Methionine and Choline Supply during the Periparturient Period Alter Plasma Amino Acid and One-Carbon Metabolism Profiles to Various Extents: Potential Role in Hepatic Metabolism and Antioxidant Status.

The objective of this study was to profile plasma amino acids (AA) and derivatives of their metabolism during the periparturient period in response to supplemental rumen-protected methionine (MET) or rumen-protected choline (CHOL). Forty cows were fed from -21 through 30 days around parturition in a 2 × 2 factorial design a diet containing MET or CHOL. MET supply led to greater circulating methionine and proportion of methionine in the essential AA pool, total AA, and total sulfur-containing compounds. Lysine in total AA also was greater in these cows, indicating a better overall AA profile. Sulfur-containing compounds (cystathionine, cystine, homocystine, and taurine) were greater in MET-fed cows, indicating an enriched sulfur-containing compound pool due to enhanced transsulfuration activity. Circulating essential AA and total AA concentrations were greater in cows supplied MET due to greater lysine, arginine, tryptophan, threonine, proline, asparagine, alanine, and citrulline. In contrast, CHOL supply had no effect on essential AA or total AA, and only tryptophan and cystine were greater. Plasma 3-methylhistidine concentration was lower in response to CHOL supply, suggesting less tissue protein mobilization in these cows. Overall, the data revealed that enhanced periparturient supply of MET has positive effects on plasma AA profiles and overall antioxidant status.

Reduced folate and serum vitamin metabolites in patients with rectal carcinoma: an open-label feasibility study of pemetrexed with folic acid and vitamin B12 supplementation.

The objectives of this single-center, open-label, phase II study were to evaluate (a) the feasibility and safety of neoadjuvant administration of pemetrexed with oral folic acid and vitamin B12 (FA/B12) in newly diagnosed patients with resectable rectal cancer and (b) intracellular and systemic vitamin metabolism. Patients were treated with three cycles of pemetrexed (500 mg/m, every 3 weeks) and FA/B12 before surgery. The reduced folates tetrahydrofolate, 5-methyltetrahydrofolate, and 5,10-methylenetetrahydrofolate were evaluated from biopsies in tumor tissue and in adjacent mucosa. Serum levels of homocysteine, cystathionine, and methylmalonic acid were also measured. All 37 patients received three cycles of pemetrexed; 89.2% completed their planned dosage within a 9-week feasibility time frame. Neither dose reductions nor study drug-related serious adverse events were reported. Reduced folate levels were significantly higher in tumor tissue compared with adjacent mucosa at baseline. After FA/B12 administration, tissue levels of reduced folates increased significantly and remained high during treatment in both tumor and mucosa until surgery. Serum levels of cystathionine increased significantly compared with baseline after FA/B12 administration, but then decreased, fluctuating cyclically during pemetrexed therapy. Homocysteine and methylmalonic acid levels decreased significantly after FA/B12 administration, and remained below baseline levels during the study. These results indicate that administration of three neoadjuvant cycles of single-agent pemetrexed, every 3 weeks, with FA/B12 in patients with resectable rectal cancer is feasible and tolerable. Tissue and serum vitamin metabolism results demonstrate the influence of pemetrexed and FA/B12 on vitamin metabolism and warrant further study.

Folic acid causes higher prevalence of detectable unmetabolized folic acid in serum than B-complex: a randomized trial.

