Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence

Nicotinamide mononucleotide alleviates endotoxin-induced acute lung injury by modulating macrophage polarization via the SIRT1/NF-κB pathway

CONTEXT

Sepsis-induced acute lung injury (ALI) is a severe condition with limited effective therapeutics; nicotinamide mononucleotide (NMN) has been reported to exert anti-inflammatory activities.

OBJECTIVE

This study explores the potential mechanisms by which NMN ameliorates sepsis-induced ALI in vivo and in vitro.

MATERIALS AND METHODS

Cultured MH-S cells and a murine model were used to evaluate the effect of NMN on sepsis-induced ALI. MH-S cells were stimulated with LPS (1 μg/mL) and NMN (500 μM) for 12 h grouping as control, LPS, and LPS + NMN. Cell viability, apoptotic status, and M1/2 macrophage-related markers were detected. The mice were pretreated intraperitoneally with NMN (500 mg/kg) and/or EX-527 (5 mg/kg) 1 h before LPS injection and randomized into 7 groups (n = 8): control, LPS, LPS + NMN, NMN, LPS + NMN + EX-527 (a SIRT1 inhibitor), LPS + EX-527, and EX-527. After 12 h, lung histopathology, W/D ratio, MPO activity, NAD+ and ATP levels, M1/2 macrophage-related markers, and expression of the SIRT1/NF-κB pathway were detected.

RESULTS

In MH-S cells, NMN significantly decreased the apoptotic rate from 12.25% to 5.74%. In septic mice, NMN improved the typical pathologic findings in lungs and reduced W/D ratio and MPO activity, but increased NAD+ and ATP levels. Additionally, NMN suppressed M1 but promoted M2 polarization, and upregulated the expression of SIRT1, with inhibition of NF-κB-p65 acetylation and phosphorylation. Furthermore, inhibition of SIRT1 reversed the effects of NMN-induced M2 macrophage polarization.

CONCLUSIONS

NMN protects against sepsis-induced ALI by promoting M2 macrophage polarization via the SIRT1/NF-κB pathway, it might be an effective strategy for preventing or treating sepsis-induced ALI.

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.

Development and testing of nanoparticles delivery for P7C3 small molecule using injury models

The use of nanoparticles (NPs) has emerged as a potential tool for safe and effective drug delivery. In the present study, we developed small molecule P7C3-based NPs and tested its efficacy and toxicity along with the tissue specific aptamer-modified P7C3 NPs. The P7C3 NPs were prepared using poly (D, L-lactic-co-glycolic acid) carboxylic acid (PLGA-COOH) polymer, were conjugated with skeletal muscle-specific RNA aptamer (A01B P7C3 NPs) and characterized for its cytotoxicity, cellular uptake, and wound healing in vitro. The A01B P7C3 NPs demonstrated an encapsulation efficiency of 30.2 ± 2.6%, with the particle size 255.9 ± 4.3 nm, polydispersity index of 0.335 ± 0.05 and zeta potential of + 10.4 ± 1.8mV. The FTIR spectrum of P7C3 NPs displayed complete encapsulation of the drug in the NPs. The P7C3 NPs and A01B P7C3 NPs displayed sustained drug release in vitro for up to 6 days and qPCR analysis confirmed A01B aptamer binding to P7C3 NPs. The C2C12 cells viability assay displayed no cytotoxic effects of all 3 formulations at 48 and 72 h. In addition, the cellular uptake of A01B P7C3 NPs in C2C12 myoblasts demonstrated higher uptake. In vitro assay mimicking wound healing showed improved wound closure with P7C3 NPs. In addition, P7C3 NPs significantly decreased TNF-α induced NF-κB activity in the C2C12/NF-κB reporter cells after 24-hour treatment. The P7C3 NPs showed 3-4-fold higher efficacy compared to P7C3 solutions in both wound-closure and inflammation assays in C2C12 cells. Furthermore, the P7C3 NPs showed 3-4-fold higher efficacy in reducing the infarct size and protected mouse hearts from ex vivo ischemia-reperfusion injury. Overall, this study demonstrates the safe and effective delivery of P7C3 NPs.

NAD+ metabolism and therapeutic strategies in cardiovascular diseases

Nicotinamide adenine dinucleotide (NAD+) is a central and pleiotropic metabolite involved in cellular energy metabolism, cell signaling, DNA repair, and protein modifications. Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Metabolic stress and aging directly affect the cardiovascular system. Compelling data suggest that NAD + levels decrease with age, obesity, and hypertension, which are all notable risk factors for CVD. In addition, the therapeutic elevation of NAD + levels reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular disorders. In preclinical models, NAD + boosting can also expand the health span, prevent metabolic syndrome, and decrease blood pressure. Moreover, NAD + storage by genetic, pharmacological, or natural dietary NAD + -increasing strategies has recently been shown to be effective in improving the pathophysiology of cardiac and vascular health in different animal models, and human health. Here, we review and discuss NAD + -related mechanisms pivotal for vascular health and summarize recent experimental evidence in NAD + research directly related to vascular disease, including atherosclerosis, and coronary artery disease. Finally, we comparatively assess distinct NAD + precursors for their clinical efficacy and the efficiency of NAD + elevation in the treatment of major CVD. These findings may provide ideas for new therapeutic strategies to prevent and treat CVD in the clinic.

Biosynthesis of vitamin B3 and NAD+: incubating HepG2 cells with the alkaloid myosmine

BACKGROUND

In the kynurenine pathway, it is reported that the essential amino acid tryptophan forms nicotinic acid (NA, vitamin B3) in biological systems. This pathway is part of the de novo pathway to perform nicotinamide adenine dinucleotide (NAD+) biosynthesis. Additionally, biosynthesis of NAD+ via the Preiss-Handler pathway involves NA and its analogue nicotinamide, both designated as niacin. Previous attempts were successful in converting myosmine (MYO) by organic synthesis to NA, and the assumption was that the alkaloid MYO, which is taken in from food, can be converted into NA by biological oxidation.

RESULT

Incubation of HepG2 cells with MYO yielded NA. Moreover, a significant increase of NAD+ compared with the control has been found.

CONCLUSION

Hence, MYO could be assumed to be the hitherto unknown origin of an alternative NA biosynthesis additionally influencing NAD+ biosynthesis positively. This novel MYO pathway may open new perspectives to improve knowledge and relevance of NA and NAD+ biosynthesis and bioactivation in cells and, moreover, in food staples, food, and diet. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Advancements in NMN biotherapy and research updates in the field of digestive system diseases

Nicotinamide mononucleotide (NMN), a crucial intermediate in NAD + synthesis, can rapidly transform into NAD + within the body after ingestion. NMN plays a pivotal role in several important biological processes, including energy metabolism, cellular aging, circadian rhythm regulation, DNA repair, chromatin remodeling, immunity, and inflammation. NMN has emerged as a key focus of research in the fields of biomedicine, health care, and food science. Recent years have witnessed extensive preclinical studies on NMN, offering valuable insights into the pathogenesis of age- and aging-related diseases. Given the sustained global research interest in NMN and the substantial market expectations for the future, here, we comprehensively review the milestones in research on NMN biotherapy over the past 10 years. Additionally, we highlight the current research on NMN in the field of digestive system diseases, identifying existing problems and challenges in the field of NMN research. The overarching aim of this review is to provide references and insights for the further exploration of NMN within the spectrum of digestive system diseases.

