A Shared EGR1-IL-32-Macrophage Polarisation Signature in Rheumatoid Arthritis and Metabolic Dysfunction-Associated...

Rheumatoid arthritis (RA) and metabolic dysfunction-associated steatotic liver disease (MASLD) frequently co-occur, but their shared molecular and immunometabolic features remain incompletely defined. We integrated population-level epidemiology, hospital-based clinical phenotyping, cross-disease transcriptomic analyses, and patient-level experimental data to systematically characterise RA-MASLD comorbidity.

The associations of RA with MASLD and hepatic fibrosis-related phenotypes were examined in 5615 adults from NHANES 2017-March 2020 using survey-weighted regression. A retrospective hospital cohort of 100 patients with RA, including 60 with RA only and 40 with RA+MASLD, was used for clinical phenotyping. Nine GEO datasets were analysed independently. Shared genes were identified by sequentially intersecting two hepatic MASLD datasets with a primary RA synovial cohort, followed by direction-concordance filtering, machine-learning prioritisation, external expression assessment, immune-signature analysis, and single-cell localisation. Serum IL-32 and peripheral blood mononuclear cell EGR1 mRNA were measured in 45 participants. Western blotting and flow cytometry were performed as exploratory analyses in a randomly selected subset of nine participants, with three participants per group.

After full adjustment, RA was not independently associated with MASLD or the assessed hepatic phenotypes in NHANES (MASLD odds ratio, 1.03; 95% confidence interval, 0.57-1.87). In the hospital cohort, patients with RA+MASLD had higher disease activity, greater hepatocellular injury, and a higher noninvasive fibrosis burden than those with RA alone. Cross-disease transcriptomic analysis identified six concordantly dysregulated genes-IL32, DHRS9, MOXD1, EGR1, RRM2, and PRC1-with EGR1 prioritised for subsequent analyses. EGR1 showed an apparent area under the curve of 0.982 in GSE135251 and an area under the curve of 0.989 in the external hepatic cohort GSE89632. EGR1 expression was inversely associated with the M2 macrophage signature score and serum IL-32 concentration. From healthy controls to the RA-only and RA+MASLD groups, EGR1 mRNA showed a stepwise decrease and serum IL-32 progressively increased. The exploratory flow-cytometric subset showed a corresponding M1-skewed macrophage polarisation pattern.

Although the population-level associations between RA and hepatic phenotypes were attenuated after cardiometabolic adjustment, the hospital cohort, transcriptomic analyses, and patient-level experimental data collectively supported a coordinated EGR1-IL-32-macrophage polarisation signature associated with RA-MASLD comorbidity. These observational findings require prospective replication and functional validation.