Adaptation of coenzyme stimulation assays for the nutritional assessment of vitamins B1, B2 and B6 using the Cobas Bio centrifugal analyser

Does thiamine supplementation affect heart failure? A systematic review and meta-analysis of randomized control trials

BACKGROUND

Heart failure is a pathophysiological condition where decreased cardiac output is observed subsequent to any structural deformity or cessation of normal function. Thiamine deficiency is one of the risk factors responsible for causing HF; other risk factors include hypertension, smoking, and obesity.

OBJECTIVE

We conducted a systemic review and meta-analysis of RCTs to scrutinize whether the heart failure patients would benefit from thiamine supplementation or not when compared to placebo.

METHODS

We selected only those double-arm randomized controlled trials (RCTs) which included participants presenting with symptomatic heart failure. We excluded all the articles published in languages other than English Language. Furthermore, all the studies other than RCTs were also omitted. Articles yielded from the electronic search were exported to EndNote Reference Library software to remove any duplicates. Analyses were done using the Review manager 5.4 tool. Mean values and standard deviations were retrieved for the continuous outcomes given as raw data.

RESULTS

The 6 RCTs selected for the statistical analysis consisted of 298 participants (158 in the intervention group, 140 in the placebo group). The outcomes resulted to be non-significant with LVEF p-value= 0.08, NT-pro BNP p-value= 0.94, LVEDV p-value= 0.53, 6MWT p-value=0.59, mortality p-value= 0.61, hospitalization p-value= 0.53 and dyspnea p-value= 0.77. Heart rate is the only significant outcome with a p-value=0.04.

CONCLUSION

To conclude, except for heart rate, thiamine supplementation had no effect on the outcomes of heart failure patients.

Protocol and application of basal erythrocyte transketolase activity to improve assessment of thiamine status

Thiamine (vitamin B1) is an essential micronutrient required as a cofactor in many metabolic processes. Clinical symptoms of thiamine deficiency are poorly defined, hence biomarkers of thiamine status are important. The erythrocyte transketolase activity coefficient (ETKac) is a sensitive measure of thiamine status, but its interpretation may be confounded where the availability of the transketolase enzyme is limited. Basal ETK activity per gram of hemoglobin provides a complementary biomarker of thiamine status; however, its measurement and calculation are poorly described. Here, we describe in detail the assessment of basal ETK activity, including the calculation of path length in microplates and the molar absorption coefficient of NADH specific to the assay, and the measurement of hemoglobin in sample hemolysates. To illustrate the application of the methods, we present ETKac and basal ETK activity from women in The Gambia and UK. In conclusion, we present a clear protocol for the measurement of basal ETK activity that will permit the harmonization of methods to improve replication between laboratories.

Riboflavin intake and status and relationship to anemia

Riboflavin in its coenzyme forms, flavin mononucleotide and flavin adenine dinucleotide, is essential for multiple redox reactions necessary for energy production, antioxidant protection, and metabolism of other B vitamins, such as niacin, pyridoxine, and folate. Erythrocyte glutathione reductase activity coefficient (EGRac) is a biomarker of riboflavin status; ratios ≥1.40 are commonly interpreted as indicating biochemical deficiency. Most research on riboflavin status comes from low-income countries and rural settings, which reported high rates of riboflavin deficiency and inadequate intake. However, some studies suggest that riboflavin deficiency, based on the functional indicator EGRac, is also of concern in middle- and high-income countries. Biochemical riboflavin deficiency that does not cause clinical symptoms may contribute to anemia, particularly among women and children. Riboflavin enhances iron absorption, and riboflavin deficiency decreases iron mobilization from stores. The current knowledge on riboflavin's role in metabolic processes and its biochemical status is summarized in this review, and the available evidence on the role of riboflavin in anemia among different populations is discussed.

Erythrocyte transketolase activity coefficient (ETKAC) assay protocol for the assessment of thiamine status

Vitamin B1 (thiamine) is an essential nutrient that acts as a cofactor for a number of metabolic processes, particularly in energy metabolism. Symptoms of classic thiamine deficiency are recognized as beriberi, although clinical symptoms are nonspecific and recognition of subclinical deficiency is difficult. Therefore, reliable biomarkers of thiamine status are required. Thiamine diphosphate is a cofactor for transketolase, including erythrocyte transketolase (ETK). The ETK activity assay as an indirect, functional marker of thiamine status has been used for over 50 years. The ETK activity assay provides a sensitive and specific biomarker of thiamine status; however, there is a lack of consensus over the cutoffs for deficiency, partly due to a lack of assay harmonization. Here, we provide a step‐by‐step protocol for the measurement of ETK activity and the calculation of the ETK activity coefficient, including detailed explanations of equipment and chemicals required and guidance for quality control procedures. Harmonization of the protocol will provide the basis for the development of internationally recognized cutoffs for thiamine insufficiency. The establishment of quality control materials and a quality assurance scheme are recommended to provide reliability. This will ensure that the ETK activity assay remains an important method for the assessment of thiamine status.

