The Soy Protein Research Committee(Japan)
Molecular analysis of the mechanism that regulates expression of soybean seed storage protein genes in response to sulfur nutrition: Toward a development of a novel strategy for molecular breeding of soybean.,
Toru FUJIWARA
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113
Rep. Soy Protein Res. Com., Jpn. 18, 1-3, 1997.
The gene encoding theɿsubunit ofɿ-conglycinin is known to be upregulated by sulfur deficiency in soybean. The gene is similarly regulated by sulfur nutrition in transgenic petunia and Arabidopsis. These responses are parts of adaptation responses of soybean to maintain levels of nitrogen and sulfur reservoir in seeds. We previously found that O-acetyl-L-serine (OAS), a precursor for cysteine biosynthesis, is found accumulated in response to sulfur deficiency and excess nitrogen supply and that exogenous application of OAS was found to upregulate the accumulation of theɿsubunit protein. These findings suggest that OAS may be a key intermediate of the regulation of theɿsubunit gene. It is reported that the accumulation of theɿsubunit proteins is also enhanced by exogenous application of ABA, similar to the effects of sulfur deficiency. Here we found that exogenous ABA elevated the levels of OAS in in vitro cultured soybean cotyledons, suggesting that OAS may as well be a key intermediate for the ABA regulation of theɿsubunit accumulation in developing soybean cotyledons.
Key words : É¿-conglycinin, O-acetyl-L-serine, sulfur nutrition, ABA, Glycine max
Activation mechanism for the vacuolar processsing enzyme.
Nagako HIRAIWA and Ikuko HARA-NISHIMURA
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444
Rep. Soy Protein Res. Com., Jpn. 18, 4-9, 1997.
Vacuolar processing enzyme(VPE)responsible for maturation of various vacuolar proteins belongs to a novel cysteine proteinase family. To explore the active site of VPE and the activation mechanism for VPEÅCwe expressed mutant VPEs in yeast Saccharomyces cerevisiae.VPE homologues have cysteine residues and histidine residues in the conserved region of the polypeptides. We substituted each of these residues, Cys83, Cys222, Cys255, Cys269 and His180, by a glycine residue to make mutant VPEs. These mutant VPE genes were introduced to pep4 strain of yeast and expressed the respective VPEs. We found that a wild VPE could complement the maturation of carboxypeptidase Y (CPY) instead of proteinase A (PEP4 gene product) in the transformant of PEP4 strain. Thus, we used the maturation of CPY for in vivo assay of VPE activity. The mutant VPEs of C255G and C269G had the activity to produce mature CPY, while the mutant VPEs of C83G, C222G and H180G had no activity. The result indicates that Cys83, Cys222 and His180 are the essential amino acid for the VPE activity. In the next step, to clarify the activation mechanism of VPE, we examined whether the conversion of proVPE into mature VPE was occurred in these transformants with mutant VPEs. The transformants expressing inactive VPE mutants, C83G, C222G and H180G, accumulated proVPE, but not mature VPEs, although the conversion of proVPE into mature VPE was observed in the transformants expressing active mutant VPEs, C255G and C269G. These findings suggest that an inactive VPE precursor is converted to an active VPE by self-catalytic proteolysis within the vacuoles. Thus, it is likely that VPE itself might regulate maturation and activation of various vacuolar proteins in the plant vacuoles.
Key words : asparaginyl endopeptidase, cysteine proteinase, vacuolar proteins, vacuolar processing enzyme (VPE), yeast
Breeding of soybean isogenic lines consisting of differnt subunits of glycinin and their biochemical characterization.
Kazuhiro YAGASAKI 1 and Keisuke KITAMURA 2
1National Agriculture Research CenterÅCTsukuba 305
2The Graduate School of Agriculture and ForestÅCTsukuba University, Tsukuba 305
Rep. Soy Protein Res. Com., Jpn. 18, 10-14, 1997.
Glycinin, a major storage protein of soybean seed, consists of six subunits, each made up of an acidic (A) and basic (B) polypeptide component linked by a single disulfide bond. Five major subunits of glycinin have been grouped into three intermediate subunit groups, i.e., group I (A1aB2, A1bB1b and A2B1b), IIa(A5A4B3) and IIb(A3B4). Isogenic lines having different glycinin subunits are now being bred. In this paper, effects of ionic strength on solubility and molecular assembling of glycinin subunits were analyzed using the breeding lines. When NaCl was added to the total protein and glycinin solution, glyicinin consisting of only group I subunits was highly soluble compared to the IIa or (and) IIb subunit at NaCl concentration lower than 0.05 M at pH 5.5. The molecular weight of glycinin consisting of only group I subunits was estimated as about 150 kDa at NaCl concentration more than 0.1 M by gel chromatography. It was half volume of wild type having all subunits of glycinin. Therefore, the gylcinin lacking both IIa and IIb subunits is not able to assemble to form the 11S structure under this ionic strength condition. Structural changes caused by a lacking of glycinin subunit(s) are expected to influence the food-processing properties of soybeans.
