The Soy Protein Research Committee(Japan)

AUTOACYLATION OF SOY PROTEINS

Makoto KITO ¹,Shigeru UTSUMI ¹, and Takashi NISHIMURA ²

¹ Research Institute for Food Science, Kyoto University
² Fuji Oil Co., Ltd

Nutr. Sci. Soy Protein, Jpn. 10, 7-12, 1989.

Soy proteins were autoacylated with palmitoyl-CoA. Soy proteins were denatured with 6 M urea and/or reduced with 0.2M 2-mercaptoethanol, and then the reagents were removed by gel filtration. The reduced, and denatured and reduced glycinins were well acylated, although the native and the denatured glycinins were not. These observations demonstrated that the cleavage of disulfide bonds was essential for the autoacylation. In addition, the autoacylation was strongly inhibited by the presence of urea and detergents. Inhibition of the autoacylation by 2-mercaptoethanol and N-ethylmaleimide and the release of palmitic acid by 2-mercaptoethanol and hydroxylamine indicated that palmitic acid was covalently linked via thioester bond to the cysteine residue. The autoacylation of glycinin was dependent on time, temperature, pH and concentrations of palmitoyl-CoA and glycinin, but independent of the saturation of fatty acids. Acylated glycinin exhibited excellent emulsification activity, compared with native glycinin. É¿-Conglycinin was not acylated with palmitoyl-CoA.

IMPROVEMENTS OF THE FUNCTIONAL PROPERTIES OF SOY PROTEIN BY HEATING IN DRY STATE

Kunihiko KOBAYASHI, Akio KATO and Naotoshi MATSUDOMI

Faculty of Agriculture, Yamaguchi University

Nutr. Sci. Soy Protein, Jpn. 10, 13-17, 1989.

The heating in dry state for 16Å`24 hr at 80Åé improved the gelling property and emulsion stability of soy protein isolate (SPI). However, the dry-heated SPI disappeared the gelling property in the presence of 2.5% NaCl. To take account of the previous results of the dry-heated dried egg white (DEW), it was suggested that the heating in dry state unfolded partially SPI and changed hydrophobic and charge balance of protein, and then the heated SPI formed the gel mainly by interaction between surface charges of the molecules of particles. The dry heating of SPI-DEW mixture caused SPI to improve gelling and emulsifying properties, but the formation of SPI-DEW complex was not demonstrated. Thus, the dry heating was proposed to be a useful method for the improvement of functional properties of soy proteins.

STUDIES ON TOFUYO FLAVOR USING SOY PROTEIN ISOLATEÅFCHANGES IN FREE AMINO ACIDS, REDUCING SUGARS AND ORGANIC ACIDS

Masaaki YASUDA, Kyuichiro NAGAMATSU and Seiji MORIKAWA

College of Agriculture, University of the Ryukyus

Nutr. Sci. Soy Protein, Jpn. 10, 18-22, 1989.

Tofuyo is an excellent vegetable protein food and is made from soybean curd that is called as tofu, by the action of microorganisms in Okinawa prefecture, Japan. It is a creamy cheese-type product with mild flavor, fine texture and good taste. However, 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 to produce uniform quality of tofuyo. Soy protein 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. This new product has more unique flavor than that of traditional product. In this study, changes in activities of enzymes (Éø-amylase, glucoamylase and protease), free amino acid composition, reducing sugars and organic acid composition during tofuyo fermentation were investigated. Protease is considered to be concerned with ripening, and amylases are concerned with providing the taste of product. Although remaining activities of Éø-amylase, glucoamylase and protease decreased to 43, 43 and 37% for initial 15-days of ripening, these values maintained until the end of 60-days of ripening, respectively. The ratio of amino nitrogen to water soluble nitrogen increased during the ripening period. Amino acids and organic acids were analyzed by high pressure liquid chromatographies. Total amino acid amount of tofuyo was found to increase during maturation. It was also found that leucine, glutamic acid, valine, arginine and serine were contained at a high level. Glutamic acid and aspartic acid of tofuyo were found to be 5.86 and 8.48 mg/100g at first, and increased with maturing time (60 days) to 356 and 200 mg/100g, respectively. It was observed that reducing sugars of tofuyo or soak increased during the ripeing period. Glucose was the main component of the reducing sugars as detected by thin layer chromatography. Isobutyric, tartaric, lactic, propionic, malic and acetic acids were found at high level. And thus, these amino acids, saccharides and organic acids were considered as the major tasty components.