Targeting organ-specific mitochondrial dysfunction to improve biological aging

In an aging society, unveiling new anti-aging strategies to prevent and combat aging-related diseases is of utmost importance. Mitochondria are the primary ATP production sites and key regulators of programmed cell death. Consequently, these highly dynamic organelles play a central role in maintaining tissue function, and mitochondrial dysfunction is a pivotal factor in the progressive age-related decline in cellular homeostasis and organ function. The current review examines recent advances in understanding the interplay between mitochondrial dysfunction and organ-specific aging. Thereby, we dissect molecular mechanisms underlying mitochondrial impairment associated with the deterioration of organ function, exploring the role of mitochondrial DNA, reactive oxygen species homeostasis, metabolic activity, damage-associated molecular patterns, biogenesis, turnover, and dynamics. We also highlight emerging therapeutic strategies in preclinical and clinical tests that are supposed to rejuvenate mitochondrial function, such as antioxidants, mitochondrial biogenesis stimulators, and modulators of mitochondrial turnover and dynamics. Furthermore, we discuss potential benefits and challenges associated with the use of these interventions, emphasizing the need for organ-specific approaches given the unique mitochondrial characteristics of different tissues. In conclusion, this review highlights the therapeutic potential of addressing mitochondrial dysfunction to mitigate organ-specific aging, focusing on the skin, liver, lung, brain, skeletal muscle, and lung, as well as on the reproductive, immune, and cardiovascular systems. Based on a comprehensive understanding of the multifaceted roles of mitochondria, innovative therapeutic strategies may be developed and optimized to combat biological aging and promote healthy aging across diverse organ systems.

Nicotinamide riboside Induced Energy Stress and Metabolic Reprogramming in BEAS-2B Cells

Nicotinamide riboside (NR), a NAD+ precursor, has received attention due to several health benefits it has induced in experimental models. Studies in cultured cells, animals, and humans consistently show increased NAD+ availability after NR supplementation, which is considered the only mode of NR action that leads to health benefits. In the present study, we show that a persistently low NR concentration (1 μM) in the growth medium of BEAS-2B human cells, grown in a monolayer, induces energy stress, which precedes a cellular NAD+ increase after 192 h. NR concentrations greater than 1 μM under the specified conditions were cytotoxic in the 2D cell culture model, while all concentrations tested in the 3D cell culture model (BEAS-2B cell spheroids exposed to 1, 5, 10, and 50 μM NR) induced apoptosis. Shotgun proteomics revealed that NR modulated the abundance of proteins, agreeing with the observed effects on cellular energy metabolism and cell growth or survival. Energy stress may activate pathways that lead to health benefits such as cancer prevention. Accordingly, the premalignant 1198 cell line was more sensitive to NR cytotoxicity than the phenotypically normal parent BEAS-2B cell line. The role of a mild energy stress induced by low concentrations of NR in its beneficial effects deserves further investigation. On the other hand, strategies to increase the bioavailability of NR require attention to toxic effects that may arise.

Efficacy of oral nicotinamide mononucleotide supplementation on glucose and lipid metabolism for adults: a systematic review with meta-analysis on randomized controlled trials

A surge of public interest in NMN supplementation has been observed in recent years. However, whether NMN supplements are effective in improving metabolic health remains unclear. The objective of the review was to assess the effects of NMN supplementation on fasting glucose, triglycerides, total cholesterol, LDL-C, and HDL-C in adults. Studies were located by searching four databases (PubMed, Embase, Cochrane, and Web of Science). Two reviewers independently conducted title/abstract and full-text screening, data extraction, and risk-of-bias assessment. Of the 4049 records reviewed, 12 studies with a total of 513 participants met the criteria for analysis. Random-effects meta-analyses found an overall significant effect of NMN supplementation in elevating blood NAD levels. However, most of the clinically relevant outcomes were not significantly different between NMN supplementation and control group. Risk-of-bias assessment using RoB2 showed some concerns in seven studies and high risk of bias in the other five studies. Together, our findings suggest that an exaggeration of the benefits of NMN supplementation may exist in the field. Although the limited number of eligible studies was sufficiently powered to detect changes in the abovementioned primary outcomes, more studies are needed to conclude about the exact effects of NMN supplementation.

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.

Discovery and characterization of a new class of NAD+-independent SIRT1 activators

The activity of sirtuin 1 (SIRT1, a member of the NAD+-dependent deacetylases family) decreases during aging as NAD+ levels naturally decline, thus increasing the risk of several age-associated diseases. Several sirtuin-activating compounds (STACs) have been developed to counteract the age-associated reduction in SIRT1 activity, and some of them are currently under development in clinical trials. STACs induce SIRT1 activation, either through allosteric activation of the enzyme in the presence of NAD+, or by increasing NAD+ levels by inhibiting its degradation or by supplying a key precursor in biosynthesis. In this study, we have identified (E)-2'-des-methyl sulindac analogues as a novel class of STACs that act also in the absence of NAD+, a peculiar behavior demonstrated through enzymatic and mass spectrometry experiments, both in vitro and in cell lines. The activation of the SIRT1 pathway was confirmed in vivo through gene expression and metabolomics analysis. Our data suggest that these compounds could serve as candidate leads for a novel therapeutic strategy aimed at addressing a key metabolic deficiency that may contribute to metabolic and age-associated diseases.

Immune infiltration and prognosis in gastric cancer: role of NAD+ metabolism-related markers

Background

This study endeavored to develop a nicotinamide adenine dinucleotide (NAD+) metabolism-related biomarkers in gastric cancer (GC), which could provide a theoretical foundation for prognosis and therapy of GC patients.

Methods

In this study, differentially expressed genes (DEGs1) between GC and paraneoplastic tissues were overlapped with NAD+ metabolism-related genes (NMRGs) to identify differentially expressed NMRGs (DE-NMRGs). Then, GC patients were divided into high and low score groups by gene set variation analysis (GSVA) algorithm for differential expression analysis to obtain DEGs2, which was overlapped with DEGs1 for identification of intersection genes. These genes were further analyzed using univariate Cox and least absolute shrinkage and selection operator (LASSO) regression analyses to obtain prognostic genes for constructing a risk model. Enrichment and immune infiltration analyses further investigated investigate the different risk groups, and qRT-PCR validated the prognostic genes.

Results

Initially, we identified DE-NMRGs involved in NAD biosynthesis, with seven (DNAJB13, CST2, THPO, CIDEA, ONECUT1, UPK1B and SNCG) showing prognostic significance in GC. Subsequent, a prognostic model was constructed in which the risk score, derived from the expression profiles of these genes, along with gender, emerged as robust independent predictors of patient outcomes in GC. Enrichment analysis linked high-risk patients to synaptic membrane pathways and low-risk to the CMG complex pathway. Tumor immune infiltration analysis revealed correlations between risk scores and immune cell abundance, suggesting a relationship between NAD+ metabolism and immune response in GC. The prognostic significance of our identified genes was validated by qRT-PCR, which confirmed their upregulated expression in GC tissue samples.

Conclusion

In this study, seven NAD+ metabolism-related markers were established, which is of great significance for the development of prognostic molecular biomarkers and clinical prognosis prediction for gastric cancer patients.

Roles of Sirtuins in Hearing Protection

Hearing loss is a health crisis that affects more than 60 million Americans. Currently, sodium thiosulfate is the only drug approved by the Food and Drug Administration (FDA) to counter hearing loss. Sirtuins were proposed as therapeutic targets in the search for new compounds or drugs to prevent or cure age-, noise-, or drug-induced hearing loss. Sirtuins are proteins involved in metabolic regulation with the potential to ameliorate sensorineural hearing loss. The mammalian sirtuin family includes seven members, SIRT1-7. This paper is a literature review on the sirtuins and their protective roles in sensorineural hearing loss. Literature search on the NCBI PubMed database and NUsearch included the keywords 'sirtuin' and 'hearing'. Studies on sirtuins without relevance to hearing and studies on hearing without relevance to sirtuins were excluded. Only primary research articles with data on sirtuin expression and physiologic auditory tests were considered. The literature review identified 183 records on sirtuins and hearing. After removing duplicates, eighty-one records remained. After screening for eligibility criteria, there were forty-eight primary research articles with statistically significant data relevant to sirtuins and hearing. Overall, SIRT1 (n = 29) was the most studied sirtuin paralog. Over the last two decades, research on sirtuins and hearing has largely focused on age-, noise-, and drug-induced hearing loss. Past and current studies highlight the role of sirtuins as a mediator of redox homeostasis. However, more studies need to be conducted on the involvement of SIRT2 and SIRT4-7 in hearing protection.

