Late-life targeting of the IGF-1 receptor improves healthspan and lifespan in female mice

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.

Timing of TORC1 inhibition dictates Pol III involvement in Caenorhabditis elegans longevity

Organismal growth and lifespan are inextricably linked. Target of Rapamycin (TOR) signalling regulates protein production for growth and development, but if reduced, extends lifespan across species. Reduction in the enzyme RNA polymerase III, which transcribes tRNAs and 5S rRNA, also extends longevity. Here, we identify a temporal genetic relationship between TOR and Pol III in Caenorhabditis elegans, showing that they collaborate to regulate progeny production and lifespan. Interestingly, the lifespan interaction between Pol III and TOR is only revealed when TOR signaling is reduced, specifically in adulthood, demonstrating the importance of timing to control TOR regulated developmental versus adult programs. In addition, we show that Pol III acts in C. elegans muscle to promote both longevity and healthspan and that reducing Pol III even in late adulthood is sufficient to extend lifespan. This demonstrates the importance of Pol III for lifespan and age-related health in adult C. elegans.

Cpt1a silencing in AgRP neurons improves cognitive and physical capacity and promotes healthy aging in male mice

Orexigenic neurons expressing agouti-related protein (AgRP) and neuropeptide Y in the arcuate nucleus (ARC) of the hypothalamus are activated in response to dynamic variations in the metabolic state, including exercise. We previously observed that carnitine palmitoyltransferase 1a (CPT1A), a rate-limiting enzyme of mitochondrial fatty acid oxidation, is a key factor in AgRP neurons, modulating whole-body energy balance and fluid homeostasis. However, the effect of CPT1A in AgRP neurons in aged mice and during exercise has not been explored yet. We have evaluated the physical and cognitive capacity of adult and aged mutant male mice lacking Cpt1a in AgRP neurons (Cpt1a KO). Adult Cpt1a KO male mice exhibited enhanced endurance performance, motor coordination, locomotion, and exploration compared with control mice. No changes were observed in anxiety-related behavior, cognition, and muscle strength. Adult Cpt1a KO mice showed a reduction in gastrocnemius and tibialis anterior muscle mass. The cross-sectional area (CSA) of these muscles were smaller than those of control mice displaying a myofiber remodeling from type II to type I fibers. In aged mice, changes in myofiber remodeling were maintained in Cpt1a KO mice, avoiding loss of physical capacity during aging progression. Additionally, aged Cpt1a KO mice revealed better cognitive skills, reduced inflammation, and oxidative stress in the hypothalamus and hippocampus. In conclusion, CPT1A in AgRP neurons appears to modulate health and protects against aging. Future studies are required to clarify whether CPT1A is a potential antiaging candidate for treating diseases affecting memory and physical activity.

HDAC1/2 inhibitor therapy improves multiple organ systems in aged mice

Aging increases the risk of age-related diseases, imposing substantial healthcare and personal costs. Targeting fundamental aging mechanisms pharmacologically can promote healthy aging and reduce this disease susceptibility. In this work, we employed transcriptome-based drug screening to identify compounds emulating transcriptional signatures of long-lived genetic interventions. We discovered compound 60 (Cmpd60), a selective histone deacetylase 1 and 2 (HDAC1/2) inhibitor, mimicking diverse longevity interventions. In extensive molecular, phenotypic, and bioinformatic assessments using various cell and aged mouse models, we found Cmpd60 treatment to improve age-related phenotypes in multiple organs. Cmpd60 reduces renal epithelial-mesenchymal transition and fibrosis in kidney, diminishes dementia-related gene expression in brain, and enhances cardiac contractility and relaxation for the heart. In sum, our two-week HDAC1/2 inhibitor treatment in aged mice establishes a multi-tissue, healthy aging intervention in mammals, holding promise for therapeutic translation to promote healthy aging in humans.

Impact of Aging and a High-Fat Diet on Adipose-Tissue-Derived Extracellular Vesicle miRNA Profiles in Mice

BACKGROUND

Middle-aged adults have the highest obesity rates, leading to significant health complications in later years. Obesity triggers the release of altered molecules, including extracellular vesicles (EVs) from excess adipose tissue (AT), contributing to various health complications. In this study, we assessed the effects of age and a high-fat diet on AT-derived EV miRNA profiles to understand their potential roles in aging and obesity.

METHOD

C57BL/6 male mice were subjected to a normal chow diet (NCD) or a high-fat diet (HFD) for either 10-12 weeks (young mice, n = 10) or 50-61 weeks (middle-aged mice, n = 12). After evaluating metabolic characteristics, peri-gonadal white AT was isolated and cultured to obtain EVs. AT-derived EV miRNAs were profiled using a NanoString miRNA panel (n = 599).

RESULTS

Middle-aged mice exhibited obesity regardless of diet. Young mice fed an HFD showed similar metabolic traits to middle-aged mice. In the NCD group, 131 differentially expressed miRNAs (DE-miRNAs) emerged in middle-aged mice compared to young mice, including miR-21, miR-148a, and miR-29a, associated with cancer, neuro/psychological disorders, and reproductive diseases. In the HFD group, 55 DE-miRNAs were revealed in middle-aged mice compared to young mice. These miRNAs were associated with significantly suppressed IGF1R activity.

CONCLUSION

This study demonstrates the potential significant impact of miRNAs of AT EVs on aging- and obesity-related diseases.

Icariin Improves Stress Resistance and Extends Lifespan in Caenorhabditis elegans through hsf-1 and daf-2-Driven Hormesis

Aging presents an increasingly significant challenge globally, driven by the growing proportion of individuals aged 60 and older. Currently, there is substantial research interest in pro-longevity interventions that target pivotal signaling pathways, aiming not only to extend lifespan but also to enhance healthspan. One particularly promising approach involves inducing a hormetic response through the utilization of natural compounds defined as hormetins. Various studies have introduced the flavonoid icariin as beneficial for age-related diseases such as cardiovascular and neurodegenerative conditions. To validate its potential pro-longevity properties, we employed Caenorhabditis elegans as an experimental platform. The accumulated results suggest that icariin extends the lifespan of C. elegans through modulation of the DAF-2, corresponding to the insulin/IGF-1 signaling pathway in humans. Additionally, we identified increased resistance to heat and oxidative stress, modulation of lipid metabolism, improved late-life healthspan, and an extended lifespan upon icariin treatment. Consequently, a model mechanism of action was provided for icariin that involves the modulation of various players within the stress-response network. Collectively, the obtained data reveal that icariin is a potential hormetic agent with geroprotective properties that merits future developments.

Combination of the biomarkers for aging and cancer? - Challenges and current status

The proportion of patients diagnosed with cancer has been shown to rise with the increasing aging global population. Advanced age is a major risk factor for morbidity and mortality in older adults. As individuals experience varying health statuses, particularly with age, it poses a challenge for medical professionals in the cancer field to obtain standardized treatment outcomes. Hence, relying solely on chronological age and disease-related parameters is inadequate for clinical decision-making for elderly patients. With functional, multimorbidity-related, and psychosocial changes that occur with aging, oncologic diseases may develop and be treated differently from younger patients, leading to unique challenges in treatment efficacy and tolerance. To overcome this challenge, personalized therapy using biomarkers has emerged as a promising solution. Various categories of biomarkers, including inflammatory, hematological, metabolic, endocrine, and DNA modification-related indicators, may display features related to both cancer and aging, aiding in the development of innovative therapeutic approaches for patients with cancer in old age. Furthermore, physical functional measurements as non-molecular phenotypic biomarkers are being investigated for their potential complementary role in structured multidomain strategies to combat age-related diseases such as cancer. This review provides insight into the current developments, recent discoveries, and significant challenges in cancer and aging biomarkers, with a specific focus on their application in advanced age.

