: Anxiety. Insomnia. Hallucinations. Methamphetamine's effects on the human brain are well documented, but researchers know relatively little about how the drug affects the body on the molecular scale. Looking at fruit flies (Drosophila melanogaster), scientists have detailed how meth disrupts chemical reactions associated with generating energy, creating sperm cells, and regulating muscles. Most interestingly, they discovered that meth-exposed fruit flies may live longer when they eat sugar. "We know that methamphetamine influences cellular processes associated with aging, it affects spermatogenesis, and it affects the heart," says University of Illinois entomologist Barry Pittendrigh. "One could almost call meth a perfect storm toxin because it does so much damage to so many different tissues in the body." How the Heck:
What's the News
By keeping tabs on protein production and gene expression while exposing fruit flies to meth, researchers discovered 34 changes in the molecular pathways that drive cells, disrupting cell structure, hormones, energy generation, sugar metabolism, sperm cell formation, as well as skeletal and cardiac muscles.
The major insight was that meth exposure may cause cells to produce energy via glycolysis, an inefficient means of energy production that breaks down glucose without using oxygen. Healthy cells use oxygen (oxidative respiration) to produce energy.
Based on this observation, the scientists then tested whether sugar metabolism is related to meth's toxicity by feeding meth-exposed flies trehalose, a common antioxidant blood sugar in insects. These sugar-fed flies lived longer, showing that "we now have evidence that increased sugar intake has a direct impact on reducing the toxicity of meth, at least in flies," as co-author Lijie Sun, of the J. Craig Venter Institute in the U.S., told COSMOS.
What's the Context:
Most meth studies on humans are more narrowly focused, looking at the impact on the brain, the heart, or reproductive organs. Because fruit flies are small, these researchers were able to take the whole organism into account, looking at "the great diversity of tissues that are being impacted.
The researchers say that meth is already known to cause rapid aging; now, by linking meth with oxidative stress, which is related to cellular aging, we now have a better idea of the smaller-scale factors in this process.
Other researchers have discovered that snails exposed to meth may have better memories.
Not So Fast: Scienists need to conduct follow-up tests on mammals before they can say for sure whether these results apply to animals beyond fruit flies. The Future Holds:
It's often said that meth users crave sugar; future research may build on this study and further tease out the link between sugar intake and meth toxicity.
Because cancer cells also rely on glycolysis to generate energy, the researchers believe that this study and similar ones could lead to a "greater understanding of the mechanisms of cancer growth."
Reference: Sun L, Li H-M, Seufferheld MJ, Walters KR Jr, Margam VM, et al. (2011) Systems-Scale Analysis Reveals Pathways Involved in Cellular Response to Methamphetamine. PLoS ONE 6(4): e18215. doi:10.1371/journal.pone.0018215
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