Influence of sulfur-amino acid content variation in plant vs animal protein on serum and tissue lipids in rats

The objective of the study was to determine the effects of methionine and cysteine supplementation of soy protein isolate and casein on serum and tissue lipid levels in rats. Sixty male, weanling, Wistar-Kyoto rats were fed two sources of protein (casein or soy protein isolate) and three variations of sulfur-amino acid supplementation (none, methionine, or cysteine). At this level of protein intake (10% by weight), rats fed soy-based diets had similar serum lipid concentrations than rats fed casein-based diets. Choline was not added to the diet in order to be able to assess independent influences of methionine and cysteine on lipid metabolism. Overall, serum lipid values were greater in rats fed proteins supplemented with methionine while the addition of cysteine produced lower lipid levels. Liver lipid concentrations were increased tremendously upon cysteine supplementation of soy protein isolate. Protein quality, as determined by protein efficiency ratio, was improved by supplementation of either sulfur-amino acid; however, methionine had the greatest effect. Results indicate that the sulfur-amino acids influence lipid metabolism in the absence of dietary choline. The mechanism by which this occurs is not known.     

The cholesterol-lowering property of soybeans fed to rats is related to the fasting duration

Numerous factors affect plasma cholesterol and, therefore, representpotential interferences with the specific effects of diet on lipid metabolism.After casein intake, serum cholesterol levels depend on many experimentalconditions in rats, such as the type of casein, the presence or absence ofcholesterol in the diet, the age and strain of rat, the diet composition, thenutritional status. The effect of fasting duration on selected parameters wasstudied in adult male Wistar rats fed a 20% casein and 1% cholesterol-based diet. No changes were observed in total serum, lipoproteins-B andHDL cholesterol and in triglyceride values after an 8 h-fast compared tonon-fasted animals. A significant decrease was induced in total andlipoproteins-B cholesterol with a 12 h-fast. A prolonged fast resulted ina significant decrease in these parameters and in triglycerides and inHDL-cholesterol levels.Fasted animals fed heated soybean meal instead of casein did not display amarked decrease in serum lipids. It appeared that the fasting effect wasmore marked in animals fed casein than in animals fed soybeans. Theseresults showed the importance of experimental conditions such as nutritional status ofanimals when blood samples are taken in studies of the hypocholesterolemiceffect of soy protein compared to casein.     

The USDA trypsin inhibitor study. IV. The chronic effects of soy flour and soy protein isolate on the pancreas in rats after two years

In two year feeding trials, histologic changes in the pancreas of the Wistar rat were evaluated after chronic dietary exposure to raw and heated, dehulled, defatted soy flour and soy protein isolates which provided a range of trypsin inhibitor (TI) concentrations from 93 to 1271 mg/100 g diet. Also investigated was the nutritional interaction of level of dietary protein with the development of pancreatic pathology. Graded levels of TI were achieved from mixtures of raw and heated soy flour or protein isolate. Dietary protein levels were 10%, 20%, and 30%; the two higher levels obtained in some diets through casein supplementation. A total of 26 diets, including casein controls, were fed to groups of 40 male rats. Growth rates with these diets were commensurate with protein quality and level. Mortality rates tended to be slightly greater in the higher protein diets, and rats fed only raw soy as a source of protein survived well.Two lesions, nodular hyperplasia (NH) and acinar adenoma (AA) constituted the major pathological findings in the pancreas, and the incidence rates of both were positively associated with the concentration of dietary TI. The incidences of pancreatic NH and AA compared to those of the corresponding casein control were significantly elevated in rats fed heated soy flour supplying 10% protein and the lowest level of TI investigated (93 mg/100 g diet). At low levels of TI (215 mg/100 g diet), supplementation by casein to raise the concentration of protein from 10% to 20% and 30% reduced the frequency of NH and AA. When the dose-response data for NH and AA was linearized by plotting the probit of percent incidence against log of TI concentration per gram of dietary protein, the response to soy flour and soy protein isolate was not significantly different. Numerous lesions commonly found in the aging rat were diagnosed, and modulation of their rate of occurrence by nutritional factors associated with the diets was apparent in some instances.Reference to a company and/or product named by the Department is only for purposes of information and does not imply approval or recommendation of the product to the exclusion of others which may also be suitable.     

Influence of dietary soybean trypsin inhibitors and DL-ethionine on sulfur amino acid adequacy of diets for young rats

Weanling male Wistar rats were fed 20% protein diets based on casein or either of two combinations of soy protein isolate and ground raw soy providing three levels of soybean trypsin inhibitors (SBTI; 0,448 and 808 mg of trypsin inhibited per 100g of diet respectively). DL-ethionine was included at three levels (0,0.05% and 0.10%) with each level of SBTI. After 4, 8 and 12 weeks ofad libitum feeding, diets containing SBTI without DL-ethionine were associated with decreases in weight gain, feed efficiency, serum cholesterol and serum urea nitrogen. Higher levels of triglycerides, glutamate pyruvate transaminase (SGPT) and altered serum free amino acid levels were also found. Increased dietary levels of DL-ethionine also resulted in deficits in growth and feed efficiency, decreased serum cholesterol, increased SGPT and similar alterations in serum free amino acids. Combination of dietary SBTI with DL-ethionine resulted in even greater growth deficits and serum cholesterol decreases as well as increases in SGPT and serum triglycerides and changes in serum free amino acid levels. Methionine deficiency in the young rats fed SBTI and DL-ethionine was indicated by the changes in serum amino acids and growth deficits. Moderation of some effects over the 12 week test period suggested decreased methionine requirements in the older rats.     

Effects of Soybean Fortification on Protein Quality of Tortilla-Based Diets Produced from Regular and Quality Protein Maize

The physiological development of laboratory rats fed with a typical indigenous tortilla diet was studied for two generations. The experiment compared casein control diet and five different types of diets: (1) a diet of tortillas obtained from fresh masa (FM); (2) regular tortillas produced from enriched dry masa flour containing vitamins B₁, B₂, niacin, folic acid, and the microminerals iron and zinc (REDMF); (3) tortillas produced from enriched dry masa flour fortified with 6% defatted soybean meal (FEDMF); (4) tortillas produced from enriched quality protein maize flour (EQPM); and (5) and, tortillas produced from enriched quality protein maize flour fortified with 3% defatted soybean meal (FEQPM). The growth of rats fed FEDMF and FEQPM diets was significantly higher (P<0.05) in both generations than their counterparts fed EQPM, REDMF, or FM diet. Animals fed quality protein maize (QPM) tortilla had the highest protein digestibility, but the FEQPM and FEDMF diets had the highest biological value (BV), net protein utilization (NPU), and protein-digestibility-corrected EAA scores (PDCEAAS). The difference among treatments was more evident in the second-generation rats. The pregnancy rate, number of newborns/litter, litter weight, and newborn survival rate was also higher for rats fed FEDMF, EQPM, and FEQPM diets than their counterparts fed REDMF and FM.     

Partial replacement of dietary casein with soy protein isolate can reduce the severity of retinoid-induced hypertriglyceridemia

Previous research carried out in an animal model of retinoid-induced hypertriglyceridemia – rats fet a 13-cis retinoic acid (13cRA)-containing diet having casein as the protein source – has demonstrated that the complete replacement of dietary casein with soy protein isolate (SPI) can decrease the severity of this condition. In this study, the effect of partially replacing dietary casein with SPI was investigated. Five groups of male Fischer 344 rats were used in a 14-day study, with two groups being fed diets having casein as the protein source, without or with 13cRA (groups A and B, respectively), and three groups being fed 13cRA-containing diets in which SPI was used to bring about the isonitrogenous replacement of 25, 50, or 100% of the casein in the formula for the diet used for group B (groups C-E, respectively). Serum triglyceride concentration for group B was significantly different ( p < 0.05) from that of groups A, D, and E (5.41 vs 2.62, 4.04, and 2.66 mmol/l, respectively). Serum cholesterol concentrations for groups D and E were significantly lower ( p < 0.05) than for groups A and B (1.63 and 1.60 vs 2.00 and 2.14 mmol/l, respectively). Thus, the isonitrogenous replacement of 50% of dietary casein with SPI can reduce the severity of retinoid-induced hypertriglyceridemia while decreasing the serum concentration of cholesterol.     

Growth,blood chemistry and histology of rats fed zincsupplemented rapeseed protein concentrates

Two rapeseed protein concentrates (RPC) supplemented with zinc oxide were fed to male and female rats at two levels providing approximately half or all of the protein in a purified basal diet containing 20% protein (N×6.25). Control groups were given either a purified basal diet with casein or a laboratory chow diet. After 16 weeks, there were no significant (P<0.05) differences in body weight except the male rats fed the casein control diet had higher body weights than did other male rats. No significant differences were observed in organ weights including thyroids, hematology, bone marrow differential counts, serum glucose, urea nitrogen, total protein, albumin/globulin ratio, cholesterol, transaminases or alkaline phosphatase. The levels of serum vitamins A and E of females fed some of the RPC diets were less than in those fed the caseincontrol diet, but equal to those in females fed laboratory chow diet. Females fed either RPC or casein in the semi-purified diets, which contained zinc oxide, exhibited kidney calcification.Bureau of Nutritional Sciences, No. 112; Food Research Institute, No. 420.     

Nutritional Status of the Protein of Corn-Soy Based Extruded Products Evaluated by Rat Bioassay

A rat bioassay was conducted to preclinically evaluate nutritional quality of two supplementary foods (SFs) developed based on corn and soy blends for feeding preschool children. The SFs prepared by extrusion cooking and subsequently modified to taste either sweet or salty provide 395 ± 2 kcal of energy and 20 ± 2 g protein per 100 g of food. The proximate constituents and energy contents of SFs were within the ranges prescribed for processed weaning foods and could satisfactorily meet the requirements of preschool children. Groups of male weanling rats were fed SFs for 4 weeks to evaluate the protein quality. The body weight gain of rats fed with SFs were significantly higher than those fed with skimmed milk powder (SMP) diet as control. The protein efficiency ratio and net protein utilization results of SFs were not significantly different (p>0.05) from values of control group. It is inferred that these SFs were nutritionally comparable to SMP.     

Effects of amylose and wheat bran on the levels of blood serum urea nitrogen (BUN), other blood parameters,growth and fecal characteristics in rats

A basal diet (containing 20% soybean protein isolate) was supplemented with limiting amino acids (AA, methionine, threonine and tryptophan); wheat bran (WB, 24.3%); amylose (AM, 10%) or a combination of AA and WB or AM to investigate their effects on the levels of blood serum urea nitrogen (BUN), other blood parameters, growth and fecal characteristics in young rats. After 3 weeks feeding, supplementation of the basal diet with AA or WB resulted in improved growth (gain/food ratio) while the addition of AM had no effect on rat growth. Addition of WB to the basal diet had no effect on BUN while the addition of AA and AM caused about 20 and 12% reduction in BUN values, respectively. Rats fed the AA-AM diet had the lowest BUN values (42% lower than those fed the basal diet). Fresh volume, fresh weight, moisture and dry weight of feces in rats fed the WB diets were about four to five fold higher than in those fed the AM diets. The results suggested that BUN may not be a good predictor of growth and protein quality in diets containing AM or a source of dietary fiber (WB).     

Long-term consumption of beef extended with soy protein by men,women and children: I. Study design,nutrient intakes,and serum zinc levels

The effect of long-term consumption, under practical conditions, of beef extended with soy protein on serum zinc levels of men, women and children was studied. Fifty-two families were randomly assigned to consume for 180 days 1 of 7 beef products: all beef, beef extended with either soy isolate, soy concentrate or soy flour (20% reconstituted soy product, 80% beef), or beef extended with each of the 3 soy products fortified with 60 mg Fe and 25 mg Zn/100g protein. The beef product was consumed by the subjects as their principal source of protein for 1 meal a day (children 1–8 yrs) or 1–2 meals a day (11 per week) for adult men and women. A control group consumed their usual self-selected diet. Diet records (4-day) of all foods and beverages consumed by the subjects were obtained pre-study and 63±7 and 126±7 days for calculation of nutrient intakes. No deleterious effects were found on the serum zinc levels when subjects consumed beef extended with soy protein for 180 days.Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable.     

