Vitamin E Supplementation in Chemical Colorectal Carcinogenesis: A Two-Edged Knife

This work investigated the effects of Vitamin E (VE) on aberrant crypt foci (ACF) incidence, oxidative stress parameters (serum and hepatic VE concentration, and homocysteine, glutathione (GSH), and malondialdehyde (MDA) levels), and expression of both cyclooxygenase-2 (COX2) and proliferating cellular nuclear antigen (PCNA) in experimental colorectal carcinogenesis. Male Wistar rats received subcutaneous injections of 1,2-dimethylhydrazine (DMH) twice a week, for two weeks (40 mg/kg), except for the Control group. Animals were separated into groups that received different amounts of VE in the diet: 0 IU (0x), 75 IU (recommended daily intake, RDI), 225 IU (3x RDI), or 1500 IU (20x RDI), during (dDMH) or after (aDMH) administration of carcinogen. The 0xdDMH and 3xdDMH groups showed decreased serum VE levels. Hepatic VE concentration was higher in 3xaDMH as compared with the other groups. All the groups, except the Control and the 0xaDMH groups, had reduced GSH levels. The 0xdDMH, 0xaDMH, and 20xaDMH groups exhibited increased MDA levels. The aDMH groups had higher ACF incidence and PCNA expression. The 0xaDMH group presented higher ACF rate, followed by 20xaDMH. Moreover, the 3xaDMH group displayed reduced ACF incidence and COX2 expression. Multivariate analysis revealed that GSH modulated homocysteine levels and COX2. These results suggested that 1500 IU of VE is hazardous, whereas 225 IU of VE has beneficial effects on chemical colorectal carcinogenesis.