Organic and inorganic nutrients are supplied to cells via transporters situated on the plasma membrane. In the present study, we identified the amino acid transporters L-type amino acid transporter (LAT)1, LAT2, basic amino acid transporter^b＋,0 (BAT) 1, system y^＋L amino acid transporter (y^＋LAT)1 and 2, and Na^＋-dependent phosphate transporter (NaPi) IIc. To clarify the roles of these transporters, we analyzed their function and nutritional regulation using Xenopus oocytes, cultured cells or rodents. This manuscript summarizes our study, incuding identification of the amino acid transporters using functional expression cloning, and phosphate homeostasis using gene targeting in mice.

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It is unclear which dietary intake standard should be used for children with abnormal body size. To assess energy expenditure in short-stature children who have no underlying disorders, we measured total energy expenditure (TEE), resting energy expenditure (REE) and respiratory quotient (RQ) using the doubly labeled water method and expired gas analysis in 8 children with short stature (5 males, 3 females: age 5.6 ± 0.7 years), and calculated their physical activity levels (PAL). The measured values were then compared with estimated values based on subjects’ age- or height-adjusted age-matched references for basal metabolic rates. We also performed a food intake survey and calculated the percentage energy intake for the three major nutritional components. The measured TEE and REE in the short-stature children were significantly higher than those estimated from the age-matched references, but did not differ from the height-adjusted age-matched estimates. PAL obtained from the measured TEE and REE also did not differ from the estimated values based on either actual age- or height-adjusted age-matched references. Percentage energy intake from carbohydrate among total energy intake was lower than shown in the Dietary Reference Intakes for Japanese. These data suggest that metabolism is enhanced in short-stature children. In addition to possible delayed development and/or genetic mutation, as has been speculated, insufficient carbohydrate intake might also contribute to the energy imbalance in short-stature children.

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This study examined the apparent inhibitory effect of fermented brown rice （FBR） on amylase activity in human saliva. When diluted human saliva was made to react for 30 minutes with a substrate mixture of FBR and soluble starch, the amount of starch remaining was significantly higher than in the control where the substrate was a mixture of normal brown rice and soluble starch. Moreover, there was no difference in the amount of starch remaining between the FBR mixture substrate and a substrate of normal brown rice with added nucleic acid （DNA･RNA）. Furthermore, there was no evident difference in amylase activity between the saliva in the presence of FBR and that in the presence of nucleic acid. However, the salivary amylase activity in the presence of FBR was significantly lower than that in the control, or for saliva in the presence of normal brown rice. In addition, the Michaelis constant （Km value） for saliva in the presence of FBR did not differ from that in the presence of nucleic acid, and furthermore was significantly higher than that of the control and saliva in the presence of normal brown rice. Finally, Lineweaver-Burk plots showed that the type of inhibition was competitive in both cases. These results suggest that FBR competitively inhibits alpha-amylase activity in human saliva.

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Age-related changes in blood fatty acid（FA）have been reported. This cross-sectional study examined age-related changes in serum FA composition among Japanese individuals aged 40 to 88 years（1,070 men and 1,098 women）. Venous blood was collected early in the morning after a fast of at least 12 h, and serum FA composition was expressed as a percentage of the total FA（wt％）. Participants were categorized into groups according to sex and age（40-49, 50-59, 60-69, 70-79, and≥80 years）. In both men and women, the proportion of n-3 polyunsaturated fatty acids（PUFAs）（wt％）including α-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid tended to increase, whereas that of n-6 PUFAs（wt％）including linoic acid and arachidonic acid tended to decrease with older age. These results suggest that the blood FA composition differs with age among community-dwelling Japanese men and women.

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