Homocyst(e)ine and risk of cardiovascular disease in the Multiple Risk Factor Intervention Trial

Peritoneal Homocysteine Clearance is Inefficient in Peritoneal Dialysis Patients

Objectives

To investigate the degree and the determinants of peritoneal homocysteine (Hcy) clearance and to compare measured Hcy clearance with the Hcy clearance predicted based on molecular weight (MW).

Design

Cross-sectional observational analysis.

Setting

Tertiary care institutional dialysis center.

Patients

Sixty-five stable peritoneal dialysis (PD) patients.

Outcome Measures

Fasting blood and 24-hour pooled dialysate effluents were collected for determination of peritoneal clearances of Hcy (CpHcy), urea (CpUr), and creatinine (CpCr). The dialysate-to-plasma creatinine ratio at 4 hours (D/P Cr 4 h) and levels of red cell folate, B12, ferritin, and C-reactive protein (CRP) were measured concurrently. Observed CpHcy was compared with predicted clearance, based on Hcy plasma protein binding and the relative molecular weights of Hcy, urea, and creatinine.

Results

Plasma concentrations of Hcy averaged 24.6 ± 1.1 μmol/L and were elevated above the upper limit of normal in 59 (91%) patients. The mean dialysate concentration of Hcy was 2.9 ± 0.3 μmol/L, equating to a daily peritoneal elimination of 34.6 ± 3.6 μmol. Observed CpHcy was closely approximated by predicted CpHcy (8.7 ± 0.6 L/week/1.73 m2vs 9.0 ± 0.3 L/week/1.73 m2respectively, p = 0.55). Patients maintained on automated PD ( n = 5) had a CpHcy similar to that of patients treated with continuous ambulatory peritoneal dialysis (8.9 ± 1.0 L/week/1.73 m2vs 8.7 ± 0.6 L/week/1.73 m2, p = 0.92). The CpHcy was significantly correlated with C-reactive protein (CRP), D/P creatinine, CpUr, CpCr, and peritoneal protein loss, but not with plasma Hcy, albumin, B12, ferritin, age, dialysis duration, peritonitis episodes, or daily dialysate effluent volume. By multivariate analysis, the only variables that remained significant independent predictors of CpHcy were CRP and D/P Cr 4 h. High and high-average transporters had a higher CpHcy than low and low-average transporters (9.7 ± 0.8 L/week/1.73 m2vs 7.0 ± 0.7 L/week/1.73 m2, p < 0.05), despite comparably elevated plasma Hcy concentrations [25.2 ± 1.5 μmol/L vs 23.4 ± 1.6 μmol/L, p = nonsignificant (NS)].

Conclusions

Elevated plasma concentrations of Hcy are not efficiently reduced by PD. The relatively low peritoneal clearance of Hcy is largely accounted for by a high degree of plasma protein binding and is significantly influenced by peritoneal membrane permeability.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY GUIDELINES FOR MANAGEMENT OF DYSLIPIDEMIA AND PREVENTION OF CARDIOVASCULAR DISEASE

OBJECTIVE

The development of these guidelines is mandated by the American Association of Clinical Endocrinologists (AACE) Board of Directors and American College of Endocrinology (ACE) Board of Trustees and adheres with published AACE protocols for the standardized production of clinical practice guidelines (CPGs).

METHODS

Recommendations are based on diligent reviews of the clinical evidence with transparent incorporation of subjective factors, according to established AACE/ACE guidelines for guidelines protocols.

RESULTS

The Executive Summary of this document contains 87 recommendations of which 45 are Grade A (51.7%), 18 are Grade B (20.7%), 15 are Grade C (17.2%), and 9 (10.3%) are Grade D. These detailed, evidence-based recommendations allow for nuance-based clinical decision-making that addresses multiple aspects of real-world medical care. The evidence base presented in the subsequent Appendix provides relevant supporting information for Executive Summary Recommendations. This update contains 695 citations of which 203 (29.2 %) are EL 1 (strong), 137 (19.7%) are EL 2 (intermediate), 119 (17.1%) are EL 3 (weak), and 236 (34.0%) are EL 4 (no clinical evidence).

CONCLUSION

This CPG is a practical tool that endocrinologists, other health care professionals, health-related organizations, and regulatory bodies can use to reduce the risks and consequences of dyslipidemia. It provides guidance on screening, risk assessment, and treatment recommendations for a range of individuals with various lipid disorders. The recommendations emphasize the importance of treating low-density lipoprotein cholesterol (LDL-C) in some individuals to lower goals than previously endorsed and support the measurement of coronary artery calcium scores and inflammatory markers to help stratify risk. Special consideration is given to individuals with diabetes, familial hypercholesterolemia, women, and youth with dyslipidemia. Both clinical and cost-effectiveness data are provided to support treatment decisions.

ABBREVIATIONS

4S = Scandinavian Simvastatin Survival Study A1C = glycated hemoglobin AACE = American Association of Clinical Endocrinologists AAP = American Academy of Pediatrics ACC = American College of Cardiology ACE = American College of Endocrinology ACS = acute coronary syndrome ADMIT = Arterial Disease Multiple Intervention Trial ADVENT = Assessment of Diabetes Control and Evaluation of the Efficacy of Niaspan Trial AFCAPS/TexCAPS = Air Force/Texas Coronary Atherosclerosis Prevention Study AHA = American Heart Association AHRQ = Agency for Healthcare Research and Quality AIM-HIGH = Atherothrombosis Intervention in Metabolic Syndrome With Low HDL/High Triglycerides trial ASCVD = atherosclerotic cardiovascular disease ATP = Adult Treatment Panel apo = apolipoprotein BEL = best evidence level BIP = Bezafibrate Infarction Prevention trial BMI = body mass index CABG = coronary artery bypass graft CAC = coronary artery calcification CARDS = Collaborative Atorvastatin Diabetes Study CDP = Coronary Drug Project trial CI = confidence interval CIMT = carotid intimal media thickness CKD = chronic kidney disease CPG(s) = clinical practice guideline(s) CRP = C-reactive protein CTT = Cholesterol Treatment Trialists CV = cerebrovascular CVA = cerebrovascular accident EL = evidence level FH = familial hypercholesterolemia FIELD = Secondary Endpoints from the Fenofibrate Intervention and Event Lowering in Diabetes trial FOURIER = Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects With Elevated Risk trial HATS = HDL-Atherosclerosis Treatment Study HDL-C = high-density lipoprotein cholesterol HeFH = heterozygous familial hypercholesterolemia HHS = Helsinki Heart Study HIV = human immunodeficiency virus HoFH = homozygous familial hypercholesterolemia HPS = Heart Protection Study HPS2-THRIVE = Treatment of HDL to Reduce the Incidence of Vascular Events trial HR = hazard ratio HRT = hormone replacement therapy hsCRP = high-sensitivity CRP IMPROVE-IT = Improved Reduction of Outcomes: Vytorin Efficacy International Trial IRAS = Insulin Resistance Atherosclerosis Study JUPITER = Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin LDL-C = low-density lipoprotein cholesterol Lp-PLA2 = lipoprotein-associated phospholipase A2 MACE = major cardiovascular events MESA = Multi-Ethnic Study of Atherosclerosis MetS = metabolic syndrome MI = myocardial infarction MRFIT = Multiple Risk Factor Intervention Trial NCEP = National Cholesterol Education Program NHLBI = National Heart, Lung, and Blood Institute PCOS = polycystic ovary syndrome PCSK9 = proprotein convertase subtilisin/kexin type 9 Post CABG = Post Coronary Artery Bypass Graft trial PROSPER = Prospective Study of Pravastatin in the Elderly at Risk trial QALY = quality-adjusted life-year ROC = receiver-operator characteristic SOC = standard of care SHARP = Study of Heart and Renal Protection T1DM = type 1 diabetes mellitus T2DM = type 2 diabetes mellitus TG = triglycerides TNT = Treating to New Targets trial VA-HIT = Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial VLDL-C = very low-density lipoprotein cholesterol WHI = Women's Health Initiative.

