Sarcosine

    Sarcosine is an amino acid made in the methylation cycle when S-adenosylmethionine (SAM) is conjugated with glycine. It can also be made by the catabolism of dimethylglycine (DMG).

    There are many dietary sources of sarcosine, including eggs, legumes, nuts, and meats. Sarcosine is also available as an over-the-counter supplement and is widely used in cosmetic formulations (toothpaste, creams, and soaps) and detergents.

    In the methylation cycle, sarcosine is created by the enzyme GNMT, which functions to control excess SAM. Some clinicians use elevated sarcosine as a marker of ‘excess methyl supplementation’ or ‘overmethylation’. There is currently no literature to support this hypothesis, but it is based on physiology.

    Sarcosine can also be produced through the breakdown of DMG.

    Sarcosine is a natural inhibitor of glycine transport in the CNS by increasing N-methyl-D-aspartate (NMDA) receptors. Synaptic NMDA receptors are not only important for basic CNS functions (respiration, motor function), but also for learning, memory, and neuroplasticity. Decreased NMDA function results in cognitive defects, and overstimulation causes excitotoxicity. Abnormalities in these receptors are implicated in many diseases and are targets for pharmacological therapy. Sarcosine has been shown to be a co-agonist for NMDA receptors. For this reason, there are many studies evaluating sarcosine as an adjunctive treatment for psychiatric illnesses such as schizophrenia, which is characterized by decreased NMDA function. In addition, using sarcosine to increase NMDA function may improve depression-like behaviors. Since DMG is essentially sarcosine with an extra methyl group, research shows that they have similar effects.

    Some studies have evaluated the use of urinary and serum sarcosine as a marker of prostate cancer progression; however, the data are mixed. These studies are based on nonspecific metabolic profiles that followed random patterns of metabolite elevation. High levels

    Elevated sarcosine may be seen with methyl donor supplementation. Dietary intake of sarcosine-rich foods (i.e., eggs, legumes, nuts, and meats) and environmental sources (i.e., toothpaste, creams, and soaps) may result in elevated levels.

    Deficiencies of nutrient cofactors within the methylation cycle (folate, vitamin B₁₂, and vitamin B₂) may contribute to elevated levels. In fact, folate therapy has been used to normalize sarcosine. Upregulation or a SNP in the GNMT enzyme within the methylation cycle may contribute to sarcosine elevations.

    Sarcosine has no known toxicity, as evidenced by the lack of phenotypic expression of inborn errors of sarcosine metabolism.

Low levels

The clinical significance of low sarcosine is unknown.

This group of markers is related to meat, poultry, and fish intake, and may be decreased in vegetarians/vegans.