Urolithin A improves Alzheimer's disease cognition and restores mitophagy and lysosomal functions

BACKGROUND

Compromised autophagy, including impaired mitophagy and lysosomal function, plays pivotal roles in Alzheimer's disease (AD). Urolithin A (UA) is a gut microbial metabolite of ellagic acid that stimulates mitophagy. The effects of UA's long-term treatment of AD and mechanisms of action are unknown.

METHODS

We addressed these questions in three mouse models of AD with behavioral, electrophysiological, biochemical, and bioinformatic approaches.

RESULTS

Long-term UA treatment significantly improved learning, memory, and olfactory function in different AD transgenic mice. UA also reduced amyloid beta (Aβ) and tau pathologies and enhanced long-term potentiation. UA induced mitophagy via increasing lysosomal functions. UA improved cellular lysosomal function and normalized lysosomal cathepsins, primarily cathepsin Z, to restore lysosomal function in AD, indicating the critical role of cathepsins in UA-induced therapeutic effects on AD.

CONCLUSIONS

Our study highlights the importance of lysosomal dysfunction in AD etiology and points to the high translational potential of UA.

HIGHLIGHTS

Long-term urolithin A (UA) treatment improved learning, memory, and olfactory function in Alzheimer's disease (AD) mice. UA restored lysosomal functions in part by regulating cathepsin Z (Ctsz) protein. UA modulates immune responses and AD-specific pathophysiological pathways.

Meeting Summary of The NYO3 5th NO-Age/AD Meeting and the 1st Norway-UK Joint Meeting on Aging and Dementia: Recent Progress on the Mechanisms and Interventional Strategies

Unhealthy aging poses a global challenge with profound healthcare and socioeconomic implications. Slowing down the aging process offers a promising approach to reduce the burden of a number of age-related diseases, such as dementia, and promoting healthy longevity in the old population. In response to the challenge of the aging population and with a view to the future, Norway and the United Kingdom are fostering collaborations, supported by a "Money Follows Cooperation agreement" between the 2 nations. The inaugural Norway-UK joint meeting on aging and dementia gathered leading experts on aging and dementia from the 2 nations to share their latest discoveries in related fields. Since aging is an international challenge, and to foster collaborations, we also invited leading scholars from 11 additional countries to join this event. This report provides a summary of the conference, highlighting recent progress on molecular aging mechanisms, genetic risk factors, DNA damage and repair, mitophagy, autophagy, as well as progress on a series of clinical trials (eg, using NAD+ precursors). The meeting facilitated dialogue among policymakers, administrative leaders, researchers, and clinical experts, aiming to promote international research collaborations and to translate findings into clinical applications and interventions to advance healthy aging.

Alzheimer's disease diagnostic accuracy by fluid and neuroimaging ATN framework

OBJECTIVES

The ATN's different modalities (fluids and neuroimaging) for each of the Aβ (A), tau (T), and neurodegeneration (N) elements are used for the biological diagnosis of Alzheimer's disease (AD). We aim to identify which ATN category achieves the highest potential for diagnosis and predictive accuracy of longitudinal cognitive decline.

METHODS

Based on the availability of plasma ATN biomarkers (plasma-derived Aβ42/40 , p-tau181, NFL, respectively), CSF ATN biomarkers (CSF-derived Aβ42 /Aβ40 , p-tau181, NFL), and neuroimaging ATN biomarkers (18F-florbetapir (FBP) amyloid-PET, 18F-flortaucipir (FTP) tau-PET, and fluorodeoxyglucose (FDG)-PET), a total of 2340 participants were selected from ADNI.

RESULTS

Our data analysis indicates that the area under curves (AUCs) of CSF-A, neuroimaging-T, and neuroimaging-N were ranked the top three ATN candidates for accurate diagnosis of AD. Moreover, neuroimaging ATN biomarkers display the best predictive ability for longitudinal cognitive decline among the three categories. To note, neuroimaging-T correlates well with cognitive performances in a negative correlation manner. Meanwhile, participants in the "N" element positive group, especially the CSF-N positive group, experience the fastest cognitive decline compared with other groups defined by ATN biomarkers. In addition, the voxel-wise analysis showed that CSF-A related to tau accumulation and FDG-PET indexes more strongly in subjects with MCI stage. According to our analysis of the data, the best three ATN candidates for a precise diagnosis of AD are CSF-A, neuroimaging-T, and neuroimaging-N.

CONCLUSIONS

Collectively, our findings suggest that plasma, CSF, and neuroimaging biomarkers differ considerably within the ATN framework; the most accurate target biomarkers for diagnosing AD were the CSF-A, neuroimaging-T, and neuroimaging-N within each ATN modality. Moreover, neuroimaging-T and CSF-N both show excellent ability in the prediction of cognitive decline in two different dimensions.

Long-Term Nicotinamide Riboside Use Improves Coordination and Eye Movements in Ataxia Telangiectasia

BACKGROUND

Supplementation of nicotinamide riboside (NR) ameliorates neuropathology in animal models of ataxia telangiectasia (A-T). In humans, short-term NR supplementation showed benefits in neurological outcome.

OBJECTIVES

The study aimed to investigate the safety and benefits of long-term NR supplementation in individuals with A-T.

METHODS

A single-arm, open-label clinical trial was performed in individuals with A-T, receiving NR over a period of 2 years. Biomarkers and clinical examinations were used to assess safety parameters. Standardized and validated neuromotor tests were used to monitor changes in neurological symptoms. Using generalized mixed models, test results were compared to expected disease progression based on historical data.

RESULTS

NAD+ concentrations increased rapidly in peripheral blood and stabilized at a higher level than baseline. NR supplementation was well tolerated for most participants. The total scores in the neuromotor test panels, as evaluated at the 18-month time point, improved for all but one participant, primarily driven by improvements in coordination subscores and eye movements. A comparison with historical data revealed that the progression of certain neuromotor symptoms was slower than anticipated.

CONCLUSIONS

Long-term use of NR appears to be safe and well tolerated, and it improves motor coordination and eye movements in patients with A-T of all ages. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Roles of NAD+ in Health and Aging

NAD+, the essential metabolite involved in multiple reactions such as the regulation of cellular metabolism, energy production, DNA repair, mitophagy and autophagy, inflammation, and neuronal function, has been the subject of intense research in the field of aging and disease over the last decade. NAD+ levels decline with aging and in some age-related diseases, and reduction in NAD+ affects all the hallmarks of aging. Here, we present an overview of the discovery of NAD+, the cellular pathways of producing and consuming NAD+, and discuss how imbalances in the production rate and cellular request of NAD+ likely contribute to aging and age-related diseases including neurodegeneration. Preclinical studies have revealed great potential for NAD+ precursors in promotion of healthy aging and improvement of neurodegeneration. This has led to the initiation of several clinical trials with NAD+ precursors to treat accelerated aging, age-associated dysfunctions, and diseases including Alzheimer's and Parkinson's. NAD supplementation has great future potential clinically, and these studies will also provide insight into the mechanisms of aging.

