Insulin-sensitivity index and carbohydrate and lipid metabolism in gestational diabetes

To study insulin action in normal and gestational diabetic pregnant women by using an insulin tolerance test.

Twenty-four women diagnosed as having gestational diabetes were compared to 22 nondiabetic, matched controls. The insulin-tolerance test (ITT) consisted of an intravenous bolus of 0.1 IU/kg of regular insulin with glucose sampling at -5, 0, 3, 5, 7, 10 and 15 minutes. The insulin sensitivity index (ISI) was assessed by using a delta G/G0 ratio (G0 = initial glycemia level, delta G = variation between G0 and glycemia level obtained at 15 minutes by calculation of the regression plot).

Two women had glucose levels < 50 mg/dL at 15 minutes, without clinical symptoms. Women with gestational diabetes had a significantly lower level than those with normal glucose tolerance. The rate of abnormal insulin resistance (ISI) (< 10th percentile in the control group) was significantly higher in the insulin-treated subgroup (8/11, 72.7%, vs. 2/12, 16.6%). ISI correlated negatively with glycemia (r = -.38, P = .01) and glycosylated hemoglobin (r = -.50, P = .001) and correlated positively with low density lipoprotein-c (r = -.40, P = .01) and apolipoprotein B (r = -.42, P = .01). In the gestational diabetes group, ISI was correlated negatively with gestational age (r = -.50, P = .01) and triglycerides (r = -.50, P = .01).

ITT seems to be a safe and rapid method of measuring in vivo insulin action in pregnant women. Women with gestational diabetes had higher insulin resistance, especially those who needed insulin therapy. Lipid profile in gestational diabetes was related to the level of insulin resistance.