Nicotinamide Mononucleotide Research Articles

The Effectiveness of Four Nicotinamide Adenine Dinucleotide (NAD+) Precursors in Alleviating the High-Glucose-Induced Damage to Hepatocytes in Megalobrama amblycephala: Evidence in NAD+ Homeostasis, Sirt1/3 Activation, Redox Defense, Inflammatory Response, Apoptosis, and Glucose Metabolism.

The administration of NAD+ precursors is a potential approach to protect against liver damage and metabolic dysfunction. However, the effectiveness of different NAD+ precursors in alleviating metabolic disorders is still poorly elucidated. The current study was performed to compare the effectiveness of four different NAD+ precursors, including nicotinic acid (NA), niacinamide (NAM), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN) in alleviating high-glucose-induced injury to hepatocytes in a fish model, Megalobrama amblycephala. An in vitro high-glucose model was successfully established to mimic hyperglycemia-induced damage to the liver, which was evidenced by the reduced cell viability, the increased transaminase activity, and the depletion of cellular NAD+ concentration. The NAD+ precursors all improved cell viability, with the maximal effect observed in NR, which also had the most potent NAD+ boosting capacity and a significant Sirt1/3 activation effect. Meanwhile, NR presented distinct and superior effects in terms of anti-oxidative stress, inflammation inhibition, and anti-apoptosis compared with NA, NAM, and NMN. Furthermore, NR could effectively benefit glucose metabolism by activating glucose transportation, glycolysis, glycogen synthesis and the pentose phosphate pathway, as well as inhibiting gluconeogenesis. Moreover, an oral gavage test confirmed that NR presented the most potent effect in increasing hepatic NAD+ content and the NAD+/NADH ratio among four NAD+ precursors. Together, the present study results demonstrated that NR is most effective in attenuating the high-glucose-induced injury to hepatocytes in fish compared to other NAD+ precursors.

Structure-guided mining and engineering of nicotinamide riboside kinase for efficient synthesis of nicotinamide mononucleotide

Nicotinamide mononucleotide (NMN) is a bioactive precursor to nicotinamide adenine dinucleotide (NAD+) and has demonstrated anti-aging activity. Nicotinamide riboside kinase (NRK) can convert nicotinamide ribose (NR) into NMN in one step, but NRKs with high catalytic efficiency are rare and are difficult to engineer. In this study, two novel NRKs from Sparassis crispa and Beauveria bassiana were identified. They displayed impressive specific activities of 6.14 U/mg and 6.66 U/mg with high substrate (NR) conversion rates. Furthermore, structural modelling analysis and semi-rational design were used to develop variants of BEANRK. Variant M1 (V172K) exhibited a 1.2-fold of the wild-type BEANRK (WT) in enzyme activity and 91 % of substrate conversion rate with improved thermal stability compared to WT. Moreover, variants generated from site-specific mutagenesis were also computationally analyzed to elucidate which interactions between key amino residues and substrates facilitated an increase in catalytic activity and conversion rate. This study not only identified new NRKs but also provided insights into which amino acid residues were pivotal to the catalytic activity of NRK, paving the way for future NRK engineering to improve the industrial production of NMN.

Development and validation of an LC-MS/MS method for quantifying NAD+ and related metabolites in mice sciatic nerves and its application to a nerve injury animal model

Recent studies highlight the pivotal roles of Nicotinamide adenine dinucleotide (NAD+) and its metabolites in aging and neurodegeneration. Accurate quantification of NAD+ and its metabolite levels in cells or tissues is crucial for advancing biochemical research and interventions targeting aging and neurodegenerative diseases. This study presents an accurate, precise, and rapid LC-MS/MS method using a surrogate matrix to quantify endogenous substances NAD+, nicotinamide mononucleotide (NMN), nicotinamide (NAM), adenosine diphosphate ribose (ADPR), and cyclic adenosine diphosphate ribose (cADPR) concentrations in mice sciatic nerves. Considering the properties of the phosphate groups in the analytes, the column and mobile phase were systematically optimized. These five polar analytes exhibited excellent analytical performance and baseline separation within 5 min on an Atlantis Premier BEH C18 AX column, with methylene phosphonic acid as a mobile phase additive. Enhanced sensitivity addressed the challenges posed by the small sample size of mice sciatic nerve and low NMN and cADPR detection. The method was fully validated, with linear correlation coefficients exceeding 0.992, precision (%relative standard deviation, RSD) values within 8.8%, and accuracy values between 92.2% and 107.3%, suggesting good reproducibility. Analytical recoveries in spiked and diluted matrix ranged from 87.8% to 104.7%, indicating the suitability of water as a surrogate matrix. Application of the method to quantify NAD+ and its metabolite levels in normal and injured mice sciatic nerve identified cADPR as a sensitive biomarker in the nerve injury model. This method is anticipated to deepen our understanding of the connections between NAD+ and its metabolites in health and disease, potentially improving diagnoses of various neurological disorders and aiding drug development for aging and neurodegenerative diseases.

