The Bidirectional Relationship Between Obstructive Sleep Apnea and Metabolic Disease

Metabolic Syndrome in Children and Adolescents: Is There a Universally Accepted Definition? Does it Matter?

The concept of metabolic syndrome (MetS) as a cluster of cardiovascular risk factors (obesity, altered glucose metabolism, dyslipidemia, and hypertension) has been around for more than 30 years. It is considered to be the result of complex interactions between centrally located fat, insulin resistance, subclinical inflammation, and other factors in genetically predisposed individuals. MetS diagnosis in adults has been linked to increased risk for cardiovascular disease (CVD) and type 2 diabetes mellitus (T2D). However, MetS in children and adolescents remains a controversial issue despite the extensive research in the field. It is still uncertain which definition should be used for its diagnosis in this age group, what is the clinical significance of such a diagnosis, and how reliably it can predict the future risk of developing CVD and T2D. Even if a child is diagnosed with MetS, management includes addressing each of the syndrome's components individually with weight loss and lifestyle modifications as the basic approach. Co-morbid conditions, such as nonalcoholic fatty liver disease, obstructive sleep apnea, and polycystic ovary syndrome should also be considered. It seems that MetS in children and adolescents should be used clinically as a conceptual framework for the identification of risk factors clustered around obesity and insulin resistance rather than a syndrome that needs to be diagnosed by measuring absolute "all-or-none" criteria.

Leptin: Master Regulator of Biological Functions that Affects Breathing

Obesity is a global epidemic in developed countries accounting for many of the metabolic and cardiorespiratory morbidities that occur in adults. These morbidities include type 2 diabetes, sleep-disordered breathing (SDB), obstructive sleep apnea, chronic intermittent hypoxia, and hypertension. Leptin, produced by adipocytes, is a master regulator of metabolism and of many other biological functions including central and peripheral circuits that control breathing. By binding to receptors on cells and neurons in the brainstem, hypothalamus, and carotid body, leptin links energy and metabolism to breathing. In this comprehensive article, we review the central and peripheral locations of leptin's actions that affect cardiorespiratory responses during health and disease, with a particular focus on obesity, SDB, and its effects during early development. Obesity-induced hyperleptinemia is associated with centrally mediated hypoventilation with decrease CO₂ sensitivity. On the other hand, hyperleptinemia augments peripheral chemoreflexes to hypoxia and induces sympathoexcitation. Thus, "leptin resistance" in obesity is relative. We delineate the circuits responsible for these divergent effects, including signaling pathways. We review the unique effects of leptin during development on organogenesis, feeding behavior, and cardiorespiratory responses, and how undernutrition and overnutrition during critical periods of development can lead to cardiorespiratory comorbidities in adulthood. We conclude with suggestions for future directions to improve our understanding of leptin dysregulation and associated clinical diseases and possible therapeutic targets. Lastly, we briefly discuss the yin and the yang, specifically the contribution of relative adiponectin deficiency in adults with hyperleptinemia to the development of metabolic and cardiovascular disease. © 2020 American Physiological Society. Compr Physiol 10:1047-1083, 2020.

Effects of different obesity-related adipokines on the occurrence of obstructive sleep apnea

Obstructive sleep apnea (OSA), characterized by recurrent episodes of apnea during sleep and daytime sleepiness, seriously affects human health and may lead to systemic organ dysfunction. The pathogenesis of OSA is complex and still uncertain, but multiple surveys have shown that obesity is an important factor, and the incidence of OSA in people with obesity is as high as 30%. Adipokines are a group of proteins secreted from adipocytes, which are dysregulated in obesity and may contribute to OSA. Here, we review the most important and representative research results regarding the correlation between obesity-related adipokines including leptin, adiponectin, omentin-1, chemerin, and resistin and OSA in the past 5 years, provide an overview of these key adipokines, and analyze possible intrinsic mechanisms and influencing factors. The existing research shows that OSA is associated with an increase in the serum levels of leptin, chemerin, and resistin and a decrease in the levels of adiponectin and omentin-1; the findings presented here can be used to monitor the development of OSA and obesity, prevent future comorbidities, and identify risk factors for cardiovascular and other diseases, while different adipokines can be linked to OSA through different pathways such as insulin resistance, intermittent hypoxia, and inflammation, among others. We hope our review leads to a deeper and more comprehensive understanding of OSA based on the relevant literature, which will also provide directions for future clinical research.

