Wünderlich syndrome caused by metastatic gastric sarcoma in the kidney. Report of a case

Two of the most important biochemical hepatic pathways in the liver are those that synthesize methionine and S-adenosylmethionine (SAM) through the methylation of homocysteine. This article reviews some recent findings in this laboratory, which demonstrate that ethanol feeding to rats impairs one of these pathways involving the enzyme methionine synthetase (MS), but by way of compensation increases the activity of the enzyme betaine:homocysteine methyl transferase (BHMT), which catalyzes the second pathway in methionine and SAM biosynthesis. It has been shown that despite the inhibition of MS, the enhanced BHMT pathway utilizes hepatic betaine pools to maintain levels of SAM. Subsequent to the above findings, it has been shown that minimal supplemental dietary betaine at the 0.5% level generates SAM twofold in control animals and fivefold in ethanol-fed rats. Concomitant with the betaine-generated SAM, ethanol-induced hepatic fatty infiltration was ameliorated. In view of the fact that SAM has already been used successfully in the treatment of human maladies, including liver dysfunction, betaine, shown to protect against the early stages of alcoholic liver injury as well as being a SAM generator, may become a promising therapeutic agent and a possible alternative to expensive SAM in the treatment of liver disease and other human maladies.     

S-adenosylmethionine generation and prevention of alcoholic fatty liver by betaine

Earlier studies by other investigators have shown that S-adenosylmethionine (SAM) has the capacity to attenuate liver injury in experimental animals. In a recent study in this laboratory, it was shown that when supplemental dietary betaine was given to control and ethanol-fed rats at the level of 0.50% (W/V), SAM levels were doubled in the livers of control animals and increased fivefold in livers of ethanol-fed rats. The increased levels of SAM in the livers of ethanol-fed animals protected the livers from fatty infiltration due to ethanol feeding. In this study, an attempt was made to determine the minimum level of dietary betaine that protects against the fatty infiltration. Levels of betaine at 0.05%, 0.10%, 0.25%, and 0.50% in semiliquid control and alcohol diets were tested in rats for 30 days. When hepatic betaine, SAM, and triglyceride levels were determined, it was demonstrated that only the dietary level of betaine at 0.50% supplied enough hepatic betaine to generate the level of SAM that was required to protect against the alcoholic steatosis resulting from the dietary ethanol. These results suggest that betaine, when given in sufficient amounts, may be a promising therapeutic agent in the treatment of liver disease.     

Disordered methionine/homocysteine metabolism in premature vascular disease. Its occurrence, cofactor therapy, and enzymology

Mild homocysteinemia occurs surprisingly often in patients with premature vascular disease. We studied the possible enzymatic sources of this mild hyperhomocysteinemia and the control of homocysteine levels in plasma by treatment of patients with the cofactors and cosubstrates of homocysteine catabolism. We assessed homocysteine metabolism in 131 patients who had premature disease in their coronary, peripheral, or cerebrovascular circulation by using a standard oral methionine-load test. Impaired homocysteine metabolism occurred in 28 patients. We assayed levels of the primary enzymes of homocysteine catabolism in cultured skin fibroblast extracts from 15 of these 28 patients. The patients' cystathionine beta-synthase levels (3.68 +/- 2.52 nmol/h per milligram of cell protein, mean +/- SD) were markedly depressed compared with those from 31 healthy adult control subjects (7.61 +/- 4.49, P < .001). The patients' levels of 5-methyltetrahydrofolate: homocysteine methyltransferase were normal. While betaine: homocysteine methyltransferase was not expressed in skin fibroblasts, 24-hour urinary betaine and N,N-dimethylglycine measurements were consistent with normal or enhanced remethylation of homocysteine by betaine: homocysteine methyltransferase in the 13 patients tested. When treated daily with choline and betaine, pyridoxine, or folic acid, there was a normalization of the postmethionine plasma homocysteine level in 16 of 19 patients. Our results indicate that mild homocysteinemia in premature vascular disease may be caused by either a folate deficiency or deficiencies in cystathionine beta-synthase activity. It does not necessarily involve deficiencies of either 5-methyltetrahydrofolate:homocysteine methyltransferase or betaine:homocysteine methyltransferase. Effective treatment regimens are also defined.     

Upper airway muscle activity and upper airway resistance in young adults during sleep

Ethanol consumption slows down the rate of hepatic protein catabolism. The present study was conducted to determine whether ethanol consumption, given by voluntary (pair) feeding or by intragastric administration, affected the peptidase activities of the proteasome in rat liver. Rats were pair-fed liquid diets containing either ethanol or isocaloric maltose-dextrin. A separate group of animals was intragastrically infused continuously with similar liquid diets containing either ethanol or isocaloric dextrose. Crude liver homogenates and their cytosolic fractions were assayed for their chymotrypsin-like (Cht-L), trypsin-like (T-L), and peptidyl-glutamyl-peptide hydrolase (PGPH) activities, using specific fluorogenic peptides as substrates. Voluntary ethanol feeding did not affect the three peptidase activities of the proteasome. However, intragastric ethanol administration caused a 35% to 40% decline in the Cht-L and the T-L activities, but did not significantly change the PGPH activity. The lower peptidase activities in cytosol samples from intragastrically ethanol-fed rats were not restored to control levels by overnight dialysis, nor by the inclusion of low levels of sodium dodecyl sulfate (SDS) or of 0.5 mmol/L adenosine triphosphate (ATP) in the proteasome assay mixture. Immunoblot analyses using anti-rat liver proteaseome exhibited equal levels of immunoreactive proteasome subunits in livers of control and ethanol-fed rats. Similar results were obtained when blots were probed with antibody made specifically against the proteasome subunit, LMP-7. The results indicate that intragastric, but not voluntary, ethanol consumption differentially affects the separate catalytic activities of the proteasome without affecting its steady-state levels. Such changes may be related to the degree of ethanol-induced oxidative stress.     

Iron increases ethanol toxicity in rat liver

Clinical evidence indicates that patients with iron overload are more susceptible to liver cell damage from alcohol than persons with normal iron stores. Iron may act as a co-factor to catalyze the lipid peroxidation induced by hepatotoxic compounds such as alcohol. To elucidate the role of iron in ethanol-induced hepatocellular damage, we developed a new experimental model in the rat. Following dietary carbonyl iron feeding for 8 weeks, animals were pair-fed a liquid ethanol diet for 4 weeks. In iron-fed animals the liver iron content was 6.4 vs. 0.5 micrograms Fe/mg protein in the controls. Blood alcohol concentrations were similar in all ethanol-fed animals. Serum alanine aminotransferase (ALT) levels were elevated to 269 +/- 49 U/l in the iron+alcohol group compared to 52 +/- 6 U/l in the other groups. There was a strong correlation between ALT levels and hepatic iron content in the ethanol-fed animals. Morphologically, the alcohol-fed rats displayed hepatic steatosis, whereas occasional inflammation and iron in Kupffer cells was seen in the iron+alcohol animals. Ultrastructurally, necrotic hepatocytes and cells phagocytosed by Kupffer cells were only encountered in the iron+alcohol group. Compared to controls, the liver content of hydroxyproline was significantly increased in the iron+alcohol group. No morphological evidence of fibrosis was noted. The present study demonstrates biochemical and morphological evidence of increased hepatocellular damage following the combination of iron and ethanol.     

