To evaluate nutritional availability of selenium contained in a low-molecular weight fraction of dark muscle of tuna, selenium content and glutathione peroxidase (GPX) activity were measured in serum and liver of mice fed a casein-based low selenium basal diet or the basal diet supplemented with selenium as sodium selenite, dark muscle of tuna or diluted HCl-extract of the dark muscle. Male weanling A/J mice were fed the low selenium diet (selenium content, 32 ng/g) for 3 weeks. After then, the mice were divided into four group; one group was fed the basal diet continuously and other 3 groups were fed the basal diet supplemented with selenium (100 ng/g) as sodium selenite, dried powder of dark muscle of tuna or dried powder of diluted HCl-extract of the dark muscle for 1 week. The serum and liver selenium content of the mice fed the selenium-supplemented diets were significantly higher than those of the mice fed the basal low selenium diet. A significantly difference due to the selenium source was observed in the elevation of selenium content; the highest elevation was observed in the mice fed the selenite-supplemented diet and the lowest elevation was observed in the mice fed diet with the diluted HCl-extract. The serum and liver GPX activity were elevated only in the mice fed the selenite-supplemented diet. These results indicate that nutritional availability of selenium contained in a low-molecular weight fraction of dark muscle of tuna is low compared to selenite or selenium contained in a protein fraction of the dark muscle.

We studied whether oyster extract protected a model mouse of non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) against steatosis and inflammation. Male C57BL/6JJmsSLC mice were randomly divided into 3 groups that were fed different diets for 6 weeks: the negative control group received a standard diet (AIN-93G), the positive control group were fed a choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD; to induce NASH) plus methionine and choline (at equivalent levels to those found in the oyster extract), and the oyster extract group were given the CDAHFD plus oyster extract. The serum biomarker levels of the mice were used as markers of liver failure. The histopathology of the liver and hepatic fibrosis (i.e., the mRNA levels of fibrosis-related genes such as Col1a1, Col3a1, Col4a1, and Ctgf) were examined in order to assess hepatic steatosis and inflammation, respectively. The mice fed the CDAHFD plus methionine and choline developed enlarged fatty livers and inflammation. However, treatment with oyster extract ameliorated the hepatic steatosis and inflammation induced by the CDAHFD. Moreover, a smaller CDAHFD-induced increase in fibrosis-related gene expression was seen in the livers of the mice fed oyster extract. These findings suggest that oyster extract suppresses non-alcoholic fatty liver disease by inhibiting steatosis.

Zinc is an essential metal but toxic to baker’s yeast at high concentration. In this report, the effect of zinc on the enzymes that generate or scavenge reactive oxygen species was analyzed. Zinc ion potently inhibited glucose 6-phosphate dehydrogenase, NADP dependent isocitrate dehydrogenase and glutathione reductase, whereas slightly activated NADPH: quinone oxidoreductase, which generates superoxide anion and hydrogen peroxide. Toxicity of zinc on yeast can be principally explained by the reactive oxygen species increased due to the inhibition of glutathione reductase.

Phosphorus (P) is used as a phosphate in a wide variety of processed foods, such as fish cakes, processed meat, cheese, frozen bakery products, and carbonated beverages. Phosphates are added to surimi and processed meat in order to improve water retention and prevent alterations during freezing. The effects of the proteins of fish (FP) and meat, which are contained in surimi and processed meat, on the calcium (Ca) and P balance have not yet been examined in vivo. Therefore, we herein investigated the influence of FP on the Ca and P balance in rats fed a high P diet. Experimental diets were formulated as follows: a normal-P (0.3% P wt/wt, potassium dihydrogen phosphate) diet, high-P (1.5% P wt/wt, potassium dihydrogen phosphate) diet, and high-polyphosphate (1.5% P wt/wt, sodium polyphosphate) diet. The protein source of each experimental diet was FP or chicken breast protein (CP). Male Wistar rats were fed the experimental diets for 4 weeks. Kidney weights and mineral concentrations were significantly higher in rats fed the high-P and high-polyphosphate diets than in rats fed the normal-P diet. While Ca and P concentrations in the kidney were significantly higher in rats fed the high-P and high-polyphosphate diets, no significant difference was observed when FP or CP was provided as the dietary protein source. Furthermore, no significant differences were observed in the effects of FP and CP on the Ca and P balance. These results suggested that FP or CP did not exert significantly different effects on mineral concentrations or the mineral balance in the kidney.

