An enzymatic measurement of the riboflavin status in man

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.

Combined isobutyryl‐CoA and multiple acyl‐CoA dehydrogenase deficiency in a boy with altered riboflavin homeostasis

In this report, we describe the case of an 11‐year‐old boy, who came to our attention for myalgia and muscle weakness, associated with inappetence and vomiting. Hypertransaminasemia was also noted, with ultrasound evidence of hepatomegaly. Biochemical investigations revealed acylcarnitine and organic acid profiles resembling those seen in MADD, that is, multiple acyl‐CoA dehydrogenase deficiencies (OMIM #231680) a rare inherited disorder of fatty acids, amino acids, and choline metabolism. The patient carried a single pathogenetic variant in the ETFDH gene (c.524G>A, p.Arg175His) and no pathogenetic variant in the riboflavin (Rf) homeostasis related genes (SLC52A1, SLC52A2, SLC52A3, SLC25A32, FLAD1). Instead, compound heterozygosity was found in the ACAD8 gene (c.512C>G, p.Ser171Cys; c.822C>A, p.Asn274Lys), coding for isobutyryl‐CoA dehydrogenase (IBD), whose pathogenic variants are associated to IBD deficiency (OMIM #611283), a rare autosomal recessive disorder of valine catabolism. The c.822C>A was never previously described in a patient. Subsequent further analyses of Rf homeostasis showed reduced levels of flavins in plasma and altered FAD‐dependent enzymatic activities in erythrocytes, as well as a significant reduction in the level of the plasma membrane Rf transporter 2 in erythrocytes. The observed Rf/flavin scarcity in this patient, possibly associated with a decreased ETF:QO efficiency might be responsible for the observed MADD‐like phenotype. The patient's clinical picture improved after supplementation of Rf, l‐carnitine, Coenzyme Q10, and also 3OH‐butyrate. This report demonstrates that, even in the absence of genetic defects in genes involved in Rf homeostasis, further targeted molecular analysis may reveal secondary and possibly treatable biochemical alterations in this pattern.

Dietary Riboflavin Intake and Riboflavin Status in Young Adult Women Living in Metro Vancouver, Canada

BACKGROUND

Nutrition surveys suggest that <10% of Canadian adults have inadequate riboflavin intakes. However, biochemical riboflavin deficiency [erythrocyte glutathione reductase activity coefficient (EGRac) ≥1.40] has been reported in 41% of young adult women living in Metro Vancouver. Canadian Chinese ethnicity comprise >25% of Vancouver's population and are postulated to have poorer riboflavin status than those of European ethnicity because they could be less likely to consume dairy products and fortified wheat.

OBJECTIVES

The objectives of this study were to determine dietary riboflavin intake and food sources, and to assess the association between riboflavin intake and status in young women of European (n = 107) and Chinese (n = 91) ethnicities living in Metro Vancouver, Canada.

METHODS

This was a cross-sectional study conducted in women (aged 19-45 y). Women were healthy, not pregnant or breastfeeding, of European or Chinese ethnicities, and not taking riboflavin-containing supplements for the past 4 mo. Dietary riboflavin intake was assessed using the past-year Diet History Questionnaire II, and riboflavin status (EGRac) was measured in fasting venous blood samples.

RESULTS

Only 7% of participants had dietary riboflavin intakes below the Estimated Average Requirement (0.9 mg/d), but 40% of women had biochemical riboflavin deficiency (EGRac ≥1.40). Although more Canadian women of European ethnicity than Chinese ethnicity had biochemical riboflavin deficiency (46% and 34%; P < 0.001), median dietary riboflavin intake did not differ (1.73 and 1.82 mg/d; P = 0.587). Dairy products and vegetables contributed the most to riboflavin intake. Energy-adjusted dietary riboflavin intake was inversely associated with EGRac (B = -0.04, 95% CI: -0.07, -0.01). However, after further adjustment the relation was not significant.

CONCLUSIONS

Overall, women of reproductive age living in Metro Vancouver, Canada, had a low prevalence of inadequate dietary riboflavin intake despite the high prevalence of apparent biochemical riboflavin deficiency.

Disruption of hepatic one-carbon metabolism impairs mitochondrial function and enhances macrophage activity in methionine-choline-deficient mice

One-carbon metabolism is a collection of metabolic cycles that supports methylation and provides one-carbon bound folates for the de novo synthesis of purine and thymidine nucleotides. The methylation of phosphatidylethanolamine to form choline has been extensively studied in the context of fatty liver disease. However, the role of one-carbon metabolism in supporting nucleotide synthesis during liver damage has not been addressed. The objective of this study is to determine how the disruption of one-carbon metabolism influences nucleotide metabolism in the liver after dietary methionine and choline restriction. Mice (n=8) were fed a methionine-choline-deficient or control diet for 3 weeks. We treated mice with the compound alloxazine (0.5 mg/kg), a known adenosine receptor antagonist, every second day during the final week of feeding to probe the function of adenosine signaling during liver damage. We found that concentrations of several hepatic nucleotides were significantly lower in methionine- and choline-deficient mice vs. controls (adenine: 13.9±0.7 vs. 10.1±0.6, guanine: 1.8±0.1 vs. 1.4±0.1, thymidine: 0.0122±0.0027 vs. 0.0059±0.0027 nmol/mg dry tissue). Treatment of alloxazine caused a specific decrease in thymidine nucleotides, decrease in mitochondrial content in the liver and exacerbation of steatohepatitis as shown by the increased hepatic lipid content and altered macrophage morphology. This study demonstrates a role for one-carbon metabolism in supporting de novo nucleotide synthesis and mitochondrial function during liver damage.

Suboptimal Biochemical Riboflavin Status Is Associated with Lower Hemoglobin and Higher Rates of Anemia in a Sample of Canadian and Malaysian Women of Reproductive Age

BACKGROUND

Riboflavin is required for several redox reactions. Clinical riboflavin deficiency occurs mainly in low-income countries, where it is associated with anemia. The functional significance of suboptimal riboflavin status in different populations and its role in anemia is not well understood.

OBJECTIVES

We assessed the biomarker status of riboflavin and its association with hemoglobin concentration and anemia in women living in Vancouver, Canada, and Kuala Lumpur, Malaysia.

METHODS

Healthy nonpregnant, nonbreastfeeding women (19-45 y) were recruited from Canada ( n = 206) and Malaysia (n = 210) via convenience sampling. Fasting blood was collected to assess riboflavin status [erythrocyte glutathione reductase activity coefficient (EGRac)], hematological indicators, soluble transferrin receptor (sTfR), ferritin, vitamin A, folate, and vitamin B-12 concentrations. Linear and logistic regression models were used to assess the association of riboflavin status with hemoglobin concentration and anemia.

