Plasma Amino Acid Concentrations Research Articles

Casein Protein Processing Strongly Modulates Post-Prandial Plasma Amino Acid Responses In Vivo in Humans.

Micellar casein is characterized as a slowly digestible protein source, and its structure can be modulated by various food processing techniques to modify its functional properties. However, little is known about the impact of such modifications on casein protein digestion and amino acid absorption kinetics and the subsequent post-prandial plasma amino acid responses. In the present study, we determined post-prandial aminoacidemia following ingestion of isonitrogenous amounts of casein protein (40 g) provided as micellar casein (Mi-CAS), calcium caseinate (Ca-CAS), or cross-linked sodium caseinate (XL-CAS). Fifteen healthy, young men (age: 26 ± 4 years, BMI: 23 ± 1 kg·m−2) participated in this randomized cross-over study and ingested 40 g Mi-Cas, Ca-CAS, and XL-CAS protein, with a ~1 week washout between treatments. On each trial day, arterialized blood samples were collected at regular intervals during a 6 h post-prandial period to assess plasma amino acid concentrations using ultra-performance liquid chromatography. Plasma amino acid concentrations were higher following the ingestion of XL-CAS when compared to Mi-CAS and Ca-CAS from t = 15 to 90 min (all p < 0.05). Plasma amino acid concentrations were higher following ingestion of Mi-CAS compared to Ca-CAS from t = 30 to 45 min (both p < 0.05). Plasma total amino acids iAUC were higher following the ingestion of XL-CAS when compared to Ca-CAS (294 ± 63 vs. 260 ± 75 mmol·L−1, p = 0.006), with intermediate values following Mi-CAS ingestion (270 ± 63 mmol·L−1, p > 0.05). In conclusion, cross-linked sodium caseinate is more rapidly digested when compared to micellar casein and calcium caseinate. Protein processing can strongly modulate the post-prandial rise in plasma amino acid bioavailability in vivo in humans.

Hemodialysis Affects Wanting and Spontaneous Intake of Protein-Rich Foods in Chronic Kidney Disease Patients

Protein-energy wasting is a risk factor for mortality and morbidity in hemodialysis patients (HD patients). Food intake could be modified by HD-related changes in the food reward system (i.e., liking and wanting of specific macronutrients). In HD patients on days with and without dialysis, we evaluated (1) the reward system for protein-, fat-, and carbohydrate-rich foods, plasma hormones, and metabolite changes; and (2) the spontaneous ad libitum intake of macronutrients. Twenty-four HD patients evaluated their liking and wanting of macronutrients at 7:30 AM and 11:30 AM on a day with and a day without dialysis. Concentrations of hormones and plasma amino acids were determined. An additional 18 HD patients ate what they wanted from a buffet lunch comprising 8 dishes on a day with and a day without dialysis. Healthy subjects, age-, sex-, and body mass index-matched, served as controls. At 11:30 AM, wanting for protein-rich foods was higher on the day with than on the day without dialysis (P<.01), bringing wanting levels close to those of healthy subjects. This increase correlated with changes in the concentrations of plasma amino acids (P<.01). HD patients ate more protein from the buffet on the day with than on the day without dialysis (P<.01) and more than healthy subjects (P<.01). In HD patients, wanting and spontaneous intake of protein-rich foods increase immediately after dialysis. This increase correlated with decreased concentrations of plasma amino acids. Thus, in clinical practice, protein-rich foods should be recommended during and after dialysis in patients with protein-energy wasting.

Effects of supplementing limiting amino acids on milk production in dairy cows consuming a corn grain and soybean meal-based diet.

