Homocysteine levels in men and women of different ethnic and cultural background living in England

Homocysteine modifies the association of coronary stenosis and HIV infection in an inner city African American population

BACKGROUND AND AIMS

People with HIV (PWH) whose disease is controlled on anti-retroviral regimens remain at an increased risk for coronary artery disease (CAD). Traditional cardiovascular risk factors do not fully explain the residual risk in PWH suggesting contributions from nontraditional factors. Homocysteine (Hcy) may be one of these as prior work in adults without HIV demonstrate that Hcy may impair endothelial function by decreasing the availability of nitric oxide, promoting the development of atherosclerosis. In addition, plasma Hcy levels are higher in PWH than in individuals living without HIV. The aim of this study was to investigate whether Hcy levels influence the association between HIV and coronary stenosis in an inner city African American population.

METHODS

African Americans from the Heart Study in Baltimore, with and without HIV, recruited from inner-city Baltimore between June 2004 and February 2015, were included in this analysis. Participants underwent coronary CT angiography to evaluate the presence of coronary stenosis, defined as luminal stenosis >10%. Hcy was measured from stored serum samples.

RESULTS

In this analysis, the median [IQR] age of the 664 participants was 56 [50-66] years; 68.1% were living with HIV and 43.1% were women. Elevated Hcy (>15 µmol/L) was more prevalent in those with coronary stenosis (23.3%, 95% CI: 18.4%-28.2%) than in those without coronary stenosis (13.1%, 95% CI: 9.7%-16.5%) (p = 0.0007), and HIV was associated with coronary stenosis in those participants with an elevated Hcy (Prevalence Ratio: 1.94, 95% CI: 1.04-3.64, p = 0.0038) and not in those with a Hcy ≤15 µmol/L (Prevalence Ratio: 1.02, 95% CI: 0.83-1.25, p = 0.87).

CONCLUSIONS

Our data suggest an association between elevated Hcy levels (>15 µmol/L) and the prevalence of coronary stenosis in PWH from this inner city African American population.

Associations of Metabolic Syndrome with Total Testosterone and Homocysteine Levels in Male Korean Workers

BACKGROUND

Low testosterone is associated with metabolic syndrome (MetS), and homocysteine (Hcy) is elevated in individuals with MetS. We investigated the relationships of total testosterone (TT) and serum Hcy levels with MetS in male Korean workers.

METHODS

We conducted a cross-sectional study including 8,606 male workers, aged 20 to 58 years, who underwent a physical examination in 2015. MetS was diagnosed based on the criteria of the 2009 harmonized definition, while the Korean standard for waist circumference (WC) was used. Participants' biochemical parameters, including TT and serum Hcy, were measured, and participants were divided into quartiles. Multiple logistic regression models were used to estimate the association of MetS and its individual components depending on TT and serum Hcy quartiles.

RESULTS

The prevalence of MetS in the study population was 16%. TT was lower in participants with MetS than in those without MetS (P<0.001). By contrast, Hcy level was similar between groups (P=0.694). In multiple logistic regression analysis, the odds ratio for the lowest TT quartile was 1.29 (95% confidence interval, 1.06 to 1.57) after adjusting for potential confounders. Participants with lower TT were more likely to have high WC, hypertriglyceridemia, and low high density lipoprotein levels. Serum Hcy levels were not significantly associated with MetS. Of the five components of MetS, only WC was significantly associated with serum Hcy.

CONCLUSION

In male Korean workers, TT may be an independent predictor of MetS, and serum Hcy levels could be a marker of abdominal obesity. However, future prospective studies are needed.

Short Sleep Duration Is Associated With Increased Serum Homocysteine: Insights From a National Survey

STUDY OBJECTIVES

Both short sleep duration and increased serum homocysteine levels are associated with cardiovascular events. However, research on the relationship between sleep duration and serum homocysteine levels is sparse. The aim of this study is to examine the association between sleep duration and serum homocysteine levels from a national database.

METHODS

In total, 4,480 eligible participants older than 20 years who had serum homocysteine data and reported sleep duration were enrolled from the US National Health and Nutrition Examination Survey of 2005 to 2006. The association between sleep duration and serum homocysteine levels was analyzed using multivariate regression models for covariate adjustment.

RESULTS

Serum homocysteine level was lowest in individuals with a sleep duration of 7 hours and increased in those with both shorter and longer self-reported total sleep time (groups were categorized into ≤ 5 hours, 6 hours, 7 hours, 8 hours, and ≥ 9 hours). After adjustment for covariates, those in the group sleeping ≤ 5 hours had significantly higher serum homocysteine levels than the reference group (sleep duration of 7 hours). In subgroup analyses by sex, body mass index (BMI), and ethnicity, the association between short sleep duration (≤ 5 hours) and higher serum homocysteine levels persisted in women, individuals with obesity (BMI ≥ 30 kg/m²), and non-Hispanic whites.

CONCLUSIONS

This study highlighted that short sleep duration was associated with higher serum homocysteine levels in women, individuals with obesity (BMI ≥ 30 kg/m²), and non-Hispanic whites; this finding might suggest increased vulnerability to cardiovascular risk or other atherothrombotic events in these groups in the context of short sleep.

Relationship of classical and non-classical risk factors with genetic variants relevant to coronary heart disease

BACKGROUND

In addition to the well established cardiovascular risk factors, evidence suggests a possible role of genetic and non-classical risk factors in the development and progression of atherothrombosis. We aimed to determine the relationship of classical and non-classical cardiovascular risk factors with candidate gene polymorphisms potentially involved in cardiovascular risk in the general Mediterranean population.

DESIGN

Cross-sectional study.

METHODS

We have determined the prevalence of classical (lipid profile, blood pressure, glycaemia, diabetes, smoking, body mass index, menopause and family history of coronary heart disease) and non-classical cardiovascular risk factors (infectious processes, homocysteinaemia, oxidative status, C-reactive protein, lipoprotein (a) and fibrinogen) in a population-based study. We analysed the relationship of these risk factors with the following five gene polymorphisms potentially involved in cardiovascular risk: ATP-binding cassette transporter A1-R219K, Peroxisome proliferator-activated receptor (PPAR)-alpha-L162V, Lipoprotein lipase (LPL)-HindIII, Paraoxonase (PON)1-Q192R, and Tumour necrosis factor (TNF)-alpha-G-308A.

