Although the importance of solar radiation for vitamin D₃ synthesis in the human body is well known, the solar exposure time required to prevent vitamin D deficiency has not been determined in Japan. This study attempted to identify the time of solar exposure required for vitamin D₃ synthesis in the body by season, time of day, and geographic location (Sapporo, Tsukuba, and Naha) using both numerical simulations and observations. According to the numerical simulation for Tsukuba at noon in July under a cloudless sky, 3.5 min of solar exposure are required to produce 5.5 μg vitamin D₃ per 600 cm² skin corresponding to the area of a face and the back of a pair of hands without ingestion from foods. In contrast, it took 76.4 min to produce the same quantity of vitamin D₃ at Sapporo in December, at noon under a cloudless sky. The necessary exposure time varied considerably with the time of the day. For Tsukuba at noon in December, 22.4 min were required, but 106.0 min were required at 09:00 and 271.3 min were required at 15:00 for the same meteorological conditions. Naha receives high levels of ultraviolet radiation allowing vitamin D₃ synthesis almost throughout the year.

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Vegetable consumption has been encouraged as a component of nutritional education for obese and insulin-resistant patients. However, the benefits of vegetable intake in a therapeutic diet on postprandial glycemic and lipidemic responses have not been clarified. We studied the effects of the intake of spinach, a green-leafy vegetable rich in dietary fiber and α-tocopherol, with a fat-rich meal on postprandial glycemic and lipidemic changes. Fourteen normal weight and 10 obese men consumed three test meals of bread, as a control, bread and butter, and bread and butter with boiled spinach. Blood samples were obtained prior to and 30, 60, 120, 180 and 240 min after consuming the test meals. Compared with the bread meal, consumption of the bread and butter meal showed a reduced peak glucose response at 30 min in normal (p<0.05) but not in obese subjects. The increase in triglyceride and decrease in LDL-cholesterol were greater after the butter-containing meal than after the bread meal (p<0.05). The α-tocopherol/lipid level decreased and remained low after the bread and butter meal, but the decrease was smaller with the spinach-containing meal in obese subjects (p<0.05). These results suggest that green-leafy vegetable intake with a fat-rich meal is effective for supplying postprandial α-tocopherol in obese subjects, but consumption of a regular-sized dish cannot be expected to improve abnormal postprandial hyperglycemic or hyperlipidemic responses.

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The aim of this study was to investigate the effects of low-glycemic index (GI) sweet potato starch on adipocytokines, pro-inflammatory status, and insulin signaling in the high-fructose diet-induced insulin-resistant rat. We randomly divided 24 insulin-resistant rats and 16 normal rats into two groups fed a diet containing 575 g/kg of starch: a low-GI sweet potato starch (S) or a high-GI potato starch (P). The four experimental groups were labeled as follows: insulin-resistant P (IR-P), insulin-resistant S (IR-S), normal P (N-P) and normal S (N-S). After 4 wk on the experimental diets, an intraperitoneal glucose tolerance test (IPGTT) was conducted, and the homeostasis model assessment (HOMA), adipocytokines, pro-inflammatory cytokines levels, and insulin signaling-related protein expression were measured. The homeostasis model assessment values were significantly lower in the IR-S than in the IR-P group, suggesting that insulin sensitivity was improved among sweet potato starch-fed rats. Levels of tumor necrosis factor-α, interleukin-6, resistin, and retinol binding protein-4 were significantly lower in the IR-S versus the IR-P group, indicating an improvement of pro-inflammatory status in sweet potato starch-fed rats. The sweet potato starch diet also significantly enhanced the protein expression of phospho-Tyr-insulin receptor substrate-1 and improved the translocation of glucose transporter 4 in the skeletal muscle. Our results illustrated that sweet potato starch feeding for 4 wk can improve insulin sensitivity in insulin-resistant rats, possibly by improving the adipocytokine levels, pro-inflammatory status, and insulin signaling.

