Functions of the sirtuin deacylase SIRT5 in normal physiology and pathobiology

SIRT5-mediated BCAT1 desuccinylation and stabilization leads to ferroptosis insensitivity and promotes cell proliferation in glioma

Glioma is a highly aggressive brain tumor with limited treatment success due to its resistance to conventional therapies. Sirtuin 5 (SIRT5) has emerged as a promising target for cancer therapy, though it exhibits dual roles in different cancer types. In this study, we investigate the role of SIRT5 in glioma and its corresponding mechanisms. Our findings demonstrate that SIRT5 expression is elevated in glioma cells both in vitro and in vivo. SIRT5 knockdown significantly reduced glioma cell proliferation and enhanced sensitivity to ferroptosis. Proteomic and metabolomic analyses identifies branched-chain amino acid (BCAA) metabolism as a key downstream pathway regulated by SIRT5 through branched-chain aminotransferase 1 (BCAT1). Specifically, SIRT5-mediated desuccinylation of BCAT1 at K39 inhibits its interaction with the E3 ligase CHIP, thereby preventing BCAT1 degradation via the ubiquitin-proteasome system. Moreover, BCAT1 overexpression reverses the proliferation inhibition and ferroptosis sensitivity observed in SIRT5-knockdown cells. Clinically, we reveal a positive correlation between SIRT5 and BCAT1 levels in glioma samples, with higher expression levels predicting more advanced glioma grades and poorer clinical outcomes. Collectively, this study highlights the critical role of SIRT5 in promoting glioma progression via metabolic regulation and ferroptosis insensitivity, offering a potential therapeutic target for glioma treatment.

SIRT5 Regulates Lipid Deposition in Goat Preadipocytes via PI3K-Akt and MAPK Signaling Pathways

Silent Information Regulator 5 (SIRT5) has been established as a crucial regulator of cellular alanylation modification. Furthermore, accumulating evidence suggests that SIRT5 plays a significant regulatory role in key metabolic pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid oxidation, all of which are closely associated with cellular lipid metabolism. Despite these advancements, the specific role of SIRT5 in regulating intramuscular fat (IMF) deposition in goats, as well as the underlying molecular mechanisms, remains largely unexplored. In this study, we cloned the complete coding sequence of the goat SIRT5 gene and, through amino acid sequence alignment, demonstrated its closest phylogenetic relationship with sheep. Additionally, we characterized the higher expression of SIRT5 during the differentiation of goat intramuscular precursor adipocytes. The silencing of SIRT5 by siRNA-mediated knockdown significantly upregulated the expression of lipogenesis-related genes and enhanced lipid deposition in goat intramuscular preadipocytes. Concurrently, SIRT5 deficiency led to the inhibition of cell proliferation and a marked reduction in apoptosis. Interestingly, although overexpression of SIRT5 promoted cell proliferation, it did not significantly alter lipid deposition in goat intramuscular precursor adipocytes. RNA sequencing (RNA-seq) analysis identified a total of 106 differentially expressed genes (DEGs) following SIRT5 silencing in goat preadipocytes, predominantly involved in the Focal adhesion, HIF-1, PI3K-Akt, and MAPK signaling pathways by KEGG pathway enrichment analysis. Notably, we successfully reversed the phenotypic effects observed in SIRT5 knockdown goat precursor adipocytes by inhibiting the PI3K-Akt and MAPK signaling pathways using the AKT inhibitor LY294002 and the p38 MAPK pathway inhibitor PD169316, respectively. In conclusion, our findings demonstrated that SIRT5 may modulate intramuscular fat deposition in goats through PI3k-Akt and MAPK signaling pathways. These results expand the gene regulatory network associated with IMF formation and provide a theoretical foundation for improving meat quality by targeting IMF deposition.

Exploring epigenetic modifications as potential biomarkers and therapeutic targets in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder and the most common motor neuron disease. Whole-genome sequencing has identified many novel ALS-associated genes, but genetics alone cannot fully explain the onset of ALS and an effective treatment is still lacking. Moreover, we need more biomarkers for accurate diagnosis and assessment of disease prognosis. Epigenetics, which includes DNA methylation and hydroxymethylation, histone modifications, chromatin remodeling, and non-coding RNAs, influences gene transcription and expression by affecting chromatin accessibility and transcription factor binding without altering genetic information. These processes play a role in the onset and progression of ALS. Epigenetic targets can serve as potential biomarkers and more importantly, the reversibility of epigenetic changes supports their potential role as versatile therapeutic targets in ALS. This review summarized the alterations in different epigenetic modulations in ALS. Additionally, given the close association between aberrant metabolic profiles characterized by hypoxia and high glycolytic metabolism in ALS and epigenetic changes, we also integrate epigenetics with metabolomics. Finally, we discuss the application of therapies based on epigenetic mechanisms in ALS. Our data integration helps to identify potential diagnostic and prognostic biomarkers and support the development of new effective therapies.

SIRT5 -mediated desuccinylation of UQCRC2 attenuates osteogenic differentiation of aged BM-MSCs through impairing mitochondrial homeostasis

BACKGROUND

The osteogenic differentiation potential of bone marrow mesenchymal stem cells (BM-MSCs) is critical for bone regeneration and repair. In recent years, the role of protein succinylation modification in regulating cellular metabolism has garnered increasing attention. However, its mechanism in osteogenic differentiation remains unclear.

METHODS

Oxygen consumption rate (OCR) and mitochondrial ROS (mtROS) were detected to assess mitochondrial function in BM-MSCs with successive passages. Alizarin red staining and western blot experiments were used to evaluate osteogenic differentiation capacity. Succinylation modification omics and Co-IP detection were conducted to determine SIRT5-mediated desuccinylation of UQCRC2.

RESULTS

Bioinformatics analysis revealed that sirtuin 5 (SIRT5) expression is upregulated with multiple rounds of BM-MSCs' passages, and is associated with biological pathways such as oxidative phosphorylation (OXPHOS), cellular senescence, and inhibition of osteogenic differentiation. Experiments in vitro confirmed the up-regulation of SIRT5 and the suppression of osteogenic differentiation with the increased times of BM-MSCs' passages. Overexpression of SIRT5 enhanced OXPHOS and elevated mtROS levels, but reduced the expression of Runx2 and osteocalcin, and decreased calcified nodules, thereby inhibiting the osteogenic differentiation of BM-MSCs. SIRT5-mediated desuccinylation of ubiquinol-cytochrome C reductase core protein 2 (UQCRC2) at the site of K250 promoted UQCRC2 translocation from cytoplasm to mitochondria, which enhanced the activity of mitochondrial respiratory complex III. It further increased mtROS, accelerated cellular senescence and inhibited the osteogenic differentiation of BM-MSCs.

CONCLUSION

SIRT5 reduces succinylation modification of UQCRC2, promotes mitochondrial respiration and mtROS, and thus reduces the osteogenic differentiation ability of BM-MSCs cells. SIRT5 might be a potential target to prevent the suppression of osteogenic differentiation of of BM-MSCs after multiple rounds passages.

Sirtuins and Resveratrol in Cardiorenal Diseases: A Narrative Review of Mechanisms and Therapeutic Potential

Aging is a very complex process, and it has been linked with Sirtuins. Sirtuin enzymes are a family of deacetylases that are related to caloric restriction and aging by modulating energy metabolism, genomic stability, and stress resistance. Up to now, seven sirtuins have been recognized. This narrative review aimed to analyze the literature produced between January 2005 and March 2025 to evaluate the role of sirtuins in chronic kidney disease and, as heart and kidney diseases are strictly interrelated, to explore their role in heart diseases and cardio-renal cross-talk. A reciprocal relationship between CKD and aging seems to exist since CKD may contribute to premature biological aging of different organ systems. SIRTs are involved in the pathophysiology of renal diseases; their activation can delay the progression of several renal diseases. Notably, an increasing number of studies linked SIRTs with different CVDs. SIRTs affect the production of mitochondrial reactive oxygen species (ROS) by modulating mitochondrial function. The imbalance of SIRT levels may increase the vulnerability to CVDs. SIRTs are involved in the pathophysiological mechanisms of HFpEF (heart failure with preserved ejection fraction) through different signaling pathways. Fibrosis is the linkage mechanism between the heart and kidney in the development of cardio-renal diseases. Current studies on sirtuins, resveratrol, and cardiorenal disease highlight their potential therapeutic benefits in regulating blood pressure, kidney function, lipid profiles, and inflammation, making them a promising area of investigation for improving cardiovascular and renal health outcomes. However, significant gaps remain. The limited availability of highly selective and potent sirtuin modulators hampers their clinical translation, as most existing compounds exhibit poor bioavailability and suboptimal pharmacokinetic properties.

