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PubMed2006

The relationship between micronuclei in human lymphocytes and selected micronutrients in vegetarians and non-vegetarians.

A vegetarian diet results in higher intake of vitamins and micronutrients, which - although providing antioxidant defence - may lead to deficiency in other micronutrients involved in DNA metabolism and stability (such as vitamins belonging to the B group). The principal difference among various vegetarian diets is the extent to which animal products are avoided. We have performed a pilot study to determine the relationship between the micronucleus frequency in lymphocytes and diet, and we compared the levels of Vitamins C and E, beta-carotene, B(12), folic acid, homocysteine and total antioxidant capacity in healthy vegetarians and non-vegetarians. The vegetarian group, consisting of 24 volunteers (13 women and 11 men), were matched for age and sex with 24 volunteers (12 women and 12 men) with a traditional dietary habit. Among the vegetarians were 13 lacto-ovo-vegetarians with average duration of vegetarian diet 10.8 years (ranging from 5 to 26 years) and 11 lacto-vegetarians with average duration of vegetarian diet 8.2 years (ranging from 3 to 15 years). Homocysteine, Vitamins C and E and beta-carotene levels in plasma were assayed by HPLC, and serum folate and Vitamin B(12) were determined with Elecsys Immunoassay tests. The total antioxidant capacity of plasma was estimated by measuring the ferric-reducing activity in a spectrophotometric assay. Micronuclei were measured in cytokinesis-blocked lymphocytes. Vegetarians had significantly higher levels of Vitamin C and beta-carotene (but not Vitamin E) in plasma compared with non-vegetarians (P<0.001). There were no significant differences in serum levels of folic acid and Vitamin B(12) between the monitored groups. Levels of folic acid in vegetarians correlated with length of vegetarianism (r=0.62, P=0.001, N=24). Vegetarians had elevated levels of homocysteine compared with non-vegetarians (P=0.007), as did vegetarian women compared with non-vegetarian women (P=0.031). We did not find any differences in total antioxidant capacity or in micronucleus frequency between the groups. Micronuclei correlated with age (r=0.62, P<0.001, N=48), women having higher frequencies than men. Multifactorial regression analysis showed significant effects of age, sex and total antioxidant capacity on micronucleus frequency (N=48, P<0.001).

Adult↗

PubMed1992

Optic neuropathy in a patient with vitamin B12 deficiency: a case report.

A 19-year-old man presented with blurring of vision for 2 weeks. He also complained of anorexia with weight loss during the past 4 months. Eight years ago, his small bowel from midportion of the jejunum, ileum, ascending colon and transverse colon were resected because of gangrene. He gave no history of exposure to tobacco, alcohol or other toxins. The bone marrow aspiration showed hypocellular with panhypoplasia. Serum vitamin B12 level was low while serum and red cell folate were within normal limits. His visual acuity was 5/200 in both eyes with centrocecal scotomas in both eyes. Other neurologic and ophthalmic examinations were found to be normal. The patient was given intramuscular injections of 1,000 micrograms of cyanocobalamin. Four months later, his visual acuity improved, serum vitamin B12 level and the bone marrow returned to be normal. This is a frank case of optic neuropathy in a patient with vitamin B12 deficiency due to a massive small bowel resection.

Adult↗

PubMed1996

The common 'thermolabile' variant of methylene tetrahydrofolate reductase is a major determinant of mild hyperhomocysteinaemia.