RESULTS

We found PPAR-alpha-V and LPL-H alleles to be associated with decreased high-density lipoprotein-cholesterol (HDL-c) concentration and with increased total cholesterol : HDL-c and triglyceride : HDL-c ratios. Regarding the non-classical risk factors, C-reactive protein concentration was higher for the PPAR-alpha-V allele. A higher oxidative status was shown in homozygotes for LPL-H and TNF-alpha-G alleles, although the latter also had lower homocysteinaemia.

CONCLUSIONS

Three of the genetic variants analysed, PPAR-alpha-L162V, LPL-HindIII, and TNF-alpha-G-308A, were associated with non-classical risk factors, specifically lipid profile, inflammation, and oxidative status.

Hypertension, diabetes and cardiovascular risk in ethnic minorities in the UK

Mortality from coronary heart disease (CHD), stroke and end-stage renal failure (ESRF) is high in South Asian (Indo-Asian) migrants in the UK. This is associated with a high prevalence of diabetes and hypertension.

Mortality from stroke and ESRF is also high in migrants to the UK of black African origin. However, CHD mortality is low in this group. This pattern of mortality is also associated with a high prevalence of hypertension and diabetes.

Conventional risk factors, such as cigarette smoking and hypercholesterolaemia, are less prevalent in ethnic minority populations in the UK and unlikely to explain the differences seen between groups, although each risk factor is likely to contribute to the variation in vascular disease within each group.

Prognostic Value of Elevated Homocysteine Levels in Korean Patients with Coronary Artery Disease: A Propensity Score Matched Analysis

BACKGROUND AND OBJECTIVES

We sought to determine whether an elevated homocysteine (Hcy) level is associated with a worse prognosis in Korean patients with coronary artery disease (CAD).

SUBJECTS AND METHODS

A total of 5839 patients (60.4% male, mean age 61.3±11.2 years) with CAD were enrolled from 2000 to 2010 at Gangnam Severance Hospital. CAD was diagnosed by invasive coronary angiography. Laboratory values including Hcy level were obtained on the day of coronary angiography and analyses were performed shortly after sampling. Patients were divided into two groups according to their Hcy levels. Baseline risk factors, coronary angiographic findings, length of follow-up, and composite endpoints including cardiac death (CD) and non-fatal myocardial infarction (NFMI) were recorded. 1:1 propensity score matched analysis was also performed.

RESULTS

Over a mean follow-up period of 4.4±2.5 years, there were 132 composite endpoints (75 CD and 57 NFMI) with an event rate of 2.3%. Mean Hcy level was 9.9±4.3 µmol/L (normal Hcy 7.9±1.5 µmol/L and elevated Hcy 13.9±5.1 µmol/L). Kaplan-Meier survival analysis showed an association of elevated Hcy level with worse prognosis (p<0.0001). In addition, a multivariate Cox regression analysis showed an association of elevated Hcy level with worse prognosis for both the entire cohort (hazard ratio [HR] 2.077, 95% confidence interval [CI] 1.467-2.941, p<0.0001) and the propensity score matched cohort (HR 1.982, 95% CI 1.305-3.009, p=0.001).

CONCLUSION

Elevated Hcy level is associated with worse outcomes in Korean patients with CAD.

Biomarkers of Coronary Artery Disease Differ Between Asians and Caucasians in the General Population

Coronary artery disease (CAD) markers have not been thoroughly investigated among Asians. The incidence of CAD, however, is rising rapidly in Asia. In this review, we systematically discuss publications that compare CAD biomarkers between Asians and Caucasians in the general population. A PubMed search yielded 5,570 hits, containing 59 articles describing 47 unique cohorts that directly compare Asians with Caucasians. Ten biomarkers were taken into account for this review: total cholesterol; triglycerides; high-density lipoprotein cholesterol; low-density lipoprotein cholesterol; C-reactive protein; glucose; insulin; glycated hemoglobin; fibrinogen; and plasminogen activator inhibitor-1. Triglycerides were 1.13-fold higher in South Asians than in Caucasians, and insulin levels were 1.33-fold higher. In Japanese and Chinese subjects, lower C-reactive protein levels were reported: 0.52 and 0.36-fold, respectively. Ethnicity-specific prognostic measures of CAD biomarkers were rarely reported. CAD biomarker levels differ between Asians and Caucasians and among Asian ethnic groups in population-based cohorts. The ethnicity-specific prognostic value of CAD biomarkers is yet to be determined.

Circadian rhythm of homocysteine is hCLOCK genotype dependent

Homocysteine (Hcy) is known to be a prognostic marker for neurological, cardiovascular and cerebrovascular diseases and several other pathophysiological conditions. A sudden surge in Hcy can increase cardiovascular events. Hemodynamic modulations are known to be associated with individual's chronotype. Therefore, precise monitoring of Hcy is crucial for evaluating its impact on risk. The aim of the present study was to investigate the rhythmicity of Hcy under controlled dietary conditions and whether this rhythmicity is under the genetic control of circadian rhythm. Five subjects were selected from 200 Malayalam speaking healthy ethnic individuals who were screened for functionally critical variants of MTHFR and hCLOCK genes. MTHFR is the rate-limiting enzyme in the methionine cycle and critical for regulating Hcy levels while hCLOCK is a critical gene responsible in regulating the day and night cycles. Rhythmicity in Hcy levels were observed in all the subjects with a consensus on a morning nadir and an evening peak. Gender specific stratification of Hcy levels were observed among similar genotypes of MTHFR and hCLOCK genes. Variations from the conventional rhythmicity of Hcy were observed among similar genotypes of MTHFR and dissimilar hCLOCK genotypes. A reduced plasma Hcy in hCLOCK rs1801260 CC genotype individuals were observed in contrast to CT genotype individuals. The study tends to suggest that Hcy and body time are genetically interdependent and throws light on some of the previously unexplained reasons for variability in Hcy levels. A population specific variation of MTHFR and hCLOCK genes also highlights ethnicity specific risk management.

Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and meta-analysis

There is strong evidence indicating that elevated plasma total homocysteine (tHcy) levels are a major independent biomarker and/or a contributor to chronic conditions, such as CVD. A deficiency of vitamin B12can elevate homocysteine. Vegetarians are a group of the population who are potentially at greater risk of vitamin B12deficiency than omnivores. This is the first systematic review and meta-analysis to appraise a range of studies that compared the homocysteine and vitamin B12levels of vegetarians and omnivores. The search methods employed identified 443 entries, from which, by screening using set inclusion and exclusion criteria, six eligible cohort case studies and eleven cross-sectional studies from 1999 to 2010 were revealed, which compared concentrations of plasma tHcy and serum vitamin B12of omnivores, lactovegetarians or lacto-ovovegetarians and vegans. Of the identified seventeen studies (3230 participants), only two studies reported that vegan concentrations of plasma tHcy and serum vitamin B12did not differ from omnivores. The present study confirmed that an inverse relationship exists between plasma tHcy and serum vitamin B12, from which it can be concluded that the usual dietary source of vitamin B12is animal products and those who choose to omit or restrict these products are destined to become vitamin B12deficient. At present, the available supplement, which is usually used for fortification of food, is the unreliable cyanocobalamin. A well-designed study is needed to investigate a reliable and suitable supplement to normalise the elevated plasma tHcy of a high majority of vegetarians. This would fill the gaps in the present nutritional scientific knowledge.

Asian indians and insulin resistance syndrome: global perspective

Insulin resistance syndrome (IRS) is a crucial factor in causation of type 2 diabetes mellitus (T2DM) in Asian Indians. Approximately one-fifth of the migrant Asian Indians have evidence of metabolic syndrome. Furthermore, insulin resistance as estimated by homeostatic model assessment (HOMA-IR) was reported to be present in one-fifth of children and young adult Asian Indians with normal body mass index (BMI) and ~45-67% of those having high BMI. The cause(s) of such high prevalence of IRS in Asian Indians is not clear; however, inherent genetic predisposition, physical inactivity, excess regional body fat, and factors associated with migration may play an important role. It is important that lifestyle factor modification to prevent IRS and T2DM in Asian Indians should start in early childhood.

Suppression of homocysteine levels by vitamin B12 and folates: age and gender dependency in the Jackson Heart Study

INTRODUCTION

To examine factors potentially contributing to premature cardiovascular disease mortality in African Americans (40% versus 20% all other populations), plasma homocysteine, serum vitamin B12 and folate levels were examined for African American participants in the Jackson Heart Study.

METHODS

Of 5192 African American Jackson Heart Study participants (21-94 years), 5064 (mean age, 55 ± 13 years; 63% female) had homocysteine levels measured via fasting blood samples, with further assessments of participants' vitamin B12 (n = 1790) and folate (n = 1788) levels. Regression analyses were used to examine age, gender, vitamin B12 and folate with homocysteine levels.

RESULTS

Homocysteine levels, a purported surrogate risk factor for cardiovascular disease, increased with age, were inversely proportional to folate and vitamin B12 levels (P < 0.001) and were higher for men of all ages.

CONCLUSIONS

The results show that, as with other populations, age, gender, vitamin B12 and folate may predict homocysteine levels for African Americans. Diet may be an important predictive factor as well, given the relationships that were observed between plasma homocysteine and serum B vitamin levels.

Vegetarian diets and public health: biomarker and redox connections

Vegetarian diets are rich in antioxidant phytochemicals. However, they may not act as antioxidants in vivo, and yet still have important signaling and regulatory functions. Some may act as pro-oxidants, modulating cellular redox tone and oxidizing redox sensitive sites. In this review, evidence for health benefits of vegetarian diets is presented from different perspectives: epidemiological, biomarker, evolutionary, and public health, as well as antioxidant. From the perspective of molecular connections between diet and health, evidence of a role for plasma ascorbic acid as a biomarker for future disease risk is presented. Basic concepts of redox-based cell signaling are presented, and effects of antioxidant phytochemicals on signaling, especially via redox tone, sulfur switches and the Antioxidant Response Element (ARE), are explored. Sufficient scientific evidence exists for public health policy to promote a plant-rich diet for health promotion. This does not need to wait for science to provide all the answers as to why and how. However, action and interplay of dietary antioxidants in the nonequilibrium systems that control redox balance, cell signaling, and cell function provide rich ground for research to advance understanding of orthomolecular nutrition and provide science-based evidence to advance public health in our aging population.

Ancestry as a determinant of mean population C-reactive protein values: implications for cardiovascular risk prediction

BACKGROUND

Eligibility for rosuvastatin treatment for cardiovascular disease prevention includes a C-reactive protein (CRP) concentration >2 mg/L. Most observational studies of CRP and cardiovascular disease have been in Europeans. We evaluated the influence of ancestry on population CRP concentration to assess the implications for statin targeting in non-Europeans.

METHODS AND RESULTS

In a systematic review and meta-analysis among 221 287 people from 89 studies, geometric mean CRP was 2.6 mg/L (95% credible interval, 2.27 to 2.96) in blacks resident in the United States (n=18 585); 2.51 mg/L (95% CI, 1.18 to 2.86) in Hispanics (n=5049); 2.34 mg/L (95% CI, 1.99 to 2.8) in South Asians (n=1053); 2.03 mg/L (95% CI, 1.77 to 2.3) in whites (n=104 949); and 1.01 mg/L (95% CI, 0.88 to 1.18) in East Asians (n=39 521). Differences were not explained by study design or CRP assay and were preserved after adjustment for age and body mass index. At age 60 years, fewer than half of East Asians but more than two thirds of Hispanics were estimated to have CRP values exceeding 2 mg/L. HapMap frequencies of CRP polymorphisms known to associate with CRP concentration but not coronary heart disease events differed by ancestry. In participant data from the Wandsworth Heart and Stroke Study including European, South Asian and African, and Caribbean-descent subjects, body mass index, systolic blood pressure, and smoking contributed to between-group differences in CRP, but the majority of the difference in CRP was unexplained.