Short-Term Assessment of Obstructive Sleep Apnea Syndrome Remission Rate after Sleeve Gastrectomy: a Cohort Study

BACKGROUND

Severe obesity is associated with a high prevalence of moderate-to-severe obstructive sleep apnea syndrome (OSA). Bariatric surgery has been shown to effectively reduce excess weight and comorbidities.

METHODS

We evaluated the remission rate of moderate-to-severe OSA (apnea-hypopnea index (AHI) ≥ 15) following sleeve gastrectomy. We performed a single-center retrospective chart review of all patients who underwent preoperative polysomnography (PSG) or polygraphy before primary sleeve gastrectomy. Patients with moderate-to-severe OSA treated by continuous positive airway pressure (CPAP) also underwent postoperative PSG. Bivariate analysis was performed to evaluate the criteria associated with remission of moderate-to-severe OSA.

RESULTS

From 2013 to 2018, 39 of 162 patients (24.1%) scheduled for sleeve gastrectomy (SG) presented moderate-to-severe OSA requiring CPAP. Postoperative PSG was performed in 36 patients a mean of 9.9 ± 6.1 months after SG. Mean BMI decreased from 47.4 ± 8.4 to 36.3 ± 7.1 kg/m² (p < 0.001), and all patients reported clinical improvement of OSA symptoms. A remission of moderate-to-severe OSA was observed in 72.2% of patients with a mean decrease of AHI from 45.8 events/h to 11.3 events/h (p < 0.001). Postoperative neck circumference was the only factor associated with OSA remission.

CONCLUSION

SG is associated with a rapid improvement of moderate-to-severe OSA partially as a result of a reduction of neck circumference. However, the absence of correlation with excess weight loss suggests that other weight-independent factors may also be involved.

The relationship between obstructive sleep apnea syndrome and obesity: A new perspective on the pathogenesis in terms of organ crosstalk

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a common disorder that has a major impact on public health. The connection between OSAS and obesity is very complex and likely represents an interaction between biological and lifestyle factors. Oxidative stress, inflammation and metabolic dysregulation are both actors involved in the pathogenesis of OSAS and obesity. Also, the current evidence suggests that gut microbiota plays a significant role in the emergence and progression of some metabolic disorders. When the relationship between OSAS and obesity is evaluated extensively, it is understood that they show mutual causality with each other, and that metabolic challenges such as impaired microbiota affect this bidirectional organ interaction, and by ensuing organ injury.

OBJECTIVES

The aim of this study is to investigate the association between OSAS and obesity, and the effect of "organ crosstalk" on the pathogenesis of the relationship and to contribute to the diagnosis and treatment options in the light of current data.

DATA SOURCE

We performed an electronic database search including PubMed, EMBASE and Web of Science. We used the following search terms: OSAS, obesity, inflammation, metabolic dysregulation and gut microbiota.

CONCLUSION

Obesity and OSAS adversely affect many organs and systems. Besides the factors affecting the diagnosis of the OSAS-obesity relationship, mutual organ interactions among the respiratory system, adipose tissue and intestines should not be ignored for prevention and treatment of OSAS and obesity. Comprehensive clinical trials addressing the efficacy and efficiency of current or potential treatments on therapeutic applications in the OSAS-obesity relationship are needed.

Obstructive sleep apnea and hypertriglyceridaemia share common genetic background: Results of a twin study

