Modulation of angiogenesis during adipose tissue development in murine models of obesity

Non-invasive optoacoustic imaging of dermal microcirculatory revascularization in diet-induced obese mice undergoing exercise intervention

Microcirculatory dysfunction has been observed in the dermal white adipose tissue (dWAT) and subcutaneous white adipose tissue (scWAT) of obese humans and has been proposed as an early prediction marker for cardio-metabolic disease progression. In-vivo visualization and longitudinal monitoring of microvascular remodeling in these tissues remains challenging. We compare the performance of two optoacoustic imaging methods, i.e. multi-spectral optoacoustic tomography (MSOT) and raster-scanning optoacoustic mesoscopy (RSOM) in visualizing lipid and hemoglobin contrast in scWAT and dWAT in a mouse model of diet-induced obesity (DIO) undergoing voluntary wheel running intervention for 32 weeks. MSOT visualized lipid and hemoglobin contrast in murine fat depots in a quantitative manner even at early stages of DIO. We show for the first time to our knowledge that RSOM allows precise visualization of the dWAT microvasculature and provides quantitative readouts of skin layer thickness and vascular density in dWAT and dermis. Combination of MSOT and RSOM resolved exercise-induced morphological changes in microvasculature density, tissue oxygen saturation, lipid and blood volume content in dWAT and scWAT. The combination of MSOT and RSOM may allow precise monitoring of microcirculatory dysfunction and intervention response in dWAT and scWAT in a mouse model for DIO. Our findings have laid out the foundation for future clinical studies using optoacoustic-derived vascular readouts from adipose tissues as a biomarker for monitoring microcirculatory function in metabolic disease.

The role of CD47 in non-neoplastic diseases

CD47 is a 50 kDa five-spanning membrane receptor that plays a crucial role in multiple cellular processes, including myeloid cell activation, neutrophils transmigration, vascular remodeling, leukocyte adhesion and trans-endothelial migration. Recent studies have revealed that CD47 is a highly expressed anti-phagocytic signal in several types of cancer, and therefore, blocking of CD47 has shown an effective therapeutic potential in cancer immunotherapy. In addition, CD47 has been found to be involved in a complex interplay with microglia and other types of cells, and increasing evidence indicates that CD47 can be targeted as part of immune modulatory strategies for non-neoplastic diseases as well. In this review, we focus on CD47 and its role in non-neoplastic diseases, including neurological disorders, atherosclerosis and autoimmune diseases. In addition, we discuss the major challenges and potential remedies associated with CD47-SIRPα-based immunotherapies.

Expression of vascular endothelial growth factor A (VEGFA), placental growth factor (PlGF) and insulin-like growth factor 1 (IGF-1) in serum from women undergoing frozen embryo transfer

VEGFA, PlGF and IGF-1 are three main angiogenic factors which play significant roles in embryo implantation. However, the relationship between serum expressions of VEGFA, PlGF and IGF-1 and pregnancy outcomes has not been fully illustrated. In this study, serum specimens were collected precisely on day 7 after the LH surge in a natural non-conception cycle from 38 infertile patients who underwent frozen embryo transfer (FET) treatment. ELISA was used to determine the concentrations of VEGFA, PlGF and IGF-1. Serum levels of VEGFA, PlGF and IGF-1 were compared between patients who conceived (n=25) and who did not (n=13). Correlation and linear regression analyses were used to investigate the correlations of serum angiogenic factors and β-hCG MoM levels in the pregnant group. The results demonstrated that no significant difference was found in serum VEGFA, PlGF or IGF-1 concentration between pregnant and non-pregnant women. Spearman correlation analysis revealed a positive correlation between IGF-1 concentration and β-hCG level in pregnant participants (rs = 0.490, p = 0.013). In conclusion, serum IGF-1 level correlated positively with β-hCG level in pregnant women, which may provide information on the prognostic value of IGF-1 in this group of women.

Thrombospondin1 antagonist peptide treatment attenuates obesity-associated chronic inflammation and metabolic disorders in a diet-induced obese mouse model

Thrombospondin1 (TSP1) is a multifunctional matricellular protein. Previously, we demonstrated that TSP1 plays a pivotal role in obesity-related inflammation and insulin resistance (IR) by modulating macrophage accumulation and activation in adipose tissue. Moreover, in our in vitro studies, a CD36-derived peptide, functioning as a TSP1 antagonist, effectively inhibited TSP1-induced proinflammatory macrophage activation. However, whether this CD36 peptide can inhibit obesity-induced inflammation and IR in vivo is unknown and determined in this study in a high fat diet-induced obese mouse model (DIO). CD36 peptide or control peptide was intraperitoneally administered into the established obese mice triweekly for 6 weeks. We found that CD36 peptide treatment didn't affect obesity or weight gain but significantly reduced proinflammatory cytokine production systemically and in visceral fat tissue. Adipose tissue exhibited fewer crown-like structures and reduced macrophage infiltration. CD36 peptide treatment also attenuated the proinflammatory phenotype of bone marrow derived macrophages from obese mice. Furthermore, CD36 peptide treatment improved glucose tolerance and insulin sensitivity, and mitigated obesity-related fatty liver disease and kidney damage. Collectively, this study suggests that the CD36 peptide, as a TSP1 antagonist, shows promise as a novel therapeutic approach for managing obesity-related metabolic disorders.

Short term effect of tetrahydrocurcumin on adipose angiogenesis in very high-fat diet-induced obesity mouse model

Tetrahydrocurcumin (THC) has been shown to possess anti-angiogenic activities. This study aims to investigate the effects of THC on adipose angiogenesis and expression of angiogenic factors that occurs in 60% high-fat diet-induced obese mice. Male ICR mice were randomly divided into 3 groups: mice fed with a low-fat diet (LFD group); mice fed with very high fat diet (VHFD group), and mice fed with VHFD supplemented with THC (300 mg/kg/day orally) (VHFD+THC treated group) for 6 weeks. Body weight (BW), food intake, fasting blood sugar (FBS), lipid profiles and visceral fats weight (VF) were measured. The microvascular density (MVD), TNF-α, VEGF, MMP-2, and MMP-9 expressions were evaluated. The VHFD group had significantly increased total cholesterol, triglyceride, food intake, BW, VF, VF/BW ratio, adipocyte size and the number of crown-liked structures as compared to LFD group. THC supplementation markedly reduced these parameters and adipocyte hypertrophy and inflammation in white adipose tissues. MVD, TNF-α, VEGF, MMP-2, and MMP-9 were over-expressed in the VHFD group. However, THC supplementation decreased MVD and reduced expression of TNF-α, VEGF, MMP-2, and MMP-9. In conclusion, THC suppressed angiogenesis in adipose tissue by the downregulation of TNF-α, VEGF, MMP-2, and MMP-9. With its effects on lipid metabolism as well as on food consumption, THC could contribute to lower visceral fat and body weight. Overall, our study demonstrated the potential benefit of THC in mitigating obesity and associated metabolic disorders along with elucidated the suppression of adipose angiogenesis as one of its underlying mechanisms.

Pathological angiogenesis: mechanisms and therapeutic strategies

In multicellular organisms, angiogenesis, the formation of new blood vessels from pre-existing ones, is an essential process for growth and development. Different mechanisms such as vasculogenesis, sprouting, intussusceptive, and coalescent angiogenesis, as well as vessel co-option, vasculogenic mimicry and lymphangiogenesis, underlie the formation of new vasculature. In many pathological conditions, such as cancer, atherosclerosis, arthritis, psoriasis, endometriosis, obesity and SARS-CoV-2(COVID-19), developmental angiogenic processes are recapitulated, but are often done so without the normal feedback mechanisms that regulate the ordinary spatial and temporal patterns of blood vessel formation. Thus, pathological angiogenesis presents new challenges yet new opportunities for the design of vascular-directed therapies. Here, we provide an overview of recent insights into blood vessel development and highlight novel therapeutic strategies that promote or inhibit the process of angiogenesis to stabilize, reverse, or even halt disease progression. In our review, we will also explore several additional aspects (the angiogenic switch, hypoxia, angiocrine signals, endothelial plasticity, vessel normalization, and endothelial cell anergy) that operate in parallel to canonical angiogenesis mechanisms and speculate how these processes may also be targeted with anti-angiogenic or vascular-directed therapies.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic diseases.

