Homocysteine is an amino acid that can build up in the blood if there are deficiencies in certain B vitamins (B6, B12, or folate). High levels of homocysteine are associated with an increased risk of heart disease and stroke.
Choline is oxidized to betaine, which is used to re-methylate homocysteine to methionine. Choline deficiency can lead to high homocysteine.
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Methionine is directly converted to homocysteine via several enzymatic steps. Elevated homocysteine is a marker of impaired methionine metabolism.
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Xu W, Wang HX, Guo X, et al.. Association of Homocysteine, Methionine, and MTHFR 677C>T Polymorphism With Cognitive Function in Older Adults: The Swedish National Study on Aging and Care in Kungsholmen. Frontiers in Aging Neuroscience (2020). https://www.frontiersin.org/articles/10.3389/fnagi.2020.00184/full
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