Pyruvate dehydrogenase complex: Metabolic link to ischemic brain injury and target of oxidative stress

• Published in: Journal of neuroscience research Vol. 79; no. 1-2; pp. 240 - 247
• Main Authors: Martin, Erica, Rosenthal, Robert E., Fiskum, Gary
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-01-2005
• Subjects: acetyl-L-carnitine; acidosis; Animals; Brain Ischemia - enzymology; Brain Ischemia - physiopathology; Energy Metabolism; Enzyme Activation - genetics; Frontal Lobe - enzymology; Heart Arrest - enzymology; Heart Arrest - physiopathology; Humans; lactate; mitochondria; Models, Biological; Neurodegenerative Diseases - enzymology; Neurodegenerative Diseases - physiopathology; Oxidative Stress - physiology; peroxynitrite; Pyruvate Dehydrogenase Complex - metabolism; Time Factors
• ISSN: 0360-4012; 1097-4547
• DOI: 10.1002/jnr.20293

The mammalian pyruvate dehydrogenase complex (PDHC) is a mitochondrial matrix enzyme complex (greater than 7 million Daltons) that catalyzes the oxidative decarboxylation of pyruvate to form acetyl CoA, nicotinamide adenine dinucleotide (the reduced form, NADH), and CO2. This reaction constitutes the bridge between anaerobic and aerobic cerebral energy metabolism. PDHC enzyme activity and immunoreactivity are lost in selectively vulnerable neurons after cerebral ischemia and reperfusion. Evidence from experiments carried out in vitro suggests that reperfusion‐dependent loss of activity is caused by oxidative protein modifications. Impaired enzyme activity may explain the reduced cerebral glucose and oxygen consumption that occurs after cerebral ischemia. This hypothesis is supported by the hyperoxidation of mitochondrial electron transport chain components and NAD(H) that occurs during reperfusion, indicating that NADH production, rather than utilization, is rate limiting. Additional support comes from the findings that immediate postischemic administration of acetyl‐L‐carnitine both reduces brain lactate/pyruvate ratios and improves neurologic outcome after cardiac arrest in animals. As acetyl‐L‐carnitine is converted to acetyl CoA, the product of the PDHC reaction, it follows that impaired production of NADH is due to reduced activity of either PDHC or one or more steps in glycolysis. Impaired cerebral energy metabolism and PDHC activity are associated also with neurodegenerative disorders including Alzheimer's disease and Wernicke‐Korsakoff syndrome, suggesting that this enzyme is an important link in the pathophysiology of both acute brain injury and chronic neurodegeneration. © 2004 Wiley‐Liss, Inc.