A radioenzymatic method for S-adenosyl-L-methionine determination in biological fluids

Wilson Disease: Epigenetic effects of choline supplementation on phenotype and clinical course in a mouse model

Wilson disease (WD), a genetic disorder affecting copper transport, is characterized by hepatic and neurological manifestations with variable and often unpredictable presentation. Global DNA methylation in liver was previously modified by dietary choline in tx-j mice, a spontaneous mutant model of WD. We therefore hypothesized that the WD phenotype and hepatic gene expression of tx-j offspring could be modified by maternal methyl supplementation during pregnancy. In an initial experiment, female tx-j mice or wild type mice were fed control or choline-supplemented diets 2 weeks prior to mating through embryonic day 17. Transcriptomic analysis (RNA-seq) on embryonic livers revealed tx-j-specific differences in genes related to oxidative phosphorylation, mitochondrial dysfunction, and the neurological disorders Huntington's disease and Alzheimer disease. Maternal choline supplementation restored the transcript levels of a subset of genes to wild type levels. In a separate experiment, a group of tx-j offspring continued to receive choline-supplemented or control diets, with or without the copper chelator penicillamine (PCA) for 12 weeks until 24 weeks of age. Combined choline supplementation and PCA treatment of 24-week-old tx-j mice was associated with increased liver transcript levels of methionine metabolism and oxidative phosphorylation-related genes. Sex differences in gene expression within each treatment group were also observed. These results demonstrate that the transcriptional changes in oxidative phosphorylation and methionine metabolism genes in WD that originate during fetal life are, in part, prevented by prenatal maternal choline supplementation, a finding with potential relevance to preventive treatments of WD.

Therapeutic use of cytoprotective agents in canine and feline hepatobiliary disease

Many medicinal, nutraceutical, and botanic extracts have been used as cytoprotective agents in liver disease. This article explains the mechanisms of action, pertinent pharmacokinetics, side effects, and clinical indications for the use of S-adenosylmethionine, N-acetylcysteine, ursodeoxycholic acid, silymarin, and vitamin E. The literature pertaining to in vitro studies, laboratory animal models, and human and veterinary clinical trials is reviewed with regards to the efficacy and use of these cytoprotective agents in hepatobiliary disease.

S-Adenosyl-L-methionine and alcoholic liver disease in animal models: implications for early intervention in human beings

In patients with severe alcoholic liver disease (i.e., cirrhosis), a deficiency of S-adenosylmethionine (SAMe) develops as a result of decreased SAMe synthetase activity. Whether a sizeable SAMe depletion occurs already at earlier stages of alcoholic liver disease has been the subject of debate. To address this issue, rats were fed alcohol (or isocaloric carbohydrate) in Lieber-DeCarli liquid diets containing adequate amounts of protein, vitamins, and lipotropic factors, including methionine. Alcohol feeding resulted in hepatic steatosis (without fibrosis) and unchanged SAMe synthetase activity, yet SAMe concentration was already greatly decreased. This most likely resulted from oxidative stress associated with the metabolism of alcohol and the induction of cytochrome P4502E1 (CYP2E1), which generates free radicals. Indeed, the decrease in hepatic SAMe correlated with parameters of oxidative stress, such as increased 4-hydroxynonenal (measured by gas chromatography-mass spectrometry) and diminished glutathione (GSH). Decreased GSH, occurring as a result of excessive GSH consumption caused by the oxidative stress, probably generated by enhanced utilization of SAMe, a precursor of GSH, thereby explaining the depletion of SAMe. In view of the known differences between rodents and primates in the metabolism of lipotropes, my colleagues and I have also studied the interaction between alcohol and SAMe in baboons and found again that, at early stages preceding the development of cirrhosis, there was already a significant lowering of hepatic SAMe concentration, associated with a striking oxidative stress documented by decreased levels and accelerated turnover of GSH. This was associated with increased lipid peroxidation and damage to cellular membranes, including those of the mitochondria, assessed by electron microscopy. Oral administration of SAMe resulted in its hepatic repletion with a corresponding attenuation of the ethanol-induced oxidative stress and liver injury, with significantly less GSH depletion, less increases in plasma aspartate aminotransferase (AST) levels, less leakage of mitochondrial glutamic dehydrogenase into the plasma, and fewer megamitochondria. In conclusion, (1) both in rodents and in non-human primates, significant SAMe depletion occurs already at early stages of alcoholic liver disease, despite the consumption of adequate diets; (2) the decreased hepatic SAMe concentration and the associated liver lesions, including mitochondrial injury, can be corrected with SAMe supplementation; and (3) accordingly, therapeutic administration of SAMe should be the subject of a comprehensive clinical trial to assess its capacity to attenuate early stages of alcoholic liver injury in human beings.

