VEGF-B: A multifaceted modulator with emerging therapeutic applications.

VEGF-B: a thing of beauty

What Is the Role of Vascular Endothelial Growth Factor-Related Molecules in Tumor Angiogenesis?

Vascular endothelial growth factor B-mediated fatty acid flux in the adipose-kidney axis contributes to lipotoxicity in diabetic kidney disease.

Parkinson's disease (PD) results from the degeneration of dopaminergic neurons in the substantia nigra and the consequent deficit of dopamine released in the striatum. Current oral dopamine replacement or surgical therapies do not address the underlying issue of neurodegeneration, they neither slow nor halt disease. Neurotrophic factors have shown preclinical promise, but the choice of an appropriate growth factor as well as the delivery has proven difficult. In this study, we used a rotenone rat midbrain culture model to identify genes that are changed after addition of the neurotoxin. (1) We challenged rat midbrain cultures with rotenone (20 nM), a pesticide that has been shown to be toxic for dopaminergic neurons and that has been a well-characterized model of PD. A gene chip array analysis demonstrated that several genes were up-regulated after the rotenone treatment. Interestingly transcriptional activation of vascular endothelial growth factor B (VEGF-B) was evident, while vascular endothelial growth factor A (VEGF-A) levels remained unaltered. The results from the gene chip array experiment were verified with real time PCR and semi-quantitative western analysis using β-actin as the internal standard. (2) We have also found evidence that exogenously applied VEGF-B performed as a neuroprotective agent facilitating neuron survival in an even more severe rotenone culture model of PD (40 nM rotenone). VEGF-B has very recently been added to the list of trophic factors that reduce effects of neurodegeneration, as was shown in an in vivo model of motor neuron degeneration, while lacking potential adverse angiogenic activity. The data of an in vivo protective effect on motor neurons taken together with the presented results demonstrate that VEGF-B is a new candidate trophic factor distinct from the GDNF family of trophic factors. VEGF-B is activated by neurodegenerative challenges to the midbrain, and exogenous application of VEGF-B has a neuroprotective effect in a culture model of PD. Strengthening this natural protective response by either adding exogenous VEGF-B or up-regulating the endogenous VEGF-B levels may have the potential to be a disease modifying therapy for PD. We conclude that the growth factor VEGF-B can improve neuronal survival in a culture model of PD.

Vascular endothelial growth factor B (VEGFB) is highly expressed in metabolically active tissues, such as the heart and skeletal muscle, suggesting a function in maintaining oxidative metabolic and contractile function in these tissues. Multiple models of heart failure have indicated a significant drop in VEGFB. However, whether there is a role for decreased VEGFB in diabetic cardiomyopathy is currently unknown. Of the VEGFB located in cardiomyocytes, there is a substantial and readily releasable pool localized on the cell surface. The immediate response to high glucose and the secretion of endothelial heparanase is the release of this surface-bound VEGFB, which triggers signaling pathways and gene expression to influence endothelial cell (autocrine action) and cardiomyocyte (paracrine effects) survival. Under conditions of hyperglycemia, when VEGFB production is impaired, a robust increase in vascular endothelial growth factor receptor (VEGFR)-1 expression ensues as a possible mechanism to enhance or maintain VEGFB signaling. However, even with an increase in VEGFR1 after diabetes, cardiomyocytes are unable to respond to VEGFB. In addition to the loss of VEGFB production and signaling, evaluation of latent heparanase, the protein responsible for VEGFB release, also showed a significant decline in expression in whole hearts from animals with chronic or acute diabetes. Defects in these numerous VEGFB pathways were associated with an increased cell death signature in our models of diabetes. Through this bidirectional interaction between endothelial cells (which secrete heparanase) and cardiomyocytes (which release VEGFB), this growth factor could provide the diabetic heart protection against cell death and may be a critical tool to delay or prevent cardiomyopathy.NEW & NOTEWORTHY We discovered a bidirectional interaction between endothelial cells (which secrete heparanase) and cardiomyocytes [which release vascular endothelial growth factor B (VEGFB)]. VEGFB promoted cell survival through ERK and cell death gene expression. Loss of VEGFB and its downstream signaling is an early event following hyperglycemia, is sustained with disease progression, and could explain diabetic cardiomyopathy.

Studies on vascular endothelial growth factor B (VEGF-B) during the past decade or so have shown that VEGF-B appears to be a mysterious molecule with obscure, if not controversial, functions.When VEGF-B was initially discovered (Grimmond et al., 1996; Olofsson et al., 1996a), it was naturally believed to be an angiogenic factor, due to its high sequence homology and similar receptor binding pattern to VEGF, the prototypic angiogenic molecule.Much of our research effort was focused on this speculated angiogenic activity of VEGF-B for a long time.However, studies into this aspect, most of the time, turned out to be disappointing because of the negative findings.Unlike VEGF-A, VEGF-B did not seem to play a significant role in inducing blood vessel growth or vascular permeability, etc (Li et al., 2009).In addition, VEGF-B deficiency in mice did not seem to matter greatly, since VEGF-Bnull mice appeared largely healthy (Aase et al.,

Reducing VEGF-B Signaling Ameliorates Renal Lipotoxicity and Protects against Diabetic Kidney Disease

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.

