NAD metabolism: Implications in aging and longevity

Smoking cessation only partially reverses cardiac metabolic and structural remodeling in mice

AIMS

Active cigarette smoking is a major risk factor for chronic obstructive pulmonary disease that remains elevated after cessation. Skeletal muscle dysfunction has been well documented after smoking, but little is known about cardiac adaptations to cigarette smoking. The underlying cellular and molecular cardiac adaptations, independent of confounding lifestyle factors, and time course of reversibility by smoking cessation remain unclear. We hypothesized that smoking negatively affects cardiac metabolism and induces local inflammation in mice, which do not readily reverse upon 2-week smoking cessation.

METHODS

Mice were exposed to air or cigarette smoke for 14 weeks with or without 1- or 2-week smoke cessation. We measured cardiac mitochondrial respiration by high-resolution respirometry, cardiac mitochondrial density, abundance of mitochondrial supercomplexes by electrophoresis, and capillarization, fibrosis, and macrophage infiltration by immunohistology, and performed cardiac metabolome and lipidome analysis by mass spectrometry.

RESULTS

Mitochondrial protein, supercomplex content, and respiration (all p < 0.03) were lower after smoking, which were largely reversed within 2-week smoking cessation. Metabolome and lipidome analyses revealed alterations in mitochondrial metabolism, a shift from fatty acid to glucose metabolism, which did not revert to control upon smoking cessation. Capillary density was not different after smoking but increased after smoking cessation (p = 0.02). Macrophage infiltration and fibrosis (p < 0.04) were higher after smoking but did not revert to control upon smoking cessation.

CONCLUSIONS

While cigarette-impaired smoking-induced cardiac mitochondrial function was reversed by smoking cessation, the remaining fibrosis and macrophage infiltration may contribute to the increased risk of cardiovascular events after smoking cessation.

Supplementation with NAD+ and its precursors: A rescue of female reproductive diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme involved in many pathophysiological processes. Supplementation with NAD+ and its precursors has been demonstrated as an emerging therapeutic strategy for the diseases. NAD+ also plays an important role in the reproductive system. Here, we summarize the function of NAD+ in various reproductive diseases and review the application of NAD+ and its precursors in the preservation of reproductive capacity and the prevention of embryonic malformations. It is shown that NAD+ shows good promise as a therapeutic approach for saving reproductive capacity.

NAD+ Supplementation Improves Mitochondrial Functions and Normalizes Glaucomatous Trabecular Meshwork Features

Glaucoma is characterized by pathological elevation of intraocular pressure (IOP) due to dysfunctional trabecular meshwork (TM), which is the primary cause of irreversible vision loss. There are currently no effective treatment strategies for glaucoma. Mitochondrial function plays a crucial role in regulating IOP within the TM. In this study, primary TM cells treated with dexamethasone were used to simulate glaucomatous changes, showing abnormal cellular cytoskeleton, increased expression of extracellular matrix, and disrupted mitochondrial fusion and fission dynamics. Furthermore, glaucomatous TM cell line GTM3 exhibited impaired mitochondrial membrane potential and phagocytic function, accompanied by decreased oxidative respiratory levels as compared to normal TM cells iHTM. Mechanistically, lower NAD+ levels in GTM3, possibly associated with increased expression of key enzymes CD38 and PARP1 related to NAD+ consumption, were observed. Supplementation of NAD+ restored mitochondrial function and cellular viability in GTM3 cells. Therefore, we propose that the aberrant mitochondrial function in glaucomatous TM cells may be attributed to increased NAD+ consumption dependent on CD38 and PARP1, and NAD+ supplementation could effectively ameliorate mitochondrial function and improve TM function, providing a novel alternative approach for glaucoma treatment.

The therapeutic perspective of NAD+ precursors in age-related diseases

Nicotinamide adenine dinucleotide (NAD+) is the fundamental molecule that performs numerous biological reactions and is crucial for maintaining cellular homeostasis. Studies have found that NAD+ decreases with age in certain tissues, and age-related NAD+ depletion affects physiological functions and contributes to various aging-related diseases. Supplementation of NAD+ precursor significantly elevates NAD+ levels in murine tissues, effectively mitigates metabolic syndrome, enhances cardiovascular health, protects against neurodegeneration, and boosts muscular strength. Despite the versatile therapeutic functions of NAD+ in animal studies, the efficacy of NAD+ precursors in clinical studies have been limited compared with that in the pre-clinical study. Clinical studies have demonstrated that NAD+ precursor treatment efficiently increases NAD+ levels in various tissues, though their clinical proficiency is insufficient to ameliorate the diseases. However, the latest studies regarding NAD+ precursors and their metabolism highlight the significant role of gut microbiota. The studies found that orally administered NAD+ intermediates interact with the gut microbiome. These findings provide compelling evidence for future trials to further explore the involvement of gut microbiota in NAD+ metabolism. Also, the reduced form of NAD+ precursor shows their potential to raise NAD+, though preclinical studies have yet to discover their efficacy. This review sheds light on NAD+ therapeutic efficiency in preclinical and clinical studies and the effect of the gut microbiota on NAD+ metabolism.

Nicotinamide phosphoribosyltransferase modulates PD-L1 in bladder cancer and enhances immunotherapeutic sensitivity

Bladder cancer (BLCA) is one of the most prevalent malignancies worldwide with a high mortality rate and poor response to immunotherapy in patients expressing lower programmed death ligand 1 (PD-L1) levels. Nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme responsible for the biosynthesis of nicotinamide adenine dinucleotide (NAD+) from nicotinamide was reported to be overexpressed in various cancers; however, the role of NAMPT in BLCA is obscure. Immunohistochemistry of tissue microarrays, a real-time polymerase chain reaction, Western blotting, proliferation assay, NAD+ quantification, transwell-migration assay, and colony-formation assay were performed to measure NAMPT and PD-L1 expression levels in patients and the effect of NAMPT inhibition on T24 cells. Our study revealed that NAMPT expression was upregulated in BLCA patients with different grades and associated with poor T-cell infiltration. Notably, FK866-mediated NAMPT inhibition decreased cell viability by depleting NAD+, and reducing the migration ability and colony-formation ability of T24 cells. Interestingly, NAMPT negatively regulated PD-L1 under an interferon (IFN)-γ-mediated microenvironment. However, exogenous NAMPT activator has no effect on PD-L1. NAD+ supplementation also only increased PD-L1 in the absence of IFN-γ. Conclusively, NAMPT is crucial for BLCA tumorigenic properties, and it regulates expression of the PD-L1 immune checkpoint protein. NAMPT could be considered a target for modulating sensitivity to immunotherapy.

Targeting NAD+ Metabolism to Modulate Autoimmunity and Inflammation

NAD+ biology is involved in controlling redox balance, functioning as a coenzyme in numerous enzymatic reactions, and is a cofactor for Sirtuin enzymes and a substrate for multiple regulatory enzyme reactions within and outside the cell. At the same time, NAD+ levels are diminished with aging and are consumed during the development of inflammatory and autoimmune diseases linked to aberrant immune activation. Direct NAD+ augmentation via the NAD+ salvage and Priess-Handler pathways is being investigated as a putative therapeutic intervention to improve the healthspan in inflammation-linked diseases. In this review, we survey NAD+ biology and its pivotal roles in the regulation of immunity and inflammation. Furthermore, we discuss emerging studies evaluate NAD+ boosting in murine models and in human diseases, and we highlight areas of research that remain unresolved in understanding the mechanisms of action of these nutritional supplementation strategies.

Discovery of a Potent Nicotinamide Phosphoribosyltransferase Activator for Improving Aging-associated Dysfunctions

Nicotinamide adenine dinucleotide (NAD+) plays a crucial role in the cellular energy metabolism pathway. Nicotinamide phosphoribosyltransferase (NAMPT) is a rate-limiting enzyme involved in the biosynthesis of NAD+. Herein, a series of new NAMPT activators were designed to increase the NAD+ levels and improve aging-associated dysfunctions. In particular, compound C8 effectively activated NAMPT and promoted the biosynthesis of NAD+. Furthermore, we demonstrated that NAMPT activator C8 possessed excellent antiaging effects both in vitro and in vivo. Activator C8 showed potent activity in delaying aging in senescent HL-7702 cells and extended the lifespan of Caenorhabditis elegans. In a naturally aging mouse model, compound C8 effectively alleviated age-related dysfunctions and markers. Therefore, NAMPT activator C8 represented a promising lead compound for the treatment of age-related diseases.

