Angiogenic Abnormalities in Diabetes Mellitus: Mechanistic and Clinical Aspects

1α,25-Dihydroxyvitamin D3 promotes angiogenesis by alleviating AGEs-induced autophagy

Diabetes mellitus (DM) induces abnormal angiogenesis and results in multiple chronic vascular complications. Previous studies showed that advanced glycation end products (AGEs) up-regulated in diabetic patients and induced a series of cellular effects such as oxidative stress, inflammation, and autophagy. 1α,25-Dihydroxyvitamin D3 (1,25D), a hormonal form of vitamin D, proved to be beneficial for vascular diseases. However, the underlying mechanism of 1,25D in angiogenesis in DM remains unclear. Using CCK8 assay and transwell assay, we found that 1,25D could partly ameliorate impaired proliferation and migration ability of endothelial cells (ECs) induced by AGEs (200 μg/mL). Furthermore, tube formation assay, Western blot, and real-time qPCR assay were conducted to demonstrate that AGEs impaired angiogenetic ability, and that angiogenesis-related gene expression (i.e., VEGFA, VEGFB, VEGFR1, VEGFR2, TGFβ1, MMP2, MMP9) in ECs and 1,25D could promote angiogenesis and angiogenetic markers expression. By using DCFH-DA, ELISA, and Western blot assay, we also found that AGEs-induced oxidative stress impaired angiogenic ability of ECs, and 1,25D alleviated angiogenesis dysfunction by inhibiting oxidative stress. Of note, AGEs-induced excessive autophagy was found to impair angiogenesis. We elucidated that the detrimental autophagy is modulated by 1,25D and AGEs via PI3K/Akt pathway. Observed together, our findings illustrated that AGEs-induced oxidative stress and autophagy resulted in angiogenic disorder and 1,25D improved angiogenesis by restraining excessive autophagy and oxidative stress, providing a novel insight for the treatment of vascular complications in DM.

Microvascular fragments in microcirculation research and regenerative medicine

Adipose tissue-derived microvascular fragments (MVF) are functional vessel segments, which rapidly reassemble into new microvasculatures under experimental in vitro and in vivo conditions. Accordingly, they have been used for many years in microcirculation research to study basic mechanisms of endothelial cell function, angiogenesis and microvascular network formation in two- and three-dimensional environments. Moreover, they serve as vascularization units for musculoskeletal regeneration and implanted biomaterials as well as for the treatment of myocardial infarction and the generation of prevascularized tissue organoids. Besides, multiple factors determining the vascularization capacity of MVF have been identified, including their tissue origin and cellular composition, the conditions for their short- and long-term storage as well as their implantation site and the general health status and medication of the recipient. The next challenging step is now the successful translation of all these promising experimental findings into clinical practice. If this succeeds, a multitude of future therapeutic applications may significantly benefit from the remarkable properties of MVF.

Fenofibrate increases circulating haematopoietic stem cells in people with diabetic retinopathy: a randomised, placebo-controlled trial

AIM/HYPOTHESIS

In two large RCTs, fenofibrate reduced the progression of diabetic retinopathy. We investigated whether fenofibrate increases circulating haematopoietic stem/progenitor cells (HSPCs), which have vascular properties and have been shown to protect from retinopathy.

METHODS

We conducted a 12 week parallel-group RCT comparing fenofibrate vs placebo. Patients with diabetic retinopathy and without other conditions that would affect HSPCs were enrolled at a tertiary diabetes outpatient clinic and randomised to receive fenofibrate or placebo based on a computer-generated sequence. Patients and study staff assessing the outcomes were blinded to group assignment. The primary endpoint was the change in the levels of circulating HSPCs, defined by expression of the stem cell markers CD34 and/or CD133. Secondary endpoints were the changes in endothelial progenitor cells, lipids, soluble mediators and gene expression. We used historical data on the association between HSPCs and retinopathy outcomes to estimate the effect of fenofibrate on retinopathy progression.

