INSIG1 and rheumatoid arthritis: In addition, functional enrichment analyses implied that HMGCR was involved in the regulation of extracellular signal-regulated kinases 1/2 (ERK1/2) cascade, ageing, and oxidation-reduction processes, and PPI network analysis revealed that HMGCR was predominantly interlinked with Janus kinase 3 (JAK3) [already known drug targets for ADs] and insulin-inducible gene 1 (INSIG1) [key regulatory factor of lipid metabolism], suggesting that HMGCR might serve as a promising therapeutic target for RA.