Frailty in mouse ageing: A conceptual approach

Unveiling frailty: comprehensive and sex-specific characterization in prematurely aging PolgA mice

Frailty, a geriatric syndrome, is assessed using the frailty phenotype (FP) and frailty index (FI). While these approaches have been applied to aging mice, their effectiveness in prematurely aging mouse models such as PolgAD257A/D257A (PolgA) has not been completely explored. We demonstrated that frailty became evident in PolgA mice around 40 weeks, validated through body weight loss, reduced walking speed, decreased physical activity, and weaker grip strength. Moreover, we also identified sex differences in these mice with females exhibiting slightly more physical decline compared to males. Frailty prevalence in PolgA mice at 40 weeks parallels that observed in naturally aging mice at 27 months and aging humans at 65-70 years. These findings contribute to understanding frailty onset and sex-specific patterns in this prematurely aging mouse model, emphasizing the significance of the PolgA mouse model in investigating aging and related disorders.

Ergothioneine promotes longevity and healthy aging in male mice

Healthy aging has emerged as a crucial issue with the increase in the geriatric population worldwide. Food-derived sulfur-containing amino acid ergothioneine (ERGO) is a potential dietary supplement, which exhibits various beneficial effects in experimental animals although the preventive effects of ERGO on aging and/or age-related impairments such as frailty and cognitive impairment are unclear. We investigated the effects of daily oral supplementation of ERGO dissolved in drinking water on lifespan, frailty, and cognitive impairment in male mice from 7 weeks of age to the end of their lives. Ingestion of 4 ~ 5 mg/kg/day of ERGO remarkably extended the lifespan of male mice. The longevity effect of ERGO was further supported by increase in life and non-frailty spans of Caenorhabditis elegans in the presence of ERGO. Compared with the control group, the ERGO group showed significantly lower age-related declines in weight, fat mass, and average and maximum movement velocities at 88 weeks of age. This was compatible with dramatical suppression by ERGO of the age-related increments in plasma biomarkers (BMs) such as the chemokine ligand 9, creatinine, symmetric dimethylarginine, urea, asymmetric dimethylarginine, quinolinic acid, and kynurenine. The oral intake of ERGO also rescued age-related impairments in learning and memory ability, which might be associated with suppression of the age-related decline in hippocampal neurogenesis and TDP43 protein aggregation and promotion of microglial shift to the M2 phenotype by ERGO ingestion. Ingestion of ERGO may promote longevity and healthy aging in male mice, possibly through multiple biological mechanisms.

Small extracellular vesicles from young plasma reverse age-related functional declines by improving mitochondrial energy metabolism

Recent investigations into heterochronic parabiosis have unveiled robust rejuvenating effects of young blood on aged tissues. However, the specific rejuvenating mechanisms remain incompletely elucidated. Here we demonstrate that small extracellular vesicles (sEVs) from the plasma of young mice counteract pre-existing aging at molecular, mitochondrial, cellular and physiological levels. Intravenous injection of young sEVs into aged mice extends their lifespan, mitigates senescent phenotypes and ameliorates age-associated functional declines in multiple tissues. Quantitative proteomic analyses identified substantial alterations in the proteomes of aged tissues after young sEV treatment, and these changes are closely associated with metabolic processes. Mechanistic investigations reveal that young sEVs stimulate PGC-1α expression in vitro and in vivo through their miRNA cargoes, thereby improving mitochondrial functions and mitigating mitochondrial deficits in aged tissues. Overall, this study demonstrates that young sEVs reverse degenerative changes and age-related dysfunction, at least in part, by stimulating PGC-1α expression and enhancing mitochondrial energy metabolism.

Role of maraviroc and/or rapamycin in the liver of IL10 KO mice with frailty syndrome

Cellular senescence and low-grade inflammation favor the acceleration of aging. The liver is an essential metabolic organ because changes related to its function are related to age-related diseases. The objective of this study was to evaluate the effects of maraviroc (MVC) and/or rapamycin (RAPA) on liver tissue in an experimental model of frailty syndrome in mice, since MVC and RAPA are two molecules able to decrease CCR5 expression, which is overexpressed in patients with frailty. Methods: Eighty male homozygous IL10KO mice were randomly assigned to one of 4 groups (n = 20): i) IL10KO group; ii) MVC group, iii) RAPA group, and iv) MVC-RAPA group. Liver samples were analyzed. Gene expression quantification and western blotting were also performed. The proinflammatory cytokines IL-6 and IL-18 were decreased in MVC and MVC/RAPA groups, IL-12 was decreased in RAPA and MVC/RAPA groups and TNF-α was decreased in all therapeutic groups. P21 was decreased in RAPA and MVC/RAPA groups, Galactosidase beta-1, was also significantly reduced in all therapeutic groups, as were NF-kB1, NF-kB2 and STAT3. In all groups, mTOR and CCL5 were significantly reduced. CCR5 expression was decreased in the MVC and MVC/RAPA groups. Conclusion: MVC and RAPA may protect against some factors involved in liver aging. More studies will be necessary to verify their clinical applications.