Ethanol administration alters the proteolytic activity of hepatic lysosomes

Protein accumulation in liver cells contributes to alcohol-induced hepatomegaly and is the result of an ethanol-elicited deceleration of protein catabolism (Alcohol Clin Exp Res 13:49, 1989). Because lysosomes are active in the degradation of most hepatic proteins, the present studies were conducted to determine whether ethanol administration altered the proteolytic activities of partially purified hepatic lysosomes. Rats were fed liquid diets containing either ethanol (36% of calories) or isocaloric maltodextrin for periods of 2-34 days. Prior to death, all animals were injected with [3H]leucine to label hepatic proteins. Rats subjected to even brief periods of ethanol feeding (2-8 days) exhibited significant hepatomegaly and hepatic protein accumulation compared with pair-fed control animals. Crude liver homogenates and isolated lysosomal-mitochondrial and cytosolic subfractions were incubated at 37 degrees C, and the acid-soluble radioactivity generated during incubation was measured as an index of proteolysis. At neutral pH, in vitro protein breakdown in incubated liver homogenates and subcellular fractions from control and ethanol-fed rats did not differ significantly. The extent of protein hydrolysis increased when samples were incubated at pH 5.5, which approximates the pH optimum for catalysis by lysosomal acid proteases. Under the latter conditions, partially purified lysosomes from control animals had 2-fold higher levels of proteolysis than corresponding fractions from ethanol-fed rats. The difference in proteolytic capacity appeared to be related to a lower latency and a higher degree of fragility of lysosomes from ethanol-fed rats at the acidic pH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ethanol administration on components of the ubiquitin proteolytic pathway in rat liver

Hepatic protein accumulation during ethanol administration may result partly from an ethanol-elicited decline in hepatic protein degradation, which we have previously shown. We conducted the current studies to examine the effects of ethanol administration on the levels of hepatic ubiquitin, an 8.5-kd protein which is an important mediator of extralysosomal protein catabolism. Rats were pair-fed liquid diets containing either ethanol (36% of calories) or isocaloric maltose-dextrin for 1 to 5 weeks. Ubiquitin was immunochemically quantified by competitive enzyme-linked immunosorbent assay (ELISA) in crude cytosol fractions from whole liver and in 12,000g supernatants of hepatocyte lysates. Ubiquitin levels in hepatic cytosol fractions of ethanol-fed rats exceeded those of controls by about 30%. Isolated hepatocytes from ethanol-fed animals also showed a 40% to 75% elevation of ubiquitin above that in cells of pair-fed controls and this difference exceeded the relative rise in hepatocellular protein. In hepatocyte lysates subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting, we detected monomeric ubiquitin and higher molecular mass ubiquitin-protein conjugates. However, the immunoblot analyses revealed no quantitative changes in the level of either free or conjugated ubiquitin. The ubiquitin conjugating activity of crude and diethyl aminoethyl-fractionated liver cytosols of ethanol-fed rats had equal capacities to those from controls in catalyzing the formation of ubiquitin-protein conjugates. Our findings indicate that chronic ethanol consumption increased the level of immunoreactive ubiquitin in rat liver. This may have resulted from enhanced ubiquitin production because of an ethanol-elicited stress response and/or decreased catabolism of ubiquitin and its conjugates. Our findings also provide no indication that the ethanol-elicited reduction in hepatic proteolysis is because of a ubiquitin-mediated mechanisms.     

High-dose vitamin E supplementation has no effect on ethanol-induced pathological liver injury

The effect of alpha-tocopherol (alpha-T) supplementation on ethanol-induced liver damage was studied. The intragastric feeding rat model was used in this study. Both normal and alpha-T supplemented animals (3125 IU/kg body weight) were fed liquid diet and ethanol for 1 mo. In pair-fed animals, ethanol was isocalorically replaced by dextrose. The blood ethanol level in the ethanol-fed groups was between 150 to 350 mg/dl. Lipid peroxidation was assessed by measuring liver thiobarbituric acid reactive substances (TBARS) and conjugated dienes. Liver damage was assessed by light microscopy. Overall, chronic ethanol treatment resulted in increase in TBARS and conjugated dienes in both normal (60% and 35%, P < .01, respectively) and alpha-T-supplemented groups (50% and 47%, P < .01, respectively). In animals receiving either dextrose or ethanol and regular diet, there was a significant inverse correlation between liver alpha-T and TBARS (r = 0.88, P < 0.01) and conjugated dienes (r = -0.75, P < .05). In contrast, in the vitamin E-supplemented rats, a significant positive correlation was observed between liver alpha-T, TBARS (r = 0.78, P < .01) and conjugated dienes (r = 0.87, P < .01). Of major significance is that alpha-T supplementation had no effect on ethanol-induced pathological changes in the liver. In conclusion, these results show that in the intragastric feeding model, alpha-T supplementation had no protective effect on ethanol-induced liver damage.     