CONCLUSIONS

Differences in CRP concentration in populations of diverse ancestry are sufficiently large to affect statin eligibility, based on a single CRP threshold of 2 mg/L, and only partially influenced by differences in variables related to cardiovascular risk. A single threshold value of CRP for cardiovascular risk prediction could lead to inequalities in statin eligibility that may not accurately reflect underlying levels of cardiovascular risk.

Body mass index is an important determinant of methylation biomarkers in women of reproductive ages

B vitamin deficiencies lead to moderate hyperhomocysteinemia, which has been associated with health and disease. However, concomitant derangements in cellular methylation, reflected by altered plasma S-adenosylmethionine (SAM) or S-adenosylhomocysteine (SAH) concentrations, may be the primary cause. Therefore, we identified determinants of homocysteine, SAM, and SAH concentrations in 336 women, aged 20-48 y, as part of a large study focusing on risk factors for reproductive disorders. Blood was obtained to determine plasma SAM, SAH, and total homocysteine (tHcy), serum vitamin B-12 and folate, RBC folate concentrations, and the related single nucleotide polymorphisms 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C > T and 1298A > C, methionine synthase reductase (MTRR) 66A > G, and nicotinamide N-methyltransferase IVS1-151G > A. Questionnaires provided information on demographics, lifestyles, and nutrient intakes. Correlation coefficients were calculated and multivariable associations were assessed with a general linear model. Serum folate was positively correlated with SAM concentrations (r = 0.159; P = 0.004). Folate and vitamin B-12 were not correlated with SAH concentrations or the SAM:SAH ratio but were inversely correlated with tHcy concentrations (serum folate r = -0.324; RBC folate r = -0.294; vitamin B-12 r = -0.307; P < 0.01). From the multivariable analysis, BMI was the strongest determinant of SAM (standardized beta = 19.145; P < 0.001) and SAH concentrations (standardized beta = 3.241; P = 0.010). MTHFR 677TT (standardized beta = 0.195; P = 0.001), B vitamin supplement use (standardized beta = -0.156; P < 0.001) and dietary protein intake (standardized beta = -0.011; P < 0.001) were the strongest determinants of tHcy concentrations. Thus, the determinants of SAM and SAH differ from those of tHcy concentrations. Given that BMI was a strong determinant of SAM concentrations, it should be included in future studies on cellular methylation.

Folate status of Ghanaian populations in London and Accra

Migration to the UK is associated with higher incidence of stroke in African populations. A low folate status has been associated with increased risk of stroke, likely to be mediated through raised plasma homocysteine concentrations. We conducted a cross-sectional study to compare blood folate and homocysteine concentrations in eighty healthy Ghanaian migrants living in London matched by sex, age and occupation to 160 individuals from an urban population in Accra, Ghana. Folate intake was determined using three 24 h recalls. Fasting blood samples were collected for the determination of serum and erythrocyte folate and plasma homocysteine concentrations and the methylenetetrahydrofolate reductase (MTHFR) 677C → T polymorphism. Reported mean folate intake was 20 % lower in London compared with Accra (P < 0·001). However, serum folate was 44 % higher, erythrocyte folate 30 % higher and plasma homocysteine was 26 % lower in subjects from London compared with those from Accra (P < 0·001). These differences persisted after adjusting for confounders including the MTHFR 677C → T mutation, which was rare in both populations. Although there were no associations between dietary folate intake and blood folates (P>0·05), folic acid supplement use, which was more prevalent in London than Accra (25 and 10 %, respectively,P = 0·004) was associated with erythrocyte folate in both populations (P < 0·01). The main predictors of plasma homocysteine concentrations were erythrocyte folate and male sex (P < 0·001). Findings from the present study suggest that migration from Ghana to the UK results in improvement of biomarkers of folate status despite the fact that reported dietary intake of folate was apparently lower in subjects from London.

Cardiovascular disease, diabetes and established risk factors among populations of sub-Saharan African descent in Europe: a literature review

Background

Most European countries are ethnically and culturally diverse. Globally, cardiovascular disease (CVD) is the leading cause of death. The major risk factors for CVD have been well established. This picture holds true for all regions of the world and in different ethnic groups. However, the prevalence of CVD and related risk factors vary among ethnic groups.

Methods

This article provides a review of current understanding of the epidemiology of vascular disease, principally coronary heart disease (CHD), stroke and related risk factors among populations of Sub-Sahara African descent (henceforth, African descent) in comparison with the European populations in Europe.

Results

Compared with European populations, populations of African descent have an increased risk of stroke, whereas CHD is less common. They also have higher rates of hypertension and diabetes than European populations. Obesity is highly prevalent, but smoking rate is lower among African descent women. Older people of African descent have more favourable lipid profile and dietary habits than their European counterparts. Alcohol consumption is less common among populations of African descent. The rate of physical activity differs between European countries. Dutch African-Suriname men and women are less physically active than the White-Dutch whereas British African women are more physically active than women in the general population. Literature on psychosocial stress shows inconsistent results.

Conclusion

Hypertension and diabetes are highly prevalent among African populations, which may explain their high rate of stroke in Europe. The relatively low rate of CHD may be explained by the low rates of other risk factors including a more favourable lipid profile and the low prevalence of smoking. The risk factors are changing, and on the whole, getting worse especially among African women. Cohort studies and clinical trials are therefore needed among these groups to determine the relative contribution of vascular risk factors, and to help guide the prevention efforts. There is a clear need for intervention studies among these populations in Europe.

Children with acute lymphoblastic leukaemia have high plasma levels of total homocysteine at time of diagnosis

OBJECTIVE

Cancer can induce venous thromboembolic complications for various reasons. As part of a greater study, acquired and congenital prothrombotic risk factors were investigated in children with leukaemia or non-Hodgkin's lymphoma and compared with similar investigations in children with congenital heart defects.

MATERIAL AND METHODS

Blood samples were taken from 60 children with newly diagnosed leukaemia or lymphoma and 133 children with congenital heart defects in the course of a scheduled cardiac catheterization. When children with cancer were in remission, analyses of acquired prothrombotic risk factors were repeated. Children with cancer were observed for symptoms of thromboembolism throughout their treatment period.

