Hypoglycemia reduces vascular endothelial growth factor A production by pancreatic beta cells as a regulator of beta cell mass

Vascular endothelial growth factor signaling in health and disease: from molecular mechanisms to therapeutic perspectives

Vascular endothelial growth factor (VEGF) signaling is a critical regulator of vasculogenesis, angiogenesis, and lymphangiogenesis, processes that are vital for the development of vascular and lymphatic systems, tissue repair, and the maintenance of homeostasis. VEGF ligands and their receptors orchestrate endothelial cell proliferation, migration, and survival, playing a pivotal role in dynamic vascular remodeling. Dysregulated VEGF signaling drives diverse pathological conditions, including tumor angiogenesis, cardiovascular diseases, and ocular disorders. Excessive VEGF activity promotes tumor growth, invasion, and metastasis, while insufficient signaling contributes to impaired wound healing and ischemic diseases. VEGF-targeted therapies, such as monoclonal antibodies and tyrosine kinase inhibitors, have revolutionized the treatment of diseases involving pathological angiogenesis, offering significant clinical benefits in oncology and ophthalmology. These therapies inhibit angiogenesis and slow disease progression, but they often face challenges such as therapeutic resistance, suboptimal efficacy, and adverse effects. To further explore these issues, this review provides a comprehensive overview of VEGF ligands and receptors, elucidating their molecular mechanisms and regulatory networks. It evaluates the latest progress in VEGF-targeted therapies and examines strategies to address current challenges, such as resistance mechanisms. Moreover, the discussion includes emerging therapeutic strategies such as innovative drug delivery systems and combination therapies, highlighting the continuous efforts to improve the effectiveness and safety of VEGF-targeted treatments. This review highlights the translational potential of recent discoveries in VEGF biology for improving patient outcomes.

Effects of Sulfonylureas and Dipeptidyl Peptidase 4 Inhibitors on Percentage Body Fat Change in Type 2 Diabetes Mellitus Patients on Metformin at 4 and 12 Weeks

Introduction Anti-diabetic drugs used for the treatment of type 2 diabetes mellitus (T2DM) have a unique effect on the body weight and fat distribution of a patient. This study aimed to find out the change in percentage body fat and body composition with the addition of sulfonylureas or dipeptidyl peptidase 4 (DPP-4) inhibitors to metformin monotherapy. Methods An observational 12-week follow-up study was conducted with a sample size of 52 patients. All patients enrolled in the study were evaluated for baseline percentage body fat and body composition parameters including total body weight, total body water, and skeletal muscle mass using the ACCUNIQ BC300, added on to either sulfonylureas or DPP-4 inhibitors over a stable dose of metformin; repeat assessment performed at 4 weeks and 12 weeks, and change in values was noted. Results Of the 52 patients, 28 patients were on sulfonylureas and 24 were on DPP-4 inhibitors. In the sulfonylurea group, there was an increase in percentage body fat from 31.97 ± 8.77% at baseline to 32.65 ± 8.94% at 12 weeks (p = 0.041), while in the DPP-4 inhibitor group, there was a decrease in percentage body fat from 31.87 ± 7.41% at baseline to 31.24 ± 8.5% at 12 weeks (p = 0.102). In the sulfonylurea group, there was a decrease in body weight from 67.25 ± 14.79 kilograms (kg) at baseline to 66.97 ± 14.62 kg at 12 weeks (p = 0.429). In the DPP-4 inhibitor group, there was a decrease in body weight from 66.56 ± 10.82 kg at baseline to 65.76 ± 12.56 kg at 12 weeks (p = 0.079). In the sulfonylurea group, total body water decreased from 32.54 ± 6.65 L at baseline to 32.06 ± 6.51 L at 12 weeks (p = 0.084), while in the DPP-4 inhibitor group, the total body water decreased from 32.46 ± 5.39 L at baseline to 32.18 ± 5.48 L at 12 weeks (p = 0.741). Skeletal muscle mass decreased from 24.78 ± 5.12 kg to 24.4 ± 5.04 kg (p = 0.041) in the sulfonylurea group and from 24.74 ± 4.2 kg to 24.53 ± 4.25 kg (p = 0.666) in the DPP-4 inhibitor group. Conclusion Our study shows that sulfonylureas are associated with an increase in percentage body fat, while there were no significant changes associated with DPP-4 inhibitors when given in addition to metformin. There are no significant changes in body weight associated with sulfonylureas or DPP-4 inhibitors in addition to metformin. Also, sulfonylureas are associated with a decrease in skeletal muscle mass after 12 weeks.

Inhibition of infantile hemangioma growth and promotion of apoptosis via VEGF/PI3K/Akt axis by 755-nm long-pulse alexandrite laser

BACKGROUND

Infantile hemangioma (IH) is a common vascular tumor in female infants, which can lead to aesthetic issues and facial scarring. This study aimed to investigate the inhibitory effects and underlying mechanisms of 755 nm long-pulsed alexandrite laser on IH.

METHODS

Hemangioma endothelial cells (HemECs) were exposed to 755 nm long-pulsed alexandrite laser to evaluate its impact on cell proliferation and apoptosis. A patient-derived xenograft model was established to assess the inhibitory effects of laser treatment on IH in vivo.

RESULTS

In vitro, 755 nm long-pulsed alexandrite laser effectively suppressed the proliferation of HemECs and induced cell apoptosis. Laser treatment significantly inhibited the volume and weight of tumors, accompanied by significant downregulation of vascular endothelial growth factor A (VEGFA), vascular endothelial growth factor receptor 2 (VEGFR2), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) expression levels in both hemangioma cells and tumors. Additionally, laser treatment resulted in the conversion of VEGFA165a to VEGFA165b. TUNEL staining demonstrated increased apoptosis in tumor cells after laser treatment, along with upregulation of cleaved caspase-3 and Bax, and downregulation of Bcl-2.

CONCLUSION

In addition to the principle of selective photothermal decomposition, modulation of the VEGF/PI3K/Akt axis may serve as a potential mechanism for IH treatment using a long pulse-width 755 nm laser. This sheds valuable light on the molecular mechanisms underlying IH pathogenesis and potential therapeutic targets while providing a theoretical basis for the safe and efficient management of proliferative IH using laser therapy.

Macrophages regulate healing-associated fibroblasts in diabetic wound

BACKGROUND

Recovery from a foot ulcer is compromised in a diabetic status, due to the impaired tissue microenvironment that consists of altered inflammation, angiogenesis and fibrosis. Phenotypic alterations in both macrophages and fibroblasts have been detected in the diabetic wound. Recently, a fibroblast subpopulation that expresses high matrix metalloproteinase 1 (MMP1), MMP3, MMP11 and Chitinase-3-Like Protein 1 (CHI3L1) was associated with a successful diabetic wound healing. However, it is not known whether these healing-associated fibroblasts are regulated by macrophages.

METHODS AND RESULTS

We used bioinformatic tools to analyze selected public databases on normal and diabetic skin from patients, and identified genes significantly altered in diabetes. In a mouse model for diabetic wound healing, we detected not only a loss of the spatiotemporal changes in interleukin 1β (IL1β), IL6, IL10 and vascular endothelial growth factor A (VEGF-A) in wound macrophages, but also a compromised expression of MMP1, MMP3, MMP11, CHI3L1 and VEGF-A in healing-associated wound fibroblasts in a diabetic status. Co-culture with diabetic macrophages significantly reduced the expression of MMP1, MMP3, MMP11, CHI3L1 and VEGF-A in fibroblasts from non-diabetic wound. Co-culture with non-diabetic macrophages or diabetic macrophages supplied with IL6 significantly increased the expression of MMP1, MMP3, MMP11, CHI3L1 and VEGF-A in fibroblasts from diabetic wound. Moreover, macrophage-specific expression of IL6 significantly improved wound healing and angiogenesis in diabetic mice.

CONCLUSIONS

Macrophages may induce the activation of wound-healing-associated fibroblasts, while the defective macrophages in diabetes may be corrected with IL6 treatment as a promising therapy for diabetic foot disease.

Association between glycated haemoglobin and the risk of chronic obstructive pulmonary disease: A prospective cohort study in UK biobank

AIMS

To investigate the association between glycated haemoglobin (HbA1c) levels and chronic obstructive pulmonary disease (COPD) incidents in the general population, and the association between HbA1c levels and mortality in patients with COPD.

