E-GEOD-40928 - The influence of folate supplementation on global gene expression in normal colonic mucosa of subjects with colorectal adenoma
Released on 1 October 2013, last updated on 2 June 2014
Background: We tested the hypothesis that short-term supplementation with a physiological dose of folate can alter global gene expression in the colon of subjects with colorectal adenoma using a randomised double blind placebo controlled trial design. Materials and Methods: Fourteen subjects with histologically confirmed colorectal adenoma, randomised to receive folic acid (400µg/d, n=6) or placebo (n=8) for 10 weeks, had blood samples and colonic tissue biopsies collected before and after the intervention. Blood samples were used to determine serum and red cell folate, plasma homocysteine, and genetic polymorphisms in methylenetetrahydrofolate reductase (MTHFR C677T) and methionine synthase (MS A2756G). RNA extracted from normal-appearing colonic tissue samples was used to determine global gene expression in the colon using Affymetrix Microarray GeneChips. Microarray results were confirmed by quantitative real time RT-PCR. Two methods were used to analyse the microarray data: (1) differences between pre- and post-intervention gene expression values in the folic acid and placebo groups separately using paired-sample t tests; (2) differences between the folic acid and placebo groups in the ratio of post-intervention to pre-intervention gene expression values using independent sample t-tests. Results: (1) Following intervention, sixty seven genes were up-regulated and 13 genes were down-regulated in the folic acid group, while 21 genes were up-regulated and none were down-regulated in the placebo group (P<0.05, adjusted for multiple testing). (2) Thirty six genes were up-regulated and 18 genes were down-regulated in the folic acid group when compared with placebo, but none of these were statistically significant after adjustment for multiple testing. These genes are involved in multiple pathways, including cell cycle, signal transduction, cell differentiation, transport, cell division, cell motility, protein transport and immune response. There were no genes involved in 1-carbon metabolism that were altered in expression, although several genes involved in neoplasia were up-regulated. Conclusions: These results indicate that while folic acid can modify gene expression, it is difficult to separate its effects from the natural variability in gene expression in the colon. Fourteen patients with colorectal adenoma were treated with either folate supplementation (6 subjects) or a placebo (8 subjects) for 10 weeks in a randomised double-blind trial. Colonic biopsies of normal tissue were taken before and after the intervention, and analysed for gene expression.
transcription profiling by array
Matthew Arno <email@example.com>, Maria Pufulete, Matthew J Arno