The Soy Protein Research Committee(Japan)

CHANGES IN LIPIDS DURING SPI STORAGE

Masao FUJIMAKI, Seiichi HOMMA, Reiko NAKAYAMA and Ko AIDA

Department of Nutrition and Food Science, Ochanomizu University

Nutr. Sci. Soy Protein, Jpn. 7, 5-8, 1986.

Trace amounts of lipids in defatted soy bean and soy protein isolate were extracted with 86% ethanol. The work was focused on the polar lipids such as glycolipid and phospholipid. The extracted lipids were applied on a silicic acid column, and then successively eluted with chloroform (simple lipid), acetone (glycolipid) and methanol (phospholipid). The simple lipid fraction was subjected to HPLC with a reverse phase column of Lichrosorb RP-18 to determine triglyceride composition. The significant difference was not found among the chromatograms of soy bean oil, defatted soy meal and soy protein isolate. The amount of glycolipid fraction of soy protein isolate was almost similar to that of defatted soy meal. This fraction was analyzed by TLC on silica gel, and four spots were detected with Éø-naphthol reagent. These soy products were allowed to stand at 40Åé for one month under RH 30 or 70%. The storage resulted in the decrease in the amounts of glycolipid fraction of the soy protein isolate under both RH 30 and 70% storages, and these fractions gave similar four spots positive with Éø-naphthol reagent to those of the 4Åé storage sample. A little increase was found in the amount of glycolipid fraction of the defatted soy meal stored under RH 70% in which only one spot was detected with Éø-naphthol reagent. The phospholipid fraction was analyzed by TLC and detected with Dittmer's reagent. The four phospholipids were found in both samples. Their amounts were large in phosphatidylcholine and phospatidylinositol, followed phosphatidylethanolamine and phosphatidic acid. The amounts of phospholipid fraction of defatted soy meal and soy protein isolate were reduced by the storages of both RH 30 and 70%. The distinct degradation was found in the phospholipid fraction of soy protein isolate stored under RH 70% among the three fractions separated, and phosphatidylethanolamine and phosphatidylcholine were remarkably reduced. The apparent increase in the simple lipid and glycolipid fractions of the defatted soy meal stored under RH 70% seems to be caused by the formation of oxidized products from phospholipid, which in turn were eluted into these two fractions of silicic acid column chromatography according to their polarity. The degradation of lipid was more remarkable in defatted soy meal than in soy protein isolate, and it is due to enzymes, as lipoxygenase still active in the defatted soy meal, which would catalyze the oxidation of lipid under high RH.

REDUCTION OF GRASSY BEANY FLAVOR IN LIPOXYGENASE DEFICIENT MUTANTS OF SOYBEANS

Teruyoshi MATOBA ¹,Hiroshi HIDAKA ², Hiroshi NARITA ²,Makoto KITO ²,Keisuke KITAMURA ³ and Norihiko KAZUMA ³

¹ Department of Food Science and Nutrition, Nara WomenÅLs University
² Research Institute for Food Science, Kyoto University
³ Faculty of Agriculture, Iwate University

Nutr. Sci. Soy Protein, Jpn. 7, 9-13, 1986.

The process of development of n-hexanal from soybean homogenate was investigated by using Glycine max var. Suzuyutaka (wild type) and the following lipoxygenase (L) deficient mutant seeds (L null); L-1 null, L-2 null, L-3 null, and L-1, -3 null. n-Hexanal was determined during the incubation of the homogenates of these seeds at 25Åé. The level of n-hexanal was the lowest in the L-2 null homogenate and the highest in the L-1, -3 null homogenate. After the addition of linoleic acid to the homogenates, the level of n-hexanal increased remarkably in the homogenates from the seeds except for L-2 null. n-Hexanal was scarcely generated in the L-2 null homogenate. These results suggest that L-2 isozyme is responsible for n-hexanal formation by using free linoleic acid as the substrate. When the soybean extract prepared from these seeds was incubated at 70Åé, n-hexanal formation was the lowest in the L-2 null soybean extract.

