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Kinetics and control of oxidative phosphorylation in rat liver mitochondria after chronic ethanol feeding.

ABSTRACT: Changes in the kinetics and regulation of oxidative phosphorylation were characterized in isolated rat liver mitochondria after 2 months of ethanol consumption. Mitochondrial energy metabolism was conceptually divided into three groups of reactions, either producing protonmotive force (Deltap) (the respiratory subsystem) or consuming it (the phosphorylation subsystem and the proton leak). Manifestation of ethanol-induced mitochondrial malfunctioning of the respiratory subsystem was observed with various substrates; the respiration rate in State 3 was inhibited by 27+/-4% with succinate plus amytal, by 20+/-4% with glutamate plus malate, and by 17+/-2% with N,N,N',N'-tetramethyl-p-phenylenediamine/ascorbate. The inhibition of the respiratory activity correlated with the lower activities of cytochrome c oxidase, the bc(1) complex, and the ATP synthase in mitochondria of ethanol-fed rats. The block of reactions consuming the Deltap to produce ATP (the phosphorylating subsystem) was suppressed after 2 months of ethanol feeding, whereas the mitochondrial proton leak was not affected. The contributions of Deltap supply (the respiratory subsystem) and Deltap demand (the phosphorylation and the proton leak) to the control of the respiratory flux were quantified as the control coefficients of these subsystems. In State 3, the distribution of control exerted by different reaction blocks over respiratory flux was not significantly affected by ethanol diet, despite the marked changes in the kinetics of individual functional units of mitochondrial oxidative phosphorylation. This suggests the operation of compensatory mechanisms, when control redistributes among the different components within the same subsystem.

SUBMITTER: Marcinkeviciute A

PROVIDER: S-EPMC1221175 | biostudies-other | 2000 Jul

REPOSITORIES: biostudies-other

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Project description:BackgroundAdaptation to chronic ethanol (EtOH) treatment of rats results in a changed functional state of the liver and greatly inhibits its regenerative ability, which may contribute to the progression of alcoholic liver disease.MethodsIn this study, we investigated the effect of chronic EtOH intake on hepatic microRNA (miRNA) expression in male Sprague-Dawley rats during the initial 24 hours of liver regeneration following 70% partial hepatectomy (PHx) using miRNA microarrays. miRNA expression during adaptation to EtOH was investigated using RT-qPCR. Nuclear factor kappa B (NFκB) binding at target miRNA promoters was investigated with chromatin immunoprecipitation.ResultsUnsupervised clustering of miRNA expression profiles suggested that miRNA expression was more affected by chronic EtOH feeding than by the acute challenge of liver regeneration after PHx. Several miRNAs that were significantly altered by chronic EtOH feeding, including miR-34a, miR-103, miR-107, and miR-122 have been reported to play a role in regulating hepatic metabolism and the onset of these miRNA changes occurred gradually during the time course of EtOH feeding. Chronic EtOH feeding also altered the dynamic miRNA profile during liver regeneration. Promoter analysis predicted a role for NFκB in the immediate-early miRNA response to PHx. NFκB binding at target miRNA promoters in the chronic EtOH-fed group was significantly altered and these changes directly correlated with the observed expression dynamics of the target miRNA.ConclusionsChronic EtOH consumption alters the hepatic miRNA expression profile such that the response of the metabolism-associated miRNAs occurs during long-term adaptation to EtOH rather than as an acute transient response to EtOH metabolism. Additionally, the dynamic miRNA program during liver regeneration in response to PHx is altered in the chronically EtOH-fed liver and these differences reflect, in part, differences in miRNA expression between the EtOH-adapted and control livers at the baseline state prior to PHx.

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Kinetics and control of oxidative phosphorylation in rat liver mitochondria after chronic ethanol feeding.

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