Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones

Estrogen produced by aromatization of gonadal androgen has an important facilitative role in male-typical aggressive behavior that is mediated through its interaction with estrogen receptors (ER) in the brain. Isoflavones found in soybeans and soy-based dietary supplements bind ER and have dose- and tissue-dependent effects on estrogen-mediated responses. Yet, effects of isoflavone-rich diets on social and aggressive behavior have not been studied. We studied the effects of long-term (15 months) consumption of diets rich in soy isoflavones on spontaneous social behavior among adult male cynomolgus macaques (Macaca fascicularis) (n = 44) living in nine stable social groups. There were three experimental conditions which differed only by the source of dietary protein: casein and lactalbumin (no isoflavones), soy protein isolate containing 0.94 mg isoflavones/g protein, and soy protein isolate containing 1.88 mg isoflavones/g protein. In the monkeys fed the higher amount of isoflavones, frequencies of intense aggressive (67% higher) and submissive (203% higher) behavior were elevated relative to monkeys fed the control diet (P's < 0.05). In addition, the proportion of time spent by these monkeys in physical contact with other monkeys was reduced by 68%, time spent in proximity to other monkeys was reduced 50%, and time spent alone was increased 30% (P's < 0.02). There were no effects of treatment on serum testosterone or estradiol concentrations or the response of plasma testosterone to exogenous gonadotropin-releasing hormone (GnRH). The results indicate that long-term consumption of a diet rich in soy isoflavones can have marked influences on patterns of aggressive and social behavior.     

Screening of soy and milk protein hydrolysates for their ability to activate the CCK1 receptor

The cholecystokinin receptor-type 1 (CCK1R) is a G-protein coupled receptor localized in the animal gastrointestinal tract. Receptor activation by the natural peptide ligand CCK leads to a feeling of satiety. In this study, hydrolysates from soy and milk proteins were evaluated for their potential to activate the CCK1R, assuming that bioactive peptides with a satiogenic effect can be used as an effective therapeutic strategy for obesity. Different protein hydrolysates were screened with a cell-based bioassay, which relies on the generation of a fluorescent signal upon receptor activation. Fluorescence was monitored using a fluorescence plate reader and confocal microscopy. Results from the fluorescence plate reader were biased by background autofluorescence of the protein hydrolysate matrices, which makes the fluorescence plate reader inappropriate for the evaluation of complex formulations. Measurements with the confocal microscope resulted in reliable and specific results. The latter approach showed that the gastrointestinal digested 7S fraction of soy protein demonstrates CCK1R activity.     

Enzyme-induced aggregation and gelation of proteins

This paper provides a brief overview of the effects of protein hydrolysis on aggregation and gel forming properties of protein systems. Among the food globular proteins, whey proteins and soy proteins are the most extensively studied for their ability to form different textures upon proteolysis. Recent studies were focused on identifying aggregating peptides and on mechanisms of aggregation and gelation.     

Biodegradable biocomposite films based on whey protein and zein: barrier, mechanical properties and AFM analysis

Whey and zein protein are byproducts of the food industries and have good film making properties. Single and laminated films were produced from zein protein and whey protein and their film properties were studied. Glycerol and olive oil were used as plasticizer for the single and laminated films. The laminated films exhibited higher ultimate tensile strength (UTS) than the single whey protein films (260% and 200% in the whey-zein-glycerol and whey-zein-olive oil films, respectively). The UTS of the whey protein films increased 2-3-fold after lamination. The laminated films showed higher barrier properties than the single whey protein films (180% in the whey protein-zein-glycerol films and 200% in the whey protein-zein-olive oil films in comparison to single whey protein films) and lower than the single zein films.     

Emulsion stabilizing properties of various chitosans in the presence of whey protein isolate

The emulsion stabilizing potential of chitosans (CN) with various molecular weights and degrees of deacetylation (CNI=1494 kDa, 78.1%DD; CNHI=694 kDa, 78.5%DD; CNHI2=319 kDa, 78.5%DD; CNHK=749 kDa, 67.7%DD) was compared in the presence of whey protein isolate. Phase separation evolutions revealed minimal stabilizing concentrations against syneresis from 0.1 to 0.125% in most CN preparations, except CNHI2 where it was higher (0.225%). Those stabilizing concentrations are the result of interfacial coadsorption saturation of CN with proteins, favouring interfacial electrostatic and steric stabilizing mechanisms. The emulsion characteristics (droplet size, limiting low-shear viscosity, and surface net charge), mostly distinctive at 0.1%CN, revealed the following order of stabilizing potentials: CNI≈CNHI>CNHK>CNHI2, which is in agreement with respective phase separation evolutions. The lower stabilizing potential of CNHI2 is explained by lower interfacial coadsorption efficiency with protein. In spite of a higher interfacial load of CNHK vs. CNI and CNHI, its lower stabilizing potential is essentially explained by a lower surface net charge.     

