SIRT3 deacetylates and increases pyruvate dehydrogenase activity in cancer cells

Cellular and molecular biology of posttranslational modifications in cardiovascular disease

Cardiovascular disease (CVD) has now become the leading cause of death worldwide, and its high morbidity and mortality rates pose a great threat to society. Although numerous studies have reported the pathophysiology of CVD, the exact pathogenesis of all types of CVD is not fully understood. Therefore, much more research is still needed to explore the pathogenesis of CVD. With the development of proteomics, many studies have successfully identified the role of posttranslational modifications in the pathogenesis of CVD, including key processes such as apoptosis, cell metabolism, and oxidative stress. In this review, we summarize the progress in the understanding of posttranslational modifications in cardiovascular diseases, including novel protein posttranslational modifications such as succinylation and nitrosylation. Furthermore, we summarize the currently identified histone deacetylase (HDAC) inhibitors used to treat CVD, providing new perspectives on CVD treatment modalities. We critically analyze the roles of posttranslational modifications in the pathogenesis of CVD-related diseases and explore future research directions related to posttranslational modifications in cardiovascular diseases.

Post-translational modifications of pyruvate dehydrogenase complex in cardiovascular disease

Pyruvate dehydrogenase complex (PDC) is a crucial enzyme that connects glycolysis and the tricarboxylic acid (TCA) cycle pathway. It plays an essential role in regulating glucose metabolism for energy production by catalyzing the oxidative decarboxylation of pyruvate to acetyl coenzyme A. Importantly, the activity of PDC is regulated through post-translational modifications (PTMs), phosphorylation, acetylation, and O-GlcNAcylation. These PTMs have significant effects on PDC activity under both physiological and pathophysiological conditions, making them potential targets for metabolism-related diseases. This review specifically focuses on the PTMs of PDC in cardiovascular diseases (CVDs) such as myocardial ischemia/reperfusion injury, diabetic cardiomyopathy, obesity-related cardiomyopathy, heart failure (HF), and vascular diseases. The findings from this review offer theoretical references for the diagnosis, treatment, and prognosis of CVD.

Beyond glucose: The crucial role of redox signaling in β-cell metabolic adaptation

OBJECTIVE

Redox signaling mediated by reversible oxidative cysteine thiol modifications is crucial for driving cellular adaptation to dynamic environmental changes, maintaining homeostasis, and ensuring proper function. This is particularly critical in pancreatic β-cells, which are highly metabolically active and play a specialized role in whole organism glucose homeostasis. Glucose stimulation in β-cells triggers signals leading to insulin secretion, including changes in ATP/ADP ratio and intracellular calcium levels. Additionally, lipid metabolism and reactive oxygen species (ROS) signaling are essential for β-cell function and health.

METHODS

We employed IodoTMT isobaric labeling combined with tandem mass spectrometry to elucidate redox signaling pathways in pancreatic β-cells.

RESULTS

Glucose stimulation significantly increases ROS levels in β-cells, leading to targeted reversible oxidation of proteins involved in key metabolic pathways such as glycolysis, the tricarboxylic acid (TCA) cycle, pyruvate metabolism, oxidative phosphorylation, protein processing in the endoplasmic reticulum (ER), and insulin secretion. Furthermore, the glucose-induced increase in reversible cysteine oxidation correlates with the presence of other post-translational modifications, including acetylation and phosphorylation.

CONCLUSIONS

Proper functioning of pancreatic β-cell metabolism relies on fine-tuned regulation, achieved through a sophisticated system of diverse post-translational modifications that modulate protein functions. Our findings demonstrate that glucose induces the production of ROS in pancreatic β-cells, leading to targeted reversible oxidative modifications of proteins. Furthermore, protein activity is modulated by acetylation and phosphorylation, highlighting the complexity of the regulatory mechanisms in β-cell function.

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.

Blocking SIG1R Along with Low Cadmium Exposure Display Anti-cancer Qualities in Both MCF7 and MDA-MB-231 Cells

Sigma-1 receptor (SIG1R) is a chaperone that modulates inositol 1,4,5-trisphosphate receptor type1 (IP3R1) calcium (Ca2+) channels on the endoplasmic reticulum. Therefore, SIG1R functions as an indirect regulator of Ca2+ and acts as an apoptosis modulator. Increased expression of SIG1R is associated with poor prognosis in breast cancers (BC), and SIG1R antagonists like BD1047 induce apoptosis. As a heavy metal, cadmium (Cd2+) is competitive with Ca2+ due to its physicochemical similarities and may trigger apoptosis at low concentrations. Our study investigated the SIG1R protein expression in 74 BC patients and found a significant increase in SIG1R expression in the triple-negative BC subtype. We also examined the apoptotic and anti-cancer effects of BD1047 in combination with CdCl2 in MCF7 and MDA-MB-213 cells. Cells were treated with CdCl2 at doses of 1 μM, 25 μM, and 50 μM, along with BD1047. Higher doses of CdCl2 were cytotoxic on both cancer cells and significantly increased DNA breaks. However, low-dose CdCl2 with BD1047 increased cell death and the apoptotic index in BC cells, although it did not exhibit cytotoxic effects on HUVEC cells. Co-administration of low-dose CdCl2 with BD1047 also reduced the migration and colony-forming ability of BC cells. Moreover, the expression of SIG1R protein in these groups decreased significantly compared to groups treated with BD1047 or low-dose CdCl2 alone. In conclusion, low-dose CdCl2 is thought to increase the apoptotic ability of BD1047 in BC cells by reducing SIG1R expression.

Sirtuin insights: bridging the gap between cellular processes and therapeutic applications

The greatest challenges that organisms face today are effective responses or detection of life-threatening environmental changes due to an obvious semblance of stress and metabolic fluctuations. These are associated with different pathological conditions among which cancer is most important. Sirtuins (SIRTs; NAD+-dependent enzymes) are versatile enzymes with diverse substrate preferences, cellular locations, crucial for cellular processes and pathological conditions. This article describes in detail the distinct roles of SIRT isoforms, unveiling their potential as either cancer promoters or suppressors and also explores how both natural and synthetic compounds influence the SIRT function, indicating promise for therapeutic applications. We also discussed the inhibitors/activators tailored to specific SIRTs, holding potential for diseases lacking effective treatments. It may uncover the lesser-studied SIRT isoforms (e.g., SIRT6, SIRT7) and their unique functions. This article also offers a comprehensive overview of SIRTs, linking them to a spectrum of diseases and highlighting their potential for targeted therapies, combination approaches, disease management, and personalized medicine. We aim to contribute to a transformative era in healthcare and innovative treatments by unraveling the intricate functions of SIRTs.

The mitochondrial multi-omic response to exercise training across rat tissues

Mitochondria have diverse functions critical to whole-body metabolic homeostasis. Endurance training alters mitochondrial activity, but systematic characterization of these adaptations is lacking. Here, the Molecular Transducers of Physical Activity Consortium mapped the temporal, multi-omic changes in mitochondrial analytes across 19 tissues in male and female rats trained for 1, 2, 4, or 8 weeks. Training elicited substantial changes in the adrenal gland, brown adipose, colon, heart, and skeletal muscle. The colon showed non-linear response dynamics, whereas mitochondrial pathways were downregulated in brown adipose and adrenal tissues. Protein acetylation increased in the liver, with a shift in lipid metabolism, whereas oxidative proteins increased in striated muscles. Exercise-upregulated networks were downregulated in human diabetes and cirrhosis. Knockdown of the central network protein 17-beta-hydroxysteroid dehydrogenase 10 (HSD17B10) elevated oxygen consumption, indicative of metabolic stress. We provide a multi-omic, multi-tissue, temporal atlas of the mitochondrial response to exercise training and identify candidates linked to mitochondrial dysfunction.

A prismatic view of the epigenetic-metabolic regulatory axis in breast cancer therapy resistance

Epigenetic regulation established during development to maintain patterns of transcriptional expression and silencing for metabolism and other fundamental cell processes can be reprogrammed in cancer, providing a molecular mechanism for persistent alterations in phenotype. Metabolic deregulation and reprogramming are thus an emerging hallmark of cancer with opportunities for molecular classification as a critical preliminary step for precision therapeutic intervention. Yet, acquisition of therapy resistance against most conventional treatment regimens coupled with tumor relapse, continue to pose unsolved problems for precision healthcare, as exemplified in breast cancer where existing data informs both cancer genotype and phenotype. Furthermore, epigenetic reprograming of the metabolic milieu of cancer cells is among the most crucial determinants of therapeutic resistance and cancer relapse. Importantly, subtype-specific epigenetic-metabolic interplay profoundly affects malignant transformation, resistance to chemotherapy, and response to targeted therapies. In this review, we therefore prismatically dissect interconnected epigenetic and metabolic regulatory pathways and then integrate them into an observable cancer metabolism-therapy-resistance axis that may inform clinical intervention. Optimally coupling genome-wide analysis with an understanding of metabolic elements, epigenetic reprogramming, and their integration by metabolic profiling may decode missing molecular mechanisms at the level of individual tumors. The proposed approach of linking metabolic biochemistry back to genotype, epigenetics, and phenotype for specific tumors and their microenvironment may thus enable successful mechanistic targeting of epigenetic modifiers and oncometabolites despite tumor metabolic heterogeneity.