TRPM2 as a conserved gatekeeper determines the vulnerability of DA neurons by mediating ROS sensing and calcium dyshomeostasis

Different dopaminergic (DA) neuronal subgroups exhibit distinct vulnerability to stress, while the underlying mechanisms are elusive. Here we report that the transient receptor potential melastatin 2 (TRPM2) channel is preferentially expressed in vulnerable DA neuronal subgroups, which correlates positively with aging in Parkinson's Disease (PD) patients. Overexpression of human TRPM2 in the DA neurons of C. elegans resulted in selective death of ADE but not CEP neurons in aged worms. Mechanistically, TRPM2 activation mediates FZO-1/CED-9-dependent mitochondrial hyperfusion and mitochondrial permeability transition (MPT), leading to ADE death. In mice, TRPM2 knockout reduced vulnerable substantia nigra pars compacta (SNc) DA neuronal death induced by stress. Moreover, the TRPM2-mediated vulnerable DA neuronal death pathway is conserved from C. elegans to toxin-treated mice model and PD patient iPSC-derived DA neurons. The vulnerable SNc DA neuronal loss is the major symptom and cause of PD, and therefore the TRPM2-mediated pathway serves as a promising therapeutic target against PD.

A comprehensive AI-driven analysis of large-scale omic datasets reveals novel dual-purpose targets for the treatment of cancer and aging

As aging and tumorigenesis are tightly interconnected biological processes, targeting their common underlying driving pathways may induce dual-purpose anti-aging and anti-cancer effects. Our transcriptomic analyses of 16,740 healthy samples demonstrated tissue-specific age-associated gene expression, with most tumor suppressor genes downregulated during aging. Furthermore, a large-scale pan-cancer analysis of 11 solid tumor types (11,303 cases and 4431 control samples) revealed that many cellular processes, such as protein localization, DNA replication, DNA repair, cell cycle, and RNA metabolism, were upregulated in cancer but downregulated in healthy aging tissues, whereas pathways regulating cellular senescence were upregulated in both aging and cancer. Common cancer targets were identified by the AI-driven target discovery platform-PandaOmics. Age-associated cancer targets were selected and further classified into four groups based on their reported roles in lifespan. Among the 51 identified age-associated cancer targets with anti-aging experimental evidence, 22 were proposed as dual-purpose targets for anti-aging and anti-cancer treatment with the same therapeutic direction. Among age-associated cancer targets without known lifespan-regulating activity, 23 genes were selected based on predicted dual-purpose properties. Knockdown of histone demethylase KDM1A, one of these unexplored candidates, significantly extended lifespan in Caenorhabditis elegans. Given KDM1A's anti-cancer activities reported in both preclinical and clinical studies, our findings propose KDM1A as a promising dual-purpose target. This is the first study utilizing an innovative AI-driven approach to identify dual-purpose target candidates for anti-aging and anti-cancer treatment, supporting the value of AI-assisted target identification for drug discovery.

Chemical mitophagy modulators: Drug development strategies and novel regulatory mechanisms

Maintaining mitochondrial homeostasis is a potential therapeutic strategy for various diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic disorders, and cancer. Selective degradation of mitochondria by autophagy (mitophagy) is a fundamental mitochondrial quality control mechanism conserved from yeast to humans. Indeed, small-molecule modulators of mitophagy are valuable pharmaceutical tools that can be used to dissect complex biological processes and turn them into potential drugs. In the past few years, pharmacological regulation of mitophagy has shown promising therapeutic efficacy in various disease models. However, with the increasing number of chemical mitophagy modulator studies, frequent methodological flaws can be observed, leading some studies to draw unreliable or misleading conclusions. This review attempts (a) to summarize the molecular mechanisms of mitophagy; (b) to propose a Mitophagy Modulator Characterization System (MMCS); (c) to perform a comprehensive analysis of methods used to characterize mitophagy modulators, covering publications over the past 20 years; (d) to provide novel targets for pharmacological intervention of mitophagy. We believe this review will provide a panorama of current research on chemical mitophagy modulators and promote the development of safe and robust mitophagy modulators with therapeutic potential by introducing high methodological standards.

Boosting NAD ameliorates hematopoietic impairment linked to short telomeres in vivo

Short telomeres are a defining feature of telomere biology disorders (TBDs), including dyskeratosis congenita (DC), for which there is no effective general cure. Patients with TBDs often experience bone marrow failure. NAD, an essential metabolic coenzyme, is decreased in models of DC. Herein, using telomerase reverse transcriptase null (Tert-/-) mice with critically short telomeres, we investigated the effect of NAD supplementation with the NAD precursor, nicotinamide riboside (NR), on features of health span disrupted by telomere impairment. Our results revealed that NR ameliorated body weight loss in Tert-/- mice and improved telomere integrity and telomere dysfunction-induced systemic inflammation. NR supplementation also mitigated myeloid skewing of Tert-/- hematopoietic stem cells. Furthermore, NR alleviated villous atrophy and inflammation in the small intestine of Tert-/- transplant recipient mice. Altogether, our findings support NAD intervention as a potential therapeutic strategy to enhance aspects of health span compromised by telomere attrition.

Cerebrospinal fluid quinolinic acid is strongly associated with delirium and mortality in hip-fracture patients

BACKGROUNDThe kynurenine pathway (KP) has been identified as a potential mediator linking acute illness to cognitive dysfunction by generating neuroactive metabolites in response to inflammation. Delirium (acute confusion) is a common complication of acute illness and is associated with increased risk of dementia and mortality. However, the molecular mechanisms underlying delirium, particularly in relation to the KP, remain elusive.METHODSWe undertook a multicenter observational study with 586 hospitalized patients (248 with delirium) and investigated associations between delirium and KP metabolites measured in cerebrospinal fluid (CSF) and serum by targeted metabolomics. We also explored associations between KP metabolites and markers of neuronal damage and 1-year mortality.RESULTSIn delirium, we found concentrations of the neurotoxic metabolite quinolinic acid in CSF (CSF-QA) (OR 2.26 [1.78, 2.87], P < 0.001) to be increased and also found increases in several other KP metabolites in serum and CSF. In addition, CSF-QA was associated with the neuronal damage marker neurofilament light chain (NfL) (β 0.43, P < 0.001) and was a strong predictor of 1-year mortality (HR 4.35 [2.93, 6.45] for CSF-QA ≥ 100 nmol/L, P < 0.001). The associations between CSF-QA and delirium, neuronal damage, and mortality remained highly significant following adjustment for confounders and multiple comparisons.CONCLUSIONOur data identified how systemic inflammation, neurotoxicity, and delirium are strongly linked via the KP and should inform future delirium prevention and treatment clinical trials that target enzymes of the KP.FUNDINGNorwegian Health Association and South-Eastern Norway Regional Health Authorities.

