GPNMB plays a protective role against obesity-related metabolic disorders by reducing macrophage inflammatory capacity

Nanovaccine loaded with seno-antigen target senescent cells to improve metabolic disorders of adipose tissue and cardiac dysfunction

The buildup of senescent cells exacerbates metabolic disorders in adipose tissue and contributes to aging-related cardiac dysfunction. Targeted clearance of senescent cells can markedly ameliorate these aging-related diseases. Here, we developed a novel nanovaccine (GK-NaV) loaded with seno-antigen that is self-assembled from the fusion of cationic protein (K36) and seno-antigen peptide (Gpnmb). The GK-NaV could be highly engulfed by bone marrow-derived dendritic cells (BMDCs) and efficiently present antigens on the cellular surface, thereby promoting DCs maturation and activation of CD8+T cells in vitro. Following subcutaneous immunization, GK-NaV not only exhibited a noticeable antigen depot effect but also markedly activated specific cellular immune responses, enhancing the immunoreactivity and cytotoxic effects of CD8+T cells. Consequently, the targeted anti-aging immunity triggered by GK-NaV demonstrated the ability to selectively eliminate senescent adipocytes and cardiomyocytes in high-fat diet (HFD)-induced progeroid mice, leading to a significant improvement in age-related metabolic disorders in adipose tissue and cardiac dysfunction. Hence, our findings indicate that immunization with GK-NaV targeting seno-antigens may represent a promising strategy for novel senolytic therapies.

Malignant mesothelioma-associated inflammatory microenvironment promotes tumor progression via GPNMB

BACKGROUND

Tumor-Associated Macrophages (TAMs) are the main immune component of the tumor stroma with heterogeneous functional activities, predominantly suppressing the immune response and promoting tumor progression, also via secretion of different factors. Among these, GPNMB (Glycoprotein non-metastatic B) is usually associated with disease progression in several tumor types. Malignant pleural mesothelioma (MPM) a severe neoplasia with poor prognosis, is characterized by an abundancy of TAMs, testifying the presence of a long-lasting inflammation which is pathogenetic of the disease. However, the role of GPNMB in MPM is unclear.

METHODS

Clinical samples from patients with MPM were used to measure RNA and protein levels of GPNMB. The functional role of GPNMB in vivo was studied in an orthotopic mouse model of mesothelioma using the murine cell lines AB1 and AB22. Experiments included in vivo tumor growth in wild type and in GPNMB-deficient mice and blocking of GPNMB-induced signaling with anti-CD44 antibodies.

RESULTS

We show that in human and murine MPM tissues the protein GPNMB is mainly produced by infiltrating TAMs. Gpnmb RNA levels in MPM patients from TCGA are significantly associated with lower survival. Using an orthotopic mouse model of mesothelioma we observed that in GPNMB-defective mice (DBA2/J mice) unable to produce the protein, tumors formed by AB1 and AB22 mesothelioma cells grow significantly less than in GPNMB-proficient mice (DBA2/J-Gpnmb+ mice), indicating that host GPNMB is involved in tumor progression. Likewise, the ectopic expression of GPNMB in AB1 and AB22 cells causes an acceleration of tumor growth in vivo, significantly different compared to mock-transduced cells. Treatment of tumor-bearing mice with blocking anti-CD44 (a major receptor for GPNMB) results in a significant reduction of tumor growth.

CONCLUSIONS

Overall, these results indicate that the protein GPNMB, a product and marker gene of TAMs, is a driver of mesothelioma progression and may constitute a promising therapeutic target.

GPNMB Suppresses Inflammation and Extracellular Matrix Degradation in Nucleus Pulposus Cells by Inhibiting Pro-Inflammatory Cytokine Production and Activation of the NF-κB Signaling Pathway

Lumbar disc herniation is primarily caused by intervertebral disc degeneration (IVDD). Nucleus pulposus (NP) cell dysfunction leads to pro-inflammatory cytokines secretion increase, causing extracellular matrix (ECM) degradation. ECM is essential for maintaining normal disc function. Glycoprotein (Transmembrane) Nmb (GPNMB) is strongly associated with inflammation, and its expression and effects in IVDD are unclear. We categorized 40 clinically collected IVDD samples using the magnetic resonance imaging (MRI)-based Pfirrmann grading system. GPNMB mRNA expression was notably suppressed in patients with severe IVDD compared with patients with mild IVDD. Increased GPNMB mRNA expression correlated with decreased Interleukin-6 (IL-6) expression and increased collagen type II (COL2A1) expression levels. We utilized lentivirus to overexpress GPNMB in IL-1β-induced NP cells to explore its function in IVDD. GPNMB overexpression inhibited pro-inflammatory cytokines Tumor necrosis factor-alpha and IL-6 secretion in IL-1β-induced NP cells, while anti-inflammatory cytokine IL-10 content was increased. In addition, GPNMB overexpression inhibited NP ECM degradation by decreasing ECM-degrading enzymes matrix metalloproteinases-3/13 and a disintegrin and metalloproteinase with thrombospondin motifs-4/5 in vitro. Mechanism studies revealed that GPNMB was bound to CD44, a receptor expressed on the NP cell surface. GPNMB overexpression inhibited nuclear factor-κB (NF-κB) p65 phosphorylation and nuclear translocation in vitro, possibly through CD44. In conclusion, GPNMB suppressed the expression of pro-inflammatory cytokines and ECM degradation in NP cells by inhibiting activation of NF-κB.