In order to clarify the potential of an oyster-extract by-product (OEBP) as a health-maintaining and -promoting food material or supplement, this study investigated the effects of lipid prepared from an OEBP (L-OEBP) on serum and liver lipid contents in rats. L-OEBP was extracted by the methods of hexane/ethanol/water, and contained 3.7% eicosapentaenoic acid (EPA), 3.3% docosahexaenoic acid (DHA), and 17.7% phospholipid. Four-week-old male Wistar rats were divided into 2 dietary groups of 6 rats each, with one group receiving a control AIN-93G diet (7% soybean oil) and the other receiving L-OEBP diet (5% soybean oil + 2% L-OEBP). After the rats had been fed their respective diets for 27 days, their serum and liver lipid contents and hepatic fatty acid-metabolizing enzyme activities were measured. Hepatic triacylglycerol (TAG) and monounsaturated fatty acid contents as well as the stearoyl-CoA desaturase index (oleic acid/stearic acid) were lower in the L-OEBP group than in the control group. Hepatic acetyl-CoA carboxylase activity was also lower in the L-OEBP group than in the control group. Therefore, L-OEBP decreased the liver TAG content in part by suppressing hepatic fatty acid synthesis. Since the current formulation of L-OEBP did not sufficiently lower the serum content of TAG or the amounts of EPA and DHA were low, further improvements are needed in its formulation and concentration of n-3 polyunsaturated fatty acid prior to its application as a lipid-lowering functional food and supplement.

Nonalcoholic fatty liver disease (NAFLD) is caused by the excessive accumulation of fat in the liver, and includes simple fatty liver and nonalcoholic steatohepatitis (NASH). Iron overload in the liver has been implicated in a pathogenesis of NASH because it induces oxidative stress. Although high-fat (HF) diets have been reported to increase hepatic iron concentrations, this remains controversial. We hypothesized that a HF diet may increase hepatic iron concentrations in the short term, but that this effect disappears when the duration of the dietary treatment is extended. In order to determine the time effects of a HF diet on hepatic iron concentrations, male Sprague-Dawley rats were fed a control (CT) or HF diet for 4, 8, or 12 weeks. The HF diet increased hepatic triacylglycerol concentrations at 4 weeks, and these levels remained stable until the end of the experimental period. Hepatocyte ballooning was observed at each week in the livers of rats fed the HF diet; however, it may have been immature at 4 weeks. Furthermore, many large and small vesicles were detected in the livers of the HF group at 8 and 12 weeks, but not at 4 weeks. Oxidative stress markers, such as the concentration of thiobarbituric acid reactive substances (TBARS) and the mRNA expression of heme oxygenase-1, in the liver were higher in the HF group than in the CT group at 8 weeks. A higher concentration of TBARS was also observed at 4 weeks. However, these differences disappeared by 12 weeks. The HF diet did not affect the mRNA expression of inflammation markers such as interleukin-6 and cluster of differentiation 45 during the experimental period. A histological examination revealed the absence of inflammation in the livers of HF rats. Hepatic iron concentrations were not affected by the HF diet throughout the experimental period. These results demonstrated that the HF diet did not affect iron concentrations in the liver.

Radish sprouts (Raphanus sativus L. ‘Kaiwaredaikon’) were hydroponically cultivated in an environment exposed to zinc at a level of 0, 20, 50, 100, and 200 ppm as zinc sulfate. Growth was inhibited in sprouts exposed to zinc at a level of 50 ppm or more. Zinc contents in sprouts increased in a manner that was dependent on zinc exposure levels up to ppm; the zinc content in sprouts exposed to 100 ppm was 83.3 μg/g fresh weight. However, no significant differences were observed in vitamin C or chlorophyll contents in sprouts irrespective of zinc exposure levels. A DNA microarray analysis was conducted and revealed that the expression of 1275 genes was significantly different between radish sprouts exposed to zinc at a level of 20 ppm and those exposed to a zinc deficiency, whereas the expression of 1379 genes was altered by a zinc excess. Gene ontology terms related to organic acid metabolism, response to a stimulus, carbohydrate metabolism, lipid metabolism, and aromatic metabolism were significantly enriched with exposure to zinc at a level of 0 ppm, while response to a stimulus, organic acid metabolism, lipid metabolism, and oxidation reduction were significantly enriched with exposure to zinc at a level of 100 ppm. No significant differences were observed in zinc transporters with a zinc excess and deficiency. These results indicate that hydroponic cultivation in an environment exposed to zinc is useful for producing radish sprouts with higher zinc contents.

