Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Nicotinamide riboside alleviates ionizing radiation-induced intestinal senescence by alleviating oxidative damage and regulating intestinal metabolism

INTRODUCTION

The intestine, frequently subjected to pelvic or abdominal radiotherapy, is particularly vulnerable to delayed effects of acute radiation exposure (DEARE) owing to its high radiation sensitivity. Radiation-induced intestinal senescence, a result of DEARE, profoundly affects the well-being and quality of life of radiotherapy patients. However, targeted pharmaceutical interventions for radiation-induced senescence are currently scarce. Our findings showcase that nicotinamide riboside(NR) effectively alleviates radiation-induced intestinal senescence, offering crucial implications for utilizing NR as a pharmacological agent to combat intestinal DEARE.

OBJECTIVES

The aim of this study was to investigate the ability of NR to reduce radiation induced intestinal senescence and explore its related mechanisms.

METHODS

Male C57BL/6J mice were randomly divided into CON, IR, and IR + NR groups. The mice in the IR and IR + NR groups were subjected to a 6.0 Gy γ-ray total body exposure. After 8 weeks, the mice in the IR + NR group received NR via gavage at a dose of 400 mg/kg/d for 21 days. Then the mice were used for sample collection.

RESULTS

Our results demonstrate that NR can significantly mitigate radiation-induced intestinal senescence. Furthermore, our findings indicate that NR can mitigate oxidative damage, restore the normal function of intestinal stem cells, regulate the disruption of the intestinal symbiotic ecosystem and address metabolic abnormalities. In addition, the underlying mechanisms involve the activation of SIRT6, SIRT7 and the inhibition of the mTORC1 pathway by NR.

CONCLUSION

In conclusion, our results reveal the substantial inhibitory effects of NR on radiation-induced intestinal senescence. These findings offer valuable insights into the potential therapeutic use of NR as a pharmacological agent for alleviating intestinal DEARE.

Metabolomics in cardiometabolic diseases: Key biomarkers and therapeutic implications for insulin resistance and diabetes

Cardiometabolic diseases-including Type 2 diabetes and obesity-remain leading causes of global mortality. Recent advancements in metabolomics have facilitated the identification of metabolites that are integral to the development of insulin resistance, a characteristic feature of cardiometabolic disease. Key metabolites, such as branched-chain amino acids (BCAAs), ceramides, glycine, and glutamine, have emerged as valuable biomarkers for early diagnosis, risk stratification, and potential therapeutic targets. Elevated BCAAs and ceramides are strongly associated with insulin resistance and Type 2 diabetes, whereas glycine exhibits an inverse relationship with insulin resistance, making it a promising therapeutic target. Metabolites involved in energy stress, including ketone bodies, lactate, and nicotinamide adenine dinucleotide (NAD⁺), regulate insulin sensitivity and metabolic health, with ketogenic diets and NAD⁺ precursor supplementation showing potential benefits. Additionally, the novel biomarker N-lactoyl-phenylalanine further underscores the complexity of metabolic regulation and its therapeutic potential. This review underscores the potential of metabolite-based diagnostics and precision medicine, which could enhance efforts in the prevention, diagnosis, and treatment of cardiometabolic diseases, ultimately improving patient outcomes and quality of life.

Nonessential amino acid is not nonessential in geriatric patients: implications for maxillofacial wound healing and bone repair

BACKGROUND

Nonessential amino acids (NEAAs) are traditionally regarded as dispensable because they can be synthesized endogenously from glucose-derived intermediates. Emerging evidence, however, shows that the capacity for de novo NEAA biosynthesis declines in aged tissues, rendering several of these molecules conditionally essential during periods of stress such as surgery or fracture repair.

MAIN BODY

In the cranio-maxillofacial arena - where bone and soft-tissue regeneration must occur in an environment already compromised by osteoporosis, multimorbidity, and restricted oral intake - insufficient NEAA supply may translate into delayed union, wound dehiscence, and heightened infection risk. This narrative review integrates biochemical, preclinical, and clinical data to map age-dependent changes in the serine/glycine, glutamine/glutamate, arginine/citrulline, cysteine/trans-sulfuration, and alanine cycles, examines their impact on osteogenesis and mucosal healing, and evaluates nutritional or pharmacological strategies to restore NEAA sufficiency. Particular attention is paid to serine-one-carbon metabolism, the intestinal-renal arginine axis, and redox-sensitive cysteine pathways, all of which are intimately linked to collagen deposition, osteoblast differentiation, and immune modulation.

CONCLUSION

We conclude that proactive optimization of NEAA status - through targeted supplementation or metabolic activation - represents a low-risk, biologically rational adjunct to enhance postoperative outcomes in geriatric maxillofacial patients.

Unraveling immunosenescence in sepsis: from cellular mechanisms to therapeutics

Sepsis is a life-threatening multiple organ dysfunction resulting from a dysregulated host response to infection, and patients with sepsis always exhibit a state of immune disorder characterized by both overwhelming inflammation and immunosuppression. The aging of immune system, namely "immunosenescence", has been reported to be correlated with high morbidity and mortality in elderly patients with sepsis. Initially, immunosenescence was considered as a range of age-related alterations in the immune system. However, increasing evidence has proven that persistent inflammation or even a short-term inflammatory challenge during sepsis could trigger accelerated aging of immune cells, which might further exacerbate inflammatory cytokine storm and promote the shift towards immunosuppression. Thus, premature immunosenescence is found in young sepsis individuals, which further aggravates immune disorders and induces the progression of sepsis. Furthermore, in old sepsis patients, the synergistic effects of both sepsis and aging may cause immunosenescence-associated alterations more significantly, resulting in more severe immune dysfunction and a worse prognosis. Therefore, it is necessary to explore the potential therapeutic strategies targeting immunosenescence during sepsis.

