Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.2 (PDK1)
 2,238 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart was decreased by alloxan-diabetes or by perfusion with media containing acetate, n-octanoate or palmitate. The total activity of the dehydrogenase was unchanged. 2. Pyruvate (5 or 25mM) or dichloroacetate (1mM) increased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart, presumably by inhibiting the pyruvate dehydrogenase kinase reaction. Alloxan-diabetes markedly decreased the proportion of active dehydrogenase in hearts perfused with pyruvate or dichloroacetate. 3. The total activity of pyruvate dehydrogenase in mitochondria prepared from rat heart was unchanged by diabetes. Incubation of mitochondria with 2-oxo-glutarate plus malate increased ATP and NADH concentrations and decreased the proportion of active pyruvate dehydrogenase. The decrease in active dehydrogenase was somewhat greater in mitochondria prepared from hearts of diabetic rats than in those from hearts of non-diabetic rats. Pyruvate (0.1-10 mM) or dichloroacetate (4-50 muM) increased the proportion of active dehydrogenase in isolated mitochondria presumably by inhibition of the pyruvate dehydrogenase kinase reaction. They were much less effective in mitochondria from the hearts of diabetic rats than in those of non-diabetic rats. 4. The matrix water space was increased in preparations of mitochondria from hearts of diabetic rats. Dichloroacetate was concentrated in the matrix water of mitochondria of non-diabetic rats (approx. 16-fold at 10 muM); mitochondria from hearts of diabetic rats concentrated dichloroacetate less effectively. 5. The pyruvate dehydrogenase phosphate phosphatase activity of rat hearts and of rat heart mitochondria (approx. 1-2 munit/unit of pyruvate dehydrogenase) was not affected by diabetes. 6. The rate of oxidation of [1-14C]pyruvate by rat heart mitochondria (6.85 nmol/min per mg of protein with 50 muM-pyruvate) was approx. 46% of the Vmax. value of extracted pyruvate dehydrogenase (active form). Palmitoyl-L-carnitine, which increased the ratio of [acetyl-CoA]/[CoA] 16-fold, inhibited oxidation of pyruvate by about 90% without changing the proportion of active pyruvate dehydrogenase.
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PMID:Regulation of pyruvate dehydrogenase in rat heart. Mechanism of regulation of proportions of dephosphorylated and phosphorylated enzyme by oxidation of fatty acids and ketone bodies and of effects of diabetes: role of coenzyme A, acetyl-coenzyme A and reduced and oxidized nicotinamide-adenine dinucleotide. 18 Sep 74

1. The proportion of active (dephosphorylated) pyruvate dehydrogenase in rat heart mitochondria was correlated with total concentration ratios of ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA. These metabolites were measured with ATP-dependent and NADH-dependent luciferases. 2. Increase in the concentration ratio of NADH/NAD+ at constant [ATP]/[ADP] and [acetyl-CoA]/[CoA] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between mitochondria incubated with 0.4mM- or 1mM-succinate and mitochondria incubated with 0.4mM-succinate+/-rotenone. 3. Increase in the concentration ratio acetyl-CoA/CoA at constant [ATP]/[ADP] and [NADH][NAD+] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between incubations in 50 micrometer-palmitotoyl-L-carnitine and in 250 micrometer-2-oxoglutarate +50 micrometer-L-malate. 4. These findings are consistent with activation of the pyruvate dehydrogenase kinase reaction by high ratios of [NADH]/[NAD+] and of [acetyl-CoA]/[CoA]. 5. Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA.
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PMID:Diabetes and the control of pyruvate dehydrogenase in rat heart mitochondria by concentration ratios of adenosine triphosphate/adenosine diphosphate, of reduced/oxidized nicotinamide-adenine dinucleotide and of acetyl-coenzyme A/coenzyme A. 19 89

