Hyperhomocysteinemic Diabetic Cardiomyopathy: Oxidative Stress, Remodeling, and Endothelial-Myocyte Uncoupling

The role of nonmyocardial cells in the development of diabetic cardiomyopathy and the protective effects of FGF21: a current understanding

Diabetic cardiomyopathy (DCM) represents a unique myocardial disease originating from diabetic metabolic disturbances that is characterized by myocardial fibrosis and diastolic dysfunction. While recent research regarding the pathogenesis and treatment of DCM has focused primarily on myocardial cells, nonmyocardial cells-including fibroblasts, vascular smooth muscle cells (VSMCs), endothelial cells (ECs), and immune cells-also contribute significantly to the pathogenesis of DCM. Among various therapeutic targets, fibroblast growth factor 21 (FGF21) has been identified as a promising agent because of its cardioprotective effects that extend to nonmyocardial cells. In this review, we aim to elucidate the role of nonmyocardial cells in DCM and underscore the potential of FGF21 as a therapeutic strategy for these cells.

PPARs in Clinical Experimental Medicine after 35 Years of Worldwide Scientific Investigations and Medical Experiments

This year marks the 35th anniversary of Professor Walter Wahli's discovery of the PPARs (Peroxisome Proliferator-Activated Receptors) family of nuclear hormone receptors. To mark the occasion, the editors of the scientific periodical Biomolecules decided to publish a special issue in his honor. This paper summarizes what is known about PPARs and shows how trends have changed and how research on PPARs has evolved. The article also highlights the importance of PPARs and what role they play in various diseases and ailments. The paper is in a mixed form; essentially it is a review article, but it has been enriched with the results of our experiments. The selection of works was subjective, as there are more than 200,000 publications in the PubMed database alone. First, all papers done on an animal model were discarded at the outset. What remained was still far too large to describe directly. Therefore, only papers that were outstanding, groundbreaking, or simply interesting were described and briefly commented on.

Association of MMP-2 genes variants with diabetic retinopathy in Tunisian population with type 2 diabetes

AIMS

Few studies investigated the association of genetic difference in metalloproteinase-2 (MMP-2) gene with diabetic retinopathy but with mixed outcome. To investigate the association between a set of MMP-2 genetic variants and the risk of diabetic retinopathy in an Arab Tunisian population with type 2 diabetes.

SUBJECTS AND METHODS

A retrospective case-control study comprising a total of 779 type 2 diabetes patients with or without diabetic retinopathy was conducted. Genotyping was prepared by TaqMan® SNP genotyping qRT-PCR. The variants used were rs243865 (C/T), rs243864 (T/G), rs243866 (G/T) and rs2285053 (C/T).

RESULTS

The minor allele frequency (MAF) of the rs243864 MMP-2 variant was significantly higher among diabetic retinopathy patients. Setting homozygous wild type genotype carrier as reference, the rs243864T/G allele was associated with increased risk of diabetic retinopathy under the dominant, recessive, and additive models which persisted when key covariates were controlled for, while a reduced risk of diabetic retinopathy progression was seen after adjustment between non-proliferative and proliferative diabetic patients. Furthermore, the heterozygous genotype GT of the rs243866 variant is positively associated with the risk of proliferative diabetic retinopathy in the additive model. A limited linkage disequilibrium (LD) was revealed between the four-matrix metalloproteinase-2 variants. Four-loci haplotype analysis identified, GCTC, TTTC, and GCTT haplotypes to be positively associated with the risk of diabetic retinopathy.

CONCLUSION

Our findings demonstrate that the MMP-2 variant rs243864 and 243866 are related to the susceptibility to diabetic retinopathy and the progression of the disease in an Arab Tunisian population with type 2 diabetes.

Different Pattern of Cardiovascular Impairment in Methylmalonic Acidaemia Subtypes

Methylmalonic acidaemia (MMA) has been reported to be associated with cardiovascular involvement, especially for the combined type with homocystinuria. We have screened 80 control subjects and 99 MMA patients (23 isolated type and 76 combined type) using electrocardiograph and echocardiography. 32 cases (34%) of ECG changes were found including sinus tachycardia (n = 11), prolonged QTc interval (n = 1), I-degree atrioventricular block (n = 1), left axis deviation (n = 5) and T wave change (n = 14). By echocardiography, 8 cases of congenital heart disease were found in 4 combined MMA patients (5.3%) including ventricular septal defect (n = 2), atrial septal defect (n = 3), patent ductus arteriosus (n = 1) and coronary artery-pulmonary artery fistula (n =2). Pulmonary hypertension (n = 2) and hypertrophic cardiomyopathy (n = 1) in combined subtype were also noted. Moreover, echocardiographic parameters were analyzed by multiple regression to clarify the influence of different subtypes on cardiac function. It was found that the left ventricular mass index (LVMI) was significantly reduced only in combined subtype [R = -3.0, 95%CI (-5.4, -0.5), P = 0.017]. For left ventricle, the mitral E' velocity was significantly reduced [isolated type: R = -1.8, 95%CI (-3.3, -0.4), P = 0.016; combined type: R = -2.5, 95%CI (-3.5, -1.5), P < 0.001], the global longitudinal strain (GLS) was the same [isolated type: R = -1.4, 95%CI (-2.3, -0.4), P = 0.007; Combined type: R = -1.1, 95%CI (-1.8, -0.4), P = 0.001], suggesting weakened left ventricular diastolic and systolic functions in both subtypes. For right ventricle, only in combined subtype, the tricuspid E' velocity was significantly reduced [R = -1.4, 95%CI (-2.6, -0.2), P = 0.021], and the tricuspid annular plane systolic excursion (TAPSE) was the same [R = -1.3, 95%CI (-2.3, -0.3), P=0.013], suggesting impaired right ventricular systolic and diastolic function. In conclusion, isolated and combined types showed different pattern of cardiac dysfunction, specifically the former only affected the left ventricle while the latter affected both ventricles. And it is necessary to perform echocardiographic screening and follow up in both MMA subtypes.

