The role of mitochondria in aging

Meta-analysis of Circulatory mitomiRs in stress Response: Unveiling the significance of miR-34a and miR-146a

BACKGROUND

MicroRNAs (miRNAs) are short, noncoding RNAs with essential roles in cellular pathways and are often associated with various diseases and stress conditions. Recently, they have been discovered in mitochondria, termed "mitomiRs," with unique functions. Mitochondria, crucial organelles for energy production and stress responses, Dysregulated mitomiRs functions and expression has been evident in stress conditions such as cardiovascular and neurodegenerative. In this meta-analysis we have systematically identified miR-34a & miR-146a as possible potential biomarkers for affliction.

METHODS

A meta-analysis was conducted to assess the potential role of miR-34a and miR-146a, two specific mitomiRs, as biomarkers in stress-related conditions. The study followed PRISMA guidelines, involving comprehensive database searches in May and September 2023. Twelve studies meeting predefined inclusion criteria were selected, and data analysis included the evaluation of miR-34a and miR-146a expression levels in various stress conditions compared to control groups. We also performed Gene ontology (GO) and Pathway enrichment analysis to observe how mitomiRs affects our body.

RESULTS

The meta-analysis revealed a significant increase in overall mitomiRs (miR-34a and miR-146a) expression levels in experimental groups experiencing different stress conditions compared to control groups (Z = 3.54, p < 0.05 using RevMan software). miR-34a demonstrated more pronounced upregulation and exhibited potential as a specific biomarker in certain stress-related conditions (Z = 2.22, p < 0.05). However, miR-146a did not show a significant difference, requiring further investigation in various stress-related contexts. The Analysis indicated a high degree of heterogeneity among the studies.

CONCLUSION

This meta-analysis emphasises the importance of mitomiRs, especially miR-34a, as potential biomarkers in the intricate interplay between stress, mitochondrial function, and disease. The study opens new avenues for exploring miRNAs' diagnostic and therapeutic applications in stress-related diseases, highlighting their pivotal role at the crossroads of molecular biology, psychology, and medicine.

Mitophagy in relation to chronic inflammation/ROS in aging

Various assaults on mitochondria occur during the human aging process, contributing to mitochondrial dysfunction. This mitochondrial dysfunction is intricately connected with aging and diseases associated with it. In vivo, the accumulation of defective mitochondria can precipitate inflammatory and oxidative stress, thereby accelerating aging. Mitophagy, an essential selective autophagy process, plays a crucial role in managing mitochondrial quality control and homeostasis. It is a highly specialized mechanism that systematically removes damaged or impaired mitochondria from cells, ensuring their optimal functioning and survival. By engaging in mitophagy, cells are able to maintain a balanced and stable environment, free from the potentially harmful effects of dysfunctional mitochondria. An ever-growing body of research highlights the significance of mitophagy in both aging and age-related diseases. Nonetheless, the association between mitophagy and inflammation or oxidative stress induced by mitochondrial dysfunction remains ambiguous. We review the fundamental mechanisms of mitophagy in this paper, delve into its relationship with age-related stress, and propose suggestions for future research directions.

Long-term demyelination and aging-associated changes in mice corpus callosum; evidence for the role of accelerated aging in remyelination failure in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disorder affecting the central nervous system. Evidence suggests that age-related neurodegeneration contributes to disability progression during the chronic stages of MS. Aging is characterized by decreased regeneration potential and impaired myelin repair in the brain. It is hypothesized that accelerated cellular aging contributes to the functional decline associated with neurodegenerative diseases. We assessed the impact of aging on myelin content in the corpus callosum (CC) and compared aging with the long-term demyelination (LTD) consequents induced by 12 weeks of feeding with a cuprizone (CPZ) diet. Initially, evaluating myelin content in 2-, 6-, and 18-month-old mice revealed a reduction in myelin content, particularly at 18 months. Myelin thickness was decreased and the g-ratio increased in aged mice. Although a lower myelin content and higher g-ratio were observed in LTD model mice, compared to the normally aged mice, both aging and LTD exhibited relatively similar myelin ultrastructure. Our findings provide evidence that LTD exhibits the hallmarks of aging such as elevated expression of senescence-associated genes, mitochondrial dysfunction, and high level of oxidative stress as observed following normal aging. We also investigated the senescence-associated β-galactosidase activity in O4+ late oligodendrocyte progenitor cells (OPCs). The senescent O4+/β-galactosidase+ cells were elevated in the CPZ diet. Our data showed that the myelin degeneration in CC occurs throughout the lifespan, and LTD induced by CPZ accelerates the aging process which may explain the impairment of myelin repair in patients with progressive MS.

Molecular Mechanisms of Genotype-Dependent Lifespan Variation Mediated by Caloric Restriction: Insight from Wild Yeast Isolates

Caloric restriction (CR) is known to extend lifespan across different species and holds great promise for preventing human age-onset pathologies. However, two major challenges exist. First, despite extensive research, the mechanisms of lifespan extension in response to CR remain elusive. Second, genetic differences causing variations in response to CR and genetic factors contributing to variability of CR response on lifespan are largely unknown. Here, we took advantage of natural genetic variation across 46 diploid wild yeast isolates of Saccharomyces species and the lifespan variation under CR conditions to uncover the molecular factors associated with CR response types. We identified genes and metabolic pathways differentially regulated in CR-responsive versus non-responsive strains. Our analysis revealed that altered mitochondrial function and activation of GCN4- mediated environmental stress response are inevitably linked to lifespan variation in response to CR and a unique mitochondrial metabolite might be utilized as a predictive marker for CR response rate. In sum, our data suggests that the effects of CR on longevity may not be universal, even among the closely related species or strains of a single species. Since mitochondrial-mediated signaling pathways are evolutionarily conserved, the dissection of related genetic pathways will be relevant to understanding the mechanism by which CR elicits its longevity effect.

Author summary

Caloric restriction (CR) is an energy-balanced nutrient intake without malnutrition to reduce food intake by 20-40%. CR leads to distinct metabolic reprogramming and adaptive changes in gene expression and, as a result, increases health and lifespan in various model organisms, from yeast to most likely primates. Besides extending lifespan, CR also holds great promise for treating many human age-onset pathologies, and the molecules underlying its effects are sought as targets of pharmaceutical aging therapeutics. However, despite extensive research, the mechanisms of lifespan extension in response to CR remain elusive. In addition, several studies in different aging models have now demonstrated that the longevity effect of CR can vary dramatically across different genotypes within a population. As such, CR might be beneficial for some yet detrimental for others, and the mechanisms underlying such genotype-dependent variation are not clear. In this study, we meet these challenges by dissecting molecular response to CR in diverse wild isolates of yeast strains, aiming to characterize pathways and molecules mediating CR's effects on replicative lifespan (RLS) diversity. We found that the RLS significantly differs across genetically diverse wild yeast isolates under CR conditions. Examining the relationships among the RLS phenotypes under CR and non-CR conditions, transcript, and metabolite provided insights into the role of mitochondrial functions in CR-mediated lifespan extension.

Puerarin Delays Mammary Gland Aging by Regulating Gut Microbiota and Inhibiting the p38MAPK Signaling Pathway

Mammary gland aging is one of the most important problems faced by humans and animals. How to delay mammary gland aging is particularly important. Puerarin is a kind of isoflavone substance extracted from Pueraria lobata, which has anti-inflammatory, antioxidant, and other pharmacological effects. However, the role of puerarin in delaying lipopolysaccharide (LPS)-induced mammary gland aging and its underlying mechanism remains unclear. On the one hand, we found that puerarin could significantly downregulate the expression of senescence-associated secretory phenotype (SASP) and age-related indicators (SA-β-gal, p53, p21, p16) in mammary glands of mice. In addition, puerarin mainly inhibited the p38MAPK signaling pathway to repair mitochondrial damage and delay mammary gland aging. On the other hand, puerarin could also delay the cellular senescence of mice mammary epithelial cells (mMECs) by targeting gut microbiota and promoting the secretion of gut microbiota metabolites. In conclusion, puerarin could not only directly act on the mMECs but also regulate the gut microbiota, thus, playing a role in delaying the aging of the mammary gland. Based on the above findings, we have discovered a new pathway for puerarin to delay mammary gland aging.