1. The conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active (dephosphorylated) complex by pyruvate dehydrogenase phosphate phosphatase is inhibited in heart mitochondria prepared from alloxan-diabetic or 48h-starved rats, in mitochondria prepared from acetate-perfused rat hearts and in mitochondria prepared from normal rat hearts incubated with respiratory substrates for 6 min (as compared with 1 min). 2. This conclusion is based on experiments with isolated intact mitochondria in which the pyruvate dehydrogenase kinase reaction was inhibited by pyruvate or ATP depletion (by using oligomycin and carbonyl cyanide m-chlorophenylhydrazone), and in experiments in which the rate of conversion of inactive complex into active complex by the phosphatase was measured in extracts of mitochondria. The inhibition of the phosphatase reaction was seen with constant concentrations of Ca2+ and Mg2+ (activators of the phosphatase). The phosphatase reaction in these mitochondrial extracts was not inhibited when an excess of exogenous pig heart pyruvate dehydrogenase phosphate was used as substrate. It is concluded that this inhibition is due to some factor(s) associated with the substrate (pyruvate dehydrogenase phosphate complex) and not to inhibition of the phosphatase as such. 3. This conclusion was verified by isolating pyruvate dehydrogenase phosphate complex, free of phosphatase, from hearts of control and diabetic rats an from heart mitochondria incubed for 1min (control) or 6min with respiratory substrates. The rates of re-activation of the inactive complexes were then measured with preparations of ox heart or rat heart phosphatase. The rates were lower (relative to controls) with inactive complex from hearts of diabetic rats or from heart mitochondria incubated for 6min with respiratory substrates. 4. The incorporation of 32Pi into inactive complex took 6min to complete in rat heart mitocondria. The extent of incorporation was consistent with three or four sites of phosphorylation in rat heart pyruvate dehydrogenase complex. 5. It is suggested that phosphorylation of sites additional to an inactivating site may inhibit the conversion of inactive complex into active complex by the phosphatase in heart mitochondria from alloxan-diabetic or 48h-starved rats or in mitochondria incubated for 6min with respiratory substrates.
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PMID:Conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active complex by the phosphate reaction in heart mitochondria is inhibited by alloxan-diabetes or starvation in the rat. 21 16

1. Sodium dichloroacetate (1mM) inhibited glucose production from L-lactate in kidney-cortex slices from fed, starved or alloxan-diabetic rates. In general gluconeogenesis from other substrates was no inhibited. 2. Sodium dichloracetate inhibited glucose production from L-lactate but no from pyruvate in perfused isolated kidneys from normal or alloxan-diabetic rats. 3. Sodium dichloroacetate is an inhibitor of the pyruvate dehydrogenase kinase reaction and it effected conversion of pyruvate dehydrogenase into its its active (dephosphorylated) form in kidney in vivo. In general, pyruvate dehydrogenase was mainly in the active form in kidneys perfused or incubated with L-lactate and the inhibitory effect of dichloroacetate on glucose production was not dependent on activation of pyruvate dehydrogenase. 4. Balance data from kidney slices showed that dichloroacetate inhibits lactate uptake, glucose and pyruvate production from lactate, but no oxidation of lactate. 5. The mechanism of this effect of dichloroactetate on glucose production from lactate has not been fully defined, but evidence suggests that it may involve a fall in tissue pyruvate concentration and inhibition of pyruvate carboxylation.
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PMID:Inhibition of lactate glucogneogenesis in rat kidney by dichloroacetate. 64

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.
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PMID:Regulation of pyruvate dehydrogenase complex activity during myocardial ischemia. 399 45

The total activity of pyruvate dehydrogenase (PDH) complex in rat hind-limb muscle mitochondria was 76.4 units/g of mitochondrial protein. The proportion of complex in the active form was 34% (as isolated), 8-14% (incubation with respiratory substrates) and greater than 98% (incubation without respiratory substrates). Complex was also inactivated by ATP in the presence of oligomycin B and carbonyl cyanide m-chlorophenylhydrazone. Ca2+ (which activates PDH phosphatase) and pyruvate or dichloroacetate (which inhibit PDH kinase) each increased the concentration of active PDH complex in a concentration-dependent manner in mitochondria oxidizing 2-oxoglutarate/L-malate. Values giving half-maximal activation were 10 nM-Ca2+, 3 mM-pyruvate and 16 microM-dichloroacetate. Activation by Ca2+ was inhibited by Na+ and Mg2+. Mitochondria incubated with [32P]Pi/2-oxoglutarate/L-malate incorporated 32P into three phosphorylation sites in the alpha-chain of PDH; relative rates of phosphorylation were sites 1 greater than 2 greater than 3, and of dephosphorylation, sites 2 greater than 1 greater than 3. Starvation ( 48h ) or induction of alloxan-diabetes had no effect on the total activity of PDH complex in skeletal-muscle mitochondria, but each decreased the concentration of active complex in mitochondria oxidizing 2-oxoglutarate/L-malate and increased the concentrations of Ca2+, pyruvate or dichloracetate required for half-maximal reactivation. In extracts of mitochondria the activity of PDH kinase was increased 2-3-fold by 48 h starvation or alloxan-diabetes, but the activity of PDH phosphatase was unchanged.
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PMID:Reversible phosphorylation of pyruvate dehydrogenase in rat skeletal-muscle mitochondria. Effects of starvation and diabetes. 633 93

