Immunohistochemical and morphometric evaluations of coronary atherosclerotic plaques associated with myocardial infarction and diabetes mellitus

Matricellular proteins in atherosclerosis development

The extracellular matrix (ECM) is an intricate network composed of various multi-domain macromolecules like collagen, proteoglycans, and fibronectin, etc., that form a structurally stable composite, contributing to the mechanical properties of tissue. However, matricellular proteins are non-structural, secretory extracellular matrix proteins, which modulate various cellular functions via interacting with cell surface receptors, proteases, hormones, and cell-matrix. They play essential roles in maintaining tissue homeostasis by regulating cell differentiation, proliferation, adhesion, migration, and several signal transduction pathways. Matricellular proteins display a broad functionality regulated by their multiple structural domains and their ability to interact with different extracellular substrates and/or cell surface receptors. The expression of these proteins is low in adults, however, gets upregulated following injuries, inflammation, and during tumor growth. The marked elevation in the expression of these proteins during atherosclerosis suggests a positive association between their expression and atherosclerotic lesion formation. The role of matricellular proteins in atherosclerosis development has remained an area of research interest in the last two decades and studies revealed these proteins as important players in governing vascular function, remodeling, and plaque formation. Despite extensive research, many aspects of the matrix protein biology in atherosclerosis are still unknown and future studies are required to investigate whether targeting pathways stimulated by these proteins represent viable therapeutic approaches for patients with atherosclerotic vascular diseases. This review summarizes the characteristics of distinct matricellular proteins, discusses the available literature on the involvement of matrix proteins in the pathogenesis of atherosclerosis and suggests new avenues for future research.

Diabetes and Ischemic Stroke: An Old and New Relationship an Overview of the Close Interaction between These Diseases

Diabetes mellitus is a comprehensive expression to identify a condition of chronic hyperglycemia whose causes derive from different metabolic disorders characterized by altered insulin secretion or faulty insulin effect on its targets or often both mechanisms. Diabetes and atherosclerosis are, from the point of view of cardio- and cerebrovascular risk, two complementary diseases. Beyond shared aspects such as inflammation and oxidative stress, there are multiple molecular mechanisms by which they feed off each other: chronic hyperglycemia and advanced glycosylation end-products (AGE) promote ‘accelerated atherosclerosis’ through the induction of endothelial damage and cellular dysfunction. These diseases impact the vascular system and, therefore, the risk of developing cardio- and cerebrovascular events is now evident, but the observation of this significant correlation has its roots in past decades. Cerebrovascular complications make diabetic patients 2–6 times more susceptible to a stroke event and this risk is magnified in younger individuals and in patients with hypertension and complications in other vascular beds. In addition, when patients with diabetes and hyperglycemia experience an acute ischemic stroke, they are more likely to die or be severely disabled and less likely to benefit from the one FDA-approved therapy, intravenous tissue plasminogen activator. Experimental stroke models have revealed that chronic hyperglycemia leads to deficits in cerebrovascular structure and function that may explain some of the clinical observations. Increased edema, neovascularization, and protease expression as well as altered vascular reactivity and tone may be involved and point to potential therapeutic targets. Further study is needed to fully understand this complex disease state and the breadth of its manifestation in the cerebrovasculature.

Dyslipidaemia in Type 1 Diabetes: Molecular Mechanisms and Therapeutic Opportunities

Cardiovascular disease (CVD) is the leading cause of death in Type 1 Diabetes (T1D). The molecular basis for atherosclerosis in T1D is heavily influenced by hyperglycaemia and its atherogenic effects on LDL. Ongoing research into the distinct pathophysiology of atherosclerosis in T1D offers exciting opportunities for novel approaches to calculate CVD risk in patients with T1D and to manage this risk appropriately. Currently, despite the increased risk of CVD in the T1D population, there are few tools available for estimating the risk of CVD in younger patients. This poses significant challenges for clinicians in selecting which patients might benefit from lipid-lowering therapies over the long term. The current best practice guidance for the management of dyslipidaemia in T1D is generally based on evidence from patients with T2D and the opinion of experts in the field. In this review article, we explore the unique pathophysiology of atherosclerosis in T1D, with a specific focus on hyperglycaemia-induced damage and atherogenic LDL modifications. We also discuss the current clinical situation of managing these patients across paediatric and adult populations, focusing on the difficulties posed by a lack of strong evidence and various barriers to treatment.

Up-regulation of FoxO1 contributes to adverse vascular remodelling in type 1 diabetic rats

Vascular complications from diabetes often result in poor outcomes for patients, even after optimized interventions. Forkhead box protein O1 (FoxO1) is a key regulator of cellular metabolism and plays an important role in vessel formation and maturation. Alterations of FoxO1 occur in the cardiovascular system in diabetes, yet the role of FoxO1 in diabetic vascular complications is poorly understood. In Streptozotocin (STZ)‐induced type 1 diabetic rats, FoxO1 expression was up‐regulated in carotid arteries at 8 weeks of diabetes that was accompanied with adverse vascular remodelling characterized as increased wall thickness, carotid medial cross‐sectional area, media‐to‐lumen ratio and decreased carotid artery lumen area. This adverse vascular remodelling induced by hyperglycaemia in diabetic rats required FoxO1 activation as pharmacological inhibition of FoxO1 with 50mg/kg AS1842856 (AS) reversed vascular remodelling in type 1 diabetic rats. The adverse vascular remodelling in type 1 diabetes mellitus (T1DM) occurred concomitantly with increases in pro‐inflammatory factors, adhesion factors, apoptosis, NOD‐like receptor family protein‐3 inflammasome activation and the phenotypic switch of arterial smooth muscle cells, which were all reversed by AS. In addition, FoxO1 inhibition counteracted the down‐regulation of its upstream mediator PDK1 in T1DM. PDK1 activator reduced FoxO1 nuclear translocation, which serves as the basis for subsequent transcriptional regulation during hyperglycaemia. Taken together, our data suggest that FoxO1 is a critical trigger for type 1 diabetes‐induced vascular remodelling in rats, and inhibition of FoxO1 thus offers a potential therapeutic option for diabetes‐associated cardiovascular diseases.

Angiogenesis in Patients with Chronic Heart Failure: Focus on Endothelial Vascular Growth Factor, Pentraxin-3 and Transforming Growth Factor Beta

Chronic heart failure (CHF) is considered the leading cause of death in patients with established cardiovascular (CVD) and metabolic diseases. Although the current treatment strategy has improved survival and clinical outcomes, the prevalence of CHF shows an increase. Current clinical guidelines for the treatment and prevention of CVD note the role of biological markers as a fairly simple and powerful tool for diagnosing, stratifying risk and predicting CHF. However, it is unclear whether all of these biological markers are equally capable of predicting cardiovascular mortality and heart failure related outcomes in patients with acute and chronic heart failure, as well as in different phenotypes of heart failure. However, the results of numerous studies demonstrate scientific interest in the processes of angiogenesis among patients with CHF. There is an impressive body of evidence linking CHF to the level of markers such as vascular endothelial growth factor, pentraxin-3, and transforming growth factor beta. The review presents the data of domestic and foreign clinical studies devoted to the study of the level of angiogenesis markers among patients with CHF.

