Effect of long-term hyperhomocysteinemia on myocardial structure and function in hypertensive rats

Demand for Water-Soluble Vitamins in a Group of Patients with CKD versus Interventions and Supplementation-A Systematic Review

BACKGROUND

Increasingly, chronic kidney disease (CKD) is becoming an inevitable consequence of obesity, metabolic syndrome, and diabetes. As the disease progresses, and through dialysis, the need for and loss of water-soluble vitamins both increase. This review article looks at the benefits and possible risks of supplementing these vitamins with the treatment of CKD.

METHODS

Data in the PubMed and Embase databases were analyzed. The keywords "chronic kidney disease", in various combinations, are associated with thiamin, riboflavin, pyridoxine, pantothenic acid, folates, niacin, cobalamin, and vitamin C. This review focuses on the possible use of water-soluble vitamin supplementation to improve pharmacological responses and the overall clinical condition of patients.

RESULTS

The mechanism of supportive supplementation is based on reducing oxidative stress, covering the increased demand and losses resulting from the treatment method. In the initial period of failure (G2-G3a), it does not require intervention, but later, especially in the case of inadequate nutrition, the inclusion of supplementation with folate and cobalamin may bring benefits. Such supplementation seems to be a necessity in patients with stage G4 or G5 (uremia). Conversely, the inclusion of additional B6 supplementation to reduce CV risk may be considered. At stage 3b and beyond (stages 4-5), the inclusion of niacin at a dose of 400-1000 mg, depending on the patient's tolerance, is required to lower the phosphate level. The inclusion of supplementation with thiamine and other water-soluble vitamins, especially in peritoneal dialysis and hemodialysis patients, is necessary for reducing dialysis losses. Allowing hemodialysis patients to take low doses of oral vitamin C effectively reduces erythropoietin dose requirements and improves anemia in functional iron-deficient patients. However, it should be considered that doses of B vitamins that are several times higher than the recommended dietary allowance of consumption may exacerbate left ventricular diastolic dysfunction in CKD patients.

CONCLUSIONS

Taking into account the research conducted so far, it seems that the use of vitamin supplementation in CKD patients may have a positive impact on the treatment process and maintaining a disease-free condition.

Homocysteine as a Predictor of Paroxysmal Atrial Fibrillation-Related Events: A Scoping Review of the Literature

High levels of homocysteine (Hcy) have been linked with adverse cardiovascular outcomes, such as arrhythmias and stroke. In the context of paroxysmal atrial fibrillation (PAF), hyperhomocysteinemia has been demonstrated to be an independent predictor of future events. The aim of this report was to address the potential value of Hcy levels in predicting future paroxysms of atrial fibrillation (AF), as well as to identify the potential mechanisms of action. We searched PubMed and the Cochrane Database on 16 January 2022. Keywords used were homocysteine or hyperhomocysteinemia paired with a total of 67 different keywords or phrases that have been implicated with the pathogenesis of AF. We included primary reports of clinical and non-clinical data in the English language, as well as systematic reviews with or without meta-analyses. We placed no time constraints on our search strategy, which yielded 3748 results. Following title review, 3293 reports were excluded and 455 reports were used for title and abstract review, after which 109 reports were finally used for full-text review. Our review indicates that Hcy levels seem to hold a predictive value in PAF. Herein, potential mechanisms of action are presented and special considerations are made for clinically relevant diagnostic procedures that could complement plasma levels in the prediction of future PAF events. Finally, gaps of evidence are identified and considerations for future clinical trial design are presented.

Low Dose of Folic Acid Can Ameliorate Hyperhomocysteinemia-Induced Cardiac Fibrosis and Diastolic Dysfunction in Spontaneously Hypertensive Rats

To evaluate whether lowering plasma homocysteine (Hcy) levels at different doses of folic acid (FA) could reduce cardiac fibrosis and diastolic dysfunction in spontaneously hypertensive rats (SHRs) with hyperhomocysteinemia (Hhcy) and investigate the possible mechanism of action.We randomly divided 32 male SHRs into control, Hhcy, Hhcy + low-dose FA (LFA), and Hhcy + high-dose FA (HFA) groups. Echocardiography and Masson staining of cardiac tissue were used to assess diastolic function and cardiac fibrosis. Blood pressure (BP) and Hcy levels were measured during the experiment. We also measured the indicators of oxidative stress (OS) and examined the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) genes and proteins using real-time polymerase chain reaction (PCR), immunohistochemistry, and western blotting to explore the possible mechanism of action.FA treatment reversed SHR cardiomyocyte interstitial and perivascular collagen deposition and diastolic dysfunction exacerbated by Hhcy. These effects were associated with promoting the translocation of Nrf2 from the cytoplasm to the nucleus, activating HO-1 expression and inhibiting OS. However, HFA did not show any additional benefit from LFA in reducing cardiac injury.Even at a low dose, FA can ameliorate Hhcy-induced cardiac fibrosis and diastolic dysfunction in SHRs by activating Nrf2/HO-1 pathway and inhibiting OS, independent of BP, providing evidence for the efficacy of LFA in the treatment of hypertension associated with Hhcy.

Hyperhomocysteinemia-induced Nrf2/HO-1 pathway suppression aggravates cardiac remodeling of hypertensive rats

ABJECTIVE

Interaction of hypertension and hyperhomocysteinemia (HHcy) leads to enhanced cardiac remodeling in hypertensive heart disease. However, the mechanism of collagen accumulation and cardiac remodeling remains unclear. In this study, we attempted to evaluate the relationship between hypertension and HHcy in the context of cardiac remodeling and to explore its mechanism of action.

METHODS

Wistar Kyoto (WKY) and spontaneous hypertension rats (SHR) were randomly divided into four groups, namely WKY group, WKY + HHcy group, SHR group and SHR + HHcy group. We measured blood pressure (BP), plasma homocysteine (Hcy), serum superoxide dismutase (SOD) and serum malondialdehyde (MDA). We also examined cardiac histopathology and gene and protein expression levels of Nrf2 and HO-1.

RESULTS

Compared with the WKY group, myocardial interstitial and perivascular collagen deposition in the WKY + HHcy group, the SHR group and the SHR + HHcy group increased successively, indicating that cardiac remodeling gradually increased, and HHcy aggravated cardiac remodeling was more serious in hypertensive rats. SOD decreased gradually in the four groups, while MDA was on the contrary. WKY + HHcy and SHR + HHcy groups both suppressed Nrf2 and HO-1 expression and inhibited the translocation of Nrf2 from cytoplasm to nucleus compared with their control groups, and the SHR + HHcy group had a stronger inhibitory effect.

