Amino Acid Groups Research Articles

The effects of amino acid supplementation on hormonal responses to resistance training overreaching

The purpose of this investigation was to examine the effects of amino acid supplementation on muscular performance and resting hormone concentrations during resistance training overreaching. Seventeen resistance-trained men were randomly assigned to either an amino acid (AA) or a placebo (P) group and underwent 4 weeks of total-body resistance training designed to induce a state of overreaching. The protocol consisted of two 2-week phases (phase 1, 3 sets of 8 exercises performed for 8-12 repetitions; phase 2, 5 sets of 5 exercises performed for 3-5 repetitions). Muscle strength and resting blood samples were determined before (T1) and at the end of each training week (T2-T5). One-repetition maximum squat and bench press decreased at T2 in the P group but not in the AA group; both groups showed similar increases in strength at T3 to T5. Significant elevations in serum creatine kinase and uric acid were observed at T2 in the P group; the elevation in creatine kinase correlated highly to reductions in 1-repetition maximum squat ( r = −0.67, r 2 = 0.45). Significant elevations in serum sex hormone–binding globulin were observed during overreaching in the P group from T2 to T5; this response was abolished in the AA group. Significant reductions in total testosterone were observed in the P group at T4 compared with T1, and total testosterone values were higher for the AA group than for the P group from T2 to T4. Serum 22-kd growth hormone concentrations were elevated at T2 to T5 in P group only. No differences were observed in resting cortisol and insulinlike growth factor 1. Hemoglobin concentrations were significantly reduced at T2 to T5 in the P group. These results indicate that the initial impact of high-volume resistance training is muscle strength reduction and hormonal/biochemical alterations. It appears that amino acid supplementation is effective for attenuating muscle strength loss during initial high-volume stress, possibly by reducing muscle damage by maintaining an anabolic environment.

Endocrine responses to the oral ingestion of a physiological dose of essential amino acids in humans

The response of insulin, human growth hormone (hGH), cortisol, leptin and ghrelin, in addition to various metabolic parameters, was measured at 10 minute intervals following the oral ingestion of a standardised physiological dose of essential amino acids (AA). Twenty-eight healthy male, fasted volunteers (aged 18-40 yrs, BMI 18.0-24.5 kg/m(2)) took part in the study; 13 volunteers in the AA group, nine subjects in an iso-caloric control group, and a further six subjects served as fasting controls. Twenty minutes after ingestion, insulin reached peak concentrations that were up to 500% higher than basal values (P<0.0001). The AA group and iso-caloric control group showed a similar insulin response. AA ingestion led to an increase in hGH secretion with maximum concentrations being 2100+/-1013% higher than the basal values (P<0.0001). In contrast, no changes in hGH concentrations were observed in the iso-caloric controls; in the fasting controls only a slight increase in hGH was found towards the end of the fasting period. While cortisol decreased significantly (P<0.01) during the study in the AA group, neither control group showed a significant change in this parameter. Changes in leptin levels remained insignificant in all three groups, whereas ghrelin showed a different profile in each of the three groups, i.e. a continuous rise towards the end of the study period (P<0.001) in the AA group, a less significant effect for the fasting group, and no effect at all in the iso-caloric control group. There was no significant correlation between the concentrations or the area under curve of the hormones measured in any of the groups. The endocrine data provided in this study indicate that a single bolus of essential AA in fasted individuals is associated with both anabolic and catabolic hormonal responses.

Differential regulation of protein dynamics in splanchnic and skeletal muscle beds by insulin and amino acids in healthy human subjects.