Beta 2-adrenergic receptor agonists are novel regulators of macrophage activation in diabetic renal and cardiovascular complications

Macrophage activation is increased in diabetes and correlated with the onset and progression of vascular complications. To identify drugs that could inhibit macrophage activation, we developed a cell-based assay and screened a 1,040 compound library for anti-inflammatory effects. Beta2-adrenergic receptor (β2AR) agonists were identified as the most potent inhibitors of phorbol myristate acetate-induced tumor necrosis factor-α production in rat bone marrow macrophages. In peripheral blood mononuclear cells isolated from streptozotocin-induced diabetic rats, β2AR agonists inhibited diabetes-induced tumor necrosis factor-α production, which was prevented by co-treatment with a selective β2AR blocker. To clarify the underlying mechanisms, THP-1 cells and bone marrow macrophages were exposed to high glucose. High glucose reduced β-arrestin2, a negative regulator of NF-κB activation, and its interaction with IκBα. This subsequently enhanced phosphorylation of IκBα and activation of NF-κB. The β2AR agonists enhanced β-arrestin2 and its interaction with IκBα, leading to downregulation of NF-κB. A siRNA specific for β-arrestin2 reversed β2AR agonist-mediated inhibition of NF-κB activation and inflammatory cytokine production. Treatment of Zucker diabetic fatty rats with a β2AR agonist for 12 weeks attenuated monocyte activation as well as pro-inflammatory and pro-fibrotic responses in the kidneys and heart. Thus, β2AR agonists might have protective effects against diabetic renal and cardiovascular complications.

Peripheral artery disease in patients with diabetes: Epidemiology, mechanisms, and outcomes

Peripheral artery disease (PAD) is the atherosclerosis of lower extremity arteries and is also associated with atherothrombosis of other vascular beds, including the cardiovascular and cerebrovascular systems. The presence of diabetes mellitus greatly increases the risk of PAD, as well as accelerates its course, making these patients more susceptible to ischemic events and impaired functional status compared to patients without diabetes. To minimize these cardiovascular risks it is critical to understand the pathophysiology of atherosclerosis in diabetic patients. This, in turn, can offer insights into the therapeutic avenues available for these patients. This article provides an overview of the epidemiology of PAD in diabetic patients, followed by an analysis of the mechanisms by which altered metabolism in diabetes promotes atherosclerosis and plaque instability. Outcomes of PAD in diabetic patients are also discussed, with a focus on diabetic ulcers and critical limb ischemia.

Functional roles of p38 mitogen-activated protein kinase in macrophage-mediated inflammatory responses

Inflammation is a natural host defensive process that is largely regulated by macrophages during the innate immune response. Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate many physiological and pathophysiological cell responses. p38 MAPKs are key MAPKs involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an essential role in regulating cellular processes, especially inflammation. In this paper, we summarize the characteristics of p38 signaling in macrophage-mediated inflammation. In addition, we discuss the potential of using inhibitors targeting p38 expression in macrophages to treat inflammatory diseases.

Cyclophilin-A: a potential screening marker for vascular disease in type-2 diabetes

The pathophysiology of vascular disease in diabetes involves abnormalities in endothelial cells, vascular smooth muscle cells, and monocytes. The metabolic abnormalities that characterize diabetes, such as hyperglycemia, increased free fatty acids, and insulin resistance, each provoke molecular mechanisms that contribute to vascular dysfunction. Several molecules have been identified as risk markers, and have been studied to prevent progression of disease and long-term complications. Markers such as C-reactive protein and monocyte chemoattractant protein-1 are used to assess risk for adverse cardiac events, but elevated levels are possible due to the presence of other risk factors as part of the natural physiological defense mechanism. In this review we discuss potential of cyclophilin-A, a secreted oxidative-stress-induced immunophilin with diverse functions. We present evidence for a significant role of cyclophilin-A in the pathogenesis of atherosclerosis in diabetes, and its potential as a marker for vascular disease in type-2 diabetes.

The distinctive nature of atherosclerotic vascular disease in diabetes: pathophysiological and morphological insights

As the incidence of diabetes mellitus continues to rise, parallel increases in the rates of diabetic atherosclerotic vascular disease are projected to impart major health and socioeconomic challenges for authorities worldwide. Diabetes results in a proatherogenic phenotype, manifesting in an accelerated, diffuse, polyvascular fashion. In this review, we highlight the pathophysiological and morphological hallmarks of diabetic atherosclerosis.

Reactive oxygen and nitrogen species in pathogenesis of vascular complications of diabetes

Macrovascular and microvascular diseases are currently the principal causes of morbidity and mortality in subjects with diabetes. Disorders of the physiological signaling functions of reactive oxygen species (superoxide and hydrogen peroxide) and reactive nitrogen species (nitric oxide and peroxynitrite) are important features of diabetes. In the absence of an appropriate compensation by the endogenous antioxidant defense network, increased oxidative stress leads to the activation of stress-sensitive intracellular signaling pathways and the formation of gene products that cause cellular damage and contribute to the vascular complications of diabetes. It has recently been suggested that diabetic subjects with vascular complications may have a defective cellular antioxidant response against the oxidative stress generated by hyperglycemia. This raises the concept that antioxidant therapy may be of great benefit to these subjects. Although our understanding of how hyperglycemia-induced oxidative stress ultimately leads to tissue damage has advanced considerably in recent years, effective therapeutic strategies to prevent or delay the development of this damage remain limited. Thus, further investigation of therapeutic interventions to prevent or delay the progression of diabetic vascular complications is needed.

Insulin resistance, metabolic stress, and atherosclerosis

Atherosclerosis, a pathological process that underlies the development of cardiovascular disease, is the primary cause of morbidity and mortality in patients with type 2 diabetes mellitus (T2DM). T2DM is characterized by hyperglycemia and insulin resistance (IR), in which target tissues fail to respond to insulin. Systemic IR is associated with impaired insulin signaling in the metabolic tissues and vasculature. Insulin receptor is highly expressed in the liver, muscle, pancreas, and adipose tissue. It is also expressed in vascular cells. It has been suggested that insulin signaling in vascular cells regulates cell proliferation and vascular function. In this review, we discuss the association between IR, metabolic stress, and atherosclerosis with focus on 1) tissue and cell distribution of insulin receptor and its differential signaling transduction and 2) potential mechanism of insulin signaling impairment and its role in the development of atherosclerosis and vascular function in metabolic disorders including hyperglycemia, hypertension, dyslipidemia, and hyperhomocysteinemia. We propose that insulin signaling impairment is the foremost biochemical mechanism underlying increased cardiovascular morbidity and mortality in atherosclerosis, T2DM, and metabolic syndrome.

