Apolipoprotein E and methylenetetrahydrofolate reductase genetic polymorphisms in relation to other risk factors for cardiovascular disease in UK Caucasians and Black South Africans

Association of APOE gene polymorphism with lipid profile and coronary artery disease in Afro-Caribbeans

OBJECTIVES

Apolipoprotein E gene (APOE) polymorphism is associated with the lipid profile and cardio-vascular disease. However, these relationships vary between ethnic groups. We evaluated, for the first time in an Afro-Caribbean population, the distribution of APOE polymorphisms and their associations with coronary artery disease (CAD), the lipid profile and other cardio-metabolic risk factors.

METHODS

We studied 712 Afro-Caribbean subjects including 220 with documented CAD and 492 healthy subjects. TaqMan assays were performed to genotype rs7412 and rs429358, the two variants that determine the APOE alleles ε2, ε3 and ε4. The association between APOE genotype and the lipid profile was analysed by comparing ε2 carriers, ε3 homozygotes and ε4 carriers.

RESULTS

The frequencies of ε2, ε3 and ε4 in the overall sample were 8%, 70% and 22%, respectively. CAD was not associated with APOE polymorphism. The total cholesterol level was higher in ε4 carriers compared with ε2 carriers: 5.07 vs 4.59 mmol/L (P = 0.016). The LDL-cholesterol level was lower in APOE ε2 carriers compared with ε3 homozygotes and ε4 carriers: 2.65 vs 3.03 and 3.17 mmol/L, respectively (p = 0.002). The total cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios were similar in the three allelic groups. APOE polymorphism was not associated with diabetes, hypertension, waist circumference or body mass index.

CONCLUSIONS

Our results indicate that APOE gene polymorphism is associated with the lipid profile but not with CAD in Afro-Caribbean people. This lack of association with CAD may be explained by the low atherogenic profile observed in ε4 carriers, which may warrant further investigation.

Apolipoprotein E genotypes and their relation to lipid levels in a rural South African population 1

Aims: Genetic variation at the apolipoprotein E (apoE) locus is an important determinant of plasma lipids. The aim of the present study was to evaluate the association between apolipoprotein E genotype and plasma lipid levels among a rural black population in South Africa. Methods: Lipid levels and apoE genotypes were studied in 505 volunteer subjects (363 women, 142 men) resident in the Dikgale demographic surveillance site. Results: Allele frequencies were found to be 0.190 for ε2, 0.518 for ε3, and 0.293 for ε4, indicating a relatively low frequency of the ε3 allele and a high frequency of the ε4 allele. To determine the effect of apoE polymorphism on lipid levels three groups were formed: namely ε2-, ε3-, and ε4-expressing groups. A significant effect of the apoE genotype on total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C)/Total cholesterol (TC) ratio, and triglycerides was observed. LDL-C was significantly lower and the HDL-C/TC ratio was significantly higher in the ε2 group compared with the ε3 and ε4 groups. Triglyceride levels were significantly higher in the ε2 group than in the ε3 group. Conclusions: With the unfavourable apoE allele distribution, and the lifestyle changes taking place in rural South African populations, preventive strategies need to be developed to limit a potential epidemic of cardiovascular disease in the black population of South Africa.

The association of MTHFR C677T gene variants and lipid profiles or body mass index in patients with diabetic and nondiabetic coronary heart disease

BACKGROUND

The aim of this study is to investigate whether methylenetetrahydrofolate reductase (MTHFR) C677T mutation is associated with the development of hyperlipoproteinemia and obesity in coronary heart disease (CHD).

METHODS

This study was carried out in 82 diabetic and 112 nondiabetic patients with CHD and in 138 CHD-free healthy controls. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and agarose gel electrophoresis techniques were used to determine the MTHFR C677T.

RESULTS

Distributions of MTHFR genotypes (C677T dbSNP: rs1801133) were similar in our study groups (P > 0.05). There was no statistical association between biochemical parameters and genotype distribution in nondiabetic CHD patients, while diabetic CC genotype carriers have elevated levels of body mass index (BMI) independently from lipid profiles (P = 0.002). In diabetic CHD patients, while evaluating the clinical parameters according to gender, it was found that gender had an impact on BMI (P = 0.013). Due to this gender effect, a multivariate analysis was conducted on the diabetic CHD patient group. The multivariate logistic regression analysis confirmed that the MTHFR-CC genotype was associated with elevated BMI levels in diabetic CHD patients (odds ratio [OR] = 5.42, P = 0.003).

CONCLUSION

The results of the present study demonstrated that possessing T allele of MTHFR C677T mutation indicates a protective association on BMI independently from other risk factors.

Association of apolipoprotein E polymorphism with maximal oxygen uptake after exercise training: a study of Chinese young adult

Background

Although a few studies have been conducted, it is still unclear whether the apolipoprotein E (APOE) polymorphism is associated with maximal oxygen uptake (VO_2max) after exercise training. The objective of this study was to examine if the APOE gene polymorphisms affect VO_2max after exercise training in Chinese young adult.