Mitochondrial dynamics at the intersection of macrophage polarization and metabolism

Macrophages are vital sentinels in innate immunity, and their functions cannot be performed without internal metabolic reprogramming. Mitochondrial dynamics, especially mitochondrial fusion and fission, contributes to the maintenance of mitochondrial homeostasis. The link between mitochondrial dynamics and macrophages in the past has focused on the immune function of macrophages. We innovatively summarize and propose a link between mitochondrial dynamics and macrophage metabolism. Among them, fusion-related FAM73b, MTCH2, SLP-2 (Stomatin-like protein 2), and mtSIRT, and fission-related Fis1 and MTP18 may be the link between mitochondrial dynamics and macrophage metabolism association. Furthermore, post-translational modifications (PTMs) of mtSIRT play prominent roles in mitochondrial dynamics-macrophage metabolism connection, such as deacetylates and hypersuccinylation. MicroRNAs such as miR-150, miR-15b, and miR-125b are also possible entry points. The metabolic reprogramming of macrophages through the regulation of mitochondrial dynamics helps improve their adaptability and resistance to adverse environments and provides therapeutic possibilities for various diseases.

Activation and inhibition of sirtuins: From bench to bedside

The sirtuin family comprises seven NAD+-dependent enzymes which catalyze protein lysine deacylation and mono ADP-ribosylation. Sirtuins act as central regulators of genomic stability and gene expression and control key processes, including energetic metabolism, cell cycle, differentiation, apoptosis, and aging. As a result, all sirtuins play critical roles in cellular homeostasis and organism wellness, and their dysregulation has been linked to metabolic, cardiovascular, and neurological diseases. Furthermore, sirtuins have shown dichotomous roles in cancer, acting as context-dependent tumor suppressors or promoters. Given their central role in different cellular processes, sirtuins have attracted increasing research interest aimed at developing both activators and inhibitors. Indeed, sirtuin modulation may have therapeutic effects in many age-related diseases, including diabetes, cardiovascular and neurodegenerative disorders, and cancer. Moreover, isoform selective modulators may increase our knowledge of sirtuin biology and aid to develop better therapies. Through this review, we provide critical insights into sirtuin pharmacology and illustrate their enzymatic activities and biological functions. Furthermore, we outline the most relevant sirtuin modulators in terms of their modes of action, structure-activity relationships, pharmacological effects, and clinical applications.

The curious case of mitochondrial sirtuin in rewiring breast cancer metabolism: Mr Hyde or Dr Jekyll?

Mammalian sirtuins are class III histone deacetylases involved in the regulation of multiple biological processes including senescence, DNA repair, apoptosis, proliferation, caloric restriction, and metabolism. Among the mammalian sirtuins, SIRT3, SIRT4, and SIRT5 are localized in the mitochondria and collectively termed the mitochondrial sirtuins. Mitochondrial sirtuins are NAD+-dependent deacetylases that play a central role in cellular metabolism and function as epigenetic regulators by performing post-translational modification of cellular proteins. Several studies have identified the role of mitochondrial sirtuins in age-related pathologies and the rewiring of cancer metabolism. Mitochondrial sirtuins regulate cellular functions by contributing to post-translational modifications, including deacetylation, ADP-ribosylation, demalonylation, and desuccinylation of diverse cellular proteins to maintain cellular homeostasis. Here, we review and discuss the structure and function of the mitochondrial sirtuins and their role as metabolic regulators in breast cancer. Altered breast cancer metabolism may promote tumor progression and has been an essential target for therapy. Further, we discuss the potential role of targeting mitochondrial sirtuin and its impact on breast cancer progression using sirtuin inhibitors and activators as anticancer agents.

Multiple omics analysis reveals the regulation of SIRT4 on lipid deposition and metabolism during the differentiation of bovine preadipocytes

The differentiation and lipid metabolism of preadipocytes are crucial processes in IMF deposition. Studies have demonstrated that SIRT4 plays essential roles in energy metabolism and redox homeostasis, with its expression being coordinately regulated by multiple transcription factors associated with energy and lipid metabolism. In this study, the findings of multiple omics analysis reveal that SIRT4 significantly up-regulates the expression of genes involved in adipogenesis and enhances the differentiation and lipid deposition of bovine preadipocytes. Furthermore, SIRT4 profoundly influences the expression pattern of metabolites by increasing the abundance of substances involved in lipid synthesis while decreasing those that promote lipid oxidative decomposition. Additionally, SIRT4 broadly up-regulates the expression levels of various lipid classes, including glycerolipids, glycerophospholipids, sphingolipids, and sterol lipids. These findings not only provide a theoretical basis for molecular breeding and genetic improvement in beef cattle, but also offer potential therapeutic approaches for energy homeostasis disorders and obesity.

SIRT5 desuccinylating IDH2 to alleviate oxidative stress in bovine mammary epithelial cells induced by ammonia

Ammonia can cause cells to produce a large amount of reactive oxygen species (ROS), leading to the oxidative stress of cells. As the main intracellular reductant, nicotinamide adenine dinucleotide phosphate (NADPH) plays a crucial role in maintaining reduced glutathione (GSH), helping to remove ROS and protect cells from oxidative damage. Our study demonstrated that SIRT5 desuccinylated isocitrate dehydrogenase 2 (IDH2) to enhance its activity, resulting in increased NADPH production. Furthermore, we observed that SIRT5 overexpression alleviated ammonia-induced high levels of ROS in bovine mammary epithelial cells. This effect was achieved by activating IDH2 through SIRT5, which increased NADPH production and GSH levels, thereby improving the antioxidant capacity to scavenge ROS and reduce the susceptibility of cell to ROS. In conclusion, our findings revealed a SIRT5-dependent mechanism that modulated intracellular NADPH homeostasis to attenuate ammonia-induced oxidative stress by enhancing IDH2 enzymatic activity.

SIRT5-mediated GLS and GDH desuccinylation attenuates the autophagy of bovine mammary epithelial cells induced by ammonia

Sirtuin 5 (SIRT5) in mitochondria possesses a strong capacity for lysine desuccinylation, involving in various biological processes. Our previous research demonstrated that NH3 regulated autophagy dependent on SIRT5 in bovine mammary epithelial cells (bMECs). Interestingly, we discovered that SIRT5 reduced the content of NH3 and glutamate by inhibiting GLS activity in bMECs, the ratio of ADP/ATP also declined. In this study, we identified that SIRT5 interacted with endogenous GLS and GDH through Co-IP assay, but had no effect on endogenous GLS and GDH expression. SIRT5 made the succinylation levels of GLS and GDH significantly declined and resulted in the reduction of GLS and GDH activity. Next, the content of ammonia and glutamate, as well as the related autophagy markers were measured, we found that SIRT5 affected the glutamine metabolism, which attenuated ammonia release in MAC-T cells, accompanying with cellular autophagy decline, reducing the formation of autophagosome. Deletion of SIRT5 gene in MAC-T cells by means of CRISPR-cas9, we found the content of NH3 and glutamate increased, as well as autophagy promoted, which could be alleviated by SIRT5 overexpression. SIRT5 KO also resulted in increase of succinylation of GLS and GDH, as well as autophagy response in bMECs. Furthermore, SIRT5 promoted the maintenance of mitochondria homeostasis. Mechanistically, SIRT5 reduced ammonia release by modulating the succinylation levels and enzymatic activities of GLS and GDH in mitochondria and promoted the maintenance of mitochondria homeostasis, as well as further attenuated ammonia-stimulated autophagy in bovine mammary epithelial cells.

l-Glutamic Acid Alleviates Mastitis in Dairy Cows by Targeting the Sirt5/Nrf2/Prdx1 Signaling Axis and Mitochondrial Function

Mastitis in dairy cows is an inflammatory disease that severely affects the health and lactation functions of dairy cows. Mitochondrial damage is closely related to the inflammatory response. How to effectively alleviate mitochondrial damage is the key to preventing and treating mastitis in dairy cows. In this study, we found elevated levels of inflammatory response and mitochondrial damage accompanied by reduced expression of Sirt5 (Sirtuin5) in cows with mastitis compared with healthy cows. This suggests that Sirt5 plays an important role in mastitis in dairy cows. Subsequently, we further analyzed mammary gland tissue from healthy and mastitis cows by untargeted metabolomics (LC-MS/MS) and screened for the differential metabolite l-glutamic acid (l-Glu). To further validate the effect of l-Glu on mastitis in dairy cows, we conducted a study using MAC-T cells. The results showed that l-Glu was able to ameliorate LPS-induced mitochondrial damage by activating Sirt5 and promoting mitochondrial fusion and the upregulation of mitochondrial membrane potential (MMP) levels. In contrast, l-Glu was unable to protect mitochondrial function after knocking down Sirt5. Furthermore, we found that l-Glu was able to upregulate the expression of nuclear factor E2-related factor (Nrf2) and peroxiredoxin 1 (Prdx1) in LPS-induced MAC-T cells, and promoted the entry of Nrf2 into the nucleus, which was reversed by knocking down Sirt5. Next, we further explored whether l-Glu alleviates mitochondrial damage through the Nrf2/Prdx1 signaling axis by using the Nrf2 inhibitor RA. The results showed that the use of RA promoted LPS-induced mitochondrial damage and blocked the protective effect of l-Glu on mitochondrial function. In conclusion, l-Glu ameliorates mitochondrial damage by targeting Sirt5 to activate the Nrf2/Prdx1 signaling axis and alleviate mastitis in dairy cows. This study provides a new target and theoretical basis for the clinical control of mastitis. l-Glu could be added as a dietary supplement to the diets of dairy cows and maintain mammary gland homeostasis, thereby protecting the health and economic value of dairy cows.

