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.
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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, (QEATM and Gene-callingTM 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.]
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