Dwarf mice and the ageing process

NF-κB-mediated developmental delay extends lifespan in Drosophila

Developmental time (or time to maturity) strongly correlates with an animal's maximum lifespan, with late-maturing individuals often living longer. However, the genetic mechanisms underlying this phenomenon remain largely unknown. This may be because most previously identified longevity genes regulate growth rate rather than developmental time. To address this gap, we genetically manipulated prothoracicotropic hormone (PTTH), the primary regulator of developmental timing in Drosophila, to explore the genetic link between developmental time and longevity. Loss of PTTH delays developmental timing without altering the growth rate. Intriguingly, PTTH mutants exhibit extended lifespan despite their larger body size. This lifespan extension depends on ecdysone signaling, as feeding 20-hydroxyecdysone to PTTH mutants reverses the effect. Mechanistically, loss of PTTH blunts age-dependent chronic inflammation, specifically in fly hepatocytes (oenocytes). Developmental transcriptomics reveal that NF-κB signaling activates during larva-to-adult transition, with PTTH inducing this signaling via ecdysone. Notably, time-restricted and oenocyte-specific silencing of Relish (an NF-κB homolog) at early 3rd instar larval stages significantly prolongs adult lifespan while delaying pupariation. Our study establishes an aging model that uncouples developmental time from growth rate, highlighting NF-κB signaling as a key developmental program in linking developmental time to adult lifespan.

Chromatin and epigenetics in aging biology

This book chapter will focus on modifications to chromatin itself, how chromatin modifications are regulated, and how these modifications are deciphered by the cell to impact aging. In this chapter, we will review how chromatin modifications change with age, examine how chromatin-modifying enzymes have been shown to regulate aging and healthspan, discuss how some of these epigenetic changes are triggered and how they can regulate the lifespan of the individual and its naïve descendants, and speculate on future directions for the field.

The impact of frailty syndrome on skeletal muscle histology: preventive effects of exercise

Frailty syndrome, a condition marked by increased vulnerability due to age-related physiological decline, exerts a profound impact on skeletal muscle structure and function. Despite its widespread prevalence, the underlying mechanisms contributing to frailty-associated muscle deterioration remain poorly elucidated. This study utilized histological and biochemical analyses in a murine model to investigate the effects of frailty syndrome on skeletal muscle. Mice were classified based on age and condition, including a subset subjected to an exercise intervention. Parameters evaluated included body weight, lean mass ratio, myofiber size and number, extracellular matrix (ECM) content, and myosin heavy chain isoform expression. Frailty syndrome led to increased body weight and ECM content, coupled with reductions in myofiber size and number, reflecting substantial structural and functional impairments in skeletal muscle. Exercise interventions effectively countered these deleterious changes, preserving myofiber morphology and reducing ECM expansion, thereby demonstrating the protective role of exercise in mitigating frailty-induced muscle deterioration. The study highlights the severe impact of frailty syndrome on skeletal muscle structure and integrity. Importantly, it underscores the potential of regular exercise as an effective therapeutic approach to prevent or reverse muscle deterioration associated with frailty, offering critical insights into managing age-related muscular degeneration.

Promoting health and survival through lowered body temperature

Core body temperature (Tb) is a long-established determinant of longevity across species. In this Perspective, we first summarize evidence demonstrating that reducing Tb increases lifespan and that lowered Tb contributes to the antiaging effects of calorie restriction. Next, we discuss recent data that diverge from prior hypotheses on the mechanisms by which Tb affects longevity, suggesting these are limited neither to the thermodynamics of nonenzymatic chemical reactions, nor reduced formation of mitochondrial reactive oxygen species nor lowered metabolic rate. Instead, recent findings in invertebrates show that cold promotes longevity via specific pathways including nutrient sensing and proteostasis, as well as modulating the thermodynamics of proteins and nucleic acids by changing their structure and function, for example, affecting temperature-sensitive ion channels, long-lived temperature-sensitive dauer mutations, base-pair stability and stem-loop RNA structures. Temperature affects the epigenetic signature and inflammation, and lowering Tb can also induce RNA-binding cold shock proteins, activate cold-sensitive kinases and differential splicing to potentially reshape the cellular environment. Finally, we reflect on important future work and the translational potential of temperature management and temperature mimetics.

The rodent aging interventions database (RAID): a data visualization tool for all studies reporting rodent lifespan extension

Numerous studies have investigated the effects of various interventions on the lifespans of mice and rats. The design of future rodent lifespan extension experiments might consider experimental parameters used in earlier investigations, but finding and reviewing all previous experiments requires a substantial resource investment. Additionally, when studied collectively, the results of previous investigations might suggest fundamental mechanisms causing age-related degeneration. Here, we report our efforts to find and aggregate data from all research reports of lifespan extension in mice or rats, which we call the "Rodent Aging Interventions Database" (RAID). We identified studies for inclusion using complex PubMed queries and by nomination from our colleagues in the field. The relevant data from each study was manually extracted and recorded in a table. A publicly available, web-based software tool was then created to enable users to visualize and filter this data in a convenient manner. Our current dataset, covering publications up to October 2022, includes 121 unique studies reporting on 212 distinct intervention protocols that extended lifespan in mice or rats. We intend to periodically update our dataset as new rodent lifespan studies are reported. RAID is publicly available at https://levf.org/raid.

Growth hormone-deficient Ames dwarf mice resist sarcopenia and exhibit enhanced endurance running performance at 24 months

Ames dwarf mice (df/df) live 50% longer than normal littermates due to a genetic defect in growth hormone (GH) signaling. The enhanced longevity of Ames dwarfs has been studied extensively in an endocrinological context of cellular metabolism and increased resistance to oxidative stress (Bartke. World J Mens Health 37(1):19, 8; Bartke 2; BartkeJ Am Aging Assoc 23(4):219, 10; Bartke. World J Mens Health 39(3):454-465, 11; Brown-Borg et al. Nature 384(6604):33-33, 1; Masternak et al. 2018). However, the skeletal muscle system is relatively unexplored, the quality of which dictates metabolic homeostasis, permits movement and exercise, and exerts paracrine effects on other organs (Delmonico and Beck Am J Lifestyle Med 11(2):167-181, 25; Evans et al. GeroScience 46(1):183, 26; Kim and Kim. Endocrinol Metab (Seoul) 35(1):1-6, 15; Masternak et al. 2018). Here, we characterize the fitness capacity and skeletal muscle morphology of Ames mice to determine if previously established longevous effects of GH deficiency extend to skeletal muscle tissue. Mutually exclusive, age-matched cohorts of male Ames mice and wildtype controls performed grip strength, rotarod, and endurance running experiments over 6 months. The largest difference in physical performance was observed in endurance running capacity, where dwarf mice outperformed wildtype controls increasingly with age. Tibialis anterior (TA) muscles were evaluated for myofiber size, quality, and environment. Ames mice show reduced myofiber cross-sectional area (CSA) paired with increased myofibers per muscle. Dwarf myofiber populations are less heterogenous in size and seemingly resist sarcopenia, as skeletal muscle from aged individuals shows youthful morphological resemblance in mean myofiber CSA, size frequency distribution, and presence of fibrotic tissue. Declines in fitness performance and myofiber integrity were observable in age-matched wildtype controls. Utilizing an established longevity model to investigate skeletal muscle function and morphology is a novel approach to gaining insight into the seemingly inverse relationship between GH signaling and mammalian longevity.