Design and evaluation of succinylated soy protein tablets as delayed drug delivery systems

The impact of succinylation on soy proteins as excipients for delayed delivery of drugs in the gastrointestinal tract was studied. Succinylation decreased protein solubility and protein charge density at pH 1.2 and increased solubility and zeta potential at pH above 4.5. Tablet erosion and swelling were decreased at pH 1.2 and increased at pH 7.5. FTIR analysis indicated polypeptide chain unfolding as a result of succinylation. Tablets of protein succinylated 50% or 100% released less than 10% of loaded riboflavin or rifampicin in 2 h at gastric pH in the presence of pepsin but released these compounds rapidly at intestinal pH. Succinylated soy protein tablets were thus gastroresistant, suggesting their use as excipients for controlled release of medicinal or nutraceutical agents.     

Properties of biopolymers produced by transglutaminase treatment of whey protein isolate and gelatin

Byproduct utilization is an important consideration in the development of sustainable processes. Whey protein isolate (WPI), a byproduct of the cheese industry, and gelatin, a byproduct of the leather industry, were reacted individually and in blends with microbial transglutaminase (mTGase) at pH 7.5 and 45 °C. When a WPI (10% w/w) solution was treated with mTGase (10 U/g) under reducing conditions, the viscosity increased four-fold and the storage modulus (G′) from 0 to 300 Pa over 20 h. Similar treatment of dilute gelatin solutions (0.5–3%) had little effect. Addition of gelatin to 10% WPI caused a synergistic increase in both viscosity and G′, with the formation of gels at concentrations greater than 1.5% added gelatin. These results suggest that new biopolymers, with improved functionality, could be developed by mTGase treatment of protein blends containing small amounts of gelatin with the less expensive whey protein.     

Segregative phase separation in agarose/whey protein systems induced by sequence-dependent trapping and change in pH

The structural properties and morphology of mixed gels made of aqueous preparations of agarose and whey protein were modified by changing thermal treatment and pH. The conformationally dissimilar polymers phase separated and this process was followed by small-deformation dynamic oscillation in shear, differential scanning calorimetry and environmental scanning electron microscopy. Experimental protocol encourages formation of a range of two-phase systems from continuous agarose matrices perforated by liquid-like whey protein inclusions to phase inverted preparations where a soft protein matrix suspends hard agarose-filler particles. These distinct morphologies have widely different mechanical moduli, which were followed by adapting a theoretical analysis (isostress-isostrain and Lewis-Nielsen blending laws) from the literature in synthetic block polymers and polyblends. Based on this framework of thought, reasonable predictions of the elastic moduli in the composite gels were made that led to patterns of solvent partition between the two polymeric networks. It was shown that proteins, in mixture with polysaccharide, exhibit favorable relative affinity (P-factor) for water molecules at a pH above their isoelectric point. This is an unexpected outcome that adds to the central finding of a single P value for the distribution of solvent between the continuous matrix and discontinuous inclusions of binary gels. It was thus proposed that phase continuity and solvent distribution in agarose/whey protein systems are under kinetic control that can be heavily governed by pH changes in the aqueous environment.     

Effect of soy and milk whey protein isolates and their hydrolysates on weight reduction in genetically obese mice

The effect on genetically obese mice of a milk whey protein isolate (WPI) and soy protein isolate (SPI) and their hydrolysates (WPI-H, SPI-H) on the rate of body fat disappearance was investigated. Male yellow KK mice were made obese by feeding with a high-fat diet containing 30% fat from 6 to 10 weeks of age. They were then fed with an energy-restricted low fat (5.0%) and high protein (35% WPI, WPI-H, SPI or SPI-H) diet for 2 weeks at the 60% level of energy intake by mice on laboratory feed. During the weight reduction period, the body weight of the WPI, WPI-H, SPI and SPI-H groups changed by -9.1, -9.1, -10.0 and -11.1 g/14 days, respectively, the reduction being significantly lower in the SPI-H group than in the WPI and WPI-H groups. The plasma total cholesterol level was significantly lower with the SPI diet, and the plasma glucose level was lower with the SPI and SPI-H diets than with the WPI and WPI-H diets. Although the body protein content was comparable in all the groups, the body fat content was significantly lower with the SPI diet than with the WPI diet, and was also significantly lower with the SPI-H diet than with the WPI and WPI-H diets. The weight of the perirenal fat pads was significantly lower with the SPI-H diet than with the WPI and WPI-H diets. These results indicate that SPI and SPI-H are suitable protein sources in an energy-restricted diet for treating obesity.     