Mechanism of Blood-Heart-Barrier Leakage: Implications for COVID-19 Induced Cardiovascular Injury

Although blood–heart-barrier (BHB) leakage is the hallmark of congestive (cardio-pulmonary) heart failure (CHF), the primary cause of death in elderly, and during viral myocarditis resulting from the novel coronavirus variants such as the severe acute respiratory syndrome novel corona virus 2 (SARS-CoV-2) known as COVID-19, the mechanism is unclear. The goal of this project is to determine the mechanism of the BHB in CHF. Endocardial endothelium (EE) is the BHB against leakage of blood from endocardium to the interstitium; however, this BHB is broken during CHF. Previous studies from our laboratory, and others have shown a robust activation of matrix metalloproteinase-9 (MMP-9) during CHF. MMP-9 degrades the connexins leading to EE dysfunction. We demonstrated juxtacrine coupling of EE with myocyte and mitochondria (Mito) but how it works still remains at large. To test whether activation of MMP-9 causes EE barrier dysfunction, we hypothesized that if that were the case then treatment with hydroxychloroquine (HCQ) could, in fact, inhibit MMP-9, and thus preserve the EE barrier/juxtacrine signaling, and synchronous endothelial-myocyte coupling. To determine this, CHF was created by aorta-vena cava fistula (AVF) employing the mouse as a model system. The sham, and AVF mice were treated with HCQ. Cardiac hypertrophy, tissue remodeling-induced mitochondrial-myocyte, and endothelial-myocyte contractions were measured. Microvascular leakage was measured using FITC-albumin conjugate. The cardiac function was measured by echocardiography (Echo). Results suggest that MMP-9 activation, endocardial endothelial leakage, endothelial-myocyte (E-M) uncoupling, dyssynchronous mitochondrial fusion-fission (Mfn2/Drp1 ratio), and mito-myocyte uncoupling in the AVF heart failure were found to be rampant; however, treatment with HCQ successfully mitigated some of the deleterious cardiac alterations during CHF. The findings have direct relevance to the gamut of cardiac manifestations, and the resultant phenotypes arising from the ongoing complications of COVID-19 in human subjects.

Multi-organ damage by covid-19: congestive (cardio-pulmonary) heart failure, and blood-heart barrier leakage

Corona virus disease-19 (covid-19) is caused by a coronavirus that is also known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and is generally characterized by fever, respiratory inflammation, and multi-organ failure in susceptible hosts. One of the first things during inflammation is the response by acute phase proteins coupled with coagulation. The angiotensinogen (a substrate for hypertension) is one such acute phase protein and goes on to explain an association of covid-19 with that of angiotensin-converting enzyme-2 (ACE2, a metallopeptidase). Therefore, it is advisable to administer, and test the efficacy of specific blocker(s) of angiotensinogen such as siRNAs or antibodies to covid-19 subjects. Covid-19 activates neutrophils, macrophages, but decreases T-helper cells activity. The metalloproteinases promote the activation of these inflammatory immune cells, therefore; we surmise that doxycycline (a metalloproteinase inhibitor, and a safer antibiotic) would benefit the covid-19 subjects. Along these lines, an anti-acid has also been suggested for mitigation of the covid-19 complications. Interestingly, there are three primary vegetables (celery, carrot, and long-squash) which are alkaline in their pH-range as compared to many others. Hence, treatment with fresh juice (without any preservative) from these vegies or the antioxidants derived from purple carrot and cabbage together with appropriate anti-coagulants may also help prevent or lessen the detrimental effects of the covid-19 pathological outcomes. These suggested remedies might be included in the list of putative interventions that are currently being investigated towards mitigating the multi-organ damage by Covid-19 during the ongoing pandemic.

Diabetic Retinopathy: Mitochondria Caught in a Muddle of Homocysteine

Diabetic retinopathy is one of the most feared complications of diabetes. In addition to the severity of hyperglycemia, systemic factors also play an important role in its development. Another risk factor in the development of diabetic retinopathy is elevated levels of homocysteine, a non-protein amino acid, and hyperglycemia and homocysteine are shown to produce synergistic detrimental effects on the vasculature. Hyperhomocysteinemia is associated with increased oxidative stress, and in the pathogenesis of diabetic retinopathy, oxidative stress-mitochondrial dysfunction precedes the development of histopathology characteristic of diabetic retinopathy. Furthermore, homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), and SAM is a co-substrate of DNA methylation. In diabetes, DNA methylation machinery is activated, and mitochondrial DNA (mtDNA) and several genes associated with mitochondrial homeostasis undergo epigenetic modifications. Consequently, high homocysteine, by further affecting methylation of mtDNA and that of genes associated with mtDNA damage and biogenesis, does not give any break to the already damaged mitochondria, and the vicious cycle of free radicals continues. Thus, supplementation of sensible glycemic control with therapies targeting hyperhomocysteinemia could be valuable for diabetic patients to prevent/slow down the development of this sight-threatening disease.

Homocysteine Disrupts Balance between MMP-9 and Its Tissue Inhibitor in Diabetic Retinopathy: The Role of DNA Methylation

High homocysteine is routinely observed in diabetic patients, and this non-protein amino acid is considered as an independent risk factor for diabetic retinopathy. Homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), which is a major methyl donor critical in DNA methylation. Hyperhomocysteinemia is implicated in increased oxidative stress and activation of MMP-9, and in diabetic retinopathy, the activation of MMP-9 facilitates capillary cell apoptosis. Our aim was to investigate the mechanism by which homocysteine activates MMP-9 in diabetic retinopathy. Human retinal endothelial cells, incubated with/without 100 μM homocysteine, were analyzed for MMP-9 and its tissue inhibitor Timp1 expressions and interactions, and ROS levels. Timp1 and MMP-9 promoters were analyzed for methylated and hydroxymethylated cytosine levels (5mC and 5hmC respectively) by the DNA capture method, and DNA- methylating (Dnmt1) and hydroxymethylating enzymes (Tet2) binding by chromatin immunoprecipitation. The results were confirmed in retinal microvessels from diabetic rats receiving homocysteine. Homocysteine supplementation exacerbated hyperglycaemia-induced MMP-9 and ROS levels and decreased Timp1 and its interactions with MMP-9. Homocysteine also aggravated Dnmts and Tets activation, increased 5mC at Timp1 promoter and 5hmC at MMP-9 promoter, and suppressed Timp1 transcription and activated MMP-9 transcription. Similar results were obtained from retinal microvessels from diabetic rats receiving homocysteine. Thus, hyperhomocysteinemia in diabetes activates MMP-9 functionally by reducing Timp1-MMP-9 interactions and transcriptionally by altering DNA methylation-hydroxymethylation of its promoter. The regulation of homocysteine could prevent/slow down the development of retinopathy and prevent their vision loss in diabetic patients.

