The remnants of proteins themselves or complexes with protein remaining no longer indigestible in the intestine are referred to as resistant proteins, which exert physiological functions similar to dietary fibers and are also better for health. In recent years, noticeable functions attributable to resistant proteins have become gradually apparent with regard to several proteinous items. Recent investigations have revealed that the relevant ingredients are either condensed in isolates or concentrates of vegetable proteins or causally brought about as a consequence of denaturation and/or entanglement in the process of preparation. Some protein components inherently insusceptible to mammalian digestive enzymes also belong to the group of resistant proteins in case of edibility irrespective of their sources. Among the medicinal benefits of several resistant proteins hitherto pointed out by animal experiments, there were preventive effects against hypercholesterolemia, constipation, corpulence, tumorigenesis (colon, liver, mammary gland), gallstone formation or poisoningL and wholesome improvements in enteric fermentation of short-chain fatty acids.
we administered high-dose vitamin E to healthy adult male volunteers and assessed the safety of such supplementation. Fourteen volunteers received daily 1, 200 IU of vitamin E (800mg of D-α-tocopherol) for 28 d and eight controls were also enrolled. The volunteers treated with vitamin E showed no abnormalities during the study period. The α-tocopherol concentrations of plasma and platelets were markedly elevated by vitamin E treatment, but there were no significant differences in platelet aggregation, coagulation, and the clinical parameters between the two groups. In conclusion, a high dose of vitamin E for 28 d had no adverse effects in healthy men.
The vitamin B6 nutritue of breast-fed infants was evaluated by vitamin B6 intake, plasma pyridoxal 5'-phosphate (PLP) concentration, and growth patterns during the infants' first 6 mo of age. Vitamin B6 intakes of 47 healthy, term infants were significantly correlated with four levels of maternal vitamin B6 supplements: 2.5, 4.0, 7.5, or 10.0mg pyridoxine (PN)⋅HCl/d and met the B6 Adequate Intake (AI, 1998) of 0.1mg/d for infants 0 to 6mo. Only infants whose mothers received 10.0mg PN⋅HCl/d exceeded or met the Recommended Dietary Allowances (RDA, 1989) of 0.3mg vitamin B6/d from 4 to 6mo of age. Plasma PLP concentrations of infants, measured at 1, 4, and 6mo of age paralleled their mother's vitamin B6 intake. Most infants showed normal growth. The findings indicated that a maternal PN⋅HCl supplement of 2.5mg/d provided an adequate amount of vitamin B6 in breast milk (0.15mg/d) for the vitamin B6 status parameters and the growth of breast-fed infants.
Volatile sulfur compounds (VS) are generated in the large intestine by the bacterial metabolism of sulfate and sulfur amino acids. VS are potentially harmful to the host. The effect of dietary supplementation of herb extracts on volatile sulfur production in the large intestine of pig was evaluated in this study. The extracts Perilla frutescens (Soyou), Mentha piperita (Peppermint), and Ajuga decumbens (Kiransou) were fed to pigs equipped with a permanent cannula at the cecum. Cecal digesta were sampled and analyzed for ammonia and short-chain fatty acids (SCFA). Sampled digesta were incubated anaerobically either with or without L-methionine for 24h to estimate volatile sulfur production in vivo. L-Methionine was supplemented to enhance methanethiol (MeSH) production. At the end of the incubation, head space concentrations of volatile sulfur compounds such as hydrogen sulfide (H2S), MeSH, and dimethyl sulfide (DMS) were determined by flame-photometric gaschromatography after the addition of 6N HCl. Sampled digesta were also subjected to the most probable number estimations for sulfate-reducing bacteria (SRB), sulfide producer from L-methionine, and MeSH producers from L-methionine. All three herb extracts signifi-cantly decreased H2S (p<0.05), MeSH (p<0.05), and ammonia (p<0.05) production, but SCFA production was not affected (p>0.05). The number of volatile sulfur-producing bacteria did not vary among groups by the dietary supplementation of these herb extracts. Serial solvent extraction was done on these herb extracts to specify the active fractions that reduce volatile sulfur production, n-Butanol fraction of all three extracts significantly reduced volatile sulfur production in vitro.