The Antiaging and Antioxidative Effects of a Combination of Resveratrol and High-Intensity Interval Training on the Frontal Lobe in Aged Rats: The Role of SIRTS 4, SIRTS 5, SOD1, and SOD2

Introduction: High-intensity interval training (HIIT) is a form of interval exercise that enhances capacity and benefits well-being. Resveratrol is a naturally occurring polyphenol prevalent in grapes and red wine, demonstrating significant health effects on the body. This study sought to evaluate the synergistic effects of swimming HIIT and resveratrol intake on the expression of SIRTs 4, SIRTs 5, and superoxide dismutases (SOD1 and SOD2) in the frontal lobe of elderly rats. Materials and Methods: Forty-five male Wistar rats, aged 22 months, were categorized into five groups: the control group (CTL), the swimming HIIT group (Ex: Exercise), the swimming HIIT with resveratrol group (R + Ex), the resveratrol group (R), and the solvent control group (vehicle). The R + Ex group engaged in high-intensity interval swimming and ingested resveratrol (10 mg/kg/day via gavage) for 6 weeks. During the initial and final sessions of each week, blood samples from the rats in the Ex and R + Ex groups were collected for lactate analysis. The proteins SIRTs 4 and 5, as well as SODs 1 and 2, were quantified using the western blot approach. Results: Integrating HIIT with resveratrol markedly enhanced the expression of SIRT4, SIRT5, and antioxidant enzymes in the frontal lobe of elderly rats. Conclusion: Resveratrol and HIIT, particularly their synergistic effects, provide antioxidant and antiaging benefits on the frontal lobe of aged rats.

A Pilot Proteomic Analysis of Huntington's Disease by Functional Capacity

Background: The molecular biology of Huntington's Disease (HD) has grown substantially, with pathological considerations extending to genetic modifiers, epigenetic changes, transcriptomics, the proteome, and the metabolome. The metabolome and proteome are especially intriguing in that they most directly reflect the functional state of the cellular environment, which may involve some combination of pathology as well as compensation. Methods: We assessed CSF proteomics from eight participants by their functional severity (TFC range 3-13), with 47 proteins having a minimum r-value of 0.7 and nominal p-values < 0.05. Results: Our exploratory data reveal correlations between progression and several processes including inflammation, ECM homeostasis and NAD+ metabolism. Conclusions: Consistently identified targets that correlate with phenotype or progression may have value, if validated, as enrichment tools in clinical trials and potentially as markers of therapeutic response.

The SIRT5-JIP4 interaction promotes osteoclastogenesis by modulating RANKL-induced signaling transduction

Receptor activator of nuclear factor kappa-B ligand (RANKL) initiates a complex signaling cascade that is crucial for inducing osteoclast differentiation and activation. RANKL-induced signaling has been analyzed in detail, and the involvement of TNF receptor-associated factor 6 (TRAF6), calmodulin-dependent protein kinase (CaMK), NF-κB, mitogen-activated protein kinase (MAPK), activator protein-1 (AP-1), and molecules that contain an immunoreceptor tyrosine-based activation motif (ITAM) has been reported. However, the precise molecular steps that regulate RANKL signaling remain largely unknown. Here, we revealed the indispensable role of a class III histone deacetylase (SIRT5) in the processes of RANKL-induced osteoclast differentiation and activation. SIRT5 expression in osteoclasts was increased during osteoclastogenesis upon stimulation with RANKL. The RANKL-induced signaling activation was suppressed in SIRT5-deficient osteoclasts but enhanced by SIRT5 overexpression. Mice with global or conditional monocytic lineage knockout of SIRT5 had increased bone mass and reduced osteoclast numbers. In the cytoplasm, SIRT5 interacted with the scaffold protein JNK-interacting protein 4 (JIP4) to finely regulate MAPK signaling, which was critical for osteoclast differentiation and activation. Pharmacological inhibition of the catalytic activity of SIRT5 effectively reversed bone loss in ovariectomized mice. Taken together, the results of this study reveal that the SIRT5-JIP4 axis is a novel positive regulator that finely regulates RANKL-induced osteoclast differentiation and suggest that targeting this axis is a therapeutic strategy for preventing osteoporotic bone loss.

Circadian Rhythms and Lung Cancer in the Context of Aging: A Review of Current Evidence

Circadian rhythm is the internal homeostatic physiological clock that regulates the 24-hour sleep/wake cycle. This biological clock helps to adapt to environmental changes such as light, dark, temperature, and behaviors. Aging, on the other hand, is a process of physiological changes that results in a progressive decline in cells, tissues, and other vital systems of the body. Both aging and the circadian clock are highly interlinked phenomena with a bidirectional relationship. The process of aging leads to circadian disruptions while dysfunctional circadian rhythms promote age-related complications. Both processes involve diverse physiological, molecular, and cellular changes such as modifications in the DNA repair mechanisms, mechanisms, ROS generation, apoptosis, and cell proliferation. This review aims to examine the role of aging and circadian rhythms in the context of lung cancer. This will also review the existing literature on the role of circadian disruptions in the process of aging and vice versa. Various molecular pathways and genes such as BMAL1, SIRT1, HLF, and PER1 and their implications in aging, circadian rhythms, and lung cancer will also be discussed.

SIRT5 inhibits glycolysis and nasal type extranodal NK/T cell lymphoma cell proliferation by catalyzing the desuccinylation of glucose-6-phosphate isomerase

BACKGROUND

Extranodal natural killer/T-cell lymphoma, nasal type (ENKTL) is a malignant tumor harboring a poor prognosis and unsatisfactory treatment outcomes. This study was performed to explore the pathogenesis and exact etiology of ENKTL. Methods Bioinformatic analysis was conducted to investigate the expression of SIRT5 and glucose-6-phosphate isomerase (GPI), as well their correlation with ENKTL overall survival. Cell proliferation ability and cell apoptosis were determined by CCK8, soft-agar colony formation and Tunel assays. Pyruvic acid and lactate production, GPI activity and F6P levels were detected to indicate glycolysis process. Succinylation modification in GPI protein was quantified by 4D label-free succinylation modification quantitative proteome. ENKTL mouse model was established by the injection of SNK6 cells.

RESULTS

SIRT5 suppressed the NKTL cell proliferation through the desuccinylation effect, while it was down-regulated in the ENKTL. SIRT5 catalyzed the desuccinylation of glycolytic enzyme GPI in ENKTL cells, which accelerated GPI protein degradation through the autophagy-lysosome system. SIRT5 inhibited glycolysis via mediating the desuccinylation of GPI, thereby suppressing ENKTL cell proliferation. The antitumor role of SIRT5 was also certified in ENKTL mouse model by targeting GPI.

CONCLUSION

SIRT5 inhibits glycolysis via catalyzed the desuccinylation of glycolytic enzyme GPI, thereby repressing ENKTL cells proliferation and tumor growth. As SIRT5 serves as a tumor suppressor in ENKTL, it may be a promising molecular target in therapy strategy.

Sirtuins as Key Regulators in Pancreatic Cancer: Insights into Signaling Mechanisms and Therapeutic Implications

Pancreatic ductal adenocarcinoma (PDAC) stands as one of the most lethal cancers, marked by rapid progression, pronounced chemoresistance, and a complex network of genetic and epigenetic dysregulation. Within this challenging context, sirtuins, NAD+-dependent deacetylases, have emerged as pivotal modulators of key cellular processes that drive pancreatic cancer progression. Each sirtuin contributes uniquely to PDAC pathogenesis. SIRT1 influences apoptosis and chemoresistance through hypoxia, enhancing glycolytic metabolism and HIF-1α signaling, which sustain tumor survival against drugs like gemcitabine. SIRT2, conversely, disrupts cancer cell proliferation by inhibiting eIF5A, while SIRT3 exerts tumor-suppressive effects by regulating mitochondrial ROS and glycolysis. SIRT4 inhibits aerobic glycolysis, and its therapeutic upregulation has shown promise in curbing PDAC progression. Furthermore, SIRT5 modulates glutamine and glutathione metabolism, offering an avenue to disrupt PDAC's metabolic dependencies. SIRT6 and SIRT7, through their roles in angiogenesis, EMT, and metastasis, represent additional targets, with modulators of SIRT6, such as JYQ-42, showing potential to reduce tumor invasiveness. This review aims to provide a comprehensive exploration of the emerging roles of sirtuins, a family of NAD+-dependent enzymes, as critical regulators within the oncogenic landscape of pancreatic cancer. This review meticulously explores the nuanced involvement of sirtuins in pancreatic cancer, elucidating their contributions to tumorigenesis and suppression through mechanisms such as metabolic reprogramming, the maintenance of genomic integrity and epigenetic modulation. Furthermore, it emphasizes the urgent need for the development of targeted therapeutic interventions aimed at precisely modulating sirtuin activity, thereby enhancing therapeutic efficacy and optimizing patient outcomes in the context of pancreatic malignancies.

