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PubMed1988

Cytoplasmic enzyme activities involved in energy and amino acid metabolism in pathological human renal cortex.

Enzyme levels of lactate dehydrogenase (LDH), alpha-hydroxybutyrate dehydrogenase (HBDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were measured in the cytosol of renal cortex samples from either normal and pathologic kidney tissue. The mean enzyme activity values, expressed in Units per gram of cytosolic protein decreased in the following order: normal cortex (LDH = 4,299 +/- 654; AST = 522 +/- 101; ALT = 197 +/- 44). chronic pyelonephritis (LDH = 2,360 +/- 876; AST = 297 +/- 117; ALT = 90 +/- 48), hydronephrosis (LDH = 2,208 +/- 1,264; AST = 279 +/- 165; ALT = 82 +/- 61), pyonephrosis (LDH = 1,410 +/- 596; AST = 158 +/- 69; ALT = 23.4 +/- 16.4) and renal tuberculosis (LDH = 1,149 +/- 481; AST = 93 +/- 34; ALT = 5.6 +/- 2.8). The decrease in the enzyme activities paralleled tissue damage and it was shown to affect cellular functionality in relation with energy and amino acid metabolism.

Alanine Transaminase↗
PubMedDate not supplied

Local effect of burn injury on glucose and amino acid metabolism by skeletal muscle.

Previous studies from our laboratory demonstrated that there is a difference in glucose metabolism by skeletal muscles from the burned versus unburned regions of the body. To further investigate the effect of proximity to the burn wound on muscle metabolism, in vitro glucose uptake as well as lactic and amino acid releases by soleus muscles, were studied 3 days following a 3-second scald burn on one hind limb of the rat. No differences in glucose uptake or lactic and amino acid releases were observed between soleus from the unburned limb of burned rats and that of controls. In comparison to these two groups, soleus from the burned limb took up 125% more glucose (p less than 0.001), and released 80% more lactic acid (p less than 0.01), 229% more alanine (p less than 0.001), 84% more glutamic acid (p less than 0.01), and over 36% more glutamine (p less than 0.05). The relatively enhanced release of lactic acid by soleus muscle from the burned limb was reduced but not eliminated by the omission of glucose from the medium. Simultaneously, the omission of glucose had no effect on the release of alanine, glutamic acid, and glutamine by the burned limb soleus. The data indicate that a mild thermal injury stimulates glucose utilization and enhances amino acid release by skeletal muscle from the burned region. Since such an effect is absent in muscle from the contralateral unburned region of the same animal, the changes are not likely to be mediated by systemic alterations in the metabolic and endocrine environment. The persistence of an enhanced amino acid release in the presence of varying glycolytic rates suggests that the burn-induced local alterations in amino acid metabolism by skeleton muscle are independent of coincident changes in glucose utilization.

Amino Acids↗
PubMed1988

Glucose and amino acid metabolism in aging man: differential effects of insulin.

Insulin is a major regulator of glucose and body protein homeostasis, both of which demonstrate age-related changes. To clarify insulin's role in these age-related changes and to compare age-related glucose and protein homeostatic responses, insulin-mediated aspects of glucose and amino acid metabolism were simultaneously examined in healthy postabsorptive young (n = 5, mean age, 25 years) and elderly (n = 5, mean age, 76 years) men. Primed constant infusions of L-[1-13C]leucine and L-[15N]alanine were administered during a basal period (0 to 180 minutes) and during four separate single rate euglycemic insulin infusions (180 to 360 minutes). Steady state insulin concentrations were 16 +/- 1, 29 +/- 3, 75 +/- 5, and 2407 +/- 56 microU/mL in the young and 23 +/- 4, 37 +/- 8, 96 +/- 11 and 3,357 +/- 249 microU/mL in the elderly at the different insulin infusion rates of 6, 10, 30, and 400 mU mU.m-2.min-1, respectively. For the 6 and 10 mU insulin infusion rates, a primed, constant infusion of [6,6 - 2H2]glucose permitted quantitation of hepatic glucose production. Glucose disposal rates adjusted for lean body mass (LBM) were lower in the elderly than in the young at the 6, 10, and 30 mU insulin infusion rates and similar in the two age groups in the 400 mU studies. Insulin dose-dependent reductions occurred in eight of ten plasma amino acids and were not influenced by age. There was an insulin dose-dependent reduction in plasma leucine flux which was similar in both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1977

[Studies on the protein and amino-acid metabolism of laying hens using 15N-labelled casein. 15N-incorporation into N-fractions and amino acids of various parts of the body].

