Homocysteine and lipoprotein(a) interact to increase CAD risk in young men and women

N-homocysteinylation of α-synuclein promotes its aggregation and neurotoxicity

The aggregation of α-synuclein plays a pivotal role in the pathogenesis of Parkinson's disease (PD). Epidemiological evidence indicates that high level of homocysteine (Hcy) is associated with an increased risk of PD. However, the molecular mechanisms remain elusive. Here, we report that homocysteine thiolactone (HTL), a reactive thioester of Hcy, covalently modifies α-synuclein on the K80 residue. The levels of α-synuclein K80Hcy in the brain are increased in an age-dependent manner in the TgA53T mice, correlating with elevated levels of Hcy and HTL in the brain during aging. The N-homocysteinylation of α-synuclein stimulates its aggregation and forms fibrils with enhanced seeding activity and neurotoxicity. Intrastriatal injection of homocysteinylated α-synuclein fibrils induces more severe α-synuclein pathology and motor deficits when compared with unmodified α-synuclein fibrils. Increasing the levels of Hcy aggravates α-synuclein neuropathology in a mouse model of PD. In contrast, blocking the N-homocysteinylation of α-synuclein ameliorates α-synuclein pathology and degeneration of dopaminergic neurons. These findings suggest that the covalent modification of α-synuclein by HTL promotes its aggregation. Targeting the N-homocysteinylation of α-synuclein could be a novel therapeutic strategy against PD.

Homocysteine predicts vascular target organ damage in hypertension and may serve as guidance for first-line antihypertensive therapy

Homocysteine is an independent risk factor for cardiovascular and cerebrovascular disease and has been proposed to contribute to vascular dysfunction. We sought to determine in a real-world clinical setting whether homocysteine levels were associated with hypertension mediated organ damage (HMOD) and could guide treatment choices in hypertension. We performed a cross-sectional analysis of prospectively collected data in 145 hypertensive patients referred to our tertiary hypertension clinic at Royal Perth Hospital and analyzed the association of homocysteine with HMOD, renin-angiotensin-aldosterone system (RAAS), and RAAS blockade. The average age of participants was 56 ± 17 years, and there was a greater proportion of males than females (89 vs. 56). Regression analysis showed that homocysteine was significantly associated with PWV (β = 1.99; 95% CI 0.99-3.0; p < .001), albumin-creatinine ratio (lnACR: β = 1.14; 95% CI 0.47, 1.8; p < .001), 24 h urinary protein excretion (β = 0.7; 95% CI 0.48, 0.92; p < .001), and estimated glomerular filtration rate (β = -29.4; 95% CI -36.35, -22.4; p < .001), which persisted after adjusting for potential confounders such as age, sex, 24 h BP, inflammation, smoking, diabetes mellitus (DM), and dyslipidemia. A positive predictive relationship was observed between plasma homocysteine levels and PWV, with every 1.0 µmol/L increase in homocysteine associated with a 0.1 m/s increase in PWV. Homocysteine was significantly associated with elevated aldosterone concentration (β = 0.26; p < .001), and with attenuation of ACEi mediated systolic BP lowering and regression of HMOD compared to angiotensin receptor blockers in higher physiological ranges of homocysteine. Our results indicate that homocysteine is associated with hypertension mediated vascular damage and could potentially serve to guide first-line antihypertensive therapy.

Potent reduction of plasma lipoprotein (a) with an antisense oligonucleotide in human subjects does not affect ex vivo fibrinolysis

It is postulated that lipoprotein (a) [Lp(a)] inhibits fibrinolysis, but this hypothesis has not been tested in humans due to the lack of specific Lp(a) lowering agents. Patients with elevated Lp(a) were randomized to antisense oligonucleotide [IONIS-APO(a)_Rx] directed to apo(a) (n = 7) or placebo (n = 10). Ex vivo plasma lysis times and antigen concentrations of plasminogen, factor XI, plasminogen activator inhibitor 1, thrombin activatable fibrinolysis inhibitor, and fibrinogen at baseline, day 85/92/99 (peak drug effect), and day 190 (3 months off drug) were measured. The mean ± SD baseline Lp(a) levels were 477.3 ± 55.9 nmol/l in IONIS-APO(a)_Rx and 362.1 ± 89.9 nmol/l in placebo. The mean± SD percentage change in Lp(a) for IONIS-APO(a)_Rx was -69.3 ± 12.2% versus -5.4 ± 6.9% placebo (P < 0.0010) at day 85/92/99 and -15.6 ± 8.9% versus 3.2 ± 12.2% (P = 0.003) at day 190. Clot lysis times and coagulation/fibrinolysis-related biomarkers showed no significant differences between IONIS-APO(a)_Rx and placebo at all time points. Clot lysis times were not affected by exogenously added Lp(a) at concentrations up to 200 nmol/l to plasma with very low (12.5 nmol/l) Lp(a) levels, whereas recombinant apo(a) had a potent antifibrinolytic effect. In conclusion, potent reductions of Lp(a) in patients with highly elevated Lp(a) levels do not affect ex vivo measures of fibrinolysis; the relevance of any putative antifibrinolytic effects of Lp(a) in vivo needs further study.

B vitamins in stroke prevention: time to reconsider

B vitamin therapy lowers plasma total homocysteine concentrations, and might be a beneficial intervention for stroke prevention; however, cyanocobalamin (a form of vitamin B12) can accelerate decline in renal function and increase the risk of cardiovascular events in patients with impaired renal function. Although early trials did not show benefit in reduction of stroke, these results might have been due to harm in participants with impaired renal function. In patients with diabetic nephropathy, cyanocobalamin is harmful, whereas B vitamins appear to reduce cardiovascular events in study participants with normal renal function. Our meta-analysis of individual patient data from two large trials of B vitamin therapy (VISP and VITATOPS) indicates that patients with impaired renal function who are exposed to high-dose cyanocobalamin do not benefit from therapy with B vitamins for the prevention of stroke (risk ratio 1·04, 95% CI 0·84-1·27), however, patients with normal renal function who are not exposed to high-dose cyanocobalamin benefit significantly from this treatment (0.78, 0·67-0·90; interaction p=0·03). The potential benefits of B vitamin therapy with folic acid and methylcobalamin or hydroxycobalamin, instead of cyanocobalamin, to lower homocysteine concentrations in people at high risk of stroke warrant further investigation.

Atherothrombotic non-ST segment elevation myocardial infarction in a 42-year-old white female with no known cardiovascular risk factors

Coronary artery disease (CAD) in the absence of known cardiovascular risk factors is rare. This is the case report of a 42-year-old white female who was admitted with a non-ST segment elevation myocardial infarction (NSTEMI). The patient had seen her general practitioner (GP) in the 2 weeks prior to this with exertional chest pain. She had no known risk factors for cardiovascular disease and other possible underlying aetiologies were ruled out. The patient underwent percutaneous coronary intervention (PCI) to the culprit lesion in the left anterior descending artery. She was discharged on guideline-directed medical therapy and the Dianette contraceptive pill she was taking was stopped. This case serves to remind us that CAD can occur in a variety of patients including premenopausal females and in the absence of known risk factors. It also emphasises that patients presenting with a convincing history of typical angina require prompt investigations, regardless of their apparent level of risk.