Cellular senescence and frailty: a comprehensive insight into the causal links

Senescent cells may have a prominent role in driving inflammation and frailty. The impact of cellular senescence on frailty varies depending on the assessment tool used, as it is influenced by the criteria or items predominantly affected by senescent cells and the varying weights assigned to these items across different health domains. To address this challenge, we undertook a thorough review of all available studies involving gain- or loss-of-function experiments as well as interventions targeting senescent cells, focusing our attention on those studies that examined outcomes based on the individual frailty phenotype criteria or specific items used to calculate two humans (35 and 70 items) and one mouse (31 items) frailty indexes. Based on the calculation of a simple "evidence score," we found that the burden of senescent cells related to musculoskeletal and cerebral health has the strongest causal link to frailty. We deem that insight into these mechanisms may not only contribute to clarifying the role of cellular senescence in frailty but could additionally provide multiple therapeutic opportunities to help the future development of a desirable personalized therapy in these extremely heterogeneous patients.

Exploring In Vivo Models of Musculoskeletal Frailty: A Comprehensive Systematic Review

Musculoskeletal frailty-a common and debilitating condition linked to aging and chronic diseases-presents a major public health issue. In vivo models have become a key tool for researchers as they investigate the condition's underlying mechanisms and develop effective interventions. This systematic review examines the current body of research on in vivo models of musculoskeletal frailty, without any time constraints. To achieve this aim, we utilized three electronic databases and incorporated a total of 11 studies. Our investigation delves into varied animal models that simulate specific features of musculoskeletal frailty, including muscle loss, bone density reduction, and functional decline. Furthermore, we examine the translational prospects of these models in augmenting our comprehension of musculoskeletal frailty and streamlining the production of groundbreaking therapeutic approaches. This review provides significant insights and guidance for healthcare researchers and practitioners who aim to combat musculoskeletal frailty, ultimately enhancing the quality of life for older adults and individuals affected by this condition.

Comprehensive longitudinal non-invasive quantification of healthspan and frailty in a large cohort (n = 546) of geriatric C57BL/6 J mice

Frailty is an age-related condition characterized by a multisystem functional decline, increased vulnerability to stressors, and adverse health outcomes. Quantifying the degree of frailty in humans and animals is a health measure useful for translational geroscience research. Two frailty measurements, namely the frailty phenotype (FP) and the clinical frailty index (CFI), have been validated in mice and are frequently applied in preclinical research. However, these two tools are based on different concepts and do not necessarily identify the same mice as frail. In particular, the FP is based on a dichotomous classification that suffers from high sample size requirements and misclassification problems. Based on the monthly longitudinal non-invasive assessment of frailty in a large cohort of mice, here we develop an alternative scoring method, which we called physical function score (PFS), proposed as a continuous variable that resumes into a unique function, the five criteria included in the FP. This score would not only reduce misclassification of frailty but it also makes the two tools, PFS and CFI, integrable to provide an overall measurement of health, named vitality score (VS) in aging mice. VS displays a higher association with mortality than PFS or CFI and correlates with biomarkers related to the accumulation of senescent cells and the epigenetic clock. This longitudinal non-invasive assessment strategy and the VS may help to overcome the different sensitivity in frailty identification, reduce the sample size in longitudinal experiments, and establish the effectiveness of therapeutic/preventive interventions for frailty or other age-related diseases in geriatric animals.

Potential antidepressant effects of a dietary supplement from Huáng qí and its complex in aged senescence-accelerated mouse prone-8 mice

Healthcare is an emerging industry with significant market potential in the 21st century. Therefore, this study aimed to evaluate the benefits of tube feeding Huáng qí and its complexes for 8 weeks on 3-month-old senescence-accelerated mouse prone-8 (SAMP8) mice, 48 in total, randomly divided into 3 groups including control, Huáng qí extract [820 mg/kg Body weight (BW)/day], and Huáng qí complexes (6.2 mL /kg BW/day), where each group consisted of males (n = 8) and females (n = 8). Behavioral tests (locomotion test and aging score assessment on week 6, the single-trial passive avoidance test on week 7, and the active shuttle avoidance test on week 8) were conducted to evaluate the ability of the mice to learn and remember. In addition, after sacrificing the animals, the blood and organs were measured for antioxidant and aging bioactivities, including malondialdehyde (MDA) content and superoxide dismutase (SOD) activity and catalase activities (CAT), and the effects on promoting aging in SAMP8 mice were investigated. The findings showed that Huáng qí enhanced locomotor performance and had anti-aging effects, with positive effects on health, learning, and memory in SAMP-8 mice (p < 0.05), whether applied as a single agent (820 mg/kg BW/day) or as a complex (6.2 mL/kg BW/day) (p < 0.05). Based on existing strengths, a more compelling platform for clinical validation of human clinical evidence will be established to enhance the development and value-added of astragalus-related products while meeting the diversified needs of the functional food market.

