A groundbreaking study has unveiled the therapeutic potential of obakulactone (OL), a natural tetracyclic triterpenoid derived from Phellodendri cortex, in combating rheumatoid arthritis (RA). This chronic autoimmune disease affects millions worldwide, often leading to debilitating joint pain and deformity. Researchers have discovered that OL targets the enzyme acyl coenzyme A thioesterase 1 (ACOT1), promoting its degradation via the ubiquitin–proteasome pathway—a cellular mechanism for protein turnover. This novel intervention rebalances unsaturated fatty acid metabolism, a key pathogenic factor in RA, and offers new directions for disease management.
Rheumatoid arthritis is characterized by persistent inflammation that leads to joint destruction and systemic complications. Current treatments, including biologics and immunosuppressants, provide symptomatic relief but often carry significant side effects and incomplete efficacy. Understanding the metabolic alterations underlying RA pathogenesis has opened avenues for metabolic reprogramming therapies. The identification of ACOT1, an enzyme pivotal in fatty acid metabolism, adds critical insight into this field’s molecular framework.
Using a well-established rat model of RA induced by complete Freund’s adjuvant, the investigative team administered OL at incremental doses over a period of 21 days. The study meticulously documented substantial improvements in clinical and histological parameters. Joint swelling was markedly reduced, and cartilage as well as synovial architecture were preserved. Furthermore, deleterious changes in immune organs such as the thymus and spleen were ameliorated. These results underscore OL’s robust anti-inflammatory and protective properties within an in vivo inflammatory milieu.
The immunomodulatory effects of OL were further revealed through detailed immunohistochemistry analysis. OL treatment significantly diminished the infiltration of CD3⁺ T lymphocytes and CD68⁺ macrophages into the synovium. Importantly, it shifted macrophage polarization away from the proinflammatory M1 phenotype towards an anti-inflammatory M2 dominance, an effect that plays a crucial role in resolving inflammation. The compound also inhibited the differentiation of CD4⁺ T cells into the pathogenic Th17 subset, which is heavily implicated in RA progression.
A critical pathological hallmark of RA involves the overproduction of proinflammatory cytokines. OL dose-dependently suppressed serum levels of IL-1β, IL-6, IL-17, and TNF-α, cytokines instrumental in perpetuating synovitis and joint destruction. Additionally, OL reduced levels of rheumatoid factor (RF), cyclic citrullinated peptide antibody (CCP-Ab), C-reactive protein (CRP), and matrix metalloproteinase-3 (MMP-3), standard biomarkers used in RA diagnosis and disease activity assessment. These immunological modulations collectively affirm OL’s capacity to suppress systemic autoimmunity.
To unravel the molecular underpinnings of OL’s action, the researchers employed multiomics approaches integrating metabolomics, mass spectrometry imaging, and proteomics. These techniques revealed that RA-induced aberrations in the biosynthesis and metabolism of unsaturated fatty acids—including arachidonic acid, linoleic acid, and α-linolenic acid—were corrected by OL treatment. These lipid mediators are central to the inflammatory cascade and their normalization is critical in disease attenuation.
Cell-based studies using primary RA synovial fibroblasts (SFs) provided mechanistic insights. OL inhibited the uncontrolled proliferation of SFs, promoted apoptosis, and curtailed the secretion of inflammatory mediators. Biophysical and biochemical assays established ACOT1 as the direct target of OL. Advanced techniques such as cellular thermal shift assays, microscale thermophoresis, and surface plasmon resonance demonstrated strong binding affinity, with dissociation constants around 6 µmol·L⁻¹, indicating potent and specific interaction.
The ubiquitin–proteasome pathway emerged as the critical route by which OL mediates ACOT1 degradation. Cycloheximide chase experiments confirmed OL reduced ACOT1 protein stability, while proteasome inhibitor MG132 abrogated this effect, underscoring the proteasome’s role. The subsequent decrease in ACOT1 expression led to reduced levels of stearoyl-CoA desaturase-1 (SCD1), a downstream effector in fatty acid metabolism, contributing to the restoration of lipid homeostasis.
