GDF15: emerging biology and therapeutic applications for obesity and cardiometabolic disease

Identifying proteins and pathways associated with multimorbidity in 53,026 adults

BACKGROUND AND AIMS

Multimorbidity, the coexistence of multiple chronic diseases, is a rapidly expanding global health challenge, carrying profound implications for patients, caregivers, healthcare systems, and society. Investigating the determinants and drivers underlying multiple chronic diseases is a priority for disease management and prevention.

METHOD

This prospective cohort study analyzed data from the 53,026 participants in the UK Biobank from baseline (2006 to 2010) across 13.3 years of follow-up. Using Cox proportional hazards regression model, we characterized shared and unique associations across 38 incident outcomes (31 chronic diseases, 6 system mortality and all-cause mortality). Furthermore, ordinal regression models were used to assess the association between protein levels and multimorbidity (0-1, 2, 3-4, or ≥ 5 chronic diseases). Functional and tissue enrichment analysis were employed for multimorbidity-associated proteins. The upstream regulators of above proteins were identified.

RESULTS

We demonstrated 972 (33.3 %) proteins were shared across at least two incident chronic diseases after Bonferroni correction (P < 3.42 × 10-7, 93.3 % of those had consistent effects directions), while 345 (11.8 %) proteins were uniquely linked to a single chronic disease. Remarkably, GDF15, PLAUR, WFDC2 and AREG were positively associated with 20-24 incident chronic diseases (hazards ratios: 1.21-3.77) and showed strong associations with multimorbidity (odds ratios: 1.33-1.89). We further identified that protein levels are explained by common risk factors, especially renal function, liver function, inflammation, and obesity, providing potential intervention targets. Pathway analysis has underscored the pivotal role of the immune response, with the top three transcription factors associated with proteomics being NFKB1, JUN and RELA.

CONCLUSIONS

Our results enhance the understanding of the biological basis underlying multimorbidity, offering biomarkers for disease identification and novel targets for therapeutic intervention.

GDF15 inhibits early-stage adipocyte differentiation by enhancing HOP2 expression and suppressing C/EBPα expression

Excessive adipocyte differentiation and accumulation contribute to the development of metabolic disorders. Growth differentiation factor 15 (GDF15) plays an essential role in energy homeostasis and is considered an anti-obesity factor; however, elevated serum levels of endogenous GDF15 have been reported in certain individuals with obesity. In this study, to gain a better understanding of this complex relationship between GDF15 levels and obesity, we investigated GDF15 expression and function during adipogenesis. Compared with mice fed a normal diet, those fed a short-term high-fat diet exhibited a reduction in epididymal white adipose tissue and serum GDF15 expression. These results were confirmed in human adipose-derived stem cells that showed reduced GDF15 expression during adipogenesis differentiation. During adipogenesis, GDF15 was primarily degraded via the autophagy lysosomal pathway, and GDF15 overexpression in pre-adipocytes inhibited adipogenesis by suppressing CCAAT enhancer binding protein alpha (C/EBPα). Furthermore, whereas we detected a reduction in homologous-pairing protein 2 (HOP2) expression during adipogenesis, expression increased in response to an overexpression of GDF15. Furthermore, following knockdown of HOP2 during GDF15 overexpression, there was no suppression of C/EBPα expression. These findings indicate that GDF15 undergoes lysosomal degradation via an autophagic pathway and suppresses adipocyte differentiation via the HOP2-mediated inhibition of C/EBPα expression. Collectively, our findings indicate that GDF15 could serve as a potential therapeutic target for the treatment of metabolic disorders.

Alterations in the proteomes of HepG2 and IHKE cells inflicted by six selected mycotoxins

Toxic fungal secondary metabolites, referred to as mycotoxins, emerge in moldy food and feed and constitute a potent but often underestimated health threat for humans and animals. They are structurally diverse and can cause diseases after dietary intake even in low concentrations. To elucidate cellular responses and identify cellular targets of mycotoxins, a bottom-up proteomics approach was used. We investigated the effects of the mycotoxins aflatoxin B1, ochratoxin A, citrinin, deoxynivalenol, nivalenol and penitrem A on the human hepatoblastoma cell line HepG2 and of ochratoxin A and citrinin on the human kidney epithelial cell line IHKE. Incubations were carried out at sub-cytotoxic concentrations to monitor molecular effects before acute cell death mechanisms predominate. Through these experiments, we were able to detect specific cellular responses that point towards the mycotoxins' mode of action. Besides very well-described mechanisms like the ribotoxicity of the trichothecenes, we observed not yet described effects on different cellular mechanisms. For instance, trichothecenes lowered the apolipoprotein abundance and aflatoxin B1 affected proteins related to inflammation, ribogenesis and mitosis. Ochratoxin A and citrinin upregulated the minichromosomal maintenance complex and nucleotide synthesis in HepG2 and downregulated histones in IHKE. Penitrem A reduced enzyme levels of the sterol biosynthesis. These results will aid in the elucidation of the toxicodynamic properties of this highly relevant class of toxins.

The Metabolic Basis of Cancer-Related Fatigue

Although we are all familiar with the sensation of fatigue, there are still profound divergences on what it represents and its mechanisms. Fatigue can take various forms depending on the condition in which it develops. Cancer-related fatigue is considered a symptom of exhaustion that is often present at the time of diagnosis, increases in intensity during cancer therapy, and does not always recede after completion of treatment. It is usually attributed to the inflammation induced by damage-associated molecular patterns released by tumor cells during cancer progression and in response to its treatment. In this review, we argue that it is necessary to go beyond the symptoms of fatigue to understand its nature and mechanisms. We propose to consider fatigue as a psychobiological process that regulates the behavioral activities an organism engages in to satisfy its needs, according to its physical ability to do so and to the capacity of its intermediary metabolism to exploit the resources procured by these activities. This last aspect is critical as it implies that these metabolic aspects need to be considered to understand fatigue. Based on the findings we have accumulated over several years of studying fatigue in diverse murine models of cancer, we show that energy metabolism plays a key role in the development and persistence of this condition. Cancer-related fatigue is dependent on the energy requirements of the tumor and the negative impact of cancer therapy on the mitochondrial function of the host. When inflammation is present, it adds to the organism's energy expenses. The organism needs to adjust its metabolism to the different forms of cellular stress it experiences thanks to specialized communication factors known as mitokines that act locally and at a distance from the cells in which they are produced. They induce the subjective, behavioral, and metabolic components of fatigue by acting in the brain. Therefore, the targeting of mitokines and their brain receptors offers a window of opportunity to treat fatigue when it is no longer adaptive but an obstacle to the quality of life of cancer survivors.

Associations between prenatal distress, mitochondrial health, and gestational age: findings from two pregnancy studies in the USA and Turkey

Objective This study examined associations between mitochondrial markers-circulating cell-free mitochondrial DNA (cf-mtDNA) and Growth Differentiation Factor-15 (GDF15)-with maternal distress and pregnancy outcomes. Method Participants were drawn from two pregnancy studies, EPI (N=187, USA) and BABIP (N=198, Turkey). Plasma cf-mtDNA and GDF15 levels were quantified using qPCR and ELISA assays. Results Plasma cf-mtDNA levels did not significantly vary across pregnancy, while plasma GDF15 levels increased from early to late pregnancy and decreased postpartum. Late 2nd trimester plasma GDF15 was negatively correlated with pre-pregnancy BMI (p=0.035) and gestational age (p=0.0048) at birth. Early 2nd trimester maternal distress was associated with lower cf-mtDNA (p<0.05) and a trend for lower GDF15. Higher pre-pregnancy BMI and late-pregnancy maternal distress were linked to smaller postpartum GDF15 declines in EPI (p<0.05). Conclusion This study reveals distinct plasma cf-mtDNA and GDF15 patterns during the perinatal period, linking mitochondrial markers to maternal distress and pregnancy outcomes.

