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Consumption of carotenoids from different vegetable sources does not diminish plasma carotenoid concentrations in the medium term, despite the finding in postprandial testing of competitive inhibitory interactions among different carotenoids.

Carrot consumption modifies cholesterol absorption and bile acids excretion and increases antioxidant status and these effects could be interesting for cardiovascular protection.

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beta,beta-Carotene 15,15'-monooxygenase (formerly termed beta,beta-carotene 15,15'-dioxygenase, EC 1.13.11.21) catalyzes the conversion of provitamin A carotenoids to retinal in vertebrate tissues. In the present study, we investigated whether preformed vitamin A or beta-carotene and its direct metabolites can regulate the enzyme activity in vivo. We found dose-dependent decreases in intestinal beta,beta-carotene monooxygenase activity after oral administration to rats of retinyl acetate (up to -79%), beta-carotene (up to -79%), apo-8'-carotenal (up to -56%), all-trans retinoic acid (up to -88%), and 9-cis retinoic acid (up to -67%). Liver beta,beta-carotene 15,15'-monooxygenase (betaCMOOX) activity was not affected. Apo-12'carotenal and the retinoic acid receptor (RAR) alpha antagonist Ro 41-5253 significantly increased the intestinal enzyme activity by 55 and 94%, respectively. When beta-carotene was administered to rats pretreated with the two cytochrome P(450) (CYP) inducers, pentobarbital and naphthoflavone, the intestinal betaCMOOX activity increased by 39%. In a transcriptional study in chickens, treatment with retinoic acid resulted in low expression of the intestinal betaCMOOX. Our data suggest that retinoids and carotenoids might regulate betaCMOOX expression by a transcriptional feedback mechanism via interaction with members of the RAR family.

Although the management of malnutrition is a priority in older people, this population shows a resistance to refeeding. Fresh bee pollen contains nutritional substances of interest for malnourished people. The aim was to evaluate the effect of fresh bee pollen supplementation on refeeding efficiency in old malnourished rats. Male 22-month-old Wistar rats were undernourished by reducing food intake for 12 weeks. The animals were then renourished for three weeks with the same diet supplemented with 0%, 5% or 10% of fresh monofloral bee pollen. Due to changes in both lean mass and fat mass, body weight decreased during malnutrition and increased after refeeding with no between-group differences (p < 0.0001). Rats refed with the fresh bee pollen-enriched diets showed a significant increase in muscle mass compared to restricted rats (p < 0.05). The malnutrition period reduced the muscle protein synthesis rate and mTOR/p70S6kinase/4eBP1 activation, and only the 10%-pollen diet was able to restore these parameters. Mitochondrial activity was depressed with food restriction and was only improved by refeeding with the fresh bee pollen-containing diets. In conclusion, refeeding diets that contain fresh monofloral bee pollen improve muscle mass and metabolism in old, undernourished rats.

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