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

Nicotinamide mononucleotide pretreatment improves long-term isoflurane anesthesia-induced cognitive impairment in mice

Postoperative cognitive dysfunction (POCD) is characterized by impaired cognitive function following general anesthesia and surgery. Oxidative stress is a significant pathophysiological manifestation underlying POCD. Previous studies have reported that the decline of nicotinamide adenine dinucleotide (NAD+) -dependent sirtuin 1 (SIRT1) contributes to the activation of oxidative stress. In this study, we investigated whether pretreatment of nicotinamide mononucleotide (NMN), an NAD+ intermediate, improves oxidative stress and cognitive function in POCD. The animal model of POCD was established in C57BL/6 J mice through 6 h isoflurane anesthesia-induced cognitive impairment. Mice were intraperitoneally injected with NMN for 7 days prior to anesthesia, after which oxidative stress and cognitive function were assessed. The level of oxidative stress was determined using flow cytometry analysis and assey kits. The fear condition test and the Y-maze test were utilized to evaluate contextual and spatial memory. Our results showed that cognitive impairment and increased oxidative stress were observed in POCD mice, as well as downregulation of NAD+ levels and related protein expressions of SIRT1 and nicotinamide phosphoribosyltransferase (NAMPT) in the hippocampus. And NMN supplementation could effectively prevent the decline of NAD+ and related proteins, and reduce oxidative stress and cognitive disorders after POCD. Mechanistically, the findings suggested that protection on cognitive function mediated by NMN pretreatment in POCD mice may be regulated by NAD+-SIRT1 signaling pathway. This study indicated that NMN preconditioning reduced oxidative stress damage and alleviated cognitive impairment in POCD mice.

Two-Photon-Excited FLIM of NAD(P)H and FAD-Metabolic Activity of Fibroblasts for the Diagnostics of Osteoimplant Survival

Bioinert materials such as the zirconium dioxide and aluminum oxide are widely used in surgery and dentistry due to the absence of cytotoxicity of the materials in relation to the surrounding cells of the body. However, little attention has been paid to the study of metabolic processes occurring at the implant-cell interface. The metabolic activity of mouse 3T3 fibroblasts incubated on yttrium-stabilized zirconium ceramics cured with aluminum oxide (ATZ) and stabilized zirconium ceramics (Y-TZP) was analyzed based on the ratio of the free/bound forms of cofactors NAD(P)H and FAD obtained using two-photon microscopy. The results show that fibroblasts incubated on ceramics demonstrate a shift towards the free form of NAD(P)H, which is observed during the glycolysis process, which, according to our assumptions, is related to the porosity of the surface of ceramic structures. Consequently, despite the high viability and good proliferation of fibroblasts assessed using an MTT test and a scanning electron microscope, the cells are in a state of hypoxia during incubation on ceramic structures. The FLIM results obtained in this work can be used as additional information for scientists who are interested in manufacturing osteoimplants.

Nicotinamide Riboside Regulates Chemotaxis to Decrease Inflammation and Ameliorate Functional Recovery Following Spinal Cord Injury in Mice

Changes in intracellular nicotinamide adenine dinucleotide (NAD+) levels have been observed in various disease states. A decrease in NAD+ levels has been noted following spinal cord injury (SCI). Nicotinamide riboside (NR) serves as the precursor of NAD+. Previous research has demonstrated the anti-inflammatory and apoptosis-reducing effects of NR supplements. However, it remains unclear whether NR exerts a similar role in mice after SCI. The objective of this study was to investigate the impact of NR on these changes in a mouse model of SCI. Four groups were considered: (1) non-SCI without NR (Sham), (2) non-SCI with NR (Sham +NR), (3) SCI without NR (SCI), and (4) SCI with NR (SCI + NR). Female C57BL/6J mice aged 6-8 weeks were intraperitoneally administered with 500 mg/kg/day NR for a duration of one week. The supplementation of NR resulted in a significant elevation of NAD+ levels in the spinal cord tissue of mice after SCI. In comparison to the SCI group, NR supplementation exhibited regulatory effects on the chemotaxis/recruitment of leukocytes, leading to reduced levels of inflammatory factors such as IL-1β, TNF-α, and IL-22 in the injured area. Moreover, NR supplementation notably enhanced the survival of neurons and synapses within the injured area, ultimately resulting in improved motor functions after SCI. Therefore, our research findings demonstrated that NR supplementation had inhibitory effects on leukocyte chemotaxis, anti-inflammatory effects, and could significantly improve the immune micro-environment after SCI, thereby promoting neuronal survival and ultimately enhancing the recovery of motor functions after SCI. NR supplementation showed promise as a potential clinical treatment strategy for SCI.

Mitochondria in Alzheimer's Disease Pathogenesis

Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disorder that primarily affects persons aged 65 years and above. It causes dementia with memory loss and deterioration in thinking and language skills. AD is characterized by specific pathology resulting from the accumulation in the brain of extracellular plaques of amyloid-β and intracellular tangles of phosphorylated tau. The importance of mitochondrial dysfunction in AD pathogenesis, while previously underrecognized, is now more and more appreciated. Mitochondria are an essential organelle involved in cellular bioenergetics and signaling pathways. Mitochondrial processes crucial for synaptic activity such as mitophagy, mitochondrial trafficking, mitochondrial fission, and mitochondrial fusion are dysregulated in the AD brain. Excess fission and fragmentation yield mitochondria with low energy production. Reduced glucose metabolism is also observed in the AD brain with a hypometabolic state, particularly in the temporo-parietal brain regions. This review addresses the multiple ways in which abnormal mitochondrial structure and function contribute to AD. Disruption of the electron transport chain and ATP production are particularly neurotoxic because brain cells have disproportionately high energy demands. In addition, oxidative stress, which is extremely damaging to nerve cells, rises dramatically with mitochondrial dyshomeostasis. Restoring mitochondrial health may be a viable approach to AD treatment.

Proteomics-Based Investigation of Different Live Prey Administered to Freshwater Dark Sleeper (Odontobutis potamophila): Examining the Effects on Glycolipids and Energy Metabolism

Live prey is characterized by balanced rich nutrients and high palatability and is widely used for the seedling cultivation of freshwater dark sleeper (Odontobutis potamophila) larvae. In this study, we evaluated the effects of four groups of paired feeding regimens (group C (Daphnia magna), group L (Limnodrilus hoffmeisteri), group H (Hypophthalmichthys molitrix fry), and group M (mixed groups C, L, and H)) on glycolipid and energy metabolism in O. potamophila larvae. We observed that fatty acid synthase (FAS) and sterol-regulatory-element-binding protein-1 (SREBP-1) mRNA levels were significantly lower in group H when compared to mRNA levels in the other three groups (p < 0.05) and that carnitine palmitoyltransferase 1α (CPT1-α) mRNA levels were significantly lower in group L when compared to group M (p < 0.05). Relative glucokinase (GK) expression levels were significantly lower in group M when compared to the other three groups (p < 0.05). Using proteomics, we analyzed and compared groups H and L and identified 457 differentially expressed proteins (DEPs), of which 151 were significantly up-regulated and 306 were significantly down-regulated. In the comparison of group M with groups C, L, and H, we found significant enrichment in glycolytic processes, the endoplasmic reticulum lumen, NAD binding, intermediate filaments, and nutrient reservoir activity. Our results provide a theoretical guidance for bait selection during larvae cultivation stages in carnivorous fish.

NAD+ dependent UPRmt activation underlies intestinal aging caused by mitochondrial DNA mutations

Aging in mammals is accompanied by an imbalance of intestinal homeostasis and accumulation of mitochondrial DNA (mtDNA) mutations. However, little is known about how accumulated mtDNA mutations modulate intestinal homeostasis. We observe the accumulation of mtDNA mutations in the small intestine of aged male mice, suggesting an association with physiological intestinal aging. Using polymerase gamma (POLG) mutator mice and wild-type mice, we generate male mice with progressive mtDNA mutation burdens. Investigation utilizing organoid technology and in vivo intestinal stem cell labeling reveals decreased colony formation efficiency of intestinal crypts and LGR5-expressing intestinal stem cells in response to a threshold mtDNA mutation burden. Mechanistically, increased mtDNA mutation burden exacerbates the aging phenotype of the small intestine through ATF5 dependent mitochondrial unfolded protein response (UPRmt) activation. This aging phenotype is reversed by supplementation with the NAD+ precursor, NMN. Thus, we uncover a NAD+ dependent UPRmt triggered by mtDNA mutations that regulates the intestinal aging.

