Radiolabeled BMIPP for imaging hepatic fatty acid metabolism: evaluation of hepatic distribution and metabolism in mice at various metabolic statuses induced by fasting in comparison with palmitic acid.

Abnormalities in hepatic fatty acid metabolism are involved in various diseases. In order to clarify the use of 123I-15-(p-iodophenyl)-3(R,S)-methylpentadecanoic acid ([123I]BMIPP) for imaging hepatic fatty acid metabolism, we determined the hepatic distribution/metabolism of [125I]BMIPP in mice at various metabolic statuses induced by fasting, and compared the results with those of [1-(14)C]palmitic acid ([1-(14)C]PA). Fed or fasted (6, 12, and 24 hour-fasted) mice were intravenously injected with [125I]BMIPP or [1-(14)C]PA. Hepatic radioactivity was measured at 1 to 120 minutes after the injection (n  =  5 to 15/time points), and radioactive lipid metabolites were analyzed by thin-layer chromatography (n  =  3/time points). The areas under the curves (AUCs) were calculated. In mice given [125I]BMIPP, the hepatic radioactivity was increased with the fasting time (AUC: 35.1, 45.5, 57.6, and 59.0 [% injected dose (ID)/g/kg]▪min for fed, 6, 12, and 24 hour-fasted). Similar characteristic changes were observed in mice given [1-(14)C]PA (100.6, 101.0, 116.5, and 121.5 [%ID/g/kg]▪min). Metabolite analysis showed that the triglyceride-fraction was increased by fasting in both groups (5.7, 12.8, 32.0, and 37.9 [%ID/g/kg]▪min for [125I]BMIPP groups; 20.6, 39.2, 66.0, and 67.9 [%ID/g/kg]▪min for [1-(14)C]PA groups). Thus, [125I]BMIPP demonstrated the changes in hepatic fatty acid metabolism induced by fasting, indicating the potential of [123I]BMIPP for imaging hepatic fatty acid metabolism.