Mushrooms contain reducing substances with chemical properties similar to ascorbic acid (ASA). In this study, the four types of reducing substances contained in Flammulina velutipes (Enokitake), Hyp-sizigus mamoreus (Bunashimeji), Pholiota nameko (Nameko), and Grifola frondosa (Maitake) were respectively purified, and the structure of each was analyzed using nuclear magnetic resonance (NMR) and other meth-ods. The results confirmed that those substances were AsA analogs and associated glycosides (6-deoxy-AsA, 6-deoxy-5-O-(α-D-xylopyranosyl)-AsA, 6-deoxy-5-O-(α-D-glucopyranosyl)-AsA, and 5-O-α-D-glucopy-ranosyl-erythro-AsA). These substances were characteristic in that sac-charide was bonded with the C-5 of the AsA analogs. Osazones were formed from the reducing substances in 19 kinds of edible mushrooms. Using thin-layer chromatography (TLC), they were developed to examine the distribution of the above reducing substances and AsA. The results showed that at least one of the above compounds was certain to be present in any mushroom; that AsA was present in very small quantities if at all; and that several substances similar to the above compounds were present.
Age-related changes of pyridinoline, a mature cross-link of collagen fibers, in tissues of guinea pigs which cannot synthesize L-ascorbic acid (AsA) were investigated. Male guinea pigs, 2 weeks old, were fed a commercial diet unitil they were 40 weeks old. Based on the data of body weight gain, it is assumed that guinea pigs require 10 weeks to reach maturity. The content of AsA in serum, adrenals, and liver of the animals increased with growth, then decreased after 8-10 weeks. The pyridinoline content in cartilage and tendon collagen was very low in 2-week-old animals, whereas it increased markedly with growth. After 10 weeks, the pyridinoline tended to decrease in cartilage collagen; however, it was not changed in tendon collagen. The age-related changes of pyridinoline content in guinea pigs cartilage were similar to those of humans-increasing with growth and decreasing after adolescence.
The alteration in the metabolic activation of N-nitroso-dimethylamine (NDMA) was investigated in the rat during dietary pyridoxine deficiency. The in vitro metabolism of NDMA by demethylase system was measured in both liver and kidney microsomes. The profile of the kidney enzyme appears similar to that of the liver indicating that at least two forms of isozymes with the low and the high Km's are present. Pyridoxine deficiency significantly increased the activity of NDMA-demthylase of both organs. The increase in the activity of NDMA-demethylase induced by dietary pyridoxine deficiency can be reversed by supplementation of pyridoxine (500μg), i.p., daily for two consecutive days. The increase in; the NADPH cytochrome c reductase activity was observed after 6 weeks on pyridoxine-deficient diet.
Glucose-6-phosphate dehydrogenase (G6PD) activity in the rat liver was elevated when the animals were fed a diet that contained 5% coconut oil or 1% corn oil plus 4% palmitic acid, in comparison with that of rats fed 5% corn oil. G6PD activity correlated inversely with the PUFA/SFA ratio of total liver phospholipid as well as the ratio of plasma membrane phospholipid. Elevation of G6PD activity was slightly affected by dietary protein. Serum insulin levels were apparently not influenced by dietary fats, and were not correlated with G6PD activity. Insulin dose-response to G6PD activity was augmented in primary cultured hepatocytes isolated from rats fed a diet with 1% corn oil plus 4% palmitic acid in comparison with those fed a diet with 5% corn oil. These findings indicate that augment in insulin dose-response to G6PD and elevation of its activity shown in rats fed diets low in polyunsaturated fatty acid are associated with lowering the PUFA/SFA ratio in plasma membrane phospholipid.
To examine whether dietary manipulation of isoenergic diets might affect microvillar structure of small intestinal epithelial cells, morphological parameters of enterocytes and microvilli in the mid-villus portion of jejunum were determined in the rats fed either high-starch (70 energy%), low-fat (7 energy%) diet or high-fat (73 energy%), low-starch (5 energy%) diet for 7 days. Feeding the high-fat diet produced an increase in the height of villus, in accordance with the elevated jejunal mucosal weight and total protein contents as compared with the high-starch diet. No appreciable change in crypt depth occurred. Scanning electron microscopy of jejunal epithelial cells revealed that the morpho-metrical parameters of the villus cells were unchanged by the diets, but the microvillar structure of each villus cell was influenced by the diets; the animals fed the high-fat diet exhibited a reduced length (28%) of micro-villus with a slight increase (12%) in diameter, showing a significantly reduced surface area of microvilli per enterocyte. The reduction in microvillar surface area of animals fed the high-fat diet was accompanied by the decrease in total proteins of the brush border membranes as well as the decrease in the activities of microvillar stalked disaccharidases, i. e., sucrase-isomaltase and lactase. These results provide an evidence that dietary manipulation, even when diets are “complete” in terms of the content of energy, protein, and other micronutrients, can modify the microvillar structure of small intestinal epithelial cells, leading to altera-tions in the digestive/absorptive surface area of villus cells.
