The Effect Of Insulin On The Intracellular Distribution Of 14(R,S)-[F-18]Fluoro-6-Thiaheptadecanoic Acid In Rats

Purpose: The aim of this study was to determine the effect of hyperinsulinemia on myocardial and hepatic distribution and metabolism of 14(R, S)-[F-18]fluoro-6-thia-heptadecanoic acid ([F-18]FTHA).Procedures: Mitochondrial retention and intracellular lipid incorporation of [F-18]FTHA were compared to that of [C-14]-2-bromopalmitate or [C-14]palmitate during hyperinsulinemic clamp vs. saline infusion in male Wistar rats.Results: Mitochondrial F-18 activity was increased in the heart (1.7 +/- 0.4 vs. 0.5 +/- 0.1% ID/g, P < 0.05), whereas it was reduced in the liver (1.1 +/- 0.3 vs. 1.8 +/- 0.4% ID/g, P < 0.05) during insulin vs. saline infusion, respectively. Mitochondrial [C-14]-2-bromopalmitate activity was affected by insulin in a similar way in both tissues. The fractional esterification of [F-18]FTHA into triglycerides was impaired compared to [C-14] palmitate in both tissues, and [F-18]FTHA was insensitive to the shift of esteirification of fatty acids into complex lipids in response to insulin.Conclusions: [F-18]FTHA is sensitive to insulin-induced modifications of free fatty acid oxidative metabolism in rats but is insensitive to changes in nonoxidative fatty acid metabolism.