Ketone kinetics in man

Abstract

1. Five normal volunteers after an overnight fast were given an injection of DL-beta hydroxybutyrate on one occasion, and an injection of acetoacetate (AcAc) on another occasion. The concentrations of D-(--)-beta-hydroxybutyrate (D-beta-OHB) and AcAc were measured every 5 minutes for 40 minutes after each injection. 2. The rate constant of disappearance (K), the volume of distribution (V) and the metabolic clearance (MCR) were calculated for the injected ketone. The values were similar for the two ketones, and therefore these values can be taken as estimates for total ketones. 3. The metabolic clearance rate of total ketones (beta-OHB plus AcAc) was also calculated from the changes in total ketone body concentration after the injection of DL-beta-OHB or AcAc which are the methods used previously. The values obtained by these methods were only 50% of that calculated from the kinetics of the injected ketone. This difference is entirely due to the differences in the apparent volume of distribution. 4. It is suggested that the best estimate of total ketone body production rate is the product of the MCR of the injected ketone and the basal concentration of total ketone bodies.