The Mitochondria-Targeted Peptide Therapeutic Elamipretide Improves Cardiac and Skeletal Muscle Function During Aging Without Detectable Changes in Tissue Epigenetic or Transcriptomic Age

Aging-related decreases in cardiac and skeletal muscle function are strongly associated with various comorbidities. Elamipretide (ELAM), a novel mitochondria-targeted peptide, has demonstrated broad therapeutic efficacy in ameliorating disease conditions associated with mitochondrial dysfunction across both clinical and pre-clinical models. Herein, we investigated the impact of 8-week ELAM treatment on pre- and post-measures of C57BL/6J mice frailty, skeletal muscle, and cardiac muscle function, coupled with post-treatment assessments of biological age and affected molecular pathways. We found that health status, as measured by frailty index, cardiac strain, diastolic function, and skeletal muscle force, is significantly diminished with age, with skeletal muscle force changing in a sex-dependent manner. Conversely, ELAM mitigated frailty accumulation and was able to partially reverse these declines, as evidenced by treatment-induced increases in cardiac strain and muscle fatigue resistance. Despite these improvements, we did not detect statistically significant changes in gene expression or DNA methylation profiles indicative of molecular reorganization or reduced biological age in most ELAM-treated groups. However, pathway analyses revealed that ELAM treatment showed pro-longevity shifts in gene expression, such as upregulation of genes involved in fatty acid metabolism, mitochondrial translation, and oxidative phosphorylation, and downregulation of inflammation. Together, these results indicate that ELAM treatment is effective at mitigating signs of sarcopenia and cardiac dysfunction in an aging mouse model, but that these functional improvements occur independently of detectable changes in epigenetic and transcriptomic age. Thus, some age-related changes in function may be uncoupled from changes in molecular biological age.

DNA methylation of transposons pattern aging differences across a diverse cohort of dogs from the Dog Aging Project

Within a species, larger individuals often have shorter lives and higher rates of age-related disease. Despite this well-known link, we still know little about underlying age-related epigenetic differences, which could help us better understand inter-individual variation in aging and the etiology, onset, and progression of age-associated disease. Dogs exhibit this negative correlation between size, health, and longevity and thus represent an excellent system in which to test the underlying mechanisms. Here, we quantified genome-wide DNA methylation in a cohort of 864 dogs in the Dog Aging Project. Age strongly patterned the dog epigenome, with the majority (66% of age-associated loci) of regions associating age-related loss of methylation. These age effects were non-randomly distributed in the genome and differed depending on genomic context. We found the LINE1 (long interspersed elements) class of TEs (transposable elements) were the most frequently hypomethylated with age (FDR < 0.05, 40% of all LINE1 regions). This LINE1 pattern differed in magnitude across breeds of different sizes- the largest dogs lost 0.26% more LINE1 methylation per year than the smallest dogs. This suggests that epigenetic regulation of TEs, particularly LINE1s, may contribute to accelerated age and disease phenotypes within a species. Since our study focused on the methylome of immune cells, we looked at LINE1 methylation changes in golden retrievers, a breed highly susceptible to hematopoietic cancers, and found they have accelerated age-related LINE1 hypomethylation compared to other breeds. We also found many of the LINE1s hypomethylated with age are located on the X chromosome and are, when considering X chromosome inactivation, counter-intuitively more methylated in males. These results have revealed the demethylation of LINE1 transposons as a potential driver of intra-species, demographic-dependent aging variation.

Model Organisms in Aging Research: Evolution of Database Annotation and Ortholog Discovery

BACKGROUND

This study aims to analyze the exploration degree of popular model organisms by utilizing annotations from the UniProtKB (Swiss-Prot) knowledge base. The research focuses on understanding the genomic and post-genomic data of various organisms, particularly in relation to aging as an integral model for studying the molecular mechanisms underlying pathological processes and physiological states.

METHODS

Having characterized the organisms by selected parameters (numbers of gene splice variants, post-translational modifications, etc.) using previously developed information models, we calculated proteome sizes: the number of possible proteoforms for each species. Our analysis also involved searching for orthologs of human aging genes within these model species.

RESULTS

Our findings indicate that genomic and post-genomic data for more primitive species, such as bacteria and fungi, are more comprehensively characterized compared to other organisms. This is attributed to their experimental accessibility and simplicity. Additionally, we discovered that the genomes of the most studied model organisms allow for a detailed analysis of the aging process, revealing a greater number of orthologous genes related to aging.

CONCLUSIONS

The results highlight the importance of annotating the genomes of less-studied species to identify orthologs of marker genes associated with complex physiological processes, including aging. Species that potentially possess unique traits associated with longevity and resilience to age-related changes require comprehensive genomic studies.

Effects of growth hormone-releasing hormone deficiency in mice beyond growth

This paper provides a critical overview on GHRH and its deficiency, discussing its multiple roles in both central and peripheral tissues. Genetically engineered mice have been instrumental in elucidating the multifaceted roles of GHRH and GH, each offering unique insights into the physiological and pathological roles of these hormones, although in many of these models dissecting the direct effect of GHRH from the effect of GH is not possible. Key findings highlight the effects of GHRH deficiency on emotional behavior, including anxiety and depression, its impact on memory and learning capabilities, as well as on adipose tissue, immune system, inflammation and pain.

Isolating the direct effects of growth hormone on lifespan and metabolism in mice

Prior studies have shown that interrupting the growth hormone/insulin-like growth factor-I (GH/IGF-I) signaling axis extends laboratory mouse lifespan, but confounding effects of additional gene or hormone deficiencies that exist in commonly used models of GH/IGF-I interruption obscure the specific effect of GH on longevity. We address this issue by using mice with a specific knockout of the GH gene and show that both males and females on a mixed genetic background display extended lifespans resulting from GH deficiency. Our physiological assessment of these mice revealed that in addition to weighing significantly less and displaying significantly greater body fat (as a percentage of body weight), GH deficient mice display significant impairments in glucose metabolism and preferential fat utilization. These data provide strong evidence that GH deficiency is directly responsible for the altered nutrient utilization and extended lifespan that is commonly observed in mouse models of GH/IGF-I interruption.

Impact of visceral adipose tissue on longevity and metabolic health: a comparative study of gene expression in perirenal and epididymal fat of Ames dwarf mice

Emerging research underscores the pivotal role of adipose tissue in regulating systemic aging processes, particularly when viewed through the lens of the endocrine hypotheses of aging. This study delves into the unique adipose characteristics in an important animal model of aging - the long-lived Ames dwarf (df/df) mice. Characterized by a Prop1df gene mutation, these mice exhibit a deficiency in growth hormone (GH), prolactin, and TSH, alongside extremely low circulating IGF-1 levels. Intriguingly, while surgical removal of visceral fat (VFR) enhances insulin sensitivity in normal mice, it paradoxically increases insulin resistance in Ames dwarfs. This suggests an altered profile of factors produced in visceral fat in the absence of GH, indicating a unique interplay between adipose tissue function and hormonal influences in these models. Our aim was to analyze the gene expression related to lipid and glucose metabolism, insulin pathways, inflammation, thermoregulation, mitochondrial biogenesis, and epigenetic regulation in the visceral (perirenal and epididymal) adipose tissue of Ames dwarf and normal mice. Our findings reveal an upregulation in the expression of key genes such as Lpl, Adrβ3, Rstn, Foxo1, Foxo3a, Irs1, Cfd, Aldh2, Il6, Tnfα, Pgc1α, Ucp2, and Ezh2 in perirenal and Akt1, Foxo3a, PI3k, Ir, Acly, Il6, Ring1a, and Ring 1b in epididymal fat in df/df mice. These results suggest that the longevity phenotype in Ames dwarfs, which is determined by peripubertal GH/IGF-1 levels, may also involve epigenetic reprogramming of adipose tissue influenced by hormonal changes. The increased expression of genes involved in metabolic regulation, tumor suppression, mitochondrial biogenesis, and insulin pathways in Ames dwarf mice highlights potentially beneficial aspects of this model, opening new avenues for understanding the molecular underpinnings of longevity and aging.

