It takes two to tango: NAD+ and sirtuins in aging/longevity control

Sirtuins modulators mitigate hypoxia-induced cell death due to changes in histone 3 acetylation, and mitochondrial function, dynamics, and content

Hypoxia is a key environmental factor linked to neurodevelopmental complications, primarily through its impact on mitochondrial dysfunction. Given that sirtuins regulate mitochondrial and cellular metabolism, we aimed to investigate whether pharmacological modulation of sirtuins could protect neurons from hypoxia-induced mitochondrial dysfunction and cell death. To explore this, primary cortical neurons from male Wistar rats (control) and Spontaneously Hypertensive Rats (a model for neonatal hypoxia and schizophrenia) were exposed to cobalt chloride (CoCl2) to chemically induce hypoxia. Neurons were also treated with Nicotinamide (50 μM), Resveratrol (0.5 μM), and Sirtinol (5 μM) to modulate sirtuin activity. We first assessed histone deacetylation, cell death, mitochondrial calcium retention capacity, mitochondrial membrane potential, and levels of reactive oxygen species (ROS). In addition, we analysed the expression of genes related to mitochondrial metabolism, dynamics, and biogenesis, as well as high-energy compound levels. Our data indicate that both chemical and neonatal hypoxia caused mitochondrial depolarization, reduced calcium retention, increased ROS levels, and elevated Nfe2l2 expression in primary cortical neurons. Hypoxia also led to increased expression of genes associated with mitochondrial biogenesis and fission, as well as reduced ATP levels and elevated pyruvate and lactate levels. Importantly, treatment with sirtuin modulators enhanced neuron viability, likely by further increasing Nfe2l2 expression and reducing ROS production. These modulators also improved metabolic outcomes, including higher ATP levels, and normalised pyruvate and lactate production, as well as mitochondrial fusion gene expression. Collectively, our findings suggest that sirtuin modulators could mitigate hypoxia-induced damage and may represent a potential therapeutic strategy for managing neurodevelopmental disorders.

E1231/SR647 protects against unilateral renal ischemia-reperfusion injury by modulating SIRT1/FOXO3 interactions with Nrf2 and NFκB pathways

Ischemia is a major contributor to acute kidney injury (AKI), for which current treatment options remain limited. One NAD+-dependent deacetylase that can preserve renal cells is SIRT1. To date, no research has directly explored the effects of E1231, a SIRT1 activator, in the context of renal ischemia-reperfusion (IR) injury. Enhancing NAD+ levels is essential for sustaining SIRT1 activity. Hence, the combined use of E1231 and SR647, a NAD+ precursor, could potentially amplify protective effects by supporting prolonged SIRT1 activation. This study is the first to investigate the therapeutic potential of combining E1231 and SR647 in mitigating unilateral renal IR injury. Rats treated with E1231/SR647 effectively demonstrated reduced tubular damage, inflammation, and necrosis. These improvements correlated with a reduced kidney-to-body weight ratio and increased urine output and flow rate. Additionally, rats with IR injury demonstrated reductions in serum creatinine, BUN, UAER, and cystatin C, as well as urinary NGAL and both serum and urinary KIM-1 levels. On the other hand, elevations in urine creatinine and creatinine CL were recorded. E1231 alone provided moderate functional recovery, which was negated when co-administered with a SIRT1 inhibitor. E1231/SR647 treatment upregulated SIRT1 levels and activity, subsequently enhancing FOXO3 activation. It also boosted Nrf2 levels and activity, upregulating the antioxidant protein expression of HO-1 and NQO1. Furthermore, E1231/SR647 reduced the inflammatory response by inhibiting NFκB activity. In conclusion, E1231/SR647 is a promising therapy that may protect renal function during ischemic events through the modulation of SIRT1/FOXO3 control over Nrf2 and NFκB pathways.

Modulation of Sirtuins to address aging related disorders through the use of selected phytochemicals

BACKGROUND

Aging is a complex phenomenon involving oxidative stress, inflammation, and cellular damage subsequently leading to various disorders, such as cardiovascular diseases, neurodegenerative disorders, diabetes, and cancer. Sirtuin (SIRT) proteins are one of the major molecular factors that affect human aging. Sirtuins are a class of NAD+-dependent enzymes that control oxidative stress response, DNA damage repair, inflammation and metabolism, all of which are involved in aging and age-related diseases.

PURPOSE

The objective of this review is to elucidate the potential role of SIRT in the aging process and modulation of SIRT pathway through selected phytochemicals like Curcumin, Resveratrol, Quercetin, and Kaempferol.

RESULTS

Studies convincedly revealed that SIRT pathway represents a promising avenue for extending the human health span and addressing age-related conditions. Phytochemicals like Curcumin, Resveratrol, Quercetin, and Kaempferol have shown excellent potential to mediate aging effects through their potent antioxidant, anti-inflammatory, and regulatory activities. These potent bioactive compounds enhance oxidative stress response, genomic integrity, neuroprotective and anti-inflammatory activities through SIRT pathway modulation. Furthermore, in addition to antiaging effects, other therapeutic benefits are also associated with each compound including nervous disorders, cancer, and metabolic disorders are also briefly highlighted. Studies reported convincing evidence that Curcumin, Resveratrol, Quercetin, and Kaempferol, effectively modulate SIRT expression/activity leading to improved cell stress tolerance, reduced oxidation and enhanced metabolic state.

CONCLUSIONS

Collectively, studies revealed the comprehensive nutraceutical significance of Curcumin, Resveratrol, Quercetin, and Kaempferol as anti-aging therapeutics and warrant future studies to exploit the full potential of these natural compounds.

SIRT5-mediated desuccinylation of the porcine deltacoronavirus M protein drives pexophagy to enhance viral proliferation

Porcine deltacoronavirus (PDCoV) is an emerging enteropathogenic coronavirus capable of infecting various animal species, including humans. In this study, we explored the roles of sirtuins (SIRTs), a conserved family of protein deacylases and mono-adenosine diphosphate-ribosyltransferases, in PDCoV replication. Surprisingly, we found that SIRT5-a unique member of SIRTs with distinct desuccinylation, demalonylation, and deglutarylation activities-is a proviral factor essential for PDCoV replication; its catalytic activities are crucial in this process. Mechanistically, SIRT5 interacts with and desuccinylates the PDCoV membrane (M) protein. This modification activates the ataxia-telangiectasia mutated (ATM) pathway, facilitates ubiquitination of peroxisomal biogenesis protein 5 (PEX5), and recruits sequestosome 1 (SQSTM1/p62) to initiate selective peroxisomal autophagy (pexophagy). The pexophagy process disrupts peroxisomal function, elevates reactive oxygen species (ROS) levels, and suppresses type I and III interferon production, thereby enhancing viral replication. We also identified lysine 207 (K207) as the primary succinylation site of the M protein. Mutations mimicking the desuccinylated or succinylated states of K207 substantially influence viral replication and the ability to induce pexophagy. These findings reveal a novel role for SIRT5 in regulating pexophagy during viral infection and suggest a therapeutic target for efforts to combat coronavirus infections.

Neuronal C/EBPβ Shortens the Lifespan via Inactivating NAMPT

The brain plays a central role in aging and longevity in diverse model organisms. Morphological and functional alteration in the aging brain elicits age-associated neuronal dysfunctions. However, the primary mechanism deteriorating the brain functions to regulate the aging process remains incompletely understood. Here, it is shown that neuronal CCAAT/enhancer binding protein β (C/EBPβ) escalation during aging dictates the frailty and lifespan via inactivating nicotinamide phosphoribosyltransferase (NAMPT). Upregulated C/EBPβ drives neuronal senescence and neuronal loss, associated with NAMPT fragmentation by active asparagine endopeptidase (AEP), leading to nicotinamide adenine dinucleotide (NAD+) depletion. Knockout of AEP or expression of AEP-resistant NAMPT N136A mutant significantly elongates the lifespan of neuronal-specific Thy 1-C/EBPβ transgenic mice. Overexpression of the C. elegans C/EBPβ ortholog cebp-2 in neurons shortens lifespan and decreases NAD+ levels, which are restored by feeding nicotinamide mononucleotide (NMN) or AEP inhibitor #11a. Feeding NMN or #11a substantially ameliorates the cognitive and motor impairments of Thy 1-C/EBPβ mice and increases the life expectancy. Notably, #11a demonstrates a better therapeutic effect than NMN in improving aging phenotype in Thy 1-C/EBPβ transgenic mice, which show accelerated aging features. Hence, blockade of AEP via therapeutic intervention may provide an unprecedented strategy for fighting aging and various age-associated diseases.

