Changes in markers of cobalamin status after cessation of oral B-vitamin supplements in elderly people with mild cobalamin deficiency.

Mildly cobalamin-deficient elderly were supplemented with 1000 microg cobalamin (group C, n=34), 1000 microg cobalamin with 400 microg folic acid (group CF, n=31) or a placebo (n=30) for 6 months. Participants provided one single blood sample 3, 5 or 7 months after cessation of supplementation to monitor early changes in plasma concentrations of cobalamin, holotranscobalamin (holoTC) and methylmalonic acid (MMA). At the end of supplementation (groups C+CF), one participant met our criteria for mild cobalamin deficiency, as did 13, 14 and 43% of the participants assessed at respectively 3, 5 and 7 months post-supplementation. Cobalamin and holoTC declined on average with 47 and 56% relative to concentrations at the end of supplementation for the group assessed at 7 months post-supplementation. Essentially similar declines were observed for those participants assessed at 3 and 5 months post-supplementation. Mean MMA concentrations increased by 15% (P=0.07) in those participants assessed at 3 and 5 months post-supplementation, and increased by 50% (P=0.002) in those participants assessed at 7 months post-supplementation. Considering MMA as a sensitive tissue marker for cobalamin status, oral supplementation may afford adequate cobalamin status for a period of up to 5 months after cessation in the majority of participants.

Routine determination of serum methylmalonic acid and plasma total homocysteine in Norway.

OBJECTIVE: To study the total number of combined analyses of methylmalonic acid (MMA) and total plasma homocysteine (tHcy) carried out during February 1998 at the Central Laboratory of Haukeland University Hospital. METHODS: Laboratory data and requester comments of 2917 subjects in whom MMA was requested during February 1998, were retrieved from the laboratory information system (LIS). In 2520 cases, the results from the combined analyses of MMA and tHcy were available. Requester comments were registered in the LIS in 1084 cases. Results from additional laboratory analyses were accessible in about 10%, of cases. RESULTS: General practitioners requested MMA and tHcy on three main indications, i.e. low cobalamin, "control" and neurological symptoms. Metabolites were requested in twice as many women than men. Furthermore, MMA was requested in younger age groups of women compared with men. Plasma tHcy and MMA showed positive correlations with age and serum creatinine, and tHcy was generally 1-2 micromol/L higher in men than in premenopausal women. In cobalamin- (serum cobalamin > 300 pmol/L) and/or folate- (serum folate > 10 nmol/L) replete subjects, the average difference in MMA or tHcy according to the highest and lowest creatinine quartiles was 0.08 and 5-6 micromol/L, respectively. Different combinations of MMA and tHcy were evaluated by using a 5 x 5 matrix of predefined concentration intervals. Based on this matrix, cobalamin and folate deficiency could be excluded or the likely diagnoses proposed in 76% of cases. Cobalamin deficiency or folate deficiency was likely in about 7% and 12% of the subjects investigated, respectively. CONCLUSIONS: A combined analysis of MMA and tHcy provides complementary diagnostic information. When interpreting MMA and tHcy values, age, gender and renal function in particular must be taken into account. Typical combinations of MMA and tHcy concentration intervals could be proposed, which could either exclude deficiency or indicate likely diagnoses and/or influence of confounders.

Homocysteine and methylmalonic acid levels in pregnant Nepali women. Should cobalamin supplementation be considered?