Coronary Artery Disease in Young Adults

Coronary heart disease (CHD) sustains a significant negative impact on hospital admissions and deaths worldwide. The prevalence of CHD in young adults is difficult to establish accurately, as these asymptomatic patients typically do not undergo diagnostic studies. In this article, the authors will focus on young adults with CHD emphasizing common and uncommon risk factors, current management and review of previous studies.

Lipoprotein (a): a Unique Independent Risk Factor for Coronary Artery Disease

The current epidemic affecting Indians is coronary artery disease (CAD), and is currently one of the most common causes of mortality and morbidity in developed and developing countries. The higher rate of CAD in Indians, as compared to people of other ethnic origin, may indicate a possible genetic susceptibility. Hence, Lp(a), an independent genetic risk marker for atherosclerosis and cardiovascular disease assumes great importance. Lp(a), an atherogenic lipoprotein, contains a cholesterol rich LDL particle, one molecule of apolipoprotein B-100 and a unique protein, apolipoprotein (a) which distinguishes it from LDL. Apo(a) is highly polymorphic and an inverse relationship between Lp(a) concentration and apo(a) isoform size has been observed. This is genetically controlled suggesting a functional diversity among the apo(a) isoforms. The LPA gene codes for apo(a) whose genetic heterogeneity is due to variations in its number of kringles. The exact pathogenic mechanism of Lp(a) is still not completely elucidated, but the structural homology of Lp(a) with LDL and plasmin is possibly responsible for its acting as a link between atherosclerosis and thrombosis. Upper limits of normal Lp(a) levels have not been defined for the Indian population. A cut off limit of 20 mg/dL has been suggested while for the Caucasian population it is 30 mg/dL. Though a variety of assays are available for its measurement, standardization of the analytical method is highly complicated as a majority of the methods are affected by the heterogeneity in apo(a) size. No therapeutic drug selectively targets Lp(a) but recently, new modifiers of apo(a) synthesis are being considered.

Role of homocysteinylation of ACE in endothelial dysfunction of arteries

The direct impact of de novo synthesis of homocysteine (Hcy) and its reactive metabolites, Hcy-S-S-Hcy and Hcy thiolactone (HCTL), on vascular function has not been fully elucidated. We hypothesized that Hcy synthesized within endothelial cells affects activity of angiotensin-converting enzyme (ACE) by direct homocysteinylation of its amino- and/or sulfhydryl moieties. This covalent modification enhances ACE reactivity toward angiotensin II (ANG II)-NADPH oxidase-superoxide-dependent endothelial dysfunction. Mesenteric and coronary arteries isolated from normal rats were incubated for 3 days with or without exogenous methionine (Met, 0.1-0.3 mM), a precursor to Hcy. Incubation of arteries in Met-free media resulted in time-dependent decreases in vascular Hcy formation. By contrast, vessels incubated with Met produced Hcy in a dose-dependent manner. There was a notably greater de novo synthesis of Hcy from endothelial than from smooth muscle cells. Enhanced levels of Hcy production significantly impaired shear stress-induced dilation and release of nitric oxide, events that are associated with elevated production of vascular superoxide. Each of these processes was attenuated by ANG II type I receptor blocker or ACE and NADPH oxidase inhibitors. In addition, in vitro exposure of purified ACE to Hcy-S-S-Hcy/HCTL resulted in formation of homocysteinylated ACE and an enhanced ACE activity. The enhanced ACE activity was confirmed in isolated coronary and mesenteric arteries that had been exposed directly to Hcy-S-S-Hcy/HCTL or after Met incubation. In conclusion, vasculature-derived Hcy initiates endothelial dysfunction that, in part, may be mediated by ANG II-dependent activation of NADPH oxidase in association with homocysteinylation of ACE.

Hyperhomocysteinemia and hyperlipoproteinemia (a) in obese South Indian men: an indication for increased cardiovascular risk

Obesity is a pathological condition which increases the risk for cardiovascular disease. The present study was designed to evaluate homocysteine, lipoprotein (a) [Lp(a)], apolipoprotein-B (apo-B), apolipoprotein-A-I (apo-A-I) and lipid indices and their association if any in obese South Indian men. Thirty obese men and thirty age-matched males with normal body weight (controls) were recruited in the study. Plasma homocysteine, Lp(a), lipid profile, apo-A-I and apo-B were estimated in all the subjects. Lipid indices such as lipid pentad index (LPI), lipid tetrad index (LTI), atherogenic index of plasma (AIP), non-high density lipoprotein (non-HDL)/high density lipoprotein (HDL) ratio and apo-B/apo-A-I ratio were calculated in all study subjects. Homocysteine, Lp(a), apo-B, apo-B/apo-A-I ratio and lipid indices were significantly increased in obese men, compared to controls. Both homocysteine and Lp(a) were positively correlated with BMI, waist, hip circumference and apo-B and negatively correlated with apo-A-I. Also we found highly significant positive correlation between homocysteine and Lp(a) levels. The data from the present study concludes that non-conventional risk factors like homocysteine, Lp (a), apo-B/apo-A-I ratio, LTI, LPI, non-HDL/HDL ratio and AIP were significantly elevated in obese Indian men, suggesting they are more prone to develop cardiovascular disease, than the age-matched men with normal body weight.

Effect of folic acid supplementation on the progression of carotid intima-media thickness: a meta-analysis of randomized controlled trials

OBJECTIVES

We conducted a meta-analysis of relevant randomized trials to assess whether folic acid supplementation reduces the progression of atherosclerosis as measured by carotid intima-media thickness (CIMT).

METHODS

This analysis included 2052 subjects from ten folic acid randomized trials with the change in CIMT reported as one of the end points. Summary estimates of weighted mean differences (WMDs) and 95% CIs were obtained by using random-effect models. Meta-regression and subgroup analyses were performed to identify the source of heterogeneity.

RESULTS

Our analysis showed that folic acid supplementation significantly reduces the progression of CIMT (WMD: -0.04 mm; 95%CI: -0.07, -0.02; P<0.001), particularly in subjects with chronic kidney disease (CKD) (WMD: -0.16 mm; 95%CI: -0.26, -0.07; P=0.0006) or high cardiovascular disease (CVD) risk (WMD: -0.05 mm; 95%CI: -0.11, 0.00; P=0.06) but not in subjects who were generally healthy with only elevated homocysteine concentrations (WMD:0.00 mm; 95%CI: -0.01, 0.01; P=0.35). Furthermore, meta-regression analysis of the data showed that the baseline CIMT levels (P=0.011) and the percent reduction of homocysteine (P<0.001) were positively related to the effect size. Consistently, a greater beneficial effect was seen in those trials with baseline CIMT levels ≥0.8 mm (WMD: -0.14 mm; 95%CI: -0.19, -0.08; P<0.0001), and a reduction in the homocysteine concentration ≥30% (WMD: -0.22 mm; 95%CI: -0.38, -0.06; P=0.009). In the corresponding comparison groups, the effect sizes were attenuated and insignificant.