Highly Bioadaptable Hybrid Conduits with Spatially Bidirectional Structure for Precision Nerve Fiber Regeneration via Gene Therapy.

Peripheral nerve deficits give rise to motor and sensory impairments within the limb. The clinical restoration of extensive segmental nerve defects through autologous nerve transplantation often encounters challenges such as axonal mismatch and suboptimal functional recovery. These issues may stem from the limited regenerative capacity of proximal axons and the subsequent Wallerian degeneration of distal axons. To achieve the integration of sensory and motor functions, a spatially differential plasmid DNA (pDNA) dual-delivery nanohydrogel conduit scaffold is devised. This innovative scaffold facilitates the localized administration of the transforming growth factor β (TGF-β) gene in the proximal region to accelerate nerve regeneration, while simultaneously delivering nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2) to the distal region to mitigate Wallerian degeneration. By promoting autonomous and selective alignment of nerve fiber gap sutures via structure design, the approach aims to achieve a harmonious unification of nerve regeneration, neuromotor function, and sensory recovery. It is anticipated that this groundbreaking technology will establish a robust platform for gene delivery in tissue engineering.

NAMPT/NAD+/PARP1 Pathway Regulates CFA-Induced Inflammatory Pain via NF-κB Signaling in Rodents.

Emerging evidence has implicated nicotinamide adenine dinucleotide (NAD+) metabolism in various inflammatory diseases. In the study, the role of NAD+ metabolism in Complete Freund's Adjuvant (CFA)-evoked inflammatory pain and the underlying mechanisms are investigated. The study demonstrated that CFA induced upregulation of nicotinamide phosphoribosyltransferase (NAMPT) in dorsal root ganglia (DRG) without significant changes in the spinal cord. Inhibition of NAMPT expression by intrathecal injection of NAMPT siRNA alleviated CFA-induced pain-like behavior, decreased NAD+ contents in DRG, and lowered poly-(ADP-ribose) polymerase 1 (PARP1) activity levels. These effects are all reversed by the supplement of nicotinamide mononucleotide (NMN). Inhibition of PARP1 expression by intrathecal injection of PARP1 siRNA alleviated CFA-induced pain-like behavior, while elevated NAD+ levels of DRG. The analgesic effect of inhibiting NAMPT/NAD+/PARP1 axis can be attributed to the downregulation of the NF-κB/IL-1β inflammatory pathway. Double immunofluorescence staining showed that the expression of NAMPT/NAD+/PARP1 axis is restricted to DRG neurons. In conclusion, PARP1 activation in response to CFA stimulation, fueled by NAMPT-derived NAD+, mediates CFA-induced inflammatory pain through NF-κB/IL-1β inflammatory pathway.

The ecto-enzyme CD38 modulates CD4T cell immunometabolic responses and participates in HIV pathogenesis.