Advances in the Synthesis and Physiological Metabolic Regulation of Nicotinamide Mononucleotide

Nicotinamide mononucleotide (NMN), the direct precursor of nicotinamide adenine dinucleotide (NAD+), is involved in the regulation of many physiological and metabolic reactions in the body. NMN can indirectly affect cellular metabolic pathways, DNA repair, and senescence, while also being essential for maintaining tissues and dynamic metabolic equilibria, promoting healthy aging. Therefore, NMN has found many applications in the food, pharmaceutical, and cosmetics industries. At present, NMN synthesis strategies mainly include chemical synthesis and biosynthesis. Despite its potential benefits, the commercial production of NMN by organic chemistry approaches faces environmental and safety problems. With the rapid development of synthetic biology, it has become possible to construct microbial cell factories to produce NMN in a cost-effective way. In this review, we summarize the chemical and biosynthetic strategies of NMN, offering an overview of the recent research progress on host selection, chassis cell optimization, mining of key enzymes, metabolic engineering, and adaptive fermentation strategies. In addition, we also review the advances in the role of NMN in aging, metabolic diseases, and neural function. This review provides comprehensive technical guidance for the efficient biosynthesis of NMN as well as a theoretical basis for its application in the fields of food, medicine, and cosmetics.

Nicotinamide riboside restores nicotinamide adenine dinucleotide levels and alleviates brain injury by inhibiting oxidative stress and neuroinflammation in a mouse model of intracerebral hemorrhage

Hemorrhagic stroke is a global health problem owing to its high morbidity and mortality rates. Nicotinamide riboside is an important precursor of nicotinamide adenine dinucleotide characterized by a high bioavailability, safety profile, and robust effects on many cellular signaling processes. This study aimed to investigate the protective effects of nicotinamide riboside against collagenase-induced hemorrhagic stroke and its underlying mechanisms of action. An intracerebral hemorrhage model was constructed by stereotactically injecting collagenase into the right striatum of adult male Institute for Cancer Research mice. After 30 minutes, nicotinamide riboside was administered via the tail vein. The mice were sacrificed at different time points for assessments. Nicotinamide riboside reduced collagenase-induced hemorrhagic area, significantly reduced cerebral water content and histopathological damage, promoted neurological function recovery, and suppressed reactive oxygen species production and neuroinflammation. Nicotinamide riboside exerts neuroprotective effects against collagenase-induced intracerebral hemorrhage by inhibiting neuroinflammation and oxidative stress.

Maintaining mitochondrial NAD+ homeostasis is key for heat-induced skeletal muscle injury prevention despite presence of intracellular cation alterations

Mitochondrial dysfunction is implicated in heat-induced skeletal muscle (SKM) injury and its underlying mechanisms remain unclear. Evidence suggests that cellular ions and molecules, including divalent cations and adenine nucleotides, are involved in the regulation of mitochondrial function. In this study, we examined Ca2+, Mg2+, and NAD+ levels in mouse C2C12 myoblasts and SKM in response to heat exposure. During heat exposure, mitochondrial Ca2+ levels increased significantly, whereas cytosolic Ca2+ levels remained unaltered. The mitochondrial Ca2+ levels in the SKM of heat-exposed mice were 28% higher compared to control mice. No changes in cytosolic Ca2+ were detected between the two groups. Following heat exposure, cytosolic and mitochondrial Mg2+ levels were reduced by 47% and 23% in C2C12 myoblasts, and by 51% and 44% in mouse SKMs, respectively. In addition, heat exposure decreased mitochondrial NAD+ levels by 32% and 26% in C2C12 myoblasts and mouse SKMs, respectively. Treatment with the NAD+ precursor nicotinamide riboside (NR) partially prevented heat-induced depletion of NAD+. Additionally, NR significantly reduced heat-increased mitochondrial fission, mitochondrial depolarization, and apoptosis in C2C12 myoblasts and mouse SKMs. No effects of NR on heat-induced changes in intracellular Ca2+ and Mg2+ levels were observed. This study provides in vitro and in vivo evidence that acute heat stress causes alterations in mitochondrial Ca2+, Mg2+, and NAD+ homeostasis. Our results suggest mitochondrial NAD+ homeostasis as a therapeutic target for the prevention of heat-induced SKM injury.

Identification of common genetic factors and immune-related pathways associating more than two autoimmune disorders: implications on risk, diagnosis, and treatment

Autoimmune disorders (ADs) are chronic conditions resulting from failure or breakdown of immunological tolerance, resulting in the host immune system attacking its cells or tissues. Recent studies report shared effects, mechanisms, and evolutionary origins among ADs; however, the possible factors connecting them are unknown. This study attempts to identify gene signatures commonly shared between different autoimmune disorders and elucidate their molecular pathways linking the pathogenesis of these ADs using an integrated gene expression approach. We employed differential gene expression analysis across 19 datasets of whole blood/peripheral blood cell samples with five different autoimmune disorders (rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, Crohn's disease, and type 1 diabetes) to get nine key genes-EGR1, RUNX3, SMAD7, NAMPT, S100A9, S100A8, CYBB, GATA2, and MCEMP1 that were primarily involved in cell and leukocyte activation, leukocyte mediated immunity, IL-17, AGE-RAGE signaling in diabetic complications, prion disease, and NOD-like receptor signaling confirming its role in immune-related pathways. Combined with biological interpretations such as gene ontology (GO), pathway enrichment, and protein-protein interaction (PPI) network, our current study sheds light on the in-depth research on early detection, diagnosis, and prognosis of different ADs.

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

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

NAD+ supplementation improves mitochondrial functions and normalizes glaucomatous trabecular meshwork features

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

Enhancing healthy aging with small molecules: A mitochondrial perspective

The pursuit of enhanced health during aging has prompted the exploration of various strategies focused on reducing the decline associated with the aging process. A key area of this exploration is the management of mitochondrial dysfunction, a notable characteristic of aging. This review sheds light on the crucial role that small molecules play in augmenting healthy aging, particularly through influencing mitochondrial functions. Mitochondrial oxidative damage, a significant aspect of aging, can potentially be lessened through interventions such as coenzyme Q10, alpha-lipoic acid, and a variety of antioxidants. Additionally, this review discusses approaches for enhancing mitochondrial proteostasis, emphasizing the importance of mitochondrial unfolded protein response inducers like doxycycline, and agents that affect mitophagy, such as urolithin A, spermidine, trehalose, and taurine, which are vital for sustaining protein quality control. Of equal importance are methods for modulating mitochondrial energy production, which involve nicotinamide adenine dinucleotide boosters, adenosine 5'-monophosphate-activated protein kinase activators, and compounds like metformin and mitochondria-targeted tamoxifen that enhance metabolic function. Furthermore, the review delves into emerging strategies that encourage mitochondrial biogenesis. Together, these interventions present a promising avenue for addressing age-related mitochondrial degradation, thereby setting the stage for the development of innovative treatment approaches to meet this extensive challenge.

