Obstructive sleep apnea and type 2 diabetes: interacting epidemics

Bispectral analysis of tracheal breath sounds for Obstructive Sleep Apnea

Obstructive Sleep Apnea (OSA) is a respiratory disorder with serious consequences that is characterized by repetitive cessation of breathing for more than 10s often associated with a drop of more than 4% in the blood's Oxygen saturation level. The gold standard for OSA diagnosis is full-night Polysomnography (PSG), which is a time-consuming, inconvenient, and costly assessment. On the other hand, our team has showed that the analysis of tracheal respiratory sounds recorded during wakefulness holds promises to be used as a simple and effective tool for screening moderate and severe OSA. In this paper, we examine the nonlinear characteristics of tracheal breath sounds and the possibility to extract features from Higher Order Spectra (HOS) for OSA screening. The data used in this study were recorded during wakefulness in two body positions, supine and upright, and during mouth and nose breathing. We estimated the bispectrum of the sounds in each respiratory cycle, calculated the median bifrequencies and the energy of the bispectrum, and investigated any statistically significant differences between the extracted features in two groups of non-OSA and severe OSA data. The differences in the features between body positions and nose/mouth breathing were also looked at. One-way ANOVA revealed significant differences in the features between non-OSA individuals and those with severe OSA. The results encourage the use of these features in future studies for OSA screening.

Impact of Obstructive Sleep Apnoea on Type 2 Diabetes and Vice Versa

Type 2 diabetes and obstructive sleep apnoea (OSA) are diseases with high prevalence and major public health impact. There is evidence that OSA is independently associated with alterations in glucose metabolism. Furthermore, OSA is a significant risk factor for the development of type 2 diabetes. Possible causes might be intermittent hypoxaemia and sleep fragmentation with increased oxidative stress and sympathetic activity, which are typical features of OSA. OSA might also be a reason for ineffective treatment of type 2 diabetes. There is further evidence that the treatment of OSA by continuous positive airway pressure (CPAP) therapy might improve glucose metabolism. On the other hand, there are also hints in the literature that type 2 diabetes might induce sleep apnoea, especially in patients with autonomic neuropathy, but that OSA also facilitates the development of neuropathy in terms of mutual interactions between OSA, type 2 diabetes and diabetic neuropathy. Based on the current scientific data, clinicians have to be aware of the relations between OSA and type 2 diabetes, both from the sleep medical and the diabetological point of view.

The cholinergic system may play a role in the pathophysiology of residual excessive sleepiness in patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) is a prevalent condition characterized by momentary cessations in breathing during sleep due to intermittent obstruction of the upper airway. OSA has been frequently associated with a number of medical comorbidities. CPAP (continuous positive airway pressure) is the gold standard treatment and is known to improve OSA symptoms, including excessive sleepiness. However, 12-14% of CPAP-treated patients continue to complain of sleepiness despite normalization of ventilation during sleep, and 6% after exclusion of other causes of EDS. This is of great concern because EDS is strongly associated with systemic health disorders, lower work performance, and a high risk of accidents. We hypothesized that decreased central cholinergic activity plays a role in the pathophysiology of residual excessive sleepiness in patients with OSA treated with CPAP. Acetylcholine (Ach) plays a large role in wakefulness physiology, and its levels are reduced in sleepiness. Herein, we discuss the potential role of the cholinergic system in this new clinical condition.

Testing the McSad depression specific classification system in patients with somatic conditions: validity and performance

Background

Valuations of depression are useful to evaluate depression interventions offered to patients with chronic somatic conditions. The only classification system to describe depression developed specifically for valuation purposes is the McSad, but it has not been used among somatic patients. The aim of this study was to test the construct validity of the McSad among diabetes and cancer patients and then to compare the McSad to the commonly used EuroQol – 5 Dimensions (EQ-5D^TM) classification system. The comparison was expected to shed light on their capacity to reflect the range of depression states experienced by somatic patients.

Methods

Cross-sectional data were collected online from 114 diabetes and 195 cancer patients; additionally, 241 cancer patients completed part of the survey on paper. Correlational analyses were performed to test the construct validity. Specifically, we hypothesized high correlations of the McSad domains with depression (Center for Epidemiological Studies Depression Scale (CES-D) and the Patient Health Questionnaire (PHQ-9)). We also expected low/moderate correlations with self-esteem (Rosenberg Self-Esteem scale - RSE) and extraversion (Eysenck Personality Questionnaire Extraversion scale - EPQ-e). Multiple linear regression analyses were run so that the proportion of variance in depression scores (CES-D, PHQ-9) explained by the McSad could be compared to the proportion explained by the EQ-5D classification system.

Results

As expected, among all patients groups, we found moderate to high correlations for the McSad domains with the CES-D (.41 to .70) and the PHQ-9 (.52 to .76); we also found low to moderate correlations with the RSE (-.21 to .-48) and the EPQ-e (.18 to .31). Linear regression analyses showed that the McSad explained a greater proportion of variance in depression (CES-D, PHQ-9) (Diabetes: 73%, 82%; Cancer: 72%, 72%) than the EQ-5D classification system (Diabetes: 47%, 59%; Cancer: 51%, 47%).

Conclusions

Findings support the construct validity of the McSad among patients with somatic conditions and demonstrate that it performs better than the EQ-5D classification system to reflect the range of depression states. For future valuation purposes, the McSad classification system could therefore be recommended to describe depression as experienced by patients with a chronic medical condition.

Obstructive sleep apnea is a predictor of abnormal glucose metabolism in chronically sleep deprived obese adults

Context

Sleep abnormalities, including obstructive sleep apnea (OSA), have been associated with insulin resistance.

Objective

To determine the relationship between sleep, including OSA, and glucose parameters in a prospectively assembled cohort of chronically sleep-deprived obese subjects.

Design

Cross-sectional evaluation of a prospective cohort study.

Setting

Tertiary Referral Research Clinical Center.

Main Outcome Measure(s)

Sleep duration and quality assessed by actigraphy, sleep diaries and questionnaires, OSA determined by a portable device; glucose metabolism assessed by oral glucose tolerance test (oGTT), and HbA₁c concentrations in 96 obese individuals reporting sleeping less than 6.5 h on a regular basis.

Results

Sixty % of subjects had an abnormal respiratory disturbance index (RDI≥5) and 44% of these subjects had abnormal oGTT results. Severity of OSA as assessed by RDI score was associated with fasting glucose (R = 0.325, p = 0.001) and fasting insulin levels (ρ = 0.217, p = 0.033). Subjects with moderate to severe OSA (RDI>15) had higher glucose concentrations at 120 min than those without OSA (RDI<5) (p = 0.017). Subjects with OSA also had significantly higher concentrations of plasma ACTH (p = 0.009). Several pro-inflammatory cytokines were higher in subjects with OSA (p<0.050). CRP levels were elevated in this sample, suggesting increased cardiovascular risk.

