Hyperhomocysteinemia but not MTHFR genotype is associated with young-onset essential hypertension

Evidence on the causal link between homocysteine and hypertension from a meta-analysis of 40 173 individuals implementing Mendelian randomization

Numerous researchers have investigated the associations among methylenetetrahydrofolate reductase gene (MTHFR) C677T polymorphism, homocysteine (Hcy) concentration, and hypertension. However, the results are controversial. Thus, a meta-analysis implementing Mendelian randomization approach was conducted to examine the hypothesis that elevated Hcy concentration plausibly contributes to increased risk of hypertension. Based on several inclusion and exclusion criteria, eligible studies were selected to explore the correlation between MTHFR C677T and hypertension risk, MTHFR C677T and Hcy concentration in hypertension, and Hcy concentration and hypertension, and they were evaluated by odds ratios (ORs), effect size (ES), and standard mean difference with their corresponding 95% confidence intervals (95% CIs), respectively. Moreover, Mendelian randomization was implemented to evaluate the relationship between Hcy and hypertension. Consequently, 14 378 cases and 25 795 controls were involved in this study and the results showed that MTHFR C677T led to an elevated risk of hypertension (for T vs C: OR = 1.27, 95% CI = 1.17-1.37; for TT vs CC: OR = 1.53, 95% CI = 1.30-1.79). Additionally, in hypertensive subjects, the pooled Hcy concentration in individuals of TT genotype was 7.74 μmol/L (95% CI: 5.25-10.23) greater than that in individuals of CC genotype. Moreover, the pooled Hcy concentration in hypertensive was 0.69 μmol/L (95% CI: 0.50-0.87) greater than that in controls. The estimated causal OR associated with hypertension was 1.32 for 5 μmol/L Hcy increment. Via MTHFR C677T polymorphism, the findings in the present study demonstrated that there exists evidence on causal link between Hcy concentration and the risk of hypertension.

Homocysteine levels and risk of essential hypertension: A meta-analysis of published epidemiological studies

BACKGROUND

Plasma homocysteine (Hcy) levels may be associated with essential hypertension (EH). However, the results of previous studies on this association are inconsistent.

METHODS

In this meta-analysis, we performed a systematic literature search of the Embase, PubMed, Cochrane Library, and Web of Science for the relevant articles dated up to March 2016. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to evaluate the estimates.

RESULTS

We included 11 studies with a total of 16,571 participants (4,830 EH cases). We found that elevated Hcy levels were associated with the risk of EH (pooled OR: 1.36, 95% CI: 1.02-1.80 in the random-effects model). However, subsequent subgroup analyses showed that elevated Hcy levels increased the EH risk in retrospective studies (OR: 1.82, 95% CI: 1.53-2.16; p < 0.001) and unadjusted studies (OR: 1.72, 95% CI: 1.43-2.07; p < 0.001), but not in perspective studies (OR: 0.99, 95% CI: 0.73-1.28; p = 0.939) and adjusted studies (OR: 1.21, 95% CI: 0.85-1.72; p = 0.297). No significant publication bias was found (p = 0.876 for Begg's test, p = 0.144 for Egger's test).

CONCLUSION

Plasma Hcy levels are associated with EH risk. However, our findings do not support a causal association between Hcy levels and EH.

Telomere length in the two extremes of abnormal fetal growth and the programming effect of maternal arterial hypertension

We tested the hypothesis that leukocyte telomere length (LTL) is associated with birth weight in both extremes of abnormal fetal growth: small (SGA) and large for gestational age newborns (LGA). Clinical and laboratory variables of the mothers and the neonates were explored; 45 newborns with appropriate weight for gestational age (AGA), 12 SGA and 12 LGA were included. Whether the differences might be explained by variation in OBFC1 (rs9419958) and CTC1 (rs3027234) genes associated with LTL was determined. A significant association between birth weight and LTL was observed; LTL was significantly shorter in LGA newborns (1.01 ± 0.12) compared with SGA (1.73 ± 0.19) p < 0.005, mean ± SE. Maternal (Spearman R = −0.6, p = 0.03) and neonatal LTL (R = −0.25, p = 0.03) were significantly and inversely correlated with maternal history of arterial hypertension in previous gestations. Neonatal LTL was not significantly associated with either rs9419950 or rs3027234, suggesting that the association between neonatal LTL and birth weight is not influenced by genetic variation in genes that modify the interindividual LTL. In conclusion, telomere biology seems to be modulated by abnormal fetal growth; modifications in telomere length might be programmed by an adverse environment in utero.

Investigation of homocysteine-pathway-related variants in essential hypertension

Hyperhomocysteinemia (hHcy) has been associated with an increased risk of cardiovascular disease and stroke. Essential hypertension (EH), a polygenic condition, has also been associated with increased risk of cardiovascular related disorders. To investigate the role of the homocysteine (Hcy) metabolism pathway in hypertension we conducted a case-control association study of Hcy pathway gene variants in a cohort of Caucasian hypertensives and age- and sex-matched normotensives. We genotyped two polymorphisms in the methylenetetrahydrofolate reductase gene (MTHFR C677T and MTHFR A1298C), one polymorphism in the methionine synthase reductase gene (MTRR A66G), and one polymorphism in the methylenetetrahydrofolate dehydrogenase 1 gene (MTHFD1 G1958A) and assessed their association with hypertension using chi-square analysis. We also performed a multifactor dimensionality reduction (MDR) analysis to investigate any potential epistatic interactions among the four polymorphisms and EH. None of the four polymorphisms was significantly associated with EH and although we found a moderate synergistic interaction between MTHFR A1298C and MTRR A66G, the association of the interaction model with EH was not statistically significant (P = 0.2367). Our findings therefore suggest no individual or interactive association between four prominent Hcy pathway markers and EH.

