Plasma Amino Acid Responses Research Articles

Absorption and safety of serum-derived bovine immunoglobulin/protein isolate in healthy adults.

PurposePrevious studies have shown that oral administration of bovine immunoglobulin protein preparations is safe and provides nutritional and intestinal health benefits. The purpose of this study was to evaluate the plasma amino acid response following a single dose of serum-derived bovine immunoglobulin/protein isolate (SBI) and whether bovine immunoglobulin G (IgG) is present in stool or in blood following multiple doses of SBI in healthy volunteers.MethodsA total of 42 healthy adults were administered a single dose of placebo or SBI at one of three doses (5 g, 10 g, or 20 g) in blinded fashion and then continued on SBI (2.5 g, 5 g, or 10 g) twice daily (BID) for an additional 2 weeks. Serial blood samples were collected for amino acid analysis following a single dose of placebo or SBI. Stool and blood samples were collected to assess bovine IgG levels.ResultsThe area under the curve from time 0 minute to 180 minutes for essential and total amino acids as well as tryptophan increased following ingestion of 5 g, 10 g, or 20 g of SBI, with a significant difference between placebo and all doses of SBI (p<0.05) for essential amino acids and tryptophan but only the 10 g and 20 g doses for total amino acids. Bovine IgG was detected in the stool following multiple doses of SBI. No quantifiable levels of bovine IgG were determined in plasma samples 90 minutes following administration of a single dose or multiple doses of SBI.ConclusionOral administration of SBI leads to increases in plasma essential amino acids during transit through the gastrointestinal tract and is safe at levels as high as 20 g/day.

Comparison of the Amino Acid and Peptide Composition and Postprandial Response of Beef, Chicken, and Whey Protein Nutritional Preparations

Background: Increasing dietary protein intake synergistically improves the effect of exercise to stimulate muscle protein synthesis. The purpose of this study was to evaluate the plasma amino acid response of two novel protein nutritional preparations, beef protein isolate (BeefISOTM) and hydrolyzed chicken protein isolate (MyoCHXTM). Methods: The postprandial plasma amino acid response over 3 hours was monitored in young adults (n=6) following consumption of 23 grams of WPC, BeefISOTM, or MyoCHXTM. Amino acid compositional analysis and molecular weight distributions of each protein were performed by HPLC. Statistical analyses were performed using one-way or two-way ANOVA where appropriate and corrected for multiple comparisons to account for the cross-over design. Results: Compositional evaluations revealed similar levels of essential and branched-chain amino acids for WPC and MyoCHXTM. While the results of this study predictably demonstrated plasma amino acids levels increased following consumption of the different proteins, the kinetics of the postprandial response was unique to each protein source. WPC and MyoCHXTM were rapidly absorbed with maximum plasma amino acid concentrations observed at 30 and 15 min, respectively. The slightly faster absorption of MyoCHXTM was associated with the increased peptide content of MyoCHXTM (greater than 76% of protein is &lt;2kDa). BeefISOTM exhibited sustained release characteristics as evidenced by increased post prandial amino acid concentrations after 3 hours. Conclusions: The protein preparations studied each had different amino acid profiles and absorption kinetics. WPC and MyoCHXTM contained a higher essential amino acid content and were rapidly absorbed with plasma amino acid concentrations peaking within 30 minutes following consumption. BeefISOTM contained a higher proportion of conditionally essential amino acids that steadily increased in plasma over 3 hours, indicating a sustained release profile for BeefISOTM. Each of these three protein preparations have been shown to facilitate similar improvements in body composition following a resistance-exercise training program. The paradoxical finding that proteins with varying composition, molecular weight, and digestibility can lead to similar effects on body composition suggests the need to evaluate proteins based on total nutritional potential rather than as a delivery vehicle for single amino acids.Key Words: Protein digestibility; amino acids; body composition; beef protein; chicken protein

Soya milk exerts different effects on plasma amino acid responses and incretin hormone secretion compared with cows’ milk in healthy, young men

Apart from the well-known action of insulin, the mechanism by which soya and cows' milk improve postprandial glycaemia control was examined. In total, twelve healthy, young, Chinese men were studied on three separate occasions, in random order with isovolumetric (322 ml) control water, soya milk and cows' milk. Plasma total amino acid concentrations increased 30 min after test meals consumption and were higher after soya milk (230 %) and cow milk (240 %) consumption compared with water. Cows' milk ingestion induced higher branched-chain amino acids (BCAA) (40 %) than soya milk. Postprandial incretin concentrations increased after meal consumption. Cows' milk meal was accompanied by higher incremental AUC (iAUC) (170 %) for glucagon-like peptide-1 (GLP-1) compared with soya milk and control (P=0·06). However, glucose-dependent insulinotropic polypeptide (GIP) concentrations increased to significantly greater levels after soya milk consumption (iAUC 60 % higher) compared with cows' milk and control. Consumption of both soya and cows' milk with carbohydrates induced a similar reduction in glycaemic response through a different mechanism, beyond insulin action. Plasma amino acids (alanine and arginine), and incretins in particular (GIP was stimulated), may be involved in the hyperinsulinaemia after soya milk meals. However, BCAA and GLP-1 release may be responsible for the reduced glycaemia after cows' milk consumption by delaying gastric emptying. This could be the result of different milk protein/amino acid composition, but also differences in milk carbohydrate composition (i.e. lactose v. sucrose). It can be concluded that soya milk is a good alternative to cows' milk with regard to glycaemic regulation, with different mechanisms involved.

Effects of Eimeria acervulina infection severity on growth performance, apparent ileal amino acid digestibility, and plasma concentrations of amino acids, carotenoids, and α1-acid glycoprotein in broilers

An experiment was conducted to evaluate growth performance, apparent ileal digestibility (AID) of amino acids, and plasma concentrations of amino acids, carotenoids, and α1-acid glycoprotein, an acute-phase protein, in broilers inoculated with graded doses of E. acervulina oocysts. Ross 308 male broilers (400 total) were housed in battery cages from 1 to 21 d post-hatch and received common corn-soybean meal-based diets throughout the experiment. At 9 d post-hatch, birds were individually weighed and allotted to 4 treatment groups with 10 replicate cages of 10 birds per cage. At 15 d post-hatch, all birds were inoculated with 1 mL of distilled water that contained 0, 2.5 × 105, 5.0 × 105, or 1.0 × 106 sporulated E. acervulina oocysts. At 21 d, birds were euthanized for collection of blood and ileal digesta. Body weight gain and feed efficiency decreased linearly (P < 0.05) with increasing E. acervulina dose. With the exception of Trp and Gly, AID values decreased (P < 0.05) linearly or quadratically for all amino acids by an average of 2.6 percentage units for birds inoculated with 1.0 × 106 oocysts compared with uninfected birds. Infection with E. acervulina caused a quadratic decrease (P < 0.05) in plasma carotenoid concentrations. Plasma concentrations of Arg and Tyr decreased linearly (P < 0.05) with increasing E. acervulina inoculation dose and plasma Gln and Asn decreased quadratically (P < 0.01). Linear increases (P < 0.05) were observed for plasma Lys, Leu, Ile, Val, Pro, and Orn as E. acervulina inoculation dose increased. Plasma α1-acid glycoprotein of broilers was not influenced (P > 0.05) by E. acervulina infection. In conclusion, E. acervulina challenge adversely impacted growth performance, plasma carotenoids, and AID of amino acids in a dose-dependent manner. However, plasma amino acid responses to graded E. acervulina inoculation doses varied considerably among amino acids. Thus, these results indicated that alterations in amino acid metabolism caused by E. acervulina infection extended beyond reduced amino acid digestibility.

