Vascular dysfunction induced by elevated glucose levels in rats is mediated by vascular endothelial growth factor

Physiological and Pathological Roles of Aldose Reductase

Aldose reductase (AR) is an aldo-keto reductase that catalyzes the first step in the polyol pathway which converts glucose to sorbitol. Under normal glucose homeostasis the pathway represents a minor route of glucose metabolism that operates in parallel with glycolysis. However, during hyperglycemia the flux of glucose via the polyol pathway increases significantly, leading to excessive formation of sorbitol. The polyol pathway-driven accumulation of osmotically active sorbitol has been implicated in the development of secondary diabetic complications such as retinopathy, nephropathy, and neuropathy. Based on the notion that inhibition of AR could prevent these complications a range of AR inhibitors have been developed and tested; however, their clinical efficacy has been found to be marginal at best. Moreover, recent work has shown that AR participates in the detoxification of aldehydes that are derived from lipid peroxidation and their glutathione conjugates. Although in some contexts this antioxidant function of AR helps protect against tissue injury and dysfunction, the metabolic transformation of the glutathione conjugates of lipid peroxidation-derived aldehydes could also lead to the generation of reactive metabolites that can stimulate mitogenic or inflammatory signaling events. Thus, inhibition of AR could have both salutary and injurious outcomes. Nevertheless, accumulating evidence suggests that inhibition of AR could modify the effects of cardiovascular disease, asthma, neuropathy, sepsis, and cancer; therefore, additional work is required to selectively target AR inhibitors to specific disease states. Despite past challenges, we opine that a more gainful consideration of therapeutic modulation of AR activity awaits clearer identification of the specific role(s) of the AR enzyme in health and disease.

Network Pharmacology Analysis of ZiShenWan for Diabetic Nephropathy and Experimental Verification of Its Anti-Inflammatory Mechanism

Background

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD). The inflammatory response plays a critical role in DN. ZiShenWan (ZSW) is a classical Chinese medicinal formula with remarkable clinical therapeutic effects on DN, but its pharmacological action mechanisms remain unclear.

Aim

In this study, a network pharmacology approach was applied to investigate the pharmacological mechanisms of ZSW in DN therapy. Based on the results of network analysis, the core targets and signaling pathways related to anti-inflammatory effect were verified via experiments in vivo.

Methods

The candidate chemical ingredients of ZSW as well as its putative targets and known therapeutic targets of DN were acquired from appropriate databases. The “herb-ingredient-target” network for ZSW in DN treatment was established. The protein–protein interaction (PPI) network of potential targets was constructed to screen the core targets. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed. In addition to biochemical and pathological indicators, the core targets and signaling pathways associated with inflammation were partially validated in db/db mice at molecular level.

Results

A total of 56 active ingredients in ZSW and 166 DN-related targets were selected from databases. A high proportion of core targets and top signaling pathways participate in inflammation. ZSW markedly alleviated renal injuries pathologically and regulated related biomarkers. In particular, ZSW significantly inhibited the exaggerated release of inflammatory cytokines such as interleukin (IL)-1β, IL-6, tumor necrosis factor receptor (TNF)-ɑ, and monocyte chemotactic protein (MCP)-1 as well as regulating p38 mitogen-activated protein kinases (MAPK) and phosphoinositide 3-kinase (PI3K)–protein kinase B (Akt) signaling pathways in db/db mice.

Conclusion

This study first comprehensively investigated the active ingredients, potential targets, and molecular mechanism of ZSW as a therapy for DN. ZSW achieved renoprotective effects in DN via regulation of multiple targets and signaling pathways, especially by alleviating inflammation. Results indicate that ZSW is a promising multi-target therapeutic approach for DN treatment.

Aldose Reductase: An Emerging Target for Development of Interventions for Diabetic Cardiovascular Complications

Diabetes is a leading cause of cardiovascular morbidity and mortality. Despite numerous treatments for cardiovascular disease (CVD), for patients with diabetes, these therapies provide less benefit for protection from CVD. These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify especially as the diabetes epidemic continues to expand. In this context, high levels of blood glucose stimulate the flux via aldose reductase (AR) pathway leading to metabolic and signaling changes in cells of the cardiovascular system. In animal models flux via AR in hearts is increased by diabetes and ischemia and its inhibition protects diabetic and non-diabetic hearts from ischemia-reperfusion injury. In mouse models of diabetic atherosclerosis, human AR expression accelerates progression and impairs regression of atherosclerotic plaques. Genetic studies have revealed that single nucleotide polymorphisms (SNPs) of the ALD2 (human AR gene) is associated with diabetic complications, including cardiorenal complications. This Review presents current knowledge regarding the roles for AR in the causes and consequences of diabetic cardiovascular disease and the status of AR inhibitors in clinical trials. Studies from both human subjects and animal models are presented to highlight the breadth of evidence linking AR to the cardiovascular consequences of diabetes.

Growth factors in the fetus and pre-adolescent offspring of hyperglycemic rats

BACKGROUND

Maternal hyperglycemia influences childhood metabolic syndrome, including obesity and hyperglycemia. We tested the hypothesis that the maternal hyperglycemia influences growth factors in the fetal and pre-adolescent offspring.

METHODS

Hyperglycemia was induced in pregnant rats on embryonic day (E)16 using streptozocin followed by implantation with insulin or placebo pellets at embryonic day 18 (E18). Fetuses at E20 and pre-adolescent pups at postnatal day 14 (P14) were studied: (1) normal untreated controls (CTL) at E20; (2) hyperglycemic placebo-treated (HPT) at E20; (3) hyperglycemic insulin-treated (HIT) at E20; (4) CTL at P14; and (5) HIT at P14. Fetal and pre-adolescent growth factors were determined.

RESULTS

Biomarkers of hypoxia were elevated in the HPT group at E20. This group did not survive to term. Maternal insulin improved fetal survival despite lower fetal body weight at E20, however, at normal birth (postnatal day 0 (P0)) and at P14, body weights and blood glucose were higher than CTL. These high levels correlated with aberrant growth factors. Maternal hyperglycemia influenced glucose-6-phosphate dehydrogenase, glucagon, insulin, interleukin-10, and leptin genes.

CONCLUSIONS

The impact of maternal hyperglycemia on pre-adolescent glucose and body weight was not a consequence of maternal overnutrition. This suggests an independent link which may affect offspring metabolic health in later life.