Professors Henriette van Praag and David Gems give the 2022 Nansen Neuroscience Lectures on "Is ageing inevitable?" in the Norwegian Academy of Science and Letters, Norway

 This is a summary of the 2022 Nansen Neuroscience Lectures. On 10 October 2022, Professors Henriette van Praag and David Gems gave the 2022 Nansen Neuroscience Lectures on the theme "Is ageing inevitable?" in the Norwegian Academy of Science and Letters, Oslo, Norway. While van Praag gave a lecture entitled "The benefits of exercise for brain function", Gems gave the 2^nd lecture discussing "What causes ageing? Lessons from The Worm". Understanding the fundamental mechanisms of ageing will pave the way to the development of future interventions to pre-empt the development of the diseases, including Alzheimer's disease and other dementias, of later life.

WIPI2 positively regulates mitophagy by promoting mitochondrial recruitment of VCP

The mammalian Atg18 ortholog WIPI2 is a key regulator of LC3 lipidation to promote autophagosome biogenesis during nonselective macroautophagy, while its functions in selective autophagy such as mitophagy remain largely unexplored. In this study, we explored the role of WIPI2 in PINK1-PRKN/parkin-mediated mitophagy. First, we found that WIPI2 is recruited to damaged mitochondria upon mitophagy induction. Second, loss of WIPI2 impedes mitochondrial damaging agents-induced mitophagy. Third, at molecular level, WIPI2 binds to and promotes AAA-ATPase VCP/p97 (valosin containing protein) to damaged mitochondria; and WIPI2 depletion blunts the recruitment of VCP to damaged mitochondria, leading to reduction in degradation of outer mitochondrial membrane (OMM) proteins and mitophagy. Finally, WIPI2 is implicated in cell fate decision as cells deficient in WIPI2 are largely resistant to cell death induced by mitochondrial damage. In summary, our study reveals a critical regulatory role of WIPI2 in mitochondrial recruitment of VCP to promote OMM protein degradation and eventual mitophagy.Abbreviations: ATG, autophagy related; CALCOCO2/NDP52, calcium binding and coiled-coil domain 2; CCCP, carbonyl cyanide chlorophenylhydrazone; CYCS, cytochrome c, somatic; HSPD1/HSP60, heat shock protein family D (Hsp60) member 1; IMM, inner mitochondrial membrane; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; NPLOC4, NPL4 homolog, ubiquitin recognition factor; OMM, outer mitochondrial membrane; OPTN, optineurin; PtdIns3P, phosphatidylinositol-3-phosphate; PINK1, PTEN induced kinase 1; PRKN/Parkin, parkin RBR E3 ubiquitin protein ligase; UBXN6/UBXD1, UBX domain protein 6; UFD1, ubiquitin recognition factor in ER associated degradation 1; VCP/p97, valosin containing protein; WIPI2, WD repeat domain, phosphoinositide interacting 2.

New hallmarks of ageing: a 2022 Copenhagen ageing meeting summary

Genomic instability, telomere attrition, epigenetic alterations, mitochondrial dysfunction, loss of proteostasis, deregulated nutrient-sensing, cellular senescence, stem cell exhaustion, and altered intercellular communication were the original nine hallmarks of ageing proposed by López-Otín and colleagues in 2013. The proposal of these hallmarks of ageing has been instrumental in guiding and pushing forward research on the biology of ageing. In the nearly past 10 years, our in-depth exploration on ageing research has enabled us to formulate new hallmarks of ageing which are compromised autophagy, microbiome disturbance, altered mechanical properties, splicing dysregulation, and inflammation, among other emerging ones. Amalgamation of the 'old' and 'new' hallmarks of ageing may provide a more comprehensive explanation of ageing and age-related diseases, shedding light on interventional and therapeutic studies to achieve healthy, happy, and productive lives in the elderly.

P. edulis Extract Protects Against Amyloid-β Toxicity in Alzheimer's Disease Models Through Maintenance of Mitochondrial Homeostasis via the FOXO3/DAF-16 Pathway

Alzheimer's disease (AD) is a common and devastating disease characterized by pathological aggregations of beta-amyloid (Aβ) plaques extracellularly, and Tau tangles intracellularly. While our understandings of the aetiologies of AD have greatly expanded over the decades, there is no drug available to stop disease progression. Here, we demonstrate the potential of Passiflora edulis (P. edulis) pericarp extract in protecting against Aβ-mediated neurotoxicity in mammalian cells and Caenorhabditis elegans (C. elegans) models of AD. We show P. edulis pericarp protects against memory deficit and neuronal loss, and promotes longevity in the Aβ model of AD via stimulation of mitophagy, a selective cellular clearance of damaged and dysfunctional mitochondria. P. edulis pericarp also restores memory and increases neuronal resilience in a C. elegans Tau model of AD. While defective mitophagy-induced accumulation of damaged mitochondria contributes to AD progression, P. edulis pericarp improves mitochondrial quality and homeostasis through BNIP3/DCT1-dependent mitophagy and SOD-3-dependent mitochondrial resilience, both via increased nuclear translocation of the upstream transcriptional regulator FOXO3/DAF-16. Further studies to identify active molecules in P. edulis pericarp that could maintain neuronal mitochondrial homeostasis may enable the development of potential drug candidates for AD.

A synergized machine learning plus cross-species wet-lab validation approach identifies neuronal mitophagy inducers inhibiting Alzheimer disease

Failed recognition and clearance of damaged mitochondria contributes to memory loss as well as Aβ and MAPT/Tau pathologies in Alzheimer disease (AD), for which there is an unmet therapeutic need. Restoring mitophagy to eliminate damaged mitochondria could abrogate metabolic dysfunction, neurodegeneration and may subsequently inhibit or slow down cognitive decline in AD models. We have developed a high-throughput machine-learning approach combined with a cross-species screening platform to discover novel mitophagy-inducing compounds from a natural product library and further experimentally validated the potential candidates. Two lead compounds, kaempferol and rhapontigenin, induce neuronal mitophagy and reduce Aβ and MAPT/Tau pathologies in a PINK1-dependent manner in both C. elegans and mouse models of AD. Our combinational approach provides a fast, cost-effective, and highly accurate method for identification of potent mitophagy inducers to maintain brain health.

