Declining NAD(+) induces a pseudohypoxic state disrupting nuclear-mitochondrial communication during aging

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.

A systematic review of the therapeutic potential of nicotinamide adenine dinucleotide precursors for cognitive diseases in preclinical rodent models

This systematic review sought to assess the impact of nicotinamide adenine dinucleotide (NAD+) precursors on cognitive impairments in several diseases in rat/mouse models. Accumulating evidence suggests that inflammation, apoptosis, oxidative stress responses, and mitochondrial dysfunction are potential factors of cognitive deficits in aging, Alzheimer's disease (AD), diabetes, traumatic brain injury (TBI), vascular dementia (VAD), and schizophrenia. NAD+ precursors have received increased interest due to their unique molecular structure targets antioxidant and inflammatory pathways and mitochondrial function. The PubMed, Scopus, Google Scholar, Embase, and Web of Science databases were searched through May 30, 2024. Studies investigating the effect of NAD+ precursors on cognitive impairments in rodent models were included. Two reviewers independently extracted and evaluated the data. The PRISMA guidelines for reporting systematic reviews were followed. Thirty preclinical studies were included in the review. Studies have revealed that treatment with NAD+ rescues cognitive deficits by inhibiting inflammation, oxidative stress, and apoptosis and improving mitochondrial function. Preclinical evidence has demonstrated that treatment with NAD+ precursors may be more effective in learning and memory recovery in AD, TBI, diabetes, aging, VAD, and schizophrenia. The outcomes of this investigation may lead to additional studies on the use of NAD+ precursors for treating human cognitive decline.

NRH, a potent NAD+ enhancer, improves glucose homeostasis and lipid metabolism in diet-induced obese mice through an active adenosine kinase pathway

AIMS

NAD+ deficiency underlies obesity-induced metabolic disturbances. This study evaluated dihydronicotinamide riboside (NRH), a potent NAD+ enhancer, in lean and obese mice and explored whether NRH operates through a unique mechanism involving adenosine kinase (ADK), an enzyme critical for NRH-driven NAD+ synthesis.

METHODS

Pharmacokinetic and pharmacodynamic analyses were performed following a single 250 mg/kg intraperitoneal injection of NRH in healthy mice. In long-term studies, lean and high-fat diet-induced obese mice were treated with 250 mg/kg NRH thrice weekly for 7 weeks. Blood NAD+ levels, body composition, energy expenditure, and glucose and lipid metabolism were monitored. To test ADK's role, the ADK inhibitor ABT702 was co-administered with NRH in obese mice.

RESULTS

NRH entered tissues unassisted and was rapidly metabolized for NAD+ biosynthesis, while ADK inhibition blocked its phosphorylation, leading to NRH accumulation in all examined tissues and possible release back into circulation. The 7-week NRH administration was well-tolerated in both lean and obese mice. In obese mice, NRH improved glucose homeostasis by boosting insulin secretion, enhancing muscle insulin signaling, and reducing hepatic gluconeogenesis. It also lowered fat mass, decreased serum lipids, and improved white adipose function. These benefits were linked to elevated tissue NAD+ levels, enhanced Sirtuin activities, and increased mitochondrial antioxidant defenses. ADK inhibition abolished these effects, confirming that NRH's direct entry into tissues and subsequent phosphorylation is essential for its full benefits.

CONCLUSION

This study establishes NRH as a promising therapeutic agent for obesity-induced metabolic dysfunction, correcting glucose intolerance and hyperlipidemia through ADK-dependent NAD+ enhancement.

Mitochondrial dysfunction and calcium homeostasis in heart failure: Exploring the interplay between oxidative stress and cardiac remodeling for future therapeutic innovations

Heart failure (HF) is a multifaceted clinical syndrome characterized by the heart's inability to pump sufficient blood to meet the body's metabolic demands. It arises from various etiologies, including myocardial injury, hypertension, and valvular heart disease. A critical aspect of HF pathophysiology involves mitochondrial dysfunction, particularly concerning calcium (Ca2+) homeostasis and oxidative stress. This review highlights the pivotal role of excess mitochondrial Ca2+ in exacerbating oxidative stress, contributing significantly to HF progression. Novel insights are provided regarding the mechanisms by which mitochondrial Ca2+ overload leads to increased production of reactive oxygen species (ROS) and impaired cellular function. Despite this understanding, key gaps in research remain, particularly in elucidating the complex interplay between mitochondrial dynamics and oxidative stress across different HF phenotypes. Furthermore, therapeutic strategies targeting mitochondrial dysfunction are still in their infancy, with limited applications in clinical practice. By summarizing recent findings and identifying these critical research gaps, this review aims to pave the way for innovative therapeutic approaches that improve the management of heart failure, ultimately enhancing patient outcomes through targeted interventions.

Mn-Specific Recognition of Guanidine Drives Selective Inhibition of Complex I

Developing structurally well-defined targeted drugs is an effective way to enhance the chemotherapy efficacy. Herein, a target mitochondrial complex I (complex I) inhibitor was developed for the key methylation site ARG-85 in the key subunit NDUFS2. Based on the unique :NH═C- group of guanidyl and the surrounding environment of ARG-85, the macrocyclic and bulky manganese porphyrin complex [MnIII(TTPPC2-)]+ was selected to insert into the gap of NDUFS2. Experimental and computational analyses revealed that the planar π system of the TTPPC2- ligand and the rotatable benzene ring stably bind between the :NH═C- group of ARG-85 and the manganese metal center, a medium-strong Lewis acid. The Mn-specific recognition of guanidine drives the selective inhibition of complex I activity. Further, MnIII(TTPPC2-)]+ was modified into targeted nanoformulation Mn NPs. In vitro and in vivo experiments confirmed the efficient and mechanism inhibition of complex I activity, offering a novel strategy for targeted drug development.

Acute hypoxia modulate macrophage phenotype accompanied with transcriptome re-programming and metabolic re-modeling

Introduction

Macrophages, which tend to aggregate in the hypoxic regions of tissues, have a significant impact on disease progression and outcome because of their plastic responsiveness to hypoxia, particularly in the early stages. Understanding macrophages'participation in hypoxia-related disorders requires demonstrating the impact of acute hypoxia on their survival, phenotype, and function.

Methods

Here we conducted a systematic evaluation of macrophage responses to hypoxia over 24 and 48 h including cell growth and activity, inflamatory response, macrophage polarization and transcriptional and metabolic changes.

Results

We found that acute hypoxia suppresses macrophage proliferation and phagocytosis function with a parallel change of transcriptome re-programming and metabolic re-modeling. Although macrophages accumulate transcriptome heterogeneity based on oxygen concentration and culture period, genes involved in hypoxia response, chemotaxis, and glycolytic process were commonly altered during acute hypoxia. Furthermore, the pro-inflammatory response of macrophages was activated during acute hypoxia concomitantly with an enhanced anti-inflammatory regulatory mechanism characterized by increased M2 macrophage population and anti-inflammatory metabolite itaconic acid. Aside from increased glycolysis, the key intermediates in the pentose phosphate pathway significantly increased, such as fructose 1,6-bisphosphate (fold change: 7.8), 6-phosphogluconate (fold change: 6.1), and ribose 5-phosphate (fold change: 3.9), which indicated that the pentose phosphate pathway was an important compensatory metabolic regulation that rules for the response of macrophages to acute hypoxia.

