Downregulation of the skeletal muscle pyruvate dehydrogenase complex in the Otsuka Long-Evans Tokushima Fatty rat both before and after the onset of diabetes mellitus

Bajotto, Gustavo; Murakami, Taro; Nagasaki, Masaru; Tamura, Tomohide; Tamura, Noriko; Harris, Robert A.; Shimomura, Yoshiharu; Sato, Yuzo

doi:10.1016/j.lfs.2004.04.016

Cited by 36 publications

(53 citation statements)

References 46 publications

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“…PDP1 and PDP2 was found to be down-regulated during starvation and diabetes adding to PDC inhibition by the up-regulation of PDK2 and PDK4 (19,20). Site 1 is phosphorylated faster than the other sites; however, in PDC all three sites could potentially be phosphorylated resulting in the hyperphosphorylation.…”

Section: Mammalian Pyruvate Dehydrogenase Complex (Pdc)mentioning

confidence: 99%

Characterization of Testis-specific Isoenzyme of Human Pyruvate Dehydrogenase

Korotchkina

Sidhu

Patel

2006

Journal of Biological Chemistry

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Pyruvate dehydrogenase (PDH), the first component of the human pyruvate dehydrogenase complex, has two isoenzymes, somatic cell-specific PDH1 and testis-specific PDH2 with 87% sequence identity in the ␣ subunit of ␣ 2 ␤ 2 PDH. The presence of functional testis-specific PDH2 is important for sperm cells generating nearly all their energy from carbohydrates via pyruvate oxidation. Kinetic and regulatory properties of recombinant human PDH2 and PDH1 were compared in this study. Site-specific phosphorylation/dephosphorylation of the three phosphorylation sites by four PDH kinases (PDK1-4) and two PDH phosphatases (PDP1-2) were investigated by substituting serines with alanine or glutamate in PDHs. PDH2 was found to be very similar to PDH1 as follows: (i) in specific activities and kinetic parameters as determined by the pyruvate dehydrogenase complex assay; (ii) in thermostability at 37°C; (iii) in the mechanism of inactivation by phosphorylation of three sites; and (iv) in the phosphorylation of sites 1 and 2 by PDK3. In contrast, the differences for PDH2 were indicated as follows: (i) by a 2.4-fold increase in binding affinity for the PDH-binding domain of dihydrolipoamide acetyltransferase as measured by surface plasmon resonance; (ii) by possible involvement of Ser-264 (site 1) of PDH2 in catalysis as evident by its kinetic behavior; and (iii) by the lower activities of PDK1, PDK2, and PDK4 as well as PDP1 and PDP2 toward PDH2. These differences between PDH2 and PDH1 are less than expected from substitution of 47 amino acids in each PDH2 ␣ subunit. The multiple substitutions may have compensated for any drastic alterations in PDH2 structure thereby preserving its kinetic and regulatory characteristics largely similar to that of PDH1. Mammalian pyruvate dehydrogenase complex (PDC)2 plays a central role in glucose oxidation by catalyzing the oxidative decarboxylation of pyruvic acid with formation of carbon dioxide, acetyl-CoA, NADH, and H ϩ (for reviews see Refs. 1-3). PDC is composed of multiple copies of the following three catalytic components: (i) pyruvate dehydrogenase (PDH) catalyzing the decarboxylation of pyruvate and reductive acetylation of the lipoyl moieties of dihydrolipoamide acetyltransferase (E2); (ii) E2 transferring acetyl moiety to CoA; (iii) and dihydrolipoamide dehydrogenase (E3) reoxidizing the reduced lipoyl moieties of E2 with the reduction of NAD ϩ to NADH (1-3). Forty eight to 60 subunits of E2and 12 subunits of E3-binding protein (BP), a noncatalytic component of mammalian PDC, form the central core of the multienzyme PDC, which binds 20 -30 tetramers of PDH, 6 -12 dimers of E3 and two regulatory enzymes, 1-2 copies of pyruvate dehydrogenase kinase (PDK), and 2-3 copies of pyruvate dehydrogenase phosphatase (PDP) (4, 5). PDK and PDP provide the finely tuned regulation of activity of PDC through reversible phosphorylation-dephosphorylation of PDH (and hence PDC) depending on cellular demand for glucose oxidation. Mammalian PDH is a tetramer consisting of two ␣ and two ␤ subunits. The hum...

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Section: Mammalian Pyruvate Dehydrogenase Complex (Pdc)mentioning

confidence: 99%

Characterization of Testis-specific Isoenzyme of Human Pyruvate Dehydrogenase

Korotchkina

Sidhu

Patel

2006

Journal of Biological Chemistry

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“…yruvate dehydogenase (PDH) complex (PDC) catalyzes the irreversible conversion of pyruvate to acetyl CoA, and dysregulation of the PDC in skeletal muscle has been suggested to be implicated in type 2 diabetes (1)(2)(3)(4). Fasting has been shown to reduce the activity of PDH in the active form (PDHa) in rat skeletal muscle (5,6), as has a high-fat diet in human muscle (7).…”

