Feeding pigs amino acids as protein-bound or in free form influences postprandial concentrations of amino acids,metabolites, and insulin

Dietary proteins need to be digested first while free amino acids (AAs) and small peptides are readily available for absorption and rapidly appear in the blood. The rapid postprandial appearance of dietary AA in the systemic circulation may result in inefficient AA utilisation for protein synthesis of peripheral tissues if other nutrients implicated in AA and protein metabolism are not available at the same time. The objective of this experiment was to compare the postprandial concentrations of plasma AA and other metabolites after the ingestion of a diet that provided AA either as proteins or as free AA and small peptides. Twenty-four male growing pigs (38.8 ± 2.67 kg) fitted with a jugular catheter were assigned to one of three diets that provided AA either in protein form (INT), free AA and small peptides (HYD), or as free AA (FAA). After an overnight fast and initial blood sampling, a small meal was given to each pig followed by serial blood collection for 360 min. Postprandial concentrations of plasma AA, glucose, insulin, and urea were then measured from the collected blood. Non-linear regression was used to summarise the postprandial plasma AA kinetics. Fasting concentrations of urea and some AA were higher (P < 0.05) while postprandial plasma insulin and glucose were lower (P < 0.01) for INT than for HYD and FAA. The area under the curve of plasma concentration after meal distribution was lower for INT for most AAs (P < 0.05), resulting in a flatter curve compared to HYD and FAA. This was the result of the slower appearance of dietary AA in the plasma when proteins are fed instead of free AA and small peptides. The flatter curve may also result from more AAs being metabolised by the intestine and liver when INT was fed. The metabolism of AA of the intestine and liver was higher for HYD than FAA. Providing AA as proteins or as free AA and small peptides affected the postprandial plasma kinetics of AA, urea, insulin, and glucose. Whether the flat kinetics when feeding proteins has a positive or negative effect on AA metabolism still needs to be explored.     

Effects of branched-chain amino acids on plasma amino acids in amyotrophic lateral sclerosis

Summary Although the cause of amyotrophic lateral sclerosis (ALS) remains unknown, biological findings suggest that the excitatory amino acid glutamate contributes to the pathogenesis of ALS. In previous studies of ALS, the therapeutic effect of the branched-chain amino acids (BCAAs) leucine, valine and isoleucine has been evaluated. The present study aimed at investigating the acute effect of BCAAs on plasma glutamate levels in ALS patients. Following two oral doses of BCAAs, significantly increased plasma levels were seen for valine (500%), isoleucine (1,377%) and leucine (927%), however the plasma level of glutamate was not affected. The plasma level of several other amino acids (tryptophan, tyrosine, phenylalanine and methionine) were found decreased after oral BCAAs, which may indicate a diminution in the rate of degradation of muscle protein and/or an increase in tissue disposal of amino acids.     

Sterols, fatty acids and free amino acids from two Helvella species

Sterols, fatty acids and free amino acids of Helvella crispa and H. monachella were investigated. They contained traces of ergosterol and a high amount of ergosta 5.22-dien-3β-ol. Linoleic acid and l-Dopa are the most abundant fatty acid and free amino acid, respectively. The aqueous extract of H. monachella inhibits prostaglandin release by rat peritoneal leucocyres in vitro.     

Protein and free amino acids in a high lysine maize double mutant

A comparative study of free amino acids and protein fractions of normal with a double mutant (su₁ o₂) was made, during endosperm development in segregating ears of a maize synthetic. Zein content showed striking differences in the two genotypes, being 7.7 and 6 times greater in the normal endosperm at 24 and 47 days after pollination respectively. This observed decrease in zein synthesis, coded by sugary-1/opaque-2 genes, causes an accumulation of alanine, glutamic and aspartic acids, glutamine and asparagine in the high lysine endosperm mutant.     

白蜡虫及其寄主植物游离氨基酸的研究

作者研究了白蜡虫越冬前后体内游离氨基酸的组成及变化 ,并通过对虫体、蜜露及被寄生植物游离氨基酸含量及百分率组成进行对比分析 ,探讨了白蜡虫对游离氨基酸的利用问题。虫体含量较高的氨基酸有丙氨酸、谷氨酸、苏氨酸、丝氨酸、缬氨酸。大部分氨基酸及其总量在越冬期下降 ,越冬以后升高 ,逐渐超过越冬前水平。虫体大量吸收的氨基酸是丙氨酸 ,利用较少的氨基酸是天门冬氨酸 ,其它氨基酸或多或少地为白蜡虫所利用。     

Assemblies of free amino acids as possible prebiotic catalysts

Our understanding of how life emerged on Earth has much to do with speculations about the ways in which prebiotic catalysts could have been formed. Since enzymes, the contemporary biological catalysts, are polymers of amino acids, we looked at the possible activity of free amino acids as catalysts. In this study it is shown experimentally that mixtures of free amino acids exert catalytic activities of -galactosidase, carbonic anhydrase, and catalase. We also observed different levels of catalytic activty of individual amino acids: some were more efficient than others. Apparently, assemblies of amino acids which were formed around substrate molecules through weak interactions, could, in principle, catalyze many prebiotic reactions. This might have been one step in the emergence of biological enzymes.     