RESULTS

EGRac (mean ± SD) values were higher, indicating poorer riboflavin status, in Malaysian compared with Canadian women (1.49 ± 0.17 compared with 1.38 ± 0.11). Likewise, riboflavin biomarker deficiency (EGRac ≥1.40) was significantly more prevalent among Malaysians than Canadians (71% compared with 40%). More Malaysian than Canadian women were anemic (hemoglobin <120 g/L; 18% compared with 7%). With use of linear regression (pooled sample; n = 416), EGRac values were negatively associated with hemoglobin concentration (r = -0.18; P < 0.001). This relation remained significant (P = 0.029) after adjusting for age, parity, ethnicity, vitamin B-12, folate, sTfR, ferritin, and vitamin A. Women with riboflavin deficiency (EGRac ≥1.40) were twice as likely to present with anemia (adjusted OR: 2.38; 95% CI: 1.08, 5.27) compared with women with EGRac <1.40.

CONCLUSIONS

Biochemical riboflavin deficiency was observed in Canadian and Malaysian women, with higher rates of deficiency among Malaysian women. Deficient biomarker status of riboflavin was a weak but significant predictor of hemoglobin and anemia, suggesting that the correction of riboflavin deficiency may potentially play a small protective role in anemia, but this requires further investigation.

Riboflavin Depletion Promotes Tumorigenesis in HEK293T and NIH3T3 Cells by Sustaining Cell Proliferation and Regulating Cell Cycle-Related Gene Transcription

BACKGROUND

Riboflavin is an essential component of the human diet and its derivative cofactors play an established role in oxidative metabolism. Riboflavin deficiency has been linked with various human diseases.

OBJECTIVE

The objective of this study was to identify whether riboflavin depletion promotes tumorigenesis.

METHODS

HEK293T and NIH3T3 cells were cultured in riboflavin-deficient or riboflavin-sufficient medium and passaged every 48 h. Cells were collected every 5 generations and plate colony formation assays were performed to observe cell proliferation. Subcutaneous tumorigenicity assays in NU/NU mice were used to observe tumorigenicity of riboflavin-depleted HEK293T cells. Mechanistically, gene expression profiling and gene ontology analysis were used to identify abnormally expressed genes induced by riboflavin depletion. Western blot analyses, cell cycle analyses, and chromatin immunoprecipitation were used to validate the expression of cell cycle-related genes.

RESULTS

Plate colony formation of NIH3T3 and HEK293T cell lines was enhanced >2-fold when cultured in riboflavin-deficient medium for 10-20 generations. Moreover, we observed enhanced subcutaneous tumorigenicity in NU/NU mice following injection of riboflavin-depleted compared with normal HEK293T cells (55.6% compared with 0.0% tumor formation, respectively). Gene expression profiling and gene ontology analysis revealed that riboflavin depletion induced the expression of cell cycle-related genes. Validation experiments also found that riboflavin depletion decreased p21 and p27 protein levels by ∼20%, and increased cell cycle-related and expression-elevated protein in tumor (CREPT) protein expression >2-fold, resulting in cyclin D1 and CDK4 levels being increased ∼1.5-fold, and cell cycle acceleration. We also observed that riboflavin depletion decreased intracellular riboflavin levels by 20% and upregulated expression of riboflavin transporter genes, particularly SLC52A3, and that the changes in CREPT and SLC52A3 correlated with specific epigenetic changes in their promoters in riboflavin-depleted HEK293T cells.

CONCLUSION

Riboflavin depletion contributes to HEK293T and NIH3T3 cell tumorigenesis and may be a risk factor for tumor development.

Riboflavin Deficiency in Rats Decreases de novo Formate Production but Does Not Affect Plasma Formate Concentration

Background: The one-carbon metabolism pathway is highly dependent on a number of B vitamins in order to provide one-carbon units for purine and thymidylate biosynthesis as well as homocysteine remethylation. Previous studies have examined folate and vitamin B-12 deficiency and their effects on formate metabolism; as of yet, to our knowledge, no studies on the effects of riboflavin deficiency on formate metabolism have been published.Objective: Our objective was to determine the effects of riboflavin deficiency on formate metabolism.Methods: Weanling male rats were randomly assigned either to control, riboflavin-replete (RR) or to experimental, riboflavin-deficient (RD) versions of the AIN-93G diet for 13 d, at which time a constant infusion of [¹³C]-formate was carried out to ascertain the effects of deficiency on formate production. Gas chromatography-mass spectrometry was used to measure plasma formate concentration and [¹³C]-formate enrichment. HPLC, LC-mass spectrometry (MS)/MS, and enzymatic assays were used for the measurement of one-carbon precursors and other metabolites.Results: RD rats had significantly lower rates of formate production (15%) as well as significantly reduced hepatic methylenetetrahydrofolate reductase activity (69%) and protein concentration (54%) compared with RR rats. There was no difference in plasma formate concentrations between the groups. Plasma serine, a potential one-carbon precursor, was significantly higher in RD rats (467 ± 73 μM) than in RR rats (368 ± 52 μM).Conclusions: Although deficiencies in folate and vitamin B-12 lead to major changes in plasma formate concentrations, riboflavin deficiency results in no significant difference; this disagrees with the prediction of a published mathematical model. Our observation of a lower rate of formate production is consistent with a role for flavoproteins in this process.

Effect of B Vitamins-fortified Foods on Primary School Children in Beijing

The objective of this study is to investigate the effect of B vitamins-fortified foods on primary school children. A controlled trial was conducted in 101 normal primary school children aged 9-11 years. They were randomly assigned to supplemental control group (S-control, n=36), riboflavin supplementation group (+riboflavin 0.625 mg/day, n=32), and B vitamin compound supplementation group (+riboflavin 0.625 mg/day, +thiamin 0.512 mg/day, +nicotinic acid 0.365 mg/day, +folic acid 0.13 mg/day, n=33) based on school classes. Urinary riboflavin excretion and erythrocyte glutathione reductase activity coefficient (EGRAC) along with erythrocyte transketolase activity (ETKA) were used to evaluate B vitamin levels in the children. AYP index, an index reflecting the brain performance ability, was chosen to assess the children's study abilities. Health education was carried out to help children and their parents adopt scientific dietary concepts. The urinary riboflavin excretion was higher in two supplementation groups (435.24 +/- 153.3 microg/g creatinine, 374.6 +/- 144.6 microg/g creatinine) than in S-control group (235.1 +/- 86.2 microg/g creatinine). Average values of EGRAC were lower in two supplementation groups (0.90 +/- 0.11, 0.80 +/- 0.10) than in S-control group (1.08 +/- 0.25). At the same time, the percentage of thiamine pyrophosphate (TPP%) decreased from 63.69 +/- 28.04 to 42.16 +/- 16.31 in B vitamin compound supplementation group. Meanwhile, AYP index increased at the end of the supplementation in two supplementation groups. B vitamins supplementation can significantly increase B vitamin level in children. Biochemical activities of riboflavin and thiamin can improve with the intake of fortified foods. The effect of B vitamin compound supplementation is better than that of single riboflavin supplementation when the effect of riboflavin's biofunction is considered. In addition, micronutrient supplementation appears to assist children's study abilities.

