Association of Serum Carotenoids and Tocopherols with [Gamma]-Glutamyltransferase: The Cardiovascular Risk Development in Young Adults (CARDIA) Study (Lipids, Lipoproteins, And Cardiovascular Risk Factors‪)‬

Serum [gamma]-glutamyltransferase (GGT) [5] is a well-known enzyme marker of alcohol consumption and liver disease (1). However, serum GGT concentrations within the reference interval have also been associated with most cardiovascular risk factors and were a predictor of future heart disease, hypertension, stroke, and type 2 diabetes (2-9). In particular, the serum GGT concentration has shown a strong graded relationship with incident diabetes, suggesting a role in the pathogenesis of diabetes (4, 8, 9). Although the mechanism underlying the above associations remains largely unknown, serum GGT may be associated with these disease outcomes through a mechanism related to oxidative stress (8, 9); recent experimental studies have shown that GGT plays an important role in antioxidant defense systems at the cellular level (10-13). Supporting the role of GGT in the oxidative stress mechanism, in our previous study (9), serum GGT values within the reference interval at baseline predicted C-reactive protein, a marker of inflammation, and F2-isoprostanes, a marker of oxidative damage to arachidonic acid, measured after 15 years in a dose-response manner. Moreover, dietary heme iron was positively associated with serum GGT concentrations, whereas most dietary antioxidants, especially vitamin C and [beta]-carotene, were inversely associated with serum GGT (14).