Progressive attenuation of myocardial vascular endothelial growth factor expression is a seminal event in diabetic cardiomyopathy: restoration of microvascular homeostasis and recovery of cardiac function in diabetic cardiomyopathy after replenishment of local vascular endothelial growth factor

Heart angiotensin II-induced cardiomyocyte hypertrophy suppresses coronary angiogenesis and progresses diabetic cardiomyopathy

To examine whether and how heart ANG II influences the coordination between cardiomyocyte hypertrophy and coronary angiogenesis and contributes to the pathogenesis of diabetic cardiomyopathy, we used Spontaneously Diabetic Torii (SDT) rats treated without and with olmesartan medoxomil (an ANG II receptor blocker). In SDT rats, left ventricular (LV) ANG II, but not circulating ANG II, increased at 8 and 16 wk after diabetes onset. SDT rats developed LV hypertrophy and diastolic dysfunction at 8 wk, followed by LV systolic dysfunction at 16 wk, without hypertension. The SDT rat LV exhibited cardiomyocyte hypertrophy and increased hypoxia-inducible factor-1α expression at 8 wk and to a greater degree at 16 wk and interstitial fibrosis at 16 wk only. In SDT rats, coronary angiogenesis increased with enhanced capillary proliferation and upregulation of the angiogenic factor VEGF at 8 wk but decreased VEGF with enhanced capillary apoptosis and suppressed capillary proliferation despite the upregulation of VEGF at 16 wk. In SDT rats, the phosphorylation of VEGF receptor-2 increased at 8 wk alone, whereas the expression of the antiangiogenic factor thrombospondin-1 increased at 16 wk alone. All these events, except for hyperglycemia or blood pressure, were reversed by olmesartan medoxomil. These results suggest that LV ANG II in SDT rats at 8 and 16 wk induces cardiomyocyte hypertrophy without affecting hyperglycemia or blood pressure, which promotes and suppresses coronary angiogenesis, respectively, via VEGF and thrombospondin-1 produced from hypertrophied cardiomyocytes under chronic hypoxia. Thrombospondin-1 may play an important role in the progression of diabetic cardiomyopathy in this model.

AngiotensinII preconditioning promotes angiogenesis in vitro via ERKs phosphorylation

AngiotensinII (AngII) is involved in not only the formation of cardiac hypertrophy but also the development of cardiac remodeling both of which are associated with myocardial angiogenesis. This study was therefore performed to clarify the effects of AngII on the formation of vasculatures by cultured cardiac microvascular endothelial cells (CMVECs) after a long-period stimulation with or without the AngII preconditioning. Incubation with AngII for 18 hrs significantly impaired the formation of capillary-like tubes comparing to that without AngII. CMVECs with AngII pretreatment for 5 and 10 min formed more capillary-like tubes than those without AngII pretreatment, suggesting that preconditioning with AngII at a lower dose for a short period could prevent the further damage of CMVECs by a higher concentration of AngII. Moreover, AngII (10(-7) M) stimulation for 5 and 10 min significantly induced the increase in extracellular signal-regulated protein kinases (ERKs) phosphorylation, and an ERKs inhibitor, PD98059, abrogated the increase in the formation of capillary-like tubes induced by the AngII-pretreatment. In conclusion, preconditioning with a lower concentration of AngII for a short period prevents the subsequent impairment of CMVECs by a higher dose of AngII, at least in part, through the increase in ERKs phosphorylation.

Amelioration of glucose control mobilizes circulating pericyte progenitor cells in type 2 diabetic patients with microangiopathy

Chronic diabetic complications result from an imbalance between vascular damage and regeneration. Several circulating lineage-committed progenitor cells have been implicated, but no data are available on pericyte progenitor cells (PPCs). Based on the evidence that PPCs increase in cancer patients after chemotherapy, we explored whether circulating PPC levels are affected by glucose control in type 2 diabetic patients, in relation to the presence of chronic complications. We enumerated peripheral blood PPCs as Syto16+CD45−CD31−CD140b+ events by flow cytometry at baseline and after 3 and 6 months of glucose control by means of add-on basal insulin therapy on top of oral agents in 38 poorly controlled type 2 diabetic patients. We found that, in patients with microangiopathy (n = 23), the level of circulating PPCs increased about 2 fold after 3 months and then returned to baseline at 6 months. In patients without microangiopathy (control group, n = 15), PPCs remained fairly stable during the whole study period. No relationship was found between change in PPCs and macroangiopathy (either peripheral, coronary, or cerebrovascular). We conclude that glucose control transiently mobilizes PPCs diabetic patients with microangiopathy. Increase in PPCs may represent a vasoregenerative event or may be a consequence of ameliorated glucose control on microvascular lesions.

High glucose-induced Ca2+ overload and oxidative stress contribute to apoptosis of cardiac cells through mitochondrial dependent and independent pathways

BACKGROUND

Cardiac cell apoptosis is the initiating factor of cardiac complications especially diabetic cardiomyopathy. Mitochondria are susceptible to the damaging effects of elevated glucose condition. Calcium overload and oxidative insult are the two mutually non-exclusive phenomena suggested to cause cardiac dysfunction. Here, we examined the effect of high-glucose induced calcium overload in calpain-1 mediated cardiac apoptosis in an in vitro setting.

METHODS

H9c2, rat ventricular myoblast cell line was treated with elevated glucose condition and the cellular consequences were studied. Intracellular calcium trafficking, ROS generation, calpain-1 activation and caspase-12 and caspase-9 pathway were studied using flow cytometry, confocal microscopy and Western blot analysis.

RESULTS

High-glucose treatment resulted in increased intracellular calcium ([Ca2+]i) which was mobilized to the mitochondria. Concomitant intra-mitochondrial calcium ([Ca2+]m) increase resulted in enhanced reactive oxygen and nitrogen species generation. These events led to mitochondrial dysfunction and apoptosis. Cardiomyocyte death exhibited several classical markers of apoptosis, including activation of caspases, appearance of annexin V on the outer plasma membrane, increased population of cells with sub-G0/G1 DNA content and nuclear condensation. Key findings include elucidation of cell signaling mechanism of high-glucose induced calcium-dependent cysteine protease calpain-1 activation, which triggers non-conventional caspases as alternate mode of cell death.

CONCLUSION

This information increases the understanding of cardiac cell death under hyperglycemic condition and can possibly be extended for designing new therapeutic strategies for diabetic cardiomyopathy.

GENERAL SIGNIFICANCE

The novel findings of the study reveal that high glucose induces apoptosis by both mitochondria-dependent and independent pathways via concomitant rise in intracellular calcium.

Neuregulin-1/ErbB signaling is impaired in the rat model of diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCP) is one of the leading causes of increased morbidity and mortality in the diabetic population. The neuregulin-1(NRG1)/ErbB signal system plays a critical role in maintenance of adult heart function. But little is known about the changes of NRG1/ErbB signal system in DCP. The aim of this study was to investigate the changes of the NRG1/ErbB signal system in DCP.