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

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

The Causal Association Analysis between Depression and Cerebrospinal Fluid: From the Perspective of Mendelian Randomization

Background

Major depressive disorder (MDD) leads to significant distress and disruption across social, occupational, and other functional domains. Although cerebrospinal fluid (CSF) biomarkers have been identified as potential indicators and therapeutic targets for depression, their causal relationship with MDD remains unclear.

Methods

We analyzed publicly available CSF metabolomics and genotype data, quantifying 338 distinct metabolites. Among these, 296 were chemically validated and classified into eight major metabolic groups, while 38 remained undefined. To assess the genetic association with depression, we used summary statistics from a GWAS (F5_DEPRESSIO dataset, including 53,313 diagnosed cases and 394,756 controls from Finland). An integrated approach combining Mendelian randomization (MR), inverse variance weighting (IVW), and linkage disequilibrium score regression (LDSC) was applied to explore the causal impact of CSF metabolites on depression risk.

Results

Our analysis identified 62 metabolites significantly associated with depression (p < 0.05). Sensitivity tests revealed heterogeneity in five metabolites: 5-hydroxyindoleacetic acid, X-19438, ethylmalonic acid, γ-glutamylglutamine, and β-alanine. A focused analysis on 14 metabolites further supported a potential causal link with depression. LDSC confirmed significant genetic heritability for metabolites such as creatinine, arginine succinate, N-acetylisourea, 3-amino-2-piperidone, and carboxyethyl-GABA. Systematic leave-one-out analyses demonstrated that these associations are driven by multiple interacting SNPs rather than a single variant.

Conclusion

This study provides novel insights into the potential causal relationship between CSF metabolites and depression, highlighting 14 key metabolites with significant associations. The robustness of these findings is supported by MR and sensitivity analyses. Further longitudinal studies are warranted to confirm the clinical relevance of these CSF biomarkers in MDD.

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

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

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

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

A new clinical age of aging research

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

NAD+ boosting increases atherosclerotic plaques and inflammation in Apoe knockout mice

BACKGROUND AND AIMS

NAD+ (nicotinamide adenine dinucleotide) is a cosubstrate of the sirtuins (SIRT) that are activated upon caloric restriction. Supplementing NAD+ precursors such as nicotinamide riboside (NR) has been reported to extend life span and combat metabolic syndrome through pan-sirtuin activation in mice. Notably, sirtuins compete with poly (ADP-ribose) polymerase (PARP)1 and CD38 for NAD+. Supplementing NAD+ precursors did not improve cardiovascular outcome in the AIM-HIGH trial. Recently, the terminal NAD+ metabolite 4PY (N1-methyl-4-pyridone-3-carboxamide) was reported to increase inflammation and to be associated with cardiovascular risk. We aimed to investigate whether NR provides atheroprotection.

METHODS

8-week-old male apolipoprotein E (Apoe) knockout mice were fed for 12 weeks a high-cholesterol diet supplemented with three NR doses: NR-, NR+, and NR++. RAW264.7 mouse macrophages and bone marrow macrophages were stimulated with oxLDL and NR.

RESULTS

NR++ enhanced plaque lesions in aortic sinus sections and increased plasma levels of TNFα, IL-6, and LDL-cholesterol. Liver and plasma NAD+ concentrations remained unchanged, but the downstream metabolite 4PY increased. In liver lysates, SIRT1 and lipoprotein receptors were decreased and CD38 increased in NR++; cleaved PARP1 and total PARylation decreased upon NR supplementation. In oxLDL-treated macrophages, high NR levels increased CD38 and CD86 expression.

CONCLUSIONS

High-dose NR supplementation in mice did not decrease but increase both aortic plaque lesions and systemic inflammation. These effects may be mediated by increased CD38 expression in macrophages, with NAD+ metabolism shifted from sirtuins towards CD38 and PARP1 pathways. Caution should be applied with presumed NAD+ boosters in patients with atherosclerosis.

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

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

Nampt: a new therapeutic target for modulating NAD+ levels in metabolic, cardiovascular, and neurodegenerative diseases

NAD+ is an important cofactor involved in regulating many biochemical processes in cells. An imbalance in NAD+/NADH ratio is linked to many diseases. NAD+ is depleted in diabetes, cardiovascular and neurodegenerative diseases, and in aging, and is increased in tumor cells. NAD+ is generated in cells via the de novo, Preiss-Handler, and salvage pathways. Most of the cellular NAD+ is generated through Nampt activation, a key rate-limiting enzyme that is involved in the salvage pathway. Restoration of NAD+/NADH balance offers therapeutic advantages for improving tissue homeostasis and function. NAD+ is known to benefit and restore the body's physiological mechanisms, including DNA replication, chromatin and epigenetic modifications, and gene expression. Recent studies elucidate the role of NAD+ in cells utilizing transgenic mouse models. Translational new therapeutics are positioned to utilize the NAD+ restoration strategies for overcoming the drawbacks that exist in the pharmacological toolkit. The present review highlights the significance of Nampt-NAD+ axis as a major player in energy metabolism and provides an overview with insights into future strategies, providing pharmacological advantages to address current and future medical needs.