Assessment of Serum Folic Acid and Homocysteine in Thalassemia Major Patients Before and After Folic Acid Supplement Cessation

BACKGROUND

Thalassemic patients have ineffective erythropoiesis. In recent treatment protocols, there are little data on folic acid supplementation for patients with thalassemia because it is supposed that regular blood transfusions prevent bone marrow hyperfunctioning.

OBJECTIVE

Investigators aimed to assess serum folic acid and homocysteine (Hcy) in thalassemia major patients before and after folic acid supplement cessation.

PATIENTS AND METHODS

This study was a before-after controlled clinical trial conducted in 17th Shahrivar Hospital, Rasht, North of Iran, during May to October 2016. The patients enrolled in this study had thalassemia major on regular blood transfusion and older than 2 years of age. They had at least a 6-month history of folic acid supplement consumption before enrollment in the study (1 mg/daily). Complete blood count, serum folic acid, and serum Hcy were measured before discontinuation of folic acid supplement. Then, patients did not receive folic acid for a month and after 1 month of folic acid cessation, the measurements were repeated. All data were entered in SPSS version 20.0 and analyzed.

RESULTS

Among the 40 patients in this study, 25 (62.5%) were female. The mean age of the participants was 21.39±11.17 years old. The mean of body mass index was 21.38±3.32 kg/m. Most of the participants had used folic acid supplement >5 years (29, 72.5%). The serum Hcy level was significantly increased (5.24±2.35 vs. 5.93±2.56; P=0.008) and serum folic acid level was decreased significantly (14.74±4.20 vs. 8.80±4.16; P<0.0001) from baseline.

CONCLUSIONS

Cessation of folic acid supplementations in beta thalassemia major patients can lead to a significant decrease in serum folic acid and increase in Hcy levels. According to our findings and efficacy of folic acid in patients with beta thalassemia major, it is recommended to use the supplementation in all patients.

Correlation Between Hyperhomocysteinemia and Outcomes of Patients With Acute Myocardial Infarction

Overwhelming clinical and epidemiological studies have identified elevated plasma total homocysteine (Hcy) as new important risk factor for atherosclerotic vascular disease. But the relationship between outcome and hyperhomocysteinemia in patients with acute myocardial infarction (AMI) has been rarely reported. This study aimed to evaluate the association between hyperhomocysteinemia and short-term outcomes of patients with AMI. Eight hundred five patients were divided into high Hcy level group (group H: N = 457) and low Hcy level group (group L: N = 348) according to the plasma Hcy levels of 15 mmol/L. The comparisons were made between 2 groups in the following aspects: sex, hypertension, diabetes, hyperlipidemia, the time for symptom from onset to percutaneous coronary intervention, homoccyteine, creatine phosphokinase isoenzyme (creatine kinase myocardial band), and the incidence of 30-day adverse events. The incidences of heart failure, cardiac rupture, death, and the total adverse cardiovascular events were statistically significantly higher in group H than in group L. But the incidence of postoperative angina pectoris and reinfarction was similar between groups. The results of logistic regression showed that the incidence of 30-day adverse events was closely related to the age and the level of Hcy. An elevated plasma total Hcy level in patients with AMI experienced pemutaneous coronary intervention may be related to the short-term outcomes. An elevated high plasma Hcy level also seems to be an independent predictor of 30-day cardiovascular events in patients with AMI.

Design and statistical issues in the homocysteinemia in kidney and end stage renal disease (HOST) study

The Homocysteine Study (HOST) Veterans Affairs Cooperative Studies Program No. 453, is a prospective, randomized, two arm, double blind study of patients with end stage renal disease (ESRD) or advanced chronic kidney disease (ACKD, defined as an estimated creatinine clearance of 30 ml/min or less). Its primary objective is to determine whether administration of high doses of three vitamins, folic acid, vitamin B6 and vitamin B12, to lower the high plasma homocysteine levels, will reduce all cause mortality. The secondary objectives are to examine whether the treatment lowers the incidence of myocardial infarction, stroke, amputation of a lower extremity, a composite of death and the foregoing three events, the plasma homocysteine level, and, in ESRD patients undergoing hemodialysis, thrombosis of the vascular access. A unique feature of this trial is that after initial evaluation at enrollment and one return visit the follow up is exclusively by phone (or, if necessary, by mail). The subject is contacted every three months throughout the duration of the study from a central location. The study drug is shipped to the patient from a central location rather supplied locally. In a two year enrollment period, 2006 patients are to be enrolled. The duration of the observation period is four to six years. Data will be stored and analyzed at a coordinating center. The study design has the power to detect a reduction in all cause mortality rate of 17%. Issues related to the unique features of the design of this study are discussed.

Lack of association between early atherosclerotic carotid artery wall lesions and serum level of homocysteine

The present study evaluated the possible association of high serum levels of homocysteine with ultrasonographic manifestations of carotid atherosclerosis in 65-year-old Finnish subjects drawn from a population-based cohort. Carotid ultrasonographic measurements were performed on 54 diabetic subjects, 97 subjects with impaired glucose tolerance and 57 normoglycaemic subjects. There were no statistically significant differences between the groups in the homocysteine levels. The median homocysteine level was higher in the subjects with a history of myocardial infarction (MI) (n=9) than in the subjects with no history of MI (14.8 [range 8.7—18.3] vs.12.3 [range 6.4—49.0] µmol/L, p=0.045). In the subjects without a history of MI or stroke, the maximal intima-media thickness (IMT) of the common carotid artery did not differ in the homocysteine quintiles. There was no association between the number of atheromatous plaques and the homocysteine level. In conclusion, although high levels of serum homocysteine were not associated with early atherosclerotic changes (i.e. increased carotid IMT or the number of plaques), high homocysteine concentrations were associated with advanced atherosclerosis (i.e. a history of MI).

Oxidative Stress in Renal Transplant Patients Who Develop Cardiovascular Disease

Cardiovascular disease limits life expectancy of successful renal transplant patients. Reactive oxygen species have been implicated in the development of atherosclerosis, and high levels could be due to increased production or a decrease in antioxidant reserve. Cardiovascular disease in renal transplant recipients could be due to elevated levels of malondialdehyde (an index of levels of reactive oxygen species) and homocysteine and reduced levels of glutathione. Renal transplant recipients with and without cardiovascular disease were studied along with healthy controls. Serum malondialdehyde, plasma homocysteine, and red blood cell glutathione were measured. The results suggest that levels of serum malondialdehyde and plasma homocysteine were higher in patients with or without cardiovascular disease compared with controls; however, the values were similar in both groups of transplant patients. Glutathione levels in red blood cells were similar in all 3 groups. Renal transplant recipients without cardiovascular disease have high levels of oxidative stress and may develop cardiovascular disease with time.

