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.

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.

Association between decreased vitamin levels and MTHFR, MTR and MTRR gene polymorphisms as determinants for elevated total homocysteine concentrations in pregnant women.

OBJECTIVES: To examine the association between methylenetetrahydrofolate reductase (MTHFR) (C677T and A1298C), methionine synthase (MTR) A2756G and methionine synthase reductase (MTRR) A66G gene polymorphisms and total homocysteine (tHcy), methylmalonic acid (MMA) and S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) levels; and to evaluate the potential interactions with folate or cobalamin (Cbl) status. SUBJECTS/METHODS: Two hundred seventy-five healthy women at labor who delivered full-term normal babies. Cbl, folate, tHcy, MMA, SAM and SAH were measured in serum specimens. The genotypes for polymorphisms were determined by PCR-restriction fragment length polymorphism (RFLP). RESULTS: Serum folate, MTHFR 677T allele and MTR 2756AA genotypes were the predictors of tHcy levels in pregnant women. Serum Cbl and creatinine were the predictors of SAM/SAH ratio and MMA levels, respectively. The gene polymorphisms were not determinants for MMA levels and SAM/SAH ratios. Low levels of serum folate were associated with elevated tHcy in pregnant women, independently of the gene polymorphisms. In pregnant women carrying MTHFR 677T allele, or MTHFR 1298AA or MTRR 66AA genotypes, lower Cbl levels were associated with higher levels of tHcy. Lower SAM/SAH ratio was found in MTHFR 677CC or MTRR A2756AA genotypes carriers when Cbl levels were lower than 142 pmol/l. CONCLUSIONS: Serum folate and MTHFR C677T and MTR A2576G gene polymorphisms were the determinants for tHcy levels. The interaction between low levels of serum Cbl and MTHFR (C677T or A1298C) or MTRR A66G gene polymorphisms was associated with increased tHcy.

Markers of B-vitamin deficiency and frailty in older women.

OBJECTIVE: To evaluate the association between markers of vitamins B12, B6 and folate deficiency and the geriatric syndrome of frailty. DESIGN: Cross-sectional study of baseline measures from the combined Women's Health and Aging Studies. SETTING: Baltimore, Maryland. PARTICIPANTS: Seven hundred three community-dwelling women, aged 70-79. MEASUREMENTS: Frailty was defined by five-component screening criteria that include weight, grip strength, endurance, physical activity and walking speed measurements and modeled as binary and 3-level polytomous outcomes. Independent variables serum vitamin B6, vitamin B12, methylmalonic acid, total homocysteine, cystathionine and folate were modeled continuously and as abnormal versus normal. RESULTS: Serum biomarker levels varied significantly by race. All analyses were race-stratified and results are reported only for Caucasian women due to small African American sample size. In polytomous logistic regression models of 3-level frailty, Caucasian women with increasing MMA, defined either continuously or using a predefined threshold, had 40-60% greater odds of being prefrail (p-values < 0.07) and 1.66-2.33 times greater odds of being frail (p-values < 0.02) compared to nonfrails after adjustment for age, education, low serum carotenoids, alcohol intake, cardiovascular disease and renal impairment. Both binary and polytomous frailty models evaluating vitamin B12 as the main exposure estimated odds ratios that were similar in trend yet slightly less significant than the MMA results. CONCLUSIONS: These results suggest that vitamin B12 deficiency may contribute to the frailty syndrome in community-dwelling older women. Future studies are needed to explore these relationships longitudinally.

Inhibition of cobalamin-dependent enzymes by cobalamin analogues in rats.

