Auditory neuropathy in Brown-Vialetto-Van Laere syndrome due to riboflavin transporter RFVT2 deficiency.

AIM: Mutations in the genes encoding the riboflavin transporters RFVT2 and RFVT3 have been identified in Brown-Vialetto-Van Laere syndrome, a neurodegenerative disorder characterized by hearing loss and pontobulbar palsy. Treatment with riboflavin has been shown to benefit individuals with the phenotype of RFVT2 deficiency. Understanding the characteristics of hearing loss in riboflavin transporter deficiency would enable early diagnosis and therapy. METHOD: We performed hearing assessments in seven children (from four families) with RFVT2 deficiency and reviewed results from previous assessments. Assessments were repeated after 12 months and 24 months of riboflavin therapy and after cochlear implantation in one individual. RESULTS: Hearing loss in these individuals was due to auditory neuropathy spectrum disorder (ANSD). Hearing loss was identified between 3 years and 8 years of age and progressed rapidly. Hearing aids were not beneficial. Riboflavin therapy resulted in improvement of hearing thresholds during the first year of treatment in those with recent-onset hearing loss. Cochlear implantation resulted in a significant improvement in speech perception in one individual. INTERPRETATION: Riboflavin transporter deficiency should be considered in all children presenting with an auditory neuropathy. Speech perception in children with ANSD due to RFVT2 deficiency may be significantly improved by cochlear implantation.

The discovery and characterization of riboflavin.

The first observation of a pigment in milk with yellow-green fluorescence can be traced to the English chemist Alexander Wynter Blyth in 1872, but it was not until the early 1930s that the substance was characterized as riboflavin. Interest in accessory food factors began in the latter half of the 19th century with the discovery of the first vitamin, thiamin. Thiamin was water soluble and given the name vitamin B(1). However, researchers realized that there were one or more additional water-soluble factors and these were called the vitamin B-2 complex. The search to identify these accessory food factors in milk, whole wheat, yeast, and liver began in the early 1900s. As there is no classical nutritional disease attributable to riboflavin deficiency, it was the growth-stimulating properties of the food extracts given to young rats that provided the tool with which to investigate and eventually extract riboflavin. Riboflavin was the second vitamin to be isolated and the first from the vitamin B-2 complex; the essential nature of the vitamin as a food constituent for man was shown in 1939.

Riboflavin supplementation does not attenuate hyperoxic lung injury in transgenic (spc-mt)hGR mice.

The aims of this study were to test the hypothesis that mice expressing mitochondrially targeted human glutathione reductase (GR) driven by a surfactant protein C promoter ((spc-mt)hGR) are functionally riboflavin deficient and that this deficiency exacerbates hyperoxic lung injury. The authors further hypothesized that dietary supplementation with riboflavin (FADH) will improve the bioactivity of GR, thus enhancing resistance to hyperoxic lung injury. Transgenic (mt-spc)hGR mice and their nontransgenic littermates were fed control or riboflavin-supplemented diets upon weaning. At 6 weeks of age the mice were exposed to either room air (RA) or >95% O(2) for up to 84 hours. GR activities (with and without exogenous FADH) and GR protein levels were measured in lung tissue homogenates. Glutathione (GSH) and glutathione disulfide (GSSG) concentrations were assayed to identify changes in GR activity in vivo. Lung injury was assessed by right lung to body weight ratios and bronchoalveolar lavage protein concentrations. The data showed that enhanced GR activity in the mitochondria of lung type II cells does not protect adult mice from hyperoxic lung injury. Furthermore, the addition of riboflavin to the diets of (spc-mt)hGR mice neither enhances GR activities nor offers protection from hyperoxic lung injury. The results indicated that modulation of mitochondrial GR activity in lung type II cells is not an effective therapy to minimize hyperoxic lung injury.

Long-term intermittent multiple micronutrient supplementation enhances hemoglobin and micronutrient status more than iron + folic acid supplementation in Bangladeshi rural adolescent girls with nutritional anemia.

