Serum gamma-glutamyltransferase levels are related to insulin sensitivity and secretion in subjects with abnormal glucose regulation.
BACKGROUND
To test the association between gamma-glutamyltransferase level and glucose regulation.


METHODS
We performed a cross-sectional analysis of 500 subjects [199 men/301 women, age 47 +/- 11 years, body mass index (BMI) 28.6 +/- 5.5 kg/m(2)] referred to Diabetes Clinics because of potential risk of type 2 diabetes mellitus (T2DM).


RESULTS
The prevalence of all glucose intolerance categories was higher in the top quartile of gamma-glutamyltransferase than in the first. Subjects with normal glucose tolerance showed lower gamma-glutamyltransferase levels compared with those with impaired glucose tolerance (IGT), impaired fasting glucose (IFG)+ IGT and T2DM (ANOVA, p < 0.0001), but not those with IFG. Homeostasis model assessment-insulin resistance (HOMA-IR) increased with increasing levels of gamma-glutamyltransferase, while the insulinogenic index/HOMA-IR ratio decreased. In an age- and sex-adjusted analysis, the top gamma-glutamyltransferase quartile was independently associated with IFG + IGT [odds ratio (OR) 2.41; 95% confidence interval (CI): 1.13-5.15] and T2DM (OR 2.77; 95% CI: 1.47-5.22). After further adjustment for BMI, alcohol intake, family history of diabetes, cigarette smoking and physical activity, the top quartile of gamma-glutamyltransferase remained an independent predictor of IFG + IGT (OR 2.62; 95% CI: 1.13-6.07) and T2DM (OR 2.39; 95% CI: 1.20-4.76). Only when transaminases and HOMA-IR have been added to the model, the top quartile of gamma-glutamyltransferase resulted no more independently associated to IFG + IGT or T2DM.


CONCLUSIONS
Gamma-glutamyltransferase is closely related to insulin resistance, reduced beta-cell function and deterioration of glucose tolerance.
Bianchi
Cristina
C
Department of Endocrinology and Metabolism, University of Pisa, Pisa, Italy.
Penno
Giuseppe
G
Crisci
Isabella
I
Daniele
Giuseppe
G
Agostini
Annalisa
A
Del Prato
Stefano
S
Miccoli
Roberto
R
D000328:Adult; D000410:Alanine Transaminase / Q000097:blood; D000704:Analysis of Variance; D019540:Area Under Curve; D001219:Aspartate Aminotransferases / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D018149:Glucose Intolerance / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology; D000078790:Insulin Secretion; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D055105:Waist Circumference; D005723:gamma-Glutamyltransferase / Q000097:blood*
D001786:Blood Glucose; D007328:Insulin; D005723:gamma-Glutamyltransferase; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase