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PubMed1976

Body weight change and nitrogen efficiencies in growing and adult rats fed diets containing various proportions of essential amino acids to total amino acids.

By using amino acid mixtures, a comparative study of nutritional effects of dietary essential amino acid proportions (EA %) has been made between growing and adult rats. Included were adult rats which were repleting from an 8-day protein depletion. It was shown that for growing rats at least 55 EA% was required to attain the maximum values of growth, nitrogen balance, nitrogen balance efficiency (nitrogen balance/nitrogen intake) and protein efficiency ratio (PER). The maximum biological value was found to be 94 at the 50 EA% level. For adult rats, at least 40 EA% was required to gain the maximum values of nitrogen balance and nitrogen balance efficiency under both maintenance and repletion. The biological values were found to be nearly 60 and 80 for maintenance and repletion, respectively.

Amino Acids↗
PubMed2005

Dietary treatment of rheumatoid cachexia with beta-hydroxy-beta-methylbutyrate, glutamine and arginine: a randomised controlled trial.

BACKGROUND & AIMS: Rheumatoid arthritis (RA) is complicated by cytokine-driven alterations in protein and energy metabolism and consequent muscle wasting (cachexia). The aim of this randomised controlled trial was to investigate the efficacy of a mixture of beta-hydroxy-beta-methylbutyrate, glutamine and arginine (HMB/GLN/ARG) as nutritional treatment for rheumatoid cachexia. METHODS: Forty RA patients supplemented their diet with either HMB/GLN/ARG or a nitrogen (7.19 g/day) and calorie (180 kcal/day) balanced mixture of alanine, glutamic acid, glycine, and serine (placebo) for 12 weeks. Body composition and other outcomes were assessed at baseline and follow-up, and analysed by mixed ANOVA. RESULTS: Dietary supplementation with HMB/GLN/ARG was not superior to placebo in the treatment of rheumatoid cachexia (groupxtime interactions P>0.05 for all outcomes). Both amino acid mixtures significantly increased (main effect of time) fat-free mass (727+/-1186 g, P<0.01), total body protein (719+/-1703 g, P=0.02), arms (112+/-183 g, P<0.01) and legs (283+/-534 g, P<0.01) lean mass, and some measures of physical function. No significant adverse event occurred during the study, but patients in the HMB/GLN/ARG group reported fewer gastrointestinal complaints compared to placebo. CONCLUSIONS: Dietary supplementation with HMB/GLN/ARG is better tolerated but not more effective in reversing cachexia in RA patients compared to the mixture of other non-essential amino acids used as placebo. Further controlled studies are necessary to confirm the beneficial anabolic and functional effects of increased nitrogen intake in this population.

Arginine↗
PubMed1990

Essential amino acids in relation to hypercholesterolemia induced in rabbits by dietary casein.

Rabbits fed a cholesterol-free, semi-purified diet containing 25% casein amino acids (25% AA) for 2 wk had significantly higher serum total and low density lipoprotein (LDL) cholesterol levels than animals fed the same diet containing 11.2% casein amino acids (11.2% AA). These results were similar to those obtained by feeding diets containing 27% and 12% casein, respectively. When rabbits were fed the 11.2% AA diet supplemented with essential amino acids to the 25% level (11.2% AA + essential AA), their LDL cholesterol level was significantly higher than that in animals fed the 11.2% AA diet supplemented with nonessential amino acids to the 25% level (11.2% AA + nonessential AA). LDL protein and phospholipid levels were significantly higher in rabbits fed the 25% AA diet than in those fed 11.2% AA and tended to be elevated in animals fed 11.2% AA + essential AA compared to those fed 11.2% AA + nonessential AA. Fecal excretion of bile acids and cholesterol was similar with all dietary regimens, and the level of liver lipids showed no correlation with the degree of hypercholesterolemia produced by dietary amino acid mixtures.

Amino Acids↗
PubMed1985

Intestinal absorption of end products from digestion of carbohydrates and proteins in the pig.

The kinetics of appearance of various nutrients in the portal vein during the postprandial period was studied in conscious pigs by means of a technique based on measurement of the porto-arterial differences in nutrient concentrations simultaneously with that of the portal blood flow rate. The rate and level of appearance of sugars in the portal vein varied with the carbohydrate ingested. It was very rapid after intake of glucose and sucrose, slower after that of maize starch and very slow after that of lactose. The absorption of the latter became very rapid again if it was hydrolysed prior to its ingestion. During absorption, some sugars (fructose or galactose) released from the corresponding sucrose and lactose, respectively during digestion, were partly metabolized into glucose by the enterocyte. The rate of absorption of amino acids released in the digestive tract varied according to the origin of the food ingested, i.e. it was more rapid after intake of wheat or fish proteins than after that of barley. In the case of barley the absorption rate of amino acids differed from that of glucose of the starch. The profile of the amino acid mixtures appearing in the portal vein during absorption differed a little from the profiles of those present in the ingested proteins in the case of essential amino acids and differed much in the case of non essential amino acids. Some essential amino acids (histidine, aromatic amino acids) appeared more rapidly and others more slowly, (lysine, sulphur amino acids, arginine). Because of transaminations, only small amounts of glutamic acid occurred in the portal vein whereas the amounts of alanine as compared to those ingested, were very large. The hierarchy of amino acid absorption was the same whatever the protein studied (fish, wheat, barley). The appearance in the portal vein of alpha-amino nitrogen from enzyme hydrolysates perfused through the duodenum was more rapid than after perfusion of a mixture of free amino acids. During digestion of diets containing 6% cellulose, large amounts of volatile fatty acids (about 2200 mmol/24 h, i.e. 2500 kJ/24h) and lactic acid (60-85 g/24 h) appeared in the portal vein.

Amino Acids↗
PubMed1974

Metabolic and hormonal effects of alternate infusion of hypertonic glucose and aminosol-glucose in premature infants.

The metabolic and hormonal effects of a short term (24-36 hrs), alternating intravenous administration of hypertonic (16%) glucose and Aminosol-glucose were investigated in premature infants. The majority of the infants under 1 500 g showed pathological signs and did not tolerate oral feeding. The purpose of the study was to explore an intravenous alimentation program capable of ensuring an improved amino acid utilization in terms of nitrogen balance, and to prevent some of the adverse effects of the amino acid mixture. It was thought that the hormonal state created by 16% glucose might increase the capacity of the tissues to utilize the amino acids. The relevant findings were as follows. 1. Plasma free fatty acids and amino acids decreased, plasma insulin and growth hormone increased markedly in response to 16% glucose. The plasma aminogram indicated a profound redistribution of amino acids. 2. Aminosol-glucose infusion after the 16% glucose, increased the concentration of amino acids, but only to the starting level. Thus the previously decreased alpha-amino nitrogen content allowed to avoid a hyperaminoacidaemia and a marked distortion of the plasma amino acid pattern. Administration of the amino acid-glucose mixture usually failed to maintain the previously stimulated insulin and growth hormone secretion. 3. The hormonal and metabolis responses to the intermittent infusion of hypertonic glucose and Aminosol-glucose were not associated with an improved nitrogen utilization. More than 50% of the administered amino acid nitrogen was excreted. 4. The metabolic acidosis observed under these condition was found to be variable, and practically compensated.

Amino Acids↗
PubMed1990

Measurement of plasma and urine amino acids by high-performance liquid chromatography with electrochemical detection using phenylisothiocyanate derivatization.

The use of reversed-phase liquid chromatography (LC) with pre-column derivatization for the analysis of amino acid mixtures is becoming established as a possible cheaper alternative to commercial amino acid analysers. The available derivatization procedures all have disadvantages when applied to clinical samples, partly due to the interferences found with body fluids when ultraviolet or fluorescence detection is used. An LC method is described for the separation of amino acids in blood or urine, using pre-column derivatization with phenylisothiocyanate (PITC), gradient elution and electrochemical detection. The use of electrochemical detection of PITC derivatives virtually eliminates interferences and enables the secondary amino acids to be measured. Examples are shown of normal urine and plasma and samples from patients with cystinuria and maple syrup urine disease.