CONCLUSION

HHcy enhanced cardiac remodeling in rats by enhancing oxidative stress, suppressing the Nrf2/HO-1 pathway and Nrf2 nuclear transport, and this inhibitory effect was stronger in the context of hypertension.

Associations of methyl donor and methylation inhibitor levels during anti-oxidant therapy in heart failure

Redox balance and methylation are crucial to homeostasis and are linked by the methionine-homocysteine cycle. We examined whether differences in methylation potential, measured as plasma levels of S-adenosyl methionine (SAM) and S-adenosyl homocysteine (SAH), occur at baseline and during anti-oxidant therapy with the xanthine oxidase inhibitor allopurinol in patients with heart failure with reduced ejection fraction. We analyzed plasma samples collected at baseline and 24 weeks in the Xanthine Oxidase Inhibition for Hyperuricemic Heart Failure Patients (EXACT-HF) study, which randomized patients with heart failure with reduced ejection fraction to allopurinol or placebo. Associations between plasma levels of SAM, SAH, SAM/SAH ratio, and outcomes, including laboratory markers and clinical events, were assessed. Despite randomization, median SAM levels were significantly lower at baseline in the allopurinol group. SAH levels at 24 weeks, and change in SAM from baseline to week 24, were significantly higher in the group of patients randomized to allopurinol compared to the placebo group. A significant correlation was observed between change in SAH levels and change in plasma uric acid (baseline to 24-week changes) in the allopurinol group. There were no significant associations between levels of SAM, SAH, and SAM/SAH ratio and clinical outcomes. Our results demonstrate significant biological variability in SAM and SAH levels at baseline and during treatment with an anti-oxidant and suggest a potential mechanism for the lack of efficacy observed in trials of anti-oxidant therapy. These data also highlight the need to explore personalized therapy for heart failure.

Small animal models of heart failure

Heart disease is a major cause of death worldwide with increasing prevalence, which urges the development of new therapeutic strategies. Over the last few decades, numerous small animal models have been generated to mimic various pathomechanisms contributing to heart failure (HF). Despite some limitations, these animal models have greatly advanced our understanding of the pathogenesis of the different aetiologies of HF and paved the way to understanding the underlying mechanisms and development of successful treatments. These models utilize surgical techniques, genetic modifications, and pharmacological approaches. The present review discusses the strengths and limitations of commonly used small animal HF models, which continue to provide crucial insight and facilitate the development of new treatment strategies for patients with HF.

Hyperhomocysteinemia and myocardial remodeling in the sand rat, Psammomys obesus

OBJECTIVE

Numerous studies have shown that a methionine-rich diet induces hyperhomocysteinemia (Hhcy), a risk factor for cardiovascular diseases. The objective of the present study was to determine the involvement of Hhcy in cardiac remodeling in the sand rat Psammomys obesus.

MATERIALS AND METHODS

An experimental Hhcy was induced, in the sand rat Psammomys obesus, by intraperitoneal injection of 300 mg/kg of body weight/day of methionine for 1 month. The impact of Hhcy on the cellular and matricial structures of the myocardium was analyzed with histological techniques (Masson trichrome and Sirius red staining). Immunohistochemistry allowed us to analyze several factors involved in myocardial remodeling, such as fibrillar collagen I and III, metalloproteases (MMP-2 and -9) and their inhibitors (TIMP-1 and -2), TGF-β1 and activated caspase 3.

RESULTS

Our results show that Hhcy induced by an excess of methionine causes, in the myocardium of Psammomys obesus, a significant accumulation of fibrillar collagens I and III at the interstitial and perivascular scales, indicating the appearance of fibrosis, which is associated with an immuno-expression increase of TGF-β1, MMP-9 and TIMP-2 and an immuno-expression decrease of MMP-2 and TIMP-1. Also, Hhcy induces apoptosis of some cardiomyocytes and cardiac fibroblasts by increasing of activated caspase 3 expression. These results highlight a remodeling of cardiac tissue in hyperhomocysteinemic Psammomys obesus.

In Vivo and In Vitro Effects of Vasopressin V2 Receptor Antagonism on Myocardial Fibrosis in Rats

BACKGROUND

Myocardial fibrosis is a major pathophysiologic substrate of heart failure with preserved ejection fraction. Vasopressin is an important therapeutic target in heart failure with preserved ejection fraction since it can modulate fluid balance, and based on a few studies, myocardial matrix deposition. Hence we examined the role of vasopressin antagonism in modulating myocardial matrix metabolism in vivo and in vitro.

MATERIALS AND METHODS

In vivo studies utilized an established model of hyperhomocysteinemia-induced myocardial fibrosis in Sprague-Dawley rats combined with high salt diet; in vivo studies also utilized the same profibrotic stimuli of homocysteine and NaCl in cultured rat cardiac fibroblasts.

RESULTS

Hyperhomocysteinemia combined with high-salt diet promoted myocardial fibrosis, profibrotic and matrix gene expression and tolvaptan attenuated all these in vivo effects. In cultured cardiac fibroblasts, combined treatment with homocysteine and NaCl increased profibrotic and matrix gene expression and activation of PI3/Akt pathway; all these effects were attenuated by tolvaptan Vasopressin levels, gene expression and V2 receptor expression were increased in vivo and in vitro on exposure to profibrotic stimuli, and tolvaptan attenuated these in vivo and in vitro effects.

CONCLUSIONS

Antagonism of vasopressin V2 receptor, via direct actions on cardiac fibroblast, attenuates myocardial matrix deposition.

