Body Protein Metabolism Research Articles

Urinary 3-methylhistidine as an index of dietary protein adequacy in the adult rat: Short term testing

Urinary excretion of 3-methylhistidine (3-MH) was evaluated as an indicator of dietary protein quality using adult rats with shortterm feeding. The effect of protein depletion and repletion on excretion of 3-MH was also studied. Four groups of 6 rats weighing between 250 and 300 grams were fed diets containing 10% protein from casein, wheat gluten, blood globin, or a complementary mixture of wheat gluten and globin. Daily variations of weight, 3-MH and creatinine, as well as 6-day means were observed. The correlation of PER with the 6-day means of urinary 3-MH was not high. Body weight changes and fractional rates of synthesis (based on estimated myofibrillar 3-MH pool size) appeared to be highly correlated to PER and sensitive to the influence of dietary protein and calorie deficiencies on body protein metabolism. 3-MH excretion, then, when used to determine fractional rates of catabolism and synthesis of myofibrillar protein, could be useful in short-term protein evaluation using adult rats.

Effect of Insulin Deficiency and Obesity on Whole Body Protein Metabolism in Man

Effect of Insulin Deficiency and Obesity on Whole Body Protein Metabolism in Man

Amino acid signals and food intake and preference: relation to body protein metabolism.

Depressed food consumption is an early response of experimental, animals to: 1) a dietary deficiency of either protein or an individual indispensable amino acid; 2) a distortion of the dietary pattern of amino acids when protein intake is low; and 3) a substantial elevation in the protein content of the diet. In each of these conditions the change in feeding behaviour is associated with alterations in concentrations of amino acids in blood but in none of them has the biochemical basis for the depressed food intake been established. The depressed food intake of rats consuming a low protein diet in which an imbalance of amino acids has been created by adding quantities of amino acids other than the one most limiting for growth, is associated with elevations in the plasma concentrations of amino acids added to create the imbalance and usually with a depression in the plasma concentration of the growth-limiting amino acid. These changes, in turn, are associated with depression of the concentration of the growth-limiting amino acid in the brain free amino acid pool. Studies in which uptake of amino acids into brain slices has been examined support the conclusion that various distortions of the plasma amino acid pattern, as the result of dietary imbalances of amino acids, can lead to depletion of the brain pool of a specific amino acid through competition between it and other amino acids in surplus in plasma for uptake into brain. The results of studies with rats in vivo of the effects on brain amino acid pools of ingestion of diets containing supplements of amino acids that compete with the growth-limiting amino acid for uptake into brain also support this conclusion. Depletion of the brain pool of the limiting amino acid as the result of feeding a diet with an amino acid imbalance can be related to overall body protein metabolism. In the young growing animal, protein synthesis is stimulated after a meal. Thus, when the diet is limiting in a single amino acid, that amino acid will be depleted from the circulating body pool. At the same time, the activities of amino acid degrading enzymes are low in animals fed a low protein diet; hence, such animals have limited capacity to degrade surpluses of amino acids. These conditions, depletion of the blood pool of the limiting amino acid and slow removal of surpluses of competing amino acids from the blood, will increase the extent of competition between other amino acids and the limiting amino acid for uptake into brain.(ABSTRACT TRUNCATED AT 400 WORDS)

Contributions of Individual Body Tissues to Nitrogen Excretion in Adult Rats Fed Protein-Deficient Diets

An attempt was made to estimate the contributions of various tissues to nitrogen (N) excretion in rats fed protein-free diet or 2 and 10% lactalbumin diets for 14 to 31 days. The contributions were calculated as differences between the amounts of dietary N utilized for tissue protein and tissue growth. The amount of dietary N utilized for tissue protein was calculated from the recovery of 15N of orally administered [15N]leucine and N intake. The following results were obtained. 1) With a 10% protein diet, the contribution of tissues to N excretion was affected more by the turnover rates of individual tissues than by the size of the tissues, but with a protein-free diet the contribution was greatly affected by the size of the tissues. 2) With 2% lactalbumin diet, the contributions were not intermediate between those with protein-free diet and 10% lactalbumin diet: urinary N excretion was similar to that with protein-free diet in spite of the difference in N intake, probably mainly because the contribution of skeletal muscle was lower. 3) Differences in the dietary protein level affected the utilization of dietary protein only a little, but influenced body protein metabolism very much.