Amino Acids↗
PubMed1984

Total parenteral nutrition with a new amino acid solution for infants.

The currently available, commercially prepared amino acid mixtures for intravenous usage do not result in completely normal plasma amino acid patterns. Taking into consideration the known imbalances that occur with the commercial preparations, we designed a new amino acid solution (AF). This solution was prepared to contain a low concentration of those amino acids usually found in increased concentrations in plasma during the course of total parenteral nutrition (TPN) with a commercially prepared product (CF) and a high concentration of branched-chain amino acids and arginine. Plasma amino acid concentrations were determined for nine infants receiving CF (Group A) and eight infants receiving AF (Group B) as the protein source while on TPN for 5 days. These data were compared to 2-h postprandial values obtained from breast-fed, growing infants serving as controls. In comparison with controls, the plasma concentrations of threonine, glycine, methionine, phenylalanine, tryptophan, and lysine were higher in infants in group A, while those of taurine, alanine, valine, cystine, isoleucine, and proline were lower. In group B, the levels of valine and leucine were slightly higher, while those of alanine, cystine, tyrosine, histidine, and proline were lower. Mean nitrogen balances in groups A and B were + 112 and + 170 mg/kg/day, respectively. Therefore, our new amino acid solution may be better for infants receiving TPN.

Amino Acids↗
PubMed2002

Methionine as a methyl group donor in growing cattle.

Holstein steers were used in two 5 x 5 Latin square experiments to evaluate the sparing of methionine by alternative sources of methyl groups (betaine and choline). Steers were housed in metabolism crates and limit-fed a soybean hull-based diet high in rumen degradable protein. To increase energy supply, ruminal infusions of volatile fatty acids and abomasal infusions of glucose were provided. An amino acid mixture, limiting in methionine, was infused abomasally to ensure that nonsulfur amino acids did not limit protein synthesis. Treatments for Exp. 1 were abomasal infusion of 1) water, 2) 2 g/d L-methionine, 3) 1.7 g/d L-cysteine, 4) 1.6 g/d betaine, and 5) 1.7 g/d L-cysteine + 1.6 g/d betaine. Treatments for Exp. 2 were abomasal infusion of 1) water, 2) 2 g/d L-methionine, 3) 8 g/d betaine, 4) 16 g/d betaine, and 5) 8 g/d choline. In both experiments, nitrogen retention increased in response to methionine (P < 0.05), demonstrating a deficiency of sulfur amino acids. Responses to cysteine, betaine, and choline were all small and not significant. The lack of response to cysteine indicates that the response to methionine was not due to transsulfuration to cysteine or that cysteine supply did not alter the flux of methionine through transsulfuration. The lack of response to betaine suggests that the steers' needs for methyl groups were met by the dietary conditions or that betaine was relatively inefficient in increasing the remethylation of homocysteine to methionine and, thereby, reducing the synthesis of cysteine from homocysteine. Under our experimental conditions, responses to methionine were likely due to a correction of a deficiency of methionine per se rather than of methyl group donors.

Abomasum↗
PubMed1981

Effect of amino acid concentration on orotic acid production by bovine mammary tissue.

Investigations were to determine if bovine mammary tissue could synthesize orotate and to assess the influence of amino acids on production of orotate. Mammary tissue from 6 Holstein cows was obtained immediately after slaughter. Tissue slices were incubated in either a modified Krebs-Ringer bicarbonate buffer, the same medium containing a physiological concentration of amino acids, or a third medium containing a fourfold concentration of the amino acid mixture. In all experiments, tissue slices were preincubated in the physiological amino acid medium for 5, 10, and 15 min (30 total min) with fresh medium changes after each incubation with one of the three treatment media for three consecutive 20-min periods. Tissue slices incubated in the physiological amino acid medium for a total of 90 min synthesized 28.5 microgram orotate/g wet tissue after correction for the initial tissue contribution. Orotate secreted by the tissue slices increased as concentration of amino acids increased. Lactose released into the medium was not affected by amino acid concentration. Bovine mammary tissue can synthesize substantial amounts of orotate, and tissue synthesis of orotate but not lactose increased as amino acid concentration increased.