Limiting amino acids (AAs) for milk production in dairy cows fed on a concentrate diet of corn grain and soybean meal was evaluated in this study. Four lactating and multiparous Holstein cows (in third or fourth parities, with an average body weight of 633 ± 49.2 kg), 8 to 9 weeks into their lactation period, were used in a 4 × 4 Latin square design. The experiment comprised four dietary treatments: (1) no intravenous infusion (control); (2) control plus intravenous infusion of an AA mixture of 6 g/d methionine, 19.1 g/d lysine, 13.8 g/d isoleucine, and 15.4 g/d valine (4AA); (3) control plus intravenous infusion of the AA mixture without methionine (no-Met); and (4) control plus intravenous infusion of the AA mixture without lysine (no-Lys). All animals were fed on a controlled diet (1 kg/d alfalfa hay, 10 kg/d silage, 14 kg/d concentrate mixture, ad libitum timothy hay). The AA composition of the diet and blood were determined using an automatic AA analyzer. Milk composition (protein, fat, lactose, urea nitrogen, and somatic cell counts) was determined using a MilkoScan. The results showed that feed intake for milk production did not differ from that of intravenous infusion using a limiting AA mixture. The 4AA treatment numerically had the highest milk yield (32.4 kg/d), although there was no difference when compared with the control (31.2 kg/d), no-Met (31.3 kg/d), and no-Lys (31.7 kg/d) treatments. The concentration of AAs in blood plasma of cows in all treatments, mainly isoleucine and valine, increased significantly compared with that of control. The no-Met treatment increased (p < 0.05) the concentration of lysine in the blood relative to the control and no-Lys treatments, whereas the no-Lys treatment increased (p < 0.05) the concentration of methionine relative to the control and no-Met treatments. In conclusion, milk production increased when feeding 10 g/d methionine to the cows, together with their concentrate diet of corn grain and soybean meal.

Derangement of Arginine and Related Amino Acids in Children Undergoing Surgery for Congenital Heart Disease With Cardiopulmonary Bypass.

Prospective observational study. The study was conducted in the Heart Center at Texas Children's Hospital. Children undergoing surgery for congenital heart disease with cardiopulmonary bypass. None. Serial perioperative blood samples were collected for quantification of amino acids, arginase, nitric oxide metabolites, and markers of organ function (lactate, Pao2/Fio2 ratio, and creatinine clearance). Thirty children (18 males) were included in the study; median (interquartile range) age 0.5 years (0.3-0.9 yr). The mean ± sd for plasma amino acid concentrations before cardiopulmonary bypass: arginine 62 ± 20 µmol/L, citrulline 24 ± 6 µmol/L, ornithine 53 ± 32 µmol/L, and glutamine 591 ± 126 µmol/L. Arginine concentration was decreased within the first 24 hours (43 ± 15 µmol/L; p = 0.004), citrulline and glutamine concentrations decreased over the first 48 hours (11 ± 4 µmol/L; p < 0.001 and 493 ± 131 µmol/L; p = 0.019, respectively) and were associated with an increase in arginase (3.8 ± 3 µg/mL; p < 0.05). There was an increase in Vasoactive-Inotropic Score (5.9 ± 19 vs 0.5 ± 2; p < 0.001), decrease in creatinine clearance (76 ± 24 vs 93 ± 31; p = 0.002), and Pao2/Fio2 ratio (243 ± 138 vs 374 ± 200; p = 0.007) comparing to baseline. A widely variable degree of arginine, citrulline, and glutamine depletion occurs in children after surgery for congenital heart disease. These findings were associated with increased arginase and coincide with some of the markers of organ perfusion.

Uptake of dietary amino acids into arterial blood during continuous enteral feeding in critically ill patients and healthy subjects

Amino acid availability is a regulatory factor of protein anabolism and is partly dependent on enteral amino acid uptake. During continuous enteral feeding, enteral amino acid uptake may vary considerably, but this has not been documented systematically. In this pragmatic study, we investigated patients in the intensive care unit (n=10) and healthy adults (n=10). The time course of essential amino acid concentrations in arterial plasma and the uptake of dietary phenylalanine were recorded during 12hours of continuous enteral feeding, using a 13C-labeled phenylalanine tracer. Plasma essential amino acid concentrations and 13C-phenylalanine enrichment reached a tentative steady state after no more than 4.5h from start of tracer infusion. There was a large intra- and inter-individual variability in both cohorts. No periodicity could be detected in the temporal variation. During continuous enteral feeding, uptake of amino acids shows large intra- and inter-individual variation. A tentative steady state of 13C-phenylalanine uptake is eventually reached. Registered at Australian New Zealand Clinical Trials Registry, trial ID ACTRN12616000593437.

Amino Acid Plasma Profiles from a Prolonged-Release Protein Substitute for Phenylketonuria: A Randomized, Single-Dose, Four-Way Crossover Trial in Healthy Volunteers.

