The 1-hour plasma glucose as a specific marker for early-phase insulin secretory defects in young adults with obesity.

AIMS: To determine whether 1-hour plasma glucose (1-h PG) during an OGTT outperforms other glycemic markers (FPG, 0.5-h PG, 2-h PG, HbA1c) in identifying impairments in insulin secretion, sensitivity, and β-cell compensation.

METHODS

We analyzed 2178 Chinese young adults (18-40 years) with obesity (BMI ≥ 28 kg/m2) and without diabetes. Associations between glycemic markers and OGTT-derived indices were assessed using adjusted correlations, regression, and ROC analyses. In a subcohort (n = 495) with frequently sampled intravenous glucose tolerance test (FSIVGTT) data, markers were evaluated against minimal-model estimates of first-phase secretion (AIRg), insulin sensitivity (SI), and disposition index (DI).

RESULTS

1-h PG showed superior performance over other glycemic markers for identifying early-phase insulin secretion defects. Among these markers, it demonstrated the strongest correlation with IGI30 (ρ =  - 0.413) and the highest discriminatory accuracy (AUC = 0.702); this was supported by FSIVGTT-derived AIRg. For insulin sensitivity, 1-h PG correlated more strongly with the Matsuda index, whereas 2-h PG was more strongly associated with FSIVGTT-derived SI. Elevated 1-h PG (≥8.6 mmol/L) identified individuals with impairments across all traits.

CONCLUSIONS

1-h PG is a specific physiological marker of early-phase insulin secretion defects, supporting its role in early phenotyping and risk stratification in young adults with obesity.