Transport of butyryl-L-carnitine, a potential prodrug, via the carnitine transporter OCTN2 and the amino acid transporter ATB0,+

Sonne R. Srinivas, Puttur D. Prasad, Nagavedi S. Umapathy, Vadivel Ganapathy, Prem S. Shekhawat

Research output: Contribution to journalArticle

42 Scopus citations

Abstract

L-Carnitine is absorbed in the intestinal tract via the carnitine transporter OCTN2 and the amino acid transporter ATB0,+. Loss-of-function mutations in OCTN2 may be associated with inflammatory bowel disease (IBD), suggesting a role for carnitine in intestinal/colonic health. In contrast, ATB0,+ is upregulated in bowel inflammation. Butyrate, a bacterial fermentation product, is beneficial for prevention/treatment of ulcerative colitis. Butyryl-L-carnitine (BC), a butyrate ester of carnitine, may have potential for treatment of gut inflammation, since BC would supply both butyrate and carnitine. We examined the transport of BC via ATB0,+ to determine if this transporter could serve as a delivery system for BC. We also examined the transport of BC via OCTN2. Studies were done with cloned ATB 0,+ and OCTN2 in heterologous expression systems. BC inhibited ATB0,+-mediated glycine transport in mammalian cells (IC 50, 4.6 ± 0.7 mM). In Xenopus laevis oocytes expressing human ATB0,+, BC induced Na+-dependent inward currents under voltage-clamp conditions. The currents were saturable with a K0.5 of 1.4 ± 0.1 mM. Na+ activation kinetics of BC-induced currents suggested involvement of two Na+ per transport cycle. BC also inhibited OCTN2-mediated carnitine uptake (IC50, 1.5 ± 0.3 μM). Transport of BC via OCTN2 is electrogenic, as evidenced from BC-induced inward currents. These currents were Na+ dependent and saturable (K0.5, 0.40 ± 0.02 μM). We conclude that ATB0,+ is a low-affinity/high-capacity transporter for BC, whereas OCTN2 is a high-affinity/low-capacity transporter. ATB0,+ may mediate intestinal absorption of BC when OCTN2 is defective.

Original languageEnglish (US)
Pages (from-to)G1046-G1053
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume293
Issue number5
DOIs
StatePublished - Nov 1 2007

Keywords

  • ATB
  • Butyrate
  • Butyryl-L-carnitine
  • Carnitine
  • Crohn's disease
  • Necrotizing enterocolitis
  • OCTN2

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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