PURPOSE: Unmetabolized folic acid (UMFA) is common in serum of elderly individuals receiving folic acid (FA)-fortified foods or supplements. We studied the effect of supplementing FA or B-complex on serum concentrations of (6S)-5-methyltetrahydropteroylglutamate [(6S)-5-CH3-H4Pte] and UMFA in elderly people and explored factors associated with detectable UMFA post-supplementation. METHODS: This is a randomized single-blind non-controlled trial on 58 elderly people using daily 400 µg FA (n = 31) or 400 µg FA, 10 µg cyanocob(III)alamin and 8 mg pyridoxine (n = 27) for a median of 23 days. Main outcome includes changes in concentrations of serum (6S)-5-CH3-H4Pte and UMFA. RESULTS: Total homocysteine declined by a median of 1.6 (p = 0.074) in the FA and 1.3 µmol/L (p = 0.009) in the B-complex arms (p = 0.66 between the arms). Serum (6S)-5-CH3-H4Pte significantly (p < 0.001 vs. baseline) increased by a median of 9.2 and 6.5 nmol/L in the FA and B-complex groups, respectively (p = 0.152 between the groups). Compared to FA, B-complex reduced cystathionine and caused lower post-intervention serum UMFA, percentage of UMFA to (6S)-5-CH3-H4Pte and prevalence of UMFA ≥ 0.21 nmol/L. Higher serum cystathionine and whole-blood folate predicted higher post-intervention serum UMFA. CONCLUSIONS: FA caused higher UMFA as compared to B-complex. Pyridoxine appears to improve folate recycling. Data on serum UMFA should be interpreted in relation to other vitamins involved in folate metabolism. Serum UMFA is suggested to play a sensory role through which the cell recognizes FA available for metabolism via dihydrofolate reductase.

Pyridoxine supplementation does not alter in vivo kinetics of one-carbon metabolism but modifies patterns of one-carbon and tryptophan metabolites in vitamin B-6-insufficient oral contraceptive users.

BACKGROUND: Low chronic vitamin B-6 status can occur in a subset of women who use oral contraceptives (OCs) with uncertain metabolic consequences. An insufficiency of cellular pyridoxal 5'-phosphate (PLP), which is the coenzyme form of vitamin B-6, may impair many metabolic processes including one-carbon and tryptophan metabolism. OBJECTIVE: We investigated the effects of vitamin B-6 supplementation on the in vivo kinetics of one-carbon metabolism and the concentration of one-carbon and tryptophan metabolites in vitamin B-6-deficient OC users. DESIGN: A primed, constant infusion of [(13)C5]methionine, [3-(13)C]serine, and [(2)H3]leucine was performed on 10 OC users (20-40 y old; plasma PLP concentrations <30 nmol/L) before and after 28 d of supplementation with 10 mg pyridoxine hydrochloric acid/d. In vivo fluxes of total homocysteine remethylation, the remethylation of homocysteine from serine, and rates of homocysteine and cystathionine production were assessed. Targeted metabolite profiling was performed, and data were analyzed by using orthogonal partial least-squares-discriminant analysis and paired t tests adjusted for multiple testing. RESULTS: Pyridoxine supplementation increased the mean ± SD plasma PLP concentration from 25.8 ± 3.6 to 143 ± 58 nmol/L (P < 0.001) and decreased the leucine concentration from 103 ± 17 to 90 ± 20 nmol/L (P = 0.007) and glycine concentration from 317 ± 63 to 267 ± 58 nmol/L (P = 0.03). Supplementation did not affect in vivo rates of homocysteine remethylation or the appearance of homocysteine and cystathionine. A multivariate analysis showed a clear overall effect on metabolite profiles resulting from supplementation. Leucine, glycine, choline, cysteine, glutathione, trimethylamine N-oxide, and the ratios glycine:serine, 3-hydroxykynurenine:kynurenine, 3-hydroxykynurenine:3-hydroxyanthranilic acid, and 3-hydroxykynurenine:anthranilic acid were significant discriminating variables. CONCLUSIONS: Consistent with previous vitamin B-6-restriction studies, fluxes of one-carbon metabolic processes exhibited little or no change after supplementation in low-vitamin B-6 subjects. In contrast, changes in the metabolic profiles after supplementation indicated perturbations in metabolism, suggesting functional vitamin B-6 deficiency. This study was registered at clinicaltrials.gov as NCT01128244.

Plasma sulfur amino acids and stearoyl-CoA desaturase activity in two Caucasian populations.