Age-Related Alterations in Immune Function and Inflammation: Focus on Ischemic Stroke

The aging of the global population poses significant scientific challenges. Moreover, the biological process of aging is the most significant risk factor for most chronic illnesses; therefore, understanding the molecular and cellular mechanisms underlying these aging-related challenges is crucial for extending the healthy lifespan of older individuals. Preventing brain aging remains a priority public health goal, and integrative and comprehensive aging analyses have revealed that immunosenescence is a potential cause of age-related brain damage and disease (e.g., stroke). Importantly, the neuroinflammatory and immune systems present two-way contact and thus can affect each other. Emerging evidence supports the numerous effects of immunosenescence- and inflammation-mediated immunity in neurologically injured brains. In this study, we briefly outline how aging alters the pathophysiology and transcriptional amplitude in patients who experienced stroke and then discuss how the immune system and its cellular components and molecular mechanisms are affected by age after stroke. Finally, we highlight emerging interventions with the potential to slow down or reduce aging and prevent stroke onset.

Revitalizing Ancient Mitochondria with Nano-Strategies: Mitochondria-Remedying Nanodrugs Concentrate on Disease Control

Mitochondria, widely known as the energy factories of eukaryotic cells, have a myriad of vital functions across diverse cellular processes. Dysfunctions within mitochondria serve as catalysts for various diseases, prompting widespread cellular demise. Mounting research on remedying damaged mitochondria indicates that mitochondria constitute a valuable target for therapeutic intervention against diseases. But the less clinical practice and lower recovery rate imply the limitation of traditional drugs, which need a further breakthrough. Nanotechnology has approached favorable regiospecific biodistribution and high efficacy by capitalizing on excellent nanomaterials and targeting drug delivery. Mitochondria-remedying nanodrugs have achieved ideal therapeutic effects. This review elucidates the significance of mitochondria in various cells and organs, while also compiling mortality data for related diseases. Correspondingly, nanodrug-mediate therapeutic strategies and applicable mitochondria-remedying nanodrugs in disease are detailed, with a full understanding of the roles of mitochondria dysfunction and the advantages of nanodrugs. In addition, the future challenges and directions are widely discussed. In conclusion, this review provides comprehensive insights into the design and development of mitochondria-remedying nanodrugs, aiming to help scientists who desire to extend their research fields and engage in this interdisciplinary subject.

L-Ergothioneine slows the progression of age-related hearing loss in CBA/CaJ mice

The naturally occurring amino acid, l-ergothioneine (EGT), has immense potential as a therapeutic, having shown promise in the treatment of other disease models, including neurological disorders. EGT is naturally uptaken into cells via its specific receptor, OCTN1, to be utilized by cells as an antioxidant and anti-inflammatory. In our current study, EGT was administered over a period of 6 months to 25-26-month-old CBA/CaJ mice as a possible treatment for age-related hearing loss (ARHL), since presbycusis has been linked to higher levels of cochlear oxidative stress, apoptosis, and chronic inflammation. Results from the current study indicate that EGT can prevent aging declines of some key features of ARHL. However, we found a distinct sex difference for the response to the treatments, for hearing - Auditory Brainstem Responses (ABRs) and Distortion Product Otoacoustic Emissions (DPOAEs). Males exhibited lower threshold declines in both low dose (LD) and high dose (HD) test groups throughout the testing period and did not display some of the characteristic aging declines in hearing seen in Control animals. In contrast, female mice did not show any therapeutic effects with either treatment dose. Further confirming this sex difference, EGT levels in whole blood sampling throughout the testing period showed greater uptake of EGT in males compared to females. Additionally, RT-PCR results from three tissue types of the inner ear confirmed EGT activity in the cochlea in both males and females. Males and females exhibited significant differences in biomarkers related to apoptosis (Cas-3), inflammation (TNF-a), oxidative stress (SOD2), and mitochondrial health (PGC1a).These changes were more prominent in males as compared to females, especially in stria vascularis tissue. Taken together, these findings suggest that EGT has the potential to be a naturally derived therapeutic for slowing down the progression of ARHL, and possibly other neurodegenerative diseases. EGT, while effective in the treatment of some features of presbycusis in aging males, could also be modified into a general prophylaxis for other age-related disorders where treatment protocols would include eating a larger proportion of EGT-rich foods or supplements. Lastly, the sex difference discovered here, needs further investigation to see if therapeutic conditions can be developed where aging females show better responsiveness to EGT.

Senotherapy, cancer, and aging

INTRODUCTION

We aimed to highlight the effects of senotherapy on the prevention and treatment of cancer in older individuals. The aim of senotherapy is to eliminate senescent cells. These cells express the senescence-associated secretory phenotype (SASP). With production of inflammatory cytokines, growth factors, and different type of proteases, the SASP is responsible for aging-associated disability and diseases. All mammalian cells experience senescence. The main agents of aging include fibroblasts and adipose cells. Senescent tumor cells may undergo genomic reprogramming and re-enter cell cycle with a stem cell phenotype.

MATERIALS AND METHODS

We conducted a Medline search for the following key words: senotherapy, senolysis, senomorphic agents. We provide a narrative review of the finding.

RESULTS

Different agents may eliminate senescent cells from cell cultures and murine models. These include metformin, rapamycin, desatinib, quercitin, fisetin, ruloxitinib, and BCL2 inhibitors. A randomized controlled study of metformin in 3,000 patients aged 65-79 without glucose intolerance aiming to establish whether senotherapy may prevent or reverse disability and aging associated diseases, including cancer, is ongoing. Senotherapy prolongs the life span and decreases the incidence of cancer in experimental animal models, as well as delays and reverses disability. Senescent tumor cells are found prior to treatment and after chemotherapy and radiation. These elements may be responsible for tumor recurrence and treatment refractoriness.

DISCUSSION

Senotherapy may have substantial effects on cancer management including decreased incidence and aggressiveness of cancer, improved tolerance of antineoplastic treatment, and prevention of relapse after primary treatment. Senotherapy may ameliorate several complications of cancer chemotherapy.

Miro-mediated mitochondrial transport: A new dimension for disease-related abnormal cell metabolism?

Mitochondria are versatile and highly dynamic organelles found in eukaryotic cells that play important roles in a variety of cellular processes. The importance of mitochondrial transport in cell metabolism, including variations in mitochondrial distribution within cells and intercellular transfer, has grown in recent years. Several studies have demonstrated that abnormal mitochondrial transport represents an early pathogenic alteration in a variety of illnesses, emphasizing its significance in disease development and progression. Mitochondrial Rho GTPase (Miro) is a protein found on the outer mitochondrial membrane that is required for cytoskeleton-dependent mitochondrial transport, mitochondrial dynamics (fusion and fission), and mitochondrial Ca2+ homeostasis. Miro, as a critical regulator of mitochondrial transport, has yet to be thoroughly investigated in illness. This review focuses on recent developments in recognizing Miro as a crucial molecule in controlling mitochondrial transport and investigates its roles in diverse illnesses. It also intends to shed light on the possibilities of targeting Miro as a therapeutic method for a variety of diseases.

Mitochondrial respiration atlas reveals differential changes in mitochondrial function across sex and age

Organ function declines with age, and large-scale transcriptomic analyses have highlighted differential aging trajectories across tissues. The mechanisms underlying shared and organ-selective functional changes across the lifespan, however, still remains poorly understood. Given the central role of mitochondria in powering cellular processes needed to maintain tissue health, we therefore undertook a systematic assessment of respiratory activity across 33 different tissues in young (2.5 months) and old (20 months) mice of both sexes. Our high-resolution mitochondrial respiration atlas reveals: 1) within any group of mice, mitochondrial activity varies widely across tissues, with the highest values consistently seen in heart, brown fat, and kidney; 2) biological sex is a significant but minor contributor to mitochondrial respiration, and its contributions are tissue-specific, with major differences seen in the pancreas, stomach, and white adipose tissue; 3) age is a dominant factor affecting mitochondrial activity, especially across different fat depots and skeletal muscle groups, and most brain regions; 4) age-effects can be sex- and tissue-specific, with some of the largest effects seen in pancreas, heart, adipose tissue, and skeletal muscle; and 5) while aging alters the functional trajectories of mitochondria in a majority of tissues, some are remarkably resilient to age-induced changes. Altogether, our data provide the most comprehensive compendium of mitochondrial respiration and illuminate functional signatures of aging across diverse tissues and organ systems.