Several disorders of amino acid (AA) metabolism are treated with a protein-restricted diet supplemented with specific AA mixtures. Delivery kinetics impacts AA absorption and plasma concentration profiles. We assessed plasma profiles after ingestion of an AA mixture engineered to prolong AA absorption with Physiomimic TechnologyTM (Test) in a randomized, single-dose, four-way crossover trial in healthy volunteers (Trial Registration: ISRCTN11016729). In a two-step hypothesis, the primary endpoints were (i) significant reduction in peak plasma concentrations (Cmax) of essential amino acids (EAAs) while (ii) maintaining EAA bioavailability (AUC0-300 min) compared to a free AA mixture (Reference). Secondary endpoints included effects on plasma profiles of other AA groups and effects on several metabolic markers. Thirty subjects completed the study. Both co-primary endpoints were met: Cmax for EAAs was 27% lower with the Test product compared to the Reference product (ratio, 0.726, p < 0.0001); overall plasma EAA levels from the two AA mixtures was within the pre-specified bioequivalence range (AUC0-300min ratio, 0.890 (95% CI: 0.865, 0.915)). These findings were supported by the results of secondary endpoints. Prolongation of AA absorption was associated with modulation of several metabolic markers. It will be important to understand whether this can improve the long-term management of disorders of AA metabolism.

Association Between Macronutrient Intakes and Sleep Quality in Middle-Aged and Older Population in Singapore

Abstract Objectives Quality sleep is essential to health and poor sleep may increase the risk of obesity and type 2 diabetes. Previous studies have reported that macronutrient intakes, such as dietary protein, may be associated with sleep quality. However research, on this relationship in older adults who often exhibit poorer sleep quality is still limited. Therefore, the objective of this research is to assess the association between macronutrient intakes and sleep quality in middle-aged and older population in Singapore. Methods In this cross-sectional study, 104 men and women (59 ± 6 years) were recruited within Singapore. Their food intakes and sleep quality were assessed using 3-day food records and Pittsburg Sleep Quality Index questionnaire, respectively. In addition, plasma amino acid concentration was measured from the collected blood samples. The relationship between diet, plasma amino acids and sleep quality were evaluated using multiple linear regression and adjusted for age, BMI and gender. Results From this study, no association were observed between total energy intake (%E) from protein and tryptophan (Trp) intakes and sleep quality parameters. However, %E from fat was positively associated with sleep efficiency (SE%) (β-coefficient = 19.6, P = 0.02). A similar positive association with SE% was also observed for mono- and poly-unsaturated fatty acids. In contrast, %E from carbohydrate was inversely associated with SE% (β-coefficient = −21.2, P = 0.03). Sugar intake was also inversely associated with sleep quality parameters. Although plasma Trp concentration was not associated with sleep quality parameters, Trp and large neutral amino acids concentration ratio was inversely associated with sleep duration (β-coefficient = −19.2, P = 0.02). Conclusions In conclusion, consuming a diet with a higher energy from fat and lower energy from carbohydrate may improve sleep quality in Singapore middle-aged and older adults. The type of fat and carbohydrate consumed may also affect sleep quality. Funding Sources This research study is funded by the National University of Singapore (Grant number: R-143–000-A03–133).

Effects of Salmon Ingestion on Post-Exercise Muscle Protein Synthesis: Exploration of Whole Protein Foods Versus Isolated Nutrients

