Intestinal alkaline phosphatase: multiple biological roles in maintenance of intestinal homeostasis and modulation by diet

Abstract

The diverse nature of intestinal alkaline phosphatase (IAP) functions has remained elusive, and it is only recently that four additional major functions of IAP have been revealed. The present review analyzes the earlier literature on the dietary factors modulating IAP activity in light of these new findings. IAP regulates lipid absorption across the apical membrane of enterocytes, participates in the regulation of bicarbonate secretion and of duodenal surface pH, limits bacterial transepithelial passage, and finally controls bacterial endotoxin-induced inflammation by dephosphorylation, thus detoxifying intestinal lipopolysaccharide. Many dietary components, including fat, protein, and carbohydrate, modulate IAP expression or activity and may be combined to sustain a high level of IAP activity. In conclusion, IAP has a pivotal role in intestinal homeostasis and its activity could be increased through the diet. This is especially true in pathological situations (e.g., inflammatory bowel diseases) in which the involvement of commensal bacteria is suspected and when intestinal AP is too low to detoxify a sufficient amount of bacterial lipopolysaccharide.

Supplementation of enzyme-treated soy protein saves dietary protein and promotes digestive and absorptive ability referring to TOR signaling in juvenile fish

“…We hypothesize that the non-effect of ETSP on AKP in fish PI might be partly related to the balance of intestinal pH. In the duodenum of human, the high AKP activity depressed pH (Lalles 2010). Nevertheless, to protect the PI mucosa from acid injury, the falling pH restrained AKP expression, forming a negative feedback loop in rat intestine (Mizumori et al 2009).…”

Cellular function and molecular structure of ecto-nucleotidases

“…LPA is detoxified by dephosphorylation of its lipid A moiety. Recent evidence suggests that IAP expressed on apical surfaces of microvillus membranes of enterocytes detoxifies LPS in the intestine, thereby preventing inflammation, sustaining barrier function, and maintaining homeostasis within intestinal flora [501][502][503][504]. This hypothesis is supported by the analysis of IAP knockout mice [505,506].…”

Effect of pectin feeding on obesity development and duodenal alkaline phosphatase activity in Sprague-Dawley rats fed with high-fat/high-energy diet

“…It has been proved that addition of pectin to the diet decreases intestinal glucose (14) and fat absorption (23) in these rats. Moreover, regarding the role of intestinal enzymes, AP is considered as a brush border-bound representative enzyme that has a broad range of roles, involving regulation of lipid absorption (16). Its activity increased markedly after fat feeding (13,17,20) and decreased after fasting, while refeeding elevated it to the pre-fasting level (26).…”

“…It has been proved that alkaline phosphatase (AP) is involved in the intestinal absorption of lipids (16). In rats, AP activity increases after fat consumption (3,20,27); it displays circadian fluctuations closely related to food intake (19), and is evidently depressed after food deprivation (26).…”