Clinical-Genomic Analysis of 1261 Patients with Ehlers-Danlos Syndrome Outlines an Articulo-Autonomic Gene Network (Entome)

Systematic evaluation of 80 history and 40 history findings diagnosed 1261 patients with Ehlers-Danlos syndrome (EDS) by direct or online interaction, and 60 key findings were selected for their relation to clinical mechanisms and/or management. Genomic testing results in 566 of these patients supported EDS relevance by their differences from those in 82 developmental disability patients and by their association with general rather than type-specific EDS findings. The 437 nuclear and 79 mitochondrial DNA changes included 71 impacting joint matrix (49 COL5), 39 bone (30 COL1/2/9/11), 22 vessel (12 COL3/8VWF), 43 vessel-heart (17FBN1/11TGFB/BR), 59 muscle (28 COL6/12), 56 neural (16 SCN9A/10A/11A), and 74 autonomic (13 POLG/25porphyria related). These genes were distributed over all chromosomes but the Y, a network analogized to an 'entome' where DNA change disrupts truncal mechanisms (skin constraint, neuromuscular support, joint vessel flexibility) and produces a mirroring cascade of articular and autonomic symptoms. The implied sequences of genes from nodal proteins to hypermobility to branching tissue laxity or dysautonomia symptoms would be ideal for large language/artificial intelligence analyses.

A biological age model based on physical examination data to predict mortality in a Chinese population

Biological age could be reflective of an individual's health status and aging degree. Limited estimations of biological aging based on physical examination data in the Chinese population have been developed to quantify the rate of aging. We developed and validated a novel aging measure (Balanced-AGE) based on readily available physical health examination data. In this study, a repeated sub-sampling approach was applied to address the data imbalance issue, and this approach significantly improved the performance of biological age (Balanced-AGE) in predicting all-cause mortality with a 10-year time-dependent AUC of 0.908 for all-cause mortality. This mortality prediction tool was found to be effective across different subgroups by age, sex, smoking, and alcohol consumption status. Additionally, this study revealed that individuals who were underweight, smokers, or drinkers had a higher extent of age acceleration. The Balanced-AGE may serve as an effective and generally applicable tool for health assessment and management among the elderly population.

In vitro and in vivo studies on the effect of a mitochondrial fusion promoter on Leydig cell integrity and function

Background: The interstitial testicular Leydig cells are responsible for the production of testosterone, which functionally deteriorate with normal aging. Decreased expression of mitochondrial steroidogenic interactome proteins and diminished mitochondrial function in aging Leydig cells suggest that mitochondrial dynamics play a role in maintaining adequate levels of testosterone. Optic atrophy 1 (OPA1) protein regulates mitochondrial dynamics and cristae formation in many cell types. Previous studies showed that increasing OPA1 expression in dysfunctional Leydig cells restored mitochondrial function and recovered androgen production to levels found in healthy Leydig cells. These findings suggested that mitochondrial dynamics may be a promising target to ameliorate diminished testosterone levels in aging males. Methods: We used twelve-month-old rats to explore the relationship between mitochondrial dynamics and Leydig cell function. Isolated Leydig cells from aged rats were treated ex vivo with the cell-permeable mitochondrial fusion promoter 4-Chloro-2-(1-(2-(2,4,6-trichlorophenyl)hydrazono)ethyl) phenol (mitochondrial fusion promoter M1), which enhances mitochondrial tubular network formation. In parallel, rats were treated with 2 mg/kg/day M1 for 6 weeks before Leydig cells were isolated. Results: Ex vivo M1-treated cells showed enhanced mitochondrial tubular network formation by transmission electron microscopy, enhanced Leydig cell mitochondrial integrity, improved mitochondrial function, and higher testosterone biosynthesis compared to controls. However, in vivo treatment of aged rats with M1 not only failed to re-establish testosterone levels to that of young rats, it also led to further reduction of testosterone levels and increased apoptosis, suggesting M1 toxicity in the testis. The in vivo M1 toxicity seemed to be tissue-specific, however. Conclusion: Promoting mitochondrial fusion may be one approach to enhancing cell health and wellbeing with aging, but more investigations are warranted. Our findings suggest that fusion promoters could potentially enhance the productivity of aged Leydig cells when carefully regulated.

Nicotinamide mononucleotide, a potential future treatment in ocular diseases

PURPOSE

The burden of ocular diseases has been gradually increasing worldwide. Various factors are suggested for the development and progression of ocular diseases, such as ocular inflammation, oxidative stress, and complex metabolic dysregulation. Thus, managing ocular diseases requires the modulation of pathologic signaling pathways through many mechanisms. Nicotinamide mononucleotide (NMN) is a bioactive molecule naturally found in life forms. NMN is a direct precursor of the important molecule nicotinamide adenine dinucleotide (NAD+), an essential co-enzyme required for enormous cellular functions in most life forms. While the recent experimental evidence of NMN treatment in various metabolic diseases has been well-reviewed, NMN treatment in ocular diseases has not been comprehensively summarized yet. In this regard, we aimed to focus on the therapeutic roles of NMN treatment in various ocular diseases with recent advances.

METHODS

How we came to our current opinion with a recent summary was described based on our own recent reports as well as a search of the related literature.

RESULTS

We found that NMN treatment might be available for the prevention of and protection from various experimental ocular diseases, as NMN treatment modulated ocular inflammation, oxidative stress, and complex metabolic dysregulation in murine models for eye diseases such as ischemic retinopathy, corneal defect, glaucoma, and age-related macular degeneration.

CONCLUSION

Our current review suggests and discusses new modes of actions of NMN for the prevention of and protection from various ocular diseases and can urge future research to obtain more solid evidence on a potential future NMN treatment in ocular diseases at the preclinical stages.

The Mst1/2-BNIP3 axis is required for mitophagy induction and neuronal viability under mitochondrial stress

Mitophagy induction upon mitochondrial stress is critical for maintaining mitochondrial homeostasis and cellular function. Here, we found that Mst1/2 (Stk3/4), key regulators of the Hippo pathway, are required for the induction of mitophagy under various mitochondrial stress conditions. Knockdown of Mst1/2 or pharmacological inhibition by XMU-MP-1 treatment led to impaired mitophagy induction upon CCCP and DFP treatment. Mechanistically, Mst1/2 induces mitophagy independently of the PINK1-Parkin pathway and the canonical Hippo pathway. Moreover, our results suggest the essential involvement of BNIP3 in Mst1/2-mediated mitophagy induction upon mitochondrial stress. Notably, Mst1/2 knockdown diminishes mitophagy induction, exacerbates mitochondrial dysfunction, and reduces cellular survival upon neurotoxic stress in both SH-SY5Y cells and Drosophila models. Conversely, Mst1 and Mst2 expression enhances mitophagy induction and cell survival. In addition, AAV-mediated Mst1 expression reduced the loss of TH-positive neurons, ameliorated behavioral deficits, and improved mitochondrial function in an MPTP-induced Parkinson's disease mouse model. Our findings reveal the Mst1/2-BNIP3 regulatory axis as a novel mediator of mitophagy induction under conditions of mitochondrial stress and suggest that Mst1/2 play a pivotal role in maintaining mitochondrial function and neuronal viability in response to neurotoxic treatment.

mtDNA extramitochondrial replication mediates mitochondrial defect effects

A high ratio of severe mitochondrial defects causes multiple human mitochondrial diseases. However, until now, the in vivo rescue signal of such mitochondrial defect effects has not been clear. Here, we built fly mitochondrial defect models by knocking down the essential mitochondrial genes dMterf4 and dMrps23. Following genome-wide RNAi screens, we found that knockdown of Med8/Tfb4/mtSSB/PolG2/mtDNA-helicase rescued dMterf4/dMrps23 RNAi-mediated mitochondrial defect effects. Extremely surprisingly, they drove mtDNA replication outside mitochondria through the Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase axis to amplify cytosolic mtDNA, leading to activation of the cGAS-Sting-like IMD pathway to partially mediate dMterf4/dMrps23 RNAi-triggered effects. Moreover, we found that the Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase axis also mediated other fly mitochondrial gene defect-triggered dysfunctions and Drosophila aging. Overall, our study demarcates the Med8/Tfb4-mtSSB/PolG2/mtDNA-helicase axis as a candidate mechanism to mediate mitochondrial defect effects through driving mtDNA extramitochondrial replication; dysfunction of this axis might be used for potential treatments for many mitochondrial and age-related diseases.

Current senolytics: Mode of action, efficacy and limitations, and their future

Senescence is a cellular state characterized by its near-permanent halted cell cycle and distinct secretory phenotype. Although senescent cells have a variety of beneficial physiological functions, progressive accumulation of these cells due to aging or other conditions has been widely shown to provoke deleterious effects on the normal functioning of the same or higher-level biological organizations. Recently, erasing senescent cells in vivo, using senolytics, could ameliorate diseases identified with an elevated number of senescent cells. Since then, researchers have struggled to develop new senolytics each with different selectivity and potency. In this review, we have gathered and classified the proposed senolytics and discussed their mechanisms of action. Moreover, we highlight the heterogeneity of senolytics regarding their effect sizes, and cell type specificity as well as comment on the exploited strategies to improve these features. Finally, we suggest some prospective routes for the novel methods for ablation of senescent cells.

