Angiopoietin-like protein 2 promotes chronic adipose tissue inflammation and obesity-related systemic insulin resistance

Adipocyte-secreted ANGPTL2 promotes hyperuricemia through inhibiting AKT/ABCG2 signaling

AIMS

Overweight and obesity are closely associated with hyperuricemia (HUA). However, the effect of obesity-induced adipokine on the level of serum uric acid (UA) has not been fully elucidated. This study aimed to determine the role of adipokine in the pathogenesis of HUA.

METHODS

Omental adipose tissues from HUA patients with obesity were collected for data-independent acquisition (DIA) proteomics analysis, and the secreted protein angiopoietin-like protein (ANGPTL2) was identified and further validated via Western blot and ELISA. Angptl2 knockout (ko) and adipocyte-specific ANGPTL2 overexpression mice were generated to establish HUA models. HK2 cells and primary renal tubule epithelial cells (RTECs) were applied to induce HUA cell model and treated with recombinant human ANGPTL2 or supernatants derived from C3H10 cells differentiated into adipocytes.

RESULT

ANGPTL2 levels were significantly elevated in the omental adipose tissue from HUA with obesity patients compared to control participants. Circulating ANGPTL2 levels were also increased, and positively correlated with serum UA levels, especially in male participants. Plasma UA levels were significantly decreased in Angptl2 ko mice, coinciding with up-regulated expression of ATP binding cassette subfamily G member 2 (ABCG2) and down-regulated glucose transporter 9 (GLUT9) in renal tissue. However, plasma UA levels were significantly increased, accompanied by decreased ABCG2 expression and enhanced GLUT9 expression after adipocyte-specific ANGPTL2 overexpression. Furthermore, adipocyte-derived ANGPTL2 increased UA level in cell supernatants through the inhibition of protein kinase B (AKT)/ABCG2 signaling in RTECs and HK2 cells.

CONCLUSION

Adipokine ANGPTL2 levels were significantly elevated in HUA patients with obesity. Circulating ANGPTL2 concentrations were independently associated with serum UA levels, particularly in obese males. Adipocyte-secreted ANGPTL2 promoted the level of UA through AKT/ABCG2 signaling in renal tubular cells. These findings establish ANGPTL2 as a critical adipokine linking obesity to hyperuricemia and suggest its potential as a novel therapeutic target for HUA.

Angiopoietin-like Protein 2 Expression is Associated With Host Wasting-Related Poor Prognosis in Colorectal Cancer

INTRODUCTION

Tumor-induced host wasting marked by malnutrition, systemic inflammation, or altered body composition is associated with poor prognosis in cancer patients. Tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) reportedly functions as a tumor promoter in some cancer contexts. This study aims to assess whether ANGPTL2 expression in tumor cells is associated with host wasting in patients with colorectal cancer.

METHODS

We retrospectively enrolled 88 patients with all-stage colorectal cancer who underwent surgical resection of the primary tumor between January 2017 and December 2017 in a single institution. Based on immunohistochemistry staining, we assessed ANGPTL2 expression in tumor cells in paraffin-embedded tumor samples from resected specimens. The association of the ANGPTL2 expression with clinicopathological factors, biomarkers of host wasting, and survival were analyzed.

RESULTS

Host wasting was associated with significantly high other causes-mortality rates in ANGPTL2-high patients (P = 0.0261) but not in ANGPTL2-low patients (P = 0.4719), suggesting that ANGPTL2 expression in colorectal cancer cells is associated with host wasting-related poor prognosis. Furthermore, ANGPTL2 expression in tumor cells was correlated with the advanced lung cancer inflammation index, which is a biomarker of host wasting (ρ = -0.3119, P = 0.0031).

CONCLUSIONS

ANGPTL2 is associated with host wasting-related poor prognosis through its association with systemic inflammation in patients with colorectal cancer. These findings overall provide novel insight into ANGPTL2 function and illustrate the essential role of tumor-host interactions in the prognosis of cancer survivors.

Adipokines: masterminds of metabolic inflammation

Adipose tissue is an immunologically active organ that controls host physiology, partly through the release of mediators termed adipokines. In obesity, adipocytes and infiltrating leukocytes produce adipokines, which include the hormones adiponectin and leptin and cytokines such as tumour necrosis factor and IL-1β. These adipokines orchestrate immune responses that are collectively referred to as metabolic inflammation. Consequently, metabolic inflammation characterizes metabolic disorders and promotes distinct disease aspects, such as insulin resistance, metabolic dysfunction-associated liver disease and cardiovascular complications. In this unifying concept, adipokines participate in the immunological cross-talk that occurs between metabolically active organs in metabolic diseases, highlighting the fundamental role of adipokines in obesity and their potential for therapeutic intervention. Here, we summarize how adipokines shape metabolic inflammation in mice and humans, focusing on their contribution to metabolic disorders in the setting of obesity and discussing their value as therapeutic targets.

Pathological Changes in Extracellular Matrix Composition Orchestrate the Fibrotic Feedback Loop Through Macrophage Activation in Dupuytren's Contracture

Dupuytren's contracture belongs to a group of fibrotic diseases that have similar mechanisms but lack effective treatment and prevention options. The excessive accumulation of connective tissue in Dupuytren's disease leads to palmar fibrosis that results in contracture deformities. The present study aimed to investigate how the tissue microenvironment in Dupuytren's contracture affects the phenotypic differentiation of macrophages, which leads to an inflammatory response and the development of chronicity in fibrotic disease. We utilized a decellularization-based method combined with proteomic analysis to identify shifts in extracellular matrix composition and the surrounding tissue microenvironment. We found that the expression of several matricellular proteins, such as MFAP4, EFEMP1 (fibulin-3), and ANGPTL2, was elevated in Dupuytren's tissue. We show that, in response to the changes in the extracellular matrix of Dupuytren's contracture, macrophages regulate the fibrotic process by cytokine production, promote myofibroblast differentiation, and increase the fibroblast migration rate. Moreover, we found that the extracellular matrix of Dupuytren's contracture directly supports the macrophage-to-myofibroblast transition, which could be another contributor to Dupuytren's disease pathogenesis. Our results suggest that interactions between macrophages and the extracellular matrix should be considered as targets for novel fibrotic disease treatment and prevention strategies in the future.

Sexually dimorphic effects of angiopoietin-like 2 on energy metabolism and hypothalamic neuropeptide regulation

BACKGROUND

Adipokines regulate body weight and metabolism by targeting the hypothalamus, influencing feeding, energy expenditure (EE) and insulin sensitivity. Angiopoietin-like 2 (Angptl2) is a pro-inflammatory adipokine linking obesity to insulin resistance. Both Angptl2 and its receptor are expressed in the central nervous system. Yet, the contribution of Angptl2 to the regulation of energy metabolism and relevant hypothalamic neuropeptides in male and female mice is unknown. We aim at determining the impact of Angptl2 knockdown (KD) on energy balance, nutrient partitioning and hypothalamic responses to a standard (STD) or high-fat diet (HFD) in mice.

METHODS

Three-month-old male and female Angptl2-KD mice and wildtype (WT) littermates were fed 16 weeks either a STD or a HFD. Body weight, food consumption and insulin sensitivity were assessed along with measurements of EE, respiratory exchange ratio (RER) and locomotor activity. We quantified the expression of Angptl2 and its receptors itga5, mag and pirb in the medio-basal hypothalamus (MBH) of WT mice, and MBH neuropeptide Y (NPY), agouti-related neuropeptide (AgRP) and proopiomelanocortin (POMC) gene expression in both KD and control fasting mice.

RESULTS

Lack of Angptl2 reduced food intake in males on both diets, and in females on HFD. In KD males, this anorexigenic effect was associated with lower body weight, increased EE, improved insulin sensitivity and lower hypothalamic orexigenic NPY expression compared to controls. Female Angptl2-KD mice however, exhibited unaltered body weight, EE and insulin sensitivity, and elevated NPY, AgRP and MC4R expression compared to controls. Fasting caused an increase in the MBH of mag expression in males and females but Angptl2 expression only in female mice.

CONCLUSIONS

Angptl2 KD improved diet-induced obesity and associated metabolic dysfunction in male mice. The lack of similar changes in female mice and divergent MBH neuropeptide profile suggest that sex-dependent mechanisms underly the anabolic effects of this proinflammatory adipokine.

