Pleiotropic role of IGF-I in obesity hypoventilation syndrome

Ketogenic diet acutely improves gas exchange and sleep apnoea in obesity hypoventilation syndrome: A non-randomized crossover study

BACKGROUND AND OBJECTIVE

Obesity hypoventilation syndrome (OHS) causes hypercapnia which is often refractory to current therapies. We examine whether hypercapnia in OHS can be improved by a ketogenic dietary intervention.

METHODS

We conducted a single-arm crossover clinical trial to examine the impact of a ketogenic diet on CO2 levels in patients with OHS. Patients were instructed to adhere to 1 week of regular diet, 2 weeks of ketogenic diet, followed by 1 week of regular diet in an ambulatory setting. Adherence was assessed with capillary ketone levels and continuous glucose monitors. At weekly visits, we measured blood gases, calorimetry, body composition, metabolic profiles, and sleep studies. Outcomes were assessed with linear mixed models.

RESULTS

A total of 20 subjects completed the study. Blood ketones increased from 0.14 ± 0.08 during regular diet to 1.99 ± 1.11 mmol/L (p < 0.001) after 2 weeks of ketogenic diet. Ketogenic diet decreased venous CO2 by 3.0 mm Hg (p = 0.008), bicarbonate by 1.8 mmol/L (p = 0.001), and weight by 3.4 kg (p < 0.001). Sleep apnoea severity and nocturnal oxygen levels significantly improved. Ketogenic diet lowered respiratory quotient, fat mass, body water, glucose, insulin, triglycerides, leptin, and insulin-like growth factor 1. Rebound hypercapnia was observed after resuming regular diet. CO2 lowering was dependent on baseline hypercapnia, and associated with circulating ketone levels and respiratory quotient. The ketogenic diet was well tolerated.

CONCLUSION

This study demonstrates for the first time that a ketogenic diet may be useful for control of hypercapnia and sleep apnoea in patients with obesity hypoventilation syndrome.

Cardiovascular disease in obesity hypoventilation syndrome - A review of potential mechanisms and effects of therapy

Cardiovascular disease is common in patients with obesity hypoventilation syndrome (OHS) and accounts in part for their poor prognosis. This narrative review article examines the epidemiology of cardiovascular disease in obesity hypoventilation syndrome, explores possible contributing factors and the effects of therapy. All studies that included cardiovascular outcomes and biomarkers were included. Overall, there is a higher burden of cardiovascular disease and cardiovascular risk factors among patients with obesity hypoventilation syndrome. In addition to obesity and sleep-disordered breathing, there are several other pathophysiological mechanisms that contribute to higher cardiovascular morbidity and mortality in OHS. There is evidence emerging that positive airway pressure therapy and weight loss have beneficial effects on the cardiovascular system in obesity hypoventilation syndrome patients, but further research is needed to clarify whether this translates to clinically important outcomes.

The use of visceral adiposity variables in the prediction of obstructive sleep apnea: evidence from a large cross-sectional study

PURPOSE

The purposes of this study were to evaluate the ability of visceral adiposity variables [the lipid accumulation product (LAP), the visceral adiposity index (VAI), and the triglyceride-glucose index (TyG)] in predicting obstructive sleep apnea hypopnea syndrome (OSAHS) and to determine the effect of sex on the prediction.

METHODS

A total of 5539 subjects admitted to the sleep center for suspected OSAHS were consecutively recruited from 2007 to 2016. Anthropometric measurements, biological indicators, Epworth sleepiness scale score, and polysomnographic variables were collected. Prediction models for diagnosing OSAHS were established in the test group by logistic regression and verified in the validation group by receiver operating characteristic (ROC) curves.

RESULTS

A total of 4703 patients were included in total. LAP and TyG were of moderate diagnostic accuracy for OSAHS, with the diagnostic efficiency differing between men and women. A prediction model was developed that combined visceral adiposity indicators with waist circumstance and the lowest SpO₂. The sensitivity of those indicators were both 84% in men and women, respectively, and their specificity were both 90%. In addition, the model was confirmed in the validation group with a sensitivity and specificity of 83% and 85% in men and 85% and 84% in women.

CONCLUSIONS

LAP and TyG were of moderate efficiency in screening for OSAHS. The prediction model provides a simple and practical screening tool for OSAHS.

