Does Homocysteine Cause Hypertension?

Metabolomics reveals serum metabolic signatures in H-type hypertension based on mass spectrometry multi-platform

BACKGROUND

H-type hypertension (HHT) is a disease combined with hyperhomocysteinaemia and hypertension (HT). This study aims to find specific metabolic changes and reveal the pathophysiological mechanism of HHT, which provide the theoretical basis for the early prevention and treatment of HHT.

METHODS

Serum samples from three groups including 53 HHT patients, 36 HT patients and 46 healthy controls (HC) were collected. The targeted and untargeted metabolomics analyses were performed to determine the metabolic changes. Based on multivariate statistical analysis, the serum potential metabolites were screened and different metabolic pathways were explored.

RESULTS

Our results demonstrated that there were 28 important potential metabolites for distinguishing HT from HHT patients. Metabolic pathway analysis showed that the different metabolic pathways between HHT and HC group were arginine biosynthesis, arginine and proline metabolism, and tyrosine metabolism. The changed metabolic pathway of HT and HC group included linoleic acid metabolism. The specific metabolic pathways of HT-HHT comparison group had phenylalanine metabolism; phenylalanine, tyrosine and tryptophan biosynthesis; glycine, serine and threonine metabolism.

CONCLUSIONS

Metabolomics analysis by mass spectrometry multi-platform revealed the differences of metabolic profiles between HHT and HT subjects. This work laid the groundwork for understanding the aetiology of HHT, and these findings may provide the useful information for explaining the HHT metabolic alterations and try to prevent HHT.

Hypertension and cystatin C account for sex differences in serum homocysteine levels in acute coronary syndrome subjects with normal serum creatinine

BACKGROUND

Hyperhomocysteinemia is one of cardiovascular disease risk factors and fasting homocysteine levels are significantly elevated in male compared to female acute coronary syndrome (ACS) patients with normal renal function. However, it is not known the sex related determinants of plasma homocysteine levels in ACS subjects without renal dysfunction.

METHODS

A total of 165 ACS participants with normal plasma creatinine who underwent coronary angiography were included in the present study. Clinical parameters, homocysteine, fasting glucose and lipid profile, hemoglobin, white blood cell, platelets, creatinine, cystatin C, blood urea nitrogen, uric acid (UA), and albumin were measured. Multivariate linear regression analyses were used to recognize the predictive factors for homocysteine.

RESULTS

The levels of plasma homocysteine were significantly higher in men than in women (P < 0.0001). In males, homocysteine (log10) was positively associated with hypertension (r = 0.569, P < 0.001), creatinine (r = 0.367, P < 0.001) and cystatin C (log10) (r = 0.333, P = 0.001). In females, homocysteine (log10) was positively correlated with age (r = 0.307, P = 0.107), hypertension (r = 0.456, P < 0.001), creatinine (r = 0.341, P = 0.008), cystatin C (log10) (r = 0.429, P = 0.001) and UA (r = 0.569, P < 0.001) whereas was negatively associated with LDL-C (r =  - 0.298, P = 0.021) and ApoB (r =  - 0.273, P = 0.033). Parameters up to statistical significance in males or females were incorporated into the stepwise linear regression models. In men, hypertension (P < 0.001) and creatinine (P = 0.031) were independently related to homocysteine. Most of the variability of homocysteine levels in males were only determined by hypertension. In women, cystatin C (log10) (P = 0.004) and hypertension (P = 0.005) were independently related to homocysteine (log10). Plasma cystatin C had a higher explanatory value than hypertension in females.

CONCLUSIONS

Hypertension and cystatin C could explain most of the sex differences in serum homocysteine levels in ACS subjects with normal serum creatinine. This finding suggested the importance of making different strategies in males and females to manage hyperhomocysteinemia effectively in ACS subjects without renal dysfunction.

Cardiovascular Complications in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an auto-immune disease of a relapsing-remitting nature that can cause multiorgan damage depending on several factors, mainly the disease activity. Young age women are the most likely to be affected by the disease and the female-to-male prevalence ratio is approximately 1:10. As the number of SLE patients has been increasing in the last few decades, the annual number of deaths due to the disease and its complications has increased as well, and one of the most important systems to which high mortality is attributed is the cardiovascular system, leading to premature atherosclerosis and other events such as endocarditis and valve disease. In addition to the classical cardiovascular risk factors, studies have found a positive correlation between SLE and other cardio-harmful diseases such as metabolic syndrome and dyslipidemia. Moreover, some of the medications used in the treatment of SLE place a heavy burden on the heart. The article reviews the shared pathophysiology of SLE and cardiovascular disease along with the most common SLE- associated cardiac risks, events, and management.

Serum folate levels and hypertension

We aimed to examine the association between serum folate levels and hypertension in Korean adults. Our study population was 6343 Korean adults whose blood pressure and folate levels were measured in the Korea National Health and Nutrition Examination Survey 2016–2018. We aggregated the study populations into quintiles according to serum folate levels (1.5–4.3, 4.4–5.7, 5.8–7.5, 7.6–10.3, and 10.4–35.9 ng/mL). Multivariable logistic and linear regression models were used to analyze the relationships between serum folate levels, blood pressure, and hypertension. The weighted average of serum folate levels was 7.4 ng/mL, and the weighted prevalence of hypertension was 30.4% in the study populations. After adjusting for all potential confounders, compared to those in the lowest quintile of serum folate levels, systolic and diastolic blood pressure of the people in the other quintiles were not significantly different. The linear relationship between serum folate levels and blood pressure was not statistically significant. The odds for hypertension were not significantly different across the quintiles of serum folate levels. This study showed high serum folate levels was not significantly associated with lowering hypertension in Korean adults.

Folic acid supplementation and blood pressure: a GRADE-assessed systematic review and dose-response meta-analysis of 41,633 participants

Hypertension is a predisposing factor for cardiovascular disease (CVD). The extant literature regarding the effects of folic acid supplementation on blood pressure (BP) is inconsistent. Therefore, this systematic review and meta-analysis of randomized controlled trials was conducted to summarize the effects of folic acid supplementation on BP. A systematic search was carried out in PubMed, Scopus, ISI Web of Science, and Cochrane library, from database inception to August 2021. Data were pooled using the random-effects method and were expressed as weighted mean difference (WMD) and 95% confidence intervals (CI). The pooled results of 22 studies, including 41,633 participants, showed that folic acid supplementation significantly decreased systolic BP (SBP) (WMD: -1.10 mmHg; 95% CI: -1.93 to -0.28; p = 0.008). Subgroup analysis showed that the results remained significant when baseline SBP was ≥120 mmHg, intervention duration was ≤6 weeks, intervention dose was ≥5 mg/d, in patients with CVD, males and females, and overweight participants, respectively. Furthermore, the changes observed in diastolic BP (DBP) (WMD: -0.24 mmHg; 95% CI: -0.37 to -0.10; p < 0.001) were also statistically significant. However, subgroup analysis showed that the results remained significant in subject with elevated DBP, long term duration of intervention (>6 weeks), low dose of folic acid (<5 mg/day), CVD patients, both sexes and male, and participants with normal BMI. Dose-response analysis showed that folic acid supplementation changed SBP and DBP significantly based on dose and duration. However, meta-regression analysis did not reveal any significant association between dose and duration of intervention with changes in SBP. The present study demonstrates the beneficial effects of folic acid supplementation on BP by decreasing both SBP and DBP.

