Measuring the oral bioavailability of protein hydrolysates derived from food sources: A critical review of current bioassays.

BACKGROUND: Food proteins are a source of hydrolysates with potentially useful biological attributes. Bioactive peptides from food-derived proteins are released from hydrolysates using exogenous industrial processes or endogenous intestinal enzymes. Current in vitro permeability assays have limitations in predicting the oral bioavailability (BA) of bioactive peptides in humans. There are also difficulties in relating the low blood levels of food-derived bioactive peptides detected in preclinical in vivo models to pharmacodynamic read-outs relevant for humans. SCOPE AND APPROACH: In this review, we describe in vitro assays of digestion, permeation, and metabolism as indirect predictors of the potential oral BA of hydrolysates and their constituent bioactive peptides. We discuss the relationship between industrial hydrolysis processes and the oral BA of hydrolysates and their peptide by-products. KEY FINDINGS: Hydrolysates are challenging for analytical detection methods due to capacity for enzymatic generation of peptides with novel sequences and also new modifications of these peptides during digestion. Mass spectrometry and peptidomics can improve the capacity to detect individual peptides released from complex hydrolysates in biological milieu.

Absorption Kinetics of Ethanolamine Plasmalogen and Its Hydrolysate in Mice.

Ethanolamine plasmalogen (PlsEtn), a subclass of ethanolamine glycerophospholipid (EtnGpl), has been reported to have many biological and dietary functions. In terms of PlsEtn absorption, some studies have reported that PlsEtn is re-esterized at the sn-2 position using lymph cannulation and the everted jejunal sac model. In this study, we aimed to better understand the uptake kinetics of PlsEtn and increase its absorption. We thus compared the uptake kinetics of PlsEtn with that of the lyso-form, in which the fatty acid at the sn-2 position was hydrolyzed enzymatically. Upon administration of EtnGpl (extracted from oysters or ascidians, 75.4 mol% and 88.4 mol% of PlsEtn ratio, respectively), the plasma PlsEtn species in mice showed the highest levels at 4 or 8 hours after administration. In the contrast, administration of the EtnGpl hydrolysate, which contained lysoEtnGpl and free fatty acids, markedly increased the plasma levels of PlsEtn species at 2 h after administration. The area under the plasma concentration-time curve (AUC), especially the AUC0-4 h of PlsEtn species, was higher with hydrolysate administration than that with EtnGpl administration. These results indicate that EtnGpl hydrolysis accelerated the absorption and metabolism of PlsEtn. Consequently, using a different experimental approach from that used in previous studies, we reconfirmed that PlsEtn species were absorbed via hydrolysis at the sn-2 position, suggesting that hydrolysis in advance could increase PlsEtn uptake.

Bioactive peptides attenuate cardiac apoptosis in spontaneously hypertensive rat hearts through activation of autophagy and mitochondrial biogenesis pathway.

Alcalase potato protein hydrolysate (APPH) might have a very important role in therapeutic effects. This study aims to examine the beneficial effects of bioactive peptides (DIKTNKPVIF [DI] and IF) from APPH supplement in the regulation of cardiac apoptosis, autophagy, and mitochondrial biogenesis pathway in spontaneously hypertensive rats (SHR). We have investigated ejection fraction, fractional shortening, Tunel assay, apoptosis, autophagy, and mitochondrial biogenesis pathway marker expression to show the efficacy of bioactive peptides in an SHR model. Bioactive peptides significantly upregulate ejection fraction and fractional shortening in SHR rats. SHR rats exhibited higher protein expression of apoptotic markers such as BAD, cytochrome c, and caspase 3. Finally, the bioactive peptides upregulate survival proteins (p-AKT/p-PI3K), autophagy (Beclin1/LC3B), and mitochondrial biogenesis (p-AMPKα/SIRT1/PGC1α/p-Foxo3a/Nrf2/CREB) marker expressions compared with the SHR groups. In summary, the bioactive peptides protect the heart tissues through the activation of autophagy and mitochondrial biogenesis pathway and thereby attenuate cardiac apoptosis in a spontaneously hypertensive rat model.

