The Soy Protein Research Committee(Japan)

CLONING OF cDNAs ENCODING SOYBEAN GLYCININ SUBUNITS WITH HIGHER CONTENTS OF METHIONINE

Shigeru UTSUMI and Makoto KITO

Research Institute for Food Science, Kyoto University

Nutr. Sci. Soy Protein, Jpn. 9, 5-9, 1988.

The nucleotide sequences of cDNA encoding glycinin A1aB1b and A2B1a subunits, which are richer in methionine than other subunits, from var. Shirotsurunoko were determined and compared with those in the case of var, Bonminori. The comparison showed the differences in the nucleotide and amino acid sequences in coding regions of both cDNAs between cultivars. In addition, we observed the presence of an alternate cDNA encoding A1aB1b subunit in var. Shirotsurunoko. These results suggest the occurrence of polymorphism of glycinin subunit genes among cultivars and even within a single cultivar. We constructed artificial glycinin subunit cDNAs by interchanging the domains of methionine-rich subunits and inserting synthetic oligonucleotide with four methionine codons. In order to study the consequences of methionine enrichment to glycinin subunits on their ability to assemble and to exhibit functional properties, we have established the expression system of glycinin subunit cDNAs employing Escherichia coli.

APPLICATION OF ICE NUCLEATION ACTIVE BACTERIUM FOR EFFICIENT FREEZE - DRYING OF FOODS

Soichi ARAI

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 9, 10-15, 1988.

Factors affecting the development of the ice nucleation activity of Erwinia ananas IN-l0 were examined, using the degree of supercooling (DS) as a parameter. An aqueous suspension of the bacterial cells or the outer membrane fraction showed two particular DS values, i. e., near 0Åé and 3Åé. The development of the DS of 0Åé required two conditions: a high cell population (or membrane concentration) and the presence of a water/glass interface in the system. Sugars inhibited the development of this type of supercooling. The ice nucleation activity was stable in the pH range of 5 to 9. On the basis of these data, a possible mechanism for the ice nucleation activity development was proposed. The application of the ice nucleation activity of the cells to the freeze-drying of high salt containing foods was attempted. It led to a shortening of their freezing times and an efficient formation of powdered products.

IMPROVEMENTS OF THE FUNCTIONAL PROPERTIES OF SOY PROTEIN BY ENZYMATIC DEAMIDATION

Kunihiko KOBAYASHI, Akio KATO and Naotoshi MATSUDOMI

Faculty of Agriculture, Yamaguchi University

Nutr. Sci. Soy Protein, Jpn. 9, 16-18, 1988.

The effects of proteolytic deamidation on the functional properties of soy proteins were investigated in a controlled condition. The emulsifying and foaming properties of soy proteins (7S globulin and 11S globulin) were improved by the treatment with chymotrypsin at pH 10. About 20% of the asparaginyl or glutaminyl residues in soy proteins were deamidated by the treatment with chymotrypsin with a slight proteolysis. In addition, the functional properties of soy proteins were also improved by the treatment with immobilized chymotrypsin at pH 10, although the deamidation rate was lower than that with free chymotrypsin. Thus, proteolytic deamidation was proposed to be a useful method for the improvement of functional properties of soy proteins.

STUDIES ON PRODUCTION OF TOFUYO USING SOY PROTEIN ISOLATEÅF DECOMPOSITION OF SOY PROTEIN DURING RIPENING PERIOD

Masaaki YASUDA, Kyuichiro NAGAMATSU and Seizi MORIKAWA

College of Agriculture, University of the Ryukyus

Nutr. Sci. Soy Protein, Jpn. 9, 19-24, 1988.