O.108 Six years experience of determination of body protein metabolism in surgical patients using L-[1- 14C] leucine

O.108 Six years experience of determination of body protein metabolism in surgical patients using L-[1- 14C] leucine

The effect of disease, drug, and diet on whole body protein metabolism in adolescents with Crohn disease and growth failure

The effect of chronic inflammation, corticosteroid therapy, and nutritional supplementation on whole body protein metabolism and growth was determined in adolescent males with Crohn disease and growth failure. Body protein status was characterized in six patients and in five healthy, age-matched controls by nitrogen balance, whole body potassium (measured as 40K), urinary creatinine excretion, and [15N]glycine turnover studies. The patients subsequently received an intragastric nutritional supplement that increased dietary protein and energy intakes by 40% for seven months. Follow-up anthropometric measurements were obtained in both groups of adolescents. Our results demonstrated that lean body mass (40K) and muscle mass (creatinine) were significantly reduced in the patients compared to the controls, despite similar nitrogen balances between both groups. Whole body nitrogen flux, rates of protein synthesis and breakdown, and net protein retention were no different between those patients with chronic inflammation, while receiving corticosteroid therapy, and their controls. Long-term nutritional supplementation significantly improved linear and ponderal growth velocities in the patients such that growth rates were commensurate with those of the healthy controls. We conclude that chronic inflammation and corticosteroid therapy are not associated with detectable alterations in protein metabolic processes at the whole body level. Rather, dietary insufficiency appears to be primarily responsible for growth failure in adolescents with Crohn disease.

Adaptation of body protein metabolism in adult and aging man

Aging causes a selective loss in lean body mass, muscle being most extensively eroded. This presentation is an analysis of the consequences of this age-related loss for protein and amino acid metabolism. The use of stable isotopes allows us to measure the dynamics of protein metabolism in the intact human subject, while the output of 3-methylhistidine permits estimates of muscle turnover to be made which show a smaller reduction in body protein turnover per kg body weight in elderly subjects. This is due to the reduced contribution by muscle protein turnover, which decreases from 30 per cent of total body protein turnover in the young adult to 20 per cent in the elderly, and can be entirely accounted for by the reduced mass of muscle, the rate of turnover per unit muscle weight being unchanged. The consequences of the changing proportions of major tissues with age has been examined for its impact on amino acid metabolism. The interaction of various organs in order to ensure metabolism of different amino acids is described. After a meal containing abundant protein, the liver selectively degraded the excess of most essential amino acids, while allowing the three branched-chain essential amino acids to pass through, so that in consequence they account for more than 50 per cent of the amino acid outflow from the splanchnic area. During this period of absorption muscle takes up amino acids, over 70 per cent being the branched-chain amino acids where they are catabolised, the nitrogen becoming available for formation of non-essential amino acids for muscle protein synthesis. The release of large amounts of glutamine from muscle is dependent on branched-chain amino acid degradation, whereas the relaese of large amounts of alanine is regulated by availability of pyruvate from glucose. The study of amino acid metabolism in elderly compared with young adults and its relationship to the declining mass of muscle with age is still in its initial stages. Metabolism of glycine at different levels of protein intake fails to demonstrate any significant effects of aging on metabolism of this amino acid. On the other hand, the flux of leucine shows a significant reduction in fasting elderly female subjects. This observation should be followed up by studying leucine kinetics following a meal of meat, in order to determine whether the reduced mass of muscle in the elderly will restrict the capacity to metabolise branched-chain amino acids. It has been concluded that the extensive age-related change in muscle mass should be explored for its impact on the nutritional requirements for branched-chain amino acids, their metabolism in health and disease, and their therapeutic uses at different ages.