OBJECTIVE: The aim of this study was to investigate homocysteine and methylmalonic acid levels as markers of functional cobalamin and folate status in pregnant Nepali women. DESIGN: Cross-sectional study. SETTING: Patan Hospital, Kathmandu, Nepal. SUBJECTS: A sub-sample (n=382) of all pregnant women (n=2856) coming for their first antenatal visit in a 12 month period, 1994-1995. The selection of the sub-sample was based on maternal haematocrit values, categorised into three groups: severely, moderately and non-anaemic women. As serum levels of total homocysteine (s-tHcy) and methylmalonic acid (s-MMA) were similar in the three groups, pooled data are presented. Women who had already received micronutrient supplementation (n=54) were excluded. The remaining women (n=328) were included in the statistical analysis. RESULTS: Overall mean values (+/-s.d.) of s-tHcy and s-MMA were 9.5 (+/-4.2) micromol/l and 0.39 (+/-0.32) micromol/l, respectively. Elevated s-tHcy (>7.5 micromol/l) was found in 68% of the women, while 61% had elevated s-MMA (>0.26 micromol/l). Low s-cobalamin values (<150 pmol/l) were observed in 49% of the women, while only 7% had low s-folate values (< or =4.5 nmol/l). s-tHcy was significantly correlated with s-MMA (r=0.28, P<0.001), s-cobalamin (r=-0.30, P<0.001) and s-folate (r=-0.24, P<0.001). s-MMA was significantly associated with s-cobalamin (r=-0.40, P<0.001), but not with s-folate. CONCLUSIONS: Functional cobalamin deficiency was very common in the study population, while functional folate deficiency was rather uncommon. We suggest considering cobalamin supplementation to pregnant Nepali women. SPONSORSHIP: The Norwegian Research Council and the Norwegian Universities Committee for Development, Research and Education.

Evaluation of indicators of cobalamin deficiency defined as cobalamin-induced reduction in increased serum methylmalonic acid.

BACKGROUND: Early detection of cobalamin deficiency is clinically important, and there is evidence that such deficiency occurs more frequently than previously anticipated. However, serum cobalamin and other commonly used tests have limited ability to diagnose a deficiency state. METHODS: We investigated the ability of hematological variables, serum cobalamin, plasma total homocysteine (tHcy), serum and erythrocyte folate, gastroscopy, age, and gender to predict cobalamin deficiency. Patients (n = 196; age range, 17-87 years) who had been referred from general practice for determination of serum cobalamin were studied. Cobalamin deficiency was defined as serum methylmalonic acid (MMA) >0.26 micromol/L with at least 50% reduction after cobalamin supplementation. ROC and logistic regression analyses were used. RESULTS: Serum cobalamin and tHcy were the best predictors, with areas under the ROC curve (SE) of 0. 810 (0.034) and 0.768 (0.037), respectively, but age, intrinsic factor antibodies, and gastroscopy gave additional information. CONCLUSIONS: When cobalamin deficiency is suspected in general practice, serum cobalamin should be the first diagnostic test, and the result should be interpreted in relation to the age of the patient. When a definite diagnosis cannot be reached, MMA and tHcy determination will provide additional discriminative information, but MMA, being more specific, is preferable for assessment of cobalamin status.

Riboflavin as a determinant of plasma total homocysteine: effect modification by the methylenetetrahydrofolate reductase C677T polymorphism.

BACKGROUND: Plasma total homocysteine (tHcy) is a risk factor for cardiovascular disease. tHcy concentrations are partly determined by folate, cobalamin, and vitamin B(6) status, and methylenetetrahydrofolate reductase (MTHFR) and other flavoenzymes are important for the biotransformation of these vitamins. This motivates the investigation of the possible relationship between riboflavin status and tHcy. METHODS: The study had a cross-sectional design and included 423 healthy blood donors, ages 19-69 years. We determined plasma tHcy, serum folate, serum cobalamin, serum creatinine, and MTHFR C677T genotype. In addition, we measured riboflavin and its two coenzyme forms, flavin mononucleotide and flavin adenine dinucleotide, in EDTA plasma by capillary electrophoresis and laser-induced fluorescence detection. RESULTS: Riboflavin determined tHcy independently in a multiple linear regression model with adjustment for sex, age, folate, cobalamin, creatinine, and MTHFR genotype (P = 0.008). tHcy was 1.4 micromol/L higher in the lowest compared with the highest riboflavin quartile. The riboflavin-tHcy relationship was modified by genotype (P = 0.004) and was essentially confined to subjects with the C677T transition of the MTHFR gene. CONCLUSIONS: Plasma riboflavin is an independent determinant of plasma tHcy. Studies on deficient populations are needed to evaluate the utility of riboflavin supplementation in hyperhomocysteinemia.

