Mitochondrial Sirtuins in Parkinson’s Disease

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

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

Succinylation modification: a potential therapeutic target in stroke

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

Dose-dependent exposure to indoxyl sulfate alters AHR signaling, sirtuins gene expression, oxidative DNA damage, and bone mineral status in rats

Indoxyl sulfate (IS), an agonist of aryl hydrocarbon receptors (AhR), can accumulate in patients with chronic kidney disease, but its direct effect on bone is not clear. The present study investigated the effect of chronic exposure to low (100 mg/kg b.w.; 100 IS) and high (200 mg/kg b.w.; 200 IS) dose of IS on bone AhR pathway, sirtuins (SIRTs) expression, oxidative DNA damage and bone mineral status in Wistar rats. The accumulation of IS was observed only in trabecular bone tissue in both doses. The differences were observed in the bone parameters, depending on the applied IS dose. The exposure to 100 IS increased AhR repressor (AhRR)-CYP1A2 gene expression, which was associated with SIRT-1, SIRT-3 and SIRT-7 expression. At the low dose group, the oxidative DNA damage marker was unchanged in the bone samples, and it was inversely related to the abovementioned SIRTs expression. In contrast, the exposure to 200 IS reduced the expression of AhRR, CYP1A, SIRT-3 and SIRT-7 genes compared to 100 IS. The level of oxidative DNA damage was higher in trabecular bone in 200 IS group. Femoral bone mineral density was decreased, and inverse relations were noticed between the level of trabecular oxidative DNA damage and parameters of bone mineral status. In conclusion, IS modulates AhR-depending signaling affecting SIRTs expression, oxidative DNA damage and bone mineral status in a dose dependent manner.

A review on SIRT3 and its natural small molecule activators as a potential Preventive and therapeutic target

Sirtuins (SIRTs) were originally characterized by yeast Sir2 as a lifespan regulator that is conserved in all three structural domains of bacteria, archaea and eukaryotes and belong to histone deacetylases consisting of seven members (SIRT1-SIRT7). Surprisingly, SIRTs have been shown to play important regulatory roles in almost all cellular functions, including mitochondrial biogenesis, oxidative stress, inflammation, cell growth, energy metabolism, neural function, and stress resistance. Among the SIRT members, sirtuin 3 (SIRT3) is one of the most important deacetylases that regulates the mitochondrial acetylation and plays a role in pathological processes, such as metabolism, DNA repair, oxidative stress, apoptosis and ferroptosis. Therefore, SIRT3 is considered as a potential target for the treatment of a variety of pathological diseases, including metabolic diseases, neurodegenerative diseases, age-related diseases and others. Furthermore, the isolation, screening, and development of SIRT3 signaling agonists, especially from natural products, have become a widely investigated objective. This paper describes the structure of SIRT3 protein, discusses the pathological process of SIRT3-mediated acetylation modification, and reviews the role of SIRT3 in diseases, SIRT3 activators and its related disease studies.

Sirtuins mediate mitochondrial quality control mechanisms: a novel therapeutic target for osteoporosis

Mitochondria plays a role in cell differentiation and apoptosis processes. Maintaining mitochondrial function is critical, and this involves various aspects of mitochondrial quality control such as protein homeostasis, biogenesis, dynamics, and mitophagy. Osteoporosis, a metabolic bone disorder, primarily arises from two factors: the dysregulation between lipogenic and osteogenic differentiation of aging bone marrow mesenchymal stem cells, and the imbalance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Mitochondrial quality control has the potential to mitigate or even reverse the effects. Among the Sirtuin family, consisting of seven Sirtuins (SIRT1-7), SIRT1-SIRT6 play a crucial role in maintaining mitochondrial quality control. Additionally, SIRT1, SIRT3, SIRT6, and SIRT7 are directly involved in normal bone development and homeostasis by modulating bone cells. However, the precise mechanism by which these Sirtuins exert their effects remains unclear. This article reviews the impact of various aspects of mitochondrial quality control on osteoporosis, focusing on how SIRT1, SIRT3, and SIRT6 can improve osteoporosis by regulating mitochondrial protein homeostasis, biogenesis, and mitophagy. Furthermore, we provide an overview of the current state of clinical and preclinical drugs that can activate Sirtuins to improve osteoporosis. Specific Sirtuin-activating compounds are effective, but further studies are needed. The findings of this study may offer valuable insights for future research on osteoporosis and the development of clinical prevention and therapeutic target strategies.

