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 radiolabeling
of biotin with the positron emission tomography (PET) radionuclide
carbon-11 ([11C]­biotin) to enable the quantitative study
of biotin trafficking in vivo. We show that intravenously administered
[11C]­biotin is quickly distributed to the liver, kidneys,
retina, heart, and brain in rodentsconsistent with the known
expression of the biotin transporterand there is a surprising
accumulation in the brown adipose tissue (BAT). Orally administered
[11C]­biotin was rapidly absorbed in the small intestine
and swiftly distributed to the same organs. Preadministration of nonradioactive
biotin inhibited organ uptake and increased excretion. [11C]­Biotin PET imaging therefore provides a dynamic in vivo map of
transporter-mediated biotin trafficking in healthy rodents. This technique
will enable the exploration of biotin trafficking in humans and its
use as a research tool for diagnostic imaging of obesity/diabetes,
bacterial infection, and cancer.