Anaemia in pregnancy: possible causes and risk factors in Nepali women.

OBJECTIVE: The aim of this study was to investigate the importance of nutritional deficiencies and infections in the development of anaemia in pregnant Nepali women. DESIGN: Case-control study. SETTING: Patan Hospital, Kathmandu, Nepal. SUBJECTS: A sub-sample (n=479) of all pregnant women (n=2856) coming for their first antenatal visit in a 12 month period, 1994-1995. Women who had already received any micronutrient supplementation (n=82), and those whose serum samples showed macroscopic haemolysis (n=7) were excluded. The remaining women (n=390) were included in the statistical analysis. They were divided into three groups; a non-anaemic control group, haematocrit (Hct)>33% (n=82), and two case-groups: moderately anaemic, Hct 25-33% (n=254), and severely anaemic, Hct<25% (n=54). RESULTS: We found high prevalences of nutritional deficiencies and intestinal infections, both among cases and controls. The prevalence of low s-ferritin was high, especially among the severely anaemic women (55.6%). In a multiple logistic regression model, the presence of low s-vitamin A, elevated s-C-reactive protein or hookworm infection was associated with a significantly increased risk of severe anaemia. The adjusted odds ratios (95% CI) were 8.38 (1.99, 35.30), 4.91 (1.22, 19.67) and 5.43 (1.20, 24.61), respectively. CONCLUSIONS: In addition to the present routine iron and folate supplementation to pregnant Nepali women, vitamin A supplementation needs to be considered. Prevention and treatment of infections should, together with dietary advice, be emphasized more strongly in the antenatal care. SPONSORSHIP: The Norwegian Research Council and the Norwegian Universities Committee for Development, Research and Education. European Journal of Clinical Nutrition (2000) 54, 3-8

Supplementation with vitamin B12 decreases homocysteine and methylmalonic acid but also serum folate in patients with end-stage renal disease.

Hyperhomocysteinemia is frequently found in patients with end-stage renal disease (ESRD). Plasma total homocysteine (tHcy) concentrations may be reduced by supplementation with folic acid or combinations of folic acid, vitamin B12, and vitamin B6. Supplementation studies with vitamin B12 alone in patients with ESRD have not yet been published. In this study, we investigated the effects of intravenous injection of cyanocobalamin (1 mg/wk for 4 weeks) in ESRD patients (N = 14) with low serum cobalamin concentrations (<180 pmol/L). All patients had elevated levels of plasma tHcy, methylmalonic acid (MMA), and cystathionine before supplementation. After supplementation, plasma tHcy and MMA decreased 35% and 48%, respectively; however, cystathionine levels were unchanged. The extent of the plasma tHcy reduction tended to be influenced by the C677T polymorphism of methylenetetrahydrofolate reductase (MTHFR). Serum cobalamin increased significantly upon supplementation, whereas serum folate levels were substantially reduced by 47%. In contrast, red blood cell (RBC) folate was unchanged. This study shows that vitamin B12 supplementation effectively decreases both MMA and plasma tHcy in ESRD patients with low B12 levels. Furthermore, it illustrates the close interrelation between vitamin B12 and folate metabolism.

Cobalamin deficiency in general practice. Assessment of the diagnostic utility and cost-benefit analysis of methylmalonic acid determination in relation to current diagnostic strategies.

