The Soy Protein Research Committee(Japan)

STUDIES ON FLAVOR OF TOFUYO ÅF A COMPARISON OF TASTY COMPONENTS BETWEEN FABRICATED ÅgTOFUYOÅh FROM SOY PROTEIN ISOLATE AND TRADITIONAL TOFUYO

Masaaki YASUDA, Seiji MORIKAWA, Tetsuya MATSUMOTO and Sakie KINJYO

College of Agriculture, University of the Ryukyus

Nutr. Sci. Soy Protein, Jpn. 12, 7-13, 1991.

Traditional tofuyo is a vegetable protein food and is made from tofu by the action of microorganisms. Fabricated tofuyo is made from soy protein isolate (SPI) as the same way of traditional one. However, they are different in tastes. In this paper, changes in activities of enzymes and formation of tasty components during both of fabricated and traditional tofuyo fermentation were investigated. Protease is considered to be concerned with ripening, and amylases are concerned with providing the taste of the product. Although remaining activities of Éø-amylase, glucoamylase and protease decreased for initial 15-days of the ripening, these values were maintained until the end of ripening, respectively. Changes in these enzymes' activities of fabricated tofuyo were similar to those of traditional one. The ratio of water soluble nitrogen to total nitrogen and that of amino nitrogen to water soluble nitrogen increased during ripening period. These values of fabricated tofuyo were higher than those of traditional one. Amino acids, organic acids and nucleic acid related compounds were analyzed by high pressure liquid chromatographies. Each free amino acid in tofuyo was increased during maturation. Amounts of glutamic acid, aspartic acid, alanine and glycine in traditional tofuyo were higher than those of fabricated one. However, amounts of leucine, arginine, tyrosine and phenylalanine in the fabricated tofuyo were higher than those of traditional one. It was observed that reducing sugars of both traditional and fabricated tofuyo increased during ripening period, and it was detected as glucose by thin layer chromatography and the method of glucose oxidase. Amount of total organic acids in fabricated tofuyo was higher than that of traditional one. Citric acid, malic acid, lactic acid and malonic acid were abundant in both of fabricated and traditional tofuyo. Amount of 5'-guanylic acid in traditional tofuyo was higher than that of fabricated one. A small amount of 5'-inosinic acid was found to occur in both of fabricated and traditional tofuyo.

IMPROVEMENT OF FUNCTIONAL PROPERTIES OF SOYBEAN GLYCININ BY PROTEIN ENGINEERING

Makoto KITO and Shigeru UTSUMI

Research Institute for Food Science, Kyoto University

Nutr. Sci. Soy Protein, Jpn. 12, 14-18, 1991.

To improve functional properties of soybean glycinin, A1aB1b proglycinin subunit was modified on the basis of the structural characteristics by means of protein engineering. The A1aB1b proglycinin subunit has two disulfide bonds Cysl2-Cys45 and Cys88-Cys298, and has a polyglutamate region in the fourth variable domain. Then, we constructed various cDNAs which encode specific variants of A1aB1b proglycinin subunit in which cysteine residues were replaced by glycine or serine to form modified glycinins Gly12, Ser88 and Gly12Ser88, and in which the polyglutamate region was deleted or replaced by polylysine, polyglutamine or polymethionine to form modified glycinins IV (Å¢Glu), IV (Lys), IV (Gln) and IV (Met). Expression plasmids carrying the modified cDNAs were constructed and expressed in Escherichia coli strain JM105. All of the modified proteins except IV (Met) accumulated as self-assembled soluble proteins in the cells at a high level. This indicates that the disulfide bonds Cys12-Cys45 and Cys88-Cys298 are not necessary to form correct conformation of glycinin molecule, and that it is possible to dramatically change the net charge of glycinin molecule. The modified glycinin Gly12, Ser88 and Gly12Ser88 expressed were purified and their gelation and gel properties were examined. All of them formed heat-induced gels and especially Ser88 exhibited excellent gel-forming ability, indicating that the change in the number and/or the topology of free sulfhydryl residues of glycinin is a powerful method for improving the gel-forming ability.

SEPARATION OF GLYCOLIPID IN SOY PROTEIN ISOLATE BY LECTIN AFFINITY CHROMATOGRAPHY

Seiichi HOMMA, Tomoko MITA and Masatsune MURATA

Department of Nutrition and Food Science, Ochanomizu University

Nutr. Sci. Soy Protein, Jpn. 12, 19-22, 1991.

Soy protein isolate (SPI) was extracted with 87% ethanol and chromatographed on a Iatrobeads column. The eluates with acetone and methanol represented glycolipid and phospholipid fractions, respectively. To separate glycolipid in the phospholipid fraction, the methanol eluate was adjusted to pH 1.4 with HCl to form insoluble materials and resulting supernatant, consisting of mostly glycolipid, was combined with glycolipid fraction. Although TLC showed 12 phospholipids, the separation of the glycolipid was found to be imperfect due to unreasonable composition of sugar, fatty acid and glycerol. The glycolipid was dispersed in water by sonic vibration and chromatographed on a ConA-lectin agarose column. The glycolipid separation was found not to be due to affinity to ConA lectin, but due to adsorption to agarose.

