Variation in gene expression profiles of peripheral blood mononuclear cells from healthy volunteers.

The normal degree of intra- and interindividual variation in gene transcription profiles of healthy human tissues has not been extensively investigated. In the study described here, microarrays were employed to analyze gene transcription in peripheral blood mononuclear cells prepared from serial blood samples that had been obtained, at weekly intervals, from apparently healthy human volunteers. Transcript levels for the majority of genes examined were found to be remarkably consistent within samples from a single donor. Conversely, marked differences were observed in samples obtained from different donors. Genes that exhibited differential expression dependent on sex, age, body mass index, and the presence of varying proportions of different leukocyte subsets were identified. These results emphasize the important contributions of genetic and environmental factors, as well as varying representation of different cell types, in determining the overall gene transcriptional profiles of human tissues. However, the study also provides evidence that, within an individual, the gene transcription profiles of sampled tissues can be comparatively stable over time.

Red grape juice inhibits iron availability: application of an in vitro digestion/caco-2 cell model.

Adequate bioavailable Fe intake is essential for optimal growth and intellectual development of infants and children. Fruit juices are nutritious and popular drinks for infants and children and are known to contain Fe uptake inhibitors (e.g., polyphenolic compounds) and a dominant promoter, ascorbic acid. Ascorbic acid is naturally present in fruit juices and is added during processing to almost all juices found in supermarkets. With these facts taken into account, an in vitro digestion/Caco-2 cell culture model was developed to compare the effects of apple, pear, white grape, red grape, prune, grapefruir, and orange juices on iron bioavailability. In two series of experiments, juices from a local supermarket were combined with FeCl(3) or commercial infant cereal fortified with elemental iron and subject to simulated gastric and intestinal digestion. Caco-2 cell ferritin formation in response to exposure to the digests served as the measure of Fe uptake. The pear, apple, grapefruit, orange, and white grape juice significantly increased Fe bioavailability from FeCl(3). For the infant cereal studies, the apple, orange, pear, and white grape juices increased the Fe bioavailability of the infant cereal. In contrast, the red grape juice and prune juice had profound inhibitory effects on iron bioavailability. These inhibitory effects were likely due to high levels of polyphenolic compounds that bind and thereby prevent absorption of soluble Fe. These inhibitory compounds appeared to counteract the promotional effects of ascorbic acid as they were in considerable molar excess relative to ascorbic acid and Fe in the digest. From a nutritional standpoint, the results suggest that individuals in need of optimal Fe absorption should avoid red grape and prune juice or at least vary the types of juices consumed. Alternatively, individuals seeking to limit Fe uptake (e.g., hemochromatitics and astronauts) may be able to utilize red grape or prune juice as effective inhibitors of Fe uptake. Consumers should be aware that the compounds that inhibit Fe availability are also linked to anticancer benefits; thus, a dietary balance of the above juices may be optimal.

Inhibition of iron uptake by phytic acid, tannic acid, and ZnCl2: studies using an in vitro digestion/Caco-2 cell model.

The objective of this study was to document the effects of phytic acid, tannic acid, and zinc on iron uptake in an in vitro digestion/Caco-2 cell culture model. The effects of phytic acid and tannic acid on iron uptake were measured at increasing molar ratios of FeCl3 to phytic acid or tannic acid. Maximal inhibition of iron uptake by phytic acid occurred at a 1:10 ratio of Fe to phytic acid. Dialyzable Fe decreased with a low Fe to phytic acid ratio but increased with Fe:phytic acid ratios greater than 1:3 indicating that more iron was soluble at higher phytic acid levels but less available. As in human studies, heme iron was less inhibited by phytic acid than nonheme iron. Tannic acid was a more potent inhibitor of nonheme iron uptake, as maximal inhibition (97.5%) of iron uptake occurred at a ratio of 1:1 or less. The addition of ZnCl2 to the digest at ratios of 1:0.5 and 1:1 decreased iron uptake by 57 and 80%, respectively. Overall, the results agree qualitatively with studies in humans and demonstrate the relative effects of these compounds on iron uptake in this model system. This study provides key information for determining iron availability under more complex meal conditions.