Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women

The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis

INTRODUCTION

Sarcopenia is associated with the loss of skeletal muscle function and mass. Nicotinamide precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), have received attention for their potential to improve NAD+ levels and mitigate age-related sarcopenia in preliminary models, though evidence on their effects in older adults remains inconclusive.

METHODS

We searched PubMed, Cochrane Library, Web of Science, and Scopus to identify randomized controlled trials (RCTs), comparing NR or NMN vs. placebo. A random-effects meta-analysis was employed to determine their impact on measures of sarcopenia such as skeletal muscle index (SMI), handgrip strength (HGS) and gait speed. A narrative synthesis was used for 5-time chair stand test (5CST), short physical performance battery (SPPB), timed-up-and-go (TUG), 6-min walking distance (6MWD), leg and chest press 80% 1RM (repetition maximum) and thigh muscle mass.

RESULTS

Included participants had a mean age range from 60.9 to 83 years. NMN supplementation showed no significant effects on SMI (n = 3; mean difference (MD): -0.42, 95% confidence interval (CI): -0.99 - 0.14, I2 = 63%, p = 0.14), HGS (One study estimating left grip; n = 5; MD: 0.61, 95%CI: -0.89 - 2.10, I2 = 0%, p = 0.42; One study estimating right grip; n = 5; MD: 0.45, 95%CI: -1.06 - 1.96, I2 = 0%, p = 0.56), gait speed (n = 4; MD: -0.01, 95%CI: -0.08 - 0.06, I2 = 0%, p = 0.79), or 5CST (n = 2; MD: -0.21, 95%CI: -0.70 - 0.29, I2 = 11%, p = 0.41). Additionally, our narrative synthesis showed that NMN did not improve knee extension strength, SPPB, or thigh muscle mass. NR supplementation was associated with a longer 6MWD among individuals with peripheral artery disease. However, lower scores in the SPPB and slower 5CST were observed in those with mild cognitive impairment.

CONCLUSIONS

Current evidence does not support NMN and NR supplementation for preserving muscle mass and function in adults with mean age of over 60 years. Future research should explore supplementation dosage, NAD+ baseline deficiency, and combined interventions.

Microbial Production of Nicotinamide Mononucleotide: Key Enzymes Discovery, Host Cells Selection, and Pathways Design and Optimization

As an important bioactive substance in cells, nicotinamide mononucleotide (NMN) has been proven to play an important role in antiaging, treatment of neurodegenerative diseases, and cardioprotection. It presents a high potential for application in the research fields of functional foods, cosmetics, healthcare products, and active pharmaceuticals. With the increased demand, whether NMN can achieve large-scale industrial production has been a wide concern. The chemical synthesis method of NMN mainly faces the problems of separation, purification, and complex process control; in contrast, biosynthesis methods such as microbial fermentation and enzyme catalysis are considered to be the mainstream of the future industrial production of NMN due to the advantages of environmental friendliness, high efficiency, and simple separation. This review first describes the physiological functions of NMN and the related areas of its applications. Subsequently, it focuses on the research progress on different synthetic pathways of NMN in biosynthetic approaches, mining and modification of key enzymes, chassis cell design and optimization, and whole-cell catalysis. Meanwhile, the regulatory strategies, methods, and process control of the microbial synthesis of NMN are also elaborated, and the synthesis efficiencies of different chassis cells are systematically compared. Finally, this review summarizes the existing problems and challenges of microbial synthesis of NMN and proposes future strategies and directions to address these issues. This work provides technical references and a theoretical basis for researching efficient NMN microbial synthesis and application.

Nicotinamide mononucleotide ameliorates hypertriglyceridemia pancreatitis via NAD+/SIRT1-mediated TXNIP suppression and NOTCH pathway for accelerated repair-associated processes

BACKGROUND & AIMS

Acute pancreatitis (AP) is a life-threatening condition, and hypertriglyceridemia (HTG) is recognized as a factor exacerbating AP and impeding pancreatic regeneration. Nicotinamide mononucleotide (NMN), a precursor in the biosynthesis of nicotinamide adenine dinucleotide (NAD+), is extensively utilized to restore NAD+ levels. However, the impact of NMN on HTG-AP has not been previously addressed, which prompted our investigation into its effects and underlying mechanisms in this study.

METHODS & RESULTS

Here, through bioinformatics analysis and in vivo experiments, we identified abnormalities in the thioredoxin system. In vitro studies revealed that NMN rescued oleic acid (OA)- and palmitic acid (PA)-induced mitochondrial dysfunction and cellular injury in pancreatic acinar cells by suppressing thioredoxin-interacting protein (TXNIP) through NAD+/sirtuin 1 (SIRT1) signaling. Repeated administration of NMN significantly ameliorated P407 and caerulein (CER)-induced pancreatic injury and dysfunction in mice. Consistently, NMN exhibited the potential to reduce inflammatory responses, lower serum lipid levels, and mitigate the accumulation of reactive oxygen species (ROS). More importantly, sustained NMN treatment inhibited the NOTCH pathway and promoted M2-type macrophage dominance during the pancreatic repair phase, influencing early or late macrophage polarization, which significantly enhanced inflammation resolution. As expected, in vitro models using mouse bone marrow-derived macrophage (BMDM), RAW 264.7, and THP-1 cells confirmed that NMN influences macrophage phenotype through the NOTCH pathway.

CONCLUSIONS

Therefore, NMN ameliorates pancreatic acinar cell injury via NAD+/SIRT1-mediated TXNIP suppression and may influence macrophage polarization by inhibiting NOTCH activation, offering a novel therapeutic strategy for the treatment and repair of HTG-AP.

High Concentrations of Circulating 2PY and 4PY-Potential Risk Factor of Cardiovascular Disease in Patients with Chronic Kidney Disease

Recently published data indicate that elevated circulating concentrations of N1-methyl-2-pyridone-5-carboxamide (2PY, also described as Met2PY) and N1-methyl-4-pyridone-5-carboxamide (4PY, also described as Met4PY), terminal catabolites of nicotinamide adenine dinucleotide (NAD+), are associated with cardiovascular disease (CVD) risk in humans. Previously, we and the others have shown that patients with advanced stages of chronic kidney disease (CKD) exhibit several-fold higher circulating 2PY and 4PY concentrations compared to healthy subjects or patients in the early stages of the disease. It is also well documented that patients with advanced CKD stages exhibit markedly elevated CVD risk, which is the main cause of premature death (in these patients). Therefore, we hypothesize that high concentrations of circulating 2PY and 4PY are important factors that may contribute to cardiovascular events and, ultimately, premature death in CKD patients. However, further, accurately controlled clinical research is needed to provide definitive answers concerning the role of 2PY and 4PY in CVD risk in CKD patients. Moreover, we are dealing with some issues related to the use of NAD+ precursors (NAD+ boosters) as drugs (also in CKD patients) and/or supplements. Due to the increase in circulating 2PY and 4PY levels during treatment with NAD+ boosters, these precursors should be used with caution, especially in patients with increased CVD risk.

Nicotinic acid riboside maintains NAD+ homeostasis and ameliorates aging-associated NAD+ decline

Liver-derived circulating nicotinamide from nicotinamide adenine dinucleotide (NAD+) catabolism primarily feeds systemic organs for NAD+ synthesis. We surprisingly found that, despite blunted hepatic NAD+ and nicotinamide production in liver-specific nicotinamide nucleotide adenylyltransferase 1 (NMNAT1) deletion mice (liver-specific knockout [LKO]), circulating nicotinamide and extra-hepatic organs' NAD+ are unaffected. Metabolomics reveals a massive accumulation of a novel molecule in the LKO liver, which we identify as nicotinic acid riboside (NaR). We further demonstrate cytosolic 5'-nucleotidase II (NT5C2) as the NaR-producing enzyme. The liver releases NaR to the bloodstream, and kidneys take up NaR to synthesize NAD+ through nicotinamide riboside kinase 1 (NRK1) and replenish circulating nicotinamide. Serum NaR levels decline with aging, whereas oral NaR supplementation in aged mice boosts serum nicotinamide and multi-organ NAD+, including kidneys, and reduces kidney inflammation and albuminuria. Thus, the liver-kidney axis maintains systemic NAD+ homeostasis via circulating NaR, and NaR supplement ameliorates aging-associated NAD+ decline and kidney dysfunction.