To determine the in vivo effect of amino acids (AAs) alone or in combination with insulin on splanchnic and muscle protein dynamics, we infused stable isotope tracers of AAs in 36 healthy subjects and sampled from femoral artery and vein and hepatic vein. The subjects were randomized into six groups and were studied at baseline and during infusions of saline (group 1), insulin (0.5 mU. kg(-1). min(-1)) (group 2), insulin plus replacement of AAs (group 3) insulin plus high-dose AAs (group 4), or somatostatin and baseline replacement doses of insulin, glucagon and GH plus high dose of AAs (group 5) or saline (group 6). Insulin reduced muscle release of AAs mainly by inhibition of protein breakdown. Insulin also enhanced AA-induced muscle protein synthesis (PS) and reduced leucine transamination. The main effect of AAs on muscle was the enhancement of PS. Insulin had no effect on protein dynamics or leucine transamination in splanchnic bed. However, AAs reduced protein breakdown and increased synthesis in splanchnic bed in a dose-dependent manner. AAs also enhanced leucine transamination in both splanchnic and muscle beds. Thus insulin's anabolic effect was mostly on muscle, whereas AAs acted on muscle as well as on splanchnic bed. Insulin achieved anabolic effect in muscle by inhibition of protein breakdown, enhancing AA-induced PS, and reducing leucine transamination. AAs largely determined protein anabolism in splanchnic bed by stimulating PS and decreasing protein breakdown.

The Effects of Amino Acid Supplementation on Muscular Performance During Resistance Training Overreaching

The purpose of this study was to examine the effects of ami-no acid supplementation on muscular strength, power, and high-intensity endurance during short-term resistance training overreaching. Seventeen resistance-trained men were randomly assigned to either an amino acid (AA) or placebo (P) group and underwent 4 weeks of total-body resistance training consisting of two 2-week phases of overreaching (phase 1: 3 X 8–12 repetitions maximum [RM], 8 exercises; phase 2: 5 X 3–5RM, 5 exercises). Muscle strength, power, and high-intensity endurance were determined before (T1) and at the end of each training week (T2-T5). One repetition maximum squat and bench press decreased at T2 in P (5.2 and 3.4 kg, respectively) but not in AA, and significant increases in 1RM squat and bench press were observed at T3-T5 in both groups. A decrease in the ballistic bench press peak power was observed at T3 in P but not AA. The fatigue index during the 20-repetition jump squat assessment did not change in the P group at T3 and T5 (fatigue index = 18.6 and 18.3%, respectively) whereas a trend for reduction was observed in the AA group (p = 0.06) at T3 (12.8%) but not T5 (15.2%; p = 0.12). These results indicate that the initial impact of high-volume resistance training overreaching reduces muscle strength and power, and it appears that these reductions are attenuated with amino acid supplementation. In addition, an initial high-volume, moderate-intensity phase of overreaching followed by a higher intensity, moderate-volume phase appears to be very effective for enhancing muscle strength in resistance-trained men.

Plasma amino acid levels with a note on membrane transport: characteristics, regulation, and metabolic significance

The plasma concentration of an amino acid (AA) is the result of its rates of appearance (Ra) in and disappearance (Rd) from plasma. As for most nutrients, AA Ra and Rd are tightly regulated and at the postabsorptive state Ra equals Rd. Factors controlling Ra are protein intake and tissue release; those controlling Rd are tissue uptake and body losses (urine, sweat, etc.). Regulation of plasma AA concentrations involves hormones, in particular insulin and glucagon, both of which induce hypoaminoacidemia (but for quite different reasons), and cortisol, which induces hyperaminoacidemia. In addition, in pathologic states, catecholamines, thyroid hormones, and cytokines modulate plasma AA levels. Peripheral availability of AAs after protein ingestion is controlled by the liver, with an activation of ureagenesis in hyperprotein feeding and repression during a hypoprotein diet. The arginine-to-citrulline pathway in the intestine plays a key role in this adaptative process. In some circumstances tissue uptake of AAs and further metabolism depend on plasma AA concentrations. Plasma glutamine level may be the driving force controlling the flux of this AA at the muscle level. Also, channeling of the arginine cellular pathways means that plasma arginine is a major controlling component of nitric oxide synthesis in endothelial and immune cells. All these features explain the excessive increase in glutamine and arginine demands, in particular for energy expenditure, leading to morbidity (e.g., gut atrophy, muscle wasting, and immune dysfunction) in stressed patients. Normoaminoacidemia is not synonymous with health because this state is observed in level 2 starvation (Ra and Rd decrease) or after minor injury (Ra and Rd increase). Hyperaminoacidemia may be the consequence of organ failure (Rd decreases) or excessive AA intake during parenteral nutrition (Ra increases). Hypoaminoacidemia is observed after organ removal (Ra decreases, e.g., decrease in citrulline concentration in short bowel syndrome) or in stress situations (Rd increases). Mere determinations of plasma AA concentrations at the basal state (i.e., postabsorptive) provide rather limited information. Their usefulness can be improved by measuring arteriovenous differences or performing time course measurements, but techniques based on stable isotopes are necessary to obtain more precise information on the behavior of a particular AA or group of AAs.