Despite abundant evidence correlating T cell CD38 expression and HIV infection pathogenesis, its role as a CD4T cell immunometabolic regulator remains unclear. We find that CD38's extracellular glycohydrolase activity restricts metabolic reprogramming after T cell receptor (TCR)-engaging stimulation in Jurkat T CD4 cells, together with functional responses, while reducing intracellular nicotinamide adenine dinucleotide and nicotinamide mononucleotide concentrations. Selective elimination of CD38's ectoenzyme function licenses them to decrease the oxygen consumption rate/extracellular acidification rate ratio upon TCR signaling and to increase cycling, proliferation, survival, and CD40L induction. Pharmacological inhibition of ecto-CD38 catalytic activity in TM cells from chronic HIV-infected patients rescued TCR-triggered responses, including differentiation and effector functions, while reverting abnormally increased basal glycolysis, cycling, and spontaneous proinflammatory cytokine production. Additionally, ecto-CD38 blockage normalized basal and TCR-induced mitochondrial morphofunctionality, while increasing respiratory capacity in cells from HIV+ patients and healthy individuals. Ectoenzyme CD38's immunometabolic restriction of TCR-involving stimulation is relevant to CD4T cell biology and to the deleterious effects of CD38 overexpression in HIV disease.

Systematic engineering for efficient production of nicotinamide mononucleotide from d-xylose and nicotinamide in Escherichia coli

β-Nicotinamide mononucleotide (NMN) is a direct precursor of the important coenzyme NAD+ in the human body and has broad application prospects in healthcare. This study engineered an Escherichia coli BL21 (DE3) strain to efficiently biosynthesize NMN from nicotinamide (NAM) and xylose. Firstly, the nicotinamide phosphoribosyltransferase (Nampt) from Chitinophaga pinensis was selected and heterologous expressed to construct the NAD+ remediation pathway for NMN synthesis from nicotinamide (NAM) and in vivo precursor phosphoribosyl pyrophosphate (PRPP). Then, the supply of PRPP was enhanced by constructing the metabolic flux from d-xylose. To facilitate NMN accumulation, the branch pathways, including PRPP competitive pathway, carbon flow competitive pathway, and NMN downstream metabolic decomposition pathway were fine-tuned using CRISPR/Cas9 editing tools. Combined with process optimization of whole-cell biocatalytic reaction, a NMN titre of 497.5 mg·L−1 was obtained. Finally, the scale-up culture was carried out on a 5 L fermenter, and the yield reached 760.2 mg·L−1. This work achieved green biosynthesis of NMN using xylose as substrate and enhanced the productivity by systematic engineering strategies, presenting more possibilities for the synthesis of NMN from a wide range of monosaccharides.

Transcriptomic and intervention evidence reveals domestic dogs as a promising model for anti-inflammatory investigation.

Domestic dogs have great potential to expand our understanding of the determinants of aging. To understand the aging pattern of domestic dogs and evaluate whether they can be used as an aging model, we performed RNA sequencing on white blood cells from domestic dogs aged 1-9 years and treated aged dogs with classical antiaging approaches. We obtained 30 RNA sequencing libraries and identified 61 age-associated genes with dynamic changes, the majority of which were related to metabolism and immune function, which may be predominant biomarkers for aging in dogs. We next treated aged dogs with canine mesenchymal stem cells (cMSCs), nicotinamide mononucleotide, and rapamycin to determine whether and how they responded to the antiaging interventions. The results showed that these treatments can significantly reduce the level of inflammatory factors (IL-6 and TNF-α). MSCs effectively improved the heart functions of aged dogs. Three key potential age-related genes (PYCR1, CCRL2, and TOX) were reversed by MSC treatment, two of which (CCRL2 and TOX) are implicated in immunity. Overall, we profiled the transcriptomic pattern of domestic dogs and revealed that they may be a good model of aging, especially in anti-inflammatory investigations.

Structural insights into Xanthomonas campestris pv. campestris NAD+ biosynthesis via the NAM salvage pathway

Nicotinamide phosphoribosyltransferase (NAMPT) plays an important role in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) via the nicotinamide (NAM) salvage pathway. While the structural biochemistry of eukaryote NAMPT has been well studied, the catalysis mechanism of prokaryote NAMPT at the molecular level remains largely unclear. Here, we demonstrated the NAMPT-mediated salvage pathway is functional in the Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) for the synthesis of NAD+, and the enzyme activity of NAMPT in this bacterium is significantly higher than that of human NAMPT in vitro. Our structural analyses of Xcc NAMPT, both in isolation and in complex with either the substrate NAM or the product nicotinamide mononucleotide (NMN), uncovered significant details of substrate recognition. Specifically, we revealed the presence of a NAM binding tunnel that connects the active site, and this tunnel is essential for both catalysis and inhibitor binding. We further demonstrated that NAM binding in the tunnel has a positive cooperative effect with NAM binding in the catalytic site. Additionally, we discovered that phosphorylation of the His residue at position 229 enhances the substrate binding affinity of Xcc NAMPT and is important for its catalytic activity. This work reveals the importance of NAMPT in bacterial NAD+ synthesis and provides insights into the substrate recognition and the catalytic mechanism of bacterial type II phosphoribosyltransferases.

