Osteopontin expression in human and murine obesity: extensive local up-regulation in adipose tissue but minimal systemic alterations

Adipocyte-secreted PRELP promotes adipocyte differentiation and adipose tissue fibrosis by binding with p75NTR to activate FAK/MAPK signaling

Adipocyte-secreted factors intricately regulate adipose tissue function, and the underlying molecular mechanisms are only partially understood. However, the function of PRELP, which is a key component of the extracellular matrix (ECM) in adipocytes, remains largely unknown. In this study, we demonstrate that PRELP was upregulated in both obese humans and mice, which exhibited a positive correlation with metabolic disorders. PRELP knockout could resist HFD-induced obesity and inhibit adipocyte differentiation. PRELP knockout improved glucose tolerance, insulin sensitivity and alleviated adipose tissue fibrosis. Mechanistically, PRELP was secreted into the ECM and bound to the extracellular domain of its receptor p75NTR in adipocytes, which further activated the FAK/MAPK (JNK, p38 MAPK, ERK1/2) signaling pathway, promoting adipocyte differentiation and exacerbating adipocyte fibrosis. Adipocyte PRELP plays a pivotal role in regulating obesity and adipose tissue fibrosis through an autocrine manner, and PRELP may be a therapeutic target for obesity and its related metabolic disorders.

Endothelial metabolic control of insulin sensitivity through resident macrophages

Endothelial cells (ECs) not only form passive blood conduits but actively contribute to nutrient transport and organ homeostasis. The role of ECs in glucose homeostasis is, however, poorly understood. Here, we show that, in skeletal muscle, endothelial glucose transporter 1 (Glut1/Slc2a1) controls glucose uptake via vascular metabolic control of muscle-resident macrophages without affecting transendothelial glucose transport. Lowering endothelial Glut1 via genetic depletion (Glut1ΔEC) or upon a short-term high-fat diet increased angiocrine osteopontin (OPN/Spp1) secretion. This promoted resident muscle macrophage activation and proliferation, which impaired muscle insulin sensitivity. Consequently, co-deleting Spp1 from ECs prevented macrophage accumulation and improved insulin sensitivity in Glut1ΔEC mice. Mechanistically, Glut1-dependent endothelial glucose metabolic rewiring increased OPN in a serine metabolism-dependent fashion. Our data illustrate how the glycolytic endothelium creates a microenvironment that controls resident muscle macrophage phenotype and function and directly links resident muscle macrophages to the maintenance of muscle glucose homeostasis.

Osteokines in Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

To critically summarize evidence on the potential role of osteokines in the pathogenesis and progression of nonalcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

There are emerging data supporting that certain osteokines, which are specific bone-derived proteins, may beneficially or adversely affect hepatic metabolism, and their alterations in the setting of osteoporosis or other bone metabolic diseases may possibly contribute to the development and progression of NAFLD. There is evidence showing a potential bidirectional association between NAFLD and bone metabolism, which may imply the existence of a liver-bone axis. In this regard, osteocalcin, osteoprotegerin, bone morphogenic protein 4 (BMP4) and BMP6 appear to have a positive impact on the liver, thus possibly alleviating NAFLD, whereas osteopontin, receptor activator of nuclear factor kappa Β ligand (RANKL), sclerostin, periostin, BMP8B, and fibroblast growth factor 23 (FGF23) appear to have a negative impact on the liver, thus possibly exacerbating NAFLD. The potential implication of osteokines in NAFLD warrants further animal and clinical research in the field that may possibly result in novel therapeutic targets for NAFLD in the future.

Osteopontin: A Key Multifaceted Regulator in Tumor Progression and Immunomodulation

The tumor microenvironment (TME) is composed of various cellular components such as tumor cells, stromal cells including fibroblasts, adipocytes, mast cells, lymphatic vascular cells and infiltrating immune cells, macrophages, dendritic cells and lymphocytes. The intricate interplay between these cells influences tumor growth, metastasis and therapy failure. Significant advancements in breast cancer therapy have resulted in a substantial decrease in mortality. However, existing cancer treatments frequently result in toxicity and nonspecific side effects. Therefore, improving targeted drug delivery and increasing the efficacy of drugs is crucial for enhancing treatment outcome and reducing the burden of toxicity. In this review, we have provided an overview of how tumor and stroma-derived osteopontin (OPN) plays a key role in regulating the oncogenic potential of various cancers including breast. Next, we dissected the signaling network by which OPN regulates tumor progression through interaction with selective integrins and CD44 receptors. This review addresses the latest advancements in the roles of splice variants of OPN in cancer progression and OPN-mediated tumor-stromal interaction, EMT, CSC enhancement, immunomodulation, metastasis, chemoresistance and metabolic reprogramming, and further suggests that OPN might be a potential therapeutic target and prognostic biomarker for the evolving landscape of cancer management.

Targeting adipocyte ESRRA promotes osteogenesis and vascular formation in adipocyte-rich bone marrow

Excessive bone marrow adipocytes (BMAds) accumulation often occurs under diverse pathophysiological conditions associated with bone deterioration. Estrogen-related receptor α (ESRRA) is a key regulator responding to metabolic stress. Here, we show that adipocyte-specific ESRRA deficiency preserves osteogenesis and vascular formation in adipocyte-rich bone marrow upon estrogen deficiency or obesity. Mechanistically, adipocyte ESRRA interferes with E2/ESR1 signaling resulting in transcriptional repression of secreted phosphoprotein 1 (Spp1); yet positively modulates leptin expression by binding to its promoter. ESRRA abrogation results in enhanced SPP1 and decreased leptin secretion from both visceral adipocytes and BMAds, concertedly dictating bone marrow stromal stem cell fate commitment and restoring type H vessel formation, constituting a feed-forward loop for bone formation. Pharmacological inhibition of ESRRA protects obese mice against bone loss and high marrow adiposity. Thus, our findings highlight a therapeutic approach via targeting adipocyte ESRRA to preserve bone formation especially in detrimental adipocyte-rich bone milieu.

Osteopontin secreted from obese adipocytes enhances angiogenesis and promotes progression of pancreatic ductal adenocarcinoma in obesity

PURPOSE

Obesity is a risk factor and poor prognostic factor for pancreatic ductal adenocarcinoma (PDAC), but the underlying mechanisms remain unclear.

METHODS

PDAC cells and obese visceral adipocytes (O-Ad) derived from mice and humans were used to analyze interactions between the two cell types, and human microvascular endothelial cells were used for angiogenesis assay. A xenograft mouse model with subcutaneously injected PDAC cells was used for animal studies. The relationship between visceral fat and prognosis was analyzed using resected tissues from PDAC patients with and without obesity.

RESULTS

Conditioned media (CM) from O-Ad significantly increased PDAC cell growth and migration and angiogenic capacity in both human and mice cells, and blocking osteopontin (OPN) in O-Ad canceled O-Ad-induced effects in both mouse and human cells. In addition, O-Ad directly increased the migratory and tube-forming capacities of endothelial cells, while blocking OPN canceled these effects. O-Ad increased AKT phosphorylation and VEGFA expression in both PDAC and endothelial cells, and OPN inhibition in O-Ad canceled those O-Ad-induced effects. In the xenograft model, PDAC tumor volume was significantly increased in obese mice compared with lean mice, whereas blocking OPN significantly inhibited obesity-accelerated tumor growth. OPN expression in adipose tissues adjacent to human PDAC tumor was significantly higher in obese patients than in non-obese patients. In PDAC patients with obesity, high OPN expression in adipose tissues was significantly associated with poor prognosis.

CONCLUSION

Obese adipocytes trigger aggressive transformation in PDAC cells to induce PDAC progression and accelerate angiogenesis via OPN secretion.