Mild hyperhomocysteinaemia is a major risk factor for vascular disease and neural tube defects (NTDs), conferring an approximately three-fold relative risk for each condition. It has several possible causes: heterozygosity for rare loss of function mutations in the genes for 5,10-methylene tetrahydrofolate reductase (MTHFR) or cystathionine-beta-synthase (CBS); dietary insufficiency of vitamin co-factors B6, B12 or folates; or homozygosity for a common 'thermolabile' mutation in the MTHFR gene which has also been associated with vascular disease and NTDs. We quantified the contribution of the thermolabile mutation to the hyperhomocysteinaemic phenotype in a working male population (625 individuals). Serum folate and vitamin B12 concentrations were also measured and their relationship with homocysteine status and MTHFR genotype assessed. The homozygous thermolabile genotype occurred in 48.4, 35.5, and 23.4% of the top 5, 10, and 20% of individuals (respectively) ranked by plasma homocysteine levels, compared with a frequency of 11.5% in the study population as a whole, establishing that the mutation is a major determinant of homocysteine levels at the upper end of the range. Serum folate concentrations also varied with genotype, being lowest in thermolabile homozygotes. The MTHFR thermolabile genotype should be considered when population studies are designed to determine the effective homocysteine-lowering dose of dietary folate supplements, and when prophylactic doses of folate are recommended for individuals.

5,10-Methylenetetrahydrofolate Reductase (FADH2)↗

PubMed2001

The influence of serum vitamin B12 and folate status on cognitive functioning in very old age.

This study examined the relationship between low levels of serum vitamin B12 and folic acid (FA) and cognitive functioning in very old age. The four subsamples of non-demented persons aged 75-96 years - normal B12/normal FA; low B12/normal FA; normal B12/low FA; and low B12/low FA, were matched for age and education. A battery of cognitive tests was administered including Clock Tests, Block Design, Trail Making Tests (TMT), Digit Span, and tests of verbal fluency. Subjects with low levels of vitamins showed deficits in Block Design, TMT-B, Digit Span Backward, and letter fluency, but not in the remaining tests. In general, the effects of FA exceeded those of B12. This pattern of results was interpreted to mean that elderly persons with low vitamin levels have difficulty when fast and accurate processing of novel information is required, but are quite efficient in utilizing pre-existing knowledge structures.

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PubMed2001

Hyperhomocysteinemia and related factors in 600 hospitalized elderly subjects.

Hyperhomocysteinemia (HHcy) is a metabolic disorder frequently occurring in the elderly population. Recently several reports have suggested abnormalities in homocysteine (tHcy) metabolism implicating HHcy as a metabolic link in the multifactorial processes characterizing many geriatric illnesses-with special emphasis on atherosclerotic vascular diseases and cognitive impairment. The present study was undertaken in a large sample of elderly hospitalized subjects to determine (1) the prevalence of HHcy, (2) the association of HHcy with vascular and cognitive disorders, and (3) the factors independently predicting Hhcy. Six hundred elderly subjects (264 men and 336 women; mean age, 79 +/- 9 years) were randomly chosen from those admitted as inpatients over a period of 3 years. In all patients, body mass index (BMI), mid-upper arm muscle area (MUAMA), plasma cholesterol, triglycerides, total proteins, albumin, lymphocyte count, creatinine, homocysteine (fasting and 4 hours after methionine oral load), serum vitamin B(6), vitamin B(12), and folate concentrations were measured. The presence of disease or use of medications known to affect homocysteine plasma levels were also recorded. The mean fasting tHcy level was 16.8 +/- 12 micromol/L in the whole sample, 18.18 +/- 13.25 micromol/L in men, and 15.86 +/- 12.14 micromol/L in women (P =.005 men v women). The mean Hcy level 4 hours after methionine load was 37.95 +/- 20.9 in the whole sample. Prevalence of hyperhomocysteinemia (fasting Hcy > or = 15 micromol/L or 4 hours after methionine load > or = 35 micromol/L) was 61% (365/600) (67% in men and 56% in women, P <.05). HHcy was rarely (8%) an isolated disorder; in addition to diabetes (20%), renal failure (48.2%), and malnutrition (20.2%), it was often associated with heart failure (30%), malignancies (20.5%), and the use of diuretics (56%) and anticonvulsant drugs (13%). Plasma homocysteine progressively increases across subjects from those with no diabetes, malnutrition, renal failure, obesity, inflammatory bowel disease, heart failure to those with 1, 2, or more concurrent diseases. Multiple stepwise regression analysis showed that 72% of plasma total fasting tHcy variability was explained by age, serum folate, plasma albumin, use of diuretics, and renal function (measured as plasma creatinine clearance). In conclusion, the present study documents that hyperhomocysteinemia, in elderly hospitalized patients is (1) a common finding, (2) frequently associated with vascular and cognitive disorders, and (3) probably a secondary phenomenon in most cases. The major predictor of high plasma homocysteine levels were age, serum folate, plasma albumin, plasma creatinine clearance, and use of diuretic drugs. These variables explain a large proportion of plasma Hcy variability.