Hyperhomocysteinemia, lipid and lipoprotein disturbances in patients with primary hypertension

PURPOSES

The main aim of the study was to answer two questions: what are the concentrations of total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, apo A-I (apolipoprotein A-I), apo B (apolipoprotein B) and Lp(a) (lipoprotein(a)) in serum of patients with primary hypertension and with hyperhomocysteinemia? Is there any correlation between the concentration of homocysteine in blood serum and investigated lipid and lipoprotein parameters in patients with primary hypertension?

MATERIAL/METHODS

We investigated 42 patients with primary hypertension, aged 22-57. The control group consisted of 20 healthy volunteers. The concentration of homocysteine in serum was evaluated using immunochemical method (FPIA - Fluorescence Polarization Immunoassay). The concentration of total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides in blood serum were estimated using enzymatic method. Apo A-I, apo B and lipoprotein(a) were assessed using nephelometric method.

RESULTS

The analysis of the results revealed statistically significant lower concentrations of HDL-cholesterol and apo A-I in blood serum of patients with primary hypertension and hyperhomocysteinemia than in the population with hypertension and normohomocysteinemia. Negative correlation between homocysteine and HDL-cholesterol as well as apo A-I has been revealed.

CONCLUSION

Quantitative analysis of the concentration of lipids and lipoproteins in blood serum in patients with primary hypertension and hyperhomocysteinemia may suggest that this type of human population might be more susceptible to atherosclerosis than those with primary hypertension and normal values of homocysteine.

Determining the Relationship Between Homocysteinemia and Biomarkers of Inflammation, Oxidative Stress and Functional Kidney Status in Patients with Diabetic Nephropathy

Background: One of the leading causes of terminal renal failure is diabetic nephropathy. The aim of this study was to determine the relationship between homocysteine levels and the biomarkers of renal function, inflammation and oxidative stress, as well as the incidence of macrovascular complications in patients with diabetic nephropathy.

Methods: Sixty-four patients with diabetic nephropathy were included in this study. They were divided according to their homocysteine levels into two groups: hyperhomocysteinemic (HHcy, n=47) and normohomocysteinemic patients (NHCy, n=17). The re sults were compared to a control group (n=20) with normal renal function and without diabetes. Besides homocysteine, cystatine C, creatinine, urea, albuminuria, creatinine clearance, lipid status parameters, apolipoprotein A-I and B, lipo protein (a), CRP, fibrinogen, oxidative LDL were determined using appropriate methods. The incidence of macro vascular diabetic complications was also determined.

Results: The results indicate that the level of renal dysfunction is greater in HHcy than in NHcy patients (p<0.05). In HHcy patients levels of oxLDL were also higher compared to NHcy patients (119.3±140.4 vs. 71.4±50.8 ng/mL, disp< 0.05) as well as fibrinogen levels (4.3±1.3 vs. 3.7±0.8 g/L, p<0.05). The in cidence of macrovascular complications is more frequent in HHcy than in NHcy patients (55.3. vs. 35.3 %, p>0.05), and in patients with macroalbuminuria compared to patients with microalbuminuria (65% vs. 39%, p<0.05).

Conclusions: It can be concluded that HHcy is significantly present in patients with diabetic nephropathy, especially if there is greater reduction of renal function. Besides that, significantly higher concentrations of inflammatory (fibrinogen) and oxidative stress (oxLDL) markers were present in HHcy patients with diabetic nephropathy compared to NHcy patients.Therefore in diabetic nephropathy patients it is useful to regularly monitor the levels of homocysteine, as well as inflammatory and markers of oxidative stress.

Management of hyperhomocysteinemia

Hyperhomocysteinemia is an established risk factor for cardiovascular disease. The modification of traditional cardiovascular risk factors has resulted in better morbidity and mortality outcomes, so the treatment of hyperhomocysteinemia is explored for a similar benefit. Vitamin B(6), vitamin B(12) and folate, as co-factors in the metabolism of homosyteine, are used in the treatment of hyperhomocysteinemia. Betaine, a methyl-donor in a separate homocysteine metabolism pathway, is also used to treat hyperhomocysteinemia. These supplements have been used in various doses and combinations for different periods of time, with favorable outcomes. There is still no concensus whether hyperhomocysteinemia can be treated with folic acid alone, or in combination with vitamin B(6) and vitamin B(12). The dose of the supplements required to normalize fasting homocysteine remains to be determined, especially in diabetic nephropathy, hemodialysis and renal transplant patients. The benefits from lowering homocysteine levels have mainly been demonstrated in surrogate cardiovascular outcomes. The treatment of hyperhomocysteinemia cannot be firmly advocated until there are trials that demonstrate a beneficial clinical endpoint. In patients who have cardiovascular disease in the absence of more established risk factors, investigation and treatment of hyperhomocysteinemia should be considered.

Interaction of folate intake and the paraoxonase Q192R polymorphism with risk of incident coronary heart disease and ischemic stroke: the atherosclerosis risk in communities study

PURPOSE

To investigate the potential interaction between folate intake and the paraoxonase 1 (PON1) Q192R polymorphism with the risk of incident coronary heart disease (CHD) and ischemic stroke in the Atherosclerosis Risk in Communities study, a population-based prospective cohort of cardiovascular disease in 15,792 white and African-American subject.

METHODS

Race-stratified Cox proportional hazards models were performed to examine the interaction between folate intake and the PON1 Q192R polymorphism.

RESULTS

A significant inverse association between folate intake and risk of incident CHD among white subjects was found (hazard rate ratio, 1.30; 95% confidence interval, 1.09-1.56; P = .004; folate intake ≤155 μg vs ≥279 μg, reference group). An interaction effect was observed between the dominant genetic model and folate intake with regards to incident ischemic stroke in white subjects (hazard rate ratio, 0.68; 95% confidence interval, 0.91-0.99; and 1.24 from 1st-4th quartile, respectively; P-trend = .05).

CONCLUSIONS

There was an interaction between folate intake and PON1 Q192 polymorphism with regard to the risk of ischemic stroke in white subjects. Future studies should investigate the interaction between additional polymorphisms within the PON1 gene and genetic variants in other folate metabolizing genes with folate intake on the risk of incident CHD and stroke.

Therapeutical approach to plasma homocysteine and cardiovascular risk reduction

Homocysteine is a sulfur-containing aminoacid produced during metabolism of methionine. Since 1969 the relationship between altered homocysteine metabolism and both coronary and peripheral atherotrombosis is known; in recent years experimental evidences have shown that elevated plasma levels of homocysteine are associated with an increased risk of atherosclerosis and cardiovascular ischemic events. Several mechanisms by which elevated homocysteine impairs vascular function have been proposed, including impairment of endothelial function, production of reactive oxygen species (ROS) and consequent oxidation of low-density lipids. Endothelial function is altered in subjects with hyperhomocysteinemia, and endothelial dysfunction is correlated with plasma levels of homocysteine. Folic acid and B vitamins, required for remethylation of homocysteine to methionine, are the most important dietary determinants of homocysteine and daily supplementation typically lowers plasma homocysteine levels; it is still unclear whether the decreased plasma levels of homocysteine through diet or drugs may be paralleled by a reduction in cardiovascular risk.