The Two Faces of Angiopoietin-Like Protein 2 in Cancer

The tumor microenvironment is composed of tumor cells and various stromal cell types, such as immune cells, fibroblasts, and vascular cells. Signaling interactions between tumor and stromal cells orchestrate the tumor microenvironment's contribution to tumor progression. Angiopoietin-like protein 2 (ANGPTL2) is a secreted glycoprotein homologous to angiopoietins. Previous studies indicate that tumor cell-derived ANGPTL2 serves as a tumor promoter. However, recent studies suggest that tumor stroma-derived ANGPTL2 shows tumor-suppressive activity by enhancing anti-tumor immune responses, supporting a dual function for ANGPTL2 in cancer pathology. Such complexity can complicate development of effective therapeutic strategies targeting ANGPTL2. In this Review, we focus on ANGPTL2 activity in the tumor microenvironment and its function in anti-cancer immunity.

Circulating Angiopoietin-like Protein 6 Levels and Clinical Features in Patients with Type 2 Diabetes

Objective The main purpose of this study was to evaluate the associations between circulating angiopoietin-like protein 6 (ANGPTL6) levels and various diabetes- and atherosclerosis-related variables in patients with type 2 diabetes. Methods Serum ANGPTL6 levels in patients with type 2 diabetes hospitalized for glycemic control and/or diabetic education were measured using a chemiluminescent immunoassay. Results Most patients had elevated hemoglobin (Hb) A1c levels; 85.7% and 71.4% of patients had HbA1c levels ≥8%, and ≥9%, respectively. ANGPTL6 levels were significantly higher in patients with type 2 diabetes than in non-diabetic controls. In patients with type 2 diabetes, ANGPTL6 was significantly and positively correlated with the duration of diabetes, systolic blood pressure, gamma-glutamyl transpeptidase, C-reactive protein (CRP), and the intimal medial complex thickness of the carotid artery (IMT), and inversely correlated with HbA1c. In the multiple regression analysis, ANGPTL6 had a significant positive association with triglyceride in one of the models in which it was included as a variable. Furthermore, ANGPTL6 also showed significant positive associations with CRP and IMT in models in which they were included as variables. Conclusion The current study suggests that circulating levels of ANGPTL6 may be negatively associated with poor glycemic control and positively associated with the degree of atherosclerosis, as reflected by IMT, in patients with type 2 diabetes, most of whom had elevated HbA1c levels.

Can Exercise-Mediated Adipose Browning Provide an Alternative Explanation for the Obesity Paradox?

Overweight patients with cardiovascular disease (CVD) tend to survive longer than normal-weight patients, a phenomenon known as the "obesity paradox". The phenotypic characteristics of adipose distribution in these patients (who survive longer) often reveal a larger proportion of subcutaneous white adipose tissue (scWAT), suggesting that the presence of scWAT is negatively associated with all-cause mortality and that scWAT appears to provide protective benefits in patients facing unhealthy states. Exercise-mediated browning is a crucial aspect of the benign remodeling process of adipose tissue (AT). Reduced accumulation, reduced inflammation, and associated adipokine secretion are directly related to the reduction in CVD mortality. This paper summarized the pathogenetic factors associated with AT accumulation in patients with CVD and analyzed the possible role and pathway of exercise-mediated adipose browning in reducing the risk of CVD and CVD-related mortality. It is suggested that exercise-mediated browning may provide a new perspective on the "obesity paradox"; that is, overweight CVD patients who have more scWAT may gain greater cardiovascular health benefits through exercise.

Prognostic value of serum angiopoietin-like protein 2 in patients with acute coronary syndrome

BACKGROUND

Angiopoietin-like protein 2 (Angptl2) is a cytokine that is released to stimulate inflammation and accelerate atherogenesis. Our study sought to assess the predictive significance of serum Angptl2 in individuals diagnosed with acute coronary syndrome (ACS) and determine whether it can enhance prognostic performance beyond the GRACE risk score.

METHODS

We recruited a total of 1060 patients with ACS in a consecutive manner. The levels of Angptl2 in serum were analyzed at baseline. The subjects were then followed up for 12 months to monitor the occurrence of major adverse cardiovascular events (MACE).

RESULTS

The level of serum Angptl2 showed a positive correlation with the GRACE score (r = 0.54, p < 0.001). Survival analysis revealed that increased levels of serum Angptl2 were associated with higher occurrence of the composite of MACE (log-rank p < 0.001) and its specific components (log-rank p = 0.011 for all-cause death, p = 0.007 for non-fatal myocardial infarction and p < 0.001 for revascularization respectively). Throughout the follow-up period, 163 instances (15.4%) of endpoint events were documented. In terms of MACE, both serum Angptl2 levels (HR: 1.178, 95% CI: 1.058-1.313, p = 0.003) and the GRACE risk score (HR: 1.181, 95% CI: 1.007-1.385, p = 0.041) emerged as significant predictors following Cox multivariate adjustment. Additionally, the addition of serum Angptl2 to the GRACE score improved the predictive capacity for prognosis [increase in area under the receiveroperating characteristic curve (AUC) from 0.740 to 0.794, p = 0.020; net reclassification improvement (NRI) = 0.401, p = 0.001; integrated discrimination improvement (IDI) = 0.022, p = 0.008].

CONCLUSION

Serum Angptl2 might be a useful prognostic biomarker and combining serum Angptl2 with the GRACE score increased the efficacy of prognosis prediction in ACS patients.

TRIAL REGISTRATION

Not applicable.

Host ANGPTL2 establishes an immunosuppressive tumor microenvironment and resistance to immune checkpoint therapy

Use of immune checkpoint inhibitors (ICIs) as cancer immunotherapy has advanced rapidly in the clinic; however, mechanisms underlying resistance to ICI therapy, including impaired T cell infiltration, low immunogenicity, and tumor "immunophenotypes" governed by the host, remain unclear. We previously reported that in some cancer contexts, tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) has tumor-promoting functions. Here, we asked whether ANGPTL2 deficiency could enhance antitumor ICI activity in two inflammatory contexts: a murine syngeneic model of colorectal cancer and a mouse model of high-fat diet (HFD)-induced obesity. Systemic ANGPTL2 deficiency potentiated ICI efficacy in the syngeneic model, supporting an immunosuppressive role for host ANGPTL2. Relevant to the mechanism, we found that ANGPTL2 induces pro-inflammatory cytokine production in adipose tissues, driving generation of myeloid-derived suppressor cells (MDSCs) in bone marrow and contributing to an immunosuppressive tumor microenvironment and resistance to ICI therapy. Moreover, HFD-induced obese mice showed impaired responsiveness to ICI treatment, suggesting that obesity-induced chronic inflammation facilitated by high ANGPTL2 expression blocks ICI antitumor effects. Our findings overall provide novel insight into protumor ANGPTL2 functions and illustrate the essential role of the host system in ICI responsiveness.

Mechanisms by which obesity regulates inflammation and anti-tumor immunity in cancer

Obesity is associated with an increased risk for 13 different cancers. The increased risk for cancer in obesity is mediated by obesity-associated changes in the immune system. Obesity has distinct effects on different types of inflammation that are tied to tumorigenesis. For example, obesity promotes chronic inflammation in adipose tissue that is tumor-promoting in peripheral tissues. Conversely, obesity inhibits acute inflammation that rejects tumors. Obesity therefore promotes cancer by differentially regulating chronic versus acute inflammation. Given that obesity is chronic, the initial inflammation in adipose tissue will lead to systemic inflammation that could induce compensatory anti-inflammatory reactions in peripheral tissues to suppress chronic inflammation. The overall effect of obesity in peripheral tissues is therefore dependent on the duration and severity of obesity. Adipose tissue is a complex tissue that is composed of many cell types in addition to adipocytes. Further, adipose tissue cellularity is different at different anatomical sites throughout the body. Consequently, the sensitivity of adipose tissue to obesity is dependent on the anatomical location of the adipose depot. For example, obesity induces more inflammation in visceral than subcutaneous adipose tissue. Based on these studies, the mechanisms by which obesity promotes tumorigenesis are multifactorial and immune cell type-specific. The objective of our paper is to discuss the cellular mechanisms by which obesity promotes tumorigenesis by regulating distinct types of inflammation in adipose tissue and the tumor microenvironment.

Angiopoietin-Like Protein 2 Expression in Tumor Cells Supports Tumor-Associated Macrophage-Induced Tumor Progression in Esophageal Cancer

BACKGROUND

Tumor-associated macrophages (TAM), a major component of the tumor microenvironment, play key roles in tumor formation and progression; however, mechanisms underlying TAM-induced tumor progression are complex and not well known. We previously reported that tumor cell-derived angiopoietin-like protein 2 (ANGPTL2) functions as a tumor promoter in some cancer contexts.

