Lelland C. Tolbert

A preliminary trial of ascorbic acid as supplemental therapy for autism

1. This study presents the results of a 30-week double-blind, placebo-controlled trial exploring the effectiveness of ascorbic acid (8g/70kg/day) as a supplemental pharmacological treatment for autistic children in residential treatment. 2. Residential school children (N = 18) were randomly assigned to either ascorbate-ascorbate-placebo treatment order group or ascorbate-placebo-ascorbate treatment order group. Each treatment phase lasted 10 weeks and behaviors were rated weekly using the Ritvo-Freeman scale. 3. Significant group by phase interactions were found for total scores and also sensory motor scores indicating a reduction in symptom severity associated with the ascorbic acid treatment. 4. These results were consistent with a hypothesized dopaminergic mechanism of action of ascorbic acid.

Effect of ascorbic acid on neurochemical, behavioral, and physiological systems mediated by catecholamines.

Abstract Ascorbic acid, at concentrations below that normally present in the brain, inhibited the dopamine-sensitive adenylate cyclase in vitro . Ascorbate had no effect on the norepinephrine-sensitive adenylate cyclase. To study the in vivo effect of ascorbic acid on central dopaminergic systems, mice (C57 B1/6J) were injected with pharmacological doses (2 g/kg) of ascorbate, which produced a significant elevation in brain ascorbate concentration. Injecting the mice with ascorbate (2 g/kg) blocked the amphetamine-induced (15 mg/kg) increase in stereotype behavior which has been reported to be mediated by dopaminergic neural systems. Ascorbate had no effect on the amphetamine-induced locomotor activity thought to be mediated by norepinephrine systems. Ascorbate (1 g/kg) attenuated apmorphine-induced hypothermia in this same strain of mice. This demonstrates the specific neurochemical, physiological, and behavioral alterations in dopaminergic systems produced by ascorbic acid and suggests possible therapeutic uses for ascorbate in conditions involving functional dopamine excess.

Abnormalities of one-carbon metabolism in psychiatric disorders: Study of methionine adenosyltransferase kinetics and lipid composition of erythrocyte membranes

Two independent lines of inquiry have implicated some disturbance of one-carbon cycle metabolism in affective disorders. Folic acid deficiency commonly leads to depression, and S-adenosylmethionine has been reported to have antidepressant properties. Methionine adenosyltransferase has been reported to be underactive in depression and schizophrenia and overactive in mania. This study reports the effects on erythrocyte methionine adenosyltransferase (MAT) kinetics (Vmax) of a 2-week treatment in a population of patients housed on a psychiatric research ward. The drug-free schizophrenic patients and depressives had, upon admission, low Vmax values, and the drug-free manic patients had high Vmax values on admission. After 2 weeks of appropriate treatment, the values for all three patient samples showed significant normalization (i.e., the levels rose in schizophrenics and depressives and fell in manics). We have further shown that pretreatment low levels of erythrocyte membrane phosphatidylcholine in depressives and high levels in manics show statistically significant normalization following 2 weeks of pharmacotherapy. The significance of these results is discussed.

Stereospecific effects of ascorbic acid and analogues on D1 and D2 agonist binding

Ascorbic acid inhibited the specific binding of both the D1 agonist, [3H] SKF 38393, and the D2 agonist, [3H] N-0437 at physiologically relevant concentrations. This inhibition was both stereospecific and receptor selective. Using ligand concentrations approximating their KDs, the IC50s for ascorbate and two structural analogues, isoascorbate and D-glucoascorbate, were determined. The rank order of IC50s at both D1 and D2 were D-glucoascorbate greater than isoascorbate greater than ascorbate. However, the IC50 for each compound was greater at D1 than D2. Evaluation of the relationship between the IC50 for ascorbate and the ligand concentration using both the D1 and the D2 ligand yielded data inconsistent with competitive inhibition models. Preliminary experiments were conducted to evaluate the site and type of inhibition with results consistent with an allostearic effect at the level of the receptor.

Gas chromatographic/mass spectrometric evidence for the identification of 6,7-dihydroxy-1, 2,3,4-tetrahydroisoquinoline as a normal constituent of rat brain: Its quantification and comparison to rat whole brain levels of dopamine

Gas chromatographic/mass spectrometric data are presented which demonstrate the presence of 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (DHTIQ) as a normal constituent of rat brain. The level of DHTIQ was calculated to be 10.0 +/- 3.0 ng/g wet weight (+/- S.D., N = 9) of brain tissue while the level of dopamine (DA) was measured as 1.22 +/- 0.22 microg/g (N = 14). The ratio of DHTIQ:DA was thus observed to be approximately 1:100. The possible formation of DHTIQ in alcoholism and schizophrenia is discussed.

