Total plasma homocysteine and restenosis after percutaneous coronary angioplasty: current evidence

Benefits of multiple micronutrient supplementation in heart failure: A comprehensive review

BACKGROUND

Multiple micronutrient supplementation has been suggested to have a role on health outcomes in patients with heart failure (HF), but the evidence is inconclusive.

OBJECTIVE

To elucidate the role of multiple micronutrient supplementation in heart failure we performed a comprehensive review of the literature.

METHODS AND RESULTS

The search in databases included PUBMED (until June 2018) to detect randomized controlled trials (RCTs) and meta-analyzes that investigated the impact of micronutrient supplementation in HF.

RESULTS

With more than 2357 titles and abstracts reviewed, we included only the studies suitable for the final review. Whether alone or in combination, micronutrients have been found to improve the health outcomes of patients with HF by improving symptoms, work capacity and left ventricular ejection fraction (LVEF), thus increasing the quality of life in these patients.

CONCLUSION

Future studies are needed to document the effects of multiple micronutrient associations in order to include them in nutritional guidelines to increase survival and to improve quality of life in patients with heart failure.

Public health significance of elevated homocysteine

Homocysteine is a sulfur amino acid whose metabolism stands at the intersection of two pathways: remethylation, which requires folic acid and vitamin B12 coenzymes; and transsulfuration, which requires pyridoxal-5'-phosphate, the vitamin B6 coenzyme. Data from a number of laboratories suggest that mild elevations of homocysteine in plasma are a risk factor for occlusive vascular disease. In the Framingham studies, we have shown that plasma homocysteine concentration is inversely related to the intake and plasma levels of folate and vitamin B6 as well as vitamin B12 plasma levels. Almost two-thirds of the prevalence of high homocysteine is attributable to low vitamin status or intake. Elevated homocysteine concentrations in plasma are a risk factor for prevalence of extracranial carotid-artery stenosis > or = 25% in both men and women. Prospectively elevated plasma homocysteine is associated with increased total and cardiovascular mortality, increased incidence of stroke, increased incidence of dementia and Alzheimer's disease, increased incidence of bone fracture, and higher prevalence of chronic heart failure. It was also shown that elevated plasma homocysteine is a risk factor for preeclampsia and maybe neural tube defects (NTD). This multitude of relationships between elevated plasma homocysteine and diseases that afflict the elderly, pregnant women, and the embryo points to the existence ofa common denominator which may be responsible for these diseases. Whether this denominator is homocysteine itself or homocysteine is merely a marker, remains to be determined.

Micronutrients in health and disease

Micronutrients play a central part in metabolism and in the maintenance of tissue function. An adequate intake therefore is necessary, but provision of excess supplements to people who do not need them may be harmful. Single micronutrient deficiency states are comparatively easily recognised and treated. Subclinical deficiency, often of multiple micronutrients, is more difficult to recognise, and laboratory assessment is often complicated by the acute phase response. Clinical benefit is most likely in those people who are severely depleted and at risk of complications, and is unlikely if this is not the case. There is little evidence for supplements leading to a reduction in the incidence of infections in the elderly population, in coronary artery disease, or in malignant disease. The best evidence for benefit is in critical illness, and in children in developing countries consuming a deficient diet. More clinical trials are required with good clinical outcomes to optimise intake in prevention and treatment of disease.

Is homocysteine important as risk factor for coronary heart disease?

AIM

Homocysteine (Hcy), a sulfur-containing amino acid product of methionine metabolism, may play an important role in the development of cardiovascular disease. In this paper we review available knowledge on the pathways leading to synthesis and degradation of Hcy, as well as on the genetic and environmental factors affecting its plasma levels, focussing on its potential role in the development of coronary heart disease.

DATA SYNTHESIS

Hyperhomocysteinemia (HHcy) is determined by genetic and environmental factors and represents a modifiable cardiovascular risk factor since vitamin supplementation has been shown to effectively lower plasma homocysteine levels. While case-control and cross-sectional studies consistently showed an association of HHcy with cardiovascular disease, prospective studies have given conflicting results. Thus, the role of HHcy in the development of coronary heart disease is still under debate. Furthermore, it remains unclear which patients should be screened for HHcy and treated to correct HHcy.

