Diabetes, Vol 44, Issue 8 911-915, Copyright © 1995 by American Diabetes Association
Excessive secretion of insulin precursors characterizes and predicts gestational diabetes
RA Swinn, NJ Wareham, R Gregory, V Curling, PM Clark, KJ Dalton, OM Edwards and S O'Rahilly
Department of Medicine, University of Cambridge, U.K.
Using assays that specifically measure insulin, intact proinsulin, and
32,33 split proinsulin, we examined the beta-cell secretory response to an
oral glucose tolerance test (OGTT) in 64 women with gestational diabetes
mellitus (GDM) and 154 pregnant normoglycemic control subjects of
comparable age and body mass index. Women with GDM were characterized by a
lower 30-min insulin increment (40.8 [34.9-47.6] vs. 58.6 [53.6-64] pmol
insulin/mmol glucose, P < 0.001; geometric mean [95% confidence
interval]) and a higher plasma insulin level at 120 min (702 [610-808] vs.
444 [400-492] pmol/l, P < 0.001). 32,33 split proinsulin levels were
elevated in GDM patients in both fasting (9.1 [7.3-11.4] vs. 6.7 [6.0-7.5]
pmol/l, P < 0.02) and 120-min (75.2 [62.9-90.0] vs. 52.2 [46.7-58.3]
pmol/l, P < 0.001) samples, respectively. Intact proinsulin levels were
significantly elevated at 120 min in the women with GDM (21.3 [18.1-25.1]
vs. 14.8 [13.4-16.3] pmol/l, P < 0.001). Thus, the qualitative
abnormalities of insulin secretion in GDM patients (low 30-min insulin
increment, high 120-min plasma insulin, and elevated 32,33 split
proinsulin) are similar to those seen in nonpregnant subjects with impaired
glucose tolerance. To determine whether measures of proinsulin-like
molecules (PLMs) might assist in the prediction of GDM, women who had a 1-h
glucose level of > 7.7 mmol/l after a 50-g glucose challenge at 28-32
weeks' gestation had insulin and PLMs measured in the 1-h sample.(ABSTRACT
TRUNCATED AT 250 WORDS)