MATERIALS AND METHODS

We investigated the association of HbA1c levels with COPD risk in the general population in the UK Biobank, using data from 420 065 participants. Survival analysis was conducted for 18 854 patients with COPD. We used restricted cubic spline analysis to assess the dose-response relationship between HbA1c levels and COPD risk and survival. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS

During a median follow-up of 12.3 years, 11 556 COPD cases were recorded. HbA1c had a non-linear relationship with COPD risk (p for non-linearity < .05). Compared with the quintile 2 (32.2-<34.3 mmol/mol), those with HbA1c levels above 38.7 mmol/mol (quintile 5) had a 22% (HR, 1.22, 95% CI: 1.15-1.30) higher risk of COPD. Compared with the HbA1c decile 2 (30.5-<32.2 mmol/mol), the HRs (95% CI) of COPD risk were 1.16 (1.03-1.30) and 1.36 (1.24-1.50) in the lowest HbA1c decile (<30.5 mmol/mol) and highest decile (≥41.0 mmol/mol), respectively. The increased COPD risk associated with HbA1c was more pronounced in younger, current smokers, passive smokers, and participants with a higher Townsend deprivation index (all p for interaction < .05). Among patients with COPD, 4569 COPD cases died (488 because of COPD) during a median follow-up of 5.4 years. Regarding COPD survival, HbA1c had a non-linear relationship with all-cause death (p for non-linearity < .05). Those with HbA1c quintile 5 (≥38.7 mmol/mol) had a 23% (HR, 1.23, 95% CI: 1.10-1.37) higher risk of all-cause death compared with the quintile 2 (32.2-<34.3 mmol/mol). Compared with the HbA1c decile 4 (33.3-<34.3 mmol/mol), those in the lowest HbA1c decile (<30.5 mmol/mol) and highest HbA1c decile (≥41.0 mmol/mol) had 22% (HR, 1.22; 95% CI: 1.01-1.47) and 28% (HR, 1.28; 95% CI: 1.11-1.48) higher risk for overall death. However, no significant association was observed between HbA1c levels and the risk of COPD-specific death.

CONCLUSIONS

Our findings indicated that lower and higher HbA1c levels were associated with a higher risk of COPD. In COPD cases, lower and higher HbA1c levels were associated with a higher COPD all-cause death risk.

Specific reprogramming of alpha cells to insulin-producing cells by short glucagon promoter-driven Pdx1 and MafA

Endogenous reprogramming of pancreas-derived non-beta cells into insulin-producing cells is a promising approach to treat type 1 diabetes (T1D). One strategy that has yet to be explored is the specific delivery of insulin-producing essential genes, Pdx1 and MafA, to pancreatic alpha cells to reprogram the cells into insulin-producing cells in an adult pancreas. In this study, we used an alpha cell-specific glucagon (GCG) promoter to drive Pdx1 and MafA transcription factors to reprogram alpha cells to insulin-producing cells in chemically induced and autoimmune diabetic mice. Our results showed that a combination of a short glucagon-specific promoter with AAV serotype 8 (AAV8) can be used to successfully deliver Pdx1 and MafA to pancreatic alpha cells in the mouse pancreas. Pdx1 and MafA expression specifically in alpha cells were also able to correct hyperglycemia in both induced and autoimmune diabetic mice. With this technology, targeted gene specificity and reprogramming were accomplished with an alpha-specific promotor combined with an AAV-specific serotype and provide an initial basis to develop a novel therapy for the treatment of T1D.

Bone-marrow derived cells do not contribute to new beta-cells in the inflamed pancreas

The contribution of bone-marrow derived cells (BMCs) to a newly formed beta-cell population in adults is controversial. Previous studies have only used models of bone marrow transplantation from sex-mismatched donors (or other models of genetic labeling) into recipient animals that had undergone irradiation. This approach suffers from the significant shortcoming of the off-target effects of irradiation. Partial pancreatic duct ligation (PDL) is a mouse model of acute pancreatitis with a modest increase in beta-cell number. However, the possibility that recruited BMCs in the inflamed pancreas may convert into beta-cells has not been examined. Here, we used an irradiation-free model to track the fate of the BMCs from the donor mice. A ROSA-mTmG red fluorescent mouse was surgically joined to an INS1Cre knock-in mouse by parabiosis to establish a mixed circulation. PDL was then performed in the INS1Cre mice 2 weeks after parabiosis, which was one week after establishment of the stable blood chimera. The contribution of red cells from ROSA-mTmG mice to beta-cells in INS1Cre mouse was evaluated based on red fluorescence, while cell fusion was evaluated by the presence of green fluorescence in beta-cells. We did not detect any red or green insulin+ cells in the INS1Cre mice, suggesting that there was no contribution of BMCs to the newly formed beta-cells, either by direct differentiation, or by cell fusion. Thus, the contribution of BMCs to beta-cells in the inflamed pancreas should be minimal, if any.

Polarized macrophages promote gestational beta cell growth through extracellular signal-regulated kinase 5 signalling

AIM

To show that depletion of pancreatic macrophages impairs gestational beta cell proliferation and leads to glucose intolerance.

MATERIALS AND METHODS

Genetic animal models were applied to study the effects of depletion of pancreatic macrophges on gestational beta-cell proliferaiton and glucose response. The crosstalk between macrophages and beta-cells was studied in vivo using beta-cell-specific extracellular-signal-regulated kinase 5 (ERK5) knockout and epidermal growth receptor (EGFR) knockout mice, and in vitro using a co-culture system.

RESULTS

Beta cell-derived placental growth factor (PlGF) recruited naïve macrophages and polarized them towards an M2-like phenotype. These macrophages then secreted epidermal growth factor (EGF), which activated extracellular signal-regulated kinase 5 (ERK5) signalling in beta cells to promote gestational beta cell proliferation. On the other hand, activation of ERK5 signalling in beta cells likely, in turn, enhanced the production and secretion of PlGF by beta cells.

CONCLUSIONS

Our study shows a regulatory loop between macrophages and beta cells through PlGF/EGF/ERK5 signalling cascades to regulate gestational beta cell growth.

Prolonged insulin-induced hypoglycaemia reduces ß-cell activity rather than number in pancreatic islets in non-diabetic rats

Pancreatic β-cells have an extraordinary ability to adapt to acute fluctuations in glucose levels by rapid changing insulin production to meet metabolic needs. Although acute changes have been characterised, effects of prolonged metabolic stress on β-cell dynamics are still unclear. Here, the aim was to investigate pancreatic β-cell dynamics and function during and after prolonged hypoglycaemia. Hypoglycaemia was induced in male and female rats by infusion of human insulin for 8 weeks, followed by a 4-week infusion-free recovery period. Animals were euthanized after 4 or 8 weeks of infusion, and either 2 days and 4 weeks after infusion-stop. Total volumes of pancreatic islets and β-cell nuclei, islet insulin and glucagon content, and plasma c-peptide levels were quantified. Prolonged hypoglycaemia reduced c-peptide levels, islet volume and almost depleted islet insulin. Relative β-cell nuclei: total pancreas volume decreased, while being unchanged relative to islet volume. Glucagon: total pancreas volume decreased during hypoglycaemia, whereas glucagon: islet volume increased. Within two days after infusion-stop, plasma glucose and c-peptide levels normalised and all remaining parameters were fully reversed after 4 weeks. In conclusion, our findings indicate that prolonged hypoglycaemia inactivates β-cells, which can rapidly be reactivated when needed, demonstrating the high plasticity of β-cells even following prolonged suppression.

Role of angiogenesis in beta-cell epithelial-mesenchymal transition in chronic pancreatitis-induced diabetes

Clinical evidence suggests that patients with chronic pancreatitis (CP) are prone to development of diabetes (chronic pancreatitis-related diabetes; CPRD), whereas the underlying mechanisms are not fully determined. Recently, we showed that the gradual loss of functional beta-cells in a mouse model for CPRD, partial pancreatic duct ligation (PDL), results from a transforming growth factor β1 (TGFβ1)-triggered beta-cell epithelial-mesenchymal transition (EMT), rather than from apoptotic beta-cell death. Here, the role of angiogenesis in CPRD-associated beta-cell EMT was addressed. We detected enhanced angiogenesis in the inflamed pancreas from CP patients by bioinformatic analysis and from PDL-mice. Inhibition of angiogenesis by specific antisera for vascular endothelial growth factor receptor 2 (VEGFR2), DC101, did not alter the loss of beta-cells and the fibrotic process in PDL-pancreas. However, DC101-mediated inhibition of angiogenesis abolished pancreatitis-induced beta-cell EMT and rendered it to apoptotic beta-cell death. Thus, our data suggest that angiogenesis promotes beta-cell survival in the inflamed pancreas, while suppression of angiogenesis turns beta-cell EMT into apoptotic beta-cell death. This finding could be informative during development of intervention therapies for CPRD.