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We aimed to identify food sources of selected trace elements (Zn, Cu, Mn, I, Se, Cr, Mo) and biotin in the Japanese diet and to assess usual dietary intakes based on the ratios of within-person to between-person variance. Subjects were 98 middle-aged dietitians living in central Japan who participated in a survey of four-season 7 consecutive day weighed diet records. Based on the latest Standard Tables of Food Composition in Japan published in 2010, food sources of selected nutrients were located according to a contribution analysis, and computed usual dietary intakes. Dietary intakes were checked with the Dietary Reference Intakes for Japanese 2010. Prevalence of inadequacy in a group was determined using the Estimated Average Requirement cut-point method. The major contributors to selected trace elements and biotin were not only meat and milk, but also traditional Japanese food items, including rice, tofu and tofu products, fish, seaweed, chicken eggs, fermented soy bean seasonings, and green tea. Medians of usual intakes were estimated for Zn (men 8.9 mg, women 8.4 mg), Cu (1.32 mg, 1.21 mg), Mn (3.73 mg, 3.76 mg), I (312 μg, 413 μg), Se (97 μg, 94 μg), Cr (10 μg, 9 μg), Mo (226 μg, 184 μg), and biotin (51.7 μg, 47.6 μg). The prevalence of inadequacy of dietary intakes was high for Zn, Cu and Cr. Regarding I, the proportion above the Tolerant Upper Level was overestimated based on the crude mean value. We first identified food sources of selected trace elements and biotin in the Japanese diet, and assessed the usual intakes.

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The primary aim of this study was to examine the effects of 48-h food deprivation on rat skeletal muscle fiber type, according to myosin heavy-chain (MyHC) isoform composition and some metabolism-related factors in both slow-type dominant and fast-type dominant muscle tissues. Male Wistar rats (7 wk old) were treated with 48-h food deprivation or ad libitum feeding as control. After the treatment, the soleus muscle (slow-type dominant) and the extensor digitorum longus (EDL, fast-type dominant) were excised. We found that 48-h food deprivation did not affect MyHC composition in either the soleus or EDL, compared with fed rats by electrophoretic separation of MyHC isoforms. However, 48-h food deprivation significantly increased the mRNA expression of fast-type MyHC2B in the EDL muscle. Moreover, food deprivation increased fatty acid metabolism, as shown by elevated levels of related serum energy substrates and mRNA expression of mitochondrial uncoupling protein (UCP) 3 and lipoprotein lipase (LPL) in both the soleus and EDL. UCP3 and LPL are generally expressed at higher levels in slow-type fibers. Furthermore, we found that food deprivation significantly decreased the protein amounts of PGC1α and phosphorylated FOXO1, which are known as skeletal muscle fiber type regulators. In conclusion, 48-h food deprivation increased mRNA expression of fast-type MyHC isoform and oxidative metabolism-related factors in EDL, whereas MyHC composition at the protein level did not change in either the soleus or EDL.

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Accurate estimation of resting energy expenditure (REE) in children and adolescents is important to establish estimated energy requirements for the Japanese population. Our objectives were 1) to determine the REE of 6- to 17-y-old Japanese children and adolescents by indirect calorimetry in order to estimate energy expenditure for this group, 2) to compare measured REE with predicted REE to determine the accuracy of predictive equations of REE for Japanese children and adolescents, and 3) to derive new predictive equations for REE for Japanese children and adolescents based on measured REE. REE was measured in 221 Japanese children and adolescents, aged 6 to 17 y old (113 boys and 108 girls) using a ventilated indirect calorimeter. Anthropometric and body composition measurements were also performed. REE expressed as absolute values increased with age in both genders, and there was a significant difference between genders in the 12-17 y age group. REE was strongly correlated with body weight (BW) and fat-free mass (FFM). REE adjusted for BW or FFM decreased with age in both genders, and a gender difference was still observed in the 12-17 y age group after this adjustment. The highest accuracy of prediction was achieved using the Dietary Reference Intake for Japanese (1969) for boys and the Molnar equation for girls. Step-down multiple regression analysis was carried out using either a combination of age, gender, BW, and height, or a combination of age, gender, FFM, and fat mass (FM). The predictive equation accounted for 75% (R²) and 76% of the variance, respectively. In conclusion, absolute REE increased and REE adjusted for BW or FFM decreased with age. The major determinant of REE was FFM, but significant gender differences were observed in the 12-17 y range for both absolute REE and adjusted REE.