The glycoprotein GPNMB protects against oxidative stress through enhanced PI3K/AKT signaling in epidermal keratinocytes

Vitiligo, an autoimmune disease caused by environmental and genetic factors, is characterized by the specific loss of epidermal melanocytes (MCs). IFN-γ, predominantly derived from MC-targeting CD8+ T cells, plays a key role in vitiligo pathogenesis. Previously, we found that glycoprotein nonmetastatic melanoma protein B (GPNMB) is specifically lost in the basal epidermal layer of vitiligo lesions and downregulated by IFN-γ in normal human epidermal keratinocytes (KCs) (NHEKs). This study aimed to determine the role of KC GPNMB in normal and vitiligo epidermis and demonstrated that GPNMB plays a protective role against H2O2-induced oxidative stress due to its extracellular domain. In contrast, the NRF2/KEEP1 system was not involved in the anti-oxidative response in NHEKs but was active in MCs. GPNMB knockdown reduced the phosphorylation levels of AKTT308 and AKTS473 after H2O2 treatment, accompanied by reduced Dickkopf-1 (DKK1) mRNA and protein production and decreased FOXM1 mRNA expression. These results suggested that GPNMB protects KCs from H2O2-induced cell death through enhanced PI3K/AKT signaling, and WNT/β-catenin/FOXM1 and DKK1/CKAP4/AKT pathways. Furthermore, a significant increase in thioredoxin-interacting protein (TXNIP) following GPNMB knockdown was observed, indicating the enhanced phosphorylation of JNK and p38 and suppression of WNT/β-catenin signaling. These results suggest that the decreased expression of epidermal GPNMB in vitiligo lesions triggers increased sensitivity to H2O2-induced oxidative stress and decreased WNT/β-catenin signaling, consistent with the pathological features of the vitiligo epidermis. These findings may enhance our understanding of vitiligo pathogenesis, provide insights into the reduced risk of epidermal cancers, and highlight novel targets for treatment.

Mechanistic study of the regulation of mitochondrial function by the GPNMB/Nrf2/NF-κB signaling pathway mediated by Quzhi Tang to alleviate chondrocyte senescence

ETHNOPHARMACOLOGICAL RELEVANCE

Quzhi Tang (QZT) is a compound formula consisting of six traditional Chinese medicinal herbs. It has achieved good clinical results in the treatment of knee osteoarthritis (KOA), and the potential drug mechanisms involved are worth exploring in depth.

MATERIALS AND METHODS

Using single-cell transcriptome analysis, this study identified the key target of senescence, GPNMB. Then, it investigated the mechanism by which QZT regulates the GPNMB/Nrf2/NF-κB signaling pathway to repair mitochondrial damage and ameliorate the process of chondrocyte senescence.

RESULTS

We collected cartilage tissues from mice and identified GPNMB as a key target of chondrocyte senescence by combining transcriptomics, histopathology, molecular biology, and immunology methods. The effects of QZT on the level of chondrocyte senescence in mice and its ameliorative effect on KOA were studied. In in vivo experiments, we explored the mechanism of GPNMB in the development of senescence in detail and revealed that, after siRNA-GPNMB interference, chondrocytes exhibited reduced impairment of mitochondrial function and senescence under equal amounts of stimuli, increasing Nrf2 expression and reducing NF-κB expression. In addition, the level of oxidative stress increased in chondrocytes overexpressing GPNMB after lentiviral infiltration, aggravating the impairment of mitochondrial function. After treatment with QZT, chondrocytes overexpressing GPNMB were able to increase Nrf2 expression, decrease NF-κB expression, repair mitochondrial damage, and improve the degree of chondrocyte aging.

CONCLUSION

We concluded that the GPNMB/Nrf2/NF-κB signaling pathway plays an important role in chondrocyte senescence and that QZT was able to reduce intracellular oxidative stress and restore impaired mitochondrial function by regulating the expression level of the GPNMB/Nrf2/NF-κB signaling pathway, reducing the level of chondrocyte senescence in the KOA process.

