scholarly journals Inactivation of rat adipocyte pyruvate dehydrogenase by palmitate. Protection against this effect by insulin in the presence of glucose

1979 ◽  
Vol 184 (1) ◽  
pp. 59-62 ◽  
Author(s):  
S R Sooranna ◽  
E D Saggerson
Keyword(s):  
Amino Acids ◽  
Fatty Acids ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Protective Action ◽  
Active Form ◽  
Rat Plasma ◽  
Epididymal Fat ◽  
Fat Pads

1. Adipocytes from rat epididymal fat-pads were incubated for 30 min with 5 mM-glucose and concentrations of lactate, pyruvate and amino acids typical of those found in rat plasma. 2. PDHa (active form of pyruvate dehydrogenase) activity was significantly increased after incubation of the cells with insulin (200 micro-i.u./ml), and decreased by incubation with palmitate (0.5–2 mM). 3. In the presence of insulin, palmitate did not decrease PDHa activity. 4. Dichloroacetate (1 mM) increased PDHa activity in the absence of palmitate to the same extent as did insulin. In the presence of dichloroacetate but the absence of insulin, palmitate decreased PDHa activity. In the presence of dichloroacetate and insulin, palmitate again did not decrease PDHa activity. 5. It is concluded that, in the presence of glucose, insulin has a strong protective action against inactivation of adipocyte PDHa by fatty acids.

scholarly journals Regulation of pyruvate dehydrogenase and pyruvate dehydrogenase phosphate phosphatase activity in rat epididymal fat-pads. Effects of starvation, alloxan-diabetes and high-fat diet

1976 ◽  
Vol 154 (1) ◽  
pp. 225-236 ◽  
Author(s):  
D Stansbie ◽  
R M Denton ◽  
B J Bridges ◽  
H T Pask ◽  
P J Randle
Keyword(s):  
Phosphatase Activity ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
High Fat Diet ◽  
Alloxan Diabetes ◽  
Mitochondrial Activity ◽  
High Fat ◽  
Epididymal Fat ◽  
Fat Pads

1. Pyruvate dehydrogenase phosphate phosphatase activity in rat epididymal fat-pads was measured by using pig heart pyruvate dehydrogenase [32P]phosphate. About 80% was found to be extramitochondrial and therefore probably not directly concerned with the regulation of pyruvate dehydrogenase activity. The extramitochondrial activity was sensitive to activation by +, but perhaps less sensitive than the mitochondrial activity.

The inhibitory effects of some adenosine nucleolipids on the lipolysis in rat epididymal fat pads in vitro

1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt
Keyword(s):  
Fatty Acids ◽  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
Inhibitory Effects ◽  
Epididymal Fat ◽  
Fat Pads

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.

Regulation by Insulin and Free Fatty Acids of Pyruvate Dehydrogenase Activity in Perfused Rat Liver

1977 ◽  
Vol 5 (4) ◽  
pp. 1000-1001 ◽  
Author(s):  
DAVID L. TOPPING ◽  
M. ANWAR GOHEER ◽  
HALDANE G. COORE ◽  
PETER A. MAYES
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Dehydrogenase Activity ◽  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Perfused Rat Liver

scholarly journals A comparison of the regulation of pyruvate dehydrogenase in mitochondria from rat brain and liver

1975 ◽  
Vol 150 (3) ◽  
pp. 397-403 ◽  
Author(s):  
R Jope ◽  
J P Blass
Keyword(s):  
Rat Brain ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Active Form ◽  
Energy Charge ◽  
Liver Mitochondria ◽  
Brain Mitochondria ◽  
Ruthenium Red ◽  
Rat Brain And Liver ◽  
Pyruvate Dehydrogenase Phosphatase

The total activity of pyruvate dehydrogenase in mitochondria isolated from rat brain and liver was 53.5 and 14.2nmol/min per mg of protein respectively. Pyruvate dehydrogenase in liver mitochondria incubated for 4 min at 37 degrees C with no additions was 30% in the active form and this activity increased with longer incubations until it was completely in the active form after 20 min. Brain mitochondrial pyruvate dehydrogenase activity was initially high and did not increase with addition of Mg2+ plus Ca2+ or partially purified pyruvate dehydrogenase phosphatase or with longer incubations. The proportion of pyruvate dehydrogenase in the active form in both brain and liver mitochondria changed inversely with changes in mitochondrial energy charge, whereas total pyruvate dehydrogenase did not change. The chelators citrate, isocitrate, EDTA, ethanedioxybis(ethylamine)tetra-acetic acid and Ruthenium Red each lowered pyruvate dehydrogenase activity in brain mitochondria, but only citrate and isocitrate did so in liver mitochondria. These chelators did not affect the energy charge of the mitochondria. Mg2+ plus Ca2+ reversed the pyruvate dehydrogenase inactivation in liver, but not brain, mitochondria. The regulation of the activation-inactivation of pyruvate dehydrogenase in mitochondria from rat brain and liver with respect to energy charge is similar and may be at least partially regulated by this parameter, and the effects of chelators differ in the two types of mitochondria.

