A role of vitamin A in the synthesis of hyaluronic acid by skin cells is well known. Hyaluronic acid is produced by corneal epithelial cells and keratocytes in the eye. We investigated whether rabbit corneal epithelial cells and keratocytes release hyaluronic acid after exposure to vitamin A compounds. Rabbit corneal epithelial cells and keratocytes were inoculated with RCGM2 medium and incubated at 37ºC under 5% CO₂ in air for 24 h. The medium was then replaced with medium containing 0.1, 1, 10, or 100 μM retinoic acid or retinol palmitate (VApal) and incubated for another 48 h. Hyaluronic acid release from both corneal epithelial cells and keratocytes during culture was increased by retinoic acid at the lower concentration of 0.1 μM and 1 μM determined with a sandwich binding protein assay kit. However, it was significantly decreased at the higher concentrations of 10 μM and 100 μM, and the cell count determined with a Neutral Red assay kit was also decreased at these concentrations. On the other hand, hyaluronic acid release from corneal epithelial cells during culture was increased by VApal at the lower concentration of 0.1 μM and 1 μM, but there was no significant difference in the cell count for either corneal epithelial cells or keratocytes in the presence of VApal at any concentration. In conclusion, it is suggested that vitamin A stimulates the release of hyaluronic acid from cultured rabbit corneal epithelial cells and keratocytes.

View full abstract

The purpose of this study was to clarify the effects of nutrients on the gonadal development of male rats kept under constant darkness as a model of disturbed daily rhythm. In the present study we examined the effects of nine water-soluble vitamins. We selected 7 water-soluble vitamins (choline, nicotinic acid (NA), pantothenic acid (PA), vitamin B6 (VB6), vitamin B1 (VB1), vitamin B2 (VB2) and folic acid (FA)) as experimental factors for the first experiment (Ex. 1) and biotin and vitamin B12 (VB12) as experimental factors for the second experiment (Ex. 2). The dietary content of these vitamins was normal or six times the normal content. Lighting condition (L.C.) was also added as a factor. Four-week-old male rats (Fischer 344 strain) were kept under constant darkness or normal lighting (12-h light/dark cycle) for 4 wk. The depression of gonadal development in the constant darkness groups (D-groups) was shown. The L.C., PA, VB6 and VB1 influenced testes development, and these three vitamins had interactions with L.C. Among the normal lighting groups (N-groups), the highest value for testes weight was observed under the normal-PA, high-VB6 and high-B1 diet; on the other hand, among the D-groups, it was observed under the high-PA, normal-VB6 and normal-VB1 diet. The results showed that the depression of gonadal development in rats kept under disturbed daily rhythm was improved by getting a high amount of PA and normal amount of VB6 and VB1.

View full abstract

Having higher bone mineral density (BMD) during growth is complexly influenced by many factors. For example, nutrition and physical exercise are key factors. However, few studies have investigated the combined effects of these factors. In this study, we investigated the effect of physical exercise and different levels of protein intake on BMD and bone strength of growing male rats. Forty-seven male Wistar rats (5 wk old) were randomized into 10% (Low), 20% (Moderate) and 40% (High) protein diet groups, and each group was further divided into exercise groups (LEx, MEx, HEx) or non-exercise groups (L, M, H). Exercise group rats were trained 6 d per week on a treadmill (25-30 m/min, 60 min) for 60 d. After being sacrificed, their BMD and bone strength were evaluated. The BMD of tibia, femoral breaking force and energy were significantly lower in the low protein diet groups than the other diet groups. In particular, the femoral breaking energy was significantly lower in the HEx group than in the H group, while there were no differences between LEx and L or MEx and M. Taken together, our data suggests that a low protein intake could suppress acquisition of bone mass and increasing bone strength during growth. Moreover, a high protein intake could also suppress bone strength during growth in which physical activity was vigorously performed. Therefore, sustaining an adequate protein intake level, around 20% protein intake, may be of significance for increasing not only bone mass but bone strength during growth.