Faulty homocysteine recycling in diabetic retinopathy

Background

Although hyperglycemia is the main instigator in the development of diabetic retinopathy, elevated circulating levels of a non-protein amino acid, homocysteine, are also associated with an increased risk of retinopathy. Homocysteine is recycled back to methionine by methylenetetrahydrofolate reductase (MTHFR) and/or transsulfurated by cystathionine β-synthase (CBS) to form cysteine. CBS and other transsulfuration enzyme cystathionine-γ-lyase (CSE), through desulfuration, generates H₂S. Methionine cycle also regulates DNA methylation, an epigenetic modification associated with the gene suppression. The aim of this study was to investigate homocysteine and its metabolism in diabetic retinopathy.

Methods

Homocysteine and H₂S levels were analyzed in the retina, and CBS, CSE and MTHFR in the retinal microvasculature from human donors with established diabetic retinopathy. Mitochondrial damage was evaluated in retinal microvessels by quantifying enzymes responsible for maintaining mitochondrial dynamics (fission-fusion-mitophagy). DNA methylation status of CBS and MTHFR promoters was examined using methylated DNA immunoprecipitation technique. The direct effect of homocysteine on mitochondrial damage was confirmed in human retinal endothelial cells (HRECs) incubated with 100 μM L-homocysteine.

Results

Compared to age-matched nondiabetic control human donors, retina from donors with established diabetic retinopathy had ~ 3-fold higher homocysteine levels and ~ 50% lower H₂S levels. The enzymes important for both transsulfuration and remethylation of homocysteine including CBS, CSE and MTHFR, were 40–60% lower in the retinal microvasculature from diabetic retinopathy donors. While the mitochondrial fission protein, dynamin related protein 1, and mitophagy markers optineurin and microtubule-associated protein 1A/1B-light chain 3 (LC3), were upregulated, the fusion protein mitofusin 2 was downregulated. In the same retinal microvessel preparations from donors with diabetic retinopathy, DNA at the promoters of CBS and MTHFR were hypermethylated. Incubation of HRECs with homocysteine increased reactive oxygen species and decreased transcripts of mtDNA-encoded CYTB.

Conclusions

Compromised transsulfuration and remethylation processes play an important role in the poor removal of retinal homocysteine in diabetic patients. Thus, regulation of their homocysteine levels should ameliorate retinal mitochondrial damage, and by regulating DNA methylation status of the enzymes responsible for homocysteine transsulfuration and remethylation, should prevent excess accumulation of homocysteine.

Hydrogen Sulfide Ameliorates Homocysteine-Induced Cardiac Remodeling and Dysfunction

Patients with diabetes, a methionine-rich meat diet, or certain genetic polymorphisms show elevated levels of homocysteine (Hcy), which is strongly associated with the development of cardiovascular disease including diabetic cardiomyopathy. However, reducing Hcy levels with folate shows no beneficial cardiac effects. We have previously shown that a hydrogen sulfide (H₂S), a by-product of Hcy through transsulfuration by cystathionine beta synthase (CBS), donor mitigates Hcy-induced hypertrophy in cardiomyocytes. However, the in vivo cardiac effects of H₂S in the context of hyperhomocysteinemia (HHcy) have not been studied. We tested the hypothesis that HHcy causes cardiac remodeling and dysfunction in vivo, which is ameliorated by H₂S. Twelve-week-old male CBS^+/− (a model of HHcy) and sibling CBS^+/+ (WT) mice were treated with SG1002 (a slow release H₂S donor) diet for 4 months. The left ventricle of CBS^+/− mice showed increased expression of early remodeling signals c-Jun and c-Fos, increased interstitial collagen deposition, and increased cellular hypertrophy. Notably, SG1002 treatment slightly reduced c-Jun and c-Fos expression, decreased interstitial fibrosis, and reduced cellular hypertrophy. Pressure volume loop analyses in CBS^+/− mice revealed increased end systolic pressure with no change in stroke volume (SV) suggesting increased afterload, which was abolished by SG1002 treatment. Additionally, SG1002 treatment increased end-diastolic volume and SV in CBS^+/− mice, suggesting increased ventricular filling. These results demonstrate SG1002 treatment alleviates cardiac remodeling and afterload in HHcy mice. H₂S may be cardioprotective in conditions where H₂S is reduced and Hcy is elevated.

Perivascular fibrosis and the microvasculature of the heart. Still hidden secrets of pathophysiology?

Perivascular fibrosis, the deposition of connective tissue around the vessels, has been demonstrated crucially involved in the development of cardiac dysfunction. Although cardiac fibrosis has been shown to be reversible under certain experimental conditions, effective anti-fibrotic therapies remain largely elusive. Therefore, perivascular fibrosis currently represents a major therapeutic target for cardiovascular diseases. The main topic of this review will be to address the mechanisms underlying perivascular fibrosis of the vasculature within the myocardium, with a special focus on perivascular fibrosis of small vessels, microvascular dysfunction and disease.

Vascular Remodeling, Oxidative Stress, and Disrupted PPARγ Expression in Rats of Long-Term Hyperhomocysteinemia with Metabolic Disturbance

Hyperhomocysteinemia, a risk factor for vascular disease, is associated with metabolic syndrome. Our study was aimed at exploring the effect of long-term hyperhomocysteinemia with metabolic disturbances on vascular remodeling. We also studied oxidative stress and expression of PPARγ in the coronary arteriole as a possible mechanism underlying vascular remodeling. Rats were treated with standard rodent chow (Control) or diet enriched in methionine (Met) for 48 weeks. Plasma homocysteine, blood glucose, serum lipids, malondialdehyde (MDA), superoxide dismutase (SOD), and nitric oxide (NO) levels were measured. Coronary arteriolar and carotid arterial remodeling was assessed by histomorphometric techniques and the expression of PPARγ in vessel wall was investigated. In Met group, an increase in the level of fasting blood glucose, serum triglyceride, total cholesterol, MDA, and NO, a decline in the serum SOD level, and increased collagen deposition in coronary and carotid arteries were found. Moreover, we detected decreased expression of PPARγ in the coronary arterioles in Met group. In summary, our study revealed metabolic disturbances in this model of long-term hyperhomocysteinemia together with vascular remodeling and suggested that impaired oxidative stress, endothelium dysfunction, and decreased PPARγ expression in the vessel wall could be underlying mechanisms.

