Plasma Amino Acid Concentrations Research Articles

The Effect of Mild Renal Dysfunction on the Assessment of Plasma Amino Acid Concentration and Insulin Resistance in Patients with Type 2 Diabetes Mellitus.

Background An increase in the levels of branched-chain amino acids (BCAAs) and certain aromatic amino acids, such as alanine, in plasma is correlated with insulin resistance (IR) in type 2 diabetes mellitus (T2DM). T2DM is a leading risk factor for chronic kidney disease. Meanwhile, renal dysfunction causes changes in plasma amino acid levels. To date, no study has examined how mild renal dysfunction and IR interact with plasma amino acid levels. This study examines the effects of IR and renal dysfunction on plasma amino acid concentrations in T2DM. Methods Data were collected from healthy male participants (controls) and male patients with T2DM between May 2018 and February 2022. Blood samples were collected after overnight fasting. IR and renal function were evaluated using the homeostasis model assessment of IR (HOMA-IR) and serum cystatin C (CysC), respectively. Results A total of 49 and 93 participants were included in the control and T2DM groups, respectively. In the T2DM group, eight amino acids (alanine, glutamic acid, glutamine, glycine, isoleucine, leucine, tyrosine, and valine) and total BCAA showed a significant correlation with HOMA-IR (p < 0.01), whereas six amino acids (γ-aminobutyric acid, citrulline, cysteine, glycine, methionine, and valine) and total BCAA showed a significant correlation with 1/CysC (p < 0.02). However, only alanine, glutamic acid, and each BCAA showed significant differences between the control group and the IR T2DM subgroup. Increases in the BCAA levels with T2DM were canceled by renal dysfunction (CysC ≥ 0.93) in patients with intermediate IR. Conclusion To use plasma BCAA concentration as a marker of IR, renal function must be considered, even in mild renal dysfunction. Increased alanine and glutamic acid levels indicate IR, regardless of mild renal dysfunction.

Comparison of Amino Acid Concentrations in Plasma and Dried Blood Spot Samples Using LC-MS/MS

Background: Dried blood spot samples are suitable for diagnosing some congenital errors of metabolism; however, they provide limited benefit in the regular monitoring of amino acids. Objectives: The present study aimed to evaluate alanine (Ala), arginine (Arg), citrulline (Cit), glutamic acid (Glu), glycine (Gly), isoleucine (Ileu), leucine (Leu), methionine (Met), ornithine (Orn), phenylalanine (Phe), tyrosine (Tyr), and valine (Val) amino acid concentrations in dried blood and plasma samples obtained simultaneously. Methods: Amino acid concentrations were determined in the plasma, and dried blood spot samples obtained simultaneously from 145 patients (50 females and 95 males). Amino acid concentrations in the plasma and dried blood spot samples were studied by LC-MS/MS using original kits. Results: There were significant differences between dried blood spots and plasma in all amino acid concentrations, except for Met and Val. Bland-Altman analysis revealed the highest mean differences in Glu (-148.1), Gly (-70.1), and Ala (-58.1). Deming regression analysis showed that plasma and dried blood spot samples were consistent concerning Cit, Met, Phe, and Tyr concentrations. Conclusions: Differences in methodology and sample can influence amino acid concentrations. Dried blood spot samples might cause errors in amino acid screening programs.

Mild Cognitive Impairment Is Associated With Markers of Muscle Weakness and Reduced Bone Density, and Specific Metabolic Alterations Despite Preserved Physical Activity

ObjectivesBone loss and frailty commonly occur in people with dementia residing in nursing homes and lead to increased risk of disabilities and poor health outcomes. Whether these systemic manifestations and related metabolic disturbances are present in older adults with Mild Cognitive impairment (MCI), who are still physically active, remains unclear. MethodsCommunity dwelling older adults without confounding comorbidities were divided, using the Montreal Cognitive Assessment (MoCA) score cut-off of 26, into two groups: non-MCI (n = 18; age: 67.3 [63.3, 71.2 y]) and MCI (n = 20; age: 71.3 [66.9, 75.7 y]). Body composition (by DXA), respiratory strength (by mouth pressure), and extremity strength (by dynamometer) were assessed. Stable isotope techniques were used to measure production and plasma concentrations of amino acids involved in muscle, bone, and brain health (tau-methylhistidine, hydroxyproline, glycine, tryptophan). Plasma enrichments were analyzed by LC-MS/MS. Statistics performed by ANCOVA with age, gender, and BMI as covariates. Significance set at P < 0.05. Results expressed as means [95% CI]. ResultsMCI participants (MoCA score: 22.5 [21.3, 23.6]) had lower respiratory muscle strength (p = 0.007) than the non-MCI group (MoCA score: 28.2 [27.5, 28.8]) but muscle mass and daily physical activity were not different. Bone density of the spine (p = 0.02) and hip (p = 0.07) were lowest in those with the lowest MoCA scores. The MCI group had lower concentrations of glycine (p = 0.0045), tryptophan corrected for large neutral amino acids (p = 0.0017), and productions of glycine (p = 0.0085), tau-methylhistidine (p = 0.05), and tryptophan (p = 0.06). MoCA score was negatively associated with plasma triglyceride (p = 0.02) and liver enzyme (AST) level (p = 0.01), but not with glucose or CRP levels. ConclusionsOlder adults with MCI are prone to low bone density and respiratory muscle weakness despite preserved physical activity. Whether these systemic manifestations are causally related to the observed metabolic alterations in MCI deserves further investigation. Funding SourcesNone

