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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.

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Department of Translational Research, University of Pisa, Pisa, Italy.
Department of Clinical and Experimental Medicine, University of Pisa, Via Savi 8, 56126, Pisa, Italy.
Sant'Anna School of Advanced Study - Pisa and CNR Institute of Clinical Physiology, Pisa, Italy.
Fondazione Toscana G. Monasterio, Pisa, Italy.
CNR Institute of Clinical Physiology, Pisa, Italy.
Department of Clinical and Experimental Medicine, University of Pisa, Via Savi 8, 56126, Pisa, Italy.



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.


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.


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.


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.


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


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