Dietary flavonoids may have a protective and therapeutic effect in Parkinson disease: A systematic review

Parkinson disease (PD) is characterized by the loss of dopaminergic neurons because of oxidative stress and neuroinflammation. Polyphenols in vegetables, known for their high antioxidant capacity, may prevent the onset, or delay the progression of the disease; among these, flavonoids are the most abundant class of polyphenols in foods. Clinical and cohort studies have evaluated the effect of polyphenol consumption on the risk of developing PD or of attenuating the symptoms after diagnosis; therefore, it is necessary to integrate the scientific evidence into making dietary recommendations. The objective of this study was to perform a systematic review of randomized controlled trials and cohort studies that have investigated the use of polyphenols in PD. The studies were identified through the PubMed, Science Direct, Scielo, and Web of Science databases. A total of 1100 studies were found; these were analyzed and filtered by 2 independent reviewers. After completion, 5 studies were included (3 randomized controlled trials and 2 cohort studies). The consumption of flavonoids, anthocyanins, or 2-5 servings/week of specific foods (apples, red wine, blueberries, and strawberries) reduces the risk of PD and associated mortality. Treatment with licorice, curcumin, or cocoa, which are rich in flavonoids and other polyphenols, improves motor function in PD patients. No statistically significant differences were found in quality of life, disease progression or nonmotor symptoms such as cognitive ability and mood. Although cohort studies suggest a neuroprotective effect, further clinical studies are urgently needed to evaluate the effect of specific flavonoids and other polyphenols in PD.

Flavonoids: Their putative neurologic roles, epigenetic changes, and gut microbiota alterations in Parkinson's disease

Parkinson's Disease (PD), a neurodegenerative disorder, is characterized by the degeneration of progressive dopaminergic (DA) neurons in the substantia nigra region of the human midbrain. Although just what causes PD remains a mystery, it is known that oxidative stress (OS) as well as mitochondrial dysfunction, neuro-inflammation, and insufficient neurotrophic support play a role in the disease's pathophysiology. Phytochemicals are a diverse small molecule group derived from plants that can be classified into numerous classes on the basis of their biological activities and chemical structure. Of these groups of phytochemicals, the most abundant, which has well-established anti-Parkinson's effects, are polyphenols. Flavonoids, including naringin and naringenin, genistein, kaempferol, anthocyanins, epigallocatechin-3-gallate, and baicalein are plant-based biologically active polyphenols, which have been shown to exhibit therapeutic potential when used as treatment for a variety of pathological illnesses, such as neurodegenerative diseases (NDs) and PD. Recently, it was reported that flavonoids have beneficial effects on PD, such as the protection of DA neurons, improvement of motor and cognitive abilities, regulation of signaling pathways, and modulation of OS and neuro-inflammation. In addition, by changing the composition of bacteria in gut microbiota, flavonoids reduce pathogenic strains and promote the growth of beneficial strains. In this context, the current paper will provide a literature review on the neurological roles that flavonoids play, as one of the most abundant phytochemical families, in PD.

CoCl2 -triggered pseudohypoxic stress induces proteasomal degradation of SIRT4 via polyubiquitination of lysines K78 and K299

SIRT4, together with SIRT3 and SIRT5, comprises the mitochondrially localized subgroup of sirtuins. SIRT4 regulates mitochondrial bioenergetics, dynamics (mitochondrial fusion), and quality control (mitophagy) via its NAD+ -dependent enzymatic activities. Here, we address the regulation of SIRT4 itself by characterizing its protein stability and degradation upon CoCl2 -induced pseudohypoxic stress that typically triggers mitophagy. Interestingly, we observed that of the mitochondrial sirtuins, only the protein levels of SIRT4 or ectopically expressed SIRT4-eGFP decrease upon CoCl2 treatment of HEK293 cells. Co-treatment with BafA1, an inhibitor of autophagosome-lysosome fusion required for autophagy/mitophagy, or the use of the proteasome inhibitor MG132, prevented CoCl2 -induced SIRT4 downregulation. Consistent with the proteasomal degradation of SIRT4, the lysine mutants SIRT4(K78R) and SIRT4(K299R) showed significantly reduced polyubiquitination upon CoCl2 treatment and were more resistant to pseudohypoxia-induced degradation as compared to SIRT4. Moreover, SIRT4(K78R) and SIRT4(K299R) displayed increased basal protein stability as compared to wild-type SIRT4 when subjected to MG132 treatment or cycloheximide (CHX) chase assays. Thus, our data indicate that stress-induced protein degradation of SIRT4 occurs through two mechanisms: (a) via mitochondrial autophagy/mitophagy, and (b) as a separate process via proteasomal degradation within the cytoplasm.

