Hypoxia-inducible factor 1α regulates a SOCS3-STAT3-adiponectin signal transduction pathway in adipocytes

Therapeutic Potential of Targeting Prokineticin Receptors in Diseases

The prokineticins (PKs) were discovered approximately 20 years ago as small peptides inducing gut contractility. Today, they are established as angiogenic, anorectic, and proinflammatory cytokines, chemokines, hormones, and neuropeptides involved in variety of physiologic and pathophysiological pathways. Their altered expression or mutations implicated in several diseases make them a potential biomarker. Their G-protein coupled receptors, PKR1 and PKR2, have divergent roles that can be therapeutic target for treatment of cardiovascular, metabolic, and neural diseases as well as pain and cancer. This article reviews and summarizes our current knowledge of PK family functions from development of heart and brain to regulation of homeostasis in health and diseases. Finally, the review summarizes the established roles of the endogenous peptides, synthetic peptides and the selective ligands of PKR1 and PKR2, and nonpeptide orthostatic and allosteric modulator of the receptors in preclinical disease models. The present review emphasizes the ambiguous aspects and gaps in our knowledge of functions of PKR ligands and elucidates future perspectives for PK research. SIGNIFICANCE STATEMENT: This review provides an in-depth view of the prokineticin family and PK receptors that can be active without their endogenous ligand and exhibits "constitutive" activity in diseases. Their non- peptide ligands display promising effects in several preclinical disease models. PKs can be the diagnostic biomarker of several diseases. A thorough understanding of the role of prokineticin family and their receptor types in health and diseases is critical to develop novel therapeutic strategies with safety concerns.

Mechanobiology of cancer cell responsiveness to chemotherapy and immunotherapy: Mechanistic insights and biomaterial platforms

Mechanical forces are central to how cancer treatments such as chemotherapeutics and immunotherapies interact with cells and tissues. At the simplest level, electrostatic forces underlie the binding events that are critical to therapeutic function. However, a growing body of literature points to mechanical factors that also affect whether a drug or an immune cell can reach a target, and to interactions between a cell and its environment affecting therapeutic efficacy. These factors affect cell processes ranging from cytoskeletal and extracellular matrix remodeling to transduction of signals by the nucleus to metastasis of cells. This review presents and critiques the state of the art of our understanding of how mechanobiology impacts drug and immunotherapy resistance and responsiveness, and of the in vitro systems that have been of value in the discovery of these effects.

Anti-Inflammatory Effect of Ethanolic Extract from Tabebuia rosea (Bertol.) DC., Quercetin, and Anti-Obesity Drugs in Adipose Tissue in Wistar Rats with Diet-Induced Obesity

Obesity is characterized by the excessive accumulation of fat, which triggers a low-grade chronic inflammatory process. Currently, the search for compounds with anti-obesogenic effects that help reduce body weight, as well as associated comorbidities, continues. Among this group of compounds are plant extracts and flavonoids with a great diversity of action mechanisms associated with their beneficial effects, such as anti-inflammatory effects and/or as signaling molecules. In the bark of Tabebuia rosea tree, there are different classes of metabolites with anti-inflammatory properties, such as quercetin. Therefore, the present work studied the effect of the ethanolic extract of T. rosea and quercetin on the mRNA of inflammation markers in obesity compared to the drugs currently used. Total RNA was extracted from epididymal adipose tissue of high-fat diet-induced obese Wistar rats treated with orlistat, phentermine, T. rosea extract, and quercetin. The rats treated with T. rosea and quercetin showed 36 and 31% reductions in body weight compared to the obese control, and they likewise inhibited pro-inflammatory molecules: Il6, Il1b, Il18, Lep, Hif1a, and Nfkb1 without modifying the expression of Socs1 and Socs3. Additionally, only T. rosea overexpressed Lipe. Both T. rosea and quercetin led to a reduction in the expression of pro-inflammatory genes, modifying signaling pathways, which led to the regulation of the obesity-inflammation state.

Maternal pre-pregnancy body mass index and offspring with overweight/obesity at preschool age: The possible role of epigenome-wide DNA methylation changes in cord blood

BACKGROUND

Epigenome-wide association studies have identified some DNA methylation sites associated with body mass index (BMI) or obesity. Studies in the Asian population are lacking.

OBJECTIVE

To examine the association of cord blood genome-wide DNA methylation (GWDm) changes with maternal pre-pregnancy BMI and children's BMI-z score at preschool age. Additionally, we also explored the genome-wide differentially methylated regions and differentially methylated probes between preschoolers with overweight/obesity and normal-weight counterparts.

METHODS

This two-stage study design included (1) a GWDm analysis of 30 mother-child pairs from 633 participants of the Zhuhai birth cohort with data on newborn cord blood, maternal pre-pregnancy BMI, and children's BMI at 3 years of age; and (2) a targeted validation analysis of the cord blood of ten children with overweight/obesity and ten matched controls to validate the CpG sites.

RESULTS

In the first stage, no significant CpG sites were found to be associated with children's BMI-z score at preschool age after FDR correction with the p-values of the CpG sites in FOXN3 (cg23501836) and ZNF264 (cg27437574) being close to 1 × 10^-6 . In the second stage, a significant difference of CpG sites in AHRR (chr5:355067-355068) and FOXN3 (chr14: 89630264-89630272 and chr14: 89630387-89630388) was found between the ten children with overweight/obesity and ten controls (p < 0.05). The CpG sites in FOXN3 (chr14:89630264-89630272 and chr14:89630295-89630296) and ZNF264 (chr19: 57703104-57703107 and chr19: 57703301-57703307) were associated with children's BMI-z score; and the CpG sites in FOXN3 (chr14: 89630264-89630272 and chr14: 89630387-89630388) were associated with maternal pre-pregnancy BMI.

CONCLUSIONS

DNA methylation in FOXN3 and AHRR is associated with overweight/obesity in preschool-aged children, and the methylation in FOXN3 and ZNF264 might be associated with children's BMI-z score. FOXN3 methylation may be associated with maternal pre-pregnancy BMI, suggesting its potential role in the children's BMI-z score or overweight/obesity. Our results provide novel insights into the mechanisms of children's obesity.

Vitamin C protects against hypoxia, inflammation, and ER stress in primary human preadipocytes and adipocytes

Dysregulation of adipose tissue involves increased cellular hypoxia, ER stress, and inflammation and altered adipokine production, contributing to the aetiology of obesity-related diseases including type 2 diabetes and cardiovascular disease. This study aimed to investigate the effects of Vitamin C supplementation on these processes in primary human preadipocytes and adipocytes. Treatment of preadipocytes and adipocytes with the proinflammatory cytokine TNFα and palmitic acid (PA), to mimic the obesogenic milieu, significantly increased markers of hypoxia, ER stress and inflammation and reduced secretion of high molecular weight (HMW) adiponectin. Importantly, Vitamin C abolished TNFα+PA induced hypoxia and significantly reduced the increases in ER stress and inflammation in both cell types. Vitamin C also significantly increased the secretion of HMW adiponectin from adipocytes. These findings indicate that Vitamin C can reduce obesity-associated cellular stress and thus provide a rationale for future investigations.