Succinylation modification-mediated upregulation of Sp1 promotes hepatocellular carcinoma cell proliferation

Hepatocellular carcinoma (HCC) remains one of the most prevalent malignant tumors globally, characterized by high incidence and mortality rates. Despite ongoing research, the underlying molecular mechanisms of HCC development are not yet fully understood. Utilizing bioinformatic analysis, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR), and Western blot assays, we identified that the expression of specificity protein 1 (Sp1) was significantly elevated in HCC cells compared to normal cells. Knockdown of the Sp1 gene led to a marked reduction in the viability and clonogenic potential of HCC cells. Further investigation revealed that the succinylation level of Sp1 was also increased in HCC cells. The upregulation of Sp1 expression was attributed to its succinylation, mediated by KAT2A, with lysine (K)562 identified as the succinylation site. Additionally, KAT2A and Sp1 were found to influence the upregulation of mTOR phosphorylation. Collectively, these findings suggest that KAT2A-promoted succinylation of Sp1 enhances the proliferative capacity of HCC cells by activating the mTOR pathway, providing a theoretical foundation for potential therapeutic strategies against HCC.

NAD+ enhancers as therapeutic agents in the cardiorenal axis

Cardiorenal diseases represent a complex interplay between heart failure and renal dysfunction, being clinically classified as cardiorenal syndromes (CRS). Recently, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism, through deficient NAD+ synthesis and/or elevated consumption, have proved to be decisive in the onset and progress of cardiorenal disease. NAD+ is a pivotal coenzyme in cellular metabolism, being significant in various signaling pathways, such as energy metabolism, DNA damage repair, gene expression, and stress response. Convincing evidence suggests that strategies designed to boost cellular NAD+ levels are a promising therapeutic option to address cardiovascular and renal disorders. Here, we review and discuss the implications of NAD+ metabolism in cardiorenal diseases, focusing on the propitious NAD+ boosting therapeutic strategies, based on the use of NAD+ precursors, poly(ADP-ribose) polymerase inhibitors, sirtuin activators, and other alternative approaches, such as CD38 blockade, nicotinamide phosphoribosyltransferase activation and combined interventions.

Lidocaine inhibits the lung cancer progression through decreasing the HIST1H2BL levels via SIRT5 mediated succinylation

Lung cancer is a malignant tumor originating from the bronchial mucosa or gland of the lung. Recently, lidocaine, a widely used amide local anesthetic, was demonstrated to inhibit many cancer progression. This research was performed to explore the specific mechanism of lidocaine in the lung cancer progression. The human normal lung epithelial cells (BEAS-2B), and NSCLC cell lines (A549 and H1299) were used and treated with lidocaine in this study. The cell biological behaviors were detected by CCK-8, wound healing and transwell assay. Besides, the mRNA and protein levels of related genes were detected by western blot. The results showed that lidocaine treatment significantly decreased the cell viability and migration of the A549 and H1299 cells. Furthermore, the lidocaine treatment significantly decreased the succinylation and protein levels of HIST1H2BL, which was reversed after SIRT5 knockdown. Additionally, HIST1H2BL knockdown decreased the cell viability and migration of the A549 and H1299 cells, while HIST1H2BL overexpression reversed the effects of lidocaine on the cell viability and migration of the A549 and H1299 cells. In conclusion, lidocaine treatment might inhibited the lung cancer progression through decreasing the SIRT5 mediated succinylation of HIST1H2BL.

Sirtuin 5-Mediated Desuccinylation of ALDH2 Alleviates Mitochondrial Oxidative Stress Following Acetaminophen-Induced Acute Liver Injury

Acetaminophen (APAP) overdose is a major cause of drug-induced liver injury. Sirtuins 5 (SIRT5) has been implicated in the development of various liver diseases. However, its involvement in APAP-induced acute liver injury (AILI) remains unclear. The present study aimed to explore the role of SIRT5 in AILI. SIRT5 expression is dramatically downregulated by APAP administration in mouse livers and AML12 hepatocytes. SIRT5 deficiency not only exacerbates liver injury and the inflammatory response, but also worsens mitochondrial oxidative stress. Conversely, the opposite pathological and biochemical changes are observed in mice with SIRT5 overexpression. Mechanistically, quantitative succinylome analysis and site mutation experiments revealed that SIRT5 desuccinylated aldehyde dehydrogenase 2 (ALDH2) at lysine 385 and maintained the enzymatic activity of ALDH2, resulting in the suppression of inflammation and mitochondrial oxidative stress. Furthermore, succinylation of ALDH2 at lysine 385 abolished its protective effect against AILI, and the protective effect of SIRT5 against AILI is dependent on the desuccinylation of ALDH2 at K385. Finally, virtual screening of natural compounds revealed that Puerarin promoted SIRT5 desuccinylase activity and further attenuated AILI. Collectively, the present study showed that the SIRT5-ALDH2 axis plays a critical role in AILI progression and might be a strategy for therapeutic intervention.

Tetrandrine targeting SIRT5 exerts anti-melanoma properties via inducing ROS, ER stress, and blocked autophagy

Tetrandrine (TET), a natural bisbenzyl isoquinoline alkaloid extracted from Stephania tetrandra S. Moore, has diverse pharmacological effects. However, its effects on melanoma remain unclear. Cellular proliferation assays, multi-omics analyses, and xenograft models were used to determine the effect of TET on melanoma. The direct target of TET was identified using biotin-TET pull-down liquid chromatograph-mass spectrometry (LC-MS), cellular thermal shift assays, and isothermal titration calorimetry (ITC) analysis. Our findings revealed that TET treatment induced robust cellular autophagy depending on activating transcription factor 6 (ATF6)-mediated endoplasmic reticulum (ER) stress. Simultaneously, it hindered autophagic flux by inducing cytoskeletal protein depolymerization in melanoma cells. TET treatment resulted in excessive accumulation of reactive oxygen species (ROS) and simultaneously triggered mitophagy. Sirtuin 5 (SIRT5) was ultimately found to be a direct target of TET. Mechanistically, TET led to the degradation of SIRT5 via the ubiquitin (Ub)-26S proteasome system. SIRT5 knockdown induced ROS accumulation, whereas SIRT5 overexpression attenuated the TET-induced ROS accumulation and autophagy. Importantly, TET exhibited anti-cancer effects in xenograft models depending on SIRT5 expression. This study highlights the potential of TET as an antimelanoma agent that targets SIRT5. These findings provide a promising avenue for the use of TET in melanoma treatment and underscore its potential as a therapeutic candidate.

The role of polydatin in inhibiting oxidative stress through SIRT1 activation: A comprehensive review of molecular targets

ETHNOPHARMACOLOGICAL RELEVANCE

Reynoutria japonica Houtt is a medicinal plant renowned for its diverse pharmacological properties, including heat-clearing, toxin-removing, blood circulation promotion, blood stasis removal, diuretic action, and pain relief. The plant is commonly utilized in Traditional Chinese Medicine (TCM), and its major bioactive constituents consist of polydatin (PD) and resveratrol (RES).

AIM OF THE STUDY

To summarize the relevant targets of PD in various oxidative stress-related diseases through the activation of Silence information regulator1 (SIRT1). Furthermore, elucidating the pharmacological effects and signaling mechanisms to establish the basis for PD's secure clinical implementation and expanded range of application.

MATERIALS AND METHODS

Literature published before November 2023 on the structural analysis and pharmacological activities of PD was collected using online databases such as Google Scholar, PubMed, and Web of Science. The keywords were "polydatin", "SIRT1" and "oxidative stress". The inclusion criteria were research articles published in English, including in vivo and in vitro experiments and clinical studies. Non-research articles such as reviews, meta-analyses, and letters were excluded.

