Background with requisite function in human metabolic processes
Deficiency
Deficiency
Biotin deficiency in humans has been clearly documented with prolonged consumption of raw egg whites, which contain biotin-binding avidin. Biotin deficiency was also observed in cases of parenteral nutrition with solutions lacking biotin given to patients with short-gut syndrome and other causes of malabsorption. Some cases of biotin deficiency were noted in infants with intractable diaper dermatitis and in those fed special formulas. Dietary deficiency in otherwise normal people is probably rare. Some patients have multiple carboxylase deficiencies and there are occasional biotinidase deficiencies. Clinical signs of deficiency include dermatitis of an erythematous and seborrheic type; conjunctivitis; alopecia; and central nervous system abnormalities such as hypotonia, lethargy, and developmental delay in infants and depression, hallucinations, and paresthesia of the extremities in adults.
Toxicity
Toxicity is not a problem because of limited intestinal absorption of biotin.
Functions
Biotin functions as a co-enzyme within several carboxylases after the carboxyl function of the vitamin becomes amide linked to the ε-amino of specific lysyl residues of the apoenzymes. In humans and other mammals, biotin operates within four carboxylases. Three of the four biotin-dependent carboxylases are mitochondrial (pyruvate carboxylase, methylcrotonyl-CoA carboxylase, and propionyl-CoA carboxylase) whereas the fourth (acetyl-CoA carboxylase) is found both in mitochondria and the cytosol. In all these cases biotin serves as carrier for the transfer of active bicarbonate into a substrate to generate a carboxyl product.
Biochemical indicators
Indicators used to estimate biotin requirements are urinary excretion and 3-hydroxyisovalerate excretion. The excretion rate of vitamin and metabolites in urine is assessed by avidin-based radioimmunoassay with HPLC. 3-Hydroxyisovalerate excretion inversely reflects the activity of β-methyl-crotonyl-CoA carboxylase, which is involved in leucine metabolism.
The present indicators for biotin status are its urinary excretion, as assessed with an avidin-based radioimmunoassay with HPLC, and 3-hydroxyisovalerate excretion. The isolation and chemical identification of more than a dozen metabolites of biotin established the main features of its use in microbes and mammals. Quantification of the major biotin metabolites was done by Zempleni et al. Both biotin and bisnorbiotin excretions decline in parallel in individuals on a diet containing raw egg whites. In these individuals the levels of urinary 3-hydroxyisovalerate, which increase as a result of decreased activity of β-methylcrotonyl-CoA carboxylase and altered leucine metabolism, rose from a normal mean of 112 to 272 μmol/24 hours. Decreased excretion of biotin, abnormally increased excretion of 3-hydroxyisovalerate, or both have been reported for overt cases of biotin deficiency. The lack of sufficient population data, however, suggests the current use of an adequate intake rather than a recommended intake as a suitable basis for recommendations.
Findings by age and life stage
The biotin content of human milk is estimated to be approximately 6 μg (24nmol)/l based on several studies that report values ranging from near 4–7 μg (16.4–28.9 nmol) /l.
Hence, the estimated intake of biotin for an infant consuming 0.75 l is 5 μg/day during the first half year and for older infants is perhaps 6 μg/day. Requirements for children and adults have been extrapolated as follows:
Adequate intake for child or adult = (adequate intake young infant) (weight adult or child/weight infant) 0.75
For pregnancy there are at present insufficient data to justify an increase in the adequate intake, although Mock et al. reported decreased urinary biotin and 3-hydroxyisovalerate in a large fraction of seemingly healthy pregnant women.
For lactation the intake may need to be increased by an additional 5 μg/day to cover the losses due to human-milk secretion.
References:
Food and Nutrition Board, Institute of Medicine/National Academy of Sciences-National Research Council. 1998. Dietary Reference Intake: Folate, Other B Vitamins, and Choline. Washington, D.C., National Academy Press.
McCormick, D.B & Greene, H.L. 1994. Vitamins. In: Tietz Textbook of Clin Chem., 2nd
edition. Burtis, V.A., Ashwood, E.R., eds. Philadelphia: W.B. Saunders, p. 1275-1316.
McCormick, D.B. 1996. Co-enzymes, Biochemistry of. In: Encyclopedia of Molecular Biology and Molecular Medicine, Vol. 1. Meyers, R.A., ed. Weinheim: VCH, p. 396-406.