Melatonin: a modulator in metabolic rewiring in T-cell malignancies

Melatonin, (N-acetyl-5-methoxytryptamine) an indoleamine exerts multifaced effects and regulates numerous cellular pathways and molecular targets associated with circadian rhythm, immune modulation, and seasonal reproduction including metabolic rewiring during T cell malignancy. T-cell malignancies encompass a group of hematological cancers characterized by the uncontrolled growth and proliferation of malignant T-cells. These cancer cells exhibit a distinct metabolic adaptation, a hallmark of cancer in general, as they rewire their metabolic pathways to meet the heightened energy requirements and biosynthesis necessary for malignancies is the Warburg effect, characterized by a shift towards glycolysis, even when oxygen is available. In addition, T-cell malignancies cause metabolic shift by inhibiting the enzyme pyruvate Dehydrogenase Kinase (PDK) which in turn results in increased acetyl CoA enzyme production and cellular glycolytic activity. Further, melatonin plays a modulatory role in the expression of essential transporters (Glut1, Glut2) responsible for nutrient uptake and metabolic rewiring, such as glucose and amino acid transporters in T-cells. This modulation significantly impacts the metabolic profile of T-cells, consequently affecting their differentiation. Furthermore, melatonin has been found to regulate the expression of critical signaling molecules involved in T-cell activations, such as CD38, and CD69. These molecules are integral to T-cell adhesion, signaling, and activation. This review aims to provide insights into the mechanism of melatonin's anticancer properties concerning metabolic rewiring during T-cell malignancy. The present review encompasses the involvement of oncogenic factors, the tumor microenvironment and metabolic alteration, hallmarks, metabolic reprogramming, and the anti-oncogenic/oncostatic impact of melatonin on various cancer cells.

Roles of NAD+ in Health and Aging

NAD+, the essential metabolite involved in multiple reactions such as the regulation of cellular metabolism, energy production, DNA repair, mitophagy and autophagy, inflammation, and neuronal function, has been the subject of intense research in the field of aging and disease over the last decade. NAD+ levels decline with aging and in some age-related diseases, and reduction in NAD+ affects all the hallmarks of aging. Here, we present an overview of the discovery of NAD+, the cellular pathways of producing and consuming NAD+, and discuss how imbalances in the production rate and cellular request of NAD+ likely contribute to aging and age-related diseases including neurodegeneration. Preclinical studies have revealed great potential for NAD+ precursors in promotion of healthy aging and improvement of neurodegeneration. This has led to the initiation of several clinical trials with NAD+ precursors to treat accelerated aging, age-associated dysfunctions, and diseases including Alzheimer's and Parkinson's. NAD supplementation has great future potential clinically, and these studies will also provide insight into the mechanisms of aging.

A gut aging clock using microbiome multi-view profiles is associated with health and frail risk

Age-related changes in the microbiome have been reported in previous studies; however, direct evidence for their association with frailty is lacking. Here, we introduce biological age based on gut microbiota (gAge), an integrated prediction model that integrates gut microbiota data from different perspectives with potential background factors for aging assessment. Simulation results show that, compared with a single model, the ensemble model can not only significantly improve the prediction accuracy, but also make full use of the data in unpaired samples. From this, we identified markers associated with age development and grouped markers into accelerated aging and mitigated aging according to their effect on the prediction. Importantly, the application of gAge to an elderly cohort with different frailty levels confirmed that gAge and its predictive residuals are closely related to the individual's health status and frailty stage, and age-related markers overlap significantly with disease and frailty characteristics. Furthermore, we applied the gAge prediction model to another independent cohort of the elderly population for aging assessment and found that gAge could effectively represent the aging population. Overall, our study explains the association between the gut microbiota and frailty, providing potential targets for the development of gut microbiota-based targeted intervention strategies for aging.

Nicotinamide Mononucleotide in the Context of Myocardiocyte Longevity

Cellular and subcellular metabolic activities are crucial processes involved in the regulation of intracellular homeostasis, including cellular and subcellular signaling pathways. Dysregulation of intracellular regulation mechanisms is catastrophic and cumulates into cell death. To overcome the issue of dysregulation of intracellular regulation mechanisms, the preservation of subcellular and extracellular components is essential to maintain healthy cells with increased longevity. Several physiopathological changes occur during cell ageing, one of which is the dysregulation of intracellular physiology of the oxidative phosphorylation process. Nicotinamide mononucleotide (NMN) remains in the debut of anti-aging therapeutic effect. Aged myocardiocyte characterized by disrupted NMN and or its precursors or signaling pathways. Simultaneously, several other pathophysiological occur that collectively impair intracellular homeostasis. The NMN role in the antiaging effect remains unclear and several hypotheses have been introduced into describing the mechanism and the potential outcomes from NMN exogenous supply. Correction of the impaired intracellular homeostasis includes correction to the NMN metabolism. Additionally, autophagy correction, which is the key element in the regulation of intracellular intoxication, including oxidative stress, unfolding protein response, and other degradation of intracellular metabolites. Several signaling pathways are involved in the regulation mechanism of NMN effects on myocardiocyte health and further longevity. NMN protects myocardiocytes from ischemic injury by reducing anabolism and, increasing catabolism and further passing the myocardiocytes into dormant status. NMN applications include ischemic heart, disease, and failed heart, as well as dilated cardiomyopathies. Cytosolic and mitochondrial NADPH are independently functioning and regulating. Each of these plays a role in the determination of the longevity of the myocardiocytes. NMN has a cornerstone in the functionality of Sirtuins, which are an essential anti-senescent intrinsic molecule. The study aims to assess the role of NMN in the longevity and antisenescent of myocardiocytes.

Impact of NAD+ metabolism on ovarian aging

Nicotinamide adenine dinucleotide (NAD+), a crucial coenzyme in cellular redox reactions, is closely associated with age-related functional degeneration and metabolic diseases. NAD exerts direct and indirect influences on many crucial cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cellular senescence, and immune cell functionality. These cellular processes and functions are essential for maintaining tissue and metabolic homeostasis, as well as healthy aging. Causality has been elucidated between a decline in NAD levels and multiple age-related diseases, which has been confirmed by various strategies aimed at increasing NAD levels in the preclinical setting. Ovarian aging is recognized as a natural process characterized by a decline in follicle number and function, resulting in decreased estrogen production and menopause. In this regard, it is necessary to address the many factors involved in this complicated procedure, which could improve fertility in women of advanced maternal age. Concerning the decrease in NAD+ levels as ovarian aging progresses, promising and exciting results are presented for strategies using NAD+ precursors to promote NAD+ biosynthesis, which could substantially improve oocyte quality and alleviate ovarian aging. Hence, to acquire further insights into NAD+ metabolism and biology, this review aims to probe the factors affecting ovarian aging, the characteristics of NAD+ precursors, and the current research status of NAD+ supplementation in ovarian aging. Specifically, by gaining a comprehensive understanding of these aspects, we are optimistic about the prominent progress that will be made in both research and therapy related to ovarian aging.

Unlocking the therapeutic potential of natural stilbene: Exploring pterostilbene as a powerful ally against aging and cognitive decline

The therapeutic potential of natural stilbenes, with a particular focus on pterostilbene (PTE), has emerged as a promising avenue of research targeting age-associated conditions encompassing cardiovascular diseases (CVD), diabetes mellitus (DM), and cognitive decline. This comprehensive investigation delves into the intricate mechanisms through which PTE, a polyphenolic compound abundant in grapes and blueberries, exerts its advantageous effects as an anti-aging agent. Central to its action is the modulation of hallmark aging processes, including oxidative damage, inflammatory responses, telomere attrition, and cellular senescence. PTE's ability to effectively penetrate the blood-brain barrier amplifies its potential for safeguarding neural health, thereby facilitating the regulation of neuronal signalling cascades, synaptic plasticity, and mitochondrial functionality. Through engagement with sirtuin proteins, it orchestrates cellular resilience, longevity, and metabolic equilibrium. Encouraging findings from preclinical studies portray PTE as a robust candidate for counteracting age-linked cognitive decline, augmenting memory consolidation, and potentially ameliorating neurodegenerative maladies such as Alzheimer's disease (AD). The synthesis of current scientific insights accentuates the promising translational prospects of PTE as a potent, naturally derived therapeutic agent against cognitive impairments associated with aging. Consequently, these collective findings lay a solid groundwork for forthcoming clinical inquiries and innovative therapeutic interventions in this realm.