Antioxidant and cytotoxic properties of protein hydrolysates obtained from enzymatic hydrolysis of Klunzinger's mullet (Liza klunzingeri) muscle

Today, consumers are looking for functional foods that promote health and prevent certain diseases in addition to provide nutritional requirements. This study aimed to evaluate the antioxidant and cytotoxic properties of Liza klunzingeri protein hydrolysates. Fish protein hydrolysates (FPHs) were prepared from L. klunzingeri muscle using enzymatic hydrolysis with papain at enzyme/substrate ratios of 1:25 and 1:50 for 45, 90 and 180 min. The antioxidant activities of the FPHs were investigated through five antioxidant assays. The cytotoxic effects on 4T1 carcinoma cell line were also evaluated. The amino acid composition and molecular weight distribution of the hydrolysate with the highest antioxidant activity were determined by HPLC. All six FPHs exhibited good scavenging activity on ABTS (IC50=0.60-0.12 mg/mL), DPPH (IC50= 3.18-2.08 mg/mL), and hydroxyl (IC50=4.13-2.07 mg/mL) radicals. They also showed moderate Fe+2 chelating capacity (IC50=2.12-12.60 mg/mL) and relatively poor ferric reducing activity (absorbance at 70 nm= 0.01-0.15, 5 mg/mL). In addition, all hydrolysates showed cytotoxic activities against the 4T1 cells (IC50=1.62-2.61 mg/mL). 94.6% of peptide in hydrolysate with the highest antioxidant activity had molecular weight less than 1,000 Da. L. klunzingeri protein hydrolysates show significant antioxidant and anticancer activities in vitro and are suggested to be used in animal studies.

Amaranth Protein Hydrolysates Efficiently Reduce Systolic Blood Pressure in Spontaneously Hypertensive Rats.

Alcalase is the enzyme of choice to release antihypertensive peptides from amaranth proteins, but the hydrolysis conditions have not been optimized yet. Furthermore, in vivo assays are needed to confirm such a hypotensive effect. Our aim was to optimize the hydrolysis of amaranth protein with alcalase and to test in vivo the hypotensive effect of the hydrolysates. A response surface analysis was carried out to optimize the hydrolysis reaction. The response variable was the Angiotensin Converting Enzyme (ACE-I) inhibition. The hydrolysis degree was determined (free alpha-amino groups measurement). The optimized hydrolysate bioavailability was assessed in the sera of mice and the hypotensive effect was assessed in spontaneously hypertensive rats. Control groups were administered captopril or water. The optimized hydrolysis conditions were: pH = 7.01, temperature = 52 °C, enzyme concentration 0.04 mU/mg, and time = 6.16 h. The optimized hydrolysate showed a 93.5% of ACE-I inhibition and a hydrolysis degree of 74.77%. After supplementation, the hydrolysate was bioavailable in mice from 5 to 60 min, and the hypotensive effect started at 4 h in spontaneously hypertensive rats (p < 0.05 vs. water group). This effect was similar to the captopril hypotensive effect for the next 3 h (p > 0.05). The use of amaranth-optimized hydrolysates as hypotensive supplements or ingredient for functional foods seems feasible.

Production of bioactive peptide hydrolysates from deer, sheep, pig and cattle red blood cell fractions using plant and fungal protease preparations.

Protease preparations from plant (papain and bromelain) and fungal (FP400 and FPII) sources were used to hydrolyze the red blood cell fractions (RBCFs) separated from deer, sheep, pig, and cattle abattoir-sourced blood. After 1, 2, 4 and 24h of hydrolysis, the antioxidant and antibacterial activities of the peptide hydrolysates obtained were investigated. The increase in trichloroacetic acid-soluble peptides over the hydrolysis period was examined using the o-phthaldialdehyde (OPA) assay and the hydrolysis profiles were illustrated using SDS-PAGE. Papain generated RBCF hydrolysates exhibited higher ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) compared to those generated with bromelain, FP400 and FPII. At certain concentrations, 24h hydrolysates of RBCF using FP400 and FPII were able to inhibit the growth of Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The results indicated that the use of proteases from plant or fungal sources can produce animal blood hydrolysates with antioxidant and antimicrobial activities.

Dietary protein structure affects endogenous ileal amino acids but not true ileal amino acid digestibility in growing male rats.

BACKGROUND: The amount of endogenous, as opposed to undigested dietary, protein in digesta is a measure of fundamental interest related to gut physiology and function. OBJECTIVE: The objective of this study was to determine whether alimentation with proteins having differing amino acid compositions influenced endogenous ileal amino acids (EIAAs) and true ileal amino acid digestibility (TIAAD) values. METHODS: Male rats (n = 8) were fed a purified diet containing 100 g/kg of 1 of 5 protein hydrolysates, each derived from a different semipurified intact protein source [gelatin, beef muscle (BM), casein, soy protein isolate (SPI), and lactalbumin] devoid of antinutritional factors or fiber. The rats were fed their respective hydrolysate-based diet for 1 d after receiving the same diet but containing the corresponding intact protein source for 7 d. Titanium dioxide was used as an indigestible marker. Ileal digesta were collected after the rats were killed, and EIAAs were determined (precipitate + retentate) after centrifugation and ultrafiltration of the digesta. The TIAAD values of the intact protein sources were determined using EIAA flows based on each protein hydrolysate. RESULTS: Mean EIAA flows differed (P < 0.05) across protein hydrolysates for most amino acids, with the mean ± SEM EIAA flows across amino acids being 262 ± 17, 253 ± 12, 248 ± 18, 226 ± 14, and 191 ± 20 mg/kg dry matter intake for the gelatin, BM, casein, SPI, and lactalbumin hydrolysates, respectively. The only difference (P < 0.05) for the mean EIAA flows across amino acids within each protein hydrolysate was observed between gelatin (262 ± 17 mg/kg) and lactalbumin (191 ± 20 mg/kg) hydrolysates. Except for Trp (P < 0.001) in gelatin and lactalbumin hydrolysates, EIAA flows determined using the casein hydrolysate were not different (P ≥ 0.05) from EIAA flows determined using the other protein hydrolysates. TIAAD values were not generally different (P ≥ 0.05) regardless of the hydrolysate used to determine the EIAA flows. CONCLUSIONS: Protein source affected EIAA flows, although the differences had little effect on TIAAD. Enzyme hydrolyzed casein is a suitable model hydrolysate for determining TIAAD with the enzyme-hydrolyzed protein-ultrafiltration technique.

Analysis of whey protein hydrolysates: peptide profile and ACE inhibitory activity

The aim of this study was to prepare enzymatic hydrolysates from whey protein concentrate with a nutritionally adequate peptide profile and the ability to inhibit angiotensin-converting enzyme (ACE) activity. The effects of the type of enzyme used (pancreatin or papain), the enzyme:substrate ratio (E:S ratio=0.5:100, 1:100, 2:100 and 3:100) and the use of ultrafiltration (UF) were investigated. The fractionation of peptides was performed by size-exclusion-HPLC, and the quantification of the components of the chromatographic fractions was carried out by a rapid Corrected Fraction Area method. The ACE inhibitory activity (ACE-IA) was determined by Reverse Phase-HPLC. All parameters tested affected both the peptide profile and the ACE-IA. The best peptide profile was achieved for the hydrolysates obtained with papain, whereas pancreatin was more advantageous in terms of ACE-IA. The beneficial effect of using a lower E:S ratio on the peptide profile and ACE-IA was observed for both enzymes depending on the conditions used to prepare the hydrolysates. The beneficial effect of not using UF on the peptide profile was observed in some cases for pancreatin and papain. However, the absence of UF yielded greater ACE-IA only when using papain.

O objetivo deste estudo foi preparar hidrolisados enzimáticos do concentrado proteico do soro de leite com perfil peptídico nutricionalmente adequado e com capacidade para inibir a atividade da enzima conversora da angiotensina (ECA). Os efeitos do tipo de enzima usado (pancreatina ou papaína), da relação enzima:substrato (E:S=0,5:100, 1:100, 2:100 e 3:100) e do uso da ultrafiltração (UF) foram investigados. O fracionamento dos peptídeos foi feito por CLAE de exclusão molecular e a quantificação dos componentes das frações cromatográficas foi realizada pelo método da Área Corrigida da Fração. A atividade inibitória da ECA (AI-ECA) foi determinada por CLAE de fase reversa. Todos os parâmetros testados afetaram tanto o perfil peptídico quanto a AI-ECA. O melhor perfil peptídico foi atingido para os hidrolisados obtidos com papaína, enquanto a pancreatina foi mais vantajosa em termos da AI-ECA. O efeito benéfico do uso de menor relação E:S sobre o perfil peptídico e a AI-ECA foi observado para ambas as enzimas dependendo das condições usadas para o preparo dos hidrolisados. O efeito benéfico da ausência da UF sobre o perfil peptídico foi observado em alguns casos para pancreatina e papaína. No entanto, a ausência da UF produziu maior AI-ECA somente quando a papaína foi usada.

Rendered-protein hydrolysates for microbial synthesis of cyanophycin biopolymer.

Cyanophycin is a poly(arginyl-aspartate) biopolymer produced and stored intracellularly by bacteria. Cyanophycin has been proposed as a renewable replacement for petrochemical-based industrial products. An abundant source of amino acids and nitrogen such as in the form of protein hydrolysates is needed for the biosynthesis of cyanophycin. Rendered proteins are largely used as a feed supplement in animal husbandry and aquaculture. New uses would expand the market size of this class of protein coproducts. We prepared and thoroughly characterized the hydrolysates of meat and bone meal, and proceeded to demonstrate for the first time that these hydrolysates could be used in the fermentative production of cyanophycin. Using the enzyme-hydrolyzed meat and bone meal preparation, we obtained crude cyanophycin product at 33-35% level of that produced using the reference casamino acids in both shake-flask and 10-L bioreactor fermentation studies. Polyacrylamide-gel electrophoresis of the cyanophycin under denaturing conditions showed the molecular weight of the isolated polyamide at 24kDa. Our results open a new avenue for the utilization of rendered protein coproducts to produce the cyanophycin biopolymer.

Obtenção de hidrolisados enzimáticos do concentrado proteico do soro de leite com baixo teor de fenilalanina / Preparation of whey protein concentrate hydrolysates with low phenylalanine content

The objective of this work was to obtain enzymatic hydrolysates of wheyprotein concentrate with low phenylalanine content. Seventeen enzymatic hydrolysates were prepared and the effects of some parameters, such as type of enzyme; enzyme: substrate ratio; substrate concentration and time of hydrolysis were evaluated. Activated carbon was used as adsorbent and showed to be efficient for removing phenylalanine, leading to values above 70%. The best results were otained using pancreatin in an enzyme: substrate ratio of 1:100, a substrate concentration of 10% after 5 hours of hydrolysis, obtaining 81.3% of removal and a final phenylalanine content of 394.1 mg/100g of hydrolysate.

El objetivo de la investigación fue la obtención de hidrolizados enzimáticos con bajo contenido de fenilalanina, a partir de concentrado proteico de suero de leche. Se prepararon 17 hidrolizados enzimáticos y se evaluó el efecto de algunos parámetros como: tipo de enzima, relación enzima: sustrato, concentración de la materia prima y tiempo de hidrólisis. Carbón activado fue utilizado como medio adsorbente, y se mostró eficaz en la remoción de fenilalanina, se obteniendo porcentuales sobre 70%. El mejor resultado fué encontrado usando pancreatina en una relación enzima: sustrato de 1:100, con concentración de materia prima de 10% y 5 horas de hidrólisis, consiguiendo 81,3% de remoción y el contenido final de fenilalaninade 394,1 mg/100g de hidrolizado

O presente trabalho teve como objetivo a obtenção de hidrolisados enzimáticos, a partir do concentrado proteico do soro do leite combaixo teor de fenilalanina. Foram preparados 17 hidrolisados enzimáticos, avaliando-se o efeito de alguns parâmetros, como tipo de enzima, relação enzima: substrato, concentração da matéria-prima e tempo de hidrólise. O carvão ativado foi utilizado como meio adsorvente, e mostrou-se eficaz na remoção da fenilalanina, obtendo-se percentuais acima de 70%. O melhor resultado foi encontrado utilizando-se apancreatina na relação enzima: substrato de 1:100, com a concentração da matéria-prima de 10% após 5 horas de hidrólise, atingindo 81,3% de remoção e o teor final de fenilalaninade 394,1mg/100g de hidrolisado.

Absorption and effectiveness of orally administered low molecular weight collagen hydrolysate in rats.

Collagen, a major extracellular matrix macromolecule, is widely used for biomedical purposes. We investigated the absorption mechanism of low molecular weight collagen hydrolysate (LMW-CH) and its effects on osteoporosis in rats. When administered to Wistar rats with either [(14)C]proline (Pro group) or glycyl-[(14)C]prolyl-hydroxyproline (CTp group), LMW-CH rapidly increased plasma radioactivity. LMW-CH was absorbed into the blood of Wistar rats in the peptide form. Glycyl-prolyl-hydroxyproline tripeptide remained in the plasma and accumulated in the kidney. In both groups, radioactivity was retained at a high level in the skin until 14 days after administration. Additionally, the administration of LMW-CH to ovariectomized stroke-prone spontaneously hypertensive rats increased the organic substance content and decreased the water content of the left femur. Our findings show that LMW-CH exerts a beneficial effect on osteoporosis by increasing the organic substance content of bone.

Plasma amino acid response after ingestion of different whey protein fractions.

BACKGROUND AND OBJECTIVES: The digestion rate of proteins and subsequent absorption of amino acids can independently modulate protein metabolism. The objective of the present study was to examine the blood amino acid response to whey protein isolate (WPI), ß-lactoglobulin-enriched WPI, hydrolysed WPI and a flavour-identical control. METHODS: Eight healthy adults (four female, four male) were recruited (mean±standard error of the mean: age, 27.0±0.76 years; body mass index, 23.2±0.8 kg/cm(2)) and after an overnight fast consumed 500 ml of each drink, each containing 25g protein, in a cross-over design. Blood was taken at rest and then every 15 min for 2 h post ingestion. RESULTS: Ingesting the ß-lactoglobulin-enriched WPI drink resulted in significantly greater plasma leucine concentrations at 45-120 min and significantly greater branched-chain amino acid concentrations at 60-105 min post ingestion compared with hydrolysed WPI. No differences were observed between WPI and ß-lactoglobulin-enriched WPI, and all protein drinks resulted in elevated blood amino acids compared with flavour-identical control. CONCLUSIONS: In conclusion, whole proteins resulted in a more rapid absorption of leucine and branched-chain amino acid into the blood compared with the hydrolysed molecular form of whey protein.

A new view concerning the effects of collagen hydrolysate intake on skin properties.

Dietary supplements (vitamins, polyphenols, micronutrients and proteins) have demonstrated beneficial effects on skin health. The classical route of administration of active compounds is by topical application and manufactures have substantial experience of formulating ingredients in this field. However, the use of functional foods or nutraceuticals for improving skin condition is increasing. The preclinical efficacy assays and bioavailability trials provide a basis from which to establish appropriate collagen hydrolysate (CH) intakes that might impact skin health outcomes. This commentary deals essentially with the general aspects of CH, bioavailability and findings of preclinical studies concerning the effects of CH intake on skin. To comprehensively study the different benefits of CH on skin, controlled clinical trials are needed in addition to the previous pre-clinical and bioavailability assays. Gaps in knowledge are identified and suggestions are made for future research.

Food-derived bioactive peptides influence gut function.