Gut microbial metabolites in MASLD: Implications of mitochondrial dysfunction in the pathogenesis and treatment

With an increasing prevalence, metabolic dysfunction-associated steatotic liver disease (MASLD) has become a major global health problem. MASLD is well-known as a multifactorial disease. Mitochondrial dysfunction and alterations in the gut bacteria are 2 vital events in MASLD. Recent studies have highlighted the cross-talk between microbiota and mitochondria, and mitochondria are recognized as pivotal targets of the gut microbiota to modulate the host's physiological state. Mitochondrial dysfunction plays a vital role in MASLD and is associated with multiple pathological changes, including hepatocyte steatosis, oxidative stress, inflammation, and fibrosis. Metabolites are crucial mediators of the gut microbiota that influence extraintestinal organs. Additionally, regulation of the composition of gut bacteria may serve as a promising therapeutic strategy for MASLD. This study reviewed the potential roles of several common metabolites in MASLD, emphasizing their impact on mitochondrial function. Finally, we discuss the current treatments for MASLD, including probiotics, prebiotics, antibiotics, and fecal microbiota transplantation. These methods concentrate on restoring the gut microbiota to promote host health.

Nicotinamide Riboside Promotes the Proliferation of Endogenous Neural Stem Cells to Repair Spinal Cord Injury

Activation of endogenous neural stem cells (NSC) is one of the most potential measures for neural repair after spinal cord injury. However, methods for regulating neural stem cell behavior are still limited. Here, we investigated the effects of nicotinamide riboside promoting the proliferation of endogenous neural stem cells to repair spinal cord injury. Nicotinamide riboside promotes the proliferation of endogenous neural stem cells and regulates their differentiation into neurons. In addition, nicotinamide riboside significantly restored lower limb motor dysfunction caused by spinal cord injury. Nicotinamide riboside plays its role in promoting the proliferation of neural stem cells by activating the Wnt signaling pathway through the LGR5 gene. Knockdown of the LGR5 gene by lentivirus eliminates the effect of nicotinamide riboside on the proliferation of endogenous neural stem cells. In addition, administration of Wnt pathway inhibitors also eliminated the proliferative effect of nicotinamide riboside. Collectively, these findings demonstrate that nicotinamide promotes the proliferation of neural stem cells by targeting the LGR5 gene to activate the Wnt pathway, which provides a new way to repair spinal cord injury.

Long-term NMN treatment increases lifespan and healthspan in mice in a sex dependent manner

Nicotinamide adenine dinucleotide (NAD) is essential for many enzymatic reactions, including those involved in energy metabolism, DNA repair and the activity of sirtuins, a family of defensive deacylases. During aging, levels of NAD + can decrease by up to 50% in some tissues, the repletion of which provides a range of health benefits in both mice and humans. Whether or not the NAD + precursor nicotinamide mononucleotide (NMN) extends lifespan in mammals is not known. Here we investigate the effect of long-term administration of NMN on the health, cancer burden, frailty and lifespan of male and female mice. Without increasing tumor counts or severity in any tissue, NMN treatment of males and females increased activity, maintained more youthful gene expression patterns, and reduced overall frailty. Reduced frailty with NMN treatment was associated with increases in levels of Anerotruncus colihominis, a gut bacterium associated with lower inflammation in mice and increased longevity in humans. NMN slowed the accumulation of adipose tissue later in life and improved metabolic health in male but not female mice, while in females but not males, NMN increased median lifespan by 8.5%, possible due to sex-specific effects of NMN on NAD + metabolism. Together, these data show that chronic NMN treatment delays frailty, alters the microbiome, improves male metabolic health, and increases female mouse lifespan, without increasing cancer burden. These results highlight the potential of NAD + boosters for treating age-related conditions and the importance of using both sexes for interventional lifespan studies.

Changes in glucose metabolism, C-reactive protein, and liver enzymes following intake of NAD + precursor supplementation: a systematic review and meta-regression analysis

BACKGROUND

There are contradictory effects regarding the effect of NAD + precursor on glucose metabolism and liver enzymes. In order to obtain a better viewpoint from them, this study aimed to comprehensively investigate the effects of NAD + precursor supplementation on glucose metabolism, C-reactive protein (CRP), and liver enzymes.

METHODS

PubMed/MEDLINE, Web of Science, SCOPUS, and Embase databases were searched using standard keywords to identify all controlled trials investigating the glucose metabolism, CRP, and liver enzymes effects of NAD + precursor. Pooled weighted mean difference (WMD) and 95% confidence intervals (95% CI) were achieved by random-effects model analysis for the best estimation of outcomes.

RESULTS

Forty-five articles with 9256 participants' were included in this article. The pooled findings showed that NAD + precursor supplementation had a significant increase in glucose (WMD: 2.17 mg/dL, 95% CI: 0.68, 3.66, P = 0.004) and HbA1c (WMD: 0.11, 95% CI: 0.06, 0.16, P < 0.001) as well as a significant decrease in CRP (WMD: -0.93 mg/l, 95% CI -1.47 to -0.40, P < 0.001) compared with control group, and was not statistically significant with respect to insulin and homeostasis model assessment of insulin resistance (HOMA-IR). However, we found no systemic changes in aspartate transaminase (AST), alanine transaminase (ALT), or alkaline phosphatase (ALP) levels after NAD + precursor supplementation. The results of the subgroup analysis showed that the intake of NAD + precursor during the intervention of more than 12 weeks caused a greater increase in the glucose level. Furthermore, Nicotinic acid supplementation (NA) causes a greater increase in glucose and HbA1c levels than nicotinamide (NE) supplementation.

CONCLUSIONS

Overall, these findings suggest that NAD + precursor supplementation might have an increase effect on glucose metabolism as well as a decrease in CRP.

Unveiling the heightened susceptibility: Exploring early hypophosphatemia in critically ill trauma patients

BACKGROUND

Phosphorus is a vital mineral crucial for various physiological functions. Critically ill trauma patients frequently experience hypophosphatemia during the immediate post-traumatic phase, potentially impacting outcomes. This study aims to investigate the incidence of early hypophosphatemia in critically major trauma patients.

METHODS

In this prospective observational study, trauma patients admitted to the intensive care unit (ICU) within one day were enrolled. These patients were categorized into Hypo-P groups and Non-hypo groups based on the development of new-onset hypophosphatemia within 72 h after feeding. The primary outcome assessed was the incidence of new-onset hypophosphatemia. The secondary outcomes included ICU and hospital stay, ventilation duration, and mortality.

RESULTS

76.1% of patients developed a new onset of hypophosphatemia within 72 h after feeding. The Hypo-P group had significantly longer ICU stays (8.1 days ± 5.5 vs. 4.4 days ± 3.1; p = 0.0251) and trends towards extended hospital stay, ventilation duration, and higher mortality. Additionally, they demonstrated significantly higher urine fractional excretion of phosphate (FEPO4) on the first ICU day (29.2% ± 14.23 vs. 19.5% ± 8.39; p = 0.0242).

CONCLUSION

Critically ill trauma patients exhibited a significantly higher incidence of early hypophosphatemia than typical ICU rates, indicating their heightened vulnerability. The significantly high urine FEPO4 underscores the crucial role of renal loss in disrupting phosphate metabolism in this early acute phase after trauma. A significant correlation was observed between hypophosphatemia and longer ICU stays. Monitoring and managing phosphate levels may influence outcomes, warranting further investigation.