The Role of Comorbidities on Aging-Induced Changes in Muscle Health and Amino Acid Kinetics

ObjectivesAging and comorbidities are known to influence amino acid metabolism, contributing to reduced muscle and cognitive dysfunction in older adults. Whether these aging-induced manifestations remain after correction for the presence of comorbidities is unclear. MethodsOlder adults were selected from the MEDIT database. The subjects were divided into two age groups: 264 young old (age 50–70 y: n = 149 with at least 1 comorbidity based on Charlson comorbidity index (CCI > 0) and n = 115 with CCI = 0), and 196 middle old (age 70–85 y: n = 119 with CCI > 0 and n = 77 with CCI = 0). Body composition was assessed by DXA, respiratory and skeletal muscle strength by mouth pressures and dynamometry, and cognition and mood by assessments and questionnaires. Postabsorptive kinetics of multiple amino acids were measured by pulse stable isotope administration and subsequent blood sampling. Plasma amino acid concentrations and enrichments were analyzed by LC-MS/MS to measure whole-body protein production (WBP) and conversion rates. Statistics are done with ANCOVA with sex and BMI and age group as independents. Results expressed as means [95% CI]. ResultsThe middle old had lower lean mass on whole body level and in the extremities (p < 0.0001), and lower respiratory (p = 0.05) and handgrip (p = 0.005) strength compared to the young old, independent of muscle health lowering effects of CCI. Although no differences were observed in cognition and mood between the groups, an age x CCI interaction was found for depression, anxiety (p = 0.03), and lean mass extremity (p = 0.04). The middle old had lower values for WBP of tau-methylhistidine (p = 0.01), hydroxyproline (P = 0.008), and taurine (p = 0.004), and plasma glutamine concentration (P = 0.016). In addition, the middle old showed higher glutamine to glutamate conversion (p = 0.02). Age x CCI interaction was observed for plasma concentration of tyrosine (p = 0.04). No differences were observed in plasma concentrations and WBP of phenylalanine and the branched-chain amino acids (leucine, valine, and isoleucine) between the groups. ConclusionsMuscle loss and weakness and specific disturbances in amino acid kinetics due to aging exist even after correction for the presence of comorbidities. Funding SourcesNone

Prediabetes Is Associated with Specific Changes in Valine Metabolism

ObjectivesRecent studies have suggested that a high plasma concentration of the branched-chain amino acids (BCAAs) can serve as a biomarker for type-2-diabetes (T2D). Whether this is also the case for prediabetes remains unclear. Our goal is to examine whether specific disturbances exist in the kinetics of the BCAAs leucine, isoleucine and valine in middle aged/older adults with prediabetes. MethodsWe measured BCAA kinetics in 70 prediabetic subjects (fasting glucose: 5.7-6.5 mM), 47 diabetic subjects (fasting glucose: ≥6.5 mM, or are taking medication to control blood glucose) and 170 healthy subjects (fasting glucose: < 5.7 mM) that were 40 years or older. In the fasted state, a pulse of stable isotopes containing leucine, isoleucine and valine was administered intravenously while blood was sampled to assess their whole body production rates (WBP). BCAA tracer enrichment and concentration analyses were done by LC-MS/MS. BCAA whole body production rates were calculated from the area under the curve (AUC). Statistics by ANCOVA corrected for age, sex, and lean body mass as covariates. Significance set at P< 0.05. Results expressed as means [95% CI]. ResultsThe subjects with prediabetes had a lower valine WBP (9492 [8256, 10913] vs. 12288 [11247, 13425] μmol/h, P = 0.0021), but a higher plasma valine concentration (185.7 [176.4, 195.6] vs. 172.2 [166.5, 178.1] μM, P = 0.0178) than the healthy control subjects. No differences in WBP or concentrations of isoleucine or leucine were observed between the groups. Diabetic subjects had the highest plasma concentration for valine across the groups (213.8 [200.4, 228.0] μM, P = < 0.0001), but without a change in the WBP of leucine, isoleucine and valine. ConclusionsPrediabetes is characterized by specific changes in the concentration and whole body production of valine. Funding SourcesNone

Increased Amino Acid Turnover and Net Protein Breakdown but Preserved Muscle and Cognitive Function in Obese Middle-Age Adults