Targeting the Electron Transport System for Enhanced Longevity

Damage to mitochondrial DNA (mtDNA) results in defective electron transport system (ETS) complexes, initiating a cycle of impaired oxidative phosphorylation (OXPHOS), increased reactive oxygen species (ROS) production, and chronic low-grade inflammation (inflammaging). This culminates in energy failure, cellular senescence, and progressive tissue degeneration. Rapamycin and metformin are the most extensively studied longevity drugs. Rapamycin inhibits mTORC1, promoting mitophagy, enhancing mitochondrial biogenesis, and reducing inflammation. Metformin partially inhibits Complex I, lowering reverse electron transfer (RET)-induced ROS formation and activating AMPK to stimulate autophagy and mitochondrial turnover. Both compounds mimic caloric restriction, shift metabolism toward a catabolic state, and confer preclinical-and, in the case of metformin, clinical-longevity benefits. More recently, small molecules directly targeting mitochondrial membranes and ETS components have emerged. Compounds such as Elamipretide, Sonlicromanol, SUL-138, and others modulate metabolism and mitochondrial function while exhibiting similarities to metformin and rapamycin, highlighting their potential in promoting longevity. The key question moving forward is whether these interventions should be applied chronically to sustain mitochondrial health or intermittently during episodes of stress. A pragmatic strategy may combine chronic metformin use with targeted mitochondrial therapies during acute physiological stress.

Oxidant-Based Cytotoxic Agents During Aging: From Disturbed Energy Metabolism to Chronic Inflammation and Disease Progression

In humans, aging is an inevitable consequence of diminished growth processes after reaching maturity. The high order of biomolecules in cells and tissues is continuously disturbed by numerous physical and chemical destructive impacts. Host-derived oxidant-based cytotoxic agents (reactive species, transition free metal ions, and free heme) contribute considerably to this damage. These agents are under the control of immediately acting antagonizing principles, which are important to ensure cell and tissue homeostasis. In this review, I apply the concept of host-derived cytotoxic agents and their interplay with antagonizing principles to the aging process. During aging, energy metabolism and the supply of tissues with dioxygen and nutrients are increasingly disturbed. In addition, a chronic inflammatory state develops, a condition known as inflammaging. The balance between oxidant-based cytotoxic agents and protective mechanisms is analyzed depending on age-based physiological alterations in ATP production. Disturbances in this balance are associated with the development of age-related diseases and comorbidities. An enhanced production of reactive species from dysfunctional mitochondria, alterations in cellular redox homeostasis, and adaptations to hypoxia are highlighted. Examples of how disturbances between oxidant-based cytotoxic agents and antagonizing principles contribute to the pathogenesis of diseases in persons of advanced age are given.

Uracil processing by SMUG1 in the absence of UNG triggers homologous recombination and selectively kills BRCA1/2-deficient tumors

Resistance to poly (ADP-ribose) polymerase (PARP) inhibitors (PARPis) is the major obstacle to their effectiveness in the treatment of homologous recombination (HR)-deficient (HRD) tumors. Hence, developing alternative treatments for HRD tumors is critical. Here, we show that targeting the uracil excision pathway kills HRD tumors, including those with PARPi resistance. We found that the interplay between the two major uracil DNA glycosylases UNG and SMUG1 is regulated by nuclear nicotinamide adenine dinucleotide (NAD+), which maintains UNG at replication forks (RFs) and restrains SMUG1 chromatin binding. In the absence of UNG, SMUG1 retention on chromatin leads to persistent abasic sites, which incision by APE1 results in PARP1 hyperactivation, stalled RFs, and RAD51 foci. In HRD cells (i.e., BRCA1/2-deficient), this leads to under-replicated DNA that, when propagated throughout mitosis, results in chromosome fragmentation and cell death. Our findings open up unique possibilities for targeted therapies for HRD tumors based on UNG inhibition and uracil accumulation in the genome.

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

Key Points

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

Background

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

Methods

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

Results

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

Conclusions

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

Clinical Trial registry name and registration number:

NCT03579693 .

Age-Dependent Changes in Taurine, Serine, and Methionine Release in the Frontal Cortex of Awake Freely-Moving Rats: A Microdialysis Study

Brain function declines because of aging and several metabolites change their concentration. However, this decrease may be a consequence or a driver of aging. It has been described that taurine levels decrease with age and that taurine supplementation increases health span in mice and monkeys, finding taurine as a driver of aging. The frontal cortex is one of the most key areas studied to know the normal processes of cerebral aging, due to its relevant role in cognitive processes, emotion, and motivation. In the present work, we analyzed by intracerebral microdialysis in vivo in the prefrontal cortex of young (3 months) and old (24 months) awake rats, the basal- and K+-evoked release of taurine, and its precursors methionine and serine. The taurine/serine/methionine (TSM) ratio was also calculated as an index of transmethylation reactions. No changes were found in the basal levels of taurine, serine, or methionine between young and aged animals. On the contrary, a significant decrease in the K+-evoked release of serine and taurine appeared in aged rats when compared with young animals. No changes were seen in methionine. TSM ratio also decreased with age in both basal- and K+-stimulated conditions. Therefore, taurine and its related precursor serine decrease with age in the frontal cortex of aged animals under K+-stimulated but not basal conditions, which supports the importance of the decline of evoked taurine in its functions at the brain level, also supporting the idea proposed by other authors of a pharmacological and/or nutritional intervention to its restoration. A deficit of precursors for transmethylation reactions in the brain with age is also considered.

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.

The enigmatic role of SIRT2 in the cardiovascular system: Deciphering its protective and detrimental actions to unlock new avenues for therapeutic intervention

Cardiovascular diseases (CVDs) are leading causes of mortality throughout the world, and hence, there is a critical need to elucidate their molecular mechanisms. The Sirtuin (SIRT) family of NAD+-dependent enzymes has recently been shown to play a critical role in cardiovascular health and disease, and several SIRT isoforms, especially SIRT1 and SIRT3, have been amply investigated. However, the precise function of SIRT2 is only partially explored. Here, we review the current understanding of the involvement of SIRT2 in various cardiovascular pathologies, such as cardiac hypertrophy, ischemia-reperfusion injury, diabetic cardiomyopathy, and vascular dysfunction, with emphasis placed on the context-dependent protective or deleterious actions of SIRT2, including its wide array of catalytic activities which span beyond deacetylation. Furthermore, the review uncovers several unresolved research gaps for SIRT2 mechanisms by which SIRT2 modulates cardiac and vascular function during development and aging, thereby paving the way for the discovery of novel therapeutic targets as well as SIRT2-targeted interventions in the prevention and treatment of various cardiovascular diseases.

