) We propose to obtain information on the relationship between vitamin B-6 (B-6) intake and cigarette associated with DNA damage and cancer. Preliminary data reveal that vitamin B-6 inadequacy increases uracil incorporation in DNA. Furthermore, smoking reduces vitamin B- 6 status and increases oxidative damage to smoking in men and women by studying functional measures of vitamin B-6 and folate metabolism which are DNA. A controlled diet study will be conducted in men and women, during which 16 subjects (8 smokers and 8 nonsmokers) will be moderately depleted of vitamin B-6 (0.5 mg B-6/d for 28 d), and then repleted using two levels of vitamin B-6 intake (1.3 and 2.1 mg/d, respectively) for successive 28d periods. Venous blood will be collected from fasting subjects weekly; 24h urine collections will be obtained daily. Vitamin B-6 metabolite concentrations [i.e., pyridoxal phosphate (PLP), pyridoxamine phosphate, pyridoxal, pyridoxine and 4-pyridoxic acid] will be determined in plasma and erythrocytes, and PLP concentrations measured in lymphocytes. Activities of erythrocyte alanine and aspartate aminotransferase will be assessed with and without added PLP. Urine will be analyzed for 4-pyridoxic acid. Lymphocytes collected on day 1 and at the end of each experimental period will be analyzed for DNA uracil content, strand breaks, and apurinic/apyridiminic sites. Lymphocyte serine hydroxymethyltransferase (SHMT) activity will be analyzed in the presence and absence of excess PLP. Relationships among vitamin B-6 status, measures of disturbances in DNA composition and smoking will be assessed. The vitamin B-6 intake which optimizes functional measures related to DNA damage and cancer prevention in men and women, smokers and nonsmokers, will be evaluated. This study will permit carefully controlled evaluation of the responsiveness of traditional and novel (i.e., lymphocyte DNA composition and SHMT activity) biochemical status measures to alterations in dietary vitamin B-6 intake and smoking, thereby providing recommendations for vitamin B-6 intake based on functional endpoints related to cancer prevention.
| Mashiyama, Susan T; Hansen, Christine M; Roitman, Esther et al. (2008) An assay for uracil in human DNA at baseline: effect of marginal vitamin B6 deficiency. Anal Biochem 372:21-31 |