Butyrate as a potential therapeutic agent for neurodegenerative disorders

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

Research progress on Sirtuins (SIRTs) family modulators

Sirtuins (SIRTs) represent a class of nicotinamide adenine dinucleotide (NAD+)-dependent protein deacetylases that exert a crucial role in cellular signal transduction and various biological processes. The mammalian sirtuins family encompasses SIRT1 to SIRT7, exhibiting therapeutic potential in counteracting cellular aging, modulating metabolism, responding to oxidative stress, inhibiting tumors, and improving cellular microenvironment. These enzymes are intricately linked to the occurrence and treatment of diverse pathological conditions, including cancer, autoimmune diseases, and cardiovascular disorders. Given the significance of histone modification in gene expression and chromatin structure, maintaining the equilibrium of the sirtuins family is imperative for disease prevention and health restoration. Mounting evidence suggests that modulators of SIRTs play a crucial role in treating various diseases and maintaining physiological balance. This review delves into the molecular structure and regulatory functions of the sirtuins family, reviews the classification and historical evolution of SIRTs modulators, offers a systematic overview of existing SIRTs modulation strategies, and elucidates the regulatory mechanisms of SIRTs modulators (agonists and inhibitors) and their clinical applications. The article concludes by summarizing the challenges encountered in SIRTs modulator research and offering insights into future research directions.

Sirt3 Protects Retinal Pigment Epithelial Cells From High Glucose-Induced Injury by Promoting Mitophagy Through the AMPK/mTOR/ULK1 Pathway

Purpose

The regulation of mitophagy by Sirt3 has rarely been studied in ocular diseases. In the present study, we determined the effects of Sirt3 on AMPK/mTOR/ULK1 signaling pathway-mediated mitophagy in retinal pigment epithelial (RPE) cells in a high glucose environment.

Methods

The mRNA expression levels of Sirt3, AMPK, mTOR, ULK1, and LC3B in RPE cells under varying glucose conditions were measured by real-time polymerase chain reaction (RT-PCR). The expressions of Sirt3, mitophagy protein, and AMPK/mTOR/ULK1 signaling pathway-related proteins were detected by Western blotting. Lentivirus (LV) transfection mediated the stable overexpression of Sirt3 in cell lines. The experimental groups were NG (5.5 mM glucose), hypertonic, HG (30 mM glucose), HG + LV-GFP, and HG + LV-Sirt3. Western blotting was performed to detect the expressions of mitophagy proteins and AMPK/mTOR/ULK1-related proteins in a high glucose environment during the overexpression of Sirt3. Reactive oxygen species (ROS) production in a high glucose environment was measured by DCFH-DA staining. Mitophagy was detected by labeling mitochondria and lysosomes with MitoTracker and LysoTracker probes, respectively. Apoptosis was detected by flow cytometry.

Results

Sirt3 expression was reduced in the high glucose group, inhibiting the AMPK/mTOR/ULK1 pathway, with diminished mitophagy and increased intracellular ROS production. The overexpression of Sirt3, increased expression of p-AMPK/AMPK and p-ULK1/ULK1, and decreased expression of p-mTOR/mTOR inhibited cell apoptosis and enhanced mitophagy.

Conclusions

Sirt3 protected RPE cells from high glucose-induced injury by activating the AMPK/mTOR/ULK1 signaling pathway.

Translational Relevance

By identifying new targets of action, we aimed to establish effective therapeutic targets for diabetic retinopathy treatment.

Pyruvate Dehydrogenase Complex in Neonatal Hypoxic-Ischemic Brain Injury

The disruption of cerebral energy metabolism in relation to brain damage has been the subject of extensive research. However, the pyruvate dehydrogenase complex (PDHC), which is primarily characterized by poor cerebral energy metabolism following brain trauma, has received relatively little study in comparison to newborn hypoxic-ischemic brain injury. Mitochondrial PDHC, a multienzyme complex that functions as a crucial hub in energy metabolism and acts as a central metabolic node to mediate pyruvate oxidation after glycolysis and fuel the Krebs cycle to meet energy demands, has been reported to be one cause of energy metabolism dysfunction according to recent studies. Here we assess the potential mechanisms of neonatal hypoxic-ischemic brain injury-related brain dysfunction mediated by PDHC and further discuss the neuroprotective effects of therapeutic medicines that target PDHC activation. We also provide a summary of recent research on medicines that target PDHC in neonates with hypoxic-ischemic brain damage. Through an understanding of the mechanisms by which it is modulated and an investigation of the neuroprotective techniques available to activate brain PDHC and improve neonatal hypoxic-ischemic impairment, our review emphasizes the significance of PDHC impairment in neonatal hypoxic-ischemic brain injury.

Copper homeostasis and cuproptosis in cancer immunity and therapy

Copper is an essential nutrient for maintaining enzyme activity and transcription factor function. Excess copper results in the aggregation of lipoylated dihydrolipoamide S-acetyltransferase (DLAT), which correlates to the mitochondrial tricarboxylic acid (TCA) cycle, resulting in proteotoxic stress and eliciting a novel cell death modality: cuproptosis. Cuproptosis exerts an indispensable role in cancer progression, which is considered a promising strategy for cancer therapy. Cancer immunotherapy has gained extensive attention owing to breakthroughs in immune checkpoint blockade; furthermore, cuproptosis is strongly connected to the modulation of antitumor immunity. Thus, a thorough recognition concerning the mechanisms involved in the modulation of copper metabolism and cuproptosis may facilitate improvement in cancer management. This review outlines the cellular and molecular mechanisms and characteristics of cuproptosis and the links of the novel regulated cell death modality with human cancers. We also review the current knowledge on the complex effects of cuproptosis on antitumor immunity and immune response. Furthermore, potential agents that elicit cuproptosis pathways are summarized. Lastly, we discuss the influence of cuproptosis induction on the tumor microenvironment as well as the challenges of adding cuproptosis regulators to therapeutic strategies beyond traditional therapy.

Alterations of SIRT1/SIRT3 subcellular distribution in aging undermine cardiometabolic homeostasis during ischemia and reperfusion

Age-related sensors Sirtuin1 (SIRT1) and Sirtuin3 (SIRT3) play an essential role in the protective response upon myocardial ischemia and/or reperfusion (I/R). However, the subcellular localization and co-regulatory network between cardiac SIRT1 and SIRT3 remain unknown, especially their effects on age-related metabolic regulation during acute ischemia and I/R. Here, we found that defects of cardiac SIRT1 or SIRT3 with aging result in an exacerbated cardiac physiological structural and functional deterioration after acute ischemic stress and failed recovery through reperfusion operation. In aged hearts, SIRT1 translocated into mitochondria and recruited more mitochondria SIRT3 to enhance their interaction during acute ischemia, acting as adaptive protection for the aging hearts from further mitochondria dysfunction. Subsequently, SIRT3-targeted proteomics revealed that SIRT1 plays a crucial role in maintaining mitochondrial integrity through SIRT3-mediated substrate metabolism during acute ischemic and I/R stress. Although the loss of SIRT1/SIRT3 led to a compromised PGC-1α/PPARα-mediated transcriptional control of fatty acid oxidation in response to acute ischemia and I/R, their crosstalk in mitochondria plays a more important role in the aging heart during acute ischemia. However, the increased mitochondria SIRT1-SIRT3 interaction promoted adaptive protection to aging-related fatty acid metabolic disorder via deacetylation of long-chain acyl CoA dehydrogenase (LCAD) during ischemic insults. Therefore, the dynamic network of SIRT1/SIRT3 acts as a mediator that regulates adaptive metabolic response to improve the tolerance of aged hearts to ischemic insults, which will facilitate investigation into the role of SIRT1/SIRT3 in age-related ischemic heart disease.

