Serum vitamin C and other biomarkers differ by genotype of phase 2 enzyme genes GSTM1 and GSTT1

Background: Glutathione S-transferases (GSTs) detoxify environmental chemicals and are involved in oxidative stress pathways. Deletion polymorphisms affect enzyme activities and have been associated with risk of disease. Objective: The objective was to clarify whether biomarkers of oxidation, antioxidation, inflammation, and nutritional factors differ by GST genotype in healthy adults. Design: Subjects (n = 383) consisted of nonsmokers and nonusers of antiinflammatory drugs and antioxidant vitamin supplements. Deletion polymorphisms of GSTM1 and GSTT1 were genotyped. F-2-isoprostanes, malondialdehyde, C-reactive protein, serum vitamin C, carotenoids, tocopherols, and other nutritional factors were assessed. Results: The concentration of serum vitamin C was higher in persons with the inactive GSTM1-0 genotype (P = 0.006). This relation was unchanged after adjustment for age, sex, BMI, or dietary vitamin C. F2-isoprostanes and malondialdehyde were lower in the GSTM1-0 and GSTT1-0 groups, respectively, but significance was lost after control for serum vitamin C. The dual deletion, GSTM1-0/GSTT1-0 (n = 37), was associated with higher serum iron and total and LDL-cholesterol concentrations (all P < 0.01) and lower malondialdehyde concentrations, which persisted after adjustment for age, sex, BMI, and serum vitamin C. Carotenoids and alpha- and gamma-tocopherols were not associated with either genotype. Conclusions: Oxidative stress and inflammation biomarkers differ by GST genotype, but serum vitamin C appears to be the most consistent factor. Examination of other relevant genes may be needed to understand the concentration and function of ascorbic acid in the GST enzyme system. This trial is registered at clinicaltrials.gov as NCT00079963. Am J Clin Nutr 2011;94:929-37.