Oroxylin A ameliorates ultraviolet radiation-induced premature skin aging by regulating oxidative stress via the Sirt1 pathway

Skin is susceptible to premature aging in response to ultraviolet (UV) radiation-induced oxidative stress, which can ultimately result in aberrant aging or age-related disorders. Accordingly, strategies that can be adopted to mitigate oxidative stress may contribute to protecting skin from induced aging-related damage, thereby offering promising approaches for the treatment of skin diseases and disorders. In this regard, oroxylin A (OA), a natural flavonoid isolated from certain plants used in traditional Chinese medicine, is considered to have notable antioxidant, anti-inflammatory, and anti-apoptotic properties, and is often used to treat certain inflammatory diseases. To date, however, there has been comparatively little research on the effects of OA with respect skin aging. In this study, we utilized UV radiation-induced mouse and cellular models of aging to assess the efficacy of OA in protecting against skin aging. Subsequently, to elucidate the potential mechanisms underlying the protective effect of OA on skin aging, we performed molecular docking analysis to investigate the involvement of the anti-aging gene Sirt1, which was further confirmed on the basis of Sirt1 gene silencing. We accordingly demonstrated that by promoting an increase in the expression of Sirt1, OA can contribute to suppressing UV-induced skin photo-aging in cells/mice by reducing oxidative stress. Furthermore, we established that by activating Sirt1, OA can also promote the dissociation of Nrf2 from Keap1 and its subsequent nuclear translocation. Collectively, our findings in this study reveal OA to be an effective natural compound that can be administered to delay the aging of skin triggered by UV, both in vivo and in vitro, by binding to Sirt1 to promote the deacetylation and nuclear translocation of Nrf2, thereby contributing to a reduction in oxidative stress. These findings may this provide a therapeutic target for the prevention of skin aging or aging-induced skin diseases.

Sirtuin 4 (Sirt4) downregulation contributes to chondrocyte senescence and osteoarthritis via mediating mitochondrial dysfunction

Chondrocyte senescence has recently been proposed as a key pathogenic mechanism in the etiology of osteoarthritis (OA). Nevertheless, the precise molecular mechanisms underlying chondrocyte senescence remain poorly understood. To address this knowledge gap, we conducted an investigation into the involvement of Sirtuin 4 (Sirt4) in chondrocyte senescence. Our experimental findings revealed a downregulation of Sirt4 expression in TBHP-induced senescent chondrocytes in vitro, as well as in mouse OA cartilage. Additionally, we observed that the knockdown of Sirt4 in chondrocytes promoted cellular senescence and cartilage degradation, while the overexpression of Sirt4 protected the cells against TBHP-mediated senescence of chondrocytes and cartilage degradation. Moreover, our findings revealed elevated levels of reactive oxygen species (ROS), abnormal mitochondrial morphology, compromised mitochondrial membrane potential, and reduced ATP production in Sirt4 knockdown chondrocytes, indicative of mitochondrial dysfunction. Conversely, Sirt4 overexpression successfully mitigated TBHP-induced mitochondrial dysfunction. Further analysis revealed that Sirt4 downregulation impaired the cellular capacity to eliminate damaged mitochondria by inhibiting Pink1 in chondrocytes, thereby enhancing the accumulation of ROS and facilitating chondrocyte senescence. Notably, the overexpression of Pink1 counteracted the effects of Sirt4 knockdown on mitochondrial dysfunction. Importantly, our study demonstrated the promise of gene therapy employing a lentiviral vector encoding mouse Sirt4, as it successfully preserved the integrity of articular cartilage in mouse models of OA. In conclusion, our findings provide compelling evidence that the overexpression of Sirt4 enhances mitophagy, restores mitochondrial function, and protects against chondrocyte senescence, thereby offering a novel therapeutic target and potential strategy for the treatment of OA.

Deep rest: An integrative model of how contemplative practices combat stress and enhance the body's restorative capacity

Engaging in contemplative practice like meditation, yoga, and prayer, is beneficial for psychological and physical well-being. Recent research has identified several underlying psychological and biological pathways that explain these benefits. However, there is not yet consensus on the underlying overlapping physiological mechanisms of contemplative practice benefits. In this article, we integrate divergent scientific literatures on contemplative practice interventions, stress science, and mitochondrial biology, presenting a unified biopsychosocial model of how contemplative practices reduce stress and promote physical health. We argue that engaging in contemplative practice facilitates a restorative state termed "deep rest," largely through safety signaling, during which energetic resources are directed toward cellular optimization and away from energy-demanding stress states. Our model thus presents a framework for how contemplative practices enhance positive psychological and physiological functioning by optimizing cellular energy consumption. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Blood-Based mtDNA Quantification Indicates Population-Specific Differences Associated with Alzheimer's Disease-Related Risk

BACKGROUND

Age is known to be the biggest risk factor for Alzheimer's disease (AD), and Mexican Americans (MAs), who are one of the fastest-aging populations in the United States, are at a uniquely elevated risk. Mitochondrial stress and dysfunction are key players in the progression of AD and are also known to be impacted by lifestyle and environmental exposures/stressors.

OBJECTIVE

This study aimed to identify population-specific differences in indicators of mitochondrial stress and dysfunction associated with AD risk that are detectable in the blood.

METHODS

Examining blood from both non-Hispanic white (NHW) and MA participants (N = 527, MA n = 284, NHW n = 243), mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) copy numbers were assessed through quantitative PCR. Data was stratified by population and sample type, and multiple linear regression analyses were performed to identify factors that may influence this phenotype of mitochondrial dysfunction.

RESULTS

In the MA cohort, there was a significant relationship between cellular mtDNA:nDNA ratio and body mass index, CDR sum of boxes score, the APOEɛ2/ɛ3 genotype, and education. Further, there was a significant relationship between cell-free mtDNA copy number and both education and CDR sum score. In the NHW cohort, there was a significant relationship between cellular mtDNA:nDNA ratio and both age and CDR sum score. Age was associated with cell-free mtDNA in the NHW cohort.

CONCLUSIONS

This evidence supports the existence of population-based differences in the factors that are predictive of this blood-based phenotype of mitochondrial dysfunction, which may be indicative of cognitive decline and AD risk.

Molecular mechanisms underlying sarcopenia in heart failure

The loss of skeletal muscle, also known as sarcopenia, is an aging-associated muscle disorder that is disproportionately present in heart failure (HF) patients. HF patients with sarcopenia have poor outcomes compared to the overall HF patient population. The prevalence of sarcopenia in HF is only expected to grow as the global population ages, and novel treatment strategies are needed to improve outcomes in this cohort. Multiple mechanistic pathways have emerged that may explain the increased prevalence of sarcopenia in the HF population, and a better understanding of these pathways may lead to the development of therapies to prevent muscle loss. This review article aims to explore the molecular mechanisms linking sarcopenia and HF, and to discuss treatment strategies aimed at addressing such molecular signals.

Estrogen-Related Receptor Agonism Reverses Mitochondrial Dysfunction and Inflammation in the Aging Kidney

A gradual decline in renal function occurs even in healthy aging individuals. In addition to aging, per se, concurrent metabolic syndrome and hypertension, which are common in the aging population, can induce mitochondrial dysfunction and inflammation, which collectively contribute to age-related kidney dysfunction and disease. This study examined the role of the nuclear hormone receptors, the estrogen-related receptors (ERRs), in regulation of age-related mitochondrial dysfunction and inflammation. The ERRs were decreased in both aging human and mouse kidneys and were preserved in aging mice with lifelong caloric restriction (CR). A pan-ERR agonist, SLU-PP-332, was used to treat 21-month-old mice for 8 weeks. In addition, 21-month-old mice were treated with a stimulator of interferon genes (STING) inhibitor, C-176, for 3 weeks. Remarkably, similar to CR, an 8-week treatment with a pan-ERR agonist reversed the age-related increases in albuminuria, podocyte loss, mitochondrial dysfunction, and inflammatory cytokines, via the cyclic GMP-AMP synthase-STING and STAT3 signaling pathways. A 3-week treatment of 21-month-old mice with a STING inhibitor reversed the increases in inflammatory cytokines and the senescence marker, p21/cyclin dependent kinase inhibitor 1A (Cdkn1a), but also unexpectedly reversed the age-related decreases in PPARG coactivator (PGC)-1α, ERRα, mitochondrial complexes, and medium chain acyl coenzyme A dehydrogenase (MCAD) expression. These studies identified ERRs as CR mimetics and as important modulators of age-related mitochondrial dysfunction and inflammation. These findings highlight novel druggable pathways that can be further evaluated to prevent progression of age-related kidney disease.