FURTHER IMPROVEMENT IN FUNCTION OF SOY PROTEIN AS ANTIOXIDANT AND ITS APPLICATION TO PREVENTION OF LINOLENATE PEROXIDATION

Fumio IBUKI, Harumi SHIMATO and Kimikazu IWAMI

Faculty of Agriculture, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 10, 23-27, 1989.

Acid-sensitive fraction (ASF) was prepared from defatted soybean mean (DSM) or soy protein isolate (SPI) with or without additional lipid removal by chloroform-methanol (2 : 1) extraction and examined for antioxidative effect against linolenate peroxidation in a powder model system at a fixed temperature (37Åé) and varied water activities (Aw=0.25, 0.55, and 0.75). The pretreatment of DSM with chloroform-methanol (2 : 1) mixture prior to ASF preparation caused a slight decrease in the antioxidant effect. In relation to this effect, ASF from SPI was somewhat superior to that from DSM. As an attempt to raise the function of SPI as antioxidant, linolenic acid was embedded in the acid-precipitated protein particles. Although the amount of linolenate embedded herein was no more than 15% of the initial administration, the fatty acid was stable against oxidation over a month at different Aws. Taking into consideration further improvements in the incorporation efficiency of polyunsaturated fatty acid, this is a practical and convenient means to enable food protein to function as prominent antioxidant.

ENTRY OF INTAKE PROTEIN - DERIVED NITROGEN INTO THE BODY ÅFA STUDY WITH 15N - LABELLED SOY PROTEIN

Soichi ARAI ¹ and Hiroko KIMURA ²

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

Nutr. Sci. Soy Protein, Jpn. 10, 28-30, 1989.

The entry of ingested soy protein-derived nitrogen into the body was investigated with 15N-labelled soy protein. The labelled soy protein was obtained as an acid-precipitated fraction from soybeans which had been harvested after fertilization with 15N ammonium sulfate. The acid-precipitated protein, containing 13.3% nitrogen and 1.75% 15N, was used to prepare a diet with a protein level of 10%. Male rats (Wistar strain) were given the diet by meal feeding and then sacrificed to investigate time-course changes in 15N in the small-intestinal tract and circulation system. A time-course change in 15N in urine was also analyzed. In the small-intestinal tract the nitrogen derived from the ingested soy protein reached a maximum 2 hr after feeding, representing almost 50% of the total nitrogen. A similar time-course profile was obtained by analysis of the amino acid nitrogen in the portal vein, whereas in the systemic blood the ingested soy protein-derived nitrogen reached a maximum 4Å`6 hr after feeding, account for 25% of the total amino acid nitrogen. Almost one-fourth of the ingested soy protein-derived nitrogen was excreted in the urine within 24 hr after feeding. The study suggests that it is possible to describe quantitatively the cascade of the dietary nitrogen after feeding by the present method using a protein labelled with the stable isotope 15N.

EFFECTS OF LONG - TERM FEEDING OF SOY PROTEIN ISOLATE ON PROTEINURIA AND AGE - RELATED CHANGES IN SOME PHYSIOLOGICAL VARIABLES IN ADULT RATS UNDER AD LIBITUM FEEDING CONDITION

Hidemichi EBISAWA, Mineko ICHIKAWA, Tomoko OZEKI and Yoshiaki FUJITA

Tokyo Metropolitan institute of Gerontology

Nutr. Sci. Soy Protein, Jpn. 10, 31-35, 1989.

Effect of long-term feeding of SPI on age-related proteinuria and some physiological variables was examined in adult rats under ad libitum feeding condition. Four-month-old rats (Wistar strain, male) were divided into two groups of 12 rats each. Groups CA and SA were fed 20% casein diet and 20% SPI diet ad libitum, respectively, until 600 days of age. SPI was comparable to casein in criteria of nitrogen balance and protein digestibility. But on day 600 of age, group SA excreted more urinary protein than that in group CA (pÅÉ0.05). Moreover, group SA showed rather higher values for serum cholesterol and triglyceride than those in group CA. Results suggest that effect of SPI on the development of age related diseases and lipid metabolism changes with the age of subjects examined.

EFFECTS OF DIETARY PROTEINS ON ENZYME AND mRNA LEVELS OF LIPOGENIC ENZYMES IN RAT LIVER

Nobuko IRITANI ¹, Naomi NISHIMOTO ¹, Hitomi FUKUDA ¹,
Akihiko KATSURADA ¹,Yohko MATSUMURA ¹ and Takehiko TANAKA ²

¹ Tezukayama Gakuin College
² Osaka University Medical School

Nutr. Sci. Soy Protein, Jpn. 10, 36-38, 1989.

