Intact Whey Protein Research Articles

Comparing the effect of homogenization and heat processing on the properties and in vitro digestion of milk from organic and conventional dairy herds.

We compared the effects of homogenization and heat processing on the chemical and in vitro digestion traits of milk from organic and conventional herds. Raw milk from organic (>50% of dry matter intake from pasture) and conventional (no access to pasture) farms were adjusted to commercial whole and nonfat milk fat standards, and processed with or without homogenization, and with high-temperature-short-time or UHT pasteurization. The milk then underwent in vitro gastrointestinal digestion. Comparison of milk from organic and conventional herds showed that the milks responded to processing in similar ways. General composition was the same among the whole milk samples and among the nonfat milk samples. Protein profiles were similar, with intact caseins and whey proteins predominant and only minor amounts of peptides. Whole milk samples from grazing cows contained higher levels of α-linolenic (C18:3), vaccenic (C18:1 trans), and conjugated linoleic acids, and lower levels of palmitic (C16:0) and stearic (C18:0) acids than samples from nongrazing cows. Processing had no effect on conjugated linoleic acid and linolenic acid levels in milk, although homogenization resulted in higher levels of C8 to C14 saturated fatty acids. Of the 9 volatile compounds evaluated, milk from grazing cows contained lower levels of 2-butanone than milk from nongrazing cows, and milk from both farms showed spikes for heptanal in UHT samples and spikes for butanoic, octanoic, nonanoic, and N-decanoic acids in homogenized samples. At the start of in vitro digestion, nonfat raw and pasteurized milk samples formed the largest acid clots, and organic milk clots were larger than conventional milk clots; UHT whole milk formed the smallest clots. Milk digests from grazing cows had lower levels of free fatty acids than digests from nongrazing cows. In vitro proteolysis was similar in milk from both farms and resulted in 85 to 95% digestibility. Overall, milk from organic/grass-fed and conventional herds responded in similar ways to typical homogenization and heat processing used in United States dairy plants and showed only minor differences in chemical traits and in vitro digestion. Findings from this research enhance our knowledge of the effect of processing on the quality traits and digestibility of milk from organic/pasture-fed and confined conventional herds and will help health-conscious consumers make informed decisions about dairy selections.

Whey Hydrolysate Supplementation Following Resistance Exercise Elicits Similar Anabolic Responses in Both Young and Older Adults

Skeletal muscle sensitivity to dietary protein and exercise typically declines during aging. However, previous data presented by our group indicates that whey protein hydrolysate (WH, di- and tri-peptide mixture) may be able to stimulate muscle anabolism at lower dosages than observed with intact whey protein in older adults. PURPOSE: To compare the effect of a minimal dose (10 g) of WH provided after resistance exercise (REx) on skeletal muscle anabolism in young and older adults. METHODS: Twenty healthy recreationally active adults (YOUNG: M=8, F=2; 25±4yr, 25±4 kg[BULLET OPERATOR]m2 | OLD: M=7, F=3; 65±4yr, 25±4 kg[BULLET OPERATOR]m2) were studied pre- and post-ingestion (PI) of 10 g of WH 1 h after high-intensity REx ([email protected]~70% 1RM, leg ext). We measured mixed-muscle protein fractional synthetic rate (FSR) and plasma BCAA concentrations by stable isotopic methods. Western-blotting was used to asses anabolic signaling and the presence of peptide transporters in muscle. Muscle biopsies from the vastus lateralis were collected at rest and during the early (0–2 h) and late (2–4 h) PI periods. Mixed muscle FSR and anabolic signaling was analyzed using a 2(group) x 3(time) mixed model ANOVA repeated across time. BCAA concentrations were modeled separately per time point using a 2 (group) x 2 (time) mixed-model ANOVA. Type I error for all analyses was set at α=0.05.Table: No title available.RESULTS: Compared with rest, increases in p-mTOR (Young: +2.0 fold, Old: +2.5 fold) and p-4E-BP1 (Young: +1.5 fold, Old: +1.4 fold) were observed in both groups at 4h PI (p<0.05). Increases in p-S6K1 were observed in both groups at 2h PI but to a greater extent in the OLD group (p <0.05). Peptide transporter-1 (PEPT1) expression was found in muscle samples from both groups. CONCLUSION: WH provided after Rex enhances muscle anabolism in older adults at a dose previously shown to be ineffective with intact whey isolate. Future studies will be required to determine if WH may aid in the long-term preservation of muscle in this population.