We aimed to evaluate the effect of bacteria involved in the nitrogen cycle on the reutilization of intestinal urea nitrogen in uremic rabbits. New Zealand white rabbits were made uremic via bilateral nephrectomy. Study and control rabbits were given live and heat-inactivated bacteria through their jejunostomies. After they were injected with 99mTc biurea intravenously, serial serum and stool levels of labeled nitrogen were assessed by instant thin-layer chromatography, and the change in the labeled-nitrogen level was determined. The serum labeled-nitrogen level increased significantly in the study group (r=0.990); however, this level decreased in the control group (r=0.662). Furthermore, the labeled-nitrogen level in the stool samples increased throughout the study in the control rabbits, but it decreased after the 6th hour in the study group. In conclusion, the results of this study suggest that when the bacterial flora of the intestinal system is changed to include bacteria involved in the nitrogen cycle in uremic rabbits, the intraintestinal and systemic nitrogen metabolisms could both be altered in favor of positive nitrogen balance.
Lymphatic absorption of docosahexaenoic acids (DHA) given as monoglyceride (MG), consisting of 1 (or 3)-species (91.4%), 2-species (4.2%) and diglyceride (DG) con-sisting of 1, 3-species (70.8%), 1 (or 3), 2-species (28.6%), were investigated in comparison with that of triglyceride (TG) and ethyl ester (EE). Rats were infused with a lipid emulsion containing 200 mg of DHA-MG, DG, TG, or EE via a gastric cannula. Lymph was collected through the thoracic lymph duct at 2h intervals for 10h and at a single collection from 10 to 30h. Physiological saline containing glucose was infused (2mL/h) throughout the lymph collection. The overall recovery of DHA at 30h after its infusion was significantly higher in the rank order DHA-MG>DG>TG=EE. Moreover, time-dependent changes in re-covery rates from 2 to 10h of DHA given as MG were significantly higher than those of the corresponding DG, TG, and EE. These results indicate that DHA-MG and DG are absorbed and transported more effectively than TG and EE forms under restricted water supply, even if they mainly consist of 1 (or 3)-species. Lymph lipids were mainly transported as TG, and a large amount of DHA was incorporated into a TG fraction in all fat types examined. Furthermore, the intramolecular distribution of DHA in lvmnh TG was similar in all grouns.
An antioxidant Was purified from human placenta extract (HPE) by using gel filtration, liquid-liquid extraction, silicagel column chromatography, and HPLC. The purified antioxidant was identified to be L-tryptophan (L-Trp). L-Trp showed higher inhibitory activity than mannitol and DMSO on the Fenton reaction-induced degradation of 2-deoxy-D-ribose. L-Trp also had much higher inhibitory activity on the cytochrome P-450-dependent lipid peroxidation than the previously identified antioxidants of HPE, L-phenylalanine, L-tyrosine and uracil. On the other hand, the inhibitory effect of L-Trp on the Fenton reactioninduced protein oxidation was smaller than that of uracil. These results suggest that L-Trp is a main antioxidant of HPE of which the effect is based on the suppression of lipid peroxidation in the oxidative stress status.
The effects of the dietary addition of orotic acid were studied on lipid levels in the rat liver and serum, 1, 2-diacylglycerol levels in some organs, activities of antioxidant liver enzymes (superoxide dismutase, glutathione peroxidase, and catalase), and serum enzyme activities (ornithine carbamoyltransferase and alanine aminotransferase), after feeding for 0, 7, 14, and 21d, respectively. Rats on the orotic acid diet accumulated more liver total lipids, triacylglycerol, and phospholipids than those on the basal diet. However, the levels of serum triacylglycerol and phospholipids of those rats were markedly decreased after 7, 14, and 21d on the diet. Dietary orotic acid increased the 1, 2-diacylglycerol levels in the liver of rats fed for 14 or 21d, but not in the ileum of small intestine, vastus lateralis muscle, and heart. The addition of orotic acid lowered the activities of liver total and Cu, Zn-superox-ide dismutase after feeding for 7, 14, and 21d. The serum ornithine carbamoyltransferase activity after 14, and 21 d and that of serum alanine aminotransferase after 7, 14, and 21d were increased. These data suggested that the increase in the activities of serum enzymes tested may result from liver damage induced by the marked accumulation of liver lipids and possibly from the increased superoxide anion because of the decreased activities of hepatic superoxide dismutase by orotic acid feeding.