Overlapping and Distinct Physical and Biological Phenotypes in Pure Frailty and Obese Frailty

BACKGROUND

Pure frailty and obese frailty are common types of frailty syndrome. However, the overlapping and distinct characteristics between pure frailty and obese frailty remain unclear. This study aims to reveal the overlapping/distinct physical and biological phenotypes of pure frailty and obese frailty, providing theoretical support for their prevention, diagnosis, and treatment.

METHOD

Mice were fed either a normal or high-fat diet and assessed at 20 months of age. They were assigned to one of the four groups: control, obesity, pure frailty, and obese frailty. Grip strength, walking speed, physical activity, endurance, and body weight were measured to determine pure frailty and obese frailty. Physical and biological phenotypes were assessed.

RESULTS

Distinct physical phenotypes were observed between pure frailty and obese frailty in terms of body weight, lean mass, fat mass, fat mass in tissue, grip strength, endurance, and physical activity, while walking speed overlapped. In biological phenotypes, levels of Smad2/3, FoxO3a, P62, LAMP-2, and cathepsin L expression were distinct, while AKT, p-AKT, mTOR, p-mTOR, p-Smad2/3, p-FoxO3a, Beclin-1, ATG7, and LC3 overlapped.

CONCLUSION

Distinct physical phenotypes observed in obese frailty are primarily attributable to the effect of obesity, with further impairment of muscle function resulting from the combined effects of frailty syndromes and obesity. Pure frailty and obese frailty share overlapping biological phenotypes, particularly in the regulation of muscle protein synthesis. Moreover, the interaction between obesity and frailty syndromes gives rise to both overlapping and distinct biological phenotypes, especially in the regulation of specific degradation signaling proteins.

Common and Uncommon Mouse Models of Growth Hormone Deficiency

Mouse models of growth hormone deficiency (GHD) have provided important tools for uncovering the various actions of GH. Nearly 100 years of research using these mouse lines has greatly enhanced our knowledge of the GH/IGF-1 axis. Some of the shared phenotypes of the 5 "common" mouse models of GHD include reduced body size, delayed sexual maturation, decreased fertility, reduced muscle mass, increased adiposity, and enhanced insulin sensitivity. Since these common mouse lines outlive their normal-sized littermates-and have protection from age-associated disease-they have become important fixtures in the aging field. On the other hand, the 12 "uncommon" mouse models of GHD described herein have tremendously divergent health outcomes ranging from beneficial aging phenotypes (similar to those described for the common models) to extremely detrimental features (such as improper development of the central nervous system, numerous sensory organ defects, and embryonic lethality). Moreover, advancements in next-generation sequencing technologies have led to the identification of an expanding array of genes that are recognized as causative agents to numerous rare syndromes with concomitant GHD. Accordingly, this review provides researchers with a comprehensive up-to-date collection of the common and uncommon mouse models of GHD that have been used to study various aspects of physiology and metabolism associated with multiple forms of GHD. For each mouse line presented, the closest comparable human syndromes are discussed providing important parallels to the clinic.

The circadian rhythm: A key variable in aging?

The determination of age-related transcriptional changes may contribute to the understanding of health and life expectancy. The broad application of results from age cohorts may have limitations. Altering sample sizes per time point or sex, using a single mouse strain or tissue, a limited number of replicates, or omitting the middle of life can bias the surveys. To achieve higher general validity and to identify less distinctive players, bulk RNA sequencing of a mouse cohort, including seven organs of two strains from both sexes of 5 ages, was performed. Machine learning by bootstrapped variable importance and selection methodology (Boruta) was used to identify common aging features where the circadian rhythms (CiR) transcripts appear as promising age markers in an unsupervised analysis. Pathways of 11 numerically analyzed local network clusters were affected and classified into four major gene expression profiles, whereby CiR and proteostasis candidates were particularly conspicuous with partially opposing changes. In a data-based interaction association network, the CiR-proteostasis axis occupies an exposed central position, highlighting its relevance. The computation of 11,830 individual transcript associations provides potential superordinate contributors, such as hormones, to age-related changes, as in CiR. In hormone-sensitive LNCaP cells, short-term supraphysiologic levels of the sex hormones dihydrotestosterone or estradiol increase the expression of the CiR transcript Bhlhe40 and the associated senescence regulator Cdkn2b (p15). According to these findings, the bilateral dysregulation of CiR appears as a fundamental protagonist of aging, whose transcripts could serve as a biological marker and its restoration as a therapeutic opportunity.

The mitochondrial-targeted peptide therapeutic elamipretide improves cardiac and skeletal muscle function during aging without detectable changes in tissue epigenetic or transcriptomic age

Aging-related decreases in cardiac and skeletal muscle function are strongly associated with various comorbidities. Elamipretide (ELAM), a novel mitochondrial-targeted peptide, has demonstrated broad therapeutic efficacy in ameliorating disease conditions associated with mitochondrial dysfunction across both clinical and pre-clinical models. ELAM is proposed to restore mitochondrial bioenergetic function by stabilizing inner membrane structure and increasing oxidative phosphorylation coupling and efficiency. Although ELAM treatment effectively attenuates physiological declines in multiple tissues in rodent aging models, it remains unclear whether these functional improvements correlate with favorable changes in molecular biomarkers of aging. Herein, we investigated the impact of 8-week ELAM treatment on pre- and post- measures of C57BL/6J mice frailty, skeletal muscle, and cardiac muscle function, coupled with post-treatment assessments of biological age and affected molecular pathways. We found that health status, as measured by frailty index, cardiac strain, diastolic function, and skeletal muscle force are significantly diminished with age, with skeletal muscle force changing in a sex-dependent manner. Conversely, ELAM mitigated frailty accumulation and was able to partially reverse these declines, as evidenced by treatment-induced increases in cardiac strain and muscle fatigue resistance. Despite these improvements, we did not detect statistically significant changes in gene expression or DNA methylation profiles indicative of molecular reorganization or reduced biological age in most ELAM-treated groups. However, pathway analyses revealed that ELAM treatment showed pro-longevity shifts in gene expression such as upregulation of genes involved in fatty acid metabolism, mitochondrial translation and oxidative phosphorylation, and downregulation of inflammation. Together, these results indicate that ELAM treatment is effective at mitigating signs of sarcopenia and heart failure in an aging mouse model, but that these functional improvements occur independently of detectable changes in epigenetic and transcriptomic age. Thus, some age-related changes in function may be uncoupled from changes in molecular biological age.

CRISPR-Cas9 mediated d3GHR knockout in HEK293 cells: Revealing the longevity associated isoform stress resilience

The Growth Hormone Receptor (GHR) gene encodes a protein that is essential for mediating the biological effects of growth hormone (GH). A series of molecular events are set off when GH binds to its receptor, resulting in a variety of physiological reactions linked to development, growth, and metabolism. Recently a particular genetic variation, within the GHR gene that is labeled as the "d3GHR," which lacks exon 3 was associated with longevity. This specific deletion isoform was connected to changes in the structure of the GHR protein, which may have an impact on the GHR's function. To test in vitro the advantage of the d3 carrier that may link to longevity, we employed the CRISPR/Cas9 technique to produce two isoforms: the homozygotes isoform (d3/d3) and the heterozygotes isoform (d3/fl) using HEK293 cell line. The CRISPR editing effectiveness was >85 %, indicating that we had successfully built the Cas9-gRNA complex that is appropriate for the GHR gene. The viability of the resulted isoform cells was examined under three environmental stressors that mimic some aging processes. In addition, we examined the GHR signaling pathway by selecting potential downstream genes in the GHR signaling cascade. The results show that heterozygotes cells demonstrated higher survival rates under UV radiation compared with the WT cells (87 % compared with 67 % for the WT cells when exposed to 2 min of UV radiation), and in fasting conditions, the d3GHR cells showed a 15 % greater viability than the WT cells. Moreover, the baseline expression levels (without intervention) of the IGF1 and JAK/STAT genes signaling pathways significantly declined in the homozygotes cells compared with the WT (p < 0.05). This noteworthy finding might offer a practical approach to test illness prevention and give the scientific community critical new insights on mechanism associated with lifespan.