Monitoring live mitochondrial metabolism in real-time using NMR spectroscopy

Investigation of mitochondrial metabolism is gaining increased interest owing to the growing recognition of the role of mitochondria in health and numerous diseases. Studies of isolated mitochondria promise novel insights into the metabolism devoid of confounding effects from other cellular organelles such as cytoplasm. This study describes the isolation of mitochondria from mouse skeletal myoblast cells (C2C12) and the investigation of live mitochondrial metabolism in real-time using isotope tracer-based NMR spectroscopy. [3-13 C1 ]pyruvate was used as the substrate to monitor the dynamic changes of the downstream metabolites in mitochondria. The results demonstrate an intriguing phenomenon, in which lactate is produced from pyruvate inside the mitochondria and the results were confirmed by treating mitochondria with an inhibitor of mitochondrial pyruvate carrier (UK5099). Lactate is associated with health and numerous diseases including cancer and, to date, it is known to occur only in the cytoplasm. The insight that lactate is also produced inside mitochondria opens avenues for exploring new pathways of lactate metabolism. Further, experiments performed using inhibitors of the mitochondrial respiratory chain, FCCP and rotenone, show that [2-13 C1 ]acetyl coenzyme A, which is produced from [3-13 C1 ]pyruvate and acts as a primary substrate for the tricarboxylic acid cycle in mitochondria, exhibits a remarkable sensitivity to the inhibitors. These results offer a direct approach to visualize mitochondrial respiration through altered levels of the associated metabolites.

Clinical chorioamnionitis at term is characterized by changes in the plasma concentration of CHCHD2/MNRR1, a mitochondrial protein

OBJECTIVE

Mitochondrial dysfunction was observed in acute systemic inflammatory conditions such as sepsis and might be involved in sepsis-induced multi-organ failure. Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 2 (CHCHD2), also known as Mitochondrial Nuclear Retrograde Regulator 1 (MNRR1), a bi-organellar protein located in the mitochondria and the nucleus, is implicated in cell respiration, survival, and response to tissue hypoxia. Recently, the reduction of the cellular CHCHD2/MNRR1 protein, as part of mitochondrial dysfunction, has been shown to play a role in the amplification of inflammatory cytokines in a murine model of lipopolysaccharide-induced systemic inflammation. The aim of this study was to determine whether the plasma concentration of CHCHD2/MNRR1 changed during human normal pregnancy, spontaneous labor at term, and clinical chorioamnionitis at term.

METHODS

We conducted a cross-sectional study that included the following groups: 1) non-pregnant women (n = 17); 2) normal pregnant women at various gestational ages from the first trimester until term (n = 110); 3) women at term with spontaneous labor (n = 50); and 4) women with clinical chorioamnionitis at term in labor (n = 25). Plasma concentrations of CHCHD2/MNRR1 were assessed by an enzyme-linked immunosorbent assay.

RESULTS

1) Pregnant women at term in labor with clinical chorioamnionitis had a significantly higher plasma CHCHD2/MNRR1 concentration than those in labor without chorioamnionitis (p = .003); 2) CHCHD2/MNRR1 is present in the plasma of healthy non-pregnant and normal pregnant women without significant differences in its plasma concentrations between the two groups; 3) there was no correlation between maternal plasma CHCHD2/MNRR1 concentration and gestational age at venipuncture; and 4) plasma CHCHD2/MNRR1 concentration was not significantly different in women at term in spontaneous labor compared to those not in labor.

CONCLUSIONS

CHCHD2/MNRR1 is physiologically present in the plasma of healthy non-pregnant and normal pregnant women, and its concentration does not change with gestational age and parturition at term. However, plasma CHCHD2/MNRR1 is elevated in women at term with clinical chorioamnionitis. CHCHD2/MNRR1, a novel bi-organellar protein located in the mitochondria and the nucleus, is released into maternal plasma during systemic inflammation.

Evidence for the participation of CHCHD2/MNRR1, a mitochondrial protein, in spontaneous labor at term and in preterm labor with intra-amniotic infection

OBJECTIVE

Intra-amniotic inflammation (IAI), associated with either microbe (infection) or danger signals (sterile), plays a major role in the pathophysiology of preterm labor and delivery. Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 2 (CHCHD2) [also known as Mitochondrial Nuclear Retrograde Regulator 1 (MNRR1)], a mitochondrial protein involved in oxidative phosphorylation and cell survival, is capable of sensing tissue hypoxia and inflammatory signaling. The ability to maintain an appropriate energy balance at the cellular level while adapting to environmental stress is essential for the survival of an organism. Mitochondrial dysfunction has been observed in acute systemic inflammatory conditions, such as sepsis, and is proposed to be involved in sepsis-induced multi-organ failure. The purpose of this study was to determine the amniotic fluid concentrations of CHCHD2/MNRR1 in pregnant women, women at term in labor, and those in preterm labor (PTL) with and without IAI.

METHODS

This cross-sectional study comprised patients allocated to the following groups: (1) mid-trimester (n = 16); (2) term in labor (n = 37); (3) term not in labor (n = 22); (4) PTL without IAI who delivered at term (n = 25); (5) PTL without IAI who delivered preterm (n = 47); and (6) PTL with IAI who delivered preterm (n = 53). Diagnosis of IAI (amniotic fluid interleukin-6 concentration ≥2.6 ng/mL) included cases associated with microbial invasion of the amniotic cavity and those of sterile nature (absence of detectable bacteria, using culture and molecular microbiology techniques). Amniotic fluid and maternal plasma CHCHD2/MNRR1 concentrations were determined with a validated and sensitive immunoassay.

RESULTS

(1) CHCHD2/MNRR1 was detectable in all amniotic fluid samples and women at term without labor had a higher amniotic fluid CHCHD2/MNRR1 concentration than those in the mid-trimester (p = 0.003); (2) the amniotic fluid concentration of CHCHD2/MNRR1 in women at term in labor was higher than that in women at term without labor (p = 0.01); (3) women with PTL and IAI had a higher amniotic fluid CHCHD2/MNRR1 concentration than those without IAI, either with preterm (p < 0.001) or term delivery (p = 0.01); (4) women with microbial-associated IAI had a higher amniotic fluid CHCHD2/MNRR1 concentration than those with sterile IAI (p < 0.001); (5) among women with PTL and IAI, the amniotic fluid concentration of CHCHD2/MNRR1 correlated with that of interleukin-6 (Spearman's Rho = 0.7; p < 0.001); and (6) no correlation was observed between amniotic fluid and maternal plasma CHCHD2/MNRR1 concentrations among women with PTL.

CONCLUSION

CHCHD2/MNRR1 is a physiological constituent of human amniotic fluid in normal pregnancy, and the amniotic concentration of this mitochondrial protein increases during pregnancy, labor at term, and preterm labor with intra-amniotic infection. Hence, CHCHD2/MNRR1 may be released into the amniotic cavity by dysfunctional mitochondria during microbial-associated IAI.

The link between obesity and aging - insights into cardiac energy metabolism

Obesity and aging are well-established risk factors for a range of diseases, including cardiovascular diseases and type 2 diabetes. Given the escalating prevalence of obesity, the aging population, and the subsequent increase in cardiovascular diseases, it is crucial to investigate the underlying mechanisms involved. Both aging and obesity have profound effects on the energy metabolism through various mechanisms, including metabolic inflexibility, altered substrate utilization for energy production, deregulated nutrient sensing, and mitochondrial dysfunction. In this review, we aim to present and discuss the hypothesis that obesity, due to its similarity in changes observed in the aging heart, may accelerate the process of cardiac aging and exacerbate the clinical outcomes of elderly individuals with obesity.

The Myc-Like Mlx Network Impacts Aging and Metabolism

The "Mlx" and "Myc" Networks share many common gene targets. Just as Myc's activity depends upon its heterodimerization with Max, the Mlx Network requires that the Max-like factor Mlx associate with the Myc-like factors MondoA or ChREBP. We show here that body-wide Mlx inactivation, like that of Myc, accelerates numerous aging-related phenotypes pertaining to body habitus and metabolism. The deregulation of numerous aging-related Myc target gene sets is also accelerated. Among other functions, these gene sets often regulate ribosomal and mitochondrial structure and function, genomic stability and aging. Whereas "MycKO" mice have an extended lifespan because of a lower cancer incidence, "MlxKO" mice have normal lifespans and a somewhat higher cancer incidence. Like Myc, Mlx, MondoA and ChREBP expression and that of their target genes, deteriorate with age in both mice and humans, underscoring the importance of life-long and balanced cross-talk between the two Networks to maintain normal aging.