Transcriptomic profiling reveals sex-specific molecular signatures of adipose endothelial cells under obesogenic conditions

Female mice display greater adipose angiogenesis and maintain healthier adipose tissue than do males upon high-fat diet feeding. Through transcriptome analysis of endothelial cells (EC) from the white adipose tissue of male and female mice high-fat-fed for 7 weeks, we found that adipose EC exhibited pronouncedly sex-distinct transcriptomes. Genes upregulated in female adipose EC were associated with proliferation, oxidative phosphorylation, and chromatin remodeling contrasting the dominant enrichment for genes related to inflammation and a senescence-associated secretory of male EC. Similar sex-biased phenotypes of adipose EC were detectable in a dataset of aged EC. The highly proliferative phenotype of female EC was observed also in culture conditions. In turn, male EC displayed greater inflammatory potential than female EC in culture, based on basal and tumor necrosis factor alpha-stimulated patterns of gene expression. Our study provides insights into molecular programs that distinguish male and female EC responses to pathophysiological conditions.

Obesity, Adipose Tissue, and Inflammation Answered in Questions

Background. Obesity is a global health problem of epidemic proportions, which is characterized by increased adipose tissue (AT) mass and significant repercussions in different body apparati and systems. AT is a special connective tissue, which contains several types of cells, in addition to adipocytes, and is a highly active endocrine and immune organ, which directly modulates many processes, including energy balance, metabolism, and inflammation. Summary. In this paper, the authors list and attempt to answer in a brief and simple way several questions regarding the complex relationships between obesity, adipose tissue, and inflammation, with the objective to provide an easy way to understand the main changes that occur in this pathological state. The questions are the following: Is adipose tissue only made up of adipocytes? Are adipocytes just a reservoir of free fatty acids? Do different types of fatty tissue exist? If so, which types? Can we further subcategorize the types of adipose tissue? Is it possible to form new adipocytes during adulthood? What is the role of inflammation? What is the role of macrophages? Are macrophages central mediators of obesity-induced adipose tissue inflammation and insulin resistance? What causes macrophage infiltration into adipose tissue? What is the role of hypoxia in AT alterations? Is there cross talk between adipocytes and immune cells? What other changes occur in AT in obesity? Does metabolically healthy obesity really exist? Is this a benign condition? Key messages. Obesity is a complex disease with numerous metabolic consequences, which are mainly the result of dysfunction that occurs in the adipose tissue of patients with this pathology. Understanding the pathophysiology of AT and the changes that occur in obesity would contribute to a better approach to patients with obesity, with the inherent medical implications that could result from this.

Progranulin: A proangiogenic factor in visceral adipose tissue in tumoral and non-tumoral visceral pathology

The connection between central obesity and the development and metastasis of various visceral tumors is largely accepted and one of the main causes seems to be the local synthesis of proangiogenic molecules. Progranulin (PRG), recently identified as an adipokine, is a novel pleiotropic growth factor acting on the proliferation and development of fast-growing epithelial cells, cancer cells, and also a proangiogenic factor whose expression is induced in activated endothelial cells. One of the molecules that seems to trigger the angiogenic activity of PRG is vascular endothelial growth factor (VEGF). Two groups of human subjects were considered and adipose tissue was processed for an immunohistochemical and morphometric study after surgery for abdominal tumoral or non-tumoral pathology. The presence of PRG in adipose pads of the omentum was analyzed and its association with VEGF, CD34 and collagen IV in tumoral and non-tumoral visceral pathology was examined. The results showed that PRG but not VEGF expression was upregulated in adipose tissue in tumoral visceral pathology. In conclusion, the involvement of the proangiogenic activity of PRG and VEGF in adipose tissue under tumor conditions may be dependent on the visceral tumor type.

Chronic Inflammation and Cancer: The Role of Endothelial Dysfunction and Vascular Inflammation

Long-lasting subclinical inflammation is associated with a wide range of human diseases, particularly at a middle and older age. Recent reports showed that there is a direct causal link between inflammation and cancer development, as several cancers were found to be associated with chronic inflammatory conditions. In patients with cancer, healthy endothelial cells regulate vascular homeostasis, and it is believed that they can limit tumor growth, invasiveness, and metastasis. Conversely, dysfunctional endothelial cells that have been exposed to the inflammatory tumor microenvironment can support cancer progression and metastasis. Dysfunctional endothelial cells can exert these effects via diverse mechanisms, including dysregulated adhesion, permeability, and activation of NF-κB and STAT3 signaling. In this review, we highlight the role of vascular inflammation in predisposition to cancer within the context of two common disease risk factors: obesity and smoking. In addition, we discuss the molecular triggers, pathophysiological mechanisms, and the biological consequences of vascular inflammation during cancer development and metastasis. Finally, we summarize the current therapies and pharmacological agents that target vascular inflammation and endothelial dysfunction.

CD47 and thrombospondin-1 regulation of mitochondria, metabolism, and diabetes

Thrombospondin-1 (TSP1) is the prototypical member of a family of secreted proteins that modulate cell behavior by engaging with molecules in the extracellular matrix and with receptors on the cell surface. CD47 is widely displayed on many, if not all, cell types and is a high-affinity TSP1 receptor. CD47 is a marker of self that limits innate immune cell activities, a feature recently exploited to enhance cancer immunotherapy. Another major role for CD47 in health and disease is to mediate TSP1 signaling. TSP1 acting through CD47 contributes to mitochondrial, metabolic, and endocrine dysfunction. Studies in animal models found that elevated TSP1 expression, acting in part through CD47, causes mitochondrial and metabolic dysfunction. Clinical studies established that abnormal TSP1 expression positively correlates with obesity, fatty liver disease, and diabetes. The unabated increase in these conditions worldwide and the availability of CD47 targeting drugs justify a closer look into how TSP1 and CD47 disrupt metabolic balance and the potential for therapeutic intervention.

Paracrine Placental Growth Factor Signaling in Response to Ionizing Radiation Is p53-Dependent and Contributes to Radioresistance

Placental growth factor (PlGF) is a pro-angiogenic, N-glycosylated growth factor, which is secreted under pathologic situations. Here, we investigated the regulation of PlGF in response to ionizing radiation (IR) and its role for tumor angiogenesis and radiosensitivity. Secretion and expression of PlGF was induced in multiple tumor cell lines (medulloblastoma, colon and lung adenocarcinoma) in response to irradiation in a dose- and time-dependent manner. Early upregulation of PlGF expression and secretion in response to irradiation was primarily observed in p53 wild-type tumor cells, whereas tumor cells with mutated p53 only showed a minimal or delayed response. Mechanistic investigations with genetic and pharmacologic targeting of p53 corroborated regulation of PlGF by the tumor suppressor p53 in response to irradiation under normoxic and hypoxic conditions, but with so far unresolved mechanisms relevant for its minimal and delayed expression in tumor cells with a p53-mutated genetic background. Probing a paracrine role of IR-induced PlGF secretion in vitro, migration of endothelial cells was specifically increased towards irradiated PlGF wild type but not towards irradiated PlGF-knockout (PIGF-ko) medulloblastoma cells. Tumors derived from these PlGF-ko cells displayed a reduced growth rate, but similar tumor vasculature formation as in their wild-type counterparts. Interestingly though, high-dose irradiation strongly reduced microvessel density with a concomitant high rate of complete tumor regression only in the PlGF-ko tumors. IMPLICATIONS: Our study shows a strong paracrine vasculature-protective role of PlGF as part of a p53-regulated IR-induced resistance mechanism and suggest PlGF as a promising target for a combined treatment modality with RT.