Microglia increase tight-junction permeability in coordination with Müller cells under hypoxic condition in an in vitro model of inner blood-retinal barrier

Microglia and Müller cells (MCs) are believed to be critically involved in hypoxia-induced blood-retinal barrier (BRB) disruption, which is a major pathogenic factor of various retinopathies. However, the underlying mechanism remains poorly defined. The inner BRB (iBRB) is primarily formed of microvascular endothelial cells (ECs) with tight junction (TJ), which are surrounded and supported by retinal glial cells. We developed a novel in vitro iBRB model sheet by sandwiching Transwell membrane with layered mouse brain microvascular ECs (bEnd.3) and mouse retinal MCs (QMMuC-1) on each side of the membrane. Using this model, we tested the hypothesis that under hypoxic condition, activated microglia produce inflammatory cytokines such as interleukin (IL)-1β, which may promote vascular endothelial growth factor (VEGF) production from MCs, leading to TJ disruption. The iBRB model cell sheets were exposed to 1% oxygen for 6 h with or without mouse brain microglia (BV2) or IL-1β. TJ structure and function were examined by zonula occludens (ZO)-1 immunostaining and fluorescein isothiocyanate permeability assay, respectively. Relative gene expression of IL-1β in BV2 under normoxic and hypoxic conditions was examined by real-time reverse transcription-polymerase chain reaction. VEGF protein concentration in QMMuC-1 supernatants was measured by enzyme-linked immunosorbent assay. The bEnd.3 cell sheet incubated with BV2 in hypoxic condition or with IL-1β in normoxic condition showed abnormal localization of ZO-1 and aberrated barrier function. Under normoxic condition, EC-MC iBRB model cell sheet showed lower permeability than bEnd.3 cell sheet. Under hypoxic conditions, the barrier function of EC-MC iBRB model cell sheet was more deteriorated compared to bEnd.3 cell sheet. Under hypoxic condition, incubation of EC-MC iBRB model cell sheet with BV2 cells or IL-1β significantly increased barrier permeability, and hypoxia-treated BV2 cells expressed significantly higher levels of IL-1β mRNA. Incubation of QMMuC-1 with IL-1β increased VEGF production. These results suggest that under hypoxic condition, microglia are activated to release proinflammatory cytokines such as IL-1β that promote VEGF production from MCs, leading to disruption of iBRB function. Modulating microglia and MCs function may be a novel approach to treat hypoxia-induced retinal BRB dysfunction.

Multifunctional agents based on benzoxazolone as promising therapeutic drugs for diabetic nephropathy

Diabetic nephropathy (DN) is resulted from activations of polyol pathway and oxidative stress by abnormal metabolism of glucose, and no specific medication is available. We designed a novel class of benzoxazolone derivatives, and a number of individuals were found to have significant antioxidant activity and inhibition of aldose reductase of the key enzyme in the polyol pathway. The outstanding compound (E)-2-(7-(4-hydroxy-3-methoxystyryl)-2-oxobenzo[d]oxazol-3(2H)-yl)acetic acid was identified to reduce urinary proteins in diabetic mice suggesting an alleviation in the diabetic nephropathy, and this was confirmed by kidney hematoxylin-eosin staining. Further investigations showed blood glucose normalization, declined in the polyol pathway and lipid peroxides, and raised glutathione and superoxide dismutase activity. Thus, we suggest a therapeutic function of the compound for DN which could be attributed to the combination of hypoglycemic, aldose reductase inhibition and antioxidant.

Chrysin Inhibits High Glucose-Induced Migration on Chorioretinal Endothelial Cells via VEGF and VEGFR Down-Regulation

Background: Diabetes mellitus (DM) is a chronic inflammatory disease, which causes multiple complications. Diabetic retinopathy (DR) is among these complications and is a dominant cause of vision loss for diabetic patients. Numerous studies have shown that chrysin, a flavonoid, has many biological activities such as anti-oxidation and anti-inflammation. However, it is rarely used in ocular diseases. In this study, we examined the inhibitory effects of flavonoid on high glucose induced migration of chorioretinal endothelial cells (RF/6A cells) and its mechanism. Materials and methods: The viability of RF/6A cells treated with chrysin was examined with a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. The migration of RF/6A cells was assessed by the transwell migration and scratch wound assays. The expression of AKT, ERK, vascular endothelial growth factor (VEGF), HIF−1α and MMP-2 were determined by western blotting. To observe the mRNA expression of VEGF receptor (VEGFR), qRT-PCR, was utilized. Results: The results showed that chrysin can dose-dependently inhibit the RF/6A cell migration in vitro transwell and the scratch wound assays which are induced by high glucose. After pretreatment of RF/6A cells with different concentrations of chrysin, they did not produce any cytotoxicity in MTT assay. Moreover, chrysin down-regulated both phosphorylated AKT and ERK, as well as attenuated the expression levels of MMP-2. It also decreased the expression of the VEGF transcription factor and VEGF. Furthermore, it was shown that chrysin could suppress the protein and mRNA expression levels of VEGFR. Conclusion: The results indicate that chrysin could down-regulate the phosphorylation of AKT, ERK and MMP-2 and reduce the effects of VEGF and VEGFR in a high glucose environment. It further inhibits the high glucose-induced migration of RE/6A cells. Therefore, chrysin may have the potential for visual protection.

Knockdown of NEAT1 exerts suppressive effects on diabetic retinopathy progression via inactivating TGF-β1 and VEGF signaling pathways

Diabetic retinopathy (DR) is complication resulted from Type 2 diabetes mellitus. Accumulating evidence has proved the functions of long noncoding RNAs (lncRNAs) in the progression of DR. Recent reports exert the numerous regulatory functions of lncRNA nuclear-enriched abundant transcript 1 (NEAT1) in various diseases. However, its implications in DR remain barely known. Therefore, this study was carried out to explore the role of NEAT1 in high-glucose (HG)-triggered injury of human retinal endothelial cells (hRECs). Here, we found the NEAT1 level was significantly elevated in patients with DR, in the retina of diabetic rats and mice. Meanwhile, hRECs under HG stimuli also exhibited an increase of NEAT1. Moreover, the loss of NEAT1 enhanced hRECs proliferation and repressed HG-induced apoptosis, which was accompanied by an upregulation of Bcl-2 and a downregulation of Bax. Subsequently, the knockdown of NEAT1 obviously reduced HG-triggered oxidative stress injury in hRECs. It was reflected that intracellular reactive oxygen species and malondialdehyde level induced by HG were repressed by NEAT1 downregulation, while superoxide dismutase activity was increased. In addition, decreased NEAT1 repressed the inflammatory processes effectively as indicated by the inactivation of inflammatory cytokines Cox-2, interleukin-6, and tumor necrosis factor-α. Furthermore, vascular endothelial growth factor A (VEGF) and transforming growth factor-β1 (TGF-β1) expression in patients with DR, DR rats, and HG-incubated hRECs was obviously increased. The silence of NEAT1 could reduce the enhanced expression of VEGF and TGF-β1 induced by HG. Hence, we concluded NEAT1 might contribute to the development of DR through activating TGF-β1 and VEGF.

What Can We Do to Preserve the Peritoneum?

Background

Long-term peritoneal dialysis may lead to peritoneal membrane failure. Loss of ultrafiltration is the most important clinical abnormality. Loss of ultrafiltration is associated with an increased number of peritoneal blood vessels, with fibrotic alterations, and with loss of mesothelium. Continuous exposure to bioincompatible dialysis solutions is likely to be important in the pathogenesis of these alterations.

Methods

This article reviews the toxicity of various constituents of dialysate, current assessments of interventions, and the results of interventions aimed at preserving the peritoneum.

