Imaging biotin trafficking in vivo with positron emission tomography.

The water-soluble vitamin biotin is essential for cellular growth, development and well-being but its absorption, distribution, metabolism, and excretion are poorly understood. This paper describes the radiolabelling of biotin with the positron emission tomography (PET) radionuclide carbon-11 ([11 C]biotin) to enable the quantitative study of biotin trafficking in vivo. We show that intravenously administered [11 C]biotin is quickly distributed to liver, kidneys, retina, heart and brain in rodents - consistent with the known expression of the biotin transporter - and a surprising accumulation in brown adipose tissue (BAT). Orally administered [11 C]biotin was rapidly absorbed in the small intestine and swiftly distributed to these same organs. Pre-administration of non-radioactive biotin inhibited organ-uptake and increased excretion. [11 C]Biotin PET imaging therefore provides a dynamic in vivo map of transporter-mediated biotin trafficking in healthy rodents. This technique will enable exploration of biotin trafficking in humans and its use as a research tool for diagnostic imaging in obesity/diabetes, bacterial infection and cancer.