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Results for “AMINO ACID METABOLISM”

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PubMed1994

Independent and combined actions of interleukin-1 beta, tumor necrosis factor alpha, and glucagon on amino acid metabolism in the isolated perfused rat liver.

Conflicting reports concerning the hepatic effects of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF alpha) in the metabolic response to injury led us to investigate the influence of physiological concentrations of these cytokines on amino acid metabolism in the isolated perfused rat liver. IL-1 beta was ineffective at a concentration of 1 ng/mL, whereas TNF alpha (0.7 ng/mL) reduced the uptake of some of the main gluconeogenic amino acids (alanine, -55.3 +/- 4.9 v -72.9 +/- 13.7 nmol.min-1.g-1 in controls, P < .05) without affecting urea synthesis. TNF alpha increased glucose uptake by 237% and inhibited that of free fatty acids (-1.6 +/- 1.4 v -9.9 +/- 6.7 nmol.min-1.g-1 in controls, P < .05). IL-1 beta and TNF alpha potentiated glucagon-induced total amino acid uptake by 56% and 87%, respectively. They also affected glucagon-activated gluconeogenesis, leading to an initial potentiation of glucose release. Thereafter, IL-1 beta inhibited glucagon action, leading to an hepatic uptake of glucose. These results indicate that (1) in the conditions of the study, IL-1 beta has no direct effect on hepatic amino acid exchanges and utilization; (2) TNF alpha which exerted an inhibitory effect on these parameters, could be involved in the reduced amino acid exchanges during the end stage of sepsis; (3) the TNF alpha-induced increase in glucose uptake could be related to an inhibition of gluconeogenesis and/or to the activation of glucose utilization by Kupffer cells; (4) IL-1 beta and TNF alpha both potentiate the action of glucagon on hepatic amino acid uptake and utilization; and (5) complex interactions between Kupffer cells and hepatocytes on the one hand and between cytokines and hormones on the other hand could account for the differences in hepatic metabolism according to the stage of the response to injury.

Amino Acids↗
PubMed1979

[Proteeae enzymes that participate in the amino acid metabolism of food products].

Biosynthesis of enzymes, catalyzing amino acid conversion in food products, and deposition of end products of protein metabolism is a current problem for hygiene-indicatory microorganisms. Results are reported of a study of decarboxylase and aminotransferase activities of a large number of Proteus strains. It was found that aminotransferases are produced by all members of this group of microorganisms, despite the specific differences in their quantitative characteristics. The composition of the different protein-containing food substrata exerts emphatic influence on the induction of these enzymes. The results of study of decarboxylase activity also point to some specific differences, applicable in the differential diagnosis. The inferences summarize the importance of the whole Proteus group as hygiene-indicatory microorganisms, producing enzymes of essential importance for the quality and biologic value of food products.

Amino Acids↗
PubMed1989

Exercise-mediated peripheral tissue and whole-body amino acid metabolism during intravenous feeding in normal man.

1. The effect of a daily submaximal exercise regimen on whole-body and peripheral tissue amino acid metabolism during weight-stable intravenous feeding (IVF) was evaluated in 11 normal volunteers. Five of the subjects performed 1 h of daily bicycle exercise at 75 W during IVF, while the remaining six subjects received IVF without daily exercise. Body nitrogen balance, leg and forearm plasma amino acid flux and whole-body kinetics were measured before and on day 10 of IVF using a [1-13C]leucine and [15N]glycine tracer. 2. At the end of the IVF period, exercised subjects demonstrated leg uptake of total amino acids (237 +/- 103 nmol min-1 100 ml-1 of tissue, mean +/- SEM) which was significantly (P less than 0.05) different than in non-exercised subjects (-1101 +/- 253 nmol min-1 100 ml-1 of tissue). 3. In the non-exercised forearm, a significant (P less than 0.05) decrease in total amino acid flux was observed in exercised subjects (-162 +/- 88 nmol min-1 100 ml-1 of tissue) compared with non-exercised subjects (-460 +/- 105 nmol min-1 100 ml-1 of tissue) on day 10 of IVF. 4. Efflux of 3-methylhistidine significantly (P less than 0.05) decreased from the leg in those subjects who performed daily exercise (-0.29 +/- 0.12 nmol min-1 100 ml-1 of tissue) compared with those subjects receiving IVF without daily exercise (-1.46 +/- 0.35 nmol min-1 100 ml-1 of tissue).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1980

Amino acid metabolism in uremia: insights gained from normal and diabetic man.

