a1 Department of Biological Resources, Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama 790-8566, Japan
We examined whether lipid metabolism in orchiectomised (ORX) rats was affected by fructose ingestion and the amount of ingested fructose. Sucrose was used as a fructose source. Sham-operated and ORX rats were fed one of the following three diets for 28 d: a maize starch-based diet without sucrose (SU0), a diet by which half or all of maize starch was replaced by sucrose (SU50 or SU100). Body-weight gain and food intake were increased by sucrose ingestion, but decreased by ORX. Plasma total cholesterol concentration was increased by ORX and dose-dependently by sucrose ingestion. Plasma TAG concentration was decreased by ORX, but was increased dose-dependently by sucrose ingestion. Plasma insulin concentration was decreased by ORX, but was not affected by sucrose ingestion. Liver TAG was increased by sucrose ingestion and ORX; however, liver cholesterol concentration was not affected by sucrose ingestion and ORX. The hepatic activity of cholesterol 7α-hydroxylase 1 was not affected by sucrose ingestion and ORX; however, faecal excretion of bile acids was decreased. The mRNA level of microsomal TAG transfer protein, which is the gene related to hepatic VLDL production, was increased by ORX and sucrose ingestion. The mRNA level of uncoupling protein-1 was decreased by ORX, but not by sucrose ingestion. Plasma insulin concentration tended to correlate with the level of sterol-regulatory element-binding protein-1c mRNA (r 0·747, P = 0·088). These results show that lipid metabolism in ORX rats would be affected by the consumption of fructose-rich sweeteners such as sucrose and high-fructose syrup.
(Received January 06 2011)
(Revised May 05 2011)
(Accepted June 06 2011)
(Online publication August 01 2011)
Abbreviations: CYP7A1, cholesterol 7α-hydroxylase 1; MTP, microsomal TAG transfer protein; ORX, orchiectomised; SREBP, sterol-regulatory element-binding protein; SU0, maize starch-based diet without sucrose; SU100, diet by which all of maize starch was replaced by sucrose; SU50, diet by which half of maize starch was replaced by sucrose; UCP-1, uncoupling protein-1