Chapter 11. Biotin

11 Biotin Donald M Mock CONTENTS History of Discovery 361 Chemistry of Biotin 362 Structure 362 Chemical Synthesis of Biotin 362 Physiology of Biotin 362 Digestion of Protein-Bound Biotin 362 Intestinal Absorption of Biotin 364 Transport of Biotin from the Intestine to Peripheral Tissues 365 Transport of Biotin into the Liver 365 Transport of Biotin into the Central Nervous System 365 Renal Handling of Biotin 366 Placental Transport of Biotin 367 Transport of Biotin into Human Milk 367 Specific Functions 367 Incorporation into Carboxylases and Histones 368 Five Mammalian Carboxylases 369 Biotin Catabolism 370 Requirement and Assessment 370 Circumstances Leading to Deficiency 370 Clinical Findings of Frank Deficiency 371 Laboratory Findings of Biotin Deficiency 371 Methodology for Measuring Biotin 371 Biochemical Pathogenesis 373 Other Effects of Deficiency 374 Diagnosis of Biotin Deficiency 375 Requirements and Allowances 375 Dietary Sources of Biotin 376 Pharmacology and Toxicity 376 Treatment of Biotin Deficiency 376 Toxicity 376 Pharmacology 376 Acknowledgments 377 References 377 HISTORY OF DISCOVERY Although a growth requirement for the ‘‘bios’’ fraction had been demonstrated in yeast, Boas was the first to demonstrate the requirement for biotin in a mammal In rats fed protein ß 2006 by Taylor & Francis Group, LLC derived from egg white, Boas observed a syndrome of severe dermatitis, hair loss, and neuromuscular dysfunction known as ‘‘egg-white injury.’’ A factor present in liver cured the egg-white injury and was named ‘‘protective factor X.’’ The critical event in this ‘‘eggwhite injury’’ of both humans and rats is the highly specific and very tight binding (Kd ¼ 10À15 M) of biotin by avidin, a glycoprotein found in egg white [1] This very high-affinity, high-specificity interaction is used in an extraordinary range of biochemical, biological, and pharmaceutical applications From an evolutionary standpoint, avidin probably serves as a bacteriostat in egg white; consistent with this hypothesis is the observation that avidin is resistant to a broad range of bacterial proteases in both the free and biotin-bound form Because avidin is also resistant to pancreatic proteases, avidin in dietary egg white binds to dietary biotin preventing absorption, thus carrying the biotin through the gastrointestinal tract Biotin is also synthesized by many intestinal microbes; the contribution of microbial biotin to absorbed biotin in the absence of egg-white feeding is unknown, but any biotin released from intestinal microbes is also bound by avidin, preventing absorption Cooked egg white does not cause biotin deficiency because cooking denatures avidin, rendering it susceptible to cleavage by pancreatic proteases and unable to interfere with absorption of biotin CHEMISTRY OF BIOTIN STRUCTURE As reviewed by Bhatia et al [2] and Bonjour [3], the structure of biotin (Figure 11.1) was independently elucidated by Kogl and du Vigneaud in the early 1940s Because biotin has three asymmetric carbons in its structure, eight stereoisomers exist Of these, only one (designated D-(þ)-biotin) is found in nature and is enzymatically active This compound is generally referred to simply as biotin or D-biotin Biocytin (e-N-biotinyl-L-lysine) is about as active as biotin on a mole basis in mammalian growth studies Biotin is a bicyclic compound One of the rings contains a ureido group (–N–CO–N–) and the other is a tetrahydrothiophene ring The tetrahydrothiophene ring has a valeric acid side chain On the basis of biotin analog binding to avidin and the X-ray crystallographic structure of the biotin:avidin complex [1], the ureido ring of biotin is the most important region for the extraordinarily tight binding of biotin to avidin Biotin also binds tightly to streptavidin, a protein secreted by Streptomyces avidinii Other studies [1] suggest that the length of the side chain or the apolar nature of the –CH2– moieties in the side chain also play a role in the binding of biotin to the hydrophobic site on (strept)avidin CHEMICAL SYNTHESIS OF BIOTIN The structure of biotin was confirmed by de novo chemical synthesis by Harrison and coworkers in the 1940s [3] The stereospecific synthesis was developed by Goldberg and Sternbach in 1949 in the laboratories of Hoffman-LaRoche [4] Additional stereospecific methods of synthesis have been published [5,6] PHYSIOLOGY OF BIOTIN DIGESTION OF PROTEIN-BOUND BIOTIN The content of biotin is highly variable among foods [7] Likewise, the proportion of free and protein-bound biotin likely varies substantially even within food groups [8,9] ‘‘Free biotin’’ is defined functionally in most studies as water extractable and dialyzable [10] ‘‘Bound biotin’’ is usually defined as biotin that is sedimentable after a water extraction of the homogenized ß 2006 by Taylor & Francis Group, LLC ß 2006 by Taylor & Francis Group, LLC O O C C HN CH H 2C NH HC CH H2C CH S CH H2C CH (CH2)4 CH Proteolysis NH2 O S C HN NH HC C N Biocytin H (CH2)4 CH OH (CH2)4 N histone Biotinidase Holocarboxylase synthetase? HN NH HC CH H 2C CH S ATP O Biotinidase? Sulfur oxidation O C Sulfur oxidation O HN NH HC CH H 2C CH S C CH CH O O (CH2)4 Biotinyl AMP NH HC CH H 2C CH O (CH2)4 2Pi C OH O AMP Biotin O C Biotin sulfoxide AMP PPi S (CH2)4 C HS-CoA HN Side chain β-oxidation OH O C HN NH HC CH H2C CH S O O (CH2)4 C Biotinyl CoA S CoA C (CH2)4 O HN NH OH HC CH H 2C CH C S O Holocarboxylase Apocarboxylase C HC C O C Histone H 2C CH H O Holocarboxylase synthetase? NH (CH2)4 N Holocarboxylase synthetase Biotinylated histone H HN C AMP O C NH O (CH2)4 S C O ε-Amino group (CH2)4 ε-Amino group NH HC O HN Biotin sulfone O (CH2)2 C O CH3 S Bisnorbiotin methyl ketone C HN NH HC CH H2C CH S O (CH2)2 Bisnorbiotin C OH FIGURE 11.1 Metabolism, degradation, and recycling of biotin as well as biotinylated enzymes and histones Ovals denote enzymes or enzyme systems; rectangles denote biotin, intermediates, metabolites, and substrates in pathways (which can also be enzymes); AMP, adenosine monophosphate; ATP, adenosine triphosphate; CoA, coenzyme A; PPi, pyrophosphate food [11,12] Bound biotin must be released to render the biotin fully detectable by either microbial or avidin-binding assays Release has generally been accomplished by enzymatic or acid-catalyzed proteolysis; these methods have likely resulted in incomplete biotin release, destruction of biotin, or both as discussed in the sections Requirement and Assessment and Dietary Sources of Biotin Proteolytic degradation of dietary protein likely yields biocytin and biotinyl oligopeptides Neither the exact mechanism of the intestinal hydrolysis of protein-bound biotin nor the relationship of digestion of protein-bound biotin to its bioavailability has been clearly elucidated, but Wolf and coworkers have postulated that biotinidase (EC 3.5.1.12, an amide hydrolase) in pancreatic secretions cleaves biocytin [13,14] Given the observation that biocytin uptake is substantially less active than that of biotin [15], this cleavage of biocytin by biotinidase may substantially enhance the bioavailability of bound biotin INTESTINAL ABSORPTION OF BIOTIN Intestinal absorption of biotin has been the subject of an excellent recent review by Said [16] His studies are the source of a substantial amount of the information concerning intestinal biotin absorption The nutritional significance of biotin synthesized by the normal intestinal microflora remains uncertain However, a considerable amount of the bacterially synthesized biotin appears to be in the free (absorbable) form, and studies in humans, rats, and mini-pigs have shown that the large intestine is capable of absorbing luminally introduced biotin Moreover, studies utilizing human-derived colonic epithelial cells have shown that these cells posses an efficient, Naþ-dependent, carrier-mediated mechanism for biotin uptake [16] Absorption of free biotin in the small intestine has been studied using several intestinal preparations including isolated loops, intestinal cells in culture, and brush-border membrane vesicles in vitro Biotin is absorbed from the lumen at the brush border by an Naþ-dependent carrier The carrier is structurally specific, requiring both a free carboxyl group on the valeric acid side chain and an intact ureido ring [17,18] The transport of biotin is temperature dependent and occurs against a concentration gradient At high concentrations, biotin transport also occurs by simple diffusion Based on a study in which biotin was administered orally in pharmacologic amounts, the bioavailability of biotin is ~100% [19] This observation provides a rational basis for the pharmacologic doses used in the treatment of biotin-responsive inborn errors of metabolism and for predicting that the bioavailability of free biotin is likely to be high for physiologic doses as well Substantial evidence indicates that the intestinal biotin transporter is encoded by the sodium-dependent multivitamin transporter (SMVT ) gene [16] SMVT expression generally parallels biotin transport Biotin uptake is competitively inhibited by pantothenic acid and lipoic acid; this observation is consistent with studies of the overexpressed SMVT, which indicate that SMVT transports pantothenic acid and lipoic acid in addition to biotin Hence the origin of the name sodium-dependent multivitamin transporter In addition, studies using gene-specific siRNA to silence the SMVT gene in human intestinal epithelial cells indicate that SMVT is the main (if not the only) biotin uptake system that operates in these cells Biotin transport is regulated by multiple factors including biotin nutritional status, enterocyte maturity, anatomic location, and ontogeny Upregulation of biotin transport occurs in response to biotin deficiency The mechanism for most of the change appears to be an increased Vmax (presumably mediated by an increased number of carriers) rather than change in the carrier affinity Biotin transport is more active in the villus cells than in the crypt cells Transport is most active in the upper small intestine and progressively less active aborally into the colon ß 2006 by Taylor & Francis Group, LLC The intestinal biotin uptake process appears to be under the regulation of intracellular protein kinase C and Ca2þ–calmodulin-mediated pathways Transcription of the SMVT gene of rats appears to be driven by three distinct promoters whereas that of humans appears to involve two distinct promoters Said has identified four distinct variants (I, II, III, IV) in the rat small and large intestine, which have significant heterogeneity in the 50 untranslated region [16] The