Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0042373 (vascular disease)
 17,070 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent epidemiological studies have suggested that hyperhomocysteinemia is associated with increased risk of vascular disease. Homocysteine is a sulphur-containing amino acid whose metabolism stands at the intersection of two pathways: remethylation to methionine, which requires folate and vitamin B12 (or betaine in an alternative reaction); and transsulfuration to cystathionine which requires vitamin B6. The two pathways are coordinated by S-adenosylmethionine which acts as an allosteric inhibitor of the methylenetetrahydrofolate reductase (MTHFR) and as an activator of cystathionine beta-synthase (CBS). Hyperhomocysteinemia arises from disrupted homocysteine metabolism. Severe hyperhomocysteinemia is due to rare genetic defects resulting in deficiencies in CBS, MTHFR, or in enzymes involved in methyl cobalamine synthesis and homocysteine methylation. Mild hyperhomocysteinemia seen in fasting condition is due to mild impairment in the methylation pathway (i.e. folate or B12 deficiencies or MTHFR thermolability). Post-methionine-load hyperhomocysteinaemia may be due to heterozygous cystathionine-beta-synthase defect or B6 deficiency. Patients with homocystinuria and severe hyperhomocysteinemia develop arterial thrombotic events, venous thromboembolism, and more seldom premature arteriosclerosis. Experimental evidence suggests that an increased concentration of homocysteine may result in vascular changes through several mechanisms. High levels of homocysteine induce sustained injury of arterial endothelial cells, proliferation of arterial smooth muscle cells and enhance expression/activity of key participants in vascular inflammation, atherogenesis, and vulnerability of the established atherosclerotic plaque. These effects are supposed to be mediated through its oxidation and the concomitant production of reactive oxygen species. Other effects of homocysteine include: impaired generation and decreased bioavailability of endothelium-derived relaxing factor/nitric oxide; interference with many transcription factors and signal transduction; oxidation of low-density lipoproteins; lowering of endothelium-dependent vasodilatation. In fact, the effect of elevated homocysteine appears multifactorial affecting both the vascular wall structure and the blood coagulation system.
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PMID:[Hyperhomocysteinemia: an independent risk factor or a simple marker of vascular disease?. 1. Basic data]. 1280 8

Homocystinuria due to cystathionine beta-synthase deficiency is the second most treatable aminoacidopathy. The reported incidence varies from 1 in 344,000 worldwide to 1 in 65,000 in Ireland. Untreated patients with homocystinuria have severe hyperhomocysteinaemia. Amongst its pathological sequelae, which include mental retardation, ectopia lentis and osteoporosis, vascular events remain the major cause of morbidity and mortality in untreated patients. Recognized modalities of treatment include pyridoxine, in combination with folic acid and vitamin B12; methionine-restricted, cystine-supplemented diet; and betaine. The natural history of vascular events is such that half will have an event before age 30 years and there is a predicted one event per 25 years at the time of maximal risk. In 158 patients with 2822 patient-years of treatment, there would be a predicted 112 events if left untreated, but instead only 17 vascular events were recorded during treatment (relative risk 0.09, 95% CI 0.036 to 0.228; p < 0.0001). Appropriate chronic treatment to lower hyperhomocysteinaemia is effective in reducing the potentially life-threatening vascular risk in patients with homocystinuria. These findings may also have relevance to the significance of mild hyperhomocysteinaemia that is commonly found in patients with premature vascular disease.
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PMID:Classical homocystinuria: vascular risk and its prevention. 1288 65

Elevated total plasma homocysteine is an independent risk factor in the development of vascular disease in humans. Cystathionine beta-synthase (CBS) is an enzyme that condenses homocysteine with serine to form cystathionine. In this article, we describe the effects of modulating CBS activity using a transgenic mouse that contains the human CBS cDNA under control of the zinc-inducible metallothionein promoter (Tg-CBS). In the presence of zinc, Tg-CBS mice have a 2- to 4-fold increase in liver and kidney CBS activity compared with nontransgenic littermates. Transgenic mice on standard mouse chow had a 45% decrease in their serum homocysteine (12.1 to 7.2 micromol/L; P<0.0001) when zinc was added to drinking water, although zinc had minimal effect on their nontransgenic siblings (13.2 micromol/L versus 13.0 micromol/L; P=NS). Tg-CBS mice maintained on a high-methionine, low-folate diet also had significantly lower serum homocysteine compared with control animals (179 micromol/L versus 242 micromol/L; P<0.02). CBS overexpression also significantly lowered serum cysteinylglycine (3.6 versus 2.8 micromol/L; P<0.003) levels and reduced the levels of many amino acids in the liver. We also found that expression of Tg-CBS rescued the severe hyperhomocysteinemia and neonatal lethality of Cbs deletion animals. Our results show that elevating CBS activity is an effective method to lower plasma homocysteine levels. In addition, the creation of an inducible mouse system to modulate plasma homocysteine will also be useful in the study of homocysteine-related vascular disease.
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PMID:Modulation of cystathionine beta-synthase level regulates total serum homocysteine in mice. 1510 97