肾脏疾病患者体液氨基酸模式

使用 DNS— cl( Dimethylamino-naphthylane-5-sulfony chloride)荧光试剂 ,标记氨基酸成 DNS— AAs( DNS_ Amino Acids) ,然后采用聚酰胺薄膜层析 ,制成具有 2 0余种 DNS— AAs的荧光薄膜层析图谱 ,选择其中所需要检测的氨基酸 ,分别经洗脱后在日本岛津 RF— 51 0荧光分光光度计上 ,进行定量检测 ,分析了 3 6例慢性肾炎患者 ,1 8例尿毒症患者血浆中 1 2种游离氨基酸和 3 5例慢性肾炎患者尿液中 1 3种游离氨基酸 ,分别与 2 9例正常人血浆和3 0例正常人尿液中游离氨基酸进行了比较 ,以此探讨肾脏疾病体液氨基酸模式的同时提供氨基酸治疗肾脏疾病的科学依据。     

Gradient of dissolved free amino acids and phytoplankton in a shallow bay

A 3 h survey of the concentrations of individual free amino acids, chlorophyll a and phytoplankton species biomass was conducted in the surface waters of a shallow bay. Significant coefficients of correlation were found between chlorophyll a, nanoflagellates, and DFAA concentrations. Although phytoplankton biomass variations sometimes relate to DFAA concentration patterns, consideration of the physiological activity of both phytoplankton and microheterotrophs would undoubtedly explain a more significant fraction of the DFAA variation.This work is a contribution of GREPMA (Groupe Régional d'Etudes Pélagiques en Manche-Atlantique)     

Regulatory effects of exogenous branched-chain amino acids in Nicotiana plumbaginifolia cell suspension cultures

Nicotiana plumbaginifolia suspension cultured cells were grown on medium supplemented with valine, leucine and isoleucine, singly or in combination. The effects of the three branched-chain amino acids on cell growth rate and on the activity of acetohydroxyacid synthase (AHAS), the first enzyme (and the main regulative site) of their biosynthetic pathway, were studied. Results showed that valine and leucine, at concentrations ranging from 10^–4 to 10^–3 M, inhibit growth, and at higher doses (from 10^–2 to 10^–1 M) AHAS activity. Growth, but not AHAS activity, was affected also by isoleucine. The addition of ammonium succinate to the culture medium, in order to counteract a possible general inhibitory effect of these compounds on nitrogen metabolism, relieved only partially their cytotoxicity. Feeding cells with equimolar mixtures of the three amino acids resulted in a minor but reproducible decrease in AHAS level, which was proportional to the dose. A similar result was obtained also on N. plumbaginifolia seedlings, suggesting that in this species a modulation of enzyme level could play a role in controlling the flow of metabolites through the pathway.Abbreviations AHAS acetohydroxyacid synthase - BCAA branched-chain amino acids - FAD flavin adenine dinucleotide - GS glutamine synthetase - TPP thiamine pyrophosphate     

Uptake of free amino acids by the diatom,Melosira mediocris

Individual ¹⁴C-labelled amino acids are rapidly removed from dilute solution in artificial sea water (0.2 mol 1^–1) by suspensions of Meliosira medocris. The rate of disappearance of radioactivity corresponds closely to removal of primary amines as determined by measurement of the rate of decrease of fluorescamine-positive material. Net removal of naturally occurring free amino acids from the sea water habitat from which the alga was isolated is demonstrated using high performance liquid chromatography. Removal of amino acids from natural sources makes a significant contribution to the carbon requirements of the alga as well as supplying significant amounts of amino nitrogen.     