Amino Acids↗
PubMed1984

[Protein-sparing mechanisms of parenteral feeding. II. Clinical aspects].

Based on primarily clinical findings this review tries to give a survey on the influence of parenteral application of single substrates, different nutritional regimens or special amino acids mixtures on acute protein losses. It can be emphasized that adequate amino acids substitution as such represents the dominating protein sparing mechanism during acute diseased states. The additional influence of calorie supply, however, is relatively limited, demonstrated by the fact, that already low-dosed carbohydrate supply shows a comparably favourable protein-sparing effect. At increased energy expenditure after major trauma or operation the relatively early use of fat emulsions--after decline of acute hormonal trauma reaction--for partial replacement of calories clearly seems to be of metabolic advantage compared to an exclusive and high-dosed carbohydrate supply. Further positive influence on acute protein losses can be expected by the adaption of the rates of amino acids supplementation to the trauma dependent alterations in behaviour of free amino acids, however, comprehensive clinical experiences are still lacking.

Amino Acids↗
PubMed2005

The effect of meal composition on specific dynamic action in burmese pythons (Python molurus).

We quantified the specific dynamic action (SDA) resulting from the ingestion of various meal types in Burmese pythons (Python molurus) at 30 degrees C. Each snake was fed a series of experimental meals consisting of amino acid mixtures, simple proteins, simple or complex carbohydrates, or lipids as well as meals of whole animal tissue (chicken breast, beef suet, and mouse). Rates of oxygen consumption were measured for approximately 4 d after feeding, and the increment above standard metabolic rate was determined and compared to energy content of the meals. While food type (protein, carbohydrate, and lipid) had a general influence, SDA was highly dependent on meal composition (i.e., amino acid composition and carbohydrate structure). For chicken breast and simple carbohydrates, the SDA coefficient was approximately one-third the energetic content of the meal. Lard, suet, cellulose, and starch were not digested and did not produce measurable SDA. We conclude that the cost of de novo protein synthesis is an important component of SDA after ingestion of protein meals because (1) simple proteins, such as gelatin and collagen, did not stimulate levels of SDA attained after consumption of complete protein, (2) incomplete mixtures of amino acids failed to elicit the SDA of a complete mixture, and (3) the inhibition of de novo protein synthesis with the drug cycloheximide caused a more than 70% decrease in SDA. Stomach distension and mechanical digestion of intact prey did not cause measurable SDA.

Amino Acids↗
PubMed2002

Amino acid infusion induces thermogenesis and reduces blood loss during hip arthroplasty under spinal anesthesia.

UNLABELLED: The thermic effect of amino acids is augmented under general anesthesia and counteracts hypothermia. Mild hypothermia may increase surgical bleeding. We studied whether amino acids also induce thermogenesis under spinal anesthesia and whether this endogenous heat production reduces bleeding during hip arthroplasty. Rectal temperature, oxygen uptake, and perioperative bleeding were measured in 22 patients receiving an IV amino acid mixture (Vamin 18), 240 kJ/h) for 1 h before and then during spinal anesthesia and in 24 control patients receiving acetated Ringer's solution. Blood loss was calculated after surgery by weighing the swabs and the content of the suction tubes after subtraction of the saline used. After surgery, the closed drains were weighed after 24 h. In the amino acid group, the preanesthesia temperature increased by 0.4 degrees C +/- 0.2 degrees C (P < 0.01) and was unchanged in controls. At end of surgery, core temperature had decreased by 0.9 degrees C +/- 0.4 degrees C in controls and by 0.4 degrees C +/- 0.3 degrees C in the amino acid patients (P < 0.01). Oxygen uptake increased by 26 +/- 7 mL/min, or 16% +/- 5% (P < 0.05), from baseline in the amino acid patients, whereas it was unchanged in the controls. Blood loss during surgery was significantly larger in the control patients (702 +/- 344 mL) than in the amino acid patients (516 +/- 272 mL) (P < 0.05). After surgery, there were no significant differences in shed blood volume. In conclusion, amino acid infusion also induced a thermogenic response under spinal anesthesia. In addition, the prevention of temperature decrease during spinal anesthesia seemed to have a positive effect on intraoperative blood loss. IMPLICATIONS: Infusion of a balanced mixture of amino acids during spinal anesthesia prevented core body temperature decrease. Bleeding was also less pronounced.

