The Soy Protein Research Committee(Japan)

STUDIES ON RIPENING MECHANISM OF TOFUYO USING SOY PROTIEN ISOLATEÅFDEGRADATION OF SOYBEAN PROTEIN BY MONASCUS - PROTEINASE

Masaaki YASUDA, Maki SAKAGUCHI and Naotada KOBAMOTO

College of Agriculture, University of the Ryukyus

Nutr. Sci. Soy Protein, Jpn. 13, 7-11, 1992.

The authors have established a simple and new method of tofuyo prepared by soy protein isolate for an "experimental model system". In this model system, changes in soybean protein and nitrogen compounds, and physical changes of the product during ripening period were examined in order to reveal ripening mechanism of tofuyo. Monascus-proteinase is considered to be served as a key enzyme for ripening of the product. It is unique and characteristic that the ripening was carried out under the presence of ethyl alcohol of awamori (distilled liquor). In this study, effects of ethyl alcohol on the activities of the purified enzyme examined, and also mode of its action toward soybean protein by the enzyme were investigated. The enzyme activities decreased as the ethyl alcohol concentration increased. When 10, 20 and 30% of ethyl alcohol were added to the reaction mixture, the relative activities were 70, 25 and 3%, of no addition treatment, respectively. The ratio of trichloroacetic acid (TCA) soluble nitrogen to total nitrogen in the reaction products was found to increase with increasing reaction time. When 0, 10 and 20% of ethyl alcohol were added to the reaction mixture, values of the ratio after incubation for 72 hrs were 82, 62 and 42%, respectively. On the other hand, the ratio of TCA insoluble nitrogen to total nitrogen decreased with increasing reaction time. The ratio of TCA insoluble nitrogen to total nitrogen under presence of a high ethyl alcohol concentration was higher than that of a low ethyl alcohol concentration. And thus, the enzyme activities were depressed by ethyl alcohol. Digestion of soybean protein by the enzyme was examined by the method of slab polyacrylamide gel electrophoresis (PAGE). When ethyl alcohol was absent, some polypeptide bands of soybean globulin such as Éø'-, Éø- and É¿-subunits in É¿-conglycinin, and acidic subunit in glycinin disappeared after 10 min incubation, but that of basic subunit in glycinin still remained after 24 hr incubation. On the other hand, when 20% of ethyl alcohol was present, polypeptide bands of Éø'-, Éø- and É¿-subunits in É¿-conglycinin disappeared, but those of acidic and basic subunits in glycinin were detected after 24 hr incubation.

DEPRESSION OF n - HEXANAL FORMATION IN SOY PROTEIN PRODUCTS

Makoto KITO and Hitoshi TAKAMURA

Research Institute for Food Science, Kyoto University

Nutr. Sci. Soy Protein, Jpn. 13, 12-14, 1992.

Soybean seeds contain three lipoxygenase isozymes. The functions of these lipoxygenase isozymes in n-hexanal generation were investigated by using mutant lines which lack two or three isozymes. In the presence of linoleic acid, the level of n-hexanal produced was highest in the lipoxygenase-1, -3 double deficient line, followed by the lipoxygenase-2, -3 double deficient, wild type, and lipoxygenase-1, -2, -3 triple deficient lines in that order, and lowest in the lipoxygenase-1, -2 double deficient line. This suggests that lipoxygenase-3 itself cannot produce the n-hexanal precursor and inhibits the n-hexanal generation through other pathways.

DEVELOPMENT IN NOVEL FUNCTIONAL FOOD MATERIALS BY HYBRIDIZATION OF SOY PROTEIN TO GALACTOMANNAN TYPE POLYSACCHARIDES

Kunihiko KOBAYASHI, Akio KATO and Naotoshi MATSUDOMI

Faculty of Agriculture, Yamaguchi University

Nutr. Sci. Soy Protein, Jpn. 13, 15-21, 1992.

In previous report (Nutr. Sci. Soy Protein, Jpn. 11, 23-28 1990), acid precipitated soy protein (APP)-dextran (Dx) and commercial soy protein (FPR)-Dx hybrids obtained by dry-heating at 60Åé, 65% relative humidity for 3 weeks were showed to be excellent as commercial emulsifiers. For practical application, the Dx was replaced by galactomannan (GM) in this report. The GM was microbial galactomannase hydrolysate of guar gum, average molecular weight 21,000Å`22,000. SDS-PAGE patterns showed by stain of protein and carbohydrate that APP+GM and FPR+GM heated mixtures for 3 weeks contained hybrids of higher molecular weight, respectively. Emulsifying properties of APP + GM heated mixture were excellent as well as commercial emulsifiers. Those of FPR+GM heated mixture were insufficient as emulsifier, because the hybridization was incomplete. Then, in a preliminary experiment, APP and FPR subtilisin hydrolysates (APPÅES and FPRÅES, respectively) of APP and FPR were used for formation of hybrid with GM by dry heating. In the results, APPÅES+GM and FPRÅES+GM heated mixtures for 2 weeks, as compared with commercial emulsifiers, were much more excellent in emulsifying properties, especially in acidic solution in which most commercial emulsifiers were limited the application. Thus, it was suggested that in case of insoluble proteins, such as soy protein isolate, gluten and zein etc., their partial hydrolysates by protease were available for preparation of proteinpolysaccharide hybrids.