Preliminary analysis of immunoregulatory mechanism of hyperhomocysteinemia-induced brain injury in Wistar-Kyoto rats

Hyperhomocysteinemia (HHcy) can be used as an independent risk factor for predicting cardiovascular disease, stroke and vitamin B12 deficiency. Patients with HHcy have elevated plasma homocysteine (Hcy) concentrations. Enhancing cerebrovascular permeability of substances such as Hcy and brain damage will synergistically increase the symptoms of hypertension, but the specific immune regulation mechanism is still not clear. The purpose of the present study was to preliminarily explore the immunomodulatory mechanism of brain damage caused by HHcy in Wistar-Kyoto (WKY) rats. A total of 60 WKYs were randomly divided into three groups: WKY control group (WKY-C group), WKY methionine group (WKY-M group) and WKY treatment group (WKY-T group; vitamin B6, B12 and folic acid were used as treatment), with 20 rats in each group. Physical examination of body weight, systolic blood pressure (SBP) and plasma Hcy content was performed routinely. The concentration of cytokines, including IL-6, IL-10, IL-17A and TGF-β, associated with T helper cell 17 (Th17) and regulatory T (Treg) cells and key regulator genes, including retinoic acid-related orphan receptor γ t (RORγt) and forkhead box P3 (FoxP3), were detected by ELISA, reverse transcription-quantitative PCR and western blotting. Th17/Treg lymphocytes were determined by flow cytometry. MRI scan was preliminarily used to detect the changes characteristic of the ischemic stroke. The results revealed that high methionine diets might have a significant effect on the body weight and SBP. The inflammatory response effect of Treg cells was significantly inhibited in the WKY-M group, and that of Th17 cells was upregulated when compared to the WKY-T group. Compared with the WKY-T group, the expression levels of IL-17A and RORγt in the WKY-M group were significantly upregulated, while the mRNA levels of FoxP3 in the WKY-M group were significantly downregulated. The diet intervention (including vitamins B6 and B12 and folic acid) could reduce the level of Hcy in the blood, but also reduce the inflammatory response and rectify the Treg/Th17 immune imbalance to ameliorate the brain tissue damage. In conclusion, the present study indicated that HHcy can promote inflammation by triggering Treg/Th17 immune imbalance to ameliorate the brain tissue damage.

Hyperhomocysteinemia and its relations to conventional risk factors for cardiovascular diseases in adult Nigerians: the REMAH study

BACKGROUND

Evidence linking homocysteine (Hcy) with cardiovascular diseases (CVD) or its risk factors are limited in a sub-Saharan black population.

OBJECTIVE

We set out to evaluate the association between Hcy and hypertension and other CVD risk factors in a population of adult Nigerians.

METHODS

Data of 156 adults aged 18-70 years was accessed from the North Central study site of the REmoving the MAsk on Hypertension (REMAH) study. Homocysteine, blood glucose and lipid profile in whole blood/serum were measured using standard laboratory methods. Hypertension was diagnosed if average of 5 consecutive blood pressure (BP) measurements obtained using a mercury sphygmomanometer was equal to or higher than 140 systolic and/or 90 mmHg diastolic or the individual is on antihypertensive medication. Hyperhomocysteinemia (HHcy) was defined as Hcy > 10 µmol/L.

RESULTS

Of the 156 participants, 72 (43.5%) were hypertensive, of whom 18 had HHcy. Subjects with HHcy were significantly (p < 0.05) older (41.5 vs. 40.6yrs), had lower HDL-cholesterol (0.6 vs. 0.8 mmol/L) and higher systolic (145.5 vs. 126.0 mmHg) and diastolic BP (92.9 vs. 79.6 mmHg), compared to those without HHcy. Intake of alcohol and a 1 yr increase in age were respectively and significantly (p < 0.05) associated with a 1.54 and 0.10 µmol/L increase in Hcy. In a multivariable model adjusted for age, sex and body mass index, a 1 µmol/L increase in Hcy, was associated with a 1.69 mmHg and 1.34 mmHg increase in systolic and diastolic pressure (p < 0.0001) respectively; and a 0.01 mmol/L decrease in HDL-cholesterol (p < 0.05).

CONCLUSION

HHcy occurs among hypertensive Nigerians and it is independently associated with age, HDL-cholesterol, systolic and diastolic BP.

A comprehensive evaluation of association between homocysteine levels and single nucleotide polymorphisms with hypertension risk: A protocol of systematic review and network meta-analysis

BACKGROUND

According to the relevant reports that single nucleotide polymorphisms (SNPs) may contribute to change of homocysteine (HCY) levels and increase the risk of hypertension (HTN). During the inconsistent results, this meta-analysis purpose is systematically review and synthesized relevant data on HCY levels and SNPs in HTN.

METHODS

The systematic search database, from the following database to find out the association studies of SNPs and HTN publications up until March 2020 from the databases of PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), the Chinese Science and Technology Periodical Database (VIP) and Wan fang databases, and Chinese Biomedical Literature Database (CBM). Network meta-analysis and Thakkinstian's algorithm were used to select the most appropriate genetic model, along with false positive report probability (FPRP) for noteworthy associations. All statistical analyses were calculated with STATA software (version 14.0; StataCorp, College Station, TX).

RESULTS

This meta-analysis will provide high-quality evidence to the effects of SNP on HTN and levels of HCY, and find between SNPs and HTN susceptibility on in all the genetic models, and choose the best one.

CONCLUSIONS

This meta-analysis will research which SNP is the most correlated with HTN risk.

REGISTRATION

INPLASY202050002.

Serum concentration of homocysteine in spontaneous feline chronic kidney disease

Serum homocysteine (Hcy) increases in people and dogs with chronic kidney disease (CKD). Hyperhomocysteinemia (HHcy) has also been associated with CKD-related hypertension and proteinuria. The aims of this study were to: (1) validate an enzymatic method for quantification of Hcy in feline serum; (2) evaluate whether HHcy was associated with the presence and severity of CKD, proteinuria or hypertension; and (3) determine whether HHcy could predict disease progression. The intra- and inter-assay coefficients of variation (CVs) and the recovery rates of linearity under dilution and spiking recovery tests of the enzymatic method were 3.1-6.7%, 11.6-12.5%, 96.9±5.4% and 96.9±5.4%, respectively. Healthy cats at risk of CKD (n=17) and cats with CKD (n=19) were sampled over a 6-month period (63 samples in total). Cats with CKD had significantly higher Hcy concentrations (P=0.005) than cats at risk. The concentration of Hcy was higher (P=0.002) in moderate-severe CKD than in mild CKD and correlated moderately with serum creatinine (P<0.0001; r=0.51). The concentration of Hcy increased with the magnitude of proteinuria and correlated weakly with urinary protein to creatinine ratio (P=0.045; r=0.26). HHcy was not associated with hypertension. At the time of enrollment, Hcy concentration was significantly higher (P=0.046) in cats that developed CKD compared to cats that remained stable. The enzymatic method for Hcy measurement in feline serum was precise and accurate. HHcy was relatively common in cats with advanced CKD and seemed to predict disease progression, but further studies are warranted.

Associations among serum folate, waist-to-hip ratio, lipid profile, and eating habits with homocysteine in an elderly Thai population

A lower serum folate level is common in older populations and is associated with increased serum homocysteine concentration. In turn, an elevated homocysteine level is associated with increased risk of cardiovascular disease and age-related diseases. Contemporary studies of folate and dietary risk factors for cardiovascular disease among the elderly population in Thailand are lacking. This cross-sectional study aimed to investigate the relationships among serum folate, homocysteine level, and nutritional status in the elderly Thai. Three hundred individuals, aged 60 years and over, underwent anthropometric and physiological measurements, and biochemical parameters, and eating habits were also determined. Folate insufficiency was found in approximately 35% of subjects. Folate and homocysteine showed a significant inverse correlation. Serum homocysteine levels rose with increasing age. Folate deficiency and high waist-to-hip ratio were associated with 7-fold and 2.5-fold increased risk for hyperhomocysteinemia, respectively. There were positive correlations between homocysteine and waist-to-hip ratio and systolic blood pressure, but a negative correlation between homocysteine and high-density lipoprotein (r = -0.239, p < 0.01), which are markers for cardiovascular disease risk. Folate negatively correlated with body mass index, waist-to-hip ratio, and diastolic blood pressure, but positively with high-density lipoprotein (r = 0.162, p < 0.01). Investigation of eating habits showed that low consumption of green leafy vegetables and high consumption of sugary foods were associated with high homocysteine levels. Given associations between nutritional status and cardiovascular disease confirmed in this study, nutrition education, holistic health promotion, and appropriate behavioral modification of eating habits represent important measures for preventing premature cardiovascular disease in the elderly Thai population.

Homocysteine Level in Children with Classic Congenital Adrenal Hyperplasia: Relationship to Carotid Intimal Wall Thickness and Left Ventricular Function

BACKGROUND/AIMS

Homocysteine is an important and independent risk factor for atherosclerotic diseases. The aim of this study was to evaluate serum levels of homocysteine in children with congenital adrenal hyperplasia (CAH) and their relation to carotid artery intima-media thickness (CA-IMT) and left ventricular (LV) function.