Isolating the Direct Effects of Growth Hormone on Lifespan and Metabolism

Prior studies show that disrupting somatotropic axis components extends laboratory mouse lifespan, but confounding effects of additional genes and hormones obscure the specific impact of growth hormone (GH) on longevity. We address this issue by using mice with a specific knockout of the GH gene, revealing that disrupting GH alone substantially increases lifespan. The longevity effects are accompanied by altered metabolic fuel utilization, directly linking GH action to aging mechanisms.

The Role of Molecular and Cellular Aging Pathways on Age-Related Hearing Loss

Aging, a complex process marked by molecular and cellular changes, inevitably influences tissue and organ homeostasis and leads to an increased onset or progression of many chronic diseases and conditions, one of which is age-related hearing loss (ARHL). ARHL, known as presbycusis, is characterized by the gradual and irreversible decline in auditory sensitivity, accompanied by the loss of auditory sensory cells and neurons, and the decline in auditory processing abilities associated with aging. The extended human lifespan achieved by modern medicine simultaneously exposes a rising prevalence of age-related conditions, with ARHL being one of the most significant. While our understanding of the molecular basis for aging has increased over the past three decades, a further understanding of the interrelationship between the key pathways controlling the aging process and the development of ARHL is needed to identify novel targets for the treatment of AHRL. The dysregulation of molecular pathways (AMPK, mTOR, insulin/IGF-1, and sirtuins) and cellular pathways (senescence, autophagy, and oxidative stress) have been shown to contribute to ARHL. However, the mechanistic basis for these pathways in the initiation and progression of ARHL needs to be clarified. Therefore, understanding how longevity pathways are associated with ARHL will directly influence the development of therapeutic strategies to treat or prevent ARHL. This review explores our current understanding of the molecular and cellular mechanisms of aging and hearing loss and their potential to provide new approaches for early diagnosis, prevention, and treatment of ARHL.

The genetic advantage of healthy centenarians: unraveling the central role of NLRP3 in exceptional healthspan

Despite extensive research into extending human healthspan (HS) and compressing morbidity, the mechanisms underlying aging remain elusive. However, a better understanding of the genetic advantages responsible for the exceptional HS of healthy centenarians (HC), who live in good physical and mental health for one hundred or more years, could lead to innovative health-extending strategies. This review explores the role of NLRP3, a critical component of innate immunity that significantly impacts aging. It is activated by pathogen-associated signals and self-derived signals that increase with age, leading to low-grade inflammation implicated in age-related diseases. Furthermore, NLRP3 functions upstream in several molecular aging pathways, regulates cellular senescence, and may underlie the robust health observed in HC. By targeting NLRP3, mice exhibit a phenotype akin to that of HC, the HS of monkeys is extended, and aging symptoms are reversed in humans. Thus, targeting NLRP3 could offer a promising approach to extend HS. Additionally, a paradigm shift is proposed. Given that the HS of the broader population is 30 years shorter than that of HC, it is postulated that they suffer from a form of accelerated aging. The term 'auto-aging' is suggested to describe accelerated aging driven by NLRP3.

Growth hormone-releasing hormone deficiency confers extended lifespan and metabolic resilience during high-fat feeding in mid and late life

Growth hormone-releasing hormone-deficient (GHRH-KO) mice have previously been characterized by lower body weight, disproportionately high body fat accumulation, preferential metabolism of lipids compared to carbohydrates, improved insulin sensitivity, and an extended lifespan. That these mice are long-lived and insulin-sensitive conflicts with the notion that adipose tissue accumulation drives the health detriments associated with obesity (i.e., diabetes), and indicates that GH signaling may be necessary for the development of adverse effects linked to obesity. This prompts investigation into the ultimate effect of diet-induced obesity on the lifespan of these long-lived mice. To this end, we initiated high-fat feeding in mid and late-life in GHRH-KO and wild-type (WT) mice. We carried out extensive lifespan analysis coupled with glucose/insulin tolerance testing and indirect calorimetry to gauge the metabolic effect of high-fat dietary stress through adulthood on these mice. We show that under high-fat diet (HFD) conditions, GHRH-KO mice display extended lifespans relative to WT controls. We also show that GHRH-KO mice are more insulin-sensitive and display less dramatic changes in their metabolism relative to WT mice, with GHRH-KO mice fed HFD displaying respiratory exchange ratios and glucose oxidation rates comparable to control-diet fed GHRH-KO mice, while WT mice fed HFD showed significant reductions in these parameters. Our results indicate that GH deficiency protects against the adverse effects of diet-induced obesity in later life.

New Insights into IGF-1 Signaling in the Heart

Insulin-like growth factor-1 (IGF-1) signaling has multiple physiological roles in cellular growth, metabolism, and aging. Myocardial hypertrophy, cell death, senescence, fibrosis, and electrical remodeling are hallmarks of various heart diseases and contribute to the progression of heart failure. This review highlights the critical role of IGF-1 and its cognate receptor in cardiac hypertrophy, aging, and remodeling.

Role of the central nervous system in cell non-autonomous signaling mechanisms of aging and longevity in mammals

Multiple organs orchestrate the maintenance of proper physiological function in organisms throughout their lifetimes. Recent studies have uncovered that aging and longevity are regulated by cell non-autonomous signaling mechanisms in several organisms. In the brain, particularly in the hypothalamus, aging and longevity are regulated by such cell non-autonomous signaling mechanisms. Several hypothalamic neurons have been identified as regulators of mammalian longevity, and manipulating them promotes lifespan extension or shortens the lifespan in rodent models. The hypothalamic structure and function are evolutionally highly conserved across species. Thus, elucidation of hypothalamic function during the aging process will shed some light on the mechanisms of aging and longevity and, thereby benefiting to human health.

Insect hormone PTTH regulates lifespan through temporal and spatial activation of NF-κB signaling during metamorphosis

The prothoracicotropic hormone (PTTH) is a well-known neuropeptide that regulates insect metamorphosis (the juvenile-to-adult transition) by inducing the biosynthesis of steroid hormones. However, the role of PTTH in adult physiology and longevity is largely unexplored. Here, we show that Ptth loss-of-function mutants are long-lived and exhibit increased resistance to oxidative stress in Drosophila. Intriguingly, we find that loss of Ptth blunt age-dependent upregulation of NF-κB signaling specifically in fly hepatocytes (oenocytes). We further show that oenocyte-specific overexpression of Relish/NF-κB blocks the lifespan extension of Ptth mutants, suggesting that PTTH regulates lifespan through oenocyte-specific NF-κB signaling. Surprisingly, adult-specific knockdown of Ptth did not prolong lifespan, indicating that PTTH controls longevity through developmental programs. Indeed, knockdown of PTTH receptor Torso in prothoracic gland (PG) during fly development prolongs lifespan. To uncover the developmental processes underlying PTTH-regulated lifespan, we perform a developmental transcriptomic analysis and identify an unexpected activation of NF-κB signaling in developing oenocytes during fly metamorphosis, which is blocked in Ptth mutants. Importantly, knockdown of Relish/NF-κB specifically in oenocytes during early pupal stages significantly prolongs the lifespan of adult flies. Thus, our findings uncover an unexpected role of PTTH in controlling adult lifespan through temporal and spatial activation of NF-κB signaling in developing hepatocytes and highlight the vital role of developmental NF-κB signaling in shaping adult physiology.