Fatty acid metabolism disorders and potential therapeutic traditional Chinese medicines in cardiovascular diseases

Cardiovascular diseases are currently the primary cause of mortality in the whole world. Growing evidence indicated that the disturbances in cardiac fatty acid metabolism are crucial contributors in the development of cardiovascular diseases. The abnormal cardiac fatty acid metabolism usually leads to energy deficit, oxidative stress, excessive apoptosis, and inflammation. Targeting fatty acid metabolism has been regarded as a novel approach to the treatment of cardiovascular diseases. However, there are currently no specific drugs that regulate fatty acid metabolism to treat cardiovascular diseases. Many traditional Chinese medicines have been widely used to treat cardiovascular diseases in clinics. And modern studies have shown that they exert a cardioprotective effect by regulating the expression of key proteins involved in fatty acid metabolism, such as peroxisome proliferator-activated receptor α and carnitine palmitoyl transferase 1. Hence, we systematically reviewed the relationship between fatty acid metabolism disorders and four types of cardiovascular diseases including heart failure, coronary artery disease, cardiac hypertrophy, and diabetic cardiomyopathy. In addition, 18 extracts and eight monomer components from traditional Chinese medicines showed cardioprotective effects by restoring cardiac fatty acid metabolism. This work aims to provide a reference for the finding of novel cardioprotective agents targeting fatty acid metabolism.

Tricin promoted ATG-7 dependent autophagic degradation of α-synuclein and dopamine release for improving cognitive and motor deficits in Parkinson's disease

Tricin, a natural nontoxic flavonoid distributed in grasses and euphorbia plants, has been reported to scavenge free radicals, possess anti-inflammatory and antioxidative effects. However, its autophagic effect on Parkinson's disease (PD) has not been elucidated. By adopting cellular and C. elegans models of PD, the autophagic effect of tricin was identified based on the level of autophagy markers (LC3-II and p62). Besides, the pharmacological effects on neurotransmitters (dopamine), inflammatory cytokines (IFN γ, TNFα, MCP-1, IL-10, IL-6 and IL-17A), histology (hematoxylin & eosin and Nissl staining) and behavioural pathology (open-field test, hindlimb clasping, Y-maze, Morris water-maze and nest building test) were also confirmed in the A53T-α-synuclein transgenic PD mouse model. Further experiments demonstrated that tricin induced autophagic flux and lowered the level of α-synuclein through AMPK-p70s6K- and ATG7-dependent mechanism. Compared to the existing clinical PD drugs, tricin mitigated pathogenesis and symptoms of PD with no observable side effects. In summary, tricin is proposed as a potential adjuvant remedy or nutraceutical for the prevention and treatment of PD.

Mitochondria and Brain Disease: A Comprehensive Review of Pathological Mechanisms and Therapeutic Opportunities

Mitochondria play a vital role in maintaining cellular energy homeostasis, regulating apoptosis, and controlling redox signaling. Dysfunction of mitochondria has been implicated in the pathogenesis of various brain diseases, including neurodegenerative disorders, stroke, and psychiatric illnesses. This review paper provides a comprehensive overview of the intricate relationship between mitochondria and brain disease, focusing on the underlying pathological mechanisms and exploring potential therapeutic opportunities. The review covers key topics such as mitochondrial DNA mutations, impaired oxidative phosphorylation, mitochondrial dynamics, calcium dysregulation, and reactive oxygen species generation in the context of brain disease. Additionally, it discusses emerging strategies targeting mitochondrial dysfunction, including mitochondrial protective agents, metabolic modulators, and gene therapy approaches. By critically analysing the existing literature and recent advancements, this review aims to enhance our understanding of the multifaceted role of mitochondria in brain disease and shed light on novel therapeutic interventions.

Gut Microbial Metabolome and Dysbiosis in Neurodegenerative Diseases: Psychobiotics and Fecal Microbiota Transplantation as a Therapeutic Approach-A Comprehensive Narrative Review

The comprehensive narrative review conducted in this study delves into the mechanisms of communication and action at the molecular level in the human organism. The review addresses the complex mechanism involved in the microbiota-gut-brain axis as well as the implications of alterations in the microbial composition of patients with neurodegenerative diseases. The pathophysiology of neurodegenerative diseases with neuronal loss or death is analyzed, as well as the mechanisms of action of the main metabolites involved in the bidirectional communication through the microbiota-gut-brain axis. In addition, interventions targeting gut microbiota restructuring through fecal microbiota transplantation and the use of psychobiotics-pre- and pro-biotics-are evaluated as an opportunity to reduce the symptomatology associated with neurodegeneration in these pathologies. This review provides valuable information and facilitates a better understanding of the neurobiological mechanisms to be addressed in the treatment of neurodegenerative diseases.