Towards personalized nicotinamide mononucleotide (NMN) supplementation: Nicotinamide adenine dinucleotide (NAD) concentration

Nicotinamide mononucleotide (NMN) is a precursor of nicotinamide adenine dinucleotide (NAD), which declines with age. Supplementation of NMN has been shown to improve blood NAD concentration. However, the optimal NMN dose remains unclear. This is a post-hoc analysis of a double-blinded clinical trial involving 80 generally healthy adults aged 40–65 years. The participants received a placebo or daily 300 mg, 600 mg, or 900 mg NMN for 60 days. Blood NAD concentration, blood biological age, homeostatic model assessment for insulin resistance, 6-minute walk test, and 36-item short-form survey (SF-36) were measured at baseline and after supplement. A significant dose-dependent increase in NAD concentration change (NADΔ) was observed following NMN supplementation, with a large coefficient of variation (29.2–113.3%) within group. The increase in NADΔ was associated with an improvement in the walking distance of 6-minute walk test and the SF-36 score. The median effect dose of NADΔ for the 6-minute walk test and SF-36 score was 15.7 nmol/L (95% CI: 10.9–20.5 nmol/L) and 13.5 nmol/L (95% CI; 10.5–16.5 nmol/L), respectively. Because of the high interindividual variability of the NADΔ after NMN supplementation, monitoring NAD concentration can provide valuable insights for tailoring personalized dosage regimens and optimizing NMN utilization.

Impact of Perinatal Arsenic Exposure on Amino Acid Neurotransmitters and Bioenergetics Molecules in the Hippocampus of Rats

Developmental neurotoxicity of Arsenic (As) is a major concern worldwide. High level As exposure is associated with several chronic diseases including adverse pregnancy and birth outcomes. However, very a lack of information on its ability to impair neurodevelopment at lower exposure. To date, there are very few animal studies during the perinatal period of As exposure. Although exposure to As induces developmental neurotoxicity, there is a lack of data regarding its specific effects on amino acid neurotransmitters and bioenergetics biomolecules in the hippocampus of developing rats exposed to As during the perinatal period (GD6-PD21). In continuation of previous studies, rats were exposed to As from gestational day (GD 6) through PD 21 with targeted doses of 0, 2.0, and 4.0 mg/kg/day, respectively. HPLC-UV method was used to estimate the level of amino acid neurotransmitters (aspartate, glutamate, homocysteine, glutamine, serine, and glycine) and the level of Adenosine 5’-Triphosphate (ATP), Adenosine Diphosphate (ADP), Adenosine Monophosphate (AMP), Nicotinamide Mononucleotide (NMN), Nicotinamide Adenine Dinucleotide (NAD+), reduced Nicotinamide Adenine Dinucleotide (NADH) in the hippocampus of rats after the exposure of As. Amino acid neurotransmitter levels, a predictive biomarker of As-induced developmental neurotoxicity were found to be altered. ATP, ADP, and AMP were also significantly impaired in the hippocampus of As-exposed rats. We have observed that the hippocampus is susceptible to As toxicity, both because of the high energy depletion and the alterations in the levels of selected amino acid neurotransmitters. Taken together, our results indicate that perinatal As exposure appears to be critical and vulnerable.