On-farm supplementation of rumen-protected niacin: A randomized clinical trial

B vitamins, including niacin (vitamin B3), are synthesized by rumen microbes, but supplementation may provide additional benefits for ruminant health and productivity. Supplementing rumen-protected niacin (RPN) during the transition period can reduce lipolysis after calving and, consequently, may improve health and fertility of dairy cattle later in lactation. Our objective was to determine if supplementing RPN during the first 21 DIM would improve the health of dairy cows on a commercial dairy farm. We hypothesized that RPN would reduce mastitis, improve fertility, and reduce risk of leaving the herd during lactation. Holstein cows were blocked by parity and projected calving date, with treatments randomly assigned to cows within each block. Cows received RPN (n = 481; 26 g/d) through a supplement dispenser in the automated milk systems (AMS) in addition to their robot pellet, or the robot pellet only (CON; n = 593). Treatments were applied for the first 21 DIM, and cows were followed for the rest of their lactation. Milk yield, milk components (wk 1-3 of lactation), pre- and postpartum BCS, health records, and reproductive records were collected. Blood was collected from a random subset of 99 cows at 3 DIM and 97 cows at 10 DIM to assess plasma concentrations of niacin, metabolic biomarkers, and biomarkers of inflammatory status. Culling, proportion of cows pregnant, and mastitis risk were analyzed using Cox proportional hazard models. Mastitis incidence was analyzed with a linear mixed model and conception risk was analyzed using a χ2 test. Supplementing RPN increased plasma nicotinamide concentration by 1,740 nM ± 410.0 nM (SE; 50% increase), but it did not affect plasma nicotinic acid concentrations. Supplementing RPN reduced plasma insulin concentrations at 3 and 10 DIM across all parities. Circulating BHB and free fatty acid concentrations were greater for cows receiving RPN; the effect was greatest in cows in third or greater parity. Plasma haptoglobin was not affected by treatment. Rumen-protected niacin increased milk yield for first- and second-parity cows by wk 9 and 13 of lactation, respectively, and increased milk yield in those groups was sustained for the rest of lactation, resulting in 658 ± 259.4 kg and 675 ± 308.9 kg more milk for RPN-supplemented first- and second-parity cows. The risk of leaving the herd, mastitis incidence, and probability of pregnancy were not affected by RPN. Inquiries into the effects of RPN supplementation and its timing on metabolism are necessary to understand optimal supplementation strategies for RPN in dairy cattle.

Xiyangshen Sanqi Danshen granules attenuated D-gal-induced C57BL/6J mouse aging through the AMPK/SIRT1 signaling pathway

BACKGROUND

Aging is a pressing global concern and is frequently accompanied by the emergence of many chronic diseases. Xiyangshen Sanqi Danshen granules (XSD) have antioxidant, anti-inflammatory and anti-fatigue functions, but the mechanism of their anti-aging effects is not clear.

METHODS

This study elucidated the anti-aging mechanism and potentially active ingredients of XSD by performing transcriptomic analysis and network pharmacological analysis in a D-galactose (D-gal)-induced C57BL/6J mouse aging model.

RESULTS

XSD improved learning and memory abilities while enhanced motor function in D-gal-induced aging mice, as shown by Morris water maze, passive avoidance test, and rotating rod test results. Additionally, XSD significantly increased the vascular pulse wave velocity (PWV), β-stiffness index and pressure strain elastic coefficient (EP), decreased carotid distensibility (CD) and decreased the expression levels of P53 and 8-OHdG in the common carotid arteries of D-gal mice. Transcriptome sequencing analysis identified that the AMPK/SIRT1 signaling pathway is the potential mechanism by which XSD attenuates aging. XSD also increased the protein levels of Ki67, AMPK, SIRT1 and the nuclear translocation of Nrf2 while decreased the protein levels of P21, P53, IL-18, 8-OHdG, nitrotyrosine, and COX-2 and the nuclear translocation of NF-κB p65 in the brains of D-gal-induced mice. The administration of the AMPK inhibitor and SIRT1 inhibitor hindered the anti-aging effect of XSD, as indicated by an elevation of 8-OHdG, COX-2, and nuclear translocation of NF-κB p65 ; and a decrease of Ki67 and the nuclear translocation of Nrf2. Network pharmacological analysis revealed that the potential active ingredients of XSD were quercetin, kaempferol, tanshinone IIA, isorhamnetin, ginsenoside F2, and cryptotanshinone.

CONCLUSION

Collectively, XSD mitigated D-gal-induced aging in C57BL/6J mice through enhancing the AMPK/SIRT1 signaling pathway. This research provides potential drugs for anti-aging and also promotes the usage of the anti-aging effect of XSD.

Too old for healthy aging? Exploring age limits of longevity treatments

It is well documented that aging elicits metabolic failures, while poor metabolism contributes to accelerated aging. Metabolism in general, and energy metabolism in particular are also effective entry points for interventions that extend lifespan and improve organ function during aging. In this review, we discuss common metabolic remedies for healthy aging from the angle of their potential age-specificity. We demonstrate that some well-known metabolic treatments are mostly effective in young and middle-aged organisms, while others maintain high efficacy independently of age. The mechanistic basis of presence or lack of the age limitations is laid out and discussed.

Association Between the Development of Sensorineural Hearing Loss and Blood NAD+ Levels

Background

Hearing loss prevalence increases with age, affecting over 25% of the global population aged 60 years or older. The aim of the study was to investigate the association between the development of sensorineural hearing loss (SNHL) and the blood levels of nicotinamide adenine dinucleotide (NAD+).

Methods

A single-center, observational study was conducted at Kawagoe Otology Institute in Japan. A total of 80 patients were included and allocated to four groups of 20 patients each: patients aged 50 - 79 years with or without unilateral sudden sensorineural hearing loss (SSNHL), and patients aged ≥ 80 years with or without bilateral age-related hearing loss (ARHL). The distribution of whole-blood NAD+ levels was investigated. We also measured oxidative stress markers (diacron-reactive oxygen metabolites (dROMs) and biological antioxidant potential (BAP)) and examined the relationship between the development of SNHL and whole-blood NAD+ levels, dROMs, and BAP.

Results

Comparison of NAD+ levels with and without hearing loss in the same age group by analysis of covariance showed a significantly lower NAD+ level in those with hearing loss than those without in the ≥ 80 age group (P = 0.047), whereas there was no difference between the two groups in the 50 - 79 age group (P = 0.232). All 80 patients, without consideration of age or type of hearing loss, were subjected to multivariate analysis to explore factors contributing to the development of hearing loss. With each 1 µM increase in the NAD+ level, the probability of developing SNHL decreased to 0.9-fold (P = 0.047), and each 1 U.CARR increase in dROMs was associated with a 1.01-fold increase in the risk of developing SNHL (P = 0.014). Whole-blood NAD+ levels in ARHL patients were significantly lower than those in non-ARHL patients. There was no association between whole-blood NAD+ and dROMs or BAP levels. This study has some limitations, including a sample size that was not large enough to detect a significant difference and an imbalance in the male-to-female ratio.

Conclusions

Decreased amount of NAD+ in the body and increased dROMs levels were associated with increased risk of developing SNHL, and the development of ARHL was especially highly associated with a decreased amount of NAD+ in the body.

Intermittent fasting in health and disease

CONTEXT

Intermittent fasting, a new-age dietary concept derived from an age-old tradition, involves repetitive cycles of fasting/calorie restriction and eating.

OBJECTIVE

We aim to take a deep dive into the biological responses to intermittent fasting, delineate the disease-modifying and cognitive effects of intermittent fasting, and also shed light on the possible side effects.

METHODS

Numerous in vitro and in vivo studies were reviewed, followed by an in-depth analysis, and compilation of their implications in health and disease.

RESULTS

Intermittent fasting improves the body's stress tolerance, which is further amplified with exercise. It impacts various pathological conditions like cancer, obesity, diabetes, cardiovascular disease, and neurodegenerative diseases.

CONCLUSION

During dietary restriction, the human body experiences a metabolic switch due to the depletion of liver glycogen, which promotes a shift towards utilising fatty acids and ketones in the system, thereby significantly impacting adiposity, ageing and the immune response to various diseases.

Sirtuin Proteins and Memory: A Promising Target in Alzheimer's Disease Therapy?

Sirtuins (SIRTs), nicotine adenine dinucleotide (+)-dependent histone deacetylases, have emerged as critical regulators in many signalling pathways involved in a wide range of biological processes. Currently, seven mammalian SIRTs have been characterized and are found across a number of cellular compartments. There has been considerable interest in the role of SIRTs in the brain due to their role in a plethora of metabolic- and age-related diseases, including their involvement in learning and memory function in physiological and pathophysiological conditions. Although cognitive function declines over the course of healthy ageing, neurological disorders including Alzheimer's disease (AD) can be associated with progressive cognitive impairments. This review aimed to report and integrate recent advances in the understanding of the role of SIRTs in cognitive function and dysfunction in the context of AD. We have also reviewed the use of selective and/or natural SIRT activators as potential therapeutic agents and/or adjuvants for AD.