Discussion

These findings highlight that acute hypoxia suppresses macrophage viability and phagocytosis, while acute hypoxia modifies the transcriptome and metabolome in specific inflammatory responses and metabolic pathways to facilitate the adaptation of macrophage in hypoxic conditions.

Ergothioneine improves healthspan of aged animals by enhancing cGPDH activity through CSE-dependent persulfidation

Ergothioneine (ET), a dietary thione/thiol, is receiving growing attention for its possible benefits in healthy aging and metabolic resilience. Our study investigates ET's effects on healthspan in aged animals, revealing lifespan extension and enhanced mobility in Caenorhabditis elegans, accompanied by improved stress resistance and reduced age-associated biomarkers. In aged rats, ET administration enhances exercise endurance, muscle mass, and vascularization, concomitant with higher NAD+ levels in muscle. Mechanistically, ET acts as an alternative substrate for cystathionine gamma-lyase (CSE), stimulating H2S production, which increases protein persulfidation of more than 300 protein targets. Among these, protein-persulfidation-driven activation of cytosolic glycerol-3-phosphate dehydrogenase (cGPDH) primarily contributes to the ET-induced NAD+ increase. ET's effects are abolished in models lacking CSE or cGPDH, highlighting the essential role of H2S signaling and protein persulfidation. These findings elucidate ET's multifaceted actions and provide insights into its therapeutic potential for combating age-related muscle decline and metabolic perturbations.

The interplay of NAD and hypoxic stress and its relevance for ageing

Nicotinamide adenine dinucleotide (NAD) is an essential regulator of cellular metabolism and redox processes. NAD levels and the dynamics of NAD metabolism change with increasing age but can be modulated via the diet or medication. Because NAD metabolism is complex and its regulation still insufficiently understood, achieving specific outcomes without perturbing delicate balances through targeted pharmacological interventions remains challenging. NAD metabolism is also highly sensitive to environmental conditions and can be influenced behaviorally, e.g., by exercise. Changes in oxygen availability directly and indirectly affect NAD levels and may result from exposure to ambient hypoxia, increased oxygen demand during exercise, ageing or disease. Cellular responses to hypoxic stress involve rapid alterations in NAD metabolism and depend on many factors, including age, glucose status, the dose of the hypoxic stress and occurrence of reoxygenation phases, and exhibit complex time-courses. Here we summarize the known determinants of NAD-regulation by hypoxia and evaluate the role of NAD in hypoxic stress. We define the specific NAD responses to hypoxia and identify a great potential of the modulation of NAD metabolism regarding hypoxic injuries. In conclusion, NAD metabolism and cellular hypoxia responses are strongly intertwined and together mediate protective processes against hypoxic insults. Their interactions likely contribute to age-related changes and vulnerabilities. Targeting NAD homeostasis presents a promising avenue to prevent/treat hypoxic insults and - conversely - controlled hypoxia is a potential tool to regulate NAD homeostasis.

Sex-specific mechanisms in vascular aging: exploring cellular and molecular pathways in the pathogenesis of age-related cardiovascular and cerebrovascular diseases

Aging remains the foremost risk factor for cardiovascular and cerebrovascular diseases, surpassing traditional factors in epidemiological significance. This review elucidates the cellular and molecular mechanisms underlying vascular aging, with an emphasis on sex differences that influence disease progression and clinical outcomes in older adults. We discuss the convergence of aging processes at the macro- and microvascular levels and their contributions to the pathogenesis of vascular diseases. Critical analysis of both preclinical and clinical studies reveals significant sex-specific variations in these mechanisms, which could be pivotal in understanding the disparity in disease morbidity and mortality between sexes. The review highlights key molecular pathways, including oxidative stress, inflammation, and autophagy, and their differential roles in the vascular aging of males and females. We argue that recognizing these sex-specific differences is crucial for developing targeted therapeutic strategies aimed at preventing and managing age-related vascular pathologies. The implications for personalized medicine and potential areas for future research are also explored, emphasizing the need for a nuanced approach to the study and treatment of vascular aging.

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.

Population aging, technological innovation and industrial differentiation

As China's aging population deepens and its pace accelerates, it is particularly crucial to rely on technological innovation to drive industrial differentiation. Is there a connection between population aging, technological innovation, and industrial differentiation? Does technological innovation have a moderating effect? Based on the panel data of 31 provinces in China from 2006 to 2022, this paper constructs the entropy index to measure the overall industrial differentiation and tertiary industrial differentiation in China, and subsequently investigates the relationship among the three using the two-way fixed effect model. The results indicate that population aging has a significant positive impact on the overall industrial differentiation in China, with a regression coefficient of 1.1025. Technological innovation plays a positive moderating role, with an interaction coefficient of 0.3489. The effects of population aging on the differentiation of the three industries differ: the regression coefficient for the primary industry is -0.6437, which is significantly negative; for the secondary industry, the regression coefficient is 0.9252, which is statistically insignificant; and for the tertiary industry, the regression coefficient is 0.1539, which is significantly positive. The government should encourage enterprises to invest in technology research and development through tax cuts and subsidies, and enterprises should absorb high-quality talents, carry out intelligent transformation of traditional industries of enterprises, and improve their competitiveness.

Exploring the Link Between Telomeres and Mitochondria: Mechanisms and Implications in Different Cell Types

Telomeres protect chromosome ends from damage, but they shorten with each cell division due to the limitations of DNA replication and are further affected by oxidative stress. This shortening is a key feature of aging, and telomerase, an enzyme that extends telomeres, helps mitigate this process. Aging is also associated with mitochondrial dysfunction, leading to increased reactive oxygen species (ROS) that exacerbate cellular damage and promote apoptosis. Elevated ROS levels can damage telomeres by oxidizing guanine and disrupting their regulation. Conversely, telomere damage impacts mitochondrial function, and activation of telomerase has been shown to reverse this decline. A critical link between telomere shortening and mitochondrial dysfunction is the DNA damage response, which activates the tumor suppressor protein p53, resulting in reduced mitochondrial biogenesis and metabolic disruptions. This highlights the bidirectional relationship between telomere maintenance and mitochondrial function. This review explores the complex interactions between telomeres and mitochondria across various cell types, from fibroblasts to sperm cells, shedding light on the interconnected mechanisms underlying aging and cellular function.

Endothelial FUNDC1 Deficiency Drives Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is associated with endothelial dysfunction. However, the cause of endothelial dysfunction and its impact on PH remain incompletely understood. We aimed to investigate whether the hypoxia-inducible FUNDC1 (FUN14 domain-containing 1)-dependent mitophagy pathway underlies PH pathogenesis and progression.