Metabolic reprogramming and crosstalk of cancer-related fibroblasts and immune cells in the tumor microenvironment

It is notorious that cancer cells alter their metabolism to adjust to harsh environments of hypoxia and nutritional starvation. Metabolic reprogramming most often occurs in the tumor microenvironment (TME). TME is defined as the cellular environment in which the tumor resides. This includes surrounding blood vessels, fibroblasts, immune cells, signaling molecules and the extracellular matrix (ECM). It is increasingly recognized that cancer cells, fibroblasts and immune cells within TME can regulate tumor progression through metabolic reprogramming. As the most significant proportion of cells among all the stromal cells that constitute TME, cancer-associated fibroblasts (CAFs) are closely associated with tumorigenesis and progression. Multitudinous studies have shown that CAFs participate in and promote tumor metabolic reprogramming and exert regulatory effects via the dysregulation of metabolic pathways. Previous studies have demonstrated that curbing the substance exchange between CAFs and tumor cells can dramatically restrain tumor growth. Emerging studies suggest that CAFs within the TME have emerged as important determinants of metabolic reprogramming. Metabolic reprogramming also occurs in the metabolic pattern of immune cells. In the meanwhile, immune cell phenotype and functions are metabolically regulated. Notably, immune cell functions influenced by metabolic programs may ultimately lead to alterations in tumor immunity. Despite the fact that multiple previous researches have been devoted to studying the interplays between different cells in the tumor microenvironment, the complicated relationship between CAFs and immune cells and implications of metabolic reprogramming remains unknown and requires further investigation. In this review, we discuss our current comprehension of metabolic reprogramming of CAFs and immune cells (mainly glucose, amino acid, and lipid metabolism) and crosstalk between them that induces immune responses, and we also highlight their contributions to tumorigenesis and progression. Furthermore, we underscore potential therapeutic opportunities arising from metabolism dysregulation and metabolic crosstalk, focusing on strategies targeting CAFs and immune cell metabolic crosstalk in cancer immunotherapy.

Therapeutic Role of Curcumin in Diabetes: An Analysis Based on Bioinformatic Findings

BACKGROUND

Diabetes is an increasingly prevalent global disease caused by the impairment in insulin production or insulin function. Diabetes in the long term causes both microvascular and macrovascular complications that may result in retinopathy, nephropathy, neuropathy, peripheral arterial disease, atherosclerotic cardiovascular disease, and cerebrovascular disease. Considerable effort has been expended looking at the numerous genes and pathways to explain the mechanisms leading to diabetes-related complications. Curcumin is a traditional medicine with several properties such as being antioxidant, anti-inflammatory, anti-cancer, and anti-microbial, which may have utility for treating diabetes complications. This study, based on the system biology approach, aimed to investigate the effect of curcumin on critical genes and pathways related to diabetes.

METHODS

We first searched interactions of curcumin in three different databases, including STITCH, TTD, and DGIdb. Subsequently, we investigated the critical curated protein targets for diabetes on the OMIM and DisGeNET databases. To find important clustering groups (MCODE) and critical hub genes in the network of diseases, we created a PPI network for all proteins obtained for diabetes with the aid of a string database and Cytoscape software. Next, we investigated the possible interactions of curcumin on diabetes-related genes using Venn diagrams. Furthermore, the impact of curcumin on the top scores of modular clusters was analysed. Finally, we conducted biological process and pathway enrichment analysis using Gene Ontology (GO) and KEGG based on the enrichR web server.

RESULTS

We acquired 417 genes associated with diabetes, and their constructed PPI network contained 298 nodes and 1651 edges. Next, the analysis of centralities in the PPI network indicated 15 genes with the highest centralities. Additionally, MCODE analysis identified three modular clusters, which highest score cluster (MCODE 1) comprises 19 nodes and 92 edges with 10.22 scores. Screening curcumin interactions in the databases identified 158 protein targets. A Venn diagram of genes related to diabetes and the protein targets of curcumin showed 35 shared proteins, which observed that curcumin could strongly interact with ten of the hub genes. Moreover, we demonstrated that curcumin has the highest interaction with MCODE1 among all MCODs. Several significant biological pathways in KEGG enrichment associated with 35 shared included the AGE-RAGE signaling pathway in diabetic complications, HIF-1 signaling pathway, PI3K-Akt signaling pathway, TNF signaling, and JAK-STAT signaling pathway. The biological processes of GO analysis were involved with the cellular response to cytokine stimulus, the cytokine-mediated signaling pathway, positive regulation of intracellular signal transduction and cytokine production in the inflammatory response.

CONCLUSION

Curcumin targeted several important genes involved in diabetes, supporting the previous research suggesting that it may have utility as a therapeutic agent in diabetes.

CYP1A1, VEGFA and Adipokine Responses of Human Adipocytes Co-exposed to PCB126 and Hypoxia

It is increasingly recognized that hypoxia may develop in adipose tissue as its mass expands. Adipose tissue is also the main reservoir of lipophilic pollutants, including polychlorinated biphenyls (PCBs). Both hypoxia and PCBs have been shown to alter adipose tissue functions. The signaling pathways induced by hypoxia and pollutants may crosstalk, as they share a common transcription factor: aryl hydrocarbon receptor nuclear translocator (ARNT). Whether hypoxia and PCBs crosstalk and affect adipokine secretion in human adipocytes remains to be explored. Using primary human adipocytes acutely co-exposed to different levels of hypoxia (24 h) and PCB126 (48 h), we observed that hypoxia significantly inhibits the PCB126 induction of cytochrome P450 (CYP1A1) transcription in a dose-response manner, and that Acriflavine (ACF)—an HIF1α inhibitor—partially restores the PCB126 induction of CYP1A1 under hypoxia. On the other hand, exposure to PCB126 did not affect the transcription of the vascular endothelial growth factor-A (VEGFA) under hypoxia. Exposure to hypoxia increased leptin and interleukin-6 (IL-6), and decreased adiponectin levels dose-dependently, while PCB126 increased IL-6 and IL-8 secretion in a dose-dependent manner. Co-exposure to PCB126 and hypoxia did not alter the adipokine secretion pattern observed under hypoxia and PCB126 exposure alone. In conclusion, our results indicate that (1) hypoxia inhibits PCB126-induced CYP1A1 expression at least partly through ARNT-dependent means, suggesting that hypoxia could affect PCB metabolism and toxicity in adipose tissue, and (2) hypoxia and PCB126 affect leptin, adiponectin, IL-6 and IL-8 secretion differently, with no apparent crosstalk between the two factors.

HIF-1α inhibitor PX-478 preserves pancreatic β cell function in diabetes

During progression of type 2 diabetes, pancreatic β cells are subjected to sustained metabolic overload. We postulated that this state mediates a hypoxic phenotype driven by hypoxia-inducible factor-1α (HIF-1α) and that treatment with the HIF-1α inhibitor PX-478 would improve β cell function. Our studies showed that the HIF-1α protein was present in pancreatic β cells of diabetic mouse models. In mouse islets with high glucose metabolism, the emergence of intracellular Ca²⁺ oscillations at low glucose concentration and the abnormally high basal release of insulin were suppressed by treatment with the HIF-1α inhibitor PX-478, indicating improvement of β cell function. Treatment of db/db mice with PX-478 prevented the rise of glycemia and diabetes progression by maintenance of elevated plasma insulin concentration. In streptozotocin-induced diabetic mice, PX-478 improved the recovery of glucose homeostasis. Islets isolated from these mice showed hallmarks of improved β cell function including elevation of insulin content, increased expression of genes involved in β cell function and maturity, inhibition of dedifferentiation markers, and formation of mature insulin granules. In response to PX-478 treatment, human islet organoids chronically exposed to high glucose presented improved stimulation index of glucose-induced insulin secretion. These results suggest that the HIF-1α inhibitor PX-478 has the potential to act as an antidiabetic therapeutic agent that preserves β cell function under metabolic overload.