Control of Fatty Acid Synthesis in White Adipose Tissue by Insulin: Coordination Between the Mitochondrial Citrate Transporter and Pyruvate Dehydrogenase

1974 ◽  
Vol 52 (10) ◽  
pp. 813-821 ◽  
Author(s):  
Carol M. Schiller ◽  
Wayne M. Taylor ◽  
Mitchell L. Halperin
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Pyruvate Dehydrogenase ◽  
Active Form ◽  
Acid Synthesis ◽  
Citrate Transporter ◽  
Maximal Activation ◽  
Initial Decrease ◽  
Preincubation Medium

The transport of citrate out of adipose tissue mitochondria is inhibited by palmitoyl-CoA. This inhibition varied inversely with the concentration of extramitochondrial exchanging anion.When adipose tissue is incubated in vitro, the rate of citrate output into the medium was increased by the addition of insulin. The tissue citrate content did not change significantly. Norepinephrine caused an initial decrease in the rate of citrate output (2.5 min). The tissue citrate content was approximately twofold higher at this time.When rats were fasted for 36 h, less than 40% of adipose tissue pyruvate dehydrogenase was in the active form. Optimal interconversion to the active form was achieved by preincubation with 4 mM Mg2+ in the absence of added Ca2+ (endogenous Ca2+ was approximately 25 μM). Citrate addition to the preincubation medium decreased this activation of pyruvate dehydrogenase. The inhibition induced by citrate correlated best with the concentration of 'free' citrate when the 'free' Mg2+ concentration was sufficient to cause near-maximal activation of pyruvate dehydrogenase.A hypothesis regarding the coordination of regulation of pyruvate conversion to fatty acids is formulated based on these findings.

Regulation of Pyruvate Dehydrogenase Activity In Rat Fat Pads And Isolated Hepatocytes by Levamisole

1993 ◽  
Vol 27 (3) ◽  
pp. 263-272 ◽  
Author(s):  
K.G. Thomaskutty ◽  
Nirmal S. Basi ◽  
Margaret L. Mckenzie ◽  
Richard H. Pointer
Keyword(s):  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Isolated Hepatocytes ◽  
Fat Pads

scholarly journals Studies on lipogenesis in vivo. Lipogenesis during extended periods of re-feeding after starvation

1968 ◽  
Vol 106 (2) ◽  
pp. 345-353 ◽  
Author(s):  
G. R. Jansen ◽  
M. E. Zanetti ◽  
C. F. Hutchison
Keyword(s):  
Fatty Acids ◽  
Corn Oil ◽  
Fat Content ◽  
Limited Access ◽  
Epididymal Fat ◽  
Extrahepatic Tissues ◽  
Ad Libitum ◽  
Access To Food ◽  
Fat Pads

1. Lipogenesis was studied in mice re-fed for up to 21 days after starvation. At appropriate times [U−14]glucose was given by stomach tube and incorporation of 14C into various lipid fractions measured. 2. In mice starved for 48hr. and then re-fed for 4 days with a diet containing 1% of corn oil, incorporation of 14C from [U−14C]glucose into liver fatty acids and cholesterol was respectively threefold and eightfold higher than in controls fed ad libitum. The percentages by weight of fatty acids and cholesterol in the liver also increased and reached peaks after 7 days. Both the radioactivity and weights of the fractions returned to control values after 10–14 days' re-feeding. These changes could be diminished by re-feeding the mice with a diet containing 20% of corn oil. Incorporation of 14C from [U−14C]glucose into extrahepatic fatty acids (excluding those of the epididymal fat pads) was not elevated during re-feeding with a diet containing either 1% or 20% of corn oil. However, incorporation of 14C from [U−14C]glucose into the fatty acids of the epididymal fat pads was increased in mice re-fed with either diet, as compared with non-starved controls. 3. Lipogenesis was also studied in mice alternately fed and starved. Mice given a diet containing 1% of corn oil for 6hr./day for 4 weeks lost weight initially and never attained the weight or carcass fat content of controls fed ad libitum. Incorporation of 14C from dietary [U−14C]-glucose into the fatty acids of the epididymal fat pads was elevated threefold in the mice allowed limited access to food, although the incorporation into the remainder of the extrahepatic fatty acids was not different from that found for controls. Mice given a diet containing 20% of corn oil for 6hr./day adapted to the limited feeding regimen quicker and in 4 weeks did attain the weight and carcass fat content of controls. Incorporation of 14C from [U−14C]glucose into the fatty acids of the epididymal fat pads and the remainder of the extrahepatic fatty acids was respectively fivefold and threefold higher than in controls fed ad libitum. 4. The elevation in liver lipogenesis during re-feeding was greatest on a diet containing 1% of corn oil, whereas in extrahepatic tissues the increase in lipogenesis was greater when the mice were re-fed or were allowed limited access to a diet containing 20% of corn oil. These results suggest that the causes of the increased rate of incorporation of 14C from [U−14C]glucose into fatty acids during re-feeding may be different in liver from that in extrahepatic tissues.