To determine which parts of the cobalamin (cbl) molecule are required for enzyme activity and which parts, if altered, might inhibit cbl-dependent enzyme activity, we synthesized 16 cbl analogues and administered them to nutritionally normal rats. The cbl analogues, with either modifications of the propionamide side chains of the A-, B-, and C-rings, the acetamide side chain of the B-ring, or the nucleotide moiety, were administered to rats by continuous 14-d subcutaneous infusion. Infusion of cbl-stimulated, cbl-dependent activity. Changes in any part of the cbl molecule always abolished stimulation and, in some cases, caused potent inhibition of both cbl-dependent enzymes. The most inhibitory analogues, OH-cbl[c-lactam], a B-ring analogue, and OH-cbl[e-dimethylamide] and OH-cbl[e-methylamide], two C-ring analogues, decreased mean liver holo-L-methylmalonyl-coenzyme A mutase activity to 65% of control values and increased serum methylmalonic acid concentrations to as high as 3,200% of the control values. Liver methionine synthetase activity was decreased to approximately 20% of the control and mean serum total homocysteine concentrations were increased to 340% of control. A similar level of inhibition was demonstrated in rats who were exposed to 28 d of inhaled nitrous oxide or a prolonged period of dietary cbl deficiency. The inhibitory cbl analogues, nitrous oxide, and diet deficiency all depleted liver cbl. The naturally occurring cbl analogues with modifications of the nucleotide moiety had no effects. We conclude that all parts of the cbl molecule are necessary for in vivo cbl-dependent enzyme activity and that modifications of the side chains of the B and C rings are associated with potent in vivo inhibition of cbl-dependent enzyme activity.

Elevation of total homocysteine in the serum of patients with cobalamin or folate deficiency detected by capillary gas chromatography-mass spectrometry.

To determine if levels of serum total homocysteine are elevated in patients with either cobalamin or folate deficiency, we utilized a new capillary gas chromatographic-mass spectrometric technique to measure total homocysteine in the serum of 78 patients with clinically confirmed cobalamin deficiency and 19 patients with clinically confirmed folate deficiency. Values ranged from 11 to 476 mumol/liter in the cobalamin-deficient patients and 77 of the 78 patients had values above the normal range of 7-22 mumol/liter as determined for 50 normal blood donors. In the cobalamin-deficient patients, serum total homocysteine was positively correlated with serum folate, mean corpuscular volume, serum lactate dehydrogenase, serum methylmalonic acid, and the degree of neurologic involvement, and inversely correlated with platelets and hematocrit. In the folate-deficient patients, values for serum total homocysteine ranged from 17 to 185 mumol/liter and 18 of the 19 patients had values above the normal range. Some patients with pernicious anemia who were intermittently treated with cyanocobalamin were found to have elevated serum levels of total homocysteine while they were free of hematologic and neurologic abnormalities. The measurement of serum total homocysteine will help define the incidence of cobalamin deficiency and folate deficiency in various patient populations.

Assay of methylmalonic acid in the serum of patients with cobalamin deficiency using capillary gas chromatography-mass spectrometry.

To determine the incidence of elevated levels of serum methylmalonic acid in patients with cobalamin deficiency, we utilized a new capillary gas chromatographic-mass spectrometric technique to measure methylmalonic acid in the serum of 73 patients with clinically confirmed cobalamin deficiency. Values ranged from 55 to 22,300 ng/ml, and 69 of the 73 patients had values above the normal range of 19-76 ng/ml as determined for 50 normal blood donors. In the cobalamin-deficient patients, serum methylmalonic acid was significantly correlated with the serum folate level and the degree of neurologic involvement. Some patients with pernicious anemia who were intermittently treated with cyanocobalamin were found to have elevated serum levels of methylmalonic acid while free of hematologic and neurologic abnormalities. A cobalamin-deficient patient is described with a normal serum cobalamin and an elevated serum methylmalonic acid. We conclude that the ability to measure methylmalonic acid in human serum will be useful in studies designed to determine the incidence of cobalamin deficiency in various patient populations.

Increased hepatic mitochondrial capacity in rats with hydroxy-cobalamin[c-lactam]-induced methylmalonic aciduria.