ENZYMATICALLY MODIFIED SOY PROTEIN PRODUCED WITH COVALENT INCORPORATION OF Åm15NÅn METHIONINEÅFITS BEHAVIOR IN THE RAT SMALL - INTESTINAL TRACT

Soichi ARAI ¹ and Hiroko KIMURA ²

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

Nutr. Sci. Soy Protein, Jpn. 7, 14-17, 1986.

It is known that when a mixture of soy protein isolate (SPI) and L-methionine ethyl ester (L-MetÅEOEt) is incubated with papain, an enzymatically modified protein (EMP), which has incorporated L-methionine in a covalent manner at to C-terminal, can be obtained. The present study first elucidated that L- [15N] -MetÅEOEt was almost similarly incorporated. When DL-[15N]-MetÅEOEt was used, the L-isomer was incorporated to produce 15N-Met-EMP. Using this product, we undertook a feeding test with rats to characterize the behavior of exogenous (dietary) methionine. The test demonstrated that 15N species existed mostly in an oligopeptide fraction of the small-intestinal content over a period of digestion of the EMP. However, 15N-Met appeared in the free form in the systemic blood over the same period. It was thus possible by using the present procedure to differentiate the behavior of the fed methionine from that of exogenous methionine.

STUDY ON QUANTITATIVE DETECTION OF SOYBEAN PROTEIN ADMIXED WITH PROCESSED MEAT PRODUCTS ÅFENZYMELINKED IMMUNO - SORBENT ASSAY OF HEAT PROCESSED SOYBEAN PROTEIN

Kyoden YASUMOTO, Toru WATSUJI, Miki SUDO, Hiroshi TODORIKI
and Tetsuya SUZUKI

Research Institute for Food Science, Kyoto University

Nutr. Sci. Soy Protein, Jpn. 7, 18-21, 1986.

Various methods have been employed for the quantitative detection of plant proteins admixd with meat products. Most of the methods so far employed, however, have proved quite untenable for quantitation of plant proteins contained in heat-processed meat products. The present paper reports the quantitative determination of the heat denatured soybean proteins by measurement of a heat stable penta-peptide designated "SP-1", which derives from a basic subunit of soybean 11S globulin. SP-1 was detected by enzyme-linked immuno-sorbent assay (ELISA). Anti SP-1 antibody was raised in mouse by injecting into the abdominal cavity the SP-1 conjugated with keyhole limpet hemocyanin (KLH) in complete Freund adjuvant. Animals were boosted weekly for 4 weeks. The ascitic fluids were withdrawn periodically and purified by passing through a KLH-linked Sephadex column. Purified SP-1 ranging from 0.1 to 640 ng/ml gave a quantitative response when evaluated from the enzyme activity of anti-mouse IgG-peroxidase conjugate bound to the immobilized KLH-SP-1 antigen in competition with added free SP-1 and produced a workable calibration curve. Soybean protein isolate which was autoclaved and subsequently digested with trypsin could be quantitated by the competitive ELISA. Satisfactory results were also obtained for defatted soybean flakes after heat treatment and subsequent trypsin digestion. A very poor response was observed with the soybean protein and flakes when assayed before trypsin digestion. The experimental results presented in this paper allowed us to conlcude that competitive ELISA for a specific peptide SP-1 can be used as a sensitive and specific tool to quantitate 11S soybean proteins in the heat processed products.

SURVEY OF BIOLOGICALLY ACTIVE PEPTIDES IN TRYPSIN-DIGEST OF SOY PROTEIN ISOLATE(SPI)

Hiroshi NAITO, Akio TAKENAKA and Tadashi NOGUCHI

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 7, 22-24, 1986.

