Alterations in Adipose-Tissue Pyruvate Dehydrogenase Activity in Starved, Fat-Fed and Diabetic Rats

1975 ◽  
Vol 3 (5) ◽  
pp. 718-720 ◽  
Author(s):  
DAVID STANSBIE ◽  
RICHARD M. DENTON ◽  
PHILIP J. RANDLE
Keyword(s):  
Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Diabetic Rats

scholarly journals Glucose metabolism in perfused skeletal muscle. Pyruvate dehydrogenase activity in starvation, diabetes and exercise

1976 ◽  
Vol 158 (2) ◽  
pp. 203-210 ◽  
Author(s):  
S A Hagg ◽  
S I Taylor ◽  
N B Ruberman
Keyword(s):  
Skeletal Muscle ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Preceding Paper ◽  
Diabetic Rats ◽  
Pyruvate Dehydrogenase Kinase ◽  
Lactate Oxidation ◽  
Pyruvate Oxidation ◽  
Measured Activity ◽  
Exercise Induced

1. The interconversion of pyruvate dehydrogenase between its inactive phosphorylated and active dephosphorylated forms was studied in skeletal muscle. 2. Exercise, induced by electrical stimulation of the sciatic nerve (5/s), increased the measured activity of (active) pyruvate dehydrogenase threefold in intact anaesthetized rated within 2 min. No further increase was seen after 15 min of stimulation. 3. In the perfused rat hindquarter, (active) pyruvate dehydrogenase activity was decreased by 50% in muscle of starved and diabetic rats. Exercise produced a twofold increase in its activity in all groups; however, the relative differences between fed, starved and diabetic groups persisted. 4. Perfusion of muslce with acetoacetate (2 mM) decreased (active) pyruvate dehydrogenase activity by 50% at rest but not during exercise. 5. Whole-tissue concentrations of pyruvate and citrate, inhibitors of (active) pyruvate dehydrogenase kinase and (inactive) pyruvate dehydrogenase phosphate phosphatase respectively, were not altered by excerise. A decrease in the ATP/ADP ratio was observed, but did not appear to be sufficient to account for the increase in (active) pyruvate dehydrogenase activity. 6. The results suggest that interconversion of the phosphorylated and dephosphorylated forms of pyruvate dehydrogenase plays a major role in the regulation of pyruvate oxidation by eomparison of enzyme activity with measurements of lactate oxidation in the perfused hindquarter [see the preceding paper, Berger et al. (1976)] suggest that pyruvate oxidation is also modulated by the concentrations of substrates, cofactors and inhibitors of (active) pyruvate dehydrogenase activity.

scholarly journals Studies on the interactions of Ca2+ and pyruvate in the regulation of rat heart pyruvate dehydrogenase activity. Effects of starvation and diabetes

1982 ◽  
Vol 202 (2) ◽  
pp. 419-427 ◽  
Author(s):  
J G McCormack ◽  
N J Edgell ◽  
R M Denton
Keyword(s):  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Synergistic Effects ◽  
Respiratory Control ◽  
Diabetic Rats ◽  
Maximum Activity ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Dehydrogenase System

1. Previous studies showed that the activation of pyruvate dehydrogenase within intact rat heart mitochondria of pyruvate is much diminished in mitochondria from starved or diabetic animals [see Kerbey, Randle, Cooper, Whitehouse, Pask & Denton (1976) Biochem. J. 154, 327-348]. In the present study, diminished responses to added Ca2+ and ADP were also found in these mitochondria. 2. Starvation or diabetes did not affect the mitochondrial respiratory control ratio of the ATP content. Moreover, starvation and diabetes did not alter the response of the intramitochondrial Ca2+-sensitive enzyme, 2-oxoglutarate dehydrogenase, to changes in the extramitochondrial concentration of Ca2+ and 2-oxoglutarate, thus indicating that there were no appreciable changes in the distribution of Ca2+ and H+ across the mitochondrial inner membrane. 3. Pyruvate, Ca2+ and ADP were found to have synergistic effects on pyruvate dehydrogenase activity, particularly in mitochondria from starved and diabetic rats. 4. The results suggest that the effects of diabetes and starvation on pyruvate dehydrogenase are not brought about by changes in the distribution of these effectors across the mitochondrial inner membrane or by changes in the intrinsic sensitivity of the kinase or phosphatase of the pyruvate dehydrogenase system to pyruvate, Ca2+ or ADP; rather it is probably that there is an increase in the maximum activity of kinase relative to that of the phosphatase. 6. The results also lend further support to the hypothesis that adrenaline may bring about the activation of pyruvate dehydrogenase in the rat heart by an increase in the intramitochondrial concentration of Ca2+.

scholarly journals Activation of pyruvate dehydrogenase in adipose tissue by insulin. Evidence for an effect of insulin on pyruvate dehydrogenase phosphate phosphatase

1975 ◽  
Vol 148 (2) ◽  
pp. 229-235 ◽  
Author(s):  
C Mukherjee ◽  
R L Jungas
Keyword(s):  
Creatine Kinase ◽  
Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Insulin Treatment ◽  
Creatine Phosphate ◽  
Epididymal Adipose Tissue ◽  
Crude Extracts ◽  
Rate Of Increase