BubR1 and SIRT2: Insights into aneuploidy, aging, and cancer

Aging is a significant risk factor for cancer which is due, in part, to heightened genomic instability. Mitotic surveillance proteins such as BubR1 play a pivotal role in ensuring accurate chromosomal segregation and preventing aneuploidy. BubR1 levels have been shown to naturally decline with age and its loss is associated with various age-related pathologies. Sirtuins, a class of NAD+-dependent deacylases, are implicated in cancer and genomic instability. Among them, SIRT2 acts as an upstream regulator of BubR1, offering a critical pathway that can potentially mitigate age-related diseases, including cancer. In this review, we explore BubR1 as a key regulator of cellular processes crucial for aging-related phenotypes. We delve into the intricate mechanisms through which BubR1 influences genomic stability and cellular senescence. Moreover, we highlight the role of NAD+ and SIRT2 in modulating BubR1 expression and function, emphasizing its potential as a therapeutic target. The interaction between BubR1 and SIRT2 not only serves as a fundamental regulatory pathway in cellular homeostasis but also represents a promising avenue for developing targeted therapies against age-related diseases, particularly cancer.

Unraveling the multifaceted role of SIRT7 and its therapeutic potential in human diseases

Sirtuins, as NAD+-dependent deacetylases, are widely found in eubacteria, archaea, and eukaryotes, and they play key roles in regulating cellular functions. Among these, SIRT7 stands out as a member discovered relatively late and studied less extensively. It is localized within the nucleus and displays enzymatic activity as an NAD+-dependent deacetylase, targeting a diverse array of acyl groups. The role of SIRT7 in important cellular processes like gene transcription, cellular metabolism, cellular stress responses, and DNA damage repair has been documented in a number of studies conducted recently. These studies have also highlighted SIRT7's strong correlation with human diseases like aging, cancer, neurological disorders, and cardiovascular diseases. In addition, a variety of inhibitors against SIRT7 have been reported, indicating that targeting SIRT7 may be a promising strategy for inhibiting tumor growth. The purpose of this review is to thoroughly look into the structure and function of SIRT7 and to explore its potential value in clinical applications, offering an essential reference for research in related domains.

The dark side of SIRT7

Sirtuin 7 (SIRT7) is a member of the sirtuin family and has emerged as a key player in numerous cellular processes. It exhibits various enzymatic activities and is predominantly localized in the nucleolus, playing a role in ribosomal RNA expression, DNA damage repair, stress response and chromatin compaction. Recent studies have revealed its involvement in diseases such as cancer, cardiovascular and bone diseases, and obesity. In cancer, SIRT7 has been found to be overexpressed in multiple types of cancer, including breast cancer, clear cell renal cell carcinoma, lung adenocarcinoma, prostate adenocarcinoma, hepatocellular carcinoma, and gastric cancer, among others. In general, cancer cells exploit SIRT7 to enhance cell growth and metabolism through ribosome biogenesis, adapt to stress conditions and exert epigenetic control over cancer-related genes. The aim of this review is to provide an in-depth understanding of the role of SIRT7 in cancer carcinogenesis, evolution and progression by elucidating the underlying molecular mechanisms. Emphasis is placed on unveiling the intricate molecular pathways through which SIRT7 exerts its effects on cancer cells. In addition, this review discusses the feasibility and challenges associated with the development of drugs that can modulate SIRT7 activity.

Cell senescence in cardiometabolic diseases

Cellular senescence has been implicated in many age-related pathologies including atherosclerosis, heart failure, age-related cardiac remodeling, diabetic cardiomyopathy and the metabolic syndrome. Here, we will review the characteristics of senescent cells and their endogenous regulators, and summarize the metabolic stressors that induce cell senescence. We will discuss the evidence of cell senescence in the onset and progression of several cardiometabolic diseases and the therapeutic potential of anti-senescence therapies.

Inhibition of Sirtuin Deacylase Activity by Peroxynitrite

Sirtuins are a class of enzymes that deacylate protein lysine residues using NAD+ as a cosubstrate. Sirtuin deacylase activity has been historically regarded as protective; loss of sirtuin deacylase activity potentially increases susceptibility to aging-related disease development. However, which factors may inhibit sirtuins during aging or disease is largely unknown. Increased oxidant and inflammatory byproduct production damages cellular proteins. Previously, we and others found that sirtuin deacylase activity is inhibited by the nitric oxide (NO)-derived cysteine post-translational modification S-nitrosation. However, the comparative ability of the NO-derived oxidant peroxynitrite (ONOO-) to affect human sirtuin activity had not yet been assessed under uniform conditions. Here, we compare the ability of ONOO- (donated from SIN-1) to post-translationally modify and inhibit SIRT1, SIRT2, SIRT3, SIRT5, and SIRT6 deacylase activity. In response to SIN-1 treatment, inhibition of SIRT1, SIRT2, SIRT3, SIRT5, and SIRT6 deacylase activity correlated with increased tyrosine nitration. Mass spectrometry identified multiple novel tyrosine nitration sites in SIRT1, SIRT3, SIRT5, and SIRT6. As each sirtuin isoform has at least one tyrosine nitration site within the catalytic core, nitration may result in sirtuin inhibition. ONOO- can also react with cysteine residues, resulting in sulfenylation; however, only SIRT1 showed detectable peroxynitrite-mediated cysteine sulfenylation. While SIRT2, SIRT3, SIRT5, and SIRT6 showed no detectable sulfenylation, SIRT6 likely undergoes transient sulfenylation, quickly resolving into an intermolecular disulfide bond. These results suggest that the aging-related oxidant peroxynitrite can post-translationally modify and inhibit sirtuins, contributing to susceptibility to aging-related disease.

NMNAT1 Is Essential for Human iPS Cell Differentiation to the Retinal Lineage

Purpose

The gene encoding nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1), a nicotinamide adenine dinucleotide synthetase localized in the cell nucleus, is a causative factor in Leber's congenital amaurosis, which is the earliest onset type of inherited retinal degeneration. We sought to investigate the roles of NMNAT1 in early retinal development.

Methods

We used human induced pluripotent stem cells (hiPSCs) and established NMNAT1-knockout (KO) hiPSCs using CRISPR/cas9 technology to reveal the roles of NMNAT1 in human retinal development.

Results

NMNAT1 was not essential for the survival and proliferation of immature hiPSCs; therefore, we subjected NMNAT1-KO hiPSCs to retinal organoid (RO) differentiation culture. The expression levels of immature hiPSC-specific genes decreased in a similar manner after organoid culture initiation up to 2 weeks in the control and NMNAT1-KO. Neuroectoderm-specific genes were induced in the control and NMNAT1-KO organoids within a few days after starting the organoid culture; PAX6 and TUBB3 were higher in NMNAT1-KO organoids up to 7 days than in the control organoids. However, the induction of genes involving retinal early development, such as RAX, which was induced at around day 10 in this culture, was considerably reduced in NMNAT1-KO organoids. Morphological examination also showed failure of retinal primordial structure formation, which became visible at around 2 weeks of the control culture, in the NMNAT1-KO organoids. Decreased intracellular NAD levels and poly(ADP-ribosyl)ation were observed in NMNAT1-KO organoids at 7 to 10 days of the culture. Mass spectrometry analysis of inhibited proteins in the poly(ADP-ribosyl)ation pathway identified poly(ADP-ribosyl)ation of poly(ADP-ribose) polymerase 1 (PARP1) as a major protein.

Conclusions

These results indicate that NMNAT1 was dispensable for neural lineage differentiation but essential for the commitment of retinal fate differentiation in hiPSCs. The NMNAT1-NAD-PARP1 axis may play a critical role in the appropriate development of human retinal lineage differentiation.