Trypsin digest of SPI showed the activity to enhance the ureogenesis of primary cultured hepatocytes of rats. The active principle in the SPI digest was partially purified by Sephadex G-25 gel filtration and CM-Sephadex chromatography. The active principle enhanced ureogenesis at the similar rate both in the presence and absence of glucagon in the culture medium. The results suggest that some physiologically active peptides can be prepared from the trypsin digest of SPI.

EFFECT OF CHRONIC FEEDING OF SOY PROTEIN ISOLATE ON THE ADVANCE OF SENESCENCE IN THE SENESCENCE ACCELERATED MOUSE (SAM)

Atsuko KOHNO, Makiko UMEZAWA, Masanori HOSOKAWA and Toshio TAKEDA

Department of Pathology, Chest Disease Research Institute, Kyoto University

Nutr. Sci. Soy Protein, Jpn. 7, 25-29, 1986.

A murine model of accelerated senescence, the Senescence Accelerated Mouse (SAM), consisting of senescence-prone (SAM-P) series and senescence resistant (SAM-R) series, was recently developed in our laboratory. Judging from the ageing characteristics such as changes in grading score with advancing age, life span, ageing dynamics and autopsy findings, the ageing pattern in this model seems to be due to an accelerated senescence rather than to a premature ageing. The present studies were undertaken to observe the effect of soy protein feeding on the grading score of senescence, deposition of senile amyloid (AS/SAM), mean life span, survival and the incidence of thymoma using SAM-P/1, SAM-P/7 and SAM-R/1 strains of mice. The experimental groups consisted of soy protein group (fed SPI as protein source) and casein group (fed casein as protein source). The growth curve of these three strains and the grading score of SAM-P/1 and SAM-P/7 revealed no significant difference between the two groups. The increase in grading score of SAM-R/1 fed soy protein diet for 18Å`22 months was suppressed compared to that fed casein diet. Survival at 18 months after the start of experiment was much greater in soy protein group (75.0%) than that in casein group (38.8%). Survivorship curves of SAM-P/1 and SAM-P/7 fed soy protein shifted slightly to the right side of the each curve of the strains fed casein diet. In SAM-P/7, the mean life span of 30% survivors in soy protein group was significantly greater than that in casein group. There were no significant differences in the severity of senile amyloid deposition and in the incidence of thymoma between the two groups of SAM-P/1 and SAM-P/7, respectively. These results suggested that chronic feeding of soy protein diet affected more efficiently to the normal ageing than to the accelerated senescence.

NUTRITIONAL REASSESSMENT OF SOY PROTEIN ISOLATE IN ADULT RATSÅFEFFECT ON AGE - RELATED PROTEINURIA

Yoshiaki FUJITA and Tomoko OZEKI

Nutrition Research Laboratory, Tokyo Metropolitan Institute of Gerontology

Nutr. Sci. Soy Protein, Jpn. 7, 30-34, 1986.

Nutritional characteristics of soy protein isolate were reassessed in adult rats in relation to protein metabolism, serum lipids and age-related proteinuria. Three-months-old rats (Wistar strain, male) were divided into 6 groups of 8 rats each. In experiment 1 (control dietary energy), animals were fed 16 g/day of 20% protein diet containing lactalbumin (LA), casein (CA) or soy protein isolate (SPI) for 6 months. In experiment 2 (50% restricted dietary energy), the other 3 groups received 8 g/day of 40% protein diet instead of 20% protein diet, respectively. From results, we concluded that in adult rats consuming a diet sufficient in protein 1) effect of SPI on whole body protein metabolism is almost the same as that in lactalbumin or casein, irrespective of dietary energy, 2) SPI functions as a hypocholesterolemic factor under control dietary energy and as a hypotriglyceridemic factor under restricted dietary energy, and 3) effect of SPI on age-related proteinuria is slightly different from that of lactalbumin or casein, but not under restricted dietary energy.