RESULTS

Total homocysteine levels were significantly raised in children with cancer (median value 10.0 micromol/L) as compared with the levels in children with congenital heart diseases (5.0 micromol/L) (p<0.001), while children with acute lymphoblastic leukaemia had the highest values. The median level of lipoprotein(a) was slightly increased in children with newly diagnosed leukaemia or lymphoma (105 mg/L versus 100 mg/L, p<0.001), and levels of coagulation inhibitors were higher (p<0.001). Total homocysteine levels normalized when children attained remission of cancer disease. Two children had symptoms of acute thrombosis.

CONCLUSIONS

Raised concentrations of total homocysteine were frequent in children with newly diagnosed cancer, but this normalized when the children were in remission. The clinical significance of our observations and the impact on venous thromboembolism have yet to be defined.

Candidate genetic variants in the fibrinogen, methylenetetrahydrofolate reductase, and intercellular adhesion molecule-1 genes and plasma levels of fibrinogen, homocysteine, and intercellular adhesion molecule-1 among various race/ethnic groups: data from the Women's Genome Health Study

BACKGROUND

Although inflammation is a core element of atherogenesis and plasma levels of fibrinogen (FGB), homocysteine, and intercellular adhesion molecule-1 (ICAM-1) differ by race/ethnicity, little is known about the role of genetic polymorphisms in the FGB, methylenetetrahydrofolate reductase (MTHFR), and ICAM-1 genes in determining plasma levels of these biomarkers. We examined the relationship between specific polymorphisms in the FGB, homocysteine, and ICAM-1 genes and their respective inflammatory biomarker concentrations at baseline in women from different race/ethnic groups.

METHODS

We genotyped specific polymorphisms in FGB (-455G>A/rs1800790), MTHFR (677C>T/rs1801133), and ICAM-1 (Lys56Met/rs5491 and Gly241Arg/rs1799969) at baseline and evaluated their relationship with respective inflammatory biomarker levels in 25,565 white, 476 African-American (black), 277 Hispanic, and 370 Asian women participating in the Women's Genome Health Study.

RESULTS

Overall, the minor allele frequencies for -455G>A were similar among white, Hispanic, and Asian women (17.2%-21.9%) but significantly lower in black women (6.6%, P < .001). The minor allele was associated with elevated FGB levels only in whites and Asians. After adjustment for age, body mass index, smoking, postmenopausal status, diabetes, hormone replacement therapy use, hypertension, and education, black women had the highest FGB levels compared to other race/ethnic groups. The minor allele frequency of the MTHFR 677C>T polymorphism was lowest in blacks (blacks 12.1%, whites 33.1%, Hispanics 39.0%, Asians 24.0%), and the T allele was only significantly associated with homocysteine levels in white women. Among whites, Hispanics, and Asians, the Lys56Met polymorphism was rare compared to the frequency in blacks (P < .001). Neither the Lys56Met nor Gly241Arg polymorphisms were common in Asians. Nonetheless, both polymorphisms were generally associated with lower ICAM-1 levels; the lowest levels were observed in black women.

CONCLUSION

We found significant associations between certain candidate genetic polymorphisms and baseline plasma levels of FGB, homocysteine, and ICAM-1 in women from various race/ethnic groups. The present investigation is hypothesis generating and suggests genetic determination of differential concentrations of these atherosclerosis-related inflammatory biomarkers differ among various race/ethnic groups.

Hyperhomocysteinemia, intima-media thickness and C677T MTHFR gene polymorphism: a correlation study in patients with cognitive impairment

OBJECTIVE

Intima-media thickness (IMT) seems associated with risk of Alzheimer disease (AD). Homocysteine (hcy) is a risk factor for vascular diseases and dementia. This study aimed at investigating the possible relationship among IMT, plasma hcy and C677T methylentetrahydrofolate reductase (MTHFR) polymorphism in relation to cognitive status.

METHODS

Sixty-three patients with cognitive impairment and 64 controls underwent biochemical, neuropsychological and carotid ultrasound assessment.

RESULTS

After age and folate adjustment, plasma hcy correlated with both Mini Mental State Examination (MMSE) score (r=-0.7, p<0.01) and IMT (r=0.7, p<0.01). Among patients with cognitive impairment, carriers of TT677 MTHFR genotype had plasma hcy (p<0.001) and IMT (p<0.01) values higher than non carriers. Furthermore, multiple regression analysis showed that MMSE scores were associated with plasma hcy (beta=-0.3, p=0.01), IMT (beta=-0.3, p=0.01) and TT677 MTHFR genotype (beta=-0.3, p=0.02). Structural equation modelling showed that the relation between hcy levels and MMSE score was partly direct (parameter estimate=-0.6; p=0.01) and partly mediated by IMT values (parameter estimate=-0.4; p=0.03). Finally, IMT resulted associated with hypertension (parameter estimate=0.8; p<0.0001).

CONCLUSION

Our findings suggest that TT677 MTHFR genotype promotes plasma homocysteine increase which in turn may favour intima-media thickening in patients with cognitive impairment. Hcy may promote neuronal damage through multiple mechanisms, including a micro-vascular damage, mediated by IMT increase, and a direct neuro-toxic effect.

Inflammatory biomarkers, race/ethnicity and cardiovascular disease

Cardiovascular disease (CVD) remains the leading cause of death in the developed world. In the United States alone, cardiovascular disease accounts for nearly 40% of deaths, at an estimated annual cost of at least US $430 billion. Notable, racial/ethnic differences in morbidity and mortality have been observed; in the United States, African Americans have the highest age-adjusted death rate from CVD, followed by Whites, Hispanics, and Asians. The underlying basis for the observed racial/ethnic disparities in CVD morbidity and mortality is likely multifactorial. Although hyperlipidemia screening and treatment has proven to be one of the most effective strategies for reducing CVD burden in the US population, it often fails to identify a substantial proportion of persons at high risk for CVD-related events. Elevations in markers of inflammation and thrombosis such as high sensitivity C-reactive protein, soluble intercellular adhesion molecule, homocysteine, and fibrinogen are also associated with increased CVD risk. However, data relating markers of inflammation and hemostasis to CVD principally come from White populations, little data are available across racial/ethnic groups. A range of barriers exist related to ethnic minority subject participation in research studies in the United States. If we are to better understand the racial differences in cardiovascular risk, these barriers must be overcome.