Urinary excretion of B-group vitamins reflects the nutritional status of B-group vitamins in rats

We have reported previously that the urinary excretion of B-group vitamins reflects recent dietary intakes of these vitamins. We also proposed reference values for the urinary levels of B-group vitamins for human subjects, and used these for evaluating human nutritional status. However, the question arises as to whether the urinary excretion of B-group vitamins in animals or human subjects decreases immediately before they become B-group vitamin insufficient or when fed a diet low in vitamins. In the present study, rats were fed a vitamin-free diet for 5 d, and changes in the levels of B-group vitamins in urine and blood were monitored. Urinary excretion of vitamin B₁, vitamin B₂, 4-pyridoxic acid (a catabolite of vitamin B₆), pantothenic acid, folate and biotin steeply decreased, and all of the values reached zero within 1–2 d. With respect to blood, the concentrations of only three of the eight B-group vitamins (vitamin B₁, pyridoxal phosphate and biotin) decreased to 15 % (P < 0·0001), 7 % (P < 0·0001) and 2 % (P < 0·0001) on day 5, respectively, compared with the values at the beginning of the experiment. The decrease was more rapid and the changes were greater in the urine samples than in the blood samples. The present data complement our previous proposal that the urinary excretion of B-group vitamins reflects the nutritional status of these vitamins.

Non-haem Iron-mediated Oxidative Stress in Haemoglobin E Beta-thalassaemia

Introduction: Haemoglobin (Hb) E beta-thalassaemia is a common thalassaemic disorder in Southeast Asia and is very common in the eastern and north-eastern parts of India. The disease cause rapid erythrocyte destruction due to the free radical mediated injury but factors for the oxidative injury are not clearly known. We investigated the free reactive iron (non-haem) mediated insult in Hb E beta-thalassaemia. Materials and Methods: Thirty Hb E beta-thalassaemic patients (age range, 3 to 15 years) who had undergone blood transfusion at least 1 month prior to sampling and 32 normal healthy individuals (age range, 18 to 30 years) were included in this study. We estimated the ferrozine detected intracellular erythrocytic free reactive iron (non-haem iron), reduced glutathione (GSH), glutathione reductase activity, cellular damage marker serum thiobarbituric acid reacting substances (TBARS) and also serum ferritin using standard methods. Results: We found that the erythrocytic free reactive iron was significantly higher (P <0.001) in Hb E beta patients and was about 30% more than in controls. The elevated level of erythrocytic non-haem iron was associated with a high level of serum TBARS which was about 86% higher in patients than in controls. The serum ferritin level was also significantly higher (P <0.001) compared to controls. The erythrocytic reduced glutathione level was significantly lower (P <0.001) at about 65% less in the patients’ group and the erythrocytic glutathione reductase enzyme was also found to be significantly lower (P <0.001) in Hb E beta-thalassaemia. Conclusions: We concluded that a significantly elevated level of erythrocytic free reactive iron and lipid peroxidation end product was associated with low erythrocytic GSH level. This reflects non-haem iron mediated cellular damage in Hb E beta-thalassaemia. Key words: Glutathione, Lipid peroxidation

Effects of methodological variation on assessment of riboflavin status using the erythrocyte glutathione reductase activation coefficient assay

Riboflavin status is usually measured as thein vitrostimulation with flavin adenine dinucleotide of the erythrocyte enzyme glutathione reductase, and expressed as an erythrocyte glutathione reductase activation coefficient (EGRAC). This method is used for the National Diet and Nutrition Surveys (NDNS) of the UK. In the period between the 1990 and 2003 surveys of UK adults, the estimated prevalence of riboflavin deficiency, expressed as an EGRAC value ≥ 1·30, increased from 2 to 46 % in males and from 1 to 34 % in females. We hypothesised that subtle but important differences in the detail of the methodology between the two NDNS accounted for this difference. We carried out an evaluation of the performance of the methods used in the two NDNS and compared against an ‘in-house’ method, using blood samples collected from a riboflavin intervention study. Results indicated that the method used for the 1990 NDNS gave a significantly lower mean EGRAC value than both the 2003 NDNS method and the ‘in-house’ method (P < 0·0001). The key differences between the methods relate to the concentration of FAD used in the assay and the duration of the period of incubation of FAD with enzyme. The details of the EGRAC method should be standardised for use in different laboratories and over time. Additionally, it is proposed that consideration be given to re-evaluating the basis of the EGRAC threshold for riboflavin deficiency.

Mild riboflavin deficiency is highly prevalent in school-age children but does not increase risk for anaemia in Côte d'Ivoire

There are few data on the prevalence of riboflavin deficiency in sub-Saharan Africa, and it remains unclear whether riboflavin status influences the risk for anaemia. The aims of this study were to: (1) measure the prevalence of riboflavin deficiency in children in south-central Côte d'Ivoire; (2) estimate the riboflavin content of the local diet; and (3) determine if riboflavin deficiency predicts anaemia and/or iron deficiency. In 5- to 15-year-old children (n281), height, weight, haemoglobin (Hb), whole blood zinc protoporphyrin (ZPP), erythrocyte glutathione reductase activity coefficient (EGRAC), serum retinol, C-reactive protein (CRP) and prevalence ofPlasmodiumspp. (asymptomatic malaria) andSchistosoma haematobium(bilharziosis) infections were measured. Three-day weighed food records were kept in twenty-four households. Prevalence of anaemia in the sample was 52 %; 59 % were iron-deficient based on an elevated ZPP concentration, and 36 % suffered from iron deficiency anaemia.Plasmodiumparasitaemia was found in 49 % of the children. Nineteen percent of the children were infected withS. haematobium. Median riboflavin intake in 5- to 15-year-old children from the food records was 0·42 mg/d, ~47 % of the estimated average requirement for this age group. Prevalence of riboflavin deficiency was 65 %, as defined by an EGRAC value >1·2. Age, elevated CRP and iron deficiency were significant predictors of Hb. Riboflavin-deficient children free of malaria were more likely to be iron deficient (odds ratio; 3·07; 95 % CI 1·12, 8·41). In conclusion, nearly two-thirds of school-age children in south-central Côte d'Ivoire are mildly riboflavin deficient. Riboflavin deficiency did not predict Hb and/or anaemia, but did predict iron deficiency among children free of malaria.

Biomarkers of nutrient exposure and status in one-carbon (methyl) metabolism

One-carbon metabolism is a network of interrelated biochemical reactions that involve the transfer of one-carbon groups from one compound to another. The coenzymes necessary for several of these reactions include the B-vitamins, folate, vitamin B-12, vitamin B-6 and riboflavin (vitamin B-2), whereas important intermediary compounds in this schema include methionine and choline. There has been renewed interest in one-carbon metabolism during the past several years, engendered by recent insights that indicate that modest dietary inadequacies of the abovementioned nutrients, of a degree insufficient to cause classical deficiency syndromes, can still contribute to important diseases such as neural tube defects, cardiovascular disease and cancer. Traditional means of assessing nutrient exposure with food frequency questionnaires, and nutrient status with plasma and urine vitamin assays, has some genuine validity and utility. Assessing the concentration of appropriate intermediary compounds, such as plasma homocysteine for folate and methylmalonic acid for vitamin B-12, provides further insights because they appear to add a degree of sensitivity that does not exist with the more traditional assays. There may also be value in developing measures that integrate the status of all these nutrients and express it as a functional "methylation capacity" of the individual. Plasma or tissue concentrations of S-adenosylmethionine and S-adenosylhomocysteine, and genomic DNA methylation are two potential candidates in this regard although much work is yet to be done to define the nature of these relationships.