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PubMed2000

Determinants of plasma total homocysteine levels in Korean chronic renal transplant recipients.

OBJECTIVE: Study the determinants of plasma total homocysteine (tHcy) levels, such as fasting levels of serum creatinine (SCr), albumin, plasma tHcy, folate, B(12), and pyridoxal-5'-phosphate (PLP) in chronic Korean renal transplant recipients (RTR). DESIGN: Cross-sectional study. SETTING: Nephrology & Transplant Service in Catholic University Kangnam St. Mary's Hospital, Seoul, Korea. PARTICIPANTS: Ninety-one chronic Korean RTR with stable renal function who were > or =6 months post-transplant. MEASURES: Used medical record review and anthropometric measurements, and overnight (10 to 14 hours) fasting blood samples were measured for plasma tHcy, PLP, folate, B(12), SCr, and albumin. RESULTS: The prevalence of hyperhomocysteinemia (tHcy > 12 micromol/L) was 56%, and 47% had low plasma folate levels (<3 ng/mL). Linear modeling with analysis of covariance adjusted for age, sex, albumin, SCr, and plasma B-vitamin status revealed that only SCr (standard regression coefficient R = +0.663, P<.001), plasma folate (R = -0.276, P =.001), and B(12) (R = -0.149, marginal, P =.08) were independent determinants of fasting tHcy levels in this patient population. CONCLUSION: Renal function is the major independent determinant of the fasting tHcy levels among chronic, stable Korean RTR, and that B-vitamin status plays a secondary role among such patients.

Adult↗

PubMed1989

Nutritional status of free-living Alzheimer's patients.

Self-reported, dietary intake and biochemical estimates of thiamine, riboflavin, folate, vitamin B-12, protein, and iron were compared in 22, free-living elders by individuals who had senile dementia of the Alzheimer's type (SDAT) and in 41 who were cognitively normal (CN). The two groups did not differ significantly in their intake of these nutrients or the number of deficiency states for intake (less than 67% RDA). Low serum transketolase (thiamin; p less than 0.055), red blood cell (RBC) folate (p less than 0.06), and serum vitamin B-12 (p less than 0.05) levels occurred more often in SDAT patients than in CN subjects. Individuals in both groups who used multivitamin supplements had significantly higher biochemical values for thiamine (p less than 0.03), riboflavin (p less than 0.01), and vitamin B-12 (p less than 0.003) than nonsupplement users. Because of the differences in vitamin B-12 and RBC folate levels between groups, a retrospective analysis was performed on a larger group of subjects drawn from a geriatric assessment clinic. Patients with SDAT had significantly lower serum vitamin B-12 (p less than 0.01) and lower RBC folate (p less than 0.03) values than CN subjects. Which mean values for vitamin B-12 and RBC folate were grouped by degree of impairment in SDAT subjects, vitamin B-12 was significantly lower in mildly and moderately impaired subjects than in those with normal cognition. Mean values for both nutrients did not differ significantly between severely impaired and CN subjects. There was a significant quadratic relationship between cognitive impairment and biochemical values for vitamin B-12.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed2001

The methionine synthase reductase (MTRR) A66G polymorphism is a novel genetic determinant of plasma homocysteine concentrations.