The physiology of the interorgan exchange of amino acids in healthy subjects and in insulin-dependent diabetics is reviewed and compared with changes observed in patients with chronic renal failure. In contrast to the diabetic, who has elevated fasting branched-chain amino acid levels and diminished muscle uptake of branched-chain amino acid following protein feeding, fasting levels of leucine, isoleucine, and valine are decreased in uremia. Furthermore, the decline in branched-chain amino acids following insulin in normal and intracellular levels of leucine and isoleucine have been reported to be normal. With respect to alanine metabolism, the diabetic state is characterized by diminished fasting alanine levels which are due to a 2-fold increase in splanchnic alanine extraction. Accordingly, gluconeogenesis can potentially account for over 30 to 40% of hepatic glucose production compared to 15 to 20% in normal man. In uremia, fasting alanine levels are normal and hepatic alanine uptake is not increased. Similarly, basal hepatic glucose production, as well as suppression of glucose production following insulin, are normal in uremic subjects. Thus, although uremia is characterized by abnormalities in the metabolism of many individual amino acids, it does not appear to share the same disturbances in alanine and branched-chain amino acid metabolism that are associated with insulin deficiency.

Amino Acids↗
PubMed1984

Amino Acid metabolism in pea leaves : utilization of nitrogen from amide and amino groups of [N]asparagine.

The flow of nitrogen from the amino and amide groups of asparagine has been followed in young pea (Pisum sativum CV Little Marvel) leaves, supplied through the xylem with (15)N-labeled asparagine. The results confirm that there are two main routes for asparagine metabolism: deamidation and transamination.Nitrogen from the amide group is found predominantly in 2-hydroxy-succinamic acid (derived from transamination of asparagine) and in the amide group of glutamine. The amide nitrogen is also found in glutamate and dispersed through a range of amino acids. Transfer to glutamineamide results from assimilation of ammonia produced by deamidation of both asparagine and its transamination products: this assimilation is blocked by methionine sulfoximine. The release of amide nitrogen as ammonia is greatly reduced by aminooxyacetate, suggesting that, for much of the metabolized asparagine, transamination precedes deamidation.The amino group of asparagine is widely distributed in amino acids, especially aspartate, glutamate, alanine, and homoserine. For homoserine, a comparison of N and C labeling, and use of a transaminase inhibitor, suggests that it is not produced from the main pool of aspartate, and transamination may play a role in the accumulation of homoserine in peas.

Journal Article↗
PubMed1986

[Protein and amino acid metabolism in the digestive tract of growing bulls. 6. Apparent digestibility of the amino acids entering the duodenum and of amino acid from feed].

After studies with young bulls provided with duodenal cannulas the apparent digestibility (AD) of the individual amino acids getting into the duodenum (AAD) was ascertained on the basis of 28 different rations. The AD of the AAD is defined as follows: AAD--AAfaeces/AAD X 100. The results thus obtained show a relative constancy, only insignificantly impaired by the consideration of the dependence of the AD of the AAD on the AA concentration in the ration. The average value for the AD of the sigma AAD was 72.5 +/- 4.9%. The dependence of the AD of the sigma AAD on the sigma AA concentration in the ration is: y = 67.8 + 0.51x +/- 4.6; r = 0.355x. In addition, the relation between AD AAD and AD AAfeed protein' each in % of AA intake and AA concentration in the ration, was studied and reported on.

Aging↗
PubMed1998

Ammonia and amino acid metabolism in skeletal muscle: human, rodent and canine models.

This review considers four experimental models for studying the dynamics of ammonia and amino acid metabolism in skeletal muscle: the rat hindlimb, the isolated dog gastrocnemius, the leg extensor for humans, and the traditional approach of humans performing two-legged exercise. The rat hindlimb is well suited for studying intense exercise with fast-twitch white fibers, but it is poorly suited for studying prolonged exercise because of rapid fatigue of major portions of the muscle and the restrictions of taking multiple blood samples. The traditional human model is limited because of the inability to quantify accurately the active muscle mass and to determine the true blood flow to the entire active tissue. Despite species differences and the various limitations of the paradigms, there are numerous consistencies in the literature. For example, human muscle and the canine gastrocnemius demonstrate similar magnitudes of efflux of ammonia, glutamine, and alanine (when indexed for the active mass) during prolonged exercise. Muscle has a large ammonia producing capacity during either intense or prolonged exercise. In prolonged exercise this is accompanied by similar productions of alanine and glutamine as well as a large uptake of glutamate. Despite the latter, the intramuscular glutamate concentration rapidly declines by more than 50% and remains constant throughout the exercise period. The leg extensor model and the canine gastrocnemius offer the greatest opportunities to quantify these responses during prolonged exercise.

Amino Acids↗
PubMed1977

The nutritional significance of inborn errors of amino acid metabolism.

Inborn errors of metabolism affect the metabolism of 7 out of 8 essential amino acids and a number of non-essential ones. Dietary treatment has been applied with varying success. The wide variations in the severity of symptoms in this group of diseases are discussed. Dietary treatment opens the possibility to collect information about the minimal requirements of most essential amino acids. These requirements are likely to be still lower than those mentioned in the WHO Report No. 522, 1976. Children who for years have lived on one of these restricted diets, provide the possibility to compare the effect of such a diet on their nutritional status with that of children living on a normal diet.

Amino Acid Metabolism, Inborn Errors↗