exit of biotin from the polarized enterocyte occurs by transport across the basolateral membrane Basolateral transport is also carrier-mediated but is independent of Naþ Basolateral transport is electrogenic and does not accumulate biotin against a concentration gradient The gene is yet to be identified TRANSPORT OF BIOTIN FROM THE INTESTINE TO PERIPHERAL TISSUES Biotin concentrations in plasma are small relative to those of other water-soluble vitamins Most biotin in plasma is free and dissolved in the aqueous phase of plasma However, small amounts are reversibly bound and covalently bound to plasma protein (~7% and 12%, respectively); binding to human serum albumin likely accounts for most of the reversible binding [10,11] Biotinidase has been proposed as a specific biotin-binding protein or biotincarrier protein for the transport into cells [20,21] A biotin-binding immunoglobulin has recently been identified in human serum An approximately fivefold higher concentration of this biotin-binding immunoglobulin was reported in patients with Graves, disease than in normal and healthy controls [22] TRANSPORT OF BIOTIN INTO THE LIVER Studies of 3T3-L1 fibroblasts [23] rat hepatocytes isolated by collagenase profusion [18,24], basolateral membrane vesicles from human liver [25,26], and HepG2 human hepatoma cells [27,28], indicate that uptake of free biotin is mediated both by diffusion and by a specialized carrier system that is dependent on an Naþ gradient, temperature, and energy Transport is electroneutral (Naþ to biotin 1:1) and specific for a free carboxyl group, but transport is not strongly specific for the structure in the region of the thiophene ring [27] Recent work from Said and coworkers provides evidence that the primary, and perhaps only, transporter for biotin into hepatocytes is coded by the SMVT gene [28] At physiologic nanomolar concentrations, biotin transport into HepG2 cells was inhibited by siRNA specific to the human SMVT; pantothenic acid uptake was also effectively inhibited by hSMVT-specific siRNA Studies in cultured rat hepatocytes have demonstrated trapping of biotin [29], presumably covalently bound in holocarboxylase enzymes and histones These studies confirm earlier studies by McCormick and recapitulate the importance of metabolic trapping of watersoluble vitamins as a mechanism for an intracellular vitamin accumulation [18] After entering the hepatocyte, biotin diffuses into the mitochondria via a pH-dependent process leading to the hypothesis that biotin enters the mitochondria in the neutral, protonated form and dissociates into the anionic form in the alkaline mitochondrial environment, thus becoming trapped by the charge [30] Biliary excretion of biotin and metabolites is quantitatively negligible based on a rat study [31] TRANSPORT OF BIOTIN INTO THE CENTRAL NERVOUS SYSTEM Using in situ rat brain perfusion, Spector and Mock [32] demonstrated that biotin is transported across the blood–brain barrier by a saturable system; the apparent Km is %100 mmol=L (a value several orders of magnitude greater than the concentration of free biotin in plasma) Transport was structurally specific Transfer of biotin directly into the cerebral spinal fluid ß 2006 by Taylor & Francis Group, LLC (CSF) via the choroid plexus did not appear to be important for biotin entry into the central nervous system (CNS) Additional studies using either intravenous or intraventricular injection of 3H-biotin into rabbits [33] indicated that biotin was cleared from the CSF more rapidly than mannitol, suggesting specific transport systems for biotin uptake into the neurons after biotin crosses the blood–brain barrier; further, biotin entry did not depend on the subsequent metabolism of biotin or immediate trapping by incorporation into brain proteins Ozand et al have described 10 patients in Saudi Arabia with a novel biotin-responsive basal ganglia disease Patients presented with subacute encephalopathy, confusion, disartria, and dysphasia progressing to cogwheel rigidity, distonia, and quadriparesis These findings improved dramatically within days in response to 5–10 mg biotin per kilogram body weight per day The symptoms recurred if biotin was discontinued [34] Zeng et al working in collaboration with this group mapped the genetic defect to chromosome 2q36.3 [35] Each affected member of the family kindreds displayed one of two missense mutations Both mutations alter the coding sequence for the SLC19A3 transporter SLC19A3 codes for a protein previously identified as a thiamine transporter and designated THTR-2 These investigators have speculated that SLC19A3 may be responsible for biotin transport or recycling in the CNS [35], although the possibility remains that biotin responsiveness is secondary to an effect on thiamine transport Vlasova and Mock have identified SLC19A3 as a gene that is highly responsive to biotin status in peripheral blood leukocytes in culture [36]; SLC19A3 is also responsive to experimental biotin deficiency induced in vivo in human subjects [37] Mardach et al have reported an 18 month old boy with sudden onset biotin-responsive coma [38] This child had a profound biotin-transporter defect in both normal and EBVtransformed lymphocytes; the parents of this child had intermediate biotin transporter activities consistent with heterozygous status Despite possessing a biotin-responsive pattern of organic aciduria consistent with multiple carboxylase deficiency, this child had normal holocarboxylase synthetase and biotinidase activities; pantothenic acid transport and SMVT gene coding sequence were normal The gene defect of this subject is under active investigation Mock has measured the concentrations of free ‘‘biotin’’ (i.e., total avidin-binding substances) in human CSF and ultrafiltrates of plasma; the ratio was 0.85 + 0.5 for 11 subjects [39] This result is similar to the CSF:plasma ratios determined for biotin by Spector and Mock in rabbits, a species that has a specific system for biotin transport across the blood– brain barrier [33] Livaniou and coworkers have also measured CSF concentrations of biotin of normal adults and adults with a variety of neurologic disorders [40] Both studies provide evidence that biotin is not highly concentrated in normal CSF Livaniou and coworkers also reported a significant reduction in CSF biotin in epileptics and subjects with multiple sclerosis RENAL HANDLING OF BIOTIN Specific systems for the reabsorption of water-soluble vitamins from the glomerular filtrate likely contribute importantly to conservation of the water-soluble vitamins [17] A biotin transport system has been identified in brush-border membrane vesicles from human kidney cortex [41,42] Uptake by brush-border membrane vesicles was electroneutral, structurally specific, saturable, occurred against a biotin concentration gradient, and was dependent on an inwardly directed Naþ gradient Biotin uptake by human-derived proximal tubular epithelial HK-2 cells is dependent on temperature, energy, and an inwardly directed Naþ gradient [43] and is inhibited by both pantothenic acid and lipoate, suggesting the involvement of SMVT Said and coworkers demonstrated that SMVT is expressed as both mRNA and protein in HK-2 cells In their study, ß 2006 by Taylor & Francis Group, LLC silencing of the SMVT gene by specific siRNA led to specific and significant inhibition of biotin uptake Studies with protein kinase C and Ca2þ–calmodulin modulators provided evidence that renal biotin uptake is under regulation via these pathways Uptake was also adaptively regulated by biotin deficiency consistent with previous studies demonstrating reduced biotin excretion early in experimentally induced biotin deficiency in human subjects [44,45] The renal clearance of biotin in normal adults and children who are not receiving biotin supplementation is ~0.4 when expressed as biotin to creatinine clearance ratio [41,46,47] In patients with biotinidase deficiency, renal wasting of biotin and biocytin occurs; biotin to creatinine clearance ratios typically exceed 1, and half-lives for biotin clearance are about half of the normal value The mechanism for the increased renal excretion of biotin in biotinidase deficiency has not been defined, but this observation suggests that there may also be a role for biotinidase in the renal handling of biotin PLACENTAL TRANSPORT OF BIOTIN Biotin concentrations are 3–17-fold greater in plasma from human fetuses than their mothers in the second trimester, consistent with active placental transport Specific systems for transport of biotin from the mother to the fetus have been reported [48–50] Studies using microvillus membrane vesicles and cultured trophoblasts [48,49] detected a saturable transport system for biotin, which was dependent on Naþ and actively accumulated biotin within the placenta with slower release into the fetal compartment However, in the isolated, perfused single cotyledon [48,49] transport of biotin across the placenta is slow relative to placental accumulation Studies using fetal facing (basolateral) membrane vesicles detected a saturable, Naþ-dependent, electroneutral, carrier-mediated uptake process, which was not as active as the biotin uptake system in the maternal facing (apical) membrane vesicles [50] SMVT was originally discovered in human chorionic carcinoma cells [51] and is expressed in normal human placenta [52] Biotin supply affects the rates of cell proliferation, biotinylation of carboxylases and histones, expression of SMVT, and progesterone secretion in chorionic carcinoma cells [53] TRANSPORT OF BIOTIN INTO HUMAN MILK Greater than 95% of the biotin in human milk is free in the aqueous phase of the skim fraction [54] A steady increase in the biotin concentration is observed during the first 18 days postpartum in about half of the women; after 18 days postpartum, biotin concentrations vary substantially [55] Bisnorbiotin accounts for about half of the total biotin plus metabolites in early and transitional human milk; biotin sulfoxide accounts for about 10% With postpartum maturation, the absolute concentration of biotin increases as well as the proportion of the total due to biotin; however, bisnorbiotin and biotin sulfoxide still account for about 25% and 8% of the total at weeks postpartum [56] The concentration of biotin in human milk exceeds the plasma concentration by 10–100fold [56], implying that a transport system exists The location and the nature of the biotin transport system for human milk have yet to be elucidated SPECIFIC FUNCTIONS In mammals, biotin serves as an essential cofactor for five carboxylases; each enzyme catalyzes a