Buckwheat noodles were studied to identify the possibility of reduced starch hydrolysis rate and glucose release after the ingestion of buckwheat meals, in comparison to the wheat-based meals. The rate of starch hydrolysis and the resistant starch (RS) formation in boiled buckwheat noodles (BWN), boiled wheat noodles (WN), boiled buckwheat groats (BWG), and white wheat bread (WB) were evaluated in vitro. The highest content of RS (total starch basis) was found in boiled BWG (6%), compared with the BWN (3.4%), WN (2.1%), and WB (0.8%). The rate of in vitro amylolysis was significantly reduced (p<0.05) in both studied buckwheat products in comparison to the reference WB. The calculated hy-drolysis index (HI) was lower in BWN (61) in comparison to WN (71), but higher in com-parison to boiled BWG (50). It is confirmed that BWN have some potential in diets designed in accordance with the dietary recommendations for diabetic patients and for healthy subjects.
The suitable development of oral tolerance against ingested dietary foods is of critical importance to escaping food allergy. Using mice as an animal model for oral tolerance against ovalbumin (OVA) as a dietary antigen, we investigated the effects of dietary protein on their immunological tolerance. Female BALB/c mice fed either a 20% or 5% protein diet were orally administered 5mg of OVA for four consecutive days, then immunized intraperitoneally with 100μg of OVA. The immunized group of mice were fed and treated in the same manner, except that they received orally distilled water for four consecutive days before receiving intraperitoneal immunization with the antigen. Immunization alone with OVA elevated the total IgE and induced the production of OVA-specific antibodies IgE, IgG, IgG1, and IgG2a in the sera of both the 20% and 5% protein diet groups. The oral administration of OVA to mice before intraperitoneal immunization significantly reduced the total IgE and OVA-specific antibodies in mice fed 5% protein diet, but it had hardly any effect on those in mice fed a 20% protein diet. When spleen cells from these groups of mice were cultured with OVA as a mitogen, they responded substantially to OVA in the immunized groups fed 20% and 5% protein diets and in the presensitized group fed 20% protein, but those from the presensitized group fed a 5% protein diet did not respond. Furthermore, when IL-4 was assayed in the spleen cell cultures of the 20% and 5% groups, mice in the presensitized group fed a 5% protein diet produced a significantly less amount of IL-4 than those fed a 20% protein diet. Moreover, irrelevant to the protein amount in the diet, the production of IFN-γ from spleen cell cultures dramatically decreased in the group without presensitization and profoundly increased in the presensitized group of mice fed a 5% protein diet. These findings suggest that a low-protein diet leads to an induction of oral tolerance against dietary antigens; this appears to involve a clear down-regulation of Th2 cytokine, IL-4.
Leucine performs a signaling role to enhance protein synthesis by phosphorylating eukaryotic initiation factor (elF) 4E-binding protein 1 (4E-BP1) and 70-kDa riboso-mal protein S6 kinase (S6K1), two key regulatory proteins involved in the initiation of mRNA translation. The purpose of the current study was to assess whether the phosphorylation of 4E-BP1 and S6K1 was increased in skeletal muscle and liver by an oral administration of Leucine to diabetic rats and to determine the in vivo contribution of insulin to a leucine-dependent induction of 4E-BP 1 and S 6K 1 phosphorylation. Food-deprived (18 h) normal and diabetic rats were orally administered 135mg/ 100g body weight L-leucine and sacrificed at 1 h after administration. Leucine administration resulted in enhanced phosphorylation of 4E-BP 1 and S 6K 1 in skeletal muscle and in liver of nondiabetic rats. The stimulatory action of leucine on the phosphorylation of 4E-BP 1 and S 6K 1 in skeletal muscle was not abolished in rats with streptozotocin-induced diabetes. In contrast, leucine administration did not stimulate the phosphorylation of 4E-BP1 and S6K1 in the liver of diabetic rats. These findings suggest that in skeletal muscle, leucine functions as a nutritional signaling molecule that independently regulates the phosphorylation states of 4E-BP 1 and S6K1. In contrast to skeletal muscle, insulin is essential in mediating the leucine-dependent induction of 4E-BP1 and S6K1 phosphorylation in liver.