GDF15-mediated enhancement of the Warburg effect sustains multiple myeloma growth via TGFβ signaling pathway

The Warburg effect, characterized by the shift toward aerobic glycolysis, is closely associated with the onset and advancement of tumors, including multiple myeloma (MM). Nevertheless, the specific regulatory mechanisms of glycolysis in MM and its functional role remain unclear. In this study, we identified that growth differentiation factor 15 (GDF15) is a glycolytic regulator, and GDF15 is highly expressed in MM cells and patient samples. Through gain-of-function and loss-of-function experiments, we demonstrated that GDF15 promotes MM cell proliferation and inhibits apoptosis. Moreover, GDF15 enhances Warburg-like metabolism in MM cells, as evidenced by increased glucose uptake, lactate production, and extracellular acidification rate, while reducing oxidative phosphorylation. Importantly, the tumor-promoting effects of GDF15 in MM cells are fermentation-dependent. Mechanistically, GDF15 was found to promote the expression of key glycolytic genes, particularly the glucose transporter GLUT1, through the activation of the TGFβ signaling pathway. Pharmacological inhibition of the TGFβ signaling pathway effectively abrogated the oncogenic activities of GDF15 in MM cells, including cell proliferation, apoptosis, and fermentation. In vivo experiments using a subcutaneous xenotransplanted tumor model confirmed that GDF15 knockdown led to a significant reduction in tumor growth, while GDF15 overexpression promoted tumor growth. Overall, our study provides insights into the molecular mechanisms underlying MM pathogenesis and highlights the potential of targeting GDF15-TGFβ signaling -glycolysis axis as a therapeutic approach for future therapeutic interventions in MM.

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.

Non-canonical Wnt signaling pathway activated NFATC3 promotes GDF15 expression in MASH: prospective analyses of UK biobank proteomic data

BACKGROUND

Our previous research demonstrated that growth differentiation factor 15 (GDF15) exhibited superior predictive capability for metabolic dysfunction-associated steatohepatitis (MASH) development with an AUC of 0.86 at 10 years before disease diagnosis. However, the specific pathways and molecular mechanisms associated with GDF15 expression during MASH development remain to be fully investigated in humans.

METHODS

A nested case-control study comprising a MASH group of 78 individuals and three age- and sex-matched control groups (156 metabolic dysfunction-associated steatosis, 78 viral hepatitis, and 156 normal liver controls) was conducted. The baseline levels of GDF15-related transcription factors and upstream signaling pathways associated with the identified transcription factors were analysed prospectively.

RESULTS

The significantly higher level of nuclear factor of activated T cells 3 (NFATC3), a transcription factor for GDF15, was identified in the circulation in MASH patients compared to controls. Expression of the non-canonical Wnt signaling pathway that is upstream of NFATC3, and its related proteins CTHRC1, FRZB, SFRP1, and SFRP4, were highest in the MASH group, suggesting a non-canonical Wnt signaling/NFATC3/GDF-15 cascade in MASH disease pathogenesis. A predictive model for MASH development based on four biomarkers (CTHRC1, FRZB, NFATC3, and GDF15) showed an AUC of 0.90 at 10 years. A protein-clinical model that included these four circulating proteins and BMI yielded an AUC of 0.93 at 10 years.

CONCLUSIONS

Non-canonical Wnt signaling pathway may activate NFATC3 to promote GDF15 expression in MASH disease pathogenesis. These molecular mechanisms provide novel insights for developing targeted therapies that could modulate the non-canonical Wnt/NFATC3/GDF15 cascade to prevent/treat MASH.

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.

Development and Validation of a Diagnostic Model for Stanford Type B Aortic Dissection Based on Proteomic Profiling

Purpose

Stanford Type B Aortic Dissection (TBAD), a critical aortic disease, has exhibited stable mortality rates over the past decade. However, diagnostic approaches for TBAD during routine health check-ups are currently lacking. This study focused on developing a model to improve the diagnosis in a population.

Patients and Methods

Serum biomarkers were investigated in 88 participants using proteomic profiling combined with machine learning. The findings were validated using ELISA in other 80 participants. Subsequently, a diagnostic model for TBAD integrating biomarkers with clinical indicators was developed and assessed using machine learning.

Results

Six differentially expressed proteins (DEPs) were identified through proteomic profiling and machine learning in discovery and derivation cohorts. Five of these (GDF-15, IL6, CD58, LY9, and Siglec-7) were further verified through ELISA validation within the validation cohort. In addition, ten blood-related indicators were selected as clinical indicators. Combining biomarkers and clinical indicators, the machine learning-based models performed well (AUC of the biomarker model = 0.865, AUC of the clinical model = 0.904, and AUC of the combined model = 0.909) using relative quantitation. The performance of the three models was verified (AUC of biomarker model = 0.866, AUC of clinical model = 0.868, and AUC of combined model = 0.886) using absolute quantitation. Crucially, the combined models outperformed individual biomarkers and clinical models, demonstrating superior efficacy.

Conclusion

Using proteomic profiling, we identified serum IL-6, GDF-15, CD58, LY9, and Siglec-7 as TBAD biomarkers. The machine-learning-based diagnostic model exhibited significant potential for TBAD diagnosis using only blood samples within the population.

Atlas of the plasma proteome in health and disease in 53,026 adults

Large-scale proteomics studies can refine our understanding of health and disease and enable precision medicine. Here, we provide a detailed atlas of 2,920 plasma proteins linking to diseases (406 prevalent and 660 incident) and 986 health-related traits in 53,026 individuals (median follow-up: 14.8 years) from the UK Biobank, representing the most comprehensive proteome profiles to date. This atlas revealed 168,100 protein-disease associations and 554,488 protein-trait associations. Over 650 proteins were shared among at least 50 diseases, and over 1,000 showed sex and age heterogeneity. Furthermore, proteins demonstrated promising potential in disease discrimination (area under the curve [AUC] > 0.80 in 183 diseases). Finally, integrating protein quantitative trait locus data determined 474 causal proteins, providing 37 drug-repurposing opportunities and 26 promising targets with favorable safety profiles. These results provide an open-access comprehensive proteome-phenome resource (https://proteome-phenome-atlas.com/) to help elucidate the biological mechanisms of diseases and accelerate the development of disease biomarkers, prediction models, and therapeutic targets.

Differential expression of plasma proteins and pathway enrichments in pediatric diabetic ketoacidosis

BACKGROUND

In children with type 1 diabetes (T1D), diabetic ketoacidosis (DKA) triggers a significant inflammatory response; however, the specific effector proteins and signaling pathways involved remain largely unexplored. This pediatric case-control study utilized plasma proteomics to explore protein alterations associated with severe DKA and to identify signaling pathways that associate with clinical variables.

METHODS

We conducted a proteome analysis of plasma samples from 17 matched pairs of pediatric patients with T1D; one cohort with severe DKA and another with insulin-controlled diabetes. Proximity extension assays were used to quantify 3072 plasma proteins. Data analysis was performed using multivariate statistics, machine learning, and bioinformatics.

RESULTS

This study identified 214 differentially expressed proteins (162 upregulated, 52 downregulated; adj P < 0.05 and a fold change > 2), reflecting cellular dysfunction and metabolic stress in severe DKA. We characterized protein expression across various organ systems and cell types, with notable alterations observed in white blood cells. Elevated inflammatory pathways suggest an enhanced inflammatory response, which may contribute to the complications of severe DKA. Additionally, upregulated pathways related to hormone signaling and nitrogen metabolism were identified, consistent with increased hormone release and associated metabolic processes, such as glycogenolysis and lipolysis. Changes in lipid and fatty acid metabolism were also observed, aligning with the lipolysis and ketosis characteristic of severe DKA. Finally, several signaling pathways were associated with clinical biochemical variables.

CONCLUSIONS

Our findings highlight differentially expressed plasma proteins and enriched signaling pathways that were associated with clinical features, offering insights into the pathophysiology of severe DKA.

Neural pathways of nausea and roles in energy balance

Our internal sensory systems encode various gut-related sensations, such as hunger, feelings of fullness, and nausea. These internal feelings influence our eating behaviors and play a vital role in regulating energy balance. Among them, the neurological basis for nausea has been the least well characterized, which has hindered comprehension of the connection between these sensations. Single-cell sequencing, along with functional mapping, has brought clarity to the neural pathways of nausea involving the brainstem area postrema. In addition, the newly discovered nausea sensory signals have deepened our understanding of the area postrema in regulating feeding behaviors. Nausea has significant clinical implications, especially in developing drugs for weight loss and metabolism. This review summarizes recent research on the neural pathways of nausea, particularly highlighting their contribution to energy balance.

