The mTOR/PGC-1α/SIRT3 Pathway Drives Reductive Glutamine Metabolism to Reduce Oxidative Stress Caused by ISKNV in CPB Cells

The role of SIRT3 in homeostasis and cellular health

Mitochondria are responsible for maintaining cellular energy levels, and play a major role in regulating homeostasis, which ensures physiological function from the molecular to whole animal. Sirtuin 3 (SIRT3) is the major protein deacetylase of mitochondria. SIRT3 serves as a nutrient sensor; under conditions of mild metabolic stress, SIRT3 activity is increased. Within the mitochondria, SIRT3 regulates every complex of the electron transport chain, the tricarboxylic acid (TCA) and urea cycles, as well as the mitochondria membrane potential, and other free radical scavengers. This article reviews the role of SIRT3 in regulating homeostasis, and thus physiological function. We discuss the role of SIRT3 in regulating reactive oxygen species (ROS), ATP, immunological function and mitochondria dynamics.

Sirtuins in macrophage immune metabolism: A novel target for cardiovascular disorders

Sirtuins (SIRT1-SIRT7), as a family of NAD+-dependent protein modifying enzymes, have various catalytic functions, such as deacetylases, dealkalylases, and deribonucleases. The Sirtuins family is directly or indirectly involved in pathophysiological processes such as glucolipid metabolism, oxidative stress, DNA repair and inflammatory response through various pathways and assumes an important role in several cardiovascular diseases such as atherosclerosis, myocardial infarction, hypertension and heart failure. A growing number of studies supports that metabolic and bioenergetic reprogramming directs the sequential process of inflammation. Failure of homeostatic restoration leads to many inflammatory diseases, and that macrophages are the central cells involving the inflammatory response and are the main source of inflammatory cytokines. Regulation of cellular metabolism has emerged as a fundamental process controlling macrophage function, but its exact signaling mechanisms remain to be revealed. Understanding the precise molecular basis of metabolic control of macrophage inflammatory processes may provide new approaches for targeting immune metabolism and inflammation. Here, we provide an update of studies in cardiovascular disease on the function and role of sirtuins in macrophage inflammation and metabolism, as well as drug candidates that may interfere with sirtuins, pointing to future prospects in this field.

Parkinson's disease pathology is directly correlated to SIRT3 in human subjects and animal models: Implications for AAV.SIRT3-myc as a disease-modifying therapy

In Parkinson's disease (PD), post-mortem studies in affected brain regions have demonstrated a decline in mitochondrial number and function. This combined with many studies in cell and animal models suggest that mitochondrial dysfunction is central to PD pathology. We and others have shown that the mitochondrial protein deacetylase, SIRT3, has neurorestorative effects in PD models. In this study, to determine whether there is a link between PD pathology and SIRT3, we analysed SIRT3 levels in human subjects with PD, and compared to age-matched controls. In the SNc of PD subjects, SIRT3 was reduced by 56.8 ± 15.5% compared to control, regardless of age (p < 0.05, R = 0.6539). Given that age is the primary risk factor for PD, this finding suggests that reduced SIRT3 may contribute to PD pathology. Next, we measured whether there was a correlation between α-synuclein and SIRT3. In a parallel study, we assessed the disease-modifying potential of SIRT3 over-expression in a seeding model of α-synuclein. In PFF rats, infusion of rAAV1.SIRT3-myc reduced abundance of α-synuclein inclusions by 30.1 ± 18.5%. This was not observed when deacetylation deficient SIRT3H248Y was transduced, demonstrating the importance of SIRT3 deacetylation in reducing α-synuclein aggregation. These studies confirm that there is a clear difference in SIRT3 levels in subjects with PD compared to age-matched controls, suggesting a link between SIRT3 and the progression of PD. We also demonstrate that over-expression of SIRT3 reduces α-synuclein aggregation, further validating AAV.SIRT3-myc as a potential disease-modifying solution for PD.