In rats, dietary restriction of the cysteine precursor methionine suppresses hepatic stearoyl-CoA desaturase (SCD)-1 expression and activity, whereas cysteine supplementation reverses these effects. In 2 independent cohorts: Hordaland Health Study (HUSK; N=2021, aged 71-74y), Norway, and Hoorn study (N=686, aged 50-87y), Netherlands, we examined the cross-sectional associations of plasma sulfur-containing compounds (SCC; methionine, S-adenosylmethionine, S-adenosylhomocysteine, homocysteine, cystathionine, total cysteine (tCys), glutathione and cysteinylglycine) with SCD-16 index (16:1n-7/16:0), estimated from fatty acid profiles of total plasma or serum lipids. Only tCys was consistently associated with SCD-16 index after adjustments for sex and age (HUSK: partial r=0.14; Hoorn: partial r=0.11, P<0.001 for both), and after further adjustments for other SCC, body fat, diet, exercise and plasma lipids (HUSK: partial r=0.07, P=0.004; Hoorn: partial r=0.12, P=0.013). Together with animal data showing an effect of dietary cysteine on SCD1, our results suggest a role for cysteine in SCD1 regulation in humans.

Methionine metabolic pathway in alcoholic liver injury.

PURPOSE OF REVIEW: To outline recent advances in the understanding of the consequences of the alterations in the methionine metabolic pathway and to present new treatment options for alcoholic liver disease (ALD). RECENT FINDINGS: ALD is a major healthcare problem worldwide. Findings in many laboratories, including ours, have demonstrated that ethanol consumption impairs several of the multiple steps in methionine metabolism that ultimately impairs the activity of many methyltransferases critical for normal functioning of the liver. Recent studies buttress the important role genetics may play in the development and progression of alcoholic liver injury. Treatment modalities using two important metabolites of the pathway, S-adenosylmethionine and betaine, have been shown to attenuate ethanol-induced liver injury in a variety of experimental models of liver disease. S-adenosylmethionine has been used in several clinical studies; however, the outcomes have been unclear and its efficacy in liver diseases continues to be debated. To date, no clinical trials have been conducted for treatment of ALD with betaine. SUMMARY: Future treatment modalities for ALD should consider loss-of-function polymorphisms in the enzymes of the methionine metabolic and related pathways. Further new treatment modalities for ALD should consider supplementation with betaine that may prove to be a promising therapeutic agent.

Cysteine and obesity: consistency of the evidence across epidemiologic, animal and cellular studies.

PURPOSE OF REVIEW: The concentrations of several plasma amino acids increase in obesity. Notably, plasma total concentrations of the sulphur amino acid cysteine (tCys) are linearly associated with fat mass in large population studies. Animal and cellular experiments support the concept that cysteine may be obesogenic. Here we review experimental and epidemiologic findings linking cysteine and related compounds with fat regulation and obesity. RECENT FINDINGS: tCys, and to a lesser extent cystathionine, are the only plasma sulphur amino acids consistently associated with human obesity, whereas glutathione is inversely associated with BMI. Supplementing cyste(i)ne in rodents decreases energy expenditure and promotes adiposity, whereas defects of cysteine-synthesizing enzymes decrease body weight. In adipocytes, cysteine inhibits lipolysis and promotes lipogenesis via H2O2 production. Unlike most plasma amino acids, tCys levels do not decrease with gastric bypass-induced weight loss, further supporting the concept that elevated cysteine may be a cause, not a consequence of obesity. Although cysteine products (glutathione, taurine and H2S) are altered in obesity, they do not appear to explain cysteine's effects on body weight. SUMMARY: Cellular, animal and epidemiologic data are consistent with the view that cysteine is obesogenic. Targeted research linking in-vitro and in-vivo findings is needed to elucidate mechanisms involved.

Excess dietary L-cysteine, but not L-cystine, is lethal for chicks but not for rats or pigs.