Conclusions

OSA is associated with impaired glucose metabolism in obese, sleep deprived individuals. Since sleep apnea is common and frequently undiagnosed, health care providers should be aware of its occurrence and associated risks.

Trial Registration

This study was conducted under the NIDDK protocol 06-DK-0036 and is listed in ClinicalTrials.gov NCT00261898

Effect of hypoxia on glucose metabolism in nondiabetic patients with obstructive sleep apnea syndrome

AIM

Obstructive sleep apnea syndrome (OSAS) may promote hyperglycemia and insulin resistance. Our aim is to investigate the effect of OSAS on the fasting plasma glucose, glycosylated hemoglobin (HbA1c), and C reactive protein (CRP) in nondiabetic patients.

MATERIAL AND METHODS

Blood parameters of consecutive 90 non diabetic patients whom polysomnografic evaluations were done in our sleep laboratory was evaluated. Among these 61 patients with normal fasting blood glucose were classified due to their apne-hipopnea index (AHI) as mild (n=16, 26.2%), moderate (n=18, 29.5%) and severe (n=27, 44.2%) OSAS. The fasting plasma glucose, HbA1c and CRP were measured.

RESULTS

Mean age of the patients was 47.7±11.2 years, 72% male. HbA1c, fasting glucose levels show positive correlation with BMI (r=.503, P=.00; r=.258, P=.045). No relation of HbA1c to apnea index nor AHI was detected while positive corelation of fasting glucose and CRP was detected (r=.262, P=.042; r=.258, P=.045). HbA1c, fasting glucose and CRP levels show negative correlation with minimum SpO2 levels (by order of r=-.302, P=.018; r=-.368, P=.004; r=-.365, P=.004). HbA1c, fasting glucose levels and CRP levels show positive correlation with mean desaturation index (time duration in which SpO2<90% by pulse oxymeter) (r=.263, P=.041; r=.311, P=.015; r=.283, P=.027).

CONCLUSIONS

Although no relation in between increased HbA1c or glucose levels and severity of OSAS was detected in nondiabetic OSAS patients, the correlation with the night hypoxia was detected. This could also show the effect of night time hypoxia on glucose metabolism in OSAS patients.

Sleep apnea, sleep disturbance, and fasting glucose variability: a pilot study

BACKGROUND

Disturbed sleep and nocturnal altered breathing are related to disturbances of glucose metabolism. The present uncontrolled observational study explores the role of these factors on the variability of fasting glycemia.

METHODS

The number and duration of nocturnal awakenings and the fasting glycemia of 97 patients with type 2 diabetes treated with diet, metformin, or gliptins were recorded over seven consecutive days. During the same time period, the main respiratory indexes-oxygen disturbance index, apnea/hypopnea index, and respiratory disturbance index-were recorded for one night.

RESULTS

The three respiratory indexes and the number of nocturnal awakenings are highly correlated with the coefficient of variation of the fasting blood glucose recorded over the 7-day period at p < .005 level. A multiple regression analysis showed that the variables in the model explained 86% of the variability.

DISCUSSION

Respiratory/sleep disturbances appear to be modulators superimposed on blood glucose levels determined by other factors.

Obstructive sleep apnea and coronary artery disease: from pathophysiology to clinical implications

Coronary artery disease (CAD) and obstructive sleep apnea (OSA) are both complex and significant clinical problems. The pathophysiological mechanisms that link OSA with CAD are complex and can influence the broad spectrum of conditions caused by CAD, from subclinical atherosclerosis to myocardial infarction. OSA remains a significant clinical problem among patients with CAD, and evidence suggesting its role as a risk factor for CAD is growing. Furthermore, increasing data support that CAD prognosis may be influenced by OSA and its treatment by continuous positive airway pressure (CPAP) therapy. However, stronger evidence is needed to definitely answer these questions. This paper focuses on the relationship between OSA and CAD from the pathophysiological effects of OSA in CAD, to the clinical implications of OSA and its treatment in CAD patients.

Neuroendocrine regulation and metabolism of glucose and lipids in primary chronic insomnia: a prospective case-control study

OBJECTIVES

To investigate the relation between primary chronic insomnia and insulin sensitivity, visceral adiposity, non alcoholic fatty liver disease and neuroendocrine hormones.

MATERIALS AND METHODS

In a case-controlled, prospective clinical trial 13 women with primary chronic insomnia according to DSM-IV criteria were compared to 12 healthy controls matched for age, sex, BMI, body composition and menopausal status. All participants had a sleep assessment including polysomnographic studies and neuropsychiatric evaluation. Insulin sensitivity was evaluated using the euglycaemic hyperinsulinemic clamp. Hepatic fat content, visceral adipose tissue and intramyocellular lipid accumulation were assessed using magnetic resonance imaging and spectroscopy. The hormonal stress axis was evaluated by measurements of midnight and early morning salivary cortisol, urinary catecholamines and plasma metanephrines. Body composition was determined using body impedance analysis and indirect calorimetry.

RESULTS

Although the diagnosis of primary chronic insomnia was made by established clinical criteria, standard polysomongraphic studies failed to identify altered sleep continuity and architecture when compared to matched controls. However, women with primary chronic insomnia showed significantly higher midnight salivary cortisol concentrations (1.46 vs. 0.76 nmol/l, p = 0.02), indicating dysregulation of the hypothalamo-pituitary-adrenal (HPA) axis. Plasma glucose and lipid concentrations, insulin sensitivity, hepatic and intramyocellular fat content, visceral adipose tissue mass and body composition did not differ between the two groups.

CONCLUSION

Healthy women with clinically diagnosed primary chronic insomnia demonstrate a dysregulation of circadian cortisol secretion despite normal sleep continuity and architecture. Increased midnight cortisol levels, however, were not associated with impaired metabolism of glucose and lipids.

Sleep apnea and risk of peptic ulcer bleeding: a nationwide population-based study

OBJECTIVE

Patients with sleep apnea sustain cessation of breath during sleep, leading to intermittent hypoxia, systemic inflammation, and sympathetic activation. These insults may contribute to initiation or progression of peptic ulcers. This retrospective matched-control cohort study explored the relationship of sleep apnea and subsequent development of peptic ulcer bleeding.

