The senescence-associated secretome as an indicator of age and medical risk

Changes in senescence markers after a weight loss intervention in older adults with obesity

BACKGROUND

Understanding how weight loss interventions in older adults with obesity impact aging biology can lay the foundation for targeted, 'geroscience-based' interventions. This study examines the association between changes in the senescence-associated secretory phenotypes (SASP) and changes in function in response to a weight loss intervention.

METHODS

We conducted a post-hoc biomarker analysis on adults aged ≥ 65 years with body mass index [BMI] ≥30 kg/m2 enrolled in a six-month, non-randomized telemedicine-delivered weight loss intervention. We assessed 16 SASP cytokines using serum samples collected pre-and post-intervention. Clinical outcomes include anthropometric and physical function measurements. A weight loss responder was defined as a loss of ≥5 % of body weight.

RESULTS

Mean age was 73.2 ± 3.9 years (73 % female), and BMI was 36.5 ± 5.2 kg/m2. Responders lost 7.6 ± 2.5 %, while non-responders lost 2.0 ± 2.3 % of weight (n = 16 per group, p < 0.001). We observed several significant associations between SASP cytokines and physical function and anthropometric measurement outcomes in age- and sex-adjusted linear models. These included grip strength and Interleukin-8 (IL-8) (b = 9.07) and Insulin-like Growth Factor 1 (IGF-1) (b = 2.6); gait speed and Thymus and Activation-Regulated Chemokine (TARC) (b = 0.46) and IL-7(b = 61 0.11); weight IL-6 (b = -6.77) and IL-15 (b = -2.53); BMI and IL-15 (b = -0.95); waist-to-hip ratio and osteopontin (b = -0.07) (p < 0.05 for all).

CONCLUSIONS

Our pilot data demonstrated an association between changes in select SASP biomarkers and increased functional ability with intentional weight loss in older adults with obesity. However, findings must be replicated in prospective randomized trials with a control group and additional SASP biomarkers.

Plasma Proteomic Signature as a Predictor of Age Advancement in People Living With HIV

Due to the increased burden of non-AIDS-related comorbidities in people living with HIV (PLHIV), identifying biomarkers and mechanisms underlying premature aging and the risk of developing age-related comorbidities is a priority. Evidence suggests that the plasma proteome is an accurate source for measuring biological age and predicting age-related clinical outcomes. To investigate whether PLHIV on antiretroviral therapy (ART) exhibit a premature aging phenotype, we profiled the plasma proteome of two independent cohorts of virally suppressed PLHIV (200HIV and 2000HIV) and one cohort of people without HIV (200FG) using O-link technology. Next, we built a biological age-prediction model and correlated age advancement (the deviation of the predicted age from the chronological age) with HIV-related factors, comorbidities, and cytokines secreted by immune cells. We identified a common signature of 77 proteins associated with chronological age across all cohorts, most of which were involved in inflammatory and senescence-related processes. PLHIV showed increased age advancement compared to people without HIV. In addition, age advancement in the 2000HIV cohort was positively associated with prior hepatitis C and cytomegalovirus (CMV) infections, non-AIDS-related comorbidities, ART duration, cumulative exposure to the protease inhibitor Ritonavir, as well as higher production of monocyte-derived proinflammatory cytokines and chemokines and lower secretion of T-cell derived cytokines. Our proteome-based predictive model is a promising approach for calculating the age advancement in PLHIV. This will potentially allow for further characterization of the pathophysiological mechanisms linked to accelerated aging and enable monitoring the effectiveness of novel therapies aimed at reducing age-related diseases in PLHIV.

Senescence as a therapeutic target in cancer and age-related diseases

Cellular senescence is a stress response that restrains the growth of aged, damaged or abnormal cells. Thus, senescence has a crucial role in development, tissue maintenance and cancer prevention. However, lingering senescent cells fuel chronic inflammation through the acquisition of a senescence-associated secretory phenotype (SASP), which contributes to cancer and age-related tissue dysfunction. Recent progress in understanding senescence has spurred interest in the development of approaches to target senescent cells, known as senotherapies. In this Review, we evaluate the status of various types of senotherapies, including senolytics that eliminate senescent cells, senomorphics that suppress the SASP, interventions that mitigate senescence and strategies that harness the immune system to clear senescent cells. We also summarize how these approaches can be combined with cancer therapies, and we discuss the challenges and opportunities in moving senotherapies into clinical practice. Such therapies have the potential to address root causes of age-related diseases and thus open new avenues for preventive therapies and treating multimorbidities.

Immunometabolism In Brain Aging and Neurodegeneration: Bridging Metabolic Pathways and Immune Responses

The complex set of interactions between the immune system and metabolism, known as immunometabolism, has emerged as a critical regulator of disease outcomes in the central nervous system. Numerous studies have linked metabolic disturbances to impaired immune responses in brain aging, neurodegenerative disorders, and brain injury. In this review, we will discuss how disruptions in brain immunometabolism balance contribute to the pathophysiology of brain dysfunction. The first part of the review summarizes the contributions of critical immune cell populations such as microglia, astrocytes, and infiltrating immune cells in mediating inflammation and metabolism in CNS disorders. The remainder of the review addresses the impact of metabolic changes on immune cell activation and disease progression in brain aging, Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, spinal cord injury, and traumatic brain injury. Furthermore, we also address the therapeutic potential of targeting immunometabolic pathways to reduce neuroinflammation and slow disease progression. By focusing on the interactions among brain immune cells and the metabolic mechanisms they recruit in disease, we present a comprehensive overview of brain immunometabolism in human health and disease.

A machine learning approach identifies cellular senescence on transcriptome data of human cells in vitro

Although cellular senescence has been recognized as a hallmark of aging, it is challenging to detect senescence cells (SnCs) due to their high level of heterogeneity at the molecular level. Machine learning (ML) is likely an ideal approach to address this challenge because of its ability to recognize complex patterns that cannot be characterized by one or a few features, from high-dimensional data. To test this, we evaluated the performance of four ML algorithms including support vector machines (SVM), random forest (RF), decision tree (DT), and Soft Independent Modelling of Class Analogy (SIMCA), in distinguishing SnCs from controls based on bulk RNA sequencing data. The dataset includes 162 in vitro samples, covering three human cell types: fibroblasts, melanocytes, and keratinocytes, and three senescence inducers: irradiation, bleomycin treatment, and replication. Under tenfold and leave-one-out cross-validation, as well as independent dataset validation, all methods provided ~ 80% or higher accuracy, with SVM reaching over 99%. Similar accuracy was achieved using expert-curated gene lists, e.g., SenMayo and CellAge, instead of our algorithm-prioritized gene list using minimum redundancy-maximum relevance (mRMR). However, only a few genes overlapped between the gene sets, suggesting a wide impact of senescence on the transcriptome. Overall, our study demonstrated a proof-of-concept for identifying senescence using ML.

Biomarkers of cellular senescence and major health outcomes in older adults

The geroscience hypothesis proposes that underlying biological processes, such as the accumulation of senescent cells, have deleterious effects on multiple tissues and increase the risk of many chronic conditions with aging. Senescent cells produce heterogenous biomarkers, also called senescence-associated secretory phenotype (SASP). Circulating concentrations of senescence biomarkers may reflect an underlying burden of senescent cells in various tissues. Plasma levels of these proteins have been associated with increased mortality and poorer physical function. The associations of them with the incidence of major age-related conditions including heart failure, cardiovascular disease, stroke, and dementia, have not been studied. We measured 35 senescence biomarkers in baseline plasma samples from 1678 participants aged 70-79 years old in the longitudinal Health ABC cohort study. Clinical outcomes were ascertained and validated over an average 11.5 year follow-up. In models adjusted for age, sex, and race, higher levels of most of senescence biomarkers were associated with increased risk of all-cause mortality, mobility limitation, and heart failure. Several were also associated with an increased risk of coronary heart disease, stroke, and dementia. Very few were associated with the risk of cancer. Proteins that were selected by Lasso regression for each outcome that commonly included GDF15 and IL6, significantly improved the prediction of mortality, mobility limitation, and heart failure compared with age, sex, and race alone. These results indicate that levels of senescence biomarkers predict an increased risk of several age-related clinical outcomes and may identify individuals most likely to benefit from senotherapeutics.

