Fig. 2

The role of the SIRT family in mediating mitochondrial quality control in chondrocytes. SIRT1 can deacetylate PGC-1α, and then coactivate the transcription of NRF-1 or NRF-2, enhancing TFAM expression, which this process promotes mitochondrial biogenesis. SIRT3 could deacetylate OPA1 to promote mitochondrial dynamics, deacetylate Parkin to contribute to mitophagy, and elevate the level of GSH to reduce ROS to maintain mitochondrial homeostasis in chondrocytes. Abbreviations: SIRT, sirtuins; SIRT1, sirtuin 1; SIRT3, sirtuin 3; SIRT6, sirtuin 6; p-AMPK, phospho-adenosine monophosphate-activated protein kinase; PGC-1α, peroxisome proliferator-activated receptor Coactivator-1α; NRF-1, nuclear respiratory factor 1; NRF-2, nuclear respiratory factor 2; TFAM, mitochondrial transcription factor A; NAD⁺, nicotinamide adenine dinucleotide; OPA1, optic atrophy-1; MFN1, mitofusin-1; MFN2, mitofusin-2; DRP1, dynamin-related protein 1; PINK1:, PTEN-induced putative kinase-1; GSH, glutathione; ROS, reactive oxygen species