Cardiovascular Protective Effects of Salvianic Acid A on db/db Mice with Elevated Homocysteine Level

The onsets of left ventricular hypertrophy (LVH) and endothelial dysfunction (ED) in diabetics, especially in those with elevated homocysteine (Hcy), precede the development of cardiovascular (CV) events. Salvianic acid A (SAA) is a renowned Traditional Chinese Medicine (TCM) that has been applied in the treatment of cardiovascular disease for many decades. In this study, we aimed (1) to investigate the CV protective effects of SAA on ameliorating LVH and ED in db/db mice with elevated blood Hcy level and (2) to decipher whether the observed CV protective effects of SAA are associated with Hcy metabolism by modulating the methylation potential and redox status in the liver of the db/db mice with elevated blood Hcy level. Our results found that the administration of SAA could significantly slow down the build-up of left ventricular mass and ameliorate ED. Immunological assay analysis on the mouse liver tissue also indicated that SAA treatment on db/db mice with elevated Hcy was associated with reduced methylation potential but improved redox status. In conclusion, we revealed that SAA has the potential to protect against the hyperglycemia- and hyperhomocysteinemia-induced oxidative stress on diabetic mice via modulation in Hcy metabolism.

Role of oxidative stress in epigenetic modification of MMP-9 promoter in the development of diabetic retinopathy

BACKGROUND

In the pathogenesis of diabetic retinopathy, damaged retinal mitochondria accelerate apoptosis of retinal capillary cells, and regulation of oxidative stress by manipulating mitochondrial superoxide dismutase (SOD2) protects mitochondrial homeostasis and prevents the development of diabetic retinopathy. Diabetes also activates matrix metalloproteinase-9 (MMP-9), and activated MMP-9 damages retinal mitochondria. Recent studies have shown a dynamic DNA methylation process playing an important role in regulation of retinal MMP-9 transcription in diabetes; the aim of this study is to investigate the role of oxidative stress in MMP-9 transcription.

METHODS

The effect of regulation of mitochondrial superoxide on DNA methylation of MMP-9 promoter region was investigated in retinal endothelial cells incubated in the presence or absence of a MnSOD mimetic MnTBAP, by quantifying the levels of 5 methyl cytosine (5mC) and hydroxyl-methyl cytosine (5hmC). The binding of DNA methylating, and of hydroxymenthylating enzymes (Dnmts and Tets, respectively), at MMP-9 promoter (by chromatin immunoprecipitation) was also evaluated. The in vitro results were confirmed in the retina of diabetic mice overexpressing SOD2.

RESULTS

MnTBAP attenuated glucose-induced decrease in 5mC levels and increase on Dnmt1 binding at the MMP-9 promoter region. MnTBAP also ameliorated alterations in 5hmC levels and Tet binding, regulated MMP-9 transcription, and prevented mitochondrial damage. Similarly, mice overexpressing SOD2 were protected from diabetes-induced alteration in MMP-9 promoter methylation, and its transcription.

CONCLUSIONS

Thus, regulation of oxidative stress by pharmacologic/genetic approaches maintains retinal mitochondrial homeostasis by ameliorating epigenetic modifications in the MMP-9 promoter region.

Cardiac tissue inhibitor of matrix metalloprotease 4 dictates cardiomyocyte contractility and differentiation of embryonic stem cells into cardiomyocytes: Road to therapy

BACKGROUND

TIMP4 (Tissue Inhibitors of Matrix Metalloprotease 4), goes down in failing hearts and mice lacking TIMP4 show poor regeneration capacity after myocardial infarction (MI). This study is based on our previous observation that administration of cardiac inhibitor of metalloproteinase (~TIMP4) attenuates oxidative stress and remodeling in failing hearts. Therefore, we hypothesize that TIMP4 helps in cardiac regeneration by augmenting contractility and inducing the differentiation of cardiac progenitor cells into cardiomyocytes.

METHODS

To validate this hypothesis, we transfected mouse cardiomyocytes with TIMP4 and TIMP4-siRNA and performed contractility studies in the TIMP4 transfected cardiomyocytes as compared to siRNA-TIMP4 transfected cardiomyocytes. We evaluated the calcium channel gene serca2a (sarcoplasmic reticulum calcium ATPase2a) and mir122a which tightly regulates serca2a to explain the changes in contractility. We treated mouse embryonic stem cells with cardiac extract and cardiac extract minus TIMP4 (using TIMP4 monoclonal antibody) to examine the effect of TIMP4 on differentiation of cardiac progenitor cells.

RESULTS

Contractility was augmented in the TIMP4 transfected cardiomyocytes as compared to siRNA-TIMP4 transfected cardiomyocytes. There was elevated expression of serca2a in the TIMP4 transformed myocytes and down regulation of mir122a. The cells treated with cardiac extract containing TIMP4 showed cardiac phenotype in terms of Ckit+, GATA4+ and Nkx2.5 expression.

CONCLUSION

This is a novel report suggesting that TIMP4 augments contractility and induces differentiation of progenitor cells into cardiac phenotype. In view of the failure of MMP9 inhibitors for cardiac therapy, TIMP4 provides an alternative approach, being an indigenous molecule and a natural inhibitor of MMP9.

Inhibition of prolyl hydroxylase 3 ameliorates cardiac dysfunction in diabetic cardiomyopathy

Prolyl hydroxylase 3 (PHD3) is a member of the prolyl hydroxylases (PHDs) family and is induced by hypoxia. It plays a critical role in regulating the abundance of hypoxia-inducible factor (HIF). Its expression is increased in diabetic rat hearts; however, its role remains unclear. We investigated the potential role and mechanism of action of PHD3 in the setting of diabetes-induced myocardial dysfunction in rats. In vivo, type 2 diabetic rat model was induced via a high-fat diet and intraperitoneal injection of streptozotocin. PHD3 expression was knocked down using lentivirus-mediated short-hairpin RNA (shRNA). In vitro, primary neonatal cardiomyocytes and H9c2 cardiomyoblasts were cultured in 33.3 mM glucose (high glucose, HG) and 5.5 mM glucose (normal glucose, NG), the latter of which was used as a control. PHD3-siRNA was used to inhibit the expression of PHD3 and to investigate the role of PHD3 in HG-induced apoptosis in H9c2 cardiomyoblasts. Rats with diabetic cardiomyopathy (DCM) exhibited severe left ventricular dysfunction as well as myocardial apoptosis and fibrosis. PHD3 expression was increased in the myocardial tissues of diabetic rats, and inhibition of PHD3 ameliorated the disease. Additionally, the inhibition of PHD3 significantly decreased HG-induced apoptosis and MAPK activation in H9c2 cardiomyoblasts. Our results suggest that PHD3 inhibition ameliorates myocardial dysfunction in the setting of diabetic cardiomyopathy.

Mitochondrial mitophagy in mesenteric artery remodeling in hyperhomocysteinemia

Although high levels of homocysteine also termed as hyperhomocysteinemia (HHcy) has been associated with inflammatory bowel disease and mesenteric artery occlusion, the mitochondrial mechanisms behind endothelial dysfunction that lead to mesenteric artery remodeling are largely unknown. We hypothesize that in HHcy there is increased mitochondrial fission due to altered Mfn‐2/Drp‐1 ratio, which leads to endothelial dysfunction and collagen deposition in the mesenteric artery inducing vascular remodeling. To test this hypothesis, we used four groups of mice: (i) WT (C57BL/6J); (ii) mice with HHcy (CBS+/−); (iii) oxidative stress resistant mice (C3H) and (iv) mice with HHcy and oxidative stress resistance (CBS+/−/C3H). For mitochondrial dynamics, we studied the expression of Mfn‐2 which is a mitochondrial fusion protein and Drp‐1 which is a mitochondrial fission protein by western blots, real‐time PCR and immunohistochemistry. We also examined oxidative stress markers, endothelial cell, and gap junction proteins that play an important role in endothelial dysfunction. Our data showed increase in oxidative stress, mitochondrial fission (Drp‐1), and collagen deposition in CBS+/− compared to WT and C3H mice. We also observed significant down regulation of Mfn‐2 (mitochondrial fusion marker), CD31, eNOS and connexin 40 (gap junction protein) in CBS+/− mice as compared to WT and C3H mice. In conclusion, our data suggested that HHcy increased mitochondrial fission (i.e., decreased Mfn‐2/Drp‐1 ratio, causing mitophagy) that leads to endothelial cell damage and collagen deposition in the mesenteric artery. This is a novel report on the role of mitochondrial dynamics alteration defining mesenteric artery remodeling.

e00283

This article is a novel report on the role of mitochondrial dynamics in mesenteric artery remodeling during hyperhomocysteinemia. The study can contribute significantly toward understanding the mesenteric mitochondrial mechanisms underpinning inflammatory bowel disease – a major clinical concern.

Homocysteine over-accumulation as the effect of potato leaves exposure to biotic stress

Homocysteine (Hcy) is a naturally occurring intermediate metabolite formed during methionine metabolism. It has been well documented that its excess can be extremely toxic to mammalian, yeast and bacterial cells. In spite of the metabolic value of Hcy known for decades, the role of this amino acid in the plant response to stress has not been recognized yet. In the presented study, using potato plant (Solanum tuberosum L.) and Phytophthora infestans as a model system, the presence and tissue localization of Hcy in leaves was examined by an immunohistochemical method. The over-production of Hcy was more evidenced in the susceptible than in the resistant genotype of potato starting from 48 hpi. Furthermore, the elevated level of Hcy was correlated in time with the up-regulation of genes engaged in its biosynthesis, e.g. cystathionine β-lyase and S-adenosyl-l-homocysteine hydrolase. The pharmacological approach with exogenous Hcy resulted in significant rise in lipid peroxidation and more potent late blight disease development in leaves of susceptible potato as well. Finally, it has been found that key defense enzymes, i.e. phenylalanine ammonia lyase and β-1,3-glucanase were up-regulated early in the resistant potato genotype, starting from 1st hpi. In turn, in the susceptible potato the time-lag in expression of these enzymes tuned with excess production of Hcy might facilitate leaf tissue colonization by pathogen. Based on obtained results it should be stated that Hcy over-accumulation is engaged in pathophysiological mechanism leading to the abolishment of the resistance and might be an informative disease hallmark both in plant and in animal system.

Diabetic retinopathy and signaling mechanism for activation of matrix metalloproteinase-9

In the pathogenesis of diabetic retinopathy, H-Ras (a small molecular weight G-protein) and matrix metalloproteinase-9 (MMP9) act as pro-apoptotic, accelerating the apoptosis of retinal capillary cells, a phenomenon that predicts its development and the activation of MMP9 is under the control of H-Ras. The goal of this study is to elucidate the cellular mechanism by which H-Ras activates MMP9 culminating in the development of diabetic retinopathy. Using isolated retinal endothelial cells, the effect of regulation of H-Ras downstream signaling cascade, Raf-1, MEK, and ERK, was investigated on glucose-induced activation of MMP9. In vitro results were confirmed in the retina obtained from diabetic mice manipulated for MMP9 gene, and also in the retinal microvasculature obtained from human donors with diabetic retinopathy. Regulation of Raf-1/MEK/ERK by their specific siRNAs and pharmacologic inhibitors prevented glucose-induced activation of MMP9 in retinal endothelial cells. In MMP9-KO mice, diabetes had no effect on retinal MMP9 activation, and H-Ras/Raf-1/MEK signaling cascade remained normal. Similarly, donors with diabetic retinopathy had increased MMP9 activity in their retinal microvessels, the site of histopathology associated with diabetic retinopathy, and this was accompanied by activated H-Ras signaling pathway (Raf-1/ERK). Collectively, these results suggest that Ras/Raf-1/MEK/ERK cascade has an important role in the activation of retinal MMP9 resulting in the apoptosis of its capillary cells. Understanding the upstream mechanism responsible for the activation of MMP9 should help identify novel molecular targets for future pharmacological interventions to inhibit the development/progression of diabetic retinopathy.

Matrix metalloproteinases in diabetic retinopathy: potential role of MMP-9

INTRODUCTION

Diabetic retinopathy remains one of the most feared complications of diabetes. Despite extensive research in the field, the molecular mechanism responsible for the development of this slow progressing disease remains unclear. In the pathogenesis of diabetic retinopathy, mitochondria are damaged and inflammatory mediators are elevated before the histopathology associated with the disease can be observed. Matrix metalloproteinases (MMPs) regulate a variety of cellular functions including apoptosis and angiogenesis. Diabetic environment stimulates the secretion of several MMPs that are considered to participate in complications, including retinopathy, nephropathy and cardiomyopathy. Patients with diabetic retinopathy and also animal models have shown increased MMP-9 and MMP-2 in their retina and vitreous. Recent research has shown that MMPs have dual role in the development of diabetic retinopathy; in the early stages of the disease (pre-neovascularization), MMP-2 and MMP-9 facilitate the apoptosis of retinal capillary cells, possibly via damaging the mitochondria, and in the later phase, they help in neovascularization.

AREAS COVERED

This article reviews the literature to evaluate the role of MMPs, especially MMP-9, in the development of diabetic retinopathy, and presents existing evidence that the inhibitors targeted toward MMP-9, depending on the duration of diabetes at the times their administration could have potential to prevent the progression of this blinding disease, and protect the vision loss.

EXPERT OPINION

Inhibitors of MMPs could have dual role: in the early stages of the diseases, inhibit capillary cell apoptosis, and if the disease has progressed to the angiogenic stage, inhibit the growth of new vessels.

Augmenting Maintenance of Sinus Rhythm in the Control of Atrial Fibrillation by Antiarrhythmic Drug Combinations

In recent years, a major development in the treatment of atrial fibrillation (AF) is the use of catheter ablation, and a significant number of patients may benefit from this mode of therapy. On a global scale, it may not be feasible to deal with most patients solely on the basis of ablation. Therefore, it is likely that much of the therapy for AF will continue to rely on antiarrhythmic agents for maintaining sinus rhythm. For many years, amiodarone and sotalol have been the dominant antiarrhythmic agents, with amiodarone being the most effective antiarrhythmic in suppressing AF; however, amiodarone use is limited due to concerns of end-organ toxicity. Upstream therapies, such as statins, fish oil, angiotensin converting enzyme (ACE) inhibitors, and angiotensin receptor blockers may also provide additive efficacy to these and other membrane-active antiarrhythmics. In recent years, a number of new agents are being developed and the first successful congener of amiodarone, dronedarone, has been shown to be effective in controlling AF and reducing cardiovascular hospitalization. This paper explores the possibility of augmenting the extent of controlling AF by combining multiple potent antiarrhythmic agents old and new.

Association of hyperhomocysteinemia with left ventricular dilatation and mass in human heart

BACKGROUND

Hyperhomocysteinemia is a risk factor for ischemic heart disease. Several other mechanisms apply also to dilative types of heart failure of various, non-ischemic etiologies. We hypothesized that hyperhomocysteinemia is associated with left ventricular (LV) dilatation and hypertrophy in dilative cardiomyopathy.

METHODS

Homocysteine was measured in 66 individuals with suspected cardiomyopathy. Cardiac magnetic resonance imaging was used to assess LV volume, mass, and wall stress.

RESULTS

Hyperhomocysteinemia (> 12 micromol/L) was found in 45 patients (68%). LV mass was greater in these patients compared with individuals with normal homocysteine (83+/-27 vs. 67+/-19 g/m(2); p<0.02). Homocysteine was increased in patients with increased brain natriuretic peptide > or = 100 pg/mL (18.3+/-5.9 vs. 14.9+/-5.1 micromol/L; p=0.018). LV mass, LV end-diastolic and end-systolic volume (LVEDV, LVESV) were significantly increased in individuals in the upper quartile compared with the lower quartile (90+/-25 vs. 65+/-18 g/m(2), p=0.021; 114+/-50 vs. 71+/-23 mL/m(2), p=0.042; 76+/-51 vs. 36+/-22 mL/m(2), p=0.045). LV dilatation (LVEDV > or = 90 mL/m(2)) was more common in hyperhomocysteinemia (> 12 micromol/L, p=0.0166). Normalized LV mass was correlated with homocysteine (r=0.346, p=0.065). Homocysteine was not significantly correlated with LVEDV (r=0.229, p=0.065), LV end-diastolic wall stress (r=0.226, p=0.069) and LV ejection fraction.

CONCLUSIONS

Hyperhomocysteinemia appears to be, at least in part, involved in a disproportional LV dilatation, where the ensuing hypertrophy is not sufficient to compensate for the increased wall stress. A potential mechanism is the hyperhomocysteinemia associated increase in oxidative stress that favors muscle fiber slippage.

Differential phosphoproteomics of fibroblast growth factor signaling: identification of Src family kinase-mediated phosphorylation events

Activation of signal transduction by the receptor tyrosine kinase, fibroblast growth factor receptor (FGFR), results in a cascade of protein-protein interactions that rely on the occurrence of specific tyrosine phosphorylation events. One such protein recruited to the activated receptor complex is the nonreceptor tyrosine kinase, Src, which is involved in both initiation and termination of further signaling events. To gain a further understanding of the tyrosine phosphorylation events that occur during FGF signaling, with a specific focus on those that are dependent on Src family kinase (SFK) activity, we have applied SILAC combined with chemical inhibition of SFK activity to search for phosphorylation events that are dependent on SFK activity in FGF stimulated cells. In addition, we used a more targeted approach to carry out high coverage phosphopeptide mapping of one Src substrate protein, the multifunctional adaptor Dok1, and to identify SFK-dependent Dok1 binding partners. From these analyses we identify 80 SFK-dependent phosphorylation events on 40 proteins. We further identify 18 SFK-dependent Dok1 interactions and 9 SFK-dependent Dok1 phosphorylation sites, 6 of which had not previously been known to be SFK-dependent.

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.

Serum N-terminal-pro-brain natriuretic peptide (NT-pro-BNP) and homocysteine levels in type 2 diabetic patients with asymptomatic left ventricular diastolic dysfunction

AIMS

: The aim of this study was to determine serum NT-proBNP and plasma Hcy levels and to explore the relationship between serum NT-proBNP and plasma Hcy levels in type 2 diabetic patients with and without asymptomatic LVDD.

METHODS

: NT-proBNP and Hcy levels were measured 31 patients with type 2 diabetes mellitus. According to echocardiographic data, diabetic patients were divided into two groups: normal LV function or LV diastolic dysfunction.

RESULTS

: Serum NT-proBNP levels in diabetic patients with LVDD were significantly higher than in diabetic patients with normal LV function and controls. The area under the receiver-operating characteristic (ROC) curve for NT-proBNP to separate normal vs. diastolic dysfunction was 0.96 in type 2 diabetic patients. Plasma Hcy levels were significantly higher in both diabetic groups than in controls. Positive correlation was noted between NT-proBNP and Hcy levels in diabetic patients with LVDD (r=0.881, p=0.0001).

CONCLUSIONS

: The correlation between elevated NT-proBNP and Hcy levels in diabetic patients with LVDD suggest an association between homocysteinemia and increased NT-proBNP secretion. Our data indicate that NT-proBNP may be a simple screening tool to select diabetic patients with LVDD requiring further examination with echocardiography.