Biomarkers and Their Relation to Cardiac Function Late After Peripartum Cardiomyopathy

BACKGROUND

Angiogenic imbalance involving the placental protein soluble Fms-like tyrosine kinase-1 (sFlt-1) and cleavage of the nursing-hormone prolactin by the enzyme cathepsin D (CD) both play a role in the pathogenesis of peripartum cardiomyopathy (PPCM). We hypothesized that angiogenic imbalance and increased activity of CD have a long-lasting impact in women with PPCM.

METHODS AND RESULTS

A nationwide Danish cohort of women with PPCM (PPCM group, n = 28), age matched women with previous preeclampsia (n = 28) and uncomplicated pregnancies (n = 28) participated in a follow-up study including biomarker analysis, exercise testing and cardiac magnetic resonance imaging. The median time to follow-up was 91 months (range 27-137 months) for the PPCM group. Levels of sFlt-1, placental growth factor, N-terminal pro-natriuretic brain peptide, and copeptin were all significantly higher in the PPCM group. More women in the PPCM group had detectable CD activity (68%) compared with the preeclampsia group (29%) and uncomplicated pregnancies group (36%) (P = .0002). Levels of angiogenic factors and biomarkers correlated inversely with maximal exercise capacity and cardiac functional parameters assessed with cardiac magnetic resonance imaging.

CONCLUSIONS

Women with PPCM had higher biomarker levels and CD activity up to 7 years after diagnosis. Higher biomarker levels correlated inversely with maximal exercise capacity and markers of cardiac dysfunction suggesting that persistent angiogenic imbalance and increased CD activity is associated with residual cardiac dysfunction.

Effects of interleukin-6 and tumor necrosis factor-α on the expression of angiogenic and collagenolytic factors in premature and mature adipocytes

OBJECTIVE

The remodeling of the vascular network and collagen in the extracellular matrix is closely associated with the expansion and dysfunction of adipose tissue. In the present study, we investigated the effects of interleukin (IL)-6 and tumor necrosis factor (TNF)-α on the expression of angiogenic factors, collagen, and collagenase and its endogenous inhibitor in premature and mature adipocytes.

METHODS

Premature and mature adipocytes were differentiated from 3T3-L1 cells and stimulated with IL-6 or TNF-α to mimic the early and late phases of obesity development. The levels of expression of angiogenic factors, including vascular endothelial cell growth factor a (Vegfa), hepatocyte growth factor (Hgf), angiopoietin (Angpt)1, and Angpt2, as well as type I collagen, matrix metallopeptidase (Mmp) 13, and tissue inhibitor of Mmp (Timp) 1, were determined using real-time reverse transcription polymerase chain reaction or enzyme-linked immunosorbent assay. Human umbilical vein endothelial cells were grown with the culture supernatant of adipocytes stimulated with/without IL-6 or TNF-α, and the formation of tube structures was evaluated.

RESULTS

IL-6 and TNF-α induced the expression of Vegfa, Hgf, and Angpt2 and decreased the expression of Angpt1 in premature adipocytes, whereas, they decreased the expression of Vegfa and Hgf in mature adipocytes. The culture supernatant of IL-6- or TNF-α-stimulated premature adipocytes induced the formation of tube structures. IL-6 and TNF-α had no effects on type I collagen expression in both premature and mature adipocytes but suppressed the expression of Mmp13 and Timp1 in mature and premature adipocytes, respectively.

CONCLUSION

The effects of IL-6 and TNF-α on the expression of angiogenic and collagenolytic factors differed between premature and mature adipocytes. This finding suggests that these inflammatory cytokines induce expansion and dysfunction of adipose tissue via angiogenesis and collagen turnover in premature and mature adipocytes.

Regulation of Obesity by Antiangiogenic Herbal Medicines

Obesity is the result of an energy imbalance caused by an increased ratio of caloric intake to energy expenditure. In conjunction with obesity, related metabolic disorders, such as dyslipidemia, atherosclerosis, and type 2 diabetes, have become global health problems. Obesity progression is thought to be associated with angiogenesis and extracellular matrix (ECM) remodeling. Angiogenesis occurs in growing adult adipose tissues, which are similar to neoplastic tissues. Adipose tissue is highly vascularized, and each adipocyte is nourished by an extensive capillary network. Adipocytes produce proangiogenic factors, such as vascular endothelial growth factor A and fibroblast growth factor 2, which promote neovascularization within the adipose tissue. Furthermore, matrix metalloproteinases (MMPs), including MMP-2 and MMP-9, play important roles in adipose tissue development and microvessel maturation by modifying the ECM. Thus, modulation of angiogenesis and MMP activity provides a promising therapeutic approach for controlling human obesity and its related disorders. Over the past decade, there has been a great increase in the use of alternative treatments, such as herbal remedies, for these diseases. This review will focus on the role of angiogenesis in adipose tissue growth and the regulation of obesity by antiangiogenic herbal medicines.

Murine double minute-2 mediates exercise-induced angiogenesis in adipose tissue of diet-induced obese mice

OBJECTIVE

This study aimed to determine the effects of physical exercise on the angio-adaptive response in adipose tissue following weight loss in a mouse model of diet-induced obesity. We hypothesized that physical exercise stimulates angiogenesis through the regulation of Vascular endothelial growth factor-A (VEGF-A) pro-/Thrombospondin-1 (TSP-1) anti-angiogenic signal under the control of the Murine double-minute 2/Forkhead box Os (Mdm2/FoxOs) axis, as reported in skeletal muscle.

METHODS

We studied the effects of 7 weeks-voluntary exercise (Ex) in C57Bl/6 control or diet-induced obese (HFS) mice on vascularization of white adipose tissue (AT).

RESULTS

Diet-induced obese sedentary (HFSsed) mice presented a powerful angiostatic control in all adipose tissues, under FoxOs protein regulation, leading to capillary rarefaction. Exercise increased expression of Mdm2, repressing the angiostatic control in favor of adipose vascular regrowth in normal chow (NCex) and HFSex mice. This phenomenon was associated with adipocytes microenvironment improvement, such as decreased adipocytes hypertrophy and adipose tissue inflammation. In addition, adipose angiogenesis stimulation by exercise through Mdm2 pro-angiogenic action, improved visceral adipose insulin sensitivity, activated browning process within subcutaneous adipose tissue (ScWAT) and decreased ectopic fat deposition (muscle, heart and liver) in obese HFSex mice. The overall result of this approach of therapy by physical exercise is an improvement of all systemic cardiometabolic parameters.

CONCLUSIONS

These data demonstrated the therapeutic efficacy of physical exercise against obesity-associated pathologies, and also offer new prospects for molecular therapies targeting the adipose angio-adaptation in obese humans.

Thrombospondin-1 in maladaptive aging responses: a concept whose time has come

Numerous age-dependent alterations at the molecular, cellular, tissue and organ systems levels underlie the pathophysiology of aging. Herein, the focus is upon the secreted protein thrombospondin-1 (TSP1) as a promoter of aging and age-related diseases. TSP1 has several physiological functions in youth, including promoting neural synapse formation, mediating responses to ischemic and genotoxic stress, minimizing hemorrhage, limiting angiogenesis, and supporting wound healing. These acute functions of TSP1 generally require only transient expression of the protein. However, accumulating basic and clinical data reinforce the view that chronic diseases of aging are associated with accumulation of TSP1 in the extracellular matrix, which is a significant maladaptive contributor to the aging process. Identification of the relevant cell types that chronically produce and respond to TSP1 and the molecular mechanisms that mediate the resulting maladaptive responses could direct the development of therapeutic agents to delay or revert age-associated maladies.

