Methylmalonic acid analysis using urine filter paper samples to screen for metabolic vitamin B12 deficiency in older adults.

Aim: Methylmalonic acid (MMA) analysis in urine represents a noninvasive approach to screening for vitamin B12 deficiency in older adults. A method allowing the analysis of MMA/creatinine in fasting urine collected on filter paper was developed/validated. Method: Dry urine specimens were eluted using a solution containing internal standards, filtrated and analyzed by ultra-performance LC-MS/MS. Results: The method allowed the chromatographic separation of MMA from succinic acid. Dried urine samples were stable for 86 days at room temperature. The MMA/creatinine ratios measured in urine collected on filter paper were highly correlated with values derived from the corresponding liquid specimens. Conclusion: This robust filter paper method might greatly improve the accessibility and cost-effectiveness of vitamin B12 deficiency screening in older adults.

Mass spectrometry analysis of urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older adults.

Aim: Vitamin B12 deficiency is characterized metabolically by increased serum and urine methylmalonic acid (MMA). Urinary MMA/creatinine ratio is suggested for screening for metabolic vitamin B12 deficiency in older populations. Results: A UPLC-MS/MS method for the analysis of urinary MMA and creatinine was developed/validated. A good separation of MMA from succinic acid, its structural isomer, was achieved. Intra- and interday accuracy biases and precision coefficients were all ≤6.3% for MMA and creatinine. Urine and serum samples of 34 individuals of the NuAge Biobank were analyzed for technical comparisons showing that urinary MMA/creatinine ratios by UPLC-MS/MS strongly correlated with GC-MS values, and with serum MMA values. Conclusion: The UPLC-MS/MS method developed is rapid/reliable for the analysis of urinary MMA/creatinine ratios.

Electrochemical sensing of vitamin B12 deficiency marker methylmalonic acid using PdAu-PPy tailored carbon fiber paper electrode.

Vitamin B12 is very important for human metabolism and its deficiency can cause anemia and the production of large red blood cells. An increased concentration of methylmalonic acid (MMA) is detected much before the transformation of blood cells, which thereby is an early indicator for mild or serious Vitamin B12 deficiency. A simple electrochemical sensor based on Palladium-Gold (PdAu) was developed by electrodeposition of PdAu nanoparticles on Polypyrrole (PPy) modified carbon fiber paper (CFP) electrode. The modified electrodes were characterized by High resolution transmission electron microscopy (HRTEM), Field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electroanalytical techniques. Differential Pulse Voltammetric (DPV) studies have established that under optimum conditions, the developed sensor exhibits a broad linear dynamic range (4.01 pM - 52.5 nM) with a very low detection limit (1.32 pM). The proposed method was effectively applied in the non-enzymatic determination of MMA at an ultralow level in human blood serum and urine samples. The method displayed high selectivity toward MMA in the presence of other interfering substances.

Vitamin B12 Deficiency in Children With Infantile Spasms: A Case-Control Study.

There have been few case reports showing association of vitamin B12 deficiency with infantile spasms. We planned this study to see if there was an association of serum vitamin B12 deficiency in children with development of infantile spasms. Cases included children with infantile spasms of ages 6 months to 3 years. The controls were children in the same age group who had global developmental delay but no history of epileptic spasms. Mean serum vitamin B12, serum homocysteine, and urinary methylmalonic acid levels were measured in both groups and compared. Children with infantile spasms had lower mean serum vitamin B12 levels (354.1 pg/mL; standard deviation 234.1 pg/mL) as compared to children with global developmental delay without spasms (466.7 pg/mL; standard deviation 285.5 pg/mL) ( P value < .05). Mean serum homocysteine level (13.9 vs 7.8 µmol/L, P = .02) and mean urinary methylmalonic acid level (68.1 mmol/mol of creatinine vs 26.1 mmol/mol of creatinine, P = .03) were elevated in children with infantile spasms than in controls. Fourteen children (35.0%) with infantile spasms were vitamin B12 deficient compared with 3 (7.50%) controls ( P = .005). Thus, vitamin B12 deficiency may have an association with infantile spasms. More studies are needed before recommending routine measurement of serum B12 levels in children with infantile spasms.