The Role of NAD+ Metabolism in Cardiovascular Diseases: Mechanisms and Prospects

Nicotinamide adenine dinucleotide (NAD+) is a promising anti-aging molecule that plays a role in cellular energy metabolism and maintains redox homeostasis. Additionally, NAD+ is involved in regulating deacetylases, DNA repair enzymes, inflammation, and epigenetics, making it indispensable in maintaining the basic functions of cells. Research on NAD+ has become a hotspot, particularly regarding its potential in cardiovascular disease (CVD). Many studies have demonstrated that NAD+ plays a crucial role in the occurrence and development of CVD. This review summarizes the biosynthesis and consumption of NAD+, along with its precursors and their effects on raising NAD+ levels. We also discuss new mechanisms of NAD+ regulation in cardiovascular risk factors and its effects of NAD+ on atherosclerosis, aortic aneurysm, heart failure, hypertension, myocardial ischemia-reperfusion injury, diabetic cardiomyopathy, and dilated cardiomyopathy, elucidating different mechanisms and potential treatments. NAD+-centered therapy holds promising advantages and prospects in the field of CVD.

A new clinical age of aging research

Aging is a major risk factor for a variety of diseases, thus, translation of aging research into practical applications is driven by the unmet need for existing clinical therapeutic options. Basic and translational research efforts are converging at a critical stage, yielding insights into how fundamental aging mechanisms are used to identify promising geroprotectors or therapeutics. This review highlights several research areas from a clinical perspective, including senescent cell targeting, alleviation of inflammaging, and optimization of metabolism with endogenous metabolites or precursors. Refining our understanding of these key areas, especially from the clinical angle, may help us to better understand and attenuate aging processes and improve overall health outcomes.

NAD depletion in skeletal muscle does not compromise muscle function or accelerate aging

Nicotinamide adenine dinucleotide (NAD) is a ubiquitous electron carrier essential for energy metabolism and post-translational modification of numerous regulatory proteins. Dysregulations of NAD metabolism are widely regarded as detrimental to health, with NAD depletion commonly implicated in aging. However, the extent to which cellular NAD concentration can decline without adverse consequences remains unclear. To investigate this, we generated a mouse model in which nicotinamide phosphoribosyltransferase (NAMPT)-mediated NAD+ biosynthesis was disrupted in adult skeletal muscle. The intervention resulted in an 85% reduction in muscle NAD+ abundance while maintaining tissue integrity and functionality, as demonstrated by preserved muscle morphology, contractility, and exercise tolerance. This absence of functional impairments was further supported by intact mitochondrial respiratory capacity and unaltered muscle transcriptomic and proteomic profiles. Furthermore, lifelong NAD depletion did not accelerate muscle aging or impair whole-body metabolism. Collectively, these findings suggest that NAD depletion does not contribute to age-related decline in skeletal muscle function.

Widely targeted metabolomics analysis reveals dynamic changes in metabolites of 'Hass' avocado during postharvest ripening period

Avocado (Persea americana Mill) is a climacteric fruit harvested at the green stage that ripens postharvest to become edible. The 'Hass' cultivar, known for its rich, buttery flavor and pear-shaped appearance, was studied for metabolite changes during postharvest ripening using UPLC-MS/MS approach. The 16-day ripening period could be divided into three stages: evolution (days 1-9), edible ripe (days 10-15) and overripe (day 16). A total of 1397 metabolites were identified across 13 classes. Among them, amino acids transitioned from conjugated to free forms, while sugars converted to monosaccharides, enhancing savory and sweet tastes. The concentration of certain secondary metabolites like terpenes, coumarins, and alkaloids increased, likely supporting antimicrobial defense, alongside a substantial increase in lipid content. Additionally, 20 compounds were screened as markers for edible ripeness. This study provides valuable insights into avocado postharvest ripening and offers references for optimizing shelf-life.

Obesity accelerates cardiovascular ageing

A global obesity pandemic, coupled with an increasingly ageing population, is exacerbating the burden of cardiovascular disease. Indeed, clinical and experimental evidence underscores a potential connection between obesity and ageing in the pathogenesis of various cardiovascular disorders. This is further supported by the notion that weight reduction not only effectively reduces major cardiovascular events in elderly individuals but is also considered the gold standard for lifespan extension, in obese and non-obese model organisms. This review evaluates the intricate interplay between obesity and ageing from molecular mechanisms to whole organ function within the cardiovascular system. By comparatively analysing their characteristic features, shared molecular and cell biological signatures between obesity and ageing are unveiled, with the intent to shed light on how obesity accelerates cardiovascular ageing. This review also elaborates on how emerging metabolic interventions targeting obesity might protect from cardiovascular diseases largely through antagonizing key molecular mechanisms of the ageing process itself. In sum, this review aims to provide valuable insight into how understanding these interconnected processes could guide the development of novel and effective cardiovascular therapeutics for a growing aged population with a concerning obesity problem.

Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD+ synthesis via enterohepatic circulation

Decreased nicotinamide adenine dinucleotide (oxidized form) (NAD+) levels are reportedly associated with several aging-related disorders. Thus, supplementation with NAD+ precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), exhibits beneficial effects against these disorders. However, the in vivo metabolic pathways of NMN and NR remain to be elucidated. In this study, we comprehensively analyzed the fate of orally and intravenously administered NMN and NR in mice using NAD+ metabolomics. We found that only a small portion of orally administered NMN and NR was directly absorbed from the small intestine and that most of them underwent gut microbiota-mediated deamidation and conversion to nicotinic acid (NA). Moreover, intravenously administered NMN and NR were rapidly degraded into nicotinamide and secreted to bile followed by deamidation to NA by gut microbiota. Thus, enterohepatic circulated NA is preferentially used in the liver. These findings showed that NMN and NR are indirectly converted to NAD+ via unexpected metabolic pathways.

PPDPF preserves integrity of proximal tubule by modulating NMNAT activity in chronic kidney diseases

Genome-wide association studies (GWAS) have identified loci associated with kidney diseases, but the causal variants, genes, and pathways involved remain elusive. Here, we identified a kidney disease gene called pancreatic progenitor cell differentiation and proliferation factor (PPDPF) through integrating GWAS on kidney function and multiomic analysis. PPDPF was predominantly expressed in healthy proximal tubules of human and mouse kidneys via single-cell analysis. Further investigations revealed that PPDPF functioned as a thiol-disulfide oxidoreductase to maintain cellular NAD+ levels. Deficiency in PPDPF disrupted NAD+ and mitochondrial homeostasis by impairing the activities of nicotinamide mononucleotide adenylyl transferases (NMNATs), thereby compromising the function of proximal tubules during injuries. Consequently, knockout of PPDPF notably accelerated the progression of chronic kidney disease (CKD) in mouse models induced by aging, chemical exposure, and obstruction. These findings strongly support targeting PPDPF as a potential therapy for kidney fibrosis, offering possibilities for future CKD interventions.

Antiageing strategy for neurodegenerative diseases: from mechanisms to clinical advances

In the context of global ageing, the prevalence of neurodegenerative diseases and dementia, such as Alzheimer's disease (AD), is increasing. However, the current symptomatic and disease-modifying therapies have achieved limited benefits for neurodegenerative diseases in clinical settings. Halting the progress of neurodegeneration and cognitive decline or even improving impaired cognition and function are the clinically meaningful goals of treatments for neurodegenerative diseases. Ageing is the primary risk factor for neurodegenerative diseases and their associated comorbidities, such as vascular pathologies, in elderly individuals. Thus, we aim to elucidate the role of ageing in neurodegenerative diseases from the perspective of a complex system, in which the brain is the core and peripheral organs and tissues form a holistic network to support brain functions. During ageing, the progressive deterioration of the structure and function of the entire body hampers its active and adaptive responses to various stimuli, thereby rendering individuals more vulnerable to neurodegenerative diseases. Consequently, we propose that the prevention and treatment of neurodegenerative diseases should be grounded in holistic antiageing and rejuvenation means complemented by interventions targeting disease-specific pathogenic events. This integrated approach is a promising strategy to effectively prevent, pause or slow down the progression of neurodegenerative diseases.

Near Infrared-Mediated Intracellular NADH Delivery Strengthens Mitochondrial Function and Stability in Muscle Dysfunction Model

Mitochondrial transfer emerges as a promising therapy for the restoration of mitochondrial function in damaged cells, mainly due to its limited immunogenicity. However, isolated mitochondria rapidly lose function because they produce little energy outside cells. Therefore, this study investigates whether near infrared (NIR)-mediated nicotinamide adenine dinucleotide (NADH) pre-treatment enhances mitochondrial function and stability in mitochondria-donor cells prior to transplantation. Clinical applications of NADH, an essential electron donor in the oxidative phosphorylation process, are restricted due to the limited cellular uptake of NADH. To address this, a photo-mediated method optimizes direct NADH delivery into cells and increases NADH absorption. L6 cells treated with NADH and irradiated with NIR enhanced NADH uptake, significantly improving mitochondrial energy production and function. Importantly, the improved functional characteristics of the mitochondria are maintained even after isolation from cells. Primed mitochondria, i.e., those enhanced by NIR-mediated NADH uptake (P-MT), are encapsulated in fusogenic liposomes and delivered into muscle cells with mitochondrial dysfunction. Compared to conventional mitochondria, P-MT mitochondria promote greater mitochondrial recovery and muscle regeneration. These findings suggest that NIR-mediated NADH delivery is an effective strategy for improving mitochondrial function, and has the potential to lead to novel treatments for mitochondrial disorders and muscle degeneration.