IL-23R is a senescence-linked circulating and tissue biomarker of aging

Cellular senescence is an aging mechanism characterized by cell cycle arrest and a senescence-associated secretory phenotype (SASP). Preclinical studies demonstrate that senolytic drugs, which target survival pathways in senescent cells, can counteract age-associated conditions that span several organs. The comparative efficacy of distinct senolytic drugs for modifying aging and senescence biomarkers in vivo has not been demonstrated. Here, we established aging- and senescence-related plasma proteins and tissue transcripts that changed in old versus young female and male mice. We investigated responsivity to acute treatment with venetoclax, navitoclax, fisetin or luteolin versus transgenic senescent cell clearance in aged p16-InkAttac mice. We discovered that age-dependent changes in plasma proteins, including IL-23R, CCL5 and CA13, were reversed by senotherapeutics, which corresponded to expression differences in tissues, particularly in the kidney. In plasma from humans across the lifespan, IL-23R increased with age. Our results reveal circulating factors as candidate mediators of senescence-associated interorgan signal transduction and translationally impactful biomarkers of systemic senescent cell burden.

GDF15/MIC-1: a stress-induced immunosuppressive factor which promotes the aging process

The GDF15 protein, a member of the TGF-β superfamily, is a stress-induced multifunctional protein with many of its functions associated with the regulation of the immune system. GDF15 signaling provides a defence against the excessive inflammation induced by diverse stresses and tissue injuries. Given that the aging process is associated with a low-grade inflammatory state, called inflammaging, it is not surprising that the expression of GDF15 gradually increases with aging. In fact, the GDF15 protein is a core factor secreted by senescent cells, a state called senescence-associated secretory phenotype (SASP). Many age-related stresses, e.g., mitochondrial and endoplasmic reticulum stresses as well as inflammatory, metabolic, and oxidative stresses, induce the expression of GDF15. Although GDF15 signaling is an effective anti-inflammatory modulator, there is robust evidence that it is a pro-aging factor promoting the aging process. GDF15 signaling is not only an anti-inflammatory modulator but it is also a potent immunosuppressive enhancer in chronic inflammatory states. The GDF15 protein can stimulate immune responses either non-specifically via receptors of the TGF-β superfamily or specifically through the GFRAL/HPA/glucocorticoid pathway. GDF15 signaling stimulates the immunosuppressive network activating the functions of MDSCs, Tregs, and M2 macrophages and triggering inhibitory immune checkpoint signaling in senescent cells. Immunosuppressive responses not only suppress chronic inflammatory processes but they evoke many detrimental effects in aged tissues, such as cellular senescence, fibrosis, and tissue atrophy/sarcopenia. It seems that the survival functions of GDF15 go awry in persistent inflammation thus promoting the aging process and age-related diseases.

The senescence-associated secretory phenotype and its physiological and pathological implications

Cellular senescence is a state of terminal growth arrest associated with the upregulation of different cell cycle inhibitors, mainly p16 and p21, structural and metabolic alterations, chronic DNA damage responses, and a hypersecretory state known as the senescence-associated secretory phenotype (SASP). The SASP is the major mediator of the paracrine effects of senescent cells in their tissue microenvironment and of various local and systemic biological functions. In this Review, we discuss the composition, dynamics and heterogeneity of the SASP as well as the mechanisms underlying its induction and regulation. We describe the various biological properties of the SASP, its beneficial and detrimental effects in different physiological and pathological settings, and its impact on overall health span. Finally, we discuss the use of the SASP as a biomarker and of SASP inhibitors as senomorphic interventions to treat cancer and other age-related conditions.

SenNet recommendations for detecting senescent cells in different tissues

Once considered a tissue culture-specific phenomenon, cellular senescence has now been linked to various biological processes with both beneficial and detrimental roles in humans, rodents and other species. Much of our understanding of senescent cell biology still originates from tissue culture studies, where each cell in the culture is driven to an irreversible cell cycle arrest. By contrast, in tissues, these cells are relatively rare and difficult to characterize, and it is now established that fully differentiated, postmitotic cells can also acquire a senescence phenotype. The SenNet Biomarkers Working Group was formed to provide recommendations for the use of cellular senescence markers to identify and characterize senescent cells in tissues. Here, we provide recommendations for detecting senescent cells in different tissues based on a comprehensive analysis of existing literature reporting senescence markers in 14 tissues in mice and humans. We discuss some of the recent advances in detecting and characterizing cellular senescence, including molecular senescence signatures and morphological features, and the use of circulating markers. We aim for this work to be a valuable resource for both seasoned investigators in senescence-related studies and newcomers to the field.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Emerging insights in senescence: pathways from preclinical models to therapeutic innovations

Senescence is a crucial hallmark of ageing and a significant contributor to the pathology of age-related disorders. As committee members of the young International Cell Senescence Association (yICSA), we aim to synthesise recent advancements in the identification, characterisation, and therapeutic targeting of senescence for clinical translation. We explore novel molecular techniques that have enhanced our understanding of senescent cell heterogeneity and their roles in tissue regeneration and pathology. Additionally, we delve into in vivo models of senescence, both non-mammalian and mammalian, to highlight tools available for advancing the contextual understanding of in vivo senescence. Furthermore, we discuss innovative diagnostic tools and senotherapeutic approaches, emphasising their potential for clinical application. Future directions of senescence research are explored, underscoring the need for precise, context-specific senescence classification and the integration of advanced technologies such as machine learning, long-read sequencing, and multifunctional senoprobes and senolytics. The dual role of senescence in promoting tissue homoeostasis and contributing to chronic diseases highlights the complexity of targeting these cells for improved clinical outcomes.

Substrate Stiffness Dictates Unique Doxorubicin-induced Senescence-associated Secretory Phenotypes and Transcriptomic Signatures in Human Pulmonary Fibroblasts

Cells are subjected to dynamic mechanical environments which impart forces and induce cellular responses. In age-related conditions like pulmonary fibrosis, there is both an increase in tissue stiffness and an accumulation of senescent cells. While senescent cells produce a senescence-associated secretory phenotype (SASP), the impact of physical stimuli on both cellular senescence and the SASP is not well understood. Here, we show that mechanical tension, modeled using cell culture substrate rigidity, influences senescent cell markers like SA-β-gal and secretory phenotypes. Comparing human primary pulmonary fibroblasts (IMR-90) cultured on physiological (2 kPa), fibrotic (50 kPa), and plastic (approximately 3 GPa) substrates, followed by senescence induction using doxorubicin, we identified unique high-stiffness-driven secretory protein profiles using mass spectrometry and transcriptomic signatures, both showing an enrichment in collagen proteins. Consistently, clusters of p21+ cells are seen in fibrotic regions of bleomycin induced pulmonary fibrosis in mice. Computational meta-analysis of single-cell RNA sequencing datasets from human interstitial lung disease confirmed these stiffness SASP genes are highly expressed in disease fibroblasts and strongly correlate with mechanotransduction and senescence-related pathways. Thus, mechanical forces shape cell senescence and their secretory phenotypes.

Osteopontin and Clinical Outcomes in Hemodialysis Patients

BACKGROUND/OBJECTIVES

Chronic kidney disease (CKD) and end-stage kidney disease (ESKD) are significant public health issues, with cardiovascular morbidity and mortality being the leading causes of death in hemodialysis patients. Osteopontin (OPN), a multifunctional glycoprotein, has emerged as a potential biomarker for vascular disease in CKD due to its role in inflammation, tissue remodeling, and calcification.

METHODS

This cohort study included 1124 hemodialysis patients from the PROGREDIRE study, a registry involving 35 dialysis units in Southern Italy. Serum osteopontin levels were measured using enzyme-linked immunosorbent assay (ELISA). The primary endpoints were all-cause and cardiovascular mortality. Multivariate Cox regression analyses were performed to assess the association between osteopontin levels and mortality, adjusting for traditional risk factors, biomarkers of inflammation, nutritional status, and ESKD-related factors.

RESULTS

During a mean follow-up of 2.8 years, 478 patients died, 271 from cardiovascular causes. Independent correlates of osteopontin included alkaline phosphatase and parathyroid hormone. Elevated osteopontin levels were significantly associated with increased all-cause mortality (HR 1.19, 95% CI 1.09-1.31, p < 0.001) and cardiovascular mortality (HR 1.22, 95% CI 1.08-1.38, p = 0.001) after adjusting for confounders.

CONCLUSIONS

Elevated osteopontin levels are associated with increased all-cause and cardiovascular mortality in hemodialysis patients. These findings implicate osteopontin in the high risk for death and cardiovascular disease in the hemodialysis population. Intervention studies are needed to definitively test this hypothesis.

