Glucagon-like peptide-1 secretion in women with gestational diabetes mellitus during and after pregnancy.

Abstract

Gestational diabetes mellitus (GDM) predisposes women to future development of Type 2 diabetes mellitus (DM2) and the two conditions share similar metabolic alterations. Recent observations suggest that a defective glucose stimulated insulin secretion by glucagon-like peptide-1 (GLP- 1) plays a role in the pathogenesis of DM2. Whether such a defect is impaired in GDM remains to be ascertained. We have determined GLP-1 secretion in response to oral glucose tolerance test (OGTT) in GDM and normal glucose tolerance (NGT) during and after pregnancy. 100-g-3h OGTT was performed in 12 GDM and 16 NGT women at 27.3 ± 4.1 weeks of gestation, for determination of plasma GLP-1, glucose, insulin, and C-peptide. Insulin sensitivity (ISI) and insulin secretion (first and second phase); as well as ISI-secretion index (ISSI) were also derived. NGT and GDM women were comparable for age pre-pregnancy body mass index (BMI) and weight gain. GDM had higher glucose area under the curve (AUC): 27,575.5 ± 3448 vs 20,685.88 ± 2715 mg/dl min (p<0.01), but lower first-phase insulin secretion (993.12±367 vs 1376.61 ± 423, p<0.05) and ISSI compared to controls (3873.23 ± 1185 vs 6232.13 ± 1734, p<0.001). When we examined GLP-1 mean levels in relation to mean glycemic values, GLP-1 secretion was inappropriately low with respect to mean glycemic values in GDM compared to NGT. At follow-up, AUCGLP-1 was significantly lower in post-partum GDM compared to post-partum NGT women (2542 ± 273 vs 10,092 ± 7367 pmol·l-1·min-1, p<0.05, respectively). Our study suggests that GLP-1 secretion in GDM women is inadequate for the prevailing glycemic levels both in pregnancy and post partum. Moreover, we cannot exclude that other important aspects of the incretin effect may be involved in GDM development.