Decreasing Intracellular Entropy by Increasing Mitochondrial Efficiency and Reducing ROS Formation-The Effect on the Ageing Process and Age-Related Damage

A hypothesis is presented to explain how the ageing process might be influenced by optimizing mitochondrial efficiency to reduce intracellular entropy. Research-based quantifications of entropy are scarce. Non-equilibrium metabolic reactions and compartmentalization were found to contribute most to lowering entropy in the cells. Like the cells, mitochondria are thermodynamically open systems exchanging matter and energy with their surroundings-the rest of the cell. Based on the calculations from cancer cells, glycolysis was reported to produce less entropy than mitochondrial oxidative phosphorylation. However, these estimations depended on the CO2 concentration so that at slightly increased CO2, it was oxidative phosphorylation that produced less entropy. Also, the thermodynamic efficiency of mitochondrial respiratory complexes varies depending on the respiratory state and oxidant/antioxidant balance. Therefore, in spite of long-standing theoretical and practical efforts, more measurements, also in isolated mitochondria, with intact and suboptimal respiration, are needed to resolve the issue. Entropy increases in ageing while mitochondrial efficiency of energy conversion, quality control, and turnover mechanisms deteriorate. Optimally functioning mitochondria are necessary to meet energy demands for cellular defence and repair processes to attenuate ageing. The intuitive approach of simply supplying more metabolic fuels (more nutrients) often has the opposite effect, namely a decrease in energy production in the case of nutrient overload. Excessive nutrient intake and obesity accelerate ageing, while calorie restriction without malnutrition can prolong life. Balanced nutrient intake adapted to needs/activity-based high ATP requirement increases mitochondrial respiratory efficiency and leads to multiple alterations in gene expression and metabolic adaptations. Therefore, rather than overfeeding, it is necessary to fine-tune energy production by optimizing mitochondrial function and reducing oxidative stress; the evidence is discussed in this paper.

Tryptophan catabolism via the kynurenine pathway regulates infection and inflammation: from mechanisms to biomarkers and therapies

BACKGROUND

L-Tryptophan (L-Trp), an essential amino acid, is the only amino acid whose level is regulated specifically by immune signals. Most proportions of Trp are catabolized via the kynurenine (Kyn) pathway (KP) which has evolved to align the food availability and environmental stimulation with the host pathophysiology and behavior. Especially, the KP plays an indispensable role in balancing the immune activation and tolerance in response to pathogens.

SCOPE OF REVIEW

In this review, we elucidate the underlying immunological regulatory network of Trp and its KP-dependent catabolites in the pathophysiological conditions by participating in multiple signaling pathways. Furthermore, the KP-based regulatory roles, biomarkers, and therapeutic strategies in pathologically immune disorders are summarized covering from acute to chronic infection and inflammation.

MAJOR CONCLUSIONS

The immunosuppressive effects dominate the functions of KP induced-Trp depletion and KP-produced metabolites during infection and inflammation. However, the extending minor branches from the KP are not confined to the immune tolerance, instead they go forward to various functions according to the specific condition. Nevertheless, persistent efforts should be made before the clinical use of KP-based strategies to monitor and cure infectious and inflammatory diseases.

Cellular senescence, DNA damage, and neuroinflammation in the aging brain

Aging may lead to low-level chronic inflammation that increases the susceptibility to age-related conditions, including memory impairment and progressive loss of brain volume. As brain health is essential to promoting healthspan and lifespan, it is vital to understand age-related changes in the immune system and central nervous system (CNS) that drive normal brain aging. However, the relative importance, mechanistic interrelationships, and hierarchical order of such changes and their impact on normal brain aging remain to be clarified. Here, we synthesize accumulating evidence that age-related DNA damage and cellular senescence in the immune system and CNS contribute to the escalation of neuroinflammation and cognitive decline during normal brain aging. Targeting cellular senescence and immune modulation may provide a logical rationale for developing new treatment options to restore immune homeostasis and counteract age-related brain dysfunction and diseases.

Alleviation of hepatic insulin resistance and steatosis with NMN via improving endoplasmic reticulum-Mitochondria miscommunication in the liver of HFD mice

The interaction between endoplasmic reticulum (ER) and mitochondria has been shown to play a key role in hepatic steatosis during chronic obesity. β-nicotinamide mononucleotide (NMN) has been reported to regulate obesity, however, its molecular mechanism at the subcellular level remains unclear. Here, NMN improved liver steatosis and insulin resistance in chronic high-fat diet (HFD) mice. RNA-seq showed that compared with the liver of HFD mice, NMN intervention enhanced fat digestion and absorption and stimulated the cholesterol metabolism signaling pathways, while impaired insulin resistance and the fatty acid biosynthesis signaling pathways. Mechanistically, NMN ameliorated mitochondrial dysfunction and ER oxidative stress in the liver of HFD mice by increasing hepatic nicotinamide adenine dinucleotide (NAD+) (P < 0.01) levels. This effect increased the contact sites (mitochondria-associated membranes [MAMs]) between ER and mitochondria, thereby promoting intracellular ATP (P < 0.05) production and mitigating lipid metabolic disturbances in the liver of HFD mice. Taken together, this study provided a theoretical basis for restoring metabolic dynamic equilibrium in the liver of HFD mice by increasing MAMs via the nutritional strategy of NMN supplementation.

Understanding oocyte ageing

Females are born with a finite and non-renewable reservoir of oocytes, which therefore decline both in number and quality with advancing age. A striking characteristic of oocyte quality is that "ageing" effects manifest whilst women are in their thirties and are therefore still chronologically and physically young. Furthermore, this decline is unrelenting and not modifiable to any great extent by lifestyle or diet. Since oocyte quality is rate-limiting for pregnancy success, as the proportion of good-quality oocytes progressively deteriorate, the chance of successful pregnancy during each 6-12-month period also decreases, becoming exponential after 37 years. Unlike oocyte quality, age-related attrition in the size of the ovarian reservoir is less impactful for natural fertility since only one mature oocyte is typically ovulated per menstrual cycle. In contrast, oocyte numbers are pivotal for in-vitro fertilization success, since larger numbers enable better-quality oocytes to be found and is important for buffering the inefficiencies of the IVF process. The ageing trajectory is accelerated in ~10% of women, so-called premature ovarian ageing, with ~1% of women at the extreme end of this spectrum with loss of ovarian function occurring before 40 years of age, termed premature ovarian insufficiency. The aim of this review was to analyze how ageing impacts the size and quality of the oocyte pool along with emerging interventions for combating low oocyte numbers and improving quality.

The significance of precisely regulating heme oxygenase-1 expression: Another avenue for treating age-related ocular disease?

Aging entails the deterioration of the body's organs, including overall damages at both the genetic and cellular levels. The prevalence of age-related ocular disease such as macular degeneration, dry eye diseases, glaucoma and cataracts is increasing as the world's population ages, imposing a considerable economic burden on individuals and society. The development of age-related ocular disease is predominantly triggered by oxidative stress and chronic inflammatory reaction. Heme oxygenase-1 (HO-1) is a crucial antioxidant that mediates the degradative process of endogenous iron protoporphyrin heme. It catalyzes the rate-limiting step of the heme degradation reaction, and releases the metabolites such as carbon monoxide (CO), ferrous, and biliverdin (BV). The potent scavenging activity of these metabolites can help to defend against peroxides, peroxynitrite, hydroxyl, and superoxide radicals. Other than directly decomposing endogenous oxidizing substances (hemoglobin), HO-1 is also a critical regulator of inflammatory cells and tissue damage, exerting its anti-inflammation activity through regulating complex inflammatory networks. Therefore, promoting HO-1 expression may act as a promising therapeutic strategy for the age-related ocular disease. However, emerging evidences suggest that the overexpression of HO-1 significantly contributes to ferroptosis due to its dual nature. Surplus HO-1 leads to excessive Fe2+ and reactive oxygen species, thereby causing lipid peroxidation and ferroptosis. In this review, we elucidate the role of HO-1 in countering age-related disease, and summarize recent pharmacological trials that targeting HO-1 for disease management. Further refinements of the knowledge would position HO-1 as a novel therapeutic target for age-related ocular disease.