Cellular Senescence: A Troy Horse in Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a chronic interstitial lung disease characterized by myofibroblast abnormal activation and extracellular matrix deposition. However, the pathogenesis of PF remains unclear, and treatment options are limited. Epidemiological studies have shown that the average age of PF patients is estimated to be over 65 years, and the incidence of the disease increases with age. Therefore, PF is considered an age-related disease. A preliminary study on PF patients demonstrated that the combination therapy of the anti-senescence drugs dasatinib and quercetin improved physical functional indicators. Given the global aging population and the role of cellular senescence in tissue and organ aging, understanding the impact of cellular senescence on PF is of growing interest. This article systematically summarizes the causes and signaling pathways of cellular senescence in PF. It also objectively analyzes the impact of senescence in AECs and fibroblasts on PF development. Furthermore, potential intervention methods targeting cellular senescence in PF treatment are discussed. This review not only provides a strong theoretical foundation for understanding and manipulating cellular senescence, developing new therapies to improve age-related diseases, and extending a healthy lifespan but also offers hope for reversing the toxicity caused by the massive accumulation of senescence cells in humans.

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.

Hallmarks of cardiovascular ageing

Normal circulatory function is a key determinant of disease-free life expectancy (healthspan). Indeed, pathologies affecting the cardiovascular system, which are growing in prevalence, are the leading cause of global morbidity, disability and mortality, whereas the maintenance of cardiovascular health is necessary to promote both organismal healthspan and lifespan. Therefore, cardiovascular ageing might precede or even underlie body-wide, age-related health deterioration. In this Review, we posit that eight molecular hallmarks are common denominators in cardiovascular ageing, namely disabled macroautophagy, loss of proteostasis, genomic instability (in particular, clonal haematopoiesis of indeterminate potential), epigenetic alterations, mitochondrial dysfunction, cell senescence, dysregulated neurohormonal signalling and inflammation. We also propose a hierarchical order that distinguishes primary (upstream) from antagonistic and integrative (downstream) hallmarks of cardiovascular ageing. Finally, we discuss how targeting each of the eight hallmarks might be therapeutically exploited to attenuate residual cardiovascular risk in older individuals.

Effects and potential mechanisms of IGF1/IGF1R in the liver fibrosis: A review

Liver fibrosis is a wound-healing response due to persistent liver damage and it may progress to cirrhosis and even liver cancer if no intervention is given. In the current cognition, liver fibrosis is reversible. So, it is of great significance to explore the related gene targets or biomarker for anti-fibrosis of liver. Insulin like growth factor 1 (IGF1) and IGF1 receptor (IGF1R) are mainly expressed in the liver tissues and play critical roles in the liver function. The present review summarized the role of IGF1/IGF1R and its signaling system in liver fibrosis and illustrated the potential mechanisms including DNA damage repair, cell senescence, lipid metabolism and oxidative stress that may be involved in this process according to the studies on the fibrosis of liver or other organs. In particular, the roles of IGF1 and IGF1R in DNA damage repair were elaborated, including membrane-localized and nucleus-localized IGF1R. In addition, for each of the potential mechanism in anti-fibrosis of liver, the signaling pathways of the IGF1/IGF1R mediated and the cell species in liver acted by IGF1 and IGF1R under different conditions were included. The data in this review will support for the study about the effect of IGF1/IGF1R on liver fibrosis induced by various factors, meanwhile, provide a basis for the study of liver fibrosis to focus on the communications between the different kinds of liver cells.

IFNγ-Stat1 axis drives aging-associated loss of intestinal tissue homeostasis and regeneration

The influence of aging on intestinal stem cells and their niche can explain underlying causes for perturbation in their function observed during aging. Molecular mechanisms for such a decrease in the functionality of intestinal stem cells during aging remain largely undetermined. Using transcriptome-wide approaches, our study demonstrates that aging intestinal stem cells strongly upregulate antigen presenting pathway genes and over-express secretory lineage marker genes resulting in lineage skewed differentiation into the secretory lineage and strong upregulation of MHC class II antigens in the aged intestinal epithelium. Mechanistically, we identified an increase in proinflammatory cells in the lamina propria as the main source of elevated interferon gamma (IFNγ) in the aged intestine, that leads to the induction of Stat1 activity in intestinal stem cells thus priming the aberrant differentiation and elevated antigen presentation in epithelial cells. Of note, systemic inhibition of IFNγ-signaling completely reverses these aging phenotypes and reinstalls regenerative capacity of the aged intestinal epithelium.

Gene regulatory Networks Reveal Sex Difference in Lung Adenocarcinoma

Lung adenocarcinoma (LUAD) has been observed to have significant sex differences in incidence, prognosis, and response to therapy. However, the molecular mechanisms responsible for these disparities have not been investigated extensively. Sample-specific gene regulatory network methods were used to analyze RNA sequencing data from non-cancerous human lung samples from The Genotype Tissue Expression Project (GTEx) and lung adenocarcinoma primary tumor samples from The Cancer Genome Atlas (TCGA); results were validated on independent data. We observe that genes associated with key biological pathways including cell proliferation, immune response and drug metabolism are differentially regulated between males and females in both healthy lung tissue, as well as in tumor, and that these regulatory differences are further perturbed by tobacco smoking. We also uncovered significant sex bias in transcription factor targeting patterns of clinically actionable oncogenes and tumor suppressor genes, including AKT2 and KRAS. Using differentially regulated genes between healthy and tumor samples in conjunction with a drug repurposing tool, we identified several small-molecule drugs that might have sex-biased efficacy as cancer therapeutics and further validated this observation using an independent cell line database. These findings underscore the importance of including sex as a biological variable and considering gene regulatory processes in developing strategies for disease prevention and management.

Insulin-Like Growth Factor 1 Receptor Deficiency Alleviates Angiotensin II-Induced Cardiac Fibrosis Through the Protein Kinase B/Extracellular Signal-Regulated Kinase/Nuclear Factor-κB Pathway

