Effects of the novel antidepressant S-adenosyl-methionine on alpha 1- and beta-adrenoceptors in rat brain

S-Adenosylmethionine (SAMe) for Neuropsychiatric Disorders: A Clinician-Oriented Review of Research

OBJECTIVE

A systematic review on S-adenosylmethionine (SAMe) for treatment of neuropsychiatric conditions and comorbid medical conditions.

DATA SOURCES

Searches were conducted in PubMed, EMBASE, PsycINFO, Cochrane Library, CINAHL, and Google Scholar databases between July 15, 2015, and September 28, 2016, by combining search terms for SAMe (s-adenosyl methionine or s-adenosyl-l-methionine) with terms for relevant disease states (major depressive disorder, MDD, depression, perinatal depression, human immunodeficiency virus, HIV, Parkinson's, Alzheimer's, dementia, anxiety, schizophrenia, psychotic, 22q11.2, substance abuse, fibromyalgia, osteoarthritis, hepatitis, or cirrhosis). Additional studies were identified from prior literature. Ongoing clinical trials were identified through clinical trial registries.

STUDY SELECTION

Of the 174 records retrieved, 21 were excluded, as they were not original investigations. An additional 21 records were excluded for falling outside the scope of this review. Of the 132 studies included in this review, 115 were clinical trials and 17 were preclinical studies.

DATA EXTRACTION

A wide range of studies was included in this review to capture information that would be of interest to psychiatrists in clinical practice.

RESULTS

This review of SAMe in the treatment of major depressive disorder found promising but limited evidence of efficacy and safety to support its use as a monotherapy and as an augmentation for other antidepressants. Additionally, preliminary evidence suggests that SAMe may ameliorate symptoms in certain neurocognitive, substance use, and psychotic disorders and comorbid medical conditions.

CONCLUSIONS

S-adenosylmethionine holds promise as a treatment for multiple neuropsychiatric conditions, but the body of evidence has limitations. The encouraging findings support further study of SAMe in both psychiatric and comorbid medical illnesses.

Double-blind, placebo-controlled pharmacodynamic studies with a nutraceutical and a pharmaceutical dose of ademetionine (SAMe) in elderly subjects, utilizing EEG mapping and psychometry

In a double-blind, placebo-controlled crossover study, the effects of S-adenosyl-l-methionine (SAMe) on brain function measures of 12 normal elderly volunteers (6 m/6 f, aged 57-73 years, mean: 61 years) were investigated by means of EEG mapping and psychometry. In random order, the subjects were orally administered a pharmaceutical dose of 1600 mg SAMe, a nutraceutical dose of 400 mg SAMe and placebo, each over a period of 15 days, with wash-out periods of 2 weeks in between. EEG recordings, psychometric tests and evaluations of tolerability and side effects were carried out 0, 1, 3 and 6 h after drug administration on days 1 and 15. Multivariate analysis based on MANOVA/Hotelling T2 tests of quantitative EEG data demonstrated significant central effects of SAMe as compared with placebo after acute, subacute and superimposed drug administration of both the nutraceutical and the pharmaceutical dose. EEG changes induced by SAMe were characterized by an increase in total power, a decrease in absolute and relative power in the delta/theta and slow alpha frequencies, an increase in absolute and relative power in the alpha-2 and beta frequencies as well as an acceleration of the alpha centroid and the centroid of the total power spectrum. The delta/theta and the beta centroid showed variable changes over time. The dominant alpha frequency was accelerated, the absolute and relative power in the dominant alpha frequency attenuated after SAMe as compared with placebo. These acute and subacute pharmaco-EEG findings in elderly subjects are typical of activating antidepressants. Time-efficacy calculations showed that acute oral administration of SAMe in both the nutraceutical and the pharmaceutical dose induced the pharmacodynamic peak effect in the first hour with a subsequent decline. The 3rd and 6th hours still showed a significant encephalotropic effect after the 1600 mg dose. The maximum EEG effect was noted after 2 weeks of oral administration of both 1600 mg/die and 400 mg/die. The superimposed dose induced significant encephalotropic effects in the 3rd hour after 400 mg and in the 3rd and 6th hours after 1600 mg as compared with pre-treatment. Dose-efficacy calculations showed that the pharmaceutical dose of 1600 mg had a more pronounced effect on the CNS than the nutraceutical dose of 400 mg, with both doses being superior to placebo. Psychometric tests concerning noopsychic and thymopsychic measures as well as critical flicker fusion frequency generally demonstrated a lack of differences between SAMe and placebo, which reflects a good tolerability of the drug in elderly subjects. This was corroborated by the findings on side effects, pulse and blood pressure.