CONCLUSIONS

Our findings indicate that folic acid supplementation is effective in reducing the progression of CIMT, particularly in subjects with CKD or high CVD risk and among trials with higher baseline CIMT levels or a larger homocysteine reduction.

Lipoprotein a levels in pediatric migraine

The purpose of this study was to examine the lipoprotein (a) [Lp(a)] levels in children with migraine to see a possible relationship between migraine and stroke via high Lp(a) levels. Plasma levels of Lp(a) were determined in 63 patients and age-matched control subjects. The mean age in the control group was 10.57 ± 3.63 years and 11.51 ± 3.19 years in the migraine patient group. The mean Lp(a) levels in control group were 10.36 ± 10.41 ng/mL and 17.09 ± 12.12 ng/mL in migraine group (P < 0.05). The median Lp(a) level in the control group was 49.38 ng/mL and was 77.62 ng/mL in the migraine group (P < 0.05). Twelve patients (19%) had Lp(a) levels of >30 ng/mL in the migraine group and 4 (6.3%) in the control group (P < 0.05). Several prothrombotic factors related to an increased risk of stroke have been studied in migraine patients. It has recently been reported that high Lp(a) concentrations represent a risk factor for migraine, thus establishing a novel plausible link between migraine and stroke. The current study suggests evidence of high Lp(a) concentrations in childhood migraine; perhaps a novel link exists between migraine and stroke.

Interaction between homocysteine and lipoprotein(a) increases the prevalence of coronary artery disease/myocardial infarction in women: a case-control study

INTRODUCTION

Our aim was to investigate the association of elevated homocysteine (Hcy) and lipoprotein(a) Lp(a) with the prevalence of coronary artery disease (CAD) and myocardial infarction (MI) and to investigate their interaction in both genders.

MATERIALS AND METHODS

955 (male/female: 578/377) consecutive patients admitted for coronary angiography were enrolled in the study. Lp(a), Hcy, vitamin B12, folic acid, MTHFR C677T polymorphism and traditional risk factors were determined.

RESULTS

619 patients had significant (≥50%) stenosis (CAD+) and 341 had MI (MI+). CAD-MI- cases (n=302) were considered as controls. Adjusted Hcy levels were significantly elevated only in the female CAD+MI+group that was related to decreased vitamin B12 levels. Lp(a) was elevated in the CAD+MI+group of both genders. Folic acid levels and MTHFR T677 allele frequency did not show significant difference. Moderate hyperhomocysteinemia (Hcy >15μmol/L) or elevated Lp(a) (>300mg/L) increased the risk of CAD (OR 2.27, CI 1.36-3.80 and OR 1.64, CI 1.03-2.61, respectively) and MI (OR 2.52, CI 1.36-4.67 and OR 1.89, CI 1.06-3.38, respectively) only in women. Only simultaneous but not isolated elevation of Hcy and Lp(a) conferred a significant, 3.6-fold risk of CAD in females and even higher (11-fold) risk in young females, which suggested an interactive effect.

CONCLUSIONS

Moderate hyperhomocysteinemia or elevated Lp(a) level associated with a risk of CAD and MI only in women. While isolated elevation of one of the two parameters represented a mild risk of CAD, their combined elevation highly increased the risk in females. No such effect was observed in males.

Nutrition and human health from a sex-gender perspective

Nutrition exerts a life-long impact on human health, and the interaction between nutrition and health has been known for centuries. The recent literature has suggested that nutrition could differently influence the health of male and female individuals. Until the last decade of the 20th century, research on women has been neglected, and the results obtained in men have been directly translated to women in both the medicine and nutrition fields. Consequently, most modern guidelines are based on studies predominantly conducted on men. However, there are many sex-gender differences that are the result of multifactorial inputs, including gene repertoires, sex steroid hormones, and environmental factors (e.g., food components). The effects of these different inputs in male and female physiology will be different in different periods of ontogenetic development as well as during pregnancy and the ovarian cycle in females, which are also age dependent. As a result, different strategies have evolved to maintain male and female body homeostasis, which, in turn, implies that there are important differences in the bioavailability, metabolism, distribution, and elimination of foods and beverages in males and females. This article will review some of these differences underlying the impact of food components on the risk of developing diseases from a sex-gender perspective.

Role of intestinal transporters in neonatal nutrition: carbohydrates, proteins, lipids, minerals, and vitamins

To support rapid growth and a high metabolic rate, infants require enormous amounts of nutrients. The small intestine must have the complete array of transporters that absorb the nutrients released from digested food. Failure of intestinal transporters to function properly often presents symptoms as "failure to thrive" because nutrients are not absorbed and as diarrhea because unabsorbed nutrients upset luminal osmolality or become substrates of intestinal bacteria. We enumerate the nutrients that constitute human milk and various infant milk formulas, explain their importance in neonatal nutrition, then describe for each nutrient the transporter(s) that absorbs it from the intestinal lumen into the enterocyte cytosol and from the cytosol to the portal blood. More than 100 membrane and cytosolic transporters are now thought to facilitate absorption of minerals and vitamins as well as products of digestion of the macronutrients carbohydrates, proteins, and lipids. We highlight research areas that should yield information needed to better understand the important role of these transporters during normal development.

Homocysteine and lipoprotein (a) correlation in ischemic stroke patients

BACKGROUND

Homocysteine and Lipoprotein (a) have been recognized as risk factors for coronary heart disease. However, their role in ischemic stroke is still not defined. Therefore the present study was undertaken to evaluate their levels and relationship in patients of ischemic stroke.

METHODS

The study was conducted in consecutive patients admitted with a diagnosis of acute ischaemic stroke and age and sex matched healthy controls. Plasma homocysteine and serum l lipoprotein (a) levels were determined in the fasting venous blood samples using ELISA and immunoturbidimetric assay respectively.

RESULTS

66 patients with ischaemic stroke (30 males, 36 females) of mean age 54.43+/-1.97 years and 72 controls (39 males, 33 females) of mean age 53.86+/-1.88 years were studied. Mean plasma homocysteine levels in the stroke patients and control groups were 28.40+/-2.08 micromol/L and 11.16+/-1.09 micromol/L respectively (p<0.001). Odds ratio for raised homocysteine levels in stroke cases was 15.7. Plasma homocysteine levels showed a positive correlation with smoking (Pearson's correlation coefficient=0.324 and p-value of 0.008), (Odds ratio=5.71). Serum Lipoprotein (a) levels in stroke cases and control group were 57.33+/-4.40 mg/dl and 23.46+/-1.09 mg/dl respectively, (p<0.001), (Odds Ratio=8.62). A positive correlation was also observed between Homocysteine and Lipoprotein (a) levels with Pearson's correlation coefficient of 0.75 and p-value<0.001.

CONCLUSIONS

Raised homocysteine and serum lipoprotein (a) levels were found to be independently associated with ischemic stroke with a significant positive correlation between the two parameters. Elevated homocysteine levels may modulate the toxicity of lipoprotein (a) in ischemic stroke.