EFFECT OF SPI ON CARCINOGENIC AND DETOXICATING METABOLITES OF DEMETHYLNITROSAMINE IN LIVER MICROSOMES OF RABBITS FED ON LOW PROTEIN DIET AND ETHANOL

Michio HOSONO ¹,Hirofumi SUZUKI ², Daisuke KAJINO ², Hiromichi ISHIZASHI ²,Seiki HORI ²,Masaharu YOSHIO ³ and Masatoshi KAKU ⁴

¹ Kyowa Synthetic Medical Laboratory
² Hyogo College of Medicine
³ Kyowakai Hospital
⁴ Kaku Clinic

Nutr. Sci. Soy Protein, Jpn. 12, 23-28, 1991.

To study how the metabolism of dimethylnitrosamine (DMN) is affected by administration of ethanol and 2 kinds of low protein diets, 24 rabbits at 18 weeks of age, assigned to four groups, each with 6 rabbits, were fed for 8 weeks on the following 4 different diets: 7% protein containing 4.8% casein and water, 7% protein containing 4.8% casein and 7.5% ethanol, 7% protein containing 4.8% soy protein isolate (SPI) and water, and 7% protein containing 4.8% SPI and 7.5% ethanol. Microsomal protein contents and cytochrome P-450 contents were greater in SPI diet groups than in casein diet groups. DMN demethylation activity and DMN denitrosation activity were greater in SPI diet groups than in casein diet groups. Chronic ethanol feeding increased DMN denitrosation activity in both low protein diet groups. The ratio of DMN demethylation activity (carcinogenic action) to DMN denitrosation activity (detoxication action) was smaller in SPI diet groups than in casein diet groups. The value of this ratio was decreased by chronic ethanol feeding in both low protein diet groups. Cytotoxic and carcinogenic actions of DMN might be reduced by 7% SPI diet due to increase of denitrosation of DMN in liver microsome and chronic 7.5% ethanol feeding alleviates metabolic activation of DMN to carcinogenic compounds.

EFFECTS OF AMINO ACIDS ON THE mRNA INDUCTIONS OF LIPOGENIC ENZYMES IN PRIMARY CULTURES OF RAT HEPATOCYTES

Nobuko IRITANI ¹,Hitomi FUKUDA ¹ and Takehiko TANAKA ²

¹ Tezukayama Gakuin College
² Osaka University Medical School

Nutr. Sci. Soy Protein, Jpn. 12, 29-33, 1991.

Effects of amino acids on the mRNA concentrations of acetyl-CoA carboxylase, fatty acid synthase, malic enzyme and glucose-6-phosphate dehydrogenase were pursued in primary cultures of rat hepatocytes during the process of the enzyme induction. Acetyl-CoA carboxylase mRNA and enzyme were induced even in the absence of amino acids. Malic enzyme mRNA also was considerably induced in the absence of amino acids. However, both essential and non-essential amino acids required to increase fatty acid synthase mRNA and essential amino acids, to increase glucose-6-phosphate dehydrogenase mRNA. In particular, the removal of lysine and tryptophan caused to decrease the mRNA and also enzyme induction. It was suggested that amino acids are differently involved in lipogenic enzyme induction before translation.

EFFECTS OF SOYBEAN PROTEIN ON PLASMA CHOLESTEROL CONCENTRATION AND FECAL STEROL EXCRETION IN ADULT FEMALES

Kayoko KANEKO ¹ and Goro KOIKE ²

¹ Faculty of Education, Yokohama National University
² Kagawa Nutrition College

Nutr. Sci. Soy Protein, Jpn. 12, 34-36, 1991.

The effects of soy protein isolate (SPI) or soybean in the diet on plasma cholesterol levels and fecal neutral sterol and bile acid excretion were examined in 8 healthy adult females. The subjects were fed diet containing SPI (SPI period) or soybean products (soybean period) corresponding to about 15 g of protein, one-fourth of the daily protein intake, for six weeks respectively. Total cholesterol and HDL-cholesterol levels in plasma were unchanged compared with the values before the experimental period by both diets. The dry weight of feces was unchanged and fecal cholesterol excretion increased in SPI period (significant) and soybean period (insignificant) compared with basal period, respectively. There were no significant changes in fecal excretion of coprostanol or bile acid by the two experimental diets, due to large inter-individual variations.

BASIC STUDIES ON SOYBEAN - ASSOCIATED ALLERGY

Soichi ARAI ¹ and Hiroko KIMURA ²

¹ Faculty of Agriculture, The University of Tokyo
² Kagawa Nutrition College

Nutr. Sci. Soy Protein, Jpn. 12, 37-40, 1991.

To study the allergenicity of major soybean proteins, we investigated the immunogenicities of purified 7S and 11S globulins as well as the soybean protein isolate "Fujipro R". Guinea pigs were immunized with each of these three samples to obtain respective sera. Double immunodiffusion tests showed that the 7S globulin had a greater immunogenicity than the others. A study was also conducted in order to lessen the immunogenicities of the three proteins by tryptic hydrolysis. Since any of them resisted the enzymatic reaction, they were heated at 60Åé or 70Åé for 90 min, prior to being treated with trypsin. This treatment, however, was found ineffective. When they were heated 80Åé for 90 min or longer and then treated with trypsin, their immunogenicities were somewhat lessened. The tryptic hydrolysis following a heat treatment at 90Åé for 5 min gave the more effective result that the hydrolysates produced from the three proteins no longer cross-reacted with their antisera.