BackgroundNon-alcoholic fatty liver disease (NAFLD) is one of the most universal liver diseases with complicated pathogenesis throughout the world. Insulin resistance is a leading risk factor that contributes to the development of NAFLD. Vascular endothelial growth factor B (VEGFB) was described by researchers as contributing to regulating lipid metabolic disorders. Here, we investigated VEGFB as a main target to regulate insulin resistance and metabolic syndrome.MethodsIn this study, bioinformatics, transcriptomics, morphological experiments, and molecular biology were used to explore the role of VEGFB in regulating insulin resistance in NAFLD and its molecular mechanism based on human samples, animal models, and cell models. RNA-seq was performed to analyze the signal pathways associated with VEGFB and NAFLD; Palmitic acid and High-fat diet were used to induce insulin-resistant HepG2 cells model and NAFLD animal model. Intracellular glucolipid contents, glucose uptake, hepatic and serum glucose and lipid levels were examined by Microassay and Elisa. Hematoxylin-eosin staining, Oil Red O staining, and Periodic acid-schiff staining were used to analyze the hepatic steatosis, lipid droplet, and glycogen content in the liver. Western blot and quantitative real-time fluorescent PCR were used to verify the expression levels of the VEGFB and insulin resistance-related signals PI3K/AKT pathway.ResultsWe observed that VEGFB is genetically associated with NAFLD and the PI3K/AKT signal pathway. After VEGFB knockout, glucolipids levels were increased, and glucose uptake ability was decreased in insulin-resistant HepG2 cells. Meanwhile, body weight, blood glucose, blood lipids, and hepatic glucose of NAFLD mice were increased, and hepatic glycogen, glucose tolerance, and insulin sensitivity were decreased. Moreover, VEGFB overexpression reduced glucolipids and insulin resistance levels in HepG2 cells. Specifically, VEGFB/VEGFR1 activates the PI3K/AKT signals by activating p-IRS1Ser307 expression, inhibiting p-FOXO1pS256 and p-GSK3Ser9 expressions to reduce gluconeogenesis and glycogen synthesis in the liver. Moreover, VEGFB could also enhance the expression level of GLUT2 to accelerate glucose transport and reduce blood glucose levels, maintaining glucose homeostasis.ConclusionsOur studies suggest that VEGFB could present a novel strategy for treating NAFLD as a positive factor.Graphical

It has been demonstrated that vascular endothelial growth factor B (VEGFB) plays a vital role in regulating vascular biological function. However, the role of VEGFB in regulating skeletal muscle cell proliferation and differentiation remains unclear. Thus, this study aimed to investigate the effects of VEGFB on C2C12 myoblast proliferation and differentiation and to explore the underlying mechanism. For proliferation, VEGFB significantly promoted the proliferation of C2C12 myoblasts with the upregulating expression of cyclin D1 and PCNA. Meanwhile, VEGFB enhanced vascular endothelial growth factor receptor 1 (VEGFR1) expression and activated the PI3K/Akt signaling pathway in a VEGFR1-dependent manner. In addition, the knockdown of VEGFR1 and inhibition of PI3K/Akt totally abolished the promotion of C2C12 proliferation induced by VEGFB, suggesting that VEGFB promoted C2C12 myoblast proliferation through the VEGFR1-PI3K/Akt signaling pathway. Regarding differentiation, VEGFB significantly stimulated the differentiation of C2C12 myoblasts via VEGFR, with elevated expressions of MyoG and MyHC. Furthermore, the knockdown of VEGFR1 rather than NRP1 eliminated the VEGFB-stimulated C2C12 differentiation. Moreover, VEGFB activated the PI3K/Akt/mTOR signaling pathway in a VEGFR1-dependent manner. However, the inhibition of PI3K/Akt/mTOR blocked the promotion of C2C12 myoblasts differentiation induced by VEGFB, indicating the involvement of the PI3K/Akt pathway. To conclude, these findings showed that VEGFB promoted C2C12 myoblast proliferation and differentiation via the VEGFR1-PI3K/Akt signaling pathway, providing new insights into the regulation of skeletal muscle development.

