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Loss of the Tight Junction Protein Claudin 15 Causes Malabsorption of Peptide in Murine Intestine
Author(s) -
Hayashi Hisayoshi,
Tajima Haruna,
Watanabe Miki,
Ishizuka Noriko
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1223.30
Subject(s) - jejunum , paracellular transport , claudin , ileum , small intestine , malabsorption , tight junction , medicine , chemistry , endocrinology , osmotic concentration , absorption (acoustics) , in vivo , biology , biochemistry , permeability (electromagnetism) , materials science , microbiology and biotechnology , composite material , membrane
It is known that the claudin family of tight junction proteins is critical in determining paracellular ionic permeability and selectivity. We have shown that loss of claudin 15 results in decreased luminal Na + concentration and glucose malabsorption in the small intestine. To gain further insight into the relationship between intestinal Na + metabolism and changes in nutrient absorption induced by the loss of claudin 15, we investigated the site of absorption of electrolytes and peptide in claudin 15 knockout (cldn15KO) mice and compared this with wild‐type mice under in vivo conditions. Mice were fed a diet supplemented with 14 C‐polyethylene glycol (PEG) 4000 as a non‐absorbable marker and 3 H‐Gly‐Sar (non‐hydrolyzable dipeptide). After feeding, the small intestine was isolated and divided into six segments, the luminal contents collected for analysis of Na + ‐concentration and the level of 14 C‐PEG4000 and 3 H‐Gly‐Sar. Gastric emptying time, assessed by measuring 14 C‐PEG4000, was not changed in cldn15KO compared to wild‐type mice. Total luminal contents in the small intestine were increased in cldn15KO mice and the sojourn time of digesta in the upper jejunum was increased 3‐fold compared with wild‐type mice. Robust Na + secretion and rate of absorption were observed in the upper jejunum in wild‐type mice and this was attenuated in cldn15KO mice. Total amount of luminal Gly‐Sar were increased, while absorption rates of Gly‐Sar were decreased, in the upper jejunum of cldn15KO mice. This implies that decrease of expression level of pepT1 and /or NHE3. Therefore, quantitative real‐time PCR was used to determine the mRNA transcription of pepT1 and NHE3. However, there was no difference between cldn15KO and wild‐type mice. We next measured Gly‐Sar‐induced short‐circuit current (Isc) in Ussing chambers systems. Upon Gly‐Sar was added to the mucosal side in wild‐type mice, robust biphasic increment of Isc was observed and this was attenuated by mucosal addition of NHE3 inhibitor S3226. In cldn15KO mice, Gly‐Sar‐induced Isc was significantly decreased compared to wild‐type mice and was not sustained the plateau phase. These results suggest that NHE3 activation mechanism(s) induced by peptide absorption was not operated properly in cldn15KO mice.