Abstract Objectives Healthy eating patterns consist of eating whole foods as opposed to single nutrients. The maintenance of skeletal muscle mass is of particular interest to overall health. As such, there is a need to underpin the role of eating nutrients within their natural whole-food matrix versus isolated nutrients on the regulation of postprandial muscle protein synthesis rates. This study assessed the effects of eating salmon, a potential food within a healthy Mediterranean style eating pattern, on the stimulation of post-exercise muscle protein synthesis rates versus eating these same nutrients in isolation in healthy young adults. Methods In a crossover design, 10 recreationally active adults (24 ± 4 y; 5 M, 5 F) performed an acute bout of resistance exercise followed by the ingestion of salmon (SAL) (20.5 g protein and 7.5 g fat) or its matched constituents in the form of crystalline amino acids and fish oil (ISO). Blood and muscle biopsies were collected at rest and after exercise at 2 and 5 h during primed continuous infusions of L-[ring-2H5]phenylalanine for the measurement of myofibrillar protein synthesis and plasma amino acid profiles. Data were analyzed by using a 2-factor (time × condition) repeated-measures ANOVA with Tukey's post hoc test. Results Plasma essential amino acid concentrations increased to a similar extent in both SAL and ISO during the postprandial period (P &amp;gt; 0.05). Likewise, postprandial plasma leucine concentrations did not differ between nutrient condition (P &amp;gt; 0.05). The post-exercise myofibrillar protein synthetic responses were similarly stimulated in both nutrition conditions early (0–2 h; 0.079 ± 0.039%/h (SAL) compared to 0.071 ± 0.078%/h (ISO); P = 0.64) and returned to baseline later (2–5 h; 0.046 ± 0.020%/h (SAL) compared to 0.038 ± 0.025%/h (ISO); P = 0.90). Similarly, there were no differences in the stimulation of myofibrillar protein synthesis rates between SAL and ISO during the entire 0–5 h recovery period (0.058 ± 0.024%/h compared to 0.045 ± 0.027%/h, respectively; P = 0.66). Conclusions We show that the ingestion of salmon or its isolated nutrients increases plasma amino acid concentrations and enhances the stimulation of post-exercise muscle protein synthesis rates with no differences in the temporal or cumulative responses in healthy young adults. Funding Sources USDA National Institute of Food and Agriculture Hatch project.

Ingestion of Free Amino Acids as Opposed to Intact Protein Increases Amino Acid Absorption but Does Not Further Augment Postprandial Muscle Protein Synthesis Rates

Abstract Objectives The rate of protein digestion and amino acid absorption determines the postprandial rise in circulating amino acids and, as such, modulates postprandial muscle protein synthesis rates. This study compares protein digestion and amino acid absorption kinetics and the subsequent muscle protein synthetic response following ingestion of intact protein versus an equivalent amount of free, crystalline amino acids. Methods Twenty-four healthy, young subjects (age: 22 ± 3 y, BMI: 23 ± 2 kg·m−2, sex: 12 M/12F) ingested 30 g intrinsically L-[1–13C]-phenylalanine and L-[1–13C]-leucine labeled milk protein (PROT; n = 12) or an equivalent amount of free amino acids (AA; n = 12). In addition, subjects received primed continuous L-[ring-2H5]-phenylalanine, L-[ring-3,5–2H2]-tyrosine, and L-[1–13C]-leucine infusions. Blood samples and muscle biopsies were obtained frequently to assess protein digestion and amino acid absorption kinetics and subsequent muscle protein synthesis rates over a 6 h postprandial period. An unpaired t-test was used to compare overall exogenous phenylalanine release in plasma. For other parameters repeated measures ANOVA were applied to determine differences between groups over time (time as within, and group as between-subjects factor). Data are expressed as mean ± SD. Results Postprandial plasma amino acid concentrations and exogenous phenylalanine appearance rates increased after ingestion of PROT and AA (both, P &amp;lt; 0.001), with a greater increase following ingestion of AA when compared to PROT (time*group interaction P &amp;lt; 0.001). Exogenous phenylalanine release in plasma assessed over the 6 h postprandial period, was greater in AA (76 ± 9%) compared with PROT (59 ± 10%; P &amp;lt; 0.001). Ingestion of AA and PROT strongly increased muscle protein synthesis rates based upon L-[ring-2H5]-phenylalanine (time effect P &amp;lt; 0.001), with no differences between groups (from 0.037 ± 0.015 to 0.053 ± 0.014%·h−1 and from 0.039 ± 0.016 to 0.051 ± 0.010%·h−1, respectively; time*group interaction P = 0.629). Conclusions Ingestion of free amino acids as opposed to intact milk protein is followed by more rapid amino acid absorption and greater postprandial plasma amino acid availability, but this does not further augment postprandial muscle protein synthesis rates. Funding Sources This research did not receive external funding.

Cross-correlation of plasma concentrations of branched-chain amino acids: A comparison between healthy participants and patients with chronic kidney disease.

