The regulation of jejunal induction of the maltase‐glucoamylase gene by a high‐starch/low‐fat diet in mice

Abstract

Maltase and glucoamylase are derived from the same mRNA and are responsible for digestion of starch in the small intestine. In this study, we examined whether jejunal expression of the maltase-glucoamylase (Mgam) gene is enhanced by a high-starch (HS) diet through changes in the binding of transcription factors and/or histone code on the gene. Seven-week-old male mice of C57BL/6J strain were fed either a low-starch (5% energy as cornstarch) or a HS (70% energy as cornstarch) diet for 7 days, and then the proximal third of jejunoileum was used for analysis of Mgam mRNA levels (real-time RT-PCR) and of the binding of transcription factors and acetylated histones on the Mgam gene (chromatin immunoprecipitation assays). We found that jejunal Mgam mRNA was increased by a HS diet in mice. Chromatin immunoprecipitation assays revealed that the HS-diet increased the acetylations of histones, bindings of a coactivator, Creb binding protein (CREBBP), and the transcriptional factors caudal type homeobox 2 (CDX2) and HNF1 homeobox (HNF1) in the promoter/enhancer and transcriptional regions of Mgam gene. This suggests that the increase in the jejunal activity of maltase and glucoamylase caused by a HS-diet in mice is regulated at the mRNA level through histone acetylation and binding of CREBBP, CDX2 and HNF1 in the promoter/enhancer and transcriptional regions of Mgam gene.