A comparative species investigation of the relative pharmacologic effects of sulfur amino acids was conducted using young chicks, rats, and pigs. Ingestion of excess Met, Cys, or Cys-Cys supplemented at 2.5-, 5.0-, 7.5-, or 10 times the dietary requirement in a corn-soybean meal diet depressed chick growth to varying degrees. Strikingly, ingestion of excess Cys at 30 g/kg Cys (7.5-times the dietary requirement) caused a chick mortality rate of 50% after only 5 d of feeding. Growth was restored and chick mortality was reduced by supplementing diets containing 25 g/kg excess Cys with KHCO3 at 10 g/kg. Additionally, mortality was prevented by supplementing the drinking water of chicks receiving 25 g/kg supplemental Cys with H2O2 (0.05% final concentration). After young rats and pigs consumed excess Cys or Cys-Cys up to 40 g/kg for 14 d, weight gain was severely depressed, but we observed no mortality. An excess of dietary Cys-Cys>or=48 g/kg caused some mortality in rats. Pigs exhibited rapid recovery from growth-depressing excesses of Cys or Cys-Cys. These results lend credence to the acute toxic effects associated with the ingestion of excess sulfur amino acids and highlight the potential for excess dietary cyst(e)ine to be more pernicious than Met in certain species.

Soy protein diet prevents hypermethioninemia caused by portacaval shunt in rats.

In hepatic disorders, abnormal plasma amino acid profiles are observed. In this study, we examined whether soy protein isolate (SPI) improved plasma methionine concentration in the model animals. Portacaval shunt (PCS) increased alanine aminotransferase (ALT) activity and methionine concentration in blood of rats fed a 40% casein diet supplemented with 0.6% methionine (casein-M diet). A 40% SPI diet supplemented with 1.28% methionine (SPI-M diet), which contained the same amount of methionine as that in 40% casein-M diet, normalized plasma ALT activity and methionine level in PCS rats. These effects of a SPI diet may be due to its amino acid composition, since an amino acid mixture diet mimicking a 40% SPI-M diet was also effective to hypermethioninemia of PCS rats. To find key enzymes for the beneficial effect of soy protein, we examined effects of a 40% SPI-M or casein-M diet on the activities of three methionine-metabolizing enzymes in liver of PCS rats. A SPI-M diet stimulated only the activity of cystathionine gamma-lyase, compared with a casein-M diet. A SPI diet has a preventive effect on hypermethioninemia, at least in part, by stimulating cystathionine gamma-lyase activity in liver and may be used for nutritional management of liver disorders with hypermethioninemia.

Two newborns with nutritional vitamin B12 deficiency: challenges in newborn screening for vitamin B12 deficiency.

Vitamin B12 deficiency causes decreased Methionine Synthase and L-Methylmalonyl-CoA Mutase activity and results in accumulation of Homocysteine, Methylmalonic acid and Propionylcarnitine. Propionylcarnitine is included in tandem mass spectrometry-based newborn screening programs for detection of certain inborn errors of metabolism. We report two asymptomatic newborns with Vitamin B12 deficiency due to maternal deficiencies. One was detected incidentally at 3 weeks of age; the second on supplemental newborn screening based on elevated Propionylcarnitine at 2 days of age. This illustrates the potential for false negative results for Vitamin B12 deficiency screening by acylcarnitine profiling in newborn screening. Homocysteine and Methylmalonic acid may be better markers of Vitamin B12 deficiency. In conclusion, we suggest measuring Methylmalonic acid, Propionylcarnitine and Homocysteine levels in blood spots in expanded newborn screening in order to detect asymptomatic newborns with Vitamin B12 deficiency. Further studies are needed to establish the sensitivity of these three markers in screening for Vitamin B12 deficiency.

Lipoic acid and ascorbic acid affect plasma free amino acids selectively in the teleost fish pacu (Piaractus mesopotamicus).