Acetylation in pathogenesis: Revealing emerging mechanisms and therapeutic prospects

Protein acetylation modifications play a central and pivotal role in a myriad of biological processes, spanning cellular metabolism, proliferation, differentiation, apoptosis, and beyond, by effectively reshaping protein structure and function. The metabolic state of cells is intricately connected to epigenetic modifications, which in turn influence chromatin status and gene expression patterns. Notably, pathological alterations in protein acetylation modifications are frequently observed in diseases such as metabolic syndrome, cardiovascular disorders, and cancer. Such abnormalities can result in altered protein properties and loss of function, which are closely associated with developing and progressing related diseases. In recent years, the advancement of precision medicine has highlighted the potential value of protein acetylation in disease diagnosis, treatment, and prevention. This review includes provocative and thought-provoking papers outlining recent breakthroughs in acetylation modifications as they relate to cardiovascular disease, mitochondrial metabolic regulation, liver health, neurological health, obesity, diabetes, and cancer. Additionally, it covers the molecular mechanisms and research challenges in understanding the role of acetylation in disease regulation. By summarizing novel targets and prognostic markers for the treatment of related diseases, we aim to contribute to the field. Furthermore, we discuss current hot topics in acetylation research related to health regulation, including N4-acetylcytidine and liquid-liquid phase separation. The primary objective of this review is to provide insights into the functional diversity and underlying mechanisms by which acetylation regulates proteins in disease contexts.

Gut-Brain Axis a Key Player to Control Gut Dysbiosis in Neurological Diseases

Parkinson's disease is a chronic neuropathy characterised by the formation of Lewy bodies (misfolded alpha-synuclein) in dopaminergic neurons of the substantia nigra and other parts of the brain. Dopaminergic neurons play a vital role in generating both motor and non-motor symptoms. Finding therapeutic targets for Parkinson's disease (PD) is hindered due to an incomplete understanding of the disease's pathophysiology. Existing evidence suggests that the gut microbiota participates in the pathogenesis of PD via immunological, neuroendocrine, and direct neural mechanisms. Gut microbial dysbiosis triggers the loss of dopaminergic neurons via mitochondrial dysfunction. Gut dysbiosis triggers bacterial overgrowth in the small intestine, which increases the permeability barrier and induces systemic inflammation. It results in excessive stimulation of the innate immune system. In addition to that, activation of enteric neurons and enteric glial cells initiates the aggregation of alpha-synuclein. This alpha-synucleinopathy thus affects all levels of the brain-gut axis, including the central, autonomic, and enteric nervous systems. Though the neurobiological signaling cascade between the gut microbiome and the central nervous system is poorly understood, gut microbial metabolites may serve as a promising therapeutic strategy for PD. This article summarises all the known possible ways of bidirectional signal communication, i.e., the "gut-brain axis," where microbes from the middle gut interact with the brain and vice versa, and highlights a unique way to treat neurodegenerative diseases by maintaining homeostasis. The tenth cranial nerve (vagus nerve) plays a significant part in this signal communication. However, the leading regulatory factor for this axis is a diet that helps with microbial colonisation and brain function. Short-chain fatty acids (SCFAs), derived from microbially fermented dietary fibres, link host nutrition to maintain intestinal homeostasis. In addition to that, probiotics modulate cognitive function and the metabolic and behavioural conditions of the body. As technology advances, new techniques will emerge to study the tie-up between gut microbes and neuronal diseases.

Preclinical Characterization of Pharmacologic NAD+ Boosting as a Promising Therapeutic Approach in Rheumatoid Arthritis

OBJECTIVE

We analyzed NAD+ metabolism in patients with rheumatoid arthritis (RA), its association with disease activity and clinical outcomes of RA, and the therapeutic potential of pharmacologic NAD+ boosting.

METHODS

Our study included 253 participants. In the first cohort, comprising 153 RA patients and 56 healthy donors, we assessed NAD+ levels and NAD+ -related gene pathways. We analyzed 92 inflammatory molecules by proximity extension assay. In the second cohort, comprising 44 RA patients starting anti-tumor necrosis factor (anti-TNF) drugs, we evaluated changes in NAD+ levels and their association with clinical response after 3 months. Mechanistic studies were performed ex vivo on peripheral blood mononuclear cells (PBMCs) from patients with RA to test the beneficial effects of NAD+ boosters, such as nicotinamide and nicotinamide riboside.

RESULTS

Reduced NAD+ levels were found in RA samples, in line with altered activity and expression of genes involved in NAD+ consumption (sirtuins, poly[ADP-ribose] polymerase, CD38), transport (connexin 43), and biosynthesis (NAMPT, NMNATs). Unsupervised clustering analysis identified a group of RA patients with the highest inflammatory profile, the lowest NAD+ levels, and the highest disease activity (as shown by the Disease Activity Score in 28 joints). NAD+ levels were modulated by anti-TNF therapy in parallel with the clinical response. In vitro studies using PBMCs from RA patients showed that nicotinamide riboside and nicotinamide increased NAD+ levels via NAMPT and NMNAT and reduced their prooxidative, proapoptotic, and proinflammatory status.

CONCLUSION

RA patients display altered NAD+ metabolism, directly linked to their inflammatory and disease activity status, which was reverted by anti-TNF therapy. The preclinical beneficial effects of NAD+ boosters, as shown in leukocytes from RA patients, along with their proven clinical safety, might pave the way for the development of clinical trials using these compounds.

Adipocyte NMNAT1 expression is essential for nuclear NAD+ biosynthesis but dispensable for regulating thermogenesis and whole-body energy metabolism

Nicotinamide adenine dinucleotide (NAD+) functions as an essential cofactor regulating a variety of biological processes. The purpose of the present study was to determine the role of nuclear NAD+ biosynthesis, mediated by nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), in thermogenesis and whole-body energy metabolism. We first evaluated the relationship between NMNAT1 expression and thermogenic activity in brown adipose tissue (BAT), a key organ for non-shivering thermogenesis. We found that reduced BAT NMNAT1expression was associated with inactivation of thermogenic gene program induced by obesity and thermoneutrality. Next, we generated and characterized adiponectin-Cre-driven adipocyte-specific Nmnat1 knockout (ANMT1KO) mice. Loss of NMNAT1 markedly reduced nuclear NAD+ concentration by approximately 70% in BAT. Nonetheless, adipocyte-specific Nmnat1 deletion had no impact on thermogenic (rectal temperature, BAT temperature and whole-body oxygen consumption) responses to β-adrenergic ligand norepinephrine administration and acute cold exposure, adrenergic-mediated lipolytic activity, and metabolic responses to obesogenic high-fat diet feeding. In addition, loss of NMNAT1 did not affect nuclear lysine acetylation or thermogenic gene program in BAT. These results demonstrate that adipocyte NMNAT1 expression is required for maintaining nuclear NAD+ concentration, but not for regulating BAT thermogenesis or whole-body energy homeostasis.

Intracellular spatiotemporal metabolism in connection to target engagement

The metabolism in eukaryotic cells is a highly ordered system involving various cellular compartments, which fluctuates based on physiological rhythms. Organelles, as the smallest independent sub-cell unit, are important contributors to cell metabolism and drug metabolism, collectively designated intracellular metabolism. However, disruption of intracellular spatiotemporal metabolism can lead to disease development and progression, as well as drug treatment interference. In this review, we systematically discuss spatiotemporal metabolism in cells and cell subpopulations. In particular, we focused on metabolism compartmentalization and physiological rhythms, including the variation and regulation of metabolic enzymes, metabolic pathways, and metabolites. Additionally, the intricate relationship among intracellular spatiotemporal metabolism, metabolism-related diseases, and drug therapy/toxicity has been discussed. Finally, approaches and strategies for intracellular spatiotemporal metabolism analysis and potential target identification are introduced, along with examples of potential new drug design based on this.

Chemical mitophagy modulators: Drug development strategies and novel regulatory mechanisms

Maintaining mitochondrial homeostasis is a potential therapeutic strategy for various diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic disorders, and cancer. Selective degradation of mitochondria by autophagy (mitophagy) is a fundamental mitochondrial quality control mechanism conserved from yeast to humans. Indeed, small-molecule modulators of mitophagy are valuable pharmaceutical tools that can be used to dissect complex biological processes and turn them into potential drugs. In the past few years, pharmacological regulation of mitophagy has shown promising therapeutic efficacy in various disease models. However, with the increasing number of chemical mitophagy modulator studies, frequent methodological flaws can be observed, leading some studies to draw unreliable or misleading conclusions. This review attempts (a) to summarize the molecular mechanisms of mitophagy; (b) to propose a Mitophagy Modulator Characterization System (MMCS); (c) to perform a comprehensive analysis of methods used to characterize mitophagy modulators, covering publications over the past 20 years; (d) to provide novel targets for pharmacological intervention of mitophagy. We believe this review will provide a panorama of current research on chemical mitophagy modulators and promote the development of safe and robust mitophagy modulators with therapeutic potential by introducing high methodological standards.