Epidemiological evidence has revealed that an elevated plasma homocysteine level (hyperhomocysteinemia) confers an increased risk of cardiovascular disease and neural tube defects. Hyperhomocysteinemia is caused by both nutritional (e.g. folate, vitamins B(6) and B(12)) and genetic factors, including functional polymorphisms of key enzymes involved in homocysteine metabolism. One such enzyme, methionine synthase reductase (MTRR), maintains adequate levels of methylcob(III)alamin, the activated cofactor for methionine synthase, which catalyzes the remethylation of homocysteine to methionine. A common MTRR polymorphism, i.e. a 66 A-->G substitution specifying an isoleucine to methionine substitution (I22M), was recently identified. To assess the influence of this polymorphism on total plasma homocysteine (tHcy), we undertook a genotype/phenotype analysis in a study population of 601 Northern-Irish men, aged 30--49, for which biochemical and genetic data relevant to folate/homocysteine metabolism had already been acquired. The 66AA genotype has a frequency of 29% in this population. We established that there was a significant influence of MTRR genotype on tHcy ranking (P=0.004) and that the 66AA genotype contributes to a moderate increase in tHcy levels across the distribution [OR 1.59 (95% CI: 1.10--2.25) for the 66AA genotype to be in the upper half of the tHcy distribution, P=0.03]. The homocysteine-elevating effect of the 66AA genotype is independent of serum folate, vitamin B(12) and vitamin B(6) levels. Based on published estimates of the enhanced cardiovascular disease risk conferred by defined increments of plasma tHcy, we estimate that 66AA homozygotes have, on average, an approximately 4% increase in cardiovascular disease risk compared to 66GG homozygotes. This study provides the first evidence that the MTRR A66G polymorphism significantly influences the circulating tHcy concentration.

Adult↗

PubMed2004

A 6-month follow-up of nutritional status in institutionalized patients with Alzheimer's disease.

OBJECTIVE: A follow up of nutritional status in institutionalized patients with Alzheimer's disease. DESIGN: Observational study. SETTING: Specialized unit for patients with Alzheimer's disease in Dijon hospital, France. SUBJECTS: Fourteen women, aged 72-92 years. ASSESSMENTS: On admission of patients to the specialized unit for dementia, body weight, body mass index, arm muscle circumference (AMC) and triceps skin fold (TSF) were measured. Serum concentrations of albumin, prealbumin, homocysteine, orosomucoide, calcium, folates, vitamins B12 and B6 and C-reactive protein were recorded. The same clinical and biological measurements were repeated at day 30, 90 and 180. RESULTS: Both mean weight and mean BMI increased throughout the study with significant differences between day 0 and day 90, and day 180 (p<0.01). The weight gain was associated with a significant increase in AMC and TSF (p<0.01 and p<0.001, respectively). There was no significant difference for values of both mean serum levels of albumin and prealbumin between day 0 and day 180. Whatever the period, serum concentrations of folates and vitamin B12 were in the normal range, while mean levels of vitamin B6 were lower than the normal range; For all these values, there was no significant difference between day 0, 30, 90, 180. Mean levels of C-reactive protein and orosomucoide and lymphocyte counts were in the normal range both at admission and day 180. No significant difference was noted between value of homocysteine at admission and at day 180. CONCLUSION: In this special care unit, the patients with Alzheimer's disease who take part in daily activities and particularly preparation of the meal don't lose weight. It is certain that future studies recording food intake and energy expenditure are necessary to explain the benefits in the nutritional status observed in patients showing dementia when they are institutionalized in a special unit.

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PubMed1997

A cost-effectiveness analysis of anemia screening before erythropoietin in patients with end-stage renal disease.