Association of homocysteine and methylene tetrahydrofolate reductase (MTHFR C677T) gene polymorphism with coronary artery disease (CAD) in the population of North India

The implications of the methylene tetrahydrofolate reductase (MTHFR) gene and the level of homocysteine in the pathogenesis of coronary artery disease (CAD) have been extensively studied in various ethnic groups. Our aim was to discover the association of MTHFR (C677T) polymorphism and homocysteine level with CAD in north Indian subjects. The study group consisted of 329 angiographically proven CAD patients, and 331 age and sex matched healthy individuals as controls. MTHFR (C677T) gene polymorphism was detected based on the polymerase chain reaction and restriction digestion with HinfI. Total homocysteine plasma concentration was measured using immunoassay. T allele frequency was found to be significantly higher in patients than in the control group. We found significantly elevated levels of mean homocysteine in the patient group when compared to the control group (p = 0.00). Traditional risk factors such as diabetes, hypertension, smoking habits, a positive family history and lipid profiles (triglyceride, total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol), were found significantly associated through univariate analysis. Furthermore, multivariable logistics regression analysis revealed that CAD is significantly and variably associated with diabetes, hypertension, smoking, triglycerides and HDL-cholesterol. Our findings showed that MTHFR C677T polymorphism and homocysteine levels were associated with coronary artery disease in the selected population.

Air pollution and homocysteine: more evidence that oxidative stress-related genes modify effects of particulate air pollution

BACKGROUND

Ambient particles are associated with cardiovascular events and recently with total plasma homocysteine. High total plasma homocysteine is a risk for human health. However, the biologic mechanisms are not fully understood. One of the putative pathways is through oxidative stress. We aimed to examine whether associations of PM2.5 and black carbon with homocysteine were modified by genotypes including HFE H63D, C282Y, CAT (rs480575, rs1001179, rs2284367, and rs2300181), NQO1 (rs1800566), GSTP1 I105V, GSTM1, GSTT1 (deletion vs. nondeletion), and HMOX-1 (any short vs. both long). We attempted to replicate identified genes in an analysis of heart rate variability and in other outcomes reported in the literature.

METHODS

Study subjects were 1000 white non-Hispanic men in the Boston area, participating in a cohort study of aging. PM2.5, black carbon, total plasma homocysteine, and other covariates were measured at several points in time between 1995 and 2006. We fit mixed models to examine effect modification of genes on associations of pollution with total plasma homocysteine.

RESULTS

Interquartile range increases in PM2.5 and black carbon (7-day moving averages) were associated with 1.5% (95% confidence interval = 0.2% to 2.8%) and 2.2% (0.6% to 3.9%) increases in total plasma homocysteine, respectively. GSTT1 and HFE C282Y modified effects of black carbon on total plasma homocysteine, and HFE C282Y and CAT (rs2300181) modified effects of PM2.5 on homocysteine. Several genotypes marginally modified effects of PM2.5 and black carbon on various endpoints. All genes with significant interactions with particulate air pollution had modest main effects on total plasma homocysteine.

CONCLUSIONS

: Effects of PM2.5 and black carbon on various endpoints appeared to be mediated by genes related to oxidative stress pathways.

Increased levels of C‐reactive protein and interleukin‐6 in hyperhomocysteinemic subjects

OBJECTIVE

Elevated plasma homocysteine concentration is considered to be an independent risk factor for cardiovascular disease. However, the mechanisms by which hyperhomocysteinemia are related to vascular disease are unclear. High-sensitivity C-reactive protein (CRP), a marker of inflammation, has been reported to be an independent predictor of future myocardial infarction among clinically healthy individuals. Interleukin (IL)-6 is a regulator of CRP and has a key role in initiation of inflammation. The aim of this study was to investigate whether individuals with increased plasma homocysteine concentrations have altered levels of serum CRP and IL-6.

MATERIAL AND METHODS

Serum concentrations of CRP and IL-6 were measured in 39 individuals with hyperhomocysteinemia and in 39 control subjects matched for gender, age and body mass index (BMI). In addition, the inflammatory effect of IL-6 on peripheral blood mononuclear cells was measured.

RESULTS

Compared to controls, hyperhomocysteinemic subjects have elevated serum levels of CRP and IL-6 (p < or =0.001 and p < 0.005, respectively). Importantly, this raised level of IL-6 was also seen in hyperhomocysteinemic individuals without accompanying hypercholesterolemia or cardiovascular disease. IL-6 increased the release of monocyte chemoattractant protein-1 from peripheral blood mononuclear cells, with particularly enhancing effects in cells from patients with hyperhomocysteinemia.

CONCLUSIONS

These data suggest that enhanced inflammation may be associated with homocysteine-related cardiovascular disease, possibly involving IL-6-related mechanisms.

Fasting total homocysteine (tHcy) concentration and mortality in older Mexican Americans

OBJECTIVES

This study examines the association between tHcy on cardiovascular and noncardiovascular mortality.

DESIGN

Longitudinal study of 1,633 Mexican Americans age>60 years recruited in 1998.

SETTING

Sacramento, California.

MEASUREMENTS

Cox proportional models were used to estimate the effects of tHcy on mortality rate in the total sample and in a subgroup of subjects without a history of cardiovascular disease at baseline.

RESULTS

About half of the cohort was born in Mexico. Among Mexican-born participants, high tHcy (>11.0 micromol/L) was associated with a higher rate of cardiovascular mortality compared to those with low tHcy concentration

CONCLUSIONS

The effect of tHcy on cardiovascular mortality is nearly 40% stronger among the immigrant group. tHcy might be an early marker of subclinical vascular pathology amongst the Mexican-born group, despite their apparently healthy profile at baseline.

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Key Words

• homocysteine
• cardiovascular mortality
• mexican americans
• nutritional biomarkers
• elderly

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MESH Headings

• Aged
• Aged, 80 and over
• Biomarkers/blood
• California/epidemiology
• Cardiovascular Diseases/ethnology
• Cardiovascular Diseases/mortality
• Female
• Homocysteine/blood
• Humans
• Longitudinal Studies
• Male
• Mexican Americans
• Mexico/ethnology
• Middle Aged
• Proportional Hazards Models

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Grants

• 1R24HD047861 NICHD NIH HHS
• P60 DK20572 NIDDK NIH HHS
• R01 DK060753 NIDDK NIH HHS
• AG12975 NIA NIH HHS
• R24 HD047861 NICHD NIH HHS
• DK60753 NIDDK NIH HHS
• R01 DK060753-03 NIDDK NIH HHS
• R03 AG033751 NIA NIH HHS
• R01 AG012975 NIA NIH HHS
• P60 DK020572-30 NIDDK NIH HHS
• P30 DK092926 NIDDK NIH HHS
• R01 AG012975-11 NIA NIH HHS
• P60 DK020572 NIDDK NIH HHS
• RWJ04823 PHS HHS

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Affiliation(s)

V Colon Lopez Department of Epidemiology, University of Michigan, School of Public Health, Ann Arbor, MI, USA.
M N Haan
A E Aiello
D Ghosh

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Homocysteine level and coronary heart disease incidence: a systematic review and meta-analysis

OBJECTIVE

To determine whether an elevated homocysteine level is an independent risk factor for the development of coronary heart disease (CHD) to aid the US Preventive Services Task Force in its evaluation of novel risk factors for incident CHD.

METHODS

Studies of homocysteine and CHD were identified by searching MEDLINE (1966 through March 2006). We obtained additional articles by reviewing reference lists from prior reviews, original studies, editorials, and Web sites and by consulting experts. We included prospective cohort studies that measured homocysteine and Framingham risk factors and the incidence of CHD in the general adult population without known CHD. Each study was quality rated using criteria developed by the US Preventive Services Task Force. We conducted a meta-analysis using a random-effects model to determine summary estimates of the risk of major CHD associated with each 5-micromol/L increase in homocysteine level. The systematic review and meta-analysis were conducted between January 25, 2005, and September 17, 2007.