Tofuyo is a unique fermented soybean food in Okinawa prefecture, Japan, and is made from tofu (soybean curd) with koji, salt and awamori (distilled liquor). It is difficult to obtain uniform quality of tofu as the raw material of tofuyo for the preparation of tofu is complicated, and accordingly not easy is to produce uniform quality of tofuyo. Soy protein gel (SP-Gel) was used instead of tofu itself in order to develop a simple and new method leading to stable production of uniform quality of tofuyo. In this study, changes in pH, acidity and protease activity in the soak, and hardness and digestion of soy protein during tofuyo fermentation were investigated. pH value of the soak was found to be 5.9 at first, and decreased with ripening time (60 days) to 5.5. The acidity of the soak raised upon ripening period. Protease originated from the koji was considered to be a key-enzyme for tofuyo fermentation. Although protease activity decreased markedly to 37% for initial 15 days of ripening under the presence of ethylalcohol of awamori, its value was almost maintained at 34% until the end of 60 day ripening. Hardness of SP-Gel of tofuyo was found to be 23.0Å~104 dyne/cm2 at first, and decreased with 60 day ripening time to 8.8 Å~104 dyne/cm2. Pure protein content of the product decreased during ripening period. It was observed by the method of slab SDS-polyacrylamide gel electrophoresis that some polypeptide bands of high molecular weight were disappeared during ripening period (0Å`60 days). After ripening for 60 days, only two bands of low molecular weight (M. W.; 12.4KÅ`24.4K) remained. Any other polypeptide bands of high molecular weight were not detected. The ratio of water soluble nitrogen to total nitrogen (called as protein solubility ratio, or ripening ratio) reached to 43% after the 60 day ripening. The ratio of 4% trichloroacetic acid soluble nitrogen to water soluble nitrogen reached to 52% after the 60 day ripening.

EFFECT OF AMINO ACID COMPOSITION ON THE INDUCTION OF LIPOGENIC ENZYMES IN CULTURED HEPATOCYTES

Hirofumi SUZUKI ¹,Masatoshi KAKU ¹,Seiki HORI ¹,Michio HOSONO ² and Setsuko KAWANO ³

¹ First Department of Physiology, Hyogo College of Medicine
² Kyowa Synthetic Medical Laboratory
³ Department of Food Science and Nutrition, Nagoya Women's University

Nutr. Sci. Soy Protein, Jpn. 9, 25-32, 1988.

Twenty-four spontaneously hypertensive rats (SHR) were divided into four groups of 6 rats each, A ; high (40%) soy protein isolate (SPI) diet and exercise group, B ; high SPI diet and non-exercise group, C ; low (10%) SPI diet and exercise group, and D ; low SPI diet and non-exercise group. All animals were allowed to feed freely throughout the study from 8 to 17-week-old. A treadmill set to 15 m/min was used for the regular exercise in which the animals ran 30 min three times a week. At 17 weeks of age, blood was drawn from the abdominal aorta of anesthetized animals and all animals were killed. Microsomes were isolated from the liver and the small intestinal mucosa, and were used for measurement of P-450 content, NADPH-P-450 reductase activity, cytochrome b5 and dimethylnitrosamine (DMN) demethylase activity by P-450. The retardation of growth and smaller relative liver weight were observed in the low SPI (C, D) groups. Concentrations of total plasma protein, albumin and creatine phosphokinase also decreased in these groups. On the contrary, microsomal proteins (14.0Å`19.8 mg/g liver) and DMN demethylase activity (1.18Å`1.60 nmol HCHO/min/mg microsomal protein) catalyzed by P-450 dependent monooxygenase, whose activity was inhibited to 36Å`48% by carbon monoxide and was reduced to about 80% by deficiency of NADPH, were increased in these groups. These changes induced by low SPI diet were not influenced by exercise. Microsomal P-450 content (1.19Å`1.52 nmol/mg microsomal protein) was not markedly effected by experimental diet but increased approximately 18% of them in the exercise (A, C) groups. NADPH-P-450 reductase activity and cytochrome b5 content did not change significantly by diet or exercise. In conclusion, the present study has shown that P-450 induced by exercise might not catalyze DMN demethylation while the other different P-450 isozyme induced by low SPI diet catalyze it. Intake of low SPI diet for a long time may promote carcinogenesis in the animals.

ENTEROHEPATIC CIRCULATION OF BILE ACIDS AND ITS AFFECTING DIETARY FACTORS

Nobuko IRITANI ¹,Hitomi FUKUDA ¹,Akihiko KATSURADA ¹ and Takehiko TANAKA ²

¹ Tezukayama Gakuin College
² Osaka University Medical School

Nutr. Sci. Soy Protein, Jpn. 9, 33-36, 1988.

