Supplementing lactating dairy cows with a vitamin B12 precursor, 5,6-dimethylbenzimidazole, increases the apparent ruminal synthesis of vitamin B12.

Cobalamin (CBL), the biologically active form of vitamin B12, and its analogs, are produced by bacteria only if cobalt supply is adequate. The analogs differ generally by the nucleotide moiety of the molecule. In CBL, 5,6-dimethylbenzimidazole (5,6-DMB) is the base in the nucleotide moiety. The present study aimed to determine if a supplement of 5,6-DMB could increase utilization of dietary cobalt for synthesis of CBL and change ruminal fermentation, nutrient digestibility, omasal flow of nutrients and ruminal protozoa counts. Eight ruminally cannulated multiparous Holstein cows (mean±standard deviation=238±21 days in milk and 736±47 kg of BW) were used in a crossover design. Cows were randomly assigned to a daily supplement of a gelatin capsule containing 1.5 g of 5,6-DMB via the rumen cannula or no supplement. Each period lasted 29 days and consisted of 21 days for treatment adaptation and 8 days for data and samples collection. Five corrinoids, CBL and four cobamides were detected in the total mixed ration and the omasal digesta from both treatments. The dietary supplement of 5,6-DMB increased (P=0.02) apparent ruminal synthesis of CBL from 14.6 to 19.6 (s.e.m. 0.8) mg/day but had no effect (P>0.1) on apparent ruminal synthesis of the four analogs. The supplement of 5,6-DMB had no effect (P>0.1) on milk production and composition, or on protozoal count, ruminal pH and concentrations of volatile fatty acids and ammonia nitrogen in rumen content. The supplement had also no effect (P>0.1) on intake, omasal flow and apparent ruminal digestibility of dry matter, organic matter, NDF, ADF and nitrogenous fractions. Plasma concentration of CBL was not affected by treatments (P=0.98). Providing a preformed part of the CBL molecule, that is, 5,6-DMB, increased by 34% the apparent ruminal synthesis of CBL by ruminal bacteria but had no effect on ruminal fermentation or protozoa count and it was not sufficient to increase plasma concentrations of the vitamin. Even though the efficiency of cobalt utilization for apparent synthesis of CBL was increased from 2.0% to 2.7% by the 5,6-DMB supplement, this improved efficiency was still very low. Further research is needed to identify the factors affecting efficiency of utilization of cobalt for synthesis of CBL by the bacterial populations in rumen.

The oldest old: red blood cell and plasma folate in African American and white octogenarians and centenarians in Georgia.

OBJECTIVE: To determine the overall folate status of a population-based multi-ethnic sample of octogenarians and centenarians and the specific dietary, demographic and physiological factors associated with observed abnormalities. DESIGN: Population-based multiethnic sample of adults aged 80 to 89 and 98 and above. SETTING: Northern Georgia, USA. PARTICIPANTS: Men and women aged 80 to 89 (octogenarians, n = 77) and 98 and older (centenarians, n = 199). ANALYSES: Wilcoxon rank sum tests, and Chi square and logistic regression analyses were used to examine associations of low and high folate status with hematological indicators and other variables of interest. RESULTS: The prevalence of low red blood cell (RBC) folate was low overall, but tended to be higher in centenarians than in octogenarians (6.5% vs. 1.3%, p = 0.058; defined as RBC folate < 317 nmol/L). The risk of having lower RBC folate (< 25th vs. > 25th percentile for RBC folate for 60yr+ in NHANES 1999-2000) was greater in association with vitamin B12 deficiency (OR = 5.36; 95%CI: 2.87-10.01), African American race (OR = 4.29; 95%CI: 2.08-8.83), and residence in a skilled nursing facility (OR = 3.25; 95%CI: 1.56-6.78) but was not influenced by age, gender, B-vitamin supplement use, high/low food score or presence of atrophic gastritis. Combined high plasma folate and low vitamin B12 status was present in some individuals (n=11), but was not associated with increased prevalence of anemia or cognitive impairment in this study. CONCLUSIONS: Low RBC folate status (< 317 nmol/L) was rare in this post folic acid fortification sample of octogenarians and centenarians. RBC folate status (< 25th percentile) was strongly associated with 1) vitamin B12 deficiency, which has strong implications for vitamin treatment, and 2) with being African American, suggesting racial disparities exist even in the oldest old.

