Pyruvate dehydrogenase complex (PDH) catalyses the oxidative decarboxylation of pyruvate to acetyl Co-A. PDH complex plays an important role in carbohydrate and lipid metabolism. Mammalian PDH complex is regulated by covalent modification. A specific PDH kinase (PDK) catalyses phosphorylation of PDH which results in inactivation whereas a specific PDH phosphatase (PDP) converts dephosphorylation and reactivation of PDH complex. PDK is a major factor influencing PDH activity. It was established that PDK activity is modified by various groups of xenobiotics. One of them are polyphenols, ubiquitous compounds in plant and also in human diet. Current interest of biological activities of polyphenolic compounds is due to their antioxidant properties. It is established that numerous polyphenols also improve carbohydrate and lipid metabolism in mammals. However, precise molecular action of these compounds is still unclear. It was also never under investigation the determination of influence of polyphenols on PDH activity. This study investigated the influence of selected catechins: catechine, epicatechine, kaffeic acid, qercetine, resveratrol and catechin-3-gallate on PDK activity in primary rat's hepatocytes culture. Liver cells were isolated from male rats and incubated with addition of different doses of catechins. Control hepatocytes were cultured under the same conditions without a ; ny catechins. After 24 hours of incubation all cultures were harvested and mitochondria were isolated. In mitochondrial protein extract PDK activity as well as expression of PDK-2 isoenzyme were assayed. PDK activity was assayed spectrophotometrically by the rate of ATP-dependent inactivation of PDH complex and activity was calculated as the first order rate constant. Expression of PDK-2 protein was assayed by Westem blott analysis. The results of study presents adverse correlation between PDK activity and concentration of tested polyphenols. It was demonstrated that addition of all tested polyphenols to culture medium remarkably decreased PDK activity comparing with control group. The degree of reduction of PDK activity strongly depends on the dose and also on the structure of particular polyphenolic compounds. It was also proved that ethanol increases PDK activity, opposite polyphenols. In conclusion, it is conceivable that chosen polyphenols affecting PDK activity modify PDH complex activity and in consequence exert an effect on glucose and lipid metabolism. Polyphenols may possibly act via PP ARα system on expression of genes of PDK in rat's hepatocytes. On the basis of above polyphenolic compounds may regulate activity of glucose and lipid metabolism.
Feb 14, 2023
Nov 21, 2012
|ZB-98948||Feb 14, 2023|
Klimek-Szczykutowicz, Marta Karolina