Portal-drained viscera and hepatic fluxes of branched-chain amino acids do not account for differences in circulating branched-chain amino acids in rats fed arginine-deficient diets

Summary Concentrations and fluxes of amino acids across the portal-drained viscera (PDV) and liver were assessed in rats fed a meal of one of three arginine-deficient diets containing either alanine or the arginine precursors, ornithine or citrulline. A previous report included findings of seven arginine-related amino acids and indicated that only the citrulline-containing diet protected blood arginine concentrations. In the present report we extend these findings and note that the concentrations and fluxes of the non-arginine-related amino acids showed remarkable consistency across diet groups. However, total branched-chain amino acid (BCAA) concentrations of arterial blood were higher in rats fed the - Arg/+ Ala and the - Arg/+ Orn diets than in rats fed the control (+ Arg) diet. The elevated BCAA correlated with higher circulating concentrations of other essential amino acids but were inversely correlated with arginine concentrations. PDV and hepatic fluxes of BCAA were not different across diet groups, indicating that amino acid absorption and hepatic utilization of BCAA were generally comparable across diet groups. Hepatic concentrations of 14 of 22 measured amino acids, including total BCAA, were correlated with their arterial concentrations. The circulating concentrations and net PDV and hepatic fluxes of rats fed the control diet were comparable to our previous observations in fed rats and illustrate the role of the liver in utilization of diet-derived essential amino acids.Abbreviations PDV portal-drained viscera - BCAA branched-chain amino acids - SSA 5-sulfosalicylic acid - PBF portal blood flow - HBF hepatic blood flow - SELSM pooled standard errors of least squares means - TAA total amino acids - NEAA nonessential amino acids - EAA essential amino acids - LNAA large neutral amino acids Mention of a trade name, proprietary product or specific equipment does not constitute a guarantee by the US Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.     

Free amino acids of maize seedlings

The free amino acids were determined in different parts of maize seedlings (seeds, roots and shoots), 0, 2, 4 and 6 days after sowing.     

Quantitative changes in free amino acids in Polytrichum formosum during development

The concentrations of each free amino acid in Polytrichum formosum have been determined for female gametangia at different developmental stages of     

The role of free amino acids in osmoregulation of cricket blood (Acheta domesticus)

The blood volume increased during normal feeding, and did not decrease during fasting at the end of the stadium. The unexpectedly high blood volume of starved crickets might be an adaptation to increase chances for moulting via stretch receptor stimulation.The amount of blood amino acids was not changed by feeding, but increased with fasting or starvation. Thus amino acid levels in the blood were not directly related to amino acid input from the gut.The blood protein concentration did not change during starvation, but the amino acid concentration was 33% higher in starved crickets that drank water as opposed to those given saline to drink. Thus amino acid levels in the blood were not related directly to blood protein concentration.The blood amino acid concentration was 19–22 mM/l in response to salt intake by feeding crickets or starved crickets drinking saline. The concentration was 32–38 mM/l when the crickets were fasting prior to and after ecdysis or when starved with water to drink during the time when they would normally be feeding. The increase of amino acids during fasting was due to a proportional increase in all amino acids augmented by a 3 × increase in tyrosine. The increase during salt depleting starvation was due to a doubling of the two predominant amino acids proline and glycine. Proline and glycine were not increased in starved crickets drinking saline, thus starvation was not the reason for the increase. This is the first instance where specific amino acids have been implicated in osmoregulation.     

Photoacoustic spectroscopy of aromatic amino acids in proteins

This paper concerns the use of photoacoustic spectroscopy (PAS) to study the presence of aromatic amino acid in proteins. We examined the aromatic amino acids in six proteins with well-known structures using absorption spectra of near ultraviolet PAS over the wavelength range 240–320 nm. The fundamental understanding of the physical and chemical properties that govern the absorption of light and a subsequent release of heat to generate a transient pressure wave was used to test the concept of monitoring aromatic amino acids with this method. Second derivative spectroscopy in the ultraviolet region of proteins was also used to study the regions surrounding the aromatics and the percentage area in each band was related in order to determine the contribution in function of the respective molar extinction coefficients for each residue. Further investigation was conducted into the interaction between sodium dodecyl sulphate (SDS) and bothropstoxin-I (BthTx-I), with the purpose of identifying the aromatics that participate in the interaction. The clear changes in the second derivative and curve-fitting procedures suggest that initial SDS binding to the tryptophan located in the dimer interface and above 10 SDS an increased intensity between 260 and 320 nm, demonstrating that the more widespread tyrosine and phenylalanine residues contribute to the SDS/BthTx-I interactions. These results demonstrate the potential of near UV-PAS for the investigation of membrane proteins/detergent complexes in which light scattering is significant.     

Effects of carbohydrate feedings on plasma free tryptophan and branched-chain amino acids during prolonged cycling

Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [VO2max = 57.8 (SE 4.1) ml kg-1 min-1] cycled for up to 255 min at a power output corresponding to VO2 at lactate threshold (approximately 68% VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg-1 body wt-1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P < 0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks.(ABSTRACT TRUNCATED AT 250 WORDS)     