Vitamin B12 deficiency in African American and white octogenarians and centenarians in Georgia.

OBJECTIVE: Test the hypotheses that vitamin B12 deficiency would be prevalent in octogenarians and centenarians and associated with age, gender, race/ethnicity, living arrangements (community or skilled nursing facility), animal food intake, B-vitamin supplement use, atrophic gastritis, folate status, and hematological indicators. DESIGN: Population-based multi-ethnic sample of adults aged 80 to 89 and 98 and above. SETTING: Northern Georgia in the United States. PARTICIPANTS: Men and women aged 80 to 89 (octogenarians, n = 80) and 98 and older (centenarians, n = 231). MEASUREMENTS: Wilcoxon signed-rank tests, Fisher's exact tests, and logistic regression analysis was used to examine the associations of vitamin B12 status with the variables of interest. RESULTS: After excluding participants receiving vitamin B12 injections (n = 17), the prevalence of vitamin B12 deficiency was higher in centenarians than in octogenarians (35.3% vs. 22.8%, p < 0.05, defined as plasma vitamin B12 < 258 pmol/L and serum methylmalonic acid > 271 nmol/L and methylmalonic acid > serum 2-methylcitrate) and in both age groups was correlated with significantly higher homocysteine (p < 0.05) and lower plasma and red cell folate (p < 0.01), but was not related to hemoglobin, anemia, mean cell volume, or macrocytosis. In logistic regression analysis, the probability of being vitamin B12-deficient was significantly increased by being a centenarian vs. octogenarian (p < 0.03), by being white vs. African American (p < 0.02), by increasing severity of atrophic gastritis (p < 0.001), and by not taking oral B-vitamin supplements (p < 0.01), but was not related to gender, living arrangements, or animal food intake. CONCLUSIONS: Centenarians and octogenarians are at high risk for vitamin B12 deficiency for many of the same reasons identified in other older adult populations. Given the numerous potential adverse consequences of poor vitamin B12 status, efforts are needed to ensure vitamin B12 adequacy in these older adults.

Transcobalamin-II variants, decreased vitamin B12 availability and increased risk of frailty.

OBJECTIVE: This project was designed to follow-up prior evidence that demonstrated a significant association between vitamin B12 transport and metabolism and the frailty syndrome in community-dwelling older women. The cross-sectional relationship between genetic variants within six candidate genes along this pathway with serum methylmalonic acid (MMA) levels and frailty was evaluated in this same population of older women. METHODS: Baseline measures were collected prior to folate fortification from 326 women in the Women's Health and Aging Studies I and II. Odds ratios and statistical tests were estimated for single SNP and haplotype via linear regression models for serum MMA, a marker for available vitamin B12, and in logistic regression models for frailty. RESULTS: Fifty-six SNPs from CBS, MTHFR, MTR, MTRR, TCN1 and TCN2 genes were genotyped. Several SNPs in MTHFR, MTR and MTRR demonstrated a modest association to elevated MMA, while SNPs in TCN2 showed significant association to the frailty syndrome. TCN2 polymorphisms, particularly one SNP reported to be in perfect LD with functional variant Pro259Arg, were significantly associated with increased odds of frailty, after adjustment for age, presence of cardiovascular disease and elevated MMA (OR = 2.25, p-value = 0.009). CONCLUSIONS: Using MMA as a marker for vitamin B12, these results suggest that TCN2 gene variants may lead to decreased vitamin B12 availability, leading to reduced energy metabolism, ultimately contributing to frailty pathology. Further studies to determine the biological role of functional TCN2 polymorphisms in frailty are needed.

Subclinical vitamin B12 deficiency in pregnant women attending an antenatal clinic in Nigeria.

SUMMARY: Inadequate vitamin B12 status in a pregnant woman increases the risk for adverse maternal and fetal outcomes. The use of serum vitamin B12 concentration alone to assess vitamin B12 status in pregnant women is unreliable because of the decrease in serum vitamin B12 levels in normal pregnancy. The combination of serum vitamin B12 and methylmalonic acid (MMA) concentrations may provide a better estimate of vitamin B12 status. We obtained blood samples from 98 pregnant women in the third trimester at an antenatal clinic in Jos, Nigeria. All subjects were taking iron and folate supplements. Twelve of the subjects had a serum vitamin B12 concentration <148 pmol/l and 18 subjects had a serum MMA level >271 nmol/l. Using a combination of low serum vitamin B12 and elevated MMA concentrations, eight subjects were classified as having subclinical vitamin B12 deficiency. Because of the potential harmful consequences of vitamin B12 deficiency in pregnant women, it would be advisable to add vitamin B12 supplements to the existing regimen of folate and iron supplements currently provided to pregnant women in Nigeria.