The Untapped Potential of Comparative Biology in Aging Research: Insights From the Extraordinary-Long-Lived Naked Mole-Rat

The search for solutions to the vagaries of aging has, historically, been akin to searching at night in the bright light under street lamps by utilizing the few preexisting and well-established animal model systems. Throughout my career as a comparative biologist, I have ventured into the darkness across 4 continents and studied over 150 different animal species, many of which have evolved remarkable adaptations to survive on the harsh and rugged fitness landscape that exists outside of the laboratory setting. In this Fellows Forum, I will discuss the main focus of my research for the last 25 years and dig deeply into the biology of the preternaturally long-lived naked mole-rat that makes it an ideal model system for the characterization of successful strategies to combat aging.

Unveiling ceramide dynamics: Shedding light on healthy aging in growth hormone-releasing hormone knockout mice

Dysregulation of growth hormone (GH) signaling consistently leads to increased lifespan in laboratory rodents, yet the precise mechanisms driving this extension remain unclear. Understanding the molecular underpinnings of the beneficial effects associated with GH deficiency could unveil novel therapeutic targets for promoting healthy aging and longevity. In our pursuit of identifying metabolites implicated in aging, we conducted an unbiased lipidomic analysis of serum samples from growth hormone-releasing hormone knockout (GHRH-KO) female mice and their littermate controls. Employing a targeted lipidomic approach, we specifically investigated ceramide levels in GHRH-KO mice, a well-established model of enhanced longevity. While younger GHRH-KO mice did not exhibit notable differences in serum lipids, older counterparts demonstrated significant reductions in over one-third of the evaluated lipids. In employing the same analysis in liver tissue, GHRH-KO mice showed pronounced downregulation of numerous ceramides and hexosylceramides, which have been shown to elicit many of the tissue defects that accompany aging (e.g., insulin resistance, oxidative stress, and cell death). Additionally, gene expression analysis in the liver tissue of adult GHRH-KO mice identified substantial decreases in several ceramide synthesis genes, indicating that these alterations are, at least in part, attributed to GHRH-KO-induced transcriptional changes. These findings provide the first evidence of disrupted ceramide metabolism in a long-lived mammal. This study sheds light on the intricate connections between GH deficiency, ceramide levels, and the molecular mechanisms influencing lifespan extension.

Candidate molecular targets uncovered in mouse lifespan extension studies

INTRODUCTION

Multiple interventions have demonstrated an increase in mouse lifespan. However, non-standardized controls, sex or strain-specific factors, and insufficient focus on targets, hinder the translation of these findings into clinical applications.

AREAS COVERED

We examined the effects of genetic and drug-based interventions on mice from databases DrugAge, GenAge, the Mouse Phenome Database, and publications from PubMed that led to a lifespan extension of more than 10%, identifying specific molecular targets that were manipulated to achieve the maximum lifespan in mice. Subsequently, we characterized 10 molecular targets influenced by these interventions, with particular attention given to clinical trials and potential indications for each.

EXPERT OPINION

To increase the translational potential of mice life-extension studies to clinical research several factors are crucial: standardization of mice lifespan research approaches, the development of clear criteria for control and experimental groups, the establishment of criteria for potential geroprotectors, and focusing on targets and their clinical application. Pinpointing the targets affected by geroprotectors helps in understanding species-specific differences and identifying potential side effects, ensuring the safety and effectiveness of clinical trials. Additionally, target review facilitates the optimization of treatment protocols and the evaluation of the clinical feasibility of translating research findings into practical therapies for humans.

In the land of not-unhappiness: On the state-of-the-art of targeting aging and age-related diseases by biomedical research

The concept of the Land of Not-Unhappiness refers to the potential achievement of eliminating the pathologies of the aging process. To inform of how close we are to settling in the land, we summarize and review the achievements of research on anti-aging interventions over the last hundred years with a specific focus on strategies that slow down metabolism, compensate for aging-related losses, and target a broad range of age-related diseases. We critically evaluate the existing interventions labeled as "anti-aging," such as calorie restriction, exercise, stem cell administration, and senolytics, to provide a down-to-earth evaluation of their current applicability in counteracting aging. Throughout the text, we have maintained a light tone to make it accessible to non-experts in biogerontology, and provide a broad overview for those considering conducting studies, research, or seeking to understand the scientific basis of anti-aging medicine.

The role of brown adipose tissue in mediating healthful longevity

There are two major subtypes of adipose tissue, i.e., white adipose tissue (WAT) and brown adipose tissue (BAT). It has been known for a long time that WAT mediates obesity and impairs healthful longevity. More recently, interest has focused on BAT, which, unlike WAT, actually augments healthful aging. The goal of this review is to examine the role of BAT in mediating healthful longevity. A major role for BAT and its related beige adipose tissue is thermogenesis, as a mechanism to maintain body temperature by producing heat through uncoupling protein 1 (UCP1) or through UCP1-independent thermogenic pathways. Our hypothesis is that healthful longevity is, in part, mediated by BAT. BAT protects against the major causes of impaired healthful longevity, i.e., obesity, diabetes, cardiovascular disorders, cancer, Alzheimer's disease, reduced exercise tolerance, and impaired blood flow. Several genetically engineered mouse models have shown that BAT enhances healthful aging and that their BAT is more potent than wild-type (WT) BAT. For example, when BAT, which increases longevity and exercise performance in mice with disruption of the regulator of G protein signaling 14 (RGS14), is transplanted to WT mice, their exercise capacity is enhanced at 3 days after BAT transplantation, whereas BAT transplantation from WT to WT mice also resulted in increased exercise performance, but only at 8 weeks after transplantation. In view of the ability of BAT to mediate healthful longevity, it is likely that a pharmaceutical analog of BAT will become a novel therapeutic modality.

Recapitulation of anti-aging phenotypes by global overexpression of PTEN in mice

The PTEN gene negatively regulates the oncogenic PI3K-AKT pathway by encoding a lipid and protein phosphatase that dephosphorylates lipid phosphatidylinositol-3,4,5-triphosphate (PIP3) resulting in the inhibition of PI3K and downstream inhibition of AKT. Overexpression of PTEN in mice leads to a longer lifespan compared to control littermates, although the mechanism is unknown. Here, we provide evidence that young adult PTENOE mice exhibit many characteristics shared by other slow-aging mouse models, including those with mutations that affect GH/IGF1 pathways, calorie-restricted mice, and mice treated with anti-aging drugs. PTENOE white adipose tissue (WAT) has increased UCP1, a protein linked to increased thermogenesis. WAT of PTENOE mice also shows a change in polarization of fat-associated macrophages, with elevated levels of arginase 1 (Arg1, characteristic of M2 macrophages) and decreased production of inducible nitric oxide synthase (iNOS, characteristic of M1 macrophages). Muscle and hippocampus showed increased expression of the myokine FNDC5, and higher levels of its cleavage product irisin in plasma, which has been linked to increased conversion of WAT to more thermogenic beige/brown adipose tissue. PTENOE mice also have an increase, in plasma and liver, of GPLD1, which is known to improve cognition in mice. Hippocampus of the PTENOE mice has elevation of both BDNF and DCX, indices of brain resilience and neurogenesis. These changes in fat, macrophages, liver, muscle, hippocampus, and plasma may be considered "aging rate indicators" in that they seem to be consistently changed across many of the long-lived mouse models and may help to extend lifespan by delaying many forms of late-life illness. Our new findings show that PTENOE mice can be added to the group of long-lived mice that share this multi-tissue suite of biochemical characteristics.

Lipid droplets, autophagy, and ageing: A cell-specific tale

Lipid droplets are the essential organelle for storing lipids in a cell. Within the variety of the human body, different cells store, utilize and release lipids in different ways, depending on their intrinsic function. However, these differences are not well characterized and, especially in the context of ageing, represent a key factor for cardiometabolic diseases. Whole body lipid homeostasis is a central interest in the field of cardiometabolic diseases. In this review we characterize lipid droplets and their utilization via autophagy and describe their diverse fate in three cells types central in cardiometabolic dysfunctions: adipocytes, hepatocytes, and macrophages.