Aged↗
PubMed1992

Changes in protein turnover after the introduction of parenteral nutrition in premature infants: comparison of breast milk and egg protein-based amino acid solutions.

Rates of protein turnover were measured in 20 infants receiving either Vamin Infant (group A) or Vamin 9 glucose (group B) as the amino acid source in total parenteral nutrition. A constant infusion of L-[1-13C]leucine was used to measure whole body leucine flux, and leucine oxidation rates were derived from measurements of total urinary nitrogen excretion. Infants were first studied when receiving only i.v. glucose and again on each of the next 4 d as total parenteral nutrition was gradually increased to a maximum of 430 mg nitrogen/kg/d and 90 nonprotein kcal/kg/d. Net protein gain and protein synthesis and breakdown rates increased progressively for all infants taken together over the study period as i.v. nutrition was increasing (p less than 0.001). There were no differences between groups in the changes in net protein gain and rates of protein synthesis and breakdown throughout the study period. Nitrogen retention on d 5 for the two groups was similar (60 +/- 16% and 67 +/- 11% in groups A and B, respectively). In a subgroup of infants, measurements were repeated on d 8, when the intake had been constant for 3 d. Protein retention was the same as on d 5, but both synthesis and breakdown were increased. It is concluded that rates of protein turnover increase significantly in response to increasing i.v. nutrition and that this elevation was not influenced by the composition of the amino acid mixture given.

Amino Acids↗
PubMed1997

15N enrichments of casein and plasma protein amino acids in cows ingesting 15N-labelled ammonium sulphate.

The aim of this work was to determine by ion-exchange liquid chromatography and isotope ratio mass spectrometry the specific 15N enrichment of amino acids in casein and plasma proteins in cows receiving three successive daily oral doses (300, 150 and 150 g) of (15NH4)2SO4 (10 atom per cent isotopic enrichment) and to examine the 15N enrichments obtained with regard to nitrogen transport and metabolism in the lactating cow. To investigate the 15N distribution in amino acids in casein and in plasma proteins, samples of 15N-labelled casein and plasma proteins were extracted either from a pool of several milkings (36-96 h after starting to administer the tracer) or from pooled venous blood (removed on the fourth day after the start of administration) from the four lactating cows. 15N enrichments of the proteins studied, expressed as atoms percent excess, were 0.2509 for casein and 0.0577 for plasma protein. Chromatographic fractionation of the amino acid mixture (protein hydrolysates) resulted in nine groups containing between one and four amino acids: Asp, Ser and Thr; Glu; Pro; Gly; Ala; Val and Met; Ileu and Leu; Tyr; Phe; His and Lys; and Arg. High 15N incorporation was demonstrated in all individual or groups of amino acids studied. In both proteins, Glu appeared to be the most enriched amino acid, Phe and Arg the least enriched. Most aliphatic molecules with a single amino group were highly enriched. The much lower (3.5-7.7-fold) enrichments in plasma protein compared with casein suggest considerable intracellular dilution at the site of liver protein synthesis. Finally, the amino acid separation methods are discussed and suggestions for improving them considered.

Amino Acids↗
PubMed1965

ACETOLACTATE METABOLISM AND THE PRESENCE OF A DIHYDROXY ACID DEHYDRATASE IN MICRO-ORGANISMS.