STUDIES ON PLANT CYSTATINS

Soichi ARAI

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 13, 22-26, 1992.

A full-length cDNA clone for a cysteine proteinase inhibitor (cystatin) was isolated from a É…gtl0 cDNA library of immature corn kernels by screening with a mixture of cDNA inserts for oryzacystatins I and II. The cDNA clone spans 960 base pairs, encoding a 135 amino acid protein containing a signal peptide fragment. The protein, named corn cystatin I, is considered to be a member of the cystatin superfamily, since it contains the commonly conserved Gln-Val-Val-Ala-Gly region that exists in most known cystatins as a probable binding site and is significantly similar to other cystatins in its overall amino acid sequence. Northern blot analysis showed that the amount of mRNA for corn cystatin I reaches a maximum 2 weeks after flowering and then decreases gradually.

SUPPLEMENTATION OF SPI PEPTIDE - BASED DIET WITH BRANCHED CHAIN AMINO ACIDS AND GLUTAMINEÅFTHEIR EFFECTS ON INTESTINAL FUNCTION AND SERUM AMINO ACID CONCENTRATION IN JEJUNECTOMIZED RATS IN CONVALESCENCE

Kaoru SUGIYAMA, Toshikatsu OKADA, Kimikazu IWAMI and Fumio IBUKI

Faculty of Agriculture, Kyoto Prefectural University

Nutr. Sci. Soy Protein, Jpn. 13, 27-33, 1992.

Wistar rats weighing about 250 g were jejunectomized between 15 cm below the pylorus and 30 cm above the ileocecal valve, and a SPI peptide (Hinute PM) - based diet for convalescence was supplemented with both branched chain amino acids and glutamine. The effect of the supplementation became conspicuous in body weight gain from a week after the jejunal resection. On the 10th day, the rats given the supplemental diets with and without these amino acids were sacrificed by drawing blood to excise small intestine. Then, the activity levels of brush border enzymes and Na+-dependent amino acid or sugar uptake capacity were investigated with five segments of the small intestine. Although there was no significant difference in enzyme activity between the jejunectomized rats with or without amino acid supplementation and the sham-operated ones, the active transport capacities for leucine and glucose tended to be somewhat higher in the vicinity of suture in the former than in the latter. It was assumed from the results of amino acid analysis that the supplementation of postoperative food with "emergency" amino acids would be effective in convalescence without risk of causing amino acid imbalance.

BIOAVAILABILITY OF METHIONINE IN SOYBEAN PEPTIDEÅF COMPARISON WITH SOYBEAN PROTEIN IN INCREASING HEPATIC É¡ - GLUTAMIYLTRANSFERASE ACTIVITY

Misao TANIGUCHI and Chizuru KINOSHITA

Department of Food and Nutrition, Nakamura Gakuen College

Nutr. Sci. Soy Protein, Jpn. 13, 34-37, 1992.

When weanling male rats were fed a 10% SPI diet for 3 weeks, hepatic É¡- glutamyltransferase (GGT) activity increased in comparison with that fed a 10% casein or laboratory chow diet. Supplement of 0.3% methionine to a 10% SPI diet suppressed increase of GGT activity, but not by cystine. By feeding a 10% soybean peptide diet, increase of GGT activity was suppressed slightly, but statistically not significant. On the other hand, significant suppression of GGT activity was observed in rats fed a purified soybean peptide diet. Response of GGT activity to glucocorticoid (GC) was demonstrated in hepatocytes prepared from weanling rats and rats fed a 10% SPI diet while response to GC was repressed during growth when fed a laboratory chow diet. Comparing with a SPI diet, response of GGT activity in primary cultured hepatocytes to GC was slightly lowered by feeding on a purified soybean peptide diet. These results indicate that low bioavailability of methionine in SPI was improved by digesting SPI to peptides and/or removing non-peptide fractions.

NUTRITIONAL EVALUATION OF SPI - DERIVED PEPTIDES IN RATS ÅF THE EFFECTS OF PEPTIDE CHAIN LENGTH ON THE DIGESTIVE INTENSITY OF OLIGO - L - METHIONINE

Hirosi HARA, Takuji SUZUKI and Shuhachi KIRIYAMA

Faculty of Agriculture, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 13, 38-42, 1992.