METHODS

We examined ANGPTL2 expression in paraffin-embedded tumor samples from resected specimens of 221 patients with esophageal cancer. Patients were subdivided into four groups based on immunohistochemistry scores described above: ANGPTL2-low/TAM-low, ANGPTL2-low/TAM-high, ANGPTL2-high/TAM-low, and ANGPTL2-high/TAM-high groups. Gene expression datasets of esophageal cancer cell lines were obtained from the cancer cell line encyclopedia public database.

RESULTS

In this study, we demonstrate that TAM infiltration is associated with poor prognosis in patients with esophageal cancer whose tumor cells show relatively higher ANGPTL2 expression levels; however, TAM infiltration did not affect prognosis in patients with ANGPTL2-low-expressing esophageal cancer, suggesting that ANGPTL2 expression in esophageal cancer cells is required for TAM-induced tumor progression. Our analysis of public datasets indicates a potential positive correlation of ANGPTL2 expression levels with that of transforming growth factor (TGF)-β, a TAM-activating factor, in esophageal cancer cell lines.

CONCLUSION

We conclude that ANGPTL2 signaling in tumor cells supports TAM-induced tumor progression and contributes to poor prognosis in patients with esophageal cancer. These findings overall provide novel insight into pro-tumor ANGPTL2 functions and illustrate the essential role of cancer cell/TAM crosstalk in cancer progression.

Hepatokines: unveiling the molecular and cellular mechanisms connecting hepatic tissue to insulin resistance and inflammation

Insulin resistance arising from Non-Alcoholic Fatty Liver Disease (NAFLD) stands as a prevalent global ailment, a manifestation within societies stemming from individuals' suboptimal dietary habits and lifestyles. This form of insulin resistance emerges as a pivotal factor in the development of type 2 diabetes mellitus (T2DM). Emerging evidence underscores the significant role of hepatokines, as hepatic-secreted hormone-like entities, in the genesis of insulin resistance and eventual onset of type 2 diabetes. Hepatokines exert influence over extrahepatic metabolism regulation. Their principal functions encompass impacting adipocytes, pancreatic cells, muscles, and the brain, thereby playing a crucial role in shaping body metabolism through signaling to target tissues. This review explores the most important hepatokines, each with distinct influences. Our review shows that Fetuin-A promotes lipid-induced insulin resistance by acting as an endogenous ligand for Toll-like receptor 4 (TLR-4). FGF21 reduces inflammation in diabetes by blocking the nuclear translocation of nuclear factor-κB (NF-κB) in adipocytes and adipose tissue, while also improving glucose metabolism. ANGPTL6 enhances AMPK and insulin signaling in muscle, and suppresses gluconeogenesis. Follistatin can influence insulin resistance and inflammation by interacting with members of the TGF-β family. Adropin show a positive correlation with phosphoenolpyruvate carboxykinase 1 (PCK1), a key regulator of gluconeogenesis. This article delves into hepatokines' impact on NAFLD, inflammation, and T2DM, with a specific focus on insulin resistance. The aim is to comprehend the influence of these recently identified hormones on disease development and their underlying physiological and pathological mechanisms.

Inhibition of angiogenesis and regenerative lung growth in Lepob/ob mice through adiponectin-VEGF/VEGFR2 signaling

Introduction

Obesity is associated with impairment of wound healing and tissue regeneration. Angiogenesis, the formation of new blood capillaries, plays a key role in regenerative lung growth after unilateral pneumonectomy (PNX). We have reported that obesity inhibits angiogenesis. The effects of obesity on post-PNX lung vascular and alveolar regeneration remain unclear.

Methods

Unilateral PNX is performed on Lep o b / o b obese mice to examine vascular and alveolar regeneration.

Results

Regenerative lung growth and expression of vascular endothelial growth factor (VEGF) and its receptor VEGFR2 induced after PNX are inhibited in Lep o b / o b obese mice. The levels of adiponectin that exhibits pro-angiogenic and vascular protective properties increase after unilateral PNX, while the effects are attenuated in Lep o b / o b obese mice. Post-PNX regenerative lung growth and increases in the levels of VEGF and VEGFR2 are inhibited in adiponectin knockout mice. Adiponectin stimulates angiogenic activities in human lung endothelial cells (ECs), which is inhibited by decreasing the levels of transcription factor Twist1. Adiponectin agonist, AdipoRon restores post-PNX lung growth and vascular and alveolar regeneration in Lep o b / o b obese mice.

Discussion

These findings suggest that obesity impairs lung vascular and alveolar regeneration and adiponectin is one of the key factors to improve lung regeneration in obese people.

The role of vascular and lymphatic networks in bone and joint homeostasis and pathology

The vascular and lymphatic systems are integral to maintaining skeletal homeostasis and responding to pathological conditions in bone and joint tissues. This review explores the interplay between blood vessels and lymphatic vessels in bones and joints, focusing on their roles in homeostasis, regeneration, and disease progression. Type H blood vessels, characterized by high expression of CD31 and endomucin, are crucial for coupling angiogenesis with osteogenesis, thus supporting bone homeostasis and repair. These vessels facilitate nutrient delivery and waste removal, and their dysfunction can lead to conditions such as ischemia and arthritis. Recent discoveries have highlighted the presence and significance of lymphatic vessels within bone tissue, challenging the traditional view that bones are devoid of lymphatics. Lymphatic vessels contribute to interstitial fluid regulation, immune cell trafficking, and tissue repair through lymphangiocrine signaling. The pathological alterations in these networks are closely linked to inflammatory joint diseases, emphasizing the need for further research into their co-regulatory mechanisms. This comprehensive review summarizes the current understanding of the structural and functional aspects of vascular and lymphatic networks in bone and joint tissues, their roles in homeostasis, and the implications of their dysfunction in disease. By elucidating the dynamic interactions between these systems, we aim to enhance the understanding of their contributions to skeletal health and disease, potentially informing the development of targeted therapeutic strategies.

Cross-talks between perivascular adipose tissue and neighbors: multifaceted nature of nereids

Perivascular adipose tissue (PVAT) is a unique fat depot surrounding blood vessels and plays a vital role in the progression of vascular remodeling and dysfunction. PVAT exhibits remarkable differences in structure, phenotype, origin, and secretome across anatomical locations. The proximity of PVAT to neighboring vascular beds favors a niche for bidirectional communication between adipocytes and vascular smooth muscle cells, endothelial cells, and immune cells. In this review, we update our understanding of PVAT's regional differences and provide a comprehensive exploration of how these differences impact cross-talks between PVAT and the vascular wall. Different PVAT depots show different degrees of vasoprotective function and resilience to pathological changes such as obesity and vasculopathies, shaping multifaceted interactions between PVAT depots and adjacent vasculatures. The depot-specific resilience may lead to innovative strategies to manage cardiometabolic disorders.

Periodontitis promotes hepatocellular carcinoma in Stelic Animal model (STAM) mice

Periodontitis is a prevalent oral inflammatory disease that leads to alveolar bone loss and may exert an adverse impact on systemic health. Periodontal disease may be associated with hepatocellular carcinoma (HCC); however, the mechanism of such an association is unknown. In this study, Stelic Animal model (STAM) mice, a model of nonalcoholic steatohepatitis (NASH)-HCC, were induced to develop periodontitis and subjected to histopathological and immunological analyses. HCC progression was greater in STAM mice with experimental periodontitis compared with that in STAM mice without experimental periodontitis. Tumor necrosis factor-α (TNFα), matrix metalloproteinase-9 (MMP9), collagen 1, and angiopoietin-like protein 2 (ANGPTL2) gene expression was significantly increased in the liver of the periodontitis group. ANGPTL2 was previously reported to be involved in the pathogenesis of periodontitis, and HCC and ANGPTL2 protein tended to be more abundant in the pocket epithelium of STAM mice with experimental periodontitis than in control STAM mice. ANGPTL2 levels in the serum of STAM mice with experimental periodontitis tended to be higher than in control STAM mice. Our results indicate that ANGPTL2 is produced in chronically inflamed periodontal tissue and then travels to the liver via the bloodstream where it accumulates to promote the progression of hepatocellular carcinoma.