Previous short-term supplementation studies showed no additional hematologic benefit of multiple micronutrients (MMN) compared with iron + folic acid (IFA) in adolescent girls. This study examines whether long-term once- or twice-weekly supplementation of MMN can improve hemoglobin (Hb) and micronutrient status more than twice-weekly IFA supplementation in anemic adolescent girls in Bangladesh. Anemic girls (n = 324) aged 11-17 y attending rural schools were given once- or twice-weekly MMN or twice-weekly IFA, containing 60 mg iron/dose in both supplements, for 52 wk in a randomized double-blind trial. Blood samples were collected at baseline and 26 and 52 wk. Intent to treat analysis showed no significant difference in the Hb concentration between treatments at either 26 or 52 wk. However, after excluding girls with hemoglobinopathy and adjustment for baseline Hb, a greater increase in Hb was observed with twice-weekly MMN at 26 wk (P = 0.045). Although all 3 treatments effectively reduced iron deficiency, once-weekly MMN produced significantly lower serum ferritin concentrations than the other treatments at both 26 and 52 wk. Both once- and twice-weekly MMN significantly improved riboflavin, vitamin A, and vitamin C status compared with IFA. Overall, once-weekly MMN was less efficacious than twice-weekly MMN in improving iron, riboflavin, RBC folic acid, and vitamin A levels. Micronutrient supplementation beyond 26 wk was likely important in sustaining improved micronutrient status. These findings highlight the potential usefulness of MMN intervention in this population and have implications for programming.

Riboflavin and mouse hepatic cell structure and function. II. Division of mitochondria during recovery from simple deficiency.

Mice which had been on a riboflavin-free diet for 6-8 wk were given daily intraperitoneal injections of riboflavin. The hepatic mitochondria, which in the deficient animals were greatly enlarged, were restored to normal dimensions within 3 days. Normalization of the mitochondrial population was brought about by division of the giant organelles. Dividing mitochondria were characterized by a membranous partition separating the inner compartment into two distinct chambers. Such organelles showed varying degrees of pinching at the level of the partition. The most common site of partition formation was at the base of a small mitochondrial bud. During the 1st day of recovery, dividing mitochondria were so common that they could be easily found in mitochondrial pellets. Injection of riboflavin into normally nourished mice also produced an apparent increase in the frequency of dividing mitochondria in the liver cells.

Study Protocol: randomised controlled trial to investigate the functional significance of marginal riboflavin status in young women in the UK (RIBOFEM).

BACKGROUND: The functional significance of moderate riboflavin deficiency as it is currently assessed is not well understood. Animal and human studies have suggested a role for riboflavin in the absorption and mobilisation of iron and as such may be important in maintaining haematological status. Recent National Diet and Nutrition Surveys in the United Kingdom have shown that young women in particular are at risk of moderate riboflavin deficiency and low iron status. METHODS/DESIGN: A randomised placebo controlled intervention trial was conducted to investigate the effect of riboflavin supplementation on various measures of haematological status in a group of moderately riboflavin deficient young women aged 19 to 25 years. Women who were low milk consumers were initially screened for riboflavin status as assessed by the erythrocyte glutathione reductase activation coefficient assay (EGRAC). One hundred and twenty three women with EGRAC values >1.40 were randomised to receive 2 mg, 4 mg riboflavin or placebo for 8 weeks. In addition 36 of these women were randomly allocated to an iron bioavailability study to investigate the effect of the intervention on the absorption or utilisation of iron using an established red cell incorporation technique. DISCUSSION: One hundred and nineteen women completed the intervention study, of whom 36 completed the bioavailability arm. Compliance was 96 +/- 6% (mean +/- SD). The most effective recruitment strategy for this gender and age group was e-communication (e-mail and website). The results of this study will clarify the functional significance of the current biochemical deficiency threshold for riboflavin status and will inform a re-evaluation of this biochemical threshold. TRIAL REGISTRATION: Current Controlled Trials Registration No. ISRCTN35811298.