The treatment efficacy of erythropoietin (EPO) in end-stage renal disease (ESRD) can be limited by deficiencies of iron, folate, or vitamin B12, by hyperparathyroidism, or by aluminum intoxication. Since EPO costs are significant, this study attempted to determine the cost-effectiveness of performing a panel of screening tests for anemia before starting EPO. Anemia screening was performed prospectively in 48 new-onset ESRD patients at the Ralph H. Johnson Veterans Affairs Medical Center before EPO treatment was started. Serum iron, transferrin, folate, vitamin B12, parathyroid hormone, and aluminum levels were determined, and transferrin saturation (Tfsat) was calculated at the first dialysis session. At presentation for dialysis, the mean hematocrit was 0.264 +/- 0.036 and the mean blood urea nitrogen was 32 +/- 2 mmol/L. Eighteen patients (37.5%) had a serum iron level lower than 7 micromol/L, suggesting iron deficiency. Twenty-five patients (52%) had Tfsat less than 0.20, consistent with overt iron deficiency. No patient was found to be vitamin B12 deficient, to be aluminum intoxicated, or to have significant hyperparathyroidism. One patient had folate deficiency. A cost-effectiveness analysis was performed assuming that (1) EPO would be given at an average starting dose of 6,000 U/wk at a cost of $14/2,000 U of EPO; (2) that without screening 1 month would elapse before a poor response was identified; and (3) that the failure to treat aluminum intoxication and hyperparathyroidism or to replete iron, vitamin B12, or folate deficiency would significantly impair the response to EPO. The Tfsat screen had a cost-effectiveness ratio of 0.2019, saving approximately $5.00 in EPO use for each dollar of test administration. All other screens had cost-effectiveness ratios greater than 1.0, indicating that their testing costs exceeded dollar savings in EPO use. In conclusion, iron deficiency is common in anemic patients starting dialysis, but other causes of anemia are not. It is imperative that current clinical practices be influenced by cost-effectiveness considerations. Given the cost of laboratory screens, and the relative ineffectiveness of the other screens examined here to identify factors known to impair the response to EPO, anemia screening before initiating EPO therapy should be limited to tests to identify iron deficiency.

Adult↗

PubMed1987

Phosphate-induced phosphoribosylpyrophosphate elevations to assess deranged folate and purine nucleotide metabolism.

Phosphoribosylpyrophosphate (PRPP) levels increase several-fold in HL-60 cells adapted to folate deficiency either by continuous passage in folate-deficient medium or by short-term incubation with 10(-8) M methotrexate (MTX). The addition of folic acid (PteGlu) or 5-formyltetrahydrofolic acid (5-CHO-H4PteGlu) in the form of Leucovorin normalizes this effect. The reactions for measuring PRPP levels are time and temperature dependent and are influenced by PRPP-reacting substances in undialyzed serum. Inorganic phosphate (PO4), when added to the assay, markedly stimulates PRPP levels in HL-60 cells and can be used to stress folate-dependent PRPP utilization for purine synthesis. The integrity of the folate-dependent pathways of purine-synthesizing cells can be sensitively assessed by measurement of PRPP levels during a 2-hr assay in the presence of PO4 in medium free of folate but containing dialyzed serum. In HL-60 cells that are folate deficient or in the presence of MTX (as low as 2 X 10(-9) M), PO4-stimulated PRPP levels remain elevated due to ineffective utilization unless folate is added to the incubation mixture. The sensitivity of this PRPP assay to metabolically assess the integrity of folate-dependent reactions in purine synthesis is comparable to that of the deoxyuridine suppression assay. Inorganic phosphate can also be used to stimulate the incorporation of purine analogs, such as 6-mercaptopurine, into intact red blood cells which may have therapeutic implications for targeting drug delivery.

Cell Line↗

PubMed2001

Hyperhomocysteinemia is related to residual glomerular filtration and folate, but not to methylenetetrahydrofolate-reductase and methionine synthase polymorphisms, in supplemented end-stage renal disease patients undergoing hemodialysis.