Effects of anti-diabetic drugs on sarcopenia: Best treatment options for elderly patients with type 2 diabetes mellitus and sarcopenia

Human life expectancy increases as society becomes more developed. This increased life expectancy poses challenges associated with the rapid aging of the population. Sarcopenia, an age-related disease, has become a worldwide health issue. Patients with sarcopenia experience decreases in muscle mass and function, becoming frail and eventually bedridden. Type 2 diabetes mellitus (T2DM) is also a major health issue; the incidence of T2DM increases with aging. T2DM is associated with reduced muscle strength and poor muscle quality and may contribute to acceleration of the aging process, augmenting age-related sarcopenia. Recent studies indicate that elderly patients with diabetes are at an increased risk for sarcopenia. Therefore, these older diabetic patients with sarcopenia need specific anti-diabetic therapies targeting not only glycemic control but also sarcopenia, with the goal of preventing sarcopenia in pre-sarcopenic patients. Presently, various types of hypoglycemic drugs are available, but which hypoglycemic drugs are better suited for geriatric T2DM patients with sarcopenia remains undetermined. In this review, we discuss the association between diabetes and sarcopenia in geriatric patients, and how anti-diabetic drugs may influence sarcopenia outcomes. This review will guide clinical workers in the selection of drugs best suited for this patient population.

Netrin-1 promotes retinoblastoma-associated angiogenesis

BACKGROUND

Retinoblastoma (Rb) is the most common intraocular cancer of infancy and childhood, with an incidence of nearly 0.006% in all live births. Although a functional loss or inactivation of both alleles of the retinoblastoma 1 (RB1) gene during retinal development appears to be the predominant etiology for Rb, genes associated with tumor angiogenesis are also likely to be involved in the development of this condition. Netrin-1 is a factor that regulates pathological angiogenesis, while its role in Rb is largely unknown. The present study examined the role of netrin-1 in Rb.

METHODS

The expression of netrin-1 in Rb was assessed using public databases and using clinical specimens by RT-qPCR for mRNA and by ELISA for protein. The expression of netrin-1 was suppressed in Rb by siRNA and the effects on cell growth were determined by a CCK-8 assay, while the effects on angiogenesis were examined in vitro using human umbilical vein endothelial cell (HUVEC) assays and in vivo by quantification of tumor vessel density.

RESULTS

Analysis of published databases revealed that the netrin-1 gene is significantly upregulated in Rb, which was confirmed by immunohistochemistry on clinical specimens. Inhibition of netrin-1 in Rb cell lines significantly reduced their effects on angiogenesis in vitro using a HUVEC co-culture assay without affecting cell growth. Inhibition of netrin-1 expression in vivo suppressed the growth of grafted Rb, and this effect could be abolished by co-expression of vascular endothelial growth factor A (VEGF-A).

CONCLUSIONS

This data demonstrated a novel role for netrin-1 in the regulation of Rb-associated cancer vascularization and may represent a novel therapeutic target for patients with Rb.

PlGF Reduction Compromises Angiogenesis in Diabetic Foot Disease Through Macrophages

Diabetic foot disease (DFD) is a common and serious complication for diabetes and is characterized with impaired angiogenesis. In addition to the well-defined role of vascular endothelial growth factor (VEGF) -A and its defect in the pathogenesis of DFD, another VEGF family member, placental growth factor (PlGF), was also recently found to alter expression pattern in the DFD patients with undetermined mechanisms. This question was thus addressed in the current study. We detected attenuated PlGF upregulation in a mouse DFD model. In addition, the major cell types at the wound to express the unique PlGF receptor, VEGF receptor 1 (VEGFR1), were macrophages and endothelial cells. To assess how PlGF regulates DFD-associated angiogenesis, we injected recombinant PlGF and depleted VEGF1R specifically in macrophages by local injection of an adeno-associated virus (AAV) carrying siRNA for VEGFR1 under a macrophage-specific CD68 promoter. We found that the angiogenesis and recovery of the DFD were both improved by PlGF injection. The PlGF-induced improvement in angiogenesis and the recovery of skin injury were largely attenuated by macrophage-specific depletion of VEGF1R, likely resulting from reduced macrophage number and reduced M2 polarization. Together, our data suggest that reduced PlGF compromises angiogenesis in DFD at least partially through macrophages.

Insulin-positive ductal cells do not migrate into preexisting islets during pregnancy

The adult pancreatic ductal system was suggested to harbor facultative beta-cell progenitors similar to the embryonic pancreas, and the appearance of insulin-positive duct cells has been used as evidence for natural duct-to-beta-cell reprogramming. Nevertheless, the phenotype and fate of these insulin-positive cells in ducts have not been determined. Here, we used a cell-tagging dye, CFDA-SE, to permanently label pancreatic duct cells through an intraductal infusion technique. Representing a time when significant increases in beta-cell mass occur, pregnancy was later induced in these CFDA-SE-treated mice to assess the phenotype and fate of the insulin-positive cells in ducts. We found that a small portion of CFDA-SE-labeled duct cells became insulin-positive, but they were not fully functional beta-cells based on the in vitro glucose response and the expression levels of key beta-cell genes. Moreover, these insulin-positive cells in ducts expressed significantly lower levels of genes associated with extracellular matrix degradation and cell migration, which may thus prevent their budding and migration into preexisting islets. A similar conclusion was reached through analysis of the Gene Expression Omnibus database for both mice and humans. Together, our data suggest that the contribution of duct cells to normal beta-cells in adult islets is minimal at best.

Protein restriction during pregnancy impairs intra-islet GLP-1 and the expansion of β-cell mass

We evaluated whether protein restriction during pregnancy alters the morphometry of pancreatic islets, the intra-islet glucagon-like peptide-1 (GLP-1) production, and the anti-apoptotic signalling pathway modulated by GLP-1. Control non-pregnant (CNP) and control pregnant (CP) rats were fed a 17% protein diet, and low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) groups were fed a 6% protein diet. The masses of islets and β-cells were similar in the LPNP group and the CNP group but were higher in the CP group than in the CNP group and were equal in the LPP group and the LPNP group. Both variables were lower in the LPP group than in the CP group. Prohormone convertase 2 and GLP-1 fluorescence in α-cells was lower in the low-protein groups than in the control groups. The least PC2/glucagon colocalization was observed in the LPP group, and the most was observed in the CP group. There was less prohormone convertase 1/3/glucagon colocalization in the LPP group than in the CP group. GLP-1/glucagon colocalization was similar in the LPP, CP and CNP groups, which showed less GLP-1/glucagon colocalization than the LPNP group. The mRNA Pka, Creb and Pdx-1 contents were higher in islets from pregnant rats than in islets from non-pregnant rats. Protein restriction during pregnancy impaired the mass of β-cells and the intra-islet GLP-1 production but did not interfere with the transcription of genes of the anti-apoptotic signalling pathway modulated by GLP-1.

Placental growth factor in beta cells plays an essential role in gestational beta-cell growth

OBJECTIVE

Pancreatic beta cells proliferate in response to metabolic requirements during pregnancy, while failure of this response may cause gestational diabetes. A member of the vascular endothelial growth factor family, placental growth factor (PlGF), typically plays a role in metabolic disorder and pathological circumstance. The expression and function of PlGF in the endocrine pancreas have not been reported and are addressed in the current study.

RESEARCH DESIGN AND METHODS

PlGF levels in beta cells were determined by immunostaining or ELISA in purified beta cells in non-pregnant and pregnant adult mice. An adeno-associated virus (AAV) serotype 8 carrying a shRNA for PlGF under the control of a rat insulin promoter (AAV-rat insulin promoter (RIP)-short hairpin small interfering RNA for PlGF (shPlGF)) was prepared and infused into mouse pancreas through the pancreatic duct to specifically knock down PlGF in beta cells, and its effects on beta-cell growth were determined by beta-cell proliferation, beta-cell mass and insulin release. A macrophage-depleting reagent, clodronate, was coapplied into AAV-treated mice to study crosstalk between beta cells and macrophages.

RESULTS

PlGF is exclusively produced by beta cells in the adult mouse pancreas. Moreover, PlGF expression in beta cells was significantly increased during pregnancy. Intraductal infusion of AAV-RIP-shPlGF specifically knocked down PlGF in beta cells, resulting in compromised beta-cell proliferation, reduced growth in beta-cell mass and impaired glucose tolerance during pregnancy. Mechanistically, PlGF depletion in beta cells reduced islet infiltration of trophic macrophages, which appeared to be essential for gestational beta-cell growth.

