SIRT4

SIRT4 is a mitochondrial member of the sirtuin family that functions as an NAD⁺-dependent metabolic regulator and is distinguished by its prominent ADP-ribosyltransferase activity toward glutamate dehydrogenase (GDH)^[1][2]. Mechanistically, SIRT4 represses mitochondrial glutamine and glutamate metabolism through ADP-ribosylation-mediated inhibition of GDH, thereby reducing amino acid-stimulated insulin secretion and modulating cellular energy homeostasis^[1][2][3]. Beyond GDH regulation, SIRT4 participates in broader metabolic control, including the regulation of fatty acid oxidation, branched-chain amino acid catabolism, and mitochondrial metabolic adaptation during nutrient stress^[4][5][6]. These functions position SIRT4 as an important regulator of mitochondrial metabolism and endocrine signaling in pancreatic β cells and other metabolically active tissues^[1][4]. In disease contexts, reduced SIRT4 activity or expression has been associated with enhanced glutamine utilization and tumor progression, whereas restoration of SIRT4 suppresses proliferation and promotes tumor-suppressive metabolic programs in multiple experimental cancer models^[7][8][9]. Compared with related mitochondrial isoforms such as SIRT3 and SIRT5, which primarily function through deacylation-dependent activation or remodeling of metabolic enzymes, SIRT4 is notable for suppressing metabolic flux through ADP-ribosylation-mediated inhibition of key mitochondrial targets^[1][10]. For experimental applications, selective SIRT4 inhibitors have recently been reported, providing emerging tools for mechanistic studies of mitochondrial metabolism, insulin secretion, and cancer-associated metabolic reprogramming^[11].