Roles of Mitochondrial Sirtuins in Mitochondrial Function, Redox Homeostasis, Insulin Resistance and Type 2 Diabetes

Excess glucose alone depress young mesenchymal stromal/stem cell osteogenesis and mitochondria activity within hours/days via NAD+/SIRT1 axis

BACKGROUND

The impact of global overconsumption of simple sugars on bone health, which peaks in adolescence/early adulthood and correlates with osteoporosis (OP) and fracture risk decades, is unclear. Mesenchymal stromal/stem cells (MSCs) are the progenitors of osteoblasts/bone-forming cells, and known to decrease their osteogenic differentiation capacity with age. Alarmingly, while there is correlative evidence that adolescents consuming greatest amounts of simple sugars have the lowest bone mass, there is no mechanistic understanding on the causality of this correlation.

METHODS

Bioinformatics analyses for energetics pathways involved during MSC differentiation using human cell information was performed. In vitro dissection of normal versus high glucose (HG) conditions on osteo-/adipo-lineage commitment and mitochondrial function was assessed using multi-sources of non-senescent human and murine MSCs; for in vivo validation, young mice was fed normal or HG-added water with subsequent analyses of bone marrow CD45- MSCs.

RESULTS

Bioinformatics analyses revealed mitochondrial and glucose-related metabolic pathways as integral to MSC osteo-/adipo-lineage commitment. Functionally, in vitro HG alone without differentiation induction decreased both MSC mitochondrial activity and osteogenesis while enhancing adipogenesis by 8 h' time due to depletion of nicotinamide adenine dinucleotide (NAD+), a vital mitochondrial co-enzyme and co-factor to Sirtuin (SIRT) 1, a longevity gene also involved in osteogenesis. In vivo, HG intake in young mice depleted MSC NAD+, with oral NAD+ precursor supplementation rapidly reversing both mitochondrial decline and osteo-/adipo-commitment in a SIRT1-dependent fashion within 1 ~ 5 days.

CONCLUSIONS

We found a surprisingly rapid impact of excessive glucose, a single dietary factor, on MSC SIRT1 function and osteogenesis in youthful settings, and the crucial role of NAD+-a single molecule-on both MSC mitochondrial function and lineage commitment. These findings have strong implications on future global OP and disability risks in light of current worldwide overconsumption of simple sugars.

Sirtuin dysregulation in Parkinson's disease: Implications of acetylation and deacetylation processes

Parkinson's disease (PD) is a progressive neurodegenerative condition that primarily affects motor function and is caused by a gradual decline of dopaminergic neurons in the brain's substantia pars compacta (Snpc) region. Multiple molecular pathways are involved in the pathogenesis, which results in impaired cellular functions and neuronal degeneration. However, the role of sirtuins, a type of NAD+-dependent deacetylase, in the pathogenesis of Parkinson's disease has recently been investigated. Sirtuins are essential for preserving cellular homeostasis because they control a number of biological processes, such as metabolism, apoptosis, and DNA repair. This review shed lights on the dysregulation of sirtuin activity in PD, highlighting the role that acetylation and deacetylation processes play in the development of the disease. Key regulators of protein acetylation, sirtuins have been found to be involved in the aberrant acetylation of vital substrates linked to PD pathology when their balance is out of balance. The hallmark characteristics of PD such as neuroinflammation, oxidative stress, and mitochondrial dysfunction have all been linked to the dysregulation of sirtuin expression and activity. Furthermore, we have also explored how the modulators of sirtuins can be a promising therapeutic intervention in the treatment of PD.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

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.

Autophagy characteristics of phytoestrogens in management and prevention of diseases: A narrative review of in-vivo and in-vitro studies

Phytoestrogens are non-steroid polyphenolic materials present in 300 plants. Regarding their structural similarities to estradiol, phytoestrogens attach to estrogen receptors and display anti- or pro-estrogenic activities. This review explored phytoestrogens' potential advantages and autophagy properties in light of their future application for disease management, highlighting how phytoestrogens could modulate autophagy. Research has examined the prospective benefits of phytoestrogens for the anticipation and management of various conditions, including signs of menopause, tumors, skin deterioration, osteoporosis, heart disease, neurodegenerative conditions, disorders of the immune system, and metabolic syndrome, owing to their therapeutic effects. As phytoestrogens can activate or inhibit autophagy, which has antioxidant, apoptotic, anti-mutagenic, anticancer, transcriptional, and genomic impacts on cancer and aging illnesses, phytoestrogens could influence diseases through the modulation of autophagy. The collaborative research on animal models, utilization of genetic techniques, and administration of pharmacologically active substances has indicated the possible therapeutic benefits of autophagy modulation in various illnesses. Further research is required to illustrate the pathways by which phytoestrogens modulate autophagy and the possible therapeutic effects on these 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).