Results

Glucose, possibly in combination with lactate, and glucose degradation products (GDPs) are likely to be the most toxic constituents of dialysate. Diabetiform peritoneal neoangiogenesis is likely to be mediated by vascular endothelial growth factor (VEGF). Release of VEGF might be influenced by glucose-induced cellular pseudohypoxia, which is likely to be increased by exposure to lactate. Glucose and GDPs are both toxic to peritoneal cells. Glucose degradation products induce the formation of advanced glycosylation end-products at a much faster rate than does glucose itself, but the relative importance of GDPs and glucose in clinical PD has not been clarified. The effects of interventions should first be assessed in long-term animal models, followed by clinical studies on peritoneal transport and on effluent markers that may reflect the status of the peritoneum. Possible interventions aim at reducing peritoneal exposure to glucose, GDPs, and lactate. Techniques include peritoneal resting, replacing some glucose-based exchanges with amino acid–based and icodextrin-based dialysate, using bicarbonate as a buffer, and administering solutions that have a low GDP content. Exposure to various dialysis solutions with a reduced GDP content has resulted in an increase in the effluent concentration of the mesothelial cell marker CA125, irrespective of the buffer used. Experimental studies in a long-term peritoneal exposure model in rats showed that the combination of a reduction in the concentration of lactate and replacement of lactate with pyruvate resulted in a reduction of the number of peritoneal blood vessels. Results of drug therapy have been studied in various animal models. Their use in patients is still experimental.

Conclusions

Strategies to preserve the peritoneum aim at reducing membrane exposure to bioincompatible solutions. Currently available dialysis fluids that are more biocompatible are likely to have some beneficial effects. Further research on the development of dialysis solutions that use combinations of osmotic agents and alternative buffers is necessary.

A Pyruvate-Buffered Dialysis Fluid Induces Less Peritoneal Angiogenesis and Fibrosis than a Conventional Solution

Background

Conventional lactate-buffered peritoneal dialysis (PD) fluids containing glucose and glucose degradation products are believed to contribute to the development of fibrosis and angiogenesis in the dialyzed peritoneum. To reduce potential negative effects of lactate, pyruvate was substituted as a buffer and its effects on peritoneal pathological alterations were studied in a chronic peritoneal exposure model in the rat.

Methods

20 Wistar rats were infused intraperitoneally with pyruvate-buffered ( n = 9) or lactate-buffered PD fluid. After 20 weeks of daily infusion, peritoneal function was assessed. In omental peritoneal tissue, the number of blood vessels was analyzed following alpha-smooth muscle actin staining. The degree of fibrosis was quantitated in Picro Sirius Red-stained sections and by assessment of the hydroxyproline content. Plasma lactate/pyruvate and beta-hydroxybutyrate/acetoacetate (BBA/AA) ratios were determined. Plasma and dialysate vascular endothelial growth factor (VEGF) levels were quantitated by ELISA.

Results

The mass transfer area coefficient of creatinine was higher and the dialysate-to-plasma ratio of sodium was lower in pyruvate-treated animals compared to the lactatetreated group (0.11 vs 0.05 mL/min, p < 0.05, and 78% vs 89%, p < 0.05). The BBA/AA ratio tended to be lower in the pyruvate animals ( p = 0.07). The number of blood vessels was lower in pyruvate-treated animals (16 vs 37 per field, p < 0.001). Total surface area, luminal area, and wall/total area of the vessels were larger in the pyruvate group. The degree of fibrosis was lower in intersegmental and perivascular areas of pyruvate-exposed animals. Effluent VEGF was higher in the pyruvate group.

Conclusions

Replacement of lactate by pyruvate resulted in changes in peritoneal solute transport, accompanied by a reduction in both peritoneal membrane angiogenesis and fibrosis, suggesting potentially novel mechanisms to reduce glucose-driven alterations to the peritoneal membrane in PD patients.

The effects of oxidative stress on the development of atherosclerosis

Atherosclerosis is a cardiovascular disease (CVD) known widely world wide. Several hypothesizes are suggested to be involved in the narrowing of arteries during process of atherogenesis. The oxidative modification hypothesis is related to oxidative and anti-oxidative imbalance and is the most investigated. The aim of this study was to review the role of oxidative stress in atherosclerosis. Furthermore, it describes the roles of oxidative/anti-oxidative enzymes and compounds in the macromolecular and lipoprotein modifications and in triggering inflammatory events. The reactive oxygen (ROS) and reactive nitrogen species (RNS) are the most important endogenous sources produced by non-enzymatic and enzymatic [myeloperoxidase (MPO), nicotinamide adenine dinucleotide phosphate (NADH) oxidase and lipoxygenase (LO)] reactions that may be balanced with anti-oxidative compounds [glutathione (GSH), polyphenols and vitamins] and enzymes [glutathione peroxidase (Gpx), peroxiredoxins (Prdx), superoxide dismutase (SOD) and paraoxonase (PON)]. However, the oxidative and anti-oxidative imbalance causes the involvement of cellular proliferation and migration signaling pathways and macrophage polarization leads to the formation of atherogenic plaques. On the other hand, the immune occurrences and the changes in extra cellular matrix remodeling can develop atherosclerosis process.

Reductive Stress-Induced Mitochondrial Dysfunction and Cardiomyopathy

The goal of this review was to summarize reported studies focusing on cellular reductive stress-induced mitochondrial dysfunction, cardiomyopathy, dithiothreitol- (DTT-) induced reductive stress, and reductive stress-related free radical reactions published in the past five years. Reductive stress is considered to be a double-edged sword in terms of antioxidation and disease induction. As many underlying mechanisms are still unclear, further investigations are obviously warranted. Nonetheless, reductive stress is thought to be caused by elevated levels of cellular reducing power such as NADH, glutathione, and NADPH; and this area of research has attracted increasing attention lately. Albeit, we think there is a need to conduct further studies in identifying more indicators of the risk assessment and prevention of developing heart damage as well as exploring more targets for cardiomyopathy treatment. Hence, it is expected that further investigation of underlying mechanisms of reductive stress-induced mitochondrial dysfunction will provide novel insights into therapeutic approaches for ameliorating reductive stress-induced cardiomyopathy.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

miR-152/LIN28B axis modulates high-glucose-induced angiogenesis in human retinal endothelial cells via VEGF signaling

Diabetic retinopathy (DR) is a serious complication of diabetes contributing to blindness in patients. Inhibiting retinal neovascularization is a potent strategy for diabetic retinopathy treatment. Reportedly, the stable expression of lin-28 homolog B (LIN28B), a member of the highly conserved RNA-binding protein LIN28 family, could promote vascular endothelial growth factor (VEGF) expression; herein, we investigated the role and mechanism of LIN28B in diabetic retinopathy progression from the perspective of microRNA (miRNA) regulation. We identified miR-152 as a miRNA that may target the LIN28B 3'-untranslated region and can be significantly downregulated under high-glucose (HG) condition. The expression of miR-152 was remarkably suppressed, whereas the expression of LIN28B was significantly increased under HG condition within both human retinal endothelial cells (hRECs) and retinal microvascular endothelial cell line (hRMECs). miR-152 overexpression significantly suppressed, while LIN28B overexpression promoted the angiogenesis and the protein levels of proangiogenesis factors in both hRECs and hRMECs. More importantly, LIN28B overexpression could remarkably attenuate the effect of miR-152 overexpression. In summary, miR-152 overexpression could inhibit HG-induced angiogenesis in both hRECs and hRMECs via targeting LIN28B and suppressing VEGF signaling. Further, in vivo experiments are needed for the application of miR-152/LIN28B axis in the treatment for diabetic retinopathy.

