Serum levels of adipocytokines, adiponectin and leptin, in patients with obstructive sleep apnea syndrome

Neuroendocrine alterations in obese patients with sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a serious, prevalent condition that has significant morbidity and mortality when untreated. It is strongly associated with obesity and is characterized by changes in the serum levels or secretory patterns of several hormones. Obese patients with OSAS show a reduction of both spontaneous and stimulated growth hormone (GH) secretion coupled to reduced insulin-like growth factor-I (IGF-I) concentrations and impaired peripheral sensitivity to GH. Hypoxemia and chronic sleep fragmentation could affect the sleep-entrained prolactin (PRL) rhythm. A disrupted Hypothalamus-Pituitary-Adrenal (HPA) axis activity has been described in OSAS. Some derangement in Thyroid-Stimulating Hormone (TSH) secretion has been demonstrated by some authors, whereas a normal thyroid activity has been described by others. Changes of gonadal axis are common in patients with OSAS, who frequently show a hypogonadotropic hypogonadism. Altogether, hormonal abnormalities may be considered as adaptive changes which indicate how a local upper airway dysfunction induces systemic consequences. The understanding of the complex interactions between hormones and OSAS may allow a multi-disciplinary approach to obese patients with this disturbance and lead to an effective management that improves quality of life and prevents associated morbidity or death.

Obstructive sleep apnea, immuno-inflammation, and atherosclerosis

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder leading to cardiovascular and metabolic complications. OSA is also a multicomponent disorder, with intermittent hypoxia (IH) as the main trigger for the associated cardiovascular and metabolic alterations. Indeed, recurrent pharyngeal collapses during sleep lead to repetitive sequences of hypoxia-reoxygenation. This IH induces several consequences such as hemodynamic, hormonometabolic, oxidative, and immuno-inflammatory alterations that may interact and aggravate each other, resulting in artery changes, from adaptive to degenerative atherosclerotic remodeling. Atherosclerosis has been found in OSA patients free of other cardiovascular risk factors and is related to the severity of nocturnal hypoxia. Early stages of artery alteration, including functional and structural changes, have been evidenced in both OSA patients and rodents experimentally exposed to IH. Impaired vasoreactivity with endothelial dysfunction and/or increased vasoconstrictive responses due to sympathetic, endothelin, and renin-angiotensin systems have been reported and also contribute to vascular remodeling and inflammation. Oxidative stress, inflammation, and vascular remodeling can be directly triggered by IH, further aggravated by the OSA-associated hormonometabolic alterations, such as insulin resistance, dyslipidemia, and adipokine imbalance. As shown in OSA patients and in the animal model, genetic susceptibility, comorbidities (obesity), and life habits (high fat diet) may aggravate atherosclerosis development or progression. The intimate molecular mechanisms are still largely unknown, and their understanding may contribute to delineate new targets for prevention strategies and/or development of new treatment of OSA-related atherosclerosis, especially in patients at risk for cardiovascular disease.