RESULTS

Forty-two participants with diabetic retinopathy were randomised and 41 completed treatment and were analysed (20 in the placebo group and 21 in the fenofibrate group). Mean age was 57.4 years, diabetes duration was 18.2 years and baseline HbA_1c was 60 mmol/mol (7.6%). When compared with placebo, fenofibrate significantly increased levels of HSPCs expressing CD34 and/or CD133. CD34⁺ HSPCs non-significantly declined in the placebo group (mean ± SD -44.2 ± 31.6 cells/10⁶) and significantly increased in the fenofibrate group (53.8 ± 31.1 cells/10⁶). The placebo-subtracted increase in CD34⁺ HSPCs from baseline was 30% (99.3 ± 43.3 cells/10⁶; p = 0.027) which, projected onto the relationship between HSPC levels and retinopathy outcomes, yielded an OR of retinopathy progression of 0.67 for fenofibrate vs placebo. Endothelial differentiation of CD34⁺ cells, estimated by the %KDR (kinase insert domain receptor) expression, was significantly reduced by fenofibrate. Fenofibrate decreased serum triacylglycerols, but the change in triacylglycerols was unrelated to the change in HSPCs. No effect was observed for endothelial progenitor cells, cytokines/chemokines (stromal-cell derived factor-1, vascular endothelial growth factor, monocyte chemoattractant protein-1) and gene expression in peripheral blood mononuclear cells.

CONCLUSIONS/INTERPRETATION

Fenofibrate increased HSPC levels in participants with diabetic retinopathy and this mechanism may explain why fenofibrate reduced retinopathy progression in previous studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01927315.

Cutaneous innervation in impaired diabetic wound healing

Type 2 diabetes is associated with several potential comorbidities, among them impaired wound healing, chronic ulcerations, and the requirement for lower extremity amputation. Disease-associated abnormal cellular responses, infection, immunological and microvascular dysfunction, and peripheral neuropathy are implicated in the pathogenesis of the wound healing impairment and the diabetic foot ulcer. The skin houses a dense network of sensory nerve afferents and nerve-derived modulators, which communicate with epidermal keratinocytes and dermal fibroblasts bidirectionally to effect normal wound healing after trauma. However, the mechanisms through which cutaneous innervation modulates wound healing are poorly understood, especially in humans. Better understanding of these mechanisms may provide the basis for targeted treatments for chronic diabetic wounds. This review provides an overview of wound healing pathophysiology with a focus on neural involvement in normal and diabetic wound healing, as well as future therapeutic perspectives to address the unmet needs of diabetic patients with chronic wounds.

Diabetes Impaired Ischemia-Induced PDGF (Platelet-Derived Growth Factor) Signaling Actions and Vessel Formation Through the Activation of Scr Homology 2-Containing Phosphatase-1

Objective

Critical limb ischemia is a major complication of diabetes characterized by insufficient collateral vessel development and proper growth factor signaling unresponsiveness. Although mainly deactivated by hypoxia, phosphatases are important players in the deregulation of proangiogenetic pathways. Previously, SHP-1 (Scr homology 2-containing phosphatase-1) was found to be associated with the downregulation of growth factor actions in the diabetic muscle. Thus, we aimed to gain further understanding of the impact of SHP-1 on smooth muscle cell (SMC) function under hypoxic and diabetic conditions.

Approach and Results

Despite being inactivated under hypoxic conditions, high glucose level exposure sustained SHP-1 phosphatase activity in SMC and increased its interaction with PDGFR (platelet-derived growth factor receptor)-β, thus reducing PDGF proangiogenic actions. Overexpression of an inactive form of SHP-1 fully restored PDGF-induced proliferation, migration, and signaling pathways in SMC exposed to high glucose and hypoxia. Nondiabetic and diabetic mice with deletion of SHP-1 specifically in SMC were generated. Ligation of the femoral artery was performed, and blood flow was measured for 4 weeks. Blood flow reperfusion, vascular density and maturation, and limb survival were all improved while vascular apoptosis was attenuated in diabetic SMC-specific SHP-1 null mice as compared to diabetic mice.

Conclusions

Diabetes and high glucose level exposure maintained SHP-1 activity preventing hypoxia-induced PDGF actions in SMC. Specific deletion of SHP-1 in SMC partially restored blood flow reperfusion in the diabetic ischemic limb. Therefore, local modulation of SHP-1 activity in SMC could represent a potential therapeutic avenue to improve the proangiogenic properties of SMC under ischemia and diabetes.