METHODS

We first analyzed FUNDC1 protein levels in lung samples from patients with PH and animal models. Using rodent PH models induced by HySu (hypoxia+SU5416) or chronic hypoxia, we further investigated PH pathogenesis and development in response to global and cell-type-specific Fundc1 loss/gain-of-function. We also investigated the spontaneous PH in mice with inducible loss of endothelial Fundc1. In addition, histological, metabolic, and transcriptomic studies were performed to delineate molecular mechanisms. Finally, findings were validated in vivo by compound deficiency of HIF2α (hypoxia-inducible factor 2α; Epas1) and pharmacological intervention.

RESULTS

FUNDC1 protein levels were reduced in PH lung vessels from clinical subjects and animal models. Global Fundc1 deficiency exacerbated PH, while its overexpression was protective. The effect of FUNDC1 was mediated by endothelial cells rather than smooth muscle cells. Further, inducible loss of endothelial Fundc1 in postnatal mice was sufficient to cause PH spontaneously, whereas augmenting endothelial Fundc1 protected against PH before and after the onset of disease. Mechanistically, Fundc1 deficiency impaired basal mitophagy in endothelial cells, leading to the accumulation of dysfunctional mitochondria, metabolic reprogramming toward aerobic glycolysis, pseudohypoxia, and senescence, likely via a mtROS-HIF2α signaling pathway. Subsequently, Fundc1-deficient endothelial cells increased IGFBP2 (insulin-like growth factor-binding protein 2) secretion that drove pulmonary arterial remodeling to instigate PH. Finally, proof-of-principle in vivo studies showed significant efficacy on PH amelioration by targeting endothelial mitophagy, pseudohypoxia, senescence, or IGFBP2.

CONCLUSIONS

Collectively, we show that FUNDC1-mediated basal mitophagy is critical for endothelial homeostasis, and its disruption instigates PH pathogenesis. Given that similar changes in FUNDC1 and IGFBP2 were observed in PH patients, our findings are of significant clinical relevance and provide novel therapeutic strategies for PH.

Nicotinamide mononucleotide restores impaired metabolism, endothelial cell proliferation and angiogenesis in old sedentary male mice

Aging is accompanied by a decline in neovascularization potential and increased susceptibility to ischemic injury. Here, we confirm the age-related impaired neovascularization following ischemic leg injury and impaired angiogenesis. The age-related deficits in angiogenesis arose primarily from diminished EC proliferation capacity, but not migration or VEGF sensitivity. Aged EC harvested from the mouse skeletal muscle displayed a pro-angiogenic gene expression phenotype, along with considerable changes in metabolic genes. Metabolomics analysis and 13C glucose tracing revealed impaired ATP production and blockade in glycolysis and TCA cycle in late passage HUVECs, which occurred at nicotinamide adenine dinucleotide (NAD⁺)-dependent steps, along with NAD+ depletion. Supplementation with nicotinamide mononucleotide (NMN), a precursor of NAD⁺, enhances late-passage EC proliferation and sprouting angiogenesis from aged mice aortas. Taken together, our study illustrates the importance of NAD+-dependent metabolism in the maintenance of EC proliferation capacity with age, and the therapeutic potential of NAD precursors.

Metabolism and metabolomics in senescence, aging, and age-related diseases: a multiscale perspective

The pursuit of healthy aging has long rendered aging and senescence captivating. Age-related ailments, such as cardiovascular diseases, diabetes, and neurodegenerative disorders, pose significant threats to individuals. Recent studies have shed light on the intricate mechanisms encompassing genetics, epigenetics, transcriptomics, and metabolomics in the processes of senescence and aging, as well as the establishment of age-related pathologies. Amidst these underlying mechanisms governing aging and related pathology metabolism assumes a pivotal role that holds promise for intervention and therapeutics. The advancements in metabolomics techniques and analysis methods have significantly propelled the study of senescence and aging, particularly with the aid of multiscale metabolomics which has facilitated the discovery of metabolic markers and therapeutic potentials. This review provides an overview of senescence and aging, emphasizing the crucial role metabolism plays in the aging process as well as age-related diseases.

Reductive stress: The key pathway in metabolic disorders induced by overnutrition

BACKGROUND

The balance of redox states is crucial for maintaining physiological homeostasis. For decades, the focus has been mainly on the concept of oxidative stress, which is involved in the mechanism of almost all diseases. However, robust evidence has highlighted that reductive stress, the other side of the redox spectrum, plays a pivotal role in the development of various diseases, particularly those related to metabolism and cardiovascular health.

AIM OF REVIEW

In this review, we present an extensive array of evidence for the occurrence of reductive stress and its significant implications mainly in metabolic and cardiovascular diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Reductive stress is defined as a shift in the cellular redox balance towards a more reduced state, characterized by an excess of endogenous reductants (such as NADH, NADPH, and GSH) over their oxidized counterparts (NAD+, NADP+, and GSSG). While oxidative stress has been the predominant mechanism studied in obesity, metabolic disorders, and cardiovascular diseases, growing evidence underscores the critical role of reductive stress. This review discusses how reductive stress contributes to metabolic and cardiovascular pathologies, emphasizing its effects on key cellular processes. For example, excessive NADH accumulation can disrupt mitochondrial function by impairing the electron transport chain, leading to decreased ATP production and increased production of reactive oxygen species. In the endoplasmic reticulum (ER), an excess of reductive equivalents hampers protein folding, triggering ER stress and activating the unfolded protein response, which can lead to insulin resistance and compromised cellular homeostasis. Furthermore, we explore how excessive antioxidant supplementation can exacerbate reductive stress by further shifting the redox balance, potentially undermining the beneficial effects of exercise, impairing cardiovascular health, and aggravating metabolic disorders, particularly in obese individuals. This growing body of evidence calls for a reevaluation of the role of reductive stress in disease pathogenesis and therapeutic interventions.

Role of sirtuins in obesity and osteoporosis: molecular mechanisms and therapeutic targets

The prevalence of obesity and osteoporosis (OP) represents a significant public health concern on a global scale. A substantial body of evidence indicates that there is a complex relationship between obesity and OP, with a correlation between the occurrence of OP and obesity. In recent years, sirtuins have emerged as a prominent area of interest in the fields of aging and endocrine metabolism. Among the various research avenues exploring the potential of sirtuins, the effects of these proteins on obesity and OP have garnered significant attention from numerous researchers. Sirtuins regulate energy balance and lipid balance, which in turn inhibit the process of adipogenesis. Additionally, sirtuins regulate the balance between osteogenic and osteoblastic activity, which protects against the development of OP. However, no study has yet provided a comprehensive discussion of the relationship between the three: sirtuins, obesity, and OP. This paper will therefore describe the relationship between sirtuins and obesity, the relationship between sirtuins and OP, and a discussion focusing on the possibility of treating OP caused by obesity by targeting sirtuins. This will be based on the common influences on the occurrence of obesity and OP (such as mesenchymal stem cells, gut microbiota, and insulin). Finally, the potential of SIRT1, an important member of sirtuins, in polyphenolic natural products for the treatment of obesity and OP will be presented. This will contribute to a better understanding of the interactions between sirtuins and obesity and bone, which will facilitate the development of new therapeutic strategies for obesity and OP in the future.