Glomerular filtration is one of the major determinants of plasma total homocysteine (tHcy). To evaluate the respective roles of residual glomerular filtration (by measuring a specific protein marker, cystatin C), genetic polymorphisms and nutritional status in tHcy blood levels in end-stage renal disease patients (ESRD) under hemodialysis and supplemented with folate, we measured tHcy, folate, vitamin B12 (B12), creatinine, cystatin C, albumin and C-reactive protein and determined the polymorphism of methylenetetrahydrofolate reductase (MTHFR) (C677T and A1289C) and of methionine synthase (MS) (A2756G) in 114 ESRD patients before hemodialysis and 76 control subjects. All patients received a folate supplementation of 700 microg/day. Hyperhomocysteinemia was observed in all patients and exceeded the upper normal limit by 2-fold in 52.4% of the patients. Serum folate was significantly increased and the B12 level was not different from controls. Folate, Cystatin C and creatinine were significantly correlated to tHcy, while no correlation was found between tHcy, albumin and C-reactive protein. No difference in genotype frequency between ESRD patients and controls was found for MTHFR A1289C and MS A2756G. The MTHFR 677TT genotype was less frequent and was associated with a significantly higher tHcy level in patients. Folate and residual glomerular filtration estimated by cystatin C and creatinine levels were two independent determinants of tHcy in ESRD patients. These data suggest that hyperhomocysteinemia is a consequence as well as a complicating factor of renal failure.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMedDate not supplied

Homocysteine, vitamin B12, and serum and erythrocyte folate in peritoneal dialysis and hemodialysis patients.

BACKGROUND: Plasma homocysteine (Hcy) is an independent risk factor for cardiovascular disease. High levels of plasma Hcy have been observed in end-stage renal disease patients. Few studies have compared peritoneal dialysis (PD) and hemodialysis (HD) patients and few data are available on erythrocyte folate (ery-F) levels in dialysis patients. OBJECTIVES: To evaluate plasma Hcy concentrations, vitamin B12 (B12), and folate status in dialysis patients; to analyze the possible causes of high Hcy levels; to follow up changes in folate and B12 concentrations after 6 months. DESIGN: A cross-sectional observational study. SETTING: Nephrology division and laboratory of hematology in a university and clinical research hospital. PATIENTS: The study included 82 patients treated with PD for 37 + 37 months and 70 patients treated with HD for 136 + 95 months. LABORATORY METHODS: Plasma Hcy was measured by the immunoenzymatic IMx Hcy FPIA method (Abbott Laboratories, Diagnostic Division, Abbott Park, IL, U.S.A.), serum folate (s-F) and ery-F by the Stratus folate fluorometric enzyme-linked assay, and B12 by the Stratus vitamin B12 fluorometric enzyme-linked assay (DADE-Behring, Newark, DE, U.S.A.). RESULTS: Ninety-six percent of PD and 97% of HD patients had Hcy levels above the cutoff (13.5 micromol/L). Homocysteine level was higher in HD than in PD patients, while the prevalence of hyperhomocysteinemia was similar with the two techniques. Erythrocyte folate was significantly higher in PD (1333 +/- 519 pmol/L) than in HD (1049 +/-511 pmol/L, p < 0.01). Statistically significant correlations were observed between Hcy and B12, s-F, ery-F, and dialysis duration. Multivariate analysis showed a strong correlation between s-F and Hcy. After 6 months there were no differences in Hcy, B12, s-F, and ery-F levels. CONCLUSIONS: Plasma Hcy levels were high in more than 95% of our dialysis patients, with no relation to the type of dialysis. Vitamin B12 and folate were normal in the majority of our patients. However, serum folate was the major determinant of Hcy levels. Such a relation between Hcy and folate suggests that levels of folate within the reference interval are inadequate for dialysis patients.

Cross-Sectional Studies↗

PubMed1999

Plasma homocysteine concentration related to diet, endothelial function and mononuclear cell gene expression among male hyperlipidaemic smokers.