Ademetionine (S-adenosylmethionine) neuropharmacology: implications for drug therapies in psychiatric and neurological disorders

Ademetionine (S-adenosylmethionine; SAMe) is a ubiquitous metabolite present in all cells and biological fluids, and serves as a methyl donor in a multitude of different methylation reactions involving proteins, phospholipids, catecholamines and DNA. Pharmaceutical preparations of some stable salts of SAMe are available for parenteral and oral use in humans, and have been shown to increase plasma and cerebrospinal fluid SAMe concentrations. In experimental studies administration of SAMe is associated with increases in brain monoamine neurotransmitters and b-adrenergic and muscarinic receptor functions. These neuropharmacological effects are postulated to be involved in the antidepressant activity of SAMe which has been confirmed in numerous controlled studies. Preliminary studies indicate that SAMe has therapeutic potential in the treatment of other CNS disorders including dementia, acquired immune deficiency syndrome (AIDS)-associated myelopathy, and brain ischaemia. This review will focus on recent experimental and clinical aspects of SAMe in the central nervous system, and the therapeutic use in psychiatric and neurological disorders.

Bioavailability and lack of toxicity of S-adenosyl-L-methionine (SAMe) in humans

STUDY OBJECTIVE

To determine if S-adenosyl-L-methionine (SAMe), a widely used dietary supplement with antidepressant properties, is significantly bioavailable, and whether toxic methylated compounds are produced with oral SAMe administration in humans. Serum homocysteine levels were also measured since alterations in these levels have been theorized in association with SAMe.

DESIGN

Unblinded pharmacokinetic trial.

SUBJECTS

Fifteen healthy volunteers.

SETTING

Clinical research unit in a psychiatric hospital.

INTERVENTION

Subjects received oral SAMe for 4 weeks; the dosage was titrated over 5 days to 1600 mg/day. Serum levels of SAMe, toxic methylated compounds (methanol, formaldehyde, and formic acid), and homocysteine were measured at baseline and at weeks 2 and 4. At baseline, a structured clinical interview for axis I disorders (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) was completed to assess for any undiagnosed psychiatric disorders. Mood was rated at baseline and at weeks 2 and 4 using the Zung Depression Rating Scale, Young Mania Rating Scale, Montgomery-Asberg Depression Rating Scale, Clinical Global Impression Scale, and the Global Assessment of Function Scale.

MEASUREMENTS AND MAIN RESULTS

After oral administration, SAMe levels were significantly elevated. Slight, likely insignificant, elevations in serum formaldehyde levels were detected in three subjects. No subject exhibited elevated homocysteine levels during SAMe treatment. One subject developed a transient mixed manic state with suicidal ideation within 2 weeks of starting SAMe; she recovered fully within 3 days of discontinuing the compound.

CONCLUSION

Oral dosages of 1600 mg/day of SAMe appear to be significantly bioavailable and nontoxic, at least regarding toxic methylated metabolites and homocysteine. However, the risk of mania in vulnerable individuals remains a serious concern.

E1 mice epilepsy shows genetic polymorphism for S-Adenosyl-L-homocysteine hydrolase

E1 mice are an animal model of human epilepsy (idiopathic complex partial seizures). We have previously demonstrated abrupt poly(A)(+) RNA expression in liver from 1-day-old E1 mouse [Mita et al., 1991. Devl. Brain Res. 64, 27-35]. In the present study, we constructed a cDNA library of the poly(A)(+) RNA. By analyzing cDNA clones and nucleotide sequences, we found a clone that was homologous to a rat gene of S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1.) (SAHH) (a key enzyme in the active methyl transfer pathway) and showed the gene polymorphism/RFLP(PstI) between the epileptic strain, E1, and the non-epileptic mother strain, ddY, as indicated in a gel electrophoresis by cleaving 2.6 kb with PstI into 1.9 kb and 0.7 kb fragment bands. F1(E1xddY) showed the heterozygosity. An attempt to determine the mutation on the genomic SAHH gene in the E1 disclosed a single nucleotide polymorphism indicated by a C-->T transition in the 8th intron, by which the PstI site was created. SAHH enzymatic activity in the liver in 1-day-old E1 mice was slight (approximately 10%), and in fact was significantly lower than that of the control ddY. Results suggested that the abrupt primary mRNA transcribed on the SAHH gene in the liver of 1-day-old E1 mice was processed partially or incompletely because of the presence of the point mutation in the intron. Accordingly, poor energy supply by the insufficient SAHH enzymatic activity in the brain postnatally may be responsible for epileptogenesis in this animal model. It is concluded that a single nucleotide SAHH gene polymorphism may be associated with epilepsy in E1 mice.

