Effect of sepsis on activity of pyruvate dehydrogenase complex in skeletal muscle and liver.
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Animals↗
Biomedical subjects
T C Vary
Publications and source records attributed to T C Vary.
Abnormal metabolic control in the septic multiple organ failure syndrome: pharmacotherapy for altered fuel control mechanisms.
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Animals↗
Pharmacologic modulation of increased release of gluconeogenic precursors from extra-splanchnic organs in sepsis.
The effect of sterile inflammation and sepsis on the release of lactate and amino acids by peripheral tissues was investigated by removing the splanchnic organs (liver and small intestines) from the circulation and monitoring changes in plasma substrates for 30 min. Functional hepatectomy was performed in rats 5-7 days following the intraperitoneal introduction of a fecal-agar pellet (1.5 ml) [sterile vs. Bacteriodes fragilis (10(8) CFU) + E. coli (10(3) CFU)]. Following functional hepatectomy, dichloroacetate, an activator of the pyruvate dehydrogenase complex, significantly inhibited both lactate and alanine release. L-cycloserine, an inhibitor of alanine aminotransferase, significantly (P less than .05) reduced alanine following hepatectomy. Methionine sulfoximine, an inhibitor of glutamine synthetase, significantly (P less than .005) decreased glutamine accumulation following functional hepatectomy in each of the conditions examined. Treatment with each of these drugs abolished the differences between control and sepsis following hepatectomy. These results demonstrate that alterations in the amino acid profiles during sepsis may be modulated in peripheral organs pharmacologically by utilizing known inhibitors of critical regulatory enzymes.
Alanine↗
Role of extra-splanchnic organs in the metabolic response to sepsis: effect of insulin.
The effect of sterile inflammation and sepsis on the release of lactate and amino acids by peripheral tissues was investigated in rats by removing the splanchnic organs (liver + small intestines) from the circulation and monitoring changes in blood metabolites over 30 min. Functional hepatectomy was performed in rats 5-7 days following the intraperitoneal introduction of a fecal-agar pellet (sterile vs. Bacteroides fragilis + E. coli). Lactate was significantly (P less than .05) increased in each of the conditions following hepatectomy but was raised to a significantly greater extent in sepsis (P less than .05). A similar response was observed for glutamine while alanine was only significantly (P less than .05) increased in sepsis following hepatectomy. Branched chain amino acids (BCAA) showed differential changes in sepsis compared to control. In control and sterile inflammation, functional hepatectomy was associated with significant decreases (P less than .05) in BCAA. In sepsis, BCAA were not decreased following hepatectomy and were significantly (P less than .05) elevated relative to control or sterile inflammation. Phenylalanine concentrations were not altered in control or sterile inflammation but were significantly elevated in sepsis (P less than .05). Insulin attenuated the accumulation of lactate and amino acids in fed control animals, following functional hepatectomy. However, in septic animals, insulin failed to prevent the rise in plasma lactate following hepatectomy.
Alanine↗
Inhibition of skeletal muscle protein synthesis in septic intra-abdominal abscess.
Chronic sepsis is always associated with profound wasting leading to increased release of amino acids from skeletal muscle. Net protein catabolism may be due to decreased rate of synthesis, increased rate of degradation, or both. To determine whether protein synthesis is altered in chronic sepsis, the rate of protein synthesis in vivo was estimated by measuring the incorporation of [3H]-phenylalanine in skeletal muscle protein in a chronic (5-day) septic rat model induced by creation of a stable intra-abdominal abscess using an E. coli + B. fragilis-infected sterile fecal-agar pellet as foreign body nidus. Septic rats failed to gain weight at rates similar to control animals, therefore control animals were weight matched to the septic animals. The skeletal muscle protein content in septic animals was significantly reduced relative to control animals (0.18 +/- 0.01 vs. 0.21 +/- 0.01 mg protein/gm wet wt; p less than 0.02). The rate of incorporation of [3H]-phenylalanine into skeletal muscle protein from control animals was 39 +/- 4 nmole/gm wet wt/hr or a fractional synthetic rate of 5.2 +/- 0.5%/day. In contrast to control animals, the fractional synthetic rate in septic animals (2.6 +/- 0.2%/day) was reduced by 50% compared to control animals (p less than 0.005). The decreased rate of protein synthesis in sepsis was not due to an energy deficit, as high-energy phosphates and ATP/ADP ratio were not altered. This decrease in protein synthesis occurred even though septic animals consumed as much food as control animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Abdomen↗
Metabolic effects of partial reversal of pyruvate dehydrogenase activity by dichloroacetate in sepsis.