Key words : soybean, glycinin, subunit composition, biochemical characterization, food-processing property
Food Seed Aspartic Proteinase : Cloning, Expression, and Application to Food Processing
Keiko ABE 1 and Tomiko ASAKURA 2
1 Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113
2 Atomi Junior College, Tokyo 112
Rep. Soy Protein Res. Com., Jpn. 18, 15-20, 1997.
An attempt was made to express oryzasin 1, a new aspartic proteinase of rice seed origin. An expression plasmid was constructed by linking a pro-oryzasin cDNA to the downstream of the region that encoded glutathione-S-transferase (GST) and a GST-oryzasin 1 fusion protein was expressed as an inclusion body in Escherichia coli. It was then solubilized with the use of a surfactant and affinity-purified to obtain a recombinant oryzasin 1 preparation, the properties of which were similar to those of original oryzasin. Next, the preparation was applied to protein bodies extracted from rice seedsÅCwith the result that their glutelin fraction was well digestedÅDThis suggests the possible utility of oryzasin 1 in modification of structures and functions of legumins including soy glycinin. A clotting phenomenon was also observed when the oryzasin 1 preparation was added to skim milk, indicating the applicability of this enzyme for improvement of functional properties of protein food materials including soy milk.
Key words : aspartic proteinase, expression
18-5 X-ray crystallography of soybean proglycinin at high resolution.
Motoyasu ADACHI, Bunzo MIKAMI and Shigeru UTSUMI
Research Institute for Food Science, Kyoto University, Uji 611
Rep. Soy Protein Res. Com., Jpn. 18, 21-24, 1997.
Glycinin is one of the most abundant storage proteins in soybean seeds. To design a modified glycinin with improved food functions at the atomic level, three-dimensional structure of glycinin has to be elucidated at high resolution. Previously, we reported the structure of the recombinant proglycinin trimer at 6.0 Å&Mac240; resolution based on the data from three kinds of heavy atom derivatives. However, it was not enough to build the model of the proglycinin at high resolution. because these derivatives had the same binding sites of heavy metals each other at pH7.6. Change of soaking conditions from pH7.6 to pH5.5 provided derivatives suitable for isomorphous replacement method. A good electron density map was made at 3.2 Å&Mac240; resolution by solvent flattening and averaging with program PHASES. We built the model of the proglycinin with R-factor of 22.7 using program XPLOR. Comparison of the structure ofÉ¿-barrel in the proglycinin with that of phaseolin showed a high similarity between those. This supports the hypothesis that both proteins are derived from a common ancestor.
Key words : crystallography, glycinin, proglycinin, soybean proteins, X-ray analysis
Chemical Modification of Soy Protein Isolate : Chemical Keratinization and Functions of Proteinous Polymer Material
Kiyoshi YAMAUCHI
Faculty of Engineering, Osaka City University, Osaka 558
Rep. Soy Protein Res. Com., Jpn. 18, 25-30, 1997.
Thiol groups(SH)were introduced chemically into soy protein isolate(SPI). The sulfur content in the modified SPI was 3-4wtÅì. The transparent film, which was obtained readily upon casting an aqueous solution of SPI-SH under air, was water-resistant and had high tensile strengthÅDThe results were explained by a formation of disulfide crosslinkings between the proteins. The film properties (tensile strength, Young's modulus, solubility, swelling degree, etc.) were compared with those of polymer films and discussed in conjunction with spectral and physicochemical data.
Key words : chemical modificationÅCprotein filmÅCpolymerÅCsoy protein isolateÅiSPIÅjÅCthiolation
Improvement of Functionalities of Soybean Protein by Heat Processing and Preparation of Transparent Gel
Naofumi KITABATAKE, Yuki FUJITA and Sadako TOKUMARU
Research Institute for Food Science, Kyoto University, Uji 611
Rep. Soy Protein Res. Com., Jpn. 18, 31-36, 1997.
Defatted soybean extract was dialyzed against distilled water at pH7.5. The dialysate was a transparent solution having less beany flavor. After heating the desalted soybean extract kept transparency even in the presence of salt(NaCl). When the desalted-soybean extract preheated under salt-free condition was heated again in the presence of NaCl(0.2 M), it gave translucent gel at a lower concentration than that of non-heated desalted-soybean extract. This translucent gel was melted by the following heating and gelified again by cooling, that is, this gel is cold-setting and gel-sol transition is reversible, which was confirmed with the measurement of dynamic viscoelasticity. Desalted-soybean extract preheated under salt-free condition could give a gel at room temperature or lower temperature only by addition of salt, and was not precipitated by the incubation at 4ÅBC, which is different from native soybean protein.
