An automated method for the microbiological assay of serum pyridoxal

Red cell N5-methyltetrahydrofolate concentrations and C677T methylenetetrahydrofolate reductase genotype in patients with stroke

AIMS

To investigate the relation between total red cell folate, red cell N(5)-methyltetrahydrofolate (N(5)MTHF) concentrations, and N(5)N(10)-methylenetetrahydrofolate reductase (MTHFR) genotypes in stroke.

METHODS

The study comprised 120 consecutive patients presenting to hospital with acute stroke. Multivitamin supplement use was recorded. Serum and red cell folate were measured by microbiological assays using Lactobacillus casei and Enterococcus faecalis, and by the DPC-BioMediq Immulite 2000 analyser. Total plasma homocysteine (tHcy), serum cobalamin, and serum vitamin B(6) were measured and the C677T MTHFR genotype determined.

RESULTS

There were no significant differences in blood tHcy or vitamin concentrations according to MTHFR genotype in the overall patient cohort. However, when patients taking vitamins were excluded, total red cell folate and red cell N(5)MTHF were significantly lower in patients with the TT genotype compared with CT or CC genotypes. In the overall cohort, irrespective of genotype, red cell folate was significantly lower when assayed microbiologically than with the Immulite assay. This discrepancy remained after exclusion of patients taking vitamins.

CONCLUSION

Total red cell folate and red cell N(5)MTHF are significantly lower in stroke patients with the TT compared with the CT and TT MTHFR genotypes, particularly those not taking vitamin supplements. Microbiological assays that measure biologically active folates provide substantially lower estimates of folate than the Immulite assay. Because folate is a key determinant of blood homocysteine values, these findings may impact on the interpretation of the strength and independence of the association between raised blood concentrations of homocysteine and atherothrombosis risk reported in most epidemiological studies.

Can black tea influence plasma total homocysteine concentrations?

BACKGROUND

Polyphenols can act as acceptors of methyl groups during the metabolism of methionine to homocysteine. This may result in elevations in plasma total homocysteine (tHcy) concentrations after ingestion of polyphenol-rich beverages such as tea.

OBJECTIVES

Our major objective was to determine whether regular, moderate-to-high intakes of black tea alter tHcy concentrations. We also assessed the relation between the degree of O-methylation of tea-derived polyphenols and the change in tHcy with regular ingestion of tea.

DESIGN

Twenty-two subjects completed a randomized, controlled crossover study. Subjects consumed 1250 mL black tea/d (5 cups each containing 2 g tea leaves in 250 mL boiled water) and 1250 mL hot water/d for 4 wk each. Fasting tHcy concentrations and 24-h urinary excretion of 4-O-methylgallic acid (4OMGA, the major O-methylated metabolite of gallic acid) were measured at the end of each period. 4OMGA was used as a marker of overall O-methylation of tea-derived polyphenols.

RESULTS

Black tea did not significantly alter mean (+/- SEM) tHcy concentrations (9.9 +/- 0.5 and 10.0 +/- 0.5 micro mol/L for the hot water and black tea periods, respectively). However, the increased excretion of 4OMGA as a consequence of black tea consumption was positively associated with the change in tHcy from the hot water period to the black tea period (r = 0.55, P = 0.008). Subjects in the bottom quartile of increase in 4OMGA excretion had a significant decrease in tHcy (-0.28 +/- 0.10 micro mol/L; P = 0.046), and those in the top quartile had a significant increase in tHcy (0.78 +/- 0.16 micro mol/L; P = 0.005).

CONCLUSIONS

Overall, regular ingestion of black tea did not alter mean tHcy concentrations. However, individual differences in O-methylation of polyphenolic compounds may influence the ultimate effects of black tea on tHcy.

Serum thiamin, pyridoxal, cobalamin and folate concentrations in young infants

Blood samples were obtained from 509 apparently healthy infants between the age of 3 and 54 weeks attending for routine checks at infant health centres. Serum was assayed for thiamin, pyridoxal, cobalamin and folate. Three hundred and five infants were being breast fed and results from these were used to construct a reference range-thiamin 2-17 micrograms/l, pyridoxal 8-39 micrograms/l, cobalamin 120-800 ng/l and folate 7-47 micrograms/l (95 percentile ranges). One hundred and thirty-four infants were being fed a manufactured milk formulation and the serum concentrations of thiamin, pyridoxal and cobalamin were significantly higher than those found in breast fed infants. Thirteen infants were receiving pasteurized cow's milk. This milk was found to have more than 3 times the folate content of human breast milk yet these infants had a significantly reduced serum level of folate.

Vitamin B6 intake and plasma pyridoxal phosphate concentrations in the first 2 weeks of life

Plasma pyridoxal phosphate concentrations were measured in 178 hospitalised neonates. A reference interval for neonates less than 7 day old, of 25 to 78 nmol/l has been established. Vitamin B6 intakes did not correlate well with plasma pyridoxal concentrations despite 26 neonates receiving less than the Recommended Allowance (0.3 mg/d) and 19 receiving amounts below which convulsions have been associated (0.1 mg/d). Ten percent of those infants fed breast milk had plasma pyridoxal phosphate levels below the reference interval compared with only 4% of those fed milk formulae. Breast milk from mothers with babies less than 14 days old had a total vitamin B6 contents reference interval of 5 to 40 micrograms/l. Twenty percent of breast milk samples had virtually no vitamin B6 detected.