Emerging Roles of SIRT5 in Metabolism, Cancer, and SARS-CoV-2 Infection

Sirtuin 5 (SIRT5) is a predominantly mitochondrial enzyme catalyzing the removal of glutaryl, succinyl, malonyl, and acetyl groups from lysine residues through a NAD+-dependent deacylase mechanism. SIRT5 is an important regulator of cellular homeostasis and modulates the activity of proteins involved in different metabolic pathways such as glycolysis, tricarboxylic acid (TCA) cycle, fatty acid oxidation, electron transport chain, generation of ketone bodies, nitrogenous waste management, and reactive oxygen species (ROS) detoxification. SIRT5 controls a wide range of aspects of myocardial energy metabolism and plays critical roles in heart physiology and stress responses. Moreover, SIRT5 has a protective function in the context of neurodegenerative diseases, while it acts as a context-dependent tumor promoter or suppressor. In addition, current research has demonstrated that SIRT5 is implicated in the SARS-CoV-2 infection, although opposing conclusions have been drawn in different studies. Here, we review the current knowledge on SIRT5 molecular actions under both healthy and diseased settings, as well as its functional effects on metabolic targets. Finally, we revise the potential of SIRT5 as a therapeutic target and provide an overview of the currently reported SIRT5 modulators, which include both activators and inhibitors.

Implications of altered sirtuins in metabolic regulation and oral cancer

Sirtuins (SIRTs 1-7) are a group of histone deacetylase enzymes with a wide range of enzyme activities that target a range of cellular proteins in the nucleus, cytoplasm, and mitochondria for posttranslational modifications by acetylation (SIRT1, 2, 3, and 5) or ADP ribosylation (SIRT4, 6, and 7). A variety of cellular functions, including mitochondrial functions and functions in energy homeostasis, metabolism, cancer, longevity and ageing, are regulated by sirtuins. Compromised sirtuin functions and/or alterations in the expression levels of sirtuins may lead to several pathological conditions and contribute significantly to alterations in metabolic phenotypes as well as oral carcinogenesis. Here, we describe the basic characteristics of seven mammalian sirtuins. This review also emphasizes the key molecular mechanisms of sirtuins in metabolic regulation and discusses the possible relationships of sirtuins with oral cancers. This review will provide novel insight into new therapeutic approaches targeting sirtuins that may potentially lead to effective strategies for combating oral malignancies.

Mitochondrial alterations in fatty liver diseases

Fatty liver diseases can result from common metabolic diseases, as well as from xenobiotic exposure and excessive alcohol use, all of which have been shown to exert toxic effects on hepatic mitochondrial functionality and dynamics. Invasive or complex methodology limits large-scale investigations of mitochondria in human livers. Nevertheless, abnormal mitochondrial function, such as impaired fatty acid oxidation and oxidative phosphorylation, drives oxidative stress and has been identified as an important feature of human steatohepatitis. On the other hand, hepatic mitochondria can be flexible and adapt to the ambient metabolic condition to prevent triglyceride and lipotoxin accumulation in obesity. Experience from studies on xenobiotics has provided important insights into the regulation of hepatic mitochondria. Increasing awareness of the joint presence of metabolic disease-related (lipotoxic) and alcohol-related liver diseases further highlights the need to better understand their mutual interaction and potentiation in disease progression. Recent clinical studies have assessed the effects of diets or bariatric surgery on hepatic mitochondria, which are also evolving as an interesting therapeutic target in non-alcoholic fatty liver disease. This review summarises the current knowledge on hepatic mitochondria with a focus on fatty liver diseases linked to obesity, type 2 diabetes and xenobiotics.

Garlic (Allium sativum L.) in diabetes and its complications: Recent advances in mechanisms of action

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia and impaired islet secretion that places a heavy burden on the global health care system due to its high incidence rate, long disease course and many complications. Fortunately, garlic (Allium sativum L.), a well-known medicinal plant and functional food without the toxicity and side effects of conventional drugs, has shown positive effects in the treatment of diabetes and its complications. With interdisciplinary development and in-depth exploration, we offer a clear and comprehensive summary of the research from the past ten years, focusing on the mechanisms and development processes of garlic in the treatment of diabetes and its complications, aiming to provide a new perspective for the treatment of diabetes and promote the efficient development of this field.

Sirtuin 1 in Host Defense during Infection

Sirtuins (SIRTs) are members of the class III histone deacetylase family and epigenetically control multiple target genes to modulate diverse biological responses in cells. Among the SIRTs, SIRT1 is the most well-studied, with a role in the modulation of immune and inflammatory responses following infection. The functions of SIRT1 include orchestrating immune, inflammatory, metabolic, and autophagic responses, all of which are required in establishing and controlling host defenses during infection. In this review, we summarize recent information on the roles of SIRT1 and its regulatory mechanisms during bacterial, viral, and parasitic infections. We also discuss several SIRT1 modulators, as potential antimicrobial treatments. Understanding the function of SIRT1 in balancing immune homeostasis will contribute to the development of new therapeutics for the treatment of infection and inflammatory disease.