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The Japanese population routinely consumes iodine-rich seaweed, thereby probably making Japan the nation with the highest iodine intake worldwide. The present study aimed to estimate the duration of dietary records (DRs) needed to calculate the usual iodine intake and to ascertain the frequency of iodine intakes above the tolerable upper intake level (UL) in the Dietary Reference Intakes for Japanese. Four 3-d DRs for the 4 seasons within a year were collected for 55 men and 58 women. On the basis of analysis of variance, the total variance in iodine intake was classified into inter-individual and intra-individual components. The frequency of appearance for high iodine intakes was estimated. The most commonly consumed types of iodine-containing food items were seaweed, milk and milk products, fish and shellfish, and tofu. The percentage contribution of intra-individual variance was markedly greater than that of inter-individual variance, and the excessive iodine intake was intermittent rather than continuous. The duration for which dietary records were required to assess the usual intake of iodine within 10% of their true mean was 6,276 d for men and 4,953 d for women. The period that transpired until a value was exceeded once was 6.3 d/occurrence for values above UL (2,200 μg), 8.5 d/occurrence for values above 3,000 μg, 9.8 d/occurrence for values above 4,000 μg, 11.2 d/occurrence for values above 5,000 μg, and 16.7 d/occurrence for values above 10,000 μg. To avoid errors in interpretation, it is inappropriate to assess the habitual nutrient intake of a nutrient that is intermittently consumed at maximal levels. It is important to assess the iodine intake in consideration of the range of the nutrient intake and of the time period in which the upper limit is exceeded.

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Proinflammatory cytokines are factors that induce ubiquitin-proteasome-dependent proteolysis in skeletal muscle, causing muscle atrophy. Although isoflavones, as potent antioxidative nutrients, have been known to reduce muscle damage during the catabolic state, the non-antioxidant effects of isoflavones against muscle atrophy are not well known. Here we report on the inhibitory effects of isoflavones such as genistein and daidzein on muscle atrophy caused by tumor necrosis factor (TNF)-α treatment. In C2C12 myotubes, TNF-α treatment markedly elevated the expression of the muscle-specific ubiquitin ligase MuRF1, but not of atrogin-1, leading to myotube atrophy. We found that MuRF1 promoter activity was mediated by acetylation of p65, a subunit of NFκB, a downstream target of the TNF-α signaling pathway; increased MuRF1 promoter activity was abolished by SIRT1, which is associated with deacetylation of p65. Of interest, isoflavones induced expression of SIRT1 mRNA and phosphorylation of AMP kinase, which is well known to stimulate SIRT1 expression, although there was no direct effect on SIRT1 activation. Moreover, isoflavones significantly suppressed MuRF1 promoter activity and myotube atrophy induced by TNF-α in C2C12 myotubes. These results suggest that isoflavones suppress myotube atrophy in skeletal muscle cells through activation of SIRT1 signaling. Thus, the efficacy of isoflavones could provide a novel therapeutic approach against inflammation-related muscle atrophy.