METHODS

This study included 36 children with classic CAH and 36 healthy children. All underwent anthropometric evaluation. Measurement of serum levels of total homocysteine was carried out. The LV mass (LVM) and function were assessed using conventional echocardiography. Duplex ultrasonography was used to measure CA-IMT.

RESULTS

Compared to the controls, the patients had higher homocysteine levels (p = 0.001), a thicker CA-IMT (p = 0.01), a higher LVM index (LVMI) (p = 0.001), and a prolonged mitral deceleration time (DcT) (p = 0.01). Abnormalities were marked in children who were uncontrolled on medical treatment. In multivariate analysis, homocysteine levels were significantly correlated with systolic (OR = 2.2; 95% CI: 1.10-1.18; p = 0.01) and diastolic blood pressures (OR = 2.9; 95% CI: 1.45-2.4; p = 0.01), atherogenic index (OR = 2.6; 95% CI: 1.33-2.89; p = 0.01), HOMA-IR (OR = 1.3; 95% CI: 1.04-1.34; p = 0.001), LVMI (OR = 2.6; 95% CI: 1.1-1.13; p = 0.001), mitral DcT (OR = 2.4; 95% CI: 1.15-2.05; p = 0.01), and CA-IMT (OR = 1.6; 95% CI: 1.16-1.57; p = 0.01).

CONCLUSIONS

Serum total homocysteine was elevated in children with classic CAH, particularly in those with poor control on medical treatment, and it was correlated with CA-IMT, LVMI, and mitral DcT. Measurement of homocysteine in children with CAH may help to identify those at high risk of developing LV dysfunction and subclinical atherosclerosis.

Hydrogen Sulfide Protects Hyperhomocysteinemia-Induced Renal Damage by Modulation of Caveolin and eNOS Interaction

The accumulation of homocysteine (Hcy) during chronic kidney failure (CKD) can exert toxic effects on the glomeruli and tubulo-interstitial region. Among the potential mechanisms, the formation of highly reactive metabolite, Hcy thiolactone, is known to modify proteins by N-homocysteinylation, leading to protein degradation, stress and impaired function. Previous studies documented impaired nitric oxide production and altered caveolin expression in hyperhomocysteinemia (HHcy), leading to endothelial dysfunction. The aim of this study was to determine whether Hhcy homocysteinylates endothelial nitric oxide synthase (eNOS) and alters caveolin-1 expression to decrease nitric oxide bioavailability, causing hypertension and renal dysfunction. We also examined whether hydrogen sulfide (H₂S) could dehomocysteinylate eNOS to protect the kidney. WT and Cystathionine β-Synthase deficient (CBS+/-) mice representing HHcy were treated without or with sodium hydrogen sulfide (NaHS), a H₂S donor (30 µM), in drinking water for 8 weeks. Hhcy mice (CBS+/-) showed low levels of plasma H₂S, elevated systolic blood pressure (SBP) and renal dysfunction. H₂S treatment reduced SBP and improved renal function. Hhcy was associated with homocysteinylation of eNOS, reduced enzyme activity and upregulation of caveolin-1 expression. Further, Hhcy increased extracellular matrix (ECM) protein deposition and disruption of gap junction proteins, connexins. H₂S treatment reversed the changes above and transfection of triple genes producing H₂S (CBS, CSE and 3MST) showed reduction of vascular smooth muscle cell proliferation. We conclude that during Hhcy, homocysteinylation of eNOS and disruption of caveolin-mediated regulation leads to ECM remodeling and hypertension, and H₂S treatment attenuates renovascular damage.

A Meta-Analysis of Folic Acid in Combination with Anti-Hypertension Drugs in Patients with Hypertension and Hyperhomocysteinemia

Folic acid is generally used to lower homocysteine concentrations and prevent stroke and cardiovascular disease (CVD) at present. However, the efficacy of therapies that lower homocysteine concentrations in reducing the risk of CVD and stroke remains controversial. Our objective was to do a meta-analysis of relevant randomized controlled trials (RCTs) to evaluate the efficacy of folic acid supplementation among patients with hypertension and Hyperhomocysteinemia (HT/HHcy). We included RCTs examining the effects of folic acid plus antihypertensive therapy compared to antihypertensive alone. Weighted Mean Difference (WMD) and Relative risk (RR) were used as a measure of the effect of folic acid on the outcome measures with a random effect model. Sixty-five studies including 7887 patients met all inclusion criteria. Among them, 49 trials reported significant effect of combination therapy for reducing SBP (systolic Blood Pressure) and DBP (Diastolic Blood Pressure) levels compared with antihypertensive alone (WMD = -7.85, WMD = -6.77, respectively). Meanwhile, folic acid supplementation apparently reduced the level of total homocysteine (WMD = 5.5). In addition, folic acid supplementation obviously reduced the risk of cardiovascular and cerebrovascular events (CVCE) by 12.9% compared with control groups. In terms of the stratified analyses, a bigger beneficial effect was seen in those RCTs with treatment duration of more than 12 weeks, a decrease in the concentration of total homocysteine of more than 25%, with folic acid fortification. Our findings indicated that folic acid supplementation was effective in the primary prevention of CVCE among HT/HHcy patients, as well as reducing the blood pressure and total homocysteine levels.

Associations of plasma homocysteine levels with peripheral systolic blood pressure and noninvasive central systolic blood pressure in a community-based Chinese population

Previous studies indicated that homocysteine (Hcy) is associated with higher peripheral systolic blood pressure (pSBP). There have been few data on the relationship between Hcy and central SBP (cSBP). A total of 4,364 Chinese subjects from the Shijingshan community in Beijing were included. cSBP and pSBP were measured with an Omron HEM-9000AI device. Subjects were 57.20 ± 8.9 years old, 37.9% were male. The median of Hcy was 11.96 μmol/L. The mean of cSBP and pSBP was 129.94 ± 18.03 mmHg and 133.25 ± 18.58 mmHg. lnHcy was associated with cSBP (adjusted β = 2.17, SE = 0.80, P = 0.007) and pSBP (adjusted β = 2.42, SE = 0.75, P = 0.001). With increasing Hcy, there were enhanced correlations of Hcy with pSBP and cSBP (p for trend between quartiles <0.01). Using Q1 for reference, the Q4 was associated with cSBP (adjusted β = 1.77, SE = 0.89, P = 0.047) and pSBP (adjusted β = 2.15, SE = 0.84, P = 0.011). The correlations were more significant in non-obese subjects than in obese subjects (cSBP: β = 4.30 vs 0.46, pSBP: β = 5.04 vs 1.18, P for interaction <0.001). Our study showed that Hcy was associated with higher cSBP and pSBP, especially in non-obese subjects.

Toll-like receptor 4 mediates vascular remodeling in hyperhomocysteinemia

Although hyperhomocysteinemia (HHcy) is known to promote downstream pro-inflammatory cytokine elevation, the precise mechanism is still unknown. One of the possible receptors that could have significant attention in the field of hypertension is toll-like receptor 4 (TLR-4). TLR-4 is a cellular membrane protein that is ubiquitously expressed in all cell types of the vasculature. Its mutation can attenuate the effects of HHcy-mediated vascular inflammation and mitochondria- dependent cell death that suppresses hypertension. In this review, we observed that HHcy induces vascular remodeling through immunological adaptation, promoting inflammatory cytokine up-regulation (IL-1β, IL-6, TNF-α) and initiation of mitochondrial dysfunction leading to cell death and chronic vascular inflammation. The literature suggests that HHcy promotes TLR-4-driven chronic vascular inflammation and mitochondria-mediated cell death inducing peripheral vascular remodeling. In the previous studies, we have characterized the role of TLR-4 mutation in attenuating vascular remodeling in hyperhomocysteinemia. This review includes, but is not limited to, the physiological synergistic aspects of the downstream elevation of cytokines found within the vascular inflammatory cascade. These events subsequently induce mitochondrial dysfunction defined by excessive mitochondrial fission and mitochondrial apoptosis contributing to vascular remodeling followed by hypertension.