DIGESTIBILITY AND NUTRITIVE VALUE OF SPI AND ITS PEPSIN DIGEST

Tadashi NOGUCHI, Shin-ichiro TAKAHASHI and Jong Hee KIM

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 12, 41-43, 1991.

Pepsin digest of SPI was prepared. This preparation was designated as SPD. By the same procedure, egg protein digest (EPD) was also prepared. Digestibility and nutritive value of SPD was assessed. SPD showed more than 90% of digestibility. When SPD was supplemented with EPD until the first limiting amino acid (methionine: requirement was settled according to National Research Council) was satisfied, the nutritive value of SPD which was evaluated by two methods, i. e. N balance studies and urinary ASP (acid soluble peptide) method (T. Noguchi et al., Br. J Nutr., 60, 321-337, 1988) showed the maximum value. When SPD was supplemented with methionine and lysine, the nutritive value was not so excellent as that of SPD supplemented with EPD, although both diets supplied all of the essential amino acids required by growing rats according to National Research Council. The above results suggest that SPD can be used as an excellent amino acid source for patients if it is used in combination with some other dietary amino acid sources.

SPECIES DIFFERENCE IN THE EFFECT OF DIETARY PROTEINS ON STEROID EXRETION(II)

Shin-ichi HAYASHI, Miwako KAMIMURA, Mariko TAKEDA and Junko YAMASHITA

Department of Nutrition, The Jikei University School of Medicine, Tokyo 105

Nutr. Sci. Soy Protein, Jpn. 12, 44-47, 1991.

In continuation from last year's study, we compared the effects of soy protein isolate (SPI) and casein in cholesterol-enriched semisynthetic diets on fecal steroid excretion rates and plasma cholesterol level of rats, mice, and Syrian hamsters. In rats, compared with casein, SPI stimulated fecal steroid excretion rates, whereas no significant difference was observed between plasma cholesterol levels of SPI-fed and casein-fed groups. In male and female ICR, male ddY and male C57BL/J6 mice, compared with casein, SPI did not show any definite differential effect either on steroid excretion rates or plasma cholesterol level. In male Syrian hamsters, SPI clearly stimulated fecal steroid excretion rates and increased the amount of radioactivity remaining in the liver and blood plasma, although it did not exert any clear effect on plasma cholesterol level, indicating that dietary proteins markedly affect cholesterol metabolism in hamsters. In conclusion, fecal steroid excretion appears to be one of important factors that determine plasma cholesterol level and that the hypocholesterolemic effect of SPI in rats, and possibly hamsters, is due, at least in part, to its stimulatory effect on fecal steroid excretion.

REGULATION OF POLYUNSATURATED FATTY ACID METABOLISM BY DIETARY SOYBEAN PROTEIN

Kazunori KOBA and Michihiro SUGANO

Faculty of Agriculture, Kyushu University

Nutr. Sci. Soy Protein, Jpn. 12, 48-51, 1991.

The effects of dietary proteins, soybean protein isolate (SPI) and casein (CAS), on linoleic acid desaturation in liver microsomes were studied in rats. Both ɢ6- and ɢ5- desaturase activities in smooth endoplasmic reticulum (ER) tended to be lower in the SPI group than in the CAS group. In rough ER the activity of ɢ6- but not ɢ5-desaturase was low in rats fed SPI. SPI significantly lowered the ratio of (20 : 3 + 20 : 4) / 18 : 2 of total lipids in the rough, smooth and total ER fractions. In the total and smooth ER fractions, the steady-state fluorescence anisotropy of 1, 6-diphenyl-1, 3, 5-hexatriene incorporated into the membrane decreased in the SPI group accompanying the reduction of the ratio of cholesterol/phospholipid, indicating an increase in the membrane fluidity. Thus, the activity of ɢ6- and ɢ5-desaturase seems to be regulated at least partly by the membrane fluidity. However, since dietary protein influenced the ɢ6-activity in rough ER without influencing the membrane fluidity, the possibility of the enzyme synthesis regulation by dietary protein was also suggested.

SOY PROTEIN AND CHOLESTEROL METABOLISM ÅF EFFECTS OF TYPE AND LEVEL OF DIETARY FAT ON THE HYPOCHOLESTEROLEMIC ACTION OF SOY PROTEIN ISOLATE IN RATS

Takuo OKITA

Fukuoka University of Education

Nutr. Sci. Soy Protein, Jpn. 12, 52-55, 1991.

Effects of the type (corn oil and butter) and level (1, 5, 10 and 20%) of dietary fat on the hypocholesterolemic action of soybean protein isolate (SPI) were examined in rats. The concentration of liver cholesterol (CHOL) tended to increase with an increase of dietary fat level in both corn oil and butter diets, whereas the concentration of plasma CHOL was decreased. The hypocholesterolemic action of SPI was inhibited by the increase in dietary fat level. The excretion of acidic steroid in feces was not different consistently between rats fed SPI and casein diets, however the excretion of neutral steroid of rats fed SPI was markedly higher than that of rats fed casein. The responses between the dietary fat level and the type of dietary protein were different. The results indicate that the mechanisms of the hypocholesterolemic action of SPI are responsible, at least in part, for the increase in neutral steroid excretion in the feces, and the dietary fat inhibited the increase in neutral steroid excretion by the SPI diets.