The protection of nicotinamide riboside against diabetes mellitus-induced bone loss via OXPHOS

Diabetes mellitus is a global disease that results in various complications, including diabetic osteoporosis. Prior studies have indicated a correlation between low levels of nicotinamide adenine dinucleotide (NAD+) and diabetes-related complications. Nicotinamide riboside (NR), a widely utilized precursor vitamin of NAD+, has been demonstrated to enhance age-related osteoporosis through the Sirt1/FOXO/β-catenin pathway in osteoblast progenitors. However, the impact of NR on bone health in diabetes mellitus remains unclear. In this study, we assessed the potential effects of NR on bone in diabetic mice. NR was administered to high-fat diet (HFD)/streptozotocin (STZ)-induced type 2 diabetic mice (T2DM), and various parameters, including metabolic indicators, bone quality, bone metabolic markers, and RNA sequences, were measured. Our findings confirmed that HFD/STZ-induced T2DM impaired bone microstructures, resulting in bone loss. NR effectively ameliorated insulin resistance, improved bone microarchitecture, and bone quality, reduced bone resorption, enhanced the Forkhead box O (FOXO) signaling pathway, mitigated the nuclear factor kappa B (NF-kB) signaling pathway, and ameliorated the disorder of the oxidative phosphorylation process (OXPHOS) in diabetic mice. In conclusion, NR demonstrated the capacity to alleviate T2DM-induced bone loss through the modulation of OXPHOS in type 2 diabetic mice. Our results underscore the potential of NR as a therapeutic target for addressing T2DM-related bone metabolism and associated diseases. Further cell-based studies under diabetic conditions, such as in vitro cultures of key cell types (e.g., osteoblasts and osteoclasts), are necessary to validate these findings.

Dipalmitoylphosphatidylcholine Lipid Vesicles for Delivering HMB, NMN, and L-Leucine in Sarcopenia Therapy

Sarcopenia, characterized by the degeneration of skeletal muscle tissue, has emerged as a significant concern in recent years. This increased awareness stems from advances in research focusing on elderly patients, which have revealed correlations between aging mechanisms and muscle degeneration, beyond the mere fact that tissues age and deteriorate over time. Consequently, the present study aims to address sarcopenia by developing and evaluating DPPC lipid vesicles that encapsulate three distinct drugs: HMB, NMN, and L-Leucine. These drugs are specifically selected for their properties, which facilitate effective interaction with the affected muscle tissue, thereby promoting desired therapeutic effects. Preliminary physicochemical analyses indicate the successful formation of spherical lipid vesicles, characterized by nanometric dimensions and stable membrane integrity. The biological investigations aimed to highlight the potential of DPPC lipid vesicles encapsulating HMB, NMN, and L-Leucine to alleviate sarcopenia-induced cytotoxicity and oxidative stress. Through a comparative evaluation of the three drug formulations, we demonstrate that drug-loaded DPPC vesicles effectively mitigate oxidative damage, preserve mitochondrial function, and maintain cytoskeletal integrity in H2O2-induced C2C12 myotubes, with HMB-loaded vesicles showing the strongest protective effects against muscle degeneration. These findings underscore the therapeutic potential of DPPC-based controlled release systems for sarcopenia treatment and highlight the need for further investigations into their mechanistic role in muscle preservation.

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

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

Effect of acipimox on skeletal muscle biochemistry, structure and function in older people with probable sarcopenia: an experimental medicine study

BACKGROUND

Skeletal muscle nicotinamide adenine dinucleotide (NAD) concentrations are low in people with sarcopenia. Increasing NAD concentrations may offer a novel therapy. This study tested if acipimox (a NAD precursor) improves skeletal muscle NAD concentration and function in people with probable sarcopenia. Participants aged 65 and over with low walk speed (< 0.8 m/s) and low muscle strength (by 2019 European Working Group criteria) were recruited to this before and after, proof-of-concept study. Participants received acipimox 250 mg orally (twice or thrice daily according to creatinine clearance) + aspirin 75 mg daily (to prevent facial flushing) for 4 weeks. Muscle biopsy of the vastus lateralis, 31P magnetic resonance spectroscopy and a 7-digital mobility assessment were performed before starting acipimox and after 3 weeks of treatment. The primary outcome was change in skeletal muscle NAD concentration. Secondary outcomes included change in phosphocreatine recovery rate and measures of physical performance. Eleven participants (8 women), mean age 78.9 years (SD 4.3), were recruited. Mean walk speed at baseline was 0.69 m/s (SD 0.07). All completed baseline and follow-up visits. Median medication adherence was 95% (range 91-104%). There was no statistically significant difference in the primary outcome of change in NAD concentrations in skeletal muscle between baseline and follow-up [median difference: - 0.003 umol/g (IQR - 0.058 to 0.210); P = 0.26] or secondary outcomes. Nineteen none-serious adverse events were reported. Although the study protocol was feasible and well tolerated, acipimox did not improve skeletal muscle NAD concentration, biochemical markers or physical function in people with probable sarcopenia.

CLINICALTRIALS

gov Identifier: ISRCTN (ISRCTN87404878).

CD38 mediates nicotinamide mononucleotide base exchange to yield nicotinic acid mononucleotide

Nicotinamide mononucleotide (NMN) is a widely investigated metabolic precursor to the prominent enzyme cofactor NAD+, where it is assumed that delivery of this compound results in its direct incorporation into NAD+via the canonical salvage/recycling pathway. Surprisingly, treatment with this salvage pathway intermediate leads to increases in nicotinic acid mononucleotide (NaMN) and nicotinic acid adenine dinucleotide, two members of the Preiss-Handler/de novo pathways. In mammals, these pathways are not known to intersect prior to the production of NAD+. Here, we show that the cell surface enzyme CD38 can mediate a base-exchange reaction on NMN, whereby the nicotinamide ring is exchanged with a free nicotinic acid to yield the Preiss-Handler/de novo pathway intermediate NaMN, with in vivo small molecule inhibition of CD38 abolishing the NMN-induced increase in NaMN and nicotinic acid adenine dinucleotide. Together, these data demonstrate a new mechanism by which the salvage pathway and Preiss-Handler/de novo pathways can exchange intermediates in mammalian NAD+ biosynthesis.