Effects of Heat Stress and Dietary Tryptophan on Performance and Plasma Amino Acid Concentrations of Broiler Chickens

Two experiments were conducted to investigate the impact of high temperature and dietary tryptophan (Trp) on performance, selected organ weights and plasma free amino acid (AA) concentrations in broiler chickens. In Experiment 1, exposure to 27-33°C of chickens for 2 weeks from 2 weeks of age did not affect growth and plasma free AA concentration except for a decrease in the concentration of plasma tyrosine (Tyr). In Experiment 2, 2-week-old birds were allocated to one of three temperature treatments; 24°C (control), 36°C (heat stress, HS) and 24°C pair-fed (24PF) for 2 weeks and fed on diets containing 50, 100 and 300% of NRC requirement for Trp. Heat stress caused a reduction of weight gain and feed intake irrespective of dietary Trp levels compared with control counterparts, while feeding of 300% Trp diet did not attenuate the reduced performance by HS exposure. In groups fed the 100% Trp diets, plasma aromatic AA (AAA) and Tyr concentrations were decreased in the HS birds compared with the 24PF group. Plasma concentrations in most of AA groups were increased by HS in chickens fed the 50% Trp diet, while those were not changed by HS in chickens fed the 300% Trp diet, compared with 24PF counterparts. The plasma Trp/LNAA (LNAA=large neutral AAs, which are comprised of BCAA, AAA and Trp) ratio was increased by HS in chickens fed the 100% Trp diet, while it was decreased in chickens fed on 50% Trp diet as compared with 24PF group. From these results, it is suggested that performance and plasma amino acid profile deranged by heat stress are modulated, at least, to be relieved from the heat stress by feeding 50% Trp diet but not at all by feeding 300% Trp diet. The involvement of altered plasma AA profiles, in particular plasma Tyr concentrations and Trp/LNAA ratio, is discussed in association with the performance characteristics of HS chickens. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 2 : 247-253)

Dietary Restriction of Single Essential Amino Acids Reduces Plasma Insulin-Like Growth Factor-I (IGF-I) but Does Not Affect Plasma IGF-Binding Protein-1 in Rats

The effects of dietary restriction of a single essential amino acid (EAA) on insulin-like growth factor-I (IGF-I) and IGF-binding protein (IGFBP)-1 were investigated in rats. Rats were fed experimental diets containing amino acid (AA) mixtures in which the concentrations of all EAA were at levels recommended by the National Research Council (control), in which a single EAA was restricted to 20% of that of the control diets (Leu(-), Lys(-), Met(-) or Thr(-)), or in which the diet was devoid of amino acids (AA(-)). To eliminate the effect of differences in energy intake, rats were fed the mean amount of food as consumed by the AA(-) group on the previous day. Growth was significantly retarded in rats fed diets restricted in just one EAA compared with that of rats fed the control diet, and further growth retardation was observed in rats fed the AA(-) diet. On the other hand, the plasma IGF-I concentrations in the groups with a single EAA restriction or in the AA(-) group were 66% (P: < 0. 05) and 50% (P: < 0.05) of that of the control group, respectively. The effect of any single EAA restriction was not significantly different from that of total AA deprivation. The plasma IGFBP-1 concentration in the control group did not differ from that of rats fed diets with the single EAA restrictions except for methionine restriction, but it was approximately 6-fold greater in the AA(-) group. Differences in plasma IGFBP-1 concentration under these conditions could be explained by differences in hepatic IGFBP-1 mRNA contents. Based on these results, we conclude that restriction of single EAA does not affect IGFBP-1 synthesis in vivo, although the deprivation of a single EAA has been reported to increase IGFBP-1 production in hepatocyte cultures. Our results also indicated that a single EAA restriction decreased IGF-I production but did not affect IGFBP-1 production. The present study suggests that not only plasma IGF-I, but also IGFBP-1, affects the magnitude of growth retardation in vivo.