Key words : soybean extract, heat processing of soy extract, cold-set gel, reversible gel, transparent gel, viscoelasticity of gel
Sorption of a Gas on Food Materials at Low Temperatures : Change in Pressure during Chilling and Thawing
Shuji ADACHI, Eiichiro ISHIDO, Yasumasa MINEMOTO and Ryuichi MATSUNO
Graduate School of Agriculture, Kyoto University, Kyoto 606-01
Rep. Soy Protein Res. Com., Jpn. 18, 37-41, 1997.
Soybean oil and activated char absorbed or adsorbed more air at lower temperatures, while the amount of air adsorbed seemed to show no significant dependence on temperature for powdery soy protein isolate, soybean peptide and maltodextrin. Water played an important role for change in pressure during chilling and thawing. The temperature at which a vessel was sealed up also influenced the change. Wetty materials which froze up during chilling showed a rise in pressure. Differential scanning calorimetry (DSC) would be useful to predict whether or not a material cuases a rise in pressure during chilling and thawing.
Key words : chilling, thawing, pressure, low temperature, differential scanning calorimetry (DSC)
Active Oxygen-radical Scavenging Activity of Soybean Proteins : Especially Soybean Lipoxygenase
Yumiko YOSHIKI, Masaaki KAWANE, Husniza HUSSAIN, Yuan HU and Kazuyoshi OKUBO
Faculty of Agriculture, Tohoku University, Sendai 981
Rep. Soy Protein Res. Com., Jpn. 18, 42-48, 1997.
Active oxygen species(X) can cause damage to biomolecules including protein and DNA. Previously, we have reported that catalytic species(Y) such as flavonoids as natural radical scavengers exhibited very weak light emission (chemiluminescence, CL) in the presense of X and receptive species(Z) such as acetaldehyde and DDMP saponin and proposed that the system of XYZ is a scavenging mechanism for active oxygen species in accordance with the CL intensity [P]=k[X][Y][Z] ; k, photon constant. In this study, soybean lipoxygenase(LOX) involved in the XYZ system was investigated. It could be concluded that(1) the LOX acted as Y and Z in the XYZ system when compered with horseradish peroxidase, cytochrome c and superoxide dismutase acted as typical Z in the system, and that (2) gallic acid had not a synergistic effect on the SOD activity of the LOX but had the effect on the HO &Mac183; scavenging, antioxidant and LOOH scavenging activities of the LOX.
Key words ÅF active oxygen, radical scavengers, chemiluminescence, XYZ system, soybean, lipoxygenase, photon emission
Improvement of Plant Proteins by the Reconstitution of Peptides
Akio KATO, Elfadil Elfadl BABIKER and Naotoshi MATSUDOMI
Faculty of Agriculture, Yamaguchi University, Yamaguchi 753
Rep. Soy Protein Res. Com., Jpn. 18, 49-54, 1997.
The reconstitution of peptide fragments in soy proteins was attempted to improve the functional properties such as solubility, removal of bitterness, emulsifying and foaming properties. Soy protein was reconstituted by microbial transglutaminase treatment of the protease digests or the mild acid hydrolysates. Although the protease digests or the acid hydrolysates of soy protein revealed the insolubility and the bitterness, the subsequent transglutaminase treatment increased the solubility and decrease the bitterness. In addition, the reconstituted soy proteins showed better emulsifying and foaming properties. These results suggest that the reconstitution of peptides using transglutaminase is a useful method for improving food functionality of soy protein.
Key words : reconstitution of soy protein, transglutaminase treatment, removal of bitterness of peptides
Synergistic Effects of Antioxidative Peptides from a Soybean Protein Digest on the Antioxidative Activity of Nonpeptidic Antioxidants
Koji MURAMOTO, Hua-Ming CHEN, Koichiro SAITO and Tomohisa OGAWA
Graduate School of Agriculture, Tohoku University, Sendai 981
Rep. Soy Protein Res. Com., Jpn. 18, 55-61, 1997.
The antioxidative properties of synthetic peptides, which were designed based on the antioxidative peptide from a soybean protein digest, were examined with regard to their antioxidative activity against the peroxidation of linoleic acid, and the scavenging effects on active oxygen and free-radical species. The antioxidative activities of these peptides in an emulsion oxidation system using 2,2'-azobis (2-amidinopropane) dihydrochloride as a radical initiator correlated well with in an aqueous system. Although the peptides had a quenching activity on singlet oxygen, they did not show antioxidative activity in an 2,2'-azobis (2,4-dimethylvaleronitrile)-induced oxidation system nor scavenging effects on 1,1-diphenyl-2-picrylhydrazyl radical and superoxide. The metal-ion chelating activities and the hydrophobicities of these peptides showed no direct correlation with their antioxidative activitiesÅDNonpeptidic antioxidantsÅCsuch as tocopherolÅCBHA and BHTÅCpotentiated the antioxidative activities of the peptidesÅDThe magnitude of the synergism had no relationship with the antioxidative activities of the peptidesÅDThe random tripeptide library consisting of two histidine or two tyrosine residues wasÅCthenÅCconstructed in order to further explore the relationship between the antioxidative activities and the synergistic effectsÅDTyr-His-Tyr was found to be the most active with or without nonpeptidic antioxidants.