Further Characterization of Multi-Organ DEARE and Protection by 16,16 Dimethyl Prostaglandin E2 in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Survivors of acute radiation exposure suffer from the delayed effects of acute radiation exposure (DEARE), a chronic condition affecting multiple organs, including lung, kidney, heart, gastrointestinal tract, eyes, and brain, and often causing cancer. While effective medical countermeasures (MCM) for the hematopoietic-acute radiation syndrome (H-ARS) have been identified and approved by the FDA, development of MCM for DEARE has not yet been successful. We previously documented residual bone marrow damage (RBMD) and progressive renal and cardiovascular DEARE in murine survivors of H-ARS, and significant survival efficacy of 16,16-dimethyl prostaglandin E2 (dmPGE2) given as a radioprotectant or radiomitigator for H-ARS. We now describe additional DEARE (physiological and neural function, progressive fur graying, ocular inflammation, and malignancy) developing after sub-threshold doses in our H-ARS model, and detailed analysis of the effects of dmPGE2 administered before (PGE-pre) or after (PGE-post) lethal total-body irradiation (TBI) on these DEARE. Administration of PGE-pre normalized the twofold reduction of white blood cells (WBC) and lymphocytes seen in vehicle-treated survivors (Veh), and increased the number of bone marrow (BM) cells, splenocytes, thymocytes, and phenotypically defined hematopoietic progenitor cells (HPC) and hematopoietic stem cells (HSC) to levels equivalent to those in non-irradiated age-matched controls. PGE-pre significantly protected HPC colony formation ex vivo by >twofold, long term-HSC in vivo engraftment potential up to ninefold, and significantly blunted TBI-induced myeloid skewing. Secondary transplantation documented continued production of LT-HSC with normal lineage differentiation. PGE-pre reduced development of DEARE cardiovascular pathologies and renal damage; prevented coronary artery rarefication, blunted progressive loss of coronary artery endothelia, reduced inflammation and coronary early senescence, and blunted radiation-induced increase in blood urea nitrogen (BUN). Ocular monocytes were significantly lower in PGE-pre mice, as was TBI-induced fur graying. Increased body weight and decreased frailty in male mice, and reduced incidence of thymic lymphoma were documented in PGE-pre mice. In assays measuring behavioral and cognitive functions, PGE-pre reduced anxiety in females, significantly blunted shock flinch response, and increased exploratory behavior in males. No effect of TBI was observed on memory in any group. PGE-post, despite significantly increasing 30-day survival in H-ARS and WBC and hematopoietic recovery, was not effective in reducing TBI-induced RBMD or any other DEARE. In summary, dmPGE2 administered as an H-ARS MCM before lethal TBI significantly increased 30-day survival and ameliorated RBMD and multi-organ and cognitive/behavioral DEARE to at least 12 months after TBI, whereas given after TBI, dmPGE2 enhances survival from H-ARS but has little impact on RBMD or other DEARE.

Frailty in rodents: Models, underlying mechanisms, and management

Frailty is a clinical geriatric syndrome characterized by decreased multisystem function and increased vulnerability to adverse outcomes. Although numerous studies have been conducted on frailty, the underlying mechanisms and management strategies remain unclear. As rodents share homology with humans, they are used extensively as animal models to study human diseases. Rodent frailty models can be classified broadly into the genetic modification and non-genetic modification models, the latter of which include frailty assessment models (based on the Fried frailty phenotype and frailty index methods) and induced frailty models. Such models were developed for use in investigating frailty-related physiological changes at the gene, cellular, molecular, and system levels, including the organ system level. Furthermore, exercise, diet, and medication interventions, in addition to their combinations, could improve frailty status in rodents. Rodent frailty models provide novel and effective tools for frailty research. In the present paper, we review research progress in rodent frailty models, mechanisms, and management, which could facilitate and guide further clinical research on frailty in older adults.

Meeting Report: Aging Research and Drug Discovery

Aging is the single largest risk factor for most chronic diseases, and thus possesses large socioeconomic interest to continuously aging societies. Consequently, the field of aging research is expanding alongside a growing focus from the industry and investors in aging research. This year’s 8th Annual Aging Research and Drug Discovery (ARDD) meeting was organized as a hybrid meeting from August 30th to September 3rd 2021 with more than 130 attendees participating on-site at the Ceremonial Hall at University of Copenhagen, Denmark, and 1800 engaging online. The conference comprised of presentations from 75 speakers focusing on new research in topics including mechanisms of aging and how these can be modulated as well as the use of AI and new standards of practices within aging research. This year, a longevity workshop was included to build stronger connections with the clinical community.

