June 18, 2013

Could "Feeling Hungry" Protect Against Alzheimer's?

Can the simple condition of “feeling hungry” protect the brain against Alzheimer’s disease?

Previous studies have suggested that caloric restriction – eating less – has two effects on mammals:
  • Reducing the risk of neurodegenerative disorders, and
  • Extending lifespan
Those findings may sounds important, but (here we go again) they have never been confirmed by carefully controlled, randomized tests on humans. I wouldn’t be surprised if those same results could be shown for humans when they eat less. Thinner people aren’t as prone to the host of metabolic problems that plague heavier people: diabetes, coronary and cardiovascular disease. The same dangerous plaques that clog arteries are also associated with Alzheimer’s.

Really? Just the Sensation of Feeling Hungry?
A new study reported in "Science Daily" seems to show that the mere feeling of hunger – not just the reduction of caloric intake – may by itself create some protection against cognitive disorder. Said Dr. Inga Kadish, assistant professor in the Department of Cell, Developmental and Integrative Biology (CDIB) within the School of Medicine at the University of Alabama at Birmingham:
This is the first paper, as far as we are aware, to show that the sensation of hunger can reduce Alzheimer's disease pathology in a mouse model of the disease. If the mechanisms are confirmed, hormonal hunger signaling may represent a new way to combat Alzheimer's disease, either by itself or combined with caloric restriction.
The Hormone Ghrelin
The researchers zeroed in on the role on ghrelin, a hormone that helps create the feeling of being hungry. The mice ate pills made of a synthetic form of the hormone, doses of which scientists could then carefully regulate. Kadish and her team hope to develop a treatment “that affected biochemical pathways downstream of hunger signals.”

If scientists can find a way to induce these potentially beneficial hunger signals WITHOUT patients having to actually reduce food consumption – or even being aware of the sensation of hunger -- preventing neurodegenerative issues like Alzheimer’s becomes simpler for people like me who sometimes find the old-fashioned mantra of “diet and exercise” less palatable than popping a pill. I wouldn’t be happy wandering around feeling hungry all the time.

Mice in the study were assigned to one of three categories:
  • Those that received the synthetic ghrelin hormone
  • Those whose caloric intake was reduced 20%
  • A control group: no hormone, no dietary changes
Three measurements were tracked:
  • Memory
  • Degree of Alzheimer’s pathology
  • Level of related, potentially harmful immune cell activation
In that first category – memory – the mice on synthetic ghrelin navigated a maze 26% faster than control group mice. Mice on limited diets outperformed control mice by 23%.

A Reduction in Beta Amyloid Plaques
In the second category – AD pathology – scientists measured the presence in the mice brains of beta amyloid, the protein plaques typically considered biomarkers of Alzheimer’s. Mice receiving ghrelin and those eating less showed significant reductions in beta amyloid pathology compared to the animals in the control group.

Finally, in that last category, mice taking ghrelin and mice eating less showed reduced activation of harmful immune cells.

So . . . we see more evidence of scientific progress in the quest toward treating – maybe even preventing – Alzheimer’s. Again, success with rodents doesn’t mean similar success will follow with humans; past studies with mice haven’t made the translation.

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