Sirtuin 1 Expression in Canine Mammary Tumors: A Pilot Study

Sirtuin 1 (SIRT1) is a protein involved in aging, cell protection, and energy metabolism in mammals. Recently, SIRT1 has been intensively studied in medical oncology, but the role of SIRT1 is still controversial, as it has been proposed as both an oncogene and a tumor suppressor. The aim of this study is to investigate the expression of SIRT1 by immunohistochemistry in canine mammary tissues, and by Western blot and immunofluorescence analysis in different canine mammary cell lines. Our results showed a decrease in SIRT1 expression from normal mammary gland tissue, and from benign and well-differentiated malignant tumors (G1) to less differentiated ones (G2-G3). Furthermore, a shift in the subcellular localization of SIRT1 from the nucleus to the cytoplasm was observed in less differentiated malignant tumors. However, further studies are needed to investigate the subcellular localization of SIRT1 in canine cancer cells and the role it may play in oncogenesis in animals.

Iron homeostasis imbalance and ferroptosis in brain diseases

Brain iron homeostasis is maintained through the normal function of blood-brain barrier and iron regulation at the systemic and cellular levels, which is fundamental to normal brain function. Excess iron can catalyze the generation of free radicals through Fenton reactions due to its dual redox state, thus causing oxidative stress. Numerous evidence has indicated brain diseases, especially stroke and neurodegenerative diseases, are closely related to the mechanism of iron homeostasis imbalance in the brain. For one thing, brain diseases promote brain iron accumulation. For another, iron accumulation amplifies damage to the nervous system and exacerbates patients' outcomes. In addition, iron accumulation triggers ferroptosis, a newly discovered iron-dependent type of programmed cell death, which is closely related to neurodegeneration and has received wide attention in recent years. In this context, we outline the mechanism of a normal brain iron metabolism and focus on the current mechanism of the iron homeostasis imbalance in stroke, Alzheimer's disease, and Parkinson's disease. Meanwhile, we also discuss the mechanism of ferroptosis and simultaneously enumerate the newly discovered drugs for iron chelators and ferroptosis inhibitors.

Neurotrophic effects of intermittent fasting, calorie restriction and exercise: a review and annotated bibliography

In the last decades, important progress has been achieved in the understanding of the neurotrophic effects of intermittent fasting (IF), calorie restriction (CR) and exercise. Improved neuroprotection, synaptic plasticity and adult neurogenesis (NSPAN) are essential examples of these neurotrophic effects. The importance in this respect of the metabolic switch from glucose to ketone bodies as cellular fuel has been highlighted. More recently, calorie restriction mimetics (CRMs; resveratrol and other polyphenols in particular) have been investigated thoroughly in relation to NSPAN. In the narrative review sections of this manuscript, recent findings on these essential functions are synthesized and the most important molecules involved are presented. The most researched signaling pathways (PI3K, Akt, mTOR, AMPK, GSK3β, ULK, MAPK, PGC-1α, NF-κB, sirtuins, Notch, Sonic hedgehog and Wnt) and processes (e.g., anti-inflammation, autophagy, apoptosis) that support or thwart neuroprotection, synaptic plasticity and neurogenesis are then briefly presented. This provides an accessible entry point to the literature. In the annotated bibliography section of this contribution, brief summaries are provided of about 30 literature reviews relating to the neurotrophic effects of interest in relation to IF, CR, CRMs and exercise. Most of the selected reviews address these essential functions from the perspective of healthier aging (sometimes discussing epigenetic factors) and the reduction of the risk for neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease) and depression or the improvement of cognitive function.

New ε-N-thioglutaryl-lysine derivatives as SIRT5 inhibitors: Chemical synthesis, kinetic and crystallographic studies

SIRT5 has been implicated in various physiological processes and human diseases, including cancer. Development of new highly potent, selective SIRT5 inhibitors is still needed to investigate disease-related mechanisms and therapeutic potentials. We here report new ε-N-thioglutaryllysine derivatives, which were designed according to SIRT5-catalysed deacylation reactions. These ε-N-thioglutaryllysine derivatives displayed potent SIRT5 inhibition, of which the potential photo-crosslinking derivative 8 manifested most potent inhibition with an IC₅₀ value of 120 nM to SIRT5, and low inhibition to SIRT1-3 and SIRT6. The enzyme kinetic assays revealed that the ε-N-thioglutaryllysine derivatives inhibit SIRT5 by lysine-substrate competitive manner. Co-crystallographic analyses demonstrated that 8 binds to occupy the lysine-substate binding site by making hydrogen-bonding and electrostatic interactions with SIRT5-specific residues, and is likely positioned to react with NAD⁺ and form stable thio-intermediates. Compound 8 was observed to have low photo-crosslinking probability to SIRT5, possibly due to inappropriate position of the diazirine group as observed in SIRT5:8 crystal structure. This study provides useful information for developing drug-like inhibitors and cross-linking chemical probes for SIRT5-related studies.