Riboflavin deficiency: early effects on post-weaning development of the duodenum in rats

The aim of this present study was to identify the earliest point at which riboflavin deficiency affects post-weaning bowel development in rats. After weaning, eighty Wistar rats were weight-matched as pairs, one animal being fed a normal synthetic diet and the other being fed the same diet but deficient in riboflavin. Body weight, feeding and rates of growth were monitored and eight pairs of animals were taken for analysis at 45, 69, 93, 117 and 141 h. Riboflavin status was monitored by determining the erythrocyte glutathione reductase activation coefficient (EGRAC), and hepatic flavins were measured by a fluorescence assay. Changes to the number and dimensions of villi and crypts in the duodenum were determined, as well as crypt division (bifurcation) and the DNA synthesis index of the crypt epithelium by bromodeoxyuridine (BrdU) labelling. Riboflavin deficiency was established in the experimental rats, as demonstrated by a significant increase in EGRAC after 45 h (P<0.001) and decreased liver flavins after 96 h (P<0.001). After 96 h a significant increase in the size and cellularity of the crypts (P<0.001 in both cases) was seen in these riboflavin-deficient animals, with a decreased incidence of bifurcating crypts and of BrdU-labelled cells. No changes to villus number or size were observed. The present study has demonstrated that developmental changes to the duodenal crypt arise shortly after circulating riboflavin measurements show evidence of deficiency. These changes primarily affect cell proliferation and crypt bifurcation, and precede long-term changes such as the reduction of villus number.

Thiamine, riboflavin, pyridoxine, and vitamin C status in premature infants receiving parenteral and enteral nutrition

BACKGROUND

There is a paucity of data about water soluble vitamin status in low birthweight infants. Therefore, the authors' objective was to assess current feeding protocols.

METHODS

The authors measured serum concentrations for riboflavin, pyridoxine, and vitamin C and functional assays for thiamine and riboflavin longitudinally in 16 premature infants (birthweight, 1,336 +/- 351 g; gestational age, 30 +/- 2.5 weeks) before receiving nutrition (time 1, 2 +/- 1 days), during supplemental or parenteral nutrition (time 2, 16 +/- 10 days) and while receiving full oral feedings (time 3, 32 +/- 15 days). In plasma, vitamin C was measured colorimetrically, and riboflavin and pyridoxine were measured using high-performance liquid chromatography. The erythrocyte transketolase test as a functional evaluation of thiamine and the erythrocyte glutathione reductase test for riboflavin were measured colorimetrically.

RESULTS

At time 1, nutrient intake of vitamins were negligible because infants were receiving intravenous glucose and electrolytes only. Intakes differed between time 2 and time 3 for thiamine (510 +/- 280 and 254 +/- 115 microg. kg-1. d-1, respectively), riboflavin (624 +/- 305 and 371 +/- 193 microg. kg-1. d-1, respectively), and pyridoxine (394 +/- 243 and 173 +/- 85 microg/100 kcal, respectively), but not for vitamin C (32 +/- 17 and 28 +/- 12 mg. kg-1. d-1, respectively). Blood levels at times 1, 2, and 3 were for thiamine (4.9 +/- 2.7%, 3.3 +/- 6.6%, and 4.1 +/- 9% erythrocyte transketolase test, respectively), riboflavin (0.91 +/- 0.31, 0.7 +/- 0.3, 0.91 +/- 0.18 erythrocyte glutathione reductase test, respectively), riboflavin (19.5 +/- 17, 23.3 +/- 8.6, 17.6 +/- 10 ng/mL, respectively), pyridoxine (32 +/- 25, 40 +/- 16, 37 +/- 26 ng/mL, respectively), and vitamin C (5.2 +/- 3, 5 +/- 2.2, 10 +/- 5 microg/mL, respectively) and did not differ at those times.

CONCLUSIONS

Current intakes of these vitamins, except for possibly vitamin C, during parenteral and enteral nutrition seem to result in adequate plasma concentrations and normal functional indices.

Serum levels assessment of vitamin A, E, C, B2 and carotenoids in malnourished and non-malnourished hospitalized elderly patients

AIMS & METHODS

Serum levels of vitamins A, E, C, B2 and carotenoids were determined in protein-energy malnourished (PEM, with body mass index, BMI<18.5 kg/m2) and non-PEM (BMI+/-18.5 kg/m2) hospitalized elderly (age > or = 65 years) patients, in the University Hospital of Faculty of Medicine of Ribeirão Preto, São Paulo University.

RESULTS

PEM (n=21) and non-PEM (n=106) patients were paired for age (73.6+/-7.3 vs. 71.6+/-5.6 years) and male percentage (65.1 vs. 52.4%). As expected, PEM elderly showed lower (P<0.05) body weight (median 43.1; range: 29.9-51.4 vs. 58.1; range: 45.7-143.5 kg), triceps skinfold (5.2+/-3.1 vs. 10.1+/-4.9 mm), and mid-arm muscle circumference (20.3+/-2.5 vs. 23.1+/-3.4 cm). Serum albumin (4.0+/-0.9 vs. 4.1+/-0.7 g/dl) and total lymphocytes count (1918.3+/-919 vs. 1842.7+/-862 mm(3)) were similar, respectively, among PEM and non-PEM patients. The percentage of biochemical riboflavin deficiency (58.8 vs. 56.2), low serum levels of vitamin A (28.6 vs. 29.6) and vitamin E (18.7 vs. 25) were similar, respectively, between PEM and non-PEM groups. The prevalence of low serum levels of water soluble vitamins was higher (P<0.01) in malnourished elderly than in the non-PEM group (ascorbic acid, 80.9 vs. 56.7%, and carotenoids, 14.3 vs. 3%, respectively).

CONCLUSIONS

These results suggest that hospitalized malnourished elderly show high percentage of low water soluble vitamin serum levels, a phenomenon possibly linked to decreased food intake, especially fruits and vegetables.

Eighteen-month follow-up of infants fed evaporated milk formula

In parts of Canada including Newfoundland and Labrador and among Aboriginal peoples, infants still consume evaporated milk (EM) formulas for cultural and economic reasons. At 3 and 6 months, full-term infants fed EM (n = 30) received low intakes of iron, thiamine, selenium and had higher weight velocity than breastfed (BF, n = 29) infants. EM infants had greater anemia, lowered transketolase activity (thiamine) and lowered glutathione peroxidase (selenium) activity (p < 0.05). To determine the later effect of early feeding deficit on nutritional status, we examined these same infants at 18 months of age. At that time, there were no differences in dietary intakes of energy, protein, zinc, copper, selenium and iron, nor in plasma levels of zinc, copper, vitamin C, nor in red blood cell activity levels of glutathione reductase (riboflavin), transketolase, glutathione peroxidase, nor in superoxide dismutase. However, EM infants weighed more and were more likely to visit a physician, have anemia, and have iron depletion than were BF infants. We conclude that infants consuming evaporated milk formulas should receive iron supplements throughout infancy.