The clinical utility in hospital-wide use of growth differentiation factor 15 as a biomarker for mitochondrial DNA-related disorders

Clinical recognition of primary mitochondrial disorders (PMD) is difficult due to the clinical and genetic heterogeneity. Whereas lactate has low sensitivity and specificity, in structured clinical studies growth differentiation factor 15 (GDF15) has shown promise with elevations in mitochondrial DNA (mtDNA)-related PMD, but its specificity has been questioned. In a tertiary care hospital-wide study, medical records were retrospectively reviewed from 418 cases where GDF15 levels were obtained by clinicians. Patients were classified into patients with PMD due to mtDNA-related defects (mtDNA maintenance, mtDNA deletions, and mtDNA-encoded tRNA variants), PMD due to structural defects or other nuclear causes, and in non-mitochondrial disease. Patients with liver disease or systemic critical illness were excluded. GDF15 was assayed in a clinical laboratory with a cutoff of 750 ng/L. There were 38 mtDNA-related PMD (GDF15 >750 pg/mL in 76%), 35 other nuclear DNA-encoded PMD or structural subunits (31% elevated GDF15), 309 non-mitochondrial disorders (13% elevated GDF15). Based on the highest Youden J-index, the optimal cut-off value to identify these target mtDNA-related disorders was 815 pg/mL, with sensitivity 76%, specificity 88%, positive predictive value of 41% and negative predictive value of 97%. At this optimized cutoff level, mtDNA-encoded PMD patients had elevated GDF15 in 76%, nuclear DNA-encoded PMD in 26%, and non-mitochondrial disorders in 11% of patients. Thus, in a real-life clinical setting, after excluding abnormal liver function and critical illness, GDF15 had good clinical utility increasing the odds at predicting mtDNA-related primary mitochondrial disorders 14-fold, but not for structural or other nuclear-encoded primary mitochondrial disorders.

A novel combined oxidative stress and extracellular matrix related predictive gene signature for keratoconus

Keratoconus (KC) is an ectatic cornea disease with high prevalence and asymptomatic at early stage, leading to decreased visual acuity and even cornea transplantation. However, the etiology mechanism of keratoconus is still poorly understood. Oxidative stress (OS) and extracellular matrix (ECM) remodeling play critical roles in keratoconus development. Here, based on keratoconus datasets from GEO database, we obtained 454 differentially expressed genes (DEGs), which were further intersected with oxidative stress (OS) and extracellular matrix (ECM) genesets from MSigDB database. A total of 17 OS- and ECM-related DEGs (OEDEGs) were identified. Feature genes were screened by least absolute shrinkage and selection operator (LASSO) and support vector machine recursive feature elimination (SVM-RFE) algorithms, and a six-gene (COL1A1, CYP1B1, MMP3, HMOX1, FOS and GDF15) classification model was developed utilizing Logistic regression (LR), Support Vector Machine (SVM) and Naïve Bayes (NB) algorithms respectively, which was further verified in internal and external cohort. Subsequently, a predictive nomogram was constructed for KC patients. Six signature genes showed a strong correlation with the infiltration level of macrophages M1, neutrophils and eosinophils. Additionally, in vitro qRT-PCR validated the decreased expression of signature genes in either keratoconus clinical samples or human cornea epithelial (HCE) cells grown on soft hydrogel substrate. Finally, we revealed that CYP1B1 and GDF15 regulate cellular proliferation and response to oxidative stress. In conclusion, the developed combined OS and ECM gene signature showed excellent performance for keratoconus prediction, providing beneficial perspectives for keratoconus pathogenesis.

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.

Brainstem BDNF neurons are downstream of GFRAL/GLP1R signalling

Growth differentiation factor 15, GDF15, and glucagon-like peptide-1 (GLP-1) analogues act through brainstem neurons that co-localise their receptors, GDNF-family receptor α-like (GFRAL) and GLP1R, to reduce food intake and body weight. However, their use as clinical treatments is partially hampered since both can also induce sickness-like behaviours, including aversion, that are mediated through a well-characterised pathway via the exterolateral parabrachial nucleus. Here, in mice, we describe a separate pathway downstream of GFRAL/GLP1R neurons that involves a distinct population of brain-derived neurotrophic factor (BDNF) cells in the medial nucleus of the tractus solitarius. Thus, BDNFmNTS neurons are required for the weight-reducing actions of both GDF15 and the GLP1RA, Exendin-4. Moreover, acute activation of BDNFmNTS neurons is sufficient to reduce food intake and drive fatty acid oxidation and might provide a route for longer-term weight loss.

Transcoronary study of biomarkers in patients with heart failure: Insights into intracardiac production

AIMS

Biomarkers are pivotal in the management of heart failure (HF); however, their lack of cardiac specificity could limit clinical utility. This study aimed to investigate the transcoronary changes and intracardiac production of these biomarkers.

METHODS

Transcoronary gradients for B-type natriuretic peptide (BNP) and five novel biomarkers-galectin-3 (Gal-3), soluble suppression of tumourigenicity 2 (sST2), tissue inhibitor of metalloproteinase 1 (TIMP-1), growth differentiation factor 15 (GDF-15) and myeloperoxidase (MPO)-were determined using femoral artery (FA) and coronary sinus (CS) samples from 30 HF patients and 10 non-HF controls. Intracardiac biomarker production was assessed in an HF canine model using real-time quantitative PCR (qPCR) and western blot (WB) analysis.

RESULTS

Compared with the control group, levels of all detected biomarkers were significantly elevated in the HF group, while transcoronary gradients were only observed for BNP, Gal-3 and TIMP-1 levels in the HF group (BNP: FA: 841.5 ± 727.2 ng/mL vs. CS: 1132.0 ± 959.1 ng/mL, P = 0.005; Gal-3: FA: 9.5 ± 3.0 ng/mL vs. CS: 19.7 ± 16.4 ng/mL, P = 0.002; and TIMP-1: FA: 286.7 ± 68.9 ng/mL vs. CS: 377.3 ± 108.9 ng/mL, P = 0.001). Real-time qPCR and WB analysis revealed significant elevation of BNP, Gal-3 and TIMP-1 in the cardiac tissues of the HF group relative to other groups.

CONCLUSIONS

This study provided evidence of transcoronary changes in BNP, Gal-3 and TIMP-1 levels in HF patients, offering insights into their intracardiac production. These findings enhance the understanding of the biology of these biomarkers and may inform their clinical application.

Growth Differentiation Factor 15 as a Marker for Chronic Ventricular Pacing

Background/Objectives: Right ventricular pacing is an effective and safe treatment option for patients experiencing symptomatic bradycardia. However, some individuals may develop left ventricular dysfunction as a consequence. Growth differentiation factor 15 (GDF-15), which is not present in a healthy adult heart, is upregulated in cardiomyocytes in response to various stress stimuli. This study aimed to explore the potential of GDF-15 as a biomarker for chronic right ventricular pacing. Methods: This single-center cross-sectional cohort study analyzed data from 265 consecutive patients (60.4% male) with either single- or dual-chamber pacemakers, all lacking pre-existing heart failure, who attended the outpatient department for routine follow-up. Chronic right ventricular (RV) pacing was defined as pacing exceeding 40% over the past year. Serum samples were collected, and GDF-15 levels were measured using a commercially available immunoassay (R&D Systems Inc., Minneapolis, MN, USA). Student's t-test was utilized to assess group differences, and receiver operating characteristic (ROC) analysis was employed to evaluate diagnostic performance. Results: When stratifying patients by pacing burden, GDF-15 levels were significantly higher in those with pacing over 40% compared to those with 40% or less (789 ± 293 pg/mL vs. 1186 ± 592 pg/mL; p < 0.001). The ROC analysis indicated that GDF-15 serves as a marker for chronic RV pacing, yielding an area under the curve of 0.713 (95% confidence interval 0.650-0.776; p < 0.001). Conclusions: This study suggests that GDF-15 may be a valuable biomarker for chronic right ventricular pacing.

Metformin inhibits migration and epithelial-to-mesenchymal transition in non-small cell lung cancer cells through AMPK-mediated GDF15 induction

The growth differentiation factor 15 (GDF15) may serve as a biomarker of metformin, which mediates the bodyweight lowering effect of metformin. However, whether GDF15 also serves as a molecular target of metformin to inhibit carcinogenesis remains largely unknown. This study examined the role and molecular mechanisms of GDF15 in the anticancer effects of metformin in non-small cell lung cancer (NSCLC) cells, which has never been reported before. We found that metformin significantly inhibited the migration of NSCLC A549 and NCI-H460 cells and reduced the expression of epithelial-to-mesenchymal transition (EMT)-related molecules, including neuro-cadherin (N-cadherin), matrix metalloproteinase 2 (MMP2), and the zinc finger transcription factor Snail, but increased epithelial cadherin (E-cadherin) expression. Furthermore, metformin increased GDF15 and its upstream transcription factors activated transcription factor 4 (ATF4) and C/EBP-homologous protein (CHOP) expressions and increased AMP-activated protein kinase (AMPK) phosphorylation in NSCLC cells. GDF15 siRNA partially reverses the inhibitory effect of metformin on NSCLC cell migration. Moreover, metformin-induced increases in GDF15, CHOP, and ATF4 expression and the inhibition of migration were partially reversed by treatment with Compound C, a specific AMPK inhibitor. Meanwhile, metformin significantly inhibited NCI-H460 xenograft tumor growth in nude mice, increased GDF15 expression, and regulated EMT- and migration-related protein expression in xenograft tumors. In conclusion, our results provide novel insights into revealing that GDF15 can serve as a potential molecular target of metformin owing to its anti-cancer effect in NSCLC, which is mediated by AMPK activation.