Methods

A total of 360 Chinese young adult (180 male and 180 female) were recruited into this gender-specific cohorts. Anthropometrics, serum lipids, and VO_2max were measured pre and post 6 months of supervised exercise training. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess the APOE gene polymorphisms.

Results

VO_2max after exercise training increased significantly higher in carriers of E2/E3 in male [odds ratio (OR) =0.68, 95% confidence interval (CI) = 0.04, 1.32; P = 0.04] and female (OR =0.62, 95% CI = 0.05, 1.18; P = 0.03). VO_2max after exercise training increased significantly higher in carriers of E3/E4 in male (OR =0.60, 95% CI = 0.09, 1.11; P = 0.02) and female (OR =0.62, 95% CI = 0.09, 1.15; P = 0.02). No significant differences were found in carriers of E2/E2, E2/E4, E3/E3, E4/E4 in either male nor female.

Conclusion

Our study found that APOE gene polymorphism was associated with VO_2max levels after exercise training in Chinese young adult. In the future, further experiments will be necessary to confirm this finding and to find the possible mechanism.

Apolipoprotein E polymorphism is associated with lower extremity deep venous thrombosis: color-flow Doppler ultrasound evaluation

Introduction

Apolipoprotein E (apoE) is a member of apolipoprotein family, and its gene polymorphisms seem to have some impact among patients with cardiovascular disease. However, its role in the lower extremity deep venous thrombosis (LEDVT) has not been well studied. The objective of this study was to investigate the potential association between APOE gene polymorphisms and LEDVT.

Materials and methods

A hospital-based case–control study was conducted in 300 patients with LEDVT by color-flow Doppler ultrasound and 300 age- and gender-matched healthy controls. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay was applied to assess the APOE gene polymorphisms.

Results

Patients with LEDVT had a significantly higher frequency of APOE E3/E4 genotype [odds ratio (OR) =1.48, 95% confidence interval (CI) = 1.05, 2.10; P = 0.03] than healthy controls. When stratifying by family history of LEDVT, it was found that patients with positive family history of LEDVT had a significantly higher frequency of APOE E3/E4 genotype (OR =1.68, 95% CI = 1.04, 0.95; P = 2.70). When stratifying by smoking status, presence of varicose veins, type 2 diabetes mellitus and any hormone administration before, no significant differences were found in any groups.

Conclusion

Our study suggested that APOE E3/E4 genotype was associated with a higher LEDVT risk. Additional studies are needed to confirm this finding.

Associations of MTHFR and MTRR polymorphisms with serum lipid levels in Chinese hypertensive patients

OBJECTIVE

To examine the effects of the methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) gene polymorphisms and their interactions with environmental factors on serum lipid levels.

METHODS

We investigated totally 340 patients with essential hypertension, from Dongzhi community, Anhui, China. High-throughput TaqMan allelic discrimination assay was used for the genotyping of MTHFR C677T (Ala222Val), MTHFR A1298C (Glu429Ala), MTRR A66G (Ile22Met), and MTRR His595Tyr.

RESULTS

Compared with the MTRR 66AA genotype carriers, the GG genotype carriers had lower serum total cholesterol (TC) levels (adjusted β ± standard error [SE]: -0.5 ± 0.2 mmol/L; P = .003) and low-density lipoprotein cholesterol (LDL-C) levels (adjusted β ± SE: -0.4 ± 0.2 mmol/L; P = .005). Their false discovery rate (FDR)-adjusted P values were 0.056 and 0.056, respectively. We further found that there was a statistically significant interaction between 677TT genotype and sex in their associations with LDL levels (P interaction = .020), and significant interaction between 677TT genotype and smoking on LDL levels (P interaction = .036). A similar pattern of interaction was found between 66GG and drinking on levels of TC (P interaction = .034) and LDL (P interaction = .020). However, there were no significant interactions observed after FDR adjustment.

CONCLUSION

Both MTHFR and MTRR gene polymorphisms could be important genetic determinants of serum lipid levels in Chinese patients with hypertension. These findings need to be replicated in a larger sample.

The carotid artery atherosclerosis burden and its relation to cardiovascular risk factors in black and white Africans with established rheumatoid arthritis: a cross-sectional study

OBJECTIVE

Black Africans currently experience a distinctly low frequency of atherosclerotic cardiovascular disease. Whether this protection persists in those with rheumatoid arthritis (RA) is unknown. We compared the carotid atherosclerosis burden and its relationships with cardiovascular (CV) risk factors between Africans with RA from a developing black and developed CV population.

METHODS

We performed high resolution B-mode ultrasonography and assessed CV risk factors in 243 patients with established RA, of whom 121 were black and 122 white. Data were analyzed in age, sex, and healthcare center-adjusted regression models.