Effect of hydrolyzed whey protein on surface morphology, water sorption, and glass transition temperature of a model infant formula

Physical properties of spray-dried dairy powders depend on their composition and physical characteristics. This study investigated the effect of hydrolyzed whey protein on the microstructure and physical stability of dried model infant formula. Model infant formulas were produced containing either intact (DH 0) or hydrolyzed (DH 12) whey protein, where DH=degree of hydrolysis (%). Before spray drying, apparent viscosities of liquid feeds (at 55°C) at a shear rate of 500 s−1 were 3.02 and 3.85 mPa·s for intact and hydrolyzed infant formulas, respectively. On reconstitution, powders with hydrolyzed whey protein had a significantly higher fat globule size and lower emulsion stability than intact whey protein powder. Lactose crystallization in powders occurred at higher relative humidity for hydrolyzed formula. The Guggenheim-Anderson-de Boer equation, fitted to sorption isotherms, showed increased monolayer moisture when intact protein was present. As expected, glass transition decreased significantly with increasing water content. Partial hydrolysis of whey protein in model infant formula resulted in altered powder particle surface morphology, lactose crystallization properties, and storage stability.

Whey Protein Hydrolysates Accelerate Rat Muscle Protein Synthesis At Lower Doses Than Intact Whey Protein

PURPOSE: The intake of whey protein is highly effective for accelerating muscle protein synthesis. Many studies have revealed that a rapid absorption rate and the leucine-rich amino-acid composition of whey protein contribute to the acceleration of muscle protein synthesis. Whey protein hydrolysates (WPH) have amino-acid composition identical to intact whey protein isolate (WPI) and are absorbed more rapidly than WPI. Our hypothesis was that WPH is a more potent accelerator for muscle protein synthesis than WPI. The aim of the present study was to compare the effects of WPH on muscle protein synthesis with WPI. METHODS: Male Sprague-Dawley (SD) rats swam for 2 h. Immediately after exercise, WPI was administered to the rats as a single dose (amounts of protein were 2.0 g/kg BW). Phe-D5 was injected via the tail vein 15 min before euthanasia for the measurement of the protein fractional synthesis rate (FSR). Rats were euthanized at designated postprandial time points (30, 60, 90 or 120 min) and triceps muscle samples were collected (n = 7-9/time point). FSR were measured to find out the time point at which FSR became highest. Subsequently, another group of male SD rats swam for 2 h. Immediately after exercise, WPH, WPI or deionized water (control, n = 8) was administered to the rats as a single dose (amounts of protein were 0.5 or 2.0 g/kg BW, n = 8/treatment/dose). Phe-D5 was injected via the tail vein 15 min before euthanasia. At the time point that the first study revealed postprandial FSR became highest, rats were anesthetized and their triceps muscles were excised to measure FSR. RESULTS: Postprandial FSR became highest at 60 min after WPI was administered (2.68+/-0.25, 3.64+/-0.19, 4.62+/-0.28, 4.19+/-0.21 and 3.99+/-0.19 %/day for 0, 30, 60, 90 and 120 min). 60 min after administration, WPH had significantly higher (p < 0.05) FSR compared to control at a dose of either 0.5 or 2.0 g/kg BW (5.21+/-0.22, 5.22+/-0.18 and 3.74+/-0.24 %/day for 0.5, 2.0 g/kg BW and control, respectively). However, WPI had significantly higher (p < 0.05) FSR compared to control only at a dose of 2.0 g/kg BW (4.51+/-0.10 and 5.09+/-0.20 for 0.5 and 2.0 g/kg BW). WPH had significantly higher (p < 0.05) FSR compared to WPI at 0.5 g/kg BW. CONCLUSIONS: Whey protein hydrolysates stimulate muscle protein synthesis at lower doses compared to intact whey protein.

