Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UMLS:C0020538 (hypertension)
170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiogenic brain damage and Alzheimer's disease caused by a progressing degenerative process are listed among the most frequent causes of dementia. These two processes are often concurrent and interrelated. Risk factors for vascular diseases including hypercholesteremia, arterial hypertension, and diabetes are also recognized risk factors for Alzheimer's disease. Results of many studies conducted in recent years suggest that the atheromatous process may be induced by elevated levels of homocysteine. Hyperhomocysteinemia first and foremost accelerates the onset of microangiopathic changes in small vessels. The mechanism underlying atherogenic action of homocysteine is still unclear. Hyperhomocysteinemia, generally assumed to have cytotoxic properties, damages endothelium in blood vessels, enhances thrombotic changes, and directly acts upon nitrogen oxide (NO), a vessel-dilating factor. Homocysteine is a metabolite of methionine. Homocysteine metabolism depends on current needs of the organism and involves either methionine reproduction (the reaction of remethylation, with such cofactors as B12 vitamin and folic acid), or cysteine synthesis (the transsulphuration reaction, with B6 vitamin as a cofactor). The normal range of plasma homocysteine concentration is assumed to be 5-14 mumol/L. The prevalence rates of hyperhomocysteinemia are 3-7% in the general population and 25% among those with vascular diseases. Elevated plasma homocysteine concentrations are due both to genetic and to environmental factors. In 2/3 of cases hyperhomocysteinemia is caused by decreased levels of folic acid, pyridoxine, and cobalamin. Deficiency of these vitamins is often seen in healthy elderly people.
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PMID:[Hyperhomocysteinemia in patients with dementia]. 1474 46

The role of hyperhomocysteinemia as independent risk factor for stroke needs to be confirmed. The aims of our study were to assess (i) the association between risk of stroke and increasing values of plasma homocysteine and (ii) the interaction between mild hyperhomocysteinemia and conventional vascular risk factors. We studied 161 consecutive patients with first-ever ischemic stroke classified using TOAST criteria and 152 neurologically healthy controls. Homocysteine was measured using high performance liquid chromatography (HPLC). Homocysteinemia was elevated in all stroke subtypes: 13.0+/-2.5 micromol/l in patients with cardioembolic disease, 13.9+/-5.4 micromol/l in those with small vessel diseases, 15.5+/-6.8 micromol/l in cases of undetermined stroke, and 17.8+/-13.5 micromol/l in patients with large vessel disease. Mean homocysteinemia was 8.10 micromol/l (SD=2.5) in controls. The logistic regression analysis showed that important independent risk factors for ischemic stroke were hypertension (p<0.0001; OR= 3.205; 95% CI, 1.788-5.742), hyperhomocysteinemia (p<0.0001; OR=1.425; 95% CI, 1.300-1562) and hyperlipidemia (p=0.018; OR=2.243; 95% CI, 1.147-4.385). Hyperhomocyst(e)inemia is an independent risk factor for all stroke subtypes and should be routinely measured and treated in stroke patients.
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PMID:Mild hyperhomocysteinemia is a risk-factor in all etiological subtypes of stroke. 1506 Aug 10

Black women have an increased risk of preeclampsia compared with white women. Plasma homocysteine is increased in preeclampsia. Homocysteine concentrations are affected by nutritional deficiencies, particularly decreased folic acid and B12, leading to increased homocysteine. Previous studies have reported racial differences in nutritional intake including folic acid. Therefore, we investigated whether there were racial differences in plasma homocysteine, folic acid, and vitamin B12 among women with preeclampsia. We tested for an association between homocysteine and folic acid and B12, and we hypothesized an inverse relationship of homocysteine and folic acid in preeclampsia, more so in black women in whom preeclampsia developed. Black women with preeclampsia (n=26) had elevated homocysteine concentrations (8.7+/-1.4 micromol/L) compared with black women with normal pregnancy (n=52, 7.6+/-0.5 micromol/L), white women with preeclampsia (n=34, 7.5+/-0.6 micromol/L), and white women with normal pregnancy (n=48, 5.5+/-0.3 micromol/L). Folic acid concentrations were lower in black women (14.1+/-0.8 ng/mL) compared with white women (18.5+/-0.9 ng/mL, P<0.01). However, plasma homocysteine was inversely related to folic acid only among black women with preeclampsia (r=-0.23, P=0.01). These racial differences may have implications for the higher rates of preeclampsia in this group and may have long-term implications for future cardiovascular risk. Racial differences in diet, adherence to folic acid supplementation, or interactions of nutritional and maternal factors warrant further study by race and pregnancy status.
Hypertension 2004 Jun
PMID:Homocysteine and folic acid are inversely related in black women with preeclampsia. 1509 66

About half of all deaths are due to cardiovascular disease and its complications. The economic burden on society and the healthcare system from cardiovascular disability, complications, and treatments is huge and becoming larger in the rapidly aging populations of developed countries. As conventional risk factors fail to account for part of the cases, homocysteine, a "new" risk factor, is being viewed with mounting interest. Homocysteine is a sulfur-containing intermediate product in the normal metabolism of methionine, an essential amino acid. Folic acid, vitamin B(12), and vitamin B(6) deficiency and reduced enzyme activities inhibit the breakdown of homocysteine, thus increasing the intracellular homocysteine concentration. Numerous retrospective and prospective studies have consistently found an independent relationship between mild hyperhomocysteinemia and cardiovascular disease or all-cause mortality. Starting at a plasma homocysteine concentration of approximately 10 micromol/l, the risk increase follows a linear dose-response relationship with no specific threshold level. Hyperhomocysteinemia as an independent risk factor for cardiovascular disease is thought to be responsible for about 10 percent of total risk. Elevated plasma homocysteine levels (> 12 micromol/l; moderate hyperhomocysteinemia) are considered cytotoxic and are found in 5 to 10 percent of the general population and in up to 40 percent of patients with vascular disease. Additional risk factors (smoking, arterial hypertension, diabetes, and hyperlipidemia) may additively or, by interacting with homocysteine, synergistically (and hence overproportionally) increase overall risk. Hyperhomocysteinemia is associated with alterations in vascular morphology, loss of endothelial antithrombotic function, and induction of a procoagulant environment. Most known forms of damage or injury are due to homocysteine-mediated oxidative stresses. Especially when acting as direct or indirect antagonists of cofactors and enzyme activities, numerous agents, drugs, diseases, and life style factors have an impact on homocysteine metabolism. Folic acid deficiency is considered the most common cause of hyperhomocysteinemia. An adequate intake of at least 400 microg of folate per day is difficult to maintain even with a balanced diet, and high-risk groups often find it impossible to meet these folate requirements. Based on the available evidence, there is an increasing call for the diagnosis and treatment of elevated homocysteine levels in high-risk individuals in general and patients with manifest vascular disease in particular. Subjects of both populations should first have a baseline homocysteine assay. Except where manifestations are already present, intervention, if any, should be guided by the severity of hyperhomocysteinemia. Consistent with other working parties and consensus groups, we recommend a target plasma homocysteine level of < 10 micromol/l. Based on various calculation models, reduction of elevated plasma homocysteine concentrations may theoretically prevent up to 25 percent of cardiovascular events. Supplementation is inexpensive, potentially effective, and devoid of adverse effects and, therefore, has an exceptionally favorable benefit/risk ratio. The results of ongoing randomized controlled intervention trials must be available before screening for and treatment of hyperhomocysteinemia can be recommended for the apparently healthy general population.
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PMID:Clinical use and rational management of homocysteine, folic acid, and B vitamins in cardiovascular and thrombotic diseases. 1525 38

Mild hyperhomocysteinemia is a probable risk factor for atherosclerotic diseases and stroke. Recently, associations of elevated plasma homocysteine concentrations in the acute phase and of MTHFR 677 TT genotype with spontaneous cervical artery dissections (sCAD) have been reported. The purpose of this study was to test this hypothesis in the currently largest sample of patients with sCAD, taking into account known factors influencing plasma homocysteine levels. Ninety-five patients with past sCAD were compared with 95 age- and sex-matched healthy individuals. Homocysteine, vitamin B6, B12, folate, and polymorphisms of methylenetetrahydrofolate reductase (MTHFR C677T), cystathionine beta-synthase (CBS 844ins68bp) and methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase/formyltetrahydrofolate synthetase (MTHFD1 G1958A) were assessed and any associations were analysed using multivariate statistics. The occurrence of sCAD was associated with elevated homocysteine levels with an odds ratio of 1.327 per 20 % percentile. Homocysteine levels were influenced by gender, smoking status, occurrence of hypertension, vitamin B12 and folate levels, and by the MTHFR TT genotype. MTHFR, CBS 844ins68bp, and MTHFD1 G1958A genotype were not independently associated with the occurrence of sCAD. These data suggest that elevated homocysteine is associated with the occurrence of sCAD. The MTHFR C677T polymorphism is associated with the homocysteine level.
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PMID:Plasma homocysteine, MTHFR C677T, CBS 844ins68bp, and MTHFD1 G1958A polymorphisms in spontaneous cervical artery dissections. 1550 5