Insulin protects against type 1 diabetes mellitus-induced ultrastructural abnormalities of pancreatic islet microcirculation

Pancreatic islet microcirculation, consisting of pancreatic islet microvascular endothelial cells (IMECs) and pericytes (IMPCs), provides crucial support for the physiological function of pancreatic islet. Emerging evidence suggests that pancreatic islet microcirculation is impaired in type 1 diabetes mellitus (T1DM). Here, we investigated the potential ultrastructural protective effects of insulin against streptozotocin (STZ)-induced ultrastructural abnormalities of the pancreatic islet microcirculation in T1DM mouse model. For this purpose, pancreatic tissues were collected from control, STZ-induced T1DM and insulin-treated mice, and a pancreatic IMECs cell line (MS1) was cultured under control, 35 mM glucose with or without 10⁻⁸ M insulin conditions. Transmission and scanning electron microscopies were employed to evaluate the ultrastructure of the pancreatic islet microcirculation. We observed ultrastructural damage to IMECs and IMPCs in the type 1 diabetic group, as demonstrated by destruction of the cytoplasmic membrane and organelles (mainly mitochondria), and this damage was substantially reversed by insulin treatment. Furthermore, insulin inhibited collagenous fiber proliferation and alleviated edema of the widened pancreatic islet exocrine interface in T1DM mice. We conclude that insulin protects against T1DM-induced ultrastructural abnormalities of the pancreatic islet microcirculation.

Type 1 diabetes patients increase CXCR4+ and CXCR7+ haematopoietic and endothelial progenitor cells with exercise, but the response is attenuated

Exercise mobilizes angiogenic cells, which stimulate vascular repair. However, limited research suggests exercise-induced increase of endothelial progenitor cell (EPCs) is completely lacking in type 1 diabetes (T1D). Clarification, along with investigating how T1D influences exercise-induced increases of other angiogenic cells (hematopoietic progenitor cells; HPCs) and cell surface expression of chemokine receptor 4 (CXCR4) and 7 (CXCR7), is needed. Thirty T1D patients and 30 matched non-diabetes controls completed 45 min of incline walking. Circulating HPCs (CD34⁺, CD34⁺CD45^dim) and EPCs (CD34⁺VEGFR2⁺, CD34⁺CD45^dimVEGFR2⁺), and subsequent expression of CXCR4 and CXCR7, were enumerated by flow cytometry at rest and post-exercise. Counts of HPCs, EPCs and expression of CXCR4 and CXCR7 were significantly lower at rest in the T1D group. In both groups, exercise increased circulating angiogenic cells. However, increases was largely attenuated in the T1D group, up to 55% lower, with CD34⁺ (331 ± 437 Δcells/mL vs. 734 ± 876 Δcells/mL p = 0.048), CD34⁺VEGFR2⁺ (171 ± 342 Δcells/mL vs. 303 ± 267 Δcells/mL, p = 0.006) and CD34⁺VEGFR2⁺CXCR4⁺ (126 ± 242 Δcells/mL vs. 218 ± 217 Δcells/mL, p = 0.040) significantly lower. Exercise-induced increases of angiogenic cells is possible in T1D patients, albeit attenuated compared to controls. Decreased mobilization likely results in reduced migration to, and repair of, vascular damage, potentially limiting the cardiovascular benefits of exercise.Trial registration: ISRCTN63739203.

MG53 inhibits angiogenesis through regulating focal adhesion kinase signalling

Mitsugumin 53 (MG53), which is expressed predominantly in striated muscle, has been demonstrated to be a myokine/cardiokine secreted from striated muscle under specific conditions. The important roles of MG53 in non-striated muscle tissues have also been examined in multiple disease models. However, no previous study has implicated MG53 in the control of endothelial cell function. In order to explore the effects of MG53 on endothelial cells, human umbilical vein endothelial cells (HUVECs) were stimulated with recombinant human MG53 (rhMG53). Then, rhMG53 uptake, focal adhesion kinase (FAK)/Src/Akt/ERK1/2 signalling pathway activation, cell migration and tube formation were determined in vitro. The efficacy of rhMG53 in regulating angiogenesis was also detected in postnatal mouse retinas. The results demonstrated that rhMG53 directly entered into endothelial cells in a cholesterol-dependent manner. The uptake of rhMG53 directly bound to FAK in endothelial cells, which resulted in a significant decrease in FAK phosphorylation at Y397. Accompanied by the dephosphorylation of FAK, rhMG53 uncoupled FAK-Src interaction and reduced the phosphorylation of Src at Y416. Consequently, the activation of FAK/Src downstream signalling pathways, such as Akt and ERK1/2, was also significantly inhibited by rhMG53. Furthermore, rhMG53 remarkably decreased HUVEC migration and tube formation in vitro and postnatal mouse retinal angiogenesis in vivo. Taken together, these data indicate that rhMG53 inhibits angiogenesis through regulating FAK/Src/Akt/ERK1/2 signalling pathways. This may provide a novel molecular mechanism for the impaired angiogenesis in ischaemic diseases.