Premature coronary artery disease in young (age <45) subjects: interactions of lipid profile, thrombophilic and haemostatic markers

BACKGROUND

Intravascular thrombogenesis is influenced by a complex interplay of procoagulant, anticoagulant, fibrinolytic, endothelial damage/dysfunction and inflammatory factors. We hypothesised that abnormalities of these biological systems would contribute to coronary artery disease presenting at a young age.

METHODS

We performed a case-control study of 142 subjects presenting with MI at a young age (<or=45 years; 'cases'), who were compared with 95 controls. We assessed for abnormalities of thrombophilia [total homocysteine (tHcy), lipoprotein (a) [Lp(a)], antiphospholipid antibodies (APA)], lipid profile [total cholesterol, HDL-cholesterol, LDL-cholesterol and triglycerides], fibrinogen and fibrin D-dimer (an index of thrombogenesis), endothelial damage/dysfunction (von Willebrand factor [vWF]), fibrinolysis (tissue plasminogen activator [t-PA antigen] and its inhibitor [PAI-1 antigen]) and inflammation (C-reactive protein [CRP]).

RESULTS

Cases had significantly higher Lp(a) (p=0.008), triglycerides (p=0.001), fibrinogen (p=0.006), fibrin D-dimer (p=0.006) and vWf (p=0.032), but lower HDL-C (p=0.003) levels. There were no significant differences in tHcy, APA titre, total cholesterol or LDL-C, t-PA, PAI-1 and CRP levels (all p=NS). In a multivariate analysis, the only variables independently associated with cases were levels of Lp(a) (p=0.015), fibrinogen (p=0.038) and D-dimer (p=0.005) levels.

CONCLUSIONS

Premature coronary artery disease is characterized by an unfavourable lipid profile, low concentrations of HDL-C and high triglyceride levels, in association with high Lp(a) and a hypercoagulable state (high fibrinogen and D-dimer levels).

Molecular targeting of proteins by L-homocysteine: mechanistic implications for vascular disease

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease, complications of pregnancy, cognitive impairment, and osteoporosis. That elevated homocysteine leads to vascular dysfunction may be the linking factor between these apparently unrelated pathologies. Although a growing body of evidence suggests that homocysteine plays a causal role in atherogenesis, specific mechanisms to explain the underlying pathogenesis have remained elusive. This review focuses on chemistry unique to the homocysteine molecule to explain its inherent cytotoxicity. Thus, the high pKa of the sulfhydryl group (pKa, 10.0) of homocysteine underlies its ability to form stable disulfide bonds with protein cysteine residues, and in the process, alters or impairs the function of the protein. Studies in this laboratory have identified albumin, fibronectin, transthyretin, and metallothionein as targets for homocysteinylation. In the case of albumin, the mechanism of targeting has been elucidated. Homocysteinylation of the cysteine residues of fibronectin impairs its ability to bind to fibrin. Homocysteinylation of the cysteine residues of metallothionein disrupts zinc binding by the protein and abrogates inherent superoxide dismutase activity. Thus, S-homocysteinylation of protein cysteine residues may explain mechanistically the cytotoxicity of elevated L-homocysteine.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Lipoprotein(a) and LDL Particle Size Are Related to the Severity of Coronary Artery Disease

BACKGROUND

The pathophysiological role and metabolic pathway of Lp(a) have not been clearly defined. An association between Lp(a) and oxidative low-density lipoprotein (LDL) were recently reported. And small dense LDL (sd-LDL) were associated with circulating malondialdehyde-modified LDL. We investigated the relationships between serum Lp(a) level and LDL particle size in coronary artery disease (CAD) patients. Further, we investigated the relationships of sd-LDL and Lp(a) with the extent and severity of CAD.

METHODS

A total of 490 patients (mean: 60.5 +/- 11.5 years old) who underwent coronary angiography to evaluate chest pain were investigated. Patients were classified into two groups, a CAD group (n = 256), who had significant stenosis observed by coronary angiogram, and a control group (n = 234), who had normal, or minimal coronary arteries. CAD severity was measured by Gensini scores. The distribution of the LDL subfraction was analyzed using a Quantimetrix Lipoprint LDL System.

RESULTS

The serum Lp(a) concentration was correlated with the fraction of sd-LDL (r = 0.193, p < 0.001) and mean LDL size (r = 0.160, p = 0.003). The Lp(a) level and mean LDL particle size were significantly correlated with a high Gensini score. LDL particle size in the CAD group was smaller than in the control group (26.74 +/- 0.64 vs. 26.43 +/- 0.93 nm, p < 0.001). The Gensini score was significantly higher in small LDL with high Lp(a) level groups.

CONCLUSION

The positive correlation of the level of Lp(a) and sd-LDL fraction were demonstrated. The mechanism of this association is not clearly defined; we can suggest that it may stem from the individual atherogenic condition that linked to increased oxidative stress. Both increased Lp(a) and sd-LDL fraction were correlated with the severity of CAD.

Elevated Lipoprotein(a) does not promote early atherosclerotic changes of the carotid arteries in young, healthy adults

BACKGROUND

Elevated levels of Lipoprotein(a) [Lp(a)] have been linked to an increased risk of ischemic cardiovascular events. Yet the mechanism by which Lp(a) might contribute to this increased risk is not clear.

METHODS

To elucidate whether high plasma levels of Lp(a) contribute to the development of early atherosclerotic vessel wall changes, the intima-media thickness of the common carotid arteries [CCA-IMT] of 151 healthy young volunteers without additional relevant cardiovascular risk factors was measured by high-resolution ultrasound. Plasma concentrations of Lp(a) were quantified and other established risk factors, such as body mass index [BMI], plasma levels of cholesterol, triglycerides and homocysteine, were determined. Furthermore, the carotid arteries were examined for the presence of plaques and stenoses.

RESULTS

Univariate analysis showed a significantly negative correlation of CCA-IMT with HDL cholesterol and positive correlations with age, BMI, total and LDL cholesterol, triglycerides and even with homocysteine, but not with Lp(a). When the study population was dichotomized according to Lp(a) levels, no statistically significant differences in CCA-IMT could be detected between persons with plasma Lp(a)<300mg/l or >or=300mg/l, respectively.

CONCLUSION

Our data suggest that elevated Lp(a) levels alone do not contribute to increased cardiovascular risk by promoting early atherogenesis in vivo.

Lipoprotein(a): A Unique Risk Factor for Cardiovascular Disease

Lipoprotein(a) (Lp(a)) is present in humans and primates. It has many properties in common with low-density lipoprotein, but contains a unique protein moiety designated apo(a), which is linked to apolipoprotein B-100 by a single disulfide bond. International standards for Lp(a) measurement and optimized Lp(a) assays insensitive to isoform size are not yet widely available. Lp(a) is a risk factor for coronary artery disease, and smaller size apo(a) is associated with coronary artery disease. The physiologic role of Lp(a) is unknown.

Resistance training lowers exercise-induced oxidative stress and homocysteine levels in overweight and obese older adults

OBJECTIVE

To compare exercise-induced oxidative stress and levels of homocysteine and cholesterol in normal-weight and overweight older adults after resistance exercise (RX).