Riboflavin status modifies the effects of methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) polymorphisms on homocysteine

Methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR), riboflavin-dependent enzymes, participate in homocysteine metabolism. Reported effects of riboflavin status on the association between the MTHFR 677C>T polymorphism and homocysteine vary, and the effects of the MTRR 66A>G or MTRR 524C>T polymorphisms on homocysteine are unclear. We tested the hypothesis that the effects of the MTHFR 677C>T, MTRR 66A>G and MTRR 524C>T polymorphisms on fasting plasma total homocysteine (tHcy) depend on riboflavin status (erythrocyte glutathionine reductase activation coefficient, optimum: <1.2; marginally deficient: 1.2-1.4; deficient: ≥1.4) in 771 adults aged 18-75 years. MTHFR 677T allele carriers with middle or low tertile plasma folate (<14.7 nmol/L) had 8.2 % higher tHcy compared to the 677CC genotype (p < 0.01). This effect was eliminated when riboflavin status was optimal (p for interaction: 0.048). In the lowest cobalamin quartile (≤273 pmol/L), riboflavin status modifies the relationship between the MTRR 66 A>G polymorphism and tHcy (p for interaction: 0.034). tHcy was 6.6 % higher in MTRR 66G allele carriers compared to the 66AA genotype with marginally deficient or optimal riboflavin status, but there was no difference when riboflavin status was deficient (p for interaction: 0.059). tHcy was 13.7 % higher in MTRR 524T allele carriers compared to the 524CC genotype when cobalamin status was low (p < 0.01), but no difference was observed when we stratified by riboflavin status. The effect of the MTHFR 677C>T polymorphism on tHcy depends on riboflavin status, that of the MTRR 66A>G polymorphism on cobalamin and riboflavin status and that of the MTRR 524C>T polymorphism on cobalamin status.

Co-occurrence of anemia, marginal vitamin B6, and folate status and depressive symptoms in older adults

Although nutrient deficiencies are thought to play roles in the development of depression, observational studies have yielded inconsistent results. This study aimed to investigate whether multiple marginal nutrient deficiencies are associated with symptoms of depression in community-dwelling older Taiwanese. Data from 1371 elderly adults recruited from the Elderly Nutrition and Health Survey in Taiwan was used in this study. Depressive symptom scores on depressed mood and emotions affecting daily life were derived from the Medical Outcomes Study Short Form-36 (SF-36). Hemoglobin, serum ferritin, plasma vitamins B(6), B(12), and folate concentration, and erythrocyte transketolase and glutathione reductase activation coefficients were measured. After adjusting for age, gender, cognitive function, physical activity, disease history, and medication in the multivariate analysis, anemia, and marginal B(6) deficiency were significantly associated with the presence of depression symptoms, respectively. In addition, co-occurrence of vitamin B(6) with low folate level and co-occurrence of anemia either with low vitamin B(6) or with folate level were all associated with the depressive mood and with depressive emotions defined by SF-36 (odds ratios [OR] in the range of 2.32-7.13, all P values ≤.05). The magnitude of the ORs is larger when the number of deficiencies increased. Elderly people with coexisting marginal deficiencies of nutrients involved in the S-adenosylmethionine and hemoglobin production were more likely to experience depressed mood and emotion that affect daily activity. Examining status of these nutrients is worthy of consideration for older adults with depressed symptoms.