The association of bacteriuria and reduced serum pyridoxal concentrations in patients with diabetes mellitus

Of 1017 patients admitted to the Royal Perth Hospital Diabetic Survey 142 were found to have significant bacteriuria. In these bacteriuric patients serum pyridoxal concentrations were significantly reduced (P = less than 0.001) when compared with 142 diabetic patients matched for age (+/- 5 years) and sex but without infection of the urinary tract. Measurements were repeated up to 6 mth after antibacterial treatment and serum pyridoxal concentrations were still low. Pyridoxal has a role in immunological competence, and it is possible that the increased incidence of urinary tract infection in patients with diabetes reflects impaired immunological competence due to pyridoxal deficiency.

Carpal tunnel syndrome, diabetes and pyridoxal

Serum pyridoxal concentrations were estimated in 13 patients who had both diabetes and carpal tunnel syndrome. The clinical features and response to treatment in these patients did not differ from that seen in non-diabetic patients with this syndrome. No significant difference in mean serum pyridoxal concentrations was noted between diabetics with carpal tunnel syndrome, diabetics without neuropathy, and normal subjects. These results indicate that carpal tunnel syndrome in diabetics is distinct from polyneuropathy in that it is not associated with a reduction in serum pyridoxal levels which is a feature of diabetic polyneuropathy.

Illegal drugs and nutrition in undergraduate students

The nutritional status of 82 marihuana-smoking students from two establishments of tertiary education was studied and compared with 63 controls. There was little difference between these two groups of students. Thirty-four per cent of those taking drugs had a diet which was deficient in one or more nutrients, compared with 30% of the controls. Four of the students who took drugs and three controls had a marginally reduced serum level of vitamin B12, but all were taking oral contraceptive agents. Sixteen marihuana-smokers had either a low folate or low pyridoxal serum level, and another three had reduced serum levels of both vitamins compared with a total of eleven among the controls. Forty-three students (52%) had used, or were using, lysergic acid diethylamide (LSD) in addition to marihuana, and 10 had used mushrooms (Psilocybe cubensis). Thirteen students appeared to be "stoned" at interview.

Serum pyridoxal concentrations in patients with diabetic neuropathy

Serum pyridoxal (vitamin B6) concentrations were measured in 50 patients with significant diabetic neuropathy. There were 24 males and 26 females with a mean age of 58.2 years and a mean duration of diabetes of 9.8 years. The level of pyridoxal was significantly lower in these patients when compared with randomly selected diabetic patients matched for age and sex without clinical evidence of neuropathy. There was no significant difference in the duration of the diabetes between the two groups. The results indicate an association between pyridoxal deficiency and neuropathy in diabetic patients.

Serum pyridoxal concentrations in children with diabetes mellitus

Serum pyridoxal concentrations were measured in 63 children with diabetes mellitus and compared with those in healthy children of the same age. Twenty-four per cent of diabetic children had concentrations below the limit of normal for age and sex. Diabetic children, as a group, had lower serum pyridoxal concentrations than healthy children.

Serum pyridoxal in patients with gastric pathology

Fasting serum pyridoxal was assayed by an automated microbiological system in 60 patients investigated for dyspepsia, patients with active peptic ulceration being excluded from the study. Gastritis was present in 30 patients, gastric carcinoma in 16, six patients had benign polyps, and, in eight patients, radiology, endoscopy, and biopsy failed to shown any abnormality. Of the 52 patients with gastric pathology, 44 had a low serum pyridoxal.

Serum pyridoxal in patients with rheumatoid arthritis

Abnormalities of tryptophan metabolism have been reported in patients with rheumatoid arthritis (RA) and it has been suggested that these abnormalities are the result of disordered vitamin B6 metabolism. Fasting serum pyridoxal, assayed by an automated microbiological system, was found to be below normal in 35 out of 42 patients with RA while a similar abnormality was found in 8 out of 35 patients with osteoarthrosis (OA). Within the RA group the abnormality could not be related to the age, sex, or drug therapy of individuals but of the 8 patients with OA and a low serum pyridoxal, 7 were receiving indomethacin either alone or in conjunction with aspirin.

Serum pyridoxal and folate concentrations in diabetics

Serum pyridoxal and folate concentrations were measured in 518 diabetics. There were 185 males and 333 females. The level of pyridoxal was significantly lower in the diabetics when compared with 371 'healthy' controls and 25% had levels below the lower limit of the normal range. No significant difference was observed between diabetics being treated by diet alone, oral hypoglycaemics or insulin. Only 20 patients had a reduced serum folate level and in 6 this was accompanied by a low pyridoxal concentration. The results suggest that diabetics may have an increased demand for pyridoxal.

Serum pyridoxal, folate, and vitamin B12 levels in institutionalized epileptics

Serum pyridoxal, folate, and vitamin B12 concentrations were measured in 68 institutionalized patients with severe epilepsy. Twenty-five patients had a reduced level of pyridoxal and thirty-three a reduced level of folate. There was no instance of a low serum vitamin B12 although in three patients the levels were found to be abnormally high. Fifteen patients had both a low serum pyridoxal and a low serum folate but there was no significant correlation. All patients had a normal hemoglobin concentration and a normal mean corpuscular volume. There was no close relationship between reduced serum vitamin levels and single or groups of anticonvulsant agents, although the size of the groups was too small to permit a detailed study.

Serum pyridoxal in active peptic ulceration

Fasting serum pyridoxal was assayed by an automated microbiological system in 50 patients with endoscopically confirmed active peptic ulceration. Thirty patients had gastric ulceration, 14 had duodenal, four had pyloric canal ulceration, and two had both a gastric and a duodenal ulcer. Serum pyridoxal was below normal in 28 of the gastric ulcer group and in one of the duodenal ulcer group. No difference in the age, sex, drug, alcohol intake, or diet could be distinguished between those two groups.