A Multifunctional Therapeutic Strategy Using P7C3 as A Countermeasure Against Bone Loss and Fragility in An Ovariectomized Rat Model of Postmenopausal Osteoporosis

By 2060, an estimated one in four Americans will be elderly. Consequently, the prevalence of osteoporosis and fragility fractures will also increase. Presently, no available intervention definitively prevents or manages osteoporosis. This study explores whether Pool 7 Compound 3 (P7C3) reduces progressive bone loss and fragility following the onset of ovariectomy (OVX)-induced osteoporosis. Results confirm OVX-induced weakened, osteoporotic bone together with a significant gain in adipogenic body weight. Treatment with P7C3 significantly reduced osteoclastic activity, bone marrow adiposity, whole-body weight gain, and preserved bone area, architecture, and mechanical strength. Analyses reveal significantly upregulated platelet derived growth factor-BB and leukemia inhibitory factor, with downregulation of interleukin-1 R6, and receptor activator of nuclear factor kappa-B (RANK). Together, proteomic data suggest the targeting of several key regulators of inflammation, bone, and adipose turnover, via transforming growth factor-beta/SMAD, and Wingless-related integration site/be-catenin signaling pathways. To the best of the knowledge, this is first evidence of an intervention that drives against bone loss via RANK. Metatranscriptomic analyses of the gut microbiota show P7C3 increased Porphyromonadaceae bacterium, Candidatus Melainabacteria, and Ruminococcaceae bacterium abundance, potentially contributing to the favorable inflammatory, and adipo-osteogenic metabolic regulation observed. The results reveal an undiscovered, and multifunctional therapeutic strategy to prevent the pathological progression of OVX-induced bone loss.

Increased expression of CD38 on endothelial cells in SARS-CoV-2 infection in cynomolgus macaques

SARS-CoV-2 infection causes activation of endothelial cells (ECs), leading to dysmorphology and dysfunction. To study the pathogenesis of endotheliopathy, the activation of ECs in lungs of cynomolgus macaques after SARS-CoV-2 infection and changes in nicotinamide adenine dinucleotide (NAD) metabolism in ECs were investigated, with a focus on the CD38 molecule, which degrades NAD in inflammatory responses after SARS-CoV-2 infection. Activation of ECs was seen from day 3 after SARS-CoV-2 infection in macaques, with increases of intravascular fibrin and NAD metabolism-associated enzymes including CD38. In vitro, upregulation of CD38 mRNA in human ECs was detected after interleukin 6 (IL-6) trans-signaling induction, which was increased in the infection. In the presence of IL-6 trans-signaling stimulation, however, CD38 mRNA silencing induced significant IL-6 mRNA upregulation in ECs and promoted EC apoptosis after stimulation. These results suggest that upregulation of CD38 in patients with COVID-19 has a protective role against IL-6 trans-signaling stimulation induced by SARS-CoV-2 infection.

Ovarian aging: energy metabolism of oocytes

In women who are getting older, the quantity and quality of their follicles or oocytes and decline. This is characterized by decreased ovarian reserve function (DOR), fewer remaining oocytes, and lower quality oocytes. As more women choose to delay childbirth, the decline in fertility associated with age has become a significant concern for modern women. The decline in oocyte quality is a key indicator of ovarian aging. Many studies suggest that age-related changes in oocyte energy metabolism may impact oocyte quality. Changes in oocyte energy metabolism affect adenosine 5'-triphosphate (ATP) production, but how related products and proteins influence oocyte quality remains largely unknown. This review focuses on oocyte metabolism in age-related ovarian aging and its potential impact on oocyte quality, as well as therapeutic strategies that may partially influence oocyte metabolism. This research aims to enhance our understanding of age-related changes in oocyte energy metabolism, and the identification of biomarkers and treatment methods.

A randomized, controlled clinical trial demonstrates improved owner-assessed cognitive function in senior dogs receiving a senolytic and NAD+ precursor combination

Age-related decline in mobility and cognition are associated with cellular senescence and NAD + depletion in dogs and people. A combination of a novel NAD + precursor and senolytic, LY-D6/2, was examined in this randomized controlled trial. Seventy dogs with mild to moderate cognitive impairment were enrolled and allocated into placebo, low or full dose groups. Primary outcomes were change in cognitive impairment measured with the owner-reported Canine Cognitive Dysfunction Rating (CCDR) scale and change in activity measured with physical activity monitors. Fifty-nine dogs completed evaluations at the 3-month primary endpoint, and 51 reached the 6-month secondary endpoint. There was a significant difference in CCDR score across treatment groups from baseline to the primary endpoint (p = 0.02) with the largest decrease in the full dose group. No difference was detected between groups using in house cognitive testing. There were no significant differences between groups in changes in measured activity. The proportion of dogs that improved in frailty and owner-reported activity levels and happiness was higher in the full dose group than other groups, however this difference was not significant. Adverse events occurred equally across groups. All groups showed improvement in cognition, frailty, and activity suggesting placebo effect and benefits of trial participation. We conclude that LY-D6/2 improves owner-assessed cognitive function over a 3-month period and may have broader, but more subtle effects on frailty, activity and happiness as reported by owners.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

Molecular mechanisms of aging and anti-aging strategies

Aging is a complex and multifaceted process involving a variety of interrelated molecular mechanisms and cellular systems. Phenotypically, the biological aging process is accompanied by a gradual loss of cellular function and the systemic deterioration of multiple tissues, resulting in susceptibility to aging-related diseases. Emerging evidence suggests that aging is closely associated with telomere attrition, DNA damage, mitochondrial dysfunction, loss of nicotinamide adenine dinucleotide levels, impaired macro-autophagy, stem cell exhaustion, inflammation, loss of protein balance, deregulated nutrient sensing, altered intercellular communication, and dysbiosis. These age-related changes may be alleviated by intervention strategies, such as calorie restriction, improved sleep quality, enhanced physical activity, and targeted longevity genes. In this review, we summarise the key historical progress in the exploration of important causes of aging and anti-aging strategies in recent decades, which provides a basis for further understanding of the reversibility of aging phenotypes, the application prospect of synthetic biotechnology in anti-aging therapy is also prospected.

Nicotinamide Mononucleotide Supplementation Alleviates Doxorubicin-Induced Multi-Organ Fibrosis

Doxorubicin (DOX) is a potent chemotherapeutic agent known for its multi-organ toxicity, especially in the heart, which limits its clinical application. The toxic side effects of DOX, including DNA damage, oxidative stress, mitochondrial dysfunction and cell apoptosis, are intricately linked to the involvement of nicotinamide adenine dinucleotide (NAD+). To assess the effectiveness of the NAD+ precursor nicotinamide mononucleotide (NMN) in counteracting the multi-organ toxicity of DOX, a mouse model was established through DOX administration, which led to significant reductions in NAD+ in tissues with evident injury, including the heart, liver and lungs. NMN treatment alleviated both multi-organ fibrosis and mortality in mice. Mechanistically, tissue fibrosis, macrophage infiltration and DOX-related cellular damage, which are potentially implicated in the development of multi-organ fibrosis, could be attenuated by NAD+ restoration. Our findings provide compelling evidence for the benefits of NMN supplementation in mitigating the adverse effects of chemotherapeutic drugs on multiple organs.

Toxicology study profile of Nicotinamide mononucleotide after acute and 90-day sub chronic dosing in Wistar rats and mutagenicity tests

Nicotinamide mononucleotide (NMN) is an intermediate in biosynthesis pathway of Nicotinamide adenine dinucleotide (NAD+), an essential cofactor in all living cells involved in fundamental biological processes. Evidence stemming from recent studies have unveiled numerous roles of NAD+ metabolism on aging, longevity, delaying the progression of age-related diseases. A three-study genetic toxicity (genetox) battery (bacterial mutagenesis, in vitro cytogenetics, and in vivo mammalian test) is usually required to confirm safety of a new dietary ingredient and this study showed the data from in vivo mutagenicity test for the first time. The acute oral LD50 of NMN was greater than 2000 mg/kg body weight with 5000 mg/kg body weight as LD50 cut-off value and was classified under "Category 5 or Unclassified" as per Globally Harmonized System of Classification and Labelling of Chemicals (GHS). Based on 90 days repeated dose toxicity test the NOAEL was considered to be NLT 800 mg NMN/kg body weight in Wistar rats. The bacterial reverse mutation test, the in vitro and in vivo chromosomal aberration test, found NMN to be non-mutagenic. In the mammalian bone marrow chromosomal aberration test, it was concluded that NMN is non clastogenic at and up to 2,000 mg/kg body weight in all the animals tested to confirm safety of a new dietary ingredient and this study showed the data from in vivo mutagenicity test for the first time.

