We examined the effects of vitamin B_1 (B_1) and fat added to a feed on their accumulation and glucose- and lipid-metabolism in the porcine liver. B_1 content in the livers of pigs fed a feed supplemented with 15 ppm B_1-supplemented feed (B+ group) was significantly higher than that in the livers of pigs fed the usual dosage of 1.5 ppm B_1 (Control group). B_1 content in the livers of pigs given a feed with 1.5 ppm B_1 plus 3% fat (F+ group) or a feed with 15 ppm B_1 plus 3% fat (B+F+ group) was significantly higher than that in pigs given a feed with 15 ppm B_1 (B+ group) or controls. The liver fat content in the B+F+ group was lower than that in the B+ group. Analysis of liver mRNA levels showed that gene expression of β-oxidation-related proteins increased in B_1-supplemented groups. Glycolytic pathway- and TCA cycle-related gene expression levels were also increased with fat supplementation. These results indicated that, in pigs with co-supplementation of high dose of B_1 and fat, glucose and lipid metabolism was enhanced in the liver.

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Few association studies on vitamin A and genetic polymorphism have been conducted so far, even though brilliant success has been achieved in translational researches on vitamin D receptor or methylene tetrahydrofolate reductase gene polymorphism. Recently, a couple of epoch-making papers have been published in vitamin A and genetic polymorphism field: 1) a common intronic single nucleotide polymorphism (SNP) (rs12591551 A/C) of the aldehyde dehydrogenase 1A2 (ALDH1A2) gene was shown to be associated with individual variations of retinoic acid concentrations in umbilical cord blood, and 2) two common intronic SNPs (rs6800566, rs13070407) of the retinoic acid receptor β (RARβ) gene were shown to be associated with individual variations of adaptive immune responses to measles vaccine. In this mini-review, these 2 pioneering works are introduced and discussed briefly.

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β-Carotene15,15'-monooxygenase (BCMO1) is a key enzyme in the metabolism of provitamin A carotinoids. This enzyme cleaves the center of dietary vitamin A carotinoids including β-carotene, α-carotene, and β-cryptoxanthin to form retinal. Retinal is produced at the first step of the conversion of provitamin A carotinoids to vitamin A. Recently, a lot of studies to evaluate the rate of β-carotene conversion using biomarkers have been performed. The rate of the conversion of provitamin A carotinoids to vitaminA is known to be highly variable in human population. On the other hand, single nucleotide polymorphisms (SNPs) for BCMO1 which exist in human genome have been analyzed and the existence of 3,483 SNPs in BCMO1 gene has been identified. Several reports have indicated the association between these SNPs and β-carotene conversion. The first report showed that T170M, a SNP of BCMO1 gene with amino acid substitution, was related to hypercarotenemia and hypovitaminosis A in the patients with carotenosis. Furthermore, it was reported that SNPs related to β-carotene conversion in the exon region, which caused amino acid substitution, were found in human population. Recently, a role of the SNP of BCMO1 gene present in the gene promoter region has been reported. In this mini review, we have focused on the relation between SNPs for BCMO1 and the bioavailability of plant-based provitamin A.

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Vitamin A (VA) supplementation (VAS) has been used to reduce the overall childhood mortality in developing countries where VA deficiency is a seriously problem. However, detailed mechanisms for the reduction of childhood mortality by VAS remain unclear. In the investigation of the effect of VAS on cytokine production using a whole blood culture protocol, the focus was paid on the relation between VAS and single nucleotide polymorphisms (SNPs) of TNF-α, IL-10 and TLR4 genes among various cytokine gene SNPs and thereby the relation between VAS and these cytokine gene SNPs was examined. As a result, there was a significant relation between VAS and only TNF-α-308 among the cytokine gene SNPs studied. VAS reduced TNF-αproduction significantly in G homozygotes, whereas VAS was found to have no effect on TNF-αproduction in A carriers. There was a borderline of significant three-way interactions among sex, VAS and TLR4+896 genotype. Thus, there was a quite limited relation between the reducing effect of VAS on cytokine production and cytokine gene polymorphisms. Therefore, further study is needed to clarify the relation between the reducing effect of VAS on cytokine production and cytokine gene polymorphisms.

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