Serum growth differentiation factor-15, glial fibrillary acidic protein, and neurofilament light chain: Their link and role in Creutzfeldt-Jakob disease

BACKGROUND

Creutzfeldt-Jakob disease (CJD) is a rapidly progressive neurodegenerative disorder characterized by neuronal damage. Emerging biomarkers, such as serum neurofilament light chain (sNfL), glial fibrillary acidic protein (sGFAP), and growth differentiation factor-15 (sGDF-15), are currently being studied for their potential use in this disease.

OBJECTIVES

This study analyzes the levels of sNfL, sGFAP, and sGDF-15, as well as their relationships, in patients with CJD compared to healthy controls (HC).

METHODS

A total of 19 CJD patients and 81 age- and sex-matched HCs were enrolled. Serum levels of sNfL and sGFAP were measured using ultrasensitive immunoassays, while sGDF-15 levels were assessed via ELISA. Statistical analyses included correlation analysis and analysis of covariance (ANCOVA) models.

RESULTS

CJD patients showed significantly higher serum levels of sNfL and sGFAP compared to HCs (p <0,001). sNfL levels were positively correlated with both sGFAP (Rho = 0,70; p < 0,001) and sGDF-15 (Rho = 0,60; p = 0,004). Interestingly, sGFAP levels were higher in female CJD patients compared to males (p = 0,001), while no significant difference in sNfL levels was observed between sexes.

CONCLUSIONS

In conclusion, this study explores the potential of sNfL, sGDF-15, and sGFAP as biomarkers in CJD patients. The higher levels of sNfL and sGFAP in CJD patients compared to healthy controls, along with the observed sex differences in sGFAP, highlight the need for further research into the interaction between astroglia and neurons in CJD, with a focus on sex as a key variable.

Growth Differentiation Factor 15 as a Biomarker for Risk Stratification in the Cardiothoracic Surgery Intensive Care Unit

Growth Differentiation Factor 15 (GDF15) is an emerging biomarker that significantly increases during acute stress responses, such as infections, and is moderately elevated in chronic and inflammation-driven conditions. While evidence suggests that high levels of GDF15 in cardiac surgery are associated with worse outcomes, its utility as an evaluator of early postoperative complications remains unclear. This study aims to characterize the postoperative profile of GDF15 in patients undergoing isolated surgical aortic valve replacement, evaluating its association with short-term outcomes. Serum samples from patients undergoing cardiac surgery were collected preoperatively and at defined postoperative time points (1 h, 6 h, 12 h, 24 h, and 48 h) to measure GDF15 levels. GDF15 levels significantly increased after surgery, peaking at 6 h. A positive correlation was observed between GDF15 levels and both cardiopulmonary bypass and aortic cross-clamp times. Notably, patients who developed postoperative acute kidney injury (AKI) or required prolonged hemodynamic support had significantly higher GDF15 levels, with increased mechanical ventilation time and extended intensive care unit length of stay. Furthermore, GDF15 levels correlated with postoperative SOFA scores at 24 h after surgery. GDF15 may be a valuable biomarker for risk stratification and guiding therapeutic decisions in cardiac surgery patients. Higher GDF15 levels were significantly associated with prolonged hemodynamic support, postoperative AKI, and measures of illness severity.

Prognostic significance of immune evasion-related genes in clear cell renal cell carcinoma immunotherapy

Clear cell renal cell carcinoma (ccRCC) represents a prevalent malignancy of the urinary system. Despite the integration of immune checkpoint inhibitors (ICIs) into the treatment paradigm for advanced RCC, resistance to immunotherapy has emerged as a pivotal determinant impacting the clinical outlook of ccRCC. Accumulating evidence underscores the pivotal role of immune evasion-related genes and pathways in enabling tumor escape from host immune surveillance, consequently influencing patients' responsiveness to immunotherapy. Nonetheless, the clinical relevance of immune evasion-related genes in ccRCC patients undergoing immunotherapy remains inadequately understood. In this study, we aggregated RNA sequencing and clinical data from ccRCC patients across three cohorts: the Cancer Genome Atlas (TCGA), CheckMate cohorts, and the JAVELIN Renal 101 trial. Leveraging a curated immune evasion-related gene set from Lawson et al., we employed the LASSO algorithm and Cox regression analysis to identify eight genes (LPAR6, RGS5, NFYC, PCDH17, CENPW, CNOT8, FOXO3, SNRPB) significantly associated with immune therapy prognosis (HR, 3.57; 95 % CI, 2.38-5.35; P<0.001). A predictive algorithm developed utilizing these genes exhibited notable accuracy in forecasting patients' progression-free survival in the training set (AUC, 0.835). Furthermore, stratification of patients by risk score revealed discernible differences in immunotherapy response and tumor microenvironment. In summary, we present a prognostic model intricately linked with immune status and treatment response. For ccRCC patients undergoing immunotherapy, this approach holds promise in aiding clinical decision-making by providing more precise and tailored treatment recommendations.

PROTAC unleashed: Unveiling the synthetic approaches and potential therapeutic applications

Proteolysis-Targeting Chimeras (PROTACs) are a novel class of bifunctional small molecules that alter protein levels by targeted degradation. This innovative approach uses the ubiquitin-proteasome system to selectively eradicate disease-associated proteins, providing a novel therapeutic strategy for a wide spectrum of diseases. This review delineates detailed synthetic approaches involved in PROTAC building blocks, including the ligand and protein binding parts, linker attached structural components of PROTACs and the actual PROTAC molecules. Furthermore, the recent advancements in PROTAC-mediated degradation of specific oncogenic and other disease-associated proteins, such as those involved in neurodegenerative, antiviral, and autoimmune diseases, were also discussed. Additionally, we described the current landscape of PROTAC clinical trials and highlighted key studies that underscore the translational potential of this emerging therapeutic modality. These findings demonstrate the versatility of PROTACs in modulating the levels of key proteins involved in various severe diseases.

Biomarkers and potential therapeutic targets driving progression of non-alcoholic steatohepatitis to hepatocellular carcinoma predicted through transcriptomic analysis

Background

Non-alcoholic steatohepatitis (NASH) is the most prevalent chronic liver condition globally, with potential progression to cirrhosis, and even hepatocellular carcinoma (HCC). The increasing prevalence of NASH underscores the urgent need for advanced diagnostic and therapeutic strategies. Despite its widespread impact, effective treatments to prevent the progression of NASH remain elusive, highlighting the critical importance of innovative molecular techniques in both the diagnosis and management of this disease.

Methods

Six microarray datasets available in GEO were used to perform Robust Rank Aggregation (RRA) to identify differentially expressed genes (DEGs).We identified 62 robust upregulated genes and 24 robust downregulated genes. These genes were undergone Gene Ontology enrichment analysis and further examination for expression correlation with NAS score. Molecular subtypes were generated using "ConsensusClusterPlus" on identified genes, which were further assessed for tumor stage relevance, expression differences in adjacent and tumor tissues, and impact on survival in TCGA liver cancer patients. Single-cell analysis was then used to explore the genes across different cell types and subgroups as well as cell-type interactions. The clinical utility of predicted core genes was highlighted through decision curve analysis, with emphasis on HCC prognosis. The GDSC database was used to evaluate the relationship between the predicted core genes and drug sensitivity, while the TIDE database was used to evaluate their relationship with immunotherapy.

Results

Four core genes, TREM2, GDF15, TTC39A, and ANXA2, were identified as key to influencing HCC prognosis and therapy responsiveness, especially immune treatment efficacy in NASH-associated HCC.

Conclusion

The core genes may act as critical biomarkers driving the progression of NASH to HCC. They are potential novel targets for the diagnosis and treatment of NASH progression, offering innovative perspectives for its clinical management.

Evaluation of the relation between subclinical systolic dysfunction defined by four-dimensional speckle-tracking echocardiography and growth differentiation factor-15 levels in patients with acromegaly

PURPOSE

In patients with acromegaly, the long-term presence of elevated GH and IGF-1 levels is associated with an unfavorable cardiovascular risk profile. We aimed to assess the relationship of four-dimensional speckle tracking echocardiographic (4DSTE) measurements with growth differentiation factor-15 (GDF-15) levels and the Framingham Cardiovascular Risk Score (FRS) in patients with acromegaly.