Sirt2 Regulates Liver Metabolism in a Sex-Specific Manner

Sirtuin-2 (Sirt2), an NAD+-dependent lysine deacylase enzyme, has previously been implicated as a regulator of glucose metabolism, but the specific mechanisms remain poorly defined. Here, we observed that Sirt2-/- males, but not females, have decreased body fat, moderate hypoglycemia upon fasting, and perturbed glucose handling during exercise compared to wild type controls. Conversion of injected lactate, pyruvate, and glycerol boluses into glucose via gluconeogenesis was impaired, but only in males. Primary Sirt2-/- male hepatocytes exhibited reduced glycolysis and reduced mitochondrial respiration. RNAseq and proteomics were used to interrogate the mechanisms behind this liver phenotype. Loss of Sirt2 did not lead to transcriptional dysregulation, as very few genes were altered in the transcriptome. In keeping with this, there were also negligible changes to protein abundance. Site-specific quantification of the hepatic acetylome, however, showed that 13% of all detected acetylated peptides were significantly increased in Sirt2-/- male liver versus wild type, representing putative Sirt2 target sites. Strikingly, none of these putative target sites were hyperacetylated in Sirt2-/- female liver. The target sites in the male liver were distributed across mitochondria (44%), cytoplasm (32%), nucleus (8%), and other compartments (16%). Despite the high number of putative mitochondrial Sirt2 targets, Sirt2 antigen was not detected in purified wild type liver mitochondria, suggesting that Sirt2's regulation of mitochondrial function occurs from outside the organelle. We conclude that Sirt2 regulates hepatic protein acetylation and metabolism in a sex-specific manner.

Multi-modal, Label-free, Optical Mapping of Cellular Metabolic Function and Oxidative Stress in 3D Engineered Brain Tissue Models

Brain metabolism is essential for the function of organisms. While established imaging methods provide valuable insights into brain metabolic function, they lack the resolution to capture important metabolic interactions and heterogeneity at the cellular level. Label-free, two-photon excited fluorescence imaging addresses this issue by enabling dynamic metabolic assessments at the single-cell level without manipulations. In this study, we demonstrate the impact of spectral imaging on the development of rigorous intensity and lifetime label-free imaging protocols to assess dynamically over time metabolic function in 3D engineered brain tissue models comprising human induced neural stem cells, astrocytes, and microglia. Specifically, we rely on multi-wavelength spectral imaging to identify the excitation/emission profiles of key cellular fluorophores within human brain cells, including NAD(P)H, LipDH, FAD, and lipofuscin. These enable development of methods to mitigate lipofuscin's overlap with NAD(P)H and flavin autofluorescence to extract reliable optical metabolic function metrics from images acquired at two excitation wavelengths over two emission bands. We present fluorescence intensity and lifetime metrics reporting on redox state, mitochondrial fragmentation, and NAD(P)H binding status in neuronal monoculture and triculture systems, to highlight the functional impact of metabolic interactions between different cell types. Our findings reveal significant metabolic differences between neurons and glial cells, shedding light on metabolic pathway utilization, including the glutathione pathway, OXPHOS, glycolysis, and fatty acid oxidation. Collectively, our studies establish a label-free, non-destructive approach to assess the metabolic function and interactions among different brain cell types relying on endogenous fluorescence and illustrate the complementary nature of information that is gained by combining intensity and lifetime-based images. Such methods can improve understanding of physiological brain function and dysfunction that occurs at the onset of cancers, traumatic injuries and neurodegenerative diseases.

Randomized Crossover Clinical Trial of Nicotinamide Riboside and Coenzyme Q10 on Metabolic Health and Mitochondrial Bioenergetics in CKD

Background

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

Methods

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

Results

The (mean±SD) age, eGFR, and BMI of the participants were 61±11 years, 37±9 mL/min/1.73m2, and 28±5 kg/m2 respectively. Of the participants, 16% had diabetes and 40% were female. Compared to placebo, NR-mediated transcriptomic changes were enriched in gene ontology (GO) terms associated with carbohydrate/lipid metabolism and immune signaling while, CoQ10 changes were enriched in immune/stress response and lipid metabolism GO terms. NR increased plasma IL-2 (estimated difference, 0.32, 95% CI of 0.14 to 0.49 pg/mL), and CoQ10 decreased both IL-13 (estimated difference, -0.12, 95% CI of -0.24 to -0.01 pg/mL) and CRP (estimated difference, -0.11, 95% CI of -0.22 to 0.00 mg/dL) compared to placebo. Both NR and CoQ10 reduced 5 series F2-Isoprostanes (estimated difference, -0.16 and -0.11 pg/mL, respectively; P<0.05 for both). NR, but not CoQ10, increased the bioenergetic health index (BHI) (estimated difference, 0.29, 95% CI of 0.06 to 0.53) and spare respiratory capacity (estimated difference, 3.52, 95% CI of 0.04 to 7 pmol/min/10,000 cells) in monocytes.

Conclusion

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

Ketogenic effect of coconut oil in ALS patients

A recent pilot study in amyotrophic lateral sclerosis (ALS) patients analyzed the effect of a Mediterranean diet (MeDi) supplemented with nicotinamide riboside (NR, a NAD+ promoter), pterostilbene (PTER, a natural antioxidant) and/or coconut oil on anthropometric variables in ALS patients. The results suggested that the MeDi supplemented with NR, PTER and coconut oil is the nutritional intervention showing the greatest benefits at anthropometric levels. Over the last 30 years, glucose intolerance has been reported in ALS patients. Thus, suggesting that an alternative source of energy may be preferential for motor neurons to survive. Ketone bodies (KBs), provided through a MeDi with a lower carbohydrate content but enriched with medium chain triglycerides, could be a therapeutic alternative to improve the neuromotor alterations associated with the disease. Nevertheless, the use of a coconut oil-supplemented diet, as potentially ketogenic, is a matter of controversy. In the present report we show that a MeDi supplemented with coconut oil increases the levels of circulating KBs in ALS patients.

Integrative analysis of single-cell RNA-seq and gut microbiome metabarcoding data elucidates macrophage dysfunction in mice with DSS-induced ulcerative colitis

Ulcerative colitis (UC) is a significant inflammatory bowel disease caused by an abnormal immune response to gut microbes. However, there are still gaps in our understanding of how immune and metabolic changes specifically contribute to this disease. Our research aims to address this gap by examining mouse colons after inducing ulcerative colitis-like symptoms. Employing single-cell RNA-seq and 16 s rRNA amplicon sequencing to analyze distinct cell clusters and microbiomes in the mouse colon at different time points after induction with dextran sodium sulfate. We observe a significant reduction in epithelial populations during acute colitis, indicating tissue damage, with a partial recovery observed in chronic inflammation. Analyses of cell-cell interactions demonstrate shifts in networking patterns among different cell types during disease progression. Notably, macrophage phenotypes exhibit diversity, with a pronounced polarization towards the pro-inflammatory M1 phenotype in chronic conditions, suggesting the role of macrophage heterogeneity in disease severity. Increased expression of Nampt and NOX2 complex subunits in chronic UC macrophages contributes to the inflammatory processes. The chronic UC microbiome exhibits reduced taxonomic diversity compared to healthy conditions and acute UC. The study also highlights the role of T cell differentiation in the context of dysbiosis and its implications in colitis progression, emphasizing the need for targeted interventions to modulate the inflammatory response and immune balance in colitis.

Mitochondrial One-Carbon Metabolism and Alzheimer's Disease

Mitochondrial one-carbon metabolism provides carbon units to several pathways, including nucleic acid synthesis, mitochondrial metabolism, amino acid metabolism, and methylation reactions. Late-onset Alzheimer's disease is the most common age-related neurodegenerative disease, characterised by impaired energy metabolism, and is potentially linked to mitochondrial bioenergetics. Here, we discuss the intersection between the molecular pathways linked to both mitochondrial one-carbon metabolism and Alzheimer's disease. We propose that enhancing one-carbon metabolism could promote the metabolic processes that help brain cells cope with Alzheimer's disease-related injuries. We also highlight potential therapeutic avenues to leverage one-carbon metabolism to delay Alzheimer's disease pathology.