The Key Genes Underlying Pathophysiology Association between Plaque Instability and Progression of Myocardial Infarction

Young patients with type 2 diabetes and myocardial infarction (MI) have higher long-term all-cause and cardiovascular mortality. In addition, the observed increased, mildly abnormal baseline lipid levels, but not lipid variability, are associated with an increased risk of atherosclerotic cardiovascular disease events, particularly MI. This study investigated differentially expressed genes (DEGs), which might be potential targets for young patients with MI and a high-fat diet (HFD). GSE114695 and GSE69187 were downloaded and processed using the limma package. A Venn diagram was applied to identify the same DEGs, and further pathway analysis was performed using Metascape. Protein-protein interaction (PPI) network analysis was then applied, and the hub genes were screened out. Pivotal miRNAs were predicted and validated using the miRNA dataset in GSE114695. To investigate the cardiac function of the screened genes, an MI mouse model, echocardiogram, and ELISA of hub genes were applied, and a correlation analysis was also performed. From aged mice fed HFD, 138 DEGs were extracted. From aged mice fed with chow, 227 DEGs were extracted. Pathway enrichment analysis revealed that DEGs in aging mice fed HFD were enriched in lipid transport and lipid biosynthetic process 1 d after MI and in the MAPK signaling pathway at 1 w after MI, suggesting that HFD has less effect on aging with MI. A total of 148 DEGs were extracted from the intersection between plaques fed with HFD and chow in young mice and MI_1d, respectively, which demonstrated increased inflammatory and adaptive immune responses, in addition to myeloid leukocyte activation. A total of 183 DEGs were screened out between plaques fed with HFD vs. chow in young mice and MI_1w, respectively, which were mainly enriched in inflammatory response, cytokine production, and myeloid leukocyte activation. After validation, PAK3, CD44, CD5, SOCS3, VAV1, and PIK3CD were demonstrated to be negatively correlated with LVEF; however, P2RY1 was demonstrated to be positively correlated. This study demonstrated that the screened hub genes may be therapeutic targets for treating STEMI patients and preventing MI recurrence, especially in young MI patients with HFD or diabetes.

DNA demethylase ALKBH1 promotes adipogenic differentiation via regulation of HIF-1 signaling

DNA 6-adenine methylation (6mA), as a novel adenine modification existing in eukaryotes, shows essential functions in embryogenesis and mitochondrial transcriptions. ALKBH1 is a demethylase of 6mA and plays critical roles in osteogenesis, tumorigenesis, and adaptation to stress. However, the integrated biological functions of ALKBH1 still require further exploration. Here, we demonstrate that knockdown of ALKBH1 inhibits adipogenic differentiation in both human mesenchymal stem cells (hMSCs) and 3T3-L1 preadipocytes, while overexpression of ALKBH1 leads to increased adipogenesis. Using a combination of RNA-seq and N6-mA-DNA-IP-seq analyses, we identify hypoxia-inducible factor-1 (HIF-1) signaling as a crucial downstream target of ALKBH1 activity. Depletion of ALKBH1 leads to hypermethylation of both HIF-1α and its downstream target GYS1. Simultaneous overexpression of HIF-1α and GYS1 restores the adipogenic commitment of ALKBH1-deficient cells. Taken together, our data indicate that ALKBH1 is indispensable for adipogenic differentiation, revealing a novel epigenetic mechanism that regulates adipogenesis.

An Explanation for the Adiponectin Paradox

The adipokine adiponectin improves insulin sensitivity. Functional signal transduction of adiponectin requires at least one of the receptors AdipoR1 or AdipoR2, but additionally the glycosyl phosphatidylinositol-anchored molecule, T-cadherin. Overnutrition causes a reduction in adiponectin synthesis and an increase in the circulating levels of the enzyme glycosyl phosphatidylinositol-phospholipase D (GPI-PLD). GPI-PLD promotes the hydrolysis of T-cadherin. The functional consequence of T-cadherin hydrolysis is a reduction in adiponectin sequestration by responsive tissues, an augmentation of adiponectin levels in circulation and a (further) reduction in signal transduction. This process creates the paradoxical situation that adiponectin levels are augmented, whereas the adiponectin signal transduction and insulin sensitivity remain strongly impaired. Although both hypoadiponectinemia and hyperadiponectinemia reflect a situation of insulin resistance, the treatments are likely to be different.

Metformin reduces macrophage HIF1α-dependent proinflammatory signaling to restore brown adipocyte function in vitro

Therapeutic potential of metformin in obese/diabetic patients has been associated to its ability to combat insulin resistance. However, it remains largely unknown the signaling pathways involved and whether some cell types are particularly relevant for its beneficial effects. M1-activation of macrophages by bacterial lipopolysaccharide (LPS) promotes a paracrine activation of hypoxia-inducible factor-1α (HIF1α) in brown adipocytes which reduces insulin signaling and glucose uptake, as well as β-adrenergic sensitivity. Addition of metformin to M1-polarized macrophages blunted these signs of brown adipocyte dysfunction. At the molecular level, metformin inhibits an inflammatory program executed by HIF1α in macrophages by inducing its degradation through the inhibition of mitochondrial complex I activity, thereby reducing oxygen consumption in a reactive oxygen species (ROS)-independent manner. In obese mice, metformin reduced inflammatory features in brown adipose tissue (BAT) such as macrophage infiltration, proinflammatory signaling and gene expression, and restored the response to cold exposure. In conclusion, the impact of metformin on macrophages by suppressing a HIF1α-dependent proinflammatory program is likely responsible for a secondary beneficial effect on insulin-mediated glucose uptake and β-adrenergic responses in brown adipocytes.

Network pharmacology-based analysis of the anti-hyperglycemic active ingredients of roselle and experimental validation

Diabetes mellitus is one of the top four leading causes of death among noncommunicable diseases worldwide, according to the World Hibiscus sabdariffa 2019. Roselle (Hibiscus sabdariffa L.), a traditional herbal medicine, has shown significant clinical anti-hyperglycemic efficacy. However, the mechanism of the treatment is not yet clear. We found that Roselle has a certain protective effect on vascular endothelial cells through this study. This study was based on network pharmacology and experimental validation. The present study made a comprehensive analysis by combining active ingredient screening, target prediction and signaling pathway analysis to elucidate the active ingredients and possible molecular mechanism of roselle for the first time, which provided theoretical and experimental basis for the development and application of roselle as an antidiabetic drug.

Mechanism and Basis of Traditional Chinese Medicine Against Obesity: Prevention and Treatment Strategies

In the last few decades, the incidences of obesity and related metabolic disorders worldwide have increased dramatically. Major pathophysiology of obesity is termed "lipotoxicity" in modern western medicine (MWM) or "dampness-heat" in traditional Chinese medicine (TCM). "Dampness-heat" is a very common and critically important syndrome to guild clinical treatment in TCM. However, the pathogenesis of obesity in TCM is not fully clarified, especially by MWM theories compared to TCM. In this review, the mechanism underlying the action of TCM in the treatment of obesity and related metabolic disorders was thoroughly discussed, and prevention and treatment strategies were proposed accordingly. Hypoxia and inflammation caused by lipotoxicity exist in obesity and are key pathophysiological characteristics of "dampness-heat" syndrome in TCM. "Dampness-heat" is prevalent in chronic low-grade systemic inflammation, prone to insulin resistance (IR), and causes variant metabolic disorders. In particular, the MWM theories of hypoxia and inflammation were applied to explain the "dampness-heat" syndrome of TCM, and we summarized and proposed the pathological path of obesity: lipotoxicity, hypoxia or chronic low-grade inflammation, IR, and metabolic disorders. This provides significant enrichment to the scientific connotation of TCM theories and promotes the modernization of TCM.

The balance of concentration between Prokineticin 2β and Prokineticin 2 modulates the food intake by STAT3 signaling

The secreted bioactive peptide prokineticin 2 (PK2) is a potent adipokine and its central and peripheral administration reduces food intake in rodents. The pk2 gene has two splice variants, PK2 and PK2L (PK2 long form), which is cleaved into an active peptide, PK2β, that preferentially binds prokineticin receptor 1 (PKR1). We investigated the role of PK2β in the regulation of food intake. We demonstrated that intraperitoneal injection of PK2β, in contrast to PK2, did not reduce food intake in mice. Exposure of hypotalamic explants to PK2, but not PK2β, induced phosphorylation of STAT3 and ERK. We also evidenced that in adipocytes from PKR1 knock-out mice, a model of obesity, there were higher PK2β levels than PK2 inducing a decreased activation of STAT3 and ERK. Our results suggest that variations in PK2 and PK2β levels, due to modulation of pk2 gene splicing processes, affect food intake in mice.

Cancer-Associated Fibroblasts: Accomplices in the Tumor Immune Evasion

Simple Summary

A growing number of studies suggest that cancer-associated fibroblasts (CAFs) modulate both myeloid and lymphoid cells through secretion of molecules (i.e., chemical function) and production of the extracellular matrix (ECM), i.e., physical function. Even though targeting functions CAFs is a relevant strategy, published clinical trials solely aimed at targeting the stroma showed disappointing results, despite being based on solid preclinical evidence. Our review dissects the interactions between CAFs and immune cells and explains how a deeper understanding of CAF subpopulations is the cornerstone to propose relevant therapies that will ultimately improve survival of patients with cancer.