METHODS

A rat model of DCP was established using a single intraperitoneal injection of streptozotocin (STZ). Cardiac function was assessed using echocardiography. The left ventricle fibrosis was evaluated using Masson's trichrome staining. The mRNA expression profiles of ErbB2 and ErbB4 receptors were evaluated using real-time polymerase chain reaction. The protein expression of NRG1 and the phosphorylation of ErbB2 and ErbB4 receptors were assessed using Western blot analysis.

RESULTS

The results showed dramatic left ventricle fibrosis and impaired left ventricle systolic function at 12 weeks after STZ-induced diabetes. This study also showed that ErbB2 and ErbB4 mRNA expression and NRG1 protein expression in the left ventricular myocardium were significantly decreased. In addition, we observed decreased phosphorylation of the ErbB2 and ErbB4 receptors at 12 weeks after the induction of diabetes.

CONCLUSIONS

These findings suggest that NRG1/ErbB signaling is impaired in DCP, which may play some roles in the pathogenesis of DCP.

Insulin-like growth factor-1 receptor activation prevents hydrogen peroxide-induced oxidative stress, mitochondrial dysfunction and apoptosis

Vascular disease is the leading cause of morbidity and mortality. Oxidative stress can cause endothelial cell apoptosis. Low insulin like growth factor-1 (IGF-1) has been linked to adverse risk profile and increased vascular disease incidence. Since IGF-1 acts as an important survival factor for multiple cell types, we undertook this study to investigate whether IGF-1 favorably affects oxidative-stress mediated apoptosis of vascular endothelial cells. Exposure to hydrogen peroxide induced apoptotic changes (e.g. DNA fragmentation, altered mitochondrial membrane potential and caspase-3 activity) in human umbilical vein endothelial cells (HUVECs) in a time dependent manner. Addition of IGF-1 blocked the oxidative-stress effect parallel to IGF-1 receptor (IGF-1R) expression, and silencing the IGF-1R with small interference RNA attenuated the IGF-1 influence. Our findings show that enhanced IGF-1 signaling inhibits oxidative-stress induced apoptosis in HUVECs by reducing mitochondrial dysfunction. Specifically the protective mechanism of IGF-1 involves preserving the mitochondrial membrane potential, maintaining the mitochondrial retention of cytochrome-c, and reducing caspase-3 activity. These results may have therapeutic implications in preventing/reducing vascular disease associated endothelial dysfunction.

Nerve growth factor gene therapy using adeno-associated viral vectors prevents cardiomyopathy in type 1 diabetic mice

Diabetes is a cause of cardiac dysfunction, reduced myocardial perfusion, and ultimately heart failure. Nerve growth factor (NGF) exerts protective effects on the cardiovascular system. This study investigated whether NGF gene transfer can prevent diabetic cardiomyopathy in mice. We worked with mice with streptozotocin-induced type 1 diabetes and with nondiabetic control mice. After having established that diabetes reduces cardiac NGF mRNA expression, we tested NGF gene therapies with adeno-associated viral vectors (AAVs) for the capacity to protect the diabetic mouse heart. To this aim, after 2 weeks of diabetes, cardiac expression of human NGF or β-Gal (control) genes was induced by either intramyocardial injection of AAV serotype 2 (AAV2) or systemic delivery of AAV serotype 9 (AAV9). Nondiabetic mice were given AAV2-β-Gal or AAV9-β-Gal. We found that the diabetic mice receiving NGF gene transfer via either AAV2 or AAV9 were spared the progressive deterioration of cardiac function and left ventricular chamber dilatation observed in β-Gal-injected diabetic mice. Moreover, they were additionally protected from myocardial microvascular rarefaction, hypoperfusion, increased deposition of interstitial fibrosis, and increased apoptosis of endothelial cells and cardiomyocytes, which afflicted the β-Gal-injected diabetic control mice. Our data suggest therapeutic potential of NGF for the prevention of cardiomyopathy in diabetic subjects.

Overexpression of angiopoietin-2 impairs myocardial angiogenesis and exacerbates cardiac fibrosis in the diabetic db/db mouse model

The angiopoietins/Tie-2 system is essential for the maintenance of vascular integrity and angiogenesis. The functional role of angiopoietin-2 (Ang-2) in the regulation of angiogenesis is dependent on other growth factors such as VEGF and a given physiopathological conditions. This study investigates the potential role of Ang-2 in myocardial angiogenesis and fibrosis formation in the diabetic db/db mouse. Diabetic db/db mice received intramyocardial administration of either adenovirus Ang-2 (Ad-CMV-Ang-2) or Ad-β-gal. The levels of Tie-2, VEGF, caspase-3, Wnt7b, fibroblast-specific protein-1 (FSP-1), and adhesion molecules (ICAM-1 and VCAM-1) expression were measured. Apoptosis, capillary density, and cardiac fibrosis were also analyzed in the db/db mouse hearts. Overexpression of Ang-2 suppressed Tie-2 and VEGF expression in db/db mouse hearts together with significant upregulation of Wnt7b expression. Overexpression of Ang-2 also sensitizes ICAM-1 and VCAM-1 expression in db/db mouse hearts. Immunohistochemical analysis revealed that overexpression of Ang-2 resulted in a gradual apoptosis as well as interstitial fibrosis formation, these leading to a significant loss of capillary density. Data from these studies were confirmed in cultured mouse heart microvascular endothelial cells (MHMEC) exposed to excessive Ang-2. Exposure of MHMEC to Ang-2 resulted in increased caspase-3 activity and endothelial apoptosis. Knockdown of Ang-2 attenuated high glucose-induced endothelial cell apoptosis. Further, counterbalance of Ang-2 by overexpression of Ang-1 reversed loss of capillary density and fibrosis formation in db/db mouse hearts. Our data demonstrate that Ang-2 increases endothelial apoptosis, sensitizes myocardial microvascular inflammation, and promotes cardiac fibrosis and thus contributes to loss of capillary density in diabetic diseases.

Role of microRNAs in diabetes and its cardiovascular complications

Diabetes is the most common metabolic disorder and is recognized as one of the most important health threats of our time. MicroRNAs (miRNAs) are a novel group of non-coding small RNAs that have been implicated in a variety of physiological processes, including glucose homeostasis. Recent research has suggested that miRNAs play a critical role in the pathogenesis of diabetes and its related cardiovascular complications. This review focuses on the aberrant expression of miRNAs in diabetes and examines their role in the pathogenesis of endothelial dysfunction, cardiovascular disease, and diabetic retinopathy. Furthermore, we discuss the potential role of miRNAs as blood biomarkers and examine the potential of therapeutic interventions targeting miRNAs in diabetes.

Role of activation of 5'-adenosine monophosphate-activated protein kinase in gastric ulcer healing in diabetic rats

BACKGROUND

The potential utility of 5'-adenosine monophosphate-activated protein kinase (AMPK)-activating agents, such as metformin, in inducing angiogenesis, could be a promising approach to promote healing of gastric ulcers complicated by diabetes mellitus. The aim of the present study was to assess the effect of a drug that activates AMPK, namely metformin, in gastric ulcer healing in streptozotocin-induced diabetic rats.

