Association of Serum Retinol Binding Protein 4 and Visceral Adiposity in Chinese Diabetes and Non-Diabetes Subjects.

Previous studies have shown that adipose-derived serum retinol binding protein 4 (RBP4) is up-regulated in insulin-resistant mouse models and in subjects with insulin resistance or type 2 diabetes. However, the association of visceral fat and serum RBP4 has not been studied. The purpose of this study was to investigate the relationship between serum RBP4 levels and regional fat distribution in Chinese non-diabetes and diabetes subjects. We measured serum RBP4 concentrations from 1033 Chinese subjects (age 52±3,477 men/556 women) enrolled in the Shanghai Diabetes Studies (SHDS) and tested the association of serum RBP4 and visceral fat accumulation. In a subgroup (25 men/26 women) of this study, we also performed euglycemic hyperinsulinemic clamp to measure insulin sensitivity. In addition, the association of fat distribution and serum RBP4 levels was also determined in a subgroup (14 men/8 women) in response to treatment of rosiglitazone, an insulin sensitizer, in patients with diabetes. We found serum RBP4 concentrations were not closely correlated with body-mass-index, but with visceral adipose accumulation in subjects with or without insulin resistance. Subjects with visceral obesity (VO) had higher serum RBP4 concentrations than those without visceral obesity (NVO) irrespective to insulin sensitivity status (mean±SEM: 27.0±0.5 vs. 24.2±0.6 µg,/ml, VO vs. NVO with insulin resistance, p<0.01; 24.8±0.8 vs. 22.9±0.5 µg/ml, VO vs. NVO without insulin resistance, p<0.05). Rosiglitazone treatment in diabetes subjects resulted in an improvement in insulin sensitivity and reduction in serum RBP4 concentration. These changes are accompanied by a reduction of visceral fat area in the subjects. The change of visceral adipose area is highly correlated with that of serum RBP4 concentration (r=0.471, p=0.027). In conclusion, visceral fat accumulation is closely associated with an elevated serum RBP4 level irrespective of insulin resistance status. Visceral fat plays an important role in the regulation of RBP4 production. [ABSTRACT FROM AUTHOR]