ANGPTL8 and intervertebral disk degenerative disorder: Previous study has demonstrated that pro‐inflammatory cytokines promoted the NP cells degeneration and accelerated the progression of IDD.18, 35 In order to investigate the pathological effect of ANGPTL8 expression in IDD, NP cells were treated with TNF‐α (50 ng/mL) for 0, 6, 12, 24 or 48 hours in vitro.