Distinct physiological characteristics and altered glucagon signaling in GHRH knockout mice: Implications for longevity

Our previous research has demonstrated that mice lacking functional growth hormone-releasing hormone (GHRH) exhibit distinct physiological characteristics, including an extended lifespan, a preference for lipid utilization during rest, mild hypoglycemia, and heightened insulin sensitivity. They also show a further increase in lifespan when subjected to caloric restriction. These findings suggest a unique response to fasting, which motivated our current study on the response to glucagon, a key hormone released from the pancreas during fasting that regulates glucose levels, energy expenditure, and metabolism. Our study investigated the effects of an acute glucagon challenge on female GHRH knockout mice and revealed that they exhibit reduced glucose production, likely due to suppressed gluconeogenesis. However, these mice showed an increase in energy expenditure. We also observed alterations in pancreatic islet architecture, with smaller islets and a reduction of insulin-producing beta cells but no changes in glucagon-producing alpha cells. Additionally, the analysis of hepatic glucagon signaling showed a decrease in glucagon receptor expression and phosphorylated CREB. In conclusion, our findings suggest that the unique metabolic phenotype observed in these long-lived mice may be partly explained by changes in glucagon signaling. Further exploration of this pathway may lead to new insights into the regulation of longevity in mammals.

Genes That Extend Lifespan May Do So by Mitigating the Increased Risk of Death Posed by Having Hypertension

BACKGROUND

Genetic factors influence lifespan. In humans, there appears to be a particularly strong genetic effect in those aged ≥ 90 years. An important contribution is nutrient sensing genes which confer cell resilience.

METHODS

Our research has been investigating the genetic factors by longitudinal studies of American men of Japanese descent living on the island of Oahu in Hawaii. This cohort began as the Honolulu Heart Program in the mid-1960s and most subjects are now deceased.

RESULTS

We previously discovered various genes containing polymorphisms associated with longevity. In recent investigations of the mechanism involved we found that the longevity genotypes ameliorated the risk of mortality posed by having a cardiometabolic disease (CMD)-most prominently hypertension. For the gene FOXO3 the protective alleles mitigated the risk of hypertension, coronary heart disease (CHD) and diabetes. For the kinase MAP3K5 it was hypertension, CHD and diabetes, for the kinase receptor PIK3R1 hypertension, CHD and stroke, and for the growth hormone receptor gene (GHR) and vascular endothelial growth factor receptor 1 gene (FLT1), it was nullifying the higher mortality risk posed by hypertension. Subjects with a CMD who had a longevity genotype had similar survival as men without CMD. No variant protected against risk of death from cancer. We have postulated that the longevity-associated genotypes reduced mortality risk by effects on intracellular resilience mechanisms. In a proteomics study, 43 "stress" proteins and associated biological pathways were found to influence the association of FOXO3 genotype with reduced mortality.

CONCLUSIONS

Our landmark findings indicate how heritable genetic components affect longevity.

Relationships among Development, Growth, Body Size, Reproduction, Aging, and Longevity - Trade-Offs and Pace-Of-Life

Relationships of growth, metabolism, reproduction, and body size to the biological process of aging and longevity have been studied for decades and various unifying "theories of aging" have been proposed to account for the observed associations. In general, fast development, early sexual maturation leading to early reproductive effort, as well as production of many offspring, have been linked to shorter lifespans. The relationship of adult body size to longevity includes a remarkable contrast between the positive correlation in comparisons between different species and the negative correlation seen in comparisons of individuals within the same species. We now propose that longevity and presumably also the rate of aging are related to the "pace-of-life." A slow pace-of-life including slow growth, late sexual maturation, and a small number of offspring, predicts slow aging and long life. The fast pace of life (rapid growth, early sexual maturation, and major reproductive effort) is associated with faster aging and shorter life, presumably due to underlying trade-offs. The proposed relationships between the pace-of-life and longevity apply to both inter- and intra-species comparisons as well as to dietary, genetic, and pharmacological interventions that extend life and to evidence for early life programming of the trajectory of aging. Although available evidence suggests the causality of at least some of these associations, much further work will be needed to verify this interpretation and to identify mechanisms that are responsible.

Insulin and aging - a disappointing relationship

Experimental studies in animal models of aging such as nematodes, fruit flies or mice have observed that decreased levels of insulin or insulin signaling promotes longevity. In humans, hyperinsulinemia and concomitant insulin resistance are associated with an elevated risk of age-related diseases suggestive of a shortened healthspan. Age-related disorders include neurodegenerative diseases, hypertension, cardiovascular disease, and type 2 diabetes. High ambient insulin concentrations promote increased lipogenesis and fat storage, heightened protein synthesis and accumulation of non-functional polypeptides due to limited turnover capacity. Moreover, there is impaired autophagy activity, and less endothelial NO synthase activity. These changes are associated with mitochondrial dysfunction and oxidative stress. The cellular stress induced by anabolic activity of insulin initiates an adaptive response aiming at maintaining homeostasis, characterized by activation of the transcription factor Nrf2, of AMP activated kinase, and an unfolded protein response. This protective response is more potent in the long-lived human species than in short-lived models of aging research resulting in a stronger pro-aging impact of insulin in nematodes and fruit flies. In humans, resistance to insulin-induced cell stress decreases with age, because of an increase of insulin and insulin resistance levels but less Nrf2 activation. These detrimental changes might be contained by adopting a lifestyle that promotes low insulin/insulin resistance levels and enhances an adaptive response to cellular stress, as observed with dietary restriction or exercise.

Effect of mitochondrial quantity and quality controls in white adipose tissue on healthy lifespan: Essential roles of GH/IGF-1-independent pathways in caloric restriction-mediated metabolic remodeling

Long-term caloric restriction is a conventional and reproducible dietary intervention to improve whole body metabolism, suppress age-related pathophysiology, and extend lifespan. The beneficial actions of caloric restriction are widely accepted to be regulated in both growth hormone/insulin-like growth factor 1-dependent and -independent manners. Although growth hormone/insulin-like growth factor 1-dependent regulatory mechanisms are well described, those occurring independent of growth hormone/insulin-like growth factor 1 are poorly understood. In this review, we focus on molecular mechanisms of caloric restriction regulated in a growth hormone/insulin-like growth factor 1-independent manner. Caloric restriction increases mitochondrial quantity and improves mitochondrial quality by activating an axis involving sterol regulatory element binding protein-c/peroxisome proliferator-activated receptor γ coactivator-1α/mitochondrial intermediate peptidase in a growth hormone/insulin-like growth factor 1-independent manner, particularly in white adipose tissue. Fibroblast growth factor 21 is also involved in this axis. Moreover, the axis may be regulated by lower leptin signaling. Thus, caloric restriction appears to induce beneficial actions partially by regulating mitochondrial quantity and quality in white adipose tissue in a growth hormone/insulin-like growth factor 1-independent manner.

Combinatorial interventions in aging

Insight on the underlying mechanisms of aging will advance our ability to extend healthspan, treat age-related pathology and improve quality of life. Multiple genetic and pharmacological manipulations extend longevity in different species, yet monotherapy may be relatively inefficient, and we have limited data on the effect of combined interventions. Here we summarize interactions between age-related pathways and discuss strategies to simultaneously retard these in different organisms. In some cases, combined manipulations additively increase their impact on common hallmarks of aging and lifespan, suggesting they quantitatively participate within the same pathway. In other cases, interactions affect different hallmarks, suggesting their joint manipulation may independently maximize their effects on lifespan and healthy aging. While most interaction studies have been conducted with invertebrates and show varying levels of translatability, the conservation of pro-longevity pathways offers an opportunity to identify 'druggable' targets relevant to multiple human age-associated pathologies.

