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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Moderate hyperhomocysteinaemia is a frequent finding in atherothrombotic cerebrovascular disease. This study confirms and extends this observation. Hyperhomocysteinaemia was present in 57 of 142 survivors with stroke (40%) and in four of 66 controls (6%). Plasma homocysteine concentrations were increased not only in carotid artery disease or lucunar stroke but also in haemorrhagic or embolic strokes. Homocysteine values were unrelated to the presence of hypertension, smoking, or hypercholesterolaemia, or to the concentrations of blood glucose, glycosylated haemoglobin, and plasma fibrinogen. Multiple regression analysis of the patient data showed that about 40% of the variation in plasma homocysteine concentrations could be predicted by the values for the homocysteine metabolism cofactors, blood folate and plasma pyridoxal 5-phosphate and by renal function as reflected in the values for serum creatinine. In patients, urine excretion of homocysteine per unit creatinine was significantly increased and strongly correlated both to the plasma homocysteine concentration and to the values for blood folate, plasma pyridoxal 5-phosphate, and serum vitamin B12. We conclude that moderate hyperhomocysteinaemia is frequently present in cases of stroke, is independent of other stroke risk factors or the type of stroke, and is partly related to renal function and the concentrations of homocysteine metabolism cofactors.
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PMID:Hyperhomocysteinaemia in stroke: prevalence, cause, and relationships to type of stroke and stroke risk factors. 158 47

Highly elevated concentrations of homocysteine measured as homocysteine or cysteine-homocysteine mixed disulfide (MDS) are found in plasma and urine in subjects with inherited abnormalities of the methionine metabolism. These subjects have a high incidence of arteriosclerotic vascular complications during childhood. Homocysteine causes endothelial cell injury and cell detachment that initiates the development of arteriosclerosis. The present study demonstrates a significantly elevated mean plasma MDS concentration in 19 patients with arteriosclerotic cerebrovascular disease compared to 17 controls. Our findings suggest that moderate homocysteinemia might be a risk factor for arteriosclerotic cerebrovascular disease.
Stroke
PMID:Moderate homocysteinemia--a possible risk factor for arteriosclerotic cerebrovascular disease. 650 11

Plasma homocysteine levels are elevated in 20-30% of all patients with premature atherosclerosis. Although elevated homocysteine levels have been recognized as an independent risk factor for myocardial infarction and stroke, the mechanism by which these elevated levels cause atherosclerosis is unknown. To understand the role of homocysteine in the pathogenesis of atherosclerosis, we examined the effect of homocysteine on the growth of both vascular smooth muscle cells and endothelial cells at concentrations similar to those observed in clinical studies. As little as 0.1 mM homocysteine caused a 25% increase in DNA synthesis, and homocysteine at 1 mM increased DNA synthesis by 4.5-fold in rat aortic smooth muscle cells (RASMC). In contrast, homocysteine caused a dose-dependent decrease in DNA synthesis in human umbilical vein endothelial cells. Homocysteine increased mRNA levels of cyclin D1 and cyclin A in RASMC by 3- and 15-fold, respectively, indicating that homocysteine induced the mRNA of cyclins important for the reentry of quiescent RASMC into the cell cycle. Furthermore, homocysteine promoted proliferation of quiescent RASMC, an effect markedly amplified by 2% serum. The growth-promoting effect of homocysteine on vascular smooth muscle cells, together with its inhibitory effect on endothelial cell growth, represents an important mechanism to explain homocysteine-induced atherosclerosis.
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PMID:Promotion of vascular smooth muscle cell growth by homocysteine: a link to atherosclerosis. 802 89

Folic acid, a water-soluble vitamin, has been used since the 1940s to treat some cases of macrocytic anemia without neurologic disease. Folate deficiency is best diagnosed with red blood cell folate levels along with macrocytosis and/or megaloblastic anemia. In addition to reversing overt deficiency, the vitamin may reduce the incidence of neural tube defects by 45% in women who receive 400 micrograms per day. It is recommended that all women of childbearing age take 400 micrograms of folate per day. Elevations in homocysteine levels, a metabolite intimately associated with folate, are also being found with increasing regularity in those with cardiovascular diseases. Homocysteine levels are reduced by folic acid administration. Therefore, there is some biologic plausibility, but not currently direct proof, for the assumption that folate supplements may prevent heart disease, stroke, and peripheral arterial disease. Controlled trials should take place before widespread food supplementation with folate is carried out on a large scale because of the possibility of outbreaks of permanent B12-related neurologic damage in those with undiagnosed pernicious anemia. However, if a patient has a premature cardiovascular event and has minimal risk factors, ordering a test to determine homocysteine level may be advisable, and if elevated, treating with folic acid supplement as long as B12 deficiency does not coexist.
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PMID:The role of folic acid in deficiency states and prevention of disease. 904 May 15