Aldo-Keto Reductases: Multifunctional Proteins as Therapeutic Targets in Diabetes and Inflammatory Disease

Aldose reductase (AR) is an NADPH-dependent aldo-keto reductase that has been shown to be involved in the pathogenesis of several blinding diseases such as uveitis, diabetic retinopathy (DR) and cataract. However, possible mechanisms linking the action of AR to these diseases are not well understood. As DR and cataract are among the leading causes of blindness in the world, there is an urgent need to explore therapeutic strategies to prevent or delay their onset. Studies with AR inhibitors and gene-targeted mice have demonstrated that the action of AR is also linked to cancer onset and progression. In this review we examine possible mechanisms that relate AR to molecular signaling cascades and thus explain why AR inhibition is an effective strategy against colon cancer as well as diseases of the eye such as uveitis, cataract, and retinopathy.

The MicroRNA-21 signaling pathway is involved in prorenin receptor (PRR) -induced VEGF expression in ARPE-19 cells under a hyperglycemic condition

PURPOSE

MicroRNAs (miRNAs/miRs) are involved in a large number of biological functions and diseases, such as cancer, cardiovascular diseases, and diabetes. MiR-21 has been reported to target Sprouty homolog 1 (SPRY1), SMAD7, and PTEN. In this study, we examined the underlying role of miR-21 in the regulation of prorenin receptor (PRR)-mediated induction of vascular endothelial growth factor (VEGF) expression via targeting SMAD7, SPRY1, and PTEN in a hyperglycemic condition.

METHODS

PRR-mediated induction of VEGF under a hyperglycemic condition (high glucose, 33mM) was studied by treating ARPE-19 cells with perindopril (10 µmol/l), which inhibits angiotensin II-mediated signaling. ARPE-19 cells exposed to normal glucose (NG, 5.5 mM) were considered as the control. To examine the role of miR-21 in the regulation of SPRY1, SMAD7, PTEN, and VEGF, ARPE-19 cells cultured in NG or high glucose were transfected with scramble negative control (Scr), a miR-21 mimic, or a miR-21 antagomir. To investigate the role of PRR and the small GTP-binding protein RAC1 in the regulation of miR-21, the expression of PRR and RAC1 was silenced by transfecting ARPE-19 cells with their corresponding siRNAs.

RESULTS

Compared with the NG control, high glucose significantly induced the expression of PRR, VEGF, VEGFR2, and miR-21 but significantly suppressed the expression of SPRY1, SMAD7, and PTEN at the transcript and protein levels. In contrast, silencing the expression of PRR significantly abolished the high glucose-induced expression of VEGF, VEGFR2, and miR-21. Knockdown of RAC1 significantly attenuated the high glucose-induced expression of LOX, CTGF, and miR-21, suggesting that PRR and RAC1 are involved in the CTGF/LOX-mediated regulation of miR-21. Furthermore, high glucose dramatically increased the levels of pERK (p44), hypoxia-inducible factor (HIF-1α), and VEGF. However, this effect was antagonized by the miR-21 antagomir, indicative of the involvement of high glucose-induced miR-21 in the regulation of VEGF through ERK signaling.

CONCLUSIONS

Our findings, for the first time, showed that the pleiotropic action of miR-21 induced the expression of pERK, HIF-1α, and VEGF in the high glucose condition by simultaneously targeting SPRY1, SMAD7, and PTEN in ARPE-19 cells. Therefore, miR-21 may serve as a potential therapeutic target for diabetes-induced retinal pathology.

The Increased Circulating Plasma Levels of Vascular Endothelial Growth Factor in Patients with Type 1 Diabetes Do Not Correlate to Metabolic Control

Aim. To characterize the plasma levels of vascular endothelial growth factor (VEGF) in type 1 diabetes mellitus (T1D) and its relation to both present and historical metabolic control and microvascular complications. Methods. Plasma levels of VEGF and routine clinical parameters were analyzed in 115 patients with long-standing T1D and 45 healthy controls (HC). All patients were under clinical routine diabetes treatment at Uppsala University Hospital. Results. The plasma levels of VEGF were increased by 37% in patients with T1D when compared to HC (18.2 ± 0.8 versus 13.2 ± 1.0 pg/ml, p < 0.001). The levels of VEGF correlated to insulin needs and BMI but not to present or historical metabolic control. The levels of VEGF were similar in patients with T1D and microvascular complications (microalbuminuria and retinopathy) when compared with patients without microvascular complications. Historical HbA1c levels were found to be the best predictor for present metabolic control. Conclusion. Circulating plasma levels of VEGF do not correlate to present or historical metabolic control in long-standing T1D and the levels are not affected by the presence of microvascular complications.

Erianin inhibits high glucose-induced retinal angiogenesis via blocking ERK1/2-regulated HIF-1α-VEGF/VEGFR2 signaling pathway

Erianin is a natural compound found in Dendrobium chrysotoxum Lindl. Diabetic retinopathy (DR) is a serious and common microvascular complication of diabetes. This study aims to investigate the inhibitory mechanism of erianin on retinal neoangiogenesis and its contribution to the amelioration of DR. Erianin blocked high glucose (HG)-induced tube formation and migration in choroid-retinal endothelial RF/6A cells. Erianin inhibited HG-induced vascular endothelial growth factor (VEGF) expression, hypoxia-inducible factor 1-alpha (HIF-1α) translocation into nucleus and ERK1/2 activation in RF/6A and microglia BV-2 cells. MEK1/2 inhibitor U0126 blocked HG-induced HIF-1α and ERK1/2 activation in both above two cells. In addition, erianin abrogated VEGF-induced angiogenesis in vitro and in vivo, and also inhibited VEGF-induced activation of VEGF receptor 2 (VEGFR2) and its downstream cRaf-MEK1/2-ERK1/2 and PI3K-AKT signaling pathways in RF/6A cells. Furthermore, erianin reduced the increased retinal vessels, VEGF expression and microglia activation in streptozotocin (STZ)-induced hyperglycemic and oxygen-induced retinopathy (OIR) mice. In conclusion, our results demonstrate that erianin inhibits retinal neoangiogenesis by abrogating HG-induced VEGF expression by blocking ERK1/2-mediated HIF-1α activation in retinal endothelial and microglial cells, and further suppressing VEGF-induced activation of VEGFR2 and its downstream signals in retinal endothelial cells.

Identifying the preferred interaction mode of naringin with gold nanoparticles through experimental, DFT and TDDFT techniques: insights into their sensing and biological applications

In this work, the binding behaviour of naringin – a flavonoid with AuNPs is explained by combining experimental and theoretical approaches.

Effects of reducing the lactate and glucose content of PD solutions on the peritoneum. Is the future GLAD?

Background. Long-term peritoneal dialysis (PD) may lead to functional and morphologic changes in the peritoneal membrane, probably because of the continuous exposure to conventional dialysis solutions.

Methods. The morphologic changes include neoangiogenesis and fibrosis. The authors of this article developed a long-term peritoneal exposure model in rats, in which the morphological alterations could be induced after daily peritoneal infusion of a 3.86% glucose/lactate-buffered conventional PD solution.

Results and Conclusions. In the present article, a review of the model and of the results obtained with various available and experimental solutions is given. It appeared that high lactate concentrations contributed to the glucose-induced neoangiogenesis by pseudohypoxia. Glucose degradation products were probably more important in the induction of peritoneal fibrosis. The promising results of a combination of amino acids, glycerol and glucose, each in a low concentration, buffered with either pyruvate or bicarbonate/lactate, are presented and discussed. The combination of glycerol, amino acids and dextrose, dissolved in a bicarbonate/lactate buffer (GLAD), may be an option for a new generation of dialysis fluids.