The thiamin, riboflavin and pyridoxine status of patients on emergency admission to hospital

The aim of this study was to assess the prevalence of thiamin, riboflavin and pyridoxine deficiencies at admission to an acute hospital. One hundred and twenty adult patients were selected at random from those admitted via the Accident and Emergency department over 3 days. Comparisons were made with a group of 80 healthy blood donors sequentially attending a local transfusion centre. The alcohol intake of 500 patients admitted sequentially via the same Accident and Emergency department was also assessed. Erythrocyte transketolase (ETK), glutathione reductase (EGR) and aspartate aminotransferase (EAA) coenzyme activation assays were used to determine thiamin, riboflavin and pyridoxine deficiencies. The prevalences of deficiency states in the inpatient group were 21, 2.7 and 32% for thiamin, riboflavin and pyridoxine deficiencies respectively with 49.2% being deficient in one or more vitamin. The mean alcohol intake in the group of patients in whom this was assessed was 9.7 units per week compared with 10 units per week amongst blood donors.

[The effect of different high riboflavin supplements during pregnancy and lactation on performance and erythrocyte glutathione reductase activity of rats]

In two experiments with 160 female Sprague-Dawley rats the influence of various dietary riboflavin supplementations during lactation and during pregnancy and lactation were examined on food intake, body mass, reproduction, hematologic profile and the erythrocyte glutathione reductase activity coefficient (EGR-AC). In the first trial rats were fed a semisynthetic, riboflavin-deficient diet, based on casein and corn starch with various riboflavin supplementations during lactation (0, 2, 4, 6, 8, 10, 12, 40, 400, 4000 mg riboflavin/kg diet). In the second experiment the rats received supplements of 1 and 20 mg riboflavin/kg diet, respectively, during pregnancy. After parturition each group was divided into three sub-groups with riboflavin supplementations during lactation of 1, 5 and 20 mg/kg diet, respectively. Both investigations ended at the 14th day of lactation. Food intake was decreased significantly by 25% and 11% in the groups without riboflavin supplementation or 1 mg riboflavin/kg diet. In the same groups body mass was reduced by 11% and 4%, respectively. With regard to the reproduction parameters the riboflavin supply influenced only the litter mass at the 14th day of lactation and only lactational supply was relevant. In both trials the results of the hematologic profile showed no differences. In riboflavin deficiency (0 or 1 mg riboflavin/kg diet, respectively) the EGR-AC was increased significantly to 1.9 and 1.8, respectively. At the supplementation of 4-5 mg riboflavin/kg diet EGR-AC reached a plateau of 1.45, which was not improved by higher supplements. Concerning the whole reproduction cycle (trial II) there was a stronger influence of the actual lactation-supply on EGR-AC, on the other hand a riboflavin deficiency in pregnancy could be compensated only partially by an optimal supply in lactation. Therefore, based on the parameter EGR-AC an optimal riboflavin supply is recommended for each part of the reproduction cycle. By means of EGR-AC also the riboflavin requirement for lactating rats was derived. Feeding a semisynthetic diet (17.4 MJ ME/kg DM, 20.8% crude protein in DM) a supplementation of 5-6 mg riboflavin/kg or a total content of 6-7 mg/kg diet is recommended.

Thiamine, riboflavin, folate, and vitamin B12 status of infants with low birth Weights receiving enteral nutrition

The purpose of the present study was to monitor the vitamin status of 14 low-birth-weight (LBW) infants (< 1,750 g birth weight) at 2 weeks and an additional four infants at 3 weeks who were receiving an enteral formula providing 247 micrograms/100 kcal thiamine, 617 micrograms/100 kcal riboflavin, 37 micrograms/100 kcal folate, and 0.55 micrograms/100 kcal vitamin B12. The mean birth weight of the 18 infants was 1,100 +/- 259 g, and mean gestational age was 29 +/- 2 weeks. Weekly blood, 24-h urine collections, and dietary intake data were obtained. For thiamine, red blood cell (RBC) transketolase activity was within the normal range for all infants. For riboflavin, RBC glutathione reductase activity was normal for all infants except one. We calculated from intake and urinary excretion data that these infants require 225 micrograms/100 kcal thiamine and 370 micrograms/100 kcal riboflavin, respectively. Mean plasma folate levels were 21 +/- 11 ng/ml at 2 weeks and 18 +/- 5 ng/ml at 3 weeks. RBC folate levels were 455 +/- 280 ng/ml at 2 weeks and 391 +/- 168 ng/ml at 3 weeks. All folate blood values were normal, except for one subject with an elevated level (59 ng/ml). Vitamin B12 plasma values were 737 +/- 394 pg/ml at 2 weeks and 768 +/- 350 pg/ml at 3 weeks, and all values were normal except for three infants with elevated values. In conclusion, appropriate vitamin status was maintained during this short observational period, during administration of this enteral formula; however, riboflavin concentrations in the enteral feed may be excessive.

A case-control study of maternal nutrition and neural tube defects in Northern Ireland

OBJECTIVE

to compare dietary intake and biochemical indices of nutritional status in women following birth of a baby/termination of a pregnancy affected by neural tube defect (NTD) and women with a normal baby.

DESIGN

quantitative, using case control methods.

SETTING

dietary records were completed by women in their own home, blood samples were taken in the local health centres.

PARTICIPANTS

15 women referred to the study following an affected pregnancy (subjects), matched with 15 women whose pregnancy outcome was normal (controls).

MEASUREMENTS AND FINDINGS

7-day weighed dietary records indicated no statistically significant differences in nutrient intake but a tendency for lower fruit and vegetable consumption in subjects than in controls. Biochemical analysis of nutritional status showed that levels of serum vitamin B12 were significantly lower in subjects, and activities of two of the nucleotide salvage pathway enzymes were significantly higher.

KEY CONCLUSIONS

the findings are consistent with the findings of other research on NTD and the metabolism of folate and vitamin B12.

IMPLICATIONS FOR PRACTICE

this study, and other research in this area, has implications for health professionals, including midwives with their particular involvement in prenatal care, and also highlights the need for a clearer focus on nutrition in nursing and midwifery education.

