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PubMed1976

Essential amino acid metabolism in maintenance dialysis patients.

Oral and I.V. administration of a mixture of essential amino acids to normal and dialysis patients revealed: 1. First pass metabolism (FPM) occurred for all administered amino acids in both normal and dialysis patients, and was variable in both populations. however, FPM appeared lower for phenylalanine and higher for methionine in the dialysis group. 2. Net metabolic clearance rate was significantly lower (p less than 0.05) for leucine, isoleucine, threonine and phenylalanine, and tended to be lower for valine and lysine in the dialysis group. 3. With the exception of phenylalanine and valine the apparent volume of distribution did not differ between normals and maintenance dialysis patients. 4. These studies indicate the existence of a variety of significant abnormalities in the metabolism of specific essential amino acids, and suggests a defect in muscle metabolism of branched-chain amino acids in maintenance dialysis patients.

Administration, Oral↗
PubMed1976

Amino acid metabolism in Friedreich's ataxia.

A study of amino acids determined by sequential Multi-sample Amino Acid Automatic Analyzer in plasma, urine and cerebrospinal fluid (CSF) in patients with Friedreich's ataxia and control subjects has revealed a number of mathematically significant variations from normal. Of practical physiological importance are the following: a high urinary excretion of alanine with slightly elevated plasma levels; a low plasma and CSF concentration of aspartic acid in the presence of normal urinary values and finally a low CSF concentration of taurine accompanied by normal plasma levels, but elevated urinary output and renal clearance rates. We postulate that the modifications in alanine and aspartic acid are less specific and probably secondary, but there could be a genetic defect in the membrane transport of taurine and the other beta-amino acids in Friedreich's ataxia.

Alanine↗
PubMed1984

Relationship between Auxin and Amino Acid Metabolism of Tobacco Protoplast-Derived Cells.

Single amino acids were found to be highly toxic to protoplast-derived cells of tobacco (Nicotiana tabacum cv Xanthi) cultured at low density in a culture medium containing a low naphthaleneacetic acid concentration (0.05 micromolar). The cytotoxicities of alanine, aspartic acid, asparagine, glutamic acid, glutamine, glycine, lysine, proline, and valine were reduced when the naphthaleneacetic acid concentration of the culture medium was increased to 1 micromolar. This selective modification of amino acid toxicity by naphthaleneacetic acid could not be correlated with modifications of uptake rates or incorporation of these amino acids into protein or amino acid-auxin conjugates. A mutant clone resistant to high naphthaleneacetic acid concentrations and affected in root morphogenesis did not display, at the cellular level, the naphthaleneacetic acidmediated modification of amino acid cytotoxicity.

Journal Article↗
PubMed1988

[Experimental study on glucose turnover and amino acid metabolism after total pancreatectomy].

Glucose turnover and plasma amino acid profile were measured in total pancreatectomized dogs to clarify the mechanism of hyperaminoacidemia after total pancreatectomy. Twenty-one male mongrel dogs underwent total gastrectomy and pancreatectomy and were divided into two groups. I(-) group (n = 11) was treated without insulin and I(+) group (n = 10) received insulin postoperatively. Another 15 dogs of S group received only splenectomy. Glucose appearance rate (Ra), plasma amino acid profile and blood sugar level (BS) were measured before operation, and on the 1st and 3rd postoperative days. Significantly higher Ra and BS were observed in I(-) group than in S group postoperatively and either decreased or unaltered by the glucagon infusion. On the other hand, Ra and BS in I(+) group were maintained at the same levels as S group and increased significantly by the glucagon infusion. Hyperaminoacidemia was observed after total pancreatectomy regardless of insulin treatment. Branched chain amino acids (BCAA) were significantly elevated in I(-) group but not in I(+) group. Glucagon infusion decreased almost all amino acids levels except BCAA in both groups. These results suggest that mechanism of hyperaminoacidemia observed in totally pancreatectomized dogs is the reduced amino acids uptake by the liver related to glucagon deficiency.

Amino Acids↗
PubMed1996

Effects of dietary protein restriction on regional amino acid metabolism in insulin-dependent diabetes mellitus.

We studied subjects with insulin-dependent diabetes mellitus (IDDM) and controls by administering primed continuous infusions of L-[1-13C,15N)]leucine and L-[2,3-13C2]alanine to measure whole body and forearm metabolism of these amino acids during ample protein intake and again after 4 wk of moderately restricted protein intake. Decreased rates of whole body protein degradation, leucine transamination, leucine oxidation, and increased forearm alanine release produced by dietary protein restriction occurred equivalently in IDDM subjects under short-term tightly managed glycemia and in controls. Dietary protein restriction did not affect whole body alanine appearance or forearm leucine appearance, disposal, or balance in IDDM subjects or controls. IDDM subjects differed from controls only in that normal forearm leucine balance was maintained at higher rates of leucine appearance and disposal. We conclude that IDDM subjects adapt normally to dietary protein restriction. Undernutrition during moderate protein deprivation in these patients likely occurs during episodes of poor glycemic control.