Metabolic changes in type 2 diabetes are reflected in peripheral blood cells, revealing aberrant cytotoxicity, a viral signature, and hypoxia inducible factor activity

BACKGROUND

Metabolic syndrome (MetS) is characterized by central obesity, insulin resistance, dysglycemia, and a pro-atherogenic plasma lipid profile. MetS creates a high risk for development of type 2 diabetes (T2DM) and cardiovascular disease (CVD), presumably by altering inflammatory responses. Presently, it is unknown how the chronic metabolic disturbances in acute hyperglycemia, MetS and T2DM affect the immune activity of peripheral blood cells.

METHODS

We performed genome-wide expression analysis of peripheral blood cells obtained from patients with T2DM (n = 6) and age-, sex- , BMI- and blood pressure-matched obese individuals with MetS (n = 4) and lean healthy normoglycemic controls (n = 3), both under fasting conditions and after controlled induction of acute hyperglycemia during a 70 min hyperglycemic clamp. Differential gene expression during fasting conditions was confirmed by real-time PCR, for which we included additional age-, sex-, BMI-, and blood pressure-matched obese individuals with (n = 4) or without (n = 4) MetS.

RESULTS

Pathway and Gene ontology analysis applied to baseline expression profiles of peripheral blood cells from MetS and T2DM patients revealed metabolic changes, highly similar to a reoviral infection gene signature in T2DM patients. Transcription factor binding site analysis indicated that increased HIF-1α activity, a transcription factor induced by either hypoxia or oxidative stress, is responsible for this aberrant metabolic profile in peripheral blood cells from T2DM patients. Acute hyperglycemia in healthy controls resulted in reduced expression of cytotoxicity-related genes, representing NK- and CD8(+) cells. In obese controls, MetS and especially T2DM patients, baseline expression of genes involved in cytotoxicity was already low, compared to healthy controls and did not further decrease upon acute hyperglycemia.

CONCLUSIONS

The reduced activity of cytotoxic genes in T2DM is explained by chronic hyperglycemia, but its acute effects are restricted to healthy controls. Genome expression of circulating leukocytes from T2DM patients differs from MetS individuals by a specific reovirus signature. Our data thus suggest a role for suppressed anti-viral capacity in the etiology of diabetes.

MicroRNA-152 represses VEGF and TGFβ1 expressions through post-transcriptional inhibition of (Pro)renin receptor in human retinal endothelial cells

PURPOSE

The (pro)renin receptor (PRR), a component of the renin-angiotensin system (RAS), plays an important role in the physiologic and pathophysiological regulation of blood pressure and fluid/electrolyte homeostasis. The RAS including the PRR has been identified in retinal endothelial cells and other ocular tissues. In this study, the potential involvement of miRNAs in the posttranscriptional regulation of PRR was investigated in human retinal endothelial cells (hRECs) under high glucose (HG) conditions.

METHODS

miRNA-152 (miR-152) was identified in silico as a potential regulator of PRR, and this was confirmed by quantitative real-time PCR (qRT-PCR) and PRR 3'-untranslated region (UTR) reporter assays. Using RNA interference, both AT1R and PRR were implicated in the HG-mediated induction of vascular endothelial growth factor (VEGF), VEGF receptor 2 (VEGFR-2), and transforming growth factor β1 (TGFβ1).

RESULTS

The downregulation of miR-152 was observed in hRECs and rat retinal tissues under HG conditions. In parallel, PRR (target of miR-152), VEGF, VEGFR-2, and TGFβ1 at mRNA levels were elevated. However, the transfection of hRECs with miR-152 mimics in HG conditions resulted in the suppression of the PRR expression, as well as reduced VEGF, VEGFR-2, and TGFβ1 production. This was reversed by transfecting cells with the antisense (antagomir) of miR-152, suggesting the glucose-induced upregulation of VEGF, VEGFR-2, and TGFβ1 is mediated through PRR, and this regulation is likely achieved through the HG-mediated modulation of miRNAs.

CONCLUSIONS

We have demonstrated that miR-152 interacting with PRR regulates downstream VEGF, VRGFR-2, and TGFβ1 expressions in hRECs in HG conditions. These studies suggest miR-152 and PRR may play a role in the pathogenesis of diabetic retinopathy (DR).

Correlation of VEGF genetic polymorphisms and lipid profile to aortic calcification

BACKGROUND

Aortic calcification is developed due to accumulation of a large amount of calcium in the aorta of the heart and it is the leading cause of aortic valve replacement and third leading cause of cardiovascular disease. The purpose of this study was to investigate the relation between aortic calcification and VEGF SNPs (-2578C>A, -1154G>A and +936C>T) and to evaluate the association of these SNPs with biochemical parameter in relation to aortic calcification.

METHODS

Aortic calcification was diagnosed by examining the posteroanterior chest X-rays by a radiologist and graded into four groups. The real-time polymerase chain reaction with melting curve analysis in LightCycler was used to genotype the VEGF SNPs.

RESULTS

Among the VEGF SNPs, a significant genetic difference was found only between the aortic calcification and control group with VEGF SNP -2578C>A but haplotypes T-A-A of (+936/-1154/-2578) were significantly different in control and aortic calcification and could enhance the aortic calcification development. By regression analysis, it was found that age, hypertension, diabetes, dyslipidemia, and hyperhomocysteinemia were found significantly different with the different genotypes of VEGF SNPs which may induce aortic calcification development.

CONCLUSION

Age, hypertension, diabetes, dyslipidemia, and hyperhomocysteinemia were established as aggravating factors for the aortic calcification in association with different VEGF genotypes.

Insulin therapy improves islet functions by restoring pancreatic vasculature in high-fat diet-fed streptozotocin-diabetic rats

BACKGROUND

In a previous study, we showed early insulin therapy could improve β-cell function in type 2 diabetic patients. However, the molecular mechanism was not clear. In the present study, we addressed this question by analyzing the pancreatic microvasculature in diabetic rats after insulin treatment.

METHODS

Diabetes was induced in rats by a combination of low dose streptozotocin (STZ; 40 mg/kg) and feeding of a high-fat diet. After the induction of diabetes, rats were treated with neutral protamine Hagedorn insulin (NPH; 6–8 U/day, s.c.) for 3 weeks. Three days after the end of treatment, rats were subjected to an intraperitoneal glucose tolerance test (IPGTT). The pancreatic microvasculature and the amount and size of the islets were evaluated by immunohistochemistry. Western blot analysis was used to determine levels of vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGF-R2) protein.

RESULTS

Treatment with NPH improved insulin secretion from β-cells during the IPGTT and increased pancreatic islet size. The density of the microvasculature in the pancreas was determined by quantification of CD31, a marker of endothelial cells. Insulin treatment increased CD31 protein levels, as well as the expression of VEGF and VEGFR2.

CONCLUSIONS

The results suggest that insulin treatment improves islet recovery by increasing angiogenesis in the pancreas. The mechanism is related to the induction of VEGF and VEGFR2 expression in diabetic rats.