METHODS

Forty male Wistar albino rats were made diabetic by intraperitoneal (i.p.) streptozotocin injection and 10 rats were injected i.p. by a single dose of physiological saline. Six weeks following streptozotocin or saline injection, gastric ulcers were induced by serosal application of acetic acid. Three days after acetic acid application, rats were divided into group 1 (nondiabetic control), group 2 (streptozotocin-injected rats), groups 3-5 (streptozotocin-injected rats treated with metformin or metformin and an inhibitor of AMPK, namely compound C or pioglitazone) for 7 days following acetic acid application.

RESULTS

Administration of metformin, but not pioglitazone, resulted in a significant decrease in the gastric ulcer area, a significant increase in epithelial regeneration assessed histologically, a significant increase in the number of microvessels in the ulcer margin, a significant increase in gastric vascular endothelial growth factor concentration and gastric von Willebrand factor as well as a significant increase in gastric phospho-AMPK. Compound C, an inhibitor of AMPK, blocked metformin-induced changes in assessed parameters suggesting that the effect of metformin was mediated mainly through activation of AMPK.

CONCLUSION

Our results suggest the feasibility of a novel treatment strategy, namely drugs activating AMPK, for patients in whom impairment of ulcer healing constitutes a secondary complication of diabetes mellitus.

TRB3 gene silencing alleviates diabetic cardiomyopathy in a type 2 diabetic rat model

OBJECTIVE

Tribbles 3 (TRB3) is associated with insulin resistance, an important trigger in the development of diabetic cardiomyopathy (DCM). We sought to determine whether TRB3 plays a major role in modulating DCM and the mechanisms involved.

RESEARCH DESIGN AND METHODS

The type 2 diabetic rat model was induced by high-fat diet and low-dose streptozotocin. We evaluated the characteristics of type 2 DCM by serial echocardiography and metabolite tests, Western blot analysis for TRB3 expression, and histopathologic analyses of cardiomyocyte density, lipids accumulation, cardiac inflammation, and fibrosis area. We then used gene silencing to investigate the role of TRB3 in the pathophysiologic features of DCM.

RESULTS

Rats with DCM showed severe insulin resistance, left ventricular dysfunction, aberrant lipids deposition, cardiac inflammation, fibrosis, and TRB3 overexpression. We found that the silencing of TRB3 ameliorated metabolic disturbance and insulin resistance; myocardial hypertrophy, lipids accumulation, inflammation, fibrosis, and elevated collagen I-to-III content ratio in DCM rats were significantly decreased. These anatomic findings were accompanied by significant improvements in cardiac function. Furthermore, with TRB3 gene silencing, the inhibited phosphorylation of Akt was restored and the increased phosphorylation of extracellular signal-regulated kinase 1/2 and Jun NH(2)-terminal kinase in DCM was significantly decreased.

CONCLUSIONS

TRB3 gene silencing may exert a protective effect on DCM by improving selective insulin resistance, implicating its potential role for treatment of human DCM.

Distinct cardiac and renal effects of ETA receptor antagonist and ACE inhibitor in experimental type 2 diabetes

Diabetic nephropathy is associated with cardiovascular morbidity. Angiotensin-converting enzyme (ACE) inhibitors provide imperfect renoprotection in advanced type 2 diabetes, and cardiovascular risk remains elevated. Endothelin (ET)-1 has a role in renal and cardiac dysfunction in diabetes. Here, we assessed whether combination therapy with an ACE inhibitor and ETA receptor antagonist provided reno- and cardioprotection in rats with overt type 2 diabetes. Four groups of Zucker diabetic fatty (ZDF) rats were treated orally from 4 (when proteinuric) to 8 mo with vehicle, ramipril (1 mg/kg), sitaxsentan (60 mg/kg), and ramipril plus sitaxsentan. Lean rats served as controls. Combined therapy ameliorated proteinuria and glomerulosclerosis mostly as a result of the action of ramipril. Simultaneous blockade of ANG II and ET-1 pathways normalized renal monocyte chemoattractant protein-1 and interstitial inflammation. Cardiomyocyte loss, volume enlargement, and capillary rarefaction were prominent abnormalities of ZDF myocardium. Myocyte volume was reduced by ramipril and sitaxsentan, which also ameliorated heart capillary density. Drug combination restored myocardial structure and reestablished an adequate capillary network in the presence of increased cardiac expression of VEGF/VEGFR-1, and significant reduction of oxidative stress. In conclusion, in type 2 diabetes concomitant blockade of ANG II synthesis and ET-1 biological activity through an ETA receptor antagonist led to substantial albeit not complete renoprotection, almost due to the ACE inhibitor. The drug combination also showed cardioprotective properties, which however, were mainly dependent on the contribution of the ETA receptor antagonist through the action of VEGF.

Diabetic cardiomyopathy

Individuals with diabetes are at a significantly greater risk of developing cardioymyopathy and heart failure despite adjusting for concomitant risks such as coronary artery disease or hypertension. This has led to the increased recognition of a distinct disease process termed as "diabetic cardiomyopathy." In this article, we perform an extensive review of the pathogenesis and treatment of this disease. From a clinical perspective, physicians should be aware of this entity, and early screening should be considered because physical evidence of early diabetic cardiomyopathy could be difficult to detect. Early detection of the disease should prompt intensification of glycemic control, concomitant risk factors, use of pharmacologic agents such as β-blockers and renin-angiotensin-aldosterone system antagosists. From a research perspective, more studies on myocardial tissue from diabetic patients are needed. Clinical trials to evaluate the development of diabetic cardiomyopathy and fibrosis in early stages of the disease, as well as clinical trials of pharmacologic intervention in patients specifically with diabetic cardiomyopathy, need to be conducted.

The cardiac (pro)renin receptor is primarily expressed in myocyte transverse tubules and is increased in experimental diabetic cardiomyopathy

BACKGROUND

The pro(renin) receptor is a 350 amino acid transmembrane protein, that on ligand binding, increases the catalytic efficiency of angiotensinogen cleavage by both prorenin and renin, augmenting angiotensin I formation at the cell surface. While implicated in a broad range of diseases, studies to date have focused on the kidney, particularly in the diabetic context. We sought to examine the site-specific expression of the pro(renin) receptor within the heart.

METHODS

Using confocal microscopy, site-specific markers and transmission electron microscopy we assessed the location of the pro(renin) receptor in the heart at both cellular/sub-cellular levels. We assessed pro(renin) receptor expression in the setting of disease and blockade of the renin-angiotensin system, using the TGR[m(Ren2)-27] model of diabetic cardiomyopathy and the direct renin inhibitor, aliskiren.

RESULTS

The pro(renin) receptor was found predominantly at the Z-disc and dyad of cardiac myocytes coinciding closely with the distributions of the vacuolar H⁺-ATPase and ryanodine receptor, known to be located within T-tubules and the sarcoplasmic reticulum's terminal cisternae, respectively. Pro(renin) receptor mRNA/protein abundance were increased ∼3-fold in the hearts of diabetic rats in association with diastolic dysfunction, myocyte hypertrophy and interstitial fibrosis (all P < 0.01). Direct renin inhibition reduced cardiac pro(renin) receptor expression in association with improved cardiac structure/function (all P < 0.05).

CONCLUSION

Together, these findings are consistent with the notion that the pro(renin) receptor is a component of the vacuolar H⁺-ATPase, and that like the latter, is increased in the setting of cardiac stress and lowered by the administration of an ostensibly cardioprotective agent.

