One-hour plasma glucose concentration during the OGTT: what does it tell about β-cell function relative to insulin...

In adults 1-h plasma glucose concentration cut-point of 155 mg/dL (8.6 mmol/L) during the oral glucose tolerance test (OGTT) is a strong predictor of future diabetes risk.

We tested the hypothesis that a 1-h glucose concentration ≥155 mg/dL is associated with lower β-cell function in overweight/obese youth.

One hundred and thirteen diabetes free overweight/obese youth aged 10-20 yr, underwent evaluation of β-cell function during a 2 h hyperglycemic clamp ∼225 mg/dL (12.5 mmol/L), and insulin sensitivity during a 3 h hyperinsulinemic-euglycemic clamp, and a standard 2 h OGTT. Body composition and abdominal adiposity were determined by DEXA and CT scan. The disposition index (DI) was calculated as the product of first-phase insulin secretion and insulin sensitivity. Subjects were divided into two categories of 1-h plasma glucose concentration: <155 mg/dL (n=69) and ≥155 mg/dL (n=44).

Youth with 1-h glucose ≥155 mg/dL had lower DI than those with 1-h glucose <155 mg/dL (295.1 ± 27.4 vs. 498.6 ± 37.7 mg/kg/min, p<0.001), independent of the glucose tolerance status. In multiple regression models, DI was the strongest contributor to 1-h glucose concentration explaining ∼21% of its variance.

Overweight/obese youth with 1-h glucose ≥155 mg/dL during the oral glucose tolerance test have a significantly lower β-cell function relative to insulin sensitivity even within the normal glucose tolerance range. Such youth may be at higher risk of future diabetes.