Comparative absorption and transport of various carotenoids in the preruminant calf.

摘要

These studies utilized the preruminant calf animal model to compare the absorption, serum appearance and lipoprotein transport of several carotenoids commonly found in the human diet. In addition, this work examined the effect of fat level in meals on the absorption of {dollar}beta{dollar}-carotene. The preruminant calf has been shown in previous studies to be an excellent model for human carotenoid absorption and metabolism.; For this model, {dollar}beta{dollar}-carotene was absorbed only through the lymphatic system and dietary fat was required for optimal {dollar}beta{dollar}-carotene absorption. The fat level of subsequent meals following an initial {dollar}beta{dollar}-carotene-containing meal was found to influence the total absorption of {dollar}beta{dollar}-carotene from the initial meal suggesting the presence of a maximum carrying capacity for {dollar}beta{dollar}-carotene transportation from the intestine from a single meal. Peak absorption of {dollar}beta{dollar}-carotene in chylomicrons was found to occur simultaneously with cholesterol but was delayed several hours as compared to triglycerides.; The preruminant calf was also shown to absorb a wide range of both polar and nonpolar carotenoids; the polarity of the carotenoid seemed to influence its transport in the blood and its residence time. The majority of serum carotenoids in the calf were found to be associated with the HDL lipoprotein fraction with the remainder being associated with the LDL fraction. The serum appearance of {dollar}beta{dollar}-carotene following a dose of {dollar}beta{dollar}-carotene in a water-soluble form was shown to be higher than that from the oil-soluble form of the carotenoid.; When calves were fed {dollar}beta{dollar}-carotene containing a high proportion of 9-cis {dollar}beta{dollar}- carotene, no 9-cis {dollar}beta{dollar}-carotene was detected in the serum suggesting the presence of a mechanism limiting the absorption and serum appearance of 9-cis {dollar}beta{dollar}-carotene. Such a mechanism may be important in the regulation of the production of 9-cis retinoic acid.; The results of these studies using the preruminant calf model agree with those results seen in human studies and provide new insight into the absorption and transport of various carotenoids commonly consumed by humans.