scholarly journals Critical evaluation of a method for estimating amino acid requirements for maintenance in the rat by measurement of the rate of 14C-labelled amino acid oxidation in vivo

1974 ◽  
Vol 32 (2) ◽  
pp. 257-272 ◽  
Author(s):  
R. J Neale ◽  
J. C Waterlow
Keyword(s):  
Amino Acid ◽  
Critical Evaluation ◽  
Specific Radioactivity ◽  
The Body ◽  
Acid Oxidation ◽  
Acid Diet ◽  
Fractional Rate ◽  
Protein Free Diet ◽  
Maintenance Requirements

1. The object of the experiments was to estimate the maintenance requirements for lysine and leucine by a radioactive method. Rats were given a single dose of 14C-labelled lysine or leucine and groups of animals were killed after 15, 20 and 30 d.2. After 20 d the specific radioactivity (SR) of protein was approximately the same in liver, muscle and viscera; it was somewhat lower in skin. Once uniform SR is achieved, the rate of loss of radioactivity is a measure of the rate of endogenous loss of the amino acid.3. The rate of loss between 20 and 30 d was measured in two ways: from the daily output of expired 14CO2, and from the decrease, over the 10 d interval, of the total amount of radioactivity retained in the body.4. For the first 15 d after administration of the labelled amino acid, all rats were given a low-protein or low-amino acid diet on which body-weight was maintained constant. For the second 15 d period some rats were kept on this diet; others were transferred either to a protein-free diet or to a diet lacking the specific amino acid (lysine or leucine) which had been administered in the labelled form.5. The fractional rate of amino acid loss in the different experiments ranged from 1.5 to 3.5%/d, being greatest with the protein-free diet. The absolute rates of loss were calculated from measurements of the total lysine and leucine content of rats.6. The best estimates of the rate of endogenous amino acid loss obtained in this way, expressed as mg/kg0.75 per d were: lysine 136, leucine 80. These estimates are higher than most estimates of maintenance requirements obtained by growth or nitrogen balance methods and possible reasons for these discrepancies are discussed.

scholarly journals In vivo Determination of Amino Acid Bioavailability in Humans and Model Animals

2005 ◽  
Vol 88 (3) ◽  
pp. 923-934 ◽  
Author(s):  
Malcolm F Fuller ◽  
Daniel Tomé
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
The Body ◽  
Whole Body ◽  
Intestinal Lumen ◽  
Stable Isotope Labelling ◽  
Ileal Digestibility ◽  
Hydrolyzed Protein ◽  
Protein Free Diet

Abstract Because the digestion of many dietary proteins is incomplete, and because there is a continuous (but variable) entry into the intestinal lumen of endogenous protein and amino acid nitrogen that is also subject to digestion, the fluxes of nitrogen, amino acids, and protein in the gut exhibit a rather complicated pattern. Methods to distinguish and quantitate the endogenous and dietary components of nitrogen and amino acids in ileal chyme or feces include the use of a protein-free diet, the enzyme-hydrolyzed protein method, different levels of protein intake, multiple regression methods, and stable-isotope labelling of endogenous or exogenous amino acids. Assessment of bioavailability can be made, with varying degrees of difficulty, in man directly but, for routine evaluation of foods, the use of model animals is attractive for several reasons, the main ones being cost and time. Various animals and birds have been proposed as models for man but, in determining their suitability as a model, their physiological, enzymological, and microbiological differences must be considered. Fecal or ileal digestibility measurements, as well as apparent and true nitrogen and amino acid digestibility measurements, have very different nutritional significance and can, thus, be used for different objectives. Measurements at the ileal level are critical for determining amino acid losses of both dietary and endogenous origin, whereas measurements at the fecal level are critical in assessing whole-body nitrogen losses. A complementary and still unresolved aspect is to take into account the recycling of intestinal nitrogen and bacterial amino acids to the body.

scholarly journals Metabolic Availability of Lysine from Oats and Whole Milk Assessed in School-Aged Children

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 949-949
Author(s):  
Katia Caballero de la Pena ◽  
Mahroukh Rafii ◽  
Ronald Ball ◽  
Paul Pencharz ◽  
Glenda Courtney-Martin ◽  
...  
Keyword(s):  
Amino Acid ◽  
Repeated Measures ◽  
Protein Quality ◽  
Energy Requirement ◽  
Food Sources ◽  
Acid Oxidation ◽  
School Aged Children ◽  
Repeated Measures Design ◽  
Acid Diet ◽  
Whole Milk