More than Heart Failure: Central Sleep Apnea and Sleep-Related Hypoventilation

Central sleep apnea (CSA) comprises a variety of breathing patterns and clinical entities. They can be classified into 2 categories based on the partial pressure of carbon dioxide in the arterial blood. Nonhypercapnic CSA is usually characterized by a periodic breathing pattern, while hypercapnic CSA is based on hypoventilation. The latter CSA form is associated with central nervous, neuromuscular, and rib cage disorders as well as obesity and certain medication or substance intake. In contrast, nonhypercapnic CSA is typically accompanied by an overshoot of the ventilation and often associated with heart failure, cerebrovascular diseases, and stay in high altitude. CSA and hypoventilation syndromes are often considered separately, but pathophysiological aspects frequently overlap. An integrative approach helps to recognize underlying pathophysiological mechanisms and to choose adequate therapeutic strategies. Research in the last decades improved our insights; nevertheless, diagnostic tools are not always appropriately chosen to perform comprehensive sleep studies. This supports misinterpretation and misclassification of sleep disordered breathing. The purpose of this article is to highlight unresolved problems, raise awareness for different pathophysiological components and to discuss the evidence for targeted therapeutic strategies.

Obesity Hypoventilation Syndrome: Weighing in on Therapy Options

Obesity hypoventilation syndrome is becoming an increasingly encountered condition both in respiratory outpatient clinics and in hospitalized patients. The health consequences and social disadvantages of obesity hypoventilation syndrome are significant. Unfortunately, the diagnosis and institution of appropriate therapy is commonly delayed when the syndrome is not recognized or misdiagnosed. Positive airway pressure therapy remains the mainstay of treatment and is effective in controlling sleep-disordered breathing and improving awake blood gases in the majority of individuals. Evidence supporting one mode of therapy over another is limited. Both continuous and bilevel therapy modes can successfully improve daytime gas exchange, with adherence to therapy an important modifiable factor in the response to treatment. Despite adherence to therapy, these individuals continue to experience excess mortality primarily due to cardiovascular events compared with those with eucapnic sleep apnea using CPAP. This difference likely arises from ongoing systemic inflammation secondary to the morbidly obese state. The need for a comprehensive approach to managing nutrition, weight, and physical activity in addition to reversal of sleep-disordered breathing is now widely recognized. Future studies need to evaluate the impact of a more aggressive and comprehensive treatment plan beyond managing sleep-disordered breathing. The impact of early identification and treatment of sleep-disordered breathing on the development and reversal of cardiometabolic dysfunction also requires further attention.

Obesity Hypoventilation Syndrome

Obesity hypoventilation syndrome is a respiratory consequence of morbid obesity that is characterized by alveolar hypoventilation during sleep and wakefulness. The disorder involves a complex interaction between impaired respiratory mechanics, ventilatory drive and sleep-disordered breathing. Early diagnosis and treatment is important, because delay in treatment is associated with significant mortality and morbidity. Available treatment options include non-invasive positive airway pressure (PAP) therapies and weight loss. There is limited long-term data regarding the effectiveness of such therapies. This review outlines the current concepts of clinical presentation, diagnostic and management strategies to help identify and treat patients with obesity-hypoventilation syndromes.

Effect of obstructive sleep apnea hypopnea syndrome on lipid profile: a meta-regression analysis

BACKGROUND

Obstructive sleep apnea (OSA) is associated with obesity, metabolic syndrome, and dyslipidemia, which may be related to decrease androgen levels found in OSA patients. Dyslipidemia may contribute to atherosclerosis leading to increasing risk of heart disease.

METHODS

Systematic review was conducted using PubMed and Cochrane library by utilizing different combinations of key words; sleep apnea, obstructive sleep apnea, serum lipids, dyslipidemia, cholesterol, total cholesterol, low density lipoprotein (LDL), high density lipoprotein (HDL), and triglyceride (TG). Inclusion criteria were: English articles, and studies with adult population in 2 groups of patients (patients with OSA and without OSA). A total 96 studies were reviewed for inclusion, with 25 studies pooled for analysis.

RESULTS

Sixty-four studies were pooled for analysis; since some studies have more than one dataset, there were 107 datasets with 18,116 patients pooled for meta-analysis. All studies measured serum lipids. Total cholesterol pooled standardized difference in means was 0.267 (p = 0.001). LDL cholesterol pooled standardized difference in means was 0.296 (p = 0.001). HDL cholesterol pooled standardized difference in means was -0.433 (p = 0.001). Triglyceride pooled standardized difference in means was 0.603 (p = 0.001). Meta-regression for age, BMI, and AHI showed that age has significant effect for TC, LDL, and HDL. BMI had significant effect for LDL and HDL, while AHI had significant effect for LDL and TG.

CONCLUSION

Patients with OSA appear to have increased dyslipidemia (high total cholesterol, LDL, TG, and low HDL).