Immunosenescence, Physical Exercise, and their Implications in Tumor Immunity and Immunotherapy

Aging is associated with a decline in immune function, termed immunosenescence, which compromises host defences and increases susceptibility to infections and cancer. Physical exercise is widely recognized for its myriad health benefits, including the potential to modulate the immune system. This review explores the bidirectional relationship between immunosenescence and physical exercise, focusing on their interplay in shaping antitumor immunity. We summarize the impact of aging on innate and adaptive immune cells, highlighting alterations that contribute to immunosenescence and cancer development. We further delineate the effects of exercise on immune cell function, demonstrating its potential to mitigate immunosenescence and enhance antitumor responses. We also discuss the implications of immunosenescence for the efficacy of immunotherapies, such as immune checkpoint inhibitors and adoptive T cell therapy, and explore the potential benefits of combining exercise with these interventions. Collectively, this review underscores the importance of understanding the complex relationship between immunosenescence, physical exercise, and antitumor immunity, paving the way for the development of innovative strategies to improve cancer outcomes in the aging population.

Circadian Rhythms and Lung Cancer in the Context of Aging: A Review of Current Evidence

Circadian rhythm is the internal homeostatic physiological clock that regulates the 24-hour sleep/wake cycle. This biological clock helps to adapt to environmental changes such as light, dark, temperature, and behaviors. Aging, on the other hand, is a process of physiological changes that results in a progressive decline in cells, tissues, and other vital systems of the body. Both aging and the circadian clock are highly interlinked phenomena with a bidirectional relationship. The process of aging leads to circadian disruptions while dysfunctional circadian rhythms promote age-related complications. Both processes involve diverse physiological, molecular, and cellular changes such as modifications in the DNA repair mechanisms, mechanisms, ROS generation, apoptosis, and cell proliferation. This review aims to examine the role of aging and circadian rhythms in the context of lung cancer. This will also review the existing literature on the role of circadian disruptions in the process of aging and vice versa. Various molecular pathways and genes such as BMAL1, SIRT1, HLF, and PER1 and their implications in aging, circadian rhythms, and lung cancer will also be discussed.

Quantitative dynamics of intracellular NMN by genetically encoded biosensor

Nicotinamide mononucleotide (NMN) is the direct precursor and a major booster of NAD+ with increasing applications in NAD+- and aging-related pathologies. However, measuring live cell NMN dynamics was not possible, leaving key questions in NMN uptake and intracellular regulation unanswered. Here we developed genetically encoded bioluminescent and fluorescent sensors to quantify subcellular NMN in live cells by engineering specific NMN-responsive protein scaffolds fused to luciferase and fluorescent proteins. The sensor dissected the multimechanistic uptake of exogenous NMN and nicotinamide riboside (NR) in live cells and further measured the NMN levels across different subcellular compartments, as well as the perturbed NMN/NAD+ ratios by external supplements. Moreover, we measured the NMN regulation by NAD(H) hydrolase Nudts and peroxisomal carrier Pxmp2 and identified Slc25a45 as a potential mitochondrial NMN regulator for its unique fingerprint on the local NMN/NAD+ ratio. Collectively, the genetically encoded sensors provide a useful tool for visualizing NMN metabolism.

Cognitive and Alzheimer's disease biomarker effects of oral nicotinamide riboside (NR) supplementation in older adults with subjective cognitive decline and mild cognitive impairment

INTRODUCTION

Age-associated depletion in nicotinamide adenine dinucleotide (NAD+) concentrations has been implicated in metabolic, cardiovascular, and neurodegenerative disorders. Supplementation with NAD+ precursors, such as nicotinamide riboside (NR), offers a potential therapeutic avenue against neurodegenerative pathologies in aging, Alzheimer's disease, and related dementias. A crossover, double-blind, randomized placebo (PBO) controlled trial was conducted to test the safety and efficacy of 8 weeks' active treatment with NR (1 g/day) on cognition and plasma AD biomarkers in older adults with subjective cognitive decline and mild cognitive impairment.

METHODS

The primary efficacy outcome was the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Secondary outcomes included plasma phosphorylated tau 217 (pTau217), glial fibrillary acidic protein (GFAP), and neurofilament light chain (NfL). Exploratory outcomes included Lumosity gameplay (z-scores) for cognition and step counts from wearables. Mixed model for repeated measures was used for between-group comparisons; paired t-tests were used for within-individual comparisons.

RESULTS

Forty-six participants aged over 55 were randomized to NR-PBO or PBO-NR groups; 41 completed baseline visits, and 37 completed the trial. NR supplementation was safe and well tolerated with no differences in adverse events reported between NR and PBO treatment phases. For the between-group comparison, there was a 7% reduction in pTau217 concentrations after taking NR, while an 18% increase with PBO (p = 0.02). No significant between-group differences were observed for RBANS, other plasma biomarkers(GFAP and NfL), Lumosity gameplay scores or step counts. For the within-individual comparison, pTau217 concentrations significantly decreased during the NR phase compared to the PBO (p = 0.02), while step counts significantly increased during the NR phase than PBO (p = 0.04).

DISCUSSION

Eight weeks NR supplementation is safe and lowered pTau217 concentrations but did not alter cognition as measured by conventional or novel digital assessments. Further research is warranted to validate NR's efficacy in altering pathological brain aging processes.

Highlights

The integrated study design combines a two-arm parallel trial with a crossover phase, offering the opportunity to enhance sample size for within-individual analysis and assess carryover effects.NR is safe but did not alter cognition as measured by multi-modal assessments in SCD/MCI.For between-group comparison, pTau217 levels decreased with NR and increased with PBO at 8-week follow-up.For within-individual comparison, step counts increased after NR and decreased after PBO.A larger, longer study with pharmacodynamic and pathophysiological biomarkers is needed to assess NR's disease-modifying effects.

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.

Inactivation of the SLC25A1 gene during embryogenesis induces a unique senescence program controlled by p53

Germline inactivating mutations of the SLC25A1 gene contribute to various human disorders, including Velocardiofacial (VCFS), DiGeorge (DGS) syndromes and combined D/L-2-hydroxyglutaric aciduria (D/L-2HGA), a severe systemic disease characterized by the accumulation of 2-hydroxyglutaric acid (2HG). The mechanisms by which SLC25A1 loss leads to these syndromes remain largely unclear. Here, we describe a mouse model of SLC25A1 deficiency that mimics human VCFS/DGS and D/L-2HGA. Surprisingly, inactivation of both Slc25a1 alleles results in alterations in the development of multiple organs, and in a severe proliferation defect by activating two senescence programs, oncogene-induced senescence (OIS) and mitochondrial dysfunction-induced senescence (MiDAS), which converge upon the induction of the p53 tumor suppressor. Mechanistically, cells and tissues with dysfunctional SLC25A1 protein undergo metabolic and transcriptional rewiring leading to the accumulation of 2HG via a non-canonical pathway and to the depletion of nicotinamide adenine dinucleotide, NAD+, which trigger senescence. Replenishing the pool of NAD+ or promoting the clearance of 2HG rescues the proliferation defect of cells with dysfunctional SLC25A1 in a cooperative fashion. Further, removal of p53 activity via RNA interference restores proliferation, indicating that p53 acts as a critical barrier to the expansion of cells lacking functional SLC25A1. These findings reveal unexpected pathogenic roles of senescence and of p53 in D/L-2HGA and identify potential therapeutic strategies to correct salient molecular alterations driving this disease.