Recently we reported that the supplementation of vitamin B6 to low vitamin B6 diet caused suppression in colon tumorigenesis and cell proliferation of azoxymethanetreated mice in a dose-dependent manner among 1, 7, and 14mg pyridoxine HCl/kg diet (J Nutr 131: 2204-2207, 2001). To examine the mechanism of the anticolon tumor effect of vitamin B6, male ICR mice were fed the diet containing 1, 7, 14, and 35 mg pyridoxine HCl/kg diet for 22 wk and simultaneously given a weekly injection of azoxymethane for an initial 10 wk. The supplementation of vitamin B6 to a low vitamin B6 diet (1 mg pyridoxine HCl/kg) suppressed the levels of colonic 8-hydroxyguanosine and 4-hydroxynonenal and in-ducible nitric oxide synthase protein. The results suggest that the preventive effect of vita-min B6 against colon tumorigenesis is at least in part mediated by reducing oxidative stress and nitric oxide production.
The present study was undertaken to estimate the effect of acerola cherry extract (ACE) pretreatment on cell proliferation and the activation of Ras signal pathway at a promotion stage of lung tumorigenesis in mice treated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Pretreatment with ACE (dose, 70mg/kg body weight and 700mg/kg body weight) inhibited increases in the levels of proliferating nuclear cell antigen and ornithine decarboxylase at the promotion stage. This treatment of ACE also sup-pressed the activation of Ras signal pathway at the same stage. These results suggest that ACE regulates abnormal cell growth at the promotion stage of lung tumorigenesis in mice treated with NNK as a result of suppression of the initiation stage.
The effect of Hatakeshimeji (Lyophyllum deeastes Sing.) mushroom on serum lipid levels was investigated in rats. When the mushroom (fruit body) powder or its hotwater extract was added at a level of 10% to a cholesterol-containing diet, the serum total cholesterol levels of rats fed the fruit body or the hot-water extract were markedly lower than that of controls, though there was no significant difference in serum HDL-cholesterol among the three groups. On a cholesterol-free diet, the addition of fruit body powder at a level of 5% significantly decreased serum total cholesterol. Serum triglycerides and phospholipids were significantly decreased in both the fruit body and hot-water extract groups. Furthermore, Hatakeshimeji in the diet significantly increased the activity of cholesterol 7α-hydroxylase, which converts cellular cholesterol to bile acids, as well as the fecal excretion of bile acids.
D-Psicose (D-ribo-2-hexulose), a C-3 epimer of D-fructose, is present in small quantities in commercial carbohydrate complexes and agricultural products. We have previously reported that D-psicose supplements in diets suppressed hepatic lipogenic enzyme activity. The lower fat accumulation in rats fed D-psicose may be due to lower lipogenesis in the liver. The present study examined the energy available in D-psicose for rat growth. Male Wistar rats received 7g daily of a basal diet to which fixed amounts of sucrose, D-fructose, or D-psicose (0.5-2.0g) were added for 20 d. Body weight gain and body energy gain increased with increases in sucrose and D-fructose, but not with D-psicose. One gram of sucrose, D-fructose, and D-psicose produced a net energy gain of 2.29, 1 and 0.007 kcal, respectively. The efficiency of energy deposition from D-psicose was 0.3% that of sucrose. The energy value of D-psicose was effectively zero. These results suggest that D-psicose is a rare sugar providing zero energy that may be useful in sweeteners for obese people as an aid for weight reduction.