Abstract Objectives The objective of this study was to assess protein quality by determining the metabolic availability (MA) of lysine from commonly consumed plant and animal-based food sources in school-aged children, using the indicator amino acid oxidation (IAAO) method. Methods Using a repeated-measures design, six healthy school-aged children randomly received 10 lysine intakes from either crystalline L-lysine (3, 6, 9, 12 mg/kg/day), moist cooked oats (9, 12 mg/kg/day), oven-baked granola (12 mg/kg/day), or whole milk (6, 9, 12 mg/kg/day). All diets provided protein at 1.5 g/kg/day and calories at 1.7x the participant´s measured resting energy requirement. All test diets were isocaloric and isonitrogenous. Every study day, breath samples were collected at baseline and during isotopic steady state and the ,13C enrichment was measured using an isotope ratio mass spectrometer. MA of lysine from food sources was determined using slope ratio analysis of ,13C-phenylalanine oxidation response to feeding lysine from whole foods compared to L-lysine from a reference crystalline amino acid diet. Results Lysine from whole milk was highly available, (∼100%, similar to our crystalline-lysine reference). The MA of lysine from cooked oats was 92.7%. When the same oats were oven-baked the availability of lysine was reduced by ∼50%. This reduction may be due to lysine loss through the Maillard reaction. Conclusions Lysine is highly metabolically available from milk and from moist cooked oats. However, dry cooking of oats reduces lysine MA considerably. The protein quality of cereal- based diets is dependent in the lysine content and bioavailability of the individual foods. Therefore, it is imperative to study how the human body utilizes this nutrient, especially in growing children. These are the first studies that assess protein quality in commonly consumed foods directly in children. This data will help build a knowledge base that can be further used to develop accurate dietary combinations that fully meet amino acid needs. Funding Sources Supported by: Dairy Farmers of Canada and National Dairy Council.

scholarly journals Quantification in vivo of the effects of different types of dietary fat on the loci of control involved in hepatic triacylglycerol secretion

1995 ◽  
Vol 308 (2) ◽  
pp. 537-542 ◽  
Author(s):  
A M B Moir ◽  
B S Park ◽  
V A Zammit
Keyword(s):  
Fatty Acids ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Branch Points ◽  
Pharmacological Agents ◽  
Acid Diet ◽  
Fractional Rate ◽  
Selective Labelling ◽  
Hepatic Triacylglycerol

Polyunsaturated fatty acids (PUFA) have been suggested to exert their hypotriglyceridaemic effect through several possible mechanisms that would be expected to decrease the rate of hepatic very-low-density-lipoprotein-triacylglycerol secretion. We have quantified the role played in vivo by changes in the pattern of partitioning of (i) acyl-CoA between oxidation and esterification, (ii) diacylglycerol between synthesis of triacylglycerol and of the major phospholipids, and (iii) triacylglycerol between secretion and storage within the liver, in response to two dietary levels of n-6 and n-3 PUFA. In order to achieve this we used the technique of selective labelling of hepatic fatty acids in vivo. Compared with a predominantly saturated fatty acid diet, both n-6 and n-3 PUFA intake resulted in a decrease in the proportion of acyl moieties that were secreted by the liver, through an increased diversion of acyl-CoA towards oxidation and a lower fractional rate of secretion of newly synthesized triacylglycerol. In addition, a diet rich in n-3 fatty acids resulted not only in a greater magnitude of these effects but also in a doubling of the partitioning of diacylglycerol towards phospholipid labelling. It is shown that the overall 50% reduction achieved by fish oil feeding in the proportion of acyl groups that were secreted by the liver was distributed over all three branch points. The contribution of each of these adaptations was quantified. The application of such an approach, i.e. the localization and in vivo quantification of the importance of loci of control, in studies on dietary and pharmacological agents that affect lipaemia, is discussed.

scholarly journals Glutamine: Metabolism and Immune Function, Supplementation and Clinical Translation

2018 ◽  
Author(s):  
Vinicius Cruzat ◽  
Marcelo Macedo Rogero ◽  
Kevin Noel Keane ◽  
Rui Curi ◽  
Philip Newsholme
Keyword(s):  
Amino Acid ◽  
The Body ◽  
Glutamine Metabolism ◽  
In Vivo Studies ◽  
Glutamine Supplementation ◽  
Bacterial Killing ◽  
Nutrition Supplementation ◽  
Wide Range

