Effect of Maternal Dietary B-Vitamin Intake on Offspring DNA Methylation Patterns, Gene Expression, Cytokinetics, and Intestinal Tumorigenesis in the Apc+/1638N Mouse Model.

摘要

Epidemiological and laboratory data have repeatedly implicated one-carbon nutrients such as folate, riboflavin (vitamin B2), vitamin B6, and vitamin B12 as being protective against various cancers, most notably those of the colorectum. Deficiencies in one or all of these nutrients have been shown in a variety of experimental settings to lead to increases in genotoxic events associated with cancer such as dysregulation of DNA methylation as well as altered expression of several genes in the Wnt signaling pathway.;The role of maternal nutriture in determining offspring disease susceptibility is increasingly recognized. Therefore, we aimed to determine whether a relationship between maternal dietary B-vitamin intake and intestinal tumorigenesis in offspring was present in a genetically engineered model of colorectal cancer. It was our central hypothesis that supplemental levels of one-carbon nutrients in the maternal diet from preconception through weaning would decrease, while deficient levels would increase, dysregulation in DNA methylation patterns in Wnt pathway genes in the offspring that preserve apoptotic function leading to a reduction in tumorigenesis.;Three groups of 6-week old female C57BL/6 mice were fed diets either deficient, replete, or supplemented with folate, vitamin B2, B 6, and B12 for 4 weeks, then mated with male Apc +/1638N mice. Females remained on their respective diets throughout mating, pregnancy and the suckling period (11 weeks total). Pups were genotyped at 3 weeks of age, and all wild type pups were sacrificed. After weaning, all Apc+/1638N pups were fed a replete diet (AIN-93) regardless of the maternal diet. At 32 weeks of age, 56% and 59% of Apc+/1638N pups born to deficient and replete mothers, respectively, exhibited tumors in the small intestine compared to 21% of pups born to supplemented mothers (p=0.031). Furthermore, a significantly (p=0.026) higher percentage of tumors collected from pups of deficient mothers (54%) displayed invasive features compared to tumors from pups of replete mothers (18%).;In the small intestine of 3-week old wild type pups as well as 32-week old Apc+/1638N pups, the expression of several negative regulators of Wnt signaling such as Apc, Sfrp1, Wif1, and Wnt5a was proportional to the concentration of B-vitamins in the maternal diet. Furthermore, the expression of Sfrp1 was significantly and inversely correlated with the degree of methylation within the promoter region of the gene. Contrary to our expectations, an increase in apoptosis was observed among pups born to deficient dams in both genotypes. Along with an elevation of beta-catenin in the small intestine, these data are consistent with the hypothesis that the maternal diet affects offspring tumorigenesis through a methylation induced de-repression of the Wnt pathway.;The results of the project described herein are among the first observations regarding maternal B-vitamin intake and offspring colorectal carcinogenesis and provide the most comprehensive dataset available to date regarding the potential mechanism mediating this effect.