Intracellular S-Adenosylhomocysteine Concentrations Predict Global DNA Hypomethylation in Tissues of Methyl-Deficient Cystathionine β-Synthase Heterozygous Mice

Because S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are the substrate and product of essential methyltransferase reactions; the ratio of SAM:SAH is frequently used as an indicator of cellular methylation potential. However, it is not clear from the ratio whether substrate insufficien...

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Published in:The Journal of nutrition 2001-11, Vol.131 (11), p.2811-2818
Main Authors: Caudill, Marie A., Wang, Jennie C., Melnyk, Stepan, Pogribny, Igor P., Collins, Michael D., Santos-Guzman, Jesus, Swendseid, Marian E., Cogger, Edward A., James, S. Jill, Jernigan, Stefanie
Format: Article
Language:English
Subjects:
Analysis of Variance
Animals
Biological and medical sciences
biomarkers
Body Weight
brain
Brain - metabolism
correlation
cystathionine
cystathionine beta-synthase
Cystathionine beta-Synthase - genetics
Cystathionine beta-Synthase - metabolism
cystathionine β-synthase
Diet
DNA
DNA Methylation
Fundamental and applied biological sciences. Psychology
Genotype
homocysteine
Homocysteine - blood
Kidney - metabolism
kidneys
liver
Liver - metabolism
Metabolisms and neurohumoral controls
methylation
Mice
Nitrogen metabolism. Proteins. Glycoproteins. Nucleic acids. Collagen
S-adenosylhomocysteine
S-Adenosylhomocysteine - metabolism
S-adenosylmethionine
testes
Vertebrates: anatomy and physiology, studies on body, several organs or systems
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Summary:Because S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are the substrate and product of essential methyltransferase reactions; the ratio of SAM:SAH is frequently used as an indicator of cellular methylation potential. However, it is not clear from the ratio whether substrate insufficiency, product inhibition or both are required to negatively affect cellular methylation capacity. A combined genetic and dietary approach was used to modulate intracellular concentrations of SAM and SAH. Wild-type (WT) or heterozygous cystathionine β-synthase (CBS +/−) mice consumed a control or methyl-deficient diet for 24 wk. The independent and combined effect of genotype and diet on SAM, SAH and the SAM:SAH ratio were assessed in liver, kidney, brain and testes and were correlated with relative changes in tissue-specific global DNA methylation. The combined results from the different tissues indicated that a decrease in SAM alone was not sufficient to affect DNA methylation in this model, whereas an increase in SAH, either alone or associated with a decrease in SAM, was most consistently associated with DNA hypomethylation. A decrease in SAM:SAH ratio was predictive of reduced methylation capacity only when associated with an increase in SAH; a decrease in the SAM:SAH ratio due to SAM depletion alone was not sufficient to affect DNA methylation in this model. Plasma homocysteine levels were positively correlated with intracellular SAH levels in all tissues except kidney. These results support the possibility that plasma SAH concentrations may provide a sensitive biomarker for cellular methylation status.
ISSN:0022-3166
1541-6100
DOI:10.1093/jn/131.11.2811