Effects of essential and non-essential amino acids on induction of lipogenic enzymes were investigated in primary cultured hepatocytes of rats. Acetyl-CoA carboxylase and malic enzyme were slightly induced by the addition of essential and/or non-essential amino acids. However glucose-6-phosphate dehydrogenase was markedly induced by the addition of essential amino acids alone to the culture medium, but was not induced by non-essential amino acids. Fatty acid synthetase was also markedly induced by a combination of both amino acid types (more than by either of amino acid alone). These results support that glucose-6-phosphate dehydrogenase and fatty acid synthetase were more protein-dependent than the other enzymes in the study of the whole animals [Katsurada, A. et al., Biochim. Biophys. Acta (1986) 877, 350-358Ån.

EFFECTS OF LONG - TERM FEEDING OF SOY PROTEIN ISOLATE ON PROTEINURIA AND AGE - RELATED CHANGES IN SOME PHYSIOLOGICAL VARIABLES IN ADULT RATS (AN INTERIM REPORT)

Fumio IBUKI, Masaru KITAGAWA and Kimikazu IWAMI

Faculty of Agriculture, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 9, 37-43, 1988.

Rats under various feeding conditions were examined for enterohepatic circulation of bile acids, especially their intestinal absorption with isolated epithelial cells. Na+ -dependent taurocholate absorption in the ileum was elevated by feeding high-fat diet over a period of 4weeks or from its mid-period, while any diurnal variation was not observed in intestinal taurocholate absorption in meal-fed rats despite of a postprandial increase in the intestinal leucine absorption in the same rats. On the other hand, there was a reverse relationship between the serum glucose level in alloxane-diabetic rats with glucose load and the extent of taurocholate uptake into the ileal epithelial cells. In order to prove the possibility that soy protein may affect reabsorption of bile salts across the intestinal wall,Åm14CÅn-taurocholate was orally administered to rats together with soy protein or casein diet, followed by sacrifice of these animals as stated intervals. The maximal radioactivity was found to move into the ileum 100 and 150 min after administration of casein and soy protein diets, respectively, being less in the former than in the latter. A similar tendency was also observed for the movement of radioactivity into the caecum. On the contrary, radioactive taurocholate had more greatly accumulated in the ileal mucosa of casein-ingested rats. It is reasonable to consider that the intraluminal bile acids are much more adsorbed by soy protein and thereby prevented from their intestinal absorption than by casein.

EFFECT OF VARIOUS HEAT TREATMENTS ON THE DIGESTIBILITY OF SOY WHEY PROTEIN

Hidemichi EBISAWA and Yoshiaki FUJITA

Nutrition Research Laboratory, Tokyo Metropolitan Institute of Gerontology

Nutr. Sci. Soy Protein, Jpn. 9, 44-48, 1988.

Effect of long-term feeding of soy protein isolate (SPI) on age-related proteinuria and some physiological variables was examined in rats receiving different amount of food. Four-month-old rats (Wistar strain, male) were divided into 4 groups of 12 rats each. Two of four groups were fed 20% casein diet (group CA) or SPI diet (group SA) ad libitum and other two (groups CR and SR) received restricted amount (10 g/day) of the same diets, until 800 days of age. This is an interim report of an 800-day examination. Results showed that until 300 days of age, 1) SPI was comparable to casein in criteria of nitrogen balance, true protein digestibility and net protein utilization (NPU), 2) SPI resulted in nonspecific influences on prevention and development of proteinuria, as well as in casein.

NUTRITIVE VALUE OF SPI EVALUATED BY A NEW METHOD BASED ON THE URINARY EXCRETION OF ACID SOLUBLE PEPTIDES

Yasuhiro KIDO, Fumiko TADA, Sachiko TERAI,
Fujiko SHIZUKA, Goro INOUE and Kyoichi KISHI

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

Nutr. Sci. Soy Protein, Jpn. 9, 49-53, 1988.

We previously reported that although trypsin inhibitor and hemagglutinin were inactivated by heating powdered soy whey protein (SWP), heating caused the browning of SWP and decreased the digestibility of protein1). In this study we first observed the effect of untreated SWP and browned SWP on the digestibility of casein consumed together with the ratio of one to two. Untreated or browned SWP did not influence the digestibility of casein. Next we tried but failed to improve the digestibility of SWP by heating SWP in ethanol solution, in solution with pH 5.0-8.5 or using salted-out and dialyzed SWP. In other experiment in vitro digestibility, the extent of browning and available lysine of various heated SWP were investigated. Untreated SWP and heat-treated SWP in 10% aqueous solution were fully digested by pepsin and pancreatin but the in vitro digestibility of dry-heated and browned SWP was poor because of low lysine availability. There was a good inverse correlation between the extent of browning and the content of available lysine. It was concluded that simple heating in water was good enough as for digestibility, protein utilization and lysine availability of SWP.