Catecholamines in patients with 22q11.2 deletion syndrome and the low-activity COMT polymorphism

OBJECTIVE

To investigate catecholamine phenotypes and the effects of a tyrosine hydroxylase inhibitor in individuals with the 22q11.2 deletion syndrome and low-activity catechol-O-methyltransferase (COMT).

BACKGROUND

Many persons with the 22q11.2 deletion syndrome suffer severe disability from a characteristic ultrarapid-cycling bipolar disorder and associated "affective storms." One etiologic hypothesis for this condition is that deletion of the COMT gene from one chromosome 22 results in increased catecholamine neurotransmission, particularly if the undeleted chromosome 22 encodes a variant of COMT with low activity.

METHODS

In a preliminary study, plasma, urine, and CSF catecholamines and catecholamine metabolites were measured in four teenage patients with a neuropsychiatric condition associated with 22q11.2 deletion and the low-activity COMT polymorphism on the nondeleted chromosome. In these four patients, and an additional institutionalized adult with the condition, an uncontrolled, open-label trial of metyrosine was administered in an attempt to lower catecholamine production and to alleviate symptoms.

RESULTS

Mild elevations of baseline CSF homovanillic acid (HVA) were found in three of four patients and a moderate reduction in CSF HVA after metyrosine treatment in the patient with the highest pretreatment concentration. The course of the five patients during the clinical trial is described.

CONCLUSIONS

In patients with the 22q11.2 deletion syndrome and low-activity COMT, controlled studies of pharmacologic agents that decrease catecholamine production, block presynaptic catecholamine storage, or enhance S-adenosylmethionine, the cosubstrate of COMT, are warranted.

ALCOHOL: its metabolism and interaction with nutrients

In the past, alcoholic liver disease was attributed exclusively to dietary deficiencies, but experimental and judicious clinical studies have now established alcohol's hepatotoxicity. Despite an adequate diet, it can contribute to the entire spectrum of liver diseases, mainly by generating oxidative stress through its microsomal metabolism via cytochrome P4502E1 (CYP2E1). It also interferes with nutrient activation, resulting in changes in nutritional requirements. This is exemplified by methionine, one of the essential amino acids for humans, which needs to be activated to S-adenosylmethionine (SAMe), a process impaired by liver disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. In baboons, SAMe attenuated mitochondrial lesions and replenished glutathione; it also significantly reduced mortality in patients with Child A or B cirrhosis. Similarly, decreased phosphatidylethanolamine methyltransferase activity is associated with alcoholic liver disease, resulting in phosphatidylcholine depletion and serious consequences for the integrity of membranes. This can be offset by polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines comprising dilinoleoylphosphatidylcholine (DLPC), which has high bioavailability. PPC (and DLPC) opposes major toxic effects of alcohol, with down-regulation of CYP2E1 and reduction of oxidative stress, deactivation of hepatic stellate cells, and increased collagenase activity, which in baboons, results in prevention of ethanol-induced septal fibrosis and cirrhosis. Corresponding clinical trials are ongoing.

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.