The Effects of Graded Levels of Calorie Restriction: XIX. Impact of Graded Calorie Restriction on Protein Expression in the Liver

Calorie restriction (CR) extends life span by modulating the mechanisms involved in aging. We quantified the hepatic proteome of male C57BL/6 mice exposed to graded levels of CR (0%-40% CR) for 3 months, and evaluated which signaling pathways were most affected. The metabolic pathways most significantly stimulated by the increase in CR, included the glycolysis/gluconeogenesis pathway, the pentose phosphate pathway, the fatty acid degradation pathway, the valine, leucine, and isoleucine degradation pathway, and the lysine degradation pathway. The metabolism of xenobiotics by cytochrome P450 pathway was activated and feminized by increased CR, while production in major urinary proteins (Mups) was strongly reduced, consistent with a reduced investment in reproduction as predicted by the disposable soma hypothesis. However, we found no evidence of increased somatic protection, and none of the 4 main pathways implied to be linked to the impact of CR on life span (insulin/insulin-like growth factor [IGF-1], nuclear factor-κB [NF-κB], mammalian Target of Rapamycin [mTOR], and sirtuins) as well as pathways in cancer, were significantly changed at the protein level in relation to the increase in CR level. This was despite previous work at the transcriptome level in the same individuals indicating such changes. On the other hand, we found Aldh2, Aldh3a2, and Aldh9a1 in carnitine biosynthesis and Acsl5 in carnitine shuttle system were up-regulated by increased CR, which are consistent with our previous work on metabolome of the same individuals. Overall, the patterns of protein expression were more consistent with a "clean cupboards" than a "disposable soma" interpretation.

Nicotinamide mononucleotide (NMN) ameliorated Nonylphenol-induced learning and memory impairment in rats via the central 5-HT system and the NAD+/SIRT1/MAO-A pathway

Nonylphenol (NP) exposure can trigger neurotoxicity and cause learning and memory impairment. Nicotinamide mononucleotide (NMN) has a therapeutic effect on neurodegenerative diseases, but the role of NMN on NP-induced learning and memory impairment is not known. Here, we examined the mitigative effect of NMN on the impaired learning and memory ability of rats exposed to NP. The NP impaired learning and memory in rats, while the low-dose intervention with NMN significantly prolonged the step-through latency of the PAT and improved the NAMPT and NMNAT1 content in brain tissue. At the same time, the NMN intervention also increased the content of 5-HTR_1A, 5-HTR₄, and 5-HTR₆ related to learning and memory in the hippocampus. In line with this, we found that the NMN intervention activated the SIRT1/MAO-A pathway in brain tissue. NMN intervention, especially at 125 mg/kg doses, may improve rats' NP-induced learning and memory impairment via the central 5-HT system and the NAD⁺/SIRT1/MAO-A pathway in the brain.

Integration of non-targeted metabolomics with network pharmacology deciphers the anxiolytic mechanisms of Platycladi Semen extracts in CUMS mice

ETHNOPHARMACOLOGICAL RELEVANCE

Platycladi Semen was recorded in Shen Nong's Herbal Classic and was considered a herbal medicine with low toxicity after long-term medication. Multiple traditional Chinese medicine prescriptions containing Platycladi Semen have been used to treat insomnia. Modern clinical practitioners commonly use Platycladi Semen to treat anxiety disorders, but there are few studies on its composition and anxiolytic mechanisms.

AIM OF THE STUDY

To describe the main components of Platycladi Semen and investigate its anxiolytic effects and mechanisms.

MATERIALS AND METHODS

The main components of Platycladi Semen were characterized by liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). The anxiolytic effects of oral Platycladi Semen were evaluated in chronic unpredictable mild stress (CUMS) induced mice. To explore the anxiolytic mechanisms of Platycladi Semen, serum non-targeted metabolomics combined with network pharmacology and molecular docking was performed.

RESULTS

Fourteen compounds were identified in the 50% methanol extract and 11 fatty acid derivatives were identified in the methyl-esterified fatty oil of Platycladi Semen. In CUMS mice, both the aqueous extract and fatty oil of Platycladi Semen had anxiolytic effects, which were shown by the increase in the time and frequency of mice entering the open arm in the elevated plus maze (EPM) experiment. Through serum non-targeted metabolomics, 34 differential metabolites were identified, and lipid metabolic pathways such as sphingolipid metabolism, steroidogenesis, alpha-linoleic acid, and linoleic acid metabolism were enriched. Through network pharmacology, 109 targets of the main components in Platycladi Semen were identified, and the 'neuroactive ligand-receptor interaction' and 'lipid metabolism' were enriched. The molecular docking results showed that the main components in Platycladi Semen could bind to the key targets such as peroxisome proliferator-activated receptor delta (PPARD), peroxisome proliferator-activated receptor alpha (PPARA), fatty acid binding protein 5 (FABP5), fatty acid binding protein 3 (FABP3), peroxisome proliferator-activated receptor gamma (PPARG), arachidonate 5-lipoxygenase (ALOX5) and fatty acid amide hydrolase (FAAH).

CONCLUSION

This study indicated that Platycladi Semen has anxiolytic effects, and the anxiolytic mechanisms may be the regulation of lipid metabolism and the neuroactive ligand-receptor interaction.

Remission of social behavior impairment by oral administration of a precursor of NAD in CD157, but not in CD38, knockout mice

Nicotinamide adenine dinucleotide (NAD) is a substrate of adenosine diphosphate (ADP)-ribosyl cyclase and is catalyzed to cyclic ADP-ribose (cADPR) by CD38 and/or CD157. cADPR, a Ca²⁺ mobilizing second messenger, is critical in releasing oxytocin from the hypothalamus into the brain. Although NAD precursors effectively play a role in neurodegenerative disorders, muscular dystrophy, and senescence, the beneficial effects of elevating NAD by NAD precursor supplementation on brain function, especially social interaction, and whether CD38 is required in this response, has not been intensely studied. Here, we report that oral gavage administration of nicotinamide riboside, a perspective NAD precursor with high bioavailability, for 12 days did not show any suppressive or increasing effects on sociability (mouse's interest in social targets compared to non-social targets) in both CD157KO and CD38KO male mice models in a three-chamber test. CD157KO and CD38KO mice displayed no social preference (that is, more interest towards a novel mouse than a familiar one) behavior. This defect was rescued after oral gavage administration of nicotinamide riboside for 12 days in CD157KO mice, but not in CD38KO mice. Social memory was not observed in CD157KO and CD38KO mice; subsequently, nicotinamide riboside administration had no effect on social memory. Together with the results that nicotinamide riboside had essentially no or little effect on body weight during treatment in CD157KO mice, nicotinamide riboside is less harmful and has beneficial effect on defects in recovery from social behavioral, for which CD38 is required in mice.

Senotherapy for lung diseases

Increasing evidence suggests that there is acceleration of lung ageing in chronic lung diseases, such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF), with the accumulation of senescent cells in the lung. Senescent cells fail to repair tissue damage and release an array of inflammatory proteins, known as the senescence-associated secretory phenotype, which drive further senescence and disease progression. This suggests that targeting cellular senescence with senotherapies may treat the underlying disease process in COPD and IPF and thus reduce disease progression and mortality. Several existing or future drugs may inhibit the development of cellular senescence which is driven by chronic oxidative stress (senostatics), including inhibitors of PI3K-mTOR signalling pathways, antagomirs of critical microRNAs and novel antioxidants. Other drugs (senolytics) selectively remove senescent cells by promoting apoptosis. Clinical studies with senotherapies are already underway in chronic lung diseases.