Challenges in anti-aging medicine-trends in biomarker discovery and therapeutic interventions for a healthy lifespan

We are facing a growing aging population, along with increasing pressure on health systems, caused by the impact of chronic co-morbidities (i.e. cancer, cardiovascular and neurodegenerative diseases) and functional disabilities as people age. Relatively simple preventive lifestyle interventions, such as dietary restriction and physical exercise, are important contributors to active and healthy aging in the general population. However, as shown in model organisms or in 'in vitro' conditions, lifestyle-independent interventions may have additional health benefits and can even be conceived as possible reversers of the aging process. Thus, pharmaceutical laboratories, research institutes, and universities are putting more and more effort into finding new molecular pathways and druggable targets to develop gerotherapeutics. One approach is to target the driving mechanisms of aging, some of which, like cellular senescence and impaired autophagy, we discussed in an update on the biology of aging at AgingFit 2023 in Lille, France. We underline the importance of carefully and extensively testing senotherapeutics, given the pleiotropism and heterogeneity of targeted senescent cells within different organs, at different time frames. Other druggable targets emerging from new putative mechanisms, like those based on transcriptome imbalance, nucleophagy, protein phosphatase depletion, glutamine metabolism, or seno-antigenicity, have been evidenced by recent preclinical studies in classical models of aging but need to be validated in humans. Finally, we highlight several approaches in the discovery of biomarkers of healthy aging, as well as for the prediction of neurodegenerative diseases and the evaluation of rejuvenation strategies.

Discovering Biological Mechanisms of Exceptional Human Health Span and Life Span

Humans age at different rates and families with exceptional longevity provide an opportunity to understand why some people age slower than others. Unique features exhibited by centenarians include a family history of extended life span, compression of morbidity with resultant extension of health span, and longevity-associated biomarker profiles. These biomarkers, including low-circulating insulin-like growth factor 1 (IGF-1) and elevated high-density lipoprotein (HDL) cholesterol levels, are associated with functional genotypes that are enriched in centenarians, suggesting that they may be causative for longevity. While not all genetic discoveries from centenarians have been validated, in part due to exceptional life span being a rare phenotype in the general population, the APOE2 and FOXO3a genotypes have been confirmed in a number of populations with exceptional longevity. However, life span is now recognized as a complex trait and genetic research methods to study longevity are rapidly extending beyond classical Mendelian genetics to polygenic inheritance methodologies. Moreover, newer approaches are suggesting that pathways that have been recognized for decades to control life span in animals may also regulate life span in humans. These discoveries led to strategic development of therapeutics that may delay aging and prolong health span.

Immune system rejuvenation—approaches and real achievements

Interest in the mechanisms of aging of the immune system has not faded over the past 100 years, and it is caused by the immune-mediated development of age-related pathology, including autoimmune organ damage, reduced vaccination efficiency, atherosclerosis, the development of cardiovascular pathology, etc. In contrast to many other organs and systems, the immune system aging begins at an early age and has more pronounced changes that lead to the development of secondary pathology, which significantly affects life expectancy. But an effective strategy to restore immune function has not been developed yet. During this time, the mechanisms of age-related dysfunction of organs and cells of both the adaptive and innate immune systems were studied in detail—thymus involution, a decrease in the potential of hematopoietic stem cells, impaired differentiation and functions of immunocompetent cells, as well as the ways of their interaction. Numerous potential therapeutic targets have been identified and various approaches have been used to implement such therapeutic interventions. The review is devoted to replacement therapy using transplantation of hematopoietic stem cells (HSCs) and young lymphoid cells and tissues, cellular and systemic factor exchange in heterochronic parabiosis, and some other widely used life extension approaches. It has been proven that cell therapy using young cells to rejuvenate the old immune system, unfortunately, often turns out to be ineffective because it does not eliminate the root cause of age-related changes. The phenomenon of inflamm-aging that develops with age can significantly affect both the aging of the organism in general and the functioning of immunocompetent cells in particular. Therefore, the most promising direction in the restoration of immune functions during aging is systemic approaches that have a complex effect on the organism as a whole and can slow down the aging process.

Aging under endocrine hormone regulation

Aging is a biological process in which the environment interacts with the body to cause a progressive decline in effective physiological function. Aging in the human body can lead to a dysfunction of the vital organ systems, resulting in the onset of age-related diseases, such as neurodegenerative and cardiovascular diseases, which can seriously affect an individual's quality of life. The endocrine system acts on specific targets through hormones and related major functional factors in its pathways, which play biological roles in coordinating cellular interactions, metabolism, growth, and aging. Aging is the result of a combination of many pathological, physiological, and psychological processes, among which the endocrine system can achieve a bidirectional effect on the aging process by regulating the hormone levels in the body. In this paper, we explored the mechanisms of growth hormone, thyroid hormone, and estrogen in the aging process to provide a reference for the exploration of endocrine mechanisms related to aging.

Devo-Aging: Intersections Between Development and Aging

There are two fundamental questions in developmental biology. How does a single fertilized cell give rise to a whole body? and how does this body later produce progeny? Synchronization of these embryonic and postembryonic developments ensures continuity of life from one generation to the next. An enormous amount of work has been done to unravel the molecular mechanisms behind these processes, but more recently, modern developmental biology has been expanded to study development in wider contexts, including regeneration, environment, disease, and even aging. However, we have just started to understand how the mechanisms that govern development also regulate aging. This review discusses examples of signaling pathways involved in development to elucidate how their regulation influences healthspan and lifespan. Therefore, a better knowledge of developmental signaling pathways stresses the possibility of using them as innovative biomarkers and targets for aging and age-related diseases.

Evaluating instruments for assessing healthspan: a multi-center cross-sectional study on health-related quality of life (HRQL) and frailty in the companion dog

Developing valid tools that assess key determinants of canine healthspan such as frailty and health-related quality of life (HRQL) is essential to characterizing and understanding aging in dogs. Additionally, because the companion dog is an excellent translational model for humans, such tools can be applied to evaluate gerotherapeutics and investigate mechanisms underlying longevity in both dogs and humans. In this multi-center, cross-sectional study, we investigated the use of a clinical questionnaire (Canine Frailty Index; CFI; Banzato et al., 2019) to assess frailty and an owner assessment tool (VetMetrica HRQL) to evaluate HRQL in 451 adult companion dogs. Results demonstrated validity of the tools by confirming expectations that frailty score increases and HRQL scores deteriorate with age. CFI scores were significantly higher (higher frailty) and HRQL scores significantly lower (worse HRQL) in old dogs (≥ 7 years of age) compared to young dogs (≥ 2 and < 6 years of age). Body size (small < 11.3 kg (25 lbs) or large > 22.7 kg (50 lbs)) was not associated with CFI or total HRQL score. However, older, larger dogs showed faster age-related decline in HRQL scores specific to owner-reported activity and comfort. Findings suggest that the clinician-assessed CFI and owner-reported VetMetrica HRQL are useful tools to evaluate two determinants of healthspan in dogs: the accumulation of frailty and the progressive decline in quality of life. Establishing tools that operationalize the assessment of canine healthspan is critical for the advancement of geroscience and the development of gerotherapeutics that benefit both human and veterinary medicine. Graphical summary of the design, results, and conclusions of the study.