RELATIONSHIP BETWEEN PLASMA CHOLESTEROL - LOWERING EFFECT OF SOYBEAN PROTEIN ISOLATE AND PHOSPHOLIPID BIOSYNTHESIS IN RATS

Kimio SUGIYAMA ¹,Shigeru SAEKI ¹,Hironori KANAMORI ¹ and Keiichiro MURAMATSU ²

¹ Faculty of Agriculture, Shizuoka University
² Faculty of Home Economics, Nagoya Women's University

Nutr. Sci. Soy Protein, Jpn. 12, 56-62, 1991.

The present study was undertaken to investigate the relationship between plasma cholesterol levels and phospholipid composition of liver microsomes in rats. The addition of 0.4% choline and/or 0.8% methionine to the choline-free diets containing casein or soybean protein isolate (SPI) increased plasma cholesterol levels, and there existed a significant positive correlation between the plasma cholesterol levels and the ratio of phosphatidylcholine (PC) to phosphatidylethanolamine (PE) of the liver. When diet was changed from SPI diet to casein diet, both plasma cholesterol levels and liver PC/PE ratio increased rapidly and reached plateau on day 2 and day 1, respectively. The significant correlation between the plasma cholesterol level and PC/PE ratio was also found in rats fed cholesterol-free diets containing either casein, SPI, lactalbumin or wheat gluten, but not in rats fed those diets with cholesterol. These findings suggest a possibility that the alteration of the liver PC/PE ratio might be one of the causes for the hypocholesterolemic efficacy of SPI observed in rats fed a cholesterol-free diet.

EFFECT OF SUPPLEMENTATION OF METHIONINE TO A SOYPROTEIN DIET ON SERUM CHOLESTEROL AND LIVER APOLIPOPROTEIN A-I mRNA IN RATS

Shinichi NIWA, Hiroaki ODA and Akira YOSHIDA

Faculty of Agriculture, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 12, 63-66, 1991.

We demonstrated previously that soy protein had a hypocholesterolemic effect in rats as compared with either casein or rice protein although fecal excretion of steroids was stimulated by either soy protein or rice protein. This hypocholesterolemic effect of soy protein was accompanied by the decrease in the serum level of apo A-I and liver apo A-I mRNA, suggesting the decreased apo A-I synthesis by soy protein might lead the decrease of HDL secretion from the liver. Soy protein contains less methionine as compared with casein. In present report, supplemental effect of methionine to a soy protein diet on serum level of cholesterol, apo A-I and liver apo A-I mRNA was investigated. Young male rats of the Wistar strain were used. Experimental diet contained 15% casein (group 1) or 15% soy protein isolate (group 2). The third group of animals were fed the 15% soy protein diet supplemented with 0.28% of methionine. The methionine content of the diet of the 3rd group was equal with the 15% casein diet. The methionine supplementation to the soy protein diet elevated the serum level of cholesterol, apo A-I and liver apo A-I mRNA. However, the serum level of cholesterol of the methionine supplemented group was still less than that of the casein diet group. These data might indicate that the soy protein diet decreases the serum level of cholesterol partially by decreasing HDL secretion from the liver due to the insufficient synthesis of apo A-I. However, other mechanism such as lowered bile acid and cholesterol absorption from the intestinal tract might also be involved in the hypocholesterolemic effect of soy protein diet.

POSTOPERATIVE CHANGES IN METABOLIC FUNCTIONS IN RATS WITH RESECTION OF SMALL INTESTINE AND ADVANTAGE OF SOY-PROTEIN PEPTIDE INTAKE

Kaoru SUGIYAMA, Kimikazu IWAMI and Fumio IBUKI

Faculty of Agriculture, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 12, 67-73, 1991.

Rats with resection of about three-fourths (between both 10 cm from the Treitz ligament and from the ileocecal valve) of small intestine were examined for curing effects of protein, peptide and amino acid mixture intakes on postoperative changes in metabolic functions. The animals had been allowed free access to 5% fructose as drinking water for 2 days after operation, and then, fed the diets containing (A) 20% SPI, (B) 20% soy-protein peptide and (C) 16.6% amino acid mixture as nitrogen sources for 4 days. Similarly the animals with abdominal incision were arranged as the corresponding controls (D), (E) and (F) to (A), (B) and (C), respectively. Although the bowel-resected groups were far inferior to the controls in food intake (i. e. body weight gain), their relations were reversed as to the ileal mucosal weight per length. Interestingly group B was the highest in nitrogen retention as well as leucine aminopeptidase activity among the former groups. Accordingly it may be said that the peptide intake is more effective in functional restoration at early stages of postoperation than the protein or amino acid intake.

RENIN AND ANGIOTENSIN - CONVERTING ENZYME INHIBITORS IN FOOD PROTEIN HYDROLYSATES

Naotoshi MATSUDOMI, Akio KATO and Kunihiko KOBAYASHI

Faculty of Agriculture, Yamaguchi University

Nutr. Sci. Soy Protein, Jpn. 12, 74-79, 1991.