The metabolic effects of dichloroacetate on carbohydrate metabolism were investigated in normal fed, sterile inflammatory, and chronic septic animals. Chronic sepsis, but not sterile inflammation, was associated with elevated plasma, liver, and skeletal muscle lactate concentrations. Sodium dichloroacetate significantly reduced both plasma and intracellular pyruvate and lactate concentrations in all conditions examined, while plasma glucose concentrations remained unchanged. Decreased tissue metabolite concentrations were associated with a significantly increased active pyruvate dehydrogenase complex in liver and skeletal muscle in each of the conditions examined. In liver, dichloroacetate fully activated (greater than 85%) the pyruvate dehydrogenase complex under all conditions. In skeletal muscle from chronic septic animals, the dichloroacetate-induced increases in active pyruvate dehydrogenase were significantly less than those observed in non-septic animals. The data suggest that although dichloroacetate can partially reverse the sepsis-induced effects on skeletal muscle pyruvate dehydrogenase activity, there may be additional regulatory factors in skeletal muscle from septic animals. The dichloroacetate stimulation of the pyruvate dehydrogenase activity may provide a pharmacological method for reducing the elevated lactate concentrations observed in chronic severe sepsis.
Abscess↗
Pharmacological reversal of abnormal glucose regulation, BCAA utilization, and muscle catabolism in sepsis by dichloroacetate.
Sepsis has been shown to decrease skeletal muscle glucose oxidation by inhibiting the pyruvate dehydrogenase activity (PDHa) and to increase proteolysis and use of branched-chain amino acids (BCAA). The effects of dichloroacetate (DCA), which reverses PDHa inhibition, were studied in skeletal muscle from a septic (S) rat model of intra-abdominal abscess (E. coli + B. fragilis) and compared to control (C) and sterile inflammatory abscess (I) animals. In one set of S, I, and C animals, DCA (1 mmol/kg) was injected intraperitoneally at 0, 30, and 60 min. Septic, but not I, rats had a twofold increase in skeletal muscle lactate concentrations over C, but no changes in pyruvate. After DCA, both lactate and pyruvate were reduced (p less than 0.001) to same level in S, I, and C. Skeletal muscle alanine was increased in S compared to I or C, but after DCA was reduced threefold in C, S, and I (p less than 0.001) suggesting that alanine synthesis may be impaired due to decreased pyruvate availability. Like alanine, skeletal muscle BCAA were increased in S compared to C, but not altered in I. Following DCA, BCAA levels in muscle from S were reduced (p less than 0.001) to values seen in C or I. Muscle phenylalanine content was significantly elevated in S (p less than 0.05) compared to C or I, but was reduced (p less than 0.05) after DCA in S but not in C or I. Decreased muscle phenylalanine associated with lowered BCAA suggests DCA may decrease septic muscle protein catabolism and/or enhance protein synthesis. Coupled with an increased PDHa and reduced lactate levels, this suggests that DCA may reverse the excess muscle catabolism and BCAA dependence of sepsis by increasing glucose and lactate oxidation and may be a useful therapeutic modality.
Acetates↗
Advanced signal-processing method for the detection, localization, and quantification of acute myocardial ischemia.
