The shape of the plasma glucose curve during an oral glucose tolerance test as an indicator of Beta cell function and insulin sensitivity in end-pubertal obese girls

It is hypothesized that the shape of the glucose curve during an oral glucose tolerance test is an early indicator of the risk for developing type 2 diabetes mellitus. In this study, we aimed to examine the shape of plasma glucose response curves and study their relationship with insulin sensitivity, insulin secretion and components of the metabolic syndrome in end-pubertal obese girls. Eighty-one end-pubertal obese girls [median (range) age: 14.4 (11.2-18.0) years; BMI: 34.6 (25.4-50.8) kg/m(²)] who underwent a 2-h oral glucose tolerance test were classified according to the shape of the glucose curve. Four shape types of the plasma glucose response curve were observed: 28 (34.6%) monophasic, 30 (37.0%) biphasic, 14 (17.3%) triphasic, and 9 (11.1%) unclassified. Patients with a monophasic shape had a higher area under the curve for glucose (p = 0.008), a lower early-phase insulin secretion (p = 0.005), and a poorer beta cell function relative to insulin sensitivity as reflected by the oral disposition index (p = 0.022) compared to the bi- and triphasic shape types. In addition, the triglyceride level and TG/HDL-C ratio was higher in patients with a monophasic shape compared to those with a biphasic shape (p = 0.040 and p = 0.048, respectively). In conclusion, end-pubertal obese girls with a monophasic plasma glucose curve are at increased risk for insulin resistance, which can contribute to the development of type 2 diabetes mellitus and cardiovascular diseases.