Carbohydrate Metabolism in Gestational Diabetes

Insulin resistance and preeclampsia in gestational diabetes mellitus

OBJECTIVE

To compare the degree of insulin resistance in women with gestational diabetes mellitus (GDM) who do and do not develop preeclampsia.

RESEARCH DESIGN AND METHODS

We conducted a prospective cohort study of initially normotensive women with GDM who underwent oral glucose tolerance tests (OGTTs), intravenous glucose tolerance tests (IVGTTs), and glucose clamp studies in the early third trimester (n = 150) and 15 months postpartum (n = 89). After delivery, the women were categorized as nonpreeclamptic or preeclamptic (systolic blood pressure [SBP] > or = 140 mmHg, diastolic blood pressure [DBP] > or = 90 mmHg, and at least >1+ proteinuria or >300 mg/24 h). Metabolic parameters between the groups were compared by chi2 or Fisher's exact tests and ANOVA with P < 0.05 as significant.

RESULTS

A total of 29 women (19%) developed preeclampsia, which was mild in 21 and severe in 8 women. At entry, there were no differences in age, weight indexes, and glycemic measures between the nonpreeclamptic and preeclamptic groups. Those with preeclampsia were significantly taller (61.5 +/- 2.4 vs. 60.1 +/- 2.3 in, P = 0.003), were more often nulliparous (38 vs. 16%, P = 0.01), and had higher entry SBP (112 +/- 10 vs. 103 +/- 6.9 mmHg, P < 0.0001) and DBP (64 +/- 9 vs. 59 +/- 5 mmHg, P = 0.002). No significant differences between the groups were found in any measures of the OGTT glucose levels, insulin sensitivity index, glucose effectiveness, acute response to glucose, or disposition index, nor were there any differences found in the euglycemic clamp measures of basal or steady-state levels of glucose, insulin, free fatty acid, hepatic glucose output, peripheral glucose clearance, C-peptide, or glucagon. At 15 months postpartum, blood pressure levels remained significantly higher in the preeclamptic group (n = 19) compared with the nonpreeclamptic group (n = 70). No differences in any glycemic or insulin resistance measures were found.

CONCLUSIONS

Women with GDM were uniformly insulin resistant. Those who developed preeclampsia, when compared with those who remained nonpreeclamptic, were not more insulin resistant in either the third trimester or 15 months postpartum. However, women who developed preeclampsia had blood pressure levels that were significantly higher, although still in the normal range, than those of women who remained nonpreeclamptic.

Abnormal carbohydrate metabolism during pregnancy : association with endothelial dysfunction

OBJECTIVE

To evaluate whether abnormal endothelial function, a common finding in premenopausal women with type 2 diabetes, is present in early states of diabetes during pregnancy, such as impaired glucose tolerance (IGT) and gestational diabetes mellitus (GDM).

RESEARCH DESIGN AND METHODS

Brachial artery flow-mediated dilatation (FMD) (endothelium-dependent) and nitrate-induced dilatation (NID) (endothelium-independent) were measured in 23 pregnant subjects with carbohydrate abnormalities (10 IGT, 13 GDM) and in 15 pregnant control subjects during the third trimester of gestation. High-resolution vascular ultrasonography was used to perform these investigations. A fasting lipid panel was obtained, and glucose and insulin values in response to a 100-g oral glucose load were also measured.

RESULTS

FMD was significantly reduced in both groups of women with abnormal carbohydrate metabolism compared with control subjects (7.6 +/- 1.1% in the IGT group and 4.1 +/- 0.9% in the GDM group vs. 10.9 +/- 1.1% in control subjects, P < 0.04 and P < 0.0001, respectively). Significant difference in FMD was also observed between IGT and GDM groups (P < 0.04). NID was comparable in the three groups. Among all subjects, FMD showed a strong independent negative correlation with glycemic area (r=-0.60, P < 0.0001).

CONCLUSIONS

Endothelial dysfunction, an early marker of macrovascular disease, is present in pregnancies complicated by IGT and GDM. This alteration, which seems to be directly related to glycemic levels, could explain, at least in part, the increased risk for concurrent hypertensive disorders during pregnancy in these women.