CONCLUSIONS

Our study suggests that increased expression of PlGF in beta cells may trigger gestational beta-cell growth through recruited macrophages.

Improved therapeutic effects on diabetic foot by human mesenchymal stem cells expressing MALAT1 as a sponge for microRNA-205-5p

Diabetic foot (DF) is a common complication of high severity for diabetes, a prevalent metabolic disorder that affects billions of people worldwide. Mesenchymal stem cells (MSCs) have a demonstrative therapeutic effect on DF, through their generation of pro-angiogenesis factors, like vascular endothelial growth factor (VEGF). Recently, genetically modified MSCs have been used in therapy and we have shown that depletion of micoRNA-205-5p (miR-205-5p) in human MSCs promotes VEGF-mediated therapeutic effects on DF. Here, we showed that a long non-coding RNA (lncRNA), MALAT1, is a competing endogenous RNA (ceRNA) for miR-205-5p, and is low expressed in human MSCs. Ectopic expression of MALAT1 in human MSCs significantly decreased miR-205-5p levels, resulting in upregulation of VEGF production and improved in vitro endothelial cell tube formation. In a DF model in immunodeficient NOD/SCID mice, transplantation of human miR-205-5p-depleted MSCs exhibited better therapeutic effects on DF recovery than control MSCs. Moreover, MALAT1-expressing MSCs showed even better therapeutic effects on DF recovery than miR-205-5p-depleted MSCs. This difference in DF recovery was shown to be associated with the levels of on-site vascularization. Together, our data suggest that MALAT1 functions as a sponge RNA for miR-205-5p to increase therapeutic effects of MSCs on DF.

Role of alternative splicing of VEGF-A in the development of atherosclerosis

Vascular endothelial cell growth factor A (VEGF-A) signaling promotes the endothelial cell proliferation, macrophage infiltration and foam cell formation, which play pivotal roles in the pathogenesis of atherosclerosis (AS). However, the role of alternative splicing of VEGF here is not known. Here, ApoE (-/-) mice supplied high-fat diet (HFD mice) were used to generate AS, while ApoE (-/-) mice supplied with normal diet (NOR mice) were used as a control. Aortic endothelial cells (AECs) and infiltrated macrophages were purified and quantified by flow cytometry. Alternative splicing of VEGF and the regulator of VEGF splicing, SRPK1, were assessed by RT-qPCR and immunoblotting in both AECs and aortic macrophages. We found that HFD mice developed AS in 12 weeks, while the NOR did not. Compared to NOR mice, HFD mice possessed significantly more AECs and AEC proliferation, and had significantly more aortic infiltrated macrophages and more apoptosis of them. Significant shift of VEGF-A splicing to pro-angiogenic VEGF₁₆₅ was detected in both AECs and macrophages from HFD mice, seemingly through upregulation of SRPK1. In vitro, SRPK1 overexpression significantly increased EC proliferation and macrophage apoptosis. Thus, our data suggest that alternative splicing of VEGF-A to pro-angiogenic VEGF₁₆₅ may contribute to the development of AS.

The Role of the Islet Niche on Beta Cell Structure and Function

The islets of Langerhans or pancreatic islets are pivotal in the control of blood glucose and are complex microorgans embedded within the larger volume of the exocrine pancreas. Humans can have ~3.2 million islets [1] which, to our current knowledge, function in a similar manner to sense circulating blood glucose levels and respond with the secretion of a mix of different hormones that act to maintain glucose concentrations around a specific set point [2]. At a cellular level, the control of hormone secretion by glucose and other secretagogues is well-understood [3]. The key signal cascades have been identified and many details of the secretory process are known. However, if we shift focus from single cells and consider cells within intact islets, we do not have a comprehensive model as to how the islet environment influences cell function and how the islets work as a whole. This is important because there is overwhelming evidence that the structure and function of the individual endocrine cells are dramatically affected by the islet environment [4,5]. Uncovering the influence of this islet niche might drive future progress in treatments for Type 2 diabetes [6] and cell replacement therapies for Type 1 diabetes [7]. In this review, we focus on the insulin secreting beta cells and their interactions with the immediate environment that surrounds them including endocrine-endocrine interactions and contacts with capillaries.

VEGF-A and blood vessels: a beta cell perspective

Reciprocal signalling between the endothelium and the pancreatic epithelium is crucial for coordinated differentiation of the embryonic endocrine and exocrine pancreas. In the adult pancreas, islets depend on their dense capillary network to adequately respond to changes in plasma glucose levels. Vascular changes contribute to the onset and progression of both type 1 and type 2 diabetes. Impaired revascularisation of islets transplanted in individuals with type 1 diabetes is linked to islet graft failure and graft loss. This review summarises our understanding of the role of vascular endothelial growth factor-A (VEGF-A) and endothelial cells in beta cell development, physiology and disease. In addition, the therapeutic potential of modulating VEGF-A levels in beta and beta-like cells for transplantation is discussed.

Evidence of a developmental origin for β-cell heterogeneity using a dual lineage-tracing technology

The Cre/loxP system has been used extensively in mouse models with a limitation of one lineage at a time. Differences in function and other properties among populations of adult β-cells is termed β-cell heterogeneity, which was recently associated with diabetic phenotypes. Nevertheless, the presence of a developmentally derived β-cell heterogeneity is unclear. Here, we have developed a novel dual lineage-tracing technology, using a combination of two recombinase systems, Dre/RoxP and Cre/LoxP, to independently trace green fluorescent Pdx1-lineage cells and red fluorescent Ptf1a-lineage cells in the developing and adult mouse pancreas. We detected a few Pdx1+/Ptf1a- lineage cells in addition to the vast majority of Pdx1+/Ptf1a+ lineage cells in the pancreas. Moreover, Pdx1+/Ptf1a+ lineage β-cells had fewer Ki-67+ proliferating β-cells, and expressed higher mRNA levels of insulin, Glut2, Pdx1, MafA and Nkx6.1, but lower CCND1 and CDK4 levels, compared with Pdx1+/Ptf1a- lineage β-cells. Furthermore, more TSQ-high, SSC-high cells were detected in the Pdx1+Ptf1a+ lineage population than in the Pdx1+Ptf1a- lineage population. Together, these data suggest that differential activation of Ptf1a in the developing pancreas may correlate with this β-cell heterogeneity.

The role of ORMDL3/ATF6 in compensated beta cell proliferation during early diabetes

Endoplasmic reticulum (ER) stress in beta cells induces a signaling network called the unfolded protein response (UPR), which plays a dual role in diabetes. A key regulator of ER-stress and UPR, the orosomucoid 1-like protein 3 (ORMDL3), has been shown to regulate airway remodeling through a major UPR protein, activating transcription factor 6 (ATF6), but the contribution of this regulatory axis to compensatory pancreatic beta cell proliferation in diabetes has not been studied. Here, we detected significantly lower levels of ORMDL3 mRNA in leukocytes of peripheral blood specimens from type 1 diabetes (T1D) children, compared to normal children. Moreover, these ORMDL3 levels in T1D children exhibited further decreases upon follow-up. ORMDL3 levels in islets from NOD mice, a mouse model for T1D in humans, showed a mild increase before diabetes onset, but a gradual decrease subsequently. In high glucose culture, beta cell proliferation, but not apoptosis, was increased by overexpression of ORMDL3 levels, likely mediated by its downstream factor ATF6. Mechanistically, ORMDL3 transcriptionally activated ATF6, which was confirmed in a promoter reporter assay. Together, our data suggest that ORMDL3 may increase beta cell proliferation through ATF6 as an early compensatory change in response to diabetes.

Simplified Purification of AAV and Delivery to the Pancreas by Intraductal Administration

Genetic manipulation is a very powerful tool for studying diabetes, pancreatitis, and pancreatic cancer. Here we discuss the use of an adeno-associated virus (AAV) vector to modify gene expression, such as to introduce a green fluorescence protein (GFP) in wild-type mice, cre recombinase in loxP mice, or to inactivate a gene with shRNA. The use of viruses for genetic modification allows for time-specific genetic changes which have advantages over time-consuming and often complex cross-breeding strategies. Here we provide a detailed approach for this process from viral production and purification through pancreatic ductal infusion. Our protocol allows efficient delivery of AAV to mediate GFP or cre expression for cell lineage tracing in the mouse pancreas or for the delivery of transgenes under a specific promoter to these cells.