The Interplay between Obesity and Inflammation

Obesity is an important condition affecting the quality of life of numerous patients and increasing their associated risk for multiple diseases, including tumors and immune-mediated disorders. Inflammation appears to play a major role in the development of obesity and represents a central point for the activity of cellular and humoral components in the adipose tissue. Macrophages play a key role as the main cellular component of the adipose tissue regulating the chronic inflammation and modulating the secretion and differentiation of various pro- and anti-inflammatory cytokines. Inflammation also involves a series of signaling pathways that might represent the focus for new therapies and interventions. Weight loss is essential in decreasing cardiometabolic risks and the degree of associated inflammation; however, the latter can persist for long after the excess weight is lost, and can involve changes in macrophage phenotypes that can ensure the metabolic adjustment. A clear understanding of the pathophysiological processes in the adipose tissue and the interplay between obesity and chronic inflammation can lead to a better understanding of the development of comorbidities and may ensure future targets for the treatment of obesity.

Adipokines and their role in acute pancreatitis

Acute pancreatitis (AP) is characterized by an inflammatory response that leads to edema and haemorrhaging of pancreatic tissue. In severe cases, it can even result in the necrosis of pancreatic tissue following activation within the pancreas. Adipokines are biologically active molecules released by adipose tissue that have a wide-ranging impact on health and disease. Adipokines are cytokines produced not only in white adipose tissue but also in the fat surrounding the pancreas, and they play a role in the body's inflammatory response. The presence of increased adipose tissue, often associated with obesity, has been linked to a heightened systemic inflammatory response in cases of AP. According to the literature, there are many adipokines. This article summarizes the role of adipokines in AP. Adipokines could be promising biomarkers for both diagnostic and new therapeutic treatment strategies in AP. However, a deeper knowledge of the signaling pathways of adipokines and their potential therapeutic role in AP is necessary.

Tumor stroma-derived ANGPTL2 potentiates immune checkpoint inhibitor efficacy

Use of immune checkpoint inhibitors (ICIs) as cancer immunotherapy has advanced rapidly in the clinic. We recently reported that tumor stroma-derived angiopoietin-like protein 2 (ANGPTL2) has tumor suppressive activity by enhancing dendritic cell-mediated CD8+ T cell anti-tumor immune responses. However, a direct impact of ANGPTL2 on ICI anti-tumor effect remains unclear. Here, we use a murine syngeneic model to show that host ANGPTL2 facilitates CD8+ T cell cross-priming and contributes to anti-tumor responses to ICIs in this context. Importantly, our analysis of public datasets indicated that ANGPTL2 expression is associated with positive responses to ICI therapy by human melanoma patients. We conclude that ANGPTL2-mediated stromal cell crosstalk facilitates anti-tumor immunity and ICI responsiveness. These findings overall provide novel insight into ANGPTL2 anti-tumor function and regulation of ICI-induced anti-tumor immunity.

Decreased Memory and Learning Ability Mediated by Bmal1/M1 Macrophages/Angptl2/Inflammatory Cytokine Pathway in Mice Exposed to Long-Term Blue Light Irradiation

Humans are persistently exposed to massive amounts of blue light via sunlight, computers, smartphones, and similar devices. Although the positive and negative effects of blue light on living organisms have been reported, its impact on learning and memory remains unknown. Herein, we examined the effects of widespread blue light exposure on the learning and memory abilities of blue light-exposed mice. Ten-week-old male ICR mice were divided into five groups (five mice/group) and irradiated with blue light from a light-emitting diode daily for 6 months. After 6 months of blue light irradiation, mice exhibited a decline in memory and learning abilities, assessed using the Morris water maze and step-through passive avoidance paradigms. Blue light-irradiated mice exhibited a decreased expression of the clock gene brain and muscle arnt-like 1 (Bmal1). The number of microglia and levels of M1 macrophage CC-chemokine receptor 7 and inducible nitric oxide synthase were increased, accompanied by a decrease in M2 macrophage arginase-1 levels. Levels of angiopoietin-like protein 2 and inflammatory cytokines interleukin-6, tumor necrosis factor-α, and interleukin-1β were elevated. Our findings suggest that long-term blue light exposure could reduce Bmal1 expression, activate the M1 macrophage/Angptl2/inflammatory cytokine pathway, induce neurodegeneration, and lead to a decline in memory.

ANGPTL2 knockdown induces autophagy to relieve alveolar macrophage pyroptosis by reducing LILRB2-mediated inhibition of TREM2

Acute lung injury (ALI) is featured with a robust inflammatory response. Angiopoietin-like protein 2 (ANGPTL2), a pro-inflammatory protein, is complicated with various disorders. However, the role of ANGPTL2 in ALI remains to be further explored. The mice and MH-S cells were administrated with lipopolysaccharide (LPS) to evoke the lung injury in vivo and in vitro. The role and mechanism of ANGPTL was investigated by haematoxylin-eosin, measurement of wet/dry ratio, cell count, terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling, reverse transcription quantitative polymerase chain reaction, immunofluorescence, enzyme-linked immunosorbent assay, detection of autophagic flux and western blot assays. The level of ANGPTL2 was upregulated in lung injury. Knockout of ANGPTL2 alleviated LPS-induced pathological symptoms, reduced pulmonary wet/dry weight ratio, the numbers of total cells and neutrophils in BALF, apoptosis rate and the release of pro-inflammatory mediators, and modulated polarization of alveolar macrophages in mice. Knockdown of ANGPTL2 downregulated the level of pyroptosis indicators, and elevated the level of autophagy in LPS-induced MH-S cells. Besides, downregulation of ANGPTL2 reversed the LPS-induced the expression of leukocyte immunoglobulin (Ig)-like receptor B2 (LILRB2) and triggering receptor expressed on myeloid cells 2 (TREM2), which was reversed by the overexpression of LILRB2. Importantly, knockdown of TREM2 reversed the levels of autophagy- and pyroptosis-involved proteins, and the contents of pro-inflammatory factors in LPS-induced MH-S cells transfected with si ANGPTL2, which was further inverted with the treatment of rapamycin. Therefore, ANGPTL2 silencing enhanced autophagy to alleviate alveolar macrophage pyroptosis via reducing LILRB2-mediated inhibition of TREM2.

Role of the angiopoietin-like protein family in the progression of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is the most frequent cause of chronic liver disease, with a range of conditions including non-alcoholic fatty liver, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Currently recognized as the liver component of the metabolic syndrome, NAFLD is intimately linked to metabolic diseases. Angiopoietin-like proteins (ANGPTLs) comprise a class of proteins that resemble angiopoietins structurally. It is closely related to obesity, insulin resistance and lipid metabolism, and may be the critical factor of metabolic syndrome. In recent years, many studies have found that there is a certain correlation between ANGPTLs and the occurrence and progression of NAFLD disease spectrum. This article reviews the possible mechanisms and roles of ANGPTL protein in the pathogenesis and progression of NAFLD.

Knockdown of ANGPTL2 promotes left ventricular systolic dysfunction by upregulation of NOX4 in mice

Background: Angiopoietin-like 2 (ANGPTL2) is a pro-inflammatory and pro-oxidant circulating protein that predicts and promotes chronic inflammatory diseases such as atherosclerosis in humans. Transgenic murine models demonstrated the deleterious role of ANGPTL2 in vascular diseases, while deletion of ANGPTL2 was protective. The nature of its role in cardiac tissues is, however, less clear. Indeed, in adult mice knocked down (KD) for ANGPTL2, we recently reported a mild left ventricular (LV) dysfunction originating from a congenital aortic valve stenosis, demonstrating that ANGPTL2 is essential to cardiac development and function. Hypothesis: Because we originally demonstrated that the KD of ANGPTL2 protected vascular endothelial function via an upregulation of arterial NOX4, promoting the beneficial production of dilatory H2O2, we tested the hypothesis that increased cardiac NOX4 could negatively affect cardiac redox and remodeling and contribute to LV dysfunction observed in adult Angptl2-KD mice. Methods and results: Cardiac expression and activity of NOX4 were higher in KD mice, promoting higher levels of cardiac H2O2 when compared to wild-type (WT) mice. Immunofluorescence showed that ANGPTL2 and NOX4 were co-expressed in cardiac cells from WT mice and both proteins co-immunoprecipitated in HEK293 cells, suggesting that ANGPTL2 and NOX4 physically interact. Pressure overload induced by transverse aortic constriction surgery (TAC) promoted LV systolic dysfunction in WT mice but did not further exacerbate the dysfunction in KD mice. Importantly, the severity of LV systolic dysfunction in KD mice (TAC and control SHAM) correlated with cardiac Nox4 expression. Injection of an adeno-associated virus (AAV9) delivering shRNA targeting cardiac Nox4 expression fully reversed LV systolic dysfunction in KD-SHAM mice, demonstrating the causal role of NOX4 in cardiac dysfunction in KD mice. Targeting cardiac Nox4 expression in KD mice also induced an antioxidant response characterized by increased expression of NRF2/KEAP1 and catalase. Conclusion: Together, these data reveal that the absence of ANGPTL2 induces an upregulation of cardiac NOX4 that contributes to oxidative stress and LV dysfunction. By interacting and repressing cardiac NOX4, ANGPTL2 could play a new beneficial role in the maintenance of cardiac redox homeostasis and function.

