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

alpha 1- and beta-adrenoceptors were studied ex vivo in the brains of rats receiving repeated daily treatment with the standard antidepressant imipramine or the atypical antidepressant S-adenosyl-L-methionine (SAM), which has minimal effects on monoamine reuptake or turnover. Consistent with past studies, a decrease in the density of beta receptors at three weeks and an increase in the affinity of alpha 1 receptors for the agonist phenylephrine at one week of treatment was observed with imipramine. By comparison, an increase in the density of beta receptors and a decrease in the affinity of alpha 1 receptors for phenylephrine was observed at one week of treatment with SAM. These changes were no longer apparent at three weeks of treatment. The results suggest that treatment with SAM does lead to changes in adrenergic neurotransmission, but that down regulation of beta receptors or increased agonist affinity of alpha 1 receptors may not be necessary for the production of antidepressant effects.

Reproductive toxicity studies of ademetionine.

S-Adenosyl-L-methionine sulphate-p-toluene sulphonate (ademetionine, SAMe), a donor of methyl groups, was examined for effects upon embryofoetal toxicity following both premating treatment and treatment during pregnancy and for peri- and post-natal toxicity in the rat at dosages of 0, 100, 200 and 400 mg/kg/d SAMe ion by subcutaneous or intravenous administration. Embryofoetal toxicity was also examined in the New Zealand White rabbit at dosages of 0, 10, 20 and 40 mg/kg/d SAMe by intravenous administration. Treatment was considered to be without adverse effect upon any of the reproductive parameters examined on either F0 or on the untreated F1 generations. There was no indication that treatment adversely affected the litter parameters including the incidences of malformations, anomalies and skeletal variants. Some slight changes in the activity of the F1 females derived from F0 animals given 400 mg/kg/d were considered to be of minimal importance. In contrast to the above, adverse effects upon the parents were noted at 400 mg/kg/d including local tissue reaction at the injection sites and retardation of body weight gain. In the intravenous studies some rigidity and dyspnoea were noted following administration. Following subcutaneous premating treatment there was also evidence of histopathological change to the kidney of the female rat. Increased water consumption was noted in this latter study and amongst females rearing offspring in the embryo foetal toxicity study in which the compound was administered intravenously. At the lower dosages administered to the rat some local tissue reaction was evident as was some retardation of body weight gain, minimal at the lowest intravenous dose.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Lack of mutagenic activity of ademetionine in vitro and in vivo.

Studies on the mutagenic activity of ademetionine (S-adenosylmethionine) tested in vitro at concentrations of 2 mg/sample and in vivo at doses up to 1500 mg/kg always gave negative responses. Moreover, a patent lack of abnormal methylated bases in the liver DNA of ademetionine-treated rats suggests that, if abnormal methylation occurs by exogenously administered ademetionine, the amount of formed methylated residues must be quite lower than that removable by the transmethylase enzymes responsible for the in vivo repair.

Biochemical and behavioural indices of striatal dopaminergic activity after 6-methyltetrahydropterin.

The biochemical effects of 6-methyltetrahydropterin (6-MPH4), a synthetic analogue of tetrahydrobiopterin (BH4), the hydroxylase cofactor, were investigated on striatal dopaminergic neurons in the rat. Although a single parenteral dose of 6-MPH4 (18 or 54 mg/kg) did not significantly increase the content of dopamine (DA) or its acidic metabolites, L-didrohyphenylanine (L-DOPA) accumulation after decarboxylase inhibition was evident in rats receiving 54 mg/kg of 6-MPH4. On the other hand, 6-MPH4 (18 mg/kg) potentiated the reserpine-induced DA metabolism as demonstrated by increased HVA levels. In a behavioural test, 6-MPH4 partially prevented haloperidol-induced catalepsy. BH4 concentrations could thus be subsaturating with respect to tyrosine hydroxylase (TH), particularly when the enzyme activity is stimulated and the results suggest that cofactor supply may have pharmacological significance.

Effect of the variations of S-adenosyl-L-methionine liver content on fat accumulation and ethanol metabolism in ethanol-intoxicated rats.

