Influence of vitamin B12 on brain methionine adenosyltransferase activity in senile dementia of the Alzheimer's type

Liver transplantation for treatment of severe S-adenosylhomocysteine hydrolase deficiency

A child with severe S-adenosylhomocysteine hydrolase (AHCY) deficiency (AHCY c.428A>G, p.Tyr143Cys; c.982T>G, p.Tyr328Asp) presented at 8 months of age with growth failure, microcephaly, global developmental delay, myopathy, hepatopathy, and factor VII deficiency. Plasma methionine, S-adenosylmethionine (AdoMet), and S-adenosylhomocysteine (AdoHcy) were markedly elevated and the molar concentration ratio of AdoMet:AdoHcy, believed to regulate a myriad of methyltransferase reactions, was 15% of the control mean. Dietary therapy failed to normalize biochemical markers or alter the AdoMet to AdoHcy molar concentration ratio. At 40 months of age, the proband received a liver segment from a healthy, unrelated living donor. Mean AdoHcy decreased 96% and the AdoMet:AdoHcy concentration ratio improved from 0.52±0.19 to 1.48±0.79 mol:mol (control 4.10±2.11 mol:mol). Blood methionine and AdoMet were normal and stable during 6 months of follow-up on an unrestricted diet. Average calculated tissue methyltransferase activity increased from 43±26% to 60±22%, accompanied by signs of increased transmethylation in vivo. Factor VII activity increased from 12% to 100%. During 6 postoperative months, head growth accelerated 4-fold and the patient made promising gains in gross motor, language, and social skills.

One-carbon metabolism and Alzheimer's disease: focus on epigenetics

Alzheimer’s disease (AD) represents the most common form of dementia in the elderly, characterized by progressive loss of memory and cognitive capacity severe enough to interfere with daily functioning and the quality of life. Rare, fully penetrant mutations in three genes (APP, PSEN1 and PSEN2) are responsible for familial forms of the disease. However, more than 90% of AD is sporadic, likely resulting from complex interactions between genetic and environmental factors. Increasing evidence supports a role for epigenetic modifications in AD pathogenesis. Folate metabolism, also known as one-carbon metabolism, is required for the production of S-adenosylmethionine (SAM), which is the major DNA methylating agent. AD individuals are characterized by decreased plasma folate values, as well as increased plasma homocysteine (Hcy) levels, and there is indication of impaired SAM levels in AD brains. Polymorphisms of genes participating in one-carbon metabolism have been associated with AD risk and/or with increased Hcy levels in AD individuals. Studies in rodents suggest that early life exposure to neurotoxicants or dietary restriction of folate and other B vitamins result in epigenetic modifications of AD related genes in the animal brains. Similarly, studies performed on human neuronal cell cultures revealed that folate and other B vitamins deprivation from the media resulted in epigenetic modification of the PSEN1 gene. There is also evidence of epigenetic modifications in the DNA extracted from blood and brains of AD subjects. Here I review one-carbon metabolism in AD, with emphasis on possible epigenetic consequences.

Subacute combined degeneration of the spinal cord in cblC disorder despite treatment with B12

Subacute combined degeneration (SCD) of the spinal cord is a characteristic complication of vitamin B12 deficiency, but it has never been neuropathologically demonstrated in a B12-inborn error of metabolism. In this report SCD is documented in a 15-year-old boy with early-onset cobalamin C (cblC) disorder. The neuropathologic findings included multifocal demyelination and vacuolation with predilection for the dorsal and lateral columns at the mid-thoracic level of the spinal cord, confirming the similarity of SCD in cblC disorder to the classic adult SCD due to vitamin B12 deficiency. SCD developed in this boy despite treatment for cblC disorder that began at 3 months of age. There is clinical and experimental evidence to suggest that a deficiency in remethylation with concomitant reduction in brain methionine may be the cause of SCD. In this patient plasma methionine levels were low without betaine and/or l-methionine supplementation and in the normal range for only a 2-year period during compliance with therapy. In cblC disorder, a consistent increase in blood methionine to high normal or above normal levels by the use of betaine and l-methionine supplementation may be helpful in preventing SCD. This is especially important now that the presymptomatic detection of cblC disorder is possible through the expansion of newborn screening.

