Value of the intravenous and oral glucose tolerance tests for detecting subtle impairments in insulin sensitivity and beta-cell function in former gestational diabetes.
OBJECTIVE
Women with former gestational diabetes mellitus (fGDM) often show defects in both insulin sensitivity and beta-cell function but it is not clear which defect plays the major role or which appears first. This might be because fGDM women are often studied as a unique group and not divided according to their glucose tolerance. Different findings might also be the result of using different tests. Our aim was to study insulin sensitivity and beta-cell function with two independent glucose tolerance tests in fGDM women divided according to their glucose tolerance.


METHODS
A total of 108 fGDM women divided into normal glucose tolerance (IGT; N = 82), impaired glucose metabolism (IGM; N = 20) and overt type 2 diabetes (T2DM; N = 6) groups, and 38 healthy control women (CNT) underwent intravenous (IVGTT) and oral glucose tolerance tests (OGTT). Measurements Insulin sensitivity and beta-cell function were assessed by both the IVGTT and the OGTT.


RESULTS
Both tests revealed impaired insulin sensitivity in the normotolerant group compared to controls (IVGTT: 4.2 +/- 0.3 vs. 5.4 +/- 0.4 10(-4) min(-1) (microU/ml)(-1); OGTT: 440 +/- 7 vs. 472 +/- 9 ml min(-1) m(-2)). Conversely, no difference was found in beta-cell function from the IVGTT. However, some parameters of beta-cell function by OGTT modelling analysis were found to be impaired: glucose sensitivity (106 +/- 5 vs. 124 +/- 7 pmol min(-1) m(-2) mm(-1), P = 0.0407) and insulin secretion at 5 mm glucose (168 +/- 9 vs. 206 +/- 10 pmol min(-1) m(-2), P = 0.003).


CONCLUSIONS
Both insulin sensitivity and beta-cell function are impaired in normotolerant fGDM but the subtle defect in beta-cell function is disclosed only by OGTT modelling analysis.
Tura
A
A
Institute of Biomedical Engineering, CNR, Padua, Italy.
Mari
A
A
Prikoszovich
T
T
Pacini
G
G
Kautzky-Willer
A
A
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000503:physiopathology; D016640:Diabetes, Gestational / Q000175:diagnosis / Q000503:physiopathology* / Q000534:rehabilitation*; D005260:Female; D018149:Glucose Intolerance / Q000175:diagnosis / Q000503:physiopathology; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D050417:Insulin-Secreting Cells / Q000502:physiology*; D011247:Pregnancy; D011379:Prognosis; D020127:Recovery of Function; D012680:Sensitivity and Specificity
D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin