These values, which vary by age and sex, include: DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people.
Intake recommendations for biotin and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the National Academies of Sciences, Engineering, and Medicine. However, serum concentrations of biotin and its catabolites are not good indicators of marginal biotin deficiency because they do not decrease sufficiently in people with marginal biotin deficiency for these changes to be detectable with existing tests. Oral administration of large doses of biotin increases serum concentrations of biotin and its metabolites. The most reliable individual markers of biotin status, including deficiency and sufficiency, are biotinylated MCC and propionyl-CoA carboxylase in white blood cells. Abnormally low urinary excretion of biotin is an indicator of biotin deficiency, as is abnormally high excretion of 3-hydroxyisovaleric acid (higher than 3.3 mmol/mol creatinine) or 3-hydroxyisovalerylcarnitine (higher than 0.06 mmol/mol creatinine) resulting from reduced activity of MCC. In healthy adults, the concentration of biotin is 133–329 pmol/L in serum and 18–127 nmol/24 hours in urine. Ī limited number of reliable indicators of biotin status is available.
The free biotin is then absorbed in the small intestine, and most biotin is stored in the liver. Gastrointestinal proteases and peptidases break down the protein-bound forms of ingested biotin into biocytin and biotin-oligopeptides, which undergo further processing by biotinidase, an enzyme, in the intestinal lumen to release free biotin. Most biotin in foods is bound to protein, although some dietary biotin is in the free form. Biotin also plays key roles in histone modifications, gene regulation (by modifying the activity of transcription factors), and cell signaling. This water-soluble vitamin is a cofactor for five carboxylases (propionyl-CoA carboxylase, pyruvate carboxylase, methylcrotonyl-CoA carboxylase, acetyl-CoA carboxylase 1, and acetyl-CoA carboxylase 2) that catalyze critical steps in the metabolism of fatty acids, glucose, and amino acids.
Introductionīiotin, a B vitamin, is an essential nutrient that is naturally present in some foods and available as a dietary supplement. For a general overview of Biotin, see our consumer fact sheet on Biotin. This is a fact sheet intended for health professionals.
0 kommentar(er)