critical step in intermediary metabolism [57,58] All five of the mammalian carboxylases catalyze the incorporation of bicarbonate into a substrate as a carboxyl group Four similar carboxylases, two other carboxylases, two decarboxylases, and a transcarboxylase are found in nonmammalian organisms Each works by a similar mechanism ß 2006 by Taylor & Francis Group, LLC INCORPORATION INTO CARBOXYLASES AND HISTONES Attachment of the biotin to the apocarboxylase (Figure 11.1) is a condensation reaction catalyzed by holocarboxylase synthetase The holocarboxylase synthetase reaction is driven thermodynamically by hydrolysis of ATP to pyrophosphate and onto inorganic phosphate An amide bond is formed between the carboxyl group of the valeric acid side chain of biotin and the e-amino group of a specific lysyl residue in the apocarboxylase The lysine residue is consistently found within a biotin acceptor sequence (A=Bio) MKM that is at the center of a 60 to 80 amino acid domain One interpretation concerning conservation of this amino acid sequence is that these residues allow the biotinylated peptide to swing the carboxyl (or acetyl) group from the site of activation to the receiving substrate [59] Much of our knowledge of the reaction mechanisms for holocarboxylase synthetase comes from studies of BirA in the analogous Escherichia coli acetyl CoA carboxylase (ACC) [60] BirA acts not only as a biotin transfer enzyme and a carboxylase, but this protein also acts as a repressor of the operand for the biosynthesis of biotin [60,61] Biotin is transferred via a two-step reaction involving biotinyl 50 AMP This intermediate remains bound to BirA producing a conformational shift that stabilizes the complex preventing unproductive release of biotinyl 50 AMP [62,63] Biotin is then transferred to a biotin carboxyl-carrier protein (BCCP) of ACC with the release of AMP Human holocarboxylase synthetase (HCLS, EC 6.3.4.10) has been cloned [64–67] HCLS is located on chromosome 21q22.1 and consists of 14 exons and 13 entrons in a span of 240 kb Comparison with BirA indicates substantial homology in some regions Studies of human mutant HCLS indicate that all forms of holocarboxylase synthetase are likely encoded by one gene Biotinylation of histones is emerging as an important histone modification; biotinylation likely interacts with other covalent modification of histones Elsewhere in this text, see an excellent review of vitamin-dependent modifications of chromatin by Zempleni and coworkers Briefly, the relative importance in biotinidase and HCLS in the biotinylation and debiotinylation of histones has yet to be elucidated and is under active investigation [68–70] HCLS is present in the nucleus in greater quantities than in the cytosol or the mitochondria [68] Gravel and Narang have produced exciting evidence that HCLS likely acts in the nucleus to catalyze the biotinylation of histones [68] and have hypothesized that biotinidase acts primarily to catalyze the debiotinylation of histones producing a biotin regeneration cycle similar to that observed for the biotinylation of apocarboxylases and the regeneration of biotin during turnover of mitochondrial proteins (Figure 11.1) As fibroblasts from patients with HCLS deficiency are severely deficient in histone biotinylation [71], a direct or indirect role for biotinidase in histone biotinylation is likely Genetic deficiencies of holocarboxylase synthetase and biotinidase cause two types of multiple carboxylase deficiency These inborn errors bear some phenotypic resemblance to biotin deficiency, especially biotinidase deficiency, but are not identical See the excellent recent review by Wolf in The Metabolic and Molecular Basis of Inherited Disease for a more detailed discussion [14] Some clinical findings and biochemical abnormalities of biotinidase deficiency resemble those of biotin deficiency (dermatitis, alopecia, conjunctivitis, ataxia, developmental delay) suggesting that they are caused by biotin deficiency [72,73] However, the signs and symptoms of biotin deficiency and biotinidase deficiency are not identical Seizures, irreversible neurosensory hearing loss, and optic atrophy have been observed in biotinidase deficiency, but not in biotin deficiency The gene for human biotinidase has been cloned, sequenced, and characterized [14] The biotinidase gene is a single copy gene of 1629 bases encoding a 543 amino acid protein; the mRNA is present in multiple tissues including heart, brain, placenta, liver, lung, skeletal muscle, kidney, and pancreas Biotinidase activity is greatest in serum, the liver, the kidney, and the adrenal gland The liver is thought to be the source of serum biotinidase ß 2006 by Taylor & Francis Group, LLC FIVE MAMMALIAN CARBOXYLASES The five biotin-dependent carboxylases are propionyl CoA carboxylase (PCC), methylcrotonyl CoA carboxylase (MCC), pyruvate carboxylase (PC), acetyl CoA carboxylase (ACC1), and acetyl CoA carboxylase (ACC2) All except ACC2 are mitochondrial enzymes In the carboxylase reaction, the carboxyl moiety is first attached to biotin at the ureido nitrogen opposite the side chain Next, the carboxyl group is transferred to the substrate The reaction is driven by the hydrolysis of ATP to ADP and inorganic phosphate ACC1 and ACC2 both catalyze the incorporation of bicarbonate into acetyl CoA to form malonyl CoA (Figure 11.2) ACC1 is located in the cytosol and produces the malonyl CoA, which is the rate-limiting substrate in fatty acid synthesis (elongation) ACC2 is located on the outer mitochondrial membrane and controls fatty acid oxidation in mitochondria through the inhibitory effect of malonyl CoA on fatty acid transport into mitochondria Pyruvate carboxylase (PC, EC 6.4.1.1) catalyzes the incorporation of bicarbonate into pyruvate to form oxaloacetate, an intermediate in the tricarboxylic acid cycle (Figure 11.2) Thus, PC catalyzes an anapleurotic reaction In gluconeogenic tissues (i.e., liver and kidney), the oxaloacetate can be converted to glucose Deficiency of PC is probably the cause of the lactic acidemia (Figure 11.2), and CNS lactic acidosis observed in biotin deficiency and biotinidase deficiency and may contribute to abnormalities in glucose regulation Methylcrotonyl CoA carboxylase (MCC, EC 6.4.1.4) catalyzes an essential step in the degradation of the branch-chained amino acid leucine (Figure 11.2) Deficient activity of MCC (whether due to the isolated MCC deficiency, HCLS deficiency, or biotin deficiency per se) leads to metabolism of its substrate 3-methylcrotonyl CoA by an alternate pathway to Isoleucine methionine 3-hydroxypropionate 2-methylcitrate } Leucine 3-hydroxyisovalerate 3-methylcrotonylglycine Acetyl CoA + C12:0 Propionyl CoA Propionyl CoA carboxylase C14:0 + HSCoA 3-methylcrotonyl CoA Methylcrotonyl CoA carboxylase Odd-chain fatty acid (e.g., C15:0) D-methylmalonyl CoA 3-methylglutaconyl CoA Succinyl CoA Glucose Oxalacetate Tricarboxylic acid cycle Pyruvate Pyruvate carboxylase Lactate Fatty acid elongation Acetyl CoA Malonyl CoA Acetyl CoA carboxylase and FIGURE 11.2 Interrelationship of pathways catalyzed by biotin-dependent enzymes (shown in boxes) Organic acids and odd-chain fatty acids accumulate because biotin deficiency causes reduced activity of biotin-dependent enzymes Hatched bars denote metabolic blocks at deficient carboxylases Ovals denote accumulation of products from alternative pathways, which are denoted by dashed arrows ß 2006 by Taylor & Francis Group, LLC 3-hydroxyisovaleric acid, 3-methylcrotonylglycine, and related organic acids (Figure 11.2) Thus, increased urinary excretion of these abnormal metabolites in the urine reflects deficient activity of MCC Propionyl CoA carboxylase (PCC, EC 6.4.1.3) catalyzes the incorporation of bicarbonate into propionyl CoA to form methylmalonyl CoA (Figure 11.2) Methylmalonyl CoA undergoes isomerization to succinyl CoA and enters the tricarboxylic acid cycle Deficiency of PCC leads to increased urinary excretion of 3-hydroxypropionic acid and 2-methylcitric acid (Figure 11.2) BIOTIN CATABOLISM Instead of incorporation into carboxylases or histones, biotin may be catabolized Biotin, possibly in the form of biotinyl CoA, can be oxidized to bisnorbiotin and tetranorbiotin (metabolites with two and four fewer carbons in the valeric acid side chain, respectively; Figure 11.1) The sulfur can be oxidized to sulfoxide and possibly sulfone Biotin, bisnorbiotin, and biotin sulfoxide are present in mole ratios of ~3:2:1 in human urine and plasma Biotin catabolism is induced during pregnancy, with cigarette smoking, and with anticonvulsant therapy, thereby increasing the ratio of biotin catabolites to biotin [74,75] and likely contributing to biotin depletion REQUIREMENT AND ASSESSMENT CIRCUMSTANCES LEADING TO DEFICIENCY The requirement for biotin by the normal human has been clearly documented in three situations: prolonged consumption of raw egg white, parenteral nutrition without biotin supplementation in patients with short-gut syndrome [39], and infant feeding with an elemental formula devoid of biotin As in Japan biotin could not legally be added as a supplement to infant formulas until 2003, all reports related to infant formula have come from Japan [76] The most recent report by Fujimoto and colleagues describes the ninth such infant and provides an excellent summary of the results of the other eight infants [76] The infants generally developed the classic cutaneous manifestations of biotin deficiency as well as the characteristic pattern of organic aciduria Often feeding of an elemental formula was instituted because of chronic diarrhea in the infant Biotinidase deficiency and zinc deficiency were ruled out in most of the infants An undiagnosed deficiency of holocarboxylase synthetase deficiency was functionally ruled out in most infants by the gradual weaning of biotin supplementation at an age when the infant would be introduced to biotin-containing foods [76] On the basis of lymphocyte carboxylase activity and plasma biotin levels, biotin deficiency likely also occurs in children with severe protein energy malnutrition; biotin deficiency may contribute to the clinical syndrome of protein energy malnutrition [77,78] Long-term anticonvulsant therapy in adults can lead to biotin depletion [79,80] The depletion can be severe enough to interfere with leucine metabolism and cause increased urinary excretion of 3-hydroxyisovaleric acid [75,81] The mechanism of biotin depletion during anticonvulsant therapy is not known, but may involve accelerated biotin catabolism based on increased urinary excretion of biotin catabolites [75,82] Impaired biotin