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Hormonal control of pyruvate dehydrogenase activity in rat liver.

ABSTRACT: A detailed study of the control of liver pyruvate dehydrogenase activity by various hormones was carried out with perfused liver and isolated hepatocytes. Vasopressin produced a significant increase in the enzyme activity in fed rats, and the time course and sensitivity of the response was similar to that of glycogen phosphorylase a. The enzyme from starved animals was resistant to hormonal activation. The possible factors involved in the above effects are discussed. Angiotensin and phenylephrine also increased pyruvate dehydrogenase activity, and the magnitude of the response was of the same order as that to vasopressin by the liver enzyme. The effects of these hormones on pyruvate dehydrogenase activity were critically dependent on extracellular Ca2+, thus suggesting a role for this ion in the mechanism of action of the hormones. Insulin did not appear to have a role in the control of the enzyme activity, as shown by its lack of effect on the enzyme. Glucagon, in contrast with previous reports, produced a rapid, transient and significant increase in pyruvate dehydrogenase activity. The physiological importance of the above effects is discussed.

SUBMITTER: Oviasu OA

PROVIDER: S-EPMC1144411 | biostudies-other | 1984 Nov

REPOSITORIES: biostudies-other

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Project description:Background & aimsAcute liver failure is a rapidly progressive deterioration of hepatic function resulting in high mortality and morbidity. Metabolic enzymes can translocate to the nucleus to regulate histone acetylation and gene expression.MethodsLevels and activities of pyruvate dehydrogenase complex (PDHC) and lactate dehydrogenase (LDH) were evaluated in nuclear fractions of livers of mice exposed to various hepatotoxins including CD95-antibody, α-amanitin, and acetaminophen. Whole-genome gene expression profiling by RNA-seq was performed in livers of mice with acute liver failure and analyzed by gene ontology enrichment analysis. Cell viability was evaluated in cell lines knocked-down for PDHA1 or LDH-A and in cells incubated with the LDH inhibitor galloflavin after treatment with CD95-antibody. We evaluated whether the histone acetyltransferase inhibitor garcinol or galloflavin could reduce liver damage in mice with acute liver failure.ResultsLevels and activities of PDHC and LDH were increased in nuclear fractions of livers of mice with acute liver failure. The increase of nuclear PDHC and LDH was associated with increased concentrations of acetyl-CoA and lactate in nuclear fractions, and histone H3 hyper-acetylation. Gene expression in livers of mice with acute liver failure suggested that increased histone H3 acetylation induces the expression of genes related to damage response. Reduced histone acetylation by the histone acetyltransferase inhibitor garcinol decreased liver damage and improved survival in mice with acute liver failure. Knock-down of PDHC or LDH improved viability in cells exposed to a pro-apoptotic stimulus. Treatment with the LDH inhibitor galloflavin that was also found to inhibit PDHC, reduced hepatic necrosis, apoptosis, and expression of pro-inflammatory cytokines in mice with acute liver failure. Mice treated with galloflavin also showed a dose-response increase in survival.ConclusionPDHC and LDH translocate to the nucleus, leading to increased nuclear concentrations of acetyl-CoA and lactate. This results in histone H3 hyper-acetylation and expression of damage response genes. Inhibition of PDHC and LDH reduces liver damage and improves survival in mice with acute liver failure. Thus, PDHC and LDH are targets for therapy of acute liver failure.Lay summaryAcute liver failure is a rapidly progressive deterioration of liver function resulting in high mortality. In experimental mouse models of acute liver failure, we found that two metabolic enzymes, namely pyruvate dehydrogenase complex and lactic dehydrogenase, translocate to the nucleus resulting in detrimental gene expression. Treatment with an inhibitor of these two enzymes was found to reduce liver damage and to improve survival.

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Hormonal control of pyruvate dehydrogenase activity in rat liver.

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