IGFBP7 is a key component of the senescence-associated secretory phenotype (SASP) that induces senescence in healthy cells by modulating the insulin, IGF, and activin A pathways

Senescent cells exert their effects through the release of various factors, collectively referred to as the senescence-associated secretory phenotype (SASP). The SASP can induce senescence in healthy cells (secondary senescence), modulate immune system function, reshape the extracellular matrix, and facilitate cancer progression.Among SASP components, certain factors act as key regulators in the induction of secondary senescence. In this study, we evaluated the role of IGFBP7, a crucial SASP component. Our results demonstrated that ROS-prostaglandin signaling is involved in the release of IGFBP7. Furthermore, neutralizing antibodies targeting IGFBP7 attenuated the SASP's pro-senescence activity. Cells incubated with IGFBP7 also entered a state of senescence.The senescence induced by IGFBP7 appears to be mediated through three primary pathways. First, IGFBP7 can bind to insulin, thereby inhibiting its anti-senescence and pro-growth effects. In addition to this inhibitory effect on the insulin pathway, IGFBP7 may enhance IGFII pro-senescence signaling by promoting its interaction with IGF2R while blocking IGF1R. These activities are dependent on ERK and AKT signaling pathways. Finally, IGFBP7 and Activin A, both of which can induce cellular senescence, appear to regulate and inhibit each other, suggesting a compensatory mechanism to prevent excessive senescence. Notably, our preliminary data indicate that IGFBP7, in addition to blocking Activin A, may interact with its receptors and induce senescence via SMAD pathways.Our findings highlight that IGFBP7, along with other members of the IGFBP family, plays a pivotal role in senescence-related signaling pathways. Therefore, IGFBP7 may serve as a potential target for anti-aging strategies aimed at reducing the burden of senescence on tissues and organs.

Persistent elevation of plasma markers of cellular senescence after hip fracture: a pilot longitudinal study

Introduction

Hip fractures may result from and contribute to accelerated biological aging. We aimed to evaluate the impact of hip fracture and its surgery on the senescence-associated secretory phenotype (SASP) index, a composite of peripheral protein markers where higher scores are thought to indicate greater levels of cellular senescence and accelerated aging.

Methods

We examined the SASP index in plasma over 12 weeks post-surgery and its prediction of long-term post-surgical functional outcomes. We included 60 older adults: 20 recruited immediately after hip fracture surgery, and 40 comparison individuals who were either healthy or suffering chronic psychosocial stress (caregiving). We assessed 22 SASP biomarkers and calculated the SASP index score for each hip fracture participant immediately following fracture surgery and 4 and 12 weeks later. Functional recovery was assessed at 12, 26, and 52 weeks after hip replacement surgery.

Results

The hip fracture group had higher SASP index scores than the comparison groups, after adjusting for potential confounding variables (p = 0.021). SASP index scores in hip fracture patients increased further by week 4 after surgery (p < 0.001), declining by week 12 but remaining elevated overall. However, the SASP index scores were not significantly associated with functional recovery after hip replacement surgery at 26 or 52 weeks after surgery. In conclusion, after hip fracture surgery SASP scores are elevated, continue to rise over time, and do not return to normal by 12 weeks post-surgery.

Discussion

Our findings support the need to investigate this phenomenon of post-operative senescence, including whether novel interventions such as senolytics would help older adults facing major surgery.

Therapeutic targeting of senescent cells in the CNS

Senescent cells accumulate throughout the body with advanced age, diseases and chronic conditions. They negatively impact health and function of multiple systems, including the central nervous system (CNS). Therapies that target senescent cells, broadly referred to as senotherapeutics, recently emerged as potentially important treatment strategies for the CNS. Promising therapeutic approaches involve clearing senescent cells by disarming their pro-survival pathways with 'senolytics'; or dampening their toxic senescence-associated secretory phenotype (SASP) using 'senomorphics'. Following the pioneering discovery of first-generation senolytics dasatinib and quercetin, dozens of additional therapies have been identified, and several promising targets are under investigation. Although potentially transformative, senotherapies are still in early stages and require thorough testing to ensure reliable target engagement, specificity, safety and efficacy. The limited brain penetrance and potential toxic side effects of CNS-acting senotherapeutics pose challenges for drug development and translation to the clinic. This Review assesses the potential impact of senotherapeutics for neurological conditions by summarizing preclinical evidence, innovative methods for target and biomarker identification, academic and industry drug development pipelines and progress in clinical trials.

NFκB dynamics-dependent epigenetic changes modulate inflammatory gene expression and induce cellular senescence

Upregulation of nuclear factor κB (NFκB) signaling is a hallmark of aging and a major cause of age-related chronic inflammation. However, its effect on cellular senescence remains unclear. Here, we show that alteration of NFκB nuclear dynamics from oscillatory to sustained by depleting a negative feedback regulator of NFκB pathway, NFκB inhibitor alpha (IκBα), in the presence of tumor necrosis factor α (TNFα) promotes cellular senescence. Sustained NFκB activity enhanced inflammatory gene expression through increased NFκB-DNA binding and slowed the cell cycle. IκBα protein was decreased under replicative or oxidative stress in vitro. Furthermore, a decrease in IκBα protein and an increase in DNA-NFκB binding at the transcription start sites of age-associated genes in aged mouse hearts suggested that nuclear NFκB dynamics may play a critical role in the progression of aging. Our study suggests that nuclear NFκB dynamics-dependent epigenetic changes regulated over time in a living system, possibly through a decrease in IκBα, enhance the expression of inflammatory genes to advance the cells to a senescent state.

Senescence Biomarkers and Trajectories of Frailty and Physical Function After Kidney Transplantation

Cellular senescence is a biological mechanism of aging and age-related diseases. The aim of this study was to examine whether senescence biomarkers are associated with frailty and physical function trajectories in patients undergoing kidney transplantation (KT). We also discussed the relationship between senescence biomarkers and KT function. In this multicenter study, we prospectively assessed plasma levels of senescence biomarkers, frailty as measured by the Physical Frailty Phenotype, and physical function as measured by the Short Physical Performance Battery prior to KT. Frailty, physical function, and KT function were also measured 1 year after KT. Variable associations were assessed using Cox and relaxed least absolute shrinkage and selection operation regression. The cohort consisted of 197 participants (mean age 53 ± 13 years, 61.4% male, and 80.2% White race). Higher pre-KT levels of macrophage-derived chemokine (MDC/CCL22) and growth differentiation factor-15 (GDF-15) were independently associated with less improvement in frailty and/or physical function during the first year after KT. Higher pre-KT levels tumor necrosis factor receptor superfamily member 6 (FAS) and MMP-9 levels were independently associated with lower KT function one year after KT. Pre-KT cellular senescence may contribute to frailty, physical function, and kidney function trajectories during the first year after KT.

Exposure to ambient air pollution mixture and senescence-associated secretory phenotype proteins among middle-aged and older women

Our study aimed to investigate the impact of environmental exposures, such as ambient air pollutants, on systemic inflammation and cellular senescence in middle-aged and older women. We utilized epidemiological data linked with exposure data of six air pollutants (particulate matters [PM10, PM2.5], sulphur dioxide [SO2], nitrogen dioxide [NO2], carbon monoxide [CO], and ozone [O3]) and blood samples of 380 peri- and postmenopausal women participants of the Korean Genome and Epidemiology Study. We measured blood high-sensitivity C-reactive protein (hsCRP) and age-related 27 circulatory senescence-associated secretory phenotypes (SASP) produced by senescent cells. We employed single exposure models to explore the general pattern of association between air pollution exposure and proteomic markers. Using quantile g-computation models, we assessed the association of six air pollutant mixtures with hsCRP and SASP proteins. In single-exposure, single-period models, nine out of the 27 SASP proteins including IFN-γ (β = 0.04, 95% CI: 0.01, 0.07 per interquartile range-increase), IL-8 (0.15, 95% CI: 0.09, 0.20), and MIP1α (0.11, 95% CI: 0.04, 0.18) were positively associated with the average level of O3 over one week. Among the age-related SASP proteins, IFN-γ (0.11, 95% CI: 0.03, 0.20) and IL-8 (0.22, 95% CI: 0.05, 0.39) were positively associated with exposure to air pollutant mixture over one week. The MIP1β was higher with an increasing one-month average concentration of the air pollutant mixture (0.11, 95% CI: 0.00, 0.21). The IL-8 showed consistently positive association with the ambient air pollutant mixture for the exposure periods ranging from one week to one year. O3 predominantly showed positive weights in the associations between air pollutant mixtures and IL-8. These findings underscore the potential of proteomic indicators as markers for biological aging attributed to short-term air pollution exposure.