Homocysteine is a graded risk factor for the incidence of stroke and for the degree of carotid atherosclerosis. Homocysteine is also a graded risk factor for the incidence of myocardial infarction but we do not know its precise relations to the severity of atherosclerosis in coronary patients. Seventy five symptomatic coronary patients were recruited for the study. Fifty of these patients had coronary artery disease only and were compared in a case-control manner to 50 healthy controls matched for age and sex. The 25 other coronary patients had also symptoms in another atherosclerotic territory (cerebral, peripheral or both) and were also compared to 25 matched controls. Mean plasma homocysteine level was significantly higher in coronary patients than in controls (11.7 +/- 0.7 mumol l-1, n = 50 versus 9.9 +/- 0.5 mumol l-1, n = 50, p < 0.05). Homocysteine in patients with symptomatic atherosclerosis in two or three arterial sites was 15.7 +/- 1.5 mumol l-1 which differed significantly from matched controls and from patients with coronary artery disease only (p = 0.01). The extent of coronary atherosclerosis evaluated by an angiographic coronary score correlated weakly to plasma homocysteine levels (r = 0.25, p < 0.05). The patients with both hypertension and high levels of homocysteine (> 11.3 mumol l-1, median value) had more severe coronary atherosclerosis (coronary score of 16.3 +/- 2.3 versus 11.9 +/- 0.9, p < 0.05) and more diffuse atherosclerosis (number of atherosclerotic territories of 1.5 +/- 0.2 versus 1.2 +/- 0.7, p = 0.08) than the coronary patients without this association. There were no other high risk association when considering the other classical risk factors. Thus, the highest levels of homocysteine were present in patients with coronary disease and another symptomatic localisation of atherosclerosis. A small gradient in the extent of coronary atherosclerosis was found with increasing levels of homocysteine. The presence of both hypertension and hyperhomocysteinemia was associated with more severe coronary atherosclerosis.
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PMID:Plasma homocysteine and the extent of atherosclerosis in patients with coronary artery disease. 926 41

Although hyperhomocysteinemia has been recognized recently as a prevalent risk factor for myocardial infarction and stroke, the mechanisms by which it accelerates arteriosclerosis have not been elucidated, mostly because the biological effects of homocysteine can only be demonstrated at very high concentrations and can be mimicked by cysteine, which indicates a lack of specificity. We found that 10-50 microM of homocysteine (a range that overlaps levels observed clinically) but not cysteine inhibited DNA synthesis in vascular endothelial cells (VEC) and arrested their growth at the G1 phase of the cell cycle. Homocysteine in this same range had no effect on the growth of vascular smooth muscle cells (VSMC) or fibroblasts. Homocysteine decreased carboxyl methylation of p21(ras) (a G1 regulator whose activity is regulated by prenylation and methylation in addition to GTP-GDP exchange) by 50% in VEC but not VSMC, a difference that may be explained by the ability of homocysteine to dramatically increase levels of S-adenosylhomocysteine, a potent inhibitor of methyltransferase, in VEC but not VSMC. Moreover, homocysteine-induced hypomethylation in VEC was associated with a 66% reduction in membrane-associated p21(ras) and a 67% reduction in extracellular signal-regulated kinase 1/2, which is a member of the mitogen-activated protein (MAP) kinase family. Because the MAP kinases have been implicated in cell growth, the p21(ras)-MAP kinase pathway may represent one of the mechanisms that mediates homocysteine's effect on VEC growth. VEC damage is a hallmark of arteriosclerosis. Homocysteine-induced inhibition of VEC growth may play an important role in this disease process.
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PMID:Inhibition of growth and p21ras methylation in vascular endothelial cells by homocysteine but not cysteine. 931 59

Fasting hyperhomocysteinemia is an independent risk factor for coronary artery disease, stroke, peripheral vascular atherosclerosis, and for arterial and venous thromboembolism. The risk for cardiovascular disease with homocysteine is similar to conventional risk factors. The interaction of hyperhomocysteinemia with hypertension and smoking is strong and the combined effect is more than multiplicative. The combined effect of homocysteine and cholesterol is additive. Homocysteine produces atherosclerosis, thromboembolism, and vascular endothelial cell injury. Vascular dysfunction produced by homocysteine may be due to endothelial cell damage. Homocysteinemia-induced atherosclerosis is probably due to various factors including endothelial cell injury, inability to sustain S-nitroso-homocysteine formation because of imbalance between production of nitric oxide by dysfunctional endothelium and homocysteine, smooth muscle cell proliferation, and thromboembolism. There is strong evidence that endothelial cell injury is associated with oxidative stress produced by homocysteine. Hyperhomocysteinemia is associated with numerous conditions, including coronary disease, stroke, peripheral vascular disease (carotid artery and cerebrovascular atherosclerosis), venous thrombosis, renal disease, diabetes mellitus, and organ transplant. Folic acid, vitamin B12 and B6 have been shown to be beneficial in reducing plasma homocysteine levels. Folic acid is specifically very effective, safe and inexpensive.
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PMID:Homocysteine, a Risk Factor for Cardiovascular Disease. 982 15