RESULTS

We identified 26 articles of good or fair quality. Most studies found elevations of 20% to 50% in CHD risk for each increase of 5 micromol/L in homocysteine level. Meta-analysis yielded a combined risk ratio for coronary events of 1.18 (95% confidence interval, 1.10-1.26) for each increase of 5 micromol/L in homocysteine level. The association between homocysteine and CHD was similar when analyzed by sex, length of follow-up, outcome, study quality, and study design.

CONCLUSION

Each increase of 5 micromol/L in homocysteine level increases the risk of CHD events by approximately 20%, independently of traditional CHD risk factors.

Traffic-related particles are associated with elevated homocysteine: the VA normative aging study

RATIONALE

Recent epidemiologic studies have shown that homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, is a risk factor for atherosclerosis, myocardial infarction, stroke, and thrombosis. Particulate air pollution has been related to cardiovascular death and hospital admission, but the underlying mechanisms are not fully elucidated.

OBJECTIVES

We examined the associations between ambient particulate air pollution and plasma concentrations of homocysteine among 960 community-residing older men (mean age, 73.6 +/- 6.9 yr).

METHODS

Total homocysteine in plasma, measured using high-performance liquid chromatography with fluorescence detection, was regressed on each ambient particulate pollutant (black carbon, organic carbon, sulfate or PM(2.5)), and effect modification by plasma and dietary B vitamins (folate, B6, and B12) was examined.

MEASUREMENTS AND MAIN RESULTS

The median concentration of total homocysteine was 10.6 micromol/L. Statistically significant positive associations of total homocysteine were observed with traffic-related particles (black carbon and organic carbon). No association was observed with sulfate, an indicator of coal combustion particles, or PM(2.5) (particulate matter < or = 2.5 microm in aerodynamic diameter). The effects of black carbon and organic carbon were more pronounced in persons with low concentrations of plasma folate and vitamin B12.

CONCLUSIONS

Exposures to ambient particles, particularly from traffic, are associated with elevated plasma total homocysteine. Homocysteine may be a component or biological marker of the oxidation pathways underlying the effect of ambient particles on the cardiovascular system.

Plasma lipoprotein (a), homocysteine, and other cardiovascular disease (CVD) risk factors in Nigerians with CVD

Elevated plasma lipoprotein (a) (Lp(a)) and total homocysteine (tHcy) concentrations, as well as fat distributions, are associated with cardiovascular disease (CVD) risk. The purpose of this study was to evaluate plasma Lp(a), tHcy, percentage body fat, anthropometric indices, and blood pressure (BP) and their relationships with each other in well-defined, hospital-based, CVD patients in a Nigerian African community. One hundred seventy patients suffering from hypertensive heart disease, hypertension, ischaemic heart disease, and myocardial infraction with the mean age of 45.3 ± 1.3 years and 58 apparently healthy volunteers with the mean age of 44.8 ±1.2 years were selected. Anthropometric indices and BP were measured. Percentage body fat, body mass index, and waist-to-hip ratio (WHR) were calculated. Plasma Lp(a) and tHcy concentrations were determined. The results showed significant increases in BP, skinfold thickness (SFT) variables, and WHR in all of the CVD patients. Plasma Lp(a) was also significantly increased (p < 0.001), whereas the slight increase in the mean tHcy was not statistically significant. Positive significant correlations were found between systolic BP, triceps, SFT, and percentage body fat (p < 0.01), whereas significant correlations were found between some body composition variables, tHcy, and systolic BP (p < 0.05). Our findings provide supportive evidence for altered plasma Lp(a) concentration in addition to some other traditional CVD risk factors in Nigerians. The role of homocysteine is not well defined.

Serum total homocysteine concentrations and risk of mortality from stroke and coronary heart disease in Japanese: The JACC study

Evidence for association between serum total homocysteine (tHcy) level and cardiovascular disease is limited in Asian populations. We conducted a nested case-control study under JACC Study. A total of 39,242 subjects aged 40-79 years provided serum samples at baseline surveys between 1988 and 1990. Control subjects were selected by matching for sex, age, community and year of serum storage. Serum tHcy levels were measured by high-performance liquid chromatography. During the 10-year follow-up, there were 444 deaths due to total cardiovascular disease, including 310 total stroke (131 hemorrhage and 101 ischemic strokes) and 134 coronary heart diseases. The risks of mortality from ischemic stroke, coronary heart disease, and total cardiovascular disease were significantly higher in individuals with the highest serum tHcy quartile (>or=15.3micromol/L) than in those with the lowest quartile (<10.5micromol/L); the respective multivariable odds ratios (95% CI) were 4.35 (1.12-16.9), 3.40 (1.17-9.86), and 1.68 (1.02-2.77). The multivariable odds ratios associated with a 5-micromol/L increase in tHcy were 1.49 (1.01-2.18), 2.01 (1.21-3.35), and 1.15 (1.00-1.32), respectively. High serum tHcy levels were associated with increased mortality from ischemic stroke, coronary heart disease and total cardiovascular disease among Japanese.

Dietary choline and betaine intakes in relation to concentrations of inflammatory markers in healthy adults: the ATTICA study

BACKGROUND

Choline and betaine are found in a variety of plant and animal foods and were recently shown to be associated with decreased homocysteine concentrations.

OBJECTIVE

The scope of this work was to investigate the associations between dietary choline and betaine consumption and various markers of low-grade systemic inflammation.

DESIGN

Under the context of a cross-sectional survey that enrolled 1514 men (18-87 y of age) and 1528 women (18-89 y of age) with no history of cardiovascular disease (the ATTICA Study), fasting blood samples were collected and inflammatory markers were measured. Dietary habits were evaluated with a validated food-frequency questionnaire, and the intakes of choline and betaine were calculated from food-composition tables.

RESULTS

Compared with the lowest tertile of choline intake (<250 mg/d), participants who consumed >310 mg/d had, on average, 22% lower concentrations of C-reactive protein (P < 0.05), 26% lower concentrations of interleukin-6 (P < 0.05), and 6% lower concentrations of tumor necrosis factor-alpha (P < 0.01). Similarly, participants who consumed >360 mg/d of betaine had, on average, 10% lower concentrations of homocysteine (P < 0.01), 19% lower concentrations of C-reactive protein (P < 0.1), and 12% lower concentrations of tumor necrosis factor-alpha (P < 0.05) than did those who consumed <260 mg/d. These findings were independent of various sociodemographic, lifestyle, and clinical characteristics of the participants.

CONCLUSIONS

Our results support an association between choline and betaine intakes and the inflammation process in free-eating and apparently healthy adults. However, further studies are needed to confirm or refute our findings.

Homocysteine lowering and cardiovascular disease risk: lost in translation

Studies of the general population have suggested that high homocysteine levels are associated with cardiovascular morbidity and mortality. In chronic kidney disease, homocysteine levels rise, and cardiovascular risk increases with declining kidney function. While some studies in this population have found an association between elevated homocysteine and cardiovascular risk, others have noted that this association is largely attenuated by adjustment for kidney function, and several studies of patients with kidney failure have found that lower homocysteine levels predict mortality. Homocysteine levels can be lowered with folate, vitamin B6 and vitamin B12. Three large, randomized, controlled trials of patients with pre-existing cardiovascular disease and two smaller, randomized, controlled trials of patients with kidney failure failed to detect any cardiovascular benefit from homocysteine-lowering vitamins. Several more interventional trials are ongoing, but the available data thus far do not support screening for or treatment of hyperhomocysteinemia.