The Expansion of Sirtuin Gene Family in Gilthead Sea Bream (Sparus aurata)-Phylogenetic, Syntenic, and Functional Insights across the Vertebrate/Fish Lineage

The Sirtuin (SIRT1-7) family comprises seven evolutionary-conserved enzymes that couple cellular NAD availability with health, nutrition and welfare status in vertebrates. This study re-annotated the sirt3/5 branch in the gilthead sea bream, revealing three paralogues of sirt3 (sirt3.1a/sirt3.1b/sirt3.2) and two of sirt5 (sirt5a/sirt5b) in this Perciform fish. The phylogeny and synteny analyses unveiled that the Sirt3.1/Sirt3.2 dichotomy was retained in teleosts and aquatic-living Sarcopterygian after early vertebrate 2R whole genome duplication (WGD). Additionally, only certain percomorphaceae and gilthead sea bream showed a conserved tandem-duplicated synteny block involving the mammalian-clustered sirt3.1 gene (psmd13-sirt3.1a/b-drd4-cdhr5-ctsd). Conversely, the expansion of the Sirt5 branch was shaped by the teleost-specific 3R WGD. As extensively reviewed in the literature, human-orthologues (sirt3.1/sirt5a) showed a high, conserved expression in skeletal muscle that increased as development advanced. However, recent sirt3.2 and sirt5b suffered an overall muscle transcriptional silencing across life, as well as an enhanced expression on immune-relevant tissues and gills. These findings fill gaps in the ontogeny and differentiation of Sirt genes in the environmentally adaptable gilthead sea bream, becoming a good starting point to advance towards a full understanding of its neo-functionalization. The mechanisms originating from these new paralogs also open new perspectives in the study of cellular energy sensing processes in vertebrates.

Recruitment of CTCF to the SIRT1 promoter after Oxidative Stress mediates Cardioprotective Transcription

Because most DNA-binding transcription factors (dbTFs), including the architectural regulator CTCF, bind RNA and exhibit di-/multimerization, a central conundrum is whether these distinct properties are regulated post-transcriptionally to modulate transcriptional programs. Here, investigating stress-dependent activation of SIRT1, encoding an evolutionarily-conserved protein deacetylase, we show that induced phosphorylation of CTCF acts as a rheostat to permit CTCF occupancy of low-affinity promoter DNA sites to precisely the levels necessary. This CTCF recruitment to the SIRT1 promoter is eliciting a cardioprotective cardiomyocyte transcriptional activation program and provides resilience against the stress of the beating heart in vivo . Mice harboring a mutation in the conserved low-affinity CTCF promoter binding site exhibit an altered, cardiomyocyte-specific transcriptional program and a systolic heart failure phenotype. This transcriptional role for CTCF reveals that a covalent dbTF modification regulating signal-dependent transcription serves as a previously unsuspected component of the oxidative stress response.

Accounting for NAD Concentrations in Genome-Scale Metabolic Models Captures Important Metabolic Alterations in NAD-Depleted Systems

Nicotinamide adenine dinucleotide (NAD) is a ubiquitous molecule found within all cells, acting as a crucial coenzyme in numerous metabolic reactions. It plays a vital role in energy metabolism, cellular signaling, and DNA repair. Notably, NAD levels decline naturally with age, and this decline is associated with the development of various age-related diseases. Despite this established link, current genome-scale metabolic models, which offer powerful tools for understanding cellular metabolism, do not account for the dynamic changes in NAD concentration. This impedes our understanding of a fluctuating NAD level's impact on cellular metabolism and its contribution to age-related pathologies. To bridge this gap in our knowledge, we have devised a novel method that integrates altered NAD concentration into genome-scale models of human metabolism. This approach allows us to accurately reflect the changes in fatty acid metabolism, glycolysis, and oxidative phosphorylation observed experimentally in an engineered human cell line with a compromised level of subcellular NAD.

Electro-Metabolic Coupling of Cumulus-Oocyte Complex

Oocyte-cumulus cell interaction is essential for oocyte maturation and competence. The bidirectional crosstalk network mediated by gap junctions is fundamental for the metabolic cooperation between these cells. As cumulus cells exhibit a more glycolytic phenotype, they can provide metabolic substrates that the oocyte can use to produce ATP via oxidative phosphorylation. The impairment of mitochondrial activity plays a crucial role in ovarian aging and, thus, in fertility, determining the success or failure of assisted reproductive techniques. This review aims to deepen the knowledge about the electro-metabolic coupling of the cumulus-oocyte complex and to hypothesize a putative role of potassium channel modulators in order to improve fertility, promote intracellular Ca2+ influx, and increase the mitochondrial biogenesis and resulting ATP levels in cumulus cells.

SIRT1, resveratrol and aging

Aging is linked to a time-associated decline in both cellular function and repair capacity leading to malfunction on an organismal level, increased frailty, higher incidence of diseases, and death. As the population grows older, there is a need to reveal mechanisms associated with aging that could spearhead treatments to postpone the onset of age-associated decline, extend both healthspan and lifespan. One possibility is targeting the sirtuin SIRT1, the founding member of the sirtuin family, a highly conserved family of histone deacetylases that have been linked to metabolism, stress response, protein synthesis, genomic instability, neurodegeneration, DNA damage repair, and inflammation. Importantly, sirtuins have also been implicated to promote health and lifespan extension, while their dysregulation has been linked to cancer, neurological processes, and heart disorders. SIRT1 is one of seven members of sirtuin family; each requiring nicotinamide adenine dinucleotide (NAD+) as co-substrate for their catalytic activity. Overexpression of yeast, worm, fly, and mice SIRT1 homologs extend lifespan in each animal, respectively. Moreover, lifespan extension due to calorie restriction are associated with increased sirtuin activity. These findings led to the search for a calorie restriction mimetic, which revealed the compound resveratrol; (3, 5, 4'-trihydroxy-trans-stilbene) belonging to the stilbenoids group of polyphenols. Following this finding, resveratrol and other sirtuin-activating compounds have been extensively studied for their ability to affect health and lifespan in a variety of species, including humans via clinical studies.

Aspirin-Mediated Acetylation of SIRT1 Maintains Intestinal Immune Homeostasis

Aspirin, also named acetylsalicylate, can directly acetylate the side-chain of lysine in protein, which leads to the possibility of unexplained drug effects. Here, the study used isotopic-labeling aspirin-d3 with mass spectrometry analysis to discover that aspirin directly acetylates 10 HDACs proteins, including SIRT1, the most studied NAD+-dependent deacetylase. SIRT1 is also acetylated by aspirin in vitro. It is also identified that aspirin directly acetylates lysine 408 of SIRT1, which abolishes SIRT1 deacetylation activity by impairing the substrates binding affinity. Interestingly, the lysine 408 of SIRT1 can be acetylated by CBP acetyltransferase in cells without aspirin supplement. Aspirin can inhibit SIRT1 to increase the levels of acetylated p53 and promote p53-dependent apoptosis. Moreover, the knock-in mice of the acetylation-mimic mutant of SIRT1 show the decreased production of pro-inflammatory cytokines and maintain intestinal immune homeostasis. The study indicates the importance of the acetylated internal functional site of SIRT1 in maintaining intestinal immune homeostasis.

Modern optical approaches in redox biology: Genetically encoded sensors and Raman spectroscopy

The objective of the current review is to summarize the current state of optical methods in redox biology. It consists of two parts, the first is dedicated to genetically encoded fluorescent indicators and the second to Raman spectroscopy. In the first part, we provide a detailed classification of the currently available redox biosensors based on their target analytes. We thoroughly discuss the main architecture types of these proteins, the underlying engineering strategies for their development, the biochemical properties of existing tools and their advantages and disadvantages from a practical point of view. Particular attention is paid to fluorescence lifetime imaging microscopy as a possible readout technique, since it is less prone to certain artifacts than traditional intensiometric measurements. In the second part, the characteristic Raman peaks of the most important redox intermediates are listed, and examples of how this knowledge can be implemented in biological studies are given. This part covers such fields as estimation of the redox states and concentrations of Fe-S clusters, cytochromes, other heme-containing proteins, oxidative derivatives of thiols, lipids, and nucleotides. Finally, we touch on the issue of multiparameter imaging, in which biosensors are combined with other visualization methods for simultaneous assessment of several cellular parameters.