Growth,hormonal status and protein turnover in rats fed on a diet containing peas (Pisum sativum L.) as the source of protein

The inclusion of peas (Pisum sativum L.) as the source of protein in the diet of growing rats brings about a reduction in growth rate as well as the impairment in the liver, muscle and spleen weights as compared with casein fed controls. Also, a fall in plasma glucose, triglycerides and protein was observed in the legume fed animals, while no changes in cholesterol levels were found. Furthermore, the rats fed on the diet containing peas showed lower levels of plasma insulin, corticosterone, IGF-I and T₄ as compared with casein controls. Liver and muscle total protein (mg) and total DNA (mg) were markedly decreased in the legume fed animals, but DNA/g, protein/DNA and RNA/protein ratios were similar in both dietary groups. Likewise, liver and muscle fractional synthesis rates were similar in the casein and legume groups, while the whole body protein synthesis is assumed to be lower in the legume fed animals due to differences in body weights. It is concluded that animals fed on a diet containing peas (Pisum sativum L.) as the only source of protein showed less adverse effects than those found with other legumes such asVicia faba L. orPhaseolus vulgaris L., in which protein quality, antinutritional factors and nutrient availability could be involved.     

Organic and Genetically Modified Soybean Diets: Consequences in Growth and in Hematological Indicators of Aged Rats

The aim of this study was to evaluate the protein quality of organic and genetically modified soy by feeding specific diets to rats. Three groups of Wistar rats (n = 10) were used, and each group was named according to the food that they ate. There was an organic soy group (OG), a genetically modified soy group (GG), and a control group (CG). All animals received water and diet ad libitum for 455 days. At the end of this period, the weight of the GG group was the same as that of the OG, and both were higher than CG. Protein intake was similar for the OG and GG, which were significantly lower (p < 0.0005) than the CG. The growth rate (GR) of the rats, albumin levels, and total levels of serum protein were comparable for all groups. Hematocrit (p < 0.04) and hemoglobin (p < 0.03) for the OG and GG were less than the CG. Although the OG and GG demonstrated reduced hematocrit and hemoglobin, both types of soy were utilized in a way similar to casein. This result suggests that the protein quality of soy is parallel to the standard protein casein in terms of growth promotion but not hematological indicators.     

The effects of low calorie diet with soy protein on cardiovascular risk factors in hyperlipidemic patients

Serum lipid abnormalities are an established risk factor for cardiovascular disease in hyperlipidemic patients. Because of the side effect of long-term medications in these patients, soy protein, as a part of healthy diet, may improve their lipid profile. The purpose of this study was to determine the effect of soy protein with low-calorie diet on lipid profiles in hyperlipidemic patient. Fifty two hyperlipidemic patients of both sex and age range of 25-65 years were participated. The patients received low-calorie diet based on 1400 kcal energy 18% protein, 24% fat and 58% carbohydrate per day for 4 weeks. The treatment group received low-calorie diet including (30 g day(-1)) of soy protein. Blood samples were obtained after an overnight (12 h) fasting period before the study and in the last day of the intervention period. Anthropometric indices and levels of serum triacylglycerol, total cholesterol, low-density lipoprotein and high-density lipoprotein were measured before and after the intervention. In groups, weight, body mass index, waist and hip circumferences were significantly reduced (p<0.05) after four weeks. In comparison with control group, the results of treatment of soy protein with low-calorie diet showed that at the end of 4th week serum low-density lipoprotein was significantly (p<0.05) decreased while an insignificant reduction was seen in total cholesterol. This study suggest that soy protein with low calorie diet for 4 weeks treatment may be safe and effective alternative therapy for diminished the cardiovascular risk factors in hyperlipidemic patients.     

Effect of coprophagy on bioavailability of iron from plant foods fed to anemic rats

Effects of coprophagy and coprophagy preventing device on iron bioavailability were evaluated in two experiments. In Experiment 1, rats were fed diets with FeSO₄, spinach, bran cereal or cornmeal as the iron source. The rats in each diet group were fitted with collars, sham-collars or not fitted with collars (control). In Experiment 2, rats were fed diets with FeSo₄ or green peas as the iron source and were fitted with collars, tail cups, sham-collars or not fitted with any device (control). Preventing coprophagy reduced hemoglobin regeneration efficiency (HRE) of rats fed bran cereal, green peas, spinach or cornmeal diets by 26 (P<.05), 24(P<.05), 22(P<.05) and 11% (not significant), respectively. Preventing coprophagy in rats fed FeSO₄ diet did not significantly reduce HRE. Sham-collaring reduced (P<.05) HRE of rats fed the FeSO₄ diet by 12 and 13% but did not significantly affect HRE in rats fed food iron sources. It was more convenient and effective to prevent coprophagy with collars than with tail cups. Differences in bioavailability between food and FeSO₄ iron due to coprophagy may be explained based on two gastrointestinal nonheme iron pools, complexed and highly soluble.     

