Gastric inhibitory polypeptide (GIP) concentration in human amniotic fluid.

Several studies report that placenta and amniotic fluid (AF) may be a source of many peptide hormones. Although the presence of gastric inhibitory polypeptide (GIP) in amniotic fluid has not been described, it is present in the fetal gut. In this study we report the presence of insulin and GIP in human AF of normal and diabetic pregnancies. GIP concentrations in the AF collected two hours after an arginine tolerance test (ATT), at 34-36 weeks of gestation, were evaluated in 8 normal and 53 diabetic pregnant women. GIP was found in all samples of AF. The mean AF-GIP concentrations were 133 +/- 19 pmol/l in controls and 111 +/- 6 pmol/l in the diabetics, being the GIP values of the diabetics belonging to White Class B significantly lower than those of normals (99 +/- 10 vs 133 +/- 19 pmol/l). The GIP/IRI molar ratio was significantly lower in the diabetics than in controls (1.2 +/- 0.2 vs 2.5 +/- 0.4); moreover the GIP/IRI molar ratio was significantly higher in AF collected from diabetic pregnant women who delivered overweight infants than in AF of normal weight infants or controls. This finding would suggest a negative feedback mechanism between GIP and insulin in fetus.