Most studies on the antioxidants, lipoic acid (LA) and ascorbic acid (AA), focused on species that, unlike teleost fish, are not scurvy-prone, and are able to synthesize AA. The antioxidant properties of LA may make it useful in aquaculture nutrition, but several effects must first be investigated, and we address here plasma free amino acids (FAA). In mammals, LA and AA in high doses were claimed to alter plasma FAA profile; to our knowledge, however, no data are available in fish. We therefore studied the effects of dietary LA and AA on plasma FAA in the South American teleost fish pacu, which is being used increasingly in aquaculture. LA treatment decreased concentrations of 18 of 23 individual FAA; specifically, dispensable and total FAA were significantly affected. Ornithine was elevated (+26%) in LA-treated fish and significantly decreased ratios of plasma [Arg]/[Orn] and other individual [FAA]/[Orn] were observed. LA and AA both affected sulfur FAA concentrations. Plasma cystine levels were significantly increased in the LA-supplemented groups. AA had little effect on most amino acids, and no interaction with LA was detected. AA supplementation did, however, significantly lower taurine (-42%) and cystathionine (-31%) levels in plasma. No effect on the branched chain:aromatic amino acid ratios was observed. The data indicate that at the dietary level studied, LA and AA independently affect selected plasma FAA in pacu, and suggest that any use of LA in particular as a dietary supplement should take into account an altered plasma FAA profile.

The relationship between plasma cholesterol, amino acids and acute phase proteins in sepsis.

The purpose of the study was to correlate degree of hypocholesterolemia to changes in plasma levels of amino acids and other metabolic variables in severely injured septic patients. Measurements included plasma cholesterol, full amino-acidograms, acute phase proteins, complementary variables and blood cell counts. The Fischer plasma molar amino acid ratio (leucine+isoleucine+valine)/(phenylalanine+tyrosine) was calculated. Plasma cholesterol for all measurements (n=145) was 3.1+/-1.1 mmol/L and, upon entry in the study, it was correlated inversely with sepsis severity score (p<0.05). Along the clinical course, changes in cholesterol were clearly paralleled by opposite changes in C-reactive protein, which was the best correlate of cholesterol (r2=0.70, p<0.0001). Furthermore cholesterol was inversely related to phenylalanine, fibrinogen, lactate and white blood cell count, and directly to the Fischer molar amino acid ratio, cystathionine, methionine, glycine and transferrin (r2 between 0.36 and 0.15, p<0.0001 for all). Within this pattern of correlations, cholesterol was also directly related to alkaline phosphatase, which accounted for the effect of cholestasis, when present. For any given value of the other variables, cholesterol increased significantly with increase in alkaline phosphatase (p<0.0001). C-reactive protein (CRP, mg/dl) and alkaline phosphatase (ALKPH, U/L) together in the same regression explained 79% of the variability of cholesterol (CHOL, mmol/L): CHOL=5.90-0.74[Log(e)CRP]+0.004[ALKPH]; multiple r2=0.79, p<0.0001. Inclusion in this regression of other variables did not increase the r2. By using only amino acid variables, the best fit was provided by a regression including the Fischer ratio and cystathionine, which explained 55% of the variability of cholesterol (multiple r2=0.55 p<0.0001), and this result was not improved by the inclusion of other amino acids. These data show that severity of hypocholesterolemia in sepsis is quantifiably related to changes in plasma amino acids, and to severity of acute phase response and metabolic decompensation. More study is needed to understand whether hypocholesterolemia in sepsis has only diagnostic or prognostic implications, or that it may also contribute actively to worsening of the disease.

Maternal methionine adenosyltransferase I/III deficiency: reproductive outcomes in a woman with four pregnancies.

