Abstract
Recent data have shown that interindividual variability in the bioavailability of vitamins A (β-carotene), D, and E, and carotenoids (lutein and lycopene), as well as that of phytosterols, is modulated by single nucleotide polymorphisms (SNPs). The identified SNPs are in or near genes involved in intestinal uptake or efflux of these compounds, as well as in genes involved in their metabolism and transport. The phenotypic effect of each SNP is usually low, but combinations of SNPs can explain a significant part of the variability. Nevertheless, results from these studies should be considered preliminary since they have not been validated in other cohorts. Guidelines for future studies are provided to ensure that sound associations are elucidated that can be used to build consolidated genetic scores that may allow recommended dietary allowances to be tailored to individuals or groups by taking into account the multiloci genotypic signature of people of different ethnic origin or even of individuals.
Highlights
Among these groups, carotenoids and PS have received much attention, and there is a wealth of studies linking the intake or the blood concentration of these compounds with parameters of human health or specific diseases
These studies allowed researchers to link this disease to mutations in two genes, ABCG5 and ABCG8, which encode for two ATP binding cassettes, sterolin-1 and sterolin-2, that work as hemitransporters [11, 79]
This curve could be moved farther to the left or to the right depending on the absorption phenotype of an individual for a specific compound: An individual with a high capacity to absorb a specific fat-soluble vitamin or phytochemical would have a lower requirement compared with the general recommended dietary allowance (RDA), while an individual with a poor capacity for absorption would have a higher requirement compared with the general RDA (Figure 5)
Summary
Three clinical trials identified genetic variations associated with variability in VE bioavailability, but two fairly different methods were used to evaluate bioavailability, leading to a potential source of result heterogeneity, as highlighted in the previous section. In a clinical trial by our group [25], the association was assessed for SNPs in genes involved in VE absorption and metabolism (3,769 SNPs in 59 candidate genes) with variability in VE bioavailability, measured as the postprandial chylomicron VE concentration, in a group of 38 healthy adult men who received a meal containing 100-IU RRR-α-tocopheryl acetate. A combination of 28 SNPs in 11 candidate genes was shown to be significantly associated with this variability Of those 11 genes, 7 had been previously associated with interindividual variability in the postprandial chylomicron triglyceride response in the same group of participants [43], while the remaining 4 encode for proteins that are involved in VE metabolism and transport. Sterol regulatory element binding transcription factor 2 (SREBF2) encodes a transcription factor controlling the expression of many genes required for cholesterol synthesis [64] and that of SLC10A2 and NPC1 like intracellular cholesterol transporter 1 (NPC1L1) [4], which encodes the main protein involved in the apical uptake of cholesterol [5] and α-tocopherol [96] into enterocytes
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