1. After refeeding fat-free diets containing various sources of protein to fasted rats, the enzyme induction of hepatic malic enzyme and glucose-6-phosphate dehydrogenase (G6PDH) was significantly lower in soybean protein, gluten and zein groups than in casein group. 2. The mRNA concentrations of G6PDH were about parallel to the enzyme induction. However, the mRNA concentrations of malic enzyme were similar among all the groups. It is suggested that different amino acid compositions affected the steps before translation of G6PDH, while the different compositions affected the translation of malic enzyme. 3. The addition of lysine and tryptophan to the zein diet increased both mRNA and enzyme levels of G6PDH and malic enzyme.

CHRONIC ADMINISTRATION OF SOY PROTEIN ISOLATE AND ETHANOL ENHANCED CARCINOGENIC INDEX ON DIMETHYLNITROSAMINE METABOLISM IN THE RABBIT LIVER MICROSOMES

Hirofumi SUZUKI¹, Masatoshi KAKU ¹, Daisuke KAJINO ¹,Seiki HORI ¹,Michio HOSONO ²,Setsuko KAWANO ³ and Masaharu YOSHIO ⁴

¹ First Department of Physiology, Hyogo College of Medicine
² Kyowa Synthetic Medical Laboratory
³ Nagoya Women's University
⁴ Kyowakai Hospital

Nutr. Sci. Soy Protein, Jpn. 10, 39-44, 1989.

Effects of chronic administration of ethanol and soy protein isolate (SPI) on the carcinogenic index, the ratio of dimethylnitrosamine (DMN) demethylation activity (carcinogenic metabolism) to DMN denitrosation activity (detoxification metabolism) were studied in the rabbit. Twenty-four adult male white rabbits were divided into 4 groups of 6 each, the first group of 21% casein diet with distilled deionized water (DDW) drink, the second group of 21% casein diet with 7.5% (W/V) ethanol drink, the third group of 21% SPI diet with DDW drink and the fourth group of 21% SPI diet with 7.5% ethanol drink. All animals were allowed to feed freely throughout the study for 8 weeks. At 8 weeks of experimental period, all animals were killed and microsomes were isolated from the liver. And cytochrome P-450 content, two microsomal P-450 related compositions, i. e., NADPH P-450 reductase activity, cytochrome b5 content, protein concentration, DMN demethylation activity and DMN denitrosation activity of these microsomes were evaluated. These P-450 related compositions were not significantly affected by ethanol in casein diet group but ethanol increased these compositions by 17.5Å`37.1% only in SPI diet group. DMN demethylation activity (1.91Å`2.9 nmol HCHO/min/mg Ms protein) was inhibited to 40.6% by carbon monoxide (CO) and was reduced to 12.3% by deficiency of NADPH, These results showed that DMN demethylation was mainly catalyzed by P-450. On the contrary, DMN denitrosation activity (0.007 Å` 0.016 nmol NO2/min/mg Ms protein) was enhanced to 125 Å` 142% by CO and was reduced to about 25% by deficiency of NADPH. Therefore, the catalytic enzyme on DMN denitrosation did not belong to P-450 and rather might by the unknown enzyme. The values of carcinogenic index (=DMN demethylation activityÅF nmol HCHO/min/mg Ms protein ÅÄ DMN denitrosation activityÅF nmol NO2/min/mg Ms protein) were about 200 in two groups without ethanol administration. Ethanol increased values of these indices to 151 Å` 227% and especially the index value in 21% SPI diet group was induced by about 230% because of strong reducing effects of 7.5% ethanol and 21% SPI on DMN denitrosation activity.

HYPOCHOLESTEROLEMIC EFFECTS OF UNDIGESTED FRACTIONS OF SOYBEAN PROTEIN IN RATS

Michihiro SUGANO, Shoichiro GOTO, Yukio YAMADA and Katsuko YOSHIDA

School of Agriculture, Kyushu University

Nutr. Sci. Soy Protein, Jpn. 10, 45-48, 1989.

The undigested fraction of soybean protein, which was prepared after exhaustive digestion with microbial proteases or porcine pepsin, exerted a marked hypocholesterolemic effect in rats fed cholesterol-enriched diets. The effect can be attributed to an increased fecal excretion of both neutral and acidic steroids. Results of a series of experiments suggested that the peptides of the undigested fraction, rather than the contaminating lipids and saponins, are responsible for its hypocholesterolemic effect.

SPECIES DIFFERENCE IN THE EFFECTS OF DIETARY PROTEIN ON CHOLESTEROL METABOLISM

Junko YAMASHITA, Yoshiko FUJITA, Miwako KAMIMURA and Shin-ichi HAYASHI

Department of Nutrition, The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 10, 49-52, 1989.