METHODS

From 2000 to 2009, patients with newly diagnosed sleep apnea were identified from the Taiwan National Health Insurance Research Database. A control group without sleep apnea, matched for age, gender, comorbidities, and medications, was selected for comparison. In both groups, subjects with history of peptic ulcer bleeding, nonspecific gastrointestinal bleeding, or malignancy were excluded. The 2 cohorts were followed up and observed for occurrence of peptic ulcer bleeding.

RESULTS

Of the 35,480 sampled patients (7096 patients with sleep apnea vs 28,384 controls), 84 (0.24%) experienced peptic ulcer bleeding during a follow-up period of 3.57±2.61 years, including 32 (0.45% of patients with sleep apnea) from the sleep apnea cohort and 52 (0.18% of control) from the control group (log-rank test, P<.0001). In comparison with subjects without development of peptic ulcer bleeding, those with peptic ulcer bleeding were older and had a higher percentage of sleep apnea, coronary artery disease, peptic ulcer, ischemic stroke, and medication for nonsteroidal anti-inflammatory drugs. By Cox regression analysis, sleep apnea, older age, and peptic ulcer history were independent predictors of peptic ulcer bleeding. Patients with sleep apnea experienced a 2.400-fold (95% confidence interval, 1.544-3.731; P<.001) higher risk for incident peptic ulcer bleeding after adjusting for other variables.

CONCLUSIONS

Sleep apnea may be an independent risk factor for peptic ulcer bleeding.

Disturbed subjective sleep in Chinese females with type 2 diabetes on insulin therapy

Objectives

The aim of this study is to investigate the prevalence and determine the possible risk factors of poor sleep quality in Chinese type 2 diabetes patients with insulin treatment.

Methods

140 type 2 diabetes patients with insulin treatments were enrolled in our study. General characteristics and laboratory testing such glycosylated hemoglobin A1c (HbA1c), fasting plasma glucose (FPG), post-prandial plasma glucose (PPG) were measured. Every patient completed Chinese version of Pittsburgh Sleep Quality Index (PSQI) questionnaire. PSQI global score>5 was defined as poor sleep quality.

Results

Global PSQI score was significantly higher in female type 2 diabetes patients with insulin treatment than male (7.52 vs 6.08, P<0.05). After adjusting for age, BMI, FPG, PPG, HbA1c and duration of diabetes, female is still an independent risk factor for poor sleep quality [OR = 2.55, 95% confidence interval (CI) = 1.24–5.27, P = 0.01].

Conclusion

The results suggest that we found poor sleep quality in female Chinese type 2 diabetes patients with insulin treatment and these findings may contribute to sleep disorder control in female type 2 diabetes.

Sleep-disordered breathing and daytime napping are associated with maternal hyperglycemia

OBJECTIVES

Sleep disturbances in pregnancy may impair glucose mechanism. This study aimed to examine associations of sleep-disordered breathing, sleep, and nap duration with 1-h glucose challenge test (GCT) levels in pregnant women after controlling for known risk factors for gestational diabetes.

METHODS

This is a case-control study of 104 pregnant women. All women underwent full polysomnography and a GCT and completed the multivariable apnea prediction and Pittsburgh Sleep Quality indexes. The primary outcome was maternal hyperglycemia measured by GCT. Bivariate and multivariable logistic regression analyses were performed.

RESULTS

Over 13 % subjects reported habitual snoring in the first trimester. Only 9.3 % women with normoglycemia (GCT < 135) were habitual snorers, whereas 45.5 % women with hyperglycemia (GCT ≥ 135) had habitual snoring (p < 0.001). Sleep-disordered breathing symptoms (loud snoring, snorting/gasping, and apneas) (odds ratio (OR) 2.85; 95 % confidence interval (CI) 1.50-5.41; p = 0.001) and total nap duration (OR 1.48; 95 % CI 0.96-2.28; p = 0.08) were associated with hyperglycemia. After adjusting for confounders, sleep-disordered breathing symptoms (OR 3.37; 95 % CI 1.44-8.32; p = 0.005) and nap duration (OR 1.64; 95 % CI 1.00-2.681.02; p = 0.05) continued to be associated with hyperglycemia. However, the primary exposure measure, the apnea/hypopnea index in the first trimester was not significantly associated with hyperglycemia (OR 1.03; 95 % CI 0.83-1.28; p = 0.77).

CONCLUSIONS

Sleep-disordered breathing symptoms and nap duration are associated with hyperglycemia. Sleep duration was not associated with hyperglycemia. Research is needed concerning whether women with sleep-disordered breathing and/or daytime napping are at risk for gestational diabetes.

Prevalence, risk factors and co-morbidities of diabetes among adults in rural Saskatchewan: the influence of farm residence and agriculture-related exposures

BACKGROUND

Although rural Canadians are reported to have higher rates of diabetes than others, little is known about the relative influence of known versus agriculture-related risk factors. The purpose of this research was to carry out a comprehensive study of prevalence, risk factors and co-morbidities of diabetes among adults in rural Saskatchewan and to determine possible differences between those living on and off farms.

METHODS

In 2010, we conducted a baseline mail-out survey (Saskatchewan Rural Health Study) of 11,982 households located in the province's four agricultural quadrants. In addition to self-reported physician-diagnosed diabetes, the questionnaire collected information from farm and small town cohorts on possible diabetes determinants including lifestyle, family history, early life factors and environmental/agricultural-related exposures. Clustering effect within households was adjusted using Generalized Estimating Equations approach.

RESULTS

Responses were obtained from 4624 (42%) households comprising 8208 males and females aged 18 years or older and 7847 self-described Caucasian participants (7708 with complete information). The overall age-standardized diabetes prevalence for the latter was 6.35% but people whose primary residence was on farms had significantly lower diabetes prevalence than those living in non-farm locations (5.11% versus 7.33% respectively; p<0.0001). Diabetes risk increased with age and affected almost 17% of those older than 65 (OR 2.57; CI' 1.63, 4.04 compared to those aged 18-45). Other known independent risk factors included family history of diabetes (OR 2.50 [CI's 1.94, 3.23] if father; OR 3.11 [CI's 2.44, 3.98] if mother), obesity (OR 2.66; CI's 1.86, 3.78), as well as lower socioeconomic status, minimal/no alcohol intake and smoking. The most original finding was that exposure to insecticides conferred an increased risk for diabetes among males (OR 1.83; CI's 1.15, 2.91). Finally, the co-morbidities with the strongest independent association with diabetes were heart disease and hypertension.

CONCLUSIONS

While known diabetes risk factors are important determinants of diabetes in the agricultural zones of Saskatchewan, on-farm residence is protective and appears related to increased outdoor activities. In contrast, we have now shown for the first time that exposure to insecticides is an independent risk factor for diabetes among men in rural Canada.