AVAILABILITY OF SOY PROTEIN PEPTIDES FOR TOTAL ENTERAL NUTRITION

Tadashi NOGUCHI, Taek Jeong NAM and Hiroshi NAITO

Department of Agricultural Chemistry, Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 9, 54-56, 1988.

Nutritive value of SPI was evaluated by employing a new method which is based on the estimation of urinary excretion of acid soluble peptides (ASP). The daily urinary excretion of ASP, expressed as per kg body weight, is known to reflect possibly the degradation rate of whole body protein. Furthermore, urinary ratio of N/ASP negatively correlates to the efficiency of dietary N. From evaluation of these new indices, the nutritive value of SPI was shown to be similar to that of isolated rice protein and to be a little better than that of wheat gluten. The urinary excretion of ASP/kg body weight in rats fed SPI was not different statistically from that of rats fed casein, gluten supplemented with lysine and threonine, or rice protein. These results suggest that SPI will become to be a good protein source for young rats if some amino acids are supplemented to it.

STUDIES ON CLINICAL APPLICATION OF SOY PEPTIDE

Masayuki SAITO and Takashi SHIMAZU

School of Medicine, Ehime University

Nutr. Sci. Soy Protein, Jpn. 9, 57-60, 1988.

Nutritional characteristics of soy protein peptides were examined in rats for the study of availability of the peptides for total enteral nutrition. Groups of female Sprague-Dawley rats (150-180g) were given a diet containing either soy protein peptides (SPT-5), soy protein (SPI), milk casein (Clinimeal) or amino acids (ED-AC). Under ad libitum feeding condition, the amount of diet intake was about 20% less in SPT-5 and SPI groups than in Clinimeal and ED-AC groups. After 16 days, the weights of body and white adipose tissue in SPT-5 and SPI groups were significantly lower than those in two other groups. When almost the same amount of diet was given through a gastric tube in combination with ad libitum feeding, there were no significant differences between groups in body weight, organ weights and values of several blood parameters. The results suggest that soy protein peptide is one of the nitrogen sources available for total enteral nutrition.

UTILIZATION EFFICIENCY OF SPI HYDROLYZATE (SPT-5) AND ITS EFFECTS ON CALCIUM AND ZINC BIOAVAILABILITIES IN PREGNANT RATS

Tatsushi KOMATSU ¹,Minoru YAMAGISHI ¹ and Keiko KOMATSU ²

¹ Unit of Nutrition in Hospital, University of Occupational and Environmental Health
² Fukuoka Junior College of Social Work and Child Education

Nutr. Sci. Soy Protein, Jpn. 9, 61-65, 1988.

The effects of soy-peptide (SPT) supplement to therapeutic diet on nutritional status of patients were examined. Two of four patients had hypoproteinemia due to protein-losing gastroenteropathy (case 1) or nephrotic syndrome (case 2). Others (cases 3 and 4) were severe obese women. Patients with hypoproteinemia, cases 1 and 2, were given jelly containing 10g of SPT for 20 weeks and 20g of SPT for 10 weeks, respectively. Two obese women, cases 3 and 4, were given basal diet of 1000 kcal for 10 days and of 800 kcal for 14 days, respectively, then given isocaloric test diet supplemented with 30g of SPT as jelly. Hypoproteinemia of two nitrogen losing patients improved by long-term intake of SPT jelly. Nitrogen balance of nephrotic patient (case 2) was negative before SPT supplement, but became positive by giving SPT jelly. Body weight of obese women reduced more rapidly during test diet period than basal diet period. However, with SPT supply, nitrogen balances of cases 3 and 4 improved to be positive, being 0.7 and 1.5 g/day, respectively. These data demonstrated that changing the proportion of nitrogen in a diet by SPT may improve nutritional status of malnourished or energy-restricted patients. In case 4, basal metabolism decreased during low energy (800 kcal) basal diet period. However, though energy content of the test diet supplemented with SPT is identical to the basal diet, basal metabolism increased during test diet period. This response may be due to thermic effect of SPT.

EFFECTS OF HIGH SPI DIET ON CALCIUM METABOLISMÅF EFFECTS OF ADDITION OF SULFUR CONTAINING AMINO ACIDS

Yoshiaki NIIYAMA, Sadaichi SAKAMOTO and Hiroyuki HORIO

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

Nutr. Sci. Soy Protein, Jpn. 9, 66-71, 1988.

Utilization efficiency of SPT-5, which is an enzymatically hydrolyzed SPI and consists of 20% free amino acids and 80% oligopeptides (av. peptide chain length, 3.3), was examined in pregnant rats. In addition, effects of SPT-5 on calcium and zinc bioavailabilities were observed. Animals were fed one of diets containing 10 or 20% SPT-5 with or without 0.3% methionine. Levels of dietary calcium and zinc were about 5.0 mg/g and 35 É g/g, respectively. Balances of nitrogen, calcium and zinc were measured during pregnancy and values were compared with those for SPI fed rats. Rats receiving the SPT-5 diets ate less and gained less than those fed the respective SPI diets, however, food efficiencies of corresponding peptide and protein-diets were identical. NPUs of the 10% SPT-5 diets without and with methionine were 49 and 68, respectively. NPU of the 20% SPT-5 diet was 45 and was not improved by methionine supplementation. On the 10% level, total retentions of calcium and zinc in SPT-5 fed rats were significantly lower than those in SPI fed rats, reflecting on mineral intakes. Increase in dietary peptide level or methionine supplementation to 10% peptide diet resulted in increased retentions of calcium and zinc. Responses of NPUs and bioavailabilities of calcium and zinc in the SPT-5 diets to increased dietary nitrogen level or methionine supplementation were similar to those observed in rats fed SPI diets.

HYPOCHOLESTEROLEMIC EFFECT OF SOY PROTEIN ISOLATE IN RATSÅFEFFECTS ON SERUM CHOLESTEROL, LINOLEATE DESATURATION AND EICOSANOID PRODUCTION

Kayoko KANEKO ¹ and Goro KOIKE ²

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

Nutr. Sci. Soy Protein, Jpn. 9, 72-76, 1988.

The effects of a high sulfur-containing amino acid (SAA) and potassium (K) intake on the calcium (Ca) excretion and retention were studied in young women. Fourteen female students were given a high protein (100 g protein/day) diet containing 52g of soy protein isolate (SPI diet) for 8 days. Then, the subjects were given a conventional diet, and thereafter they were received the second experimental diet containing SPI and 2.0g of sulfur-containing amino acids (SPI + SAAÅEdiet) and the third diet adding 3.0g of potassium bicarbonate to the second one (SPI + SAA K diet) for 7 days each. Intakes of SAAs and K from SPI, SPI + SAA and SPI + SAAÅEK diets were 3.36, 5.34 and 5.35 g/day and 974, 980 and 2,141 mg/day, respectively. Urinary Ca, S, K, ammonia and titratable acid excretion increased and urinary pH decreased in SPI + SAA diet period in a manner similar to the meat diet reported previously, compared to SPI diet period. Consequently, SAA supplemented diet had a significantly negative effect on Ca retention. In SPI + SAAÅEK diet period urinary K excretion markedly increased, however, excretions in urinary Ca, ammonia and titratable acid were reversed and urinary pH increased as compared to SPI + SAA diet period. These effects were similar to those adding of apples to the meat diet reported previously. Fecal Ca excretions were not affected by the supplements of SAA or SAA and K. The results suggest that the hypercalciuria induced by high meat diet is caused by its high content of SAA and may be reversed by the consumption of potassium rich foodstuffs.

EFFECT OF DIETARY PROTEINS ON PLASMA CHOLESTEROL CONCENTRATION OF MICE

Michihiro SUGANO and Kazunori KOBA

Kyusyu University School of Agriculture

Nutr. Sci. Soy Protein, Jpn. 9, 77-81, 1988.

The interactions of dietary protein (soy protein or casein) and fat (palm olein or mold oil) on various lipid parameters were studied in rats. The fatty acid composition of the dietary fats was comparable except for the proportions of polyunsaturated fatty acids: mold oil contributed É¡-linoleinic acid (GLA) at the expense of a portion of the linoleic acid in palm olein. When rats were fed casein rather than soy protein, serum cholesterol levels were higher irrespective of the fat source. Mold oil reduced a cholesterolemic potential of casein. Soy protein increased fecal steroid excretion. The ratio of arachidonate to linoleate in phosphatidylcholine from serum and liver was markedly higher in the casein than in the soy protein groups, whereas mold oil predictably improved the protein-dependent reduction. However, the aortic production of prostacyclin was not influenced largely by dietary protein type and was stimulated by GLA. No protein-fat interaction was observed on the concentration of plasma thromboxane A2. The physiological significance of reduced linoleate desaturation by soy protein is not clear, since the protein did not disturb the balance of eicosanoids.