RESULTS

PD has been found to have significantly protective and curative effects on diseases associated with oxidative stress by regulating SIRT1-related targets including peroxisome proliferator-activated receptor γ coactivator 1-alpha (PGC-1α), nuclear factor erythroid2-related factor 2 (Nrf2), high mobility group box 1 protein (HMGB1), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), p38/p53, as well as endothelial nitric oxide synthase (eNOs), among others. Strong evidence suggests that PD is an effective natural product for treating diseases related to oxidative stress.

CONCLUSION

PD holds promise as an effective treatment for a wide range of diseases, with SIRT1-mediated oxidative stress as its potential pathway.

The role of novel protein acylations in cancer

Novel protein acylations are a class of protein post-translational modifications, such as lactylation, succinylation, crotonylation, palmitoylation, and β-hydroxybutyrylation. These acylation modifications are common in prokaryotes and eukaryotes and play pivotal roles in various key cellular processes by regulating gene transcription, protein subcellular localization, stability and activity, protein-protein interactions, and protein-DNA interactions. The diversified acylations are closely associated with various human diseases, especially cancer. In this review, we provide an overview of the distinctive characteristics, effects, and regulatory factors of novel protein acylations. We also explore the various mechanisms through which novel protein acylations are involved in the occurrence and progression of cancer. Furthermore, we discuss the development of anti-cancer drugs targeting novel acylations, offering promising avenues for cancer treatment.

SIRT5 exacerbates eosinophilic chronic rhinosinusitis by promoting polarization of M2 macrophage

BACKGROUND

Previous studies implied that local M2 polarization of macrophage promoted mucosal edema and exacerbated TH2 type inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP). However, the specific pathogenic role of M2 macrophages and the intrinsic regulators in the development of CRS remains elusive.

OBJECTIVE

We sought to investigate the regulatory role of SIRT5 in the polarization of M2 macrophages and its potential contribution to the development of CRSwNP.

METHODS

Real-time reverse transcription-quantitative PCR and Western blot analyses were performed to examine the expression levels of SIRT5 and markers of M2 macrophages in sinonasal mucosa samples obtained from both CRS and control groups. Wild-type and Sirt5-knockout mice were used to establish a nasal polyp model with TH2 inflammation and to investigate the effects of SIRT5 in macrophage on disease development. Furthermore, in vitro experiments were conducted to elucidate the regulatory role of SIRT5 in polarization of M2 macrophages.

RESULTS

Clinical investigations showed that SIRT5 was highly expressed and positively correlated with M2 macrophage markers in eosinophilic polyps. The expression of SIRT5 in M2 macrophages was found to contribute to the development of the disease, which was impaired in Sirt5-deficient mice. Mechanistically, SIRT5 was shown to enhance the alternative polarization of macrophages by promoting glutaminolysis.

CONCLUSIONS

SIRT5 plays a crucial role in promoting the development of CRSwNP by supporting alternative polarization of macrophages, thus providing a potential target for CRSwNP interventions.

Role of novel protein acylation modifications in immunity and its related diseases

The cross-regulation of immunity and metabolism is currently a research hotspot in life sciences and immunology. Metabolic immunology plays an important role in cutting-edge fields such as metabolic regulatory mechanisms in immune cell development and function, and metabolic targets and immune-related disease pathways. Protein post-translational modification (PTM) is a key epigenetic mechanism that regulates various biological processes and highlights metabolite functions. Currently, more than 400 PTM types have been identified to affect the functions of several proteins. Among these, metabolic PTMs, particularly various newly identified histone or non-histone acylation modifications, can effectively regulate various functions, processes and diseases of the immune system, as well as immune-related diseases. Thus, drugs aimed at targeted acylation modification can have substantial therapeutic potential in regulating immunity, indicating a new direction for further clinical translational research. This review summarises the characteristics and functions of seven novel lysine acylation modifications, including succinylation, S-palmitoylation, lactylation, crotonylation, 2-hydroxyisobutyrylation, β-hydroxybutyrylation and malonylation, and their association with immunity, thereby providing valuable references for the diagnosis and treatment of immune disorders associated with new acylation modifications.

SIRT1: a novel regulator in colorectal cancer

The class-III histone deacetylase SIRT1 is the most extensively investigated sirtuin deacetylase. It is resistant to the broad deacetylase inhibitor trichostatin A and depends on oxidized nicotinamide adenine nucleotide (NAD+). SIRT1 plays a crucial role in the tumorigenesis of numerous types of cancers, including colorectal cancer (CRC). Accumulating evidence indicates that SIRT1 is a therapeutic target for CRC; however, the function and underlying mechanism of SIRT1 in CRC still need to be elucidated. Herein, we provide a detailed and updated review to illustrate that SIRT1 regulates many processes that go awry in CRC cells, such as apoptosis, autophagy, proliferation, migration, invasion, metastasis, oxidative stress, resistance to chemo-radio therapy, immune evasion, and metabolic reprogramming. Moreover, we closely link our review to the clinical practice of CRC treatment, summarizing the mechanisms and prospects of SIRT1 inhibitors in CRC therapy. SIRT1 inhibitors as monotherapy in CRC or in combination with chemotherapy, radiotherapy, and immune therapies are comprehensively discussed. From epigenetic regulation to its potential therapeutic effect, we hope to offer novel insights and a comprehensive understanding of SIRT1's role in CRC.

Sirtuin 5 (SIRT5) Suppresses Tumor Growth by Regulating Mitochondrial Metabolism and Synaptic Remodeling in Gliomas

Sirtuin 5 (SIRT5) is increasingly recognized as a key regulator of cellular metabolism, which is commonly dysregulated in cancer cells, resulting in enhanced proliferation and tumor progression. To investigate the clinicopathologic implications of SIRT5 dysregulation in glioblastoma, we performed comprehensive analyses of transcriptomic data and functional verifications using in vitro and in vivo glioblastoma models. We found that higher SIRT5 expression levels were associated with a favorable prognosis in glioma patients. Knockdown of SIRT5 significantly enhanced glioblastoma cell growth. Our data suggest its potential role in regulating mitochondrial metabolism in gliomas. Furthermore, SIRT5 is also significantly correlated with synaptic remodeling pathways. Our findings indicate a tumor-suppressive role for SIRT5 that extends beyond regulating cancer metabolism, by which it may function through modulating neuroplasticity. Understanding these cellular interactions provides nuanced insights into the multifaceted role of SIRT5 and the broader therapeutic implications of this for the development of novel treatment strategies.

Sirt1: An Increasingly Interesting Molecule with a Potential Role in Bone Metabolism and Osteoporosis

Osteoporosis (OP) is a common metabolic bone disease characterized by low bone mass, decreased bone mineral density, and degradation of bone tissue microarchitecture. However, our understanding of the mechanisms of bone remodeling and factors affecting bone mass remains incomplete. Sirtuin1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent deacetylase that regulates a variety of cellular metabolisms, including inflammation, tumorigenesis, and bone metabolism. Recent studies have emphasized the important role of SIRT1 in bone homeostasis. This article reviews the role of SIRT1 in bone metabolism and OP and also discusses therapeutic strategies and future research directions for targeting SIRT1.

Mechanism of desuccinylation of G6PD mediated by SIRT7 to promote vitiligo disease progression

BACKGROUND

Sirtuin 7 (SIRT7) is pivotal in diverse diseases progression. Importantly, SIRT7 is associated with melanin production. However, whether SIRT7 regulates vitiligo is unclear. Therefore, we aimed to investigate the effects of SIRT7 on pigmentation and the modification of glucose 6-phosphate dehydrogenase (G6PD).

METHODS

After knockdown SIRT7 and G6PD, pigmentation of melanocytes was evaluated using commercial kits, immunofluorescence, and Western blot analysis. The succinylation of G6PD mediated by SIRT7 was analyzed using co-immunoprecipitation, immunofluorescence, Western blot analysis, and cycloheximide-chase experiment.

RESULTS

We found that SIRT7 was highly expressed in vitiligo skin lesions. Knockdown of SIRT7 increased tyrosinase activity, melanin content, and the levels of α-melanocyte-stimulating hormone, MITF, TYR, TRP1, and TRP2. Additionally, SIRT7 directly interacted with G6PD. Silenced SIRT7 promoted the succinylation of G6PD and enhanced its protein stability. G6PD knockdown reversed the effect of reduced SIRT7 expression on melanin production.

CONCLSUION

Silencing of SIRT7 promotes pigmentation of melanocytes by succinylating G6PD, suggesting that SIRT7-mediated G6PD desuccinylation may promote vitiligo progression.