Background The renin-angiotensin system plays a crucial role in the development of heart failure, and Ang II (angiotensin II) acts as the critical effector of the renin-angiotensin system in regulating cardiac fibrosis. However, the mechanisms of cardiac fibrosis are complex and still not fully understood. IGF1R (insulin-like growth factor 1 receptor) has multiple functions in maintaining cardiovascular homeostasis, and low-dose IGF1 treatment is effective in relieving Ang II-induced cardiac fibrosis. Here, we aimed to investigate the molecular mechanism of IGF1R in Ang II-induced cardiac fibrosis. Methods and Results Using primary mouse cardiac microvascular endothelial cells and fibroblasts, in vitro experiments were performed. Using C57BL/6J mice and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9)-mediated IGF1R heterozygous knockout (Igf1r+/-) mice, cardiac fibrosis mouse models were induced by Ang II for 2 weeks. The expression of IGF1R was examined by quantitative reverse transcription polymerase chain reaction, immunohistochemistry, and Western blot. Mice heart histologic changes were evaluated using Masson and picro sirius red staining. Fibrotic markers and signal molecules indicating the function of the Akt (protein kinase B)/ERK (extracellular signal-regulated kinase)/nuclear factor-κB pathway were detected using quantitative reverse transcription polymerase chain reaction and Western blot. RNA sequencing was used to explore IGF1R-mediated target genes in the hearts of mice, and the association of IGF1R and G-protein-coupled receptor kinase 5 was identified by coimmunoprecipitation. More important, blocking IGF1R signaling significantly suppressed endothelial-mesenchymal transition in primary mouse cardiac microvascular endothelial cells and mice in response to transforming growth factor-β1 or Ang II, respectively. Deficiency or inhibition of IGF1R signaling remarkably attenuated Ang II-induced cardiac fibrosis in primary mouse cardiac fibroblasts and mice. We further observed that the patients with heart failure exhibited higher blood levels of IGF1 and IGF1R than healthy individuals. Moreover, Ang II treatment significantly increased cardiac IGF1R in wild type mice but led to a slight downregulation in Igf1r+/- mice. Interestingly, IGF1R deficiency significantly alleviated cardiac fibrosis in Ang II-treated mice. Mechanistically, the phosphorylation level of Akt and ERK was upregulated in Ang II-treated mice, whereas blocking IGF1R signaling in mice inhibited these changes of Akt and ERK phosphorylation. Concurrently, phosphorylated p65 of nuclear factor-κB exhibited similar alterations in the corresponding group of mice. Intriguingly, IGF1R directly interacted with G-protein-coupled receptor kinase 5, and this association decreased ≈50% in Igf1r+/- mice. In addition, Grk5 deletion downregulated expression of the Akt/ERK/nuclear factor-κB signaling pathway in primary mouse cardiac fibroblasts. Conclusions IGF1R signaling deficiency alleviates Ang II-induced cardiac fibrosis, at least partially through inhibiting endothelial-mesenchymal transition via the Akt/ERK/nuclear factor-κB pathway. Interestingly, G-protein-coupled receptor kinase 5 associates with IGF1R signaling directly, and it concurrently acts as an IGF1R downstream effector. This study suggests the promising potential of IGF1R as a therapeutic target for cardiac fibrosis.

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.

Ageing-associated phenotypes in mice

Ageing is a continuous process in life featuring progressive damage accumulation that leads to physiological decline, functional deterioration and ultimately death of an organism. Based on the relatively close anatomical and physiological similarity to humans, the mouse has been proven as a valuable model organism in ageing research over the last decades. In this review, we survey methods and tools currently in use to assess ageing phenotypes in mice. We summarize a range of ageing-associated alterations detectable at two major levels of analysis: (1) physiology and pathophysiology and (2) molecular biomarkers. Age-sensitive phenotypes provided in this article may serve to inform future studies targeting various aspects of organismal ageing in mice. In addition, we discuss conceptual and technical challenges faced by previous ageing studies in mice and, where possible, provide recommendations on how to resolve some of these issues.

The Native Microbiome Member Chryseobacterium sp. CHNTR56 MYb120 Induces Trehalose Production via a Shift in Central Carbon Metabolism during Early Life in C. elegans

Aging is the system-wide loss of homeostasis, eventually leading to death. There is growing evidence that the microbiome not only evolves with its aging host, but also directly affects aging via the modulation of metabolites involved in important cellular functions. The widely used model organism C. elegans exhibits high selectivity towards its native microbiome members which confer a range of differential phenotypes and possess varying functional capacities. The ability of one such native microbiome species, Chryseobacterium sp. CHNTR56 MYb120, to improve the lifespan of C. elegans and to promote the production of Vitamin B6 in the co-colonizing member Comamonas sp. 12022 MYb131 are some of its beneficial effects on the worm host. We hypothesize that studying its metabolic influence on the different life stages of the worm could provide further insights into mutualistic interactions. The present work applied LC-MS untargeted metabolomics and isotope labeling to study the impact of the native microbiome member Chryseobacterium sp. CHNTR56 MYb120 on the metabolism of C. elegans. In addition to the upregulation of biosynthesis and detoxification pathway intermediates, we found that Chryseobacterium sp. CHNTR56 MYb120 upregulates the glyoxylate shunt in mid-adult worms which is linked to the upregulation of trehalose, an important metabolite for desiccation tolerance in older worms.

Intrinsic and environmental basis of aging: A narrative review

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

Activation of insulin-like growth factor-1 receptor (IGF-1R) promotes growth of colorectal cancer through triggering the MEX3A-mediated degradation of RIG-I

Insulin-like growth factor-1 receptor (IGF-1R) has been made an attractive anticancer target due to its overexpression in cancers. However, targeting it has often produced the disappointing results as the role played by cross talk with numerous downstream signalings. Here, we report a disobliging IGF-1R signaling which promotes growth of cancer through triggering the E3 ubiquitin ligase MEX3A-mediated degradation of RIG-I. The active β-arrestin-2 scaffolds this disobliging signaling to talk with MEX3A. In response to ligands, IGF-1Rβ activated the basal βarr2 into its active state by phosphorylating the interdomain domain on Tyr64 and Tyr250, opening the middle loop (Leu130‒Cys141) to the RING domain of MEX3A through the conformational changes of βarr2. The models of βarr2/IGF-1Rβ and βarr2/MEX3A could interpret the mechanism of the activated-IGF-1R in triggering degradation of RIG-I. The assay of the mutants βarr2^Y64A and βarr2^Y250A further confirmed the role of these two Tyr residues of the interlobe in mediating the talk between IGF-1Rβ and the RING domain of MEX3A. The truncated-βarr2 and the peptide ATQAIRIF, which mimicked the RING domain of MEX3A could prevent the formation of βarr2/IGF-1Rβ and βarr2/MEX3A complexes, thus blocking the IGF-1R-triggered RIG-I degradation. Degradation of RIG-I resulted in the suppression of the IFN-I-associated immune cells in the TME due to the blockade of the RIG-I-MAVS-IFN-I pathway. Poly(I:C) could reverse anti-PD-L1 insensitivity by recovery of RIG-I. In summary, we revealed a disobliging IGF-1R signaling by which IGF-1Rβ promoted cancer growth through triggering the MEX3A-mediated degradation of RIG-I.

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.

Targeting the biology of aging with mTOR inhibitors

Inhibition of the protein kinase mechanistic target of rapamycin (mTOR) with the Food and Drug Administration (FDA)-approved therapeutic rapamycin promotes health and longevity in diverse model organisms. More recently, specific inhibition of mTORC1 to treat aging-related conditions has become the goal of basic and translational scientists, clinicians and biotechnology companies. Here, we review the effects of rapamycin on the longevity and survival of both wild-type mice and mouse models of human diseases. We discuss recent clinical trials that have explored whether existing mTOR inhibitors can safely prevent, delay or treat multiple diseases of aging. Finally, we discuss how new molecules may provide routes to the safer and more selective inhibition of mTOR complex 1 (mTORC1) in the decade ahead. We conclude by discussing what work remains to be done and the questions that will need to be addressed to make mTOR inhibitors part of the standard of care for diseases of aging.

The effect of metformin on influenza vaccine responses in nondiabetic older adults: a pilot trial

BACKGROUND

Aging is associated with progressive declines in immune responses leading to increased risk of severe infection and diminished vaccination responses. Influenza (flu) is a leading killer of older adults despite availability of seasonal vaccines. Geroscience-guided interventions targeting biological aging could offer transformational approaches to reverse broad declines in immune responses with aging. Here, we evaluated effects of metformin, an FDA approved diabetes drug and candidate anti-aging drug, on flu vaccination responses and markers of immunological resilience in a pilot and feasibility double-blinded placebo-controlled study.