The digestive intensity of oligo-L-methionine (OM) was observed in rats fed OM containing diets based SPI, peptic digest of SPI (SPI-LP) and small peptide of SPI (SPI-SP). The growth potency of a 10% SPI-LP diet was significantly higher than that of a 10% SPI-SP diet. Supplementary effect of 0.3% OM to SPI-SP diet tended to be higher than that to SPI diet. Porto-arterial difference of methionine derived from OM, which is an absorptive indication of early stages of feeding, was higher in the SPI-LP group than in the SPI group. The digestibility of OM evaluated by fecal excretion of undigested OM in the rats fed the SPI-LP and SPI-SP based diets were significantly higher than that in the rats fed the SPI diet. When dietary protein level was increased to 20%, the differences of OM digestibility between the protein sources were similar to those in the 10% protein groups. But, the digestibility of OM in the 20% protein diet fed rats were lower than those in the 10% protein diet fed rats. The OM digestibilities of the SPI-SP groups were similar to those of the SPI-LP groups in both 10% and 20% protein levels. These results represent that the gastrointestinal functions associated with OM digestion in the rats fed SPI-LP and SPI-SP were higher than those in the rats fed SPI. The lower digestibility of OM in 20% protein groups suggest that not only the pancreatic protease secretion, but also the competitive inhibitory activity of dietary protein in the lumen was responsible for the OM digestion in the gut.

EFFECT OF SPI INTAKE ON THE LIVER CONTENT OF MESSENGER RNAs OF INSULIN - LIKE GROWTH FACTOR BINDING PROTEINS - 1 AND - 3 IN RATS

Asako TAKENAKA, Shin-ichiro TAKAHASHI and Tadashi NOGUCHI

Faculty of Agriculture, The University of Tokyo

Nutr. Sci. Soy Protein, Jpn. 13, 43-45, 1992.

Messenger RNAs of insulin-like growth factor binding protein (IGFBP) -1 and IGFBP-3 were determined in the liver of rats fed on SPI diet, SPI diet supplemented with methionine, casein diet, and protein-free diet. IGFBP-1 mRNA increased significantly in the liver of the rats fed on the protein-free or SPI diet compared with those fed on the casein diet. However, when SPI diet was supplemented with methionine, IGFBP-1 mRNA content in liver was depressed greatly. On the other hand, liver IGFBP-3 mRNA content did not differ significantly among the 4 dietary groups. These results show that the nutritive value of SPI for young growing rats can be improved significantly by supplementing methionine.

EFFECTS OF SOY PROTEIN ISOLATE ON SUCROSE - INDUCED OBESITY IN POST - WEANLING RATS

Eiko HARA ¹ and Takashi SHIMAZU ²

¹ Imabari Meitoku Junior College
² School of Medicine, Ehime University

Nutr. Sci. Soy Protein, Jpn. 13, 46-49, 1992.

Effects of dietary soy protein isolate (SPI) on sucrose-induced fat accumulation were examined in rats after weaning. Rats were fed experimental diets containing 20% casein or 20% SPI for 9 days and then they were forced to drink 15% sucrose solution for 12 days. Although they drank about 20 mL of the sucrose solution per day which amounted to approximately 20% of total calorie intake, increase in the total calorie intake was not observed as compared with water-drunk controls. Body weight gain in sucrose-drunk or SPI-fed rats tended to be less than that in water-drunk or casein-fed rats. Tissue weight and triglyceride (TG) content of the brown adipose tissue (BAT) were increased by sucrose drinking or by SPI feeding. However, serum TG levels were significantly lower in SPI-fed rats, whether they drank sucrose or tap water, despite the TG contents of liver were higher in these animals. These results indicate that SPI has a serum lipid-lowering effect presumably by suppressing the release of TG (lipoprotein) from the liver.

EFFECTS OF SOY PEPTIDES ON WEIGHT REDUCTION IN HYPOTHALAMIC OBESE MICE

Masayuki SAITO

Faculty of Veterinary Medicine, Hokkaido University

Nutr. Sci. Soy Protein, Jpn. 13, 50-52, 1992.

Effects of dietary soy peptides on body weight and brown adipose tissue (BAT) thermogenesis were examined in hypothalamic obese mice induced by the treatment with goldthioglucose or monosodium glutamate. When the obese mice were fed on a diet containing soy peptides as a very low calorie diet (VLCD), they lost body weight more and had smaller parametrial white adipose tissue than lean control mice, while gastrocnemius muscle weight decreased little. The thermogenic activity of BAT, assessed from GDP-binding to mitochondria, was decreased in obese mice compared with control mice, but it was increased after feeding the soy peptide diet. Thus, soy peptide seems to be available to VLCD for the treatment of obesity.

EFFECTS OF SOYÅFPEPTIDE CONSUMPTION ON DIET INDUCED THERMOGENESIS

Tatsushi KOMATSU ¹,Keiko KOMATSU ² and Minoru YAMAGISHI ³

¹ Department of Nutrition in Hospital, Universtiy of Occupational and Environmental Health
² Fukuoka Prefectural University
³ Department of Pediatrics, University of Occupational and Environmental Health

Nutr. Sci. Soy Protein, Jpn. 13, 53-58, 1992.

The effect of nitrogen source on the thermic response was investigated in six male subjects. Each subject consumed four different test meals on a different day. The basal diet (BD) contained 800 kcal and 30 g of protein without protein supplement. The other three test meals contained 800 kcal and supplemented with 15 g of different nitrogen sources (total protein level is 45 g), such as lactalbumin (LA), soy protein isolate (SPI) and soypeptide (SPT). Energy expenditure (EE) was measured by indirect calorimetry using the Douglas bag technique before and 30-min intervals until 3 hours after test meal. Blood samples were collected before and 30 minutes after meal. All subjects showed a significant increase over base line in EE after all test meals. The cumulative increases in EE after meals were 29.9Å}8.9, 35.9Å}9.0, 34.6Å}15.5 and 44.3Å}10.8 kcal/3h for BD, LA, SPI and SPT, respectively, indicating no significant effect of nitrogen sources. The mean increments of plasma insulin and glucagon concentrations after meal were slightly larger in LA and in LA and SPT, respectively than in other meals. Compared to fasting level, plasma T4 elevated after SPT meal while plasma T3 did not change after all test meals. These data suggest that, though the effect of nitrogen source on the acute thermic response within 3 hours is not clear, T4 induced by SPT meal may have some effect on chronic thermogenesis in long term over 24 hours.

EFFECT OF SOY PROTEIN ON URINARY ALBUMIN EXCRETION AND GLOMERULAR FILTRATION RATE IN SPONTANEOUSLY DEVELOPED DIABETIC WBN/Kob RATS

Yoshio IKEDA and Yutaka MORI

Third Department of Internal Medicine, Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 13, 59-63,1992.

To evaluate the effects of chronic protein loading on urinary albumin excretion (UAE) and glomerular filtration rate (GFR), 45 diabetic WBN/Kob rats aged 8 months were given 15 g per day of 5, 20 and 40% protein diets from different sources for 9 weeks. Codfish, pork and soybean were used as protein source and 9 kinds of diets were made. Plasma urea nitrogen levels decreased in all of 5% protein diet-fed groups and increased in all of 40% protein diet-fed groups significantly. UAE decreased significantly in all of 5% protein diet-fed groups. However, there was no significant difference in UAE between codfish, pork and soybean diets. UAE in 40% protein diet-fed groups increased although it was not statistically significant. Urinary NAG excretion also decreased significantly in all of 5% protein diet-fed groups. Although creatinine clearance rate (Ccr) decreased in all of 5% protein diet-fed groups, no significant increase of Ccr was observed in 40% protein diet-fed groups. These results suggest that the effect of chronic protein loading may differ with the previous data concerning the effect of acute protein loading and an important factor in prevention of development of diabetic nephropathy is protein intake rather than kind of protein.

EFFECTS OF SOY PROTEIN ISOLATE ON RECOVERY OF IMMUNOSUPPRESSION INDUCED BY ORGANOTIN COMPOUNDS

Masashi NAITOH, Ayami MORIMOTO, Yasuaki ARAKAWA and Hideo KOISHI

School of Food and Nutritional Sciences, University of Shizuoka

Nutr. Sci. Soy Protein, Jpn. 13, 64-69, 1992.

Effects of soy protein isolate (SPI) on recovery of immunosuppression induced by organotin compounds were studied in rats. Rats were divided into two groups in which one fed casein diet and the other fed SPI diet for 8 weeks. Both diets contained 24% protein. Experimental diet contained 5 ppm of dibutyltin-chloride (DBTC). In control groups, thymus weight and number of thymocyte of rats fed SPI diet were less than those of rats fed casein diet. In experimental groups, the body weights of rats were not changed compared with those of control but the weight of thymus gland and number of thymocyte reduced to some half of those of control after one week. Continuing the same diet, however, the weight of thymus and number of thymocyte draw near the control value after 8 weeks. Rats fed SPI diet significantly less reduced the weight of thymus and number of thymocyte and catched up faster to the control than the rats fed casein diet after 8 weeks.