Treatment of rats with the vitamin B12 analogue hydroxy-cobalamin[c-lactam] (HCCL) impairs methylmalonyl-CoA mutase function and leads to methylmalonic aciduria due to intracellular accumulation of propionyl and methylmalonyl-CoA. Since accumulation of these acyl-CoAs disrupts normal cellular regulation, the present investigation characterized metabolism in hepatocytes and liver mitochondria from rats treated subcutaneously with HCCL or saline (control) by osmotic minipump. Consistent with decreased methylmalonyl-CoA mutase activity, 14CO2 production from 1-14C-propionate (1 mM) was decreased by 76% and 82% after 2-3 wk and 5-6 wk of HCCL treatment, respectively. In contrast, after 5-6 wk of HCCL treatment, 14CO2 production from 1-14C-pyruvate (10 mM) and 1-14C-palmitate (0.8 mM) were increased by 45% and 49%, respectively. In isolated liver mitochondria, state 3 oxidation rates were unchanged or decreased, and activities of the mitochondrial enzymes, citrate synthetase, succinate dehydrogenase, carnitine palmitoyltransferase, and glutamate dehydrogenase (expressed per milligram mitochondrial protein) were unaffected by HCCL treatment. In contrast, activities of the same enzymes were significantly increased in both liver homogenate (expressed per gram liver) and isolated hepatocytes (expressed per 10(6) cells) from HCCL-treated rats. The mitochondrial protein per gram liver, calculated on the basis of the recovery of the mitochondrial enzymes, increased by 39% in 5-6 wk HCCL-treated rats. Activities of lactate dehydrogenase, catalase, cyanide-insensitive palmitoyl-CoA oxidation, and arylsulfatase A in liver were not affected by HCCL treatment. Hepatic levels of mitochondrial mRNAs were elevated up to 10-fold in HCCL-treated animals as assessed by Northern blot analysis. Thus, HCCL treatment is associated with enhanced mitochondrial oxidative capacity and an increased mitochondrial protein content per gram liver. Increased mitochondrial oxidative capacity may be a compensatory mechanism in response to the metabolic insult induced by HCCL administration.

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.

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.

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.

Vitamin B(12) deficiency and depression in physically disabled older women: epidemiologic evidence from the Women's Health and Aging Study.

OBJECTIVE: It has been hypothesized that adequate concentrations of vitamin B(12) and folate are essential to maintain the integrity of the neurological systems involved in mood regulation, but epidemiologic evidence for such a link in the general population is unavailable. This study examined whether community-dwelling older women with metabolically significant vitamin B(12) or folate deficiency are particularly prone to depression. METHOD: Serum levels of vitamin B(12), folate, methylmalonic acid, and total homocysteine were assayed in 700 disabled, nondemented women aged 65 years and over living in the community. Depressive symptoms were measured by means of the Geriatric Depression Scale and categorized as no depression, mild depression, and severe depression. RESULTS: Serum homocysteine levels, serum folate levels, and the prevalences of folate deficiency and anemia were not associated with depression status. The depressed subjects, especially those with severe depression, had a significantly higher serum methylmalonic acid level and a nonsignificantly lower serum vitamin B(12) level than the nondepressed subjects. Metabolically significant vitamin B(12) deficiency was present in 14.9% of the 478 nondepressed subjects, 17. 0% of the 100 mildly depressed subjects, and 27.0% of the 122 severely depressed women. After adjustment for sociodemographic characteristics and health status, the subjects with vitamin B(12) deficiency were 2.05 times as likely to be severely depressed as were nondeficient subjects. CONCLUSIONS: In community-dwelling older women, metabolically significant vitamin B(12)deficiency is associated with a twofold risk of severe depression.

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.

Prevalence of cobalamin deficiency in the Framingham elderly population.

To determine whether the increased prevalence of low serum cobalamin concentrations in elderly people represents true deficiency, serum concentrations of cobalamin and folate and of metabolites that are sensitive indicators of cobalamin deficiency were measured in 548 surviving members of the original Framingham Study cohort. Serum cobalamin concentrations < 258 pmol/L were found in 222 subjects (40.5%) compared with 17.9% of younger control subjects (P < 0.001). Serum methylmalonic acid and total homocysteine concentrations were markedly elevated in association with cobalamin values < 258 pmol/L in 11.3% and 5.7%, respectively, of the cohort. Both metabolites were increased in 3.8% of the cohort, associated with significantly lower erythrocyte counts and higher mean cell volumes. Serum metabolites correlated best with serum cobalamin values, even when subnormal determinations were excluded. The prevalence of cobalamin deficiency was > or = 12% in a large sample of free-living elderly Americans. Many elderly people with "normal" serum vitamin concentrations are metabolically deficient in cobalamin or folate.