Impact and consequences of dietary riboflavin deficiency treatment on flesh quality loss in on-growing grass carp (Ctenopharyngodon idella).

Fish is among the cheapest and most promising sources of animal protein. The main edible portion of fish is muscle. This study explored the impact of dietary riboflavin on fish flesh quality and showed the possible role of muscle antioxidant defense in flesh quality in relation to dietary riboflavin. On-growing grass carp (initial average weight of 275.82 ± 0.57 g) were fed diets containing graded levels of riboflavin (0.63, 1.95, 3.98, 6.02, 7.96, and 10.04 mg kg-1 diet) for eight weeks. The results indicated that compared with the optimal riboflavin levels (3.98 and/or 6.02 mg riboflavin per kg diet), riboflavin deficiency treatment (0.63 mg riboflavin per kg diet) significantly reduced the muscle nutrients, including the protein, lipid, flavor amino acid, and total essential amino acid contents. Furthermore, the muscle shear force, pH value, and hydroxyproline concentration were reduced, while the muscle cooking loss and lactic acid content increased (P < 0.05). Compared with optimal riboflavin levels, the riboflavin deficiency treatment increased the reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl contents, while riboflavin treatments of 3.98-10.04 mg riboflavin per kg diet showed the lowest ROS and MDA contents (P < 0.05). Compared with the optimal riboflavin levels, the riboflavin deficiency treatment decreased the activities of copper/zinc superoxide dismutase (CuZnSOD), glutathione reductase (GR), catalase (CAT), and glutathione peroxidase (GPx), and reduced the glutathione (GSH) content (P < 0.05). Furthermore, the relative mRNA levels of antioxidant enzymes, including CuZnSOD, CAT, GR and GPx, and antioxidant-related signaling molecules, including NF-E2-related factor 2 (Nrf2) and casein kinase 2, were down-regulated, while those of Kelch-like ECH-associated protein 1b were up-regulated (P < 0.05). Collectively, the present study indicates that riboflavin deficiency treatment reduces the flesh quality, partly due to inhibition of the antioxidant defense through the Nrf2 signaling pathway, while optimal riboflavin levels reverse these negative effects.

Supplementation with iron and riboflavin enhances dark adaptation response to vitamin A-fortified rice in iron-deficient, pregnant, nightblind Nepali women.

BACKGROUND: Nightblindness affects 16-52% of pregnant women in areas of Nepal and in some cases persists after vitamin A treatment. Iron and riboflavin affect vitamin A utilization and photoreceptor function, respectively, and pilot data in the study population showed a high prevalence of iron and riboflavin deficiencies. OBJECTIVE: The objective was to assess the effect of supplemental iron and riboflavin on pupillary threshold (PT) and plasma retinol in nightblind, pregnant Nepali women given vitamin A-fortified rice. DESIGN: Nightblind pregnant women were randomly assigned to receive, 6 d/wk under supervision for 6 wk, a vitamin A-fortified rice curry dish providing 850 microg retinal activity equivalents/d with either a 30-mg Fe and 6-mg riboflavin (FeR + VA) capsule or a placebo control (VA only) capsule. Hemoglobin, erythrocyte riboflavin, and plasma ferritin and retinol were measured before and after the intervention. Dark adaptation was assessed by PT score. RESULTS: Women who were iron deficient at baseline (n=38) had significantly greater improvement in PT score with iron and riboflavin supplementation than without (P=0.05). Iron and riboflavin supplements significantly reduced the prevalences of riboflavin deficiency (from 60% to 6%; P<0.0001), iron deficiency anemia (from 35% to 15%; P<0.007), and abnormal PT (from 87% to 30%; P<0.05) from baseline. Mean increases in erythrocyte riboflavin (P<0.0001) and plasma ferritin (P=0.01) were greater in the FeR + VA group than in the VA only group. CONCLUSIONS: Iron deficiency may limit the efficacy of vitamin A to normalize dark adaptation in pregnant Nepali women. Further studies are needed to assess the effect of simultaneous delivery of iron and vitamin A for the treatment of nightblindness.

