Circulating homocysteine levels in sustained and white coat hypertension

The significance of homocysteine in patients with hypertension

Cardiovascular disease is the most common cause of death in developed countries. Important factors leading to ischemic heart disease and strokes are hypertension and high levels of homocysteine in blood serum. The coexistence of these two factors significantly increases the risk of these diseases and premature deaths. Many studies indicate that patients with hypertension are significantly more likely to demonstrate increased blood serum homocysteine levels than those with normal blood pressure. This may be caused by a higher incidence of overweight, high intake of salt and increased uric acid levels. It has been shown that both these factors increase the prevalence of hypertension and lead to higher homocysteine levels. However, the results of some studies indicate that arterial hypertension and homocysteinemia are causally related. It was shown, among other things, that high homocysteine levels damage the endothelium and reduce nitric oxide synthesis, which may directly lead to hypertension. Serum homocysteine levels are slightly higher in patients with white coat hypertension than they are in healthy individuals and may therefore also increase the risk of cardiovascular diseases. Several authors have also shown that the levels of homocysteine in blood serum are higher in so-called non-dippers, i.e., patients with no night-time pressure drop. The lack of a 10%–20% decrease in blood pressure at night is associated with increased cardiovascular complications. Strokes occur especially frequently in older people with arterial hypertension and hyperhomocysteinemia. The administration of B vitamins and folic acid significantly reduces serum homocysteine levels. The administration of this acid also slightly, but statistically significantly, increases the effectiveness of hypotensive drugs. Large meta-analyses meta-analysis indicate that the increased supply of folic acid in patients with hypertension significantly reduces the risk of stroke. Such management is particularly effective in patients with hypertension and hyperhomocysteinemia.

The differential diagnostic value of serum homocysteine for white coat hypertension

Objective

To assess the value of serum homocysteine (Hcy) in differential diagnosis of white coat hypertension (WCH).

Results

In this retrospective study, serum Hcy levels were elevated in hypertensive patients (P < 0.001) compared to WCH patients. Serum Hcy levels were positively correlated with 24-h mean systolic blood pressure, r = 0.1378, P < 0.001. The results of the receiving operating characteristic (ROC) curve showed that the AUC value of Hcy was 0.80 (95% CI, 0.77–0.83), the cut-off value was 13.8 μmol/L, the sensitivity was 68.58% and the specificity 87.21%. In the prospective study, the AUC value of Hcy was 0.73 (95% CI: 0.67–0.78), higher than N - terminal pro - brain natriuretic peptide(NT-pro-BNP) (0.64, 95% CI:0.58–0.70) and cystatin C (Cys-C) (0.62, 95% CI:0.55–0.68). Hcy, NT-proBNP and Cys-C combined, provided a better indication of a differential diagnosis of WCH, than Hcy alone.

Materials and Methods

This investigation involved both a retrospective and a prospective study. Clinical data including blood pressure, age, sex, height, weight, BMI, smoking status, past history, and behavioral electrocardiogram of patients who had undergone 24-hour ambulatory blood pressure monitoring (ABPM) with elevated clinical blood pressure (BP) were recorded. Pearson correlation analysis was used to test the correlation between Hcy and BP. The ROC curve was used to analyze the value of measuring Hcy levels in differential diagnosis of WCH.

Conclusions

Serum Hcy was decreased in WCH patients and therefore could be a biomarker for differential diagnosis of WCH.

Vitamin D levels in white coat and sustained hypertension

OBJECTIVE

The plasma levels of vitamin D in patients with white coat hypertension (WCHT) have not been studied previously. The aim of this study was to evaluate vitamin D levels in WCHT and compare with sustained hypertension (SHT) and with normotension (NT).

PATIENTS AND METHODS

Fifty-three normotensive, 42 WCHT, and 59 SHT patients were recruited in this study. The participants were matched for age, sex, and BMI. The vitamin D levels were determined using the electrochemiluminescence immunoassay method.