Therapeutic application of natural products: NAD+ metabolism as potential target

BACKGROUND

Nicotinamide adenine dinucleotide (NAD⁺) metabolism is involved in the entire physiopathological process and is critical to human health. Long-term imbalance in NAD⁺ homeostasis is associated with various diseases, including non-alcoholic fatty liver disease, diabetes mellitus, cardiovascular diseases, neurodegenerative disorders, aging, and cancer, making it a potential target for effective therapeutic strategies. Currently, several natural products that target NAD⁺ metabolism have been widely reported to have significant therapeutic effects, but systematic summaries are lacking.

PURPOSE

To summarize the latest findings on the prevention and treatment of various diseases through the regulation of NAD⁺ metabolism by various natural products in vivo and in vitro models, and evaluate the toxicities of the natural products.

METHODS

PubMed, Web of Science, and ScienceDirect were searched using the keywords "natural products sources," "toxicology," "NAD⁺ clinical trials," and "NAD⁺," and/or paired with "natural products" and "diseases" for studies published within the last decade until January 2023.

RESULTS

We found that the natural products mainly include phenols (curcumin, cyclocurcumin, 4-hydroxybenzyl alcohol, salvianolic acid B, pterostilbene, EGCG), flavonoids (pinostrobin, apigenin, acacetin, tilianin, kaempferol, quercetin, isoliquiritigenin, luteolin, silybin, hydroxysafflor yellow A, scutellarin), glycosides (salidroside), quinones (emodin, embelin, β-LAPachone, shikonin), terpenoids (notoginsenoside R1, ginsenoside F2, ginsenoside Rd, ginsenoside Rb1, ginsenoside Rg3, thymoquinone, genipin), pyrazines (tetramethylpyrazine), alkaloids (evodiamine, berberine), and phenylpropanoids (ferulic acid). These natural products have antioxidant, energy-producing, anti-inflammatory, anti-apoptotic and anti-aging effects, which mainly influence the NAMPT/NAD⁺/SIRT, AMPK/SIRT1/PGC-1α, Nrf2/HO-1, PKCs/PARPs/NF-κB, and AMPK/Nrf2/mTOR signaling pathways, thereby regulating NAD⁺ metabolism to prevent and treat various diseases. These natural products have been shown to be safe, tolerable and have fewer adverse effects in various in vivo and in vitro studies and clinical trials.

CONCLUSION

We evaluated the toxic effects of natural products and summarized the available clinical trials on NAD⁺ metabolism, as well as the recent advances in the therapeutic application of natural products targeting NAD⁺ metabolism, with the aim to provide new insights into the treatment of multiple disorders.

Mitochondria: It is all about energy

Mitochondria play a key role in both health and disease. Their function is not limited to energy production but serves multiple mechanisms varying from iron and calcium homeostasis to the production of hormones and neurotransmitters, such as melatonin. They enable and influence communication at all physical levels through interaction with other organelles, the nucleus, and the outside environment. The literature suggests crosstalk mechanisms between mitochondria and circadian clocks, the gut microbiota, and the immune system. They might even be the hub supporting and integrating activity across all these domains. Hence, they might be the (missing) link in both health and disease. Mitochondrial dysfunction is related to metabolic syndrome, neuronal diseases, cancer, cardiovascular and infectious diseases, and inflammatory disorders. In this regard, diseases such as cancer, Alzheimer's, Parkinson's, amyotrophic lateral sclerosis (ALS), chronic fatigue syndrome (CFS), and chronic pain are discussed. This review focuses on understanding the mitochondrial mechanisms of action that allow for the maintenance of mitochondrial health and the pathways toward dysregulated mechanisms. Although mitochondria have allowed us to adapt to changes over the course of evolution, in turn, evolution has shaped mitochondria. Each evolution-based intervention influences mitochondria in its own way. The use of physiological stress triggers tolerance to the stressor, achieving adaptability and resistance. This review describes strategies that could recover mitochondrial functioning in multiple diseases, providing a comprehensive, root-cause-focused, integrative approach to recovering health and treating people suffering from chronic diseases.

