scholarly journals Effects of altered pyruvate dehydrogenase activity on contracting skeletal muscle bioenergetics

2019 ◽  
Vol 316 (1) ◽  
pp. R76-R86 ◽  
Author(s):  
Jonathan D. Kasper ◽  
Ronald A. Meyer ◽  
Daniel A. Beard ◽  
Robert W. Wiseman
Keyword(s):  
Steady State ◽  
Pyruvate Dehydrogenase ◽  
Primary Source ◽  
Atp Synthesis ◽  
Synthesis Rate ◽  
Resonance Spectroscopy ◽  
Phosphate Potential ◽  
Muscle Energetics ◽  
Atp Production

During aerobic exercise (>65% of maximum oxygen consumption), the primary source of acetyl-CoA to fuel oxidative ATP synthesis in muscle is the pyruvate dehydrogenase (PDH) reaction. This study investigated how regulation of PDH activity affects muscle energetics by determining whether activation of PDH with dichloroacetate (DCA) alters the dynamics of the phosphate potential of rat gastrocnemius muscle during contraction. Twitch contractions were induced in vivo over a broad range of intensities to sample submaximal and maximal aerobic workloads. Muscle phosphorus metabolites were measured in vivo before and after DCA treatment by phosphorus nuclear magnetic resonance spectroscopy. At rest, DCA increased PDH activation compared with control (90 ± 12% vs. 23 ± 3%, P < 0.05), with parallel decreases in inorganic phosphate (Pi) of 17% (1.4 ± 0.2 vs. 1.7 ± 0.1 mM, P < 0.05) and an increase in the free energy of ATP hydrolysis (ΔGATP) (−66.2 ± 0.3 vs. −65.6 ± 0.2 kJ/mol, P < 0.05). During stimulation DCA increased steady-state phosphocreatine (PCr) and the magnitude of ΔGATP, with concomitant reduction in Pi and ADP concentrations. These effects were not due to kinetic alterations in PCr hydrolysis, resynthesis, or glycolytic ATP production and altered the flow-force relationship between mitochondrial ATP synthesis rate and ΔGATP. DCA had no significant effect at 1.0- to 2.0-Hz stimulation because physiological mechanisms at these high stimulation levels cause maximal activation of PDH. These data support a role of PDH activation in the regulation of the energetic steady state by altering the phosphate potential (ΔGATP) at rest and during contraction.

scholarly journals Mitochondrial function and increased convective O2 transport: implications for the assessment of mitochondrial respiration in vivo

2013 ◽  
Vol 115 (6) ◽  
pp. 803-811 ◽  
Author(s):  
Gwenael Layec ◽  
Luke J. Haseler ◽  
Joel D. Trinity ◽  
Corey R. Hart ◽  
Xin Liu ◽  
...  
Keyword(s):  
Blood Flow ◽  
Mitochondrial Function ◽  
Mitochondrial Respiration ◽  
Near Infrared ◽  
Reactive Hyperemia ◽  
Atp Synthesis ◽  
Synthesis Rate ◽  
Resonance Spectroscopy ◽  
Doppler Ultrasound Imaging

Although phosphorus magnetic resonance spectroscopy (31P-MRS)-based evidence suggests that in vivo peak mitochondrial respiration rate in young untrained adults is limited by the intrinsic mitochondrial capacity of ATP synthesis, it remains unknown whether a large, locally targeted increase in convective O2 delivery would alter this interpretation. Consequently, we examined the effect of superimposing reactive hyperemia (RH), induced by a period of brief ischemia during the last minute of exercise, on oxygen delivery and mitochondrial function in the calf muscle of nine young adults compared with free-flow conditions (FF). To this aim, we used an integrative experimental approach combining 31P-MRS, Doppler ultrasound imaging, and near-infrared spectroscopy. Limb blood flow [area under the curve (AUC), 1.4 ± 0.8 liters in FF and 2.5 ± 0.3 liters in RH, P < 0.01] and convective O2 delivery (AUC, 0.30 ± 0.16 liters in FF and 0.54 ± 0.05 liters in RH, P < 0.01), were significantly increased in RH compared with FF. RH was also associated with significantly higher capillary blood flow ( P < 0.05) and faster tissue reoxygenation mean response times (70 ± 15 s in FF and 24 ± 15 s in RH, P < 0.05). This resulted in a 43% increase in estimated peak mitochondrial ATP synthesis rate (29 ± 13 mM/min in FF and 41 ± 14 mM/min in RH, P < 0.05) whereas the phosphocreatine (PCr) recovery time constant in RH was not significantly different ( P = 0.22). This comprehensive assessment of local skeletal muscle O2 availability and utilization in untrained subjects reveals that mitochondrial function, assessed in vivo by 31P-MRS, is limited by convective O2 delivery rather than an intrinsic mitochondrial limitation.