Amelioration of Alzheimer's disease pathology by mitophagy inducers identified via machine learning and a cross-species workflow

A reduced removal of dysfunctional mitochondria is common to aging and age-related neurodegenerative pathologies such as Alzheimer’s disease (AD). Strategies for treating such impaired mitophagy would benefit from the identification of mitophagy modulators. Here we report the combined use of unsupervised machine learning (involving vector representations of molecular structures, pharmacophore fingerprinting and conformer fingerprinting) and a cross-species approach for the screening and experimental validation of new mitophagy-inducing compounds. From a library of naturally occurring compounds, the workflow allowed us to identify 18 small molecules, and among them two potent mitophagy inducers (Kaempferol and Rhapontigenin). In nematode and rodent models of AD, we show that both mitophagy inducers increased the survival and functionality of glutamatergic and cholinergic neurons, abrogated amyloid-β and tau pathologies, and improved the animals’ memory. Our findings suggest the existence of a conserved mechanism of memory loss across the AD models, this mechanism being mediated by defective mitophagy. The computational–experimental screening and validation workflow might help uncover potent mitophagy modulators that stimulate neuronal health and brain homeostasis.

Two potent mitophagy inducers, identified and characterized via unsupervised machine learning and a cross-species screening approach, ameliorated the pathology of Alzheimer’s disease in worms and mice.

Compromised autophagy and mitophagy in brain ageing and Alzheimer's diseases

Alzheimer's disease (AD) is one of the most persistent and devastating neurodegenerative disorders of old age, and is characterized clinically by an insidious onset and a gradual, progressive deterioration of cognitive abilities, ranging from loss of memory to impairment of judgement and reasoning. Despite years of research, an effective cure is still not available. Autophagy is the cellular 'garbage' clearance system which plays fundamental roles in neurogenesis, neuronal development and activity, and brain health, including memory and learning. A selective sub-type of autophagy is mitophagy which recognizes and degrades damaged or superfluous mitochondria to maintain a healthy and necessary cellular mitochondrial pool. However, emerging evidence from animal models and human samples suggests an age-dependent reduction of autophagy and mitophagy, which are also compromised in AD. Upregulation of autophagy/mitophagy slows down memory loss and ameliorates clinical features in animal models of AD. In this review, we give an overview of autophagy and mitophagy and their link to the progression of AD. We also summarize approaches to upregulate autophagy/mitophagy. We hypothesize that age-dependent compromised autophagy/mitophagy is a cause of brain ageing and a risk factor for AD, while restoration of autophagy/mitophagy to more youthful levels could return the brain to health.

Amyloid-β toxicity modulates tau phosphorylation through the PAX6 signalling pathway

The molecular link between amyloid-β plaques and neurofibrillary tangles, the two pathological hallmarks of Alzheimer's disease, is still unclear. Increasing evidence suggests that amyloid-β peptide activates multiple regulators of cell cycle pathways, including transcription factors CDKs and E2F1, leading to hyperphosphorylation of tau protein. However, the exact pathways downstream of amyloid-β-induced cell cycle imbalance are unknown. Here, we show that PAX6, a transcription factor essential for eye and brain development which is quiescent in adults, is increased in the brains of patients with Alzheimer's disease and in APP transgenic mice, and plays a key role between amyloid-β and tau hyperphosphorylation. Downregulation of PAX6 protects against amyloid-β peptide-induced neuronal death, suggesting that PAX6 is a key executor of the amyloid-β toxicity pathway. Mechanistically, amyloid-β upregulates E2F1, followed by the induction of PAX6 and c-Myb, while Pax6 is a direct target for both E2F1 and its downstream target c-Myb. Furthermore, PAX6 directly regulates transcription of GSK-3β, a kinase involved in tau hyperphosphorylation and neurofibrillary tangles formation, and its phosphorylation of tau at Ser356, Ser396 and Ser404. In conclusion, we show that signalling pathways that include CDK/pRB/E2F1 modulate neuronal death signals by activating downstream transcription factors c-Myb and PAX6, leading to GSK-3β activation and tau pathology, providing novel potential targets for pharmaceutical intervention.

GAK and PRKCD are positive regulators of PRKN-independent mitophagy

The mechanisms involved in programmed or damage-induced removal of mitochondria by mitophagy remains elusive. Here, we have screened for regulators of PRKN-independent mitophagy using an siRNA library targeting 197 proteins containing lipid interacting domains. We identify Cyclin G-associated kinase (GAK) and Protein Kinase C Delta (PRKCD) as regulators of PRKN-independent mitophagy, with both being dispensable for PRKN-dependent mitophagy and starvation-induced autophagy. We demonstrate that the kinase activity of both GAK and PRKCD are required for efficient mitophagy in vitro, that PRKCD is present on mitochondria, and that PRKCD facilitates recruitment of ULK1/ATG13 to early autophagic structures. Importantly, we demonstrate in vivo relevance for both kinases in the regulation of basal mitophagy. Knockdown of GAK homologue (gakh-1) in C. elegans or knockout of PRKCD homologues in zebrafish led to significant inhibition of basal mitophagy, highlighting the evolutionary relevance of these kinases in mitophagy regulation.

GAK and PRKCD are positive regulators of PRKN-independent mitophagy

The mechanisms involved in programmed or damage-induced removal of mitochondria by mitophagy remains elusive. Here, we have screened for regulators of PRKN-independent mitophagy using an siRNA library targeting 197 proteins containing lipid interacting domains. We identify Cyclin G-associated kinase (GAK) and Protein Kinase C Delta (PRKCD) as regulators of PRKN-independent mitophagy, with both being dispensable for PRKN-dependent mitophagy and starvation-induced autophagy. We demonstrate that the kinase activity of both GAK and PRKCD are required for efficient mitophagy in vitro, that PRKCD is present on mitochondria, and that PRKCD facilitates recruitment of ULK1/ATG13 to early autophagic structures. Importantly, we demonstrate in vivo relevance for both kinases in the regulation of basal mitophagy. Knockdown of GAK homologue (gakh-1) in C. elegans or knockout of PRKCD homologues in zebrafish led to significant inhibition of basal mitophagy, highlighting the evolutionary relevance of these kinases in mitophagy regulation.