In mice, plasma cholesterol level was elevated moderately by feeding high-fat semisynthetic diets and markedly in genetically obese (ob/ob) strain. In contrast to the results with rats, plasma cholesterol level of mice was not affected by dietary proteins, namely casein and soy protein isolate (SPI), in either normal, goldthioglucose (GTG)-obese, or the genetically obese mice. Also in contrast to the results with rats, sum of fecal neutral and acidic steroid excretions was not much affected by dietary proteins in mice. These results strongly suggested that, in rats but not in mice, casein caused hypercholesterolemia because of its very low ability to stimulate fecal steroid excretion compared with SPI. It was also noticed that feeding SPI diet caused an increase in the proportion of HDL-cholesterol in normal mice.

LIVER CHOLESTEROL - LOWERING ACTIVITY OF SOYBEAN PROTEIN ISOLATE IN RATS

Shigeru SAEKI, Osamu KANAUCHI, Eri HOSOYA and Shuhachi KIRIYAMA

Faculty of Agriculture, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 10, 53-57, 1989.

In rats fed a cholesterol-free purified diet, soybean protein isolate (SPI) showed a cholesterol-lowering activity not only in plasma, but also in the liver when compared with that of casein. The differences of rate of sterol synthesis between groups were not responsible for the responses of the liver and plasma cholesterol concentration to dietary proteins : the rates of sterol synthesis in vivo in the liver and the small intestine were significantly higher in SPI-fed rats. The casein-induced higher level of plasma cholesterol was mainly due to the increase in HDL-cholesterol. The liver cholesterol level rapidly responded to the change in dietary protein, which was highly correlated with the changes of HDL-cholesterol and LCAT activity. However, the addition of Met to the SPl diet increased HDL-cholesterol to the casein-induced level, but the liver cholesterol remained at a low level. Furthermore, although the plasma cholesterol level was significantly higher in rats fed a diet containing the casein-type amino acid mixture than in rats fed a diet containing the SPI-type amino acid mixture, there was no significant difference in the liver cholesterol levels between these groups. These results would imply that the regulatory mechanism for the liver cholesterol level differs from that for plasma cholesterol level.

HYPOCHOLESTEROLEMIC EFFECTS OF SOY PROTEINÅF EFFECTS OF DIETARY PROTEIN LEVEL ON FATTY ACID PROFILES OF PHOSPHATIDYLCHOLINE AND FECAL STEROID EXCRETION IN RATS

Takuo OKITA

Fukuoka University of Education

Nutr. Sci. Soy Protein, Jpn. 10, 58-62, 1989.

Effects of different dietary levels (10Å`30%) of soy protein and casein on various lipid parameters were examined in rats. The concentration of plasma and liver cholesterol (CHOL) tended to decrease with an increasing dietary protein level, in particular when the diet contained CHOL. The hypocholesterolemic effect of soy protein was evident with CHOL-enriched diets. The ratio of arachidonate to linoleate in plasma and liver phosphatidylcholine tended to elevate accompanying with an increasing dietary protein level, although it was considerably lower in soy protein than in casein : The ratio increased when the dietary protein level increased. The results indicated that the hypocholesterolemic effect of soy protein is influenced by not only the level but also dietary CHOL. The degree of the conversion of linoleate to arachidonate also depended on the level and type of dietary protein.

NUTRITIONAL SPECIFICITY OF SOYPROTEIN ISOLATE FOR CHOLESTEROL METABOLISM IN RATS

Akira YOSHIDA, Hiroaki ODA and Hideo FUKUI

School of Agriculture, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 10, 63-66, 1989.

We previously reported that the serum level of cholesterol in rats fed soy protein diet was lower than that in rats fed either rice protein diet or casein diet although fecal excretion of bile acids was stimulated by both soy protein diet and rice protein diet. These results suggest the stimulated fecal bile acids may not be a main reason of hypocholesterolemic effect of soy protein diet. In the present experiment time course of serum level of cholesterol and fecal excretion of bile acids were investigated. The effects of dietary protein on excretion of lipoproteins from the liver, cholesterol absorption and lipoprotein lipase were also investigated. Serum levels of cholesterol in rats fed the soy protein diet were lower as compared with the casein or rice protein diet group even after one or two days of feeding of the experimental diets and kept the lower values thereafter. However, the fecal excretion of bile acids was higher for both soy protein and rice protein diet groups. Serum cholesterol and triglyceride were elevated after intravenous injection of tyloxapol, and these elevations were lower in soy protein diet group. Absorption of cholesterol was determined by dual isotope ratio method but it was not significantly affected by the difference of dietary proteins tested. The activity of lipoprotein lipase showed no correlation with the serum level of cholesterol. The results suggest the importance of early metabolic changes in lipoprotein secretion from the liver and also in the synthesis of cholesterol and apolipoproteins in the liver by the difference of dietary proteins.

