Rôle de l'homocystéine en pathologie

Homocysteine is an intermediate byproduct derived from the metabolism of an essential amino acid called methionine. For the past 30 years, homocysteine has been considered a potential cause of atherosclerosis. Mild hyperhomocysteinemia, which is sometimes associated with a low plasma level of vitamin B6, B12 and folic acid, is now a proven cardiovascular risk factor. Its level is closely related to experimental and clinical events as diverse as acute myocardial infarction, stroke, dementia, and venous thrombo-embolic disease. Its direct incrimination in causing these events remains uncertain and controversial. Indeed, even if vitamin supplementation has clearly proven its efficiency on lowering plasma levels of homocysteine, recent studies do not show any positive effect of vitamin therapy on cardiovascular events. Some hypotheses have been evocated to explain this lack of efficacy. A potential role of hyperhomocysteinemia has been proposed in some diseases: age-related macular degeneration, cognitive abnormalities, osteoporosis, neural tube defects, depression, schizophrenia, inflammatory bowel disease and colon tumors.