Homocystinuria and psychiatric disorder: a case report

Deficiency of cystathionine beta-synthase (CBS) is the commonest cause of primary homocystinuria. Homocysteine metabolism is intimately linked with the metabolism of folate, vitamin B12 (cobalamin) and pyridoxine. It is hypothesised that the pathogenesis of neuropsychiatric manifestations in homocystinuria, folate and cobalamin deficiencies are related to imbalance neurotransmitters in the CNS through disturbances in the pathways linking the metabolism of homocysteine and these vitamins. Although neuropsychiatric disorders are relatively common among patients with homocystinuria, it is not well recognised as the causative factor among patients presenting with neuropsychiatric disorders. A 31 year old woman presented with a three week history of delirium and inappropriate and labile affect. There was no history suggestive of drug or alcohol abuse, nutritional deficiency or organic disorders. EEG, cerebral CT, MRI and microbiological investigations did not reveal any organic causes. Because of a diagnosis of pyridoxine-responsive homocystinuria seven years previously, the possibility of homocystinuria was considered and investigated. Laboratory tests revealed macrocytosis and a high concentration of urinary total homocystine. Commencement of pyridoxine at 400 mg/day resulted in disappearance of homocystine in urine within four days with remarkable clinical improvement. Homocystinuria should be considered in the differential diagnosis of unexplained neuropsychiatric disorders in patients who have past or family history of homocystinuria, mental retardation, thromboembolic episodes, vascular diseases or clinical and laboratory features resembling folate and/or vitamin B12 deficiencies. Homocystinuria-associated neuropsychiatric disturbances can easily be treated with pyridoxine in 50% of cases.

Role of homocysteine in age-related vascular and non-vascular diseases

Homocysteine (Hcy) may represent a metabolic link in the pathogenesis of atherosclerotic vascular diseases and old-age dementias. Hyperhomocysteinemia is an independent risk factor for coronary artery disease and peripheral vascular disease, and is also associated with cerebrovascular disease; specifically, the risk of extracranial carotid atherosclerosis significantly increases in relation to Hcy levels. Hcy is a reliable marker of vitamin B12 deficiency, a common condition in the elderly which is known to induce neurological deficits including cognitive impairment; a high prevalence of folate deficiency has been reported in psychogeriatric patients suffering from depression and dementia. Both these vitamins occupy a key position in the remethylation and synthesis of S-adenosylmethionine (SAMe), a major methyl donor in CNS; therefore, deficiencies in either of these vitamins lead to a decrease in SAMe and increase in Hcy, which can be critical in the aging brain. Another pathogenetic mechanism linking high Hcy levels to reduced cognitive performances in the elderly might be represented by excitotoxicity, since hyperhomocysteinemia may lead to an excessive production of homocysteic acid and cysteine sulphinic acid, which act as endogenous agonists of NMDA receptors. Considering the reasonably high prevalence in the general population of a genetic predisposition to a thermolabile form of the enzyme 5,10-methylenetetrahydrofolate reductase (MTHFR), hyperhomocysteinemia can be seen as the result of multiple genetic and environmental factors leading to vascular and/or neurodegenerative disorders where age-related involutive phenomena represent a common pathogenetic ground. Systematic studies in different psychogeriatric conditions monitoring Hcy levels and clinical features before and after vitamin supplementation are therefore highly recommended.

Down-regulation of S-adenosylhomocysteine hydrolase in the active methyl transfer system in the brain of genetically epileptic El mice

To study the role of cerebral methylation in epileptogenesis, we investigated the active methyl transfer pathway in the brain of genetically epileptic El mice. We examined S-adenosylhomocysteine (AdoHcy) hydrolase activity (by high performance liquid chromatography), the corresponding mRNA levels (by competitive reverse transcription-polymerase chain reaction), as well as S-adenosylmethionine (AdoMet) and AdoHcy levels in epileptic El and non-epileptic control ddY mice. The level of AdoHcy, a potent feedback inhibitor in the methyl transfer system, was relatively high throughout growth, particularly in 15 week old El mice where it was increased approximately 20% compared to control ddY mice. AdoHcy hydrolase activity in the El mice brain did not increase during growth, which was confirmed by the finding that mRNA synthesis from the hydrolase gene behaved likewise. In contrast, ddY mice exhibited a gradual increase in the mRNA synthesis up to three fold and 20% increase in the enzyme activity at 15 weeks of age compared to those of El mice in which the seizure frequency was 100%. The levels of AdoMet, a versatile methyl donor, did not change throughout growth. We concluded that the down-regulation of AdoHcy hydrolase results in the accumulation of AdoHcy, possibly inducing an unstable state including seizures in the El mouse brain. El mice predisposed to epilepsy may be characterized by disordered feedback regulation of the AdoMet-dependent methyl transfer pathway.

