Abstract
BACKGROUND: Although retinol binding protein 4 (RBP4) has been implicated in insulin resistance in experimental studies, the association between RBP4 and risk of type 2 diabetes remains unclear. We assessed this association in a Chinese population, and pooled our results with those from two prior studies. METHODS: Plasma RBP4 levels were measured among 571 incident type 2 diabetes cases and 571 controls nested within the Singapore Chinese Health Study. All participants were free of diabetes, cancer and cardiovascular disease at blood collection (1999-2004). Incident cases of physician-diagnosed diabetes were self-reported at subsequent interviews (2006-2010). RESULTS: Plasma RBP4 levels were significantly higher in men than women, and the respective median values were 30 (interquartile range: 24-35) μg/mL and 25 (interquartile range: 21-31) μg/mL, respectively. With adjustment for diabetes risk factors, compared to the lowest quartile, the odds ratio (OR) and confidence interval (CI) for risk of type 2 diabetes associated with the highest quartile of RBP4 levels were 1.23 (0.73-2.07; P-trend = 0.14) in all subjects, 0.63 (0.27-1.45; P-trend = 0.65) in men, and 2.29 (1.05-5.00; P-trend = 0.018) in women. The difference in the risk estimates between men and women was statistically significant (P-interaction = 0.032). When we pooled our results with two prior studies, ORs (95% CIs) comparing high versus low category of RBP4 was 1.01 (0.70-1.46; I (2) = 8.2%; P-heterogeneity = 0.34) in men, and 1.73 (1.28-2.33; I (2) = 0%; P-heterogeneity = 0.80) in women. CONCLUSIONS: Increased plasma RBP4 levels were associated with higher risk of type 2 diabetes in women but not in men.