Homocystinuria is a congenital metabolic disorder, and has been known as life-threatening risk factor of vascular disease including ischemic stroke. We report a case of cerebral infarction due to homocystinuria. The patient was a 21-year-old woman exhibiting left hemiparesis and a previous history of ectopia lentis. Magnetic resonance imaging showed multiple fresh infarctions in the right frontal and temporal lobes, basal ganglia, corona radiata, and internal capsule. The right common carotid angiogram demonstrated complete occlusion at the origin of the right internal carotid artery. Further investigation clarified increased level of serum methionine and homocysteine and urinary homocystin due to cystathionine beta-synthase deficiency. Homocystinuria was diagnosed as the cause of cerebral infarction. The patient was treated by low methionine diet and administration of folic acid, cobalamin, and aspirin. It should be recognized that some patients with homocystinuria are missed in the neonatal screening for congenital metabolic disorders. Recent studies indicated that the homocysteinemia is one of risk factors of ischemic stroke in the general population as well as in the patients of homocystinuria. We recommend metabolic screening for homocystinuria, when treating a juvenile patient with ischemic stroke of unknown etiology.
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PMID:[A case of young adult presenting with cerebral infarction caused by homocystinuria]. 1555 67

Homocystinuria is an autosomal recessive inborn error of metabolism that is most often caused by mutation in the cystathionine beta-synthase (CBS) gene. Patients may develop serious clinical manifestations such as lens dislocation, mental retardation, osteoporosis, and atherothrombotic vascular disease. Over 100 mutations have been reported, but so far, none have been reported in Korea. Mutation analysis of the CBS gene in six Korean patients with homocystinuria was performed by direct sequencing. Eight mutations were identified, including four known mutations (T257M, R336C, T353M, and G347S) and four novel mutations (L154Q, A155V, del234D, and A288T). All patients were compound heterozygotes. To characterize these mutations, normal or mutated forms of CBS were cloned into pcDNA3.1 expression vector followed by transfection into mammalian cells for transient expression. Whereas the expression levels of mutant proteins were comparable to that of normal control, enzyme activities of all the mutant forms were significantly decreased. In addition, a novel single nucleotide polymorphism, R18C, was identified, which showed one-third to two-thirds the enzyme activity of wild type and 1% of the allele frequency in normal control. The spectrum of mutations observed in Korean patients bears less resemblance to those observed in Western countries.
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PMID:Identification and functional analysis of cystathionine beta-synthase gene mutations in patients with homocystinuria. 1620 33

Down's syndrome (DS) or trisomy 21 is the most common genetic cause of mental retardation, and adults with DS develop Alzheimer type of disease (AD). Cystathionine beta-synthase (CBS) is encoded on chromosome 21 and deficiency in its activity causes homocystinuria, the most common inborn error of sulfur amino acid metabolism and characterized by mental retardation and vascular disease. Here, we show that the levels of CBS in DS brains are approximately three times greater than those in the normal individuals. CBS is localized to astrocytes and those surrounding senile plaques in the brains of DS patients with AD. The over-expression of CBS may cause the developmental abnormality in cognition in DS children and that may lead to AD in DS adults.
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PMID:Cystathionine beta-synthase is enriched in the brains of Down's patients. 1627 69

Homocystinuria is an autosomal recessive disease most commonly caused by mutations in cystathionine beta-synthase (CBS). In this study we present the mutation analysis of 36 Colombian individuals from 10 unrelated kindred, with 11 individuals clinically classified as homocystinuric. Mutation analysis of the CBS gene revealed p.T191M, a prevalent mutation in Spain and Portugal, in the homozygous state in seven of the unrelated patients. Genotype-phenotype assessment of the p.T191M homozygous patients showed a high level of variability, including different severity in one pair of affected siblings. None of the patients responded biochemically to treatment with pharmacological doses of pyridoxine and folic acid as revealed by essentially unchanged homocysteine levels. This study offered a unique opportunity to study 18 heterozygous (p.T191M/wt) relatives of the homocystinuric patients. One atypical finding was that many of them presented with above average total homocysteine levels, putting them at an increased risk for vascular disease. Cryptorchidism was present in three of the cases, one of which presented also with Klinefelter syndrome. In addition to the previously described p.T191M mutation, a new mutation, p.A288T, was identified in a single individual. In this paper we present the first characterization, at a molecular level, of patients with homocystinuria from Colombia.
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PMID:High prevalence of CBS p.T191M mutation in homocystinuric patients from Colombia. 1647 May 95