The protective effect of S-adenosyl-L-methionine against rat liver steatosis induced by chronic ethanol ingestion was investigated. S-Adenosyl-L-methionine given during ethanol treatment prevented steatosis and accelerated recovery from steatosis when given after ethanol withdrawal. It also caused a slight inhibition of blood ethanol consumption in both acutely and chronically intoxicated rats. About 30% inhibition of alcohol dehydrogenase, but not of the microsomal ethanol oxidation system, occurred in rats subjected to acute ethanol toxicity as well as in normal rats as a consequence of S-adenosyl-L-methionine treatment. A comparison between S-adenosyl-L-methionine and pyrazole, as concerns inhibition of ethanol oxidation and fat accumulation, revealed that a greater inhibition of ethanol metabolism by pyrazole was associated with incomplete prevention of steatosis, while a lower inhibition by S-adenosyl-L-methionine was coupled to a complete prevention. Ethanol induced a drastic decrease of reduced glutathione liver content as well as 630 and 133% increases of blood and liver acetaldehyde contents, respectively. S-Adenosyl-L-methionine treatment almost completely reconstituted the liver reduced glutathione pool and caused a large decrease of the liver and blood acetaldehyde contents. 1-Chloro-2,4-dinitrobenzene, which depletes the cellular reduced glutathione, and diethylethanolamine, an inhibitor of the phosphatidylethanolamine methylation, abolished the S-adenosyl-L-methionine-induced modifications of the reduced glutathione, acetaldehyde, and triacylglycerol contents in the liver of ethanol-treated rats. Neither S-adenosyl-L-methionine nor reduced glutathione inhibitors affected the liver acetaldehyde dehydrogenase activity. It is suggested that, although S-adenosyl-L-methionine induced a small inhibition of ethanol metabolism in the liver, its antisteatosic effect could largely depend on its role as a modulator of the reduced glutathione liver content.

S-adenosyl-L-methionine protection against alpha-naphthylisothiocyanate-induced cholestasis in the rat.

The effect of S-adenosyl-L-methionine (SAMe) on cholestasis induced by alpha-naphthylisothiocyanate (ANIT) was studied in rats. SAMe significantly attenuated both bile flow impairment and elevated values of serum bilirubin, glutamic pyruvic transaminase and alkaline phosphatase in ANIT-treated animals. These results suggest that SAMe protects the rat liver against the toxic effects of ANIT.

Inhibition of lymphocyte function by a naturally occurring nucleoside: 5'-methylthioadenosine (MTA).

The link between immunodeficiencies and nucleoside metabolism is exemplified by the inherited deficiencies of adenosine deaminase and purine nucleoside phosphorylase which are associated with an abnormal development of the immune system. In this report we show that high doses of methylthioadenosine (MTA), a natural purine nucleoside, inhibit both the mitogen-induced blastogenesis of human peripheral blood lymphocytes (PBL) and the pokeweed mitogen (PWM)-driven in vitro immunoglobulin synthesis by PBL in a non-toxic and reversible fashion. Our data support the view that both T and B cells are sensitive to MTA inhibition and that PWM-driven Ig production is more affected by MTA than the mitogen-induced PBL proliferation. The observation that MTA causes an evident inhibition of in vitro PWM-driven Ig secretion when added four days after the start of the cultures suggests that MTA can exert its activity not only on proliferation but also on differentiation of B cells.

Anti-inflammatory activity of S-adenosyl-L-methionine in animal models: possible interference with the eicosanoid system.

In rats, the anti-inflammatory activity of parenteral S-adenosyl-L-methionine (SAMe) in carrageenin- and nystatin-induced oedemas and in carrageenin-induced pleurisy was tested. The capability of the drug to inhibit the production of PG-like material in sponge exudates and by peritoneal leukocytes during bacterial phagocytosis was also evaluated. Two of these experimental models were used to administer the compound by the oral route in order to see whether oral and injected SAMe had similar effects. The results obtained show that SAMe can exert anti-inflammatory activity by inhibiting the oedema and pleurisy in rats and PG-like material production in inflammatory exudates and in the phagocytosis process by leukocytes. The mechanism of action of SAMe is discussed.

S-adenosyl-L-methionine antagonizes oral contraceptive-induced bile cholesterol supersaturation in healthy women: preliminary report of a controlled randomized trial.

Recent experimental investigations have shown that S-adenosyl-L-methionine (SAMe) reverses estrogen-induced bile secretion impairment. The mechanism of this action seems to be related to the capability of SAMe both to inactivate catecholestrogens by methylation reaction and to methylate membrane phospholipids increasing the liver plasma membrane fluidity reduced by the estrogens. Aim of this investigation was to know whether SAMe also prevents oral contraceptive-induced cholesterol supersaturation of gallbladder bile in humans. To six healthy nonobese women whose bile cholesterol saturation index increased from a mean basal value of 0.77 (SD 0.22) to 1.20 (SD 0.38) (p less than 0.01) after two cycles of treatment with oral contraceptives containing 50 micrograms ethynylestradiol, plus 250 micrograms d-norgestrel, 200 mg SAMe per os tid was administered in addition to the oral contraceptive for other two cycles. The bile cholesterol saturation index decreased to 0.88 (SD 0.26) (p less than 0.05 versus oral contraceptive value). These results indicate that SAMe antagonizes biliary lipid changes induced by estrogen-progestin containing oral contraceptive and suggest its potential usefulness in women on oral contraceptive treatment to prevent lithogenic bile secretion.