Obstructive sleep apnea is associated with an increased risk of hypertension, diabetes and dyslipidaemia. Both obstructive sleep apnea and its comorbidities are at least partly heritable, suggesting a common genetic background. Our aim was to analyse the heritability of the relationship between obstructive sleep apnea and its comorbidities using a twin study. Forty-seven monozygotic and 22 dizygotic adult twin pairs recruited from the Hungarian Twin Registry (mean age 51 ± 15 years) attended an overnight diagnostic sleep study. A medical history was taken, blood pressure was measured, and blood samples were taken for fasting glucose, total cholesterol, triglyceride, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and lipoprotein (a). To evaluate the heritability of obstructive sleep apnea and its comorbidities bivariate analysis was performed with an adjustment for age, gender, body mass index (BMI) and smoking after false discovery rate correction and following exclusion of patients on lipid-lowering and antidiabetic medications. There was a significant correlation between indices of obstructive sleep apnea severity, such as the apnea-hypopnea index, oxygen desaturation index and percentage of sleep time spent with oxygen saturation below 90%, as well as blood pressure, serum triglyceride, lipoprotein (a) and glucose levels (all p < .05). The bivariate analysis revealed a common genetic background for the correlations between serum triglyceride and the oxygen desaturation index (r = .63, p = .03), as well as percentage of sleep time spent with oxygen saturation below 90% (r = .58, p = .03). None of the other correlations were significantly genetically or environmentally determined. This twin study demonstrates that the co-occurrence of obstructive sleep apnea with hypertriglyceridaemia has a genetic influence and heritable factors play an important role in the pathogenesis of dyslipidaemia in obstructive sleep apnea.

Obstructive Sleep Apnea Exacerbates Glucose Dysmetabolism and Pancreatic β-Cell Dysfunction in Overweight and Obese Nondiabetic Young Adults

PURPOSE

This study aimed to investigate the effects of obstructive sleep apnea (OSA) on the pancreatic β-cells dysfunction and their implications in the glucose dysmetabolism of overweight and obese nondiabetic young adults.

MATERIALS AND METHODS

The cross-sectional analysis included 422 subjects (261 males/161 females) with the mean age of 27.77 ± 7.51 years and average body mass index (BMI) of 34.84 ± 5.69 kg/m². All subjects underwent polysomnography (PSG), oral glucose tolerance-insulin releasing test (OGTT-IRT) and serum glycosylated hemoglobin A1 (HbA1c) measurement. The glucose metabolism and pancreatic β-cell function in relation to measures of OSA were determined adjustment for important confounders such as age and sex.

RESULTS

OSA subjects accounted for 54.91% in the normal glucose tolerance (NGT) group and 72.11% in the prediabetes (preDM) group (P =0.001). HbA1c was the highest in the preDM subjects with severe OSA. In the NGT subjects, the 1-h glucose level significantly elevated with the OSA severity, and the homeostasis model assessment-β (HOMA-β) was negatively related to nocturnal mean SpO₂ (P <0.05). In the preDM subjects, HOMA-β, early phase insulinogenic index (∆I₃₀/∆G₃₀), total area under the curve of insulin in 180 min (AUC-I₁₈₀), and the oral disposition index (DI_O) were the lowest in the severe OSA group. DI_O was associated with higher oxygen desaturation index (ODI) and lower nocturnal mean SpO₂, and AUC-I₁₈₀ was negatively related to TS90 (P <0.05).

CONCLUSION

Our study indicated higher prevalence of OSA in overweight and obese nondiabetic young adults, especially preDM subjects. The impaired glucose tolerance was observed early after glucose intake in the NGT subjects. OSA induces compensatory increase in the pancreatic β-cell function in the NGT subjects, while pancreatic β-cell dysfunction is present in the preDM subjects with severe OSA.

A usability study of an internet-delivered behavioural intervention tailored for children with residual insomnia symptoms after obstructive sleep apnea treatment

Better Nights, Better Days (BNBD) is a 5-session online intervention designed to treat insomnia in 1-10-year-old children (Corkum et al. 2016). Obstructive sleep apnea (OSA) and insomnia commonly occur in children and, after surgical treatment for OSA, it is estimated that up to 50% of children may continue to suffer from insomnia symptoms. Access to insomnia interventions following OSA treatment is limited as there are few programs available, few trained practitioners to deliver these programs, and limited recognition that these problems exist. The current study involved the usability testing of an internet-based parent-directed session of BNBD tailored towards the needs of children (ages 4-10 years) who experience residual insomnia symptoms after treatment of OSA. This new session was added to the BNBD program. Participants (n = 43) included 6 parents, 17 sleep experts, and 20 front-line healthcare providers who completed and provided feedback on the new session. Participants completed a feedback questionnaire, with both quantitative and qualitative questions, after reviewing the session. Quantitative responses analyzed via descriptive statistics suggested that the session was primarily viewed as helpful by most participants, and open-ended qualitative questions analyzed by content analyses generated a mix of positive and constructive feedback. The results provide insights on how to optimally tailor the BNBD program to meet the needs of the target population and suggest that testing the session on a larger scale would be beneficial.

