Regional acetate kinetics and oxidation in human volunteers

We have used a 3-h primed continuous infusion of [1,2-13C]acetate in five fasted (24 h) volunteers to quantify splanchnic and leg acetate metabolism (protocol 1). Fractional extraction of acetate by both tissues was high ( approximately 70%), and simultaneous uptake and release of acetate were observed. Labeled carbon recovery in CO2 was 37.9 +/- 2.3% at the whole body level, 37.7 +/- 1.5% across the splanchnic bed, and 37.3 +/- 2.9% across the leg. Furthermore, we calculated whole body labeled carbon recovery during 15 h of [1, 2-13C]acetate infusion in three volunteers (protocol 2). Whole body acetate carbon recovery in CO2 was significantly higher (66.7 +/- 4. 5%) after 15 h of tracer infusion than after 3 h. We conclude that acetate is rapidly taken up by the leg and splanchnic tissues and that the percent recovery of CO2 from the oxidation of acetate is heavily dependent on the length of acetate tracer infusion. In the postabsorptive state, labeled carbon recovery from acetate across the leg and the splanchnic region is similar to the whole body CO2 recovery.