Plasma concentrations of branched-chain amino acids (BCAAs) are known to exhibit strong intercorrelations; however, the associated regulatory mechanism is not sufficiently understood. Furthermore, the mechanisms underlying the intercorrelation changes in metabolic disorders with the disease are unclear. Therefore, plasma BCAAs in patients with chronic kidney disease (CKD) were examined. This study included a healthy group of older participants (Group C; n=87, 46 males, 41 females) who had undergone health examinations at Sanyudo Hospital and a group of CKD patients (Group CKD; n=71, 49 males, 22 females) receiving maintenance hemodialysis at the same hospital. Samples from Group C were collected 12h after fasting. CKD samples were collected before and after hemodialysis (pre-HD and post-HD, respectively), without 12h fasting. The samples were analyzed for 38amino acids by SRL Inc., using liquid chromatography-mass spectrometry (LC-MS). Differences between the plasma BCAA concentrations of Group C and pre-HD were determined. Dialysis-induced BCAA losses were different for each BCAA. However, strong intercorrelations between the plasma concentrations of each BCAA were maintained. In addition, the regression lines did not converge at the origin and were in different positions for groups C, pre-HD, and post-HD. A different distribution of the constant (b) for each group was observed for each BCAA correlation when a in the regression line (Y=aX+b) was fixed at the value for Group C, and b was calculated. Strong intercorrelations among plasma concentrations of BCAAs were maintained in CKD patients both pre- and post-dialysis, whereas the changes in the plasma concentrations of each BCAA were different. We speculate that there is a novel mechanism that selectively regulates each BCAA and suggest that changes in the constant of the regression formula for correlation may have a novel function as an index for renal contribution to BCAA metabolism.

Effects of military training on plasma amino acid concentrations and their associations with overreaching.

The diagnosis of overtraining syndrome and overreaching poses a great challenge. Military training aims at improving the physical performance of the conscripts, but an excessive training load could also lead to overreaching. This study of Finnish conscripts provides new insights into the pathophysiology of overreaching and overtraining through amino acids concentrations. In addition to confirming the possible use of plasma glutamine/glutamate concentration to indicate and predict overreaching, we made a novel finding, i.e. low alanine and arginine concentrations might have a role in performance decrement and fatigue related to overreaching. Moreover, this study is the first to show the possible association between amino acids with putative neuronal properties and overreaching. Thus, the present findings might help to detect and prevent overreaching and offer a reliable diagnostic approach. In order to avoid overreaching, military training should be planned more periodically and individually, especially during the first four weeks of military service.

End-Stage Renal Disease Patients Lose a Substantial Amount of Amino Acids during Hemodialysis

ABSTRACTBackgroundPoor nutritional status is frequently observed in end-stage renal disease patients and associated with adverse clinical outcomes and increased mortality. Loss of amino acids (AAs) during hemodialysis (HD) may contribute to protein malnutrition in these patients.ObjectiveWe aimed to assess the extent of AA loss during HD in end-stage renal disease patients consuming their habitual diet.MethodsTen anuric chronic HD patients (mean ± SD age: 67.9 ± 19.3 y, BMI: 23.2 ± 3.5 kg/m2), undergoing HD 3 times per week, were selected to participate in this study. Spent dialysate was collected continuously and plasma samples were obtained directly before and after a single HD session in each participant. AA profiles in spent dialysate and in pre-HD and post-HD plasma were measured through ultra-performance liquid chromatography to determine AA concentrations and, as such, net loss of AAs. In addition, dietary intake before and throughout HD was assessed using a 24-h food recall questionnaire during HD. Paired-sample t tests were conducted to compare pre-HD and post-HD plasma AA concentrations.ResultsDuring an HD session, 11.95 ± 0.69 g AAs were lost via the dialysate, of which 8.26 ± 0.46 g were nonessential AAs, 3.69 ± 0.31 g were essential AAs, and 1.64 ± 0.17 g were branched-chain AAs. As a consequence, plasma total and essential AA concentrations declined significantly from 2.88 ± 0.15 and 0.80 ± 0.05 mmol/L to 2.27 ± 0.11 and 0.66 ± 0.05 mmol/L, respectively (P < 0.05). AA profiles of pre-HD plasma and spent dialysate were similar. Moreover, AA concentrations in pre-HD plasma and spent dialysate were strongly correlated (Spearman's ρ = 0.92, P < 0.001).ConclusionsDuring a single HD session, ∼12 g AAs are lost into the dialysate, causing a significant decline in plasma AA concentrations. AA loss during HD can contribute substantially to protein malnutrition in end-stage renal disease patients. This study was registered at the Netherlands Trial Registry (NTR7101).