Transport of reduced glutathione in hepatic mitochondria and mitoplasts from ethanol-treated rats: effect of membrane physical properties and S-adenosyl-L-methionine

Ethanol intake depletes the mitochondrial pool of reduced glutathione (GSH) by impairing the transport of GSH from cytosol into mitochondria. S-Adenosyl-L-methionine (SAM) supplementation of ethanol-fed rats restores the mitochondrial pool of GSH. The purpose of the current study was to determine the effect of ethanol feeding on the kinetic parameters of mitochondrial GSH transport, the fluidity of mitochondria, and the effect of SAM on these changes. Male Sprague-Dawley rats were fed ethanol-liquid diet for 4 weeks supplemented with either SAM or N-acetylcysteine (NAC). SAM-supplementation of ethanol-fed rats restored the mitochondrial GSH pool but NAC administration did not. Kinetic studies of GSH transport in isolated mitochondria revealed two saturable, adenosine triphosphate (ATP)-stimulated components that were affected significantly by chronic ethanol feeding: lowering Vmax (0.22 and 1.6 in ethanol case vs. 0.44 and 2.7 nmol/15 sec/mg protein in controls) for both low and high affinity components with the latter showing an increased Km (15.5 vs. 8.9, mmol/L in ethanol vs. control). Mitochondria from SAM-supplemented ethanol-fed rats showed kinetic features of GSH transport similar to control mitochondria. Determination of membrane fluidity revealed an increased order parameter in ethanol compared with control mitochondria, which was restricted to the polar head groups of the bilayer and was prevented by SAM but not NAC supplementation of ethanol-fed rats. The changes elicited in mitochondria by ethanol were confined to the inner membrane; mitoplasts from ethanol-fed rats showed features similar to those of intact mitochondria such as impaired transport of GSH and increased order parameter. A different mitochondrial transporter, adenosine diphosphate (ADP)/ATP translocator, was unaffected by ethanol feeding. Furthermore, fluidization of mitochondria or mitoplasts from ethanol-fed rats by treatment with a fatty acid derivative restored their ability to transport GSH to control levels. Thus, ethanol-induced impaired transport of GSH into mitochondria is selective, mediated by decreased fluidity of the mitochondrial inner membrane, and prevented by SAM treatment.     

S-adenosylmethionine metabolism and DNA methylation in hydrazine-treated rats

The treatment of rats with hepatotoxic doses of hydrazine (NH2-NH2) induces the rapid formation of 7-methylguanine and O6-methylguanine in liver DNA. The methyl moiety in these reactions might be derived from the cellular S-adenosylmethionine pool because radioactivity administered to these rats as methionine rapidly appears in the DNA as methylated guanine. An increased incorporation of radioactivity into 5-methylcytosine was previously reported followed by subsequent suppression. This increased radiolabeling of 5-methylcytosine coincided with time of maximal DNA guanine methylation. To determine the nature of S-adenosylmethionine metabolism during the period of DNA methylation induced by hydrazine treatment, and to determine if the increased radiolabeling of 5-methylcytosine at this time reflected an actual increase in 5-methylcytosine synthesis, liver DNA synthesis and S-adenosylmethionine levels and turnover were assayed. Liver S-adenosylmethionine concentrations varied slightly between control rats and hydrazinetreated rats during the first five hours after hydrazine administration, and no difference was detectable in the incorporation of administered [3H]methionine into S-adenosylmethionine. Because S-adenosylmethionine specific radioactivity in hydrazine-treated rats was not different from control rats, the previously observed increased radiolabeling of 5-methylcytosine appeared to represent an actual increase in synthesis. This conclusion was supported by finding that incorporation of radioactive thymidine into DNA was also accelerated immediately following hydrazine administration, again followed by a decrease. 5-Methylcytosine sythesis, therefore, appears to follow DNA synthesis during hydrazine toxicity, and formation of 7-methylguanine and O6-methylguanine in liver DNA of hydrazine-treated rats occurs during a short period of increased DNA sythesis and 5-methylcytosine formation very early in hydrazine toxicity.     

