Fluorinated Carnitine Derivatives as Tools to Visualise Carnitine Transport and Metabolism

Carnitine and its acyl derivatives are essential for the transport of fatty acids from the cytosol into the mitochondrial matrix for β-oxidation, which supplies the cell with energy. Altered transport and metabolism of carnitine are associated with multiple diseases and disorders, including heart disease, insulin resistance, and cancer. Fluorinated carnitine derivatives have the potential to measure aberrant carnitine metabolism in these disorders using ¹⁹F-NMR and mass spectrometry. Furthermore, by radiolabeling carnitines with fluorine-18, altered carnitine utilisation may be visualised in vivo using positron emission tomography (PET) imaging. Here, the design and synthesis of a fluorinated carnitine derivative, fluoromethylcarnitine (FMC), and its radiolabelled equivalent, [¹⁸F]fluoromethylcarnitine ([¹⁸F]FMC), are described, and their ability to quantitatively measure carnitine transport and downstream metabolism in a variety of settings are shown, from simple cell models to living subjects. Finally, [¹⁸F]FMC PET is used to visualise elevated carnitine utilisation in a xenograft model of non-small cell lung cancer.