Adiponectin in Patients with Obstructive Sleep Apnea Syndrome: Course and Physiological Relevance

BACKGROUND: Adiponectin is an adipocyte-derived hormone with anti-inflammatory and insulin-sensitizing properties. Insulin resistance is a typical feature of the obstructive sleep apnea syndrome (OSAS). OBJECTIVES: Since nasal continuous positive airway pressure (nCPAP) treatment improves insulin sensitivity in patients with OSAS, we investigated serum adiponectin levels before and during nCPAP treatment to clarify possible interactions between the adiponectin levels and insulin sensitivity in patients with OSAS. METHODS: Thirty nondiabetic, obese patients with OSAS (mean age 56.4 +/- 11.1 years; apnoea-hypopnoea index (AHI) 46.03 +/- 19.57) underwent CPAP treatment. Adiponectin levels and the levels of proinflammatory cytokines and proteins reflecting platelet activation regulated on activation normally T cell expressed and secreted (RANTES) and soluble P-selectin (sCD62p), as well as the insulin sensitivity index were measured before, and after 2 days and 3 months of CPAP treatment. RESULTS: Insulin sensitivity increased significantly under nCPAP treatment, whereas adiponectin levels decreased after 2 days of nCPAP treatment, but returned to baseline levels after 3 months of nCPAP treatment. The increase in insulin sensitivity was more pronounced in patients with the highest adiponectin levels at baseline (p = 0.021) after adjustment for body fat (p = 0.003). During treatment, changes in adiponectin levels were highly predictable by the insulin sensitivity index. CONCLUSIONS: We found a significant relation between adiponectin and the insulin sensitivity index in overweight patients with OSAS. The lack of a long-lasting change in adiponectin may be explained by the overwhelming influence of the body mass index on adiponectin secretion, which was unchanged during nCPAP treatment.