Four pregnancies in a women with moderately severe deficiency of methionine adenosyltransferase I/III (MAT I/III) activity are reported. She is an apparent homozygote for a point mutation in MAT1A, the gene that encodes the catalytically active subunit of MAT I/III. This mutation reduces the activity of her expressed enzyme to some 11% of wild-type. She was the first such individual identified in the United States, and these are the first pregnancies known in anyone with this extent of MAT I/III deficiency. No adverse effects were noted in the mother. Three normal babies resulted, but fetal arrest was detected in one embryo at 10-11 weeks gestation. Plasma methionine concentrations remained virtually constant at their elevated levels of 300-350 micromol/L throughout the pregnancies. Plasma free choline was below the reference range. In view of the evidence that maternal choline delivery to the fetus is important for brain development, it was suggested the patient ingest two eggs daily from gestation week 17. Plasma choline and phosphatidylcholine tended to rise during such supplementation. Plasma cystathionine concentrations rose progressively to far above normal during these pregnancies, but not during pregnancies in control women. This may be explained by delivery of excessive methionine to the fetus, with consequent increased cystathionine synthesis by fetal tissues. Because fetal tissues lack gamma-cystathionase, presumably cystathionine accumulated abnormally in the fetus and was transferred in abnormal amounts back to the mother. Plasma and urinary concentrations of methionine transamination metabolites rose during pregnancy for reasons that remain obscure.

Does a single vitamin B-supplementation induce functional vitamin B-deficiency?

In a pilot study we measured the effect of three different combinations of the vitamins B6, folate and B12 on the serum concentrations of homocysteine, cystathionine and methylmalonic acid in five healthy young men without hyperhomocysteinemia. The results indicate that there are still undescribed interactions between vitamin B6 and folate, suggesting that these two vitamins should be given together to avoid depletion of the one not given. With regard to the well known metabolic pathways of methionine and cysteine, this confirms the hypothesis that a combined supplementation with the vitamins B6 and folate (and B12) is superior to folate alone in order to lower homocysteine.

Homocysteine levels in patients treated with lipid apheresis: effect of a vitamin therapy.

BACKGROUND: Patients treated with lipid apheresis already suffer from familial hypercholesterolemia and severe coronary heart disease: any additional risk factor is dangerous for these patients. Hyperhomocysteinemia has been recognized as an independent risk factor for atherosclerotic disease. We checked the frequency of hyperhomocysteinemia in lipid apheresis patients and measured the effect of a vitamin therapy. MATERIALS AND METHODS: Sixteen heterozygous patients (10 males, 6 females) were studied, who were being treated by three different apheresis procedures. Homocysteine was measured using an enzyme conversion immunoassay. Cystathionine and methylmalonic acid were assessed by gas chromatography/mass spectrometry. Serum levels of folic acid, vitamin B12, and vitamin B6 were also determined. The patients received a vitamin therapy (3 mg folate, 60 microg cyanocobalamine, 10 mg pyridoxine hydrochloride daily) for 12 weeks. RESULTS: In 9 out of 16 patients, plasma homocysteine levels were found to be elevated (> 12 micromol L(-1)). Cystathionine concentrations were also increased, especially in those patients with elevated homocysteine. Methylmalonic acid levels were not elevated. Serum folic acid, vitamin B6, and vitamin B12 concentrations were initially in the normal range and not correlated to plasma homocysteine. The vitamin therapy reduced the plasma homocysteine concentrations in all patients significantly by 33%. Among those patients with elevated homocysteine levels, the optimal range < 12 micromol L(-1) for homocysteine was rarely reached. CONCLUSIONS: In patients treated with lipid apheresis, a hyperhomocysteinemia can be frequently seen. The constellation of both elevated homocysteine and cystathionine levels points to the existence of tissue vitamin deficiencies, folate and vitamin B-6, which were improved by vitamin supplements. Because methylmalonic acid was mostly normal, a vitamin B-12 deficiency was not proven.

Homocysteine metabolism in children with Down syndrome: in vitro modulation.