SIRTUIN 5 ALLEVIATES EXCESSIVE MITOCHONDRIAL FISSION VIA DESUCCINYLATION OF ATPASE INHIBITORY FACTOR 1 IN SEPSIS-INDUCED ACUTE KIDNEY INJURY

ABSTRACT

Sepsis-induced acute kidney injury (SAKI) poses a significant clinical challenge with high morbidity and mortality. Excessive mitochondrial fission has been identified as the central pathogenesis of sepsis-associated organ damage, which is also implicated in the early stages of SAKI. Sirtuin 5 (SIRT5) has emerged as a central regulator of cellular mitochondrial function; however, its role in the regulation of sepsis-induced excessive mitochondrial fission in kidney and the underlying mechanism remains unclear. In this study, SAKI was modeled in mice through cecal ligation and puncture, and in human renal tubular epithelial (HK-2) cells stimulated with lipopolysaccharide (LPS), to mimic the cell SAKI model. Our findings revealed that septic mice with a SIRT5 knockout exhibited shortened survival times and elevated levels of renal injury compared to wild-type mice, suggesting the significant involvement of SIRT5 in SAKI pathophysiology. Additionally, we observed that SIRT5 depletion led to increased renal mitochondrial fission, while the use of a mitochondrial fission inhibitor (Mdivi-1) reversed the detrimental effects caused by SIRT5 depletion, emphasizing the pivotal role of SIRT5 in preventing excessive mitochondrial fission. In vitro experiments demonstrated that the overexpression of SIRT5 effectively mitigated the adverse effects of LPS on HK-2 cells viability and mitochondrial fission. Conversely, downregulation of SIRT5 decreased HK-2 cells viability and exacerbated LPS-induced mitochondrial fission. Mechanistically, the protective function of SIRT5 may be in part, ascribed to its desuccinylating action on ATPase inhibitory factor 1. In conclusion, this study provides novel insights into the underlying mechanisms of SAKI, suggesting the possibility of identifying future drug targets in terms of improved mitochondrial dynamics by SIRT5.

SIRT5-Mediated Desuccinylation of RAB7A Protects Against Cadmium-Induced Alzheimer's Disease-Like Pathology by Restoring Autophagic Flux

Cadmium (Cd) is a neurotoxic contaminant that induces cognitive decline similar to that observed in Alzheimer's disease (AD). Autophagic flux dysfunction is attributed to the pathogenesis of AD, and this study aimed to investigate the effect of autophagy on environmental Cd-induced AD progression and the underlying mechanism. Here, Cd exposure inhibited autophagosome-lysosome fusion and impaired lysosomal function, leading to defects in autophagic clearance and then to APP accumulation and nerve cell death. Proteomic analysis coupled with Ingenuity Pathway Analysis (IPA) identified SIRT5 as an essential molecular target in Cd-impaired autophagic flux. Mechanistically, Cd exposure hampered the expression of SIRT5, thus increasing the succinylation of RAB7A at lysine 31 and inhibiting RAB7A activity, which contributed to autophagic flux blockade. Importantly, SIRT5 overexpression led to the restoration of autophagic flux blockade, the alleviation of Aβ deposition and memory deficits, and the desuccinylation of RAB7A in Cd-exposed FAD4T mice. Additionally, SIRT5 levels decrease mainly in neurons but not in other cell clusters in the brains of AD patients according to single-nucleus RNA sequencing data from the public dataset GSE188545. This study reveals that SIRT5-catalysed RAB7A desuccinylation is an essential adaptive mechanism for the amelioration of Cd-induced autophagic flux blockade and AD-like pathogenesis.

Sirtuin 5 alleviates apoptosis and autophagy stimulated by ammonium chloride in bovine mammary epithelial cells

Ammonia (NH3) is an irritating and harmful gas that affects cell apoptosis and autophagy. Sirtuin 5 (SIRT5) has multiple enzymatic activities and regulates NH3-induced autophagy in tumor cells. In order to determine whether SIRT5 regulates NH3-induced bovine mammary epithelial cell apoptosis and autophagy, cells with SIRT5 overexpression or knockdown were generated and in addition, bovine mammary epithelial cells were treated with SIRT5 inhibitors. The results showed that SIRT5 overexpression reduced the content of NH3 and glutamate in cells by inhibiting glutaminase activity in glutamine metabolism, and reduced the ratio of ADP/ATP. The results in the SIRT5 knockdown and inhibitor groups were comparable, including increased content of NH3 and glutamate in cells by activating glutaminase activity, and an elevated ratio of ADP/ATP. It was further confirmed that SIRT5 inhibited the apoptosis and autophagy of bovine mammary epithelial cells through reverse transcription-quantitative PCR, western blot, flow cytometry with Annexin V FITC/PI staining and transmission electron microscopy. In addition, it was also found that the addition of LY294002 or Rapamycin inhibited the PI3K/Akt or mTOR kinase signal, decreasing the apoptosis and autophagy activities of bovine mammary epithelial cells induced by SIRT5-inhibited NH3. In summary, the PI3K/Akt/mTOR signal involved in NH3-induced cell autophagy and apoptosis relies on the regulation of SIRT5. This study provides a new theory for the use of NH3 to regulate bovine mammary epithelial cell apoptosis and autophagy, and provides guidance for improving the health and production performance of dairy cows.

Human SIRT5 variants with reduced stability and activity do not cause neuropathology in mice

SIRT5 is a sirtuin deacylase that removes negatively charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal conditions, the phenotypes of SIRT5 deficiency are quite subtle. Here, we identify two homozygous SIRT5 variants in patients suspected to have mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generated a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology, or other gross phenotypes. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, but are likely not by themselves the primary pathogenic cause of the neuropathology observed in the patients.

The dual role of sirtuins in cancer: biological functions and implications

Sirtuins are pivotal in orchestrating numerous cellular pathways, critically influencing cell metabolism, DNA repair, aging processes, and oxidative stress. In recent years, the involvement of sirtuins in tumor biology has garnered substantial attention, with a growing body of evidence underscoring their regulatory roles in various aberrant cellular processes within tumor environments. This article delves into the sirtuin family and its biological functions, shedding light on their dual roles-either as promoters or inhibitors-in various cancers including oral, breast, hepatocellular, lung, and gastric cancers. It further explores potential anti-tumor agents targeting sirtuins, unraveling the complex interplay between sirtuins, miRNAs, and chemotherapeutic drugs. The dual roles of sirtuins in cancer biology reflect the complexity of targeting these enzymes but also highlight the immense therapeutic potential. These advancements hold significant promise for enhancing clinical outcomes, marking a pivotal step forward in the ongoing battle against cancer.

Mitochondrial sirtuin 3 and role of natural compounds: the effect of post-translational modifications on cellular metabolism

Sirtuins (SIRTs) are a family of proteins with enzymatic activity. In particular, they are a family of class III NAD+-dependent histone deacetylases and ADP-ribosyltransferases. NAD+-dependent deac(et)ylase activities catalyzed by sirtuin include ac(et)ylation, propionylation, butyrylation, crotonylation, manylation, and succinylation. Specifically, human SIRT3 is a 399 amino acid protein with two functional domains: a large Rossmann folding motif and NAD+ binding, and a small complex helix and zinc-binding motif. SIRT3 is widely expressed in mitochondria-rich tissues and is involved in maintaining mitochondrial integrity, homeostasis, and function. Moreover, SIRT3 regulates related diseases, such as aging, hepatic, kidney, neurodegenerative and cardiovascular disease, metabolic diseases, and cancer development. In particular, one of the most significant and damaging post-translational modifications is irreversible protein oxidation, i.e. carbonylation. This process is induced explicitly by increased ROS production due to mitochondrial dysfunction. SIRT3 is carbonylated by 4-hydroxynonenal at the level of Cys280. The carbonylation induces conformational changes in the active site, resulting in allosteric inhibition of SIRT3 activity and loss of the ability to deacetylate and regulate antioxidant enzyme activity. Phytochemicals and, in particular, polyphenols, thanks to their strong antioxidant activity, are natural compounds with a positive regulatory action on SIRT3 in various pathologies. Indeed, the enzymatic SIRT3 activity is modulated, for example, by different natural polyphenol classes, including resveratrol and the bergamot polyphenolic fraction. Thus, this review aims to elucidate the mechanisms by which phytochemicals can interact with SIRT3, resulting in post-translational modifications that regulate cellular metabolism.

Lysine succinylation analysis reveals the effect of Sirt5 on synovial fibroblasts in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is an autoimmune disease with complex etiology, and its pathological mechanism remains unclear. Our aim was to explore the effect of protein succinylation on RA by silencing Sirt5, sequencing succinylated proteins, and analyzing the sequencing results to identify potential biomarkers. We wanted to gain a clearer understanding of RA pathogenesis, quantitative assessment of succinylated proteins in Fibroblast-like synoviocytes (FLS) from RA patients using liquid chromatography- tandem mass spectrometry and enrichment analysis investigated using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). A total of 679 proteins and 2,471 lysine succinylation sites were found in RA patients, and 436 differentially expressed proteins and 1,548 differentially expressed succinylation sites were identified. Among them, 48 succinylation sites were upregulated in 38 proteins and 144 succinylation sites were downregulated in 82 proteins. Bioinformatics showed that succinylated proteins were significantly enriched in amino and fatty acid metabolisms. Results indicated that Sirt5 can affect various biological processes involved in RA FLSs, and succinylation caused by silencing Sirt5 plays a major role in RA progression. This study provides further understanding of RA pathogenesis and may facilitate searching for potential RA biomarkers.

