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Colorful carrots get a new use, producing tracers to study the brain

By Ann Liu, PhD

Researchers are using carrots to produce a new tracer that will help scientists study vision and brain function. The results of this study were presented in the “Carotenoid and Retinoid Interactive Group: Bioavailability and Metabolism of Carotenoids and Vitamin A” on March 29 by Joshua Smith and John Erdman, PhD, from the University of Illinois at Urbana-Champaign.

Lutein is a carotenoid which accumulates in the retina of the eye and may protect the eyes from damage, especially age-related macular degeneration. It also accumulates in certain areas of the brain and may be beneficial for cognitive performance. However, little is known about how lutein accumulates in tissues such as the brain or how these tissues metabolize it. This led researchers to embark on a mission to develop lutein labeled with a non-radioactive, stable tracer (carbon-13) as a tool to study the metabolism of lutein in tissues.

Enter the colorful carrots. Carrots are a good source of lutein, but the amount of lutein can vary depending on the variety of carrot. Researchers tested seven different carrot cultivars that ranged in color from red to yellow to purple to see which one produced the most lutein. Then they had to culture the carrot cells in flasks and optimize the growing conditions to increase lutein production.

Once they figured out the optimal growing conditions, the carrot cells were fed carbon-13 labeled glucose. The lutein then had to be extracted using reverse-phase high performance liquid chromatography, and incorporation of the carbon-13 tracer was assessed using mass spectrometry. Approximately 58% of the lutein extracted from the carrot cells was uniformly labeled with carbon-13.

So what’s next for this new tracer lutein? The researchers plan to use it to study tissue accumulation of lutein in animal models before embarking on any studies in humans. They will also be going back to the lab bench to see if there are any more changes they can make to further improve their lutein yield.

This research was funded by a grant from Abbott Nutrition through the Center for Nutrition, Learning, and Memory at the University of Illinois.