GDF15, an emerging key player in human aging

Exercise alters transcriptional profiles of senescence and gut barrier integrity in intestinal crypts of aging mice

Senescence is the gradual process of aging in tissues and cells, and a primary cause of aging-associated diseases. Among them, intestinal stem cells (ISCs) experience exhaustion during aging, leading to reduced regenerative capacity in the intestinal crypt, which impairs intestinal function and contributes to systemic health issues. Given the critical role ISCs play in maintaining intestinal homeostasis, preventing their senescence is essential for preserving intestinal function. Among the various strategies proposed to slow cellular senescence, regular exercise has emerged as one of the most well-known and widely accepted interventions. Here, we examined how exercise affects the small intestine in an aging mouse model. Using single-cell RNA sequencing, we found that signaling pathways and gene expression related to DNA replication and cell cycle progression were upregulated in ISCs. Additionally, genes promoting ribosome biogenesis showed increased expression in both ISCs and transit amplifying cells. Exercise also recovered Wnt signaling inhibition, potentially influencing ISC differentiation. Furthermore, exercise increased Reg3g expression in Paneth cells and improved gut barrier function, contrasting with findings from a diet-induced obese mouse model. This suggests that regular exercise helps inhibit the aging of ISCs in multiple ways, contributing to the maintenance of intestinal homeostasis.

Super-resolution imaging informed scRNA sequencing analysis reveals the critical role of GDF15 in rejuvenating aged hematopoietic stem cells

Although changes in mitochondrial morphology consistently associated with the aging of hematopoietic stem cells (HSCs), the specific molecular and cellular mechanisms involved are partially unclear. Live-cell super-resolution (SR) microscopy has been used to identify distinct HSC subsets that characterized by mitochondria unique morphologies and spatial distributions. The integration of SR microscopy with single-cell RNA sequencing enabled the classification of approximately 200 HSCs from young and aged mice into 5 discrete clusters. These clusters displayed molecular profiles that corresponded to the observed mitochondria states. An integrated approach combining RNA biomarker analysis and potential regulon assessment revealed previously unrecognized roles of GDF15 in mediating mitochondrial signals and morphologies that influence HSC fate. Thus, combining SR imaging with a bioinformatics pipeline provides an effective method for identifying key molecular players in specific phases of cellular transition, even with a relatively small dataset.

Age-Associated Increase in Growth Differentiation Factor 15 Levels Correlates With Central Arterial Stiffness and Predicts All-Cause Mortality in a Sardinian Population Cohort

BACKGROUND

Growth differentiation factor 15 (GDF-15) levels are emerging as a candidate biomarker of aging. The present study aimed to: (1) characterize the association of GDF-15 with the continuum of arterial stiffening, assessed as carotid-femoral pulse wave velocity, as age increases; (2) determine the predictive role of serum GDF-15 levels on mortality; and (3) identify genetic determinants of serum GDF-15 levels.

METHODS AND RESULTS

Serum levels of GDF-15 and established cardiovascular risk factors, including pulse wave velocity, were assessed in a large (4736 individual) Sardinian population. Serum levels of GDF-15, which can be reliably measured repeatedly over time, increase with age; are associated with a stiffer aorta; "mediate" a large proportion of the age-associated increase in arterial stiffness; pose risks because of their association with greater mortality; and are significantly associated with the variant rs11549407, which causes thalassemia major in homozygosity.

CONCLUSIONS

Because of its consistent ability to predict functional and clinical outcomes, including all-cause mortality, we conclude that GDF-15 serum levels serve as a robust biomarker for the continuum from health to the emergence of clinical disease during aging and, subsequently, to the likelihood of mortality.

Therapy-induced senescence is a transient drug resistance mechanism in breast cancer

BACKGROUND

Therapy-induced senescence (TIS) is considered a permanent cell cycle arrest following DNA-damaging treatments; however, its irreversibility has recently been challenged. Here, we demonstrate that escape from TIS is universal across breast cancer cells. Moreover, TIS provides a reversible drug resistance mechanism that ensures the survival of the population, and could contribute to relapse.

METHODS

TIS was induced in four different breast cancer cell line with high-dose chemotherapy and cultured until cells escaped TIS. Parental, TIS and repopulating cells were analyzed by bulk and single-cell RNA sequencing and surface proteomics. A genetically engineered mouse model of triple-negative breast cancer was used to prove why current senolytics cannot overcome TIS in tumors.

RESULTS

Screening the toxicity of a diverse panel of FDA-approved anticancer drugs revealed that TIS meditates resistance to half of these compounds, despite their distinct mechanism of action. Bulk and single-cell RNA sequencing, along with surface proteome analysis, showed that while parental and repopulating cells are almost identical, TIS cells are significantly different from both, highlighting their transient nature. Furthermore, investigating dozens of known drug resistance mechanisms offered no explanation for this unique drug resistance pattern. Additionally, TIS cells expressed a gene set associated with immune evasion and a potential KRAS-driven escape mechanism from TIS.

CONCLUSION

Our results reveal that TIS, as a transient drug resistance mechanism, could contribute to overcome the immune response and to relapse by reverting to a proliferative stage.

Metformin-mediated protection against Immunosenescence in diabetic cardiomyopathy: The potential roles of GDF-15 and klotho proteins

Diabetic cardiomyopathy (DCM) is a global health concern. However, studies examining the effect of metformin on diabetes-induced cardiac myocyte aging are lacking. This study aimed to investigate the protective effect of metformin against DCM involving modulation of macrophage phenotypes, growth differentiation factor-15 (GDF-15), and the anti-aging protein Klotho. Diabetes was induced in male Wistar rats using streptozotocin. Diabetic and nondiabetic rats were treated with metformin (200 mg/kg/day) and saline (control). DCM, inflammation, adhesion molecules, immunometabolic, and GDF-15 biomarkers were assessed using immunoassays. Western blotting was used to analyze Klotho expression. Macrophage phenotypes, senescence-associated-galactosidase (SA-β-gal), and p16INK4a were examined using immunohistochemistry, whereas the heart sections were histologically examined. The untreated diabetic rats showed increased serum troponin I and creatine kinase-MB levels, reflecting cardiac damage, which was confirmed via morphological changes and senescence. Klotho expression was decreased, indicating cardiac aging. Treatment with metformin reduced the heart weight-body weight ratio and lowered cardiac injury, inflammation, and adhesion molecule biomarker levels. It also reversed the histopathological changes induced by diabetes. It shifted macrophage polarization toward the M2 phenotype, decreased p16INK4a and SA-β-gal expression, and enhanced Klotho and GDF-15 expression. These findings revealed that diabetes induces cardiac aging by increasing senescence markers and decreasing the expression of Klotho. Metformin treatment protects against DCM by modulating macrophage phenotypes, attenuating immunosenescence-related dysregulation, and enhancing GDF-15 and Klotho expressions. Thus, metformin has potential clinical implications in alleviating DCM.

Serum Growth Differentiation Factor 15 is Negatively Associated with Leukocyte Telomere Length

BACKGROUND

Telomere length(TL)and mitochondrial DNA copy number(mtDNAcn) are classic biomarker of aging. Recently, growth differentiation factor 15(GDF15) has attracted considerable attention as a vital component in the aging process.

METHODS

The present study aimed to study the relationship between GDF15 and telomere length and mtDNAcn.This was a cross-sectional analysis nested in a longitudinal cohort study conducted in Changping District, Beijing, from 2014 to 2021. Serum GDF15,leukocyte lelomere length(LTL) and mtDNAcn were determined in 802 subjects.LTL and mtDNAcn was quantified by real-time PCR assay. Multivariate linear regression and restricted cubic spline diagram were used for statistical analysis.

RESULTS

Subjects with higher GDF15 were older,had larger waist circumference, higher systolic blood pressure and glycated hemoglobin A1c (HbA1c),shorter LTL and tended to had less mtDNAcn. In correlation analysis, GDF15 was positively correlated with age, while LTL and mtDNAcn were negatively correlated with age.After adjusting for confounding factors,GDF15 was negatively associated with LTL (β = -0.120, 95%CI [-0.197, -0.042], p = 0.003) and the association was linear(p for nonlinear = 0.645), while the negative association between GDF15 and mtDNAcn did not reach significance.In the stratified analyses,the negative associations between GDF15 and LTL were more prominent in women, overweight individuals, or subjects with abnormal glucose tolerance (AGT), but similar results were observed in younger and older subjects.