RESULTS

The mean±SD common carotid intima-media thickness (cIMT) was 0.694±0.097 mm in black and 0.712±0.136 mm in white patients (adjusted p=0.8). Plaque prevalence was also similar in black compared to white cases (35.5% and 44.3%, respectively; adjusted OR 0.83, 95% CI 0.32-2.20, p=0.7). Interactions between population grouping and several CV risk factors were independently associated with cIMT and plaque. In stratified analysis, that is, in each population group separately, risk factors associated with cIMT or/and plaque comprised the systolic blood pressure (p=0.02), serum cholesterol/high-density lipoprotein cholesterol ratio (p=0.004), C-reactive protein concentrations (p=0.01), and the presence of extraarticular manifestations (p=0.01) in whites but, contrastingly, the Arthritis Impact Measurement Scales tension score (p=0.04) and use of nonsteroidal antiinflammatory agent (p=0.03) in black patients. The Framingham score was significantly associated with atherosclerosis only in whites (p<0.0001).

CONCLUSION

The carotid atherosclerosis burden is similar in black compared to white Africans with RA, but relationships between modifiable CV risk factors and atherosclerosis vary substantially among Africans with RA.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

Association of methylenetetrahydrofolate reductase C677T polymorphism and serum lipid levels in the Guangxi Bai Ku Yao and Han populations

Background

The association of methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and serum lipid profiles is still controversial in diverse ethnics. Bai Ku Yao is an isolated subgroup of the Yao minority in China. The aim of the present study was to eveluate the association of MTHFR C677T polymorphism and several environmental factors with serum lipid levels in the Guangxi Bai Ku Yao and Han populations.

Methods

A total of 780 subjects of Bai Ku Yao and 686 participants of Han Chinese were randomly selected from our previous stratified randomized cluster samples. Genotyping of the MTHFR C677T was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

The levels of serum total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (Apo) AI and ApoB were lower in Bai Ku Yao than in Han (P < 0.05-0.001). The frequency of C and T alleles was 77.4% and 22.6% in Bai Ku Yao, and 60.9% and 39.1% in Han (P < 0.001); respectively. The frequency of CC, CT and TT genotypes was 58.7%, 37.3% and 4.0% in Bai Ku Yao, and 32.6%, 56.4% and 11.0% in Han (P < 0.001); respectively. The levels of TC and LDL-C in both ethnic groups were significant differences among the three genotypes (P < 0.05-0.01). The T allele carriers had higher serum TC and LDL-C levels than the T allele noncarriers. The levels of ApoB in Han were significant differences among the three genotypes (P < 0.05). The T allele carriers had higher serum ApoB levels as compared with the T allele noncarriers. The levels of TC, TG and LDL-C in Bai Ku Yao were correlated with genotypes (P < 0.05-0.001), whereas the levels of LDL-C in Han were associated with genotypes (P < 0.001). Serum lipid parameters were also correlated with sex, age, body mass index, alcohol consumption, cigarette smoking, and blood pressure in the both ethnic groups.

Conclusions

The differences in serum TC, TG, LDL-C and ApoB levels between the two ethnic groups might partly result from different genotypic and allelic frequencies of the MTHFR C677T or different MTHFR gene-enviromental interactions.

Genetic variants associated with fasting blood lipids in the U.S. population: Third National Health and Nutrition Examination Survey

BACKGROUND

The identification of genetic variants related to blood lipid levels within a large, population-based and nationally representative study might lead to a better understanding of the genetic contribution to serum lipid levels in the major race/ethnic groups in the U.S. population.

METHODS

Using data from the second phase (1991-1994) of the Third National Health and Nutrition Examination Survey (NHANES III), we examined associations between 22 polymorphisms in 13 candidate genes and four serum lipids: high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglycerides (TG). Univariate and multivariable linear regression and within-gene haplotype trend regression were used to test for genetic associations assuming an additive mode of inheritance for each of the three major race/ethnic groups in the United States (non-Hispanic white, non-Hispanic black, and Mexican American).

RESULTS

Variants within APOE (rs7412, rs429358), PON1 (rs854560), ITGB3 (rs5918), and NOS3 (rs2070744) were found to be associated with one or more blood lipids in at least one race/ethnic group in crude and adjusted analyses. In non-Hispanic whites, no individual polymorphisms were associated with any lipid trait. However, the PON1 A-G haplotype was significantly associated with LDL-C and TC. In non-Hispanic blacks, APOE variant rs7412 and haplotype T-T were strongly associated with LDL-C and TC; whereas, rs5918 of ITGB3 was significantly associated with TG. Several variants and haplotypes of three genes were significantly related to lipids in Mexican Americans: PON1 in relation to HDL-C; APOE and NOS3 in relation to LDL-C; and APOE in relation to TC.

CONCLUSIONS

We report the significant associations of blood lipids with variants and haplotypes in APOE, ITGB3, NOS3, and PON1 in the three main race/ethnic groups in the U.S. population using a large, nationally representative and population-based sample survey. Results from our study contribute to a growing body of literature identifying key determinants of plasma lipoprotein concentrations and could provide insight into the biological mechanisms underlying serum lipid and cholesterol concentrations.

