Non-altered incretin secretion in women with impaired fasting plasma glucose in the early stage of pregnancy: a case control study

BACKGROUNDS: Glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) may be involved in pathogenesis of gestational diabetes mellitus (GDM). The aim was to compare GLP-1 and GIP production in fasting state and during 3 h mixed meal tolerance test (MMTT) measured by mean area under the curve (AUC) between pregnant women with normal and impaired fasting glucose in an early phase of pregnancy, and healthy non-pregnant controls. METHODS: This study was undertaken as a case–control study. Repeated measurement of fasting plasma glucose ≥ 5.1 mmol/L and < 7.0 mmol/L during the first trimester of pregnancy and exclusion of overt diabetes according to IADSPG criteria was used to find women with impaired fasting glucose (n = 22). Age-matched controls consisted of healthy pregnant (n = 25) and non-pregnant (n = 24) women. In addition to incretins, anthropometric parameters and markers of insulin resistance and beta-cell function were assessed. Variables were summarized as median (interquartile range). RESULTS: Fasting GLP-1 and GIP concentration or their AUC during MMTT did not significantly differ between pregnant women with impaired fasting plasma glucose [GLP-1(AUC) 19.0 (53.1) and GIP(AUC) 302 (100) pg/mL/min] and healthy pregnant women [GLP-1(AUC) 16.7 (22.3) and GIP(AUC) 297 (142) pg/mL/min] or non-pregnant controls [GLP-1(AUC) 16.8 (9.8) and for GIP(AUC) 313 (98) pg/mL/min]. Although women with impaired fasting glucose were more obese and showed decreased beta-cell function, there were not significant correlations between incretin production and parameters of insulin secretion, insulin resistance, or obesity. CONCLUSIONS: Women with impaired fasting plasma glucose did not show altered incretin production in the first trimester of pregnancy. In contrast to type 2 diabetes, impaired incretin secretion does not seem to play a major role in the early development of GDM.