PDHA1 hyperacetylation-mediated lactate overproduction promotes sepsis-induced acute kidney injury via Fis1 lactylation

The increase of lactate is an independent risk factor for patients with sepsis-induced acute kidney injury (SAKI). However, whether elevated lactate directly promotes SAKI and its mechanism remain unclear. Here we revealed that downregulation of the deacetylase Sirtuin 3 (SIRT3) mediated the hyperacetylation and inactivation of pyruvate dehydrogenase E1 component subunit alpha (PDHA1), resulting in lactate overproduction in renal tubular epithelial cells. We then found that the incidence of SAKI and renal replacement therapy (RRT) in septic patients with blood lactate ≥ 4 mmol/L was increased significantly, compared with those in septic patients with blood lactate < 2 mmol/L. Further in vitro and in vivo experiments showed that additional lactate administration could directly promote SAKI. Mechanistically, lactate mediated the lactylation of mitochondrial fission 1 protein (Fis1) lysine 20 (Fis1 K20la). The increase in Fis1 K20la promoted excessive mitochondrial fission and subsequently induced ATP depletion, mitochondrial reactive oxygen species (mtROS) overproduction, and mitochondrial apoptosis. In contrast, PDHA1 activation with sodium dichloroacetate (DCA) or SIRT3 overexpression decreased lactate levels and Fis1 K20la, thereby alleviating SAKI. In conclusion, our results show that PDHA1 hyperacetylation and inactivation enhance lactate overproduction, which mediates Fis1 lactylation and exacerbates SAKI. Reducing lactate levels and Fis1 lactylation attenuate SAKI.

Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Hepatic Lipid Metabolism in Layer Hens with Fatty Liver Hemorrhagic Syndrome

The feeding of high-energy and low-protein diets often induces fatty liver hemorrhagic syndrome (FLHS) in laying hens. However, the mechanism of hepatic fat accumulation in hens with FLHS remains uncertain. In this research, a comprehensive hepatic proteome and acetyl-proteome analysis was performed in both normal and FLHS-affected hens. The results indicated that the upregulated proteins were primarily associated with fat digestion and absorption, the biosynthesis of unsaturated fatty acids, and glycerophospholipid metabolism, while the downregulated proteins were mainly related to bile secretion and amino acid metabolism. Furthermore, the significant acetylated proteins were largely involved in ribosome and fatty acid degradation, and the PPAR signaling pathway, while the significant deacetylated proteins were related to valine, leucine, and isoleucine degradation in laying hens with FLHS. Overall, these results demonstrate that acetylation inhibits hepatic fatty acid oxidation and transport in hens with FLHS, and mainly exerts its effects by affecting protein activity rather than expression. This study provides new nutritional regulation options to alleviate FLHS in laying hens.

Sirtuin-3-Mediated Cellular Metabolism Links Cardiovascular Remodeling with Hypertension

Hypertension can cause structural and functional abnormalities in the cardiovascular system, which can be attributed to both hemodynamic and nonhemodynamic factors. These alterations are linked with metabolic changes and are induced by pathological stressors. Sirtuins are enzymes that act as stress sensors and regulate metabolic adaptation by deacetylating proteins. Among them, mitochondrial SIRT3 performs a crucial role in maintaining metabolic homeostasis. Evidence from experimental and clinical studies has shown that hypertension-induced decreases in SIRT3 activity can lead to cellular metabolism reprogramming and, subsequently, increased susceptibility to endothelial dysfunction, myocardial hypertrophy, myocardial fibrosis, and heart failure. This review presents recent research advances in SIRT3-mediated metabolic adaptation in hypertensive cardiovascular remodeling.

The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.

Usefulness of pyruvate dehydrogenase-E1α expression to determine SUVmax cut-off value of [18F]FDG-PET for predicting lymph node metastasis in lung cancer

A more accurate cut-off value of maximum standardized uptake value (SUVmax) in [¹⁸F]fluorodeoxyglucose positron emission tomography/computed tomography ([¹⁸F]FDG-PET/CT) is necessary to improve preoperative nodal staging in patients with lung cancer. Overall, 223 patients with lung cancer who had undergone [¹⁸F]FDG-PET/CT within 2 months before surgery were enrolled. The expression of glucose transporter-1, pyruvate kinase-M2, pyruvate dehydrogenase-E1α (PDH-E1α), and carbonic anhydrase-9 was evaluated by immunohistochemistry. Clinicopathological background was retrospectively investigated. According to PDH-E1α expression in primary lesion, a significant difference (p = 0.021) in SUVmax of metastatic lymph nodes (3.0 with PDH-positive vs 4.5 with PDH-negative) was found, but not of other enzymes. When the cut-off value of SUVmax was set to 2.5, the sensitivity and specificity were 0.529 and 0.562, respectively, and the positive and negative predictive values were 0.505 and 0.586, respectively. However, when the cut-off value of SUVmax was set according to PDH-E1α expression (2.7 with PDH-positive and 3.2 with PDH-negative), the sensitivity and specificity were 0.441 and 0.868, respectively, and the positive and negative predictive values were 0.738 and 0.648, respectively. The SUVmax cut-off value for metastatic lymph nodes depends on PDH-E1α expression in primary lung cancer. The new SUVmax cut-off value according to PDH-E1α expression showed higher specificity for [¹⁸F]FDG-PET in the diagnosis of lymph node metastasis.

Changes of energy metabolism in failing heart and its regulation by SIRT3

Heart failure (HF) is the leading cause of hospitalization in elderly patients and a disease with extremely high morbidity and mortality rate worldwide. Although there are some existing treatment methods for heart failure, due to its complex pathogenesis and often accompanied by various comorbidities, there is still a lack of specific drugs to treat HF. The mortality rate of patients with HF is still high, highlighting an urgent need to elucidate the pathophysiological mechanisms of HF and seek new therapeutic approaches. The heart is an organ with a very high metabolic intensity, mainly using fatty acids, glucose, ketone bodies, and branched-chain amino acids as energy substrates to supply energy for the heart. Loss of metabolic flexibility and metabolic remodeling occurs with HF. Sirtuin3 (SIRT3) is a member of the NAD⁺-dependent Sirtuin family located in mitochondria, and can participate in mitochondrial physiological functions through the deacetylation of metabolic and respiratory enzymes in mitochondria. As the center of energy metabolism, mitochondria are involved in many physiological processes. Maintaining stable metabolic and physiological functions of the heart depends on normal mitochondrial function. The damage or loss of SIRT3 can lead to various cardiovascular diseases. Therefore, we summarize the recent progress of SIRT3 in cardiac mitochondrial protection and metabolic remodeling.

The mitochondrial multi-omic response to exercise training across tissues

Mitochondria are adaptable organelles with diverse cellular functions critical to whole-body metabolic homeostasis. While chronic endurance exercise training is known to alter mitochondrial activity, these adaptations have not yet been systematically characterized. Here, the Molecular Transducers of Physical Activity Consortium (MoTrPAC) mapped the longitudinal, multi-omic changes in mitochondrial analytes across 19 tissues in male and female rats endurance trained for 1, 2, 4 or 8 weeks. Training elicited substantial changes in the adrenal gland, brown adipose, colon, heart and skeletal muscle, while we detected mild responses in the brain, lung, small intestine and testes. The colon response was characterized by non-linear dynamics that resulted in upregulation of mitochondrial function that was more prominent in females. Brown adipose and adrenal tissues were characterized by substantial downregulation of mitochondrial pathways. Training induced a previously unrecognized robust upregulation of mitochondrial protein abundance and acetylation in the liver, and a concomitant shift in lipid metabolism. The striated muscles demonstrated a highly coordinated response to increase oxidative capacity, with the majority of changes occurring in protein abundance and post-translational modifications. We identified exercise upregulated networks that are downregulated in human type 2 diabetes and liver cirrhosis. In both cases HSD17B10, a central dehydrogenase in multiple metabolic pathways and mitochondrial tRNA maturation, was the main hub. In summary, we provide a multi-omic, cross-tissue atlas of the mitochondrial response to training and identify candidates for prevention of disease-associated mitochondrial dysfunction.

Comprehensive analysis of cuproptosis-related prognostic gene signature and tumor immune microenvironment in HCC

Background: Copper is an indispensable mineral element involved in many physiological metabolic processes. Cuproptosis is associated with a variety of cancer such as hepatocellular carcinoma (HCC). The objective of this study was to examine the relationships between the expression of cuproptosis-related genes (CRGs) and tumor characteristics, including prognosis and microenvironment of HCC. Methods: The differentially expressed genes (DEGs) between high and low CRGs expression groups in HCC samples were identified, and further were analyzed for functional enrichment analysis. Then, CRGs signature of HCC was constructed and analyzed utilizing LASSO and univariate and multivariate Cox regression analysis. Prognostic values of CRGs signature were evaluated by Kaplan-Meier analysis, independent prognostic analysis and nomograph. The expression of prognostic CRGs was verified by Real-time quantitative PCR (RT-qPCR) in HCC cell lines. In addition, the relationships between prognostic CRGs expression and the immune infiltration, tumor microenvironment, antitumor drugs response and m6A modifications were further explored using a series of algorithms in HCC. Finally, ceRNA regulatory network based on prognostic CRGs was constructed. Results: The DEGs between high and low CRG expression groups in HCC were mainly enriched in focal adhesion and extracellular matrix organization. Besides, we constructed a prognostic model that consists of CDKN2A, DLAT, DLST, GLS, and PDHA1 CRGs for predicting the survival likelihood of HCC patients. And the elevated expression of these five prognostic CRGs was substantially in HCC cell lines and associated with poor prognosis. Moreover, immune score and m6A gene expression were higher in the high CRG expression group of HCC patients. Furthermore, prognostic CRGs have higher mutation rates in HCC, and are significantly correlated with immune cell infiltration, tumor mutational burden, microsatellite instability, and anti-tumor drug sensitivity. Then, eight lncRNA-miRNA-mRNA regulatory axes that affected the progression of HCC were predicted. Conclusion: This study demonstrated that the CRGs signature could effectively evaluate prognosis, tumor immune microenvironment, immunotherapy response and predict lncRNA-miRNA-mRNA regulatory axes in HCC. These findings extend our knowledge of cuproptosis in HCC and may inform novel therapeutic strategies for HCC.