Association of methylenetetrahydrofolate reductase gene 677C>T polymorphism with hypertension in older women in a population of Buenos Aires City

We examined the relationship between the 677C >T polymorphism in the MTHFR gene and tHcy in normotensive (NT) and hypertensive (HT) subjects and the influence of sex and age in a cross-sectional study. Smoking habits, history of vascular disease, diabetes, and tHcy were significantly associated with T allele as hypertension risk factors. The T allele was significantly related with higher tHcy in (i) men versus women (P < .01), (ii) men and women older than 47 years versus the younger ones (P < .05 and P < .001, respectively), (iii) HT women versus NT women (P < .01), and (iv) older HT women versus older NT women (P < .01). We found an association between the 677C>T MTHFR polymorphism and tHcy with hypertension that in women is manifested with age.

Postgraduate Symposium The MTHFR C677T polymorphism, B-vitamins and blood pressure

High blood pressure (BP) and elevated homocysteine are reported as independent risk factors for CVD and stroke in particular. The main genetic determinant of homocysteine concentrations is homozygosity (TT genotype) for the C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene, typically found in approximately 10% of Western populations. The B-vitamins folate, vitamin B12and vitamin B6are the main nutritional determinants of homocysteine, with riboflavin more recently identified as a potent modulator specifically in individuals with the TT genotype. Although observational studies have reported associations between homocysteine and BP, B-vitamin intervention studies have shown little or no BP response despite decreases in homocysteine. Such studies, however, have not considered the MTHFR C677T polymorphism, which has been shown to be associated with BP. It has been shown for the first time that riboflavin is an important determinant of BP specifically in individuals with the TT genotype. Research generally suggests that 24 h ambulatory BP monitoring provides a more accurate measure of BP than casual measurements and its use in future studies may also provide important insights into the relationship between the MTHFR polymorphism and BP. Further research is also required to investigate the association between specific B-vitamins and BP in individuals with different MTHFR genotypes in order to confirm whether any genetic predisposition to hypertension is correctable by B-vitamin intervention. The present review will investigate the evidence linking the MTHFR C677T polymorphism to BP and the potential modulating role of B-vitamins.

Methylenetetrahydrofolate reductase TT genotype as a predictor of cardiovascular risk in hypertensive adolescents

Methylenetetrahydrofolate reductase (MTHFR) is associated with homocysteine level. In deficit of MTHFR, cardiovascular risk is increased with hyperhomocysteinemia and hypomethionemia. Mutation of the MTHFR gene is associated with the risk for premature cardiovascular diseases. However, the association between MTHFR mutation and cardiovascular risk is still controversial. The purposes of this study were to determine whether MTHFR genotype is associated with cardiovascular risks in hypertensive adolescents and to investigate the association between MTHFR genotype and carotid intima-media thickness (IMT). Forty-three hypertensive adolescents were included in this study. Serum lipid levels, insulin, vitamin B(12), folate, renin, aldosterone, angiotensin converting enzyme, and homocysteine levels were evaluated. The carotid IMT and diameter were estimated by ultrasound. Brachial-ankle pulse wave velocity was also measured. Polymerase chain reaction was conducted to amplify genomic DNA fragment containing C677T position of the MTHFR gene. The height, weight, body mass index, obesity index, arm circumference, fat mass, and fat distribution were significantly greater in patients with C677T mutation. The C677T mutation group showed significantly greater carotid IMT, higher homocysteine, and lower folic acid levels than the normal genotype group. Interpretation of MTHFR genotype might be useful in predicting the development of premature coronary artery disease in hypertensive adolescents.

Polymorphism of methylenetetrahydrofolate reductase gene (C677T MTHFR) is not a confounding factor of the relationship between serum uric acid level and the prevalence of hypertension in Japanese men

BACKGROUND

The association between serum uric acid (UA) and the prevalence of hypertension, and the relationship between methylenetetrahydrofolate reductase (MTHFR) polymorphism and hypertension remains unclear. The aim of the present study was to investigate whether the C677T MTHFR mutation genotype (VV) is independently associated with the prevalence of hypertension or blood pressure (BP), and examined any interaction of MTHFR and UA with BP.

METHODS AND RESULTS

Participants were randomly selected from all residents (aged 40-69 years) in a rural county of Japan, and the data for the men (n=335) were analyzed. ;Hypertension' was defined as systolic BP >or=140 and/or diastolic BP >or=90 mmHg and/or being administered antihypertensive medication. Serum UA level was independently associated with the prevalence of hypertension (odds ratio (95% confidence interval) =2.7 (1.2-5.9), p=0.047) for the highest tertile of serum UA (>or=398.5 micromol/L (6.7 mg/dl)) vs that of the lowest tertile (<321.2 micromol/L (5.4 mg/dl)), but the MTHFR mutation was not independently associated with prevalence of hypertension or BP. No interaction of the MTHFR mutation and serum UA with BP was found.

CONCLUSIONS

The mutation of C677T MTHFR was not independently associated with the prevalence of hypertension or BP levels although serum UA was. Furthermore, the relationship between serum UA and BP was not modulated by the MTHFR mutation in Japanese men.