EFFECTS OF SOYBEAN ON LIPID DIGESTIBILITY AND FECAL EXCRETION OF NEUTRAL STEROLS IN YOUNG MEN ON A HIGH-CHOLESTEROL DIET

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

¹ Faculty of Science of Living, Osaka City University
² School of Food and Nutritional Sciences, University of Shizuoka

Nutr. Sci. Soy Protein, Jpn. 10, 67-70, 1989.

The digestibility of lipids and the fecal excretion of neutral sterols were examined in five healthy young men on a diet of soy protein isolate (SPI) and a soybean diet, each lasting for 2 weeks. The intake of energy was 43 kcal/kg/day and that of protein was 0.8 g/kg/day. Half (by weight)of the protein of the diet was SPI or soybeans. Lipids accounted for 25% of the energy of the diets. The mean cholesterol intake from egg yolk was 1.6 g/day. Both diets were therefore high-cholesterol diets, but total cholesterol and HDL-cholesterol levels in the plasma were unchanged from the base line by both diets. The dry weight of feces with the soybean diet was about 1.7 times that with the SPI diet. The lipid level in the feces with soybean diet was significantly higher than with the SPI diet, but the levels of neutral sterols and cholesterol tended to be lower. Overall, the fecal excretion of lipids with the soybean diet was about 2.4 times that with the SPI diet. Digestion of lipids in the intestine was significantly decreased by the soybean diet. The total amount of neutral sterols and cholesterol excreted into the feces was about the same with the two diets.

AVAILABILITY OF SOY PROTEIN PEPTIDE IN ENTERAL NUTRITION

Mika IHARA, Masaharu OHNAKA and Yoshiaki NIIYAMA

School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 10, 71-75, 1989.

The effects of dietary nitrogen forms (protein or peptides) and feeding condition (nibbling or continuous feeding) on growth and energy and nitrogen utilization were examined in young adult rats. Groups of the male Wistar rats were given a diet containing either 20% soy protein isolate (SPI) or soy protein peptides (SPT) ad libitum for 7 days. Other group of rats were fed a liquid diet containing SPT by continuous infusion (SPTc). Gross energy efficiency and nitrogen retention, which were estimated from energy and nitrogen balances, respectively, were higher in SPT group than those in SPI group. As the food intake in SPI fed rats was less than that in SPT fed rats, we could not conclude that peptides were better source than protein for energy and nitrogen utilization. The paradoxical relationships between food efficiency (body weight gain / food intake) and gross energy efficiency or PER (body weight gain / protein intake) and nitrogen retention rate in SPT and SPTc groups were observed, suggesting that parameters, such as food efficiency or PER based on body weight gain, were not necessarily adequate in assessing the nutritional values of a liquid diet. Briefly say, it was proved that soy protein peptides with average chain length of 3.3 were useful nitrogen source for enteral nutrition.

DEMINERALIZATION OF ENZYMIC HYDROLYSATE OF SPI (HINUTE PM) AND ABSORPTION OF DESALTED PREPARATION IN RAT SMALL INTESTINE IN VITRO

Yukihiro NAKABOU ¹, Reiko UTSUNOMIYA ¹, Takeshi SUZUKI ¹, Miyuki WATANABE ¹,Hiroshi HAGIHIRA ¹,Takaki MATSUO ²,Minoru KIMOTO ² and Yoshie OHSHIMA ²

¹ Department of Nutrition, School of Medicine, The University of Tokushima
² Fuji Oil Co., Ltd.

Nutr. Sci. Soy Protein, Jpn. 10, 76-80, 1989.