Riboflavin status in acute ischaemic stroke.

BACKGROUND: There is experimental evidence that riboflavin (vitamin B2) supplementation reduces oxidative damage and cerebral oedema following acute stroke. OBJECTIVE: To measure riboflavin levels in acute stroke before and after supplementation with this vitamin. DESIGN: Ninety-six acute ischaemic stroke patients had their riboflavin status measured at baseline and then randomly assigned to receive 5 mg of oral riboflavin and other B-group vitamins within 12 h of the stroke onset and then daily or no B-vitamins for 14 days. Non-fasting venous blood was obtained at baseline, days 7 and 14 post-randomization for measurement of riboflavin status using erythrocyte glutathione reductase activity coefficient (EGRAC). EGRAC is a measure of riboflavin tissue saturation. This assay has the advantage of being extremely stable and sensitive. EGRAC values are inversely proportional to riboflavin status, so that values greater than 1.3 indicate biochemical deficiency. RESULTS: Fifty-one per cent of patients studied were riboflavin deficient at baseline. Fourteen days of riboflavin supplementation significantly improved the measure of B2 status compared with the control group. Seven out of 37 patients in the supplement group (19%) were riboflavin deficient compared with 22 out of 39 patients (56%) in the control group at the end of the treatment period (P=0.035 for the differences in cumulative changes between groups over 2 weeks). CONCLUSIONS: A high proportion of acute stroke patients were biochemically deficient of riboflavin immediately post-infarct. Supplementation with 5 mg of riboflavin for 2 weeks significantly improved riboflavin status; however, the clinical significance of these findings is not yet known.

Riboflavin status, MTHFR genotype and blood pressure: current evidence and implications for personalised nutrition.

Clinical deficiency of the B-vitamin riboflavin (vitamin B2) is largely confined to developing countries; however accumulating evidence indicates that suboptimal riboflavin status is a widespread problem across the developed world. Few international data are available on riboflavin status as measured by the functional biomarker, erythrocyte glutathione reductase activation coefficient, considered to be the gold standard index. One important role of riboflavin in the form of flavin dinucleotide is as a co-factor for the folate-metabolising enzyme methylenetetrahydrofolate reductase (MTHFR). Homozygosity for the common C677T polymorphism in MTHFR, affecting over 10 % of the UK and Irish populations and up to 32 % of other populations worldwide, has been associated with an increased risk of CVD, and more recently with hypertension. This review will explore available studies reporting riboflavin status worldwide, the interaction of riboflavin with the MTHFR C677T polymorphism and the potential role of riboflavin in personalised nutrition. Evidence is accumulating for a novel role of riboflavin as an important modulator of blood pressure (BP) specifically in individuals with the MTHFR 677TT genotype, with results from a number of recent randomised controlled trials demonstrating that riboflavin supplementation can significantly reduce systolic BP by 5-13 mmHg in these genetically at risk adults. Studies are however required to investigate the BP-lowering effect of riboflavin in different populations and in response to doses higher than 1·6 mg/d. Furthermore, work focusing on the translation of this research to health professionals and patients is also required.

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.

Relationship between changes in properties and contents of riboflavin derivatives of NADPH-cytochrome P-450 reductase in the liver microsomes of riboflavin-deficient rats.

Weanling male rats were fed a riboflavin-deficient diet for 5-8 weeks, and the decrease in NADPH-cytochrome P-450 reductase (FpT) activity in the liver microsomes was compared with the contents of riboflavin derivatives. The decrease of FpT activity for the reduction of cytochrome c was greater than that for the reduction of ferricyanide. The FpT's of riboflavin-deficient and control rats were indistinguishable in the Ouchterlony immunodiffusion test against anti-FpT, and were shown to have the same molecular weight of 78,000 by SDS-polyacrylamide slab gel electrophoresis. However, the purified FpT of the riboflavin-deficient rats contained 14.2, 4.9, and 1.9 nmol of FAD, FMN, and riboflavin per mg of protein, respectively, while that of the control rats contained 10.6 and 9.5 nmol of FAD and FMN per mg of protein, respectively. After riboflavin injection into the riboflavin-deficient rats, NADPH-cytochrome c reductase activity and FMN content of the FpT were restored to the control levels in 36 h, NADPH-ferricyanide reductase activity recovered in 18 h, and riboflavin content diminished in 18 h. On incubation of the purified FpT of the riboflavin-deficient rats with FMN, NADPH-cytochrome c reductase activity and FMN content were restored to those of control rats. These results indicated that a part of FMN in the FpT of the riboflavin-deficient rats was replaced with FAD and riboflavin.