NAD-Driven Sirtuin Activation by Cordyceps sinensis Extract: Exploring the Adaptogenic Potential to Promote Skin Longevity

In recent years, there has been increasing interest in utilizing Traditional Chinese Medicine principles and natural bioactive compounds to combat age-related ailments and enhance longevity. A Cordyceps sinensis mycelium hydroethanolic extract (CsEx), which was standardized in cordycepin and adenosine using UHPLC-DAD, was investigated for its adaptogenic properties using in vitro assays and a double-blind, placebo-controlled clinical trial involving 40 subjects. The CsEx demonstrated activity at a concentration of 0.0006%, significantly increasing sirtuin expression (SirT1: +33%, SirT3: +10%, SirT6: +72%, vs. CTR, p < 0.05) and NAD+ synthesis in HaCat cells (+20% vs. CTR, p < 0.001). Moreover, the CsEx boosted ATP production by 68% in skin cells, correlating with higher skin energy values (+52.0% at D28, p < 0.01) in the clinical trial. Additionally, CsEx notably reduced cytosolic reactive oxygen species (ROS) by 30% in HaCaT cells (p < 0.05) and enhanced collagen production both in vitro (+69% vs. CTR, p < 0.01) and in vivo (+10% vs. D0, p < 0.01), confirmed by ultrasound examination. Furthermore, CsEx's stimulation of fibroblasts, coupled with its antioxidant and energizing properties, led to a significant reduction in wrinkles by 28.0% (D28, p < 0.001). This study underscores Cordyceps sinensis hydroethanolic extract's potential in regulating skin cell energy metabolism and positively influencing the mechanisms associated with skin longevity control.

Distinct Histone H3 Lysine 27 Modifications Dictate Different Outcomes of Gene Transcription

Site-specific histone modifications have long been recognized to play an important role in directing gene transcription in chromatin in biology of health and disease. However, concrete illustration of how different histone modifications in a site-specific manner dictate gene transcription outcomes, as postulated in the influential "Histone code hypothesis", introduced by Allis and colleagues in 2000, has been lacking. In this review, we summarize our latest understanding of the dynamic regulation of gene transcriptional activation, silence, and repression in chromatin that is directed distinctively by histone H3 lysine 27 acetylation, methylation, and crotonylation, respectively. This represents a special example of a long-anticipated verification of the "Histone code hypothesis."

Fructobacillus fructosus OS-1010 strain stimulates intestinal cells to secrete exosomes that activate muscle cells

Fructobacillus is a lactic-acid bacterium recently identified in fructose-rich environments. Fructobacillus is also known to exhibit unusual growth characteristics due to an incomplete gene encoding alcohol/acetaldehyde hydrogenase, which results in an imbalance in the nicotinamide adenine mononucleotide (NAD+)/NADN levels. Recently, the addition of d-fructose to the culture medium of Fructobacillus strains increased the intracellular nicotinamide mononucleotide (NMN) content. In the present study, we evaluated the functionality of Fructobacillus that produces high levels of NMN, using one substrain (Fructobacillus fructosus OS-1010). Therefore, in this study, we examined its functionality in the interaction between intestinal cells and muscle cells. The results showed that supernatant derived from intestinal epithelial cells (Caco-2 cells) treated with F. fructosus OS-1010 activated muscle cells (C2C12 cells). Further analysis revealed that Caco-2 cells treated with F. fructosus OS-1010 secreted exosomes known as extracellular vesicles, which activated the muscle cells. Furthermore, pathway analysis of the target genes of miRNA in exosomes revealed that pathways involved in muscle cell activation, including insulin signaling and cardiac muscle regulation, neurotrophic factors, longevity, and anti-aging, can be activated by exosomes. In other words, F. fructosus OS-1010 could activate various cells such as the skin and muscle cells, by secreting functional exosomes from the intestinal tract.

Mechanistic Insights into the Multiple Functions of Niacinamide: Therapeutic Implications and Cosmeceutical Applications in Functional Skincare Products

Niacinamide (or nicotinamide) is a small-molecule hydrosoluble vitamin with essential metabolic functions in mammalian cells. Niacinamide has become a key functional ingredient in diverse skincare products and cosmetics. This vitamin plays a pivotal role in NAD+ synthesis, notably contributing to redox reactions and energy production in cutaneous cells. Via diversified biochemical mechanisms, niacinamide is also known to influence human DNA repair and cellular stress responses. Based on decades of safe use in cosmetics, niacinamide recently gained widespread popularity as an active ingredient which aligns with the "Kligman standards" in skincare. From a therapeutic standpoint, the intrinsic properties of niacinamide may be applied to managing acne vulgaris, melasma, and psoriasis. From a cosmeceutical standpoint, niacinamide has been widely leveraged as a multipurpose antiaging ingredient. Therein, it was shown to significantly reduce cutaneous oxidative stress, inflammation, and pigmentation. Overall, through multimodal mechanisms, niacinamide may be considered to partially prevent and/or reverse several biophysical changes associated with skin aging. The present narrative review provides multifactorial insights into the mechanisms of niacinamide's therapeutic and cosmeceutical functions. The ingredient's evolving role in skincare was critically appraised, with a strong focus on the biochemical mechanisms at play. Finally, novel indications and potential applications of niacinamide in dermal fillers and alternative injectable formulations were prospectively explored.

Endothelium-specific SIRT7 targeting ameliorates pulmonary hypertension through Krüpple-like factor 4 deacetylation

AIMS

Pulmonary hypertension (PH) is a pulmonary vascular disease characterized by a high mortality rate. Pulmonary arterial endothelium cells (PAECs) serve as a primary sensor of various environmental cues, such as shear stress and hypoxia, but PAEC dysfunction may trigger vascular remodelling during the onset of PH. This study aimed to illustrate the role of Sirtuin 7 (SIRT7) in endothelial dysfunction during PH and explore the potential therapeutic strategy for PH.

METHODS AND RESULTS

SIRT7 levels were measured in human and murine experimental PH samples. Bioinformatic analysis, immunoprecipitation, and deacetylation assay were used to identify the association between SIRT7 and Krüpple-like factor 4 (KLF4), a key transcription factor essential for endothelial cell (EC) homeostasis. Sugen5416 + hypoxia (SuHx)-induced PH mouse models and cell cultures were used for the study of the therapeutic effect of SIRT7 for PH. SIRT7 level was significantly reduced in lung tissues and PAECs from PH patients and the SuHx-induced PH mouse model as compared with healthy controls. Pulmonary endothelium-specific depletion of Sirt7 increased right ventricular systolic pressure and exacerbated right ventricular hypertrophy in the SuHx-induced PH model. At the molecular level, we identified KLF4 as a downstream target of SIRT7, which deacetylated KLF4 at K228 and inhibited the ubiquitination-proteasome degradation. Thus, the SIRT7/KLF4 axis maintained PAEC homeostasis by regulating proliferation, migration, and tube formation. PAEC dysfunction was reversed by adeno-associated virus type 1 vector-mediated endothelial overexpression of Sirt7 or supplementation with nicotinamide adenine dinucleotide (NAD)+ intermediate nicotinamide riboside which activated Sirt7; both approaches successfully reversed PH phenotypes.

CONCLUSION

The SIRT7/KLF4 axis ensures PAEC homeostasis, and pulmonary endothelium-specific SIRT7 targeting might constitute a PH therapeutic strategy.

Current Trends in Sirtuin Activator and Inhibitor Development

Sirtuins are NAD+-dependent protein deacylases and key metabolic regulators, coupling the cellular energy state with selective lysine deacylation to regulate many downstream cellular processes. Humans encode seven sirtuin isoforms (Sirt1-7) with diverse subcellular localization and deacylase targets. Sirtuins are considered protective anti-aging proteins since increased sirtuin activity is canonically associated with lifespan extension and decreased activity with developing aging-related diseases. However, sirtuins can also assume detrimental cellular roles where increased activity contributes to pathophysiology. Modulation of sirtuin activity by activators and inhibitors thus holds substantial potential for defining the cellular roles of sirtuins in health and disease and developing therapeutics. Instead of being comprehensive, this review discusses the well-characterized sirtuin activators and inhibitors available to date, particularly those with demonstrated selectivity, potency, and cellular activity. This review also provides recommendations regarding the best-in-class sirtuin activators and inhibitors for practical research as sirtuin modulator discovery and refinement evolve.

