Expression of miRNA in different regions of the colon: An investigation in Zucker(fa/fa) rats

The role of obesity in regulation of microRNA (miRNA) expression in distal and proximal colon was assessed: (1) isolation and quantification methods for miRNAs were established in rat liver tissue; (2) miRNA expression patterns were compared using miRNA PCR arrays in lean proximal and distal colonic tissue; and (3) the influence of obesity on miRNA expression in these colonic regions was investigated by screening cancer miRNA coding genes in colonic mucosal samples from Zucker obese and lean rats. Up-regulation of 20 miRNAs was observed in obese liver tissue. Colonic mucosal miRNA expression patterns and abundance differed for distal and proximal colonic regions in both lean and obese tissue. Obesity exerted a profound region-specific effect on miRNA expression patterns and levels indicating biologically distinct tissue in distal and proximal colon. Obesity markedly affects miRNA gene regulation, and miRNA is a key molecular player in the genesis of colon cancer.