Preclinical and clinical evidence of NAD+ precursors in health, disease, and ageing

NAD⁺ is a fundamental molecule in human life and health as it participates in energy metabolism, cell signalling, mitochondrial homeostasis, and in dictating cell survival or death. Emerging evidence from preclinical and human studies indicates an age-dependent reduction of cellular NAD⁺, possibly due to reduced synthesis and increased consumption. In preclinical models, NAD⁺ repletion extends healthspan and / or lifespan and mitigates several conditions, such as premature ageing diseases and neurodegenerative diseases. These findings suggest that NAD⁺ replenishment through NAD⁺ precursors has great potential as a therapeutic target for ageing and age-predisposed diseases, such as Alzheimer's disease. Here, we provide an updated review on the biological activity, safety, and possible side effects of NAD⁺ precursors in preclinical and clinical studies. Major NAD⁺ precursors focused on by this review are nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), and the new discovered dihydronicotinamide riboside (NRH). In summary, NAD⁺ precursors have an exciting therapeutic potential for ageing, metabolic and neurodegenerative diseases.

TNF-α-dependent neuronal necroptosis regulated in Alzheimer's disease by coordination of RIPK1-p62 complex with autophagic UVRAG

Background: Neuronal death is a major hallmark of Alzheimer's disease (AD). Necroptosis, as a programmed necrotic process, is activated in AD. However, what signals and factors initiate necroptosis in AD is largely unknown. Methods: We examined the expression levels of critical molecules in necroptotic signaling pathway by immunohistochemistry (IHC) staining and immunoblotting using brain tissues from AD patients and AD mouse models of APP/PS1 and 5×FAD. We performed brain stereotaxic injection with recombinant TNF-α, anti-TNFR1 neutralizing antibody or AAV-mediated gene expression and knockdown in APP/PS1 mice. For in vitro studies, we used TNF-α combined with zVAD-fmk and Smac mimetic to establish neuronal necroptosis models and utilized pharmacological or molecular biological approaches to study the signaling pathways. Results: We find that activated neuronal necroptosis is dependent on upstream TNF-α/TNFR1 signaling in both neuronal cell cultures and AD mouse models. Upon TNF-α stimulation, accumulated p62 recruits RIPK1 and induces its self-oligomerization, and activates downstream RIPK1/RIPK3/MLKL cascade, leading to neuronal necroptosis. Ectopic accumulation of p62 is caused by impaired autophagy flux, which is mediated by UVRAG downregulation during the TNF-α-promoted necroptosis. Notably, UVRAG overexpression inhibits neuronal necroptosis in cell and mouse models of AD. Conclusions: We identify a finely controlled regulation of neuronal necroptosis in AD by coordinated TNF-α signaling, RIPK1/3 activity and autophagy machinery. Strategies that could fine-tune necroptosis and autophagy may bring in promising therapeutics for AD.

Crosstalk among DNA Damage, Mitochondrial Dysfunction, Impaired Mitophagy, Stem Cell Attrition, and Senescence in the Accelerated Ageing Disorder Werner Syndrome

Werner syndrome (WS) is an accelerated ageing disease caused by multiple mutations in the gene encoding the Werner DNA helicase (WRN). The major clinical features of WS include wrinkles, grey hair, osteoporosis, and metabolic phenomena such as atherosclerosis, diabetes, and fatty liver, and resemble those seen in normal ageing, but occur earlier, in middle age. Defective DNA repair resulting from mutations in WRN explain the majority of the clinical features of WS, but the underlying mechanisms driving the larger metabolic dysfunction remain elusive. Recent studies in animal models of WS and in WS patient cells and blood samples suggest the involvement of impaired mitophagy, NAD+ depletion, and accumulation of damaged mitochondria in metabolic dysfunction. This mini-review summarizes recent progress in the understanding of the molecular mechanisms of metabolic dysfunction in WS, with the involvement of DNA damage, mitochondrial dysfunction, mitophagy reduction, stem cell impairment, and senescence. Future studies on NAD+ and mitophagy may shed light on potential therapeutic strategies for the WS patients.

Autophagy in healthy aging and disease

Autophagy is a fundamental cellular process that eliminates molecules and subcellular elements, including nucleic acids, proteins, lipids and organelles, via lysosome-mediated degradation to promote homeostasis, differentiation, development and survival. While autophagy is intimately linked to health, the intricate relationship among autophagy, aging and disease remains unclear. This Review examines several emerging features of autophagy and postulates how they may be linked to aging as well as to the development and progression of disease. In addition, we discuss current preclinical evidence arguing for the use of autophagy modulators as suppressors of age-related pathologies such as neurodegenerative diseases. Finally, we highlight key questions and propose novel research avenues that will likely reveal new links between autophagy and the hallmarks of aging. Understanding the precise interplay between autophagy and the risk of age-related pathologies across organisms will eventually facilitate the development of clinical applications that promote long-term health.

DNA Damage-Induced Neurodegeneration in Accelerated Ageing and Alzheimer's Disease

DNA repair ensures genomic stability to achieve healthy ageing, including cognitive maintenance. Mutations on genes encoding key DNA repair proteins can lead to diseases with accelerated ageing phenotypes. Some of these diseases are xeroderma pigmentosum group A (XPA, caused by mutation of XPA), Cockayne syndrome group A and group B (CSA, CSB, and are caused by mutations of CSA and CSB, respectively), ataxia-telangiectasia (A-T, caused by mutation of ATM), and Werner syndrome (WS, with most cases caused by mutations in WRN). Except for WS, a common trait of the aforementioned progerias is neurodegeneration. Evidence from studies using animal models and patient tissues suggests that the associated DNA repair deficiencies lead to depletion of cellular nicotinamide adenine dinucleotide (NAD⁺), resulting in impaired mitophagy, accumulation of damaged mitochondria, metabolic derailment, energy deprivation, and finally leading to neuronal dysfunction and loss. Intriguingly, these features are also observed in Alzheimer’s disease (AD), the most common type of dementia affecting more than 50 million individuals worldwide. Further studies on the mechanisms of the DNA repair deficient premature ageing diseases will help to unveil the mystery of ageing and may provide novel therapeutic strategies for AD.