[Maternal and neonatal vitamin B12 deficiency detected by expanded newborn screening]. / Anyai és újszülöttkori B12-vitamin-hiány felismerése kiterjesztett újszülöttkori szuréssel.

INTRODUCTION: Infant vitamin B12 deficiency can manifest as a severe neurodegenerative disorder and is usually caused by maternal deficiency due to vegetarian diet or pernicious anaemia. Its early recognition and treatment can prevent potentially serious and irreversible neurologic damage. Biochemically, vitamin B12 deficiency leads to an accumulation of methylmalonic acid, homocysteine, and propionylcarnitine. Expanded newborn screening using tandem mass spectrometry may identify neonatal and maternal vitamin B12 deficiency by measurement of propionylcarnitine and other metabolites in the dried blood spot sample of newborns. AIM: To summarize our experiences gained by screening for vitamin B12 deficiency. METHOD: Clinical and laboratory data of vitamin B12-deficient infants diagnosed in Szeged Screening Centre were retrospectively analysed. RESULTS: In Hungary, expanded newborn screening was introduced in 2007. Since then approximately 395 000 newborns were screened in our centre and among them, we identified four newborns with vitamin B12 deficiency based on their screening results. In three cases an elevated propionylcarnitine level and in the fourth one a low methionine level were indicative of vitamin B12 deficiency. We also detected an additional vitamin B12-deficient infant with neurological symptoms at 4 months of age, after a normal newborn screening, because of elevated urinary methylmalonic acid concentration. Vitamin B12 deficiency was secondary to maternal autoimmune pernicious anaemia in all the five infants. As a result of the recognized cases the incidence of infant vitamin B12 deficiency in the East-Hungarian region was 1.26/100 000 births, but the real frequency may be higher. Conslusions: Optimizing the cut off values of current screening parameters and measuring of methylmalonic acid and/or homocysteine in the dried blood spot, as a second tier test, can improve recognition rate of vitamin B12 deficiency. Orv Hetil. 2017; 158(48): 1909-1918.

Urinary levels of early kidney injury molecules in children with vitamin B12 deficiency. / Niveles de moléculas de detección temprana de daño renal en la orina en niños con deficiencia de vitamina B12.

The aim of this study was to investigate urine early kidney injury molecules, including human kidney injury molecule-1 (KIM-1), liver-type fatty-acid binding protein (L-FABP), N-acetyl-b-D-glucosaminidase A (NAG), and neutrophil gelatinase-associated lipocalin (NGAL) in children with vitamin B12 (cobalamin) deficiency (CD). Twelve children with vitamin B12 deficiency and 20 healthy matched controls were included. Hematologic parameters, serum urea, creatinine (Cr), electrolytes, B12 and folate levels were recorded. Estimated glomerular filtration rate (eGFR) was calculated. Urine protein, electrolytes, andurinary early markers were measured. Patients with CD had significantly higher urine electrolyte/Cr ratios (p <0.05). Significantly higher urinary KIM-1/Cr, L-FABP/Cr, NAG/Cr and NGAL/Cr were found in CD group (p <0.05). Significant negative correlations were found between levels of serum B12 and urinary markers in the patients (p <0.05). Increased urinary kidney injury molecules and electrolytes in children with B12 deficiency suggest a possible subclinical renal dysfunction, which cannot be determined by conventional kidney function tests.