Proteomic Profiling of Endothelial Cell Secretomes After Exposure to Calciprotein Particles Reveals Downregulation of Basement Membrane Assembly and Increased Release of Soluble CD59

Calciprotein particles (CPPs) are essential circulating scavengers of excessive Ca2+ and PO43- ions, representing a vehicle that removes them from the human body and precludes extraskeletal calcification. Having been internalised by endothelial cells (ECs), CPPs induce their dysfunction, which is accompanied by a remarkable molecular reconfiguration, although little is known about this process's extracellular signatures. Here, we applied ultra-high performance liquid chromatography-tandem mass spectrometry to perform a secretome-wide profiling of the cell culture supernatant from primary human coronary artery ECs (HCAECs) and internal thoracic artery ECs (HITAECs) treated with primary CPPs (CPP-P), secondary CPPs (CPP-S), magnesiprotein particles (MPPs), or Ca2+/Mg2+-free Dulbecco's phosphate-buffered saline (DPBS) for 24 h. Incubation with CPP-P/CPP-S significantly altered the profiles of secreted proteins, delineating physiological and pathological endothelial secretomes. Neither pathway enrichment analysis nor the interrogation of protein-protein interactions detected extracellular matrix- and basement membrane-related molecular terms in the protein datasets from CPP-P/CPP-S-treated ECs. Both proteomic profiling and enzyme-linked immunosorbent assay identified an increased level of protectin (CD59) and reduced levels of osteonectin (SPARC), perlecan (HSPG2), and fibronectin (FN1) in the cell culture supernatant upon CPP-P/CPP-S treatment. Elevated soluble CD59 and decreased release of basement membrane components might be considered as potential signs of dysfunctional endothelium.

Oral Spore-Based Probiotic Supplementation Alters Post-Prandial Expression of mRNA Associated with Gastrointestinal Health

Background/Objectives: Unregulated post-prandial dietary endotoxemia may accumulate over time and underlie the development of chronic disease (e.g., leaky gut, inflammatory bowel disease, etc.), for which oral probiotic supplementation may be a prophylactic. The purpose of this study was to determine if 45 d of oral spore-based probiotic supplementation altered gastrointestinal-associated mRNA expression following a high-fat meal. Methods: A subset of apparently healthy individuals from a larger study who had dietary endotoxemia at baseline completed 45 d of supplementation with either a placebo (rice flour; n = 10) or spore-based probiotic (Megasporebiotic™; Novonesis, Kongens Lyngby, Denmark; Bacillus indicus (HU36™), Bacillus subtilis (HU58™), Bacillus coagulans (SC208™), and Bacillus licheniformis (SL-307), and Bacillus clausii (SC109™); n = 10). Venous blood was collected in Paxgene RNA tubes prior to (PRE), 3 h, and 5 h after consumption of a high-fat meal (85% of the daily fat RDA and 65% of the daily calorie needs). Total RNA was analyzed for 579 mRNAs of interest (Nanostring nCounter Sprint; Seattle, WA, USA). After normalization to housekeeping controls and calculation of differential expression relative to PRE and controlled for FDR, 15 mRNAs were determined to be significantly changed at either 3 h and/or 5 h post-prandial in the probiotic group but not in the placebo group. Results: Significant mRNA expressions were associated with gastrointestinal tract barrier function (four mRNAs: BATF3, CCR6, CXCR6, and PDCD2), gastrointestinal immunity (four mRNAs: CLEC5A, IL7, CARD9, and FCER1G), or future IBD risk (seven mRNAs: PD-L1, CSF1R, FAS, BID, FADD, GATA3, and KIR3DL). Conclusions: Collectively, the present findings may support the notion that post-prandial immune response to eating is enhanced following 45 d of probiotic supplementation.

Sex-dependent effects in the aged melanoma tumor microenvironment influence invasion and resistance to targeted therapy

There is documented sex disparity in cutaneous melanoma incidence and mortality, increasing disproportionately with age and in the male sex. However, the underlying mechanisms remain unclear. While biological sex differences and inherent immune response variability have been assessed in tumor cells, the role of the tumor-surrounding microenvironment, contextually in aging, has been overlooked. Here, we show that skin fibroblasts undergo age-mediated, sex-dependent changes in their proliferation, senescence, ROS levels, and stress response. We find that aged male fibroblasts selectively drive an invasive, therapy-resistant phenotype in melanoma cells and promote metastasis in aged male mice by increasing AXL expression. Intrinsic aging in male fibroblasts mediated by EZH2 decline increases BMP2 secretion, which in turn drives the slower-cycling, highly invasive, and therapy-resistant melanoma cell phenotype, characteristic of the aged male TME. Inhibition of BMP2 activity blocks the emergence of invasive phenotypes and sensitizes melanoma cells to BRAF/MEK inhibition.

Fisetin as a senotherapeutic agent: Evidence and perspectives for age-related diseases

Fisetin, a flavonoid naturally occurring in plants, fruits, and vegetables, has recently gained attention for its potential role as a senotherapeutic agent for the treatment of age-related chronic diseases. Senotherapeutics target senescent cells, which accumulate with age and disease, in both circulating immune cell populations and solid organs and tissues. Senescent cells contribute to development of many chronic diseases, primarily by eliciting systemic chronic inflammation through their senescence-associated secretory phenotype. Here, we explore whether fisetin as a senotherapeutic can eliminate senescent cells, and thereby alleviate chronic diseases, by examining current evidence from in vitro studies and animal models that investigate fisetin's impact on age-related diseases, as well as from phase I/II trials in various patient populations. We discuss the application of fisetin in humans, including challenges and future directions. Our review of available data suggests that targeting senescent cells with fisetin offers a promising strategy for managing multiple chronic diseases, potentially transforming future healthcare for older and multimorbid patients. However, further studies are needed to establish the safety, pharmacokinetics, and efficacy of fisetin as a senotherapeutic, identify relevant and reliable outcome measures in human trials, optimize dosing, and better understand the possible limitations of fisetin as a senotherapeutic agent.

Mediating role of accelerated aging in the association between depression and mortality risk: findings from NHANES

OBJECTIVE

To investigate the association between depression, accelerated biological aging, and mortality risk, and to assess whether accelerated aging mediates the relationship between major depression and mortality risk.

METHODS

A prospective cohort of 12,761 participants aged 20 years or older from the 2005-2010 cycle of the National Health and Nutrition Examination Survey (NHANES) was analyzed. Depression was assessed using the Patient Health Questionnaire-9 (PHQ-9), with scores of ≥ 10 indicating major depression. Accelerated biological aging was measured using phenotypic age acceleration (PhenoAgeAccel). Multivariable linear regression models and subgroup analyses were used to examine the association between depression and accelerated aging, while weighted multivariable Cox proportional hazards regression models and subgroup analyses assessed the impact of major depression on mortality risk. Mediation analysis was performed to assess whether PhenoAgeAccel mediated the relationship between major depression and mortality outcomes.

RESULTS

Among the 12,761 adults, the weighted mean age was 46.6 years, with 48.8% being male, and 6.9% experiencing major depression. The results showed a positive association between major depression and PhenoAgeAccel (β: 0.61, 95% CI: 0.06-1.16). Over a median follow-up duration of 11.3 years (interquartile range: 9.9-13.1), major depression was associated with increased all-cause mortality (HR: 1.35, 95% CI: 1.13-1.62) and cardiovascular mortality (HR: 1.73, 95% CI: 1.18-2.54). However, the relationship with cancer mortality was not statistically significant after full adjustment for confounding factors. The mediation analysis further revealed that PhenoAgeAccel accounted for 10.32% and 5.12% of the associations between major depression and all-cause mortality, and cardiovascular mortality, respectively.

CONCLUSION

Depression is associated with accelerated aging and contributes to increased all-cause and cardiovascular mortality. Accelerated aging partially mediates the association between major depression and mortality risk. Our findings highlight the urgent need to incorporate mental health care into public health strategies to delay population aging and reduce mortality risk.