Co-suppression of VEGF-A and VEGF-C inhibits development of experimental hemangioma

Vascular endothelial growth factor A (VEGF-A) plays a critical role in the development and progression of Infantile hemangioma (IH), the most common vascular tumor occurring during infancy. However, a role of VEGF-C in IH remains unclear. Here, we addressed this question. The expression of VEGF family members in hemangiomas at involuting-phase and at proliferating-phase was compared, by RT-qPCR and by ELISA. VEGF-A and VEGF-C were suppressed by specific short-hairpin interfering RNA (shRNA), respectively. Cell growth was determined in an MTT assay. Cell proliferation was assessed by BrdU incorporation and analysis of cell-cycle regulators by Western blotting. Cell apoptosis was assessed by Annexin V assay and analysis of apoptosis-associated proteins by Western blotting. The effects of VEGF-A suppression, or VEGF-C suppression, or both, on hemangioma growth were analyzed in vivo by bioluminescence assay and by weight of the implanted tumor. Significantly higher levels of VEGF-A and VEGF-C were detected in the proliferating-phase of the hemangiomas than in the involuting-phase of the hemangiomas. Suppression of either VEGF-A or VEGF-C decreased hemangioma cell growth, likely through inhibition of proliferation and enhancement of the apoptosis, while suppression of both VEGF-A and VEGF-C had a more pronounced effect than suppression of either VEGF-A or VEGF-C alone. VEGF-A and VEGF-C seemed to regulate proliferation and apoptosis through different proteins. Suppression of both VEGF-A and VEGF-C had a more pronounced effect than suppression of either one on the growth of the implanted hemangiomas In vivo. Thus, co-suppression of VEGF-A and VEGF-C has better inhibitory effects on the growth of hemangioma.

INGAP-PP effects on β-cell mass and function are related to its positive effect on islet angiogenesis and VEGFA production

Our aim was to determine whether islet angiogenesis and VEGFA production/release participate in the mechanism by which INGAP-PP enhances β-cell function and mass. We used two models: a) in vivo (normal rats injected with INGAP-PP for 10 days) and b) in vitro (normal islets cultured for 4 days with INGAP-PP, VEGFA, Rapamycin, and the specific VEGF-Receptor inhibitor, SU5416). INGAP-PP administration enhanced insulin secretion, β-cell mass, islet vascularization, and angiogenesis without affecting glucose homeostasis. Normal islets cultured with INGAP-PP and VEGFA increased insulin and VEGFA secretion while apoptosis decreased. INGAP-PP-induced effects were prevented by both Rapamycin and SU5416. INGAP-PP effects on β-cell mass and function were significantly associated with a positive effect on islet angiogenesis and VEGFA production/release. VEGF-A possibly potentiates INGAP-PP effect through mTORC pathway.

Endogenous Reprogramming of Alpha Cells into Beta Cells, Induced by Viral Gene Therapy, Reverses Autoimmune Diabetes

Successful strategies for treating type 1 diabetes need to restore the function of pancreatic beta cells that are destroyed by the immune system and overcome further destruction of insulin-producing cells. Here, we infused adeno-associated virus carrying Pdx1 and MafA expression cassettes through the pancreatic duct to reprogram alpha cells into functional beta cells and normalized blood glucose in both beta cell-toxin-induced diabetic mice and in autoimmune non-obese diabetic (NOD) mice. The euglycemia in toxin-induced diabetic mice and new insulin+ cells persisted in the autoimmune NOD mice for 4 months prior to reestablishment of autoimmune diabetes. This gene therapy strategy also induced alpha to beta cell conversion in toxin-treated human islets, which restored blood glucose levels in NOD/SCID mice upon transplantation. Hence, this strategy could represent a new therapeutic approach, perhaps complemented by immunosuppression, to bolster endogenous insulin production. Our study thus provides a potential basis for further investigation in human type 1 diabetes.

Metformin inhibits development of diabetic retinopathy through microRNA-497a-5p

Metformin is an AMP-activated protein kinase activator that is widely prescribed for treating type 2 diabetes. Recently, metformin was reported to slow down the development and alleviate the severity of diabetic retinopathy (DR). However, the underlying mechanisms remain unclear. Here, we used an alloxan-induced diabetes mouse model to study the effects of metformin on the development of DR as well as the mechanisms. We found that DR was induced in alloxan-treated mice 10 weeks after alloxan treatment, and treatment of metformin did not prevent the occurrence of alloxan-induced diabetes. However, metformin significantly alleviated the severity of DR, seemingly through attenuating the retina neovascularization. Moreover, the total vascular endothelial cell growth factor A (VEGF-A) mRNA in mouse eyes was not altered by metformin, but the protein levels was decreased. Further analysis showed that metformin may inhibit the VEGF-A protein translation through inducing a VEGF-A-targeting microRNA, microRNA-497a-5p, resulting in reduced retina neovascularization. Thus, our study suggests a previously unappreciated role of metformin in the prevention of development of DR.

ERK5 plays an essential role in gestational beta-cell proliferation

OBJECTIVES

Restoring a functional beta-cell mass is a fundamental goal in treating diabetes. A complex signalling pathway network coordinates the regulation of beta-cell proliferation, although a role for ERK5 in this network has not been reported. This question was addressed in this study.

MATERIALS AND METHODS

We studied the activation of extracellular-signal-regulated kinase 5 (ERK5) in pregnant mice, a well-known mouse model of increased beta-cell proliferation. A specific inhibitor of ERK5 activation, BIX02189, was intraperitoneally injected into the pregnant mice to suppress ERK5 signalling. Beta-cell proliferation was determined by quantification of Ki-67⁺ beta cells. Beta-cell apoptosis was determined by TUNEL assay. The extent of beta-cell proliferation was determined by beta-cell mass. The alteration of ERK5 activation and CyclinD1 levels in purified mouse islets was examined by Western blotting.

RESULTS

Extracellular-signal-regulated kinase 5 phosphorylation, which represents ERK5 activation, was significantly upregulated in islets from pregnant mice. Suppression of ERK5 activation by BIX02189 in pregnant mice significantly reduced beta-cell proliferation, without affecting beta-cell apoptosis, resulting in increases in random blood glucose levels and impairment of glucose response of the mice. ERK5 seemed to activate CyclinD1 to promote gestational beta-cell proliferation.

CONCLUSIONS

Extracellular-signal-regulated kinase 5 plays an essential role in the gestational augmentation of beta-cell proliferation. ERK5 may be a promising target for increasing beta-cell mass in diabetes patients.

VEGF, the underlying factor for metabolic syndrome; fact or fiction?

Metabolic syndrome (MetS) is currently diagnosed by the co-presence of at least three of the five following abnormalities: abdominal obesity, dysglycaemia, elevated serum triglycerides, low high-density cholesterol (HDL) and finally elevated blood pressure. Metabolic syndrome increases the risk of developing cardiovascular disease and diabetes. This review is on the associations between MetS and vascular endothelial growth factor (VEGF). VEGF induces migration and proliferation of endothelial cells (ECs), increases vascular permeability and has a role in tumor growth, adipose tissue expansion, age-related macular degeneration and diabetic retinopathy. Circulating levels of VEGFs are elevated in obese individuals and it has also been suggested that VEGF is secreted from adipose tissues, especially from intra-abdominal adipose tissue. There is abundant evidence to support that poor glycemic control in diabetic patients is associated with increased plasma VEGF, which in turn may cause hypertension and several vascular complications in diabetic patients. Circulating VEGF levels are increased in children and young adults with type 1 diabetes mellitus and middle-aged diabetic patients with proliferative retinopathy. It has been revealed that plasma VEGF increases in patients with hyperlipidemia and may trigger the development of atherosclerosis. It can be concluded that there is a positive association between VEGF and components of MetS. Because of the importance of this relationship, more investigations are needed in this field.

