著者
平岡 真実 香川 靖雄
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.89, no.2, pp.59-64, 2015-02-25 (Released:2017-08-10)

It is known that individuals respond differently to the same dietary intake differently. Nutrigenetics is an essential discipline to study gene-based differences in response to dietary components for nutrition and dietetics practice. One of the best-known examples for nutrigenetics is the polymorphism of methylenetetrahydrofolate reductase (MTHFR) C677T. The presence of the C677T mutation in MTHFR gene is associated with a reduction of MTHFR enzyme activity. This reduction of MTHFR enzyme activity may cause an increase in plasma homocysteine level which becomes risk factors for cardiovascular disease, cognitive impairment and neural tube defects. Plasma homocysteine level is responsive to intervention with folic acid and related vitamin B group. "Sakado Folate Projects" is a health promotion with personalized nutrition intervention based on MTHFR C677T polymorphisms for prevention of these diseases associated with hyperhomocysteinemia. An increase in serum folate level and a decrease in serum homocysteine level were observed at 4 months after the onset of this intervention and these changes were particularly marked in individuals with TT genotype. This finding suggests that personalized nutrition intervention based on genetic information is effective in motivating individuals to change their lifestyle habit.
著者
宮内 正厚 中島 英彰 平井 千津子
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.88, no.7, pp.349-357, 2014-07-25 (Released:2017-08-10)
被引用文献数
1

In recent years, the importance of solar exposure for vitamin D synthesis in the human body has been pointed out. The solar exposure time necessary for the synthesis of vitamin D depends largely on geographical location, season, time of day, weather, exposed skin area, etc. Using numerical simulations we estimated that if 10 μg vitamin D were to be synthesized entirely by solar exposure to skin type III (SPT), which is considered to be the most typical skin type for Japanese people, it would necessitate 6.4 min horizontal exposure of a 600 cm^2 skin area, corresponding to the face and the back of both hands, under cloudless sky at 12:00 o'clock in July in Tsukuba. Under the same conditions, it would take 20.8 min to reach 1 MED (Minimum Erythemal Dose) which is thought to be the harmful UV exposure level for human skin. In other words, approximately 31% of the time before the skin gets red is enough for the synthesis of 10 μg vitamin D a day. On the other hand, in Sapporo which is located in the northern part of the Japanese Archipelago, the corresponding durations are 8.4 min and 27.0 min, respectively under the same conditions as in Tsukuba, whereas the necessary time in December would be 139 min and 296 min, respectively. Although the sufficient amount of vitamin D cannot be obtained by short-time exposure to solar radiation, it is thought that long-time exposure might not damage the skin. It can be concluded that for a skin area of 600 cm^2 in horizontal position, exposure time until damage would occur is generally 3 times larger than what is necessary for the synthesis of 10 μg vitamin D under strong UV radiation. It should be noted that generally, with a larger exposed skin area the solar exposure time for vitamin D synthesis could be considerably shortened.
著者
天野 晶子 石神 昭人
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.83, no.1, pp.24-26, 2009-01-25 (Released:2017-10-10)
参考文献数
21
被引用文献数
1
著者
槇島 誠
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.85, no.2, pp.47-56, 2011-02-25 (Released:2017-10-10)
参考文献数
51

Nuclear receptors belonging to the NR1H and NR1I subfamilies, including vitamin D receptor (VDR, NR1I1), control cholesterol and bile acid metabolism. Bile acids are detergents essential for the digestion and intestinal absorption of hydrophobic nutrients, such as triacylglycerol, cholesterol and lipid-soluble vitamins, including vitamin D.Primary bile acids are generated from cholesterol and are secreted in bile as glycine and taurine conjugates. The intestinal microflora convert the primary bile acids to the secondary bile acids, including lithocholic acid (LCA). VDR, a receptor for 1,25-dihydroxyvitamin D_3(1,25(OH)_2D_3), acts as a bile acid receptor with specificity for the secondary bile acid LCA and its derivatives. VDR activation by 1,25(OH)_2D_3 or LCA induces the xenobiotic metabolism of bile acids. Synthetic LCA derivatives induce tissue VDR activation without inducing hypercalcemia in mice. VDR acts as a bile acid sensor as well as an endocrine receptor for vitamin D signaling.
著者
吉澤 透 茅田 誠也
出版者
日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.68, no.8, pp.478-480, 1994-08-25
著者
井上 聡
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.83, no.2, pp.59-64, 2009-02-25 (Released:2017-10-10)
参考文献数
21

Vitamin K is a critical nutrient in the bone metabolism. We have demonstrated that SXR, a nuclear receptor steroid and xenobiotic receptor, expressed in bone cells could be activated by vitamin K_2 as a ligand. vitamin K_2 regulates the expression of various bone-related genes in osteoblastic cells. We have identified novel SXR targets that were up-regulated by vitamin K_2 in human osteoblastic cells. Tsukushi, a small leucine-rich repeat proteoglycan, has been shown to contribute to vitamin K-dependent collagen accumulation. Thus, we have discovered an alternative pathway of vitamin K action in the bone via transcriptional regulation utilizing nuclear receptor SXR.
著者
赤井 翔太 生城 浩子 澤井 大樹 林 秀行 神谷 信夫 宮原 郁子
出版者
公益社団法人 日本ビタミン学会
雑誌
ビタミン (ISSN:0006386X)
巻号頁・発行日
vol.88, no.7, pp.358-365, 2014

Homoserine dehydrogenase catalyzes the conversion of L-aspartate-4-semialdehyde to L-homoserine. Homoserine dehydrogenase is required for the biosynthesis of the three essential amino acids, i.e. lysine, methionine, and isoleucine, from aspartic acid. This enzyme attracts attention also as a promising antifungal drug target. We have determined the crystal structures of homoserine dehydrogenase from Thermus thermophilus HB8 in both substrate-free form and homoserine-binding form by X-ray diffraction. Crystallization conditions were surveyed at 293 K by using a hanging-drop vapor-diffusion method. The substrate-free form was solved to 1.4 Å resolution and the homoserine-binding form was solved to 2.0 Å resolution. The homoserine dehydrogenase was a dimer with each subunit composed of three distinct domains, nucleotide-binding, dimerization, and substrate-binding domain. In the homoserine-binding forms, the amino group of homoserine made a hydrogen bond to the side chain carboxylate of Glu180. This hydrogen bond induced the conformation change of Thr165-Pro183 loop, which made the loop close to the active site. The substrate homoserine was rigidly recognized by several amino acid residues in the enzyme active site, indicating that Lys99 or Lys195 would be an essential catalytic residue to facilitate hydride transfer.