Alcoholic liver disease: new insights in pathogenesis lead to new treatments

Much progress has been made in the understanding of the pathogenesis of alcoholic liver disease, resulting in improvement of prevention and therapy, with promising prospects for even more effective treatments. The most successful approaches that one can expect to evolve are those that deal with the fundamental cellular disturbances resulting from excessive alcohol consumption. Two pathologic concepts are emerging as particularly useful therapeutically. Whereas it continues to be important to replenish nutritional deficiencies, when present, it is crucial to recognize that because of the alcohol-induced disease process, some of the nutritional requirements change. This is exemplified by methionine, which normally is one of the essential amino acids for humans, but needs to be activated to S-adenosylmethionine (SAMe), a process impaired by the disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. Indeed, SAMe was found to attenuate mitochondrial lesions in baboons, replenish glutathione, and significantly reduce mortality in patients with Child A or B cirrhosis. Similarly, polyenylphosphatidylcholine (PPC) corrects the ethanol-induced hepatic phospholipid depletion as well as the decreased phosphatidylethanolamine methyltransferase activity and opposes oxidative stress. It also deactivates hepatic stellate cells, whereas its dilinoleoyl species (DLPC) increases collagenase activity, resulting in prevention of ethanol-induced septal fibrosis and cirrhosis in the baboon. Clinical trials with PPC are ongoing in patients with alcoholic liver disease. Furthermore, enzymes useful for detoxification, such as CYP2E1, when excessively induced, become harmful and should be downregulated. PPC is one of the substances with anti-CYP2E1 properties that is now emerging. Another important aspect is the association of alcoholic liver disease with hepatitis C: a quarter of all patients with alcoholic liver disease also have markers of HCV infection, with an even higher incidence in some urban areas but, at present, no specific therapy is available since interferon is contraindicated in that population. However, in addition to antiviral medications, agents that oppose oxidative stress and fibrosis should also be tested for hepatitis C treatment since these two processes contribute much to the pathology and mortality associated with the virus. In addition to antioxidants (such as PPC, silymarin, alpha-tocopherol and selenium), anti-inflammatory medications (corticosteroids, colchicine, anticytokines) are also being tested as antifibrotics. Transplantation is now accepted treatment in alcoholics who have brought their alcoholism under control and who benefit from adequate social support but organ availability is still the major limiting factor and should be expanded more aggressively. Finally, abstinence from excessive drinking is always indicated; it is difficult to achieve but agents that oppose alcohol craving are becoming available and they should be used more extensively.

Measurement of plasma S-adenosylmethionine and S-adenosylhomocysteine as their fluorescent isoindoles

The low levels of S-adenosylmethionine (AdoMet) and S-adenosylhomocysteine (AdoHcy) in plasma can be measured by formation of the fluorescent isoindole derivatives of these compounds. The procedure involves an initial separation of AdoMet and AdoHcy in deproteinized plasma by HPLC on a C-8 column followed by derivatization with naphthalenedialdehyde and cyanide for 10 min at pH 9.0. The fluorescent derivatives of AdoMet and AdoHcy are then chromatographed by HPLC on a C-18 column monitored with a fluorescence monitor. The formation of the isoindole goes to 85% completion and the overall recovery of standards added to plasma is about 65%. Correction for recovery is made by addition of known quantities of AdoMet and AdoHcy to plasma. Normal values (+/- SE) for AdoMet were 102.7 nM +/- 9.9 and for AdoHcy were 22.7 +/- 3.1.

Detection and characterization of a protein isoaspartyl methyltransferase which becomes trapped in the extracellular space during blood vessel injury

Injury to rat blood vessels in vivo was found to release intracellular pools of protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT) into the extracellular milieu, where it becomes trapped. This trapped cohort of PIMT is able to utilize radiolabeled S-adenosyl-L-methionine (AdoMet) introduced into the circulation to methylate blood vessel proteins containing altered aspartyl residues. As further shown in this study, methylated substrates are detected only at the specific site of injury. In vitro studies more fully characterized this endogenous PIMT activity in thoracic aorta and inferior vena cava. Methylation kinetics, immunoblotting, and the lability of methylated substrates at mild alkaline pH were used to demonstrate that both types of blood vessel contain an endogenous protein D-aspartyl/L-isoaspartyl carboxyl methyltransferase (PIMT). At least 50% of the PIMT activity is resistant to nonionic detergent extraction, suggesting that the enzyme activity becomes trapped within or behind the extracellular matrix (ECM). Quantities of lactate dehydrogenase (LDH), another soluble enzyme of presumed intracellular origin, were found to be similarly trapped in the extracellular space of blood vessels.