Lysine acetylation plays a role in the allograft-induced stress response of the pearl oyster (Pinctada fucata martensii)

Implanting a spherical nucleus into a recipient oyster is a critical step in artificial pearl production using the pearl oyster Pinctada fucata martensii. However, little is known about the role of post-translational modifications (PTMs) in the response of the pearl oyster to this operation. Lysine acetylation, a highly conserved PTM, may be an essential adaptive strategy to manage multiple biotic or abiotic stresses. We conducted the first lysine acetylome analysis of the P. f. martensii gill 12 h after nucleus implantation, using tandem mass tags (TMT) labeling and K^ac affinity enrichment. We identified 2443 acetylated sites in 1301 proteins, and 1511 sites on 895 proteins were quantitatively informative. We found 25 conserved motifs from all of the identified lysine sites, particularly motifs K^ac H, K^ac S, and K^ac Y were strikingly conserved, of which K^ac Y, K^ac H, Y K^ac, K^ac K, K^ac *K, K^ac R, and K^ac F which have been observed in other species and are therefore highly conserved. We identified 58 sites that were significantly differently acetylated in P. f. martensii in response to allograft (|fold change|>1.2, P-value ≤ 0.05); 38 newly acetylated and 20 deacetylated. According to GO functional analysis, subcellar location, and KOG classIfication, these proteins were divided into four categories: cytoskeleton, response to stimulus, metabolism, and other. The differentially acetylated proteins (DAPs) enriched pathways include aminoacyl-tRNA biosynthesis, salmonella infection, and longevity regulating pathway-worm-Caenorhabditis elegans (nematode). Parallel reaction-monitoring (PRM) validation of the differential acetylation of 10 randomly selected differentially acetylated sites from the acetylome analysis. These results indicated that our acetylome analysis results were sufficiently reliable and reproducible. These results provide an essential resource for in-depth exploration of the stress responses and adaptation mechanisms associated with lysine acetylation in marine invertebrates and P. f. martensii.

Tumor glycolysis, an essential sweet tooth of tumor cells

Cancer cells undergo metabolic alterations to meet the immense demand for energy, building blocks, and redox potential. Tumors show glucose-avid and lactate-secreting behavior even in the presence of oxygen, a process known as aerobic glycolysis. Glycolysis is the backbone of cancer cell metabolism, and cancer cells have evolved various mechanisms to enhance it. Glucose metabolism is intertwined with other metabolic pathways, making cancer metabolism diverse and heterogeneous, where glycolysis plays a central role. Oncogenic signaling accelerates the metabolic activities of glycolytic enzymes, mainly by enhancing their expression or by post-translational modifications. Aerobic glycolysis ferments glucose into lactate which supports tumor growth and metastasis by various mechanisms. Herein, we focused on tumor glycolysis, especially its interactions with the pentose phosphate pathway, glutamine metabolism, one-carbon metabolism, and mitochondrial oxidation. Further, we describe the role and regulation of key glycolytic enzymes in cancer. We summarize the role of lactate, an end product of glycolysis, in tumor growth, and the metabolic adaptations during metastasis. Lastly, we briefly discuss limitations and future directions to improve our understanding of glucose metabolism in cancer.

Role of NAD+ and FAD in Ischemic Stroke Pathophysiology: An Epigenetic Nexus and Expanding Therapeutic Repertoire

The redox coenzymes viz., oxidized β-nicotinamide adenine dinucleotide (NAD⁺) and flavin adenine dinucleotide (FAD) by way of generation of optimal reducing power and cellular energy currency (ATP), control a staggering array of metabolic reactions. The prominent cellular contenders for NAD⁺ utilization, inter alia, are sirtuins (SIRTs) and poly(ADP-ribose) polymerase (PARP-1), which have been significantly implicated in ischemic stroke (IS) pathogenesis. NAD⁺ and FAD are also two crucial epigenetic enzyme-required metabolites mediating histone deacetylation and poly(ADP-ribosyl)ation through SIRTs and PARP-1 respectively, and demethylation through FAD-mediated lysine specific demethylase activity. These enzymes and post-translational modifications impinge on the components of neurovascular unit, primarily neurons, and elicit diverse functional upshots in an ischemic brain. These could be circumstantially linked with attendant cognitive deficits and behavioral outcomes in post-stroke epoch. Parsing out the contribution of NAD⁺/FAD-synthesizing and utilizing enzymes towards epigenetic remodeling in IS setting, together with their cognitive and behavioral associations, combined with possible therapeutic implications will form the crux of this review.

The role of NAD metabolism in neuronal differentiation

BACKGROUND

Nicotinamide adenine dinucleotide (NAD) metabolism is involved in redox and non-redox reactions that regulate several processes including differentiation of cells of different origins. Here, the role of NAD metabolism in neuronal differentiation, which remains elusive so far, was investigated.

MATERIAL AND METHODS

A protein-protein interaction network between neurotrophin signaling and NAD metabolic pathways was built. Expression of NAD biosynthetic enzymes in SH-SY5Y cells during retinoic acid (RA)/brain derived neurotrophic factor (BDNF) differentiation, was evaluated. The effects of NAD biosynthetic enzymes QPRT and NAPRT inhibition in neurite outgrowth, cell viability, NAD availability and histone deacetylase (HDAC) activity, were analysed in RA- and BDNF-differentiated cells.

RESULTS

Bioinformatics analysis revealed the interaction between NAD biosynthetic enzyme NMNAT1 and NTRK2, a receptor activated by RA/BDNF sequential treatment. Differences were found in the expression of NAD biosynthetic enzymes during neuronal differentiation, namely, increased QPRT gene expression along the course of RA/BDNF treatment and NAPRT protein expression after a 5-day treatment with RA. QPRT inhibition in BDNF-differentiated SH-SY5Y cells resulted in less neuritic length per cell, decreased expression of the neuronal marker β-III Tubulin and also decreased NAD⁺ levels and HDAC activity. NAPRT inhibition had no effect in neuritic length per cell, NAD⁺ levels and HDAC activity. Of note, NAD supplementation along with RA, but not with BDNF, resulted in considerable cell death.

CONCLUSIONS

Taken together, our results show the involvement of NAD metabolism in neuronal differentiation, specifically, the importance of QPRT-mediated NAD biosynthesis in BDNF-associated SH-SY5Y differentiation and suggest additional roles for NAPRT beyond NAD production in RA-differentiated cells.

The Role and Therapeutic Perspectives of Sirtuin 3 in Cancer Metabolism Reprogramming, Metastasis, and Chemoresistance

Sirtuin 3 (SIRT3), the nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase, acts as a metabolic modulator mainly located in mitochondria via regulating the process of the relevant biochemical processes by targeting crucial mediators. Recently, owing to its dual role in cancer, SIRT3 has attracted extensive attention. Cancer cells have different metabolic patterns from normal cells, and SIRT3-mediated metabolism reprogramming could be critical in the cancer context, which is closely related to the mechanism of metabolism reprogramming, metastasis, and chemoresistance in tumor cells. Therefore, it is crucial to elucidate the relevant pathological mechanisms and take appropriate countermeasures for the progression of clinical strategies to inhibit the development of cancer. In this review, existing available data on the regulation of cancer metabolism reprogramming, metastasis, and chemoresistance progression of SIRT3 are detailed, as well as the status quo of SIRT3 small molecule modulators is updated in the application of cancer therapy, aiming to highlight strategies directly targeting SIRT3-mediated tumor-suppressing and tumor-promoting, and provide new approaches for therapy application. Furthermore, we offer an effective evidence-based basis for the evolvement of potential personalized therapy management strategies for SIRT3 in cancer settings.

Role of sirtuins in esophageal cancer: Current status and future prospects

Esophageal cancer (EC) is a malignant cancer that still has a poor prognosis, although its prognosis has been improving with the development of multidisciplinary treatment modalities such as surgery, chemotherapy and radiotherapy. Therefore, identifying specific molecular markers that can be served as biomarkers for the prognosis and treatment response of EC is highly desirable to aid in the personalization and improvement of the precision of medical treatment. Sirtuins are a family of nicotinamide adenine dinucleotide (NAD+)-dependent proteins consisting of seven members (SIRT1-7). These proteins have been reported to be involved in the regulation of a variety of biological functions including apoptosis, metabolism, stress response, senescence, differentiation and cell cycle progression. Given the variety of functions of sirtuins, they are speculated to be associated in some manner with cancer progression. However, while the role of sirtuins in cancer progression has been investigated over the past few years, their precise role remains difficult to characterize, as they have both cancer-promoting and cancer-suppressing properties, depending on the type of cancer. These conflicting characteristics make research into the nature of sirtuins all the more fascinating. However, the role of sirtuins in EC remains unclear due to the limited number of reports concerning sirtuins in EC. We herein review the current findings and future prospects of sirtuins in EC.