Diagnosing cobalamin deficiency is often difficult. We investigated the diagnostic strategies that 224 general practitioners used to assess cobalamin status and the criteria on which they based their decisions to supplement patients. From all serum cobalamin analyses carried out at a single laboratory during 1993, individuals with serum cobalamin concentrations <300 pmol/L were identified, and one patient per general practitioner was included. When serum methylmalonic acid (s-MMA) values >0.376 micromol/L were used as the "reference standard" for cobalamin deficiency, the serum cobalamin assay had a diagnostic sensitivity of 0.40 and a specificity of 0.98. With the same reference standard, the diagnostic accuracy of the physicians' decision to supplement patients had the same specificity but a higher sensitivity (0.51). Cost-benefit analysis indicated that measurement of s-MMA can be recommended in patients with serum cobalamin >60-90 pmol/L and <200-220 pmol/L, depending on its diagnostic accuracy.

Determinants and vitamin responsiveness of intermediate hyperhomocysteinemia (> or = 40 micromol/liter). The Hordaland Homocysteine Study.

From 1992-93, we screened 18,043 subjects, aged 40-67 yr, and found 67 cases (0.4%) with total plasma homocysteine (tHcy) > or = 40 micromol/liter. Compared to 329 controls, the cases had lower plasma folate and cobalamin levels, lower intake of vitamin supplements, consumed more coffee, and were more frequently smokers. Homozygosity for the C677T mutation in the methylenetetrahydrofolate reductase gene was observed in 73.1% of the cases and 10.2% of the controls. Only seven cases with cobalamin deficiency and one with homocystinuria received specific therapeutic instructions. 2 yr after the screening, 58 subjects were reinvestigated. 41 still had tHcy > 20 micromol/liter, and in 37 of these, intervention with low dose folic acid (0.2 mg/d) was started. Notably, 34 of 37 (92%) had homozygosity for the C677T mutation. Plasma tHcy was reduced in all but two after 7 wk, and became normal within 7 mo in 21 of 37 subjects. Most of the remaining subjects obtained a normal tHcy level with 5 mg/d of folic acid. We conclude that most subjects with hyperhomocysteinemia > or = 40 micromol/liter in the general population have the C677T mutation combined with low folate status. Daily supplement of low dose folic acid will reduce and often normalize their tHcy level.

Kinetics of total plasma homocysteine in subjects with hyperhomocysteinemia due to folate or cobalamin deficiency.

Hyperhomocysteinemia in cobalamin and folate deficiency reflects an imbalance between influx and elimination of homocysteine (Hcy) in plasma. We investigated the kinetics of total Hcy (tHcy) in plasma after peroral Hcy administration in 19 volunteers with hyperhomocysteinemia (mean +/- SD: 67.1 +/- 39.5 mumol/L; range: 23.5-142.8 mumol/L) before and after supplementation with cobalamin and/or folate. Vitamin therapy decreased plasma tHcy to 21.8 +/- 14.1 mumol/L (range: 9.6-57.9 mumol/L) but caused only a marginal decline in the area under the curve (AUC) by 8% and plasma half-life by 21%. Using the equations for steady-state kinetics, these data indicate that mean plasma tHcy clearance is normal and that massive export of Hcy from tissues into plasma is the major cause of hyperhomocysteinemia in cobalamin or folate deficiency. However, the spread in AUC and plasma half-life values was large in hyperhomocysteinemia subjects, suggesting marked individual variability in tHcy clearance. Plasma methionine after Hcy loading did not increase before (0.9 +/- 6.8 mumol/L) but increased normally (12.8 +/- 4.6 mumol/L) after vitamin therapy, and the methionine response discriminated between vitamin-deficient and vitamin-replete subjects. In cobalamin- or folate-deficient subjects, only 6.5 +/- 3.0% of the Hcy dose was excreted unchanged in the urine, demonstrating that urinary Hcy excretion does not explain normal tHcy plasma clearance in subjects with impaired Hcy remethylation. Our data suggest that hyperhomocysteinemia in folate and cobalamin deficiency is related to increased influx of Hcy to plasma, and that the methionine synthase function is not an important determinant of elimination of Hcy from plasma. The large interindividual difference in Hcy clearance may be explained by variable adaptation to impaired methionine synthase function through increased Hcy flux through alternate metabolic pathways.