Re-emphasizing early Alzheimer's disease pathology starting in select entorhinal neurons, with a special focus on mitophagy

The entorhinal-hippocampal system contains distinct networks subserving declarative memory. This system is selectively vulnerable to changes of ageing and pathological processes. The entorhinal cortex (EC) is a pivotal component of this memory system since it serves as the interface between the neocortex and the hippocampus. EC is heavily affected by the proteinopathies of Alzheimer's disease (AD). These appear in a stereotypical spatiotemporal manner and include increased levels of intracellular amyloid-beta Aβ (iAβ), parenchymal deposition of Aβ plaques, and neurofibrillary tangles (NFTs) containing abnormally processed Tau. Increased levels of iAβ and the formation of NFTs are seen very early on in a population of neurons belonging to EC layer II (EC LII), and recent evidence leads us to believe that this population is made up of highly energy-demanding reelin-positive (RE+) projection neurons. Mitochondria are fundamental to the energy supply, metabolism, and plasticity of neurons. Evidence from AD postmortem brain tissues supports the notion that mitochondrial dysfunction is one of the initial pathological events in AD, and this is likely to take place in the vulnerable RE + EC LII neurons. Here we review and discuss these notions, anchored to the anatomy of AD, and formulate a hypothesis attempting to explain the vulnerability of RE + EC LII neurons to the formation of NFTs. We attempt to link impaired mitochondrial clearance to iAβ and signaling involving both apolipoprotein 4 and reelin, and argue for their relevance to the formation of NFTs specifically in RE + EC LII neurons during the prodromal stages of AD. We believe future studies on these interactions holds promise to advance our understanding of AD etiology and provide new ideas for drug development.

A research agenda for ageing in China in the 21st century (2nd edition): Focusing on basic and translational research, long-term care, policy and social networks

One of the key issues facing public healthcare is the global trend of an increasingly ageing society which continues to present policy makers and caregivers with formidable healthcare and socio-economic challenges. Ageing is the primary contributor to a broad spectrum of chronic disorders all associated with a lower quality of life in the elderly. In 2019, the Chinese population constituted 18 % of the world population, with 164.5 million Chinese citizens aged 65 and above (65+), and 26 million aged 80 or above (80+). China has become an ageing society, and as it continues to age it will continue to exacerbate the burden borne by current family and public healthcare systems. Major healthcare challenges involved with caring for the elderly in China include the management of chronic non-communicable diseases (CNCDs), physical frailty, neurodegenerative diseases, cardiovascular diseases, with emerging challenges such as providing sufficient dental care, combating the rising prevalence of sexually transmitted diseases among nursing home communities, providing support for increased incidences of immune diseases, and the growing necessity to provide palliative care for the elderly. At the governmental level, it is necessary to make long-term strategic plans to respond to the pressures of an ageing society, especially to establish a nationwide, affordable, annual health check system to facilitate early diagnosis and provide access to affordable treatments. China has begun work on several activities to address these issues including the recent completion of the of the Ten-year Health-Care Reform project, the implementation of the Healthy China 2030 Action Plan, and the opening of the National Clinical Research Center for Geriatric Disorders. There are also societal challenges, namely the shift from an extended family system in which the younger provide home care for their elderly family members, to the current trend in which young people are increasingly migrating towards major cities for work, increasing reliance on nursing homes to compensate, especially following the outcomes of the 'one child policy' and the 'empty-nest elderly' phenomenon. At the individual level, it is important to provide avenues for people to seek and improve their own knowledge of health and disease, to encourage them to seek medical check-ups to prevent/manage illness, and to find ways to promote modifiable health-related behaviors (social activity, exercise, healthy diets, reasonable diet supplements) to enable healthier, happier, longer, and more productive lives in the elderly. Finally, at the technological or treatment level, there is a focus on modern technologies to counteract the negative effects of ageing. Researchers are striving to produce drugs that can mimic the effects of 'exercising more, eating less', while other anti-ageing molecules from molecular gerontologists could help to improve 'healthspan' in the elderly. Machine learning, 'Big Data', and other novel technologies can also be used to monitor disease patterns at the population level and may be used to inform policy design in the future. Collectively, synergies across disciplines on policies, geriatric care, drug development, personal awareness, the use of big data, machine learning and personalized medicine will transform China into a country that enables the most for its elderly, maximizing and celebrating their longevity in the coming decades. This is the 2nd edition of the review paper (Fang EF et al., Ageing Re. Rev. 2015).

Cockayne syndrome proteins CSA and CSB maintain mitochondrial homeostasis through NAD+ signaling

Cockayne syndrome (CS) is a rare premature aging disease, most commonly caused by mutations of the genes encoding the CSA or CSB proteins. CS patients display cachectic dwarfism and severe neurological manifestations and have an average life expectancy of 12 years. The CS proteins are involved in transcription and DNA repair, with the latter including transcription‐coupled nucleotide excision repair (TC‐NER). However, there is also evidence for mitochondrial dysfunction in CS, which likely contributes to the severe premature aging phenotype of this disease. While damaged mitochondria and impaired mitophagy were characterized in mice with CSB deficiency, such changes in the CS nematode model and CS patients are not fully known. Our cross‐species transcriptomic analysis in CS postmortem brain tissue, CS mouse, and nematode models shows that mitochondrial dysfunction is indeed a common feature in CS. Restoration of mitochondrial dysfunction through NAD⁺ supplementation significantly improved lifespan and healthspan in the CS nematodes, highlighting mitochondrial dysfunction as a major driver of the aging features of CS. In cerebellar samples from CS patients, we found molecular signatures of dysfunctional mitochondrial dynamics and impaired mitophagy/autophagy. In primary cells depleted for CSA or CSB, this dysfunction can be corrected with supplementation of NAD⁺ precursors. Our study provides support for the interconnection between major causative aging theories, DNA damage accumulation, mitochondrial dysfunction, and compromised mitophagy/autophagy. Together, these three agents contribute to an accelerated aging program that can be averted by cellular NAD⁺ restoration.

Iron out, mitophagy in! A way to slow down hepatocellular carcinoma

Mitochondrial homeostasis is necessary for the maintenance of cellular function and neuronal survival. Mitochondrial quality is tightly regulated by mitophagy, in which defective/superfluous mitochondria are degraded and recycled. Here, Hara et al demonstrate that induction of mitophagy via iron depletion suppresses the development of hepatocellular carcinoma (HCC). This work suggests turning up mitophagy as a potential therapeutic strategy against liver cancer.

Targeting NAD+ in translational research to relieve diseases and conditions of metabolic stress and ageing

Nicotinamide adenine dinucleotide (NAD+) plays a fundamental role in life and health through the regulation of energy biogenesis, redox homeostasis, cell metabolism, and the arbitration of cell survival via linkages to apoptosis and autophagic pathways. The importance of NAD+ in ageing and healthy longevity has been revealed from laboratory animal studies and early-stage clinical testing. While basic researchers and clinicians have investigated the molecular mechanisms and translation potential of NAD+, there are still major gaps in applying laboratory science to design the most effective trials. This mini-review was based on the programme and discussions of the 3rd NO-Age Symposium held at the Akershus University Hospital, Norway on the 28th October 2019. This symposium brought together leading basic researchers on NAD+ and clinicians who are leading or are going to perform NAD+ augmentation-related clinical studies. This meeting covered talks about NAD+ synthetic pathways, subcellular homeostasis of NAD+, the benefits of NAD+ augmentation from maternal milk to offspring, current clinical trials of the NAD+ precursor nicotinamide riboside (NR) on Ataxia-Telangiectasia (A-T), Parkinson's disease (PD), post-sepsis fatigue, as well as other potential NR-based clinical trials. Importantly, a consensus is emerging with respect to the design of clinical trials in order to measure meaningful parameters and ensure safety.

