VEGF-B Improves Metabolic Health through Vascular Pruning of Fat

Extracellular vesicles from cyclic mice modulate liver transcriptome in estroupause mice independent of age

Extracellular vesicles (EVs) of different sizes are secreted by cells and may contain microRNAs (miRNAs) among its cargo. These miRNAs in EVs can induce changes in gene expression and function of recipient cells. In different cells EVs content can change with age and physiological state affecting tissue function. Based on this, the aim of this study was to characterize the miRNA content and role of small EVs (sEVs) from cyclic female mice in the modulation of liver transcriptome in estropausal mice. Two-month-old female mice were induced to estropause using 4-vinylcyclohexene diepoxide (VCD). At six months of age, VCD-treated mice were divided into placebo group (VCD) and sEVs treated group (VCD + sEVs), which received 10 injections at 3-day intervals of sEVs isolated from serum of donor cyclic female mice. A group of cyclic mice also received placebo injection and served as controls (CTL). sEVs injection in mice undergoing estropause had no effect on body mass, insulin sensitivity or organ weight. We observed ten miRNAs differentially regulated in serum sEVs of VCD compared to CTL mice. In the liver we observed 931 genes differentially expressed in VCD + sEVs compared to VCD mice. Interestingly, eight pathways were up-regulated in liver by VCD treatment and down-regulated by sEVs treatment, indicating that sEVs from cyclic mice can reverse changes promoted by estropause in liver. The expression of Cyp4a12a, which is male-specific, was elevated in VCD females but not normalized by sEVs treatment. Our findings indicate that miRNA content in sEVs is regulated by estropause in mice independent of age. Additionally, treatment of estropausal mice with sEVs from cyclic mice can partially reverse changes in the liver transcriptome.

EXOSOMES FROM CYCLIC MICE MODULATE LIVER TRANSCRIPTOME IN ESTROUPAUSE MICE INDEPENDENT OF AGE

Background

Exosomes are extracellular vesicles secreted by cells that contain microRNAs (miRNAs). These miRNAs can induce changes in gene expression and function of recipient cells. In different cells exosome content can change with age and physiological state affecting tissues function and health.

Aims

Therefore, the aim of this study was to characterize the miRNA content and role of exosomes from cyclic female mice in the modulation of liver transcriptome in estropausal mice.

Main Methods

Two-month-old female mice were induced to estropause using 4-vinylcyclohexene diepoxide (VCD). At six months of age VCD-treated mice were divided in control group (VCD) and exosome treated group (VCD+EXO), which received 10 injections at 3-day intervals of exosomes extracted from serum of cyclic female mice (CTL).

Key findings

Exosome injection in estropausal mice had no effect on body mass, insulin sensitivity or organ weight. We observed ten miRNAs differentially regulated in serum exosomes of VCD compared to CTL mice. In the liver we observed 931 genes differentially expressed in VCD+EXO compared to VCD mice. Interestingly, eight pathways were up-regulated in liver by VCD treatment and down-regulated by exosome treatment, indicating that exosomes from cyclic mice can reverse changes promoted by estropause in liver. Cyp4a12a expression which is male-specific was increased in VCD females and not reversed by exosome treatment.

Significance

Our findings indicate that miRNAs content in exosomes is regulated by estropause in mice independent of age. Additionally, treatment of estropausal mice with exosomes from cyclic mice can partially reverse changes in liver transcriptome.

Adipose endothelial cells mastering adipose tissues metabolic fate

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

Reducing VEGFB expression regulates the balance of glucose and lipid metabolism in mice via VEGFR1