1-Methylnicotinamide promotes hepatic steatosis in mice: A potential mechanism in chronic alcohol-induced fatty liver disease

Alcohol abuse and its related diseases are the major risk factors for human health. Alcohol-related liver disease (ALD) is a leading cause of morbidity and mortality worldwide. Although the mechanism of ALD has been widely investigated, liver metabolites associated with long-term alcohol intake-induced hepatic steatosis have not been well explored. In this study, we aimed to investigate the role and mechanisms of 1-methylnicotinamide (1-MNA), a metabolite during nicotinamide adenine dinucleotide (NAD⁺) metabolism, in the pathogenesis of ALD. C57BL/6 wild-type mice were subjected to chronic alcohol feeding with or without 1-MNA (50 mg/kg/day). Our data showed that 1-MNA administration significantly enhanced chronic alcohol consumption-induced hepatic steatosis. Mechanistic studies revealed that alcohol-increased hepatic protein levels of sterol regulatory element-binding transcription factor (SREBP-1c), a key enzyme that regulates lipid lipogenesis, were enhanced in mice administered with 1-MNA, regardless of alcohol feeding. Consistently, alcohol-increased mRNA and protein levels of hepatic diacylglycerol o-acyltransferase 2 (DGAT2) and very low-density lipoprotein receptor (VLDLR) were also exacerbated by 1-MNA administration. Alcohol-induced hepatic endoplasmic reticulum (ER) stress was enhanced by 1-MNA administration, which was evidenced by increased protein levels of binding immunoglobulin protein (BIP), phosphorylated- protein kinase r-like ER kinase (PERK), activating transcription factor 4 (ATF4), and C/EBP-homologous protein (CHOP) in the mouse liver. Overall, this study demonstrated that 1-MNA serves as a pathogenic factor in the development of ALD. Targeting liver 1-MNA levels may serve as a promising therapeutic approach for improving hepatic steatosis in ALD.

Metabolic reprograming of cancer as a therapeutic target

Our understanding of metabolic reprogramming in cancer has tremendously improved along with the technical progression of metabolomic analysis. Metabolic changes in cancer cells proved much more complicated than the classical Warburg effect. Previous studies have approached metabolic changes as therapeutic and/or chemopreventive targets. Recently, several clinical trials have reported anti-cancer agents associated with metabolism. However, whether cancer cells are dependent on metabolic reprogramming or favor suitable conditions remains nebulous. Both scenarios are possibly intertwined. Identification of downstream molecules and the understanding of mechanisms underlying reprogrammed metabolism can improve the effectiveness of cancer therapy. Here, we review several examples of the metabolic reprogramming of cancer cells and the therapies targeting the metabolism-related molecules as well as discuss practical approaches to improve the next generation of cancer therapies focused on the metabolic reprogramming of cancer.

Epigenome-wide association study of plasma lipids in West Africans: the RODAM study

BACKGROUND

DNA-methylation has been associated with plasma lipid concentration in populations of diverse ethnic backgrounds, but epigenome-wide association studies (EWAS) in West-Africans are lacking. The aim of this study was to identify DNA-methylation loci associated with plasma lipids in Ghanaians.

METHODS

We conducted an EWAS using Illumina 450k DNA-methylation array profiles of extracted DNA from 663 Ghanaian participants. Differentially methylated positions (DMPs) were examined for association with plasma total cholesterol (TC), LDL-cholesterol, HDL-cholesterol, and triglycerides concentrations using linear regression models adjusted for age, sex, body mass index, diabetes mellitus, and technical covariates. Findings were replicated in independent cohorts of different ethnicities.

FINDINGS

We identified one significantly associated DMP with triglycerides (cg19693031 annotated to TXNIP, regression coefficient beta -0.26, false discovery rate adjusted p-value 0.001), which replicated in-silico in South African Batswana, African American, and European populations. From the top five DMPs with the lowest nominal p-values, two additional DMPs for triglycerides (CPT1A, ABCG1), two DMPs for LDL-cholesterol (EPSTI1, cg13781819), and one for TC (TXNIP) replicated. With the exception of EPSTI1, these loci are involved in lipid transport/metabolism or are known GWAS-associated loci. The top 5 DMPs per lipid trait explained 9.5% in the variance of TC, 8.3% in LDL-cholesterol, 6.1% in HDL-cholesterol, and 11.0% in triglycerides.

INTERPRETATION

The top DMPs identified in this study are in loci that play a role in lipid metabolism across populations, including West-Africans. Future studies including larger sample size, longitudinal study design and translational research is needed to increase our understanding on the epigenetic regulation of lipid metabolism among West-African populations.

FUNDING

European Commission under the Framework Programme (grant number: 278901).

The Depletion of NAMPT Disturbs Mitochondrial Homeostasis and Causes Neuronal Degeneration in Mouse Hippocampus

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme in the salvaging synthesis pathway of the nicotinamide adenine dinucleotide (NAD). Both NAMPT and NAD progressively decline upon aging and neurodegenerative diseases. The depletion of NAMPT induces mitochondrial dysfunction in motor neurons and causes bioenergetic stress in neurons. However, the roles of NAMPT in hippocampus neurons need to be further studied. Using floxed Nampt (Nampt^flox/flox) mice, we knocked out Nampt specifically in the hippocampus CA1 neurons by injecting rAAV-hSyn-Cre-APRE-pA. The depletion of NAMPT in hippocampus neurons induced cognitive deficiency in mice. Nevertheless, no morphological change of hippocampus neurons was observed with immunofluorescent imaging. Under the transmission electron microscope, we observed mitochondrial swollen and mitochondrial number decreasing in the cell body and the neurites of hippocampus neurons. In addition, we found the intracellular Aβ (6E10) increased in the hippocampus CA1 region. The intensity of Aβ42 remained unchanged, but it tended to aggregate. The GFAP level, an astrocyte marker, and the Iba1 level, a microglia marker, significantly increased in the mouse hippocampus. In the primary cultured rat neurons, NAMPT inhibition by FK866 decreased the NAD level of neurons at > 10^-9 M. FK866 dropped the mitochondrial membrane potential in the cell body of neurons at > 10^-9 M and in the dendrite of neurons at > 10^-8 M. FK866 decreased the number and shortened the length of branches of neurons at > 10^-7 M. Together, likely due to the injury of mitochondria, the decline of NAMPT level can be a critical risk factor for neurodegeneration.

Nicotinamide Mononucleotide Alleviates Osteoblast Senescence Induction and Promotes Bone Healing in Osteoporotic Mice

Combating the accumulated senescent cells and the healing of osteoporotic bone fractures in the older remains a significant challenge. Nicotinamide mononucleotide (NMN), a precursor of NAD+, is an excellent candidate for mitigating aging-related disorders. However, it is unknown if NMN can alleviate senescent cell induction and enhance osteoporotic bone fracture healing. Here we show that NMN treatment partially reverses the effects of tumor necrosis factor-alpha (TNF-α) on human primary osteoblasts (HOBs): senescent cell induction, diminished osteogenic differentiation ability, and intracellular NAD+ and NADH levels. Mechanistically, NMN restores the mitochondrial dysfunction in HOBs induced by TNF-α evidenced by increased mitochondrial membrane potential and reduced reactive oxidative species and mitochondrial mass. NMN also increases mitophagy activity by down-regulating P62 expression and up-regulating light chain 3B-II protein expression. In addition, the cell senescence protective effects of NMN on HOBs are mitigated by a mitophagy inhibitor (Bafilomycin A1). In vivo, NMN supplementation attenuates senescent cell induction in growth plates, partially prevents osteoporosis in an ovariectomized mouse model, and accelerates bone healing in osteoporotic mice. We conclude that NMN can be a novel and promising therapeutic candidate to enhance bone fracture healing capacity in the older.

Nicotinamide adenine dinucleotide metabolism and arterial stiffness after long-term nicotinamide mononucleotide supplementation: a randomized, double-blind, placebo-controlled trial

Many animal studies have shown that oral administration of the nicotinamide adenine dinucleotide (NAD⁺) precursor nicotinamide mononucleotide (NMN) prevents the reduction of NAD⁺ levels in organs and tissues, helping alleviate aging-related diseases. However, there are very few clinical reports of NMN supplementation in humans. Thus, this study aimed to investigate the influence of a 12-week NMN oral supplementation on biochemical and metabolic health parameters. A 12-week randomized, double-blind, placebo-controlled, parallel-group clinical trial was conducted. A total of 36 healthy middle-aged participants received one capsule of either 125 mg NMN or placebo twice a day. Among the NAD⁺ metabolites, the levels of nicotinamide in the serum were significantly higher in the NMN intake group than in the placebo group. Pulse wave velocity values indicating arterial stiffness tended to decrease in the NMN intake group. However, no significant difference was found between the two groups. Long-term NMN supplementation at 250 mg/day was well tolerated and did not cause adverse events. NMN safely and effectively elevated NAD⁺ metabolism in healthy middle-aged adults. Additionally, NMN supplementation showed potential in alleviating arterial stiffness.