RESULTS

Healthy older adults (non-diabetic/non-prediabetic, age: 74.4 ± 1.7 years) were randomized to metformin (n = 8, 1500 mg extended release/daily) or placebo (n = 7) treatment for 20 weeks and were vaccinated with high-dose flu vaccine after 10 weeks of treatment. Peripheral blood mononuclear cells (PBMCs), serum, and plasma were collected prior to treatment, immediately prior to vaccination, and 1, 5, and 10 weeks post vaccination. Increased serum antibody titers were observed post vaccination with no significant differences between groups. Metformin treatment led to trending increases in circulating T follicular helper cells post-vaccination. Furthermore, 20 weeks of metformin treatment reduced expression of exhaustion marker CD57 in circulating CD4 T cells.

CONCLUSIONS

Pre-vaccination metformin treatment improved some components of flu vaccine responses and reduced some markers of T cell exhaustion without serious adverse events in nondiabetic older adults. Thus, our findings highlight the potential utility of metformin to improve flu vaccine responses and reduce age-related immune exhaustion in older adults, providing improved immunological resilience in nondiabetic older adults.

Metabolic Syndrome as a Risk Factor for Alzheimer's Disease: A Focus on Insulin Resistance

Alzheimer's disease (AD) is the main type of dementia and is a disease with a profound socioeconomic burden due to the lack of effective treatment. In addition to genetics and environmental factors, AD is highly associated with metabolic syndrome, defined as the combination of hypertension, hyperlipidemia, obesity and type 2 diabetes mellitus (T2DM). Among these risk factors, the connection between AD and T2DM has been deeply studied. It has been suggested that the mechanism linking both conditions is insulin resistance. Insulin is an important hormone that regulates not only peripheral energy homeostasis but also brain functions, such as cognition. Insulin desensitization, therefore, could impact normal brain function increasing the risk of developing neurodegenerative disorders in later life. Paradoxically, it has been demonstrated that decreased neuronal insulin signalling can also have a protective role in aging and protein-aggregation-associated diseases, as is the case in AD. This controversy is fed by studies focused on neuronal insulin signalling. However, the role of insulin action on other brain cell types, such as astrocytes, is still unexplored. Therefore, it is worthwhile exploring the involvement of the astrocytic insulin receptor in cognition, as well as in the onset and/or development of AD.

Dietary supplementation of clinically utilized PI3K p110α inhibitor extends the lifespan of male and female mice

Diminished insulin and insulin-like growth factor-1 signaling extends the lifespan of invertebrates^1-4; however, whether it is a feasible longevity target in mammals is less clear^5-12. Clinically utilized therapeutics that target this pathway, such as small-molecule inhibitors of phosphoinositide 3-kinase p110α (PI3Ki), provide a translatable approach to studying the impact of these pathways on aging. Here, we provide evidence that dietary supplementation with the PI3Ki alpelisib from middle age extends the median and maximal lifespan of mice, an effect that was more pronounced in females. While long-term PI3Ki treatment was well tolerated and led to greater strength and balance, negative impacts on common human aging markers, including reductions in bone mass and mild hyperglycemia, were also evident. These results suggest that while pharmacological suppression of insulin receptor (IR)/insulin-like growth factor receptor (IGFR) targets could represent a promising approach to delaying some aspects of aging, caution should be taken in translation to humans.

Perinatal Obesity Sensitizes for Premature Kidney Aging Signaling

Chronic Kidney Disease (CKD), a global health burden, is strongly associated with age-related renal function decline, hypertension, and diabetes, which are all frequent consequences of obesity. Despite extensive studies, the mechanisms determining susceptibility to CKD remain insufficiently understood. Clinical evidence together with prior studies from our group showed that perinatal metabolic disorders after intrauterine growth restriction or maternal obesity adversely affect kidney structure and function throughout life. Since obesity and aging processes converge in similar pathways we tested if perinatal obesity caused by high-fat diet (HFD)-fed dams sensitizes aging-associated mechanisms in kidneys of newborn mice. The results showed a marked increase of γH2AX-positive cells with elevated 8-Oxo-dG (RNA/DNA damage), both indicative of DNA damage response and oxidative stress. Using unbiased comprehensive transcriptomics we identified compartment-specific differentially-regulated signaling pathways in kidneys after perinatal obesity. Comparison of these data to transcriptomic data of naturally aged kidneys and prematurely aged kidneys of genetic modified mice with a hypomorphic allele of Ercc1, revealed similar signatures, e.g., inflammatory signaling. In a biochemical approach we validated pathways of inflammaging in the kidneys after perinatal obesity. Collectively, our initial findings demonstrate premature aging-associated processes as a consequence of perinatal obesity that could determine the susceptibility for CKD early in life.

Dietary Walnuts Preserve Aspects of Health Span and Alter the Hippocampal Lipidome in Aged High-Fat Diet-Fed Mice

Evidence continues to accrue that aging and its diseases can be delayed by pharmacologic and dietary strategies that target the underlying hallmarks of the aging process. However, identifying simple, safe, and effective dietary strategies involving the incorporation of whole foods that may confer some protection against the aging process is also needed. Recent observational studies have suggested that nut consumption can reduce mortality risk in humans. Among these, walnuts are particularly intriguing, given their high content of n-3 fatty acids, fiber, and antioxidant and anti-inflammatory compounds. To this end, 12-month-old male CB6F1 mice were provided either a defined control low-fat diet (LFD), a control high-fat diet (HFD), or an isocaloric HFD containing 7.67% walnuts by weight (HFD + W), and measures of healthspan and related biochemical markers (n = 10-19 per group) as well as survival (n = 20 per group) were monitored. Mice provided the HFD or HFD + W demonstrated marked weight gain, but walnuts lowered baseline glucose (p < 0.05) and tended to temper the effects of HFD on liver weight gain (p < 0.05) and insulin tolerance (p = 0.1). Additional assays suggested a beneficial effect on some indicators of health with walnut supplementation, including preservation of exercise capacity and improved short-term working memory, as determined by Y maze (p = 0.02). However, no effect was observed via any diet on inflammatory markers, antioxidant capacity, or survival (p = 0.2). Ingenuity Pathway Analysis of the hippocampal transcriptome identified two processes predicted to be affected by walnuts and potentially linked to cognitive function, including estrogen signaling and lipid metabolism, with changes in the latter confirmed by lipidomic analysis. In summary, while walnuts did not significantly improve survival on a HFD, they tended to preserve features of healthspan in the context of a metabolic stressor with aging.

Cell non-autonomous regulation of cerebrovascular aging processes by the somatotropic axis

Age-related cerebrovascular pathologies, ranging from cerebromicrovascular functional and structural alterations to large vessel atherosclerosis, promote the genesis of vascular cognitive impairment and dementia (VCID) and exacerbate Alzheimer's disease. Recent advances in geroscience, including results from studies on heterochronic parabiosis models, reinforce the hypothesis that cell non-autonomous mechanisms play a key role in regulating cerebrovascular aging processes. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) exert multifaceted vasoprotective effects and production of both hormones is significantly reduced in aging. This brief overview focuses on the role of age-related GH/IGF-1 deficiency in the development of cerebrovascular pathologies and VCID. It explores the mechanistic links among alterations in the somatotropic axis, specific macrovascular and microvascular pathologies (including capillary rarefaction, microhemorrhages, impaired endothelial regulation of cerebral blood flow, disruption of the blood brain barrier, decreased neurovascular coupling, and atherogenesis) and cognitive impairment. Improved understanding of cell non-autonomous mechanisms of vascular aging is crucial to identify targets for intervention to promote cerebrovascular and brain health in older adults.