In recent years, studies have demonstrated that vascular endothelial growth factor B (VEGFB) can affect the metabolism of fatty acids and glucose, and it is expected to become a target for the diagnosis and treatment of metabolic diseases such as obesity and diabetes. At present, the specific mechanism that VEGFB regulates lipid and glucose metabolism balance is not completely understood. The present study used systemic VEGFB gene-knockout mice to investigate the effects of downregulation of the VEGFB gene on lipid metabolism and insulin secretion, and to explore the mechanism of the VEGFB pathway involved in the regulation of glucose and lipid metabolism. The morphological changes in the liver and pancreas of mice after VEGFB gene deletion were observed under a light microscope and a scanning electron microscope, and the effects of VEGFB gene deletion on lipid metabolism and blood glucose balance were detected by a serological technique. The detection indexes included total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol. Simultaneously, fasting blood glucose, glycosylated hemoglobin A1c (HbA1c), fasting insulin and glucagon were measured. Insulin sensitivity was assessed by using the insulin tolerance tests and glucose tolerance tests, and function of β-cell islets was evaluated by using the insulin resistance index (HOMA-IR) and pancreatic β-cell secretion index (HOMA-β). Τhe protein expression changes of vascular endothelial growth factor receptor 1 (VEGFR1) and vascular endothelial growth factor receptor 2 (VEGFR2) in mouse islets were detected by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) after the VEGFB gene was knocked down to analyze the mechanism of VEGFB that may be involved in glucose and lipid metabolism. It was observed that after VEGFB was knocked down, mouse hepatocytes exhibited steatosis and increased secretory vesicles in islet cells. The lipid metabolism indexes such as TG, TC and LDL increased significantly; however, the levels of FBS, postprandial blood glucose and HbA1c decreased, whereas the glucose tolerance increased. Serum insulin secretion increased and HOMA-IR decreased since VEGFB was knocked down. Western blotting and RT-qPCR results revealed that the expression levels of VEGFR1 and neuropilin-1 decreased after the VEGFB gene was knocked down, while the expression levels of VEGFA and VEGFR2 increased. The absence of VEGFB may be involved in the regulation of glucose and lipid metabolism in mice by activating the VEGFA/VEGFR2 signaling pathway. VEGFB is expected to become a new target for the treatment of metabolic diseases such as obesity and diabetes. At present, the mechanism of VEGFB involved in regulating lipid metabolism and glucose metabolism is not completely clear. It was identified that downregulating VEGFB improved lipid metabolism and insulin resistance. The role of VEGFB/VEGFR1 pathway and other family members in regulating glucose and lipid metabolism was detected, which provided a theoretical and experimental basis for VEGFB to affect the regulation of glucose and lipid metabolism balance.

Vascular endothelial growth factor B exerts lipid-lowering effect by activating AMPK via VEGFR1

As an ambiguous member of vascular endothelial growth factor family, VEGF-B has long been poorly understood in its function. Recent researches showed VEGF-B isoforms exerted their metabolic effect through indirectly activating the VEGF-A/VEGFR2 pathway. Here, we report the lipid-lowing effect of VEGF-B via VEGFR1. We investigated the effect of VEGF-B on lipid metabolism in vivo and in vitro approaches. Treatment of mice with VEGF-B recombinant protein repressed HFD-induced body weight gain. This treatment also alleviated obesity associated hyperlipidemia and fatty liver disease. In the muscle and liver of VEGF-B-treated HFD mice were observed increased protein expression of carnitine palmitoyltransferase-1 (CPT-1) and the phosphorylation of ACC and AMP-activated protein kinase (AMPK). This effect was confirmed in HepG2 cells incubated with VEFG-B in which the increased AMPK activation and CPT-1 expression occurs due to activation of Calcium/calmodulin-dependent Protein Kinase β (CaMKKβ) by VEFG-B. VEGF-B increased expression of key genes responsible for lipid oxidation while reducing those for fatty acid synthesis in vivo and in vitro. In addition, the selective inhibitor of VEGFR1 blocked the lipid clearance effect of VEGF-B in HepG2. Our study unraveled unknown role of VEGF-B/VEGFR1 signaling in regulating lipid metabolism. Furthermore, our findings indicate that VEGF-B may have beneficial effects for the treatment of dyslipidemia.

miR-345-5p regulates adipogenesis via targeting VEGF-B

Adipocyte differentiation involves a series of highly synergistic processes, including clone amplification, proliferation arrest, and terminal differentiation. However, the mechanisms that control these different steps remain unclear. Emerging studies support that miRNAs play an important role in regulating adipogenesis. In this study, we found that the expression of miR-345-5p decreased during adipogenic differentiation, and overexpression of miR-345-5p reduced lipid accumulation in adipocytes and the expression of adipocyte related genes essential to lipogenic transcription, fatty acid synthesis and fatty acid transport. In addition, miR-345-5p directly targeted the 3'UTR of vascular endothelial growth factor B, and miR-345-5p mimic inhibited the expression of vascular endothelial growth factor B at both mRNA and protein levels. In conclusion, our results demonstrate that miR-345-5p inhibits adipocyte differentiation via targeting vascular endothelial growth factor B.