scholarly journals Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action

1997 ◽  
Vol 83 (3) ◽  
pp. 867-874 ◽  
Author(s):  
T. W. Ryschon ◽  
M. D. Fowler ◽  
R. E. Wysong ◽  
A.-R. Anthony ◽  
R. S. Balaban
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Production Rate ◽  
Human Skeletal Muscle ◽  
Atp Synthesis ◽  
High Energy ◽  
High Energy Phosphates ◽  
Muscle Action ◽  
Atp Production

Ryschon, T. W., Fowler, R. E. Wysong, A.-R. Anthony, and R. S. Balaban. Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action. J. Appl. Physiol. 83(3): 867–874, 1997.—The purpose of this study was to estimate the efficiency of ATP utilization for concentric, eccentric, and isometric muscle action in the human tibialis anterior and extensor digitorum longus in vivo. A dynamometer was used to quantitate muscle work, or tension, while simultaneous 31P-nuclear magnetic resonance data were collected to monitor ATP, phosphocreatine, inorganic phosphate, and pH. The relative efficiency of the actions was estimated in two ways: steady-state effects on high-energy phosphates and a direct comparison of ATP synthesis rates with work. In the steady state, the cytosolic free energy dropped to the lowest value with concentric activity, followed by eccentric and isometric action for comparative muscle tensions. Estimates of ATP synthesis rates revealed a mechanochemical efficiency [i.e., ATP production rate/work (both in J/s)] of 15.0 ± 1.3% in concentric and 34.7 ± 6.1% in eccentric activity. The estimated maximum ATP production rate was highest in concentric action, suggesting an activation of energy metabolism under these conditions. By using direct measures of metabolic strain and ATP turnover, these data demonstrate a decreasing metabolic efficiency in human muscle action from isometric, to eccentric, to concentric action.

Activation of glycolysis in human muscle in vivo

1997 ◽  
Vol 273 (1) ◽  
pp. C306-C315 ◽  
Author(s):  
K. E. Conley ◽  
M. L. Blei ◽  
T. L. Richards ◽  
M. J. Kushmerick ◽  
S. A. Jubrias
Keyword(s):  
Muscle Activation ◽  
Feedback Regulation ◽  
Atp Synthesis ◽  
Resonance Spectroscopy ◽  
Control Mechanisms ◽  
Atp Production ◽  
Proton Production ◽  
Sugar Phosphates ◽  
Glycolytic Rate

We tested the cytoplasmic control mechanisms for glycolytic ATP synthesis in human wrist flexor muscles. The forearm was made ischemic and activated by maximal twitch stimulation of the median and ulnar nerves in 10 subjects. Kinetic changes in phosphocreatine, Pi, ADP, ATP, sugar phosphates, and pH were measured by 31P magnetic resonance spectroscopy at 7.1-s intervals. Proton production was determined from pH and tissue buffer capacity during stimulation. Glycolysis was activated between 30 and 50 stimulations, and the rate did not significantly change through the stimulation period. The independence of glycolytic rate on [Pi], [ADP], or [AMP] indicates that feedback regulation by these metabolites could not account for this activation of glycolysis. However, glycolytic H+ and ATP production increased sixfold from 0.5 to 3 Hz, indicating that glycolytic rate reflected muscle activation frequency. This dependence of glycolytic rate on muscle stimulation frequency and independence on metabolite levels is consistent with control of glycolysis by Ca2+.

In vivo NMR investigation of intramuscular glucose metabolism in conscious rats

1997 ◽  
Vol 273 (1) ◽  
pp. E139-E148 ◽  
Author(s):  
B. M. Jucker ◽  
A. J. Rennings ◽  
G. W. Cline ◽  
K. F. Petersen ◽  
G. I. Shulman
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Nmr Spectroscopy ◽  
Pyruvate Dehydrogenase ◽  
Glycogen Synthesis ◽  
Synthesis Rate ◽  
Conscious Rats ◽  
Pyruvate Carboxylation ◽  
13C Nuclear Magnetic Resonance