Nicotinamide mononucleotide enhances the developmental potential of mouse early embryos exposed to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) exposure severely affects the health of animals and humans, including early embryonic development, but the effective approaches to improve the quality of embryos exposed to PFOA have not been explored. Here, we report that nicotinamide mononucleotide (NMN) can be used to attenuate the impairment of mouse early embryos caused by PFOA exposure. We find that NMN supplementation maintains the normal spindle assembly and proper chromosome alignment by restoring the acetylation level of microtubule to enhance the mitotic capacity of embryos at zygotic cleavage stage under PFOA exposure. In addition, NMN exerts its beneficial effect by enhancing mitochondrial function and eliminating accumulated reactive oxygen species (ROS), which in turn alleviates DNA damage and apoptosis in PFOA-exposed 2-cell embryos. Moreover, NMN ameliorates the quality of PFOA-exposed blastocysts via recovering the octamer-binding transcription factor 4 (Oct4) expression, the actin dynamics, and the total number of cells. Collectively, our findings demonstrate that supplementation with NMN is a feasible strategy to restore the compromised early embryonic development under PFOA exposure, providing a scientific basis for application of NMN to increase the female fertility.

Roles of Sirtuins in Cardiovascular Diseases: Mechanisms and Therapeutics

Cardiovascular diseases (CVDs) are experiencing a rapid surge and are widely recognized as the leading cause of mortality in the current aging society. Given the multifactorial etiology of CVDs, understanding the intricate molecular and cellular mechanisms is imperative. Over the past 2 decades, many scientists have focused on Sirtuins, a family of nicotinamide adenine dinucleotide-dependent deacylases. Sirtuins are highly conserved across species, from yeasts to primates, and play a crucial role in linking aging and diseases. Sirtuins participate in nearly all key physiological and pathological processes, ranging from embryogenic development to stress response and aging. Abnormal expression and activity of Sirtuins exist in many aging-related diseases, while their activation has shown efficacy in mitigating these diseases (eg, CVDs). In terms of research, this field has maintained fast, sustained growth in recent years, from fundamental studies to clinical trials. In this review, we present a comprehensive, up-to-date discussion on the biological functions of Sirtuins and their roles in regulating cardiovascular biology and CVDs. Furthermore, we highlight the latest advancements in utilizing Sirtuin-activating compounds and nicotinamide adenine dinucleotide boosters as potential pharmacological targets for preventing and treating CVDs. The key unresolved issues in the field-from the chemicobiological regulation of Sirtuins to Sirtuin-targeted CVD investigations-are also discussed. This timely review could be critical in understanding the updated knowledge of Sirtuin biology in CVDs and facilitating the clinical accessibility of Sirtuin-targeting interventions.

Adipokine isthmin-1 is a potential predictor of abnormal urine Na+ excretion and insulin resistance for primary hypertension

BACKGROUND

Isthmin-1 (ISM1) plays an important role in maintaining glucose homeostasis and lipid metabolism. However, the relationship between circulating ISM1 and hypertension remains unclear. This study was aimed to investigate the association between serum ISM1 levels and blood pressure and evaluate value of circulating ISM1 for predicting abnormal Na+ excretion and insulin resistance.

METHODS

Four hundred sixty-eight individuals newly diagnosed with primary hypertension and 582 healthy individuals were initially screened. 84 participants were eligible for this case-control study. Serum ISM1 levels were assessed using ELISA. Spearman correlation analysis and partial correlation analysis were conducted to confirm the correlation. Multiple linear regression analysis was used to assess the independent association of serum ISM1 concentration with blood pressure. The receiver operating characteristic (ROC) curve was employed to evaluate the sensitivity of ISM1 in predicting abnormal Na+ excretion and insulin resistance in hypertensive subjects.

RESULTS

The serum ISM1 levels of hypertensive individuals were higher than that of healthy individuals. ISM1 levels were positively associated with systolic blood pressure (SBP), diastolic blood pressure (DBP) and brachial-ankle pulse wave velocity, but negatively associated with nocturnal urine Na+ concentration and excretion. These associations remained significant even after adjusting for age, body mass index, sex, heart rate, glucose, total cholesterol and estimated glomerular filtration rate. Multiple linear regression analysis revealed that SBP was an independent factor associated with serum ISM1 levels. The area under receiver operating characteristic curve (AUROC) for predicting low urine Na+ excretion and insulin resistance were 0.873 and 0.740, respectively.

CONCLUSIONS

Serum ISM1 levels were positively associated with SBP and DBP. ISM1 may serve as a potential biomarker of abnormal urine Na+ excretion and insulin resistance in primary hypertensive individuals.

TRIAL REGISTRATION

Registered on chictr.org.cn 18/04/2024 (Registration number: ChiCTR2400083204).

Ovarian Aging: The Silent Catalyst of Age-Related Disorders in Female Body

Age-related diseases have emerged as a global concern as the population ages. Consequently, understanding the underlying causes of aging and exploring potential anti-aging interventions is imperative. In females, the ovaries serve as the principal organs responsible for ovulation and the production of female hormones. The aging ovaries are related to infertility, menopause, and associated menopausal syndromes, with menopause representing the culmination of ovarian aging. Current evidence indicates that ovarian aging may contribute to dysfunction across multiple organ systems, including, but not limited to, cognitive impairment, osteoporosis, and cardiovascular disease. Nevertheless, due to the widespread distribution of sex hormone receptors throughout the body, ovarian aging affects not only these specific organs but also influences a broader spectrum of age-related diseases in women. Despite this, the impact of ovarian aging on overall age-related diseases has been largely neglected. This review provides a thorough summary of the impact of ovarian aging on age-related diseases, encompassing the nervous, circulatory, locomotor, urinary, digestive, respiratory, and endocrine systems. Additionally, we have outlined prospective therapeutic approaches for addressing both ovarian aging and age-related diseases, with the aim of mitigating their impacts and preserving women's fertility, physical health, and psychological well-being.

Mitochondrial calcium uptake declines during aging and is directly activated by oleuropein to boost energy metabolism and skeletal muscle performance

Mitochondrial calcium (mtCa2+) uptake via the mitochondrial calcium uniporter (MCU) couples calcium homeostasis and energy metabolism. mtCa2+ uptake via MCU is rate-limiting for mitochondrial activation during muscle contraction, but its pathophysiological role and therapeutic application remain largely uncharacterized. By profiling human muscle biopsies, patient-derived myotubes, and preclinical models, we discovered a conserved downregulation of mitochondrial calcium uniporter regulator 1 (MCUR1) during skeletal muscle aging that associates with human sarcopenia and impairs mtCa2+ uptake and mitochondrial respiration. Through a screen of 5,000 bioactive molecules, we identify the natural polyphenol oleuropein as a specific MCU activator that stimulates mitochondrial respiration via mitochondrial calcium uptake 1 (MICU1) binding. Oleuropein activates mtCa2+ uptake and energy metabolism to enhance endurance and reduce fatigue in young and aged mice but not in muscle-specific MCU knockout (KO) mice. Our work demonstrates that impaired mtCa2+ uptake contributes to mitochondrial dysfunction during aging and establishes oleuropein as a novel food-derived molecule that specifically targets MCU to stimulate mitochondrial bioenergetics and muscle performance.

Nicotinamide Phosphoribosyltransferase Acetylation Mediating Muscle Dysfunction Contributes to Sleep Apnoea in Obesity

BACKGROUND

Obstructive sleep apnoea (OSA) occurs frequently among individuals with obesity, which is attributed to upper airway muscle dysfunction. Muscle function is regulated by the dynamic balance of the nicotinamide adenine dinucleotide (NAD+) and its reduced form (NADH), which is controlled by the enzyme nicotinamide phosphoribosyltransferase (NAMPT). Elevated NAMPT levels have been found in individuals with obesity. However, the role of NAMPT in obesity-induced muscle impairment has not been fully clarified.

