The effect of the addition of acetoacetate or fatty acids on the oxidation of glucose, and vice versa, in rat brain minces was studied. The results suggested that acetoacetate spares the oxidation of glucose by rat brain, but only slightly. Ketosis induced by starvation or fat feeding had little effect on this sparing action. Acetoacetate appeared to lower glucose oxidation, at least in part, by diversion of a higher portion of the glucose to lactate.
The oxygen consumption was essentially the same in the minces prepared from normal or ketotic rats. Addition of glucose to the medium containing acetoacetate increased oxygen consumption and acetoacetate oxidation to the same degree. In contrast, palmitate oxidation was decreased when glucose was added to the medium.
These in vitro studies indicate that glucose is the preferred substrate for rat brain energy production in both the normal and ketotic states.