Butyrate specifically modulatesMUCgene expression in intestinal epithelial goblet cells deprived of glucose

Abstract

The mucus layer covering the gastrointestinal mucosa is considered the first line of defense against aggressions arising from the luminal content. It is mainly composed of high molecular weight glycoproteins called mucins. Butyrate, a shortchain fatty acid produced during carbohydrate fermentation, has been shown to increase mucin secretion. The aim of this study was to test 1) whether butyrate regulates the expression of various MUC genes, which are coding for protein backbones of mucins, and 2) whether this effect depends on butyrate status as the major energy source of colonocytes. Butyrate was provided at the apical side of human polarized colonic goblet cell line HT29-Cl.16E in glucose-rich or glucose-deprived medium. In glucose-rich medium, butyrate significantly increased MUC3 and MUC5B expression (1.6-fold basal level for both genes), tended to decrease MUC5AC expression, and had no effect on MUC2 expression. In glucose-deprived medium, i.e., when butyrate was the only energy source available, MUC3 and MUC5B increase persisted, whereas MUC5AC expression was significantly enhanced (3.7-fold basal level) and MUC2 expression was strikingly increased (23-fold basal level). Together, our findings show that butyrate is able to upregulate colonic mucins at the transcriptional level and even better when it is the major energy source of the cells. Thus the metabolism of butyrate in colonocytes is closely linked to some of its gene-regulating effects. The distinct effects of butyrate according to the different MUC genes could influence the composition and properties of the mucus gel and thus its protective function. mucin; short-chain fatty acids; energy source; human colonic cell line THE MUCUS LAYER, COVERING the gastrointestinal mucosa, is considered the first line of defense against mechanical, chemical, or microbiological aggressions arising from the luminal contents (14). Mucus is mostly composed of mucins, i.e., glycoproteins of high molecular weight, whose protein backbones are encoded by MUC genes. So far, at least 15 different MUC genes have been identified in humans (15,32). In the large intestinal mucosa, the main MUC genes are MUC2, and to a lesser extent MUC1, MUC3, and MUC4. MUC2 codes for the main secreted mucin in the colon, whereas MUC1, MUC3, and MUC4 mainly code for membrane-located mucins but also present splicing variants coding for secreted mucins (50). Apart from their gel-forming protective function, some membrane-linked mucins, such as MUC1 (22) and MUC4 (12), exhibit specific functions in adhesion and cell signaling.MUC gene expression is altered in many colonic diseases. MUC2 is overexpressed in mucinous colorectal carcinoma, whereas its expression is particularly low in nonmucinous carcinoma (17, 43). MUC5AC and MUC6 expressions are abnormally induced in colon adenoma (6, 9). Aberrant expression of MUC genes (8) as well as modifications of their transcription (34, 45) have also been observed in inflammatory bowel disease. In addition, the thickness of the mucus layer is reduced in ulce...

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Evaluation of the application of enemas containing sucralfate in tissue content of neutral and acid mucins in experimental model of diversion colitis

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Expression of D-type cyclins in colon cancer and in cell lines from colon carcinomas

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