Improvement of the functional properties of whey protein hydrolysate by conjugation with maltodextrin

The impact of conjugation with maltodextrin on selected functional properties (i.e., solubility and thermal stability) of intact whey protein isolate (WPI) and whey protein hydrolysate (WPH) was determined. Conjugation of WPI and WPH (degree of hydrolysis 9.3%) with maltodextrin (MD) was achieved by heating solutions of 5% WPI or WPH with 5% MD, initial pH 8.2, at 90 °C for up to 24 h. The WPH had 55.4% higher levels of available amino groups compared with the WPI, which contributed to more rapid and extensive conjugation of WPH-MD, compared with WPI-MD. The WPI-MD and WPH-MD solutions heated for 8 h had significantly higher (P < 0.05) protein solubility than the respective WPI and WPH heated control solutions, in the pH range 4.0–5.0. Conjugation of WPI and WPH with MD enhanced the stability to heat-induced changes, such as turbidity development, gelation or precipitation, in the presence of 40 mm added NaCl.

Improving thermal stability of hydrolysed whey protein-based infant formula emulsions by protein–carbohydrate conjugation

Whey protein hydrolysate (WPH) ingredients are commonly used in the manufacture of partially-hydrolysed infant formulae. The heat stability of these emulsion-based formulae is often poor, compared with those made using intact whey protein. The objective of this study was to improve the heat stability of WPH-based emulsions by conjugation of WPH with maltodextrin (MD) through wet heating. Emulsions stabilised by different protein ingredients, whey protein isolate (WPIE), whey protein hydrolysate (WPHE), heated WPH (WPH-HE), and WPH conjugated with MD (WPH-CE) were prepared and heat treated at 75°C, 95°C or 100°C for 15min. Changes in viscosity, fat globule size distribution (FGSD) and microstructure, evaluated using confocal laser scanning microscopy (CLSM), were used to monitor the effects of hydrolysis, pre-heating and conjugation on the heat stability of the emulsions. Heat stability increased in the order WPHE<WPIE<<WPH-HE<<<WPH-CE; emulsions WPHE, WPIE and WPH-HE destabilised on heating at 75°C, 95°C or 100°C, respectively. Flocculation and coalescence of oil droplets were mediated by protein aggregation (as evidenced by CLSM) on heat treatment of WPH-HE emulsion at 100°C, while no changes in FGSD or microstructure were observed in WPH-CE emulsion on heat treatment at 100°C, demonstrating the excellent thermal stability of emulsions prepared with the conjugated WPH ingredient, due principally to increased steric stabilisation as a result of conjugation.

Water sorption and diffusion properties of spray-dried dairy powders containing intact and hydrolysed whey protein

The aim was to compare the effect of intact or hydrolysed whey protein in spray-dried lactose/protein powders on water diffusion properties and microstructure. Dispersions of protein/lactose (0.21:1) containing either intact or hydrolysed whey protein were spray-dried at pilot scale, and physical properties were determined. Lactose/hydrolysed whey protein powders had significantly increased (P < 0.05) particle density, resulting in lower bulk density and occluded air, and higher interstitial air. Moisture sorption analysis at 25 °C showed that dispersions containing intact whey protein exhibited lactose crystallisation at a lower relative humidity (RH) compared to the dispersions containing hydrolysed whey protein. Hydrolysed whey protein dispersions had a lower monolayer moisture value (mm) than intact whey protein dispersions, as calculated using the Guggenheim–Anderson–de Boer (GAB) equation. Water diffusivity, determined at 25 °C from water sorption kinetics and the application of a mathematical model based on Fick's 2nd law, was significantly different (P < 0.05) with respect to the presence of intact or hydrolysed whey protein over the RH range examined (0–60% RH), except at 40% RH. The presence of hydrolysed whey protein resulted in a significantly higher (P < 0.05) water diffusivity in powders, with potential implications for hygroscopicity, caking, stickiness and flowability in humid environments.