Abstract

Cancer-associated fibroblasts (CAFs) are prominent cells within the tumor microenvironment, by communicating with other cells within the tumor and by secreting the extracellular matrix components. The discovery of the immunogenic role of CAFs has made their study particularly attractive due to the potential applications in the field of cancer immunotherapy. Indeed, CAFs are highly involved in tumor immune evasion by physically impeding the immune system and interacting with both myeloid and lymphoid cells. However, CAFs do not represent a single cell entity but are divided into several subtypes with different functions that may be antagonistic. Considering that CAFs are orchestrators of the tumor microenvironment and modulate immune cells, targeting their functions may be a promising strategy. In this review, we provide an overview of (i) the mechanisms involved in immune regulation by CAFs and (ii) the therapeutic applications of CAFs modulation to improve the antitumor immune response and the efficacy of immunotherapy.

Homocysteine promotes hepatic steatosis by activating the adipocyte lipolysis in a HIF1α-ERO1α-dependent oxidative stress manner

Hyperhomocysteinemia (HHcy) is related to liver diseases, such as nonalcoholic fatty liver (NAFL). Although the precise pathogenesis of NAFL is still largely unknown, the links between organs seem to play a vital role. The current study aimed to explore the role of white adipose tissue in homocysteine (Hcy)-induced NAFL. Blood samples from nonhyperhomocysteinemia or hyperhomocysteinemia individuals were collected to assess correlation between Hcy and triglyceride (TG) or free fatty acids (FFAs) levels. C57BL/6 mice were maintained on a high-methionine diet or administered with Hcy (1.8 g/L) in the drinking water to establish an HHcy mouse model. We demonstrated that Hcy activated adipocyte lipolysis and that this change was accompanied by an increased release of FFAs and glycerol. Excessive FFAs were taken up by hepatocyte, which resulted in lipid accumulation in the liver. Treatment with acipimox (0.08 g kg ⁻¹ day ⁻¹), a potent chemical inhibitor of lipolysis, markedly decreased Hcy-induced NAFL. Mechanistically, hypoxia-inducible factor 1α (HIF1α)-endoplasmic reticulum oxidoreductin 1α (ERO1α) mediated pathway promoted H₂O₂ accumulation and induced endoplasmic reticulum (ER) overoxidation, ER stress and more closed ER-lipid droplet interactions, which were responsible for activating the lipolytic response. In conclusion, this study reveals that Hcy activates adipocyte lipolysis and suggests the potential utility of targeted ER redox homeostasis for treating Hcy-induced NAFL.

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Hcy elevates adipocyte lipolysis process.

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Inhibition of adipocyte lipolysis via acipimox improves the Hcy-induced nonalcoholic fatty liver.

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Adipocyte lipolytic response relies on ERO1α-mediated oxidative stress.

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Activation of adipocyte HIF1α mediates ERO1α upregulation.

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Deficiency of adipocyte HIF1α alleviates the Hcy-induced lipolytic response and nonalcoholic fatty liver.

Adiponectin: The Potential Regulator and Therapeutic Target of Obesity and Alzheimer's Disease

Animal and human mechanistic studies have consistently shown an association between obesity and Alzheimer’s disease (AD). AD, a degenerative brain disease, is the most common cause of dementia and is characterized by the presence of extracellular amyloid beta (Aβ) plaques and intracellular neurofibrillary tangles disposition. Some studies have recently demonstrated that Aβ and tau cannot fully explain the pathophysiological development of AD and that metabolic disease factors, such as insulin, adiponectin, and antioxidants, are important for the sporadic onset of nongenetic AD. Obesity prevention and treatment can be an efficacious and safe approach to AD prevention. Adiponectin is a benign adipokine that sensitizes the insulin receptor signaling pathway and suppresses inflammation. It has been shown to be inversely correlated with adipose tissue dysfunction and may enhance the risk of AD because a range of neuroprotection adiponectin mechanisms is related to AD pathology alleviation. In this study, we summarize the recent progress that addresses the beneficial effects and potential mechanisms of adiponectin in AD. Furthermore, we review recent studies on the diverse medications of adiponectin that could possibly be related to AD treatment, with a focus on their association with adiponectin. A better understanding of the neuroprotection roles of adiponectin will help clarify the precise underlying mechanism of AD development and progression.

New role for ceramide in hypoxia and insulin resistance

Ceramides are significant metabolic products of sphingolipids in lipid metabolism and are associated with insulin resistance and hepatic steatosis. In chronic inflammatory pathological conditions, hypoxia occurs, the metabolism of ceramide changes, and insulin resistance arises. Hypoxia-inducible factors (HIFs) are a family of transcription factors activated by hypoxia. In hypoxic adipocytes, HIF-1α upregulates pla2g16 (a novel HIF-1α target gene) gene expression to activate the NLRP3 inflammasome pathway and stimulate insulin resistance, and adipocyte-specific Hif1a knockout can ameliorate homocysteine-induced insulin resistance in mice. The study on the HIF-2α—NEU3—ceramide pathway also reveals the role of ceramide in hypoxia and insulin resistance in obese mice. Under obesity-induced intestinal hypoxia, HIF-2α increases the production of ceramide by promoting the expression of the gene Neu3 encoding sialidase 3, which is a key enzyme in ceramide synthesis, resulting in insulin resistance in high-fat diet-induced obese mice. Moreover, genetic and pathophysiologic inhibition of the HIF-2α—NEU3—ceramide pathway can alleviate insulin resistance, suggesting that these could be potential drug targets for the treatment of metabolic diseases. Herein, the effects of hypoxia and ceramide, especially in the intestine, on metabolic diseases are summarized.

Pathophysiological implications of hypoxia in human diseases

Oxygen is essentially required by most eukaryotic organisms as a scavenger to remove harmful electron and hydrogen ions or as a critical substrate to ensure the proper execution of enzymatic reactions. All nucleated cells can sense oxygen concentration and respond to reduced oxygen availability (hypoxia). When oxygen delivery is disrupted or reduced, the organisms will develop numerous adaptive mechanisms to facilitate cells survived in the hypoxic condition. Normally, such hypoxic response will cease when oxygen level is restored. However, the situation becomes complicated if hypoxic stress persists (chronic hypoxia) or cyclic normoxia-hypoxia phenomenon occurs (intermittent hypoxia). A series of chain reaction-like gene expression cascade, termed hypoxia-mediated gene regulatory network, will be initiated under such prolonged or intermittent hypoxic conditions and subsequently leads to alteration of cellular function and/or behaviors. As a result, irreversible processes occur that may cause physiological disorder or even pathological consequences. A growing body of evidence implicates that hypoxia plays critical roles in the pathogenesis of major causes of mortality including cancer, myocardial ischemia, metabolic diseases, and chronic heart and kidney diseases, and in reproductive diseases such as preeclampsia and endometriosis. This review article will summarize current understandings regarding the molecular mechanism of hypoxia in these common and important diseases.