Astaxanthin Attenuates Homocysteine-Induced Cardiotoxicity in Vitro and in Vivo by Inhibiting Mitochondrial Dysfunction and Oxidative Damage

Homocysteine (Hcy) as an independent risk factor contributes to the occurrence and development of human cardiovascular diseases (CVD). Induction of oxidative stress and apoptosis was commonly accepted as the major mechanism in Hcy-induced cardiotoxicity. Astaxanthin (ATX) as one of the most powerful antioxidants exhibits novel cardioprotective potential against Hcy-induced endothelial dysfunction. However, the protective effect and mechanism of ATX against Hcy-induced cardiotoxicity in cardiomyocytes have not been elucidated yet. Herein, H9c2 rat cardiomyocytes and Hcy-injured animal model were employed in the present study. The MTT, flow cytometry analysis (FCM), TUNEL-DAPI and western blotting results all demonstrated that ATX significantly alleviated Hcy-induced cytotoxicity in H9c2 cells through inhibition of mitochondria-mediated apoptosis. The JC-1 and Mito-tracker staining both revealed that ATX pre-treatment blocked Hcy-induced mitochondrial dysfunction by regulating Bcl-2 family expression. Moreover, DCFH-DA and Mito-SOX staining showed that ATX effectively attenuated Hcy-induced oxidative damage via scavenging intracellular reactive oxygen species (ROS). Importantly, the ELISA and immunohistochemical results indicated that Hcy-induced cardiotoxicity in vivo was also significantly inhibited by ATX through inhibition of oxidative damage and apoptosis, and improvement of the angiogenesis. Taken together, our results demonstrated that ATX suppressed Hcy-induced cardiotoxicity in vitro and in vivo by inhibiting mitochondrial dysfunction and oxidative damage. Our findings validated the strategy of using ATX may be a highly efficient way to combat Hcy-mediated human CVD.

Preconditioning potential of purmorphamine: a hedgehog activator against ischaemic reperfusion injury in ovariectomised rat heart

OBJECTIVE

The present study was been designed to investigate the role and pharmacological potential of hedgehog in oestrogen-deficient rat heart.

METHODS

Oestrogen deficiency was produced in female Wistar rats by the surgical removal of both ovaries and these animals were used four weeks later. Isolated rat heart was subjected to 30 min ischaemia followed by 120 min of reperfusion (I/R). The heart was subjected to pharmacological preconditioning with the hedgehog agonist purmorphamine (1μM) and GDC-0449, a hedgehog antagonist, in the last episode of reperfusion before I/R. Myocardial infarction was assessed in terms of the increase in lactate dehydrogenase (LDH), creatinine kinase-MB (CK-MB), myeloperoxidase (MPO) level and infarct size (triphenyltetrazolium chloride staining). Immunohistochemistry analysis was done for the assessment of tumour necrosis factor (TNF)-α level in cardiac tissue. eNOS expression was estimated by rt-PCR.

RESULTS

Pharmacological preconditioning with purmorphamine significantly attenuated I/R-induced myocardial infarction, TNF-α, MPO level and release of LDH and CK-MB compared to the I/R control group. However, GDC-0449 prevented the ameliorative preconditioning effect of estradiol.

CONCLUSION

It may be concluded that the hedgehog agonist purmorphamine prevents the ovariectomised heart from ischaemic reperfusion injury.

Elevated plasma homocysteine level is possibly associated with skin sclerosis in a series of Japanese patients with systemic sclerosis

Homocysteine is a sulfhydryl-containing amino acid that is derived from dietary methionine, and there has been increasing evidence that elevated plasma homocysteine levels are associated with increased risk of cardiovascular diseases, including carotid, coronary and peripheral arterial disease (PAD). The association of plasma homocysteine levels with peripheral vascular involvements, such as Raynaud phenomenon (RP), digital ulcers (DU) in systemic sclerosis (SSc) patients has not been well studied. The objective of this study was to examine plasma homocysteine levels and their clinical associations in patients with SSc. Plasma homocysteine levels in 151 Japanese patients with SSc and 20 healthy controls were examined. No significant differences were observed in plasma homocysteine levels between SSc patients and healthy individuals. Demographic and clinical features of the SSc patients revealed that severe skin sclerosis, anti-topoisomerase I antibody positivity, complications of DU, acro-osteolysis (AO) and interstitial lung disease (ILD) were significantly more prevalent among the patients with elevated plasma homocysteine levels. The plasma homocysteine levels were positively correlated with modified Rodnan total skin score. The plasma homocysteine levels in the SSc patients with DU, AO and ILD were significantly higher than those in the SSc without DU, AO and ILD, respectively. Plasma homocysteine levels did not correlate with either the mean or max intima-media thickness (IMT) or plaque score, suggesting that plasma homocysteine levels might not be associated with carotid artery atherosclerosis in SSc patients. The measurement of plasma homocysteine levels in SSc patients might be useful for the risk stratifications of severe skin sclerosis, DU and AO.

Influence of serum adiponectin level and SNP +45 polymorphism of adiponectin gene on myocardial fibrosis

Adiponectin plays an important role in the development of hypertension, atherosclerosis, and cardiomyocyte hypertrophy, but very little was known about the influence of serum adiponectin or the adiponectin gene polymorphism on myocardial fibrosis. Our study investigates the influence of the SNP +45 polymorphism of the adiponectin gene and serum levels of adiponectin on myocardial fibrosis in patients with essential hypertension. A case-control study was conducted on 165 hypertensive patients and 126 normotensive healthy controls. The genotypes of adiponectin gene polymorphisms were detected by the polymerase chain reaction (PCR) method. Serum concentrations of procollagen were measured by a double antibody sandwich enzyme-linked immunosorbent assay (ELISA) in all subjects. The integrated backscatter score (IBS) was measured in the left ventricular myocardium using echocardiography. The serum levels of adiponectin in hypertensive patients were significantly lower than those in the normal control group ((2.69±1.0) μg/ml vs. (4.21±2.89) μg/ml, respectively, P<0.001). The serum levels of type-I procollagen carboxyl end peptide (PICP) and type-III procollagen ammonia cardinal extremity peptide (PIIINP) in the hypertension group were significantly higher than those in the control group. In the hypertension group, serum levels of adiponectin were significantly and negatively related to the average acoustic intensity and corrected acoustic intensity of the myocardium (r=0.46 and 0.61, respectively, P<0.05 for both). The serum levels of PICP and PIIINP were significantly different among the three genotypes of SNP +45 (P<0.01). Logistic regression analyses showed that sex and genotype (GG+GT) were the major risk factors of myocardial fibrosis in hypertensive patients (OR=5.343 and 3.278, respectively, P<0.05). These data suggest that lower levels of adiponectin and SNP +45 polymorphism of the adiponectin gene are likely to play an important role in myocardial fibrosis in hypertensive patients.

