tailieunhanh - Chapter 071. Vitamin and Trace Mineral Deficiency and Excess (Part 7)

Biotin Biotin is a water-soluble vitamin that plays a role in gene expression, gluconeogenesis, and fatty acid synthesis and serves as a CO 2 carrier on the surface of both cytosolic and mitochondrial carboxylase enzymes. The vitamin also functions in the catabolism of specific amino acids (., leucine). Excellent food sources of biotin include organ meat such as liver or kidney, soy, beans, yeast, and egg yolks; however, egg white contains the protein avidin, which strongly binds the vitamin and reduces its bioavailability. Biotin deficiency due to low dietary intake is rare; rather, deficiency is due to inborn errors of metabolism | Chapter 071. Vitamin and Trace Mineral Deficiency and Excess Part 7 Biotin Biotin is a water-soluble vitamin that plays a role in gene expression gluconeogenesis and fatty acid synthesis and serves as a CO2 carrier on the surface of both cytosolic and mitochondrial carboxylase enzymes. The vitamin also functions in the catabolism of specific amino acids . leucine . Excellent food sources of biotin include organ meat such as liver or kidney soy beans yeast and egg yolks however egg white contains the protein avidin which strongly binds the vitamin and reduces its bioavailability. Biotin deficiency due to low dietary intake is rare rather deficiency is due to inborn errors of metabolism. Biotin deficiency has been induced by experimental feeding of egg white diets and in patients with short bowels who received biotin-free parenteral nutrition. In the adult biotin deficiency results in mental changes depression hallucinations paresthesia anorexia and nausea. A scaling seborrheic and erythematous rash may occur around the eyes nose and mouth as well as on the extremities. In infants biotin deficiency presents as hypotonia lethargy and apathy. In addition the infant may develop alopecia and a characteristic rash that includes the ears. The laboratory diagnosis of biotin deficiency can be established based on a decreased urinary concentration or an increased urinary excretion of 3-hydroxyisovaleric acid after a leucine challenge. Treatment requires pharmacologic doses of biotin using up to 10 mg d. No toxicity is known. Pantothenic Acid Vitamin B5 Pantothenic acid is a component of coenzyme A and phosphopantetheine which are involved in fatty acid metabolism and the synthesis of cholesterol steroid hormones and all compounds formed from isoprenoid units. In addition pantothenic acid is involved in the acetylation of proteins. The vitamin is excreted in the urine and the laboratory diagnosis of deficiency is made on the basis of low urinary vitamin levels. The vitamin

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