RESULTS

Plasma vitamin D levels were significantly lower in SHT than in the WCHT and NT groups (26.4±4.9, 34.3±3.6, and 36±5 ng/ml, respectively), and were similar in the WCHT and NT groups. There was a negative correlation between vitamin D levels and blood pressure parameters such as clinic systolic blood pressure (SBP), clinic diastolic blood pressure (DBP), 24-h SBP, 24-h DBP, daytime SBP, daytime DBP, night-time SBP, and night-time DBP (r=-0.554, -0.419, -0.629, -0.427, -0.559, -0.534, -0.607, -0.462, respectively, and all P<0.001) in the entire study group. Clinic SBP (B±SE=-0.97±0.037, P=0.009) and 24-h SBP (B±SE=-0.138±0.055, P=0.013) were identified as predictors for vitamin D levels in the entire study group.

CONCLUSION

Our data show that sustained hypertensive patients have lower vitamin D levels than white coat hypertensive and normotensive individuals. White coat hypertensive patients without other cardiovascular risk factors have higher vitamin D levels than sustained hypertensive patients, suggesting that they have a lower cardiovascular risk.

Closer look at white-coat hypertension

This review aims to clarify novel concepts regarding the clinical and laboratory aspects of white-coat hypertension (WCHT). Recent studies on the clinical and biological implications of WCHT were compared with existing knowledge. Studies were included if the WCHT patients were defined according to the 2013 European Society of Hypertension guidelines, i.e., an office blood pressure (BP) of ≥ 140/90 mmHg, a home BP of ≤ 135/85 mmHg, and a mean 24-h ambulatory BP of ≤ 130/80 mmHg. WCHT studies published since 2000 were selected, although a few studies performed before 2000 were used for comparative purposes. True WCHT was defined as normal ABPM and home BP readings, and partial WCHT was defined as an abnormality in one of these two readings. The reported prevalence of WCHT was 15%-45%. The incidence of WCHT tended to be higher in females and in non-smokers. Compared with normotensive (NT) patients, WCHT was associated with a higher left ventricular mass index, higher lipid levels, impaired fasting glucose, and decreased arterial compliance. The circadian rhythm in WCHT patients was more variable than in NT patient’s, with a higher pulse pressure and non-dipping characteristics. Compared with sustained hypertension patients, WCHT patients have a better 10-year prognosis; compared with NT patients, WCHT patients have a similar stroke risk, but receive more frequent drug treatment. There are conflicting results regarding WCHT and markers of endothelial damage, oxidative stress and inflammation, and the data imply that WCHT patients may have a worse prognosis. Nitric oxide levels are lower, and oxidative stress parameters are higher in WCHT patients than in NT patients, whereas the antioxidant capacity is lower in WCHT patients than in NT patients. Clinicians should be aware of the risk factors associated with WCHT and patients should be closely monitored especially to identify target organ damage and metabolic syndrome.

White-coat hypertension

1. Numerous studies have examined whether white-coat hypertension (WCHT) is associated with increased cardiovascular risk, but with definitions of WCHT that were not sufficiently robust, results have been inconsistent. The aim of the present review was to standardize the evidence by only including studies that used a definition of WCHT consistent with international guidelines. 2. Published studies were reviewed for data on vascular dysfunction, target organ damage, risk of future sustained hypertension and cardiovascular events. 3. White-coat hypertension has a population prevalence of approximately 15% and is associated with non-smoking and slightly elevated clinic blood pressure. Compared with normotensives, subjects with WCHT are at increased cardiovascular risk due to a higher prevalence of glucose dysregulation, increased left ventricular mass index and increased risk of future diabetes and hypertension. 4. In conclusion, management of a patient with WCHT should focus on cardiovascular risk factors, particularly glucose intolerance, not blood pressure alone.

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.