Obesity reduces mammary epithelial cell TGFβ1 activity through macrophage-mediated extracellular matrix remodeling

Obesity is a risk factor for breast cancer in postmenopausal and high‐risk premenopausal women. Changes within the obese breast microenvironment may increase breast cancer risk. Transforming growth factor beta‐1 (TGFβ1) is a major regulator of mammary epithelial stem/progenitor cells, and its activity is dysregulated under conditions of obesity. Using a high‐fat diet model of obesity in mice and breast tissue from women, we observed that TGFβ1 activity is reduced in breast epithelial cells in obesity. Breast ducts and lobules demonstrated increased decorin in the extracellular matrix (ECM) surrounding epithelial cells, and we observed that decorin and latent TGFβ1 complexed together. Under conditions of obesity, macrophages expressed higher levels of decorin and were significantly increased in number surrounding breast epithelial cells. To investigate the relationship between macrophages and decorin expression, we treated obese mice with either IgG control or anti‐F4/80 antibodies to deplete macrophages. Mice treated with anti‐F4/80 antibodies demonstrated reduced decorin surrounding mammary ducts and enhanced TGFβ1 activity within mammary epithelial cells. Given the role of TGFβ1 as a tumor suppressor, reduced epithelial TGFβ1 activity and enhanced TGFβ1 within the ECM of obese mammary tissue may enhance breast cancer risk.

Thrombospondin-I is a critical modulator in non-alcoholic steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) is a progressive liver disease characterized by dysregulated lipid metabolism and chronic inflammation ultimately resulting in fibrosis. Untreated, NAFLD may progress to non-alcoholic steatohepatitis (NASH), cirrhosis and death. However, currently there are no FDA approved therapies that treat NAFLD/NASH. Thrombospondin-I (TSP-1) is a large glycoprotein in the extracellular matrix that regulates numerous cellular pathways including transforming growth factor beta 1 (TGF-β1) activation, angiogenesis, inflammation and cellular adhesion. Increased expression of TSP-1 has been reported in various liver diseases; however, its role in NAFLD/NASH is not well understood. We first examined TSP-1 modulation in hepatic stellate cell activation, a critical initiating step in hepatic fibrosis. Knockdown or inhibition of TSP-1 attenuated HSC activation measured by alpha smooth muscle actin (α-SMA) and Collagen I expression. To investigate the impact of TSP-1 modulation in context of NAFLD/NASH, we examined the effect of TSP-1 deficiency in the choline deficient L-amino acid defined high fat diet (CDAHFD) model of NASH in mice by assessing total body and liver weight, serum liver enzyme levels, serum lipid levels, liver steatosis, liver fibrosis and liver gene expression in wild type (WT) and TSP-1 null mice. CDAHFD fed mice, regardless of genotype, developed phenotypes of NASH, including significant increase in liver weight and liver enzymes, steatosis and fibrosis. However, in comparison to WT, CDAHFD-fed TSP-1 deficient mice were protected against numerous NASH phenotypes. TSP-1 null mice exhibited a decrease in serum lipid levels, inflammation markers and hepatic fibrosis. RNA-seq based transcriptomic profiles from the liver of CDAHFD fed mice determined that both WT and TSP-1 null mice exhibited similar gene expression signatures following CDAHFD, similar to biophysical and histological assessment comparison. Comparison of transcriptomic profiles based on genotype suggested that peroxisome proliferator activated receptor alpha (PPARα) pathway and amino acid metabolism pathways are differentially expressed in TSP-1 null mice. Activation of PPARα pathway was supported by observed decrease in serum lipid levels. Our findings provide important insights into the role of TSP-1 in context of NAFLD/NASH and TSP-1 may be a target of interest to develop anti-fibrotic therapeutics for NAFLD/NASH.

Role of VEGFs in metabolic disorders

Obesity and metabolic disorders are important public health problems. In this review, the role of vasculature network and VEGF in the adipose tissue maintenance and supplementation is discussed. Angiogenesis is a key process implicated in regulation of tissues homeostasis. Dysregulation of new blood vessels formation may be crucial and contribute to the onset of several pathological conditions, including metabolic syndrome-associated disorders. Adipose tissue homeostasis is fine regulated by vascular network. Vessels support adipose structure. Vasculature modulates the balance between positive and negative regulator factors. In white adipose tissue, vascular endothelial growth factor (VEGF) controls the metabolic activities of adipocytes promoting the trans-differentiation from white to beige phenotype. Trans-differentiation results in an increase of energy consumption. VEGF exerts an opposite effect on brown adipose tissue, where VEGF increases oxygen supply and improves energy expenditure inducing the whitening of adipocytes.

Inter-organ cross-talk in metabolic syndrome

Maintenance of systemic homeostasis and the response to nutritional and environmental challenges require the coordination of multiple organs and tissues. To respond to various metabolic demands, higher organisms have developed a system of inter-organ communication through which one tissue can affect metabolic pathways in a distant tissue. Dysregulation of these lines of communication contributes to human pathologies, including obesity, diabetes, liver disease and atherosclerosis. In recent years, technical advances such as data-driven bioinformatics, proteomics and lipidomics have enabled efforts to understand the complexity of systemic metabolic cross-talk and its underlying mechanisms. Here, we provide an overview of inter-organ signals and their roles in metabolic control, and highlight recent discoveries in the field. We review peptide, small-molecule and lipid mediators secreted by metabolic tissues, as well as the role of the central nervous system in orchestrating peripheral metabolic functions. Finally, we discuss the contributions of inter-organ signalling networks to the features of metabolic syndrome.

Sick fat: the good and the bad of old and new circulating markers of adipose tissue inflammation

Adipose tissue (AT) is one of the largest endocrine organs contributing to metabolic homeostasis. The functional pleiotropism of AT depends on its ability to secrete a large number of hormones, cytokines, extracellular matrix proteins and growth factors, all influencing many local and systemic physiological and pathophysiological processes. In condition of chronic positive energy balance, adipocyte expansion, hypoxia, apoptosis and stress all lead to AT inflammation and dysfunction, and it has been demonstrated that this sick fat is a main risk factor for many metabolic disorders, such as type 2 diabetes mellitus, fatty liver, cardiovascular disease and cancer. AT dysfunction is tightly associated with aberrant secretion of bioactive peptides, the adipocytokines, and their blood concentrations often reflect the expression in the AT. Despite the existence of an association between AT dysfunction and systemic pro-inflammatory state, most of the circulating molecules detectable in obese and dysmetabolic individuals do not identify specifically the condition of sick fat. Based on this premise, this review provides a concise overview of "classic" and novel promising adipocytokines associated with AT inflammation and discusses possible critical approaches to their interpretation in clinical practice.

Age- and BMI-Associated Expression of Angiogenic Factors in White Adipose Tissue of Children

The growth of adipose tissue and its vasculature are tightly associated. Angiogenic factors have been linked to obesity, yet little is known about their expression during early childhood. To identify associations of angiogenic factors with characteristics on individual and tissue level, subcutaneous white adipose tissue samples were taken from 45 children aged 0-9 years undergoing elective surgery. We measured the expression of vascular endothelial growth factor A (VEFGA), fibroblast growth factor 1 and 2 (FGF1, FGF2), angiopoietin 1 and 2 (ANGPT1, ANGPT2), TEK receptor tyrosine kinase (TEK), and von Willebrand factor (VWF). In addition, we determined the mean adipocyte size in histologic tissue sections. We found positive correlations of age with FGF1 and FGF2 and a negative correlation with ANGPT2, with pronounced differences in the first two years of life. FGF1, FGF2, and ANGPT1 correlated positively with adipocyte size. Furthermore, we identified a correlation of ANGPT1 and TEK with body mass index-standard deviation score (BMI-SDS), a measure to define childhood obesity. Except for ANGPT2, all angiogenic factors correlated positively with the endothelial marker VWF. In sum, our findings suggest that differences related to BMI-SDS begin early in childhood, and the analyzed angiogenic factors possess distinct roles in adipose tissue biology.