Effects of Obstructive Sleep Apnea-Hypopnea Syndrome on Serum Carcinoembryonic Antigen Levels in Patients with Type 2 Diabetes Mellitus

Background

Type 2 diabetes mellitus (T2DM) is related to the serum carcinoembryonic antigen (CEA) level, which is used as a marker of colorectal cancer. Obstructive sleep apnea-hypopnea syndrome (OSAS) has been recently reported to have cancer-promoting effects. The aim of our study was to observe the effect of OSAS on serum levels of CEA in patients with T2DM.

Material/Methods

We enrolled 401 T2DM patients in this study. There were 244 patients with OSAS and 157 patients without OSAS.

Results

The CEA level in T2DM patients with OSAS was higher than that in those without OSAS (p<0.05). The participants with AHI scores ≥30 had higher CEA levels than those with 5≤ AHI scores <30 (p<0.05). The AHI score and ODI score were independently associated with increased risk of high CEA level in T2DM patients (odds ratio [OR]=1.052, 95% confidence interval [CI]: 1.011~1.095) and (OR=1.214, 95% CI: 1.070~1.377). Moreover, among male T2DM patients, the AHI score and ODI score had a linear correlation with the CEA level; this association was also observed in T2DM patients who smoked, had an HbA1c level ≥7%, or had a BMI ≥28 kg/m² (all p<0.05).

Conclusions

The AHI score and ODI score were positively associated with the CEA level in T2DM patients. The relationship was stronger in male T2DM patients and in those who smoked, were obese, or had poor glycemic control. The mechanism may be related to metabolic disorders, and the potential increased risk of colorectal cancer should be investigated in a prospective study.

Domiciliary use of transcutaneous electrical stimulation for patients with obstructive sleep apnoea: a conceptual framework for the TESLA home programme

Obstructive sleep apnoea (OSA) is a global health problem of increasing prevalence. Effective treatments are available with continuous positive airway pressure (CPAP) therapy and mandibular advancement devices (MAD). However, there is limited long-term adherence to therapy, as CPAP and MAD require permanent usage to avoid recurrence of the symptoms and adverse ill health. Alternative treatments would aid in the treatment cascade to manage OSA effectively whenever standard therapy has been trialled and failed. Hypoglossal nerve stimulation (HNS), an invasive approach to stimulate the pharyngeal dilator muscles of the upper airway during sleep, has been approved for the treatment of OSA by several healthcare systems in recent years. In parallel to the development of HNS, a non-invasive approach has been developed to deliver electrical stimulation. Transcutaneous electrical stimulation in obstructive sleep apnoea (TESLA) uses non-invasive electrical stimulation to increase neuromuscular tone of the upper airway dilator muscles of patients with OSA during sleep. Data from previous feasibility studies and randomised controlled trials have helped to identify a subgroup of patients who are "responders" to this treatment. However, further investigations are required to assess usability, functionality and task accomplishment of this novel treatment. Consideration of these factors in the study design of future clinical trials will strengthen research methodology and protocols, improve patient related outcome measures and assessments, to optimise this emerging therapeutical option. In this review, we will introduce a conceptual framework for the TESLA home programme highlighting qualitative aspects and outcomes.

Brain Circuitry for Arousal from Apnea

We wanted to understand the brain circuitry that awakens the individual when there is elevated CO₂ or low O₂ (e.g., during sleep apnea or asphyxia). The sensory signals for high CO₂ and low O₂ all converge on the parabrachial nucleus (PB) of the pons, which contains neurons that project to the forebrain. So, we first deleted the vesicular glutamate transporter 2, necessary to load glutamate into synaptic vesicles, from neurons in the PB, and showed that this prevents awakening to high CO₂ or low O₂ We then showed that PB neurons that express calcitonin gene-related peptide (CGRP) show cFos staining during high CO₂ Using CGRP-Cre-ER mice, we expressed the inhibitory opsin archaerhodopsin just in the PB^CGRP neurons. Photoinhibition of the PB^CGRP neurons effectively prevented awakening to high CO₂, as did photoinhibition of their terminals in the basal forebrain, amygdala, and lateral hypothalamus. The PB^CGRP neurons are a key mediator of the wakening response to apnea.