SMAD3/Stat3 Signaling Mediates β-Cell Epithelial-Mesenchymal Transition in Chronic Pancreatitis-Related Diabetes

Many patients with chronic pancreatitis develop diabetes (chronic pancreatitis-related diabetes [CPRD]) through an undetermined mechanism. Here we used long-term partial pancreatic duct ligation (PDL) as a model to study CPRD. We found that long-term PDL induced significant β-cell dedifferentiation, followed by a time-dependent decrease in functional β-cell mass-all specifically in the ligated tail portion of the pancreas (PDL-tail). High levels of transforming growth factor β1 (TGFβ1) were detected in the PDL-tail and were mainly produced by M2 macrophages at the early stage and by activated myofibroblasts at the later stage. Loss of β-cell mass was then found to result from TGFβ1-triggered epithelial-mesenchymal transition (EMT) by β-cells, rather than resulting directly from β-cell apoptosis. Mechanistically, TGFβ1-treated β-cells activated expression of the EMT regulator gene Snail in a SMAD3/Stat3-dependent manner. Moreover, forced expression of forkhead box protein O1 (FoxO1), an antagonist for activated Stat3, specifically in β-cells ameliorated β-cell EMT and β-cell loss and prevented the onset of diabetes in mice undergoing PDL. Together, our data suggest that chronic pancreatitis may trigger TGFβ1-mediated β-cell EMT to lead to CPRD, which could substantially be prevented by sustained expression of FoxO1 in β-cells.

Insulin treatment restores islet microvascular vasomotion function in diabetic mice

BACKGROUND

The microcirculation plays an important role in the pathogenesis of diabetes and its complications. We hypothesized that pancreatic islet microvascular (PIM) vasomotion, as a parameter of pancreatic islet microcirculation function, is abnormal in diabetic mice and that insulin treatment may reverse this dysfunction.

METHODS

Mice were randomly assigned to non-diabetic control, untreated diabetic, and insulin-treated diabetic groups (n = 6 in each group). Separate groups of streptozotocin (STZ)-induced diabetic and high-fat diet-fed mice were used as a model of hyperglycemia. Insulin-treated diabetic mice were treated with 1-1.5 IU/day insulin for 1 week. Laser Doppler monitors were used to evaluate PIM vasomotion. Morphological and ultrastructural changes in islet endothelial cells were determined by immunohistochemistry and transmission electron microscopy. Glucagon, insulin, vascular endothelial growth factor (VEGF)-A, and platelet endothelial cell adhesion molecule (PECAM-1) expression was determined by immunohistochemistry and Western blotting.

RESULTS

In both untreated diabetic groups, the pancreatic islet microcirculation was unable to regulate PIM vasomotion. The rhythm of vasomotion was irregular, and the average blood perfusion, amplitude, frequency, and relative velocity of vasomotion were significantly lower than in non-diabetic controls. Insulin treatment restored the functional status of PIM vasomotion. In islet endothelial cells from both untreated diabetic groups, the mitochondria were swollen with disarrangement of the cristae, and the distribution of PECAM-1 was discontinuous. Insulin treatment significantly increased the reduced expression of PECAM-1 in both untreated diabetic groups and VEGF-A expression in untreated STZ-diabetic mice.

CONCLUSION

The results suggest that the functional status of PIM vasomotion is impaired in diabetic mice but can be restored by insulin.

Suppression of microRNA-205-5p in human mesenchymal stem cells improves their therapeutic potential in treating diabetic foot disease

Diabetes is a prevalent disease endangering human health, while diabetic foot disease (DF) is one of the most severe complications of diabetes. Mesenchymal stem cells (MSCs) have been used in DF treatment, taking advantage of the differentiation potential of MSCs into endothelial cells and their production and secretion of trophic factors like vascular endothelial growth factor (VEGF). Molecular modification of MSCs to improve their therapeutic effects has been recently applied in treating other diseases, but not yet in DF. Here, we found that micoRNA-205-5p (miR-205-5p) is expressed in human MSCs, and miR-205-5p inhibits protein translation of VEGF through its interaction with 3'-UTR of the VEGF mRNA. Expression of antisense of miR-205-5p (as-miR-205-5p) significantly increased both cellular and secreted VEGF by MSCs, which significantly improved the therapeutic effects of MSCs on DF-associated wound healing in diabetic NOD/SCID mice. Together, our data suggest that miR-205-5p suppression in MSCs may improve their therapeutic effects on DF, seemingly through augmentation of VEGF-mediated vascularization.

Intra-islet endothelial cell and β-cell crosstalk: Implication for islet cell transplantation

The intra-islet microvasculature is a critical interface between the blood and islet endocrine cells governing a number of cellular and pathophysiological processes associated with the pancreatic tissue. A growing body of evidence indicates a strong functional and physical interdependency of β-cells with endothelial cells (ECs), the building blocks of islet microvasculature. Intra-islet ECs, actively regulate vascular permeability and appear to play a role in fine-tuning blood glucose sensing and regulation. These cells also tend to behave as “guardians”, controlling the expression and movement of a number of important immune mediators, thereby strongly contributing to the physiology of islets. This review will focus on the molecular signalling and crosstalk between the intra-islet ECs and β-cells and how their relationship can be a potential target for intervention strategies in islet pathology and islet transplantation.

Forkhead Box Protein 1 (FoxO1) Inhibits Accelerated β Cell Aging in Pancreas-specific SMAD7 Mutant Mice

The mechanisms underlying the effects of exocrine dysfunction on the development of diabetes remain largely unknown. Here we show that pancreatic depletion of SMAD7 resulted in age-dependent increases in β cell dysfunction with accelerated glucose intolerance, followed by overt diabetes. The accelerated β cell dysfunction and loss of proliferation capacity, two features of β cell aging, appeared to be non-cell-autonomous, secondary to the adjacent exocrine failure as a "bystander effect." Increased Forkhead box protein 1 (FoxO1) acetylation and nuclear retention was followed by progressive FoxO1 loss in β cells that marked the onset of diabetes. Moreover, forced FoxO1 expression in β cells prevented β cell dysfunction and loss in this model. Thus, we present a model of accelerated β cell aging that may be useful for studying the mechanisms underlying β cell failure in diabetes. Moreover, we provide evidence highlighting a critical role of FoxO1 in maintaining β cell identity in the context of SMAD7 failure.

YT521 promotes metastases of endometrial cancer by differential splicing of vascular endothelial growth factor A

The malignancy of endometrial carcinoma (EC) largely results from its high invasive feature. The regulation of the mRNA splicing of vascular endothelial growth factor A (VEGF-A) is critical for EC-associated cancer vascularization and invasion. Recently, we have reported that poorly prognostic EC had high levels of YT521, a newly defined RNA splicing protein. However, whether YT521 may similarly regulate the splicing of VEGF-A in EC is unknown. Here, we showed that EC specimens contained significantly higher levels of YT521, compared to the adjacent non-tumor endometrial tissue. Higher levels of YT521 were detected in EC specimens with metastases. High-YT521 EC is associated with poor patient survival. In order to examine whether YT521 may regulate VEGF-A mRNA splicing in EC, we transfected an EC cell line HEC-1A with different doses of YT521 mimics. We found that YT521 dose-dependently increased the ratio of VEGF-165 vs VEGF-121 at both mRNA and protein level, suggesting that YT521 may promote VEGF-A mRNA splicing to favor a VEGF-165 isoform. Moreover, the increases in the ratio of VEGF-165 vs VEGF-121 by YT521 overexpression resulted in increases in EC cell invasion, while decreases in the ratio of VEGF-165 vs VEGF-121 by YT521 depletion resulted in decreases in EC cell invasion in a transwell cell migration assay. Further, overexpression of VEGF-165, but not overexpression of VEGF-121, increased EC cell invasiveness. Finally, a strong correlation was detected between the ratio of VEGF-165 vs VEGF-121 and the levels of YT521 in EC specimens. Together, these data suggest that YT521 may promote EC metastases by regulating mRNA splicing of VEGF-A.

Ginsenoside Rh2 inhibits invasiveness of glioblastoma through modulation of VEGF-A

The malignancy of glioblastoma multiforme (GBM) is largely due to its local invasion and the presence of the tumor in the relatively restrained region in the brain. Hence, effective prevention of the cancer cell invasion is substantially critical for controlling the growth and deterioration of GBM. We have recently reported the role of ginsenoside Rh2 (GRh2) in suppressing the growth of GBM through EGFR/PI3k/Akt/mTor signaling pathways. Here, we further showed that GRh2 efficiently inhibited the cancer vascularization in vivo. In vitro, GRh2 dose-dependently inhibited the protein, but not messenger RNA (mRNA) of vascular endothelial growth factor A (VEGF-A) in GBM cells. We then examined the underlying mechanisms and found that GRh2 increased the levels of miR-497, which bound to 3'UTR of VEGF-A mRNA to inhibit its translation. Together, our data demonstrate a previously unappreciated role for GRh2 in inhibition of GBM-associated cancer vascularization, which may contribute to the effects of GRh2 on suppression of GBM cancer growth and invasion.