Cation-exchange resin chromatography using Amberlite IR 120B was performed to remove ashes contained in Hinute PM. Concentrations of minerals were reduced from 6.2% in the crude preparation to 2.4% in the refined preparation and contaminated sugars were also reduced from 4.4% to 0.9% by the treatment. HPLC profile of the refined preparation showed a decrease in percentage of peptides with high molecular weight and an increase in percentage of peptides with low molecular weight, indicating that large peptides in the crude preparation were partially removed by the chromatography. Since in concomitant with removal of some large peptides, concentrations of free amino acids increased from 19.5% in the crude preparation to 33.3% in the refined preparation, mean chain length of amino acid residues decreased from 2.9 to 2.1. The rates of absorption of amino acids from crude Hinute PM, refined Hinute PM and an amino acid mixture simulating crude Hinute PM were observed by the everted sac method in the rat jejunum and ileum. Total amount of amino acids absorbed from three substrates in the jejunum was the following order : an amino acid mixture simulating Hinute PM > refined Hinute PM > crude Hinute PM and in the ileum : refined Hinute PM > an amino acid mixture > Hinute PM. Total amount of amino acids absorbed from the refined preparation was 24% more in the jejunum and 51% more in the ileum than that from the crude preparation. The amount of acidic amino acids absorbed from an amino acid mixture was 43Å`45% of the total non-essential amino acids absorbed, while acidic amino acids were absorbed less than 10% from the both preparations. These results suggest that the refined preparation is more effectively absorbed than the crude preparation and the both preparation contain a considerable amount of oligopeptides with acidic amino acids resistant to hydrolysis with peptidases.

AVAILABILITY OF SOY PROTEIN PEPTIDES FOR TOTAL ENTERAL NUTRITION

Masayuki SAITO

Faculty of Veterinary Medicine, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 10, 81-83, 1989.

Effects of dietary soy protein peptides on energy expenditure were examined in rats, with special reference to the thermogenic activity of brown adipose tissue (BAT). Groups of female Sprague-Dawley rats (150-170 g) were given a diet containing either soy protein peptides (SP) or amino acids (ED) for 13 days. Regardless of peptide (amino acid) content (7 and 18%) in the diet, body weight gain (Å¢BW) was less in SP group than ED group, while the former ate more. Thus, the energy efficiency (Å¢BW/food intake) was decreased under the SP diet, suggesting an increase in energy expenditure, i. e., heat production. In accordance with this, GDP binding to BAT mitochondria, an index of the thermogenic activity of this tissue, was increased under the SP diet.

EFFECTS OF NITROGEN SUPPLEMENT USING SOYBEAN PEPTIDE ON DIET THERAPY WITH ENERGY RESTRICTION TO OBESE CHILDREN

Tatsushi KOMATSU ¹,Keiko KOMATSU ²,Mie MATUO ³, Masato NAGATA ³ and Minoru Yamagishi ⁴

¹ Unit of Nutrition in Hospital, University of Occupational and Environmental Health
² Fukuoka Junior College of Social Work and Child Education
³ Nagata Hospital
⁴ School of Medicine, Universtiy of Occupational and Environmental Health

Nutr. Sci. Soy Protein, Jpn. 10, 84-88, 1989.

A 16-18 day study was conducted to examine effects of soybean peptide (SPT) supplement to energy restricted 1000 kcal diet on body weight and body fat loss and energy expenditure in 11 simple obese children aged 7Å`14 yr. Obesity degrees were 35Å`91% over their ideal body weight. The supplementation of 30g SPT to 1000 kcal diet containing 50Å`55 g protein was carried out for 7Å`10 days in the second half of the experimental period. The average body weight loss during hospitalization was 3.1Å}1.2 kg (range 1.2 to 5.6 kg). Reduction rate of weight did not reduce after the supplement. Basal metabolism decreased by the weight loss, but the decrease of it stopped after SPT supplement. The total skinfold thickness (triceps + subscapular + abdomen) during supplement decreased significantly more than given 1000 kcal diet only. As nitrogen balance improved and serum rapid turnover proteins did not decrease after supplement, protein nutriture of energy restricted obese children was well maintained.

EFFECTS OF SOY PROTEIN DIET (20 g/day) ON PLASMA AND LIPOPROTEIN LIPIDS BASED ON APO E PHENOTYPES

Haruo NAKAMURA, Emiko MIYAJIMA and Katsunori IKEWAKI

First Department of Medicine, National Defense Medical College

Nutr. Sci. Soy Protein, Jpn. 10, 89-93, 1989.

The aim of the present study is to investigate the effects of partial substitution of dietary protein with soy on plasma and lipoprotein lipids based on apo E phenotype among 15 normal volunteers. Twenty g / day of soy protein substitution for four weeks reduced plasma and LDL-cholesterol significantly. Subjects with apo E3/E3 showed consistent and significant reduction in LDL-cholesterol, while subjects with apo E4/E4, E4/E3 showed transient decrease. Plasma apo B levels significantly decreased only in the subjects with E3/E3. Plasma triglyceride remained unchanged among all cases. However, subjects with E3/E3 revealed significant reduction in triglyceride. Present results indicate that relatively higher removal of apo B containing lipoproteins may occur on the soy protein diet, and that 20 g/day substitution of protein seems to be still effective for reducing plasma and lipoprotein lipids.

