Modulation of human glutathione S-transferases by botanically defined vegetable diets

Glutathione S-transferases (GSTs) conjugate activated xenobiotics with glutathione; thus, GST induction may improve detoxification and excretion of potentially harmful compounds. Using a randomized cross-over design, we tested the hypothesis that, in humans, serum GST-alpha concentration (GST-alpha) and GST activity increase with vegetable consumption and that this effect is GSTM1 genotype dependent. Twenty-one men (10 GSTM1-null and 11 GSTM1+) and 22 women (15 GSTM1-null and 7 GSTM1+), nonsmokers, 20-40 years of age and not on medications, ate four 6-day controlled diets: basal (vegetable-free), and basal supplemented with three botanically defined groups of vegetables (i.e., brassica, allium, and apiaceous). Fasting blood samples, collected on the last 2 days of each feeding period, were analyzed for GST-alpha, serum GST activity [against 1-chloro-2,4-dinitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl)] and peripheral-lymphocyte GST-mu activity (against trans-stilbene oxide). The brassica, but not allium or apiaceous, vegetable diets (relative to the basal diet) increased GST-alpha by 26% (P = 0.005) and GST (NBD-Cl) activity by 7% (P = 0.02) in the GSTM1-null individuals, particularly the women. Apiaceous vegetable supplementation decreased GST-alpha in the GSTM1+ men (P = 0.03). Among the GSTM1+ women, both brassica and the allium diets increased GST-mu activity by 18% (P = 0.02) and 26% (P = 0.001), respectively. The vegetable diets had no effect on GST (CDNB) activity, irrespective of GSTM1 genotype or sex. These results demonstrate that GSTM1 genotype has a significant effect on GST responses to diet and that brassica vegetables are most effective at inducing GST-alpha, whereas both brassica and allium vegetables induce GST-mu. GST responses were more pronounced in women than men, but it is not clear from this study whether this is a dose-per-body-weight or a sex-specific effect.

Measurement of urinary estrogen metabolites using a monoclonal enzyme-linked immunoassay kit: assay performance and feasibility for epidemiological studies

We evaluated an enzyme-linked immunoassay kit (Estramet 2/16) for the measurement of 2-hydroxyestrone (2-OH E1) and 16-alpha hydroxyestrone (16 alpha-OH E1), major metabolites of estradiol. Urine samples from 14 healthy premenopausal women on days 1, 8, 15, and 22 of their menstrual cycle were assayed along with standards, kit controls, and in-house controls. The intra-assay percentage CVs of 2-OH E1, 16 alpha-OH E1, and the 2-OH E1: 16 alpha-OH E1 ratio were 6.8, 7.4, and 1.8, respectively; the interassay percentage CVs were 15.3, 30.7, and 23.3, respectively. The assay linearity was between 0 and 40 ng/ml. The mean 2-OH E1:16 alpha-OH E1 ratio was relatively constant throughout the day, but it increased by around 50% between the follicular and luteal portions of the menstrual cycle. Individual reagent kits within each lot for 16 alpha-OH E1 were stable for 2 weeks. There was considerable lot-to-lot variation over a 5-month period. In lots used during the last 2 months of the study, values of 2-OH E1 from in-house controls increased by 30-50%, and those of 16 alpha-OH E1 by 50-100%, relative to values obtained initially on the same samples. Depending on the lot, the ratio of the two metabolites ranged from 2 to 5.5. These data suggest that the assay is useful for studies where samples can be assayed with the same kit lot over a period of not more than 2 weeks, but that it is not now suitable for studies that extend over a long enough period of time so that multiple kit lots are required.