Impact of mesenchymal stem cell-secretome-loaded hydrogel on proliferative and migratory activities of hyperglycemic fibroblasts

Disruption of the reparative process, often found in diabetic patients, results in chronic, non-healing wounds that significantly impact a patient's quality of life. This highlights the need of new therapeutic options to improve the healing of diabetic wounds. In this study, we focused on developing a cell-free hydrogel dressing loaded with mesenchymal stem cell (MSC)-conditioned media (CM) to potentially improve the healing of hard-to-heal wounds. We simulated a hyperglycemic environment by incubating human dermal fibroblasts in a high glucose environment (30 mM) and validated that MSC-CM rescued the impaired functions (proliferation and migration) of hyperglycemic fibroblasts. Further, we investigated the effect of loading MSC-CM in gelatin methacrylate (GelMA)-poly (ethylene glycol) diacrylate (PEGDA) hybrid hydrogels in improving the proliferative activity of glucose-treated fibroblasts. The controlled release of bioactive factors from MSC-CM loaded GelMA-PEGDA hydrogels promoted the metabolic activity of hyperglycemic fibroblasts. In addition, the growth rate of hyperglycemic fibroblasts was found to be similar to that of normal fibroblasts. Our observations, thus, suggest the potential application of cell-free, MSC-secretome-loaded hydrogel in the healing of diabetic or chronic wounds.

Diabetic Endothelial Cells Differentiated From Patient iPSCs Show Dysregulated Glycine Homeostasis and Senescence Associated Phenotypes

Induced pluripotent stem cells derived cells (iPSCs) not only can be used for personalized cell transfer therapy, but also can be used for modeling diseases for drug screening and discovery in vitro. Although prior studies have characterized the function of rodent iPSCs derived endothelial cells (ECs) in diabetes or metabolic syndrome, feature phenotypes are largely unknown in hiPSC-ECs from patients with diabetes. Here, we used hiPSC lines from patients with type 2 diabetes mellitus (T2DM) and differentiated them into ECs (dia-hiPSC-ECs). We found that dia-hiPSC-ECs had disrupted glycine homeostasis, increased senescence, and impaired mitochondrial function and angiogenic potential as compared with healthy hiPSC-ECs. These signature phenotypes will be helpful to establish dia-hiPSC-ECs as models of endothelial dysfunction for understanding molecular mechanisms of disease and for identifying and testing new targets for the treatment of endothelial dysfunction in diabetes.

Autologous Peripheral Blood Mononuclear Cells for Limb Salvage in Diabetic Foot Patients with No-Option Critical Limb Ischemia

Peripheral blood mononuclear cells (PBMNCs) are reported to prevent major amputation and healing in no-option critical limb ischemia (NO-CLI). The aim of this study is to evaluate PBMNC treatment in comparison to standard treatment in NO-CLI patients with diabetic foot ulcers (DFUs). The study included 76 NO-CLI patients admitted to our centers because of CLI with DFUs. All patients were treated with the same standard care (control group), but 38 patients were also treated with autologous PBMNC implants. Major amputations, overall mortality, and number of healed patients were evaluated as the primary endpoint. Only 4 out 38 amputations (10.5%) were observed in the PBMNC group, while 15 out of 38 amputations (39.5%) were recorded in the control group (p = 0.0037). The Kaplan-Meier curves and the log-rank test results showed a significantly lower amputation rate in the PBMNCs group vs. the control group (p = 0.000). At two years follow-up, nearly 80% of the PBMNCs group was still alive vs. only 20% of the control group (p = 0.000). In the PBMNC group, 33 patients healed (86.6%) while only one patient healed in the control group (p = 0.000). PBMNCs showed a positive clinical outcome at two years follow-up in patients with DFUs and NO-CLI, significantly reducing the amputation rate and improving survival and wound healing. According to our study results, intramuscular and peri-lesional injection of autologous PBMNCs could prevent amputations in NO-CLI diabetic patients.