View full abstract

The possible role of eating rate in promoting obesity has long been of interest. We examined the association between rate of eating and overweight status in Japanese children and adolescents. This Japanese cross-sectional study included 15,974 children (6-11 y; 7,956 boys and 8,018 girls) and 8,202 adolescents (12-15 y; 3,944 boys and 4,258 girls). Rate of eating was self-reported according to five categories. Body mass index (BMI) was calculated from self-reported body weight and height. Overweight was defined according to the International Obesity Task Force age- and sex-specific BMI cutoffs. The overall prevalence of overweight was 13.2%. Rate of eating was positively associated with the risk of overweight, independent of protein, fat, and dietary fiber intakes. Multivariate odds ratios (95% confidence intervals) for overweight in the very slow, relatively slow, medium, relatively fast, and very fast categories were 0.31 (0.20, 0.49), 0.49 (0.40, 0.60), 1 (reference), 2.81 (2.42, 3.26), and 4.49 (3.47, 5.81) in male children; 0.42 (0.31, 0.58), 0.49 (0.41, 0.59), 1 (reference), 2.74 (2.27, 3.31), and 5.69 (3.75, 8.63) in female children; 0.13 (0.03, 0.54), 0.43 (0.28, 0.65), 1 (reference), 2.31 (1.88, 2.84), and 3.84 (2.77, 5.31) in male adolescents; and 0.55 (0.30, 1.01), 0.46 (0.33, 0.65), 1 (reference), 1.30 (0.99, 1.71), and 1.49 (0.84, 2.65) in female adolescents, respectively (all p for trend<0.0001). In conclusion, this large cross-sectional study in Japan showed that a higher rate of eating was independently positively associated with an increasing risk of overweight in children and adolescents.

View full abstract

Evidence on factors associated with misreporting of energy intake is limited, particularly in non-Western populations. We examined the characteristics of under- and over-reporters of energy intake in young Japanese women. Subjects were 3,956 female Japanese dietetic students aged 18-20 y (mean body mass index: 20.9 kg/m²). Energy intake was assessed using a comprehensive self-administered diet history questionnaire. Estimated energy requirement was calculated based on self-reported information on age, body height and weight, and physical activity with the use of an equation from the US Dietary Reference Intakes. Under-, acceptable, and over-reporters of energy intake were identified based on the ratio of energy intake to estimated energy requirement, according to whether the individual's ratio was below, within, or above the 95% confidence limits of the expected ratio of 1.0 (<0.70, 0.70-1.30, and >1.30, respectively). Risk of being an under- or over-reporter of energy intake compared to an acceptable reporter was analyzed using multiple logistic regression. The percentage of under-, acceptable, and over-reporters of energy intake was 18.4, 73.1, and 8.4%, respectively. Under-reporting was associated with overweight or obesity, perception that one's own weight was too heavy or light, lower dietary consciousness, active lifestyle, living without family, and living in a city (compared with a metropolitan area). Over-reporting was associated with sedentary lifestyle only. This study of lean young Japanese women showed that energy intake misreporting, particularly under-reporting, was common and differential among populations. Particularly, perceived weight status was associated with under-reporting of energy intake, independent of actual weight status.

View full abstract

There is little evidence regarding the associations between bone growth and environmental factors among growing children, especially in Asians. The aim of this cross-sectional study was to search for the promotion factors of bone growth in Japanese children during growth. The study subjects were male (n=333) and pre/post-menarcheal female (n=179/n=68) school children aged 8-14 y. Bone status at the calcaneus was evaluated by quantitative ultrasound (Benus III), and the bone area ratio (BAR) was used as an evaluation index. Dietary intakes were assessed via brief self-administered diet history questionnaires. The participants were asked to record all of their activities for 3 d (2 weekdays and 1 holiday). They were also required to provide the most recent anthropometric measurement records at their schools and answer questions about the frequency of fractures and, for females, the length of time since menarche. Multiple regression analysis with dummy variables demonstrated that age, magnesium (more than the RDA), vitamin B₁ (more than the RDA), mean physical activity intensity per day (more than 1.7 METs), vitamin C (more than the RDA) and calcium (more than the RDA) were significantly positive influential factors of BAR for males. For premenarcheal females, age, vitamin A (more than the RDA), BMI, and mean physical activity intensity per day (more than 1.7 METs) were significantly positive influential factors of BAR, and for postmenarcheal females, only BMI and age were significantly positive influential factors of BAR. The results suggest that several manageable factors correlate with the bone mass, and the associations differ depending on gender and menarcheal status.