Effects of white European, African Caribbean and South Asian ethnicity on homocysteine levels in patients with systolic heart failure

BACKGROUND

Patients with heart failure of any cause have elevated homocysteine compared to healthy controls. A number of studies in the UK and other western countries have documented higher levels of homocysteine among South Asian than among White European or African Caribbean subjects both in health and in disease, and have suggested that dietary deficiency of folate is the main cause for the difference.

METHODS

Plasma homocysteine, vitamin B(12), and folate levels were measured in a multiethnic UK heart failure clinic population (n=112), and compared to matched control subjects (n=131).

RESULTS

Plasma homocysteine levels were significantly higher in heart failure patients than controls (p<0.001), a result that was consistent across all ethnic groups. There was no difference in homocysteine levels by ethnic group in either patients (p=0.898) or controls (p=0.368). There was no significant difference in levels of folate or B(12) among patients or controls. Using a stepwise linear regression model, homocysteine levels in patients and controls were independently associated with age (p<0.001), vitamin B(12) (p<0.001), folate (p<0.001) and healthy control status (p<0.001), but not with gender, ethnicity, diabetes status, smoking status or BNP levels.

CONCLUSION

This study does not provide evidence of ethnic differences in homocysteine levels between White European, South Asian, and African Caribbean subjects with systolic heart failure. The lack of difference in levels of folate or B(12) among patients or controls, suggests that homocysteine levels - and differences previously seen between South Asians and other ethnic groups - may be driven by dietary factors.

Relation between soluble intercellular adhesion molecule-1, homocysteine, and fibrinogen levels and race/ethnicity in women without cardiovascular disease

Although certain markers of inflammation and hemostasis are elevated in persons at risk of future cardiovascular events, data assessing the relation between inflammatory and hemostatic markers of vascular risk and race/ethnicity are limited. Thus, in a cross-sectional analysis of the Women's Health Study (WHS), baseline soluble intercellular adhesion molecule-1 (ICAM-1), homocysteine, and fibrinogen were measured in 23,687 women without a history of cardiovascular disease. In 22,677 white, 242 Hispanic, 428 black, and 340 Asian women, the distribution of median ICAM-1 levels was significantly lower in black (311.9 ng/ml, interquartile range [IQR] 220.1 to 380.0) and Asian (312.7 ng/ml, IQR 267.3 to 362.3) women than white (343.1 ng/ml, IQR 301.9 to 394.9) and Hispanic (351.9 ng/ml, IQR 305.9 to 404.2) women (p <0.001). Although homocysteine was marginally lower in Asian women (p = 0.05), fibrinogen was higher in black women than their counterparts. After controlling for body mass index, hypertension, diabetes, smoking, alcohol use, family history of myocardial infarction, education, hormone use, and lipids, ICAM-1 remained significantly lower in black and Asian women. Meanwhile, homocysteine was lower in Asian women and fibrinogen remained higher in black women than their counterparts. In conclusion, this cross-sectional analysis shows that baseline fibrinogen, ICAM-1, and homocysteine vary by self-reported race/ethnicity.

Role of lifestyle factors on plasma homocysteine levels in Parkison's disease patients treated with levodopa

Many papers documented that Parkinson's disease (PD) patients treated with levodopa (L-dopa) shows elevated plasma homocysteine (Hcy) levels. Several lifestyle factors are able to influence plasma Hcy levels. We review the evidence that L-dopa therapy is related with an increase in plasma Hcy levels and that several behaviours could be able to cause changes in plasma Hcy concentrations. Therefore, there are reasons to suggest that a healthy lifestyle lowering Hcy may prevent this potential iatrogenic complication during L-dopa therapy. Moreover, at present, no controlled prospective studies have evaluated this phenomenon.

Effect of regular exercise on homocysteine concentrations: the HERITAGE Family Study

We investigated whether regular aerobic exercise could affect plasma total homocysteine (tHcy), and whether there were sex-related or racial differences in tHcy changes. Data were available for 816 black and white men and women, aged 17-65 years, 711 of whom completed a 20 week aerobic exercise training program. The tHcy concentration was measured in frozen plasma samples by an HPLC method. In Blacks, tHcy did not change with exercise training [men -0.5 (SD 3.7) micromol/l, women 0.0 (2.2) micromol/l) but increased significantly in Whites (men +0.3 (1.7) micromol/l, women +0.2 (1.6) micromol/l). No sex-related differences were found in either racial group. Changes in tHcy correlated negatively with baseline homocysteine (r = -0.40, P < 0.0001). Homocysteine levels of the "High" (hyperhomocysteinemia) (>or=15 micromol/l) group (n = 30) decreased significantly with regular aerobic exercise from 23.1 (12.1) to 19.6 (7.6) micromol/l. Homocysteine levels of the "Normal" group increased slightly from 8.2 +/- 2.2 to 8.5 +/- 2.4 micromol/l. Men exhibit racial differences for tHcy responses to exercise training. Regular aerobic exercise has favorable effects on individuals with hyperhomocysteinemia, but tHcy slightly increased in individuals within the normal range.

Cardiovascular risk factors in minorities

Recent clinical trials have confirmed the value of intervention on major risk factors, particularly hypertension and hyperlipidemia, in preventing the progression and clinical sequelae of atherosclerosis. Less is known about the prevalence and impact of atherosclerosis risk factors in minorities. A review of recent literature reporting the prevalence of established and new predictors of atherosclerotic events in minority populations and the inclusion of minorities in clinical trials is presented. The prevalence of risk factors differs considerably in minority populations. The role of "premature" coronary death and the level of some risk factors, particularly obesity and blood pressure in African descendants and high triglycerides, low high-density lipoproteins, and diabetes in some Hispanics, is higher than in whites. With few exceptions, however, minorities have not been included in clinical trials in sufficient numbers to determine whether significant differences in the benefit of risk factor intervention exists. Prevalence of key risk factors differs among minority groups. Risk factor intervention should be pursued in minority groups but with the understanding that clinical trials have not ruled out the possibility of qualitative or quantitative differences in response rates among different groups.