McCormick, D.B. 1997. Co-enzymes, Biochemistry. In: Encyclopedia of Human Biology 2nd edition. Dulbecco, R., ed.-in-chief. San Diego: Academic Press, p. 847-64.
McCormick, D.B. 1988. Biotin. In: Modern Nutrition in Health and Disease, 6th edition. Shils, M.E., Young, V.R., eds. Philadelphia: Lea & Febiger, p. 436-9.
Mock, D.M. 1996. Biotin. In: Present Knowledge in Nutrition, 7th edition. Ziegler, E.E., Filer, L.J., Jr., eds. p. 220-35. Washington, D.C.: International Life Sciences Institute- Nutrition Foundation.
Mock, N.I., Malik, M.I., Stumbo, P.J., Bishop, W.P. & Mock, D.M. 1997. 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: 951-8.
McCormick, D.B. & Wright, L.D. 1971. The metabolism of biotin and analogues. In: Comprehensive Biochemistry, Vol. 21. Florkin, M., Stotz, E.H., eds. p. 81-110. Amsterdam: Elsevier.
McCormick, D.B. 1976. Biotin. In: Present Knowledge in Nutrition, 4th edition. Hegsted, M., ed. Washington, D.C.: The Nutrition Foundation, p. 217-25.
Zempleni, J., McCormick, D.B. & Mock, D.M. 1997. Identification of biotin sulfone, bisnorbiotin methylketone, and tetranorbiotin-l-sulfoxide in Human urine. Am. J. Clin. Nutr., 65: 508-11.
Mock, D.M., deLorimer, A.A., Liebman, W.M., Sweetman, L. & Baker, H. 1981. Biotin deficiency: an unusual complication of parenteral alimentation. N. Engl. J. Med., 304: 820-3.
Carlson, G.L., Williams, N., Barber, D., Shaffer, J.L., Wales, S., Isherwood, D., Shenkin, A. & Irving, M.H. 1995. Biotin deficiency complicating long-term parenteral nutrition in an adult patient. Clin. Nutr., 14: 186-90.
Paul, A.A., Southgate, D.A.T. McCance & Widdowson's. 1978. The Composition of Foods. London: H.M. Stationery Office.
Hirano, M., Honma, K., Daimatsu, T., Hayakawa, K., Oizumi, J., Zaima, K. & Kanke, Y. 1992. Longitudinal variations of biotin content in Human milk. Int. J. Vit. Nutr. Res., 62: 281-2.
Mock, D.M., Stadler, D.D., Stratton, S.L. & Mock, N.I. 1997. Biotin status assessed longitudinally in pregnant women. J. Nutr., 127: 710-6.
Functions
Biotin functions as a co-enzyme within several carboxylases after the carboxyl function of the vitamin becomes amide linked to the ε-amino of specific lysyl residues of the apoenzymes. In humans and other mammals, biotin operates within four carboxylases. Three of the four biotin-dependent carboxylases are mitochondrial (pyruvate carboxylase, methylcrotonyl-CoA carboxylase, and propionyl-CoA carboxylase) whereas the fourth (acetyl-CoA carboxylase) is found both in mitochondria and the cytosol. In all these cases biotin serves as carrier for the transfer of active bicarbonate into a substrate to generate a carboxyl product.
Biochemical indicators
Indicators used to estimate biotin requirements are urinary excretion and 3-hydroxyisovalerate excretion. The excretion rate of vitamin and metabolites in urine is assessed by avidin-based radioimmunoassay with HPLC. 3-Hydroxyisovalerate excretion inversely reflects the activity of β-methyl-crotonyl-CoA carboxylase, which is involved in leucine metabolism.
The present indicators for biotin status are its urinary excretion, as assessed with an avidin-based radioimmunoassay with HPLC, and 3-hydroxyisovalerate excretion. The isolation and chemical identification of more than a dozen metabolites of biotin established the main features of its use in microbes and mammals. Quantification of the major biotin metabolites was done by Zempleni et al. Both biotin and bisnorbiotin excretions decline in parallel in individuals on a diet containing raw egg whites. In these individuals the levels of urinary 3-hydroxyisovalerate, which increase as a result of decreased activity of β-methylcrotonyl-CoA carboxylase and altered leucine metabolism, rose from a normal mean of 112 to 272 μmol/24 hours. Decreased excretion of biotin, abnormally increased excretion of 3-hydroxyisovalerate, or both have been reported for overt cases of biotin deficiency. The lack of sufficient population data, however, suggests the current use of an adequate intake rather than a recommended intake as a suitable basis for recommendations.