CONCLUSIONS

This study found a linear negative association between GDF 15 and LTL,which was more prominent in women, overweight or AGT subjects.These results supported that GDF15 might be a reliable biomarker of aging.

Cooperation between inhibitory immune checkpoints of senescent cells with immunosuppressive network to promote immunosenescence and the aging process

The accumulation of senescent cells within tissues promotes the aging process by remodelling the functions of the immune system. For many years, it has been known that senescent cells secrete pro-inflammatory cytokines and chemokines, a phenotype called the senescence-associated secretory phenotype (SASP). Chemokines and colony-stimulating factors stimulate myelopoiesis and recruit myeloid cells into aging tissues. Interestingly, recent studies have demonstrated that senescent cells are not only secretory but they also express an increased level of ligand proteins for many inhibitory immune checkpoint receptors. These ligands represent "don't eat me" markers in senescent cells and moreover, they are able to induce an exhaustion of many immune cells, such as surveying natural killer (NK) cells, cytotoxic CD8+ T cells, and macrophages. The programmed cell death protein-1 (PD-1) and its ligand PD-L1 represent the best known inhibitory immune checkpoint pathway. Importantly, the activation of inhibitory checkpoint receptors, e.g., in chronic inflammatory states, can also induce certain immune cells to differentiate toward their immunosuppressive phenotype. This can be observed in myeloid derived suppressor cells (MDSC), tissue regulatory T cells (Treg), and M2 macrophages. Conversely, these immunosuppressive cells stimulate in senescent cells the expression of many ligand proteins for inhibitory checkpoint receptors. Paradoxically, senescent cells not only promote the pro-inflammatory state but they maintain it at a low-grade level by expressing ligands for inhibitory immune checkpoint receptors. Thus, the cooperation between senescent cells and immunosuppressive cells enhances the senescence state of immune cells, i.e., immune senescence/exhaustion, and cellular senescence within tissues via bystander effects.

Soluble urokinase plasminogen activator receptor (suPAR) as a prognostic biomarker in acutely admitted patients with atrial fibrillation

Background

Atrial fibrillation (AF) is associated with a higher incidence of stroke, heart failure, and mortality. Risk assessment of clinical outcomes in patients hospitalized acutely with AF remains a challenge.

Purpose

To investigate if soluble urokinase plasminogen activator receptor (suPAR) levels at admission to the Emergency Department (ED) are associated with 1-year all-cause mortality in patients admitted with AF.

Methods

A prospective cohort study of patients consecutively admitted to the medical ED of a university hospital in Copenhagen, Denmark, between 2020 and 2022 with symptoms of COVID-19. Patients were included if they were admitted with AF as the primary or secondary diagnosis. All patients had suPAR measured at the index admission, and follow-up was up to 1 year. The association between suPAR and 1-year mortality was investigated with multivariate Cox regression. We adjusted for age, sex, smoking, C-reactive protein, creatinine, hemoglobin, albumin, and comorbidities.

Results

Of the 7,258 patients included during the period, 362 (5.0%) patients were admitted with AF as the primary or secondary diagnosis. Due to missing data, 23 (6.4%) patients were excluded. Among the remaining 339 patients, 68 (20.1%) patients were dead at follow-up. The multivariate Cox regression showed that elevated suPAR was independently associated with an increased risk of 1-year mortality, with a hazard ratio of 1.12 (95% confidence interval: 1.05-1.20, p < 0.001).

Conclusion

Elevated suPAR levels were significantly associated with 1-year all-cause mortality in patients acutely admitted with AF to the ED.

Targeting senescent hepatocytes for treatment of metabolic dysfunction-associated steatotic liver disease and multi-organ dysfunction

Senescent hepatocytes accumulate in metabolic dysfunction-associated steatotic liver disease (MASLD) and are linked to worse clinical outcomes. However, their heterogeneity and lack of specific markers have made them difficult to target therapeutically. Here, we define a senescent hepatocyte gene signature (SHGS) using in vitro and in vivo models and show that it tracks with MASLD progression/regression across mouse models and large human cohorts. Single-nucleus RNA-sequencing and functional studies reveal that SHGS+ hepatocytes originate from p21+ cells, lose key liver functions and release factors that drive disease progression. One such factor, GDF15, increases in circulation alongside SHGS+ burden and disease progression. Through chemical screening, we identify senolytics that selectively eliminate SHGS+ hepatocytes and improve MASLD in male mice. Notably, SHGS enrichment also correlates with dysfunction in other organs. These findings establish SHGS+ hepatocytes as key drivers of MASLD and highlight a potential therapeutic strategy for targeting senescent cells in liver disease and beyond.

Genetically supported targets and drug repurposing for brain aging: A systematic study in the UK Biobank

Brain age gap (BAG), the deviation between estimated brain age and chronological age, is a promising marker of brain health. However, the genetic architecture and reliable targets for brain aging remains poorly understood. In this study, we estimate magnetic resonance imaging (MRI)-based brain age using deep learning models trained on the UK Biobank and validated with three external datasets. A genome-wide association study for BAG identified two unreported loci and seven previously reported loci. By integrating Mendelian Randomization (MR) and colocalization analysis on eQTL and pQTL data, we prioritized seven genetically supported druggable genes, including MAPT, TNFSF12, GZMB, SIRPB1, GNLY, NMB, and C1RL, as promising targets for brain aging. We rediscovered 13 potential drugs with evidence from clinical trials of aging and prioritized several drugs with strong genetic support. Our study provides insights into the genetic basis of brain aging, potentially facilitating drug development for brain aging to extend the health span.

Growth and differentiation factor 15: An emerging therapeutic target for brain diseases

Growth and differentiation factor 15 (GDF15), a member of the transforming growth factor-βsuperfamily, is considered a stress response factor and has garnered increasing attention in recent years due to its roles in neurological diseases. Although many studies have suggested that GDF15 expression is elevated in patients with neurodegenerative diseases (NDDs), glioma, and ischemic stroke, the effects of increased GDF15 expression and the potential underlying mechanisms remain unclear. Notably, many experimental studies have shown the multidimensional beneficial effects of GDF15 on NDDs, and GDF15 overexpression is able to rescue NDD-associated pathological changes and phenotypes. In glioma, GDF15 exerts opposite effects, it is both protumorigenic and antitumorigenic. The causes of these conflicting findings are not comprehensively clear, but inhibiting GDF15 is helpful for suppressing tumor progression. GDF15 is also regarded as a biomarker of poor clinical outcomes in ischemic stroke patients, and targeting GDF15 may help prevent this disease. Thus, we systematically reviewed the synthesis, transcriptional regulation, and biological functions of GDF15 and its related signaling pathways within the brain. Furthermore, we explored the potential of GDF15 as a therapeutic target and assessed its clinical applicability in interventions for brain diseases. By integrating the latest research findings, this study provides new insights into the future treatment of neurological diseases.

Senescent alveolar type II epithelial cells-secreted GDF15 promotes silicosis progression via interfering intercellular communication

BACKGROUND

Silicosis is a chronic fibrotic pulmonary disease caused by consistent inhalation of respirable crystalline-free silica dust. The senescence of alveolar epithelial type II cells (ATII) is considered the initiation of pulmonary fibrosis. As a secreted protein, growth differentiation factor 15 (GDF15) was found intimately associated with the severity of lung diseases via senescence. Therefore, we speculate that GDF15 may involved in silica-induced pulmonary fibrosis.

METHODS

Co-culture was performed to observe the pro-fibrotic effect of GDF15, which is secreted from the silica-induced senescence ATII cells, on peripheral effector cells. We further explored GDF15-related signaling pathways via ChIP and IP assays. GDF15 siRNA lipid nanoparticles, anti-aging compound β-nicotinamide mononucleotide (NMN), and the Chinese traditional drug Bazibushen (BZBS) were used individually to intervene silicosis progress.