Evolutionary adaptation in the laboratory and the process of retrograde engineering augment autotrophic proliferation in Saccharomyces cerevisiae

Genetic engineering provides various avenues for CO2 transformation into biological matter or bio-substances, aiding in mitigating the unsustainable utilization of organic raw materials that contribute detrimentally to global warming. The employment of widely recognized industrial microorganisms, like Saccharomyces cerevisiae, for the creation of innovative carbon (C) biomanufacturing frameworks may detach biological technology from raw materials with potential substitute applications in agricultural output. Lately, the primary C utilization of S. cerevisiae was rewired through a systematic manipulation strategy, enabling the resultant strains to achieve autotrophic growth with a maximum growth rate (μmax) of 0.002 h−1, which was subsequently enhanced to 0.02 h−1 via evolutionary engineering. By employing retrograde gene manipulation to manipulate Copy Number Variations (CNVs) variations happening in the genes encoding hexokinase and nicotinamide mononucleotide adenylyltransferase (NMNAT) following evolution, we assessed their impact on the enhanced self-sustaining characteristics. The modified CNVs induced reduced catalytic capabilities in potential bifurcation reactions and energy-balancing-related chemical processes. Moreover, we demonstrate how subsequent evolution enables peroxisomal intake and augments proliferation in self-sustaining circumstances. The genetically modified S. cerevisiae strains provide a foundation for the advancement of a versatile innovation that harnesses CO2 for the manufacturing of high-value goods, including cellular organic matter, specialized catalysts, and compounds while circumventing the consumption of organic raw materials alongside potential substitute applications in agricultural output. Additionally, the detection and validation of three critical mechanisms might facilitate the assimilation of foreign CBB cycles or analogous routes to foreign microorganisms.

Nicotinamide Mononucleotide (NMN) Works in Type 2 Diabetes through Unexpected Effects in Adipose Tissue, Not by Mitochondrial Biogenesis.

Nicotinamide mononucleotide (NMN) has emerged as a promising therapeutic intervention for age-related disorders, including type 2 diabetes. In this study, we confirmed the previously observed effects of NMN treatment on glucose uptake and investigated its underlying mechanisms in various tissues and cell lines. Through the most comprehensive proteomic analysis to date, we discovered a series of novel organ-specific effects responsible for glucose uptake as measured by the IPGTT: adipose tissue growing (suggested by increased protein synthesis and degradation and mTOR proliferation signaling upregulation). Notably, we observed the upregulation of thermogenic UCP1, promoting enhanced glucose conversion to heat in intermuscular adipose tissue while showing a surprising repressive effect on mitochondrial biogenesis in muscle and the brain. Additionally, liver and muscle cells displayed a unique response, characterized by spliceosome downregulation and concurrent upregulation of chaperones, proteasomes, and ribosomes, leading to mildly impaired and energy-inefficient protein synthesis machinery. Furthermore, our findings revealed remarkable metabolic rewiring in the brain. This involved increased production of ketone bodies, downregulation of mitochondrial OXPHOS and TCA cycle components, as well as the induction of well-known fasting-associated effects. Collectively, our data elucidate the multifaceted nature of NMN action, highlighting its organ-specific effects and their role in improving glucose uptake. These findings deepen our understanding of NMN's therapeutic potential and pave the way for novel strategies in managing metabolic disorders.

A metabolic signature for NADSYN1-dependent congenital NAD deficiency disorder.

Nicotinamide adenine dinucleotide (NAD) is essential for embryonic development. To date, biallelic loss-of-function variants in 3 genes encoding nonredundant enzymes of the NAD de novo synthesis pathway - KYNU, HAAO, and NADSYN1 - have been identified in humans with congenital malformations defined as congenital NAD deficiency disorder (CNDD). Here, we identified 13 further individuals with biallelic NADSYN1 variants predicted to be damaging, and phenotypes ranging from multiple severe malformations to the complete absence of malformation. Enzymatic assessment of variant deleteriousness in vitro revealed protein domain-specific perturbation, complemented by protein structure modeling in silico. We reproduced NADSYN1-dependent CNDD in mice and assessed various maternal NAD precursor supplementation strategies to prevent adverse pregnancy outcomes. While for Nadsyn1+/- mothers, any B3 vitamer was suitable to raise NAD, preventing embryo loss and malformation, Nadsyn1-/- mothers required supplementation with amidated NAD precursors (nicotinamide or nicotinamide mononucleotide) bypassing their metabolic block. The circulatory NAD metabolome in mice and humans before and after NAD precursor supplementation revealed a consistent metabolic signature with utility for patient identification. Our data collectively improve clinical diagnostics of NADSYN1-dependent CNDD, provide guidance for the therapeutic prevention of CNDD, and suggest an ongoing need to maintain NAD levels via amidated NAD precursor supplementation after birth.