Secreted GDF15 maintains transcriptional responses during DNA damage-mediated senescence in human beta cells

Type 1 diabetes (T1D) is a chronic metabolic disease resulting from an autoimmune destruction of pancreatic beta cells. Beta cells activate various stress responses during the development of T1D, including senescence, which involves cell cycle arrest, prosurvival signaling, and a proinflammatory secretome termed the senescence-associated secretory phenotype (SASP). We previously identified growth and differentiation factor 15 (GDF15) as a major SASP factor in human islets and human EndoC-βH5 beta cells in a model of DNA damage-mediated senescence that recapitulates features of senescent beta cells in T1D. Soluble GDF15 has been shown to exert protective effects on human and mouse beta cells during various forms of stress relevant to T1D; therefore, we hypothesized that secreted GDF15 may play a prosurvival role during DNA damage-mediated senescence in human beta cells. We found that elevated GDF15 secretion was associated with endogenous senescent beta cells in an islet preparation from a T1D donor, supporting the validity of our DNA damage model. Using antibody-based neutralization, we found that secreted endogenous GDF15 was not required for senescent human islet or EndoC cell viability. Rather, neutralization of GDF15 led to reduced expression of specific senescence-associated genes, including GDF15 itself and the prosurvival gene BCL2-like protein 1 (BCL2L1). Taken together, these data suggest that SASP factor GDF15 is not required to sustain senescent human islet viability, but it is required to maintain senescence-associated transcriptional responses.NEW & NOTEWORTHY Beta cell senescence is an emerging contributor to the pathogenesis of type 1 diabetes, but candidate therapeutic targets have not been identified in human beta cells. In this study, we examined the role of a secreted factor, GDF15, and found that although it is not required to maintain viability during senescence, it is required to fine-tune gene expression programs involved in the senescence response during DNA damage in human beta cells.

Controversies and Conundrums in Cardiac Cachexia: Key Questions About Wasting in Patients With HFrEF

Cardiac cachexia is characterized by unintentional catabolic weight loss, decreased appetite, and inflammation and is common in patients with stage D (advanced) heart failure with reduced ejection fraction (HFrEF). Cardiac cachexia and related muscle-wasting syndromes are markers of, and a consequence of, the heart failure (HF) syndrome. Although many potential modalities for identifying cardiac cachexia exist, the optimal definition, diagnostic tools, and treatment options for cardiac cachexia remain unclear. Furthermore, it remains unclear whether attempts to reverse muscle wasting prior to advanced HF surgeries, such as left ventricular assist devices and heart transplantation, can improve outcomes. It is important that HF clinicians and dietitians are aware of the pathophysiology and mechanisms of muscle-wasting syndromes in patients with HF, to aid in the recognition and risk stratification of advanced HFrEF. Although the opportunities and rationale for attempting to address cardiac cachexia prior to advanced HF surgeries are uncertain, recent publications suggest that control of the neurohumoral syndrome of advanced HF may be important to permit the recovery of skeletal muscle mass.

Multicohort study testing the generalisability of the SASKit-ML stroke and PDAC prognostic model pipeline to other chronic diseases

OBJECTIVES

To validate and test the generalisability of the SASKit-ML pipeline, a prepublished feature selection and machine learning pipeline for the prediction of health deterioration after a stroke or pancreatic adenocarcinoma event, by using it to identify biomarkers of health deterioration in chronic disease.

DESIGN

This is a validation study using a predefined protocol applied to multiple publicly available datasets, including longitudinal data from cohorts with type 2 diabetes (T2D), inflammatory bowel disease (IBD), rheumatoid arthritis (RA) and various cancers. The datasets were chosen to mimic as closely as possible the SASKit cohort, a prospective, longitudinal cohort study.

DATA SOURCES

Public data were used from the T2D (77 patients with potential pre-diabetes and 18 controls) and IBD (49 patients with IBD and 12 controls) branches of the Human Microbiome Project (HMP), RA Map (RA-MAP, 92 patients with RA, 22 controls) and The Cancer Genome Atlas (TCGA, 16 cancers).

METHODS

Data integration steps were performed in accordance with the prepublished study protocol, generating features to predict disease outcomes using 10-fold cross-validated random survival forests.

OUTCOME MEASURES

Health deterioration was assessed using disease-specific clinical markers and endpoints across different cohorts. In the HMP-T2D cohort, the worsening of glycated haemoglobin (HbA1c) levels (5.7% or more HbA1c in the blood), fasting plasma glucose (at least 100 mg/dL) and oral glucose tolerance test (at least 140) results were considered. For the HMP-IBD cohort, a worsening by at least 3 points of a disease-specific severity measure, the "Simple Clinical Colitis Activity Index" or "Harvey-Bradshaw Index" indicated an event. For the RA-MAP cohort, the outcome was defined as the worsening of the "Disease Activity Score 28" or "Simple Disease Activity Index" by at least five points, or the worsening of the "Health Assessment Questionnaire" score or an increase in the number of swollen/tender joints were evaluated. Finally, the outcome for all TCGA datasets was the progression-free interval.

RESULTS

Models for the prediction of health deterioration in T2D, IBD, RA and 16 cancers were produced. The T2D (C-index of 0.633 and Integrated Brier Score (IBS) of 0.107) and the RA (C-index of 0.654 and IBS of 0.150) models were modestly predictive. The IBD model was uninformative. TCGA models tended towards modest predictive power.

CONCLUSIONS

The SASKit-ML pipeline produces informative and useful features with the power to predict health deterioration in a variety of diseases and cancers; however, this performance is disease-dependent.

A nutrigeroscience approach: Dietary macronutrients and cellular senescence

Cellular senescence, a process in which a cell exits the cell cycle in response to stressors, is one of the hallmarks of aging. Senescence and the senescence-associated secretory phenotype (SASP)-a heterogeneous set of secreted factors that disrupt tissue homeostasis and promote the accumulation of senescent cells-reprogram metabolism and can lead to metabolic dysfunction. Dietary interventions have long been studied as methods to combat age-associated metabolic dysfunction, promote health, and increase lifespan. A growing body of literature suggests that senescence is responsive to diet, both to calories and specific dietary macronutrients, and that the metabolic benefits of dietary interventions may arise in part through reducing senescence. Here, we review what is currently known about dietary macronutrients' effect on senescence and the SASP, the nutrient-responsive molecular mechanisms that may mediate these effects, and the potential for these findings to inform the development of a nutrigeroscience approach to healthy aging.

Effects of intermittent senolytic therapy on bone metabolism in postmenopausal women: a phase 2 randomized controlled trial

Preclinical evidence demonstrates that senescent cells accumulate with aging and that senolytics delay multiple age-related morbidities, including bone loss. Thus, we conducted a phase 2 randomized controlled trial of intermittent administration of the senolytic combination dasatinib plus quercetin (D + Q) in postmenopausal women (n = 60 participants). The primary endpoint, percentage changes at 20 weeks in the bone resorption marker C-terminal telopeptide of type 1 collagen (CTx), did not differ between groups (median (interquartile range), D + Q -4.1% (-13.2, 2.6), control -7.7% (-20.1, 14.3); P = 0.611). The secondary endpoint, percentage changes in the bone formation marker procollagen type 1 N-terminal propeptide (P1NP), increased significantly (relative to control) in the D + Q group at both 2 weeks (+16%, P = 0.020) and 4 weeks (+16%, P = 0.024), but was not different from control at 20 weeks (-9%, P = 0.149). No serious adverse events were observed. In exploratory analyses, the skeletal response to D + Q was driven principally by women with a high senescent cell burden (highest tertile for T cell p16 (also known as CDKN2A) mRNA levels) in which D + Q concomitantly increased P1NP (+34%, P = 0.035) and reduced CTx (-11%, P = 0.049) at 2 weeks, and increased radius bone mineral density (+2.7%, P = 0.004) at 20 weeks. Thus, intermittent D + Q treatment did not reduce bone resorption in the overall group of postmenopausal women. However, our exploratory analyses indicate that further studies are needed testing the hypothesis that the underlying senescent cell burden may dictate the clinical response to senolytics. ClinicalTrials.gov identifier: NCT04313634 .

Mechanisms of Senescence and Anti-Senescence Strategies in the Skin

The skin is the layer of tissue that covers the largest part of the body in vertebrates, and its main function is to act as a protective barrier against external environmental factors, such as microorganisms, ultraviolet light and mechanical damage. Due to its important function, investigating the factors that lead to skin aging and age-related diseases, as well as understanding the biology of this process, is of high importance. Indeed, it has been reported that several external and internal stressors contribute to skin aging, similar to the aging of other tissues. Moreover, during aging, senescent cells accumulate in the skin and express senescence-associated factors, which act in a paracrine manner on neighboring healthy cells and tissues. In this review, we will present the factors that lead to skin aging and cellular senescence, as well as ways to study senescence in vitro and in vivo. We will further discuss the adverse effects of the accumulation of chronic senescent cells and therapeutic agents and tools to selectively target and eliminate them.

Associations of Serum GDF-15 Levels with Physical Performance, Mobility Disability, Cognition, Cardiovascular Disease, and Mortality in Older Adults

Background

Growth differentiation factor 15 (GDF-15) is a member of the TGFβ superfamily secreted by many cell types and found at higher blood concentrations as chronological age increases (1). Given the emergence of GDF-15 as a key protein associated with aging, it is important to understand the multitude of conditions with which circulating GDF-15 is associated.