RESULTS

SiO2 and etoposide-stimulated MLE-12 cells showed senescence phenotype and secreted substantial GDF15, which is consistent with over-expressed GDF15 in lung tissues from silica-induced pulmonary fibrosis. The results further demonstrated that senescence ATII cells could facilitate co-cultured epithelial cell epithelial-mesenchymal transition (EMT) and fibroblast activation in a GDF15-dependent manner. Mechanistically, p53 regulates GDF15 transcription and secretion in senescence ATII cells. Moreover, secreted GFD15 performed its pro-fibrotic role by directly binding to TGF-βR via autocrine and paracrine manners. Also, lipid nanoparticles targeting GDF15 or cell senescence inhibitor NMN and BZBS showed efficient anti-fibrotic effects in vivo.

CONCLUSIONS

Our results elucidate that senescence ATII cell-secreted GDF15 plays a vital role in promoting silicosis by influencing surrounding cells, and provides scientific clues for the selection of potential therapeutic drugs for silicosis.

Impact of physical activity on physical function, mitochondrial energetics, ROS production, and Ca2+ handling across the adult lifespan in men

Aging-related muscle atrophy and weakness contribute to loss of mobility, falls, and disability. Mitochondrial dysfunction is widely considered a key contributing mechanism to muscle aging. However, mounting evidence positions physical activity as a confounding factor, making unclear whether muscle mitochondria accumulate bona fide defects with aging. To disentangle aging from physical activity-related mitochondrial adaptations, we functionally profiled skeletal muscle mitochondria in 51 inactive and 88 active men aged 20-93. Physical activity status confers partial protection against age-related decline in physical performance. Mitochondrial respiration remains unaltered in active participants, indicating that aging per se does not alter mitochondrial respiratory capacity. Mitochondrial reactive oxygen species (ROS) production is unaffected by aging and higher in active participants. In contrast, mitochondrial calcium retention capacity decreases with aging regardless of physical activity and correlates with muscle mass, performance, and the stress-responsive metabokine/mitokine growth differentiation factor 15 (GDF15). Targeting mitochondrial calcium handling may hold promise for treating aging-related muscle impairments.

Mapping the GDF15 Arm of the Integrated Stress Response in Human Cells and Tissues

Mitochondrial stress activates the integrated stress response (ISR) and triggers cell-cell communication through secretion of the metabokine growth differentiation factor 15 (GDF15). However, the gene network underlying the ISR remains poorly defined, particularly across metabolically diverse cellular states and tissues. Using RNAseq data from fibroblasts subjected to metabolic perturbations, we develop an ISR GDF15 index quantifying the GDF15 arm of the ISR activation in human cells. Validation of ISR GDF15 index across 44 postmortem human tissues illustrates how this index can be applied to investigate tissue-specific and age-related ISR activation.

Association between inflammatory biomarkers and the cognitive response to a multidomain intervention: secondary longitudinal analyses from the MAPT study

The aim of this study is to evaluate the association of systemic inflammation measured by plasma biomarkers with the change in cognitive function among participants from the Multidomain Alzheimer Preventive Trial (MAPT) exposed to the multidomain intervention (MI). Secondary analysis of the MAPT longitudinal data. MAPT is a randomized, placebo-controlled trial with 3 interventional groups (omega-3 only, MI only, omega-3 plus MI) and a control group. We tested the association of the change in cognitive function with inflammatory biomarkers (tumoral necrosis factor receptor-1 (TNFR1), monocyte chemoattractant protein-1 (MCP1), Growth Differentiation Factor-15 (GDF15), Interleukin-6 (IL6) and C reactive protein (CRP)) using mixed-effects models. A subgroup analysis was performed in those exposed to the MI. The response to the MI was defined as the change in the composite cognitive score over the 2-year clinical follow-up period. by modeling the response to the intervention and identifying "good responders", i.e., those in the 5th quintile of response at the end of the intervention period (2 years after the measurement of inflammatory markers). We included 1,527 participants (mean age 75.3, SD = 4.4; 64% female). Higher levels of GDF15 and TNFR1 were associated with a worse trajectory in the cognitive composite score in adjusted models. "Good responders" had an estimated mean change in the composite score of 0.051 (SD 0.062) over two years of intervention, compared to -0.136 (SD = 0.111) for the "not-good responders". Higher IL6 levels were associated with a decreased likelihood of being a "good responder" (OR = 0.22, p = 0.018, 95% CI 0.06; 0.78), with similar results for CRP (OR = 0.48, p = 0.009, 95% CI 0.28; 0.84). Higher inflammation was associated with a worse cognitive trajectory among nondemented participants and a lower likelihood of being classified as a "good responder" in those receiving a MI. Further confirmation of these findings could lead to the use of systemic inflammation as inclusion or stratification criteria in prevention trials.

Therapeutic Effects of GDF6-Overexpressing Mesenchymal Stem Cells through Upregulation of the GDF15/SIRT1 Axis in Age-Related Hearing Loss

BACKGROUND

It has been reported the therapeutic effects of mesenchymal stem cells (MSCs) on hearing loss. This study explored the therapeutic effects of growth differentiation factor 6 (GDF6) overexpression-induced MSCs (MSCs-GDF6) on age-related hearing loss (ARHL) and its underlying mechanisms.

METHODS

Reverse transcription-quantitative PCR and western blotting were used to evaluate gene expression. Flow cytometry and immunofluorescence assays were performed for the detection of apoptosis and autophagy, respectively. Hearing function and loss of outer hair cells (HCs) in ARHL rats were measured using the auditory brainstem response and cochlear silver nitrate staining, respectively. MSC proliferation was evaluated with the Cell Counting Kit-8 assay.

RESULTS

Growth differentiation factor 15 (GDF15) and sirtuin 1 (SIRT1) expression was significantly decreased in hydrogen peroxide (H2O2)-induced House Ear Institute-Organ of Corti 1 (HEI-OC1) cells and the cochlea of ARHL rats. Elevated apoptosis and blocked autophagic flux were uncovered in H2O2-induced HEI-OC1 cells and ARHL rats. GDF15 overexpression inhibited apoptosis and restored autophagic flux in vitro and in vivo. Meanwhile, GDF15 positively regulated SIRT1 protein expression. MSCs-GDF6 not only upregulated GDF15 and SIRT1 expression but also suppressed apoptosis and restored autophagic flux to reduce loss of HCs and hearing loss in ARHL rats.

CONCLUSIONS

MSCs-GDF6 prevented loss of HCs to relieve ARHL by inhibiting apoptosis and restoring autophagic flux, likely in association with upregulation of the GDF15/SIRT1 axis.

Geroscience in heart failure: the search for therapeutic targets in the shared pathobiology of human aging and heart failure

Age is a major risk factor for heart failure, but one that has been historically viewed as non-modifiable. Emerging evidence suggests that the biology of aging is malleable, and can potentially be intervened upon to treat age-associated chronic diseases, such as heart failure. While aging biology represents a new frontier for therapeutic target discovery in heart failure, the challenges of translating Geroscience research to the clinic are multifold. In this review, we propose a strategy that prioritizes initial target discovery in human biology. We review the rationale for starting with human omics, which has generated important insights into the shared (patho)biology of human aging and heart failure. We then discuss how this knowledge can be leveraged to identify the mechanisms of aging biology most relevant to heart failure. Lastly, we provide examples of how this human-first Geroscience approach, when paired with rigorous functional assessments in preclinical models, is leading to early-stage clinical development of gerotherapeutic approaches for heart failure.

Proteomics Reveals Age as Major Modifier of Inflammatory CSF Signatures in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Multiple sclerosis (MS) can start as relapsing or progressive. While their clinical features and treatment responses are distinct, it has remained uncertain whether their pathomechanisms differ. A notable age-related effect on MS phenotype and response to immunotherapies is well acknowledged, but the underlying pathophysiologic reasons are yet to be fully elucidated. We aimed to identify disease-specific and age-related proteomic signatures using a comprehensive targeted proteomic analysis.

METHODS

In our retrospective cohort study, we analyzed the CSF and serum proteome of age-matched individuals with treatment-naïve relapsing-remitting and primary progressive MS, neurologic controls (NC), and individuals with neuroborreliosis using targeted proteomics and validated findings in an independent cohort. Proteomic results were integrated with clinical and laboratory covariates.

RESULTS

Among 2,500 proteins, 47 CSF proteins were distinct between individuals with MS (n = 60) and NC (n = 20), with a subset also differing from those with neuroborreliosis (n = 8). We identified MS-associated proteins, including novel candidate biomarkers such as LY9 and JCHAIN, and putative treatment targets, such as SLAMF7, BCMA, and IL5RA, for which drugs are already licensed in other indications. The CSF proteome differences between relapsing and progressive MS were minimal, but major changes were noted in individuals older than 50 years, indicating a shift from MS-associated inflammatory to age-related protein signature. NEFL was the only serum protein that differed between individuals with MS and controls.

