Validation of two-pool model for in vivo ketone body kinetics

Previous studies have indicated that simultaneous infusions of two ketone body tracers ([¹³C]acetoacetate and [¹⁴C]β-hydroxybutyrate) provide accurate estimates of exogenous ketone body inflow when an open two-pool model is employed. In the present studies, net hepatic ketone body production was determined from surgically placed arterial, portal venous, and hepatic venous catheters in conscious diabetic (n = 6) and 4-day fasted (n = 7) dogs. [¹³C]acetoacetate and [¹⁴C]β-hydroxybutyrate were infused simultaneously, and ketone body production was calculated from either acetoacetate (AcAc) single-isotope data, β-hydroxybutyrate (β-OHB) single-isotope data, the sum of individual fluxes, or the two-pool model. In fasted animals, both the AcAc single-isotope calculation and the sum of individual fluxes overestimated net hepatic production by ~50% (P < 0.05), whereas the β-OHB single-isotope calculation and the two-pool model gave accurate estimates. In the diabetic animals, the β-OHB single-isotope calculation underestimated net hepatic production by ~30% (P < 0.05). The sum of individual fluxes overestimated net hepatic production by ~46% (P < 0.05), whereas both AcAc single-isotope calculation and the two-pool model gave accurate estimates. In conclusion, single-isotope methods give erroneous estimates of net hepatic production of ketone bodies. In contrast, a two-pool model provided an accurate estimate of net hepatic production and thus appears to be suitable for determination of ketone body kinetics in humans.