Findings by age and life stage
The biotin content of human milk is estimated to be approximately 6 μg (24nmol)/l based on several studies that report values ranging from near 4–7 μg (16.4–28.9 nmol) /l.
Hence, the estimated intake of biotin for an infant consuming 0.75 l is 5 μg/day during the first half year and for older infants is perhaps 6 μg/day. Requirements for children and adults have been extrapolated as follows:
Adequate intake for child or adult = (adequate intake young infant) (weight adult or child/weight infant) 0.75
For pregnancy there are at present insufficient data to justify an increase in the adequate intake, although Mock et al. reported decreased urinary biotin and 3-hydroxyisovalerate in a large fraction of seemingly healthy pregnant women.
For lactation the intake may need to be increased by an additional 5 μg/day to cover the losses due to human-milk secretion.
References:
Food and Nutrition Board, Institute of Medicine/National Academy of Sciences-National Research Council. 1998. Dietary Reference Intake: Folate, Other B Vitamins, and Choline. Washington, D.C., National Academy Press.
McCormick, D.B & Greene, H.L. 1994. Vitamins. In: Tietz Textbook of Clin Chem., 2nd
edition. Burtis, V.A., Ashwood, E.R., eds. Philadelphia: W.B. Saunders, p. 1275-1316.
McCormick, D.B. 1996. Co-enzymes, Biochemistry of. In: Encyclopedia of Molecular Biology and Molecular Medicine, Vol. 1. Meyers, R.A., ed. Weinheim: VCH, p. 396-406.
McCormick, D.B. 1997. Co-enzymes, Biochemistry. In: Encyclopedia of Human Biology 2nd edition. Dulbecco, R., ed.-in-chief. San Diego: Academic Press, p. 847-64.
McCormick, D.B. 1988. Biotin. In: Modern Nutrition in Health and Disease, 6th edition. Shils, M.E., Young, V.R., eds. Philadelphia: Lea & Febiger, p. 436-9.
Mock, D.M. 1996. Biotin. In: Present Knowledge in Nutrition, 7th edition. Ziegler, E.E., Filer, L.J., Jr., eds. p. 220-35. Washington, D.C.: International Life Sciences Institute- Nutrition Foundation.
Mock, N.I., Malik, M.I., Stumbo, P.J., Bishop, W.P. & Mock, D.M. 1997. 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: 951-8.
McCormick, D.B. & Wright, L.D. 1971. The metabolism of biotin and analogues. In: Comprehensive Biochemistry, Vol. 21. Florkin, M., Stotz, E.H., eds. p. 81-110. Amsterdam: Elsevier.
McCormick, D.B. 1976. Biotin. In: Present Knowledge in Nutrition, 4th edition. Hegsted, M., ed. Washington, D.C.: The Nutrition Foundation, p. 217-25.
Zempleni, J., McCormick, D.B. & Mock, D.M. 1997. Identification of biotin sulfone, bisnorbiotin methylketone, and tetranorbiotin-l-sulfoxide in Human urine. Am. J. Clin. Nutr., 65: 508-11.
Mock, D.M., deLorimer, A.A., Liebman, W.M., Sweetman, L. & Baker, H. 1981. Biotin deficiency: an unusual complication of parenteral alimentation. N. Engl. J. Med., 304: 820-3.
Carlson, G.L., Williams, N., Barber, D., Shaffer, J.L., Wales, S., Isherwood, D., Shenkin, A. & Irving, M.H. 1995. Biotin deficiency complicating long-term parenteral nutrition in an adult patient. Clin. Nutr., 14: 186-90.
Paul, A.A., Southgate, D.A.T. McCance & Widdowson's. 1978. The Composition of Foods. London: H.M. Stationery Office.
Hirano, M., Honma, K., Daimatsu, T., Hayakawa, K., Oizumi, J., Zaima, K. & Kanke, Y. 1992. Longitudinal variations of biotin content in Human milk. Int. J. Vit. Nutr. Res., 62: 281-2.
Mock, D.M., Stadler, D.D., Stratton, S.L. & Mock, N.I. 1997. Biotin status assessed longitudinally in pregnant women. J. Nutr., 127: 710-6.
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