METHODS

A total of 110 participants (70 moderate-to-severe OSA vs. 40 mild or no OSA) underwent electrical impedance mammography and polysomnography. C57BL/6J mice with high-fat diet-induced obesity (DIO) and control group were utilized for their characterizations, which included forced running wheel tests, glucose tolerance tests, haematoxylin and eosin staining, immunostaining, magnetic resonance imaging, whole-body plethysmography, electromyographic techniques, western blot, NAMPT enzymatic activity assays and NAD+/NADH ratio measurements.

RESULTS

Patients with moderate-severe OSA have a significant decrease in lean mass percentage of upper airway muscles compared with those in controls (p < 0.01). In vivo, a high-fat diet reduced the levels of NAD-dependent deacetylase sirtuin-1 (SIRT1) (p < 0.01), which plays a crucial role in the deacetylation of NAMPT. The reduction in SIRT1-mediated NAMPT deacetylation (p < 0.001) resulted in decreased NAMPT activity (p < 0.01), leading to a decrease in NAD+/NADH ratio (p < 0.05) and decreased the myosin heavy chain isoform (MyHC) I level (p < 0.05), thereby affecting the effectiveness of upper airway muscle and ultimately leading to upper airway collapse (101.0 vs. 81.7 pixels, p = 0.02). The introduction of estradiol mitigated high-fat diet-induced muscle dysfunction by enhancing expression of SIRT1 and inhibiting the acetylation of NAMPT, reducing upper airway collapse (81.7 vs. 96.7 pixels, p = 0.06).

CONCLUSIONS

These findings highlight the crucial role of SIRT1-mediated NAMPT deacetylation on obesity-induced muscle dysfunction, suggesting targeting NAMPT has the potential to reverse the obesity induced muscle dysfunction and provide effective treatment options for OSA.

Emerging interactions between mitochondria and NAD+ metabolism in cardiometabolic diseases

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme for redox reactions and regulates cellular catabolic pathways. An intertwined relationship exists between NAD+ and mitochondria, with consequences for mitochondrial function. Dysregulation in NAD+ homeostasis can lead to impaired energetics and increased oxidative stress, contributing to the pathogenesis of cardiometabolic diseases. In this review, we explore how disruptions in NAD+ homeostasis impact mitochondrial function in various cardiometabolic diseases. We discuss emerging studies demonstrating that enhancing NAD+ synthesis or inhibiting its consumption can ameliorate complications of this family of pathological conditions. Additionally, we highlight the potential role and therapeutic promise of mitochondrial NAD+ transporters in regulating cellular and mitochondrial NAD+ homeostasis.

NAD World 3.0: the importance of the NMN transporter and eNAMPT in mammalian aging and longevity control

Over the past five years, systemic NAD+ (nicotinamide adenine dinucleotide) decline has been accepted to be a key driving force of aging in the field of aging research. The original version of the NAD World concept was proposed in 2009, providing an integrated view of the NAD+-centric, systemic regulatory network for mammalian aging and longevity control. The reformulated version of the concept, the NAD World 2.0, was then proposed in 2016, emphasizing the importance of the inter-tissue communications between the hypothalamus and peripheral tissues including adipose tissue and skeletal muscle. There has been significant progress in our understanding of the importance of nicotinamide mononucleotide (NMN), a key NAD+ intermediate, and nicotinamide phosphoribosyltransferase (NAMPT), particularly extracellular NAMPT (eNAMPT). With these exciting developments, the further reformulated version of the concept, the NAD World 3.0, is now proposed, featuring multi-layered feedback loops mediated by NMN and eNAMPT for mammalian aging and longevity control.

Evaluation of the Role of PnuC Gene in Enhancing Nicotinamide Mononucleotide Synthesis

The PnuC gene plays a crucial role in the complex processes related to the absorption and synthesis of the nicotinamide mononucleotide (NMN) precursor. NMN, a nicotinamide adenine dinucleotide (NAD+) precursor, is important for cellular energy metabolism, DNA repair, and antiaging. This study focuses on elucidating the precursor absorption mechanism and the specific function of the PnuC gene in encoding membrane transport proteins, as well as its impact on the regulation and dynamics of NMN within the cell. This understanding aims to provide insights into its potential effects on metabolic balance, illustrated through two NAD+ biosynthesis pathways based on renewable and readily available cytoplasmic resources, assessing the potential of PnuC gene expression in clarifying complex interactions within regulation mechanisms. Enhanced expression analysis of the PnuC gene has initiated discussions on its potential applications in treating aging-related diseases and dysfunctions, contributing to cellular health maintenance.

α-methyltryptophan-mediated protection against diabetic nephropathy in db/db mice as studied with a metabolomics approach

Introduction

Diabetic nephropathy (DN), a major complication of diabetes, presents with poor clinical outcomes and affects patients throughout their lifetime. α-Methyltryptophan (α-MT) is a blocker of the amino acid transporter. SLC6A14 and also an inhibitor of indoleamine 2,3-dioxygenase-1 (IDO1).

Methods

In this study, we employed a nuclear magnetic resonance-based metabolomic approach to investigate the therapeutic effects of α-MT in a db/db mouse model of DN and explore the underlying molecular mechanisms.

Results

The results of the study demonstrated that α-MT significantly reduced the urinary excretion of albumin and creatinine, improved kidney function, and decreased renal fibrosis in db/db mice. Metabolomic analyses of kidney tissues and urine samples indicated that db/db mice displayed increased activity of the enzyme IDO1, and alongside pronounced metabolic disturbances. These disturbances are chiefly characterized by alterations in amino acid metabolism, energy production pathways, membrane biochemical features, and nicotinamide metabolism, all of which have been implicated in mTOR signaling and apoptotic pathways.

Discussion

Administration of α-MT to db/db mice showed evidence of IDO1 inhibition and rectification of metabolic dysfunctions with concurrent suppression of mTOR signaling and apoptosis. These findings highlight the potential of α-MT as a promising therapeutic agent for diabetic nephropathy.

NAD Pathways in Diabetic Coronary Heart Disease: Unveiling the Key Players

Diabetic coronary heart disease is a global medical problem that poses a serious threat to human health, and its pathogenesis is complex and interconnected. Nicotinamide adenine dinucleotide (NAD) is an important small molecule used in the body that serves as a coenzyme in redox reactions and as a substrate for non-redox processes. NAD levels are highly controlled by various pathways, and increasing evidence has shown that NAD pathways, including NAD precursors and key enzymes involved in NAD synthesis and catabolism, exert both positive and negative effects on the pathogenesis of diabetic coronary heart disease. Thus, the mechanisms by which the NAD pathway acts in diabetic coronary heart disease require further investigation. This review first briefly introduces the current understanding of the intertwined pathological mechanisms of diabetic coronary heart disease, including insulin resistance, dyslipidemia, oxidative stress, chronic inflammation, and intestinal flora dysbiosis. Then, we mainly review the relationships between NAD pathways, such as nicotinic acid, tryptophan, the kynurenine pathway, nicotinamide phosphoribosyltransferase, and sirtuins, and the pathogenic mechanisms of diabetic coronary heart disease. Moreover, we discuss the potential of targeting NAD pathways in the prevention and treatment of diabetic coronary heart disease, which may provide important strategies to modulate its progression.

Harnessing lactic acid bacteria for nicotinamide mononucleotide biosynthesis: a review of strategies and future directions

Nicotinamide mononucleotide (NMN), one of the crucial precursors of nicotinamide adenine dinucleotide, has garnered considerable interest for its pharmacological and anti-aging effects, conferring potential health and economic benefits for humans. Lactic acid bacteria (LAB) are one of the most important probiotics, which is commonly used in the dairy industry. Due to its probiotic properties, it presents an attractive platform for food-grade NMN production. LAB have also been extensively utilized to enhance the functional properties of pharmaceuticals and cosmetics, making them promising candidates for large-scale up synthesis of NMN. This review provides an in-depth analysis of various metabolic engineering strategies, including enzyme optimization, pathway rewiring, and fermentation process enhancements, to increase NMN yields in LAB. It explores both CRISPR/Cas9 and traditional methods to manipulate key biosynthetic pathways. In particular, this study discussed future research directions, emphasizing the application of synthetic biology, systems biology, and AI-driven optimization to further enhance NMN production. It provides invaluable insights into developing scalable and industrially relevant processes for NMN production to meet the growing market demand.