EFFECT OF SPI INTAKE ON PLASMA SOMATOMEDIN C CONCENTRATION IN RATS

Tadashi NOGUCHI, Yutaka MIURA and Jong Hee KIM

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 10, 94-95, 1989.

Plasma immunoreactive somatomedin C concentration before and after acid-ethanol extraction was determined in rats fed a protein-free diet or diets containing 12% casein, SPI, or SPI supplemented with methionine. Plasma somatomedin C concentration both before and after acid-ethanol extraction was significantly lower in rats fed the SPI diet or the protein-free diet than in those fed the casein diet. Furthermore, somatomedin C mRNA content in the liver of the rats fed the SPI or protein-free diet was apparently lower than in that of rats fed the casein diet. If the plasma somatomedin C is important for protein anabolism as it is suggested by many authors, the above results show that the nutritive value of SPI could be improved by supplementing methionine.

METABOLIC FATES OF CARBON SKELETONS OF AMINO ACIDS IN GROWING RATS FED ON THE SOY PROTEIN ISOLATE DIETS

Hideyuki TANAKA and Masaji OGURA

Faculty of Agriculture, Utsunomiya University

Nutr. Sci. Soy Protein, Jpn. 10, 96-102, 1989.

The metabolic responses to dietary protein intake have been investigated in growing rats fed on the diets containing graded levels (0, 5, 10, 15, 20, 30, and 40 protein calorie percent, PC%) of the soy protein isolate "Fujipro R" at 4100 kcal of metabolizable energy per kg of diet. Body weight gain and food efficiency reached a plateau at 20 PC% in the diet. Protein efficiency ratio (PER) attained a maximum at 10 PC%, being estimated to be 2.4 for soy protein isolate while 3.9 for purified whole egg protein. The body protein retention increased from 0 to 20 PC%, and thereafter it remained almost constant. As for body composition, the carcass lipid content gave a blunt peak from 5 to 20 PC% and the liver lipid content at 5 PC% was significantly increased to a level of the so-called fatty liver. At 12 hr after the intraperitoneal injection of L - [U-14C] methionine and L - [U-14C] threonine, the percentage recoveries of the radioactivity in body protein, lipid and soluble fractions were approximately 70, 3 and 10% of the injected dose, respectively. The overall oxidative degradation of labeled methionine and threonine to expired 14CO2 was depressed at the lower PC%, but it increased gradually at higher PC% in the diet. The results suggest that the carbon skeleton of methionine or threonine is preferentially utilized for protein synthesis, and that the metabolic response of these amino acids to protein intake changes at around 20 PC%, where the growth rate reached its maximum.

EFFECTS OF SPI OR SPI HYDROLYSATE DIET ON THE RESISTANCE TO STREPTOCOCCAL INFECTION IN MICE

Shigeru YAMAMOTO ¹ and Fusao OTA ²

¹ Faculty of Medicine, University of the Ryukyus
² School of Dentistry, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 10, 103-105, 1989.

Effects of SPI or SPI hydrolysate diet on the resistance against a bacterial infection were studied in mice. Female ddy strain weaning mice were fed 20% casein (control), 40% casein, 40% soy protein or 40% SPI hydrolysate diet. On day 15 on the diets, the mice were injected intraperitoneally with 5 Å~ 103 group B streptococci/g body weight and their survival rates were observed for the following 10 days. The food intakes and growth of animals of all the groups were similar. The resistances of mice fed 40% casein, SPI or SPI hydrolysate were not different statistically.

EFFECT OF SOY PROTEIN ISOLATE ON AMELIORATION OF NUTRITIONAL STATUS IN PORTACAVAL SHUNTED RATS

Yasuhiro KIDO, Fumiko TADA, Fujiko SHIZUKA, Reiko INAI,
Goro INOUE and Kyoichi KISHI

School of Medicine, The University of Tokushima

Nutr. Sci. Soy Protein, Jpn. 10, 106-112, 1989.

The effect of soy protein isolate (SPI) on amelioration of nutritional status was examined in adult rats with portacaval shunt (PCS) using sham-operated rats as controls. Animals were fed a diet containing 10, 20 or 40% protein for 2 weeks. Protein sources were SPI and 1.5% methionine supplemented casein. Food intake and body weight gain of PCS rats were lower than those of controls in 40% protein diet group. Liver weight was decreased by PCS, but the decrease was not affected by dietary protein level and source. The plasma BCAA/AAA ratio was significantly reduced by PCS, but there was no difference between the rats fed SPI and casein diets. With an increase in dietary protein, the plasma and brain methionine concentrations increased in PCS rats fed casein diet as compared with the control, but not in rats fed SPI diets. These results suggest that the use of SPI as a protein source in the nutritional treatment of liver cirrhosis may be useful for improving abnormal methionine metabolism.