Comparison of body protein metabolism during total parenteral nutrition using glucose or glucose and fat as the energy source

Direct measurement of body protein metabolism using L-(1- 14C) leucine during total parenteral nutrition following cholecystectomy demonstrated no significant difference between isocaloric isonitrogenous regimens containing glucose alone (n = 5) or with a fat emulsion (n = 5) as the energy substrates. It would appear that providing the obligatory requirement for glucose is met (about 150g d −1), fat and carbohydrate calories are inter-changeable with regards to fueling protein metabolism in the early period following moderately severe trauma.

Glycine nitrogen metabolism in man

[ 15N]Glycine is a commonly used tracer for measuring human whole body protein metabolism, even though the metabolism of the glycine N is not well defined for man. In this work, glycine N metabolism was studied by measuring the transfer of 15N from [ 15N]glycine to other plasma amino acids and urea. [ 15N]Glycine was given orally, every 4 hr for 60 hr to 6 young adult men, maintained on a 1.5 g kg −1d −1 egg protein diet. The 15N enrichments of plasma glycine, serine, and urea were measured during the entire 60 hr period. Although both glycine and serine 15N enrichments rose throughout the period (95% of plateau being reached by 33 hr), serine 15N enrichment was about half that of glycine from the first blood sample (4 hr) on. Plasma urea 15N reached only 88% of its predicted plateau value by 50 hr. The 15N enrichments in other plasma amino acids were determined in the plasma samples taken after isotopic steady state had been reached for glycine and serine (40–60 hr). The 15N enrichments relative to plasma [ 15N]glycine were serine 54%, urea 20%, glutamine/glutamate amino-N 15%, alanine 7%, leucine, isoleucine, valine, ornithine, proline, and methionine 3%–8%. Insignificant 15N was found in the remaining plasma amino acids. When the size of the various free amino acid pools were considered, 97% of the administered 15N in free amino acids was estimated to be in glycine, serine, glutamine/glutamate, and alanine amino-N. These data illustrate the rapid interconversion of glycine and serine in man and show that 15N from these amino acids can enter the major transaminating pool of amino acids via glutamate and alanine.

Whole body protein and amino acid metabolism: relation to protein quality evaluation in human nutrition.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTWhole body protein and amino acid metabolism: relation to protein quality evaluation in human nutritionVernon R. Young, Nevin S. Scrimshaw, and Dennis M. BierCite this: J. Agric. Food Chem. 1981, 29, 3, 440–447Publication Date (Print):May 1, 1981Publication History Published online1 May 2002Published inissue 1 May 1981https://doi.org/10.1021/jf00105a003RIGHTS & PERMISSIONSArticle Views157Altmetric-Citations26LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (4 MB) Get e-Alerts Get e-Alerts

The Changing Pattern of Whole Body Protein Metabolism in Aging Humans

Dynamic aspects of whole body protein (nitrogen) metabolism were explored in healthy young adults and elderly men and women. Measurements were made of the rate of whole body protein breakdown, with the aid of 15N-glycine, and the rate of muscle protein breakdown, as estimated from urinary N tau-methylhistidine excretion. The results also were evaluated in relation to obligatory (endogenous) urinary nitrogen losses, previously determined in this laboratory for the two age groups. Rates of whole body and muscle protein breakdown, per unit body weight, were lower in elderly subjects than in young adults. Muscle accounted for a mean of 27% of whole body protein breakdown in young adults and 20% or less (p less than 0.01) in elderly subjects. Daily obligatory N loss was positively correlated (p less than 0.01) with whole body protein breakdown. It was calculated that muscle contributed less to the obligatory N output in elderly subjects than in young adults. These results indicate a change in the distribution of whole body protein metabolism during aging in human subjects, with muscle making a lower contribution to total body protein metabolism in elderly subjects compared with young adults.