Evidence for early oxidative stress in acute pancreatitis. Clues for correction

Pancreatic oxidative stress with depletion of pancreatic glutathione is an early feature in all tested models of acute pancreatitis, and sooner or later the problem extends to the lung, irrespective of disease severity, whether toward spontaneous recovery or death from multisystem organ failure. We, therefore, sought evidence of oxidative stress in the human disease by analyzing admission blood samples. We found it from high concentrations of oxidatively altered linoleic acid in serum and vitamin C in plasma (p < 0.001 vs controls or a group of other acute abdominal crises where the proportion of patients with admission Apache II scores < or > 8 was similar). These changes were accompanied by subnormal levels of ascorbic acid in plasma (p < 0.001); selenium (p < 0.001), beta-carotene (p < 0.001), and alpha-tocopherol in serum (p = 0.005 for its molar ratio to cholesterol). Paradoxically, the plasma concentration of S-adenosylmethionine was elevated (p = 0.02), suggesting that this proximate bioactive metabolite of the essential amino acid had backtracked because its intracellular metabolism down the methionine trans-sulfuration pathway toward glutathione synthesis was disrupted. The aberrations transcended putative etiological factor, duration of symptoms, or disease severity. We conclude: (1) that oxidative stress has pervaded the vascular compartment by the time of admission in patients with acute pancreatitis, and, (2) that blood micronutrient antioxidant profiles at this stage are consistent not only with compromised intracellular capacity to synthesize/refurbish glutathione, but also vulnerability of intra- and extracellular lipid targets.

S-adenosylmethionine levels in psychiatric and neurological disorders: a review

INTRODUCTION

S-adenosylmethionine (SAMe) is an important methyl donor in over 35 methylation reactions involving DNA, proteins, phospholipids and catechol- and indole- amines.

MATERIAL AND METHODS

This article reviews the studies that have examined brain and blood levels of SAMe in several psychological, neurological and metabolic disorders.

RESULTS

Although studies have found no consistent changes in whole blood SAMe levels in psychiatric patients, other investigators have found low cerebrospinal fluid (CSF) SAMe levels in patients with neurological disorders such as Alzheimer's dementia, subacute combined degeneration of the spinal cord (SACD), and HIV-related neuropathies, as well as in patients with metabolic disorders such as 5, 10-CH2-H4 folate reductase deficiency.

CONCLUSION

Intravenous or oral administration of SAMe thus represents a possible treatment for these neurological and metabolic disorders.

S-adenosylmethionine blood levels in major depression: changes with drug treatment

INTRODUCTION

The relationship between plasma levels of S-adenosylmethionine (SAMe), an endogenous methyl donor, and clinical response were studied in patients with a DSM-III-R diagnosis of major depression.

MATERIAL AND METHODS

A double-blind randomized protocol comparing oral SAMe with oral desipramine, involving a total of 26 patients, was employed.

RESULTS

At the end of the 4-week trial, 62% of the patients treated with SAMe and 50% of the patients treated with desipramine had significantly improved. Regardless of the type of treatment, patients with a 50% decrease in their Hamilton Depression Scale (HAM-D) score showed a significant increase in plasma SAMe concentration.

CONCLUSION

The significant correlation between plasma SAMe levels and the degree of clinical improvement in depressed patients regardless of the type of treatment suggests that SAMe may play an important role in regulating mood.