SIRT7: a novel molecular target for personalized cancer treatment?

The Sirtuin family of NAD+-dependent enzymes assumes a pivotal role in orchestrating adaptive responses to environmental fluctuations and stress stimuli, operating at both genomic and metabolic levels. Within this family, SIRT7 emerges as a versatile player in tumorigenesis, displaying both pro-tumorigenic and tumor-suppressive functions in a context-dependent manner. While other sirtuins, such as SIRT1 and SIRT6, exhibit a similar dual role in cancer, SIRT7 stands out due to distinctive attributes that sharply distinguish it from other family members. Among these are a unique key role in regulation of nucleolar functions, a close functional relationship with RNA metabolism and processing -exceptional among sirtuins- and a complex multienzymatic nature, which provides a diverse range of molecular targets. This review offers a comprehensive overview of the current understanding of the role of SIRT7 in various malignancies, placing particular emphasis on the intricate molecular mechanisms employed by SIRT7 to either stimulate or counteract tumorigenesis. Additionally, it delves into the unique features of SIRT7, discussing their potential and specific implications in tumor initiation and progression, underscoring the promising avenue of targeting SIRT7 for the development of innovative anti-cancer therapies.

Diminished NAD+ levels and activation of retrotransposons promote postovulatory aged oocyte (POAO) death

Death is the fate of postovulatory aged or unfertilized oocytes (POAO) in many animals. However, precise molecular mechanisms are yet to be discovered. Here, we demonstrate that increased amounts of reactive oxygen species (ROS), calcium ion (Ca+2) channels, and retrotransposon activity induce apoptosis, which in turn causes POAO death. Notably, suppression of ROS, Ca+2 channels, and retrotransposons delayed POAO death. Further, we found that the histone H4K12 and K16 acetylation increased via downregulation of NAD+ and NAD+ -dependent histone deacetylase SIRT3. Furthermore, adding NMN, sodium pyruvate, or CD38 inhibition delayed the death of postovulatory aged oocytes. Finally, we demonstrate the conservation of retrotransposon-induced DNA damage-dependent POAO death in higher-order vertebrates. Our findings suggest that POAO mortality is caused by cyclic cascade metabolic interactions in which low NAD+ levels increase histone acetylation by inhibiting histone deacetylases, resulting in an increase in retrotransposons, ROS, and Ca+2 channel activity and thus contributing to DNA damage-induced apoptosis.

Geroscience and pathology: a new frontier in understanding age-related diseases

Geroscience, a burgeoning discipline at the intersection of aging and disease, aims to unravel the intricate relationship between the aging process and pathogenesis of age-related diseases. This paper explores the pivotal role played by geroscience in reshaping our understanding of pathology, with a particular focus on age-related diseases. These diseases, spanning cardiovascular and cerebrovascular disorders, malignancies, and neurodegenerative conditions, significantly contribute to the morbidity and mortality of older individuals. We delve into the fundamental cellular and molecular mechanisms underpinning aging, including mitochondrial dysfunction and cellular senescence, and elucidate their profound implications for the pathogenesis of various age-related diseases. Emphasis is placed on the importance of assessing key biomarkers of aging and biological age within the realm of pathology. We also scrutinize the interplay between cellular senescence and cancer biology as a central area of focus, underscoring its paramount significance in contemporary pathological research. Moreover, we shed light on the integration of anti-aging interventions that target fundamental aging processes, such as senolytics, mitochondria-targeted treatments, and interventions that influence epigenetic regulation within the domain of pathology research. In conclusion, the integration of geroscience concepts into pathological research heralds a transformative paradigm shift in our understanding of disease pathogenesis and promises breakthroughs in disease prevention and treatment.

Sirtuins Affect Cancer Stem Cells via Epigenetic Regulation of Autophagy

Sirtuins (SIRTs) are stress-responsive proteins that regulate several post-translational modifications, partly by acetylation, deacetylation, and affecting DNA methylation. As a result, they significantly regulate several cellular processes. In essence, they prolong lifespan and control the occurrence of spontaneous tumor growth. Members of the SIRT family have the ability to govern embryonic, hematopoietic, and other adult stem cells in certain tissues and cell types in distinct ways. Likewise, they can have both pro-tumor and anti-tumor effects on cancer stem cells, contingent upon the specific tissue from which they originate. The impact of autophagy on cancer stem cells, which varies depending on the specific circumstances, is a very intricate phenomenon that has significant significance for clinical and therapeutic purposes. SIRTs exert an impact on the autophagy process, whereas autophagy reciprocally affects the activity of certain SIRTs. The mechanism behind this connection in cancer stem cells remains poorly understood. This review presents the latest findings that position SIRTs at the point where cancer cells and autophagy interact. Our objective is to highlight the various roles of distinct SIRTs in cancer stem cell-related functions through autophagy. This would demonstrate their significance in the genesis and recurrence of cancer and offer a more precise understanding of their treatment possibilities in relation to autophagy.

Antiaging Strategies and Remedies: A Landscape of Research Progress and Promise

Aging is typified by a gradual loss of physiological fitness and accumulation of cellular damage, leading to deteriorated functions and enhanced vulnerability to diseases. Antiaging research has a long history throughout civilization, with many efforts put forth to understand and prevent the effects of aging. Multiple strategies aiming to promote healthy aging and extend the lifespan have been developed including lifestyle adjustments, medical treatments, and social programs. A multitude of antiaging medicines and remedies have also been explored. Here, we use data from the CAS Content Collection to analyze the publication landscape of recent research related to antiaging strategies and treatments. We review the recent advances and delineate trends in research headway of antiaging knowledge and practice across time, geography, and development pipelines. We further assess the state-of-the-art antiaging approaches and explore their correlations with age-related diseases. The landscape of antiaging drugs has been outlined and explored. Well-recognized and novel, currently evaluated antiaging agents have also been summarized. Finally, we review clinical applications of antiaging products with their development pipelines. The objective of this review is to summarize current knowledge on preventive strategies and treatment remedies in the field of aging, to outline challenges and evaluate growth opportunities, in order to further efforts to solve the problems that remain.

Mitochondrial dysfunction and therapeutic perspectives in osteoporosis

Osteoporosis (OP) is a systemic skeletal disorder characterized by reduced bone mass and structural deterioration of bone tissue, resulting in heightened vulnerability to fractures due to increased bone fragility. This condition primarily arises from an imbalance between the processes of bone resorption and formation. Mitochondrial dysfunction has been reported to potentially constitute one of the most crucial mechanisms influencing the pathogenesis of osteoporosis. In essence, mitochondria play a crucial role in maintaining the delicate equilibrium between bone formation and resorption, thereby ensuring optimal skeletal health. Nevertheless, disruption of this delicate balance can arise as a consequence of mitochondrial dysfunction. In dysfunctional mitochondria, the mitochondrial electron transport chain (ETC) becomes uncoupled, resulting in reduced ATP synthesis and increased generation of reactive oxygen species (ROS). Reinforcement of mitochondrial dysfunction is further exacerbated by the accumulation of aberrant mitochondria. In this review, we investigated and analyzed the correlation between mitochondrial dysfunction, encompassing mitochondrial DNA (mtDNA) alterations, oxidative phosphorylation (OXPHOS) impairment, mitophagy dysregulation, defects in mitochondrial biogenesis and dynamics, as well as excessive ROS accumulation, with regards to OP (Figure 1). Furthermore, we explore prospective strategies currently available for modulating mitochondria to ameliorate osteoporosis. Undoubtedly, certain therapeutic strategies still require further investigation to ensure their safety and efficacy as clinical treatments. However, from a mitochondrial perspective, the potential for establishing effective and safe therapeutic approaches for osteoporosis appears promising.