absorption [83,84], impaired biotin transport in plasma, or impaired renal reclamation biotin [20] may also contribute to biotin depletion Studies of biotin status during pregnancy provide evidence that a marginal degree of biotin deficiency develops in at least one-third of women during normal pregnancy [85,86] Although the degree of biotin deficiency was not severe enough to produce overt manifestations of biotin deficiency, the deficiency was sufficiently severe to produce metabolic ß 2006 by Taylor & Francis Group, LLC derangements A similar marginal degree of biotin deficiency causes high rates of fetal malformations in some mammals [87] Moreover, data from a multivitamin supplementation study provide significant, although indirect, evidence that the marginal degree of biotin deficiency that occurs spontaneously in normal human gestation is teratogenic [88] Biotin deficiency has also been reported or inferred in several other clinical circumstances These include Leiner’s disease, sudden infant death syndrome, renal dialysis, gastrointestinal diseases, and alcoholism [39] CLINICAL FINDINGS OF FRANK DEFICIENCY Whether caused by egg-white feeding or omission of biotin from total parenteral nutrition, the clinical findings of frank biotin deficiency in adults and older children have been quite similar to those reported by Sydenstricker in his pioneering study of egg-white feeding [39,89] Typically, the findings began to appear gradually after several weeks to months for egg-white feeding Six months to three years typically elapsed between the initiation of total intravenous feeding without biotin and the onset of the findings of biotin deficiency [39,90] Thinning of hair, often with loss of hair color, was reported in most patients A skin rash described as scaly (seborrheic) and red (eczematous) was present in the majority; in several, the rash was distributed around the eyes, nose, and mouth Depression, lethargy, hallucinations, and paresthesias of the extremities were prominent neurologic symptoms in the majority of adults In infants who developed biotin deficiency, the signs and symptoms of biotin deficiency began to appear within to months after initiation of total parenteral nutrition or biotinfree formula This earlier onset may reflect an increased biotin requirement because of growth The rash typically appeared first around the eyes, nose, and mouth; ultimately, the ears and perineal orifices were involved (periorificial) The appearance of the rash was similar to that of cutaneous candidiasis (i.e., an erythematous base and crusting exudates); typically, Candida could be cultured from the lesions The rash of biotin deficiency is similar, but not identical to the rash of zinc deficiency [76] In infants, hair loss, including eyebrows and lashes, can occur after to months of parenteral nutrition These cutaneous manifestations, in conjunction with an unusual distribution of facial fat, have been dubbed ‘‘biotin deficiency facies.’’ The most striking neurologic findings in biotin-deficient infants were hypotonia, lethargy, and developmental delay A peculiar withdrawn behavior was noted and may reflect the same CNS dysfunction diagnosed as depression in the adult patients LABORATORY FINDINGS OF BIOTIN DEFICIENCY Methodology for Measuring Biotin Methods for measuring biotin at pharmacologic and physiologic concentrations have been reviewed [39] For measuring biotin at physiologic concentrations found in plasma and urine (i.e., 100 pmol=L to 100 nmol=L), a variety of assays have been proposed, and a limited number have been used to study biotin nutriture All the published studies of biotin nutriture have used one of three basic types of biotin assays: (a) bioassays (most studies), (b) avidinbinding assays (several recent studies), or (c) fluorescent derivative and complex assays (a few published studies) Bioassays generally have adequate sensitivity to measure biotin in blood and urine Radiometric bioassays offer both sensitivity and precision However, the bacterial bioassays (and perhaps the eukaryotic bioassays as well) suffer interference from unrelated substances and variable growth response to biotin analogs; these bioassays can give conflicting results if biotin is bound to protein [39] Avidin-binding assays generally measure the ability of biotin to one of the following: (a) to compete with radiolabeled biotin for binding to avidin (isotope dilution assays), ß 2006 by Taylor & Francis Group, LLC (b) to bind to 125I-avidin and thus prevent 125I-avidin (or enzyme-coupled avidin) from binding to a biotinylated protein adsorbed to plastic (sequential, solid phase assay), or (c) to prevent the binding of a biotinylated enzyme to avidin and thereby prevent the consequent inhibition of an enzyme activity Other methods detect the postcolumn enhancement of fluorescence activity caused either by the mixing of the column eluate with fluorescent-labeled avidin or derivatization of biotin and metabolites by a fluorescent agent before separation by HPLC [91–93] Avidin-binding assays using novel detection systems such as electrochemical detection [94], bioluminescence linked through glucose-6-phosphate dehydrogenase [95], or a double antibody technique [96] have been published and may offer some advantages in terms of sensitivity Avidin-binding assays have been criticized for remaining cumbersome, requiring highly specialized equipment or reagents, or performing poorly when applied to biological fluids Avidin-binding assays detect all avidin-binding substances, although the relative detectability of biotin and analogs varies between analogs and between assays, depending on how the assay is conducted (e.g., competitive vs sequential) Assays that couple chromatographic separation of biotin analogs with subsequent avidin-binding assays of the chromatographic fractions are more sensitive and chemically specific [85,91,93] These assays have been used in several studies that provide new insights into biotin nutrition [44,74,97–99] A problem in the area of biotin analytical technology that remains unaddressed is the disagreement among the various bioassays and avidin-binding assays concerning the true concentration of biotin in human plasma Reported mean values range from ~500 to >10,000 pmol=L Although commonly used to assess biotin status in a variety of clinical populations, the putative indexes of biotin status had not been previously studied during progressive biotin deficiency To address this issue, Mock and coworkers [44] induced progressive biotin deficiency by feeding egg white The urinary excretion of biotin declined dramatically with time on the egg-white diet, reaching frankly abnormal values in eight of nine subjects by day 20 of egg-white feeding Bisnorbiotin excretion declined in parallel with urinary biotin, providing evidence for regulation of catabolism of the biotin metabolic pools By day 14 of egg-white feeding, 3-hydroxyisovaleric acid excretion was abnormally increased in all nine subjects, providing evidence that biotin depletion decreases the activity of the biotindependent enzyme MCC and alters intermediary metabolism of leucine earlier in the course of experimental biotin deficiency than previously appreciated Serum concentrations of free biotin as measured by HPLC separation and avidin-binding assay decreased to abnormal values in less than half of the subjects Thus, these studies provide objective confirmation of the impression of many investigators in this field [100] that blood biotin concentration is not an early or sensitive indicator of impaired biotin status Plasma concentrations of biotin (i.e., total avidin-binding substances) are higher in term infants than older children and, for reasons that are not simply related to dietary intake, decline after weeks of breast feeding or feeding a formula containing 11 mg=L of biotin Infant formulas supplemented with 300 mg=L produce plasma concentrations ~20-fold greater than normal [101]; consequences of these higher levels, if any, are unknown Odd-chain fatty acid accumulation is a marker of biotin deficiency [102–105] Several groups have independently demonstrated increases in the percentage composition of oddchain fatty acids (e.g., 15:0, 17:0, etc.) in hepatic, cardiac, or serum phospholipids in the biotin-deficient rat and chick Moreover, Mock and coworkers detected accumulation of oddchain fatty acids in red cell membranes and plasma lipids of subjects in whom biotin deficiency was induced experimentally [99] and in the plasma of patients who developed biotin deficiency during parenteral nutrition [106] The accumulation of odd-chain fatty acid is thought to result from PCC deficiency, based on the observation that the isolated genetic deficiency of PCC and related disorders cause an accumulation of odd-chain fatty acids in ß 2006 by Taylor & Francis Group, LLC plasma, red blood cells, and liver [107,108] Apparently, the accumulation of propionyl CoA leads to the substitution of propionyl CoA moiety for acetyl CoA in the ACC reaction, and hence, to the ultimate incorporation of a three carbon, rather than a two carbon, moiety during fatty acid elongation [109] Biochemical Pathogenesis The mechanisms by which biotin deficiency produces specific signs and symptoms remain to be completely delineated However, several recent studies have given new insights into the biochemical pathogenesis of biotin deficiency The assumption of most studies is that the clinical findings of biotin deficiency result directly or indirectly from deficient activities of the five biotin-dependent carboxylases However, the recently elucidated role of biotin as a covalent modifier of histones and other evolving roles of the effects of biotin open the possibility that these mechanisms may also contribute to the phenotype of biotin deficiency Sander and coworkers initially suggested that the CNS effects of biotinidase deficiency (and, by implication, biotin deficiency) might be mediated through deficiency of PC and the attendant CNS lactic acidosis As brain PC activity declined more slowly than hepatic PC activity during progressive biotin deficiency in the rat, these investigators discounted this mechanism However, subsequent studies suggest their original hypothesis is correct Diamantopoulos et al [110] expanded the hypothesis by proposing that deficiency of brain biotinidase (which is already quite low in the normal brain) [111] combined with biotin deficiency leads to a deficiency of brain pyruvate carboxylase and, in turn, to CNS accumulation of lactic acid This CNS lactic acidosis is postulated to be the primary mediator of the hypotonia, seizures, ataxia, and