Relation of Absolute or Relative Adiposity to Insulin Resistance, Retinol Binding Protein-4, Leptin, and Adiponectin in Type 2 Diabetes

BACKGROUND Central fat mass (CFM) correlates with insulin resistance and increases the risk of type 2 diabetes and cardiovascular complications; however, peripheral fat mass (PFM) is associated with insulin sensitivity. The aim of this study was to investigate the relation of absolute and relative regional adiposity to insulin resistance index and adipokines in type 2 diabetes. METHODS Total of 83 overweighted-Korean women with type 2 diabetes were enrolled, and rate constants for plasma glucose disappearance (K(ITT)) and serum adipokines, such as retinol binding protein-4 (RBP4), leptin, and adiponectin, were measured. Using dual X-ray absorptiometry, trunk fat mass (in kilograms) was defined as CFM, sum of fat mass on the lower extremities (in kilograms) as PFM, and sum of CFM and PFM as total fat mass (TFM). PFM/TFM ratio, CFM/TFM ratio, and PFM/CFM ratio were defined as relative adiposity. RESULTS Median age was 55.9 years, mean body mass index 27.2 kg/m(2), and mean HbA1c level 7.12±0.84%. K(ITT) was positively associated with PMF/TFM ratio, PMF/CFM ratio, and negatively with CFM/TFM ratio, but was not associated with TFM, PFM, or CFM. RBP4 levels also had a significant relationship with PMF/TFM ratio and PMF/CFM ratio. Adiponectin, leptin, and apolipoprotein A levels were related to absolute adiposity, while only adiponectin to relative adiposity. In correlation analysis, K(ITT) in type 2 diabetes was positively related with HbA1c, fasting glucose, RBP4, and free fatty acid. CONCLUSION These results suggest that increased relative amount of peripheral fat mass may aggravate insulin resistance in type 2 diabetes.