Regulation of hypoxia-inducible factor 1 and the loss of the cellular response to hypoxia in diabetes

Diabetes is frequently associated with hypoxia and is known to impair ischaemia-induced neovascularisation and other forms of adaptive cell and tissue responses to low oxygen levels. Hyperglycaemia appears to be the driving force of such deregulation. Recent data indicate that destabilisation of hypoxia-inducible factor 1 (HIF-1) is most likely the event that transduces hyperglycaemia into the loss of the cellular response to hypoxia in most diabetic complications. HIF-1 is a critical transcription factor involved in oxygen homeostasis that regulates a variety of adaptive responses to hypoxia, including angiogenesis, metabolic reprogramming and survival. Thus, destabilisation of HIF-1 is likely to have a negative impact on cell and tissue adaptation to low oxygen. Indeed, destabilisation of HIF-1 by high glucose levels has serious consequences in various organs and tissues, including myocardial collateralisation, wound healing, renal, neural and retinal function, as a result of poor cell and tissue responses to low oxygen. This review aims to integrate and summarise some of the most recent developments, including new proposed molecular models, on this research topic, particularly in terms of their implications for potential therapeutic approaches for the prevention or treatment of some of the diabetic complications characterised by impaired cellular and tissue responses to hypoxia.

Cell-based therapies for diabetic complications

In recent years, accumulating experimental evidence supports the notion that diabetic patients may greatly benefit from cell-based therapies, which include the use of adult stem and/or progenitor cells. In particular, mesenchymal stem cells and the circulating pool of endothelial progenitor cells have so far been the most studied populations of cells proposed for the treatment of vascular complications affecting diabetic patients. We review the evidence supporting their use in this setting, the therapeutic benefits that these cells have shown so far as well as the challenges that cell-based therapies in diabetic complications put out.

Regulation of hypoxia-inducible factor 1 and the loss of the cellular response to hypoxia in diabetes

Diabetes is frequently associated with hypoxia and is known to impair ischaemia-induced neovascularisation and other forms of adaptive cell and tissue responses to low oxygen levels. Hyperglycaemia appears to be the driving force of such deregulation. Recent data indicate that destabilisation of hypoxia-inducible factor 1 (HIF-1) is most likely the event that transduces hyperglycaemia into the loss of the cellular response to hypoxia in most diabetic complications. HIF-1 is a critical transcription factor involved in oxygen homeostasis that regulates a variety of adaptive responses to hypoxia, including angiogenesis, metabolic reprogramming and survival. Thus, destabilisation of HIF-1 is likely to have a negative impact on cell and tissue adaptation to low oxygen. Indeed, destabilisation of HIF-1 by high glucose levels has serious consequences in various organs and tissues, including myocardial collateralisation, wound healing, renal, neural and retinal function, as a result of poor cell and tissue responses to low oxygen. This review aims to integrate and summarise some of the most recent developments, including new proposed molecular models, on this research topic, particularly in terms of their implications for potential therapeutic approaches for the prevention or treatment of some of the diabetic complications characterised by impaired cellular and tissue responses to hypoxia.

Concise review: Mesenchymal stem cell treatment of the complications of diabetes mellitus

Mesenchymal stem cells (MSCs) are multipotent, self-renewing cells that can be found in almost all postnatal organs and tissues. The main functional characteristics of MSCs are their immunomodulatory ability, capacity for self-renewal, and differentiation into mesodermal tissues. The ability of MSCs to differentiate into several cell types, including muscle, brain, vascular, skin, cartilage, and bone cells, makes them attractive as therapeutic agents for a number of diseases including complications of diabetes mellitus. We review here the potential of MSCs as new therapeutic agents in the treatment of diabetic cardiomyopathy, diabetic nephropathy, diabetic polyneuropathy, diabetic retinopathy, and diabetic wounds. Also, in this review we discuss the current limitations for MSCs therapy in humans. Stem Cells 2011;29:5–10

Coronary vein infusion of multipotent stromal cells from bone marrow preserves cardiac function in swine ischemic cardiomyopathy via enhanced neovascularization

Few reports have examined the effects of adult bone marrow multipotent stromal cells (MSCs) on large animals, and no useful method has been established for MSC implantation. In this study, we investigate the effects of MSC infusion from the coronary vein in a swine model of chronic myocardial infarction (MI). MI was induced in domestic swine by placing beads in the left coronary artery. Bone marrow cells were aspirated and then cultured to isolate the MSCs. At 4 weeks after MI, MSCs labeled with dye (n=8) or vehicle (n=5) were infused retrogradely from the anterior interventricular vein without any complications. Left ventriculography (LVG) was performed just before and at 4 weeks after cell infusion. The ejection fraction (EF) assessed by LVG significantly decreased from baseline up to a follow-up at 4 weeks in the control group (P<0.05), whereas the cardiac function was preserved in the MSC group. The difference in the EF between baseline and follow-up was significantly greater in the MSC group than in the control group (P<0.05). The MSC administration significantly promoted neovascularization in the border areas compared with the controls (P<0.0005), though it had no affect on cardiac fibrosis. A few MSCs expressed von Willebrand factor in a differentiation assay, but none of them expressed troponin T. In quantitative gene expression analysis, basic fibroblast growth factor and vascular endothelial growth factor (VEGF) levels were significantly higher in the MSC-treated hearts than in the controls (P<0.05, respectively). Immunohistochemical staining revealed VEGF production in the engrafted MSCs. In vitro experiment demonstrated that MSCs significantly stimulated endothelial capillary network formation compared with the VEGF protein (P<0.0001). MSC infusion via the coronary vein prevented the progression of cardiac dysfunction in chronic MI. This favorable effect appeared to derive not from cell differentiation, but from enhanced neovascularization by angiogenic factors secreted from the MSCs.

Ca(2+) channel blocker benidipine promotes coronary angiogenesis and reduces both left-ventricular diastolic stiffness and mortality in hypertensive rats

BACKGROUND

The beneficial cardiac effects of some Ca(2+) channel blockers have been attributed to blood pressure reduction, but these pleiotropic effects require further investigation. We compared the effects of benidipine, which has beneficial cardiac effects, and nitrendipine, which does not, in an animal model of hypertensive diastolic heart failure (DHF).

METHODS AND RESULTS

Male Dahl salt-sensitive rats were fed a high-salt diet from age 7 weeks to induce hypertension and were either vehicle or orally administered benidipine (3 mg/kg daily) or nitrendipine (10 mg/kg daily) from age 10 to 18 weeks. Control rats were maintained on a low-salt diet. In vehicle-treated rats, left-ventricular (LV) fractional shortening was preserved but LV end-diastolic pressure was increased, indicative of DHF. Benidipine and nitrendipine had similar antihypertensive effects and reduced both LV weight and cardiomyocyte hypertrophy. Benidipine reduced LV diastolic stiffness and mortality to a greater extent than did nitrendipine. Benidipine, but not nitrendipine, also reduced lung weight. The extent of interstitial fibrosis and the abundance of mRNAs for prohypertrophic, profibrotic, or proinflammatory genes in the left ventricle were reduced by benidipine and nitrendipine. Benidipine, but not nitrendipine, increased capillary density and restored the expression of hypoxia-inducible factor 1alpha, vascular endothelial growth factor, and endothelial nitric oxide synthase in the left ventricle.