Frailty and pain, human studies and animal models

The hypothesis that pain can predispose to frailty development has been recently investigated in several clinical studies suggesting that frailty and pain may share some mechanisms. Both pain and frailty represent important clinical and social problems and both lack a successful treatment. This circumstance is mainly due to the absence of in-depth knowledge of their pathological mechanisms. Evidence of shared pathways between frailty and pain are preliminary. Indeed, many clinical studies are observational and the impact of pain treatment, and relative pain-relief, on frailty onset and progression has never been investigated. Furthermore, preclinical research on this topic has yet to be performed. Specific researches on the pain-frailty relation are needed. In this narrative review, we will attempt to point out the most relevant findings present in both clinical and preclinical literature on the topic, with particular attention to genetics, epigenetics and inflammation, in order to underline the existing gaps and the potential future interventional strategies. The use of pain and frailty animal models discussed in this review might contribute to research in this area.

IL-6 can singlehandedly drive many features of frailty in mice

Frailty is a geriatric syndrome characterized by age-related declines in function and reserve resulting in increased vulnerability to stressors. The most consistent laboratory finding in frail subjects is elevation of serum IL-6, but it is unclear whether IL-6 is a causal driver of frailty. Here, we characterize a new mouse model of inducible IL-6 expression (IL-6^TET-ON/+ mice) following administration of doxycycline (Dox) in food. In this model, IL-6 induction was Dox dose-dependent. The Dox dose that increased IL-6 levels to those observed in frail old mice directly led to an increase in frailty index, decrease in grip strength, and disrupted muscle mitochondrial homeostasis. Littermate mice lacking the knock-in construct failed to exhibit frailty after Dox feeding. Both naturally old mice and young Dox-induced IL-6^TET-ON/+ mice exhibited increased IL-6 levels in sera and spleen homogenates but not in other tissues. Moreover, Dox-induced IL-6^TET-ON/+ mice exhibited selective elevation in IL-6 but not in other cytokines. Finally, bone marrow chimera and splenectomy experiments demonstrated that non-hematopoietic cells are the key source of IL-6 in our model. We conclude that elevated IL-6 serum levels directly drive age-related frailty, possibly via mitochondrial mechanisms.

The pharmaceuticalisation of 'healthy' ageing: Testosterone enhancement for longevity

The United Nations estimates that the world's population will reach 8.5 billion by 2030, and the populations of most countries are expected to grow older. This is case for many developed countries, including Australia, the United Kingdom, Canada, the United States of America, and member states of the European Union. Older cohorts will comprise a larger proportion of overall populations, driven in part by our increases in life expectancy. An ageing population poses challenges for governments; notably, older people tend to have multiple, chronic health conditions which can place a burden of health budgets. At the same time, we are witnessing a shift in how we respond to the health needs of our populations, with global drug policy acknowledging that some substances are contributing to increased morbidity and mortality (e.g. opioids) while others may have beneficial therapeutic effects (e.g. psylocibin, cannabis). There is general agreement that as men age their levels of testosterone decrease, and there is some evidence to suggest that there have been population-level declines in testosterone which are not associated with age. Anecdotally, testosterone is accessed by men seeking to self-medicate in the belief that they are experiencing low testosterone levels. There has also been a rise in anti-ageing clinics in the United States, providing access to testosterone replacement therapy (TRT). The non-medical use of testosterone can result in a number of adverse health events, including complications from the use of black market or underground products. Placing testosterone under a new prescribing regime may address some of these concerns, but is society ready for this change, and if so, what would this regime look like? This paper will explore the issue of how society responds to enhancement for longevity, or how we increasingly use pharmaceuticals to address and prevent illness, with a specific focus on testosterone and testosterone deficiency.

Evaluation of pro-inflammatory cytokines in frail Tunisian older adults

The present study was undertaken to evaluate serum levels of pro-inflammatory cytokines in Tunisian older adults and to examine the relationships between inflammatory marker levels, geriatric, and biochemical parameters. A cross-sectional study was conducted in a population of Tunisian older adults (N = 141, aged 65 and over). Patients were recruited from the Department of Internal Medicine, Fattouma Bourguiba University Hospital (Monastir, Tunisia) and from a nursing home (Sousse, Tunisia). Comprehensive geriatric assessment, history taking and examination including functional and nutritional assessment were done for each participant. Enzyme-linked immunosorbent assay (ELISA) test was used to measure serum cytokine (TNF-α, IL-8, IL-6) levels. The modified Short Emergency Geriatric Assessment score (SEGAm) were used to classify patients as 51 very-frail, 40 frail, and 50 non-frail. The age of the participants (80 men, 61 women) ranged from 65 to 97 years. Serum levels of TNF-α, IL-8 and C-reactive protein (CRP) were significantly higher in very-frail participants compared to frail and non-frail ones. However, no significant differences in IL-6 levels were detected among frailty groups. After adjustment for age, CRP and IL-8 levels remained significantly associated with frailty. Analysis of the receiver operating characteristic (ROC) curve corresponding to IL-8 showed an area under the curve of 0.7 (p = 0.003; 95% CI [0.58-0.81]) and a predictive threshold of 5.27 pg/ml. Positive correlations were found between frailty score, IL-6, and IL-8 levels. In addition, a significant positive correlation was observed between IL-8 levels and Timed Up and Go test results. However, a negative correlation was observed between Mini Nutritional Assessment Short-Form score, IL-6 and CRP levels, as well as between Activities of Daily Living score and serum levels of TNF-α, IL-6, and CRP. In conclusion, the key findings of this study collectively support a role of pro-inflammatory cytokines, TNF-α, CRP, and especially IL-8 in the development of frailty in older adults.