Apparent ruminal synthesis and intestinal disappearance of vitamin B12 and its analogs in dairy cows.

The aim of the project was to calculate the apparent synthesis or destruction of cobalamin (vitamin B(12)) and its analogs in the rumen as well as their apparent intestinal disappearance in dairy cows. Four lactating cows were fed a diet supplemented with cobalt alone (0.76 mg/kg of DM; control) or with cobalt and vitamin B(12) (cyanocobalamin, 500 mg/d; treated). In addition to cobalamin, the only biologically active molecule for the cow, 7 analogs were identified in duodenal and ileal digesta: cobinamide, which lacks the base, ribose, and phosphate groups; and 6 other molecules in which the base, 5,6-dimethylbenzimidazole, is replaced by cresol, 2-CH(3)-adenine, adenine, 2-CH(3)-S-adenine, or 5-OH-benzimidazole, or an unidentified cobamine. Small amounts of cobalamin and cobinamide were detected in the total mixed ration, but apparent synthesis of all forms took place in rumen. During the control period, cobalamin represented 38% of the total amounts of corrinoids produced in rumen. Approximately 11% of the average daily intake of cobalt was used for apparent ruminal synthesis of corrinoids, of which only 4% was incorporated into cobalamin. Only 20% of the supplement of cyanocobalamin was recovered at the duodenal level; cobinamide appeared to be the major product of degradation of supplementary cyanocobalamin in the rumen. During the control and treatment periods, there was an apparent intestinal disappearance of cobalamin and 5-OH-benzimidazole cobamide only; only the apparent intestinal disappearance of cobalamin differed between the 2 periods. Although cobalamin was not the major form synthesized by ruminal microflora and, even if supplementary cyanocobalamin was extensively destroyed by ruminal microflora, based on calculations of apparent intestinal disappearance, cobalamin seems to be the major form absorbed in the small intestine.

S-Adenosylhomocysteine hydrolase deficiency: a second patient, the younger brother of the index patient, and outcomes during therapy.

S-Adenosylhomocysteine (AdoHcy) hydrolase deficiency has been proven in a human only once, in a recently described Croatian boy. Here we report the clinical course and biochemical abnormalities of the younger brother of this proband. This younger brother has the same two mutations in the gene encoding AdoHcy hydrolase, and has been monitored since birth. We report, as well, outcomes during therapy for both patients. The information obtained suggests that the disease starts in utero and is characterized primarily by neuromuscular symptomatology (hypotonia, sluggishness, psychomotor delay, absent tendon reflexes, delayed myelination). The laboratory abnormalities are markedly increased creatine kinase and elevated aminotransferases, as well as specific amino acid aberrations that pinpoint the aetiology. The latter include, most importantly, markedly elevated plasma AdoHcy. Plasma S-adenosylmethionine (AdoMet) is also elevated, as is methionine (although the hypermethioninaemia may be absent or nonsignificant in the first weeks of life). The disease seems to be at least to some extent treatable, as shown by improved myelination and psychomotor development during dietary methionine restriction and supplementation with creatine and phosphatidylcholine.

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.

Homocystinuria due to cystathionine beta-synthase deficiency: novel biochemical findings and treatment efficacy.