Assessment of the environmental and genetic factors influencing prevalence of metabolic syndrome in Saudi Arabia

Metabolic syndrome (MS) is a combination of factors that increases the risk of cardiovascular atherosclerotic diseases including diabetes, obesity, dyslipidemia, and high blood pressure. Cardiovascular diseases are one of the leading causes of death in the adult Saudi population where the increase in cardiovascular-related mortality is augmented by the rise in the prevalence of MS. Metabolic syndrome is a multi-factorial disorder influenced by interactions between genetic and environmental components. This review aims to provide a comprehensive assessment of studied environmental and genetic factors explaining the prevalence of MS in the Kingdom of Saudi Arabia. Additionally, this review aims to illustrate factors related to the population genetics of Saudi Arabia, which might explain a proportion of the prevalence of MS.

Vasodilator activity of hydrogen sulfide (H2S) in human mesenteric arteries

The role of endogenous H₂S has been highlighted as a gaseous transmitter. The vascular smooth muscle inhibitory effects of H₂S have been characterized in isolated aorta and mesenteric arteries in rats and mice. Our study was aimed at investigating the vascular effects of H₂S on human isolated mesenteric arteries and examining the underlying mechanisms involved. All experiments were performed on rings (4-8mm long) of human mesenteric arteries obtained from patients undergoing abdominal surgery. Ethical approval was obtained from the Ethics Committee of the University Hospital of the University of Florence (app. N. 2015/0024947). The effect of NaHS, an H₂S donor, was determined using noradrenaline pre-contracted human isolated mesenteric rings. NaHS evoked a concentration-dependent relaxation (EC₅₀ 57μM). In contrast, homocysteine, an endogenous precursor of H₂S, failed to affect human isolated mesenteric rings. Vasorelaxant response to NaHS was reduced by endothelium removal, application of the nitric oxide synthase inhibitor L-NAME and ODQ inhibitor of cyclic GMP. SQ 22536, an adenylate-cyclase inhibitor, failed to block NaHS-induced vasorelaxation. Inhibition of endogenous prostanoid production by indomethacin significantly reduced NaHS induced vasorelaxation. The role of potassium channels was also examined: blockers of the Ca²⁺-dependent potassium channel, charybdotoxin and apamin, failed to have any influence on the relaxant response to NaHS on this vascular tissue. In summary, H₂S induced relaxation of isolated rings of human mesenteric arteries. Endothelium-dependent related mechanisms with the stimulation of ATP-sensitive potassium channels represents important cellular mechanisms for H₂S effect on human mesenteric arteries.

Fractions of Total Plasma Homocysteine in Patients with Ischemic Stroke Before the Age of 55 Years

The mechanism responsible for the association between elevated circulating homocysteine levels and ischemic stroke remains unclear. Therefore, the authors assessed total plasma homocysteine (tHcy) and its fractions (free [fHcy] and protein-bound [bHcy] homocysteine) in patients with ischemic stroke before the age of 55 years. Fifty patients (23 men, mean age 46.8 ±7.6 years) with ischemic stroke or transient ischemic attacks, with symptoms lasting <72 hours were enrolled. In this group: 32 (64%) patients had hypertension; 12 (24%), ischemic heart disease (IHD); and 20 (40%), type 2 diabetes mellitus (DM). The control group consisted of 30 matched healthy individuals (17 men, mean age 44.6 ±6.2 years). The tHcy, fHcy, and bHcy levels were determined by high-performance liquid chromatography. tHcy and its fractions did not differ significantly between patients and controls. However, stroke patients with hypertension had significantly higher concentrations of tHcy and bHcy compared to stroke patients without hypertension (tHcy 13.0 ±3.3 vs 10.7 ±3.2 µmol/L, p<0.05; bHcy 9.7 ±2.6 vs 7.8 ±2.3 µmol/L, p<0.01, respectively); fHcy was borderline significant: 3.1 (1.5-6.5) vs 2.5 (1.8-5.3) µmol/L, p=0.05. The presence of IHD, DM, hyperlipoproteinemia, clinical subtypes of stroke, smoking, and family history of stroke did not influence these parameters. In the group of 50 patients, tHcy correlated with mean systolic blood pressure (BP) ( r =0.3, p<0.05) and bHcy correlated with mean systolic and mean diastolic BP ( r =0.3, p<0.05). These findings suggest an association between hypertension and redox status of Hcy in patients with ischemic stroke before the age of 55 years. This observation supports the hypothesis that elevated BP may contribute to Hcy-related vascular injury.

Homocysteine and hydrogen sulfide in epigenetic, metabolic and microbiota related renovascular hypertension

Over the past several years, hydrogen sulfide (H₂S) has been shown to be an important player in a variety of physiological functions, including neuromodulation, vasodilation, oxidant regulation, inflammation, and angiogenesis. H₂S is synthesized primarily through metabolic processes from the amino acid cysteine and homocysteine in various organ systems including neuronal, cardiovascular, gastrointestinal, and kidney. Derangement of cysteine and homocysteine metabolism and clearance, particularly in the renal vasculature, leads to H₂S biosynthesis deregulation causing or contributing to existing high blood pressure. While a variety of environmental influences, such as diet can have an effect on H₂S regulation and function, genetic factors, and more recently epigenetics, also have a vital role in H₂S regulation and function, and therefore disease initiation and progression. In addition, new research into the role of gut microbiota in the development of hypertension has highlighted the need to further explore these microorganisms and how they influence the levels of H₂S throughout the body and possibly exploiting microbiota for use of hypertension treatment. In this review, we summarize recent advances in the field of hypertension research emphasizing renal contribution and how H₂S physiology can be exploited as a possible therapeutic strategy to ameliorate kidney dysfunction as well as to control blood pressure.

Interactions of Methylenetetrahydrofolate Reductase C677T Polymorphism with Environmental Factors on Hypertension Susceptibility

Hypertension is considered to be the result of genes, environment, and their interactions. Among them age, sex, tobacco use, alcohol consumption, and being overweight/obesity are well documented environmental determinants, and methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is nominated as a potential genetic candidate. However, the synergistic effect of the MTHFR C677T polymorphism with these environmental factors on the risk of hypertension has received little attention. The aim of this study was to explore the associations of the MTHFR C677T polymorphism, environmental factors, and their interactions with hypertension predisposition in a Northern Chinese Han population. A total of 708 participants were enrolled in the study. The genotypes of the MTHFR C677T were determined by a TaqMan assay. We found that participants of an older age, being overweight/obesity, with a smoking habit, drinking habit, or carrying the 677T allele were at an increased risk of hypertension. Additionally, there existed marginally significant interactions of the polymorphism with age and overweight/obesity. However, future large, well-designed studies in Chinese and other populations, as well as mechanistic studies, are still needed to validate our findings, especially considering that the interactions observed in our study were only marginally significant.

Functional Polymorphism rs13306560 of the MTHFR Gene Is Associated With Essential Hypertension in a Mexican-Mestizo Population

BACKGROUND

Polymorphisms of methylenetetrahydrofolate reductase (MTHFR) have been associated with diastolic blood pressure, hypertension, and other cardiovascular diseases; however, results of these studies are still controversial. In this study, we sought to determine whether 2 functional variants (rs1801133 and rs13306560) within the MTHFR are associated with hypertension in Mexican-Mestizos.

METHODS AND RESULTS

We performed a case-control study with 1214 subjects including adults and children to test for the association of both single nucleotide polymorphisms with essential hypertension. The adult group included 764 participants (372 patients and 391 controls) and the group of children included 418 participants (209 patients and 209 controls). rs13306560 was associated with essential hypertension in adults (odds ratio, 4.281; 95% confidence interval, 1.841-9.955; P=0.0003) with a statistical power >0.8. In children, none of the polymorphisms was associated with essential hypertension. In addition, we assessed the effect of the rs13306560 polymorphism on the MTHFR promoter region by means of luciferase reporter gene assays using human umbilical vein endothelial cells. Cells transfected with the pMTHFRaLUC construct showed an ≈25% reduction in luciferase activity (P=0.003). Furthermore, the promoter activity was reduced considerably by in vitro methylation of CpG sequences.

CONCLUSIONS

Our data suggest that the rs13306560 polymorphism of the MTHFR may be part of the observed hypertension process in Mexican-Mestizo populations, but further studies are warranted. In addition, the allele A of the rs13306560 polymorphism as well as the in vitro methylation of CpGs reduced the promoter activity of the MTHFR regulatory region.

Association of homocysteinaemia with hyperglycaemia, dyslipidaemia, hypertension and obesity

AIM

Hyperhomocysteinaemia and the metabolic syndrome are associated with increased cardiovascular risk. We investigated whether there is a link between the metabolic syndrome or its components and homocysteine levels in a population without cardiovascular disease.

