Further studies found that curcumin protects against IDD progression by decreasing levels of IL-1β, IL-6, iNOS, COX-2, TGF-β1/2, and MMP-9, while promoting the expression of brain-derived neurotrophic factor (BDNF) (Hu et al., 2017). Here, BDNF is linked to intervertebral disk degenerative disorder.