View full abstract

The effects of oral ingestion of a hot water extract of matured fruit of the date palm tree (Phoenix dactylifera L.) on allergic responses were investigated in mite-sensitized mice. Sneezing and nose rubbing events in mice given a date extract-added diet were significantly lower than in those given an extract-free (control) diet. The serum total and mite antigen-specific immunoglobulin (Ig) E levels, and the number of spleen interleukin-4⁺CD4⁺, IgE⁺B220⁺ and FcεRIα⁺CD117⁺ cells was significantly lower in mice given the date extract-added diet than in those given the control diet. Chlorogenic acid, pelargonin and ferulic acid significantly reduced the number of IgE⁺B220⁺ cells, while chlorogenic acid and pelargonin significantly decreased the number of FcεRIα⁺CD117⁺ cells in mouse spleen cell cultures. These results suggest that some polyphenols in the date may reduce mite-induced allergic symptoms in mice via a decrease in the number of IgE-producing plasma cells and high-affinity IgE receptor-expressing mast cells.

View full abstract

Polygonum cuspidatum has been broadly utilized as a herbal medicine in Asia, but the outline of the polyphenol compounds in the plant has not been characterized well. In the present study, the major polyphenolic components were isolated from the roots of P. cuspidatum, and identified as resveratrol and its glucosides, resveratroloside and polydatin. On the other hand, chlorogenic acid was found to be one of the polyphenolic components in the leaves and stems of the plant. Next, we elucidated that resveratrol derivatives and chlorogenic acid exhibit α-glucosidase inhibitory activities, and resveratroloside exhibits the same inhibitory activity as quercetin does. Furthermore, DPPH radical scavenging activities of antioxidants including resveratrol derivatives and chlorogenic acid derivatives were examined by initial rate analyses of their reactions. Subsequently, it was revealed that resveratrol derivatives have slow-acting effects on the radical scavenging activity and that chlorogenic acid derivatives exhibit very fast-acting effects.

View full abstract

Fructooligosaccharides (FOS) are indigestible oligosaccharides that increase the expression of calbindin-D9k and consequently increase calcium absorption by the colon in rats. The molecular mechanism of the increased expression of calbindin-D9k resulting from FOS ingestion has not been elucidated. Short-chain fatty acids (SCFAs), namely, fermentation products of FOS by intestinal bacteria have been hypothesized as direct effectors of calbindin-D9k gene expression. To test this hypothesis, SCFAs were added to Caco-2 human intestinal epithelial cells, and changes in the levels of transcription of genes for calbindin-D9k, and transcription factors (vitamin D receptor: VDR, caudal homeobox-2: Cdx-2, hepatocyte nuclear factor 1-α: HNF1-α) were determined by quantitative reverse transcription polymerase chain reaction. Addition of sodium propionate or sodium butyrate to cell cultures increased levels of calbindin-D9k mRNA to 731% (p<0.05) and 321% (p<0.05), respectively. However, addition of these SCFAs did not affect the levels of mRNA VDR, Cdx-2, or HNF1-α. In conclusion, addition of SCFAs to cultured Caco-2 cells results in elevation of calbindin-D9k mRNA, consistent with the expected role of SCFAs as mediators of the increase of calcium absorption in rats that were fed with FOS.

