Scientists Discover That Most Fruit Flies on Meth Die From Anorexia

Posted on August 5, 2012

University of Illinois entomology professor Barry Pittendrigh (left), postdoctoral researcher Kent Walters and their colleagues recently conducted a study tracking metabolic and behavioral changes in fruit flies on methamphetamine. The new study has found that fruit flies exposed to meth often die as a result of anorexia. The meth-fed flies drastically reduce their food intake and increase their physical activity, just as humans do. The new findings are described here in The Journal of Toxicological Sciences.

The abuse of methamphetamine can have significant harmful side effects in humans. It burdens the body with toxic metabolic byproducts. It weakens the heart, muscles and bones. It also alters energy metabolism in the brain and kills brain cells. Previous studies have shown that the fruit fly Drosophila melanogaster is a good model organism for studying the effects of methamphetamine on the body and brain.

Some studies found that supplementing the fly's diet with added glucose or other metabolic precursors slowed the damaging effects of exposure to methamphetamine. Human meth users are known to crave sugary drinks, an indication their sugar metabolism is also altered by meth use.

Professor Pittendrigh says, "But previous research has not spelled out exactly how methamphetamine use affects energy metabolism. Either it alters the expression of metabolic genes and/or the function of proteins, or it changes behaviors related to feeding and activity."

The researchers monitored the fruit flies' energy reserves and other byproducts of metabolism in response to meth exposure - both with and without the addition of dietary glucose. They also tracked how meth affected the flies' feeding behavior, activity levels and respiration rates.

The researchers found that levels of triglycerides and glycogen decreased steadily with meth exposure over a 48-hour period, suggesting that meth induced a negative caloric balance. The flies' metabolic rate also declined in response to meth exposure, the opposite of what would be expected if metabolic changes were driving the depletion of triglycerides and glycogen.

Walters says, "We found that methamphetamine in the diet increased the flies' locomotor activity two-fold and decreased their food consumption by 60 to 80 percent. This is very similar to what has been observed in humans for whom amphetamines can cause increased physical activity and decreased appetite."

The researchers also found that adding glucose to the flies' diet slowed the rate of decline and death of the meth-fed flies.

Walters says, "While methamphetamine exposure has a lot of other toxic effects that also undermine an animal's health, we show that meth exposure leads to anorexia and the resulting caloric deficit exhausts the animal's metabolic reserves. This is likely a primary factor in meth-induced mortality."



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