METHODS

From the population sample of 382 participants (286 females and 96 males) we isolated those reflecting the metabolic syndrome and determined their homocysteine levels. We then evaluated the association of homocysteine with hyperglycaemia, hypertriglyceridaemia, hypercholesterolaemia, hypertension and obesity, using a significance level of p = 0.05. Enzymatic methods were used for all biochemical parameters.

RESULTS

We found the statistical relationship between homocysteine and the metabolic syndrome as follows: hyperglycaemia (p = 0.175), hypertriglyceridaemia (p = 0.442), hypercholesterolaemia (p = 0.480), obesity (p = 0.080); and hypertension: systolic pressure (p = 0.002) and diastolic pressure (p = 0.033).

CONCLUSION

We found no statistically significant association between baseline plasma homocysteine levels and the metabolic syndrome, except for hypertension.

The metabolic syndrome is associated with an increased risk of colorectal polyps independent of plasma homocysteine

BACKGROUND/AIMS

The links between the metabolic syndrome and homocysteine in relation to the risk of colorectal polyps are not understood. The purpose of this study was to investigate the association between the metabolic syndrome and homocysteine and further analyze the relationship between these two factors and the risk of colorectal polyps.

METHODS

This was a case-control study. A total of 135 participants with colorectal polyps (cases) and 110 participants without polyps (controls) were recruited.

RESULTS

There were 59 participants with the metabolic syndrome in the case group and 36 participants with the metabolic syndrome in the control group. The metabolic syndrome and its individual components, except for serum triglycerides, and homocysteine were associated with the risk of colorectal polyps. When the association of the metabolic syndrome and homocysteine with the risk of colorectal polyps was simultaneously considered, the association between homocysteine and the risk of colorectal polyps disappeared, but waist circumference, systolic and diastolic blood pressure, high-density lipoprotein cholesterol, and the metabolic syndrome itself were still significant risk factors for the development of colorectal polyps.

CONCLUSION

Although the metabolic syndrome and plasma homocysteine were individually related to the risk of colorectal polyps, the metabolic syndrome was a major contributing factor in relation to the risk of colorectal polyps independent of plasma homocysteine.

Homocysteine in renovascular complications: hydrogen sulfide is a modulator and plausible anaerobic ATP generator

Homocysteine (Hcy) is a non-protein amino acid derived from dietary methionine. High levels of Hcy, known as hyperhomocysteinemia (HHcy) is known to cause vascular complications. In the mammalian tissue, Hcy is metabolized by transsulfuration enzymes to produce hydrogen sulfide (H2S). H2S, a pungent smelling gas was previously known for its toxic effects in the central nervous system, recent studies however has revealed protective effects in a variety of diseases including hypertension, diabetes, inflammation, atherosclerosis, and renal disease progression and failure. Interestingly, under stress conditions including hypoxia, H2S can reduce metabolic demand and also act as a substrate for ATP production. This review highlights some of the recent advances in H2S research as a potential therapeutic agent targeting renovascular diseases associated with HHcy.

Associations of MTHFR gene polymorphisms with hypertension and hypertension in pregnancy: a meta-analysis from 114 studies with 15411 cases and 21970 controls

BACKGROUND

Several epidemiological studies have investigated the associations of methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms with hypertension (H) or hypertension in pregnancy (HIP). However, the results were controversial. We therefore performed a comprehensive meta-analysis to provide empirical evidences on the associations.

METHODOLOGIES

The English and Chinese databases were systematically searched to identify relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to evaluate the strength of the associations. Meta-regression, subgroup analysis, sensitivity analysis, cumulative meta-analysis and assessment of publication bias were performed in our study.

PRINCIPAL FINDINGS

A total of 114 studies with 15411 cases and 21970 controls were included, 111 studies with 15094 cases and 21633 controls for the C677T polymorphism and 21 with 2533 cases and 2976 controls for the A1298C polymorphism. Overall, the C677T polymorphism was significantly associated with H and HIP (H & HIP: OR = 1.26, 95% CI = 1.17-1.34; H: OR = 1.36, 95% CI = 1.20-1.53; HIP: OR = 1.21, 95% CI = 1.08-1.32). Stratified analysis by ethnicity revealed a significant association among East Asians and Caucasians, but not among Latinos, Black Africans, and Indians and Sri Lankans. In the stratified analyses according to source of controls, genotyping method, sample size and study quality, significant associations were observed in all the subgroups, with the exception of population based subgroup in H studies and large sample size and "others" genotyping method subgroups in HIP studies. For the A1298C polymorphism, no significant association was observed either in overall or subgroup analysis under all genetic models.

CONCLUSIONS

This meta-analysis suggests that the MTHFR C677T rather than A1298C polymorphism may be associated with H & HIP, especially among East Asians and Caucasians.

Association between C-reactive protein and homocysteine with the subcomponents of metabolic syndrome in stable patients with bipolar disorder and schizophrenia

BACKGROUND

Previous studies revealed high prevalence of metabolic syndrome (MetS) in patients with bipolar disorder and schizophrenia. C-Reactive protein (CRP) and homocysteine have also both emerged as independent risk factors for the development of cardiovascular disease (CVD) but are less investigated in psychiatric disorders.

AIMS

The aim of this study was to ascertain which specific subcomponents of MetS are associated with levels of CRP and homocysteine in patients with bipolar disorder and schizophrenia.

METHODS

Our sample consisted of patient group (n = 122) (60 bipolar and 62 schizophrenic patients) treated with second-generation antipsychotics (SGA) and healthy controls (n = 59). MetS was defined according to NCEP ATP-III criteria; the cut-off point for elevated CRP was set up at 5 mg/l and for hyperhomocysteinemia at 15 μmol/l.

RESULTS

In the patient group, homocysteine was correlated with waist circumference, systolic and diastolic blood pressure, triglycerides and blood glucose, while CRP was correlated with waist circumference and diastolic blood pressure. Patients with hyperhomocysteinemia had an 8.442 times higher chance to have met the criteria for MetS while elevated CRP was not a significant predictor of MetS.

CONCLUSIONS

There is a complex association between CRP and homocysteine with specific subcomponents of MetS in patients with bipolar disorder and schizophrenia. Given the high risk of cardiovascular disorders in psychiatric patients, these relationships deserve further investigation. Clinically, it could be useful to include the measurement of homocysteine and CRP levels in routine psychiatric diagnostic procedures.

Big-endothelin 1 (big ET-1) and homocysteine in the serum of dogs with chronic kidney disease

This study was aimed at determining the serum concentration of homocysteine (Hcy) and big endothelin-1 (big ET-1, the precursor of endothelin) in dogs with chronic kidney disease (CKD) with and without hypertension, proteinuria and inflammation, in order to explore their role as biomarkers of hypertension associated with CKD. Hcy and big ET-1 were measured using an enzyme-linked immunosorbent assay and an enzymatic cyclic reaction, respectively, in dogs with CKD staged, as proposed by the International Renal Interest Society (IRIS), using serum creatinine, urinary protein to creatinine (UPC) ratio and systolic blood pressure, and classified as affected or not by inflammation based on the serum concentration of C-reactive protein (CRP). Serum Hcy was significantly higher in dogs of IRIS stages II, III and IV compared with controls and in proteinuric compared with non-proteinuric dogs. No differences relating to the degree of hypertension or to the CRP concentration were found. Serum big ET-1 significantly increased in dogs of IRIS stage IV compared with controls, in proteinuric compared with non-proteinuric dogs, in dogs with severe hypertension compared with those without hypertension, and in dogs with increased CRP compared to those with normal CRP concentrations. Hcy only correlated with serum creatinine but big ET-1 significantly correlated with serum creatinine, UPC ratio, systolic blood pressure, and increased CRP. In conclusion, both Hcy and big ET-1 increase in dogs with CKD. Although further research is needed, big ET-1, but not Hcy, may also be considered as a biomarker of hypertension.

High-dose folic acid supplementation effects on endothelial function and blood pressure in hypertensive patients: a meta-analysis of randomized controlled clinical trials

OBJECTIVE

Folic acid supplementation has been shown to be an effective agent for improving endothelial function, a prognostic factor for cardiovascular disease; but its effects on systolic and diastolic blood pressure in hypertensive individuals has been met with mixed results. Therefore, the purpose of this study was to provide a comprehensive meta-analysis of randomized controlled trials to investigate the effect of high-dose folic acid supplementation on blood pressure and endothelial function in hypertensive patients.

