Serum Levels of Retinol-Binding Protein 4 and Adiponectin in Women with Polycystic Ovary Syndrome: Associations with Visceral Fat But No Evidence for Fat Mass-Independent Effects on Pathogenesis in This Condition

Abstract

Insulin resistance, which associates with levels of retinol-binding protein 4 (RBP4) and adiponectin, is implicated in the development of polycystic ovary syndrome (PCOS). The objective of the study was to explore the potential contribution of RBP4 and adiponectin in the etiology of PCOS and their relationships with specific fat depot measurements. This was a cross-sectional study. Serum RBP4 and adiponectin levels were compared between 50 PCOS cases and 28 female controls (including 22 body mass index/fat mass-matched pairs) and correlated with specific fat depot (including visceral) axial magnetic resonance imaging cross-sectional area measurements. All subjects were of U.K. British/Irish origin. Serum levels of RBP4 (automated immunonephelometric assay) and adiponectin [immunoassay: total and high molecular weight (HMW)]. Data are reported as geometric mean (sd, range) and optionally adjusted for fat mass and age. Between the 50 PCOS cases and 28 controls, serum RBP4 levels were indistinguishable [39.0 microg/ml (31.0, 49.0) vs. 41.6 microg/ml (32.7, 52.9), respectively, unadjusted P = 0.24; adjusted P = 0.55]. Total (and HMW) adiponectin levels were lower in PCOS cases [total adiponectin 19.9 microg/ml (14.2, 27.8) vs. 25.8 microg/ml (17.7, 37.7), respectively, unadjusted P = 2.4 x 10(-3); adjusted P = 0.10]. For the paired-sample analyzes, there were no differences in RBP4 (P = 0.09), total adiponectin (P = 0.06), HMW adiponectin (P =0.19), or HMW to total adiponectin ratio (P = 0.98). In PCOS cases, L4-visceral fat area was associated positively with RBP4 (r(2) = 0.34, P = 0.01) and negatively with HMW to total adiponectin ratio (r(2) = -0.44, P = 1.3 x 10(-3)). Controls showed similar relationships. Although associated with visceral fat, serum RBP4 and adiponectin levels do not play important, fat-mass-independent primary roles in the development of PCOS.