Folate, vitamin B12, vitamin B6 and homocysteine: impact on pregnancy outcome

Good clinical practice recommends folic acid supplementation 1 month prior to pregnancy and during the first trimester to prevent congenital malformations. However, high rates of fetal growth and development in later pregnancy may increase the demand for folate. Folate and vitamins B12 and B6 are required for DNA synthesis and cell growth, and are involved in homocysteine metabolism. The primary aim of this study was to determine if maternal folate, vitamin B12, vitamin B6 and homocysteine concentrations at 18-20 weeks gestation are associated with subsequent adverse pregnancy outcomes, including pre-eclampsia and intrauterine growth restriction (IUGR). The secondary aim was to investigate maternal B vitamin concentrations with DNA damage markers in maternal lymphocytes. A prospective observational study was conducted at the Women's and Children's Hospital, Adelaide, South Australia. One hundred and thirty-seven subjects were identified prior to 20 weeks gestation as at high or low risk for subsequent adverse pregnancy outcome by senior obstetricians. Clinical status, dietary information, circulating micronutrients and genome damage biomarkers were assessed at 18-20 weeks gestation. Women who developed IUGR had reduced red blood cell (RBC) folate (P < 0.001) and increased plasma homocysteine concentrations (P < 0.001) compared with controls. Maternal DNA damage, represented by micronucleus frequency and nucleoplasmic bridges in lymphocytes, was positively correlated with homocysteine (r = 0.179, P = 0.038 and r = 0.171, P = 0.047, respectively). Multivariate regression analysis revealed RBC folate was a strong predictor of IUGR (P = 0.006). This study suggests that low maternal RBC folate and high homocysteine values in mid pregnancy are associated with subsequent reduced fetal growth.

Erythrocyte transketolase activity, markers of cardiac dysfunction and the diagnosis of infantile beriberi

Background

Infantile beriberi is a potentially lethal manifestation of thiamin deficiency, associated with traditional post-partum maternal food avoidance, which persists in the Lao PDR (Laos). There are few data on biochemical markers of infantile thiamin deficiency or indices of cardiac dysfunction as potential surrogate markers.

Methodology/Principal Findings

A case control study of 47 infants with beriberi and age-matched afebrile and febrile controls was conducted in Vientiane, Laos. Basal and activated erythrocyte transketolase activities (ETK) and activation (α) coefficients were assayed along with plasma brain natriuretic peptide, N-terminal pro-brain natriuretic peptide and troponin T. Basal ETK (and to a lesser extent activated ETK) and plasma troponin T were the only infant biochemical markers that predicted infantile beriberi. A basal ETK≤0.59 micromoles/min/gHb gave a sensitivity (95%CI) of 75.0 (47.6 to 92.7)% and specificity (95%CI) of 85.2 (66.3 to 95.8)% for predicting infantile beriberi (OR (95%CI) 15.9 (2.03–124.2); p = 0.008) (area under ROC curve = 0.80). In contrast, the α coefficient did not discriminate between cases and controls. Maternal basal ETK was linearly correlated with infant basal ETK (Pearson's r = 0.66, p<0.001). The odds of beriberi in infants with detectable plasma troponin T was 3.4 times higher in comparison to infants without detectable troponin T (OR 3.4, 95%CI 1.22–9.73, p = 0.019). Detectable troponin T had a sensitivity (95%CI) of 78.6 (59.0 to 91.7) % and specificity (95%CI) of 56.1 (39.7 to 71.5) % for predicting infantile beriberi.

Conclusions/Significance

Basal ETK is a more accurate biochemical marker of infantile beriberi than the activation coefficient. Raised plasma troponin T may be a useful indicator of infantile beriberi in infants at risk and in the absence of other evident causes.

Infantile beriberi, or clinical thiamin (vitamin B1) deficiency in infants, is a forgotten disease in Asia, where ∼100 years ago it was a major public health problem. Children aged ∼2–3 months present in cardiac failure but usually rapidly improve if given thiamin injections. It remains relatively common in Vientiane, Lao PDR (Laos) probably because of prolonged intra- and post-partum maternal food avoidance behaviours. There has been very little recent research on the best diagnostic techniques. We conducted a case control study of 47 infants with beriberi and age-matched afebrile and febrile controls in Vientiane. The conventional measures of thiamin deficiency, basal and activated erythrocyte transketolase activities (ETK) and activation (α) coefficients, were assayed along with three markers of cardiac dysfunction - plasma brain natriuretic peptide, N-terminal pro-brain natriuretic peptide, and troponin T. Basal ETK was a better biochemical marker of infantile beriberi than the activation coefficient. Raised plasma troponin T may be a useful indicator of infantile beriberi in babies at risk and in the absence of other evident causes.

Clinically unapparent infantile thiamin deficiency in Vientiane, Laos

Background

Beriberi occurs in Vientiane, Lao PDR, among breastfed infants. Clinical disease may be the tip of an iceberg with subclinical thiamin deficiency contributing to other illnesses. Thiamin treatment could improve outcome.