Effects of direct Renin inhibition on myocardial fibrosis and cardiac fibroblast function

Myocardial fibrosis, a major pathophysiologic substrate of heart failure with preserved ejection fraction (HFPEF), is modulated by multiple pathways including the renin-angiotensin system. Direct renin inhibition is a promising anti-fibrotic therapy since it attenuates the pro-fibrotic effects of renin in addition to that of other effectors of the renin-angiotensin cascade. Here we show that the oral renin inhibitor aliskiren has direct effects on collagen metabolism in cardiac fibroblasts and prevented myocardial collagen deposition in a non-hypertrophic mouse model of myocardial fibrosis. Adult mice were fed hyperhomocysteinemia-inducing diet to induce myocardial fibrosis and treated concomitantly with either vehicle or aliskiren for 12 weeks. Blood pressure and plasma angiotensin II levels were normal in control and hyperhomocysteinemic mice and reduced to levels lower than observed in the control group in the groups treated with aliskiren. Homocysteine-induced myocardial matrix gene expression and fibrosis were also prevented by aliskiren. In vitro studies using adult rat cardiac fibroblasts also showed that aliskiren attenuated the pro-fibrotic pattern of matrix gene and protein expression induced by D,L, homocysteine. Both in vivo and in vitro studies demonstrated that the Akt pathway was activated by homocysteine, and that treatment with aliskiren attenuated Akt activation. In conclusion, aliskiren as mono-therapy has potent and direct effects on myocardial matrix turnover and beneficial effects on diastolic function.

Moderate hyperhomocysteinemia provokes dysfunction of cardiovascular autonomic system and liver oxidative stress in rats

Hyperhomocysteinemia (HHcy) is associated with cardiovascular disease, atherosclerosis and reactive oxygen species generation. Thus, our aim was to investigate whether there was an association between HHcy, blood pressure, autonomic control and liver oxidative stress. Male Wistar rats were divided into 2 groups and treated for 8weeks: one group (control, CO) received tap water, while the other group (methionine, ME) was given a 100mg/kg of methionine in water by gavage. Two catheters were implanted into the femoral artery and vein to record arterial pressure (AP) and heart rate (HR) and drug administration. Signals were recorded by a data acquisition system. Baroreflex sensitivity was evaluated by HR responses to AP changes induced by vasoactive drugs. HR variability and AP variability were performed by spectral analysis in time and frequency domains to evaluate the contribution of the sympathetic and parasympathetic modulation. Lipid peroxidation and antioxidant enzyme activities were evaluated by measuring superoxide dismutase, catalase and glutathione peroxidase in liver homogenates. The ME group presented a significant increase in systolic arterial pressure (118±9 vs 135±6mmHg), diastolic arterial pressure (81±6 vs. 92±4) and mean arterial pressure (95±7 vs. 106±6). In addition, pulse interval variability presented a significant decrease (41%), while the low frequency component of AP was significantly increased (delta P=6.24mmHg(2)) in the ME group. We also found a positive association between lipid peroxidation and cardiac sympathetic modulation, sympathetic and vagal modulation ratio and systolic pressure variability. Collectively, these findings showed that HHcy induced dysfunction of cardiovascular autonomic system and liver oxidative stress.

Rodent models of heart failure: an updated review

Heart failure (HF) is one of the major health and economic burdens worldwide, and its prevalence is continuously increasing. The study of HF requires reliable animal models to study the chronic changes and pharmacologic interventions in myocardial structure and function and to follow its progression toward HF. Indeed, during the past 40 years, basic and translational scientists have used small animal models to understand the pathophysiology of HF and find more efficient ways of preventing and managing patients suffering from congestive HF (CHF). Each species and each animal model has advantages and disadvantages, and the choice of one model over another should take them into account for a good experimental design. The aim of this review is to describe and highlight the advantages and drawbacks of some commonly used HF rodents models, including both non-genetically and genetically engineered models, with a specific subchapter concerning diastolic HF models.

Adverse myocardial effects of B-vitamin therapy in subjects with chronic kidney disease and hyperhomocysteinaemia

BACKGROUND & AIMS

Hyperhomocysteinaemia (HHCY), a common finding in patients with chronic kidney disease (CKD), has been shown to contribute to adverse cardiac remodelling and failure. We hypothesised that in human subjects with CKD, HHCY would be associated with myocardial dysfunction, and that homocysteine (HCY)-lowering therapy would improve myocardial remodelling and heart-failure (HF) outcomes.

METHODS AND RESULTS

Post hoc analysis of the Homocysteinemia in Kidney and End Stage Renal Disease (HOST) trial (n=2056) was performed to determine if HCY-lowering therapy with high dose B vitamins affects HF outcomes in patients with CKD. In addition, effects on myocardial remodelling were assessed in a subgroup of 220 trial subjects who had transthoracic echocardiograms done before study randomisation and during the course of the study as part of their routine clinical care. HF outcomes were not significantly affected by treatment compared to the placebo. HCY levels were inversely correlated with diastolic function (R=-0.21; p=0.038). Vitamin therapy resulted in a significant increase in left atrial size (+0.15±0.8 cm vs. -0.13±0.07 cm; p=0.0095). No other echocardiographic parameters were significantly associated with baseline HCY levels or changes with vitamin therapy.

CONCLUSION

HHCY is associated with diastolic dysfunction in patients with CKD. However, B-vitamin therapy did not improve HF outcomes despite lowering of plasma HCY levels, and was associated with an increase in left atrial size, which is a surrogate for worsening left ventricular diastolic dysfunction. These findings suggest that high-dose B vitamin therapy may be harmful in patients with CKD.

Methoxistasis: integrating the roles of homocysteine and folic acid in cardiovascular pathobiology

Over the last four decades, abnormalities in the methionine-homocysteine cycle and associated folate metabolism have garnered great interest due to the reported link between hyperhomocysteinemia and human pathology, especially atherothrombotic cardiovascular disease. However, clinical trials of B-vitamin supplementation including high doses of folic acid have not demonstrated any benefit in preventing or treating cardiovascular disease. In addition to the fact that these clinical trials may have been shorter in duration than appropriate for modulating chronic disease states, it is likely that reduction of the blood homocysteine level may be an oversimplified approach to a complex biologic perturbation. The methionine-homocysteine cycle and folate metabolism regulate redox and methylation reactions and are, in turn, regulated by redox and methylation status. Under normal conditions, a normal redox-methylation balance, or “methoxistasis”, exists, coordinated by the methionine-homocysteine cycle. An abnormal homocysteine level seen in pathologic states may reflect a disturbance of methoxistasis. We propose that future research should be targeted at estimating the deviation from methoxistasis and how best to restore it. This approach could lead to significant advances in preventing and treating cardiovascular diseases, including heart failure.