In this study of a canine heart model of localized reversible ischemia, a computer-based single-processing method is developed to detect and localize the epicardial projections of ischemic myocardial electrocardiograms (ECGs) during the cardiac activation, rather than the repolarization, phase. This is done by transforming ECG signals from an epicardial sensor array into the multichannel spectral domain and identifying three decision variables: (1) the frequency in hertz of the spectral peak (f0), its frequency band width 50% below the peak value (w0), and the maximum eigenvalue difference of the ECG signal's autocorrelation matrix (e0). With use of the histograms of the f0, w0, and e0 parameters of 3256 ECGs from normal and 957 from ischemic areas of myocardium obtained from 12 dogs, it was possible to predict ischemia in a new test group of nine animals from a Neyman-Pearson (NP) test in which the threshold probabilities of detecting ischemia for each decision variable are compared with those of detecting normality. Quantification of each sensor area by the NP tests revealed that, compared with the control, ECG spectra with decreased F0 and w0 and increased e0 relative to their respective thresholds had increased myocardial lactate (p less than 0.01), decreased adenosine triphosphate (ATP) (p less than 0.05), and reduced creatine phosphate (p less than 0.01). Prediction of f0 (p less than 0.0006) as a continuous variable could be obtained from the regression of the myocardial levels of ATP plus creatine phosphate, which demonstrated that this decision variable appears to directly reflect myocardial energetics. It appears that an advanced signal-processing method for ECG array data can be used to detect, localize, and quantify reversible myocardial ischemia.
Adenosine Triphosphate↗
Modulation of pyruvate dehydrogenase kinase activity in cultured hepatocytes by glucagon and n-octanoate.
The activity of pyruvate dehydrogenase kinase in extracts of mitochondria from rat hepatocytes cultured for 21 h in medium 199 was increased 2.5-fold by the presence of 55 nM-glucagon and 1 mM-sodium n-octanoate in the culture medium. The change was comparable with that induced in vivo by 48 h starvation. The potential contribution of branched-chain complex to estimates of PDH-complex activity in rat liver mitochondria has been defined.
Animals↗
A biochemical basis for depressed ketogenesis in sepsis.
Several investigators have demonstrated a diminished rate of ketogenesis during inflammatory or infectious states despite the availability of free fatty acids supplied to the liver. The biochemical mechanism for this effect is unknown. Malonyl-CoA has been proposed to be a regulator of ketogenesis. Malonyl-CoA levels are low in states of rapid ketogenesis such as starvation or diabetes and high in states of reduced ketogenesis such as carbohydrate feeding. In the present study, the effect of an intra-abdominal abscess on the level of hepatic malonyl-CoA was investigated in four groups of animals (fed control, sterile inflammation, small chronic septic abscess, large chronic septic abscess). Liver samples were frozen in situ 5 days following the intraperitoneal introduction of a rat-fecal agar pellet inoculated with a known bacterial flora which generated an abscess [sterile inflammatory; B. fragilis 10(8)/ml + E. coli 10(2)/ml (small, 0.8 ml or large, 1.5 ml) abscess pellet]. The level of malonyl-CoA in normal fed rats was 5.0 +/- 0.6 nmol/gm wet wt (n = 9). The malonyl-CoA level was not altered in animals with a sterile inflammation. However, hepatic malonyl-CoA levels were significantly increased in small (10 +/- 1 nmole/gm wet wt) (p less than 0.05; n = 9) or large (12 +/- 1 nmol/gm wet wt) (p less than 0.01; n = 14) septic abscess rats compared to control fed and sterile inflammatory rats. Hepatic ketone bodies (beta-hydroxybutyrate and acetoacetate) did not increase in sepsis over control or sterile inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetyl Coenzyme A↗
Effect of sepsis on activity of pyruvate dehydrogenase complex in skeletal muscle and liver.
The effect of chronic sepsis on the concentration of active pyruvate dehydrogenase complex has been investigated in liver and skeletal muscle of normal, sterile inflammatory, and chronic septic (small and large abscess) animals. Hyperdynamic sepsis was induced by the intraperitoneal introduction of a rat fecal-agar pellet of known size and bacterial composition (Escherichia coli + Bacteroides fragilis). Total pyruvate dehydrogenase complex activity was not altered in either liver or skeletal muscle in any of the conditions studied. In hepatic tissue, sterile inflammation increased the proportion of active complex 2.5-fold compared with control. The same increase in the concentration of active complex was observed in animals with a small abscess. When the abscess size was increased (large abscess), the concentration of active complex was decreased relative to sterile inflammatory or small abscess septic animals. In contrast to liver, sterile inflammation did not alter the proportion of active complex in skeletal muscle. Sepsis (either small or large septic abscess) resulted in threefold decrease in the concentration of active complex relative to control or sterile inflammatory animals. Changes in the concentration of active complex did not appear to be dependent on the ATP/ADP concentration ratio or tissue pyruvate levels but were consistent with changes in the acetyl-coenzyme A-to-coenzyme A concentration ratio. The mechanism responsible for altered concentration of active complex may be mediated through changes in the activity of the pyruvate dehydrogenase kinase, secondary to alterations in the effector concentration ratios.