Beyond adiponectin and leptin: adipose tissue-derived mediators of inter-organ communication

The breakthrough discoveries of leptin and adiponectin more than two decades ago led to a widespread recognition of adipose tissue as an endocrine organ. Many more adipose tissue-secreted signaling mediators (adipokines) have been identified since then, and much has been learned about how adipose tissue communicates with other organs of the body to maintain systemic homeostasis. Beyond proteins, additional factors, such as lipids, metabolites, noncoding RNAs, and extracellular vesicles (EVs), released by adipose tissue participate in this process. Here, we review the diverse signaling mediators and mechanisms adipose tissue utilizes to relay information to other organs. We discuss recently identified adipokines (proteins, lipids, and metabolites) and briefly outline the contributions of noncoding RNAs and EVs to the ever-increasing complexities of adipose tissue inter-organ communication. We conclude by reflecting on central aspects of adipokine biology, namely, the contribution of distinct adipose tissue depots and cell types to adipokine secretion, the phenomenon of adipokine resistance, and the capacity of adipose tissue to act both as a source and sink of signaling mediators.

Tissue-mimicking gelatin scaffolds by alginate sacrificial templates for adipose tissue engineering

When adipose tissue (AT) is impaired by trauma or disease, AT engineering could provide a shelf-ready structural and functional restoration as alternative to current clinical treatments, which mainly aim at aesthetic replacement. Yet, the lack of an efficient vascular network within the scaffolds represents a major limitation to their translation application in patients. Here, we propose the use of microstructured crosslinked gelatin hydrogels with an embedded prevascular channel as scaffolding materials for AT engineering. The scaffolds are fabricated using - simultaneously - alginate-based microbeads and 3D printed filaments as sacrificial material encapsulated in gelatin at the point of material fabrication and removed post-crosslinking. This method yields the formation of microstructures that resemble the micro-architecture of physiological human fat tissue and of microvessels that can facilitate vascularization through anastomosis with patients' own blood vessels. The cytocompatible method used to prepare the gelatin scaffolds showed structural stability over time while allowing for cell infiltration and protease-based remodeling/degradation. Scaffolds' mechanical properties were also designed to mimic the one of natural breast adipose tissue, a key parameter for AT regeneration. Scaffold's embedded channel (∅ = 300-400 µm) allowed for cell infiltration and enabled blood flow in vitro when an anastomosis with a rat blood artery was performed using surgical glue. In vitro tests with human mesenchymal stem cells (hMSC) showed colonization of the porous structure of the gelatin hydrogels, differentiation into adipocytes and accumulation of lipid droplets, as shown by Oil Red O staining. STATEMENT OF SIGNIFICANCE: The potential clinical use of scaffolds for adipose tissue (AT) regeneration is currently limited by an unmet simultaneous achievement of adequate structural/morphological properties together with a promoted scaffold vascularization. Sacrificial materials, currently used either to obtain a tissue-mimicking structure or hollow channels to promote scaffold' vascularization, are powerful versatile tools for the fabrication of scaffolds with desired features. However, an integrated approach by means of sacrificial templates aiming at simultaneously achieving an adequate AT-mimicking structure and hollow channels for vascularization is missing. Here, we prove the suitability of crosslinked gelatin scaffolds obtained by using sacrificial alginate microbeads and 3D printed strands to achieve proper features and hollow channels useful for scaffolds vascularization.

Anti-angiogenic isoform of vascular endothelial growth factor-A in cardiovascular and renal disease

Accumulating evidence suggests that pathologic interactions between the heart and the kidney can contribute to the progressive dysfunction of both organs. Recently, there has been an increase in the prevalence of cardiovascular disease (CVD) and chronic kidney disease (CKD) due to increasing obesity rates. It has been reported that obesity causes various heart and renal disorders and appears to accelerate their progression. Vascular endothelial growth factor-A (VEGF-A) is a major regulator of angiogenesis and vessel permeability, and is associated with CVD and CKD. It is now recognized that alternative VEGF-A gene splicing generates VEGF-A isoforms that differ in their biological actions. Proximal splicing that includes an exon 8a sequence results in pro-angiogenic VEGF-A₁₆₅a, whereas distal splicing inclusive of exon 8b yields the anti-angiogenic isoform of VEGF-A (VEGF-A₁₆₅b). This review highlights several recent preclinical and clinical studies on the role of VEGF-A₁₆₅b in CVD and CKD as a novel function of VEGF-A. This review also discusses potential therapeutic approaches of the use of VEGF-A in clinical settings as a potential circulating biomarker for CVD and CKD.

Myeloid-specific deletion of thrombospondin 1 protects against inflammation and insulin resistance in long-term diet-induced obese male mice

Thrombospondin 1 (TSP1) is a multifunctional matricellular protein. Recent studies demonstrate that TSP1 is highly expressed in adipose tissue (AT) and positively associated with AT inflammation and insulin resistance (IR). In this study, the contribution of different cellular sources of TSP1 to obesity-induced metabolic complications is determined by using mice with either adipocyte or myeloid/macrophage-specific deletion of TSP1 in a diet-induced obese model. The results demonstrated that neither adipocyte nor myeloid/macrophage-specific deletion of TSP1 affected the development of long-term high-fat diet-induced obesity. Adipocyte-specific deletion of TSP1 did not protect mice from obesity-induced inflammation and IR. On the contrary, obese mice with myeloid/macrophage loss of TSP1 had reduced macrophage accumulation in AT, which was accompanied with reduced inflammation and improved glucose tolerance and insulin sensitivity compared with obese control mice. Reduced macrophage-derived-TGF-β1 signaling and adipose tissue fibrosis were also observed in long-term high-fat-fed mice with myeloid/macrophage-specific TSP1 deletion. Moreover, in vitro experiments demonstrated an autocrine effect of TSP1-mediated TGF-β activation in macrophages in obesity. Collectively this study highlights the critical contribution of myeloid/macrophage-derived TSP1 to obesity-associated chronic inflammation and IR, which may serve as a new therapeutic target for metabolic disease.

Plasticity of Adipose Tissue-Derived Stem Cells and Regulation of Angiogenesis

Adipose tissue is recognized as an important organ with metabolic, regulatory, and plastic roles. Adipose tissue-derived stem cells (ASCs) with self-renewal properties localize in the stromal vascular fraction (SVF) being present in a vascular niche, thereby, contributing to local regulation of angiogenesis and vessel remodeling. In the past decades, ASCs have attracted much attention from biologists and bioengineers, particularly, because of their multilineage differentiation potential, strong proliferation, and migration abilities in vitro and high resistance to oxidative stress and senescence. Current data suggest that the SVF serves as an important source of endothelial progenitors, endothelial cells, and pericytes, thereby, contributing to vessel remodeling and growth. In addition, ASCs demonstrate intriguing metabolic and interlineage plasticity, which makes them good candidates for creating regenerative therapeutic protocols, in vitro tissue models and microphysiological systems, and tissue-on-chip devices for diagnostic and regeneration-supporting purposes. This review covers recent achievements in understanding the metabolic activity within the SVF niches (lactate and NAD+ metabolism), which is critical for maintaining the pool of ASCs, and discloses their pro-angiogenic potential, particularly, in the complex therapy of cardiovascular and cerebrovascular diseases.