Effects of whey proteins on glycaemia and insulinaemia to an oral glucose load in healthy adults; a dose–response study

Whey proteins have insulinogenic properties and the effect appears to be mediated from a postprandial plasma amino-acid (AA) response. The aim was to study the possible dose-response relationship between whey intake and glycaemic-, insulinaemic- and plasma AA responses. Twelve healthy volunteers participated in the study. They were provided three whey protein drinks, containing 4.5, 9 or 18 g protein as breakfast meals in random order. All meals contained 25 g available carbohydrates (glucose). The same amount of glucose in water was used as reference. Linear dose-response relations were found between whey protein intake and postprandial glycaemia, insulinaemia and plasma AAs. The two highest doses, 18 g and 9 g, significantly reduced postprandial glycaemia (incremental area under the curve (iAUC) 0-120 min; P ≤ 0.05). The 18 g dose significantly increased the insulin response (iAUC 0-120 min; P ≤ 0.05). All measured plasma AAs (15 in total), except glutamic acid, responded in a dose-dependent way, and the 9 and 18 g doses resulted in significantly higher plasma levels of AAs compared with the reference. Whey protein affects glycaemia, insulinaemia and plasma AAs to a glucose load in a dose-dependent manner. Comparatively low doses of whey protein (9 g) reduced postprandial glycaemia significantly when added to a carbohydrate-rich meal.

Whey Protein Supplementation During Resistance Training Augments Lean Body Mass

Compared to soy, whey protein is higher in leucine, absorbed quicker and results in a more pronounced increase in muscle protein synthesis.Objective: To determine whether supplementation with whey promotes greater increases in muscle mass compared to soy or carbohydrate, we randomized non-resistance-trained men and women into groups who consumed daily isocaloric supplements containing carbohydrate (carb; n = 22), whey protein (whey; n = 19), or soy protein (soy; n = 22).Methods: All subjects completed a supervised, whole-body periodized resistance training program consisting of 96 workouts (∼9 months). Body composition was determined at baseline and after 3, 6, and 9 months. Plasma amino acid responses to resistance exercise followed by supplement ingestion were determined at baseline and 9 months.Results: Daily protein intake (including the supplement) for carb, whey, and soy was 1.1, 1.4, and 1.4 g·kg body mass−1, respectively. Lean body mass gains were significantly (p < 0.05) greater in whey (3.3 ± 1.5 kg) than carb (2.3 ± 1.7 kg) and soy (1.8 ± 1.6 kg). Fat mass decreased slightly but there were no differences between groups. Fasting concentrations of leucine were significantly elevated (20%) and postexercise plasma leucine increased more than 2-fold in whey. Fasting leucine concentrations were positively correlated with lean body mass responses.Conclusions: Despite consuming similar calories and protein during resistance training, daily supplementation with whey was more effective than soy protein or isocaloric carbohydrate control treatment conditions in promoting gains in lean body mass. These results highlight the importance of protein quality as an important determinant of lean body mass responses to resistance training.

Nitrogen Retention and Plasma Amino Acid Responses in Mature Geldings Fed Three Dietary Concentrations of Lysine

Six mature Quarter Horse geldings (age, 11.5 ± 4.7 years; body weight [BW], 526 ± 9.2 kg) were used in a replicated 3 × 3 Latin square design to determine the effects of three dietary lysine (Lys) levels on nitrogen (N) retention and plasma amino acid (AA) concentrations. The geldings were fed a basal diet of concentrate and Bermuda grass hay supplemented with synthetic essential amino acids (EAA) to meet estimated requirements for EAA. Geldings were fed one of three dietary treatments: (1) a basal diet deficient in Lys (L−; 0.027 g of Lys•kg−1 BW•d−1); (2) a basal diet supplemented with synthetic Lys to meet National Research Council (NRC; 2007) requirements (L+; 0.036 g of Lys•kg−1 BW•d−1); or (3) a basal diet supplemented at twice the recommended Lys requirement (2 × L; 0.070 g Lys•kg−1 BW•d−1). Horses fed the 2 × L diet had higher N intakes (P = .0056) than horses fed either the L− or L+ diet. However N retention (P = .63) was not different between treatments. Plasma Lys was greater (P < .0001) in 2 × L than L− and L+ diets. Plasma threonine (Thr; P < .01), methionine (Met; P = .03), and total plasma non-EAA (P < .05) concentrations decreased as dietary Lys increased. These results suggest N retention is not a good response criterion for evaluating the AA requirements of mature horses. However, plasma AA data indicated more efficient use of Thr and Met when horses were fed dietary Lys in concentrations greater than the current requirement recommended by the Nutrient Requirements of Horses (National Research Council, 2007).