EFFECT OF SOYBEAN PROTEIN ISOLATE ON CAFFEINE - INDUCED HYPERCALCIURIA IN RATS

Shigeru SAEKI ¹, Kimio SUGIYAMA ¹, Yoshiyuki SUGIURA ¹,
Norio YAMANAKA ¹,Yukari TANAKA ¹ and Keiichiro MURAMATSU ²

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

Nutr. Sci. Soy Protein, Jpn. 13, 70-75, 1992.

The present study was undertaken to examine the effects of dietary proteins on caffeineinduced hypercalciuria in rats. When caffeine was added to a 25% casein diet at the graded levels (0.10Å`0.30%), the urinary calcium (Ca) excretion was significantly increased at the levels of 0.25 and 0.30% of caffeine. Caffeine also exhibited a decrease in breaking force of femur. When 0.30% caffeine was added to the diet containing one of various proteins such as casein, sardine protein, soybean protein isolate and wheat gluten adjusted the nitrogen content of each diet to the same level as that in the 25% casein diet, the urinary Ca excretion was significantly higher in rats fed wheat gluten than in those fed the other proteins. The addition of caffeine to a high protein diet containing casein produced a significant increase in the urinary Ca excretion in rats fed a high protein diet containing soybean protein isolate. The urinary Ca excretion was not correlated with the sulfur amino acid content of the proteins used here. These findings indicate that the caffeine-induced hypercalciuria would be modulated by the type and the level of dietary protein, although the effect of dietary protein appears not to be related to differences in the sulfur amino acid content.

EFFECT OF SOYBEAN WHEY PROTEIN ON SKIN TUMOR IN MICE

Shigeru YAMAMOTO ¹, Kayoko UEZU ¹,Liu ASATO ¹,Porn-ngarm LIMTRAKUL ² and Maitree SUTTAJIT ²

¹ Faculty of Medicine, University of the Ryukyus
² Faculty of Medicine, Chiang Mai University

Nutr. Sci. Soy Protein, Jpn. 13, 76-79, 1992.

We studied the effect of soybean whey protein on skin tumor promotion by two-stage carcinogenesis method. Mice were given SPI (Fujipro R) diet or SPI diet supplemented with soybean whey protein. After a week on the diets, the hair of mice was shaved and tumor initiator was applied. Then tumor promoter was applied twice a week on the same area of the skin throughout the experiment. The percentage of tumor-bearing mice and the average number and volume of tumor after 14 weeks on the treatment were lower in the whey diet group than in the SPI diet group. The result indicates the anticarcinogenic effect of soybean whey protein.

EFFECTS OF PHYTATE REMOVAL FROM SPI HYDROLYZATE ON THE CALCIUM AND ZINC BIOAVAILABILITIES IN THE GROWING RATS

Yoshiaki NIIYAMA ¹,Sadaichi SAKAMOTO ¹,Kazuko OKADA ¹,Takaharu MATSUO ² and Minoru KIMOTO²

¹ Department of Nutrition, School of Medicine, The University of Tokushima
² Fuji Oil Company

Nutr. Sci. Soy Protein, Jpn. 13, 80-85, 1992.

Effect of phytic acid removal from SPI hydrolyzate on mineral bioavailabilities was examined in weanling rats. For phytate removal, the SPI hydrolyzate solution was adjusted to pH 4.5 with citric acid and then passed through a column packed with ion exchange resin. Accordingly, three diets of SPI-hydrolyzate (designated as SP), SPI-hydrolyzate with citric acid (SCP) and SPI-hydrolyzate without phytate (SC) were tested for mineral bioavailability. Dietary levels (%) of citric acid and phytic acid were 0 and 0.62 in SP, 2.3 and 0.60 in SCP and 1.7 and 0.01 in SC, respectively. Calcium and zinc contents in the three diets were 0.5 g/kg and 35 mg/kg, respectively. After measurements of calcium and zinc balances during final 6 days of 3 week feeding period, mineral contents in tissues (plasma, kidney and femur) were determined. Apparent absorption and retention of dietary calcium were negatively correlated with the amounts of dietary citric acid and phytate, while those of dietary zinc were not influenced by dietary phytate, showing that the phytate-less SPI hyrolyzate was beneficial for calcium utilization. Nephrocalcinosis found in SP group did not appear in SCP and SC groups, indicating citric acid prevented renal calcium accumulation. Effect of dietary citric acid on renal calcium was examined histologically and chemically in rats fed diets containing different protein sources.

PREPARATION OF HYPOALLERGENIC SOYBEAN PRODUCTSÅF IDENTIFICATION OF ALLERGENIC PROTEINS IN SOYBEANS

Tadashi OGAWA, Hideaki TSUJI and Noriko BANDO

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

Nutr. Sci. Soy Protein, Jpn. 13, 86-91, 1992.