DISCUSSION

This study unveils a unique CSF proteomic signature in MS, providing new pathophysiologic insights and identifying novel biomarker candidates and potential therapeutic targets. Our findings highlight similar immunologic mechanisms in relapsing and progressive MS and underscore aging's profound effect on the intrathecal immune response. This aligns with the observed lower efficacy of immunotherapies in the elderly, thus emphasizing the necessity for alternative therapeutic approaches in treating individuals with MS beyond the age of 50.

Overexpression of Growth Differentiation Factor 15 Reduces Neuronal Cell Damage Induced by Oxygen-Glucose Deprivation/Reoxygenation via Inhibiting Endoplasmic Reticulum Stress-Mediated Ferroptosis

Growth differentiation factor 15 (GDF15) can be induced under various stress conditions. This study aimed to explore the role of GDF15 in oxygen-glucose deprivation/reoxygenation (OGD/R)-induced HT22 cells. OGD/R was employed to induce the HT22 cell model, and GDF15 expression was upregulated via transfection. Subsequently, the effects on inflammatory factors, oxidative stress markers, apoptosis-related proteins, and ferroptosis markers were detected. Relevant indicators were evaluated using techniques such as ELISA, probes, flow cytometry, and western blotting. Furthermore, changes in these phenotypes under the influence of the endoplasmic reticulum (ER) stress agonist tunicamycin (TM) were evaluated. The result showed that GDF15 was significantly up-regulated in OGD/R-treated HT22 cells. Overexpression of GDF15 significantly reduced the levels of inflammatory factors tumor necrosis factor-α, IL (interleukin)-1β, and IL-6, inhibited the production of reactive oxygen species and MDA, and improved activity of superoxide dismutase and GSH-Px. Flow cytometry and western blotting results showed that GDF15 overexpression significantly reduced cell apoptosis, reduced caspase3 activity, and regulated the expression of Bcl2 and Bax. In addition, overexpression of GDF15 reduces the levels of ferroptosis markers by inhibiting ER stress. ER stress inducer TM can reverse the protective effects of GDF15 overexpression and promote inflammation, oxidative stress, and apoptosis. This study shows that overexpression of GDF15 reduces OGD/R-induced HT22 cell damage, and ER stress-mediated ferroptosis is included in the regulatory mechanisms. This provides a theoretical basis for GDF15 as a new target for the treatment of cerebral ischemia-reperfusion injury.

Plasma proteomics identify biomarkers and undulating changes of brain aging

Proteomics enables the characterization of brain aging biomarkers and discernment of changes during brain aging. We leveraged multimodal brain imaging data from 10,949 healthy adults to estimate brain age gap (BAG), an indicator of brain aging. Proteome-wide association analysis across 4,696 participants of 2,922 proteins identified 13 significantly associated with BAG, implicating stress, regeneration and inflammation. Brevican (BCAN) (β = -0.838, P = 2.63 × 10-10) and growth differentiation factor 15 (β = 0.825, P = 3.48 × 10-11) showed the most significant, and multiple, associations with dementia, stroke and movement functions. Dysregulation of BCAN affected multiple cortical and subcortical structures. Mendelian randomization supported the causal association between BCAN and BAG. We revealed undulating changes in the plasma proteome across brain aging, and profiled brain age-related change peaks at 57, 70 and 78 years, implicating distinct biological pathways during brain aging. Our findings revealed the plasma proteomic landscape of brain aging and pinpointed biomarkers for brain disorders.

The mitochondrial integrated stress response: A novel approach to anti-aging and pro-longevity

The ISR is a cellular signaling pathway that responds to various physiological changes and types of stimulation. The mitochondrial integrated stress response (ISRmt) is a stress response specific to mitochondria which is initiated by eIF2α phosphorylation and is responsive to mitochondrial stressors. The ISRmt triggers diverse metabolic responses reliant on activating transcription factor 4 (ATF4). The preliminary phases of ISRmt can provoke an adaptive stress response that antagonizes age-related diseases and promotes longevity. In this review, we provide an overview of the molecular mechanisms of the ISRmt, with a particular focus on its potential as a therapeutic target for age-related disease and the promotion of longevity.

Epilepsy and brain health: a large prospective cohort study

BACKGROUND

Epilepsy, as a chronic noncommunicable disease with recurrent seizures, may be a marker of deterioration or alteration in other underlying neurological diseases. This study aimed to investigate the relationship of epilepsy with brain function, other common brain disorders, and their underlying mechanisms.

METHODS

The study was based on clinical diagnostic and test data from 426,527 participants in the UK Biobank, of whom 3,251 were diagnosed with epilepsy at baseline. Multiple linear and Cox regression models were used to explore the association between epilepsy, brain function, and other brain disorders.

RESULTS

This study demonstrated consistent deleterious effects of epilepsy on cognitive and motor function and mental health. The risk of neurological diseases and psychiatric disorders was significantly elevated in the epilepsy population during the 17-year follow-up period, according to the longitudinal analysis. We also identified several brain regions associated with epilepsy, including the pallidum, hippocampus, and precentral regions. Mediation analyses revealed mediating effects of peripheral markers and proteins (e.g., GGT, HDL, ACE2, and GDF15), suggesting that liver function and lipid metabolism may be involved in the development of other brain disorders in individuals with epilepsy.

CONCLUSIONS

Our study provides robust evidence of the association between epilepsy and poor brain health, underscoring the importance of early intervention for epilepsy.

Increased GDF-15 in chronic male patients with schizophrenia: correlation with body mass index and cognitive impairment

Growth Differentiation Factor-15 (GDF-15) is a pleiotropic cytokine that plays a significant role in metabolism and inflammation. Elevated serum levels of GDF-15 have been associated with mood disorders. We propose that GDF-15 may potentially influence cognitive impairment and metabolism in male patients with chronic schizophrenia (CS), although there is limited research on this topic. This study compared serum GDF-15 levels in 72 male patients with CS and 85 healthy controls (HC). The severity of psychotic symptoms was assessed using the Positive and Negative Syndrome Scale (PANSS), while cognitive performance was evaluated with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The male CS patients performed worse than the healthy controls in both the total score and all subscales of the RBANS. Serum GDF-15 concentrations were significantly higher in the male CS patients compared to the healthy controls. Furthermore, the log-transformed serum GDF-15 concentrations in male CS patients were positively correlated with BMI and negatively correlated with Delayed Memory scores, Immediate Memory, and the total RBANS score. This preliminary study suggests that elevated serum GDF-15 levels in male patients with chronic schizophrenia may play a role in cognitive function and BMI regulation.

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.

Targeting the GDF15 Signalling for Obesity Treatment: Recent Advances and Emerging Challenges

The growth differentiation factor 15 (GDF15)-glial cell-derived neurotrophic factor family receptor alpha-like (GFRAL) pathway plays a crucial role in the regulation of metabolism, appetite and body weight control. Obesity is an increasingly prevalent chronic disease worldwide, necessitating effective treatment strategies. Recent preclinical and clinical studies have highlighted that targeting the GDF15-GFRAL signalling pathway is a promising approach for treating obesity, particularly because it has minimal impact on skeletal muscle mass, which is essential to preserve during weight loss. Given its distinctive mechanisms, the GDF15-GFRAL axis represents an attractive target for addressing various metabolic disorders, especially obesity. In this review, we will explore how the GDF15-GFRAL axis is regulated, its distribution in the body and its role in the regulation of metabolism, appetite and obesity. Additionally, we will discuss recent advances and potential challenges in targeting the GDF15-GFRAL axis for obesity treatment.

GDF15 propeptide promotes bone metastasis of castration-resistant prostate cancer by augmenting the bone microenvironment

BACKGROUND

Bone metastasis (BM) is a common and fatal condition in patients with castration-resistant prostate cancer (CRPC). However, there are no useful blood biomarkers for CRPC with BM, and the mechanism underlying BM is unclear. In this study, we investigated precise blood biomarkers for evaluating BM that can improve the prognosis of patients with CRPC.

