"Energy Source" Implicated in Dementia

By Jane Farrell

Researchers now know that a specific energy source is crucial to cells that maintain cognitive function. That discovery could lead to a better understanding of the cognitive decline in illnesses such as Alzheimer’s and multiple sclerosis.

The source, NAD (nicotinamide adenine dinucleotide), is a molecule that harvests energy from nutrients in food and converts into a usable form for cells.

The findings, by researchers from Washington University in St. Louis, were published in The EMBO Journal, a publication of the European Molecular Biology Organization, and The Journal of Neuroscience.

“We are interested in understanding how cells make NAD and what implications that has for cellular function, especially in the context of aging and longevity,” said Shin-ichiro Imai, MD, PhD, professor of developmental biology and of medicine. “We know, for example, NAD levels decrease with age in tissues such as muscle and fat. We wanted to find out if the same is true in the brain.”

In their research, investigators looked at the relationship between NAD and two types of brain cells: adult neural stem cells, responsible for maintaining supplies of neurons and their supporting cells, and forebrain neurons, vital for performing complex cognitive tasks.

They found that NAD levels decreased with age in the mouse hippocampus, a vital region of the brain for cognition. And that can leave cells especially vulnerable to deterioriation.

“Neural stem cells are very metabolically expensive, so you might expect them to be particularly vulnerable to loss of an energy source,” said first author Liana Roberts Stein, PhD, postdoctoral researcher in Imai’s lab. “There are other energy sources for brain cells, such as glucose, but no one had ever looked at where NAD is coming from in these cells.”

 Stein said that the discovery “could be relevant in conditions involving loss of cells that make this insulation, like multiple sclerosis.”