The USDA trypsin inhibitor study. III. Sequential development of pancreatic pathology in rats

Weanling male, Wistar rats (40 per diet) were maintained on 15 diets which provided 4 graded trypsin inhibitor (TI) levels (93, 215, 337, and 577 mg/100g diet) repeated at 3 levels of protein (10%, 20%, and 30%). Raw and heated (toasted) soy flour provided 10% protein in the diet, while casein was added to increase the protein level to 20% and 30%. Three diets containing only casein as the protein source, at 10%, 20%, and 30% were included. Histologic changes occurring in the pancreas were evaluated in approximately 5 rats from each diet at 3 month intervals, beginning at 6 months, for 22 months. Criteria for the diagnosis of the observed histologic changes in the pancreas are discussed. Ultrastructure of the endocrine cells in the gastrointestinal mucosa was also examined.Pancreatic acinar cell density, as determined morphometrically, was reduced throughout the study in rats fed the 577 mg TI/100 g diet, indicating hypertrophy at the cellular level. Nodular hyperplasia was observed in the first sacrifice group at 6 months. Incidence of the lesion was positively related to both time of exposure and level of dietary TI. Acinar adenoma was first observed at 18 months and was most prevalent in rats fed the highest concentration of TI.Endocrine cells of the duodenal mucosa which contain cholecystokinin (so-called I cells) contained a denser population of secretory granules in animals fed the high TI diet compared with I cells from control animals, leading to the speculation that production and secretion of cytoplasmic hormones was increased in TI treated rats.Reference to a company and/or product named by the Department is only for purposes of information and does not imply approval or recommendation of the product to the exclusion of others which may also be suitable.     

Effect of dietary fibres on bioavailability of vitamin A and thiamine

Different sources of dietary fibre (cellulose, pectin, Isabgol, cabbage and guava) were fed to weaning rats for 5 weeks to study their effect on serum vitamins. Both the plant foods (cabbage and guava) were analysed for dietary fibre. Guava was found to be a good source of dietary fibre constituting 51.77% of dry pulp, whereas cabbage contained only 16.17%. Cellulose was the major component of dietary fibre in both the plant foods. The concentration of vitamin A and thiamine in the serum of fibre-fed rats was significantly lower than that of rats on a fibre-free diet. However, the amount of vitamin A in serum decreased significantly with the increase in level of dietary fibre, but the decrease was non-significant in the case of thiamine.     

The USDA trypsin inhibitor study. II. Timed related biochemical changes in the pancreas of rats

A total of 600 rats was distributed equally among 15 diets formulated from mixtures of raw and toasted soy flour and casein so as to provide 5 different levels of trypsin inhibitor (TI) at 3 levels of protein (10%, 20%, and 30%). Animals were sacrificed at the end of 6 months and at 3-month intervals thereafter over a period of 22 months. Increases in the secretory activity of the pancreas, as measured by trypsin and chymotrypsin activities in the pancreas and small intestines, were associated with increasingly higher levels of TI and protein but did not change appreciably with time. Hypertrophy and hyperplasia of the pancreas, as reflected by changes in pancreas weight and RNA and DNA content, developed at an early stage (6 months) and were likewise positively correlated with the levels of TI and protein in the diet. Although the hypertrophic response remained unchanged with time, hyperplasia became more pronounced as the period of exposure to TI was prolonged. The peptide test confirmed the stimulatory effect of TI on the pancreas, but some functional impairment was noted in those animals which had been fed raw soy flour for 18 months of or longer. The appearance of nodules on the pancreas was observed by gross inspection after 15 months, and these became larger and more numerous with time. The incidence of nodules was highly correlated with the level of TI in the diet and was highest when the diet contained 20% protein.     