Alanine, arginine, cysteine, and proline, but not glutamine, are substrates for, and acute mediators of, the liver-α-cell axis in female mice.

The aim of this study was to identify the amino acids that stimulate glucagon secretion in mice and whose metabolism depends on glucagon receptor signaling. Pancreata of female C57BL/6JRj mice were perfused with 19 individual amino acids and pyruvate (at 10 mM), and secretion of glucagon was assessed using a specific glucagon radioimmunoassay. Separately, a glucagon receptor antagonist (GRA; 25-2648, 100 mg/kg) or vehicle was administered to female C57BL/6JRj mice 3 h before an intraperitoneal injection of four different isomolar amino acid mixtures (in total 7 µmol/g body wt) as follows: mixture 1 contained alanine, arginine, cysteine, and proline; mixture 2 contained aspartate, glutamate, histidine, and lysine; mixture 3 contained citrulline, methionine, serine, and threonine; and mixture 4 contained glutamine, leucine, isoleucine, and valine. Blood glucose, plasma glucagon, amino acid, and insulin concentrations were measured using well-characterized methodologies. Alanine (P = 0.03), arginine (P < 0.0001), cysteine (P = 0.01), glycine (P = 0.02), lysine (P = 0.02), and proline (P = 0.03), but not glutamine (P = 0.9), stimulated glucagon secretion from the perfused mouse pancreas. However, when the four isomolar amino acid mixtures were administered in vivo, the four mixtures elicited similar glucagon responses (P > 0.5). Plasma concentrations of total amino acids in vivo were higher after administration of GRA when mixture 1 (P = 0.004) or mixture 3 (P = 0.04) were injected. Our data suggest that alanine, arginine, cysteine, and proline, but not glutamine, are involved in the acute regulation of the liver-α-cell axis in female mice, as they all increased glucagon secretion and their disappearance rate was altered by GRA.

Effect of Intermittent or Continuous Feed on Muscle Wasting in Critical Illness: A Phase 2 Clinical Trial

Acute skeletal muscle wasting in critical illness is associated with excess morbidity and mortality. Continuous feeding may suppress muscle protein synthesis as a result of the muscle-full effect, unlike intermittent feeding, which may ameliorate it. Does intermittent enteral feed decrease muscle wasting compared with continuous feed in critically ill patients? In a phase 2 interventional single-blinded randomized controlled trial, 121 mechanically ventilated adult patients with multiorgan failure were recruited following prospective informed consultee assent. They were randomized to the intervention group (intermittent enteral feeding from six 4-hourly feeds per 24 h, n= 62) or control group (standard continuous enteral feeding, n= 59). The primary outcome was 10-day loss of rectus femoris muscle cross-sectional area determined by ultrasound. Secondary outcomes included nutritional target achievements, plasma amino acid concentrations, glycemic control, and physical function milestones. Muscle loss was similar between arms (-1.1%[95%CI, -6.1%to -4.0%]; P= .676). More intermittently fed patients received 80%or more of target protein (OR, 1.52 [1.16-1.99]; P< .001) and energy (OR, 1.59 [1.21-2.08]; P= .001). Plasma branched-chain amino acid concentrations before and after feeds were similar between arms on trial day 1 (71 μM [44-98 μM]; P= .547) and trial day 10 (239 μM [33-444 μM]; P= .178). During the 10-day intervention period the coefficient of variation for glucose concentrations was higher with intermittent feed (17.84 [18.6-20.4]) vscontinuous feed (12.98 [14.0-15.7]; P< .001). However, days with reported hypoglycemia and insulin usage were similar in both groups. Safety profiles, gastric intolerance, physical function milestones, and discharge destinations did not differ between groups. Intermittent feeding in early critical illness is not shown to preserve muscle mass in this trial despite resulting in a greater achievement of nutritional targets than continuous feeding. However, it is feasible and safe. ClinicalTrials.gov; No.: NCT02358512; URL: www.clinicaltrials.gov.

Feeding Agroindustrial Byproducts to Light Lambs: Influence on Growth Performance, Diet Digestibility, Nitrogen Balance, Ruminal Fermentation, and Plasma Metabolites.