Disruption of mitochondria-associated ER membranes impairs insulin sensitivity and thermogenic function of adipocytes

The prevalence and healthcare burden of obesity and its related metabolic disorders such as type 2 diabetes (T2D) are increasing rapidly. A better understanding of the pathogenesis of these diseases helps to find the therapeutic strategies. Mitochondria and endoplasmic reticulum (ER) are two important organelles involved in the maintenance of intracellular Ca²⁺ and ROS homeostasis. Their functional defects are thought to participate in the pathogenesis of insulin resistance or T2D. The proper structure and function of the mitochondria-associated ER membranes (MAMs) is required for efficient communication between the ER and mitochondria and defects in MAMs have been shown to play a role in metabolic syndrome and other diseases. However, the detailed mechanism to link MAMs dysfunction and pathogenesis of insulin resistance or T2D remains unclear. In the present study, we demonstrated that the proteins involved in .MAMs structure are upregulated and the formation of MAMs is increased during adipogenic differentiation of 3T3-L1 preadipocytes. Disruption of MAMs by knocking down GRP75, which is responsible for connecting ER and mitochondria, led to the impairment of differentiation and ROS accumulation in 3T3-L1 preadipocytes. Most importantly, the differentiated 3T3-L1 adipocytes with GRP75 knockdown displayed inactivation of insulin signaling pathway upon insulin stimulation. Moreover, GRP75 knockdown impaired thermogenesis and glucose utilization in brown adipocytes, the adipocytes with abundant mitochondria that regulate whole-body energy homeostasis. Taken together, our findings suggest that MAMs formation is essential for promoting mitochondrial function and maintaining a proper redox status to enable the differentiation of preadipocytes and normal functioning such as insulin signaling and thermogenesis in mature adipocytes.

The Role of SIRT3 in Exercise and Aging

The health benefits of regular exercise are well established. Nonetheless, the molecular mechanism(s) responsible for exercise-induced health benefits remain a topic of debate. One of the key cell-signaling candidates proposed to provide exercise-induced benefits is sirtuin 3 (SIRT3). SIRT3, an NAD+ dependent mitochondrial deacetylase, positively modulates many cellular processes, including energy metabolism, mitochondrial biogenesis, and protection against oxidative stress. Although the exercise-induced change in SIRT3 signaling is a potential mechanism contributing to the health advantages of exercise on aging, studies investigating the impact of exercise on SIRT3 abundance in cells provide conflicting results. To resolve this conundrum, this narrative review provides a detailed analysis of the role that exercise-induced changes in SIRT3 play in providing the health and aging benefits associated with regular physical activity. We begin with an overview of SIRT3 function in cells followed by a comprehensive review of the impact of exercise on SIRT3 expression in humans and other mammalians. We then discuss the impact of SIRT3 on aging, followed by a thorough analysis of the cell-signaling links between SIRT3 and exercise-induced adaptation. Notably, to stimulate future research, we conclude with a discussion of key unanswered questions related to exercise, aging, and SIRT3 expression.

Sirtuin 3 Deficiency Aggravates Kidney Disease in Response to High-Fat Diet through Lipotoxicity-Induced Mitochondrial Damage

Sirtuin 3 (SIRT3) is the primary mitochondrial deacetylase that controls the antioxidant pathway and energy metabolism. We previously found that renal Sirt3 expression and activity were reduced in mice with type 2 diabetic nephropathy associated with oxidative stress and mitochondrial abnormalities and that a specific SIRT3 activator improved renal damage. SIRT3 is modulated by diet, and to assess whether Sirt3 deficiency aggravates mitochondrial damage and accelerates kidney disease in response to nutrient overloads, wild-type (WT) and Sirt3^−/− mice were fed a high-fat-diet (HFD) or standard diet for 8 months. Sirt3^−/− mice on HFD exhibited earlier and more severe albuminuria compared to WT mice, accompanied by podocyte dysfunction and glomerular capillary rarefaction. Mesangial matrix expansion, tubular vacuolization and inflammation, associated with enhanced lipid accumulation, were more evident in Sirt3^−/− mice. After HFD, kidneys from Sirt3^−/− mice showed more oxidative stress than WT mice, mitochondria ultrastructural damage in tubular cells, and a reduction in mitochondrial mass and energy production. Our data demonstrate that Sirt3 deficiency renders mice more prone to developing oxidative stress and mitochondrial abnormalities in response to HFD, resulting in more severe kidney diseases, and this suggests that mitochondria protection may be a method to prevent HFD-induced renal injury.

Therapeutic Potential and Activity Modulation of the Protein Lysine Deacylase Sirtuin 5

Sirtiun 5 (SIRT5) is a NAD+-dependent protein lysine deacylase primarily located in mitochondria. SIRT5 displays an affinity for negatively charged acyl groups and mainly catalyzes lysine deglutarylation, desuccinylation, and demalonylation while possessing weak deacetylase activity. SIRT5 substrates play crucial roles in metabolism and reactive oxygen species (ROS) detoxification, and SIRT5 activity is protective in neuronal and cardiac physiology. Moreover, SIRT5 exhibits a dichotomous role in cancer, acting as context-dependent tumor promoter or suppressor. Given its multifaceted activity, SIRT5 is a promising target in the design of activators or inhibitors that might act as therapeutics in many pathologies, including cancer, cardiovascular disorders, and neurodegeneration. To date, few cellular-active peptide-based SIRT5 inhibitors (SIRT5i) have been described, and potent and selective small-molecule SIRT5i have yet to be discovered. In this perspective, we provide an outline of SIRT5's roles in different biological settings and describe SIRT5 modulators in terms of their mode of action, pharmacological activity, and structure-activity relationships.

