Retinol binding protein 4 (RBP4), a protein secreted by adipocytes and bound in plasma to transthyretin (TTR), has been associated with obesity, the early phase of insulin resistance, metabolic syndrome, and type 2 diabetes mellitus. The objective of this study was to elucidate the relationship between RBP4, TTR, triglyceride (TG) and type 2 diabetes risk in rural Thailand.
We measured the serum RBP4, TTR, glucose, triglyceride and insulin levels, and glucose tolerance of 167 volunteers from Sung Noen District, Nakhon Ratchasima Province, Thailand. Student’s t-test, Pearson’s correlation and logistic regression analysis were used to evaluate the relationships between RBP4, TTR and type 2 diabetes markers.
RBP4 and TTR levels, as well as homeostatic model assessment of insulin resistance (HOMA-IR) values, were significantly elevated among subjects with high triglyceride levels (p < 0.01, p < 0.05, p < 0.05, respectively). Triglyceride levels correlated with RBP4 (r = 0.34, p < 0.001) and TTR (r = 0.26, p < 0.01) levels, as well as HOMA-IR values (r = 0.16, p < 0.05). After adjustment for age and gender, the risk of hypertriglyceridemia was 3.7 times greater (95% CI =1.42–9.73, p = 0.008) in the highest RBP4 tertile as compared to the lowest tertile. Similarly, the highest TTR and HOMA-IR tertiles had greater risk of hypertriglyceridemia at 3.5 (95% CI = 1.30–9.20, p = 0.01) and 3.6 (95% CI = 1.33–9.58, p = 0.01) times higher than the respective lowest tertiles. The correlation between TTR and blood glucose was statistically significant (r = 0.18, p < 0.05), but not found this relationship in RBP4.
The associations of RBP4 and TTR with hypertriglyceridemia and insulin resistance may have important implications for the risk of heart disease and stroke.