Endothelial-derived small extracellular vesicles support B-cell acute lymphoblastic leukemia development

PURPOSE

The bone marrow niche plays an important role in leukemia development. However, the contributions of different niche components to leukemia development and their underlying mechanisms remain largely unclear.

METHOD

Cre/LoxP-based conditional knockout technology was used to delete VPS33B or ANGPTL2 gene in niche cells. Murine B-ALL model was established by overexpressing the N-Myc oncogene in hematopoietic stem progenitor cells. The frequency of leukemia cells and immunophenotypic B220+ CD43+ LICs was detected by flow cytometry. SEVs was isolated by sequential centrifugation and mass spectrometry was performed to analyze the different components of SEVs. Immunoprecipitation and western blot were used to measure the interaction of VPS33B and ANGPTL2.

RESULTS

Here, we showed that specific knockout of vascular protein sorting 33b (Vps33b) in endothelial cells (ECs), but not megakaryocytes or mesenchymal stem cells, resulted in a significant decrease in the secretion of small extracellular vesicles (SEVs) and a delay in the development of B-cell lymphoblastic leukemia (B-ALL). Vps33b knockdown endothelial cells contained much lower levels of SEVs that contained angiopoietin-like protein 2 (ANGPTL2) than the control cells. Importantly, conditional knockout of Angptl2 in ECs significantly delayed B-ALL progression. Moreover, C-terminal region of ANGPTL2 (aa247-471) could directly interact with Sec1-like domain 1 of VPS33B (aa1-aa146). We further demonstrated that the point mutations R399H and G402S in ANGPTL2 led to a dramatic decrease in the secretion of ANGPTL2-SEVs. We also showed that wild-type ANGPTL2-containing SEVs, but not mutant ANGPTL2-containing SEVs, significantly enhanced B-ALL development.

CONCLUSION

In summary, our findings indicate that the secretion of ANGPTL2-containing SEVs in ECs sustains the leukemogenic activities of B-ALL cells, which is fine-tuned by the direct interaction of VPS33B and ANGPTL2. These findings reveal that niche-specific SEVs play an important role in B-ALL development.

Adipocyte hypertrophy associates with in vivo postprandial fatty acid metabolism and adipose single-cell transcriptional dynamics

Adipocyte hypertrophy is associated with metabolic complications independent of obesity. We aimed to determine: 1) the association between adipocyte size and postprandial fatty acid metabolism; 2) the potential mechanisms driving the obesity-independent, hypertrophy-associated dysmetabolism in vivo and at a single-cell resolution. Tracers with positron emission tomography were used to measure fatty acid metabolism in 40 men and women with normal or impaired glucose tolerance (NCT02808182), and single nuclei RNA-sequencing (snRNA-seq) to determine transcriptional dynamics of subcutaneous adipose tissue (AT) between individuals with AT hypertrophy vs. hyperplasia matched for sex, ethnicity, glucose-tolerance status, BMI, total and percent body fat, and waist circumference. Adipocyte size was associated with high postprandial total cardiac fatty acid uptake and higher visceral AT dietary fatty acid uptake, but lower lean tissue dietary fatty acid uptake. We found major shifts in cell transcriptomal dynamics with AT hypertrophy that were consistent with in vivo metabolic changes.

Transcriptomic analysis of sheep hypothalamus discloses regulatory genes potentially involved in sex-dependent differences in body weight of progeny born to dams supplemented with omega-3 fatty acids or methionine during late-gestation

Fetal programming research conducted in sheep has reported sexually dimorphic responses on growth of the progeny born to in-utero methionine or omega-3 fatty acids supplementation. However, the biological mechanism behind the nutrient by sex interaction as a source of variation in offspring body weight is still unknown. A high-throughput RNA sequencing data of hypothalamus samples from 17 lambs were used in the current study to identify differentially expressed genes (DEGs) between males and females born to dams supplemented with different nutrients during late-gestation. Ewes received a basal diet without omega-3 fatty acids or methionine supplementation as the control (CONT); omega-3 fatty acids supplementation (FAS), or methionine supplementation (METS). A list of regulated genes was generated. Data were compared as CONT vs. FAS and CONT vs. METS. For CONT vs. METS, a treatment by sex interaction was found (adjusted P-value < 0.05) on 121 DEGs (112 upregulated and 9 downregulated) on female lambs born to METS compared with METS males. Importantly, with the sex interaction term, more than 100 genes were upregulated in female lamb's hypothalamuses born to METS. Gene Ontology (GO) and Ingenuity Pathway Analysis (IPA) were performed using the DEGs from female lambs. Terms under biological process (related to morphogenesis, organism, and tissue development), cellular component (related to chromatin, extracellular components), and molecular function (involved in chromatin structure and transcription and factors linked to binding DNA) were presented (adjusted P-value < 0.05) for GO. For the IPA, the top-scoring network was developmental disorder, endocrine system development and function, and organ morphology. Only a few differences were observed in the comparison between the interaction of sex and treatment for the CONT vs. FAS comparison. The markedly increased number of DEGs substantially involved in developmental and growth processes indicates the extent to which maternal methionine supplementation causes the sexually dimorphic effects observed in the offspring.

A novel memory-like Tfh cell subset is precursor to effector Tfh cells in recall immune responses

T follicular helper (Tfh) cells, essential for germinal center reactions, are not identical, with different phenotypes reported. Whether, when, and how they generate memory cells is still poorly understood. Here, through single-cell RNA-sequencing analysis of CXCR5+Bcl6+ Tfh cells generated under different conditions, we discovered, in addition to PD-1hi effector Tfh cells, a CD62L+PD1low subpopulation. CD62L-expressing Tfh cells developed independently from PD-1+ cells and not in direct contact with B cells. More importantly, CD62L+ Tfh cells expressed memory- and stemness-associated genes, and with better superior long-term survival, they readily generated PD-1hi cells in the recall response. Finally, KLF2 and IL7R, also highly expressed by CD62L+ Tfh cells, were required to regulate their development. Our work thus demonstrates a novel Tfh memory-like cell subpopulation, which may benefit our understanding of immune responses and diseases.

Adolescent obesity and ANGPTL8: correlations with high sensitivity C-reactive protein, leptin, and chemerin

Angiopoietin-like proteins (ANGPTLs) mediate many metabolic functions. We had recently reported increased plasma levels of ANGPTL8 in obese adults of Arab ethnicity. However, data on ANGPTL8 levels in adolescent obesity is lacking. Arab population is characterized by a rapid transition, due to sudden wealth seen in the post-oil era, in lifestyle, food habits and extent of physical activity. We adopted a cross-sectional study on Arab adolescents from Kuwait to examine the role of ANGPTL8 in adolescent obesity. The study cohort included 452 adolescents, aged 11-14 years, recruited from Middle Schools across Kuwait. BMI-for-age growth charts were used to categorize adolescents as normal-weight, overweight, and obese. ELISA and bead-based multiplexing assays were used to measure plasma levels of ANGPTL8 and other inflammation and obesity-related biomarkers. Data analysis showed significant differences in the plasma levels of ANGPTL8 among the three subgroups, with a significant increase in overweight and obese children compared to normal-weight children. This observation persisted even when the analysis was stratified by sex. Multinomial logistic regression analysis illustrated that adolescents with higher levels of ANGPTL8 were 7 times more likely to become obese and twice as likely to be overweight. ANGPTL8 levels were correlated with those of hsCRP, leptin and chemerin. ANGPTL8 level had a reasonable prognostic power for obesity with an AUC of 0.703 (95%-CI=0.648-0.759). These observations relating to increased ANGPTL8 levels corresponding to increased BMI-for-age z-scores indicate that ANGPTL8, along with hsCRP, leptin and chemerin, could play a role in the early stages of obesity development in children. ANGPTL8 is a potential early marker for adolescent obesity and is associated with well-known obesity and inflammatory markers.