Second Boyd Orr Memorial Lecture. Regulation of body protein metabolism in relation to diet.

Second Boyd Orr Memorial Lecture. Regulation of body protein metabolism in relation to diet.

Whole body protein turnover in aging man

To explore the effects of aging on dynamic aspects of whole body protein metabolism in man, the 15N-glycine infusion method of Picou and Taylor-Roberts was used to estimate rates of total body protein synthesis and breakdown in both young adults and elderly subjects. Nine healthy elderly subjects, 4 male and 5 female, 65–91 yr old, participated in the study. Results obtained with 4 young men and 4 young women, 18–25 yr old, were used for comparative purposes. Total body protein synthesis and breakdown rates, per day and per unit body weight per day, were lower in women than in men and significantly lower in elderly women than in young women. Urinary creatinine was used to estimate muscle mass, and whole body 40K to calculate body cell mass. Whole body protein synthesis and breakdown rates, per unit creatinine, were higher in the elderly than in the young adults. Expressed per unit body cell mass, the rates were higher in elderly men than in young men, and a similar, but not statistically significant, difference was observed between elderly and young women. From these results it appears that whole body protein synthesis declines with age in man and is associated with the loss of body cell mass. There is also a redistribution in the pattern of whole body protein synthesis and breakdown as aging progresses, with the visceral organs making a progressively greater contribution to whole body protein metabolism than the skeletal musculature.

Total human body protein synthesis in relation to protein requirements at various ages.

THE intensity of body and tissue protein metabolism per kg declines with increased adult body size in mammals1. This fall parallels a similar progressive decline in the intensity of energy metabolism2–4. It has also been concluded that protein metabolism per unit of body weight is about four to five times faster in young rats than in adult man1; this pattern of change extends to cellular and subcellular aspects of protein metabolism, such as plasma albumin synthesis, liver RNA content and enzyme activity1,5. Similarly, the rate of protein synthesis per kg total body weight declines during growth and development within a species, such as the rat6. This parameter again parallels the reduction in the intensity of energy metabolism which occurs during the growth period3.

Nutritional Evaluation of Dietary Proteins with Regard to Body Protein Metabolism in Adult Rats Using Purified Whole Egg Protein as a Standard Reference

A new method for the preparation of whole egg protein was presented and its qualification as a standard reference for evaluating dietary protein was made in the course of this experiment: e.g., Purity, 96.5% and Biological value, 99.9. The amino acid composition was almost identical with that shown in the table of FAO (1970).Using this whole egg protein, casein and yeast, the nutritive values of dietary proteins in the adult rats at the normal level of body protein and in those after 8 day’s protein depletion were compared. It was found that the evaluation after protein depletion had a tendency to overestimate the nutritive value of proteins rather making the difference little between each other. The significance of the relative evaluation by use of the purified whole egg protein was discussed with special regard to the actual retention of body nitrogen, i.e., the net nitrogen retention.

Further Studies on the Effect of Dietary Carbohydrate and Fat on Protein Metabolism in Rats

A systematic experiment has been carried out in attempting to elucidate the biochemical mechanism underlying “protein sparing” action of dietary carbohydrate and fat. A more simplified experimental condition was employed in the present investigation in comparison with that in our previous experimental design; the effect of dietary carbohydrate and fat on the body protein metabolism was examined in the absence of any protein in the diet. Feeding of either carbohydrate or fat caused a marked decrease in the level of urinary nitrogen and urea. The ingestion of either carbohydrate or fat by rats resulted in a reduction of the rate of ureogenesis in the rat liver with the concomitant decrease in the activities of hepatic amino acid-catabolizing enzymes, e.g., threonine dehydratase, tryptophan pyrrolase, arginase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase and glutamic dehydrogenase (except in fat-fed animals). The feeding of either carbohydrate or fat did not result in changes in the level of free amino nitrogen in blood, indicating that the supply of amino acid may not exert an important role in the ureogenesis in liver. The overall results indicate that the reduction of the activities of hepatic amino acid-catabolizing enzymes elicited by the feeding of either carbohydrate or fat may govern protein metabolism in the rat body.