Age-related modification of dopaminergic and beta-Adrenergic receptor system: restoration to normal activity by modifying membrane fluidity with S-adenosylmethionine.

Microviscosity of membranes prepared from striata and cortex of 3 or 30-month-old rats was measured by fluorescence polarization and electron spin resonance. The viscosity of the hydrophobic core of the lipid bilayer was significantly increased in striatal but not in cortical membranes of old rats. In old rats the incorporation of methyl groups into phosphatidylcholine was significantly lower than in young rats. beta-Adrenergic specific binding sites were reduced in striata, cortex and pineal gland of old rats. In the striata of these animals, [3H] spiperone specific binding sites and dopamine-stimulated adenylate cyclase were also low. A chronic treatment of old rats with S-adenosyl-L-methionine, the cofactor in phospholipid methylation, lowered microviscosity to normal values in striata but not in the cortex. In the same old rats, the beta-receptor in striata and pineal gland returned towards juvenile values; in the cortex, the modification was in the same direction but did not reach significance. Neither putative dopaminergic receptors nor the adenylate cyclase age-dependent decrease was modified by treatment with S-adenosyl-L-methionine.

Transmethylation, transsulfuration, and aminopropylation reactions of S-adenosyl-L-methionine in vivo.

S-Adenosylmethionine (AdoMet) is metabolized through three main pathways, i.e. (a) transfer of its methyl group to a variety of methyl acceptors, (b) decarboxylation followed by aminopropylation leading to polyamine synthesis, and (c) cleavage of the bond between the sulfur atom and carbon 4 of the amino acid chain, resulting in formation of methylthioadenosine and homoserine thiolactone. In this study the metabolism of AdoMet through these pathways was studied after intravenous administration to rats of [1-14C]-, [3,4-14C]-, [methyl-14C]-, and [35S]AdoMet at various doses. The relative utilization of AdoMet and methionine was also investigated. The results show that intravenously administered AdoMet is efficiently metabolized in vivo up to the highest tested dose (250 mumol X kg-1 body weight), about two-thirds of the metabolized compound being utilized via transmethylation and cleavage to methylthioadenosine and one-third via decarboxylation. The efficient incorporation of the methyl group of AdoMet into muscle creatine indicates unambiguously that the compound is taken up and metabolized by the liver. Moreover, intravenously administered AdoMet is shown to be a better precursor than methionine both in creatine formation and in the utilization of the sulfur atom in transsulfuration reactions.

Reversal of intrahepatic cholestasis of pregnancy in women after high dose S-adenosyl-L-methionine administration.

Previous investigations have indicated that S-adenosyl-L-methionine (SAMe) leads to reversal of estrogen-induced bile flow impairment in rats. This randomized, single-blind clinical trial was performed to determine whether SAMe reverses intrahepatic cholestasis of pregnancy (ICP) which occurs in hypersensitive women associated with increased estrogen levels in late pregnancy. Eighteen women with ICP were randomly divided into three groups of six and treated for 20 days as follows: Group I received 200 mg per day of i.v. SAMe; Group II received 800 mg per day of i.v. SAMe; Group III served as control. At the beginning of the study, clinical and biochemical parameters were similar among groups. After 10 and 20 days of treatment with the higher dose of SAMe, the mean values of serum transaminases, conjugated bilirubin and total bile acids fell significantly in respect to initial levels; opposite results were found in the other two treatment groups. The final values of these selected parameters were lower in the group of subjects treated with 800 mg per day SAMe than in the other two groups of women. Pruritus graded on a 0 to 4+ scale significantly was reduced only in patients treated with the higher dose of SAMe. These results indicate a trend toward remission of ICP in women treated with 800 mg per day SAMe and suggest that SAMe administration may be a new therapeutic modality for ICP.

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

Current methods for the radioenzymatic assay of S-adenosyl-L-methionine (AdoMet) in biological fluids have been modified in order to increase sensitivity. The modified procedure has allowed to measure AdoMet content also in plasma and cerebrospinal fluid where the concentrations have been found to range between 17 and 72 ng/ml in the different animal species.