Senescence-accelerated mouse prone 8 mice exhibit specific morphological changes in the small intestine during senescence and after pectin supplemented diet

Impairment of gastrointestinal function and reduction of nutrient absorption associated with aging contribute to increased risk of malnutrition in the elderly population, resulting in physical weakness and vulnerability to disease. The present study was performed to examine the relationships between aging-associated morphological changes of the small intestine and nutrient malabsorption using senescence-accelerated mouse prone 8 (SAMP8) mice. Comparison of the morphology of the small intestine of young (22-week-old) and senescent (43-week-old) SAMP8 mice showed no significant changes in villus length, while the mRNA expression levels of secretory cell marker genes were significantly reduced in senescent mice. In addition, crypts recovered from the small intestine of senescent mice showed a good capacity to form intestinal organoids ex vivo, suggesting that the regenerative capacity of intestinal stem cells (ISCs) was unaffected by accelerated senescence. These results indicated that changes induced by accelerated senescence in the small intestine of SAMP8 mice are different from changes reported previously in normal aging mouse models. Biochemical analyses of serum before and during senescence also indicated that senescent SAMP8 mice are not in a malabsorption state. Furthermore, a diet supplemented with persimmon pectin had a mild effect on the small intestine of senescent SAMP8 mice. Intestinal villus length was slightly increased in the medial part of the small intestine of pectin-fed mice. In contrast, intestinal crypt formation capacity was enhanced by the pectin diet. Organoid culture derived from the small intestine of mice fed pectin exhibited a greater number of lobes per organoid compared with those from mice fed a control diet, and Lyz1 and Olfm4 mRNA levels were significantly increased. In conclusion, accelerated senescence induced exclusive changes in the small intestine, which were not related to nutrient malabsorption. Therefore, the SAMP8 strain may not be a suitable model to evaluate the effects of aging on intestinal homeostasis and nutrient absorption impairment.

Effects of long-term in vivo micro-CT imaging on hallmarks of osteopenia and frailty in aging mice

In vivo micro-CT has already been used to monitor microstructural changes of bone in mice of different ages and in models of age-related diseases such as osteoporosis. However, as aging is accompanied by frailty and subsequent increased sensitivity to external stimuli such as handling and anesthesia, the extent to which longitudinal imaging can be applied in aging studies remains unclear. Consequently, the potential of monitoring individual mice during the entire aging process-from healthy to frail status-has not yet been exploited. In this study, we assessed the effects of long-term in vivo micro-CT imaging-consisting of 11 imaging sessions over 20 weeks-on hallmarks of aging both on a local (i.e., static and dynamic bone morphometry) and systemic (i.e., frailty index (FI) and body weight) level at various stages of the aging process. Furthermore, using a premature aging model (PolgA(D257A/D257A)), we assessed whether these effects differ between genotypes. The 6th caudal vertebrae of 4 groups of mice (PolgA(D257A/D257A) and PolgA(+/+)) were monitored by in vivo micro-CT every 2 weeks. One group was subjected to 11 scans between weeks 20 and 40 of age, whereas the other groups were subjected to 5 scans between weeks 26-34, 32-40 and 40-46, respectively. The long-term monitoring approach showed small but significant changes in the static bone morphometric parameters compared to the other groups. However, no interaction effect between groups and genotype was found, suggesting that PolgA mutation does not render bone more or less susceptible to long-term micro-CT imaging. The differences between groups observed in the static morphometric parameters were less pronounced in the dynamic morphometric parameters. Moreover, the body weight and FI were not affected by more frequent imaging sessions. Finally, we observed that longitudinal designs including baseline measurements at young adult age are more powerful at detecting effects of in vivo micro-CT imaging on hallmarks of aging than cross-sectional comparisons between multiple groups of aged mice subjected to fewer imaging sessions.