Innate immune cells link dietary cues to normal and abnormal metabolic regulation

A slew of common metabolic disorders, including type 2 diabetes, metabolic dysfunction-associated steatotic liver disease and steatohepatitis, are exponentially increasing in our sedentary and overfed society. While macronutrients directly impact metabolism and bioenergetics, new evidence implicates immune cells as critical sensors of nutritional cues and important regulators of metabolic homeostasis. A deeper interrogation of the intricate and multipartite interactions between dietary components, immune cells and metabolically active tissues is needed for a better understanding of metabolic regulation and development of new treatments for common metabolic diseases. Responding to macronutrients and micronutrients, immune cells play pivotal roles in interorgan communication between the microbiota, small intestine, metabolically active cells including hepatocytes and adipocytes, and the brain, which controls feeding behavior and energy expenditure. This Review focuses on the response of myeloid cells and innate lymphocytes to dietary cues, their cross-regulatory interactions and roles in normal and aberrant metabolic control.

Sensitive Profiling of Mouse Liver Membrane Proteome Dysregulation Following a High-Fat and Alcohol Diet Treatment

Alcohol consumption and high-fat (HF) diets often coincide in Western society, resulting in synergistic negative effects on liver function. Although studies have analyzed the global protein expression in the context of alcoholic liver disease (ALD) and metabolic dysfunction-associated steatotic liver disease (MASLD), none has offered specific insights on liver dysregulation at the membrane proteome level. Membrane-specific profiling of metabolic and compensatory phenomena is usually overshadowed in conventional proteomic workflows. In this study, we use the Peptidisc method to isolate and compare the membrane protein (MP) content of the liver with its unique biological functions. From mice fed with an HF diet and ethanol in drinking water, we annotate over 1500 liver proteins with half predicted to have at least one transmembrane segment. Among them, we identify 106 integral MPs that are dysregulated compared to the untreated sample. Gene Ontology analysis reveals several dysregulated membrane-associated processes like lipid metabolism, cell adhesion, xenobiotic processing, and mitochondrial membrane formation. Pathways related to cholesterol and bile acid transport are also mutually affected, suggesting an adaptive mechanism to counter the upcoming steatosis of the liver model. Taken together, our Peptidisc-based profiling of the diet-dysregulated liver provides specific insights and hypotheses into the role of the transmembrane proteome in disease development, and flags desirable MPs for therapeutic and diagnostic targeting.

Glycoprotein non-metastatic melanoma protein B (GPNMB): An attractive target in atherosclerosis

Atherosclerosis (AS), the leading cause of cardiovascular diseases, is heavily influenced by inflammation, lipid accumulation, autophagy, and aging. The expression of glycoprotein non-metastatic melanoma B (GPNMB) has been observed to correlate with lipid content, inflammation, and aging, progressively increasing as atherosclerosis advances through its various stages, from baseline to early and advanced phases. However, the interaction between GPNMB and AS is controversial. Knockout of GPNMB has been shown to increase atherosclerotic plaque burden in mice. Conversely, targeted elimination of GPNMB-positive cells reduced atherosclerotic burden. These seemingly contradictory findings underscore the complexity of the issue and highlight the need for further research to reconcile these discrepancies and to elucidate the precise role of GPNMB in the pathogenesis of AS.

Seno-antigen-pulsed dendritic cell vaccine induce anti-aging immunity to improve adipose tissue senescence and metabolic abnormalities

Anti-aging immunity induced by vaccines was recently reported to enable the elimination of senescent cells. However, the initial immune response to vaccination declines with age, and there is evidence that elderly dendritic cells (DCs) have a reduced capacity to stimulate T cells. Identification of alternative anti-aging vaccine is therefore warranted. Here, we developed a DC vaccine that delivers a cationic protein (CP) fused with the seno-antigen peptides Gpnmb (Gpnmb-CP) into DCs. The Gpnmb-CP-pulsed DC vaccine (Gpnmb-CP-DC) efficiently presented antigens and activated CD8+ T cells, leading to enhanced immune cytotoxicity and memory responses in CD8+ T cells. Thus, the targeted anti-aging immunity triggered by Gpnmb-CP-DC has the ability to selectively eliminate senescent adipocytes and effectively improve age-related metabolic abnormalities in both high-fat diet (HFD)-induced young and aged mice models, as well as in natural aging mouse model. In contrast, the Gpnmb-CP protein vaccine exhibits minimal efficacy in aged mice model. Furthermore, we observed a decreased phagocytic capacity for antigens in aging DCs, accompanied by an upregulation of the immune checkpoint PDL1 expression and a noticeable decline in activated CD8+ T cell. Hence, Gpnmb-CP-DC emerges as a promising vaccine candidate, demonstrating the capacity to induce potent anti-aging immunity, mitigating adipose tissue senescence and metabolic abnormalities, while resilient to the senescent environment of the organism.