Effect of an enriched drink on cognitive function in frail elderly persons

BACKGROUND

Many elderly persons report that they have difficulties learning new things and remembering names, plans, and conversations. Because decreased cognitive function in elderly persons is potentially related to their poor nutritional status, provision of essential nutrients may improve cognitive function. The authors wanted to determine whether consumption of an enriched drink, including moderate doses of all essential micronutrients, improves cognitive function in frail elderly persons.

METHODS

Frail, white adults (n=101) who were aged 65 years or older with a body mass index<or=25 kg/m2 were selected for this randomized, double-blind, placebo-controlled trial. They received either an enriched drink or a placebo product for 6 months. Before and after the intervention, participants' cognitive function was assessed (word learning test [WLT], WLT delayed, category fluency [CF] for animals and professions, and recognition memory test for words [RMTW]) and blood biochemical analyses (vitamin B12, homocysteine) were performed.

RESULTS

Sixty-seven residents completed the study period. After 6 months, significant differences were noted in changes of the WLT (0.9+/-0.3 vs -0.1+/-0.3; p=.014) and CF professions (1.2+/-0.7 vs -0.6+/-0.5; p=.017) in the supplement group (n=34) compared with the placebo group (n=33). No significant differences were observed in WLT delayed, RMTW, and CF animals. The plasma vitamin B12 concentration increased (105+/-50 vs 8 +/-16; p=.003) and the homocysteine concentration decreased (-6.3+/-5.9 vs -0.3+/-2.9; p=.000) in the supplement group compared with the placebo group.

CONCLUSIONS

This study contributes to the evidence that nutritional supplementation may improve neuropsychological performance in frail elderly persons.

Presenilin 1 gene silencing by S-adenosylmethionine: a treatment for Alzheimer disease?

Presenilin 1 (PS1) is a key factor for beta-amyloid (Ab) formation in Alzheimer disease (AD). Homocysteine accumulation, frequently observed in AD patients, may be a sign of a metabolic alteration in the S-adenosylmethionine (SAM) cycle, which generates the overexpression of genes controlled by methylation of their promoters, when the cytosine in CpG moieties becomes unmethylated. The methylation of a gene involved in the processing of amyloid precursor protein may prevent Ab formation by silencing the gene. Here we report that SAM administration, in human neuroblastoma SK-N-SH cell cultures, downregulates PS1 gene expression and Ab production.

Vitamin B12 deficiency in dementia and cognitive impairment: the effects of treatment on neuropsychological function

BACKGROUND

Vitamin B12 assay is part of the routine investigation of dementia, although few studies have investigated the effects of treatment on cognition. We examined the effects of B12 treatment on neuropsychological function and disease progression in patients presenting with dementia or cognitive impairment.

METHODS

From 1432 patients who were assessed at the Bristol Memory Disorders Clinic, 125 patients with low serum B12 were identified. Sixty-six patients presenting with dementia, and 22 with cognitive impairment were seen for a second assessment after treatment. Changes in neuropsychological test scores were compared with those of patients with normal serum B12, matched by age and diagnosis.

RESULTS

The majority of patients with low serum B12 had normal Hb and MCV values. We found no cases of reversible B12 deficiency dementia. The B12 treatment patients who presented with dementia showed no significant improvement, and no less deterioration, in their neuropsychological function than their matched group. However, a treatment effect was demonstrated among the patients presenting with cognitive impairment. These improved significantly compared to matched patients on the verbal fluency test (p<0.01).

CONCLUSION

All patients with cognitive impairment should be investigated for B12 deficiency. Vitamin B12 treatment may improve frontal lobe and language function in patients with cognitive impairment, but rarely reverses dementia.