Protective role of fibrates in cardiac ischemia/reperfusion

Prevention of myocardial injury has been considered as the most important therapeutic challenge of today. Fibrates, the agonists of the peroxisome proliferator-activated receptor (PPAR)-a receptor, have been regarded as potent therapeutic agents in this context. Hence, the present study has been designed to investigate the effect of fibrates, i.e., Clofibrate and Fenofibrate, the potent agonists PPAR-a, on ischemia-reperfusion (I/R)-induced myocardial injury. The isolated Langendorff-perfused rat hearts were subjected to global ischemia for 30 minutes followed by reperfusion for 120 minutes. Myocardial infarct size and the release of lactate dehydrogenase (LDH) and creatine kinase (CK) in coronary effluent have been conducted to assess the degree of cardiac injury. Moreover, the oxidative stress in the heart was assessed by measuring lipid peroxidation, superoxide anion generation, and reduced glutathione. Clofibrate and Fenofibrate showed cardioprotection against I/R-induced myocardial injury in rat hearts as assessed in terms of reductions in myocardial infarct size, LDH, and CK levels in coronary effluent along with reduction in I/R-induced oxidative stress. It may be concluded that the observed cardioprotective potential of Clofibrate and Fenofibrate against I/R-induced myocardial injury was due to the reductions in infarct size and oxidative stress.

Cardioprotective potential of simvastatin in the hyperhomocysteinemic rat heart

The present study investigated the probable role of simvastatin, 3-hydroxymethyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitor, in abrogated cardioprotection in hyperhomocysteinemic (Hhcy) rat hearts. Isolated Langendorff's perfused normal and Hhcy rat hearts were subjected to 30-min global ischemia (I) followed by 120-min reperfusion (R). Assessment of myocardial damage was done by measuring infarct size and analyzing the release of lactate dehydrogenase (LDH) and creatine kinase (CK-MB) in coronary effluent. In addition, the oxidative stress in the heart was assessed by measuring lipid peroxidation and superoxide anion generation. I/R produced myocardial injury in normal and Hhcy rat hearts by increasing myocardial infarct size, LDH and CK in coronary effluent and oxidative stress. Hhcy rat hearts showed enhanced myocardial injury and high oxidative stress as compared to normal hearts. Treatment with Simvastatin (10 μMol) afforded cardioprotection against I/R-induced myocardial injury in normal and hyperhomocysteinemic rat hearts as assessed in terms of reductions in myocardial infarct size, LDH and CK levels in coronary effluent and oxidative stress. The reductions in the high degree of oxidative stress may be responsible for the observed cardioprotection afforded by simvastatin against I/R-induced myocardial injury in normal and hyperhomocysteinemic rat hearts.

Methyl donor deficiency induces cardiomyopathy through altered methylation/acetylation of PGC-1α by PRMT1 and SIRT1

Cardiomyopathies occur by mechanisms that involve inherited and acquired metabolic disorders. Both folate and vitamin B12 deficiencies are associated with left ventricular dysfunction, but mechanisms that underlie these associations are not known. However, folate and vitamin B12 are methyl donors needed for the synthesis of S-adenosylmethionine, the substrate required for the activation by methylation of regulators of energy metabolism. We investigated the consequences of a diet lacking methyl donors in the myocardium of weaning rats from dams subjected to deficiency during gestation and lactation. Positron emission tomography (PET), microscope and metabolic examinations evidenced a myocardium hypertrophy, with cardiomyocyte enlargement, disturbed mitochondrial alignment, lipid droplets, decreased respiratory activity of complexes I and II and decreased S-adenosylmethionine:S-adenosylhomocysteine ratio. The increased concentrations of triglycerides and acylcarnitines were consistent with a deficit in fatty acid oxidation. These changes were explained by imbalanced acetylation/methylation of PGC-1α, through decreased expression of SIRT1 and PRMT1 and decreased S-adenosylmethionine:S-adenosylhomocysteine ratio, and by decreased expression of PPARα and ERRα. The main changes of the myocardium proteomic study were observed for proteins regulated by PGC-1α, PPARs and ERRα. These proteins, namely trifunctional enzyme subunit α-complex, short chain acylCoA dehydrogenase, acylCoA thioesterase 2, fatty acid binding protein-3, NADH dehydrogenase (ubiquinone) flavoprotein 2, NADH dehydrogenase (ubiquinone) 1α-subunit 10 and Hspd1 protein, are involved in fatty acid oxidation and mitochondrial respiration. In conclusion, the methyl donor deficiency produces detrimental effects on fatty acid oxidation and energy metabolism of myocardium through imbalanced methylation/acetylation of PGC-1α and decreased expression of PPARα and ERRα. These data are of pathogenetic relevance to perinatal cardiomyopathies.

Homocysteine induces phosphatidylserine exposure in cardiomyocytes through inhibition of Rho kinase and flippase activity

AIMS

Increased levels of homocysteine (Hcy) form an independent risk factor for cardiovascular disease. In a previous study we have shown that Hcy induced phosphatidylserine (PS) exposure to the outer leaflet of the plasma membrane in cardiomyocytes, inducing a pro-inflammatory phenotype. In the present study the mechanism(s) involved in Hcy-induced PS exposure were analyzed.

METHODS

H9c2 rat cardiomyoblasts were subjected to 2.5 mM D,L-Hcy and analyzed for RhoA translocation and activity, Rho Kinase (ROCK) activity and expression and flippase activity. In addition, the effect of ROCK inhibition with Y27632 on Hcy-induced PS exposure and flippase activity was analyzed. Furthermore, GTP and ATP levels were determined.

RESULTS

Incubation of H9c2 cells with 2.5 mM D,L-Hcy did not inhibit RhoA translocation to the plasma membrane. Neither did it inhibit activation of RhoA, even though GTP levels were significantly decreased. Hcy did significantly inhibit ROCK activation, but not its expression, and did inhibit flippase activity, in advance of a significant decrease in ATP levels. ROCK inhibition via Y27632 did not have significant added effects on this.

CONCLUSION

Hcy induced PS exposure in the outer leaflet of the plasma membrane in cardiomyocytes via inhibition of ROCK and flippase activity. As such Hcy may induce cardiomyocytes vulnerable to inflammation in vivo in hyperhomocysteinaemia patients.