Different roles of myofibroblasts in the tumorigenesis of nonsmall cell lung cancer

Myofibroblasts play a critical role in the cancer cell growth, invasion, and tumor-associated vascularization during the carcinogenesis of nonsmall cell lung cancer (NSCLC), whereas the underlying molecular bases are not completely understood. We isolated Lin-negative, Sca1-low, and CD49e-high myofibroblasts from the NSCLC tissues of the patients and modified the levels of either transforming growth factor β 1 (TGFβ1) or vascular endothelial growth factor A (VEGF-A) in these cells. We found that coculture with TGFβ1-overexpressing myofibroblasts significantly decreased the NSCLC cell growth in an MTT assay through proliferation suppression rather than modulation of cell apoptosis, while significantly increased the NSCLC cell invasiveness in either a transwell migration assay or a scratch wound healing migration assay. However, modulation of TGFβ1 levels in myofibroblasts did not significantly alter vessel formation in a human umbilical vein endothelial cells (HUVECs) transwell collagen gel assay. On the other hand, overexpression of VEGF-A in myofibroblasts significantly increased vessel formation in the HUVECs transwell collagen gel assay. Together, these data suggest that myofibroblasts may regulate cancer cell growth and invasion through TGFβ1 but modulate cancer-associated neovascularization through VEGF-A. Hence, targeting different signaling pathways in myofibroblasts may delicately control NSCLC growth and invasion.

VEGF-activated miR-144 regulates autophagic survival of prostate cancer cells against Cisplatin

Cisplatin is a commonly used chemotherapy drug for prostate cancer (PC). However, some PCs are resistant to cisplatin treatment, while the molecular mechanisms underlying the resistance of PCs to cisplatin are not completely understood. In this study, we found that cisplatin dose-dependently activated Beclin-1 in two PC cell lines, PC3 and LNCap. Autophagy suppression significantly increased the cisplatin-induced cell death of these PC cells in a CCK-8 assay. Moreover, microRNA (miR)-144 levels were significantly downregulated in cisplatin-treated PC cells, in a VEGF-dependent manner. Bioinformatics analysis showed that miR-144 targeted the 3'-UTR of Beclin-1 mRNA to inhibit its translation, which was confirmed by luciferase reporter assay. In PC patients after cisplatin treatment, low miR-144 levels appeared to predict poor outcome of patients' survival. Together, these data suggest that cisplatin may induce VEGF to suppress miR-144 levels in PC cells, which subsequently upregulates Beclin-1 to increase autophagic cell survival against cisplatin-induced cell death. Upregulation of miR-144 or suppression of cell autophagy may improve the outcome of cisplatin therapy in PC.

Hypoxic resistance of KRAS mutant tumor cells to 3-Bromopyruvate is counteracted by Prima-1 and reversed by N-acetylcysteine

Background

The metabolic inhibitor 3-bromopyruvate (3-BrPA) is a promising anti-cancer alkylating agent, shown to inhibit growth of some colorectal carcinoma with KRAS mutation. Recently, we demonstrated increased resistance to 3-BrPA in wt p53 tumor cells compared to those with p53 silencing or mutation. Since hypoxic microenvironments select for tumor cells with diminished therapeutic response, we investigated whether hypoxia unequally increases resistance to 3-BrPA in wt p53 MelJuso melanoma harbouring (Q61L)-mutant NRAS and wt BRAF, C8161 melanoma with (G12D)-mutant KRAS (G464E)-mutant BRAF, and A549 lung carcinoma with a KRAS (G12S)-mutation. Since hypoxia increases the toxicity of the p53 activator, Prima-1 against breast cancer cells irrespective of their p53 status, we also investigated whether Prima-1 reversed hypoxic resistance to 3-BrPA.

Results

In contrast to the high susceptibility of hypoxic mutant NRAS MelJuso cells to 3-BrPA or Prima-1, KRAS mutant C8161 and A549 cells revealed hypoxic resistance to 3-BrPA counteracted by Prima-1. In A549 cells, Prima-1 increased p21CDKN1mRNA, and reciprocally inhibited mRNA expression of the SLC2A1-GLUT1 glucose transporter-1 and ALDH1A1, gene linked to detoxification and stem cell properties. 3-BrPA lowered CAIX and VEGF mRNA expression. Death from joint Prima-1 and 3-BrPA treatment in KRAS mutant A549 and C8161 cells seemed mediated by potentiating oxidative stress, since it was antagonized by the anti-oxidant and glutathione precursor N-acetylcysteine.

Conclusions

This report is the first to show that Prima-1 kills hypoxic wt p53 KRAS-mutant cells resistant to 3-BrPA, partly by decreasing GLUT-1 expression and exacerbating pro-oxidant stress.

Soluble Flt-1 improves the repair of ankle joint injury in rats

The ankle injuries create great pain to a great number of patients worldwide. Past studies have focused on the development of practical treatments to relieve pain and improve recovery, but the molecular mechanisms underlying the ankle injuries, especially the local inflammation in the damaged ankle joint, have been rarely studied. Moreover, although reduction of production and secretion of pro-inflammatory cytokines may reduce the pain and promote the recovery, a practical approach is currently lacking. Here, we detected significantly higher levels of placental growth factor (PLGF) and pro-inflammatory cytokines in the joint fluid from the patients of acute ankle joint injury (AAJI). Interestingly, the levels of PLGF and pro-inflammatory cytokines in the joint fluid strongly correlated. In order to examine whether PLGF may regulate the production and secretion of pro-inflammatory cytokines in the injured joint, we used a rat carrageenan-induced ankle injury model for AAJI in humans. We injected soluble Flt-1 (sFlt-1) into the articular cavity of the injured ankle joint to block PLGF signaling and found that injection of sFlt-1 significantly improved the rat behavior in activity wheels test, which appeared to result from reduced secretion of the pro-inflammatory cytokines in the ankle joint. Thus, our study suggests that blocking PLGF signaling may be a novel therapeutic approach for treating AAJI in humans.

Epidermal Growth Factor Receptor Signaling Regulates β Cell Proliferation in Adult Mice

A thorough understanding of the signaling pathways involved in the regulation of β cell proliferation is an important initial step in restoring β cell mass in the diabetic patient. Here, we show that epidermal growth factor receptor 1 (EGFR) was significantly up-regulated in the islets of C57BL/6 mice after 50% partial pancreatectomy (PPx), a model for workload-induced β cell proliferation. Specific deletion of EGFR in the β cells of adult mice impaired β cell proliferation at baseline and after 50% PPx, suggesting that the EGFR signaling pathway plays an essential role in adult β cell proliferation. Further analyses showed that β cell-specific depletion of EGFR resulted in impaired expression of cyclin D1 and impaired suppression of p27 after PPx, both of which enhance β cell proliferation. These data highlight the importance of EGFR signaling and its downstream signaling cascade in postnatal β cell growth.

Reduction in placental growth factor impaired gestational beta-cell proliferation through crosstalk between beta-cells and islet endothelial cells

Reduced placental growth factor (PLGF) during pregnancy is known to be a reason for developing preeclampsia (PE) and gestational diabetes mellitus (GDM), but the underlying mechanisms remain unclear. Recently, it has been shown that reduced PLGF may induce GDM through suppressing beta-cell mass growth in a PI3k/Akt signalling-dependent manner. Here, we dissected the interaction between beta-cells and islet endothelial cells in this model. We analysed proliferation of beta-cells and islet endothelial cells at different time points of gestation in mice. We cultured mouse islet endothelial cells (MS1), with or without PLGF. We cultured primary mouse beta-cells in conditioned media from PLGF-treated MS1. We cultured MS1 cells in conditioned media from proliferating beta-cells that were activated with conditioned media from PLGF-treated MS1 cells. We analysed cell proliferation by BrdU incorporation. We analysed cell growth by a MTT assay. We found that during mouse gestation, the increases in cell proliferation occurred earlier in beta-cells than in islet endothelial cells. In vitro, PLGF itself failed to induce proliferation of MS1 cells. However, conditioned media from the PLGF-treated MS1 cells induced beta-cell proliferation, resulting in increases in beta-cell number. Moreover, proliferation of MS1 cells significantly increased when MS1 cells were cultured in conditioned media from proliferating beta-cells activated with conditioned media from PLGF-treated MS1 cells. Thus, our data suggest that gestational PLGF may stimulate islet endothelial cells to release growth factors to promote beta-cell proliferation, and proliferating beta-cells in turn release endothelial cell growth factor to increase proliferation of endothelial cells. PE-associated reduction in PLGF impairs these processes to result in islet growth impairment, and subsequently the onset of GDM.