RELATIONSHIP BETWEEN EFFECT OF METHIONINE ON PLASMA CHOLESTEROL LEVEL AND DIETARY PROTEIN (CASEIN AND SOY PROTEIN ISOLATE) LEVEL IN RATS

Junko YAMASHITA, Miwako KAMIMURA and Shin-ichi HAYASHI

Department of Nutrition, The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 9, 82-85, 1988.

Effects of dietary proteins were examined on plasma cholesterol concentration of female ICR mice under various conditions. Half of them had been made hyperphagic by a treatment with goldthioglucose (GTG), which slightly elevated plasma cholesterol level. Marked elevation of plasma cholesterol level was brought about by feeding high-fat diets, while a basal low level was maintained by feeding low-fat diets or a laboratory chow. In GTG-treated mice fed either high-fat or low-fat diets for 3 weeks, no difference was observed in plasma cholesterol level between casein- and SPI-fed mice. In normal mice fed high-fat diets for 3 weeks, SPI rather showed a slight hypercholesterolemic effect compared with casein. In normal mice fed low-fat diets for 3 weeks, SPI showed a slight hypocholesterolemic effect. However, no such hypocholesterolemic effect of SPI was observed in normal mice fed low-fat diets for either 1 week or 13 weeks and in lean control mice fed similar diets for 6 weeks. A marked hypercholesterolemia of an identical degree was observed in genetically obese (ob/ob) mice fed either low-fat casein, low-fat SPI, or a laboratory chow. It was concluded that SPI did not exert a significant hypocholesterolemic effect in mice, in contrast to results with other species of animals like rabbits, pigs, and rats. Taken together with our last year's observation that SPI did not cause any stimulatory effect on fecal excretion of neutral sterols in mice, the present result suggests that the hypocholesterolemic effect of SPI observed in other species of animals is due to stimulation of fecal sterol excretions.

CHARACTERISTIC EFFECT OF SOY PROTEIN ISOLATE ON CHOLESTEROL METABOLISM IN RATS (III)

Kimio SUGIYAMA, Akio OHISHI and Keiichiro MURAMATSU

Faculty of Agriculture, Shizuoka University

Nutr. Sci. Soy Protein, Jpn. 9, 86-92, 1988.

The relationship between the effect of dietary supplementation with methionine on plasma cholesterol level and dietary protein level was investigated with rats fed high cholesterol diets containing varied levels of casein (1, 15, 20, 25, 40%) or soy protein isolate (SPI) (10, 25, 40%). The addition of 0.8% methionine to 10% casein diet decreased plasma cholesterol level, whereas it increased plasma cholesterol level when added to diets containing casein at a 20% or more. In contrast, methionine supplementation did not increase plasma cholesterol in rats fed SPI diets irrespective of protein level. Fecal excretion of neutral steroids and bile acids was higher in rats fed SPI diets than in rats fed casein diets, and methionine supplementation tended to increase fecal excretion of bile acids. Although there was a tendency to exist significant correlations among fecal excretion of bile acids, liver cholesterol 7Éø-hydroxylase activity and liver glutathione level, these parameters did not necessarily correlate with plasma cholesterol level. The differential effects of methionine supplementation of casein and SPI diets on plasma cholesterol level were discussed in relation to the difference in glycine content of both proteins.

EFFECTS OF SOY PROTEIN ISOLATE ON FECAL STEROL EXCRETION AND PLASMA CHOLESTEROL IN YOUNG MEN (II)

Akira YOSHIDA and Hiroaki ODA

School of Agriculture, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 9, 93-96, 1988.