Effect of Previous High Fat Diet on Body Protein Metabolism in Rats

Effect of Previous High Fat Diet on Body Protein Metabolism in Rats

Effects of insulin on amino acid release and urea formation in perfused rat liver.

ARTICLESEffects of insulin on amino acid release and urea formation in perfused rat liverCE Mondon, and GE MortimoreCE Mondon, and GE MortimorePublished Online:01 Jan 1967https://doi.org/10.1152/ajplegacy.1967.212.1.173MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByInsulin regulation of gluconeogenesis3 September 2017 | Annals of the New York Academy of Sciences, Vol. 1411, No. 1Isolated perfused liver model: the rat and guinea pig comparedNutrition, Vol. 20, No. 5Effects of insulin and glucose on urea synthesis in normal man, independent of pancreatic hormone secretionJournal of Hepatology, Vol. 21, No. 3Amino acid metabolism in isolated perfused rat liverJournal of Surgical Research, Vol. 49, No. 1Effects of insulin and glucagon on the incorporation of [14C]glycine into the protein of the liver and opercular muscle of the eel in vitroGeneral and Comparative Endocrinology, Vol. 51, No. 2Effects of insulin and glucagon on amino acid transport into the liver and opercular muscle of the eel in vitroGeneral and Comparative Endocrinology, Vol. 51, No. 2Effects of insulin and glucagon on the uptake of amino acids from arterial blood by canine ileumDigestive Diseases and Sciences, Vol. 26, No. 2Perifused monolayer cultures of rat hepatocytes as an improved in vitro system for studies on ureogenesisExperimental Cell Research, Vol. 124, No. 2THE EFFECT OF INSULIN AND HYDROCORTISONE ON THE ISOLATED RAT LIVER7 November 2014 | Australian and New Zealand Journal of Surgery, Vol. 48, No. 5Effect of bovine insulin on the incorporation of [14C]glycine into protein and carbohydrate in liver and muscle of hagfish, Eptatretus stoutiGeneral and Comparative Endocrinology, Vol. 36, No. 1Effect of acute uremia on insulin removal by the isolated perfused rat liver and muscleMetabolism, Vol. 27, No. 2Effect of insulin in vitro on the isolated, perfused alloxan-diabetic rat liverDiabetologia, Vol. 14, No. 1Lysosomal sequestration of intracellular protein as a regulatory step in hepatic proteolysis.Journal of Biological Chemistry, Vol. 252, No. 19The role of insulin in regulating protein catabolism in mammalian cellsInternational Journal of Biochemistry, Vol. 7, No. 6-7Effect of Insulin on Albumin Production and Incorporation of 14 C-leucine into Proteins in Isolated Parenchymal Liver Cells from Normal Rats.Acta Physiologica Scandinavica, Vol. 94, No. 2[4] The perfused rat liverOsmotic alterations of the lysosomal system during rat liver perfusion: Reversible suppression by insulin and amino acidsBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 338, No. 2Proteolysis in homogenates of perfused rat liver: Responses to insulin, glucagon and amino acidsBiochemical and Biophysical Research Communications, Vol. 54, No. 1Effects of Hypophysectomy on Amino Acid Metabolism and Gluconeogenesis in the Perfused Rat LiverJournal of Biological Chemistry, Vol. 248, No. 13The glucose-alanine cycleMetabolism, Vol. 22, No. 2Compartmentation of Free Valine and Its Relation to Protein Turnover in Perfused Rat LiverJournal of Biological Chemistry, Vol. 247, No. 9Nutritional aspects of amino acid metabolism9 February 2010 | British Journal of Nutrition, Vol. 27, No. 2Nutritional aspects of amino acid metabolism9 February 2010 | British Journal of Nutrition, Vol. 27, No. 2Effects of Catecholamines on MetabolismNutritional aspects of amino acid metabolism9 March 2007 | British Journal of Nutrition, Vol. 26, No. 3Effect of Previous High Fat Diet on Body Protein Metabolism in RatsThe Journal of Nutrition, Vol. 101, No. 7Regulation of tyrosine transminase degradation in the isolated perfused rat liver by cycloheximide and insulinBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 230, No. 2Physiologie und Biochemie der endokrinen Regulationen und KorrelationenInterrelations between lipid and carbohydrate metabolismNaunyn-Schmiedebergs Archiv f�r Pharmakologie, Vol. 269, No. 2-4REFERENCESNitrogen metabolism in the perfused rat liverBiochimica et Biophysica Acta (BBA) - General Subjects, Vol. 222, No. 1Inhibition by Insulin of Valine Turnover in LiverJournal of Biological Chemistry, Vol. 245, No. 9Free Amino Acid Pools and Their Role in RegulationControl of Gluconeogenesis from Amino Acids in the Perfused Rat LiverJournal of Biological Chemistry, Vol. 244, No. 20Effects of Glucagon on Amino Acid Transport and Utilization in the Perfused Rat LiverJournal of Biological Chemistry, Vol. 244, No. 20The effect of insulin on the metabolism of lipids and on urea formation by the perfused rat liverMetabolism, Vol. 17, No. 3Role of Adenosine 3′,5′-Monophosphate in the Effects of Insulin and Anti-insulin Serum on Liver MetabolismJournal of Biological Chemistry, Vol. 243, No. 5The role of cyclic AMP in the control of liver metabolismAdvances in Enzyme Regulation, Vol. 6 More from this issue > Volume 212Issue 1January 1967Pages 173-178 Copyright & PermissionsCopyright © 1967 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1967.212.1.173PubMed6015999History Published online 1 January 1967 Published in print 1 January 1967 Metrics