Hepatic betaine-homocysteine methyltransferase activity in the chicken is influenced by dietary intake of sulfur amino acids, choline and betaine

There is much interest in the metabolism of homocysteine, because elevated plasma homocysteine [hyperhomocyst(e)inemia] is an independent risk factor for the development of cardiovascular disease. Four chick assays were conducted to determine the effects of varying dietary sulfur amino acids, choline and betaine on the activity of hepatic betaine-homocysteine methyltransferase (BHMT), an enzyme likely to be important in modulating plasma homocysteine. In Experiment 1, chicks were fed a purified crystalline amino acid diet containing adequate sulfur amino acids and choline. Excess dietary methionine, or the combination of excess cystine with choline or betaine, caused a small increase (P < 0.05) in BHMT activity. In Experiment 2, use of a methionine-deficient purified diet resulted in a threefold increase (P < 0.05) in BHMT activity, and addition of choline or betaine further increased (P < 0.05) BHMT activity. In Experiment 3, use of a methionine-deficient corn-peanut meal diet increased BHMT (P < 0.05) relative to that of chicks supplemented with adequate methionine, and addition of surfeit choline to the methionine-deficient basal diet caused a further increase (P < 0.05). In Experiment 4, addition of both surfeit choline and surfeit betaine to the methionine-deficient corn-peanut meal diet caused an increase (P < 0.05) in BHMT activity relative to that observed in chicks fed the methionine-deficient basal diet. These assays show that large increases in BHMT activity can be produced under methionine-deficient conditions, especially in the presence of excess choline or betaine.     

Effects of chronic alcohol consumption on enzyme activities and active methionine absorption in the small intestine of pregnant rats

The present study evaluates the effect of chronic alcohol intake on the intestinal transport of methionine during pregnancy. For this purpose, we have used an in vitro technique that allows measurement of the unidirectional influx of the amino acids across the brush-border membrane of the rat mid-jejunum, and the basolateral membrane enzyme Na+, K+-ATPase was also evaluated in the duodenum and jejunum. For chronic alcohol treatment, the rats were fed a liquid diet containing ethanol (36% of calories) or an isocaloric diet-(pair-fed control) for 5 weeks before and during pregnancy. Animals were killed at 21 days of gestation. Results from the kinetic analysis revealed that chronic ethanol treatment reduces the maximum transport (Jm) of methionine uptake when compared with controls. Further experiments performed in the presence and absence of sodium have shown that ethanol selectively inhibited Na+-dependent methionine transport. At the same time, this treatment significantly reduced the levels of Na+, K+-ATPase in ethanol-fed rats compared with the controls. Alterations in methionine intestinal transport in pregnant alcohol-fed rats may contribute to the ethanol-induced fetal growth abnormalities.     

Filgrastim restores interleukin-2 production in blood from patients with advanced human immunodeficiency virus infection