1. The growth characteristics of nine micro-organisms on complex broth and defined media, usually with a single nitrogen source (other than vitamins), were examined as a necessary step before growth of cells for enzyme assays. Six of these bacteria gave a positive colour test with a creatine-potassium hydroxide reagent, indicating the presence of acetoin, which other investigators have shown is formed via the intermediate, alpha-acetolactate. 2. Cell-free extracts of exponential-phase cells of Bacillus subtilis, Staphylococcus aureus, Proteus morganii, Acetobacter rancens (two strains), A. kuetzingianus, A. acetosus, Acetomonas (Acetobacter) melanogenus and Acetomonas (Acetobacter) suboxydans (A.T.C.C. no. 621) were found to contain the enzyme, dihydroxy acid dehydratase (2,3-dihydroxy acid hydro-lyase). 3. The specific activity of the dehydratase from organisms grown on valine- and isoleucine-deficient media was greater than those grown on a complex broth or media containing complete amino acid mixtures. The omission of valine plus isoleucine from a medium containing 19 amino acids caused an increase in the dehydratase specific activity of Staphylococcus aureus and Proteus morganii. 4. The rate of keto acid formation from alphabeta-dihydroxyisovalerate by extracts of six of the above-named organisms was faster than, but somewhat proportional to, the similar rate from alphabeta-dihydroxy-beta-methyl-n-valerate as substrate. 5. These findings may be related to acetolactate synthesis, acetoin formation and valine-isoleucine biosynthesis in the above-mentioned micro-organisms.

Acetobacter↗
PubMed1985

Induction of intestinal ornithine decarboxylase by single amino acid feeding.

Intestinal and hepatic ornithine decarboxylase (ODC) activities increased to a peak 4 h after administration of a diet containing casein or an amino acid mixture simulating that of casein to rats starved for 12 h. All amino acids except cysteine with a two or three carbon skeleton, including those with a D-configuration, and alpha-amino-isobutyric acid (AIB) strongly induced intestinal ODC when given in the diet or administered intragastrically. Amino acids with a four carbon skeleton were far less effective as inducers and other amino acids did not induce intestinal ODC at all. The amino acids that induced hepatic ODC showed no particular structural characteristics: glycine and cysteine were very effective, threonine, tryptophan, methionine, and phenylalanine were less effective, and serine, valine, isoleucine, and histidine were only slightly effective. Elevation of ODC activity after amino acid administration was not due to stabilization of the enzyme protein with the amino acids. Intestinal ODC was induced by intragastric but not intraperitoneal injection of glycine, although these treatments resulted in similar increases in the tissue concentration of glycine. On the contrary, hepatic ODC was induced by glycine regardless of the administration route. Intestinal ODC was also induced only in the segment of the intestine perfused with a solution of an amino acid with which the activity increased in the feeding experiment. These results suggest that the accumulation of an amino acid per se is not a trigger for induction of intestinal ODC and that an amino acid must act on the mucosal surface to induce the enzyme.

Amino Acids↗
PubMed1990

Effect of plasma amino acid replacement on glucagon and substrate responses to insulin-induced hypoglycemia in humans.

A defective glucagon response impairs glucose recovery from insulin-induced hypoglycemia in some insulin-dependent (type I) diabetic patients. Our objective was to determine whether the glucagon response to insulin-induced hypoglycemia could be stimulated in nondiabetic humans. Because insulin reduces plasma amino acid concentrations, and amino acids are known to stimulate glucagon secretion, we investigated the effect of amino acid replacement during insulin infusion on the glucagon response to hypoglycemia in six healthy nondiabetic subjects. In two separate studies, blood glucose was clamped at the postabsorptive level during a constant infusion of insulin (0.05 U.kg-1.h-1) for 3 h. Blood glucose was then reduced to 45 mg/dl over 20 min. Hormone and substrate concentrations during recovery from hypoglycemia were monitored for 2 h. In the control study, normal saline was infused, and in the other study, an amino acid mixture was infused to prevent the insulin-induced fall in plasma amino acids. Amino acid replacement did not change the basal glucagon levels but resulted in a more robust glucagon response to hypoglycemia (from 184 +/- 24 to 292 +/- 36 pg/ml) than in the control study (from 176 +/- 30 to an average 229 +/- 32 pg/ml, P less than 0.01). Plasma concentrations of epinephrine, norepinephrine, cortisol, and growth hormones increased during hypoglycemia, but the magnitude of the response was not different between the control and amino acid-replacement studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