SIRT3 is a mitochondrial NAD-dependent protein deacetylase that regulates cellular energy metabolism by deacetylating key metabolic enzymes including ACSS1, IDH, GDH, SOD2, and ATP synthase subunits. Beyond acetylation, SIRT3 acts as a deacylase, catalyzing delactylation of proteins such as cyclin E2 and histone H4. In response to metabolic stress, SIRT3 deacetylates transcription factor FOXO3 to promote mitochondrial DNA transcription and activates the PRKAA1/AMPK signaling cascade to suppress lipogenesis. SIRT3 also regulates ceramide metabolism and hepatic lipogenesis through deacetylation of ceramide synthases. Recent studies reveal additional roles in maintaining mitochondrial dynamics—SIRT3 deacetylates dynamin-related protein 1 to prevent excessive mitochondrial fission 1—and in preserving cellular homeostasis; SIRT3 depletion leads to heterochromatin disorganization and accelerated senescence in mesenchymal stem cells 2. Clinically, SIRT3 dysfunction associates with multiple diseases: low SIRT3 expression in hepatocellular carcinoma promotes lactylated cyclin E2-driven growth, which SIRT3 activation by honokiol reverses 3; SIRT3 agonists including resveratrol reduce ferroptosis and mitigate intestinal ischemia-reperfusion injury 4; and SIRT3 activation improves outcomes in osteoarthritis, Parkinson disease, and diabetes-associated periodontitis. These findings position SIRT3 as a therapeutic target across metabolic, neurological, and inflammatory diseases.