ObjectivesSkeletal muscle weakness has been observed in obese patients despite preserved or even greater lean body mass. Additionally, the presence of obesity-related comorbidities is a recognized risk factor for cognitive dysfunction and mood disturbances. Metabolism of several amino acids (AAs) including the Branched-chain Amino Acids (BCAAs) is altered in obesity but whether these disturbances are associated with muscle and cognitive dysfunction remain underexplored.Methods159 subjects were divided, using the BMI cut-off of 30 kg/m2, into two groups: 79 non-obese (32 males/47 females, age 48.5 [43.3, 53.7], BMI 25.2 [24.6, 25.7] kg/m2) and 80 obese (31 males/49 females, age 54.3 [51.0, 57.6], BMI 38.3 [36.9, 39.6] kg/m2). Postabsorptive whole-body production (WBP) rates of several AAs were measured by IV pulse of stable isotopes including BCAAs, Phenylalanine (Phe), Tyrosine (Tyr), Glutamate (Glu), and Tryptophan (Trp). Plasma amino acid enrichments and concentrations were analyzed by LC-MS/MS. Large Neutral Amino Acids (LNAA) was calculated as the sum of BCAAs, Phe, and Tyr. Body composition (DXA), hand and leg peak strength and endurance (isokinetic dynamometer), cognitive function (Stroop, TMT), and mood (POMS, HADS) were assessed. Statistics performed by ANCOVA with age, gender, and lean body mass as covariates. Significance at P < 0.05. Results expressed as means [95% CI].ResultsObese subjects had higher concentrations of plasma Leu (12%, P = 0.0097), Ile (7%, P = 0.0310), Tyr (23%, P < 0.0001), and Glu (40%, P = 0.0001). The obese group was also characterized by elevated WBP of BCAAs (8%, P = 0.0343), Phe (12%, P = 0.0003), Tyr (18%, P = 0.0005) and increased whole-body net protein breakdown (Phe to Tyr conversion, 11%, P = 0.0212). Both groups had similar muscle and cognitive functions but obese individuals had greater scores for self-reported depressive symptoms (P = 0.0273), anger (P = 0.0234), fatigue (P = 0.0098), and tension (P = 0.0158). No changes in Trp metabolism were found but obese subjects had elevated LNAA (7%, P = 0.0170) resulting in increased systemic Trp availability to the brain (P = 0.0014).ConclusionsObese subjects have preserved muscle and cognitive function despite greater whole-body net protein breakdown and increased turnover of several AAs involved in muscle metabolism and serotonin synthesis.Funding SourcesNone.

Plasma Amino Acid Concentrations in Patients with Alcohol and/or Cocaine Use Disorders and Their Association with Psychiatric Comorbidity and Sex.

(1) Background: Co-occurrence of mental and substance use disorders (SUD) is prevalent, but complicates their clinical courses, and specific biomarkers are required. Amino acids are altered in primary mental disorders; however, little is known about SUD and psychiatric comorbidity. Because most psychiatric disorders and biomarkers show sex differences, we investigated amino acids in men and women with alcohol and/or cocaine use disorders (AUD and/or CUD) and psychiatric comorbidity. (2) Methods: A cross-sectional study was conducted in 295 participants, who were divided into four groups (AUD, n = 60; CUD, n = 41; AUD + CUD, n = 64; and control, n = 130). Participants were clinically assessed, and plasma amino acid concentrations were analyzed in relation to sex, diagnosis of SUD and psychiatric comorbidity (3) Results: In the total sample, there were sex differences, and women showed lower Iso, Leu, Gln and Glu than men. While patients with CUD and AUD + CUD had higher Glu, Gly, Orn and Ser than controls, patients with AUD showed no differences. In SUD, patients with psychiatric comorbidity had lower Orn and higher Ala than non-comorbid patients in the AUD group. (4) Conclusions: There was a dysregulation of plasma amino acids in abstinent patients with SUD. However, our results suggest the importance of considering the clinical characteristics and sex in the validity of amino acids as potential biomarkers for SUD.

The acute effects of insect vs. beef-derived protein on postprandial plasma aminoacidemia, appetite hormones, appetite sensations, and energy intake in healthy young men