Pathobiochemistry of Aging and Neurodegeneration: Deregulation of NAD+ Metabolism in Brain Cells

NAD+ plays a pivotal role in energy metabolism and adaptation to external stimuli and stressful conditions. A significant reduction in intracellular NAD+ levels is associated with aging and contributes to the development of chronic cardiovascular, neurodegenerative, and metabolic diseases. It is of particular importance to maintain optimal levels of NAD+ in cells with high energy consumption, particularly in the brain. Maintaining the tissue level of NAD+ with pharmacological tools has the potential to slow down the aging process, to prevent the development of age-related diseases. This review covers key aspects of NAD+ metabolism in terms of brain metabolic plasticity, including NAD+ biosynthesis and degradation in different types of brain cells, as well as its contribution to the development of neurodegeneration and aging, and highlights up-to-date approaches to modulate NAD+ levels in brain cells.

Association of serum metabolites with frailty phenotype and its components: a cross-sectional case-control study

New insights into the metabolic mechanisms of frailty are needed. This study aimed to identify serum metabolites linked to frailty phenotype and its component through gas chromatography-mass spectrometry metabolomic analysis among community-dwelling older individuals. An exploratory, cross-sectional case-control study. Setting and participants: The participants were recruited from the ''Otassha Study,'' a cohort study conducted in Itabashi Ward, Tokyo, targeting women aged 65 years and older. The study population included 39 frail and 76 robust individuals. Metabolomic analysis was performed using the GCMS-TQTM8040 NX system and the Smart Metabolites Database Ver.2 to explore the primary metabolite characteristic of a frailty state. Conditional logistic regression analysis was conducted with frailty as the outcome and with metabolites as exposures. Concentrations of seven metabolites, including caffeine, catechol, paraxanthine, niacinamide, 5-hydroxymethyl-2-furoic acid, daidzein, and cytosine were lower in the frail than in the robust individuals. Odds ratios [95% confidence intervals] for frailty by halving the value were significant for catechol (1.26 [1.00, 1.59]), 5-hydroxymethyl-2-furoic acid (1.28 [1.04, 1.58]), caffeine (1.37 [1.07, 1.75]), paraxanthine (1.18 [1.00, 1.39]), and daidzein (1.29 [1.02, 1.62]). Furthermore, distinct patterns of metabolites associated with specific frailty symptoms, such as muscle weakness, fatigue, and reduced physical activity, were identified, especially with 5-hydroxymethyl-2-furoic acid and caffeine commonly associated with these components. Metabolomic analysis identified metabolites associated with frailty. In particular, low levels of caffeine, catechol, paraxanthine, niacinamide, 5-hydroxymethyl-2-furoate, daidzein, and cytosine contributed to frailty. These results provide new insights into the pathophysiology of frailty through metabolomic analysis.

Nicotinamide mononucleotide suppresses cellular senescence and increases aquaporin 5 expression in the submandibular gland of aged male mice to ameliorate aging-related dry mouth

Dry mouth results from decreased saliva secretion due to aging or drug side effects. Decreased saliva secretion causes dryness in the oral cavity that makes swallowing difficult and increases the risk of aspiration pneumonia. There are few fundamental treatments for dry mouth. Here we investigated whether treatment of old mice with nicotinamide mononucleotide (NMN) improved factors associated with dry mouth. Young (16-week-old) and old (113-week-old) male mice were treated subcutaneously with saline or NMN (300 mg/kg) once every two days for four weeks and saliva secretion was measured. The amount of nicotinamide adenine dinucleotide (NAD+) in salivary gland tissues was measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Gene expression in the intestinal tract and salivary glands was measured by real-time PCR. The population of cells with acetylation in the submandibular gland was quantified by immunohistological staining. SA-β-gal activity in the submandibular gland was measured to assess cell senescence. Statistical analysis was performed by one-way analysis of variance with Tukey post hoc analysis. The submandibular glands from old mice treated with NMN exhibited increased saliva secretion and NAD+ levels, which both decrease with aging. In addition, the submandibular glands from NMN-treated old mice had decreased acetylation, numbers of senescent cells, and levels of senescence-associated secretory phenotype (SASP) factors, which all increase with aging, as well as increased aquaporin5 (AQP5) mRNA expression. NMN administration may improve dry mouth by regulating cellular senescence in the submandibular gland and increasing expression of AQP5, a water channel involved in saliva secretion, to inhibit age-related decreases in saliva secretion. It is necessary to elucidate further mechanism and confirm its effectiveness in humans.

Effect of nicotinamide riboside on airway inflammation in COPD: a randomized, placebo-controlled trial

Chronic obstructive pulmonary disease (COPD) is a progressive, incurable disease associated with smoking and advanced age, ranking as the third leading cause of death worldwide. DNA damage and loss of the central metabolite nicotinamide adenine dinucleotide (NAD+) may contribute to both aging and COPD, presenting a potential avenue for interventions. In this randomized, double-blind, placebo-controlled clinical trial, we treated patients with stable COPD (n = 40) with the NAD+ precursor nicotinamide riboside (NR) for 6 weeks and followed-up 12 weeks later. The primary outcome was change in sputum interleukin-8 (IL-8) from baseline to week 6. The estimated treatment difference between NR and placebo in IL-8 after 6 weeks was -52.6% (95% confidence interval (CI): -75.7% to -7.6%; P = 0.030). This effect persisted until the follow-up 12 weeks after the end of treatment (-63.7%: 95% CI -85.7% to -7.8%; P = 0.034). For secondary outcomes, NR treatment increased NAD+ levels by more than twofold in whole blood, whereas IL-6 levels in plasma remained unchanged. In exploratory analyses, treatment with NR showed indications of upregulated gene pathways related to genomic integrity in the airways and reduced epigenetic aging, possibly through a reduction in cellular senescence. These exploratory analyses need to be confirmed in future trials. ClinicalTrials.gov identifier: NCT04990869 .

Function of NAD metabolism in white adipose tissue: lessons from mouse models

Nicotinamide Adenine Dinucleotide (NAD) is an endogenous substance in redox reactions and regulates various functions in metabolism. NAD and its precursors are known for their anti-ageing and anti-obesity properties and are mainly active in the liver and muscle. Boosting NAD+ through supplementation with the precursors, such as nicotinamide mononucleotide (NMN) or nicotinamide riboside (NR), enhances insulin sensitivity and circadian rhythm in the liver, and improves mitochondrial function in the muscle. Recent evidence has revealed that the adipose tissue could be another direct target of NAD supplementation by attenuating inflammation and fat accumulation. Moreover, murine studies with genetically modified models demonstrated that nicotinamide phosphoribosyltransferase (NAMPT), a NAD regulatory enzyme that synthesizes NMN, played a critical role in lipogenesis and lipolysis in an adipocyte-specific manner. The tissue-specific effects of NAD+ metabolic pathways indicate a potential of the NAD precursors to control metabolic stress particularly via focusing on adipose tissue. Therefore, this narrative review raises an importance of NAD metabolism in white adipose tissue (WAT) through a variety of studies using different mouse models.

Climbing the longevity pyramid: overview of evidence-driven healthcare prevention strategies for human longevity

Longevity medicine is an emerging and iterative healthcare discipline focusing on early detection, preventive measures, and personalized approaches that aim to extend healthy lifespan and promote healthy aging. This comprehensive review introduces the innovative concept of the "Longevity Pyramid." This conceptual framework delineates progressive intervention levels, providing a structured approach to understanding the diverse strategies available in longevity medicine. At the base of the Longevity Pyramid lies the level of prevention, emphasizing early detection strategies and advanced diagnostics or timely identification of potential health issues. Moving upwards, the next step involves lifestyle modifications, health-promoting behaviors, and proactive measures to delay the onset of age-related conditions. The Longevity Pyramid further explores the vast range of personalized interventions, highlighting the importance of tailoring medical approaches based on genetic predispositions, lifestyle factors, and unique health profiles, thereby optimizing interventions for maximal efficacy. These interventions aim to extend lifespan and reduce the impact and severity of age-related conditions, ensuring that additional years are characterized by vitality and wellbeing. By outlining these progressive levels of intervention, this review offers valuable insights into the evolving field of longevity medicine. This structured framework guides researchers and practitioners toward a nuanced strategic approach to advancing the science and practice of healthy aging.