delayed development seen in biotinidase deficiency Additional support for the CNS lactic acidosis hypothesis has come from direct measurements of CSF lactic acid in children with either biotinidase deficiency or isolated pyruvate carboxylase deficiency and from the rapid resolution of lactic acidemia and CNS abnormalities in patients who have developed biotin deficiency during parental nutrition [39] The work of Suchy and coworkers has provided evidence against an etiologic role for disturbances in brain fatty acid composition in the CNS dysfunction [103,112] Several studies have demonstrated abnormalities in metabolism of fatty acids in biotin deficiency and have suggested that these abnormalities are important in the pathogenesis of the skin rash and hair loss The cutaneous manifestations of biotin deficiency and essential fatty acid deficiency are similar but not identical and the pathogenesis likely involves impaired lipid synthesis For example, Munnich et al [113] described a 12 year old boy with multiple carboxylase deficiency; in retrospect, the enzymatic defect was almost certainly biotinidase deficiency [114] The child presented with alopecia and periorificial scaly dermatitis Oral administration of ‘‘unsaturated fatty acids composed of 11% C18:1, 71% C18:2, 8% C18:3, and 0.3% C20:4’’ at a rate of ‘‘2–400 mg=day’’ plus twice daily topical administration of the same mixture of fatty acids ‘‘resulted in dramatic improvement of the dermatologic condition’’ and hair growth Lactic acidosis and organic aciduria remained the same Three studies in the rat support the possibility of abnormal polyunsaturated fatty acid (PUFA) metabolism as a cause of the cutaneous manifestations of biotin deficiency Kramer et al [102] and Mock et al [104] have reported significant abnormalities in the n-6 phospholipids of blood, liver, and heart Watkins and Kratzer also found abnormalities of n-6 phospholipids in liver and heart of biotin-deficient chicks [115] Several investigators have speculated [103–109,111,114,116,117] that these abnormalities in PUFA composition might result in abnormal composition or metabolism of the prostaglandins and related substances derived from these PUFAs However, these studies did not directly address the ß 2006 by Taylor & Francis Group, LLC question of an etiologic role To address that question, Mock [118] examined the effect of supplementation of the n-6 PUFA (as intralipid) on the cutaneous manifestations of biotin deficiency in a nutrient interaction experiment Supplementation of n-6 PUFA prevented the development of the cutaneous manifestations of biotin deficiency in a group of rats that were as biotin deficient (based on biochemical measurements) as the biotin-deficient control group The rats not receiving the supplemental n-6 fatty acids did develop the classic rash and hair loss This study provides evidence that an abnormality in n-6 PUFA metabolism plays a pathogenic role in the cutaneous manifestations of biotin deficiency and that the effect of the n-6 PUFA cannot be attributed to biotin sparing OTHER EFFECTS OF DEFICIENCY Subclinical biotin deficiency has been shown to be teratogenic in several species including chicken, turkey, mouse, rat, and hamster [39] Fetuses of mouse dams with degrees of biotin deficiency too mild to produce the characteristic cutaneous or CNS findings developed micrognathia, cleft palate, and micromelia [119–123] The incidence of malformation increased with the degree of biotin deficiency to a maximum incidence of ~90% Differences in teratogenic susceptibility among rodent species have been reported; a corresponding difference in biotin transport from the mother to the fetus has been proposed as the cause [124] Bain et al have hypothesized that biotin deficiency affects bone growth by affecting synthesis of prostaglandins from n-6 fatty acid [125] This effect on bone growth might be the mechanism for the skeletal malformations caused by biotin deficiency On the basis of studies of cultured lymphocytes in vitro and of rats and mice in vivo, biotin is required for normal function of a variety of immunological cells These functions include production of antibodies, immunological reactivity, protection against sepsis, macrophage function, differentiation of T and B lymphocytes, afferent immune response, and cytotoxic T-cell response [126–131] However, in rats in which only moderate biotin deficiency was induced, immune function was not strikingly impaired Specifically, neither phenotype nor organ redistribution of lymphocytes occurred, and mitogen T-cell proliferation, mitogen-induced interferon-g, and interleukin-4, and IgG antibody responses and natural killer cell activity were not affected by moderate biotin deficiency [123] In humans, Okabe et al [132] have reported that patients with Crohn’s disease have depressed natural killer activity caused by biotin deficiency and are responsive to biotin supplementation In patients with biotinidase deficiency, Cowan et al [133] have demonstrated defects in both T-cell and B-cell immunity However, supplementation of 750 mg of biotin per day for 14 days in normal subjects actually caused a significant decrease in peripheral blood monocyte proliferation as well as release of interleukin-1b and interleukin-2 [122] Evidence is accumulating that biotin has stimulatory effects on genes whose actions favor lowering blood glucose concentrations; these include insulin, insulin receptor, and both pancreatic and hepatic glucokinase Biotin also decreases expression of hepatic phosphoenolpyruvate carboxykinase, a key enzyme in gluconeogenesis by the liver Thus, the net effect observed from biotin in whole animal and cell culture studies favors hypoglycemia These observations are in accord with studies detecting impaired glucose tolerance and decreased glucose utilization in biotin-deficient rats Recently, pharmacologic amounts of biotin have been reported to lower postprandial glucose concentrations and improve tolerance to glucose in genetically diabetic mice strains and in individuals with Type I and Type II diabetes In a similar fashion, older studies indicating that biotin deficiency interferes with lipid metabolism and pharmacologic biotin therapy improves hyperglycemia have been confirmed in recent studies in individuals with hypertriglyceridemia This topic is the subject of an excellent recent review by Fernandez-Mejia [134] ß 2006 by Taylor & Francis Group, LLC DIAGNOSIS OF BIOTIN DEFICIENCY The diagnosis of biotin deficiency has been established by demonstrating reduced PCC activity in peripheral blood lymphocytes [135,136], reduced urinary excretion of biotin [44,45], increased urinary excretion of the characteristic organic acids discussed earlier [45,99], and resolution of the signs and symptoms of deficiency in response to biotin supplementation Plasma and serum levels of biotin, whether measured by bioassay or avidin-binding assay, have not uniformly reflected biotin deficiency [44,85,100] The clinical response to administration of biotin has been dramatic in all well-documented cases of biotin deficiency Within a few weeks, healing of the rash has been striking, and growth of healthy hair was generally present after 1–2 months of biotin supplementation In infants, hypotonia, lethargy, and depression generally resolved within 1–2 weeks of biotin supplementation; accelerated mental and motor development followed REQUIREMENTS AND ALLOWANCES Data providing an accurate estimate of the biotin requirement for infants, children, and adults are lacking [137]; as a result, recommendations often conflict among countries [39] Data providing an accurate estimate of the requirement for biotin administered parenterally are also lacking For parenteral administration, uncertainty about the true metabolic requirement for biotin is compounded by lack of information concerning the effects of infusing biotin systemically and continuously (rather than the usual postprandial absorption into intestinal portal blood) Despite these limitations, recommendations for biotin supplementation have been formulated for oral and parenteral intake from preterm infants through adults [137–139] These recommendations are given in Table 11.1 One published study describes infants parenterally supplemented [140]; normal plasma levels of biotin were detected in term infants supplemented at 20 mg=day and increased plasma levels of biotin were detected in preterm infants supplemented at 13 mg=day (note that the units for plasma biotin should be picogram per milliliter in this publication [140]) TABLE 11.1 Recommended Intake of Biotin Age Preterm infants Infants up to months Infants 7–12 months Children 1–3 years Children 4–8 years Children 9–13 years Children 14–18 years Adults Pregnancy Lactation Safe and Adequate Daily Oral Intakes (mg) Daily Parenteral Intakes (mg) 5 12 20 25 30 30 35 5–8 mg kgÀ1 20 20 20 20 20 20 60 — — Sources: National Research Council in Recommended Dietary Allowances, 11th ed., Food and Nutrition Board Institute of Medicine National Academy Press, Washington, DC, 1998, 374–389; Greene, H.L., Hambridge, K.M., Schanler, R., and Tsang, R.C., Am J Clin Nutr., 48, 1324, 1988; Greene, H.L and Smidt, L.J in Nutritional Needs of the Preterm Infant, Tsang, R.C., Lucas, A., Uauy, R., and Zlotkin, S., eds., Williams & Wilkins, Baltimore, MD, 1993, 121–133 ß 2006 by Taylor & Francis Group, LLC An important factor in the current uncertainty concerning the biotin requirement is the possibility that biotin synthesized by intestinal bacteria may contribute significantly to absorbed biotin If so, the required intake would be reduced and might be dependent on factors that influence the density and species distribution of intestinal flora Unfortunately, few data are available for assessing the actual magnitude of the absorbed microbial biotin DIETARY SOURCES OF BIOTIN There is no published evidence that biotin can be synthesized by mammals; thus, the higher animals must derive biotin from other sources The ultimate source of biotin appears to be de novo synthesis by bacteria, primitive eukaryotic organisms such as yeast, molds, and algae, and some plant species Most measurements of the biotin content of various foods have used bioassays [141–145] Recent publications [12,146] provide evidence that the values are likely to contain substantial errors However, some worthwhile generalizations can still be made Biotin is widely distributed in natural foodstuffs, but the absolute content of even the richest sources is low when compared with the content of most other water-soluble vitamins Foods relatively rich in biotin include