APOE distribution in world populations with new data from India and the UK

BACKGROUND

The APOE gene and its protein product is associated with a number of plasma proteins like very-low density lipoprotein (VLDL), high density lipoprotein (HDL) chylomicrons, chylomicron remnants, and plays a crucial role in lipid metabolism. The APOE gene is polymorphic and common alleles (*E2, *E3 and *E4) have been associated with a number of common and complex diseases in different populations. Due to their crucial role in metabolism and clinical significance, it is imperative that allelic variation in different populations is analysed to evaluate the usage of APOE in an evolutionary and clinical context.

AIM

We report allelic variation at the APOE locus in three European and four Indian populations and evaluate global patterns of genetic variation at this locus. The large, intricate and unexpected heterogeneity of this locus in its global perspective may have insightful consequences, which we have explored in this paper.

SUBJECT AND METHODS

Apolipoprotein E genotypes were determined in four population groups (Punjabi Sikhs, Punjabi Hindus, Maria Gonds and Koch, total individuals = 497) of India and three regionally sub-divided British populations (Nottinghamshire, East Midlands and West Midlands, total individuals = 621). The extent and distribution of APOE allele frequencies were compared with 292 populations of the world using a variety of multivariate methods.

RESULTS

Three alleles, APOE*E2, APOE*E3 and APOE*E4, were observed with contrasting variation, although *E4 was absent in the tribal population of Koch. Higher heterozygosities (>43%) in British populations reflected their greater genetic diversity at this locus. The overall pattern of allelic diversity among these populations is comparable to many European and Indian populations. At a global level, higher frequencies of the *E2 allele were observed in Africa and Oceania (0.099 +/- 0.083 and 0.111 +/- 0.052, respectively). Similarly, *E4 allele averages were higher in Oceania (0.221 +/- 0.149) and Africa (0.209 +/- 0.090), while Indian and Asian populations showed the highest frequencies of *E3 allele. The coefficient of gene differentiation was found to be highest in South America (9.6%), although the highest genetic diversity was observed in Oceania (48.7%) and Africa (46.3%). APOE*E2 revealed a statistically significant decreasing cline towards the north in Asia (r = -0.407, d.f. = 70, p < 0.05), which is not compatible with the coronary heart disease statistics in this continent. APOE*E4 showed a significant increasing cline in North European populations. Spatial autocorrelation analysis shows that the variation at this locus is influenced by 'isolation by distance' with a strong positive correlation for lower distances up to 1313 km.

CONCLUSION

Overall APOE allelic variation in UK and Indian populations is comparable to previous studies but in tribal populations *E4 allele frequency was very low or absent. At a global level allelic variation shows that geography, isolation by distance, genetic drift and possibly pre-historical selection are responsible for shaping the spectrum of genetic variation at the APOE gene. Overall, APOE is a good anthropogenetic and clinical diagnostic marker.

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.

Pharmacogenetic study of methylenetetrahydrofolate reductase and thymidylate synthase in Japanese and assessment of ethnic and gender differences

OBJECTIVES

We investigated the four polymorphisms of the 5,10-methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TYMS) genes that are related to the pharmacologically active sites of methotrexate for the treatment of rheumatoid arthritis in 102 healthy Japanese adults and assessed the possibility of ethnic and gender differences.

METHODS

Polymorphisms of MTHFR C677T, A1298C, the two or three 28-bp tandem repeats in the TYMS 5'-untranslated regions (UTR), and the 6-bp deletion/insertion in the TYMS 3'-UTR were measured using polymerase chain reaction with restriction fragment length polymorphism method. Published data on allelic frequencies by ethnic group and gender were collected from Medline.

RESULTS

Allelic frequencies in healthy Japanese adults were: MTHFR 677T allele 41%, MTHFR 1298C allele 22%, TYMS 5'-UTR 3R allele 84%, and TYMS 3'-UTR-6-bp allele 59%. Significant differences were found in the distribution of MTHFR C677T between black and Japanese populations, of TYMS 5'-UTR alleles between Caucasian or black and Japanese populations, and of TYMS 3'-UTR alleles between Caucasian and Japanese populations (p < 0.001). Moreover, a gender difference was found in TYMS 3'-UTR allelic frequency in Japanese (p = 0.015).

CONCLUSION

Ethnic and gender variations in the distribution of these allelic frequencies may associate with the difference in the effects of methotrexate in rheumatoid arthritis patients.