Key words : soybean protein hydrolysate, antioxidative peptide, antioxidant, synergistic effect
Purification and Characterization of Soybean Allergen Gly m Bd 28K
Tadashi OGAWA, Noriko BANDO and Rintaro YAMANISHI
School of Medicine, The University of Tokushima, Tokushima 770
Rep. Soy Protein Res. Com., Jpn. 18, 62-67, 1997.
Gly m Bd 28K (Gm28K) is one of the major allergens of soybean. In the present study, a monoclonal antibody (mAb) against Gm28K was prepared and Gm28K was purified from defatted soybean flakes by using immunoaffinity chromatography with the mAb as a ligand. The purified allergen was found to be a glycoprotein with molecular mass of 26 kDa and pI 6.1. During the purification, the allergen gave more acidic protein species with the same molecular mass, suggesting that the allergen is unstable. From the N-terminal amino acid sequence of Gm28K (FHDDEGGDKKSPKSLFLMS-STR-) and the sugar composition it was shown that Gm28K is a new glycoprotein with an Asn-linked sugar moiety at the 20th residueÅiAsnÅjfrom the N-terminal.
Key words : soybean, allergen, monoclonal antibody, glycoprotein, Gly m Bd 28K
Effect of Soybean Protein Co-feeding on Immune Response to Fed Protein Antigens
Noriko NINOMIYA, Kenji YAMAGUCHI and Tsukasa MATSUDA
School of Agricultural Sciences, Nagoya University, Nagoya 464-01
Rep. Soy Protein Res. Com., Jpn. 18, 68-73, 1997.
Kunitz soybean trypsin inhibitor (KSTI) is one of the causative allergens of soybean food allergy, and it would reduce digestibility of food proteins and might affect the adsorption of undigested food protein antigens through intestinal epithelium. KSTI (20mg) was intra-gastrically administered to mice and, then, the mice was killed and the small intestinal content was recovered. Intact KSTI was detected in the intestinal content by immunoblot analysis using anti-KSTI antibody, and trypsin activity of the intestinal content was inhibited almost completely. To examine the effect of trypsin inhibition on antibody response to fed protein antigens, egg lysozyme as a model antigen was intra-gastrically administered to B10.A mice with and without KSTI, and the serum IgG and IgE responses to administered lysozyme (LY) were measured by ELISA. The antibody responce of mice given LY with KSTI were not higher than those of mice without KSTI, suggesting that co-administration of KSTI does not enhance the antibody responses to intra-gastrically administered protein antigens.
Key wordsÅFKunitz soybean trypsin inhibitor (KSTI), food allergen, oral antigen, lysozyme
Studies on Anti-allergic Effect of Soybean Peptides : Effect on Chemical Mediator Releasing Activity of Rat Peritoneal Exudate Cells
Koji YAMADA 1, Shin-ichi YUNOKI 1, Mitsuo MORI 1, Yousuke SUNADA 1 , Michiko NONAKA 1, Hirofumi TACHIBANA 1 and Michihiro SUGANO 2
1 Faculty of Agriculture, Kyushu University, Fukuoka 812-81
2 Faculty of Human Life Sciences, Prefectural University of Kumamoto, Kumamoto 862
Rep. Soy Protein Res. Com., Jpn. 18, 74-77, 1997.
It has been shown that soybean proteins and peptides interfere with the metabolism of polyunsaturated fatty acids which are related to the occurrence of food allergies. Thus, the effect of soybean proteins and peptides on allergic reaction was examined. At first, rat peritoneal exudate cells were stimulated with calcium ionophore in the presence of these components and found that they suppressed leukotriene B4 (LTB4) release from the cells. Then Sprague-Dawley rats were fed purified diets containing safflower or perilla oil at the 10Åì level and casein or soybean protein at the 20Åì level for 3 weeks and the effect on chemical mediator releasing activity of rat peritoneal exudate cells was examined. Histamine and LTB4 releasing activities of the cells were lower in rats fed soy protein than in rats fed casein. These results indicate a possibility that ingestion of soybean protein suppresses allergic responce.
Key words : soybean protein, polyunsaturated fatty acid, peritoneal exudate cells (PEC), leukotriene B4(LTB4), perilla oil
Effect of the Formulated Diets Containing Soy Protein Isolate as the Sole Protein Source on Rats Suffering from Galactosamine-induced Hepatitis or Type II Diabetes Mellitus
Tadashi NOGUCHI and Tomomi HIDAKA
Graduate School of Agricultural and Life SciencesÅCThe University of TokyoÅCTokyo 113
Rep. Soy Protein Res. Com., Jpn. 18, 78-81, 1997.