One-carbon metabolism disturbances in affective disorders: A preliminary report

Methionine adenosyltransferase (MAT) activity (Vmax) and the relative amount of phosphatidylcholine (% PC) were measured in erythrocytes of up to 30 DSM-III diagnosed manic, 17 unipolar depressed patients, and 28 normal controls. Manic subjects had significantly higher and depressed subjects significantly lower MAT Vmax than normals. The relative amount of PC was in the low range for the depressives, and in the high range for the manics. Depressive patients present, in these tests, similar abnormalities to those seen previously in schizophrenic patients. Clinical and diagnostic implications of these findings are discussed.

Increased Serotonin Receptor Density and Platelet GPIIb/IIIa Activation Among Smokers

This study sought to determine whether depressive symptoms and/or platelet serotonin receptor (5HT2A) density are associated with increased platelet activation (PA) found among smokers. Flow cytometric detection of PA was used to study 36 smokers and 16 nonsmokers, aged 18 to 48 years. Subjects were tested at baseline and after either smoking 2 cigarettes (smokers) or a similar resting interval (nonsmokers). Assessment of PA included both platelet secretion and fibrinogen receptor (GPIIb/IIIa) binding. Platelet 5HT2A receptor binding and saturation were tested using [3H]LSD, and depressive symptoms were measured using the Beck Depression Inventory. Platelet 5HT2A receptor density was increased among smokers versus nonsmokers (82.7+/-67.7 versus 40.0+/-20.2 fmol/mg protein; P<0.005), and there was a dose-dependent relationship between receptor density and packs/d among smokers. Baseline wound-induced GPIIb/IIIa binding at 1 minute and GPIIb/IIIa binding in response to collagen stimulation in vitro was increased among smokers (P<0.05); there were no changes in PA among smokers after smoking, and platelet secretion was not elevated among smokers. Depressive symptoms were associated with 5HT2A receptor density among nonsmokers (P<0.005), but no such relationship was evident among smokers; PA was unrelated to 5HT2A receptor density in either group. The findings indicate that smoking is associated with increased platelet serotonin receptor density and with increased GPIIb/IIIa receptor binding, although these 2 factors are not related to each other or to depressive symptoms among smokers. Serotonergic dysfunction may be an important factor in the development of cardiovascular disease among smokers.

Role of the One-Carbon Cycle in Neuropsychiatry

This paper reviews the work available to date suggesting that elements of the one-carbon cycle may be involved in psychiatric illnesses. Two enzymes of the one-carbon cycle (in erythrocytes) – methionine adenosyltransferase (MAT) and serine hydroxymethyltransferase (SHMT) – have been reported by our group to be underactive in schizophrenia and depression and overactive in mania. This correlates with the reported anti-depressant effects of S-adenosylmethionine in humans. SHMT has also been found by another group to be underactive in serum of schizophrenics. This defect appears to be linked to abnormalities in the distribution of phospholipids in the membrane, with a relative deficiency of phosphatidylcholine and a relative excess of phosphatidylserine. Evidence showing that medications do not appear to be responsible for these findings will be presented. A review is then made of the role of transmethylation systems for lipids and proteins in cellular control systems. Lipid transmethylation is related in many systems to receptor-final messenger coupling and so to information transfer across the membrane. Protein methylation is involved in many cellular systems including chemotaxis in bacteria and leucocytes, neurotransmitter release, sperm motility and calmodulin function.

The effect of toxin from Leiurus quinquestriatus scorpion venom on the polymerization and stability of microtubules

The venom of the scorpion Leiurus quinquestriatus, well-known for its actions on voltage-sensitive sodium channels, has now been shown to have pronounced effects on the in vitro polymerization and stability of neuronal microtubules purified by temperature-dependent cycles of assembly and disassembly. The crude venom, at concentrations as low as 100 micrograms/ml, alters both the extent of tubulin polymerization, as monitored by turbidity, and the appearance of polymerized material under electron microscopic examination. Structures formed in the presence of the venom retain the temperature sensitivity characteristic of normal microtubules, but respond to calcium ions abnormally with a dispersal of ordered structures, as reflected by both increased light scattering and electron microscopic analysis. Fractionation of the crude venom suggested that the active component was the same as the polypeptide neurotoxin which interacts with voltage-sensitive sodium channels and this identity was subsequently verified. Thus, the effect on microtubules of highly purified L. quinquestriatus sodium channel toxin obtained from an independent source was indistinguishable from that of the crude venom. These results indicate that the sodium channel toxin from L. quinquestriatus is also a potent cytoskeletal agent in vitro. This finding may be related to the growing body of evidence suggesting that the neuronal cytoskeleton plays a functional role in the maintenance of membrane excitability.

Temporal relationship between clinical changes and MAT changes following ECT

We report one-carbon metabolism changes in a depressed women whose treatment has consisted solely of electroconvulsive therapy (ECT) without concurrent use of antidepressant medication, lithium, or neuroleptics. Our MAT enzyme assay technique has been reproted previously (Morere et al 1986), and was carried out without knowledge of the patients identity or clinical status