Research Biomarker Category Methylation Panel - Genova Diagnostics

Methylation Panel - Genova Diagnostics

Methylation is a biochemical process in which methyl groups (CH3) are transferred or donated between molecules, thereby changing their structure and function. This happens billions of times per second in every cell throughout the body. The methylation cycle is dependent on amino acids, vitamin cofactors, and minerals obtained from the diet to ensure adequate function of this biochemical pathway.

The incredibly vast processes in the body that depend upon methylation are what ultimately make functional testing for methylation impairment a valuable clinical tool. Some of these processes include, but are not limited to:

- creatine production for skeletal muscle contraction

- DNA and RNA synthesis

- gene regulation (epigenetics)

- hormone regulation and detoxification

- energy production

- cell membrane repair

- fat metabolism

- myelination

- immune function

- neurotransmitter production and metabolism

- vascular endothelial function and nitric oxide production

To keep these processes functioning optimally, there is a necessary balance between many different biochemical pathways. What is termed the “methylation cycle” involves an interplay between folate metabolism, methionine metabolism, and homocysteine transsulfuration.

The body continually adapts these interconnected pathways in order to maintain homeostasis.

However, key amino acid deficiencies, a lack of vitamin and mineral cofactors, genetic enzymatic predispositions, and a wide array
of oxidative stressors can impact multiple enzymes leading to a disruption in a patient’s overall methylation status.

Betaine

Optimal range: 21 - 71 micromol/L

- Betaine (trimethylglycine) can be used to turn homocysteine back into methionine

- Betaine is derived from dietary choline (Meats, eggs, and beets)

- Betaine is used for: Methylation / Osmolyte, under cell stress (mainly in kidneys)

Betaine/Choline Ratio

Optimal range: 2.6 - 7.7 Ratio

Betaine and choline can be obtained from the diet or synthesized de novo.

Betaine is derived from dietary choline – nuts, cauliflower and broccoli, beets, meats, and eggs.

Choline is a lipotrope, in that it helps to mobilize fat from the liver. Phosphatidylcholine, a derivative, is required for the production of hepatic very-low-density lipoprotein and the mobilization of fat from the liver. Therefore, choline deficiency can result in fatty liver and liver abnormalities.

Choline

Optimal range: 5.2 - 13 micromol/L

Choline is a nutrient that supports various bodily functions, including cellular growth and metabolism. The body makes some choline, but the majority comes from dietary sources.

Cyst(e)ine

Optimal range: 271 - 392 micromol/L

Cysteine is a nonessential sulfur-containing amino acid. It is obtained from the diet and is also endogenously made from cystathionine. Dietary cysteine sources include poultry, eggs, beef, and whole grains. [L]

Cystathionine

Optimal range: 74 - 369 nanomol/L

Because cystathionine is an intermediate of the transsulfuration pathway, elevation of this biomarker may indicate a backup of the transsulfuration pathway. Conversion of cystathionine to glutathione requires necessary cofactors, such as vitamin B6, zinc, glycine, and magnesium. Therefore, transient elevations of this metabolite may indicate increased need for these cofactors.

Dimethylglycine (DMG)

Optimal range: 1.6 - 5 micromol/L

The amino acid derivative dimethylglycine (DMG) is produced when betaine (trimethylglycine) donates a methyl group to homocysteine for re-methylation back to methionine. This methyl donation is mediated by the enzyme betaine homocysteine methyltransferase (BHMT). Elevations in DMG act as a negative feedback by inhibiting this enzymatic conversion. [L]

Glutathione

Optimal range: 669 - 5000 micromol/L

Glutathione (GSH) is a tripeptide comprised of three amino acids (cysteine, glycine, and glutamic acid). Glutathione is the body’s most potent intracellular antioxidant. It exists intracellularly in either an oxidized or reduced state.

GSH acts as an antioxidant, free radical scavenger, and detoxifying agent. Excessive formation of reactive oxygen species (ROS), including hydrogen peroxide (H2O2), is toxic to the cell. Hence, the metabolism of these free radicals are critical, and they are tightly controlled. [L]

Glycine

Optimal range: 181 - 440 micromol/L

Glycine is a nonessential amino acid with many important physiologic functions. It is one of three amino acids that make up glutathione. Glycine’s dietary sources include meat, fish, legumes, and gelatins.