To explore the pathogenesis of cystathionine beta-synthase (CBS) deficiency and to test the efficacy of pharmacological therapy we examined a panel of metabolites in nine homocystinuric patients under treated and/or untreated conditions. Off pharmacological treatment, the biochemical phenotype was characterized by accumulation of plasma total homocysteine (median 135 micromol/L) and blood S -adenosylhomocysteine (median 246 nmol/L), and by normal levels of guanidinoacetate and creatine. In addition, enhanced remethylation was demonstrated by low serine level (median 81 micromol/L), and by increased concentration of methionine (median 76 micromol/L) and N -methylglycine (median 6.8 micromol/L). Despite the substantially blocked transsulphuration, which was evidenced by undetectable cystathionine and severely decreased total cysteine levels (median 102 micromol/L), blood glutathione was surprisingly not depleted (median 1155 micromol/L). In 5 patients in whom pharmacological treatment was withdrawn, the differences of median plasma total homocysteine levels (125 micromol/L after withdrawal versus 33 micromol/L under treatment conditions), total cysteine levels (139 versus 211 micromol/L) and plasma serine levels (53 versus 103 micromol/L) on and off treatment demonstrated the efficacy of long-term pyridoxine/betaine administration ( p <0.05). The treatment also decreased blood S -adenosylhomocysteine level (133 versus 59 nmol/L) with a borderline significance. In summary,our study shows that conventional treatment of CBS deficiency by diet and pyridoxine/betaine normalizes many but not all metabolic abnormalities associated with CBS deficiency. We propose that the finding of low plasma serine concentration in untreated CBS-deficient patients merits further exploration since supplementation with serine might be a novel and safe component of treatment of homocystinuria.

Association of folate intake and serum homocysteine in elderly persons according to vitamin supplementation and alcohol use.

BACKGROUND: The serum total homocysteine concentration (tHcy), an indicator of folate status and a possible risk factor for vascular disease, is elevated with impaired renal function and poor vitamin B-12 status, which are common in the elderly. OBJECTIVE: Our objective was to determine the association between tHcy, folate intake, alcohol consumption, and other lifestyle factors in elderly persons. DESIGN: This cross-sectional study used linear regression to model changes in tHcy. Subjects were 278 men and women aged 66-94 y studied in 1993. RESULTS: Total folate intake was negatively associated with tHcy in models adjusted for age, sex, serum creatinine, and serum albumin. We found an interaction between food folate intake and supplement use. Food folate intake had an inverse dose-response relation with tHcy that was limited to nonusers of supplements. Predicted tHcy was 1.5 micromol/L lower in users of supplements containing folate and vitamin B-12 than in nonusers and was independent of food folate intake. We found a positive dose-response relation of coffee and tea intake with tHcy, a positive association for alcohol intake of > or = 60 drinks/mo compared with low intake, and an interaction of alcohol use with folate intake and supplement use. Compared with alcohol users, nonusers had higher predicted tHcy and a lower inverse dose-response relation of food folate intake with tHcy. CONCLUSIONS: The inverse association between folate intake and tHcy was strongest among nonusers of supplements and among alcohol drinkers. Identifying modifiable factors related to tHcy, a possible risk factor for vascular disease, is especially important in elderly persons.

Effects of parenteral cysteine and glutathione feeding in a baboon model of severe prematurity.

BACKGROUND: The availability of cysteine for glutathione synthesis is low in premature infants with respiratory distress. OBJECTIVE: The effects of gestational age, oxygen delivery, and cysteine infusion or glutathione infusion, or both, on plasma total cysteine and other methionine metabolites were studied in a baboon model of severe premature birth with respiratory distress. DESIGN: Premature baboons were studied as part of the multiinvestigator National Institutes of Health Collaborative Project on Bronchopulmonary Dysplasia. Premature baboons, 125 d (69% of term) or 140 d (78% of term) of gestational age, were maintained in neonatal intensive care units for

Racial differences in prevalence of cobalamin and folate deficiencies in disabled elderly women.

BACKGROUND: Many previous investigations of cobalamin and folate status were performed in white populations. OBJECTIVE: Our objective was to determine whether there are racial differences in the prevalence of cobalamin and folate deficiency. DESIGN: The study was a cross-sectional comparison of baseline serum cobalamin, folate, methylmalonic acid (MMA), total homocysteine (tHcy), and creatinine concentrations, complete blood count, and vitamin supplementation in 550 white and 212 African American subjects from a cohort of physically disabled older women. RESULTS: The mean (+/-SD) serum MMA concentration was significantly higher in whites than in African Americans: 284 +/- 229 compared with 218 +/- 158 nmol/L (P = 0.0001). tHcy concentration was higher in African Americans than in whites: 12.4 +/- 7.0 compared with 10.9 +/- 4.6 micromol/L (P = 0.001). Serum cobalamin was lower in whites (P = 0.0002). Cobalamin deficiency (serum cobalamin <258 pmol/L and MMA >271 nmol/L) was more frequent in the white women (19% compared with 8%; P < 0.0003). Folate deficiency (serum folate <11.4 nmol/L, tHcy >13.9 micromol/L, and MMA <271 nmol/L) was more prevalent in African Americans than in whites (5% compared with 2%; P = 0.01). Multivitamin use was associated with lower tHcy but not with MMA concentrations. Regression models showed that age >85 y, African American race, serum creatinine >90 micromol/L, and high MMA concentration were all significantly correlated with higher tHcy. Creatinine > 90 micromol/L, white race, and folate concentration were positively associated with MMA concentration. CONCLUSIONS: Cobalamin deficiency with elevated serum MMA concentration is more prevalent in elderly white than in African American women and elevated serum tHcy and folate deficiency are more prevalent in elderly African American than in white women.