Decidual Vasculopathy and Spiral Artery Remodeling Revisited III: Hypoxia and Re-oxygenation Sequence with Vascular Regeneration

Aim: Spiral artery remodeling at early pregnancy is characterized by two distinct mechanisms with two morphologic features, namely, trophoblastic-dependent vascular invasion with “plugging”, and trophoblastic-independent mural muscular hypertrophy/hyperplasia, both of which lead to the blocking or narrowing of the arterial lumen with the consequence of reduced maternal blood flow to the developing embryo. Methods: Review of historic literature in light of the new discovery of CD56 (NCAM) expression on endovascular trophoblasts at late gestation, in relation to placental lateral growth with vascular regeneration. Results: Reduced maternal blood flow to the embryo results in a hypoxic condition critical for trophectoderm differentiation and proliferation. Hypoxia is also important for the development of hemangioblasts of vasculogenesis, and hematopoiesis of the placental villi. Up to 13 weeks, both uteroplacental and fetoplacental circulations are established and hypoxic condition relieved for normal fetal/placenta development by ultrasonography. The persistence of trophoblastic plugging and/or mural muscular hypertrophy/hyperplasia leads to persistent reduced maternal blood flow to the placenta, resulting in persistent hypoxia and increased angiogenesis, with a constellation of pathologic features of maternal vascular malperfusion atlate gestation. Wilm’s tumor gene (WT1) expression appears to be central to steroid and peptide hormonal actions in early pregnancy, and vascular regeneration/restoration after pregnancy. Conclusions: Spiral artery remodeling at early pregnancy leads to hypoxia with vascular transformation, and the establishment of uteroplacental circulation results in relief of hypoxia. The hypoxia–re-oxygenation sequence may provide insights into the mechanism of normal fetal/placental development and associated pregnancy complications, such as preeclampsia.

Platycodon grandiflorus Root Ethanol Extract Induces Lipid Excretion, Lipolysis, and Thermogenesis in Diet-Induced Obese Mice

Adipocytes regulate lipid metabolism according to physiological energy requirements. A dysfunctional lipid metabolism can lead to obesity and its complications such as hepatic steatosis, diabetes, and hyperlipidemia. In our study, the impact of Platycodon grandiflorus root ethanol extract (PGH) on lipid excretion and thermogenesis-related markers in diet-induced obesity mice was analyzed. Our data show that PGH elevated fatty acid uptake in epididymal adipose tissue by increasing Cd36, Slc27a1, Ffar2, and Ffar4 expression, which led to decreased blood free fatty acid concentrations. Moreover, PGH normalized body weight and fat mass in diet-induced obese mice by increasing lipolysis (Plin1, Atgl, and Hsl) and fatty acid oxidation. Changes in the levels of browning-related genes, enzyme activity of carnitine palmitoyltransferase, and the overall transcriptome (Bmp4, Cidec, Ucp3, Sirt3, and Cox4i1) led to promote brown adipose tissue-like features (browning) in epididymal white adipose tissue and enhanced energy expenditure. Our results suggest that PGH promotes lipid excretion and thermogenic function in high-fat diet-induced obese mice, which are mediated by regulation of fat metabolism.

Multiancestry Genome-Wide Association Study of Lipid Levels Incorporating Gene-Alcohol Interactions

A person's lipid profile is influenced by genetic variants and alcohol consumption, but the contribution of interactions between these exposures has not been studied. We therefore incorporated gene-alcohol interactions into a multiancestry genome-wide association study of levels of high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides. We included 45 studies in stage 1 (genome-wide discovery) and 66 studies in stage 2 (focused follow-up), for a total of 394,584 individuals from 5 ancestry groups. Analyses covered the period July 2014-November 2017. Genetic main effects and interaction effects were jointly assessed by means of a 2-degrees-of-freedom (df) test, and a 1-df test was used to assess the interaction effects alone. Variants at 495 loci were at least suggestively associated (P < 1 × 10-6) with lipid levels in stage 1 and were evaluated in stage 2, followed by combined analyses of stage 1 and stage 2. In the combined analysis of stages 1 and 2, a total of 147 independent loci were associated with lipid levels at P < 5 × 10-8 using 2-df tests, of which 18 were novel. No genome-wide-significant associations were found testing the interaction effect alone. The novel loci included several genes (proprotein convertase subtilisin/kexin type 5 (PCSK5), vascular endothelial growth factor B (VEGFB), and apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (APOBEC1) complementation factor (A1CF)) that have a putative role in lipid metabolism on the basis of existing evidence from cellular and experimental models.