Mechanical and circulating biomarkers in isolated clinic hypertension

1. This review examines the current evidence for altered mechanical and circulating biomarkers in isolated clinic hypertension and their potential significance. 2. Arterial stiffness, as assessed by central pulse wave velocity, is influenced by multiple cardiovascular risk factors; however, an independent association with isolated clinic hypertension (ICHT) has not been convincingly shown in four small studies. 3. Endothelial dysfunction, as assessed by brachial artery flow-mediated vasodilation, circulating levels of endothelial markers (e.g. nitrite/nitrate, von Willebrand factor, endothelin-1) and/or circulating levels of inhibitors of vascular nitric oxide (plasma asymmetric dimethylarginine, homocysteine), has been shown to be present in established hypertension and to a variable and inconsistent extent in subjects with ICHT. 4. Evidence of increased oxidative stress in ICHT versus normotensive subjects was found in two of three studies. 5. Circulating inflammatory markers C-reactive protein and plasminogen activator inhibitor-1 were significantly increased in two of three and two of two studies, respectively, in ICHT compared with normotensive subjects. 6. Urinary albumin excretion is a marker of both arterial and renal disease. The consensus from seven studies in patients with ICHT is that albuminuria is not an independent marker for ICHT. 7. Studies to date assessing biomarkers in ICHT have been small and cross-sectional. Larger, long-term longitudinal studies of arterial functional and circulating biomarkers are required to assess the potential vascular impact of ICHT.

Influence of mental stress on the plasma homocysteine level and blood pressure change in young men

Objective. This study aimed to determine whether mental stress influences the plasma total homocysteine level or blood pressure in young men. Method. Twenty-seven male university students were assigned to a normal blood pressure group (24-h systolic blood pressure <125 mmHg and diastolic blood pressure <75 mmHg; 13 subjects) or a high blood pressure group (24-h systolic blood pressure > or =125 mmHg, or 24-h diastolic blood pressure > or =75 mmHg; 14 subjects). Wearing an ambulatory blood pressure monitoring device, subjects rested for 30 minutes, underwent an arithmetic test for 15 minutes, and rested again for 15 minutes. Blood samples were taken before and after the test. Plasma total homocysteine levels were measured. Heart rate, blood pressure, and sympathovagal balance were determined during the test. Results. The mean total homocysteine level at rest in the high blood pressure group was slightly, but not significantly, higher than that in the normal blood pressure group. The resting total homocysteine level was significantly higher in subjects with parental history of hypertension than in those without (p < 0.01). Blood pressure, heart rate, and the plasma total homocysteine level were increased significantly by mental stress (p < 0.05). The change in total homocysteine correlated significantly with the changes in systolic blood pressure and sympathovagal balance (p < 0.05). Conclusion. Resting total homocysteine level was significantly higher in male students with a parental history of hypertension than in those without. It was shown that mental stress elevates heart rate, blood pressure, sympathovagal activity, and the plasma total homocysteine level in young men.

Comparison of Pulse Wave Analysis Between Persons With White Coat Hypertension and Normotensive Persons

White coat hypertension (WCH) is considered by some but not all investigators to be a benign condition without increased cardiovascular risk. Pulse wave analysis is a noninvasive method to measure how the reflected pressure wave interacts with central aortic blood pressure (BP) and to assess how it is related to vascular stiffness. The purpose of the study was to compare central aortic BP in normotensive and WCH participants. WCH participants were identified after ambulatory BP monitoring. Normotensive participants served as controls. Using radial artery applanation tonometry, aortic pulse wave analysis was performed. Augmentation index (AI), AI75, and differences in systolic BP between central aortic and peripheral vasculatures were calculated. Results show a difference in AI, AI75, (AI standardized to a heart rate of 75 beats per minute), and central aortic systolic pressures between WCH and normotensive participants. The WCH group had significantly higher systolic BP and pulse pressure; however, these were still within the normal range. In summary, WCH participants had increased central aortic pressures compared with normotensives, supporting the potential for increased cardiovascular risk in WCH.