Homocysteine levels are associated with MTHFR A1298C polymorphism in Indian population

An elevated level of homocysteine is an independent risk factor for cardiovascular diseases and is associated with other complex disorders. Homocysteine levels can be elevated due to dietary and/or genetic factors. A majority of Indian population have a low level of vitamin B12 (presumably due to vegetarian diet)--a critical nutritional factor, deficiency of which results in hyperhomocysteinemia. Hence, polymorphisms in the genes responsible for homocysteine metabolism can be perceived to have a greater impact in relation to hyperhomocysteinemia in Indian population. For this reason, the effects of diet and/or methylenetetrahydrofolate reductase (MTHFR) polymorphism were assessed in 200 individuals having varying homocysteine levels. Homocysteine levels were significantly elevated in individuals adhering to a vegetarian diet (P = 0.019) or having MTHFR A1298C polymorphism (P = 0.006). The minor allele frequency (MAF) of MTHFR C677T and A1298C was 0.15 and 0.44 respectively in this cohort. Since the MAF of these polymorphisms differed considerably from Caucasian and other Asian populations, frequencies of these polymorphisms were also determined in more than 400 individuals from different ethnic populations, selected from the entire country based on their geographical location and linguistic lineage, and was found to be similar to that of our cohort. The fact that MTHFR A1298C polymorphism is significantly associated with homocysteine levels, and that the CC genotype is present at a higher frequency in the Indian population, makes it extremely relevant in terms of its potential impact on hyperhomocysteinemia.

The effect of MTHFR(C677T) genotype on plasma homocysteine concentrations in healthy children is influenced by gender

OBJECTIVE

To explore the influence of gender, together with folate status, on the relation between the common methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and plasma total homocysteine (tHcy) concentrations in healthy children.

DESIGN

Cross-sectional study by face-to-face interview.

SETTING AND SUBJECTS

A total of 186 sixth-grade students participated from twelve randomly selected primary schools in Volos, Greece.

METHODS

Fasting tHcy, folate, and vitamin B(12) were measured in plasma. The MTHFR genotypes were determined. Anthropometric and dietary intake data by 24-h recall were collected.

RESULTS

Geometric means for plasma tHcy, plasma folate and energy-adjusted dietary folate did not differ between females and males. The homozygous mutant TT genotype was associated with higher tHcy only in children with lower plasma folate concentrations (<19.9 nmol/l, P = 0.012). As a significant gender interaction was observed (P = 0.050), we stratified the lower plasma folate group by gender and found that the association between the genotype and tHcy was restricted to males (P = 0.026). Similar results were obtained when folate status was based on estimated dietary folate. Specifically, only TT males that reported lower dietary folate consumption (<37 microg/MJ/day) had tHcy that was significantly higher than tHcy levels of C-allele carriers (P = 0.001).

CONCLUSIONS

Under conditions of lower folate status (as estimated by either plasma concentration or reported dietary consumption), gender modifies the association of the MTHFR(C677T) polymorphism with tHcy concentrations in healthy children.

SPONSORSHIP

Kellog Europe.

Homocysteine, MTHFR C677T gene polymorphism, folic acid and vitamin B 12 in patients with retinal vein occlusion

Background

Many available data have suggested that hyperhomocysteinaemia, an established independent risk factor for thrombosis (arterial and venous), may be associated with an increased risk of retinal vein occlusion (RVO).

Aim of the study

To evaluate homocysteine metabolism in consecutive caucasian patients affected by RVO from Northern Italy.

Patients and Methods

69 consecutive patients from Northern Italy (mean age 64.1 ± 14.6 yy) with recent RVO, were tested for plasma levels of homocysteine (tHcy: fasting and after loading with methionine), cyanocobalamine and folic acid levels (CMIA-Abbot) and looking for MTHFR C677T mutation (Light Cycler-Roche) and compared to 50 volunteers, enrolled as a control group.

Results

Fasting levels of tHcy were significantly higher in patients than in controls: mean value 14.7 ± 7.7 vs 10.2 ± 8 nmol/ml. Post load levels were also significantly higher: mean value 42.7 ± 23.7 vs 30.4 ± 13.3 nmol/ml; Total homocysteine increase was also evaluated (i.e. Δ-tHcy) after methionine load and was also significantly higher in patients compared to control subjects: mean Δ-tHcy 27.8 ± 21.5 vs 21.0 ± 16 nmol/ml (normal value < 25 nmol/ml). Furthermore, patients affected by RVO show low folic acid and/or vitamin B12 levels, although differences with control group did not reach statistical significance. Heterozygous and homozygous MTHFR mutation were respectively in study group 46% and 29% vs control group 56% and 4%.

Conclusion

our data confirm that hyperhomocysteinaemia is a risk factor for RVO, and also that TT genotype of MTHFR C677T is more frequently associated with RVO: if the mutation per se is a risk factor for RVO remains an open question to be confirmed because another study from US did not reveal this aspect.

Hyperomocysteinemia is modifiable risk factor for thrombotic diseases. Therefore, a screening for tHcy plasma levels in patients with recent retinal vein occlusion could allow to identify patients who might benefit from supplementation with vitamins and normalization of homocysteine levels, in fasting and after methionine load.

Lack of association of methylenetetrahydrofolate reductase 677C>T mutation with coronary artery disease in a Pakistani population

Pakistanis belong to the South Asian population which has the highest known rate of coronary artery disease. Folic acid deficiency also appears to be highly prevalent in this population. Methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism decreases the activity of this enzyme and can be associated with mild to moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with coronary artery disease. To assess the value of genotyping the MTHFR 677C>T dimorphism, we carried out a case-control study of dimorphism 677C>T for putative association with myocardial infarction (MI) among Pakistani nationals. We investigated a sample population of 622 Pakistanis consisting of 225 controls and 397 patients with clinical diagnosis of acute MI (AMI). MTHFR C677T alleles were determined by assays based on polymerase chain reaction and restriction endonuclease analysis. Frequencies of C alleles were 0.87 among controls and 0.86 among AMI patients. The MTHFR 677C>T dimorphism showed no association with MI (χ² = 0.25, 1df, P=0.62), serum levels of folate and vitamin B12 and plasma level of vitamin B6. A significant association, however, was found between homozygous 677T genotype and plasma levels of homocysteine. Multivariate analysis of the data showed that in case of log homocysteine, age and MTHFR genotypes were significantly different (P<0.001). In case of B12, smoking and age were found to be statistically significant (P<0.001), while in case of serum folate only smoking was found to be significant (P<0.001). The results indicate that MTHFR 677C>T polymorphism, though associated with homocysteine levels, confers no significant risk of coronary artery disease in the Pakistani population investigated here. We suggest that the higher incidence of AMI in South Asia occurs through mechanisms other than the MTHFR related pathways.

