Increased risk of Myocardial infarction is associated with which amino acid?
Homocysteine is a metabolite of the methionine cycle, is a strong independant risk factor for cardiovascular disease. Homocysteine is said to have a role in both atherogenesis and thrombogenesis. Risk factors for Atheresclerosis: Hypercholesterolemia Low HDL level Hypeension Male gender Diabetes mellitus Family with premature coronary aery disease High lipoprotein level Cigarette smoking Post menopausal state Hyper fibrinogenemia Hyperhomoeysteinemia Physical inactivity Obesity Angiotensin conveing enzyme polymorphism Homocysteine (Hcy) is a sulfydryl aminoacid that lies at an impoant metabolic branch point of methionine metabolism, between remethylation and transulfuration pathways. This lead to the formation of methionine and cystathionine respectively. Several enzymes regulate these pathways under normal condition in the presence of Vit. B12, B6 and Folic acid. Abnormality in any of the enzymes or vitamin deficiency may give rise to hyperhomocysteinemia. Hyperhomocysteinemia has been classified as: Moderate (Hcy >15 to 30 mmol/L), Intermediate (Hcy >30 to 100 .mmol/L) and Severe (Hcy >100 mmol/L) Hyperhomocysteinemia and CVD Hyperhomocysteinemia induce smooth muscle proliferation, accelerate oxidation of LDL cholesterol, impair endothelial derived nitric oxide, decrease synthesis of heparan sulphate proteoglycan and also induce proinflammatory changes in the vessel wall. The exact mechanism of atherothrombosis associated with yperhomocysteinemia is not clear. Several studies have pointed to an association with inhibition of thrombomodulin activity, reduction of protein c activation, increased platelet aggregation, and predisposition to endothelial injury. Ref: Harrison's, Principles of internal medicine,16th Edition, Page 1432
Valine
Ornithine
Methionine
Homocystine