BACKGROUND & AIMS: Malondialdehyde and acetaldehyde react together with proteins and form hybrid protein conjugates designated as MAA adducts, which have been detected in livers of ethanol-fed rats. The aim of this study was to examine the immune response to MAA adducts and other aldehyde adducts during long-term ethanol exposure. METHODS: Rats were pair-fed for 7 months with a liquid diet containing either ethanol or isocaloric carbohydrate. Circulating antibody titers against MAA adducts and acetaldehyde adducts were measured and characterized in these animals. RESULTS: A significant increase in antibody titers against MAA-adducted proteins was observed in the ethanol-fed animals. Competitive inhibitions of antibody binding indicated that the circulating antibodies against MAA-modified proteins in the ethanol-fed rats recognized mainly a specific, chemically defined MAA epitope. Antibody titers to reduced and nonreduced acetaldehyde adducts were very low, and no significant differences were observed between ethanol-fed and control animals. Significant plasma immunoreactivity to not only MAA-adducted but also unmodified rat liver proteins (cytosol, microsomes, and especially plasma membrane) were also observed in the ethanol-fed rats. CONCLUSIONS: Long-term ethanol feeding generates circulating antibodies not only against MAA epitopes but possibly also against unmodified, native (self) protein epitopes, suggesting that MAA adducts could trigger harmful autoimmune responses.     

Inhibition of DNA methylation by S-adenosylethionine with the production of methyl-deficient DNA in regenerating rat liver

Ethionine, a liver carcinogen, was administered p.o. (300 mg/kg) to rats 17 hr after partial hepatectomy. At 6 hr after administration of the ethionine, hepatic S-adenosylethionine levels were 30- to 40-fold greater than the hepatic level of S-adenosylmethionine. A 10-fold ratio of S-adenosylethionine to S-adenosylmethionine still persited at 24 hr after ethionine administration. When given at 17 hr after partial hepatectomy, ethionine produced a 30% inhibition of DNA synthesis, measured by the incorporation of [methyl-3H]thymidine at 23 to 24 hr after partial hepatectomy (6 to 7 hr after ethionine administration). DNA synthesized during this interval was methyl deficient as judged by the reduced incorporation of radioactivity from L-[methyl-3H]methionine into 5-methylcytosine residues of DNA. In an assay for DNA methylation in vitro using whole nuclei, the methyl-deficient DNA was methylated by S-adenosylmethionine 8 times more than was control DNA; the DNA methylation was competitively inhibited by S-adenosylethionine. These data suggest that S-adenosylethionine, formed in vivo from ethionine, competitively inhibits the methylation of DNA in vivo by S-adenosylmethionine, resulting in the production of methyl-deficient DNA.     

Early alcoholic liver injury: formation of protein adducts with acetaldehyde and lipid peroxidation products, and expression of CYP2E1 and CYP3A

The formation of protein adducts with reactive aldehydes resulting from ethanol metabolism and lipid peroxidation has been suggested to play a role in the pathogenesis of alcoholic liver injury. To gain further insight on the contribution of such aldehydes in alcoholic liver disease, we have compared the appearance of acetaldehyde, malondialdehyde, and 4-hydroxynonenal adducts with the expression of cytochrome P-450IIE1, and cytochrome P-4503A enzymes in the liver of rats fed alcohol with a high-fat diet for 2 to 4 weeks according to the Tsukamoto-French procedure and in control rats (high-fat liquid diet or no treatment). Urine alcohol and serum aminotransferase levels were recorded, and the liver pathology was scored from 0 to 10 according to the presence of steatosis, inflammation, necrosis, and fibrosis. The ethanol treatment resulted in the accumulation of fat, mild necrosis and inflammation, and a mean liver pathology score of 3 (range: 1 to 5). Liver specimens from the ethanol-fed animals with early alcohol-induced liver injury were found to contain perivenular, hepatocellular acetaldehyde adducts. Malondialdehyde and 4-hydroxynonenal adducts were also present showing a more diffuse staining pattern with occasional sinusoidal reactions. In the control animals, a faint positive reaction for the hydroxynonenal adduct occurred in some of the animals fed the high fat diet, whereas no specific staining was observed in the livers from the animals receiving no treatment. Expression of both CYP2E1 and CYP3A correlated with the amount of protein adducts in the liver of alcohol-treated rats. Distinct CYP2E1-positive immunohistochemistry was seen in 3 of 7 of the ethanol-fed animals. In 5 of 7 of the ethanol-fed animals, the staining intensities for CYP3A markedly exceeded those obtained from the controls. The present findings indicate that acetaldehyde and lipid peroxidation-derived adducts are generated in the early phase of alcohol-induced liver disease. The formation of protein adducts appears to be accompanied by induction of both CYP2E1 and CYP3A.     