El objetivo de este estudio fue investigar los niveles de moléculas de detección temprana de daño renal en la orina, que incluyen la molécula 1 de lesión renal en humanos (KIM-1), la proteína hepática transportadora de ácidos grasos (L-FABP), el N-acetil-b-D-glucosaminidasa A (NAG) y la lipocalina asociada con la gelatinasa de neutrófilos (NGAL), en niños con deficiencia de vitamina B12 (cobalamina).Seincluyeron 12 niños condeficiencia de vitamina B12 y 20 niños sanos en el grupo de referencia emparejado. Se registraron los parámetros hematológicos, la urea en suero, la creatinina (Cr), los electrolitos, y los niveles de vitamina B12 y folato. Se calculó la tasa de filtración glomerular estimada (TFGe). Se midieronlosnivelesdeproteínas, electrolitos y marcadoresde deteccióntemprana en laorina. Lospacientescon deficiencia de cobalamina tenían un cociente significativamente superior de electrolitos/Cr en la orina (p < 0,05). Se hallaron niveles significativamente superiores de KIM-1/Cr, L-FABP/ Cr, NAG/Cr y N GAL / Cr en la orina en el grupo con deficiencia de cobalamina (p < 0,05). En estos pacientes, también se hallaron correlaciones negativas significativas entre los niveles de vitamina B12 en suero y los marcadores en la orina (p < 0,05). El aumento de los electrolitos y de las moléculas marcadoras de lesión renal en la orina en los niños con deficiencia de vitamina B12 sugiere una posible disfunción renal subclínica, que no puede determinarse mediante las pruebas funcionales renales convencionales.

Reliable and powerful laboratory markers of cobalamin deficiency in the newborn: plasma and urinary methylmalonic acid.

BACKGROUND: Diagnosing cobalamin deficiency is critical, given the high prevalence of cobalamin deficiency particularly in developing countries. Measuring serum cobalamin levels is of limited diagnostic sensitivity, in other words its specificity and sensitivity are low. The present study investigated the changes in the levels of metabolic markers - plasma homocysteine, plasma methylmalonic acid (MMA) and urinary MMA - of cobalamin metabolism. METHODS: Plasma cobalamin and serum folic acid were studied in 206 pregnant women over the last four prenatal weeks. Plasma cobalamin, folic acid, homocysteine, MMA from umbilical cord blood and urinary MMA in newborns were studied. RESULTS: Plasma cobalamin values were low in 66% of the mothers. There was a positive correlation between maternal and neonatal plasma cobalamin values (r = 0.72, p < 0.001). B12 was strongly inversely associated with plasma MMA, urine MMA and plasma homocysteine. To predict cobalamin deficiency, sensitivities of plasma MMA, urinary MMA and homocysteine were 96.4%, 95.6% and 88.2%, respectively. And positive predictive values (PPV) were 96.2%, 96.9% and 86% for plasma MMA, urinary MMA and plasma homocysteine levels, respectively. CONCLUSION: Plasma MMA and urinary MMA B12 are the most robust markers of cobalamin deficiency. As a non-invasive method, urinary MMA is a sensitive method in demonstrating cobalamin deficiency in the newborn.

Don't forget methylmalonic acid quantification in symptomatic exclusively breast-fed infants.

Vitamin B12 deficiency can lead to serious haematological and neurological signs in infants. The reported clinical cases of vitamin B12 deficiency were found in exclusively breast-fed infants whose asymptomatic mothers were diagnosed later with pernicious anaemia. For the infants, the diagnosis required urinary methylmalonic acid quantification (grossly elevated in these two cases) and treatment rapidly improved the clinical signs. These cases underline the serious consequences of vitamin B12 deficiency in infants and the helpful role of early methylmalonic acid quantification for diagnosis.

A vitamin B-12 supplement of 500 µg/d for eight weeks does not normalize urinary methylmalonic acid or other biomarkers of vitamin B-12 status in elderly people with moderately poor vitamin B-12 status.