Methodology/Principal Findings

A cohort of 778 sick infants admitted during one year without clinical evidence of beriberi were studied prospectively and erythrocyte transketolase assays (ETK) performed. Biochemical thiamin deficiency was defined both in terms of the activation coefficient (α>31%) and basal ETK activity <0.59 micromoles/min/gHb. Of the 778 infants, median (range) age was 5 (0–12) months, 79.2% were breastfed, 5.1% had α>31% and 13.4 % basal ETK<0.59 micromoles/min/gHb. Infants ≥2 months old had a higher frequency of biochemical markers of thiamin deficiency. Mortality was 5.5% but, among infants ≥2 months old, mortality was higher in those with basal ETK<0.59 micromoles/min/gHb (3/47, 6.4%) than in those with basal ETK≥0.59 micromoles/min/gHb (1/146, 0.7%) (P = 0.045, relative risk = 9.32 (95%CI 0.99 to 87.5)). Multivariate regression analysis indicated that infant age ≥2 months and fewer maternal years of schooling were independently associated with infant basal ETK<0.59 micromoles/min/gHb.

Conclusions/Significance

Clinically unapparent thiamin deficiency is common among sick infants (≥2 months old) admitted to hospital in Vientiane. This may contribute to mortality and a low clinical threshold for providing thiamin to sick infants may be needed.

Infantile beriberi, or clinical thiamin (vitamin B1) deficiency in infants, is a forgotten disease in Asia, where 100 years ago it was a major public health problem. Infants with this deficiency, commonly aged ∼ 2–3 months, present in cardiac failure but usually rapidly improve if given thiamin injections. It remains relatively common in Vientiane, Lao PDR (Laos), probably because of prolonged intra- and post-partum food avoidance behaviours. Clinical disease may be the tip of an iceberg with subclinical thiamin deficiency contributing to sickness in infants without overt clinical beriberi. We therefore recruited 778 sick infants admitted during one year at Mahosot Hospital, Vientiane, without clinical evidence of beriberi, and performed erythrocyte transketolase (ETK) assays. 13.4 % of infants had basal ETK<0.59 micromoles/min/gHb suggesting biochemical thiamin deficiency. Mortality was 5.5% but, among infants ≥2 months old, mortality was higher in those with basal ETK<0.59 micromoles/min/gHb (3/47, 6.4%) than in those with basal ETK≥0.59 micromoles/min/gHb (1/146, 0.7%) (P = 0.045, relative risk = 9.32 (95%CI 0.99 to 87.5)). We conclude that clinically unapparent thiamin deficiency is common among sick infants (≥2 months old) admitted to hospital in Vientiane. This may contribute to mortality and a low clinical threshold for providing thiamin to sick infants may be needed.

Acute absorption of folic acid from a fortified low-fat spread

OBJECTIVE

To explore the feasibility of low-fat spreads as vehicles for folic acid (FA) fortification by determining the acute absorption of FA from a fortified spread.

DESIGN

Double blind, crossover study to test each of the following treatments administered at 1-weekly intervals: (A) 20 g low-fat (40%) spread fortified with 200 microg FA and a placebo tablet; (B) 20 g low-fat placebo spread and a 200 microg FA tablet; (C) 20 g low-fat placebo spread and a placebo tablet.

SUBJECTS

A total of 13 male volunteers, aged 31.8+/-13.2 y.

MAIN OUTCOME MEASURES

Plasma total folate concentrations, measured before and up to 10 h after each treatment (n=10 samples per treatment).

RESULTS

Plasma folate concentrations were significantly increased compared with baseline values 1 h after administration of the FA tablet, and 1.5 h after the FA spread, and remained significantly higher than the baseline values for up to 7 h after both treatments. The maximum plasma folate response (R(max)), corrected for baseline values and 'placebo response', was established between 1 and 3 h postprandially in response to both FA spread and FA tablet, and no significant difference in R(max) was found between the two treatments (13.4 vs 14.4 nmol/l, P=0.9). The acute absorption of FA from fortified spread relative to that from the tablet, calculated on the basis of area under the plasma folate response curve, was 67% (P=0.04).

CONCLUSION

The absorption of FA from fortified low-fat spread, although lower than from a tablet, is effective. These results suggest that low-fat spreads, typically associated with fat-soluble vitamin fortification, may also be considered feasible as vehicles for FA fortification.