Elevated total plasma homocysteine concentrations (tHcy), both fasting and post-methionine load, have been established as risk factors for vascular disease. Recently, we described the association of a 31 bp variable number of tandem repeats (VNTR) in the cystathionine beta-synthase (CBS) gene with both CBS enzyme activity and tHcy concentrations. In the present study, we determined the 31 bp VNTR genotypes in 2598 individuals of the Framingham Offspring Study and studied the association between this genotype and fasting, 2-h post-methionine load and delta (ie increase upon methionine loading) tHcy concentrations in 1416 subjects. We observed a positive association between the number of repeat units of the CBS 31 bp VNTR and both postload and delta tHcy concentrations. Adjustment for possible effect modifying factors like age, sex and vitamin (B6, B12 and folate) status did not change this observation. We hereby confirm the results of our earlier study, in which we found that this 31 bp VNTR is a genetic determinant of post-methionine load tHcy concentrations. Since also post-methionine load tHcy concentrations are found to be associated with an increased risk for cardiovascular disease (CVD), this 31 bp VNTR may be considered a risk factor for CVD.
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PMID:Association of a 31 bp VNTR in the CBS gene with postload homocysteine concentrations in the Framingham Offspring Study. 1679 Nov 40

The exact mechanism(s) by which hyperhomocysteinaemia promotes vascular disease remains unclear. Moreover, recent evidence suggests that the beneficial effect of folic acid on endothelial function is independent of homocysteine-lowering. In the present study the effect of a low (400 microg/70 kg/day) and high (5 mg/70 kg/day) dose folic acid supplement on endothelium-dependent relaxation in the isolated perfused mesenteric bed of heterozygous cystathionine beta-synthase deficient mice was investigated. Elevated total plasma homocysteine and impaired relaxation responses to methacholine were observed in heterozygous mice. In the presence of N(G)-nitro-L-arginine methyl ester relaxation responses in wild-type tissues were reduced, but in heterozygous tissues were abolished. Clotrimazole and 18alpha-glycyrrhetinic acid, both inhibitors of non-nitric oxide/non-prostanoid-induced endothelium-dependent relaxation, reduced responses to methacholine in wild-type but not heterozygous tissues. The combination of N(G)-nitro-L-arginine methyl ester and either clotrimazole or 18alpha-glycyrrhetinic acid completely inhibited relaxation responses in wild-type tissues. Both low and high dose folic acid increased plasma folate, reduced total plasma homocysteine and reversed endothelial dysfunction in heterozygous mice. A greater increase in plasma folate in the high dose group was accompanied by a more significant effect on endothelial function. In the presence of N(G)-nitro-L-arginine methyl ester, a significant residual relaxation response was evident in tissues from low and high dose folic acid treated heterozygous mice. These data suggest that the impaired mesenteric relaxation in heterozygous mice is largely due to loss of the non-nitric oxide/non-prostanoid component. While low dose folic acid may restore this response in a homocysteine-dependent manner, the higher dose has an additional effect on nitric oxide-mediated relaxation that would appear to be independent of homocysteine lowering.
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PMID:Differential effects of low and high dose folic acid on endothelial dysfunction in a murine model of mild hyperhomocysteinaemia. 1704 83

Homocystinuria is a metabolic disorder caused by a deficiency of cystathionine beta-synthase (CBS). The major clinical symptoms of this disease are mental retardation, lens dislocation, vascular disease with life-threatening thromboembolisms, and skeletal deformities. The major treatments for CBS deficiency include pharmacologic doses of pyridoxine or dietary restriction of methionine. There is currently no effective long-term treatment to lower the elevated plasma levels of homocysteine. However, gene therapy could be an effective novel approach for the treatment of homocystinuria. A recombinant adeno- associated virus vector carrying human CBS cDNA (rAAV-hCBS) was constructed and administered to CBS-/- mice by intramuscular (IM) and intraperitoneal (IP) injections. Serum homocysteine concentrations significantly decreased in treated mice compared with age-matched controls two weeks after treatment. The treated CBS-/- mice had life spans 3-7 days longer compared with untreated CBS-/- mice. In CBS-/- mice treated with rAAV-hCBS via IP injection, the vector was detected in all organs examined including liver, spleen, and kidney, and CBS gene expression was observed by immunohistochemical staining in the liver. These results indicate the efficacy of gene delivery and demonstrate the possibility of gene therapy mediated by AAV gene transfer in this mouse model of homocystinuria.
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PMID:Recombinant adeno-associated virus mediated gene transfer in a mouse model for homocystinuria. 1720 41


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