Final answer:
Elevated homocysteine levels can increase the risk of certain health conditions. Several factors raise homocysteine levels, including gene mutations, diet, and certain substances. However, the methylation of homocysteine to methionine does not raise homocysteine levels.
Step-by-step explanation:
Elevated homocysteine levels can potentially increase the risk of certain health conditions, including cardiovascular disease. Factors that are known to raise homocysteine levels include mutations in the methylenetetrahydrofolate reductase or cystathionine beta-synthase genes, a high-methionine diet, and the presence of homocysteine-thiolactone and N-homocysteinylated protein. However, one factor that is not known to raise homocysteine levels is the methylation of homocysteine to methionine.