The glycemic, insulinemic and plasma amino acid responses to equi-carbohydrate milk meals, a pilot- study of bovine and human milk

BackgroundDairy proteins, in particular the whey fraction, exert insulinogenic properties and facilitate glycemic regulation through a mechanism involving elevation of certain plasma amino acids, and stimulation of incretins. Human milk is rich in whey protein and has not been investigated in this respect.MethodNine healthy volunteers were served test meals consisting of human milk, bovine milk, reconstituted bovine whey- or casein protein in random order. All test meals contributed with 25g intrinsic or added lactose, and a white wheat bread (WWB) meal was used as reference, providing 25g starch. Post-prandial levels in plasma of glucose, insulin, incretins and amino acids were investigated at time intervals for up to 2 h.ResultsAll test meals elicited lower postprandial blood glucose responses, expressed as iAUC 0–120 min compared with the WWB (P < 0.05). The insulin response was increased following all test meals, although only significantly higher after whey. Plasma amino acids were correlated to insulin and incretin secretion (iAUC 0–60 min) (P ≤ 0.05). The lowered glycemia with the test meals (iAUC 0–90 min) was inversely correlated to GLP-1 (iAUC 0–30 min) (P ≤ 0.05).ConclusionThis study shows that the glycemic response was significantly lower following all milk/milk protein based test meals, in comparison with WWB. The effect appears to originate from the protein fraction and early phase plasma amino acids and incretins were involved in the insulin secretion. Despite its lower protein content, the human milk was a potent GLP-1 secretagogue and showed insulinogenic properties similar to that seen with reconstituted bovine whey-protein, possibly due to the comparatively high proportion of whey in human milk.

Effect of Intake of Different Dietary Protein Sources on Plasma Amino Acid Profiles at Rest and after Exercise

The authors undertook 2 crossover-designed studies to characterize plasma amino acid (AA) responses to the intake of 20 g of protein. In Study 1, 15 untrained and overnight-fasted subjects consumed 20 g protein from skim milk, soy milk, beefsteak, boiled egg, and a liquid meal supplement. In Study 2, 10 fasted endurance-trained subjects consumed 20 g protein from a protein-rich sports bar at rest and after a 60-min submaximal ride. Plasma AA concentrations were measured immediately before and for 180 min after food ingestion using a gas-chromatography flame-ionization detection technique. A pharmacokinetic analysis was undertaken for profiles of total AAs (TAA), essential AAs, branched-chain AAs (BCAA), and leucine. Although area-under-the-curve values for plasma TAA were similar across protein sources, the pattern of aminoacidemia showed robust differences between foods, with liquid forms of protein achieving peak concentrations twice as quickly after ingestion as solid protein-rich foods (e.g., ~50 min vs ~100 min) and skim milk achieving a significantly faster peak leucine concentration than all other foods (~25 min). Completing exercise before ingesting protein sources did not cause statistically significant changes in the pattern of delivery of key AAs, BCAAs, and leucine apart from a 20-40% increase in the rate of elimination. These results may be useful to plan the type and timing of intake of protein-rich foods to maximize the protein synthetic response to various stimuli such as exercise.

Effects of protein quantity and source (animal versus plant) on appetite and plasma amino acid responses in energy‐restricted subjects

This study was designed to assess appetitive and plasma amino acid (AA) responses to protein (P) intakes that span the acceptable macronutrient distribution range and predominantly from meat vs. plant sources. Thirty‐four overweight/obese subjects (53±12 y, BMI 30.8±2.6 kg/m2 mean ± SD) were randomly assigned to consume diets with 750 kcal/d below energy need and beef/pork (5M:12F) or soy/pulses (6M:11F). All subjects randomly completed 3, 28d trials with the diets containing 10, 20 or 30% energy from P. On day 28 of each trial, subjects consumed a trial‐specific test meal and rated hunger and fullness before and 25, 60, 120, 180 and 240 min after eating. AAs were measured in 5 subjects each from the two P source groups. Postprandial (PP) branched chain, essential, and large neutral AA and leucine (weighted averages) were higher for beef/pork vs. soy/pulses (p&lt;0.05) and progressively higher with increasing P intake (p&lt;0.01). PP hunger was lower and fullness was higher than fasting (p&lt;0.001). The hunger response was greater for 30 vs. 20 and 10 % P, whereas P quantity did not affect fullness. Protein source did not affect hunger or fullness. PP hunger and fullness responses were not related to PP AA responses. Higher protein intake from meat or plant sources promotes reduced hunger, unrelated to differential plasma amino acid responses to feeding.Support: The Beef Checkoff, National Pork Board, and NIH RR025761Grant Funding Source: The Beef Checkoff, National Pork Board, and NIH RR025761

