Teodoro Bottiglieri

Homocysteine, folate, methylation, and monoamine metabolism in depression

OBJECTIVES Previous studies suggest that folate deficiency may occur in up to one third of patients with severe depression, and that treatment with the vitamin may enhance recovery of the mental state. There are, however, difficulties in interpreting serum and red cell folate assays in some patients, and it has been suggested that total plasma homocysteine is a more sensitive measure of functional folate (and vitamin B12) deficiency. Other studies suggest a link between folate deficiency and impaired metabolism of serotonin, dopamine, and noradrenaline (norepinephrine), which have been implicated in mood disorders. A study of homocysteine, folate, and monoamine metabolism has, therefore, been undertaken in patients with severe depression. METHODS In 46 inpatients with severe DSM III depression, blood counts, serum and red cell folate, serum vitamin B12, total plasma homocysteine, and, in 28 patients, CSF folate, S-adenosylmethionine, and the monoamine neurotransmitter metabolites 5HIAA, HVA, and MHPG were examined. Two control groups comprised 18 healthy volunteers and 20 patients with neurological disorders, the second group undergoing CSF examination for diagnostic purposes. RESULTS Twenty four depressed patients (52%) had raised total plasma homocysteine. Depressed patients with raised total plasma homocysteine had significant lowering of serum, red cell, and CSF folate, CSF S-adenosylmethionine and all three CSF monoamine metabolites. Total plasma homocysteine was significantly negatively correlated with red cell folate in depressed patients, but not controls. CONCLUSIONS Utilising total plasma homocysteine as a sensitive measure of functional folate deficiency, a biological subgroup of depression with folate deficiency, impaired methylation, and monoamine neurotransmitter metabolism has been identified. Detection of this subgroup, which will not be achieved by routine blood counts, is important in view of the potential benefit of vitamin replacement.

High-Dose B Vitamin Supplementation and Cognitive Decline in Alzheimer Disease: A Randomized Controlled Trial

CONTEXT Blood levels of homocysteine may be increased in Alzheimer disease (AD) and hyperhomocysteinemia may contribute to disease pathophysiology by vascular and direct neurotoxic mechanisms. Even in the absence of vitamin deficiency, homocysteine levels can be reduced by administration of high-dose supplements of folic acid and vitamins B(6) and B(12). Prior studies of B vitamins to reduce homocysteine in AD have not had sufficient size or duration to assess their effect on cognitive decline. OBJECTIVE To determine the efficacy and safety of B vitamin supplementation in the treatment of AD. DESIGN, SETTING, AND PATIENTS A multicenter, randomized, double-blind controlled clinical trial of high-dose folate, vitamin B(6), and vitamin B(12) supplementation in 409 (of 601 screened) individuals with mild to moderate AD (Mini-Mental State Examination scores between 14 and 26, inclusive) and normal folic acid, vitamin B(12), and homocysteine levels. The study was conducted between February 20, 2003, and December 15, 2006, at clinical research sites of the Alzheimer Disease Cooperative Study located throughout the United States. INTERVENTION Participants were randomly assigned to 2 groups of unequal size to increase enrollment (60% treated with high-dose supplements [5 mg/d of folate, 25 mg/d of vitamin B(6), 1 mg/d of vitamin B(12)] and 40% treated with identical placebo); duration of treatment was 18 months. MAIN OUTCOME MEASURE Change in the cognitive subscale of the Alzheimer Disease Assessment Scale (ADAS-cog). RESULTS A total of 340 participants (202 in active treatment group and 138 in placebo group) completed the trial while taking study medication. Although the vitamin supplement regimen was effective in reducing homocysteine levels (mean [SD], -2.42 [3.35] in active treatment group vs -0.86 [2.59] in placebo group; P < .001), it had no beneficial effect on the primary cognitive measure, rate of change in ADAS-cog score during 18 months (0.372 points per month for placebo group vs 0.401 points per month for active treatment group, P = .52; 95% confidence interval of rate difference, -0.06 to 0.12; based on the intention-to-treat generalized estimating equations model), or on any secondary measures. A higher quantity of adverse events involving depression was observed in the group treated with vitamin supplements. CONCLUSION This regimen of high-dose B vitamin supplements does not slow cognitive decline in individuals with mild to moderate AD. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00056225.