New insights into molecular mechanisms of diabetic kidney disease

Diabetic kidney disease remains a major microvascular complication of diabetes and the most common cause of chronic kidney failure requiring dialysis in the United States. Medical advances over the past century have substantially improved the management of diabetes mellitus and thereby have increased patient survival. However, current standards of care reduce but do not eliminate the risk of diabetic kidney disease, and further studies are warranted to define new strategies for reducing the risk of diabetic kidney disease. In this review, we highlight some of the novel and established molecular mechanisms that contribute to the development of the disease and its outcomes. In particular, we discuss recent advances in our understanding of the molecular mechanisms implicated in the pathogenesis and progression of diabetic kidney disease, with special emphasis on the mitochondrial oxidative stress and microRNA targets. Additionally, candidate genes associated with susceptibility to diabetic kidney disease and alterations in various cytokines, chemokines, and growth factors are addressed briefly.

Possible effects of glimepiride beyond glycemic control in patients with type 2 diabetes: a preliminary report

Background

The purpose of this study was to elucidate the effects of glimepiride on the levels of biomarkers related to cardiovascular regulation in patients with type 2 diabetes mellitus.

Methods and results

Thirty-four patients with type 2 diabetes received glimepiride for 24 weeks. Significant decreases in the levels of glyceraldehyde-derived advanced glycation end products, (glycer-AGE: toxic AGE), eotaxin and fibroblast growth factor (FGF)-2 were recognized after the administration of glimepiride. Moreover, there were trends for there to be increases in the levels of granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF), and decreases in the levels of fractalkine, soluble CD40 ligand (sCD40L), macrophage inflammatory protein (MIP)-β, vascular endothelial growth factor (VEGF) and soluble receptor for AGE (sRAGE).

Conclusions

Glimepiride may have potent anti-oxidative, anti-inflammatory and angiogenic properties and it may potentially repair tissue damage by decreasing the levels of toxic AGE and increasing colony-stimulating factors.

Pilot study of Doppler optical coherence tomography of retinal blood flow following laser photocoagulation in poorly controlled diabetic patients

PURPOSE

To investigate the effect of panretinal photocoagulation (PRP) on retinal blood flow and shear rate using Doppler Fourier-domain optical coherence tomography (FD-OCT) in poorly controlled diabetics with proliferative diabetic retinopathy (PDR).

METHODS

This was a prospective interventional pilot study in patients with a new clinical diagnosis of PDR. Retinal blood flow and vessel diameter were measured using Doppler FD-OCT according to a previously described method, immediately before PRP treatment and 7 to 8 weeks after the last PRP session.

RESULTS

Ten patients with poorly controlled PDR (mean hemoglobin A1C = 9.2 ± 2.0%) and 10 control subjects were included in the study. PDR patients had significantly lower blood flow (∼25%) than control subjects both at baseline (P = 0.01) and after PRP (P = 0.003). Compared to controls, venous and arterial velocities were significantly decreased in diabetics at baseline (∼27%; P < 0.001 and 0.017, respectively) as well as after PRP (P < 0.001 and 0.006, respectively). Compared to controls, venous and arterial shear rates were significantly reduced in diabetics at baseline (∼27%; P = 0.002, 0.03) and after PRP (P = 0.002, 0.03). PRP in this group of PDR patients did not have a statistically significant effect on retinal blood flow or vessel parameters, though there was a trend for decreased arterial diameter (P = 0.09).

CONCLUSIONS

This is the first study to use Doppler FD-OCT to quantify functional changes in retinal vascular parameters in poorly controlled PDR patients. Compared to controls, blood flow parameters in these patients were decreased at baseline, but did not decrease further following PRP, with important implications related to diabetes control, endothelial function, and therapeutic response.

VEGF levels in plasma in relation to platelet activation, glycemic control, and microvascular complications in type 1 diabetes

OBJECTIVE

Increased levels of vascular endothelial growth factor (VEGF) in human plasma samples have suggested that circulating VEGF is a cause of endothelial dysfunction in diabetes mellitus. However, artificial release of VEGF from platelets as a source of VEGF in plasma samples, as also occurs in serum samples, has not been ruled out in these studies.

RESEARCH DESIGN AND METHODS

We determined VEGF levels in plasma collected in both citrate and PECT, a medium that inactivates platelets, in a cross-sectional cohort of 21 healthy subjects and 64 patients with type 1 diabetes. In addition, we evaluated whether VEGF levels in both types of plasma correlated with the presence of diabetes, glycemic control, markers of in vivo or ex vivo platelet activation, and degree of diabetic retinopathy and nephropathy.

RESULTS

VEGF levels were invariably low in PECT plasma of both nondiabetic and diabetic subjects and were unrelated to any other diabetes-related variable studied. In contrast, VEGF levels in citrate plasma were 150% higher in diabetic patients than in control subjects and correlated with diabetes-related variables. Multiple linear regression analysis showed that levels of platelet factor 4, a marker for ex vivo platelet activation, and HbA1c were the independent predictors of VEGF levels in citrate plasma. Platelet activation, in vivo and ex vivo, was similar in diabetic persons and control subjects.

CONCLUSIONS

Like serum, citrate plasma is not suitable for reliable measurements of circulating VEGF. The low levels of VEGF in vivo, as represented by measurements in PECT plasma in our study, do not support a role of circulating VEGF in endothelial dysfunction in type 1 diabetes. Higher levels of VEGF in citrate plasma samples of diabetic persons do not represent the in vivo situation, but mainly originate from higher artificial ex vivo release from platelets correlating with the degree of glycemic control.

Sulodexide improves renal function through reduction of vascular endothelial growth factor in type 2 diabetic rats

AIMS

Sulodexide is a promising therapeutic drug for the management of diabetic nephropathy. Although sulodexide has demonstrated a renoprotective effect through its ability to restore glomerular ionic permselectivity, the exact mechanism is still not clear. We investigated the effects of long-term sulodexide treatment on diabetic nephropathy in Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats.

MAIN METHODS

Diabetic rats were treated with or without sulodexide at 10mg/kg/day in the drinking water for nine months. Renal morphology and changes in VEGF and p38 mitogen-activated protein kinase (p38 MAPK), urinary levels of albumin (UAE) and urinary VEGF excretion were determined. To define the direct effects of sulodexide, we performed an in vitro experiment using podocytes.

KEY FINDINGS

UAE was significantly higher in OLETF rats than in control LETO rats, and the sulodexide group showed significantly decreased UAE after six months of treatment. Interestingly, urinary VEGF levels were also significantly decreased in the sulodexide-treated group. In accordance with UAE and urinary VEGF changes, the renal expression of profibrotic molecules was significantly decreased after sulodexide treatment. In addition, the activation of p38 MAPK, assessed by measuring the level of phospho-specific p38 MAPK, increased in diabetic renal tissues and was markedly suppressed by sulodexide treatment. In cultured podocytes, sulodexide treatment significantly decreased high glucose-induced p38 MAPK activation and VEGF synthesis.

SIGNIFICANCE

Sulodexide directly suppresses VEGF synthesis through the p38 MAPK pathway in podocytes, and these results suggest that sulodexide may provide renoprotection via suppression of renal VEGF synthesis independently of glomerular basement membrane ionic permselectivity in type 2 diabetic rats.