MTHFR 677 CT/MTHFR 1298 CC genotypes are associated with increased risk of hypertension in Indians

The goals of our present study were to measure plasma homocysteine levels and determine their association with methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) in essential hypertensive subjects. Plasma total homocysteine and folic acid levels were measured in essential hypertensive patients (n = 153) before and after oral supplementation with either 5 mg folic acid tablet/day or 5 mg placebo/day for 4 weeks and compared with age and sex matched normotensive controls (n = 133). MTHFR gene polymorphisms (C677T and A1298C) were studied by restriction fragment length polymorphism and correlated with plasma homocysteine levels. Homocysteine levels were significantly higher in hypertensive patients as compared to controls and showed a negative correlation with plasma folate levels. Folic acid supplementation (5 mg/day) for 4 weeks resulted in a significant decrease in plasma homocysteine concentrations in these patients. Patients carrying MTHFR 677T allele (OR = 1.90; 95%CI: 1.14-3.19) or MTHFR 1298C (OR = 2.6, 95%CI: 1.55-4.40) allele were at increased risk of hypertension. The frequency of co-occurrence of MTHFR 677 CT/1298 CC genotypes was significantly higher in the patients compared to controls (P < 0.05) and was associated with increased risk of hypertension (OR = 3.54, 95%CI: 0.37-4.30). Subjects with MTHFR 1298 CC genotype had significantly higher homocysteine levels compared to those with MTHFR 1298 AA genotype (P < 0.05). Our results indicate that MTHFR 677T and 1298C alleles and co-occurrence of MTHFR 677 CT/MTHFR 1298 CC genotypes are associated with increased risk of hypertension and MTHFR 1298 CC genotype is associated with higher homocysteine levels in our subjects.

The mean platelet volume in patients with essential and white coat hypertension

Mean platelet volume (MPV), a determinant of platelet function, is a newly emerging risk factor for atherothrombosis. The risk profile of white coat hypertension has not yet been completely clear. The present study was designed to evaluate MPV in white coat hypertensive subjects compared with essential hypertensive patients and normotensive subjects. We selected 36 essential hypertensive patients, 36 white coat hypertensive subjects and 36 normotensive control subjects matched for age, gender, and body mass index. MPV was very significantly higher in essential hypertensives and white coat hypertensives than in normotensives (P < 0.00); it was also higher in essential hypertensives than in white coat hypertensives (P < 0.05). Platelet counts were not different among the study groups (P > 0.05). MPV was positively correlated with ambulatory diastolic blood pressure in essential hypertension and white coat hypertension groups (P < 0.05). In conclusion, our data suggests one possible mechanism by which white coat hypertensive subjects may be at increased cardiovascular risk.

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.

Single nucleotide polymorphism in CTH associated with variation in plasma homocysteine concentration

Plasma total homocysteine (tHcy) concentration, an independent risk factor of atherosclerosis, has numerous genetic and environmental determinants. While the thermolabile polymorphism in MTHFR encoding methylenetetrahydrofolate reductase is the best-studied genetic factor associated with variation in plasma tHCy, other candidate genes are being evaluated. Recently, we discovered that cystathioninuria was caused by mutations in the CTH gene encoding cystathionine gamma-lyase, an enzyme that converts cystathionine to cysteine in the trans-sulfuration pathway. We also identified a common single nucleotide polymorphism (SNP), namely c.1364G>T (S403I) in exon 12 of CTH. In the current analysis, we studied the association of genotypes of this SNP with plasma tHcy concentrations in 496 Caucasian subjects. CTH 1364T/T homozygotes had significantly higher mean plasma tHcy concentration than subjects with other genotypes, and the effect sizes of CTH and MTHFR genotypes were similar. The findings suggest that common variation in CTH may be a determinant of plasma tHcy concentrations.