SIRT4 in ageing

Ageing is a phenomenon in which cells, tissues and organs undergo systemic pathological changes as individuals age, leading to the occurrence of ageing-related diseases and the end of life. It is associated with many phenotypes known as ageing characteristics, such as genomic instability, nutritional imbalance, mitochondrial dysfunction, cell senescence, stem cell depletion, and an altered microenvironment. The sirtuin family (SIRT), known as longevity proteins, is thought to delay ageing and prolong life, and mammals, including humans, have seven family members (SIRT1-7). SIRT4 has been studied less among the sirtuin family thus far, but it has been reported that it has important physiological functions in organisms, such as promoting DNA damage repair, participating in the energy metabolism of three substances, inhibiting inflammatory reactions and apoptosis, and regulating mitochondrial function. Recently, some studies have demonstrated the involvement of SIRT4 in age-related processes, but knowledge in this field is still scarce. Therefore, this review aims to analyse the relationship between SIRT4 and ageing characteristics as well as some age-related diseases (e.g., cardiovascular diseases, metabolic diseases, neurodegenerative diseases and cancer).

Role of SIRT3 in mitochondrial biology and its therapeutic implications in neurodegenerative disorders

Sirtuin 3 (SIRT3), a mitochondrial deacetylase expressed preferentially in high-metabolic-demand tissues including the brain, requires NAD⁺ as a cofactor for catalytic activity. It regulates various processes such as energy homeostasis, redox balance, mitochondrial quality control, mitochondrial unfolded protein response (UPRmt), biogenesis, dynamics and mitophagy by altering protein acetylation status. Reduced SIRT3 expression or activity causes hyperacetylation of hundreds of mitochondrial proteins, which has been linked with neurological abnormalities, neuro-excitotoxicity and neuronal cell death. A body of evidence has suggested, SIRT3 activation as a potential therapeutic modality for age-related brain abnormalities and neurodegenerative disorders.

Dietary Phenolic Compounds: Their Health Benefits and Association with the Gut Microbiota

Oxidative stress causes various diseases, such as type II diabetes and dyslipidemia, while antioxidants in foods may prevent a number of diseases and delay aging by exerting their effects in vivo. Phenolic compounds are phytochemicals such as flavonoids which consist of flavonols, flavones, flavanonols, flavanones, anthocyanidins, isoflavones, lignans, stilbenoids, curcuminoids, phenolic acids, and tannins. They have phenolic hydroxyl groups in their molecular structures. These compounds are present in most plants, are abundant in nature, and contribute to the bitterness and color of various foods. Dietary phenolic compounds, such as quercetin in onions and sesamin in sesame, exhibit antioxidant activity and help prevent cell aging and diseases. In addition, other kinds of compounds, such as tannins, have larger molecular weights, and many unexplained aspects still exist. The antioxidant activities of phenolic compounds may be beneficial for human health. On the other hand, metabolism by intestinal bacteria changes the structures of these compounds with antioxidant properties, and the resulting metabolites exert their effects in vivo. In recent years, it has become possible to analyze the composition of the intestinal microbiota. The augmentation of the intestinal microbiota by the intake of phenolic compounds has been implicated in disease prevention and symptom recovery. Furthermore, the “brain–gut axis”, which is a communication system between the gut microbiome and brain, is attracting increasing attention, and research has revealed that the gut microbiota and dietary phenolic compounds affect brain homeostasis. In this review, we discuss the usefulness of dietary phenolic compounds with antioxidant activities against some diseases, their biotransformation by the gut microbiota, the augmentation of the intestinal microflora, and their effects on the brain–gut axis.

Redox Modulation of Mitochondrial Proteins in the Neurotoxicant Models of Parkinson's Disease

Significance: Mitochondrial proteins regulate the oxidative phosphorylation, cellular metabolism, and free radical generation. Redox modulation alters the mitochondrial proteins and instigates the damage to dopaminergic neurons. Toxicants contribute to Parkinson's disease (PD) pathogenesis in conjunction with aging and genetic factors. While oxidative modulation of a number of mitochondrial proteins is linked to xenobiotic exposure, little is known about its role in the toxicant-induced PD. Understanding the role of redox modulation of mitochondrial proteins in complex cellular events leading to neurodegeneration is highly relevant. Recent Advances: Many toxicants are shown to inhibit complex I or III and elicit free radical production that alters the redox status of mitochondrial proteins. Implication of redox modulation of the mitochondrial proteins makes them a target to comprehend the underlying mechanism of toxicant-induced PD. Critical Issues: Owing to multifactorial etiology, exploration of onset and progression and treatment outcomes needs a comprehensive approach. The article explains about a few mitochondrial proteins that undergo redox changes along with the promising strategies, which help to alleviate the toxicant-induced redox imbalance leading to neurodegeneration. Future Directions: Although mitochondrial proteins are linked to PD, their role in toxicant-induced parkinsonism is not yet completely known. Preservation of antioxidant defense machinery could alleviate the redox modulation of mitochondrial proteins. Targeted antioxidant delivery, use of metal chelators, and activation of nuclear factor erythroid 2-related factor 2, and combinational therapy that encounters multiple free radicals, could ameliorate the redox modulation of mitochondrial proteins and thereby PD progression.