Mechanisms of disease: lessons from ethnicity in the role of triglyceride metabolism in ischemic heart disease

Mean risk factor levels in various ethnic groups illustrate the potential importance of triglyceride metabolism in the risk for ischemic heart disease (IHD). Serum triglyceride concentrations are a surrogate for a range of potentially atherogenic disturbances in lipoprotein species, including increased concentrations of remnants of VLDL and chylomicron metabolism, increased small, dense LDL concentrations and reduced HDL concentrations. Differences between at-risk groups in lipoprotein profiles reflect alterations in the metabolism of triglycerides that might be greater than differences observed when only circulating triglyceride concentrations are measured. This atherogenic lipoprotein profile is typically found in association with increased visceral fat, insulin resistance and type 2 diabetes and might be a characteristic of Asian Indian ethnicity. By contrast, despite being relatively insulin resistant, Afro-Caribbean men in the UK have a low risk of IHD and lack the adverse lipoprotein profile. This could result from secretion of relatively large proportions of their VLDL as small, triglyceride-poor particles, levels of which are not augmented in response to loss of insulin action. These considerations re-endorse the potential importance of triglyceride metabolism in IHD and present opportunities for identifying useful areas in which drug targets for reducing IHD risk can be sought.

Avaliação do polimorfismo no gene da metilenotetrahidrofolato redutase e concentração de folato e vitamina B12 em pacientes portadores do HIV-1 em tratamento com anti-retrovirais

Neste trabalho, investigamos concentração da vitamina B12 e folato, considerando-se a influência dos genótipos da metilenotetrahidrofolato redutase, o perfil imunológico e a terapia antiretroviral utilizada na população brasileira portadora do HIV. Um grupo de 86 indivíduos portadores do HIV-1 e 29 doadores de sangue foram recrutados para compor a casuística. Entre os infectados pelo HIV-1, observou-se menor concentração de B12 no grupo com maior número de linfócitos TCD4+. Não encontramos diferença na distribuição genotípica para as mutações MTHFR C677T e A1298C entre infectados e não infectados pelo HIV-1. Indivíduos portadores do HIV, genótipo C677C, apresentaram concentrações menores de B12 em relação ao grupo controle de mesmo genótipo. A terapia antiretroviral não mostrou qualquer influência nos valores de folato e vitamina B12. Estudos adicionais são necessários para reavaliar a prevalência de menores concentrações de B12 e folato e de hiperhomocisteinemia na população portadora do HIV sob a ótica do uso de HAART e da melhoria na sobrevida dos pacientes.

High prevalence of hyperhomocysteinemia related to folate deficiency and the 677C-->T mutation of the gene encoding methylenetetrahydrofolate reductase in coastal West Africa

BACKGROUND

Moderate hyperhomocysteinemia is a risk for neural tube defect and neurodegenerative and vascular diseases and has nutritional, metabolic, and genetic determinants. Its prevalence in sub-Saharan Africa remains unknown.

OBJECTIVE

Our goal was to evaluate the prevalence of hyperhomocysteinemia and the influence of nutritional, metabolic, and genetic determinants in savanna and coastal regions of Togo and Benin.

DESIGN

Volunteers were recruited from coastal (C groups; n = 208) and savanna (S group; n = 68) regions. Vitamin B-12, folate, total homocysteine (tHcy), cystatin C (a marker of glomerular filtration), and inflammatory and nutritional protein markers were measured in plasma, and the methylenetetrahydrofolate reductase (MTHFR) 677C-->T and 1298A--> C polymorphisms and the methionine synthase 2756A-->G polymorphism were examined in genomic DNA.

RESULTS

Moderate hyperhomocysteinemia (tHcy > 15 micromol/L) was recorded in 62.3% and 29.4% of the subjects from the coast and savanna, respectively (P < 0.0001). A histogram distribution of tHcy in the coastal groups showed a distinct group, C2 (15% of the total group), with tHcy > 28 micro mol/L. Folate < 6.75 nmol/L (lower quartile) and MTHFRCT/TT genotype were the 2 main risk factors for moderate hyperhomocysteinemia in the whole population [odds ratios: 5.3 (95% CI: 2.5, 11.2; P < 0.0001) and 4.9 (1.6, 14.8; P = 0.0048), respectively] and in the C2 group [odds ratios: 15.9 (4.5, 56.8; P < 0.0001) and 9.0 (2.3, -35.2; P = 0.0017), respectively]. Cystatin C was another potent risk factor in the C2 group.

CONCLUSION

A high prevalence of hyperhomocysteinemia in coastal West Africa, related to folate concentrations and the MTHFR 677 T allele, suggests the need to evaluate the influence of hyperhomocysteinemia on disease in this area.

Prevalence and Role of Methylenetetrahydrofolate Reductase 677 C→T and 1298 A→C Polymorphisms in Coronary Artery Disease in Arabs

Context.—Previous studies reported an association of 677 C→T and 1298 A→C methylenetetrahydrofolate reductase (MTHFR) variants with coronary artery disease (CAD). No previous studies concerning the prevalence of these 2 MTHFR variants or their possible association with CAD in Arabs are currently available in the literature.

Objective.—To determine the prevalence of MTHFR variants and their potential relevance to CAD among Arabs.

Design.—We used polymerase chain reaction and restriction enzyme digestion to determine the prevalence of these 2 MTHFR polymorphisms in 625 healthy blood donors (BDs) and 545 angiographically confirmed CAD patients of Arab origin.