Respiratory mechanics and ventilatory control in overlap syndrome and obesity hypoventilation

The overlap syndrome of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD), in addition to obesity hypoventilation syndrome, represents growing health concerns, owing to the worldwide COPD and obesity epidemics and related co-morbidities. These disorders constitute the end points of a spectrum with distinct yet interrelated mechanisms that lead to a considerable health burden. The coexistence OSA and COPD seems to occur by chance, but the combination can contribute to worsened symptoms and oxygen desaturation at night, leading to disrupted sleep architecture and decreased sleep quality. Alveolar hypoventilation, ventilation-perfusion mismatch and intermittent hypercapnic events resulting from apneas and hypopneas contribute to the final clinical picture, which is quite different from the “usual” COPD. Obesity hypoventilation has emerged as a relatively common cause of chronic hypercapnic respiratory failure. Its pathophysiology results from complex interactions, among which are respiratory mechanics, ventilatory control, sleep-disordered breathing and neurohormonal disturbances, such as leptin resistance, each of which contributes to varying degrees in individual patients to the development of obesity hypoventilation. This respiratory embarrassment takes place when compensatory mechanisms like increased drive cannot be maintained or become overwhelmed.

Although a unifying concept for the pathogenesis of both disorders is lacking, it seems that these patients are in a vicious cycle. This review outlines the major pathophysiological mechanisms believed to contribute to the development of these specific clinical entities. Knowledge of shared mechanisms in the overlap syndrome and obesity hypoventilation may help to identify these patients and guide therapy.

Growth hormone secretion among adult patients with Prader-Willi syndrome due to different genetic subtypes

BACKGROUND

Patients with Prader-Willi syndrome (PWS) due to maternal uniparental disomy of the chromosome 15 (UPD15) have fewer facial features, less hypopigmentation and higher levels of psychosis compared to subjects with deletion in chromosome 15 (del15q11-q13). PWS individuals carrying the larger type I (TI) deletion suffer from greater behavioral problems than patients with the smaller type II (TII) deletion. Few data are currently available on the relationship existing between endocrine abnormalities in PWS subjects and the different genotypes.

AIM

To investigate the stimulated GH levels in PWS patients with different types of deletion and those with UPD15.

SUBJECTS AND METHODS

Thirty-seven patients, 14 males, aged 17.5-41.2 yr, with PWS due to TI deletion (no.=6), TII deletion (no.=15) or UPD15 (no.=16), were studied. Pituitary GH secretion was evaluated by dynamic testing with GHRH+arginine.

RESULTS

Both the mean peak GH response and the integrated GH secretion (GH area under the curve and GH area under the curve corrected for basal values) for the UPD15 patients (4.6 ± 1.6 μg/l, 241.6 ± 71.7 μg/l/h and 228.3 ± 71.6 μg/l/h, respectively) were lower than that observed in all subjects with del15q11-q13 (9.1±1.8 μg/l, 547.0 ± 132.3 μg/l/h and 514.9 ± 127.6 μg/l/h: p<0.005), as well as in TI (7.7 ± 1.2 μg/l: p<0.02; 424.2 ± 88.8 and 393.4 ± 88.8 μg/l/h: p<0.05) and TII (9.6 ± 2.6 μg/l, 587.9 ± 174.2 μg/l/h and 555.4 ± 167.6 μg/l/h: p<0.01) deletion groups. TI and TII groups had similar stimulated GH levels and integrated GH secretion.

CONCLUSIONS

Our results point at differentiating the pattern of GH secretion by genetic subtypes, with higher GH responses in typical deletion subjects when compared to patients with UPD15.

Obesity hypoventilation syndrome: mechanisms and management

Obesity hypoventilation syndrome describes the association between obesity and the development of chronic daytime alveolar hypoventilation. This syndrome arises from a complex interaction between sleep-disordered breathing, diminished respiratory drive, and obesity-related respiratory impairment, and is associated with significant morbidity and mortality. Therapy directed toward reversing these abnormalities leads to improved daytime breathing, with available treatment options including positive pressure therapy, weight loss, and pharmacological management. However, a lack of large-scale, well-designed studies evaluating these various therapies has limited the development of evidence-based treatment recommendations. Although treatment directed toward improving sleep-disordered breathing is usually effective, not all patients tolerate mask ventilation and awake hypercapnia may persist despite effective use. In the longer term, weight loss is desirable, but data on the success and sustainability of this approach in obesity hypoventilation are lacking. The review outlines the major mechanisms believed to underlie the development of hypoventilation in this subgroup of obese patients, their clinical presentation, and current therapy options.