Discovery of Obacunone as a TGR5 Agonist from Rhizoma coptidis: Affinity Screening, Functional Verification and Transcriptional Analysis

TL;DR

This study identifies obacunone in Rhizoma coptidis as a TGR5 agonist, offering insights into its role in metabolic regulation and potential therapeutic use.

Contribution

The study introduces obacunone as a novel TGR5 agonist from Rhizoma coptidis, validated through multiple experimental techniques.

Findings

Obacunone was identified as a TGR5 agonist with a KD of 101 μM and EC50 of 9.6 μM.

Transcriptomic analysis showed HMOX1 as the most significantly upregulated gene in response to obacunone.

Abstract

Rhizoma coptidis (RC), known as Huang Lian, is widely used for treating diabetes in Traditional Chinese Medicine. G protein-coupled bile acid receptor 1 (TGR5) is a potential therapeutic target for glucose-lipid metabolic disorders due to its capacity to stimulate glucagon-like peptide-1 (GLP-1) secretion. However, whether RC contains ingredients targeting TGR5 remains unclear. In this study, we screened 330 secondary metabolites of RC via molecular docking and identified obacunone as a top candidate. We confirmed binding using Cell Membrane Chromatography (CMC) and quantified affinity via Surface Plasmon Resonance (SPR), determining a KD of 101 μM. cAMP assays identified obacunone as an activator of TGR5. Subsequently, concentration-dependent cAMP assays characterized it as a partial agonist with an EC50 of 9.6 μM. Finally, transcriptomic profiling revealed a stress adaptation response, identifying Heme Oxygenase 1 (HMOX1) as the most significantly upregulated gene (padj = 9.99 × 10−72, log2FoldChange = 1.65). These findings contribute to understanding the pharmacological profile of RC and provide a screening example for identifying components with GPCR activity in RC.

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