Meta-hallmarks of aging and cancer

Both aging and cancer are characterized by a series of partially overlapping "hallmarks" that we subject here to a meta-analysis. Several hallmarks of aging (i.e., genomic instability, epigenetic alterations, chronic inflammation, and dysbiosis) are very similar to specific cancer hallmarks and hence constitute common "meta-hallmarks," while other features of aging (i.e., telomere attrition and stem cell exhaustion) act likely to suppress oncogenesis and hence can be viewed as preponderantly "antagonistic hallmarks." Disabled macroautophagy and cellular senescence are two hallmarks of aging that exert context-dependent oncosuppressive and pro-tumorigenic effects. Similarly, the equivalence or antagonism between aging-associated deregulated nutrient-sensing and cancer-relevant alterations of cellular metabolism is complex. The agonistic and antagonistic relationship between the processes that drive aging and cancer has bearings for the age-related increase and oldest age-related decrease of cancer morbidity and mortality, as well as for the therapeutic management of malignant disease in the elderly.

Long-Term IGF1 Stimulation Leads to Cellular Senescence via Functional Interaction with the Thioredoxin-Interacting Protein, TXNIP

The growth hormone (GH)–insulin-like growth factor-1 (IGF1) signaling pathway plays a major role in orchestrating cellular interactions, metabolism, growth and aging. Studies from worms to mice showed that downregulated activity of the GH/IGF1 pathway could be beneficial for the extension of lifespan. Laron syndrome (LS) is an inherited autosomal recessive disorder caused by molecular defects of the GH receptor (GHR) gene, leading to congenital IGF1 deficiency. Life-long exposure to minute endogenous IGF1 levels in LS is associated with low stature as well as other endocrine and metabolic deficits. Epidemiological surveys reported that patients with LS have a reduced risk of developing cancer. Studies conducted on LS-derived lymphoblastoid cells led to the identification of a novel link between IGF1 and thioredoxin-interacting protein (TXNIP), a multifunctional mitochondrial protein. TXNIP is highly expressed in LS patients and plays a critical role in cellular redox regulation by thioredoxin. Given that IGF1 affects the levels of TXNIP under various stress conditions, including high glucose and oxidative stress, we hypothesized that the IGF1–TXNIP axis plays an essential role in helping maintain a physiological balance in cellular homeostasis. In this study, we show that TXNIP is vital for the cell fate choice when cells are challenged by various stress signals. Furthermore, prolonged IGF1 treatment leads to the establishment of a premature senescence phenotype characterized by a unique senescence network signature. Combined IGF1/TXNIP-induced premature senescence can be associated with a typical secretory inflammatory phenotype that is mediated by STAT3/IL-1A signaling. Finally, these mechanistic insights might help with the understanding of basic aspects of IGF1-related pathologies in the clinical setting.

Decreased lifespan in female "Munchkin" actors from the cast of the 1939 film version of The Wizard of Oz does not support the hypothesis linking hypopituitary dwarfism to longevity

In laboratory mice, pituitary dwarfism caused by genetic reduction or elimination of the activity of growth hormone (GH) significantly extends lifespan. The effects of congenital pituitary dwarfism on human longevity are not well documented. To analyse the effects of untreated pituitary dwarfism on human lifespan, the longevity of a diverse group of widely known little people, the 124 adults who played "Munchkins" in the 1939 movie The Wizard of Oz was investigated. Survival of "Munchkin" actors with those of controls defined as cast members of The Wizard of Oz and those of other contemporary Academy Award winning Hollywood movies was compared. According to the Kaplan-Meier survival curves, survival of female and male "Munchkin" actors was shorter than cast controls and Hollywood controls of respective sexes. Cox regression analyses showed that female "Munchkin" actors had significantly higher risk ratios compared to both female cast controls (RR, 1.70; 95% CI, 1.05 to 2.77) and female Hollywood controls (RR, 1.52; 95% CI, 1.03 to 2.24). Similar trends were also discernible for men, albeit point estimates were not significant. The lack of lifespan extension in "Munchkin" actors does not support the hypothesis that hereditary GH deficiency regulates longevity in humans.

Evidence for preserved insulin responsiveness in the aging rat brain

Insulin appears to exert salutary effects in the central nervous system (CNS). Thus, brain insulin resistance has been proposed to play a role in brain aging and dementia but is conceptually complex and unlikely to fit classic definitions established in peripheral tissues. Thus, we sought to characterize brain insulin responsiveness in young (4-5 months) and old (24 months) FBN male rats using a diverse set of assays to determine the extent to which insulin effects in the CNS are impaired with age. When performing hyperinsulinemic-euglycemic clamps in rats, intracerebroventricular (ICV) infusion of insulin in old animals improved peripheral insulin sensitivity by nearly two-fold over old controls and comparable to young rats, suggesting preservation of this insulin-triggered response in aging per se (p < 0.05). We next used an imaging-based approach by comparing ICV vehicle versus insulin and performed resting state functional magnetic resonance imaging (rs-fMRI) to evaluate age- and insulin-related changes in network connectivity within the default mode network. In aging, lower connectivity between the mesial temporal (MT) region and other areas, as well as reduced MT signal complexity, was observed in old rats, which correlated with greater cognitive deficits in old. Despite these stark differences, ICV insulin failed to elicit any significant alteration to the BOLD signal in young rats, while a significant deviation of the BOLD signal was observed in older animals, characterized by augmentation in regions of the septal nucleus and hypothalamus, and reduction in thalamus and nucleus accumbens. In contrast, ex vivo stimulation of hippocampus with 10 nM insulin revealed increased Akt activation in young (p < 0.05), but not old rats. Despite similar circulating levels of insulin and IGF-1, cerebrospinal fluid concentrations of these ligands were reduced with age. Thus, these data highlight the complexity of capturing brain insulin action and demonstrate preserved or heightened brain responses to insulin with age, despite dampened canonical signaling, thereby suggesting impaired CNS input of these ligands may be a feature of reduced brain insulin action, providing further rationale for CNS replacement strategies.

Aquilaria crassna Leaf Extract Ameliorates Glucose-Induced Neurotoxicity In Vitro and Improves Lifespan in Caenorhabditis elegans

Hyperglycemia is one of the important causes of neurodegenerative disorders and aging. Aquilaria crassna Pierre ex Lec (AC) has been widely used to relieve various health ailments. However, the neuroprotective and anti-aging effects against high glucose induction have not been investigated. This study aimed to investigate the effects of hexane extract of AC leaves (ACH) in vitro using human neuroblastoma SH-SY5Y cells and in vivo using nematode Caenorhabditis elegans. SH-SY5Y cells and C. elegans were pre-exposed with high glucose, followed by ACH treatment. To investigate neuroprotective activities, neurite outgrowth and cell cycle progression were determined in SH-SY5Y cells. In addition, C. elegans was used to determine ACH effects on antioxidant activity, longevity, and healthspan. In addition, ACH phytochemicals were analyzed and the possible active compounds were identified using a molecular docking study. ACH exerted neuroprotective effects by inducing neurite outgrowth via upregulating growth-associated protein 43 and teneurin-4 expression and normalizing cell cycle progression through the regulation of cyclin D1 and SIRT1 expression. Furthermore, ACH prolonged lifespan, improved body size, body length, and brood size, and reduced intracellular ROS accumulation in high glucose-induced C. elegans via the activation of gene expression in the DAF-16/FoxO pathway. Finally, phytochemicals of ACH were analyzed and revealed that β-sitosterol and stigmasterol were the possible active constituents in inhibiting insulin-like growth factor 1 receptor (IGFR). The results of this study establish ACH as an alternative medicine to defend against high glucose effects on neurotoxicity and aging.