Decreased blood levels of ethanol and acetaldehyde by S-adenosyl-L-methionine in humans.

In view of the protective effects of SAM on alcohol-induced fatty liver degeneration, an investigation has been carried out to see if this compound accelerates the clearance of ethanol and acetaldehyde in humans. Both parameters were significantly lower after SAM, indicating the capability of exogenous SAM to favour the inactivation of ethanol without increasing blood levels of acetaldehyde.

Pharmacokinetics of S-adenosyl-L-methionine in healthy volunteers.

S-Adenosyl-L-methionine (AdoMet) kinetics was studied in 6 male subjects given 100 and 500 mg i.v. Drug concentrations in plasma and urine were assayed using a radioenzymatic method. Pharmacokinetic parameters were estimated according to an open two-compartment model. The apparent volumes of distribution after the 100 and 500 mg doses were 407 +/- 27 and 443 +/- 36 ml/kg (mean +/- SEM), terminal half-lives 81 +/- 8 and 101 +/- 7 min and body clearances 3.7 +/- 0.5 and 3.1 +/- 0.2 ml/min per kg. Urinary excretion was 34 +/- 3 and 40 +/- 2% of the administered dose. The results demonstrate that drug disposition occurs more via metabolism than via renal excretion, and it is not dependent on the administered dose. Binding of AdoMet to serum proteins is negligible.

The effect of S-Adenosyl-L-methionine on ischemia-induced disturbances of brain phospholipid in the gerbil.

Brain ischemia was produced in gerbils (Meriones unguiculatus) by the bilateral ligation of the carotid arteries with reported procedures. Changes in the energy status of brain demonstrated that carotid ligation was effective. At different time intervals from ligation, groups of gerbils were given either saline of S-Adenosyl-L-methionine (SAMe) by the intraventricular (i.v.) route (1.6 mg/Kg body wt. twice, at each 10 min interval), or by the intraperitoneal (i.p.) administration (200 mg/Kg body wt.) or subcutaneously (s.c.) with 40 mg/Kg body wt, daily, for two weeks. Control animals, with and without SAMe, together with the ischemic groups, were decapitated directly into liquid nitrogen, 10 min after ligation. Brain neutral and polar lipid, together with free fatty acids, which were all labeled in vivo by the intraventricular injection of [1-14C]arachidonic acid 2 hr prior to ligation, were extracted, purified and separated by conventional procedures. SAMe when injected i.v. or i.p. noticeably corrected the changes in polar lipid by reversing the decrease of brain phosphatidylcholine and choline plasmalogen, as well as of their labeling, which was due to ischemia. Concurrently with this action, SAMe treatment (i.v. and i.p.) also provided to some extent to re-establish the normal level of labeling of ethanolamine lipids. When SAMe was given s.c., no effect was present. SAMe had no effect on the increase of free fatty acid and diglyceride due to ischemia. The prevention by SAMe of the changes of choline lipids suggests that a stimulation of the methyltransferase reaction may occur in the ischemic brain, due to increased substrate (SAMe) availability. This effect may be important for cell survival, since membrane phospholipid derangements alter the properties of the membrane.

S-adenosylmethionine protects against erythrocyte membrane alterations induced in rabbits by cholesterol-rich diet.

In the erythrocyte membranes of rabbits fed a cholesterol rich diet for two months the cholesterol/phospholipid ratio was twice higher than in controls. The same diet induced a significant decrease in membrane fluidity and acetylcholinesterase activity. Two daily administrations of 25 mg X kg-1 b.w.-1 of S-adenosylmethionine (SAMe) have shown to protect against membrane alterations induced by hypercholesterolemic regimen. This observation would suggest the use of SAMe in those pathological conditions like hyperlipoproteinemias and liver diseases where membrane alterations are reported.

Anti-inflammatory activity of S-adenosyl-L-methionine: interference with the eicosanoid system.

S-adenosyl-L-methionine (SAMe) displays anti-inflammatory as well as antalgic activity without damaging the gastrointestinal mucosa in experimental animals. In fact, carrageenin-induced edema in rats and writhings provoked in mice by phenylquinone and acetic acid are controlled by SAMe in a dose dependent manner. Since PG-like substance concentration in the inflammatory exudate decreased in SAMe-treated animals the mode of action of this compound is also discussed, in view of SAMe ability to interfere with the eicosanoid system.