1. The mechanism by which insulin activates pyruvate dehydrogenase in rat epididymal adipose tissue was further investigated. 2. When crude extracts, prepared from tissue segments previously exposed to insulin (2m-i.u/ml) for 2min, were supplemented with Mg-2+, Ca-2+, glucose and hexokinase and incubated at 30 degrees C, they displayed an enhanced rate of increase in pyruvate dehydrogenase activity compared with control extracts. 3. When similar extracts were instead supplemented with fluoride, ADP, creatine phosphate and creatine kinase, the rate of decrease in pyruvate dehydrogenase activity observed during incubation at 30 degrees C was unaffected by insulin treatment. 4. It is suggested that insulin increases the fraction of pyruvate dehydrogenase present in the tissue in the active dephospho form by increasing the activity of pyruvate dehydrogenase phosphate phosphatase.

The Regulation of Adipose Tissue Pyruvate Dehydrogenase Activity of Dietary Fiber

1987 ◽  
Vol 19 (05) ◽  
pp. 187-190 ◽  
Author(s):  
J. Ogunwole ◽  
E. Knight ◽  
J. Adkins ◽  
K. Thomaskutty ◽  
R. Pointer
Keyword(s):  
Adipose Tissue ◽  
Dietary Fiber ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase

scholarly journals Persistence of the effect of insulin on pyruvate dehydrogenase activity in rat white and brown adipose tissue during the preparation and subsequent incubation of mitochondria

1984 ◽  
Vol 217 (2) ◽  
pp. 441-452 ◽  
Author(s):  
R M Denton ◽  
J G McCormack ◽  
S E Marshall
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Plasma Membranes ◽  
Pyruvate Dehydrogenase Kinase ◽  
Epididymal Adipose Tissue ◽  
Short Term ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose

Increases in the amount of the active non-phosphorylated form of pyruvate dehydrogenase in rat epididymal adipose tissue, as a result of incubation with insulin, persist not only during the preparation of mitochondria but also during subsequent incubation of coupled mitochondria in the presence of respiratory substrates. No effect on insulin was found if the hormone was added directly to mitochondria in the presence or absence of added plasma membranes. Concentrations of several possible regulators of pyruvate dehydrogenase kinase (ATP, ADP, NADH, NAD+, acetyl-CoA, CoA and potassium) were measured in rat epididymal-adipose-tissue mitochondria incubated under conditions where differences in pyruvate dehydrogenase activity persist as a result of insulin action. No alterations were found, and it is suggested that inhibition of the kinase is not the principal means by which insulin activates pyruvate dehydrogenase. The intramitochondrial concentration of magnesium was also unaffected. Differences in pyruvate dehydrogenase activity in interscapular brown adipose tissue associated with manipulation of plasma insulin concentrations of cold-adapted rats were also shown to persist during the preparation and subsequent incubation of mitochondria in the presence or absence of GDP. It is pointed out that the persistence of the effect of insulin on pyruvate dehydrogenase in incubated mitochondria will facilitate the recognition of the mechanism of this action of the hormone. Evidence that the short-term action of insulin involves an increase in pyruvate dehydrogenase phosphate phosphatase activity rather than inhibition of that of pyruvate dehydrogenase kinase is discussed.

Lactate Production and Pyruvate Dehydrogenase Activity in Fat and Skeletal Muscle From Diabetic Rats

Diabetes ◽  
1992 ◽  
Vol 41 (12) ◽  
pp. 1547-1554 ◽  
Author(s):  
C. E. Mondon ◽  
I. R. Jones ◽  
S. Azhar ◽  
C. B. Hollenbeck ◽  
G. M. Reaven
Keyword(s):  
Skeletal Muscle ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Lactate Production ◽  
Diabetic Rats

scholarly journals Effect of insulin on pyruvate metabolism in epididymal adipose tissue of the rat. Correlation of intracellular pyruvate contents and pyruvate dehydrogenase activity

1973 ◽  
Vol 134 (4) ◽  
pp. 885-889 ◽  
Author(s):  
Bruce G. Berman ◽  
Mitchell L. Halperin
Keyword(s):  
Adipose Tissue ◽  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Epididymal Adipose Tissue ◽  
Pyruvate Metabolism ◽  
Time Period ◽  
Intracellular Content

A method is described to measure the intracellular content of pyruvate and lactate in epididymal adipose tissue of the rat. The intracellular pyruvate concentration was approx. 330μm. Intracellular pyruvate contents and the rates of pyruvate output were increased when NNN′N′-tetramethyl-p-phenylenediamine was added, and decreased in the presence of alanine. Insulin addition caused an increase in intracellular pyruvate contents only at the earlier time-period studied (1.5min as against 20min). Pyruvate dehydrogenase activity was increased in adipose tissue incubated in vitro with insulin. This increase occurred subsequent to the rise in the intracellular pyruvate content induced by insulin addition. The possible physiological implications are discussed.

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