RESEARCH METHODS AND PROCEDURES

This interventional study was conducted at a wellness center. Forty-nine older adults (age range, 60 to 72 years) were stratified by BMI (<25 kg/m(2) normal weight, > or =25 kg/m(2) overweight/obese) and then randomly assigned to either a control non-exercise group or an RX group. The RX group completed a 6-month training program. Exercise-induced lipid hydroperoxides (PEROXs) and thiobarbituric-reactive acid substances, homocysteine, lipoprotein a, cholesterol, and high-density lipoprotein cholesterol were measured before and after the 6-month RX program.

RESULTS

PEROXs and thiobarbituric-reactive acid substances were lower in both the overweight/obese and normal-weight RX-trained groups compared with control groups (p < 0.05). Homocysteine levels were lower in both overweight/obese and normal-weight RX groups compared with control groups (p < 0.05). Lipoprotein a, total cholesterol, and high-density lipoprotein cholesterol were not different in normal-weight and overweight/obese groups before or after RX. The change in muscle strength was correlated with homocysteine at 6 months (r = -0.452, p < 0.05), whereas the change in PEROXs was correlated with the change in body fat (r = -0.329).

DISCUSSION

To our knowledge, these data are the first to show that RX reduces exercise-induced oxidative stress and homocysteine regardless of adiposity, indicating that this protection can be afforded in an older, overweight/obese population as effectively as in healthy older adults. These data suggest that RX may afford some protection against emerging cardiovascular risk factors using a mode of exercise that supports body weight.

Homocysteine, vitamin B12 and folate levels in premature coronary artery disease

BACKGROUND

Hyperhomocysteinemia is known as an independent risk factor of atherosclerosis, but the probable role of hyperhomocysteinemia in premature Coronary Artery Disease (CAD) is not well studied. The aim of this study was to assess the role of hyperhomocysteinemia, folate and Vitamin B12 deficiency in the development of premature CAD.

METHODS

We performed an analytical case-control study on 294 individuals under 45 years (225 males and 69 females) who were admitted for selective coronary angiography to two centers in Tehran.

RESULTS

After considering the exclusion criteria, a total number of 225 individuals were enrolled of which 43.1% had CAD. The mean age of participants was 39.9 +/- 4.3 years (40.1 +/- 4.2 years in males and 39.4 +/- 4.8 years in females). Compared to the control group, the level of homocysteine measured in the plasma of the male participants was significantly high (14.9 +/- 1.2 versus 20.3 +/- 1.9 micromol/lit, P = 0.01). However there was no significant difference in homocysteine level of females with and without CAD (11.8 +/- 1.3 versus 11.5 +/- 1.1 micromol/lit, P = 0.87). Mean plasma level of folic acid and vitamin B12 in the study group were 6.3 +/- 0.2 and 282.5 +/- 9.1 respectively. Based on these findings, 10.7% of the study group had folate deficiency while 26.6% had Vitamin B12 deficiency. Logistic regression analysis for evaluating independent CAD risk factors showed hyperhomocysteinemia as an independent risk factor for premature CAD in males (OR = 2.54 0.95% CI 1.23 to 5.22, P = 0.01). Study for the underlying causes of hyperhomocysteinemia showed that male gender and Vitamin B12 deficiency had significant influence on incidence of hyperhomocysteinemia.

CONCLUSION

We may conclude that hyperhomocysteinemia is an independent risk factor for CAD in young patients (below 45 years old)--especially in men--and vitamin B12 deficiency is a preventable cause of hyperhomocysteinemia.

Myocardial infarction in young adults

Although myocardial infarction (MI) mainly occurs in patients older than 45, young men or women can suffer MI. Fortunately, its incidence is not common in patients younger than 45 years. However, the disease carries a significant morbidity, psychological effects, and financial constraints for the person and the family when it occurs at a young age. The causes of MI among patients aged less than 45 can be divided into four groups: (1) atheromatous coronary artery disease; (2) non-atheromatous coronary artery disease; (2) hyper-coagulable states; (4) MI related to substance misuse. There is a considerable overlap between all the groups. This article reviews the literature and highlights the practical issues involved in the management of young adults with MI.

C-Reactive Protein and Other Emerging Blood Biomarkers to Optimize Risk Stratification of Vulnerable Patients

Several emerging plasma biomarkers may ultimately prove useful in risk stratification and prognosis of cardiovascular disease. The clinical utility of these biomarkers will depend on their ability to provide a reflection of the underlying atherosclerotic burden or activity; the ability to provide reliable, accurate, and cost-effective information; and the ability to predict future events. High-sensitivity C-reactive protein (hs-CRP) fulfills many, if not all, of these criteria, and blood levels of hs-CRP are now commonly used in clinical practice to improve vascular risk prediction in primary and secondary prevention across all levels of low-density lipoprotein-cholesterol (LDL-C), all levels of the Framingham Risk Score, and all levels of metabolic syndrome. High-sensitivity C-reactive protein may also have clinical relevance as an adjunct to LDL-C for both the targeting and monitoring of statin therapy. Accumulating evidence suggests that several other selected emerging biomarkers may also potentially prove useful in the diagnosis and prognosis of cardiovascular disease. Specifically, data are accumulating on the potential clinical utility of lipoprotein-associated lipoprotein-associated phospholipase A2, myeloperoxidase, oxidized LDL, lipoprotein (a), isoprostanes, and small, dense LDL. This review focuses on hs-CRP and these emerging plasma biomarkers, and their potential diagnostic and prognostic utility in cardiovascular disease. Plasma biomarkers that reflect the clinical potential of atherothrombotic disease may allow more precise risk stratification and prognostication in high-risk populations, and perhaps earlier diagnosis and intervention in patients at risk for or with occult cardiovascular disease.

Lipoprotein(a) in atherosclerotic plaques recruits inflammatory cells through interaction with Mac‐1 integrin

Lipoprotein(a) [Lp(a)], consisting of LDL and the unique constituent apolipoprotein(a) [apo(a)], which contains multiple repeats resembling plasminogen kringle 4, is considered a risk factor for the development of atherosclerotic disorders. However, the underlying mechanisms for the atherogenicity of Lp(a) are not completely understood. Here, we define a novel function of Lp(a) in promoting inflammatory cell recruitment that may contribute to its atherogenicity. Through its apo(a) moiety Lp(a) specifically interacts with the beta2-integrin Mac-1, thereby promoting the adhesion of monocytes and their transendothelial migration in a Mac-1-dependent manner. Interestingly, the interaction between Mac-1 and Lp(a) was strengthened in the presence of proatherogenic homocysteine and was blocked by plasminogen/angiostatin kringle 4. Through its interaction with Mac-1, Lp(a) induced activation of the proinflammatory transcription factor NFkappaB, as well as the NFkappaB-related expression of prothrombotic tissue factor. In atherosclerotic coronary arteries Lp(a) was found to be localized in close proximity to Mac-1 on infiltrating mononuclear cells. Taken together, our data demonstrate that Lp(a), via its apo(a) moiety, is a ligand for the beta2-integrin Mac-1, thereby facilitating inflammatory cell recruitment to atherosclerotic plaques. These observations suggest a novel mechanism for the atherogenic properties of Lp(a).