Sex differences in plasma amino acid and fat free mass responses to military training

Diet, exercise, and energy status influence amino acid (AA) availability and contribute to the regulation of skeletal muscle mass. Whether altering these factors through training influence plasma AA levels and the maintenance of muscle mass in young adults has not been determined. This study assessed body composition and plasma AA levels in US Army recruits (n=209, 118 males, 91 females, 23 ± 5 yr) at baseline and every three weeks during basic combat training (BCT). Body weight decreased in men but remained stable in women during BCT (sex‐by‐time interaction, P &lt; 0.05). Fifty‐eight percent of recruits gained fat free mass (FFM) during BCT, with more (P &lt; 0.05) females (88%) gaining FFM then males (36%). Total plasma AA levels increased (P &lt; 0.05) during BCT, with greater (P &lt; 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched‐chain amino acids (BCAA) levels were increased (P &lt; 0.05) in females but did not change in males (sex‐by‐time interaction, P &lt; 0.05). Independent of sex, changes in EAA and individual BCAA levels from baseline were associated (P &lt; 0.05) with changes in FFM, with greater (P &lt; 0.05) increases in AA concentrations observed for those who gained FFM. This data demonstrates the differential FFM and plasma AA responses to military training in males and females. Supported by USAMRMC.

Plasma Amino Acid Response in Mature Geldings Fed Three Concentrations of Lysine

Plasma Amino Acid Response in Mature Geldings Fed Three Concentrations of Lysine

Supplemental leucine's influence on plasma glucose, insulin, and amino acid responses in Quarter Horse yearlings

Supplemental leucine's influence on plasma glucose, insulin, and amino acid responses in Quarter Horse yearlings

Effects of leucine or whey protein addition to an oral glucose solution on serum insulin, plasma glucose and plasma amino acid responses in horses at rest and following exercise

Providing protein or amino acid mixtures in combination with glucose to post exercise in man has resulted in increases in the post feeding insulin response and in muscle glycogen and protein synthesis rates. However, whether protein and/or amino acids can modify the post exercise insulin responses in horses remains to be fully elucidated. To determine whether whey protein or leucine addition to a glucose solution affects the post gavage plasma insulin, glucose and amino acid responses in horses and whether these responses are different following a period of exercise vs. rest. Six mature, conditioned Thoroughbreds received a nasogastric gavage containing either 1 g/kg bwt glucose (G), G + 0.3 g/kg bwt whey protein (GW) or G + 0.3 g/kg bwt leucine (GL), following a period of either rest (R) or an exercise test on a high speed treadmill (EX). Each horse was studied under all 6 treatment conditions, separated by 10 day intervals. Blood samples were collected pre-exercise/rest, pregavage and at regular intervals up to 300 min post gavage. Plasma was analysed for glucose and amino acid concentrations and serum insulin concentrations were determined. There was a significantly (P < 0.05) greater insulin response in GL-R and GL-EX when compared to the other treatments. When compared to rest, post exercise plasma glucose responses were lower in G and GW but unchanged following GL administration. Plasma alanine concentrations were elevated post exercise in all EX treatments. With the exception of markedly elevated plasma leucine concentrations after GL-R and GL-EX, the plasma concentrations of all indispensable amino acids decreased during the post gavage period. Leucine but not whey protein augmented the serum insulin response to an oral glucose load. Leucine supplementation warrants further investigation as a means to increase the rate of post exercise muscle glycogen synthesis in horses.