A Comprehensive Overview of the Complex Role of Oxidative Stress in Aging, The Contributing Environmental Stressors and Emerging Antioxidant Therapeutic Interventions

Introduction

Aging is a normal, inevitable, irreversible, and progressive process which is driven by internal and external factors. Oxidative stress, that is the imbalance between prooxidant and antioxidant molecules favoring the first, plays a key role in the pathophysiology of aging and comprises one of the molecular mechanisms underlying age-related diseases. However, the oxidative stress theory of aging has not been successfully proven in all animal models studying lifespan, meaning that altering oxidative stress/antioxidant defense systems did not always lead to a prolonged lifespan, as expected. On the other hand, animal models of age-related pathological phenotypes showed a well-correlated relationship with the levels of prooxidant molecules. Therefore, it seems that oxidative stress plays a more complicated role than the one once believed and this role might be affected by the environment of each organism. Environmental factors such as UV radiation, air pollution, and an unbalanced diet, have also been implicated in the pathophysiology of aging and seem to initiate this process more rapidly and even at younger ages.

Aim

The purpose of this review is to elucidate the role of oxidative stress in the physiology of aging and the effect of certain environmental factors in initiating and sustaining this process. Understanding the pathophysiology of aging will contribute to the development of strategies to postpone this phenomenon. In addition, recent studies investigating ways to alter the antioxidant defense mechanisms in order to prevent aging will be presented.

Conclusions

Careful exposure to harmful environmental factors and the use of antioxidant supplements could potentially affect the biological processes driving aging and slow down the development of age-related diseases. Maybe a prolonged lifespan could not be achieved by this strategy alone, but a longer healthspan could also be a favorable target.

GrpE is involved in mitochondrial function and is an effective target for RNAi-mediated pest and arbovirus control

Laodelphax striatellus is a sap-feeding pest and the main insect vector of rice stripe virus (RSV). There is an urgent need to identify molecular targets to control this insect pest and plant arboviruses. In this study, we identified a L. striatellus gene (named LsGrpE) encoding a GroP-E-like protein. We found that the LsGrpE protein localized to mitochondria. Using gene-specific dsRNA to interfere with the expression of LsGrpE led to a significant increase in insect mortality, and most of the surviving insects could not develop into adults. Further analyses revealed that LsGrpE deficiency caused mitochondrial dysfunction and inhibited the insulin pathway, resulting in diabetes-like symptoms such as elevated blood sugar, inactive behaviour, developmental delay, and death. In addition, LsGrpE deficiency significantly reduced the RSV titre in surviving L. striatellus, and indirectly prevented viral vertical transmission by reducing the number of adults. We generated transgenic rice plants expressing LsGrpE-specific dsRNA, and the dsRNA was acquired by L. striatellus during feeding, resulting in increased insect mortality and the prevention of arboviral transmission. This study clarifies the function of LsGrpE and demonstrates that LsGrpE can be used as a molecular target of plant-generated dsRNA to resist this sap-feeding pest, a17nd therefore, its transmitted arboviruses.

Regulatory Effects of Statins on SIRT1 and Other Sirtuins in Cardiovascular Diseases

Adverse cardiovascular disease (CVD) outcomes, such as sudden cardiac death, acute myocardial infarction, and stroke, are often catastrophic. Statins are frequently used to attenuate the risk of CVD-associated morbidity and mortality through their impact on lipids and they may also have anti-inflammatory and other plaque-stabilization effects via different signaling pathways. Different statins, including atorvastatin, rosuvastatin, pravastatin, pitavastatin, and simvastatin, are administered to manage circulatory lipid levels. In addition, statins are potent inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase via modulating sirtuins (SIRTs). During the last two decades, SIRTs have been investigated in mammals and categorized as a family of nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases (HDACs) with significant oxidative stress regulatory function in cells—a key factor in extending cell lifespan. Recent work has demonstrated that statins upregulate SIRT1 and SIRT2 and downregulate SIRT6 in both in vitro and in vivo experiments and clinical trials. As statins show modulatory properties, especially in CVDs, future investigations are needed to delineate the role of SIRT family members in disease and to expand knowledge about the effects of statins on SIRTs. Here, we review what is currently known about the impact of statins on SIRTs and how these changes correlate with disease, particularly CVDs.

Sirtuin deficiency and the adverse effects of fructose and uric acid synthesis

Fructose metabolism and hyperuricemia have been shown to drive insulin resistance, metabolic syndrome, hepatic steatosis, hypertension, inflammation, and innate immune reactivity in experimental studies. We suggest that these adverse effects are at least in part the result of suppressed activity of sirtuins, particularly Sirtuin1. Deficiency of sirtuin deacetylations is a consequence of reduced bioavailability of its cofactor nicotinamide adenine dinucleotide (NAD+). Uric acid-induced inflammation and oxidative stress consume NAD+ and activation of the polyol pathway of fructose and uric acid synthesis also reduces the NAD+-to-NADH ratio. Variability in the compensatory regeneration of NAD+ could result in variable recovery of sirtuin activity that may explain the inconsistent benefits of treatments directed to reduce uric acid in clinical trials. Here, we review the pathogenesis of the metabolic dysregulation driven by hyperuricemia and their potential relationship with sirtuin deficiency. In addition, we discuss therapeutic options directed to increase NAD+ and sirtuins activity that may improve the adverse effects resulting from fructose and uric acid synthesis.

