MTOR and rheumatoid arthritis: IL-34 may metabolically reprogram macrophages toward a hyper-glycolytic M1-like phenotype upregulating glucose transporter 1 (GLUT1), mammalian target of rapamycin (mTOR), and hypoxia-induced factor 1α (HIF-1α) in the RA synovium (11, 43); however, we need further clarification on whether this is a general mechanism of IL-34, applicable to any physiological or pathological condition.