Lipoprotein(a) and atherosclerosis: new perspectives on the mechanism of action of an enigmatic lipoprotein

Although elevated plasma concentrations of lipoprotein(a) (Lp(a)) have been identified as a risk factor for coronary heart disease, the pathophysiologic and physiologic roles of Lp(a) continue to elude basic researchers and clinicians alike. Lp(a) is a challenging lipoprotein to study because it has a complex structure consisting of a low-density lipoprotein-like moiety to which is covalently attached the unique glycoprotein apolipoprotein(a) (apo(a)). Apo(a) contains multiply repeated kringle domains that are similar to a sequence found in the fibrinolytic proenzyme plasminogen; differing numbers of kringle sequences in apo(a) give rise to Lp(a) isoform size heterogeneity. In addition to elevated plasma concentrations of Lp(a), apo(a) isoform size has been identified as a risk factor for coronary heart disease, although studies addressing this relationship have been limited. The similarity of Lp(a) to low-density lipoprotein and plasminogen provides an enticing link between the processes of atherosclerosis and thrombosis, although a clear demonstration of this association in vivo has not been provided. Clearly, Lp(a) is a risk factor for both atherothrombotic and purely thrombotic events; a plethora of mechanisms to explain these clinical findings has been provided by both in vitro studies as well as animal models for Lp(a).

Molecular targeting by homocysteine: a mechanism for vascular pathogenesis

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease. Although there is a growing body of evidence that homocysteine plays a causal role in atherogenesis, specific mechanisms to explain the underlying pathology have remained elusive. This review focuses on chemistry unique to the homocysteine molecule to explain its inherent cytotoxicity. Thus, the high pKa of the sulfhydryl group (pKa=10.0) of homocysteine underlies its ability to form stable disulfide bonds with protein cysteine residues, and in the process, alters or impairs the function of the protein. Albumin, fibronectin, transthyretin, annexin II, and factor V have now been identified as molecular targets for homocysteine, and in the case of albumin, the mechanism of targeting has been elucidated.

Plasma homocysteine and lipoprotein (a) levels in Turkish patients with metabolic syndrome

High serum total homocysteine (tHcy) and lipoprotein (a) [Lp(a)] levels are independent risk factors for cardiovascular disease. In this study, we examined the relationship of tHcy and Lp(a) levels with the components of metabolic syndrome. Fifty-one patients diagnosed with metabolic syndrome (median age: 38 [range 25-48] years) and 50 healthy subjects (median age: 35 [26-48] years) were included in the study. We used the National Cholesterol Education Program criteria to define metabolic syndrome. Total tHcy concentrations were measured by using an IMX (Abbott Diagnostics, Abbott Park, IL, USA). Lipoprotein (a) was measured by immunonephelometry using Behring nephrometer method (Behring BN 100, Behring, Germany). Total homocysteine and Lp(a) levels were found to be higher in the metabolic syndrome group than in the control group (tHcy: 24.2 vs 13.4 micromol/l, P < 0.01 and Lp(a): 34.9 vs 15.8 mg/dl, P < 0.01). Vitamin B12 levels were lower in the metabolic syndrome group than in the control group (214 pg/ml vs 247 pg/ml, P < 0.01). In partial correlation, tHcy and Lp(a) concentrations were unrelated to metabolic syndrome or to the components of metabolic syndrome, including fasting serum triglycerides, HDL-cholesterol, fasting glucose, blood pressure, or body mass index. tHcy levels were strongly related only to the vitamin B12 concentration. The risk of cardiovascular disease is higher in patients with metabolic syndrome compared with the normal population. High tHcy and Lp(a) levels should be evaluated in this group of patients in addition to the evaluation of the parameters of metabolic syndrome.

Oxidized phospholipids, Lp(a) lipoprotein, and coronary artery disease

BACKGROUND

Lp(a) lipoprotein binds proinflammatory oxidized phospholipids. We investigated whether levels of oxidized low-density lipoprotein (LDL) measured with use of monoclonal antibody E06 reflect the presence and extent of obstructive coronary artery disease, defined as a stenosis of more than 50 percent of the luminal diameter.

METHODS

Levels of oxidized LDL and Lp(a) lipoprotein were measured in a total of 504 patients immediately before coronary angiography. Levels of oxidized LDL are reported as the oxidized phospholipid content per particle of apolipoprotein B-100 (oxidized phospholipid:apo B-100 ratio).

RESULTS

Measurements of the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels were skewed toward lower values, and the values for the oxidized phospholipid:apo B-100 ratio correlated strongly with those for Lp(a) lipoprotein (r=0.83, P<0.001). In the entire cohort, the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels showed a strong and graded association with the presence and extent of coronary artery disease (i.e., the number of vessels with a stenosis of more than 50 percent of the luminal diameter) (P<0.001). Among patients 60 years of age or younger, those in the highest quartiles for the oxidized phospholipid:apo B-100 ratio and Lp(a) lipoprotein levels had odds ratios for coronary artery disease of 3.12 (P<0.001) and 3.64 (P<0.001), respectively, as compared with patients in the lowest quartile. The combined effect of hypercholesterolemia and being in the highest quartiles of the oxidized phospholipid:apo B-100 ratio (odds ratio, 16.8; P<0.001) and Lp(a) lipoprotein levels (odds ratio, 14.2; P<0.001) significantly increased the probability of coronary artery disease among patients 60 years of age or younger. In the entire study group, the association of the oxidized phospholipid:apo B-100 ratio with obstructive coronary artery disease was independent of all clinical and lipid measures except one, Lp(a) lipoprotein. However, among patients 60 years of age or younger, the oxidized phospholipid:apo B-100 ratio remained an independent predictor of coronary artery disease.

CONCLUSIONS

Circulating levels of oxidized LDL are strongly associated with angiographically documented coronary artery disease, particularly in patients 60 years of age or younger. These data suggest that the atherogenicity of Lp(a) lipoprotein may be mediated in part by associated proinflammatory oxidized phospholipids.

Relevance of post-methionine homocysteine and lipoprotein (a) in evaluating the cardiovascular risk in young CAD patients

BACKGROUND

Aims of our study were to evaluate the prevalence of high lipoprotein (a) [Lp(a)] and homocysteine levels - both in the fasting state (FHcy) and post-methionine (PMHcy) - in young coronary artery disease (CAD) patients, and to investigate the role of genetic and environmental factors for hyperhomocysteinaemia.

MATERIALS AND METHODS

We studied 140 patients with angiographically documented CAD (24 women </= 55 years and 116 men </= 50 years) and 140 healthy subjects as controls.