Uptake and metabolism of S-adenosyl-L-methionine by Leishmania mexicana and Leishmania braziliensis promastigotes

Promastigotes of Leishmania mexicana and Leishmania braziliensis incorporate S-adenosyl-L-[3H-methyl]methionine (AdoMet) against a concentration gradient through a saturable system. This concentrative uptake requires metabolic energy and is sensitive to temperature and sulfhydryl reagents such as N-ethyl maleimide. Intracellular AdoMet exchanges with external AdoMet. At steady state, unaltered ADoMet in the intracellular pool is at about a 1800-fold concentration in relation to that found in the external medium. Glucose, galactose and ribose did not stimulate uptake rates. Incorporated AdoMet goes into the soluble AdoMet pool, where a small fraction is metabolized, chiefly into methylthioadenosine, decarboxylated AdoMet and methanol. After a 60 min pulse the radioactivity associated with the [3H]AdoMet incorporated disappears with a half-time of 2 h. Transmethylation reactions were analyzed following [3H]AdoMet incorporation. Fractionation experiments indicate that 45-62% and 30-42% of the radioactivity is incorporated into lipids and protein methyl esters respectively, with 5-14% present in the soluble pool of parasites. Sinefungin or its cyclic derivative (1 and 10 micrograms ml-1) in the incubation medium produces 58% and 64% inhibition of AdoMet incorporation into Leishmania promastigotes. Most transmethylation reactions are inhibited, as there is a 50% decrease in the total radioactivity present in both the base-labile and lipidic fraction, with a parallel increase in the percentage of radioactivity in the soluble pool. Previous results give evidence of the importance of AdoMet in American Leishmania promastigote metabolism.

Antioxidant therapy for recurrent pancreatitis: biochemical profiles in a placebo-controlled trial

The usefulness of micronutrient antioxidant therapy for recurrent (non-gallstone) pancreatitis has recently been endorsed by a 20-week double-blind double-dummy cross-over trial in 20 patients. Treatment was delivered as two types of tablets, providing daily doses of 600 micrograms organic selenium, 9000 i.u. beta-carotene, 0.54 g vitamin C, 270 i.u. vitamin E and 2 g methionine. We report antioxidant profiles in blood samples collected before entry, at the cross-over stage and upon completion of trial. Baseline serum concentrations of selenium, beta-carotene and vitamin E in the patients were significantly lower than in healthy controls, were unaltered by placebo and normalized by active treatment, but reverted to basal values in the subgroup that received placebo subsequently. The baseline serum concentration of a free radical marker--the 9-cis, 11-trans isomer of linoleic acid--was significantly higher in the patients than in controls, fell inexplicably in the placebo phase and fell further upon active treatment. Discriminant analysis eliminated the overlap in free radical marker and selenium concentrations between control sera on the one hand and baseline or post-placebo samples from the patients on the other: antioxidant treatment normalized the relationship between these biochemical parameters. Subnormal baseline serum levels of S-adenosylmethionine drifted downwards upon active treatment whereas a sharp rise was noted when a relapse of pancreatitis occurred during the placebo phase. The results confirm that adequate exposure to antioxidants in the active treatment phase was associated with amelioration of oxidative stress, and that there was no residual effect 10 weeks after switching over to placebo treatment. Furthermore, the paradoxical behaviour of S-adenosylmethionine may imply that the beneficial effect of micronutrient antioxidants in recurrent pancreatitis is linked with preservation of the methionine trans-sulfuration pathway in pancreatic acinar cells.

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 Alzheimer's dementia suggesting a possible disturbance of methylation in such patients and the need for trials of SAM treatment.

Isocratic high performance liquid chromatographic analysis of S-adenosylmethionine and S-adenosylhomocysteine in animal tissues: the effect of exposure to nitrous oxide

A simple isocratic high performance liquid chromatographic method for the simultaneous measurement of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) in animal tissues is described. The direct injection of perchloric acid tissue extracts and rapid resolution of both compounds in a single run reduces any sampling and analytical errors in determining the SAM/SAH ratio, a measure of methylation reactions. The method has been used to determine changes in brain SAM/SAH ratios after exposure of rats to nitrous oxide.