Plasma Amino Acid Responses after Consumption of Beverages with Varying Protein Type

To examine how different proteins in a carbohydrate-protein beverage affect postprandial amino acid (AA), glucose, and insulin responses. Two randomized, repeated-measures experiments were performed. In one, 10 volunteers drank 3 carbohydrate-protein beverages (380 kcal, 76 g carbohydrate, 19 g protein, 2 g fat) in separate (>7 days) trials, each differing in protein type. All drinks consisted of cocoa (4 g) and nonfat dry milk (1 g) supplemented with casein (CAS), whey (WP), or a casein and whey blend (CAS-WP). Ten additional volunteers consumed the same drinks after 60 min of varying-intensity exercise (60% and 85% VO2peak). Blood glucose, insulin, glucose-dependent insulinotrophic polypeptide (GIP), and AAs were measured every 15-30 min for 4 hr after beverage consumption. Branched-chain AA concentrations peaked at 30 min and did not differ between beverages at rest (0.69 +/- 0.12 mmol/L) or postexercise (0.70 +/- 0.07 mmol/L). There were no significant differences between beverages with respect to initial (time 0-60) or total area under the curve (time 0-240) for any outcome measures at rest or postexercise. High-carbohydrate beverages containing various proportions of milk proteins procured from a supplier to the commercial industry had no impact on AA concentration. Retrospective chemical analysis of commercial proteins showed that casein was partially hydrolyzed; therefore, consumers should carefully consider the manufacturer (to ensure that the product contains intact protein) or other factors (i.e., cost or taste) when procuring these beverages for their purported physiological effects.

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), β-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/cm2) 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 β-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 β-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.

Acute effects of breakfasts containing α-lactalbumin, or gelatin with or without added tryptophan, on hunger, ‘satiety’ hormones and amino acid profiles

Proteins are the most satiating macronutrients. Tryptophan (TRP) may contribute to the satiating effect, as it serves as a precursor for the anorexigenic neurotransmitter serotonin. To address the role of TRP in the satiating properties of dietary protein, we compared three different breakfasts, containing either alpha-lactalbumin (high in TRP), gelatin (low in TRP) or gelatin with added TRP (gelatin+TRP, high in TRP), on appetite. Twenty-four subjects (22-29 kg/m2; aged 19-37 years) received a subject-specific breakfast at t = 0 with 10, 55 and 35 % energy from protein, carbohydrate and fat respectively in a randomised, single-blind design. Hunger, glucagon-like peptide (GLP)-1, ghrelin, amino acid concentrations and energy intake during a subsequent lunch were determined. Suppression of hunger was stronger 240 min after the breakfast with alpha-lactalbumin compared with gelatin and gelatin+TRP. Total plasma amino acid concentrations were lower with alpha-lactalbumin compared with gelatin with or without TRP (from t = 180-240 min). TRP concentrations were higher after alpha-lactalbumin than after gelatin with or without TRP from t = 0-100 min, whereas from t = 100-240 min, TRP concentrations were lower after gelatin than after alpha-lactalbumin and gelatin+TRP. The plasma ratio of TRP to other large neutral amino acids (LNAA) was, only at t = 100 min, lower after gelatin+TRP than after the other breakfasts. Plasma amino acid responses, TRP concentrations and TRP:LNAA ratios were not correlated with hunger. GLP-1 and ghrelin concentrations were similar for all diets. Energy intake during a subsequent lunch was similar for all diets. Summarised, an alpha-lactalbumin breakfast suppresses hunger more than a gelatin or gelatin+TRP breakfast. This cannot be explained by (possible) differences found in TRP concentrations and TRP:LNAA ratios in the breakfasts and in plasma, as well as in circulating total amino acids, GLP-1 and ghrelin.

Comparison of the effects of a high- and normal-casein breakfast on satiety, ‘satiety’ hormones, plasma amino acids and subsequent energy intake