Targeting Mitochondrial Sirtuins in Age-Related Neurodegenerative Diseases and Fibrosis

Aging is a natural and complex biological process that is associated with widespread functional declines in numerous physiological processes, terminally affecting multiple organs and tissues. Fibrosis and neurodegenerative diseases (NDs) often occur with aging, imposing large burdens on public health worldwide, and there are currently no effective treatment strategies for these diseases. Mitochondrial sirtuins (SIRT3-5), which are members of the sirtuin family of NAD+-dependent deacylases and ADP-ribosyltransferases, are capable of regulating mitochondrial function by modifying mitochondrial proteins that participate in the regulation of cell survival under various physiological and pathological conditions. A growing body of evidence has revealed that SIRT3-5 exert protective effects against fibrosis in multiple organs and tissues, including the heart, liver, and kidney. SIRT3-5 are also involved in multiple age-related NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Furthermore, SIRT3-5 have been noted as promising targets for antifibrotic therapies and the treatment of NDs. This review systematically highlights recent advances in knowledge regarding the role of SIRT3-5 in fibrosis and NDs and discusses SIRT3-5 as therapeutic targets for NDs and fibrosis.

Effects of Different Dietary Starch Sources and Digestible Lysine Levels on Carcass Traits, Serum Metabolites, Liver Lipid and Breast Muscle Protein Metabolism in Broiler Chickens

This study investigated the effects of digestible lysine (dLys) in different dietary starch sources on liver lipid metabolism and breast muscle protein metabolism in broiler chickens. The experimental design was a 3 × 3 two-factor completely randomized design. A total of 702 one-day-old male Arbor Acres Plus broilers were randomly divided into nine treatments of six replicate cages with thirteen birds each. The treatments consisted of three different starch sources (corn, cassava and waxy corn) with three different dLys levels (1.08%, 1.20% and 1.32%). The trial lasted from 1 to 21 days. Carcass traits, serum metabolites, breast muscle protein and liver lipid metabolism were evaluated. A significant interaction effect (p < 0.05) for dietary starch sources and dLys levels was noted in the percentage of abdominal fat and gene expression related to breast muscle protein metabolism throughout the experimental period. The waxy corn starch diet and a 1.08% dLys level in the diet increased both the percentage of abdominal fat (p < 0.01) and blood total cholesterol (p < 0.05) in the broilers. The waxy corn starch diet significantly upregulated the mRNA expressions of Eif4E, AMPK, FABP1, ACC and CPT1 (p < 0.05). The 1.32% dLys level significantly upregulated the mRNA expressions of mTOR, S6K1, Eif4E, AMPK and PPARα (p < 0.05) and significantly downregulated the mRNA expressions of MuRF and Atrogin-1 (p < 0.05). In summary, the waxy corn starch diet resulted in significantly higher expression levels of fat-synthesis-related genes than lipolysis-related genes, leading to abdominal fat deposition in broilers. Increasing the level of dLys in the diet increased the protein content in muscle by promoting protein synthesis and inhibiting protein degradation and also promoted the expression of lipolysis-related genes, thereby degrading the generation of abdominal fat in broilers. Our findings signify that increasing the dLys level to 1.32% when using the waxy corn starch diet could improve carcass traits.

High-throughput virtual screening of marine algae metabolites as high-affinity inhibitors of ISKNV major capsid protein: An analysis of in-silico models and DFT calculation to find novel drug molecules for fighting infectious spleen and kidney necrosis virus (ISKNV)

Infectious Spleen and Kidney Necrosis Virus (ISKNV) is linked to severe infections that cause significant financial losses in global aquaculture. ISKNV enters the host cell through its major capsid protein (MCP), and the resulting infection can lead to mass mortality of fish. Even though several drugs and vaccines are at various stages of clinical testing, none are currently available. Thus, we sought to assess the potential of seaweed compounds to block viral entrance by inhibiting the MCP. The Seaweed Metabolite Database (1110 compounds) was assessed for potential antiviral activity against ISKNV using high throughput virtual screening. Forty compounds with docking scores of ≥8.0 kcal/mol were screened further. The inhibitory molecules BC012, BC014, BS032, and RC009 were predicted by the docking and MD techniques to bind the MCP protein significantly with binding affinities of -9.2, -9.2, -9.9, and -9.4 kcal/mol, respectively. Also, ADMET characteristics of the compounds indicated drug-likeness. According to this study, marine seaweed compounds may operate as viral entrance inhibitors. For their efficacy to be established, in-vitro and in-vivo testing is required.