Homocysteine-induced cardiomyocyte apoptosis and plasma membrane flip-flop are independent of S-adenosylhomocysteine: a crucial role for nuclear p47(phox)

We previously found that homocysteine (Hcy) induced plasma membrane flip-flop, apoptosis, and necrosis in cardiomyocytes. Inactivation of flippase by Hcy induced membrane flip-flop, while apoptosis was induced via a NOX2-dependent mechanism. It has been suggested that S-adenosylhomocysteine (SAH) is the main causative factor in hyperhomocysteinemia (HHC)-induced pathogenesis of cardiovascular disease. Therefore, we evaluated whether the observed cytotoxic effect of Hcy in cardiomyocytes is SAH dependent. Rat cardiomyoblasts (H9c2 cells) were treated under different conditions: (1) non-treated control (1.5 nM intracellular SAH with 2.8 μM extracellular L -Hcy), (2) incubation with 50 μM adenosine-2,3-dialdehyde (ADA resulting in 83.5 nM intracellular SAH, and 1.6 μM extracellular L -Hcy), (3) incubation with 2.5 mM D, L -Hcy (resulting in 68 nM intracellular SAH and 1513 μM extracellular L -Hcy) with or without 10 μM reactive oxygen species (ROS)-inhibitor apocynin, and (4) incubation with 100 nM, 10 μM, and 100 μM SAH. We then determined the effect on annexin V/propodium iodide positivity, flippase activity, caspase-3 activity, intracellular NOX2 and p47(phox) expression and localization, and nuclear ROS production. In contrast to Hcy, ADA did not induce apoptosis, necrosis, or membrane flip-flop. Remarkably, both ADA and Hcy induced a significant increase in nuclear NOX2 expression. However, in contrast to ADA, Hcy additionally induced nuclear p47(phox) expression, increased nuclear ROS production, and inactivated flippase. Incubation with SAH did not have an effect on cell viability, nor on flippase activity, nor on nuclear NOX2-, p47phox expression or nuclear ROS production. HHC-induced membrane flip-flop and apoptosis in cardiomyocytes is due to increased Hcy levels and not primarily related to increased intracellular SAH, which plays a crucial role in nuclear p47(phox) translocation and subsequent ROS production.

Fattening by deprivation: methyl balance and perinatal cardiomyopathy

Folate deficiency during pregnancy is associated with reduced birth weight, and a low birth weight is associated with increased cardiometabolic risk in adulthood. In the study by Moreno Garcia, Guéant-Rodriguez and colleagues reported in the current issue of the Journal of Pathology, the effect of methyl group deprivation in pregnancy on the neonatal myocardium was investigated. By utilizing a diet deficient in folate, vitamin B(12) and choline, the authors created a significant deficit of methyl groups in the fetus. During the weaning period and the concomitant shift from the relative hypoxia and glucose dependence of the gestational period to the aerobic, milk-derived high-fat metabolic environment of the weaning phase, the offspring developed a myocardial hypertrophy associated with disordered fatty acid oxidation and mitochondrial dysfunction. The functionality of PGC-1α, a master regulator of metabolic pathways including mitochondrial energetics and fatty acid oxidation, was found to be reduced in the methyl-deprived group, due to an imbalance in the ratio of methylation to acetylation. This study demonstrates that maternal methyl deprivation could 'prime' the fetus by reducing its ability to oxidize fatty acids in the myocardium, thereby causing lipid accumulation and myocardial hypertrophy during exposure to high-fat diet in the weaning phase. This study has important implications for clinical perinatal cardiomyopathy and for the effect of maternal methyl group deprivation on the future risk of cardiovascular disease, and also potentially in enhancing the understanding of the elusive link between hyperhomocysteinaemic states in the adult and cardiovascular disease.

Homocysteine thiolactone induces cardiac dysfunction: role of oxidative stress

This study investigates the cardiac functioning in male Wistar rats after treatments with methionine and homocysteine thiolactone (HcyT). The rats were distributed into 3 groups and treated for 8 weeks. Group I was the control (CO) group, given water, group II was treated with methionine, and group III with HcyT (100 mg/kg). Morphometric and functional cardiac parameters were evaluated by echocardiography. Superoxide dismutase (SOD), catalase, and glutathione S-transferase activities, chemiluminescence, thiobarbituric acid reactive substances, and immunocontent were measured in the myocardium. Hyperhomocysteinemiawas observed in rats submitted to the both treatments. The results showed diastolic function was compromised in HcyT group, seen by the increase of E/A (peak velocity of early (E) and late (A) diastolic filling) ratio, decrease in deceleration time of E wave and left ventricular isovolumic relaxation time. Myocardial performance index was increased in HcyT group and was found associated with increased SOD immunocontent. HcyT group demonstrated an increase in SOD, catalase, and glutatione S-transferase activity, and chemiluminescence and thiobarbituric acid reactive substances. Overall, these results indicated that HcyT induces a cardiac dysfunction and could be associated with oxidative stress increase in the myocardium.

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.

Quo vadis: whither homocysteine research?

Four decades of research on the link between hyperhomocysteinemia and cardiovascular disease has led to a crossroads. Several negative studies on the role of homocysteine-lowering B-vitamin therapy in reducing the risk of atherothrombotic cardiovascular disease have dampened enthusiasm for this important field of research. In this review, we assess the present state of homocysteine research and suggest potential avenues that would help to clarify the purported link between the plasma homocysteine level and cardiovascular risk. We address several questions raised by the findings of various basic, epidemiological and clinical studies and attempt to construct a framework that we believe will allow us to address the fundamental unresolved issues in this controversial area, specifically focusing on the risk of coronary vascular disease and cardiac failure. This review should allow researchers to deconstruct this complex field into separate areas that, when addressed adequately, may lead to findings that elucidate the overall link between hyperhomocysteinemia and cardiovascular disease and allow the design of appropriate clinical trials.

A review of state-of-the-art stereology for better quantitative 3D morphology in cardiac research

The aim of stereological methods in biomedical research is to obtain quantitative information about three-dimensional (3D) features of tissues, cells, or organelles from two-dimensional physical or optical sections. With immunogold labeling, stereology can even be used for the quantitative analysis of the distribution of molecules within tissues and cells. Nowadays, a large number of design-based stereological methods offer an efficient quantitative approach to intriguing questions in cardiac research, such as "Is there a significant loss of cardiomyocytes during progression from ventricular hypertrophy to heart failure?" or "Does a specific treatment reduce the degree of fibrosis in the heart?" Nevertheless, the use of stereological methods in cardiac research is rare. The present review article demonstrates how some of the potential pitfalls in quantitative microscopy may be avoided. To this end, we outline the concepts of design-based stereology and illustrate their practical applications to a wide range of biological questions in cardiac research. We hope that the present article will stimulate researchers in cardiac research to incorporate design-based stereology into their study designs, thus promoting an unbiased quantitative 3D microscopy.