Regulation of blood pyridoxal phosphate in riboflavin deficiency in man.

Synthesis and breakdown of pyridoxal phosphate by erythrocytes were studied in subjects with oral lesions before and after treatment with riboflavin. In vivo conversion of pyridoxine to pyridoxal phosphate as well as in vitro synthesis of pyridoxal phosphate by erythrocytes were lower in subjects with lesions of the mouth and improved markedly after treatment with riboflavin. Erythrocyte phosphatase activity, with pyridoxal phosphate as substrate, was lower in riboflavin-deficient subjects and showed an increase after treatment with riboflavin.

Riboflavin requirement of Filipino women.

The level of riboflavin intake that will correct riboflavin deficiency in seven non-pregnant and in twelve pregnant Filipino women was determined in order to reassess the adequacy of the current Recommended Dietary Allowance (RDA) for riboflavin in Filipinos. Increasing levels of riboflavin were given to the subjects who were rated as riboflavin-deficient based on an initial erythrocyte glutathione reductase activation coefficient (EGR-AC) of greater than or equal to 1.3 in screening. The minimum riboflavin requirement, defined as the intake of riboflavin required to achieve an EGR-AC of less than 1.3, was estimated from the regression of EGR-AC on riboflavin intake (mg/1000 kcal). The estimates of minimum riboflavin requirement from the non-pregnant women ranged from 0.16 to 0.42 with a mean of 0.35 +/- 0.09 (SD) mg/1000 kcal. For the pregnant subjects, the estimates of minimum riboflavin requirement ranged from 0.36 to 0.81 with a mean of 0.58 +/- 0.18 (SD) mg/1000 kcal. Adding 30% to the mean, to cover the upper limits of 97.5% of the population, the estimated RDA for non-pregnant women is 0.46/1000 kcal. This value is approximately equal to the 1976 Philippine RDA of 0.5 mg riboflavin/1000 kcal. For pregnant women, adding 30% to the mean minimum requirement of 0.58 mg/1000 kcal, the estimated RDA is 0.75 mg/1000 kcal or 1.75 mg/day computed at the energy allowance of 2350 kcal during pregnancy. This value is 25% higher than the current Philippine RDA of 1.4 mg/day for pregnant women.(ABSTRACT TRUNCATED AT 250 WORDS)

Vitamin supplements to Indian women using low dosage oral contraceptives.

Effect of continuous and intermittent vitamin supplements on vitamin status, serum proteins and lipids were examined in Indian women of low-income group, receiving a low-dose oral contraceptive over a period of 3-6 months. To find out non-specific time related changes, vitamin supplemented and unsupplemented control groups of non-OC users were also examined. OC treatment did not change serum chemistry significantly. The significant biochemical changes were: altered tryptophan metabolism and elevated plasma vitamin A levels. Former could be prevented by administering multivitamins containing 10 mg vitamin B6 daily or twice the dose daily for the 7 non-hormone days in the cycle. Vitamin supplements produced significant improvement in pre-existing deficiencies of riboflavin, pyridoxine and folic acid. Continuous supplementation regimen was slightly superior, but more expensive than the intermittent supplementation regimen. In view of the high prevalence of vitamin deficiency among the low-income group women of developing countries, the delivery system for oral contraceptive can be effectively used for giving vitamin supplements as well.

Protective effect of riboflavin on suppression of growth caused by oxidized oil.