A native phosphoribosyltransferase, PncB, is the key NMN synthase in Bacillus subtilis

Nicotinamide mononucleotide (NMN) is a precursor of NAD+, its efficient bio-production through microbial fermentation has rarely been reported. Bacillus subtilis was postulated to lack the inherent ability of NMN biosynthesis, however, certain level of NMN (53.67 mg/L) was detected in the fermentation broth containing nicotinamide. An endogenous enzyme (PncB) previously annotated as a nicotinic acid phosphotransferase was identified to be involved in the key synthetic reaction, since the deletion of pncB revoked the production of NMN, while the enhanced expression of PncB significantly increased the titer of NMN (110.0 mg/L). The structural simulation of PncB revealed the possible catalytic mechanisms of NMN forming. The NMN synthesis was further boosted by removing a possible deamidase (CinA), the yield of extracellular NMN reached 202.9 mg/L. After introducing the NMN transporter PnuC into the host cell, the fermentation level of NMN increased by another 65.34 %. And, with 20 g/L glucose and 10 g/L NAM supplemented in the medium, a maximal of 1.21 g/L of NMN was accumulated, signifying the potential of biological production of NMN using food-grade Bacillus subtilis.

Molecular mechanism of NAD+ and NMN binding to the Nudix homology domains of DBC1

Deleted in breast cancer 1 (DBC1) is a human nuclear protein that modulates the activities of various proteins involved in cell survival and cancer progression. Oxidized form of nicotinamide adenine dinucleotide (NAD+) is suggested to bind to the Nudix homology domains (NHDs) of DBC1, thereby regulating DBC1-Poly (ADP-ribose) polymerase 1 (PARP1) interactions, resulting in the restoration of DNA repair. Using Nuclear Magnetic Resonance (NMR) and Isothermal Titration Calorimetry (ITC), we confirmed NAD+ and its precursor nicotinamide mononucleotide (NMN) both bind the NHD domain of DBC1 (DBC1354–396). NAD+ likely interacts with DBC1354–396 through hydrogen bonding, with a binding affinity (8.99 μM) nearly twice that of NMN (17.0 μM), and the key binding sites are primarily residues E363 and D372, in the agreement with Molecular Docking experiments. Molecular Dynamics (MD) simulation further demonstrated E363 and D372's anchoring role in the binding process. Additional mutagenesis experiments of E363 and D372 confirmed their critical involvement of ligand-protein interactions. These findings lead to a better understanding of how NAD+ and NMN regulate DBC1, thereby offering insights for the development of targeted therapies and drug research focused on DBC1-associated tumors.

EFFICACY OF NICOTINAMIDE MONONUCLEOTIDE SUPPLEMENTATION (NMN) IN BLOOD NICOTINAMIDE ADENINE DINUCLEOTIDE (NAD) FOR ANTI-AGING IN ADULTS: A SYSTEMATIC REVIEW

Aging is a risk factor for various chronic diseases such as diabetes, dyslipidemia, metabolic, neurological, and cardiovascular disease, and other age-related disorders. Nicotinamide mononucleotide (NMN) is one of the endogenous intermediate molecules in nicotinamide adenine dinucleotide (NAD) biosynthesis, and its biological function is known to be related to an increase in NAD concentration. NAD levels decline and are critical for human health and longevity. The material and methods using a systematic review of RCT, with participants of healthy adults aged between 20-65 years old, agreed to take NMN supplementation compared to Placebo. The inclusion criteria are RCT studies regarding NMN administration with an outcome to prevent aging using primary objective measurement of blood nicotinamide adenine dinucleotide (NAD) concentration. Trial quality was assessed using the JBI checklist. We included six studies with an average duration of intervention between 10-12 weeks with a dosage of NMN 250-900mg/day. All six studies showed that NMN supplementation can significantly improve blood NAD concentration and cause only mild adverse effects during the trial. In conclusion, NMN supplementation has a significant clinical impact in preventing adult aging.

