GYS1 and rheumatoid arthritis: Interestingly, among these genes, only GYS1 gene expression was significantly increased in RA FLSs compared to OA FLSs and HC FLSs, and GYS1 protein expression was also increased in FLSs and ST from RA patients, suggesting that GYS1-mediated glycogen synthesis may result in glycogen accumulation in RA FLSs.