Insulin resistance syndrome (metabolic syndrome) and obesity in Asian Indians: evidence and implications

OBJECTIVES

This review describes prevalence, determinants, and possible pathophysiologic mechanisms and suggests management and research directions for insulin resistance syndrome (metabolic syndrome) in Asian Indians.

METHOD

We reviewed the topic using the terms Asian Indians, Asians, South Asians, and Indians coupled with the terms insulin resistance, hyperinsulinemia, metabolic syndrome, and obesity from the databases Pubmed (National Library of Medicine, Bethesda, MD, USA) and Current Contents (Institute for Scientific Information, Thomson Scientific, Philadelphia, PA, USA) and from non-indexed publications of the medical research and governmental institutions in India.

RESULTS

Asian Indians have a high prevalence of insulin resistance syndrome that may underlie their greater than normal tendency to develop diabetes mellitus and early atherosclerosis. Important reasons could be their excess body fat and adverse body fat patterning including abdominal adiposity even when the body mass index is within the currently defined normal limits. Some of these features have been reported at birth and childhood. Whether Asian Indians also have tendency to develop insulin resistance de novo, independent of total or regional adiposity, needs further investigation. Underlying genetic tendency or early-life adverse events may contribute to such a phenotype, but lifestyle factors alone or modulated by inherited factors appear to play an important role because obesity and dyslipidemia become worse with urbanization and migration. Systemic stress may contribute to insulin resistance syndrome in the intra-country and inter-country migrant Asian Indians.

CONCLUSIONS

High prevalences of excess body fat, adverse body fat patterning, hypertriglyceridemia, and insulin resistance beginning at a young age have been consistently recorded in Asian Indians irrespective of their geographic locations. These data suggest that primary prevention strategies should be initiated early in this ethnic group.

Folate and homocysteine interrelationships including genetics of the relevant enzymes

PURPOSE OF REVIEW

Inadequate folate status has been linked to risk of a wide range of adverse health conditions throughout life, from birth defects and complications of pregnancy to cardiovascular disease, cancer and cognitive dysfunction in the elderly. In many instances these risks are manifested through elevated plasma homocysteine. This review focuses on current research into the contribution of genetic variability to folate status and disease predisposition.

RECENT FINDINGS

Some dozen potentially important polymorphisms in folate-related genes have been examined for disease associations or for their role in determining the level of plasma homocysteine. In most instances, the effects are either modest, not significant, or undetectable. However, the mechanism by which the 677C-->T variant of methylenetetrahydrofolate reductase determines homocysteine status has become clearer with the elucidation of a critical role for riboflavin in modulating the plasma homocysteine of TT homozygotes. Moreover, several new metaanalyses have confirmed an association of this variant with vascular disease, probably through low folate status and elevated plasma homocysteine.

SUMMARY

There are enormous difficulties in attempting to assess the contribution of minor genetic variability to nutrient status, against major background differences due to ethnicity, age, gender, lifestyle, dietary habits and disease status. Nevertheless, this is an important goal in the future management of chronic multifactorial disease. The present research into the genetic components of folate and homocysteine variability is paving the way towards an eventual capacity to ensure optimal folate status in every individual and, consequently, to reduce their risk of developing such diseases.

Age and Gender Affect the Relation between Methylenetetrahydrofolate Reductase C677T Genotype and Fasting Plasma Homocysteine Concentrations in the Framingham Offspring Study Cohort

The C677T variant of methylenetetrahydrofolate reductase (MTHFR), a key enzyme in the remethylation of homocysteine to methionine, is a frequent genetic cause of mild hyperhomocysteinemia among individuals with low folate status. However, little is known about the influence of subject characteristics, such as age and sex, on the relation between the C677T MTHFR polymorphism and fasting plasma total homocysteine (tHcy) concentrations. The aim of the present study was to explore the influence of age and gender, together with folate status, on the association between the C677T polymorphism and tHcy concentrations. The C677T genotype was determined for 1820 participants from the fifth examination of the Framingham Offspring Study. Mean age of the participants was 56 y (range 28-82 y). The allelic distribution was not different from the Hardy-Weinberg equilibrium, with a TT frequency comparable in men and women (14%). Geometric mean tHcy was 15% higher in men than in women (P < 0.001), and women had significantly higher plasma folate levels (P < 0.001). Geometric mean tHcy was significantly higher in TT participants (P = 0.001) than in participants with the CC and CT genotypes among those with plasma folate <12.5 nmol/L, but not among those with higher folate status. Because of a significant age and sex interaction (P = 0.02), we further stratified the low folate group by age and sex, and observed that the association between genotype and tHcy was confined to men <55 y old (P < 0.001). Our results suggest that age and sex modify the contribution of the MTHFR C677T mutation to fasting tHcy concentrations.

Lack of association between polymorphisms in angiotensin-converting-enzyme and methylenetetrahydrofolate reductase genes and normal cognitive ageing in humans

The hypothesis that polymorphisms at two candidate genes that code for angiotensin-converting-enzyme (ACE) and methylenetetrahydrofolate reductase (MTHFR) are associated with normal cognitive ageing was tested using a sample (n=536) of healthy 80-year-old people who were born in 1921 and whose cognitive ability at age 11 was measured in the Scottish Mental Survey 1932. Cognitive ability at age 11 and age 80 was assessed using the Moray House Test. Cognitive ageing was defined as the change in IQ from age 11 to 80. There was no significant association between the tested ACE and MTHFR polymorphisms and IQ score at age 11, IQ at age 80, and IQ change (all P>0.05). The ACE genotypes deviated significantly from Hardy-Weinberg equilibrium proportions (P=0.02), which could indicate that this gene is under selection. Polymorphisms at the two studied genes are unlikely to be risk factors for normal cognitive ageing.