Advances in tenascin-C biology

Tenascin-C is an extracellular matrix glycoprotein that is specifically and transiently expressed upon tissue injury. Upon tissue damage, tenascin-C plays a multitude of different roles that mediate both inflammatory and fibrotic processes to enable effective tissue repair. In the last decade, emerging evidence has demonstrated a vital role for tenascin-C in cardiac and arterial injury, tumor angiogenesis and metastasis, as well as in modulating stem cell behavior. Here we highlight the molecular mechanisms by which tenascin-C mediates these effects and discuss the implications of mis-regulated tenascin-C expression in driving disease pathology.

Targeting fibrosis for the treatment of heart failure: a role for transforming growth factor-β

Chronic heart failure (CHF) is a growing health problem in developed nations. The pathological accumulation of extracellular matrix is a key contributor to CHF in both diabetic and nondiabetic states, resulting in progressive stiffening of the ventricular walls and loss of contractility. Proinflammatory disease processes, including inflammatory cytokine activation, contribute to accumulation of extracellular matrix in the heart. Transforming growth factor-β is a key profibrotic cytokine mediating fibrosis. Current therapeutic strategies do not directly target the profibrotic inflammatory processes occurring in the heart and hence there is a clear unmet clinical need to develop new therapeutic agents targeting fibrosis. Accordingly, strategies that inhibit proinflammatory cytokine activation and pathological accumulation of extracellular matrix (ECM) provide a potential therapeutic target for prevention of heart failure. This review focuses on the therapeutic targeting of TGF-β in the prevention of pathological fibrosis in the heart.

Transforming growth factor beta 1 as a biomarker of diabetic peripheral neuropathy: cross-sectional study

BACKGROUND

Simple and efficient screening methods are lacking for diabetic peripheral neuropathy (DPN), the most common and most difficult to treat of the long-term diabetic complications. Increased levels of transforming growth factor beta 1 (TGFbeta1) in type 2 diabetic patients (T2DM) plays an immunomodulatory role in diabetic nephropathy and, possibly, in atherosclerotic evolution. Since preliminary interrelationships between experimental DPN and TGFbeta1 have been observed, we sought to assess whether TGFbeta1 could be a biomarker molecule for human DPN.

MATERIALS AND METHODS

Cross-sectional cohort study focused on the assessment of the interrelationships between TGFbeta1 levels, cardiovascular disease (CVD), diabetic nephropathy (DNF), and neuropathy (DPN) in a group of T2DM patients (N=180; male 117, female 63) randomly selected from the North Catalonia Diabetes Study. DPN was diagnosed using clinical and neurophysiology evaluation. Incipient DNF was assessed by microalbuminuria (MAU). Total TGFbeta1 (without acidification) was measured by immunoassay by ELISA (Promega).

RESULTS

DPN correlated with age, time of diabetes duration, MAU, CVD, and TGFbeta1 (P<.0001). Log-transformed TGFbeta1 (logTGbeta1) was significantly higher in patients with DPN than in those without (P<.0005). LogTGFbeta1 (OR=7.5; P=.006), age (OR=1.1; P<.0005), and logMAU (OR=2.0; P=.016) appear as significant estimators of the occurrence of DPN in our series. The integrated ROC curve evaluation with these three parameters expressed an important sensitivity (78.1%), specificity (76.0%), positive predictive value (79.2%), and negative predictive value (70.3%) in relation to DPN presence.

DISCUSSION

TGFbeta1 stands as an important biomarker molecule for DFN and DPN screening in our series. Further prospective studies are warranted.

Advanced glycation end product-mediated matrix metallo-proteinase-9 and apoptosis via renin-angiotensin system in type 2 diabetes

AIM

Advanced glycation end products (AGE) play a key role in diabetic vascular complications, whereas matrix metalloproteinases (MMPs) and apoptosis contribute to plaque instability. This study was conducted to investigate the association of AGE-mediated MMP-9 and apoptosis with the renin-angiotensin system (RAS). We also examined the correlation between plasma HbA1c levels and plaque parameters.

METHODS

We used autopsy specimens from the aortae and coronary arteries of patients with or without diabetes (n=11, each group) for the immunohistochemistry of AGE, MMP-9, angiotensin-converting enzyme (ACE), and the receptor for AGE (RAGE). Apoptosis was determined by TUNEL staining.

RESULTS

The proportions of AGE accumulation, MMP-9 expression and apoptosis in intimal areas of both aortic and coronary specimens of diabetics were greater than in nondiabetics. MMP-9 expression and apoptosis were correlated with AGE accumulation. RAGE expression was significantly increased in diabetic specimens compared to nondiabetes. Interestingly, the expression of ACE in diabetic specimens was increased and also correlated with AGE accumulation, RAGE expression, MMP-9 expression, and apoptosis in all specimens from diabetics and nondiabetics. Plasma levels of HbA1c were linearly correlated with AGE accumulation, MMP-9, apoptosis, and ACE expression.

CONCLUSION

The present study shows that AGE/RAGE-related MMP-9 expression and apoptosis were correlated with ACE expression in diabetic plaques and that RAS may be involved in AGE-dependent diabetic vascular complications.

Induction of proinflammatory cytokines by long-chain saturated fatty acids in human macrophages

Increased circulating free fatty acids in subjects with type 2 diabetes may contribute to activation of macrophages, and thus the development of atherosclerosis. In this study, we investigated the effect of the saturated fatty acids (SFA) palmitate, stearate, myristate and laurate, and the unsaturated fatty acid linoleate, on the production of proinflammatory cytokines in phorbol ester-differentiated THP-1 cells, a model of human macrophages. Palmitate induced secretion and mRNA expression of TNF-alpha, IL-8 and IL-1 beta, and enhanced lipopolysaccharide (LPS)-induced IL-1 beta secretion. Proinflammatory cytokine secretion was also induced by stearate, but not by the shorter chain SFA, myristate and laurate, or linoleate. Triacsin C abolished the palmitate-induced cytokine secretion, suggesting that palmitate activation to palmitoyl-CoA is required for its effect. Palmitate-induced cytokine secretion was decreased by knockdown of serine palmitoyltransferase and mimicked by C(2)-ceramide, indicating that ceramide is involved in palmitate-induced cytokine secretion. Palmitate phosphorylated p38 and JNK kinases, and blocking of these kinases with specific inhibitors diminished the palmitate-induced cytokine secretion. Palmitate also activated the AP-1 (c-Jun) transcription factor. Knockdown of MyD88 reduced the palmitate-induced IL-8, but not TNF-alpha or IL-1 beta secretion. In conclusion, our data suggest that the long-chain SFA induce proinflammatory cytokines in human macrophages via pathways involving de novo ceramide synthesis. This might contribute to the activation of macrophages in atherosclerotic plaques, especially in type 2 diabetes.

