Analysis of the factors contributing to serum retinol binding protein and transthyretin levels in Japanese adults

Objective: We examined various factors possibly related to metabolic syndrome, particularly focusing on nutritional assessment proteins such as retinol binding protein (RBP) and transthyretin (TTR), and remnant lipoproteins. Materials and Methods: Fasting serum lipid was analyzed in 58 Japanese adult volunteers (33 men and 25 women, 42.5 +/- 10.1 years old). Results: The lipid profiles of the subjects were classified by lipoprotein polyacrylamide gel electrophoretic patterns into Types S (n = 10), A (n = 37), and N (n = 11), according to the method described in Internal Medicine 42: 244, 2003. RBP and TTR were significantly higher in Type N than in Types S and A. In multivariate analysis, RBP was accounted for by remnant-like particle-triglyceride (RLP-TG), interleukin 6, body mass index and low-density lipoprotein (LDL)-cholesterol (adjusted R-2 = 0.621). TTR was accounted for by lipoprotein(a), adiponectin and RLP-TG (adjusted R-2 = 0.415). Malondialdehyde-LDL was significantly accounted for by LDL-cholesterol and RLP-cholesterol (adjusted R-2 = 0.601). Lipoprotein(a) and LDL-cholesterol were independent variables for oxidized LDL antigen (adjusted R-2 = 0.620). High-sensitivity C-reactive protein was accounted for by interleukin 6, immunoreactive insulin and oxidized LDL antigen (adjusted R-2 = 0.361). Uric acid and body mass index were independent variables for adiponectin (adjusted R-2 = 0.429). Conclusion: RBP and TTR may be useful as convenient and simple clinical markers of overnutrition and possibly of metabolic syndrome.