CONCLUSIONS

Benidipine reduced LV diastolic stiffness and increased survival, effects likely attributable predominantly to promotion of coronary angiogenesis rather than to attenuation of interstitial fibrosis. Benidipine may thus be more effective than purely L-type Ca(2+) channel blockers in preventing hypertensive DHF.

Transplantation of healthy but not diabetic outgrowth endothelial cells could rescue ischemic myocardium in diabetic rabbits

OBJECTIVE

There are two types of endothelial progenitor cell (EPC) in circulation, early EPC and outgrowth endothelial cell (OEC). Diabetes impairs the function of EPC, but it is not clear whether transplantation of OECs can rescue ischemic myocardium in diabetes. In this study, we compared the function of diabetic and healthy OECs in vitro. Then we administered diabetic and healthy OECs intramyocardially and compared their contribution to vasculogenesis in diabetic rabbits.

METHODS

Outgrowth endothelial cells from diabetic and healthy rabbits were isolated and subjected to in vitro proliferation, tube-forming, angiogenic cytokine assays. Exogenous diabetic and healthy OECs were analyzed for therapeutic efficacy in an acute ischemia model of diabetic rabbits. LV function was assessed using echocardiography. The capillary density and fibrosis area were evaluated. MRNA expression of VEGF and bFGF was analyzed using relative realtime quantitive PCR.

RESULTS

Proliferation, tube-forming, secretion of VEGF and bFGF of diabetic OECs were significantly reduced compared with healthy OECs. In diabetic rabbits, healthy OECs transplantation could increase capillary density and improve cardiac function, decrease fibrosis area compared with diabetic OEC and the control group. Real time PCR indicated that mRNA expression of VEGF and bFGF were augmented more in the healthy OEC group than those in the control and diabetic OEC groups.

CONCLUSIONS

These findings suggest that diabetes impairs the function of OECs. Transplantation of healthy OECs may rescue the ischemic myocardium by neovasculogenesis and paracrine effect in diabetic rabbits. However, autologous transplantation of diabetic OEC could not enhance cardiac function.

Mitochondrial fragmentation and superoxide anion production in coronary endothelial cells from a mouse model of type 1 diabetes

AIMS/HYPOTHESIS

Mitochondria frequently change their shapes by fusion and fission and these morphological dynamics play important roles in mitochondrial function and development as well as programmed cell death. The goal of this study is to investigate whether: (1) mitochondria in mouse coronary endothelial cells (MCECs) isolated from diabetic mice exhibit increased fragmentation; and (2) chronic treatment with a superoxide anion (O(2)(-)) scavenger has a beneficial effect on mitochondrial fragmentation in MCECs.

METHODS

MCECs were freshly isolated and lysed for protein measurement, or cultured to determine mitochondrial morphology and O(2)(-) production. For the ex vivo hyperglycaemia experiments, human coronary endothelial cells were used.

RESULTS

Elongated mitochondrial tubules were observed in MCECs isolated from control mice, whereas mitochondria in MCECs from diabetic mice exhibited augmented fragmentation. The level of optic atrophy 1 (OPA1) protein, which leads to mitochondrial fusion, was significantly decreased, while dynamin-related protein 1 (DRP1), which leads to mitochondrial fission, was significantly increased in MCECs from diabetic mice. Diabetic MCECs exhibited significantly higher O(2)(-) concentrations in cytosol and mitochondria than control MCECs. Administration of the O(2)(-) scavenger TEMPOL to diabetic mice for 4 weeks led to a significant decrease in mitochondrial fragmentation without altering the levels of OPA1 and DRP1 proteins in MCECs. High-glucose treatment for 24 h significantly induced mitochondrial fragmentation, which was restored by TEMPOL treatment. In addition, excess O(2)(-) production, either in cytosol or in mitochondria, significantly increased mitochondrial fragmentation.

CONCLUSIONS/INTERPRETATION

These data suggest that lowering the O(2)(-) concentration can restore the morphological change in mitochondria and may help improve mitochondrial function in diabetic MCECs.

miR-1/miR-206 regulate Hsp60 expression contributing to glucose-mediated apoptosis in cardiomyocytes

Hsp60 is an important component of defense mechanisms against diabetic myocardial injury; however, the cause of Hsp60 reduction in the diabetic myocardium remains unknown. After stimulation of cardiomyocytes with high glucose in vivo and in vitro, significant up-regulation of miR-1/miR-206 and post-transcriptional modulation of Hsp 60 were observed. Serum response factor (SRF) and the MEK1/2 pathway were involved in miR-1 and miR-206 expression in cardiomyocytes. miR-1 and miR-206 regulated Hsp60 expression post-transcriptionally and accelerated cardiomyocyte apoptosis through Hsp60. These results revealed that miR-1 and miR-206 regulate Hsp60 expression, contributing to high glucose-mediated apoptosis in cardiomyocytes.

Non-viral gene therapy for myocardial engineering

Despite significant advances in surgical and pharmacological techniques, myocardial infarction (MI) remains the main cause of morbidity in the developed world because no remedy has been found for the regeneration of infarcted myocardium. Once the blood supply to the area in question is interrupted, the inflammatory cascade, among other mechanisms, results in the damaged tissue becoming a scar. The goals of cardiac gene therapy are essentially to minimize damage, to promote regeneration, or some combination thereof. While the vector is, in theory, less important than the gene being delivered, the choice of vector can have a significant impact. Viral therapies can have very high transfection efficiencies, but disadvantages include immunogenicity, retroviral-mediated insertional mutagenesis, and the expense and difficulty of manufacture. For these reasons, researchers have focused on non-viral gene therapy as an alternative. In this review, naked plasmid delivery, or the delivery of complexed plasmids, and cell-mediated gene delivery to the myocardium will be reviewed. Pre-clinical and clinical trials in the cardiac tissue will form the core of the discussion. While unmodified stem cells are sometimes considered therapeutic vectors on the basis of paracrine mechanisms of action basic understanding is limited. Thus, only genetically modified cells will be discussed as cell-mediated gene therapy.

The protective effect of thalidomide on left ventricular function in a rat model of diabetic cardiomyopathy

AIMS

To evaluate the protective effect of thalidomide, a potent anti-inflammatory drug, on the development of diabetic cardiomyopathy (DMCMP).

METHODS AND RESULTS

We induced type 1 diabetes using streptozocin in 8-week-old Sprague-Dawley rats, divided them into two groups-a thalidomide treatment group (DM-T, n = 15) and a non-treatment group (DM-N, n = 15)-and compared them with a normal control (n = 10). Ten weeks after diabetes induction, heart and lung mass indices were higher in the DM-N group compared with the control group. In the DM-T group, increases in heart and lung mass indices were attenuated compared with the DM-N group. On echocardiographic examination, systolic and diastolic mitral annulus velocities were impaired in the DM-N group, but they remained normal in the DM-T group. On haemodynamic analyses, left ventricular (LV) systolic function, represented by end-systolic elastance (0.35 ± 0.14 vs. 0.18 ± 0.07 mmHg/μl, P < 0.001) and preload-recruitable stroke work (90.5 ± 24.3 vs. 51.8 ± 22.0 mmHg, P < 0.001), was preserved in the DM-T group compared with the DM-N group. Likewise, deterioration of LV diastolic function was attenuated in the DM-T group. Increases in serum levels of TNF-α were attenuated in the DM-T group compared with the DM-N group. On histological analysis, thalidomide treatment lowered total myocardial collagen content and the expression of TNF-α, IL-1β, ICAM-1, and VCAM-1.