Hyperhomocysteinemia and thrombosis: an overview

CONTEXT

Homocysteine, a sulfur-containing amino acid, absent in natural diets, is a metabolic intermediary in transmethylation and transsulfuration reactions. Such reactions are essential to normal cellular growth, differentiation, and function. Excess homocysteine is associated with vascular disease and related disorders.

OBJECTIVE

To review homocysteine metabolism, the pathogenesis and classification of hyperhomocysteinemia, and the published literature investigating the association of homocysteine and methylenetetrahydrofolate reductase defects with arterial and venous thromboembolism and related disorders. The role of vitamin supplementation in patients with hyperhomocysteinemia is addressed.

DATA SOURCES

Published medical and scientific literature. Articles addressing the objectives were selected and reviewed. Pertinent studies and conclusions were summarized, grouped, and contrasted.

CONCLUSIONS

The association of hyperhomocysteinemia and arterial and venous thrombosis is controversial. Severe hyperhomocysteinemia is associated with atherosclerosis. The effect of mild hyperhomocysteinemia is less certain. Coinheritance of methylenetetrahydrofolate reductase defects and factor V Leiden is likely to increase the risk of venous thromboembolism. The association of methylenetetrahydrofolate reductase defects combined with no additional thrombophilic risk factors with venous thrombosis is less clear. High doses of folic acid to lower homocysteine levels might not be necessary.

Homocysteine and cardiovascular disease: a review of the evidence

Elevated homocysteine (HCY) levels can be caused by a number of factors, including folate and B-vitamin deficiency, pre-existing atherosclerotic disease, diabetes and various drugs. Epidemiological evidence, as well as data from retrospective and prospective studies, supports an association between elevated HCY levels and increased risk of cardiovascular disease (CVD). However, whether lowering HCY levels by administration of folate and vitamins B6 and B12 is associated with any significant decrease in vascular risk remains the subject of ongoing debate. Although the major studies that have reported to date show that vitamin supplementation was associated with a decrease in HCY levels, this failed to have any significant effect on cardiovascular risk. Furthermore, although some lipid-modifying treatments have been shown to increase HCY levels, there is no evidence that this attenuates or compromises the beneficial effects of such treatments on cardiovascular risk. Taken together, these data suggest that HCY is a marker, rather than a cause, of CVD and therefore do not provide support for routine screening for and treatment of elevated HCY to prevent CVD. Data from ongoing clinical trials are awaited to clarify this issue.

Influence of high homocysteine and low folate plasmatic levels in medium-term prognosis after acute coronary syndromes

BACKGROUND

To test prospectively whether moderate hyperhomocysteinemia and low folate levels could have an influence in the prognosis of 155 patients who presented with an acute coronary syndrome.

METHODS AND RESULTS

After a mean follow-up of 13.4+/-7.4 months, patients with low folate levels had higher percentages of cardiovascular death and major cardiovascular events (33% vs. 5%, p<0.001; 44% vs. 22%, p<0.05) and patients with high homocysteine levels had a higher percentage of major cardiovascular events (31% vs. 14.5%, p<0.03). Kaplan-Meier survival estimates analysis showed that patients with low folate levels had a significantly higher probability of cardiovascular death and lower free-of-events survival (log rank statistic: 21.17, p<0.001 and 6.59, p=0.01). Patients with high homocysteine levels had a lower free-of-events survival (log rank statistic: 4.95, p=0.02). Different survival multivariate analysis model showed that the presence of low folate levels was an independent predictor of cardiovascular death (hazard ratio 8.85, 95% confidence interval 2.6-29.3, p<0.000) and high homocysteine levels was identified as independent predictor of major cardiovascular events (hazard ratio 2.34, 95% confidence interval 1.07-5.12, p<0.03).

CONCLUSIONS

Low folate levels and moderate hyperhomocysteinemia were identified as independent predictors of cardiovascular events in the follow-up.

The puzzle of dietary fat intake and risk of ischemic stroke: a brief review of epidemiologic data

While coronary heart disease (CHD) and ischemic stroke share some major risk factors, limited epidemiologic data on dietary fats and vascular disease risk indicate that ischemic stroke is affected differently by these fatty acids than is CHD. The established associations between types of fat and CHD do not appear to apply to ischemic stroke. One explanatory hypothesis for the paradoxical observations is that arteriosclerosis in different types of cerebral arteries has different causal patterns. Fatty acids or blood lipids might not be as important as other factors, such as blood pressure, in the pathogenesis of a certain type of ischemic stroke. However, confirmatory data on the associations of fatty acids and subtype of ischemic stroke, including lacunar, atherosclerotic, and cardioembolic infarction, are lacking. The purpose of this review is to summarize the epidemiologic data on dietary fat and fatty acids in relation to ischemic stroke. Future investigations are needed to examine the effects of fatty acids on subtype of ischemic stroke and to clarify the possible differences of dietary fat in relation to ischemic stroke and CHD.

Thermolabile methylenetetrahydrofolate reductase C677T polymorphism and homocysteine are risk factors for coronary artery disease in Moroccan population

Increased plasma total homocysteine (tHcy) levels have been shown to be a risk factor for coronary artery disease (CAD). The common methylenetetrahydrofolate reductase C677T (MTHFR C677T) polymorphism has been reported to be a strong predictor of mild hyperhomocysteinaemia (HHcy). We assessed whether this mutation was associated with increased risk of CAD and plasma levels of tHcy. We also evaluated interactions between this polymorphism, mild elevated tHcy levels and conventional risk factors of CAD. Method. Using PCR-RFLP analysis, we studied the frequency of the C677T genotypes and its effect on CAD and on tHcy concentrations in 400 subjects without and with CAD angiographically confirmed. There were 210 subjects with CAD and 190 subjects without CAD. Results. The frequencies of the C677T genotypes were 53% (59.5% in controls versus 48.1% in cases), 34.8% (32.1 in controls versus 37.1 in cases), and 11.8% (8.4% in controls versus 14.8% in cases), respectively, for 677CC, 677CT, and 677TT. The genotype frequencies were significantly different between case and control groups (P < .05). The 677T allele enhances the risk of CAD associated to HHcy (P < .01). In multivariate analysis models, MTHFR C677T polymorphism effect on CAD was masked by other risk factors. HHcy was only and independently influenced by MTHFR polymorphism and smoking habits, and it is a strong predictor of CAD independently of conventional risk factors. Conclusion. Our data suggest that HHcy is strongly and independently associated to CAD risk increase; and MTHFR C677T polymorphism and smoking habits were the main predictors of tHcy levels. The CAD risk increase is mainly associated with mild HHcy in 677TT, whereas in 677CT and 677CC it is mainly associated with the conventional risk factors.

Air pollution, smoking, and plasma homocysteine

BACKGROUND

Mild hyperhomocysteinemia is independently associated with an increased risk of cardiovascular disease. Air pollution exposure induces short-term inflammatory changes that may determine hyperhomocysteinemia, particularly in the presence of a preexisting proinflammatory status such as that found in cigarette smokers.

OBJECTIVE

We examined the relation of air pollution levels with fasting and postmethionine-load total homocysteine (tHcy) in 1,213 normal subjects from Lombardia, Italy.