Aging Rate Indicators: Speedometers for Aging Research in Mice

A "biomarker of aging" is conceptualized as an index of how far an individual has moved along the path from youth to old age. In contrast, an aging rate indicator (ARI) represents a measure of speed, rather than distance, that is, a measure of how rapidly the individual is moving toward the phenotypic changes typical of old age. This essay presents and reviews recent data suggesting common characteristics of slow-aging mice, whether the slowed aging is caused by a mutant allele, the calorie restriction diet, or drugs that slow aging and extend mean and maximal lifespan. Some of the candidate ARIs, shared by nine varieties of slow-aging mice, are physiological changes seen in fat, fat-associated macrophages, muscle, liver, brain, and plasma. Others are molecular measurements, reflecting activity of mTORC1, selective mRNA translation, or each of six MAP kinases in two distinct MAPK cascades in liver, muscle, or kidney. Changes in ARIs are notable in young adult mice after 8 months of drug or diet exposure, are detectable in mutant mice at least as early as 4-6 months of age, and persist until at least 18-22 months. Many of the candidate ARIs are thought to play an influential role in cognition, inflammation, exercise responses, and control of metabolic rate, and are thus plausible as modulators of age-related physiological and neurological illnesses. In principle, screening for drugs that induce alterations in ARIs in normal young adult mice might facilitate the search for preventive medicines that can retard aging and late-life illnesses in mice or in human populations.

Decreased IGF1R attenuates senescence and improves function in pancreatic β-cells

Introduction

The enhanced β-cell senescence that accompanies insulin resistance and aging contributes to cellular dysfunction and loss of transcriptional identity leading to type 2 diabetes (T2D). While senescence is among the 12 recognized hallmarks of aging, its relation to other hallmarks including altered nutrient sensing (insulin/IGF1 pathway) in β-cells is not fully understood. We previously reported that an increased expression of IGF1R in mouse and human β-cells is a marker of older β-cells; however, its contribution to age-related dysfunction and cellular senescence remains to be determined.

Methods

In this study, we explored the direct role of IGF1R in β-cell function and senescence using two independent mouse models with decreased IGF1/IGF1R signaling: a) Ames Dwarf mice (Dwarf +/+), which lack growth hormone and therefore have reduced circulating levels of IGF1, and b) inducible β-cell-specific IGF1R knockdown (βIgf1rKD) mice.

Results

Compared to Dwarf+/- mice, Dwarf+/+ mice had lower body and pancreas weight, lower circulating IGF1 and insulin levels, and lower IGF1R and p21Cip1 protein expression in β-cells, suggesting the suppression of senescence. Adult βIgf1rKD mice showed improved glucose clearance and glucose-induced insulin secretion, accompanied by decreased p21Cip1 protein expression in β-cells. RNA-Seq of islets isolated from these βIgf1rKD mice revealed the restoration of three signaling pathways known to be downregulated by aging: sulfide oxidation, autophagy, and mTOR signaling. Additionally, deletion of IGF1R in mouse β-cells increased transcription of genes important for maintaining β-cell identity and function, such as Mafa, Nkx6.1, and Kcnj11, while decreasing senescence-related genes, such as Cdkn2a, Il1b, and Serpine 1. Decreased senescence and improved insulin-secretory function of β-cells were also evident when the βIgf1rKD mice were fed a high-fat diet (HFD; 60% kcal from fat, for 5 weeks).

Discussion

These results suggest that IGF1R signaling plays a causal role in aging-induced β-cell dysfunction. Our data also demonstrate a relationship between decreased IGF1R signaling and suppressed cellular senescence in pancreatic β-cells. Future studies can further our understanding of the interaction between senescence and aging, developing interventions that restore β-cell function and identity, therefore preventing the progression to T2D.

Distinct longevity mechanisms across and within species and their association with aging

Lifespan varies within and across species, but the general principles of its control remain unclear. Here, we conducted multi-tissue RNA-seq analyses across 41 mammalian species, identifying longevity signatures and examining their relationship with transcriptomic biomarkers of aging and established lifespan-extending interventions. An integrative analysis uncovered shared longevity mechanisms within and across species, including downregulated Igf1 and upregulated mitochondrial translation genes, and unique features, such as distinct regulation of the innate immune response and cellular respiration. Signatures of long-lived species were positively correlated with age-related changes and enriched for evolutionarily ancient essential genes, involved in proteolysis and PI3K-Akt signaling. Conversely, lifespan-extending interventions counteracted aging patterns and affected younger, mutable genes enriched for energy metabolism. The identified biomarkers revealed longevity interventions, including KU0063794, which extended mouse lifespan and healthspan. Overall, this study uncovers universal and distinct strategies of lifespan regulation within and across species and provides tools for discovering longevity interventions.

Extracellular Matrix Dynamics as an Emerging yet Understudied Hallmark of Aging and Longevity

The biomechanical properties of extracellular matrices (ECM) and their consequences for cellular homeostasis have recently emerged as a driver of aging. Here we review the age-dependent deterioration of ECM in the context of our current understanding of the aging processes. We discuss the reciprocal interactions of longevity interventions with ECM remodeling. And the relevance of ECM dynamics captured by the matrisome and the matreotypes associated with health, disease, and longevity. Furthermore, we highlight that many established longevity compounds promote ECM homeostasis. A large body of evidence for the ECM to qualify as a hallmark of aging is emerging, and the data in invertebrates is promising. However, direct experimental proof that activating ECM homeostasis is sufficient to slow aging in mammals is lacking. We conclude that further research is required and anticipate that a conceptual framework for ECM biomechanics and homeostasis will provide new strategies to promote health during aging.

Age-Related Hormones Changes and Its Impact on Health Status and Lifespan

The increase in life expectancy is accompanied with an increased consultation of age-related pathologies including endocrine disorders. Two main areas are focusing the attention of medical and social research in older population: the diagnosis and care of this heterogeneous population, and the interventional measures potentially useful to mitigate age-related functional declines and to increase health and quality of lifespan. Thus, better understanding the physiopathology of aging and establishing accurate diagnostic and personalized approaches are a priority and currently an unmet need of the medical community. The endocrine system plays a major role in survival and lifespan through regulating vital processes such as energy consumption and optimizing the stress response among others. The aim of this paper is to review the physiological evolution of the main hormonal functions in aging and its clinical translation to improve our approach to the aging patient.

Growth Hormone and Aging

Growth hormone (GH) secretion declines with aging (somatopause). One of the most controversial issues in aging is GH treatment of older adults without evidence of pituitary pathology. Although some clinicians have proposed reversing the GH decline in the older population, most information comes from not placebo-controlled studies. Although most animal studies reported an association between decreased GH levels (or GH resistance) and increased lifespan, human models have shown contradictory reports on the consequences of GH deficiency (GHD) on longevity. Currently, GH treatment in adults is only indicated for individuals with childhood-onset GHD transitioning to adulthood or new-onset GHD due to hypothalamic or pituitary pathologic processes.

Comparative analysis between Open Field and Elevated Plus Maze tests as a method for evaluating anxiety-like behavior in mice

Anxiety is being increasingly diagnosed in the elderly population. In this sense, epidemiologic data have linked late-life anxiety disorders to increased cognitive decline, morbidity, and even mortality. In addition, studies have already reported the influence of the environment on the association between aging and anxiety. Therefore, the present study aimed to conduct a comparative analysis between Elevated Plus Maze (EPM) and Open Field (OF) tests as methods for evaluating mice's anxiety-like behavior, considering environmental and age variables. For this, eighty Female albino Swiss mice aged 6, 12, and 18 months were housed in an impoverished environment (IE) and enriched environment (EE). Following this, the animals were tested in EPM and OF tests. The environment and age affect the anxiety-like behavior of the mice in the OF, with a difference between the animals of 6 and 18 months, only in the EE (p < 0.021). However, in the EPM, it does not occur. Despite that, the environment affected the distance traveled by the mice in the EPM, where the IE animals showed greater exploratory activity than the EE, only in the 18-month group (p < 0.001). No environmental influences were detected in the OF. Concerning age, in the EPM, animals in the 18-month-old group traveled shorter distances compared to the 6-month group (p < 0.001) and the 12-month group (p < 0.001), only in EE. In turn, in the OF there was a decrease in the distance traveled in the 18-month group compared to the 6-month group (p = 0.012), only in the IE. Thus, the divergences between the results of EPM and OF instigate a better evaluation of the parameters analyzed in each test.