Hypoxia‑inducible factor‑1α regulates Lipin1 differently in pre‑adipocytes and mature adipocytes

Hypoxia-inducible factor (HIF)-1α is a transcription factor that is activated in low oxygen conditions. Adipose tissues are poorly oxygenated in patients with obesity. The low oxygen conditions in obese adipose tissues induce HIF‑1α in adipocytes. Previous studies using genetically modified mice suggest that HIF‑1α contributes to dysfunction in adipocytes. Lipin1 is a bifunctional protein that works as a phosphatidate phosphatase and transcriptional coactivator, which regulates lipid metabolism and adipogenesis, respectively. HIF‑1α directly regulates Lipin1 in hepatocytes. However, the regulation of Lipin1 by HIF‑1α in adipocytes is not well determined. Therefore, the present study investigated the regulation of Lipin1 by HIF‑1α in adipocytes. Expression levels of Lipin1 were reduced in epididymal adipose tissues of adipocyte‑specific HIF‑1α knockout mice, indicating that HIF‑1α regulates Lipin1 in adipocytes. In differentiated mature adipocytes, a HIF‑1α activator, dimethyloxallyl glycine (DMOG), was demonstrated to increase Lipin1, and a HIF‑1α inhibitor, 3‑(5'‑hydroxymethyl‑2'‑furyl)-1‑benzylindazole (YC‑1), reversed this increase, indicating that HIF‑1α regulates Lipin1 in differentiated adipocytes. However, during differentiation of pre‑adipocytes into adipocytes, YC‑1 increased Lipin1 even though HIF‑1α was decreased. The differentiation efficiency increased with YC‑1 treatment. In addition, DMOG reduced Lipin1 expression levels during differentiation despite increased HIF‑1α. Under these conditions, differentiation efficiency was reduced. These results suggest that Lipin1 is negatively regulated by HIF‑1α in pre‑adipocytes. Our results show that regulation of Lipin1 by HIF‑1α is different in adipocytes and pre‑adipocytes.

HIF1α inhibits LPS-mediated induction of IL-6 synthesis via SOCS3-dependent CEBPβ suppression in human dental pulp cells

Hypoxia-inducible factor 1 alpha (HIF1α) is a transcriptional factor that plays a key role in the regulation of various molecules expressed in hypoxic conditions. Ischemic/hypoxic conditions are regarded as a distinct characteristic of dental pulp inflammation due to the encasement of pulp tissue within the rigid tooth structure. This study was performed to examine the role of HIF1α in the regulation of interleukin (IL)-6, a proinflammatory cytokine expressed in inflamed dental pulp, in lipopolysaccharide (LPS)-stimulated human dental pulp cells (hDPCs). LPS stimulation promoted the expression of IL-6 in hDPCs, while HIF1α suppressed the expression of IL-6. Moreover, HIF1α induced suppressor of cytokine signaling 3 (SOCS3) expression in LPS-stimulated hDPCs, and SOCS3 activity led to downregulate expression of CCAAT enhancer-binding protein beta (CEBPβ), an inducer of IL-6. LPS stimulation promoted HIF1α expression in hDPCs and mouse pulp tissue explants cultured under hypoxic conditions. These findings suggest that HIF1α negatively regulates IL-6 synthesis in LPS-stimulated hDPCs via upregulation of SOCS3 and subsequent downregulation of CEBPβ.

Macrophage metabolic reprogramming aggravates aortic dissection through the HIF1α-ADAM17 pathway✰

Background

Aortic dissection is a severe inflammatory vascular disease with high mortality and limited therapeutic options. The hallmarks of aortic dissection comprise aortic inflammatory cell infiltration and elastic fiber disruption, highlighting the involvement of macrophage. Here a role for macrophage hypoxia-inducible factor 1-alpha (HIF-1α) in aortic dissection was uncovered.

Methods

Immunochemistry, immunofluorescence, western blot and qPCR were performed to test the change of macrophage HIF-1α in two kinds of aortic dissection models and human tissues. Metabolomics and Seahorse extracellular flux analysis were used to detect the metabolic state of macrophages involved in the development of aortic dissection. Chromatin Immunoprecipitation (ChIP), enzyme-linked immunosorbent assay (ELISA) and cytometric bead array (CBA) were employed for mechanistic studies.

Findings

Macrophages involved underwent distinct metabolic reprogramming, especially fumarate accumulation, thus inducing HIF-1α activation in the development of aortic dissection in human and mouse models. Mechanistic studies revealed that macrophage HIF-1α activation triggered vascular inflammation, extracellular matrix degradation and elastic plate breakage through increased a disintegrin and metallopeptidase domain 17 (ADAM17), identified as a novel target gene of HIF-1α. A HIF-1α specific inhibitor acriflavine elicited protective effects on aortic dissection dependent on macrophage HIF-1α.

Interpretation

This study reveals that macrophage metabolic reprogramming activates HIF-1α and subsequently promotes aortic dissection progression, suggesting that macrophage HIF-1α inhibition might be a potential therapeutic target for treating aortic dissection.

The Transcriptional Regulator Id2 Is Critical for Adipose-Resident Regulatory T Cell Differentiation, Survival, and Function

Adipose regulatory T cells (aTregs) have emerged as critical cells for the control of local and systemic inflammation. In this study, we show a distinctive role for the transcriptional regulator Id2 in the differentiation, survival, and function of aTregs in mice. Id2 was highly expressed in aTregs compared with high Id3 expression in lymphoid regulatory T cells (Tregs). Treg-specific deletion of Id2 resulted in a substantial decrease in aTregs, whereas Tregs in the spleen and lymph nodes were unaffected. Additionally, loss of Id2 resulted in decreased expression of aTreg-associated markers, including ST2, CCR2, KLRG1, and GATA3. Gene expression analysis revealed that Id2 expression was essential for the survival of aTregs, and loss of Id2 increased cell death in aTregs due to increased Fas expression. Id2-mediated aTreg depletion resulted in increased systemic inflammation, increased inflammatory macrophages and CD8⁺ effector T cells, and loss of glucose tolerance under standard diet conditions. Thus, we reveal an unexpected and novel function for Id2 in mediating differentiation, survival, and function of aTregs that when lost result in increased metabolic perturbation.

Hypoxia-Inducible Factors and the Regulation of Lipid Metabolism

Oxygen deprivation or hypoxia characterizes a number of serious pathological conditions and elicits a number of adaptive changes that are mainly mediated at the transcriptional level by the family of hypoxia-inducible factors (HIFs). The HIF target gene repertoire includes genes responsible for the regulation of metabolism, oxygen delivery and cell survival. Although the involvement of HIFs in the regulation of carbohydrate metabolism and the switch to anaerobic glycolysis under hypoxia is well established, their role in the control of lipid anabolism and catabolism remains still relatively obscure. Recent evidence indicates that many aspects of lipid metabolism are modified during hypoxia or in tumor cells in a HIF-dependent manner, contributing significantly to the pathogenesis and/or progression of cancer and metabolic disorders. However, direct transcriptional regulation by HIFs has been only demonstrated in relatively few cases, leaving open the exact and isoform-specific mechanisms that underlie HIF-dependency. This review summarizes the evidence for both direct and indirect roles of HIFs in the regulation of genes involved in lipid metabolism as well as the involvement of HIFs in various diseases as demonstrated by studies with transgenic animal models.

Metabolomic and lipidomic plasma profile changes in human participants ascending to Everest Base Camp

At high altitude oxygen delivery to the tissues is impaired leading to oxygen insufficiency (hypoxia). Acclimatisation requires adjustment to tissue metabolism, the details of which remain incompletely understood. Here, metabolic responses to progressive environmental hypoxia were assessed through metabolomic and lipidomic profiling of human plasma taken from 198 human participants before and during an ascent to Everest Base Camp (5,300 m). Aqueous and lipid fractions of plasma were separated and analysed using proton (1H)-nuclear magnetic resonance spectroscopy and direct infusion mass spectrometry, respectively. Bayesian robust hierarchical regression revealed decreasing isoleucine with ascent alongside increasing lactate and decreasing glucose, which may point towards increased glycolytic rate. Changes in the lipid profile with ascent included a decrease in triglycerides (48-50 carbons) associated with de novo lipogenesis, alongside increases in circulating levels of the most abundant free fatty acids (palmitic, linoleic and oleic acids). Together, this may be indicative of fat store mobilisation. This study provides the first broad metabolomic account of progressive exposure to environmental hypobaric hypoxia in healthy humans. Decreased isoleucine is of particular interest as a potential contributor to muscle catabolism observed with exposure to hypoxia at altitude. Substantial changes in lipid metabolism may represent important metabolic responses to sub-acute exposure to environmental hypoxia.