Mitochondrial Sirtuins in Chronic Degenerative Diseases: New Metabolic Targets in Colorectal Cancer

Sirtuins (SIRTs) are a family of class III histone deacetylases (HDACs) consisting of seven members, widely expressed in mammals. SIRTs mainly participate in metabolic homeostasis, DNA damage repair, cell survival, and differentiation, as well as other cancer-related biological processes. Growing evidence shows that SIRTs have pivotal roles in chronic degenerative diseases, including colorectal cancer (CRC), the third most frequent malignant disease worldwide. Metabolic alterations are gaining attention in the context of CRC development and progression, with mitochondrion representing a crucial point of complex and intricate molecular mechanisms. Mitochondrial SIRTs, SIRT2, SIRT3, SIRT4 and SIRT5, control mitochondrial homeostasis and dynamics. Here, we provide a comprehensive review on the latest advances on the role of mitochondrial SIRTs in the initiation, promotion and progression of CRC. A deeper understanding of the pathways by which mitochondrial SIRTs control CRC metabolism may provide new molecular targets for future innovative strategies for CRC prevention and therapy.

Mitochondrial sirtuins genetic variations and gastric cancer risk: Evidence from retrospective observational study

AIMS

The purpose of the present study was to analyze the role of selected polymorphisms of SIRT3 and SIRT5 in gastric carcinogenesis.

METHODS

For this study, 500 blood samples of GC patients and 500 blood samples of healthy individuals were collected. Six selected polymorphisms of mitochondrial sirtuins were analyzed for analysis using Tetra-Arms PCR followed by DNA sequencing.

RESULTS

Mutant allele frequencies of selected polymorphisms [rs3782116 (p < 0.0001), rs6598072 (p < 0.0001) and rs11246020 (p < 0.0001), rs938222 (p = 0.0136), rs3757261 (p = 0.0005) and rs2841511 (p = 0.0015)] were observed significant higher in GC patients vs controls. Haplotype analysis was performed, and 51 haplotypes were generated using haploview software. Among these haplotypes, eleven haplotypes were found associated with a significantly increased risk of GC. Furthermore, SNP-SNP interaction showed a significant correlation between studied SNPs and GC risk. Kaplan Meier analysis showed that mutant allele frequencies of selected polymorphisms are linked with a significant decrease in survival of GC patients CONCLUSIONS: It can be concluded that selected SNPs may be associated with enhanced risk of GC and hence can be potential prognostic markers for prognosis and predisposition of GC.

Redox Homeostasis in Cardiovascular Disease: The Role of Mitochondrial Sirtuins

Cardiovascular disease (CVD) is still the leading cause of death worldwide. Despite successful advances in both pharmacological and lifestyle strategies to fight well-established risk factors, the burden of CVD is still increasing. Therefore, it is necessary to further deepen our knowledge of the pathogenesis of the disease for developing novel therapies to limit even more its related morbidity and mortality. Oxidative stress has been identified as a common trait of several manifestations of CVD and could be a promising target for innovative treatments. Mitochondria are a major source of oxidative stress and sirtuins are a family of enzymes that generate different post-translational protein modifications, thus regulating important cellular processes, including cell cycle, autophagy, gene expression, and others. In particular, three sirtuins, SIRT3, SIRT4, and SIRT5 are located within the mitochondrial matrix where they regulate energy production and antioxidant pathways. Therefore, these sirtuins are strongly involved in the balance between oxidant and antioxidant mechanisms. In this review, we summarize the activities of these sirtuins with a special focus on their role in the control of oxidative stress, in relation to energy metabolism, atherosclerosis, and CVD.

Astaxanthin as a Novel Mitochondrial Regulator: A New Aspect of Carotenoids, beyond Antioxidants

Astaxanthin is a member of the carotenoid family that is found abundantly in marine organisms, and has been gaining attention in recent years due to its varied biological/physiological activities. It has been reported that astaxanthin functions both as a pigment, and as an antioxidant with superior free radical quenching capacity. We recently reported that astaxanthin modulated mitochondrial functions by a novel mechanism independent of its antioxidant function. In this paper, we review astaxanthin’s well-known antioxidant activity, and expand on astaxanthin’s lesser-known molecular targets, and its role in mitochondrial energy metabolism.

Mitochondrial sirtuins, metabolism, and aging

Maintaining metabolic homeostasis is essential for cellular and organismal health throughout life. Of the multiple signaling pathways that regulate metabolism, such as PI3K/AKT, mTOR, AMPK, and sirtuins, mammalian sirtuins also play unique roles in aging. By understanding how sirtuins regulate metabolic processes, we can start to understand how they slow down or accelerate biological aging. Here, we review the biology of SIRT3, SIRT4, and SIRT5, known as the mitochondrial sirtuins due to their localization in the mitochondrial matrix. First, we will focus on canonical pathways that regulate metabolism more broadly and how these are integrated with aging regulation. Then, we will summarize the current knowledge about functional differences between SIRT3, SIRT4, and SIRT5 in metabolic control and integration in signaling networks. Finally, we will discuss how mitochondrial sirtuins regulate processes associated with aging and oxidative stress, calorie restriction and disease.

