Synthesis and initial evaluation of 17-(11)C-heptadecanoic acid for measurement of myocardial fatty acid metabolism.

Fatty acid oxidation defects are being increasingly identified as causes of abnormal heart function and sudden death in children. Children with medium-chain acyl-coenzyme A (acyl-CoA) dehydrogenase defects can metabolize fatty acids labeled in the carboxylic acid end of the compound. Accordingly, our goal was to label a long-chain fatty acid in the omega-position and evaluate its myocardial kinetics. Heptadecanoic acid, a 17-carbon fatty acid, was labeled in the C-17 position with (11)C by the general process of coupling (11)C-methyliodide to t-butyl-15-hexadecanoate. Yield was approximately 5%-10% end-of-bombardment. Subsequently, evaluation studies were performed on isolated perfused rat hearts and in intact, anesthetized dogs. The myocardial uptake and efflux of 17-(11)C-heptadecanoic acid were compared with those of 1-(11)C-palmitate. With the exception of delayed efflux of tracer reflecting the temporal delay for beta-oxidation, the washout of 17-(11)C-heptadecanoic acid from the heart mirrored that of 1-(11)C-palmitate in isolated rat hearts and in intact dogs with PET. 17-(11)C-Heptadecanoic acid may be a useful tracer for the identification of defects in fatty acid metabolism in subjects with medium- and short-chain fatty acid oxidation defects.