Understanding the metabolic syndrome: a modeling perspective

The prevalence of obesity is growing at an alarming rate, placing many at risk for developing diabetes, hypertension, sleep apnea, or a combination of disorders known as "metabolic syndrome". The evidence to date suggests that metabolic syndrome results from an imbalance in the mechanisms that link diet, physical activity, glucose-insulin control, and autonomic cardiovascular control. There is also growing recognition that sleep-disordered breathing and other forms of sleep disruption can contribute significantly to autonomic dysfunction and insulin resistance. Chronic sleep deprivation resulting from sleep-disordered breathing or behavioral causes can lead to excessive daytime sleepiness and lethargy, which in turn contribute to increasing obesity. Analysis of this complex dynamic system using a model-based approach can facilitate the delineation of the causal pathways that lead to the emergence of the metabolic syndrome. In this paper, we provide an overview of the main physiological mechanisms associated with obesity and sleep-disordered breathing that are believed to result in metabolic and autonomic dysfunction, and review the models and modeling approaches that are relevant in characterizing the interplay among the multiple factors that underlie the development of the metabolic syndrome.

Relationship between sleep disorders and the risk for developing type 2 diabetes mellitus

Sleep is increasingly being recognized as an important factor in the homeostasis of multiple body functions, including blood glucose metabolism. One of the most common sleep disorders, obstructive sleep apnea, is not only highly prevalent in patients with type 2 diabetes mellitus, but may contribute to the development of abnormalities in blood glucose metabolism. Evidence suggests that effectively treating sleep apnea, specifically with continuous positive airway pressure, improves glycemic and nonglycemic outcomes. Other common sleep disorders, such as insufficient sleep, shift work disorder, and restless legs syndrome, may also have a significant influence on the development and management of diabetes and its complications. The purpose of this article is to review the recent literature on the relationship between sleep disorders and blood glucose metabolism.

A randomized, double-blind, placebo-controlled study of an oral, extended-release formulation of phentermine/topiramate for the treatment of obstructive sleep apnea in obese adults

STUDY OBJECTIVES

To evaluate safety and efficacy of phentermine 15 mg plus extended-release topiramate 92 mg for treatment of moderate to severe obstructive sleep apnea (OSA) in obese adults.

DESIGN

This phase 2, randomized, double-blind, placebo-controlled study included 2-week screening and 28-week treatment periods. Overnight polysomnography was performed at baseline, Week 8, and Week 28.

SETTING

Single-center study conducted from August 2008 to September 2009.

PARTICIPANTS

Forty-five subjects with moderate to severe OSA not receiving positive airway pressure (PAP) treatment with body mass index of 30-40 kg/m(2).

INTERVENTIONS

Subjects were randomized to receive placebo (n = 23) or phentermine 15 mg plus extended-release topiramate 92 mg (n = 22). Both groups received lifestyle-modification counseling.

MEASUREMENTS AND RESULTS

Primary endpoint, change in apnea-hypopnea index (AHI), significantly favored phentermine 15 mg plus extended-release topiramate 92 mg (-31.5 events/h, 95% CI: -40.0, -22.9) over placebo (-16.6 events/h, 95% CI: -25.0, -8.2) at Week 28 (P =0.0084). At Week 28, there was a 10.2% (95% CI: -12.7, -7.6; 10.8 kg, 95% CI: -13.5, -8.0) mean decrease in weight in the phentermine 15 mg plus extended-release topiramate 92 mg group compared with 4.3% (95% CI: -6.6, -2.0; 4.7 kg, 95% CI: -7.2, -2.2) in the placebo group (P = 0.0006) and a positive, significant (P = 0.0003) correlation between percent change in weight and change in AHI. Significant improvements in overnight oxygen saturation and reduction in blood pressure compared with placebo were observed. Phentermine 15 mg plus extended-release topiramate 92 mg was well tolerated with low adverse event rates.

CONCLUSIONS

Phentermine 15 mg plus extended-release topiramate 92 mg induced significant weight reductions and concomitant improvements in OSA and related symptoms vs placebo. This suggests weight loss mediated by phentermine 15 mg plus extended-release topiramate 92 mg may be useful in treatment of moderate to severe OSA in obese subjects unable or unwilling to comply with PAP treatment.

Sleep disturbances and low psychological well-being are associated with an increased risk of autoimmune diabetes in adults. Results from the Nord-Trøndelag Health Study

AIMS

To investigate whether sleep disturbances and low psychological well-being are associated with an increased risk of autoimmune diabetes in adults (including LADA and type 1 diabetes) and type 2 diabetes.

METHODS

We used data from the Norwegian HUNT Study (n = 53,394) and estimated the risk of developing autoimmune diabetes in adults (n = 138) and type 2 diabetes (n = 1895) between 1984 and 2008 in relation to baseline self-reported psychological well-being and sleep problems.

RESULTS

Sleep disturbances and low psychological well-being were associated with an increased risk of autoimmune diabetes (hazard ratio 1.84, 95% confidence interval 1.10-3.09), primarily linked to poor sleep in men (1.83, 1.05-3.20) and low well-being in women (2.50, 1.03-6.54). Similar associations were seen with type 2 diabetes in relation to sleep problems (1.25, 1.08-1.44) in men and low well-being (1.34, 1.16-1.54), in both men and women. In autoimmune diabetes, these factors were associated with lower anti-GAD levels (177 vs. 306 WHO units/ml, p = 0.04).

CONCLUSIONS

Our findings indicate that psychosocial factors influence the risk of autoimmune diabetes in adults, possibly through mechanisms related to insulin resistance. This supports the notion that the aetiology of autoimmune diabetes with adult onset in some respects is similar to that of type 2 diabetes.

Obesity and obstructive sleep apnea--clinical significance of weight loss

Obesity is a major health burden that contributes to increased morbidity and mortality. Obesity is also the most important risk factor for obstructive sleep apnea (OSA); at least 70% of patients are obese. OSA as such, has been linked with increased cardiovascular morbidity and mortality, and OSA patients often display metabolic syndrome. The exact underlying mechanisms behind these associations are complex and not fully understood. In obese individuals, weight reduction and increased physical activity form cornerstones for the prevention and treatment of metabolic syndrome, and recent controlled intervention trials strongly suggest that weight reduction together with a healthy diet and increased physical activity may correct or at least improve the symptoms of OSA. However, regardless of promising results in terms of symptoms of OSA and the undoubted metabolic benefits of changing lifestyles, weight reduction as a treatment of OSA is still underrated by many clinicians. Based on the current knowledge, clinicians should revise their previous attitudes, including suspicions about weight reduction as an effective treatment for OSA patients. Nevertheless, we also need large well-controlled trials on the effects of different weight reduction programs among OSA patients to determine the overall efficacy of different treatment modalities and their long-term success.

