S-adenosylmethionine and S-adenosylhomocysteine in plasma and cerebrospinal fluid in Rett syndrome and the effect of folinic acid supplementation.

Rett syndrome is a neurodevelopmental disorder characterized by cognitive and locomotor regression and stereotypic hand movements. The disorder is caused by mutations in the X chromosomal MECP2 a gene encoding methyl CpG-binding protein. It has been associated with disturbances of cerebral folate homeostasis, as well as with speculations on a compromised DNA-methylation. Folinic acid is the stable form of folate. Its derived intermediate 5-MTHF supports the conversion of homocysteine to methionine, the precursor of S-adenosylmethionine (SAM). This in turn donates its methyl group to various acceptors, including DNA, thereby being converted to S-adenosylhomocysteine (SAH). The SAM/SAH ratio reflects the methylation potential. The goal of our study was to influence DNA methylation processes and ameliorate the clinical symptoms in Rett syndrome. Therefore we examined the hypothesis that folinic acid supplementation, besides increasing cerebrospinal fluid (CSF) 5-MTHF (p = 0.003), influences SAM and SAH and their ratio. In our randomized, double-blind crossover study on folinic acid supplementation, ten female Rett patients received both folinic acid and placebo for 1 year each. It was shown that both SAM and SAH levels in the CSF remained unchanged following folinic acid administration (p = 0.202 and p = 0.097, respectively) in spite of a rise of plasma SAM and SAH (p = 0.007; p = 0.009). There was no significant change in the SAM/SAH ratio either in plasma or CSF. The apparent inability of Rett patients to upregulate SAM and SAH levels in the CSF may contribute to the biochemical anomalies of the Rett syndrome. Our studies warrant further attempts to promote DNA methylation in the true region of interest, i.e. the brain.

Evidence for hypomethylation in two children with acute lymphoblastic leukemia and leukoencephalopathy.

BACKGROUND: The prognosis of patients with acute lymphoblastic leukemia (ALL) in childhood has improved with intensive chemotherapy. In particular, central nervous system (CNS) leukemia has been well controlled by the presymptomatic administration of intrathecal methotrexate (MTX), high dose systemic MTX, and irradiation. However, the prolonged intrathecal administration and/or the administration of high doses of systemic MTX, especially when combined with irradiation, can lead to leukoencephalopathy (LE), a serious CNS complication of such prophylaxis. Because the mechanisms by which MTX causes this complication have not been elucidated, the authors investigated the transmethylation status of the cerebrospinal fluid (CSF) in two children with ALL and LE to investigate the pathophysiology of that disorder. METHODS: The levels of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) were measured in the CSF of 2 children with ALL and LE, 7 children with ALL only who were undergoing presymptomatic administration of MTX, and 18 reference children in whom diagnostic lumbar puncture was indicated for other reasons. A sensitive, high performance liquid chromatography (HPLC) method was used with fluorescence detection. RESULTS: The concentrations of SAM in the CSF were lower in the patients with ALL during treatment with MTX compared with the reference children. The SAM levels in the 2 patients with both ALL and LE were slightly lower than the levels in the 7 patients with ALL only. The SAH concentrations in the CSF were higher in the patients with ALL and LE compared with the patients with ALL only and the reference children. The mean concentration of SAH in the CSF was similar in the reference children to that found in the 7 patients with ALL only. The SAM-to-SAH ratios were lower in the 2 patients with ALL and LE and in the 7 patients with ALL only compared with the reference children. The ratios in the patients with ALL and LE were still lower than in those with ALL only, thus providing supporting evidence of hypomethylation in the 2 patients with ALL and LE. CONCLUSIONS: The data suggest that the treatment of children with ALL using MTX causes subclinical hypomethylation and that progressive hypomethylation in the CNS, as evidenced in the 2 patients with ALL and LE, may be responsible for the demyelination in the LE induced by MTX.