Clinical Efficacy and Safety of Angiogenesis Inhibitors: Sex Differences and Current Challenges

Vasoactive molecules, such as vascular endothelial growth factor (VEGF) and endothelins, share cytokine-like activities and regulate endothelial cell (EC) growth, migration and inflammation. Some endothelial mediators and their receptors are targets for currently approved angiogenesis inhibitors, drugs that are either monoclonal antibodies raised towards VEGF, or inhibitors of vascular receptor protein kinases and signaling pathways. Pharmacological interference with the protective functions of ECs results in a similar spectrum of adverse effects. Clinically, the most common side effects of VEGF signaling pathway inhibition include an increase in arterial pressure, left ventricular (LV) dysfunction ultimately causing heart failure, and thromboembolic events, including pulmonary embolism, stroke, and myocardial infarction. Sex steroids such as androgens, progestins, and estrogen and their receptors (ERα, ERβ, GPER; PR-A, PR-B; AR) have been identified as important modifiers of angiogenesis, and sex differences have been reported for anti-angiogenic drugs. This review article discusses the current challenges clinicians are facing with regard to angiogenesis inhibitor treatments, including the need to consider sex differences affecting clinical efficacy and safety. We also propose areas for future research taking into account the role of sex hormone receptors and sex chromosomes. Development of new sex-specific drugs with improved target and cell-type selectivity likely will open the way personalized medicine in men and women requiring antiangiogenic therapy and result in reduced adverse effects and improved therapeutic efficacy.

Growth Factor Deregulation and Emerging Role of Phosphatases in Diabetic Peripheral Artery Disease

Peripheral artery disease is caused by atherosclerosis of lower extremity arteries leading to the loss of blood perfusion and subsequent critical ischemia. The presence of diabetes mellitus is an important risk factor that greatly increases the incidence, the progression and the severity of the disease. In addition to accelerated disease progression, diabetic patients are also more susceptible to develop serious impairment of their walking abilities through an increased risk of lower limb amputation. Hyperglycemia is known to alter the physiological development of collateral arteries in response to ischemia. Deregulation in the production of several critical pro-angiogenic factors has been reported in diabetes along with vascular cell unresponsiveness in initiating angiogenic processes. Among the multiple molecular mechanisms involved in the angiogenic response, protein tyrosine phosphatases are potent regulators by dephosphorylating pro-angiogenic tyrosine kinase receptors. However, evidence has indicated that diabetes-induced deregulation of phosphatases contributes to the progression of several micro and macrovascular complications. This review provides an overview of growth factor alterations in the context of diabetes and peripheral artery disease, as well as a description of the role of phosphatases in the regulation of angiogenic pathways followed by an analysis of the effects of hyperglycemia on the modulation of protein tyrosine phosphatase expression and activity. Knowledge of the role of phosphatases in diabetic peripheral artery disease will help the development of future therapeutics to locally regulate phosphatases and improve angiogenesis.

Inhibitory effects of Paris saponin I, II, Ⅵ and Ⅶ on HUVEC cells through regulation of VEGFR2, PI3K/AKT/mTOR, Src/eNOS, PLCγ/ERK/MERK, and JAK2-STAT3 pathways

Rhizoma Paris is a popular Chinese medicine in clinics. It contains four main saponins which are its major bioactive compounds. These saponins are Paris saponin I, II, VI and VII (PSI, PSII, PSVI and PSVII, respectively). Up to now, the research using HUVEC cells to evaluate the anti-angiogenic activity of four saponins is blank. The purpose of this study was to evaluate the anti-angiogenic properties (also known as angiotoxicity) of the four saponins in Rhizoma Paris on vascular endothelial cells-HUVEC cells, and to investigate the underlying mechanism, which has not been studied before. In this study, MTT assay, Lactate dehydrogenase (LDH) assay, wound healing experiments, transwell cell invasion assay, tubule formation experiment, DAPI staining, AV-PI double staining, and cell cycle analysis were used to determine the effects of Paris saponins. The results showed that, with increases in concentrations of PSI, PSII, PSVI and PSVII, the viability of HUVEC cells decreased significantly. In addition, four saponins dose-dependent enhanced LDH release and inhibited HUVEC cell migration, invasion, and angiogenesis. In terms of mechanism, PSI significantly inhibited protein expression in multiple signaling pathways. In particular, with the VEGF2 as the target, it activate the downstream PI3K / AKT / mTOR, SRC / eNOS, P38, PLCγ / ERK / MERK and JAK2/STAT3 signaling pathways. In conclusion, PSI, PSII, PSVI and PSVII can inhibit endothelial cell proliferation, migration and invasion, block endothelial cell cycle, induce endothelial cell apoptosis, act on protein expression in several anti-angiogenic signaling pathways, and finally inhibit angiogenesis in vitro. This study provides further data support for the clinical application of Paris saponins as antiangiogenic drugs.