Optimisation and validation of a sensitive high-performance liquid chromatography assay for routine measurement of pyridoxal 5-phosphate in human plasma and red cells using pre-column semicarbazide derivatisation

There are few studies in which direct measurement of vitamin B6 status in both plasma and red cells has been assessed. The aims of the present study were to evaluate the use of a simple, robust HPLC method of direct pyridoxal 5'-phosphate (PLP) measurement in plasma and red cells and to assess its use in establishing reference ranges in a healthy population. A reverse phase HPLC method with pre-column derivatisation using semicarbazide for the simultaneous measurement of PLP, its degradation product, 4-pyridoxic acid (PA) and pyridoxal (PL) in plasma and red cells was developed. Pre-column derivatisation, reverse phase chromatography and detection procedures were optimised. The recovery, precision, linearity and sensitivity of the assay for plasma and red cell PLP, PA and PL was established. The recovery of PLP was greater than 95% for both plasma and red cell samples. The Intra and Inter batch imprecision for PLP was less than 6% and 7%, respectively. The method for PLP was linear up to at least 1000 nmol/l and the detection limit was 2.1 nmol/l (limit of quantification; 5.8 nmol/l). Accuracy of PLP measurements in plasma were acceptable, showing a mean bias of 4.5% from the mean value of laboratories (N=34) participating in an external quality assurance scheme. Geometric mean (95% reference intervals) for plasma and red cell PLP in the healthy subjects (N=126) were 56 (21-138) nmol/l and 410 (250-680) pmol/g Hb, respectively. There was a strong positive correlation (r(2)=0.81) between plasma and red cell PLP levels in the reference population. The HPLC method described was found to be suitable for the routine measurement of PLP in both plasma and red cells.

Effect of riboflavin supplementation on plasma homocysteine in elderly people with low riboflavin status

OBJECTIVE

To investigate the effect of riboflavin supplementation on plasma homocysteine (tHcy) concentrations in healthy elderly people with sub-optimal riboflavin status.

DESIGN

A double-blind, randomized, placebo-controlled riboflavin supplementation trial.

SETTING

Community based study in Northern Ireland.

SUBJECTS

From a screening sample of 101 healthy elderly people, 52 had sub-optimal riboflavin status (erythrocyte glutathione reductase activation coefficient, EGRAC>or=1.20) and were invited to participate in the study.

INTERVENTION

The intervention had two parts. Part 1 was a 12 week randomized double blind, placebo-controlled intervention with riboflavin (1.6 mg/day). Following completion of part 1, the placebo group went on to part 2 of the study which involved supplementation with folic acid (400 micro g/day) for 6 weeks followed by folic acid and riboflavin (1.6 mg/day) for a further 12 weeks, with a 16 week washout period post-supplementation. The purpose of part 2 was: (a) to address the possibility that homocysteine-lowering in response to riboflavin may be obscured by a much greater effect of folate, and that, once folate status was optimized, a dependence of homocysteine on riboflavin might emerge; and (b) to demonstrate that these subjects had homocysteine concentrations which could be lowered by nutritional intervention.

RESULTS

Although riboflavin supplementation significantly improved riboflavin status in both parts 1 and 2 of the study (P<0.001 for each), tHcy concentrations were unaffected (P=0.719). In contrast, folic acid supplementation (study part 2) resulted in a homocysteine lowering of 19.6% (P=0.001).

CONCLUSION

Despite the metabolic dependency of tHcy on riboflavin, it did not prove to be an effective homocysteine-lowering agent, even in the face of sub-optimal riboflavin status.

Angular stomatitis and riboflavin status among adolescent Bhutanese refugees living in southeastern Nepal

BACKGROUND

Between 1990 and 1993, fear of ethnic persecution led 83,000 ethnic Nepalese to flee from Bhutan to refugee camps in Nepal, where they remained at the time of this study. Reported cases of angular stomatitis (AS), ie, thinning or fissuring at the mouth angles, increased 6-fold from December 1998 to March 1999, from 5.5 to 35.6 cases per 1000 per month. This increase came after the removal of a fortified cereal from rations.

OBJECTIVES

The main objectives were to assess the prevalence of AS and of low concentrations of riboflavin, folate, vitamin B-12, and iron by using biochemical measures; to determine whether riboflavin status was associated with AS; and to assess the potential of AS as a screening measure for low riboflavin concentrations.

DESIGN

In October 1999, we performed a survey among a random sample of 463 adolescent refugees in which we conducted interviews and physical examinations and obtained blood specimens for riboflavin assessment. Riboflavin status was assessed with the erythrocyte glutathione reductase (EC 1.6.4.2) activity coefficient. After we excluded those adolescents who had taken vitamins during the past month, 369 were eligible for analyses.