METHODS

A single-center, cross-sectional study was conducted. The study included 40 acromegaly and 32 age- and gender-matched controls. Anthropometric, biochemical, and echocardiographic assessments were performed. GDF-15 levels were measured using ELISA.

RESULTS

In the controlled acromegaly group, global longitudinal (GLS), circumferential (GCS), area (GAS), and radial (GRS) strain measurements identified by 4DSTE were lower than those of the controls (p < 0.05). Moreover, strain parameters were lower in active acromegaly patients than in controls, but the difference was not statistically significant. The GLS was negatively correlated with age, the estimated disease duration, and FRS. Serum GDF-15 levels showed no significant difference between the acromegaly and control groups. In patients with acromegaly, serum GDF-15 levels were positively correlated with age, waist-to-hip ratio, systolic and diastolic blood pressure, FRS, fasting plasma glucose, and HbA1c, but not with strain parameters. The multiple regression analysis revealed that FRS was an independent factor associated with serum GDF-15 levels in patients with acromegaly and the overall cohort (p < 0.001).

CONCLUSION

Our study demonstrates that while LVEF was within normal limits, global strain parameters (GLS, GCS, GAS, and GRS) measured by using a novel imaging technique, 4DSTE, were lower in patients with acromegaly, suggesting the presence of subclinical systolic dysfunction in patients with acromegaly. GDF-15 can be a potential predictor of cardiovascular risk in patients with acromegaly.

Curcumol effectively improves obesity through GDF15 induction via activation of endoplasmic reticulum stress response

The escalating prevalence of obesity presents a formidable global health challenge, underscoring the imperative for efficacious pharmacotherapeutic interventions. However, current anti-obesity medications often exhibit limited efficacy and adverse effects, necessitating the exploration of alternative therapeutic approaches. Growth differentiation factor 15 (GDF15) has emerged as a promising target for obesity management, given its crucial role in appetite control and metabolic regulation. In this study, we aimed to investigate the efficacy of curcumol, a sesquiterpene compound derived from plants of the Zingiberaceae family, in obesity treatment. Our findings demonstrate that curcumol effectively induces the expression of GDF15 through the activation of the endoplasmic reticulum stress pathway. To confirm the role of GDF15 as a critical target for curcumol's function, we compared the effects of curcumol in wild-type mice and Gdf15-knockout mice. Using a high-fat diet-induced obese murine model, we observed that curcumol led to reduced appetite and altered dietary preferences mediated by GDF15. Furthermore, chronic curcumol intervention resulted in promising anti-obesity effects. Additionally, curcumol administration improved glucose tolerance and lipid metabolism in the obese mice. These findings highlight the potential of curcumol as a GDF15 inducer and suggest innovative strategies for managing obesity and its associated metabolic disorders. In conclusion, our study provides evidence for the efficacy of curcumol in obesity treatment by inducing GDF15 expression. The identified effects of curcumol on appetite regulation, dietary preferences, glucose tolerance, and lipid metabolism emphasize its potential as a therapeutic agent for combating obesity and related metabolic disorders.

Health implications of racial differences in serum growth differentiation factor levels among men with obesity

Growth differentiation factor (GDF15) has been considered a biomarker and recently a hormonal driver for diseases in different populations. However, the role of GDF15 as a biomarker of health outcomes in obese men from different racial/ethnic background has not been evaluated. The objective of this study was to investigate the racial/ethnic differences on the relationship between GDF15 and markers of glucometabolic status, hormonal profile, body composition and bone mineral density (BMD) in obese men. One hundred ninety-three obese men from diverse racial/ethnic backgrounds were enrolled. BMD and body composition were measured by dual energy X-ray absorptiometry. Serum GDF15, osteocalcin, C-terminal telopeptide, sclerostin, adiponectin, leptin, estradiol, testosterone, follicle-stimulating hormone, luteinizing hormone, 25-hydroxyvitamin D, lipid profile, and hemoglobin A1C (A1C) were measured. Non-African Americans (NAA) had significantly higher GDF15 level than African Americans (AA). Level was also higher in patients with type 2 diabetes (T2DM). In both the groups GDF15 correlated with A1C and lean mass. However. GDF15 correlated  with body fat, LDL total cholesterol and femoral neck BMD only in NAA and with appendicular lean mass only in AA. Ethnicity, total cholesterol and T2DM were found to be independent predictors of GDF15. We conclude that GDF15 may influence glucometabolic status, body composition and bone parameters which may affect cardiovascular risk and osteoporosis  between races.

Exercise-regulated lipolysis: Its role and mechanism in health and diseases

Exercise has received considerable attention because of its importance not just in regulating physiological function, but also in ameliorating multiple pathological processes. Among these processes, lipolysis may play an important role in exercise-induced benefits. It is generally accepted that active lipolysis contributes to breakdown of fats, leading to the release of free fatty acids (FFAs) that serve as an energy source for muscles and other tissues during exercise. However, the significance of lipolysis in the context of exercise has not been fully understood. This review comprehensively outlines the potential regulatory mechanisms by which exercise stimulates lipolysis. The potential roles of exercise-mediated lipolysis in various physiological and pathological processes are also summarized. Additionally, we also discussed the potential non-classical effects of key lipolytic effectors induced by exercise. This will enhance our understanding of how exercise improves lipolytic function to bring about beneficial effects, offering new insights into potential therapeutic avenues for promoting health and alleviating diseases.

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.

Immunogenicity assessment strategy for a chemically modified therapeutic protein in clinical development

The clinical immunogenicity assessment for complex multidomain biological drugs is challenging due to multiple factors that must be taken into consideration. Here, we describe a strategy to overcome multiple bioanalytical challenges in order to assess anti-drug antibodies (ADA) for a novel and unique chemically modified protein therapeutic. A risk-centered approach was adopted to evaluate the immunogenic response to a modified version of human growth differentiation factor 15 (GDF15) connected to an albumin-binding fatty acid via a polyethylene glycol (PEG) linker. Key steps include monitoring anti-drug antibodies (ADAs), using a standard tiered approach of screening and confirmation. To deepen our understanding of ADA response, as a third tier of immunogenicity assessment, novel extensive characterization using a set of assays was developed, validated, and used routinely in clinical sample analysis. This characterization step included performance of titration, mapping of ADA response including anti-GDF15 and anti-PEG-fatty-acid antibody characterization, and assessment of the neutralizing anti-drug antibodies (NAbs) using cell-based assays for immunogenicity in parallel. The analytical methods were applied during two clinical trials involving both healthy volunteers and overweight or obese patients. We observed low incident rates for ADA and no ADAs against the PEG linker with fatty acid conjugation. In one of the clinical studies, we identified neutralizing ADAs. The proposed novel strategy of extensive characterization proved effective for monitoring the presence of ADAs and NAbs and can be used to support clinical development of a broad range of chemically modified proteins and multidomain biotherapeutics.

Elevated serum growth differentiation factor 15 and decorin predict the fibrotic progression of metabolic dysfunction-associated steatotic liver disease

Mitochondrial dysfunction with oxidative stress contributes to metabolic dysfunction-associated steatotic liver disease (MASLD) progression. We aimed to evaluate the fibrosis predictive efficacy of a novel non-invasive diagnostic panel using metabolic stress biomarkers. From a population-based general cohort, 144 subjects with MASLD were recruited in the development group and underwent magnetic resonance imaging-based liver examinations, anthropometric and laboratory tests. As an external validation group, 41 patients enrolled in a biopsy-evaluated MASLD cohort participated in this study. Liver fat content and stiffness were measured by magnetic resonance (MR) imaging-proton density fat fraction and MR elastography (MRE), respectively. Serologic stress biomarkers were quantitated by ELISA. Multivariate regression showed that waist-to-height ratio, growth differentiation factor-15 (GDF15), γ-glutamyltransferase, decorin, and alkaline-phosphatase were independent predictors of hepatic fibrosis (rank-ordered by Wald). The area under receiver-operator characteristics curve [AUROC (95% CI)) of the metabolic stress index for fibrosis (MSI-F) was 0.912 (0.85‒0.98) and 0.977 (0.92‒1.00) in development and validation groups, respectively. MSI-F also had better diagnostic accuracy (82.6‒92.4%) than other fibrosis indices in the both study cohorts. MSI-F consistently differentiated fibrosis severities across cohorts of MRE-evaluated general population and biopsy-proven patients with MASLD, while other indices showed no or less discrimination. MSI-F, as a novel non-invasive index based on a stress-stimulated protective hormone GDF15 and decorin, effectively predicted hepatic fibrosis. Furthermore, MSI-F may serve as pre-screening tool to increase the population that could be excluded from further evaluation, reducing unnecessary invasive investigations more effectively than other indices.