The effect of casein phosphopeptides (CPP) on bone me-tabolism was studied in the ectopic bone induced by the implantation of decalcified bone matrix in rats. Forty-two Wistar male rats of 7 weeks old were fed low calcium diets (0.39% of calcium) with or without supplying 0.50% of CPP, or a control diet (0.91% of calcium) without CPP supplementation. After a 1-week preliminary period, each rat was sub-cutaneously implanted with 30mg of demineralized bone matrix powder. Fourteen and 21 days after the implantation, the implants were harvested from 7 rats of each group. Calcium content in the graft was not significantly different among all groups on day 14. Subsequently, the content of calcium rapidly increased in the grafts irrespective of diets given. However, the graft of the CPP- group contained less calcium than the other groups and the calcium content was more in the control rats compared to the CPP+ animals on day 21. Alkaline phosphatase activity (an index of bone and cartilage calcification) was lower in the control group than in the CPP+ group on day 14. The enzyme activity subsequently decreased in the control group but the activity was not changed in the other groups. As a result, the activity of alkaline phosphatase was lower in the control animals than in the other rats on day 21. Tartrate-resistant acid phosphatase activity (an index of bone resorp-tion) was higher in the CPP- group compared to the control on day 14. On day 21, the activity was higher in the CPP- group compared to the others. Histological study indicated that the number of osteoclastic cells was larger in the CPP- rats than in the other animals on day 21. These results suggest that CPP supplementation mitigates the reduction of calcium content in bone of rats fed a low calcium diet and that this action of CPP is due to the suppression of bone resorption, which is involved in the reduction of osteoclast differentiation.
The effects of dietary medium-chain triglyceride (MCT) on the concentration of plasma ketone bodies in enterectomized and normal rats were examined, together with the effects on plasma glucose, plasma immuno-reactive insulin, and liver function. Four groups of enter-ectomized rats and four groups of normal rats were fed experimental diets containing 0, 6, 11, or 21% of MCT by weight for 6 days. All animals including normal rats received meal-feeding for 3 h once a day. On day 3, concentration of plasma ketone bodies in enterectomized rats increased dose-dependently with dietary MCT and the level was higher than that in normal rats. However, all the values in enterectomized rats never exceeded 2mM, the maximum physiological concentration. In contrast, plasma glucose in the enterectomized rats showed a tendency to decrease more clearly and dose-dependently with dietary MCT, followed by a marked increase of insulin secretion compared with those in normal rats. On the final day, no significant differences in the results of liver function tests were observed among these groups. These results indicate that the MCT-induced ketosis was within an acceptable range, and dietary MCT is useful for the suppression of increase in plasma glucose following a surgical operation without any disadvantageous effects on liver function.
To investigate effects of eicosapentaenoic (EPA) and do-cosahexaenoic acids (DHA) on acute inflammation, we fed rats either of the following four diets: an EPA-rich diet for 5 or 15 days, a DHA-rich diet for 5 or 15 days, a control diet for 5 or 15 days, and standard chow for 15 days. At the end of diets, the carrageenan-induced swelling of footpads was measured. Peritoneal cells were analyzed for their fatty acids in the phospholipid fraction. The swelling was similarly reduced in the EPA and DHA groups (p<0.05, if fed for 15 days) compared with rats fed the control diet for 15 days. The mean proportion of arachidonic acid (AA) to the sum of highly unsaturated fatty acids was correlated (γ=0.87) to the mean degree of swelling among all dietary groups (n=7). Effects of EPA and DHA might be explained by the reduced availability of AA for eicosanoid formation represented by the proportion of AA.
Magnesium (Mg) is an essential dietary element that plays important roles, acting as a cofactor of many enzymes. Rats fed a Mg-deficient diet have been reported to exhibit auricular and facial peripheral hyperemia and hemorrhage. Moreover, increased intake of calcium (Ca) or phosphorus (P) has been reported to impair apparent absorption of Mg. We tried to induce such typical inflammation in Mg-deficient rats by feeding low-Mg, high-Ca, and high-P diets. Increas-ing concentrations of Ca or P in the experimental diets significantly decreased the apparent absorption of Mg. And all rats fed the low-Mg (0.25mg/g diet), high-Ca (10.4mg/g diet), and high-P (12.0mg/g diet) diet exhibited auricular and facial peripheral.hyperemia and hemorrhage. Then, we used the low-Mg, high-Ca, and high-P diet to investigate the effects of the fructooligosaccharides (FO) on absorption of Mg and skin inflammation. In the rats fed FO-containing (1 or 5%) diet, apparent absorption of Mg was significantly increased as compared with that of the control (FO 0%) group. In the rats fed a 5% FO-containing diet and sufficient Mg (0.50mg/g), auricular and facial peripheral hyperemia and hemorrhage were significantly reduced. We concluded that FO increased the Mg absorption in rats fed a low-Mg, high-Ca, and high-P diet. Moreover, FO reduced inflammation in Mg-deficient rats, such as periph-eral hyperemia and hemorrhage.