RESULTS

AS was common (26.8%; 95% CI: 22.3, 31.3), the prevalence of low riboflavin concentrations was high (85.8%; 80.7, 90.9), and riboflavin status was associated with AS. Adolescents with AS had significantly lower riboflavin concentrations than did adolescents without AS (P = 0.02). The adjusted odds ratio for AS and low riboflavin concentrations was 5.1 (1.55, 16.5).

CONCLUSION

Globally, riboflavin deficiency is rare. Its emergence in food-dependent populations can be a harbinger of other B-vitamin deficiencies.

Plasma Homocysteine Is Not Subject to Seasonal Variation

Background: Studies investigating the relationship between plasma total homocysteine (tHcy) and vascular disease usually rely on a single measurement. Little information is available, however, on the seasonal variability of plasma tHcy. The aim of this study was to investigate the seasonal variation in fasting plasma tHcy and related B-vitamin intake and status in a group of people who did not consume fortified foods or take B-vitamin supplements.

Methods: In this longitudinal study, a group of 22 healthy people were followed for 1 year. A fasting blood sample and dietary information were collected from each individual every 3 months, i.e., at the end of each season.

Results: There was no significant seasonal variation in plasma tHcy or in B-vitamin intake or status with the exception of red cell folate (significantly lower in spring compared with autumn or winter) and serum folate (significantly lower in spring compared with the other seasons). Although the between-person variation in plasma tHcy was high (47%), the within-person variation was low (11%). This low variation, combined with the low methodologic imprecision of 3.8%, yielded a high reliability coefficient for plasma tHcy (0.97).

Conclusions: Although there was a small seasonal variation in folate status, there was no corresponding seasonal variation in plasma tHcy. The high reliability coefficient for plasma tHcy suggests that a single measurement is reflective of an individual’s average plasma tHcy concentration, thus indicating its usefulness as a potential predictor of disease. This, however, needs to be confirmed in different subgroups of the population.

Low-dose vitamin B-6 effectively lowers fasting plasma homocysteine in healthy elderly persons who are folate and riboflavin replete

BACKGROUND

Current data suggest that physiologic doses of vitamin B-6 have no significant homocysteine-lowering effect. It is possible that an effect of vitamin B-6 was missed in previous trials because of a much greater effect of folic acid, vitamin B-12, or both.

OBJECTIVE

The aim of this study was to investigate the effect of low-dose vitamin B-6 supplementation on fasting total homocysteine (tHcy) concentrations in healthy elderly persons who were made replete with folate and riboflavin.

DESIGN

Twenty-two healthy elderly persons aged 63-80 y were supplemented with a low dose of vitamin B-6 (1.6 mg/d) for 12 wk in a randomized, double-blind, placebo-controlled trial after repletion with folic acid (400 microg/d for 6 wk) and riboflavin (1.6 mg/d for 18 wk); none of the subjects had a vitamin B-12 deficiency.

RESULTS

Folic acid supplementation lowered fasting tHcy by 19.6% (P < 0.001). After folic acid supplementation, baseline tHcy concentrations ranged from 6.22 to 23.52 micromol/L and 10 subjects had suboptimal vitamin B-6 status (plasma pyridoxal-P < 20 nmol/L). Two-way analysis of variance showed that the significant improvement in vitamin B-6 status in response to vitamin B-6 supplementation (on the basis of both pyridoxal-P: and the erythrocyte aspartate aminotransferase activation coefficient) was reflected in a significant reduction in plasma tHcy of 7.5%.

CONCLUSIONS

Low-dose vitamin B-6 effectively lowers fasting plasma tHcy in healthy subjects who are both folate and riboflavin replete. This suggests that any program aimed at the treatment or prevention of hyperhomocysteinemia should include vitamin B-6 supplementation.

Prevalence of thiamin deficiency in anorexia nervosa

OBJECTIVE

Deficiency of thiamin (vitamin B1) causes a range of neuropsychiatric symptoms that resemble those reported in patients with anorexia nervosa (AN) but the prevalence of thiamin deficiency in AN has not been reliably established. This study was designed to investigate the prevalence of thiamin deficiency in AN.

METHOD

Thirty-seven patients attending a specialist eating disorders unit and meeting all or some of the DSM-IV criteria for AN were compared with 50 blood donor controls. All subjects underwent measurement of erythrocyte transketolase activation following the addition of thiamin pyrophosphate, the standard biochemical test for thiamin deficiency. Deficiency was defined as a result more than 2 SD above the mean of the control population.