Diets for the rats suffering from galactosamine-induced hepatitis or type II diabetes mellitus were formulated using soy protein isolateÅiSPIÅjas the sole source of protein. The diet for hepatitis rats was formulated by increasing branched-chain amino acids and decreasing aromatic amino acids and methionine. On the contrary, the diet for diabetic rats was formulated by decreasing branched-chain amino acids. The rats received the diet for hepatitis showed lower plasma GOT value suggesting the favorable effect of the diet. OLETF (Otsuka Long Evans Tokushima Fatty) rats which were fed the diet for diabetes after 45 weeks of age showed improved body weight loss and mortality. The results suggest that modification of dietary amino acids is effective for prevention or improvement of the symptoms of glactosamine-induced hepatitis or type II diabetes mellitus.
Key words : galactosamine-induced hepatitis, SPI diet, diabetes millitus, high branched-chain amino acid diet, low branched-chain amino acid diet
Effects of Dietary Soybean Protein on Insulin Receptor Gene Expression and Activities, and Obese Gene Expression
Nobuko IRITANI, Tomomi SUGIMOTO, Hitomi FUKUDA and Masumi KOMIYA
Tezukayama Gakuin College, Sakai 590-01
Rep. Soy Protein Res. Com., Jpn. 18, 82-86, 1997.
To investigate the effects of different dietary fatty acids and proteins on insulin receptor gene expression, Wistar fatty rats (genetically obese, non-insulin-dependent diabetes mellitus ; NIDDM) and their lean littermates were fed a casein or soybean protein diet containing 9 % hydrogenated beef tallow (plus 1% corn oil), 10% corn oil or fish oil for 3wk. The insulin receptor mRNA concentrations in livers and adipose tissues were higher in rats fed soybean protein/hydrogenated beef tallow than in those fed any other protein/fat combination. In the lean rats, the insulin binding capacity of receptors was higher in the soybean protein group than in the casein group. In the obese rats, however, the insulin binding capacity was not affected by dietary protein or fat type, being lower than in the lean rats. Although the insulin binding capacities to receptors did not always coincide with insulin receptor gene expression, the gene expression relative to tissue weight suggests that dietary soybean protein may help to reduce the insulin resistance of NIDDM, but only in the case of low content of polyunsaturated fatty acids in diet. Polyunsaturated fatty acids appeared to induce the insulin resistance. The mRNA concentrations of obese gene in adipose tissue were higher in the obese rats than in the lean rats regardless of dietary groups. The gene expression tended to be lower in the soybean groups of obese rats.
Key words : soybean protein, polyunsaturated fatty acids, insulin receptor gene expression, obese rat, non-insulin-dependent diabetes mellitus (NIDDM)
Influence of Soy Protein on Renal Hypertrophy and IGF-I Gene Expression in Diabetic Rats
Kazunori UTSUNOMIYA 1 and Yoshio IKEDA 2
1 Department of Internal Medicine(III), The Jikei University School of Medicine, Tokyo 105
2 Center for General Health Care, The Jikei University School of Medicine, Tokyo 105
Rep. Soy Protein Res. Com., Jpn. 18, 87-91, 1997.
One of early renal manifestations of diabetes mellitus includes renal hypertrophy which is preceded by an accumulation of IGF-I peptide in the kidney. Protein nutrition has a profound influence on renal hypertrophy in diabetes. In this study, we examined the influence of proteins of different quality on renal hypertrophy and IGF-I mRNA expression in renal cortex using diabetic rats. Male Wistar rats were made diabetic with intravenous injection of streptozotocin (STZ). Then, the rats were divided into four groups, namely the normal controls, the diabetic rats fed with regular diet, the diabetic rats fed with 35% casein diet and the diabetic rats fed with 35% soy protein diet. Killing the rats at one week after induction of diabetes, we weighed the kidney. Extracting total RNA from renal cotices, we examined IGF-I mRNA expression with Northern blot analysis. Compared to the normal controls, the kidney weight was increased in the diabetic rats on regular diet and further increased on casein diet. However, there was no significant difference in the kidney weight between the diabetic rats on regular and soy protein diet. Renal IGF-I mRNA expression was also increased in the diabetic rats and further increased with casein feeding. In contrast, soy protein had no additional influence on renal IGF-I in the diabetic rats. These data suggest that quality difference in ingested protein is closely related to the development of renal hypertrophy in diabetes through renal IGF-I mRNA expression.
Key words : diabetic nephropathy, renal hypertrophy, IGF-I, soy protein, casein
Effects of Soy Protein, Amino Acid Mixture and Ethanol Extracts on Arterial Lesions in Apo E-deficient Mice
Wei-Hua NI and Katsumi IMAIZUMI
Faculty of Agriculture, Kyushu University, Fukuoka 812-81
Rep. Soy Protein Res. Com., Jpn. 18, 92-95, 1997.