ACUTE AND CHRONIC RESPONSES OF PANCREATIC EXOCRINE CARBOXYPEPTIDASE A SECRETION TO DIFFERENT DIETARY PROTEINS AND OLIGOMETHIONINE IN RATS

Shuhachi KIRIYAMA, Hideyuki CHIJI and Yuki KUNIEDA

Faculty of Agriculture, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 7, 35-40, 1986.

1. Acute effects of dietary proteins on the rate of oligomethionine digestion associated with pancreatic exocrine protease secretion : Methionine (Met) is the common first limiting amino acid in both 8% casein (8C) and 10% soybean protein isolate (10S) diets, and has a significant supplementary effect to these diets as assessed by rat growth. Similarly when 8C diet was supplemented with 0.3% oligomethionine preparation (a mixture of hexa- and hepta-peptides, abbreviated as OM) weanling rats grew at the same rate as that attained with a 8C+Met or 10S + Met diet. When OM was supplemented to 10S diet, however, little or no growth promotion was observed. The first aim of this study was to clarify the mechanism by which OM digestion or absorption was changed by the kind of dietary protein used. Rats maintained on 25C and 25S diets for 2 weeks were refed a 8C + 3% OM or 10S + 3% OM diet (2 g each) after overnight fast, and portal blood was collected 30 min after the start of the refeeding. Met concentration of the portal blood plasma (PBP) from rats refed the 8C+3OM diet was significantly higher than that of rats refed 8C, 10S, or 10S + 3% OM, irrespective of prefed dietary proteins. These differences in OM digestibility paralleled trypsin or carboxypeptidase A (CPA) activity in small intestinal contents.
2. Adaptive increase in pancreatic carboxypeptidase A activity and OM - digestion due to chronic ingestion of OM : Rats prefed 8C or l0S diet with or without added 3% OM for 2 weeks were fasted overnight and refed 8C or 8C + 3% OM (2 g each). Met concentration in PBP and pancreatic CPA, trypsin, and chymotrypsin activities were determined 30 min after refeeding. Only the rats previously consumed OM showed a significantly higher Met concentration in PBP in response to refeeding the OM-containing diet. Pancreatic CPA level was also significantly higher in rats fed OM previously. From these results, we concluded that luminal OM-digestion is increased by concurrent ingestion of the protein such as casein that is known to have potential capacity to stimulate pancreatic exocrine protease secretion, and that prolonged OM-feeding specifically enhances pancreatic CPA production, probably via stimulation of unknown secretagogue-releasing site different from that dietary protein interacts with.

EFFECT OF METHIONINE SUPPLEMENTATION TO A LOW SOY PROTEIN DIET ON THE BRAIN FREE AMINO ACIDS, SEROTONIN AND CATECHOLAMINES IN RATS

Akira YOSHIDA, Hidehiko YOKOGOSHI and M. DIKSHIT

School of Agriculture, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 7, 41-46, 1986.

Effects of methionine supplementation to a low soy protein diet on the brain free amino acids, serotonin and catecholamines in rats were investigated for the study of safe range of methionine supplementation. Male young rats of the Wistar strain were fed a 9% soy protein basal diet or methionine supplemented diets. The basal diet contained about 0.23% of sulfur amino acids and the supplemented levels of methionine in diets were 0.5, 1.0, 2.0 or 4.0%. Animals were fed the experimental diets for 8 days. At the end of the experimental period, animals were sacrificed and serum and brain free amino acids, brain serotonin and catecholamines were determined. Dietary supplementation of 0.5% of methionine significantly improved the body weight gain of rats, 1% of methionine supplementation improved less significantly and further supplementation decreased the body weight gains as compared to the control group. Brain tryptophan concentration decreased with 2 or 4% of supplementation of methionine together with the decrease in brain concentration of serotonin and 5-hydroxyindole acetic acid. Similarly, high level of supplementation (2 and 4%) of methionine decreased the brain level of norepinephrine. These results indicate the supplementation of methionine over 1% to the low soy protein diet decreased not only the body weight gain but also decreased the neurotransmitters, serotonin and catecholamines in the brain.

