Preliminary study on insulin resistance and pancreatic beta cell function in pregnant women with gestational diabetes mellitus

[Abstract] Objective To study the distinguishing features of insulin resistance and pancreatic β-cell secretion in mid-term pregnant patients with different blood glucose levels,and to investigate the possible pathogenesis of gestational diabetes (GDM).Methods A total of 2 489 pregnant women during the second trimester (gestational age 24-28 weeks) with positive 50 g GCT test were included in the study.Based on the results of oral 75 g glucose tolerance test,the patients were divided into GDM group and normal glucose tolerance (NGT) group,the GDM group were further divided into four groups according to levels of blood glucose:1 h postprandial blood glucose abnormality only (GDM-1,≥ 10.0 mmol/L),2h postprandial blood glucose abnormality only (GDM-2,≥8.5 mmol/L),fasting glucose abnormality only (GDM-3,≥ 5.1 mmol/L) and two or more glucose abnormality (GDM-4).In homeostasis model assessment,insulin resistance index(HOMA-IR),[3-cell function (HOMA-β3),area under curve of glucose (AUCG),area under curve of insulin (AUCI),ratio of 60-minute insulin increase to 60-minute glucose increase (△I60/△G60),and insulin sensitivity index composite (ISI) were assessed and compared between NGT and GDM1-4 groups.Results (1) AUCG,AUCI,and HOMA-IR in the GDM group were statistically higher than those in NGT group (P＜0.05),while HOMA-[β and ISI in the GDM group were lower than those in NGT group (P＜0.05).(2) HOMA-IR was higher in GDMI,3 and 4 groups compared with NGT group(P＜0.01).The level of HOMA-β in GDM1,2 groups was similar with NGT group,but was significantly decreased in GDM3,4 groups(P＜0.01).ISI was significantly decreased in GDMI,2,3,and 4 groups compared with NGT group(P＜0.01).Conclusions Patients with gestational diabetes manifest stronger insulin resistance and significant impaired insulin secretion compared with normal pregnancies.Abnormal fasting blood glucose levels are usually accompanied with insufficient fasting insulin levels.Patients with higher postprandial glucose secrete less insulin after glucose loading,and those with multiple time points of glucose abnormality show impaired insulin secretion,in both basal and after glucose challenge. Key words: Diabetes mellitus, gestational;  Insulin resistance;  β-cell function