Effects of dietary soy protein, soy amino acid mixture and ethanol extracted soy protein on serum lipids and atherosclerotic lesions in apo E-deficient mice were examined. Soy protein, compared with casein, prevented atherosclerotic lesionsÅCalthough serum cholesterol levels were not influenced. Soy protein simulated amino acids and ethanol extracted soy protein were partially effective to the lesion. Soy protein ethanol extracts had no significant effect on the lesion and serum cholesterol. These results show antiatherogenic effect of soy protein is attributed to protein.
Key words : atherosclerosis, soy protein, casein, isoflavone, apo E-deficient mice
Effects of Soybean Peptide on Suppression of Body Fat Accumulation in Exercised Mice
Kengo ISHIHARA, Koichiro ONUKI, Masato SAITO and Tohru FUSHIKI
Graduate School of Agriculture, Kyoto University, Kyoto 606-01
Rep. Soy Protein Res. Com., Jpn. 18, 96-100, 1997.
Chronic administration of soybean peptide beverage suppressed body fat accumulation of mice. Mice were fed with commercial chow and 5% soybean digestion peptide solution during endurance swimming every 2 days for 5 weeks. The same effect was observed in using 5% amino acid mixture beverage which simulated the soybean peptide. In this study, we investigated the influence of branched-chain amino acid (BCAA) content, which is higher in the soybean peptide. Mice were given 5% amino acid mixture beverage whose content of BCAA was decreasedÅDAfter 45 days of training and administration, the mass of the epididymal and peripheral fat was still significantly smaller than control. These results suggested that BCAA content may not be relevant to suppression of body fat accumulation.
Key words : body fat content, swimming exercise, soybean peptide, branched-chain amino acid
Stimulation of Sympathetic Nervous System by Soy Protein : An Examination of Energy Expenditure of Rats with Doubly Labeled Water Method
Shin-ichi HAYASHI 1, Hiroko TAKIZAWA 1, Senya MATSUFUJI 1 and Takamasa IWAKI 2
1 Second Department of Biochemistry, The Jikei University School of MedicineÅCTokyo 105
2 Laboratory Animal Facilities, The Jikei University School of Medicine, Tokyo 105
Rep. Soy Protein Res. Com., Jpn. 18, 101-104, 1997.
We tried to examine possible effect of soy protein to stimulate energy expenditure of rats by using the doubly labeled water method, in which the rate of loss of body water labeled with either deuterium or 18O is determined and the difference in the rate (KO-KD) indicates the rate of CO2 production. SD rats fed either casein or soy protein isolate (SPI) diet were injected i.p. with 0.5 g each of D2O and H218O. After either 30 min or 4 days, blood was obtained from cervical artery under anesthesia, and contents of both stable isotopes were measured with mass spectrometer. We obtained results indicating that, in contrast to our expectation, nearly twice amounts of CO2 were produced by rats fed casein, compared to rats fed SPI. The validity of this result needs to be evaluated under further refined conditions.
Key words : doubly labeled water method, energy expenditure, soy protein, stable isotopes, rat, mass spectrometry
Action of Secondary Bile Acid as a Potent Promoter in Colonic Tumorigenesis and Preventive Effect of HMF Diet against Cancer Risk
Kimikazu IWAMI 1, Naoyuki ADZUMA 1, Yumiko TAGUCHI 1, Hitoshi SUDA 1, Tohru SAEKI 1, Ryuhei KANAMOTO 1 and Yasunari TSUCHIHASHI 2
1 Faculty of Agriculture, Kyoto Prefectural University, Kyoto 606
2 University Hospital, Kyoto Prefectural University of Medicine, Kyoto 602
Rep. Soy Protein Res. Com., Jpn. 18, 105-111, 1997.
Azoxymethane-treated male Fischer-344 rats were fed for 39 weeks casein diet (group A), HMF diet (group B), deoxycholate-supplemented casein diet (group C) and deoxycholate-supplemented HMF diet (group D), respectively, from which the colons were excised and examined for tumor development. Firstly, tumors visible to the naked eye were picked up to make a comparison between both groups without and with deoxycholate loading. As a result of Fisher's test, tumor incidence in groups A and B was significantly different at P=0.01 from that in groups C and D. In other words, deoxycholate served as a potent promoter in colonic tumorigenesis. With respect to a comparison between both C and D groups, a clear distinction was observed for tumor size (t-test, P<0.001) but not for tumor incidence (Fisher's test, P>0.2). For this reason, the colons without seemingly visible tumors were inspected over again through a magnifier and faint prominentiae 'bud tumors' were tentatively ranked with half a tumor altogether. The rats of each group were arranged in order of their bearing tumors, followed by non-parametric Mann-Whitney test. Consequently a gap in arrangement between both C and D groups proved to be significant at P<0.05, implying that HMF diet was more effective in retardation of colonic tumorigenesis than casein diet probably through the capture of secondary bile acids. In this connection, large-size tumors of which thin slices were pathologically inspected under the microscope were all diagnosed as highly-developed adenocarcinomas. Secondly, the stimulatory or damaging effect of secondary bile acids on cell proliferation was investigated in order to obtain some information about their cancer-promotive action. In view of a preliminary approach, mouse fetal fibroblast 3T3 cells were used for this experimental purposeDThe culture medium containing cholic acid or its related conjugate in the range of 0.2 to 1.0 mM did not affect the proliferation of 3T3 cells. Alternatively the presence of dihydroxybile acids such as deoxycholate and chenodeoxycholate at more than 0.6 mM did not only suppress the proliferation of viable cells but also affected its restoration after removal of the bile acids. A similar effect was observed for monohydroxybile acid 'lithocholate', although being a little different in restoration after its removal. Further information is required to reasonably explain the cancer-promotive risk of these bile acids in connection with such a cell toxicity.