A cardiologist view of vascular disease in diabetes

Diabetes mellitus is a potent risk factor for the development of a wide spectrum of cardiovascular (CV) complications. The complex metabolic milieu accompanying diabetes alters blood rheology, the structure of arteries and disrupts the homeostatic functions of the endothelium. These changes act as the substrate for end-organ damage and the occurrence of CV events. In those who develop acute coronary syndromes, patients with diabetes are more likely to die, both in the acute phase and during follow-up. Patients with diabetes are also more likely to suffer from chronic cardiac failure, independently of the presence of large vessel disease, and also more likely to develop stroke, renal failure and peripheral vascular disease. Preventing vascular events is the primary goal of therapy. Optimal cardiac care for the patient with diabetes should focus on aggressive management of traditional CV risk factors to optimize blood glucose, lipid and blood pressure control. Targeting medical therapy to improve plaque stability and diminish platelet hyper-responsiveness reduces the frequency of events associated with atherosclerotic plaque burden. In patients with critical lesions, revascularization strategies, either percutaneous or surgical, will often be necessary to improve symptoms and prevent vascular events. Improved understanding of the vascular biology will be crucial for the development of new therapeutic agents to prevent CV events and improve outcomes in patients with diabetes.

Diabetes-associated macrovasculopathy: pathophysiology and pathogenesis

The complications associated with diabetic vasculopathy are commonly grouped into two categories: microvascular and macrovascular complications. In diabetes, macrovascular disease is the commonest cause of mortality and morbidity and is responsible for high incidence of vascular diseases such as stroke, myocardial infarction and peripheral vascular diseases. Macrovascular diseases are traditionally thought of as due to underlying obstructive atherosclerotic diseases affecting major arteries. Pathological changes of major blood vessels leading to functional and structural abnormalities in diabetic vessels include endothelial dysfunction, reduced vascular compliance and atherosclerosis. Besides, advanced glycation end product formation interacts with specific receptors that lead to overexpression of a range of cytokines. Haemodynamic pathways are activated in diabetes and are possibly amplified by concomitant systemic hypertension. Apart from these, hyperglycaemia, non-enzymatic glycosylation, lipid modulation, alteration of vasculature and growth factors activation contribute to development of diabetic vasculopathy. This review focuses on pathophysiology and pathogenesis of diabetes-associated macrovasculopathy.

ROLE OF MACROPHAGES IN COMPLICATIONS OF TYPE 2 DIABETES

1. Macrophage accumulation is a feature of Type 2 diabetes and is associated with the development of diabetic complications (nephropathy, atherosclerosis, neuropathy and retinopathy). The present article reviews the current evidence that macrophages contribute to the complications of Type 2 diabetes. 2. Macrophage-depletion studies in rodent models have demonstrated a causal role for macrophages in the development of diabetic complications. 3. Components of the diabetic milieu (high glucose, advanced glycation end-products and oxidized low-density lipoprotein) promote macrophage accumulation (via induction of chemokines and adhesion molecules) and macrophage activation within diabetic tissues. 4. Macrophages mediate diabetic injury through a variety of mechanisms, including production of reactive oxygen species, cytokines and proteases, which result in tissue damage leading to sclerosis. 5. A number of existing and experimental therapies can indirectly reduce macrophage-mediated injury in diabetic complications. The present article discusses the use of these therapies, given alone and in combination, in suppressing macrophage accumulation and activity. 6. In conclusion, current evidence supports a critical role for macrophages in the evolution of diabetic complications. Present therapies are limited in slowing the progression of macrophage-mediated injury. Novel strategies that are more specific at targeting macrophages may provide better protection against the development of Type 2 diabetic complications.

Role of vascular reactive oxygen species in development of vascular abnormalities in diabetes

Macrovascular and microvascular diseases are currently the principal causes of morbidity and mortality in patients with diabetes. Oxidative stress has been postulated to be a major contributor to the pathogenesis of these events. There is considerable evidence that many biochemical pathways adversely affected by hyperglycemia and other substances that are found at elevated levels in diabetic patients are associated with the generation of reactive oxygen species, ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensation by the endogenous antioxidant defense network, increased oxidative stress leads to the activation of stress-sensitive intracellular signaling pathways and the formation of gene products that cause cellular damage and contribute to the late complications of diabetes. It has recently been suggested that diabetic subjects with vascular complications may have a defective cellular antioxidant response against the oxidative stress generated by hyperglycemia. This raises the concept that antioxidant therapy may be of great interest in these patients. Although our understanding of how hyperglycemia-induced oxidative stress ultimately leads to tissue damage has advanced considerably in recent years, effective therapeutic strategies to prevent or delay the development of this damage remain limited. Thus, further investigations of therapeutic interventions to prevent or delay the progression of diabetic vascular complications are needed.

'Correction:' Serum transforming growth factor beta-1 (TGF-beta-1) levels in diabetic patients are not associated with pre-existent coronary artery disease

Background

The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM). The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM).

Methods

Patients (n = 135, 30–80 years) referred for coronary angiography were submitted to clinical and laboratory evaluation, and the coronary angiograms were evaluated by two operators blinded to clinical characteristics. CAD was defined as the presence of a 70% stenosis in one major coronary artery, and DM was characterized as a fasting glycemia > 126 mg/dl or known diabetics (personal history of diabetes or previous use of anti-hyperglycemic drugs or insulin). Based on these criteria, study patients were classified into four groups: no DM and no CAD (controls, C n = 61), DM without CAD (D n = 23), CAD without DM (C-CAD n = 28), and CAD with DM (D-CAD n = 23). Baseline differences between the 4 groups were evaluated by the χ² test for trend (categorical variables) and by ANOVA (continuous variables, post-hoc Tukey). Patients were then followed-up during two years for the occurrence of MACE (cardiac death, stroke, myocardial infarction or myocardial revascularization). The association of candidate variables with the occurrence of 2-year MACE was assessed by univariate analysis.