METHODS

We comprehensively examined culture supernatants from four prostate cancer (PCa) cell lines using Orbitrap mass spectrometry to identify specific proteins secreted abundantly by PCa cells. The effects of this protein to PCa cells, osteoblasts, osteoclasts were examined, and BM mouse model. In addition, we measured the plasma concentration of this protein in CRPC patients for whom bone scan index (BSI) by bone scintigraphy was performed.

RESULTS

A total of 2,787 proteins were identified by secretome analysis. We focused on GDF15 propeptide (GDPP), which is secreted by osteoblasts, osteoclasts, and PCa cells. GDPP promoted the proliferation, invasion, and migration of PC3 and DU145 CRPC cells, and GDPP aggravated BM in a mouse model. Importantly, GDPP accelerated bone formation and absorption in the bone microenvironment by enhancing the proliferation of osteoblasts and osteoclasts by upregulating individual transcription factors such as RUNX2, OSX, ATF4, NFATc1, and DC-STAMP. In clinical settings, including a total of 416 patients, GDPP was more diagnostic of BM than prostate-specific antigen (PSA) (AUC = 0.92 and 0.78) and the seven other blood biomarkers (alkaline phosphatase, lactate dehydrogenase, bone alkaline phosphatase, tartrate-resistant acid phosphatase 5b, osteocalcin, procollagen I N-terminal propeptide and mature GDF15) in patients with CRPC. The changes in BSI over time with systemic treatment were correlated with that of GDPP (r = 0.63) but not with that of PSA (r = -0.16).

CONCLUSIONS

GDPP augments the tumor microenvironment of BM and is a novel blood biomarker of BM in CRPC, which could lead to early treatment interventions in patients with CRPC.

Older patients affected by COVID-19: investigating the existence of biological phenotypes

INTRODUCTION

COVID-19 provides an opportunity to examine biological phenotypes (observable morphological, functional and biological characteristics) in individuals who experience the same acute condition, potentially revealing differences in response to acute external stressors. The aim our study was to investigate biological phenotypes in older patients hospitalized for COVID-19, exploiting a panel of aging biomarkers.

METHODS

Data were gathered from the FRACOVID Project, an observational multicenter study, aimed to evaluate the impact of frailty on health-related outcomes in patients 60 + with COVID-19 in Northern Italy. A hierarchical cluster analysis was run using log-transformed and scaled values of TNF-a, IL-1 beta, IL-6, PAI-1, GDF-15, NT-proBNP, and Cystatin C evaluated at admission.

RESULTS

Eighty-one participants (mean age 75.3 years; 60.5% male) were evaluated. Frailty was identified in 42% of the sample and 27.2% were unable to ambulate outdoors. The mean hospital stay was 24.7 days, with an in-hospital mortality rate of 18.5%. Three biological phenotypes were found: (1) 'inflammatory', with high inflammatory biomarkers; (2) 'organ dysfunction', characterized by elevated cystatin C and NT-proBNP, and lower inflammatory markers; and (3) 'unspecific', with lower NT-proBNP and GDF-15 levels, and intermediate concentrations of other biomarkers. The 'organ dysfunction' phenotype showed the highest mean age and prevalence of frailty, disability, and chronic diseases. The 'inflammatory' phenotype showed the highest burden of respiratory and systemic signs and symptoms of infection.

CONCLUSION

Biological phenotypes might be used to identify different clinical and functional phenotypes in individuals affected by COVID-19.

Is age more than a number? Accounting for adult development and aging in the study of psychoneuroimmunology, stress, and health

Traditional stress-and-health models link stressors to their health consequences through a well-characterized cascade. Most of the research assumes that the stress-health sequence unfolds in the same way across adulthood, whether a person is 25 years old or 80. Taking a "developmental" or "lifespan" approach has been synonymous with studying the lasting health impacts of early life experiences. However, theories and evidence from adult development and geroscience suggest that stress-health dynamics evolve in important ways over the adult lifespan-from the stressors that we encounter, to the emotion regulation strategies that we use to confront challenges, to the psychosocial resources at our disposal, to the cellular milieu, and thus to the magnitude of stressors' biological and functional consequences. This critical review synthesizes theoretical perspectives and selected empirical literature on the social-emotional and biological dimensions of aging to promote an Integrative Model of Aging, Stress, and Health. Through this integration, the model illustrates how an interdisciplinary, developmental perspective can enrich our understanding of stress's consequences for health across adulthood. It also seeks to guide a new generation of research questions that confront aging with a multidimensional approach. The piece concludes with personal reflections on the foundational legacy of the author's mentor, Dr. Janice Kiecolt-Glaser.

GDF-15 and mtDNA Deletions Are Useful Biomarkers of Mitochondrial Dysfunction in Insulin Resistance and PCOS

There is no literature available about the growth differentiation factor-15 (GDF-15) biomarker in combination with mitochondrial DNA (mtDNA) deletions in insulin resistance (IR), and polycystic ovary syndrome (PCOS); however, it would be useful to achieve optimal metabolic status and improve pregnancy success. In this study, the role of GDF-15 and mtDNA deletions as biomarkers in the pathogenesis of IR and PCOS was investigated. In our study, 81 female patients who were treated for IR and/or PCOS and 41 healthy controls were included. GDF-15 levels in patients showed a marked increase compared to controls. Elevated GDF-15 levels were found in 12 patients; all of them had a BMI > 25 kg/m2, which is associated with reactive hyperinsulinemia. The presence of mitochondrial dysfunction was mainly observed in the IR-only subgroup. The increase in plasma levels of GDF-15 and the prevalence of mtDNA deletions is directly proportional to body mass index. The more marked metabolic abnormalities required more intensive drug therapy with a parallel increase in plasma GDF-15 levels. Elevated levels of GDF-15 and the presence of mitochondrial DNA deletions may be a consequence of carbohydrate metabolism disorders in patients and thus a predictor of the process of accelerated aging.

Transcription factor EGR2 alleviates autoimmune uveitis via activation of GDF15 to modulate the retinal microglial phenotype

Uveitis is a vision-threatening disease primarily driven by a dysregulated immune response, with retinal microglia playing a pivotal role in its progression. Although the transcription factor EGR2 is known to be closely associated with uveitis, including Vogt-Koyanagi-Harada disease and Behcet's disease, and is essential for maintaining the dynamic homeostasis of autoimmunity, its exact role in uveitis remains unclear. In this study, diminished EGR2 expression was observed in both retinal microglia from experimental autoimmune uveitis (EAU) mice and inflammation-induced human microglia cell line (HMC3). We constructed a mice model with conditional knockout of EGR2 in microglia and found that EGR2 deficiency resulted in increased intraocular inflammation. Meanwhile, EGR2 overexpression downregulated the expression of inflammatory cytokines as well as cell migration and proliferation in HMC3 cells. Next, RNA sequencing and ChIP-PCR results indicated that EGR2 directly bound to its downstream target growth differentiation factor 15 (GDF15) and further regulated GDF15 transcription. Furthermore, intravitreal injection of GDF15 recombinant protein was shown to ameliorate EAU progression in vivo. Meanwhile, knockdown of GDF15 reversed the phenotype of EGR2 overexpression-induced microglial inflammation in vitro. In summary, this study highlighted the protective role of the transcription factor EGR2 in AU by modulating the microglial phenotype. GFD15 was identified as a downstream target of EGR2, providing a unique target for uveitis treatment.

Exosomes Derived from Meningitic Escherichia coli-Infected Brain Microvascular Endothelial Cells Facilitate Astrocyte Activation

Numerous studies have shown that exosomes play a regulatory role in a variety of biological processes as well as in disease development and progression. However, exosome-mediated intercellular communication between brain microvascular endothelial cells (BMECs) and astrocytes during meningitic Escherichia coli (E. coli)-induced neuroinflammation remains largely unknown. Here, by using in vivo and in vitro models, we demonstrate that exosomes derived from meningitic E. coli-infected BMECs can activate the inflammatory response of astrocytes. A label-free quantitation approach coupled with LC-MS/MS was used to compare the exosome proteomic profiles of human BMECs (hBMECs) in response to meningitic E. coli infection. A total of 57 proteins exhibited significant differences in BMEC-derived exosomes during the infection. Among these proteins, growth differentiation factor 15 (GDF15) was significantly increased in BMEC-derived exosomes during the infection, which triggered the Erk1/2 signaling pathway and promoted the activation of astrocytes. The identification and characterization of exosome protein profiles in BMECs during meningitic E. coli infection will contribute to the understanding of the underlying pathogenic mechanisms from the perspective of intercellular communication between BMECs and astrocytes, and provide new insights for future prevention and treatment of E. coli meningitis.