Evidence for Multiple Signaling Pathways in the Regulation of Gene Expression by Amino Acids in Human Cell Lines

In mammals, plasma concentrations of amino acids (AA) are affected by nutritional or pathologic conditions. Alterations in AA profiles have been reported as a result of a deficiency of any one of the essential AA, a dietary imbalance of AA or an insufficient intake of protein. In recent years, evidence has accumulated that AA availability regulates the expression of several genes involved in the regulation of a number of cellular functions or AA metabolism. Nevertheless, the molecular mechanisms involved in the AA regulation of mammalian gene expression are limited, particularly the signaling pathways mediating the AA response. This work provides a better understanding of the signaling pathways involved in the AA control of gene expression. We studied the expression of C/EBP homologous protein (CHOP) and asparagine synthetase (AS) in response to deprivation of a single AA and investigated the possible link between protein synthesis inhibition due to amino acid limitation and gene expression. We have shown the following: 1) several mechanisms are involved in the AA control of gene expression. When omitted from the culture medium, each AA can activate one (or several) specific signaling pathways leading to the regulation of one specific pattern of genes. 2) AA limitation by itself can induce gene expression independently of a cellular stress due to protein synthesis inhibition. Together, these results suggest that AA control of gene expression involves several specific mechanisms by which one AA (or one group of AA) can activate one signaling pathway and thus alter one specific pattern of gene expression.

Parenteral amino acid intake alters the anabolic actions of insulin-like growth factor I in rats.

The anabolic properties of insulin-like growth factor (IGF) I are attenuated by oral diets that are low in protein. However, it is not known whether parenteral nutrition (PN) providing a low amino acid (AA) input will influence IGF-I action. With the use of a rat model, this study examined the interaction between AA input (1.27 and 0.62 g N. kg body wt(-1). 24 h(-1), AA and 1/2AA groups, respectively) and recombinant human IGF-I (rhIGF-I, 2.5 mg. kg body wt(-1). 24 h(-1)) infusion on the composition of the carcass and organs and on plasma insulin, IGF-I, IGF-binding protein 1 (IGFBP-1), and acid-labile subunit (ALS) concentrations. Carcass protein deposition only occurred in the AA groups (P < 0.003) and was not influenced by administration of rhIGF-I. However, visceral protein loss persisted in the AA group but was prevented by rhIGF-I infusion. The changes in water content of the carcass and the organs were generally in the expected proportion of normal lean tissue. The accumulation of lipid that follows the infusion of the AA-deficient PN was prevented by rhIGF-I infusion, which may indicate an improved energy utilization. Neither serum insulin nor ALS concentrations were influenced by the level of AA infusion but were reduced by rhIGF-I administration. However, plasma IGF-I levels were elevated by higher AA infusion and by IGF-I administration. Also, IGFBP-1 concentrations were reduced by the higher AA infusion and increased with rhIGF-I administration. Interestingly, there was a significant interaction effect between both of these influences. It is concluded that free IGF-I concentration, which may be regulated by IGFBP-1 through a direct effect of AAs on the liver, may have an important role in regulating anabolism in visceral and possibly skeletal tissue during PN.

The response of dairy cows to intravascular administration of two mixtures of amino acids

Previous work by this group (Metcalf et al 1996) has shown that milk protein concentration can be increased by jugular infusion of different mixtures of amino acids (AA). The current experiment was designed in part to investigate which groups of AA had the greatest effect in stimulating milk protein content.