Varietal differences of carbohydrates in defatted soybean flour and soy protein isolate by-products

Soy protein isolates (SPI) were prepared from 12 soybean lines grown in Harrow, Ontario and by-products (fibers and wheys) from SPI making were saved. The identification and quantification of soluble sugars in defatted flours, fibers and wheys were carried out using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) and with a colorimetric method for uronic acids. Defatted flours and fibers were acid hydrolyzed, then analyzed by HPAEC-PAD for monosaccharide composition. The results showed varietal differences in the carbohydrate composition suggesting different applications for these defatted flours and their SPI by-products.     

White adipose tissue genome wide-expression profiling and adipocyte metabolic functions after soy protein consumption in rats

Obesity is associated with an increase in adipose tissue mass due to an imbalance between high dietary energy intake and low physical activity; however, the type of dietary protein may contribute to its development. The aim of the present work was to study the effect of soy protein versus casein on white adipose tissue genome profiling, and the metabolic functions of adipocytes in rats with diet-induced obesity. The results showed that rats fed a Soy Protein High-Fat (Soy HF) diet gained less weight and had lower serum leptin concentration than rats fed a Casein High-Fat (Cas HF) diet, despite similar energy intake. Histological studies indicated that rats fed the Soy HF diet had significantly smaller adipocytes than those fed the Cas HF diet, and this was associated with a lower triglyceride/DNA content. Fatty acid synthesis in isolated adipocytes was reduced by the amount of fat consumed but not by the type of protein ingested. Expression of genes of fatty acid oxidation increased in adipose tissue of rats fed Soy diets; microarray analysis revealed that Soy protein consumption modified the expression of 90 genes involved in metabolic functions and inflammatory response in adipose tissue. Network analysis showed that the expression of leptin was regulated by the type of dietary protein and it was identified as a central regulator of the expression of lipid metabolism genes in adipose tissue. Thus, soy maintains the size and metabolic functions of adipose tissue through biochemical adaptations, adipokine secretion, and global changes in gene expression.     

Secretion of whey acidic protein and cystatin is down regulated at mid-lactation in the red kangaroo (Macropus rufus)

Milk collected from the red kangaroo (Macropus rufus) between day 100 and 260 of lactation showed major changes in milk composition at around day 200 of lactation, the time at which the pouch young begins to temporarily exit the pouch and eat herbage. The carbohydrate content of milk declined abruptly at this time and although there was only a small increase in total protein content, SDS PAGE analysis of milk revealed asynchrony in the secretory pattern of individual proteins. The levels of alpha-lactalbumin, beta-lactoglobulin, serum albumin and transferrin remain unchanged during lactation. In contrast, the protease inhibitor cystatin, and the putative protease inhibitor whey acidic protein (WAP) first appeared in milk at elevated concentrations after approximately 150 days of lactation and then ceased to be secreted at approximately 200 days. In addition, a major whey protein, late lactation protein, was first detected in milk around the time whey acidic protein and cystatin cease to be secreted and was present at least until day 260 of lactation. The co-ordinated, but asynchronous secretion of putative protease inhibitors in milk may have several roles during lactation including tissue remodelling in the mammary gland and protecting specific proteins in milk required for physiological development of the dependent young.     

Biotechnological approaches for the value addition of whey

Whey, the liquid remaining after milk fat and casein have been separated from whole milk, is one of the major disposal problems of the dairy industry, and demands simple and economical solutions. In view of the fast developments in biotechnological techniques, alternatives of treating whey by transforming lactose present in it to value added products have been actively explored. Whey can be used directly as a substrate for the growth of different microorganisms to obtain various products such as ethanol, single-cell protein, enzymes, lactic acid, citric acid, biogas and so on. In this review, a comprehensive and illustrative survey is made to elaborate the various biotechnological innovations/techniques applied for the effective utilization of whey for the production of different bioproducts.     