CONCLUSION

In an animal model of DMCMP, deterioration of LV systolic and diastolic function was partially prevented by thalidomide treatment.

Cardiac-specific overexpression of HIF-1{alpha} prevents deterioration of glycolytic pathway and cardiac remodeling in streptozotocin-induced diabetic mice

Defective glycolysis and angiogenesis in the heart of diabetic patients and in experimental diabetic animal models have been reported. The aim of this study was to determine whether overexpression of hypoxia-inducible factor (HIF)-1alpha protects from myocardial injury in diabetic mice by increasing myocardial glycolysis and angiogenesis. Cardiac-specific HIF-1alpha-overexpressing transgenic and age-matched wild-type control mice were treated with streptozotocin to induce diabetes. Changes in glucose transporters, glycolytic enzymes, angiogenic factors and cardiac morphology were examined in the hearts by real-time RT-PCR, Western blotting, enzymatic assay, and histological assays. HIF-1alpha overexpression elevated hexokinase II (HK-II) protein level and total HK activity in nondiabetic heart and prevented the decreases in HK-II mRNA, protein, and total HK activity in diabetic heart. In addition, the reduction of glucose transporter I, but not glucose transporter 4, was restored in HIF transgenic mouse heart along with a recovery of myocardium ATP production. HIF-1alpha overexpression also normalized diabetes-reduced vascular endothelial growth factor concentration along with a sustained myocardial capillary density and an inhibition of cardiomyocyte hypertrophy and cardiac fibrosis. Therefore, elevation of HIF-1alpha provides a cardiac protection from diabetic-induced impairment in glucose metabolism and angiogenesis via up-regulation of HIF-1 target genes.

Alpha tocopherol use in the management of diabetic cardiomyopathy: lessons learned from randomized clinical trials

Although animal studies suggested that there may be a role for antioxidants (especially alpha-tocopherol) as therapy for heart failure (HF), the results obtained from human trials are disappointing. The variability in the response to antioxidant therapy may be due to genetic polymorphisms in enzymes involved in oxidative stress. We strongly believe that we do not have enough data supporting the use of antioxidant treatment in the management of HF patients, including a diabetic subset.

Activation of protein kinase C isoforms and its impact on diabetic complications

Both cardio- and microvascular complications adversely affect the life quality of patients with diabetes and have been the leading cause of mortality and morbidity in this population. Cardiovascular pathologies of diabetes have an effect on microvenules, arteries, and myocardium. It is believed that hyperglycemia is one of the most important metabolic factors in the development of both micro- and macrovascular complications in diabetic patients. Several prominent hypotheses exist to explain the adverse effect of hyperglycemia. One of them is the chronic activation by hyperglycemia of protein kinase (PK)C, a family of enzymes that are involved in controlling the function of other proteins. PKC has been associated with vascular alterations such as increases in permeability, contractility, extracellular matrix synthesis, cell growth and apoptosis, angiogenesis, leukocyte adhesion, and cytokine activation and inhibition. These perturbations in vascular cell homeostasis caused by different PKC isoforms (PKC-alpha, -beta1/2, and PKC-delta) are linked to the development of pathologies affecting large vessel (atherosclerosis, cardiomyopathy) and small vessel (retinopathy, nephropathy and neuropathy) complications. Clinical trials using a PKC-beta isoform inhibitor have been conducted, with some positive results for diabetic nonproliferative retinopathy, nephropathy, and endothelial dysfunction. This article reviews present understanding of how PKC isoforms cause vascular dysfunctions and pathologies in diabetes.

Evaluation of contractile function and inotropic reserve with tissue velocity, strain and strain rate imaging in streptozotocin-induced diabetes

AIMS

The aim of the present study was to evaluate left ventricular (LV) function and contractile reserve (CR) with Doppler myocardial imaging (DMI) in a small animal model for type 1 diabetes.

METHODS AND RESULTS

Cardiac function was assessed in anaesthetized Wistar rats 6 and 8 weeks after injection of 60 mg/kg of streptozotocin. At 6 weeks of diabetes, colour DMI echocardiography was performed at rest and during incremental dosages of dobutamine (5, 10, 20 microg/kg/min). Left ventricular fractional shortening was decreased after 8 weeks of follow-up [36 +/- 5 (D) vs. 41 +/- 4% (C); P = 0.049]. After 6 weeks of diabetes, DMI measurements were reduced in the diabetic rats in the inferolateral wall at rest [systolic velocity: 2.5 +/- 0.4 (D) vs. 4.4 +/- 0.3 (C) cm/s; P < 0.001; systolic strain rate: 12.2 +/- 3.4 (D) vs. 17.4 +/- 3.2 (C) 1/s; P = 0.012] and during inotropic stimulation [delta velocity (cm/s): 0.2 +/- 0.1 (D) vs. 0.5 +/- 0.3 (C)/5 microg dobutamine; P = 0.002; delta strain rate (1/s): 1.4 +/- 0.9 (D) vs. 3.3 +/- 2.2 (C)/5 microg dobutamine; P = 0.049]. Furthermore, the intraventricular delay in time-to-peak systolic strain was larger in diabetes [20 +/- 18 (D) vs. 10 +/- 7 (C) ms; P= 0.01]. Systolic mitral annular velocity was also lower in the diabetic rats at rest [2.7 +/- 0.4 (D) vs. 3.5 +/- 0.4 (C) cm/s; P < 0.001] and in response to dobutamine [delta velocity (cm/s): 0.1 +/- 0.1 (D) vs. 0.3 +/- 0.2 (C)/5 microg dobutamine; P = 0.013].

CONCLUSION

In experimental diabetes, a reduction in radial and longitudinal LV function and CR can be detected with DMI before the onset of a reduced global LV function.

Usefulness of mitral annulus velocity for the early detection of left ventricular dysfunction in a rat model of diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DMCMP) is characterized by myocardial dysfunction regardless of coronary artery disease in diabetic patients. The features of LV dysfunction in rat model of type 1 DM induced by streptozocin, are variable and controversial. Thus, we tested the usefulness of tissue Doppler imaging in the early detection of ventricular dysfunction in a rat model of DMCMP.

METHODS

Diabetes was induced by intra-peritoneal injection of streptozocin (70 mg/kg) in 8 weeks of Sprague-Dawley rat. Diagnosis of diabetes was defined as venous glucose level over 350 mg/dL 48 hrs after streptozocin injection. Echocardiography was done at baseline and 10 weeks after diabetes induction both in diabetes group (n=15) and normal control (n=10). After echocardiography at 10 weeks, invasive hemodynamic measurement using miniaturized conductance catheter was done in both groups.