We report a 13-year-old girl with nephropathic cystinosis on chronic peritoneal dialysis who presented with two episodes of stroke. Laboratory evaluation showed severe hyperhomocysteinemia (108 mumol/l). Further testing revealed that she was homozygous for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) gene. Treatment with folic acid and vitamin B12 lowered plasma homocysteine to less than 20 mumol/l. No further episodes of stroke occurred over a follow-up of 12 months. Homocysteine levels should be measured in patients with chronic renal failure, since simple and safe treatment with folic acid and vitamin B12 is effective in lowering the plasma homocysteine level in patients with the thermolabile MTHFR allele.
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PMID:Cerebral vascular complication and hyperhomocysteinemia in a cystinotic uremic child. 1010 Feb 95

Homocystinuria, an inherited disease in which plasma levels of homocysteine are high, was discovered in the sixties and it soon became clear that the affected patients had striking features of generalized atherosclerosis. The most common causes of death were arterial and venous thrombosis, stroke, or myocardial infarction. Observations in this human model of hyperhomocysteinemia led to studies in the general population whose findings suggest - though not conclusively- that homocysteine is a cardiovascular risk factor. The same is true for patients with chronic renal failure who almost always have moderate to severe high blood homocysteine levels. Homocysteine accumulates in relation to the concentration of its precursor, S-adenosylhomocysteine, a powerful competitive transmethylation inhibitor. Inhibition of a methyltransferase required to repair damaged proteins has actually been detected in uremic patients' red blood cells. However, in view of the multiple, widespread metabolic roles of S-adenosylmethionine-dependent methyltransferases, in many organs and tissues including the vascular endothelium, hypomethylation is currently interpreted as one of homocysteine's most important mechanisms of action. Various biological compounds, including small molecules and nucleic acids, as well as proteins, which are involved in the pathophysiology of thrombosis and atherosclerosis, are all potential targets of hypomethylation. Epidemiological studies and experimental models tend to confirm that homocysteine is both a cardiovascular risk factor and a uremic toxin, acting through different mechanisms.
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PMID:Homocysteine, a new cardiovascular risk factor, is also a powerful uremic toxin. 1049 66

Homocysteine (HC) at concentrations of from 0.05 to 1.0 mM caused dose-dependent loss of [Mg2+]i in cultured cerebral vascular smooth muscle cells (VSMC), whereas cysteine and methionine (its metabolic products) failed to interfere with changes in [Mg2+]i. HC, methionine and cysteine did not produce any changes in [Ca2+]i. Lowering [Mg2+]o to 0.3 mM resulted in elevation of [Ca2+]i and loss of [Mg2+]i. Depletion of [Mg2+]i, induced by HC, was potentiated by low Mg2+. Preincubation of these cells with vitamin B6, vitamin B12, folic acid, alone, did not alter [Ca2+]i or [Mg2+]i. Likewise, concomitant addition of vitamin B6, vitamin B12, or folic acid, together with HC (1 mM) did not change the reduction in [Mg2+]i induced by HC. However, concomitant addition of HC and the three vitamins inhibited completely the loss of [Mg2+]i. Exposure of these cells to each vitamin, alone, or combination of the three vitamins failed to interfere with reduction in [Mg2+]i induced by low [Mg2+]i, but it did suppress the rise in [Ca2+]i. Interestingly, in the presence of low [Mg2+]o, the vitamin combination did not retard depletion of [Mg2+]i. The present findings are compatible with the hypothesis that an increased serum HC concentration causes abnormal metabolism of Mg2+ in cerebral VSMC, thus priming these cells for HC-induced atherogenesis, cerebral vasospasm and stroke. Our results suggest the need for the three B-vitamins, together with normal physiological levels of Mg2+, in order to prevent [Mg2+]i depletion and occlusive cerebral vascular diseases induced by homocysteinemia.
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PMID:Extracellular magnesium regulates effects of vitamin B6, B12 and folate on homocysteinemia-induced depletion of intracellular free magnesium ions in canine cerebral vascular smooth muscle cells: possible relationship to [Ca2+]i, atherogenesis and stroke. 1055 43


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