Novel multi-targeted inhibitors suppress ocular neovascularization by regulating unique gene sets

Neovascular diseases, such as many cancers and ocular disorders, are life threatening and devastating. Although anti-vascular endothelial growth factor A (VEGF-A) therapy is available, many patients are not responsive and drug resistance can develop. To try to overcome these problems, combination therapy targeting VEGF-A and platelet-derived growth factor B (PDGF-B) was tested. However, one obvious drawback was that the other VEGF and PDGF family members were not inhibited and therefore could compensate. Indeed, this was, at least to some extent, demonstrated by the disappointing outcomes. To this end, we designed novel multi-targeted inhibitors that can block most of the VEGF and PDGF family members simultaneously by making a fusion protein containing the ligand-binding domains of vascular endothelial growth factor receptor 1 (VEGFR1), vascular endothelial growth factor receptor 2 (VEGFR2) and platelet-derived growth factor receptor beta (PDGFRβ), which can therefore act as a decoy blocker for most of the VEGF and PDGF family members. Indeed, in cultured cells, the novel inhibitors suppressed the migration and proliferation of both vascular endothelial cells and smooth muscle cells, and abolished VEGFR2 and PDGFRβ activation. Importantly, in a choroidal neovascularization model in vivo, the novel inhibitor inhibited ocular neovascularization more efficiently than the mono-inhibitors against VEGFR or PDGFR alone respectively. Mechanistically, a genome-wide microarray analysis unveiled that the novel inhibitor regulated unique sets of genes that were not regulated by the mono-inhibitors, further demonstrating the functional uniqueness and superiority of the novel inhibitor. Together, we show that the multi-targeted inhibitors that can block VEGFR1, VEGFR2 and PDGFRβ simultaneously suppress pathological angiogenesis more efficiently than monotherapy, and may therefore have promising therapeutic value for the treatment of neovascular diseases.

Association between the expression of vascular endothelial growth factors and metabolic syndrome or its components: a systematic review and meta-analysis

BACKGROUND

Several studies have linked vascular endothelial growth factors (VEGFs) with metabolic syndrome or its components. However, there has been no systematic appraisal of the findings of these studies to date. The current systematic review and meta-analysis was conducted to explore this association.

METHODS

PubMed, EMBASE, the Cochrane library, and clinical trials registries were used to retrieve peer-reviewed clinical studies that had evaluated the association of VEGFs with metabolic syndrome or its components without applying language and date restrictions. The final search was performed on 29 September 2017.

RESULTS

We included 32 studies in this systematic review and meta-analysis, of which 16 studies (19 study arms) were included in the meta-analysis and remaining studies were qualitatively assessed. Overall, VEGF-A, VEGF-B and VEGF-C were strongly associated with metabolic syndrome or its components. The components of metabolic syndrome varied in their association. Obesity was not correlated with increased VEGF-A expression (p = 0.12), whereas VEGF-B and VEGF-C expression was significantly higher in those with obesity. In contrast, hyperglycemia in type 1 diabetes was strongly associated with increased VEGF-A levels (p < 0.00001), as was type 2 diabetes (p = 0.0006). The studies included in the qualitative analysis similarly showed an increase in VEGF family expression in people with metabolic syndrome, and with its components.

CONCLUSION

The increased concentrations of vascular endothelial growth factors are variably associated with metabolic syndrome or its components. Each VEGF protein has a unique set of associations with the disease state.

The role of vascular endothelial growth factor-B in metabolic homoeostasis: current evidence

It has been shown that adipose tissue and skeletal muscles in lean individuals respond to meal-induced hyperinsulinemia by increase in perfusion, the effect not observed in patients with metabolic syndrome. In conditions of hyperglycaemia and hypertriglyceridemia, this insufficient vascularization leads to the liberation of reactive oxygen species (ROS), and disruption of nitric oxide (NO) synthesis and endothelial signalling responsible for the uptake of circulating fatty acids (FAs), whose accumulation in skeletal muscles and adipose tissue is widely associated with the impairment of insulin signalling. While the angiogenic role of VEGF-A and its increased circulating concentrations in obesity have been widely confirmed, the data related to the metabolic role of VEGF-B are diverse. However, recent discoveries indicate that this growth factor may be a promising therapeutic agent in patients with metabolic syndrome. Preclinical studies agree over two crucial metabolic effects of VEGF-B: (i) regulation of FAs uptake and (ii) regulation of tissue perfusion via activation of VEGF-A/vascular endothelial growth factor receptor (VEGFR) 2 (VEGFR2) pathway. While in some preclinical high-fat diet studies, VEGF-B overexpression reverted glucose intolerance and stimulated fat burning, in others it further promoted accumulation of lipids and lipotoxicity. Data from clinical studies point out the changes in circulating or tissue expression levels of VEGF-B in obese compared with lean patients. Potentially beneficial effects of VEGF-B, achieved through enhanced blood flow (increased availability of insulin and glucose uptake in target organs) and decreased FAs uptake (prevention of lipotoxicity and improved insulin signalling), and its safety for clinical use, remain to be clarified through future translational research.