Intriguingly, the decreased ACOT1 activity and altered lipid metabolism disrupted major intracellular signaling pathways pivotal in RA pathogenesis. OL inhibited the activation of Janus kinase (JAK)–signal transducer and activator of transcription (STAT) and phosphoinositide 3-kinase (PI3K)–protein kinase B (AKT) pathways. These pathways play central roles in synovial fibroblast hyperproliferation, inflammation, and joint destruction. OL’s modulation of these pathways aligns with its observed anti-inflammatory and antifibrotic effects.
Further validation included rescue and inhibitor experiments, firmly establishing that OL’s therapeutic efficacy stems from its targeting of ACOT1 and consequent regulation of the arachidonic acid metabolic axis and the downstream JAK–STAT/PI3K–AKT signaling networks. This dual metabolic and signaling intervention is particularly innovative, addressing RA pathology on multiple biological levels.
Given RA’s chronic and systemic nature, with a global prevalence estimated at 1%, and the limitations of current therapies, OL’s discovery is a significant leap forward. By illuminating the critical involvement of fatty acid metabolic reprogramming and protein degradation pathways, this work paves the way for the development of novel, effective, and safer therapeutics. OL and similar molecules targeting ACOT1 hold promise as next-generation treatments for patients grappling with RA’s debilitating effects.
This seminal research enriches our understanding of RA pathogenesis and has broad implications for metabolic and immune-targeted strategies. It exemplifies the power of integrating natural product chemistry, molecular biology, multiomics, and pharmacology to identify innovative therapeutic avenues. As such, it commands attention in the fields of immunology, rheumatology, and drug discovery, heralding a new era of precision medicine for autoimmune diseases.
The study titled “Obakulactone Alleviates Rheumatoid Arthritis by Promotion of ACOT1 Degradation via the Ubiquitin‒Proteasome Pathway and Restoration of Unsaturated Fatty Acid Homeostasis” is authored by Hongda Liu, Le Yang, Yu Yang, Huan Tang, Junling Ren, Hui Sun, Xin Sun, Songyuan Tang, Chong Qiu, Ye Sun, Jigang Wang, Guangli Yan, Ling Kong, Ying Han, and Xijun Wang. The comprehensive work is published in the journal Engineering and can be accessed openly for further reading.
Subject of Research:
Therapeutic potential and molecular mechanism of obakulactone in rheumatoid arthritis via targeting ACOT1 and fatty acid metabolism.
Article Title:
Obakulactone Alleviates Rheumatoid Arthritis by Promotion of ACOT1 Degradation via the Ubiquitin‒Proteasome Pathway and Restoration of Unsaturated Fatty Acid Homeostasis.
News Publication Date:
29-Jan-2026
Web References:
https://doi.org/10.1016/j.eng.2025.10.029
https://www.sciencedirect.com/journal/engineering
Image Credits:
Hongda Liu, Le Yang et al.
Keywords
Rheumatoid arthritis, obakulactone, ACOT1, ubiquitin–proteasome pathway, unsaturated fatty acid metabolism, arachidonic acid, synovial fibroblasts, JAK–STAT signaling, PI3K–AKT signaling, inflammation, apoptosis, macrophage polarization.
Tags: ACOT1 degradation mechanismsACOT1 enzyme modulationanimal models of rheumatoid arthritiscartilage protection in autoimmune disordersfatty acid homeostasis in autoimmune diseasemetabolic reprogramming in rheumatoid arthritisnatural tetracyclic triterpenoids for inflammationnovel therapeutic targets for RAobakulactone rheumatoid arthritis treatmentPhellodendri cortex bioactive compoundsubiquitin–proteasome pathway in arthritisunsaturated fatty acid metabolism in RA
