Is Serum Gamma-Glutamyltransferase a Biomarker of Xenobiotics, Which Are Conjugated by Glutathione?

A meta-analysis of 10 prospective cohort studies,1 includ-ing our own,2 reported that serum -glutamyltrans-ferase (GGT) predicted incident vascular events. This meta-analysis posed one important, but unsolved question: why does serum GGT predict incident vascular events? In addition to vascular events, serum GGT predicts various important clinical outcomes including type 2 diabetes, metabolic syn-drome, and renal problems.3–5 Serum GGT has traditionally been used as a marker of alcohol consumption; however, alcohol consumption cannot explain the disease relationships with serum GGT because these associations have been observed among nondrinkers as well as drinkers. The other prevailing interpretations are that serum GGT predicts clinical outcomes as a marker of nonalcoholic fatty liver disease (NAFLD) or oxidative stress.6–8 Although both of these explanations have some