Kinetic characteristics of propofol-induced inhibition of electron-transfer chain and fatty acid oxidation in human and rodent skeletal and cardiac muscles

AbstractIntroductionPropofol causes a profound inhibition of fatty acid oxidation (FAO) and reduces spare electron transfer chain (ETC) capacity in a range of human and rodent cells and tissues – a feature that might be related to the pathogenesis of Propofol Infusion Syndrome. We aimed to explore the mechanism of propofol-induced alteration of bioenergetic pathways by describing its kinetic characteristics.MethodsWe obtained samples of skeletal and cardiac muscle from Wistar rat (n=3) and human subjects: vastus lateralis from hip surgery patients (n=11) and myocardium from brain-dead organ donors (n=10). We assessed mitochondrial functional indices using standard SUIT protocol and high resolution respirometry in fresh tissue homogenates with or without short-term exposure to a range of propofol concentration (2.5-100 μg/ml). After finding concentrations of propofol causing partial inhibition of a particular pathways, we used that concentration to construct kinetic curves by plotting oxygen flux against substrate concentration during its stepwise titration in the presence or absence of propofol. By spectrophotometry we also measured the influence of the same propofol concentrations on the activity of isolated respiratory complexes.ResultsWe found that human muscle and cardiac tissues are more sensitive to propofol-mediated inhibition of bioenergetic pathways than rats tissue. In human homogenates, palmitoyl carnitine-driven respiration was inhibited at much lower concentrations of propofol than that required for a reduction of ETC capacity, suggesting FAO inhibition mechanism different from downstream limitation or carnitine-palmitoyl transferase-1 inhibition. Inhibition of Complex I was characterised by more marked reduction of Vmax, in keeping with non-competitive nature of the inhibition and the pattern was similar to the inhibition of Complex II or ETC capacity. There was no inhibition of Complex IV nor increased leak through inner mitochondrial membrane with up to 100 μg/ml of propofol. If measured in isolation by spectrophotometry, propofol 10 μg/ml did not affect the activity of any respiratory complexes.ConclusionIn human skeletal and heart muscle homogenates, propofol in concentrations that are achieved in propofol-anaesthetized patients, causes a direct inhibition of fatty acid oxidation, in addition to inhibiting flux of electrons through inner mitochondrial membrane. The inhibition is more marked in human as compared to rodent tissues.

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Kinetic characteristics of propofol-induced inhibition of electron-transfer chain and fatty acid oxidation in human and rodent skeletal and cardiac muscles

PLoS ONE ◽

10.1371/journal.pone.0217254 ◽

2019 ◽

Vol 14 (10) ◽

pp. e0217254

Author(s):

Tomáš Urban ◽

Petr Waldauf ◽

Adéla Krajčová ◽

Kateřina Jiroutková ◽

Milada Halačová ◽

...

Keyword(s):

Electron Transfer ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Acid Oxidation ◽

Kinetic Characteristics ◽

Electron Transfer Chain ◽

Cardiac Muscles ◽

Transfer Chain

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Primary and Secondary Carnitine Deficiency Syndromes

Journal of Child Neurology ◽

10.1177/0883073895010002s03 ◽

1995 ◽

Vol 10 (2_suppl) ◽

pp. 2S8-2S24 ◽

Cited By ~ 69

Author(s):

Roser Pons ◽

Darryl C. De Vivo

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

Mitochondrial Membrane ◽

Carnitine Deficiency ◽

Carnitine Palmitoyltransferase ◽

Acid Oxidation ◽

Inner Mitochondrial Membrane ◽

Chain Acyl ◽

Membrane Bound ◽

Long Chain

The objective of this article is to review primary and secondary causes of carnitine deficiency, emphasizing recent advances in our knowledge of fatty acid oxidation. It is now understood that the cellular metabolism of fatty acids requires the cytosolic carnitine cycle and the mitochondrial β-oxidation cycle. Carnitine is central to the translocation of the long chain acyl-CoAs across the inner mitochondrial membrane. The mitochondrial β-oxidation cycle is composed of a newly described membrane-bound system and the classic matrix compartment system. Very long chain acyl-CoA dehydrogenase and the trifunctional enzyme complex are embedded in the inner mitochondrial membrane, and metabolize the long chain acyl-CoAs. The chain shortened acyl-CoAs are further degraded by the well-known system in the mitochondrial matrix. Numerous metabolic errors have been described in the two cycles of fatty acid oxidation; all are transmitted as autosomal recessive traits. Primary or secondary carnitine deficiency is present in all these clinical conditions except carnitine palmitoyltransferase type I and the classic adult form of carnitine palmitoyltransferase type II deficiency. The sole example of primary carnitine deficiency is the genetic defect involving the active transport across the plasmalemmal membrane. This condition responds dramatically to oral carnitine therapy. The secondary carnitine deficiencies respond less obviously to carnitine replacement. These conditions are managed by high carbohydrate, low fat frequent feedings, and vitamin/cofactor supplementation (eg, carnitine, glycine, and riboflavin). Medium chain triglycerides may be useful in the dietary management of patients with inborn errors of the cytosolic carnitine cycle or the mitochondrial membrane-bound long chain specific β-oxidation system. (J Child Neurol 1995;10(Suppl):2S8-2S24).