Antihypertensive and cardioprotective effects of the dipeptide isoleucine-tryptophan and whey protein hydrolysate.

Angiotensin-converting enzyme inhibitors are treatment of choice in hypertensive patients. Clinically used inhibitors exhibit a structural similarity to naturally occurring peptides. This study evaluated antihypertensive and cardioprotective effects of ACE-inhibiting peptides derived from food proteins in spontaneously hypertensive rats. Isoleucine-tryptophan (in vitro IC50 for ACE = 0.7 μm), a whey protein hydrolysate containing an augmented fraction of isoleucine-tryptophan, or captopril was given to spontaneously hypertensive rats (n = 60) over 14 weeks. Two further groups, receiving either no supplement (Placebo) or intact whey protein, served as controls. Systolic blood pressure age-dependently increased in the Placebo group, whereas the blood pressure rise was effectively blunted by isoleucine-tryptophan, whey protein hydrolysate and captopril (-42 ± 3, -38 ± 5, -55 ± 4 mm Hg vs. Placebo). At study end, myocardial mass was lower in isoleucine-tryptophan and captopril groups but only partially in the hydrolysate group. Coronary flow reserve (1 μm adenosine) was improved in isoleucine-tryptophan and captopril groups. Plasma ACE activity was significantly decreased in isoleucine-tryptophan, hydrolysate and captopril groups, but in aortic tissue only after isoleucine-tryptophan or captopril treatment. This was associated with lowered expression and activity of matrix metalloproteinase-2. Following isoleucine-tryptophan and captopril treatments, gene expression of renin was significantly increased indicating an active feedback within renin-angiotensin system. Whey protein hydrolysate and isoleucine-tryptophan powerfully inhibit plasma ACE resulting in antihypertensive effects. Moreover, isoleucine-tryptophan blunts tissue ACE activity, reduces matrix metalloproteinase-2 activity and improves coronary flow reserve. Thus, whey protein hydrolysate and particularly isoleucine-tryptophan may serve as innovative food additives with the goal of attenuating hypertension.

Whey Protein Hydrolysate but not Whole Whey Protein Protects Against 7,12-Dimethylbenz(a)anthracene-Induced Mammary Tumors in Rats

Effects of intact and processed bovine milk proteins on development of chemically induced mammary tumors in female rats were compared. AIN-93G diets were made with 20% casein (CAS), casein hydrolysate (CASH), intact whey protein (IWP), or whey protein hydrolysate (WPH). Pregnant Sprague-Dawley rats were fed the diets starting at Gestational Day 4. Offspring were fed the same diet. At 50 days, female offspring (44–49/group) were gavaged with sesame oil containing 80 mg/kg of the mammary carcinogen dimethylbenzanthracene (DMBA) and euthanized 62 days posttreatment. Rats fed WPH had an adenocarcinoma incidence of 17% compared to the rats fed CAS, CASH, and IWP diets (34%, 33%, and 36% respectively) (P < 0.001). Median palpable tumor latency for rats fed WPH was greater (61 days, P < 0.001) compared to CAS (44 days), CASH (42 days) and IWP (45 days). Tumor multiplicity was also lower (1.5 vs. 3.0, P < 0.05) in rats fed WPH than in CAS and CASH fed groups. Results demonstrate that hydrolytic processing of whey protein is required for this diet to be effective in reducing DMBA-induced mammary tumors. The bioactive compounds produced during whey protein processing and mechanisms underlying the anticancer effects of WPH are yet to be identified.

Improved Functional Characteristics of Whey Protein Hydrolysates in Food Industry.