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Fatty acid (FA) compositions in tissues are related to metabolic disorders, and consequently the appropriate management of underlying FA compositions in tissues is considered to be important. However, the relationship among the serum lipid profiles, the FA composition of the red blood cell (RBC) membranes and genetic variations in the fatty acid desaturase (FADS) genes in Japanese men is unclear. In this study, the subjects recruited were 137 Japanese men, 40 to 60 y old, who had a regular health checkup. Their serum lipid profile and the relative FA composition of the RBC membranes were measured. They were genotyped for the single nucleotide polymorphisms (SNPs) rs174553, rs174546, rs99780 and rs174583 in FADS gene. Multiple regression analysis was conducted to detect the relationship among hyperlipidemia, the FA composition of the RBC and the FADS genotypes. As a result, the homozygous genotype for the minor alleles in rs174553, rs174546, rs99780 were found to be associated with lower low-density lipoprotein cholesterol (LDL-C) levels and a lower LDL-C/total-cholesterol ratio. The homozygous genotype for the minor alleles reduced the risk of high LDL-C level (R²=0.50, β=−0.20, p=0.009), whereas, the arachidonic acid (AA) levels in the carriers of the homozygous genotype for the minor alleles tended to be lower compared with the carriers of the major alleles. However, no significant differences were observed in any FA level among the three genotypes for four SNPs. These results indicate that the appropriate management of serum LDL-C levels depending on genetic predisposition in FADS genotypes should be encouraged.

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Indocalamus latifolius (Keng) McClure leaf is a popular food material in East Asia due to its antioxidant and anticorrosive activities. To utilize it more effectively, we investigated the discrepancy of antioxidant activities and active compound content in Indocalamus latifolius leaf along with the altitude change. Total flavonoids, phenolics, titerpenoids and eight characteristic active constituents, i.e, orientin, isoorientin, vitexin, homovitexin, p-coumaric acid, chlorogenic acid, caffeic acid, and ferulic acid, were determined by UV-spectrophotometer and synchronous RP-HPLC, respectively. Antioxidant activity was measured using DPPH and FRAP methods. Our data showed that the content of TP and TF, DPPH radical scavenging ability and ferric reduction power of Indocalamus latifolius leaf changed as altitude altered, with the trends of decreasing gradually when lower than 700 m and then increasing to 1,000 m. Chlorogenic acid and orientin were the main characteristic compounds in Indocalamus latifolius leaf and were also affected by altitude. Our result indicated that higher altitude with an adverse environment is conducive to secondary metabolite accumulation for Indocalamus latifolius. It would provide a theoretical basis to regulate the leaf collection conditions in the industrial use of Indocalamus latifolius leaf.

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Most Japanese women do not consume the estimated average requirement of vitamin B₆ (1.7 mg/d) during pregnancy. Nevertheless, these deficiencies are not reported. We investigated a nutritional biomarker of vitamin B₆ in pregnant Japanese women as well as their vitamin B₆ intakes. Vitamin B₆ intakes in the first, second, and third trimesters of pregnancy, and 1 mo after delivery were 0.79±0.61 (n=56), 0.81±0.29 (n=71), 0.90±0.35 (n=92), and 1.00±0.31 (n=44) mg/d, respectively. Plasma pyridoxal 5'-phosphate (PLP) concentrations in the first, second, and third trimesters of pregnancy, and 1 mo after delivery were 57.1±27.6 (n=56), 23.3±16.7 (n=71), 18.3±12.5 (n=92), and 43.9±33.4 (n=44) nmol/L, respectively. The plasma concentrations significantly decreased in the second and third trimesters of pregnancy compared to values from the first trimester (p<0.05), and these concentrations returned to the values of the first trimester of pregnancy 1 mo after birth.

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Sialic acid (SA) is an important nutrient but few studies have examined the link between dietary intake and breast milk sialic acid. The purpose of this observational study was to assess the potential relationship between human breast milk sialic acid levels and dietary nutrition intake 40 d postpartum. The study population included 90 healthy women who were lactating. Human breast milk SA concentrations were measured using fluorescence detector-high performance liquid chromatography (HPLC-FLD) analysis and nutritional intake was estimated by a computerized validated food frequency questionnaire. SA in human breast milk was bound to free oligosaccharides (82.35%), protein (15.27%) and free sialic acid (2.37%). The findings of this study indicate that subjects with higher milk SA levels showed statistically higher levels of vitamin A compared with subjects with lower SA levels (423.48±172.29 vs 602.22±126.46 μg/d, p=0.000). In addition, there was a certain association (standardized coefficients=0.713; p=0.000) between breast milk SA and vitamin A intake in healthy young subjects. This study demonstrated that dietary vitamin A intake has a certain relationship with breast milk SA concentrations. This may be attributed to the influence of vitamin A on sialic acid glycoprotein and sialic acid mucopolysaccharide in the human body or the common food sources for vitamin A and sialic acid. Additional study is required to further investigate this relationship.