Glutamine is the most abundant and versatile amino acid in the body. In health and disease, the rate of glutamine consumption by immune cells is similar or greater than glucose. For instance, in vitro and in vivo studies have determined that glutamine is an essential nutrient for lymphocyte proliferation and cytokine production, macrophage phagocytic plus secretory activities and neutrophil bacterial killing. Glutamine release to the circulation and availability is mainly controlled by key metabolic organs, such as the gut, liver and skeletal muscles. During catabolic/hypercatabolic situations glutamine can become essential for metabolic function, but its availability may be compromised due to impairment of homeostasis in the inter-tissue metabolism of amino acids. For this reason, glutamine is currently part of clinical nutrition supplementation protocols and/or recommended for immune suppressed individuals. However, in a wide range of catabolic/hypercatabolic situations (e.g. ill/critically ill, post-trauma, sepsis, exhausted athletes) it is currently difficult to determine whether glutamine parenteral or enteral supplementation should be recommended based on the amino acid plasma concentration (glutaminemia). Although the beneficial immune based effects of glutamine supplementation is already established, many questions and evidence for positive in vivo outcomes still remain to be presented. Therefore, this paper provides an integrated review on how glutamine metabolism in key organs is important to cells of the immune system. We also discuss glutamine metabolism, action and important issues related to the effects of glutamine supplementation in catabolic situations.

Critical Evaluation of an in Vitro Model for Evaluation of Platelet Reactivity of Biomaterials

1987 ◽  
Vol 110 ◽  
Author(s):  
Raymond Connolly ◽  
Norman Shoenfeld ◽  
Karen Ramberg ◽  
Allan D. Callow
Keyword(s):  
In Vitro Model ◽  
Platelet Reactivity ◽  
Platelet Rich Plasma ◽  
Critical Evaluation ◽  
The Body ◽  
Test Material ◽  
In Vitro Test ◽  
Vitro Model

AbstractAn in vitro model for measuring platelet reactivity to a variety of biomaterial candidates for vascular grafts is described. A model consisting of a standard area of test material exposed to freshly labeled In platelets in plasma was evaluated. The platelets were isolated from ACD anticoagulated blood and resuspended in ACD plasma. It has been previously demonstrated that platelets so treated circulate in the body and will deposit on biomaterials exposed to the blood in vivo. The in vitro test consisted of an incubation of the platelets and materials at 37°C for one hour. At the end of the incubation, the platelet rich plasma was removed and the materials washed and removed for gamma counting. Platelet reactivity was normalized as a percentage of the counts on the material to counts in an aliquot of the platelet-plasma incubation media. The maximum uptake of platelets occurred within one hour. Platelets from three species, human, baboon, and dog were tested. Platelet uptake by Dacron and PTFE were in the range of 30–40% and 1–5% respectively. This is in accord with the known reactivity of these two vascular graft materials in vivo.A second series of studies were conducted with physically and pharmacologically inactivated platelets and inert particles. Those studies suggest that the initial results do not represent a biologic event but may reflect the porosity of the materials. This emphasizes the necessity of adequately defining an in vitro model against known in vivo activity.

scholarly journals Effects of L-amino Acids on Human Peripheral Neutrophil Granulocyte Activation

2014 ◽  
Vol 8 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Sándor Sipka ◽  
Tamás Keresztes ◽  
Ildikó Kovács ◽  
Sándor Sipka Jr ◽  
Sándor Baráth ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ex Vivo ◽  
The Body ◽  
Human Neutrophils ◽  
Neutrophil Granulocyte ◽  
Amino Acid Supplementation ◽  
Glucose Levels ◽  
Serum Glutamate