Results

The mean age was 58.2 ± 0.9 years, and 51% were men. Patients with CAD had a higher mean age (p = 0.011) and a higher percentage were male (p = 0.040). There were no significant baseline differences between the 4 groups regarding hypertension, smoking status, blood pressure levels, lipid levels or inflammatory markers. TGF-β1 was similar between patients with or without CAD or DM (35.1 ×/÷ 1.3, 33.6 ×/÷ 1.6, 33.9 ×/÷ 1.4 and 31.8 ×/÷ 1.4 ng/ml in C, D, C-CAD and D-CAD, respectively, p = 0.547). In the 2-year follow-ip, independent predictors of 2-year MACE were age (p = 0.007), C-reactive protein (p = 0.048) and systolic blood pressure (p = 0.008), but not TGF-β1.

Conclusion

Serum TGF-β1 was not associated with CAD or MACE occurrence in patients with or without DM.

Oxidative stress, glucose metabolism, and the prevention of type 2 diabetes: pathophysiological insights

With the rising epidemic of type 2 diabetes worldwide, including the United States, the death and disability due to the suboptimal control of cardiovascular disease associated with this epidemic has made prevention of type 2 diabetes emerge as a primary strategic intervention. Several modalities have been assessed in large randomized controlled trials for diabetes prevention such as lifestyle interventions and various pharmacologic agents. Included in these agents are metformin, thiazolidinediones, acarbose, angiotensin converting enzyme inhibitors, as well as angiotensin receptor blockers. Abrogation of oxidative stress appears to be a common soil hypothesis that explains the favorable effects of these agents on glucose metabolism, including the prevention of diabetes and its complications. This comprehensive review highlights the role of oxidative stress in the pathogenesis of diabetes, with emphasis on the major clinical trials conducted on prevention of type 2 diabetes.

Factors influencing hemorrhagic transformation in ischemic stroke: a clinicopathological comparison

As hemorrhagic transformation (HTr) is a frequent complication and can worsen the outcome of acute ischemic stroke, our aim was to assess the risk factors of HTr. Using the database of our neuropathological laboratory, 245 consecutive acute ischemic stroke patients were analyzed. An exploratory logistic regression procedure was carried out to find the best multiple model identifying the factors associated with HTr. The autopsy revealed ischemic infarct in 175 (71%) and ischemic infarct with HTr in 70 (29%) patients. Mean age was 71.5 +/- 11.4 years (mean +/- SD) and 74.8 +/- 10.2 years (mean +/- SD), respectively. The multiple model confirmed age in case of embolic stroke, and diabetes mellitus and infarct size as independent risk factors of HTr. It seems that not serum glucose level but diabetes mellitus in the case history is an independent predictor of HTr.

Elevation of monocyte-derived microparticles in patients with diabetic retinopathy

Diabetic retinopathy is associated with microvascular damage and capillary occlusions which are common features of the microangiopathy in diabetes. Monocyte-derived microparticles (MDMPs) are released from activated monocytes and enhance the procoagulant activity, and also activate adhesion reactions. These are key events in the development of capillary occlusion. The MDMPs level in the blood, and platelet activation markers (platelet-derived microparticles (PDMPs), CD62P and CD63) were measured by flow cytometry in 72 diabetic patients. The plasma levels of intracellular adhesion molecule-1 (ICAM-1) and P-selectin were analyzed by ELISA. The level of MDMPs was significantly correlated with the levels of PDMPs (r=0.52, P<0.001), CD62P (r=0.37, P=0.001), CD63 (r=0.31 and P=0.007), P-selectin (r=0.38, P=0.001), and ICAM-1 (r=0.31, P=0.009). The MDMPs level increased with the progression of the diabetic retinopathy: 81+/-14/10(4)platelets (plts) in patients without retinopathy (n=10); 88+/-8/10(4)plts with mild or moderate non-proliferative diabetic retinopathy (NPDR, n=12); 95+/-8/10(4)plts with severe NPDR (n=24); and 112+/-9/10(4)plts with proliferative diabetic retinopathy (PDR) (n=26). The MDMPs level in patients with areas of capillary occlusion (123+/-10/10(4)plts, n=25) was significantly higher than that in patients without areas of capillary occlusion (84+/-5/10(4)plts, n=25; P=0.0008). These correlations suggest that increased levels of MDMPs may accelerate the progression of diabetic retinopathy.

Should all diabetic patients receive statins?

Diabetes is known to play a causal role in promoting both microvascular and macrovascular complications. Reducing rates of end-organ damage has been a key objective of multiple clinical trials. In addition to the roles of glycemic and blood pressure control, it is evident that lipid reduction via statin therapy independently helps to reduce the risk of primary and secondary vascular events. This effect seems to remain intact across a broad range of lipid levels, suggesting additional mechanisms for efficacy of statin medications beyond cholesterol reduction. The demonstrated safety and data from recent trials lend support to the argument that all people with diabetes should be started on statin therapy regardless of their cholesterol level. It is also plausible that treating the underlying mechanisms of vascular dysfunction, inflammation, and injury so prevalent in diabetic patients would have similar implications for the patient identified as having insulin resistance or metabolic syndrome.

Peripheral arterial disease in patients with diabetes

Peripheral arterial disease (PAD) is a chronic, lifestyle-limiting disease and is an independent predictor of cardiovascular and cerebrovascular ischemic events. Despite the recognition that PAD is associated with a marked increase in the risk of ischemic events, this particular manifestation of systemic atherosclerosis is largely underdiagnosed and undertreated. The risk of PAD is markedly increased among individuals with diabetes, and ischemic event rates are higher in diabetic individuals with PAD than in comparable non-diabetic populations. Consequently, early diagnosis and treatment of PAD in patients with diabetes is critically important in order to reduce the risk of cardiovascular events, minimize the risk of long-term disability, and improve quality of life. A diagnosis of PAD in patients with diabetes mandates a multi-faceted treatment approach, involving aggressive risk-factor modification, antiplatelet therapy, and revascularization procedures. The American Diabetes Association recently issued a consensus statement on the epidemiology, pathophysiology, diagnosis, and management of PAD in patients with diabetes. This article will review the clinical implications of the consensus statement and highlight the treatment options available in order to help prevent future ischemic events in diabetic individuals with PAD.

Oxidative stress and diabetic cardiovascular complications

Diabetes diagnoses are increasing at an alarming rate worldwide. The majority of diabetes-related deaths arise from cardiovascular complications such as myocardial infarction, stroke, and peripheral vascular disease. Oxidative stress has been demonstrated to be present in animal models as well as in patients with diabetes and has been suggested as a possible contributor to the accelerated atherosclerosis seen in diabetics. The generation of reactive oxygen species in diabetes occurs via several mechanisms and is initiated not only by glucose, but also by other substances that are found at elevated levels in diabetic patients. The resulting oxidative stress leads to a number of proatherogenic events. The elucidation of the mechanisms of oxidative stress in diabetes and their relationship with atherosclerosis could potentially identify molecular targets of therapy for this condition and its cardiovascular consequences.