Plasma vitamin B-12 is the most commonly used biomarker of vitamin B-12 status, but the predictive value for low vitamin B-12 status is poor. The urinary methylmalonic acid (uMMA) concentration has potential as a functional biomarker of vitamin B-12 status, but the response to supplemental vitamin B-12 is uncertain. A study was conducted to investigate the responsiveness of uMMA to supplemental vitamin B-12 in comparison with other biomarkers of vitamin B-12 status [plasma vitamin B-12, serum holotranscobalamin (holoTC), plasma MMA] in elderly people with moderately poor vitamin B-12 status. A double-blind, placebo-controlled, randomized 8-wk intervention study was carried out using vitamin B-12 supplements (500 µg/d, 100 µg/d, and 10 µg/d cyanocobalamin) in 100 elderly people with a combined plasma vitamin B-12 <250 pmol/L and uMMA ratio (µmol MMA/mmol creatinine) >1.5. All biomarkers had a dose response to supplemental vitamin B-12. Improvements in plasma vitamin B-12 and serum holoTC were achieved at cobalamin supplements of 10 µg/d, but even 500 µg/d for 8 wk did not normalize plasma vitamin B-12 in 8% and serum holoTC in 12% of people. The response in uMMA was comparable with plasma MMA; 15-25% of people still showed evidence of metabolic deficiency after 500 µg/d cobalamin for 8 wk. There was a differential response in urinary and plasma MMA according to smoking behavior; the response was enhanced in ex-smokers compared with never-smokers. uMMA offers an alternative marker of metabolic vitamin-B12 status, obviating the need for blood sampling.

Serum vitamin B(12) concentrations among mothers and newborns and follow-up study to assess implication on the growth velocity and the urinary methylmalonic acid excretion.

OBJECTIVE: Cobalamin (B(12)) deficiency has been reported in infants born to mothers with low cobalamin intake. Early diagnosis of vitamin B(12) deficiency in infants is critical for the prevention of neurobehavioral disorders. We investigated the relationship between serum vitamin B(12) level in newborns and in their healthy mothers who consumed an omnivorous diet. Anthropometry was studied longitudinally to assess the growth velocity of the infants. Urinary methylmalonic acid (MMA) excretion of 6-month old infants was compared retrospectively as the biomarker correlated with the initial serum vitamin B(12) concentrations. METHODS: Serum cobalamin and blood hemoglobin were determined in 84 pairs of newborns and their mothers. Urinary MMA excretion was measured in the same subjects during the first 6 months of the post partum period. RESULTS: At birth, median serum cobalamin levels were 152.0 pmol/L in the mothers and 296.6 pmol/L in the newborns. Maternal and neonatal serum cobalamin levels had no effect on growth velocity during the first six months of postnatal life. Serum maternal and neonatal cobalamin levels were inversely associated with urinary MMA excretion. CONCLUSION: Early diagnosis of vitamin B(12) status in neonates and infants is crucial, particularly in nutritionally deprived areas. Biochemical measurement of plasma cobalamin or its metabolic marker MMA is highly recommended. Urinary MMA measurement in cobalamin diagnostics provides an advantage in that blood sampling is not required. A vitamin B(12) taskforce should be created to alleviate vitamin deficiency and its negative consequences.

Altered red cell membrane compositions related to functional vitamin B(12) deficiency manifested by elevated urine methylmalonic acid concentrations in patients with schizophrenia.

