Resistin - the link between adipose tissue dysfunction and insulin resistance in patients with obstructive sleep apnea

Background: Resistin is an adipocytokine, associated with obesity and inflammation. Its exact role in insulin resistance and diabetes in the general population is still controversial. The relation between resistin plasma levels, insulin resistance and risk of impaired glucose metabolism in OSA patients has not been investigated. Materials and methods: Plasma levels of resistin were measured in 67 patients with OSA and impaired glucose metabolism. 34,7% (23/67) had diabetes; 40% (27/67) patients had impaired glucose tolerance(IGT); 25,3%(17/67) had normal glucose metabolism (NGM). The association between resistin, BMI, obesity, markers of insulin resistance, oxidative stress and sleep study characteristics was analysed. The different groups of patients were compared in regards to glucometabolic parameters and biomarkers of oxidative stress - isoprostanes and insulin resistance free fatty acids (FFA). Results: Plasma levels of resistin were higher in patients with diabetes (6,12 +/- 5,93ng/ml), compared to those with IGT (3,85 +/- 2,81ng/ml, p-0,021) and NGM (3,77 +/- 3,23, p-0,043). Resistin did not differ between patients with IGT and NGM (p-0,954). In OSA patients with BMI>40 resistin plasma levels correlated neither to the clinical parameters (BMI, IRI, HOMA-I, HbA1C, AHI, desaturation index), nor to the biomarkers of oxidative stress and insulin resistance. Free fatty acids (0,232>0,177mmol/l, p-0,037) were higher in diabetics in comparison to NGM. Conclusions: Plasma resistin levels in OSA patients with BMI>40 are independent of insulin resistance and are not associated with the parameters, characterising the oxidative stress or severity of OSA. Resistin could be used in a multiple panel of clinical and biomarkers to discern patients with diabetes from those with IGT; in OSA patients with BMI > 40 resistin together with HbA1C could discern patients with diabetes from those with NGM. In OSA patients with BMI > 40 FFA and HbA1C are useful clinical markers in assessing the risk of dysglycaemia among patients with normal and IGT.