Effect of chronic ethanol feeding on hepatic microsomal glycerophosphate acyltransferase activity

The activity and submicrosomal distribution of alpha-glycerophosphate acyltransferase (GPAT) were studied in rats fed ethanol for 6 wk. GPAT activity was also measured in rats after 10 days of alcohol feeding, 22 days of phenobarbital administration, or 24 days on a high fat (71% of total calories) diet. After 6 wk of ethanol feeding, GPAT activity was increased 73% when expressed per milligram of protein and 133% when expressed per 100 g of body weight (P < 0.005). GPAT activity was more abundant in the smooth than in the rough microsomes of both control and ethanol-fed rats when expressed per milligram of microsomal protein and when expressed per gram of liver; the smooth microsomes accounted for most of the increased GPAT activity after ethanol. 10 days of ethanol feeding or 22 days of phenobarbital administration did not increase GPAT activity. Feeding a high fat diet for 24 days increased GPAT activity per milligram of protein to an extent similar to that observed after chronic ethanol administration. When expressed per 100 g of body weight, however, the increase was much greater after ethanol. The significance of these findings in vivo has not been elucidated. Increased GPAT activity might contribute to the persistence of alcoholic fatty liver and the development of hyperlipemia.     

Evidence for S-adenosylmethionine independent catabolism of methionine in the rat

Experiments conducted with rats in vivo comparing the metabolism of methionine and S-methyl-L-cysteine and in vitro comparing methionine, S-methyl-L-cysteine and S-adenosyl-L-methionine indicate that a substantial portion of the oxidative metabolism of the methionine methyl group occurs by pathways that are independent of S-adenosylmethionine formation. Inclusion of 1.2% or 2.4% of S-methyl-L-cysteine in a diet containing 3% of L-methionine depressed the conversion of the methionine methyl and carboxyl carbons to CO2 by 39% and 28%, and 52% and 33%, respectively, for the two levels of S-methyl-L-cysteine. Inclusion of 1.65% of methionine in a diet containing 2.4% of S-methyl-L-cysteine did not affect the conversion of the methyl group of S-methylcysteine to CO2, but 3% of methionine depressed the conversion of the S-methylcysteine methyl group to CO2 to 87% of control values. Greater inhibitions were seen when these substrates were compared in a liver homogenate. In a rat liver homogenate system optimized for the conversion of the methyl group of methionine to CO2, the rate of conversion of the methyl group of S-adenosyl-L-methionine to CO2 was less than 1% of that of methionine even when the concentration of S-adenosylmethionine was saturating. Addition of saturating levels of unlabeled S-adenosymethionine to the homogenate system did not effect the rate of conversion of the methionine methyl carbon to CO2. Although S-adenosylmethionine-dependent metabolism of methionine, leading to incorporation of the methyl carbon into sarcosine and serine, could be demonstrated in liver homogenates, essentially all of the CO2 produced from the methionine methyl group was derived by a pathway or pathways independent of S-adenosylmethionine formation. Formaldehyde and formate have been tentatively identified as intermediates in catabolism of the methionine methyl group by this (these) pathway(s).     