Do multiple physiological OCT biomarkers indicate age-related decline in rod mitochondrial function in C57BL/6J mice?

Purpose

To test the hypothesis that rod photoreceptor mitochondria function in vivo progressively declines over time.

Methods

2, 12, and 24 month-old dark- and light-adapted C57BL/6J (B6J) mice were examined by OCT. We measured (i) an index of mitochondrial configuration within photoreceptors measured from the profile shape aspect ratio (MCP/AR) of the hyperreflective band posterior to the external limiting membrane (ELM), (ii) a proxy for energy-dependent pH-triggered water removal, the thickness of the ELM-retinal pigment epithelium (ELM-RPE), and its correlate (iii) the hyporeflective band (HB) signal intensity at the photoreceptor tips. Visual performance was assessed by optokinetic tracking.

Results

In 2 and 24 month-old mice, MCP/AR in both inferior and superior retina was smaller in light than in dark; no dark-light differences were noted in 12 month-old mice. Dark-adapted inferior and superior, and light-adapted superior, ELM-RPE thickness increased with age. The dark-light difference in ELM-RPE thickness remained constant across all ages. All ages showed a decreased HB signal intensity magnitude in dark relative to light. In 12 month-old mice, the dark-light difference in HB magnitude was greater than in younger and older mice. Anatomically, outer nuclear layer thickness decreased with age. Visual performance indices were reduced at 24 month-old compared to 2 month-old mice.

Conclusion

While the working hypothesis was not supported herein, the results raise the possibility of a mid-life adaptation in rod mitochondrial function during healthy aging in B6J mice based on OCT biomarkers, a plasticity that occurred prior to declines in visual performance.

Exercise mitigates age-related metabolic diseases by improving mitochondrial dysfunction

The benefits of regular physical activity are related to delaying and reversing the onset of ageing and age-related disorders, including cardiomyopathy, neurodegenerative diseases, cancer, obesity, diabetes, and fatty liver diseases. However, the molecular mechanisms of the benefits of exercise or physical activity on ageing and age-related disorders remain poorly understood. Mitochondrial dysfunction is implicated in the pathogenesis of ageing and age-related metabolic diseases. Mitochondrial health is an important mediator of cellular function. Therefore, exercise alleviates metabolic diseases in individuals with advancing ageing and age-related diseases by the remarkable promotion of mitochondrial biogenesis and function. Exerkines are identified as signaling moieties released in response to exercise. Exerkines released by exercise have potential roles in improving mitochondrial dysfunction in response to age-related disorders. This review comprehensive summarizes the benefits of exercise in metabolic diseases, linking mitochondrial dysfunction to the onset of age-related diseases. Using relevant examples utilizing this approach, the possibility of designing therapeutic interventions based on these molecular mechanisms is addressed.

The rod synapse in aging wildtype and Dscaml1 mutant mice

The retina is an intricately organized neural tissue built on cone and rod pathways for color and night vision. Genetic mutations that disrupt the proper function of the rod circuit contribute to blinding diseases including retinitis pigmentosa and congenital stationary night blindness (CSNB). Down Syndrome cell adhesion molecule like 1 (Dscaml1) is expressed by rods, rod bipolar cells (RBCs), and sub-populations of amacrine cells, and has been linked to a middle age onset of CSNB in humans. However, how Dscaml1 contributes to this visual deficit remains unexplored. Here, we probed Dscaml1's role in the maintenance of the rod-to-RBC synapse using a loss of function mouse model. We used immunohistochemistry to investigate the anatomical formation and maintenance of the rod-to-RBC synapse in the young, adult, and aging retina. We generated 3D reconstructions, using serial electron micrographs, of rod spherules and RBCs to measure the number of invaginating neurites, RBC dendritic tip number, and RBC mitochondrial morphology. We find that while rod-to-RBC synapses form and are maintained, similar to wildtype, that there is an increase in the number of invaginating neurites in rod spherules, a reduction in RBC dendritic tips, and reduced mitochondrial volume and complexity in the Dscaml1 mutant retina compared to controls. We also observed precocious sprouting of RBC dendrites into the outer nuclear layer (ONL) of the Dscaml1 mutant retina compared to controls. These results contribute to our knowledge of Dscaml1's role in rod circuit development and maintenance and give additional insight into possible genetic therapy targets for blinding diseases and disorders like CSNB.

Interleukin-6 Drives Mitochondrial Dysregulation and Accelerates Physical Decline: Insights From an Inducible Humanized IL-6 Knock-In Mouse Model

Chronic activation of inflammatory pathways (CI) and mitochondrial dysfunction are independently linked to age-related functional decline and early mortality. Interleukin 6 (IL-6) is among the most consistently elevated chronic activation of inflammatory pathways markers, but whether IL-6 plays a causative role in this mitochondrial dysfunction and physical deterioration remains unclear. To characterize the role of IL-6 in age-related mitochondrial dysregulation and physical decline, we have developed an inducible human IL-6 (hIL-6) knock-in mouse (TetO-hIL-6mitoQC) that also contains a mitochondrial-quality control reporter. Six weeks of hIL-6 induction resulted in upregulation of proinflammatory markers, cell proliferation and metabolic pathways, and dysregulated energy utilization. Decreased grip strength, increased falls off the treadmill, and increased frailty index were also observed. Further characterization of skeletal muscles postinduction revealed an increase in mitophagy, downregulation of mitochondrial biogenesis genes, and an overall decrease in total mitochondrial numbers. This study highlights the contribution of IL-6 to mitochondrial dysregulation and supports a causal role of hIL-6 in physical decline and frailty.

N6-Methyladenine Progressively Accumulates in Mitochondrial DNA during Aging

N6-methyladenine (6mA) in the DNA is a conserved epigenetic mark with various cellular, physiological and developmental functions. Although the presence of 6mA was discovered a few years ago in the nuclear genome of distantly related animal taxa and just recently in mammalian mitochondrial DNA (mtDNA), accumulating evidence at present seriously questions the presence of N6-adenine methylation in these genetic systems, attributing it to methodological errors. In this paper, we present a reliable, PCR-based method to determine accurately the relative 6mA levels in the mtDNA of Caenorhabditis elegans, Drosophila melanogaster and dogs, and show that these levels gradually increase with age. Furthermore, daf-2(-)-mutant worms, which are defective for insulin/IGF-1 (insulin-like growth factor) signaling and live twice as long as the wild type, display a half rate at which 6mA progressively accumulates in the mtDNA as compared to normal values. Together, these results suggest a fundamental role for mtDNA N6-adenine methylation in aging and reveal an efficient diagnostic technique to determine age using DNA.

Insights from a 30-year journey: function, regulation and therapeutic modulation of PD1

PD1 was originally discovered in 1992 as a molecule associated with activation-induced cell death in T cells. Over the past 30 years, it was found that PD1 has a critical role in avoiding overactivation-induced cell death and autoimmunity, whereas its inhibition unleashes anticancer immunity. Here, we outline the journey from the discovery of PD1 to its role as a breakthrough target in cancer immunotherapy. We describe its regulation and function and examine how a mechanistic understanding of PD1 signalling suggests a central function in setting the T cell activation threshold, thereby controlling T cell proliferation, differentiation, exhaustion and metabolic status. This threshold theory, in combination with new insights into T cell metabolism and a better understanding of immune cell modulation by the microbiota, can provide guidance for the development of efficient combination therapies. Moreover, we discuss the mechanisms underlying immune-related adverse events after PD1-targeted therapy and their possible treatment.

Insights on the role of L-lactate as a signaling molecule in skin aging

L-lactate is a catabolite from the anaerobic metabolism of glucose, which plays a paramount role as a signaling molecule in various steps of the cell survival. Its activity, as a master tuner of many mechanisms underlying the aging process, for example in the skin, is still presumptive, however its crucial position in the complex cross-talk between mitochondria and the process of cell survival, should suggest that L-lactate may be not a simple waste product but a fine regulator of the aging/survival machinery, probably via mito-hormesis. Actually, emerging evidence is highlighting that ROS are crucial in the signaling of skin health, including mechanisms underlying wound repair, renewal and aging. The ROS, including superoxide anion, hydrogen peroxide, and nitric oxide, play both beneficial and detrimental roles depending upon their levels and cellular microenvironment. Physiological ROS levels are essential for cutaneous health and the wound repair process. Aberrant redox signaling activity drives chronic skin disease in elderly. On the contrary, impaired redox modulation, due to enhanced ROS generation and/or reduced levels of antioxidant defense, suppresses wound healing via promoting lymphatic/vascular endothelial cell apoptosis and death. This review tries to elucidate this issue.