The response of dairy cows to intravascular administration of two mixtures of amino acids

Previous work by this group (Metcalf et al 1996) has shown that milk protein concentration can be increased by jugular infusion of different mixtures of amino acids (AA). The current experiment was designed in part to investigate which groups of AA had the greatest effect in stimulating milk protein content.

Growth Potencies and Effects on Digestive Functions of an Amino Acid and a Casein Diet in Rats of Three Strains.

Nutritive values and effects on the digestive functions of chronic feeding of an amino acid (AA) diet were compared with those of feeding a casein diet used three strains of male weanling rats under conditions of maximum growth. We demonstrated that the responsiveness to the casein and amino acid diet were different between rat strains. Growth and food intake in the AA group were clearly less than those in the casein group in Tokushima-Wistar rats, both parameters were the same in SLC-Wistar-St rats, and only growth was less in Sprague-Dawley rats fed the AA diet. The weights of stomach and small intestine, and the ileum activities of sucrase in all strains rats fed an AA diet were higher than those rats fed a casein diet, which indicates that larger and longer chyme remaining in the lumen, and slower absorption of nutrients in the AA groups.

Mechanisms of protein conservation during xylitol infusion after burn injury in rats: isotope kinetics and indirect calorimetry

In order to study the mechanisms by which nutrients influence post-trauma metabolism, Sprague-Dawley rats received a 25% full-thickness burn and were randomly assigned to receive 12.5 g kg-1 bodyweight (BW) per day amino acids (AA) only, AA and 14.7 g hydrous glucose kg-1 BW per day or AA and 14.7 g hydrous xylitol kg-1 BW per day. After 4 days of hypocaloric feeding, rats receiving xylitol had a cumulative nitrogen balance of +213 +/- 82 mg N, which was significantly (P less than 0.001) better compared with either the AA with only -493 +/- 61 mg N or the AA and glucose group (P less than 0.01) with -160 +/- 101 mg N. During glucose infusion reduction of insulin-mediated fat oxidation was partially compensated by an increase in glucose oxidation. Xylitol infusions resulted in increased glucose oxidation compared with the amino acid only group without simultaneously reduced fat oxidation. Although glucose and xylitol are calorically similar, their protein sparing properties and metabolic action after injury cannot be based entirely upon their caloric equivalent.

Only water-exposed carboxyl groups are protonated during the transition to the cation-free blue bacteriorhodopsin

FTIR (Fourier-transform-infrared) difference spectra between cation-free blue and purple bacteriorhodopsin were recorded. The results indicate that during the blue to purple transition no isomerization of the chromophore takes place. It is further observed that approx. 14 water-exposed carboxyl groups ofamino acids are protonated in blue bacteriorhodopsin. The groups were deprotonated during the blue to purple transition. Protonation of carboxyl groups in the interior of the protein, which are not accessible to water, can be excluded.

Calorie-Protein Deficiencies and the Immune Response of the Chicken: II. Cell-Mediated Immunity

Calorie-protein deficiency affects humoral immunity in the chicken. Secondary responses to sheep-red blood cells, a T-dependent antigen, were lower in birds fed diets two-thirds deficient in calories (C), amino acids (AA), or both (C/AA). These results led us to question what effects might be found in cell-mediated immunity after nutritional deficiency. Birds fed the same diets as in our previous study showed no reduction in total white blood cells, absolute lymphocytes, or absolute heterophils. Splenic lymphocytes from 3- or 7-week-old nutritionally deficient chickens with the exception of the AA group at 7 weeks, produced a nonsignificant increase in graft-versus-host (GvH) response of 12-day-old embryos. Thymic cells from 3-week-old nutritionally deficient birds were not deficient in the GvH potential.Thymic histology revealed reduced cellularity in AA-deficient birds. The reduced cellularity may not have been in response to stress since the mean corticosterone levels were not significantly different. Birds fed the deficient diets for 10 weeks had a significantly reduced delayed hypersensitivity response to human gamma globulin. The results indicate that the chickens’ ability to produce a GvH response was not compromised and that T-cell subpopulations may have differential sensitivities to nutritional deficiencies.