Oxyberberine suppressed the carbon tetrachloride-induced liver fibrosis by inhibiting liver inflammation in a sirtuin 3-dependent manner in mice

Previous studies have shown that oxyberberine (OBB), a novel gut microbiota metabolite of berberine, exhibited prominent protective property against acute liver injury and non-alcoholic fatty liver diseases, however, the effect of OBB on liver fibrosis and its potential mechanisms remain largely unknown. This study was aimed to study the effects of OBB on carbon tetrachloride (CCl4)-induced liver fibrosis and tried to clarify the potential mechanisms by focusing on regulating of sirtuin 3 (SIRT3)-mediated liver inflammation. OBB significantly alleviated the liver injury and fibrosis in CCl4-treated C57/BL6 mouse livers. OBB evidently down-regulated the expression of inflammatory factors and reduced the levels of inflammatory factors in CCl4-treated mouse livers. Noteworthy, CCl4-treated decreased the mRNA and protein expression of SIRT3, and treatment with OBB notably increased the expression of SIRT3 both in transcriptional and translational levels in CCl4-treated mice livers. OBB also suppressed the cell viability of TGF-β1-stimulated JS-1 cells and inhibited the protein expression of α-SMA but increased the expression of SIRT3 in stimulated JS-1 cells. Moreover, depletion of SIRT3 weakened the anti-inflammatory effects of OBB in stimulated JS-1 cells. Interestingly, the anti-liver injury and anti-fibrotic effects of OBB could be available in CCl4-treated WT (129S1/SvImJ) mice but were unavailable in CCl4-treated SIRT3 knockout (KO) mice. In addition, the anti-inflammatory effect of OBB was only found in CCl4-treated WT mice but was not in SIRT3 KO mice. Collectively, these findings suggested that OBB suppressed the liver injury and fibrosis through inhibition of liver inflammation in a SIRT3-dependent manner in CCl4-treated mice.

Proteomic profiling reveals the potential mechanisms and regulatory targets of sirtuin 4 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's mouse model

Introduction

Parkinson's disease (PD), as a common neurodegenerative disease, currently has no effective therapeutic approaches to delay or stop its progression. There is an urgent need to further define its pathogenesis and develop new therapeutic targets. An increasing number of studies have shown that members of the sirtuin (SIRT) family are differentially involved in neurodegenerative diseases, indicating their potential to serve as targets in therapeutic strategies. Mitochondrial SIRT4 possesses multiple enzymatic activities, such as deacetylase, ADP ribosyltransferase, lipoamidase, and deacylase activities, and exhibits different enzymatic activities and target substrates in different tissues and cells; thus, mitochondrial SIRT4 plays an integral role in regulating metabolism. However, the role and mechanism of SIRT4 in PD are not fully understood. This study aimed to investigate the potential mechanism and possible regulatory targets of SIRT4 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice.

Methods

The expression of the SIRT4 protein in the MPTP-induced PD mouse mice or key familial Parkinson disease protein 7 knockout (DJ-1 KO) rat was compared against the control group by western blot assay. Afterwards, quantitative proteomics and bioinformatics analyses were performed to identify altered proteins in the vitro model and reveal the possible functional role of SIRT4. The most promising molecular target of SIRT4 were screened and validated by viral transfection, western blot assay and reverse transcription quantitative PCR (RT-qPCR) assays.

Results

The expression of the SIRT4 protein was found to be altered both in the MPTP-induced PD mouse mice and DJ-1KO rats. Following the viral transfection of SIRT4, a quantitative proteomics analysis identified 5,094 altered proteins in the vitro model, including 213 significantly upregulated proteins and 222 significantly downregulated proteins. The results from bioinformatics analyses indicated that SIRT4 mainly affected the ribosomal pathway, propionate metabolism pathway, peroxisome proliferator-activated receptor (PPAR) signaling pathway and peroxisome pathway in cells, and we screened 25 potential molecular targets. Finally, only fatty acid binding protein 4 (FABP4) in the PPAR signaling pathway was regulated by SIRT4 among the 25 molecules. Importantly, the alterations in FABP4 and PPARγ were verified in the MPTP-induced PD mouse model.

Discussion

Our results indicated that FABP4 in the PPAR signaling pathway is the most promising molecular target of SIRT4 in an MPTP-induced mouse model and revealed the possible functional role of SIRT4. This study provides a reference for future drug development and mechanism research with SIRT4 as a target or biomarker.

