Diabetes Care, Vol 19, Issue 6 591-596, Copyright © 1996 by American Diabetes Association
Glucose and amino acid turnover in untreated gestational diabetes
DM Zimmer, AM Golichowski, CA Karn, G Brechtel, AD Baron and SC Denne
Department of Obstetrics and Gynecology, Indiana University School of Medicine, Indianapolis 46202-5210, USA.
OBJECTIVE: Although gestational diabetes affects as many as 3% of all
pregnant women, specific aspects of glucose and protein metabolism in this
population have not been clearly delineated. We tested the hypothesis that
gestational diabetes mellitus (GDM) results in increased glucose production
and proteolysis during fasting. RESEARCH DESIGN AND METHODS: Using tracer
isotope infusions, the rate of appearance (Ra) of glucose, leucine,
phenylalanine and tyrosine, phenylalanine hydroxylation, leucine oxidation,
and urea nitrogen excretion were determined after an overnight fast in 10
GDM subjects, within 2 weeks of diagnosis and before initiation of
treatment, and in a matched control group of nine healthy nondiabetic
pregnant women. RESULTS: Fasting glucose Ra was similar in GDM patients and
control subjects (GDM, 12.8 +/- 1.1 vs. control subjects, 12.8 +/- 0.9
mumol . kg-1 . min-1). Leucine and phenylalanine Ra (reflecting
proteolysis) also were not different between GDM patients and control
subjects (GDM leucine Ra, 128 +/- 14 vs. control subjects, 124 +/- 5;
phenylalanine Ra GDM, 35 +/- 4 vs. control subjects, 40 +/- 2 mumol . kg-1
. h-1). Furthermore, leucine oxidation and phenylalanine hydroxylation were
not increased in GDM subjects, urea nitrogen excretion was actually lower
in GDM patients. However, fasting insulin concentrations were significantly
elevated in GDM subjects (GDM, 165 +/- 35 vs. control subjects, 30 +/- 5
pmol/l; P < 0.01). CONCLUSIONS: Hepatic glucose release and whole-body
proteolysis in GDM patients were remarkably similar to matched pregnant
control subjects. This was achieved with insulin concentrations three- to
fivefold higher than normal, suggesting significant insulin resistance for
both glucose and protein metabolism in GDM.