URINARY BIOTIN ANALOGS INCREASE IN HUMANS DURING CHRONIC SUPPLEMENTATION - THE ANALOGS ARE BIOTIN METABOLITES

In human subjects, the metabolic origins of bisnorbiotin and biotin su lfoxide were determined by measuring the urinary excretion of each aft er chronic administration of large oral doses of biotin. For 2 wk, 14 adult volunteers consumed 1,200 mu g of biotin per day, an amount simi lar to 20 times the daily dietary intake. With the use of a high-perfo rmance liquid chromatography/avidin-binding assay in untimed urine sam ples obtained before the first dose of biotin and after the 14th dose, concentrations of biotin, bisnorbiotin, and biotin sulfoxide were mea sured. Excretion was expressed as concentration ratios to urinary crea tinine. Bisnorbiotin and biotin sulfoxide excretion increased 85-fold (P < 0.0001) and 114-fold (P < 0.0001), respectively. The molar percen tages of bisnorbiotin and biotin sulfoxide decreased from 28 to 14% (P = 0.006) and from 9 to 5% (P. = 0.017), respectively. These data prov ide evidence that the bisnorbiotin and biotin sulfoxide found in human urine are biotin metabolites. Furthermore, we infer that chronic cons umption of large amounts of biotin does not substantially saturate the human biotin pathways of biotransformation.