METHODS

Twelve randomized controlled trials published between 1970 and December 2007 were identified using Medline and a manual search. All 12 studies used hypertensive subjects who were supplemented with at least 5000 mug/d of folic acid for between 2 and 16 weeks. Three separate meta-analyses were carried out using a random-effects model, and the overall effect sizes were calculated for changes in systolic and diastolic blood pressures and for changes in endothelial function as measured through the percentage of change in flow-mediated dilation.

RESULTS

The pooled estimate of effect of folic acid supplementation on systolic and diastolic blood pressure was -2.03 mm Hg (95% confidence interval [CI], -3.63 to -0.43; P = .04) and 0.01 mm Hg (95% CI, -1.12 to 1.13; not significant), respectively. The pooled estimate of effect of folic acid supplementation on change in flow-mediated dilation was 1.61% (95% CI, 1.27 to 1.96; P = .000).

CONCLUSION

Based upon the studies used in this meta-analysis, supplementation with at least 5000 mug/d of folic acid, for a minimum of 6 weeks, can lower systolic blood pressure slightly; but the real clinical benefit is achieved through improved endothelial function.

Evidence for somatic gene conversion and deletion in bipolar disorder, Crohn's disease, coronary artery disease, hypertension, rheumatoid arthritis, type-1 diabetes, and type-2 diabetes

BACKGROUND

During gene conversion, genetic information is transferred unidirectionally between highly homologous but non-allelic regions of DNA. While germ-line gene conversion has been implicated in the pathogenesis of some diseases, somatic gene conversion has remained technically difficult to investigate on a large scale.

METHODS

A novel analysis technique is proposed for detecting the signature of somatic gene conversion from SNP microarray data. The Wellcome Trust Case Control Consortium has gathered SNP microarray data for two control populations and cohorts for bipolar disorder (BD), cardiovascular disease (CAD), Crohn's disease (CD), hypertension (HT), rheumatoid arthritis (RA), type-1 diabetes (T1D) and type-2 diabetes (T2D). Using the new analysis technique, the seven disease cohorts are analyzed to identify cohort-specific SNPs at which conversion is predicted. The quality of the predictions is assessed by identifying known disease associations for genes in the homologous duplicons, and comparing the frequency of such associations with background rates.

RESULTS

Of 28 disease/locus pairs meeting stringent conditions, 22 show various degrees of disease association, compared with only 8 of 70 in a mock study designed to measure the background association rate (P < 10-9). Additional candidate genes are identified using less stringent filtering conditions. In some cases, somatic deletions appear likely. RA has a distinctive pattern of events relative to other diseases. Similarities in patterns are apparent between BD and HT.

CONCLUSIONS

The associations derived represent the first evidence that somatic gene conversion could be a significant causative factor in each of the seven diseases. The specific genes provide potential insights about disease mechanisms, and are strong candidates for further study.

Homocysteine and Hypertension in Diabetes: Does PPARgamma Have a Regulatory Role?

Dysfunction of macro- and microvessels is a major cause of morbidity and mortality in patients with cardio-renovascular diseases such as atherosclerosis, hypertension, and diabetes. Renal failure and impairment of renal function due to vasoconstriction of the glomerular arteriole in diabetic nephropathy leads to renal volume retention and increase in plasma homocysteine level. Homocysteine, which is a nonprotein amino acid, at elevated levels is an independent cardio-renovascular risk factor. Homocysteine induces oxidative injury of vascular endothelial cells, involved in matrix remodeling through modulation of the matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) axis, and increased formation and accumulation of extracellular matrix protein, such as collagen. In heart this leads to increased endothelial-myocyte uncoupling resulting in diastolic dysfunction and hypertension. In the kidney, increased matrix accumulation in the glomerulus causes glomerulosclerosis resulting in hypofiltration, increased renal volume retention, and hypertension. PPARγ agonist reduces tissue homocysteine levels and is reported to ameliorate homocysteine-induced deleterious vascular effects in diabetes. This review, in light of current information, focuses on the beneficial effects of PPARγ agonist in homocysteine-associated hypertension and vascular remodeling in diabetes.

Relationship between renal resistive index and inflammation in untreated hypertensive patients

The aim of this study was to evaluate the relationship between renal resistive index and inflammation in untreated hypertensive patients. Sixty-one hypertensive patients (male/female: 38/23, aged 45.8 +/- 8.3 years, and mean hypertension duration 28.2 +/- 35.6 months) and 40 (male/female: 23/17, aged 42.7 +/- 8.5 years) healthy control subjects were included in the study. Renal resistive index was positively correlated with age (P = 0.016, r = 0.308), pulse pressure (P = 0.022, r = 0.294), C-reactive protein (P = 0.00, r = 0.757), urinary albumin excretion (P = 0.003, r = 0.371) and negatively correlated with creatinine clearance (P = 0.042, r = -0.262) in the hypertensive group. The hypertensive group was further divided in two groups according to the renal resistive index; < 0.60 and > 0.60. In the > 0.60 group, age (48.0 +/- 7.3 versus 42.8 +/- 8.9 years, P = 0.01) and C-reactive protein levels (7.4 +/- 1.5 versus 4.0 +/- 1.6 mg/L, P = 0.01) were higher, and creatinine clearance (95.5 +/- 22.1 versus 109.1 +/- 25.3 mL/min, P = 0.04) was lower than the < 0.60 group. Renal resistive index was higher in the nondippers than the dippers (0.61 +/- 0.04 versus 0.58 +/- 0.03, P = 0.003). Renal resistive index is associated with inflammation and may be a useful marker, together with albuminuria, in hypertensive patients when evaluating hypertensive renal damage.

Study on homocysteine levels and methylenetetrahydrofolate reductase gene variant (C677T) in a population of Buenos Aires City

The substitution of cytosine (C) by thymine (T) at nucleotide 677 of the methylenetetrahydrofolate reductase (MTHFR) gene, which converts an alanine to a valine residue, is a frequent polymorphism with reduced specific activity, associated with moderate increase in plasma homocysteine levels (tHcy) and risk of vascular diseases.

OBJECTIVES

This study was designed to investigate an association of this polymorphism with tHcy and vascular risk factors.

METHODS

We used a cross-sectional study on subjects affiliated to three health centers from Buenos Aires city. The diagnosis of hypertension was ascertained by patients' clinical history. Only subjects under long-term antihypertensive treatment were included.

RESULTS

Samples from 138 physically active individuals (44 men and 94 women) randomly selected were included. The mean tHcy was significantly higher amongst hypertensives (HT) than normotensives (NT). The risk of hypertension was compared in subjects with CC genotype and the combined number of subjects with at least one T allele (CT/TT). There was no significant difference regarding the risk of hypertension between NT and HT groups in the overall sample. However, as obesity is considered a risk factor for hypertension development, when only HT (n = 29) and NT (n = 66) subjects with body mass index below 30 kg/m(2) (BMI<30) were compared, subjects bearing CT/TT presented a significantly higher risk of hypertension than those bearing the CC genotype and significantly higher concentration of tHcy.

CONCLUSIONS

Our results indicate an association of hyper-tHcy and MTHFR C677T mutation with hypertension. MTHFR C677T mutation may contribute to hypertension or affect the development of hypertension through hyperhomocysteinemia.

Clinical Use and Pathogenetic Basis of Laboratory Tests for the Evaluation of Primary Arterial Hypertension

This review focuses on the laboratory biochemical tests that are useful in the diagnostic approach to the hypertensive patient. A "minimal" diagnostic laboratory work-up, including a small number of tests that are simple and relatively inexpensive, is first described. Because these tests provide basic information on the presence of major cardiovascular (CV) risk factors and target organ damage, and might give some clues to the presence of a secondary form of hypertension (HT), they should be performed on all patients presenting with HT. Other tests that are aimed at assessing the overall CV risk, a major determinant of prognosis that dictates the therapeutic strategy in the individual HT patient, are then discussed. They allow identification of major CV risk factors and associated clinical conditions which, if present, lead to a substantial change of therapeutic strategy. The role of C-reactive protein as a marker of atherosclerosis and its predictive value for CV events are also discussed. Finally, a section is devoted to tests that are currently confined to research purposes, such as markers of endothelial function including endothelin-1, homocysteine and genetic analysis.