Lipid Storage, Lipolysis, and Lipotoxicity in Obesity

The ratio of free fatty acid (FFA) turnover decreases significantly with the expansion of white adipose tissue. Adipose tissue and dietary saturated fatty acid levels significantly correlate with an increase in fat cell size and number. The G0/G1 switch gene 2 increases lipid content in adipocytes and promotes adipocyte hypertrophy through the restriction of triglyceride (triacylglycerol: TAG) turnover. Hypoxia in obese adipose tissue due to hypertrophic adipocytes results in excess deposition of extracellular matrix (ECM) components. Cluster of differentiation (CD) 44, as the main receptor of the extracellular matrix component regulates cell-cell and cell-matrix interactions including diet-induced insulin resistance. Excess TAGs, sterols, and sterol esters are surrounded by the phospholipid monolayer surface and form lipid droplets (LDs). Once LDs are formed, they grow up because of the excessive amount of intracellular FFA stored and reach a final size. The ratio of FFA turnover/lipolysis decreases significantly with increases in the degree of obesity. Dysfunctional adipose tissue is unable to expand further to store excess dietary lipids, increased fluxes of plasma FFAs lead to ectopic fatty acid deposition and lipotoxicity. Reduced neo-adipogenesis and dysfunctional lipid-overloaded adipocytes are hallmarks of hypertrophic obesity linked to insulin resistance. Obesity-associated adipocyte death exhibits feature of necrosis-like programmed cell death. Adipocyte death is a prerequisite for the transition from hypertrophic to hyperplastic obesity. Increased adipocyte number in obesity has life-long effects on white adipose tissue mass. The positive correlation between the adipose tissue volume and magnetic resonance imaging proton density fat fraction estimation is used for characterization of the obesity phenotype, as well as the risk stratification and selection of appropriate treatment strategies. In obese patients with type 2 diabetes, visceral adipocytes exposed to chronic/intermittent hyperglycemia develop a new microRNAs' (miRNAs') expression pattern. Visceral preadipocytes memorize the effect of hyperglycemia via changes in miRNAs' expression profile and contribute to the progression of diabetic phenotype. Nonsteroidal anti-inflammatory drugs, metformin, and statins can be beneficial in treating the local or systemic consequences of white adipose tissue inflammation. Rapamycin inhibits leptin-induced LD formation. Collectively, in this chapter, the concept of adipose tissue remodeling in response to adipocyte death or adipogenesis, and the complexity of LD interactions with the other cellular organelles are reviewed. Furthermore, clinical perspective of fat cell turnover in obesity is also debated.

Intermittent fasting favorably modulates adipokines and potentially attenuates atherosclerosis

Adipose tissue is now recognized as an endocrine organ that secretes bioactive molecules called adipokines. These biomolecules regulate key physiological functions, including insulin sensitivity, energy metabolism, appetite regulation, endothelial function and immunity. Dysregulated secretion of adipokines is intimately associated with obesity, and translates into increased risk of obesity-related cardiovasculo-metabolic diseases. In particular, emerging evidence suggests that adipokine imbalance contributes to the pathogenesis of atherosclerosis. One of the promising diet regimens that is beneficial in the fight against obesity and cardiometabolic disorders is intermittent fasting (IF). Indeed, IF robustly suppresses inflammation, meditates weight loss and mitigates many aspects of the cardiometabolic syndrome. In this paper, we review the main adipokines and their role in atherosclerosis, which remains a major contributor to cardiovascular-associated morbidity and mortality. We further discuss how IF can be employed as an effective management modality for obesity-associated atherosclerosis. By exploring a plethora of the beneficial effects of IF, particularly on inflammatory markers, we present IF as a possible intervention to help prevent atherosclerosis.

Macrophage-associated markers of metaflammation are linked to metabolic dysfunction in pediatric obesity

BACKGPOUND

Metabolically driven chronic low-grade adipose tissue inflammation, so-called metaflammation, is a central feature in obesity. This inflammatory tone is largely driven by adipose tissue macrophages (ATM), which express pro- and anti-inflammatory markers and cytokines such as, e.g., IL-1 receptor antagonist (IL-1RA), CD163 and osteopontin (OPN). Metaflammation ultimately leads to the development of cardiometabolic diseases. This study aimed to evaluate the association between selected adipose tissue macrophage-associated markers and metabolic comorbidities in pediatric obesity.

METHODS

From a pediatric cohort with obesity (n = 108), clinically thoroughly characterized including diverse routine blood parameters, oral glucose tolerance test and liver MRI, plasma IL-1RA, soluble (s)CD163 and OPN were measured by ELISA.

RESULTS

We observed significantly higher IL-1RA, sCD163, and OPN levels in the plasma of children with metabolic-dysfunction associated fatty liver disease (MAFLD) and metabolic syndrome. Moreover, IL-1RA and sCD163 correlated with hepatic disease and apoptosis markers alanine aminotransferase and CK-18. IL-1RA concentrations additionally correlated with insulin resistance, while children with disturbed glucose metabolism had significantly higher levels of sCD163.

CONCLUSION

MAFLD and other metabolic disorders in pediatric patients with obesity are associated with an elevation of adipose tissue macrophage-related inflammation markers.

Osteopontin-driven T-cell accumulation and function in adipose tissue and liver promoted insulin resistance and MAFLD

OBJECTIVE

This study investigated the contribution of osteopontin/secreted phosphoprotein 1 (SPP1) to T-cell regulation in initiation of obesity-driven adipose tissue (AT) inflammation and macrophage infiltration and the subsequent impact on insulin resistance (IR) and metabolic-associated fatty liver disease (MAFLD) development.

METHODS

SPP1 and T-cell marker expression was evaluated in AT and liver according to type 2 diabetes and MAFLD in human individuals with obesity. The role of SPP1 on T cells was evaluated in Spp1-knockout mice challenged with a high-fat diet.

RESULTS

In humans with obesity, elevated SPP1 expression in AT was parallel to T-cell marker expression (CD4, CD8A) and IR. Weight loss reversed AT inflammation with decreased SPP1 and CD8A expression. In liver, elevated SPP1 expression correlated with MAFLD severity and hepatic T-cell markers. In mice, although Spp1 deficiency did not impact obesity, it did improve AT IR associated with prevention of proinflammatory T-cell accumulation at the expense of regulatory T cells. Spp1 deficiency also decreased ex vivo helper T cell, subtype 1 (Th1) polarization of AT CD4+ and CD8+ T cells. In addition, Spp1 deficiency significantly reduced obesity-associated liver steatosis and inflammation.

CONCLUSIONS

Current findings highlight a critical role of SPP1 in the initiation of obesity-driven chronic inflammation by regulating accumulation and/or polarization of T cells. Early targeting of SPP1 could be beneficial for IR and MAFLD treatment.

Adipokines in obesity and metabolic-related-diseases

The discovery of leptin in the 1990s led to a reconsideration of adipose tissue (AT) as not only a fatty acid storage organ, but also a proper endocrine tissue. AT is indeed capable of secreting bioactive molecules called adipokines for white AT or batokines for brown/beige AT, which allow communication with numerous organs, especially brain, heart, liver, pancreas, and/or the vascular system. Adipokines exert pro or anti-inflammatory activities. An equilibrated balance between these two sets ensures homeostasis of numerous tissues and organs. During the development of obesity, AT remodelling leads to an alteration of its endocrine activity, with increased secretion of pro-inflammatory adipokines relative to the anti-inflammatory ones, as shown in the graphical abstract. Pro-inflammatory adipokines take part in the initiation of local and systemic inflammation during obesity and contribute to comorbidities associated to obesity, as detailed in the present review.

Obesity and Fibrosis: Setting the Stage for Breast Cancer

Obesity is a rising health concern and is linked to a worsened breast cancer prognosis. Tumor desmoplasia, which is characterized by elevated numbers of cancer-associated fibroblasts and the deposition of fibrillar collagens within the stroma, may contribute to the aggressive clinical behavior of breast cancer in obesity. A major component of the breast is adipose tissue, and fibrotic changes in adipose tissue due to obesity may contribute to breast cancer development and the biology of the resulting tumors. Adipose tissue fibrosis is a consequence of obesity that has multiple sources. Adipocytes and adipose-derived stromal cells secrete extracellular matrix composed of collagen family members and matricellular proteins that are altered by obesity. Adipose tissue also becomes a site of chronic, macrophage-driven inflammation. Macrophages exist as a diverse population within obese adipose tissue and mediate the development of fibrosis through the secretion of growth factors and matricellular proteins and interactions with other stromal cells. While weight loss is recommended to resolve obesity, the long-term effects of weight loss on adipose tissue fibrosis and inflammation within breast tissue are less clear. Increased fibrosis within breast tissue may increase the risk for tumor development as well as promote characteristics associated with tumor aggressiveness.