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The objective of the present study was to determine the maximum dose of resistant maltodextrin (Fibersol^®-2, a non-viscous water-soluble dietary fiber), that does not induce transitory diarrhea. Ten healthy adult subjects (5 men and 5 women) ingested Fibersol^®-2 at increasing dose levels of 0.7, 0.8, 0.9, 1.0, and 1.1 g/kg body weight (bw). Each administration was separated from the previous dose by an interval of 1 wk. The highest dose level that did not cause diarrhea in any subject was regarded as the maximum non-effective level for a single dose. The results showed that no subject of either sex experienced diarrhea at dose levels of 0.7, 0.8, 0.9, or 1.0 g/kg bw. At the highest dose level of 1.1 g/kg bw, no female subject experienced diarrhea, whereas 1 male subject developed diarrhea with muddy stools 2 h after ingestion of the test substance. Consequently, the maximum non-effective level for a single dose of the resistant maltodextrin Fibersol^®-2 is 1.0 g/kg bw for men and >1.1 g/kg bw for women. Gastrointestinal symptoms were gurgling sounds in 4 subjects (7 events) and flatus in 5 subjects (9 events), although no association with dose level was observed. These symptoms were mild and transient and resolved without treatment.

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The mechanisms by which resveratrol (3,4',5-trihydroxy-trans-stilbene) elicits diverse health benefits remain unclear because the intracellular target molecules of resveratrol are poorly defined. We screened resveratrol-binding proteins from lysates of MCF-7 breast cancer cells using resveratrol-affinity resin, which was constructed by immobilizing 4'-amino-3,5-dihydroxy-trans-stilbene on activated CH-Sepharose. On SDS-PAGE, two bands were detected as proteins that specifically bound to the resveratrol-affinity resin. One of these, a 30-kDa protein, was identified as human carbonyl reductase 1 (CBR1) by hybrid linear ion trap/time-of-flight mass spectrometry. Similarly, recombinant CBR1 bound to the resveratrol-affinity resin in the absence of resveratrol, but not in the presence of resveratrol. Among its activities, CBR1 catalyzes a NADPH-dependent reduction of the anticancer drug doxorubicin to the cardiotoxin doxorubicinol. The effects of doxorubicin on viability of MCF-7 cells were enhanced by resveratrol, 3,5-dihydroxy-4'-methoxy-trans-stilbene, 3,4'-dihydroxy-5-methoxy-trans-stilbene, and 4'-amino-3,5-dihydroxy-trans-stilbene at concentrations of 1 and 10 μM. Resveratrol and these derivatives inhibited CBR1 activities to a similar degree at concentrations of 100 and 200 μM. However, 3,5-dimethoxy-4'-hydroxy-trans-stilbene and m-hydroquinone had no influence on doxorubicin cytotoxicity or CBR1 activity. Resveratrol inhibited CBR1 activity through an apparent mix of competitive (Ki=55.8 μM) and noncompetitive (αKi=164 μM; α=2.98) inhibition kinetics. These results indicate that (i) resveratrol enhances the cytotoxic effects of doxorubicin on MCF-7 cells; (ii) the moiety that contains the 3,5-dihydroxyl groups of resveratrol, but not the m-hydroquinone structure alone, is required to bind CBR1; and (iii) resveratrol acts as a mixed-type inhibitor of CBR1 activity on doxorubicin.

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