Investigating the role and regulation of GPNMB in progranulin-deficient macrophages

Introduction

Progranulin (PGRN) is a holoprotein that is internalized and taken to the lysosome where it is processed to individual granulins (GRNs). PGRN is critical for successful aging, and insufficient levels of PGRN are associated with increased risk for developing neurodegenerative diseases like AD, PD, and FTD. A unifying feature among these diseases is dysregulation of peripheral immune cell populations. However, considerable gaps exist in our understanding of the function(s) of PGRN/GRNs in immune cells and their role in regulating central-peripheral neuroimmune crosstalk. One of the most upregulated genes and proteins in humans with GRN haploinsufficiency and in aged Grn knock-out (KO) mice is glycoprotein non-metastatic B (GPNMB) but its normal role within the context of immune crosstalk has not been elucidated.

Methods

To address this gap, peritoneal macrophages (pMacs) from 5-to-6-month old WT and Grn KO mice were assessed for Gpnmb expression and stimulation-dependent cytokine release in the presence or absence of the Gpnmb extracellular domain (ECD). Cellular localization, as well as inhibition of, the microphthalmia-associated transcription factor (MITF) was assessed to determine its mechanistic role in Gpnmb overexpression in Grn KO pMacs.

Results

We observed an increase in GPNMB protein and mRNA as a result of insufficient progranulin in peripheral immune cells at a very early age relative to previous reports on the brain. Stimulation-dependent cytokine release was decreased in the media of Grn KO pMacs relative to WT controls; a phenotype that could be mimicked in WT pMacs with the addition og GPNMB ECD. We also found that MITF is dysregulated in Grn KO pMacs; however, its nuclear translocation and activity are not required to rescue the immune dysregulation of Grn KO macrophages, suggesting redundancy in the system.

Discussion

These findings highlight the fact that knowledge of early-stage disease mechanism(s) in peripheral populations may inform treatment strategies to delay disease progression at an early, prodromal timepoint prior to development of neuroinflammation and CNS pathology.

Biofluid GPNMB/osteoactivin as a potential biomarker of ageing: A cross-sectional study

Background

Glycoprotein non-metastatic melanoma B (GPNMB)/osteoactivin was first identified in the human melanoma cell lines. GPNMB plays a key role in the anti-inflammatory and antioxidative functions as well as osteoblast differentiation, cancer progression, and tissue regeneration. Recently, GPNMB was used as an anti-aging vaccine for mice. The present study aimed to investigate the potential of biofluid GPNMB as an aging biomarker in humans using serum and urine samples from an aging Chinese population.

Methods

We analyzed RNA-sequencing data (GSE132040) from 17 murine organs across different ages to assess the gene expression of potential ageing biomarkers. Spearman's correlation coefficients were used to evaluate the relationship between gene expression and age. Meanwhile, a cross-sectional population study was conducted, which included 473 participants (aged 25-91 years), a representative subset of participants from the Peng Zu Study on Healthy Ageing in China (Peng Zu Cohort). Biofluid GPNMB levels were measured by ELISA. The associations of serum and urine GPNMB levels with various clinical and anthropometrical indices were assessed using ANOVA, Kruskal-Wallis H test, and univariate and multivariate linear regression analyses.

Results

In mice, the Gpnmb mRNA expression levels showed a significant positive association with age in multiple organs in mice (P < 0.05). In Peng Zu Cohort, biofluid (both serum and urine) GPNMB levels showed a positive correlation with age (P < 0.05). Univariate linear regression analysis revealed that serum GPNMB levels were negatively associated with skeletal muscle mass index (SMI, P < 0.05) and insulin-like growth factor 1 (IGF-1, P < 0.05), and urine GPNMB levels showed a negative association with total bile acids (TBA, P < 0.05). Multivariate linear regression analysis further indicated that serum GPNMB levels negatively correlated with the systemic immune-inflammation index (SII, P < 0.05), and the urine GPNMB levels maintained a negative association with TBA (P < 0.05), additionally, urine GPNMB levels in men were significantly lower than in women (P < 0.05).

Conclusions

The biofluid GPNMB was a strong clinical biomarker candidate for estimating biological aging.

