Alzheimer’s disease and other age-related brain disorders may be the result of a catastrophic energy shortage that develops in the brain as tiny chemical fires inside nerve cells flicker and go dark, a researcher said.
Examinations of the brains of people who have died of Alzheimer’s or Huntington’s disease have found elevated levels of genetic mutations in the chemical powerhouses called mitochondria, said Douglas C. Wallace, a geneticist at the Emory University School of Medicine in Atlanta.
“It’s well established that our energy capacity declines with age,” Wallace said Wednesday at a genetics meeting at the Jackson Laboratory in Bar Harbor. “The brain is the organ most reliant on energy.”
The idea that the brain’s cells might gradually run out of energy with aging could help explain why people who inherit a disease such as Alzheimer’s don’t show symptoms until late in life, Wallace said.
With many inherited diseases, the havoc caused by genetic mutations can begin at conception, but the picture is more complex with disorders such as Alzheimer’s, Huntington’s and Parkinson’s disease, Wallace said. Those diseases are often related to inherited genetic abnormalities, but the abnormalities seemingly have no effect for decades.
Wallace has proposed that the inherited mutations are somehow related to mitochondria. As the number of mitochondrial mutations increase with age, the mitochondria stop working and the cells in which they reside die.
Because brain cells are heavy energy users, they may be the first to die as these mutations increase, Wallace said. The death of brain cells would in turn give rise to brain disorders.
Nancy Wexler of Columbia University, a pioneer in Huntington’s disease research, said other researchers have found they can produce a brain disorder similar to Huntington’s disease by giving rats or monkeys a poison that kills mitochondria. It’s another line of evidence that mitochondria are important in the disease, she said.
Wallace studied brains of people who had died of Huntington’s disease and compared them with the brains of people who had died of other causes. Huntington’s victims had 11 times the level of mitochondrial mutations in their temporal lobes.