BACKGROUND: Elevated plasma concentration of homocysteine is an independent risk factor for development of cardiovascular diseases. MATERIALS AND METHODS: We evaluated potential links between homocysteine and atherothrombogenesis by relating the plasma concentration of homocysteine to (i) dietary antioxidants and omega-3 fatty acids (and determined influence of intervention with antioxidants or omega-3 fatty acids); (ii) markers of endothelial cell function; and (iii) peripheral blood mononuclear cell mRNA levels. RESULTS: We observed an inverse relationship between the plasma homocysteine concentration and dietary intake of vegetables, vitamin C and beta-carotene and between homocysteine and the serum concentration of folate, vitamin B12 and omega-3 fatty acids. Intervention with antioxidants or omega-3 fatty acids did not affect plasma homocysteine concentration. The plasma levels of cysteinylglycine and vitamin B12 correlated positively with circulating E-selectin and VCAM-1, respectively, whereas folate in serum and blood correlated negatively with P-selectin. A negative correlation was found between the concentrations of homocysteine and von Willebrand factor. Negative and positive correlations were found between plasma homocysteine and the mononuclear cell mRNA levels of peroxisome proliferator activated receptor delta (PPAR delta) and c-myc respectively. A negative correlation was also found between plasma homocysteine and mononuclear cell mRNA levels of the proteoglycan serglycin. Homocysteine was not correlated with serum activity of glutathione peroxidase or with the mRNA level of glutathione peroxidase in mononuclear cells. CONCLUSION: The plasma homocysteine level was negatively correlated with dietary intake of vegetables, including vitamins C and E, and serum omega-3 fatty acids, whereas supplementation with antioxidants or omega-3 fatty acids did not affect plasma homocysteine concentration. Homocysteine was not associated with circulating adhesion molecules or increased procoagulant activity, but homocysteine may alter mononuclear cell gene expression. Cysteine showed no significant correlation with these parameters.

Adult↗

PubMed1985

Vitamin B12 (cobalamin) and folate blood levels in geriatric reference group as measured by two kits.

For serum vitamin B12 levels there was little apparent difference between a geriatric healthy reference group and a hospitalized group for the total population studied; however, the hospitalized males did have an increased prevalence of values less than normal range. The frequency distribution for both sexes of the geriatric reference group gave lower range limits than manufacturer's normal range. (68-632 vs 133-708 pmol/L for Becton Dickinson, and 125-609 vs 179-930 pmol/L for Bio-Rad, using 95% non-parametric limits). For folate there was an increased incidence in values of less than normal in the hospitalized group versus the geriatric reference group, but there was no difference in the ranges calculated for the latter compared to either manufacturer's normal range derived from a younger population. Comparison of results by two manufacturers' kit methods confirmed Bio-Rad's claim to increased low-end sensitivity of standard curve in range of clinical interest.

Age Factors↗

PubMedDate not supplied

[Intravenous folinic acid and vitamin B12 supplementation and homocysteine concentration in hemodialysis patients].

INTRODUCTION: Hyperhomocysteinemia is one of the causes of the increased incidence of cardiovascular disease in uremia. Since homocysteine (Hcy) metabolism depends on the availability of folate and vitamin B12, we have measured the effects of chronic i.v. supplementation of folinic acid and vitamin B12 in a group of patients on maintenance hemodialysis. METHODS: We compared the blood concentration of total Hcy (tHcy), vitamin B12 and folate and the intraerythrocyte concentration of folate in a group of 27 hemodialysis patients (Treated group), given an i.v supplementation with folinic acid (0.9 mg) and Vitamin B12 (cyanocobalamine 1.5 mg and hydroxycobalamine 1.5 mg) three times per week at the end of each dialysis session with those measured in a similar group of 28 hemodialysis patients without supplementation (No Treatment group). The patients were also characterized for the thermolabile variant (mutation C667-->T) of the enzyme methylene-tetrahydrofolate reductase (tMTHFR). RESULTS: High plasma levels (< 11.7 micromol/L) of tHcy were observed in 54/55 patients. T patients had Hcy values significantly lower than NT ones (31.7+/-3.6 vs. 1.1+/-8.3micromol/L, p < 0.05). Serum vitamin B12 (1200 73.6 vs. 762+/-72.2 pmol/L, p < 0.001) and intraerythrocyte folate levels were also significantly higher in the T group (2176+/-127 vs. 1511+/-156, p < 0.005), while no significant difference was observed for serum folate. The distribution of tMTHFR genotypes was similar in the two groups. Homozygous patients showed higher levels of Hcy in comparison with wild type patients both in the whole population (62.32+/-15.9 vs.30.43+/-3.2, p < 0.05) and in the NT group (87.8+/-25.3 vs.36.8+/-13.1., p < 0.05), while no significant difference was observed among genotypes in the T group. CONCLUSIONS: Uremic patients on hemodialysis, when supplemented with even low i.v. dose of folinic acid and vitamin B12, show significantly lower plasma levels of tHcy than non-supplemented patients.