Glycine is a major collagen and elastin component, which are the most abundant proteins in the body. Like taurine, it is an amino acid necessary for bile acid conjugation; therefore, it plays a key role in lipid digestion and absorption. [L] Glycine is the precursor to various important metabolites such as porphyrins, purines, heme, and creatine. It acts both as an inhibitory neurotransmitter in the CNS (via its interaction with strychnine-sensitive glycine receptors), and as an excitatory neurotransmitter on N-methyl-D-aspartate (NMDA) receptors. [L]

Homocysteine

Optimal range: 3.7 - 10.4 micromol/L

- Homocysteine is often used as an indicator of methylation status

- Clinicians aim for optimal: 2-10μmol/L

- Homocysteine must be recycled back into methionine

Met/Sulf Balance Ratio

Optimal range: 0.55 - 0.64 Ratio

This calculated ratio is called the ‘Met/Sulf Balance’ and it compares analytes between the methylation pathway and transsulfuration pathways.

Biomarker levels are compared proportionately allowing potential insight into which of the pathways is being favored.

The four analytes from the main methylation pathway that are used in the Met/Sulf Balance are SAM, SAH, methionine, and homocysteine. The four analytes from the transsulfuration pathway are cystathionine, cysteine, taurine, and glutathione.

Methionine

Optimal range: 23 - 38 micromol/L

Methionine is an essential amino acid that plays an important role in the methylation cycle.

Methylation Balance Ratio

Optimal range: 1.03 - 1.2 Ratio

Compares 8 different biomarkers
– 4 biomarkers with a methyl group to give
– 4 biomarkers that have had a methyl group removed

The clinical utility of the Methylation Balance Ratio is that it represents a potential way to detect subtle methylation imbalance prior to alterations in the SAM/SAH ratio.

Methylated Metabolites are:
- SAM
- Methionine
- Betaine
- Serine

Un-Methylated Metabolites are:
- SAH
- Homocysteine
- DMG
- Sarcosine

Methylation Index (SAM/SAH Ratio)

Optimal range: 2.2 - 6.4 micromol/L

S-adenosylhomocysteine (SAH)

Optimal range: 16 - 41 nanomol/L

S-adenosylhomocysteine (SAH) is the end-product of methylation reactions in the body. SAM ultimately donates a methyl group for methylation (DNA, detoxification, etc.) resulting in SAH formation. SAH is also the metabolic precursor of all the homocysteine (Hcy) produced in the body. In literature, SAH is sometimes referred to as AdoHcy.

S-adenosylmethionine (SAM)

Optimal range: 65 - 150 nanomol/L

- The methylation cycle is all about making sure there is adequate SAM (S-adenosylmethionine)

- SAM is overwhelmingly the body’s main methyl donor

- Think of SAM as the body’s methylation currency

- SAM can donate a methyl group wherever it is needed

Sarcosine

Optimal range: 3670 - 6743 nanomol/L

Serine

Optimal range: 91 - 161 micromol/L

Serine is a nonessential amino acid used in protein biosynthesis. In the folate cycle, glycine and serine are interconverted by the enzyme serine hydroxymethyltransferase (SHMT). Glycine accepts a methyl donor from 5-10 MTHF and becomes serine; therefore, serine is methylated glycine. [L] These methyltransferase reactions and interconversions are readily reversible depending on the needs of the folate cycle. [L]

Taurine

Optimal range: 50 - 139 micromol/L

Taurine differs from other amino acids because a sulfur group replaces the carboxyl group of what would be the non-essential amino acid, β-alanine. It takes part in biochemical reactions and is not fully incorporated into proteins. In most tissues, it remains a free amino acid. Taurine’s highest concentration is in muscle, platelets, and the central nervous system. Taurine is mainly obtained via dietary sources (dairy, shellfish, turkey, energy drinks), but can also come from sulfur amino acid metabolism (methionine and cysteine). [L], [L]