A Pilot Trial of Nicotinamide Riboside and Coenzyme Q10 on Inflammation and Oxidative Stress in CKD

Key Points

Nicotinamide riboside and coenzyme Q10 supplementation showed distinct beneficial effects on whole-blood transcriptome, inflammatory cytokines, and oxidative stress. Nicotinamide riboside treatment altered the expression of genes associated with metabolism and immune response coinciding with a decrease in markers of oxidative stress. Coenzyme Q10 supplementation altered genes associated with lipid metabolism coinciding with reductions in markers of oxidative stress and inflammatory cytokines.

Background

Mitochondria-driven oxidative/redox stress and inflammation play a major role in CKD pathophysiology. Compounds targeting mitochondrial metabolism may improve mitochondrial function, inflammation, and redox stress; however, there is limited evidence of their efficacy in CKD.

Methods

We conducted a pilot, randomized, double-blind, placebo-controlled crossover trial comparing the effects of 1200 mg/d of coenzyme Q10 (CoQ10) or 1000 mg/d of nicotinamide riboside (NR) supplementation with placebo in 25 patients with moderate-to-severe CKD (eGFR <60 ml/min per 1.73 m2). We assessed changes in blood transcriptome using 3′-Tag-Seq gene expression profiling and changes in prespecified secondary outcomes of inflammatory and oxidative stress biomarkers. For a subsample of participants (n =14), we assessed lymphocyte and monocyte bioenergetics using an extracellular flux analyzer.

Results

The (mean±SD) age, eGFR, and body mass index of the participants were 61±11 years, 37±9 ml/min per 1.73 m2, and 28±5 kg/m2, respectively. Of the participants, 16% had diabetes and 40% were female. Compared with placebo, NR-mediated transcriptomic changes were enriched in gene ontology terms associated with carbohydrate/lipid metabolism and immune signaling, whereas CoQ10 changes were enriched in immune/stress response and lipid metabolism gene ontology terms. NR increased plasma IL-2 (estimated difference, 0.32; 95% confidence interval [CI], 0.14 to 0.49 pg/ml), and CoQ10 decreased both IL-13 (estimated difference, −0.12; 95% CI, −0.24 to −0.01 pg/ml) and C-reactive protein (estimated difference, −0.11; 95% CI, −0.22 to 0.00 mg/dl) compared with placebo. Both NR and CoQ10 reduced five-series F2-isoprostanes (estimated difference, −0.16 and −0.11 pg/ml, respectively; P < 0.05 for both). NR, but not CoQ10, increased the Bioenergetic Health Index (estimated difference, 0.29; 95% CI, 0.06 to 0.53) and spare respiratory capacity (estimated difference, 3.52; 95% CI, 0.04 to 7 pmol/min per 10,000 cells) in monocytes.

Conclusions

Six weeks of NR and CoQ10 improved markers of oxidative stress, inflammation, and cell bioenergetics in patients with moderate-to-severe CKD.

Clinical Trial registry name and registration number:

NCT03579693 .

Glibenclamide targets MDH2 to relieve aging phenotypes through metabolism-regulated epigenetic modification

Mitochondrial metabolism-regulated epigenetic modification is a driving force of aging and a promising target for therapeutic intervention. Mitochondrial malate dehydrogenase (MDH2), an enzyme in the TCA cycle, was identified as an anti-aging target through activity-based protein profiling in present study. The expression level of MDH2 was positively correlated with the cellular senescence in Mdh2 knockdown or overexpression fibroblasts. Glibenclamide (Gli), a classic anti-glycemic drug, was found to inhibit the activity of MDH2 and relieve fibroblast senescence in an MDH2-dependent manner. The anti-aging effects of Gli were also further validated in vivo, as it extended the lifespan and reduced the frailty index of naturally aged mice. Liver specific Mdh2 knockdown eliminated Gli's beneficial effects in naturally aged mice, reducing p16INK4a expression and hepatic fibrosis. Mechanistically, MDH2 inhibition or knockdown disrupted central carbon metabolism, then enhanced the methionine cycle flux, and subsequently promoted histone methylation. Notably, the tri-methylation of H3K27, identified as a crucial methylation site in reversing cellular senescence, was significantly elevated in hepatic tissues of naturally aged mice with Mdh2 knockdown. Taken together, these findings reveal that MDH2 inhibition or knockdown delays the aging process through metabolic-epigenetic regulation. Our research not only identified MDH2 as a potential therapeutic target and Gli as a lead compound for anti-aging drug development, but also shed light on the intricate interplay of metabolism and epigenetic modifications in aging.

Nicotinamide: A Multifaceted Molecule in Skin Health and Beyond

Nicotinamide (NAM), the amide form of vitamin B3, is a precursor to essential cofactors nicotinamide adenine dinucleotide (NAD⁺) and NADPH. NAD⁺ is integral to numerous cellular processes, including metabolism regulation, ATP production, mitochondrial respiration, reactive oxygen species (ROS) management, DNA repair, cellular senescence, and aging. NAM supplementation has demonstrated efficacy in restoring cellular energy, repairing DNA damage, and inhibiting inflammation by suppressing pro-inflammatory cytokines release. Due to its natural presence in a variety of foods and its excellent safety profile-even at high doses of up to 3 g/day-NAM is extensively used in the chemoprevention of non-melanoma skin cancers and the treatment of dermatological conditions such as blistering diseases, atopic dermatitis, rosacea, and acne vulgaris. Recently, its anti-aging properties have elevated NAM's prominence in skincare formulations. Beyond DNA repair and energy replenishment, NAM significantly impacts oxidative stress reduction, cell cycle regulation, and apoptosis modulation. Despite these multifaceted benefits, the comprehensive molecular mechanisms underlying NAM's actions remain not fully elucidated. This review consolidates recent research to shed light on these mechanisms, emphasizing the critical role of NAM in cellular health and its therapeutic potential. By enhancing our understanding, this work underscores the importance of continued exploration into NAM's applications, aiming to inform future clinical practices and skincare innovations.