BACKGROUND: Abnormal cell membrane composition and functional cobalamin (vitamin B(12)) deficiency was reported in schizophrenic individuals. We aimed to investigate the relationship between cobalamin state and cell membrane composition in patients with schizophrenia. METHODS: Malondialdehyde (MDA), cholesterol, and phospholipid classes in the erythrocyte membranes of 18 schizophrenic and 20 healthy individuals of the same age and sex distribution were determined. Serum vitamin B(12), plasma total homocysteine, serum folate, and urine methylmalonic acid (uMMA) concentrations were measured in both groups. RESULTS: In the schizophrenic group, uMMA, membrane MDA, membrane cholesterol, membrane phosphatidylinositol concentrations were significantly higher and the membrane phosphatidylserine concentrations were lower than the control group values. In schizophrenic individuals, uMMA concentrations have a significant positive correlation with membrane MDA and a negative correlation with membrane cholesterol concentrations (P<0.05). The negative correlation of uMMA with membrane cholesterol concentrations may be a biological response to the increased membrane rigidity. Also, a free radical elevation related to the elevated uMMA concentrations in the erythrocyte membrane, might reflect the role of methylmalonic acid (MMA) in membrane damage. CONCLUSION: Our present findings suggest that, functional vitamin B(12) deficiency representing itself by MMA elevations in schizophrenic individuals could damage cell membrane.

Neurodegeneration and chronic renal failure in methylmalonic aciduria--a pathophysiological approach.

In the last decades the survival of patients with methylmalonic aciduria has been improved. However, the overall outcome of affected patients remains disappointing. The disease course is often complicated by acute life-threatening metabolic crises, which can result in multiple organ failure or even death, resembling primary defects of mitochondrial energy metabolism. Biochemical abnormalities during metabolic derangement, such as metabolic acidosis, ketonaemia/ketonuria, lactic acidosis, hypoglycaemia and hyperammonaemia, suggest mitochondrial dysfunction. In addition, long-term complications such as chronic renal failure and neurological disease are frequently found. Neuropathophysiological studies have focused on various effects caused by accumulation of putatively toxic organic acids, the so-called 'toxic metabolite' hypothesis. In previous studies, methylmalonate (MMA) has been considered as the major neurotoxin in methylmalonic aciduria, whereas more recent studies have highlighted a synergistic inhibition of mitochondrial energy metabolism (pyruvate dehydrogenase complex, tricarboxylic acid cycle, respiratory chain, mitochondrial salvage pathway of deoxyribonucleoside triphosphate (dNTP)) induced by propionyl-CoA, 2-methylcitrate and MMA as the key pathomechanism of inherited disorders of propionate metabolism. Intracerebral accumulation of toxic metabolites ('trapping' hypothesis') is considered a biochemical risk factor for neurodegeneration. Secondary effects of mitochondrial dysfunction, such as oxidative stress and impaired mtDNA homeostasis, contribute to pathogenesis of these disorders. The underlying pathomechanisms of chronic renal insufficiency in methylmalonic acidurias are not yet understood. We hypothesize that renal and cerebral pathomechanisms share some similarities, such as an involvement of dicarboxylic acid transport. This review aims to give a comprehensive overview on recent pathomechanistic concepts for methylmalonic acidurias.

Testicular injury to rats fed on soybean protein-based vitamin B12-deficient diet can be reduced by methionine supplementation.

We have previously reported that rats fed on a vitamin B12 (B12)-deficient diet containing 180 g soybean protein per kg diet showed marked histologic damage in their testes. In this paper, we report the effect of B12-deficiency on B12-dependent methionine synthase in the rats' testes and the effect of methionine supplementation of the diet on testicular damage. Rats were fed the soybean protein-based B12-deficient diet for 120 d. We confirmed that those rats were in serious B12-deficiency by measuring urinary methylmalonic acid excretion and B12 content in tissues. Methionine synthase activity in the testis of the B12-deficient rats was less than 2% of that in B12-supplemented (control) rats. To complement disrupted methionine biosynthesis, methionine was supplied in the diet. A supplement of 5 g D,L-methionine per kg diet to the B12-deficient diet did not affect urinary methylmalonic acid excretion of B12-deficient rats. The testicular histology of rats fed the methionine-supplemented B12-deficient diet was almost indistinguishable from that of control rats. Thus, we conclude that the lowered testicular methionine synthase activity is the primary cause of the histologic damage due to B12-deficiency and that methionine supplementation to the diet can reduce the damage. These findings would indicate the importance of the methionine synthase activity, especially for testicular function.