Diabetes mellitus impairs circulating proangiogenic granulocytes

AIMS/HYPOTHESIS

Cardiovascular risk in diabetes is at least in part attributable to defective angiogenesis. Since diabetes negatively affects blood cells involved in angiogenesis, we herein evaluated whether diabetes impairs proangiogenic granulocytes (PAGs).

METHODS

We characterised and quantified PAGs as CD49d⁺ granulocytes in peripheral blood of participants with type 2 or type 1 diabetes and in non-diabetic control participants. We evaluated PAG antigenic profile and assessed in vitro functional properties of CD49d⁺ granulocytes using 2D and 3D angiogenesis assays. We also quantified PAGs before and after glucose control with a sodium-glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin. In parallel, we measured Ly6G⁺CD49d⁺ PAGs in streptozotocin-induced type 1-like diabetic mice vs non-diabetic control mice.

RESULTS

PAGs were composed of eosinophils (>80%) and neutrophils (<20%). Within both populations, CD49d identified CXCR4^high/VEGFR1^high cells. CD49d⁺ granulocytes supported in vitro angiogenesis by endothelial cells significantly more than CD49d^- control granulocytes, and physically interacted with endothelial cells. Granulocytes from type 2 diabetic participants had a profoundly impaired capacity to stimulate endothelial cell tubule formation compared with those from non-diabetic control participants. CD49d⁺ PAGs were reduced by 30-40% and were functionally impaired in diabetic vs control individuals. PAG levels inversely correlated with plasma glucose (r = -0.25; p = 0.025) and significantly increased 1.8-times after glucose control with dapagliflozin, which reduced HbA_1c by 1.0% (11 mmol/mol). Levels of Ly6G⁺CD49d⁺ PAGs were also significantly reduced also in type 1 diabetic mice vs control mice.

CONCLUSIONS/INTERPRETATION

We illustrate a significant impairment of PAGs in diabetes and provide evidence for a direct role of hyperglycaemia. These findings add mechanistic information to explain the defective angiogenesis in diabetes. Graphical abstract.

Role of VEGF-A and LRG1 in Abnormal Angiogenesis Associated With Diabetic Nephropathy

Diabetic nephropathy (DN) is an important public health concern of increasing proportions and the leading cause of end-stage renal disease (ESRD) in diabetic patients. It is one of the most common long-term microvascular complications of diabetes mellitus that is characterized by proteinuria and glomerular structural changes. Angiogenesis has long been considered to contribute to the pathogenesis of DN, whereas the molecular mechanisms of which are barely known. Angiogenic factors associated with angiogenesis are the major candidates to explain the microvascular and pathologic finds of DN. Vascular endothelial growth factor A (VEGF-A), leucine-rich α-2-glycoprotein 1, angiopoietins and vasohibin family signal between the podocytes, endothelium, and mesangium have important roles in the maintenance of renal functions. An appropriate amount of VEGF-A is beneficial to maintaining glomerular structure, while excessive VEGF-A can lead to abnormal angiogenesis. LRG1 is a novel pro-angiogenic factors involved in the abnormal angiogenesis and renal fibrosis in DN. The imbalance of Ang1/Ang2 ratio has a role in leading to glomerular disease. Vasohibin-2 is recently shown to be in diabetes-induced glomerular alterations. This review will focus on current understanding of these angiogenic factors in angiogenesis and pathogenesis associated with the development of DN, with the aim of evaluating the potential of anti-angiogenesis therapy in patients with DN.