The role of placental growth factor (PlGF) and its receptor system in retinal vascular diseases

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. Upon binding to VEGF- and neuropilin-receptor sub-types, PlGF modulates a range of neural, glial and vascular cell responses that are distinct from VEGF-A. As PlGF expression is selectively associated with pathological angiogenesis and inflammation, its blockade does not affect the healthy vasculature. PlGF actions have been extensively described in tumor biology but more recently there has been accumulating preclinical evidence that indicates that this growth factor could have an important role in retinal diseases. High levels of PlGF have been found in aqueous humor, vitreous and/or retina of patients exhibiting retinopathies, especially those with diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD). Expression of this growth factor seems to correlate closely with many of the key pathogenic features of early and late retinopathy in preclinical models. For example, studies using genetic modification and/or pharmacological treatment to block PlGF in the laser-induced choroidal neovascularization (CNV) model, oxygen-induced retinopathy model, as well as various murine diabetic models, have shown that PlGF deletion or inhibition can reduce neovascularization, retinal leakage, inflammation and gliosis, without affecting vascular development or inducing neuronal degeneration. Moreover, an inhibitory effect of PlGF blockade on retinal scarring in the mouse CNV model has also been recently demonstrated and was found to be unique for PlGF inhibition, as compared to various VEGF inhibition strategies. Together, these preclinical results suggest that anti-PlGF therapy might have advantages over anti-VEGF treatment, and that it may have clinical applications as a standalone treatment or in combination with anti-VEGF. Additional clinical studies are clearly needed to further elucidate the role of PlGF and its potential as a therapeutic target in ocular diseases.

Clinical Presentation of Preeclampsia and the Diagnostic Value of Proteins and Their Methylation Products as Biomarkers in Pregnant Women with Preeclampsia and Their Newborns

Preeclampsia (PE) is a disorder which affects 1-10% of pregnant women worldwide. It is characterised by hypertension and proteinuria in the later stages of gestation and can lead to maternal and perinatal morbidity and mortality. Other than the delivery of the foetus and the removal of the placenta, to date there are no therapeutic approaches to treat or prevent PE. It is thus only possible to reduce PE-related mortality through early detection, careful monitoring, and treatment of the symptoms. For these reasons the search for noninvasive, blood-borne, or urinary biochemical markers that could be used for the screening, presymptomatic diagnosis, and prediction of the development of PE is of great urgency. So far, a number of biomarkers have been proposed for predicting PE, based on pathophysiological observations, but these have mostly proven to be unreliable and inconsistent between different studies. The clinical presentation of PE and data gathered for the biochemical markers placental growth factor (PlGF), soluble Feline McDonough Sarcoma- (fms-) like tyrosine kinase-1 (sFlt-1), asymmetric dimethylarginine (ADMA), and methyl-lysine is being reviewed with the aim of providing both a clinical and biochemical understanding of how these biomarkers might assist in the diagnosis of PE or indicate its severity.

Three-dimensional volume fluorescence-imaging of vascular plasticity in adipose tissues

Objective

The vascular system is central to sustaining tissue survival and homeostasis. Blood vessels are densely present in adipose tissues and exert essential roles in their metabolism. However, conventional immunohistochemistry methods have intrinsic limitations in examining the 3D vascular network in adipose tissues as well as other organs in general.

Methods

We established a 3D volume fluorescence-imaging technique to visualize the vasculatures in mouse adipose tissues by combining the optimized steps of whole-mount immunolabeling, tissue optical clearing, and lightsheet volume fluorescence-imaging. To demonstrate the strength of this novel imaging procedure, we comprehensively assessed the intra-adipose vasculatures under obese conditions or in response to a cold challenge.

Results

We show the entirety of the vascular network in mouse adipose tissues on the whole-tissue level at a single-capillary resolution for the first time in the field. We accurately quantify the pathological changes of vasculatures in adipose tissues in wild-type or obese mice (ob/ob, db/db, or diet-induced obesity). In addition, we identify significant and reversible changes of the intra-adipose vasculatures in the mice subjected to cold challenge (i.e., 4°). Furthermore, we demonstrate that the cold-induced vascular plasticity depends on the sympathetic-derived catecholamine signal and is involved in the beiging process of white adipose tissues.

Conclusions

We report a 3D volume fluorescence-imaging procedure that is compatible with many areas of vascular research and is poised to serve the field in future investigations of the vascular system in adipose tissues or other research scenarios.

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3D vascular network in adipose tissues is visualized at single-capillary resolution.

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Pathological remodeling of vasculatures is characterized under the obese conditions.

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Vascular plasticity during cold challenge is involved in the beiging process of WAT.

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Sympathetic-derived catecholamine signal regulates the vascular plasticity in WAT.

Antiangiogenic Herbal Composition Ob-X Reduces Abdominal Visceral Fat in Humans: A Randomized, Double-Blind, Placebo-Controlled Study

Adipose tissue growth is angiogenesis-dependent, and angiogenesis inhibitors can regulate adipose tissue mass by cutting off the blood supply. We examined whether antiangiogenic herbal composition Ob-X can reduce fast-growing abdominal fat, especially visceral fat in humans by inhibiting angiogenesis. Eighty abdominally obese subjects (body mass index: 25-29.9 kg/m², waist circumference: exceeding 90 cm for males and 85 cm for females) participated in a 12-week randomized, double-blind, placebo-controlled human study to evaluate the efficacy and safety of Ob-X. 690 mg of Ob-X was administered orally twice a day. The Ob-X group showed a noticeable reduction in visceral fat of 20.5% after the 12-week treatment as compared to baseline measured by computed tomography. The change in visceral fat in the Ob-X group was statistically significant as compared to the placebo group (p = 0.0495) and 1.9 times higher than in the placebo group. Therefore, angiogenesis inhibitor Ob-X has the potential to improve obesity-related metabolic syndrome by reducing dangerous visceral fat.

Placental growth factor (PlGF) is linked to inflammation and metabolic disorders in mice with diet-induced obesity

Placental growth factor (PlGF), a member of the vascular endothelial growth factor (VEGF) sub-family, plays a major role in angiogenesis and vasculogenesis. Previous study demonstrated that PlGF-overexpressing transgenic (Tg) mice had gestational loss. In addition, PlGF secretion was up-regulated in isolated T lymphocytes (T-cell) upon CD3/CD28 stimulation, suggesting that PlGF could be a regulator of T-cell differentiation and development. T-cells are well known to play a critical role in obesity-induced inflammation. Therefore, to verify the possible link of diet-induced obesity (DIO) with inflammation and related metabolic disorders, such as insulin resistance, we fed high-fat diet (HFD) to Tg mice for 16 weeks. Adiposity and glucose intolerance significantly increase in Tg mice fed a HFD (Tg HFD) compared to wild-type (WT) mice fed HFD (WT HFD). In addition, macrophage infiltrations were significantly higher in the epididymal white adipose tissue (EWAT), liver, and pancreatic islets of Tg HFD mice compared to WT HFD mice. In the in vitro study, we showed that isolated CD4⁺ T-cells from Tg mice further differentiate into type 1 (Th1) and type 17 (Th17) helper T-cells via CD3/CD28 stimulation. Furthermore, we observed that the pro-inflammatory cytokines IL-6, IL-17, and TNFα, are remarkably increased in Tg mice compared to WT mice. These findings demonstrate that PlGF overexpression in T-cells might lead to inflammatory T-cell differentiation and accumulation in adipose tissue (AT) or metabolism-related tissues, contributing to the development of systemic metabolic disorders. Thus, PlGF may provide an effective therapeutic target in the management of obesity-induced inflammation and related metabolic disorders.

