GLS and rheumatoid arthritis: Our finding that PDGF or IL-17 augmented the GLS1 expression in RA-FLS at a mRNA level further supported the notion that glutaminolysis is important in RA-FLS metabolism, although we did not confirm the upregulation of GLS1 at the protein level nor the change in the intracellular glutamine and glutamate levels after IL-17 or PDGF stimulation.