Abstracts
1997 Digestive Disease Week

Identification and comparative analysis of human colonocyte short chain fatty acid response genes.

AM Hanly, NJ Emenaker, Y-W Liu, PF Predki, SG Shenoy, MP McKenna, MD Basson. Department of Surgery, Yale University, and CT VA Healthcare System, New Haven, CT, and CuraGen Corporation, Branford CT.

Short chain fatty acids (SCFA's) produced by bacterial fermentation of dietary fiber may promote colonocytic differentiation. The most common SCFA's are n-butyrate, propionate, and acetate. Previous studies by our laboratory suggest that butyrate and propionate are substantially more potent than acetate. In the present study, we sought to define a set of SCFA-response (SCFA-r) genes in the human adenocarcinoma cell line Caco-2 and to determine whether such genes are similarly modulated by equimolar butyrate and propionate. The expression of 3000 random genes was analyzed using high throughput Quantitative Expression Analysis, (QEA^TM and Gene-calling^TM informatic software, CuraGen Corp). The cDNA generated from Caco-2 mRNA was fragmented, fluorescently tagged and analyzed by ultra-high resolution electrophoresis. Data analysis revealed that SCFA substantially modulated the expression of approximately 1% of the 3000 genes studied. Nine SCFA-responsive genes were selected for identification by sequencing and crossreferencing with public data bases. The changes in gene expression for each identified gene in response to SCFA treatment are shown to the right, expressed as the fold increase or decrease in gene expression compared to control values in untreated cells. SCFA appear to regulate the expression of a wide range of genes in human (Caco-2) colonocytes, including intracellular signalling kinases (#'s 1,2) and proteins related to cell motility (#'s 4,5,8) as well as standard differentiation markers (#'s 3,6) and one previously described gene of unknown function (#9) and one previously unknown gene (#7). Furthermore, substantial differences in effects on gene expression were observed between equimolar butyrate (open bars) and propionate (shaded bars) for all but one of these genes (#'s 2-9). These data suggest the magnitude and selectivity of the colonocyte response to SCFA, and offer a new tool for identifying SCFA-r genes which may be important in the activity of dietary fiber in protecting against colon cancer. In addition, these data strongly suggest that different SCFA, at equimolar and physiologically relevant concentrations, are likely to have substantially different effects on colonocyte biology. Consumption of dietary fibers yielding different SCFA ratios may exert different effects on colonic mucosal biology. [Figure not available.]