This review focuses on the enhanced functional characteristics of enzymatic hydrolysates of whey proteins (WPHs) in food applications compared to intact whey proteins (WPs). WPs are applied in foods as whey protein concentrates (WPCs), whey protein isolates (WPIs), and WPHs. WPs are byproducts of cheese production, used in a wide range of food applications due to their nutritional validity, functional activities, and cost effectiveness. Enzymatic hydrolysis yields improved functional and nutritional benefits in contrast to heat denaturation or native applications. WPHs improve solubility over a wide range of pH, create viscosity through water binding, and promote cohesion, adhesion, and elasticity. WPHs form stronger but more flexible edible films than WPC or WPI. WPHs enhance emulsification, bind fat, and facilitate whipping, compared to intact WPs. Extensive hydrolyzed WPHs with proper heat applications are the best emulsifiers and addition of polysaccharides improves the emulsification ability of WPHs. Also, WPHs improve the sensorial properties like color, flavor, and texture but impart a bitter taste in case where extensive hydrolysis (degree of hydrolysis greater than 8%). It is important to consider the type of enzyme, hydrolysis conditions, and WPHs production method based on the nature of food application.

Whey proteins have beneficial effects on intestinal enteroendocrine cells stimulating cell growth and increasing the production and secretion of incretin hormones

Whey protein has been indicated to curb diet-induced obesity, glucose intolerance and delay the onset of type 2 diabetes mellitus. Here the effects of intact crude whey, intact individual whey proteins and beta-lactoglobulin hydrolysates on an enteroendocrine (EE) cell model were examined. STC-1 pGIP/neo cells were incubated with several concentrations of yogurt whey (YW), cheese whey (CW), beta-lactoglobulin (BLG), alpha-lactalbumin (ALA) and bovine serum albumin (BSA). The findings demonstrate that BLG stimulates EE cell proliferation, and also GLP-1 secretion (an effect which is lost following hydrolysis with chymotrypsin or trypsin). ALA is a highly potent GLP-1 secretagogue which also increases the intracellular levels of GLP-1. Conversely, whey proteins and hydrolysates had little impact on GIP secretion. This appears to be the first investigation of the effects of the three major proteins of YW and CW on EE cells. The anti-diabetic potential of whey proteins should be further investigated.

Dietary Whey Protein Hydrolysates Increase Skeletal Muscle Glycogen Levels via Activation of Glycogen Synthase in Mice

Previously, we have shown that consuming carbohydrate plus whey protein hydrolysates (WPHs) replenished muscle glycogen after exercise more effectively than consuming intact whey protein or branched-chain amino acids (BCAAs). The mechanism leading to superior glycogen replenishment after consuming WPH is unclear. In this 5 week intervention, ddY mice were fed experimental diets containing WPH, a mixture of whey amino acids (WAAs), or casein (control). After the intervention, gastrocnemius muscle glycogen levels were significantly higher in the WPH group (4.35 mg/g) than in the WAA (3.15 mg/g) or control (2.51 mg/g) groups. In addition, total glycogen synthase (GS) protein levels were significantly higher in the WPH group (153%) than in the WAA (89.2%) or control groups, and phosphorylated GS levels were significantly decreased in the WPH group (51.4%). These results indicate that dietary WPH may increase the muscle glycogen content through increased GS activity.

Beneficial Effects of Resistance Exercise on Glycemic Control Are Not Further Improved by Protein Ingestion