A number of patients with atopic dermatitis are considered to be suffering from food allergy. Soybeans are known as one major allergenic foods and the allergenicity resides in protein fractions. It is of important to define the allergenic components in soybeans in order to develop hypoallergenic soybean products for soybean-sensitive patients. IgE-binding proteins (allergens) have been characterized by SDS-PAGE and immunoblot methods using sera of the patients with atopic dermatitis. About 15 components of soybean proteins were recognized by patient's sera and about two-thirds of them were assigned to the components in the 7S-globulin fraction. A unique protein with a molecular mass of about 30-kDa in the 7S-globulin fraction bound most strongly and frequently with the patient's IgEs, which was named as Gly m Bd 30k, a major allergen in soybeans. Éø-Subunit of É¿-conglycinin was also found to be allergenic, while Éø'- and É¿-subunits were not reactive. Kunitz soybean trypsin inhibitor was scarcely recognized by the patient's sera. Sera of almost all patients were shown to lack the IgEs recognizing the proteins in the 11S-globulin fraction. This fact suggests that conglycinin may be less allergenic to the soybean-sensitive patients with atopic dermatitis.

EFFECTS OF DIETARY PROTEIN CONTENT AND SPECIES ON GENE EXPRESSION AND INDUCTION OF LIPOGENIC ENZYMES IN RAT LIVER

Nobuko IRITANI ¹,Hiroko HOSOMI ¹ Hitomi FUKUDA ¹ and Takehiko TANAKA ²

¹ Tezukayama Gakuin College
² Osaka University Medical School

Nutr. Sci. Soy Protein, Jpn. 13, 92-96, 1992.

The effects of dietary protein content and species on gene expression and induction of lipogenic enzymes, and triglyceride levels in rat liver were investigated. The mRNA concentrations of lipogenic enzymes were generally high in the 10% protein diet, suggesting that the mRNA induction is carbohydrate-dependent. On the other hand, the enzyme activities of acetyl-CoA carboxylase and ATP-citrate lyase were not altered with dietary protein content, that of malic enzyme tended to be increased and those of fatty acid synthase and glucose-6-phosphate dehydrogenase, particularly the latter, were increased in the 20, 30 and 40% protein diet groups. It appeared that protein feeding was required for the translation. The triglyceride content of the liver was low in the 10% protein diet and high in the 30-40% protein diet groups. Although these results were similar in the casein- or soy protein-fed rats, the levels were always lower in the soy protein than in the casein. The urinary excretion of norepinephrine tended to be higher in the soy protein group. Energy metabolic rate might be increased by feeding soy protein.

NUTRITIONAL SPECIFICITY OF SOY PROTEIN DIET FOR LIPID METABOLISM IN RATS

Shinichi NIWA, Hiroaki ODA and Akira YOSHIDA

School of Agriculture, Nagoya University

Nutr. Sci. Soy Protein, Jpn. 13, 97-100, 1992.

We demonstrated previously that soyprotein had a hypocholesterolemic effect in rats as compared with either casein or rice protein although fecal excretion of steroids was stimulated by either soyprotein or riceprotein. We concluded that the soyprotein diet decreased the serum level of cholesterol partially decreasing the secretion of lipoproteins from the liver due to the insufficient synthesis of apolipoproteins. In the present paper, we investigated the effect of dietary protein on the LDL-receptor and LDL-receptor related protein (LRP) in the liver. Male rats of the Wistar strain were fed 15% protein diets. Dietary proteins were either casein, soyprotein isolate (SPI), or riceprotein concentrate. Experimental period was 1 or 7 days, and LDL-receptor and LRP in liver membrane fraction were estimated by Western blotting analyses. The results indicated that both LDL-receptor and LRP were not affected by the dietary proteins tested. HMG-CoA reductase activity and its mRNA in livers of rats fed either SPI or riceprotein diet were similarly higher than those of rats fed the casein diet. These results further suggest the importance of apolipoprotein syntheses and their secretion from the liver for controlling the serum level of cholesterol together with the fecal excretion of bile acids.

EFFECTS OF DIETARY PROTEINS ON PLASMA CHOLESTEROL LEVEL AND FECAL STEROID EXCRETION RATES IN VARIOUS SPECIES OF ANIMALS

Shin-ichi HAYASHI, Miwako NAKAGAWA, Sanae TERASAKI,
Hiroko TAKIZAWA and Youichi MIYAZAKI

Department of Nutrition, The Jikei University School of Medicine

Nutr. Sci. Soy Protein, Jpn. 13, 101-104, 1992.