Abscess↗
Inhibition of carnitine palmitoyl-CoA transferase activity and fatty acid oxidation by lactate and oxfenicine in cardiac muscle.
High concentrations of lactate and oxfenicine inhibit fatty acid oxidation in cardiac muscle. The site of this inhibition was investigated in isolated perfused rat hearts. In hearts perfused with glucose (11 mM) and [U-14 C]palmitate (1.0 mM), addition of 5 mM lactate caused a 38% reduction in 14CO2 production. Tissue levels of long-chain acyl carnitine decreased suggesting that inhibition occurred at either fatty acyl CoA synthetase or carnitine-acyl CoA transferase. Cytosolic levels of acyl-CoA are low compared with mitochondrial levels and changes in acyl-CoA within the cytosolic compartment cannot be estimated directly. Consequently, the rate of conversion of 14C-palmitate to neutral lipids was used as an indicator of cytosolic acyl CoA levels. Lactate caused a 100% increase in 14C-fatty acid conversion to triglycerides suggesting that cytosolic levels of acyl-CoA increased in association with decreased acyl-carnitine. This indicates that lactate inhibited FFA oxidation at the level of carnitine-acyl CoA transferase. Oxfenicine (2 mM) reduced fatty acid oxidation by 45%, decreased acyl-carnitine levels by 80%, and increased conversion of 14C-palmitate to neutral lipids by 44%, suggesting that oxfenicine also inhibits fatty acid oxidation at the level of carnitine-acyl CoA transferase. These data further indicate that carnitine-acyl CoA transferase is an important site of control in the pathway of fatty acid oxidation.
Acyl Coenzyme A↗
Regulation of pyruvate dehydrogenase complex activity during myocardial ischemia.
The effect of ischemia on the concentration of active pyruvate dehydrogenase (PDH) complex has been investigated in glucose-perfused hearts of normal rats fed a normal diet or a high-fat diet or starved for 48 hr and in hearts from alloxan-diabetic rats. Global ischemia induced by low flow (approximately equal to 1 ml/min) lowered the concentration of active complex under most conditions employed. Parallel studies of the effect of anoxia and of potassium arrest of the heart indicated that the effect of low-flow ischemia may result from decreased mechanical activity of the heart as a consequence of tissue hypoxia; the enzymatic mechanism may be activation of PDH kinase by increased reduction of mitochondrial NAD. In hearts of normal rats fed a normal diet, global ischemia induced by zero flow increased the concentration of active complex. Evidence is given that this may result from a combination of anoxia and acidosis. In aerobic perfusions, concentrations of active complex were ranked in the order: normal diet greater than high-fat diet greater than 48-hr starved greater than alloxan-diabetic. This order was maintained when the concentration of active complex was lowered by global ischemia induced by zero flow.
Adenosine Diphosphate↗
Molecular mechanisms regulating myocardial glucose oxidation.
In heart muscle regulation of pyruvate dehydrogenase (PDH) complex activity by reversible phosphorylation is the major determinant of glucose oxidation under physiological conditions and in diabetes. Altered mitochondrial concentrations of effectors of PDH kinase and phosphatase (metabolites, Ca2+, H+) appear to explain effects of oxidation of lipid fuels, myocardial contraction and ischaemia on PDH complex activity. The effects of diabetes and starvation are mediated in addition by protein(s) which increase the activity of PDH kinase. End product inhibition by NADH may be important in ischaemia.
Animals↗
The effect of ischaemia on the activity of pyruvate dehydrogenase complex in rat heart.