RESULTS

Both FHcy [13.2 (5.4-45.8) vs. 9.0 (5.1-24) micromol L(-1)); P < 0.0001] and PMHcy [(39.4 (9.0-66.4) vs. 25.2 (16.4-33.9); P < 0.0001] were significantly higher in patients than in controls. Lp(a) levels were significantly higher in patients than in controls (200 (3-1486) mg L(-1) vs. 97 (10-412) mg L(-1); P < 0.0001). At the multivariate analysis, adjusted for the classical cardiovascular risk factors and creatinine levels, the OR (95% CI) for CAD at young age significantly increased in the fourth quartile of the distribution of FHcy, PMHcy and Lp(a) levels [FHcy: 14.9 (4.1-58), P < 0.0001; PMHcy: 19.2 (4.0-86.3); P < 0.0001; Lp(a): 19.6 (4.7-78.6): < 0.0001]. Vitamin deficiencies were detected in 28/140 (20%) patients. The prevalence of the homozygous C677T (+/+) methylenetetrahydrofolatereductase genotype was higher, but not significantly different, in patients (22.8%) than in controls (18.6%). The allele frequency of the 844ins68 insertion variant in the cystathionine beta-synthase gene was 0.08 in the control group and 0.06 in the patient group.

CONCLUSIONS

Results of the present study indicate the usefulness of including fasting and post-methionine Hcy, and Lp(a) determination in the diagnostic panels of young CAD patients, in order to obtain a better assessment of their cardiovascular risk profile.

Total homocysteine levels relation with chronic complications of diabetes, body composition, and other cardiovascular risk factors in a population of patients with diabetes mellitus type 2

OBJECTIVE

The significance of hyperhomocysteinemia in type 2 diabetes is further complicated by the multiple ways of considering impaired renal function and vitamin status. The aim of our study was to analyze the relationship between total homocysteine (tHcy) in a population of type 2 diabetic patients and chronic complications. We also analyzed the relationship between tHcy and the body composition of these patients and other cardiovascular risk factors.

DESIGN

In a cross-sectional study, a total of 155 patients with diabetes mellitus attending in our diabetes service (90 females/65 males) were enrolled in a consecutive way.

MATERIAL AND METHODS

All enrolled patients underwent the following examinations: (i) biochemical cardiovascular risk factors including total cholesterol, triglyceride, lipoprotein (a), low-density lipoprotein (LDL-cholesterol), high-density lipoprotein (HDL-cholesterol), glucose, HbA(1c), fibrinogen, homocysteine, vitamin B12, folate, and microalbuminuria; and (ii) fat mass assessed by body mass index, weight, percentage of fat mass, and tricipital skinfold.

RESULTS

Patients were divided in two groups (Group I: tHcy> or =15 micromol/l; Group II: tHcy<15 micromol/l). Smoking habit was similar in both groups. A prevalence of cerebrovascular accident was present in 3.3% in the total group. This prevalence was not different in both groups (7.4% vs. 2.3%; ns) (OR 3.3; 95% CI 0.49-19.68). The prevalence of coronary heart disease in the total group was 5.8% without statistical differences between groups (3.5% vs. 6.3%; ns) (OR 0.57; 95% CI 0.065-4.53). Concerning macrovascular complications, only peripheral vascular disease prevalence was higher in Group I (16% vs. 3.1%; P<0.05; OR 5.33; 95% CI 1.18-21.5). A prevalence of nephropathy was higher in Group I (93.3% vs. 12.8%; P<0.05; OR 7.15; 95% CI 2.9-17.9). No statistical differences were detected in prevalence of retinopathy (global group 41.9%) (42.5% vs. 40.9%; ns) (OR 1.75; 95% CI 0.78-3.9). Also, peripheral neuropathy was similar in both groups (7.1% vs. 6.5%; ns) (OR 1.1; 95% CI 0.15-8.2). No correlation was detected among homocysteine and anthropometric parameters (body mass index, weight, percentage of fat mass, fat mass, and tricipital skinfold). Elevated levels of fibrinogen, lipoprotein (a), microalbuminuria, and blood pressure were detected in Group I.

CONCLUSION

The present study shows that elevation of plasma tHcy levels in type 2 diabetic patients is associated with a higher prevalence of peripheral arteriopathy and nephropathy. Our data suggest that hyperhomocysteinemia is not associated with fat mass but it is associated with high levels of fibrinogen, lipoprotein (a), microalbuminuria, and blood pressure levels.

Lipoprotein(a): an elusive cardiovascular risk factor

Lipoprotein (a) [Lp(a)], is present only in humans, Old World nonhuman primates, and the European hedgehog. Lp(a) has many properties in common with low-density lipoprotein (LDL) but contains a unique protein, apo(a), which is structurally different from other apolipoproteins. The size of the apo(a) gene is highly variable, resulting in the protein molecular weight ranging from 300 to 800 kDa; this large variation may be caused by neutral evolution in the absence of any selection advantage. Apo(a) influences to a major extent metabolic and physicochemical properties of Lp(a), and the size polymorphism of the apo(a) gene contributes to the pronounced heterogeneity of Lp(a). There is an inverse relationship between apo(a) size and Lp(a) levels; however, this pattern is complex. For a given apo(a) size, there is a considerable variation in Lp(a) levels across individuals, underscoring the importance to assess allele-specific Lp(a) levels. Further, Lp(a) levels differ between populations, and blacks have generally higher levels than Asians and whites, adjusting for apo(a) sizes. In addition to the apo(a) size polymorphism, an upstream pentanucleotide repeat (TTTTA(n)) affects Lp(a) levels. Several meta-analyses have provided support for an association between Lp(a) and coronary artery disease, and the levels of Lp(a) carried in particles with smaller size apo(a) isoforms are associated with cardiovascular disease or with preclinical vascular changes. Further, there is an interaction between Lp(a) and other risk factors for cardiovascular disease. The physiological role of Lp(a) is unknown, although a majority of studies implicate Lp(a) as a risk factor.

Epidemiology, pathophysiology and therapeutic implications of lipoprotein(a) in kidney disease

Chronic kidney disease is associated with a tremendously increased risk for cardiovascular disease. Traditional risk factors for cardiovascular disease, however, show a diminished predictive power in these patients compared with the general population. This review provides an overview of lipoprotein(a), which is considered a nontraditional risk factor. The characteristic genetic and nongenetic changes of lipoprotein(a) in kidney disease are discussed and set into the context of risk prediction. In particular, genetically determined apolipoprotein(a) polymorphism is a powerful risk predictor for cardiovascular disease and total mortality in these patients. Finally, the limited interventional strategies available to lower lipoprotein(a) are considered.

Premature coronary artery disease: clinical risk factors and prognosis

Coronary artery disease (CAD) that becomes manifest in young adults can have devastating consequences. Additionally, the study of young patients with CAD may provide insight into the genetic basis of coronary disease. Over the past few years, our understanding of risk factors in this population has been expanded to include social, environmental, and emotional factors. The identification of genetic markers for disease is just beginning. Also, it has recently been shown that CAD in young adults has a poor long-term prognosis, meaning that clinicians caring for these patients must be aggressive in risk factor control.