In vivo 13C nuclear magnetic resonance (NMR) spectroscopy was used to determine quantitatively the flux of muscle glycolysis, glycogen synthesis, pyruvate dehydrogenase, and pyruvate carboxylation in the hindlimb of conscious rats. 13C NMR spectroscopy was used to observe [1-13C]glucose label precursor incorporation into intramuscular [1-13C]glycogen, [3-13C]lactate, and [3-13C]alanine during a hyperglycemic (approximately 11 mM)-hyperinsulinemic (10 mU.kg-1.min-1) clamp. The glycogen synthesis rate was calculated to be 224 +/- 23 nmol.g-1.min-1. The kinetic data obtained from the label turnover in the intramuscular C-3 lactate and C-3 alanine metabolite pools, as well as in plasma C-3 lactate and C-3 alanine, were combined with a steady-state rate analysis to determine the glycolytic flux (67.4 +/- 10.1 nmol.g-1.min-1). Steady-state isotopomer analysis of glutamate and pyruvate in skeletal muscle tissue extracts was used to determine the anaplerotic contribution of substrate via pyruvate carboxylation (Vpc). The pyruvate dehydrogenase flux (Vpdh) was calculated after a steady-state flux correction for Vpc. Calculated values of Vpc and Vpdh were 24.8 +/- 4.3 and 110.0 +/- 18.7 nmol.g-1.min-1, respectively. In addition, [2-13C]acetate was used in a separate study to determine that pyruvate carboxylation was the major pathway for anaplerosis in skeletal muscle under conditions of hyperglycemia-hyperinsulinemia.

scholarly journals Muscle energetics changes throughout maturation: a quantitative 31P-MRS analysis

2010 ◽  
Vol 109 (6) ◽  
pp. 1769-1778 ◽  
Author(s):  
Anne Tonson ◽  
Sébastien Ratel ◽  
Yann Le Fur ◽  
Christophe Vilmen ◽  
Patrick J. Cozzone ◽  
...  
Keyword(s):  
Energy Demand ◽  
Recovery Period ◽  
Exercise Bout ◽  
Oxidative Capacity ◽  
Recovery Phase ◽  
Resonance Spectroscopy ◽  
Compensatory Mechanism ◽  
Muscle Energetics ◽  
Atp Production

We quantified energy production in 7 prepubescent boys (11.7 ± 0.6 yr) and 10 men (35.6 ± 7.8 yr) using 31P-magnetic resonance spectroscopy to investigate whether development affects muscle energetics, given that resistance to fatigue has been reported to be larger before puberty. Each subject performed a finger flexions exercise at 0.7 Hz against a weight adjusted to 15% of their maximal voluntary strength for 3 min, followed by a 15-min recovery period. The total energy cost was similar in both groups throughout the exercise bout, whereas the interplay of the different metabolic pathways was different. At the onset of exercise, children exhibited a higher oxidative contribution (50 ± 15% in boys and 25 ± 8% in men, P < 0.05) to ATP production, whereas the phosphocreatine breakdown contribution was reduced (40 ± 10% in boys and 53 ± 12% in men, P < 0.05), likely as a compensatory mechanism. The anaerobic glycolysis activity was unaffected by maturation. The recovery phase also disclosed differences regarding the rates of proton efflux (6.2 ± 2.5 vs. 3.8 ± 1.9 mM·pH unit−1·min−1, in boys and men, respectively, P < 0.05), and phosphocreatine recovery, which was significantly faster in boys than in men (rate constant of phosphocreatine recovery: 1.3 ± 0.5 vs. 0.7 ± 0.4 min−1; Vmax: 37.5 ± 14.5 vs. 21.1 ± 12.2 mM/min, in boys and men, respectively, P < 0.05). Our results obtained in vivo clearly showed that maturation affects muscle energetics. Children relied more on oxidative metabolism and less on creatine kinase reaction to meet energy demand during exercise. This phenomenon can be explained by a greater oxidative capacity, probably linked to a higher relative content in slow-twitch fibers before puberty.

scholarly journals Muscle oxygenation and ATP turnover when blood flow is impaired by vascular disease

2002 ◽  
Vol 16 (3-4) ◽  
pp. 317-334 ◽  
Author(s):  
Graham J. Kemp ◽  
Neil Roberts ◽  
William E. Bimson ◽  
Ali Bakran ◽  
Simon P. Frostick
Keyword(s):  
Vascular Disease ◽  
Near Infrared ◽  
Atp Synthesis ◽  
Normal Subjects ◽  
Synthesis Rate ◽  
Resonance Spectroscopy ◽  
Muscle Creatine Kinase ◽  
Muscle Energy Metabolism ◽  
Atp Supply