Sustained Intermittent Hypoxemia Induces Adiponectin Oligomers Redistribution and a Tissue-Specific Modulation of Adiponectin Receptor in Mice

Introduction: Hypoxemia is a critical component of several respiratory diseases and is known to be involved in the processes underlying co-morbidities associated to such disorders, notably at the cardiovascular level. Circulating level of Adiponectin (Ad), known as a metabolic regulator and cardio-protective hormone was previously suggested to be reduced by hypoxia but consequences of such variation are unclear. The evaluation of the specific effect of hypoxemia on Ad forms and receptors could improve the understanding of the involvement of Ad axis in hypoxemia-related diseases.

Methods: Ad-pathway components were investigated in a murine model of sustained intermittent hypoxemia (FiO₂ 10%, 8 h/day, 35 days).

Results: Sustained intermittent hypoxemia (SIH) induced a redistribution of Ad multimers in favor of HMW forms, without change in total plasmatic level. Mice submitted to hypoxia also exhibited tissue-specific modification of adiporeceptor (AdipoR) protein level without mRNA expression change. A decreased AdipoR2 abundance was observed in skeletal muscle and heart whereas AdipoR1 level was only reduced in muscle. No change was observed in liver regarding AdipoR. Lipid profile was unchanged but glucose tolerance increased in hypoxemic mice.

Conclusion: Sustained intermittent hypoxemia, per se, modify Ad oligomerization state as well as AdipoR protein abundance in a tissue-specific way. That suggests alteration in Ad-dependant pathways in pathological conditions associated to SIH. Investigation of Ad-pathway components could therefore constitute useful complementary criteria for the clustering of patients with hypoxemia-related diseases and management of co-morbidities, as well as to develop new therapeutic strategies.

The role of hypoxia-inducible factors in metabolic diseases

Hypoxia-inducible factors (HIFs), a family of transcription factors activated by hypoxia, consist of three α-subunits (HIF1α, HIF2α and HIF3α) and one β-subunit (HIF1β), which serves as a heterodimerization partner of the HIFα subunits. HIFα subunits are stabilized from constitutive degradation by hypoxia largely through lowering the activity of the oxygen-dependent prolyl hydroxylases that hydroxylate HIFα, leading to their proteolysis. HIF1α and HIF2α are expressed in different tissues and regulate target genes involved in angiogenesis, cell proliferation and inflammation, and their expression is associated with different disease states. HIFs have been widely studied because of their involvement in cancer, and HIF2α-specific inhibitors are being investigated in clinical trials for the treatment of kidney cancer. Although cancer has been the major focus of research on HIF, evidence has emerged that this pathway has a major role in the control of metabolism and influences metabolic diseases such as obesity, type 2 diabetes mellitus and non-alcoholic fatty liver disease. Notably increased HIF1α and HIF2α signalling in adipose tissue and small intestine, respectively, promotes metabolic diseases in diet-induced disease models. Inhibition of HIF1α and HIF2α decreases the adverse diet-induced metabolic phenotypes, suggesting that they could be drug targets for the treatment of metabolic diseases.

Downregulation of HIF complex in the hypothalamus exacerbates diet-induced obesity

Hypothalamic hypoxia-inducible factor-1 (HIF-1) can regulate whole-body energy homeostasis in response to changes in blood glucose, suggesting that it acts as a sensor for systemic energy stores. Here, we hypothesized that hypothalamic HIF-1 could be affected by diet-induced obesity (DIO). We used eight-week old, male C57Bl6 mice, fed normal chow diet or with high fat diet for 1, 3, 7, 14 and 28 days. The expression of HIF-1alpha and HIF-1beta was measured by PCR and western blotting and its hypothalamic distribution was evaluated by fluorescence microscopy. Inhibition of HIF-1beta in arcuate nucleus of hypothalamus was performed using stereotaxic injection of shRNA lentiviral particles and animals were grouped under normal chow diet or high fat diet for 14 days. Using bioinformatics, we show that in humans, the levels of HIF-1 transcripts are directly correlated with those of hypothalamic transcripts for proteins involved in inflammation, regulation of apoptosis, autophagy, and the ubiquitin/proteasome system; furthermore, in rodents, hypothalamic HIF-1 expression is directly correlated with the phenotype of increased energy expenditure. In mice, DIO was accompanied by increased HIF-1 expression. The inhibition of hypothalamic HIF-1 by injection of an shRNA resulted in a further increase in body mass, a decreased basal metabolic rate, increased hypothalamic inflammation, and glucose intolerance. Thus, hypothalamic HIF-1 is increased during DIO, and its inhibition worsens the obesity-associated metabolic phenotype. Thus, hypothalamic HIF-1 emerges as a target for therapeutic intervention against obesity.

Homocysteine causes vascular endothelial dysfunction by disrupting endoplasmic reticulum redox homeostasis

Endothelial dysfunction induced by hyperhomocysteinemia (HHcy) plays a critical role in vascular pathology. However, little is known about the role of endoplasmic reticulum (ER) redox homeostasis in HHcy-induced endothelial dysfunction. Here, we show that Hcy induces ER oxidoreductin-1α (Ero1α) expression with ER stress and inflammation in human umbilical vein endothelial cells and in the arteries of HHcy mice. Hcy upregulates Ero1α expression by promoting binding of hypoxia-inducible factor 1α to the ERO1A promoter. Notably, Hcy rather than other thiol agents markedly increases the GSH/GSSG ratio in the ER, therefore allosterically activating Ero1α to produce H₂O₂ and trigger ER oxidative stress. By contrast, the antioxidant pathway mediated by ER glutathione peroxidase 7 (GPx7) is downregulated in HHcy mice. Ero1α knockdown and GPx7 overexpression protect the endothelium from HHcy-induced ER oxidative stress and inflammation. Our work suggests that targeting ER redox homeostasis could be used as an intervention for HHcy-related vascular diseases.

Adipocyte-derived Lysophosphatidylcholine Activates Adipocyte and Adipose Tissue Macrophage Nod-Like Receptor Protein 3 Inflammasomes Mediating Homocysteine-Induced Insulin Resistance

The adipose Nod-like receptor protein 3 (NLRP3) inflammasome senses danger-associated molecular patterns (DAMPs) and initiates insulin resistance, but the mechanisms of adipose inflammasome activation remains elusive. In this study, Homocysteine (Hcy) is revealed to be a DAMP that activates adipocyte NLRP3 inflammasomes, participating in insulin resistance. Hcy-induced activation of NLRP3 inflammasomes were observed in both adipocytes and adipose tissue macrophages (ATMs) and mediated insulin resistance. Lysophosphatidylcholine (lyso-PC) acted as a second signal activator, mediating Hcy-induced adipocyte NLRP3 inflammasome activation. Hcy elevated adipocyte lyso-PC generation in a hypoxia-inducible factor 1 (HIF1)-phospholipase A2 group 16 (PLA2G16) axis-dependent manner. Lyso-PC derived from the Hcy-induced adipocyte also activated ATM NLRP3 inflammasomes in a paracrine manner. This study demonstrated that Hcy activates adipose NLRP3 inflammasomes in an adipocyte lyso-PC-dependent manner and highlights the importance of the adipocyte NLRP3 inflammasome in insulin resistance.

Echinomycin inhibits adipogenesis in 3T3-L1 cells in a HIF-independent manner

Obesity is a risk factor for many diseases including diabetes, cancer, cardiovascular disease, and chronic kidney disease. Obesity is characterized by the expansion of white adipose tissue (WAT). Hypertrophy and hyperplasia of adipocytes cause tissue hypoxia followed by inflammation and fibrosis. Its trigger, preadipocyte differentiation into mature adipocytes, is finely regulated by transcription factors, signal molecules, and cofactors. We found that echinomycin, a potent HIF-1 inhibitor, completely inhibited adipogenesis in 3T3-L1 WAT preadipocytes by affecting the early phase of mitotic clonal expansion. The dose required to exert the effect was surprisingly low and the time was short. Interestingly, its inhibitory effect was independent of HIF-1 pathways. Time-course DNA microarray analysis of drug-treated and untreated preadipocytes extracted a major transcription factor, CCAAT/enhancer-protein β, as a key target of echinomycin. Echinomycin also inhibited adipogenesis and body weight gain in high fat diet mice. These findings highlight a novel role of echinomycin in suppressing adipocyte differentiation and offer a new therapeutic strategy against obesity and diabetes.