Diagnostic significance of urinary thiodiglycolic acid as a possible tool for studying the role of vitamins B12 and folates in the metabolism of thiolic substances.

We have found that the determination of thiodiglycolic acid (TDGA) in urine may help to characterize metabolic imbalance of substances participating in methionine synthesis, which leads to hyperhomocystinuria. From the metabolic scheme, based on a proper combination of known facts, we attempted to theoretically explain and to demonstrate the possibilities of TDGA formation via different ways of homocysteine transformation. This scheme was used in evaluating the results obtained by testing urine of a woman suffering from impaired function of methionine synthase reductase (CblE type of homocystinuria). The amount of TDGA excreted in her morning urine was very sensitive to the changes in her treatment based upon a combination of N5-formyl tetrahydrofolate, betaine and vitamin B12. Vitamin B12 given in the evening either alone or together with betaine increased the TDGA excretion in the morning urine up to ten times. On the other hand, in the absence of vitamin B12, betaine in combination with N5-formyl tetrahydrofolate hindered the appearance of TDGA in the morning urine. Generally, the determination of TDGA in urine of an appropriately pretreated patient may indicate the degree of success of the treatment.

Plasma cobalamin and folate and their metabolic markers methylmalonic acid and total homocysteine among Egyptian children before and after nutritional supplementation with the probiotic bacteria Lactobacillus acidophilus in yoghurt matrix.

OBJECTIVE: To evaluate the biopotency of the viable probiotic Lactobacillus acidophilus (La1) in yoghurt matrix consumed by Egyptian children on their plasma vitamin B12 and folate levels, and their metabolic markers methylmalonic acid (MMA) and total homocysteine (t-Hcy). METHODS: A randomized nutritional supplementation trial (42 days duration) was performed in free-living children of both sexes (11 years old). The La1 in yoghurt matrix was administered to provide 1012 colony-forming units/subject/day. Blood sampling for the analysis of plasma vitamin B12, folate and t-Hcy was performed by standardized methods. Five-hour urine collection was used for the analysis of MMA and t-Hcy. RESULTS: Initially 33.3% of the children presented with biochemical vitamin B12 deficiency (<208 pg/ml), while one-fifth (21%) were biochemically deficient in folate (<3 ng/ml folate/ml plasma or 0.68 nmol/l). Fifty percent of the children presented with high plasma t-Hcy (>15.0 micromol/l). The daily consumption of the probiotic La1 yoghurt for 42 days significantly improved the mean levels of plasma vitamin B12 (P<0.05) and folate (P<0.01) among the studied children compared with the respective baseline data. On the other hand, the average levels of plasma t-Hcy and urinary MMA decreased significantly (P<0.05) at the termination of the 42-day nutritional supplementation, compared with the respective initial mean levels. The consumption of the probiotic yoghurt was also associated with a significant (chi2=8.0; P<0.01) reduction in the percentage prevalence of anemia (hemoglobin <120 g/l). CONCLUSION: The long-term ingestion of viable probiotic La1 potentially promoted the overall nutritional status of the studied children.

Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons.

OBJECTIVES: We sought to determine the cutoffs of fasting urinary methylmalonic acid (MMA) indicating elevated and mildly elevated serum MMA concentrations in older persons. METHODS: We studied 113 female Chinese vegetarians older than 55 y with normal renal function. Fasting serum samples were obtained for measurement of vitamin B12, MMA, and folate and tests of renal function. A fasting urine sample was collected for MMA measurement by the stable-isotope dilution method. The correlation between serum and urinary MMA levels was examined. The optimal cutoffs of urinary MMA for predicting elevated and mildly elevated serum MMA were estimated by use of receiver operating characteristic curves. RESULTS: Fasting urinary and serum MMA levels were linearly correlated. Pearson's correlation coefficient was 0.94. The cutoff of fasting urinary MMA of 2 microM/mM of creatinine had a sensitivity of 79%, a specificity of 85%, and a positive predictive value of 93% for elevated serum MMA (> 0.4 microM/L). A cutoff of 1.5 microM/mM of creatinine had a sensitivity of 86%, a specificity of 85%, and a positive predictive value of 95% for mildly elevated serum MMA (> 0.3 microM/L). Both cutoffs had high positive predictive values for subnormal vitamin B12 concentrations. CONCLUSION: Overnight fasting urinary MMA concentrations have a strong linear relation to serum MMA in older vegetarians without renal impairment. Urinary MMA is potentially useful as a screening tool for metabolic vitamin B12 deficiency in older persons.

