Effect of obesity and glycemic control on serum lipocalins and insulin-like growth factor axis in type 2 diabetic patients

Obesity, insulin resistance (IR), and progressive decline in pancreatic β-cell function are major features of type 2 diabetes mellitus (T2DM). Altered adipokines contribute to obesity-induced IR. Hence understanding of adipokines’ relation to obesity and glycemic control could be useful to improve disease outcomes. We aimed at determination of serum retinol binding protein-4 (RBP-4), lipocalin-2 (LCN-2), insulin-like growth factor-I (IGF-I), and its binding protein-3 (IGFBP-3) levels in T2DM patients with the impact of obesity and glycemic control on them and their relation to β-cell function. Serum insulin, RBP-4, LCN-2, IGF-I, and IGFBP-3 estimated by ELISA were examined in 32 T2DM patients and age- and sex-matched 20 healthy controls. Significant elevation was observed in serum RBP-4 (P < 0.001), LCN-2 (P < 0.01), and IGF-I/IGFBP-3 molar ratio (P < 0.05) in T2DM patients in comparison with healthy controls. There was no significant difference in them between nonobese and obese diabetics. However, RBP-4 and IGF/IGFBP-3 molar ratio were higher in uncontrolled than in controlled diabetic patients at P < 0.001 and P < 0.01, respectively. Moreover, RBP-4, LCN-2, and IGF-I/IGFBP-3 molar ratio were negatively correlated with β-cell function. In conclusion, serum RBP-4 and IGF-I/IGFBP-3 molar ratio but not LCN-2 were prominently elevated with poor glycemic control rather than obesity in T2DM patients. Whereas, declining β-cell function is associated with elevation of serum RBP-4, LCN-2 as well as IGF-I/IGFBP-3 molar ratio.