Glucose Curve Morphology and Peak Time as Biomarkers of Metabolic Health

The oral glucose tolerance test (OGTT) is widely used to assess glucose tolerance, but the conventional 2-hour post-prandial glucose value faces limited reliability. Alternative OGTT-derived indices such as the shape of the glucose curve and the time to glucose peak may offer additional insights into metabolic health. This study examined whether these indices can serve as biomarkers of metabolic risk. Normoglycemic adults (N=85 [males: 40; females: 45] Age: 26.9±4.6 years; BMI: 23.1±2.4 kg/m2) underwent a 3-hour OGTT, with repeated measurements of blood glucose, insulin, and free fatty acids (FFA). Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp. Energy expenditure (EE) and sleep respiratory quotient (RQ) were measured by metabolic chamber, and body composition by the EchoMRI-AH™. Participants were classified by glucose curve morphology (monophasic vs. biphasic) and glucose peak time (early: ≤30 min vs. late: >30 min). Compared with monophasic group, biphasic group showed lower post-prandial glucose (p<0.05), with no differences in 3-hour glucose area under the curve (AUC), insulin AUC, insulin sensitivity, FFA, EE, RQ, or body fat. In contrast, early peak exhibited lower post-prandial glucose, 3-hour insulin AUC, 2-hour FFA AUC, RQ, and body fat, with higher EE (p<0.05) and a trend towards higher insulin sensitivity (p=0.0592), compared with the late peak group. Biphasic glucose curves and early glucose peak time indicate better glucose tolerance and insulin sensitivity. Compared to glucose curve morphology, glucose peak time demonstrated stronger discriminative index of metabolic health and could serve as an additional biomarker of the OGTT for identifying potential diabetes risks.