Leptin attenuates the osteogenic induction potential of BMP9 by increasing β-catenin malonylation modification via Sirt5 down-regulation

BMP9 has demonstrated significant osteogenic potential. In this study, we investigated the effect of Leptin on BMP9-induced osteogenic differentiation. Firstly, we found Leptin was decreased during BMP9-induced osteogenic differentiation and serum Leptin concentrations were increased in the ovariectomized (OVX) rats. Both in vitro and in vivo, exogenous expression of Leptin inhibited the process of osteogenic differentiation, whereas silencing Leptin enhanced. Exogenous Leptin could increase the malonylation of β-catenin. However, BMP9 could increase the level of Sirt5 and subsequently decrease the malonylation of β-catenin; the BMP9-induced osteogenic differentiation was inhibited by silencing Sirt5. These data suggested that Leptin can inhibit the BMP9-induced osteogenic differentiation, which may be mediated through reducing the activity of Wnt/β-catenin signalling via down-regulating Sirt5 to increase the malonylation level of β-catenin partly.

AAV-mediated upregulation of VDAC1 rescues the mitochondrial respiration and sirtuins expression in a SOD1 mouse model of inherited ALS

Mitochondrial dysfunction represents one of the most common molecular hallmarks of both sporadic and familial forms of amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder caused by the selective degeneration and death of motor neurons. The accumulation of misfolded proteins on and within mitochondria, as observed for SOD1 G93A mutant, correlates with a drastic reduction of mitochondrial respiration and the inhibition of metabolites exchanges, including ADP/ATP and NAD+/NADH, across the Voltage-Dependent Anion-selective Channel 1 (VDAC1), the most abundant channel protein of the outer mitochondrial membrane. Here, we show that the AAV-mediated upregulation of VDAC1 in the spinal cord of transgenic mice expressing SOD1 G93A completely rescues the mitochondrial respiratory profile. This correlates with the increased activity and levels of key regulators of mitochondrial functions and maintenance, namely the respiratory chain Complex I and the sirtuins (Sirt), especially Sirt3. Furthermore, the selective increase of these mitochondrial proteins is associated with an increase in Tom20 levels, the receptor subunit of the TOM complex. Overall, our results indicate that the overexpression of VDAC1 has beneficial effects on ALS-affected tissue by stabilizing the Complex I-Sirt3 axis.

Succinylation modification: a potential therapeutic target in stroke

Stroke is a leading cause of mortality and disability worldwide. Ischemic cell death triggered by the compromised supply of blood oxygen and glucose is one of the major pathophysiology of stroke-induced brain injury. Impaired mitochondrial energy metabolism is observed minutes after stroke and is closely associated with the progression of neuropathology. Recently, a new type of post-translational modification, known as lysine succinylation, has been recognized to play a significant role in mitochondrial energy metabolism after ischemia. However, the role of succinylation modification in cell metabolism after stroke and its regulation are not well understood. We aimed to review the effects of succinylation on energy metabolism, reactive oxygen species generation, and neuroinflammation, as well as Sirtuin 5 mediated desuccinylation after stroke. We also highlight the potential of targeting succinylation/desuccinylation as a promising strategy for the treatment of stroke. The succinylation level is dynamically regulated by the nonenzymatic or enzymatic transfer of a succinyl group to a protein on lysine residues and the removal of succinyl catalyzed by desuccinylases. Mounting evidence has suggested that succinylation can regulate the metabolic pathway through modulating the activity or stability of metabolic enzymes. Sirtuins, especially Sirtuin 5, are characterized for their desuccinylation activity and have been recognized as a critical regulator of metabolism through desuccinylating numerous metabolic enzymes. Imbalance between succinylation and desuccinylation has been implicated in the pathophysiology of stroke. Pharmacological agents that enhance the activity of Sirtuin 5 have been employed to promote desuccinylation and improve mitochondrial metabolism, and neuroprotective effects of these agents have been observed in experimental stroke studies. However, their therapeutic efficacy in stroke patients should be validated.

Restoration of epigenetic impairment in the skeletal muscle and chronic inflammation resolution as a therapeutic approach in sarcopenia

Sarcopenia is an age-associated loss of skeletal muscle mass, strength, and function, accompanied by severe adverse health outcomes, such as falls and fractures, functional decline, high health costs, and mortality. Hence, its prevention and treatment have become increasingly urgent. However, despite the wide prevalence and extensive research on sarcopenia, no FDA-approved disease-modifying drugs exist. This is probably due to a poor understanding of the mechanisms underlying its pathophysiology. Recent evidence demonstrate that sarcopenia development is characterized by two key elements: (i) epigenetic dysregulation of multiple molecular pathways associated with sarcopenia pathogenesis, such as protein remodeling, insulin resistance, mitochondria impairments, and (ii) the creation of a systemic, chronic, low-grade inflammation (SCLGI). In this review, we focus on the epigenetic regulators that have been implicated in skeletal muscle deterioration, their individual roles, and possible crosstalk. We also discuss epidrugs, which are the pharmaceuticals with the potential to restore the epigenetic mechanisms deregulated in sarcopenia. In addition, we discuss the mechanisms underlying failed SCLGI resolution in sarcopenia and the potential application of pro-resolving molecules, comprising specialized pro-resolving mediators (SPMs) and their stable mimetics and receptor agonists. These compounds, as well as epidrugs, reveal beneficial effects in preclinical studies related to sarcopenia. Based on these encouraging observations, we propose the combination of epidrugs with SCLI-resolving agents as a new therapeutic approach for sarcopenia that can effectively attenuate of its manifestations.

Set7/9 aggravates ischemic brain injury via enhancing glutamine metabolism in a blocking Sirt5 manner

The aberrant expression of methyltransferase Set7/9 plays a role in various diseases. However, the contribution of Set7/9 in ischemic stroke remains unclear. Here, we show ischemic injury results in a rapid elevation of Set7/9, which is accompanied by the downregulation of Sirt5, a deacetylase reported to protect against injury. Proteomic analysis identifies the decrease of chromobox homolog 1 (Cbx1) in knockdown Set7/9 neurons. Mechanistically, Set7/9 promotes the binding of Cbx1 to H3K9me2/3 and forms a transcription repressor complex at the Sirt5 promoter, ultimately repressing Sirt5 transcription. Thus, the deacetylation of Sirt5 substrate, glutaminase, which catalyzes the hydrolysis of glutamine to glutamate and ammonia, is decreased, promoting glutaminase expression and triggering excitotoxicity. Blocking Set7/9 eliminates H3K9me2/3 from the Sirt5 promoter and normalizes Sirt5 expression and Set7/9 knockout efficiently ameliorates brain ischemic injury by reducing the accumulation of ammonia and glutamate in a Sirt5-dependent manner. Collectively, the Set7/9-Sirt5 axis may be a promising epigenetic therapeutic target.

SIRT5 promote malignant advancement of chordoma by regulating the desuccinylation of c-myc

Chordoma is a relatively rare and locally aggressive malignant tumor. Sirtuin (SIRT)5 plays pivotal roles in various tumors, but the role of SIRT5 in chordoma has not been found. This study was performed to investigate the regulatory effects of SIRT5 on cell proliferation, migration, and invasion and the underlying mechanism in chordoma. A xenograft tumor mouse model was established to assess tumor growth. Reverse transcription-quantitative polymerase chain reaction was used to analyze the mRNA levels of SIRT5 and c-myc. The effects of SIRT5 and c-myc on cell proliferation, migration, and invasion of chordoma cells were detected by cell counting kit-8, colony formation, and Transwell assays. The interaction between SIRT5 and c-myc was evaluated by co-immunoprecipitation (IP) assay. The succinylation of c-myc was analyzed by IP and Western blot. The results showed that SIRT5 expression was upregulated in chordoma tissues and cells. SIRT5 interacted with c-myc to inhibit the succinylation of c-myc at K369 site in human embryonic kidney (HEK)-293T cells. Silencing of SIRT5 suppressed the cell proliferation, migration, and invasion of chordoma cells, while the results were reversed after c-myc overexpression. Moreover, silencing SIRT5 suppressed tumor growth in mice. These findings suggested that SIRT5 promoted the malignant advancement of chordoma by regulating the desuccinylation of c-myc.