Methods

We pooled data from 1,174 randomly selected Health ABC Study (Health ABC) participants and 1,503 Cardiovascular Health Study (CHS) participants to evaluate the risk of various conditions and age-related outcomes across levels of GDF-15. The primary outcomes were (1) risk of mobility disability and falls; (2) impaired cognitive function; (3) and increased risk of cardiovascular disease and total mortality.

Results

The pooled study cohort had a mean age of 75.4 +/-4.4 years. Using a Bonferroni-corrected threshold, our analyses show that high levels of GDF-15 were associated with a higher risk of severe mobility disability (HR: 2.13 [1.64, 2.77]), coronary heart disease (HR: 1.47 [1.17, 1.83]), atherosclerotic cardiovascular disease (HR: 1.56 [1.22, 1.98]), heart failure (HR: 2.09 [1.66, 2.64]), and mortality (HR: 1.81 [1.53, 2.15]) when comparing the highest and lowest quartiles. For CHS participants, analysis of extreme quartiles in fully adjusted models revealed a 3.5-fold higher risk of dementia (HR: 3.50 [1.97, 6.22]).

Conclusions

GDF-15 is associated with several age-related outcomes and diseases, including mobility disability, impaired physical and cognitive performance, dementia, cardiovascular disease, and mortality. Each of these findings demonstrates the importance of GDF-15 as a potential biomarker for many aging-related conditions.

Detailing the biomedical aspects of geroscience by molecular data and large-scale "deep" bioinformatics analyses

As scientists investigated the molecular mechanisms of the biology of aging, they discovered that these are malleable and can enhance healthy longevity by intervening in the drivers of aging, which are leading to disease, dysfunction and death. These exciting observations gave birth to the field of geroscience. As the mechanisms of aging affect almost all mechanisms of life, detailed molecular mechanistic knowledge must be gained or expanded by considering and integrating as many types of data as possible, from genes and transcripts to socioenvironmental factors. Such a large-scale integration of large amounts of data will in turn profit from "deep" bioinformatics analyses that provide insights beyond contextualizing and interpreting the data in the light of knowledge from databases such as the Gene Ontology. The authors suggest that "deep" bioinformatics, employing methods based on artificial intelligence, will be a key ingredient of future analyses.

The PRC2 complex epigenetically silences GATA4 to suppress cellular senescence and promote the progression of breast cancer

BACKGROUND

The transcription factor GATA4 is pivotal in cancer development but is often silenced through mechanisms like DNA methylation and histone modifications. This silencing suppresses the transcriptional activity of GATA4, disrupting its normal functions and promoting cancer progression. However, the precise molecular mechanisms and implications of GATA4 silencing in tumorigenesis remain unclear. Here, we aim to elucidate the mechanisms underlying GATA4 silencing and explore its role in breast cancer progression and its potential as a therapeutic target.

METHODS

The GATA4-breast cancer prognosis link was explored via bioinformatics analyses, with GATA4 expression measured in breast tissues. Functional gain/loss experiments were performed to gauge GATA4's impact on breast cancer cell malignancy. GATA4-PRC2 complex interaction was analyzed using silver staining and mass spectrometry. Chromatin immunoprecipitation, coupled with high-throughput sequencing, was used to identify GATA4-regulated downstream target genes. The in vitro findings were validated in an in situ breast cancer xenograft mouse model.

RESULTS

GATA4 mutation and different breast cancer subtypes were correlated, suggesting its involvement in disease progression. GATA4 suppressed cell proliferation, invasion, and migration while inducing apoptosis and senescence in breast cancer cells. The GATA4-PRC2 complex interaction silenced GATA4 expression, which altered the regulation of FAS, a GATA4 downstream gene. In vivo experiments verified that GATA4 inhibits tumor growth, suggesting its regulatory function in tumorigenesis.

CONCLUSIONS

This comprehensive study highlights the epigenetic regulation of GATA4 and its impact on breast cancer development, highlighting the PRC2-GATA4-FAS pathway as a potential target for therapeutic interventions in breast cancers.

Endothelial dysfunction: molecular mechanisms and clinical implications

Cardiovascular disease (CVD) and its complications are a leading cause of death worldwide. Endothelial dysfunction plays a crucial role in the initiation and progression of CVD, serving as a pivotal factor in the pathogenesis of cardiovascular, metabolic, and other related diseases. The regulation of endothelial dysfunction is influenced by various risk factors and intricate signaling pathways, which vary depending on the specific disease context. Despite numerous research efforts aimed at elucidating the mechanisms underlying endothelial dysfunction, the precise molecular pathways involved remain incompletely understood. This review elucidates recent research findings on the pathophysiological mechanisms involved in endothelial dysfunction, including nitric oxide availability, oxidative stress, and inflammation-mediated pathways. We also discuss the impact of endothelial dysfunction on various pathological conditions, including atherosclerosis, heart failure, diabetes, hypertension, chronic kidney disease, and neurodegenerative diseases. Furthermore, we summarize the traditional and novel potential biomarkers of endothelial dysfunction as well as pharmacological and nonpharmacological therapeutic strategies for endothelial protection and treatment for CVD and related complications. Consequently, this review is to improve understanding of emerging biomarkers and therapeutic approaches aimed at reducing the risk of developing CVD and associated complications, as well as mitigating endothelial dysfunction.

The infrapatellar fat pad in inflammaging, knee joint health, and osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis and accounts for nearly $140 billion in annual healthcare expenditures only in the United States. Obesity, aging, and joint injury are major risk factors for OA development and progression, but the mechanisms contributing to pathology remain unclear. Emerging evidence suggests that cellular dysregulation and inflammation in joint tissues, including intra-articular adipose tissue depots, may contribute to disease severity. In particular, the infrapatellar fat pad (IFP), located in the knee joint, which provides a protective cushion for joint loading, also secretes multiple endocrine factors and inflammatory cytokines (inflammaging) that can regulate joint physiology and disease. Correlates of cartilage degeneration and OA-associated disease severity include inflammation and fibrosis of IFP in model organisms and human studies. In this article, we discuss recent progress in understanding the roles and regulation of intra-articular fat tissue in regulating joint biology and OA.

Methods to Investigate the Secretome of Senescent Cells

The word "secretome" was first used to describe the proteins that cells secrete under different circumstances; however, recent studies have proven the existence of other molecules such as RNA and chemical compounds in the secretome. The study of secretome has significance for the diagnosis and treatment of disease as it provides insight into cellular functions, including immune responses, development, and homeostasis. By halting cell division, cellular senescence plays a role in both cancer defense and aging by secreting substances known as senescence-associated secretory phenotypes (SASP). A variety of techniques could be used to analyze the secretome: protein-based approaches like mass spectrometry and protein microarrays, nucleic acid-based methods like RNA sequencing, microarrays, and in silico prediction. Each method offers unique advantages and limitations in characterizing secreted molecules. Top-down and bottom-up strategies for thorough secretome analysis are became possible by mass spectrometry. Understanding cellular function, disease causes, and proper treatment targets is aided by these methodologies. Their approaches, benefits, and drawbacks will all be discussed in this review.

Women With a History of Preeclampsia Exhibit Accelerated Aging and Unfavorable Profiles of Senescence Markers

BACKGROUND

Senescence, a mechanism of cellular aging, which is characterized by irreversible proliferation arrest and a proinflammatory secretory phenotype, has been documented in women with preeclampsia. As cellular senescence can persist and progress, we postulated that it is associated with accelerated aging phenotype and accumulation of comorbidities in women with a history of preeclampsia.

METHODS

We included a cohort of women with a history of preeclampsia (n=40) age- and parity-matched to a group of referent women with normotensive pregnancies (n=40). Women with prior major cardiovascular events, neurological, or autoimmune conditions were excluded. We collected urine and blood samples to study markers of aging, data on multimorbidity at the time of enrollment, and prospectively followed them for events over the course of 6 years, on average.

RESULTS

Women with a history of preeclampsia exhibited unfavorable aging profiles compared with referent women, including decreased urinary α-Klotho (P=0.018); increased leptin (P=0.016) and leptin/adiponectin ratio (P=0.027), and increased extracellular vesicles positive for tissue factor (P=0.025). Women with a history of preeclampsia likewise had a higher rate of comorbidities at the time of enrollment (P=0.003) and had a 4× higher risk of developing major cardiovascular events compared with referent women (P=0.003).

CONCLUSIONS

Our data suggest that a history of preeclampsia is associated with accelerated aging as indicated by senescence marker differences and the accumulation of multimorbidity later in life. Targeting cellular senescence may offer novel, mechanism-based approaches for the diagnosis and treatment of adverse health outcomes in women with a history of preeclampsia.