Association between serum levels of GDF-15, suPAR, PIVKA-II, sdLDL and clinical outcomes in hospitalized COVID-19 patients

To quantify the circulating levels of novel serum biomarkers including GDF-15, PIVKA-II, sdLDL, suPAR, and of CRP in hospitalized COVID-19 patients compared with healthy subjects, and to evaluate their association(s) with outcomes in COVID-19. We considered patients with confirmed COVID-19, hospitalized in an Internal Medicine ward. The clinical characteristics were collected, including the number and type of comorbidities. Serum levels of GDF-15, PIVKA-II, suPAR, sdLDL, as well as CRP were measured. As outcomes, we considered Intensive Care Unit (ICU) transfer or death, as well as the length of stay (days) and in-hospital complications. Data were statistically analyzed, as appropriate, and a p value < 0.05 was considered significant. Ninety-three patients and 20 healthy controls were enrolled. COVID-19 patients vs. controls showed higher median levels of GDF-15 (p < 0.0001), PIVKA-II (p < 0.0001) and sdLDL (p = 0.0002), whereas no difference was observed for suPAR. In COVID-19 patients, the most frequent comorbidities were arterial hypertension (62.4%) and cardiovascular disease (30.1%). GDF-15 levels positively correlated with age (r = 0.433, p < 0.0001), and this correlation was confirmed for suPAR (r = 0.308, p = 0.003) and CRP (Rho = 0.40 p < 0.0001), but not for PIVKA-II and sdLDL. Higher GDF-15 levels were associated with a higher number of comorbidities (p = 0.021). The median length of stay was 22 (15; 30) days. During hospitalization, 15 patients (16%) were ICU transferred, and 6 (6.45%) died. GDF-15 serum levels correlated with the length of stay (rho = 0.27 p = 0.010), and were associated with ICU transfer or death (p = 0.003), as well as PIVKA-II (p = 0.038) and CRP (p < 0.001). Moreover, higher GDF-15 and PIVKA-II serum levels were associated with infectious complications (p = 0.008 and p = 0.017, respectively). In this cohort of hospitalized COVID-19 patients, novel inflammatory biomarkers, including GDF-15, suPAR and PIVKA II were associated with some patient's clinical characteristics, complications, and poor outcomes.

Neutralizing antibody against GDF15 for treatment of cancer-associated cachexia

GDF15 (growth differentiation factor 15), also known as macrophage inhibitory cytokine 1 (MIC-1), is a circulating protein involved in the regulation of energy balance and weight control. Elevated levels of GDF15 have been associated with cachexia and reduced survival rates in cancer patients. Through the activation of the GFRAL (GDNF-family receptor α-like)-RET (Rearranged during Transfection) signaling pathway, GDF15 can induce weight loss, making it a potential target for treating cachexia. Currently, there are no approved antibody drugs specifically targeting GDF15 for cancer cachexia treatment. However, efforts have been made to develop antibody-based therapeutics against this emerging target. In this study, we generated a monoclonal antibody KY-NAb-GDF15 against GDF15 that effectively blocks downstream signaling mediated by GFRAL upon stimulation by GDF15. This antibody demonstrates robust neutralizing activity and exhibits high binding specificity. Importantly, our findings indicate that this antibody holds promise in alleviating cancer-induced cachexia and mitigating chemotherapy-induced weight loss, thereby offering significant therapeutic potential for managing cancer cachexia.

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.

Biomarkers in Heart Failure with Preserved Ejection Fraction: A Perpetually Evolving Frontier

Heart failure with preserved ejection fraction (HFpEF) represents a complex clinical syndrome, often very difficult to diagnose using the available tools. As the global burden of this disease is constantly growing, surpassing the prevalence of heart failure with reduced ejection fraction, during the last few years, efforts have focused on optimizing the diagnostic and prognostic pathways using an immense panel of circulating biomarkers. After the paradigm of HFpEF development emerged more than 10 years ago, suggesting the impact of multiple comorbidities on myocardial structure and function, several phenotypes of HFpEF have been characterized, with an attempt to find an ideal biomarker for each distinct pathophysiological pathway. Acknowledging the limitations of natriuretic peptides, hundreds of potential biomarkers have been evaluated, some of them demonstrating encouraging results. Among these, soluble suppression of tumorigenesis-2 reflecting myocardial remodeling, growth differentiation factor 15 as a marker of inflammation and albuminuria as a result of kidney dysfunction or, more recently, several circulating microRNAs have proved their incremental value. As the number of emerging biomarkers in HFpEF is rapidly expanding, in this review, we aim to explore the most promising available biomarkers linked to key pathophysiological mechanisms in HFpEF, outlining their utility for diagnosis, risk stratification and population screening, as well as their limitations.

Growth differentiation factor 15 (GDF15) levels are associated with malnutrition in acutely admitted older adults

BACKGROUND AND AIMS

The aging process is often accompanied by high risk of malnutrition and elevated levels of growth differentiation factor 15 (GDF15). GDF15 is an increasingly recognized biomarker for regulation of metabolism, but few studies have investigated the connection between GDF15 and malnutrition in older age and how it relates to other features of aging such as decreased appetite and physical function. Therefore, we investigated the associations between GDF15 levels and nutritional status, appetite, and physical function in acutely admitted older adults.

METHODS

Plasma GDF15 levels were measured using immunoassays in 302 older adults (≥65 years) admitted to the emergency department (ED). Nutritional status was evaluated with the Mini Nutritional Assessment Short-Form (MNA®-SF), appetite was evaluated with the Simplified Nutritional Appetite Questionnaire (SNAQ), and physical function was evaluated with handgrip strength (HGS), 30-s chair stand test (30s-RSS), and gait speed (GS). Associations between GDF15 and each outcome was determined by logistic regression adjusted for age, sex, and C-reactive protein (CRP).

RESULTS

Each doubling in plasma GDF15 level was associated with an adjusted odds ratio (OR) (95% confidence interval) of 1.59 (1.10-2.29, P = 0.01) for risk of malnutrition compared to normal nutrition and 1.19 (0.85-1.69, P = 0.3)) for malnutrition compared to risk of malnutrition. Each doubling in GDF15 was associated with an adjusted OR of 1.63 (1.21-2.23)) for having poor appetite, 1.46 (1.07-1.99) for having low HGS, 1.74 (1.23-2.51) for having low 30s-RSS, and 1.99 (1.39-2.94) for having low GS.

CONCLUSION

Among older adults admitted to the ED, higher GDF15 levels were significantly associated with malnutrition, poor appetite, and low physical function independent of age, sex, and CRP.

p16High immune cell - controlled disease tolerance as a broad defense and healthspan extending strategy

The ability of an organism to overcome infectious diseases has traditionally been linked to killing invading pathogens. Accumulating evidence, however, indicates that, apart from restricting pathogen loads, organismal survival is coupled to an additional yet poorly understood mechanism called disease tolerance. Here we report that p16High immune cells play a key role in establishing disease tolerance. We found that the FDA-approved BNT162b2 mRNA COVID-19 vaccine is a potent and rapid inducer of p16High immune subsets both in mice and humans. In turn, p16High immune cells were indispensable for counteracting different lethal conditions, including LPS-induced sepsis, acute SARS-CoV-2 infection and ionizing irradiation. Mechanistically, we propose that activation of TLR7 or a low physiological activity of STING is sufficient to induce p16High immune subset that, in turn, establishes a low adenosine environment and disease tolerance. Furthermore, containing these signals within a beneficial range by deleting MDA5 that appeared sufficient to maintain a low activity of STING, induces p16High immune cells and delays organ deterioration upon aging with improved healthspan. Our data highlight the beneficial role of p16High immune subsets in establishing a low adenosine environment and disease tolerance.