In exercising muscle, creatine kinase ensures that mismatch between ATP supply and ATP use results in net phosphocreatine (PCr) splitting. This,inter alia, makes31P magnetic resonance spectroscopy a useful tool for studying muscle ‘energy metabolism’ noninvasivelyin vivo. We combined this with near–infrared spectroscopy (NIRS) to study ATP synthesis and oxygenation in calf muscle of normal subjects and patients with peripheral vascular disease. Experimental and clinical details and basic data have been published elsewhere (G.J. Kemp et al.,Journal of Vascular Surgery34 (2001), 1103–10); we here propose an analysis of interactions between metabolic ‘error signals’ and cellular PO2(estimated from NIRS changes, provisionally assumed to reflect deoxymyoglobin). Post–exercise PCr recovery is monoexponential, and the linear relationship between PCr resynthesis rate (= oxidative ATP synthesis) and the perturbation in PCr (conceptually the simplest error signal) is consistent with negative feedback. In patients the inferred ‘mitochondrial capacity’ (= oxidative ATP synthesis at ‘zero’ PCr) is decreased by 53±6%, leading to reduced oxidative ATP contribution in exercise, because of increased deoxygenation. Increased PCr perturbation partially outweighs cellular hypoxia, but as low cellular PO2is required for capillary–mitochondrion O2diffusion, rate–signal relationships may overstate maximum oxidative ATP synthesis rate.

scholarly journals Aerobic Growth of Escherichia coli Is Reduced, and ATP Synthesis Is Selectively Inhibited when Five C-terminal Residues Are Deleted from the ϵ Subunit of ATP Synthase

2015 ◽  
Vol 290 (34) ◽  
pp. 21032-21041 ◽  
Author(s):  
Naman B. Shah ◽  
Thomas M. Duncan
Keyword(s):  
Escherichia Coli ◽  
Atp Synthase ◽  
Atp Hydrolysis ◽  
Atp Synthesis ◽  
Intrinsic Rate ◽  
Synthesis Rate ◽  
Final Segment ◽  
Rotary Catalysis

F-type ATP synthases are rotary nanomotor enzymes involved in cellular energy metabolism in eukaryotes and eubacteria. The ATP synthase from Gram-positive and -negative model bacteria can be autoinhibited by the C-terminal domain of its ϵ subunit (ϵCTD), but the importance of ϵ inhibition in vivo is unclear. Functional rotation is thought to be blocked by insertion of the latter half of the ϵCTD into the central cavity of the catalytic complex (F1). In the inhibited state of the Escherichia coli enzyme, the final segment of ϵCTD is deeply buried but has few specific interactions with other subunits. This region of the ϵCTD is variable or absent in other bacteria that exhibit strong ϵ-inhibition in vitro. Here, genetically deleting the last five residues of the ϵCTD (ϵΔ5) caused a greater defect in respiratory growth than did the complete absence of the ϵCTD. Isolated membranes with ϵΔ5 generated proton-motive force by respiration as effectively as with wild-type ϵ but showed a nearly 3-fold decrease in ATP synthesis rate. In contrast, the ϵΔ5 truncation did not change the intrinsic rate of ATP hydrolysis with membranes. Further, the ϵΔ5 subunit retained high affinity for isolated F1 but reduced the maximal inhibition of F1-ATPase by ϵ from >90% to ∼20%. The results suggest that the ϵCTD has distinct regulatory interactions with F1 when rotary catalysis operates in opposite directions for the hydrolysis or synthesis of ATP.

Abstract MP247: Mitochondrial Complex V Is Regulated By GRK2 In The Heart

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Kimberly Ferrero ◽  
Jessica M Pfleger ◽  
Kurt Chuprun ◽  
Eric Barr ◽  
Erhe Gao ◽  
...  
Keyword(s):  
Atp Synthase ◽  
Cardiac Injury ◽  
Atp Synthesis ◽  
Cardiac Metabolism ◽  
Neonatal Rat ◽  
Interacting Proteins ◽  
Atp Production

