scholarly journals The regulation of hepatic carbon flux by pyruvate dehydrogenase and pyruvate dehydrogenase kinase during long-term food restriction

1993 ◽  
Vol 296 (1) ◽  
pp. 217-223 ◽  
Author(s):  
M C Sugden ◽  
R M Grimshaw ◽  
M J Holness
Keyword(s):  
Food Intake ◽  
Pyruvate Dehydrogenase ◽  
Food Restriction ◽  
Kinase Activity ◽  
Polynomial Regression ◽  
Glycogen Synthesis ◽  
Critical Role ◽  
Active Form ◽  
Pyruvate Dehydrogenase Kinase ◽  
Hepatic Glycogen

The present study investigated the effects of chronic food restriction (achieved by limiting access to food to 2 h daily for up to 8 weeks) on the activity of the active form of pyruvate dehydrogenase (PDHa) in liver. Accelerated and exaggerated activation of hepatic PDH in response to a meal, previously demonstrated to occur within 10 days of food restriction, was demonstrated to persist for 4 and 8 weeks of food restriction, despite a food intake of only 50-60% of controls. Activation of hepatic PDH during feeding in rats subjected to food restriction for 4 weeks was dependent on continued food intake. As a consequence, hepatic PDHa activities in food-restricted rats were suppressed relative to controls for 19 h of the 24 h daily cycle. Curve-fitting by second-order polynomial regression analysis demonstrated a significant positive correlation between hepatic PDHa activity and lipogenic rate over the range of PDHa activities observed during the 2 h feeding period. Increased lipogenesis during feeding in food-restricted rats was not at the expense of hepatic glycogen synthesis or deposition; measurement of concurrent rates of glycogenesis and lipogenesis revealed simultaneous flux through both pathways, but specific activation of lipogenesis. The accelerated re-activation of hepatic PDH observed within 1 h of feeding in rats subjected to 4 weeks of food restriction was facilitated by a failure of the 22 h interprandial fasting period to induce a stable increase in hepatic PDH kinase activity. The present study indicates differential regulation of hepatic PDH kinase activity during periods of food withdrawal between food-restricted rats and starved/re-fed control rats. Such regulation occupies a critical role in determining the rate of activation of hepatic PDH during feeding. In turn, increased activity of hepatic PDHa during feeding in food-restricted rats bears a close positive relationship with hepatic lipogenic rate.

scholarly journals Pyruvate dehydrogenase kinase/activator in rat heart mitochondria, Assay, effect of starvation, and effect of protein-synthesis inhibitors of starvation

1982 ◽  
Vol 206 (1) ◽  
pp. 103-111 ◽  
Author(s):  
A L Kerbey ◽  
P J Randle
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
High Speed ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Pyruvate Dehydrogenase Kinase ◽  
Heart Mitochondria ◽  
Supernatant Fraction ◽  
Kidney Mitochondria

Purified pig heart pyruvate dehydrogenase complex is denuded of its intrinsic pyruvate dehydrogenase kinase activity by sedimentation from dilute solution (60 munits/ml). Kinase activity is restored by a supernatant fraction prepared by high-speed centrifugation of rat heart mitochondrial extracts; the factor responsible is referred to as kinase/activator. Kinase/activator was also assayed by its ability to accelerate NgATP-induced inactivation in dilute solutions of unprocessed complex (50 munits/ml). With this assay it has been shown that the activity of kinase/activator in heart mitochondria is increased 3-6 fold by starvation of rats for 48 h. This increase was prevented completely by cycloheximide treatment and prevented partially by puromycin treatment of rats during starvation. The concentration of kinase/activator in heart mitochondria fell during 20 h of re-feeding of 48 h-starved rats; this fall was correlated with an increase in the proportion of complex in the active form. Kinase/activator was also extracted from ox kidney mitochondria, and on gel filtration (Sephadex G-100, superfine grade) was eluted close to the void volume. Kinase/activator (ox kidney or rat heart) was thermolabile, non-diffusable on dialysis, and inactivated by trypsin. The results of this study appear to show increased cytoplasmic synthesis in starvation of pyruvate dehydrogenase kinase and/or of an activator of the kinase.