Exploring the role of parthanatos in CNS injury: Molecular insights and therapeutic approaches

BACKGROUND

Central nervous system (CNS) injury causes severe organ damage due to both damage resulting from the injury and subsequent cell death. However, there are currently no effective treatments for countering the irreversible loss of cell function. Parthanatos is a poly (ADP-ribose) polymerase 1 (PARP-1)-dependent form of programmed cell death that is partly responsible for neural cell death. Consequently, the mechanism by which parthanatos promotes CNS injury has attracted significant scientific interest.

AIM OF REVIEW

Our review aims to summarize the potential role of parthanatos in CNS injury and its molecular and pathophysiological mechanisms. Understanding the role of parthanatos and related molecules in CNS injury is crucial for developing effective treatment strategies and identifying important directions for future in-depth research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Parthanatos (from Thanatos, the personification of death according to Greek mythology) is a type of programmed cell death that is initiated by the overactivation of PARP-1. This process triggers a cascade of reactions, including the accumulation of poly(ADP-ribose) (PAR), the nuclear translocation of apoptosis-inducing factor (AIF) after its release from mitochondria, and subsequent massive DNA fragmentation caused by migration inhibitory factor (MIF) forming a complex with AIF. Secondary molecular mechanisms, such as excitotoxicity and oxidative stress-induced overactivation of PARP-1, significantly exacerbate neuronal damage following initial mechanical injury to the CNS. Furthermore, parthanatos is not only associated with neuronal damage but also interacts with various other types of cell death. This review focuses on the latest research concerning the parthanatos cell death pathway, particularly considering its regulatory mechanisms and functions in CNS damage. We highlight the associations between parthanatos and different cell types involved in CNS damage and discuss potential therapeutic agents targeting the parthanatos pathway.

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.

Nicotinamide Mononucleotide and Nicotinamide Riboside Reverse Ovarian Aging in Rats Via Rebalancing Mitochondrial Fission and Fusion Mechanisms

PURPOSE

This study examined the effects of nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) on folliculogenesis and mitochondrial dynamics (fission and fusion mechanisms) in ovaries of middle-aged female rats.

METHODS

Experimental groups were young, middle-aged (control), middle-aged + NMN and middle-aged + NR. NMN was administered at a concentration of 500 mg/kg intraperitoneally but NR at a concentration of 200 mg/kg by gavage. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels were analyzed by ELISA. Hematoxylin-eosin staining sections were used for histopathological examination and follicles-counting. Expression levels of mitochondrial fission (Drp1, Mff and Fis1) and fusion (Mfn1, Mfn2, Opa1, Fam73a and Fam73b) genes as well as Sirt1 gene were analyzed by RT-PCR. Expression levels of fission-related proteins (DRP1, MFF, FIS1 and SIRT1) were analyzed by Western Blot.

RESULTS

Higher ovarian index, more corpus luteum and antral follicles were detected in NMN and NR groups compared to the control. NMN or NR could rebalance LH/FSH ratio. The control group was determined to possess higher expression levels of fission genes and lower expression levels of fusion genes when compared the young group. In comparison with the control group, both NMN and NR group were found to exhibit less mitochondrial fission but more mitochondrial fussion. Higher gene and protein levels for Sirt1 were measured in NMN and NR groups compared to the control group.

CONCLUSION

This study reveals that NMN alone or NR alone can rebalance mitochondrial dynamics by decreasing excessive fission in middle-aged rat ovaries, thus alleviating mitochondrial stress and correcting aging-induced folliculogenesis abnormalities.

Channeling Nicotinamide Phosphoribosyltransferase (NAMPT) to Address Life and Death

Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in NAD+ biosynthesis via salvage of NAM formed from catabolism of NAD+ by proteins with NADase activity (e.g., PARPs, SIRTs, CD38). Depletion of NAD+ in aging, neurodegeneration, and metabolic disorders is addressed by NAD+ supplementation. Conversely, NAMPT inhibitors have been developed for cancer therapy: many discovered by phenotypic screening for cancer cell death have low nanomolar potency in cellular models. No NAMPT inhibitor is yet FDA-approved. The ability of inhibitors to act as NAMPT substrates may be associated with efficacy and toxicity. Some 3-pyridyl inhibitors become 4-pyridyl activators or "NAD+ boosters". NAMPT positive allosteric modulators (N-PAMs) and boosters may increase enzyme activity by relieving substrate/product inhibition. Binding to a "rear channel" extending from the NAMPT active site is key for inhibitors, boosters, and N-PAMs. A deeper understanding may fulfill the potential of NAMPT ligands to regulate cellular life and death.

A Molecular Perspective and Role of NAD+ in Ovarian Aging

The decline in female fecundity is linked to advancing chronological age. The ovarian reserve diminishes in quantity and quality as women age, impacting reproductive efficiency and the aging process in the rest of the body. NAD+ is an essential coenzyme in cellular energy production, metabolism, cell signaling, and survival. It is involved in aging and is linked to various age-related conditions. Hallmarks associated with aging, diseases, and metabolic dysfunctions can significantly affect fertility by disturbing the delicate relationship between energy metabolism and female reproduction. Enzymes such as sirtuins, PARPs, and CD38 play essential roles in NAD+ biology, which actively consume NAD+ in their enzymatic activities. In recent years, NAD+ has gained much attention for its role in aging and age-related diseases like cancer, Alzheimer's, cardiovascular diseases, and neurodegenerative disorders, highlighting its involvement in various pathophysiological processes. However, its impact on female reproduction is not well understood. This review aims to bridge this knowledge gap by comprehensively exploring the complex interplay between NAD+ biology and female reproductive aging and providing valuable information that could help develop plans to improve women's reproductive health and prevent fertility issues.

A molecular circuit linking the BCR to the NAD biosynthetic enzyme NAMPT is an actionable target in Richter syndrome

ABSTRACT

This works defines, to the best of our knowledge, for the first time a molecular circuit connecting nicotinamide mononucleoside phosphoribosyl transferase (NAMPT) activity to the B-cell receptor (BCR) pathway. Using 4 distinct xenograft models derived from patients with Richter syndrome (RS-PDX), we show that BCR cross-linking results in transcriptional activation of the nicotinamide adenine dinucleotide (NAD) biosynthetic enzyme NAMPT, with increased protein expression, in turn, positively affecting global cellular NAD levels and sirtuins activity. NAMPT blockade, by using the novel OT-82 inhibitor in combination with either BTK or PI3K inhibitors (BTKi or PI3Ki), induces rapid and potent apoptotic responses in all 4 models, independently of their mutational profile and the expression of the other NAD biosynthetic enzymes, including nicotinate phosphoribosyltransferase. The connecting link in the circuit is represented by AKT that is both tyrosine- and serine-phosphorylated by PI3K and deacetylated by sirtuin 1 and 2 to obtain full kinase activation. Acetylation (ie, inhibition) of AKT after OT-82 administration was shown by 2-dimensional gel electrophoresis and immunoprecipitation. Consistently, pharmacological inhibition or silencing of sirtuin 1 and 2 impairs AKT activation and induces apoptosis of RS cells in combination with PI3Ki or BTKi. Lastly, treatment of RS-PDX mice with the combination of PI3Ki and OT-82 results in significant inhibition of tumor growth, with evidence of in vivo activation of apoptosis. Collectively, these data highlight a novel application for NAMPT inhibitors in combination with BTKi or PI3Ki in aggressive lymphomas.