Angiopoietin-Like Proteins: Cardiovascular Biology and Therapeutic Targeting for the Prevention of Cardiovascular Diseases

Despite the best pharmacologic tools available, cardiovascular diseases (CVDs) remain a major cause of morbidity and mortality in developed countries. After 2 decades of research, new therapeutic targets, such as angiopoietin-like proteins (ANGPTLs), are emerging. ANGPTLs belong to a family of 8 members, from ANGPTL1 to ANGPTL8; they have structural homology with angiopoietins and are secreted in the circulation. ANGPTLs display a multitude of physiological and pathologic functions; they contribute to inflammation, angiogenesis, cell death, senescence, hematopoiesis, and play a role in repair, maintenance, and tissue homeostasis. ANGPTLs-particularly the triad ANGPTL3, 4, and 8-have an established role in lipid metabolism through the regulation of triacylglycerol trafficking according to the nutritional status. Some ANGPTLs also contribute to glucose metabolism. Therefore, dysregulation in ANGPTL expression associated with abnormal circulating levels are linked to a plethora of CVD and metabolic disorders including atherosclerosis, heart diseases, diabetes, but also obesity and cancers. Because ANGPTLs bind to different receptors according to the cell type, antagonists are therapeutically inadequate. Recently, direct inhibitors of ANGPTLs, mainly ANGPTL3, have been developed, and specific monoclonal antibodies and antisense oligonucleotides are currently being tested in clinical trials. The aim of the current review is to provide an up-to-date preclinical and clinical overview on the function of the 8 members of the ANGPTL family in the cardiovascular system, their contribution to CVD, and the therapeutic potential of manipulating some of them.

The Proinflammatory Role of ANGPTL8 R59W Variant in Modulating Inflammation through NF-κB Signaling Pathway under TNFα Stimulation

BACKGROUND

Angiopoietin-like protein 8 (ANGPTL8) is known to regulate lipid metabolism and inflammation. It interacts with ANGPTL3 and ANGPTL4 to regulate lipoprotein lipase (LPL) activity and with IKK to modulate NF-κB activity. Further, a single nucleotide polymorphism (SNP) leading to the ANGPTL8 R59W variant associates with reduced low-density lipoprotein/high-density lipoprotein (LDL/HDL) and increased fasting blood glucose (FBG) in Hispanic and Arab individuals, respectively. In this study, we investigate the impact of the R59W variant on the inflammatory activity of ANGPTL8.

METHODS

The ANGPTL8 R59W variant was genotyped in a discovery cohort of 867 Arab individuals from Kuwait. Plasma levels of ANGPTL8 and inflammatory markers were measured and tested for associations with the genotype; the associations were tested for replication in an independent cohort of 278 Arab individuals. Impact of the ANGPTL8 R59W variant on NF-κB activity was examined using approaches including overexpression, luciferase assay, and structural modeling of binding dynamics.

RESULTS

The ANGPTL8 R59W variant was associated with increased circulatory levels of tumor necrosis factor alpha (TNFα) and interleukin 7 (IL7). Our in vitro studies using HepG2 cells revealed an increased phosphorylation of key inflammatory proteins of the NF-κB pathway in individuals with the R59W variant as compared to those with the wild type, and TNFα stimulation further elevated it. This finding was substantiated by increased luciferase activity of NF-κB p65 with the R59W variant. Modeled structural and binding variation due to R59W change in ANGPTL8 agreed with the observed increase in NF-κB activity.

CONCLUSION

ANGPTL8 R59W is associated with increased circulatory TNFα, IL7, and NF-κB p65 activity. Weak transient binding of the ANGPTL8 R59W variant explains its regulatory role on the NF-κB pathway and inflammation.

Effects of In Utero PFOS Exposure on Epigenetics and Metabolism in Mouse Fetal Livers

Prenatal exposure to perfluorooctanesulfonate (PFOS) increases fetus' metabolic risk; however, the investigation of the underlying mechanism is limited. In this study, pregnant mice in the gestational days (GD, 4.5-17.5) were exposed to PFOS (0.3 and 3 μg/g of body weight). At GD 17.5, PFOS perturbed maternal lipid metabolism and upregulated metabolism-regulating hepatokines (Angptl4, Angptl8, and Selenop). Mass-spectrometry imaging and whole-genome bisulfite sequencing revealed, respectively, selective PFOS localization and deregulation of gene methylation in fetal livers, involved in inflammation, glucose, and fatty acid metabolism. PCR and Western blot analysis of lipid-laden fetal livers showed activation of AMPK signaling, accompanied by significant increases in the expression of glucose transporters (Glut2/4), hexose-phosphate sensors (Retsat and ChREBP), and the key glycolytic enzyme, pyruvate kinase (Pk) for glucose catabolism. Additionally, PFOS modulated the expression levels of PPARα and PPARγ downstream target genes, which simultaneously stimulated fatty acid oxidation (Cyp4a14, Acot, and Acox) and lipogenesis (Srebp1c, Acaca, and Fasn). Using human normal hepatocyte (MIHA) cells, the underlying mechanism of PFOS-elicited nuclear translocation of ChREBP, associated with a fatty acid synthesizing pathway, was revealed. Our finding implies that in utero PFOS exposure altered the epigenetic landscape associated with dysregulation of fetal liver metabolism, predisposing postnatal susceptibility to metabolic challenges.

ANGPTL2 promotes immune checkpoint inhibitor-related murine autoimmune myocarditis

Use of immune checkpoint inhibitors (ICIs) as cancer immunotherapy advances rapidly in the clinic. Despite their therapeutic benefits, ICIs can cause clinically significant immune-related adverse events (irAEs), including myocarditis. However, the cellular and molecular mechanisms regulating irAE remain unclear. Here, we investigate the function of Angiopoietin-like protein 2 (ANGPTL2), a potential inflammatory mediator, in a mouse model of ICI-related autoimmune myocarditis. ANGPTL2 deficiency attenuates autoimmune inflammation in these mice, an outcome associated with decreased numbers of T cells and macrophages. We also show that cardiac fibroblasts express abundant ANGPTL2. Importantly, cardiac myofibroblast-derived ANGPTL2 enhances expression of chemoattractants via the NF-κB pathway, accelerating T cell recruitment into heart tissues. Our findings suggest an immunostimulatory function for ANGPTL2 in the context of ICI-related autoimmune inflammation and highlight the pathophysiological significance of ANGPTL2-mediated cardiac myofibroblast/immune cell crosstalk in enhancing autoimmune responses. These findings overall provide insight into mechanisms regulating irAEs.

LILRB2/PirB mediates macrophage recruitment in fibrogenesis of nonalcoholic steatohepatitis

Inhibition of immunocyte infiltration and activation has been suggested to effectively ameliorate nonalcoholic steatohepatitis (NASH). Paired immunoglobulin-like receptor B (PirB) and its human ortholog receptor, leukocyte immunoglobulin-like receptor B (LILRB2), are immune-inhibitory receptors. However, their role in NASH pathogenesis is still unclear. Here, we demonstrate that PirB/LILRB2 regulates the migration of macrophages during NASH by binding with its ligand angiopoietin-like protein 8 (ANGPTL8). Hepatocyte-specific ANGPTL8 knockout reduces MDM infiltration and resolves lipid accumulation and fibrosis progression in the livers of NASH mice. In addition, PirB^-/- bone marrow (BM) chimeras abrogate ANGPTL8-induced MDM migration to the liver. And yet, PirB ectodomain protein could ameliorate NASH by sequestering ANGPTL8. Furthermore, LILRB2-ANGPTL8 binding-promoted MDM migration and inflammatory activation are also observed in human peripheral blood monocytes. Taken together, our findings reveal the role of PirB/LILRB2 in NASH pathogenesis and identify PirB/LILRB2-ANGPTL8 signaling as a potential target for the management or treatment of NASH.

Angiopoietin-like 2 Protein and Hidradenitis Suppurativa: A New Biomarker for Disease Severity

Hidradenitis suppurativa (HS) is a chronic inflammatory disease whose pathogenesis is not fully understood at present. The role of proinflammatory cytokines, several adipokines, retinol-binding protein 4, angiopoietin-2 and other molecules has been previously reported. Angiopoietin-like 2 protein (ANGPTL2) is a glycoprotein belonging to the angiopoietin-like family that may play a pivotal role in the pathogenesis of several chronic inflammatory diseases. To our knowledge, the role of serum ANGPTL2 levels in HS has not been assessed to date. In the current case-control study, we aimed to investigate serum ANGPTL2 levels in HS patients and controls and to assess whether ANGPTL2 levels could be associated with the severity of HS. Ninety-four patients with HS and sixty controls of similar age and sex were included in the study. Demographic, anthropometric, and clinical data, as well as routine laboratory parameters and serum concentrations of ANGPTL2, were assessed in all participants. HS patients had significantly higher serum ANGPTL2 levels than controls after adjusting for confounders. Moreover, ANGPTL2 concentrations positively correlated with disease duration and severity. Our results indicate for the first time that serum ANGPTL2 concentrations are elevated in HS patients compared to controls and correlate with the duration of the disease. Besides, ANGPTL2 might serve as a biomarker of HS severity.