Monoamine Oxidase-Dependent Pro-Survival Signaling in Diabetic Hearts Is Mediated by miRNAs

Diabetes leads to cardiomyopathy and heart failure, the leading cause of death for diabetic patients. Monoamine oxidase (MAO) inhibition in diabetic cardiomyopathy prevents oxidative stress, mitochondrial and endoplasmic reticulum stress and the development of diastolic dysfunction. However, it is unclear whether, in addition to the direct effects exerted on the mitochondria, MAO activity is able to post-transcriptionally regulate cardiomyocyte function and survival in diabetes. To this aim, we performed gene and miRNA expression profiling in cardiac tissue from streptozotocin-treated mice (model of type 1 diabetes (T1D)), administered with either vehicle or MAOs inhibitor pargyline for 12 weeks. We found that inhibition of MAO activity in T1D hearts leads to profound transcriptomic changes, affecting autophagy and pro-survival pathways activation. MAO activity in T1D hearts increased miR-133a-3p, -193a-3p and -27a-3p expression. These miRNAs target insulin-like growth factor receptor 1 (Igf1r), growth factor receptor bound protein 10 and inositol polyphosphate 4 phosphatase type 1A, respectively, all components of the IGF1R/PI3K/AKT signaling pathway. Indeed, AKT activation was significantly downregulated in T1D hearts, whereas MAO inhibition restored the activation of this pro-survival pathway. The present study provides an important link between MAO activity, transcriptomic changes and activation of pro-survival signaling and autophagy in diabetic cardiomyopathy.

Fine-Tuning Cardiac Insulin-Like Growth Factor 1 Receptor Signaling to Promote Health and Longevity

BACKGROUND

The insulin-like growth factor 1 (IGF1) pathway is a key regulator of cellular metabolism and aging. Although its inhibition promotes longevity across species, the effect of attenuated IGF1 signaling on cardiac aging remains controversial.

METHODS

We performed a lifelong study to assess cardiac health and lifespan in 2 cardiomyocyte-specific transgenic mouse models with enhanced versus reduced IGF1 receptor (IGF1R) signaling. Male mice with human IGF1R overexpression or dominant negative phosphoinositide 3-kinase mutation were examined at different life stages by echocardiography, invasive hemodynamics, and treadmill coupled to indirect calorimetry. In vitro assays included cardiac histology, mitochondrial respiration, ATP synthesis, autophagic flux, and targeted metabolome profiling, and immunoblots of key IGF1R downstream targets in mouse and human explanted failing and nonfailing hearts, as well.

RESULTS

Young mice with increased IGF1R signaling exhibited superior cardiac function that progressively declined with aging in an accelerated fashion compared with wild-type animals, resulting in heart failure and a reduced lifespan. In contrast, mice with low cardiac IGF1R signaling exhibited inferior cardiac function early in life, but superior cardiac performance during aging, and increased maximum lifespan, as well. Mechanistically, the late-life detrimental effects of IGF1R activation correlated with suppressed autophagic flux and impaired oxidative phosphorylation in the heart. Low IGF1R activity consistently improved myocardial bioenergetics and function of the aging heart in an autophagy-dependent manner. In humans, failing hearts, but not those with compensated hypertrophy, displayed exaggerated IGF1R expression and signaling activity.

CONCLUSIONS

Our findings indicate that the relationship between IGF1R signaling and cardiac health is not linear, but rather biphasic. Hence, pharmacological inhibitors of the IGF1 pathway, albeit unsuitable for young individuals, might be worth considering in older adults.

The Less We Eat, the Longer We Live: Can Caloric Restriction Help Us Become Centenarians?

Striving for longevity is neither a recent human desire nor a novel scientific field. The first article on this topic was published in 1838, when the average human life expectancy was approximately 40 years. Although nowadays people on average live almost as twice as long, we still (and perhaps more than ever) look for new ways to extend our lifespan. During this seemingly endless journey of discovering efficient methods to prolong life, humans were enthusiastic regarding several approaches, one of which is caloric restriction (CR). Where does CR, initially considered universally beneficial for extending both lifespan and health span, stand today? Does a lifelong decrease in food consumption represent one of the secrets of centenarians’ long and healthy life? Do we still believe that if we eat less, we will live longer? This review aims to summarize the current literature on CR as a potential life-prolonging intervention in humans and discusses metabolic pathways that underlie this effect.

Insulin-like growth factor I sensitization rejuvenates sleep patterns in old mice

Sleep disturbances are common during aging. Compared to young animals, old mice show altered sleep structure, with changes in both slow and fast electrocorticographic (ECoG) activity and fewer transitions between sleep and wake stages. Insulin-like growth factor I (IGF-I), which is involved in adaptive changes during aging, was previously shown to increase ECoG activity in young mice and monkeys. Furthermore, IGF-I shapes sleep architecture by modulating the activity of mouse orexin neurons in the lateral hypothalamus (LH). We now report that both ECoG activation and excitation of orexin neurons by systemic IGF-I are abrogated in old mice. Moreover, orthodromical responses of LH neurons are facilitated by either systemic or local IGF-I in young mice, but not in old ones. As orexin neurons of old mice show dysregulated IGF-I receptor (IGF-IR) expression, suggesting disturbed IGF-I sensitivity, we treated old mice with AIK3a305, a novel IGF-IR sensitizer, and observed restored responses to IGF-I and rejuvenation of sleep patterns. Thus, disturbed sleep structure in aging mice may be related to impaired IGF-I signaling onto orexin neurons, reflecting a broader loss of IGF-I activity in the aged mouse brain.

Nutrient-Response Pathways in Healthspan and Lifespan Regulation

Cellular, small invertebrate and vertebrate models are a driving force in biogerontology studies. Using various models, such as yeasts, appropriate tissue culture cells, Drosophila, the nematode Caenorhabditis elegans and the mouse, has tremendously increased our knowledge around the relationship between diet, nutrient-response signaling pathways and lifespan regulation. In recent years, combinatorial drug treatments combined with mutagenesis, high-throughput screens, as well as multi-omics approaches, have provided unprecedented insights in cellular metabolism, development, differentiation, and aging. Scientists are, therefore, moving towards characterizing the fine architecture and cross-talks of growth and stress pathways towards identifying possible interventions that could lead to healthy aging and the amelioration of age-related diseases in humans. In this short review, we briefly examine recently uncovered knowledge around nutrient-response pathways, such as the Insulin Growth Factor (IGF) and the mechanistic Target of Rapamycin signaling pathways, as well as specific GWAS and some EWAS studies on lifespan and age-related disease that have enhanced our current understanding within the aging and biogerontology fields. We discuss what is learned from the rich and diverse generated data, as well as challenges and next frontiers in these scientific disciplines.

Mechanisms in Graves Eye Disease: Apoptosis as the End Point of Insulin-Like Growth Factor 1 Receptor Inhibition

