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Activities of cardiac and hepatic pyruvate dehydrogenase complex are decreased after surgical stress
Insights
Surgical stress significantly reduces pyruvate dehydrogenase complex (PDHa) activity in rat hearts and livers, impacting glucose metabolism. Reactivation occurred when fat metabolism was inhibited, suggesting a role in glucose conservation during stress.
Area of Science:
- Biochemistry
- Physiology
- Metabolic Regulation
Background:
- The pyruvate dehydrogenase complex (PDHa) is crucial for carbohydrate metabolism.
- Surgical stress can profoundly alter metabolic pathways.
- Understanding PDHa regulation during stress is vital for patient recovery.
Purpose of the Study:
- To investigate the impact of surgical stress on cardiac and hepatic PDHa activity in rats.
- To explore the relationship between PDHa activity, plasma fatty acids, and lipolysis during surgical stress.
Main Methods:
- Fed rats were subjected to surgery.
- Cardiac and hepatic PDHa activities were measured at various post-operative time points.
- Plasma fatty acid concentrations and lipolysis inhibition were assessed.
Main Results:
- PDHa activity decreased within 4 hours of surgery, with maximum inhibition at 24 hours.
- Reduced PDHa activity persisted for days post-surgery (4th day for liver, 8th for heart).
- Decreased PDHa correlated with increased plasma fatty acids; lipolysis inhibition reactivated PDHa.
Conclusions:
- Surgical stress inhibits PDHa activity in the heart and liver.
- Fatty acid oxidation and multisite phosphorylation likely regulate PDHa during stress.
- PDHa inhibition may be a mechanism for glucose conservation following surgery and trauma.
Abstract:
The work investigated the effects of surgical stress on the activities of cardiac and hepatic pyruvate dehydrogenase complex (active form, PDHa) in fed rats. PDHa activities in heart and liver were decreased within 4h of surgery with maximum inhibition at 24h after surgery. PDHa activities remained low until the fourth (liver) and eighth (heart) post-operative days. The decreased activities found at 4h and 24h after surgery were associated with increased plasma fatty acid concentrations, and inhibition of lipolysis resulted in reactivation of the enzyme complex. The results are discussed with reference to the control of pyruvate dehydrogenase activities by the oxidation of fat fuels and multisite phosphorylation in stress states, and its possible importance in glucose conservation after surgery and trauma.