View full abstract

Diallyl disulfide (DADS) is a major sulfur compound of garlic, and exerts anti-inflammatory, immune-modulatory, and enhancing sympathetic activity effects. However, it still remains unclear how DADS affects the distribution of white blood cell subsets, which is essential to execute effective immune responses and partially regulated by adrenal glucocorticoids. Therefore, we examined the dose-dependent effects of DADS administration on the circulating number of white blood cells (WBCs) and lymphocyte subsets, and plasma corticosterone concentration in rats. Male 10-wk-old Sprague Dawley rats were divided into the DADS-free and DADS-orally administered (dose=10, 20, and 40 mg/kg BW) groups. Blood samples were collected from the tail vein at 0, 1, 2, 4, and 6 h after the administration. DADS administration decreased dose- and time-dependently the circulating number of total WBCs, total lymphocytes, and monocytes. Within the lymphocyte subsets, the circulating number of T-lymphocytes and B-lymphocytes was significantly reduced 4 h after DADS administration in a dose-dependent manner, although that of natural killer (NK) cells was not affected. On the other hand, although DADS administration did not significantly change the circulating number of neutrophils, the circulating number of eosinophils and basophils showed a decreasing tendency after DADS administration. In contrast, plasma corticosterone concentration was increased 2 h after DADS administration in a dose-dependent manner. These results suggest that DADS administration reduces the circulating number of monocytes and lymphocytes, including especially acquired immune cells, via the action of corticosterone, and the effects are induced in a dose-dependent manner.

View full abstract

The purpose of this study was to determine whether ornithine affects the rate of tissue protein synthesis in male rats. Two experiments were done on five or two groups of young rats (5 wk) given diets containing 0.15, 0.3, 0.5 or 0.7% ornithine-HCl added to a 20% casein diet for 1 d (only one 3 h period) (Experiment 1), and given a diet containing 0 or 0.7% ornithine-HCl added to a 20% casein diet for 10 d (Experiment 2). The plasma concentration of growth hormone (GH) was the highest in rats fed 0.5 and 0.7% ornithine added to the 20% casein diet. The fractional rates of protein synthesis in brain regions, liver and gastrocnemius muscle increased significantly with the 20% casein+0.7% ornithine diet compared with the 20% casein diet. In brain regions, liver and gastrocnemius muscle, the RNA activity [g protein synthesized/(g RNA·d)] significantly correlated with the fractional rate of protein synthesis. The RNA concentration (mg RNA/g protein) was not related to the fractional rate of protein synthesis in any organ. The present results suggest that the treatment of young rats with ornithine is likely to increase the concentration of plasma GH and the rate of protein synthesis in the tissues, and that RNA activity is at least partly related to the fractional rate of tissue protein synthesis.

View full abstract

Wasabi is a plant of Japanese origin. It belongs to the family Brassicaceae and produces various isothiocyanates (ITCs). To clarify the type I allergies inhibited by wasabi ITCs, we investigated the inhibitory effect on chemical mediator release from dinitrophenylated bovine serum albumin (DNP-BSA)-stimulated RBL-2H3 rat basophilic leukemia cells. Allyl ITC (AITC), sec-butyl ITC (s-BuITC), and 3-butenyl ITC (3-BuITC), which have 3 or 4 carbon chains, inhibited histamine release but did not inhibit the release of leukotriene B4 (LTB4) or cysteinyl LTs (CysLTs). 4-Pentenyl ITC (4-PeITC) and 5-hexenyl ITC (5-HeITC), which have 5 or 6 carbon chains and an unsaturated bond at the end, inhibited LTB4 release but did not inhibit the release of histamine or CysLTs. 6-Methylthiohexyl ITC (6-MTITC), 6-methylsulfinylhexyl ITC (6-MSITC), and 6-methylsulfonylhexyl ITC (6-MSFITC), which have a sulfur atom inserted at the end of a 6-carbon chain, inhibited the release of histamine, LTB4, and CysLTs and the elevation in intracellular Ca²⁺. These results suggest that wasabi ITCs inhibited type I allergies by inhibiting chemical mediator release and that the inhibitory effects on each chemical mediator were due to differences in the side chain structure of the wasabi ITCs.

View full abstract