A mutation associated with stress resistance in mice is associated with human grip strength and mortality

Hand grip strength (GS) is a valid and reliable predictor of future morbidity and mortality and is considered a useful indicator of aging. In this paper, we use results from the genetic analysis in animal studies to evaluate associations for GS, frailty, and subsequent mortality among humans. Specifically, we use data from the Health and Retirement Survey (HRS) to investigate the association between three polymorphisms in a candidate frailty gene (Tiam1) and GS. Results suggest that the A allele in rs724561 significantly reduces GS among older adults in the US (b = -0.340; p < .006) and is significantly associated with self-reported weakness (b = 0.221; p = .036). This same polymorphism was weakly associated (one-tailed) with an increased risk of mortality (b = 1.091; p < .093) and adjustments for GS rendered this association statistically non-significant (b = 1.048; p < .361). Overall, our results provide tentative evidence that the Tiam1 gene may be associated with frailty development, but we encourage further studies.

Relevance of oxidative stress and inflammation in frailty based on human studies and mouse models

Frailty represents a state of vulnerability and increases the risk of negative health outcomes, which is becoming an important public health problem. Over recent years, multiple independent studies have attempted to identify biomarkers that can predict, diagnose, and monitor frailty at the biological level. Among them, several promising candidates have been associated with frailty status including antioxidants and free radicals, and also inflammatory response biomarkers. In this review, we will summarize the more recent advances in this field. Moreover, the identification of scales and measurements to detect and quantify frailty in aged mice, as well as the generation of mouse models, have started to unravel the underlying biological and molecular mechanisms of frailty. We will discuss them here with an emphasis on murine models with overexpression of glucose-6-phosphate dehydrogenase and loss of function of superoxide dismutase and interleukin 10, which reveal that altered oxidative stress and inflammation pathways are involved in the physiopathology of frailty. In summary, we provide the current available evidence, from both human cohorts and experimental animal models, that highlights oxidative damage and inflammation as relevant biomarkers and drivers of frailty.

Implications of maraviroc and/or rapamycin in a mouse model of fragility

Background: As age increases, the risk of developing fragility also increases. Improving the knowledge of frailty could contribute to maintaining the functional ability of elderly people. Interleukin (IL)-10 homozygous knockout mice (IL-10^tm/tm [IL10KO]) constitute an excellent tool for the study of frailty. Because patients with frailty demonstrate an overexpression of CCR5, rapamycin (RAPA) and/or maraviroc (MVC), two molecules able to decrease CCR5 expression, were evaluated.

Results: Muscle myostatin was reduced in all the therapeutic groups but the MVC group (p <0.001 for RAPA and MVC-RAPA) and in serum samples (p <0.01 for all the groups). Serum CK levels were also significantly lower in MVC and RAPA groups (p <0.01 in both cases). Lower AST levels were observed in all the therapeutic groups (p <0.05 for all of them). The apoptotic effector caspase-3 was significantly lower in MVC and RAPA groups (p<0.05 in both cases). Combined treatment with MVC-RAPA showed a synergistic increase in p-AKT, p-mTOR and SIRT1 levels.

Conclusions: MVC and RAPA show a protective role in some factors involved in frailty. More studies are needed to prove their clinical applications.

Material and methods: Eighty male homozygous IL10KOs were randomly assigned to one of 4 groups (n= 20): i) IL10KO group (IL10KO); ii) IL10KO receiving MVC in drinking water (MVC group), iii) IL10KO receiving RAPA in drinking water (RAPA group), and finally, iv) MVC-RAPA group that received MVC and RAPA in drinking water. Blood and muscle samples were analysed. Survival analysis, frailty index calculation, and functional assessment were also performed.

Exploring the potential of salivary and blood immune biomarkers to elucidate physical frailty in institutionalized older women

Identification of older populations at increased risk of physical frailty using biochemical approaches could improve screening accuracy. The aim of this study was to study the relationship between immune markers and independent components of physical frailty in institutionalized older women. A sample of 358 institutionalized-dwelling women, aged 75 years and older, were assessed for biosocial factors and general health status, pro and anti-inflammatory cytokines, sex steroid hormones, salivary anti-microbial proteins, blood cells counts and the five Fried's physical frailty components that allowed for classification of the sample into frail, prefrailty and not-frail subgroups. Results showed that cytokines IL-6, IL-10, IL-1β, TNF-α, and the TNF-α/IL-10 ratio, mean corpuscular haemoglobin, salivary cortisol and α-amylase were all associated with frailty. Weakness and Exhaustion were the frailty components that were most strongly associated with these biomarkers. Salivary α-amylase was the biomarker that best explained frailty, as it was associated with all five components of physical frailty, and could be used as a potential screening tool. Future research needs to investigate the causal-effect association between salivary innate immune makers, susceptibility to infection and frailty.