Requirement of aldose reductase for the hyperglycemic activation of protein kinase C and formation of diacylglycerol in vascular smooth muscle cells

Activation of protein kinase C (PKC) has been linked to the development of secondary diabetes complications. However, the underlying molecular mechanisms remain unclear. We examined the contribution of aldose reductase, which catalyzes the first, and the rate-limiting, step of the polyol pathway of glucose metabolism, to PKC activation in vascular smooth muscle cells (VSMCs) isolated from rat aorta and exposed to high glucose in culture. Exposure of VSMCs to high glucose (25 mmol/l), but not iso-osmotic mannitol, led to an increase in total membrane-associated PKC activity, which was prevented by the aldose reductase inhibitors tolrestat or sorbinil or by the ablation of aldose reductase by small interfering RNA (siRNA). The VSMCs were found to express low levels of sorbitol dehydrogenase, and treatment with the sorbitol dehydrogenase inhibitor CP-166572 did not prevent high-glucose-induced PKC activation. Stimulation with high glucose caused membrane translocation of conventional (alpha, beta1, beta2, and gamma) and novel (delta and epsilon) isoforms of PKC. Inhibition of aldose reductase prevented membrane translocation of PKC-beta2 and -delta and delayed the activation of PKC-beta1 and -epsilon, whereas membrane translocation of PKC-alpha and -gamma was not affected. Treatment with tolrestat prevented phosphorylation of PKC-beta2 and -delta. High glucose increased the formation of diacylglycerol (DAG) and enhanced phosphorylation of phospholipase C-gamma1 (PLC-gamma1). Inhibition of aldose reductase prevented high glucose-induced DAG formation and phosphorylation of PLC-gamma1 and PLC-beta2 and -delta. Inhibition of phospholipid hydrolysis by D609, but not by the synthetic alkyl-1-lysophospholipid 1-O-octadecyl-2-O-methyl-rac-glycerophosphocholine, or edelfosine, prevented DAG formation. Treatment with sorbinil decreased the levels of reactive oxygen species in high-glucose-stimulated VSMCs. Hence, inhibition of aldose reductase, independent of sorbitol dehydrogenase, appears to be effective in diminishing oxidative stress and hyperglycemic changes in signaling events upstream to the activation of multiple PKC isoforms and PLC-gamma1 and may represent a useful approach for preventing the development of secondary vascular complications of diabetes.

Impact of age and hyperglycemia on the mechanical behavior of intact human coronary arteries: an ex vivo intravascular ultrasound study

Despite their advantages, percutaneous coronary interventional procedures are less effective in diabetic patients. Changes in the mechanical properties of vascular walls secondary to long-term hyperglycemia as well as other factors such as age may influence coronary distensibility. This investigation is aimed at deciphering the extent of these effects on distensibility of postmortem human coronary arteries in a controlled manner. Excised human left anterior descending (LAD) coronary arteries were obtained within 24 h postmortem. With the use of intravascular ultrasound, vascular deformation was analyzed at midregions of 51 moderate lesions. Intraluminal pressure was systematically altered using a computerized pressure pump system and monitored by a pressure-sensing guidewire. Distensibility, a normalized compliance term, was defined as the change in lumen area normalized by the initial reference area over a given pressure interval. With the use of multivariate analysis and repeated-measures ANOVA, coronary distensibility was independently influenced by hyperglycemia and age (P < 0.05) through the entire pressure range. Within physiological pressure range, distensibility was significantly reduced with age in nonhyperglycemic coronary specimens (10.55 +/- 4.41 vs. 6.99 +/- 2.45, x10(3) kPa(-1), P = 0.01), whereas the hyperglycemic vessels were stiff even in the younger group (7.90 +/- 5.82 vs. 7.20 +/- 3.36, x10(3) kPa(-1), P = 0.79). Similar results were observed with stiffness index and elastic modulus of the arteries. Hyperglycemia and age independently influenced the distensibility of moderately atherosclerotic LAD coronary arteries. The stiffening with age was overshadowed in the hyperglycemic group by as-yet-undetermined factors.

Oxidative stress and diabetic vascular complications

Vascular complications of diabetes represent the leading cause of morbidity and mortality in affected patients. Production of reactive oxygen species is increased in diabetic patients, especially in those with poor glycemic control. Reactive oxygen species affect vascular smooth muscle cell growth and migration, endothelial function, including abnormal endothelium-dependent relaxation and expression of a proinflammatory phenotype, and modification of the extracellular matrix. All of these events contribute to the development of diabetic microvascular and macrovascular complications, suggesting that the sources of reactive oxygen species and the signaling pathways that they modify may represent important therapeutic targets.

Functional dichotomy: glutathione and vitamin E in homeostasis relevant to primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a complex chronic neurological disease that can result in blindness. The goal of understanding the aetiology of POAG is to be able to target effective treatment to individuals who will eventually go blind without it. Epidemiological studies of POAG have not specifically addressed the possibility that nutrition may play a role in the development of POAG. A handful of papers have considered that nutrition may have an impact on POAG patients. POAG is not believed to be a 'vitamin-deficiency disease'. The concept of 'vitamin-deficiency diseases' and the recommended daily allowances have not kept pace with the growing understanding of the cellular and molecular functions of vitamins and other micronutrients. The aetiology of POAG remains a mystery. Discoveries in cell physiology can be assimilated from the literature and applied to known homeostatic mechanisms of the eye. In this way the possible roles of nutritional components involved in the aetiology of POAG can be described. The mechanisms may be subject to many influences in ways that have yet to be defined. Two distinct changes in the trabecular meshwork can be identified: trabecular meshwork changes that cause intra-ocular pressure to increase and trabecular meshwork changes that are directly correlated to optic nerve atrophy. Compelling evidence suggests that collagen trabecular meshwork extracellular matrix (ECM) remodelling is correlated to increased intraocular pressure in POAG. Elastin trabecular meshwork ECM remodelling is correlated to POAG optic nerve atrophy. There appear to be two different pathways of ECM remodelling and apoptosis induction in POAG. The pathway for collagen remodelling and apoptosis induction seems to be exogenously influenced by water-soluble antioxidants, for example, glutathione. The pathway for elastin remodelling and apoptosis induction seems to be influenced by endogenous lipid-soluble antioxidants, for example, vitamin E. Roles can be defined for antioxidants in the two different pathways of ECM remodelling and apoptosis induction. This suggests that antioxidants are important in maintaining cellular homeostasis relevant to the aetiology of POAG.

In vivo hyperglycemia and its effect on Glut-1 expression in the embryonic heart

BACKGROUND

Maternal diabetes exposes embryos to periods of hyperglycemia. Glucose is important for normal cardiogenesis, and Glut-1 is the predominant glucose transporter in the embryo.