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

Metabolic evidence that deficiencies of vitamin B-12 (cobalamin), folate, and vitamin B-6 occur commonly in elderly people.

Measurements of the serum concentrations of the metabolites homocysteine, cystathionine, methylmalonic acid, and 2-methylcitric acid, which accumulates when vitamin B-12-, folate-, and vitamin B-6-dependent enzymatic reactions are impaired, should provide a better indication of intracellular deficiency of these vitamins. We measured the serum concentration of these vitamins and the four metabolites in 99 healthy young people, 64 healthy elderly subjects, and 286 elderly hospitalized patients. A low serum vitamin B-12 concentration was found in 6% and 5%, low folate in 5% and 19%, and low vitamin B-6 in 9% and 51%, and one or more metabolites were elevated in 63% and 83% of healthy elderly subjects and elderly hospitalized patients, respectively. These results strongly suggest that the prevalence of tissue deficiencies of vitamin B-12, folate, and vitamin B-6 as demonstrated by the elevated metabolite concentrations is substantially higher than that estimated by measuring concentrations of the vitamins.

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.

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.

Cerebrospinal fluid methylmalonic acid levels in normal subjects and patients with cobalamin deficiency.

We measured methylmalonic acid, which accumulates in the blood and tissues of patients with cobalamin deficiency, in the CSF of 65 patients using capillary-gas chromatography and mass spectrometry. In 58 control patients, methylmalonic acid concentrations were always higher in CSF than in serum (mean CSF: serum ratio, 2.65; range, 1.17 to 7.78). In contrast, in six patients with elevated serum methylmalonic acid levels due to renal failure, CSF concentrations were normal in five and the CSF: serum ratio was less than one in four. In three patients with neuropsychiatric syndromes due to cobalamin deficiency and one patient with a normal serum cobalamin level who was an abuser of nitrous oxide, CSF concentrations were markedly increased (mean level, 600 times that of controls), out of proportion to those in the serum (mean CSF: serum ratio, 8.38; range, 3.5 to 13.5). The potential usefulness of CSF metabolite levels in the diagnosis of cobalamin deficiency is undetermined.

Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies.

PURPOSE: Patients with cobalamin (vitamin B12) deficiency usually lack many of the classic features of severe megaloblastic anemia; because of the low diagnostic specificity of decreased serum cobalamin levels, demonstrating the deficiency unequivocally is often difficult. We examined the sensitivity of measuring serum concentrations of methylmalonic acid and total homocysteine for diagnosing patients with clear-cut cobalamin deficiency and compared the results with those of patients with clear-cut folate deficiency. PATIENTS AND METHODS: Serum metabolites were measured for all patients seen from 1982 to 1989 at two university hospitals who met the criteria for cobalamin and folate deficiency states and for such patients seen from 1968 to 1981 from whom stored sera were available. In all, 406 patients had 434 episodes of cobalamin deficiency and 119 patients had 123 episodes of folate deficiency. Criteria for deficiency states included serum vitamin levels, hematologic and neurologic findings, and responses to therapy. Responses were documented in 97% of cobalamin-deficient patients and 76% of folate-deficient patients. Metabolite levels were measured by modified techniques using capillary-gas chromatography and mass spectrometry. RESULTS: Most of the cobalamin-deficient patients had underlying pernicious anemia; two thirds were blacks or Latinos. Hematocrits were normal in 28% and mean cell volumes in 17%. Of the 434 episodes of cobalamin deficiency, 98.4% of serum methylmalonic acid levels and 95.9% of serum homocysteine levels were elevated (greater than 3 standard deviations above the mean in normal subjects). Only one patient had normal levels of both metabolites. Serum homocysteine levels were increased in 91% of the 123 episodes of folate deficiency. Methylmalonic acid was elevated in 12.2% of the folate-deficient patients; in all but one, the elevation was attributable to renal insufficiency or hypovolemia. CONCLUSIONS: For the cobalamin-deficient patients, measuring serum metabolite concentrations proved to be a highly sensitive test of deficiency. We conclude that normal levels of both methylmalonic acid and total homocysteine rule out clinically significant cobalamin deficiency with virtual certainty.