RESULTS

Ten weeks after diabetes induction, heart and lung mass indexes of diabetes were larger than those of normal control (3.2+/-0.3 vs. 2.4+/-0.2 mg/g, p<0.001, 5.5+/-1.1 vs. 3.6+/-0.6 mg/g, p<0.001, respectively). In echocardiographic data, s' (2.4+/-0.4 vs. 3.1+/-0.5 cm/s, p<0.001), e' velocity of mitral annulus (2.9+/-0.6 vs. 3.8+/-1.1 cm/s, p<0.001), and E/e' ratio (27.1+/-5.6 vs. 19.7+/-2.6, p<0.001) were impaired in diabetes group. In hemodynamic measurement, there were no differences in ejection fraction, peak dP/dt between the diabetic group and normal control. However, load independent indexes of contractility, the slope of the end-systolic pressure volume relation (0.18+/-0.07 vs. 0.62+/-0.18 mmHg/microL, p<0.001) and preload recruitable stroke work (51.8+/-22.0 vs. 90.9+/-22.5 mmHg, p<0.001) were impaired in diabetic group compared to normal control.

CONCLUSION

In a rat model of diabetic cardiomyopathy, tissue Doppler imaging of mitral annulus can be a good modality for early detection of myocardial dysfunction.

Targeting apoptosis in the heart of streptozotocin-induced diabetic rats

OBJECTIVES

The aim of the current study was to address the issue of cardiomyocyte apoptosis as a possible contributor in the development of diabetic cardiomyopathy and whether it would be possible to suppress this apoptosis by the use of a peroxisome proliferator-activated receptor (PPAR)-alpha agonist (fenofibrate) or a PPAR-gamma agonist (rosiglitazone).

METHODS

Ten normal male albino rats (group I) were injected intraperitoneally (IP) by a single dose of saline and served as a control for group II. Thirty male albino rats were made diabetic by IP streptozotocin (STZ) injection and were divided into 3 groups: group II (nontreated diabetic rats), groups III and IV (diabetic rats treated with PPAR-gamma agonist (rosiglitazone), and PPAR-alpha agonist (fenofibrate) respectively, for 12 weeks starting 1 week following STZ injection.

RESULTS

The studied drugs decreased left ventricular to body weight ratio and cardiac: caspase-3, tumor necrosis factor-alpha, hydroxyproline, free fatty acids (FFAs) as well as triglycerides (TGs) and improved oxidative stress parameters as well as left ventricular papillary muscle developed tension (DT).

CONCLUSIONS

The results of the current study support the hypothesis that apoptosis plays a key role in the pathophysiology of diabetic cardiomyopathy and demonstrate that the use of PPAR-alpha and -gamma agonists might have a protective role against diabetic cardiomyopathy.

Vitamin B1 analog benfotiamine prevents diabetes-induced diastolic dysfunction and heart failure through Akt/Pim-1-mediated survival pathway

BACKGROUND

The increasing incidence of diabetes mellitus will result in a new epidemic of heart failure unless novel treatments able to halt diabetic cardiomyopathy early in its course are introduced. This study aimed to determine whether the activity of the Akt/Pim-1 signaling pathway is altered at critical stages of diabetic cardiomyopathy and whether supplementation with vitamin B1 analog benfotiamine (BFT) helps to sustain the above prosurvival mechanism, thereby preserving cardiomyocyte viability and function.

METHODS AND RESULTS

Untreated streptozotocin-induced type 1 or leptin-receptor mutant type 2 diabetic mice showed diastolic dysfunction evolving to contractile impairment and cardiac dilatation and failure. BFT (70 mg/kg(-1)/d(-1)) improved diastolic and systolic function and prevented left ventricular end-diastolic pressure increase and chamber dilatation in both diabetic models. Moreover, BFT improved cardiac perfusion and reduced cardiomyocyte apoptosis and interstitial fibrosis. In hearts of untreated diabetic mice, the expression and activity of Akt/Pim-1 signaling declined along with O-N-acetylglucosamine modification of Akt, inhibition of pentose phosphate pathway, activation of oxidative stress, and accumulation of glycation end products. Furthermore, diabetes reduced pSTAT3 independently of Akt. BFT inhibited these effects of diabetes mellitus, thereby conferring cardiomyocytes with improved resistance to high glucose-induced damage. The phosphoinositide-3-kinase inhibitor LY294002 and dominant-negative Akt inhibited antiapoptotic action of BFT-induced and Pim-1 upregulation in high glucose-challenged cardiomyocytes.

CONCLUSIONS

These results show that BFT protects from diabetes mellitus-induced cardiac dysfunction through pleiotropic mechanisms, culminating in the activation of prosurvival signaling pathway. Thus, BFT merits attention for application in clinical practice.

The accelerated post-infarction progression of cardiac remodelling is associated with genetic changes in an untreated streptozotocin-induced diabetic rat model

AIMS

The mechanism by which diabetes mellitus exacerbates myocardial injury and the incidence of heart failure after acute myocardial infarction (AMI), remains unclear. We studied the severity of cardiac dysfunction and time-dependent gene expression in a hyperglycaemic rat model with AMI.

METHODS AND RESULTS

The diabetic model was produced by injection of streptozotocin in Sprague-Dawley rats. Ten weeks after induction of diabetes, AMI was induced by ligation of the left anterior descending coronary artery. Cardiac function and left ventricular (LV) dimensions were evaluated using two-dimensional echocardiography. Structural changes were assessed by histological examination. Gene expression profile was documented by using affymetrix genechip U230 2.0 array and real time-PCR. During 56 days post-AMI, lower survival rates, worse LV function, more severe fibrosis, and larger LV diameters were identified in diabetic rats compared with non-diabetic rats. A total 1221 genes involved in processes, such as glucose metabolism, fatty acid metabolism, extracellular matrix, and apoptosis, were found to be differentially expressed between diabetic and non-diabetic rats, of these 770 were up-regulated and 451 down-regulated. Up-regulation of the genes was found 1-2 weeks earlier in diabetic rats than in non-diabetic rats.

CONCLUSION

The present data suggest that hyperglycaemia up-regulates remodelling-related genes, which may be responsible for the worse outcomes in diabetics than in non-diabetics after AMI.

Role of protein kinase C in diabetic complications

Hyperglycemia is an important factor in the development of macrovascular and microvascular complications in all diabetic patients. Several hypotheses have been postulated to explain the adverse effect of hyperglycemia on the vasculature; and one of these hypotheses is the activation of specific isoforms of protein kinase C (PKC) by diabetes. In this review, we summarize the molecular mechanisms of PKC activation and its relationship to diabetic complications. PKC activity regulates vascular permeability, contractility, extracellular matrix synthesis, hormone receptor turnover and proliferation, cell growth, angiogenesis, cytokine activation and leukocyte adhesion. All of these properties are abnormal in diabetes and are correlated with increased diacylglycerol-PKC pathway and PKCα, β1/2 and δ isoforms activation in the retina, aorta, heart and renal glomeruli.