Is the anti-aging effect of ACE2 due to its role in the renin-angiotensin system?-Findings from a comparison of the aging phenotypes of ACE2-deficient, Tsukuba hypertensive, and Mas-deficient mice

Angiotensin converting enzyme 2 (ACE2) functions as an enzyme that produces angiotensin 1-7 (A1-7) from angiotensin II (AII) in the renin-angiotensin system (RAS). We evaluated aging phenotypes, especially skeletal muscle aging, in ACE2 systemically deficient (ACE2 KO) mice and found that ACE2 has an antiaging function. The characteristic aging phenotype observed in ACE2 KO mice was not reproduced in mice deficient in the A1-7 receptor Mas or in Tsukuba hypertensive mice, a model of chronic AII overproduction, suggesting that ACE2 has a RAS-independent antiaging function. In this review, the results we have obtained and related studies on the aging regulatory mechanism mediated by RAS components will be presented and summarized. We evaluated the aging phenotype of ACE2 systemically deficient (ACE2 KO) mice, particularly skeletal muscle aging, and found that ACE2 has an antiaging function. The characteristic aging phenotype observed in ACE2 KO mice was not reproduced in Mas KO mice, angiotensin 1-7 receptor-deficient mice or in Tsukuba hypertensive mice, a model of chronic angiotensin II overproduction, suggesting that the antiaging functions of ACE2 are independent of the renin-angiotensin system (RAS).

Potential Synergistic Supplementation of NAD+ Promoting Compounds as a Strategy for Increasing Healthspan

Disrupted biological function, manifesting through the hallmarks of aging, poses one of the largest threats to healthspan and risk of disease development, such as metabolic disorders, cardiovascular ailments, and neurodegeneration. In recent years, numerous geroprotectors, senolytics, and other nutraceuticals have emerged as potential disruptors of aging and may be viable interventions in the immediate state of human longevity science. In this review, we focus on the decrease in nicotinamide adenine dinucleotide (NAD+) with age and the supplementation of NAD+ precursors, such as nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), in combination with other geroprotective compounds, to restore NAD+ levels present in youth. Furthermore, these geroprotectors may enhance the efficacy of NMN supplementation while concurrently providing their own numerous health benefits. By analyzing the prevention of NAD+ degradation through the inhibition of CD38 or supporting protective downstream agents of SIRT1, we provide a potential framework of the CD38/NAD+/SIRT1 axis through which geroprotectors may enhance the efficacy of NAD+ precursor supplementation and reduce the risk of age-related diseases, thereby potentiating healthspan in humans.

The Influence of Mitochondrial Energy and 1C Metabolism on the Efficacy of Anticancer Drugs: Exploring Potential Mechanisms of Resistance

Mitochondria are the main energy factory in living cells. To rapidly proliferate and metastasize, neoplastic cells increase their energy requirements. Thus, mitochondria become one of the most important organelles for them. Indeed, much research shows the interplay between cancer chemoresistance and altered mitochondrial function. In this review, we focus on the differences in energy metabolism between cancer and normal cells to better understand their resistance and how to develop drugs targeting energy metabolism and nucleotide synthesis. One of the differences between cancer and normal cells is the higher nicotinamide adenine dinucleotide (NAD+) level, a cofactor for the tricarboxylic acid cycle (TCA), which enhances their proliferation and helps cancer cells survive under hypoxic conditions. An important change is a metabolic switch called the Warburg effect. This effect is based on the change of energy harvesting from oxygen-dependent transformation to oxidative phosphorylation (OXPHOS), adapting them to the tumor environment. Another mechanism is the high expression of one-carbon (1C) metabolism enzymes. Again, this allows cancer cells to increase proliferation by producing precursors for the synthesis of nucleotides and amino acids. We reviewed drugs in clinical practice and development targeting NAD+, OXPHOS, and 1C metabolism. Combining novel drugs with conventional antineoplastic agents may prove to be a promising new way of anticancer treatment.

Deletion of Nmnat1 in Skeletal Muscle Leads to the Reduction of NAD+ Levels but Has No Impact on Skeletal Muscle Morphology and Fiber Types

Nicotinamide adenine dinucleotide (NAD⁺) is a coenzyme that mediates many redox reactions in energy metabolism. NAD⁺ is also a substrate for ADP-ribosylation and deacetylation by poly (ADP-ribose) polymerase and sirtuin, respectively. Nicotinamide mononucleotide adenylyltransferase 1 (Nmnat1) is a NAD⁺ biosynthesizing enzyme found in the nucleus. Recent research has shown that the maintaining NAD⁺ levels is critical for sustaining muscle functions both in physiological and pathological conditions. However, the role of Nmnat1 in skeletal muscle remains unexplored. In this study, we generated skeletal muscle-specific Nmnat1 knockout (M-Nmnat1 KO) mice and investigated its role in skeletal muscle. We found that NAD⁺ levels were significantly lower in the skeletal muscle of M-Nmnat1 KO mice than in control mice. M-Nmnat1 KO mice, in contrast, had similar body weight and normal muscle histology. Furthermore, the distribution of muscle fiber size and gene expressions of muscle fiber type gene expression were comparable in M-Nmnat1 KO and control mice. Finally, we investigated the role of Nmnat1 in muscle regeneration using cardiotoxin-induced muscle injury model, but muscle regeneration appeared almost normal in M-Nmnat1 KO mice. These findings imply that Nmnat1 has a redundancy in the pathophysiology of skeletal muscle.

Oncometabolic role of mitochondrial sirtuins in glioma patients

Mitochondrial sirtuins have diverse role specifically in aging, metabolism and cancer. In cancer, these sirtuins play dichotomous role as tumor suppressor and promoter. Previous studies have reported the involvement of sirtuins in different cancers. However, till now no study has been published with respect to mitochondrial sirtuins and glioma risks. Present study was purposed to figure out the expression level of mitochondrial sirtuins (SIRT3, SIRT4, SIRT5) and related genes (GDH, OGG1-2α, SOD1, SOD2, HIF1α and PARP1) in 153 glioma tissue samples and 200 brain tissue samples from epilepsy patients (taken as controls). To understand the role of selected situins in gliomagenesis, DNA damage was measured using the comet assay and oncometabolic role (oxidative stress level, ATP level and NAD level) was measured using the ELISA and quantitative PCR. Results analysis showed significant down-regulation of SIRT4 (p = 0.0337), SIRT5 (p<0.0001), GDH (p = 0.0305), OGG1-2α (p = 0.0001), SOD1 (p<0.0001) and SOD2 (p<0.0001) in glioma patients compared to controls. In case of SIRT3 (p = 0.0322), HIF1α (p = 0.0385) and PARP1 (p = 0.0203), significant up-regulation was observed. ROC curve analysis and cox regression analysis showed the good diagnostic and prognostic value of mitochondrial sirtuins in glioma patients. Oncometabolic rate assessment analysis showed significant increased ATP level (p<0.0001), NAD+ level [(NMNAT1 (p<0.0001), NMNAT3 (p<0.0001) and NAMPT (p<0.04)] and glutathione level (p<0.0001) in glioma patients compared to controls. Significant increased level of damage ((p<0.04) and decrease level of antioxidant enzymes include superoxide dismutase (SOD, p<0.0001), catalase (CAT, p<0.0001) and glutathione peroxidase (GPx, p<0.0001) was observed in patients compared to controls. Present study data suggest that variation in expression pattern of mitochondrial sirtuins and increased metabolic rate may have diagnostic and prognostic significance in glioma patients.

Potential Therapeutic Effects of NAMPT-Mediated NAD Biosynthesis in Depression In Vivo

This study aimed to investigate the potential therapeutic effects of nicotinamide phosphoribosyltransferase (NAMPT)-mediated adenine dinucleotide (NAD) biosynthesis in depression models in vivo. Nampt^flox/flox mice were used to evaluate the role of NAMPT in depression. NAMPT and NAD levels in the prefrontal cortex (PFC) were measured, and depression-associated behavior, cognitive function, and social interaction were evaluated. The expression levels of BDNF, pCREB, CREB, monoamine neurotransmitters, and corticosterone (CORT) were also detected in the PFC. The contents of NAMPT and NAD decreased in the PFC in Nampt^flox/flox mice. Nampt^flox/flox mice showed depression-like behaviors, cognitive function deterioration, decreased social ability, and decreased dominance. Meanwhile, there were decreased expression levels of the pCREB/CREB ratio, but not BDNF, in the PFC. Levels of DA, 5-HT, and NE were decreased, and CORT was activated in the PFC of Nampt^flox/flox mice. Additionally, the role of NAMPT-NAD was examined in rats treated with nicotinamide riboside (NR) after being exposed to chronic unexpected mild stress (CUMS). NR reversed the decreased NAMPT expression in the PFC and HIP, and the NAD content in the PFC, but not HIP in rats with CUMS-induced depression. NR also improved depressive- and anxiolytic-like behaviors, locomotor activity, and cognitive function. BDNF expression and the pCREB/CREB ratio were significantly increased in both the PFC and HIP after NR treatment. The activation of CORT and decreased content of DA were reversed after NR treatment in the PFC. There was no difference in the 5-HT content among groups in both the PFC and HIP. Taken together, NAD synthesis induced by NAMPT could be associated with depression-like behaviors in mice, and the elevated NAD level by NR improved depression in rats.