Plasma β-amyloid and white matter lesions in AD, MCI, and cerebral amyloid angiopathy

Background: Microvascular brain injury, typically measured by extent of white matter hyperintensity (WMH) on MRI, is an important contributor to cognitive impairment in the elderly. Recent studies suggest a role for circulating β-amyloid peptide in microvascular dysfunction and white matter disease. Methods: The authors performed a cross-sectional study of clinical, biochemical, and genetic factors associated with WMH in 54 subjects with Alzheimer disease (AD) or mild cognitive impairment (AD/MCI) and an independent group of 42 subjects with cerebral amyloid angiopathy (CAA). Extent of WMH was determined by computer-assisted volumetric measurement normalized to intracranial size (nWMH). Biochemical measurements included plasma concentrations of the 40- and 42-amino acid species of β-amyloid (Aβ40 and Aβ42) detected by specific enzyme-linked immunosorbent assays. Results: Plasma Aβ40 concentrations were associated with nWMH in both groups (correlation coefficient = 0.48 in AD/MCI, 0.42 in CAA, p ≤ 0.005). Plasma Aβ40 remained independently associated with nWMH after adjustment for potential confounders among age, hypertension, diabetes, homocysteine, creatinine, folate, vitamin B12, and APOE genotype. The presence of lacunar infarctions was also associated with increased Aβ40 in both groups. nWMH was greater in CAA (19.8 cm3) than AD (11.1 cm3) or MCI (10.0 cm3; p < 0.05 for both comparisons). Conclusions: Plasma β-amyloid 40 concentration is independently associated with extent of white matter hyperintensity in subjects with Alzheimer disease, mild cognitive impairment, or cerebral amyloid angiopathy. If confirmed in longitudinal studies, these data would suggest circulating β-amyloid peptide as a novel biomarker or risk factor for microvascular damage in these common diseases of the elderly.

Gaba, γ-hydroxybutyric acid, and neurological disease

γ‐Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. GABA is converted from glutamic acid by the action of glutamic acid decarboxylase (GAD) of which two isoforms exist GAD65 and GAD67. GABA then is broken down, both within the cell and in the synaptic cleft by GABA transaminase to form succinic semialdehyde. In turn, succinic semialdehyde is converted either to succinic acid by succinic semialdehyde dehydrogenase or into γ‐hydroxybutyric acid (GHB) by succinic semialdehyde reductase. Because GABA modulates the majority of inhibition that is ongoing in the brain, perturbations in GABAergic inhibition have the potential to result in seizures. Therefore, the most common disorder in which GABA is targeted as a treatment is epilepsy. However, other disorders such as psychiatric disease, spasticity, and stiff‐person syndrome all have been related to disorders of GABAergic function in the brain. This review covers the roles of GABAergic neurotransmission in epilepsy, anxiety disorders, schizophrenia, stiff‐person syndrome, and premenstrual dysphoric disorder. In the final section of this review, the GABA metabolite GHB is discussed in terms of its physiological significance and its role in epilepsy, sleep disorders, drug and alcohol addiction, and an inborn error of GABA metabolism, succinic semialdehyde dehydrogenase deficiency. Ann Neurol 2003;54 (suppl 6):S3–S12

Cerebrospinal fluid S-adenosylmethionine in depression and dementia: effects of treatment with parenteral and oral S-adenosylmethionine.

Cerebrospinal fluid (CSF) S-adenosylmethionine (SAM) levels were significantly lower in severely depressed patients than in a neurological control group. The administration of SAM either intravenously or orally is associated with a significant rise of CSF SAM, indicating that it crosses the blood-brain barrier in humans. These observations provide a rational basis for the antidepressant effect of SAM, which has been confirmed in several countries. CSF SAM levels were low in a group of patients with Alzheimers dementia suggesting a possible disturbance of methylation in such patients and the need for trials of SAM treatment.

Homocysteine and folate metabolism in depression.

Homocysteine is a sensitive marker of folate and vitamin B12 deficiency. Numerous studies have confirmed the association between folate deficiency and depression. It is not completely understood whether homocysteine is solely a marker for folate deficiency or if it may play a more direct role in the expression of mood disorders. This review describes the biochemical, neurochemical and clinical correlations of folate deficiency and hyperhomocysteinemia in relation to depression.

Protein Phosphatase 2A Methyltransferase Links Homocysteine Metabolism with Tau and Amyloid Precursor Protein Regulation

Alzheimers disease (AD) neuropathology is characterized by the accumulation of phosphorylated tau and amyloid-β peptides derived from the amyloid precursor protein (APP). Elevated blood levels of homocysteine are a significant risk factor for many age-related diseases, including AD. Impaired homocysteine metabolism favors the formation of S-adenosylhomocysteine, leading to inhibition of methyltransferase-dependent reactions. Here, we show that incubation of neuroblastoma cells with S-adenosylhomocysteine results in reduced methylation of protein phosphatase 2A (PP2A), a major brain Ser/Thr phosphatase, most likely by inhibiting PP2A methyltransferase (PPMT). PP2A methylation levels are also decreased after ectopic expression of PP2A methylesterase in Neuro-2a (N2a) cells. Reduced PP2A methylation promotes the downregulation of Bα-containing holoenzymes, thereby affecting PP2A substrate specificity. It is associated with the accumulation of both phosphorylated tau and APP isoforms and increased secretion of β-secretase-cleaved APP fragments and amyloid-β peptides. Conversely, incubation of N2a cells with S-adenosylmethionine and expression of PPMT enhance PP2A methylation. This leads to the accumulation of dephosphorylated tau and APP species and increased secretion of neuroprotective α-secretase-cleaved APP fragments. Remarkably, hyperhomocysteinemia induced in wild-type and cystathionine-β-synthase +/− mice by feeding a high-methionine, low-folate diet is associated with increased brain S-adenosylhomocysteine levels, PPMT downregulation, reduced PP2A methylation levels, and tau and APP phosphorylation. We reported previously that downregulation of neuronal PPMT and PP2A methylation occur in affected brain regions from AD patients. The link between homocysteine, PPMT, PP2A methylation, and key CNS proteins involved in AD pathogenesis provides new mechanistic insights into this disorder.