Vitamin B-12 deficiency in the elderly: current dilemmas.

Vitamin B-12 deficiency is present in up to 15% of the elderly population as documented by elevated methylmalonic acid with or without elevated total homocysteine concentrations in combination with low or low-normal vitamin B-12 concentrations. Clinical signs and symptoms of vitamin B-12 deficiency are insensitive in elderly subjects and comorbidity in these subjects makes responses to therapy difficult to interpret. Many elderly subjects with hyperhomocysteinemia have undiagnosed vitamin B-12 deficiency with elevated serum methylmalonic acid concentrations. Therefore, such elderly subjects should not receive folic acid supplementation before their vitamin B-12 status is diagnosed. Oral vitamin B-12 supplementation may be effective in lowering serum methylmalonic acid values in the elderly. However, the dose of vitamin B-12 in most common multivitamin preparations is too low for this purpose. Research efforts should be directed toward determining practical methods for diagnosing and treating vitamin B-12 deficiency in the millions of elderly subjects with undiagnosed deficiency.

Vitamin supplementation and other variables affecting serum homocysteine and methylmalonic acid concentrations in elderly men and women.

OBJECTIVE: An elevated serum concentration of the metabolite, homocysteine (Hcys): 1) can indicate folate or vitamin B12 deficiency, 2) is an independent risk factor for vascular disease. The metabolite, methylmalonic acid (MMA), is elevated in deficiency of vitamin B12, but not folate. The purpose of this study was to determine the effect of self-selected vitamin supplementation and other variables on serum Hcys and MMA concentrations in elderly men and women. METHODS: Serum concentrations of Hcys, MMA, folate and vitamin B12 were measured for elderly volunteers, age 68-96 years, and compared for those consuming (26 men, 25 women) and not consuming (24 men, 25 women) self-selected vitamin supplements. RESULTS: Compared with the nonsupplemented group, the supplemented group had lower mean serum MMA (208 +/- 162 vs. 241 +/- 98 nmol/L [+/- SD]) and Hcys (9.5 +/- 2.6 vs. 11.2 +/- 2.7 mumol/L); and higher serum vitamin B12 (391 +/- 174 vs 292 +/- 107 pmol/L), and serum folate (46 +/- 15 vs. 24 +/- 10 nmol/L) p < 0.05. Among all 100 subjects, the prevalence of serum vitamin B12 < 221 pmol/L (300 pg/mL) was 18; MMA > 271 nmol/L, 16; Hcys > 16.2 mumol/L, 3; folate < 5.0 nmol/L, none. Based on serum vitamin B12 < 221 nmol/L with elevated serum MMA, vitamin B12 deficiency was probable in seven subjects, of whom two were supplemented. All three subjects with elevated serum Hcys had elevated serum MMA as well, suggesting vitamin B12 deficiency or renal insufficiency. A stepwise linear regression model for serum Hcys explained 61.7% of the variance, and included (in order) serum creatinine, folate, vitamin B12, albumin, age and body mass index (BMI). A model with serum MMA replacing serum vitamin B12 explained 64.1% of the variance in serum Hcys. Folate did not enter the model for supplemented subjects, supporting a "threshold effect": serum Hcys was inversely related to serum folate at lower serum folate (nonsupplemented subjects), but at higher serum folate (supplemented subjects), the relationship was flat. In supplemented subjects, serum Hcys was still related to vitamin B12 status, confirming that tissue deficiency of the vitamin was present. CONCLUSIONS: Results showed potential usefulness of serum MMA and Hcys in identifying subclinical or tissue deficiency of vitamin B12. Clinicians should be aware of the risk of vitamin B12 deficiency in older people and of current screening algorithms using serum metabolites. These elderly volunteers had generally good folate status; nevertheless, some subjects seemed likely to benefit from an improvement in folate status that would reduce their serum Hcys within the normal range. The role of serum creatinine in the normal range in predicting serum Hcys, a vascular disease risk factor, remains unexplained.

