HIF-1α acts as a key regulator during inflammation, increasing pro-inflammatory cytokines (e.g., TNF-α, IL-1β, IL-6, and IL-8), matrix metalloproteinases (e.g., MMP-1, MMP-3, and MMP-9) (Figure 3), and pathways of glucose metabolism in rheumatoid arthritis (RA) [46]. Here, MMP9 is linked to rheumatoid arthritis.