Plasma levels of homocysteine in patients with white-coat hypertension

Elevated levels of plasma homocysteine (Hcy) is an independent risk factor for cardiovascular diseases. The risk profile of white-coat hypertension (WCHT) is not yet completely clear. In this study, we aim to determine the levels of plasma Hcy in a group of patients with WCHT, and to obtain clinical results by comparing WCHT group with hypertensive and healthy groups. Age, sex and body mass index were matched for 15 normal subjects, 15 patients with WCHT and 15 patients with essential hypertension, and they were included in the study. We measured levels of plasma Hcy in all groups. Levels of plasma Hcy were significantly higher in patients with sustained hypertension than in WCHT group (p = 0.03). They were also significantly higher in patients with WCHT than in control group (p = 0.02). Our data suggest that WCHT subjects are at an increased cardiovascular risk, although this was lower than the risk in patients with sustained hypertension.

White-coat hypertension: a clinical review

White-coat hypertension (WCHT), also called 'isolated office or clinic hypertension', is defined as the occurrence of blood pressure (BP) values higher than normal when measured in the medical environment, but within the normal range during daily life, usually defined as average daytime ambulatory BP (ABP) or home BP values (<135 mm Hg systolic and <85 mm Hg diastolic). The prevalence of WCHT varies from 15% to over 50% of all patients with mildly elevated office BP (OBP) values. In untreated hypertensive patients, the probability of WCHT especially increases with female gender and a mildly elevated OBP level. The value of other possible determinants such as (non) smoking status, duration of hypertension, left ventricular mass, number of OBP measurements, educational level, etc. is less consistently shown. Although, for various reasons, studies evaluating the long-term effects of WCHT are not always easy to interpret, most data indicate that persons with WCHT have a worse or equal cardiovascular prognosis than normotensives, but a better one than those with sustained hypertension. WCHT is sometimes considered a prehypertensive state, but data on the long-term evolution of subjects with WCHT are scarce. Patients with WCHT and a high cardiovascular risk or proven target organ damage should be pharmacologically treated. Subjects with uncomplicated WCHT should probably not receive medical therapy, but a close follow-up, including regular assessment of other risk factors and measurement of OBP (every 6 months) and ABP (every 1 or 2 years), is warranted.

Plasma Homocysteine, Hypertension Incidence, and Blood Pressure Tracking

Plasma homocysteine is cross-sectionally associated with blood pressure in large, community-based studies. It is unknown whether elevated plasma homocysteine predicts hypertension incidence. We investigated the relations of baseline plasma total homocysteine levels to hypertension incidence and blood pressure tracking in 2104 Framingham Heart Study participants (mean age, 57 years; 58% women), who were free of hypertension, myocardial infarction, heart failure, atrial fibrillation, or renal failure at baseline. Baseline mean+/-SD plasma homocysteine was 10.1+/-3.7 micromol/L. On follow-up 4 years from baseline, 360 persons (17.1%) had developed hypertension, and 878 persons (41.7%) had progressed to a higher blood pressure stage. In unadjusted analyses, a 1-SD higher log homocysteine value was associated with increased odds of developing hypertension (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.05 to 1.32) and increased odds of blood pressure progression (OR, 1.17; 95% CI, 1.07 to 1.27). The relations of plasma homocysteine to the incidence of hypertension or blood pressure progression were statistically nonsignificant in age- and sex-adjusted logistic regression models (OR, 0.98; 95% CI, 0.87 to 1.11 and OR, 1.05; 95% CI, 0.96 to 1.16, respectively) and in multivariable models adjusted for age, sex, body mass index, diabetes, interim weight change, smoking, serum creatinine, baseline blood pressure, and blood pressure category (OR, 0.92; 95% CI, 0.81 to 1.06 and OR, 1.07; 95% CI, 0.97 to 1.18, respectively). In conclusion, we found no major relation of baseline plasma homocysteine levels to hypertension incidence or longitudinal blood pressure progression in a large, community-based cohort of nonhypertensive individuals after adjustment for age, sex, and other important covariates.