Nursing diagnoses in patients with leukemia

Valproate (VPA) has been shown to induce neural tube defects (NTDs) in humans and mice, but the mechanism of action has not been elucidated. Folate supplementation has been reported to prevent the defect. It was the aim of our experiment to reveal effects of VPA and of folate coadministration on amino acid metabolism in an NTD mouse model. After treating pregnant mice intraperitoneally with 2.1 mmol VPA/kg body weight, plasma homocysteine concentrations were found to be increased. Coadministration of 4 mg/kg folate decreased this level. Plasma methionine levels were reduced under both experimental conditions. Fifteen min after treating mice with 3 mmol VPA/kg body weight, hepatic levels of both S-adenosylmethionine (SAM) and S-adenosylhomocysteine were found to be increased by +175% and +348%, respectively; but the levels had normalized again 30 min after VPA injection. Simultaneously, plasma methionine and serine levels had decreased by -43% and -51%, respectively, while homocysteine and cysteine increased by +71% and +81%, respectively. Reduced glutathione (GSH) decreased by -45%, but total glutathione did not change. These changes were statistically significant, and they occurred dose-dependently. We proposed that VPA induces methionine deficiency inhibition of folate metabolism and homocysteine remethylation, increase in aminothiols, and suppression of the GSH system in maternal blood within 1 h after application. These changes may be responsible for the teratogenic potential of VPA. Folate may prevent NTDs by changing homocysteine catabolism.     

Altered T-lymphocyte responsiveness to polyclonal cell activators is responsible for liver cell necrosis in alcohol-fed rats

The role of T-cell activation in alcoholic liver disease was investigated in rats fed alcohol and subsequently exposed to concanavalin A (Con A). Following Con A injection (20 mg/kg body weight), greater increases in liver-to-body weight ratio and ALT levels were observed at 12 and 24 hr in rats fed ethanol, compared with control rats fed sucrose. Furthermore, increases in serum interleukin-6 and tumor necrosis factor-alpha levels were noted in ethanol-fed rats, with maximal levels detected at 4 hr declining thereafter, but remaining above control levels at 24 hr. Analysis of T-cell subpopulations showed an increased percentage of CD4+, CD5+, and CD8+ T cells in blood from all groups, but not in liver perfusate. In contrast, a significant increase in the percentage of activated CD25+ T cells was detected in both blood and liver perfusate from rats fed ethanol even 24 hr after Con A injection. When CD4+ and CD8+ T cells from liver perfusate were cultured in the absence or presence of Con A, an increase in interleukin-6 and tumor necrosis factor-alpha production in supernatants was observed in ethanol-fed rats. In cultures stimulated with Con A, a 2- to 8-fold increase in cytokine production was detected, with intrahepatic CD4+ T cells being the major source. Immunohistological analysis revealed infiltration of CD4+ T cells around portal vein and central vein areas associated with fatty liver and severe hepatic necrosis. The results suggest that alcohol consumption induced a dysregulated T-cell population that mediated hepatic necrosis following polyclonal activation with Con A.     

Choline deficiency and methotrexate treatment induces marked but reversible changes in hepatic folate concentrations, serum homocysteine and DNA methylation rates in rats

OBJECTIVE: The study compared the effects of feeding rats a choline deficient (CD) diet or injecting low doses of methotrexate (MTX) on hepatic folate concentration and distribution, homocysteine (Hcy) concentration and DNA methylation. METHODS: Thirty rats were divided into three groups and were fed either a choline sufficient (CS) or deficient diet (CD), or injected with low doses of MTX (0.1 mg/kg/day) for 2 weeks. Half the animals of each group were sacrificed and the remaining CD and MTX animals were fed repletion diets without methotrexate administration for two additional weeks. RESULTS: CD or MTX resulted in a significantly lower folate concentrations (25-50%) compared to the control group. Folate distribution in the treated animals was associated with elongation of the glutamate chains: higher proportion of hexa (from 14%, control, to 35%, choline, p < 0.05), hepta (from 5% to 16%, p < 0.05), and appearance of octaglutamyl folates. MTX administration resulted in a similar pattern of hepatic folate distribution. Two weeks following the MTX administration and the restoration of an adequate choline diet for 2 weeks restored the hepatic folate levels to the control animals. CONCLUSIONS: Results are discussed based on the possibility that CD and MTX treatment appear to impair the capacity of tissues to incorporate folate in only 2 weeks and affect other biomarkers of one-carbon metabolism such as Hcy concentration and DNA methylation. This adverse picture was partially reversed in a relative short time by simply feeding an adequate CS diet and discontinuing MTX injections.