Results.—For the 677 C→T variant within the CAD group, 64.2% were homozygous wild-type C/C, 32.1% were heterozygous C/T, and 3.7% were homozygous T/T genotype. Within the BD group tested for the 677 C→T variant, 72.2% were homozygous wild-type C/C, 25.8% were heterozygous C/T, and 2% were homozygous T/T genotype. Within the CAD group tested for the 1298 A→C variant (n = 540), 45.7% were homozygous wild-type A/A, 46.9% were heterozygous A/C, and 7.4% were homozygous C/C genotype. Within the BD group tested for the 1298 A→C variant (n = 625), 39.4% were homozygous wild-type A/A, 51.5% were heterozygous A/C, and 9.1% were homozygous C/C genotype. The distribution and allele frequency of these 2 MTHFR variants followed the Hardy-Weinberg equilibrium and were similar in the CAD and BD study groups. The prevalence of the 677 C→T and 1298 A→C compound heterozygosity was 9.6% for the BD group and 12.3% for the CAD group.

Conclusion.—The 2 MTHFR variants tested in this study, individually or compound, are not associated with CAD. Therefore, neither of these 2 variants can be considered an independent risk factor or a predictor for CAD in this population.

Low frequency of mutated methylenetetrahydrofolate reductase 677C-->T and 1298A-->C genetics single nucleotide polymorphisms (SNPs) in Sub-Saharan populations

5,10-Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) are two of the key enzymes in the folate/vitamin B12-dependent remethylation of homocysteine to methionine. The frequencies of MTHFR single nucleotide polymorphisms (SNPs), 677C-->T, 1298A-->C, 1317T-->C and of MTR, 2756A-->G, have been widely studied in Caucasians, but they have never been reported simultaneously in a large population from Sub-Saharan Africa. Presently, we report the prevalence of these SNPs and their relationship to homocysteine in 240 subjects recruited in West Africa. The frequencies of the mutant genotypes 677TT (0.8%) and 1298CC (2%) were lower than that usually observed in Caucasians, while the frequency of the mutant 1317CC was higher (16%). We formed a systematic association of the mutated MTHFR 677C-->T SNP with a 1298A/1317T common haplotype. The MTHFR mutant genotype 677TT was associated with an intermediate hyperhomocysteinemia (92.4 +/- 6.0 micromol/l) higher than that described in Caucasians. The 2756A-->G SNP in the MTR was similarly distributed in Africans compared to Caucasians. In conclusion, the MTHFR 677TTor 1298CC genotypes are much rarer in Africans than in Caucasians. The 677TT low frequency may be related to the high effect of this mutation on homocysteine metabolism in the environmental conditions of this African region.

Genetic vulnerability following traumatic brain injury: the role of apolipoprotein E

Apolipoprotein E (APOE) is thought to be responsible for the transportation of lipids within the brain, maintaining structural integrity of the microtubule within the neurone, and assisting with neural transmission. Possession of the APOE epsilon4 allele has also been shown to influence neuropathological findings in patients who die from traumatic brain injury, including the accumulation of amyloid beta protein. Previous clinical studies reporting varying outcome severities of traumatic brain injury, including cognitive and functional recovery, all support the notion that APOE epsilon4 allele possession is associated with an unfavourable outcome. Evidence from experimental and clinical brain injury studies confirms that APOE plays an important role in the response of the brain to injury.

Gender, ethnicity and genetics in cardiovascular disease: part 1: Basic principles

Prior to 1993, most drug efficacy and safety trials were conducted in white males, although gender and racial differences in pharmacodynamics and pharmacokinetics have been documented since the early 1900s. Over the last 2 decades, supported by the FDA and legislation, attempts to include more women and minorities in clinical drug trials have been made, with limited success. Yet, there are important differences in pathophysiology and pharmacogenetics, as well as pharmacotherapeutic effectiveness. This is the first of 2 articles that review the basic scientific principles of such differences. In particular, genetic polymorphisms of cardiovascular candidate genes and drug metabolism are described. The pharmacodynamic and pharmacokinetic variations among genders and ethnicities are summarized.

Apolipoprotein E polymorphism and outcome after closed traumatic brain injury: influence of ethnic and regional differences

OBJECT

The presence of the apolipoprotein E-epsilon4 (APOE-epsilon4) allele is reported to be associated with poor outcome after traumatic brain injury (TBI). This study was performed to determine if the presence of the APOE-epsilon4 allele influenced outcome in a cohort of black patients with TBI who had homogeneous neuropathological findings.

METHODS

Venous blood was collected at the time of admission to determine the APOE genotype in black Zulu-speaking patients who presented with traumatic cerebral contusions. The frequency of the APOE-epsilon4 allele's appearance was correlated with outcome at a minimum of 6 months of follow up. Univariate and multivariate analyses were performed to determine independent risk factors and to control for confounding factors. In 110 black Zulu-speaking patients with traumatic cerebral contusions, genotypes for APOE were analyzed. Eleven of 45 (24.4%) with the APOE-epsilon4 allele experienced a poor outcome, compared with 10 (15.4%) of 65 without this allele (p = 0.34). Both patients with homozygous APOE-epsilon4 alleles experienced a good outcome (Glasgow Outcome Score 5). Univariate and multivariate analysis revealed no significant relationship in patients with the APOE-epsilon4 allele with regard to age, admission Glasgow Comas Scale score, contusion volume, type of neurosurgical management, and outcome. The risk of a poor outcome was, however, greater in patients with the APOE-epsilon4 allele (relative risk 1.59; 95% confidence interval 0.74-3.42).

