Short-Chain Fatty Acids Increase the Level of Calbindin-D9k Messenger RNA in Caco-2 Cells

Fructooligosaccharides (FOS) are indigestible oligosaccharides that increase the expression of calbindin-D9k and consequently increase calcium absorption by the colon in rats. The molecular mechanism of the increased expression of calbindin-D9k resulting from FOS ingestion has not been elucidated. Short-chain fatty acids (SCFAs), namely, fermentation products of FOS by intestinal bacteria have been hypothesized as direct effectors of calbindin-D9k gene expression. To test this hypothesis, SCFAs were added to Caco-2 human intestinal epithelial cells, and changes in the levels of transcription of genes for calbindin-D9k, and transcription factors (vitamin D receptor: VDR, caudal homeobox-2: Cdx-2, hepatocyte nuclear factor 1-alpha: HNF1-alpha) were determined by quantitative reverse transcription polymerase chain reaction. Addition of sodium propionate or sodium butyrate to cell cultures increased levels of calbindin-D9k mRNA to 731% (p<0.05) and 321% (p<0.05), respectively. However, addition of these SCFAs did not affect the levels of mRNA VDR, Cdx-2, or HNF1-alpha. In conclusion, addition of SCFAs to cultured Caco-2 cells results in elevation of calbindin-D9k mRNA, consistent with the expected role of SCFAs as mediators of the increase of calcium absorption in rats that were fed with FOS.