MicroRNAs are involved in homocysteine-induced cardiac remodeling

Elevated level of homocysteine (Hcy) called hyperhomocysteinemia (HHcy) is one of the major risk factors for chronic heart failure. Although the role of Hcy in cardiac remodeling is documented, the regulatory mechanism involved therein is still nebulous. MicroRNAs (miRNAs) and dicer have been implicated in regulation of cardiovascular diseases. Dicer is the only known enzyme involved in miRNA maturation. We investigated the involvement of dicer and miRNA in Hcy-induced cardiac remodeling. HL-1 cardiomyocytes were cultured in different doses of Hcy. Total RNA was isolated and RT-PCR and real-time PCR was performed for dicer, MMP-2,-9, TIMP-1,-3, and NOX-4. MiRNA microarray was used for analyzing the differential expression of miRNAs. Individual miRNA assay was also done. Western blotting was used to assess the MMP-9 expression in HHcy cardiomyocytes. The RT-PCR results suggest that dicer expression is enhanced in HHcy cardiomyocytes suggesting its involvement in cardiac remodeling caused due to high dose of Hcy. On the other hand, high dose of Hcy increased NOX-4 expression, a marker for oxidative stress. Additionally, HHcy cardiomyocytes showed elevated levels of MMP-2,-9 and TIMP-1,-3, and reduced expression of TIMP-4, suggesting cardiac remodeling due to oxidative stress. The miRNA microarray assay revealed differential expression of 11 miRNAs and among them miR-188 show dramatic downregulation. These findings suggest that dicer and miRNAs especially miR-188 are involved in Hcy-induced cardiac remodeling.

Nitrotyrosinylation, remodeling and endothelial-myocyte uncoupling in iNOS, cystathionine beta synthase (CBS) knockouts and iNOS/CBS double knockout mice

Increased levels of homocysteine (Hcy), recognized as hyperhomocysteinemia (HHcy), were associated with cardiovascular diseases. There was controversy regarding the detrimental versus cardio protective role of inducible nitric oxide synthase (iNOS) in ischemic heart disease. The aim of this study was to test the hypothesis that the Hcy generated nitrotyrosine by inducing the endothelial nitric oxide synthase, causing endothelial-myocyte (E-M) coupling. To differentiate the role of iNOS versus constitutive nitric oxide synthase (eNOS and nNOS) in Hcy-mediated nitrotyrosine generation and matrix remodeling in cardiac dysfunction, left ventricular (LV) tissue was analyzed from cystathionine beta synthase (CBS) heterozygote knockout, iNOS homozygote knockout, CBS-/+/iNOS-/- double knockout, and wild-type (WT) mice. The levels of nitrotyrosine, MMP-2 and -9 (zymographic analysis), and fibrosis (by trichrome stain) were measured. The endothelial-myocyte function was determined in cardiac rings. In CBS-/+ mice, homocysteine was elevated and in iNOS-/- mice, nitric oxide was significantly reduced. The nitrotyrosine and matrix metalloproteinase-9 (MMP-9) levels were elevated in double knockout and CBS-/+ as compared to WT mice. Although MMP-2 levels were similar in CBS-/+, iNOS-/-, and CBS-/+/iNOS-/-, the levels were three- to fourfold higher than WT. The levels of collagen were similar in CBS-/+ and iNOS-/-, but they were threefold higher than WT. Interesting, the levels of collagen increased sixfold in double knockouts, compared to WT, suggesting synergism between high Hcy and lack of iNOS. Left ventricular hypertrophy was exaggerated in the iNOS-/- and double knockout, and mildly increased in the CBS-/+, compared to WT mice. The endothelial-dependent relaxation was attenuated to the same extent in the CBS-/+ and iNOS-/-, compared to WT, but it was robustly blunted in double knockouts. The results concluded that homocysteine generated nitrotyrosine in the vicinity of endothelium, caused MMP activation and endothelium-myocyte uncoupling. The generation of nitrotyrosine was independent of iNOS.

Reversal of systemic hypertension-associated cardiac remodeling in chronic pressure overload myocardium by ciglitazone

Elevated oxidative stress has been characterized in numerous disorders including systemic hypertension, arterial stiffness, left ventricular hypertrophy (LVH) and heart failure. The peroxisome proliferator activated receptor gamma (PPARγ) ameliorates oxidative stress and LVH. To test the hypothesis that PPARγ decreased LVH and cardiac fibrosis in chronic pressure overload, in part, by increasing SOD, eNOS and elastin and decreasing NOX4, MMP and collagen synthesis and degradation, chronic pressure overload analogous to systemic hypertension was created in C57BL/6J mice by occluding the abdominal aorta above the kidneys (aortic stenosis-AS). The sham surgery was used as controls. Ciglitazone (CZ, a PPARγ agonist, 4 µg/ml) was administered in drinking water. LV function was measured by M-Mode Echocardiography. We found that PPARγ protein levels were increased by CZ. NOX-4 expression was increased by pressure-overload and such an increase was attenuated by CZ. SOD expression was not affected by CZ. Expression of iNOS was induced by pressure-overload, and such an increase was inhibited by CZ. Protein levels for MMP2, MMP-9, MMP-13 were induced and TIMP levels were decreased by pressure-overload. The CZ mitigated these levels. Collagen synthesis was increased and elastin levels were decreased by pressure-overload and CZ ameliorated these changes. Histochemistry showed that CZ inhibited interstitial and perivascular fibrosis. Echocardiography showed that CZ attenuated the systolic and diastolic LV dysfunction induced by pressure-overload. These observations suggested that CZ inhibited pressure-overlaod-induced cardiac remodeling, and inhibition of an induction of NOX4, iNOS, MMP-2/MMP-13 expression and collagen synthesis/degradation may play a role in pressure-overload induced cardiac remodeling.

From oxygen sensing to heart failure: role of thioredoxin

Oxidative stress has been widely recognized to be involved in the pathogenesis of cardiopulmonary disorders. In ischemic heart diseases, it is involved not only in the development of atherosclerosis but also in ongoing ischemic injury, especially in the reperfusion process. Cardiomyopathy is another cardiac disorder in which oxidative stress is involved. In diabetic cardiomyopathy, homocysteine, a well-known source of oxidative stress, is believed to play major roles in its development. Thioredoxin (TRX) is a redox-acting protein ubiquitously present in the human body. It also is inducible by a wide variety of oxidative stresses. TRX is a multifunctional protein and has anti-inflammatory and antiapoptotic effects, as well as antioxidative effects. It is therefore feasible to think that TRX is a potential therapy for cardiac disease. Moreover, serum TRX is a well-recognized biomarker of various diseases involving oxidative stress, and this is also the case for cardiac disorders. Here we discuss how TRX is useful as a biomarker of and therapeutic agent for cardiopulmonary disorders, especially focusing on ischemic heart disease, myocarditis and oxygen sensing, and acute respiratory distress syndrome.