The effect of ischaemia on the concentration of active pyruvate dehydrogenase complex has been investigated in glucose perfused hearts of normal rats fed a normal diet or a high fat diet or starved for 48 h; and in hearts from alloxan-diabetic rats. Global ischaemia induced by low flow (approx. 1 ml/min) lowered the concentration of active complex under most of the experimental conditions employed. Parallel studies showed that anoxia and K+ arrest of the heart had effects similar to that of ischaemia and suggested that hypoxia and decreased mechanical activity of the heart may be responsible for effects of low flow ischaemia. Evidence is reviewed that the effects of low flow ischaemia, K+ arrest and anoxia may be mediated through activation of pyruvate dehydrogenase kinase by increased reduction of mitochondrial NAD+. In hearts of normal rats on a normal diet, global ischaemia induced by zero flow and regional ischaemia induced by coronary artery ligation increased the concentration of active complex. Evidence is given that this may result from a combination of anoxia and acidosis. In aerobic perfusions at 60 mmHg, concentrations of active complex were ranked in the order: normal diet greater than high fat diet greater than 48 h starved greater than alloxan diabetic. This order was maintained when the concentration of active complex was increased by perfusion at 120 mmHg or lowered by global ischaemia induced by zero flow.
Adenosine Triphosphate↗
Fatty acid and glucose utilization in isolated, working newborn pig hearts.
The effects of exogenous fatty acids on glucose uptake were assessed in isolated, working newborn pig hearts in which great vessel pressures were controlled (mean 55 mmHg) and oxygenated nutrient buffer was recirculated through the heart for 30 or 60 min. When palmitate (1.5 mM) or octanoate (1.0 mM) were added to buffer containing 10 mM glucose and 100 mU insulin/ml, glucose uptake, as measured by 3H2O production from D-[2-3H]glucose, was suppressed to less than one-half that observed when glucose alone was present. Increased tissue levels of glucose 6-phosphate, fructose 6-phosphate, and citrate following perfusion in the presence of exogenous fatty acids were consistent with decreased glycolytic activity due to inhibition of phosphofructokinase. Measurements of carnitine in perfused and unperfused hearts indicated that total carnitine levels in neonatal hearts are similar to those of adult pigs. Increased tissue levels of long-chain acyl carnitine, acetyl carnitine, and citrate in hearts perfused with palmitate and glucose in combination with extensive fatty acid uptake and marked suppression of glycolysis indicated that the newborn pig heart is capable of utilizing fatty acids as a primary energy source.
Animals↗
Sodium dependence of carnitine transport in isolated perfused adult rat hearts.
In heart muscle, the intracellular carnitine concentration is approximately 40 times higher than the plasma carnitine concentration, suggesting the existence of an active transport process. At physiological serum carnitine concentrations (44 microM), 80% of total myocardial carnitine uptake occurs via a carrier-mediated transport system. The mechanism of this carrier-mediated transport was studied in isolated perfused rat hearts. Carnitine transport showed an absolute dependence on the extracellular sodium concentration. The rate of carnitine transport was linearly related to the perfusate sodium concentration at every perfusate carnitine concentration examined (15-100 microM). Total removal of extracellular sodium completely abolished the carrier-mediated transport. Decreasing the perfusate potassium concentration from a control of 5.9 to 0.6 mM stimulated transport by 35%, whereas increasing the extracellular potassium concentration from 5.9 to 25 mM reduced transport by 60%. The carrier-mediated transport was inversely proportional to the extracellular potassium concentration. Acetylcholine (10(-3) M), isoproterenol (10(-7) M), or ouabain (10(-3) did not alter the rate of carnitine transport. Addition of tetrodotoxin (10(-5) stimulated carnitine transport by about 40%, while gramicidin S (5 X 10(-6) M) decreased uptake by about 18% relative to control. The data provide evidence that carnitine transport by cardiac cells occurs by a Na+-dependent cotransport mechanism that is dependent on the Na+ electrochemical gradient.
Acetylcholine↗
Control of myocardial levels of CoA and carnitine.
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Animals↗