Ketogenic response to medium-chain triglyceride load in the rat.

We studied ketonemia induced in rats by a single oral load of medium-chain triglycerides (MCT) (C8:0 50.5%, C10:0 48.0%, C12:0 1.0%). Medium-chain fatty acids, rather than being incorporated into the lipids synthesized by the liver, are oxidized there, with high production of ketone bodies. Severe and long-lasting hyperketonemia developed rapidly. With increased MCT loads, ketonemia also increased, although not linearly. The level of the hyperketonemia seemed equal in the two sexes. Ingestion of MCT by fasting rats caused an additional rise in ketonemia. Long-chain triglycerides were not ketogenic, since their constituent fatty acids are incorporated into lipids and are thus less subject to oxidation. Lipids induce less severe ketonemia in genetically obese rats than in normal-weight rats.