CONCLUSIONS

The authors recorded no relationship between APOE-epsilon4 allele status and outcome after TBI in black patients. Given the high regional susceptibility to the APOE gene, further studies, possibly even community-based investigations and studies conducted in other geographic areas, are probably warranted.

Prevalence of the methylenetetrahydrofolate reductase 677C > T mutation in the Mediterranean Spanish population. Association with cardiovascular risk factors

Methylenetetrahydrofolate reductase (MT-HFR) is a key enzyme involved in folate metabolism. A common cytosine (C) to a thymine (T) mutation at nucleotide 677 (677C > T) in the MTHFR gene which converts an alanine residue to a valine, has been related with several biochemical phenotypes and with cardiovascular risk, depending on the population studied. Our objective was to estimate the prevalence of the 677C > T mutation in a large and randomly selected sample (289 men and 427 women) from the Mediterranean Spanish population, and to test the association between this genetic variant and some cardiovascular risk factors. For both genders, the prevalence of CC, CT and TT subjects was 32.0, 52.2 and 15.8%, respectively. The frequency (95% confidence interval) of the 677T allele was 0.44 (0.40-0.48) in men and 0.40 (0.37-0.44) in women. This prevalence was significantly different from other European countries, and among the highest reported in the world for any healthy population. We found no association between the 677C > T gene variants and age, body mass index (BMI), total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides or diastolic blood pressure in men and women. However, in men, a statistically significant increase of systolic blood pressure with the number of mutant alleles was found (122.2 mmHg in CC, 125.1 mmHg in CT and 128.5 mmHg in TT subjects; p for trend = 0.030). This association remained significant (p = 0.047) even after adjustment for age, BMI, alcohol consumption, tobacco smoking, education and physical activity.

The emergence of cardiovascular disease during urbanisation of Africans

OBJECTIVE

To review the available data on risk factors for cardiovascular disease (CVD), the influence of urbanisation of Africans on these risk factors, and to examine why stroke emerges as a higher risk than ischaemic heart disease (IHD) in the health transition of black South Africans.

DESIGN

A review of published data on mortality from and risk factors of CVD in South Africans.

SETTING

South Africa.

SUBJECTS

South African population groups and communities.

METHODS

The available data on the contribution of stroke and IHD to CVD mortality in South Africa are briefly reviewed, followed by a comparison of published data on the prevalence and/or levels of CVD risk factors in the different South African population groups. The impact of urbanisation of black South Africans on these risk factors is assessed by comparing rural and urban Africans who participated in the Transition and Health during Urbanisation of South Africans (THUSA) study.

RESULTS AND CONCLUSIONS

The mortality rates from CVD confirmed that stroke is a major public health problem amongst black South Africans, possibly because of an increase in hypertension, obesity, smoking habit and hyperfibrinogenaemia during various stages of urbanisation. The available data further suggest that black South Africans may be protected against IHD because of favourable serum lipid profiles (low cholesterol and high ratios of high-density lipoprotein cholesterol) and low homocysteine values. However, increases in total fat and animal protein intake of affluent black South Africans, who can afford Western diets, are associated with increases in body mass indices of men and women and in total serum cholesterol. These exposures may increase IHD risk in the future.

Subclinical protein malnutrition is a determinant of hyperhomocysteinemia

OBJECTIVES

Hyperhomocysteinemia is regarded as a public health problem of increasing importance likely to contribute to vascular disorders and premature mortality. Folate, cobalamin, pyridoxine, and riboflavin dietary deficiencies are currently regarded as causative factors. However, several investigations have indicated that the theory of vitamin B deprivation provides only a partial explanation for the observed abnormalities of sulfur-containing amino acids. We investigated the potential contributory role played by protein malnutrition.

METHODS

For that purpose, three cohorts of 20 adult patients presenting stage I, II, and III goiter underwent careful medical history, dietary inquiry, and clinical examination. Their overall health and nutrition states were assessed with classic anthropometry, measurement of vitamin B blood parameters, visceral protein markers, essential amino acids, total homocysteine, and cystathionine.

RESULTS

The concentrations of transthyretin, seven essential amino acids, and cystathionine progressively decreased as the thyroid gland increased. Methionine was the sole essential amino acid whose values did not change; total homocysteine was unique in that increased levels correlated negatively with transthyretin values. Taken together, the data point to a progressive deterioration of protein nutrition status impairing the transsulfuration pathway and is best explained by an acquired defect of cystathionine-beta-synthase activity.