Vertical sleeve gastrectomy improves ventilatory drive through a leptin-dependent mechanism

Obesity hypoventilation syndrome (OHS) is a serious disorder characterized by daytime hypercapnia, disordered breathing, and a reduction in chemosensitivity. Vertical sleeve gastrectomy (VSG), a bariatric surgical procedure resulting in weight loss and weight-independent improvements in glucose metabolism, has been observed to substantially improve sleep-disordered breathing. However, it is unclear if the ventilatory effects of VSG are secondary to weight loss or the marked change in metabolic physiology. Using preclinical mouse models, we found that VSG leads to an improvement in the hypercapnic ventilatory response (HCVR) and reductions in circulating leptin levels independent of reductions in body mass, fat mass, and caloric intake. In the absence of leptin, VSG continues to improve body mass, fat mass, and glucose tolerance in ob/ob mice but no longer affects HCVR. However, the HCVR of ob/ob mice can be returned to wild-type levels with leptin treatment. These data demonstrate that VSG improves chemosensitivity and ventilatory drive via a leptin-dependent mechanism. Clinically, these data downgrade the relative contribution of physical, mechanical load in the pathogenesis of OHS, and instead point to physiological components of obesity, including alterations in leptin signaling, as key drivers in OHS.

Oxidative Stress Markers and Severity of Obstructive Sleep Apnea

Oxidative stress underlies both obstructive sleep apnea (OSA) and atherosclerosis. The aim of the study was to assess the markers of oxidative stress in plasma at different stages of OSA in non-smoking obese Caucasian males aged 41-60, with normal oral glucose tolerance test. All patients were subjected to clinical and polysomnographic examinations. The stage of OSA severity was set according to the following criteria of the apnea-hypopnea index (AHI): AHI < 5/h - no disease (OSA-0; n = 26), AHI 5-15/h - mild disease (OSA-1; n = 26), AHI 16-30/h - moderate disease (OSA-2: n = 27), and AHI > 30/h obstructive episodes per hour - severe disease (OSA-3; n = 27). Plasma total antioxidant status (TAS) and thiobarbituric acid-reacting substances (TBARS), reflecting the level of lipid peroxides, were determined spectrophotometrically. We found that TAS decreased and TBARS increased significantly from OSA-0 to OSA-3. We conclude that the oxidative stress markers are conducive to setting the severity of OSA in normoglycemic patients.

Upper airway stimulation in obstructive sleep apnea improves glucose metabolism and reduces hedonic drive for food

Upper airway stimulation is a new and effective second-line treatment for obstructive sleep apnea, but possible consequences on glucose metabolism and central regulation of food intake are unclear. Twenty patients were prospectively studied before and 12 months after obstructive sleep apnea treatment by upper airway stimulation. Respiratory parameters and daytime sleepiness were assessed to document effectiveness of treatment. Glucose metabolism was assessed by the oral glucose tolerance test, and hedonic versus homeostatic drive to eat was characterized. At 12 months, upper airway stimulation significantly improved measures of obstructive sleep apnea (all p < 0.01). Despite no change in body weight, fasting C-peptide insulin resistance index (p = 0.01) as well as insulin and C-peptide levels at 60 min during the oral glucose tolerance test (p < 0.02) were reduced. Hedonic drive to eat was strongly reduced (p < 0.05), while leptin and ghrelin remained unchanged (p > 0.15). Upper airway stimulation is effective in treatment of obstructive sleep apnea and improves glucose metabolism. Reduced hedonic drive to eat might contribute to these metabolic improvements. These promising findings are in need for long-term controlled evaluation of metabolic sequelae of upper airway stimulation and to mechanistically evaluate the metabolic benefits of upper airway stimulation in patients with obstructive sleep apnea.