Experimental data so far obtained in our laboratory concerning effects of soy protein isolate (SPI), compared with casein, on plasma cholesterol level and fecal steroid excretion as compared between rats, mice and Syrian hamsters were collectively evaluated. Of 11 experiments with rats, SPI lowered plasma cholesterol level significantly in 5 experiments and tended to do so, though not significant statistically, in 3 experiments, whereas it stimulated fecal steroid excretion in 8 experiments, In contrast, of 10 experiments with mice, SPI never exhibited hypocholesterolemic effect and did not stimulate fecal steroid excretion in all but one experiments. Of 4 experiments with Syrian hamsters, SPI lowered plasma cholesterol level significantly in one experiment and tended to do so in 2 experiments, whereas it stimulated fecal steroid excretion in 3 experiments. These results strongly suggest that (1) SPI does not exhibit hypocholesterolemic effect in mice since it does not stimulate fecal steroid excretion, (2) SPI exhibits often, but not always, hypocholesterolemic effect in rats and hamsters since it stimulates fecal steroid excretion in these species of animals, and (3) although fecal steroid excretion is an important factor that determines plasma cholesterol level, there must be other factors that also affect plasma cholesterol level, It should be noted that it appeared to be casein rather than SPI that showed species specific response in cholesterol metabolism. Thus casein does not stimulate fecal steroid excretion in rats and hamsters, causing hypercholesterolemia, whereas it stimulates steroid excretion in mice, as well as SPI does, thus not causing hypercholesterolemia in this species. Of the 4 experiments with hamsters, SPI caused higher contents of radioactive steroids in liver in 3 experiments and in plasma in all experiments, indicating suppression of transfer of radioactive cholesterol from the plasma into peripheral tissues. Growth of hamsters were retarded when they were fed high-fat diets containing 0.5 percent cholesterol and 0.125 percent cholate. The retardation of growth, however, was significantly less in SPI-fed group than casein-fed group. These results indicated that SPI and casein exert quite different influence to cholesterol transport and metabolism in the body.

HYPOCHOLESTEROLEMIC EFFECT OF UNDIGESTED FRACTION OF SOYBEAN PROTEIN

Michihiro SUGANO, Takashi OGAWA and Marites GATCHALIAN-YEE

Faculty of Agriculture, Kyushu University

Nutr. Sci. Soy Protein, Jpn. 13, 105-107, 1992.

The undigested fraction (UDF) of soybean protein exerted a significant hypocholesterolemic activity in rats even under the experimental protocols in which the diet free of cholesterol was given. Thus, UDF prevented an age-related rise in serum cholesterol. There was a gradual decrease in serum cholesterol with an increasing proportion of UDF in the casein diet, and a 50% replacement produced a reasonable reduction. The cholesterol-lowering effect of UDF could be attributable to an enhancement of fecal steroid excretion. In addition, UDF appeared to interfere with the desaturation of linoleic acid to arachidonic acid more than soybean protein as compared with casein. Therefore, multifunctional potential may be expected to UDF.

EFFECT OF SOY PROTEIN AND/OR SOY FIBER ON SERUM AND LIVER LIPID CONCENTRATION IN THE RAT

Fujiko SHIZUKA, Yoshinobu MATSUMOTO, Kaori AIHARA,
Yuko TAKEUCHI, Yasuhiro KIDO and Kyoichi KISHI

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

Nutr. Sci. Soy Protein, Jpn. 13, 108-114, 1992.

The hypolipidemic effect of soy protein isolate (SPI) and/or soy fiber was compared with casein, or cellulose and pectin, as protein or dietary fibers, respectively, in the rat fed diets supplemented with or without cholesterol, with corn oil or lard as dietary lipid. The concentration of serum triglyceride but not cholesterol was lower in rats fed SPI than casein regardless of dietary cholesterol levels or lipid sources. Soy fiber introduced into casein diet supplemented with cholesterol also decreased the concentration of serum triglyceride, which was not further decreased by feeding SPI. Pectin prevented the increase of serum and liver cholesterol caused by feeding 1% cholesterol supplemented diet, but the hypocholesterolemic effect of soy fiber as well as cellulose was not observed. However, when supplementation of cholesterol in the diet was decreased to 0.5%, soy fiber lowered serum cholesterol than cellulose. Neither SPI nor soy fiber clearly prevented the accumulation of liver lipids induced by feeding cholesterol.

EFFECT OF ENERGY RESTRICTION OR EXERCISE ON NITROGEN BALANCE IN YOUNG WOMEN FED A CONVENTIONAL LOW PROTEIN DIET CONTAINING SOY PROTEIN ISOLATE

Kayoko KANEKO ¹,Goro KOIKE ² and Mitsuyo AIKYO ²

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

Nutr. Sci. Soy Protein, Jpn. 13, 115-121, 1992.