Alanine↗
PubMed1990

Glucose uptake and amino acid metabolism in perfused hearts from tumor-bearing rats.

The purpose of this study was to evaluate whether heart glucose metabolism can account for elevated heart oxygen consumption in a tumor-bearing host. This is the first report of altered metabolism in perfused hearts from tumor-bearing animals. Glucose, glycerol, lactate, and amino acid metabolism was examined under steady-state conditions in isolated perfused hearts from sarcoma-bearing rats and compared to the metabolism in hearts from starved (96 hr) and fed control rats. Heart dry weight was reduced by 10% in tumor-bearing rats and by 30% in starved rats when compared to freely fed control animals. Cardiac glucose uptake was decreased in tumor-bearing rats (206 +/- 33 mumoles/hr/g dry wt) compared to both starved (298 +/- 18) and fed control rats (293 +/- 25). Hearts from both fed and starved controls released lactate and glycerol at significant rates during perfusion which was not evident in hearts from tumor-bearing rats. The release of individual amino acids from working hearts during perfusion was different among the animal groups with a severe depression of both glutamine and alanine release in tumor-bearing rats. In starved rats alanine release was normal although glutamine release was depressed by more than 50%. The net release of all amino acids was lowest in hearts from tumor-bearing rats, intermediate in the starved animals, and highest in the control animals, while the nonmetabolized amino acids (phenylalanine, tyrosine, methionine) were released at increased rates only from tumor-host hearts, indicating an increased net breakdown of some cardiac proteins in tumor-bearing animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1994

Sulfur amino acid metabolism in Schizosaccharomyces pombe: occurrence of two O-acetylhomoserine sulfhydrylases and the lack of the reverse transsulfuration pathway.

The fission yeast Schizosaccharomyces pombe has a unique organization of sulfur amino acid metabolism: it has two distinct O-acetylhomoserine sulfhydrylases (homocysteine synthases). Similar to Enterobacteriaceae, S. pombe lacks cystathionine beta-synthase and cystathionine gamma-lyase-the enzymes of the reverse transsulfuration pathway, by which methionine is readily metabolized to cysteine-a likely effector in the sulfur metabolite repression system. Consequently no repression of sulfate assimilation is observed when methionine is added to the growth medium.

Amino Acids, Sulfur↗
PubMed2005

Direct effects of proteasome inhibitor AdaAhx3L3VS on protein and amino acid metabolism in rat skeletal muscle.

Proteasome inhibitors are novel potential drugs for therapy of many diseases, and their effects are not fully understood. We investigated direct effects of peptide vinylsulfone inhibitor AdaAhx3L3VS on protein and amino acids metabolism in rat skeletal muscle. Soleus and extensor digitorum longus muscles were incubated in a medium containing 30 micromol/l AdaAhx3L3VS or no inhibitors. Total proteolysis was determined according to the rates of tyrosine release into the medium during incubation. The rates of leucine oxidation and protein synthesis were evaluated during incubation in medium containing L-[1-14C]leucine. Amino acid concentrations in the medium were measured using HPLC. AdaAhx3L3VS decreased tyrosine release into the medium by 21 and 19 %, decreased leucine incorporation into proteins by 22 and 12 %, and increased leucine oxidation by 24 and 19 % in soleus and extensor digitorum longus muscles, respectively. The release of amino acids into the medium was reduced. We conclude that AdaAhx3L3VS significantly decreased proteolysis and protein synthesis and increased leucine oxidation.

Amino Acids↗
PubMed1989

Carbohydrate, lipid and amino acid metabolism of insulin-dependent diabetic patients regulated by an artificial beta-cell unit.

To characterize the effects of artificial beta-cell directed insulin therapy on carbohydrate, lipid and amino acid metabolism, five insulin-dependent diabetic patients were challenged with a 100-g glucose meal while on conventional (single or split mixed insulin injections) therapy and again after 72 hr on an artificial beta-cell unit. It was verified that the high levels of blood glucose of the conventionally treated diabetics were marked reduced toward normal by the artificial beta-cell therapy, while the blood lactate and pyruvate concentrations increased significantly to levels higher than in normal controls. The elevated levels of FFA, glycerol, and ketones in the diabetics under conventional therapy were entirely normalized during the artificial beta-cell regulation. Furthermore, the artificial beta-cell insulin therapy showed capable to restore the abnormalities in the blood profiles of alanine, glutamine and branched-chain amino acids, exceeding in some points the normal response. It was also detected hyperinsulinemia in the diabetics treated with the artificial beta-cell unit and no change in the pancreatic beta-cell function during this period of regulation, evidenced by low and unchanged blood levels of C-peptide. Marked suppression of pancreatic alpha-cell secretion was detected by the significant decrease of the hyperglucagonemia in the conventionally treated diabetics by the artificial beta-cell therapy. These studies reveal that the artificial beta-cell insulin therapy is capable of restoring to normal not only the abnormal glucose metabolism of conventionally treated diabetics, but also other substrate metabolism related to the lipid and protein homeostasis of the organism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1975

[Studies on the protein and amino acid metabolism of laying hens using 15N labeled casein. 4. Fecal excretion of nitrogen and amino acids, digestibility of crude protein and absorption of basic amino acids].