CONCLUSIONS

Hyperhomocysteinemia may arise from the shrinking of endogenous nitrogen pools as a result of decreased protein intake or stress-induced increased losses. Raised total homocysteine may result from the attempt of the malnourished and/or stressed body to preserve methionine homeostasis.

Differences in N-acetylation genotypes between Caucasians and Black South Africans: implications for cancer prevention

Polymorphic N-acetyltransferase genes (NAT1 and NAT2) determine rapid or slow acetylation phenotypes, which are believed to affect cancer risk related to environmental exposure. Black South Africans have a unique incidence pattern of environment-related cancers, but genetic characteristics of this population are mostly unknown. In this study, we compared NAT1 and NAT2 allele distributions in 101 Black South Africans and 112 UK Caucasians. Frequencies of the rapid alleles were significantly higher in Black South Africans for both NAT1 and NA72. Putative rapid NAT1 genotypes due to the presence of either NAT1*10 or NAT1*11 were found in 74.3% of Black South Africans (only NAT1*10) and 42.0% of UK Caucasians (P < 0.0001). Similarly, NAT2 analysis showed that the presence of NA12*4, NAT2*12A, NAT2*12B, NA72*12C, and NAT2*13 alleles provided significantly higher (P = 0.0001) frequency of rapid acetylation genotypes among Black South Africans (60.4%) than in the Caucasian group (33.9%). The rapid acetylation genotype in Caucasians usually depended on the NAT2*4 allele presence. The significant differences in N-acetylation genotypes can be among the factors determining a distinctive cancer morbidity and mortality pattern observed in Black South Africans. Both further genetic characterization of different populations and development of preventive strategies adopted for ethnicities with different genetic backgrounds are needed to deal adequately with the emerging health care problems in developing multiethnic societies.

Gene-nutrient interactions: dietary behaviour associated with high coronary heart disease risk particularly affects serum LDL cholesterol in apolipoprotein E epsilon4-carrying free-living individuals

Apolipoprotein E (ApoE) genotype influence on the relationship between dietary risk factors for cardiovascular disease and blood serum lipid levels was investigated in 132 free-living individuals participating in the European Prospective Investigation of Cancer (EPIC) study. All subjects (age 40-69) were clinically healthy and provided information on their usual diet. ApoE genotype and serum lipid concentrations were determined in all subjects. Relationships of intake of dietary constituents with serum lipid levels were compared in different genotype groups. There was a significant correlation between total serum cholesterol and intake of energy derived from total fat (r 0.195; P 0.025) and saturated fat (r 0.174; P 0.046) in the cohort as a whole. However, individuals with the ApoE epsilon3/epsilon4 genotype displayed a much stronger positive correlation between LDL cholesterol level and the percentage of energy derived from intake of saturated fat (r 0.436; P 0.043). There were no significant associations in the groups with epsilon3/epsilon3 or epsilon2/epsilon2 & epsilon2/epsilon3 genotype. A significant positive correlation between alcohol consumption and HDL cholesterol level was present in individuals bearing ApoE epsilon2 allele. These findings support current public health recommendations that saturated fat consumption should be reduced in order to reduce coronary heart disease risk. Total cholesterol concentrations were positively related to saturated fat intake in the cohort as a whole, but elevated LDL cholesterol levels associated with high saturated fat intake can be expected particularly in those individuals who combine a 'risky' dietary behaviour with the presence of the epsilon4 variant of ApoE.

Associations of apolipoprotein E concentration and polymorphism with lipids and apolipoprotein levels in Chinese from Beijing and Shanghai

The association of apolipoprotein E concentration and common polymorphism (codons 112/158) with lipid and apolipoprotein concentrations was studied in two Chinese healthy population samples from Beijing (n=99) and Shanghai (n=67). Body mass index and apolipoproteins E and AI and triglyceride concentrations were significantly different between the two populations (0.001<p<0.05), but apolipoprotein E common allele frequencies were not significantly different. Apolipoprotein E concentration was independently associated with apolipoproteins B and AI, total cholesterol and triglyceride concentrations in the Beijing group, but only with total cholesterol and apolipoprotein AI concentrations in the Shanghai group. Apolipoprotein E polymorphism was significantly associated with apolipoproteins E and AI, and triglyceride concentrations in the Beijing subjects (0.001<p<0.01), whereas apolipoprotein E polymorphism was significantly related only to apolipoprotein E concentration in the Shanghai group (p<0.001). This preliminary study with a limited number of subjects shows that the relations between both apolipoprotein E genotypes and concentration with lipid traits are not the same in the two studied Chinese populations.

Chlamydia pneumoniae and cardiovascular disease: an evolutionary perspective on infectious causation and antibiotic treatment

Evolutionary considerations implicate infectious causation of atherosclerosis and help to resolve different risk factors as parts of an overall process of disease causation. An evolutionary approach also provides insight for the timing of research efforts to provide better control of pathogen evolution. In particular, evolutionary considerations emphasize the need to understand the transmissibility of Chlamydia pneumoniae from systemic infections in order to control the evolution of antibiotic resistance.