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Deutsch (EUR)07. Epigenetics and DNA Methylation
07 · Epigenetics and DNA Methylation
DNA contains genetic information, but cells do not use it in the same way everywhere. Epigenetics explores mechanisms that regulate gene activity without changing the order of DNA letters. DNA methylation is one of these mechanisms.
What is epigenetics?
A liver cell and a nerve cell generally have the same genetic information but different roles. This difference is partly related to which genes they use. Chemical marks on DNA and on the proteins around which it is organised help regulate its accessibility. Some of these patterns are maintained when cells divide. [1]
A change in the DNA sequence itself. An MTHFR gene variant is one example.
A change affecting the regulation of genetic information without altering its sequence. A change in a methylation mark is one example.
DNA methylation and histone modifications
During DNA methylation, enzymes attach methyl groups to particular sites on DNA. Histones are proteins around which DNA is wrapped; chemical modifications to these proteins also influence chromatin organisation and gene activity. [1]
The meaning of a mark depends on its location and the cell type. The idea of universally “switching on good genes” is an oversimplification.
Methylation, folate, B12 and homocysteine
Methyl groups are also transferred in metabolic reactions that do not directly involve DNA. One related area is folate metabolism and the conversion of homocysteine to methionine. The term “methylation cycle” therefore does not mean the cell cycle or a test of the activity of all genes. [2, 3]
| Term | Role | What this does not establish |
|---|---|---|
| Folate and 5-MTHF | Folate participates in the transfer of one-carbon units; 5-MTHF is one of its forms. | Not everyone automatically needs methylfolate. |
| Vitamin B12 | It is a cofactor for methionine synthase, an enzyme involved in converting homocysteine to methionine. | The name methylcobalamin alone does not demonstrate cellular rejuvenation. |
| Choline and betaine (TMG) | Choline is a precursor of betaine, which can provide a methyl group in another pathway for converting homocysteine. | A higher intake of methyl donors is not a universal way to improve epigenetic regulation. |
| Homocysteine | A metabolite whose level is influenced by several factors, including the status of certain vitamins and kidney function. | Its level is not a direct measurement of DNA methylation. |
A nutrient's biochemical role and the effects of supplementing it are two different questions. For example, lowering homocysteine with vitamins does not, by itself, demonstrate a reduced risk of heart attack. [2–4]
MTHFR: a genetic variant is not automatically a diagnosis
The MTHFR gene provides instructions for an enzyme involved in folate metabolism. The common C677T and A1298C variants are often called “MTHFR mutations”, but they should not be equated with rare, severe disorders affecting this enzyme. [5]
According to the CDC, people with common MTHFR variants can also process folic acid. A result therefore does not mean an “inability to methylate” and is not, on its own, a reason to avoid folic acid. Fatigue or other nonspecific symptoms cannot be explained solely by such a result. [5]
Epigenetic clocks and biological age
Epigenetic clocks are computational models that use methylation patterns. Horvath's 2013 model estimated age using 353 DNA sites across different tissues. It is a scientific tool, rather than a direct reading of the “true age” of every organ. [6]
An MTHFR genetic test identifies a DNA sequence variant. An epigenetic test examines methylation marks. These are different tests, and their results are not interchangeable.
A lower number on an epigenetic clock does not, by itself, demonstrate a longer lifespan. It matters which model was used and whether changes in health outcomes were also demonstrated. [7]
What is being studied in diet and lifestyle research?
Researchers investigate links between epigenetic changes and nutrition, physical activity, stress and other environmental influences. However, an observed association does not necessarily establish a cause or the effectiveness of a particular intervention. [1]
An analysis of the randomised CALERIE trial found a small change in the DunedinPACE measure following two years of calorie restriction. No significant effect was found for the PhenoAge and GrimAge clocks. The authors emphasised the need for longer follow-up of health outcomes. This is neither evidence of universal “rejuvenation” nor a guide to starvation. [7]
Claims about inherited trauma also require care. The maintenance of patterns during cell division and their transmission between generations of people are not the same thing; the latter requires separate evidence.
Frequently asked questions
Does epigenetics change the DNA sequence itself?
Epigenetic mechanisms regulate how genetic information is used without changing the order of DNA letters. Genetic variants are a different type of change.
Does DNA methylation always switch a gene off?
It should not be understood as a universal off switch. Its significance depends on the location of the mark and the cellular context.
Does a common MTHFR variant mean I need methylfolate?
Not automatically. People with common variants can also process folic acid. The name of a variant alone does not determine an individual's needs.
Does an epigenetic test prove that a supplement extends life?
No. A change in a test result is a change in a biomarker. Demonstrating a longer lifespan or less disease requires appropriate clinical studies.
What should you remember?
Epigenetics helps explain gene regulation. DNA methylation, folate metabolism and MTHFR variants are related, but they are not identical. When assessing claims about biological age, distinguish the mechanism, the test result and the demonstrated health benefit.
Scientific and professional sources
- NHGRI: Epigenomics Fact Sheet.
- NIH ODS: Folate – Health Professional Fact Sheet.
- NIH ODS: Vitamin B12 – Health Professional Fact Sheet.
- NIH ODS: Choline – Health Professional Fact Sheet.
- CDC: MTHFR Gene Variant and Folic Acid Facts.
- Horvath (2013): DNA methylation age of human tissues and cell types.
- Waziry et al. (2023): analysis of DNA methylation in the CALERIE trial.