Evaluation of safety and effectiveness of NAD in different clinical conditions: a systematic review

Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide cofactor that is present in cells and in several important biological processes, including oxidative phosphorylation and production of adenosine triphosphate, DNA repair, calcium-dependent secondary messenger and gene expression. The purpose of this systematic review is to examine whether the coenzyme formulae NAD+ and NADH are safe and effective when acting as a supplement to humans. This systematic review of randomized clinical trials performed a search in six electronic databases: PubMed, MEDLINE (ovid), Embase, Cochrane CENTRAL (clinical trials), Web of Science, and Scopus. Secondary search included the databases (e.g., Clinical trials.gov, Rebec, Google Scholar - advance). Two reviewers assessed and extracted the studies independently. The risk of bias in studies was performed using version 2 of the Cochrane risk of bias tool for randomized trials. This review includes 10 studies, with a total of 489 participants. The studies included different clinical conditions, such as chronic fatigue syndrome (CFS), older adults, Parkinson's disease, overweight, postmenopausal prediabetes, and Alzheimer's disease. Based on studies, the supplementation with NADH and precursors was well tolerated and observed clinical results such as, a decrease in anxiety conditions and maximum heart rate was observed after a stress test, increased muscle insulin sensitivity, insulin signaling. Quality of life, fatigue intensity, and sleep quality among others were evaluated on patients with CFS. All studies showed some side effects, thus, the most common associated with NADs use are muscle pain, nervous disorders, fatigue, sleep disturbance, and headaches. All adverse events cataloged by the studies did not present a serious risk to the health of the participants. Overall, these findings support that the oral administration of NADH can be associated to an increase in general quality of life and improvement on health parameters (e.g., a decrease in anxiety, maximum heart rate, inflammatory cytokines in serum, and cerebrospinal fluid). NADH supplementation is safe and has a low incidence of side effects. Future investigations are needed to evidence the clinical benefits regarding specific diseases and doses administered.

Integrated annotation prioritizes metabolites with bioactivity in inflammatory bowel disease

Microbial biochemistry is central to the pathophysiology of inflammatory bowel diseases (IBD). Improved knowledge of microbial metabolites and their immunomodulatory roles is thus necessary for diagnosis and management. Here, we systematically analyzed the chemical, ecological, and epidemiological properties of ~82k metabolic features in 546 Integrative Human Microbiome Project (iHMP/HMP2) metabolomes, using a newly developed methodology for bioactive compound prioritization from microbial communities. This suggested >1000 metabolic features as potentially bioactive in IBD and associated ~43% of prevalent, unannotated features with at least one well-characterized metabolite, thereby providing initial information for further characterization of a significant portion of the fecal metabolome. Prioritized features included known IBD-linked chemical families such as bile acids and short-chain fatty acids, and less-explored bilirubin, polyamine, and vitamin derivatives, and other microbial products. One of these, nicotinamide riboside, reduced colitis scores in DSS-treated mice. The method, MACARRoN, is generalizable with the potential to improve microbial community characterization and provide therapeutic candidates.

Nicotinamide Riboside, an NAD + Precursor, Protects Against Cardiac Mitochondrial Dysfunction in Fetal Guinea Pigs Exposed to Gestational Hypoxia

Gestational hypoxia inhibits mitochondrial function in the fetal heart and placenta contributing to fetal growth restriction and organ dysfunction. NAD + deficiency may contribute to a metabolic deficit by inhibiting oxidative phosphorylation and ATP synthesis. We tested the effects of nicotinamide riboside (NR), an NAD + precursor, as a treatment for reversing known mitochondrial dysfunction in hypoxic fetal hearts. Pregnant guinea pigs were housed in room air (normoxia) or placed in a hypoxic chamber (10.5%O2) for the last 14 days of gestation (term = 65 days) and administered either water or NR (1.6 mg/ml) in the drinking bottle. Fetuses were excised at term, and NAD + levels of maternal liver, placenta, and fetal heart ventricles were measured. Indices of mitochondrial function (complex IV activity, sirtuin 3 activity, protein acetylation) and ATP synthesis were measured in fetal heart ventricles of NR-treated/untreated normoxic and hypoxic animals. Hypoxia reduced fetal body weight in both sexes (p = 0.01), which was prevented by NR. Hypoxia had no effect on maternal liver NAD + levels but decreased (p = 0.04) placenta NAD + levels, the latter normalized with NR treatment. Hypoxia had no effect on fetal heart NAD + but decreased (p < 0.05) mitochondrial complex IV and sirtuin 3 activities, ATP content, and increased mitochondrial acetylation, which were all normalized with maternal NR. Hypoxia increased (p < 0.05) mitochondrial acetylation in female fetal hearts but had no effect on other mitochondrial indices. We conclude that maternal NR is an effective treatment for normalizing mitochondrial dysfunction and ATP synthesis in the hypoxic fetal heart.

Chlorella-Loaded Antibacterial Microneedles for Microacupuncture Oxygen Therapy of Diabetic Bacterial Infected Wounds

Hypoxia and infection are urgent clinical problems in chronic diabetic wounds. Herein, living Chlorella-loaded poly(ionic liquid)-based microneedles (PILMN-Chl) are constructed for microacupuncture oxygen and antibacterial therapy against methicillin-resistant Staphylococcus aureus (MRSA)-infected chronic diabetic wounds. The PILMN-Chl can stably and continuously produce oxygen for more than 30 h due to the photosynthesis of the loaded self-supported Chlorella. By combining the barrier penetration capabilities of microneedles, the continuous and sufficient oxygen supply of Chlorella, and the sterilization activities of PIL, the PILMN-Chl can accelerate chronic diabetic wounds in vivo by topical targeted sterilization and hypoxia relief in deep parts of wounds. Thus, the self-oxygen produced microneedles modality may provide a promising and facile therapeutic strategy for treating chronic, hypoxic, and infected diabetic wounds.

Urinary phenotyping of SARS-CoV-2 infection connects clinical diagnostics with metabolomics and uncovers impaired NAD+ pathway and SIRT1 activation

OBJECTIVES

The stratification of individuals suffering from acute and post-acute SARS-CoV-2 infection remains a critical challenge. Notably, biomarkers able to specifically monitor viral progression, providing details about patient clinical status, are still not available. Herein, quantitative metabolomics is progressively recognized as a useful tool to describe the consequences of virus-host interactions considering also clinical metadata.

METHODS

The present study characterized the urinary metabolic profile of 243 infected individuals by quantitative nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography mass spectrometry (LC-MS). Results were compared with a historical cohort of noninfected subjects. Moreover, we assessed the concentration of recently identified antiviral nucleosides and their association with other metabolites and clinical data.

RESULTS

Urinary metabolomics can stratify patients into classes of disease severity, with a discrimination ability comparable to that of clinical biomarkers. Kynurenines showed the highest fold change in clinically-deteriorated patients and higher-risk subjects. Unique metabolite clusters were also generated based on age, sex, and body mass index (BMI). Changes in the concentration of antiviral nucleosides were associated with either other metabolites or clinical variables. Increased kynurenines and reduced trigonelline excretion indicated a disrupted nicotinamide adenine nucleotide (NAD+) and sirtuin 1 (SIRT1) pathway.

CONCLUSIONS

Our results confirm the potential of urinary metabolomics for noninvasive diagnostic/prognostic screening and show that the antiviral nucleosides could represent novel biomarkers linking viral load, immune response, and metabolism. Moreover, we established for the first time a casual link between kynurenine accumulation and deranged NAD+/SIRT1, offering a novel mechanism through which SARS-CoV-2 manipulates host physiology.