The effects of a TGR5 agonist and a dipeptidyl peptidase IV inhibitor on dextran sulfate sodium-induced colitis in mice.

Taisuke Sakanaka, Takuya Inoue, Naoki Yorifuji, Munetaka Iguchi, Kaori Fujiwara, Ken Narabayashi, Kazuki Kakimoto, Sadaharu Nouda, Toshihiko Okada, Takanori Kuramoto, Kumi Ishida, Yosuke Abe, Toshihisa Takeuchi, Eiji Umegaki, Yasutada Akiba, Jonathan D Kaunitz, Kazuhide Higuchi

Index: J. Gastroenterol. Hepatol. 30 Suppl 1 , 60-5, (2015)

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Abstract

Luminal nutrients stimulate enteroendocrine L cells to release gut hormones, including intestinotrophic glucagon-like peptide-2 (GLP-2). Because L cells express the bile acid receptor TGR5 and dipeptidyl peptidase-IV (DPPIV) rapidly degrades GLPs, we hypothesized that luminal TGR5 activation may attenuate intestinal injury via GLP-2 release, which is enhanced by DPPIV inhibition.Intestinal injury was induced in mice by administration of dextran sulfate sodium (DSS) in drinking water (free access to water containing 5% DSS for 7 days). The selective TGR5 agonist betulinic acid (BTA) and the DPPIV inhibitor sitagliptin phosphate monohydrate (STG) were administered orally for 7 days. Male C57BL/6 mice (6-7 weeks old) were divided into five groups: normal control group, disease control group, BTA low group (drinking water containing 15 mg/L BTA), BTA high group (50 mg/L BTA), and BTA high + STG (3 mg/kg, i.g.) group.The selective TGR5 agonist BTA dose-dependently suppressed disease activity index and mRNA expression of the pro-inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in the colon. Nevertheless, STG administration had little additive effect on BTA-induced protection. Fibroblast activation protein mRNA expression, but not expression of other DPP family members, was increased in the colon of DSS-treated mice with increased mucosal DPPIV. Co-administration of the selective GLP-2 antagonist GLP-2 (3-33) reversed the effect of BTA.The selective TGR5 agonist BTA ameliorated DSS-induced colitis in mice via the GLP-2 pathway with no effect of DPPIV inhibition, suggesting that other DPP enzymatic activity is involved in GLP-2 degradation.© 2015 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.