This 2021 cell study investigated a dietary supplement’s role in preventing nerve disease:

“A loss of epigenetic control has been implicated in development of neurodegenerative diseases. Previous studies have implicated aberrant DNA and histone methylation in multiple sclerosis (MS) disease pathogenesis.

We have previously reported that methyl donor betaine is depleted in MS and is linked to changes in histone H3 trimethylation (H3K4me3) in neurons. We have also shown that betaine increases histone methyltransferase activity by activating chromatin bound betaine homocysteine S-methyltransferase (BHMT).

A hallmark of MS is the death of oligodendrocytes, the cells responsible for wrapping axons in myelin in the central nervous system and maintaining a healthy sheath. In demyelinating diseases like MS, oligodendrocyte progenitor cells (OPCs) fail to differentiate and make more myelin, resulting in sclerotic lesions.

Promoting differentiation of OPCs and generation of myelin is of great interest as a novel MS therapy. Waves of gene regulation (repression and activation) need to occur to promote myelination.

This BHMT-betaine methylation pathway ensures availability of S-adenosylmethionine (SAM) for a variety of DNA and histone methylation processes. OPC survival and differentiation are dependent upon DNA and histone methylation, and both processes require SAM.

BHMT uses betaine to remethylate homocysteine to methionine. Betaine can be taken in through the diet or synthesized through the oxidation of choline in mitochondria.

We demonstrated that oligodendrocyte gene expression can be modulated by betaine supplementation through the BHMT-betaine methylation pathway. Our study suggests that dietary betaine supplementation may prove to be a therapeutic agent for MS and other demyelinating disorders.”

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0250486 “The BHMT-betaine methylation pathway epigenetically modulates oligodendrocyte maturation”

I started taking betaine 16 years ago. Didn’t know of these effects until reading this study.

Treating psychopathological symptoms will somehow resolve causes? had more on betaine (aka trimethyl glycine). Current dose is 1.5 grams twice daily.