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Regulation of fatty acid oxidation in untrained vs. trained men during exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1998.274.3.e510 ◽

1998 ◽

Vol 274 (3) ◽

pp. E510-E515 ◽

Cited By ~ 20

Author(s):

Labros S. Sidossis ◽

Robert R. Wolfe ◽

Andrew R. Coggan

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Mitochondrial Membrane ◽

Fat Oxidation ◽

Cycle Ergometer ◽

Acid Oxidation ◽

Trained Group ◽

Sedentary Group ◽

The Difference

We have recently shown that increased carbohydrate flux decreases fat oxidation during exercise by inhibition of fatty acid entry into the mitochondria. Because endurance training reduces the rate of carbohydrate flux during exercise, we hypothesized that training increases fat oxidation by relieving this inhibition. To test this hypothesis, five sedentary and five endurance-trained men exercised on a cycle ergometer at an oxygen consumption (V˙o 2) of ∼2.0 l/min, representing 80 and 40% peakV˙o 2, respectively. [1-13C]oleate and [1-14C]octanoate, long- and medium-chain fatty acids, respectively, were infused for the duration of the studies. Carbohydrate oxidation was significantly higher in the sedentary group (196 ± 9 vs. 102 ± 17 μmol ⋅ kg−1 ⋅ min−1, P < 0.05). Oleate oxidation was higher in the trained group (3.8 ± 0.6 vs. 1.9 ± 0.3 μmol ⋅ kg−1 ⋅ min−1, P < 0.05), whereas octanoate oxidation was not different between the two groups. The percentage of oleate that was taken up by tissues and oxidized was higher in the trained group (76 ± 7 vs. 58 ± 3%, P < 0.05). However, the percentage of octanoate taken up and oxidized was not different (82 ± 3 vs. 85 ± 4%, not significant). Because octanoate, unlike oleate, can freely diffuse across the mitochondrial membrane, the present results suggest that the difference in fatty acid oxidation between trained and untrained individuals may be due to enhanced fatty acid entry into the mitochondria.

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Roles of key active-site residues in flavocytochrome P450 BM3

Biochemical Journal ◽

10.1042/bj3390371 ◽

1999 ◽

Vol 339 (2) ◽

pp. 371-379 ◽

Cited By ~ 118

Author(s):

Michael A. NOBLE ◽

Caroline S. MILES ◽

Stephen K. CHAPMAN ◽

Dominikus A. LYSEK ◽

Angela C. MACKAY ◽

...

Keyword(s):

Electron Transfer ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Active Site ◽

Side Chain ◽

Acid Oxidation ◽

Dodecanoic Acid ◽

Wild Type ◽

Active Site Residues ◽

P450 Bm3

The effects of mutation of key active-site residues (Arg-47, Tyr-51, Phe-42 and Phe-87) in Bacillus megaterium flavocytochrome P450 BM3 were investigated. Kinetic studies on the oxidation of laurate and arachidonate showed that the side chain of Arg-47 contributes more significantly to stabilization of the fatty acid carboxylate than does that of Tyr-51 (kinetic parameters for oxidation of laurate: R47A mutant, Km 859 µM, kcat 3960 min-1; Y51F mutant, Km 432 µM, kcat 6140 min-1; wild-type, Km 288 µM, kcat 5140 min-1). A slightly increased kcat for the Y51F-catalysed oxidation of laurate is probably due to decreased activation energy (ΔG‡) resulting from a smaller ΔG of substrate binding. The side chain of Phe-42 acts as a phenyl ‘cap ’ over the mouth of the substrate-binding channel. With mutant F42A, Km is massively increased and kcat is decreased for oxidation of both laurate (Km 2.08 mM, kcat 2450 min-1) and arachidonate (Km 34.9 µM, kcat 14620 min-1; compared with values of 4.7 µM and 17100 min-1 respectively for wild-type). Amino acid Phe-87 is critical for efficient catalysis. Mutants F87G and F87Y not only exhibit increased Km and decreased kcat values for fatty acid oxidation, but also undergo an irreversible conversion process from a ‘fast ’ to a ‘slow ’ rate of substrate turnover [for F87G (F87Y)-catalysed laurate oxidation: kcat ‘fast ’, 760 (1620) min-1; kcat ‘slow ’, 48.0 (44.6) min-1; kconv (rate of conversion from fast to slow form), 4.9 (23.8) min-1]. All mutants showed less than 10% uncoupling of NADPH oxidation from fatty acid oxidation. The rate of FMN-to-haem electron transfer was shown to become rate-limiting in all mutants analysed. For wild-type P450 BM3, the rate of FMN-to-haem electron transfer (8340 min-1) is twice the steady-state rate of oxidation (4100 min-1), indicating that other steps contribute to rate limitation. Active-site structures of the mutants were probed with the inhibitors 12-(imidazolyl)dodecanoic acid and 1-phenylimidazole. Mutant F87G binds 1-phenylimidazole > 10-fold more tightly than does the wild-type, whereas mutant Y51F binds the haem-co-ordinating fatty acid analogue 12-(imidazolyl)dodecanoic acid > 30-fold more tightly than wild-type.