Twelve Weeks of High-Intensity Interval Training Alters Adipose Tissue Gene Expression but Not Oxylipin Levels in People with Non-Alcoholic Fatty Liver Disease

Lifestyle modifications, including increased physical activity and exercise, are recommended for non-alcoholic fatty liver disease (NAFLD). Inflamed adipose tissue (AT) contributes to the progression and development of NAFLD and oxylipins such as hydroxyeicosatetraenoic acids (HETE), hydroxydocosahexanenoic acids (HDHA), prostaglandins (PEG₂), and isoprostanoids (IsoP), which all may play a role in AT homeostasis and inflammation. To investigate the role of exercise without weight loss on AT and plasma oxylipin concentrations in NAFLD subjects, we conducted a 12-week randomized controlled exercise intervention. Plasma samples from 39 subjects and abdominal subcutaneous AT biopsy samples from 19 subjects were collected both at the beginning and the end of the exercise intervention. In the AT of women, a significant reduction of gene expression of hemoglobin subunits (HBB, HBA1, HBA2) was observed within the intervention group during the 12-week intervention. Their expression levels were negatively associated with VO₂max and maxW. In addition, pathways involved in adipocyte morphology alterations significantly increased, whereas pathways in fat metabolism, branched-chain amino acids degradation, and oxidative phosphorylation were suppressed in the intervention group (p < 0.05). Compared to the control group, in the intervention group, the ribosome pathway was activated, but lysosome, oxidative phosphorylation, and pathways of AT modification were suppressed (p < 0.05). Most of the oxylipins (HETE, HDHA, PEG₂, and IsoP) in plasma did not change during the intervention compared to the control group. 15-F_2t-IsoP significantly increased in the intervention group compared to the control group (p = 0.014). However, this oxylipin could not be detected in all samples. Exercise intervention without weight loss may influence the AT morphology and fat metabolism at the gene expression level in female NAFLD subjects.

Kidney stone matrix proteins: Role in stone formation

Stone formation is induced by an increased level of urine crystallization promoters and reduced levels of its inhibitors. Crystallization inhibitors include citrate, magnesium, zinc, and organic compounds such as glycosaminoglycans. In the urine, there are various proteins, such as uromodulin (Tamm-Horsfall protein), calgranulin, osteopontin, bikunin, and nephrocalcin, that are present in the stone matrix. The presence of several carboxyl groups in these macromolecules reduces calcium oxalate monohydrate crystal adhesion to the urinary epithelium and could potentially protect against lithiasis. Proteins are the most abundant component of kidney stone matrix, and their presence may reflect the process of stone formation. Many recent studies have explored the proteomics of urinary stones. Among the stone matrix proteins, the most frequently identified were uromodulin, S100 proteins (calgranulins A and B), osteopontin, and several other proteins typically engaged in inflammation and immune response. The normal level and structure of these macromolecules may constitute protection against calcium salt formation. Paradoxically, most of them may act as both promoters and inhibitors depending on circumstances. Many of these proteins have other functions in modulating oxidative stress, immune function, and inflammation that could also influence stone formation. Yet, the role of these kidney stone matrix proteins needs to be established through more studies comparing urinary stone proteomics between stone formers and non-stone formers.

Lactoferrin, Osteopontin and Lactoferrin–Osteopontin Complex: A Critical Look on Their Role in Perinatal Period and Cardiometabolic Disorders

Milk-derived bioactive proteins have increasingly gained attention and consideration throughout the world due to their high-quality amino acids and multiple health-promoting attributes. Apparently, being at the forefront of functional foods, these bioactive proteins are also suggested as potential alternatives for the management of various complex diseases. In this review, we will focus on lactoferrin (LF) and osteopontin (OPN), two multifunctional dairy proteins, as well as to their naturally occurring bioactive LF–OPN complex. While describing their wide variety of physiological, biochemical, and nutritional functionalities, we will emphasize their specific roles in the perinatal period. Afterwards, we will evaluate their ability to control oxidative stress, inflammation, gut mucosal barrier, and intestinal microbiota in link with cardiometabolic disorders (CMD) (obesity, insulin resistance, dyslipidemia, and hypertension) and associated complications (diabetes and atherosclerosis). This review will not only attempt to highlight the mechanisms of action, but it will critically discuss the potential therapeutic applications of the underlined bioactive proteins in CMD.

VEGF promotes tendon regeneration of aged rats by inhibiting adipogenic differentiation of tendon stem/progenitor cells and promoting vascularization

Studies have shown that the stem cell microenvironment is a key factor for stem cell maintenance or differentiation. In this study, we compared the expression of 23 cytokines such as IL-6, IL-10, and TNFα between young and aged rats during patellar tendon repair by cytokine microarray, and found that significant difference between IL-10, G-CSF, and VEGF at 3, 7, or 14 days post-operatively. The effects of these factors on adipogenic differentiation of TPSCs were examined through western blot and oil red O experiments. It was shown that VEGF had an inhibitive effect on the adipogenic differentiation of TPSCs. SPP-1 was figured out as our target by RNA sequencing and confirmed by western blot in vitro. Further in vivo studies showed that adipocyte accumulation was also decreased in the tendons of aged rats after injection of VEGF and the histological score and biomechanical property were also improved via targeting SPP-1. Furthermore, histochemical results showed that vascularization of the injury sites was significantly elevated. In conclusion, VEGF not only plays an important role in decreasing adipocyte accumulation but also improves vascularization of the tendon during aged tendon healing. We believe active regulation of VEGF may improve the treatment of age-related tendon diseases and tendon injuries.

The Novel-miR-659/SPP1 Interaction Regulates Fat Deposition in Castrated Male Pigs

Simple Summary

Castration is a standard method for eliminating boar taint in industrial hog production, but it also causes enormous fat accumulation in the carcass. Secreted phosphoprotein 1 (SPP1) was selected to investigate its functions on the regulation of adipose deposition based on our previous data. In the present study, SPP1 overexpression and interference bidirectionally verified that SPP1 inhibited adipogenic differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Testosterone-treated cell models were used to simulate the androgen status of intact pigs, and testosterone addition influenced SPP1 mRNA levels during the differentiation of pBMSCs. Moreover, we identified novel-miR-659 and targeted the 3′ untranslated region of SPP1 based on bioinformatics analysis and dual-luciferase assays, and found that the novel-miR-659 upregulation promoted adipogenesis while novel-miR-659 downregulation suppressed adipogenesis in pBMSCs detected by Oil Red O staining and adipogenic markers. Collectively, the interaction between novel-miR-659 and SPP1 can regulate adipose accumulation in castrated male pigs. Our data provide a theoretical basis for further study on the fat deposition mechanism caused by castration.

Abstract

Castration is usually used to remove boar taint in commercial pork production, but the adipose accumulation was increased excessively, which affected the meat quality of pigs. Based on our previous study, secreted phosphoprotein 1 (SPP1) was significantly differentially expressed between castrated and intact male pigs. However, the role of SPP1 in regulating adipose growth and fat storage caused by castration is unknown. In this study, SPP1 was identified to inhibit adipogenesis by the expression of adipogenic markers PPARγ and FABP4 as well as Oil red staining assay during differentiation of porcine bone marrow mesenchymal stem cells (pBMSCs). Subsequently, testosterone was used to treat pBMSCs to simulate the androgen status of intact pigs. Compared with the control groups without testosterone, the SPP1 expression in the testosterone group was markedly increased in the late stage of pBMSCs differentiation. Furthermore, novel-miR-659 was predicted by TargetScan and miRDB to target SPP1 and verified through a dual-luciferase reporter assay. Oil Red O staining assay indicated that novel-miR-659 overexpression significantly promoted adipogenesis, whereas novel-miR-659 inhibition suppressed adipogenesis. The expressions of adipogenic markers PPARγ and FABP4 showed the same tendency. Taken together, our study found that the targeted interaction between novel-miR-659 and SPP1 is involved in regulation of fat deposition in castrated male pigs.

Thromboinflammatory Processes at the Nexus of Metabolic Dysfunction and Prostate Cancer: The Emerging Role of Periprostatic Adipose Tissue

Simple Summary

As overweight and obesity increase among the population worldwide, a parallel increase in the number of individuals diagnosed with prostate cancer was observed. There appears to be a relationship between both diseases where the increase in the mass of fat tissue can lead to inflammation. Such a state of inflammation could produce many factors that increase the aggressiveness of prostate cancer, especially if this inflammation occurred in the fat stores adjacent to the prostate. Another important observation that links obesity, fat tissue inflammation, and prostate cancer is the increased production of blood clotting factors. In this article, we attempt to explain the role of these latter factors in the effect of increased body weight on the progression of prostate cancer and propose new ways of treatment that act by affecting how these clotting factors work.

