Influence of constant positive airway pressure therapy on lipid storage, muscle metabolism and insulin action in obese patients with severe obstructive sleep apnoea syndrome

Aim: To observe the effect of constant positive airway pressure (CPAP) therapy on regional lipid deposition, muscle metabolism and glucose homeostasis in obese patients with obstructive sleep apnoea syndrome (OSAS). Methods: A total of 29 obese patients underwent assessment before and after a minimum of 12-week CPAP therapy. Abdominal adipose tissue was assessed using magnetic resonance imaging. Intramyocellular lipid (IMCL) and skeletal muscle creatine were assessed using H-1-magnetic resonance spectroscopy. Fasting venous and arterial blood were collected. Glucose control was assessed using the homeostatic model. A subgroup of six patients were also evaluated for skeletal muscle pH, phosphocreatine (PCr) and mitochondrial function using P-31-magnetic resonance spectroscopy. The sample was divided according to CPAP therapy, with regular users defined as a minimum nightly use of >= 4 h; 19 subjects were regular and 10 were irregular CPAP users. Results: Visceral adipose tissue volume and circulating leptin were reduced with regular CPAP use but not with irregular CPAP use. Regular CPAP use also produced an increase in skeletal muscle creatine and resting PCr and a decrease in muscle pH. Neither the regular nor irregular CPAP users showed any change in IMCL content, insulin sensitivity scores or mitochondrial function. Conclusions: These data show that regular CPAP therapy reduces visceral adipose tissue and leptin and improves skeletal muscle metabolites. In obese patients with severe OSAS, regular CPAP use does not improve glucose control, suggesting that the influence of obesity on glucose control dominates over any potential effect of OSAS.