Adult↗

PubMed2005

Simultaneous quantification of homocysteine and folate in human serum or plasma using liquid chromatography/tandem mass spectrometry.

A unified extraction and quantification procedure based on stable isotope-dilution liquid chromatography/tandem mass spectrometry (LC/MS/MS) has been developed for the simultaneous determination of total homocysteine and folate (5-methyltetrahydrofolic acid and folic acid) levels in human serum and plasma. This is the first report documenting the simultaneous extraction and quantification of these structurally dissimilar analytes. Analytes are quantitatively isolated from samples (500 microL) prior to LC/MS/MS analysis using a two-step stabilization process combined with C18 solid-phase extraction. The method exhibits excellent linearity over 4 orders of magnitude for each analyte. Measurement repeatability (RSD, N = 2) ranged from 0.3% to 3% for all analytes over 1 day of analysis. Total method variability (RSD, N = 6) ranged from 0.7% to 10% for all analytes over three independent days of analysis. The accuracy and practical applicability of the method were demonstrated by applying the method to the quantitative determination of each analyte in a new NIST serum Standard Reference Material (NIST SRM 1955 Homocysteine and Folate in Frozen Human Serum) and in a small subset of normal donor plasma samples.

Chromatography, Liquid↗

PubMed2001

Homocysteine, vitamin B12, serum and erythrocyte folate in peritoneal dialysis patients.

Plasma homocysteine (tHcy) is an important risk factor for atherosclerosis in dialysis patients. Few data were reported on the prevalence and severity of hyperhomocysteinemia in peritoneal dialysis (PD) patients. In addition, little attention was paid to the search of factors possibly involved in the pathogenesis of hyperhomocysteinemia in these patients. A cross-sectional study was performed in 107 stable PD patients. None of them was given folate or vitamin B12 supplementation before or during the study. Plasma tHcy, serum vitamin B12, serum and erythrocyte folate were measured by immunoenzymatic methods. Genetic analysis of the methylentetrahydrofolate-reductase thermolabile mutation (tMTHFR) was performed in 61 patients. 97% of patients had tHcy levels higher than normal. tHcy was not different between men and women, patients with or without malnutrition, with or without clinically evident atherosclerotic vasculopathy, with or without anemia. tHcy levels were significantly higher in homozygotes for the tMTHFR mutation than in patients carrying the wild type form. Significant univariate correlation was found between hyperhomocysteinemia and time since the start of dialysis, serum and erythrocyte folate and vitamin B12. The best fitted model equation was log tHcy = 108.53 + 0.1606 (duration of dialysis) -1.1053 (s-F) -0.7980 (age) 0.0215 (vitamin B12). Our results agree with those reported by other authors in hemodialysis patients. Despite the large number of PD patients with normal serum vitamin B12 and folate status, the relation between tHcy and vitamin B12 or folate suggests that the supplementation of these vitamins could be useful irrespective of their serum levels, especially in younger patients or in those treated for a long period of time with peritoneal dialysis.

Aged↗