Effects of Aging on Glucose and Lipid Metabolism in Mice

Aging is accompanied by multiple molecular changes that contribute to aging associated pathologies, such as accumulation of cellular damage and mitochondrial dysfunction. Tissue metabolism can also change with age, in part, because mitochondria are central to cellular metabolism. Moreover, the cofactor NAD+, which is reported to decline across multiple tissues during aging, plays a central role in metabolic pathways such as glycolysis, the tricarboxylic acid cycle, and the oxidative synthesis of nucleotides, amino acids, and lipids. To further characterize how tissue metabolism changes with age, we intravenously infused [U-13C]-glucose into young and old C57BL/6J, WSB/EiJ, and diversity outbred mice to trace glucose fate into downstream metabolites within plasma, liver, gastrocnemius muscle, and brain tissues. We found that glucose incorporation into central carbon and amino acid metabolism was robust during healthy aging across these different strains of mice. We also observed that levels of NAD+, NADH, and the NAD+/NADH ratio were unchanged in these tissues with healthy aging. However, aging tissues, particularly brain, exhibited evidence of upregulated fatty acid and sphingolipid metabolism reactions that regenerate NAD+ from NADH. These data suggest that NAD+-generating lipid metabolism reactions may help to maintain the NAD+/NADH ratio during healthy aging.

A luminescent-based protocol for NAD+/NADH detection in C. elegans, mice, and human whole blood

Here, we present a NAD+/NADH detection assay for evaluating NAD+, NADH, and NAD+/NADH ratio across diverse biological models, including Caenorhabditis elegans, mouse muscle tissue, mouse whole blood, and human whole blood. We describe steps for sample collection and preparation from different models as well as detection and calculation of NAD+ and NADH levels. This protocol is applicable for quantifying cellular/tissue NAD+ and NADH levels across different biological models.

Lithocholic acid binds TULP3 to activate sirtuins and AMPK to slow down ageing

Lithocholic acid (LCA) is accumulated in mammals during calorie restriction and it can activate AMP-activated protein kinase (AMPK) to slow down ageing1. However, the molecular details of how LCA activates AMPK and induces these biological effects are unclear. Here we show that LCA enhances the activity of sirtuins to deacetylate and subsequently inhibit vacuolar H+-ATPase (v-ATPase), which leads to AMPK activation through the lysosomal glucose-sensing pathway. Proteomics analyses of proteins that co-immunoprecipitated with sirtuin 1 (SIRT1) identified TUB-like protein 3 (TULP3), a sirtuin-interacting protein2, as a LCA receptor. In detail, LCA-bound TULP3 allosterically activates sirtuins, which then deacetylate the V1E1 subunit of v-ATPase on residues K52, K99 and K191. Muscle-specific expression of a V1E1 mutant (3KR), which mimics the deacetylated state, strongly activates AMPK and rejuvenates muscles in aged mice. In nematodes and flies, LCA depends on the TULP3 homologues tub-1 and ktub, respectively, to activate AMPK and extend lifespan and healthspan. Our study demonstrates that activation of the TULP3-sirtuin-v-ATPase-AMPK pathway by LCA reproduces the benefits of calorie restriction.

Lithocholic acid phenocopies anti-ageing effects of calorie restriction

Calorie restriction (CR) is a dietary intervention used to promote health and longevity1,2. CR causes various metabolic changes in both the production and the circulation of metabolites1; however, it remains unclear which altered metabolites account for the physiological benefits of CR. Here we use metabolomics to analyse metabolites that exhibit changes in abundance during CR and perform subsequent functional validation. We show that lithocholic acid (LCA) is one of the metabolites that alone can recapitulate the effects of CR in mice. These effects include activation of AMP-activated protein kinase (AMPK), enhancement of muscle regeneration and rejuvenation of grip strength and running capacity. LCA also activates AMPK and induces life-extending and health-extending effects in Caenorhabditis elegans and Drosophila melanogaster. As C. elegans and D. melanogaster are not able to synthesize LCA, these results indicate that these animals are able to transmit the signalling effects of LCA once administered. Knockout of AMPK abrogates LCA-induced phenotypes in all the three animal models. Together, we identify that administration of the CR-mediated upregulated metabolite LCA alone can confer anti-ageing benefits to metazoans in an AMPK-dependent manner.

The structural Basis of NMN synthesis catalyzed by NadV from Haemophilus ducreyi

NMN is a precursor in the biosynthesis of NAD+, a molecule that plays a crucial role within cells. Supplementation with NMN can elevate NAD+ levels in the blood, improving symptoms of diabetes, neurodegenerative diseases, and cancer, as well as providing anti-aging benefits. Escherichia coli was engineered to heterologously express nicotinamide phosphoribosyltransferase (Nampt), enabling the recombinant E. coli to synthesize NAD derivatives from nicotinamide. The 3D structure of Nadv complexed with NAM and NMN was determined to explore the molecular mechanism by which Nadv catalyzes NMN synthesis. NAM binds at two sites: one at the catalytic site and one at the allosteric binding site, while NMN binds exclusively at the catalytic site. In both structural models, a loop between β15 and β16 is missing, likely due to its high flexibility, leading to diffuse electron density. Compared with other resolved Nampt structures, an additional 12-amino-acid loop was identified after α-helix 12 near the catalytic site. This study lays the groundwork for the engineering of Nadv, facilitating its efficient application in biological synthesis of NMN.

Mitochondrial DNA Damage and Its Repair Mechanisms in Aging Oocytes

The efficacy of assisted reproductive technologies (ARTs) in older women remains constrained, largely due to an incomplete understanding of the underlying pathophysiology. This review aims to consolidate the current knowledge on age-associated mitochondrial alterations and their implications for ovarian aging, with an emphasis on the causes of mitochondrial DNA (mtDNA) mutations, their repair mechanisms, and future therapeutic directions. Relevant articles published up to 30 September 2024 were identified through a systematic search of electronic databases. The free radical theory proposes that reactive oxygen species (ROS) inflict damage on mtDNA and impair mitochondrial function essential for ATP generation in oocytes. Oocytes face prolonged pressure to repair mtDNA mutations, persisting for up to five decades. MtDNA exhibits limited capacity for double-strand break repair, heavily depending on poly ADP-ribose polymerase 1 (PARP1)-mediated repair of single-strand breaks. This process depletes nicotinamide adenine dinucleotide (NAD⁺) and ATP, creating a detrimental cycle where continued mtDNA repair further compromises oocyte functionality. Interventions that interrupt this destructive cycle may offer preventive benefits. In conclusion, the cumulative burden of mtDNA mutations and repair demands can lead to ATP depletion and elevate the risk of aneuploidy, ultimately contributing to ART failure in older women.