Association of blood lead and homocysteine levels among lead exposed subjects in Vietnam and Singapore

OBJECTIVES

Lead and homocysteine are both linked to cardiovascular disease. With this in mind, the authors evaluated the relation between blood lead and homocysteine in people aged 19-66 years in two Asian populations.

METHODS

This cross-sectional study comprised 183 workers from a lead stabiliser factory in Singapore and 323 workers from a battery factory in Vietnam. Workers were occupationally exposed to lead. Blood lead was analysed using atomic absorption spectrophotometry while plasma homocysteine was measured using high performance liquid chromatography.

RESULTS

Chinese subjects had the lowest blood lead levels while the Indians had the highest. Controlling for age, sex and race, an increase of 1 microg/dl in blood lead was associated with an increase of 0.04 micromol/l of homocysteine on the log scale. Gender and ethnicity seemed to be strongly associated with the relation between lead and homocysteine. The positive relation between lead and homocysteine among the Vietnamese subjects was significant (Pearson's r = 0.254, p<0.01). When blood lead levels were divided by quartiles, the correlation coefficient between blood lead levels in the 4th quartile and homocysteine among the Vietnamese was higher (r = 0.405, p<0.01). Overall, an increase of 1 microg/dl in blood lead in all the Vietnamese subjects was associated with an increase of 0.05 micromol/l increase in homocysteine on the log scale. However, in the 4th quartile, the same increase was associated with an increase of 0.41 micromol/l of homocysteine on the log scale.

CONCLUSIONS

Blood lead was found to be associated with homocysteine levels in this Asian sample. Although we cannot determine causality from cross-sectional data, it is sensible to consider the probability that this relation could explain one of the mechanisms of the impact of lead on the cardiovascular system. More studies would be needed to confirm this inference.

A meta-analysis of association between C677T polymorphism in the methylenetetrahydrofolate reductase gene and hypertension

The C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene was implicated to be associated with hypertension due to its role in catalyzing the formation of 5-methylenetetrahydrofolate, a co-substrate for the conversion of homocysteine to methionine. Association studies were reported in different populations; however, a great number of subsequent studies have produced contrary results, possibly reflecting inadequate statistical power. With the cumulative data in recent years in both Caucasian and Asian populations, it was necessary to carry out a comprehensive analysis of previous findings. In this meta-analysis, we combined 26 English and Chinese studies in Caucasian and Asian populations published up to November 2006 to give a new picture of the role of the C677T polymorphism in the MTHFR gene. Evidence of significant association was detected between C677T polymorphism and hypertension in both populations. Additionally, the significant association between C677T polymorphism and hypertension/hypertension-in-pregnancy suggested that this polymorphism was one independent risk factor of hypertension.

Hyperhomocysteinemia and cardiovascular risk in postmenopausal women: the role of folate supplementation

In the postmenopausal period, cardiovascular diseases are a frequent chronic condition leading to high risk of myocardial infarction and death. Recently hyperhomocysteinemia and even mildly elevated plasma concentrations of homocysteine have been recognized as independent risk factors for vascular damage predisposing to arteriosclerosis. Elevated plasma levels of homocysteine induce vascular endothelial damage and are frequently associated with low folate levels.

In this review we evaluate literature data on some aspects related to menopause and homocysteine metabolism. In particular, we show the effect of folic acid supplementation on homocysteine concentrations and on homocysteine-related thiols, such as cysteine and cysteine-glycine, as well as the relationship with glucose, insulin, and lipidic metabolism in postmenopausal women. We also analyze the influence of folate supplementation on endothelial function, by brachial artery flow-mediated dilatation (endothelium-dependent) and nitroglycerine-induced dilatation (endothelium-independent) before and after a methionine load.

Folate administration in postmenopausal women is able to reduce high plasma homocysteine levels and to modify impaired endothelial function induced by hyperhomocysteinemia.

Clin Chem Lab Med 2007;45:130–5.

The Hordaland Homocysteine Study: a community-based study of homocysteine, its determinants, and associations with disease

The Hordaland Homocysteine Study (HHS) is a population-based study of more than 18,000 men and women in the county of Hordaland in Western Norway. The first investigation (HHS-I) took place in 1992-93, when the subjects were aged 40-67 y. In 1997-99, a follow-up study (HHS-II) of 7,053 subjects was carried out. In this large population, plasma levels of total homocysteine (tHcy) are associated with several physiologic and lifestyle factors and common diseases. Increasing age, male sex, smoking, coffee consumption, high blood pressure, unfavorable lipid profile, high creatinine, and the MTHFR 677C > T polymorphism are among the factors associated with increased tHcy levels; physical activity, moderate alcohol consumption, and a good folate or vitamin B-12 status are associated with lower tHcy levels. Subjects with raised tHcy levels have increased risk of cardiovascular morbidity, cardiovascular and noncardiovascular mortality, and are more likely to suffer from depression and from cognitive deficit (elderly). Among women, raised tHcy levels are associated with decreased bone mineral density and increased risk of osteoporosis. Women with raised tHcy levels also have an increased risk of having suffered from pregnancy complications and an adverse pregnancy outcome. Significant associations between tHcy and clinical outcomes are usually observed for tHcy levels > 15 micromol/L, but for most conditions, there is a continuous concentration-response relation with no apparent threshold concentration. Overall, the findings from HHS indicate that a raised tHcy level is associated with multiple clinical conditions, whereas a low tHcy level is associated with better physical and mental health.

The MTHFR CT polymorphism confers a high risk for stroke in both homozygous and heterozygous T allele carriers with Type 2 diabetes

OBJECTIVE

Individuals with Type 2 diabetes are at increased risk of stroke. Plasma homocysteine (tHcy) is an independent risk factor for cardiovascular (CV) disease. The methylene-tetrahydrofolate reductase (MTHFR) gene polymorphism (thermolabile variant C(677)T) is associated with CV risk, partly as a result of increased Hcy, especially in homozygous subjects.

AIM

To relate the occurrence of the MTHFR polymorphism with stroke prevalence by examining allelic frequency and genotype distribution in 165 subjects with Type 2 diabetes studied for the presence of thermolabile C(677)T MTHFR mutation.

RESULTS

Mean age was 67.7 years, and tHcy 18.2 micromol/l. T allele frequency was 38.5%. MTHFR genotypes were: normal (CC) 40%; heterozygous (CT) 43%; homozygous (TT) 17%. Serum levels of folic acid and B12 vitamin were within normal limits. Stroke prevalence was 14%. Sixty-four per cent of stroke-free subjects had the normal C allele vs. 46% in stroke subjects. The frequencies of genotypes (CC-CT-TT) were (%): 44-41-15 in stroke-free vs. 17-57-26 in stroke patients. Coronary (CAD) and peripheral artery disease (PAD) were common in all groups, with no differences according to genotypes. Stroke prevalence was markedly higher in genotypes CT and TT (18 and 21%) compared with CC (6%). Mean tHcy levels were higher in TT subjects.

CONCLUSION

The allelic frequency of C(677)T MTHFR mutation in Type 2 diabetes subjects with stroke is markedly different from that of subjects without stroke. Genotypic characteristics suggest that C(677)T MTHFR mutation confers a higher risk for stroke to both homozygous and heterozygous T allele carriers that cannot be ascribed solely to raised tHcy and/or lower folate status in CT subjects, nor to phenotypic expression of conventional risk factors for stroke. The impact of the MTHFR polymorphism on stroke may result from T allele-linked deleterious effects, or C allele-linked protection. Confirmatory studies are warranted, as this cohort was not randomly selected, and a type 1 error cannot be ruled out.

Changes in lifestyle and total homocysteine in relation to MTHFR(C677T) genotype: the Inter99 study

BACKGROUND

Reduction in total homocysteine (tHcy) may be clinically relevant in the prevention of cardiovascular disease (CVD) in the general population.

OBJECTIVE

To examine the effects of changes in various lifestyle habits and lifestyle related biological CVD risk markers on changes in tHcy in relation to MTHFR(C677T) genotype.

DESIGN

A 1 year follow-up study.

SETTING

Copenhagen County, Denmark.