Culprit or Bystander: Defective Mitophagy in Alzheimer's Disease

Mitophagy is a selective engulfment and degradation of damaged mitochondria through the cellular autophagy machinery, a major mechanism responsible for mitochondrial quality control. Increased accumulation of damaged mitochondria in the Alzheimer's disease (AD) human brain are evident, although underlying mechanisms largely elusive. Recent studies indicate impaired mitophagy may contribute to the accumulation of damaged mitochondria in cross-species AD animal models and in AD patient iPSC-derived neurons. Studies from AD highlight feed-forward vicious cycles between defective mitophagy, and the principal AD pathological hallmarks, including amyloid-β plaques, tau tangles, and inflammation. The concomitant and intertwined connections among those hallmarks of AD and the absence of a real humanized AD rodent model present a challenge on how to determine if defective mitophagy is an early event preceding and causal of Tau/Aβ proteinopathies. Whilst further studies are required to understand these relationships, targeting defective mitophagy holds promise as a new therapeutic strategy for AD.

The NAD+-mitophagy axis in healthy longevity and in artificial intelligence-based clinical applications

Nicotinamide adenine dinucleotide (NAD+) is an important natural molecule involved in fundamental biological processes, including the TCA cycle, OXPHOS, β-oxidation, and is a co-factor for proteins promoting healthy longevity. NAD+ depletion is associated with the hallmarks of ageing and may contribute to a wide range of age-related diseases including metabolic disorders, cancer, and neurodegenerative diseases. One of the central pathways by which NAD+ promotes healthy ageing is through regulation of mitochondrial homeostasis via mitochondrial biogenesis and the clearance of damaged mitochondria via mitophagy. Here, we highlight the contribution of the NAD+-mitophagy axis to ageing and age-related diseases, and evaluate how boosting NAD+ levels may emerge as a promising therapeutic strategy to counter ageing as well as neurodegenerative diseases including Alzheimer's disease. The potential use of artificial intelligence to understand the roles and molecular mechanisms of the NAD+-mitophagy axis in ageing is discussed, including possible applications in drug target identification and validation, compound screening and lead compound discovery, biomarker development, as well as efficacy and safety assessment. Advances in our understanding of the molecular and cellular roles of NAD+ in mitophagy will lead to novel approaches for facilitating healthy mitochondrial homoeostasis that may serve as a promising therapeutic strategy to counter ageing-associated pathologies and/or accelerated ageing.

NAD+ augmentation restores mitophagy and limits accelerated aging in Werner syndrome

Metabolic dysfunction is a primary feature of Werner syndrome (WS), a human premature aging disease caused by mutations in the gene encoding the Werner (WRN) DNA helicase. WS patients exhibit severe metabolic phenotypes, but the underlying mechanisms are not understood, and whether the metabolic deficit can be targeted for therapeutic intervention has not been determined. Here we report impaired mitophagy and depletion of NAD+, a fundamental ubiquitous molecule, in WS patient samples and WS invertebrate models. WRN regulates transcription of a key NAD+ biosynthetic enzyme nicotinamide nucleotide adenylyltransferase 1 (NMNAT1). NAD+ repletion restores NAD+ metabolic profiles and improves mitochondrial quality through DCT-1 and ULK-1-dependent mitophagy. At the organismal level, NAD+ repletion remarkably extends lifespan and delays accelerated aging, including stem cell dysfunction, in Caenorhabditis elegans and Drosophila melanogaster models of WS. Our findings suggest that accelerated aging in WS is mediated by impaired mitochondrial function and mitophagy, and that bolstering cellular NAD+ levels counteracts WS phenotypes.

NAD+ in Brain Aging and Neurodegenerative Disorders

NAD⁺ is a pivotal metabolite involved in cellular bioenergetics, genomic stability, mitochondrial homeostasis, adaptive stress responses, and cell survival. Multiple NAD⁺-dependent enzymes are involved in synaptic plasticity and neuronal stress resistance. Here, we review emerging findings that reveal key roles for NAD⁺ and related metabolites in the adaptation of neurons to a wide range of physiological stressors and in counteracting processes in neurodegenerative diseases, such as those occurring in Alzheimer's, Parkinson's, and Huntington diseases, and amyotrophic lateral sclerosis. Advances in understanding the molecular and cellular mechanisms of NAD⁺-based neuronal resilience will lead to novel approaches for facilitating healthy brain aging and for the treatment of a range of neurological disorders.

Mitophagy and Neuroprotection

Neurodegenerative diseases are strongly age-related and currently cannot be cured, with a surge of patient numbers in the coming decades in view of the emerging worldwide ageing population, bringing healthcare and socioeconomic challenges. Effective therapies are urgently needed, and are dependent on new aetiological mechanisms. In neurons, efficient clearance of damaged mitochondria, through the highly evolutionary conserved cellular process termed mitophagy, plays a fundamental role in mitochondrial and metabolic homeostasis, energy supply, neuronal survival, and health. Conversely, defective mitophagy leads to accumulation of damaged mitochondria and cellular dysfunction, contributing to ageing and age-predisposed neurodegeneration. Here, we discuss the contribution of defective mitophagy in these diseases, and underlying molecular mechanisms, and highlight novel therapeutics based on new discovered mitophagy-inducing strategies.

Microglial mitophagy mitigates neuroinflammation in Alzheimer's disease

In neurons, defective mitophagy results in accumulation of damaged mitochondria, and finally leading to various neurodegenerative diseases, including Alzheimer's disease (AD). However, how mitophagy is defective in AD as well as how defective mitophagy contributes to AD is not fully understood. We give commentary on recent progress of this topic, highlighting the importance of mitophagy not only in neurons, but also in microglia, in forestalling pathology and cognitive decline in different animal models of AD.