Changes of some vitamin levels during and after normal pregnancy

Most vitamin status parameters change significantly during pregnancy. A number of factors have been associated with this hypovitaminaemia of pregnancy. From our data, it was concluded that the initial value of a vitamin status parameter was by far the main determinant of the changes of vitamin levels during pregnancy: the higher the value, the steeper the decrease. Some hormonal variables were associated with these changes as well. This is highly suggestive of a resetting of vitamin homeostasis in blood, with a retention of vitamins in maternal tissues. The postpartum changes of vitamin levels provide insight into the 'net cost' of vitamins during pregnancy. Most serum blood levels of vitamins normalized shortly after delivery. Serum vitamin B6 levels increased slowly with 25% below the acceptable range at 6 months postpartum. However, the GGOT stimulation ratio, indicative for vitamin B6 cellular content, was completely normal at the time. Serum folacin was the only exception, with 45% serum levels in the marginal or deficient range; 20% of this group had deficient or marginal red cell folacin levels as well. This indicates that the 'net cost' of folacin during pregnancy is considerable, and repletion of folacin stores takes more than 6 months.

[Serum levels of vitamin A, E, C and B2, carotenoid and zinc in hospitalized elderly patients]

Serum levels of carotenoids, zinc and vitamins A, E, C and B2 were measured in al (n = 202) the elderly patients hospitalized in different wards of the hospital studied from February 1986 to October 1988. The study was conducted on 130 men and 72 women with a mean age of 67.8 years (range: 60 to 88 years). The percentage of nutritional deficiency was 59.5% for zinc, 56.5% for vitamin C, 34.5% for vitamin B2, 25.9% for vitamin E, 13.2% for vitamin A, and 6.8% for carotenoids. Elderly patients with leucoses, megaesophagus, chronic obstructive pulmonary disease, and congestive heart failure represent a group with a high prevalence of deficiency both of zinc and of the vitamins under study. These results show the importance of detecting deficiencies of these micronutrients and provide a basis for a more rational approach to the treatment of elderly patients.

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.

Thiamine, riboflavin, folate, and vitamin B12 status of low birth weight infants receiving parenteral and enteral nutrition

Thirty infants were randomly assigned to receive either 3 mL of MVI-Pediatric supplement (PAR3 group, parenterally fed) or 2 mL (PAR2 group, parenterally fed). For the first week, 100% received total parenteral nutrition (TPN), 50% by the second, and less than 33% by the third. Eighteen control infants received enteral feeds of infant formula. Baseline (before TPN) and subsequent weekly blood samples, dietary data, and 24-hour urine collections were obtained. The adequacies of thiamine and riboflavin were assessed by the thiamine pyrophosphate effect and erythrocyte glutathione reductase activity, respectively. Urinary thiamine and riboflavin levels were measured by fluorometry. Plasma folate, red blood cell folate, urinary folate, and plasma vitamin B12 concentrations were determined by radioassay. No differences between groups were observed in thiamine pyrophosphate effect, erythrocyte glutathione reductase activity, urinary B1 or B2, or red blood cell folate levels at any time. Plasma folate differed (p less than .05) among the PAR3 group (24 +/- 7 ng/mL), and both the PAR2 (13 +/- 5 ng/mL) and enterally fed (ENT) groups (16 +/- 3 ng/mL) before the initiation of feeds, at week 1 (PAR3 = 32 +/- 15 ng/mL; PAR2 = 18 +/- 4 ng/mL; ENT = 19 +/- 9, ng/mL) and between the PAR3 (30 +/- 16 ng/mL) and PAR2 (16 +/- 4 ng/mL) infants at week 2. Plasma vitamin B12 levels differed among the ENT groups (551 +/- 287 pg/mL) and both the parenteral groups (PAR2 = 841 +/- 405 pg/mL; PAR3 = 924 +/- 424 pg/mL) at week 1 and between the ENT (530 +/- 238 pg/mL) and PAR3 (999 +/- 425 pg/mL) groups at week 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Riboflavin intakes and status of morbidly obese females during the first postoperative year following gastroplasty

Eighteen women participated in a prospective study to assess the need for supplemental riboflavin after gastroplasty. Three groups of five patients received either a placebo or 0.6 or 1.2 mg riboflavin daily for up to 12 months, except during months 4 and 7 when all participants were given a "one-a-day" supplement containing 1.7 mg riboflavin. Dietary intakes of riboflavin decreased from 1.43 +/- 0.17 mg before the operation to 0.70 +/- 0.07 mg at 3 months, and then increased to 1.02 +/- 0.17 mg by 6 months. Even at 12 months, only 33% of the subjects had dietary intakes greater than or equal to 1.2 mg. All those with total intakes less than or equal to 1.7 mg at 3 months had impaired riboflavin status, as indicated by an erythrocyte gluthatione reductase activity coefficient greater than 1.40 and an erythrocyte riboflavin concentration less than 372 nmol/L. In contrast, 62% of the same subjects had urinary riboflavin excretion in the acceptable range. Supplemental intake of 1.7 mg riboflavin appeared to prevent tissue depletion in all subjects.

Flavin analogs with antimalarial activity as glutathione reductase inhibitors

10-(4'-Chlorophenyl)-3-methylflavin has antimalarial activity in vitro and in vivo (Cowden et al., J Med Chem 31: 799, 1988). This flavin analog and two of its derivatives were found to inhibit the antioxidant flavoenzyme glutathione reductase from human erythrocytes in its isolated form as well as in hemolysates. The mixed-type inhibition was completely reversible, the Ki-values being of the order of 1 microM. Surprisingly, the drugs were not competitive with FAD, but with GSSG, one of the enzyme's substrates. Malaria parasite glutathione reductase, extracted from Plasmodium falciparum, could also be inhibited by the compounds. Studies on the effects of the substances on P. falciparum in vitro, which were demonstrated morphologically and by growth inhibition, confirmed previous observations with 10-(4'-chlorophenyl)-3-methylflavin and showed similar parasiticidal characteristics for the two new derivatives. The activities of five other erythrocytic enzymes tested were not impaired by the drugs, nor was the nucleotide metabolism of erythrocytes and/or parasites significantly changed. Permeation into red blood cells was demonstrated for one compound by 19F-NMR-spectroscopy. Inhibition of glutathione reductase might contribute to, or account for, the antimalarial activity of this group of flavin analogs.

Postoperative nasogastric tube feeding in patients with head and neck cancer: a prospective assessment of nutritional status and well-being

The effects of controlled continuous nasogastric tube feeding with a non-elemental liquid diet (Nutrison high energy) were studied 1 day before, and 1 week and 3 weeks after radical surgery mostly for cancer of the tongue or floor of the mouth in 20 patients. Since the actually administered 89% of a planned dose of 32 kcal/kg body weight/day given to the first eight patients (group A) proved inadequate to prevent a decrease of body fat mass, the energy dose given to 12 successive patients (group B) was increased. The administration of 95% of 43 kcal/kg body weight/day to group B patients appeared to be sufficient. A marked decrease of the 24 h urinary excretion of creatinine and 3-methylhistidine was observed at 1 week and still existed at 3 weeks after operation in both groups. The decrease was significant in group A amounting to some 40% for both metabolites. In group B creatinine excretion decreased by some 20% (n.s.) and 3-methylhistidine by some 35% (n.s.). These findings suggest diminished muscle protein breakdown, even in the presence of an ample nutritional supply of energy and protein. A transient decrease of serum albumin, iron and zinc in all patients is likely not to be related to nutritional intake, but to surgery itself. Analysis of trace minerals and vitamins in blood and amino acids in serum and urine showed no deficiencies or amino acid imbalance. Assessment of the psychosocial impact of the nasogastric tube feeding regimen revealed gastro-intestinal complaints in a minority, and feelings of being deprived of the act of eating and drinking in the majority of patients.