Effect of Sirt3 on retinal pigment epithelial cells in high glucose through Foxo3a/ PINK1-Parkin pathway mediated mitophagy

Sirt3 is closely associated with mitophagy. This study aimed to investigate the effect and potential mechanism of Sirt3 on mitophagy in retinal pigment epithelium (RPE) in a high glucose environment. The expression levels of Sirt3, Foxo3a, PINK1, Parkin and LC3B in RPE subjected to high-glucose (HG, 30 mM D-glucose) conditions were detected by RT-PCR and western blotting. Dichloro-dihydro-fluorescein diacetate (DCFH-DA) staining was used to detect the level of reactive oxygen species (ROS) in RPE treated with HG. MitoTracker and LysoTracker probes were used to label mitochondria and lysosomes, respectively, to observe the occurrence of autophagy. Sirt3-dependent regulation of mitophagy through the Foxo3a/PINK1-Parkin pathway was further investigated by virus transfection-mediated Sirt3 overexpression and PINK1 silencing. The effect of Sirt3 overexpression on apoptosis was detected by flow cytometry. The Sirt3 expression was decreased, the Foxo3a/PINK1-Parkin pathway was inhibited, intracellular ROS level was increased, and mitophagy was attenuated in RPE under HG condition. Sirt3 overexpression activated the Foxo3a/PINK1-Parkin signaling pathway and mitophagy, and inhibited cell apoptosis. Silencing PINK1 inhibited the effect of Sirt3 overexpression on mitophagy. In summary, Sirt3 can activate mitophagy through the Foxo3a/PINK1-Parkin pathway and reduce HG-induced apoptosis of RPE. This study provides a new direction to understand the pathogenesis and develop a potential therapeutic target for diabetic retinopathy.

Post-translational modifications on mitochondrial metabolic enzymes in cancer

Mitochondrion is the powerhouse of the cell. The research of nearly a century has expanded our understanding of mitochondrion, far beyond the view that mitochondrion is an important energy generator of cells. During the initiation, growth and survival of tumor cells, significant mitochondrial metabolic changes have taken place in the important enzymes of respiratory chain and tricarboxylic acid cycle, mitochondrial biogenesis and dynamics, oxidative stress regulation and molecular signaling. Therefore, mitochondrial metabolic proteins are the key mediators of tumorigenesis. Post-translational modification is the molecular switch that regulates protein function. Understanding how these mitochondria-related post-translational modification function during tumorigenesis will bring new ideas for the next generation of cancer treatment.

Focus on Molecular Functions of Anti-Aging Deacetylase SIRT3

SIRT3 is a protein lysine deacetylase with a prominent role in the maintenance of mitochondrial integrity, which is a vulnerable target in many diseases. Intriguingly, cellular aging is reversible just by SIRT3 overexpression, which raises many questions about the role of SIRT3 in the molecular anti-aging mechanisms. Therefore, functions of SIRT3 were analyzed through the interaction network of 407 substrates collected by data mining. Results of the pathway enrichment and gene function prediction confirmed functions in the primary metabolism and mitochondrial ATP production. However, it also suggested involvement in thermogenesis, brain-related neurodegenerative diseases Alzheimer's (AD), Parkinson's, Huntington's disease (HD), and non-alcoholic fatty liver disease. The protein node prioritization analysis identified subunits of the complex I of the mitochondrial respiratory chain (MRC) as the nodes with the main regulatory effect within the entire interaction network. Additional high-ranked nodes were succinate dehydrogenase subunit B (SDHB), complex II, and ATP5F1, complex V of MRC. The analysis supports existence of the NADH/NAD+ driven regulatory feedback loop between SIRT3, complex I (MRC), and acetyl-CoA synthetases, and existence of the nuclear substrates of SIRT3. Unexplored functions of SIRT3 substrates such as LMNA and LMNB; HIF-1a, p53, DNA-PK, and PARK7 are highlighted for further scientific advances. SIRT3 acts as a repressor of BACE1 through the SIRT3-LKB1-AMPK-CREB-PGC1A-PPARG-BACE1 (SIRT3-BACE1), which functions are fitted the best by the Circadian Clock pathway. It forms a new working hypothesis as the therapeutical target for AD treatment. Other important pathways linked to SIRT3 activity are highlighted for therapeutical interventions.

The Pyruvate Dehydrogenase Complex in Sepsis: Metabolic Regulation and Targeted Therapy

Anaerobic glycolysis is the process by which glucose is broken down into pyruvate and lactate and is the primary metabolic pathway in sepsis. The pyruvate dehydrogenase complex (PDHC) is a multienzyme complex that serves as a critical hub in energy metabolism. Under aerobic conditions, pyruvate translocates to mitochondria, where it is oxidized into acetyl-CoA through the activation of PDHC, thereby accelerating aerobic oxidation. Both phosphorylation and acetylation affect PDHC activity and, consequently, the regulation of energy metabolism. The mechanisms underlying the protective effects of PDHC in sepsis involve the regulation on the balance of lactate, the release of inflammatory mediators, the remodeling of tricarboxylic acid (TCA) cycle, as well as on the improvement of lipid and energy metabolism. Therapeutic drugs that target PDHC activation for sepsis treatment include dichloroacetate, thiamine, amrinone, TNF-binding protein, and ciprofloxacin. In this review, we summarize the recent findings regarding the metabolic regulation of PDHC in sepsis and the therapies targeting PDHC for the treatment of this condition.

The Mitochondrial Antioxidant Sirtuin3 Cooperates with Lipid Metabolism to Safeguard Neurogenesis in Aging and Depression

Neural stem cells (NSCs), crucial for memory in the adult brain, are also pivotal to buffer depressive behavior. However, the mechanisms underlying the boost in NSC activity throughout life are still largely undiscovered. Here, we aimed to explore the role of deacetylase Sirtuin 3 (SIRT3), a central player in mitochondrial metabolism and oxidative protection, in the fate of NSC under aging and depression-like contexts. We showed that chronic treatment with tert-butyl hydroperoxide induces NSC aging, markedly reducing SIRT3 protein. SIRT3 overexpression, in turn, restored mitochondrial oxidative stress and the differentiation potential of aged NSCs. Notably, SIRT3 was also shown to physically interact with the long chain acyl-CoA dehydrogenase (LCAD) in NSCs and to require its activation to prevent age-impaired neurogenesis. Finally, the SIRT3 regulatory network was investigated in vivo using the unpredictable chronic mild stress (uCMS) paradigm to mimic depressive-like behavior in mice. Interestingly, uCMS mice presented lower levels of neurogenesis and LCAD expression in the same neurogenic niches, being significantly rescued by physical exercise, a well-known upregulator of SIRT3 and lipid metabolism. Our results suggest that targeting NSC metabolism, namely through SIRT3, might be a suitable promising strategy to delay NSC aging and confer stress resilience.

Jian-Pi-Yi-Shen Formula Alleviates Chronic Kidney Disease in Two Rat Models by Modulating QPRT/NAD+/SIRT3/Mitochondrial Dynamics Pathway

Objective

Jian-Pi-Yi-Shen formula (JPYSF) is a traditional Chinese herbal decoction and has been used for treating chronic kidney disease (CKD) in clinics for decades. However, the potential mechanisms have not been fully elucidated. This study was designed to test the efficacy of JPYSF in treating CKD and explore the underlying mechanism.

Methods

Two CKD rat models were established by 5/6 nephrectomy (5/6 Nx) and feeding with adenine-containing feed, respectively. The intervention dose of JPYSF was 10.89 g/kg/d by gastric irrigation. Renal function was assessed by serum creatinine (Scr) and blood urea nitrogen (BUN). Periodic acid-Schiff (PAS) and Masson's trichrome staining were used to evaluate renal histopathological changes. The levels of nicotinamide adenine dinucleotide (NAD⁺) were measured by using the enzyme-linked immunosorbent assay kit. The proteins expressions of renal fibrosis, quinolinate phosphoribosyltransferase (QPRT), sirtuin 3 (SIRT3), and mitochondrial dynamics were determined and quantified by Western blot analysis.

Results

The results show that administration of JPYSF significantly lowered Scr and BUN levels, improved renal tubular atrophy and interstitial fibrosis, and decreased renal extracellular matrix deposition in two CKD rat models. In addition, CKD rats exhibited suppressed QPRT/NAD⁺/SIRT3 signal, increased mitochondrial fission, and decreased mitochondrial fusion. JPYSF treatment promoted QPRT/NAD⁺/SIRT3 signal and restored mitochondrial fission/fusion balance.