NUTRITIVE VALUE OF SOYBEAN WHEY PROTEIN IN YOUNG RATS AND HUMAN ADULTS

Kyoichi KISHI ¹, Sachiko TERAI ¹, Sachiko Ooguri ¹,
Fujiko SHIZUKA ¹,Shigeru YAMAMOTO ¹ and Goro INOUE ²

¹ Department of Nutrition, School of Medicine, The University of Tokushima
² Koshien University

Nutr. Sci. Soy Protein, Jpn. 7, 47-52, 1986.

Soybean whey contains 7Å`9% of the total protein present in the soybean meal and the quality of soybean whey protein is supposed to be higher than that of acid precipitated soy protein isolate (SPI). However, soybean whey is presently discarded as a waste product of SPI processing because of antinutritional components and presents a waste disposal problem. In the present study we determined the digestibility and the utilization of soybean whey protein (SWP) in growing rats (Expt. 1) and human adults (Expt. 2). SWP was separated from whey solution (pH 4.5 supernatant) by ultrafiltration (MW = 40,000) and was heated at 168Åé for two minutes followed by lyophilization. In experiment 1, male rats of the Wistar strain weighing about 60g were fed ad libitum 3, 5, 10 and 15% (N Å~ 6.25) SWP, 10% SPI, 0.3% methionine supplemented 10% SPI (SM) and 10% casein (C) for 21 days. Rats receiving SWP showed lower food intake but comparable weight gain with SM and C groups of rats. The weight gain of SPI group was lowest among groups. The digestibility of SWP was lower than SPI and C but net protein utilization was similar to SM and better than SPI and C. In experiment 2, four healthy male subjects received a SPI diet and a SWP diet for 10 days each at 90 mg/kg/day of N intake. Dry fecal weight was significantly heavier in SWP than SPI (28.8 vs. 21.0 g/day). Thus the digestibility of SWP (92.2%) was lower than SPI (99.5%). However, the biological value of SWP was comparable to SPI. It was concluded that the quality of SWP used in the present study was higher but the digestibility was lower than those of SPI.

EFFECT OF SUPPLEMENTING METHIONINE TO SOY PROTEIN ISOLATE ON THE PROTEIN UTILIZATION IN MALE ADULT HUMANS (3rd Report)

Tetsuzo TAKAHASHI ¹ and Tetsuo YAMADA ²

¹ Faculty of Home Economics and Science, Tokyo Kasei University
² Institute of Health and Sports Sciences, University of Tsukuba

Nutr. Sci. Soy Protein, Jpn. 7, 53-58, 1986.

As the results of the previous two studies, four of the five subjects showed the improved nitrogen balance by the addition of methionine to soy protein isolate (SPI) under the condition of nitrogen intake levels of 90 and 75 mg/kg/day. Further study on the effect of supplementation of methionine to SPI on the protein utilization was conducted in five healthy young men. They were given one-day protein free diet, four-day low protein habitual diet and then nine-day SPI diet containing 60 mg N/kg/day. After the first experiment, the second experiment, in which the SPI diet was supplemented with L-methionine at a level of 1.0% of protein, was repeated. Energy intake was approximately 42Å`44 kcal/kg/day. The nitrogen balance was improved by the addition of methionine in four of the subjects. The result was the same as obtained in the previous studies. One subject, to whom the methionine supplementation produced no beneficial effect, attended all of the three studies and showed the same tendency. One subject was non-athlete, while remaining four subjects were athlete. The effect of addition of methionine was observed more markedly in the daytime than in bed.

EFFECTS OF METHIONINE SUPPLEMENTATION TO SOY PROTEIN ISOLATE ON PROTEIN UTILIZATION IN YOUNG MEN - IN CASE OF LOW ENERGY INTAKE -

Toyoko OKUDA, Hiroko MIYOSHI, Yuriko OI, Yoshimi TAKIGAWA,
Keiko SHIMOKOJIN and Hideo KOISHI

Faculty of Science of Living, Osaka City University

Nutr. Sci. Soy Protein, Jpn. 7, 59-63, 1986.