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

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

Acute exercise boosts NAD+ metabolism of human peripheral blood mononuclear cells

Nicotinamide adenine dinucleotide (NAD+) coenzymes are the central electron carriers in biological energy metabolism. Low NAD+ levels are proposed as a hallmark of ageing and several diseases, which has given rise to therapeutic strategies that aim to tackle these conditions by boosting NAD+ levels. As a lifestyle factor with preventive and therapeutic effects, exercise increases NAD+ levels across various tissues, but so far human trials are mostly focused on skeletal muscle. Given that immune cells are mobilized and redistributed in response to acute exercise, we conducted two complementary trials to test the hypothesis that a single exercise session alters NAD+ metabolism of peripheral blood mononuclear cells (PBMCs). In a randomized crossover trial (DRKS00017686) with 24 young adults (12 female) we show that acute exercise increases gene expression and protein abundance of several key NAD+ metabolism enzymes with high conformity between high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT). In a longitudinal exercise trial (DRKS00029105) with 12 young adults (6 female) we confirm these results and reveal that - similar to skeletal muscle - NAD+ salvage is pivotal for PBMCs in response to exercise. Nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of NAD+ salvage pathway, displayed a pronounced increase in gene expression during exercise, which was accompanied by elevated intracellular NAD+ levels and reduced serum levels of the NAD+ precursor nicotinamide. These results demonstrate that acute exercise triggers NAD+ biosynthesis of human PBMCs with potential implications for immunometabolism, immune effector function, and immunological exercise adaptions.

Nicotinamide Mononucleotide Restores NAD+ Levels to Alleviate LPS-Induced Inflammation via the TLR4/NF-κB/MAPK Signaling Pathway in Mice Granulosa Cells

Inflammation disrupts the normal function of granulosa cells (GCs), which leads to ovarian dysfunction and fertility decline. Inflammatory conditions such as polycystic ovary syndrome (PCOS), primary ovarian insufficiency (POI), endometriosis, and age-related ovarian decline are often associated with chronic low-grade inflammation. Nicotinamide mononucleotide (NMN) is an important precursor of NAD+ and has gained attention for its potential to modulate cellular metabolism, redox homeostasis, and mitigate inflammation. This study investigated the protective roles of NMN against lipopolysaccharide LPS-mediated inflammation in GCs. The results of this experiment demonstrated that LPS had negative effects on GCs in term of reduced viability and proliferation rates and upregulated the production of pro-inflammatory cytokines, including interleukin-1 beta (IL-1β), interleukin-6 (IL-6), cyclooxygenase-2 (Cox-2), and tumor necrosis factor-alpha (TNF-α). Notably, the levels of NAD+ and NAD+/NADH ratio in GCs were reduced in response to inflammation. On the other hand, NMN supplementation restored the NAD+ levels and the NAD+/NADH ratio in GCs and significantly reduced the expression of pro-inflammatory markers at both mRNA and protein levels. It also enhanced cell viability and proliferation rates of GCs. Furthermore, NMN also reduced apoptosis rates in GCs by downregulating pro-apoptotic markers, including Caspase-3, Caspase-9, and Bax while upregulating anti-apoptotic marker Bcl-2. NMN supplementation significantly reduced reactive oxygen species ROS and improved steroidogenesis activity by restoring the estradiol (E2) and progesterone (P4) levels in LPS-treated GCs. Mechanistically, this study found that NMN suppressed the activation of the TLR4/NF-κB/MAPK signaling pathways in GCs, which regulates inflammatory processes. In conclusion, the findings of this study revealed that NMN has the potential to reduce LPS-mediated inflammatory changes in GCs by modulating NAD+ metabolism and inflammatory signaling pathways. NMN supplementation can be used as a potential therapeutic agent for ovarian inflammation and related fertility disorders.

The muscle stem cell case of Benjamin Button: rejuvenating muscle regenerative capacity through nutraceuticals

Aging negatively affects the capacity of muscle stem cells (MuSCs) to regenerate muscle. In this issue of the JCI, Ancel, Michaud, and colleagues used a high-content imaging screen to identify nicotinamide and pyridoxine as promoters of MuSC function. The combination of the two compounds promoted MuSC function in vivo in aged mice and in primary cells isolated from older individuals. Furthermore, the two compounds were lower in the circulation of older men, paralleling decreases in lean mass and gait speed. These results advance the translational perspective of rejuvenating MuSC function through nutraceuticals.

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

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

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

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

Acute nicotinamide riboside supplementation increases human cerebral NAD+ levels in vivo

PURPOSE

The purpose of this study was to determine the effect of acute nicotinamide riboside (NR) supplementation on cerebral nicotinamide adenine dinucleotide (NAD+) levels in the human brain in vivo by means of downfield proton MRS (DF 1H MRS).

METHODS

DF 1H MRS was performed on 10 healthy volunteers in a 7.0 T MRI scanner with spectrally selective excitation and spatially selective localization to determine cerebral NAD+ levels on two back-to-back days: once after an overnight fast (baseline) and once 4 h after oral ingestion of nicotinamide riboside (900 mg). Additionally, two more baseline scans were performed following the same paradigm to assess test-retest reliability of the NAD+ levels in the absence of NR.