CONCLUSIONS

Available information collectively suggests that although HHcy can be regarded as a minor risk factor for coronary heart disease, it interacts with other risk factors in triggering new events in patients with known CAD. Thus, the treatment of mild HHcy with folate supplementation is appropriate in particular in high risk patients or patients with established CAD who do not present with the "traditional" risk factors.

The drug-based pipeline against restenosis

More than 1 million percutaneous coronary interventions (PCIs) are performed yearly worldwide. Restenosis is the recurrent narrowing that can occur within 6 months following an initially successful PCI. Although drug-eluting stents have accomplished remarkable success, restenosis has not been eliminated and optimisation of both the polymers and drugs associated with them is desirable. This article reviews the presently available and potential preventive approaches against restenosis, including the sirolimus and paclitaxel drug-eluting stents.

Saratin (an inhibitor of platelet-collagen interaction) decreases platelet aggregation and homocysteine-mediated postcarotid endarterectomy intimal hyperplasia in a dose-dependent manner

BACKGROUND

This study investigated Saratin's (Merck KGaA, Darmstadt, Germany) prevention of platelet adhesion and intimal hyperplasia at different doses and in the hyperhomocystinemia rat carotid endarterectomy (CEA) model.

METHODS

Rats were divided into two groups: (1) platelet adhesion or (2) luminal stenosis because of intimal hyperplasia. At CEA, rats received 0, 0.5, 5.0, 10.0, or 20.0 microg Saratin on the artery. Post-CEA platelet aggregation was evaluated by standard error of the mean. Intimal hyperplasia group received either (1) control or (2) 4.5 g/kg DL-homocystine diets for two weeks followed by CEA and treated with diluent or 5.0 microg Saratin. Endpoints included platelet adhesion, intimal hyperplasia, plasma homocysteine (HCys), and its metabolic enzymes cystathionine beta-synthase (CBS) and methylenetetrahydrofolate reductase (MTHFR).

RESULTS

Platelet adhesion: post-CEA, platelet adhesion was reduced by 63%, 67%, and 67% in Saratin doses > or =5.0 microg. Intimal hyperplasia: 5.0 microg Saratin in the HCys group decreased intimal hyperplasia by 45% compared with the non-Saratin-treated HCys group. Plasma HCys levels were not altered with Saratin treatment in the HCys groups nor were CBS or MTHFR.

CONCLUSIONS

Saratin significantly inhibited platelet adhesion at > or =5.0 microg, and Saratin at 5.0 microg attenuated luminal stenosis in a hyperhomocysteinemic rat CEA model.

Homocysteine and cardiovascular disease

Research over the past decade has shown that elevated levels of homocysteine have a strong association with all forms of atherothrombotic disease and venous thromboembolism. This association is particularly strong for coronary disease and newer data indicate that screening for homocysteine levels may be warranted in those with unexplained thrombotic tendencies and in young patients who develop coronary events or disease without the usual predisposing factors such as hypertension, smoking, hypercholesterolemia, or diabetes. Although the link between hyperhomocysteinemia and cardiac disease has not been conclusively shown to be causal as yet, data are emerging that lowering homocysteine levels may be beneficial in patients at high risk. Such lowering can be done safely and inexpensively with increased intake of fruits and vegetables and in those patients who are particularly at high risk using supplementation with folic acid and the B vitamins. Preliminary studies have shown that lowering homocysteine levels in this manner may slow the progression of atherosclerosis in coronary and carotid vessels. No mortality data exist yet showing that reducing homocysteine reduces cardiac or total mortality, although it is likely that ongoing and planned trials that are underway will shed light on these important questions soon.

Homocysteine and reactive oxygen species in metabolic syndrome, type 2 diabetes mellitus, and atheroscleropathy: the pleiotropic effects of folate supplementation

Homocysteine has emerged as a novel independent marker of risk for the development of cardiovascular disease over the past three decades. Additionally, there is a graded mortality risk associated with an elevated fasting plasma total homocysteine (tHcy). Metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM) are now considered to be a strong coronary heart disease (CHD) risk enhancer and a CHD risk equivalent respectively. Hyperhomocysteinemia (HHcy) in patients with MS and T2DM would be expected to share a similar prevalence to the general population of five to seven percent and of even greater importance is: Declining glomerular filtration and overt diabetic nephropathy is a major determinant of tHcy elevation in MS and T2DM.