小菜蛾感染球孢白僵菌后血淋巴游离氨基酸的测定

通过高效液相色谱（HPLC）对感染球孢白僵菌后小菜蛾血淋巴游离氨基酸含量进行测定,结果表明染菌后小菜蛾幼虫体内氨基酸含量明显低于对照组,主要是由于菌株在虫体内营养生长消耗和虫体内的养分所致;小菜蛾幼虫体内具有菌株营养生长所必需的氨基酸,因此可以认为小菜蛾是白僵菌的敏感寄主;各处理组间各种游离氨基酸在量上存在一定的差异,是由于不同发育阶段的虫体与菌株及不同类型菌株营养生长所必需的游离氨基酸含量不同所造成的。     

Application of cross-linked beta-cyclodextrin polymer for adsorption of aromatic amino acids

Beta-cyclodextrin (beta-CyD) was cross-linked by hexamethylene diisocyanate and the polymer was investigated for adsorption of aromatic amino acids (AAA) from phosphate buffer. High adsorption rates were observed at the beginning and the adsorption equilibrium was then gradually achieved in about 45 min. The adsorption of AAA decreased with the increase of initial concentration and also temperature. Under the same conditions, the adsorption efficiencies of AAA were in the order of L-tryptophan (L-Trp) > L-phenylalanine (L-Phe) > L-tyrosine (L-Tyr). Much higher adsorption values, up to 52.4 and 43.0 mg/g for L-Trp and L-Phe, respectively, at 50 mmol/L and 3.2 mg/g for L-Tyr at 2 mmol/L, were obtained with the beta-CyD polymer at 37 degrees C. It was shown that the adsorption of AAA on the beta-CyD polymer was consistent with the Freundlich isotherm equation. The adsorption of mixed aromatic amino acids and branched-chain amino acids (BCAA) showed that AAA were preferentially adsorbed with adsorption efficiencies 10-24%, while those of BCAA were lower than 2%. It seems that the structure and hydrophobicity of amino acid molecules are responsible for the difference in adsorption, by influencing the strength of interactions between amino acid molecule and the polymer.     

Beneficial role of amino acids in mitigating cytoskeletal actin glycation and improving F-actin content: In vitro

Aims: The actin filaments present in circulating leukocytes facilitate their passage through microvenules and capillaries by helping in their deformability. Decreased deformability of granulocytes is now known to cause occlusion of the retinal microcapillaries leading to hypoxia and the subsequent development of diabetic retinopathy. Structural and functional loss of proteins, due to non-enzymatic glycation and glycoxidation, has been reported to cause diabetic pathogenesis. As amino acids have been earlier reported to have antidiabetic properties, the present study involves the investigation of the susceptibility of the cytoskeletal actin to glycation and its mitigation by free amino acids. This study also involves quantifying F-actin in cultured mononuclear cells obtained from diabetic and normal healthy volunteers and on the effect of glucose and free amino acids on F-actin content. Methods: Commercial non-muscle actin and actin immuno-pre-cipitated from granulocytes obtained from (a) normal healthy human volunteers and (b) patients with type 2 diabetes mellitus were subjected to glycation studies using [U] ¹⁴C glucose. The effect of free amino acids, as antiglycating agents, was determined using various concentrations of lysine, arginine, alanine, aspartic acid and glutamic acid. F-actin content in cultured mononuclear cells was estimated by flow cytometry using fluorescein isothiocynate (FITC)-Phalloidin. Results: Commercial actin at physiological conditions of pH and temperature was found to undergo non-enzymatic glycation. The extent of in vitro glycation was significantly low (P<0.001) in actin isolated from patients with type2 diabetes when compared to the non-diabetic group, suggesting an increased in vitro structural modification of actin in patients with diabetes. All the free amino acids tested were found to have varying degrees of antiglycating effect. The F-actin content in the intact mononuclear cells obtained from diabetic patients was found to be low when compared with normal healthy volunteers (P<0.001). Similarly the F-actin content was significantly low when the normal mononuclear cells were incubated with glucose. This effect was reversed upon the addition of free amino acids to the incubation mixture. Conclusions: Free amino acids can play a positive role in improving leukocyte deformability by mitigating cytoskeletal actin glycation and improving F-actin content.     

Regulation of protein synthesis by branched-chain amino acids in vivo

Recent advances in the understanding of mRNA translation have facilitated molecular studies on the regulation of protein synthesis by nutrients and the interplay between nutrients and hormonal signals. Numerous reports have established that, in skeletal muscle, the branched-chain amino acids (BCAAs) have the unique ability to initiate signal transduction pathways that modulate translation initiation. Of the BCAAs, leucine is the most potent. Oral administration of leucine to food-deprived rats enhances muscle protein synthesis, in part, through activation of the mRNA binding step of translation initiation. Interestingly, leucine signaling in skeletal muscle differs from that in liver, suggesting that the responses may be tissue specific. The purpose of this paper was to briefly review the current knowledge of how BCAAs act as regulators of protein synthesis in physiologically important tissues, with particular focus on the mechanisms by which BCAAs regulate translation initiation.