Insulin key in neuron regeneration

Age may not cause our nervous system to deteriorate, according to new research from the Yale School of Medicine.

Axons, or nerve fibers, tend to grow and repair themselves more slowly as they age, and Yale researchers have discovered that insulin pathways, already known for regulating life span, also regulate neurons’ ability to regenerate. Their findings, published Thursday in the journal Neuron, show that the brain’s regulation of neuronal health span is independent of its regulation of life span. The findings have implications for developing more effective treatments for neurological injuries, said Alexandra Byrne, lead author of the study and a postdoctoral fellow in genetics at the Yale School of Medicine.

“An aged neuron’s inability to regenerate [is] not simply a secondary consequence of a decrepit animal,” she said. “Instead, the insulin pathway is actively inhibiting regeneration in the neurons of aged animals.”

The researchers observed neurons in the tiny worm C. elegans, an ideal organism for study since it shares many genes with mammals, Byrne said. By manipulating insulin pathways, the researchers were able to create two types of worms: one set whose axons regenerated more easily and had normal life spans, and another set whose minds deteriorated normally but lived longer lives. The insulin pathway’s regulation of axon regeneration, the study shows, is independent of the process to regulate life span.

“Our finding that insulin regulates motor neuron regeneration adds to our understanding of the regeneration response,” Byrne said.

The discovery could have major implications, Byrne said, in cases of spinal cord injury and other instances of nerve damage. Neurons’ inability to regenerate is also characteristic of neurodegenerative conditions, including stroke and glaucoma.

Valerie Reinke, co-author of the study and professor of genetics at the Yale School of Medicine, said in an email to the News Sunday that her interest in the study originated from the issue of understanding how neurons grow and divide.

About 200,000 people are currently living with spinal cord injury in the United States, according to the Centers for Disease Control and Prevention.

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