Metabolism of vascular smooth muscle cells in vascular diseases

Vascular smooth muscle cells (VSMCs) are the fundamental component of the medial layer of arteries and are essential for arterial physiology and pathology. It is becoming increasingly clear that VSMCs can alter their metabolism to fulfill the bioenergetic and biosynthetic requirements. During vascular injury, VSMCs switch from a quiescent "contractile" phenotype to a highly migratory and proliferative "synthetic" phenotype. Recent studies have found that the phenotype switching of VSMCs is driven by a metabolic switch. Metabolic pathways, including aerobic glycolysis, fatty acid oxidation, and amino acid metabolism, have distinct, indispensable roles in normal and dysfunctional vasculature. VSMCs metabolism is also related to the metabolism of endothelial cells. In the present review, we present a brief overview of VSMCs metabolism and how it regulates the progression of several vascular diseases, including atherosclerosis, systemic hypertension, diabetes, pulmonary hypertension, vascular calcification, and aneurysms, and the effect of the risk factors for vascular disease (aging, cigarette smoking, and excessive alcohol drinking) on VSMC metabolism to clarify the role of VSMCs metabolism in the key pathological process.

Increased expression of hypoxia inducible factor-1 alpha and vascular endothelial growth factor is associated with diabetic gastroparesis

BACKGROUND

Gastroparesis is a recognized complication of diabetes but its pathogenic mechanism incompletely understood. Our aim was to determine whether HIF-1α and VEGF are secreted from gastric tissue is a fundamental factor that drives diabetic gastroparesis.

METHODS

Diabetes was induced in Sprague-Dawley by a single intraperitoneal injection of 65 mg/kg streptozotocin. After 4 and 12 weeks, rats were euthanized for assaying body weight, blood glucose, gastric acid secretion and gastric emptying. Morphologic changes in gastric mucosa were observed by the light microscope. Expression of HIF-1α and VEGF were assessed using immunohistochemistry, RT-PCR and Western blot analyses.

RESULTS

Compared with control group, blood glucose were significantly increased and body weight were markedly decreased in streptozotocin-induced diabetes. Gastric emptying was significantly decreased in diabetic rats compared to the control group at different times. The number of parietal cells was obviously decreased, and vacuolated degeneration in diabetic rats. Gastric acid secretion in diabetic group was significantly decreased, and expression of HIF-1α and VEGF were significantly increased in the diabetic group.

CONCLUSION

These results indicated that overexpression of HIF-1α and VEGF in the gastric mucosa and played a pivotal role in the progression of diabetic gastroparesis.

Glycation of fibronectin inhibits VEGF-induced angiogenesis by uncoupling VEGF receptor-2-c-Src crosstalk

Glycation of extracellular matrix proteins has been demonstrated to contribute to the pathogenesis of vascular complications. However, no previous report has shown the role of glycated fibronectin (FN) in vascular endothelial growth factor (VEGF)‐induced angiogenesis. Thus, this study aimed to investigate the effects of glycated FN on VEGF signalling and to clarify the molecular mechanisms involved. FN was incubated with methylglyoxal (MGO) in vitro to synthesize glycated FN, and human umbilical vein endothelial cells (HUVECs) were seeded onto unmodified and MGO‐glycated FN. Then, VEGF‐induced angiogenesis and VEGF‐induced VEGF receptor‐2 (VEGFR‐2) signalling activation were measured. The results demonstrated that normal FN‐positive bands (260 kD) vanished and advanced glycation end products (AGEs) appeared in MGO‐glycated FN and glycated FN clearly changed to a higher molecular mass. The glycation of FN inhibited VEGF‐induced VEGF receptor‐2 (VEGFR‐2), Akt and ERK1/2 activation and VEGF‐induced cell migration, proliferation and tube formation. The glycation of FN also inhibited the recruitment of c‐Src to VEGFR‐2 by sequestering c‐Src through receptor for AGEs (RAGE) and the anti‐RAGE antibody restored VEGF‐induced VEGFR‐2, Akt and ERK1/2 phosphorylation, endothelial cell migration, proliferation and tube formation. Furthermore, the glycation of FN significantly inhibited VEGF‐induced neovascularization in the Matrigel plugs implanted into subcutaneous tissue of mice. Taken together, these data suggest that the glycation of FN may inhibit VEGF signalling and VEGF‐induced angiogenesis by uncoupling VEGFR‐2‐c‐Src interaction. This may provide a novel mechanism for the impaired angiogenesis in diabetic ischaemic diseases.