The gene for cystathionine beta-synthase (CBS) is located on chromosome 21 and is overexpressed in children with Down syndrome (DS), or trisomy 21. The dual purpose of the present study was to evaluate the impact of overexpression of the CBS gene on homocysteine metabolism in children with DS and to determine whether the supplementation of trisomy 21 lymphoblasts in vitro with selected nutrients would shift the genetically induced metabolic imbalance. Plasma samples were obtained from 42 children with karyotypically confirmed full trisomy 21 and from 36 normal siblings (mean age 7.4 years). Metabolites involved in homocysteine metabolism were measured and compared to those of normal siblings used as controls. Lymphocyte DNA methylation status was determined as a functional endpoint. The results indicated that plasma levels of homocysteine, methionine, S-adenosylhomocysteine, and S-adenosylmethionine were all significantly decreased in children with DS and that their lymphocyte DNA was hypermethylated relative to that in normal siblings. Plasma levels of cystathionine and cysteine were significantly increased, consistent with an increase in CBS activity. Plasma glutathione levels were significantly reduced in the children with DS and may reflect an increase in oxidative stress due to the overexpression of the superoxide dismutase gene, also located on chromosome 21. The addition of methionine, folinic acid, methyl-B(12), thymidine, or dimethylglycine to the cultured trisomy 21 lymphoblastoid cells improved the metabolic profile in vitro. The increased activity of CBS in children with DS significantly alters homocysteine metabolism such that the folate-dependent resynthesis of methionine is compromised. The decreased availability of homocysteine promotes the well-established "folate trap," creating a functional folate deficiency that may contribute to the metabolic pathology of this complex genetic disorder.

Long-term effects of vitamin B(12), folate, and vitamin B(6) supplements in elderly people with normal serum vitamin B(12) concentrations.

BACKGROUND: In the elderly, deficiencies of folate, cobalamin (vitamin B(12)) and pyridoxal phosphate (vitamin B(6)) are common. The metabolites homocysteine, methylmalonic acid, 2-methylcitric acid and cystathionine have been reported to be sensitive markers of these vitamin deficiencies. OBJECTIVE: The long-term (269 days) effect of an intramuscular vitamin supplement containing 1 mg vitamin B(12), 1.1 mg folate, and 5 mg vitamin B(6) on serum concentrations of homocysteine (tHcy), methylmalonic acid (MMA), 2-methylcitric acid (2-MCA), and cystathionine (Cysta) was studied in 49 elderly subjects with normal levels of vitamin B(12). METHODS: Vitamin supplement was administered 8 times over a 21-day period, metabolite concentrations were measured until day 269 (e.g. 248 days after the end of vitamin supplementation). RESULTS: From day 0 to 21, the serum levels of the 3 vitamins increased significantly, after cessation of supplementation the levels returned to baseline within the follow-up period. The MMA, 2-MCA and tHcy levels decreased during the treatment period significantly and did not reach baseline values within the 248-day period. Cysta levels did not differ significantly from baseline, either during or after treatment. CONCLUSION: MMA and 2-MCA levels rather reflect the availability of vitamins, especially cobalamin, than the actual serum levels. Since deficiencies of folate, cobalamin and pyridoxal phosphate in the elderly may cause hyerhomocysteinemia and hence may have unfavorable effects on mental performance, determination of MMA and 2-MCA levels in elderly patients with mental disturbances may be a cost-effective measure to improve or maintain mental performance.

Evidence of altered homocysteine metabolism in chronic renal failure.

The fasting serum concentrations of total homocysteine and metabolites of transsulfuration (cystathionine, cysteine, methylmalonic acid, 2-methylcitric acid) and remethylation (methionine) were determined by gas chromatography-mass spectrometry in 40 nondialyzed patients with chronic renal disease and in 50 patients with end-stage renal disease requiring chronic maintenance hemodialysis. The nondialyzed patients and 28 of the dialysis patients did not receive additional vitamin supplementations. Twenty-two of the dialysis patients received daily oral vitamin preparations containing 10 mg pyridoxine (vitamin B(6)), 6 microg cyanocobalamin (vitamin B(12)), and 1 mg folic acid. In the nondialyzed patients, linear regression analysis showed positive correlations between serum concentrations of creatinine and total homocysteine (r = 0.68, p < 0.0001), cystathionine (r = 0.73, p < 0. 0001), methylmalonic acid (r = 0.77, p < 0.0001), and 2-methylcitric acid (r = 0.81, p < 0.0001). Serum homocysteine was positively correlated with serum concentrations of cystathionine (r = 0.59, p < 0.0001), cysteine (r = 0.69, p = 0.004), methylmalonic acid (r = 0. 64, p = 0.0001), and 2-methylcitric acid (r = 0.64, p < 0.0001). There was no significant correlation between serum concentrations of homocysteine and methionine (r = -0.14, p = 0.63). In the hemodialysis patients receiving oral vitamin supplementation, serum homocysteine and cystathionine concentrations were significantly lower than in hemodialysis patients not receiving vitamins (homocysteine 21.8 +/- 1.1 vs. 33.2 +/- 3.7 micromol/l, p = 0.0004; cystathionine 2,075.9 +/- 387.1 vs. 3,171.3 +/- 680.2 nmol/l, p = 0. 02; mean +/- SEM). In summary, our results show increased intermediate products of the transsulfuration pathway, but no increase in remethylation of homocysteine in chronic renal disease, including end-stage renal disease requiring chronic maintenance dialysis.

