Retinol binding-protein 4 (RBP4), a recently identified adipokine and retinol transporter, has been shown to play a causative role in insulin resistance, an underpinning between obesity and colon neoplasia. Yet, the relationship between RPB4 and cancer, including colon neoplasia is largely unexplored. We carried out a cross-sectional study to determine the risk association between RBP4 and colon adenomas. We determined pre-diagnostic serum levels of RBP4 in 626 patients undergoing screening colonoscopies from January 2006 to March 2007. The cases had statistically significant higher levels of RBP4 than the controls (58.5µg/mL ± 38.2 vs. 51.9µg/mL ± 32.5, p=0.03). Multivariate logistic regression model revealed a statistically significant overall association of RBP4 with risk of colon adenoma (OR = 3.10 for each increment of 35µg/mL, CI = 1.15 – 8.66; p = 0.03). Stratified analysis by the median BMI showed that the risk association was largely limited to those with BMI < 27.8 kg/m2. Compared to those in the bottom tertile of RBP4, the ORs for the 2nd and 3rd tertiles were 1.84 (CI = 0.89–3.8) and 2.14 (CI = 1.08–4.23) respectively (p for trend = 0.03); there was little evidence for such an association among those with BMI ≥ 27.8 kg/m2. This is the first study to show colon adenoma risk association with high circulating levels of RBP4. Further study is merited to investigate the mechanism that underlies the RBP4-colon neoplasia link.
Keywords: RBP4; colon adenoma; insulin resistance; retinol-binding protein 4.