egg yolk, liver, nuts, legumes, and some vegetables [12,146] The average daily dietary biotin intake has been estimated to be ~35–70 mg using a microbial assay [141,147–149] PHARMACOLOGY AND TOXICITY TREATMENT OF BIOTIN DEFICIENCY Pharmacologic doses of biotin (e.g., 1–20 mg) have been used to treat most patients with biotin deficiency and biotin-related inborn errors For two patients, parenteral administration of physiologic amounts of biotin (100 mg=day) was adequate to cause resolution of the signs and symptoms of biotin deficiency and to prevent their recurrence [39] However, abnormal organic aciduria persisted for at least 10 weeks in one patient receiving 100 mg=day, suggesting that this dose may not have been adequate to restore tissue biotin levels to normal over that time In pregnant women with increased 3-hydroxyisovaleric acid excretion treatment with 300 mg of biotin for weeks resulted in decreased 3-hydroxyisovaleric acid excretion in every woman, but 3-hydroxyisovaleric acid excretion did not return to normal in of 13 women Likely, this organic aciduria indicates that biotin status at the tissue level was not restored entirely to normal Whether this degree of deficiency is sufficient to cause significant, subtle morbidity is currently not known TOXICITY Daily doses up to 200 mg orally and up to 10–20 mg intravenously for over months have been given to treat biotin-responsive inborn errors of metabolism and acquired biotin deficiency; toxicity has not been reported [14] PHARMACOLOGY Mounting reports of biotin deficiency in commercial animals and humans have led to several studies of plasma levels, pharmacokinetics, and bioavailability after acute or chronic oral, intramuscular, or intravenous administration of biotin in cattle [150], swine [151,152], and human subjects [19,153,154] ß 2006 by Taylor & Francis Group, LLC Doses greater than 300 mg result in high biotin concentrations in blood and the urinary excretion of a large proportion as the unchanged vitamin [153–155] Increased blood concentrations of bisnorbiotin and biotin sulfoxide [155] and urine excretion rates [156] of bisnorbiotin and biotin sulfoxide are also observed These observations are consistent with the metabolites originating from human tissues rather than enteric bacteria ACKNOWLEDGMENTS With appreciation to Maribeth Mock, Nell Matthews Mock, and Cindy Henrich for graphic and processing support REFERENCES Green, N.M., Avidin and streptavidin, in Methods in Enzymology, Wilchek, M and Bayer, E., eds., Academic Press, New York, 1990, Vol 186, pp 51–67 Bhatia, D., Borenstein, B., Gaby, S., Gordon, H., Iannarone, A., Johnson, L., Machlin, L.J., Mergens, W., Scheiner, J., Scott, J., and Waysek, E., Vitamins, Part XIII: Biotin, in Encyclopedia of Food Science and Technology, Hui, Y.U., ed., John Wiley & Sons, New York, 1992, pp 2764–2770 Bonjour, J.-P., Biotin, in Handbook of Vitamins, 2nd ed., Machlin, L.J., ed., Marcel Dekker, New York, 1991, pp 393–427 Sternbach, L.H., Biotin, in Comprehensive Biochemistry, Florkin, M and Stotz, E.G., eds., Elsevier, New York, 1963, pp 66–81 Miljkovic, D., Velimirovic, S., Csanadi, J., and Popsavin, V., Studies directed towards stereospecific synthesis of oxybiotin, biotin, and their analogs Preparation of some new 2,5,anhydro-xylitol derivatives, J Carbohydr Chem., 8, 457–467, 1989 Deroose, F.D and DeClercq, P.J., Novel enantioselective syntheses of (þ)-biotin, J Org Chem., 60, 321–330, 1995 Lampen, J.O., Bahler, G.P., and Peterson, W.H., The occurrence of free and bound biotin, J Nutr., 23, 11–21, 1942 Combs, G.F., Biotin, in The Vitamins: Fundamental Aspects in Nutrition and Health, Academic Press, San Diego, 1992, pp 329–343 Frigg, M., Bio-availability of biotin in cereals, Poult Sci., 55, 2310–2318, 1976 10 Mock, D.M and Malik, M.I., Distribution of biotin in human plasma: Most of the biotin is not bound to protein, Am J Clin Nutr., 56, 427–432, 1992 11 Mock, D.M and Lankford, G., Studies of the reversible binding of biotin to human plasma, J Nutr., 120, 375–381, 1990 12 Staggs, C.G., Sealey, W.M., McCabe, B.J., and Mock, D.M., Determination of the biotin content of select foods using accurate and sensitive HPLC=avidin binding, J Food Composit Anal., 17, 767–776, 2004 13 Wolf, B., Heard, G., McVoy, J.R.S., and Raetz, H.M., Biotinidase deficiency: The possible role of biotinidase in the processing of dietary protein-bound biotin, J Inherit Metab Dis., (Suppl 2), 121–122, 1984 14 Wolf, B., Disorders of biotin metabolism, in The Metabolic and Molecular Basis of Inherited Disease, 8th ed., Scriver, C.R., Beaudet, A.L., Sly, W.S., and Valle, D., eds., McGraw-Hill, New York, 2001, pp 3151–3177 15 Said, H.M., Thuy, L.P., Sweetman, L., and Schatzman, B., Transport of the biotin dietary derivative biocytin (N-biotinyl-L-lysine) in rat small intestine, Gastroenterology, 104, 75–80, 1993 16 Said, H.M., Recent advances in carrier-mediated intestinal absorption of water-soluble vitamins, Annu Rev Physiol., 66 (January), 419–446, 2004 17 Bowman, B.B., McCormick, D.B., and Rosenberg, I.H., Epithelial transport of water-soluble vitamins, Ann Rev Nutr., 9, 187–199, 1989 18 McCormick, D.B and Zhang, Z., Cellular assimilation of water-soluble vitamins in the mammal: Riboflavin, B6, biotin, and C, Proc Soc Exp Biol Med., 202, 265–270, 1993 ß 2006 by Taylor & Francis Group, LLC 19 Zempleni, J and Mock, D.M., Bioavailability of biotin given orally to humans in pharmacologic doses, Am J Clin Nutr., 69, 504–508, 1999 20 Chauhan, J and Dakshinamurti, K., Role of human serum biotinidase as biotin-binding protein, Biochem J., 256, 265–270, 1988 21 Wolf, B., Biotinidase: Its role in biotinidase deficiency and biotin metabolism, J Nutr Biochem., 16 (7), 441–445, 2005 22 Nagamine, T., Takehara, K., Fukui, T., and Mori, M., Clinical evaluation of biotin-binding immunoglobulin in patients with Graves’ disease, Clin Chim Acta, 226 (1), 47–54, 1994 23 Cohen, N.D and Thomas, M., Biotin transport into fully differentiated 3T3-L1 cells, Biochem Biophys Res Commun., 108 (4), 1508–1516, 1982 24 Boumendil-Podevin, E.F and Podevin, R.A., Nicotinic acid transport by brush border membrane vesicles from rabbit kidney, Am J Physiol Renal Fluid Electrolyte Physiol., 240, F185–F191, 1989 25 Said, H.M., Korchid, S., and Horne, D.W., Transport of biotin in basolateral membrane vesicles of rat liver, Am J Physiol., 259, G865–G872, 1990 26 Said, H.M., Hoefs, J., Mohammadkhani, R., and Horne, D., Biotin transport in human liver basolateral membrane vesicles: A carrier-mediated, Naþ gradient-dependent process, Gastroenterology, 10, 2120–2125, 1992 27 Said, H.M., Ma, T.Y., and Kamanna, V.S., Uptake of biotin by human hepatoma cell line, Hep G(2): A carrier-mediated process similar to that of normal liver, J Cell Physiol., 161 (3), 483–489, 1994 28 Balamurugan, K., Ortiz, A., and Said, H.M., Biotin uptake by human intestinal and liver epithelial cells: Role of the SMVT system, Am J Physiol Gastrointest Liver Physiol., 285 (1), G73–G77, 2003 29 Weiner, D and Wolf, B., Biotin uptake, utilization, and efflux in normal and biotin-deficient rat hepatocytes, Biochem Med Metab Biol., 46, 344–363, 1991 30 Said, H.M., McAlister-Henn, L., Mohammadkhani, R., and Horne, D.W., Uptake of biotin by isolated rat liver mitochondria, Am J Physiol., 263, G81–G86, 1992 31 Zempleni, J., Green, G.M., Spannagel, A.U., and Mock, D.M., Biliary excretion of biotin and biotin metabolites is quantitatively minor in rats and pigs, J Nutr., 127, 1496–1500, 1997 32 Spector, R and Mock, D.M., Biotin transport through the blood–brain barrier, J Neurochem., 48, 400–404, 1987 33 Spector, R and Mock, D.M., Biotin transport and metabolism in the central nervous system, Neurochem Res., 13 (3), 213–219, 1988 34 Ozand, P.T., Gascon, G.G., Al Essa, M., Joshi, S., Al Jishi, E., Bakheet, S., Al Watban, J., Al-Kawi, M.Z., and Dabbagh, O., Biotin-responsive basal ganglia disease: A novel entity, Brain, 121, 1267–1279, 1999 35 Zeng, W., Al-Yamani, E., Acierno, J., Slaugenhaupt, S., Gillis, T., Macdonald, M., Ozand, P., and Gusella, J., Biotin-responsive basal ganglia disease maps to 2q36.3 and is due to mutations in SLC19A3., Am J Hum Genet., 77 (1), 16–26, 2005 36 Vlasova, T.I and Mock, D.M., Biotin deficiency reduces expression of SLC19A3, a potential biotin transporter, and decreases expression of several biotin-related genes in the peripheral blood mononuclear cells (PBMC) of normal humans, in Experimental Biology, 2004, Washington, DC, FASEB, select.biosis.org=faseb=eb2004_data=FASEB009278.html, 2004 37 Vlasova, T.I., Stratton, S.L., Wells, A.M., Mock, N.I., and Mock, D.M., Biotin deficiency reduces expression of SLC19A3, a potential biotin transporter, in leukocytes from human blood, J Nutr., 135 (1), 42–47, 2005 38 Mardach, R., Zempleni, J., Wolf, B., Cress, S., Boylan, J., Roth, S., Cederbaum, S., and Mock, D., Biotin dependency due to a defect in biotin transport, J Clin Invest., 109 (12), 1617–1623, 2002 39 Mock, D.M., Biotin, in Present Knowledge in Nutrition, 6th ed., Brown, M., ed., International Life Sciences Institute—Nutrition Foundation, Blacksburg, VA, 1990, pp 189–207 40 Livaniou, E., Nyalala, J., Anagnostouli, M., Papageorgiou, C., Evangelatos, G., and Ithakissios, D., Determination of biotin levels in cerebrospinal fluid samples, J Pharm Biomed Anal., 21 (4), 875–879, 1999 41 Baumgartner, E.R., Suormala, T., and Wick, H., Biotinidase deficiency associated with renal loss of biocytin and biotin, J Inherit Metab Dis., (Suppl 2), 123–125, 1985 42 Baur, B and Baumgartner, E.R., Na(þ)-dependent biotin transport into brush-border membrane vesicles from human kidney cortex, Pflugers Archiv: Eur J Physiol., 422, 499–505, 1993 ß 2006 by Taylor & Francis Group, LLC 43 Chatterjee, N.S., Kumar, C.K., Ortiz, A., Rubin, S., and Said, H.M., Molecular mechanism of the intestinal biotin transport process, Am J Physiol., 277 (Cell Physiol., 46), C605–C613, 1999 44 Mock, N.I., Malik, M.I., Stumbo, P.J., Bishop, W.P., and Mock, D.M., Increased urinary excretion of 3-hydroxyisovaleric acid and decreased urinary excretion of biotin are sensitive early indicators of decreased status in experimental biotin deficiency, Am J Clin Nutr., 65, 951–958, 1997 45 Mock, D.M., Henrich, C.L., Carnell, N., and Mock, N.I., Indicators of marginal biotin deficiency and repletion in humans: Validation of 3-hydroxyisovaleric acid excretion and a leucine challenge, Am J Clin Nutr., 76, 1061–1068, 2002 46 Baumgartner, E.R., Suormala, T., and Wick, H., Biotinidase deficiency: Factors responsible for the increased biotin requirement, J Inherit Metab Dis., (Suppl 1), 59–64, 1985 47 Baumgartner, E.R., Suormala, T., and Wick, H., Biotin-responsive multiple carboxylase deficiency (MCD): Deficient biotinidase activity associated with renal loss of biotin, J Inherit Metab Dis., (Suppl 1), 59–64, 1985 48 Karl, P.I and Fisher, S.E., Biotin transport in microvillous membrane vesicles, cultured trophoblasts and the isolated perfused cotyledon of the human placenta, Am J Physiol., 262, C302–C308, 1992 49 Schenker, S., Hu, Z., Johnson, R.F., Yang, Y., Frosto, T., Elliott, B.D., Henderson, G.I., and Mock, D.M., Human placental biotin transport: Normal characteristics and effect of ethanol, Alcohol Clin Exp Res., 17 (3), 566–575, 1993 50 Hu, Z.