Overview of growth differentiation factor 15 (GDF15) in metabolic diseases

GDF15 is a stress response cytokine and a distant member of the transforming growth factor beta (TGFβ) superfamily, its levels increase in response to cell stress and certain diseases in the serum. To exert its effects, GDF15 binds to glial-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL), which was firstly identified in 2017 and highly expressed in the brain stem. Many studies have demonstrated that elevated serum GDF15 is associated with anorexia and weight loss. Herein, we focus on the biology of GDF15, specifically how this circulating protein regulates appetite and metabolism in influencing energy homeostasis through its actions on hindbrain neurons to shed light on its impact on diseases such as obesity and anorexia/cachexia syndromes. It works as an endocrine factor and transmits metabolic signals leading to weight reduction effects by directly reducing appetite and indirectly affecting food intake through complex mechanisms, which could be a promising target for the treatment of energy-intake disorders.

Metabolomic signatures of inflammation and metabolic dysregulation in relation to colorectal cancer risk

BACKGROUND

Inflammation and metabolic dysregulation are associated with increased risk of colorectal cancer (CRC); the underlying mechanisms are not fully understood. We characterized metabolomic signatures of inflammation and metabolic dysregulation and evaluated the association of the signatures and individual metabolites with CRC risk.

METHODS

Among 684 incident CRC cases and 684 age-matched controls in the Nurses' Health Study (n = 818 women) and Health Professionals Follow-up Study (n = 550 men), we applied reduced rank and elastic net regression to 277 metabolites for markers of inflammation (C-reactive protein, interleukin 6, tumor necrosis factor receptor superfamily member 1B, and growth differentiation factor 15) or metabolic dysregulation (body mass index, waist circumference, C-peptide, and adiponectin) to derive metabolomic signatures. We evaluated the association of the signatures and individual metabolites with CRC using multivariable conditional logistic regression. All statistical tests were 2-sided.

RESULTS

We derived a signature of 100 metabolites that explained 24% of variation in markers of inflammation and a signature of 73 metabolites that explained 27% of variation in markers of metabolic dysregulation. Among men, both signatures were associated with CRC (odds ratio [OR] = 1.34, 95% confidence interval [CI] = 1.07 to 1.68 per 1-standard deviation increase, inflammation; OR = 1.25, 95% CI = 1.00 to 1.55 metabolic dysregulation); neither signature was associated with CRC in women. A total of 11 metabolites were individually associated with CRC and biomarkers of inflammation or metabolic dysregulation among either men or women.

CONCLUSION

We derived metabolomic signatures and identified individual metabolites associated with inflammation, metabolic dysregulation, and CRC, highlighting several metabolites as promising candidates involved in the inflammatory and metabolic dysregulation pathways for CRC incidence.

Prognostic significance of growth differentiation factor-15 across age in chronic heart failure

AIMS

Growth differentiation factor-15 (GDF15), a cytokine in the transforming growth factor family, is up-regulated in stress and inflammatory conditions and is elevated in patients with heart failure (HF). However, the age-specific attributes and prognostic significance of GDF15 across age remain unknown in chronic HF (CHF).

METHODS AND RESULTS

Serum levels of GDF15 were examined in 942 hypertensive patients (median 68 years) with CHF from the SUPPORT trial across the four age groups [under 50 (n = 73), 51-59 (n = 158), 60-69 (n = 296), and 70-79 years (n = 415)] and in the continuous spectrum. Clinical correlates of GDF15 were explored using the classic stepwise and LASSO (least absolute shrinkage and selection operator) regression approaches. Interaction terms with age were tested in the LASSO regression approach. The associations with the composite outcome of HF hospitalization or all-cause death were investigated across ages. Median GDF15 levels (pg/mL) increased along with aging, from 691 in under 50 years to 855 in 51-59 years, 1114 in 60-69 years, and 1516 in 70-79 years (trend P < 0.001). Age, sex, systolic blood pressure, history of diabetes, ischaemic heart disease, left ventricular (LV) end-systolic dimension, LV ejection fraction, estimated glomerular filtration rate, haemoglobin, N-terminal pro-brain natriuretic peptide (NT-proBNP), troponin, C-reactive protein, and the use of angiotensin-converting enzyme inhibitors, diuretics, and statins were mutually selected as clinical covariates of GDF15. The LASSO regression analysis identified significant interactions between age and the history of diabetes and NT-proBNP, with particularly robust associations in patients aged between 60 and 70 years. During the mean follow-up of 8.6 years, 474 composite endpoints of HF hospitalization or death occurred. GDF15 was associated with a higher risk of HF hospitalization or all-cause death [adjusted hazard ratio 1.84 (95% confidence interval 1.45-2.33)], with a particularly heightened risk in patients aged around 70 years (Pinteraction = 0.0008). The model with GDF15 on top of other established risk factors yielded marginally higher C-statistics compared with the model without GDF15 (0.803 and 0.796, P = 0.045). The additive value of GDF15 on top of other established risk factors appeared similar across ages. A universal cut-off value of 1400 pg/mL performed well in discriminating between those with and without HF hospitalization or death.

CONCLUSIONS

Some clinical correlates of GDF15 have an interaction with age. GDF15 is an important determinant of cardiovascular endpoints, particularly in patients aged around 70 years. The additive value of GDF15 appeared consistent across ages, suggesting the use of a universal cut-off value.

Different roles of circulating and intramuscular GDF15 as markers of skeletal muscle health

Introduction

Growth Differentiation Factor 15 (GDF15) is a mitokine expressed in response to various stresses whose circulating levels increase with age and are associated with numerous pathological conditions, including muscle wasting and sarcopenia. However, the use of circulating GDF15 (c-GDF15) as a biomarker of sarcopenia is still debated. Moreover, the role of GDF15 intracellular precursor, pro-GDF15, in human skeletal muscle (SM-GDF15) is not totally understood. In order to clarify these points, the association of both forms of GDF15 with parameters of muscle strength, body composition, metabolism and inflammation was investigated.

Methods

the levels of c-GDF15 and SM-GDF15 were evaluated in plasma and muscle biopsies, respectively, of healthy subjects (HS) and patients with lower limb mobility impairment (LLMI), either young (<40 years-old) or old (>70 years-old). Other parameters included in the analysis were Isometric Quadriceps Strength (IQS), BMI, lean and fat mass percentage, Vastus lateralis thickness, as well as circulating levels of Adiponectin, Leptin, Resistin, IGF-1, Insulin, IL6, IL15 and c-PLIN2. Principal Component Analysis (PCA), Canonical Discriminant Analysis (CDA) and Receiving Operating Characteristics (ROC) analysis were performed.

Results

c-GDF15 but not SM-GDF15 levels resulted associated with decreased IQS and IGF-1 levels in both HS and LLMI, while only in LLMI associated with increased levels of Resistin. Moreover, in LLMI both c-GDF15 and SM-GDF15 levels were associated with IL-6 levels, but interestingly SM-GDF15 is lower in LLMI with respect to HS. Furthermore, a discrimination of the four groups of subjects based on these parameters was possible with PCA and CDA. In particular HS, LLMI over 70 years or under 40 years of age were discriminated based on SM-GDF15, c-GDF15 and Insulin levels, respectively.

Conclusion

our data support the idea that c-GDF15 level could be used as a biomarker of decreased muscle mass and strength. Moreover, it is suggested that c-GDF15 has a different diagnostic significance with respect to SM-GDF15, which is likely linked to a healthy and active state.

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.

Downregulation of PLIN2 in human dermal fibroblasts impairs mitochondrial function in an age-dependent fashion and induces cell senescence via GDF15

Perilipin 2 (PLIN2) is a lipid droplet (LD)-coating protein playing important roles in lipid homeostasis and suppression of lipotoxicity in different tissues and cell types. Recently, a role for PLIN2 in supporting mitochondrial function has emerged. PLIN2 dysregulation is involved in many metabolic disorders and age-related diseases. However, the exact consequences of PLIN2 dysregulation are not yet completely understood. In this study, we knocked down (KD) PLIN2 in primary human dermal fibroblasts (hDFs) from young (mean age 29 years) and old (mean age 71 years) healthy donors. We have found that PLIN2 KD caused a decline of mitochondrial function only in hDFs from young donors, while mitochondria of hDFs from old donors (that are already partially impaired) did not significantly worsen upon PLIN2 KD. This mitochondrial impairment is associated with the increased expression of the stress-related mitokine growth differentiation factor 15 (GDF15) and the induction of cell senescence. Interestingly, the simultaneous KD of PLIN2 and GDF15 abrogated the induction of cell senescence, suggesting that the increase in GDF15 is the mediator of this phenomenon. Moreover, GDF15 KD caused a profound alteration of gene expression, as observed by RNA-Seq analysis. After a more stringent analysis, this alteration remained statistically significant only in hDFs from young subjects, further supporting the idea that cells from old and young donors react differently when undergoing manipulation of either PLIN2 or GDF15 genes, with the latter being likely a downstream mediator of the former.

