Allspice and Clove As Source of Triterpene Acids Activating the G Protein-Coupled Bile Acid Receptor TGR5

Abstract

Worldwide, metabolic diseases such as obesity and type 2 diabetes have reached epidemic proportions. A major regulator of metabolic processes that gained interest in recent years is the bile acid receptor TGR5 (Takeda G protein-coupled receptor 5). This G protein-coupled membrane receptor can be found predominantly in the intestine, where it is mainly responsible for the secretion of the incretins glucagon-like peptide 1 (GLP-1) and peptide YY (PYY). The aim of this study was (i) to identify plant extracts with TGR5-activating potential, (ii) to narrow down their activity to the responsible constituents, and (iii) to assess whether the intestinal microbiota produces transformed metabolites with a different activity profile. Chenodeoxycholic acid (CDCA) served as positive control for both, the applied cell-based luciferase reporter gene assay for TGR5 activity and the biotransformation assay using mouse fecal slurry. The suitability of the workflow was demonstrated by the biotransformation of CDCA to lithocholic acid resulting in a distinct increase in TGR5 activity. Based on a traditional Tibetan formula, 19 plant extracts were selected and investigated for TGR5 activation. Extracts from the commonly used spices Syzygium aromaticum (SaroE, clove), Pimenta dioica (PdioE, allspice), and Kaempferia galanga (KgalE, aromatic ginger) significantly increased TGR5 activity. After biotransformation, only KgalE showed significant differences in its metabolite profile, which, however, did not alter its TGR5 activity compared to non-transformed KgalE. UHPLC-HRMS (high-resolution mass spectrometry) analysis revealed triterpene acids (TTAs) as the main constituents of the extracts SaroE and PdioE. Identification and quantification of TTAs in these two extracts as well as comparison of their TGR5 activity with reconstituted TTA mixtures allowed the attribution of the TGR5 activity to TTAs. EC50s were determined for the main TTAs, i.e., oleanolic acid (2.2 ± 1.6 μM), ursolic acid (1.1 ± 0.2 μM), as well as for the hitherto unknown TGR5 activators corosolic acid (0.5 ± 1.0 μM) and maslinic acid (3.7 ± 0.7 μM). In conclusion, extracts of clove, allspice, and aromatic ginger activate TGR5, which might play a pivotal role in their therapeutic use for the treatment of metabolic diseases. Moreover, the TGR5 activation of SaroE and PdioE could be pinpointed solely to TTAs.

Oleanolic acid reprograms the liver to protect against hepatotoxicants, but is hepatotoxic at high doses

“…Oleanolic acid is a Takeda G protein receptor 5 (TGR5) agonist . TGR5 (also called G‐protein‐coupled bile acid receptor, GPBAR1) is an important bile acid receptor expressed in cholangiocytes.…”

“…Although the benefits of targeting the TGR5 receptor help maintain bile acid homeostasis, TGR5 activation is also associated with risks of histopathological changes, tumorigenesis, pruritus and others . Unlike bile acids, OA is a TGR5 agonist, but not (or a weak) FXR agonist . Intradermal injection of bile acids or TGR5 agonist OA stimulated analgesia and scratching behaviour, which was attenuated in Tgr5‐KO mice but exacerbated in Tgr5‐Tg mice …”

“…19 Oleanolic acid is a Takeda G protein receptor 5 (TGR5) agonist. 17,59 TGR5 (also called G-protein-coupled bile acid receptor, GPBAR1) is an important bile acid receptor expressed in cholangiocytes. Activation of TGR5 in biliary epithelial cells promotes chloride and bicarbonate secretion and triggers cell proliferation.…”

“…[83][84][85] Unlike bile acids, OA is a TGR5 agonist, but not (or a weak) FXR agonist. 17,59,86 Intradermal injection of bile acids or TGR5 agonist OA stimulated analgesia and scratching behaviour, which was attenuated in Tgr5-KO mice but exacerbated in Tgr5-Tg mice. 87,88 TGR5 activation by OA induced the expression of IL-1β and TNFα in the murine macrophage cell line RAW264.7 or in murine Kupffer cells.…”

Streptomyces spp. From Ethiopia Producing Antimicrobial Compounds: Characterization via Bioassays, Genome Analyses, and Mass Spectrometry

“…To identify the antimicrobial compounds in the active extracts, an analytical strategy previously established was employed (Ladurner et al, 2017 ). The crude extracts obtained from both SSF and LSF were diluted to a concentration of 1 mg/mL and first analyzed by high-performance liquid chromatography (HPLC) on an UltiMate 3000 RSLC-series system (Dionex/Thermo Fisher Scientific, Germering, Germany) coupled in parallel to a Corona ultra RS charged aerosol detector (CAD, Dionex/Thermo Fisher Scientific) and an HCT 3D quadrupole ion trap mass spectrometer (MS) equipped with an orthogonal ESI source (Bruker Daltonics, Bremen, Germany).…”