-Q., Henderson, G.I., Mock, D.M., and Schenker, S., Biotin uptake by basolateral membrane of human placenta: Normal characteristics and role of ethanol, Proc Soc Biol Exp Med., 206 (4), 404–408, 1994 51 Prasad, P.D., Ramamoorthy, S., Leibach, F.H., and Ganapathy, V., Characterization of a sodiumdependent vitamin transporter mediating the uptake of pantothenate, biotin and lipoate in human placental choriocarcinoma cells, Placenta, 18, 527–533, 1997 52 Wang, H., Huang, W., Fei, Y.J., Xia, H., Fang-Yeng, T.L., Leibach, F.H., Devoe, L.D., Ganapathy, V., and Prasad, P.D., Human placental Naþ-dependent multivitamin transporter, J Biol Chem., 274, 14875–14883, 1999 53 Crisp, S., Griffin, J., White, B., Toombs, C., Camporeale, G., Said, H.M., and Zempleni, J., Biotin supply affects rates of cell proliferation, biotinylation of carboxylases and histones, and expression of the gene encoding the sodium-dependent multivitamin transporter in JAr choriocarcinoma cells, Eur J Nutr., 43 (1), 23–31, 2004 54 Mock, D.M., Mock, N.I., and Langbehn, S.E., Biotin in human milk: Methods, location, and chemical form, J Nutr., 122, 535–545, 1992 55 Mock, D.M., Mock, N.I., and Dankle, J.A., Secretory patterns of biotin in human milk, J Nutr., 122, 546–552, 1992 56 Mock, D.M., Stratton, S.L., and Mock, N.I., Concentrations of biotin metabolites in human milk, J Pediatr., 131 (3), 456–458, 1997 57 McMahon, R.J., Biotin in metabolism and molecular biology, Annu Rev Nutr., 22, 221–239, 2002 58 Mock, D., Biotin: Physiology, dietary sources and requirements, in Encyclopedia of Human Nutrition, 2nd ed., Caballero, B., Allen, L., and Prentice, A., eds., Academic Press, London, 2004 59 Browner, M.F., Taroni, F., Sztul, E., and Rosenberg, L.B., Sequence analysis, biogenesis, and mitochondrial import of the alpha-subunit of rat liver propionyl-CoA carboxylase, J Biol Chem., 264, 12680–12685, 1989 60 Chapman-Smith, A and Cronan, J., The enzymatic biotinylation of proteins: A post-translational modification of exceptional specificity, Trends Biochem Sci., 24 (9), 359–363, 1999 61 Cronan, J.E., Jr., The E coli bio operon: Transcriptional repression by an essential protein modification enzyme, Cell, 58, 427–429, 1989 62 Xu, Y and Beckett, D., Kinetics of biotinyl-50 -adenylate synthesis catalyzed by the Escherichia coli repressor of biotin biosynthesis and the stability of the enzyme-product complex, Biochemistry, 33, 7354–7360, 1994 63 Beckett, D., The Escherichia coli biotin regulatory system: A transcriptional switch, J Nutr Biochem., 16 (7), 411–415, 2005 ß 2006 by Taylor & Francis Group, LLC 64 Suzuki, Y., Aoki, Y., Ishida, Y., Chiba, Y., Iwamatsu, A., Kishino, T., Niikawa, N., Matsubara, Y., and Narisawa, K., Isolation and characterization of mutations in the human holocarboxylase synthetase cDNA, Nat Genet., (2), 122–128, 1994 65 Leon-Del-Rio, A., Leclerc, D., Akerman, B., Wakamatsu, N., and Gravel, R., Isolation of a cDNA encoding human holocarboxylase synthetase by functional complementation of a biotin auxotroph of Escherichia coli, Proc Natl Acad Sci., USA, 92 (10), 4626–4630, 1995 66 Campeau, E and Gravel, R.A., Expression in Escherichia coli of N- and C-terminally deleted human holocarboxylase synthetase Influence of the N-terminus on biotinylation and identification of a minimum functional protein, J Biol Chem., 276 (15), 12310–12316, 2001 67 Yang, X., Aoki, Y., Li, X., Sakamoto, O., Hiratsuka, M., Kure, S., Taheri, S., Christensen, E., Inui, K., Kubota, M., Ohira, M., Ohki, M., Kudoh, J., Kawasaki, K., Shibuya, K., Shintani, A., Asakawa, S., Minoshima, S., Shimizu, N., Narisawa, K., Matsubara, Y., and Suzuki, Y., Structure of human holocarboxylase synthetase gene and mutation spectrum of holocarboxylase synthetase deficiency, Hum Genet., 109 (5), 526–534, 2001 68 Gravel, R and Narang, M., Molecular genetics of biotin metabolism: Old vitamin, new science, J Nutr Biochem., 16 (7), 428–431, 2005 69 Ballard, T., Wolff, J., Griffin, J., Stanley, J., van Calcar, S., and Zempleni, J., Biotinidase catalyzes debiotinylation of histones, Eur J Nutr., 41 (2), 78–84, 2002 70 Stanley, C., Hymes, J., and Wolf, B., Identification of alternatively spliced human biotinidase mRNAs and putative localization of endogenous biotinidase, Mol Genet Metab., 81 (4), 300–312, 2004 71 Narang, M.A., Dumas, R., Ayer, L.M., and Gravel, R.A., Reduced histone biotinylation in multiple carboxylase deficiency patients: A nuclear role for holocarboxylase synthetase, Hum Mol Genet., 13 (1), 15–23, 2004 72 Wolf, B., Heard, G.S., McVoy, J.R.S., and Grier, R.E., Biotinidase deficiency, Ann N.Y Acad Sci., 447, 252–262, 1985 73 Mock, D.M., Delorimer, A.A., Liebman, W.M., Sweetman, L., and Baker, H., Biotin deficiency complicating parenteral alimentation, in Biotin, Dakshinamurti, K and Bhagavan, H., eds., New York Academy of Science, New York, 1985, pp 314–334 74 Mock, D.M., Quirk, J.G., and Mock, N.I., Marginal biotin deficiency during normal pregnancy, Am J Clin Nutr., 75, 295–299, 2002 75 Mock, D.M and Dyken, M.E., Biotin catabolism is accelerated in adults receiving long-term therapy with anticonvulsants, Neurology, 49 (5), 1444–1447, 1997 76 Fujimoto, W., Inaoki, M., Fukui, T., Inoue, Y., and Kuhara, T., Biotin deficiency in an infant fed with amino acid formula, J Dermatol., 32 (4), 256–261, 2005 77 Velazquez, A., Martin-del-Campo, C., Baez, A., Zamudio, S., Quiterio, M., Aguilar, J.L., PerezOrtiz, B., Sanchez-Ardines, M., Guzman-Hernandez, J., and Casanueva, E., Biotin deficiency in protein-energy malnutrition, Eur J Clin Nutr., 43, 169–173, 1988 78 Velazquez, A., Teran, M., Baez, A., Gutierrez, J., and Rodriguez, R., Biotin supplementation affects lymphocyte carboxylases and plasma biotin in severe protein-energy malnutrition, Am J Clin Nutr., 61, 385–391, 1995 79 Krause, K.-H., Berlit, P., and Bonjour, J.-P., Impaired biotin status in anticonvulsant therapy, Ann Neurol., 12, 485–486, 1982 80 Krause, K.-H., Berlit, P., and Bonjour, J.-P., Vitamin status in patients on chronic anticonvulsant therapy, Int J Vitam Nutr Res., 52 (4), 375–385, 1982 81 Krause, K.-H., Kochen, W., Berlit, P., and Bonjour, J.-P., Excretion of organic acids associated with biotin deficiency in chronic anticonvulsant therapy, Int J Vitam Nutr Res., 54, 217–222, 1984 82 Mock, D.M., Mock, N.I., Lombard, K.A., and Nelson, R.P., Disturbances in biotin metabolism in children undergoing long-term anticonvulsant therapy, J Pediatr Gastroenterol Nutr., 26 (3), 245–250, 1998 83 Said, H.M., Mock, D.M., and Collins, J.C., Regulation of biotin intestinal transport in the rat: Effect of biotin deficiency and supplementation, Am J Physiol., 256 (2 Pt 1), G306–G311, 1989 84 Said, H.M., Redha, R., and Nylander, W., Biotin transport and anticonvulsant drugs, Am J Clin Nutr., 49, 127–131, 1989 85 Mock, D.M., Stadler, D.D., Stratton, S.L., and Mock, N.I., Biotin status assessed longitudinally in pregnant women, J Nutr., 127 (5), 710–716, 1997 ß 2006 by Taylor & Francis Group, LLC 86 Mock, N.I., Evans, T.T., and Mock, D.M., Biotin supplementation during pregnancy reverses depleted biotin status as assessed by excretion of urinary 3-hydroxyisovaleric acid (3HIA), FASEB J., 13 (5), A923, 1999 87 Mock, D.M., Mock, N.I., Stewart, C.W., LaBorde, J.B., and Hansen, D.K., Marginal biotin deficiency is teratogenic in ICR mice, J Nutr., 133, 2519–2525, 2003 88 Zempleni, J and Mock, D.M., Marginal biotin deficiency is teratogenic, Proc Soc Exp Biol Med., 223 (1), 14–21, 2000 89 Sydenstricker, V.P., Singal, S.A., Briggs, A.P., DeVaughn, N.M., and Isbell, H., Observations on the ‘egg white injury’ in man, JAMA, 118, 1199–1200, 1942 90 Mock, D.M., Water-soluble vitamin supplementation and the importance of biotin, in Textbook on Total Parenteral Nutrition in Children: Indications, Complications, and Pathophysiological Considerations, Lebenthal, E., ed., Raven Press, New York, 1986, pp 89–108 91 Przyjazny, A., Hentz, N.G., and Bachass, L.G., Sensitive and selective liquid chromatographic postcolumn reaction detection system for biotin and biocytin using a homogeneous fluorophorelinked assay, J Chromatogr., 654, 79–86, 1993 92 Stein, J., Hahn, A., Lembcke, B., and Rehner, G., High-performance liquid chromatographic determination of biotin in biological materials after crown ether-catalyzed fluorescence derivatization with panacyl bromide, Anal Biochem., 200, 89–94, 1992 93 Lahely, S., Ndaw, S., Arella, F., and Hasselmann, C., Determination of biotin in foods by highperformance liquid chromatography with post-column derivatization and fluorimetric detection, Food Chem., 65, 253–258, 1999 94 Sugawara, K., Tanaka, S., and Nakamura, H., Electrochemical determination of avidin–biotin binding using an electroactive biotin derivative as a marker, Bioelectrochem Bioenerg., 33, 205–207, 1994 95 Terouanne, B., Bencheich, M., Balaguer, P., Boussioux, A.M., and Nicolas, J.C., Bioluminescent assays using glucose-6-phosphate dehydrogenase: Application to biotin and streptavidin detection, Anal Biochem., 180, 43–49, 1989 96 Thuy, L.P., Sweetman, L., and Nyhan, W.L., A new immunochemical assay for biotin, Clin Chim Acta, 202 (3), 191–198, 1991 97 Mock, N.I., Evans, T., and Mock, D.M., Urinary 3-hydroxypropionic acid is not an early indicator of biotin deficiency, FASEB J., 12, A247, 1998 98 Stratton, S.L., Bogusiewicz, A., Mock, M.M., Mock, N.I., Wells, A.M., and Mock, D.M., Lymphocyte propionyl-CoA Carboxylase and its activation by biotin are sensitive indicators of marginal biotin deficiency in humans, Am J Clin Nutr., 84, 384–388, 2006 99 Mock, D.M., Henrich-Shell, C.L., Carnell, N., Stumbo, P., and Mock, N.I., 3-hydroxypropionic acid and methylcitric acid are not reliable indicators of marginal biotin deficiency, J Nutr., 134, 317–320, 2004 100 Bonjour, J.