Role of epicardial adipose tissue in human atrial fibrillation

A recent meta-analysis among which four reports were conducted in Japan demonstrated that epicardial adipose tissue (EAT) is closely associated with an increased risk of atrial fibrillation (AF) recurrence after catheter ablation. We previously investigated the role of EAT in AF in humans. Left atrial (LA) appendage samples were obtained from AF patients during cardiovascular surgery. Histologically, the severity of fibrotic EAT remodeling was associated with LA myocardial fibrosis. Total collagen in the LA myocardium (i.e., LA myocardial fibrosis) was positively correlated with proinflammatory and profibrotic cytokines/chemokines, including interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α, in EAT. Human peri-LA EAT and abdominal subcutaneous adipose tissue (SAT) were obtained by autopsy. EAT- or SAT-derived conditioned medium was applied to the rat LA epicardial surface using an organo-culture system. EAT-conditioned medium induced atrial fibrosis in organo-cultured rat atrium. The profibrotic effect of EAT was greater than that of SAT. The fibrotic area of the organo-cultured rat atrium treated with EAT from patients with AF was greater than in patients without AF. Treatment with human recombinant angiopoietin-like protein 2 (Angptl2) induced fibrosis in organo-cultured rat atrium, which was suppressed by concomitant treatment with anti-Angptl2 antibody. Finally, we attempted to detect fibrotic EAT remodeling on computed tomography (CT) images, which demonstrated that the percent change in EAT fat attenuation was positively correlated with EAT fibrosis. Based on these findings, we conclude that the percent change in EAT fat attenuation determined using CT non-invasively detects EAT remodeling.

ANGPTL2 promotes VEGF-A synthesis in human lung cancer and facilitates lymphangiogenesis

Lung cancer is an extremely common cancer and metastatic lung cancer has a greatly low survival rate. Lymphangiogenesis is essential for the development and metastasis of lung cancer. The adipokine angiopoietin-like protein 2 (ANGPTL2) regulates tumor progression and metastasis, although the functions of ANGPTL2 in lung cancer are unknown. Analysis of data from TCGA genomics program, the GEPIA web server and the Oncomine database revealed that higher levels of ANGPTL2 expression were correlated with progressive disease and lymph node metastasis. ANGPTL2 enhanced VEGF-A-dependent lymphatic endothelial cell (LEC) tube formation and migration. Integrin α5β1, p38 and nuclear factor (NF)-κB signaling mediated ANGPTL2-regulated lymphangiogenesis. Importantly, overexpression ANGPTL2 facilitated tumor growth and lymphangiogenesis in vivo. Thus, ANGPTL2 is a promising therapeutic object for treating lung cancer.

The molecular link between obesity and genomic instability in cancer development

Obesity has been known to be a major risk factor for various types of cancers for several decades. More recently, the relationship between dysregulated adipokines and cancer development has been the focus of much research. Adipose tissue is an important endocrine organ that secretes adipokines that affect both autocrine and paracrine signaling. These adipokines modulate inflammation, induce insulin resistance, and regulate their own behavior and production. Adipokine-production dysregulation is due to physiological changes in adipose tissue that prompt molecular modifications, including low-grade inflammation and the stimulatory production of reactive oxygen species. Additionally, studies have linked DNA damage response, genomic instability, and the innate immune response to tumorigenesis. Further investigation of adipokines and their role in the promotion of genomic instability may clarify the link between obesity and cancer, as well as elucidate potential pharmaceutical targets. In this review, we discuss the progress of recent literature, focusing on the impact of adipokines, genomic instability, and the innate immune response on increasing the risk of cancer.

ANGPTL2 binds MAG to efficiently enhance oligodendrocyte differentiation

BACKGROUND

Oligodendrocytes have robust regenerative ability and are key players in remyelination during physiological and pathophysiological states. However, the mechanisms of brain microenvironmental cue in regulation of the differentiation of oligodendrocytes still needs to be further investigated.

RESULTS

We demonstrated that myelin-associated glycoprotein (MAG) was a novel receptor for angiopoietin-like protein 2 (ANGPTL2). The binding of ANGPTL2 to MAG efficiently promoted the differentiation of oligodendrocytes in vitro, as evaluated in an HCN cell line. Angptl2-null mice had a markedly impaired myelination capacity in the early stage of oligodendrocyte development. These mice had notably decreased remyelination capacities and enhanced motor disability in a cuprizone-induced demyelinating mouse model, which was similar to the Mag-null mice. The loss of remyelination ability in Angptl2-null/Mag-null mice was similar to the Angptl2-WT/Mag-null mice, which indicated that the ANGPTL2-mediated oligodendrocyte differentiation effect depended on the MAG receptor. ANGPTL2 bound MAG to enhance its phosphorylation level and recruit Fyn kinase, which increased Fyn phosphorylation levels, followed by the transactivation of myelin regulatory factor (MYRF).

CONCLUSION

Our study demonstrated an unexpected cross-talk between the environmental protein (ANGPTL2) and its surface receptor (MAG) in the regulation of oligodendrocyte differentiation, which may benefit the treatment of many demyelination disorders, including multiple sclerosis.

ANGPTL2 Deletion Attenuates Neuroinflammation and Cognitive Dysfunction Induced by Isoflurane in Aged Mice through Modulating MAPK Pathway

Postoperative cognitive dysfunction (POCD) is a well-known complication after surgery with cognitive impairments. Angiopoietin-like protein 2 (ANGPTL2) has been found to be associated with inflammation. However, the role of ANGPTL2 in inflammation of POCD is unclear. Here, mice were subjected into isoflurane anesthesia. It was demonstrated that isoflurane increased ANGPTL2 expression and promoted pathological change in brain tissues. However, downregulation of ANGPTL2 alleviated the pathological change and elevated learning and memory abilities, improving isoflurane-induced cognitive dysfunction in mice. In addition, isoflurane-induced cell apoptosis and inflammation were repressed via ANGPTL2 knockdown in mice. Downregulation of ANGPTL2 was also verified to suppress isoflurane-induced microglial activation, evidenced by a decrease of Iba1 and CD86 expressions and an increase of CD206 expression. Further, the isoflurane-induced MAPK signaling pathway was repressed through downregulation of ANGPTL2 in mice. In conclusion, this study proved that downregulation of ANGPTL2 attenuated isoflurane-induced neuroinflammation and cognitive dysfunction in mice via modulating the MAPK pathway, which provided a new therapeutic target for POCD.

Adipose endothelial cells mastering adipose tissues metabolic fate

Dynamic communication within adipose tissue depends on highly vascularized structural characteristics to maintain systemic metabolic homoeostasis. Recently, it has been noted that adipose endothelial cells (AdECs) act as essential bridges for biological information transmission between adipose-resident cells. Hence, paracrine regulators that mediate crosstalk between AdECs and adipose stromal cells were summarized. We also highlight the importance of AdECs to maintain adipocytes metabolic homoeostasis by regulating insulin sensitivity, lipid turnover and plasticity. The differential regulation of AdECs in adipose plasticity often depends on vascular density and metabolic states. Although choosing pro-angiogenic or anti-angiogenic therapies for obesity is still a matter of debate in clinical settings, the growing numbers of drugs have been confirmed to play an anti-obesity effect by affecting vascularization. Pharmacologic angiogenesis intervention has great potential as therapeutic strategies for obesity.

