Association between serum retinol-binding protein 4 and small dense low-density lipoprotein cholesterol levels in young adult women

Background: Serum retinol-binding protein 4 (RBP4) and small dense low-density lipoprotein (sdLDL) have been suggested to be associated with insulin resistance, but no information is available on the relationship between RBP4 and sdLDL. Methods: We determined serum RBP4, sdLDL-cholesterol, and other metabolic variables on 38 young women, aged 19-29 years. The homeostatic model assessment of insulin resistance (HOMA-IR) was used for the estimation of insulin resistance. Results: In simple regression analyses, RBP4 levels had significant correlations with total cholesterol (r = 0.354, P = 0.029), LDL-cholesterol (r = 0.396, P = 0.014), and sdLDL-cholesterol (r = 0.510, P = 0.001) levels. The sdLDL-cholesterol levels also correlated significantly with total cholesterol (r = 0.402, P = 0.012), LDL-cholesterol (r = 0.627, P < 0.001) and triglycerides (r = 0.449, P = 0.005). Stepwise multiple regression analyses showed only sdLDL-cholesterol (β coefficient (ß) = 0.510, P = 0.001) level was a significant independent predictor of RBP4 levels (adjusted R² = 0.240), whereas RBP4 (ß = 0.289, P = 0.026) level was one of major factors affecting sdLDL-cholesterol levels (adjusted R² = 0.519). There was no significant association of HOMA-IR with RBP4 or sdLDL levels. Conclusions: We showed an independent linkage between serum RBP4 and sdLDL-cholesterol levels in young adult women. These findings may contribute to understanding of lipoprotein metabolisms involved in diabetes and cardiovascular disease.