Conclusion

In conclusion, administration of JPYSF effectively alleviated CKD progression in two rat models, which may be related with regulation of the QPRT/NAD⁺/SIRT3/mitochondrial dynamics pathway.

Pyruvate dehydrogenase E1α represents a reliable prognostic predictor for patients with non-small cell lung cancer resected via curative operation

Background

Lung cancer is associated with a high morbidity and mortality rate worldwide; however, no reliable and independent prognostic predictor for non-small cell lung cancer (NSCLC) after curative surgery is available. Glucose metabolism is correlated with cancer cell proliferation. Pyruvate dehydrogenase E1α (PDH-E1α) catalyzes the conversion of pyruvate to acetyl-CoA and promotes aerobic glucose metabolism. In this study, we examined the relationship between PDH-E1α expression and clinicopathological factors associated with NSCLC to identify a reliable prognostic predictor of NSCLC after curative surgery.

Methods

A total of 445 patients with NSCLC who underwent curative resection were enrolled in this study. PDH-E1α expression was evaluated via immunohistochemistry. We analyzed the correlation between PDH-E1α expression and clinicopathological features of the patients.

Results

In total, 248 (56%) of the 445 patients with NSCLC were PDH-E1α-positive, and 197 patients were PDH-E1α-negative. PDH-E1α positivity was significantly correlated with the presence of adenocarcinoma (P<0.001) compared to the PDH-E1α-negative group. Patients with NSCLC showing PDH-E1α-negative expression had a significantly poorer overall survival rate (P=0.007) than those showing PDH-E1α-positive expression, especially at stage II. Patients with PDH-E1α negative expression also showed a poorer disease-free survival rate (P=0.02). Multivariate analysis revealed that PDH-E1α negativity (P=0.037) and male sex (P<0.001) were significantly correlated with a poor overall survival.

Conclusions

PDH-E1α may represent a reliable prognostic predictor for NSCLC in patients that have recently undergone curative resection, especially at stage II.

A Comprehensive Proteome and Acetyl-Proteome Atlas Reveals Molecular Mechanisms Adapting to the Physiological Changes From Pre-laying to Peak-Laying Stage in Liver of Hens (Gallus gallus)

Along with sexual maturity, the liver undergoes numerous metabolic processes to adapt the physiological changes associated with egg-laying in hens. However, mechanisms regulating the processes were unclear. In this study, comparative hepatic proteome and acetyl-proteome between pre- and peak-laying hens were performed. The results showed that the upregulated proteins were mainly related to lipid and protein biosynthesis, while the downregulated proteins were mainly involved in pyruvate metabolism and were capable of inhibiting gluconeogenesis and lactate synthesis in peak-laying hens compared with that in pre-laying hens. With unchanged expression level, the significant acetylated proteins were largely functioned on activation of polyunsaturated fatty acid oxidation in peroxisome, while the significant deacetylated proteins were principally used to elevate medium and short fatty acid oxidation in mitochondria and oxidative phosphorylation. Most of the proteins which involved in gluconeogenesis, lipid transport, and detoxification were influenced by both protein expression and acetylation. Taken overall, a novel mechanism wherein an alternate source of acetyl coenzyme A was produced by activation of FA oxidation and pyruvate metabolism to meet the increased energy demand and lipid synthesis in liver of laying hens was uncovered. This study provides new insights into molecular mechanism of adaptation to physiological changes in liver of laying hens.

Dynamic regulation of mitochondrial pyruvate metabolism is necessary for orthotopic pancreatic tumor growth

BACKGROUND

Pyruvate dehydrogenase complex (PDC) plays a central role in carbohydrate metabolism, linking cytoplasmic glycolysis to the mitochondrial tricarboxylic acid (TCA) cycle. PDC is a conserved E1-E2-E3 dehydrogenase with a PDHA1 and PDHB heterotetramer functioning as the E1 subunit. PDHA1 contains three serine residues that can be reversibly phosphorylated by a dedicated family of four inhibitory pyruvate dehydrogenase kinases (PDHK1-4) and two reactivating phosphatases (PDP1, 2). Hypoxia induces the expression of PDHK1 and PDHK3 and hyperphosphorylates PDHA1. The role of PDC in metabolic reprogramming and tumor progression appears to be for the integration of oncogenic and environmental signals which supports tumor growth.

METHODS

To isolate the function of the serine-dependent regulation of PDC, we engineered MiaPaca2 cells to express PDHA1 protein with either intact serines at positions 232, 293, and 300 or all the combinations of non-phosphorylatable alanine substitution mutations. These lines were compared in vitro for biochemical response to hypoxia by western blot, metabolic activity by biochemical assay and Seahorse XF flux analysis, and growth in media with reduced exogenous metabolites. The lines were also tested for growth in vivo after orthotopic injection into the pancreata of immune-deficient mice.

RESULTS

In this family of cells with non-phosphorylatable PDHA1, we found reduced hypoxic phosphorylation of PDHA1, decreased PDH enzymatic activity in normoxia and hypoxia, decreased mitochondrial function by Seahorse flux assay, reduced in vitro growth of cells in media depleted of lipids, and reduced growth of tumors after orthotopic transplantation of cells into the pancreata of immune-deficient mice.

CONCLUSIONS

We found that any substitution of alanine for serine at regulatory sites generated a hypomorphic PDC. However, the reduced PDC activity was insensitive to further reduction in hypoxia. These cells had a very modest reduction of growth in vitro, but failed to grow as tumors indicating that dynamic PDC adaptation to microenvironmental conditions is necessary to support pancreatic cancer growth in vivo.

Sirtuin 3 regulates mitochondrial protein acetylation and metabolism in tubular epithelial cells during renal fibrosis

Proximal tubular epithelial cells (TECs) demand high energy and rely on mitochondrial oxidative phosphorylation as the main energy source. However, this is disturbed in renal fibrosis. Acetylation is an important post-translational modification for mitochondrial metabolism. The mitochondrial protein NAD+-dependent deacetylase sirtuin 3 (SIRT3) regulates mitochondrial metabolic function. Therefore, we aimed to identify the changes in the acetylome in tubules from fibrotic kidneys and determine their association with mitochondria. We found that decreased SIRT3 expression was accompanied by increased acetylation in mitochondria that have separated from TECs during the early phase of renal fibrosis. Sirt3 knockout mice were susceptible to hyper-acetylated mitochondrial proteins and to severe renal fibrosis. The activation of SIRT3 by honokiol ameliorated acetylation and prevented renal fibrosis. Analysis of the acetylome in separated tubules using LC-MS/MS showed that most kidney proteins were hyper-acetylated after unilateral ureteral obstruction. The increased acetylated proteins with 26.76% were mitochondrial proteins which were mapped to a broad range of mitochondrial pathways including fatty acid β-oxidation, the tricarboxylic acid cycle (TCA cycle), and oxidative phosphorylation. Pyruvate dehydrogenase E1α (PDHE1α), which is the primary link between glycolysis and the TCA cycle, was hyper-acetylated at lysine 385 in TECs after TGF-β1 stimulation and was regulated by SIRT3. Our findings showed that mitochondrial proteins involved in regulating energy metabolism were acetylated and targeted by SIRT3 in TECs. The deacetylation of PDHE1α by SIRT3 at lysine 385 plays a key role in metabolic reprogramming associated with renal fibrosis.

Melatonin inhibits lung cancer development by reversing the Warburg effect via stimulating the SIRT3/PDH axis

Recently, the morbidity and mortality from lung cancer have continued to increase. Mitochondrial dysfunction plays a key role in apoptosis, proliferation, and the bioenergetic reprogramming of cancer cells, especially for energy metabolism. Herein, we investigated the ability of melatonin (MLT) to influence lung cancer growth and explored the association between mitochondrial functions and the progression of lung tumors. The deacetylase, sirtuin 3 (Sirt3), is a pivotal player in maintenance of mitochondrial function, among participating in ATP production by regulating the acetylone and pyruvate dehydrogenase complex (PDH). We initially found that MLT inhibited lung cancer growth in the Lewis mouse model. Similarly, we observed that MLT inhibited the proliferation of lung cancer cells (A549, PC9, and LLC cells), and the underlying mechanism of MLT was related to reprogramming cancer cell metabolism, accompanied by a shift from cytosolic aerobic glycolysis to oxidative phosphorylation (OXPHOS). These changes were accompanied by higher ATP production, an elevated ATP production-coupled oxygen consumption rate (QCR), higher ROS levels, higher mito-ROS levels, and lower lactic acid secretion. Additionally, we observed that MLT improved mitochondrial membrane potential and the activities of complexes Ⅰ and Ⅳ in the electron transport chain. Importantly, we also found and verified that the foregoing changes resulted from activation of Sirt3 and PDH. As a result of these changes, MLT significantly enhanced mitochondrial energy metabolism to reverse the Warburg effect via increasing PDH activity with stimulation of Sirt3. Collectively, these findings suggest the potential use of melatonin as an anti-lung cancer therapy and provide a mechanistic basis for this proposal.

