Characterization of β-cell function and insulin resistance in overweight Chinese adolescents with normal glucose tolerance

This study aimed to investigate the characteristics of insulin resistance and β-cell secretion in healthy adolescents. A total of 124 adolescents with normal glucose tolerance (NGT) were divided according to BMI into normal weight (n=31; control), overweight (n=52) and obese (n=41) groups. Oral glucose tolerance tests were performed, and blood glucose (G0, G30 and G120) and insulin (I0, I30 and I120) levels at 0, 30 and 120 min, respectively, were measured. The homeostasis model assessment estimate of insulin resistance (HOMA-IR) and early insulin release index (IRI) were calculated to evaluate insulin sensitivity and early β-cell secretion. The G0, G120 levels and the natural logarithm (Ln) of I30 and ΔI30/ΔG30 were similar in the overweight and obese groups, but significantly higher compared with those of the normal weight group (P<0.05). LnI0 and LnHOMA-IR progressively increased (P<0.01) in correlation with the degree of obesity among the three groups. LnΔI30/ΔG30 and LnHOMA-IR were significantly positively correlated with the indices of obesity (P<0.001 and P<0.05, respectively). LnHOMA-IR was also positively correlated with the insulin levels at 30 and 120 min (r=0.454 and 0.314, respectively; P<0.001). In healthy adolescents, insulin resistance progressively increased with increased body mass index (BMI), but the compensatory increase in early insulin secretion was limited.