Simple SummaryFeeding agroindustrial byproducts to ruminants can have multiple benefits, such as lowering feeding costs, reducing competition with human food, decreasing environmental impact associated with byproducts disposal, and improving the quality of animal products. In order to use these byproducts in practical feeding, their effects on animal performance and health should be assessed. In this study, we evaluated the effect of replacing 44% of conventional feeds in a high-cereal concentrate for light lambs with three byproducts: Corn distiller’s dried grains with solubles (18%), dried citrus pulp (18%), and exhausted olive cake (8%), all of which are highly produced in the Mediterranean area. We observed that the inclusion of these byproducts did not affect feed intake, growth performance, ruminal fermentation (with exception of NH3-N concentrations), or plasma metabolites in growing lambs. Compared with the high-cereal concentrate, feeding the concentrate including the byproducts resulted in a reduction of potentially human-edible ingredients from 64.4% to 38.7%. In conclusion, 44% of cereal grains and protein feeds in the concentrate for light lambs can be replaced with a mixture of corn distiller’s dried grains with solubles, dried citrus pulp, and exhausted olive cake without negatively affecting growing performance and animal health.The objective of this study was to evaluate the effect of replacing cereals and protein concentrates in a high-cereal concentrate (control) for light lambs with corn distiller’s dried grains with solubles (DDGS; 18%), dried citrus pulp (DCP; 18%), and exhausted olive cake (EOC; 8%) in a byproduct (BYP) concentrate on growth performance, digestibility, ruminal fermentation, and plasma metabolites. Two homogeneous groups of Lacaune lambs (13.8 kg ± 0.25 kg) were fed one of each concentrates and barley straw ad libitum until reaching about 26 kg body weight. There were no differences between groups on feed intake, average daily gain, or feed conversion ratio, but the control diet had greater (p < 0.001) dry matter digestibility. Diet had no effect on post-mortem ruminal pH and total volatile fatty acid concentrations and profile, but NH3-N concentrations were lower (p = 0.003) for the BYP-fed group compared with the control one. However, plasma concentrations of amino acids, total proteins, urea, and hepatic enzymes were not affected by the diet. In conclusion, 44% of feed ingredients in the concentrate for light lambs can be replaced with a mixture of corn DDGS, DCP, and EOC without negatively affecting growing performance and animal health.

Impact of enteral arginine supplementation on lysine metabolism in humans: A proof-of-concept for lysine-related inborn errors of metabolism.

Patients with lysine-related inborn errors of metabolism (pyridoxine-dependent epilepsy [PDE] and glutaric aciduria type 1 [GA1]), follow a lysine-restricted diet with arginine-fortified lysine-free amino acid formula and additional oral arginine supplementation as a newer therapy for PDE. The rationale of arginine supplementation is based on arginine's ability to compete with lysine transport across cell membranes via shared transporter systems. Adequate doses of arginine required to competitively inhibit enteral lysine uptake has not been studied in humans This proof-of-concept study investigates the effect of incremental enteral arginine doses on whole-body lysine oxidation using an in vivo stable isotope tracer, L-[1-13 C] lysine, in healthy humans. Five healthy men completed six study days each consuming one dose of l-arginine HCl per study day; range = 50-600 mg/kg/d. Lysine intake was at DRI (30 mg/kg/d). Breath samples were analysed for L-[1-13 C] lysine oxidation to 13 CO2 using an isotope ratio mass spectrometer. Plasma amino acid concentrations were analysed using an amino acid analyser. Increasing doses of l-arginine HCl caused a linear decrease in whole-body lysine oxidation. Plasma arginine concentration increased, and plasma lysine concentration decreased below normal range with high arginine intakes. We provide the first empirical evidence of arginine-lysine antagonism in response to increasing oral arginine doses. Results suggest 300-600 mg/kg/d of l-arginine HCl and lysine intake restricted to DRI is needed to reduce enteral lysine uptake and systemic lysine oxidation. This could potentially lead to a recommended dose for arginine in lysine-related inborn errors of metabolism.

Effects of Casein Hydrolysate Ingestion on Thermoregulatory Responses in Healthy Adults during Exercise in Heated Conditions: A Randomized Crossover Trial.