Four colostomized Leghorn hens were fed, during 6 days, 15N-labelled casein as sole protein source. Two animals were slaughtered 48 hours, the other two 144 hours after the last 15N-application. The share of TCE-soluble N in total N averaged 16% for the body parts analysed, i.e. meat, bone, liver, kidneys, oviducts, residual viscera and other. The variation of the lysine, histidine and arginine levels in the body parts ranged from 3.6 to 7.9 g, 1.1. to 3.7 g and 6.4 to 7.4 g in 16.7 g hydrolysate N, respectively. Except for feathers, the analysed body parts contained and excess amount of heavy nitrogen. The degree of labelling was found to depend on the time of slaughtering after the tracer application. In the liver and in the oviduct being metabolically active organs, the 15N-excess in the total N fraction decreased by 45% between the 2nd and the 6th days after 15N-feeding, whilst in the meat it went down by 20%. The decline of the 15N-concentration in the TCE-soluble N compounds was faster than in the total N-fraction. Out of the body samples analysed, the lysine of the liver having 0.26 atom % 15N-excess was found to be more strongly labelled in hens 1 and 2. The amino acid arginine reached about the same level of labelling, the 15N-frequency of histidine being the lowest.

Amino Acids↗
PubMed1976

Effects of brief starvation on muscle amino acid metabolism in nonobese man.

A reduction in the release of substrate amino acids from skeletal muscle largely explains the decrease in gluconeogenesis characterizing prolonged starvation. Brief starvation is associated with an increase in gluconeogenesis, suggesting increased release of amino acids from muscle. In the present studies, accelerated amino acid release from skeletal muscle induced by brief starvation was sought to account for the accompanying augmentation of gluconeogenesis. To do this amino acid balance across forearm muscles was quantified in 15 postabsorptive (overnight fasted) subjects and in 7 subjects fasted for 60 h. Fasting significantly reduced basal insulin (11.3-7.5 muU/ml) and increased glucagon (116-134 pg/ml). Muscle release of the principal glycogenic amino acids increased. Alanine release increased 59.4%. The increase in release for all amino acids averaged 69.4% and was statistically significant for threonine, serine, glycine, alanine, alpha-aminobutyrate, methionine, tyrosine, and lysine. Thus, with brief starvation, muscle release of glycogenic amino acids increases strikingly. This contrasts with the reduction of amino acid release characterizing prolonged starvation. The adaptation of peripheral tissue metabolism to brief starvation is best explained by the decrease in insulin.

Adult↗
PubMed1987

Isolated perfused rat liver: an experimental model for studies on ammonium and amino acid metabolism.

Isolated perfused rat liver is a well-established experimental model for studies on hepatic amino acid and ammonia metabolism. Some aspects and modifications of the liver-perfusion technique are discussed. Perfusion studies with the intact liver have the fundamental advantage that the structural and functional organization of the liver is preserved; however, the experimental system is more complex in view of subcellular and intercellular compartmentation and the recently demonstrated metabolic interactions of different cell populations at the acinar level. These problems of complexity by compartmentation can be largely solved by introducing further techniques such as organ spectrophotometry, the retrograde/antegrade perfusion technique, use of micro-oxygen-electrodes, use of selective inhibitors, radiolabeled compounds, different fractionation techniques of the liver tissue. By means of these approaches, intracellular events can be followed up not only indirectly by analyzing the composition of the perfusate before and after a liver passage, but also directly in the different subcellular and subacinar compartments of a structurally and metabolically intact liver.

Amino Acids↗
PubMed2004

Reducing plasma HIV RNA improves muscle amino acid metabolism.

We reported (Yarasheski KE, Zachwieja JJ, Gischler J, Crowley J, Horgan MM, and Powderly WG. Am J Physiol Endocrinol Metab 275: E577-E583, 1998) that AIDS muscle wasting was associated with an inappropriately low rate of muscle protein synthesis and an elevated glutamine rate of appearance (Ra Gln). We hypothesized that high plasma HIV RNA caused dysregulation of muscle amino acid metabolism. We determined whether a reduction in HIV RNA (> or =1 log) increased muscle protein synthesis rate and reduced R(a) Gln and muscle proteasome activity in 10 men and 1 woman (22-57 yr, 60-108 kg, 17-33 kg muscle) with advanced HIV (CD4 = 0-311 cells/microl; HIV RNA = 10-375 x 10(3) copies/ml). We utilized stable isotope tracer methodologies ([13C]Leu and [15N]Gln) to measure the fractional rate of mixed muscle protein synthesis and plasma Ra Gln in these subjects before and 4 mo after initiating their first or a salvage antiretroviral therapy regimen. After treatment, median CD4 increased (98 vs. 139 cells/microl, P = 0.009) and median HIV RNA was reduced (155,828 vs. 100 copies/ml, P = 0.003). Mixed muscle protein synthesis rate increased (0.062 +/- 0.005 vs. 0.078 +/- 0.006%/h, P = 0.01), Ra Gln decreased (387 +/- 33 vs. 323 +/- 15 micromol.kg fat-free mass(-1).h(-1), P = 0.04), and muscle proteasome chymotrypsin-like catalytic activity was reduced 14% (P = 0.03). Muscle mass was only modestly increased (1 kg, P = not significant). We estimated that, for each 10,000 copies/ml reduction in HIV RNA, approximately 3 g of additional muscle protein are synthesized per day. These findings suggest that reducing HIV RNA increases muscle protein synthesis and reduces muscle proteolysis, but muscle protein synthesis relative to whole body protein synthesis rate is not restored to normal, so muscle mass is not substantially increased.

