Intestinal beta-carotene 15,15 '-dioxygenase activity is markedly enhancedin copper-deficient rats fed on high-iron diets and fructose

The purpose of the present work was to examine effects of the Cu-Fe interac tion on intestinal beta-carotene 15,15 '-dioxygenase activity when a wide r ange of dietary Fe (deficiency to excess) was used in relation to Cu status of rats. The effect of dietary carbohydrates was also examined since they play a role in the Cu-Fe interaction in vivo. Weanling male Sprague-Dawley rats (n 72) were divided into twelve dietary groups, which were fed on eith er low-, normal-, or high-Fe levels (0.9, 9.0, and 90.0 mmol Fe/kg diet res pectively) combined with Cu-adequate or -deficient levels (0.94 and 0.09 mm ol Cu/kg diet respectively) and with starch or fructose in the diets. The d ata showed that both Fe concentration and beta-carotene 15,15 '-dioxygenase activity in small intestinal mucosa were enhanced with increasing dietary Fe and with Cu deficiency v. Cu adequacy. Dietary fructose did not aggravat e the Fe-enhancement, related to Cu deficiency, in the small intestine; how ever, fructose increased the intestinal dioxygenase activity in rats fed on normal- or high-Fe diets when compared with starch controls. Thus, the hig hest intestinal dioxygenase activity associated with the lowest hepatic ret inol (total) concentration was found in rats fed on the Cu-deficient, high- Fe, fructose-based diet. Finally, a positive linear relationship was found between the dioxygenase activity and Fe concentration in intestinal mucosa. In conclusion, the data indicate that beta-carotene 15,15 '-dioxygenase ac tivity requires Fe as cofactor in vivoand the enzyme is modulated by the th ree dietary components: Cu, Fe, and fructose.