scholarly journals Role of protein–protein interactions in the regulation of pyruvate dehydrogenase kinase activity

2005 ◽  
Vol 387 (1) ◽  
pp. 147-153 ◽  
Author(s):  
Alina TUGANOVA ◽  
Kirill M. POPOV
Keyword(s):  
Protein Interactions ◽  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Critical Role ◽  
Pyruvate Dehydrogenase Kinase ◽  
Mutual Orientation ◽  
Titration Calorimetry ◽  
Protein Protein Interactions ◽  
Glutathione S Transferase

The transacetylase component (E2) of PDC (pyruvate dehydrogenase complex) plays a critical role in the regulation of PDHK (pyruvate dehydrogenase kinase) activity. The present study was undertaken to investigate further the molecular mechanism by which E2 modulates the activity of PDHK. In agreement with the earlier results, it was found that the inner L2 (lipoyl-bearing domain 2) of E2 expressed with or without the C-terminal hinge region had little, if any, effect on the kinase activity, indicating a lack of direct allosteric effect of L2 on PDHK. In marked contrast, significant activation of PDHK was observed with the construct consisting of L2 and the E1BD (E1-binding domain) of E2 (L2-E1BD didomain) suggesting that co-localization and/or mutual orientation of PDHK and E1, facilitated by E2 binding, largely account for the activation of PDHK by the transacetylase component. Isothermal titration calorimetry and glutathione S-transferase pull-down assays established that binding of adenyl nucleotides to the PDHK molecule facilitated the release of L2 domain. In contrast, binding of the L2 domain caused a significant decrease in the affinity of PDHK for ATP. The cross-talk in binding of adenyl nucleotides and the L2 domain to PDHK may indicate the existence of a highly integrated mechanism whereby the exchange of lipoyl-bearing domains presented to PDHK by E2 is coupled with ADP/ATP exchange.

Brief food restriction increases FA oxidation and glycogen synthesis under insulin-stimulated conditions

2002 ◽  
Vol 282 (4) ◽  
pp. R1210-R1218 ◽  
Author(s):  
Michelle Z. Tucker ◽  
Lorraine P. Turcotte
Keyword(s):  
Fatty Acid ◽  
Insulin Sensitivity ◽  
Food Intake ◽  
Glucose Uptake ◽  
Food Restriction ◽  
Glycogen Synthesis ◽  
Palmitate Uptake ◽  
Ad Libitum ◽  
Muscle Triglyceride ◽  
White Gastrocnemius

To determine the effects of brief food restriction on fatty acid (FA) metabolism, hindlimbs of F344/BN rats fed either ad libitum (AL) or food restricted (FR) to 60% of baseline food intake for 28 days were perfused under hyperglycemic-hyperinsulinemic conditions (20 mM glucose, 1 mM palmitate, 1,000 μU/ml insulin, [3-3H]glucose, and [1-14C]palmitate). Basal glucose and insulin levels were significantly lower ( P < 0.05) in FR vs. AL rats. Palmitate uptake (34.3 ± 2.7 vs. 24.5 ± 3.1 nmol/g/min) and oxidation (3.8 ± 0.2 vs. 2.7 ± 0.3 nmol · g−1 · min−1) were significantly higher ( P < 0.05) in FR vs. AL rats, respectively. Glucose uptake was increased in FR rats and was accompanied by significant increases in red and white gastrocnemius glycogen synthesis, indicating an improvement in insulin sensitivity. Although muscle triglyceride (TG) levels were not significantly different between groups, glucose uptake and total preperfusion TG concentration were negatively correlated ( r 2 = 0.27, P < 0.05). In conclusion, our results show that under hyperglycemic-hyperinsulinemic conditions, brief FR resulted in an increase in FA oxidative disposal that may contribute to the improvement in insulin sensitivity.