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.

Effects of vitamin B12, folate, and vitamin B6 supplements in elderly people with normal serum vitamin concentrations.

In a prospective, multicentre, double-blind controlled study, the effect of an intramuscular vitamin supplement containing 1 mg vitamin B12, 1.1 mg folate, and 5 mg vitamin B6 on serum concentrations of methylmalonic acid (MMA), homocysteine (HCYS), 2-methylcitric acid (2-MCA), and cystathionine (CYSTA) was compared with that of placebo in 175 elderly subjects living at home and 110 in hospital. Vitamin supplement and placebo were administered eight times over a 3-week period. Vitamin supplement but not placebo significantly reduced all four metabolite concentrations at the end of the study in both study groups. The maximum effects of treatment were usually seen within 5-12 days. Initially elevated metabolite concentrations returned to normal in a higher proportion of the vitamin than of the placebo group: 92% vs 20% for HYCS; 82% vs 20% for MMA; 62% vs 25% for 2-MCA; and 42% vs 25% for CYSTA. The response rate to vitamin supplements supports the notion that metabolic evidence of vitamin deficiency is common in the elderly, even in the presence of normal serum vitamin levels. Metabolite assays permit identification of elderly subjects who may benefit from vitamin supplements.

Changes in plasma methionine and total homocysteine levels in patients receiving methotrexate infusions.

Methotrexate reduces intracellular pools of 5-methyltetrahydrofolate and could result in reduced conversion of homocysteine to methionine by methionine synthetase. This study was designed to investigate the effects of moderate dose to very high dose methotrexate on methionine and total homocysteine as reflections of methotrexate induced intracellular events. Methionine and total homocysteine were measured prior to, during, and following twenty-six 24-h i.v. infusions of 33.6 g/m2 methotrexate (very high dose methotrexate) in 16 children with acute lymphocytic leukemia and seven 4-h i.v. infusions of 8 g/m2 methotrexate (high dose methotrexate) in 5 children with osteogenic sarcoma. Amino acids were measured by gas chromatography/mass spectrophotometry. Mean methionine levels decreased by 70.0 +/- 3.1% (SE) with very high dose methotrexate and 72.6 +/- 5.9% with high dose methotrexate at 24 and 4.5 h, respectively, after beginning methotrexate infusions. Mean total homocysteine levels increased by 61.7 +/- 3.1% with very high dose methotrexate and 55.6 +/- 17.5% with high dose methotrexate at 36 and 24 h, respectively, after beginning methotrexate infusions. No consistent or significant changes were noted in levels of total cysteine, leucine, isoleucine, or valine. Similar changes did not occur in patients receiving prednisone, vincristine, daunomycin, and intrathecal methotrexate as therapy for acute lymphocytic leukemia. These changes in homocysteine and methionine may reflect biological effects of methotrexate that may predict cytotoxicity of methotrexate.

Measurements of iron absorption from prenatal multivitamin--mineral supplements.

Although prenatal multivitamin--mineral supplements containing 60 to 65 mg of iron, taken once daily, are used widely to assure that pregnant women absorb the approximately 3.5 mg of supplemental iron per day that they require, there have been no studies concerning the absorption of iron from these preparations. Using cross-over studies in groups of normal nonpregnant women of childbearing age, such iron absorption was assessed using a technique in which absorption is calculated from the measured increase in serum iron after the oral ingestion of iron in various forms. With each of 4 different brands of prenatal supplements, mean iron absorption was less than the required 3.5 mg and ranged from 1.8 to 3.0 mg. These values were significantly less (P less than .01) than the 8.1 mg that was absorbed from 65 mg of iron alone. Decreased iron absorption in the prenatal supplements was shown to be due to inhibition by calcium carbonate and magnesium oxide and, in some cases, to poor iron release. When one of the 4 brands was reformulated to contain less calcium carbonate and less magnesium oxide, mean iron absorption increased to 4.5 mg. It is concluded that the amount of iron absorbed from many prenatal multivitamin--mineral supplements is significantly less than with standard forms of iron in nonpregnant women and that bioavailability studies should be performed on pregnant patients to determine whether these commercial preparations provide adequate amounts of iron during pregnancy.