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.
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PMID:The effect of ischaemia on the activity of pyruvate dehydrogenase complex in rat heart. 648 14

The pyruvate dehydrogenase (PDH) complex undergoes reversible phosphorylation catalyzed by a PDH kinase (inactivating) and a PDH phosphatase (activating). In skeletal muscle, a decreased proportion of active PDH (PDHa) complex limits glucose oxidation in insulin-deficient states. The time-course for reactivation of the PDH complex by insulin in skeletal muscle of diabetic rats is important to understanding the potential mode of the action of insulin in regulating glucose metabolism. A single injection of insulin (1 U/kg) completely reversed the effects of alloxan-diabetes on PDHa activity within 1 hour. The normalization of the effects of diabetes on PDHa activity by insulin was maintained for a minimum of 6 hours. The increase in PDHa activity occurred before an insulin-induced decrease in plasma free fatty acids levels, demonstrating a dissociation between the antilipolytic effects of insulin and its ability to activate the PDH complex. PDH kinase activity was not normalized to control values following a single injection of insulin. Therefore, acute (1 to 6 hours) insulin-mediated activation of the PDH complex does not result from a decrease in PDH kinase activity. However, longer-term insulin therapy (1 U/kg body weight; twice daily) restored both PDHa and PDH kinase activities. The results are consistent with the hypothesis that activation of the PDH complex immediately following insulin administration is not mediated by a decreased PDH kinase activity. However, with daily insulin therapy in diabetes, activation of the PDH complex results from decreased PDH kinase activity.
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PMID:Insulin-induced activation of pyruvate dehydrogenase complex in skeletal muscle of diabetic rats. 849 17

For centuries, mulberry leaf has been used in traditional Chinese medicine for the treatment of diabetes. This study aims to test the prevention effects of a proprietary mulberry leaf extract (MLE) and a formula consisting of MLE, fenugreek seed extract, and cinnamon cassia extract (MLEF) on insulin resistance development in animals. MLE was refined to contain 5% 1-deoxynojirimycin by weight. MLEF was formulated by mixing MLE with cinnamon cassia extract and fenugreek seed extract at a 6:5:3 ratio (by weight). First, the acute toxicity effects of MLE on ICR mice were examined at 5 g/kg BW dose. Second, two groups of normal rats were administrated with water or 150 mg/kg BW MLE per day for 29 days to evaluate MLE's effect on normal animals. Third, to examine the effects of MLE and MLEF on model animals, sixty SD rats were divided into five groups, namely, (1) normal, (2) model, (3) high-dose MLE (75 mg/kg BW) treatment; (4) low-dose MLE (15 mg/kg BW) treatment; and (5) MLEF (35 mg/kg BW) treatment. On the second week, rats in groups (2)-(5) were switched to high-energy diet for three weeks. Afterward, the rats were injected (ip) with a single dose of 105 mg/kg BW alloxan. After four more days, fasting blood glucose, post-prandial blood glucose, serum insulin, cholesterol, and triglyceride levels were measured. Last, liver lysates from animals were screened with 650 antibodies for changes in the expression or phosphorylation levels of signaling proteins. The results were further validated by Western blot analysis. We found that the maximum tolerance dose of MLE was greater than 5 g/kg in mice. The MLE at a 150 mg/kg BW dose showed no effect on fast blood glucose levels in normal rats. The MLE at a 75 mg/kg BW dose and MLEF at a 35 mg/kg BW dose, significantly (p < 0.05) reduced fast blood glucose levels in rats with impaired glucose and lipid metabolism. In total, 34 proteins with significant changes in expression and phosphorylation levels were identified. The changes of JNK, IRS1, and PDK1 were confirmed by western blot analysis. In conclusion, this study demonstrated the potential protective effects of MLE and MLEF against hyperglycemia induced by high-energy diet and toxic chemicals in rats for the first time. The most likely mechanism is the promotion of IRS1 phosphorylation, which leads to insulin sensitivity restoration.
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PMID:Prevention Effects and Possible Molecular Mechanism of Mulberry Leaf Extract and its Formulation on Rats with Insulin-Insensitivity. 2705 86