Cardiometabolic aspects of the polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder amongst women of reproductive age and is associated with various metabolic perturbations, in addition to chronic anovulation and factors related to androgen excess. In general, women live longer than men and develop cardiovascular disease at an older age. However, women with PCOS, as compared with age- and body mass index-matched women without the syndrome, appear to have a higher risk of insulin resistance, hyperinsulinemia, glucose intolerance, dyslipidemia, and an increased prothrombotic state, possibly resulting in a higher rate of type 2 diabetes mellitus, fatty liver disease, subclinical atherosclerosis, vascular dysfunction, and finally cardiovascular disease and mortality. Further alterations in PCOS include an increased prevalence of sleep apnea, as well as various changes in the secretion and/or function of adipokines, adipose tissue-derived proinflammatory factors and gut hormones, all of them with direct or indirect influences on the complex signaling network that regulates metabolism, insulin sensitivity, and energy homeostasis. Reviews on the cardiometabolic aspects of PCOS are rare, and our knowledge from recent studies is expanding rapidly. Therefore, it is the aim of the present review to discuss and to summarize the current knowledge, focusing on the alterations of cardiometabolic factors in women with PCOS. Further insight into this network of factors may facilitate finding therapeutic targets that should ameliorate not only ovarian dysfunction but also the various cardiometabolic alterations related to the syndrome.

Obesity and metabolic syndrome: association with chronodisruption, sleep deprivation, and melatonin suppression

Obesity has become an epidemic in industrialized and developing countries. In 30 years, unless serious changes are made, a majority of adults and many children will be classified as overweight or obese. Whereas fatness alone endangers physiological performance of even simple tasks, the associated co-morbidity of obesity including metabolic syndrome in all its manifestations is a far more critical problem. If the current trend continues as predicted, health care systems may be incapable of handling the myriad of obesity-related diseases. The financial costs, including those due to medical procedures, absenteeism from work, and reduced economic productivity, will jeopardize the financial well-being of industries. The current review summarizes the potential contributions of three processes that may be contributing to humans becoming progressively more overweight: circadian or chronodisruption, sleep deficiency, and melatonin suppression. Based on the information provided in this survey, life-style factors (independent of the availability of abundant calorie-rich foods) may aggravate weight gain. Both epidemiological and experimental data support associations between disrupted physiological rhythms, a reduction in adequate sleep, and light-at-night-induced suppression of an essential endogenously produced molecule, melatonin. The implication is that if these problems were corrected with life-style changes, body-weight could possibly be more easily controlled.

The relationship between obstructive sleep apnea and self-reported stroke or coronary heart disease in overweight and obese adults with type 2 diabetes mellitus

STUDY OBJECTIVES

Type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) are common, increasingly recognized as comorbid conditions, and individually implicated in the development of cardiovascular disease (CVD). We sought to determine the association between OSA and CVD in an overweight and obese population with T2DM.

DESIGN

Cross-sectional.

SETTING

Ancillary study to the Look AHEAD trial.

PARTICIPANTS

Three hundred five participants of the Sleep AHEAD study who underwent unattended full polysomnography at home with measurement of the apnea-hypopnea index (AHI).

MEASUREMENTS AND RESULTS

Self-reported prevalent CVD was obtained at the initial assessment of the parent study and included a history of the following conditions: stroke, carotid endarterectomy, myocardial infarction, coronary artery bypass grafting, and percutaneous coronary intervention. Logistic regression was used to assess the association of OSA, measured continuously and categorically, with prevalent CVD. OSA was present (AHI ≥ 5) in 86% of the population, whereas the prevalence of all forms of CVD was just 14%. The AHI was associated with stroke with an adjusted odds ratio (95% confidence interval) of 2.57 (1.03, 6.42). Neither the continuously measured AHI nor the categories of OSA severity were significantly associated with the other forms of CVD assessed.

CONCLUSIONS

We found suggestive evidence of a greater prevalence of stroke at greater values of the AHI. OSA was not associated with prevalent coronary heart disease in the Sleep AHEAD trial. Future studies should confirm the link between OSA and stroke and examine mechanisms that link OSA to stroke in adults with T2DM.

Sleep and cardiometabolic function in obese adolescent girls with polycystic ovary syndrome

OBJECTIVE

To compare the polysomnography findings and cardiometabolic function among adolescent girls with polycystic ovary syndrome (PCOS) and matched female and male controls.

METHOD

Retrospective chart review of electronic medical records of 28 girls with PCOS (age: 16.8±1.9 years, body mass index (BMI) Z-score 2.4±0.4), 28 control females (age: 17.1±1.8, BMI Z-score 2.4±0.3) and 28 control males (age: 16.6±1.6, BMI Z-score 2.5±0.5) in a tertiary care centre.

RESULTS

The prevalence of obstructive sleep apnoea (OSA) was higher in girls with PCOS compared to control females (16/28 (57%) vs. 4/28(14.3%), p<0.01); however, it was comparable to that of the control males (16/28(57%) vs. 21/28(75%), p=0.4). Girls with PCOS had a significantly higher prevalence of insulin resistance compared to control females and control males (20/28 (71.4%) vs. 9/22 (41.0%) (p=0.04) vs. 8/23 (34.8%) (p=0.01). Among girls with PCOS, those with OSA had significantly higher proportions of metabolic syndrome (MetS) (9/16 (56.3%) vs. 1/12 (8.3%) p=0.03), higher insulin resistance (14/16 (87.5%) vs. 6/12 (50%), p=0.04), elevated daytime systolic blood pressure (128.4±12.8 vs. 115.6±11.4, p<0.01), lower high-density lipoprotein (HDL) (38.6±8.7 vs. 49±10.9, p=0.01) and elevated triglycerides (TG) (149.7±87.7 vs. 93.3±25.8, p=0.03) compared to those without OSA.

CONCLUSIONS

We report a higher prevalence of OSA and metabolic dysfunction in a selected group of obese girls with PCOS referred with sleep-related complaints compared to BMI-matched control girls without PCOS. We also report higher prevalence of cardiometabolic dysfunction in girls with PCOS and OSA compared to girls with PCOS without OSA.