Nausea, vomiting and conflict in pregnancy: The adaptive significance of Growth-Differentiation Factor 15

Nausea and vomiting in pregnancy (NVP) is heritable, common and aversive, and its extreme, hyperemesis gravidarum (HG), can be highly deleterious to the mother and fetus. Recent influential studies have demonstrated that HG is caused predominantly by high levels of Growth-Differentiation Factor 15 (GDF15), a hormone produced by the placenta in substantial amounts. This work has led to calls for therapeutic modulation of this hormone to reduce GDF15 levels and ameliorate HG risk. I describe three main lines of evidence relevant to the hypothesis that GDF15 production is typically adaptive for the fetus, in the context of enhanced placental invasion, reduced rates of miscarriage and preterm birth and higher birth weight. These considerations highlight the medical implications of maternal-fetal conflict, in the context of tradeoffs between aversive symptoms during gestation, rare disorders of pregnancy with major adverse effects and moderate fitness-enhancing benefits to fetuses.

Proteomics validate circulating GDF-15 as an independent biomarker for COVID-19 severity

Introduction

Growth differentiation factor 15 (GDF-15) was originally described as a stress-induced cytokine, and a biomarker of aging and cardiovascular diseases. We hypothesized that circulating GDF-15 would be associated with COVID-19 disease severity. Herein, we explored this hypothesis in a large cohort of COVID-19 patients.

Methods

Blood samples were collected from 926 COVID-19 adult patients and from 285 hospitalized controls from the Biobanque Québécoise de la COVID-19 (BQC19). COVID-19 severity was graded according to the WHO criteria. SOMAscan proteomics assay was performed on 50µL of plasma. ELISA were performed on 46 selected participants with left-over plasma to validate differences in plasma GDF-15 levels. Statistical analyses were conducted using GraphPad Prism 9.0 and SPSS. P values < 0.01 were considered significant.

Results

Proteomics showed that plasma GDF-15 levels were higher in COVID-19 patients compared to hospitalized controls. GDF-15 levels increased with COVID-19 severity. COVID-19 patients presenting with comorbidities including diabetes, cancer, chronic obstructive pulmonary disease (COPD) and cardiovascular disease had higher GDF-15 levels. ELISA revealed significant elevation of GDF-15 until 30 days after hospitalization. Plasma GDF-15 elevation was correlated with older age. Moreover, GDF-15 levels correlated with pro-inflammatory cytokine interleukin-6 (IL-6) and inflammation marker C-reactive protein (CRP) as well as soluble levels of its putative receptor CD48. No association was established between anti-SARS-CoV-2 IgG levels and plasma GDF-15 levels.

Conclusions

This study confirms GDF-15 as a biomarker for COVID-19 severity. Clinical evaluation of GDF-15 levels could assist identification of persons at high-risk of progressing to severe disease, thus improving patient care.

Proteome profiling of home-sampled dried blood spots reveals proteins of SARS-CoV-2 infections

BACKGROUND

Self-sampling of dried blood spots (DBS) offers new routes to gather valuable health-related information from the general population. Yet, the utility of using deep proteome profiling from home-sampled DBS to obtain clinically relevant insights about SARS-CoV-2 infections remains largely unexplored.

METHODS

Our study involved 228 individuals from the general Swedish population who used a volumetric DBS sampling device and completed questionnaires at home during spring 2020 and summer 2021. Using multi-analyte COVID-19 serology, we stratified the donors by their response phenotypes, divided them into three study sets, and analyzed 276 proteins by proximity extension assays (PEA). After normalizing the data to account for variances in layman-collected samples, we investigated the association of DBS proteomes with serology and self-reported information.

RESULTS

Our three studies display highly consistent variance of protein levels and share associations of proteins with sex (e.g., MMP3) and age (e.g., GDF-15). Studying seropositive (IgG+) and seronegative (IgG-) donors from the first pandemic wave reveals a network of proteins reflecting immunity, inflammation, coagulation, and stress response. A comparison of the early-infection phase (IgM+IgG-) with the post-infection phase (IgM-IgG+) indicates several proteins from the respiratory system. In DBS from the later pandemic wave, we find that levels of a virus receptor on B-cells differ between seropositive (IgG+) and seronegative (IgG-) donors.

CONCLUSIONS

Proteome analysis of volumetric self-sampled DBS facilitates precise analysis of clinically relevant proteins, including those secreted into the circulation or found on blood cells, augmenting previous COVID-19 reports with clinical blood collections. Our population surveys support the usefulness of DBS, underscoring the role of timing the sample collection to complement clinical and precision health monitoring initiatives.

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.

Associations of circulating GDF15 with combined cognitive frailty and depression in older adults of the MARK-AGE study

Growth differentiation factor-15 (GDF15) might be involved in the development of cognitive frailty and depression. Therefore, we evaluated cross-sectional associations of plasma GDF15 with combined cognitive-frailty-and-depression in older (i.e. ≥ 55 years) and younger adults of the MARK-AGE study. In the present work, samples and data of MARK-AGE ("European study to establish bioMARKers of human AGEing") participants (N = 2736) were analyzed. Cognitive frailty was determined by the global cognitive functioning score (GCF) and depression by the Self-Rating Depression Scale (SDS score). Adults were classified into three groups: (I) neither-cognitive-frailty-nor-depression, (II) either-cognitive-frailty-or-depression or (III) both-cognitive-frailty-and-depression. Cross-sectional associations were determined by unadjusted and by age, BMI, sex, comorbidities and hsCRP-adjusted linear and logistic regression analyses. Cognitive frailty, depression, age and GDF15 were significantly related within the whole study sample. High GDF15 levels were significantly associated with both-cognitive-frailty-and-depression (adjusted β = 0.177 [0.044 - 0.310], p = 0.009), and with low GCF scores and high SDS scores. High GDF15 concentrations and quartiles were significantly associated with higher odds to have both-cognitive-frailty-and-depression (adjusted odds ratio = 2.353 [1.267 - 4.372], p = 0.007; and adjusted odds ratio = 1.414 [1.025 - 1.951], p = 0.035, respectively) independent of age, BMI, sex, comorbidities and hsCRP. These associations remained significant when evaluating older adults. We conclude that plasma GDF15 concentrations are significantly associated with combined cognitive-frailty-and-depression status and, with cognitive frailty and depressive symptoms separately in old as well as young community-dwelling adults.

Circulating biomarkers of inflammaging and Alzheimer's disease to track age-related trajectories of dementia: Can we develop a clinically relevant composite combination?

Alzheimer's disease (AD) is a rapidly growing global concern due to a consistent rise of the prevalence of dementia which is mainly caused by the aging population worldwide. An early diagnosis of AD remains important as interventions are plausibly more effective when started at the earliest stages. Recent developments in clinical research have focused on the use of blood-based biomarkers for improve diagnosis/prognosis of neurodegenerative diseases, particularly AD. Unlike invasive cerebrospinal fluid tests, circulating biomarkers are less invasive and will become increasingly cheaper and simple to use in larger number of patients with mild symptoms or at risk of dementia. In addition to AD-specific markers, there is growing interest in biomarkers of inflammaging/neuro-inflammaging, an age-related chronic low-grade inflammatory condition increasingly recognized as one of the main risk factor for almost all age-related diseases, including AD. Several inflammatory markers have been associated with cognitive performance and AD development and progression. The presence of senescent cells, a key driver of inflammaging, has also been linked to AD pathogenesis, and senolytic therapy is emerging as a potential treatment strategy. Here, we describe blood-based biomarkers clinically relevant for AD diagnosis/prognosis and biomarkers of inflammaging associated with AD. Through a systematic review approach, we propose that a combination of circulating neurodegeneration and inflammatory biomarkers may contribute to improving early diagnosis and prognosis, as well as providing valuable insights into the trajectory of cognitive decline and dementia in the aging population.