Common Genetic Factors May Play a Role in the Relationships Between Body Composition, Adipokines, and Low-Back-Pain-Related Disability

In this study, we evaluated the contribution of the putative genetic factors into the established associations between selected circulating adipokine levels, body composition measurements, and low-back-pain-related disability scores (LBP_DS). A total of 1078 individuals from 98 nuclear families (with 1 to 11 siblings per family) were examined. A detailed self-report questionnaire was used to collect LBP disability data; body composition (fat, skeletal muscle mass, and extracellular water (ECW)) was assessed using the bioimpedance method; plasma levels of adipokines were measured by ELISA. Pedigree-based statistical analysis methods were used, including family-based variance component analysis (VCA) and principal phenotype analysis (PPA), to estimate the contribution of potential genetic and environmental factors. The VCA revealed a significant additive genetic component in LBP_DS and for the selected body composition phenotypes and adipokines. The study also revealed that both adipokines (GDF-15, chemerin, and follistatin) and body composition variables (BMI, fat mass/weight, waist circumference, and ECW) were genetically correlated with LBP_DS. Next, PPA generated two synthetic phenotypes: PPCT (combining cytokines) and PPBC (combining body composition variables). There was no significant correlation between the putative genetic factors underlying the created PPs. However, each of them displayed a significant genetic correlation with LBP_DS. These findings indicate that genetic factors that are assumingly common for several adipokine variations and several body composition measurements, respectively, presumably have a pleotropic genetic influence on the LBP_DS variation, independently from one another. This, in turn, suggests that the alleged genetic factors employing pleiotropic effects on LBP_DS have a complex and probably non-overlapping composition.

Growth differentiation factor 15 (GDF15) predicts relapse free and overall survival in unresected locally advanced non-small cell lung cancer treated with chemoradiotherapy

INTRODUCTION

Growth differentiation factor 15 (GDF15) is a cytokine of the TGFβ family. Here, we analyzed GDF15 levels in patients with locally advanced non-small cell lung cancer (LA-NSCLC) who participated in OCOG-ALMERA (NCT02115464), a phase II randomized clinical trial, that investigated metformin in combination with standard of care concurrent chemoradiotherapy (cCRT). OCOG-ALMERA was not able to demonstrate benefit in the metformin arm. Therefore, biomarker studies are needed to better define stratification parameters for future trials.

METHODS

Patients were randomized to treatment with platinum-based chemotherapy and concurrent chest radiotherapy (60-66 Gy), with or without metformin (2000 mg/d). The trial collected tumor volume parameters, survival outcomes, and patient blood plasma at baseline, during (weeks 1 and 6) and 6 months after cCRT. Plasma GDF15 levels were assayed with the ELISA method. Statistical analyses explored associations between GDF15, survival outcomes, and radiotherapy tumor volumes.

RESULTS

Baseline plasma levels of GDF15 were elevated in study patients, they increased during cCRT (p < 0.001), and the addition of metformin was associated with a further increase (week 6, p = 0.033). Baseline GDF15 levels correlated with the radiotherapy gross target volume (GTV, p < 0.01), while week 1 of radiotherapy levels correlated with radiotherapy planned target volume (PTV, p < 0.006). In multivariate analysis, baseline plasma GDF15 was prognostic for poor relapse-free (RFS) and overall survival (OS) (p = 0.005 and p = 0.002, respectively).

CONCLUSIONS

GDF15 is a plasma marker that responds to the treatment of unresected LA-NSCLC with cCRT and metformin. GDF15 levels correspond with tumor volume and increased GDF15 levels predict for poor RFS and OS. These results require validation in larger clinical trial datasets.

GDF15 is required for maintaining subcutaneous adipose tissue lipid metabolic signature

Recent research has identified growth differentiation factor 15 (GDF15) as a crucial factor in various physiological and pathological processes, particularly in energy balance regulation. While the role of GDF15 in modulating energy metabolism through hindbrain GDNF family receptor alpha-like (GFRAL) signaling has been extensively studied, emerging evidence suggests direct peripheral metabolic actions of GDF15. Using knockout mouse models, we investigated GDF15 and GFRAL's roles in adipose tissue metabolism. Our findings indicate that C57BL/6/129/SvJ Gdf15-KO mice exhibit impaired expression of de novo lipogenesis enzymes in subcutaneous adipose tissue (sWAT). In contrast, C57BL/6J Gfral-KO mice showed no impairments compared to wild-type (WT) littermates. RNA-Seq analysis of sWAT in Gdf15-KO mice revealed a broad downregulation of genes involved in lipid metabolism. Importantly, our study uncovered sex-specific effects, with females being more affected by GDF15 loss than males. Additionally, we observed a fasting-induced upregulation of GDF15 gene expression in sWAT of both mice and humans, reinforcing this factor's role in adipose tissue lipid metabolism. In conclusion, our research highlights an essential role for GDF15 in sWAT lipid metabolic homeostasis. These insights enhance our understanding of GDF15's functions in adipose tissue physiology and underscore its potential as a therapeutic target for metabolic disorders.

GDF15 attenuates sepsis-induced myocardial dysfunction by inhibiting cardiomyocytes ferroptosis via the SOCS1/GPX4 signaling pathway

Sepsis is a systemic inflammatory response syndrome triggered by infection, presenting with symptoms such as fever, increased heart rate, and low blood pressure. In severe cases, it can lead to multiple organ dysfunction, posing a life-threatening risk. Sepsis-induced cardiomyopathy (SIC) is a critical factor in the poor prognosis of septic patients, leading to myocardial dysfunction characterized by cell death, inflammation, and diminished cardiac function. Ferroptosis, an iron-dependent form of programmed cell death, is a key mechanism causing cardiomyocyte damage in SIC. Growth differentiation factor 15 (GDF15), a member of the TGF-β superfamily, is associated with various cardiovascular diseases and can inhibit oxidative stress, reduce reactive oxygen species (ROS), and suppress ferroptosis. Elevated serum GDF15 levels in sepsis are correlated with organ injuries, suggesting its potential as a therapeutic target. However, its role and mechanisms in SIC remain unclear. Glutathione peroxidase 4 (GPX4), the only enzyme capable of reducing lipid peroxides within cells, protects cells by reducing lipid peroxidation levels and inhibiting ferroptosis. Investigating the regulatory factors of GPX4 may provide a theoretical basis for SIC treatment. In this study, a mouse SIC model revealed that elevated GDF15 exerts a protective effect. Antagonizing GDF15 exacerbates myocardial damage. Through transcriptomic analysis and other methods, we confirmed that GDF15 inhibits the expression of SOCS1 by activating the ALK5-SMAD2/3 pathway, thereby activates the JAK2/STAT3 pathway, promotes the transcription of GPX4, inhibits ferroptosis in cardiomyocytes, and plays a myocardial protective role in SIC.

Lactation affects postweaning metabolic profiles, but not follicle size in multiparous sows

Young sows mobilise body reserves to support milk production during lactation, resulting in a negative energy balance (NEB). This NEB affects the development of follicles and oocytes that give rise to the next litter. Decreased IGF1 levels due to a NEB are thought to play a role in this process. As this has hardly been studied in multiparous sows, the current study focused on relations between lactation BW loss (%), metabolic hormones, and follicle development in multiparous sows at Day 0 and Day 4 after weaning. A total of 31 sows of parity 4.7 ± 2.5 were killed at either Day 0 or Day 4 after weaning. Average BW loss during lactation was 3.3 ± 4.5%, while average backfat loss was 4.1 ± 0.3 mm. The metabolic profile confirmed the metabolic impact of lactation as both non-esterified fatty acid (NEFA), and creatinine levels were higher at Day 0 than that at Day 4. Conversely, serum levels of IGF1 and growth differentiation factor 15 levels were lower on Day 0 than on Day 4. A higher BW loss (%) was related to higher NEFA levels on Day 0, but not on Day 4. IGF1 concentrations in serum and follicle fluid were similar at Day 0 and Day 4 and were not related to follicle size on these days. In conclusion, although lactation affected postweaning metabolic profiles in these multiparous sows, follicle size was not related to these profiles, probably due to the relatively mild BW loss of these sows. IGF1 concentrations were less affected by lactation and did not seem to limit follicle development, as it does in sows experiencing high weight loss.