Corrective role of chickpea intake on a dietary-induced model of hypercholesterolemia

A feeding trial was conducted in order to evaluate the potential effect on the lipid profile in a experimentally induced situation of hypercholesterolemia of a previously uninvestigated legume (Cicer aretinum L.) widely included in Mediterranean and Latinamerican human diets. Rats fed on a hypercholesterolemic diet containing saturated fat, cholesterol and cholic acid (H) had 123 percent higher serum cholesterol and 62 percent greater triacylglycerols levels than the animals receiving casein (C) protein. The LDL and VLDL cholesterol levels were 1330 percent and 35 percent higher, respectively, and HDL cholesterol 34 percent lower in the group of animals given the H diet as compared to controls. Further feeding of the hypercholesterolemic rats with animal protein (HC) resulted in a significant decrease of triacylglycerols (–70 percent), which reflected the decrease in the VLDL fraction. These effects on the lipid metabolism were more marked when the legumeCicer aretinum L. was present in the diet (HL). Significantly decreased concentrations of total cholesterol (–54 percent) and triacylglycerols (–70 percent) as well as the levels of LDL (–54 percent) and VLDL (–70 percent) were seen in rats fed chickpeas. In conclusion, a differential hypocholesterolemic effect between dietary casein and chickpea intake in a model of hypercholesterolemia induced by the diet was found, with beneficial effects on the lipid metabolism when legume was included in the diet as compared to casein. This suggests, for apparently the first time, that chickpea consumption may have a corrective effect in some alterations of the lipid profile.Abbreviations ANF Antinutritional factors - CD Cardiovascular disease - C Casein diet (Control diet) - H Hypercholesterolemic diet - L Legume diet - SD standard deviation     

Effect of Iron Status in Rats on the Absorption of Metal Ions from Plant Ferritin

An isolate of lead-ferritin obtained from soybean seeds sprouted in 25 mM of PbNO₃ was introduced into the diet of both iron-deficient and iron non-deficient male rats. After a 21-day administration period, statistical differences in the lead accumulation in the femurs of the rats were noted. Iron-deficient rats accumulated more than four times the amount of lead in their bones than rats without iron-deficiency. No further decrease was observed in haemoglobin concentrations in the groups of animals fed with lead isolates, either iron-deficient or iron non-deficient. Also, no differences in the mean corpuscular haemoglobin (MCH) and mean corpuscular volume (MCV) were observed at the end of the experiment in the group of iron non-deficient rats fed with lead-ferritin isolate compared to the control group of iron non-deficient rats. In the iron-deficient group fed with lead-ferritin isolate, a small increase in haemoglobin concentrations, MCH, MCV and mean corpuscular haemoglobin concentrations (MCHC) was recorded. The results presented in this paper confirm that lead from the tested preparation—lead ferritin isolate—was better absorbed by those rats with induced iron deficiency anaemia. Additionally, we may also suspect based on the obtained results that absorption of ferritin-iron depends on iron status in the body.     

Pancreatic and intestinal enzyme activities in rats in response to balanced and unbalanced plant diets

To simulate the effects of nutritionally adequate and inadequate vegetariandiets, rats were fed, for 28 days, an isonitrogenous, isocaloric, amino acidunbalanced cereal diet (CD) deficient in lysine and tryptophan or abalanced cereal-legume diet (CLD). The impact of these diets on enzymesresponsible for digestion of proteins and carbohydrates were measured.Neither experimental diet significantly affected the animal's final weight orfeed consumption in comparison with controls fed a standard mixed dietfrom plant and animal sources. However, during the first three weeks, theweight gain of rats fed the CD was significantly lower (p<0.01;p<0.05) than that of the controls. CD fed rats also had a higher feedefficiency ratio (p<0.05), demonstrating increased feed consumptionper unit of body weight. They also had decreased pancreatic-amylase activity (p<0.05), serum phytolytic and zoolytic-amylase activity (p<0.05) and serum protein level(p<0.05) than the controls. Activity of pancreatic trypsin and intestinalenzymes (sucrase, maltase, aminopeptidase N) were the same as in thecontrols. In rats fed CLD, growth, food consumption, and enzyme activitiesdid not change, however serum protein and glucose levels were higher(p<0.025; p<0.005) than in the controls. It is hypothesized thatdecrease in -amylase activity was mostly related to the tryptophandeficiency in the CD because this enzyme contains the highest amount oftryptophan units among all tested enzymes.