PurposeTo investigate the mechanisms underpinning modifications in glucose homeostasis and insulin sensitivity 24 h after a bout of resistance exercise (RE) with or without protein ingestion.MethodsTwenty-four healthy males were assigned to a control (CON; n = 8), exercise (EX; n = 8) or exercise plus protein condition (EX+PRO; n = 8). Muscle biopsy and blood samples were obtained at rest for all groups and immediately post-RE (75% 1RM, 8×10 repetitions of leg-press and extension exercise) for EX and EX+PRO only. At 24 h post-RE (or post-resting biopsy for CON), a further muscle biopsy was obtained. Participants then consumed an oral glucose load (OGTT) containing 2 g of [U-13C] glucose during an infusion of 6, 6-[2H2] glucose. Blood samples were obtained every 10 min for 2 h to determine glucose kinetics. EX+PRO ingested an additional 25 g of intact whey protein with the OGTT. A final biopsy sample was obtained at the end of the OGTT.ResultsFasted plasma glucose and insulin were similar for all groups and were not different immediately post- and 24 h post-RE. Following RE, muscle glycogen was 26±8 and 19±6% lower in EX and EX+PRO, respectively. During OGTT, plasma glucose AUC was lower for EX and EX+PRO (75.1±2.7 and 75.3±2.8 mmol·L−1∶120 min, respectively) compared with CON (90.6±4.1 mmol·L−1∶120 min). Plasma insulin response was 13±2 and 21±4% lower for EX and CON, respectively, compared with EX+PRO. Glucose disappearance from the circulation was ∼12% greater in EX and EX+PRO compared with CON. Basal 24 h post-RE and insulin-stimulated PAS-AS160/TBC1D4 phosphorylation was greater for EX and EX+PRO.ConclusionsPrior RE improves glycemic control and insulin sensitivity through an increase in the rate at which glucose is disposed from the circulation. However, co-ingesting protein during a high-glucose load does not augment this response at 24 h post-exercise in healthy, insulin-sensitive individuals.

Effect of premeal consumption of whey protein and its hydrolysate on food intake and postmeal glycemia and insulin responses in young adults

Dairy protein ingestion before a meal reduces food intake and, when consumed with carbohydrate, reduces blood glucose. The objective was to describe the effect of whey protein (WP) or its hydrolysate (WPH) when consumed before a meal on food intake, pre- and postmeal satiety, and concentrations of blood glucose and insulin in healthy young adults. Two randomized crossover studies were conducted. WP (10-40 g) in 300 mL water was provided in experiment 1, and WP (5-40 g) and WPH (10 g) in 300 mL water were provided in experiment 2. At 30 min after consumption, the subjects were fed an ad libitum pizza meal (experiment 1) or a preset pizza meal (12 kcal/kg, experiment 2). Satiety, blood glucose, and insulin were measured at baseline and at intervals both before and after the meals. In experiment 1, 20-40 g WP suppressed food intake (P < 0.0001) and 10-40 g WP reduced postmeal blood glucose concentrations and the area under the curve (AUC) (P < 0.05). In experiment 2, 10-40 g WP, but not WPH, reduced postmeal blood glucose AUC and insulin AUC in a dose-dependent manner (P < 0.05). The ratio of cumulative blood glucose to insulin AUCs (0-170 min) was reduced by > or =10 g WP but not by 10 g WPH. WP consumed before a meal reduces food intake, postmeal blood glucose and insulin, and the ratio of cumulative blood glucose to insulin AUCs in a dose-dependent manner. Intact WP, but not WPH, contributes to blood glucose control by both insulin-dependent and insulin-independent mechanisms. This trial was registered at clinicaltrials.gov as NCT00988377 and NCT00988182.

Antioxidant properties of whey protein hydrolysates as measured by three methods

Four microbial proteases (Alcalase, Flavourzyme, Neutrase and Protamex) were used for the preparation of whey protein hydrolysates. The aim of this research was to find out whether these hydrolysates can be used as a source of whey derived antioxidants. Hydrolyzed samples, including their unhydrolyzed protein solutions were tested by the ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) decolorization assay, by the total radical-trapping potential method and by the assay of liposomes peroxidation (fluorescence photometry). Antioxidant properties were enhanced by hydrolysis in most of cases. Alcalase hydrolysates were found as the most effective antioxidants as determined by ABTS assay (~50% of antioxidant activity at 0.1 mg ml−1 of hydrolysate in reaction) and fluorescence photometry. Liposomes were oxidized ~50% less (1.1 μM of α-tocopherol equivalent) with Alcalase hydrolysates additive (at 5.85 mg ml−1 of hydrolysate in reaction). Hydrolysates did not inhibit the oxidation of liposomes at concentrations below 1.0 mg ml−1 in reaction. On the contrary, results of total trapping potential method did not agree with findings observed in other tests. In this assay, Neutrase hydrolysates showed the best antioxidant properties. Pro-oxidant properties were observed in solutions containing (prior to the enzyme Protamex addition only) intact whey protein as determined by the measurement of the liposome peroxidation. The ABTS assay was optimized for the evaluation of the antioxidant activity in whey protein hydrolysates. The reaction time should be prolonged to avoid underestimation of the antioxidant activity.