Increased hepatic pyruvate dehydrogenase kinase activity in fed hyperthyroid rats: studies in vivo and with cultured hepatocytes

1996 ◽  
Vol 119 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Mary C. Sugden ◽  
Lee G.D. Fryer ◽  
David A. Priestman ◽  
Karen A. Orfali ◽  
Mark J. Holness
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Kinase ◽  
Cultured Hepatocytes

Overexpression of pyruvate dehydrogenase kinase 4 in heart perturbs metabolism and exacerbates calcineurin-induced cardiomyopathy

2008 ◽  
Vol 294 (2) ◽  
pp. H936-H943 ◽  
Author(s):  
Guixiang Zhao ◽  
Nam Ho Jeoung ◽  
Shawn C. Burgess ◽  
Kimberly A. Rosaaen-Stowe ◽  
Takeshi Inagaki ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Pyruvate Dehydrogenase ◽  
Marked Decrease ◽  
Active Form ◽  
Pyruvate Dehydrogenase Kinase ◽  
Metabolic Flexibility ◽  
Energy Demands ◽  
Pyruvate Dehydrogenase Kinase 4 ◽  
Fatty Acid Catabolism

The heart adapts to changes in nutritional status and energy demands by adjusting its relative metabolism of carbohydrates and fatty acids. Loss of this metabolic flexibility such as occurs in diabetes mellitus is associated with cardiovascular disease and heart failure. To study the long-term consequences of impaired metabolic flexibility, we have generated mice that overexpress pyruvate dehydrogenase kinase (PDK)4 selectively in the heart. Hearts from PDK4 transgenic mice have a marked decrease in glucose oxidation and a corresponding increase in fatty acid catabolism. Although no overt cardiomyopathy was observed in the PDK4 transgenic mice, introduction of the PDK4 transgene into mice expressing a constitutively active form of the phosphatase calcineurin, which causes cardiac hypertrophy, caused cardiomyocyte fibrosis and a striking increase in mortality. These results demonstrate that cardiac-specific overexpression of PDK4 is sufficient to cause a loss of metabolic flexibility that exacerbates cardiomyopathy caused by the calcineurin stress-activated pathway.

Increased pyruvate dehydrogenase kinase activity in response to sepsis

1991 ◽  
Vol 260 (5) ◽  
pp. E669-E674 ◽  
Author(s):  
T. C. Vary
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Dehydrogenase Kinase ◽  
Sterile Inflammation ◽  
Stable Factor ◽  
Skeletal Muscle Mitochondria ◽  
Dependent Inactivation ◽  
Significant Difference

The effect of sterile inflammation and sepsis on the proportion of active pyruvate dehydrogenase complex (PDH) in mitochondria isolated from skeletal muscle has been investigated. The proportion of active PDH in mitochondria isolated from septic animals was significantly reduced compared with control under all incubation conditions examined, even in the presence of inhibitors of the PDH kinase. There was no significant difference between control and sterile inflammation in any of the incubations examined. The rate constant for ATP-dependent inactivation of the PDH complex in mitochondrial extracts from control animals was -0.42 min-1 (r = 0.993; P less than 0.001) and was not altered in mitochondrial extracts from sterile inflammatory animals (-0.43 min-1; r = 0.999; P less than 0.001). However, rate constants for inactivation in septic animals was significantly increased over twofold to -1.08 min-1 (r = 0.987; P less than 0.001) (P less than 0.001 vs. control or sterile inflammation). In the presence of inhibitors of the PDH kinase reaction (2.5 mM pyruvate or 1 mM dichloroacetate), inactivation of PDH after addition of ATP was significantly greater in mitochondrial extracts from septic than either control or sterile inflammatory animals. These results suggest that sepsis, but not sterile inflammation, induces a stable factor in skeletal muscle mitochondria that increased PDH kinase activity.