RESULTS

NR supplementation increased mean NAD+ concentration compared to the baseline (0.458 ± 0.053 vs. 0.392 ± 0.058 mM; p < 0.001). The additional two baseline scans demonstrated no differences in mean NAD+ concentrations (0.425 ± 0.118 vs. 0.405 ± 0.082 mM; p = 0.45), and no difference from the first baseline scan (F(2, 16) = 0.907; p = 0.424).

CONCLUSION

These preliminary results confirm that acute NR supplementation increases cerebral NAD+ levels in healthy human volunteers and shows the promise of DF 1H MRS utility for robust detection of NAD+ in humans in vivo.

Absorption, anti-inflammatory, antioxidant, and cardioprotective impacts of a novel fasting mimetic containing spermidine, nicotinamide, palmitoylethanolamide, and oleoylethanolamide: A pilot dose-escalation study in healthy young adult men

This pilot dose-escalation study evaluated the absorption and metabolism of a novel fasting mimetic formulation containing spermidine, nicotinamide, palmitoylethanolamide (PEA), and oleoylethanolamide (OEA) taken as oral supplements in young adults. Five healthy men consumed a standardized breakfast, followed by control (wheat flour) or low, medium, or high doses of supplements containing spermidine, nicotinamide, PEA, and OEA 2 hours later. Blood was drawn at 0, 1, 2, and 4 hours after the supplement (2, 3, 4, and 6 hours postprandial). Plasma concentrations of spermidine, 1-methylnicotinamide, PEA and OEA were quantified by liquid chromatography-mass spectrometry. The secretion of tumor necrosis factor alpha and production of reactive oxygen species by stimulated macrophages incubated with plasma, and cholesterol efflux capacity of plasma were analyzed. Plasma 1-methylnicotinamide, PEA, and OEA concentrations increased after supplement intake (P < .05). Spermidine concentrations decreased in the control arm (P < .05) but not the supplement arms. Net incremental area under the curve for tumor necrosis factor alpha and reactive oxygen species in stimulated macrophages decreased when incubated with plasma following supplement intake (P < .05). Intake of the combined supplements showed they were bioavailable and increased in plasma in a dose-dependent manner and provide preliminary data showing enhanced plasma anti-inflammatory and antioxidant functions. This trial was registered at clinicaltrials.gov (NCT05017428).

NAD+ depletion is central to placental dysfunction in an inflammatory subclass of preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy and a major cause of maternal/perinatal adverse health outcomes with no effective therapeutic strategies. Our group previously identified distinct subclasses of PE, one of which exhibits heightened placental inflammation (inflammation-driven PE). In non-pregnant populations, chronic inflammation is associated with decreased levels of cellular NAD+, a vitamin B3 derivative involved in energy metabolism and mitochondrial function. Interestingly, specifically in placentas from women with inflammation-driven PE, we observed the increased activity of NAD+-consuming enzymes, decreased NAD+ content, decreased expression of mitochondrial proteins, and increased oxidative damage. HTR8 human trophoblasts likewise demonstrated increased NAD+-dependent ADP-ribosyltransferase (ART) activity, coupled with decreased mitochondrial respiration rates and invasive function under inflammatory conditions. Such adverse effects were attenuated by boosting cellular NAD+ levels with nicotinamide riboside (NR). Finally, in an LPS-induced rat model of inflammation-driven PE, NR administration (200 mg/kg/day) from gestational days 1-19 prevented maternal hypertension and fetal/placental growth restriction, improved placental mitochondrial function, and reduced inflammation and oxidative stress. This study demonstrates the critical role of NAD+ in maintaining placental function and identifies NAD+ boosting as a promising preventative strategy for PE.

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.

Urolithin A and nicotinamide riboside differentially regulate innate immune defenses and metabolism in human microglial cells

Introduction

During aging, many cellular processes, such as autophagic clearance, DNA repair, mitochondrial health, metabolism, nicotinamide adenine dinucleotide (NAD+) levels, and immunological responses, become compromised. Urolithin A (UA) and Nicotinamide Riboside (NR) are two naturally occurring compounds known for their anti-inflammatory and mitochondrial protective properties, yet the effects of these natural substances on microglia cells have not been thoroughly investigated. As both UA and NR are considered safe dietary supplements, it is equally important to understand their function in normal cells and in disease states.

Methods

This study investigates the effects of UA and NR on immune signaling, mitochondrial function, and microglial activity in a human microglial cell line (HMC3).

Results

Both UA and NR were shown to reduce DNA damage-induced cellular senescence. However, they differentially regulated gene expression related to neuroinflammation, with UA enhancing cGAS-STING pathway activation and NR displaying broader anti-inflammatory effects. Furthermore, UA and NR differently influenced mitochondrial dynamics, with both compounds improving mitochondrial respiration but exhibiting distinct effects on production of reactive oxygen species and glycolytic function.

Discussion

These findings underscore the potential of UA and NR as therapeutic agents in managing neuroinflammation and mitochondrial dysfunction in neurodegenerative diseases.

NAD+ homeostasis and its role in exercise adaptation: A comprehensive review

Nicotinamide adenine dinucleotide (NAD+) is a crucial coenzyme involved in catalyzing cellular redox reactions and serving as a substrate for NAD+-dependent enzymes. It plays a vital role in maintaining tissue homeostasis and promoting healthy aging. Exercise, a well-established and cost-effective method for enhancing health, can influence various pathways related to NAD+ metabolism. Strategies such as supplementing NAD+ precursors, modulating NAD+ synthesis enzymes, or inhibiting enzymes that consume NAD+ can help restore NAD+ balance and improve exercise performance. Various overlapping signaling pathways are known to play a crucial role in the beneficial effects of both NAD+ and exercise on enhancing health and slowing aging process. Studies indicate that a combined strategy of exercise and NAD+ supplementation could synergistically enhance athletic capacity. This review provides an overview of current research on the interactions between exercise and the NAD+ network, underscoring the significance of NAD+ homeostasis in exercise performance. It also offers insights into enhancing exercise capacity and improving aging-related diseases through the optimal use of exercise interventions and NAD+ supplementation methods.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Mitochondrial Dysfunction-Evoked DHODH Acetylation is Involved in Renal Cell Ferroptosis during Cisplatin-Induced Acute Kidney Injury