The purpose of this study was to evaluate the acute effects of ingesting beef- and insect-derived protein on postprandial plasma amino acid and appetite hormone concentrations, appetite sensations, and ad libitum energy intake. In a randomized, double-blind, crossover study, 20 young men (23 (SD: 4) y) completed two trials during which arterialized blood samples and VAS questionnaires were collected at baseline, and over 300-min after ingestion of beverages with similar energy and macronutrient content containing 25 g beef- or insect-derived (cricket) protein. Blood samples were analyzed for plasma amino acid and appetite hormone concentrations, while VAS questionnaires were applied to assess appetite sensations. After each trial, an ad libitum meal was immediately provided to assess energy intake. Adjusted mean postprandial incremental area under the curve (iAUC) was greater for cricket vs. beef-derived protein for plasma leucine, branched-chain amino acid, and essential amino acid concentrations (all P &lt; 0.0001). Adjusted mean postprandial iAUC for hunger was lower following beef (-3030 (SE: 860)) vs. cricket-derived (-1197 (SE: 525)) protein (Difference: -1833 (95% CI: -3358, -308); P = 0.02), but was not different for other appetite sensations or appetite hormones (all P &gt; 0.05). Adjusted mean ad libitum energy intake was 4072 (SE: 292) and 4408 (SE: 316) kJ following beef- and cricket-derived protein (Difference: -336 (95% CI: -992, 320); P = 0.30). Acute ingestion of cricket and beef-derived protein leads to differences in postprandial plasma amino acid concentrations, but elicits similar effects on appetite hormones, appetite sensations, and ad libitum energy intake in young men.

Influence of hempseed cake inclusion on growth performance, carcass characteristics, feeding behavior, and blood parameters in finishing heifers.

As the hemp industry continues to develop in the United States, there is an increasing interest in feeding byproducts of industrial hemp production to livestock. A completely randomized design experiment using crossbred finishing heifers (initial body weight [BW] ± SE = 494 ± 10 kg) was conducted to determine the effects of feeding hempseed cake in a corn-based finishing diet (10% forage) formulated to meet or exceed ruminally degradable and metabolizable protein requirements on growth performance, carcass characteristics, feeding behavior, and plasma parameters. Dietary treatments were the inclusion of 20% (dry matter [DM] basis) of dried corn distillers grains plus solubles (DDGS, n = 16) or hempseed cake (HEMP, n = 15). Cattle were housed in two pens, had ad libitum access to feed and water, and individual intakes and feeding behavior were monitored using the Insentec feeding system. Cattle were fed treatment diets for 111 d, and every 14 d BW were measured and blood samples were collected. Blood plasma was analyzed for glucose, urea nitrogen, and individual amino acids, and results were analyzed using repeated-measures analysis in SAS. Final BW, average daily gain, gain:feed, and hot carcass weight decreased (P ≤ 0.05) by 2.3%, 7.7%, 7.7%, and 2.6%, respectively, in heifers fed the HEMP diet than in heifers fed the DDGS diet. Net energy for maintenance and gain (Mcal/kg of feed, DM basis), estimated based on heifer intake and performance, were greater (P = 0.02) for the DDGS diet than for the HEMP diet. All other performance and carcass characteristics were not different (P ≥ 0.20) between treatments. Heifers fed the HEMP diet had greater (P < 0.05) plasma urea nitrogen concentration in samples from each collection day compared with heifers fed the DDGS diet, although there was a treatment-by-day interaction (P < 0.01) because of variability in the magnitude of treatment differences over time. Plasma glucose concentration was not influenced (P = 0.17) by dietary treatment. Plasma concentrations of total amino acids, nonessential amino acids, and essential amino acids were not different between treatments (P ≥ 0.09), although there were several interactions between treatment and day (P ≤ 0.04) for individual amino acids. These data suggest that hempseed cake has a lower net energy for maintenance and gain relative to DDGS when adequate metabolizable protein is supplied, while still providing adequate nutrition to support the acceptable performance of finishing cattle.

Plasma Amino Acid Appearance and Status of Appetite Following a Single Meal of Red Meat or a Plant-Based Meat Analog: A Randomized Crossover Clinical Trial

ABSTRACTBackgroundRed meat is a nutrient-dense food and a dietary staple. A new generation of plant-based meat analogs (PBMAs) have been designed to mimic the experience of eating meat, but there is limited evidence about their digestive efficacy and nutritional quality.ObjectivesWe compared the postprandial digestive response of a single meal containing meat commercially raised in New Zealand, including lamb, on-farm pasture-raised beef (Pasture), or grain-finished beef (Grain) with a PBMA (Beyond Burger; Beyond Meat) sold through consumer retail. The primary outcome was the appearance of amino acids in plasma. Secondary outcomes included glucose and insulin, appetite assessment, and anthropometry.MethodsThirty healthy men (20–34 y) participated in a double-blinded randomized crossover trial. Each consumed 1 of the 4 test meals on 4 occasions separated by a washout period of at least 1 wk, following an overnight fast. The meal was a burrito-style wrap containing meat or PBMAs, vegetables, salsa, and seasonings in a flour tortilla. The amount of Pasture, Grain, Lamb, or BB was 220 g raw (∼160 g cooked). Venous blood samples were collected over 4 h. Appetite and hunger status was scored with visual analog scales.ResultsPre-meal amino acid concentrations in plasma did not differ by group (P > 0.9), although several nonessential amino acids differed strongly according to participant BMI. Postprandial amino acids peaked at 2–3 h in all groups. The BB meal produced significantly lower plasma concentrations of total, essential, branched-chain, and non-proteogenic amino acids than the Lamb, Pasture, or Grain meals, based on AUC. There were no significant differences between meal groups in scores for hunger, fullness, or cravings.ConclusionsRed meat meals exhibited greater bioavailability of amino acids compared with the PBMA (BB). Pasture versus Grain origins of the beef had little influence on participants’ responses. This trial was registered at ClinicalTrials.gov as NCT04545398.