Mitophagy and NAD+ inhibit Alzheimer disease

Our latest publication on the inhibition of Alzheimer disease (AD) through mitophagy consolidates the 'defective mitophagy hypothesis of AD etiology'. Dementia (majorly AD) affects over 50 million people worldwide, and for AD there is no cure. AD leads to progressive loss of cognition, and pathological hallmarks of AD include aggregates of amyloid-β peptides extracellularly and MAPT (microtubule associated protein tau) intracellularly. However, there is no conclusive link between these pathological markers and cognitive symptoms. Anti-AD drug candidates have repeatedly failed, which led us to investigate other molecular etiologies to guide drug development. Mitochondria produce the majority of cellular ATP, affect Ca²⁺ and redox signaling, and promote developmental and synaptic plasticity. Mitochondrial dysfunction and accumulation of damaged mitochondria are common in brain tissues from AD patients and transgenic AD animal models, but the underlying molecular mechanisms are not fully understood. Damaged mitochondria are removed through multiple pathways, the major 2 being mitophagy and the ubiquitin proteasome pathway. Mitophagy is essential for clearance of damaged mitochondria to maintain mitochondrial homeostasis, ATP production, and neuronal activity and survival. These pieces of evidence converge on the 'defective mitophagy hypothesis of AD etiology', and the current cross-species study provides strong support for this hypothesis.

Sarcopenia, Aging and Prospective Interventional Strategies

Sarcopenia, or age-related muscle decline, occurs in most organisms and burdens both human health and the healthcare system. As our population ages, additional options for treating sarcopenia are needed. Mitochondrial dysfunction is implicated in the onset of sarcopenia, so therapies directed at improving mitochondrial function in muscle should be considered. Many naturally-occurring compounds, derived from commonly consumed foods, possess anti-sarcopenic effects, such asnicotinamide riboside, tomatidine, and Urolithin A. These naturally-occurring compounds can improve mitochondrial health and efficiency by modulating mitochondrial biogenesis, cellular stress resistance, or mitophagy. Further research should assess whether compounds that improve mitochondrial health can attenuate sarcopenia in humans.

Vitamin D3 activates the autolysosomal degradation function against Helicobacter pylori through the PDIA3 receptor in gastric epithelial cells

Helicobacter pylori (H. pylori) is a common human pathogenic bacterium. Once infected, it is difficult for the host to clear this organism using the innate immune system. Increased antibiotic resistance further makes it challenging for effective eradication. However, the mechanisms of immune evasion still remain obscure, and novel strategies should be developed to efficiently eliminate H. pylori infection in stomachs. Here we uncovered desirable anti-H. pylori effect of vitamin D3 both in vitro and in vivo, even against antibiotic-resistant strains. We showed that H. pylori can invade into the gastric epithelium where they became sequestered and survived in autophagosomes with impaired lysosomal acidification. Vitamin D3 treatment caused a restored lysosomal degradation function by activating the PDIA3 receptor, thereby promoting the nuclear translocation of PDIA3-STAT3 protein complex and the subsequent upregulation of MCOLN3 channels, resulting in an enhanced Ca²⁺ release from lysosomes and normalized lysosomal acidification. The recovered lysosomal degradation function drives H. pylori to be eliminated through the autolysosomal pathway. These findings provide a novel pathogenic mechanism on how H. pylori can survive in the gastric epithelium, and a unique pathway for vitamin D3 to reactivate the autolysosomal degradation function, which is critical for the antibacterial action of vitamin D3 both in cells and in animals, and perhaps further in humans. Abbreviations: 1,25D3: 1α, 25-dihydroxyvitamin D3; ATG5: autophagy related 5; Baf A1: bafilomycin A₁; BECN1: beclin 1; CagA: cytotoxin-associated gene A; CFU: colony-forming unit; ChIP-PCR: chromatin immunoprecipitation-polymerase chain reaction; Con A: concanamycin A; CQ: chloroquine; CRISPR: clustered regularly interspaced short palindromic repeats; CTSD: cathepsin D; GPN: Gly-Phe-β-naphthylamide; H. pylori: Helicobacter pylori; LAMP1: lysosomal associated membrane protein 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MCOLN1: mucolipin 1; MCOLN3: mucolipin 3; MCU: mitochondrial calcium uniporter; MOI: multiplicity of infection; NAGLU: N-acetyl-alpha-glucosaminidase; PDIA3: protein disulfide isomerase family A member 3; PMA: phorbol 12-myristate 13-acetate; PRKC: protein kinase C; SQSTM1: sequestosome 1; STAT3: signal transducer and activator of transcription 3; SS1: Sydney Strain 1; TRP: transient receptor potential; VacA: vacuolating cytotoxin; VD3: vitamin D3; VDR: vitamin D receptor.

Nicotinamide Improves Aspects of Healthspan, but Not Lifespan, in Mice

The role in longevity and healthspan of nicotinamide (NAM), the physiological precursor of NAD⁺, is elusive. Here, we report that chronic NAM supplementation improves healthspan measures in mice without extending lifespan. Untargeted metabolite profiling of the liver and metabolic flux analysis of liver-derived cells revealed NAM-mediated improvement in glucose homeostasis in mice on a high-fat diet (HFD) that was associated with reduced hepatic steatosis and inflammation concomitant with increased glycogen deposition and flux through the pentose phosphate and glycolytic pathways. Targeted NAD metabolome analysis in liver revealed depressed expression of NAM salvage in NAM-treated mice, an effect counteracted by higher expression of de novo NAD biosynthetic enzymes. Although neither hepatic NAD⁺ nor NADP⁺ was boosted by NAM, acetylation of some SIRT1 targets was enhanced by NAM supplementation in a diet- and NAM dose-dependent manner. Collectively, our results show health improvement in NAM-supplemented HFD-fed mice in the absence of survival effects.

In Vitro and In Vivo Detection of Mitophagy in Human Cells, C. Elegans, and Mice

Mitochondria are the powerhouses of cells and produce cellular energy in the form of ATP. Mitochondrial dysfunction contributes to biological aging and a wide variety of disorders including metabolic diseases, premature aging syndromes, and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Maintenance of mitochondrial health depends on mitochondrial biogenesis and the efficient clearance of dysfunctional mitochondria through mitophagy. Experimental methods to accurately detect autophagy/mitophagy, especially in animal models, have been challenging to develop. Recent progress towards the understanding of the molecular mechanisms of mitophagy has enabled the development of novel mitophagy detection techniques. Here, we introduce several versatile techniques to monitor mitophagy in human cells, Caenorhabditis elegans (e.g., Rosella and DCT-1/ LGG-1 strains), and mice (mt-Keima). A combination of these mitophagy detection techniques, including cross-species evaluation, will improve the accuracy of mitophagy measurements and lead to a better understanding of the role of mitophagy in health and disease.