Meta-Inflammation and Metabolic Reprogramming of Macrophages in Diabetes and Obesity: The Importance of Metabolites

Diabetes mellitus type II and obesity are two important causes of death in modern society. They are characterized by low-grade chronic inflammation and metabolic dysfunction (meta-inflammation), which is observed in all tissues involved in energy homeostasis. A substantial body of evidence has established an important role for macrophages in these tissues during the development of diabetes mellitus type II and obesity. Macrophages can activate into specialized subsets by cues from their microenvironment to handle a variety of tasks. Many different subsets have been described and in diabetes/obesity literature two main classifications are widely used that are also defined by differential metabolic reprogramming taking place to fuel their main functions. Classically activated, pro-inflammatory macrophages (often referred to as M1) favor glycolysis, produce lactate instead of metabolizing pyruvate to acetyl-CoA, and have a tricarboxylic acid cycle that is interrupted at two points. Alternatively activated macrophages (often referred to as M2) mainly use beta-oxidation of fatty acids and oxidative phosphorylation to create energy-rich molecules such as ATP and are involved in tissue repair and downregulation of inflammation. Since diabetes type II and obesity are characterized by metabolic alterations at the organism level, these alterations may also induce changes in macrophage metabolism resulting in unique macrophage activation patterns in diabetes and obesity. This review describes the interactions between metabolic reprogramming of macrophages and conditions of metabolic dysfunction like diabetes and obesity. We also focus on different possibilities of measuring a range of metabolites intra-and extracellularly in a precise and comprehensive manner to better identify the subsets of polarized macrophages that are unique to diabetes and obesity. Advantages and disadvantages of the currently most widely used metabolite analysis approaches are highlighted. We further describe how their combined use may serve to provide a comprehensive overview of the metabolic changes that take place intracellularly during macrophage activation in conditions like diabetes and obesity.

Hesperetin suppresses LPS/high glucose-induced inflammatory responses via TLR/MyD88/NF-κB signaling pathways in THP-1 cells

BACKGROUND/OBJECTIVES

Unregulated inflammatory responses caused by hyperglycemia may induce diabetes complications. Hesperetin, a bioflavonoid, is a glycoside in citrus fruits and is known to have antioxidant and anticarcinogenic properties. However, the effect of inflammation on the diabetic environment has not been reported to date. In this study, we investigated the effect of hesperetin on proinflammatory cytokine secretion and its underlying mechanistic regulation in THP-1 macrophages with co-treatment LPS and hyperglycemic conditions.

MATERIALS/METHODS

THP-1 cells differentiated by PMA (1 μM) were cultured for 48 h in the presence or absence of hesperetin under normoglycemic (5.5 mM/L glucose) or hyperglycemic (25 mM/L glucose) conditions and then treated with LPS (100 ng/mL) for 6 h before harvesting. Inflammation-related proteins and mRNA levels were evaluated by enzyme-linked immunosorbent assay, western blot, and quantitative polymerase chain reaction analyses.

RESULTS

Hesperetin (0-100 μM, 48 h) treatment did not affect cell viability. The tumor necrosis factor-α and interleukin-6 levels increased in cells co-treated with LPS under hyperglycemic conditions compared to normoglycemic conditions, and these increases were decreased by hesperetin treatment. The TLR2/4 and MyD88 activity levels increased in cells co-treated with LPS under hyperglycemic conditions compared to normoglycemic conditions; however, hesperetin treatment inhibited the TLR2/4 and MyD88 activity increases. In addition, nuclear factor-κB (NF-κB) and Acetyl-NF-κB levels increased in response to treatment with LPS under hyperglycemic conditions compared to normoglycemic conditions, but those levels were decreased when treated with hesperetin. SIRT3 and SIRT6 expressions were increased by hesperetin treatment.

CONCLUSIONS

Our results suggest that hesperetin may be a potential agent for suppressing inflammation in diabetes.

SIRT3-mediated mitochondrial unfolded protein response weakens breast cancer sensitivity to cisplatin

BACKGROUND

Mitochondrial unfolded protein response plays an important role in the occurrence and development of breast cancer. However, the role of mitochondrial unfolded protein response (UPR^mt) in the sensitivity of breast cancer to cisplatin chemotherapy has not yet been cleared.

OBJECTIVES

The purpose of this study is to explore the role of mitochondrial unfolded protein response in breast cancer sensitivity to cisplatin.

METHODS

In this study, qRT-PCR, Western blotting, Immunofluorescence, CCK-8, Colony formation, Transwell assay and TUNEL staining assay were used to confirm the role of UPR^mt in breast cancer cells treated with cisplatin.

RESULTS

Cisplatin increased the levels of UPR^mt including CLPP, HSP60, LONP1 in MCF7 and MDA-MB-231 cells. UPR^mt inducer Nicotinamide ribose (NR) could promote the proliferation and invasion of breast cancer cells treated with cisplatin. Importantly, SIRT3 was discovered to increase UPR^mt in breast cancer cells and silencing of SIRT3 could inhibit the effect of NR in breast cancer.

CONCLUSIONS

UPR^mt regulated by SIRT3 could protect breast cancer cell from cisplatin. Controlling SIRT3-induced UPR may be a potential therapeutic target to increase the sensitivity of breast cancer chemotherapy.

Potential biomarkers and targets of mitochondrial dynamics

Mitochondrial dysfunction contributes to the imbalance of cellular homeostasis and the development of diseases, which is regulated by mitochondria-associated factors. The present review aims to explore the process of the mitochondrial quality control system as a new source of the potential diagnostic biomarkers and/or therapeutic targets for diseases, including mitophagy, mitochondrial dynamics, interactions between mitochondria and other organelles (lipid droplets, endoplasmic reticulum, endosomes, and lysosomes), as well as the regulation and posttranscriptional modifications of mitochondrial DNA/RNA (mtDNA/mtRNA). The direct and indirect influencing factors were especially illustrated in understanding the interactions among regulators of mitochondrial dynamics. In addition, mtDNA/mtRNAs and proteomic profiles of mitochondria in various lung diseases were also discussed as an example. Thus, alternations of mitochondria-associated regulators can be a new category of biomarkers and targets for disease diagnosis and therapy.

