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Obes Surg. 2018 May;28(5):1363-1371. doi: 10.1007/s11695-017-3017-7.

γ-Glutamyltransferase Fractions in Obese Subjects with Type 2 Diabetes: Relation to Insulin Sensitivity and Effects of Bariatric Surgery.

Author information

1
Department of Translational Research, University of Pisa, Pisa, Italy.
2
Department of Clinical and Experimental Medicine, University of Pisa, Via Savi 8, 56126, Pisa, Italy.
3
Sant'Anna School of Advanced Study - Pisa and CNR Institute of Clinical Physiology, Pisa, Italy.
4
Fondazione Toscana G. Monasterio, Pisa, Italy.
5
CNR Institute of Clinical Physiology, Pisa, Italy.
6
Department of Clinical and Experimental Medicine, University of Pisa, Via Savi 8, 56126, Pisa, Italy. monica.nannipieri@dmi.unipi.it.

Abstract

BACKGROUND/OBJECTIVES:

Gamma-glutamyltranspeptidase (GGT) levels are an independent risk marker for the development of type 2 diabetes (T2DM). We investigated the relationship between the newly identified serum GGT fractions and glucose metabolism in obese subjects before and after bariatric surgery.

SUBJECTS/METHODS:

Twenty-nine T2DM subjects, wait-listed for Roux-en-Y gastric bypass (RYGB; n = 21) or laparoscopic sleeve gastrectomy (LSG; n = 8), received a 5-h mixed meal test before (T0), 15 days (T15), and 1 year after surgery (T365). Insulin sensitivity was assessed by the OGIS index and β-cell function by C-peptide analysis; fractional GGT (b-, s-, m-, and f-GGT) analysis was performed by gel-filtration chromatography.

RESULTS:

At T15, total GGT activity decreased by 40% after LSG (p = 0.007) but remained unchanged after RYGB. At T365, all patients showed a reduction in total GGT, in particular b-GGT (≥ 60%) and m-GGT (≥ 50%). In patients with biopsy-proven steatohepatitis (n = 10), total, b-, s-, and m-GGT fractions at T0 were significantly higher than in patients with low-grade steatosis (p = 0.016, 0.0003, and 0.005, respectively); at T365, there was a significant fall in total GGT as well as in each fraction in both groups. In a multiple regression model, b-GGT was the only fraction related to insulin sensitivity (p = 0.016; β coeff. = - 14.0) independently of BMI, fasting glucose, and triglycerides.

CONCLUSIONS:

While GGT activity is generally associated with impaired glucose metabolism, fractional GGT analysis showed that the b-GGT fraction specifically and independently tracks with insulin resistance.

KEYWORDS:

B-GGT fraction; Gamma-glutamyltransferase; Insulin sensitivity; NASH

PMID:
29170860
DOI:
10.1007/s11695-017-3017-7

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