Abstract: Abstract: Objective To investigate the characteristics of plasma glucose, insulin secretion and changes of insulin resistance (IR) after a glucose load in obese children, and to predict islet β-cell function. Methods A total of 635 obese children were classified into normal glucose tolerance (NGT) group (n=483), impaired glucose regulation (IGR) group (n= 112) and type 2 diabetes mellitus (DM) group (n=40) based on their glucose levels. Subjects were also divided into G1 group (23 kg/m2 ≤BMI＜30 kg/m2 , n=393) and G2 group (BMI≥30 kg/m2 , n=242) based on their different BMI levels. Level of fast plasma glucose (FPG, 0.5 h-PG, 1 h-PG, 2 h-PG and 3 h-PG) and insulin (FINS, 0.5 h-INS, 1 h-INS, 2 h-INS and 3 h- INS) were measured 0 h, 0.5 h, 1 h, 2 h and 3 h after a glucose load. Insulin resistance index (HOMA-IR), whole body insulin sensitivity index (WBISI), function of pancreatic beta-cell (HOMA- β), first-phase insulin secretion index (ΔI30/ ΔG30) and area under curve of insulin (AUCI) were calculated and compared between groups. Results The value of insulin at each time point was significantly higher in IGR group than that of NGT group. The values of insulin at 0.5 h, 1 h, and 2 h were significantly lower in DM group than those of IGR group, respectively (all P＜0.05). Compared with NGT group, AUCI, HOMA- IR and HOMA- β increased, but WBISI and ΔI30/ΔG30 decreased in IGR group (all P＜0.05). HOMA- IR increased but WBISI, HOMA-β and ΔI30/ΔG30 decreased in DM group (all P＜0.05). Compared with IGR group, AUCI, HOMA-β and ΔI30/ΔG30 decreased in DM group (all P＜0.05). Values of FINS, AUCI, HOMA-IR, 2h-PG and HOMA-β were significantly higher in G2 group than those of G1 group, but WBISI decreased (all P＜0.05). There were no significant differences in FPG and ΔI30/ΔG30 between these two groups. Conclusion From NGT, IGR to DM, the peak of insulin secretion is postponed, insulin resistance is getting heavier and the compensation of insulin secretion after a glucose load is increased first and then decreased.

Key words: obesity, blood glucose, insulin resistance, insulin- secreting cells, diabetes mellitus, type 2, glucose tolerance test, child