Antidepressant treatment and chemical sympathectomy fail to modulate alpha 1-adrenoceptor sensitivity in mouse eye

The mydriatic response to alpha 1-adrenergic agonists was used as a functional index of postsynaptic alpha 1-adrenoceptors in mouse iris dilator muscle. Topical ocular application of methoxamine or phenylephrine caused dose-related mydriasis which was inhibited by pretreatment with prazosin or phentolamine. Chemical sympathectomy with topical 6-hydroxydopamine (6-OHDA) produced supersensitivity to phenylephrine but not methoxamine. Daily antidepressant treatment for 14 days with desipramine (10 mg/kg, i.p.), amitriptyline (10 mg/kg, i.p.), fluoxetine (2 mg/kg, i.p.), or moclobemide (40 mg/kg, i.p.) did not alter the response to methoxamine. Central alpha 1-adrenoceptors labelled with [3H]prazosin were similarly unaffected except for a modest downregulation produced by fluoxetine. These results demonstrate that postsynaptic alpha 1-adrenoceptors in mouse CNS and iris dilator muscle are refractory to manipulations known to alter their sensitivity in other tissues.

Has iprindole an alpha adrenergic activity?

1. Acute administration of iprindole potentiated the toxicity of 1-norepinephrine and increased the intensity of oxotremorine-induced tremors. 2. On the forced swimming test combination iprindole with imipramine reduced the duration of immobility. 3. The action of yohimbine on the locomotor activity was antagonized by a pre-injection of iprindole. 4. Iprindole increased and prolonged exophthalmia and loss of righting reflex induced by xylazine. 5 All these results seems indicate that iprindole has an indirect alpha 1 and alpha 2 adrenergic activity.

Efficacy of S-adenosyl-L-methionine in speeding the onset of action of imipramine

A double-blind clinical trial was carried out to evaluate the efficacy of S-adenosyl-L-methionine (SAMe) in speeding the onset of action of imipramine (IMI). SAMe is a naturally occurring substance that has been shown to possess antidepressant activity with a rapid mode of onset and minimal side effects. Sixty-three outpatients with moderate to severe depression were included in the study. After an initial 1-week placebo period, only 40 patients entered the active treatment phase. During the first 2 weeks of the trial, half of these patients received 200 mg/day of SAMe intramuscularly, while the other half received placebo. Simultaneously, oral IMI was administered to all patients at a fixed dose of 150 mg/day. The onset of clinical response was determined by evaluating patients every second day. By the end of week 2, the parenteral treatment was suppressed and IMI was adjusted according to individual needs. Depressive symptoms decreased earlier in the patients who were receiving the SAMe-IMI combination than in those who were receiving the placebo-IMI combination.

Antidepressant activity of S-adenosyl-L-methionine in mice and rats

S-Adenosyl-L-methionine (SAM), main methyl donor, was tested in mice and rats in several models which are predictive of possible antidepressant activity. In the forced swimming test in rats the effect of SAM was compared with that of the tricyclic antidepressant amitriptyline. SAM decreased dose-dependently immobility time in the forced swimming test in mice and rats, these effects being antagonized by haloperidol and prazosin (the latter only in rats). Locomotor or exploratory activity in mice and rats was not increased by SAM. D-Amphetamine-induced locomotor hyper-activity in rats was increased by repeated (14 days, twice daily) treatment with SAM. Behavioural stimulation induced by D-amphetamine or L-dopa (given with benserazide) in mice was not changed by a single dose of SAM. The drug reduced hypothermia induced by apomorphine in mice. Hypothermia induced by reserpine or clonidine in mice was not antagonized. SAM increased the amplitude of the acoustic startle reflex. The above results indicate that the psychopharmacological profile of SAM resembles that of antidepressants in only some tests. The mechanism by which SAM produces its antidepressant effect needs further investigation.