Toenail samples were collected from 62 healthy subjects (36 males and 26 females, 25.2 ± 9.6 yr) in Osaka Prefecture of Japan and their selenium contents were determined by inductively coupled plasma-mass spectrometry and compared to those described in several previous reports. Maximum, minimum, mean, standard deviation and median values of the selenium in 62 toenail samples were 2.13, 0.18, 0.77, 0.32 and 0.77 μg/g, respectively. The mean value obtained was similar to values in the eastern and western USA area and lower than values in a seleniferous area of the USA and higher than values in New Zealand, Finland and most European countries where the selenium intake were about 50 μg/d or less. These results indicate that toenail selenium is a good indicator for averaged selenium intake.

In recent years, several reports have shown that a number of mineral and trace element deficiencies arise. Similarly, the risk of excessive intake of mineral and trace elements is increased by intake of dietary supplements accompanied with foods. It is important to know nutritional status of mineral and trace elements. However, there is still no reliable indicator of dietary intake of mineral and trace elements. We examined the possibility to use the urinary excretion as an indicator of dietary intake of calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu) and manganese (Mn). Urinary excretions of Mg and Zn were correlated positively with the dietary intakes of Mg and Zn. We compared the relationships between dietary intakes and urinary excretion among five groups: usual dietary group, excess meet intake group, excess fish intake group, excess soy bean intake group and excess seaweed group, Urinary excretions of Mg and Zn were increased slightly in the excess meat intake group, but were decreased in the excess soy beans intake group and the excess seaweed intake group, compared to the usual dietary group. Urinary excretion of mineral and trace elements is likely to be determined by dietary intake including other factors such as the absorption from intestinal tract. These results suggested that the urinary excretion Mg and Zn could be a useful indicator of dietary Mg and Zn intake.

Carnosine (β–alanyl histidine) plays essential roles in the exercise performance since it has various beneficial characteristics including pH buffering, anti-oxidant, anti–glycation, anti-crosslink activities. To investigate the effects of carnosine in the exercise of horses, we analyzed the amount of carnosine in the muscles of thoroughbred horse using high performance liquid chromatography (HPLC) equipped with a carbon column. We found the high concentrations of carnosine in horse muscles, but not of anserine (1-methyl carnosine). We detected neither carnosine nor anserine in other tissues including liver, kidney, jejunum, spleen and aorta, and found only a small amount of carnosine in esophagus, bladder, and stomach. We also investigated the variations in carnosine concentration among five muscles (flexor capri radius, triceps branchii, masseter, gluteus medius, sternocleidomastoid), and found that the gluteus medius exhibited the highest concentration of carnosine These results suggest the relationship between carnosine and muscle fiber types. Our developed methods are useful for the investigation of carnosine and the exercise performance.

When dogs have food allergy, home-prepared food can be desired. Further, some owners prefer to cook for their dogs. However, it is difficult for dog owners to formulate nutritionally well-balanced home-prepared foods. Therefore, we designed recipes of home-prepared food satisfying AAFCO dog foods nutrient profiles, i.e., nutritionally complete foods. In addition, we emphasized the recipes for veterinarians and pet-food dietitians easily advising to owners and for owners easily purchasing ingredients at a local market. We formulated nutritionally complete foods consisting of basal food, supplementary food and trace nutrient preparations; the basal food is the main sources of protein and carbohydrate and its ingredients are selected from routinely-used foodstuffs by general household, supplementary foods consisting of fixed ingredients are for increasing trace nutrient concentration. We mainly referred Food Composition Database in Japan for estimating nutrient concentrations in foods. Metabolizable-energy (ME) content was calculated with modified Atwater factors and the nutritional adequacy was assessed by the estimated dietary nutrient-concentrations on the ME basis. The basal foods almost satisfied protein and essential-amino-acid concentrations but many trace nutrients were inadequate. The addition of supplementary foods to basal foods makes many of trace nutrients adequate but calcium, zinc, copper, and vitamin E were still inadequate. Thus, these trace nutrients were added as vitamin and mineral preparations. We also determined proximate composition and mineral concentration in chicken meat and bone, indicating that chicken meat and bone can substitute for calcium preparation in the complete foods. Using our method of design for dog foods, dog owners easily prepare nutritionally complete foods satisfying AAFCO dog foods nutrient profiles.