Soluble Urokinase-Type Plasminogen Activator Receptor (suPAR), Growth Differentiation Factor-15 (GDF-15), and Soluble C5b-9 (sC5b-9) Levels Are Significantly Associated with Endothelial Injury Indices in CAR-T Cell Recipients

Endothelial injury indices, such as Endothelial Activation and Stress Index (EASIX), modified EASIX (m-EASIX), and simplified EASIX (s-EASIX) scores, have been previously associated with chimeric antigen receptor-T (CAR-T) cell immunotherapy complications. Soluble urokinase-type plasminogen activator receptor (suPAR), growth differentiation factor-15 (GDF-15), and soluble C5b-9 (sC5b-9) have been described as markers of endothelial injury post-hematopoietic stem cell transplantation. In the current study, we examined whether suPAR, GDF-15, and sC5b-9 levels were associated with endothelial injury indices in adult CAR-T cell recipients. The levels of these markers were measured in patients before CAR-T cell infusion and in healthy individuals with immunoenzymatic methods. We studied 45 CAR-T cell recipients and 20 healthy individuals as the control group. SuPAR, GDF-15, and sC5b-9 levels were significantly higher in the patients' group compared to the healthy control group (p < 0.001, in all comparisons). SuPAR levels at baseline were associated with the m-EASIX scores calculated at the same time point (p = 0.020), while suPAR and GDF-15 concentrations were correlated with EASIX scores at day 14 post-infusion (p < 0.001 in both comparisons). Moreover, sC5b-9 levels were correlated with the s-EASIX scores at infusion (p = 0.008) and the EASIX scores at day 14 (p = 0.005). In our study, sC5b9, suPAR, and GDF-15 levels were found to reflect endothelial injury in CAR-T cell recipients.

Hepatocyte-specific GDF15 overexpression improves high-fat diet-induced obesity and hepatic steatosis in mice via hepatic FGF21 induction

GDF15 and FGF21, stress-responsive cytokines primarily secreted from the liver, are promising therapeutic targets for metabolic dysfunction-associated steatotic liver disease (MASLD). However, the interaction between GDF15 and FGF21 remains unclear. We examined the effects of hepatocyte-specific GDF15 or FGF21 overexpression in high-fat diet (HFD)-fed mice for 8 weeks. Hydrodynamic injection of GDF15 or FGF21 sustained high circulating levels of GDF15 or FGF21, respectively, resulting in marked reductions in body weight, epididymal fat mass, insulin resistance, and hepatic steatosis. In addition, GDF15 treatment led to early reduction in body weight despite no change in food intake, indicating the role of GDF15 other than appetite loss. GDF15 treatment increased liver-derived serum FGF21 levels, whereas FGF21 treatment did not affect GDF15 expression. GDF15 promoted eIF2α phosphorylation and XBP1 splicing, leading to FGF21 induction. In murine AML12 hepatocytes treated with free fatty acids (FFAs), GDF15 overexpression upregulated Fgf21 mRNA levels and promoted eIF2α phosphorylation and XBP1 splicing. Overall, continuous exposure to excess FFAs resulted in a gradual increase of β-oxidation-derived reactive oxygen species and endoplasmic reticulum stress, suggesting that GDF15 enhanced this pathway and induced FGF21 expression. GDF15- and FGF21-related crosstalk is an important pathway for the treatment of MASLD.

Growth differentiation factor 15: Emerging role in liver diseases

Growth differentiation factor 15 (GDF15) is a cell stress-response cytokine within the transforming growth factor-β (TGFβ) superfamily. It is known to exert diverse effects on many metabolic pathways through its receptor GFRAL, which is expressed in the hindbrain, and transduces signals through the downstream receptor tyrosine kinase Ret. Since the liver is the core organ of metabolism, summarizing the functions of GDF15 is highly important. In this review, we assessed the relevant literature regarding the main metabolic, inflammatory, fibrogenic, tumorigenic and other effects of GDF15 on different liver diseases, including Metabolic dysfunction-associated steatotic liver disease(MASLD), alcohol and drug-induced liver injury, as well as autoimmune and viral hepatitis, with a particular focus on the pathogenesis of MASLD progression from hepatic steatosis to MASH, liver fibrosis and even hepatocellular carcinoma (HCC). Finally, we discuss the prospects of the clinical application potential of GDF15 along with its research and development progress. With better knowledge of GDF15, increasing in-depth research will lead to a new era in the field of liver diseases.

The brain-body energy conservation model of aging

Aging involves seemingly paradoxical changes in energy metabolism. Molecular damage accumulation increases cellular energy expenditure, yet whole-body energy expenditure remains stable or decreases with age. We resolve this apparent contradiction by positioning the brain as the mediator and broker in the organismal energy economy. As somatic tissues accumulate damage over time, costly intracellular stress responses are activated, causing aging or senescent cells to secrete cytokines that convey increased cellular energy demand (hypermetabolism) to the brain. To conserve energy in the face of a shrinking energy budget, the brain deploys energy conservation responses, which suppress low-priority processes, producing fatigue, physical inactivity, blunted sensory capacities, immune alterations and endocrine 'deficits'. We term this cascade the brain-body energy conservation (BEC) model of aging. The BEC outlines (1) the energetic cost of cellular aging, (2) how brain perception of senescence-associated hypermetabolism may drive the phenotypic manifestations of aging and (3) energetic principles underlying the modifiability of aging trajectories by stressors and geroscience interventions.

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.

Exerkines: Benign adaptation for exercise and benefits for non-alcoholic fatty liver disease

Exercise has multiple beneficial effects on human metabolic health and is regarded as a "polypill" for various diseases. At present, the lack of physical activity usually causes an epidemic of chronic metabolic syndromes, including obesity, cardiovascular diseases, and non-alcoholic fatty liver disease (NAFLD). Remarkably, NAFLD is emerging as a serious public health issue and is associated with the development of cirrhosis and hepatocellular carcinoma. Unfortunately, specific drug therapies for NAFLD and its more severe form, non-alcoholic steatohepatitis (NASH), are currently unavailable. Lifestyle modification is the foundation of treatment recommendations for NAFLD and NASH, especially for exercise. There are under-appreciated organs that crosstalk to the liver during exercise such as muscle-liver crosstalk. Previous studies have reported that certain exerkines, such as FGF21, GDF15, irisin, and adiponectin, are beneficial for liver metabolism and have the potential to be targeted for NAFLD treatment. In addition, some of exerkines can be modified for the new proteins and get enhanced functions, like IL-6/IC7Fc. Another importance of exercise is the physiological adaptation that combats metabolic diseases. Thus, this review aims to summarize the known exerkines and utilize a multi-omics mining tool to identify more exerkines for the future research. Overall, understanding the mechanisms by which exercise-induced exerkines exert their beneficial effects on metabolic health holds promise for the development of novel therapeutic strategies for NAFLD and related diseases.

The role of GDF15 in attenuating noise-induced hidden hearing loss by alleviating oxidative stress

Noise-induced hidden hearing loss (HHL) is a newly uncovered form of hearing impairment that causes hidden damage to the cochlea. Patients with HHL do not have significant abnormalities in their hearing thresholds, but they experience impaired speech recognition in noisy environments. However, the mechanisms underlying HHL remain unclear. In this study, we developed single-cell transcriptome profiles of the cochlea of mice with HHL, detailing changes in individual cell types. Our study revealed a transient threshold shift, reduced auditory brainstem response wave I amplitude, and decreased number of ribbon synapses in HHL mice. Our findings suggest elevated oxidative stress and GDF15 expression in cochlear hair cells of HHL mice. Notably, the upregulation of GDF15 attenuated oxidative stress and auditory impairment in the cochlea of HHL mice. This suggests that a therapeutic strategy targeting GDF15 may be efficacious against HHL.

Plasma proteomic signatures for type 2 diabetes mellitus and related traits in the UK Biobank cohort

Aims/hypothesis

The plasma proteome holds promise as a diagnostic and prognostic tool that can accurately reflect complex human traits and disease processes. We assessed the ability of plasma proteins to predict type 2 diabetes mellitus (T2DM) and related traits.