RESULTS

Fourteen patients (38%) had results in the deficient range; 7 (19%) met the most stringent published criterion for deficiency. Deficiency was not related to duration of eating restraint, frequency of vomiting, or alcohol consumption.

DISCUSSION

Thiamin deficiency may account for some of the neuropsychiatric symptoms of AN and routine screening or supplementation may be indicated.

JO’Reilly D. Vitamin B1 Status Assessed by Direct Measurement of Thiamin Pyrophosphate in Erythrocytes or Whole Blood by HPLC: Comparison with Erythrocyte Transketolase Activation Assay

Background: The concentration of thiamin diphosphate (TDP) in erythrocytes is a useful index of thiamin status. We describe an HPLC method for TDP and its results in patients at risk of thiamin deficiency.

Methods: We used reversed-phase HPLC with postcolumn derivatization with alkaline potassium ferricyanide and fluorescence detection. Samples were deproteinized and injected directly onto a C18 column. TDP concentrations in erythrocytes were compared with those in whole blood. Reference intervals for erythrocyte TDP (n = 147; 79 males and 68 females; mean age, 54 years) and whole blood TDP (n = 124; 68 males and 56 females; mean age, 54 years) were determined in an apparently healthy population. We compared erythrocyte TDP with results of the erythrocyte transketolase activation test in 63 patients who were considered at risk of thiamin deficiency.

Results: The method was linear to at least 200 μg/L. The between-run CV was &lt;8%. The lower limit of quantification for both whole blood and packed erythrocytes was 300 pg on column with a detection limit of 130 pg on column. Recovery of TDP from blood samples was &gt;90%. TDP in erythrocytes correlated strongly with that in whole blood (r = 0.97). Reference intervals for erythrocyte and whole blood TDP were 280–590 ng/g hemoglobin and 275–675 ng/g hemoglobin, respectively. Of the 63 patients suspected of thiamin deficiency, 46 were normal by both TDP and activation tests, 13 were deficient by both tests, 1 was deficient by the activation test but had normal erythrocyte TDP concentrations, and 4 were normal by the activation test but had low TDP.

Conclusions: The HPLC method is precise and yields results similar to the erythrocyte activation assay.

Thiamine deficiency and malaria in adults from southeast Asia

BACKGROUND

Thiamine deficiency (beriberi) is common in some parts of southeast Asia. Acute thiamine deficiency can mimic many complications of malaria, such as encephalopathy and lactic acidosis. We examined the incidence of thiamine deficiency in adults admitted to hospital with malaria in Thailand.

METHODS

For this prospective study, we recruited consecutive patients with malaria or other febrile illness who presented to Paholpolpayuhasena Hospital, Kanchanaburi, Thailand, between May and July, 1992. We used the activation coefficient (alpha) for transketolase activity in erythrocytes to measure thiamine deficiency (defined as alpha>1.31) in patients with severe and uncomplicated malaria and in controls (patients' relatives and healthy volunteers). To exclude the possibility of interference in the assays, transketolase activity was also measured in erythrocytes used to culture parasites.

FINDINGS

12 (52%) of 23 patients with severe malaria and ten (19%) of 54 patients with uncomplicated malaria had alpha values above the normal range (p<0.0001 and p=0.0014, respectively, compared with controls), which indicated severe thiamine deficiency. Thiamine deficiency was more severe in patients with cerebral malaria than in those with uncomplicated malaria and the controls (p=0.008).

INTERPRETATION

In adults admitted to hospital in Thailand, thiamine deficiency commonly complicates acute falciparum malaria, particularly in severe infections, and could contribute to dysfunction of the central nervous system.

Indicators of vitamin and mineral status in athletes' blood: a review

This review examines the hypothesis that vitamin and mineral status in athletes is inadequate for optimal sports performance. The review is based on indicators determined from blood and on studies published since 1980. Most of the studies did not find micronutrient status in athletes to be different from untrained controls. The serum ferritin concentration in females was lower than in males (27 vs. 78 micrograms.L-1), and the prevalence of low serum ferritin concentration was higher in female athletes than in untrained female controls (37 vs. 23%). Supplementation of water-soluble vitamins and iron was associated with an improvement in the corresponding indicators. Excluding a few studies with mildly anemic subjects, improvements in indicators of micronutrient status were not associated with enhanced athletic performance. Consequently, the levels of indicators of micronutrient status seen in athletes' blood were apparently compatible with optimal physical performance.