The Clinical Potential of Ademetionine (S-Adenosylmethionine) in Neurological Disorders

SummaryThis review focuses on the biochemical and clinical aspects of methylation in neuropsychiatrie disorders and the clinical potential of their treatment with ademetionine (S-adenosylmethionine; SAMe). SAMe is required in numerous transmethylation reactions involving nucleic acids, proteins, phospholipids, amines and other neurotransmitters. The synthesis of SAMe is intimately linked with folate and vitamin B12 (cyanocobalamin) metabolism, and deficiencies of both these vitamins have been found to reduce CNS SAMe concentrations. Both folate and vitamin B12 deficiency may cause similar neurological and psychiatric disturbances including depression, dementia, myelopathy and peripheral neuropathy. SAMe has a variety of pharmacological effects in the CNS, especially on monoamine neurotransmitter metabolism and receptor systems. SAMe has antidepressant properties, and preliminary studies indicate that it may improve cognitive function in patients with dementia. Treatment with methyl donors (betaine, methionine and SAMe) is associated with remyelination in patients with inborn errors of folate and C-l (one-carbon) metabolism. These studies support a current theory that impaired methylation may occur by different mechanisms in several neurological and psychiatric disorders.

Cerebral Vascular Dysfunction Mediated by Superoxide in Hyperhomocysteinemic Mice

Background and Purpose— Hyperhomocysteinemia is an emerging risk factor for stroke, but little is known about effects of hyperhomocysteinemia on cerebral vascular function. We tested the hypothesis that chronic hyperhomocysteinemia in mice causes endothelial dysfunction in cerebral arterioles through a mechanism that involves superoxide. Methods— Mice heterozygous for a targeted disruption of the cystathionine β-synthase gene (Cbs +/−) and their wild type littermates (Cbs +/+) were fed either a control diet or a high-methionine diet for 10 to 12 months. Results— Plasma total homocysteine was elevated with the high-methionine diet compared with the control diet for both Cbs +/+ (7.9±1.0 versus 5.0±0.5 μmol/L; P <0.05) and Cbs +/− (20.5±3.1 versus 8.2±0.9 μmol/L; P <0.001) mice. Dilatation of cerebral arterioles (≈30 μm baseline diameter) was measured in vivo in response to the endothelium-dependent dilator acetylcholine or the endothelium-independent dilator nitroprusside. Vasodilatation to acetylcholine was impaired with the high-methionine diet compared with the control diet for both Cbs +/+ and Cbs +/− mice (P <0.01). Dilatation of arterioles to acetylcholine was restored toward normal by the superoxide scavenger tiron (P <0.05). Vasodilatation to nitroprusside was not influenced by Cbs genotype or diet. Dihydroethidium (DHE) staining for vascular superoxide was elevated in Cbs +/− mice fed the high-methionine diet and was inhibited by apocynin or Nω-nitro-l-arginine methyl ester, implicating NAD(P)H oxidase and nitric oxide synthase as potential sources of superoxide. Conclusions— Superoxide is a key mediator of endothelial dysfunction in the cerebral circulation during diet-induced hyperhomocysteinemia.

Pharmacologic rescue of lethal seizures in mice deficient in succinate semialdehyde dehydrogenase

Succinate semialdehyde dehydrogenase (ALDH5A1, encoding SSADH deficiency is a defect of 4-aminobutyric acid (GABA) degradation that manifests in humans as 4-hydroxybutyric (gamma-hydroxybutyric, GHB) aciduria. It is characterized by a non-specific neurological disorder including psychomotor retardation, language delay, seizures, hypotonia and ataxia. The current therapy, vigabatrin (VGB), is not uniformly successful. Here we report the development of Aldh5a1-deficient mice. At postnatal day 16–22 Aldh5a1−/− mice display ataxia and develop generalized seizures leading to rapid death. We observed increased amounts of GHB and total GABA in urine, brain and liver homogenates and detected significant gliosis in the hippocampus of Aldh5a1−/− mice. We found therapeutic intervention with phenobarbital or phenytoin ineffective, whereas intervention with vigabatrin or the GABAB receptor antagonist CGP 35348 (ref. 2) prevented tonic-clonic convulsions and significantly enhanced survival of the mutant mice. Because neurologic deterioration coincided with weaning, we hypothesized the presence of a protective compound in breast milk. Indeed, treatment of mutant mice with the amino acid taurine rescued Aldh5a1−/− mice. These findings provide insight into pathomechanisms and may have therapeutic relevance for the human SSADH deficiency disease and GHB overdose and toxicity.