PKM and rheumatoid arthritis: Metabolomic studies have indicated that the abnormal activation of glycolysis in FLS is an important mechanism for the early onset of RA, which includes increased glucose consumption and lactate export and increased expression of glucose transporter 1 (GLUT1), hexokinase 2 (HK2), and pyruvate kinase M2 (PKM2) (Masoumi et al.