September 1, 2010

Hunger improves mental clarity

For all you living on a calorically restricted diet, it turns out that you may be doing more than extending your lifespan—you may also be improving your mental clarity and wakefulness.

This revelation isn't a huge surprise to me. Several years ago I used to fast on a regular basis. The first couple of days were awful, but I remember feeling uncharacteristically alert and energetic as the fast went on. I could never account for this increase in brain power, but scientists at Washington University in St. Louis may have finally uncovered the mechanism behind this phenomenon.

New research in fruit flies suggests that hunger may provide a way to stay awake without feeling groggy or mentally challenged. It turns out that the need for nourishment pushes aside the need for sleep. While experimenting on fruit flies, the researchers discovered that starvation nearly tripled the amount of time they could survive without sleep.

What they found was that the ability to resist the effects of sleep loss was linked to a protein that helps the fruit fly brain manage its storage and use of lipids, a class of molecules that includes fats such as cholesterol and fat-soluble vitamins such as vitamins A and D.

"The major drugs we have to either put people to sleep or keep them awake are all targeted to a small number of pathways in the brain, all of them having to do with neurotransmission," says Paul Shaw, PhD, assistant professor of neurobiology and anatomy. "Modifying lipid processing with drugs may provide us with a new way of tackling sleep problems that is more effective or has fewer side effects."

Scientists have long known that there is a complex relationship between sleep and dietary metabolism. Inadequate sleep results in obesity and contributes to the development of diabetes and coronary disease. But until now, no one had connected genes linked to lipids with regulation of the need for sleep; the results fit into a growing awareness that organisms use lipids for much more than energy storage.

"It's becoming apparent that fats serve as signaling molecules in a number of contexts. If you identify the appropriate lipids involved in sleep regulation and figure out how to control them, you may be able to decrease suffering associated with loss of sleep or the need to stay awake," says Clay Semenkovich, MD, a Washington University lipid expert not directly involved in the study.

Shaw uses fruit flies as models for sleep's effects in higher organisms. He has proven that flies enter a state comparable to sleep, showing that they have periods of inactivity where greater stimulation is required to rouse them. Like humans, flies deprived of sleep one day will try to make up for it by sleeping more the next day—what's called sleep debt. Sleep-deprived flies also perform poorly on a simple test of learning ability.

Scientists tested the starving, sleepless flies for two markers of sleep debt: an enzyme in saliva and the flies' ability to learn to associate a light with an unpleasant stimulus. Both tests showed that the starving flies were not getting sleepy.

Studies in other labs have shown that starvation or, in the case of human volunteers, fasting leads to less sleep. More recent research has also shown that starvation can change the activity levels of genes that manage storage and use of lipids.

"From an evolutionary perspective, this makes sense," says Matt Thimgan, PhD, a postdoctoral research associate. "If you're starving, you want to make sure you're on the top of your game cognitively, to improve your chances of finding food rather than becoming food for someone else."


1 comment:

Jay Dugger said...

Does the work also track mood changes following hunger? I dislike trading off greater mental vigor and increased irritability.