Background: Lipid metabolism plays a crucial role in immune cell plasticity, influencing activation, differentiation and function. Inflammation alters this metabolism, contributing to disease progression. Extensive analyses of these profiles in chronic inflammatory diseases such as Rheumatoid Arthritis (RA) using high throughput metabolomic techniques could improve the characterization of disease pathogenesis.

Objectives: This study aimed to analyze the circulating lipid and inflammatory profiles from RA patients, explore their association with disease activity, investigate their modulation by biological and targeted synthetic therapies and identify underlying mechanisms of the altered lipid metabolism.

Methods: A total of 250 RA patients were recruited and clinical data as well as blood samples were collected. A cohort of healthy donors (HDs) matched by age and sex was included. Nuclear Magnetic Resonance (NMR) spectroscopy from Nightingale LTD, which covers over 200 markers, was used to analyze the lipid profile in serum. The levels of inflammatory molecules in serum were also assessed by proximity extension assay technology (Olink/Cobiomic). Additionally, a prospective follow-up was conducted on a subgroup of patients with active RA undergoing treatment with bDMARDs (TNFi:n=50, IL6Ri:n=15) or JAK inhibitors (n=20) for 6 months. Samples obtained before and after therapy were evaluated to analyze changes in lipid and clinical profiles. In vitro studies, using Bodipy staining assays to examine lipid accumulation, and PCR assays to examine expression levels of genes related to lipid metabolism, were carried out in HEPG2 liver cells treated with serum from active RA patients. Statistical analyses integrated all data.

Results: Patients were classified into groups of high (n=68) and moderate-low (n=182) disease activity according to DAS28-CRP activity index. Approximately 100 lipid markers showed significant alterations between groups. Notably, patients with high disease activity exhibited reduced circulating levels of most lipids, including apolipoproteins, fatty acids, cholines, phospholipids, lipoproteins, and total lipid, cholesterol and triglyceride contents. Interestingly, proatherogenic markers such as LDL and VLDL-related lipids were found to be reduced. Multiple negative correlations were found between levels of these lipid markers and levels of acute phase reactants (CRP, ESR), autoantibodies (ACPAS, RF); cardiovascular risk [Carotid intima media thickness -CIMT-, CV risk SCORE, traditional CV risk factors and past events], and hepatic parameters (AST, ALT, GGT levels). In the parallel analysis of the inflammatory profile, patients were categorized into the same activity groups (High vs Moderate-low), and 18 proinflammatory proteins were found to be differentially expressed between the two groups, including several cytokines, chemokines, and growth factors, with higher levels observed in the high-activity group. These inflammatory proteins also correlated with the evaluated clinical parameters (inflammation, autoimmunity, CV risk, liver damage) and above all, showed numerous negative correlations with the altered lipid molecules previously identified, indicating a shared dysregulation between the lipid and inflammatory profiles in high disease activity. Follow-up studies revealed that after 6 months of therapy, the altered lipid markers showed significant modulation, paralleling clinical-analytical improvements in active RA patients, including common and specific molecules modulated by each drug. Finally, in vitro studies revealed differences in lipid accumulation in HepG2 cells treated with serum from active RA patients compared to HDs. Genes related to lipid metabolism were also differentially expressed in HEPG2 cells treated with serum from active patient compared with HDs. Specifically, genes related to lipolysis (ATGL, MGLL, P-HSL), beta-oxidation (ACSL4), lipid transport (LOX-1, CD36), scavenger receptors (LDLR, VLDLR) and lipid-inflammatory regulation (PPARG) were over expressed in the active RA group, whereas genes related to lipogenesis and cholesterol homeostasis (SREBP1, SREBP2) were under expressed. Moreover, the addition of TNFi, IL6Ri or JAK inhibitors balanced gene expression mirroring in-vivo therapeutic effect.

Conclusion: Patients with active RA exhibit a significantly reduced lipid profile, closely linked to their inflammatory and autoimmune profiles. Biological therapies and JAK inhibitors restore the altered lipid metabolism in parallel with clinical improvement. Changes observed on in vitro studies suggest an adaptive strategy in response to the high inflammatory burden in active RA patients, where the liver might enhance energy mobilization via lipolysis while suppressing new lipid synthesis. This strategy may lead to metabolic dysfunction and enhanced CV risk, potentially reversed by b/tsDMARDs. Ongoing studies will further clarify this hypothesis.

REFERENCES: NIL.

Acknowledgements: Supported by ISCIII (PI21/0591, PI24/00959, CD21/00187 and RICOR-21/0002/0033), and RYC2021-033828-I; co-financed by European Union.

Disclosure of Interests: None declared.

© The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.