METHODS

We obtained hourly concentrations of particulate matter < 10 mum in aerodynamic diameter (PM(10)) and gaseous pollutants (carbon monoxide, nitrogen dioxide, sulfur dioxide(,) ozone) from 53 monitoring sites covering the study area. We applied generalized additive models to compute standardized regression coefficients controlled for age, sex, body mass index, smoking, alcohol, hormone use, temperature, day of the year, and long-term trends.

RESULTS

The estimated difference in tHcy associated with an interquartile increase in average PM(10) concentrations in the 24 hr before the study was nonsignificant [0.4%; 95% confidence interval (CI), -2.4 to 3.3 for fasting; and 1.1%, 95% CI, -1.5 to 3.7 for postmethionine-load tHcy]. In smokers, 24-hr PM(10) levels were associated with 6.3% (95% CI, 1.3 to 11.6; p < 0.05) and 4.9% (95% CI, 0.5 to 9.6; p < 0.05) increases in fasting and postmethionine-load tHcy, respectively, but no association was seen in nonsmokers (p-interaction = 0.005 for fasting and 0.039 for postmethionine-load tHcy). Average 24-hr O(3) concentrations were associated with significant differences in fasting tHcy (6.7%; 95% CI, 0.9 to 12.8; p < 0.05), but no consistent associations were found when postmethionine-load tHcy and/or 7-day average O(3) concentrations were considered.

CONCLUSIONS

Air particles may interact with cigarette smoking and increase plasma homocysteine in healthy subjects.

Progressive glycosylation of albumin and its effect on the binding of homocysteine may be a key step in the pathogenesis of vascular damage in diabetes mellitus

The majority of diabetes research to date has rightly focussed on the direct effects of hyperglycaemia on tissues and a number of theories relating to the pathogenesis of vascular disease have been proposed. This research is important as until methods are found to achieve glycaemic control in all diabetic patients, prophylactic interventions to prevent vasculopathy will be required. One of the major blood proteins, human albumin is known to be covalently modified by extended incubation with glucose, leading to an impairment of ligand binding. One of the important ligands bound by albumin is homocysteine. There is increasing and compelling clinical, experimental and epidemiological evidence that homocysteine, and in particular the free unbound fraction, is vasculotoxic. If homocysteine binding to albumin is impaired by increasing glycosylation of albumin then either drugs which reduce homocysteine levels (pyridoxine, folic acid and cobalamin) or inhibit glycosylation (aminoguanidines) may be of benefit in the prevention of vascular damage in diabetic patients.

Serial measurements of plasma homocysteine levels in early and late phases of ischemic stroke

High plasma levels of homocysteine (Hcy) may predispose to ischemic stroke (IS), but results of previous studies have been conflicting. We decided to determine in IS patients whether their Hcy levels are elevated, whether levels vary at different time points following stroke, whether levels are associated with stroke severity, outcome, recurrence, etiology, infarct volume, or risk factors, and whether levels are correlated with hemostatic factors or C-reactive protein values. We measured plasma Hcy levels in 102 consecutive IS patients on admission and at 1 week, 1 month, and 3 months after stroke and once in 102 control subjects. Hemostatic factors were measured in 55 patients. Compared with controls, plasma Hcy levels in patients were significantly lower on admission but not at later time points, with levels increasing by week and remaining at this level for 3 months. Hcy levels showed a positive correlation with age and a negative correlation with Mini-Mental State Examination (MMSE) scores. Plasma Hcy levels inversely correlated with plasminogen activator inhibitor type-1. Decreased Hcy levels on admission may reflect the strength of the acute-phase response rather than a pathogenetic event. The negative correlation between Hcy levels and MMSE scores is more probably age-related than stroke-related.

Homocysteine and outcome in young patients with acute coronary syndromes

BACKGROUND

Despite the well-known pro-thrombotic and pro-inflammatory plasma homocysteine effects, it remains uncertain whether these effects can be associated with an adverse cardiac outcome in young patients admitted with acute coronary syndromes.

METHODS

Homocysteine levels were determined within 24 h after admission in 244 consecutive patients aged less than 56 years who presented with an acute coronary syndrome. We evaluated the relationship between homocysteine and both short-term (death, myocardial [re]infarction), and long-term prognosis (death, recurrent acute coronary syndrome and/or ischemic stroke), after 3.4+/-1.7 years of follow-up.

RESULTS

Homocysteine levels were similar in patients both with and without in-hospital event: 8.65 (5.36-10.48) vs. 8.98 (7.38-11.13) micromol/l, p=NS. However, patients who presented with the combined event during follow-up had higher homocysteine levels than those free of the event: 10.54 (7.90-11.76) micromol/l vs. 8.52 (7.11-10.23) micromol/l, p=0.001. Patients who either died (13.78 vs. 8.87 micromol/l, p=0.012) or had a myocardial infarction (10.75 vs. 8.76 micromol/l, p=0.006) or unstable angina (10.46 vs. 8.76, p=0.006) during follow-up had higher homocysteine levels. According to the Cox regression analysis: age [hazard ratio 1.05, CI 95%, 0.99-1.10], left ventricular ejection fraction < or =40% [hazard ratio 1.93, CI 95%, 0.98-3.79], and homocysteine tertile 3 [hazard ratio 2.05, CI 95%, 1.13-3.71] were the significant determinants of the combined adverse event during follow-up. Although 41 (18%) of patients presented the TT genotype of the methylen-tetrahydrofolate-reductase thermolabile variant mutation, its occurrence had a neutral effect on morbid-mortality.

CONCLUSIONS

High homocysteine levels at admission strongly predict late cardiac events in young patients with acute coronary syndromes.

Lipoprotein particles, insulin, adiponectin, C-reactive protein and risk of coronary heart disease among men with metabolic syndrome

We tested the hypotheses whether nuclear magnetic resonance (NMR) determined lipoprotein particles, insulin and adiponectin, and C-reactive protein (CRP) and white blood cell (WBC) count as markers of inflammation predicted risk of coronary heart disease (CHD) death among 428 men age 35-57 years with metabolic syndrome (MetSyn) in a matched case control study within the multiple risk factor intervention trial. Blood samples collected at entry into the study and stored at -60 degrees C were obtained from central storage for blood analyte analysis. Two hundred and fourteen men with MetSyn who died of CHD were matched with 214 men with MetSyn who did not die of CHD during 18 years of follow-up. Cases were matched to controls on age, study group, number of factors present in the MetSyn, and presence or absence of a nonfatal CVD event during the trial. Mortality follow-up was determined using the National Death Index. Higher levels of high density lipoprotein particles (HDL-P), especially medium-sized HDL-P [hazard ratio (95% confidence interval) 0.45 (0.25-0.83, P<0.01), quartile 1 as compared to quartile 4], were associated with lower risk of CHD death. Low density lipoprotein (LDL) particles were not associated with increased risk of CHD. Elevated LDL cholesterol (LDL-C), smoking and WBC count were, but levels of adiponectin, insulin and CRP were not significantly related to CHD death. In multivariate models adjusting for smoking and LDL-C, medium HDL-P and WBC count remained independent predictors of CHD death. Number of HDL particles, especially medium-sized HDL particles and WBC count were independent predictors of CHD death among men with MetSyn.