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

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

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

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

Nicotinamide N-methyltransferase (NNMT): A key enzyme in cancer metabolism and therapeutic target

Emerging research has positioned Nicotinamide N-methyltransferase (NNMT) as a key player in oncology, with its heightened expression frequently observed across diverse cancers. This increased presence is tightly linked to tumor initiation, proliferation, and metastasis. The enzymatic function of NNMT is centered on the methylation of nicotinamide (NAM), utilizing S-adenosylmethionine (SAM) as the methyl donor, which results in the generation of S-adenosyl-L-homocysteine (SAH) and methyl nicotinamide (MNAM). This metabolic process reduces the availability of NAM, necessary for Nicotinamide adenine dinucleotide (NAD+) synthesis, and generates SAH, precursor to homocysteine (Hcy). These alterations are theorized to foster the resilience, expansion, and invasiveness of cancer cells. Furthermore, NNMT is implicated in enhancing cancer malignancy by affecting multiple signaling pathways, such as phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT), cancer-associated fibroblasts (CAFs) and 5-Methyladenosine (5-MA), epithelial-mesenchymal transition (EMT), and epigenetic mechanisms. Upregulation of NNMT metabolism plays a key role in the formation and maintenance of the tumour microenvironment. While the use of small molecule inhibitors and RNA interference (RNAi) to target NNMT has shown therapeutic promise, the full extent of NNMT's influence on cancer is not yet fully understood, and clinical evidence is limited. This article systematically describes the relationship between the functional metabolism of NNMT enzymes and the cancer and tumour microenvironments, describing the mechanisms by which NNMT contributes to cancer initiation, proliferation, and metastasis, as well as targeted therapies. Additionally, we discuss the future opportunities and challenges of NNMT in targeted anti-cancer treatments.

The role of CYP-sEH derived lipid mediators in regulating mitochondrial biology and cellular senescence: implications for the aging heart

Cellular senescence is a condition characterized by stable, irreversible cell cycle arrest linked to the aging process. The accumulation of senescent cells in the cardiac muscle can contribute to various cardiovascular diseases (CVD). Telomere shortening, epigenetic modifications, DNA damage, mitochondrial dysfunction, and oxidative stress are known contributors to the onset of cellular senescence in the heart. The link between mitochondrial processes and cellular senescence contributed to the age-related decline in cardiac function. These include changes in mitochondrial functions and behaviours that arise from various factors, including impaired dynamics, dysregulated biogenesis, mitophagy, mitochondrial DNA (mtDNA), reduced respiratory capacity, and mitochondrial structural changes. Thus, regulation of mitochondrial biology has a role in cellular senescence and cardiac function in aging hearts. Targeting senescent cells may provide a novel therapeutic approach for treating and preventing CVD associated with aging. CYP epoxygenases metabolize N-3 and N-6 polyunsaturated fatty acids (PUFA) into epoxylipids that are readily hydrolyzed to diol products by soluble epoxide hydrolase (sEH). Increasing epoxylipids levels or inhibition of sEH has demonstrated protective effects in the aging heart. Evidence suggests they may play a role in cellular senescence by regulating mitochondria, thus reducing adverse effects of aging in the heart. In this review, we discuss how mitochondria induce cellular senescence and how epoxylipids affect the senescence process in the aged heart.

Hydrogen sulfide mitigates mitochondrial dysfunction and cellular senescence in diabetic patients: Potential therapeutic applications

Diabetes induces a pro-aging state characterized by an increased abundance of senescent cells in various tissues, heightened chronic inflammation, reduced substance and energy metabolism, and a significant increase in intracellular reactive oxygen species (ROS) levels. This condition leads to mitochondrial dysfunction, including elevated oxidative stress, the accumulation of mitochondrial DNA (mtDNA) damage, mitophagy defects, dysregulation of mitochondrial dynamics, and abnormal energy metabolism. These dysfunctions result in intracellular calcium ion (Ca2+) homeostasis disorders, telomere shortening, immune cell damage, and exacerbated inflammation, accelerating the aging of diabetic cells or tissues. Hydrogen sulfide (H2S), a novel gaseous signaling molecule, plays a crucial role in maintaining mitochondrial function and mitigating the aging process in diabetic cells. This article systematically explores the specific mechanisms by which H2S regulates diabetes-induced mitochondrial dysfunction to delay cellular senescence, offering a promising new strategy for improving diabetes and its complications.

A Redox-Shifted Fibroblast Subpopulation Emerges in the Fibrotic Lung

Idiopathic pulmonary fibrosis (IPF) is an aggressive and, thus far, incurable disease characterized by aberrant fibroblast-mediated extracellular matrix deposition. Our understanding of the disease etiology is incomplete; however, there is consensus that a reduction-oxidation (redox) imbalance plays a role. In this study, we use the autofluorescent properties of two redox molecules, NAD(P)H and FAD, to quantify changes in their relative abundance in living lung tissue of mice with experimental lung fibrosis and in freshly isolated cells from mouse lungs and humans with IPF. Our results identify cell population-specific intracellular redox changes in the lungs in experimental and human fibrosis. We focus particularly on redox changes within collagen-producing cells, where we identified a bimodal distribution of NAD(P)H concentrations, establishing NAD(P)Hhigh and NAD(P)Hlow subpopulations. NAD(P)Hhigh fibroblasts exhibited elevated profibrotic gene expression and decreased collagenolytic protease activity relative to NAD(P)Hlow fibroblasts. The NAD(P)Hhigh population was present in healthy lungs but expanded with time after bleomycin injury, suggesting a potential role in fibrosis progression. We identified a similar increased abundance of NAD(P)Hhigh cells in freshly dissociated lungs of subjects with IPF relative to control subjects, as well as similar reductions in collagenolytic activity in this cell population. These data highlight the complexity of redox state changes in experimental and human pulmonary fibrosis and the need for selective approaches to restore redox imbalances in the fibrotic lung.

Is there a rationale for hyperbaric oxygen therapy in the patients with Post COVID syndrome? : A critical review

The SARS-CoV-2 pandemic has resulted in 762 million infections worldwide from 2020 to date, of which approximately ten percent are suffering from the effects after infection in 2019 (COVID-19) [1, 40]. In Germany, it is now assumed that at least one million people suffer from post-COVID condition with long-term consequences. These have been previously reported in diseases like Myalgic Encephalomyelitis (ME) and Chronic Fatigue Syndrome (CFS). Symptoms show a changing variability and recent surveys in the COVID context indicate that 10-30 % of outpatients, 50 to 70% of hospitalised patients suffer from sequelae. Recent data suggest that only 13% of all ill people were completely free of symptoms after recovery [3, 9]. Current hypotheses consider chronic inflammation, mitochondrial dysfunction, latent viral persistence, autoimmunity, changes of the human microbiome or multilocular sequelae in various organ system after infection. Hyperbaric oxygen therapy (HBOT) is applied since 1957 for heart surgery, scuba dive accidents, CO intoxication, air embolisms and infections with anaerobic pathogens. Under hyperbaric pressure, oxygen is physically dissolved in the blood in higher concentrations and reaches levels four times higher than under normobaric oxygen application. Moreover, the alternation of hyperoxia and normoxia induces a variety of processes at the cellular level, which improves oxygen supply in areas of locoregional hypoxia. Numerous target gene effects on new vessel formation, anti-inflammatory and anti-oedematous effects have been demonstrated [74]. The provision of intermittently high, local oxygen concentrations increases repair and regeneration processes and normalises the predominance of hyperinflammation. At present time only one prospective, randomized and placebo-controlled study exists with positive effects on global cognitive function, attention and executive function, psychiatric symptoms and pain interference. In conclusion, up to this date HBO is the only scientifically proven treatment in a prospective randomized controlled trial to be effective for cognitive improvement, regeneration of brain network and improvement of cardiac function. HBOT may have not only theoretical but also potential impact on targets of current pathophysiology of Post COVID condition, which warrants further scientific studies in patients.