Peptides that inhibit renin and angiotensin-converting enzyme (ACE) were investigated in some food protein hydrolysates prepared with protease. Renin inhibitory peptides were included in hydrolysates of egg white proteins, whey proteins and soy proteins. The peptides in hydrolysates of bovine serum albumin and ovalbumin were found to have a powerful inhibitory activity against renin. The ACE inhibitory peptides were also contained in the hydrolysates of caseins, gluten and gliadin, except for the food protein hydrolysates having renin inhibitory peptides. The comparison of food protein hydrolysates with pepsin and trypsin was done on the inhibitory activities against renin and ACE. The renin inhibitory activities of the hydrolysates of gluten, ÉøS-casein and soy proteins were increased remarkably by the hydrolysis with pepsin, as compared to that with trypsin. On the other hand, the ACE inhibitory activities of the hydrolysates of ovalbumin and soyproteins with pepsin were similar to those of their hydrolysates with trypsin. From these results, it was suggested that the inhibitory peptides against renin may differ from those against ACE.

EFFECTS OF DIET CONTAINING SOYBEAN PEPTIDE OR LACTALBUMIN ON BASAL ENERGY EXPENDITURE OF OBESE CHILDREN REDUCING BODY WEIGHT AND ON THERMOGENESIS AFTER MEAL

Tatsushi KOMATSU ¹,Keiko KOMATSU ²,Mie SHIRAISHI ²,Masato NAGATA ³ and Minoru YAMAGISHI ⁴

¹ Department of Nutrition in Hospital, University of Occupational and Environmental Health
² Fukuoka Junior College of Social Work and Child Education
³ Nagata Hospital
⁴ Department of Pediatrics, University of Occupational and Environmental Health

Nutr. Sci. Soy Protein, Jpn. 12, 80-84, 1991.

In the study 1 the influence of soy peptide (SPT) and lactalbumin (LA) supplement to energy restricted 1000 kcal diets on basal energy expenditure (BEE) was examined in obese children. Following a low energy standard period for 5Å`7 days, test diet period for 8Å`10 days was set up. During test diet period, 13 and 10 patients were given 30 g of SPT and LA as the protein supplement food, respectively. BEE was measured at start and end of each period. In the study 2 the thermic effect of meal was examined during 3h in a subject received 700 kcal diet containing 20 g of SPT and isoenergetic diet containing 20 g of LA. Indirect calorimetry was used to measure the energy expenditure in the two studies. After test diet period in the study 1, decrease in BEE of the obese children losing body weight was suppressed by receiving SPT diet. But decrease in BEE of those receiving LA diet was found. Increases in energy expenditure after meal with SPT or LA were found in the study 2. The response to the SPT diet was higher than the LA diet. With the SPT diet, it took 20 min to attain the peak energy expenditure and highest respiratory quotient. But with the LA diet, it took more than the SPT diet. The results suggest that diet induced thermogenesis is affected not only by protein level but also by variety of protein source in the diet.

NUTRITIONAL EVALUATION OF DIETARY PROTEIN AND PEPTIDES USING OLIGO - L - METHIONINE AS A PROBE FOR DIGESTIVE FUNCTIONS (II)

Shuhachi KIRIYAMA ¹,Xiaohong YIN ¹,Hiroshi HARA ¹ and Hideyuki CHIJI ²

¹ Faculty of Agriculture, Hokkaido University
² Fuji Women's College

Nutr. Sci. Soy Protein, Jpn. 12, 85-90, 1991.

We demonstrated that the pepsin hydrolysate of SPI (H-SPI) enhanced the absorption of oligo-L-methionine (OM) in early stages of feeding. Pancreatic protease secretions were increased by direct infusion of casein, SPI and H-SPI into the duodenum under pentobarbital anesthesia, and H-SPI tended to be higher than SPI in the secretion of chymotrypsin and carboxypeptidase A. In vitro digestibility of H-SPI by bile-pancreatic juice was higher than that of SPI and similar to casein. In order to increase the solubility of SPI, we prepared deamidated SPI (D-SPI) and examined the supplementary effects of OM to a low D-SPI diet, and estimated the OM absorption and pancreatic protease secretions after feeding of D-SPI diet. All parameters with D-SPI were identical to those with SPI. We conclude that the effects of H-SPI on the increases of OM absorption and pancreatic secretions are not responsible for its solubility and those may attribute to the effects of certain peptides contained in H-SPI.

EFFECTS OF SOY PEPTIDES ON ENERGY METABOLISM IN OBESE ANIMALS

Masayuki SAITO

Faculty of Veterinary Medicine, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 12, 91-94, 1991.

Effects of dietary soy protein peptides on body weight and brown adipose tissue (BAT) thermogenesis were examined in hypothalamic obese animals. Groups of gold-thioglucose induced obese mice were given a diet containing either soy peptides (SP) or amino acids (ED). Under conditions of ad libitum feeding and mildly restricted feeding, the SP group lost body weight more and had smaller parametrial white adipose tissue than the ED group, while gastrocnemius muscle weight was almost the same in the two groups. Similar effects of SP on body weight were also found in obese rats with ventromedial hypothalamic lesions. In these obese rats, the thermogenic activity of BAT, assessed from GDP-binding to mitochondria, was decreased in the ED group compared with the SP group. Thus, SP was more effective in body weight reduction, probably due to the enhancement of BAT thermogenesis.

CHANGES IN FREE AND PEPTIDE - FORM AMINO ACIDS IN PLASMA AFTER ADMINISTRATION OF SPI HYDROLYZATE (SPT - 5)

Yoshiaki NIIYAMA and Sachinobu MANABE

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 12, 95-98,1991.