Ramulus Mori (Sangzhi) Alkaloids Ameliorate Obesity-Linked Adipose Tissue Metabolism and Inflammation in Mice

Obesity has become a global epidemic disease as it is closely associated with a chronic low-grade inflammatory state that results in metabolic dysfunction. Ramulus Mori (Sangzhi) alkaloids (SZ-A) derived from Morus alba L. were licensed to treat type 2 diabetes (T2DM) in 2020. In this study, we explored the effect of SZ-A on adipose tissue metabolism and inflammation using an obesity model induced by a high-fat diet (HFD). C57BL/6J mice were fed high fat for 14 weeks and followed by SZ-A 400 mg/kg treatment via gavage for another six weeks, during which they were still given the high-fat diet. The results showed that SZ-A notably reduced body weight and serum levels of lipid metabolism-related factors, such as triglycerides (TG) and total cholesterol (TC); and inflammation-related factors, namely tumor necrosis factor alpha (TNFα), interleukin 6 (IL6), fibrinogen activator inhibitor-1 (PAI-1), angiopoietin-2 (Ang-2), and leptin (LEP), in the HFD-induced mice. SZ-A increased the protein and mRNA expression of lipid metabolism-related factors, including phosphorylated acetyl coenzyme A carboxylase (p-ACC), phosphorylated hormone-sensitive triglyceride lipase (p-HSL), adipose triglyceride lipase (ATGL), and peroxisome proliferator-activated receptor-alpha (PPARα), in adipose tissue. Immunohistochemistry results demonstrated that SZ-A significantly reduced the infiltration of pro-inflammatory M1-type macrophages in epididymal fat. The data also suggested that SZ-A down-regulates the transcriptional levels of inflammatory factors Il6, Tnfα, monocyte chemoattractant protein-1 (Mcp1), and F4/80, and up-regulates interleukin 4 (Il4), interleukin 10 (Il10), and interleukin 13 (Il13) in adipose tissue. Overall, the results indicate that SZ-A exhibits potential in regulating lipid metabolism and ameliorating obesity-linked adipose inflammation.

Angiopoietin-like 2 is essential to aortic valve development in mice

Aortic valve (AoV) abnormalities during embryogenesis are a major risk for the development of aortic valve stenosis (AVS) and cardiac events later in life. Here, we identify an unexpected role for Angiopoietin-like 2 (ANGPTL2), a pro-inflammatory protein secreted by senescent cells, in valvulogenesis. At late embryonic stage, mice knocked-down for Angptl2 (Angptl2-KD) exhibit a premature thickening of AoV leaflets associated with a dysregulation of the fine balance between cell apoptosis, senescence and proliferation during AoV remodeling and a decrease in the crucial Notch signalling. These structural and molecular abnormalities lead toward spontaneous AVS with elevated trans-aortic gradient in adult mice of both sexes. Consistently, ANGPTL2 expression is detected in human fetal semilunar valves and associated with pathways involved in cell cycle and senescence. Altogether, these findings suggest that Angptl2 is essential for valvulogenesis, and identify Angptl2-KD mice as an animal model to study spontaneous AVS, a disease with unmet medical need.

Hepatic ER stress suppresses adipose browning through ATF4-CIRP-ANGPTL3 cascade

Hepatic endoplasmic reticulum (ER) stress is a hallmark of obesity-induced liver steatosis and contributes to the progress of steatosis and insulin resistance in liver. However, its influence on adipose function is still unclear. Here, we identify a hepatic ER stress-induced activating transcription factor 4 (ATF4)-cold-inducible RNA-binding protein (CIRP)-angiopoietin-related protein3 (ANGPTL3) cascade critical for the regulation of adipose browning. We find that obesity increases CIRP expression in liver through ER stress-induced ATF4. CIRP in turn binds to the 3' UTR and increases mRNA stability of ANGPTL3. ANGPTL3 secreted from liver suppresses uncoupling protein 1 expression through integrin α_vβ₃ and c-Jun N-terminal kinase in adipose tissue. While hepatic expression of either ATF4, CIRP, or ANGPTL3 suppresses adipose browning, knockdown of CIRP and ANGPTL3 in liver or administration of integrin α_vβ₃ inhibitor cilengitide increases adipose browning process. Taken together, we identify a communication mechanism to link hepatic ER stress and adipose browning that may imply a reciprocal regulation of obesity and liver steatosis.

Angiopoietin-Like Protein 2 Is Increased in Obese Mouse Models of Lung Injury

Objective

To investigate the regulatory role of angiopoietin-1ike protein 2 (Angptl 2) in the pathogenesis of acute respiratory distress syndrome (ARDS).

Methods

A high-fat diet (HFD) and tail vein injection of 0.1 ml/kg oleic acid were used to induce acute lung injury (ALI) and ARDS models, and male Kunming mice were randomly divided into four groups: control group (injected with normal saline), ALI group (injected with oleic acid), HFD group (injection of normal saline), and ARDS group (HFD+injection of oleic acid). The degree of lung injury was assessed by lung histopathology score and lung injury index. At the same time, the mRNA and protein expression levels of Angptl 2 in lung tissue were also detected to determine the relationship between Angptl 2 and ARDS.

Results

Lee's index of the HFD group and ARDS group was significantly higher than that of the control group and ALI group (P < 0.05), and the lung injury index of the ARDS group was significantly higher than that of the ALI group. The expression of Angptl 2 in the lung tissue of the ALI group and ARDS group was significantly different, and the Angptl 2 mRNA level was the highest in the ARDS group. Immunohistochemistry showed that the alveolar walls of the ALI group and ARDS group were severely collapsed, and the ARDS group had the greatest Angptl 2 aggregation at the site of edema exudation.

Conclusion

Collectively, obesity might be mediated by Angptl 2 and promotes lung injury. Immunohistochemistry analysis showed that the expression of the receptor on alveolar walls was correlated with Angptl 2, which increased alveolar wall permeability, edema fluid exudation, and alveolar wall collapse. Thus, Angptl 2 might be a target for improving the treatment of ARDS.

Adipose tissue-to-breast cancer crosstalk: Comprehensive insights

The review focuses on mechanistic evidence for the link between obesity and breast cancer. According to the IARC study, there is sufficient evidence that obesity is closely related to a variety of cancers. Among them, breast cancer is particularly disturbed by adipose tissue due to the unique histological structure of the breast. The review introduces the relationship between obesity and breast cancer from two aspects, including factors that promote tumorigenesis or metastasis. We summarize alterations in adipokines and metabolic pathways that contribute to breast cancer development. Breast cancer metastasis is closely related to obesity-induced pro-inflammatory microenvironment, adipose stem cells, and miRNAs. Based on the mechanism by which obesity causes breast cancer, we list possible therapeutic directions, including reducing the risk of breast cancer and inhibiting the progression of breast cancer. We also discussed the risk of autologous breast remodeling and fat transplantation. Finally, the causes of the obesity paradox and the function of enhancing immunity are discussed. Evaluating the balance between obesity-induced inflammation and enhanced immunity warrants further study.

Obesity: a perfect storm for carcinogenesis

Obesity-related cancers account for 40% of the cancer cases observed in the USA and obesity is overtaking smoking as the most widespread modifiable risk factor for carcinogenesis. Here, we use the hallmarks of cancer framework to delineate how obesity might influence the carcinogenic hallmarks in somatic cells. We discuss the effects of obesity on (a) sustaining proliferative signaling; (b) evading growth suppressors; (c) resisting cell death; (d) enabling replicative immortality; (e) inducing angiogenesis; (f) activating invasion and metastasis; (g) reprogramming energy metabolism; and (h) avoiding immune destruction, together with its effects on genome instability and tumour-promoting inflammation. We present the current understanding and controversies in this evolving field, and highlight some areas in need of further cross-disciplinary focus. For instance, the relative importance of the many potentially causative obesity-related factors is unclear for each type of malignancy. Even within a single tumour type, it is currently unknown whether one obesity-related factor consistently plays a predominant role, or if this varies between patients or, even in a single patient with time. Clarifying how the hallmarks are affected by obesity may lead to novel prevention and treatment strategies for the increasingly obese population.

The molecular signaling of exercise and obesity in the microbiota-gut-brain axis

Obesity is one of the major pandemics of the 21st century. Due to its multifactorial etiology, its treatment requires several actions, including dietary intervention and physical exercise. Excessive fat accumulation leads to several health problems involving alteration in the gut-microbiota-brain axis. This axis is characterized by multiple biological systems generating a network that allows bidirectional communication between intestinal bacteria and brain. This mutual communication maintains the homeostasis of the gastrointestinal, central nervous and microbial systems of animals. Moreover, this axis involves inflammatory, neural, and endocrine mechanisms, contributes to obesity pathogenesis. The axis also acts in appetite and satiety control and synthesizing hormones that participate in gastrointestinal functions. Exercise is a nonpharmacologic agent commonly used to prevent and treat obesity and other chronic degenerative diseases. Besides increasing energy expenditure, exercise induces the synthesis and liberation of several muscle-derived myokines and neuroendocrine peptides such as neuropeptide Y, peptide YY, ghrelin, and leptin, which act directly on the gut-microbiota-brain axis. Thus, exercise may serve as a rebalancing agent of the gut-microbiota-brain axis under the stimulus of chronic low-grade inflammation induced by obesity. So far, there is little evidence of modification of the gut-brain axis as a whole, and this narrative review aims to address the molecular pathways through which exercise may act in the context of disorders of the gut-brain axis due to obesity.