S-adenosyl-L-methionine attenuates alcohol-induced liver injury in the baboon

Chronic ethanol consumption by baboons (50% of energy from a liquid diet) for 18 to 36 mo resulted in significant depletion of hepatic S-adenosyl-L-methionine concentration: 74.6 +/- 2.4 nmol/gm vs. 108.9 +/- 8.2 nmol/gm liver in controls (p less than 0.005). The depletion was corrected with S-adenosyl-L-methionine (0.4 mg/kcal) administration (102.1 +/- 15.4 nmol/gm after S-adenosyl-L-methionine-ethanol, with 121.4 +/- 11.9 nmol/gm in controls). Ethanol also induced a depletion of glutathione (2.63 +/- 0.13 mumol/gm after ethanol vs. 4.87 +/- 0.36 mumol/gm in controls) that was attenuated by S-adenosyl-L-methionine (3.89 +/- 0.51 mumol/gm in S-adenosyl-L-methionine-methanol vs. 5.22 +/- 0.53 mumol/gm in S-adenosyl-L-methionine controls). There was a significant correlation between hepatic S-adenosyl-L-methionine and glutathione level (r = 0.497; p less than 0.01). After the baboons received ethanol, we observed the expected increase in circulating levels of the mitochondrial enzyme glutamic dehydrogenase: 95.1 +/- 21.4 IU/L vs. 13.4 +/- 1.8 IU/L; p less than 0.001, whereas in a corresponding group of animals given S-adenosyl-L-methionine with ethanol, the values were only 30.3 +/- 7.1 IU/L (vs. 9.6 +/- 0.7 IU/L in the S-adenosyl-L-methionine controls). This attenuation by S-adenosyl-L-methionine of the ethanol-induced increase in plasma glutamic dehydrogenase (p less than 0.005) was associated with a decrease in the number of giant mitochondria (assessed in percutaneous liver biopsy specimens), with a corresponding change in the activity of succinate dehydrogenase, a mitochondrial marker enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

S-adenosyl-L-methionine. A review of its pharmacological properties and therapeutic potential in liver dysfunction and affective disorders in relation to its physiological role in cell metabolism

S-Adenosyl-L-methionine (SAMe) is a naturally occurring molecule distributed to virtually all body tissues and fluids. It is of fundamental importance in a number of biochemical reactions involving enzymatic transmethylation, contributing to the synthesis, activation and/or metabolism of such compounds as hormones, neurotransmitters, nucleic acids, proteins, phospholipids and certain drugs. The administration of a stable salt of SAMe, either orally or parenterally, has been shown to restore normal hepatic function in the presence of various chronic liver diseases (including alcoholic and non-alcoholic cirrhosis, oestrogen-induced and other forms of cholestasis), to prevent or reverse hepatotoxicity due to several drugs and chemicals such as alcohol, paracetamol (acetaminophen), steroids and lead, and to have antidepressant properties. In all of these studies SAMe has been very well tolerated, a finding of great potential benefit given the well-known adverse effects of tricyclic antidepressants with which it has been compared in a few trials. Thus, with its novel mechanisms of action and good tolerability, SAMe is an interesting new therapeutic agent in several diverse disease conditions, but its relative value remains to be determined in appropriate comparisons with other treatment modalities in current use.

A method for the measurement of S-adenosylmethionine in small volume samples of cerebrospinal fluid or brain using high-performance liquid chromatography-electrochemistry

A method for the measurement of S-adenosylmethionine in cerebrospinal fluid and brain using high-performance liquid chromatography with electrochemical detection is described. The method is based upon the catechol O-methyltransferase-catalyzed methylation of dihydroxybenzylamine to its 3- and 4-methoxy derivatives and measurement of the latter. Detection limits are 0.1 pmol for 3- and 4-methoxyhydroxybenzylamine, recovery is 100%, and variability is less than 8%. HPLC measurement of 3- and 4-methoxyhydroxybenzylamine is linear up to at least 100 pmol injected. The use of a nonbiological catechol in the assay minimizes interference from endogenous and exogenous catechols and the wide limits of linearity allows the assay of small volumes of cerebrospinal fluid or brain extract without further concentration or dilution.