Methods

Clinical, genetic, and high-throughput proteomic data from three subcohorts of UK Biobank participants were analyzed for association with dual-energy x-ray absorptiometry (DXA) derived truncal fat (in the adiposity subcohort), estimated maximum oxygen consumption (VO2max) (in the fitness subcohort), and incident T2DM (in the T2DM subcohort). We used least absolute shrinkage and selection operator (LASSO) regression to assess the relative ability of non-proteomic and proteomic variables to associate with each trait by comparing variance explained (R2) and area under the curve (AUC) statistics between data types. Stability selection with randomized LASSO regression identified the most robustly associated proteins for each trait. The benefit of proteomic signatures (PSs) over QDiabetes, a T2DM clinical risk score, was evaluated through the derivation of delta (Δ) AUC values. We also assessed the incremental gain in model performance metrics using proteomic datasets with varying numbers of proteins. A series of two-sample Mendelian randomization (MR) analyses were conducted to identify potentially causal proteins for adiposity, fitness, and T2DM.

Results

Across all three subcohorts, the mean age was 56.7 years and 54.9% were female. In the T2DM subcohort, 5.8% developed incident T2DM over a median follow-up of 7.6 years. LASSO-derived PSs increased the R2 of truncal fat and VO2max over clinical and genetic factors by 0.074 and 0.057, respectively. We observed a similar improvement in T2DM prediction over the QDiabetes score [Δ AUC: 0.016 (95% CI 0.008, 0.024)] when using a robust PS derived strictly from the T2DM outcome versus a model further augmented with non-overlapping proteins associated with adiposity and fitness. A small number of proteins (29 for truncal adiposity, 18 for VO2max, and 26 for T2DM) identified by stability selection algorithms offered most of the improvement in prediction of each outcome. Filtered and clustered versions of the full proteomic dataset supplied by the UK Biobank (ranging between 600-1,500 proteins) performed comparably to the full dataset for T2DM prediction. Using MR, we identified 4 proteins as potentially causal for adiposity, 1 as potentially causal for fitness, and 4 as potentially causal for T2DM.

Conclusions/Interpretation

Plasma PSs modestly improve the prediction of incident T2DM over that possible with clinical and genetic factors. Further studies are warranted to better elucidate the clinical utility of these signatures in predicting the risk of T2DM over the standard practice of using the QDiabetes score. Candidate causally associated proteins identified through MR deserve further study as potential novel therapeutic targets for T2DM.

A plasma proteomic signature for atherosclerotic cardiovascular disease risk prediction in the UK Biobank cohort

Background

While risk stratification for atherosclerotic cardiovascular disease (ASCVD) is essential for primary prevention, current clinical risk algorithms demonstrate variability and leave room for further improvement. The plasma proteome holds promise as a future diagnostic and prognostic tool that can accurately reflect complex human traits and disease processes. We assessed the ability of plasma proteins to predict ASCVD.

Method

Clinical, genetic, and high-throughput plasma proteomic data were analyzed for association with ASCVD in a cohort of 41,650 UK Biobank participants. Selected features for analysis included clinical variables such as a UK-based cardiovascular clinical risk score (QRISK3) and lipid levels, 36 polygenic risk scores (PRSs), and Olink protein expression data of 2,920 proteins. We used least absolute shrinkage and selection operator (LASSO) regression to select features and compared area under the curve (AUC) statistics between data types. Randomized LASSO regression with a stability selection algorithm identified a smaller set of more robustly associated proteins. The benefit of plasma proteins over standard clinical variables, the QRISK3 score, and PRSs was evaluated through the derivation of Δ AUC values. We also assessed the incremental gain in model performance using proteomic datasets with varying numbers of proteins. To identify potential causal proteins for ASCVD, we conducted a two-sample Mendelian randomization (MR) analysis.

Result

The mean age of our cohort was 56.0 years, 60.3% were female, and 9.8% developed incident ASCVD over a median follow-up of 6.9 years. A protein-only LASSO model selected 294 proteins and returned an AUC of 0.723 (95% CI 0.708-0.737). A clinical variable and PRS-only LASSO model selected 4 clinical variables and 20 PRSs and achieved an AUC of 0.726 (95% CI 0.712-0.741). The addition of the full proteomic dataset to clinical variables and PRSs resulted in a Δ AUC of 0.010 (95% CI 0.003-0.018). Fifteen proteins selected by a stability selection algorithm offered improvement in ASCVD prediction over the QRISK3 risk score [Δ AUC: 0.013 (95% CI 0.005-0.021)]. Filtered and clustered versions of the full proteomic dataset (consisting of 600-1,500 proteins) performed comparably to the full dataset for ASCVD prediction. Using MR, we identified 11 proteins as potentially causal for ASCVD.

Conclusion

A plasma proteomic signature performs well for incident ASCVD prediction but only modestly improves prediction over clinical and genetic factors. Further studies are warranted to better elucidate the clinical utility of this signature in predicting the risk of ASCVD over the standard practice of using the QRISK3 score.

Hypothesis paper: GDF15 demonstrated promising potential in Cancer diagnosis and correlated with cardiac biomarkers

BACKGROUND

Cardiovascular toxicity represents a significant adverse consequence of cancer therapies, yet there remains a paucity of effective biomarkers for its timely monitoring and diagnosis. To give a first evidence able to elucidate the role of Growth Differentiation Factor 15 (GDF15) in the context of cancer diagnosis and its specific association with cardiac indicators in cancer patients, thereby testing its potential in predicting the risk of CTRCD (cancer therapy related cardiac dysfunction).

METHODS

Analysis of differentially expressed genes (DEGs), including GDF15, was performed by utilizing data from the public repositories of the Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO). Cardiomyopathy is the most common heart disease and its main clinical manifestations, such as heart failure and arrhythmia, are similar to those of CTRCD. Examination of GDF15 expression was conducted in various normal and cancerous tissues or sera, using available database and serum samples. The study further explored the correlation between GDF15 expression and the combined detection of cardiac troponin-T (c-TnT) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP), assessing the combined diagnostic utility of these markers in predicting risk of CTRCD through longitudinal electrocardiograms (ECG).

RESULTS

GDF15 emerged as a significant DEG in both cancer and cardiomyopathy disease models, demonstrating good diagnostic efficacy across multiple cancer types compared to healthy controls. GDF15 levels in cancer patients correlated with the established cardiac biomarkers c-TnT and NT-proBNP. Moreover, higher GDF15 levels correlated with an increased risk of ECG changes in the cancer cohort.

CONCLUSION

GDF15 demonstrated promising diagnostic potential in cancer identification; higher GDF15, combined with elevated cardiac markers, may play a role in the monitoring and prediction of CTRCD risk.

Sensory sentinels: Neuroimmune detection and food allergy

Food allergy is classically characterized by an inappropriate type-2 immune response to allergenic food antigens. However, how allergens are detected and how that detection leads to the initiation of allergic immunity is poorly understood. In addition to the gastrointestinal tract, the barrier epithelium of the skin may also act as a site of food allergen sensitization. These barrier epithelia are densely innervated by sensory neurons, which respond to diverse physical environmental stimuli. Recent findings suggest that sensory neurons can directly detect a broad array of immunogens, including allergens, triggering sensory responses and the release of neuropeptides that influence immune cell function. Reciprocally, immune mediators modulate the activation or responsiveness of sensory neurons, forming neuroimmune feedback loops that may impact allergic immune responses. By utilizing cutaneous allergen exposure as a model, this review explores the pivotal role of sensory neurons in allergen detection and their dynamic bidirectional communication with the immune system, which ultimately orchestrates the type-2 immune response. Furthermore, it sheds light on how peripheral signals are integrated within the central nervous system to coordinate hallmark features of allergic reactions. Drawing from this emerging evidence, we propose that atopy arises from a dysregulated neuroimmune circuit.

Double-side role of short chain fatty acids on host health via the gut-organ axes

Short chain fatty acids (SCFA) exist in dietary foods and are produced by the fermentation of gut microbiota, and are considered an important element for regulating host health. Through blood circulation, SCFA produced in the gut and obtained from foods have an impact on the intestinal health as well as vital organs of the host. It has been recognized that the gut is the "vital organ" in the host. As the gut microbial metabolites, SCFA could create an "axis" connecting the gut and to other organs. Therefore, the "gut-organ axes" have become a focus of research in recent years to analyze organism health. In this review, we summarized the sources, absorption properties, and the function of SCFA in both gut and other peripheral tissues (brain, kidney, liver, lung, bone and cardiovascular) in the way of "gut-organ axes". Short chain fatty acids exert both beneficial and pathological role in gut and other organs in various ways, in which the beneficial effects are more pronounced. In addition, the beneficial effects are reflected in both preventive and therapeutic effects. More importantly, the mechanisms behinds the gut and other tissues provided insight into the function of SCFA, assisting in the development of novel preventive and therapeutic strategies for maintaining the host health.