The importance of plasma amino acid profiling in the diagnosis of inborn errors of metabolism: analytical – prospective study

Introduction. Inborn errors of metabolism (IEM) make up a large group of disorders caused by an inherited defect of proteins that have enzymatic, carrier, receptor or structural roles. The cumulative prevalence of IEM in different populations is around 1:500 – 800 newborns, despite the fact that some of these disorders are extremely rare when taken individually. Early recognition and intervention are essential to avoiding disastrous consequences associated with IEM. The phenotype of IEM patients is very heterogeneous and only in combination with specialized metabolic test it can lead to a correct diagnosis. The aim of the study was defined as evaluation of importance of plasma amino acid profile in the diagnosis of IEM. Material and methods. Plasma amino acids quantification have been performed by high performance liquid chromatography on Shimadzu LC-20 with post column derivatization with OPA in 15 patients aged from 0 to 13 years old, selected through medical genetic counseling, based on inclusion and exclusion criteria. Inform consent has been signed by parents after receiving all necessary information regarding the study. Additionally, liquid chromatography-tandem mass spectrometry (LC-MS/MS) on dried blood spots and Nuclear Magnetic Resonance Spectroscopy (H1-NMR) on urine has been done as complementary tests. Results. The first line investigations showed acid-base imbalance (33,3%), hypoglycemia (46,6%), high lactate level (46,6%) and high ammonia level (20%). Plasma amino acid concentrations were abnormal in 4 patients (27%). Increased glycine (544 μmol/L, reference values 70,72 – 256,36 μmol/L), along with elevated glycine in cerebrospinal fluid (CSF) / plasma ratio (0,147, normal &lt; 0.02) was detected in a patient with seizures, coma, and respiratory arrest indicating non-ketotic hyperglycinemia. High level of phenylalanine (Phe 1568µmol/L, reference values 26.52 – 221 µmol/L) has been identified in a patient suspected for Phenylketonuria after neonatal screening results (Phe &gt; 3mg/dL). Also the ratio Phe / Tyr around 17 was specifically appreciated as for classical form of PKU. High alanine concentration (&gt; 450 µmol/L) has been observed in two patients presenting severe metabolic acidosis and high lactate level, suggesting for a metabolic error with mitochondrial involvement. The results from extended newborn screening and NMR spectroscopy narrowed the spectrum of suspected diseases, facilitating the diagnosis. Molecular genetic tests are required for the confirmation of disease in all cases. Conclusions. Quantitative amino acids analysis is an important tool for the diagnosis of “intoxication type” of IEMs and nutritional monitoring of individuals with already established diagnosis.

Essential Amino Acid Regulation of Protein Turnover to Support Skeletal Muscle Health with Age

Skeletal muscle (SM) is vital for both long term health and quality of life. Recent research suggests an increase in catabolic signals with age triggers pathologic conditions, such as sarcopenia. Although results from in vitro studies model how essential amino acids (EAA) can regulate muscle protein synthesis (MPS), the relevance of these models to muscle protein breakdown (MPB), and the presence of physiological plasma amino acid concentrations (PAA) remain to be established. Therefore, the objective of this study was to determine the effects of EAA with (0.2, 1.0, and 3.0 x PAA) in a young (passages 2‐10) and aging (passages 16‐24) C2C12 murine muscle cell model. We hypothesized that increased levels of EAA will increase MPS in aging cells and suppress MPB via the mTORC1 pathway when compared to young cells. Myoblasts were seeded (1x105) into 6‐well plates and differentiated into myotubes when they reached 80% confluency. Myotubes were serum and AA starved for 24 hours before receiving one of the following treatments: control (CON), 0.2 x PAA, 1.0 x PAA, 3.0 x PAA with or without rapamycin (100 nm; RAP) for 1, 6, and 24 hours. All treatments were performed in triplicate and then each experiment was repeated three times, yielding nine wells per treatment. Proteins related to sensing of AA and protein synthesis and degradation were assessed using Western Blot. Rapamycin inhibited phosphorylation of p70 S6 kinase 1 (p70S6K1) and 4E binding protein 1 (4E‐BP1), downstream targets of mTORC1, in both CON and AA‐treated young and aged cells. Phosphorylation of 4EBP1 and p70S6K1 was significantly increased (p&lt;0.05) in both young and aged cells following all PAA treatments. However, there was no significance after 24 hours of AA supplementation in aged cells. Particularly, after 6 hours of treatment all doses significantly increased (p&lt;0.0001) phosphorylation of p70S6K1 in both young and aged cells. 0.2 x PAA and 3.0 x PAA elicited a significantly greater response in 4EBP1 phosphorylation in young cells compared to the CON after 6 hours of treatment, whereas a dose of 3.0 x PAA induced a similar response in aged cells. In conclusion, in a C2C12 myotube model, increasing EAA concentrations downregulates the expression of translation initiation factors in young and aging cells. Specifically, it takes a 3.0 x PAA to elicit a response in aging cells, whereas young cells respond to lower physiological concentrations of 0.2 x PAA and 1.0 x PAA. Therefore, it can be proposed increasing EAA may be effective for adjusting the rate of MPS and MPB via the mTORC1 pathway in both young and aging muscle cells.