Oxidative and nitrosative stress and apoptosis in the liver of rats fed on high methionine diet: protective effect of taurine

OBJECTIVE

There are few reports about the direct toxic effects of hyperhomocysteinemia on the liver. We investigated oxidative and nitrosative stresses and apoptotic and necrotic changes in the liver of rats fed a high-methionine (HM) diet (2%, w/w) for 6 mo. We also investigated whether taurine, an antioxidant amino acid, is protective against an HM-diet-induced toxicity in the liver.

METHODS

Lipid peroxide levels, nitrotyrosine formation, and non-enzymatic and enzymatic antioxidants were determined in livers of rats fed an HM diet. In addition, apoptosis-related proteins, proapoptotic Bax and antiapoptotic B-cell lymphoma-2 expressions, apoptotic cell count, histopathologic appearance in the liver, and alanine transaminase and aspartate transaminase activities in the serum were investigated.

RESULTS

Plasma homocysteine levels and serum alanine transaminase and aspartate transaminase activities were increased after the HM diet. This diet resulted in increases in lipid peroxide and nitrotyrosine levels and decreases in non-enzymatic and enzymatic antioxidants in liver homogenates in rats. Bax expression increased, B-cell lymphoma-2 expression decreased, and apoptotic cell number increased in livers of rats fed an HM diet. Inflammatory reactions, microvesicular steatosis, and hepatocyte degeneration were observed in the liver after the HM diet. Taurine (1.5%, w/v, in drinking water) administration and the HM diet for 6 mo was found to decrease serum alanine transaminase and aspartate transaminase activities, hepatic lipid peroxide levels, and nitrotyrosine formation without any change in serum homocysteine levels. Decreases in Bax expression, increases in B-cell lymphoma-2 expression, decreases in apoptotic cell number, and amelioration of histopathologic findings were observed in livers of rats fed with the taurine plus HM diet.

CONCLUSION

Our results indicate that taurine has protective effects on hyperhomocysteinemia-induced toxicity by decreasing oxidative and nitrosative stresses, apoptosis, and necrosis in the liver.

Effect of mast cell stabilizers in hyperhomocysteinemia-induced cardiac hypertrophy in rats

BACKGROUND

The present study has been designed to investigate the effect of sodium cromoglycate and ketotifen, mast cell stabilizers in hyperhomocysteinemia-induced cardiac hypertrophy in rats.

METHODS

Rats were administered L-methionine (1.7 g/kg/day PO) for 8 weeks to produce hyperhomocysteinemia. Sodium cromoglycate (24 mg/kg/day IP) and ketotifen (1mg/kg/day IP) treatments were started from first day of administration of L-methionine and continued for 8 weeks. The development of cardiac hypertrophy was assessed in terms of measuring mean arterial blood pressure (MABP), ratio of left ventricular (LV) weight to body weight (LVW/BW), LV wall thickness (LVWT), LV protein content, and LV collagen content. Further, the oxidative stress in heart was assessed by measuring lipid peroxidation, superoxide anion generation, and reduced glutathione (GSH). Moreover, the cardiomyocyte diameter and LV mast cell density were determined using hematoxylin-eosin and toluidine blue staining, respectively.

RESULTS

The L-methionine administration produced hyperhomocysteinemia, which significantly increased MABP, oxidative stress, and density of mast cells and consequently produced cardiac hypertrophy by increasing cardiomyocyte diameter, LVW/BW, LVWT, LV protein and collagen content. However, sodium cromoglycate and ketotifen treatments significantly attenuated hyperhomocysteinemia-induced oxidative stress and pathological cardiac hypertrophy without significantly altering MABP. Moreover, sodium cromoglycate and ketotifen treatments did not affect serum homocysteine levels.

CONCLUSIONS

Thus, it may be concluded that hyperhomocysteinemia-induced cardiac hypertrophy is associated with an increase in oxidative stress and density of mast cells in heart. Sodium cromoglycate and ketotifen may have attenuated hyperhomocysteinemia-induced pathological cardiac hypertrophy, possibly by reducing oxidative stress and preventing the degranulation and increase in density of mast cells.

Effect of anti-oxidant treatment on hyperhomocysteinemia-induced myocardial fibrosis and diastolic dysfunction

BACKGROUND

Recent studies demonstrate that hyperhomocysteinemia is a risk factor for heart failure. Oxidant stress is a major mediator of the pathogenic effects of hyperhomocysteinemia.

METHODS

We utilized a rat model of diet-induced hyperhomocysteinemia to examine whether treatment with an anti-oxidant vitamin (C&E) combination will prevent hyperhomocysteinemia-induced myocardial fibrosis.

RESULTS

Dietary anti-oxidant therapy attenuated hyperhomocysteinemia-induced increases in myocardial oxidant stress and myocardial fibrosis, and diastolic dysfunction.

CONCLUSIONS

Hyperhomocysteinemia acts via oxidant stress to promote myocardial fibrosis and dysfunction. Dietary anti-oxidant therapy could be an important preventive and therapeutic strategy in diastolic heart failure.

Inhibition of left ventricular remodelling in spontaneously hypertensive rats by G alpha q-protein carboxyl terminus imitation polypeptide GCIP-27 is not entirely dependent on blood pressure

The G(q)-protein is located at the convergent point in the signal transduction pathway that leads to ventricular remodelling. In G-protein signalling pathways, the carboxyl terminus of the G(alpha)-subunit plays a vital role in G-protein-receptor interaction. The aim of the present study was to explore the effects of a synthetic G(alphaq) carboxyl terminus imitation peptide, namely GCIP-27, on left ventricular (LV) remodelling and blood pressure in spontaneous hypertensive rats (SHR). In the present study, 10, 30 or 90 microg/kg, i.p., GCIP-27 was administered for 8 weeks to SHR. In addition, another two groups of SHR were treated with either 6 mg/kg losartan or vehicle (saline). Wistar-Kyoto rats were used as controls. Systolic blood pressure (SBP) was measured using the standard tail-cuff method once every 2 weeks. At the end of the experiment, the LV mass index (LVMI) was evaluated. In addition, LV structure and function, collagen content, microstructure and ultrastructure were examined using echocardiography, the hydroxyproline assay, routine light microscopy and transmission electron microscopy, respectively. In the losartan- and GCIP-27 (10, 30 and 90 microg/kg)-treated groups, SBP was decreased significantly compared with that of the vehicle (saline) group. However, even at the highest concentration used, the hypotensive effect of GCIP-27 was weaker than that of losartan. For example, after 8 weeks treatment, SBP had decreased by 30.4% in the losartan-treated group compared with decreases of 10.5, 13.1 and 18.5% in the 10, 30 and 90 microg/kg GCIP-27-treated groups, respectively. Both GCIP-27 (10, 30 and 90 microg/kg) and losartan (6 mg/kg) significantly reduced LV posterior wall thickness, the thickness of the interventricular septum, collagen content and LVMI, with the effects of GCIP-27 at all three concentrations tested being greater than those of losartan. In conclusion, GCIP-27 effectively attenuates LV remodelling in SHR and the antiremodelling effect may not be dependent entirely on decreases in blood pressure.