Rapamycin ameliorates brain damage and maintains mitochondrial dynamic balance in diabetic rats subjected to middle cerebral artery occlusion

To investigate the effect of rapamycin on mitochondrial dynamic balance in diabetic rats subjected to cerebral ischemia-reperfusion injury. Male Sprague Dawley (SD) rats (n = 78) were treated with high fat diet combined with streptozotocin injection to construct diabetic model in rats. Transient middle cerebral artery occlusion (MCAO) of 2 hours was induced and the brains were harvested after 1 and 3 days of reperfusion. Rapamycin was injected intraperitoneally for 3 days prior to and immediately after operation, once a day. The neurological function was assessed, infarct volumes were measured and HE staining as well as immunohistochemistry were performed. The protein of hippocampus was extracted and Western blotting were performed to detect the levels of mTOR, mitochondrial dynamin related proteins (DRP1, p-DRP1, OPA1), SIRT3, and Nix/BNIP3L. Diabetic hyperglycemia worsened the neurological function performance (p < 0.01), enlarged infarct size (p < 0.01) and increased ischemic neuronal cell death (p < 0.01). The increased damage was associated with elevations of p-mTOR, p-S6, and p-DRP1; and suppressions of SIRT3 and Nix/BNIP3L. Rapamycin ameliorated diabetes-enhanced ischemic brain damage and reversed the biomarker alterations caused by diabetes. High glucose activated mTOR pathway and caused mitochondrial dynamics toward fission. The protective effect of rapamycin against diabetes-enhanced ischemic brain damage was associated with inhibiting mTOR pathway, redressing mitochondrial dynamic imbalance, and elevating SIRT3 and Nix/BNIP3L expression.

Glutamine Transporter SLC1A5 Regulates Ionizing Radiation-Derived Oxidative Damage and Ferroptosis

Ionizing radiation-derived oxidative stress and ferroptosis are one of the most important biological effects on destroying the liver tumor, whereas radioresistance of liver tumor remains a leading cause of radiotherapy (RT) failure mainly because of the protective antiferroptosis, in which oxidative stress and subsequent lipid peroxidation are the key initiators. Thus, it is of great importance to overcome ferroptosis resistance to improve the therapeutic efficacy of RT in liver tumor patients. Irradiation-resistant HepG2 cells (HepG2-IRR) were established by long-term exposure to X-ray (2 to 8 Gy), and targeted metabolomics analysis revealed an obvious increase in intracellular amino acids in HepG2-IRR cells upon ferroptosis stress. Among these amino acids with obvious changes, N-acetylglutamine, a derivative of glutamine, is essential for the redox homeostasis and progression of tumor cells. Interestingly, the treatment of glutamine starvation could promote the ferroptosis effect significantly, whereas glutamine supplementation reversed the ferroptosis effect completely. Consistent with the changes in amino acids pattern, the glutamine transporter SLC1A5 was verified in liver tumor samples from TCGA training and validation cohorts as an independent prognostic amino acid-ferroptosis gene (AFG). A risk score for screening prognosis based on the SLC1A5, SLC7A11, ASNS, and TXNRD1 demonstrated that a high-risk score was correlated with poor survival. In vitro studies had shown that the knockdown of SLC1A5 resulted in a significant decrease in cell viability and promoted lipid peroxidation and oxidative damage introduced by irradiation (10 Gy). Collectively, our findings indicated that SLC1A5 may act as a suppressor gene against ferroptosis and can be a potential target for ionizing radiation mediated effects.