Subcellular NAD+ pools are interconnected and buffered by mitochondrial NAD. Nat Metab 2024;6:2319-2337. [PMID: 39702414 DOI: 10.1038/s42255-024-01174-w]

The coenzyme NAD+ is consumed by signalling enzymes, including poly-ADP-ribosyltransferases (PARPs) and sirtuins. Ageing is associated with a decrease in cellular NAD+ levels, but how cells cope with persistently decreased NAD+ concentrations is unclear. Here, we show that subcellular NAD+ pools are interconnected, with mitochondria acting as a rheostat to maintain NAD+ levels upon excessive consumption. To evoke chronic, compartment-specific overconsumption of NAD+, we engineered cell lines stably expressing PARP activity in mitochondria, the cytosol, endoplasmic reticulum or peroxisomes, resulting in a decline of cellular NAD+ concentrations by up to 50%. Isotope-tracer flux measurements and mathematical modelling show that the lowered NAD+ concentration kinetically restricts NAD+ consumption to maintain a balance with the NAD+ biosynthesis rate, which remains unchanged. Chronic NAD+ deficiency is well tolerated unless mitochondria are directly targeted. Mitochondria maintain NAD+ by import through SLC25A51 and reversibly cleave NAD+ to nicotinamide mononucleotide and ATP when NMNAT3 is present. Thus, these organelles can maintain an additional, virtual NAD+ pool. Our results are consistent with a well-tolerated ageing-related NAD+ decline as long as the vulnerable mitochondrial pool is not directly affected.

Synergistic ROS Reduction Through the Co-Inhibition of BRAF and p38 MAPK Ameliorates Senescence

Reactive oxygen species (ROS)-mediated damage to macromolecules and cellular organelles is one of the major causes of senescence. Therapeutic strategies that lower ROS levels have been proposed as important treatments for senescence, but effective mechanisms for reducing ROS levels have not been discovered. Here, we aimed to find a combination that has a synergistic effect on ROS reduction using senomorphics known to reduce ROS. Combination treatment with BRAF inhibitor SB590885 and p38 MAPK inhibitor SB203580 showed a synergistic effect on ROS reduction compared to treatment with either drug alone. The synergistic effect of ROS reduction through this combination led to a synergistic effect that restored mitochondrial function and ameliorated senescence-associated phenotypes. To elucidate the underlying mechanism by which the synergistic effect of the two drugs reverses senescence, we performed RNA sequencing and identified metallothionein 2A (MT2A) as a key gene. MT2A was upregulated in response to combination therapy, and overexpression of MT2A led to a decrease in ROS and subsequent recovery of senescence-associated phenotypes, similar to the effects of combination therapy. Taken together, we found a drug combination that showed synergistic effects on ROS reduction, which contributed to the recovery of senescence-associated phenotypes through MT2A gene regulation. This study opens up a new avenue in aging research by demonstrating that combination therapy with existing senomorphics can enhance the ability to reverse senescence and that similar reversal effects can be achieved through gene regulation regulated by combination therapy.

The Aging Stomach: Clinical Implications of H. pylori Infection in Older Adults-Challenges and Strategies for Improved Management

Aging is a multifactorial biological process characterized by a decline in physiological function and increasing susceptibility to various diseases, including malignancies and gastrointestinal disorders. Helicobacter pylori (H. pylori) infection is highly prevalent among older adults, particularly those in institutionalized settings, contributing to conditions such as atrophic gastritis, peptic ulcer disease, and gastric carcinoma. This review examines the intricate interplay between aging, gastrointestinal changes, and H. pylori pathogenesis. The age-associated decline in immune function, known as immunosenescence, exacerbates the challenges of managing H. pylori infection. Comorbidities and polypharmacy further increase the risk of adverse outcomes in older adults. Current clinical guidelines inadequately address the specific needs of the geriatric population, who are disproportionately affected by antibiotic resistance, heightened side effects, and diagnostic complexities. This review focuses on recent advancements in understanding H. pylori infection among older adults, including epidemiology, diagnostics, therapeutic strategies, and age-related gastric changes. Diagnostic approaches must consider the physiological changes that accompany aging, and treatment regimens need to be carefully tailored to balance efficacy and tolerability. Emerging strategies, such as novel eradication regimens and adjunctive probiotic therapies, show promise for improving treatment outcomes. However, significant knowledge gaps persist regarding the impact of aging on H. pylori pathogenesis and treatment efficacy. A multidisciplinary approach involving gastroenterologists, geriatricians, and other specialists is crucial to providing comprehensive care for this vulnerable population. Future research should focus on refining diagnostic and therapeutic protocols to bridge these gaps, ultimately enhancing clinical outcomes and reducing the burden of H. pylori-associated diseases in the aging population.

Nicotinamide Riboside and CD38: Covalent Inhibition and Live-Cell Labeling

Nicotinamide adenine dinucleotide (NAD+) is required for a myriad of metabolic, signaling, and post-translational events in cells. Its levels in tissues and organs are closely associated with health conditions. The homeostasis of NAD+ is regulated by biosynthetic pathways and consuming enzymes. As a membrane-bound protein with robust NAD+ hydrolase activity, cluster of differentiation 38 (CD38) is a major degrader of NAD+. Deficiency or inhibition of CD38 enhances NAD+ levels in vivo, resulting in various therapeutic benefits. As a metabolic precursor of NAD+, nicotinamide mononucleotide can be rapidly hydrolyzed by CD38, whereas nicotinamide riboside (NR) lacks CD38 substrate activity. Given their structural similarities, we explored the inhibition potential of NR. To our surprise, NR exhibits marked inhibitory activity against CD38 by forming a stable ribosyl-ester bond with the glutamate residue 226 at the active site. Inspired by this discovery, we designed and synthesized a clickable NR featuring an azido substitution at the 5'-OH position. This cell-permeable NR analogue enables covalent labeling and imaging of both extracellular and intracellular CD38 in live cells. Our work discovers an unrecognized molecular function of NR and generates a covalent probe for health-related CD38. These findings offer new insights into the role of NR in modulating NAD+ metabolism and CD38-mediated signaling as well as an innovative tool for in-depth studies of CD38 in physiology and pathophysiology.