Changes in levels of free and peptide-form amino acids in plasma were investigated in SPT-5 bolus-fed rats and compared with the previous results in meal-fed rats. Male Sprague- Dawley young adult rats (about 270g) were starved for 11 hours and then were bolus-fed a liquid diet containing 2g of SPT-5 at 10ÅF00. After feeding, concentration of free amino acids increased immediately with a peak at 1 hour and decreased to fasting level within 3 to 5 hours. This finding was similar to the result in meal-feeding. On the other hand, concentrations of peptide-form amino acids, particularly of Asp, Glu and Ala, were decreased significantly for 2 to 5 hours after feeding and then restored to fasting level. Changes in amino acid patterns of free and peptide-form amino acids after feeding did not reflect the composition of dietary SPT-5. Average peptide chain length decreased significantly 1 hour after the feeding and kept small for 5 hours. These results indicated that a large amount of ingested oligopeptides entered into blood stream as free form of amino acids, not peptide form of amino acids. Present and previous results also showed that comparable amounts of endogenous oligopeptide to amounts of free amino acids existed constantly in plasma and various tissues. Further studies are required to elucidate origin, fates and significance of oligopeptides in plasma.

EFFECT OF SOY PROTEIN ISOLATE ON SKIN TUMOR IN MICE

Ming-Fu WANG ¹,Sung-Fung LO ¹ ,Kayoko UEZU ², Sumie SHINJO ²,Liu ASATO ² and Shigeru YAMAMOTO ²

¹ Department of Food and Nutrition, Providence University, (Taichung, Taiwan)
² Research Center of Comprehensive Medicine, Faculty of Medicine,
University of the Ryukyus

Nutr. Sci. Soy Protein, Jpn. 12, 99-101, 1991.

Anticarcinogenic effect of soy protein has been reported. However, soy protein consists of various protein fractions and the functional fraction is not well known. In this experiment, the effect of the major fraction of soy protein (SPI : soy protein isolate) on skin tumor promotion was studied by two-stage carcinogenesis method. Mice were given 20 and 40% casein or SPI diets. After a week on the diets, the hair of mice was shaved and tumor initiator was applied. Then tumor promoter was applied twice a week on the same area of the skin throughout the experiment. The percentage of tumor-bearing mice and the average number and volume of tumor after 16 weeks on the treatment were not different among the 4 dietary groups, indicating that the anticarcinogenic effect of soy protein is due to the fractions other than SPI.

NUTRITIONAL - PHYSIOLOGICAL CONSIDERATION FOR THE SUPPLEMENTARY EFFECT OF METHIONINE TO THE DIETARY SOYBEAN PROTEINÅF ESPECIALLY FOR THE SALT PREFERENCE

Shuichi KIMURA, Fumiki MORIMATSU and Michiko ITOH

Faculty of Agriculture, Tohoku University

Nutr. Sci. Soy Protein, Jpn. 12, 102-106, 1991.

To clear whether all kind of proteins had reducing effects on sodium chloride intake, the effects of dietary protein source on appetite or preference for sodium chloride were studied. It was found that the reducing effect depends not only on dietary levels, but also on the protein sources. In both SHR and Wistar-slc rats, cumulative NaCl intake of soybean protein groups was significantly higher than that of animal protein diet groups. However, the supplement of methionine to soybean protein led to reduce NaCl intake. In this experiment, it was shown that glutamic acid, one of the Umami substances, in free amino acids of soybean protein diet was considerably lower than that of meat protein diet. Since Umami substances have the reducing effect for NaCl intake, it may be one of the reason for low reducing effect of soybean protein diet group for preference to NaCl. On the other hand, in our previous study, it was found that the serum free amino acid patterns were affected by the dietary protein level. We found that the rats fed a low protein diet showed a higher concentration of glutamic acid in serum as compared with that of the groups given high protein diets. In this study, it was observed that glutamic acid level in serum from rats fed soybean protein isolate (SPI) was considerably higher than that of meat protein (MP) and purified egg protein groups. However, glutamic acid level of methionine added SPI group showed a significantly lower than that of SPI group. These facts suggest that the supplement of methionine to SPI leads to the recovery of this serum free amino acid pattern, especially glutamic acid level. These observations also lead to speculation that the high concentration of glutamic acid in the serum of rats induced by some nutritional status such as low protein diet feeding is a reason why the rats fed low protein diet did not choose monosodium L-glutamate solution. It should be emphasized that the serum glutamic acid level is an important signal for central nervous system. We need further studies to prove meaningful informations.

EFFECT OF CYSTINE AND METHIONINE INTAKE ON INCIDENCE OF PROTEINURIA IN ADULT RATS

Hidemichi EBISAWA, Mineko ICHIKAWA, Tomoko OZEKI and Yoshiaki FUJITA

Division of Physiological Aging Research, Tokyo Metropolitan Institute of Gerontology

Nutr. Sci. Soy Protein, Jpn. 12, 107-113, 1991.