Glycoprotein Non-metastatic Melanoma Protein B (GPNMB) Protects Against Neuroinflammation and Neuronal Loss in Pilocarpine-induced Epilepsy via the Regulation of Microglial Polarization

Epilepsy is a progressive neurodegenerative disease highlighted by recurrent seizures, neuroinflammation, and the loss of neurons. Microglial dysfunction is commonly found in epileptic foci and contributes to neuroinflammation in the initiation and progression of epilepsy. Glycoprotein non-metastatic melanoma protein B (GPNMB), a transmembrane glycoprotein, has been involved in the microglial activation and neuroinflammation response. The present study investigated the functional significance of GPNMB in epilepsy. A proven model of epilepsy was established by intraperitoneal injection of pilocarpine to male Sprague Dawley rats. Lentivirus vectors carrying GPNMB or GPNMB short hairpin RNA (shGPNMB) were injected into the hippocampus to induce overexpression or knockdown of GPNMB. GPNMB expression was significantly upregulated and overexpression of GPNMB in the hippocampus reduced seizure activity and neuronal loss after status epilepticus (SE). We here focused on the effects of GPNMB deficiency on neuronal injury and microglia polarization 28 days after SE. GPNMB knockdown accelerated neuronal damage in the hippocampus, evidenced by increased neuron loss and neuronal cell apoptosis. Following GPNMB knockdown, M1 polarization (iNOS) and secretion of pro-inflammatory cytokines IL-6, IL-1β, and TNF-α were increased, and M2 polarization (Arg1) and secretion of anti-inflammatory cytokines IL-4, IL-10, and TGF-β were decreased. BV2 cells were used to further confirm the regulatory role of GPNMB in modulating phenotypic transformations and inflammatory cytokine expressions in microglia. In conclusion, these results indicated that GPNMB suppressed epilepsy through repression of hippocampal neuroinflammation, suggesting that GPNMB might be considered the potential neurotherapeutic target for epilepsy management and play a protective role against epilepsy by modulating the polarization of microglia.

Aging impairs cold-induced beige adipogenesis and adipocyte metabolic reprogramming

The energy-burning capability of beige adipose tissue is a potential therapeutic tool for reducing obesity and metabolic disease, but this capacity is decreased by aging. Here, we evaluate the impact of aging on the profile and activity of adipocyte stem and progenitor cells (ASPCs) and adipocytes during the beiging process in mice. We found that aging increases the expression of Cd9 and other fibro-inflammatory genes in fibroblastic ASPCs and blocks their differentiation into beige adipocytes. Fibroblastic ASPC populations from young and aged mice were equally competent for beige differentiation in vitro, suggesting that environmental factors suppress adipogenesis in vivo. Examination of adipocytes by single nucleus RNA-sequencing identified compositional and transcriptional differences in adipocyte populations with aging and cold exposure. Notably, cold exposure induced an adipocyte population expressing high levels of de novo lipogenesis (DNL) genes, and this response was severely blunted in aged animals. We further identified Npr3, which encodes the natriuretic peptide clearance receptor, as a marker gene for a subset of white adipocytes and an aging-upregulated gene in adipocytes. In summary, this study indicates that aging blocks beige adipogenesis and dysregulates adipocyte responses to cold exposure and provides a resource for identifying cold and aging-regulated pathways in adipose tissue.

Temporal Single-Cell Sequencing Analysis Reveals That GPNMB-Expressing Macrophages Potentiate Muscle Regeneration

Macrophages play a crucial role in coordinating the skeletal muscle repair response, but their phenotypic diversity and the transition of specialized subsets to resolution-phase macrophages remain poorly understood. To address this issue, we induced injury and performed single-cell RNA sequencing on individual cells in skeletal muscle at different time points. Our analysis revealed a distinct macrophage subset that expressed high levels of Gpnmb and that coexpressed critical factors involved in macrophage-mediated muscle regeneration, including Igf1, Mertk, and Nr1h3. Gpnmb gene knockout inhibited macrophage-mediated efferocytosis and impaired skeletal muscle regeneration. Functional studies demonstrated that GPNMB acts directly on muscle cells in vitro and improves muscle regeneration in vivo. These findings provide a comprehensive transcriptomic atlas of macrophages during muscle injury, highlighting the key role of the GPNMB macrophage subset in regenerative processes. Targeting GPNMB signaling in macrophages could have therapeutic potential for restoring skeletal muscle integrity and homeostasis.