The effect of a subnormal vitamin B-6 status on homocysteine metabolism.

Homocysteine, an atherogenic amino acid, is either remethylated to methionine or metabolized to cysteine by the transsulfuration pathway. The biochemical conversion of homocysteine to cysteine is dependent upon two consecutive, vitamin B-6-dependent reactions. To study the effect of a selective vitamin B-6 deficiency on transsulfuration, we performed oral methionine load tests on 22 vitamin B-6-deficient asthma patients treated with theophylline (a vitamin B-6 antagonist) and 24 age- and sex-matched controls with a normal vitamin B-6 status. Both groups had normal circulating vitamin B-12 and folate concentrations. Methionine loading resulted in significantly higher increases in circulating total homocyst(e)ine (P < 0.01) and cystathionine (P < 0.05) concentrations in vitamin B-6-deficient patients compared with controls. 6 wk of vitamin B-6 supplementation (20 mg/d) significantly (P < 0.05) reduced post-methionine load increases in circulating total homocyst(e)ine concentrations in deficient subjects, but had no significant effect on the increase in total homocyst(e)ine concentrations in controls. The increases in post-methionine load circulating cystathionine concentrations were significantly (P < 0.01) reduced in both groups after vitamin supplementation. It is concluded that a vitamin B-6 deficiency may contribute to impaired transsulfuration and an abnormal methionine load test, which is associated with premature vascular disease.

Carbon tetrachloride-induced hepatic injury is associated with global DNA hypomethylation and homocysteinemia: effect of S-adenosylmethionine treatment.

Carbon tetrachloride (CCl4) administration to rats produces hepatic cirrhosis and supplementation with S-adenosylmethionine (SAM) can partially prevent CCl4-induced liver injury. These effects are thought to be caused by oxidative stress and the subsequent formation of free radicals, but the mechanism whereby this occurs and the accurate nature of the mechanisms by which SAM exerts its protective action are not well understood. The effect of short-term administration of CCl4 on hepatic DNA methylation and on SAM and S-adenosylhomocysteine (SAH) were assessed. CCl4 administration to rats for 3 weeks resulted in hypomethylation of liver DNA, determined by comparing the extent to which DNA from livers of control or treated animals could be methylated in vitro using [3H-methyl] SAM as methyl donor. This CCl4 effect on DNA methylation was corrected by the administration of SAM (10 mg/kg/d, intramuscularly), with values of methyl groups incorporation comparable with those observed in the control animals. hepatic SAM was decreased by CCl4 (65.3 +/- 5.27 vs. 102.2 +/- 4.89 nmol/g; P < .05) and SAH was increased (69.5 +/- 14.6 vs. 29.4 +/- 3.83 nmol/g; P < .05). This led to a marked reduction of the SAM/SAH ratio (the methylation ratio) from 3.47 in control rats to 0.94 in CCl4-treated animals (P < .05). SAM treatment partially prevented (P < .05) the reduction of the ratio SAM/SAH induced by CCl4. CCl4 also induced a marked elevation of serum homocysteine levels (more than 20-fold; P < .001), which was partially prevented by SAM administration.(ABSTRACT TRUNCATED AT 250 WORDS)