Nampt/SIRT2/LDHA pathway-mediated lactate production regulates follicular dysplasia in polycystic ovary syndrome

Decreased nicotinamide adenine dinucleotide (NAD+) content has been shown to contribute to metabolic dysfunction during aging, including polycystic ovary syndrome (PCOS). However, the effect of NAD+ on ovulatory dysfunction in PCOS by regulating glycolysis has not been reported. Based on the observations of granulosa cells (GCs) transcriptome data from the Gene Expression Omnibus (GEO) database, the signal pathways including glycolysis and nicotinate-nicotinamide metabolism were significantly enriched, and most genes of the above pathway like LDHA and SIRT2 were down-regulated in PCOS patients. Therefore, the PCOS rat model was established by combining letrozole with a high-fat diet (HFD), we demonstrate that in vivo supplementation of nicotinamide mononucleotide (NMN) significantly improves the ovulatory dysfunction by facilitating the follicular development, promoting luteal formation, as well the fertility in PCOS rats. Furthermore, target energy metabolomics and transcriptome results showed that NMN supplementation ameliorates the lactate production by activating glycolytic process in the ovary. In vitro, when NAD+ synthesis and SIRT2 expression were inhibited, lactate content in KGN cells was decreased and LDHA expression was significantly inhibited. We confirmed that FK866 can enhance the acetylation of LDHA on 293T cells by Co-immunoprecipitation (Co-IP) assay. We also observed that inhibition of NAD+ synthesis can reduce the activity and increase the apoptosis of KGN cells. Overall, these benefits of NMN were elucidated and the Nampt/SIRT2/LDHA pathway mediated lactate production in granulosa cells played an important role in the improvement of follicular development disorders in PCOS. This study will provide experimental evidence for the clinical application of NMN in the treatment of PCOS in the future.

Effects of Nicotinamide Mononucleotide on Glucose and Lipid Metabolism in Adults: A Systematic Review and Meta-analysis of Randomised Controlled Trials

PURPOSE OF REVIEW

Supplementation of nicotinamide mononucleotides (NMN) has been claimed to improve metabolic function. We reviewed human randomised controlled trials (RCTs) of NMN to evaluate its effect on markers of glucose and lipid metabolism.

RECENT FINDINGS

Eight RCTs on NMN (dosage ranged 250-2000 mg/d for a duration of 14 days to 12 weeks) involving a total of 342 middle-age/older adults (49% females, mainly non-diabetic) reporting at least one outcome on glucose control or lipid profile published in 2021-2023 were reviewed. The random-effects meta-analyses indicated no significant benefit of NMN on fasting glucose, fasting insulin, glycated hemoglobin, homeostatic model assessment for insulin resistance and lipid profile. Based on the small number of RCTs involving mainly relatively healthy adults, short-term supplementation of NMN of 250-2000 mg/d did not show significantly positive impacts on glucose control and lipid profile.

De novo biosynthesis and nicotinamide biotransformation of nicotinamide mononucleotide by engineered yeast cells

β-Nicotinamide mononucleotide (NMN) is a precursor of NAD+ in mammals. Research on NAD+ has demonstrated its crucial role against aging and disease. Here two technical paths were established for the efficient synthesis of NMN in the yeast Pichia pastoris, enabling the production of NMN from the low-cost nicotinamide (NAM) or basic carbon sources. The yeast host was systematically modified to adapt to the biosynthesis and accumulation of NMN. To improve the semi-biosynthesis of NMN from NAM, nicotinamide phosphoribosyltransferases were expressed intracellular to evaluate their catalytic activities. The accumulation of extracellular NMN was further increased by the co-expression of an NMN transporter. Fine-tuning of gene expression level produced 72.1 mg/L NMN from NAM in flasks. To achieve de novo biosynthesis NMN, a heterologous biosynthetic pathway was reassembled in yeast cells. Fine-tuning of pathway nodes by the modification of gene expression level and enhancement of precursor generation allowed efficient NMN synthesis from glucose (36.9 mg/L) or ethanol (57.8 mg/L) in flask. Lastly, cultivations in a bioreactor in fed-batch mode achieved an NMN titre of 1004.6 mg/L at 165 h from 2 g NAM and 868 g glucose and 980.4 mg/L at 91 h from 160 g glucose and 557 g ethanol respectively. This study provides a foundation for future optimization of NMN biosynthesis by engineered yeast cell factories.

Potential implications of natural compounds on aging and metabolic regulation

Aging is generally accompanied by a progressive loss of metabolic homeostasis. Targeting metabolic processes is an attractive strategy for healthy-aging. Numerous natural compounds have demonstrated strong anti-aging effects. This review summarizes recent findings on metabolic pathways involved in aging and explores the anti-aging effects of natural compounds by modulating these pathways. The potential anti-aging effects of natural extracts rich in biologically active compounds are also discussed. Regulating the metabolism of carbohydrates, proteins, lipids, and nicotinamide adenine dinucleotide is an important strategy for delaying aging. Furthermore, phenolic compounds, terpenoids, alkaloids, and nucleotide compounds have shown particularly promising effects on aging, especially with respect to metabolism regulation. Moreover, metabolomics is a valuable tool for uncovering potential targets against aging. Future research should focus on identifying novel natural compounds that regulate human metabolism and should delve deeper into the mechanisms of metabolic regulation using metabolomics methods, aiming to delay aging and extend lifespan.

Nicotinamide Mononucleotide Improves Endometrial Homeostasis in a Rat Model of Polycystic Ovary Syndrome by Decreasing Insulin Resistance and Regulating the Glylytic Pathway

SCOPE

Polycystic ovary syndrome (PCOS) is a common endocrine disorder that can lead to insulin resistance (IR) and dysregulation of glucose metabolism, resulting in an imbalance in the endometrial environment, which is unfavorable for embryo implantation of PCOS. This study aims to investigate whether nicotinamide mononucleotide (NMN) improves the stability of the endometrium in a rat model of PCOS and identifies whether it is related to reduce IR and increase glycolysis levels and its potential signaling pathway.

METHODS AND RESULTS

Female Sprague-Dawley (SD) rats are fed letrozole and a high-fat diet (HFD) to form the PCOS model, then the model rats are treated with or without NMN. It randomly divided into control, PCOS, and PCOS-NMN groups according to the feeding and treating method. Compared with the PCOS group, the regular estrous cycles are restored, the serum androgen (p<0.01) and fasting insulin levels (p<0.05) are reduced, and endometrial morphology (p<0.05) is improved in NMN-PCOS group. Furthermore, NMN inhibits endometrial cell apoptosis, improves endometrial decidualization transition, reduces IR, restores the expression of glycolysis rate-limiting enzymes, and activates the PI3K/AKT pathway in the uterus.

CONCLUSIONS

These results suggest that NMN enhances endometrial tissue homeostasis by decreasing uterine IR and regulating the glycolysis through the PI3K/AKT pathway.

Effects of Supplementation with NAD + Precursors on Metabolic Syndrome Parameters: A Systematic Review and Meta-Analysis

Intracellular levels of NAD +  regulate metabolism, among other ways, through enzymes that use NAD +  as a substrate, capable of inducing catabolic processes, such as lipid oxidation, glucose uptake, and mitochondrial activity. In several model organisms, administering precursor compounds for NAD + synthesis increases its levels, improves lipid and glucose homeostasis, and reduces weight gain. However, evidence of the effects of these precursors on human patients needs to be better evaluated. Therefore, we carried out a systematic review and meta-analysis of randomized clinical trials that assessed the effects of NAD +  precursors on Metabolic Syndrome parameters in humans. We based our methods on PRISMA 2020. Our search retrieved 429 articles, and 19 randomized controlled trials were included in the meta-analysis. We assessed the risk of bias with the Rob 2 algorithm and summarized the quality of evidence with the GRADE algorithm. Supplementation with NAD +  precursors reduced plasma levels of total cholesterol and triglycerides in volunteers, but the intervention did not significantly affect the other outcomes analyzed. Three of the included articles presented a high risk of bias. The quality of evidence varied between very low and low due to the risk of bias, imprecision, and indirectness. The number of participants in outcomes other than lipidemia is still generally tiny; therefore, more clinical trials evaluating these parameters will increase the quality of the evidence. On the other hand, quality randomized studies are essential to assess better the effects of NAD +  precursors on lipidemia.

Novel Approach to Skin Anti-Aging: Boosting Pharmacological Effects of Exogenous Nicotinamide Adenine Dinucleotide (NAD+) by Synergistic Inhibition of CD38 Expression

Nicotinamide adenine dinucleotide (NAD+) is indispensable for the regulation of biological metabolism. Previous studies have revealed its role in aging and degenerative diseases, while crucially showing that supplementation with NAD+ or its precursors could ameliorate or reverse the progression of aging. Despite extensive evidence for the role and action of NAD+ in aging, its pharmacological activity on the skin, or even its mechanism, has not been elucidated. In this study, we established a novel approach to effectively utilize NAD+ for skin anti-aging by enhancing the pharmacological efficacy of exogenous NAD+ using a phytochemical complex consisting of quercetin, and enoxolone through inhibition of CD38. Through the comprehensive in vitro experiments based on human fibroblasts, we observed that exogenous NAD+ could exert protective effects against both extrinsic aging induced by ultraviolet light exposure and intrinsic aging. Additionally, we found that its effects were significantly boosted by quercetin and enoxolone. In this in-depth study, we demonstrated that these beneficial effects are mediated by improved sirtuin activation, autophagy, and mitochondrial functionality. Our approach is expected to verify the applicability of the topical application of NAD+ and offer more effective solutions for the unmet needs of patients and consumers who demand more effective anti-aging effects.