Frailty Quantified by the "Valencia Score" as a Potential Predictor of Lifespan in Mice

The development of frailty scores suitable for mice and which resemble those used in the clinical scenario is of great importance to understand human frailty. The aim of the study was to determine an individual frailty score for each mouse at different ages and analyze the association between the frailty score and its lifespan. For this purpose, the "Valencia Score" for frailty was used. Thus, a longitudinal study in mice was performed analyzing weight loss, running time and speed, grip strength and motor coordination at the late-adult, mature and old ages (40, 56 and 80 weeks old, respectively). These parameters are equivalent to unintentional weight loss, poor endurance, slowness, weakness, and low activity level, respectively, in humans. A cut-off point was used to identify frail mice for each criterion. All the measurements were also performed on chronologically adult prematurely aging mice. The results show that by using the "Valencia Score" for frailty a prematurely aged phenotype can be identified even during the adulthood of animals. This opens up the possibility of carrying out preventive long-term interventions. Moreover, the individual frailty score of a given mouse at the late-adult, mature and old ages is shown to be a relevant predictor of its lifespan.

Sublethal whole-body irradiation causes progressive premature frailty in mice

There is an unmet need to develop and validate therapies that can treat or at least prevent premature therapy-induced frailty, multi-morbidity and mortality in long-term tumour survivors. In an approach to develop a first mouse model for therapy-induced long-term frailty, we irradiated male C57Bl/6 mice at 5-6 months of age sub-lethally with 3 × 3 Gy (whole body) and assessed subsequent frailty for up to 6 months using a Rockwood-type frailty index (FI). Frailty scorers were trained to obtain excellent inter- and intra-observer reproducibility. Irradiated mice developed progressive frailty approximately twice as fast as controls. This was premature frailty; it was phenotypically identical to that in non-irradiated mice at higher age. As expected, frailty was associated with decreased cognition and predicted mortality. In irradiated mice, frailty and neuromuscular performance, measured by Rotarod and Hanging Wire tests, were not associated with each other, probably because of long-term decreased body weights after irradiation. We conclude that progressive frailty following sub-lethal irradiation comprises a sensitive and easy to use test bed for interventions to stop premature ageing in long-term tumour survivors.

Frailty index as a biomarker of lifespan and healthspan: Focus on pharmacological interventions

Although survival has been the focus of aging research for many years, the field is rapidly evolving towards incorporating healthspan and health indices in studies that explore aging-related outcomes. Frailty is one such measure that is tightly correlated with human aging. Several frailty measures have been developed that focus on phenotypes of aging, including physical, cognitive and metabolic health that define healthspan. The extent at which cumulative deficits associated with frailty predict functional characteristics of healthy aging and longevity is currently unknown. A growing consensus for the use of animal models has emerged to evaluate a composite measure of frailty that provides a translational basis to understanding human frailty. In this review, we will focus on the impact of several anti-aging interventions, some of which have been characterized as caloric restriction (CR) mimetics such as metformin, rapamycin, and resveratrol as well as more novel approaches that are emerging in the field - nicotinamide adenine dinucleotide precursors, small molecule activators of sirtuins, and senolytics - on a number of frailty measurements associated with aging-related outcomes in mice and discuss the translatability of such measures to human frailty.

Potential role of E4orf1 protein in aging-associated impairment in glycemic control

Aging constitutes a major risk factor for the development of type-2 diabetes (T2D) where glucose tolerance declines with age, resulting in a high prevalence of T2D and impaired glucose tolerance in the elderly population. Currently more than half of the 20 million U.S. adults with T2D are above the age of 60, and the largest increase in T2D prevalence is expected in the elderly. Obesity is a causative factor for T2D associated insulin resistance and hyperglycemia. Furthermore, the aging process is accelerated by hyperglycemia and effective treatment options are limited for the vulnerable aging population. One of the mechanisms contributing to aging associated hyperglycemia is resistance to insulin-mediated glucose disposal. Chronic hyperglycemia also accelerates aging by increasing pro-inflammatory milieu leading to impaired immune function. Although currently available anti-diabetic agents improve glycemic control, they have potential serious side effects in some cases. Therefore, additional and better drugs are urgently needed for treatment of insulin resistance and aging associated health risk factors. This review presents the novel use of a microbial protein, E4orf1 as a potential anti-diabetic agent, which functions independent of insulin and obesity, highlighting the role of unique sources for future drug development.

Identifying and Implementing Endpoints for Geriatric Mice

The types of changes in physical appearance and behavior that occur in elderly people similarly develop in elderly animals. Signs and symptoms that might cause concern in younger people or mice may be normal in their elderly but generally healthy counterparts. Although numerous scoring methods have been developed to assess rodent health, these systems were often designed for young adults used in specific types of research, such as cancer or neurologic studies, and therefore may be suboptimal for assessing aging rodents. Approaches known as frailty assessments provide a global evaluation of the health of aged mice, rats, and people, and mouse frailty scores correlate well with the likelihood of death. Complementing frailty assessment, prediction of imminent death in aged mice can often be accomplished by focusing on 2 objective parameters-body weight and temperature. Before they die, many (but not all) mice develop marked reductions in body weight and temperature, thus providing signs that close monitoring, intervention, or preemptive euthanasia may be necessary. Timely preemptive euthanasia allows antemortem collection of data and samples that would be lost if spontaneous death occurred; preemptive euthanasia also limits terminal suffering. These approaches to monitoring declining health and predicting death in elderly research mice can aid in establishing and implementing timely interventions that both benefit the research and reduce antemortem suffering.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Differential effects of chronic stress in young-adult and old female mice: cognitive-behavioral manifestations and neurobiological correlates