Abstract

The increased global prevalence of metabolic disorders including obesity, insulin resistance, metabolic syndrome and diabetes is mirrored by an increased incidence of prostate cancer (PCa). Ample evidence suggests that these metabolic disorders, being characterized by adipose tissue (AT) expansion and inflammation, not only present as risk factors for the development of PCa, but also drive its increased aggressiveness, enhanced progression, and metastasis. Despite the emerging molecular mechanisms linking AT dysfunction to the various hallmarks of PCa, thromboinflammatory processes implicated in the crosstalk between these diseases have not been thoroughly investigated. This is of particular importance as both diseases present states of hypercoagulability. Accumulating evidence implicates tissue factor, thrombin, and active factor X as well as other players of the coagulation cascade in the pathophysiological processes driving cancer development and progression. In this regard, it becomes pivotal to elucidate the thromboinflammatory processes occurring in the periprostatic adipose tissue (PPAT), a fundamental microenvironmental niche of the prostate. Here, we highlight key findings linking thromboinflammation and the pleiotropic effects of coagulation factors and their inhibitors in metabolic diseases, PCa, and their crosstalk. We also propose several novel therapeutic targets and therapeutic interventions possibly modulating the interaction between these pathological states.

Network Analyses Reveal Negative Link Between Changes in Adipose Tissue GDF15 and BMI During Dietary-induced Weight Loss

CONTEXT

Adipose tissue (AT) transcriptome studies provide holistic pictures of adaptation to weight and related bioclinical settings changes.

OBJECTIVE

To implement AT gene expression profiling and investigate the link between changes in bioclinical parameters and AT gene expression during 3 steps of a 2-phase dietary intervention (DI).

METHODS

AT transcriptome profiling was obtained from sequencing 1051 samples, corresponding to 556 distinct individuals enrolled in a weight loss intervention (8-week low-calorie diet (LCD) at 800 kcal/day) followed with a 6-month ad libitum randomized DI. Transcriptome profiles obtained with QuantSeq sequencing were benchmarked against Illumina RNAseq. Reverse transcription quantitative polymerase chain reaction was used to further confirm associations. Cell specificity was assessed using freshly isolated cells and THP-1 cell line.

RESULTS

During LCD, 5 modules were found, of which 3 included at least 1 bioclinical variable. Change in body mass index (BMI) connected with changes in mRNA level of genes with inflammatory response signature. In this module, change in BMI was negatively associated with changes in expression of genes encoding secreted protein (GDF15, CCL3, and SPP1). Through all phases of the DI, change in GDF15 was connected to changes in SPP1, CCL3, LIPA and CD68. Further characterization showed that these genes were specific to macrophages (with LIPA, CD68 and GDF15 expressed in anti-inflammatory macrophages) and GDF15 also expressed in preadipocytes.

CONCLUSION

Network analyses identified a novel AT feature with GDF15 upregulated with calorie restriction induced weight loss, concomitantly to macrophage markers. In AT, GDF15 was expressed in preadipocytes and macrophages where it was a hallmark of anti-inflammatory cells.

Osteopontin, a bridge links osteoarthritis and osteoporosis

Osteoarthritis (OA) is the most prevalent joint disease characterized by degradation of articular cartilage, inflammation, and changes in periarticular and subchondral bone of joints. Osteoporosis (OP) is another systemic skeletal disease characterized by low bone mass and bone mineral density (BMD) accompanied by microarchitectural deterioration in bone tissue and increased bone fragility and fracture risk. Both OA and OP are mainly affected on the elderly people. Recent studies have shown that osteopontin (OPN) plays a vital role in bone metabolism and homeostasis. OPN involves these biological activities through participating in the proliferation, migration, differentiation, and adhesion of several bone-related cells, including chondrocytes, synoviocytes, osteoclasts, osteoblasts, and marrow mesenchymal stem cells (MSCs). OPN has been demonstrated to be closely related to the occurrence and development of many bone-related diseases, such as OA and OP. This review summarizes the role of OPN in regulating inflammation activity and bone metabolism in OA and OP. Furthermore, some drugs that targeted OPN to treat OA and OP are also summarized in the review. However, the complex mechanism of OPN in regulating OA and OP is not fully elucidated, which drives us to explore the depth effect of OPN on these two bone diseases.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

The multifaceted progenitor fates in healthy or unhealthy adipose tissue during obesity

While obesity is defined as an excessive fat accumulation conferring a risk to metabolic health, increased adipose mass by itself does not fully explain obesity's propensity to promote metabolic alterations. Adipose tissue regulates multiple processes critical for energy homeostasis and its dysfunction favors the development and perpetuation of metabolic diseases. Obesity drives inflammatory leucocyte infiltration in adipose tissue and fibrotic transformation of the fat depots. Both features associate with metabolic alterations such as impaired glucose control and resistance to fat mass loss. In this context, adipose progenitors, an heterogenous resident population of mesenchymal stromal cells, display functions important to shape healthy or unhealthy adipose tissue expansion. We, here, outline the current understanding of adipose progenitor biology in the context of obesity-induced adipose tissue remodeling.

Plasmatic osteopontin and vascular access dysfunction in hemodialysis patients: a cross-sectional, case-control study (The OSMOSIS Study)

BACKGROUND AND AIMS

Despite close follow-up of patients with native arteriovenous fistulas (AVFs), up to 10% experience thrombosis each year. The OSMOSIS Study (Osteopontin as a Marker of Stenosis) tested the hypothesis that the systemic osteopontin level, a pro-inflammatory mediator related to vascular remodelling and intimal hyperplasia, increases in AVF stenosis, and may be used in clinical surveillance.

METHODS

Our cross-sectional study compared the level of plasmatic osteopontin (pOPN) between patients with a well-functioning AVF (control group) and patients who required revision of their AVF due to stenosis (stenosis group). Blood samples were collected before dialysis (control group) or before intervention (stenosis group) from the AVF arm, and from the opposite arm as a within-subject control. pOPN level was measured by enzyme-linked immunosorbent assay.

RESULTS

A total of 76 patients were included in the study. Baseline characteristics were similar between the groups (mean age, 70 years; men, 63%; AVF duration, 39 months), apart from prevalence of type 2 diabetes (T2D) (control group, 33%; stenosis group, 57%; p = 0.04). pOPN levels were similar between the AVF arm and the contralateral arm (551 ± 42 ng/mL vs. 521 ± 41 ng/mL, respectively, p = 0.11, paired t-test). Patients in the stenosis group displayed a higher pOPN level than patients in the control group (650.2 ± 59.8 ng/mL vs. 460.5 ± 61.2, respectively, p = 0.03; two-way ANOVA). T2D was not identified as an associated factor in a multivariate analysis (p = 0.50).

CONCLUSIONS

The level of pOPN in hemodialysis patients was associated with the presence of AVF stenosis requiring intervention. Thus, its potential as a diagnostic biomarker should be assessed in a vascular access surveillance program.

New Angiogenic Regulators Produced by TAMs: Perspective for Targeting Tumor Angiogenesis

Simple Summary

Since the targeting of a single pro-angiogenic factor fails to improve oncological disease outcome, significant efforts have been made to identify new pro-angiogenic factors that could compensate for the deficiency of current therapy or act independently as single drugs. Our review aims to present the state-of-the art for well-known and recently described factors produced by macrophages that induce and regulate angiogenesis. A number of positive and negative regulators of angiogenesis in the tumor microenvironment are produced by tumor-associated macrophages (TAMs). Accumulating evidence has indicated that, apart from the well-known angiogenic factors, there are plenty of novel angiogenesis-regulating proteins that belong to different classes. We summarize the data regarding the direct or indirect mechanisms of the interaction of these factors with endothelial cells during angiogenesis. We highlight the recent findings that explain the limitations in the efficiency of current anti-angiogenic therapy approaches.