Effects of L-methionine supplementation to the soy protein isolate (SPI) were examined in five healthy young men receiving low energy diet. After one day of a protein free diet, the subjects were given a standard energy SPI diet (44.0Å}3.5 kcal/kg/day) for 3 days and then were given a low energy SPI diet (35.2Å}2.8 kcal/kg/day) for 8 days. The SPI diet contains 100 mg N/kg/day. After 3 days of a standard protein diet (200 mg N/kg/day, 44.0Å}3.5 kcal/kg/day), the SPI diet was repeated. The second SPI diet (SPI + Met) was supplemented with methionine at a level of 1.5% of protein. Nitrogen balances determined on the SPI diet and the SPI+Met diet for the final 4 days were negative. Supplementation of methionine to the low energy SPI diet did not show any significant difference on nitrogen balance, availability of food energy and blood status.

EFFECTS OF DIETARY AMINO ACIDS ON LIPOGENIC ENZYME INDUCTION IN RAT LIVERS

Nobuko IRITANI ¹,Akemi SUGA 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. 7, 64 -67, 1986.

The inductions of liver lipogenic enzymes were markedly lower in rats fed soybean protein than in those fed casein. The triglyceride levels in plasma and especially in liver were also lower in the soybean group. When dietary protein was replaced with amino acids to simulate casein or soybean protein, the effects on the levels of glucose-6-phosphate dehydrogenase and malic enzyme were still found but were not as great, while no effects were found on acetyl-CoA carboxylase and fatty acid synthetase. Supplement with 1% of cystine to the casein diet or the casein amino acid diet decreased the inductions of glucose-6-phosphate dehydrogenase and malic enzyme, and removal of cystine from the amino acid diet increased the inductions. However, the supplement and removal of cystine did not effect on any induction of acetyl-CoA carboxylase and fatty acid synthetase. Thus, it is suggested that some effects can be ascribed to the amino acid composition and some to the protein itself.

EFFECTS OF FOOD PROTEINS (SPI, GLUTEN, OVALBUMIN AND CASEIN) AND THEIR PROTEOLYTIC PRODUCTS ON BILE ACID REABSORPTION IN RAT SMALL INTESTINE IN RELATION TO PLASMA CHOLESTEROL - LOWERING EFFECT

Fumio IBUKI and Kimikazu IWAMI

Faculty of Agriculture, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 7, 68-75, 1986.

Male Wistar rats weighing 110Å`120 g were divided into (A) casein, (B) ovalbumin, (C) SPI and (D) gluten groups (n=6Å`8), which were fed ad libitum the corresponding diets for 3 weeks. The diets of C and D groups were supplemented with the limiting amino acids, respectively, so that no significant difference was observed in growth among the four groups. During the feeding period, the daily faeces were collected and stored at -20Åé until use. At the 3rd week, all rats were sacrificed to collect blood to excise tissues. The plasma cholesterol was C

EFFECTS OF DIETARY PROTEIN ON FECAL STEROL EXCRETIONS

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

Department of Nutrition, The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 7, 76-79, 1986.

(1) Male Sprague-Dawley rats were maintained on various diets and plasma cholesterol levels and sterol excretions in feces were compared at 9, 13, and 29 weeks of age. (2) Plasma cholesterol level was highest in rats fed 25% casein, lowest in rats fed either 25% SPI or laboratory chow, and within medium range in rats fed either 50% casein or 25% gluten. (3) In general, fecal excretions of both neutral and acidic sterols were smallest in rats fed 25% casein, largest in rats fed laboratory chow, second largest in rats fed 25% SPI, and within medium range in rats fed either 50% casein or 25% gluten. (4) The inverse correlation observed between plasma cholesterol level and fecal excretion of sterols indicated that the hypocholesterolemic effect of SPI or of laboratory chow is mainly mediated by increased excretion of sterols into feces.