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

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

Characteristics and mechanisms of T-cell senescence: A potential target for cancer immunotherapy

Immunosenescence, the aging of the immune system, leads to functional deficiencies, particularly in T cells, which undergo significant changes. While numerous studies have investigated age-related T-cell phenotypes in healthy aging, senescent T cells have also been observed in younger populations during pathological conditions like cancer. This review summarizes the recent advancements in age-associated alterations and markers of T cells, mechanisms, and the relationship between senescent T cells and the tumor microenvironment. We also discuss potential strategies for targeting senescent T cells to prevent age-related diseases and enhance tumor immunotherapy efficacy.

Single-cell profiling of trabecular meshwork identifies mitochondrial dysfunction in a glaucoma model that is protected by vitamin B3 treatment

Since the trabecular meshwork (TM) is central to intraocular pressure (IOP) regulation and glaucoma, a deeper understanding of its genomic landscape is needed. We present a multimodal, single-cell resolution analysis of mouse limbal cells (includes TM). In total, we sequenced 9,394 wild-type TM cell transcriptomes. We discovered three TM cell subtypes with characteristic signature genes validated by immunofluorescence on tissue sections and whole-mounts. The subtypes are robust, being detected in datasets for two diverse mouse strains and in independent data from two institutions. Results show compartmentalized enrichment of critical pathways in specific TM cell subtypes. Distinctive signatures include increased expression of genes responsible for 1) extracellular matrix structure and metabolism (TM1 subtype), 2) secreted ligand signaling to support Schlemm's canal cells (TM2), and 3) contractile and mitochondrial/metabolic activity (TM3). ATAC-sequencing data identified active transcription factors in TM cells, including LMX1B. Mutations in LMX1B cause high IOP and glaucoma. LMX1B is emerging as a key transcription factor for normal mitochondrial function and its expression is much higher in TM3 cells than other limbal cells. To understand the role of LMX1B in TM function and glaucoma, we single-cell sequenced limbal cells from Lmx1b V265D/+ mutant mice. In V265D/+ mice, TM3 cells were uniquely affected by pronounced mitochondrial pathway changes. This supports a primary role of mitochondrial dysfunction within TM3 cells in initiating the IOP elevation that causes glaucoma in these mice. Importantly, treatment with vitamin B 3 (nicotinamide), to enhance mitochondrial function and metabolic resilience, significantly protected Lmx1b mutant mice from IOP elevation.

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

SCOPE

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

METHODS AND RESULTS

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

CONCLUSIONS

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

The role of phagocytic cells in aging: insights from vertebrate and invertebrate models

While the main role of phagocytic scavenger cells consists of the neutralization and elimination of pathogens, they also keep the body fluids clean by taking up and breaking down waste material. Since a build-up of waste is thought to contribute to the aging process, these cells become particularly pertinent in the research field of aging. Nevertheless, a direct link between their scavenging functions and the aging process has yet to be established. Integrative approaches involving various model organisms hold promise to elucidate this potential, but are lagging behind since the diversity and evolutionary relationship of these cells across animal species remain unclear. In this perspective, we review the current knowledge associating phagocytic scavenger cells with aging in vertebrate and invertebrate animals, as well as put forward important questions for further exploration. Additionally, we highlight future challenges and propose a constructive approach for tackling them.

Branched-chain α-ketoacids aerobically activate HIF1α signalling in vascular cells

Hypoxia-inducible factor 1α (HIF1α) is a master regulator of biological processes in hypoxia. Yet, the mechanisms and biological consequences of aerobic HIF1α activation by intrinsic factors, particularly in normal (primary) cells, remain elusive. Here we show that HIF1α signalling is activated in several human primary vascular cells in normoxia and in vascular smooth muscle cells of normal human lungs. Mechanistically, aerobic HIF1α activation is mediated by paracrine secretion of three branched-chain α-ketoacids (BCKAs), which suppress PHD2 activity via direct inhibition and via LDHA-mediated generation of L-2-hydroxyglutarate. BCKA-mediated HIF1α signalling activation stimulated glycolytic activity and governed a phenotypic switch of pulmonary artery smooth muscle cells, which correlated with BCKA metabolic dysregulation and pathophenotypic changes in pulmonary arterial hypertension patients and male rat models. We thus identify BCKAs as previously unrecognized signalling metabolites that aerobically activate HIF1α and that the BCKA-HIF1α pathway modulates vascular smooth muscle cell function, an effect that may be relevant to pulmonary vascular pathobiology.

Hypoxia-mediated rescue of retinal ganglion cells deficient in mitochondrial complex I is independent of the hypoxia-inducible factor pathway

Continuous exposure to environmental hypoxia (11% O2) has been shown to markedly slow the progressive degeneration of retinal ganglion cells (RGCs) in a mouse model of mitochondrial optic neuropathy with RGC-specific deletion of the key mitochondrial complex I accessory subunit ndufs4. As a first step toward identifying the therapeutic mechanism of hypoxia in this model, we conducted a series of experiments to investigate the role of the hypoxia-inducible factor (HIF) regulatory pathway in RGC neuroprotection. Vglut2-Cre; ndufs4loxP/loxP mice were crossed with strains bearing floxed alleles of the negative HIF regulatory vhl or of the two major HIF α-subunit isoforms, Hif1α and Hif2α. Deletion of vhl within ndufs4-deficient RGCs failed to prevent RGC degeneration under normoxia, indicating that HIF activation is not sufficient to achieve RGC rescue. Furthermore, the rescue of ndufs4-deficient RGCs by hypoxia remained robust despite genetic inactivation of Hif1α and Hif2α. Our findings demonstrate that the HIF pathway is entirely dispensable to the rescue of RGCs by hypoxia. Future efforts to uncover key HIF-independent molecular pathways induced by hypoxia in this mouse model may be of therapeutic relevance to mitochondrial optic neuropathies such as Leber hereditary optic neuropathy.

Crocetin Delays Brain and Body Aging by Increasing Cellular Energy Levels in Aged C57BL/6J Mice

Aging is usually accompanied by mitochondrial dysfunction, reduced energy levels, and cell death in the brain and other tissues. Mitochondria play a crucial role in maintaining cellular energy through oxidative phosphorylation (OXPHOS). However, OXPHOS is impaired as the mitochondrial oxygen supply decreases with age. We explored whether pharmacologically increased oxygen diffusion by crocetin can restore OXPHOS and help delay the aging of the brain and other vital organs. We found that aged mice treated with crocetin for four months displayed significantly improved memory behavior, neuromuscular coordination, and ATP and NAD+ levels in the brain and other vital organs, leading to an increased median life span. The transcriptomic analysis of hippocampi from crocetin-treated mice revealed that enhanced brain energy level was caused by the upregulation of genes linked to OXPHOS, and their expression was close to that in young mice. The chronic treatment of aged astrocytes also showed improved mitochondrial membrane potential and energy state of the cells. Moreover, chronic treatment with crocetin did not cause any oxidative stress. Our data suggest that restoring OXPHOS and the normal energy state of the cell can delay aging and enhance longevity. Therefore, molecules such as crocetin should be further explored to treat age-related diseases.

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

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

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.