Abstract

Angiogenesis is crucial to the supply of a growing tumor with nutrition and oxygen. Inhibition of angiogenesis is one of the main treatment strategies for colorectal, lung, breast, renal, and other solid cancers. However, currently applied drugs that target VEGF or receptor tyrosine kinases have limited efficiency, which raises a question concerning the mechanism of patient resistance to the already developed drugs. Tumor-associated macrophages (TAMs) were identified in the animal tumor models as a key inducer of the angiogenic switch. TAMs represent a potent source not only for VEGF, but also for a number of other pro-angiogenic factors. Our review provides information about the activity of secreted regulators of angiogenesis produced by TAMs. They include members of SEMA and S100A families, chitinase-like proteins, osteopontin, and SPARC. The COX-2, Tie2, and other factors that control the pro-angiogenic activity of TAMs are also discussed. We highlight how these recent findings explain the limitations in the efficiency of current anti-angiogenic therapy. Additionally, we describe genetic and posttranscriptional mechanisms that control the expression of factors regulating angiogenesis. Finally, we present prospects for the complex targeting of the pro-angiogenic activity of TAMs.

Endocrine role of bone in the regulation of energy metabolism

Bone mainly functions as a supportive framework for the whole body and is the major regulator of calcium homeostasis and hematopoietic function. Recently, an increasing number of studies have characterized the significance of bone as an endocrine organ, suggesting that bone-derived factors regulate local bone metabolism and metabolic functions. In addition, these factors can regulate global energy homeostasis by altering insulin sensitivity, feeding behavior, and adipocyte commitment. These findings may provide a new pathological mechanism for related metabolic diseases or be used in the diagnosis, treatment, and prevention of metabolic diseases such as osteoporosis, obesity, and diabetes mellitus. In this review, we summarize the regulatory effect of bone and bone-derived factors on energy metabolism and discuss directions for future research.

Plasticity of Epididymal Adipose Tissue in Response to Diet-Induced Obesity at Single-Nucleus Resolution

Adipose tissues display a remarkable ability to adapt to the dietary status. Here, we have applied single-nucleus RNA-seq to map the plasticity of mouse epididymal white adipose tissue at single-nucleus resolution in response to high-fat-diet-induced obesity. The single-nucleus approach allowed us to recover all major cell types and to reveal distinct transcriptional stages along the entire adipogenic trajectory from preadipocyte commitment to mature adipocytes. We demonstrate the existence of different adipocyte subpopulations and show that obesity leads to disappearance of the lipogenic subpopulation and increased abundance of the stressed lipid-scavenging subpopulation. Moreover, obesity is associated with major changes in the abundance and gene expression of other cell populations, including a dramatic increase in lipid-handling genes in macrophages at the expense of macrophage-specific genes. The data provide a powerful resource for future hypothesis-driven investigations of the mechanisms of adipocyte differentiation and adipose tissue plasticity.

Divergent genes in gerbils: prevalence, relation to GC-biased substitution, and phenotypic relevance

Background

Two gerbil species, sand rat (Psammomys obesus) and Mongolian jird (Meriones unguiculatus), can become obese and show signs of metabolic dysregulation when maintained on standard laboratory diets. The genetic basis of this phenotype is unknown. Recently, genome sequencing has uncovered very unusual regions of high guanine and cytosine (GC) content scattered across the sand rat genome, most likely generated by extreme and localized biased gene conversion. A key pancreatic transcription factor PDX1 is encoded by a gene in the most extreme GC-rich region, is remarkably divergent and exhibits altered biochemical properties. Here, we ask if gerbils have proteins in addition to PDX1 that are aberrantly divergent in amino acid sequence, whether they have also become divergent due to GC-biased nucleotide changes, and whether these proteins could plausibly be connected to metabolic dysfunction exhibited by gerbils.

Results

We analyzed ~ 10,000 proteins with 1-to-1 orthologues in human and rodents and identified 50 proteins that accumulated unusually high levels of amino acid change in the sand rat and 41 in Mongolian jird. We show that more than half of the aberrantly divergent proteins are associated with GC biased nucleotide change and many are in previously defined high GC regions. We highlight four aberrantly divergent gerbil proteins, PDX1, INSR, MEDAG and SPP1, that may plausibly be associated with dietary metabolism.

Conclusions

We show that through the course of gerbil evolution, many aberrantly divergent proteins have accumulated in the gerbil lineage, and GC-biased nucleotide substitution rather than positive selection is the likely cause of extreme divergence in more than half of these. Some proteins carry putatively deleterious changes that could be associated with metabolic and physiological phenotypes observed in some gerbil species. We propose that these animals provide a useful model to study the ‘tug-of-war’ between natural selection and the excessive accumulation of deleterious substitutions mutations through biased gene conversion.

Osteopontin: The Molecular Bridge between Fat and Cardiac-Renal Disorders

Osteopontin (OPN) is a multifaceted matricellular protein, with well-recognized roles in both the physiological and pathological processes in the body. OPN is expressed in the main organs and cell types, in which it induces different biological actions. During physiological conditioning, OPN acts as both an intracellular protein and soluble excreted cytokine, regulating tissue remodeling and immune-infiltrate in adipose tissue the heart and the kidney. In contrast, the increased expression of OPN has been correlated with the severity of the cardiovascular and renal outcomes associated with obesity. Indeed, OPN expression is at the “cross roads” of visceral fat extension, cardiovascular diseases (CVDs) and renal disorders, in which OPN orchestrates the molecular interactions, leading to chronic low-grade inflammation. The common factor associated with OPN overexpression in adipose, cardiac and renal tissues seems attributable to the concomitant increase in visceral fat size and the increase in infiltrated OPN⁺ macrophages. This review underlines the current knowledge on the molecular interactions between obesity and the cardiac–renal disorders ruled by OPN.

The up-regulation of markers of adipose tissue fibrosis by visfatin in pre-adipocytes as well as obese children and adolescents

Adipocytes are surrounded by a three-dimensional network of extracellular matrix (ECM) proteins. Aberrant ECM accumulation and remodeling leads to adipose tissue fibrosis. Visfatin is one of the adipocytokines that is increased in obesity and is implicated in insulin resistance. The objective of this study was to investigate the effect of visfatin on major components of ECM remodeling. In this study, plasma levels of both endotrophin and visfatin in obese children and adolescents were significantly higher than those in control subjects and they showed a positive correlation with each other. Treatment of 3T3-L1 pre-adipocytes with visfatin caused significant up-regulation of Osteopontin (Opn), Collagen type VI (Col6), matrix metalloproteinases MMP-2 and MMP-9. By using inhibitors of major signaling pathways it was shown that visfatin exerted its effect on Col6a3 gene expression through PI3K, JNK, and NF-кB pathways, while induced Opn gene expression via PI3K, JNK, MAPK/ERK, and NOTCH1. Our conclusion is that, the relationship between visfatin, endotrophin and insulin resistance parameters in obesity as well as increased expression of ECM proteins by visfatin suggests adipose tissue fibrosis as a mechanism for devastating effects of visfatin in obesity.

Identification and characterization of adipose surface epitopes

Adipose tissue is a central regulator of metabolism and an important pharmacological target to treat the metabolic consequences of obesity, such as insulin resistance and dyslipidemia. Among the various cellular compartments, the adipocyte cell surface is especially appealing as a drug target as it contains various proteins that when activated or inhibited promote adipocyte health, change its endocrine function and eventually maintain or restore whole-body insulin sensitivity. In addition, cell surface proteins are readily accessible by various drug classes. However, targeting individual cell surface proteins in adipocytes has been difficult due to important functions of these proteins outside adipose tissue, raising various safety concerns. Thus, one of the biggest challenges is the lack of adipose selective surface proteins and/or targeting reagents. Here, we discuss several receptor families with an important function in adipogenesis and mature adipocytes to highlight the complexity at the cell surface and illustrate the problems with identifying adipose selective proteins. We then discuss that, while no unique adipocyte surface protein might exist, how splicing, posttranslational modifications as well as protein/protein interactions can create enormous diversity at the cell surface that vastly expands the space of potentially unique epitopes and how these selective epitopes can be identified and targeted.

Transcriptome analysis of the adipose tissue in a mouse model of metabolic syndrome identifies gene signatures related to disease pathogenesis

The white adipose tissue (WAT) contributes to the metabolic imbalance observed in obesity and the metabolic syndrome (MetS) by mechanisms that are poorly understood. The aim of this study was to monitor changes in the transcriptome of epididymal WAT during the development of MetS. ApoE3L.CETP mice were fed a high fat (HFD) or a low-fat (LFD) diet for different time periods. Adipose RNA was analyzed by microarrays. We found an increasing number of differentially expressed transcripts during MetS development. In mice with MetS, 1396 transcripts were differentially expressed including transcripts related to immune/inflammatory responses and extracellular matrix enzymes, suggesting significant inflammation and tissue remodeling. The top list of pathways included focal adhesion, chemokine, B and T cell receptor and MAPK signaling. The data identify for the first time adipose gene signatures in apoE3L.CETP mice with diet-induced MetS and might open new avenues for investigation of potential biomarkers or therapeutic targets.