The nexus between VEGF and NFκB orchestrates a hypoxia-independent neovasculogenesis

Nuclear Factor-Kappa B [NFκB] activation triggers the elevation of various pro-angiogenic factors that contribute to the development and progression of diabetic vasculopathies. It has been demonstrated that vascular endothelial growth factor [VEGF] activates NFκB signaling pathway. Under the ischemic microenvironments, hypoxia-inducible factor-1 [HIF-1] upregulates the expression of several proangiogenic mediators, which play crucial roles in ocular pathologies. Whereas YC-1, a soluble guanylyl cyclase [sGC] agonist, inhibits HIF-1 and NFκB signaling pathways in various cell and animal models. Throughout this investigation, we examined the molecular link between VEGF and NFκB under a hypoxia-independent microenvironment in human retinal microvascular endothelial cells [hRMVECs]. Our data indicate that VEGF promoted retinal neovasculogenesis via NFκB activation, enhancement of its DNA-binding activity, and upregulating NFκB/p65, SDF-1, CXCR4, FAK, αVβ3, α5β1, EPO, ET-1, and MMP-9 expression. Conversely, YC-1 impaired the activation of NFκB and its downstream signaling pathways, via attenuating IκB kinase phosphorylation, degradation and activation, and thus suppressing p65 phosphorylation, nuclear translocation, and inhibiting NFκB-DNA binding activity. We report for the first time that the nexus between VEGF and NFκB is implicated in coordinating a scheme that upregulates several pro-angiogenic molecules, which promotes retinal neovasculogenesis. Our data may suggest the potential use of YC-1 to attenuate the deleterious effects that are associated with hypoxia/ischemia-independent retinal vasculopathies.

Phytochemicals in ocular health: Therapeutic potential and delivery challenges

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are the leading causes of blindness in adults. The impact of these conditions on the quality of life is increasing in significance with a rise in life expectancy. The role of hyperglycemia, oxidative stress and inflammatory responses in the development and/or progression of DR and AMD, and several other sight threatening ocular diseases, is well established. In proliferative retinopathy, signals sent by the retina for nourishment, triggers the growth of fragile and abnormal blood vessels. Changes in ocular pressure may lead to rupture of these blood vessels causing severe vision problems. Recent in vitro and preclinical studies demonstrate that certain phytochemicals possessing potent antioxidant and anti-inflammatory activity and ocular blood flow enhancing properties may be very useful in the treatment of, or as a prophylactic measure for, DR and AMD. Apart from these properties they have also been investigated for their anti-bacterial, hormonal, enzyme stimulation, and anti-angiogenic activities. The attractive aspect of these potential therapeutic candidates is that they can act on multiple pathways identified in the etiology of DR, AMD, cataract and other ocular diseases. However, results from clinical trials have been somewhat ambiguous, raising questions about the concentrations of these bioflavonoids achieved in the neural retina following oral administration. Unfortunately, as of date, an efficient noninvasive means to deliver therapeutic agents/candidates to the back-of-the eye is still not available. This review examines some of these promising natural agents and discusses the challenges encountered in delivering them to the posterior segment ocular tissues through the oral route.

The NAD ratio redox paradox: why does too much reductive power cause oxidative stress?

The reductive power provided by nicotinamide adenine dinucleotides is invaluable for several cellular processes. It drives metabolic reactions, enzymatic activity, regulates genetic expression and allows for the maintenance of a normal cell redox status. Therefore, the balance between the oxidized (NAD(+)) and the reduced (NADH) forms is critical for the cell's proper function and ultimately, for its survival. Being intimately associated with the cells' metabolism, it is expected that alterations to the NAD(+)/NADH ratio are to be found in situations of metabolic diseases, as is the case of diabetes. NAD(+) is a necessary cofactor for several enzymes' activity, many of which are related to metabolism. Therefore, a decrease in the NAD(+)/NADH ratio causes these enzymes to decrease in activity (reductive stress), resulting in an altered metabolic situation that might be the first insult toward several pathologies, such as diabetes. Here, we review the importance of nicotinamide adenine dinucleotides in the liver cell and its fluctuations in a state of type 2 diabetes mellitus.

Urinary MCP-1 and RBP: independent predictors of renal outcome in macroalbuminuric diabetic nephropathy

BACKGROUND

Albuminuria has been considered a sine qua non condition for the diagnosis of diabetic nephropathy (DN) and has been widely used as a surrogate outcome of chronic kidney disease (CKD). However, recent data suggest that albuminuria may fail as a biomarker in a subset of patients, and the search for novel markers is intense.

METHODS

We analyzed the role of urinary RBP and of serum and urinary cytokines (TGF-beta, MCP-1 and VEGF) as predictors of the risk of dialysis, doubling of serum creatinine or death (primary outcome, PO) in 56 type 2 diabetic patients with macroalbuminuric DN.

RESULTS

Mean follow-up time was 30.7±10 months. Urinary RBP and MCP-1 were significantly higher in patients presenting the PO, whereas no difference was shown for TGF-β or VEGF. In the Cox regression, urinary RBP, MCP-1 and VEGF were positively associated and serum VEGF was inversely related to the risk of the PO. However, after adjustments for creatinine clearance, proteinuria, and blood pressure only urinary RBP (OR 11.6; 95% CI 2.7-49.2, p=0.001 for log RBP) and urinary MCP-1 (OR 11.0; 95% CI 1.6-76.4, p=0.02 for log MCP-1) remained as significant independent predictors of the PO.

CONCLUSION

Urinary RBP and MCP-1 are independently related to the risk of CKD progression in patients with macroalbuminuric DN. Whether these biomarkers have a role in the setting of normoalbuminuria and microalbuminuria in DN should be further investigated.

Short-term fasting reduces the extent of myocardial infarction and incidence of reperfusion arrhythmias in rats

The effect of three-day fasting on cardiac ischemic tolerance was investigated in adult male Wistar rats. Anesthetized open-chest animals (pentobarbitone 60 mg/kg, i.p.) were subjected to 20-min left anterior descending coronary artery occlusion and 3-h reperfusion for infarct size determination. Ventricular arrhythmias were monitored during ischemia and at the beginning (3 min) of reperfusion. Myocardial concentrations of beta-hydroxybutyrate and acetoacetate were measured to assess mitochondrial redox state. Short-term fasting limited the infarct size (48.5+/-3.3 % of the area at risk) compared to controls (74.3+/-2.2 %) and reduced the total number of premature ventricular complexes (12.5+/-5.8) compared to controls (194.9+/-21.9) as well as the duration of ventricular tachycardia (0.6+/-0.4 s vs. 18.8+/-2.5 s) occurring at early reperfusion. Additionally, fasting increased the concentration of beta-hydroxybutyrate and beta-hydroxybutyrate/acetoacetate ratio (87.8+/-27.0) compared to controls (7.9+/-1.7), reflecting altered mitochondrial redox state. It is concluded that three-day fasting effectively protected rat hearts against major endpoints of acute I/R injury. Further studies are needed to find out whether these beneficial effects can be linked to altered mitochondrial redox state resulting from increased ketogenesis.

The pathogenesis of early retinal changes of diabetic retinopathy

Recent successful trials of antibodies to vascular endothelial growth factor (VEGF) in diabetic retinopathy implicate this cytokine as a major cause of diabetic retinopathy (DR) and diabetic macular oedema (DME). The mechanisms which cause VEGF to be over-expressed to cause the vasculopathy are not entirely clear. This review explores the earliest changes to the retina in DR and the factors that predispose or prevent DR, including sleep apnoea, receptor degenerations laser treatment and VEGF polymorphism. The review also presents the evidence that retinal hypoxia, existing in the earliest stages, causes DR. This hypoxia is much increased by dark adaptation, indicating a new and possibly superior therapy.