Homocysteine

Elevated homocysteine levels are associated with a variety of vascular diseases. Specifically, hyperhomocysteinemia is a risk factor for coronary artery disease, cerebrovascular disease, and peripheral arterial disease. Laboratory-based strategies for its detection and quantification have evolved to meet the increasing need for accuracy in risk prediction. Although new technologies have been developed over the past 2 decades that have enhanced the precision of measurement, universal guidelines for circulating homocysteine determination remain lacking.

Serum Homocysteine and Long-Term Risk of Myocardial Infarction and Sudden Death in Patients with Coronary Heart Disease

We have prospectively evaluated the risk of incident coronary events in association with serum total homocysteine in patients with preexisting chronic coronary heart disease. A nested case-control design was used. Total homocysteine concentration was measured in baseline fasting serum samples from patients with chronic coronary heart disease enrolled in the Bezafibrate Infarction Prevention Study (n = 3,090) who developed coronary events during 6.2 years of follow-up (n = 69). They were matched for age and gender with controls without subsequent cardiovascular events. Elevated homocysteine levels were associated with 2.5 times higher risk of subsequent coronary events and each 5 mumol/l increment was associated with a 25% higher risk.

The Nutrition, Aging, and Memory in Elders (NAME) study: design and methods for a study of micronutrients and cognitive function in a homebound elderly population

BACKGROUND

Micronutrient status can affect cognitive function in the elderly; however, there is much to learn about the precise effects. Understanding mediating factors by which micronutrient status affects cognitive function would contribute to elders' quality of life and their ability to remain in the home.

OBJECTIVES

The Nutrition, Aging, and Memory in Elders (NAME) Study is designed to advance the current level of knowledge by investigating potential mediating factors by which micronutrient status contributes to cognitive impairment and central nervous system abnormalities in the elderly. NAME targets homebound elders because they are understudied and particularly at risk for poor nutritional status.

METHODS

Subjects are community-based elders aged 60 and older, recruited through area Aging Services Access Points. The NAME core data include demographics; neuropsychological testing and activities of daily living measures; food frequency, health and behavioral questionnaires; anthropometrics; gene status; plasma micronutrients, homocysteine, and other blood determinants. A neurological examination, psychiatric examination, and brain MRI and volumetric measurements are obtained from a sub-sample.

RESULTS

Preliminary data from first 300 subjects are reported. These data show that the NAME protocol is feasible and that the enrolled subjects are racially diverse, at-risk, and had similar basic demographics to the population from which they were drawn.

CONCLUSION

The goal of the NAME study is to evaluate novel relationships between nutritional factors and cognitive impairment. These data may provide important information on potential new therapeutic strategies and supplementation standards for the elderly to maintain cognitive function and potentially reduce the public health costs of dementia.

Serum homocysteine is related to food intake in adolescents: the Child and Adolescent Trial for Cardiovascular Health

BACKGROUND

An understanding of the relation in adolescents between serum homocysteine and foods rich in vitamin B-6, vitamin B-12, and folate is important because high homocysteine concentrations in childhood and adolescence may be a risk factor for later cardiovascular disease. However, little is known about the relation between food intake and homocysteine in adolescents.

OBJECTIVE

Five years after national folic acid fortification of enriched grain products, cross-sectional relations between food intake and serum homocysteine concentrations were examined in 2695 adolescents [x age: 18.3 (range: 15-20) y] enrolled in the Child and Adolescent Trial for Cardiovascular Health.

DESIGN

A nonfasting blood specimen was analyzed for serum homocysteine, folate, and vitamins B-6 and B-12. Dietary intake was assessed by using a food-frequency questionnaire. Multiple regression analyses were used to evaluate the relation of intakes of whole grains, refined grains, fruit, vegetables, dairy products, red and processed meats, and poultry with serum homocysteine concentrations after adjustment for demographic characteristics, lifestyle factors, and food intake.

RESULTS

Serum homocysteine concentrations were lower with greater intakes of whole grains (P for trend = 0.002), refined grains (P for trend = 0.02), and dairy foods (P for trend <0.001); were higher with greater intake of poultry (P for trend = 0.004); and were not related to intakes of fruit, vegetables, or red or processed meat. After additional adjustment for serum B vitamins, the relations of serum homocysteine with most food groups were attenuated.

CONCLUSION

These observational findings suggest a beneficial effect of whole-grain, refined-grain, and dairy products on serum homocysteine concentrations in an adolescent population.

Homocysteine: role and implications in atherosclerosis

Hyperhomocysteinemia promotes atherosclerosis and is most commonly caused by B-vitamin deficiencies, especially folic acid, B(6), and B(12); genetic disorders; certain drugs; and renal impairment. Elevated homocysteine promotes atherosclerosis through increased oxidant stress, impaired endothelial function, and induction of thrombosis. Prospective studies have shown that elevated plasma homocysteine concentrations increase risk of cardiovascular disease by twofold and risk of cerebrovascular disease to a lesser degree. Hyperhomocysteinemia should be identified in patients with progressive or unexplained atherosclerosis and treated appropriately. Treatment of hyperhomocysteinemia is primarily through vitamin supplementation; folic acid and vitamins B(6) and B(12) are the mainstay of therapy. Betaine and 5-methyl tetrahydro-folate are also effective in lowering homocysteine levels. Treatment of moderately elevated plasma homocysteine in patients without atherosclerosis should be deferred until the completion of randomized outcome trials.

No effect of homocysteine-lowering therapy on vascular inflammation and haemostasis in peripheral arterial occlusive disease

BACKGROUND

Although peripheral arterial occlusive disease (PAOD) is significantly associated with elevated homocysteine levels, the clinical relevance of hyperhomocysteinaemia for the prevention and progression of PAOD is still unknown.

MATERIALS AND METHODS

A total of 65 patients suffering from symptomatic PAOD with elevated homocysteine levels were randomized onto placebo or B-vitamins (50 mg thiaminhydrochlorid, 50 mg pyridoxine, and 0.05 mg cyanocobalamin), plus 5 mg folic acid daily for 6 weeks. Serum levels of folic acid, vitamin B12, creatinine, ultra-sensitive C-reactive protein (usCRP), interleukin (IL)-6, IL-8, IL-18, monocyte-chemo-attractant-protein-1 (MCP-1) and plasma levels of homocysteine, tissue factor (TF) and tissue factor pathway inhibitor (TFPI) were determined on the 1st day and 42nd day. Primary outcome was reduction of homocysteine, secondary outcomes were reduction of usCRP, IL-6, IL-8, Il-18, MCP-1, TF and TFPI.

RESULTS

The mean reduction of homocysteine concentration was 33% (95%CI 33.36-55.76, or 18.9+/-5.4 micromol L-1-12.6+/-2.8 micromol L-1, P=0) in the B-vitamin group compared with 1% in the placebo group. Folic acid (P=0) and vitamin B12 (P=0) increased significantly in the verum group, but both remained unchanged in the control group. No treatment effect of lowering of homocysteine on any markers of haemostasis (TF, TFPI) or inflammation (usCRP, IL-6, IL-8, IL-18 and MCP-1) was observed.

CONCLUSION

Although homocysteine is associated with vascular disease risk in the general population and in particular with PAOD, marked lowering of homocysteine concentrations by folic acid and B-vitamin supplementation does not influence inflammatory responses involving usCRP, IL-6, IL-8, IL-18 and MCP-1, nor tissue factor. These results provide evidence against a major effect of hyperhomocysteinaemia on vascular chronic inflammation or coagulation in patients with symptomatic peripheral arterial occlusive disease.