Mitochondrial Sirtuins in Reproduction

Mitochondria act as hubs of numerous metabolic pathways. Mitochondrial dysfunctions contribute to altering the redox balance and predispose to aging and metabolic alterations. The sirtuin family is composed of seven members and three of them, SIRT3-5, are housed in mitochondria. They catalyze NAD+-dependent deacylation and the ADP-ribosylation of mitochondrial proteins, thereby modulating gene expression and activities of enzymes involved in oxidative metabolism and stress responses. In this context, mitochondrial sirtuins (mtSIRTs) act in synergistic or antagonistic manners to protect from aging and aging-related metabolic abnormalities. In this review, we focus on the role of mtSIRTs in the biological competence of reproductive cells, organs, and embryos. Most studies are focused on SIRT3 in female reproduction, providing evidence that SIRT3 improves the competence of oocytes in humans and animal models. Moreover, SIRT3 protects oocytes, early embryos, and ovaries against stress conditions. The relationship between derangement of SIRT3 signaling and the imbalance of ROS and antioxidant defenses in testes has also been demonstrated. Very little is known about SIRT4 and SIRT5 functions in the reproductive system. The final goal of this work is to understand whether sirtuin-based signaling may be taken into account as potential targets for therapeutic applications in female and male infertility.

Progress on mitochondrial silence information regulator family in epilepsy

SIRT3, SIRT4 and SIRT5 are located in mitochondria and also known as mitochondrial sirtuins. They play important roles in regulating many cellular functions including cell survival, cell cycle or apoptosis, DNA repair and metabolism. Mitochondrial sirtuins are involved in the protection of mitochondrial integrity and energy metabolism under stress regulating the expression of neurotransmitter receptors, neurotrophins, extracellular matrix proteins and various transcription factors, thus involved in epileptogenesis triggered by both genetic or acquired factors. Here we review research progress on the actions of mitochondrial sirtuin in epilepsy; and discuss the challenges and perspectives of mitochondrial sirtuin as a potential therapeutic target for epilepsy.

Sirtuins: Potential Therapeutic Targets for Defense against Oxidative Stress in Spinal Cord Injury

Spinal cord injury (SCI) is one of the most incapacitating neurological disorders. It involves complex pathological processes that include a primary injury and a secondary injury phase, or a delayed stage, which follows the primary injury and contributes to the aggravation of the SCI pathology. Oxidative stress, a key pathophysiological event after SCI, contributes to a cascade of inflammation, excitotoxicity, neuronal and glial apoptosis, and other processes during the secondary injury phase. In recent years, increasing evidence has demonstrated that sirtuins are protective toward the pathological process of SCI through a variety of antioxidant mechanisms. Notably, strategies that modulate the expression of sirtuins exert beneficial effects in cellular and animal models of SCI. Given the significance and novelty of sirtuins, we summarize the oxidative stress processes that occur in SCI and discuss the antioxidant effects of sirtuins in SCI. We also highlight the potential of targeting sirtuins for the treatment of SCI.

Understanding the role of histone deacetylase and their inhibitors in neurodegenerative disorders: Current targets and future perspective

Neurodegenerative diseases are a group of pathological conditions that cause motor inc-ordination (jerking movements), cognitive and memory impairments result from degeneration of neurons in a specific area of the brain. Oxidative stress, mitochondrial dysfunction, excitotoxicity, neuroinflammation, neurochemical imbalance and histone deacetylase enzymes (HDAC) are known to play a crucial role in neurodegeneration. HDAC is classified into four categories (class I, II, III and class IV) depending upon their location and functions. HDAC1 and 2 are involved in neurodegeneration, while HDAC3-11 and class III HDACs are beneficial as neuroprotective. HDACs are localized in different parts of the brain- HDAC1 (hippocampus and cortex), HDAC2 (nucleus), HDAC3, 4, 5, 7 and 9 (nucleus and cytoplasm), HDAC6 & HDAC7 (cytoplasm) and HDAC11 (Nucleus, cornus ammonis 1 and spinal cord). In pathological conditions, HDAC up-regulates glutamate, phosphorylation of tau, and glial fibrillary acidic proteins while down-regulating BDNF, Heat shock protein 70 and Gelsolin. Class III HDACs are divided into seven sub-classes (SIRT1-SIRT7). Sirtuins are localized in the different parts of the brain and neuron -Sirt1 (nucleus), Sirt2 (cortex, striatum, hippocampus and spinal cord), Sirt3 (mitochondria and cytoplasm), Sirt4, Sirt5 & Sirt6 (mitochondria), Sirt7 (nucleus) and Sirt8 (nucleolus). SIRTs (1, 3, 4, and 6) are involved in neuronal survival, proliferation and modulating stress response, and SIRT2 is associated with Parkinsonism, Huntington’s disease and Alzheimer’s disease, whereas SIRT6 is only associated with Alzheimer’s disease. In this critical review, we have discussed the mechanisms and therapeutic targets of HDACs that would be beneficial for the management of neurodegenerative disorders.