RELATIONSHIP BETWEEN AMINO ACID COMPOSITION OF SOY PROTEIN ISOLATE AND PLASMA CHOLESTEROL LEVELS IN RATS

Kimio SUGIYAMA and Keiichiro MURAMATSU

Faculty of Agriculture, Shizuoka University

Nutr. Sci. Soy Protein, Jpn. 7, 80-85, 1986.

Experiments were conducted to investigate the relationship between amino acid composition of dietary protein and plasma cholesterol levels with rats fed diets containing amino acid mixture essentially simulating casein or soy protein isolate (SPI) in the presence or absence of dietary cholesterol. A higher plasma cholesterol level induced by feeding the casein-simulating amino acid mixture diet was decreased by reducing dietary Met content (or increasing Cys content) in both animals fed high cholesterol and cholesterol-free diets. Although the amino acid mixture resembling SPI led to a lower plasma cholesterol level, the deprivation of Cys (or increase in Met) and/or Gly from the amino acid diets caused the enhancement of plasma cholesterol level. Elevation of plasma cholesterol level which was induced by relatively high Met (or low Cys) diets was markedly depressed by the omission of dietary choline. The results suggest that the differential effect of casein and SPI on the plasma cholesterol level might be attributable to the different composition of sulfur amino acids and Gly.

HYPOCHOLESTEROLEMIC EFFECT OF SOY PROTEIN ISOLATE IN RATS (Ö•)ÅFDIETARY PROTEIN - DEPENDENT CHANGE IN INTESTINAL CHOLESTEROGENESIS

Michihiro SUGANO, Hirosuke OKU and Takashi IDE

Kyushu University School of Agriculture

Nutr. Sci. Soy Protein, Jpn. 7, 86-89, 1986.

In the present study, the effects of dietary proteins on rat intestinal 3-hydroxy-3- methylglutaryl-CoA (HMG-CoA) reductase and serum lipids were compared. When the diet was changed from a commercial non-purified diet to a purified diet containing either soybean protein or casein as a protein source, the reductase activity in the jejunum increased progressively while that in the ileum decreased. The extent of the change in the jejunal activity was prominent in rats fed soybean protein. When the casein diet was replaced by the soybean protein diet, the enzyme activity increased progressively both in the jejunum and ileum. The protein-dependent change became apparent within 1 to 3 days. Among the various animal (sardine and lactalbumin) and vegetable (soybean and wheat gluten) proteins tested, soybean protein was the one that had a specific effect on the intestinal reductase. The concentrations of serum cholesterol were in rats fed vegetable proteins, while only soybean protein exerted the hepatic cholesterol-lowering action.

EFFECT OF SOY PROTEIN ISOLATE ON PLATELET AGGREGATION IN RATS, SHRSP

Meng-Tsan CHIANG, Michio KOMAI and Shuichi KIMURA

Faculty of Agriculture, Tohoku University

Nutr. Sci. Soy Protein, Jpn. 7, 90-93, 1986.

Effects of soy protein isolate (SPI) diet on plasma lipid level and platelet aggregation in SHRSP and Wistar Kyoto rats (WKY) were studied in comparison with casein diet. The levels of plasma total cholesterol and triglycerides were decreased in SHRSP fed 20% SPI diet and drunk 1% NaCl solution for 30 days, whereas there was no change in WKY. In addition, the rise of systolic blood pressure was significantly repressed in SHRSP fed SPI diet after 30 days. It is noteworthy that the platelet aggregation in WKY fed SPI diet is lower when compared with casein diet. These results indicate that antiatherosclerotic effect of SPI is considerable compared with the animal protein in stroke-prone animal model.

