A novel partial agonist of GPBA reduces blood glucose level in a murine glucose tolerance test.

Abstract

GPBA is a G protein-coupled receptor that is activated by bile acids. Because activation of GPBA leads to increased cAMP levels and secretion of incretins and insulin, GPBA has been proposed as a promising drug target for the treatment of metabolic syndrome. Previously, we have developed a ligand-screening system to identify novel agonists of GPBA by means of a fusion protein of GPBA with G protein stimulatory α subunit (Gsα) and by a [35S]GTPγS-binding assay. To express the GPBA-Gsα fusion protein, transgenic silkworms were employed in this study, and cell membrane fractions were prepared from their fat body or pupae. We applied them to the screening of a chemical library that contains 10,625 compounds from the RIKEN Natural Products Depository (NPDepo). Eventually, a unique partial agonist, GUM2, was successfully identified. Our results indicated that the GPCR-Gα fusion proteins were beneficial for ligand identification and that the transgenic silkworms were useful for large-scale production of GPCRs. In HEK293 cells transiently expressing GPBA, GUM2 showed 50% effective concentration (EC50) of 3.5 ± 2.4μM and induced GPBA internalization as effectively as did an endogenous agonist, TLC. We also confirmed that GUM2 stimulates insulin secretion in MIN6 cells. Moreover, a single 2mg/kg dose of GUM2 significantly reduced blood glucose levels in mice during an intraperitoneal glucose tolerance test even though GUM2 is only a partial agonist with a low intrinsic activity. We concluded that GUM2 is a good candidate for research on GPBA signaling under physiological conditions and for the development of GPBA-targeting therapeutic compounds.

• Authors: Rina Enomoto, Aya Kurosawa, Yoshiaki Nikaido, Misaki Mashiko, Toshihiko Saheki, Nozomi Nakajima, Satoshi Kuroiwa, Michinari Otobe, Maki Ohsaki, Kazuya Tooyama, Yusuke Inoue, Nobuo Kuwabara, Osamu Kikuchi, Tadahiro Kitamura, Itaru Kojima, Yuko Nakagawa, Tamio Saito, Hiroyuki Osada, Mizuko Futahashi, Hideki Sezutsu, Shigeki Takeda
• Journal: European journal of pharmacology (Eur J Pharmacol) Vol. 814 Pg. 130-137 (Nov 05 2017) ISSN: 1879-0712 [Electronic] Netherlands
• PMID: 28823924 (Publication Type: Journal Article)
• Copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical References

• Biological Products
• Blood Glucose
• Insulin
• Receptors, G-Protein-Coupled

Topics

• Animals
• Biological Products (pharmacology)
• Blood Glucose (metabolism)
• Glucose Tolerance Test
• HEK293 Cells
• Humans
• Insulin (metabolism)
• Insulin Secretion
• Intracellular Space (drug effects, metabolism)
• Larva (metabolism)
• Mice
• Pupa (metabolism)
• Receptors, G-Protein-Coupled (agonists)