Effect of dietary fructose on in vitro and in vivo fatty acid synthesis in the rat

Abstract

Diets containing either glucose or fructose as the only source of carbohydrate were fed to rats. [U- 14C] Glucose and [U- 14C] fructose incorporation into fatty acids by liver slices from these animals indicated that the results obtained were markedly affected by substrate concentration. At a level of 10 mM fructose incorporation into hepatic fatty acids was greater than that observed with glucose; however, the reverse was true when the substrate concentration was increased to 100 mM. High levels of fructose in the incubation medium markedly depressed ATP levels in liver slices and also inhibited [ 14C]-acetate incorporation into fatty acids. Rats fed fructose had higher hepatic ATP levels than did rats fed glucose. In vivo estimates of fatty acid synthesis were obtained using [ 14C] acetate as well as 3H 2. These determinations indicated that while the total capacity of the animal to synthesize fatty acids was unchanged, the relative importance of the liver was increased and that of the extra-hepatic tissues decreased when fructose, rather than glucose, was fed to rats.