Folate treatment and unbalanced methylation and changes of allelic expression induced by hyperhomocysteinaemia in patients with uraemia.
BACKGROUND
Hyperhomocysteinaemia occurs in several genetically determined and acquired disorders and is highly prevalent in patients with uraemia. In these disorders, homocysteine precursor S-adenosylhomocysteine, a powerful competitive inhibitor of S-adenosylmethionine-dependent methyltransferases, is increased, suggesting unbalanced methylation. We aimed to investigate whether DNA hypomethylation is present in patients with uraemia who also have hyperhomocysteinaemia and whether regulation of specific classes of genes, dependent on DNA methylation, is compromised.


METHODS
We selected men with hyperhomocysteinaemia and uraemia who were having standard haemodialysis treatment, and compared them with healthy male controls. We measured the homocysteine concentration from plasma samples and obtained DNA and RNA samples from peripheral mononuclear cells. DNA methylation was assessed by cytosine extension assay and by Southern blotting. Allelic expression of pseudoautosomal and imprinted genes was investigated by analysis of suitable restriction fragment length polymorphisms.


RESULTS
Total DNA hypomethylation was higher in patients than in controls (z score -4.593, p=0.0006) and allelic expression was changed in both sex-linked and imprinted genes. The shift from monoallelic to biallelic expression was dependent on homocysteine concentrations. Folate therapy, a common method to reduce hyperhomocysteinaemia, restored DNA methylation to normal levels and corrected the patterns of gene expression.


CONCLUSIONS
Our results suggest that hyperhomocysteinaemia affects epigenetic control of gene expression, which can be reverted by folate treatment. Our data support the hypothesis that the toxic action of homocysteine can be mediated by macromolecule hypomethylation.
Ingrosso
Diego
D
Department of Biochemistry and Biophysics F Cedrangolo, School of Medicine and Surgery, Second University of Naples, Naples, Italy. diego.ingrosso@unina2.it <diego.ingrosso@unina2.it>
Cimmino
Amelia
A
Perna
Alessandra F
AF
Masella
Lucia
L
De Santo
Natale G
NG
De Bonis
Maria Luigia
ML
Vacca
Marcella
M
D'Esposito
Maurizio
M
D'Urso
Michele
M
Galletti
Patrizia
P
Zappia
Vincenzo
V
D000328:Adult; D000368:Aged; D015897:Comorbidity; D019175:DNA Methylation / Q000187:drug effects*; D005492:Folic Acid / Q000627:therapeutic use*; D015870:Gene Expression / Q000187:drug effects; D006579:Heterozygote; D006801:Humans; D020138:Hyperhomocysteinemia / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D007962:Leukocytes / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D011110:Polymorphism, Genetic; D050683:R-SNARE Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics; D006435:Renal Dialysis; D012307:Risk Factors; D014511:Uremia / Q000150:complications*
C094335:H19 long non-coding RNA; D008565:Membrane Proteins; D050683:R-SNARE Proteins; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; C121241:VAMP7 protein, human; D007335:Insulin-Like Growth Factor II; D005492:Folic Acid