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

Pilegaard, Henriette; Birk, Jesper B.; Sacchetti, Massimo; Mourtzakis, Marina; Dg, Hardie; Stewart, G. A.; Neufer, P. Darrell; Saltin, Bengt; Hall, Gerrit van; Wojtaszewski, Jørgen F. P.

doi:10.2337/db06-0152

Cited by 67 publications

(89 citation statements)

References 38 publications

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“…Thus, results by Nellemann et al (47) could have been influenced by a muscle fiber type-dependent regulation not detected in their whole-muscle biopsy preparation. An inverse relationship between PDH-E1a phosphorylation and PDHa activity has been shown in human skeletal muscle during exercise (48). Thus, findings in the current study suggest an increased PDHa activity in response to insulin in type II fibers only.…”

Section: Discussionsupporting

confidence: 58%

Human Muscle Fiber Type–Specific Insulin Signaling: Impact of Obesity and Type 2 Diabetes

et al. 2014

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Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulinmediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber type-specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic subjects before and after a hyperinsulinemiceuglycemic clamp. Type I fibers compared with type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), and pyruvate dehydrogenase-E1a (PDH-E1a) and a lower protein content of Akt2, TBC1 domain family member 4 (TBC1D4), and TBC1D1. In type I fibers compared with type II fibers, the phosphorylation response to insulin was similar (TBC1D4, TBC1D1, and GS) or decreased (Akt and PDH-E1a). Phosphorylation responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS, and PDH-E1a) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared with lean and obese subjects. We conclude that human type I muscle fibers compared with type II fibers have a higher glucose-handling capacity but a similar sensitivity for phosphoregulation by insulin.Skeletal muscle is important for whole-body insulinstimulated glucose disposal (1), and skeletal muscle insulin resistance is a common phenotype of obesity and type 2 diabetes (T2D) (2). Skeletal muscle is a heterogeneous tissue composed of different fiber types, which can be divided according to myosin heavy chain (MHC) isoform expression. Studies in rodents show that insulin-stimulated glucose uptake in the oxidative type I fiber-dominant muscles is higher than in muscles with a high degree of glycolytic type II fibers (3-6). Whether this phenomenon is due to differences in locomotor activity of individual muscles or a direct consequence of the fiber-type composition is largely unknown. In incubated rat muscle, insulin-induced glucose uptake was higher (;100%) in type IIa (oxidative/glycolytic) compared with IIx and IIb (glycolytic) fibers (7,8), suggesting that insulin-mediated glucose uptake is related to the oxidative capacity of the muscle fiber. In humans, a positive correlation between proportions of type I fibers in muscle and whole-body insulin sensitivity has been demonstrated (9-11). Furthermore, insulin-stimulated glucose transport in human muscle strips was associated with the relative type I fiber content (12). Thus, it is likely that human type I fibers are more important than type II fibers for maintaining glucose homeostasis in response to insulin. Indeed, a decreased proportion of type I fibers has been found in various insulin resistant states such as the metabolic syndrome (9), obesity (13,14), T2D in some (10,13,14) but not all (12,15) studies and following bedrest (16), as well as in tetraplegic patients (17), ...

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Section: Discussionsupporting

confidence: 58%

Human Muscle Fiber Type–Specific Insulin Signaling: Impact of Obesity and Type 2 Diabetes

et al. 2014

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“…Although lipoic acid is a critical cofactor of PDC, knockdown of LASY did not appear to have an immediate effect on the phosphorylation state of PDC, which is inversely related to its activity (15) (Supplementary Fig. 3).…”

Section: Discussionmentioning

confidence: 99%

Lipoic Acid Synthase (LASY)

Padmalayam¹,

Hasham

Uday³

et al. 2009

Diabetes

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OBJECTIVE-Lipoic acid synthase (LASY) is the enzyme that is involved in the endogenous synthesis of lipoic acid, a potent mitochondrial antioxidant. The aim of this study was to study the role of LASY in type 2 diabetes.RESEARCH DESIGN AND METHODS-We studied expression of LASY in animal models of type 2 diabetes. We also looked at regulation of LASY in vitro under conditions that exist in diabetes. Additionally, we looked at effects of LASY knockdown on cellular antioxidant status, inflammation, mitochondrial function, and insulin-stimulated glucose uptake.RESULTS-LASY expression is significantly reduced in tissues from animal models of diabetes and obesity compared with ageand sex-matched controls. In vitro, LASY mRNA levels were decreased by the proinflammatory cytokine tumor necrosis factor (TNF)-␣ and high glucose. Downregulation of the LASY gene by RNA interference (RNAi) reduced endogenous levels of lipoic acid, and the activities of critical components of the antioxidant defense network, increasing oxidative stress. Treatment with exogenous lipoic acid compensated for some of these defects. RNAi-mediated downregulation of LASY induced a significant loss of mitochondrial membrane potential and decreased insulinstimulated glucose uptake in skeletal muscle cells. In endothelial cells, downregulation of LASY aggravated the inflammatory response that manifested as an increase in both basal and TNF-␣-induced expression of the proinflammatory cytokine, monocyte chemoattractant protein-1 (MCP-1). Overexpression of the LASY gene ameliorated the inflammatory response.CONCLUSIONS-Deficiency of LASY results in an overall disturbance in the antioxidant defense network, leading to increased inflammation, insulin resistance, and mitochondrial dysfunction. Diabetes 58:600-608, 2009 T ype 2 diabetes is the most prevalent chronic metabolic disease in the world. In the past decade, considerable evidence has accumulated implicating oxidative stress as a key factor that accelerates the onset and progression of type 2 diabetes. Chronic oxidative stress causes inflammation and mitochondrial dysfunction and culminates in insulin resistance, which ultimately progresses to diabetes. Oxidative stress also promotes cellular dysfunction and damage, leading to the development of secondary complications of diabetes. The underlying cause of redox imbalance is a deficiency in the endogenous antioxidant network. This deficiency would result in an inability to combat excessive amounts of reactive oxygen species (ROS) and tip the balance in favor of oxidative stress.Redox balance is maintained by an antioxidant defense network within mitochondria, consisting of stress-responsive enzymes such as superoxide dismutase (SOD), catalase and reduced glutathione (GSH), and antioxidants. The antioxidant defense network is activated in response to excessive production of ROS in the mitochondria, thereby neutralizing the ROS before they inflict damage on cellular molecules. Lipoic acid is a potent mitochondrial antioxidant that plays a central role in...