Effect of human growth hormone on the distribution of amino acids between plasma and erythrocytes in pituitary dwarfism.

Abstract. To examine the effects of human growth hormone (hGH) on amino acid (AA) transport across the erythrocyte membrane, simultaneous determinations of 14 acidic and neutral AA concentrations in red cells and in plasma, and of gamma-glutamyltranspeptidase (GGTP) activity in red cell membrane were performed in 10 patients with pituitary dwarfism before and/or after hGH therapy. Blood samples were obtained at 0, 1, and 2 h after 4 IU of hGH injection. As AA concentrations in red cells showed wide fluctuations physiologically, samples from 5 normal children at the same intervals served as control. AA distribution was expressed as the concentration ratio of red cell to plasma (R/P). Aspartate and glutamate (group I AAs) showed great intracellular fluctuation concomitantly, which did not appear to be associated with hGH administration. R/P values of most of AAs were significantly decreased in untreated patients (P &lt; 0.01–0.001 vs control), and changes after hGH were very small. In contrast, GH-treated patients exhibited large variance of changes in R/P of threonine, serine, glycine and alanine (group II AAs) at 2 h after hGH loading. However, R/P ratio of cystine, valine, methionine, isoleucine, leucine, tyrosine and phenylalanine (group III AAs) remained low or further depressed by hGH therapy. GGTP activity was also reduced in the untreated patients, while GH-treated patients revealed normal or supranormal GGTP activities. Between GGTP activity and integrated R/P of group II and III AAs, a statistically significant correlation was noted (r = 0.766, P &lt; 0.001). These results suggest that physiologically a dynamic equilibrium exists between AAs in red cells and those in plasma, the transport system of which appears to be different in each group of AAs. hGH seems to exert promoting effects on the shift of AAs across the red cell membrane, at least in part by the activation of gammaglutamyl cycle.

Plasma amino acid relationships during parenteral nutrition.

The plasma amino acidfs of 17 patients were studied before and during total parenteral nutrition (TPN). The amino acid (AA) pattern changed similarly for all patients. The AA concentration changes relative to preinfusion (PAER) were the most informative index of change. Two groups of AA were defined, the "branched chain" group (five amino acids) and the "hepatic" group (four amino acids) based on the correlation of PAER values. Comparison of PAER values with the ratio of AA intake to requirement indicated that the requirements of the sick patients were more similar to those of children than those of healthy adults.

Structural isomorphism of verbal and visual art

No findings are available regarding the association of the dietary amino acid (AA) intakes with the risk of chronic kidney disease (CKD) in adults. We aimed to assess the association between dietary AA patterns and incidence of CKD in adults.This study was conducted within the framework of Tehran Lipid and Glucose Study on 4,233 adults, who were free of CKD at baseline (2009-2011) and were followed for 3.1 years (2011-2014). The principal component analysis was used based on 8 AA groups to characterize major AA patterns. Multivariable logistic regression models were used to estimate the risk of CKD across quartiles of dietary AA pattern scores.Three major AA patterns were extracted: (1) higher loads of branched-chain, alcoholic, and aromatic AAs; (2) higher loads of acidic AAs, proline, and lower load of alkaline AAs and small AAs; and (3) higher loads of sulfuric AAs and small AAs. The mean ± standard deviation age of participants (45.9% male) was 39.4 ± 11.7 at baseline and the incidence of CKD was 12.1% (513 cases) after 3.1 years of follow-up. The highest score of first dietary AA pattern tended to be associated with an increased risk of CKD (odds ratio = 1.43, 95% confidence interval1.06-1.93); however, the second pattern was related to a decreased risk of CKD (odds ratio = 0.71, 95% confidence interval: 0.52-0.97) in the multivariable model.These novel findings suggest that the dietary AA patterns may modify risk of CKD.