Circulatory amino acid responses to milk consumption in dairy and lactose intolerant individuals

Background/objectivesSelf-reported digestive intolerance to dairy foods is common. As dairy can be an important source of dietary protein, this study aimed to identify whether milk protein digestion is compromised in individuals with digestive intolerance.Subjects/methodsAdult women (n = 40) were enroled in this double-blinded, randomised cross-over trial, with digestive symptoms characterised using a lactose challenge and self-reported digestive symptom questionnaire. Participants were classified as either lactose intolerant (LI, n = 10), non-lactose dairy intolerant (NLDI, n = 20) or dairy tolerant (DT, n = 10). In a randomised sequence, participants consumed three different kinds of milk (750 ml); conventional milk (CON), a2 Milk™ (A2M), and lactose-free conventional milk (LF-CON). Circulatory plasma amino acid (AA) concentrations were measured at baseline and every 30 min until 3 h post-ingestion.ResultsIn all participants across all milk types, plasma AA concentrations (AUC0-180) increased after milk ingestion with no significant differences in responses observed between milk types or participants (P > 0.05), with the exception of the suppressed lysine response in the DT group following A2M ingestion, relative to the other two groups and milk types (P < 0.05).ConclusionMilk protein digestion, as determined by circulatory AAs, is largely unaffected by dairy- and lactose- intolerances.

Amino Acid Metabolism and Protein Turnover in Lean and Obese Humans During Exercise-Effect of IL-6 Receptor Blockade.

Interleukin-6 (IL-6) is implicated in skeletal muscle wasting and in regulating skeletal muscle hypertrophy in the healthy state. This work aimed to determine the role of IL-6 in regulating systemic protein and amino acid metabolism during rest, exercise, and recovery in lean and obese humans. In a nonrandomized, single-blind design, 12 lean and 9 obese individuals were infused first with 0.9% saline (Saline), secondly with the IL-6 receptor antibody tocilizumab (Acute IL-6R ab), and 21 days later with saline while still under tocilizumab influence (Chronic IL-6R ab). Outcome measures were determined before, during, and after 90 minutes of exercise at 40% Wattmax by isotope dilution technique, using primed continuous infusion of L-[ring-D5]phenylalanine and L-[D2]tyrosine. Main outcomes measures included systemic protein turnover and plasma amino acid concentrations. We saw no effect of acute or chronic IL-6 receptor blockade on protein turnover. In lean individuals, chronic IL-6 receptor blockade increased plasma concentrations of total amino acids (rest Δ + 186 μmol/L; 95% CI, 40-332; recovery Δ + 201 μmol/L; 95% CI, 55-347) and essential amino acids (rest Δ + 43 μmol/L; 95% CI, 12-76; recovery Δ + 45 μmol/L; 95% CI, 13-77) independently of exercise but had no such effect in obese individuals (total amino acids rest Δ + 63 μmol/L; 95% CI, -170 to 295, recovery Δ - 23 μmol/L, 95% CI, -256 to 210; essential amino acids rest Δ + 26 μmol/L; 95% CI, -21 to 73, recovery Δ + 11 μmol/L; 95% CI, -36 to 58). IL-6 receptor blockade has no effect on protein turnover in fasting lean and obese humans during rest, exercise, and recovery. Chronic IL-6 receptor blockade increases total and essential amino acid concentrations only in lean individuals.

Neither Incretin or Amino Acid Responses, nor Casein Content, Account for the Equal Insulin Response Following Iso-Lactose Loads of Natural Human and Cow Milk in Healthy Young Adults.