Several studies have observed renal cell ferroptosis during cisplatin-induced acute kidney injury (AKI). However, the mechanism is not completely clear. In this study, oxidized arachidonic acid (AA) metabolites are increased in cisplatin-treated HK-2 cells. Targeted metabolomics showed that the end product of pyrimidine biosynthesis is decreased and the initiating substrate of pyrimidine biosynthesis is increased in cisplatin-treated mouse kidneys. Mitochondrial DHODH, a key enzyme for pyrimidine synthesis, and its downstream product CoQH2, are downregulated. DHODH overexpression attenuated but DHODH silence exacerbated cisplatin-induced CoQH2 depletion and lipid peroxidation. Mechanistically, renal DHODH acetylation is elevated in cisplatin-exposed mice. Mitochondrial SIRT3 is reduced in cisplatin-treated mouse kidneys and HK-2 cells. Both in vitro SIRT3 overexpression and in vivo NMN supplementation attenuated cisplatin-induced mitochondrial DHODH acetylation and renal cell ferroptosis. By contrast, Sirt3 knockout aggravated cisplatin-induced mitochondrial DHODH acetylation and renal cell ferroptosis, which can not be attenuated by NMN. Additional experiments showed that cisplatin caused mitochondrial dysfunction and SIRT3 SUMOylation. Pretreatment with mitochondria-target antioxidant MitoQ alleviated cisplatin-caused mitochondrial dysfunction, SIRT3 SUMOylation, and DHODH acetylation. MitoQ pretreatment protected against cisplatin-caused AKI and renal cell ferroptosis. Taken together, these results suggest that mitochondrial dysfunction-evoked DHODH acetylation partially contributes to renal cell ferroptosis during cisplatin-induced AKI.

Potential implications of natural compounds on aging and metabolic regulation

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

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

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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.

Regulation of and challenges in targeting NAD+ metabolism

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

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

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

Molecular mechanisms of mitochondrial homeostasis regulation in neurons and possible therapeutic approaches for Alzheimer's disease

Alzheimer's disease (AD) is a neurological disease with memory loss and cognitive decline, which affects a large proportion of the aging population. Regrettably, there are no drug to reverse or cure AD and drug development for the primary theory of amyloid beta deposition has mostly failed. Therefore, there is an urgent need to investigate novel strategies for preventing AD. Recent studies demonstrate that imbalance of mitochondrial homeostasis is a driver in Aβ accumulation, which can lead to the occurrence and deterioration of cognitive impairment in AD patients. This suggests that regulating neuronal mitochondrial homeostasis may be a new strategy for AD. We summarize the importance of mitochondrial homeostasis in AD neuron and its regulatory mechanisms in this review. In addition, we summarize the results of studies indicating mitochondrial dysfunction in AD subjects, including impaired mitochondrial energy production, oxidative stress, imbalance of mitochondrial protein homeostasis, imbalance of fusion and fission, imbalance of neuronal mitochondrial biogenesis and autophagy, and altered mitochondrial motility, in hope of providing possible therapeutic approaches for AD.

The effect of niacin on inflammatory markers and adipokines: a systematic review and meta-analysis of interventional studies

PURPOSE

Niacin (nicotinic acid), known for its lipid-modifying effects, has been explored for its potential anti-inflammatory properties and potential to affect adipokines secretion from adipose tissue. The aim of this systematic review and meta-analysis was to assess the effects of niacin on inflammatory markers and adipokines.

METHODS

A comprehensive search was conducted across five databases: PubMed, Scopus, Cochrane Library, Embase, and ISI Web of Science. Randomized controlled trials exploring the effects of niacin on inflammatory markers (CRP, IL-6, TNF-α) and adipokines (Adiponectin, Leptin) were included. Pooled effect sizes were analysed using a random-effects model, and additional procedures including subgroup analyses, sensitivity analysis and dose-response analysis were also performed.

RESULTS

From an initial 1279 articles, fifteen randomized controlled trials (RCTs) were included. Niacin administration demonstrated a notable reduction in CRP levels (SMD: -0.88, 95% CI: -1.46 to -0.30, p = 0.003). Subgroup analyses confirmed CRP reductions in trials with intervention durations ≤ 24 weeks, doses ≤ 1000 mg/day, and elevated baseline CRP levels (> 3 mg/l). The meta-analysis of IL-6 and TNF-α revealed significant TNF-α reductions, while IL-6 reduction did not reach statistical significance. Niacin administration also substantially elevated Adiponectin (SMD: 3.52, 95% CI: 0.95 to 6.1, p = 0.007) and Leptin (SMD: 1.90, 95% CI: 0.03 to 3.77, p = 0.04) levels.

CONCLUSION

Niacin treatment is associated with significant reductions in CRP and TNF-α levels, suggesting potential anti-inflammatory effects. Additionally, niacin positively influences adipokines, increasing Adiponectin and Leptin levels. These findings provide insights for future research and clinical applications targeting inflammation and metabolic dysregulation.

Nicotinic acid improves mitochondrial function and associated transcriptional pathways in older inactive males

Objectives

To examine the effect of the NAD+ precursor, nicotinic acid (NA), for improving skeletal muscle status in sedentary older people.