Metformin inhibits development of diabetic retinopathy through inducing alternative splicing of VEGF-A

Previous studies have shown that metformin, an AMP-activated protein kinase activator widely prescribed for type 2 diabetes, is especially beneficial in cases of diabetic retinopathy (DR) with undetermined mechanisms. Here, we used a streptozotocin-induced diabetes model in mice to study the effects of metformin on the development of DR. We found that 10 weeks after STZ treatment, DR was induced in STZ-treated mice, regardless treatment of metformin. However, metformin alleviated the DR, seemingly through attenuating the retina neovascularization. The total vascular endothelial cell growth factor A (VEGF-A) in eyes was not altered by metformin, but the phosphorylation of the VEGF receptor 2 (VEGFR2) was decreased, which inhibited VEGF signaling. Further analysis showed that metformin may induce VEGF-A mRNA splicing to VEGF120 isoform to reduce its activation of the VEGFR2. These findings are critical for generating novel medicine for DR treatment.

PNA lectin for purifying mouse acinar cells from the inflamed pancreas

Better methods for purifying human or mouse acinar cells without the need for genetic modification are needed. Such techniques would be advantageous for the specific study of certain mechanisms, such as acinar-to-beta-cell reprogramming and pancreatitis. Ulex Europaeus Agglutinin I (UEA-I) lectin has been used to label and isolate acinar cells from the pancreas. However, the purity of the UEA-I-positive cell fraction has not been fully evaluated. Here, we screened 20 widely used lectins for their binding specificity for major pancreatic cell types, and found that UEA-I and Peanut agglutinin (PNA) have a specific affinity for acinar cells in the mouse pancreas, with minimal affinity for other major pancreatic cell types including endocrine cells, duct cells and endothelial cells. Moreover, PNA-purified acinar cells were less contaminated with mesenchymal and inflammatory cells, compared to UEA-I purified acinar cells. Thus, UEA-I and PNA appear to be excellent lectins for pancreatic acinar cell purification. PNA may be a better choice in situations where mesenchymal cells or inflammatory cells are significantly increased in the pancreas, such as type 1 diabetes, pancreatitis and pancreatic cancer.

The Beta Cell in Its Cluster: Stochastic Graphs of Beta Cell Connectivity in the Islets of Langerhans

Pancreatic islets of Langerhans consist of endocrine cells, primarily α, β and δ cells, which secrete glucagon, insulin, and somatostatin, respectively, to regulate plasma glucose. β cells form irregular locally connected clusters within islets that act in concert to secrete insulin upon glucose stimulation. Due to the central functional significance of this local connectivity in the placement of β cells in an islet, it is important to characterize it quantitatively. However, quantification of the seemingly stochastic cytoarchitecture of β cells in an islet requires mathematical methods that can capture topological connectivity in the entire β-cell population in an islet. Graph theory provides such a framework. Using large-scale imaging data for thousands of islets containing hundreds of thousands of cells in human organ donor pancreata, we show that quantitative graph characteristics differ between control and type 2 diabetic islets. Further insight into the processes that shape and maintain this architecture is obtained by formulating a stochastic theory of β-cell rearrangement in whole islets, just as the normal equilibrium distribution of the Ornstein-Uhlenbeck process can be viewed as the result of the interplay between a random walk and a linear restoring force. Requiring that rearrangements maintain the observed quantitative topological graph characteristics strongly constrained possible processes. Our results suggest that β-cell rearrangement is dependent on its connectivity in order to maintain an optimal cluster size in both normal and T2D islets.

High or low blood glucose levels are detrimental to human health. The hormone-secreting cells primarily responsible for maintaining glucose at physiologically appropriate levels are embedded in small clusters within the pancreas, the so-called islets of Langerhans. These islets have an irregular arrangement of cells, β cells that secrete insulin, α cells that secrete glucagon, and other cells with less well-understood functions. While the arrangement of β cells is irregular, these cells need to be touching for the islet to respond to glucose with insulin secretion. We first use a mathematical formalism called graph theory to show that cell arrangements in islets from diabetic and control donors are significantly different. The question we then address is: Is there some set of moves of islet cells that will preserve the observed arrangement? The aim is to gain insight into the biological processes by which islets are formed and maintained. We find moves on β-cell graphs that leave the same significant aspects of cell arrangements unchanged. These moves turn out to be severely restricted, and suggest that β cells may prefer to move from larger clusters but can move to a cluster of any size, possibly to maximize their exposure to blood vessels.

Thyroid carcinoma cells produce PLGF to enhance metastasis

Cancer neovascularization is essential for metastasis of thyroid carcinoma. However, the underlying molecular mechanisms are ill-defined. Recently, placental growth factor (PLGF) has been shown to play critical roles in the pathological angiogenesis through regulating matrix metalloproteinases (MMPs); here, we were prompted to examine the role of PLGF in the metastasis of thyroid carcinoma. We found that the PLGF and MMP9 levels strongly correlated in the thyroid carcinoma specimen. Higher PLGF and MMP9 levels were detected in the thyroid carcinoma with metastasis. Using a human thyroid carcinoma cell line, TT, we found that overexpression of PLGF in TT cells increased expression of MMP9, while inhibition of PLGF in TT cells decreased expression of MMP9. However, modification of MMP9 levels in TT cells did not affect PLGF levels, suggesting that PLGF may regulate MMP9 in thyroid carcinoma cells. Moreover, application of a specific MAPK p42/p44 inhibitor, but not the application of a specific MAPK p38 inhibitor or specific Akt or JNK inhibitors, substantially abolished the effect of PLGF on MMP9 activation, suggesting that PLGF may increase expression of MMP9 via p42/p44 signaling pathway. Together, these data suggest that antagonizing PLGF in thyroid carcinoma cells may be a promising therapy to suppress cancer metastasis.

Intracranial pancreatic islet transplantation increases islet hormone expression in the rat brain and attenuates behavioral dysfunctions induced by MK-801 (dizocilpine)

The treatment of rodents with non-competitive antagonist of the N-Methyl-D-aspartate (NMDA) receptor, MK-801 (dizocilpine), induces symptoms of psychosis, deficits in spatial memory and impairment of synaptic plasticity. Recent studies have suggested that insulin administration might attenuate the cognitive dysfunctions through the modulatory effect on the expression of NMDA receptors and on the brain insulin signaling. Intrahepatic pancreatic islet transplantation is known as an efficient tool for correcting impaired insulin signaling. We examined the capacity of syngeneic islets grafted into the cranial subarachnoid cavity to attenuate behavioral dysfunctions in rats exposed to MK-801. Animals were examined in the open field (OF) and the Morris Water Maze (MWM) tests following acute or subchronic administration of MK-801. We found well-vascularized grafted islets expressing insulin, glucagon and somatostatin onto the olfactory bulb and prefrontal cortex. Significantly higher levels of insulin were detected in the hippocampus and prefrontal cortex of transplanted animals compared to the non-transplanted rats. All animals expressed normal peripheral glucose homeostasis for two months after transplantation. OF tests revealed that rats exposed to MK-801 treatment, showed hyper-responsiveness in motility parameters and augmented center field exploration compared to intact controls and these effects were attenuated by the grafted islets. Moreover, in the MWM, the rats treated with MK-801 showed impairment of spatial memory that were partially corrected by the grafted islets. In conclusion, intracranial islet transplantation leads to the expression of islet hormones in the brain and attenuates behavioral and cognitive dysfunctions in rats exposed to MK-801 administration without altering the peripheral glucose homeostasis.

Larynx carcinoma regulates tumor-associated macrophages through PLGF signaling

Cancer neovascularization plays an essential role in the metastasis of larynx carcinoma (LC). However, the underlying molecular mechanisms are not completely understood. Recently, we reported that placental growth factor (PLGF) regulates expression of matrix metalloproteinase 3 (MMP3) through ERK/MAPK signaling pathway in LC. Here, we show that MMP9 upregulated in LC, and appeared to be mainly produced by M2 macrophages (tumor-associated macrophages (TAM)). In a transwell co-culture system, PLGF secreted by LC cells triggered macrophage polarization to a TAM subtype that releases MMP9. Moreover, MMP9 was found to be activated in the PLGF-polarized TAM via transforming growth factor β (TGFβ) receptor signaling activation. Furthermore, PLGF in LC cells induced macrophage polarization in vivo, and significantly promoted the growth of LC. Thus, together with our previous work, our study highlights a pivotal role of cross-talk between TAM and LC in regulating the metastasis of LC.