Adult↗
PubMed1989

Acute effects of insulin-like growth factor I on glucose and amino acid metabolism in the awake fasted rat. Comparison with insulin.

To elucidate the acute metabolic actions of insulin-like growth factor I (IGF-I), we administered a primed (250 micrograms/kg), continuous (5 micrograms/kg.min) infusion of human recombinant (Thr 59) IGF-I or saline to awake, chronically catheterized 24-h fasted rats for 90 min. IGF-I was also infused while maintaining euglycemia (glucose clamp technique) and its effects were compared to those of insulin. IGF-I infusion caused a twofold rise in IGF-I levels and a 75-85% decrease in plasma insulin. When IGF-I alone was given, plasma glucose fell by 30-40 mg/dl (P less than 0.005) due to a transient twofold increase (P less than 0.05) in glucose uptake; hepatic glucose production and plasma FFA levels remained unchanged. IGF-I infusion with maintenance of euglycemia produced a sustained rise in glucose uptake and a marked stimulation of [3-3H]glucose incorporation into tissue glycogen, but still failed to suppress glucose production and FFA levels. IGF-I also produced a generalized 30-40% reduction in plasma amino acids, regardless of whether or not hypoglycemia was prevented. This was associated with a decrease in leucine flux and a decline in the incorporation of [1-14C]leucine into muscle and liver protein (P less than 0.05). When insulin was infused in a dosage that mimicked the rise in glucose uptake seen with IGF-I, nearly identical changes in amino acid metabolism occurred. However, insulin suppressed glucose production by 65% and FFA levels by 40% (P less than 0.001). Furthermore, insulin was less effective than IGF-I in promoting glycogen synthesis. We conclude that (a) IGF-I produces hypoglycemia by selectively enhancing glucose uptake; (b) IGF-I is relatively ineffective in suppressing hepatic glucose production or FFA levels; and (c) IGF-I, like insulin, lowers circulating amino acids by reducing protein breakdown rather than by stimulating protein synthesis. Thus, IGF-I's metabolic actions in fasted rats are readily distinguished from insulin.

Amino Acids↗
PubMed1978

Effect of 6-hydroxydopamine on brain and blood catecholamine, ammonia, and amino acid metabolism in rats subjected to high pressure oxygen induced convulsions.

Effects of 6-hydroxydopamine (6-OHDA) on rat brain and blood adrenaline (A), noradrenaline (NA), ammonia (NH3), gamma-aminobutyric acid (GABA), and amino acid metabolism prior to and after high pressure oxygen (OHP) induced convulsions have been studied. 6-OHDA reduces GABA and glutamate (Glu) rior to OHP exposure in rat brain so that the concentration is even equal to that seen in nondrugged animals after convulsion. Concomitantly, 6-OHDA reduces the latency of OHP-induced convulsion significantly, and increases brain NH3, glutamine, and asparagine significantly. Although 6-OHDA, in increasing dosage, elevates blood A concentration, convulsion produces a significant further increase in A. Blood NA was not significantly changed in drugged, convulsed animals and was much less than blood NA concentrations in nondrugged convulsed animals. Increasing doses of 6-OHDA also increase NH3 in the blood significantly and convulsion increases its concentration further. Latency of convulsion seems to be related to certain monoamine levels since in some drugged animals where A and total catecholamines are still reduced 96 h after the first of two doses of 6-OHDA, NA concentrations are recovered to relatively normal and the convulsion latency time is also increased although it remains significantly abbreviated from undrugged animals' convulsion time. Low brain GABA levels seem to be a prime effector of convulsive activity.

Amino Acids↗
PubMed1988

[Energy and amino acid metabolism in the human brain under Disoprivan anesthesia with various paCO2 values].

