Normal secretion of the incretin hormones glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 during gestational diabetes mellitus.

BACKGROUND AND AIM: Gestational diabetes mellitus (GDM) and type 2 diabetes mellitus (DM2) are suggested to be caused by the same metabolic disorder. Defects in gut hormone-dependent regulation of beta-cell function (entero-insular axis) have been proposed to contribute to the pathogenesis of DM2. The aim of study was to evaluate whether an impaired secretion of glucagon-like peptide-1 (GLP-1) and/or glucose-dependent insulinotropic polypeptide (GIP) could play a role in the development of carbohydrate disorders during pregnancy.

SUBJECTS AND METHODS: The study group (GDM) consisted of 13 gestational women with diabetes mellitus in whom GDM was diagnosed according to the World Health Organization criteria (75-g oral glucose tolerance test (OGTT)). The control group consisted of 13 pregnant women with normal glucose tolerance (NGT), matched according to age and duration of pregnancy. For all patients, plasma glucose, insulin, GLP-1 and GIP concentrations were evaluated after an OGTT, i.e. at 0, 30, 60, 90 and 120 min after glucose load.

RESULTS: Fasting plasma glucose concentrations were similar in both groups, but the 0-120 min area under the curve (AUC) for glucose was significantly greater in the GDM group than in the NGT group (p < 0.0005). Fasting insulin concentration was higher (p < 0.05) and the 2-h insulin response (AUCtotal) was significantly greater (p = 0.01) in the GDM group than in the NGT group. Insulin resistance was significantly higher in GDM compared with control women (homeostasis model assessment, p = 0.003). Fasting GLP-1 concentrations were higher in the GDM group (p = 0.05), but no differences were observed in GLP-1 response (AUC) between the studied groups. Fasting and stimulated GIP response did not differ between groups at any time of the study (p > 0.05). Positive correlations were observed between fasting GLP-1 and insulin concentration (r = 0.56, p < 0.004) and between fasting GLP-1 and insulin resistance (r = 0.43, p < 0.029).

CONCLUSION: An impaired secretion of GLP-1 and GIP does not seem to play a major role in the pathogenesis of GDM.