of cardiac function/remodeling (echocardiography). At the end of the protocol, cardiac interstitial fibrosis and hypertrophy are evaluated by RT-qPCR and histology (Sirius Red and WGA staining, respectively). Assessment of insulin signaling pathway is performed by Western blot. IH induces sympathetic hyperactivity in MI mice, demonstrated by a modification of the sympathovagal balance (LF increase). Paroxetine treatment abolishes the increase in LF in MI-IH condition and restores mRNA expression of β1 and β2 adrenergic receptors. MI-IH induces systemic insulin resistance compared to MI-N condition, which is prevented by Paroxetine treatment. In addition, Paroxetine treatment improves insulin signaling in the liver of MI-IH mice (pIRβ and pAKT). IH exacerbates cardiac interstitial fibrosis and worsens contractile dysfunction in MI mice, resulting in a significant decrease in ejection fraction (19.4 ± 2.1% vs. 29.9 ± 3.6% in IH vs. N respectively, P < 0.05). The effect of paroxetine on cardiac remodeling and function is currently being analyzed. These findings demonstrate that IH induces cardiac sympathetic hyperactivity and insulin resistance, which could contribute to the worsening of ischemic heart disease via GRK2.

Features of Obstructive Sleep Apnea in Children with and without Comorbidities.

To compare the clinical and polysomnographic features of obstructive sleep apnea (OSA) in children with adenotonsillar hypertrophy (Group A) and comorbidities (Group B). A five-year prospective study using nocturnal polysomnography before and after treatment. We included 168 patients: 121 in Group A and 47 in Group B, with differences in age (6.5 ± 3 vs. 8.6 ± 4 years; p < 0.001), body mass index (BMI) (18 ± 4 vs. 20 ± 7 kg/m2; p < 0.05), neck circumference (28 ± 4 vs. 30 ± 5 cm; p < 0.05), and obesity (17% vs. 30%; p < 0.05). Group B patients were more likely to have facial anomalies (p < 0.001), macroglossia (p < 0.01), dolichocephaly (p < 0.01), micrognathia (p < 0.001), and prognathism (p < 0.05). Adenotonsillectomy was performed in 103 Group A patients (85%) and 28 Group B patients (60%) (p < 0.001). In B, 13 children (28%) received treatment with continuous positive airway pressure (CPAP) and 2 (4%) with bilevel positive airway pressure (BiPAP), compared with 7 in Group A (6%) (p < 0.001). Maxillofacial surgery was more common in Group B (p < 0.01). Clinical and polysomnography parameters improved significantly in both groups after therapeutic intervention, though Group A showed better results. Obesity and facial anomalies are more frequent in childhood OSA patients with comorbidities, who often require combination therapy, such as ventilation and surgery.

Obstructive sleep apnea and metabolic syndrome.

Metabolic syndrome (MS) is a heterogeneous condition associated with increased cardiovascular risk. There is growing evidence from experimental, translational, and clinical investigations that has suggested that obstructive sleep apnea (OSA) is associated with prevalent and incident components of MS and MS itself. The biological plausibility is supportive, primarily related to one of the main features of OSA, namely intermittent hypoxia: increased sympathetic activation with hemodynamic repercussions, increased hepatic glucose output, insulin resistance through adipose tissue inflammation, pancreatic β-cell dysfunction, hyperlipidemia through the worsening of fasting lipid profiles, and the reduced clearance of triglyceride-rich lipoproteins. Although there are multiple related pathways, the clinical evidence relies mainly on cross-sectional data preventing any causality assumptions. The overlapping presence of visceral obesity or other confounders such as medications challenges the ability to understand the independent contribution of OSA on MS. In this review, werevisit the evidence on how OSA/intermittent hypoxia could mediate adverse effects of MS parameters independent of adiposity. Particular attention is devoted to discussing recent evidence from interventional studies. Thisreviewdescribes the research gaps, the challenges in the field, perspectives, and the need for additional high-quality data from interventional studies addressing the impact of not only established but promising therapies for OSA/obesity.

Potential Pathophysiological Pathways in the Complex Relationships between OSA and Cancer.

Several epidemiological and clinical studies have suggested a relationship between obstructive sleep apnea (OSA) and a higher incidence or severity of cancer. This relationship appears to be dependent on a myriad of factors. These include non-modifiable factors, such as age and gender; and modifiable or preventable factors, such as specific comorbidities (especially obesity), the use of particular treatments, and, above all, the histological type or location of the cancer. Heterogeneity in the relationship between OSA and cancer is also related to the influences of intermittent hypoxemia (a hallmark feature of OSA), among others, on metabolism and the microenvironment of different types of tumoral cells. The hypoxia inducible transcription factor (HIF-1α), a molecule activated and expressed in situations of hypoxemia, seems to be key to enabling a variety of pathophysiological mechanisms that are becoming increasingly better recognized. These mechanisms appear to be operationally involved via alterations in different cellular functions (mainly involving the immune system) and molecular functions, and by inducing modifications in the microbiome. This, in turn, may individually or collectively increase the risk of cancer, which is then, further modulated by the genetic susceptibility of the individual. Here, we provide an updated and brief review of the different pathophysiological pathways that have been identified and could explain the relationship between OSA and cancer. We also identify future challenges that need to be overcome in this intriguing field of research.

The role of ferroptosis in chronic intermittent hypoxia-induced cognitive impairment.

Obstructive sleep apnea (OSA) is a sleep disorder that may lead to cognitive impairment. The primary pathophysiological feature of OSA is chronic intermittent hypoxia (CIH), but the underlying mechanisms of CIH are not known. There have been few studies on the role of ferroptosis, a novel form of programmedcell death, during CIH-induced cognitive impairment. Therefore, this paper examined ferroptosis' effect on CIH-mediated cognitive impairment. The study randomized twenty-four Sprague-Dawley (SD) male rats to control or CIH group. CIH rats were subjected to intermittent hypoxia for 4weeks. Rat learning and memory were analyzed by the Morris water maze (MWM) test. Alterations of hippocampal neuronal ultrastructure were observed by transmission electron microscopy (TEM). Malondialdehyde (MDA) and ferrous iron (Fe2+) levels and superoxide dismutase (SOD) and reduced glutathione (GSH) contents were determined. Ferroptosis-associated protein levels were examined by Western blotting. The MWM test indicated that rats in the CIH group exhibited neurocognitive impairment. TEM showed that CIH induced mitochondrial damage. Significant increases in Fe2+ and MDA levels were observed in the CIH group, and GSH and SOD levels were decreased. Expression of Acyl-CoA synthetase long-chain family member 4 (ACSL4) increased, and glutathione peroxidase 4 (GPX4) protein levels were decreased, suggesting that ferroptosis was induced in CIH model rats. The NF-E2-related factor 2 (Nrf2) protein level in the CIH group was decreased. Ferroptosis had an essential effect on CIH-mediated cognitive impairment, and it may occur via Nrf2 dysregulation. These findings lay a solid foundation for the subsequent study of OSA-associated cognitiveimpairment offering potential evidence for the development of therapeutic strategies.