Changes in uptake of vitamin B(12) and trace metals in brains of mice treated with clioquinol

Clioquinol is a hydroxyquinoline antibiotic that has been associated with severe side-effects in the CNS. The syndrome caused by clioquinol treatment, subacute myelo-optic neuropathy (SMON), is considered as one of the worst drug disasters of this century. The precise biochemical mechanism behind SMON is not fully understood. Clioquinol can form strong lipophilic chelates with divalent cations and therefore it has been speculated that the drug may disturb the retention of vitamin B(12) through chelation of Co(2+). In the present study, the tissue distribution and uptake capacity of [57Co]cyanocobalamin were estimated in mice treated with clioquinol or saline. The concentrations of some trace metals were also determined in brain tissue. Accumulation of vitamin B(12) in the brain and its concentration in blood were decreased by clioquinol treatment. The mean concentrations of several trace metals were also lowered in the brain while the concentration of cobalt in the brain was not affected, suggesting that clioquinol does not bind to the cobalt in vitamin B(12). Moreover, a significant decrease in the levels of S-adenosylmethionine (SAM) was observed in the brain after clioquinol treatment. This may be a consequence of decreased vitamin B(12) levels. From these results, it can be concluded that chronic treatment with clioquinol may alter the tissue homeostasis of vitamin B(12) in the brain.

Methionine adenosyltransferase activity in erythrocytes and spinal cord of patients with sporadic amyotrophic lateral sclerosis

The role of transmethylation mechanisms in the etiology of amyotrophic lateral sclerosis (ALS) is hitherto unexplored. The activity of L-methionine S-adenosyltransferase (MAT), a regulatory enzyme of S-adenosylmethionine biosynthesis, was investigated in erythrocytes of 21 patients with ALS, spinal cord specimens of 7 ALS patients, and matched controls. In ALS patients the activity of MAT in erythrocytes was sex-dependent. In comparison with controls, the male group presented a 33% higher V(max) (P < 0.05) and a 41% decrease in the affinity of MAT for methionine (K(m), P < 0.05). The type of ALS onset (limb or bulbar), age, or duration of the disease did not influence erythrocyte MAT activity. In the spinal cord, the activity of MAT was homogeneously distributed through dorsal horn, ventral horn, and white matter. Comparisons between data from controls and ALS patients and analysis of sex effect showed no significant differences. The kinetic difference of erythrocyte MAT in the male group of ALS patients might be interesting to explore since it is well known that there is a male predominance of 1.5 to 2. 5:1 in ALS.

Regulation of methionine adenosyltransferase catalytic activity and messenger RNA in SH-SY5Y human neuroblastoma cells

The human neuroblastoma cell line SH-SY5Y was used to study the regulation of methionine adenosyltransferase (MAT II; E.C.2.5.1.6.) catalytic activity and transcript levels in cells of neuronal origin. The cells were exposed for 24 hr to a medium containing different concentrations of methionine (MAT substrate) as well as medium deficient of methionine. Furthermore, cells were treated with hydroxycobalamin, SAM, and the competitive MAT inhibitor cycloleucine. The MAT catalytic activity was inversely correlated to methionine concentrations, e.g. MAT Vmax increased 2-fold in cells grown in methionine-deficient medium as compared with cells cultured under standard conditions. Interestingly, MAT Km also increased from 9.04 +/- 0.44 to 12.08 +/- 0.83 in the methionine-deficient medium. Hydroxycobalamin caused an increase in activity at 40 microM while a decrease was observed at higher concentrations (100, 200, and 400 microM). Cycloleucine caused a significant inhibition of MAT catalytic activity, i.e. the inhibition was approximately 50% in the presence of 4 mM cycloleucine. The relevance of these results for the understanding of observations on MAT catalytic activity in brains of patients with Alzheimer's disease is discussed.