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 beta-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 (G(0), G(30) and G(120)) and insulin (I-0, I-30 and I-120) 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 beta-cell secretion. The G(0), G(120) levels and the natural logarithm (Ln) of I-30 and Delta I-30/Delta G(30) were similar in the overweight and obese groups, but significantly higher compared with those of the normal weight group (P<0.05). LnI(0) and LnHOMA-IR progressively increased (P<0.01) in correlation with the degree of obesity among the three groups. Ln Delta I-30/Delta G(30) 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.