Preclinical studies have shown the therapeutic potential of VEGF-B (vascular endothelial growth factor B) in revascularization of the ischemic myocardium, but the associated cardiac hypertrophy and adverse side effects remain a concern. To understand the importance of endothelial proliferation and migration for the beneficial versus adverse effects of VEGF-B in the heart, we explored the cardiac effects of autocrine versus paracrine VEGF-B expression in transgenic and gene-transduced mice. We used single-cell RNA sequencing to compare cardiac endothelial gene expression in VEGF-B transgenic mouse models. Lineage tracing was used to identify the origin of a VEGF-B-induced novel endothelial cell population and adeno-associated virus-mediated gene delivery to compare the effects of VEGF-B isoforms. Cardiac function was investigated using echocardiography, magnetic resonance imaging, and micro-computed tomography. Unlike in physiological cardiac hypertrophy driven by a cardiomyocyte-specific VEGF-B transgene (myosin heavy chain alpha-VEGF-B), autocrine VEGF-B expression in cardiac endothelium (aP2 [adipocyte protein 2]-VEGF-B) was associated with septal defects and failure to increase perfused subendocardial capillaries postnatally. Paracrine VEGF-B led to robust proliferation and myocardial migration of a novel cardiac endothelial cell lineage (VEGF-B-induced endothelial cells) of endocardial origin, whereas autocrine VEGF-B increased proliferation of VEGF-B-induced endothelial cells but failed to promote their migration and efficient contribution to myocardial capillaries. The surviving aP2-VEGF-B offspring showed an altered ratio of secreted VEGF-B isoforms and developed massive pathological cardiac hypertrophy with a distinct cardiac vessel pattern. In the normal heart, we found a small VEGF-B-induced endothelial cell population that was only minimally expanded during myocardial infarction but not during physiological cardiac hypertrophy associated with mouse pregnancy. Paracrine and autocrine secretions of VEGF-B induce expansion of a specific endocardium-derived endothelial cell population with distinct angiogenic markers. However, autocrine VEGF-B signaling fails to promote VEGF-B-induced endothelial cell migration and contribution to myocardial capillaries, predisposing to septal defects and inducing a mismatch between angiogenesis and myocardial growth, which results in pathological cardiac hypertrophy.

The vascular endothelial growth factor (VEGF) family has recently expanded by the identification and cloning of three additional members, namely VEGF-B, VEGF-C, and VEGF-D. In this study we demonstrate that VEGF-B binds selectively to VEGF receptor-1/Flt-1. This binding can be blocked by excess VEGF, indicating that the interaction sites on the receptor are at least partially overlapping. Mutating the putative VEGF receptor-1/Flt-1 binding determinants Asp63, Asp64, and Glu67 to alanine residues in VEGF-B reduced the affinity to VEGF receptor-1 but did not abolish binding. Mutational analysis of conserved cysteines contributing to VEGF-B dimer formation suggest a structural conservation with VEGF and platelet-derived growth factor. Proteolytic processing of the 60-kDa VEGF-B186 dimer results in a 34-kDa dimer containing the receptor-binding epitopes. The binding of VEGF-B to its receptor on endothelial cells leads to increased expression and activity of urokinase type plasminogen activator and plasminogen activator inhibitor 1, suggesting a role for VEGF-B in the regulation of extracellular matrix degradation, cell adhesion, and migration.

VEGFB167 drives tumor progression by modulating the immune microenvironment.

A second isoform and the genomic structures of mouse and human vascular endothelial growth factor B are described. Both genes consist of seven coding exons and span about 4 kilobases of DNA. The two identified isoforms of vascular endothelial growth factor B are generated by alternative splicing where different splice acceptor sites in exon 6 introduce a frameshift and a partial use of different but overlapping reading frames. Consequently, the COOH-terminal domains in the two isoforms show no resemblance. Mouse and human cDNA clones for the novel isoform of vascular endothelial growth factor B encoded a secreted protein of 186 amino acid residues. Expression in transfected cells generated a protein of 25 kDa which upon secretion was modified by O-linked glycosylation and displayed a molecular mass of 32 kDa under reducing conditions. The protein was expressed as a disulfide-linked homodimer, and heterodimers were generated when coexpressed with vascular endothelial growth factor. The entirely different COOH-terminal domains in the two isoforms of vascular endothelial growth factor B imply that some functional properties of the two proteins are distinct.

Vascular endothelial growth factor B (VEGF-B) is one of the enigmatic members of the VEGF family. The knowledge gap about VEGF-B expression and how its levels are altered in diabetic eyes were the focus of this investigation that was addressed by comparing and correlating vitreous VEGF-B between diabetic and non-diabetic patients. VEGF-B levels were measured by enzyme-linked immunosorbent assay in vitreous samples (n = 33) from diabetic (n = 25) and non-diabetic (n = 8) patients. Results were compared between groups. Optical coherence tomography from diabetic patients was evaluated for central retinal thickness (CRT) and macular volume (MV). Mean vitreous VEGF-B concentration was higher in diabetic (18.82 ± 1.44 pg/mL) vs. non-diabetic patients (17.90 ± 0.32 pg/mL) (p = 0.006), and in proliferative diabetic retinopathy (PDR) (19.03 ± 1.52 pg/mL) vs. non-PDR (NPDR) patients (18.18 ±0.96 pg/mL) (p = 0.025). In diabetic retinopathy (DR) patients, correlation between VEGF-B and CRT (μm) was positive and moderate: rs = 0.441 (p ≤ 0.05) and the correlation between VEGF-B and MV (mm3) was positive and robust: rs = 0.716 (p ≤ 0.01). VEGF-B levels are overexpressed in vitreous of diabetic patients, and the levels are higher in developed stages of DR. Correlation results show that CRT and MV increase with increased levels of VEGF-B. Targeting VEGF-B inhibition may have therapeutic beneficial implications.