Sadenozilmetionin

S-adenozilmetionin, commonly known as S-adenosyl-L-methionine (SAMe), is a naturally occurring sulfonium compound produced in human cells from methionine and ATP by the enzyme methionine adenosyltransferase. It acts as a universal methyl donor in numerous transmethylation reactions and participates in transsulfuration and polyamine synthesis. After donating a methyl group, SAMe is converted to S-adenosylhomocysteine (SAH), which is hydrolyzed to homocysteine and adenosine. The SAMe/SAH ratio influences cellular methylation capacity and gene regulation.

Biological role and metabolism: SAMe is formed mainly in the liver and other tissues, where it participates in a network of methylation reactions essential for neurotransmitter synthesis, membrane phospholipid production, and nucleotide metabolism. SAH is a potent inhibitor of methyltransferases, so the balance between SAMe and SAH modulates methylation status. Homocysteine produced from SAH can be remethylated to methionine or enter the transsulfuration pathway to cysteine, linking SAMe metabolism to folate and vitamin B12 status.

Clinical use and evidence: SAMe is sold as a dietary supplement for mood disorders, osteoarthritis, and liver disease. Some randomized trials suggest antidepressant effects in mild-to-moderate depression and comparable benefit to NSAIDs for certain osteoarthritis symptoms; evidence for liver disease remains mixed. It is not approved as a prescription drug in many jurisdictions and regulatory status varies by country.

Safety and guidelines: SAMe is generally well tolerated but may cause gastrointestinal upset, nausea, dry mouth, dizziness, or insomnia. It can trigger manic episodes in bipolar disorder and may interact with antidepressants, potentially affecting serotonin levels. Use during pregnancy or breastfeeding is not well established; consult a clinician before use, especially with liver disease or other medications.

Regulatory status and availability: In the United States, SAMe is available as a dietary supplement and not FDA-approved as a drug. In some countries it is prescribed for specific indications; regulatory oversight varies.