Pathomolecular effects of homocysteine on the aging process: A new theory of aging

Homocysteine has been associated with the most common age-related diseases but never associated with the acceleration of the aging process. This theoretical paper will try to demonstrate the pro-aging effects of homocysteine at the molecular, cellular, and organ level. High homocysteine levels in homocystinuria are associated with premature disease of the cardiovascular, skeletal, neurological, and other systems. These observations are similar to those noted in the aging process and should be considered as a progeroid syndrome. There is enough scientific evidence to support that homocysteine accelerates the aging process at the cellular and at the organism level. Most importantly, decreasing homocysteine levels by dietary or pharmacological interventions could prolong maximum life span in humans and/or delay the onset of the most common age-related diseases.

Increased vaginal oxidative stress, apoptosis, and inducible nitric oxide synthase in a diabetic rat model: implications for vaginal fibrosis

OBJECTIVE

To determine whether vaginal fibrosis occurs in diabetic animals and is associated with oxidative stress and cell death and with the expression of inducible nitric oxide synthase (iNOS), as a putative antifibrotic mechanism.

DESIGN

Research experimental project.

SETTING

University research laboratory.

ANIMAL(S)

Female Wistar rats.

INTERVENTION(S)

Female rats were injected with streptozotocin or saline and killed at 3 months. The vaginas were excised and processed for paraffin-embedded sections (n = 6 per group) or were frozen for biochemical and molecular biology procedures.

MAIN OUTCOME MEASURE(S)

Immunohistochemistry and quantitative image analysis were applied to tissue sections to measure alpha-smooth muscle actin, transforming growth factor beta1, plasminogen activator inhibitor, NOS isoforms, Cu/Zn superoxide dismutase, apoptotic index, and nitrotyrosine. Xanthine dehydrogenase, reactive oxygen species (ROS), and hydroxyproline were measured in fresh vaginal tissue (n = 5 per group). Reactive oxygen species also were determined in blood.

RESULT(S)

Diabetes was associated with vaginal fibrosis, as evidenced by increased collagen, transforming growth factor beta1, plasminogen activator inhibitor, and apoptosis, and by decreased alpha-smooth muscle actin. The increment of ROS and the reduction of superoxide dismutase indicated oxidative stress in diabetic tissue, accompanied by iNOS induction and increased nitric oxide-ROS reaction.

CONCLUSION(S)

Diabetes in the rat causes oxidative stress and fibrosis in the vagina, which may be compensated partially by iNOS induction to reduce ROS.

Arrhythmia and neuronal/endothelial myocyte uncoupling in hyperhomocysteinemia

Elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with arrhythmogenesis and sudden cardiac death (SCD). Hcy decreases constitutive neuronal and endothelial nitric oxide (NO), and cardiac diastolic relaxation. Hcy increases the iNOS/NO, peroxynitrite, mitochondrial NADPH oxidase, and suppresses superoxide dismutase (SOD) and redoxins. Hcy activates matrix metalloproteinase (MMP), disrupts connexin-43 and increases collagen/elastin ratio. The disruption of connexin-43 and accumulation of collagen (fibrosis) disrupt the normal pattern of cardiac conduction and attenuate NO transport from endothelium to myocyte (E-M) causing E-M uncoupling, leading to a pro-arrhythmic environment. The goal of this review is to elaborate the mechanism of Hcy-mediated iNOS/NO in E-M uncoupling and SCD. It is known that Hcy creates arrhythmogenic substrates (i.e. increase in collagen/elastin ratio and disruption in connexin-43) and exacerbates heart failure during chronic volume overload. Also, Hcy behaves as an agonist to N-methyl-D-aspartate (NMDA, an excitatory neurotransmitter) receptor-1, and blockade of NMDA-R1 reduces the increase in heart rate-evoked by NMDA-analog and reduces SCD. This review suggest that Hcy increases iNOS/NO, superoxide, metalloproteinase activity, and disrupts connexin-43, exacerbates endothelial-myocyte uncoupling and cardiac failure secondary to inducing NMDA-R1.

Diabetic cardiomyopathy: where are we 40 years later?

Diabetic cardiomyopathy is a cardiac disease that arises as a result of the diabetic state, independent of vascular or valvular pathology. It manifests initially as asymptomatic diastolic dysfunction, which progresses to symptomatic heart failure. The compliance of the heart wall is decreased and contractile function is impaired. The pathophysiology is incompletely understood, but appears to be initiated both by hyperglycemia and changes in cardiac metabolism. These changes induce oxidative stress and activate a number of secondary messenger pathways, leading to cardiac hypertrophy, fibrosis and cell death. Alterations in contractile proteins and intracellular ions impair excitation-contraction coupling, while decreased autonomic responsiveness and autonomic neuropathy impair its regulation. Extensive structural abnormalities also occur, which have deleterious mechanical and functional consequences.

Homocysteine and heart failure: a review of investigations from the Framingham Heart Study

High plasma homocysteine levels are associated with a moderately increased risk of cardiovascular disease, particularly of atherosclerotic events. We review the association of plasma homocysteine with heart failure, with a specific focus on a series of previously published investigations from the community-based Framingham Heart Study that evaluated the relations of plasma homocysteine levels with overt heart failure, and with its key antecedents, echocardiographic left ventricular (LV) mass and hypertension. In the Framingham sample, higher plasma homocysteine levels were associated with increased risk of new-onset heart failure in both men and women, with a more continuous and graded relation being observed in women. A positive relation between homocysteine and LV mass was observed in women, but not in men; this may underlie the stronger relations of homocysteine to heart failure risk in women. Plasma homocysteine was not associated with hypertension incidence prospectively in either sex. The relations of increased homocysteine to heart failure (in both sexes) and to greater LV mass (in women) noted in the Framingham sample should be confirmed in other community-based samples. Secondary analyses of heart failure outcomes in ongoing randomized clinical trials may provide insights into whether lowering of plasma homocysteine levels is associated with a reduction in LV mass and/or a reduction of heart failure risk.