Objective: The objective was to investigate the early (20 minutes) effects of 21 L-amino acids on the activation of human neutrophils and to determine in healthy individuals the effects of a meal on the 1) number and relative luminescence unit (RLU) of peripheral neutrophils, 2) serum glutamate and glucose levels and 3) mTOR signaling network. Methods: The RLU of neutrophils stimulated by Ca2+ ionophor (CaI) and phorbol myristate acetate (PMA) following amino acid supplementation (3 x 10-4 M) or after consuming a meal was determined. L-glutamate was measured by HPLC. Results: All amino acids resulted in significant inhibitions of neutrophil RLU, except for arginine, which stimulated neutrophils. The ratios of amino acid induced inhibition were significantly higher in the cells stimulated by PMA than by CaI. The consumption of a meal resulted in a significant serum glutamate elevation compared to baseline (2.3 versus 0.9 x10-4 M) 90 minutes after ingestion of the meal. It was independent of the body mass index and returned near fasting levels after 150 minutes. The number of neutrophils was significantly elevated 90 minutes after the meal but the PMA induced RLU was significantly decreased. Conclusion: Our ex vivoand in vivoresults suggest that the L-amino acids, independent of their metabolic significance, may continuosly and quickly modify the activity of human peripheral neutrophils, and also the outcome of various immunologic reactions. The activation of the mTORC1 complex likely involves a transient impairment in the function of mTORC2 complex in these processes.

scholarly journals The effect of starvation on branched-chain 2-oxo acid oxidation in rat muscle

1984 ◽  
Vol 219 (1) ◽  
pp. 253-260 ◽  
Author(s):  
A J M Wagenmakers ◽  
J H Veerkamp
Keyword(s):  
Amino Acid ◽  
Protein Degradation ◽  
Specific Radioactivity ◽  
Acid Oxidation ◽  
Oxidative Decarboxylation ◽  
Precursor Pool ◽  
Oxidation Rates ◽  
Branched Chain Amino Acid ◽  
Endogenous Protein ◽  
Branched Chain

Oxidative-decarboxylation rates of branched-chain amino acids in rat hemidiaphragm and of branched-chain 2-oxo acids in hemidiaphragm, soleus muscle and heart slices of 110-120 g rats were increased considerably by 3-4 days of starvation, when they were calculated from the specific radioactivity in the medium. When the supply from endogenous protein degradation to the oxidation-precursor pool was severely limited by transaminase inhibitors, oxidative-decarboxylation rates of branched-chain 2-oxo acids rose significantly. Since this apparent increase was relatively larger in preparations from fed rats than from 3-days-starved rats, the differences in oxidation rates with nutritional state became less or even not significant. With rat heart the smaller dilution of the oxidation precursor pool after starvation is in accordance with the reported decrease in protein breakdown. Since protein degradation increases with starvation in skeletal muscles, we suggest that the amino acid pool arising from protein degradation is more segregated from the oxidation precursor pool in muscles from starved than from fed rats. We conclude that starvation increases branched-chain amino acid and 2-oxo acid oxidation in skeletal and cardiac muscle considerably less than has been suggested by previous studies.

scholarly journals Available versus digestible amino acids – new stable isotope methods

2012 ◽  
Vol 108 (S2) ◽  
pp. S306-S314 ◽  
Author(s):  
Rajavel Elango ◽  
Crystal Levesque ◽  
Ronald O. Ball ◽  
Paul B. Pencharz
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Stable Isotope ◽  
Growing Pigs ◽  
The Body ◽  
Whole Body ◽  
Food Protein ◽  
Adult Humans

The nutritive value of food protein sources is dependent on the amino acid composition and the bioavailability of the nutritionally indispensable amino acids. Traditionally the methods developed to determine amino acid bioavailability have focused on intestinal absorption or digestibility, which is calculated as the percent of amino acid intake that does not appear in digesta or faeces. Traditional digestibility based methods do not always account for gut endogenous amino acid losses or absorbed amino acids which are unavailable due to the effect of heat processing and the presence of anti-nutritional factors, though methods have been developed to address these issues. Furthermore, digestibility based methods require the use of animal models, thus there is a need to developin vivomethods that can be applied directly in human subjects to identify the proportion of dietary amino acids which is bioavailable, or metabolically available to the body for protein synthesis following digestion and absorption. The indicator amino acid oxidation (IAAO) method developed in our laboratory for humans has been systematically applied to determine almost all indispensable amino acid requirements in adult humans. Oxidation of the indicator amino acid is inversely proportional to whole body protein synthesis and responds rapidly to changes in the bioavailability of amino acids for metabolic processes. Using the IAAO concept, we developed a newin vivomethod in growing pigs, pregnant sows and adult humans to identify the metabolic availability of amino acids in foods. The stable isotope based metabolic availability method is suitable for rapid and routine analysis in humans, and can be used to integrate amino acid requirement data with dietary amino acid availability of foods.

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