OSA and atherosclerosis

Untreated obstructive sleep apnea (OSA) is increasingly recognized as a risk factor contributing to cardiovascular morbidity and mortality. Research in recent decades has uncovered many components of the complex pathological events leading to the atherosclerotic vascular diseases in OSA, which involve heightened oxidative stress as a result of intermittent hypoxia, vascular inflammation, activation of platelet and coagulation cascades, endothelial dysfunction and ultimately the formation of atherosclerotic plagues. The close association of OSA and conventional cardiovascular risk factors including hypertension, diabetes mellitus, dyslipidemia and obesity adds to the adverse cardiovascular sequelae. Further studies are required to clarify further on the pathophysiological processes, and the effect size of OSA therapy, and other potential preventive strategies.

Obstructive sleep apnea and type 2 diabetes: is there a link?

Type 2 diabetes is a chronic illness that is increasing in epidemic proportions worldwide. Major factors contributing to the development of type 2 diabetes include obesity and poor lifestyle habits (e.g., excess dietary intake and limited physical activity). Despite the proven efficacy of lifestyle interventions and the use of multiple pharmacological agents, the economic and public health burden of type 2 diabetes remains substantial. Obstructive sleep apnea (OSA) is a treatable sleep disorder that is pervasive among overweight and obese adults, who represent about two thirds of the U.S. population today. An ever-growing number of studies have shown that OSA is associated with insulin resistance, glucose intolerance and type 2 diabetes, independent of obesity. Evidence from animal and human models that mimic OSA provides potential mechanisms for how OSA may alter glucose metabolism. Up to 83% of patients with type 2 diabetes suffer from unrecognized OSA and increasing severity of OSA is associated with worsening glucose control. However, it is still unclear whether OSA may lead to the development of diabetes over time. More data from large-scale longitudinal studies with rigorous assessments of diabetes and OSA are needed. In addition, there is still controversy whether continuous positive airway pressure (CPAP) treatment of OSA improves glucose metabolism. Large-scale randomized-controlled trials of CPAP treatment of OSA with well-validated assessments of insulin sensitivity and glucose tolerance are needed. These studies may reveal that OSA represents a novel, modifiable risk factor for the development of prediabetes and type 2 diabetes.

Obstructive sleep apnea and abnormal glucose metabolism

Obstructive sleep apnea (OSA) is a chronic disorder that is prevalent, especially in subjects with obesity or diabetes. OSA is related to several metabolic abnormalities, including diabetes, insulin resistance, hypertension, and cardiovascular diseases. Although Koreans are less obese than Caucasians, the prevalence of OSA is comparable in both groups. Thus, the impact of OSA on metabolism may be similar. Many epidemiologic and experimental studies have demonstrated that OSA is associated with glucose intolerance and insulin resistance via intermittent hypoxia, sleep fragmentation, and sleep deprivation. The effect of continuous positive airway pressure treatment on glucose metabolism is still controversial. Randomized controlled trials are needed to evaluate the ability of OSA treatment to reduce the risk of diabetes and insulin resistance in subjects without diabetes and to ameliorate glucose control in patients with diabetes.

Functional neuroanatomy and sleep-disordered breathing: implications for autonomic regulation

A major concern with sleep-disordered breathing conditions, which include obstructive sleep apnea (OSA), central apnea, and congenital central hypoventilation syndrome (CCHS), is the high incidence of accompanying autonomic dysfunction and metabolic disorders. Patients with OSA show exaggerated sympathetic tone, leading to hypertension, cardiac arrhythmia, profuse sweating, impaired cerebral perfusion, and stroke. In addition, OSA appears in 86% of obese Type II diabetic patients, suggesting common deleterious processes. Autonomic deficiencies also appear in CCHS patients, who are often hypoglycemic. The impaired autonomic control may stem from injury to central sympathetic and parasympathetic regulatory areas resulting from apnea-related inflammation, hypoxia, or perfusion-related consequences in OSA, and genetic mutation repercussions in CCHS. Disturbed sleep organization from apnea arousals may also disrupt hormonal release. Brain areas affected in both OSA and CCHS include cortical and limbic regions that influence hypothalamic-regulated sympathetic control and hormone release, essential for glycemic regulation, as well as parasympathetic nuclei influencing the pancreas and other viscera, and raphé serotonergic sites, important for thermal and vascular regulation. Brain injury and altered functional responses appear in OSA and CCHS, assessed with magnetic resonance imaging techniques, in areas which show regional gray matter loss, alterations of free water within tissue, loss of axonal integrity, and disruption of functional responses to autonomic and ventilatory challenges. Evaluation of neural injury and distortion in functional signals to autonomic challenges in localized brain areas can provide insights into common pathological mechanisms for dysregulation of hormonal release and autonomic processes in sleep-disordered breathing and metabolic disorders.

Elucidating nature's solutions to heart, lung, and blood diseases and sleep disorders

Evolution has provided a number of animal species with extraordinary phenotypes. Several of these phenotypes allow species to survive and thrive in environmental conditions that mimic disease states in humans. The study of evolved mechanisms responsible for these phenotypes may provide insights into the basis of human disease and guide the design of new therapeutic approaches. Examples include species that tolerate acute or chronic hypoxemia like deep-diving mammals and high-altitude inhabitants, as well as those that hibernate and interrupt their development when exposed to adverse environments. The evolved traits exhibited by these animal species involve modifications of common biological pathways that affect metabolic regulation, organ function, antioxidant defenses, and oxygen transport. In 2006, the National Heart, Lung, and Blood Institute released a funding opportunity announcement to support studies that were designed to elucidate the natural molecular and cellular mechanisms of adaptation in species that tolerate extreme environmental conditions. The rationale for this funding opportunity is detailed in this article, and the specific evolved mechanisms examined in the supported research are described. Also highlighted are past medical advances achieved through the study of animal species that have evolved extraordinary phenotypes as well as the expectations for new understanding of nature's solutions to heart, lung, blood, and sleep disorders through future research in this area.

Continuous positive airway pressure and type 2 diabetes mellitus

Obstructive sleep apnea (OSA) is a sleep disorder, increasingly recognized. It is commonly present in obese persons, treated with continuous positive airway pressure (CPAP), being the gold standard. The disorder has been associated with diabetes mellitus and possibly related to hypoxia per se, increased sympathetic activity, disturbed hypothalamic-pituitary-adrenal axis and increased inflammatory cytokines and leptin, all of which can adversely affect both glucose metabolism and insulin sensitivity. Given this association and the presence of common risk factors, this review assessed the impact of CPAP on diabetes mellitus through various metabolic parameters including HbA1c, nocturnal glucose and insulin resistance, in addition to the effect of CPAP on the prevention of diabetes mellitus. Results have been conflicting; Randomized controlled trials are recommended to allow objective and definite conclusions.