Propofol like thiopental and etomidate, suppresses cortical electrical activity in a dose-related manner, which leads to a 36% decrease in cerebral oxygen uptake and a 51% decrease in cerebral blood flow after an induction dose of 2 mg/kg followed by a maintenance dose of 0.2 mg/kg per min. In this study, the effects of propofol and varying paCO2 values on cerebral energy and amino acid metabolism were examined. METHODS. Eleven male patients between 49 and 63 years of age who were about to undergo coronary artery bypass surgery were studied. Measurements were performed with the patient awake (I), during steady-state maintenance anesthesia after propofol 2 mg/kg as an induction dose with 0.2 mg/kg per min by infusion with normocapnia (paCO2 39.9 +/- 3.1 mm Hg) (II), during hypocapnia (paCO2 29.9 +/- 2.6 mmHg) (III), and during hypercapnia (paCO2 50.6 +/- 3.3 mmHg) (IV). Cerebral blood flow was measured using the argon wash-in technique. A catheter was advanced into the superior bulb of the right internal jugular vein for measurement of cerebral oxygen, glucose, lactate, and amino acid uptake and release, which were calculated by multiplying the arterial-cerebral venous oxygen and substrate difference by the cerebral blood flow. Lactate/glucose index was calculated from the equation. Formula: see text. where a-vD lactate and a-vD glucose represent the arterial-cerebral venous substrate differences in mmol/l. Cerebral electrical activity was recorded by Fourier analysis of the EEG.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed2006

The case for regulating indispensable amino acid metabolism: the branched-chain alpha-keto acid dehydrogenase kinase-knockout mouse.

BCAAs (branched-chain amino acids) are indispensable (essential) amino acids that are required for body protein synthesis. Indispensable amino acids cannot be synthesized by the body and must be acquired from the diet. The BCAA leucine provides hormone-like signals to tissues such as skeletal muscle, indicating overall nutrient sufficiency. BCAA metabolism provides an important transport system to move nitrogen throughout the body for the synthesis of dispensable (non-essential) amino acids, including the neurotransmitter glutamate in the central nervous system. BCAA metabolism is tightly regulated to maintain levels high enough to support these important functions, but at the same time excesses are prevented via stimulation of irreversible disposal pathways. It is well known from inborn errors of BCAA metabolism that dysregulation of the BCAA catabolic pathways that leads to excess BCAAs and their alpha-keto acid metabolites results in neural dysfunction. In this issue of Biochemical Journal, Joshi and colleagues have disrupted the murine BDK (branched-chain alpha-keto acid dehydrogenase kinase) gene. This enzyme serves as the brake on BCAA catabolism. The impaired growth and neurological abnormalities observed in this animal show conclusively the importance of tight regulation of indispensable amino acid metabolism.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1984

Amino acid metabolism in the brain with convulsive disorders. Part 2: The effects of anticonvulsants on convulsions and free amino acid patterns in the brain of El mouse.

To elucidate the changes of free amino acid patterns in brains of El mice induced by several anticonvulsants, the free amino acid levels in brains were measured by an amino acid autoanalyzer 24 hours after intraperitoneal injection of PB, PHT or vitamin B6 or subcutaneous injection of ACTH. Compared to the preconvulsion group, the total free amino acid level increased in the ACTH group clearly. In the PB group, the levels of threonine, glutamine, lysine, histidine and homocarnosine increased and that of ornithine decreased; in the PHT group, an increase of glutamine and histidine and a decrease of beta-alanine and ornithine were observed; in the ACTH group, an increase of aspartic acid, threonine, serine, glutamic acid, glutamine, alanine and GABA and a decrease of cystathionine and ornithine were also observed; and in the vitamin B6 group, an increase of taurine and a decrease of cystathionine were recognized. These facts suggest that the sedative activity of these drugs except ACTH might be partially explained by the increase of inhibitory amino acids in the brain, such as glutamine, homocarnosine and taurine, and that of ACTH by the dehydration of the brain, resulting in concentration of many free amino acids.

Adrenocorticotropic Hormone↗
PubMed1975

[Studies on the protein and amino acid metabolism of laying hens using 15N labeled casein. 2. 15N incorporation into the N fractions and basic amino acids of the hen stomach and into the contents of the crop and stomach].

4 colostomated laying hens received 15N labelled casein as sole protein source for a period of 6 days. Two birds each were slaughtered on the 8th and 12th day of experiment. 23.5% of the total N in the glandular stomach and the gizzard were TCE soluble. The amino acid composition of the gastric proteins was broader than that of the proteins of flesh, with the exception of lysine and histidine. The atom % 15N' of the N of the stomach was roughly the same as that of the protein N; the level of labelling in the TCE soluble N fraction was only slightly higher. 2 and 6 days after the final administration of tracer N an appreciable proportion of 15N was found in the N fractions and in the basic amino acids contained in the crop and the stomach. From this is may be concluded that a considerable portion of the N-containing substances previously absorbed were secreted into the lumen of the crop and the stomach.

Amino Acids↗