EFFECT OF SOY PROTEIN DIET IN PATIENTS WITH LIVER CIRRHOSIS

Takashi YOSHIDA and Yasutoshi MUTO

School of Medicine, Gifu University

Nutr. Sci. Soy Protein, Jpn. 10, 113-116, 1989.

Six patients with liver cirrhosis were administered a soy protein rich (50% of total protein) vegetable protein diet (protein 80 g/day, energy 2,100 kcal/day) for 4 weeks. There were no significant changes in blood ammonia level, plasma amino acid concentration and transaminase activity during soy protein diet period. Concentration of plasma proteins, i.e., total protein and albumin decreased slightly but insignificantly.

USEFULNESS OF SOY PEPTIDE IN THE PATIENTS WITH CROHNÅL S DISEASE

Tadao BAMBA, Nobuo CHIKAMOCHI, Kenji FUSE and Shiro HOSODA

Shiga University of Medical Science

Nutr. Sci. Soy Protein, Jpn. 10, 117-121, 1989.

Elemental diet containing amino acid mixture is recognized as the primary therapy in the patients with Crohn's disease. As peptides are more easily absorbed than amino acids from the intestine, we studied the effect of peptides as intraluminal substrates on the brush border membrane enzymes and the absorption of amino acids and peptides in the hamster, which fed elemental diet containing either amino acid mixture (AA) or peptides (SP) for 4 weeks. Aminopeptidase activity significantly increased in the group fed SP than in the group fed AA, while maltase activity was almost the same between two groups. Potential difference of L-leucine and glycyl-leucine significantly increased in the group fed SP, and PDmax of them was also significantly higher in the group fed SP than in the group fed AA, but Kt value was almost the same between two groups. On the contrary, PDmax and Kt value of d-glucose were nearly the same between two groups. Therefore, peptide as intraluminal substrates may not only induce the aminopeptidase but also affect the amino acid transporter as well as peptide ones. Clinically, the nutritional assessment was studied in the patients with Crohn's disease, who were given the diet having total energy 1800 kcal made by soy peptide (90 g/day) as nitrogen, fat (20 g/day) and carbohydrate (290 g/day). The body weight, total protein and cholesterol levels in the patients with Crohn's disease increased and serum aminogram was well balanced during the administration of soy peptide. In conclusion, soy peptide may be useful to maintain the nutritional state and improvement of Crohn's disease patients.

THE LONG - TERM EFFECT OF SOY PROTEIN ON GLUCOSE UTILIZATION AND INSULIN SENSITIVITY OF THE PERIPHERAL TISSUE

Manabu NARIMIYA, Kenji ISHII and Yoshio IKEDA

The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 10, 122-126, 1989

The effect of protein on the glucose utilization and insulin sensitivity of rat hindlimb muscles was investigated. The present study was aimed mainly at its long-term effect. Studies were performed on male Wistar rats, weighing about 250 g. First, rats were given soy protein or albumin orally, and one hour later they were prepared for hindlimb perfusion. Second, for the purpose of studying the long-term effect of soy protein, rats were fed soy protein diet ad libitum for 4 weeks, and then the hindlimb perfusion was attempted. Plasma glucose and insulin concentrations were comparable in the two groups when soy protein or albumin was orally given respectively. The clearance of glucose by hindlimb skeletal muscle was examined in the absence of added insulin among the two groups, compared with the control. The soy protein and the albumin fed rat groups cleared glucose from the medium approximately 60 and 40%, respectively, more than did the control, whereas at various insulin levels, the clearance of glucose by hindlimb skeletal muscle was comparable among the three groups. The four week feeding of the soy protein diet or the control diet brought about a significant rise in basal plasma glucose concentration, however, the rise was comparable in the two groups. But there was no significant difference in plasma insulin concentration. The clearance of glucose by hindlimb skeletal muscle was comparable in the two groups in the absence of added insulin and at perfusate insulin levels of 62.5 and 125 É U/ml, while the soy protein diet caused a significant rise at a perfusate insulin level of 500 É U/ml. The four week feeding of each diet, however, decreased the clearance of glucose by hindlimb skeletal muscle at a respective perfusate insulin level.

The soy protein protein reserch(Japan)