The relation of serum 25-hydroxyvitamin-D levels with severity of obstructive sleep apnea and glucose metabolism abnormalities

Obstructive sleep apnea (OSA) and 25-hydroxyvitamin-D₃ (25-OH-D) deficiency are two separate disorders associating with obesity, inflammation, and impaired glucose metabolism. We aimed to investigate the vitamin D status of OSA patients regarding to potential links between lower vitamin D levels and abnormal glucose metabolism, which is one of the main adverse outcomes of OSA. Study group is composed of 190 non-diabetic subjects who were suspected of having OSA. Subjects undergone polysomnography and were grouped due to apnea-hypopnea indices (AHI) as controls (AHI < 5, n = 47), mild OSA (5 ≤ AHI < 15, n = 46), moderate OSA (15 ≤ AHI < 30, n = 47), and severe OSA (AHI ≥ 30, n = 50). Serum 25-OH-D, HbA₁c, insulin levels were measured and 75-g oral glucose tolerance test was performed. Serum 25-OH-D level (ng/ml) of OSA patients were lower than control subjects (17.4 ± 6.9 vs. 19.9 ± 7.8), and decrement was parallel to severity of OSA; as 18.2 ± 6.4 (5 ≤ AHI < 15), 17.5 ± 7.4 (15 ≤ AHI < 30), and 16.3 ± 6.9 (AHI > 30), respectively (P = 0.097, r = -0.13). However, severe female OSA patients had significantly lower 25-OH-D levels (11.55 ng/ml), while control males had the highest mean value (21.7 ng/ml) (P < 0.001). Frequency of insulin resistance (IR) was 48%, prediabetes 41%, diabetes 16% in OSA patients. Mean 25-OH-D level of insulin resistant subjects (HOMA-IR ≥ 2.7, n = 77, AHI = 35.5) was lower than non-insulin resistant subjects (HOMA-IR < 2.7, n = 113, AHI = 19.8) as 16.18 ± 7.81 versus 19.2 ± 6.6, respectively (P = 0.004). 25-OH-D level of 91 non-diabetic subjects (n = 91, AHI = 19.7) was 19.5 ± 7.4, prediabetics (n = 75, AHI = 28.7) was 17.45 ± 6.9, and diabetics (n = 24, AHI = 46.3) was 13.8 ± 5.3 (P = 0.02). We showed that subjects with more severe OSA indices (AHI ≥ 15) tended to present lower vitamin D levels correlated to increased prevalence of IR, prediabetes, and diabetes. Vitamin D deficiency may play a role and/or worsen OSA's adverse outcomes on glucose metabolism. OSA patients may be considered for supplementation treatment which was shown to ameliorate abnormal glucose metabolism and inflammation.

Effect of continuous positive airway pressure therapy on glucose control

Obstructive sleep apnea (OSA) and diabetes mellitus are both highly prevalent disorders. There has been a recent recognition of an association between insulin resistance and sleep apnea. Continuous positive airway pressure (CPAP) has emerged as an effective therapy for treatment of OSA and has been shown to positively influence numerous pathophysiological factors that contribute to cardiovascular risk. There is emerging data that explores the influence of CPAP therapy, insulin sensitivity and glycemic control. In the current review, we examine this literature critically and formulate a synopsis that summarizes the current knowledge in this field.

Obstructive sleep apnea syndrome and perioperative complications: a systematic review of the literature

Obstructive sleep apnea syndrome (OSAS) is a common sleep related breathing disorder. Its prevalence is estimated to be between 2% and 25% in the general population. However, the prevalence of sleep apnea is much higher in patients undergoing elective surgery. Sedation and anesthesia have been shown to increase the upper airway collapsibility and therefore increasing the risk of having postoperative complications in these patients. Furthermore, the majority of patients with sleep apnea are undiagnosed and therefore are at risk during the perioperative period. It is important to identify these patients so that appropriate actions can be taken in a timely fashion. In this review article, we will discuss the epidemiology of sleep apnea in the surgical population. We will also discuss why these patients are at a higher risk of having postoperative complications, with the special emphasis on the role of anesthesia, opioids, sedation, and the phenomenon of REM sleep rebound. We will also review how to identify these patients preoperatively and the steps that can be taken for their perioperative management.

Risk for obstructive sleep apnea in obese, nondiabetic adults varies with insulin resistance status

PURPOSE

Obstructive sleep apnea (OSA) is an increasingly common sleep disorder, especially among obese adults. Early identification of adults at risk for OSA would be of substantial benefit; however, the magnitude of the obesity epidemic requires that screening be performed judiciously. The study's aim was to utilize questionnaires that assess OSA risk and symptoms to test the hypothesis that the most insulin-resistant subset of obese individuals is at highest risk for OSA.

METHODS

Nondiabetic, overweight to obese volunteers underwent direct quantification of insulin sensitivity by measuring steady-state plasma glucose concentrations during the insulin suppression test. Insulin-sensitive and insulin-resistant individuals were administered the Berlin and STOP questionnaires to determine OSA risk status, and Epworth Sleepiness Scale (ESS) to evaluate daytime sleepiness. Fasting insulin and lipid/lipoprotein measurements were performed.

RESULTS

Insulin-mediated glucose disposal differed threefold (p < 0.001) between equally obese, insulin-resistant (n = 22) and insulin-sensitive (n = 14) individuals, associated with higher fasting insulin and triglyceride and lower high-density lipoprotein cholesterol (HDL-C) concentrations in insulin-resistant individuals. Fourteen (64 %) insulin-resistant as compared with 2 (14 %) insulin-sensitive individuals were found to be at high risk for OSA by both questionnaires (p < 0.01). Whereas half of insulin-resistant individuals met the ESS criteria for excessive daytime sleepiness, only one insulin-sensitive individual did (p = 0.011).

CONCLUSIONS

High risk for OSA and excessive daytime sleepiness is prevalent among the insulin-resistant subgroup of obese individuals. Surrogate estimates of insulin resistance based on fasting insulin, triglycerides, and/or HDL-C can be used to help identify those obese adults who would benefit most from OSA screening and referral for polysomnography.

Chronobiological Effects on Obesity

The development of obesity is the consequence of a multitude of complex interactions between both genetic and environmental factors. It has been suggested that the dramatic increase in the prevalence of obesity over the past 30 years has been the result of environmental changes that have enabled the full realization of genetic susceptibility present in the population. Among the many environmental alterations that have occurred in our recent history is the ever-increasing dyssynchrony between natural cycles of light/dark and altered patterns of sleep/wake and eating behavior associated with our "24-hour" lifestyle. An extensive research literature has established clear links between increased risk for obesity and both sleep deprivation and shift work, and our understanding of the consequences of such dyssynchrony at the molecular level is beginning to emerge. Studies linking alterations in cellular circadian clocks to metabolic dysfunction point to the increasing importance of chronobiology in obesity etiology.