Chromatographic and radioimmunological methods for the determination of 5'-deoxy-5'-methylthioadenosine in biological fluids

Two specific methods for the determination of 5'-deoxy-5'-methylthioadenosine (MTA) in biological samples have been developed. The chromatographic procedure requires a preliminary step on a phenylboronate column to remove non-cis-diol compounds. The sample is then analysed using a high-performance liquid chromatography system equipped with a reversed-phase column. 5'-Deoxy-5'-methyl-thio[2-3H]adenosine with high specific activity was synthesized and employed as an internal standard. An alternative radioimmunoassay (RIA) procedure has also been developed. The RIA method is based on competition between the unlabelled thio-ether and 3H-labelled MTA for the binding to a specific antiserum. Anti-MTA antibodies were obtained from rabbits immunized with the nucleoside covalently linked to carrier proteins. Both the chromatographic and RIA procedures gave identical results when employed to determine MTA in human urine.

Pharmacologic aspects of S-adenosylmethionine. Pharmacokinetics and pharmacodynamics

Several studies in animals have shown the efficacy of parenteral S-adenosylmethionine (SAMe) as an anti-inflammatory drug. In this article, data are reported on plasma kinetics, distribution, and metabolism of SAMe after oral administration since preference is given to oral dosage in the usual clinical practice. The results demonstrate the intestinal absorption of SAMe and its active metabolism. Experiments confirm the anti-inflammatory activity of the drug by the oral route. Results are also reported on the analgesic effect of SAMe.

Metabolism of S-adenosyl-L-methionine in intact human erythrocytes

Freshly isolated human erythrocytes contain S-adenosyl-L-methionine (AdoMet) at a concentration of about 3.5 mumol/l cells. When such cells are incubated in a medium containing 30 microM L-methionine, 18 mM D-glucose and 118 mM sodium phosphate (pH 7.4), intracellular AdoMet levels continuously decrease to a value of about 0.1 microM after 24 h. This occurs in spite of the fact that the cellular concentrations of the substrates for the AdoMet synthetase reaction, ATP and L-methionine, remain relatively constant. In a search for incubation conditions that lead to stable levels of AdoMet in incubated cells, we have developed a sodium-Hepes-buffered medium which includes 1 mM adenine and a stoichiometric excess of MgCl2 over its ligand, phosphate. The inclusion of magnesium ion (and a reduction in phosphate) appears to increase intracellular free Mg2+, which is required for full activity of the erythrocyte AdoMet synthetase. Even in the presence of MgCl2, however, the AdoMet pool level can drop 4-6-fold within the first 2 h of incubation. We present evidence that suggests that this initial fall in the cellular AdoMet level may be due to the activation of AdoMet-dependent protein carboxyl methyltransferase, an enzyme which accounts for a large fraction of the total cellular AdoMet utilization. Adenine, or related compounds in the medium may prevent this activation, although the mechanism of this action is not clear at present.

A sensitive high-performance liquid chromatographic procedure with fluorometric detection for the analysis of decarboxylated S-adenosylmethionine and analogs in urine samples

A highly sensitive HPLC method for the determination of decarboxylated S-adenosylmethionine (dc-SAM) by fluorometric detection was developed. The reaction of dc-SAM and its analogs with chloroacetaldehyde leads to the corresponding 1,N6-etheno derivatives. These highly fluorescent derivatives were fully characterized through their proton nuclear magnetic resonance spectra and/or mass spectra. This derivatization procedure has been applied to the analysis of dc-SAM in rat and human urine. After a simple cation exchange column prepurification, the urine extracts were derivatized with chloroacetaldehyde and analyzed by reversed-phase HPLC with fluorometric detection. The method allowed the determination of subpicomole amounts of dc-SAM and was shown to be highly reproducible with the use of decarboxylated S-adenosylethionine as internal standard. The application of the method to the analysis of urine of rats treated with MDL 72175, a potent ornithine decarboxylase inhibitor, showed that the dc-SAM levels increased in a dose-related fashion.