Biosynthesis of Nicotinamide Mononucleotide: Synthesis Method, Enzyme, and Biocatalytic System.

Nicotinamide mononucleotide (NMN) has garnered substantial interest as a functional food product. Industrial NMN production relies on chemical methods, facing challenges in separation, purification, and regulatory complexities, leading to elevated prices. In contrast, NMN biosynthesis through fermentation or enzyme catalysis offers notable benefits like eco-friendliness, recyclability, and efficiency, positioning it as a primary avenue for future NMN synthesis. Enzymatic NMN synthesis encompasses the nicotinamide-initial route and nicotinamide ribose-initial routes. Key among these is nicotinamide riboside kinase (NRK), pivotal in the latter route. The NRK-mediated biosynthesis is emerging as a prominent trend due to its streamlined route, simplicity, and precise specificity. The essential aspect is to obtain an engineered NRK that exhibits elevated activity and robust stability. This review comprehensively assesses diverse NMN synthesis methods, offering valuable insights into efficient, sustainable, and economical production routes. It spotlights the emerging NRK-mediated biosynthesis pathway and its significance. The establishment of an adenosine triphosphate (ATP) regeneration system plays a pivotal role in enhancing NMN synthesis efficiency through NRK-catalyzed routes. The review aims to be a reference for researchers developing green and sustainable NMN synthesis, as well as those optimizing NMN production.

Supplementation of nicotinamide mononucleotide diminishes COX-2 associated inflammatory responses in macrophages by activating kynurenine/AhR signaling

Cyclooxygenase-2 (COX-2) is an inducible enzyme responsible for prostaglandin synthesis during inflammation and immune responses. Our previous results show that NAD+ level decreased in activated macrophages while nicotinamide mononucleotide (NMN) supplementation suppressed the inflammatory responses via restoring NAD+ level and downregulating COX-2. However, whether NMN downregulates COX-2 in mouse model of inflammation, and its underlying mechanism needs to be further explored. In the present study, we established LPS- and alum-induced inflammation model and demonstrated that NMN suppressed the inflammatory responses in vivo. Quantitative proteomics in mouse peritoneal macrophages identified that NMN activated AhR signaling pathway in activated macrophages. Furthermore, we revealed that NMN supplementation led to IDO1 activation and kynurenine accumulation, which caused AhR nuclear translocation and activation. On the other hand, AhR or IDO1 knockout abolished the effects of NMN on suppressing COX-2 expression and inflammatory responses in macrophages. In summary, our results demonstrated that NMN suppresses inflammatory responses by activating IDO-kynurenine-AhR pathway, and suggested that administration of NMN in early-stage immuno-activation may cause an adverse health effect.

Inhibitors of NAD+ Production in Cancer Treatment: State of the Art and Perspectives.

The addiction of tumors to elevated nicotinamide adenine dinucleotide (NAD+) levels is a hallmark of cancer metabolism. Obstructing NAD+ biosynthesis in tumors is a new and promising antineoplastic strategy. Inhibitors developed against nicotinamide phosphoribosyltransferase (NAMPT), the main enzyme in NAD+ production from nicotinamide, elicited robust anticancer activity in preclinical models but not in patients, implying that other NAD+-biosynthetic pathways are also active in tumors and provide sufficient NAD+ amounts despite NAMPT obstruction. Recent studies show that NAD+ biosynthesis through the so-called "Preiss-Handler (PH) pathway", which utilizes nicotinate as a precursor, actively operates in many tumors and accounts for tumor resistance to NAMPT inhibitors. The PH pathway consists of three sequential enzymatic steps that are catalyzed by nicotinate phosphoribosyltransferase (NAPRT), nicotinamide mononucleotide adenylyltransferases (NMNATs), and NAD+ synthetase (NADSYN1). Here, we focus on these enzymes as emerging targets in cancer drug discovery, summarizing their reported inhibitors and describing their current or potential exploitation as anticancer agents. Finally, we also focus on additional NAD+-producing enzymes acting in alternative NAD+-producing routes that could also be relevant in tumors and thus become viable targets for drug discovery.