Toward Ultrasound Molecular Imaging of Endothelial Dysfunction in Diabetes: Targets, Strategies, and Challenges

Diabetes vasculopathy is a significant complication of diabetes mellitus (DM), and early identification and timely intervention can effectively slow the progression. Accumulating studies have shown that diabetes causes vascular complications directly or indirectly through a variety of mechanisms. Direct imaging of the endothelial molecular changes not only identifies the early stage of diabetes vasculopathy but also sheds light on the precise treatment. Targeted ultrasound contrast agent (UCA)-based ultrasound molecular imaging (UMI) can noninvasively detect the expression status of molecular biomarkers overexpressed in the vasculature, thereby being a potential strategy for the diagnosis and treatment response evaluation of DM. Amounts of efforts have been focused on identification of the molecular targets expressed in the vasculature, manufacturing strategies of the targeted UCA, and the clinical translation for the diagnosis and evaluation of therapeutic efficacy in both micro- and macrovasculopathy in DM. This review summarizes the latest research progress on endothelium-targeted UCA and discusses their promising future and challenges in diabetes vasculopathy theranostics.

Investigating the Role and Regulation of GPNMB in Progranulin-deficient Macrophages

Progranulin is a holoprotein that is critical for successful aging, and insufficient levels of progranulin are associated with increased risk for developing age-related neurodegenerative diseases like AD, PD, and FTD. Symptoms can vary widely, but a uniting feature among these different neurodegenerative diseases is prodromal peripheral immune cell phenotypes. However, there remains considerable gaps in the understanding of the function(s) of progranulin in immune cells, and recent work has identified a novel target candidate called GPNMB. We addressed this gap by investigating the peritoneal macrophages of 5-6-month-old Grn KO mice, and we discovered that GPNMB is actively increased as a result of insufficient progranulin and that MITF, a transcription factor, is also dysregulated in progranulin-deficient macrophages. These findings highlight the importance of early-stage disease mechanism(s) in peripheral cell populations that may lead to viable treatment strategies to delay disease progression at an early, prodromal timepoint and extend therapeutic windows.

Aging impairs cold-induced beige adipogenesis and adipocyte metabolic reprogramming

The energy-burning capability of beige adipose tissue is a potential therapeutic tool for reducing obesity and metabolic disease, but this capacity is decreased by aging. Here, we evaluate the impact of aging on the profile and activity of adipocyte stem and progenitor cells (ASPCs) and adipocytes during the beiging process. We found that aging increases the expression of Cd9 and other fibro-inflammatory genes in fibroblastic ASPCs and blocks their differentiation into beige adipocytes. Fibroblastic ASPC populations from young and aged mice were equally competent for beige differentiation in vitro, suggesting that environmental factors suppress adipogenesis in vivo. Examination of adipocytes by single nucleus RNA-sequencing identified compositional and transcriptional differences in adipocyte populations with age and cold exposure. Notably, cold exposure induced an adipocyte population expressing high levels of de novo lipogenesis (DNL) genes, and this response was severely blunted in aged animals. We further identified natriuretic peptide clearance receptor Npr3, a beige fat repressor, as a marker gene for a subset of white adipocytes and an aging-upregulated gene in adipocytes. In summary, this study indicates that aging blocks beige adipogenesis and dysregulates adipocyte responses to cold exposure and provides a unique resource for identifying cold and aging-regulated pathways in adipose tissue.

Roles of Activin A and Gpnmb in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD)

Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as nonalcoholic fatty liver disease [NAFLD]) and metabolic dysfunction-associated steatohepatitis (MASH, formerly known as nonalcoholic steatohepatitis [NASH]) are leading chronic liver diseases, driving cirrhosis, hepatocellular carcinoma, and mortality. MASLD/MASH is associated with increased senescence proteins, including Activin A, and senolytics have been proposed as a therapeutic approach. To test the role of Activin A, we induced hepatic expression of Activin A in a murine MASLD/MASH model. Surprisingly, overexpression of hepatic Activin A dramatically mitigated MASLD, reducing liver steatosis and inflammation as well as systemic fat accumulation, while improving insulin sensitivity. Further studies identified a dramatic decrease in the lipid-associated macrophages marker glycoprotein NMB (Gpnmb) by Activin A, and Gpnmb knockdown in the same model produced similar benefits and transcriptional changes to Activin A expression. These studies reveal a surprising protective role for Activin A in MASLD and the potential for SASP proteins to have context-specific beneficial effects. Moreover, they implicate both Activin A and Gpnmb as potential therapeutic targets for this condition.