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“…Ser 232 (site 3) has been reported to be phosphorylated by PDK1 primarily expressed in heart muscle (4), while the two latter phosphorylation sites are thought to be the dominant in skeletal muscle (17,19,32). In addition to these three sites, a new phosphorylation site has been identified at PDH Ser 295 (www.phosida.com), but to our knowledge the regulation of this site has never been examined.…”

Section: Antibodiesmentioning

confidence: 99%

“…556433; BD Biosciences). Protein levels of the PDH-E1␣ subunit and PDH-E1␣ phosphorylation at Ser 293 and Ser 300 were determined using in-house made antibodies as previously described (32), and PDK4 protein as well as phosphorylation of PDH-E1␣ Ser 295 were determined using new in-house made antibodies as described above.…”

Section: Sds-page and Western Blot Analysismentioning

confidence: 99%

PGC-1α increases PDH content but does not change acute PDH regulation in mouse skeletal muscle

Kiilerich

Adser

Jakobsen

et al. 2010

American Journal of Physiology-Regulatory, Integrative and Comp

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The aim of this study was to test whether the transcriptional coactivator peroxisome proliferator-activated receptor (PPAR)-␥ coactivator (PGC)1␣ regulates the content of pyruvate dehydrogenase (PDH)-E1␣ and influences PDH activity through regulation of pyruvate dehydrogenase kinase-4 (PDK4) expression and subsequently PDH phosphorylation. PGC-1␣ whole body knockout (KO), muscle-specific PGC-1␣ overexpressing mice (MCK PGC-1␣), and littermate wild-type (WT) mice underwent two interventions known to affect PDH. Quadriceps muscles were removed from fed and 24-h fasted mice as well as at 6 h of recovery after 1-h running and from mice that did not run acutely. PDH-E1␣ protein content and PDH-E1␣ phosphorylation were lower in PGC-1␣ KO and higher in MCK PGC-1␣ mice at rest, but, while MCK PGC-1␣ had higher PDK4 protein content, KO of PGC-1␣ had no effect on PDK4 protein content. The differences in phosphorylation partly vanished when expressing phosphorylation relative to the PDH-E1␣ content with only a maintained elevated phosphorylation in MCK PGC-1␣ mice. Fasting upregulated PDK4 protein in PGC-1␣ KO, MCK PGC-1␣ and WT mice, but this was not consistently associated with increased PDH-E1␣ phosphorylation. Downregulation of the activity of PDH in the active form (PDHa) at 6-h recovery from exercise in both the PGC-1␣ KO and MCK PGC-1␣ mice and the association between PDH-E1␣ phosphorylation and PDHa activity in PGC-1␣ KO mice indicate that PGC-1␣ is not required for these responses. In conclusion, PGC-1␣ regulates PDH-E1␣ protein content in parallel with mitochondrial oxidative proteins, but does not seem to influence PDH regulation in mouse skeletal muscle in response to fasting and in recovery from exercise. pyruvate dehydrogenase kinase THE TRANSCRIPTIONAL COACTIVATOR peroxisome proliferator-activated receptor (PPAR)-␥ coactivator (PGC)1␣ has been shown to influence the oxidative capacity of skeletal muscle through both regulation of mitochondrial biogenesis (24,38) and capillarization of skeletal muscle (1,22). Thus, PGC-1␣ knockout (KO) mice have reduced capillarization and decreased expression of proteins in oxidative metabolism in skeletal muscle (23,25), while PGC-1␣ overexpression mice have increased capillarization and increased expression of oxidative enzymes in skeletal muscle (24,47). In accordance with these effects on skeletal muscle oxidative capacity, PGC-1␣ KO mice have lower endurance exercise capacity and muscle-specific PGC-1␣ overexpression (MCK PGC-1␣) mice have improved endurance exercise capacity relative to wildtype (WT) mice (5,11,23). These effects on exercise performance may, however, not only be due to PGC-1␣-induced effects on oxidative capacity, but also in part be due to PGC-1␣-mediated regulation of substrate choice. This possibility is supported by the findings that MCK PGC-1␣ overexpression mice exhibit lower respiratory exchange ratio during treadmill running reflecting higher fat oxidation (5). The molecular mechanisms behind this have, however, not yet been clarified.The pyruv...

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

Cited by 67 publications

References 38 publications

Human Muscle Fiber Type–Specific Insulin Signaling: Impact of Obesity and Type 2 Diabetes

Human Muscle Fiber Type–Specific Insulin Signaling: Impact of Obesity and Type 2 Diabetes

Lipoic Acid Synthase (LASY)

PGC-1α increases PDH content but does not change acute PDH regulation in mouse skeletal muscle

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