Nanomedicine for obesity treatment

Obesity, as a chronic condition, has been a serious public health issue over the last decades both in the affluent Western world and developing countries. As reported, the risk of several serious diseases increases with weight gain, including type 2 diabetes, coronary heart disease, cancer, and respiratory diseases. In addition to lifestyle modifications, pharmacotherapy has become an important strategy to control weight gain. However, most of the anti-obesity drugs often show poor outcome for weight-loss and cause severe adverse effects. This review surveys recent advances in nanomedicine as an emerging strategy for obesity treatment with an emphasis on the enhanced therapeutic efficiency and minimized side effects. The insights for future development are also discussed.

Targeted disruption of the iNOS gene improves adipose tissue inflammation and fibrosis in leptin-deficient ob/ob mice: role of tenascin C

BACKGROUND/OBJECTIVES

Obesity is related to a dynamic extracellular matrix (ECM) remodeling, which involves the synthesis and degradation of different proteins, such as tenascin C (TNC) in the adipose tissue (AT). Given the functional relationship between leptin and inducible nitric oxide synthase (iNOS), our aim was to analyze the impact of the absence of the iNOS gene in AT inflammation and ECM remodeling in ob/ob mice.

SUBJECTS/METHODS

The expression of genes involved in inflammation and ECM remodeling was evaluated in 10-week-old male double knockout (DBKO) mice simultaneously lacking the ob and iNOS genes as well as in ob/ob mice classified into three groups [control, leptin-treated (1 mg kg^-1 day^-1) and pair-fed].

RESULTS

Leptin deficiency increased inflammation and fibrosis in AT. As expected, leptin treatment improved the obesity phenotype. iNOS deficiency in ob/ob mice improved insulin sensitivity, AT inflammation, and ECM remodeling, as evidenced by lower AT macrophage infiltration and collagen deposition, a downregulation of proinflammatory and profibrogenic genes Tnf, Emr1, Hif1a, Col6a1, Col6a3, and Tnc, as well as lower circulating TNC levels. Interestingly, leptin upregulated TNC expression and release in 3T3-L1 adipocytes, and iNOS knockdown in 3T3-L1 fat cells produced a significant decrease in basal and leptin-induced Tnc expression.

CONCLUSIONS

Ablation of iNOS in leptin-deficient mice improved AT inflammation and ECM remodeling-related genes, attenuating fibrosis, and metabolic dysfunction. The activation of iNOS by leptin is necessary for the synthesis and secretion of TNC in adipocytes, suggesting an important role of this alarmin in the development of AT inflammation and fibrosis.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Adipose tissue angiogenesis in obesity

Adipose tissue is the most plastic tissue in all multicellular organisms, being constantly remodelled along with weight gain and weight loss. Expansion of adipose tissue must be accompanied by that of its vascularisation, through processes of angiogenesis, whereas weight loss is associated with the regression of blood vessels. Adipose tissue is thus among the tissues that have the highest angiogenic capacities. These changes of the vascular bed occur through close interactions of adipocytes with blood vessels, and involve several angiogenic factors. This review presents studies that are the basis of our understanding of the regulation of adipose tissue angiogenesis. The growth factors that are involved in the processes of angiogenesis and vascular regression are discussed with a focus on their potential modulation for the treatment of obesity. The hypothesis that inflammation of adipose tissue and insulin resistance could be related to altered angiogenesis in adipose tissue is presented, as well as the beneficial or deleterious effect of inhibition of adipose tissue angiogenesis on metabolic diseases.

Long-Term Effects of Weight Loss and Exercise on Biomarkers Associated with Angiogenesis

Background: We tested the effect of weight loss on circulating levels of the angiogenic factors VEGF and pigment epithelium-derived factor (PEDF) in postmenopausal overweight/obese women, 18 months after completing a year-long 4-arm randomized controlled trial of behavioral weight loss and/or exercise versus control (i.e., 30 months postrandomization).Methods: The 439 overweight/obese, postmenopausal women, ages 50 to 75 years, were randomized to: diet (goal: 10% weight loss, N = 118), exercise (225 min/wk moderate-to-vigorous activity, N = 117), diet + exercise (N = 117), or control (N = 87). At 12 months, 399 women gave a blood sample; 156 returned at 30 months. Biomarkers were measured by immunoassay. Changes were compared using generalized estimating equations, adjusting for baseline BMI, age, and race/ethnicity.Results: Participants randomized to diet, exercise, and diet + exercise arms had greater reductions in VEGF at 30 months (-14.1% P = 0.02; -19.7% P = 0.003; -14.5% P = 0.002, respectively) versus controls (-4.5%). There were no statistically significant changes in PEDF in any intervention arm. Participants maintaining ≥10% of baseline weight loss at 30 months had greater reductions in VEGF versus those who gained weight/had no weight change (-22.3% vs. -10.2% respectively, P = 0.002). Participants maintaining any weight loss had significantly lower levels of PEDF at 30 months versus those who gained weight/no weight change.Conclusions: Sustained weight loss via diet and/or exercise results in reductions in angiogenic factors, and can be maintained up to 30-month follow-up. Limitations include relatively small numbers, and possible bias toward more successful weight loss among women who returned at 30 months.Impact: Maintaining weight loss can achieve long-term reductions in biomarkers of angiogenesis that can persist up to 18 months after completion of a weight loss intervention. Cancer Epidemiol Biomarkers Prev; 26(12); 1788-94. ©2017 AACR.

Vascular Endothelial Regulation of Obesity-Associated Insulin Resistance

Obesity is a worldwide epidemic that predisposes individuals to metabolic complications, such as type 2 diabetes mellitus and non-alcoholic fatty liver disease, all of which are related to an imbalance between food intake and energy expenditure. Identification of the pathogenic molecular mechanisms and effective therapeutic approaches are urgently needed. A well-accepted paradigm is that crosstalk between organs/tissues contributes to diseases. Endothelial dysfunction characterizes metabolic disorders and the related vascular complications. Over the past two decades, overwhelming studies have focused on mechanisms that lead to endothelial dysfunction. New investigations, however, have begun to appreciate the opposite direction of the crosstalk: endothelial regulation of metabolism, although the underlying mechanisms remain to be elucidated. This review summarizes the evidence that supports the concept of endothelial regulation of obesity and the associated insulin resistance in fat, liver, and skeletal muscles, the classic targets of insulin. Outstanding questions and future research directions are highlighted. Identification of the mechanisms of vascular endothelial regulation of metabolism may offer strategies for prevention and treatment of obesity and the related metabolic complications.

Angiopoietin-2 in white adipose tissue improves metabolic homeostasis through enhanced angiogenesis

Despite many angiogenic factors playing crucial roles in metabolic homeostasis, effects of angiopoietin-2 (ANG-2) in adipose tissue (AT) remain unclear. Utilizing a doxycycline-inducible AT-specific ANG-2 overexpression mouse model, we assessed the effects of ANG-2 in AT expansion upon a high-fat diet (HFD) challenge. ANG-2 is significantly induced, with subcutaneous white AT (sWAT) displaying the highest ANG-2 expression. ANG-2 overexpressing mice show increased sWAT vascularization and are resistant to HFD-induced obesity. In addition, improved glucose and lipid metabolism are observed. Mechanistically, the sWAT displays a healthier expansion pattern with increased anti-inflammatory macrophage infiltration. Conversely, ANG-2 neutralization in HFD-challenged wild-type mice shows reduced vascularization in sWAT, associated with impaired glucose tolerance and lipid clearance. Blocking ANG-2 causes significant pro-inflammatory and pro-fibrotic changes, hallmarks of an unhealthy AT expansion. In contrast to other pro-angiogenic factors, such as vascular endothelial growth factor-A (VEGF-A), this is achieved without any enhanced beiging of white AT.