Impact of osteopontin on the development of non-alcoholic liver disease and related hepatocellular carcinoma

BACKGROUND & AIMS

Osteopontin, a multifunctional protein and inflammatory cytokine, is overexpressed in adipose tissue and liver in obesity and contributes to the induction of adipose tissue inflammation and non-alcoholic fatty liver (NAFL). Studies performed in both mice and humans also point to a potential role for OPN in malignant transformation and tumour growth. To fully understand the role of OPN on the development of NAFL-derived hepatocellular carcinoma (HCC), we applied a non-alcoholic steatohepatitis (NASH)-HCC mouse model on osteopontin-deficient (Spp1^-/- ) mice analysing time points of NASH, fibrosis and HCC compared to wild-type mice.

METHODS

Two-day-old wild-type and Spp1^-/- mice received a low-dose streptozotocin injection in order to induce diabetes, and were fed a high-fat diet starting from week 4. Different cohorts of mice of both genotypes were sacrificed at 8, 12 and 19 weeks of age to evaluate the NASH, fibrosis and HCC phenotypes respectively.

RESULTS

Spp1^-/- animals showed enhanced hepatic lipid accumulation and aggravated NASH, as also increased hepatocellular apoptosis and accelerated fibrosis. The worse steatotic and fibrotic phenotypes observed in Spp1^-/- mice might be driven by enhanced hepatic fatty acid influx through CD36 overexpression and by a pathological accumulation of specific diacylglycerol species during NAFL. Lack of osteopontin lowered systemic inflammation, prevented HCC progression to less differentiated tumours and improved overall survival.

CONCLUSIONS

Lack of osteopontin dissociates NASH-fibrosis severity from overall survival and HCC malignant transformation in NAFLD, and is therefore a putative therapeutic target only for advanced chronic liver disease.

A high-fat diet rich in corn oil exaggerates the infarct size and memory impairment in rats with cerebral ischemia and is associated with suppressing osteopontin and Akt, and activating GS3Kβ, iNOS, and NF-κB

The increase in osteopontin (OPN) levels after stroke induces neural protection by activating Akt signaling and inhibiting GS3Kβ, iNOS, and NF-κB. This study investigated the effect of a high-fat diet rich in corn oil (CO-HFD) on infarct size and memory function in rats after induction of cerebral ischemia in rats and investigated its effect on the expression of OPN/Akt/iNOS/NF-κB signaling pathways. Rats were initially fed a standard diet (STD, 3.82 kcal/g; 9.4%, from fat) or a CO-HFD (5.4 kcal/g, 40% from fat) for 12 weeks. Then, both groups were further subdivided into either sham group or group exposed to cerebral ischemia by the middle cerebral artery occlusion (MCAO) protocol. Compared with sham-operated rats fed STD diet, neurological scores and both short- and long-term memory functions were significantly impaired in sham-operated CO-HFD-fed rats. In addition, brains collected from CO-HFD-fed rats showed lower protein levels of OPN, p-Akt (Thr³⁰⁸), p-GS3Kβ (Ser⁹), and Bcl-2 and had higher protein levels of iNOS, cleaved caspase-3, nuclear NF-κB p65, and cytoplasmic cytochrome C. However, once exposed to MCAO surgery, similar but more profound alterations of all these biochemical parameters with more severe impairment in short- and long-term memory functions and larger infarct size were noticed in the brains of CO-HFD-fed rats as compared with STD-fed rats exposed to MCAO. In conclusion, chronic consumption of CO-HFD induces memory impairments and worsens memory function recovery and infarct size after cerebral ischemia in rats by reducing levels of OPN, inhibiting the activation of Akt and activating iNOS and NF-κB.

The CD153 vaccine is a senotherapeutic option for preventing the accumulation of senescent T cells in mice

Senotherapy targeting for senescent cells is designed to attenuate age-related dysfunction. Senescent T cells, defined as CD4⁺ CD44^high CD62L^low PD-1⁺ CD153⁺ cells, accumulate in visceral adipose tissues (VAT) in obese individuals. Here, we show the long-lasting effect of using CD153 vaccination to remove senescent T cells from high-fat diet (HFD)-induced obese C57BL/6J mice. We administered a CD153 peptide-KLH (keyhole limpet hemocyanin) conjugate vaccine with Alhydrogel (CD153-Alum) or CpG oligodeoxynucleotide (ODN) 1585 (CD153-CpG) and confirmed an increase in anti-CD153 antibody levels that was sustained for several months. After being fed a HFD for 10–11 weeks, adipose senescent T cell accumulation was significantly reduced in the VAT of CD153-CpG-vaccinated mice, accompanied by glucose tolerance and insulin resistance. A complement-dependent cytotoxicity (CDC) assay indicated that the mouse IgG2 antibody produced in the CD153-CpG-vaccinated mice successfully reduced the number of senescent T cells. The CD153-CpG vaccine is an optional tool for senolytic therapy.

Senotherapy, the removal of aged T cells, is an effective approach to attenuate age-related diseases. Here the authors report a CD153 targeting vaccine that prevents the accumulation of senescent adipose tissue T cells in mice on high-fat diet, which is associated with improved glucose tolerance.

Downregulation of osteopontin inhibits browning of white adipose tissues through PI3K-AKT pathway in C57BL / 6 mice

Brown adipose tissue (BAT) plays important roles in regulating energy homeostasis and combating obesity. Accordingly, increasing the abundance and/or activating BAT would be effective and promising approaches to combat obesity and obesity-relative diseases. Our previous data in vitro have shown that osteopontin (OPN) induces the brown adipogenesis in 3T3-L1 cells via a phosphatidylinositol 3 kinase (PI3K)-AKT pathway. However, it is currently unknown whether OPN exerts such an effect on animals in vivo. Therefore, in the study we sought to investigate the pro-browning effects of OPN and to explore its underlying mechanisms by transfecting with Ad-GFP-aP2-OPN-shRNA to specifically down-regulate the OPN of white adipose tissue (WAT) in mice. Our present results show that downregulation of OPN in WAT exacerbates obesity and inhibits WAT-browning. Moreover, immunohistochemical results also exhibit that the downregulation of OPN significantly diminishes the expression and sub-cellular localization of UCP-1, PRDM16 and PGC-1α. Besides, the western blotting results reveal that the expression levels of PI3K, AKT-pS473 and PPARγ markedly reduce. Consequently, we conclude that the downregulation of OPN inhibits the browning of WAT through inhibiting the expression of PPARγ mediated by the PI3K-AKT pathway. The findings suggest that OPN is involved in regulation of WAT-browning and regulating its expression would become a potential strategy to combat obesity and obesity-relative metabolic diseases.

NK cells induce hepatic ER stress to promote insulin resistance in obesity through osteopontin production

High-fat diet (HFD) induced hepatic endoplasmic reticulum (ER) stress drives insulin resistance (IR) and steatosis. NK cells in adipose tissue play an important role in the pathogenesis of IR in obesity. Whether NK cells in the liver can induce hepatic ER stress and thus promote IR in obesity is still unknown. We demonstrate that HFD-fed mice display elevated production of proinflammatory cytokine osteopontin (OPN) in hepatic NK cells, especially in CD49a⁺ DX5^- tissue-resident NK (trNK) cells. Obesity-induced ER stress, IR, and steatosis in the liver are ameliorated by ablating NK cells with neutralizing antibody in HFD-fed mice. OPN treatment enhances the expression of ER stress markers, including p-PERK, p-eIF2, ATF4, and CHOP in both murine liver tissues and HL-7702, a human liver cell line. Pretreatment of HL-7702 cells with OPN promotes hyperactivation of JNK and subsequent decrease of tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1), resulting in impaired insulin signaling, which can be reversed by inhibiting ER stress. Collectively, we demonstrate that hepatic NK cells induce obesity-induced hepatic ER stress, and IR through OPN production.

