Role of lysophosphatidylcholine in brush-border intestinal alkaline phosphatase release and restoration

Takanari Nakano, Ikuo Inoue, David H. Alpers, Yasutada Akiba, Shigehiro Katayama, Rina Shinozaki, Jonathan D. Kaunitz, Susumu Ohshima, Masumi Akita, Seiichiro Takahashi, Iwao Koyama, Makoto Matsushita, Tsugikazu Komoda

Research output: Contribution to journalArticlepeer-review

43 Scopus citations

Abstract

Intestinal alkaline phosphatase (IAP) is a brush-border membrane ectoenzyme (BBM-IAP) that is released into the lumen (L-IAP) after a high-fat diet. We examined the effects of oil feeding and the addition of mixed-lipid micelles on the formation of L-IAP in oil-fed rat intestine, Caco-2 cell monolayers, and mouse intestinal loops. We localized IAP in the duodenum of rats fed corn oil using fluorescence microscopy with enzyme-labeled fluorescence-97 as substrate. Four hours after oil feeding, L-IAP increased ∼10-fold accompanied by the loss of BBM-IAP, consistent with BBM-IAP release. Rat IAP isozyme mRNAs progressively increased 4-6 h after oil feeding, followed by the increase of IAP activity in the subapical location at 6 h, consistent with the restoration of IAP protein. Postprandial lipid-micelle components, sodium taurocholate with or without oleic acid, mono-oleylglycerol, cholesterol, or lysophosphatidylcholine (lysoPC) were applied singly or as mixedlipid micelles to the apical surface of polarized Caco-2 cell monolayers. LysoPC increased L-IAP >10-fold over basal release. LysoPC released IAP into the apical medium more than other intestinal brush-border enzymes, 5′-nucleotidase, sucrase, aminopeptidase N, and lactase, without comparable lactate dehydrogenase release or cell injury. LysoPC increased human IAP mRNA levels by 1.5-fold in Caco-2 cells. Luminally applied lysoPC also increased release of IAP preferentially in mouse intestinal loops. These data show that lysoPC accelerates the formation of L-IAP from BBM-IAP, followed by enhanced IAP synthesis, suggesting the role that lysoPC might play in the turnover of brush-border proteins.

Original languageEnglish
Pages (from-to)G207-G214
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume297
Issue number1
DOIs
StatePublished - Jul 2009

Keywords

  • Caco-2 cells
  • Enzyme-labeled fluorescence-97
  • Lipid absorption
  • Small intestine

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