Muscle and splanchnic acetate kinetics in humans

We have quantified regional acetate kinetics in nomial human volunteers for the firs time, irsing a primed continuous infusion ( 1 5 μmol/kg/min) of 1,2-¹³C acetate and an adaptation of a recently described method using gas-chromatography mass-spectrometry analysis. After an overnight last, a catheter for tracer infusion was placed in a peripheral won and sampling catheters were placed in a femora! artery and femoral vein and in (lie hepatic vein. Healthy volunteers were studied in the tasted state and during hypcrgfyccmia (glucose" 150mg/dl) Blood flow, as wdl as breath CO;, plasma acetate and blood CO; concentration and enrichment were measured. Across both the leg and the splanchnic region simultaneous uptake and release of plasma acetate was demonstrated. However net uptake occured. Leg accounted for 8.S±0.4% (mean±SE) of total acetate uptake, and 6.0±0 5% of total acetate release Extrapolated to the whole body, skeletal musde accounted for 50 8±2 5% of acetate uptake and 36.1±3.0% release whereas the splanchnic region accounted for 18711 3% and 10.9±1.0% of uptake and release, respectively Fractional extraction, however, was 23 8±7.1% greater across the splanchnic bed than across the leg Hyperglycemia increased fractional extraction in both tissues. The percent uptake oxidized decreased across the splanchnic region during hypergrycernia (64.0±5 9% vs 30.5±3.5%). Although the intestine is thought to produce acetate, our data show that if this is the case the acetate released by the gut is mainly taken up by the fiver rather than being released into the systemic circulation. Thus, a site other than muscle or the splanchnic region nust represent the major site of net acetate release.