Effects of dietary cystine and methionine levels on the incidence of proteinuria were examined in terms of urinary protein excretion, N-acetyl-É¿-D-glucosaminidase (NAG) activity in urine and cathepsin B activity in glomeruli. Six male Wistar rats (120 days of age) were given 13g of 20% casein diet supplemented with 0.43% or 0.94% L-cystine, or 20% SPI diet supplemented with 1.18% of L-methionine until 280 days of age. Increase in cystine intake resulted in increase of urinary protein excretion. But methionine had a trend to decrease it. NAG activity in urine was measured to examine the relationships between cystine or methionine intake and injury of proximal tubules. A significant correlation between cystine intake and NAG activity in urine was observed. Activity of cathepsin B in glomeruli was measured to examine the possibility that dietary cystine affects the permeability of glomerular basement membrane. Activity of cathepsin B in glomeruli increased with elevation of cystine intake. Increase in methionine intake had no significant effect on NAG activity in urine and cathepsin B activity in glomeruli. These results suggest that increased urinary protein excretion in rats fed cystine supplemented diet may result from injuries in glomerular basement membrane and proximal tubules by dietary cystine.

EFFECT OF SOY PROTEIN DIET ON PLASMA AMMONIA AND FREE AMINO ACIDS IN PORTACAVAL SHUNTED RATS

Yasuhiro KIDO, Fumiko TADA, Fujiko SHIZUKA and Kyoichi KISHI

Department of Nutrition, School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 12, 114-120, 1991.

In the previous report (1989) we showed that soy protein isolate (SPI) was superior to casein supplemented with 1.5% methionine (relative to crude protein) at 40 (NÅ~6.25)% protein level in adult rats with portacaval anastomosis (PCA rats). Furthermore, free methionine concentration in plasma and brain of PCA rats remarkably increased in casein group but not in SPI group. In the present study, therefore, the effects of dietary methionine and cystine on tissue free amino acids (experiment 1) and brain monoamine metabolites (experiment 2) were studied in PCA rats fed 40% protein diets. Supplementation of methionine to SPI did not increase tissue methionine concentration even though dietary methionine level was similar to 1.5% methionine supplemented casein. Supplementation of cystine to methionine supplemented casein maintained tissue sulfur amino acid concentrations within normal range. It was suggested that abnormally high ratio of methionine to cystine (about 9) resulted in marked increase of tissue methionine concentration. In the second experiment, the metabolites of dopamine and serotonin in dialysates of the striatum in the brain were not influenced by hyperammonemia or hypermethioninemia in PCA rats.

EFFECTS OF SOY PROTEIN DIETS ON NUTRITIONAL STATUS OF THE CIRRHOTIC PATIENTS (II)

Masahiko KATO, Takashi YOSHIDA, Hisataka MORIWAKI and Yasutoshi MUTO

First Department of Internal Medicine, School of Medicine, Gifu University

Nutr. Sci. Soy Protein, Jpn. 12, 121-126, 1991.

It has been reported that soy protein (SP) is useful as one component of basal diet for cirrhotic patients with protein-intolerant state. The present study was carried out to determine the most appropriate proportion of soy protein in a basal diet for cirrhotic patients. Twenty three cirrhotic patients were divided into 3 groups, each of which received one of 3 different test diets for 4 weeks. All diets provided 2000 kcal energy and 70g protein/day, and compositional ratio of protein was as follows: Group I (n = 7) : 50% SP-free vegetable protein (VP) and 50% animal protein (AP), Group II (n = 8) : 50% VP, 25% SP and 25% AP and Group III (n = 8) : 50% VP and 50% SP. Physical status, liver function tests, serum levels of total protein, albumin, ammonia and rapid turnover proteins, as well as plasma free amino acids, BCAA, AAA and BCAA/AAA ratio were examined before and 1, 2, 3, and 4 weeks after the administration. Patients' energy intake of each diet in Groups I,II and III was 1720 Å} 84 kcal (86.0 Å} 4.2%), 1764 Å} 176 kcal (87.4 Å} 7.9%) and 1593 Å} 341 kcal (79.7 Å} 17.0%), respectively, and protein intake was 66.5 Å} 37.3 g (93.0 Å} 19.0%), 67.2 + 10.8 g (96.0 Å} 10.8%) and 58.1Å} 11.4g (83.1 Å} 16.3%), respectively. Five of 8 patients in Group III discontinued the intake of the test diet during the observation period. No significant changes were observed in physical status, liver function tests, serum levels of total protein, albumin, rapid turnover protein or ammonia before and 4 weeks after administration of test diets. Levels of plasma valine and total BCAA significantly elevated 4 weeks after administration in Group III (pÅÉ0.05 and pÅÉ0.01, respectively). BCAA/AAA ratio was significantly reduced 4 weeks after administration in Group I. We conclude that the compositional ratio of Group II is the most appropriate one, being based on its excellent compliance and beneficial effect of the soy protein itself.

EFFECT OF SOYBEAN TRYPSIN INHIBITOR ON PANCREATIC ISLETS IN WBN/Kob RATS

Yoshio IKEDA, Yutaka MORI and Junichi YOKOYAMA

Third Department of Internal Medicine, The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 12, 127-129, 1991.