Effect of energy restriction by reducing energy intake and addition of aerobic exercise on nitrogen (N) balance was studied in non-obese thirteen female students aged 19 to 22 years old. Six of them were fed in order two experimental diets containing 145 and 175 mg N/kg/day and low energy as 1.25 times of basal metabolism (BM) for 10 days each. Other seven subjects performed aerobic exercise (jogging and ergometer exercise) at energy expenditure of about 200 kcal/day during two 10-day experimental periods given low in energy (1.44 times of BM) and N at intake levels of 145 and 175 mg/kg/day. Calculated energy balance was negative about 200 to 300 kcal/day in both groups. Means of weight loss during 10 days of experimental periods were 0.6 to 1.0 kg, not significantly different between two groups or N intake levels in a group. Both groups were able to establish N balance at two levels of N intake, and N balances were improved slightly when N intake increased from 145 to 175 mg/kg/day in both groups. The group exercised in addition to energy restriction achieved more positive N balance than sedentary group. Combined the results of the present experiment with the previous data (1987), a significant regression equation in N intake (x) and N balance (y) was calculated and the figure of 139 mg-N/kg-BW/day as intersection of the regression line with zero balance was obtained. N requirement was increased 45% compared with that supplied adequate energy reported previously (1988).

USEFULNESS OF SOYBEAN PEPTIDES AS A NITROGEN SOURCE IN THE PATIENTS WITH MALABSORPTION SYNDROME

Tadao BAMBA, Masaya SASAKI, Takuzo NAMBU and Shiro HOSODA

Second Department of Internal Medicine, Shiga University of Medical Science

Nutr. Sci. Soy Protein, Jpn. 13, 122-126, 1992.

Fat digestion and absorption are easily and often disturbed in the patients with malabsorption syndrome, compared to other nutrients. Therefore, the contents of fat in diets or enteral nutrients will affect the nutritional improvement of the patients. Body weight and serum albumin were significantly decreased in patients with moderate fat malabsorption, when daily fat intake was less than 10 g/day. On the other hand, peptides are more easily absorbed than amino acids. In this meeting, we previously reported that peptides as an intraluminal substrate induced aminopeptidase in brush border membrane, and increased the peptide transporters as well as amino acid transporters. The patients with intestinal diseases including Crohn's disease were administered soybean peptide drinks (3 bottles/day, 30 g as protein), when the nutritional treatment of the patients was gradually changed from enteral nutrition to ordinary diet. In general, the nutritional state tends to be reduced during adaptation to diets. However, the supplementation with soybean peptide drinks to diet seemed to help maintaining the nutritional state of the patients.

EFFECTS OF SOY - PEPTIDE ON PLASMA LIPIDS FOR 4 WEEKS

Haruo NAKAMURA and Emiko MIYAJIMA

National Defence Medical College

Nutr. Sci. Soy Protein, Jpn. 13, 127-129, 1992.

Since our previous results concerning the effects of soy protein intake by normal volunteers on plasma lipids showed the significant decrease of plasma cholesterol by the intake of 20-40g protein per day. We investigated last year to find out minimal dosage capable to reduce plasma cholesterol by administering 14 g/day of protein to the 13 normal volunteers for 2 weeks and failed to achieve significant decrease. In this experiment, we further extended the administration period to 4 weeks in order to assess whether plasma cholesterol would decrease at the period. Total cholesterol increased slightly and significantly. However, this increase was found due to the changes in the subjects with lower plasma cholesterol level. LDL-cholesterol, HDL-cholesterol and triglyceride remained almost unchanged. Apoprotein E reduced significantly without changing apoprotein A-I and B. HDL3 cholesterol increased significantly. In conclusion, present results confirmed the previous experiment that it would be required to administer at least 20 g/day to decrease plasma cholesterol.

EFFECTS OF SOY PROTEIN DIET ON LIPID METABOLISM IN PATIENTS WITH HYPERLIPIDEMIA AND WITH ISCHEMIC HEART DISEASE ÅF CORRELATION BETWEEN SOY PROTEIN INTAKE AND LIPIDS LEVELS

Hiromitsu TAMACHI ¹, Tomooki IWAMOTO ¹, Koji NAKAYAMA ¹,Yoshiko NAKAYAMA ¹, Yuichi FUSEGAWA ¹, Yutaka SHINA ¹,Yuichiro GOTO ¹Hiroaki ISHII ², Honami FUJII ² and Miho HIDA ²

¹ Tokai University School of Medicine
² Tokai University Hospital

Nutr. Sci. Soy Protein, Jpn. 13, 130-136, 1992

The effects of substituting soy protein for protein in the basal diet on lipid metabolism were investigated in eight male patients with ischemic heart disease. Administration of basal diet, substituted with 12g of soy protein for one week resulted in lowered levels of serum TG, VLDL-C and VLDL-TG significantly, and produced a tendency to lower levels of VLDLphospholipid and ApoB/ApoA-I ratios, suggesting that 12g of soy protein intake may improve TG metabolism in patients with ischemic heart disease.

The soy protein protein reserch(Japan)