The GPCR kinase GRK2 is highly expressed the heart; importantly, during cardiac injury or heart failure (HF) both levels and activity of GRK2 increase. The role of GRK2 during HF is canonically studied upstream of β-adrenergic desensitization. However, GRK2 has a large interactome and noncanonical functions for this kinase are being uncovered. We have discovered that in the heart, GRK2 translocates to mitochondria ( mtGRK2 ) following injury and is associated with negative effects on cardiac metabolism. Thus, we have sought to identify the mechanism(s) by which GRK2 can regulate mitochondrial function. We hypothesize that mtGRK2 interacts with proteins which regulate bioenergetics and substrate utilization, and this never-before-described role may partially explain the altered mitochondrial phenotype seen following cardiac injury or HF. Stress-induced mitochondrial translocation of GRK2 was validated in neonatal rat ventricular myocytes, murine heart tissue and a cardiac-derived cell line. Consequently, the GRK2 interactome was mapped basally and under stress conditions in vitro, in vivo , and with tagged recombinant peptides. GRK2-interacting proteins were isolated via immunoprecipitation and analyzed via liquid chromatography-mass spectroscopy (LCMS). Proteomics analysis (IPA; Qiagen) identified mtGRK2 interacting proteins which were also involved in mitochondrial dysfunction. Excitingly, Complexes I, II, IV and V (ATP synthase) of the electron transport chain (ETC) were identified in the subset of mtGRK2-dysfunction partners. Several mtGRK2-ETC interactions were increased following stress, particularly those in Complex V. We further established that mtGRK2 phosphorylates some of the subunits of Complex V, particularly the ATP synthase barrel which is critical for ATP production in the heart. Specific amino acid residues on these subunits have been identified using PTM-LCMS and are currently being validated in a murine model of myocardial infarction. To support these data, we have also determined that alterations in either the levels or kinase activity of GRK2 appear to alter the enzymatic activity of Complex V in vitro , thus altering ATP production. In summary, the phosphorylation of the ATP synthesis machinery by mtGRK2 may be regulating some of the phenotypic effects of injured or failing hearts such as increased ROS production and reduced fatty acid metabolism. Research is ongoing in our lab to elucidate the novel role of GRK2 in regulating mitochondrial bioenergetics and cell death, thus uncovering an exciting, druggable novel target for rescuing cardiac function in patients with injured and/or failing hearts.

scholarly journals Nuclear Expression of a Mitochondrial DNA Gene: Mitochondrial Targeting of Allotopically Expressed Mutant ATP6 in Transgenic Mice

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
David A. Dunn ◽  
Carl A. Pinkert
Keyword(s):  
Mitochondrial Dna ◽  
Atp Synthesis ◽  
Serum Lactate ◽  
Superior Performance ◽  
Synthesis Rate ◽  
Mitochondrial Targeting ◽  
Biochemical Tests ◽  
Balance Beam ◽  
Protein Levels

Nuclear encoding of mitochondrial DNA transgenes followed by mitochondrial targeting of the expressed proteins (allotopic expression; AE) represents a potentially powerful strategy for creating animal models of mtDNA disease. Mice were created that allotopically express either a mutant (A6M) or wildtype (A6W)mt-Atp6transgene. Compared to non-transgenic controls, A6M mice displayed neuromuscular and motor deficiencies (wire hang, pole, and balance beam analyses;P<0.05), no locomotor differences (gait analysis;P<0.05) and enhanced endurance in Rota-Rod evaluations (P<0.05). A6W mice exhibited inferior muscle strength (wire hang test;P<0.05), no difference in balance beam footsteps, accelerating Rota-Rod, pole test and gait analyses; (P<0.05) and superior performance in balance beam time-to-cross and constant velocity Rota-Rod analyses (P<0.05) in comparison to non-transgenic control mice. Mice of both transgenic lines did not differ from non-transgenic controls in a number of bioenergetic and biochemical tests including measurements of serum lactate and mitochondrial MnSOD protein levels, ATP synthesis rate, and oxygen consumption (P>0.05). This study illustrates a mouse model capable of circumventingin vivomitochondrial mutations. Moreover, it provides evidence supporting AE as a tool for mtDNA disease research with implications in development of DNA-based therapeutics.

scholarly journals Complex I is bypassed during high intensity exercise

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Avlant Nilsson ◽  
Elias Björnson ◽  
Mikael Flockhart ◽  
Filip J. Larsen ◽  
Jens Nielsen
Keyword(s):  
High Intensity ◽  
Complex I ◽  
Atp Synthesis ◽  
Metabolic Model ◽  
High Intensity Exercise ◽  
Whole Body ◽  
Synthesis Rate ◽  
Proteomics Data ◽  
Exercise Tests

Abstract Human muscles are tailored towards ATP synthesis. When exercising at high work rates muscles convert glucose to lactate, which is less nutrient efficient than respiration. There is hence a trade-off between endurance and power. Metabolic models have been developed to study how limited catalytic capacity of enzymes affects ATP synthesis. Here we integrate an enzyme-constrained metabolic model with proteomics data from muscle fibers. We find that ATP synthesis is constrained by several enzymes. A metabolic bypass of mitochondrial complex I is found to increase the ATP synthesis rate per gram of protein compared to full respiration. To test if this metabolic mode occurs in vivo, we conduct a high resolved incremental exercise tests for five subjects. Their gas exchange at different work rates is accurately reproduced by a whole-body metabolic model incorporating complex I bypass. The study therefore shows how proteome allocation influences metabolism during high intensity exercise.

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