Bioactive peptides either present in foods or released from food proteins during digestion have a wide range of physiological effects, including on gut function. Many of the bioactive peptides characterized to date that influence gut motility, secretion, and absorption are opioid agonists or antagonists. The authors review a body of experimental evidence that demonstrates an effect of peptides from food proteins on endogenous (nondietary) protein flow at the terminal ileum of simple-stomached mammals, including adult humans. At least some dietary peptides (1000-5000 Da) significantly enhance the loss of protein from the small intestine, causing an increased amount of protein to enter the colon. Food-derived peptides appear to either stimulate protein secretion into the gut lumen or inhibit amino acid reabsorption or influence both processes simultaneously. The effect of dietary peptides on small-intestine secretory-protein dynamics is discussed in the context of the major components of gut endogenous protein, sloughed cells, enzymatic secretions, mucin, and bacterial protein.

Collagen hydrolysate for the treatment of osteoarthritis and other joint disorders: a review of the literature.

BACKGROUND: There is a need for an effective treatment for the millions of people in the United States with osteoarthritis (OA), a degenerative joint disease. The demand for treatments, both traditional and non-traditional, will continue to grow as the population ages. SCOPE: This article reviews the medical literature on the preclinical and clinical research on a unique compound, collagen hydrolysate. Articles were obtained through searches of the PubMed database (www.pubmed.gov) through May 2006 using several pairs of key words (collagen hydrolysate and osteoarthritis; collagen hydrolysate and cartilage; collagen hydrolysate and chondrocytes; collagen hydrolysate and clinical trial) without date limits. In addition, other sources of information, such as abstracts presented at scientific congresses and articles in the German medical literature not available on PubMed, were reviewed and included based on the authors' judgment of their relevance to the topic of the review. FINDINGS: According to published research, orally administered collagen hydrolysate has been shown to be absorbed intestinally and to accumulate in cartilage. Collagen hydrolysate ingestion stimulates a statistically significant increase in synthesis of extracellular matrix macromolecules by chondrocytes (p < 0.05 compared with untreated controls). These findings suggest mechanisms that might help patients affected by joint disorders such as OA. Four open-label and three double-blind studies were identified and reviewed; although many of these studies did not provide key information--such as the statistical significance of the findings--they showed collagen hydrolysate to be safe and to provide improvement in some measures of pain and function in some men and women with OA or other arthritic conditions. CONCLUSION: A growing body of evidence provides a rationale for the use of collagen hydrolysate for patients with OA. It is hoped that ongoing and future research will clarify how collagen hydrolysate provides its clinical effects and determine which populations are most appropriate for treatment with this supplement.

Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates.

In the present study, we identified several food-derived collagen peptides in human blood after oral ingestion of some gelatin hydrolysates. Healthy human volunteers ingested the gelatin hydrolysates (9.4-23 g) from porcine skin, chicken feet, and cartilage after 12 h of fasting. Negligible amounts of the peptide form of hydroxyproline (Hyp) were observed in human blood before the ingestion. After the oral ingestion, the peptide form of Hyp significantly increased and reached a maximum level (20-60 nmol/mL of plasma) after 1-2 h and then decreased to half of the maximum level at 4 h after the ingestion. Major constituents of food-derived collagen peptides in human serum and plasma were identified as Pro-Hyp. In addition, small but significant amounts of Ala-Hyp, Ala-Hyp-Gly, Pro-Hyp-Gly, Leu-Hyp, Ile-Hyp, and Phe-Hyp were contained.

Gastric emptying, gastric secretion and enterogastrone response after administration of milk proteins or their peptide hydrolysates in humans.

