2005 Volume 51 Issue 6 Pages 426-432
We have previously shown, through evidence that the expression of calbindinD9k protein shows a dose-dependent change in the intestine, that calbindin-D9k plays a role in the ability of a fructooligosaccharide (FOS) diet to increase calcium absorption. This study shows that the regulation of calbindin-D9k expression occurs at the transcriptional level in a segment-specific manner, decreasing in the proximal intestine and increasing in the colorectal segment. To determine the transcriptional regulation of the FOS diet on calbindinD9k expression, two transcription factors, vitamin D receptor (VDR) and cdx-2, were analyzed during 1 0 d feeding of the FOS diet. The mRNA expression of VDR and cdx-2 was influenced by the FOS diet and showed a segment-specific change. In the proximal small intestine, there was a significant correlation between the changes in both mRNAs (r=0.69, p<0.01), while the expression of calbindin-D9k correlated neither with VDR nor with cdx2. This means that the transcriptional change induced by the FOS diet was not regulated by VDR and cdx-2. In the colorectal segment, there were significant correlations between gene expressions of calbindin-D9k vs. VDR, r=0.73, p<0.01 and calbindin-D9k vs. cdx-2, r=0.52, p<0.05. These results suggested that both transcription factors, VDR and cdx-2, were involved in the regulation of calbindin-D9k gene expression in the colorectal segment during the process through which the FOS diet enhanced calcium absorption.