Detection of triglyceride metabolism in white blood cells using a novel fluorescently labeled long chain fatty acid analogue

123I-15-(p-iodophenyl)-(R,S)-methyl pentadecanoic acid (123I-BMIPP) is a long-chain fatty acid (LCFA) analog developed to examine myocardial LCFA metabolism and has been used as a tracer for nuclear cardiology. However, its use is limited because of the specialized features of cardiac scintigraphy. In this study, a novel BMIPP-based probe, in which iodine-123 was replaced with a fluorescent compound, was used to extend the application of 123I-BMIPP to ex vivo analysis of fatty acid metabolism. To confirm that fluorescently labeled BMIPP-based probe (fluorescent BMPP) is effective for the detection of LCFA metabolism ex vivo, we performed fluorescence-activated cell sorting (FACS) analysis for the incorporation of fluorescent BMPP using white blood cells from human peripheral blood. FACS analysis showed that the incorporation of fluorescent BMPP into white blood cells was dose-dependent. Fluorescence intensities of cells incorporating fluorescent BMPP were attenuated after incubation in non-fluorescent BMPP medium, suggesting that these cells could export the probe. Neutrophils from a patient with primary triglyceride deposit cardiomyovasculopathy, a rare type of triglyceride (TG) metabolism disorders, showed lower BMPP export and was ameliorated after treatment with tricaprin. These results suggest that fluorescent BMPP could be imported to and exported from cells through the same mechanism as 123I-BMIPP, reflecting the mechanism that occurs for LCFAs during TG metabolism. This study shows that fluorescent BMPP has the potential to be used as a probe for the diagnosis of TG metabolic diseases ex vivo.