Biotin production and the growth of the strains of Bifido-bacterium adolescentis, B. bifidum, B. breve, B, infantis, and B. longum were studied. These five strains showed heavy growth on BL medium. But when yeast extract medium (carbon source, glucose) was used, the extent of their growth was significantly decreased, one-half or less than that of the growth on BL medium. B. bifidum grew well on yeast extract medium containing oligosaccharides, such as isomaltooligosaccharide, and produced biotin extracellularly. The utilization of oligosaccharides in biotin production by these five strains was investigated.
The purpose of the present study was to investigate the effect of monounsaturated fatty acid (MUFA), in particular oleic acid, under fixed P/S and n-6/n-3 ratios on serum and liver lipid metabolism in rats. The male Sprague-Dawley rats aged 28 days were fed diets low in MUFA (LM) or high in MUFA (HM) with or without 1% cholesterol for 4 weeks. The experimental diets contained 10% (w/w) fat. The body weight gain, food efficiency, and liver weight were comparable among the groups except for an increase in liver weight by dietary cholesterol. When cholesterol-added diets were fed, the concentration of serum cholesterol in the HM group was higher than that of the corresponding LM group at second week and at the end of experiment. The concentration of serum triacylglycerol in rats fed a cholesterol-enriched HM diet was markedly lower than that of cholesterol-free counterpart. Both MUFA and choles-terol tended to increase serum low density lipoprotein-cholesterol concen-tration, but they had no interaction. Serum high density lipoprotein-cholesterol in cholesterol-enriched groups was lower than that in the cholesterol-free counterparts, but it was independent of the MUFA con-tent. Dietary cholesterol markedly increased the concentration of liver cholesterol and triacylglycerol and the increase in liver cholesterol was more marked in the HM group than in the LM group, while the level of liver triacylglycerol was comparable. The fecal excretion of neutral and acidic steroids increased when 1% cholesterol was added to the diets, irrespective of the MUFA content in the diets. Thus, the results indicate that the proposed beneficial effect of MUFA on cholesterol can be modified when diet contains cholesterol.
We have reported that soybean milk is an excellent source for increasing bone mineral density (BMD) and mechanical bone strength. However, it is not known what kind of components in soybean milk affect bone metabolism. Consequently, the purpose of this study is to find the effective components in soybean milk on bone metabolism. It might be some peptide in soybean milk. Therefore, in this study the soybean milk was separated into two different preparations according to molecular weight: a high-molecular-weight soybean milk, and a low-molecular-weight soybean milk. Then, the effect of the peptides in soybean milk on bone metabolism was examined. After producing the experimental osteoporotic model rats, they were divided into four groups. The BMD and the mechanical bone strength of the three experimental groups, whose diet contained a soybean milk, a high-molecular soybean milk, or a low-molecular soybean milk (soybean milk peptide) were significantly higher than those of the control group. Moreover, the intestinal Ca absorption for the three experimental groups was significant-ly increased. From these results, the peptides in the soybean milk are effective for the acceleration of the intestinal Ca absorption. It is possible to assume that the mechanism for increasing the BMD and the mechan-ical strength in the three experimental groups was due to increasing the intestinal Ca absorption by alimenting the soybean milk, the high-molecular soybean milk or the low-molecular soybean milk.
Effects of dietary oat, barley, and guar gums on serum and liver triglyceride or cholesterol concentrations were examined in diet-induced hypertriglyceridemic rats. Male Sprague-Dawley rats were fed a hypertriglyceridemic diet that contained 20% coconut oil, 17.5% fruc-tose, 17.5% sucrose, and 5% cellulose at 4 weeks of age for 14 days. In the gum-supplemented diets, 2% cellulose was replaced by oat gum, barley gum, or guar gum. Hypertriglyceridemia was observed in the control group, whereas serum cholesterol concentration was not in-creased. All of the gums lowered serum and liver cholesterol concentra-tions except barley gum which had no significant effect on liver cholester-ol. Both oat and barley gums suppressed the elevation of serum and liver triglyceride concentrations but guar gum had no effect.