Integrating glycolysis, citric acid cycle, pentose phosphate pathway, and fatty acid beta-oxidation into a single computational model

The metabolic network of a living cell is highly intricate and involves complex interactions between various pathways. In this study, we propose a computational model that integrates glycolysis, the pentose phosphate pathway (PPP), the fatty acids beta-oxidation, and the tricarboxylic acid cycle (TCA cycle) using queueing theory. The model utilizes literature data on metabolite concentrations and enzyme kinetic constants to calculate the probabilities of individual reactions occurring on a microscopic scale, which can be viewed as the reaction rates on a macroscopic scale. However, it should be noted that the model has some limitations, including not accounting for all the reactions in which the metabolites are involved. Therefore, a genetic algorithm (GA) was used to estimate the impact of these external processes. Despite these limitations, our model achieved high accuracy and stability, providing real-time observation of changes in metabolite concentrations. This type of model can help in better understanding the mechanisms of biochemical reactions in cells, which can ultimately contribute to the prevention and treatment of aging, cancer, metabolic diseases, and neurodegenerative disorders.

Premature aging and reduced cancer incidence associated with near-complete body-wide Myc inactivation

MYC proto-oncogene dysregulation alters metabolism, translation, and other functions in ways that support tumor induction and maintenance. Although Myc+/- mice are healthier and longer-lived than control mice, the long-term ramifications of more complete Myc loss remain unknown. We now describe the chronic consequences of body-wide Myc inactivation initiated postnatally. "MycKO" mice acquire numerous features of premature aging, including altered body composition and habitus, metabolic dysfunction, hepatic steatosis, and dysregulation of gene sets involved in functions that normally deteriorate with aging. Yet, MycKO mice have extended lifespans that correlate with a 3- to 4-fold lower lifetime cancer incidence. Aging tissues from normal mice and humans also downregulate Myc and gradually alter many of the same Myc target gene sets seen in MycKO mice. Normal aging and its associated cancer predisposition are thus highly linked via Myc.

Immunomodulatory Effects of SGLT2 Inhibitors-Targeting Inflammation and Oxidative Stress in Aging

Given that the increase in the aging population has grown into one of the largest public health issues, inflammation and oxidative stress, which are closely associated with the aging process, became a focus of recent research. Sodium-glucose co-transporter 2 (SGLT2) inhibitors, a group of drugs initially developed as oral antidiabetics, have shown many beneficial effects over time, including improvement in renal function and cardioprotective effects. It has been shown that SGLT2 inhibitors, as a drug class, have an immunomodulatory and antioxidative effect, affecting endothelial function as well as metabolic parameters. Therefore, it is not surprising that various studies have investigated the potential mechanisms of action of SGLT2 inhibitors in age-related diseases. The proposed mechanisms by which SGLT2 inhibitors can achieve their anti-inflammatory effects include influence on AMPK/SIRT1/PGC-1α signaling, various cytokines, and the NLRP3 inflammasome. The antioxidative effect is related to their action on mitochondria and their influence on the signaling pathways of transforming growth factor β and nuclear erythroid 2-related factor 2/antioxidant response element. Also, SGLT2 inhibitors achieve their anti-inflammatory and antioxidative effects by affecting metabolic parameters, such as uric acid reduction, stimulation of ketogenesis, reduction of body weight, lipolysis, and epicardial fat tissue. Finally, SGLT2 inhibitors display anti-atherosclerotic effects that modulate inflammatory reactions, potentially resulting in improvement in endothelial function. This narrative review offers a complete and comprehensive overview of the possible pathophysiologic mechanisms of the SGLT2 inhibitors involved in the aging process and development of age-related disease. However, in order to use SGLT2 inhibitor drugs as an anti-aging therapy, further basic and clinical research is needed to elucidate the potential effects and complex mechanisms they have on inflammation processes.

Hypoxia-inducible factor 1 signaling drives placental aging and can provoke preterm labor

Most cases of preterm labor have unknown cause, and the burden of preterm birth is immense. Placental aging has been proposed to promote labor onset, but specific mechanisms remain elusive. We report findings stemming from unbiased transcriptomic analysis of mouse placenta, which revealed that hypoxia-inducible factor 1 (HIF-1) stabilization is a hallmark of advanced gestational timepoints, accompanied by mitochondrial dysregulation and cellular senescence; we detected similar effects in aging human placenta. In parallel in primary mouse trophoblasts and human choriocarcinoma cells, we modeled HIF-1 induction and demonstrated resultant mitochondrial dysfunction and cellular senescence. Transcriptomic analysis revealed that HIF-1 stabilization recapitulated gene signatures observed in aged placenta. Further, conditioned media from trophoblasts following HIF-1 induction promoted contractility in immortalized uterine myocytes, suggesting a mechanism by which the aging placenta may drive the transition from uterine quiescence to contractility at the onset of labor. Finally, pharmacological induction of HIF-1 via intraperitoneal administration of dimethyloxalyl glycine (DMOG) to pregnant mice caused preterm labor. These results provide clear evidence for placental aging in normal pregnancy, and demonstrate how HIF-1 signaling in late gestation may be a causal determinant of the mitochondrial dysfunction and senescence observed within the trophoblast as well as a trigger for uterine contraction.

Informing the Cannabis Conjecture: From Life's Beginnings to Mitochondria, Membranes and the Electrome-A Review

Before the late 1980s, ideas around how the lipophilic phytocannabinoids might be working involved membranes and bioenergetics as these disciplines were "in vogue". However, as interest in genetics and pharmacology grew, interest in mitochondria (and membranes) waned. The discovery of the cognate receptor for tetrahydrocannabinol (THC) led to the classification of the endocannabinoid system (ECS) and the conjecture that phytocannabinoids might be "working" through this system. However, the how and the "why" they might be beneficial, especially for compounds like CBD, remains unclear. Given the centrality of membranes and mitochondria in complex organisms, and their evolutionary heritage from the beginnings of life, revisiting phytocannabinoid action in this light could be enlightening. For example, life can be described as a self-organising and replicating far from equilibrium dissipating system, which is defined by the movement of charge across a membrane. Hence the building evidence, at least in animals, that THC and CBD modulate mitochondrial function could be highly informative. In this paper, we offer a unique perspective to the question, why and how do compounds like CBD potentially work as medicines in so many different conditions? The answer, we suggest, is that they can modulate membrane fluidity in a number of ways and thus dissipation and engender homeostasis, particularly under stress. To understand this, we need to embrace origins of life theories, the role of mitochondria in plants and explanations of disease and ageing from an adaptive thermodynamic perspective, as well as quantum mechanics.

Changes in the Mitochondria in the Aging Process-Can α-Tocopherol Affect Them?

Aerobic organisms use molecular oxygen in several reactions, including those in which the oxidation of substrate molecules is coupled to oxygen reduction to produce large amounts of metabolic energy. The utilization of oxygen is associated with the production of ROS, which can damage biological macromolecules but also act as signaling molecules, regulating numerous cellular processes. Mitochondria are the cellular sites where most of the metabolic energy is produced and perform numerous physiological functions by acting as regulatory hubs of cellular metabolism. They retain the remnants of their bacterial ancestors, including an independent genome that encodes part of their protein equipment; they have an accurate quality control system; and control of cellular functions also depends on communication with the nucleus. During aging, mitochondria can undergo dysfunctions, some of which are mediated by ROS. In this review, after a description of how aging affects the mitochondrial quality and quality control system and the involvement of mitochondria in inflammation, we report information on how vitamin E, the main fat-soluble antioxidant, can protect mitochondria from age-related changes. The information in this regard is scarce and limited to some tissues and some aspects of mitochondrial alterations in aging. Improving knowledge of the effects of vitamin E on aging is essential to defining an optimal strategy for healthy aging.

Intrinsic and environmental basis of aging: A narrative review

Longevity has been a topic of interest since the beginnings of humanity, yet its aetiology and precise mechanisms remain to be elucidated. Aging is currently viewed as a physiological phenomenon characterized by the gradual degeneration of organic physiology and morphology due to the passage of time where both external and internal stimuli intervene. The influence of intrinsic factors, such as progressive telomere shortening, genome instability due to mutation buildup, the direct or indirect actions of age-related genes, and marked changes in epigenetic, metabolic, and mitochondrial patterns constitute a big part of its underlying endogenous mechanisms. On the other hand, several psychosocial and demographic factors, such as diet, physical activity, smoking, and drinking habits, may have an even more significant impact on shaping the aging process. Consequentially, implementing dietary and exercise patterns has been proposed as the most viable alternative strategy for attenuating the most typical degenerative aging changes, thus increasing the likelihood of prolonging lifespan and achieving successful aging.