EFFECT OF SOY PROTEIN ISOLATE ON LIPID METABOLISM IN MEN

Masayuki MATSUSHITA ¹, Seiki NAMBU ¹, Hideki KOH ¹, Masako WAKI ¹,Shigeki FUJII ¹, Yasuko NISHIOHEDA ¹, Motoo TSUSHIMA ¹,
Teruaki NARIKAWA ², Michio FURUSAWA ² and Tadao NAKANO ²

¹ Division of Atherosclerosis and Metabolism, Department of Internal Medicine National Cardiovascular Center
² Division of Nutritional Education, National Cardiovascular Center

Nutr. Sci. Soy Protein, Jpn. 7, 94-99, 1986.

Two experiments were carried out to examine the effect of soy protein isolate (S
PI) on the lipid metabolism in men. In the first experiment, eight male hospital
ized subjects (mean age 57 years, range 48-70 years), six with normocholesterole
mia and two with hypercholesterolemia, were standardized on a diet (1,100 kcal/d
ay) for 6 weeks preceding the addition of SPI. Then all subjects were given an i
socaloric SPI diet containing 25 g of SPI (36% of total protein content) for 8 days. Serum cholesterol, triglyceride and HDL-cholesterol were measured. In the second experiment, one male and three female hospitalized subjects with hypercholesterolemia (mean age 66 years, range 61-74 years) were standardized on a butter load diet (1,860 kcal/day, P/S ratio: 0.6) for 11 days preceding the addition of SPI. Then an isocaloric butter loading SPI diet containing 25 g of SPI (23% of total protein content) for 9 days. Serum cholesterol, triglyceride, HDL-cholesterol, VLDL-cholesterol (total and free), VLDL-triglyceride and apo A-I, A-II, B, C-II, E were measured. The results obtained were as follows: 1) In normocholesterolemic subjects, total cholesterol level in serum decreased on the restricted energy intake. However, no significant hypocholesterolemic effect of SPI was observed on the restriction of energy. 2) In two hypercholesterolemic subjects, their total cholesterol levels were not reduced by the restricted energy intake and SPI obviously diminished total cholesterol level within the normal range in a few days. 3) In four hypercholesterolemic subjects, the butter load diet without the restricted energy intake was increased total cholesterol level in serum significantly (pÅÉ0.05). Total cholesterol and apo B levels were unchanged despite of the addition of SPI. 4) SPI diminished serum triglyceride level significantly (pÅÉ0.05) and had a tendency to increase HDL-cholesterol level (pÅÉ0.10) on the butter loading SPI diet. 5) No remarkable changes of serum apo A-I, A-II, C-II levels and ratios of apo A-I/apo A-II and apo C-II/apo E were observed before and after the addition of SPI on the butter load diet. 6) SPI reduced the ratio of VLDL free/total cholesterol in three hypercholesterolemic subjects with high ratio before the addition of SPI. It was indicated that SPI had no significant hypocholesterolemic effect without the restricted energy intake but improved the catabolic disturbance of VLDL.

EFFECT OF SOY PROTEIN DIET IN PATIENTS WITH LIVER CIRRHOSIS

Yasutoshi MUTO and Takashi YOSHIDA

1st Department of Internal Medicine, School of Medicine. Gifu University

Nutr. Sci. Soy Protein, Jpn. 7, 100-104, 1986

Twelve patients with cirrhosis were administrated a soy protein rich (40Å`50%) vegetable protein diet (protein 70 g, energy 2,000 kcal). There were statistically significant reductions of blood ammonia level from 91.0Å}41.3 to 64.9Å}21.9 É g/ml (pÅÉ0.05) after three day administration of soy protein diet. No significant changes in concentrations of blood urea nitrogen and plasma amino acids. Two patients with chronic hepatic encephalopathy were treated with soy-protein rich diet for long term (more than 3 weeks). In patient on low protein diet (30 g/day), soy protein diet significantly decreased blood ammonia level and increased plasma albumin concentration. However, recurrence of hepatic encephalopathy was observed in 2 weeks after administration of high protein diet (60 g/day).

The soy protein protein reserch(Japan)