Prevalence and correlates of disordered sleep in southeast asian indians with type 2 diabetes

BACKGROUND

Sleep disturbances are common in individuals with diabetes. Patients with diabetes have higher rates of insomnia, excessive daytime sleepiness and increased incidence of restless leg syndrome. The purpose of our study was to investigate the prevalence and determine the predictors of sleep dysfunction in patients with type 2 diabetes in a southeast Asian Indian population.

METHODS

We enrolled 120 patients with type 2 diabetes who attended an endocrinology clinic in a tertiary-care hospital. After we collected their demographic data, we recorded their anthropometric measurements. Fasting, postprandial blood glucose values and glycosylated hemoglobin (HbA1c) values were then obtained. Quality of sleep was evaluated in all the patients through the Pittsburgh Sleep Quality Index (PSQI), which is a questionnaire that assesses sleep quality and disturbances over a monthlong period. A Global Sleep Quality score ≥5 discriminates between good and poor sleepers.

RESULTS

The mean global PSQI score was 7.08 (standard deviation, 3.89), which suggested poor sleep quality in this population. Sixty-nine percent of patients had a global PSQI score ≥5, indicating that they were "poor sleepers." The global PSQI score positively correlated with the duration of diabetes and was also independent of other variables such as age, gender, body mass index, HbA1c, or medications.

CONCLUSION

We found a high prevalence of sleep dysfunction in patients with type 2 diabetes. We also found a significant correlation between duration of diabetes and quality of sleep, independent of other variables. It is important for physicians to address the quality and duration of sleep in patients with type 2 diabetes.

Relation of sleep quality and sleep duration to type 2 diabetes: a population-based cross-sectional survey

OBJECTIVES

To investigate the association between self-reported sleep duration, sleep quality and the prevalence of diabetes in a contemporary sample of Chinese adults.

DESIGN

Cross-sectional survey.

SETTING

Community-based investigation in Xuzhou, China.

PARTICIPANTS

16 893 Chinese men and women aged 18-75 who fulfilled the inclusion and exclusion criteria were enrolled.

PRIMARY AND SECONDARY OUTCOME MEASURES

Self-reported quality and duration of sleep were obtained by questionnaire, and type 2 diabetes was assessed by fasting blood glucose. Sleep quality was categorised as good, common or poor. Sleep duration was measured by average hours of sleep per night, with categories of ≤6 h, 6-8 h and ≥8 h. A logistic regression model was used to evaluate the association between sleep duration or sleep quality and diabetes.

RESULTS

Both poor quality of sleep and short sleep duration (≤6 h) were associated with increased prevalence of diabetes, with higher rates in relatively healthy Chinese people. Compared with the group with good quality of sleep and 6-8 h sleep duration, diabetes was the most prevalent in individuals with poor sleep quality and ≤6 h sleep duration (OR 1.41, 95% CI 1.07 to 1.85) and in those with poor sleep quality who slept ≥8 h (OR 1.39, 95% CI 0.85 to 2.26), even after adjustment for a large number of further possible factors.

CONCLUSIONS

The results suggest that sleep of poor quality and short duration is associated with diabetes.

Increased serum levels of advanced glycation end-products is associated with severity of sleep disordered breathing but not insulin sensitivity in non-diabetic men with obstructive sleep apnoea

BACKGROUND

Patients with diabetes mellitus are known to have increased serum levels of advanced glycation end-products (AGEs), and this is also associated with insulin resistance. This study aimed to investigate the relationship between serum AGEs and insulin sensitivity in non-diabetic subjects with obstructive sleep apnoea (OSA).

METHODS

Adult males with no known comorbidities were recruited from the sleep clinic of a university teaching hospital. They underwent overnight in-laboratory polysomnography. Fasting blood was taken to measure serum AGE and plasma glucose levels. Insulin sensitivity was estimated using the short insulin tolerance test.

RESULTS

In total, 105 subjects with a mean age of 43.5 (standard deviation [SD] 9.2)years, mean body mass index of 27.1 (SD 4.0)kg/m(2), and median apnoea-hypopnoea index (AHI) of 17 (interquartile range 5-46) were analysed. Serum AGE levels were significantly higher in subjects with OSA (AHI ≥5), compared with those without OSA (AHI <5) (3.9 [SD 1.2] vs. 3.2 [SD 0.8]μg/ml, respectively; P=0.037) after adjusting for confounders. AGE levels were positively correlated with AHI (r=0.318, P=0.001), but not with insulin sensitivity. AGE levels decreased in subjects with moderate-to-severe OSA who received continuous positive airway pressure (CPAP) treatment for three months (n=18, P=0.017).

CONCLUSIONS

Serum AGE levels correlate with AHI in non-diabetic adult males. This relationship cannot be explained by insulin sensitivity. Supporting the hypothesis of a direct relationship between AHI and AGEs, AGE levels were found to decline with CPAP therapy.

Attenuation of glucose-induced insulin secretion by intermittent hypoxia via down-regulation of CD38

AIMS

Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation during sleep, the development of daytime sleepiness, and deterioration in the quality of life. Accumulating evidence suggests the association of intermittent hypoxia (IH), a hallmark of SAS, and type 2 diabetes independently on body mass index and waist circumference. In addition to insulin resistance, the progression to type 2 diabetes is dependent on the impairment of glucose-induced insulin secretion (GIS) from pancreatic β-cells. However, the direct effects of IH on GIS are elusive.

MAIN METHODS

HIT-T15 hamster β-cells and isolated rat islets were exposed to 64 cycles/24 h of IH (5 min hypoxia/10 min normoxia) or normoxia for 24 h. Changes of GIS and gene expression in IH-treated β-cells were analyzed by ELISA and real-time RT-PCR, respectively.

KEY FINDINGS

After IH treatment, GIS both from IH-treated HIT-T15 cells and isolated rat islets were significantly attenuated. The level of insulin mRNA was unchanged by IH. The mRNA levels of glucose transporter 2 (Glut2), glucokinase (GK), sulfonylurea receptor1 (SUR1), and L-type Ca2+channel1.2 (Cav1.2) in IH-treated-islets were similar to those in normoxia-treated islets. In contrast, the mRNA level of CD38 in IH-treated islets was significantly lower than that in normoxia-treated islets. The reporter gene assay revealed that the transcription of CD38 was attenuated by IH, and the transfection of CD38 expression vector recovered the attenuation of GIS by IH.

SIGNIFICANCE

These results indicate that IH stress directly attenuates GIS from β-cells via the down-regulation of CD38.