The Surveys on the Urea and Allantoin Excretion and Other Criteria from Rats Fed “Threonine Imbalanced” or “Corrected” Diet

Weanling male rats of Wistar strain were fed ad libitum 7 or 8% casein-α-starch diet supplemented with 0.3% DL-methionine with (+Thr) or without (-Thr) added 0.36% DL-threonine for 12 days. Urine was collected 3 times for 3 days each at one-day interval. The urine sample was analysed for allantoin, urea and total N. There was no difference between the values of growth rate, liver and carcass fat con-tent, protein efficiency ratio and % N retention of -Thr and +Thr groups, whereas urea excretions of -Thr groups were significantly higher (over 2 times) than those of +Thr and allantoin excretions were consistently lower in the former when dietary protein level was 8%. These results suggest again that urinary urea may be a most sensitive external indicator for detecting the differential changes in body protein metabolism, which are caused by slight modification of dietary amino acid composition.

RED CELL STROMA AND HEMOGLOBIN METABOLISM IN ANEMIC DOGS

Red cell stroma protein and hemoglobin can be labeled by feeding C(14) lysine during periods of active blood regeneration following anemia. Stroma proteins are produced and a maximum concentration of the C(14) label appears 2 to 3 days earlier than with hemoglobin,-which is to say that stroma building precedes hemoglobin construction. The concentration of isotope in stroma protein may exceed its concentration in hemoglobin during regeneration following anemia due to blood loss. Diets favorable for hemoglobin regeneration may force the hemoglobin isotope concentration above that of the stroma protein. In hemolytic anemias great reserves of red cell building material are stored in the body. These stores may modify the curves of isotope concentration in red cells during the recovery periods. When finally formed, the mature red cells show little or no evidence of participation in general body protein metabolism during their life in the circulation.