The causal relation of total Homocysteine (tHcy) to coronary heart diseases (CHD) is unclear. In vitro studies suggest a proinflammatory effect. Among 32,826 women from the Nurses' Health Study who provided blood samples in 1989-1990, 237 CHD events were documented during 8 years of follow-up. The cases (1:2) were matched to controls on age, smoking, and month of blood draw. Plasma tHcy was inversely associated with blood levels of folate (partial r = -0.3, P < 0.0001) and B1(2) (r = -0.2, P < 0.0001) and with dietary intake of folate (r = -0.1, P < 0.01) and B(2) vitamin (r = -0.1, P = 0.01). tHcy was positively associated with soluble tumor necrosis receptor (sTNF-R) 1 and 2 (partial r = 0.2, P < 0.0001). In a multivariate model adjusted for age, smoking, BMI, parental history, hypertension, diabetes, postmenopausal hormone use, physical activity and alcohol intake, the relative risk of CHD between the extreme quartiles of tHcy was 1.66 (95% CI; 1.05-2.64, P trend = 0.02). The association was not appreciably attenuated after further adjustments for sTNF-R1, sTNF-R2, CRP, or Total Cholesterol:/HDL-c ratio. tHcy is an independent risk predictor of CHD and modestly associated with TNF-receptors. However, the inflammatory biomarkers measured could not explain its role in CHD.
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PMID:Homocysteine as a risk factor for coronary heart diseases and its association with inflammatory biomarkers, lipids and dietary factors. 1553 Sep 13

There are significant associations between moderate increases in serum homocysteine and three cardiovascular diseases: ischemic heart disease, deep vein thrombosis and pulmonary embolism, and stroke. An association between the presence of abdominal aortic aneurysm and elevated homocysteine plasma levels has been indicated. Although chronic systemic hypertension is the most common factor predisposing the aorta to dissection, homocysteinemia has never been known as the risk for aortic dissection except for that with Marfan syndrome. Homocysteinemia is suggested to be the risk for aortic dissection in Marfan syndrome and spontaneous cervical artery dissection. Reduced fibrillin-1 deposition into the extracellular matrix is found not only in Marfan syndrome but also in isolated ascending aortic aneurysm and dissection. The reduced matrix deposition produces a mild form of weakness of elastic tissue, which predisposes to ascending aortic aneurysm and dissection in patients who do not have the Marfan syndrome. The defect in fibrillin-1 leads to: (1) formation of elastin that is abnormally aggregated and more easily degraded by matrix metalloproteinases than is normal elastin; (2) upregulation of the synthesis of matrix metalloproteinases; (3) progressive destruction of connective tissue by these enzymes; (4) development of thoracic aortic aneurysms. Homocysteine causes premature breakdown in the arterial elastic fibers by activation of the elastolytic activities. Irreversible homocysteinylation of long-lived proteins should lead to cumulative damage and progressive clinical manifestations, and fibrillin-1 is seen as the paradigm of extracellular connective tissue proteins that are specially susceptible to homocysteine (and presumably homocysteine thiolactone) attack. The authors hereupon propose a novel hypothesis that homocysteine plays an important role in development of aortic dissection and that homocysteinemia is one of the risk factors for aortic dissection.
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PMID:Homocysteinemia is a risk factor for aortic dissection. 1578 May 1

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.
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PMID:Hyperhomocysteinemia: an additional risk factor in white coat hypertension. 1587 8

In order to determine the relationship between homocysteine levels and renal function, a cross-sectional study was carried out at out-patients clinic division of Nephrology and Hypertension Sanglah General Hospital Denpasar. Patients selected for the study were those with creatinine levels of 1.5-8.0 mg/dl aged 18 to 60 years. All eligible patients were examined for serum creatinine levels. At the same time blood samples were drawn for the examinations of total fasting Homocysteine levels. Creatinine clearance was calculated by Cockcroft-Gault formula, serum creatinine levels were examined by Jaffe method and total fasting Homocysteine levels were examined by fluorescence polarization immunoassay method (FPIA) method. If fasting plasma homocysteine levels were correlated with some related factors including creatinine clearance, reciprocal creatinine levels, age and gender, it was shown that only age (r=0.39, p=0.04) and creatinine clearance (r=0.39, p=0.04) had moderate and significant correlation with homocysteine levels. If both creatinine clearance and age as independent factors were correlated with fasting plasma homocysteine levels using multiple regression analysis, it was shown that both variable had strong (r=0.5) and significant relationship (p=0.03), yielding regression equations: Hcy (mmol/L) = -0.20 Cct (ml/mnt) + 0.21 age (ys) + 12.8. In conclusions, in patients with pre-dialytic chronic renal failure both creatinine clearance and age are strong predictors to plasma homocysteine levels.
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PMID:Relationship between creatinine clearance and plasma homocysteine levels in predialytic chronic renal failure patients. 1593 97

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.
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PMID:Beta blocker effects on plasma homocysteine levels in patients with hypertension. 1603 96


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