Food ingestion has been shown to affect thermoregulation during exercise, while the impact of protein degradant consumption remains unclear. We investigated the effects of casein hydrolysate ingestion on thermoregulatory responses during exercise in the heat. In a randomized, placebo-controlled, double-blind, crossover trial, five men and five women consumed either 5 g of casein hydrolysate or placebo. Thirty minutes after ingestion, participants cycled at 60% VO2max until voluntary exhaustion wearing a hot-water (43 °C) circulation suit. Exercise time to exhaustion, body core temperature, forearm sweat rate, and forearm cutaneous vascular conductance did not differ different between the conditions. However, chest sweat rate and mean skin temperature increased upon casein hydrolysate ingestion compared with placebo during exercise. Increased chest sweat rate upon casein hydrolysate ingestion was associated with elevated sudomotor sensitivity to increasing body core temperature, but not the temperature threshold for initiating sweating. A positive correlation was found between chest sweat rate and plasma total amino acid concentration during exercise. These results suggest that casein hydrolysate ingestion enhances sweating heterogeneously by increasing peripheral sensitivity of the chest’s sweating mechanism and elevating skin temperature during exercise in the heat. However, the physiological link between plasma amino acid concentration and sweat rate remains unclear.

Changes in plasma amino acid concentrations in overweight and obese men after weight loss program including dietary modification and aerobic exercise

Changes in plasma amino acid concentrations in overweight and obese men after weight loss program including dietary modification and aerobic exercise

Plasma Concentration of Branched Chain Amino Acids are Not Related to Improvements in Insulin Sensitivity after 12 W of Intensive Exercise in Sedentary Dysglycemic and Normoglycemic Men

Plasma concentration of branched-chain amino acids (BCAAs) is associated with insulin resistance. However, it is unknown if the insulin sensitizing effect of exercise can be explained by BCAAs. In agreement with previous reports, we found that plasma BCAAs concentration was higher, and transcription of BCAA catabolic enzymes in skeletal muscle (SkM) and subcutaneous white adipose tissue (ScWAT) was lower in dysglycemic (DG) than normoglycemic (NG) men. Twelve weeks of intensive exercise enhanced insulin sensitivity by ~40% in both groups, as quantified by euglycemic hyperinsulinemic clamp, but no changes were observed in plasma BCAAs concentrations. However, pathway analyses of mRNA sequencing data predicted enhanced BCAA catabolism in both SkM and ScWAT, which mediated the effect of exercise on insulin sensitivity. Our results suggest that the insulin sensitizing effect of exercise cannot be explained by plasma BCAAs, but imply that tissue catabolism of BCAAs may be linked to regulation of insulin sensitivity.

Changes in plasma amino acids metabolites, caused by long-term IGF-I deficiency, are reversed by IGF-I treatment – A pilot study

Laron Syndrome (LS), (OMIM# 262500), a rare recessively inherited disease caused by deletions or mutations of the GH receptor, gene characterized by dwarfism with low or undetectable serum IGF-I in the presence of high serum GH. In addition to dwarfism, the IGF-I deficiency leads to metabolic abnormalities including aberrations in protein biosynthesis and homeostasis. The only available treatment for LS patients is (r)IGF-I administration.The present study was aimed to determine the plasma concentrations of specific amino acids and their metabolites in the blood of untreated and IGF-I-treated LS patients.The study involved a total of 10 LS patients (3 untreated and 7 treated), 2 heterozygote mothers and 3aged subjects. Forty healthy boys and girls served as controls.The analysis of amino acids and their metabolites was performed using the LC-MS/MS analysis and Waters Acc-Q Tag ultra-derivatization kit. Serum IGF-I levels were measured by a one-step sandwich chemiluminescence immunoassay.The results revealed that long-term IGF-I deficiency in LS patients led to abnormal changes in the plasma amino acids metabolism, such as low levels of plasma citrulline, sarcosine and taurine that increased upon IGF-I replacement. The plasma amino acid levels of the heterozygous family members resembled those of the untreated LS patients, whereas the pattern in the 2 double heterozygote sisters previously treated with IGF-I resembled that of the presently IGF-I-treated patients. In addition, plasma ɑ-amino adipic acid levels were elevated in both untreated and IGF-I-treated patients.In summary our data revealed that LS patients, a condition associated with congenital IGF-I deficiency, have an abnormal plasma amino acid metabolism that is partially restored by IGF-I treatment.