METHODS

Pregnant mice were exposed to 6 or 12 hr hyperglycemia during organogenesis using intraperitoneal (IP) injections of D-glucose on gestational day (GD) 9.5 (plug = GD 0.5). Embryos were examined for morphology and total cardiac protein, and embryonic hearts were evaluated for Glut-1 protein and mRNA expression immediately after treatment (GD 9.75, GD 10.0), as well as on GD 10.5 and GD 12.5.

RESULTS

IP glucose injections were effective in producing sustained maternal hyperglycemia. Maternal hyperglycemia for 6 or 12 hr on GD 9.5, followed by normoglycemia, produced a decrease in overall size and total cardiac protein in embryos evaluated on GD 10.5 but no difference on GD 12.5. Cardiac Glut-1 expression was immediately upregulated in embryos exposed to 6 or 12 hr maternal hyperglycemia. On GD 10.5, cardiac Glut-1 expression was not different in embryos exposed to maternal hyperglycemia for 6 hr but was downregulated in embryos exposed for 12 hr. On GD 12.5, cardiac Glut-1 expression in embryos exposed to maternal hyperglycemia on GD 9.5 for 6 or 12 hr, followed by normoglycemia, was not different from controls. The temporal pattern was the same for Glut-1 protein and mRNA expression.

CONCLUSIONS

Hyperglycemia-induced alterations in Glut-1 expression likely interfere with balance of glucose available to the embryonic heart that may affect cardiac morphogenesis.

Correlation between cardiovascular disease and diabetes mellitus: current concepts

Individuals exhibiting precursor symptoms of diabetes mellitus or reaching diagnostic thresholds for diabetes are at increased risk of death due to cardiovascular disease (CVD). Moreover, patients with diabetes alone, as well as those who have diabetes paired with established CVD, remain undertreated for cardiovascular risk factors. The clear correlation between these disease processes has led many to speculate that they share common pathogenetic processes. Recent research has made it increasingly evident that the core metabolic defects that mark diabetes, including impaired glucose tolerance, insulin resistance, and proinflammatory and prothrombotic states, lead to endothelial dysfunction and accelerate atherogenesis. Moreover, increases in sympathetic tone with diabetes are associated with changes in cardiac and vascular function that lead to hypertension, left ventricular dysfunction, and cardiac autonomic neuropathy; such changes set the stage for arrhythmia, silent infarction, and sudden death. Furthermore, diabetes-related changes in metabolic and autonomic functioning, as well as increases in inflammatory and thrombotic signaling, compromise the ability of myocardial and vascular tissue to remodel after injury and to recover and sustain functionality. Because potentiation of atherogenesis and cardiac dysfunction occurs in the presence of early diabetic symptoms as well as in the established disease, early implementation of strategies to reduce cardiovascular risk factors and to slow diabetes progression may help to improve long-term outcomes for at-risk individuals. Such interventions may include well-established treatments for hypertension and dyslipidemia, diet improvements, weight loss, and exercise as well as novel pharmacologic interventions aimed at newly identified therapeutic targets.

Pathogenesis and protection of ischemia and reperfusion injury in myocardium

The important factors that influence the progress of ischemic cardiac lesion are blood flow condition and abnormal cardiac metabolism. Myocardial ischemia is promoted by either an increase in oxygen demand or a shortage of oxygen supply. The Na(+)-Ca(++) ion exchange mechanism is very important for myocardial contraction and cell damage. Na(+)-K(+)ATPase and Ca(++)ATPase are enzyme histochemically localized in subsarcolemmal cisterns, sarcolemmal reticulum and capillary endothelium, and keep myocardial function. These ATPases are impaired by anoxia, superoxides and free radicals. The reduction of O(2) results in the production of superoxides as well as hydrogen peroxide (H(2)O(2)). H(2)O(2) is highly diffusible and induces cell damage. H(2)O(2) appears to affect not only lipids but also intramembranous proteins embedded in the cell membrane. The hydroxyl radical (OH) also participates in lipid hyperoxidation. In the pathogenesis of ischemic and/or reperfused heart disease, ischemia induces rapid or gradual changes in all membrane systems and causes reversible or irreversible injury including necrotic and apoptotic cell death. Advanced glycation end products (AGEs) accumulation induced by diabetic conditioning is an etiologic factor inducing cardiomyopathy. The AGEs protein affects cell changes such as increased number, transformation, functional disturbance and cytokine elimination. In coronary arteries, the migration of smooth muscle cells caused by the taking up of AGEs proteins through the receptor (RAGE), and cytokine discharge are suggested. AGEs accumulation may induce diabetic macroangiopathy through RAGE, and the increase in the level of RAGE expression by endothelial cells could be a reason that diabetes mellitus accelerates atherosclerosis. On the other hand, we also reported that hyperglycemia was a promoting factor of ischemic heart injury in diabetic animals. Ischemic preconditioning is a useful phenomenon that limits myocardial damage. We foused on protein kinase C (PKC), mitogen-activated protein kinase (MAPK) and mitochondrial ATP-dependent potassium (mitoK(ATP)) channel as mediator or end which effector are necessary for adaptation. The opening of the mitoK(ATP) channel induces the depolarization of mitochondria, reducing Ca(++)overload during reperfusion. The regeneration of myocardial cells is confirmed using embryonic stem cells. Myocardial cells that exhibit self-pulsation are generated from mesenchymal stem cells in mesodermal tissues of the bone marrow.

Gene therapy targeting monocyte chemoattractant protein-1 for vascular disease

Monocyte chemoattractant protein-1 (MCP-1) has been shown to play an essential role in the pathogenesis of arteriosclerosis and other vascular diseases, such as restenosis after arterial injury, by recruiting monocytes into the arterial wall. We devised a new strategy for anti-MCP-1 gene therapy against arteriosclerosis by transfecting an amino-terminal deletion mutant (7ND), which lacks the amino-terminal amino acids 2 to 8 of the human MCP-1 gene, into a remote organ (skeletal muscles). Intramuscular transduction with the mutant MCP-1 gene suppressed inflammatory and proliferative changes and arteriosclerosis formation induced by the chronic inhibition of nitric oxide synthesis in rats. 7ND gene transfection also inhibited the initiation, progression, and destabilization of atherosclerosis in Apolipoprotein E-knockout mice. Moreover, the strategy reduced restenosis after balloon injury in rabbits, rats, and monkeys, or neointimal formation after stent implantation in monkeys. This new strategy may be a useful and feasible gene therapy against atherosclerosis and restenosis after angioplasty.