Regulation of glycolysis in brown adipocytes by HIF-1α

Brown adipose tissue takes up large amounts of glucose during cold exposure in mice and humans. Here we report an induction of glucose transporter 1 expression and increased expression of several glycolytic enzymes in brown adipose tissue from cold-exposed mice. Accordingly, these genes were also induced after β-adrenergic activation of cultured brown adipocytes, concomitant with accumulation of hypoxia inducible factor-1α (HIF-1α) protein levels. HIF-1α accumulation was dependent on uncoupling protein 1 and generation of mitochondrial reactive oxygen species. Expression of key glycolytic enzymes was reduced after knockdown of HIF-1α in mature brown adipocytes. Glucose consumption, lactate export and glycolytic capacity were reduced in brown adipocytes depleted of Hif-1α. Finally, we observed a decreased β-adrenergically induced oxygen consumption in Hif-1α knockdown adipocytes cultured in medium with glucose as the only exogenously added fuel. These data suggest that HIF-1α-dependent regulation of glycolysis is necessary for maximum glucose metabolism in brown adipocytes.

Adiponectin deficiency rescues high-fat diet-induced hepatic injury, apoptosis and autophagy loss despite persistent steatosis

Background &aims:Low levels of adiponectin (APN), an adipose-derived adipokine, are associated with obesity and non-alcoholic steatohepatitis although its role in high-fat diet-induced hepatic injury and steatosis remains unclear. Here we hypothesized that APN deficiency alters fat diet-induced hepatic function. To this end, we examined the effect of APN deficiency on high-fat diet-induced hepatic injury, apoptosis and steatosis.

METHODS

Adult wild type and APN knockout mice were fed a low- or high-fat diet for 20 weeks. Serum levels of liver enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), cholesterol, hepatic triglycerides, steatosis, pro-inflammatory cytokines, apoptosis and autophagy were examined.

RESULTS

High-fat feeding led to elevated body (48.2%) and liver weights (18.8%), increased levels of ALT (87.8%), serum cholesterol (104.4%), hepatic triglycerides (305.6%) and hepatic fat deposition as evidenced by Oil Red O staining, along with a reduced AST/ALT ratio and unchanged AST. Although APN knockout itself did not affect hepatic function and morphology, it reconciled fat diet-induced hepatic injury (P<0.05 vs WT-HF group) without reversing changes in body and liver weights, serum cholesterol and hepatic steatosis. In addition, fat diet intake promoted AMPK phosphorylation, p62 accumulation and apoptosis, including elevated Bax and cleaved Caspase-3 and downregulated Bcl-2, along with suppressed phosphorylation of Akt, STAT3 and JNK, and the autophagy makers Atg7, Beclin-1 and LC3B (P<0.05 vs WT-LF group) without affecting hepatic interlelukin-6 and tumor necrosis factor-α levels, the effects were reversed or significantly attenuated by APN knockout (P<0.05 vs WT-HF group). In vitro study using HepG2 cells revealed that STAT3 activation rescued palmitic acid-induced cell injury whereas STAT3 inhibition nullified APN knockdown-offered beneficial effects.

CONCLUSIONS

Our results revealed that high-fat diet intake promotes hepatic steatosis, apoptosis and interrupted autophagy. APN knockout elicits protective effect against hepatic injury possibly associated with autophagy regulation despite persistent hepatic steatosis.

Rb family proteins enforce the homeostasis of quiescent hematopoietic stem cells by repressing Socs3 expression

The mechanisms regulating the homeostasis of HSCs remain poorly understood. Here, Kim et al. identify the Rb/E2f module as a central molecular hub in the regulation of cell cycle and homeostasis in HSCs. This mechanism drives the enforced differentiation of proliferative HSCs to avoid their unnecessary accumulation.

Prolonged exit from quiescence by hematopoietic stem cells (HSCs) progressively impairs their homeostasis in the bone marrow through an unidentified mechanism. We show that Rb proteins, which are major enforcers of quiescence, maintain HSC homeostasis by positively regulating thrombopoietin (Tpo)-mediated Jak2 signaling. Rb family protein inactivation triggers the progressive E2f-mediated transactivation of Socs3, a potent inhibitor of Jak2 signaling, in cycling HSCs. Aberrant activation of Socs3 impairs Tpo signaling and leads to impaired HSC homeostasis. Therefore, Rb proteins act as a central hub of quiescence and homeostasis by coordinating the regulation of both cell cycle and Jak2 signaling in HSCs.

Metabolism-Centric Overview of the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a degenerative brain disease and the most common cause of dementia. AD is characterized by the extracellular amyloid beta (Aβ) plaques and intraneuronal deposits of neurofibrillary tangles (NFTs). Recently, as aging has become a familiar phenomenon around the world, patients with AD are increasing in number. Thus, many researchers are working toward finding effective therapeutics for AD focused on Aβ hypothesis, although there has been no success yet. In this review paper, we suggest that AD is a metabolic disease and that we should focus on metabolites that are affected by metabolic alterations to find effective therapeutics for AD. Aging is associated with not only AD but also obesity and type 2 diabetes (T2DM). AD, obesity, and T2DM share demographic profiles, risk factors, and clinical and biochemical features in common. Considering AD as a kind of metabolic disease, we suggest insulin, adiponectin, and antioxidants as mechanistic links among these diseases and targets for AD therapeutics. Patients with AD show reduced insulin signal transductions in the brain, and intranasal injection of insulin has been found to have an effect on AD treatment. In addition, adiponectin is decreased in the patients with obesity and T2DM. This reduction induces metabolic dysfunction both in the body and the brain, leading to AD pathogenesis. Oxidative stress is known to be induced by Aβ and NFTs, and we suggest that oxidative stress caused by metabolic alterations in the body induce brain metabolic alterations, resulting in AD.

Tumor-associated fibrosis as a regulator of tumor immunity and response to immunotherapy

Tumor-associated fibrosis is characterized by unchecked pro-fibrotic and pro-inflammatory signaling. The components of fibrosis including significant numbers of cancer-associated fibroblasts, dense collagen deposition, and extracellular matrix stiffness, are well appreciated regulators of tumor progression but may also be critical regulators of immune surveillance. While this suggests that the efficacy of immunotherapy may be limited in highly fibrotic cancers like pancreas, it also suggests a therapeutic opportunity to target fibrosis in these tumor types to reawaken anti-tumor immunity. This review discusses the mechanisms by which fibrosis might subvert tumor immunity and how to overcome these mechanisms.

SHP2, SOCS3 and PIAS3 Expression Patterns in Medulloblastomas: Relevance to STAT3 Activation and Resveratrol-Suppressed STAT3 Signaling

BACKGROUND

Activated STAT3 signaling is critical for human medulloblastoma cells. SHP2, SOCS3 and PIAS3 are known as the negative regulators of STAT3 signaling, while their relevance to frequent STAT3 activation in medulloblastomas remains unknown.

METHODS

Tissue microarrays were constructed with 17 tumor-surrounding noncancerous brain tissues and 61 cases of the classic medulloblastomas, 44 the large-cell medulloblastomas, and 15 nodular medulloblastomas, which were used for immunohistochemical profiling of STAT3, SHP2, SOCS3 and PIAS3 expression patterns and the frequencies of STAT3 nuclear translocation. Three human medulloblastoma cell lines (Daoy, UW228-2 and UW228-3) were cultured with and without 100 μM resveratrol supplementation. The influences of resveratrol in SHP2, SOCS3 and PIAS3 expression and SOCS3 knockdown in STAT3 activation were analyzed using multiple experimental approaches.