Nicotinamide mononucleotide ameliorates ionizing radiation-induced spermatogenic dysfunction in mice by modulating the glycolytic pathway

Radiotherapy, a common cancer treatment, leads to infertility in male cancer survivors, particularly young and middle-aged patients. Nicotinamide mononucleotide (NMN), a precursor of nicotinamide adenine dinucleotide (NAD +), plays crucial roles in energy metabolism, DNA repair, and gene expression. The purpose of this study is to investigate the protective effects and underlying mechanisms of NMN against ionizing radiation (IR)-induced testicular injury and spermatogenic dysfunction in an adult male mouse model. To assess the effects of NMN, single whole-body γ-ray irradiation is used to induce testicular injury and spermatogenic dysfunction in adult male mice. NMN is orally administered at 500 mg/kg before and after IR exposure. The structural and cellular damage to the testes caused by 5 Gy γ-ray irradiation, as well as the protective effect of NMN on testicular spermatogenic dysfunction, are evaluated. The serum hormone testosterone, LH, and FSH levels, as well as testicular NAD +, lactate, and pyruvate levels, are detected. Furthermore, the expressions of the apoptosis-related genes Bcl-2, Bax, and Caspase-3 and the rate-limiting enzymes HK2, PKM2, and LDHA, which are potentially associated with the mechanism of injury, are examined. The results demonstrate that 5 Gy γ-ray irradiation exposure causes a decrease in the serum testosterone, LH, and FSH levels in adult male mice, as well as in the testicular NAD +, lactate, and pyruvate levels, and causes damage to the testicular structure and cells. Morphometric analysis reveal a decrease in the testis mass, seminiferous tubule diameter, and height of the germinal epithelium. The sperm quantity, motility, and testicular volume are reduced in the 5 Gy group but are restored by NMN supplementation. NMN intervention downregulates the expressions of proapoptotic genes ( Bax and Caspase-3) and upregulates the expression of an antiapoptotic gene ( Bcl- 2). Sertoli cells marker genes ( WT-1, GATA-4, SOX9, and vimentin) and glycolysis rate-limiting enzyme-encoding genes ( HK2, PKM2, and LDHA) are significantly upregulated. In summary, NMN has a positive regulatory effect on testicular spermatogenic dysfunction in male mice induced by ionizing radiation. This positive effect is likely achieved by promoting the proliferation of spermatogenic cells and activating glycolytic pathways. These findings suggest that NMN supplementation may be a potential protective strategy to prevent reproductive damage to male subjects from ionizing radiation.

Feasibility of telehealth exercise and nicotinamide riboside supplementation in survivors of childhood cancer at risk for diabetes: A pilot randomized controlled trial

BACKGROUND

Childhood cancer survivors (CCS) have a 50% higher risk of diabetes mellitus (DM) compared with the general population. Interventions in survivors with prediabetes (fasting glucose 100-125 mg/dL or hemoglobin A1c 5.7%-6.4%) may mitigate the development of DM and its attendant morbidity, but there is limited information on the feasibility of secondary prevention in this setting.

METHODS

This 6-week pilot feasibility 1:1 randomized controlled trial enrolled 20 CCS on a structured telehealth exercise program ± nicotinamide riboside (NR), a nicotinamide adenine dinucleotide precursor. Feasibility metrics were: (1) ≥50% of eligible CCS enrolled onto study; (2) ≥70% of participants completed baseline and end-of-study assessments; (3) ≥70% compliance with exercise and NR. Secondary endpoints included changes in biomarkers associated with glucose homeostasis and muscle health.

RESULTS

Median age (years) at cancer diagnosis was 16.5 (range, 1.5-21.5) and 35.5 (range, 18.0-67.0) at study enrollment. Enrollment rate was 87%, and 85% of participants completed baseline and end-of-study assessments. The mean percentage of exercise sessions completed was 86.6%; NR compliance was > 90%. There were no severe adverse events attributable to study interventions. Secondary endpoints were not significantly different between study arms at study completion. Myostatin decrease was observed in participants who completed a higher median number of exercise sessions and was associated with decreased intramuscular adipose tissue and increased lower extremity muscle cross-sectional area.

CONCLUSIONS

A telehealth exercise intervention ± NR supplementation was feasible in CCS with prediabetes. Future studies in larger cohorts may be needed to evaluate their beneficial effects on muscle health and DM risk among CCS.

Measurement of Mitochondrial Respiration in Human and Mouse Skeletal Muscle Fibers by High-Resolution Respirometry

Mitochondrial function, a cornerstone of cellular energy production, is critical for maintaining metabolic homeostasis. Its dysfunction in skeletal muscle is linked to prevalent metabolic disorders (e.g., diabetes and obesity), muscular dystrophies, and sarcopenia. While there are many techniques to evaluate mitochondrial content and morphology, the hallmark method to assess mitochondrial function is the measurement of mitochondrial oxidative phosphorylation (OXPHOS) by respirometry. Quantification of mitochondrial OXPHOS provides insight into the efficiency of mitochondrial oxidative energy production and cellular bioenergetics. A high-resolution respirometer provides highly sensitive, robust measurements of mitochondrial OXPHOS in permeabilized muscle fibers by measuring real-time changes in mitochondrial oxygen consumption rate. The use of permeabilized muscle fibers, as opposed to isolated mitochondria, preserves mitochondrial networks, maintains mitochondrial membrane integrity, and ultimately allows for more physiologically relevant measurements. This system also allows for the measurement of fuel preference and metabolic flexibility - dynamic aspects of muscle energy metabolism. Here, we provide a comprehensive guide for mitochondrial OXPHOS measurements in human and mouse skeletal muscle fibers using a high-resolution respirometer. Skeletal muscle groups are composed of different fiber types that vary in their mitochondrial fuel preference and bioenergetics. Using a high-resolution respirometer, we describe methods for evaluating both aerobic glycolytic and fatty acid substrates to assess fuel preference and metabolic flexibility in a fiber-type-dependent manner. The protocol is versatile and applicable to both human and rodent muscle fibers. The goal is to enhance the reproducibility and accuracy of mitochondrial function assessments, which will improve our understanding of an organelle important to muscle health.

Synergistic anti-aging effect of Dendrobium officinale polysaccharide and spermidine: A metabolomics analysis focusing on the regulation of lipid, nucleotide and energy metabolism

The importance of synergy has been underscored in recent medical research for augmenting the efficacy of therapeutic interventions, targeting multiple biological pathways simultaneously. Our prior research elucidated that Dendrobium officinale polysaccharide (DOP) has the potential to prolong the lifespan of Caenorhabditis elegans (C. elegans) via regulating gut microbiota. Concurrently, spermidine (Spd), as a mimicking caloric restriction, facilitates autophagy and exerts a pronounced anti-aging effect. To enhance the anti-aging capabilities of DOP, we conducted a comprehensive study examining the combined effects of DOP and Spd in C. elegans, incorporating metabolomics analysis to investigate the underlying mechanisms. A combination of 250 mg/L DOP and 29.0 mg/L Spd yielded the most favorable outcomes in lifespan extension, evidencing a synergistic effect with a combination index (CI) of 0.65. In oxidative and heat stress tolerance assays, the observed CIs were 0.50 and 0.33, respectively. Metabolomic analysis highlighted significant alterations in metabolites related to lipid, nucleotide and energy metabolism, notably regulating glycerol 3-phosphate, linoleoyl glycerol, docosapentaenoic acid and β-nicotinamide mononucleotide, nicotinamide adenine dinucleotide. The effects of DS on lipid metabolism were further validated using Oil Red O staining and triglyceride level in C. elegans. The results indicated that DS may primarily be via modulating lipid metabolism. To further confirm these findings, a high-fat diet-induced mouse model was employed. Consequently, it can be inferred that the synergistic anti-aging impact of DOP and Spd is likely mediated primarily through alterations in lipid metabolic processes.