Why Is Longevity Still a Scientific Mystery? Sirtuins-Past, Present and Future

The sirtuin system consists of seven highly conserved regulatory enzymes responsible for metabolism, antioxidant protection, and cell cycle regulation. The great interest in sirtuins is associated with the potential impact on life extension. This article summarizes the latest research on the activity of sirtuins and their role in the aging process. The effects of compounds that modulate the activity of sirtuins were discussed, and in numerous studies, their effectiveness was demonstrated. Attention was paid to the role of a caloric restriction and the risks associated with the influence of careless sirtuin modulation on the organism. It has been shown that low modulators' bioavailability/retention time is a crucial problem for optimal regulation of the studied pathways. Therefore, a detailed understanding of the modulator structure and potential reactivity with sirtuins in silico studies should precede in vitro and in vivo experiments. The latest achievements in nanobiotechnology make it possible to create promising molecules, but many of them remain in the sphere of plans and concepts. It seems that solving the mystery of longevity will have to wait for new scientific discoveries.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

New Insights on the Role of Bioactive Food Derivatives in Neurodegeneration and Neuroprotection

Over the last three decades, neurodegenerative diseases have received increasing attention due to their frequency in the aging population and the social and economic burdens they are posing. In parallel, an era's worth of research in neuroscience has shaped our current appreciation of the complex relationship between nutrition and the central nervous system. Particular branches of nutrition continue to galvanize neuroscientists, in particular the diverse roles that bioactive food derivatives play on health and disease. Bioactive food derivatives are nowadays recognized to directly impact brain homeostasis, specifically with respect to their actions on cellular mechanisms of oxidative stress, neuroinflammation, mitochondrial dysfunction, apoptosis and autophagy. However, ambiguities still exist regarding the significance of the influence of bioactive food derivatives on human health. In turn, gut microbiota dysbiosis is emerging as a novel player in the pathogenesis of neurodegenerative diseases. Currently, several routes of communication exist between the gut and the brain, where molecules are either released in the bloodstream or directly transported to the CNS. As such, bioactive food derivatives can modulate the complex ecosystem of the gut-brain axis, thus, targeting this communication network holds promises as a neuroprotective tool. This review aims at addressing one of the emerging aspects of neuroscience, particularly the interplay between food bioactive derivatives and neurodegeneration. We will specifically address the role that polyphenols and omega-3 fatty acids play in preventing neurodegenerative diseases and how dietary intervention complements available pharmacological approaches.

Role of Sirtuins in Physiology and Diseases of the Central Nervous System

Silent information regulators, sirtuins (SIRTs), are a family of enzymes which take part in major posttranslational modifications of proteins and contribute to multiple cellular processes, including metabolic and energetic transformations, as well as regulation of the cell cycle. Recently, SIRTs have gained increased attention as the object of research because of their multidirectional activity and possible role in the complex pathomechanisms underlying human diseases. The aim of this study was to review a current literature evidence of SIRTs' role in the physiology and pathology of the central nervous system (CNS). SIRTs have been demonstrated to be crucial players in the crosstalk between neuroinflammation, neurodegeneration, and metabolic alterations. The elucidation of SIRTs' role in the background of various CNS diseases offers a chance to define relevant markers of their progression and promising candidates for novel therapeutic targets. Possible diagnostic and therapeutic implications from SIRTs-related investigations are discussed, as well as their future directions and associated challenges.

MiR-29a inhibits MPP + - Induced cell death and inflammation in Parkinson's disease model in vitro by potential targeting of MAVS

Parkinson's disease (PD) primarily affects the motor system and is the second most common age-related neurodegenerative disorder after Alzheimer's disease. Mitochondrial complex I deficiency and functional abnormalities are implicated in the development of PD. MicroRNA-29a (miR-29a) has emerged as a critical miRNA in PD. This study aims to investigate the protective role of miR-29a in MPP+ in SH-SY5Y cell lines in vitro PD model by targeting mitochondrial antiviral signaling protein (MAVS). Administration of MPP + inhibited miR-29a expression in SH-SY5Y cell lines. Our findings prove that miR-29a mimic treatment decreased cell death, ROS production, MAVS, p-IRF3, p-NFκBp65, IL-6, cleaved caspase-3, cleaved-PARP, LC3BII, and death while increasing glutathione peroxidase 1 and manganese superoxide dismutase after MPP + treatment in SH-SY5Y cells. Furthermore, MAVS expression was significantly corrected with the above genes in our in vitro model of PD. Luciferase activity analysis also confirmed that miR-29a specific binding 3'UTR of MAVS repressed expression. In conclusion, this research provides novel insight into a neuroprotective pathway of miR-29a and could thus serve as a possible therapeutic target for improving the treatment of PD.