Generally, the faeces of laying hens fed 15N casein rations were found to contain equal proportions of TCE-precipitable and TCE-soluble nitrogen. Considerable variations were observed to occur between the 64 samples investigated (27%-75%) and no explanation was found to account for this fact. The content of basic amino acids in faecal proteins was found to differ considerably from that of the proteins in the intestinal contents. A high lysine content was found after the feeding of wheat. The present trial substantiated this result, provided the casein contained a certain proportion of non-available lysine. The apparent and true digestibility of dietary N was 88% or 91%, that of 15N (2nd and 6th day of experiment) and 92%. During the feeding of labelled casein a higher level of N labelling was found in the TCE-soluble portion of the faeces, whereas on the 8th to 12th day a higher level of labelling was observed in the TCE-precipitable portion of the faeces. The peak of 15N excretion occurred on the 3rd day of experiment. When 15N administration terminated the atom% 15N in the faeces and in urine was found to decrease rapidly approximating the initial level of labelling asymptotically.

Amino Acids↗
PubMedDate not supplied

[The effect of straw meal on the crude protein and amino acid metabolism and the digestibility of crude nutrients in broiler breeding hens. 3. Digestibility of amino acids].

In two experiments with colostomized broiler hens the influence of a straw meal supplement on the apparent digestibility of the amino acids of the ration and the 15N labelled basic amino acids in wheat was studied. In experiment 1 the animals received 120 g mixed feed plus 0, 20, 30 and 40 g straw meal per animal and day. The digestibility of the amino acids decreased on average from 86% to 83%, 80% and 79% with the growing straw intake. In contrast to the control variant, 20 g straw meal intake resulted in a significant decrease of digestibility for lysine, histidine, glycine, tyrosine, phenylalanine, cystine and methionine. 30 and 40 g straw meal reduced significantly the digestibility of all amino acids with the exception of arginine. The amino acid composition of the crude protein in faeces changed only very slightly due to the straw supplement. In experiment 2 15N labelled wheat was a component of the ration. Of the 15N labelled amino acids lysine, histidine and arginine, 88, 90 and 95% were apparently digested. The adaptation of the animals to straw meal intake did not change the digestibility of the amino acids.

Amino Acids↗
PubMed1987

Amino acid metabolism during the anabolic phase of severely burned patients: with special reference to sulphur amino acids.

Owing to the high content of cyst(e)ine and sulphated mucopolysaccharides in skin tissues, an increased demand for sulphur amino acids could be expected during the anabolic phase in severely burned patients. As a marker for sulphur amino acid deficiency, leucocyte glutathione, methionine and taurine concentrations and urinary excretion of sulphur amino acids and inorganic sulphate were followed in five severely burned patients during a 5-month period (1-6 months post injury). Reduced leucocyte concentrations of glutathione, methionine and taurine, and decreased urinary excretion of inorganic sulphate, methionine, cyst(e)ine and taurine were observed, and were most pronounced 2 or 3 months after injury. Simultaneously a minor decrease in urinary output and leucocyte concentration of branched-chain amino acids and serine were also found, whereas normal levels of glycine, threonine, and glutamine were registered. The episode of limited availability of sulphur amino acids coincides with the period of most intensive collagen and keratin resynthesis of burned skin tissue.

Amino Acids↗
PubMed2003

Beneficial effects of branched-chain amino acids on altered protein and amino acid metabolism in liver cirrhosis: evaluation in a model of liver cirrhosis induced in rats with carbon tetrachloride.

The effect of branched-chain amino acids (BCAA) on the metabolism of protein, amino acids and ammonia was examined in rats with cirrhosis, with a special emphasis on the efficacy of early administration of BCAA. Liver cirrhosis was induced in rats by intraperitoneal injections of carbon tetrachloride (CCl(4)). The rats were divided into three groups: early-, late- and untreated. The early- and late-treated groups were given BCAA rich food from the early and late stage of liver cirrhosis, while the untreated group was given standard food throughout. Concentrations of amino acids and ammonia in the plasma and the ornithine carbamyl transferase (OCT) activity in the liver were evaluated, and compared with control group after 15 weeks maintenance. Ammonia was significantly higher in the late- and untreated groups, but not in the early-treated group. BCAA, tyrosine, and methionine were significantly lower in the untreated and late-treated groups. Glutamine increased significantly in the un-, late- and early-treated groups. However, no significant differences were found among three groups. A significant difference was found in 3-methyl histidine (3-MH) between the early- and late-treated groups. This study suggests that the administration of BCAA from early stage of liver cirrhosis inhibits breakdown of protein and improves metabolism of protein, amino acids and ammonia.

Journal Article↗