Identifying protein aggregation mechanisms and quantifying aggregation rates from combined monomer depletion and continuous scattering

Parallel temperature initial rates (PTIR) from chromatographic separation of aggregating protein solutions are combined with continuous simultaneous multiple sample light scattering (SMSLS) to make quantitative deductions about protein aggregation kinetics and mechanisms. PTIR determines the rates at which initially monomeric proteins are converted to aggregates over a range of temperatures, under initial-rate conditions. Using SMSLS for the same set of conditions provides time courses of the absolute Rayleigh scattering ratio, I_R(t), from which a potentially different measure of aggregation rates can be quantified. The present report compares these measures of aggregation rates across a range of solution conditions that result in different aggregation mechanisms for anti-streptavidin (AS) immunoglobulin gamma-1 (IgG1). The results illustrate how the two methods provide complementary information when deducing aggregation mechanisms, as well as cases where they provide new mechanistic details that were not possible to deduce in previous work. Criteria are presented for when the two techniques are expected to give equivalent results for quantitative rates, the potential limitations when solution non-idealities are large, as well as a comparison of the temperature dependence of AS-IgG1 aggregation rates with published data for other antibodies.     

Effects of soy protein and genistein on blood glucose, antioxidant enzyme activities, and lipid profile in streptozotocin-induced diabetic rats

In the current study, the effect of soy protein and genistein, one of the main isoflavones in soybeans, on blood glucose, lipid profile, and antioxidant enzyme activities in streptozotocin (STZ)-induced diabetic rats was investigated. Male Sprague-Dawley rats were divided into nondiabetic control, STZ, STZ-genistein supplemented group (STZ-G; 600 mg/kg diet), and STZ-isolated soy protein supplemented group (STZ-ISP; 200 g/kg diet). Diabetes was induced by a single injection of STZ (50 mg/kg BW) freshly dissolved in 0.1 mol/L citrate buffer (pH 4.5) into the intraperitonium. Diabetes was confirmed by measuring the fasting blood glucose concentration 48-h post-injection. The rats with blood glucose level above 350 mg/dL were considered to be diabetic. Genistein and ISP were supplemented in the diet for 3 weeks. The supplementation of genistein and ISP increased the plasma insulin level but decreased the HbA(IC) level of the STZ-induced diabetic rats. The supplementation of genistein and ISP increased the glucokinase level of the STZ-induced diabetic rats. A significant reduction in glucose-6-phosphatase was observed in the groups treated with genistein and ISP in comparison with the diabetic control group. Hepatic superoxide dismutase, catalase, and glutathione peroxidase activities of the STZ-induced diabetic rats were significantly decreased in comparison with the control rats. Administering genistein and ISP to the STZ-induced diabetic rats significantly increased those enzyme activities. The concentration of thiobarbituric acid reactive substances in the STZ-induced diabetic rats was significantly elevated, while the genistein and ISP supplement decreased it to the control concentration. Genistein and ISP supplements seem to be beneficial for correcting the hyperglycemia and preventing diabetic complications.     

Emulsion-stabilizing properties of chitosan in the presence of whey protein isolate: Effect of the mixture ratio, ionic strength and pH

The emulsion-stabilizing properties of a chitosan preparation were compared as a function of the whey protein isolate/chitosan mixture ratio (WPI/CNI) and the ionic strength (μ), at pH 5.5 and 6.0. At both pH conditions, general decreases in emulsion stability towards charge neutralization flocculation and syneresis were observed at WPI/CNI > 5. This was particularly evident at pH 6.0, due to a lower surface net charge (lower electrostatic stabilization). In counterpart, when μ was increased, the higher load of chitosan at pH 6.0 produced higher stabilities (higher steric stabilization), in spite of comparable decreases of surface net charge at both pH conditions. The transition from soluble to insoluble protein–chitosan complex formation in mixtures at pH 6.0 and WPI/CNI > 5.0 was due to an emulsion destabilization towards syneresis, whereas soluble complex formation at pH 5.5 also produced syneresis. It showed that soluble protein–chitosan adsorbing complex formation prior homogenization is not essentially linked to emulsion stabilization.     

