Endocrine Abstracts

Objective: Insulin resistance (IR) has been reported in first-degree male relatives of patients with IC (FDMR). Retinol binding protein-4 (RBP4) has been shown to be increased in IR. We hypothesized that RBP4 would be: 1) increased in FDMR compared with controls and 2) correlated with features of IR.

Methods: The study was approved by Leeds (West) Research Ethics Committee. We measured RBP4 in 162 healthy FDMR previously found to be more insulin resistant than 161 healthy male age-, sex- and BMI-matched controls. We used an in-house sandwich ELISA, calibrated against Bio-Rad Liquichek Immunology, Control Level 3 (Bio-Rad Laboratories, Hertfordshire, UK). We estimated insulin sensitivity by calculating HOMA-IR.

Results: Triglyceride, total and LDL-cholesterol were increased in FDMR (P<0.05). Fasting plasma glucose was no different; but impaired glucose tolerance or type 2 diabetes were diagnosed in 13.3% FDMR and 4.8% controls on glucose tolerance testing. Insulin was increased in FDMR: 9.6 vs 6.7 mU/ml (P<0.01), as was HOMA-IR: 2.2 vs 1.5 (P<0.01). Mean RBP4 was 36.0 (range 12–67) μg/ml in relatives and 36.5 (range 15–84) μg/ml in controls (P=0.814). Across all subjects, RBP4 correlated weakly with BMI (r_s 0.12, P=0.03), waist hip ratio (r_s 0.14, P=0.02), triglyceride (r_s 0.24, P<0.01) and total cholesterol (r_s 0.14, P=0.02). Log triglyceride was the only variable independently related to log RBP4 in multiple regression analysis.

Conclusions: Although RBP4 was weakly associated with adiposity and some features of IR, it was not associated with insulin or HOMA-IR. RBP4 was also no different in BMI-matched groups of markedly different insulin sensitivity, suggesting that RBP4 is not directly related to IR in this group.