DACH-LIGA homocystein (german, austrian and swiss homocysteine society): consensus paper on the rational clinical use of homocysteine, folic acid and B-vitamins in cardiovascular and thrombotic diseases: guidelines and recommendations

About half of all deaths are due to cardiovascular disease and its complications. The economic burden on society and the healthcare system from cardiovascular disability, complications, and treatments is huge and getting larger in the rapidly aging populations of developed countries. As conventional risk factors fail to account for part of the cases, homocysteine, a "new" risk factor, is being viewed with mounting interest. Homocysteine is a sulfur-containing intermediate product in the normal metabolism of methionine, an essential amino acid. Folic acid, vitamin B12, and vitamin B6 deficiencies and reduced enzyme activities inhibit the breakdown of homocysteine, thus increasing the intracellular homocysteine concentration. Numerous retrospective and prospective studies have consistently found an independent relationship between mild hyperhomocysteinemia and cardiovascular disease or all-cause mortality. Starting at a plasma homocysteine concentration of approximately 10 micromol/l, the risk increase follows a linear dose-response relationship with no specific threshold level. Hyperhomocysteinemia as an independent risk factor for cardiovascular disease is thought to be responsible for about 10% of total risk. Elevated plasma homocysteine levels (>12 micromol/l; moderate hyperhomocysteinemia) are considered cytotoxic and are found in 5 to 10% of the general population and in up to 40% of patients with vascular disease. Additional risk factors (smoking, arterial hypertension, diabetes, and hyperlipidemia) may additively or, by interacting with homocysteine, synergistically (and hence over-proportionally) increase overall risk. Hyperhomocysteinemia is associated with alterations in vascular morphology, loss of endothelial anti-thrombotic function, and induction of a procoagulant environment. Most known forms of damage or injury are due to homocysteine-mediated oxidative stress. Especially when acting as direct or indirect antagonists of cofactors and enzyme activities, numerous agents, drugs, diseases, and lifestyle factors have an impact on homocysteine metabolism. Folic acid deficiency is considered the most common cause of hyperhomocysteinemia. An adequate intake of at least 400 microg of folate per day is difficult to maintain even with a balanced diet, and high-risk groups often find it impossible to meet these folate requirements. Based on the available evidence, there is an increasing call for the diagnosis and treatment of elevated homocysteine levels in high-risk individuals in general and patients with manifest vascular disease in particular. Subjects of both populations should first have a baseline homocysteine assay. Except where manifestations are already present, intervention, if any, should be guided by the severity of hyperhomocysteinemia. Consistent with other working parties and consensus groups, we recommend a target plasma homocysteine level of <10 micromol/l. Based on various calculation models, reduction of elevated plasma homocysteine concentrations may theoretically prevent up to 25% of cardiovascular events. Supplementation is inexpensive, potentially effective, and devoid of adverse effects and, therefore, has an exceptionally favorable benefit/risk ratio. The results of ongoing randomized controlled intervention trials must be available before screening for, and treatment of, hyperhomocysteinemia can be recommended for the apparently healthy general population.

Homocysteine and lipoprotein levels following resistance training in older adults

This investigation examined the effect of 6 months of high- or low-intensity resistance exercise on serum homocysteine and lipoprotein (a) levels in adults aged 60-80 years. Forty-three men and women completed the study protocol. Subjects were randomly assigned to a control (n=10), low-intensity (LEX, n=18), or high-intensity (HEX, n=15) group. Subjects performed 6 months of resistance training at either 50% of their one-repetition maximum for 13 repetitions (LEX) or 80% of one-repetition maximum for eight repetitions (HEX) 3 times per week for 24 weeks. The load was increased by 5% when their rating of perceived exertion dropped below 18. One-repetition maximum; serum homocysteine; lipoprotein (a); total and high-density lipoprotein cholesterol; and dietary intake of vitamins B12, B6, and folic acid were measured pre- and poststudy. Upper and lower body strength significantly (p<0.05) increased for the LEX and HEX groups. Serum homocysteine decreased 5.30% and 5.34% for the LEX and HEX groups, respectively (p<0.05), but increased 6.1% for the control group. A significant increase in lipoprotein (a) levels was noted in the control and LEX groups from pre- to poststudy. No significant differences were noted either pre- or poststudy for total and high-density lipoprotein cholesterol or any dietary variables. These data indicate that significant reductions in serum levels of homocysteine in the elderly can be derived from resistance exercise training.

Homocysteine and hemostatic disorder as a risk factor for myocardial infarction at a young age

INTRODUCTION

Hyperhomocysteinemia is a coronary risk factor, but its pathophysiologic mechanism remains unclear.

MATERIALS AND METHODS

The importance of hyperhomocysteinemia in the pathogenesis of early myocardial infarction, was determined in case-control study of 127 men with a first early myocardial infarction <or=45 years and 150 age-matched male controls. We measured plasma concentrations of homocysteine, fibrinogen, antithrombin, tissue factor, tissue factor pathway inhibitor, tissue plasminogen activator, plasminogen activator inhibitor-I, plasminogen, alpha(2)-antiplasmin, lipoprotein(a), protein C, protein S, factor VII, and activated factor VII.

RESULTS

Homocysteine concentrations were higher in patients with early myocardial infarction than in controls (11.2+/-5.3 and 8.3+/-5.0 micromol/l, respectively, P<0.001). Hyperhomocysteinemia was associated with early myocardial infarction (odds ratio=2.22, P<0.001) by multivariate logistic regression analysis. Tissue factor, antithrombin, plasminogen, tissue plasminogen activator, plasminogen activator inhibitor-I, lipoprotein(a), diabetes, and smoking also had associations. In a stepwise logistic regression analysis, hyperhomocysteinemia was the strongest predictor of early myocardial infarction (R(2)=0.19, P<0.001). Hyperhomocysteinemia also had positive correlations with tissue factor (rho=0.26, P=0.009), tissue factor pathway inhibitor (rho=0.23, P=0.020), and tissue plasminogen activator (rho=0.25, P=0.011) in patients with early myocardial infarction, but not in controls.

CONCLUSIONS

Hyperhomocysteinemia is an independent risk factor for early myocardial infarction, and is associated with a hypercoagulable state mediated by the extrinsic coagulation cascade.

Lipoprotein(a): an emerging cardiovascular risk factor

Lipoprotein(a) is a cholesterol-enriched lipoprotein, consisting of a covalent linkage joining the unique and highly polymorphic apolipoprotein(a) to apolipoprotein B100, the main protein moiety of low-density lipoproteins. Although the concentration of lipoprotein(a) in humans is mostly genetically determined, acquired disorders might influence synthesis and catabolism of the particle. Raised concentration of lipoprotein(a) has been acknowledged as a leading inherited risk factor for both premature and advanced atherosclerosis at different vascular sites. The strong structural homologies with plasminogen and low-density lipoproteins suggest that lipoprotein(a) might represent the ideal bridge between the fields of atherosclerosis and thrombosis in the pathogenesis of vascular occlusive disorders. Unfortunately, the exact mechanisms by which lipoprotein(a) promotes, accelerates, and complicates atherosclerosis are only partially understood. In some clinical settings, such as in patients at exceptionally low risk for cardiovascular disease, the potential regenerative and antineoplastic properties of lipoprotein(a) might paradoxically counterbalance its athero-thrombogenicity, as attested by the compatibility between raised plasma lipoprotein(a) levels and longevity.