Glucagon and insulin responses after ingestion of different amounts of intact and hydrolysed proteins

Ingestion of dietary protein is known to induce both insulin and glucagon secretion. These responses may be affected by the dose and the form (intact or hydrolysed) in which protein is ingested. The aim of the study was to investigate the effect of different amounts of intact protein and protein hydrolysate of a vegetable (soya) and animal (whey) protein on insulin and glucagon responses and to study the effect of increasing protein loads for both intact protein and protein hydrolysate in man. The study employed a repeated-measures design with Latin-square randomisation and single-blind trials. Twelve healthy non-obese males ingested three doses (0.3, 0.4 and 0.6 g/kg body weight) of intact soya protein (SPI) and soya protein hydrolysate (SPH). Another group of twelve healthy male subjects ingested three doses (0.3, 0.4 and 0.6 g/kg body weight) of intact whey protein (WPI) and whey protein hydrolysate (WPH). Blood was sampled before (t = 0) and 15, 30, 60, 90 and 120 min after protein ingestion for insulin, glucagon and glucose determination. SPI induced a higher total area under the curve for insulin and glucagon than SPH while no difference between WPI and WPH was found. Insulin and glucagon responses increased with increasing protein load for SPI, SPH, WPI and WPH, but the effect was more pronounced for glucagon. A higher dose of protein or its hydrolysate will result in a lower insulin:glucagon ratio, an important parameter for the control of postprandial substrate metabolism. In conclusion, insulin and glucagon responses were protein and hydrolysate specific.

Similar 24h anabolic response to intact and hydrolysed whey protein ingested postexercise in elderly subjects

Since peptides are absorbed faster than intact proteins it was hypothesized that ingestion of protein hydrolysate after resistance exercise would cause a greater anabolic response than intact protein as timing is of significance in elderly. Muscle protein turnover was measured during a 27 h infusion of L-[1-13C]-leucine in 7 healthy (5M and 2F) aged 71(4) yr (mean(SEM)) who received on separate days carbohydrate with intact, IP or hydrolyzed whey protein, HP (0.25g/kg ~ 18g) over a 2h period after resistance exercise. Arteriovenous samples and muscle biopsies were obtained. Evaluated 1–1.5 h postexercise net balance of leucine was positive, although highest (p<0.05) in IP (0.38 ± 0.07 v 0.09 ± 0.08 mg*h−1*leg−1). Accordingly, was AUC of art-[leucine] higher in IP than HP (6.2 ± 0.5 v 5.4 ± 0.4 mmol/L). Subsequently, no difference was observed. Further, no differences were observed at any time point between IP and HP for protein synthesis, breakdown or oxidation. Muscle fractional synthetic rate was not different between IP an HP over 4 (0.07 ± 0.01 v 0.09 ± 0.01 %/h) or 24 hours post-exercise (0.08 ± 0.01 v 0.09 ± 0.01 %/h). These results suggest that protein ingested after resistance exercise in elderly results in a transient positive net protein synthesis, with no overall difference in the anabolic response between intact and hydrolysed whey.