Key words : colon cancer risk, secondary bile acids, cultured 3T3 cells, anti-tumorigenicity of HMF, suppression of cell proliferation
Effect of Soybean Trypsin Inhibitor and Isoflavone on Chemically Induced Skin Tumor in Mice
Chika MIYAGI 1, Sumie SHINJO 1, Yuko MIYAGI 1,Megumi KUBA 1, Mika TOUMA 1, Ming-Fu WANG 2, Kiyoharu TAKAMATSU 3, Takashi YAMAMOTO 3 and Shigeru YAMAMOTO 4
1 Faculty of Medicine, University of the Ryukyus, Okinawa 903-01
2 Department of Food and Nutrition, Providence University, Taichung, Taiwan
3 Applied Research Institute, Fuji Oil Co., Izumisano 598
4 School of Medicine, The University of Tokushima, Tokushima 770
Rep. Soy Protein Res. Com., Jpn. 18, 112-119, 1997.
Isoflavone and trypsin inhibitor are known as anti-carcinogenic substances of soybean. Whenever we eat soybean products, we usually ingest both components, therefore, we do not know the individual and comparative effects of them. In this study, 2 experiments were conducted to compare the effects of isoflavone and trypsin inhibitor on chemically-induced skin tumor in mice. In Experiment 1, hairless mice were fed control diet (isoflavone-free, trypsin inhibitor-free), soybean protein isolate diet (isoflavone 60 mg/100 g, trypsin inhibitor 459 U/100 g), whey diet (isoflavone 56 mg/100 g, trypsin inhibitor 1,448 U/100 g) or soybean embryo bud diet (isoflavone 37 mg/100 gÅjfor 24 wks. On the 7th day on the diet, tumor initiator was applied on the back of the mice. One week later, the tumor promoter was also applied at the same area (twice weekly) until the end of the study. The tumors over 1 mm in diameter were excised and weighedÅDIn Experiment 2, the mice were fed control diet (isoflavone-free, trypsin inhibitor-free), 2% embryo bud diet (isoflavone 15 mg/100 g), 5% embryo bud diet (isoflavone 38 mg/100 g), or whey diet (trypsin inhibitor 1,440 U/100 g) for 16 wks. Other methods were the same as those in Experiment 1. The results showed that the effects of both isoflavone and trypsin inhibitor on skin tumor were not statistically significant, however, the effects of trypsin inhibitor in two experiments were rather opposite, isoflavone in both experiments showed adverse effects, soybean protein isolate had little effect, and the effect of dose in isoflavone was not observed. The present study indicates that the anti-carcinogenic effect of soybean varies complicatedly depending upon the combination and concentration of isoflavone and trypsin inhibitor.
Key words : trypsin inhibitor, isoflavone, skin tumor, mouse
Effects of Cow Milk, Soybean Milk and Their Fermented Products on DMBA Induced Mammary Tumorigenesis
Susumu YANAGI 1, Shunsuke IMAI 2, Hitoshi YOKOYAMA 3, Hideo SUGANO 3 and Kiyoharu TAKAMATSU 3
1 Nara Medical University College of Nursing, Kashihara 634
2 Nara Prefectural Institute of Public Health, Nara 630
3 Applied Research Institute, Fuji Oil Co,. Izumisano 598
Rep. Soy Protein Res. Com., Jpn. 18, 120-124, 1997.
We studied effects of soybean milk, cow milk and their respective fermented products on promoting stage of rat mammary tumorigenesis induced by 7,12-dimethylbenz(a) anthracene (DMBA). One week after an administration of 5 mg DMBA the rats were divided into 5 groups, and drinking water of each experimental group was replaced with one of the following drinks, i.e., deionized water (control), soybean milk (SBM), cow milk (milk), fermented SBMÅiFSBMÅjor fermented cow milkÅiyogurtÅj. The rats were allowed to ingest a laboratory chow and the drinks freely. All the animals were sacrificed by the end of 20th weeks after DMBA administration. Diameter and weight of all tumors were determined and the tumors were subjected to histological examination. The tumor incidences of all the experimental groups were significantly higher than that of the control. The number of mammary tumors was the lowest in the control and the highest in both the milk and the SBM groups, but the difference was statistically insignificant. The average tumor weight and the tumor weight per tumor-bearing rat were the lowest in the SBM group and significantly lower compared with those of the milk group. The serum cholesterol was significantly lower in the control, the SBM and the FSBM groups than in the milk and the yogurt groups. In comparison with cow milk the result shows that soybean milk does not inhibit the tumor incidence, but significantly inhibits the growth of tumors.