The present study was conducted to clarify the effects of vitamin C on mucosal IgA induction in the jejunum and ileum of weanling mice. Weanling mice were fed rodent feed or 500 ppm L-ascorbic acid supplemented rodent feed for 7, 14 or 21 days. Supplemental L-ascorbic acid increased the numbers of IgA antibody-secreting cells (ASC) in the jejunum and ileum of weanling mice after 14 days of treatment, but IgA ASC in the jejunum and ileum after 7 and 21 days of treatment were not affected by the treatment. Supplemental L-ascorbic acid had no effects on IgA concentrations in the jejunum, ileum, feces and serum of weanling mice. These results indicate that supplementation of L-ascorbic acid is slightly effective to enhance the numbers of IgA ASC in the jejunum and ileum of weanling mice.

Biotin functions as an essential cofactor for carboxylases in mammals. Dietary biotin exists in protein-bound and free forms and the ratio of free to total biotin varies among foods. In this study, we measured the urinary excretion of biotin in healthy women after the intake of biotin powder (the ratio of free biotin; 100%), boiled egg (40.3%) or almond (0.5%), each of which contains 50 μg of biotin, and analyzed the effect of chemical forms of biotin on biotin bioavailability. When the biotin powder was ingested, the peak of urinary excretion was shown at the point of 2 hours after intake. Meanwhile, when foods were ingested, the peak was at 4 hours. Biotin excretion after the ingestion of almond tended to be high compared with that of boiled egg, even though the ratio of free biotin in almond was almost zero. These findings indicate that the absorption of food biotin was influenced by chemical forms of biotin and other nutrients.

Recent exponential progress in next-generation DNA sequencing technology enables researchers to sequence entire genome of various organisms for the first time at a reasonably low cost. Nowadays, there are a lot of reports concerning sequenced genome information, and they considerably contribute to understanding of the biological functions of unknown genes at molecular level. In this manuscript, we describe the current status of genome analysis of lactic acid bacteria and the perspective of d-amino acid researches targeting lactic acid bacteria based on their genome information.

Nutritional level of iron exhibits linear dose-effect relationship with blood hemoglobin up to its normal concentration during recovery from severe iron deficiency in rats. This relationship is used for measurement of bioavailability of food iron by the official methods of AOAC international. Hemoglobin regeneration efficiency method was improved using a longer depletion period and a longer repletion period as an easier and simpler alternative. The dose-effect relationship between dietary iron and blood hemoglobin yields a sigmoid curve in a wider range of dietary iron level, starting a feeding from normal iron status of animals. The analysis of dose-effect relationship between dietary iron and various iron parameters may give a definite basis of iron requirements and a division of severity of iron deficiency for experimental rats.

Amino acid is generally divided into two groups, d- or l-form, based on its chirality. The physiological role of d-amino acid has not been clarified in details as compared with that of l-amino acid. But recently, the production mechanism and function of d-amino acid in food have been studied extensively. We found that the concentration of d-amino acid in sake brewed with kimoto tended to be high. These d-amino acids were produced mainly by lactic acid bacteria such as Leuconostoc mesenteroides and Lactobacillus sakei in kimoto and increased taste of sake. We are interested in which compound in medium is effective for d-amino acid production by lactic acid bacteria. We focused on citric acid in de Man, Rogosa, Sharpe medium that is a member of citrate cycle, one of major metabolic pathways in microorganism.

In this minireview, we describe the effect of citrate on growth and metabolism in various lactic acid bacteria in relation to our studies on d-amino acid production of Lactobacillus sakei.