Glucose Absorption in Gestational DiabetesMellitus DuringanOralGluc ose Tolerance Test

OBJECTIVE—Women with gestational diabetes mellitus (GDM) show reduced insulin sensitivity and markedly elevated glucose excursions. After delivery, GDM mostly reverts to normal glucose tolerance (NGT), although leaving an increased risk of type 2 diabetes. Because gastrointestinal function changes during pregnancy causing vomiting, constipation, or reduced motility, we thought that gut glucose absorption in GDM or pregnancy might be altered to affect circulating glucose excursions. RESEARCH DESIGN AND METHODS—By undergoing 180-min oral glucose tolerance tests (OGTTs), pregnant women with GDM (GDMpreg; n =1 5, BMI =3 26 2k g/m 2 ,a ged 336 1 years) were compared with NGT women (NGTpreg;n=7,BMI=2861kg/m 2 ,aged3462years), matchingformajoranthropometriccharacteristics(eachP.0.2).Afterdelivery(6–7monthslater), both groups were studied the same way. We computed and mathematically modeled gut glucose absorption from insulin-mediated glucose disappearance and endogenous glucose production (EGP). Whole-body insulin sensitivity was calculated using the Clamp-like Index. RESULTS—GDMpreg showed 16–25% higher plasma glucose concentrations (P , 0.04) during the final 2 h of OGTT, similar EGP, but lower (P , 0.01) insulin sensitivity (2.7 6 0.2 mg z kg 21 zmin 21 vs.NGTpreg:4.560.8mgzkg 21 zmin 21 ).InGDMpreg,gutglucoseabsorptionrates were #52% lower from 30 to 120 min (P , 0.03 vs. conditions after delivery or NGTpreg). In contrast,glucoseabsorptionratesinNGTpregwerecomparableduringandafterpregnancy.None of the studied women developed diabetes after delivery. CONCLUSIONS—In GDMpreg, OGTT gut glucose absorption is markedly lower during hyperglycemia, whereas both glycemia and glucose absorption in NGTpreg are comparable between pregnant and postpartum states. Thus, hyperglycemia in GDM does not seem to result from too rapid or increased glucose absorption. Diabetes Care 34:1475–1480, 2011