Physical training and fasting erythrocyte activities of free radical scavenging enzyme systems in sedentary men

Effects of 10 weeks of physical training on free radical scavenging enzyme systems in erythrocytes were investigated in 7 sedentary healthy male students. The training consisted of running over 5 km, 6 times/week. Their maximum oxygen uptake and 12 min walk-run performance increased significantly after training. Of the antioxidant enzyme systems examined in the erythrocytes, both catalase activity and concentration and total glutathione reductase (GR) activity also showed significant increases following the training. The erythrocyte GR activity coefficient also increased significantly. These results suggest that chronic aerobic exercise increases riboflavin requirements and has some positive effects on antioxidative processes.

Water-soluble vitamins in cancer patients on parenteral nutrition: a prospective study

Forty-three patients with mild weight loss were studied prospectively to determine whether the parenteral water-soluble vitamin doses in a commercially available preparation (MVI concentrate; USV Laboratories, Tarrytown, NY) maintained serum, red blood cell (RBC), and urinary concentrations of water-soluble vitamins in stressed cancer patients receiving total parenteral nutrition (TPN). Patients were divided into three groups: (1) oral diet, no intravenous vitamins given; (2) TPN plus 5 ml MVI; and (3) TPN plus 10 ml MVI. Vitamins C, B1, B2, B3, B6, and niacin were measured initially and weekly during a 6-week study period. Caloric and nitrogen balances were quantified. Most of the patients in all three groups had normal blood or urine levels of all water-soluble vitamins. No clinical evidence of vitamin deficiency or MVI toxicity was detected. The recommended parenteral dosages of vitamin C (100 mg/day) and B3 (15 mg/day) provided measurably adequate levels in all patients. Levels of vitamins B1, B2, B6, and niacin that were less than the normal range were noted in 4-40% of patients receiving the recommended daily dosages of 3 mg, 3.6 mg, 4 mg, and 40 mg, respectively. These deficiencies appeared to improve in group III patients who received twice the recommended parenteral vitamin dosages, although they did not completely disappear. Niacin deficiency appeared to be the most prevalent, occurring in 40% of patients studied. Since intravenous doses of B1, B2, B6, and niacin are safe and well tolerated, it appears that increased daily amounts of these vitamins should be given to cancer patients on parenteral nutrition.

Riboflavin nutritional status and flavoprotein enzymes in streptozotocin-diabetic rats

Riboflavin nutritional status was assessed on the basis of activity coefficients of glutathione reductase in erythrocyte hemolysates of normal and streptozotocin-diabetic rats. Activity coefficient values higher than 1.3 were regarded as evidence of riboflavin deficiency. All diabetic animals were found to be riboflavin-deficient, with activity coefficient values of 1.47-2.11. Treatment of diabetic rats with either insulin or riboflavin returned their activity coefficients to normal. Rats fed a restricted diet had normal activity coefficient values. The erythrocyte glutathione reductase activity was significantly lower in diabetic rats, and the augmentation of enzyme activity in the presence of flavin-adenine dinucleotide (FAD) was 72% compared to 16% in normal rats. Hepatic activities of glutathione reductase and succinate dehydrogenase, both FAD-containing enzymes, were significantly lower in diabetic than in normal rats. Like activity coefficient values, all enzyme activities were normalized after insulin or riboflavin treatments. These data suggest that insulin and riboflavin enhance the synthesis of erythrocyte and hepatic FAD. The results of the present study suggest that experimental diabetes causes riboflavin deficiency, which in turn decreases erythrocyte and hepatic flavoprotein enzyme activities. These changes can be corrected for by either insulin or riboflavin. The pathogenesis of riboflavin deficiency in diabetes mellitus is not clearly understood. The data of the present study provide evidence in addition to the previous findings of an increased prevalence of riboflavin deficiency in genetically diabetic KK mice.

Dietary intake, nutritional status and well-being of cancer patients: a prospective study

Changes in dietary intake, nutritional status, body composition and well-being were studied in 108 cancer patients over a period of 20 weeks. The patients, constituting a group of elderly women with uterine cancer, a group of elderly men with urological cancer and a group of male and female patients of various ages with malignant lymphoma, were prospectively followed during and after aggressive treatment given with curative intent. Detailed information on the dietary intake was measured by a dietary history and cross-check method covering the 2 months prior to the onset of therapy and a 48-hr dietary record which was applied seven times during the observation period. The nutritional status was monitored by anthropometric measurements and laboratory assays in blood and urine. The patient's well-being was assessed by the use of standard performance scales by the observers and the application of patient's questionnaires concerning complaints, ability to self-care, mobility and daily activities. The main results are described here, indicating that: (1) most patients studied had a more than adequate diet during the 2 months preceding cancer therapy when compared to the Dutch Recommended Dietary Allowances; (2) the impact on dietary intake and nutritional status was relatively minor and generally transient; and (3) the treatment course was accompanied by distinct changes of well-being associated with, but not necessarily resulting from or leading to, changes of dietary intake.

Transient riboflavin depletion in preterm infants

Biochemical riboflavin status was measured in 68 preterm infants who were receiving either human milk or a preterm infant formula (containing riboflavin, 1.8 mg/l) during the first few weeks of life. The relation between riboflavin status, type of diet, and time of introduction of a multivitamin supplement containing riboflavin was analysed and the duration of phototherapy was recorded. Those who received the multivitamin supplement on or before day 7 of life seldom became deficient and no significant difference between diets was seen in this group. Of those who received the supplement after day 7, human milk fed infants commonly developed abnormal riboflavin status (18 out of 23 infants) compared with a small and significantly lower incidence in the formula fed group. Dietary effects on riboflavin status seemed to outweigh in importance those of phototherapy. It is concluded that the riboflavin content of human milk, which may be lowered by photodegradation, is not sufficient to ensure normal biochemical status in preterm infants. The larger amounts provided by a multivitamin supplement or by a preterm infant formula may, however, prevent biochemical deficiency. The desirability (and safety) of routine riboflavin supplementation of preterm infants is discussed.

FAD-induced in vitro activation of glutathione reductase in the lens of B2 deficient rats

We studied the FAD-induced in vitro stimulation of lenticular glutathione reductase in riboflavin-deficient rats. The stimulatory effect of FAD on lenticular glutathione reductase in rats fed a B2-deficient diet for 4 weeks was remarkably higher than in paired control rats fed a B2-supplemented basal diet and control rats had ad libitum access to a B2-supplemented basal diet. The in vitro FAD stimulation effect on rat lenticular glutathione reductase represents a sensitive indicator of the B2 deficient status.