ARTICLE HIGHLIGHTS

Glycoprotein Non-Metastatic Protein B (GPNMB): The Missing Link Between Lysosomes and Obesity

As a result of an unhealthy diet and limited physical activity, obesity has become a widespread pandemic worldwide and is an important predictor for the development of cardiovascular disease. Obesity is often characterized by a pro-inflammatory environment in white adipose tissue (WAT), mainly due to increased macrophage infiltration. These immune cells boost their lipid concentrations by accumulating the content of dying adipocytes. As the lysosome is highly involved in lipid handling, the progressive lipid accumulation may result in lysosomal stress and a metabolic shift. Recent studies have identified glycoprotein non-metastatic melanoma protein B (GPNMB) as a novel marker of inflammatory diseases. GPNMB is a type I transmembrane protein on the cell surface of various cell types, such as macrophages, dendritic cells, osteoblasts, and microglia, from which it can be proteolytically cleaved into a soluble molecule. It is induced by lysosomal stress via microphthalmia-associated transcription factor and thus has been found to be upregulated in many lysosomal storage disorders. In addition, a clear connection between GPNMB and obesity was recently established. GPNMB was shown to have protective and anti-inflammatory effects in most cases, preventing the progression of obesity-related metabolic disorders. In contrast, soluble GPNMB likely has the opposite effect and promotes lipogenesis in WAT. This review aims to summarize and clarify the role of GPNMB in the progression of obesity and to highlight its potential use as a biomarker for lipid-associated disorders.

Progranulin and GPNMB: interactions in endo-lysosome function and inflammation in neurodegenerative disease

BACKGROUND

Alterations in progranulin (PGRN) expression are associated with multiple neurodegenerative diseases (NDs), including frontotemporal dementia (FTD), Alzheimer's disease (AD), Parkinson's disease (PD), and lysosomal storage disorders (LSDs). Recently, the loss of PGRN was shown to result in endo-lysosomal system dysfunction and an age-dependent increase in the expression of another protein associated with NDs, glycoprotein non-metastatic B (GPNMB).

MAIN BODY

It is unclear what role GPNMB plays in the context of PGRN insufficiency and how they interact and contribute to the development or progression of NDs. This review focuses on the interplay between these two critical proteins within the context of endo-lysosomal health, immune function, and inflammation in their contribution to NDs.

SHORT CONCLUSION

PGRN and GPNMB are interrelated proteins that regulate disease-relevant processes and may have value as therapeutic targets to delay disease progression or extend therapeutic windows.

Serum glycoprotein non-metastatic melanoma protein B (GPNMB) level as a potential biomarker for diabetes mellitus-related cataract: A cross-sectional study

BACKGROUND

Diabetes mellitus (DM), a metabolic disease that has attracted significant research and clinical attention over the years, can affect the eye structure and induce cataract in patients diagnosed with DM. Recent studies have indicated the relationship between glycoprotein non-metastatic melanoma protein B (GPNMB) and DM and DM-related renal dysfunction. However, the role of circulating GPNMB in DM-associated cataract is still unknown. In this study, we explored the potential of serum GPNMB as a biomarker for DM and DM-associated cataract.

METHODS

A total of 406 subjects were enrolled, including 60 and 346 subjects with and without DM, respectively. The presence of cataract was evaluated and serum GPNMB levels were measured using a commercial enzyme-linked immunosorbent assay kit.

RESULTS

Serum GPNMB levels were higher in diabetic individuals and subjects with cataract than in those without DM or cataract. Subjects in the highest GPNMB tertile group were more likely to have metabolic disorder, cataract, and DM. Analysis performed in subjects with DM elucidated the correlation between serum GPNMB levels and cataract. Receiver operating characteristic (ROC) curve analysis also indicated that GPNMB could be used to diagnose DM and cataract. Multivariable logistic regression analysis illustrated that GPNMB levels were independently associated with DM and cataract. DM was also found to be an independent risk factor for cataract. Further surveys revealed the combination of serum GPNMB levels and presence of DM was associated with a more precise identification of cataract than either factor alone.

CONCLUSIONS

Increased circulating GPNMB levels are associated with DM and cataract and can be used as a biomarker of DM-associated cataract.

Cellular Landscapes of Nondiseased Human Cardiac Valves From End-Stage Heart Failure-Explanted Heart

BACKGROUND

Exploring the mechanisms of valvular heart disease at the cellular level may be useful to identify new therapeutic targets; however, the comprehensive cellular landscape of nondiseased human cardiac valve leaflets remains unclear.

METHODS

The cellular landscapes of nondiseased human cardiac valve leaflets (5 aortic valves, 5 pulmonary valves, 5 tricuspid valves, and 3 mitral valves) from end-stage heart failure patients undergoing heart transplantation were explored using single-cell RNA sequencing. Bioinformatics was used to identify the cell types, describe the cell functions, and investigate cellular developmental trajectories and interactions. Differences among the 4 types of cardiac valves at the cellular level were summarized. Pathological staining was performed to validate the key findings of single-cell RNA sequencing. An integrative analysis of our single-cell data and published genome-wide association study-based and bulk RNA sequencing-based data provided insights into the cell-specific contributions to calcific aortic valve diseases.