Homocysteine induces cell death in H9C2 cardiomyocytes through the generation of peroxynitrite

Homocysteine (HCY) is toxic on blood vessels, but a potential direct toxicity of HCY on the heart is unknown. We addressed this issue by exposing H9C2 cardiomyocytes to HCY (0.1-5 mM) for up to 6h. At these concentrations, HCY reduced cell viability, induced necrosis and apoptosis and triggered the cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP). This was associated with the intracellular generation of the potent oxidant peroxynitrite. Removing peroxynitrite by the decomposition catalyst FeTPPS considerably reduced LDH release, DNA fragmentation, cleavage of caspase-3 and PARP, and restored normal cell morphology. In additional experiments performed in primary rat ventricular cardiomyocytes, HCY (1 mM, 6h) activated the phosphorylation of the MAP kinases ERK and JNK, two essential stress signaling kinases regulating myocardial apoptosis, hypertrophy and remodeling. These results provide the first demonstration that HCY kills cardiomyocytes through the generation of peroxynitrite and can activate key signaling cascades in the myocardium.

Hyperhomocysteinemia and Myocardial Expression of Brain Natriuretic Peptide in Rats

Background: Hyperhomocysteinemia (HHcy) has been linked to impaired left ventricular function and clinical class in patients with chronic heart failure. We hypothesized that HHcy stimulates myocardial brain natriuretic peptide (BNP) expression and induces adverse left ventricular remodeling.

Methods: We randomized 50 rats into 5 groups. Groups Co1 and Co2 (controls) received a typical diet. Groups Meth, Hcy1, and Hcy2 were fed the same diet supplemented with 2.4% methionine, 1% homocystine, and 2% homocystine, respectively. After 12 weeks, we measured total plasma homocysteine (tHcy) and BNP in plasma and tissue, and we performed histomorphometric analyses.

Results: All animals had comparable baseline body weight [mean (SD) 234 (26) g] and total circulating Hcy [4.7 (1.7) μmol/L]. After 12 weeks of treatment, total circulating Hcy increased in Meth, Hcy1, and Hcy2 [27.3 (8.8), 40.6 (7.0), and 54.0 (46.0) μmol/L, respectively] and remained unchanged in Co1 and Co2. Serum BNP significantly increased in 1 of 10 animals in Meth, 3 of 10 animals in Hcy1, and 3 of 10 animals in Hcy2. Median (25th–75th percentile) BNP tissue concentrations in Hcy1 and Hcy2 were 55% higher than in the corresponding controls [Co1 vs Hcy1, 225 (186–263) vs 338 (262–410) pg/mg protein, P = 0.05; Co2 vs Hcy2, 179 (107–261) vs 308 (192–429) pg/mg protein, P = 0.12]. In the Meth group, BNP expression was comparable to that of controls [200 (159–235) vs 225 (186–263) pg/mg protein, P = 0.32]. The percentage of perivascular and interstitial collagen and mast cell infiltration were comparable in all groups, indicating no adverse cardiac remodeling.

Conclusion: Three months of intermediate HHcy stimulated increased cardiac BNP expression that was not accompanied by adverse cardiac remodeling.

Rodent models of heart failure

Heart failure, a complex disorder with heterogeneous aetiologies remains one of the most threatening diseases known. It is a clinical syndrome attributable to a multitude of factors that begins with the compensatory response known as hypertrophy, followed by a decompensated state that finally results in heart failure. Given the lack of a unified theory of heart failure, future research efforts are required to unify and synthesize our current understanding of the multiple mechanisms that control remodelling in heart under various stress conditions. During the past few decades, use of animal models has provided new insights into the complex pathogenesis of this syndrome. Rodents have contributed significantly in the understanding of the pathogenesis and progression of heart failure. With the advent of the transgenic era, rodent models have revolutionized preclinical research associated with heart failure. These models combined with physiological measurements of cardiac hemodynamics, are expected to yield more valuable information regarding the molecular mechanisms of heart failure and aid in the discovery of novel therapeutic targets. However, all animal models used have advantages and limitations, and the issues determining transfer from preclinical to clinical require critical evaluation. The present review focuses upon rodent models of heart failure.

Homocysteine, brain natriuretic peptide and chronic heart failure: a critical review

Chronic heart failure (CHF) is a major public health problem causing considerable morbidity and mortality. Recently, plasma homocysteine (HCY) has been suggested to be significantly increased in CHF patients. This article reviews the relation between hyperhomocysteinemia (HHCY) and CHF. Clinical data indicate that HHCY is associated with an increased incidence, as well as severity, of CHF. In addition, HCY correlates with brain natriuretic peptide (BNP), a modern biochemical marker of CHF, which is used for diagnosis, treatment guidance and risk assessment. Animal studies showed that experimental HHCY induces systolic and diastolic dysfunction, as well as an increased BNP expression. Moreover, hyperhomocysteinemic animals exhibit an adverse cardiac remodeling characterized by accumulation of interstitial and perivascular collagen. In vitro superfusion experiments with increasing concentrations of HCY in the superfusion medium stimulated myocardial BNP release independent from myocardial wall stress. Thus, clinical and experimental data underline a correlation between HHCY and BNP supporting the role of HHCY as a causal factor for CHF. The mechanisms leading from an elevated HCY level to reduced pump function and adverse cardiac remodeling are a matter of speculation. Existing data indicate that direct effects of HCY on the myocardium, as well as nitric oxide independent vascular effects, are involved. Preliminary data from small intervention trials have initiated the speculation that HCY lowering therapy by micronutrients may improve clinical as well as laboratory markers of CHF.

In conclusion, HHCY might be a potential etiological factor in CHF. Future studies need to explore the pathomechanisms of HHCY in CHF. Moreover, larger intervention trials are needed to clarify whether modification of plasma HCY by B-vitamin supplementation improves the clinical outcome in CHF patients.

Clin Chem Lab Med 2007;45:1633–44.