Incubation of NAD(P)H2: glutathione oxidoreductase (EC 1.6.4.2) with flavin adenine dinucleotide for maximal stimulation in the measurement of riboflavin status

Some modifications to the erythrocytes glutathione reductase assay for riboflavin status are described. 2. Cusum analysis of results collected on a quality-control (QC) haemolysate, analysed separately at the beginning and end of each batch of samples over a period of 20 weeks, suggested that the activation coefficient (AC) was higher at the end of a batch than at the beginning. 3. The higher AC was due to higher FAD-stimulated enzyme activities of the QC samples measured at the end of the day, by comparison with the beginning, and this suggested that the conditions of assay were not optimal. 4. The conditions required to achieve maximal coupling of FAD to glutathione reductase (NAD(P)H2: glutathione oxidoreductase; EC 1.6.4.2) were therefore examined and found to be 15 min at 35 degrees by comparison with the 5-7 min incubation used by most workers. 5. Alternatively, where samples are prepared in batches, the enzyme and FAD should be pre-incubated in the reaction mixture for 2 h at 4 degrees or 1 h at 25 degrees before the standard incubation of 5 min at 35 degrees. 6. Additionally, the use of cummulative sum (cusum) analysis on the QC results suggested that there was a slight deterioration of QC samples after 4-weeks storage. However, the QC results obtained, remained within 2 standard deviations of initial results over a 20-week period, suggesting that the deterioration was very slight.

Diet and vitamin nutrition of the high esophageal cancer risk population in Linxian, China

In order to examine the nutritional status of the population of Linxian (in Henan, China) known to be at high risk for esophageal cancer (EC), we analyzed blood samples and conducted 3-day dietary surveys on 3 groups of normal adults, age 40-50, from Henan province. Two groups were from Linxian, where the EC mortality rate is about 138/100,000 (Group C, consisting of volunteers with a family history of EC, and Group NC, consisting of those who did not have a family history of EC). The third group, Group F, was from Fanxian, where the EC mortality rate is about 24/100,000. The average plasma retinol level was found to be about 0.27 micrograms/ml in all 3 groups; about 13%-20% of the individuals had a level less than 0.2 micrograms/ml. The average plasma carotene level of all 3 groups appeared to be adequate, ranging from 0.5-1.0 micrograms/ml. About 23% of the subjects in both Groups C and NC had low (less than 2 micrograms/ml) plasma ascorbate levels; in Group F, 16% had low ascorbate levels. Less than 12% of the individuals in each of the 3 groups had erythrocyte glutathione reductase activation coefficients less than 1.2, indicating a widely occurring riboflavin deficiency. Consumption of alcoholic beverages was not found to be a contributing factor to EC. The results of the present study reveal a deficiency of vitamins in the study populations, but do not indicate that the average nutritional status of the volunteers in Group C was worse than that of Groups NC and F with regard to vitamin A, ascorbate, and riboflavin.

Riboflavin status in infants born in rural Gambia, and the effect of a weaning food supplement

Riboflavin status was measured in infants between birth and two years of age, by the erythrocyte glutathione reductase (NAD(P)H2: glutathione oxidoreductase, EC 1.6.4.2) test on finger-prick blood samples. The infants were living in three rural Gambian villages: Keneba, Manduar and Kanton Kundar; those in Keneba were receiving a weaning food supplement between three and 12 months, which provided 0.15 to 0.20 mg riboflavin per day, in addition to their normal intake from breast milk and locally available weaning foods, which provided 0.13 to 0.21 mg/day over the same age range. On the basis of currently accepted criteria of biochemical normality, the unsupplemented infants were born deficient and, in the absence of a supplement, remained so throughout their first two years of life, with only a minor, short-lived improvement during the first few months. In the supplemented group, however, riboflavin status fell within normal limits for the duration of the supplement, but rapidly deteriorated again once the supplement was withdrawn. It is concluded that infants born to deficient mothers are usually deficient at birth, and remain so throughout suckling and weaning on to locally available foods. The daily requirement, to achieve satisfactory biochemical status, is thus greater than 0.13 to 0.21 mg/day, and probably approaches 0.4 mg/day, for most individuals up to the age of one year.

A biochemical evaluation of the erythrocyte glutathione reductase (EC 1.6.4.2) test for riboflavin status. 1. Rate and specificity of response in acute deficiency

1. Acute riboflavin deficiency was produced in weanling rats by feeding a deficient diet and using tailcups to prevent refection. Animals were killed at weekly interval for 7 weeks, by the end of which they had become severely deficient, and mortality was high.

2. Growth of the deficient animals virtually ceased in the early stages of deficiency; food intake was severely and progressively depressed. Liver: body-weight increased markedly; packed cell volume fell at a late stage only. Pathological signs accumulated throughout the deficiency but were not closely related to the biochemical changes within the deficient group.

3. The activation coefficient (stimulated: basal activity; AC) of glutathione oxidoreductase (EC 1.6.4.2; glutathione reductase; GR) in erythrocytes rose to a mean value of 3–8 after 3 weeks, and subsequently remained almost constant: this change was not seen in pair-fed or ud lib.-fed controls. Both deficient and pair-fed animals exhibited a twofold reduction in FAD-stimulated erythrocyteGR activity at an early stage. In liver, both deficient and pair-fed groups showed a major progressive fall in FAD-stimulated GR activity, but only the deficient group showed an increase in AC, which occurred towards the later stages of the experiment. In skin, too, the deficient group showed an increase in AC during the terminal stages.

4. Hepatic, intestinal and brain succinate: (acceptor) oxidoreductase (EC 1.3.99,1; succinate dehydrogenase) activity fell relatively early during deficiency; in liver and intestine this was at least partly shared by the pair-fed group, and therefore attributable to inanition. Changes in hepatic NADH:(acceptor) oxidoreductase (EC I.6.99.3; NADH dehydrogenase) activity appeared to be entidy attributable to inanition.

5. An early reduction was observed in hepatic ATP: riboflavin 5-phosphotransferase (EC2.7.1.26; flavo- kinase) activity in the deficient group, values falling by nearly half within 1 week, and then remaining almost constant. Similar but smaller changes were seen in renal flavokinase activity. Hepatic ATP: FMN adenylyltrans- ferase (EC2.7.7.2; FAD pyrophosphorylase) was unchanged until the third week, at which point it rose sharply to a new plateau in the deficient group; in kidney it did not respond. These changes were not observed in pair-fed or ad-lib.-fed controls.

6. Hepatic flavin levels fell dramatically during the first 2 weeks of deficiency, FAD being conserved at the expense of FMN. Smaller changes were observed in kidney.

7. Of the processes which are affected by riboflavin deficiency, AC of erythrocyte GR (EGRAC) responds earlier, more dramatically and more specifically than most others, with the possible exception of hepatic flavin levels and flavokinase. Potentially, it is therefore a good index of over-all body riboflavin status, but in acute deficiency the rate of response of many variables is not related to the final extent of response; consequently the correlation between EGRAC and other riboflavin-sensitive processes is less satisfactory than it would be in an equilibrium situation.