Application of modular control analysis to inhibition of the adenine nucleotide translocator by palmitoyl-CoA.

Modular kinetic analysis was used to characterize inhibition of adenine nucleotide translocation by palmitoyl-CoA in isolated rat-liver mitochondria. To this purpose, oxidative phosphorylation has been divided into two modules with the fraction of matrix ATP as linking intermediate. The adenine nucleotide translocator is the matrix ATP-consuming module and the remainder of oxidative phosphorylation (ATP synthesis, respiratory chain and transport of phosphates and respiratory substrate) is the matrix ATP-producing module. We found that palmitoyl-CoA inhibits ATP-consuming module (ANT) and has no effect on ATP-producing module. There were no significant differences between kinetic curves obtained with oligomycin and myxothiazol, inhibitors that have opposite effect on membrane potential, suggesting that the use of the fraction of matrix ATP as the only intermediate is a good approximation. A new method has been used to determine the fraction of ATP in the mitochondrial matrix

Modular kinetic analysis of the adenine nucleotide translocator-mediated effects of palmitoyl-CoA on the oxidative phosphorylation in isolated rat liver mitochondria

To test whether long-chain fatty acyl-CoA esters link obesity with type 2 diabetes through inhibition of the mitochondrial adenine nucleotide translocator, we applied a system-biology approach, dual modular kinetic analysis, with mitochondrial membrane potential (Delta psi) and the fraction of matrix ATP as intermediates. We found that 5 mu mol/l palmitoyl-CoA inhibited adenine nucleotide translocator, without direct effect on other components of oxidative phosphorylation. Indirect effects depended on how oxidative phosphorylation was regulated. When the electron donor and phosphate acceptor were in excess, and the mitochondrial "work" flux was allowed to vary, palmitoyl-CoA decreased phosphorylation flux by 38% and the fraction of ATP in the medium by 39%. Delta psi increased by 15 mV, and the fraction of matrix ATP increased by 46%. Palmitoyl-CoA had a stronger effect when the flux through the mitochondrial electron transfer chain was maintained constant: Delta psi increased by 27 mV, and the fraction of matrix ATP increased 2.6 times. When oxidative phosphorylation flux was kept constant by adjusting the rate using hexokinase, A psi and the fraction of ATP were not affected. Palmitoyl-CoA increased the extramitochondrial AMP concentration significantly. The effects of palmitoyl-CoA in our model system support the proposed mechanism linking obesity and type 2 diabetes through an effect on adenine nucleotide translocator.</p

Palmitate and oleate have distinct effects on the inflammatory phenotype of human endothelial cells.

Free fatty acids may create a state of continuous and progressive damaging to the vascular wall manifested by endothelial dysfunction. In this study we determine the mechanisms by which fatty acids palmitate (C16:0) and oleate (C18:1) affect intracellular long chain acyl-CoA (LCAC) content, energy metabolism, cell survival and proliferation and activation of NF-κB in cultured endothelial cells. A 48-h exposure of human umbilical vein endothelial cells (HUVEC) to 0.5 mM palmitate or 0.5 mM oleate increased total long chain acyl-CoA (LCAC) content 1.7 and 2 fold, respectively and decreased AT

Metabolic control of mitochondrial properties by adenine nucleotide translocator determines palmitoyl-CoA effects.

Inhibition of the mitochondrial adenine nucleotide translocator (ANT) by long-chain acyl-CoA esters has been proposed to contribute to cellular dysfunction in obesity and type 2 diabetes by increasing formation of reactive oxygen species and adenosine via effects on the coenzyme Q redox state, mitochondrial membrane potential (Δψ) and cytosolic ATP concentrations. We here show that 5 μm palmitoyl-CoA increases the ratio of reduced to oxidized coenzyme Q (Q

Functioning phosphorylation in liver mitochondria of high-fat diet fed rats.

AbstractWe proposed that inhibition of mitochondrial adenine nucleotide translocator (ANT) by long chain acyl-CoA (LCAC) underlies the mechanism associating obesity and type 2 diabetes. Here we test that after long-term exposure to a high-fat diet (HFD): (i) there is no adaptation of the mitochondrial compartment that would hinder such ANT inhibition, and (ii) ANT has significant control of the relevant aspects of oxidative phosphorylation. After 7 weeks, HFD induced a 24±6% increase in hepatic LCAC concentration and accumulation of the oxidative stress marker Nε-(carboxymethyl)lysine. HFD did not significantly affect mitochondrial copy number, oxygen uptake, membrane potential (Δψ), ADP/O ratio, and the content of coenzyme Q9, cytochromes b and a+a3. Modular kinetic analysis showed that the kinetics of substrate oxidation, phosphorylation, proton leak, ATP-production and ATP-consumption were not influenced significantly. After HFD-feeding ANT exerted considerable control over oxygen uptake (control coefficient C=0.14) and phosphorylation fluxes (C=0.15), extra- (C=0.23) and intramitochondrial (C=−0.56) ATP/ADP ratios, and Δψ (C=−0.11). We conclude that although HFD induces accumulation of LCAC and Nε-(carboxymethyl)lysine, oxidative phosphorylation does not adapt to these metabolic challenges. Furthermore, ANT retains control of fluxes and intermediates, making inhibition of this enzyme a more probable link between obesity and type 2 diabetes

Genome-wide analysis of yeast stress survival and tolerance acquisition to analyze the central trade-off between growth rate and cellular robustness

A genome-wide analysis of the acquisition of stress cross-tolerance shows that reduction of growth rate is an important determinant of severe stress survival. Cellular functions important for the coupling of growth rate to stress resistance are identified, as are those required for cross-tolerance acquisition independent of growth rate reduction