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confidence: 99%

PDH-E1α Dephosphorylation and Activation in Human Skeletal Muscle During Exercise

et al. 2006

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To investigate pyruvate dehydrogenase (PDH)-E1␣ subunit phosphorylation and whether free fatty acids (FFAs) regulate PDH activity, seven subjects completed two trials: saline (control) and intralipid/heparin (intralipid). Each infusion trial consisted of a 4-h rest followed by a 3-h two-legged knee extensor exercise at moderate intensity. During the 4-h resting period, activity of PDH in the active form (PDHa) did not change in either trial, yet phosphorylation of PDH-E1␣ site 1 (PDH-P1) and site 2 (PDH-P2) was elevated in the intralipid compared with the control trial. PDHa activity increased during exercise similarly in the two trials. After 3 h of exercise, PDHa activity remained elevated in the intralipid trial but returned to resting levels in the control trial. Accordingly, in both trials PDH-P1 and PDH-P2 decreased during exercise, and the decrease was more marked during intralipid infusion. Phosphorylation had returned to resting levels at 3 h of exercise only in the control trial. Thus, an inverse association between PDH-E1␣ phosphorylation and PDHa activity exists. Short-term elevation in plasma FFA at rest increases PDH-E1␣ phosphorylation, but exercise overrules this effect of FFA on PDH-E1␣ phosphorylation leading to even greater dephosphorylation during exercise with intralipid infusion than with saline. Diabetes 55:3020 -3027, 2006

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“…This concept is also illustrated by changes in heart PDC in starvation and diabetes (10). The increase in PDK4 and diminished expression of PDP1 in skeletal muscle of Otsuka Long Evans Tokushima Fatty rats before the onset of the genetically determined diabetes type 2 also indicated the importance of dual control of the kinase and phosphatase components of PDC (39). These hormonal and dietary factors center upon the changes in mRNA of specific isoforms of PDK and PDP and the expression of these proteins, properties that do not always go hand in hand (8,11,12).…”

Section: Discussionmentioning

confidence: 93%

“…Assay of PDK-The assay of PDK was based on the rate of inactivation of PDC by ATP catalyzed by the PDK component of the complex, a first order rate reaction that is basically similar to that described by Bajotto et al (39). The active nonphosphorylated residual activity of PDC was measured spectrophotometrically (16).…”

Section: Measurement Of Ipg-p and Ipg-a-mentioning

confidence: 99%

Reciprocal Control of Pyruvate Dehydrogenase Kinase and Phosphatase by Inositol Phosphoglycans: Dynamic State Set by “Push-Pull” System

McLean

Kunjara

Greenbaum

et al. 2008

Journal of Biological Chemistry

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Reversible phosphorylation of proteins regulates numerous aspects of cell function, and abnormal phosphorylation is causal in many diseases. Pyruvate dehydrogenase complex (PDC) is central to the regulation of glucose homeostasis. PDC exists in a dynamic equilibrium between de-phospho-(active) and phosphorylated (inactive) forms controlled by pyruvate dehydrogenase phosphatases (PDP1,2) and pyruvate dehydrogenase kinases (PDK1-4). In contrast to the reciprocal regulation of the phospho-/de-phospho cycle of PDC and at the level of expression of the isoforms of PDK and PDP regulated by hormones and diet, there is scant evidence for regulatory factors acting in vivo as reciprocal "on-off" switches. Here we show that the putative insulin mediator inositol phosphoglycan P-type (IPG-P) has a sigmoidal inhibitory action on PDK in addition to its known linear stimulation of PDP. Thus, at critical levels of IPG-P, this sigmoidal/linear model markedly enhances the switchover from the inactive to the active form of PDC, a "push-pull" system that, combined with the developmental and hormonal control of IPG-P, indicates their powerful regulatory function. The release of IPGs from cell membranes by insulin is significant in relation to diabetes. The chelation of IPGs with Mn 2؉ and Zn 2؉ suggests a role as "catalytic chelators" coordinating the traffic of metal ions in cells. Synthetic inositol hexosamine analogues are shown here to have a similar linear/sigmoidal reciprocal action on PDC exerting push-pull effects, suggesting their potential for treatment of metabolic disorders, including diabetes. Pyruvate dehydrogenase complex (PDC),2 an enzyme at the interface between glycolysis and the citric acid cycle, is influenced by dietary and hormonal control and by phosphorylation/dephosphorylation reactions, the former regulated by pyruvate dehydrogenase kinases (PDK1-4) and the latter by dedicated mitochondrial pyruvate dehydrogenase phosphatases (PDP1,2) (1-4). Phosphorylation forms the basis of the dynamic state of cell cycling networks, thus the balance between the active (de-phospho-) and the inactive (phospho-) forms of PDC is dependent upon the regulation of PDK and PDP (2,5,6). Cycling between two phosphorylated states is, classically, one mode of control, permitting rapid alterations in catalytic activity, e.g. in response to insulin, adrenaline, shifts in Ca 2ϩ distribution, and effector molecules. In addition, adaptive changes due to altered hormonal or dietary states, such as diabetes, starvation, or high fat/high carbohydrate diets, and related changes in the expression of isoforms of PDK and PDP in a tissue-specific manner regulate the phosphorylation state of the PDC (2, 7-12). The profile of the regulation of PDK1-4 to activation by NADH and to NADH plus acetyl CoA and ATP, together with differences in the apparent K i values for ADP, confers upon tissues individual patterns of response to alterations in metabolite profile linked to hormonal and dietary changes (2, 3, 9 -12).Inositol phosphoglycans (IPGs) are bro...

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Downregulation of the skeletal muscle pyruvate dehydrogenase complex in the Otsuka Long-Evans Tokushima Fatty rat both before and after the onset of diabetes mellitus

Cited by 36 publications

References 46 publications

Characterization of Testis-specific Isoenzyme of Human Pyruvate Dehydrogenase

Characterization of Testis-specific Isoenzyme of Human Pyruvate Dehydrogenase

PDH-E1α Dephosphorylation and Activation in Human Skeletal Muscle During Exercise

Reciprocal Control of Pyruvate Dehydrogenase Kinase and Phosphatase by Inositol Phosphoglycans: Dynamic State Set by “Push-Pull” System

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