Targeting ACLY efficiently inhibits SARS-CoV-2 replication

The Coronavirus Disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the biggest public health challenge the world has witnessed in the past decades. SARS-CoV-2 undergoes constant mutations and new variants of concerns (VOCs) with altered transmissibility, virulence, and/or susceptibility to vaccines and therapeutics continue to emerge. Detailed analysis of host factors involved in virus replication may help to identify novel treatment targets. In this study, we dissected the metabolome derived from COVID-19 patients to identify key host factors that are required for efficient SARS-CoV-2 replication. Through a series of metabolomic analyses, in vitro, and in vivo investigations, we identified ATP citrate lyase (ACLY) as a novel host factor required for efficient replication of SARS-CoV-2 wild-type and variants, including Omicron. ACLY should be further explored as a novel intervention target for COVID-19.

SIRT3 regulates mitochondrial biogenesis in aging-related diseases

Sirtuin 3 (SIRT3), the main family member of mitochondrial deacetylase, targets the majority of substrates controlling mitochondrial biogenesis via lysine deacetylation and modulates important cellular functions such as energy metabolism, reactive oxygen species production and clearance, oxidative stress, and aging. Deletion of SIRT3 has a deleterious effect on mitochondrial biogenesis, thus leading to the defect in mitochondrial function and insufficient ATP production. Imbalance of mitochondrial dynamics leads to excessive mitochondrial biogenesis, dampening mitochondrial function. Mitochondrial dysfunction plays an important role in several diseases related to aging, such as cardiovascular disease, cancer and neurodegenerative diseases. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) launches mitochondrial biogenesis through activating nuclear respiratory factors. These factors act on genes, transcribing and translating mitochondrial DNA to generate new mitochondria. PGC1α builds a bridge between SIRT3 and mitochondrial biogenesis. This review described the involvement of SIRT3 and mitochondrial dynamics, particularly mitochondrial biogenesis in aging-related diseases, and further illustrated the role of the signaling events between SIRT3 and mitochondrial biogenesis in the pathological process of aging-related diseases.

The Role of Mitochondrial Quality Control in Cognitive Dysfunction in Diabetes

Type 2 diabetes (T2DM) is a well known risk factor for Alzheimer’s disease. Mitochondria are the center of intracellular energy metabolism and the main source of reactive oxygen species. Mitochondrial dysfunction has been identified as a key factor in diabetes-associated brain alterations contributing to neurodegenerative events. Defective insulin signaling may act in concert with neurodegenerative mechanisms leading to abnormalities in mitochondrial structure and function. Mitochondrial dysfunction triggers neuronal energy exhaustion and oxidative stress, leading to brain neuronal damage and cognitive impairment. The normality of mitochondrial function is basically maintained by mitochondrial quality control mechanisms. In T2DM, defects in the mitochondrial quality control pathway in the brain have been found to lead to mitochondrial dysfunction and cognitive impairment. Here, we discuss the association of mitochondrial dysfunction with T2DM and cognitive impairment. We also review the molecular mechanisms of mitochondrial quality control and impacts of mitochondrial quality control on the progression of cognitive impairment in T2DM.

Hallmarks of Metabolic Reprogramming and Their Role in Viral Pathogenesis

Metabolic reprogramming is a hallmark of cancer and has proven to be critical in viral infections. Metabolic reprogramming provides the cell with energy and biomass for large-scale biosynthesis. Based on studies of the cellular changes that contribute to metabolic reprogramming, seven main hallmarks can be identified: (1) increased glycolysis and lactic acid, (2) increased glutaminolysis, (3) increased pentose phosphate pathway, (4) mitochondrial changes, (5) increased lipid metabolism, (6) changes in amino acid metabolism, and (7) changes in other biosynthetic and bioenergetic pathways. Viruses depend on metabolic reprogramming to increase biomass to fuel viral genome replication and production of new virions. Viruses take advantage of the non-metabolic effects of metabolic reprogramming, creating an anti-apoptotic environment and evading the immune system. Other non-metabolic effects can negatively affect cellular function. Understanding the role metabolic reprogramming plays in viral pathogenesis may provide better therapeutic targets for antivirals.