Human milk contains <50% less protein (casein) than cow milk, but is equally effective in insulin secretion despite lower postingestion hyperaminoacidemia. Such potency of human milk might be modulated either by incretins (glucagon-like polypeptide-1,GLP-1); glucose-inhibitory-polypeptide, GIP), and/or by milk casein content. Healthy volunteers of both sexes were fed iso-lactose loads of two low-protein milks, i.e., human [Hum] (n = 8) and casein-deprived cow milk (Cow [↓Cas]) (n = 10), as well as loads of two high-protein milks, i.e., cow (n = 7), and casein-added human-milk (Hum [↑Cas]) (n = 7). Plasma glucose, insulin, C-peptide, incretins and amino acid concentrations were measured for 240′. All milks induced the same transient hyperglycemia. The early [20′–30′] insulin and C-peptide responses were comparable among all milk types apart from the low-protein (Cow [↓Cas]) milk, where they were reduced by <50% (p < 0.05 vs. others). When comparing the two high-protein milks, GLP-1 and GIP [5’–20’] responses with the (Hum [↑Cas]) milk were lower (by ≈2–3 fold, p < 0.007 and p < 0.03 respectively) than those with cow milk, whereas incretin secretion was substantially similar. Plasma amino acid increments largely reflected the milk protein content. Thus, neither casein milk content, nor incretin or amino acid concentrations, can account for the specific potency of human milk on insulin secretion, which remains as yet unresolved.

Cheese Ingestion Increases Muscle Protein Synthesis Rates Both at Rest and During Recovery from Exercise in Healthy, Young Males: A Randomized Parallel-Group Trial

ABSTRACTBackgroundProtein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored.ObjectivesTo compare the impact of ingesting 30 g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males.MethodsIn this randomized, parallel-group intervention trial, 20 healthy males aged 18–35 y ingested 30 g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercises. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time × Group (× Leg) ANOVA.ResultsPlasma total amino acid concentrations increased after protein ingestion (Time: P < 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time × Group: P < 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 ± 0.014 to 0.055 ± 0.018%·h–1 and 0.034 ± 0.008 to 0.056 ± 0.010%·h–1 at rest and even more following exercise from 0.031 ± 0.010 to 0.067 ± 0.013%·h–1 and 0.030 ± 0.008 to 0.063 ± 0.010%·h–1, respectively (Time: all P < 0.05; Time × Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time × Group: both P > 0.05).ConclusionCheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30 g protein is ingested at rest or during recovery from exercise in healthy, young males.

Oxidative stress biomarkers and free amino acid concentrations in the blood plasma of moderately exercised horses indicate adaptive response to prolonged exercise training.

Oxidative stress caused by routine physical stressors may negatively impact the performance of equine athletes; thus, the present study identifies oxidative biomarkers in the blood plasma of exercising horses. Stock-type horses were subject to a standardized moderate-intensity exercise protocol 3 times per week for 8wk. Exercise protocol followed NRC guidelines consisting of 30% walk, 55% trot, and 15% canter, with a target heart rate (HR) of 90 BPM. Blood plasma was collected in wk 1, 2, 7, and 8 immediately before and 0, 30, 60, and 90min after exercise and analyzed for total antioxidant capacity (TAC), thiobarbituric acid reactive substance (TBARS), glutathione peroxidase activity (GPx), and superoxide dismutase activity (SOD). Data were analyzed as repeated measures with wk, d, time, and their interactions as fixed effects. The TAC on day 2 (0.40mM Trolox) was 7.5% greater than on day 3 (P = 0.013). There were wk × d × time interactions for SOD, TBARS, and GPx (P < 0.001). The TBARS remained at pre-exercise baseline (d-1 wk-1; 2.7 µM malondialdehyde) for most collection times within weeks 1, 7, and 8 (P ≥ 0.058); however, TBARS increased by 0.24 to 0.41 µM on day 2 of week 2 post-exercise (P < 0.001) and remained similarly elevated on day 3 pre- and immediately post-exercise (P < 0.001). The GPx similarly remained at baseline (172.6 µM/min; P ≥ 0.621) but increased by 48.18 to 83.4 µM/min at most collection times on days 1 and 2 of week 2 (P ≤ 0.023). The SOD remained at baseline (167.2 U/ mL; P ≥ 0.055) until increasing by 11.28 to 15.61 U/mL at 30min post-exercise on day 1, week 1 and at most collection times on day 3, week 8 (P ≤ 0.043). Amino acids with antioxidant properties such as Met, Tyr, and Trp drastically decreased from weeks 2 to 8 (P < 0.001). Met and Tyr also decreased from -60 to 90min (P < 0.047), whereas there was no time effect on Trp concentration (P = 0.841). The current study indicates the time-dependent nature of oxidative stress concerning persistent stressors such as exercise.

The effects of maternal supplementation of rumen-protected lysine during the close-up dry period on newborn metabolism and growth in Holstein calves.

