Methylation status in healthy subjects with normal and high serum folate concentration.
OBJECTIVE
We assessed the impact of high serum folate concentration on erythrocyte S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) concentrations, SAM/SAH ratio, CpG methylation levels across the promoter region of the extracellular superoxide dismutase (ec-SOD) gene, and ec-SOD activity in healthy men.


METHODS
Serum folate levels were measured in 111 subjects who were categorized in quintiles according to their folate status. Subjects located at the lowest, middle, and upper quintiles were selected for assessment of SAM and SAH by high-performance liquid chromatography, C677T genotype of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, ec-SOD methylation of CpG sites in lymphocytes genomic DNA by bisulfate treatment, and ec-SOD activity by a chemical assay.


RESULTS
Sixteen subjects were in the lowest serum folate quintile (<23.6 nmol/L), 17 in the middle (>34-<42 nmol/L), and 14 in the highest (>45nmol/L). SAM concentration was higher in the upper than in the middle and lowest quintiles (5.57 +/- 1.58, 2.52 +/- 0.97, 2.29 +/- 1.2 micromol/L; P < 0.0001). SAH concentration was higher in the upper compared with the lowest quintile (0.76 +/- 0.24 versus 0.52 +/- 0.23 micromol/L, P < 0.001). There were no differences in the SAM/SAH ratio, ec-SOD activity, methylation status of CpG sites of the ec-SOD gene, and TMTHFR C677T genotype between groups.


CONCLUSIONS
Serum folate concentrations in the highest quintile among healthy humans are associated with increased erythrocyte SAM and SAH concentrations, but not with SAM/SAH ratio or with methylation levels of CpG sites across the promoter region of the ec-SOD gene. Further research is required to determine if these findings are beneficial or harmful.
Hirsch
Sandra
S
Aging and Chronic Diseases Laboratory, INTA, University of Chile, Santiago, Chile. shirsch@inta.cl
Ronco
Ana María
AM
Guerrero-Bosagna
Carlos
C
de la Maza
María Pía
MP
Leiva
Laura
L
Barrera
Gladys
G
Llanos
Miguel
M
Alliende
M Angelica
MA
Silva
Francisca
F
Bunout
Daniel
D
D000328:Adult; D000368:Aged; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005492:Folic Acid / Q000097:blood*; D005838:Genotype; D006801:Humans; D008297:Male; D008745:Methylation; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D009752:Nutritional Status; D012435:S-Adenosylhomocysteine / Q000097:blood*; D012436:S-Adenosylmethionine / Q000097:blood*; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D014803:Vitamin B Complex / Q000097:blood; D055815:Young Adult
D014803:Vitamin B Complex; D012436:S-Adenosylmethionine; D005492:Folic Acid; D012435:S-Adenosylhomocysteine; D013482:Superoxide Dismutase; D042965:Methylenetetrahydrofolate Reductase (NADPH2)