Polymorphisms in the vascular endothelial growth factor gene and the risk of diabetic retinopathy in Chinese patients with type 2 diabetes

PURPOSE

To investigate whether single nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor (VEGF) gene are associated with diabetic retinopathy (DR) in a cohort of Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 268 patients with T2DM (129 with DR and 139 without DR) were recruited and enrolled in the study. Patients with T2DM were assigned to a DR group or a diabetic-without-retinopathy group, based on the duration of diabetes and grading of fundus images. Genotypes of eight SNPs in the VEGF gene (rs699947, rs833061, rs13207351, rs2010963, rs833069, rs2146323, rs3025021, and rs3025039) were analyzed using a mass-array genotyping system, and an association study was performed.

RESULTS

After adjusting for covariates, a significant association of DR was observed with the homozygous genotype of the minor allele for promoter SNPs rs699947 (odds ratio (OR)=3.54, 95% confidence interval (CI): 1.12-11.19), rs833061 (OR=3.72, 95% CI: 1.17-11.85) and rs13207351 (OR=3.76, 95% CI: 1.21-11.71). A significant association of DR was also observed with haplotype ACA, as defined by minor alleles of promoter SNPs rs699947, rs833061, and rs13207351 (OR=1.52, 95% CI: 1.03-2.24), and haplotype GAA, as defined by SNPs rs2010963, rs833069, and rs2146323 (OR=1.62, 95% CI: 1.08-2.41).

CONCLUSIONS

Our data suggest that polymorphisms in the promoter region of the VEGF gene increase the risk of DR in Chinese patients with T2DM.

Vascular dysfunction in the diabetic placenta: causes and consequences

The development and functioning of the human fetoplacental vascular system are vulnerable to the maternal diabetic milieu. These vessels are in direct continuum with the fetal vascular system and are therefore also vulnerable to fetal endocrine derangements. Increased angiogenesis, altered junctional maturity and molecular occupancy, together with increased leakiness, constitute a well-described phenotype of vessels in the Type 1 diabetic human placenta and can be related to increased levels of placental vascular endothelial growth factor. The causes of these observed changes, whether maternal hyperglycaemia or fetal hyperinsulinaemia, still remain to be shown in the human placenta. Mechanistic studies using different vascular systems have shown high glucose and insulin to have profound vascular effects, with elevations in vascular endothelial growth factor, nitric oxide and protein kinase C being behind alterations in junctional adhesion molecules such as occludin and vascular endothelial-cadherin and vascular leakage of albumin. The role of advanced glycation products and oxidative stress in this vascular pathology is also discussed. The altered molecular mechanisms underlying the vascular changes in the diabetic human placenta may reflect similar consequences of high glucose and hyperinsulinaemia.

Aldose reductase inhibitor ameliorates renal vascular endothelial growth factor expression in streptozotocin-induced diabetic rats

PURPOSE

The vascular endothelial growth factor (VEGF) expression of podocyte is one of the well-known major factors in development of diabetic nephropathy. In this study, we investigated the effects of aldose reductase inhibitor, fidarestat on diabetic nephropathy, and renal VEGF expression in a type 1 diabetic rat model.

MATERIALS AND METHODS

Twenty four Sprague-Dawley male rats which were performed intraperitoneal injection of streptozotocin and normal six rats were divided into four groups including a normal control group, untreated diabetic control group, aldose reductase (AR) inhibitor (fidarestat, 16 mg kg(-1) day(-1)) treated diabetic group, and angiotensin receptor blocker (losartan, 20 mg kg(-1) day(-1)) treated diabetic group. We checked body weights and blood glucose levels monthly and measured urine albumin-creatinine ratio (ACR) at 8 and 32 weeks. We extracted the kidney to examine the renal morphology and VEGF expressions.

RESULTS

The ACR decreased in fidarestat and losartan treated diabetic rat groups than in untreated diabetic group (24.79 +/- 11.12, 16.11 +/- 9.95, and 84.85 +/- 91.19, p < 0.05). The renal VEGF messenger RNA (mRNA) and protein expression were significantly decreased in the fidarestat and losartan treated diabetic rat groups than in the diabetic control group.

CONCLUSION

We suggested that aldose reductase inhibitor may have preventive effect on diabetic nephropathy by reducing renal VEGF overexpression.

Early neural and vascular dysfunctions in diabetic rats are largely sequelae of increased sorbitol oxidation

These experiments were undertaken to assess the importance of cytoplasmic (c) sorbitol oxidation versus mitochondrial (m) pyruvate oxidation in mediating neural and vascular dysfunction attributable to hyperglycemia in diabetic rats. Increased oxidation of sorbitol is coupled to enzymatic reduction of free oxidized NAD(+)c to reduced NADHc, manifested by an increased ratio of NADH to NAD(+)c. Likewise, increased oxidation of pyruvate is coupled to reduction of NAD(+)m to NADHm, which increases the NADH/NAD(+)m ratio. Specific inhibitors of sorbitol production or sorbitol oxidation normalized: increased diabetic nerve NADH/NAD(+)c, impaired nerve-conduction velocity, and vascular dysfunction in sciatic nerve, retina, and aorta; however, they had little or no impact on increased NADH/NAD(+)m. These observations provide, for the first time, strong in vivo evidence for the primacy of sorbitol oxidation versus. pyruvate oxidation in mediating the metabolic imbalances, impaired nerve conduction, and vascular dysfunction evoked by diabetes. These findings are consistent with (a) the fact that oxidation of sorbitol produces "prooxidant" NADHc uncoupled from subsequent production of "antioxidant" pyruvate required for reoxidation of NADHc to NAD(+)c by lactate dehydrogenase, and (b) the hypothesis that neural and vascular dysfunction in early diabetes are caused primarily by increased NADHc, which fuels superoxide production by NADH-driven oxidases.

Role of the VEGF 936 C/T polymorphism in diabetic microvascular complications in type 2 diabetic patients

AIM

Vascular endothelial growth factor (VEGF) is important in the pathogenesis of diabetic microvascular complications and the genetic polymorphism of this gene may contribute to the development and progression of diabetic microvascular complications. In this study, we investigated whether a genetic polymorphism of VEGF is associated with diabetic complications.

METHODS

A total of 398 type 2 diabetic patients and 526 healthy controls were enrolled. The study subjects were divided based on the state of nephropathy, retinopathy and neuropathy. The VEGF 936 C/T polymorphism was evaluated using standard PCR techniques, and plasma and urinary levels of VEGF were determined by enzyme-linked immunosorbent assay.

RESULTS

There was no difference in VEGF genotype distribution between the control and diabetic patients based on the state of diabetic nephropathy and neuropathy. However, a higher frequency of the TT genotype was observed in patients with proliferative diabetic retinopathy. Additionally, plasma levels of VEGF were significantly higher in the TT genotype. However, urinary levels of VEGF did not show a significant relationship with the VEGF genotype. Urinary VEGF levels showed a significant relationship with urinary albumin excretion, proteinuria, serum creatinine level and creatinine clearance, as well as fasting blood glucose levels, postprandial 2 h glucose levels and C-reactive protein.

CONCLUSION

Our study suggests that the 936 C/T polymorphism of the VEGF gene may be an important factor determining plasma VEGF levels and that its polymorphism is related with diabetic retinopathy. Urinary levels of VEGF are not associated with plasma VEGF levels and associated with the stage of diabetic nephropathy.