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Relevance of fatty acid oxidation in regulation of the outer mitochondrial membrane permeability for ADP

FEBS Letters ◽

10.1016/s0014-5793(01)03171-4 ◽

2001 ◽

Vol 509 (2) ◽

pp. 245-249 ◽

Cited By ~ 5

Author(s):

Adolfas Toleikis ◽

Julius Liobikas ◽

Sonata Trumbeckaite ◽

Daiva Majiene

Keyword(s):

Fatty Acid ◽

Membrane Permeability ◽

Fatty Acid Oxidation ◽

Mitochondrial Membrane ◽

Acid Oxidation ◽

Outer Mitochondrial Membrane ◽

Mitochondrial Membrane Permeability

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Induction of Acyl-CoA Dehydrogenases and Electron Transfer Flavoprotein and Their Roles in Fatty Acid Oxidation in Rat Liver Mitochondria1

The Journal of Biochemistry ◽

10.1093/oxfordjournals.jbchem.a133652 ◽

1981 ◽

Vol 90 (6) ◽

pp. 1751-1756 ◽

Cited By ~ 22

Author(s):

Shuichi FURUTA ◽

Shoko MAYAZAWA ◽

Takeshi HASHIMOTO

Keyword(s):

Electron Transfer ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Rat Liver ◽

Acid Oxidation ◽

Electron Transfer Flavoprotein ◽

Acyl Coa Dehydrogenases

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Translocator Protein (TSPO) Affects Mitochondrial Fatty Acid Oxidation in Steroidogenic Cells

Endocrinology ◽

10.1210/en.2015-1795 ◽

2016 ◽

Vol 157 (3) ◽

pp. 1110-1121 ◽

Cited By ~ 45

Author(s):

Lan N. Tu ◽

Amy H. Zhao ◽

Mahmoud Hussein ◽

Douglas M. Stocco ◽

Vimal Selvaraj

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

Mitochondrial Membrane ◽

Translocator Protein ◽

Acid Oxidation ◽

Mitochondrial Fatty Acid Oxidation ◽

Mitochondrial Fatty Acid ◽

Mitochondrial Functions ◽

Tspo Expression

Abstract Translocator protein (TSPO), also known as the peripheral benzodiazepine receptor, is a highly conserved outer mitochondrial membrane protein present in specific subpopulations of cells within different tissues. In recent studies, the presumptive model depicting mammalian TSPO as a critical cholesterol transporter for steroidogenesis has been refuted by studies examining effects of Tspo gene deletion in vivo and in vitro, biochemical testing of TSPO cholesterol transport function, and specificity of TSPO-mediated pharmacological responses. Nevertheless, high TSPO expression in steroid-producing cells seemed to indicate an alternate function for this protein in steroidogenic mitochondria. To seek an explanation, we used CRISPR/Cas9-mediated TSPO knockout steroidogenic MA-10 Leydig cell (MA-10:TspoΔ/Δ) clones to examine changes to core mitochondrial functions resulting from TSPO deficiency. We observed that 1) MA-10:TspoΔ/Δ cells had a shift in substrate utilization for energy production from glucose to fatty acids with significantly higher mitochondrial fatty acid oxidation (FAO), and increased reactive oxygen species production; and 2) oxygen consumption rate, mitochondrial membrane potential, and proton leak were not different between MA-10:TspoΔ/Δ and MA-10:Tspo+/+ control cells. Consistent with this finding, TSPO-deficient adrenal glands from global TSPO knockout (Tspo−/−) mice also showed up-regulation of genes involved in FAO compared with the TSPO floxed (Tspofl/fl) controls. These results demonstrate the first experimental evidence that TSPO can affect mitochondrial energy homeostasis through modulation of FAO, a function that appears to be consistent with high levels of TSPO expression observed in cell types active in lipid storage/metabolism.

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