Redox interactions of immune cells and muscle in the regulation of exercise-induced pain and analgesia: implications on the modulation of muscle nociceptor sensory neurons

The mechanistic interactions among redox status of leukocytes, muscle, and exercise in pain regulation are still poorly understood and limit targeted treatment. Exercise benefits are numerous, including the treatment of chronic pain. However, unaccustomed exercise may be reported as undesirable as it may contribute to pain. The aim of the present review is to evaluate the relationship between oxidative metabolism and acute exercise-induced pain, and as to whether improved antioxidant capacity underpins the analgesic effects of regular exercise. Preclinical and clinical studies addressing relevant topics on mechanisms by which exercise modulates the nociceptive activity and how redox status can outline pain and analgesia are discussed, in sense of translating into refined outcomes. Emerging evidence points to the role of oxidative stress-induced signaling in sensitizing nociceptor sensory neurons. In response to acute exercise, there is an increase in oxidative metabolism, and consequently, pain. Instead, regular exercise can modulate redox status in favor of antioxidant capacity and repair mechanisms, which have consequently increased resistance to oxidative stress, damage, and pain. Data indicate that acute sessions of unaccustomed prolonged and/or intense exercise increase oxidative metabolism and regulate exercise-induced pain in the post-exercise recovery period. Further, evidence demonstrates regular exercise improves antioxidant status, indicating its therapeutic utility for chronic pain disorders. An improved comprehension of the role of redox status in exercise can provide helpful insights into immune-muscle communication during pain modulatory effects of exercise and support new therapeutic efforts and rationale for the promotion of exercise.

A comprehensive review of Sirtuins: With a major focus on redox homeostasis and metabolism

Sirtuins are Class III protein deacetylases with seven conserved isoforms. In general, Sirtuins are highly activated under cellular stress conditions in which NAD⁺ levels are increased. Nevertheless, regulation of Sirtuins extends far beyond the influences of cellular NAD⁺/NADH ratio and a rapidly expanding body of evidence currently suggests that their expression and catalytic activity are highly kept under control at multiple levels by various factors and processes. Owing to their intrinsic ability to enzymatically target various intracellular proteins, Sirtuins are prominently involved in the regulation of fundamental biological processes including inflammation, metabolism, redox homeostasis, DNA repair and cell proliferation and senescence. In fact, Sirtuins are well established to regulate and reprogram different redox and metabolic pathways under both pathological and physiological conditions. Therefore, alterations in Sirtuin levels can be a pivotal intermediary step in the pathogenesis of several disorders. This review first highlights the mechanisms involved in the regulation of Sirtuins and further summarizes the current findings on the major functions of Sirtuins in cellular redox homeostasis and bioenergetics (glucose and lipid metabolism).

Genetic Manipulation of Sirtuin 3 Causes Alterations of Key Metabolic Regulators in Melanoma

The mitochondrial sirtuin SIRT3 plays key roles in cellular metabolism and energy production, which makes it an obvious target for the management of cancer, including melanoma. Previously, we have demonstrated that SIRT3 was constitutively upregulated in human melanoma and its inhibition resulted in anti-proliferative effects in vitro in human melanoma cells and in vivo in human melanoma xenografts. In this study, we expanded our data employing knockdown and overexpression strategies in cell culture and mouse xenografts to further validate and establish the pro-proliferative function of SIRT3 in melanocytic cells, and its associated potential mechanisms, especially focusing on the metabolic regulation. We found that short-hairpin RNA (shRNA) mediated SIRT3 knockdown in G361 melanoma cells showed diminished tumorigenesis in immunodeficient Nu/Nu mice. Conversely, SIRT3 overexpressing Hs294T melanoma cells showed increased tumor growth. These effects were consistent with changes in markers of proliferation (PCNA), survival (Survivin) and angiogenesis (VEGF) in xenografted tissues. Further, in in vitro culture system, we determined the effect of SIRT3 knockdown on glucose metabolism in SK-MEL-2 cells, using a PCR array. SIRT3 knockdown caused alterations in a total of 37 genes involved in the regulation and enzymatic pathways of glucose (32 genes) and glycogen (5 genes) metabolism. Functions annotation of these identified genes, using the ingenuity pathway analysis (IPA), predicted cumulative actions of decreased cell viability/proliferation, tumor growth and reactive oxygen species (ROS), and increased apoptosis in response to SIRT3 knockdown. Further, IPA gene network analysis of SIRT3 modulated genes revealed the interactions among these genes in addition to several melanoma-associated genes. Sirtuin pathway was identified as one of the top canonical pathways showing the interaction of SIRT3 with metabolic regulatory genes along with other sirtuins. IPA analysis also predicted the inhibition of HIF1α, PKM, KDM8, PPARGC1A, mTOR, and activation of P53 and CLPP; the genes involved in major cancer/melanoma-associated signaling events. Collectively, these results suggest that SIRT3 inhibition affects cellular metabolism, to impart an anti-proliferative response against melanoma.

The antiviral sirtuin 3 bridges protein acetylation to mitochondrial integrity and metabolism during human cytomegalovirus infection

Regulation of mitochondrial structure and function is a central component of infection with viruses, including human cytomegalovirus (HCMV), as a virus means to modulate cellular metabolism and immune responses. Here, we link the activity of the mitochondrial deacetylase SIRT3 and global mitochondrial acetylation status to host antiviral responses via regulation of both mitochondrial structural integrity and metabolism during HCMV infection. We establish that SIRT3 deacetylase activity is necessary for suppressing virus production, and that SIRT3 maintains mitochondrial pH and membrane potential during infection. By defining the temporal dynamics of SIRT3-substrate interactions during infection, and overlaying acetylome and proteome information, we find altered SIRT3 associations with the mitochondrial fusion factor OPA1 and acetyl-CoA acyltransferase 2 (ACAA2), concomitant with changes in their acetylation levels. Using mutagenesis, microscopy, and virology assays, we determine OPA1 regulates mitochondrial morphology of infected cells and inhibits HCMV production. OPA1 acetylation status modulates these functions, and we establish K834 as a site regulated by SIRT3. Control of SIRT3 protein levels or enzymatic activity is sufficient for regulating mitochondrial filamentous structure. Lastly, we establish a virus restriction function for ACAA2, an enzyme involved in fatty acid beta-oxidation. Altogether, we highlight SIRT3 activity as a regulatory hub for mitochondrial acetylation and morphology during HCMV infection and point to global acetylation as a reflection of mitochondrial health.

Given their functions in cellular metabolism and immune responses, mitochondria are targeted and disrupted by numerous prevalent viral pathogens, including human cytomegalovirus (HCMV). To characterize mechanisms underlying mitochondrial regulation during HCMV infection in human fibroblasts, this study integrates enzyme-substrate interaction studies, mass spectrometry quantification of protein abundance and acetylation, mutagenesis, microscopy, and virology assays. These analyses establish a link between the mitochondrial acetylation status and mitochondrial structure and metabolism during HCMV infection. We demonstrate that the mitochondrial deacetylase SIRT3 acts in host defense by modulating proteins that regulate mitochondrial structure and fatty acid oxidation. SIRT3 helps to maintain mitochondrial integrity through several mechanisms, including regulation of mitochondrial pH, membrane potential, and the balance between mitochondrial fission and fusion. As excess mitochondrial acetylation is detrimental to mitochondrial metabolism, the virus-induced alterations in SIRT3 functions and mitochondrial acetylation may be linked to known HCMV pathologies, such as the metabolic syndrome and cardiac hypertrophy.

The Importance of Mitochondrial Pyruvate Carrier in Cancer Cell Metabolism and Tumorigenesis

Simple Summary

The characteristic metabolic hallmark of cancer cells is the massive catabolism of glucose by glycolysis, even under aerobic conditions—the so-called Warburg effect. Although energetically unfavorable, glycolysis provides “building blocks” to sustain the unlimited growth of malignant cells. Aberrant glycolysis is also responsible for lactate accumulation and acidosis in the tumor milieu, which fosters hypoxia and immunosuppression. One of the mechanisms used by cancer cells to increase glycolytic flow is the negative regulation of the proteins that conform the mitochondrial pyruvate carrier (MPC) complex, which transports pyruvate into the mitochondrial matrix to be metabolized in the tricarboxylic acid (TCA) cycle. Evidence suggests that MPC downregulation in tumor cells impacts many aspects of tumorigenesis, including cancer cell-intrinsic (proliferation, invasiveness, stemness, resistance to therapy) and -extrinsic (angiogenesis, anti-tumor immune activity) properties. In many cancers, but not in all, MPC downregulation is associated with poor survival. MPC regulation is therefore central to tackling glycolysis in tumors.