Looking for the philosopher's stone: Emerging approaches to target the hallmarks of aging in the skin

Senescence and epigenetic alterations are two important hallmarks of cellular aging. During aging, cells subjected to stress undergo many cycles of damage and repair before finally entering either apoptosis or senescence, a permanent state of cell cycle arrest. The first biomarkers of senescence to be identified were increased ß-galactosidase activity and induction of p16INK4a. Another feature of senescent cells is the senescence-associated secretory phenotype (SASP), a complex secretome containing more than 80 pro-inflammatory factors including metalloproteinases, growth factors, chemokines and cytokines. The secretome is regulated through a dynamic process involving a self-amplifying autocrine feedback loop and activation of the immune system. Senescent cells play positive and negative roles depending on the composition of their SASP and may participate in various processes including wound healing and tumour suppression, as well as cell regeneration, embryogenesis, tumorigenesis, inflammation and finally aging. The SASP is also a biomarker of age, biological aging and age-related diseases. Recent advances in anti-age research have shown that senescence can be now prevented or delayed by clearing the senescent cells or mitigating the effects of SASP factors, which can be achieved by a healthy lifestyle (exercise and diet), and senolytics and senomorphics, respectively. An alternative is tissue rejuvenation, which can be achieved by stimulating aged stem cells and reprogramming deprogrammed aged cells. These non-clinical findings will open up new avenues of clinical research into the development of treatments capable of preventing or treating age-related pathologies in humans.

Increased Pretransplant Inflammatory Biomarkers Predict Death With Function After Kidney Transplantation

BACKGROUND

Chronic systemic inflammation is associated with mortality in patients with chronic kidney disease, cardiovascular disease, and diabetes. The goal of this study was to examine the relationship between pretransplant inflammatory biomarkers (growth differentiation factor-15 [GDF-15], interleukin-6 [IL-6], soluble tumor necrosis factor receptor-1, monokine induced by gamma interferon/chemokine [C-X-C motif] ligand 9 [MIG/CXCL9], monocyte chemoattractant protein-1, soluble FAS, tumor necrosis factor-α, interleukin-15, and interleukin-1β) and death with function (DWF) after kidney transplantation (KT).

METHODS

We retrospectively measured inflammatory biomarker levels in serum collected up to 1 y before KT (time from blood draw to KT was 130 ± 110 d) in recipients transplanted between January 2006 and December 2018. Kaplan-Meier estimation, Cox regression, and Gradient Boosting Machine modeling were used to examine the relationship between inflammatory biomarkers and DWF.

RESULTS

Our cohort consisted of 1595 KT recipients, of whom 62.9% were male and 83.2% were non-Hispanic White. Over a mean follow-up of 7.4 ± 3.9 y, 21.2% of patients (n = 338) experienced DWF. Patients with the highest quartile levels of GDF-15 (>4766 pg/mL), IL-6 (>6.11 pg/mL), and MIG/CXCL9 (> 5835 pg/mL) had increased rates of DWF, and each predicted mortality independently of the others. When adjusted for clinical factors (age, diabetes, etc), the highest quartile levels of GDF-15 and IL-6 remained independently associated with DWF. Adding inflammatory markers to a clinical Cox model improved the C-statistic for DWF from 0.727 to 0.762 using a Gradient Boosting Machine modeling approach.

CONCLUSIONS

These findings suggest that pre-KT serum concentrations of GDF-15, IL-6, and MIG/CXCL9 may help to risk stratify and manage patients undergoing KT and suggests that chronic inflammation may play a role in mortality in KT recipients.

Towards Healthy Longevity: Comprehensive Insights from Molecular Targets and Biomarkers to Biological Clocks

Aging is a complex and time-dependent decline in physiological function that affects most organisms, leading to increased risk of age-related diseases. Investigating the molecular underpinnings of aging is crucial to identify geroprotectors, precisely quantify biological age, and propose healthy longevity approaches. This review explores pathways that are currently being investigated as intervention targets and aging biomarkers spanning molecular, cellular, and systemic dimensions. Interventions that target these hallmarks may ameliorate the aging process, with some progressing to clinical trials. Biomarkers of these hallmarks are used to estimate biological aging and risk of aging-associated disease. Utilizing aging biomarkers, biological aging clocks can be constructed that predict a state of abnormal aging, age-related diseases, and increased mortality. Biological age estimation can therefore provide the basis for a fine-grained risk stratification by predicting all-cause mortality well ahead of the onset of specific diseases, thus offering a window for intervention. Yet, despite technological advancements, challenges persist due to individual variability and the dynamic nature of these biomarkers. Addressing this requires longitudinal studies for robust biomarker identification. Overall, utilizing the hallmarks of aging to discover new drug targets and develop new biomarkers opens new frontiers in medicine. Prospects involve multi-omics integration, machine learning, and personalized approaches for targeted interventions, promising a healthier aging population.

Biomarkers of Aging and Relevant Evaluation Techniques: A Comprehensive Review

The risk of developing chronic illnesses and disabilities is increasing with age. To predict and prevent aging, biomarkers relevant to the aging process must be identified. This paper reviews the known molecular, cellular, and physiological biomarkers of aging. Moreover, we discuss the currently available technologies for identifying these biomarkers, and their applications and potential in aging research. We hope that this review will stimulate further research and innovation in this emerging and fast-growing field.

Growth Differentiation Factor 15 and Diet Quality Trajectory Interact to Determine Frailty Incidence among Middle-Aged Urban Adults

BACKGROUND

Elevated plasma growth differentiation factor 15 (GDF15) and poor diet quality may be associated with increased frailty incidence, although their interactive associations have not been assessed in urban middle-aged adults.

OBJECTIVES

We aimed to examine GDF15 and its interactive association with diet quality in relation to frailty incidence among a sample of middle-aged urban adults.

METHODS

The relationship between GDF15 and diet quality trajectories in relation to incident frailty was examined in a longitudinal study of participants in the Healthy Aging in Neighborhoods of Diversity across the Life Span (2004-2017). Serum GDF15 concentration and frailty incidence were primary exposure and outcome, respectively. Group-based trajectory models were used to assess diet quality trajectories (≤3 visits/participant, N = 945, N' = 2247 observations) using the Healthy Eating Index 2010 version (HEI-2010), Dietary Inflammatory Index, and mean adequacy ratio (MAR). Cox proportional hazards models were used, testing interactive associations of GDF15 and diet quality trajectories with frail/prefrail incidence (N = 400 frailty-free at first visit, N' = 604 observations, n = 168 incident frail/prefrail).

RESULTS

Both elevated GDF15 and lower diet quality trajectories were associated with a lower probability of remaining nonfrail (≤13 y follow-up). Among females, the "high diet quality" HEI-2010 trajectory had a hazard ratio (HR) of 0.15 [95% confidence interval (CI): 0.04, 0.54; P = 0.004; fully adjusted model] when compared with the "low diet quality" trajectory group. Among males only, there was an antagonistic interaction between lower HEI-2010 trajectory and elevated GDF15. Specifically, the HR for GDF15-frailty in the higher diet quality trajectory group (high/medium combined), and among males, was 2.69 (95% CI: 1.06, 6.62; P = 0.032), whereas among the lower diet quality trajectory group, the HR was 0.94 (95% CI: 0.49, 1.80; P = 0.86). Elevated GDF15 was independently associated with frailty among African American adults.

CONCLUSIONS

Pending replication, we found an antagonistic interaction between GDF15 and HEI-2010 trajectory in relation to frailty incidence among males.

Growth and differentiation factor-15: A link between inflammaging and cardiovascular disease

Age-related disorders are closely linked to the accumulation of senescent cells. The senescence-associated secretory phenotype (SASP) sustains and progresses chronic inflammation, which is involved in cellular and tissue dysfunction. SASP-related growth and differentiation factor-15 (GDF-15) is an immunoregulatory cytokine that is coupled to aging and thus may have a regulatory role in the development and maintenance of atherosclerosis, a major cause of cardiovascular disease (CVD). Although the effects of GDF-15 are tissue-specific and dependent on microenvironmental changes such as inflammation, available data suggest that GDF-15 has a significant role in CVD. Thus, GDF-15 is a promising biomarker and potential therapeutic target for atherosclerotic CVD.

