Acetoacetate metabolism of rats fed high fat or restricted calorie diets

Ethyl-¹⁴C-acetoacetate was used to trace oxidation and metabolism of acetoacetate when rats were fed a high fat diet (80% of total calories from beef tallow or corn oil, carbohydrate free), a high carbohydrate diet (2% corn oil) or a high carbohydrate diet with restriction of calories to one half of ad lib. consumption for two weeks. The rate of expiration of¹⁴CO₂ in all groups of animals did not differ significantly and was not related to plasma concentration of acetoacetate. The high fat diets slightly enhanced the oxidation of acetoacetate to¹⁴CO₂ over a 3 hr period compared to other diets. Incorporation of acetoacetate into fatty acids did not differ significantly among groups. Rats fed the high carbohydrate diet ad lib. incorporated into liver cholesterol more acetoacetate than did any other group, but dietary unsaturated fat resulted in greater incorporation of acetoacetate into cholesterol than saturated fat. High calorie and high beef tallow groups were ketonemic but the low concentration of plasma acetoacetate in rats fed a high corn oil diet indicates that unsaturated fatty acids are not ketogenic. The data show that utilization of acetoacetate is not significantly reduced in a ketonemic condition and support the premise that overproduction of ketone bodies is the cause of ketonemia. Rats appeared to be normal during the two-week period when no carbohydrate was included in the diet. Presented at the AOCS Meeting, Chicago, October, 1967.