Abstract

Pyruvate is a key molecule in the metabolic fate of mammalian cells; it is the crossroads from where metabolism proceeds either oxidatively or ends with the production of lactic acid. Pyruvate metabolism is regulated by many enzymes that together control carbon flux. Mitochondrial pyruvate carrier (MPC) is responsible for importing pyruvate from the cytosol to the mitochondrial matrix, where it is oxidatively phosphorylated to produce adenosine triphosphate (ATP) and to generate intermediates used in multiple biosynthetic pathways. MPC activity has an important role in glucose homeostasis, and its alteration is associated with diabetes, heart failure, and neurodegeneration. In cancer, however, controversy surrounds MPC function. In some cancers, MPC upregulation appears to be associated with a poor prognosis. However, most transformed cells undergo a switch from oxidative to glycolytic metabolism, the so-called Warburg effect, which, amongst other possibilities, is induced by MPC malfunction or downregulation. Consequently, impaired MPC function might induce tumors with strong proliferative, migratory, and invasive capabilities. Moreover, glycolytic cancer cells secrete lactate, acidifying the microenvironment, which in turn induces angiogenesis, immunosuppression, and the expansion of stromal cell populations supporting tumor growth. This review examines the latest findings regarding the tumorigenic processes affected by MPC.

Global analysis of lysine acetylome reveals the potential role of CCL18 in non-small cell lung cancer

C-C motif chemokine 18 (CCL18) belongs to the chemokine CC family and is predominantly secreted by M2-tumor-associated macrophages. It has been reported to be associated with various diseases and malignancies. Previous studies showed that CCL18 promotes metastasis by activating downstream kinases. However, it remains unknown whether CCL18 regulates post-translational modifications, other than phosphorylation, during tumorigenesis. Here, we demonstrate that CCL18 is up-regulated in non-small cell lung cancer (NSCLC) and is involved in regulating the lysine acetylome in A549 cells. Using the combination of SILAC labeling and high-efficiency acetylation enrichment methods, we identified 1372 lysine acetylation (Kac) sites on 796 proteins in CCL18-treated A549 cells. Among the identified Kac sites, 147 from 126 proteins were down-regulated and seven from five proteins were up-regulated with fold changes more than two and the p-value less than 0.05. Bioinformatics analysis further showed that the proteins with down-regulated acetylation play critical roles in glycolysis, oxidative phosphorylation, tricarboxylic acid cycle, and pentose phosphate pathway in A549 cells. These results suggest that CCL18 may be involved in the development of NSCLC by regulating acetylation of the proteins in many fundamental cellular processes, especially the metabolic reprogramming of tumor cells.

SIRT3 (Sirtuin-3) Prevents Ang II (Angiotensin II)-Induced Macrophage Metabolic Switch Improving Perivascular Adipose Tissue Function

OBJECTIVE

Infiltrated macrophages actively promote perivascular adipose tissue remodeling and represent a dominant population in the perivascular adipose tissue microenvironment of hypertensive mice. However, the role of macrophages in initiating metabolic inflammation remains uncertain. SIRT3 (sirtuin-3), a NAD-dependent deacetylase, is sensitive to metabolic status and mediates adaptation responses. In this study, we investigated the role of SIRT3-mediated metabolic shift in regulating NLRP3 (Nod-like receptor family pyrin domain-containing 3) inflammasome activation. Approach and Results: Here, we report that Ang II (angiotensin II) accelerates perivascular adipose tissue inflammation and fibrosis, accompanied by NLRP3 inflammasome activation and IL (interleukin)-1β secretion in myeloid SIRT3 knockout (SIRT3-/-) mice. This effect is associated with adipose tissue mitochondrial dysfunction. In vitro studies indicate that the deletion of SIRT3 in bone marrow-derived macrophages induces IL-1β production by shifting the metabolic phenotype from oxidative phosphorylation to glycolysis. Mechanistically, SIRT3 deacetylates and activates PDHA1 (pyruvate dehydrogenase E1 alpha) at lysine 83, and the loss of SIRT3 leads to PDH activity decrease and lactate accumulation. Knocking down LDHA (lactate dehydrogenase A) or using carnosine, a buffer against lactic acid, attenuates IL-1β secretion. Furthermore, the blockade of IL-1β from macrophages into brown adipocytes restores thermogenic markers and mitochondrial oxygen consumption. Moreover, NLRP3 knockout (NLRP3-/-) mice exhibited reduced IL-1β production while rescuing the mitochondrial function of brown adipocytes and alleviating perivascular adipose tissue fibrosis.

CONCLUSIONS

SIRT3 represents a potential therapeutic target to attenuate NLRP3-related inflammation. Pharmacological targeting of glycolytic metabolism may represent an effective therapeutic approach.

Regulation of SIRT2 by Wnt/β-catenin signaling pathway in colorectal cancer cells

Activation of the Wnt/β-catenin pathway is one of the hallmarks of colorectal cancer (CRC). Sirtuin 2 (SIRT2) protein has been shown to inhibit CRC proliferation. Previously, we reported that SIRT2 plays an important role in the maintenance of normal intestinal cell homeostasis. Here, we show that SIRT2 is a direct target gene of Wnt/β-catenin signaling in CRC cells. Inhibition or knockdown of Wnt/β-catenin increased SIRT2 promoter activity and mRNA and protein expression, whereas activation of Wnt/β-catenin decreased SIRT2 promoter activity and expression. β-Catenin was recruited to the promoter of SIRT2 and transcriptionally regulated SIRT2 expression. Wnt/β-catenin inhibition increased mitochondrial oxidative phosphorylation (OXPHOS) and CRC cell differentiation. Moreover, inhibition of OXPHOS attenuated the differentiation of CRC cells induced by Wnt/β-catenin inhibition. In contrast, inhibition or knockdown of SIRT2 decreased, while overexpression of SIRT2 increased, OXPHOS activity and differentiation in CRC cells. Consistently, inhibition or knockdown or SIRT2 attenuated the differentiation induced by Wnt/β-catenin inhibition. These results demonstrate that SIRT2 is a novel target gene of the Wnt/β-catenin signaling and contributes to the differentiation of CRC cells.

Mitochondrial Sirtuins and Doxorubicin-induced Cardiotoxicity

Doxorubicin (DOX) is the most effective and extensively used treatment for many tumors. However, its clinical use is hampered by its cardiotoxicity. DOX-induced mitochondrial dysfunction, which causes reactive oxygen species (ROS) generation, cardiomyocyte death, bioenergetic failure, and decreased cardiac function, is a very important mechanism of cardiotoxicity. These cellular processes are all linked by mitochondrial sirtuins (SIRT3-SIRT4). Mitochondrial sirtuins preserve mitochondrial function by increasing mitochondrial metabolism, inhibiting ROS generation by activating the antioxidant enzyme manganese-dependent superoxide dismutase (MnSOD), decreasing apoptosis by activating the forkhead homeobox type O (FOXO) and P53 pathways, and increasing autophagy through AMP-activated protein kinase (AMPK)/mTOR signaling. Thus, sirtuins function at the control point of many mechanisms involved in DOX-induced cardiotoxicity. In this review, we focus on the role of mitochondrial sirtuins in mitochondrial biology and DOX-induced cardiotoxicity. A further aim is to highlight other mitochondrial processes, such as autophagy (mitophagy) and mitochondrial quality control (MQC), for which the effect of mitochondrial sirtuins on cardiotoxicity is unknown.

NAD+ metabolism, stemness, the immune response, and cancer

NAD⁺ was discovered during yeast fermentation, and since its discovery, its important roles in redox metabolism, aging, and longevity, the immune system and DNA repair have been highlighted. A deregulation of the NAD⁺ levels has been associated with metabolic diseases and aging-related diseases, including neurodegeneration, defective immune responses, and cancer. NAD⁺ acts as a cofactor through its interplay with NADH, playing an essential role in many enzymatic reactions of energy metabolism, such as glycolysis, oxidative phosphorylation, fatty acid oxidation, and the TCA cycle. NAD⁺ also plays a role in deacetylation by sirtuins and ADP ribosylation during DNA damage/repair by PARP proteins. Finally, different NAD hydrolase proteins also consume NAD⁺ while converting it into ADP-ribose or its cyclic counterpart. Some of these proteins, such as CD38, seem to be extensively involved in the immune response. Since NAD cannot be taken directly from food, NAD metabolism is essential, and NAMPT is the key enzyme recovering NAD from nicotinamide and generating most of the NAD cellular pools. Because of the complex network of pathways in which NAD⁺ is essential, the important role of NAD⁺ and its key generating enzyme, NAMPT, in cancer is understandable. In the present work, we review the role of NAD⁺ and NAMPT in the ways that they may influence cancer metabolism, the immune system, stemness, aging, and cancer. Finally, we review some ongoing research on therapeutic approaches.