Editorial of Special Issue "Sirtuins in Health and Disease"

The discovery and characterization of sirtuins as NAD+-dependent deacylases have transformed our understanding of post-translational protein regulation [...].

Dietary and Protective Factors to Halt or Mitigate Progression of Autoimmunity, COVID-19 and Its Associated Metabolic Diseases

COVID-19 is without any doubt the worst pandemic we have faced since the H1N1 virus outbreak. Even if vaccination against SARS-CoV-2 infection is becoming increasingly available, a more feasible approach for COVID-19 prevention and therapy is still needed. Evidence of a pathological link between metabolic diseases and severe forms of COVID-19 has stimulated critical reflection and new considerations. In particular, an abnormal immune response observed in certain patients with SARS-CoV-2 infection suggested possible common predisposing risk factors with autoimmune diseases such as Type 1 Diabetes (T1D). Correct supplementation with dietary factors may be key to preventing and counteracting both the underlying metabolic impairment and the complications of COVID-19. A set of agents may inhibit the cytokine storm and hypercoagulability that characterize severe COVID-19 infection: vitamin D3, omega-3 polyunsaturated fatty acids, polyphenols like pterostilbene, polydatin and honokiol, which can activate anti-inflammatory and antioxidant sirtuins pathways, quercetin, vitamin C, zinc, melatonin, lactoferrin and glutathione. These agents could be highly beneficial for subjects who have altered immune responses. In this review, we discuss the antiviral and metabolic effects of these dietary factors and propose their combination for potential applications in the prevention and treatment of COVID-19. Rigorous studies will be fundamental for validating preventive and therapeutic protocols that could be of assistance to mitigate disease progression following SARS-CoV-2 infection.

The Pleiotropic Function of Human Sirtuins as Modulators of Metabolic Pathways and Viral Infections

Sirtuins (SIRTs) are nicotinamide adenine dinucleotide-dependent histone deacetylases that incorporate complex functions in the mechanisms of cell physiology. Mammals have seven distinct members of the SIRT family (SIRT1-7), which play an important role in a well-maintained network of metabolic pathways that control and adapt the cell to the environment, energy availability and cellular stress. Until recently, very few studies investigated the role of SIRTs in modulating viral infection and progeny. Recent studies have demonstrated that SIRT1 and SIRT2 are promising antiviral targets because of their specific connection to numerous metabolic and regulatory processes affected during infection. In the present review, we summarize some of the recent progress in SIRTs biochemistry and their emerging function as antiviral targets. We also discuss the potential of natural polyphenol-based SIRT modulators to control their functional roles in several diseases including viral infections.

Mitochondria, Oxidative Stress, cAMP Signalling and Apoptosis: A Crossroads in Lymphocytes of Multiple Sclerosis, a Possible Role of Nutraceutics

Multiple sclerosis (MS) is a complex inflammatory and neurodegenerative chronic disease that involves the immune and central nervous systems (CNS). The pathogenesis involves the loss of blood–brain barrier integrity, resulting in the invasion of lymphocytes into the CNS with consequent tissue damage. The MS etiology is probably a combination of immunological, genetic, and environmental factors. It has been proposed that T lymphocytes have a main role in the onset and propagation of MS, leading to the inflammation of white matter and myelin sheath destruction. Cyclic AMP (cAMP), mitochondrial dysfunction, and oxidative stress exert a role in the alteration of T lymphocytes homeostasis and are involved in the apoptosis resistance of immune cells with the consequent development of autoimmune diseases. The defective apoptosis of autoreactive lymphocytes in patients with MS, allows these cells to perpetuate, within the CNS, a continuous cycle of inflammation. In this review, we discuss the involvement in MS of cAMP pathway, mitochondria, reactive oxygen species (ROS), apoptosis, and their interaction in the alteration of T lymphocytes homeostasis. In addition, we discuss a series of nutraceutical compounds that could influence these aspects.

SIRT1/SIRT3 Modulates Redox Homeostasis during Ischemia/Reperfusion in the Aging Heart

Ischemia/reperfusion (I/R) injury is the central cause of global death in cardiovascular diseases, which is characterized by disorders such as angina, stroke, and peripheral vascular disease, finally causing severe debilitating diseases and death. The increased rates of morbidity and mortality caused by I/R are parallel with aging. Aging-associated cardiac physiological structural and functional deterioration were found to contribute to abnormal reactive oxygen species (ROS) production during I/R stress. Disturbed redox homeostasis could further trigger the related signaling pathways that lead to cardiac irreversible damages with mitochondria dysfunction and cell death. It is notable that sirtuin proteins are impaired in aged hearts and are critical to maintaining redox homeostasis via regulating substrate metabolism and inflammation and thus preserving cardiac function under stress. This review discussed the cellular and functional alterations upon I/R especially in aging hearts. We propose that mitochondria are the primary source of reactive oxygen species (ROS) that contribute to I/R injury in aged hearts. Then, we highlight the cardiomyocyte protection of the age-related proteins Sirtuin1 (SIRT1) and Sirtuin1 (SIRT3) in response to I/R injury, and we discuss their modulation of cardiac metabolism and the inflammatory reaction that is involved in ROS formation.