Testing the amount of nicotinamide mononucleotide and urolithin A as compared to the label claim

Healthy Longevity Medicine aims to optimize health by targeting aging processes across the lifespan. Addressing accelerated aging involves adaptation of lifestyle and the use of geroprotective drugs and supplements, including nutritional supplements and bioactive compounds. The Food and Drug Administration, under the Dietary Supplement Health and Education Act, categorizes bioactive compounds and medicinal products as dietary supplements. While numerous companies sell ingredients that can be deemed geroprotectors, there's limited oversight in their quality control. Governmental safety authorities only verify the presence of prohibited compounds, not the accuracy of ingredients listed on labels.Here, Nicotinamide mononucleotide and Urolithin A supplements, easily accessible online or in pharmacies, were tested for their active ingredient content. Results showed a significant deviation from the labeled amounts, ranging from + 28.6% to -100%. This indicates a considerable disparity in the quality of geroprotective supplements.To address this variability, collaboration between and within societies representing healthcare professionals, industry and regulatory bodies is imperative to ensure the quality of geroprotective supplements.

Ingestion of β-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adults in a double-blind randomized, placebo-controlled study

The study evaluated how ingestion of nicotinamide mononucleotide (NMN) for 12 weeks by older adults affected blood nicotinamide adenine dinucleotide (NAD +) levels and physical function, particularly walking function. Information concerning sleep, and stress was also collected as secondary endpoints. In this randomized, placebo-controlled, double-blind, parallel-group comparison study, 60 participants were randomly allocated into a placebo group or NMN group. Members of the NMN group consumed 250 mg/day NMN for 12 weeks. Motor function tests, blood NAD metabolite analysis, and questionnaires were conducted at the start of the study and 4 and 12 weeks after intake. This trial was registered at umin.ac.jp/ctr as UMIN000047871 on June 22nd, 2022.At primary outcome, at both 4 weeks and 12 weeks, the NMN and placebo groups had no significant differences in a stepping test. At secondary outcomes, after 12 weeks of NMN intake, the NMN group had a significantly shorter 4-m walking time than the placebo group as well as significantly higher blood levels of NAD + and its metabolites. A significant negative correlation was observed between the change in the 4-m walking time and the change in blood NAD + , N1-methyl-2-pridone-5-carboxamide (2-PY), and N1-methyl-4-pridone-3-carboxamide (4-PY) at 12 weeks. The NMN group had improved sleep quality at 12 weeks relative to the placebo group as evidenced by lower scores for "Daytime dysfunction" and "Global PSQI" on the Pittsburgh Sleep Questionnaire. No adverse effects related to test substance consumption were observed. Together, these results indicate that NMN intake could increase blood NAD + levels, maintain walking speed, and improve sleep quality in older adults. Interventions involving NMN aimed at maintaining walking speed could contribute to extended healthy life expectancy.

NAD metabolism and heart failure: Mechanisms and therapeutic potentials

Nicotinamide adenine dinucleotide provides the critical redox pair, NAD+ and NADH, for cellular energy metabolism. In addition, NAD+ is the precursor for de novo NADP+ synthesis as well as the co-substrates for CD38, poly(ADP-ribose) polymerase and sirtuins, thus, playing a central role in the regulation of oxidative stress and cell signaling. Declines of the NAD+ level and altered NAD+/NADH redox states have been observed in cardiometabolic diseases of various etiologies. NAD based therapies have emerged as a promising strategy to treat cardiovascular disease. Strategies that reduce NAD+ consumption or promote NAD+ production have repleted intracellular NAD+ or normalized NAD+/NADH redox in preclinical studies. These interventions have shown cardioprotective effects in multiple models suggesting a great promise of the NAD+ elevating therapy. Mechanisms for the benefit of boosting NAD+ level, however, remain incompletely understood. Moreover, despite the robust pre-clinical studies there are still challenges to translate the therapy to clinic. Here, we review the most up to date literature on mechanisms underlying the NAD+ elevating interventions and discuss the progress of human studies. We also aim to provide a better understanding of how NAD metabolism is changed in failing hearts with a particular emphasis on types of strategies employed and methods to target these pathways. Finally, we conclude with a comprehensive assessment of the challenges in developing NAD-based therapies for heart diseases, and to provide a perspective on the future of the targeting strategies.

The versatile multi-functional substance NMN: its unique characteristics, metabolic properties, pharmacodynamic effects, clinical trials, and diverse applications

β-nicotinamide mononucleotide (NMN) is a naturally occurring biologically active nucleotide widely present in organisms and an inherent substance in the human body. As a critical intermediate in synthesizing coenzyme I (NAD+), it widely participates in multiple biochemical reactions in the human body and is closely related to immunity, metabolism, and other factors. In recent years, NMN has rapidly developed and made significant progress in medicine, food, and healthcare. However, there is currently a lack of comprehensive reports on the research progress of NMN, as well as exploration and analysis of the current research achievements and progress of NMN. Therefore, this review is based on retrieving relevant research on NMN from multiple databases at home and abroad, with the retrieval time from database establishment to 20 May 2024. Subsequently, literature search, reading, key information extraction, organization, and summarization were conducted with the aim of providing a comprehensive and in-depth analysis of the characteristics, metabolic pathways, pharmacological effects, progress in human clinical trials, and wide applications of NMN in drug development and food applications. Furthermore, it offers personal insights into NMN's potential future developments and advancements to present the current development state and existing challenges comprehensively. Ultimately, this review aims to provide guidance and serve as a reference for the future application, innovation, and progression of NMN research.

Nicotinamide mononucleotide supplementation rescues mitochondrial and energy metabolism functions and ameliorates inflammatory states in the ovaries of aging mice

Noninvasive pharmacological strategies like nicotinamide mononucleotide (NMN) supplementation can effectively address age-related ovarian infertility by maintaining or enhancing oocyte quality and quantity. This study revealed that ovarian nicotinamide adenine dinucleotide levels decline with age, but NMN administration significantly restores these levels, preventing ovarian atrophy and enhancing the quality and quantity of ovulated oocytes. Improvements in serum hormone secretion and antioxidant factors, along with decreased expression of proinflammatory factors, were observed. Additionally, a significant increase in the number of ovarian follicles in aging individuals was noted. Scanning electron microscopy data indicated that NMN significantly alters the density and morphology of lipid droplets and mitochondria in granulosa cells, suggesting potential targets and mechanisms. Transcriptomic analysis and validation experiments collectively suggested that the beneficial effects of NMN on aging ovaries are mediated through enhanced mitochondrial function, improved energy metabolism, and reduced inflammation levels. Our results suggest that NMN supplementation could improve the health status of aging ovaries and enhance ovarian reserve, offering new insights into addressing fertility challenges in older women through assisted reproductive technology.

Regulation of and challenges in targeting NAD+ metabolism

Nicotinamide adenine dinucleotide, in its oxidized (NAD+) and reduced (NADH) forms, is a reduction-oxidation (redox) co-factor and substrate for signalling enzymes that have essential roles in metabolism. The recognition that NAD+ levels fall in response to stress and can be readily replenished through supplementation has fostered great interest in the potential benefits of increasing or restoring NAD+ levels in humans to prevent or delay diseases and degenerative processes. However, much about the biology of NAD+ and related molecules remains poorly understood. In this Review, we discuss the current knowledge of NAD+ metabolism, including limitations of, assumptions about and unappreciated factors that might influence the success or contribute to risks of NAD+ supplementation. We highlight several ongoing controversies in the field, and discuss the role of the microbiome in modulating the availability of NAD+ precursors such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), the presence of multiple cellular compartments that have distinct pools of NAD+ and NADH, and non-canonical NAD+ and NADH degradation pathways. We conclude that a substantial investment in understanding the fundamental biology of NAD+, its detection and its metabolites in specific cells and cellular compartments is needed to support current translational efforts to safely boost NAD+ levels in humans.

Mechanisms of the NAD+ salvage pathway in enhancing skeletal muscle function

Nicotinamide adenine dinucleotide (NAD+) is crucial for cellular energy production, serving as a coenzyme in oxidation-reduction reactions. It also supports enzymes involved in processes such as DNA repair, aging, and immune responses. Lower NAD+ levels have been associated with various diseases, highlighting the importance of replenishing NAD+. Nicotinamide phosphoribosyltransferase (NAMPT) plays a critical role in the NAD+ salvage pathway, which helps sustain NAD+ levels, particularly in high-energy tissues like skeletal muscle.This review explores how the NAMPT-driven NAD+ salvage pathway influences skeletal muscle health and functionality in aging, type 2 diabetes mellitus (T2DM), and skeletal muscle injury. The review offers insights into enhancing the salvage pathway through exercise and NAD+ boosters as strategies to improve muscle performance. The findings suggest significant potential for using this pathway in the diagnosis, monitoring, and treatment of skeletal muscle conditions.