FNDC5 and intervertebral disk degenerative disorder: Mechanistically, FNDC5/irisin activated autophagy through the AMPK/mTOR signaling pathways to inhibit CS (e.g., increased expression of p16INK4a and SA-β-gal positive cells) and apoptosis (e.g., increased cleaved-caspase3 and TUNEL-positive cells) in NP cells and ameliorated senescence and IDD in a rat model [149].