Placental senescence pathophysiology is shared between peripartum cardiomyopathy and preeclampsia in mouse and human

Peripartum cardiomyopathy (PPCM) is an idiopathic form of pregnancy-induced heart failure associated with preeclampsia. Circulating factors in late pregnancy are thought to contribute to both diseases, suggesting a common underlying pathophysiological process. However, what drives this process remains unclear. Using serum proteomics, we identified the senescence-associated secretory phenotype (SASP), a marker of cellular senescence associated with biological aging, as the most highly up-regulated pathway in young women with PPCM or preeclampsia. Placentas from women with preeclampsia displayed multiple markers of amplified senescence and tissue aging, as well as overall increased gene expression of 28 circulating proteins that contributed to SASP pathway enrichment in serum samples from patients with preeclampsia or PPCM. The most highly expressed placental SASP factor, activin A, was associated with cardiac dysfunction or heart failure severity in women with preeclampsia or PPCM. In a murine model of PPCM induced by cardiomyocyte-specific deletion of the gene encoding peroxisome proliferator-activated receptor γ coactivator-1α, inhibiting activin A signaling in the early postpartum period with a monoclonal antibody to the activin type II receptor improved heart function. In addition, attenuating placental senescence with the senolytic compound fisetin in late pregnancy improved cardiac function in these animals. These findings link senescence biology to cardiac dysfunction in pregnancy and help to elucidate the pathogenesis underlying cardiovascular diseases of pregnancy.

Influence of Growth Differentiation Factor 15 on Intraocular Pressure in Mice

Growth differentiation factor 15 (GDF15), a stress-sensitive cytokine, and a distant member of the transforming growth factor β superfamily, has been shown to exhibit increased levels with aging, and in various age-related pathologies. Although GDF15 levels are elevated in the aqueous humor (AH) of glaucoma (optic nerve atrophy) patients, the possible role of this cytokine in the modulation of intraocular pressure (IOP) or AH outflow is unknown. The current study addresses this question using transgenic mice expressing human GDF15 and GDF15 null mice, and by perfusing enucleated mouse eyes with recombinant human GDF15 (rhGDF15). Treatment of primary cultures of human trabecular meshwork cells with a telomerase inhibitor, an endoplasmic reticulum stress-inducing agent, hydrogen peroxide, or an autophagy inhibitor resulted in significant elevation in GDF15 levels relative to the respective control cells. rhGDF15 stimulated modest but significant increases in the expression of genes encoding the extracellular matrix, cell adhesion proteins, and chemokine receptors (C-C chemokine receptor type 2) in human trabecular meshwork cells compared with controls, as deduced from the differential transcriptional profiles using RNA-sequencing analysis. There was a significant increase in IOP in transgenic mice expressing human GDF15, but not in GDF15 null mice, compared with the respective wild-type control mice. The AH outflow facility was decreased in enucleated wild-type mouse eyes perfused with rhGDF15. Light microcopy-based histologic examination of the conventional AH outflow pathway tissues did not reveal identifiable differences between the GDF15-targeted and control mice. Taken together, these results reveal the modest elevation of IOP in mice expressing human GDF15 possibly stemming from decreased AH outflow through the trabecular pathway.

Restoration of epigenetic impairment in the skeletal muscle and chronic inflammation resolution as a therapeutic approach in sarcopenia

Sarcopenia is an age-associated loss of skeletal muscle mass, strength, and function, accompanied by severe adverse health outcomes, such as falls and fractures, functional decline, high health costs, and mortality. Hence, its prevention and treatment have become increasingly urgent. However, despite the wide prevalence and extensive research on sarcopenia, no FDA-approved disease-modifying drugs exist. This is probably due to a poor understanding of the mechanisms underlying its pathophysiology. Recent evidence demonstrate that sarcopenia development is characterized by two key elements: (i) epigenetic dysregulation of multiple molecular pathways associated with sarcopenia pathogenesis, such as protein remodeling, insulin resistance, mitochondria impairments, and (ii) the creation of a systemic, chronic, low-grade inflammation (SCLGI). In this review, we focus on the epigenetic regulators that have been implicated in skeletal muscle deterioration, their individual roles, and possible crosstalk. We also discuss epidrugs, which are the pharmaceuticals with the potential to restore the epigenetic mechanisms deregulated in sarcopenia. In addition, we discuss the mechanisms underlying failed SCLGI resolution in sarcopenia and the potential application of pro-resolving molecules, comprising specialized pro-resolving mediators (SPMs) and their stable mimetics and receptor agonists. These compounds, as well as epidrugs, reveal beneficial effects in preclinical studies related to sarcopenia. Based on these encouraging observations, we propose the combination of epidrugs with SCLI-resolving agents as a new therapeutic approach for sarcopenia that can effectively attenuate of its manifestations.

Brief Report: Relationship Between Adiposity and Biomarkers of Aging and Frailty Among Adults Aging With HIV

BACKGROUND

This study examined the relationships among adiposity, handgrip, physical function, inflammation (ie, senescence-associated secretory phenotype chemokines as biomarkers of aging and frailty), and sex hormones in aging people with HIV.

METHODS

This cross-sectional exploratory study included 150 people with HIV aged ≥40 years (67.3% of participants were male). Our measures included (1) body mass index and waist circumference as measures of adiposity; (2) handgrip as a measure of muscle strength; (3) short physical performance battery as a measure of physical function; (4) interleukin-6, tumor necrosis factor alpha receptor II, high sensitivity C-reactive protein, C-X-C motif chemokine 10, and C-X3-C motif chemokine ligand 1 also known as fractalkine as senescence-associated secretory phenotype chemokines; and (5) free testosterone, estradiol, sex hormone-binding globulin, and dehydroepiandrosterone as sex hormones. Quantile regression analyses were used to identify relationships among inflammatory markers and hormones with age, adiposity, handgrip, and physical function.

RESULTS

Overall, 74% (n = 111) of participants were classified as overweight or obese and 53.3% (n = 80) presented with abdominal obesity. After controlling for age and sex, body mass index was positively associated with estradiol (β = 0.043, P < 0.01), and waist circumference was positively associated with high sensitivity C-reactive protein (β = 2.151, P < 0.01). After controlling for sex, age was positively associated with C-X-C motif chemokine 10 (β = 0.024, P = 0.03) and tumor necrosis factor alpha receptor II (β = 2.205, P = 0.01). After controlling for age and sex, short physical performance battery was negatively associated with dehydroepiandrosterone (β = -0.004, P = 0.01); no statistically significant associations were observed for handgrip.

CONCLUSION

Adiposity levels and aging were associated with inflammation (ie, C-X-C motif chemokine 10, tumor necrosis factor alpha receptor II, and high sensitivity C-reactive protein) among people with HIV aged 40 years and older.

A molecular index for biological age identified from the metabolome and senescence-associated secretome in humans

Unlike chronological age, biological age is a strong indicator of health of an individual. However, the molecular fingerprint associated with biological age is ill-defined. To define a high-resolution signature of biological age, we analyzed metabolome, circulating senescence-associated secretome (SASP)/inflammation markers and the interaction between them, from a cohort of healthy and rapid agers. The balance between two fatty acid oxidation mechanisms, β-oxidation and ω-oxidation, associated with the extent of functional aging. Furthermore, a panel of 25 metabolites, Healthy Aging Metabolic (HAM) index, predicted healthy agers regardless of gender and race. HAM index was also validated in an independent cohort. Causal inference with machine learning implied three metabolites, β-cryptoxanthin, prolylhydroxyproline, and eicosenoylcarnitine as putative drivers of biological aging. Multiple SASP markers were also elevated in rapid agers. Together, our findings reveal that a network of metabolic pathways underlie biological aging, and the HAM index could serve as a predictor of phenotypic aging in humans.

Targeting vascular senescence in cardiovascular disease with aging

Aging is a major risk factor for atherosclerosis and cardiovascular disease (CVD). Two major age-associated arterial phenotypes, endothelial dysfunction and large elastic arterial stiffness, are autonomous predictors of future CVD diagnosis and contribute to the progression of CVD in older adults. Senescent cells lose the capacity to proliferate but remain metabolically active and secrete inflammatory factors termed senescence-associated secretory phenotype (SASP), leading to an increase in inflammation and oxidative stress. Accumulation of senescent cells is linked with the progression of age-related diseases and has been known to play a role in cardiovascular disease. In this brief review, we describe the characteristics and mechanisms of senescent cell accumulation and how senescent cells promote endothelial dysfunction and arterial stiffness. We focus on a range of novel therapeutic strategies aimed at reducing the burden of endothelial dysfunction leading to atherosclerosis through targeting senescent cells. Studies have begun to investigate a specific class of drugs that are able to selectively eliminate senescent cells, termed senolytics, which have shown great promise in reversing the aging phenotype and ameliorating pathologies in age-related disorders, creating a new opportunity for aging research. Generating therapies targeting the elimination of senescent cells would improve health span and increase longevity, making senolytics a promising therapy for cardiovascular diseases.