Endocrine Abstracts

Objective: Adiposity, insulin resistance, and hyperandrogenism are features of the polycystic ovary syndrome (PCOS). Retinol-binding protein 4 (RBP4) secreted from adipose and liver tissue has been linked to insulin resistance. We here address the impact of RBP4 on insulin resistance in PCOS and its usability to identify women with metabolic syndrome or impaired glucose metabolism (IGT or diabetes).

Design: RBP4 was determined in plasma of 115 PCOS women. Associations with insulin resistance, body composition, and hyperandrogenemia were investigated by correlation and multiple linear regression analyses in 110 non-diabetics. Receiver operating characteristic (ROC) curve analysis was used to evaluate RBP4’s usability for identifying impaired glucose metabolism or impaired glucose metabolism.

Results: RBP4 increased over tertiles of insulin resistance (P=0.009). RBP4 correlated with insulin resistance (HOMA%S (R=−0.286, P=0.002)), WHR (R=0.233, P=0.034), and DEXA-lean body mass (R=0.282, P=0.016) but not with BMI, DEXA-total or -trunk fat mass, hsCRP, free testosterone, DHEAS, androstendione and 17β-estradiol. Adjusted for age, BMI, smoking and IGT the association between RBP4 and HOMA%S remained significant (P=0.032). However, RBP4 explained only 4.6% of the variation of HOMA%S. RBP4 was higher in metabolic syndrome and in impaired glucose metabolism, but its usability to identify women with metabolic syndrome or impaired glucose metabolism was low (AUCs 0.631, P=0.041 or 0.660, P=0.016).

Conclusions: In PCOS RBP4 has a small independent impact on insulin resistance. It is neither correlated to hyperandrogenemia, 17β-estradiol or other adrenal steroids nor to markers of adiposity in general. Furthermore, RBP4 does not appear suitable for screening metabolic syndrome or impaired glucose metabolism.