When oxidized corn oil (100 nmol in terms of malondialdehyde/day/rat) was administered to a riboflavin-deficient rat, the body weight gain was markedly suppressed. However, when 20 microgram of riboflavin/day/rat was administered with the oxidized corn oil, reasonable growth and normal flavin levels in the liver, kidney and heart could be attained, though they were somewhat less than those of the animals fed on the normal diet containing non-oxidized corn oil. It was noted that the elevation of lipid peroxide level in blood plasma of animals administered with the oxidized oil was effectively prevented by riboflavin. These results indicate the protective effect of riboflavin on suppression of growth caused by the oxidized oil.

The effects of riboflavin administration on iron metabolism parameters in a school-going population.

The effect of riboflavin administration on iron metabolism was studied in a group of riboflavin-deficient children with Erythrocyte Glutathione Reductase (EC 1.6.4.2) reactivation above 1.20. The results have shown that the administration of riboflavin has resulted in a decrease of serum iron as well as in transferrin saturation which was accompanied by an increase in blood hemoglobin in subjects with initially lower hemoglobin values (less than or equal to 13.5 g/100 ml). There was, however, no change in blood hemoglobin in the group with initially higher hemoglobin values (greater than or equal to 14.0 g/100 ml). The results suggest that inadequate riboflavin intake may affect the iron utilization. The possible mechanism of riboflavin action on iron utilization is discussed.

Effects of pyridoxine and riboflavin supplementation on physical fitness in young adolescents.

The effects of pyridoxine and riboflavin supplementation on physical fitness was studied in a group of children with higher prevalence of subclinical, biochemically defined pyridoxine and riboflavin deficiencies. One hundred and thirteen children aged 12-14 years were allocated to three groups to receive daily (except Sundays) for two months either a placebo or a supplement of pyridoxine or riboflavin. The supplementation resulted in marked improvement of pyridoxine and riboflavin nutrition status and was followed by disappearance of respective biochemical deficiencies. The improvement in pyridoxine biochemical status was also accompanied by a slight and statistically significant increase in physical fitness (p less than 0.05) assessed by bicycle ergometer technique. The increase in physical fitness in the riboflavin supplemented group was statistically non-significant (p greater than 0.05). In both supplemented groups there was a significant increase in physical fitness in subjects with initially deficient biochemical vitamin status whereas supplementation had no effect on physical fitness in subjects with initially high biochemical values.

Riboflavin status of institutionalised and non-institutionalised aged.

A combined dietary, biochemical and clinical study was carried out on 196 aged subjects residing at home and institutions (hospital, residential accommodation and sheltered dwelling) to evaluate the nutritional status of riboflavin and to assess the effect of regular vitamin supplementation. The dietary intake of vitamin B2 was below two-thirds of the recommended in 33.3 per cent males and 17l9 per cent females. Biochemical deficiency of riboflavin was noted in 7.1 per cent subjects by erythrocyte glutathione reductase (EGR) activity coefficient (AC) test. An association between activity coefficient and low intake was found when the coefficient was greater than or equal to 1.30. There was no significant correlation between activity coefficient and dietary vitamin B2/day or vitamin B2/100 g protein. Regular oral administration of multivitamin (containing 2.5 mg vitamin B2) prevented biochemical deficiency of the vitamin. Clinical signs of riboflavin deficiency were not seen except in one female subject of sheltered dwelling.

[Effect of l-carnitine on the expression of glycine conjugates in rats in experimental B2-hypovitaminosis]. / Vliianie l-karnitina na ékspretsiiu glitsinovykh kon"ugatov u krys pri éksperimental'nom B2-gipovitaminoze.

The dynamic of glycine conjugates excretion in riboflavin deficient (RFD) rats was studied. The excretion of isovaleryl-, n-butyryl-, isobutyryl-,2-Me-butyryl- and hexanoylglycines by the RFD rats considerably increased from 1 week of the experiment and reached a plateau after 5 week. Under L-carnitine supplementation the acylglycines (isobutyryl- and isovaleryl) as well as some organic acids excretion was diminished.