Synthetic α-Tocopherol (α-Toc) contains equal amounts of eight different stereoisomers of α-Toc arising from three asymmetric carbons (2-position in the chroman ring and 4'- and 8'-position in side chain tail). We investigated the distribution and biodiscrimination of α-Toc stereoisomers in rat tissues and in human bloods using a new chiral HPLC method. According to these results, we suggested that 2R-and 2S-isomers were easily transported into the liver from the plasma and the 2R-isomers were preferentially released from the liver into the blood, whereas the 2S-isomers were remained in the liver. In addition, we examined the biodiscrimination of α-Toc stereoisomers during intestinal absorption in situ and in vitro. Consequently, we suggested that the discrimination of α-Toc stereoisomers does not occur during absorption in small intestine. We presumed that this mechanism was performed by α-tocopherol transfer protein (α-TTP) in liver. According to this result, it became clear that a α-TTP was able to discriminate α-Toc stereoisomers, preferentially to transport RRR-α-Toc than SRR-α-Toc from the liposomes.

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It has recently been emphasized that increasing peak bone mass during the human growth period is important in preventing osteoporosis. Exercise and nutrition are two major environmental factors which determine the peak bone mass acquired during growth. In this study, we investigated the vitamine D intake of 466 female senior high school students on the purpose of assessing the influence of vitamin D and other nutritional intake on peak bone mass. The average daily calcium intake by these females was low (497.2±230.6 mg). Only 30.0 % of the subjects satisfied the minimum daily calcium requirement for adults (600 mg). The daily vitamin D intake was equal to or greater than the minimum daily requirement for adults in 60.7 % of all subjects. However, daily vitamin D intake showed a bi-model distribution, with peaks in both the high and low ends of the range. Thus, daily vitamine D intake varied greatly among individual subjects. Lumbar vertebral bone mass was not correlated with daily calcium intake but was significantly correlated with vitamin D intake (r=0.484). The ratio between vitamin D intake and calcium intake was significantly positively correlated with lumbar vertebral bone mass (r=0.550). This means that high vitamin D intake has a favorable effect on lumbar vertebral bone mass even if calcium intake is low. When the effects of vitamin D intake on lumbar vertebral bone mass were analyzed in subjects divided into three groups according to their calcium intake, the effects of higher vitamine D intake in increasing bone mass became more marked as the calcium intake decreased. These findings suggest that vitamin D intake is a very important factor in terms the peak bone mass in female senior high school students, whose calcium intake is often relatively low.

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Menaquinone-7(MK-7) and phylloquinone (vitamin K_1), which are vitamin K homologues n foods, were purified from the fermented soybean (natto) and soybean, respectively. The effect of MK-7 and K_1 in the metaphyseal tissues obtained from rat femur in vitro was investigated. Bone tissue was cultured for 24 or 48 hr in the presence or absence of MK-7 in the range of 10^<-7> to 10^<-5> M. The presence of MK-7(10^<-5>M) caused a significant increase of calcium content and alkaline phosphatase (ALP) activity in the bone tissue. Bone DNA content and bone glucose consumption were not changed by the addition of MK-7(10^<-5>M). Meanwhile, the presence of MK-4(10^<-5>M) caused a significant increase of ALP activity in the bone tissue, while K_1(10^<-5>M) did not have the effect .These results suggest that MK-7 can directly act on the femoral metaphyseal tissues of rat femur in vitro.

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