Breeding severely vitamin B12-deficient mice as model animals.

Newborn mice weaned from mice fed on a B12-deficient diet during pregnancy and lactation were fed on a B12-deficient diet for 90 days after weaning, and the state of B12 deficiency was evaluated. The effect of B12 deficiency on the testicular tissue was also examined. The body weight of the mice fed on a B12-deficient diet for 90 days was slightly lower than that of the control mice administrated CN-B12, and the urinary excretion of methylmalonic acid (MMA) was increased. The B12 concentrations in the liver and testes were markedly depressed by B12 deficiency, being about 13 and 10 pmol/g, respectively, on day 90. The testes weight was clearly reduced by B12 deficiency. The testes weight/100 g body weight was also lowered. Clear morphological changes were observed in the testicular tissue of the B12-deficient mice. These results showed that mice in a severely B12-deficient state could be produced by dietary B12 deprivation. These B12-deficient mice could be useful as model animals not only for elucidating the functions of B12 in vivo, but also for biochemical studies.

Characterization of corrinoid compounds from a Japanese black tea (Batabata-cha) fermented by bacteria.

A Japanese fermented black tea (Batabata-cha) contained a considerable amount of vitamin B(12) (456 +/- 39 ng per 100 g dry tea leaves and 2.0 +/- 0.3 ng per 100 mL of tea drink). A corrinoid compound was partially purified and characterized from the tea leaves. The patterns of the purified compound by the silica gel 60 thin-layer chromatography and C18 reversed phased high-performance liquid chromatography were identical to those of authentic vitamin B(12). When 20 week old vitamin B(12) deficient rats, which excreted substantial amounts (about 250 mg/day) of methylmalonic acid in urine as an index of vitamin B(12) deficiency, were fed the tea drink (50 mL/day, 1 ng of vitamin B(12)) for 6 weeks, urinary methylmalonic acid excretion (169 +/- 29 mg/day) of the tea drink-supplemented 26 week old rats decreased significantly relative to that (250 +/- 32 mg/day) of the deficient rats. The results indicate that the vitamin B(12) found in the fermented black tea is bioavailable in mammals.

Proteinuria in cubilin-deficient patients with selective vitamin B12 malabsorption.

Selective vitamin B(12) malabsorption or Gräsbeck-Imerslund disease (megaloblastic anemia 1) is frequently accompanied by proteinuria. The malabsorption-proteinuric syndrome of Finnish patients is caused by a defect in the multiligand receptor cubilin. We studied the urinary proteins of control subjects and 13 adult patients with three defined cubilin mutations (FM1, FM2, FM3), all diagnosed during childhood and subsequently observed. The overall kidney function was unimpaired and did not deteriorate with time. The excretion of total protein and albumin, and to lesser extent of transferrin, immunoglobulin light chains, and alpha(1)- and beta(2)-microglobulins, was clearly elevated in 3 patients, mildly elevated in 3, and hardly or not at all increased in the rest. The urinary cobalamin-intrinsic factor receptor was low in 5 patients studied and lowest in the group with clear-cut proteinuria. The proteinuria was not of the classical glomerular or tubular type, but apparently due to the lack of cubilin function needed for tubular reabsorption of some, but not all, proteins of the primary urine.