Association between glucose peak time in oral glucose tolerance test and insulin secretion during pregnancy

This study aimed to develop an efficient method for evaluating islet function in pregnant women by analyzing the peak times of plasma glucose and insulin secretion during an oral glucose tolerance test.

This prospective study included 2601 pregnant women at 24-28 weeks using the oral glucose tolerance test and pancreatic islet function test. Pregnant women were divided into four groups: GR1, GR2, GR3, and GR4, based on the glucose peaks at 30, 60, 120, and 180 min. They were also classified as two insulin types: Peak 1 and Peak 2 according to the peak time of insulin secretion before and after 60 and 120 min, respectively. Two main analyses were conducted in four groups and two types: 1) evaluation of islet function and 2) correlation of the peak time between glucose and insulin secretion. Analyses included evaluation of pancreatic β-cell function, Spearman correlation to assess the relationship between glucose and insulin peak times, and multivariate logistic regression to identify independent predictors of Peak 2.

The overall insulin sensitivity and immediate insulin secretion of GR3 and GR4 were worse than those of GR1 and GR2. Pregnant women in Peak 2 had increased insulin resistance and defects in insulin secretion. The Spearman correlation coefficient was 0.54, indicating a moderate positive correlation between the peak times of blood glucose and insulin secretion. Multivariate logistic regression identified GR4 (odds ratio [OR] 8.30; 95% confidence interval [CI] 2.49-27.73; p-value < 0.001) and the 120-min glucose level (OR 2.94; 95% CI 2.39-3.60; p-value < 0.001) as independent predictors of the Peak 2 insulin secretion pattern in pregnant women with gestational diabetes mellitus. Among normal pregnant women, multivariate regression similarly showed that GR4 (OR 10.11; 95% CI 3.94-25.94; p-value < 0.001) and the 120-min glucose level (OR 4.37; 95% CI 3.30-5.79; p-value < 0.001) were independent predictors of the Peak 2 secretion pattern.

The delayed peak time of both glucose and insulin secretion could be used as indicators to evaluate poor insulin secretion function in pregnant women.