Impact of diabetes on coronary stenosis and coronary artery calcification detected by electron-beam computed tomography in symptomatic patients

OBJECTIVE

Ischemic heart disease is a pivotal complication for diabetic patients. Electron-beam computed tomography (EBCT) represents the only noninvasive method that allows for accurate quantification of coronary artery calcification that reflects underlying atherosclerotic disease. Although coronary calcium score (CCS) cut points that predict the presence of angiographic stenosis have been established in nondiabetic individuals, it is not known whether coronary calcifications in diabetic patients are associated with the presence of significant coronary stenoses. In this study, we evaluated the relationship between coronary calcifications and angiographic stenosis in symptomatic patients with or without type 2 diabetes.

RESEARCH DESIGN AND METHODS

In this study, 282 patients (204 men and 78 women) with chest pain, including 101 diabetic patients and 181 nondiabetic patients (mean age 63 +/- 9.6 years), underwent coronary angiography and EBCT with determination of CCS using Agatston's method. Luminal stenosis >or= 50% was defined as significant coronary stenosis.

RESULTS

Angiography identified 205 patients with significant stenoses (89 of 101 diabetic patients, 114 of 181 nondiabetic patients). The sensitivity and specificity of EBCT to detect significant coronary stenosis were not significantly different between diabetic and nondiabetic patients. In diabetic patients, a CCS >or=90 was associated with 75% sensitivity and 75% specificity, whereas a CCS >or=200 was associated with 64% sensitivity and 83% specificity.

CONCLUSIONS

We demonstrated that calcification of the coronary arteries in symptomatic diabetic patients is well associated with severity of coronary stenosis, as in nondiabetic patients.

Arterial wall chondroitin sulfate proteoglycans: diverse molecules with distinct roles in lipoprotein retention and atherogenesis

Chondroitin sulfate proteoglycans (CSPGs) of the arterial wall are generally considered to be atherogenic because of their ability to trap cholesterol-rich lipoproteins in vitro. Nevertheless, CSPGs are a diverse group of molecules with a long evolutionary history and distinct biologic functions. The three principal CSPGs in the arterial wall are versican, which is part of the hyalectan gene family; and decorin and biglycan, which are members of a separate gene family, the small leucine-rich proteoglycans. Importantly, there is now substantial evidence that the different molecular species of CSPGs participate unequally in lipoprotein retention, and that they exert unequal regulatory effects that are related to atherogenesis. Recently available murine models with genetic manipulations that affect CSPGs now allow causal studies of the roles of these molecules to be conducted in vivo, with occasionally surprising results. Moreover, tools are being developed to examine human genetic variations that are relevant to CSPGs, which may provide additional important insights into the human disease. The era in which proteoglycans are regarded as a nondescript backdrop, playing purely nonspecific structural roles, is over. Studies in manipulated animals and in human populations will continue to reveal precise, dynamic roles for these fascinating and ancient molecules.

High glucose induces cell death of cultured human aortic smooth muscle cells through the formation of hydrogen peroxide

Alterations of the vessel structure, which is mainly determined by smooth muscle cells through cell growth and/or cell death mechanisms, are characteristic of diabetes complications. We analysed the influence of high glucose (22 mM) on cultured human aortic smooth muscle cell growth and death, as hyperglycaemia is considered one of the main factors involved in diabetic vasculopathy. Growth curves were performed over 96 h in medium containing 0.5% foetal calf serum. Cell number increased by 2 - 4 fold over the culture period in the presence of 5.5 mM (low) glucose, while a 20% reduction in final cell number was observed with high glucose. Under serum-free conditions, cell number remained constant in low glucose cultures, but a 40% decrease was observed in high glucose cultures, suggesting that high glucose may induce increased cell death rather than reduced proliferation. Reduced final cell number induced by high glucose was also observed after stimulation with 5 or 10% foetal calf serum. The possible participation of oxidative stress was investigated by co-incubating high glucose with different reactive oxygen species scavengers. Only catalase reversed the effect of high glucose. Intracellular H(2)O(2) content, visualized with 2',7'-dichlorofluorescein and quantified by flow cytometry, was increased after high glucose treatment. To investigate the cell death mechanism induced by high glucose, apoptosis and necrosis were quantified. No differences were observed regarding the apoptotic index between low and high glucose cultures, but lactate dehydrogenase activity was increased in high glucose cultures. In conclusion, high glucose promotes necrotic cell death through H(2)O(2) formation, which may participate in the development of diabetic vasculopathy.

Alteration of antioxidants during the progression of heart disease in streptozotocin-induced diabetic rats

Involvement of oxidative stress is implicated in the progression of complication of diabetes mellitus. With respect to heart diseases, we have studied role of oxidative stress/antioxidants using rats treated with streptozotocin to induce diabetes (DM). Hemodynamic and echocardiographic measurements showed thickening of the wall and an increase in the internal dimension of the left ventricle (LV) in DM rats at 8th week. Decrease in diastolic posterior wall velocity and rate of LV pressure change, and increase in LV end diastolic pressures also proved cardiac dysfunction. These changes were further developed in DM rats after 12 weeks. Utilizing rat hearts at 8th and 12th weeks, the following estimations were performed. There was a decrease in the activity of Mn-superoxide dismutase (SOD), suggesting abnormal mitochondrial metabolism of reactive oxygen species. The level of glutathione (GSH) decreased concomitant with a decrease in the expression of gamma-glutamylcysteine synthetase (gamma-GCS). The expression of transforming growth factor-beta1 (TGF-beta1), known as a growth factor and a suppressor of GSH synthesis, elevated in DM rat hearts. Immunohistochemical estimation showed an increase in type IV collagen in DM hearts. Collectively, it was suggested a linkage between mitochondrial damage to generate reactive oxygen species and inactivation of Mn-SOD and elevation of the expression of TGF-beta1 to lead suppression of GSH synthesis and induction of fibrous change for the consequent cardiac dysfunction in DM.

Thapsigargin induces apoptosis in cultured human aortic smooth muscle cells

Vascular remodeling is a key feature of many pathologic states, including atherosclerosis, or hypertension. Vascular smooth muscle cells participate in determining the vessel structure by several mechanisms such as cell migration, cell growth, or cell death (necrosis or apoptosis). Here we report that thapsigargin, an inhibitor of endoplasmic reticulum Ca2+ -adenosine triphosphatase (ATPase), is able to induce apoptosis in human vascular smooth muscle cells (HVSMCs). Apoptosis was assessed by three different methods: differential chromatin binding dye staining. cytoplasmic histone-associated DNA fragments detection by enzyme-linked immunosorbent assay (ELISA) and terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). When HVSMCs were treated for 1 h with thapsigargin (100 nM-10 microM), there was a concentration-dependent increase in both parameters 24 h after the thapsigargin pulse. When a time-course experiment was performed, both parameters were significantly enhanced from 3 to 6 h after the exposure to thapsigargin. We conclude that thapsigargin promotes apoptosis in HVSMCs, providing a useful tool for the study of programmed cell death in human vascular smooth muscle.