-P., Biotin in human nutrition, in Biotin, Dakshinamurti, K and Bhagavan, H., eds., New York Academy of Sciences, New York, 1985, pp 97–104 101 Livaniou, E., Mantagos, S., Kakabakos, S., Pavlou, V., Evangelatos, G., and Ithakissios, D.S., Plasma biotin levels in neonates, Biol Neonate, 59, 209–212, 1991 102 Kramer, T.R., Briske-Anderson, M., Johnson, S.B., and Holman, R.T., Effects of biotin deficiency on polyunsaturated fatty acid metabolism in rats, J Nutr., 114, 2047–2052, 1984 103 Suchy, S.F., Rizzo, W.B., and Wolf, B., Effect of biotin deficiency and supplementation on lipid metabolism in rats: Saturated fatty acids, Am J Clin Nutr., 44, 475–480, 1986 104 Mock, D.M., Mock, N.I., Johnson, S.B., and Holman, R.T., Effects of biotin deficiency on plasma and tissue fatty acid composition: Evidence for abnormalities in rats, Pediatr Res., 24 (3), 396–403, 1988 105 Watkins, B.A and Kratzer, F.H., Tissue lipid fatty acid composition of biotin-adequate and biotin-deficient chicks, Poult Sci., 66, 306–313, 1987 106 Mock, D.M., Johnson, S.B., and Holman, R.T., Effects of biotin deficiency on serum fatty acid composition: Evidence for abnormalities in humans, J Nutr., 118, 342–348, 1988 107 Wendel, U., Baumgartner, R., van der Meer, S.B., and Spaapen, L.J.M., Accumulation of oddnumbered long-chain fatty acids in fetuses and neonates with inherited disorders of propionate metabolism, Pediatr Res., 29 (4), 403–405, 1991 ß 2006 by Taylor & Francis Group, LLC 108 Kishimoto, Y., Williams, M., Moser, H.W., Hignite, C., and Biemann, K., Branched-chain and odd-numbered fatty acids and aldehydes in the nervous system of a patient with deranged vitamin B12 metabolism, J Lipid Res., 14, 69–77, 1973 109 Fenton, W and Rosenberg, L.E., Disorders of propionate and methylmalonate metabolism, in The Metabolic and Molecular Bases of Inherited Disease, Scriver, C.R., Beaudet, A.L., Sly, W.S., and Valle, D., eds., McGraw-Hill, New York, 1995, pp 1423–1449 110 Diamantopoulos, N., Painter, M.J., Wolf, B., Heard, G.S., and Roe, C., Biotinidase deficiency: Accumulation of lactate in the brain and response to physiologic doses of biotin, Neurology, 36, 1107–1109, 1986 111 Suchy, S.F., McVoy, J.R.S., and Wolf, B., Neurologic symptoms of biotinidase deficiency: Possible explanation, Neurology, 35, 1510–1511, 1985 112 Suchy, S.F., Brown, S.B., Goodman, S.I., and Wolf, B., Diagnosis of biotin deficiency prior to the appearance of cutaneous symptoms, Pediatr Res., 16, 179A, 1982 113 Munnich, A., Saudubray, J.M., Coude, F.K., Charpentier, C., Saurat, J.H., and Frezal, J., Fatty-acidresponsive alopecia in multiple carboxylase deficiency, Lancet, (8177), 1080–1081, 1980 114 Wolf, B., Grier, R.E., Allen, R.J., Goodman, S.I., and Kien, C.L., Biotinidase deficiency: An enzymatic defect in late-onset multiple carboxylase deficiency, Clin Chim Acta, 131, 273–281, 1983 115 Watkins, B.A and Kratzer, F.H., Effect of oral dosing of lactobacillus strains on gut colonization and liver biotin in broiler chicks, Poult Sci., 62, 2088–2094, 1983 116 Marshall, M.W., The nutritional importance of biotin an update, Nutr Today, 22 (6), 26–30, 1987 117 Watkins, B.A and Kratzer, F.H., Dietary biotin effects on polyunsaturated fatty acids in chick tissue lipids and prostaglandin E2 levels in freeze-clamped hearts, Poult Sci., 66, 1818–1828, 1987 118 Mock, D.M., Evidence for a pathogenic role of v6 polyunsaturated fatty acid in the cutaneous manifestations of biotin deficiency, J Pediatr Gastroenterol Nutr., 10, 222–229, 1990 119 Watanabe, T and Endo, A., Teratogenic effects of maternal biotin deficiency in mouse embryos examined at midgestation, Teratology, 42, 295–300, 1990 120 Watanabe, T., Dietary biotin deficiency affects reproductive function and prenatal development in hamsters, J Nutr., 123 (12), 2101–2108, 1993 121 Watanabe, T., Dakshinamurti, K., and Persaud, T.V.N., Biotin influences palatal development of mouse embryos in organ culture, J Nutr., 125, 2114–2121, 1995 122 Zempleni, J., Helm, R.M., and Mock, D.M., In vivo biotin supplementation at a pharmacologic dose decreases proliferation rates of human peripheral blood mononuclear cells and cytokine release, J Nutr., 131 (5), 1479–1484, 2001 123 Helm, R.M., Mock, N.I., Simpson, P., and Mock, D.M., Certain immune markers are not good indicators of mild to moderate biotin deficiency in rats, J Nutr., 132, 3231–3236, 2001 124 Watanabe, T and Endo, A., Species and strain differences in teratogenic effects of biotin deficiency in rodents, J Nutr., 119, 255–261, 1989 125 Bain, S.D., Newbrey, J.W., and Watkins, B.A., Biotin deficiency may alter tibiotarsal bone growth and modeling in broiler chicks, Poult Sci., 67, 590–595, 1988 126 Rabin, B.S., Inhibition of experimentally induced autoimmunity in rats by biotin deficiency, J Nutr., 113, 2316–2322, 1983 127 Pruzansky, J and Axelrod, A.E., Antibody production to diphtheria toxoid in vitamin deficiency states, Proc Soc Exp Biol Med., 89, 323–325, 1955 128 Petrelli, F., Moretti, P., and Campanati, G., Studies on the relationships between biotin and the behaviour of B and T lymphocytes in the guinea pig, Experientia, 37, 1204–1206, 1981 129 Kung, J.T., MacKenzie, C.G., and Talmage, D.W., The requirement for biotin and fatty acids in the cytotoxic T-cell response, Cell Immunol., 48, 100–110, 1979 130 Kumar, M and Axelrod, A.E., Cellular antibody synthesis in thiamin, riboflavin, biotin and folic acid-deficient rats, Proc Soc Exp Biol Med., 157, 421–423, 1978 131 Ba´ez-Saldan˜a, A., Dı´az, G., Espinoza, B., and Ortega, E., Biotin deficiency induces changes in subpopulations of spleen lymphocytes in mice, Am J Clin Nutr., 67, 431–437, 1998 132 Okabe, N., Urabe, K., Fujita, K., Yamamoto, T., and Yao, T., Biotin effects in Crohn’s disease, Dig Dis Sci., 33 (11), 1495–1496, 1988 133 Cowan, M.J., Wara, D.W., Packman, S., Yoshino, M., Sweetman, L., and Nyhan, W., Multiple biotin-dependent carboxylase deficiencies associated with defects in T-cell and B-cell immunity, Lancet, (8134), 115–118, 1979 ß 2006 by Taylor & Francis Group, LLC 134 Fernandez-Mejia, C., Pharmacologic effects of biotin, J Nutr Biochem., 16, 424–427, 2005 135 Mock, D.M., Henrich, C.L., Carnell, N., Mock, N.I., and Swift, L., Lymphocyte propionyl-CoA carboxylase and accumulation of odd-chain fatty acid in plasma and erythrocytes are useful indicators of marginal biotin deficiency, J Nutr Biochem., 13 (8), 462–470, 2002 136 Mock, D.M., Mock, M.M., Bogy, C.D., Mock, N.I., and Stratton, S.L., Lymphocyte propionylCoA carboxylase (PCC) and activation of PCC by biotin are useful indicators of marginal biotin deficiency in humans, FASEB J., 19 (4), A55, 2005 137 National Research Council, Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline, in Recommended Dietary Allowances, 11th ed., Food and Nutrition Board Institute of Medicine National Academy Press, Washington, DC, 1998, pp 374–389 138 Greene, H.L., Hambridge, K.M., Schanler, R., and Tsang, R.C., Guidelines for the use of vitamins, trace elements, calcium, magnesium, and phosphorus in infants and children receiving total parenteral nutrition: Report of the Subcommittee on Pediatric Parenteral Nutrient Requirements for the Committee on Clinical Practice Issues of The American Society for Clinical Nutrition, Am J Clin Nutr., 48, 1324–1342, 1988 139 Greene, H.L and Smidt, L.J., Water soluble vitamins: C, B1, B2, B6, niacin, pantothenic acid, and biotin, in Nutritional Needs of the Preterm Infant, Tsang, R.C., Lucas, A., Uauy, R., and Zlotkin, S., eds., Williams & Wilkins, Baltimore, MD, 1993, pp 121–133 140 Moore, M.C., Greene, H.L., and Phillips, B., Evaluation of a pediatric multiple vitamin preparation for total parenteral nutrition in infants and children: I Blood levels of water-soluble vitamins, Pediatrics, 77, 530–538, 1986 141 Hardinge, M.G and Crooks, H., Lesser known vitamins in food, J Am Diet Assoc., 38, 240–245, 1961 142 Wilson, J and Lorenz, K., Biotin and choline in foods—Nutritional importance and methods of analysis: A review, Food Chem., 4, 115–129, 1979 143 Hoppner, K and Lampi, B., The biotin content of breakfast cereals, Nutr Rep Int., 28 (4), 793– 798, 1983 144 Pennington, J.A.T., Biotin, in Bowes and Church’s Food Values of Portions Commonly Used, 15th ed., Lippincott, Philadelphia, 1989 145 Guilarte, T.R., Analysis of biotin levels in selected foods using a radiometric-microbiological method, Nutr Rep Int., 32 (4), 837–845, 1985 146 Teague, A.M., Sealey, W.M., McCabe-Sellers, B., and Mock, D., Biotin is stable in frozen foods, FASEB J., 18 (4), A143 (abst), 2004 147 Hoppner, K., Lampi, B., and Smith, D.C., An appraisal of the daily intakes of vitamin B12, pantothenic acid and biotin from a composite Canadian diet, Can Inst Food Sci Technol J., 11 (2), 71–74, 1978 148 Bull, N.L and Buss, D.H., Biotin, pantothenic acid and vitamin E in the British household food supply, Hum Nutr.: Appl Nutr., 36A, 125–129, 1982 149 Lewis, J and Buss, D.H., Trace nutrients: Minerals and vitamins in the British household food supply, Br J Nutr., 60, 413–424, 1988 150 Frigg, M., Straub, O.C., and Hartmann, D., The bioavailability of supplemental biotin in cattle, Int J Vit Nutr Res., 63, 122–128, 1993 151 Bryant, K.L., Kornegay, E.T., Knight, J.W., and Notter, D.R., Uptake and clearance rates of biotin in pig plasma following biotin injections, Int J Vit Nutr Res., 60, 52–57, 1989 152 Misir, R and Blair, R., Biotin bioavailability from protein supplements and cereal grains for weanling pigs, Can J Anim Sci., 68, 523–532, 1988 153 Bitsch, R., Salz, I., and Ho¨tzel, D., Studies on bioavailability of oral biotin doses for humans, Int J Vit Nutr Res., 59, 65–71, 1989 154 Clevidence, B., Marshall, M., and Canary, J.J., Biotin levels in plasma and urine of healthy adults consuming physiological levels of biotin, Nutr Res., 8, 1109–1118, 1988 155 Mock, D.M and Mock, N.I., Serum concentrations of bisnorbiotin and biotin sulfoxide increase during both acute and chronic biotin supplementation, J Lab Clin Med., 129, 384–388, 1997 156 Mock, D.M and Heird, G.M., Urinary biotin analogs increase in humans during chronic supplementation: The analogs are biotin metabolites, Am J Physiol Endocrinol Metab., 272, 83–87, 1997 ß 2006 by Taylor & Francis Group, LLC ß 2006 by Taylor & Francis Group, LLC  ... (Figure 11.2 ) BIOTIN CATABOLISM Instead of incorporation into carboxylases or histones, biotin may be catabolized Biotin, possibly in the form of biotinyl CoA, can be oxidized to bisnorbiotin... (CH2)2 Bisnorbiotin C OH FIGURE 11.1 Metabolism, degradation, and recycling of biotin as well as biotinylated enzymes and histones Ovals denote enzymes or enzyme systems; rectangles denote biotin, ... receiving biotin supplementation is ~0.4 when expressed as biotin to creatinine clearance ratio [41,46,47] In patients with biotinidase deficiency, renal wasting of biotin and biocytin occurs; biotin