DOI:http://dx.doi.org/10.7554/eLife.24071.001

The ominous triad of adipose tissue dysfunction: inflammation, fibrosis, and impaired angiogenesis

There are three dominant contributors to the pathogenesis of dysfunctional adipose tissue (AT) in obesity: unresolved inflammation, inappropriate extracellular matrix (ECM) remodeling and insufficient angiogenic potential. The interactions of these processes during AT expansion reflect both a linear progression as well as feed-forward mechanisms. For example, both inflammation and inadequate angiogenic remodeling can drive fibrosis, which can in turn promote migration of immune cells into adipose depots and impede further angiogenesis. Therefore, the relationship between the members of this triad is complex but important for our understanding of the pathogenesis of obesity. Here we untangle some of these intricacies to highlight the contributions of inflammation, angiogenesis, and the ECM to both "healthy" and "unhealthy" AT expansion.

Placental growth factor: What hematologists need to know

Although first identified in placenta, the angiogenic factor known as placental growth factor (PlGF) can be widely expressed in ischemic or damaged tissues. Recent studies have indicated that PlGF is a relevant factor in the pathobiology of blood diseases including hemoglobinopathies and hematologic malignancies. Therapies for such blood diseases may one day be based upon these and ongoing investigations into the role of PlGF in sickle cell disease, acute and chronic leukemias, and complications related to hematopoietic cell transplantation. In this review, we summarize recent studies regarding the potential role of PlGF in blood disorders and suggest avenues for future research.

Obesity and Cancer: An Angiogenic and Inflammatory Link

With the current epidemic of obesity, a large number of patients diagnosed with cancer are overweight or obese. Importantly, this excess body weight is associated with tumor progression and poor prognosis. The mechanisms for this worse outcome, however, remain poorly understood. We review here the epidemiological evidence for the association between obesity and cancer, and discuss potential mechanisms focusing on angiogenesis and inflammation. In particular, we will discuss how the dysfunctional angiogenesis and inflammation occurring in adipose tissue in obesity may promote tumor progression, resistance to chemotherapy, and targeted therapies such as anti-angiogenic and immune therapies. Better understanding of how obesity fuels tumor progression and therapy resistance is essential to improve the current standard of care and the clinical outcome of cancer patients. To this end, we will discuss how an anti-diabetic drug such as metformin can overcome these adverse effects of obesity on the progression and treatment resistance of tumors.

Effects of sleeve gastrectomy and rs9930506 FTO variants on angiopoietin/Tie-2 system in fat expansion and M1 macrophages recruitment in morbidly obese subjects

Angiogenesis in inflammation are hallmarks for adipose tissue expansion in obesity. The role of angiopoietin/Tie-2 system in adipose tissue expansion and immune cell recruitment is unclear. We studied the effect of sleeve gastrectomy and the influence of FTO rs9930506 polymorphism on Tie-2, angiopoietin-1 and angiopoietin-2 expression in morbid obesity. Fifteen morbidly obese subjects (4 men and 11 women) aged 24-55 years were followed-up 3 and 6 months after sleeve gastrectomy. Serum sTie-2, angiopoietin-1, angiopoietin-2, and hypoxia-inducible factor-1α concentrations were determined by ELISA. Tie-2 and its ligands in visceral and subcutaneous adipose tissue were localized by immunohistochemistry. Tie-2 expression was measured by flow cytometry in circulating monocytes and infiltrated macrophages. Comparisons before and after sleeve gastrectomy were carried out using ANOVA for repeated measures. rs9930506FTO genotyping was performed by PCR-RFLP. Circulating sTie-2 and angiopoietin-2 were higher before sleeve gastrectomy. Tie-2 and angiopoietin-2 mRNA levels were higher in subcutaneous adipose tissue than visceral and both decreased after surgery. Monocytes and infiltrated macrophages showed a pro-inflammatory phenotype, with increased Tie-2 expression that decreased 3 and 6 months after sleeve gastrectomy. Baseline sTie-2 correlated inversely with adiponectin levels. At baseline the rs9930506FTO AG ó GG genotypes carriers had more 34 kg than genotype carriers of rs9930506 AA. Weight and body mass index decreased at 6 months. We found that angiopoietin/Tie-2 system is mainly expressed in subcutaneous adipose tissue, contributing to expandability, fat accumulation, and monocytes attachment in obesity. Bariatric surgery favorably modifies the pro-angiogenic profile, allowed a reduced angiogenic expression in the circulation and adipose tissue.

Placental Growth Factor Is Secreted by the Human Endometrium and Has Potential Important Functions during Embryo Development and Implantation

Embryo implantation requires synchronized dialogue between the receptive endometrium and activated blastocyst via locally produced soluble mediators. During the mid-secretory (MS) phase of the menstrual cycle, increased glandular secretion into the uterine lumen provides important mediators that modulate the endometrium and support the conceptus during implantation. Previously we demonstrated the importance of vascular endothelial growth factor (VEGF) in the human uterus, particularly with respect to embryo implantation. In the current study, proteomic analysis of human uterine lavage fluid identified the presence of placental growth factor (PlGF) a homolog of VEGF, that binds the VEGF receptor 1 (VEGFR1). Analysis of immunostaining for PlGF in human endometrial tissue across the menstrual cycle (from both fertile and infertile women) revealed PlGF was predominantly localised to glandular and luminal epithelial cells, with staining in the decidualising stromal cells surrounding the maternal spiral arteries in the secretory phase of the menstrual cycle. Immunoreactive PlGF was also detected in subpopulations of endometrial leukocytes. Functional studies demonstrated that culturing mouse embryos with recombinant human (rh)PlGF enhanced blastocyst cell number and outgrowth. Furthermore, treatment of human endometrial epithelial cells (EEC) with rhPlGF enhanced EEC adhesion. Taken together, these data demonstrate that PlGF is abundant in the human endometrium, and secreted into the uterine lumen where it mediates functional changes in cellular adhesion with important roles in implantation.

Depot-specific differences in angiogenic capacity of adipose tissue in differential susceptibility to diet-induced obesity

Objective

Adipose tissue (AT) expansion requires AT remodeling, which depends on AT angiogenesis. Modulation of AT angiogenesis could have therapeutic promise for the treatment of obesity. However, it is unclear how the capacity of angiogenesis in each adipose depot is affected by over-nutrition. Therefore, we investigated the angiogenic capacity (AC) of subcutaneous and visceral fats in lean and obese mice.

Methods

We compared the AC of epididymal fat (EF) and inguinal fat (IF) using an angiogenesis assay in diet-induced obese (DIO) mice and diet-resistant (DR) mice fed a high-fat diet (HFD). Furthermore, we compared the expression levels of genes related to angiogenesis, macrophage recruitment, and inflammation using RT-qPCR in the EF and IF of lean mice fed a low-fat diet (LFD), DIO mice, and DR mice fed a HFD.

Results

DIO mice showed a significant increase in the AC of EF only at 22 weeks of age compared to DR mice. The expression levels of genes related to angiogenesis, macrophage recruitment, and inflammation were significantly higher in the EF of DIO mice than in those of LFD mice and DR mice, while expression levels of genes related to macrophages and their recruitment were higher in the IF of DIO mice than in those of LFD and DR mice. Expression of genes related to angiogenesis (including Hif1a, Vegfa, Fgf1, Kdr, and Pecam1), macrophage recruitment, and inflammation (including Emr1, Ccr2, Itgax, Ccl2, Tnf, and Il1b) correlated more strongly with body weight in the EF of HFD-fed obese mice compared to that of IF.

Conclusions

These results suggest depot-specific differences in AT angiogenesis and a potential role in the susceptibility to diet-induced obesity.

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Angiogenic capacity (AC) of visceral fat is greater in DIO mice than in DR mice.

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AC of subcutaneous fat is not different between DIO and DR mice.

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AC of visceral fat correlated more strongly with body weight than subcutaneous fat.

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Fat depot-specific differences in AC exist in mice.

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The depot specificity may differentially contribute to the susceptibility to obesity.