Differential stimulation of muscle protein synthesis in elderly humans following isocaloric ingestion of amino acids or whey protein

To counteract the debilitating progression of sarcopenia, a protein supplement should provide an energetically efficient anabolic stimulus. We quantified net muscle protein synthesis in healthy elderly individuals (65–79 yrs) following ingestion of an isocaloric intact whey protein supplement (WY; n=8) or an essential amino acid supplement (EAA; n=7). Femoral arterio-venous blood samples and vastus lateralis muscle biopsy samples were obtained during a primed, constant infusion of L-[ring- 2H 5]phenylalanine. Net phenylalanine uptake and mixed muscle fractional synthetic rate (FSR) were calculated during the post-absorptive period and for 3.5 h following ingestion of 15 g EAA or 15 g whey. After accounting for the residual increase in the intracellular phenylalanine pool, net post-prandial phenylalanine uptake was 53.4±9.7 mg phe leg −1 (EAA) and 21.7±4.6 mg phe leg −1 (WY), ( P<0.05). Postabsorptive FSR values were 0.056±0.004% h −1 (EAA) and 0.049±0.006% h −1 (WY), ( P>0.05). Both supplements stimulated FSR ( P<0.05), but the increase was greatest in the EAA group with values of 0.088±0.011% h −1 (EAA) and 0.066±0.004% h −1 (WY), ( P<0.05). While both EAA and WY supplements stimulated muscle protein synthesis, EAAs may provide a more energetically efficient nutritional supplement for elderly individuals.

Heat stability of oil-in-water emulsions formed with intact or hydrolysed whey proteins: influence of polysaccharides

The heat stability of emulsions (4 wt% corn oil) formed with whey protein isolate (WPI) or extensively hydrolysed whey protein (WPH) products and containing xanthan gum or guar gum was examined after a retort treatment at 121 °C for 16 min. At neutral pH and low ionic strength, emulsions stabilized with both 0.5 and 4 wt% WPI (intact whey protein) were stable against retorting. The amount of β-lactoglobulin (β-lg) at the droplet surface increased during retorting, especially in the emulsion containing 4 wt% protein, whereas the amount of adsorbed α-lactalbumin (α-la) decreased markedly. Addition of xanthan gum or guar gum caused depletion flocculation of the emulsion droplets, but this flocculation did not lead to their aggregation during heating. In contrast, the droplet size of emulsions formed with WPH increased during heat treatment, indicating that coalescence had occurred. The coalescence during heating was enhanced considerably with increasing concentration of polysaccharide in the emulsions, up to 0.12% and 0.2% for xanthan gum and guar gum, respectively; whey peptides in the WPH emulsions formed weaker and looser, mobile interfacial structures than those formed with intact whey proteins. Consequently, the lack of electrostatic and steric repulsion resulted in the coalescence of flocculated droplets during retort treatment. At higher levels of xanthan gum or guar gum addition, the extent of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase.

Hyperglycemia after protein ingestion concurrent with injection of a GLP-1 receptor agonist in rats: a possible role for dietary peptides

Protein ingestion after injection of the glucagon-like peptide-1 receptor agonist Exendin-4 (Ex-4) causes hyperglycemia in rats. The objectives of this study were to determine the components of protein digestion responsible for this effect and to associate it with changes in the concentrations of other metabolites and hormones. Two experiments were conducted. In the first experiment, food-deprived rats were gavaged with intact whey (WP) or albumin protein, their hydrolysates, amino acid mixtures (1 g/2.5 ml), or water 5 min after injection of either PBS or Ex-4 (0.5 microg/rat). Tail vein blood was analyzed for glucose over 2 h. In the second experiment, food-deprived rats were gavaged with WP with or without Ex-4. Groups of conscious rats were killed by decapitation either before, or at selected times after gavage. Plasma concentrations of glucose, amino acids, free fatty acids (FFA), glycerol, insulin, glucagon, and leptin were measured. In experiment 1, blood glucose was higher when intact proteins and protein hydrolysates, but not amino acid mixtures, were given with than without Ex-4 (P < 0.05). In experiment 2, concentrations of glucose, FFA, and the ratio of tyrosine to branched-chain amino acid were higher (P < 0.01), but leptin and essential amino acid concentrations were lower (P < 0.05), and insulin, glucagon, and glycerol were similar when WP was given with or without Ex-4. We conclude that the hyperglycemia caused by the administration of Ex-4 concurrently with dietary protein arises from the action of peptides released during digestion and their interaction with Ex-4 in the regulation of glucose, fatty acid, and amino acid metabolism.