The present study compared the effects of a high- and normal-casein-protein breakfast on satiety, 'satiety' hormones, plasma amino acid responses and subsequent energy intake. Twenty-five healthy subjects (BMI 23.9 (SEM 0.3) kg/m2; age 22 (SEM 1) years) received a subject-specific standardised breakfast (20% of daily energy requirements): a custard with casein as the single protein source with either 10, 55 and 35 (normal-casein breakfast) or 25, 55 and 20 (high-casein breakfast) % of energy (En%) from protein, carbohydrate and fat respectively in a randomised, single-blind design. Appetite profile (visual analogue scale; VAS), plasma glucose, insulin, glucagon-like peptide 1, ghrelin and amino acid concentrations were determined for 4 h; here the sensitive moment in time for lunch was determined. Subjects came for a second set of experiments and received the same custards for breakfast, and an ad libitum lunch was offered at 180 min after breakfast; energy intake was assessed. There were increased scores of fullness and satiety after the 25 En% casein-custard compared with the 10 En% casein-custard, particularly at 180 min (26 (SEM 4) v. 11 (SEM 5) mm VAS; P<0.01) and 240 min (13 (SEM 5) v. -1 (SEM 5) mm VAS; P<0.01). This coincided with prolonged elevated plasma amino acid concentrations; total amino acids and branched-chain amino acids were higher after the 25 En% casein-custard compared with the 10 En% casein-custard at 180 and 240 min (P<0.001). There was no difference in energy intake (3080 (SEM 229) v. 3133 (SEM 226) kJ for 25 En% and 10 En% respectively; NS) from the ad libitum lunch. In conclusion, a breakfast with 25% of energy from casein is rated as being more satiating than a breakfast with 10% of energy from casein at 3 and 4 h after breakfast, coinciding with prolonged elevated concentrations of plasma amino acids, but does not reduce subsequent energy intake.

Effects of high or normal casein-, soy-, or whey with or without GMP- protein breakfasts on satiety, ‘satiety’ hormones, and plasma amino acid responses.

Dietary protein seems to play an important role in body weight regulation. The objective of the study was to compare the effects of high or normal casein-, soy-, or whey with or without glycomacropeptide (GMP)-protein breakfasts on satiety, ‘satiety’ hormones, and plasma amino acid responses. Twenty-five healthy subjects (mean+sem BMI:23.9+0.3 kg/m2;age:22+1 years) received a subject-specific standardized breakfast (20% of daily energy requirements); a custard with either casein, soy, or whey±GMP as protein source with either 10/55/35 (normal) or 25/55/20 (high)En% protein/carbohydrate/fat in a randomized, single-blind design. Appetite profile (Visual Analogue Scale,VAS), plasma glucose, insulin, GLP-1, ghrelin, and amino acid (AA) concentrations were determined up to 4 h. The breakfast with 25En% casein–custard was more satiating than the 10En%casein-custard(p

Co-Ingestion of a Protein Hydrolysate with or without Additional Leucine Effectively Reduces Postprandial Blood Glucose Excursions in Type 2 Diabetic Men

This study examined postprandial plasma insulin and glucose responses after co-ingestion of an insulinotropic protein (Pro) hydrolysate with and without additional free leucine with a single bolus of carbohydrate (Cho). Male patients with long-standing Type 2 diabetes (n = 10) and healthy controls (n = 10) participated in 3 trials in which plasma glucose, insulin, and amino acid responses were determined after the ingestion of beverages of different composition (Cho: 0.7 g/kg carbohydrate, Cho+Pro: 0.7 g/kg carbohydrate with 0.3 g/kg protein hydrolysate, or Cho+Pro+Leu: 0.7 g/kg carbohydrate, 0.3 g/kg protein hydrolysate and 0.1 g/kg free leucine). Plasma insulin responses [expressed as area under the curve (AUC)] were 141 and 204% greater in patients with Type 2 diabetes and 66 and 221% greater in the controls in the Cho+Pro and Cho+Pro+Leu trials, respectively, compared with those in the Cho trial (P < 0.05). The concomitant plasma glucose responses were 15 and 12% lower in the patients with Type 2 diabetes and 92 and 97% lower in the control group in the Cho+Pro and Cho+Pro+Leu trials, respectively, compared with those in the Cho trial (P < 0.05). Plasma leucine concentrations correlated with the insulin response in all subjects (r = 0.43, P < 0.001). We conclude that co-ingestion of a protein hydrolysate with or without additional free leucine strongly augments the insulin response after ingestion of a single bolus of carbohydrate, thereby significantly reducing postprandial blood glucose excursions in patients with long-standing Type 2 diabetes.