Sachiko Takase

Higher expression of jejunal LPH gene in rats fed the high-carbohydrate/low-fat diet compared with those fed the low-carbohydrate/high-fat diet is associated with in vitro binding of Cdx-2 in nuclear proteins to its promoter regions

It has been previously demonstrated that the expression of lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) genes are higher in rats fed a high-carbohydrate/low-fat (HCT) diet than in those fed a low-carbohydrate/high-fat (LCT) diet. In the present study, using a nuclear run-on assay we clearly show that higher expression of LPH and SI genes in jejunum of rats fed the HCT diet compared with those fed a LCT diet was regulated at the transcription levels. DNase I foot printing analysis of the 5 flanking region of the rat LPH gene demonstrated that by incubating the jejunal nuclear extract the protected region was conserved as the same sequence as the homeodomain protein-binding element designated as CE-LPH1. UV-cross linking and electromobility shift assay in vitro clearly showed that Cdx-2 was including proteins bound to CE-LPH1. Moreover, in vitro binding of Cdx-2 to CE-LPH1 as well as SIF1, a cis-element identified as the binding element of Cdx-2 on the SI gene, in jejunal nuclear extracts of rats fed a HCT diet were greater than those fed a LCT diet. These results suggest that in vitro binding of Cdx-2 to CE-LPH1 as well as SIF1 in jejunal nuclear extracts is associated with the higher expression of the LPH and SI genes in rats fed the HCT diet compared with those fed a LCT diet.

Feeding rats a high fat/carbohydrate ratio diet reduces jejunal S/I activity ratio and unsialylated galactose on glycosylated chain of S-I complex.

AIMSnWe examined whether decreasing jejunal sucrase/isomaltase (S/I) activity ratio by feeding rats a high fat/carbohydrate ratio diet is regulated by changing glycosylated chains on the S-I complex.nnnMAIN METHODSnJejunal activities of sucrase, isomaltase and beta-1,4-galactosyltransferase were examined in rats fed a high fat/carbohydrate or a low fat/carbohydrate ratio diet. The amount of galactose and mannose in the glycosylated chain on the S-I complex in rats fed both diets was determined using RCA(120) and Con A lectins, respectively. The effects of reducing unsialylated galactose from the glycosylated chain on the S-I complex were assessed by determining sucrase activity in purified S-I complex treated with beta-galactosidase.nnnKEY FINDINGS AND SIGNIFICANCEnFeeding rats a high fat/carbohydrate ratio diet reduced jejunal S/I activity ratio in mucosal homogenates and purified fractions. The level of unsialylated galactose in glycosylated chains on the S-I complex was reduced by feeding rats a high fat/carbohydrate ratio diet. The form with reduced levels of unsialylated galactose had lower sucrase activity than that with more unsialylated galactose. The reduction of galactose on the S-I complex by beta-galactosidase in vitro reduced sucrase activity. Feeding rats a high fat/carbohydrate ratio diet also reduced jejunal beta-1,4-galactosyltransferase activity. Taken together, decreasing the S/I activity ratio by feeding rats a high fat/carbohydrate diet is associated with the reduction of unsialylated galactose on the glycosylated chain of the S-I complex.