Background: Graves' eye disease, also called Graves' orbitopathy (GO), is a potentially debilitating autoimmune disease associated with retro-orbital inflammation and tissue expansion, involving both fibroblasts and adipocytes, resulting in periorbital edema, worsening proptosis, and muscle dysfunction with diplopia and may ultimately threaten sight. Accumulating evidence has indicated that autoantibodies to the thyrotropin receptor (TSHR), which induce the hyperthyroidism of Graves' disease, also help mediate the pathogenesis of the eye disease in susceptible individuals through TSHR expression on retro-orbital cells. Since it has long been known that the effects of insulin-like growth factor 1 (IGF-1) and thyrotropin are additive, recent clinical trials with a human monoclonal IGF-1 receptor blocking antibody (teprotumumab; IGF-1R-B-monoclonal antibody [mAb]) have demonstrated its ability to induce significant reductions in proptosis, diplopia, and clinical activity scores in patients with GO. However, the molecular mechanisms by which such an antibody achieves this result is unclear. Methods: We have used Li-Cor In-Cell Western, Western blot, and immunohistochemistry to define levels of different proteins in mouse and human fibroblast cells. Proteomic array was also used to define pathway signaling molecules. Using CCK-8 and BrdU cell proliferation ELISA, we have analyzed proliferative response of these cells to different antibodies. Results: We now show that a stimulating TSHR antibody was able to induce phosphorylation of the IGF-1R and initiate both TSHR and IGF-1R signaling in mouse and human fibroblasts. IGF-1R-B-mAb (1H7) inhibited all major IGF-1R signaling cascades and also reduced TSHR signaling. This resulted in the antibody-induced suppression of autophagy as shown by inhibition of multiple autophagy-related proteins (Beclin1, LC3a, LC3b, p62, and ULK1) and the induction of cell death by apoptosis as evidenced by activation of cleaved caspase 3, FADD, and caspase 8. Furthermore, this IGF-1R-blocking mAb suppressed serum-induced perkin and pink mitophagic proteins. Conclusions: Our observations clearly indicated that stimulating TSHR antibodies were able to enhance IGF-1R activity and contribute to retro-orbital cellular proliferation and inflammation. In contrast, an IGF-1R-B-mAb was capable of suppressing IGF-1R signaling leading to retro-orbital fibroblast/adipocyte death through the cell-extrinsic pathway of apoptosis. This is likely the major mechanism involved in proptosis reduction in patients with Graves' eye disease treated by IGF-1R inhibition.

Role of cellular retinol-binding protein, type 1 and retinoid homeostasis in the adult mouse heart: A multi-omic approach

The main active metabolite of Vitamin A, all-trans retinoic acid (RA), is required for proper cellular function and tissue organization. Heart development has a well-defined requirement for RA, but there is limited research on the role of RA in the adult heart. Homeostasis of RA includes regulation of membrane receptors, chaperones, enzymes, and nuclear receptors. Cellular retinol-binding protein, type 1 (CRBP1), encoded by retinol-binding protein, type 1 (Rbp1), regulates RA homeostasis by delivering vitamin A to enzymes for RA synthesis and protecting it from non-specific oxidation. In this work, a multi-omics approach was used to characterize the effect of CRBP1 loss using the Rbp1^-/- mouse. Retinoid homeostasis was disrupted in Rbp1^-/- mouse heart tissue, as seen by a 33% and 24% decrease in RA levels in the left and right ventricles, respectively, compared to wild-type mice (WT). To further inform on the effect of disrupted RA homeostasis, we conducted high-throughput targeted metabolomics. A total of 222 metabolite and metabolite combinations were analyzed, with 33 having differential abundance between Rbp1^-/- and WT hearts. Additionally, we performed global proteome profiling to further characterize the impact of CRBP1 loss in adult mouse hearts. More than 2606 unique proteins were identified, with 340 proteins having differential expression between Rbp1^-/- and WT hearts. Pathway analysis performed on metabolomic and proteomic data revealed pathways related to cellular metabolism and cardiac metabolism were the most disrupted in Rbp1^-/- mice. Together, these studies characterize the effect of CRBP1 loss and reduced RA in the adult heart.

Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis

The association between IGF‐1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta‐analysis investigates this complex relationship between IGF‐1 and all‐cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta‐analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF‐1 and were conducted among adults. A random‐effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all‐cause mortality. Nineteen studies involving 30,876 participants were included. Meta‐analysis of the 19 eligible studies showed that with respect to the low IGF‐1 category, higher IGF‐1 was not associated with increased risk of all‐cause mortality (HR = 0.84, 95% CI = 0.68–1.05). Dose–response analysis revealed a U‐shaped relation between IGF‐1 and mortality HR. Pooled results comparing low vs. middle IGF‐1 showed a significant increase of all‐cause mortality (HR = 1.33, 95% CI = 1.14–1.57), as well as comparing high vs. middle IGF‐1 categories (HR = 1.23, 95% CI = 1.06–1.44). Finally, we provide data on the association between IGF‐1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF‐1 increase mortality risk, with a specific 120–160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF‐1 levels and mortality.

Single-cell Transcriptomic Profiling of the Hypothalamic Median Eminence during Aging

Aging is a slow and progressive natural process that compromises the normal functions of cells, tissues, organs and systems. The aging of the hypothalamic median eminence (ME), a structural gate linking neural and endocrine systems, may impair hormone release, energy homeostasis and central sensing of circulating molecules, leading to systemic and reproductive aging. However, the molecular and cellular features of ME aging remain largely unknown. Here we describe the transcriptional landscape of young and middle-aged mouse ME at single-cell resolution, revealing the common and cell-type-specific transcriptional changes with age. The transcriptional changes in cell-intrinsic programs, cell-cell crosstalk and cell-extrinsic factors highlight five molecular features of ME aging and also implicate several potentially druggable targets at cellular, signaling and molecular levels. Importantly, our results suggest that vascular and leptomeningeal cells (VLMCs) may lead the asynchronized aging process among diverse cell types and drive local inflammation and cellular senescence via a unique secretome. Together, our study uncovers how intrinsic and extrinsic features of each cell type in the hypothalamic ME are changed by the aging process, which will facilitate our understanding of brain aging and provide clues for efficient anti-aging intervention at the middle-aged stage.

Bridging the Gap: A Geroscience Primer for Neuroscientists With Potential Collaborative Applications

While neurodegenerative diseases can strike at any age, the majority of afflicted individuals are diagnosed at older ages. Due to the important impact of age in disease diagnosis, the field of neuroscience could greatly benefit from the many of the theories and ideas from the biology of aging-now commonly referred as geroscience. As discussed in our complementary perspective on the topic, there is often a "silo-ing" between geroscientists who work on understanding the mechanisms underlying aging and neuroscientists who are studying neurodegenerative diseases. While there have been some strong collaborations between the biology of aging and neuroscientists, there is still great potential for enhanced collaborative effort between the 2 fields. To this end, here, we review the state of the geroscience field, discuss how neuroscience could benefit from thinking from a geroscience perspective, and close with a brief discussion on some of the "missing links" between geroscience and neuroscience and how to remedy them. Notably, we have a corresponding, concurrent review from the neuroscience perspective. Our overall goal is to "bridge the gap" between geroscience and neuroscience such that more efficient, reproducible research with translational potential can be conducted.

Molecular mechanisms of dietary restriction promoting health and longevity

Dietary restriction with adequate nutrition is the gold standard for delaying ageing and extending healthspan and lifespan in diverse species, including rodents and non-human primates. In this Review, we discuss the effects of dietary restriction in these mammalian model organisms and discuss accumulating data that suggest that dietary restriction results in many of the same physiological, metabolic and molecular changes responsible for the prevention of multiple ageing-associated diseases in humans. We further discuss how different forms of fasting, protein restriction and specific reductions in the levels of essential amino acids such as methionine and the branched-chain amino acids selectively impact the activity of AKT, FOXO, mTOR, nicotinamide adenine dinucleotide (NAD⁺), AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21), which are key components of some of the most important nutrient-sensing geroprotective signalling pathways that promote healthy longevity.

Extending human healthspan and longevity: a symposium report

For many years, it was believed that the aging process was inevitable and that age-related diseases could not be prevented or reversed. The geroscience hypothesis, however, posits that aging is, in fact, malleable and, by targeting the hallmarks of biological aging, it is indeed possible to alleviate age-related diseases and dysfunction and extend longevity. This field of geroscience thus aims to prevent the development of multiple disorders with age, thereby extending healthspan, with the reduction of morbidity toward the end of life. Experts in the field have made remarkable advancements in understanding the mechanisms underlying biological aging and identified ways to target aging pathways using both novel agents and repurposed therapies. While geroscience researchers currently face significant barriers in bringing therapies through clinical development, proof-of-concept studies, as well as early-stage clinical trials, are underway to assess the feasibility of drug evaluation and lay a regulatory foundation for future FDA approvals in the future.