RESULTS

SHP2, SOCS3 and PIAS3 levels are reduced in medulloblastomas in vivo and in vitro, of which PIAS3 downregulation is more reversely correlated with STAT3 activation. In resveratrol-suppressed medulloblastoma cells with STAT3 downregulation and decreased incidence of STAT3 nuclear translocation, PIAS3 is upregulated, the SHP2 level remains unchanged and SOCS3 is downregulated. SOCS3 proteins are accumulated in the distal ends of axon-like processes of resveratrol-differentiated medulloblastoma cells. Knockdown of SOCS3 expression by siRNA neither influences cell proliferation nor STAT3 activation or resveratrol sensitivity but inhibits resveratrol-induced axon-like process formation.

CONCLUSION

Our results suggest that (1) the overall reduction of SHP2, SOCS3 and PIAS3 in medulloblastoma tissues and cell lines; (2) the more inverse relevance of PIAS3 expression with STAT3 activation; (3) the favorable prognostic values of PIAS3 for medulloblastomas and (4) the involvement of SOCS3 in resveratrol-promoted axon regeneration of medulloblastoma cells.

Selecting optimal combinations of transcription factors to promote axon regeneration: Why mechanisms matter

Recovery from injuries to the central nervous system, including spinal cord injury, is constrained in part by the intrinsically low ability of many CNS neurons to mount an effective regenerative growth response. To improve outcomes, it is essential to understand and ultimately reverse these neuron-intrinsic constraints. Genetic manipulation of key transcription factors (TFs), which act to orchestrate production of multiple regeneration-associated genes, has emerged as a promising strategy. It is likely that no single TF will be sufficient to fully restore neuron-intrinsic growth potential, and that multiple, functionally interacting factors will be needed. An extensive literature, mostly from non-neural cell types, has identified potential mechanisms by which TFs can functionally synergize. Here we examine four potential mechanisms of TF/TF interaction; physical interaction, transcriptional cross-regulation, signaling-based cross regulation, and co-occupancy of regulatory DNA. For each mechanism, we consider how existing knowledge can be used to guide the discovery and effective use of TF combinations in the context of regenerative neuroscience. This mechanistic insight into TF interactions is needed to accelerate the design of effective TF-based interventions to relieve neuron-intrinsic constraints to regeneration and to foster recovery from CNS injury.

Obesity and cancer: the role of adipose tissue and adipo-cytokines-induced chronic inflammation

Adipose tissue in addition to its ability to keep lipids is now recognized as a real organ with both metabolic and endocrine functions. Recent studies demonstrated that in obese animals is established a status of adipocyte hypoxia and in this hypoxic state interaction between adipocytes and stromal vascular cells contribute to tumor development and progression. In several tumors such as breast, colon, liver and prostate, obesity represents a poor predictor of clinical outcomes. Dysfunctional adipose tissue in obesity releases a disturbed profile of adipokines with elevated levels of pro-inflammatory factors and a consequent alteration of key signaling mediators which may be an active local player in establishing the peritumoral environment promoting tumor growth and progression. Therefore, adipose tissue hypoxia might contribute to cancer risk in the obese population. To date the precise mechanisms behind this obesity-cancer link is not yet fully understood. In the light of information provided in this review that aims to identify the key mechanisms underlying the link between obesity and cancer we support that inflammatory state specific of obesity may be important in obesity-cancer link.

Action of nicotinic acid on the reversion of hypoxic-inflammatory link on 3T3-L1 adipocytes

Background

Hypoxia resulting from adipocyte expansion is considered the basis of the inflammatory milieu observed in Metabolic Syndrome. Nicotinic acid can act on adipocytes interfering on the inflammatory response. In this study, we investigated the role of HIF-1 α (hypoxia-inducible factor -1 alpha) in the inflammatory process induced by hypoxia. The effect of nicotinic acid on the PPARs (peroxisome proliferator-activated receptors) expression during the inflammatory response was assessed over its action under HIF-1 α in 3T3-L1 adipocytes submitted to hypoxia.

Methods

3T3-L1 adipocytes were pre-treated with nicotinic acid and incubated under hypoxic conditions. The level of adipokines and HIF-1 α were quantified using immunoassays. Adipokine expression was measured using real-time PCR, whereas PPARs and HIF-1 α expression were analyzed by western blot. The statistical significance of the differences between variables studied was determined by analysis of variance (ANOVA) complemented by Bonferroni’s test.

Results

The results demonstrated an increase in leptin and PAI-1 (plasminogen activator inhibitor-1) expression, while adiponectin production decreased under hypoxia. In parallel, induction with hypoxia enhanced HIF-1 α expression, despite causing reduced expression of PPAR α and PPAR γ. However, nicotinic acid reversed adipokine modulation under hypoxic conditions, leading to decreased HIF-1 α expression and increased PPARs expression.

Conclusions

Our findings suggest that nicotinic acid blunt the inflammatory response resulting from hypoxia by the reduction of HIF-1 α expression and concomitant increase of PPARs α and γ expression in 3T3-L1 adipocytes.

Methylation and microRNA-mediated epigenetic regulation of SOCS3

Epigenetic gene silencing of several genes causes different pathological conditions in humans, and DNA methylation has been identified as one of the key mechanisms that underlie this evolutionarily conserved phenomenon associated with developmental and pathological gene regulation. Recent advances in the miRNA technology with high throughput analysis of gene regulation further increased our understanding on the role of miRNAs regulating multiple gene expression. There is increasing evidence supporting that the miRNAs not only regulate gene expression but they also are involved in the hypermethylation of promoter sequences, which cumulatively contributes to the epigenetic gene silencing. Here, we critically evaluated the recent progress on the transcriptional regulation of an important suppressor protein that inhibits cytokine-mediated signaling, SOCS3, whose expression is directly regulated both by promoter methylation and also by microRNAs, affecting its vital cell regulating functions. SOCS3 was identified as a potent inhibitor of Jak/Stat signaling pathway which is frequently upregulated in several pathologies, including cardiovascular disease, cancer, diabetes, viral infections, and the expression of SOCS3 was inhibited or greatly reduced due to hypermethylation of the CpG islands in its promoter region or suppression of its expression by different microRNAs. Additionally, we discuss key intracellular signaling pathways regulated by SOCS3 involving cellular events, including cell proliferation, cell growth, cell migration and apoptosis. Identification of the pathway intermediates as specific targets would not only aid in the development of novel therapeutic drugs, but, would also assist in developing new treatment strategies that could successfully be employed in combination therapy to target multiple signaling pathways.

Vascular reactivity and biomarkers of endothelial function in healthy subjects exposed to acute hypobaric hypoxia

AIMS

The aim of this study was to evaluate the effects of acute hypobaric hypoxia (HH) on vascular reactivity and biochemical markers associated with endothelial function (EF).

MAIN METHODS

Ten healthy subjects were exposed to a simulated altitude of 4,000 meters above sea level for 4 hours in a hypobaric chamber. Vascular reactivity was measured by the flow-mediated vasodilatation (FMVD) test. Endothelin-1, high sensitive-C reactive protein (hsCRP), vascular cell adhesion molecule 1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), paraoxonase and adiponectin levels, and FMVD were evaluated before and after the exposure.

KEY FINDINGS

Subjects were young (age: 32±6 years), lean [body mass index: 23.9±2.0kg/m(2), waist circumference: 77(IQR: 72-80) cm], and presented normal clinical and biochemical parameters. No significant changes were evidenced in FMVD in response to HH (pre: 0.45 (0.20-0.70) vs. during: 0.50 (0.20-1.22) mm; p=0.594). On the other hand, endothelin-1 (+54%, p<0.05), hsCRP (+37%, p<0.001), IL-6 (+75%, p<0.05), TNF-α (+75%, p<0.05), and adiponectin (-39%, p<0.01) levels were significantly altered post-HH. FMVD was increased in 7 subjects, and it was decreased in 3 individuals during HH exposure. Interestingly, when EF biomarkers were compared between these two subgroups of subjects, only post exposure-adiponectin levels were significantly different (49±5 vs. 38±6μg/ml, respectively, p<0.05).

SIGNIFICANCE

HH exposure had an effect on endothelin-1, adiponectin, hsCRP, IL-6, and TNF-α concentration. However, adiponectin was the only biomarker associated with an altered vascular reactivity.