scholarly journals Phosphorylation state of cytosolic and mitochondrial adenine nucleotides and of pyruvate dehydrogenase in isolated rat liver cells

1976 ◽  
Vol 156 (1) ◽  
pp. 91-102 ◽  
Author(s):  
E A Siess ◽  
O H Wieland
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Adenine Nucleotides ◽  
Active Form ◽  
Inverse Correlation ◽  
Liver Cells ◽  
Diabetic Rats ◽  
Pyruvate Dehydrogenase Kinase ◽  
Intact Cells ◽  
Phosphorylation State

1. Cytosolic and mitochondrial ATP and ADP concentrations of liver cells isolated from normal fed, starved and diabetic rats were determined. 2. The cytosolic ATP/ADP ratio was 6,9 and 10 in normal fed, starved and diabetic rats respectively. 3. The mitochondrial ATP/ADP ratio was 2 in normal and diabetic rats and 1.6 in starved rats. 4. Adenosine increased the cytosolic and lowered the mitochondrial ATP/ADP ratio, whereas atractyloside had the opposite effect. 5. Incubation of the hepatocytes with fructose, glycerol or sorbitol led to a fall in the ATP/ADP ratio in both the cytosolic and the mitochondrial compartment. 6. The interrelationship between the mitochondrial ATP/ADP ratio and the phosphorylation state of pyruvate dehydrogenase in intact cells was studied. 7. In hepatocytes isolated from fed rats an inverse correlation between the mitochondrial ATP/ADP ratio and the active form of pyruvate dehydrogenase (pyruvate dehydrogenase a) was demonstrable on loading with fructose, glycerol or sorbitol. 8. No such correlation was obtained with pyruvate or dihydroxyacetone. For pyruvate, this can be explained by inhibition of pyruvate dehydrogenase kinase. 9. Liver cells isolated from fed animals displayed pyruvate dehydrogenase a activity twice that found in vivo. Physiological values were obtained when the hepatocytes were incubated with albumin-oleate, which also yielded the highest mitochondrial ATP/ADP ratio.

scholarly journals Interaction between the individual isoenzymes of pyruvate dehydrogenase kinase and the inner lipoyl-bearing domain of transacetylase component of pyruvate dehydrogenase complex

2002 ◽  
Vol 366 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Alina TUGANOVA ◽  
Igor BOULATNIKOV ◽  
Kirill M. POPOV
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Tight Binding ◽  
Enzymic Activity ◽  
Pyruvate Dehydrogenase Kinase ◽  
Size Exclusion ◽  
Apparent Dissociation Constant ◽  
The Individual ◽  
Dehydrogenase Complex

Protein—protein interactions play an important role in the regulation of enzymic activity of pyruvate dehydrogenase kinase (PDK). It is generally believed that the binding of PDK to the inner lipoyl-bearing domain L2 of the transacetylase component E2 of pyruvate dehydrogenase complex largely determines the level of kinase activity. In the present study, we characterized the interaction between the individual isoenzymes of PDK (PDK1—PDK4) and monomeric L2 domain of human E2, as well as the effect of this interaction on kinase activity. It was found that PDK isoenzymes are markedly different with respect to their affinities for L2. PDK3 demonstrated a very tight binding, which persisted during isolation of PDK3—L2 complexes using size-exclusion chromatography. Binding of PDK1 and PDK2 was readily reversible with the apparent dissociation constant of approx. 10μM for both isoenzymes. PDK4 had a greatly reduced capacity for L2 binding (relative order PDK3>PDK1 = PDK2>PDK4). Monomeric L2 domain alone had very little effect on the activities of either PDK1 or PDK2. In contrast, L2 caused a 3-fold increase in PDK3 activity and approx. 37% increase in PDK4 activity. These results strongly suggest that the interactions between the individual isoenzymes of PDK and L2 domain are isoenzyme-specific and might be among the major factors that determine the level of kinase activity of particular isoenzyme towards the pyruvate dehydrogenase complex.

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