Kuntai capsule attenuates premature ovarian insufficiency by activating the FOXO3/SIRT5 signaling pathway in mice: A comprehensive study using UHPLC-LTQ-Orbitrap and integrated pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Classical prescriptions are not only a primary method of clinical treatment in traditional Chinese medicine (TCM) but also represent breakthroughs in the inheritance and development of this field. Kuntai capsule (KTC), a formulation based on a classical prescription, comprises six TCMs: Rehmanniae Radix Praeparata, Coptidis Rhizoma, Paeoniae Radix Alba, Scutellariae Radix, Asini Corii Colla, and Poria. This formulation possesses various beneficial effects, such as nourishing yin and blood, clearing heat and purging fire, and calming the nerves and relieving annoyance. The investigation of the efficacy and mechanism of KTC in regulating anti-aging factors in the treatment of premature ovarian insufficiency (POI) is not only a prominent topic in classical prescription research but also a crucial issue in the treatment of female reproductive aging using TCM.

AIM OF THE STUDY

To evaluate the therapeutic effect of KTC on POI and its underlying mechanism.

MATERIALS AND METHODS

Healthy and specific pathogen-free (SPF) female Kunming mice aged 6-8 weeks were selected. After acclimatization, the mice were randomly divided into a control, model, and high, middle, and low dose groups of KTC (1.6, 0.8, and 0.4 mg/kg, respectively). Except for the control group, the animals in the other groups were administered a single intraperitoneal injection of 120 mg/kg cyclophosphamide and 30 mg/kg Busulfan to induce the model of POI. After modeling, the mice were treated with the corresponding drugs for 7 days. Serum and ovarian tissues were collected, and the levels of serum follicle-stimulating hormone (FSH), estradiol (E2), and superoxide dismutase 2 (SOD2) were determined using enzyme-linked immunosorbent assay (ELISA). The chemical composition of KTC was characterized and analyzed using ultra-high-pressure liquid chromatography-linear ion trap-Orbitrap tandem mass spectrometry. A "drug-component-target-pathway-disease" network was constructed using network pharmacology research methods to identify the key active components of KTC in treating POI and to elucidate its potential mechanism. The protein expression of the FOXO3/SIRT5 pathway was detected by western blotting.

RESULTS

Compared to the model group, the high-dose group of KTC showed a significant increase in ovarian index, significant increase in levels of E2 and SOD2, and a significant decrease in FSH levels. Through systematic analysis of the chemical constituents of KTC, 69 compounds were identified, including 7 organic acids, 14 alkaloids, 28 flavonoids, 15 terpenoids, 2 lignans, 2 phenylpropanoids, and 1 sugar. Based on network pharmacology research methods, it was determined that KTC exerts its therapeutic effect on POI through multiple components (paeoniflorin and malic acid), multiple targets (FOXO3 and SIRT5), and multiple pathways (prolactin signaling pathway, longevity regulating pathway, and metabolic pathways). The accuracy of the network pharmacology prediction was further validated by detecting the protein expression of SIRT5 and FOXO3a, which showed a significant increase in the middle and high-dose groups of KTC compared to the model group.

CONCLUSIONS

KTC may effectively treat POI through a multi-component, multi-target, multi-pathway approach, providing an experimental basis for using KTC based on classical prescriptions in the treatment of POI.

Sirtuin 5 regulates acute myeloid leukemia cell viability and apoptosis by succinylation modification of glycine decarboxylase

Acute myeloid leukemia (AML) is a blood system malignancy where sirtuin 5 (SIRT5) is abnormally expressed in AML cell lines. This study aimed to investigate the SIRT5 effects on the viability and apoptosis of AML cell lines. The mRNA and protein expression levels of succinylation regulatory enzyme in clinical samples and AML cell lines were detected by real-time quantitative polymerase chain reaction and western blotting while cell viability was measured using cell counting kit-8 assay. The apoptosis rate was assessed with flow cytometry. The interaction between SIRT5 and glycine decarboxylase (GLDC) was determined by co-immunoprecipitation and immunofluorescence staining techniques. Results indicated higher mRNA and protein expression levels of SIRT5 in clinical AML samples of AML than in normal subjects. Similarly, cell viability was inhibited, and apoptosis was promoted by downregulating SIRT5, in addition to inhibition of SIRT5-mediated GLDC succinylation. Moreover, rescue experiment results showed that GLDC reversed the effects of SIRT5 knockdown on cell viability and apoptosis. These results, in combination with SIRT5 and GLDC interactions, suggested that SIRT5 was involved in mediating AML development through GLDC succinylation. SIRT5 inhibits GLDC succinylation to promote viability and inhibit apoptosis of AML cells, suggesting that SIRT5 encourages the development of AML.

Morphine induces HADHA succinylation, while HADHA desuccinylation alleviates morphine tolerance by influencing autophagy

Morphine tolerance is an important factor in unsatisfactory analgesia. HADHA is a crucial enzyme in fatty acid β-oxidation. In this study, we investigated the potential significance of HADHA in a mechanism that might cause morphine tolerance related to functional changes in energy metabolism and further explored the effect of HADHA desuccinylation on morphine tolerance. Rats received daily intrathecal injections of 10 µg of morphine for a duration of 7 consecutive days, and pain thresholds were measured using the mechanical withdrawal threshold (MWT) and thermal tail flick latency (TFL) tests. µ-Opioid receptor (MOR), LC3-I/II, and P62 expression and HADHA succinylation were assessed. HADHA succinylation was analyzed by liquid chromatography-tandem mass spectrometry (LC‒MS/MS) and parallel reaction monitoring (PRM). Morphine influenced the LC3II/LC3I ratio and P62 expression level, which are crucial indicators of autophagy, and stimulated HADHA succinylation. Additionally, HADHA was selectively bound by the desuccinylase SIRT5, and SIRT5 overexpression decreased HADHA succinylation, reduced P62 expression, and alleviated morphine tolerance.

The (patho)physiological roles of the individual deacylase activities of a sirtuin

Since the discovery of the sirtuin family founding member (i.e., the yeast silent information regulator 2 (sir2) protein) in 2000, more and more sirtuin proteins have been identified and are currently known to be present in organisms from all the three kingdoms of life (i.e., bacteria, archaea, and eukarya). Seven sirtuin proteins have been identified in mammals including humans, that is, SIRT1/2/3/4/5/6/7. Sirtuin proteins are a class of enzymes with primary catalytic activity being the β-nicotinamide adenine dinucleotide (β-NAD+ or NAD+)-dependent deacylation from the Nε-acyl-lysine residues on cellular proteins. Many sirtuins (e.g., human SIRT1/2/3/4/5/6/7) have been found to each possess multiple individual deacylase activities acting on Nε-acyl-lysine substrates with different acyl groups ranging from the simple formyl and acetyl to the more complex groups like succinyl and myristoyl; however, our current knowledge on the (patho)physiological roles of these individual deacylase activities is still limited, which could be due to the currently still thin research toolbox for investigation (i.e., the deacylase-selective sirtuin mutant and inhibitor/activator). In this article, an updated account on the subject matter will be presented with biochemical and medicinal chemistry perspectives.

Cardiovascular aging: spotlight on mitochondria

Mitochondria are cellular organelles critical for ATP production and are particularly relevant to cardiovascular diseases including heart failure, atherosclerosis, ischemia-reperfusion injury, and cardiomyopathies. With advancing age, even in the absence of clinical disease, mitochondrial homeostasis becomes disrupted (e.g., redox balance, mitochondrial DNA damage, oxidative metabolism, and mitochondrial quality control). Mitochondrial dysregulation leads to the accumulation of damaged and dysfunctional mitochondria, producing excessive reactive oxygen species and perpetuating mitochondrial dysfunction. In addition, mitochondrial DNA, cardiolipin, and N-formyl peptides are potent activators of cell-intrinsic and -extrinsic inflammatory pathways. These age-related mitochondrial changes contribute to the development of cardiovascular diseases. This review covers the impact of aging on mitochondria and links these mechanisms to therapeutic implications for age-associated cardiovascular diseases.

Succinate as a signaling molecule in the mediation of liver diseases

Succinate, one of the intermediates of the tricarboxylic acid (TCA) cycle, plays an essential role in the metabolism of mitochondria and the production of energy, and is considered as a signaling molecule in metabolism as well as in initiation and progression of hepatic diseases. Of note, succinate activates a downstream signaling pathway through GPR91, and elicits a variety of intracellular responses, such as succinylation, production of reactive oxygen species (ROS), stabilization of hypoxia-inducible factor-1α (HIF-1α), and significant impact in cellular metabolism because of the pivotal role in the TCA cycle. Therefore, it is intriguing to deeply elucidate signaling mechanisms of succinate in hepatic fibrosis, metabolic reprogramming in inflammatory or immune responses, as well as carcinogenesis. This manuscript intends to review current understanding of succinate in mediating metabolism, inflammatory and immunologic reactions in liver diseases in order to establish molecular basis for the development of therapeutic strategies.