Stress-related psychopathology is highly prevalent among elderly individuals and is associated with detrimental effects on mood, appetite and cognition. Conversely, under certain circumstances repeated mild-to-moderate stressors have been shown to enhance cognitive performance in rodents and exert stress-inoculating effects in humans. As most stress-related favorable outcomes have been reported in adolescence and young-adulthood, this apparent disparity could result from fundamental differences in how aging organisms respond to stress. Furthermore, given prominent age-related alterations in sex hormones, the effect of chronic stress in aging females remains a highly relevant yet little studied issue. In the present study, female C57BL/6 mice aged 3 (young-adult) and 20-23 (old) months were subjected to 8 weeks of chronic unpredictable stress (CUS). Behavioral outcomes were measured during the last 3 weeks of the CUS protocol, followed by brain dissection for histological and molecular end points. We found that in young-adult female mice, CUS resulted in decreased anxiety-like behavior and enhanced cognitive performance, whereas in old female mice it led to weight loss, dysregulated locomotion and memory impairment. These phenotypes were paralleled by differential changes in the expression of hypothalamic insulin and melanocortin-4 receptors and were consistent with an age-dependent reduction in the dynamic range of stress-related changes in the hippocampal transcriptome. Supported by an integrated microRNA (miRNA)-mRNA expression analysis, the present study proposes that, when confronted with ongoing stress, neuroprotective mechanisms involving the upregulation of neurogenesis, Wnt signaling and miR-375 can be harnessed more effectively during young-adulthood. Conversely, we suggest that aging alters the pattern of immune activation elicited by stress. Ultimately, interventions that modulate these processes could reduce the burden of stress-related psychopathology in late life.

A Clinically Relevant Frailty Index for Aging Rats

Frailty is a clinical syndrome that is increasingly prevalent during aging. Frailty involves the confluence of reduced strength, speed, physical activity, and endurance and is associated with adverse health outcomes. The present study adapts existing clinical and preclinical indices of frailty to the Fischer (F344) rat. Male F344 rats (n = 133; 17 mo) completed a battery of behavioral tasks, including forelimb wire suspension (strength), rotarod (speed), open field (physical activity), and inclined screen (endurance). Rats that performed poorly (lowest quintile) on two tasks were considered mildly frail (17.29%, n = 23), and rats that performed poorly on 3-4 tasks were considered frail (2.26%, n = 3). Logistic regression of 100-day survival revealed that mildly frail rats were 3.8 times and frail rats were 27.5 times more likely to die during that period than nonfrail rats (p = .038; 95% confidence interval: 2.030, 372.564). The selected criterion tests, cutoff points, and index provide a potential tool for identifying frailty in aged F344 rats, which is consistent with existing frailty indices for humans and mice.

Implementation of the mouse frailty index

Frailty is considered a state of high vulnerability for adverse health outcomes for people of the same age. Those who are frail have higher mortality, worse health outcomes, and use more health care services than those who are not frail. Despite this, little is known about the biology of frailty, the effect of frailty on pharmacological or surgical outcomes, and potential interventions to attenuate frailty. In humans, frailty can be quantified using a frailty index (FI) based on the principle of deficit accumulation. The recent development of an FI in naturally ageing mice provides an opportunity to conduct frailty research in a validated preclinical model. The mouse FI has been successfully used across a wide range of applications; however, there are some factors that should be considered in implementing this tool. This review summarises the current literature, presents some original data, and suggests areas for future research on the current applications of the mouse FI, inter-rater reliability of the FI, the effect of observer characteristics and environmental factors on mouse FI scores, and the individual items that make up the FI assessment. The implementation of this tool into preclinical frailty research should greatly accelerate translational research in this important field.

A Frailty Index Based On Deficit Accumulation Quantifies Mortality Risk in Humans and in Mice

Although many common diseases occur mostly in old age, the impact of ageing itself on disease risk and expression often goes unevaluated. To consider the impact of ageing requires some useful means of measuring variability in health in animals of the same age. In humans, this variability has been quantified by counting age-related health deficits in a frailty index. Here we show the results of extending that approach to mice. Across the life course, many important features of deficit accumulation are present in both species. These include gradual rates of deficit accumulation (slope = 0.029 in humans; 0.036 in mice), a submaximal limit (0.54 in humans; 0.44 in mice), and a strong relationship to mortality (1.05 [1.04–1.05] in humans; 1.15 [1.12–1.18] in mice). Quantifying deficit accumulation in individual mice provides a powerful new tool that can facilitate translation of research on ageing, including in relation to disease.