There are multiple metabolic toxicities resulting in an excess of reactive oxygen species associated with MS, T2DM, and the accelerated atherosclerosis (atheroscleropathy). HHcy is associated with an increased risk of cardiovascular disease, and its individual role and how it interacts with the other multiple toxicities are presented.

The water-soluble B vitamins (especially folate and cobalamin-vitamin B₁₂) have been shown to lower HHcy. The absence of the cystathionine beta synthase enzyme in human vascular cells contributes to the importance of a dual role of folic acid in lowering tHcy through remethylation, as well as, its action of being an electron and hydrogen donor to the essential cofactor tetrahydrobiopterin. This folate shuttle facilitates the important recoupling of the uncoupled endothelial nitric oxide synthase enzyme reaction and may restore the synthesis of the omnipotent endothelial nitric oxide to the vasculature.

Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion

Background: Measurement of plasma total homocysteine has become common as new methods have been introduced. A wide range of disorders are associated with increased concentrations of total homocysteine. The purpose of this review is to provide an international expert opinion on the practical aspects of total homocysteine determinations in clinical practice and in the research setting and on the relevance of total homocysteine measurements as diagnostic or screening tests in several target populations.

Methods: Published data available on Medline were used as the basis for the recommendations. Drafts of the recommendations were critically discussed at meetings over a period of 3 years.

Outcome: This review is divided into two sections: (a) determination of homocysteine (methods and their performance, sample collection and handling, biological determinants, reference intervals, within-person variability, and methionine loading test); and (b) risk assessment and disease diagnosis (homocystinuria, folate and cobalamin deficiencies, cardiovascular disease, renal failure, psychiatric disorders and cognitive impairment, pregnancy complications and birth defects, and screening of elderly and newborns). Each of these subsections concludes with a separate series of recommendations to assist the clinician and the research scientist in making informed decisions. The review concludes with a list of unresolved questions.

Pharmacologic prevention of both restenosis and atherosclerosis progression: AGI-1067, probucol, statins, folic acid and other therapies

PURPOSE OF REVIEW

In this article, the authors intend to provide an update on clinical trials of pharmacologic prevention of restenosis after percutaneous coronary interventions, placed in the perspective of the use of orally administered therapy for the prevention of atherosclerosis progression and clinical events.

RECENT FINDINGS

AGI-1067, the mono-succinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed v-protectants. It has strong antioxidant properties equipotent to those of probucol and antiinflammatory properties. It inhibits gene expression of VCAM-1 and MCP-1 and has been effective at preventing atherosclerosis in all tested animal models including the non-human primate. In the Canadian Antioxidant Restenosis Trial (CART) 1, AGI-1067 and probucol improved lumen dimensions at the site of percutaneous coronary intervention. AGI-1067 also improved luminal dimensions of non-intervened coronary reference segments in the Canadian Antioxidant Restenosis Trial, which suggests a direct antiatherosclerosis effect. Probucol reduced post-percutaneous coronary intervention restenosis and progression of carotid atherosclerosis in other clinical trials. Although statins reduce atherosclerotic events, they do not appear to have a significant effect on restenosis. The failure of folate therapy to protect against restenosis in the Folate After Coronary Intervention Trial (FACIT) occurred despite significant reductions in homocysteine levels.

SUMMARY

Prevention of both post-percutaneous coronary intervention restenosis and atherosclerosis progression with a pharmacologic agent such as AGI-1067 may be an attractive treatment paradigm. Two important trials that test the antioxidant/antiinflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial 2, which assesses its value for the reduction of both atherosclerosis progression and post-percutaneous coronary interventions restenosis, and the Aggressive Reduction of Inflammation Stops Events (ARISE) trial which is evaluating its effects on cardiovascular events.