SUBJECTS

Statistical analyses were based on a population-based sample of 915 men and women aged 30-60 years assessed to be at increased CVD risk at baseline and therefore offered lifestyle intervention and re-examination after one year.

RESULTS

None of the studied lifestyle changes-- smoking, physical activity, dietary habits, and coffee, tea, and alcohol consumption-- was significantly associated with changes in tHcy, either overall, or in any of the MTHFR genotype subgroups. In addition, changes in tHcy did not differ between participants randomized to low- and high-intensity lifestyle intervention. However, the MTHFR TT genotype was associated with a significant decrease in tHcy compared with the CC/CT genotype in which an increase was observed. In addition, changes in tHcy were associated with changes in several of the biological CVD risk markers: weight, total cholesterol, HDL cholesterol, LDL cholesterol and systolic blood pressure.

CONCLUSIONS

Our results indicate that tHcy may not be reduced by lifestyle changes; additionally, they suggest that tHcy may be related to biological CVD risk markers through a lifestyle independent pathway.

Homocysteine and hypertension in persons with spinal cord injury

STUDY DESIGN

Cross-sectional analysis of a convenience sample of locally recruited participants, including both patients and volunteers.

OBJECTIVES

To determine whether there is an association between plasma homocysteine and hypertension in persons with spinal cord injury (SCI).

SETTING

Spinal Cord Injury Service of the Veterans Affairs Palo Alto Medical Center (California, United States of America).

METHODS

The incidence of hypertension, dyslipidemia, insulin resistance, and the presence of metabolic syndrome were determined in 168 individuals with SCI (mean age 50.2 +/- 12.8 years). Fasting lipids, insulin, glucose, plasma homocysteine, and anthropometric data was gathered for each subject.

RESULTS

Blood pressure values (P < 0.001) and mean arterial pressure (P < 0.05) increased with higher plasma homocysteine levels. Homocysteine values were also significantly greater among individuals with hypertension compared with those who were normotensive or prehypertensive (P < 0.0001). There was an inverse relationship between plasma homocysteine levels and glomerular filtration rate and effective renal plasma flow (P < 0.05).

CONCLUSIONS

Plasma homocysteine levels are elevated in persons with SCI who have hypertension and inversely related to renal function, which suggests that renal dysfunction may be a link between homocysteine and hypertension in persons with SCI.

SPONSORSHIP

Funded by the VA Rehabilitation Research and Development Service, Merit Review Grant #B2549R.

Elevated levels of plasma homocysteine in postmenopausal women in Burkina Faso

BACKGROUND

Low levels of plasma homocysteine have been found in children and adult populations living in Burkina Faso in association with a low prevalence of coronary heart disease.

METHODS

Based on this finding, the levels of plasma homocysteine and other thiols (cysteine, cysteinylglycine, glutathione) in postmenopausal women living in Burkina Faso were evaluated with the aim of investigating whether age and life conditions influence plasma homocysteine and other thiol levels.

RESULTS

It was found that in older postmenopausal women the mean level of homocysteine was higher (16.4+/-6.6 micromol/L) than in fertile women (6.8+/-1.2 micromol/L) and that this increase was correlated with cysteine levels (166.6+/-44.6 micromol/L). While the glutathione level in postmenopausal women was lower (3.6+/-2.3 micromol/L) compared with fertile women (7.0+/-1.7 micromol/L), cysteinylglycine levels were within the normal range (29.9+/-9.3 micromol/L). No correlation was found between homocysteine levels and serum folate, vitamin B(12), vitamin B(6), cystatin C and serum creatinine levels. The older the women were, the higher were their plasma homocysteine levels: levels up to 20.2+/-9.1 micromol/L were found in those >70 years old.

CONCLUSIONS

The elevated levels of homocysteine in the postmenopausal women of Burkina Faso must be viewed as a characteristic of older age and its metabolic consequences.

Effects of insulin on methionine and homocysteine kinetics in type 2 diabetes with nephropathy

Although hyperhomocysteinemia, an independent cardiovascular risk factor, is common in type 2 diabetes with nephropathy, the mechanism(s) of this alteration is not known. In healthy humans, hyperinsulinemia increases methionine transmethylation, homocysteine transsulfuration, and clearance. No such data exist in type 2 diabetes either in the fasting state or in response to hyperinsulinemia. To this purpose, seven male type 2 diabetic patients with albuminuria (1.2 +/- 0.4 g/day, three with mild to moderate renal insufficiency) and seven matched control subjects were infused for 6 h with L-[methyl-(2)H(3), 1-(13)C]methionine. Methionine flux, transmethylation, and disposal into proteins as well as homocysteine remethylation, transsulfuration, and clearance were determined before and after euglycemic hyperinsulinemia (approximately 1,000 pmol/l). In type 2 diabetic subjects, homocysteine concentration was twofold greater (P < 0.01) and methionine transmethylation and homocysteine clearance lower (from approximately 15 to >50% and from approximately 40 to >100%, respectively; P < 0.05) than in control subjects. The insulin-induced increments of methionine transmethylation, homocysteine transsulfuration, and clearance were markedly reduced in type 2 diabetic subjects (by more than threefold, P < 0.05 or less vs. control subjects). In contrast, methionine methyl and carbon flux were not increased in the patients. In conclusion, pathways of homocysteine disposal are impaired in type 2 diabetes with nephropathy, both in postabsorptive and insulin-stimulated states, possibly accounting for the hyperhomocysteinemia of this condition.

Hyperhomocysteinemia: an additional risk factor in white coat hypertension

The association between homocysteine and sustained hypertension (HT) has been studied. The aim of this study was to assess homocysteine levels in white coat hypertension (WCH) as an indicator of increased risk in the development of cardiovascular diseases. WCH was defined as clinical hypertension and a daytime ambulatory blood pressure of < 135/85 mmHg. Plasma levels of homocysteine were determined in patients with WCH, hypertension, and normotension (NT). The study group included 100 subjects, 33 with WCH (16 males, 17 females) aged 49.1 +/- 1.9; 35 sustained hypertensives (17 males,18 females) aged 48.5 +/- 1.7 and 32 normotensive control subjects (15 males, 17 females) aged 48.8 +/- 2.2. The subjects were matched for age, gender, and body mass index. Patients with a smoking habit, dyslipidemia, or diabetes mellitus were not included in the study. Homocysteine levels were analyzed by ELISA. Plasma homocysteine levels were significantly higher in the WCH group compared to the controls (12.32 +/- 1.07 versus 5.35 +/- 1.38 micromol/L; P < 0.001) and the WCH group had significantly lower homocysteine values than the hypertensives (19.03 +/- 0.76 micromol/L P < 0.001). Total cholesterol and tri-glycerides were not different among the groups. There were no statistically significant differences in urinary albumin excretion (UAE) or creatinine clearance between the three groups. Hypertensive retinopathy was observed in the WCH group, but was less severe and less frequent compared to HTs. LVMI was greater in the WCH group compared to the NTs, but significantly less than HTs. The data demonstrate that WCH is associated with high levels of homocysteine. The increase in homocysteine level in WCH is not as high as in SHT. Since an elevated plasma homocysteine level is a strong risk factor for coronary artery disease and there was target organ damage in our WCH group, we conclude that WCH should not be considered to be an innocent trait.

Beta blocker effects on plasma homocysteine levels in patients with hypertension

Recent studies have shown that hyperhomocysteinemia might play a role in the pathogenesis of hypertension. The effects of antihypertensive agents on plasma homocysteine levels have not been tested extensively. We investigated the effects of beta-blocker therapy on homocysteine levels in patients with hypertension. In the study, 120 patients with newly diagnosed hypertension were enrolled. All patients received metoprolol succinate 100 mg/day initially. If blood pressure was above normal on the 15th day of follow-up, the metoprolol dosage was doubled. Before initiation of the antihypertensive medication and after the fourth month of treatment, homocysteine levels were measured. Of the 120 patients enrolled, 39 could not complete the study. Homocysteine levels decreased significantly by the end of the fourth month when compared with basal values (13.5+/-4.5 micromol/l versus 12.4+/-4.9 micromol/l; P = 0.001). There was no relation between homocysteine level and blood pressure control. There was a significant decrease in homocysteine levels in the women treated in this study (P = 0.001); however, this effect was absent in men (P = 0.185). We demonstrate that metoprolol succinate treatment significantly decreases plasma homocysteine levels in patients with hypertension, especially in women.