Coadministration of adenoviral vascular endothelial growth factor and angiopoietin-1 enhances vascularization and reduces ventricular remodeling in the infarcted myocardium of type 1 diabetic rats

OBJECTIVE

Hyperglycemia impairs angiogenesis in response to ischemia, leading to ventricular remodeling. Although the effects of overexpressing angiogenic growth factors have been studied in inducing angiogenesis, the formation of functional vessels remains a challenge. The present study evaluates the reversal of diabetes-mediated impairment of angiogenesis in the infarcted diabetic rat myocardium by proangiogenic gene therapy.

RESEARCH DESIGN AND METHODS

Ad*VEGF and Ad*Ang1 were intramyocardially administered in combination immediately after myocardial infarction to nondiabetic and diabetic rats. Ad*LacZ was similarly administered to the respective control groups. The hearts were excised for molecular and immunohistochemical analysis at predetermined time points. The myocardial function was measured by echocardiography 30 days after the intervention.

RESULTS

We observed reduced fibrosis and increased capillary/arteriolar density along with reduced ventricular remodeling, as assessed by echocardiography in the treated diabetic animals compared with the nontreated diabetic controls. We also observed increased phosphorylated mitogen-activated protein kinase-activated protein kinase-2, 2 days after the treatment and increased expression of vascular endothelial growth factor (VEGF), Flk-1, angiopoietin-1 (Ang-1), Tie-2, and survivin, 4 days after treatment in the diabetic animals. Gel shift analysis revealed that the combination gene therapy stimulated the DNA binding activity of nuclear factor-kappaB in the diabetic animals.

CONCLUSIONS

Our preclinical data demonstrate the efficacy of coadministration of adenoviral VEGF and Ang-1 in increasing angiogenesis and reducing ventricular remodeling in the infarcted diabetic myocardium. These unique results call for the initiation of a clinical trial to assess the efficacy of this therapeutic strategy in the treatment of diabetes-related human heart failure.

Role of endothelial progenitor cells in diabetes mellitus

Endothelial progenitor cells (EPCs) are bone marrow-derived cells involved in endothelial healing and angiogenesis. EPCs are considered an integrated component of the cardiovascular system, which promotes vascular health. Derangement of EPC biology in diabetes has been hailed as a novel concept in the pathogenesis of micro- and macro-vascular complications. Additionally, EPCs are considered to be disease biomarkers, as they provide an index of cardiovascular risk. The mechanisms leading to EPC dysfunction in diabetes may include defective mobilization from bone marrow to peripheral blood and reduced half-life. Hyperglycemia is considered the major determinant of microvascular complications, while other mechanisms concur to increase the risk of cardiovascular disease in diabetic patients. EPCs may represent a novel pathophysiological connection to understand development and progression of diabetic complications.

Vascular endothelial growth factor inhibition by dRK6 causes endothelial apoptosis, fibrosis, and inflammation in the heart via the Akt/eNOS axis in db/db mice

OBJECTIVE

Vascular endothelial growth factor (VEGF), which is associated with the stimulation of angiogenesis and collateral vessel synthase, is one of the crucial factors involved in cardiac remodeling in type 2 diabetes.

RESEARCH DESIGN AND METHODS

We investigated VEGF inhibition by dRK6 on the heart in an animal model of type 2 diabetes. Male db/db and db/m mice either were treated with dRK6 starting at 7 weeks of age for 12 weeks (db/db-dRK6 and db/m-dRK6) or were untreated.

RESULTS

Cardiac dysfunction and hypertrophy were noted by echocardiogram and molecular markers in the db/db-dRK6 mice. The presence of diabetes significantly suppressed the expression of VEGF receptor (VEGFR)-1 and VEGFR-2, phospho-Akt, and phospho-endothelial nitric oxide synthase (eNOS) in the heart. In db/db-dRK6 mice, dRK6 completely inhibited VEGFR-2, phospho-Akt, and phospho-eNOS expression, whereas no effect on VEGFR-1 was observed. Cardiac fibrosis, microvascular scarcity associated with an increase in apoptotic endothelial cells, and inflammation were prominent, as well as increase in antiangiogenic growth factors. Cardiac 8-hydroxy-deoxyguanine and hypoxia-inducible factor-1alpha expression were significantly increased. No such changes were found in the other groups, including the db/m-dRK6 mice. The number of apoptotic human umbilical vein endothelial cells was increased by dRK6 in a dose-dependent manner only at high glucose concentrations, and this was associated with a decrease in phospho-Akt and phospho-eNOS related to oxidative stress.

CONCLUSIONS

Our results demonstrated that systemic blockade of VEGF by dRK6 had deleterious effects on the heart in an animal model of type 2 diabetes; dRK6 induced downregulation of the VEGFR-2 and Akt-eNOS axis and enhancement of oxidative stress.

Decreased cardiac expression of vascular endothelial growth factor and redox imbalance in murine diabetic cardiomyopathy

Type 1 diabetes is associated with a unique form of cardiomyopathy that is present without atherosclerosis. Redox imbalance and/or changes in vascular endothelial growth factor (VEGF) expression have been associated with diabetes-related cardiomyopathy. However, the mechanisms of these changes and their interrelationships remain unclear. Using a murine type 1 diabetes model, we tested the hypothesis that alterations in cardiac performance are associated with decreased cardiac microvascular prevalence, as well as downregulation of VEGF isoforms. We also investigated oxidative stress as a contributor to regulate individual VEGF isoforms and microvascular rarefaction. Significant and rapid hyperglycemia was observed at 1 wk post-streptozotocin (STZ) and persisted throughout the 5-wk study. Left ventricular (LV) fractional shortening was reduced at week 1 and 5 post-STZ insult relative to age-matched controls. We also observed the early reduction in E/A ratio at 1 wk. Immunostaining for CD31 and digital image analysis demonstrated a 35% reduction in microvessels/myocardial area, indicative of rarefaction, which was highly correlated with fractional shortening. Furthermore, a significant increase in the prevalence of protein 3-nitrotyrosine was observed in the diabetic cardiac tissue, which was inversely associated with microvascular rarefaction. The expressions of three VEGF isoforms were significantly reduced to different extents. The reduction of VEGF(164) was associated with GSSG accumulation. These data demonstrate that the mouse model of STZ-induced diabetes has hallmark features observed in humans with respect to nonischemic systolic and diastolic performance and microvascular rarefaction, which are associated with changes in VEGF isoform expression and redox imbalance in the myocardium.

Coronary vessel development and insight towards neovascular therapy

Formation of the coronary arteries consists of a precisely orchestrated series of morphogenetic and molecular events which can be divided into three distinct processes: vasculogenesis, angiogenesis and arteriogenesis (Risau 1997; Carmeliet 2000). Even subtle perturbations in this process may lead to congenital coronary artery anomalies, as occur in 0.2-1.2% of the general population (von Kodolitsch et al. 2004). Contrary to the previously held dogma, the process of vasculogenesis is not limited to prenatal development. Both vasculogenesis and angiogenesis are now known to actively occur within the adult heart. When the need for regeneration arises, for example in the setting of coronary artery disease, a reactivation of embryonic processes ensues, redeploying many of the same molecular regulators. Thus, an understanding of the mechanisms of embryonic coronary vasculogenesis and angiogenesis may prove invaluable in developing novel strategies for cardiovascular regeneration and therapeutic coronary angiogenesis.