Structure and properties of carboxymethyl cellulose/soy protein isolate blend edible films crosslinked by Maillard reactions

Edible films based on carboxymethyl cellulose (CMC) and soy protein isolate (SPI), compatibilized by glycerol, were prepared by solution casting. The effects of CMC content on blend structure, thermal stability, water solubility and water sorption, and mechanical properties were systematically investigated. Fourier transform infrared (FTIR) spectra showed that Maillard reactions occurred between CMC and SPI, and X-ray diffraction (XRD) scans indicated that the Maillard reactions greatly reduced the crystallinity of SPI. According to differential scanning calorimetry (DSC) analysis, CMC/SPI blends had a single glass transition temperature (T_g) between 75 and 100 °C, indicating that CMC and SPI form one phase blends. Increasing the CMC content improved the mechanical properties and reduced the water sensitivity of blend films. The results indicate that the structure and properties of SPI edible films were modified and improved by blending with CMC.     

Effect of physicochemical properties of peptides from soy protein on their antimicrobial activity

Antimicrobial peptides (AMPs) kill microbial cells through insertion and damage/permeabilization of the cytoplasmic cell membranes and has applications in food safety and antibiotic replacement. Soy protein is an attractive, abundant natural source for commercial production of AMPs. In this research, explicit solvent molecular dynamics (MD) simulation was employed to investigate the effects of (i) number of total and net charges, (ii) hydrophobicity (iii) hydrophobic moment and (iv) helicity of peptides from soy protein on their ability to bind to lipid bilayer and their transmembrane aggregates to form pores. Interaction of possible AMP segments from soy protein with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPC/POPG) bilayers, a mimic of bacterial cell membrane, was investigated. Pore formation was insensitive to helicity and occurred for hydrophobicity threshold in the range of −0.3–0 kcal/mol, hydrophobic moment threshold of 0.3 kcal/mol, net charge threshold of 2. Though low hydrophobicity and high number of charges help in the formation of water channel for transmembrane aggregates, insertion of peptides with these properties requires overcome of energy barrier, as shown by potential of mean force calculations, thereby resulting in low antimicrobial activity. Experimental evaluation of antimicrobial activity of these peptides against Gram positive L. monocytogenes and Gram negative E. coli as obtained by spot-on-lawn assay was consistent with simulation results. These results should help in the development of guidelines for selection of peptides with antimicrobial activity based on their physicochemical properties.     

A soy supplement and tamoxifen inhibit sexual behavior in female rats

In addition to displaying proceptive (hopping and darting) and receptive (lordosis) behaviors during a sexual encounter with a male, female rodents will regulate the timing of the encounter by engaging in a series of approaches and withdrawals from the male, a behavior termed paced mating behavior. Proceptive, receptive, and paced mating behaviors are all regulated by, and sensitive to, estrogen and progesterone, suggesting that compounds capable of disrupting these critical hormones may also perturb the display of female sexual behavior. The present experiments examined the impact of the selective estrogen receptor modulator (SERM) tamoxifen and a popular soy phytoestrogen dietary supplement on female sexual behavior in rats. Ovariectomized female rats were given either tamoxifen (TAMOX) by implant or the soy supplement through the diet then injected with estradiol benzoate (EB, 10 microg) or oil followed 48 h later with an injection of progesterone (P, 500 microg). Animals were then tested for sexual behavior 4 h after the P injection. Neither compound had any effect on sexual behavior when administered in conjunction with P alone; however, both significantly diminished receptive behavior, as measured by the lordosis quotient (LQ), in animals primed with both EB and P. Similarly, the hopping and darting rate was also significantly depressed in both the soy- and TAMOX-treated animals, compared to the EB- and P-treated controls, with the soy-treated animals showing significantly less proceptive behavior than the TAMOX-treated animals. Finally, soy but not TAMOX significantly attenuated paced mating behavior in animals compared to the EB- and P-treated controls. These results demonstrate that both the soy supplement and TAMOX act as estrogen antagonists on both proceptive and receptive behavior in female rats.     

The effect of whey protein hydrolyzates on the lactic acid fermentation

Summary The batch fermentation of whey permeate to lactic acid was improved markedly by the addition of enzymehydrolyzed whey protein. Acid concentrations greater than 90 g/l were achieved at a productivity of 4.3 g/l per h and a 98% substrate use. Cell mass concentration reached 6 g/l. The acid productivity achieved is somewhat higher than that typical for fermentation of whole whey. The process economics, based on in-house hydrolyzate preparation, look promising. Presented in this paper are the experimental results showing the effects of hydrolyzate concentration on acid and cell mass production.