MAVS Antagonizes Human Stem Cell Senescence as a Mitochondrial Stabilizer

Mitochondrial dysfunction is a hallmark feature of cellular senescence and organ aging. Here, we asked whether the mitochondrial antiviral signaling protein (MAVS), which is essential for driving antiviral response, also regulates human stem cell senescence. To answer this question, we used CRISPR/Cas9-mediated gene editing and directed differentiation techniques to generate various MAVS-knockout human stem cell models. We found that human mesenchymal stem cells (hMSCs) were sensitive to MAVS deficiency, as manifested by accelerated senescence phenotypes. We uncovered that the role of MAVS in maintaining mitochondrial structural integrity and functional homeostasis depends on its interaction with the guanosine triphosphatase optic atrophy type 1 (OPA1). Depletion of MAVS or OPA1 led to the dysfunction of mitochondria and cellular senescence, whereas replenishment of MAVS or OPA1 in MAVS-knockout hMSCs alleviated mitochondrial defects and premature senescence phenotypes. Taken together, our data underscore an uncanonical role of MAVS in safeguarding mitochondrial homeostasis and antagonizing human stem cell senescence.

Mitochondria-derived peptide SHLP2 regulates energy homeostasis through the activation of hypothalamic neurons

Small humanin-like peptide 2 (SHLP2) is a mitochondrial-derived peptide implicated in several biological processes such as aging and oxidative stress. However, its functional role in the regulation of energy homeostasis remains unclear, and its corresponding receptor is not identified. Hereby, we demonstrate that both systemic and intracerebroventricular (ICV) administrations of SHLP2 protected the male mice from high-fat diet (HFD)-induced obesity and improved insulin sensitivity. In addition, the activation of pro-opiomelanocortin (POMC) neurons by SHLP2 in the arcuate nucleus of the hypothalamus (ARC) is involved in the suppression of food intake and the promotion of thermogenesis. Through high-throughput structural complementation screening, we discovered that SHLP2 binds to and activates chemokine receptor 7 (CXCR7). Taken together, our study not only reveals the therapeutic potential of SHLP2 in metabolic disorders but also provides important mechanistic insights into how it exerts its effects on energy homeostasis.

A Clinical Qualification Protocol Highlights Overlapping Genomic Influences and Neuro-Autonomic Mechanisms in Ehlers-Danlos and Long COVID-19 Syndromes

A substantial fraction of the 15% with double-jointedness or hypermobility have the traditionally ascertained joint-skeletal, cutaneous, and cardiovascular symptoms of connective tissue dysplasia and its particular manifestation as Ehlers-Danlos syndrome (EDS). The holistic ascertainment of 120 findings in 1261 EDS patients added neuro-autonomic symptoms like headaches, muscle weakness, brain fog, chronic fatigue, dyspnea, and bowel irregularity to those of arthralgia and skin laxity, 15 of these symptoms shared with those of post-infectious SARS-CoV-2 (long COVID-19). Underlying articulo-autonomic mechanisms guided a clinical qualification protocol that qualified DNA variants in 317 genes as having diagnostic utility for EDS, six of them identical (F2-LIFR-NLRP3-STAT1-T1CAM1-TNFRSF13B) and eighteen similar to those modifying COVID-19 severity/EDS, including ADAMTS13/ADAMTS2-C3/C1R-IKBKG/IKBKAP-PIK3C3/PIK3R1-POLD4/POLG-TMPRSS2/TMPRSS6-WNT3/WNT10A. Also, contributing to EDS and COVID-19 severity were forty and three genes, respectively, impacting mitochondrial functions as well as parts of an overlapping gene network, or entome, that are hypothesized to mediate the cognitive-behavioral, neuro-autonomic, and immune-inflammatory alterations of connective tissue in these conditions. The further characterization of long COVID-19 natural history and genetic predisposition will be necessary before these parallels to EDS can be carefully delineated and translated into therapies.

Activating Mitochondrial Sirtuin 3 in Chondrocytes Alleviates Aging-Induced Fibrocartilage Layer Degeneration and Promotes Healing of Degenerative Rotator Cuff Injury

The present study aimed to examine the impact of mitochondrial sirtuin 3 (SIRT3) on the degenerative rotator cuff injury, which is a prevalent issue among the elderly population primarily due to aging-related tissue degradation. The study hypothesized that SIRT3, as a major deacetylase in mitochondria, is a significant factor in controlling the quality of mitochondria and the deterioration of fibrocartilage, a crucial component of the rotator cuff. Results showed that the aging process led to weakened biomechanical properties and degeneration of the fibrocartilage layer in mice, accompanied by a decrease in SIRT3 expression. SIRT3 activation ameliorated the aging-related disruption of chondrocyte phenotype and fibrocartilage degradation. SIRT3 activator honokiol improved the phenotype of senescent chondrocytes and promoted rotator cuff healing in aged mice through SIRT3 activation. In conclusion, the findings suggested that the decline in SIRT3 levels with age contributes to rotator cuff degeneration and chondrocyte senescence, and that SIRT3 activation through the use of honokiol is an effective approach for promoting rotator cuff healing in the elderly population.

Potential Therapeutic Functions of PU-91 and Quercetin in Personalized Cybrids Derived from Patients with Age-Related Macular Degeneration, Keratoconus, and Glaucoma

The aim of this study is to investigate the therapeutic potential of higher doses of PU-91, quercetin, or in combination on transmitochondrial cybrid cell lines with various mtDNA haplogroups derived from patients with age-related macular degeneration (AMD), glaucoma (Glc), keratoconus (KC), and normal (NL) individuals. Cybrids were treated with PU-91 (P) (200 µM) alone, quercetin (Q) (20 µM) alone, or a combination of PU-91 and quercetin (P+Q) for 48 h. Cellular metabolism and the intracellular levels of reactive oxygen species (ROS) were measured by MTT and H2DCFDA assays, respectively. Quantitative real-time PCR was performed to measure the expression levels of genes associated with mitochondrial biogenesis, antioxidant enzymes, inflammation, apoptosis, and senescence pathways. PU-91(P) (i) improves cellular metabolism in AMD cybrids, (ii) decreases ROS production in AMD cybrids, and (iii) downregulates the expression of LMNB1 in AMD cybrids. Combination treatment of PU-91 plus quercetin (P+Q) (i) improves cellular metabolism in AMD, (ii) induces higher expression levels of TFAM, SOD2, IL6, and BAX in AMD cybrids, and (iii) upregulates CDKN1A genes expression in all disease cybrids. Our study demonstrated that the P+Q combination improves cellular metabolism and mitochondrial biogenesis in AMD cybrids, but senescence is greatly exacerbated in all cybrids regardless of disease type by the P+Q combined treatment.

Mitochondrial DNA Release in Innate Immune Signaling

According to the endosymbiotic theory, most of the DNA of the original bacterial endosymbiont has been lost or transferred to the nucleus, leaving a much smaller (∼16 kb in mammals), circular molecule that is the present-day mitochondrial DNA (mtDNA). The ability of mtDNA to escape mitochondria and integrate into the nuclear genome was discovered in budding yeast, along with genes that regulate this process. Mitochondria have emerged as key regulators of innate immunity, and it is now recognized that mtDNA released into the cytoplasm, outside of the cell, or into circulation activates multiple innate immune signaling pathways. Here, we first review the mechanisms through which mtDNA is released into the cytoplasm, including several inducible mitochondrial pores and defective mitophagy or autophagy. Next, we cover how the different forms of released mtDNA activate specific innate immune nucleic acid sensors and inflammasomes. Finally, we discuss how intracellular and extracellular mtDNA release, including circulating cell-free mtDNA that promotes systemic inflammation, are implicated in human diseases, bacterial and viral infections, senescence and aging.

Novel Potential Targets for Function-Promoting Therapies: Orphan Nuclear Receptors, Anti-inflammatory Drugs, Troponin Activators, Mas Receptor Agonists, and Urolithin A

In recent years, several new classes of therapies have been investigated with their potential for restoring or improving physical functioning in older adults. These have included Mas receptor agonists, regulators of mitophagy, skeletal muscle troponin activators, anti-inflammatory compounds, and targets of orphan nuclear receptors. The present article summarizes recent developments of the function-promoting effects of these exciting new compounds and shares relevant preclinical and clinical data related to their safety and efficacy. The development of novel compounds in this area is expanding and likely will need the advent of a new treatment paradigm for age-associated mobility loss and disability.