Key words : mammary tumorigenesis, 7,12-dimethylbenz(a)anthracene(DMBA), soybean milk, cow milk
Inhibitory Effect of Soybean Hypocotyls on Epstein-Barr Virus Early Antigen Induction and Skin Tumor Promotion
Yukihiro ZAIZEN 1, Harukuni TOKUDA 2, Hoyoku NISHINO 2 and Masazumi TAKESHITA 1
1 Department of Biochemistry, Oita Medical University, Oita 879-55
2 Department of Biochemistry, Kyoto Prefectural University of Medicine, Kyoto 602
Rep. Soy Protein Res. Com., Jpn. 18, 125-129, 1997.
The in vitro anti-tumor promoting effect of hypocotyls from fresh soybeans was evaluated. The dimethyl sulfoxide extracts of hypocotyls showed stronger inhibitory effect than that of soybeans on Epstein-Barr virus early antigen activation induced by 12-O-tetradecanoylphorbol-13-acetate. Daidzin, one of isoflavones with the highest content in hypocotyls, was also inhibitory. An in vivo evaluation of anti-tumor promoting activity of hypocotyls against the mice skin also revealed a significant inhibitory effect on tumor formation.
Key words : soybean hypocotyl, anti-tumor promoting effect, Epstein-Barr virus-early antigen, mouse skin tumor, isoflavonoid
Anti-carcinogenic Effect of Isoflavonoids in Soybeans
Hoyoku NISHINO
Department of Biochemistry, Kyoto Prefectural University of Medicine, Kyoto 602
Rep. Soy Protein Res. Com., Jpn. 18, 130-134, 1997.
Cancer preventive activity of soybean constituents has been studied, and isoflavonoids were proposed as possible principle to reduce the risk of mammary and prostate cancer. In the present study, we showed that genistein, an isoflavonoid in soybeans, inhibited the proliferation of human prostate cancer cell line DU145 in a dose-dependent manner, and its IC50 was calculated to be arround 20É M. Genistein was also proven to inhibit tumor promoter-enhanced phospholipid synthesis in cultured cells, which may play a role to suppress tumor promotion in vivo. Furthermore, genistein showed inhibitory tendency in spontaneus liver tumorigenesis in C3H/He male mice. Confirmation of anti-carcinogenic action of genistein is the important project in future.
Key words : isoflavonoids, genistein, anti-tumor promoter activity, anti-liver carcinogenesis
Effect of Soy Protein on Serum Lipids, Platelet Aggregation Hemostatic Markers and Progression of Atherosclerosis in Hyperlipidemic Patients
Masako WAKI 1, Motoo TSUSHIMA 2, Naoko YAMASHITA 2, Kayoko RYOHMOTO 2, Ryohya KOMATSU 2 and Hideki KOH 2
1 Shimada Municipal Hospital, Shimada 427
2 National Cardiovascular Center, Suita 565
Rep. Soy Protein Res. Com., Jpn. 18, 135-140, 1997.
This study was conducted to investigate the long-term effect of soy protein on serum lipids, platelet aggregation, hemostatic markers, and atherosclerosis of lower abdominal aorta. Fifteen middle-aged hypercholesterolemic females, randomly assigned to take 9 g/day of soy protein or 400 mL/day of low-fat milk, were examined at baseline and after one year. Nine subjects with soy protein did not show any significant changes in serum levels of cholesterol (mÅ}SD ; 248Å}37 mg/100 mL at baseline and 258Å}42 mg/100 mL after one-year intake of soy protein), triglyceride, HDL-cholesterol, apoproteins A1, A2, B, C2, C3 and E, platelet aggregation induced by ADP, or hemostatic markers (fibrinogen, PAI-1, D-dimer, plasminogen, AT-III, bTG and PF4). Arterial calcification (ACV) and wall thickening and volume (AWV) in lower abdominal aorta were estimated by computed tomography at baseline and one year of the study. In soy protein group, ACV did not progress during the study and the increase in AWV was smaller than that in low-fat milk group, although the difference between the groups was not reached the significance. Further examination is awaited to clarify the clinical effectiveness of soy protein to inhibit the progression of early atherosclerosis in hypercholesterolemic patients.
Key words : soy protein, milk, atherosclerosis, platelet aggregation, hemostatic markers
The soy protein protein reserch(Japan)