RESULTS

Six cell types were identified among 128 412 cells from nondiseased human cardiac valve leaflets. Valvular interstitial cells were the largest population, followed by myeloid cells, lymphocytes, valvular endothelial cells, mast cells, and myofibroblasts. The 4 types of cardiac valve had distinct cellular compositions. The intercellular communication analysis revealed that valvular interstitial cells were at the center of the communication network. The integrative analysis of our single-cell RNA sequencing data revealed key cellular subpopulations involved in the pathogenesis of calcific aortic valve diseases.

CONCLUSIONS

The cellular landscape differed among the 4 types of nondiseased cardiac valve, which might explain their differences in susceptibility to pathological remodeling and valvular heart disease.

Circulating Adipokines and Hepatokines Serve as Diagnostic Markers during Obesity Therapy

Allocation of morbidly obese patients to either conservative therapy options-such as lifestyle intervention and/or low-calorie diet (LCD)-or to bariatric surgery-preferably sleeve gastrectomy or Roux-en-Y gastric bypass (RYGB)-represents a crucial decision in order to obtain sustainable metabolic improvement and weight loss. The present study encompasses 160 severely obese patients, 81 of whom participated in an LCD program, whereas 79 underwent RYGB surgery. The post-interventional dynamics of physiologically relevant adipokines and hepatokines (ANGPTL4, CCL5, GDF15, GPNMB, IGFBP6), as well as their correlation with fat mass reduction and improvement of liver fibrosis, were analyzed. Systemic GDF15 was characterized as an excellent predictive marker for hepatic fibrosis as well as type 2 diabetes mellitus. Of note, baseline GDF15 serum concentrations were positively correlated with NFS and HbA1c levels after correction for BMI, suggesting GDF15 as a BMI-independent marker of hepatic fibrosis and T2D in obese individuals. Specific GDF15 cut-off values for both diseases were calculated. Overall, the present data demonstrate that circulating levels of specific adipokines and hepatokines are regulated with therapy-induced fat loss and metabolic improvement and might, therefore, serve as biomarkers for the success of obesity therapy strategies.

Expression pattern and clinical value of Key RNA methylation modification regulators in ischemic stroke

Ischemic stroke (IS) is one of the major causes of death and disability worldwide, and effective diagnosis and treatment methods are lacking. RNA methylation, a common epigenetic modification, plays an important role in disease progression. However, little is known about the role of RNA methylation modification in the regulation of IS. The aim of this study was to investigate RNA methylation modification patterns and immune infiltration characteristics in IS through bioinformatics analysis. We downloaded gene expression profiles of control and IS model rat brain tissues from the Gene Expression Omnibus database. IS profiles were divided into two subtypes based on RNA methylation regulators, and functional enrichment analyses were conducted to determine the differentially expressed genes (DEGs) between the subtypes. Weighted gene co-expression network analysis was used to explore co-expression modules and genes based on DEGs. The IS clinical diagnosis model was successfully constructed and four IS characteristic genes (GFAP, GPNMB, FKBP9, and CHMP5) were identified, which were significantly upregulated in IS samples. Characteristic genes were verified by receiver operating characteristic curve and real-time quantitative PCR analyses. The correlation between characteristic genes and infiltrating immune cells was determined by correlation analysis. Furthermore, GPNMB was screened using the protein-protein interaction network, and its regulatory network and the potential therapeutic drug chloroquine were predicted. Our finding describes the expression pattern and clinical value of key RNA methylation modification regulators in IS and novel diagnostic and therapeutic targets of IS from a new perspective.

GPNMB: a potent inducer of immunosuppression in cancer

The immune system is comprised of both innate and adaptive immune cells, which, in the context of cancer, collectively function to eliminate tumor cells. However, tumors can actively sculpt the immune landscape to favor the establishment of an immunosuppressive microenvironment, which promotes tumor growth and progression to metastatic disease. Glycoprotein-NMB (GPNMB) is a transmembrane glycoprotein that is overexpressed in a variety of cancers. It can promote primary tumor growth and metastasis, and GPNMB expression correlates with poor prognosis and shorter recurrence-free survival in patients. There is growing evidence supporting an immunosuppressive role for GPNMB in the context of malignancy. This review provides a description of the emerging roles of GPNMB as an inducer of immunosuppression, with a particular focus on its role in mediating cancer progression by restraining pro-inflammatory innate and adaptive immune responses.

Senolytic vaccination: a new mandate for cardiovascular health?

Senescent cell accumulation is increasingly associated with a number of age-related cardiovascular diseases. Now, a new manuscript in Nature Aging suggests that a novel vaccine-based strategy might provide a targeted method to eliminate the senescent cell population.