This study aimed to evaluate the effects of rumen-protected lysine (RPL) supplementation during the close-up period on blood metabolites and calf growth. Forty multiparous Holstein dams were selected based on parity, body condition score, and expected calving date, and randomly assigned to a group: with RPL (n = 22) or without (control [CON], n = 18). RPL dams were supplied daily with 80 g of RPL from Day 21 before the expected calving date to parturition. Blood samples were obtained from the dams before the start of supplementation, 1 week before calving, and immediately after calving, and from calves immediately after birth and weekly until 8 weeks of age. Body weight measurements were performed immediately after birth in all calves and at weekly intervals until 8 weeks of age in female calves. No significant difference was observed in serum metabolite levels and plasma amino acid concentrations between the RPL and CON dams before supplementation, whereas plasma lysine concentrations tended to be higher in RPL dams immediately after calving (p = 0.07). Serum total protein levels (p < 0.05) were higher, whereas plasma total amino acid, total essential amino acid, total non-essential amino acid, and other amino acid concentrations were lower in the calves of RPL dams than those of CON dams (p < 0.05). There were no significant differences in calf birth weight between the two groups, although female calves of RPL dams (n = 7) had higher serum total protein (p < 0.05) and tended to have greater body weight (p = 0.09) from 1 to 8 weeks of age than those of CON dams (n = 11). Overall, RPL supplementation during the close-up period may increase placenta-mediated amino acid transfer to the foetus and enhance protein synthesis in the calf, leading to improved weight gain during the suckling period.

An evaluation of elevated branched-chain amino acid inclusions on the performance of broiler chickens offered reduced-crude protein, wheat-based diets from 7 to 28 days post-hatch

The physiological functions of essential branched chain amino acids (BCAA) are important in broiler nutrition, but antagonistic BCAA interactions may become evident. Given the increased implementation of reduced-crude protein (CP) diets, this study aimed to investigate whether elevated leucine inclusions in reduced-CP diets would advantage broiler growth performance, provided concomitant elevations in isoleucine and valine were employed. A total of 378 off-sex male Ross 308 broilers were allocated to 9 dietary treatments, each with 7 replicate cages and 6 birds in each. All diets were wheat-based with 190 g/kg CP. The dietary treatments comprised 3 leucine inclusions (12.71, 15.02, 17.33 g/kg) and 3 isoleucine plus valine inclusions (17.21, 20.32, 23.45 g/kg) in a 3 × 3 factorial array. The assessed parameters included growth performance, relative abdominal fat-pad weights, nutrient utilisation, apparent jejunal and ileal digestibility coefficients and disappearance rates of starch, protein (N), amino acids and free amino acid concentrations in systemic plasma. Elevated BCAA inclusions did not enhance growth performance; indeed, elevating isoleucine plus valine from 17.21 to 20.32 g/kg in the 15.02 g/kg leucine diet significantly compromised weight gain by 6.82% (1325 versus 1422 g/bird). However, elevating isoleucine plus valine inclusions from 17.21 to 20.32 g/kg decreased relative fat-pad weights by 8.49% (9.05 versus 9.89 g/kg; P = 0.046). Elevating leucine levels significantly depressed energy utilisation, AME and AMEn, by 0.39 MJ in both instances. Dietary enrichment with leucine had diverse impacts on amino acid digestibility coefficients coupled with free amino acid plasma concentrations. Increasing dietary leucine concentrations improved ileal digestibility of leucine by 4.74% (0.906 versus 0.865) but also significantly increased ileal digestibility coefficients of another 10 amino acids by an average of 3.37% ranging from 1.60% (methionine) to 4.96% (threonine). Overall, elevations of BCAA in wheat-based, reduced-CP diets did not advantage broiler growth performance. The likelihood is that several factors are responsible for this lack of response and consideration is given to these possibilities in this paper.

Metabolic changes induced by dapagliflozin, an SGLT2 inhibitor, in Japanese patients with type 2 diabetes treated by oral anti-diabetic agents: A randomized, clinical trial

AimWe aimed to determine whether SGLT2 inhibitor dapagliflozin treatment affects body composition and amino acid (AA) metabolism. MethodsFifty-two overweight patients treated by oral antidiabetic agents were randomly assigned to dapagliflozin (Dapa) or a standard treatment (Con) and followed for 24 weeks. The primary outcome was the change in body mass (BM) between baseline and week 24. Body composition, intrahepatic triglyceride (IHTG) content, and plasma AA concentrations were examined as secondary outcomes. ResultsThe change in BM was significantly larger in the Dapa than in the Con group, with a difference in the mean change of −1.72 kg (95 %CI: −2.85, −0.59; P = 0.004) between the groups. Total fat mass was reduced by dapagliflozin treatment, but fat-free mass was maintained. IHTG content was significantly reduced in the Dapa than in the Con (P = 0.033). Changes in AAs showed small differences between the groups, but only serine concentrations were significantly reduced in the Dapa. Intra-group analysis showed that positive associations were observed between changes in branched chain AA concentrations and body composition only in the Dapa. ConclusionsDapagliflozin treatment causes a reduction in BM mainly by reducing fat mass. AA metabolism shows subtle changes with dapagliflozin treatment.