GH and Senescence: A New Understanding of Adult GH Action

Replicative senescence occurs due to an inability to repair DNA damage and activation of p53/p21 and p16INK4 pathways. It is considered a preventive mechanism for arresting proliferation of DNA-damaged cells. Stably senescent cells are characterized by a senescence-associated secretory phenotype (SASP), which produces and secretes cytokines, chemokines, and/or matrix metalloproteinases depending on the cell type. SASP proteins may increase cell proliferation, facilitating conversion of premalignant to malignant tumor cells, triggering DNA damage, and altering the tissue microenvironment. Further, senescent cells accumulate with age, thereby aggravating age-related tissue damage. Here, we review a heretofore unappreciated role for growth hormone (GH) as a SASP component, acting in an autocrine and paracrine fashion. In senescent cells, GH is activated by DNA-damage-induced p53 and inhibits phosphorylation of DNA repair proteins ATM, Chk2, p53, and H2AX. Somatotroph adenomas containing abundant intracellular GH exhibit increased somatic copy number alterations, indicative of DNA damage, and are associated with induced p53/p21. As this pathway restrains proliferation of DNA-damaged cells, these mechanisms may underlie the senescent phenotype and benign nature of slowly proliferating pituitary somatotroph adenomas. In highly proliferative cells, such as colon epithelial cells, GH induced in response to DNA damage suppresses p53, thereby triggering senescent cell proliferation. As senescent cells harbor unrepaired DNA damage, GH may enable senescent cells to evade senescence and reenter the cell cycle, resulting in acquisition of harmful mutations. These mechanisms, at least in part, may underlie pro-aging effects of GH observed in animal models and in patients with chronically elevated GH levels.

Targeting IGF1R signaling for brain aging and Alzheimer's disease

The role of IGF1R signaling in the brain and its relationship to aging and neurological dysfunction is controversial. Because it was shown that low IGF1R activity consistently improved myocardial bioenergetics and function in hearts from aging mice, but not hearts from young mice, it was of interest to investigate this relationship in brain aging. We used CRISPR technology to develop a mouse model with targeted replacement of mouse IGF1R with the equivalent of the human R407H (IGF1R^R407H) variant enriched in centenarians with a reduction in IGF1R protein activity. Middle-aged mice show improved cognitive performance thus possibly modeling IGF1R signaling in the aging brain, similar to what was reported in the aging heart. Because Alzheimer's disease (AD) is an age-related disease, specific IGF1R^R407H pathways could be therapeutic targets in mice with AAV vector-based AD as well as for overall brain aging.

IGF1R is a mediator of sex-specific metabolism in mice: Effects of age and high-fat diet

OBJECTIVE

We aimed to investigate the short and long-term metabolic consequences of IGF1R systemic gene deficiency in mice.

METHODS

UBC-CreERT2, Igf1r^fl/fl mutant mice were used to suppress IGF1R signaling in adult tissues by inducing postnatal generalized Igf1r deletion with tamoxifen. Animals were analyzed at two different ages: i) 13-weeks old young mice, and ii) 12-months old middle-aged mice. In addition, the effects of 10 weeks-long high-fat diet (HFD) were investigated in middle-aged mice.

RESULTS

Young IGF1R-deficient mice were insulin-resistant, with high IGF1, growth hormone (GH) and IGFBP3, as well as low IGFBP2 circulating levels. Males also presented increased triglycerides in liver. In contrast, middle-aged mice did not clearly show all of these alterations, suggesting possible compensatory effects. Middle-aged IGF1R-deficient male mice were able to counteract the negative effects induced by aging and HFD in adiposity, inflammation and glucose metabolism. A metabolic sexual dimorphism dependent on IGF1R was observed, especially in middle-aged mice.

CONCLUSIONS

These results demonstrate that IGF1R is involved in metabolic homeostasis, with effects modulated by diet-induced obesity and aging in a sex dependent manner. Thus, IGF1R deficiency in mice is proposed as a useful tool to understand metabolic alterations observed in patients with IGF1R gene deletions.

Effects of Exercise Training on Anabolic and Catabolic Hormones with Advanced Age: A Systematic Review

Background

Ageing is accompanied by decreases in physical capacity and physiological regulatory mechanisms including altered hormonal regulation compared with age-matched sedentary people. The potential benefits of exercise in restoring such altered hormone production and secretion compared to age-matched physically inactive individuals who are ageing remains unclear.

Objectives

The aim of this systematic review was to summarise the findings of exercise training in modulating levels of ostensibly anabolic and catabolic hormones in adults aged > 40 years.

Methods

We searched the following electronic databases (to July 2021) without a period limit: Cochrane Library, PubMed, Science Direct, Scopus, SPORTDiscus and Web of Science. Additionally, a manual search for published studies in Google Scholar was conducted for analysis of the ‘grey literature’ (information produced outside of traditional commercial or academic publishing and distribution channels). The initial search used the terms ‘ageing’ OR ‘advanced age’ OR ‘old people’ OR ‘older’ OR elderly’ AND ‘anabolic hormones’ OR ‘catabolic hormones’ OR ‘steroid hormones’ OR ‘sex hormones’ OR ‘testosterone’ OR ‘cortisol’ OR ‘insulin’ OR ‘insulin-like growth factor-1’ OR ‘IGF-1’ OR ‘sex hormone-binding globulin’ OR ‘SHBG’ OR ‘growth hormone’ OR ‘hGH’ OR ‘dehydroepiandrosterone’ OR ‘DHEA’ OR ‘dehydroepiandrosterone sulfate (DHEA-S)’ AND ‘exercise training’ OR ‘endurance training’ OR ‘resistance training’ OR ‘ strength training’ OR ‘weight-lifting’ OR ‘high-intensity interval training’ OR ‘high-intensity interval exercise’ OR ‘high-intensity intermittent training’ OR ‘high-intensity intermittent exercise’ OR ‘interval aerobic training’ OR ‘interval aerobic exercise’ OR ‘intermittent aerobic training’ OR ‘intermittent aerobic exercise’ OR ‘high-intensity training’ OR ‘high-intensity exercise’ OR ‘sprint interval training’ OR ‘sprint interval exercise’ OR ‘combined exercise training’ OR ‘anaerobic training’. Only eligible full texts in English or French were considered for analysis.

Results

Our search identified 484 records, which led to 33 studies for inclusion in the analysis. Different exercise training programs were used with nine studies using endurance training programs, ten studies examining the effects of high-intensity interval training, and 14 studies investigating the effects of resistance training. Most training programs lasted ≥ 2 weeks. Studies, regardless of the design, duration or intensity of exercise training, reported increases in testosterone, sex hormone-binding globulin (SHBG), insulin-like growth factor-1 (IGF-1), human growth hormone (hGH) or dehydroepiandrosterone (DHEA) (effect size: 0.19 < d < 3.37, small to very large) in both older males and females. However, there was no consensus on the effects of exercise on changes in cortisol and insulin in older adults.

Conclusion

In conclusion, findings from this systematic review suggest that exercise training increases basal levels of testosterone, IGF-1, SHBG, hGH and DHEA in both male and females over 40 years of age. The increases in blood levels of these hormones were independent of the mode, duration and intensity of the training programs. However, the effects of long-term exercise training on cortisol and insulin levels in elderly people are less clear.