WBN/Kob rats are spontaneously developed diabetic model animals with endocrine-exocrine pancreatic insufficiency due to distinct pancreatic fibrosis. We previously reported the oral administration of soybean trypsin inhibitor (SBTI) has the trophic effect on exocrine tissue in WBN/Kob rats. In the present study, we examined the effect of SBTI on pancreatic islets in WBN/Kob rats. The preventive effect on 1 month-old male rats without pancreatic lesion was examined during a 20-month period (from 1 to 21 months of age). Male WBN/Kob rats were divided into three groups which were fed with the diets containing 2.0% (=613 U/kg/day), 0.5% (=153 U/kg/day), or 0% (=20 U/kg/day) SBTI. There was no significant difference in incidence of glycosuria at 21 months of age. The weight of pancreata and tissue contents of pancreatic digestive enzymes in rats treated with SBTI for 20 months were significantly increased compared with those in non-treated rats. Histologically, in pancreata of SBTI-treated rats, although the exocrine tissue was hypertrophic, the deformity of islets and decreased number of B cells and A cells were observed as same as in pancreata of non-treated rats. And there were no significant differences in tissue contents of insulin and glucagon between SBTI-treated and non-treated rats. We conclude that orally administered SBTI has the trophic effect on exocrine tissue but no effect on the pancreatic islets in male WBN/Kob rats.

EFFECT OF SOY - PEPTIDE ON PLASMA LIPIDS

Haruo NAKAMURA and Emiko MIYAJIMA

First Department of Internal Medicine, National Defense Medical College

Nutr. Sci. Soy Protein, Jpn. 12, 130-132, 1991.

Our previous results concerning the effects of soy protein intake by normal volunteers on plasma lipids indicated the significant reduction of plasma cholesterol by the 20-40g intake per day. In order to assess the minimum dosage capable to decrease plasma lipids, we administered 14g of soy-peptide to 13 healthy volunteers for 2 weeks. Total cholesterol, LDL-cholesterol, HDL-cholesterol and triglyceride remained almost unchanged in all subjects. Apoproteins A-I, B and E also remained unaltered. Lipid compositions of VLDL, LDL and HDL did not change significantly. Four subjects with relatively high blood cholesterol showed the mild reduction of their cholesterol and LDL-cholesterol. Therefore, present result indicates the minimal dosage of soy-protein may be about 14-15 g/day to reduce blood cholesterol.

CLINICAL EVALUATION OF SOY PROTEIN FOR THE PATIENT WITH MALABSORPTION

Nobuo CHIKAMOCHI, Tomonori HOSODA, Tadao BAMBA and Shiro HOSODA

Second Department of Internal Medicine, Shiga Universtiy of Medical Science

Nutr. Sci. Soy Protein, Jpn. 12, 133-139, 1991.

Anticancer drugs make the injury of gastrointestinal mucosa with various degrees depending on the dosage. We investigated the absorption of dipeptide and amino acids from the impaired small intestinal mucosa of the rats, by using short-circuit current method after 3 days of intraperitoneal injection of 300 mg/kg of cyclophosphamide (CPM). Kinetic parameters of Jmax and Km were calculated for Gly-Gly, Gly, Pro and Lys in control and CPM groups. Jmax value of Gly was significantly decreased in CPM group, but not of Gly-Gly, Pro and Lys. There were no differences in Km values of Gly-Gly, Gly, Pro and Lys between two groups. The results indicate that peptide transport carrier is more resistant to CPM than amino acid transport carriers. This means peptide is more useful than amino acids on small intestinal mucosal damage. Clinical nutritional assessment was studied in a patient with malabsorption and protein losing enteropathy due to Crohn's disease. He was given only elemental diet of 2400 kcal/day and then a diet replaced a part of elemental diet with 70-120g of soy protein. During the administration of soy protein, serum albumin was increased and CRP was improved and general condition was getting better. In conclusion, soy protein may be useful to maintain the nutritional state as well as the improvement of malabsorption, by the appropriate combination with elemental diet.

EFFECTS OF SOY PROTEIN DIET ON LIPID METABOLISM IN PATIENTS WITH HYPERLIPIDEMIA AND WITH ISCHEMIC HEART DISEASE (II)

Hiromitsu TAMACHI ¹, Yuichi FUSEGAWA ¹,Yuichiro GOTO ¹,Honami FUJII ², Hiroaki ISHII ² and Emilio H. MORIGUCHI ³

¹ School of Medicine, Tokai University
² Unit of Nutrition, Tokai University Hospital
³ Institute of Geriatrics, Pontifical - Catholic University

Nutr. Sci. Soy Protein, Jpn. 12, 140-146, 1991

The effects of partial substituting soy protein isolate (SPI) for dietary animal protein on lipid metabolism were investigated in 8 patients with hyperlipidemia and 3 healthy volunteers. Twenty g/day of SPI substitution for two weeks lowered levels of serum cholesterol, phospholipid, LDL-cholesterol, apoprotein B, apo B/apo A-I ratio and apoprotein E (in the previous report), but had no significant effect on, either lipid composition (%) of major lipoprotein (HDL, LDL, VLDL), or the mean levels of HDL subfractions, or postheparin plasma lipase [PHPL, hepatic TG lipase (HTGL), lipoprotein lipase (LPL)] activities. However, ratios of HDL2-C/HDL3-C slightly increased and those of HTGL/LPL activity decreased. The changes in HTGL activity with SPI diet had positive correlations with those of HDL-C and HDL3-C, and also those of LPL had a positive correlation with HDL3-C. No correlation among the changes of serum cholesterol, phospholipid, LDL-cholesterol, apoprotein B, apoprotein E and those of HTGL activities were observed.

The soy protein protein reserch(Japan)