CD44 contributes to hyaluronan-mediated insulin resistance in skeletal muscle of high-fat-fed C57BL/6 mice

Extracellular matrix hyaluronan is increased in skeletal muscle of high-fat-fed insulin-resistant mice, and reduction of hyaluronan by PEGPH20 hyaluronidase ameliorates diet-induced insulin resistance (IR). CD44, the main hyaluronan receptor, is positively correlated with type 2 diabetes. This study determines the role of CD44 in skeletal muscle IR. Global CD44-deficient (cd44^-/-) mice and wild-type littermates (cd44^+/+) were fed a chow diet or 60% high-fat diet for 16 wk. High-fat-fed cd44^-/- mice were also treated with PEGPH20 to evaluate its CD44-dependent action. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp (ICv). High-fat feeding increased muscle CD44 protein expression. In the absence of differences in body weight and composition, despite lower clamp insulin during ICv, the cd44^-/- mice had sustained glucose infusion rate (GIR) regardless of diet. High-fat diet-induced muscle IR as evidenced by decreased muscle glucose uptake (Rg) was exhibited in cd44^+/+ mice but absent in cd44^-/- mice. Moreover, gastrocnemius Rg remained unchanged between genotypes on chow diet but was increased in high-fat-fed cd44^-/- compared with cd44^+/+ when normalized to clamp insulin concentrations. Ameliorated muscle IR in high-fat-fed cd44^-/- mice was associated with increased vascularization. In contrast to previously observed increases in wild-type mice, PEGPH20 treatment in high-fat-fed cd44^-/- mice did not change GIR or muscle Rg during ICv, suggesting a CD44-dependent action. In conclusion, genetic CD44 deletion improves muscle IR, and the beneficial effects of PEGPH20 are CD44-dependent. These results suggest a critical role of CD44 in promoting hyaluronan-mediated muscle IR, therefore representing a potential therapeutic target for diabetes.

Relevance of Leptin and Other Adipokines in Obesity-Associated Cardiovascular Risk

Obesity, which is a worldwide epidemic, confers increased risk for multiple serious conditions including type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. Adipose tissue is considered one of the largest endocrine organs in the body as well as an active tissue for cellular reactions and metabolic homeostasis rather than an inert tissue only for energy storage. The functional pleiotropism of adipose tissue relies on its ability to synthesize and release a large number of hormones, cytokines, extracellular matrix proteins, and growth and vasoactive factors, which are collectively called adipokines known to influence a variety of physiological and pathophysiological processes. In the obese state, excessive visceral fat accumulation causes adipose tissue dysfunctionality that strongly contributes to the onset of obesity-related comorbidities. The mechanisms underlying adipose tissue dysfunction include adipocyte hypertrophy and hyperplasia, increased inflammation, impaired extracellular matrix remodeling, and fibrosis together with an altered secretion of adipokines. This review describes the relevance of specific adipokines in the obesity-associated cardiovascular disease.

Effect of Myristica fragrans extract on total body composition in cafeteria diet induced obese rats

It is of interest to evaluate the effect of Myristica fragrans on body composition of cafeteria diet induced obese rats. Thirty rats (150-160g) grouped into 5 and each group contains 6 rats. Group-1 was normal control and 2-5 groups were fed with cafeteria diet for 15 weeks to induce obesity. From 16th week to 25th week test drugs were given as mentioned in the experimental protocol. Body weight, BMI, changes in body composition was measured by TOBEC, adipose tissue weights, organ weights, abdominal circumference were measured according to standard methods. After 70days of treatment with MFE 200mg/kg, 400mg/kg Body weight reduced by 9.29%, 12.87% respectively. BMI was also decreased. Abdominal circumference, total fat percentage, organ weights, was substantially reduced. At 400mg/kg of MFE has shown maximum potentiality when compared with 200mg/kg. Orlistat 50mg was used as standard drug. Tetrahydrofuran, flavonoids, saponins, present in Myristica fragrans has shown anti obesity activity. Our findings explain the potentiality of phytochemicals as a potent anti obesity agent, provide scientific evidence for its traditional use and suggest the possible mechanism of action.

Extracellular Matrix Remodeling of Adipose Tissue in Obesity and Metabolic Diseases

The extracellular matrix (ECM) is a network of different proteins and proteoglycans that controls differentiation, migration, repair, survival, and development, and it seems that its remodeling is required for healthy adipose tissue expansion. Obesity drives an excessive lipid accumulation in adipocytes, which provokes immune cells infiltration, fibrosis (an excess of deposition of ECM components such as collagens, elastin, and fibronectin) and inflammation, considered a consequence of local hypoxia, and ultimately insulin resistance. To understand the mechanism of this process is a challenge to treat the metabolic diseases. This review is focused at identifying the putative role of ECM in adipose tissue, describing its structure and components, its main tissue receptors, and how it is affected in obesity, and subsequently the importance of an appropriate ECM remodeling in adipose tissue expansion to prevent metabolic diseases.

Increased plasma osteopontin levels are associated with nonalcoholic fatty liver disease in patients with type 2 diabetes mellitus

Nonalcoholic fatty liver disease (NAFLD) commonly occurs in patients with type 2 diabetes mellitus (T2DM). Osteopontin (OPN) is a multifunctional protein with pleiotropic physiological functions. This study aimed to investigate the interrelation between circulating OPN and NAFLD in T2DM patients. Overall, 249 subjects were classified into 4 groups: 53 patients with NAFLD and T2DM; 57 with newly diagnosed T2DM; 59 with NAFLD; and 80 healthy age- and sex-matched controls. Serum OPN was measured by ELISA. The OPN distribution in the pooled data was divided into quartiles; significant trends across increasing quartiles were estimated by the Cochran-Armitage trend test. Compared with the controls, circulating OPN concentrations were significantly elevated in NAFLD patients and T2DM patients with or without NAFLD. Serum OPN levels were higher in the overweight/obese group than that in the lean group. Circulating OPN levels were positively correlated with CRP, age, BMI, SBP, DBP, HbA1c, UA, TGs, WBCs, neutrophils, FBG, and HOMA-IR and negatively correlated with ADP, albumin and HDL. Age, albumin, HbA1c, HDL and hsCRP were independently related to circulating OPN. The relative risks for NAFLD, T2DM and T2DM with NAFLD increased significantly along with increasing OPN quartiles based on the Cochran-Armitage trend test. OPN is an optimal predictor in the diagnosis of T2DM with NAFLD and T2DM and may contribute to the aggravation of the metabolic state.

Antibody-mediated targeting of cleavage-specific OPN-T cell interactions

T cells are crucial players in obesity-mediated adipose tissue inflammation. We hypothesized that osteopontin (OPN), an inflammatory protein with enhanced activity when proteolytically cleaved, affects the number of viable T cells in adipose tissue and assessed inhibition of the interaction between T cells and thrombin and matrix metalloproteinases-cleaved OPN using antibodies and postimmune sera. Gene expression of T cell markers in adipose tissue from wild-type (wt) and Spp1-/- (OPN deficient) mice was analyzed after 16 weeks of high fat diet (HFD) or low fat diet (LFD) feeding. CD3, CD8 and OPN gene expression in omental adipose tissue from individuals with obesity was measured. OPN-T cell interactions were assessed with a fluorescence-based adhesion assay and blocked with antibodies targeting OPN. Comparison of T cell gene expression in adipose tissue from wt and Spp1-/- mice showed that OPN affected the number of T cells while in humans, levels of OPN correlated with T cell markers in omental adipose tissue. The interaction between T cells and cleaved OPN was blocked by postimmune sera following OPN peptide vaccinations and with monoclonal antibodies. In conclusion, levels of OPN affected the number of T cells in obesity and antibodies against cleaved OPN antagonize OPN-T cell interactions.

Comparative Secretome Analyses of Primary Murine White and Brown Adipocytes Reveal Novel Adipokines

The adipose organ, including white and brown adipose tissues, is an important player in systemic energy homeostasis, storing excess energy in form of lipids while releasing energy upon various energy demands. Recent studies have demonstrated that white and brown adipocytes also function as endocrine cells and regulate systemic metabolism by secreting factors that act locally and systemically. However, a comparative proteomic analysis of secreted factors from white and brown adipocytes and their responsiveness to adrenergic stimulation has not been reported yet. Therefore, we studied and compared the secretome of white and brown adipocytes, with and without norepinephrine (NE) stimulation. Our results reveal that carbohydrate-metabolism-regulating proteins are preferably secreted from white adipocytes, while brown adipocytes predominantly secrete a large variety of proteins. Upon NE stimulation, an increased secretion of known adipokines is favored by white adipocytes while brown adipocytes secreted higher amounts of novel adipokines. Furthermore, the secretory response between NE-stimulated and basal state was multifaceted addressing lipid and glucose metabolism, adipogenesis, and antioxidative reactions. Intriguingly, NE stimulation drastically changed the secretome in brown adipocytes. In conclusion, our study provides a comprehensive catalogue of novel adipokine candidates secreted from white and brown adipocytes with many of them responsive to NE. Given the beneficial effects of brown adipose tissue activation on its endocrine function and systemic metabolism, this study provides an archive of novel batokine candidates and biomarkers for activated brown adipose tissue.