Effect of thyroxine treatment on exogenous myocardial lactate oxidation

1982 ◽  
Vol 243 (5) ◽  
pp. H722-H728
Author(s):  
M. Fintel ◽  
A. H. Burns
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Acid Oxidation ◽  
Lactate Oxidation ◽  
Thyroxine Treatment ◽  
Heart Preparation ◽  
Mitochondrial Oxidation ◽  
Working Rat Heart

The effect of thyroxine treatment on myocardial lactate oxidation was examined by use of an isolated, working rat heart preparation. Thyroxine treatment, both acute and chronic, was associated with a decrease in lactate oxidation, when the heart was perfused with a physiological blend of substrates (free fatty acids, lactate, and glucose). This decrease in lactate oxidation was not caused by a generalized impairment in mitochondrial oxidation of acetyl coenzyme A (CoA), as oxygen consumption was normal and fatty acid oxidation was elevated in the treated animals. The block in lactate oxidation was localized to the conversion of pyruvate to acetyl CoA, as indicated by the depressed oxidation of pyruvate and lactate. Thyroxine treatment was associated with a decrease in pyruvate dehydrogenase activity. The decrease in pyruvate dehydrogenase activity was reversible and was attributed to the enhanced myocardial oxidation of free fatty acids.

scholarly journals Effects of protein phosphatase inhibitors on the regulation of insulin-sensitive enzymes within rat epididymal fat-pads and cells

1991 ◽  
Vol 276 (3) ◽  
pp. 649-654 ◽  
Author(s):  
G A Rutter ◽  
A C Borthwick ◽  
R M Denton
Keyword(s):  
Okadaic Acid ◽  
Pyruvate Dehydrogenase ◽  
Protein Phosphatase ◽  
Acid Treatment ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Phosphatase Inhibitors ◽  
Epididymal Fat ◽  
Protein Phosphatase Inhibitors ◽  
Fat Pads

1. The effects of the protein phosphatase inhibitors okadaic acid and microcystin LR on the regulation by insulin of pyruvate dehydrogenase and acetyl-CoA carboxylase have been studied in rat epididymal fat-pads and isolated cells. These inhibitors both completely blocked the phosphatase activity (against phosphorylase a) present in extracts of epididymal fat-pads, with half-maximal effects in the nanomolar range. 2. Okadaic acid treatment of pads and cells lowered the activity of acetyl-CoA carboxylase assayed in tissue extracts, both before and after treatment of the extracts with the activator, citrate. Further, okadaic acid treatment abolished the 2-3-fold difference in activity observed between extracts from control and insulin-treated tissues, assayed without prior treatment with citrate. 3. Incubation of pads with [32P]Pi, sufficient to label the intracellular pool of ATP, demonstrated that okadaic acid increased the overall phosphorylation of acetyl-CoA carboxylase on a number of distinct sites, as judged by two-dimensional mapping of tryptic peptides. These included the ‘I-peptide’ [Brownsey & Denton (1982) Biochem. J. 202, 77-86], the phosphorylation of which may be associated with the stimulation of the activity of the enzyme by insulin, as well as inhibitory phosphorylation sites. 4. Incubation with 1 microM-okadaic acid had no effect on the basal level of active pyruvate dehydrogenase apparent after tissue extraction, but abolished the 2-3-fold increase in this parameter which was elicited by insulin in the absence of okadaic acid. However, okadaic acid treatment did not affect the persistent increase in active pyruvate dehydrogenase levels which was apparent in mitochondria subsequently isolated from insulin-treated pads and re-incubated with an oxidizable substrate. It is concluded that the effects of okadaic acid are exerted through changes in metabolite concentrations rather than some direct action on the signalling pathway whereby insulin stimulates pyruvate dehydrogenase. 5. Microcystin LR did not mimic the effects of okadaic acid on intact cells and pads described above.

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