We have reported that dietary glucomannan and non-digestible oligosaccharides increase colonic alkaline phosphatase （EC3.1.3.1; ALP） activity by upregulating the expression of Alpi-1 （an ALP gene）. The altered ALP activity was positively correlated with changes in fecal mucin concentration, Bifidobacterium or Lactobacillus to total bacteria ratio, and cecal n-butyrate concentration in rats fed a high-fat （HF） diet. We studied the effects of dietary inulin （a soluble, fermentable dietary fiber） and chitosan （an insoluble dietary fiber derived from crustaceans such as crabs and shrimps） on the colonic ALP activity by feeding male Sprague‒Dawley rats a 30% lard diet only or a 30% lard diet containing either 4% inulin or 4% chitosan for two weeks. Colonic ALP activity, gene expression, and gut luminal variables, including mucins, organic acids, and some bacteria, were measured. Rats fed an HF diet with inulin showed a significant increase in colonic ALP activity, increased colonic Alpi-1 gene expression, and significant increases in fecal Bifidobacterium spp. ratio, fecal mucin concentration, and cecal n-butyrate and lactate concentrations. Dietary chitosan did not significantly increase these factors, including colonic ALP activity; however, there was a slight increase in fecal mucin concentration. Conversely, it increased fecal Bacteroides ratio and cecal succinate concentration. We presume that dietary fibers should be soluble and fermentable in the large intestine and cecum to induce colorectal ALP activity.
Key Words: inulin, chitosan, alkaline phosphatase, mucin, n-butyrate |