We previously demonstrated that the supplementation of small amounts of xenobiotics such as PCB, DDT and others produced hypercholesterolemia in rats without addition of cholesterol in the diet. This hypercholesterolemia is mainly due to the induction of liver HMG Co-A reductase activity leading to the increased synthesis of cholesterol. When dietary source of protein was soy protein isolate, the elevation of serum cholesterol by PCB is less than that of rats fed the casein diet. However, the addition of 0.5% of methionine to the 20% SPI basal diet together with 0.02% of PCB increased the serum level of cholesterol significantly. When rats were fed the 15% casein diet which contained the same amount of total sulfur-amino acids but more methionine, serum level of cholesterol was significantly elevated by PCB without additional supplement of methionine. Addition of cystine to the PCB containing SPI diet didn't affect the serum level of cholesterol significantly. Dietary PCB induced liver HMG Co-A reductase activity, when dietary protein was casein. On the other hand, when dietary protein was soy protein isolate, the induction of HMG Co-A reductase activity was observed only when the diet was supplemented with PCB together with methionine. The 20% SPI diet contained enough sulfur-amino acid for maximum growth of rats. Therefore, methionine seems to have a specific role for the induction of liver HMGCoA reductase activity and for the elevated synthesis of liver cholesterol. The addition of methionine to the 20% SPI diet containing PCB didn't affect the fecal excretion of bile acids of rats. In in vitro experiment, it was shown that the HMG Co-A reductase activity of liver homogenates was elevated significantly by the addition of glutathione in the incubation medium. Methionine may have a role to elevate the liver concentration of glutathione. However, the supplementation of cystine to the diet also elevated the liver glutathione, therefore, methionine may play a role not only in elevating the tissue level of glutathione but also in other function for the induction of hypercholesterolemia due to dietary xenobiotics.

EFFECT OF SOY PROTEIN DIET IN PATIENTS WITH LIVER CIRRHOSIS (II)

Toyoko OKUDA ¹, Hiroko MIYOSHI ¹, Kazumi SASAKI ¹,Rituko SATAKE ¹,Yukari HIRATUKA ¹ and Hideo KOISHI ²

¹ Faculty of the Science of Living, Osaka City University
² Department of Food and Nutritional Science, University of Shizuoka

Nutr. Sci. Soy Protein, Jpn. 9, 97-100, 1988.

The effects of the substitution of soy protein isolate for milk protein in the diet on plasma cholesterol levels and the fecal excretion of neutral sterols were examined in five healthy young men. In the experimental diets, 25% of the energy was in the form of fat, 67% was carbohydrates and 8% was protein. The intakes of energy and protein were about 43 kcal/kg/day and 0.8 g/kg/day, respectively. The cholesterol intake was 25 mg/kg/day from egg yolk. The subjects were fed a soy protein isolate (SPI) diet and then a skim milk diet for 2 weeks each time. There was a 6-day break period between the two diets. In the milk and SPI diets, half of the protein was skim milk and SPI, respectively. During the milk diet, total and LDL-cholesterols and also the atherogenic index significantly increased, but they were unchanged during the SPI diet period. No significant differences in fecal excretion of neutral sterols and cholesterol were noted between the two dietary periods. There were no differences in serum insulin and plasma glucagon concentrations just after the last breakfast in the two dietary periods.

THE EFFECT OF SOYBEAN PROTEIN ON INSULIN SENSITIVITYÅFTHE FIRST REPORT

Satoshi NAGANAWA, Youichiro ITOH, Masahiro YAMATOH,Takashi YOSHIDA and Yasutoshi MUTO

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

Nutr. Sci. Soy Protein, Jpn. 9, 101-113, 1988.

Soy protein and animal protein diets, containing 2100 kcal of energy and 70 g of protein, were administered to seven cirrhotic patients and four controls for three days to compare the nutritional effects of vegetable and animal protein diets. In cirrhotic patients, lower tendencies of most serum amino acid concentrations in the soy protein diet group were seen than those in the animal protein diet group after the 3 day examination period. On the other hand, percentage intake of the soy protein diet was apparently higher both in energy (94.4 Å} 5.9 vs. 76.6 Å}15.1%, p<0.05) and in protein (91.4 �} 7.7 vs. 77.5 �} 13.4%, p<0.05). Small differences were found in blood ammonia level, Fischer's ratio, serum GABA concentration and fecal bacterial flora. Thus, it would be useful to administer the soy protein diet to cirrhotic patients so as to prevent the protein malnutritional state. Furthermore, there were no significant differences in plasma BCAA concentration and Fischer's ratio before and after long-term administration of soy protein diet to patients with decompensated liver cirrhosis.

The soy protein protein reserch(Japan)