BACKGROUND: The influence of protein fractionation on gastric emptying and rate of appearance of their constituent amino acids in peripheral blood remains unknown. AIM OF THE STUDY: To examine the influence of the degree of protein fractionation on gastric emptying, gastric secretion, amino acid absorption and enterogastrone response, after the intragastric administration of complete cow milk proteins or their respective peptide hydrolysates in man. METHODS: Six healthy males were randomized to receive one of the following four solutions: whey whole protein (W), casein whole protein (C), whey peptide hydrolysate (WHY) or casein hydrolysate (CAHY). All solutions were matched for volume (600 mL), nitrogen content (9.3 g/L), energy density (1069-1092 kJ/L), osmolality (288-306 mosmol/kg), pH (6.9-7.0) and temperature (37 degrees C). RESULTS: Solutions were emptied at similar rates, with mean half-times of (mean +/- SEM) 21.4 +/- 1.3, 19.3 +/- 2.2, 18.0 +/- 2.5 and 19.4 +/- 2.8 min, for the WHY, CAHY, C and W, respectively. The rates of intestinal absorption of water and amino acids were similar with the exception of the casein protein solution, for which the speed of intestinal amino acid absorption was slower (p < 0.05). The peptide hydrolysates elicited about 50% more gastric secretion than the whole protein solutions ( p < 0.05),which was accompanied by higher glucose-dependent insulinotropic polipeptide (GIP) plasma levels during the first 20 min of the gastric emptying process. Similar glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) plasma responses were elicited by the four solutions. CONCLUSIONS: The rate of gastric emptying and the plasma GLP-1 and PYY responses to feeding with cow milk protein solutions in humans are independent of the degree of protein fractionation and are not altered by small differences in the amino acid composition or protein solubility. In contrast, the GIP response is accentuated when milk proteins are delivered as peptide hydrolysates.

Gastric emptying and fluid availability after ingestion of glucose and soy protein hydrolysate solutions in man.

The double sampling gastric aspiration method was used to measure the effect of energy content on the rate of gastric emptying of glucose and soy protein hydrolysate solutions. The net rate of absorption of water from these solutions was assessed using deuterium oxide as a tracer for water. Six healthy male subjects were each studied on four separate occasions using a test drink volume of 600 ml. The half emptying times (t 1/2, median (range)) of the iso-energetic soy protein hydrolysate (6P, 60 g l(-1), 36 (14-39) min) and glucose (7G, 70 g l(-1), 25 (19-29) min) solutions were similar. These two solutions (6P, 7G) delivered energy to the small intestine at similar rates, and resulted in similar rates of accumulation of the deuterium tracer in the circulation. The dilute glucose solution (LG, 23 g l(-1)) was emptied faster (t 1/2 13 (11-19) min) and resulted in a faster rate of tracer accumulation in the circulation than any of the other solutions, including the iso-osmotic soy protein solution (LG 311 +/- 5 mosmol kg(-1), 6P 321 +/- 24 mosmol kg(-1)). The concentrated soy protein hydrolysate solution (12P, 120 g l(-1)) emptied more slowly (t 1/2 80 (44-120) min) than the more dilute solutions. The rate of energy delivery to the small intestine from 12P was similar to that from 6P for the first 50 min after ingestion, and similar to that from 7G at all sample points. These results indicate that the iso-energetic solutions of glucose and soy protein hydrolysate used in this study are emptied from the stomach at similar rates and result in similar rates of fluid availability after ingestion.

Amino acid composition of soybean protein increased postprandial carbohydrate oxidation in diabetic mice.

The effects of an amino acid mixture simulating dietary soybean protein on the postprandial energy metabolism was investigated using type II diabetic mice. KK-A(y) strain mice were fed restrictive isoenergetic and isonitrogenous diets (35% of energy as protein and 5% as fat) based on either casein, soybean protein isolate hydrolysate (SPI-H), SPI-HET (ethanol unsoluble fraction of SPI-H), SPI-AA and casein-AA (amino acid mixtures simulating SPI-H and casein). To measure dietary carbohydrate oxidation, the animals were fed a diet containing (13)C-glucose. Postprandial respiratory quotient and expired (13)CO(2) were higher in the SPI-AA than in the casein-AA group, as the differences were similarly observed in mice fed SPI-H and casein diet. No significant differences were observed in the postprandial respiratory quotient and expired (13)CO(2) between the SPI-H and SPI-HET group. In conclusion, this study on food-restricted mice indicates that the amino acid mixtures simulating SPI-H or casein could affect postprandial energy metabolism in diabetic mice, as observed in those fed SPI-H or casein in the form of peptide or protein.