The Aging Process: A Metabolomics Perspective

Aging process is characterized by a progressive decline of several organic, physiological, and metabolic functions whose precise mechanism remains unclear. Metabolomics allows the identification of several metabolites and may contribute to clarifying the aging-regulated metabolic pathways. We aimed to investigate aging-related serum metabolic changes using a metabolomics approach. Fasting blood serum samples from 138 apparently healthy individuals (20−70 years old, 56% men) were analyzed by Proton Nuclear Magnetic Resonance spectroscopy (1H NMR) and Liquid Chromatography-High-Resolution Mass Spectrometry (LC-HRMS), and for clinical markers. Associations of the metabolic profile with age were explored via Correlations (r); Metabolite Set Enrichment Analysis; Multiple Linear Regression; and Aging Metabolism Breakpoint. The age increase was positively correlated (0.212 ≤ r ≤ 0.370, p < 0.05) with the clinical markers (total cholesterol, HDL, LDL, VLDL, triacylglyceride, and glucose levels); negatively correlated (−0.285 ≤ r ≤ −0.214, p < 0.05) with tryptophan, 3-hydroxyisobutyrate, asparagine, isoleucine, leucine, and valine levels, but positively (0.237 ≤ r ≤ 0.269, p < 0.05) with aspartate and ornithine levels. These metabolites resulted in three enriched pathways: valine, leucine, and isoleucine degradation, urea cycle, and ammonia recycling. Additionally, serum metabolic levels of 3-hydroxyisobutyrate, isoleucine, aspartate, and ornithine explained 27.3% of the age variation, with the aging metabolism breakpoint occurring after the third decade of life. These results indicate that the aging process is potentially associated with reduced serum branched-chain amino acid levels (especially after the third decade of life) and progressively increased levels of serum metabolites indicative of the urea cycle.

NAD+ metabolism in peripheral neuropathic pain

Nicotinamide adenine dinucleotide (NAD⁺) is an omnipresent metabolite that participates in redox reactions. Multiple NAD⁺-consuming enzymes are implicated in numerous biological processes, including transcription, signaling, and cell survival. Multiple pieces of evidence have demonstrated that NAD⁺-consuming enzymes, including poly(ADP-ribose) polymerases (PARPs), sirtuins (SIRTs), and sterile alpha and TIR motif-containing 1 (SARM1), play major roles in peripheral neuropathic pain of various etiologies. These NAD⁺ consumers primarily participate in peripheral neuropathic pain via mechanisms such as mitochondrial dysfunction, oxidative stress, and inflammation. Furthermore, NAD⁺ synthase and nicotinamide phosphoribosyltransferase (NAMPT) have recently been found to contribute to the regulation of pain. Here, we review the evidence indicating the involvement of NAD⁺ metabolism in the pathological mechanisms of peripheral neuropathic pain. Advanced understanding of the molecular and cellular mechanisms associated with NAD⁺ in peripheral neuropathic pain will facilitate the development of novel treatment options for diverse types of peripheral neuropathic pain.

The inflammatory response, a mixed blessing for muscle homeostasis and plasticity

Skeletal muscle makes up almost half the body weight of heathy individuals and is involved in several vital functions, including breathing, thermogenesis, metabolism, and locomotion. Skeletal muscle exhibits enormous plasticity with its capacity to adapt to stimuli such as changes in mechanical loading, nutritional interventions, or environmental factors (oxidative stress, inflammation, and endocrine changes). Satellite cells and timely recruited inflammatory cells are key actors in muscle homeostasis, injury, and repair processes. Conversely, uncontrolled recruitment of inflammatory cells or chronic inflammatory processes leads to muscle atrophy, fibrosis and, ultimately, impairment of muscle function. Muscle atrophy and loss of function are reported to occur either in physiological situations such as aging, cast immobilization, and prolonged bed rest, as well as in many pathological situations, including cancers, muscular dystrophies, and several other chronic illnesses. In this review, we highlight recent discoveries with respect to the molecular mechanisms leading to muscle atrophy caused by modified mechanical loading, aging, and diseases. We also summarize current perspectives suggesting that the inflammatory process in muscle homeostasis and repair is a double-edged sword. Lastly, we review recent therapeutic approaches for treating muscle wasting disorders, with a focus on the RANK/RANKL/OPG pathway and its involvement in muscle inflammation, protection and regeneration processes.

Impact of Nuclear De Novo NAD+ Synthesis via Histone Dynamics on DNA Repair during Cellular Senescence To Prevent Tumorigenesis

NAD⁺ synthesis is a fundamental process in living cells. The effects of local metabolite production on chromatin influence the epigenetic status of chromatin in DNA metabolism. We have previously shown that K5 acetylation of H2AX by TIP60 is required for the ADP ribosylation activity of PARP-1, for histone H2AX exchange at DNA damage sites. However, the detailed molecular mechanism has remained unclear. Here, we identified de novo NAD synthetase 1 (NAD syn1) as a novel binding partner to H2AX. The enzymatic activity of NAD syn1 is crucial for the ADP ribosylation activity of PARP-1 for the H2AX dynamics at sites of DNA damage. Inhibition of the NAD synthetase activity in the cell nucleus decreased the overall cellular NAD⁺ concentration, leading to cellular senescence. Accordingly, the acetylation-dependent H2AX dynamics and homologous recombination repair were suppressed, leading to increased tumorigenesis. Our findings have revealed the importance of de novo NAD⁺ production in the cell nucleus for protection against the decreased DNA repair capacity caused by cellular senescence and thus against tumorigenesis.

Porcine placental extract increase the cellular NAD levels in human epidermal keratinocytes

Nicotinamide adenine dinucleotide (NAD) is an essential cofactor for numerous enzymes involved in energy metabolism. Because decreasing NAD levels is a common hallmark of the aging process in various tissues and organs, maintaining NAD levels has recently been of interest for the prevention of aging and age-related diseases. Although placental extract (PE) are known to possess several anti-aging effects, the NAD-boosting activity of PE remains unknown. In this study, we found that porcine PE (PPE) significantly increased intracellular NAD levels in normal human epidermal keratinocytes (NHEKs). PPE also attenuated the NAD depletion induced by FK866, an inhibitor of nicotinamide phosphoribosyltransferase (NAMPT). Interestingly, only the fraction containing nicotinamide mononucleotide (NMN), nicotinamide riboside (NR), and nicotinamide (NAM) restored NAD content in NHEKs in the absence of NAMPT activity. These results suggest that PPE increases intracellular NAD by providing NAD precursors such as NMN, NR, and NAM. Finally, we showed that the application of PPE to the stratum corneum of the reconstructed human epidermis significantly ameliorated FK866-induced NAD depletion, suggesting that topical PPE may be helpful for increasing skin NAD levels. This is the first study to report the novel biological activity of PE as an NAD booster in human epidermal cells.

Epigenetic regulation of aging: implications for interventions of aging and diseases

Aging is accompanied by the decline of organismal functions and a series of prominent hallmarks, including genetic and epigenetic alterations. These aging-associated epigenetic changes include DNA methylation, histone modification, chromatin remodeling, non-coding RNA (ncRNA) regulation, and RNA modification, all of which participate in the regulation of the aging process, and hence contribute to aging-related diseases. Therefore, understanding the epigenetic mechanisms in aging will provide new avenues to develop strategies to delay aging. Indeed, aging interventions based on manipulating epigenetic mechanisms have led to the alleviation of aging or the extension of the lifespan in animal models. Small molecule-based therapies and reprogramming strategies that enable epigenetic rejuvenation have been developed for ameliorating or reversing aging-related conditions. In addition, adopting health-promoting activities, such as caloric restriction, exercise, and calibrating circadian rhythm, has been demonstrated to delay aging. Furthermore, various clinical trials for aging intervention are ongoing, providing more evidence of the safety and efficacy of these therapies. Here, we review recent work on the epigenetic regulation of aging and outline the advances in intervention strategies for aging and age-associated diseases. A better understanding of the critical roles of epigenetics in the aging process will lead to more clinical advances in the prevention of human aging and therapy of aging-related diseases.