Lack of association between indices of vitamin B1, B2, and B6 status and exercise-induced blood lactate in young adults

By means of a 5-week vitamin B-complex supplementation, associations between indices of vitamin B1, B2, and B6 status (activation coefficients [AC] for erythrocyte transketolase, glutathione reductase, and aspartate aminotransferase) and exercise-induced blood lactate concentration were studied. Subjects, 42 physically active college students (18-32 yrs), were randomized into vitamin (n = 22) and placebo (n = 20) groups. Before the supplementation there were no differences in ACs or basal enzyme activities between the groups. The ACs were relatively high, suggesting marginal vitamin status. In the vitamin group, all three ACs were lower (p < 0.0001) after supplementation: transketolase decreased from 1.16 (1.14-1.18) (mean and 95% confidence interval) to 1.08 (1.06-1.10); glutathione reductase decreased from 1.33 (1.28-1.39) to 1.14 (1.11-1.17); and aspartate aminotransferase decreased from 2.04 (1.94-2.14) to 1.73 (1.67-1.80). No changes were found after placebo. Despite improved indices of vitamin status, supplementation did not affect exercise-induced blood lactate concentration. Hence no association was found between ACs and blood lactate. It seems that marginally high ACs do not necessarily predict altered lactate metabolism.

Dietary intake and thiamin, iron, and zinc status in elite Nordic skiers during different training periods

This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcal/day (CV 19.1%) in male skiers, 2,754 kcal/day (CV 3.7%) in male controls, 2,812 kcal/day (CV 9.1%) in female skiers, and 2,013 kcal/day (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-11.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity.

Thiamine, riboflavin, and pyridoxine deficiencies in a population of critically ill children

The unexpected autopsy finding of Wernicke encephalopathy in three children who died after prolonged enteral feeding prompted us to examine the incidence of thiamine deficiency in three high-risk pediatric populations. We also measured riboflavin and pyridoxine activity in the same groups. We used activated enzyme assays (erythrocyte transketolase, glutathione reductase, aspartate aminotransferase) to assess tissue stores of the dependent vitamin cofactors (thiamine (vitamin B1), riboflavin (vitamin B2), and pyridoxine (vitamin B6), respectively). Using our own reference ranges based on data from 80 healthy adults and children, we prospectively investigated the B vitamin status of three groups of children: (1) 27 patients who were fed solely by nasogastric tube for more than 6 months, (2) 80 children admitted to a pediatric intensive care unit for more than 2 weeks, and (3) 6 children receiving intensive chemotherapy. The upper limits for stimulated enzyme activity in control subjects were unaffected by age or gender (16% for transketolase, 63% for glutathione reductase, 123% for aspartate aminotransferase). Using these limits, 10 (12.5%) of 80 patients receiving intensive care and 4 of 6 patients receiving chemotherapy were thiamine deficient. Elevated levels returned to normal after thiamine supplementation. No patients were pyridoxine deficient, but 3 (3.8%) of the 80 patients receiving intensive care and 1 of the 6 patients receiving chemotherapy were also riboflavin deficient. We conclude that unrecognized thiamine deficiency is common in our pediatric intensive care and oncology groups. This potentially fatal but treatable disease can occur in malnourished patients of any age and is probably underdiagnosed among chronically ill children. Our findings may be applicable to other high-risk pediatric groups.

The evaluation of erythrocyte thiamin diphosphate as an indicator of thiamin status in man, and its comparison with erythrocyte transketolase activity measurements

HPLC measurement of the major physiological form of thiamin, thiamin diphosphate, in erythrocytes (ETDP) has been assessed as an indicator of thiamin status and compared with erythrocyte transketolase activity (ETKA) before and after activation with exogenous thiamin diphosphate (TDP effect). The comparison was made by following the response of the parameters to incubation of erythrocytes with thiamin and by measurements in alcoholic, elderly and student groups. All parameters were responsive to the thiamin content of their environment, but ETDP was at least as sensitive as TDP effect and more sensitive than ETKA in reflecting thiamin uptake and utilisation by erythrocytes. There was a better correlation between ETDP and ETKA than between ETDP and TDP effect. All the groups showed a significant positive correlation between ETDP and ETKA, but only the elderly and the alcoholic groups showed a significant negative correlation between ETDP and TDP effect. The lack of correlation between ETDP and TDP effect in the student group may be due to the relative imprecision of TDP effect measurements at the lower end of the reference range. ETDP is more stable than ETKA in frozen erythrocytes, is easier to standardise and is not affected by various factors which can influence the enzyme assay. Measurement of ETDP is, therefore, recommended for first line assessment of thiamin status.