The multiple functions and mechanisms of osteopontin

Osteopontin (OPN) is a highly phosphorylated glycophosphoprotein having acidic characteristics and rich in aspartic acid. OPN, a multifunctional protein, has important functions on cardiovascular diseases, cancer, diabetes and kidney stone diseases and in the process of inflammation, biomineralization, cell viability and wound healing. Osteopontin acts on organisms by playing a key role in secretion levels of interleukin-10 (IL-10), interleukin-12 (IL-12), interleukin-3 (IL-3), interferon-γ (IFN-γ), integrin αvB3, nuclear factor kappa B (NF-kB), macrophage and T cells, regulating the osteoclast function and affecting CD44 receptors. The aim of the present review is to address majority of different functions of OPN protein which are known, suspected or suggested through the data obtained about this protein yet.

The Frequency of Metabolic Syndrome and Serum Osteopontin Levels in Survivors of Childhood Acute Lymphoblastic Leukemia

PURPOSE

Metabolic syndrome (MetS) and obesity have increasingly been reported in survivors of childhood cancer. Osteopontin (OPN) is primarily synthesized in adipose tissue and is thought to have a role in obesity and the development of insulin resistance (IR). The aim of this study was to investigate the frequency of MetS in survivors of acute lymphoblastic leukemia (ALL) and to establish the relationship between serum OPN levels and anthropometric measurements and glucose metabolism.

METHODS

A total 50 survivors of ALL (median age: 10.5 years; post-treatment interval 4.54 ± 2.48 years), and 20 healthy children (median age: 11 years) were included in the study. Anthropometric measurements were taken, and serum glucose, insulin, homeostasis model assessment and IR index (HOMA-IR index), lipoprotein, thyroid hormone levels, and OPN levels were measured.

RESULTS

Twenty-one (42%) survivors were overweight/obese, 2 (5.1%) survivors had MetS, 7 (14%) survivors had IR, and 19 (38%) survivors had dyslipidemia. Fasting insulin levels and HOMA-IR of the overweight/obese survivors were significantly higher than those of the normal-weight survivors (p < 0.05 and p < 0.01) and control group (p < 0.01 and p < 0.01). The serum OPN level was significantly lower in the overweight/obese survivor than in the normal-weight survivor and control group (37.42 ng/mL [range, 27.32-62.07], 69.02 ng/mL [range, 40.29-88.21], and 85.7 ng/mL [range 67.7-102.3]; p < 0.01, p < 0.001, respectively). Serum OPN levels were inversely correlated with anthropometric measurements and HOMA-IR index in all the subjects.

CONCLUSION

Our results showed that obesity and IR are associated with decreased serum OPN levels in childhood survivors of ALL.

Osteopontin may be a driver of abdominal aortic aneurysm formation

OBJECTIVE

Previous in vitro and animal studies have suggested that osteopontin (OPN), an inflammatory extracellular matrix protein, is involved in the formation and growth of abdominal aortic aneurysms (AAAs). However, the mechanism by which this occurs continues to be nebulous. The relationship between OPN and inflammation-suppressing lymphocytes present in the human AAA condition was investigated and presented herein.

METHODS

Serum OPN concentrations were measured in healthy, risk factor-matched non-AAA and AAA patients by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was used to determine the source of OPN secretion using aortic tissue collected from multiorgan donors and AAA patients undergoing open surgical repair. Vascular smooth muscle cells (VSMCs) were exposed to various inflammatory mediators, and OPN expression was evaluated by quantitative reverse transcriptase-polymerase chain reaction and ELISA. The inflammatory nature of OPN and the aortic wall was determined using a TR1 suppressor cell induction assay as a surrogate and characterized by ELISA and fluorescence-activated cell sorting.

RESULTS

OPN was found to be elevated in both the plasma and aortic homogenate of AAA patients compared with controls. On immunohistochemistry, OPN localized to the tunica media of the diseased aorta but was minimally expressed in healthy aorta. In vitro, cigarette smoke extract was the most potent stimulator of OPN secretion by VSMCs and increased both messenger RNA and supernatant concentrations. OPN demonstrated an ability to inhibit the induction of interleukin 10-secreting TR1 lymphocytes, a depleted population in the AAA patient, from naive precursors. Last, neutralizing receptor targets of OPN in the setting of AAA homogenate coincubation abrogated the inhibition of TR1 induction.

CONCLUSIONS

OPN, secreted by the VSMCs of the tunica media, is elevated in the circulating plasma and aortic wall of patients with AAA. It can inhibit the induction of the TR1 suppressor cell, leading to an overall proinflammatory state contributing to progressive aortic wall breakdown and dilation.

Physical activity and hypocaloric diet recovers osteoblasts homeostasis in women affected by abdominal obesity

Obesity is a multifactorial disease linked to metabolic chronic disorders such as diabetes, and hypertension. Also, it has recently been associated with skeletal alterations and low bone mineral density. We previously demonstrated that exposure of osteoblasts to sera of sedentary subjects affected by obesity alters cell homeostasis in vitro, leading to disruption of intracellular differentiation pathways and cellular activity. Thus, the purpose of the present study has been to evaluate whether sera of sedentary obese women, subjected to physical activity and hypocaloric diet, could recover osteoblast homeostasis in vitro as compared to the sera of same patients before intervention protocol. To this aim, obese women were evaluated at time 0 and after 4, 6, and 12 months of individualized prescribed physical activity and hypocaloric diet. Dual-energy-X-ray absorptiometry measurements were performed at each time point, as well as blood was collected at the same points. Cells were incubated with sera of subjects before and after physical activity as described: obese at baseline and after for 4, 6, and 12 months of physical activity and nutritional protocol intervention. Osteoblasts exposed to sera of patients, who displayed increased lean and decreased fat mass (from 55.5 ± 6.5 to 57.1 ± 5.6% p ≤ 0.05; from 44.5 ± 1.1 to 40.9 ± 2.6% p ≤ 0.01 respectively), showed a time-dependent increase of Wnt/β-catenin signaling, versus cells exposed to sera of obese patients before intervention protocol, suggesting recovery of osteoblast homeostasis upon improvement of body composition. An increase in β-catenin nuclear accumulation and nuclear translocation was also observed, accompanied by an increase in Adiponectin receptor 1 protein expression, suggesting positive effect on cell differentiation program. Furthermore, a decrease in sclerostin amount and an increase of type 1 procollagen amino-terminal-propeptide were depicted as compared to baseline, proportionally to the time of physical activity, suggesting a recovery of bone remodeling modulation and an increase of osteoblast activity induced by improvement of body composition. In conclusion, our results show for the first time that sera of obese sedentary women who increased lean mass and decreased fat mass, by physical activity and hypocaloric diet, rescue osteoblasts differentiation and activity likely due to a reactivation of Wnt/β-catenin-pathway, suggesting that a correct life style can improve skeletal metabolic alteration induced by obesity.

Meta-fibrosis links positive energy balance and mitochondrial metabolism to insulin resistance

Obesity and insulin resistance often emerge from positive energy balance and generally are linked to low-grade inflammation. This low-grade inflammation has been called “meta-inflammation” because it is a consequence of the metabolic dysregulation that can accompany overnutrition. One means by which meta-inflammation is linked to insulin resistance is extracellular matrix expansion secondary to meta-inflammation, which we define here as “meta-fibrosis”. The significance of meta-fibrosis is that it reflects a situation in which the extracellular matrix functions as a multi-level integrator of local (for example, mitochondrial reactive oxygen species production) and systemic (for example, inflammation) inputs that couple to cellular processes creating insulin resistance. While adipose tissue extracellular matrix remodeling has received considerable attention, it is becoming increasingly apparent that liver and skeletal muscle extracellular matrix remodeling also contributes to insulin resistance. In this review, we address recent advances in our understanding of energy balance, mitochondrial energetics, meta-inflammation, and meta-fibrosis in the development of insulin resistance.