Gene knockout and metabolome analysis of carnitine/organic cation transporter OCTN1.
OBJECTIVE
Solute carrier OCTN1 (SLC22A4) is an orphan transporter, the physiologically important substrate of which is still unidentified. The aim of the present study was to examine physiological roles of OCTN1.


METHODS
We first constructed octn1 gene knockout (octn1 ( -/- )) mice. Metabolome analysis was then performed to identify substrates in vivo. The possible association of the substrate identified with diseased conditions was further examined.


RESULTS
The metabolome analysis of blood and several organs indicated complete deficiency of a naturally occurring potent antioxidant ergothioneine in octn1 ( -/- ) mice among 112 metabolites examined. Pharmacokinetic analyses after oral administration revealed the highest distribution to small intestines and extensive renal reabsorption of [(3)H]ergothioneine, both of which were much reduced in octn1 ( -/- ) mice. The octn1 ( -/- ) mice exhibited greater susceptibility to intestinal inflammation under the ischemia and reperfusion model. The blood ergothioneine concentration was also much reduced in Japanese patients with Crohn's disease, compared with healthy volunteers and patients with another inflammatory bowel disease, ulcerative colitis.


CONCLUSIONS
These results indicate that OCTN1 plays a pivotal role for maintenance of systemic and intestinal exposure of ergothioneine, which could be important for protective effects against intestinal tissue injuries, providing a possible diagnostic tool to distinguish the inflammatory bowel diseases.
Division of Pharmaceutical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, 920-1192, Japan.
Yukio
Y
Kato
Yoshiyuki
Y
Kubo
Daisuke
D
Iwata
Sayaka
S
Kato
Tomohisa
T
Sudo
Tomoko
T
Sugiura
Takashi
T
Kagaya
Tomohiko
T
Wakayama
Akiyoshi
A
Hirayama
Masahiro
M
Sugimoto
Kazushi
K
Sugihara
Shuichi
S
Kaneko
Tomoyoshi
T
Soga
Masahide
M
Asano
Masaru
M
Tomita
Toshiyuki
T
Matsui
Morimasa
M
Wada
Akira
A
Tsuji
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D015139:Blotting, Southern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003424:Crohn Disease / Q000235:genetics / Q000378:metabolism; D004880:Ergothioneine / Q000097:blood / Q000493:pharmacokinetics; D005260:Female; D005838:Genotype; D006801:Humans; D007408:Intestinal Absorption / Q000235:genetics / Q000502:physiology; D007422:Intestines / Q000098:blood supply; D007511:Ischemia / Q000473:pathology; D007564:Japan; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D055432:Metabolomics; D051379:Mice; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D008875:Middle Aged; D027701:Organic Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D015427:Reperfusion Injury / Q000473:pathology; D013056:Spectrophotometry, Ultraviolet; D027981:Symporters; D055815:Young Adult
D000975:Antioxidants; D002352:Carrier Proteins; D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; C109807:SLC22A4 protein, human; C491659:Slc22a4 protein, mouse; D027981:Symporters; D004880:Ergothioneine