Methods

In a double-blind, randomised, placebo-controlled design, 18 sedentary yet otherwise healthy older (65-75 y) males were assigned to 2-weeks of NA (acipimox; 250 mg × 3 daily, n=8) or placebo (PLA, n=10) supplementation. At baseline, and after week 1 and week 2 of supplementation, a battery of functional, metabolic, and molecular readouts were measured.

Results

Resting and submaximal respiratory exchange ratio was lower (p<0.05) after 2 weeks in the NA group only, but maximal aerobic and anaerobic function and glucose handling were unchanged (p>0.05). Bayesian statistical modelling identified that leak, maximal coupled and maximal uncoupled mitochondrial respiratory states, increased over the 2-week supplemental period in the NA group (probability for a positive change (pd) 85.2, 90.8 and 95.9 %, respectively) but not in PLA. Citrate synthase and protein content of complex II (SDHB) and V (ATP5A) electron transport chain (ETC) components increased over the 2-week period in the NA group only (pd 95.1, 74.5 and 82.3 %, respectively). Mitochondrial and myofibrillar protein synthetic rates remained unchanged in both groups. NA intake altered the muscle transcriptome by increasing the expression of gene pathways related to cell adhesion/cytoskeleton organisation and inflammation/immunity and decreasing pathway expression of ETC and aerobic respiration processes. NAD+-specific pathways (e.g., de novo NAD+ biosynthetic processes) and genes (e.g., NADSYN1) were uniquely regulated by NA.

Conclusions

NA might be an effective strategy for improving ageing muscle mitochondrial health.

Mitochondria as Nutritional Targets to Maintain Muscle Health and Physical Function During Ageing

The age-related loss of skeletal muscle mass and physical function leads to a loss of independence and an increased reliance on health-care. Mitochondria are crucial in the aetiology of sarcopenia and have been identified as key targets for interventions that can attenuate declines in physical capacity. Exercise training is a primary intervention that reduces many of the deleterious effects of ageing in skeletal muscle quality and function. However, habitual levels of physical activity decline with age, making it necessary to implement adjunct treatments to maintain skeletal muscle mitochondrial health and physical function. This review provides an overview of the effects of ageing and exercise training on human skeletal muscle mitochondria and considers several supplements that have plausible mechanistic underpinning to improve physical function in ageing through their interactions with mitochondria. Several supplements, including MitoQ, urolithin A, omega-3 polyunsaturated fatty acids (n3-PUFAs), and a combination of glycine and N-acetylcysteine (GlyNAC) can improve physical function in older individuals through a variety of inter-dependent mechanisms including increases in mitochondrial biogenesis and energetics, decreases in mitochondrial reactive oxygen species emission and oxidative damage, and improvements in mitochondrial quality control. While there is evidence that some nicotinamide adenine dinucleotide precursors can improve physical function in older individuals, such an outcome seems unrelated to and independent of changes in skeletal muscle mitochondrial function. Future research should investigate the safety and efficacy of compounds that can improve skeletal muscle health in preclinical models through mechanisms involving mitochondria, such as mitochondrial-derived peptides and mitochondrial uncouplers, with a view to extending the human health-span.

ACAD9 treatment with bezafibrate and nicotinamide riboside temporarily stabilizes cardiomyopathy and lactic acidosis

Pathogenic ACAD9 variants cause complex I deficiency. Patients presenting in infancy unresponsive to riboflavin have high mortality. A six-month-old infant presented with riboflavin unresponsive lactic acidosis and life-threatening cardiomyopathy. Treatment with high dose bezafibrate and nicotinamide riboside resulted in marked clinical improvement including reduced lactate and NT-pro-brain type natriuretic peptide levels, with stabilized echocardiographic measures. After a long stable period, the child succumbed from cardiac failure with infection at 10.5 months. Therapy was well tolerated. Peak bezafibrate levels exceeded its EC50. The clinical improvement with this treatment illustrates its potential, but weak PPAR agonist activity of bezafibrate limited its efficacy.

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.

Nicotinamide riboside ameliorates survival time and motor dysfunction in an MPTP-Induced Parkinson's disease zebrafish model through effects on glucose metabolism and endoplasmic reticulum stress

Nicotinamide riboside (NR) is a precursor and exogenous supplement of nicotinamide adenine dinucleotide (NAD+). NR has been shown to play a beneficial role in a variety of neurodegenerative diseases. A phase 1 clinical trial identified NR as a potential neuroprotective therapy for Parkinson's disease (PD). However, the mechanism of action of NR in PD has not been fully elucidated. Therefore, the present study aimed to investigate the potential effects of NR on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish and its underlying mechanisms. The results showed that NR improved motor dysfunction, survival time, dopamine neurons, and peripheral neurons, as well as the NAD+ levels in the MPTP-affected PD zebrafish model. In addition, transcriptome sequencing analysis revealed that, after NR treatment, differentially expressed genes were significantly enriched in the glucose metabolism and protein processing pathways in the endoplasmic reticulum (ER). Quantitative PCR (qPCR) revealed that the mRNA levels of the glycoheterotrophic enzyme (involved in glucose metabolism) were significantly decreased, and the glycolytic enzyme mRNA expression levels were significantly increased. The results of the non-targeted metabolomic analysis showed that NR treatment significantly increased the levels of metabolites such as nicotinic acid ,nicotinamide, d-glucose (from the gluconeogenesis and glycolysis metabolism pathways) and some glucogenic amino acids, such as glutamine. Importantly, NR ameliorated MPTP-induced endoplasmic reticulum stress (ERS) in the PD zebrafish model through the Perk-Eif2α-Atf4-Chop pathway. These results highlight the neuroprotective effect of NR in the present PD zebrafish model through modulation of glucose metabolism and ERS via the Perk-Eif2α-Atf4-Chop pathway and provide valuable mechanistic insights into the treatment of PD.