Linkage 4/2: Cafeteria Addiction, The Case of the Missing Negative Results

natscicover_20100401Just a few things from around the world of science this week…

Addiction researchers often speculate that abused drugs such as cocaine and nicotine hijack the brain systems responsible for the more natural pursuits of food and sex. Many studies have shown that food, particularly delicious food, can activate brain reward areas, but a new paper by Paul Johnson and Paul Kenny at Scripps Research Institute in Florida made one of the most convincing arguments yet for “food addiction” resembling drug addiction. Rats given unlimited access to a “cafeteria diet” (bacon, cheesecake, frosting and more – yum!) showed not only the expected weight gain, but also a reduced sensitivity to reward. In other words, when rats got fat, the usual good stuff wasn’t quite as rewarding, requiring them to seek even more reward to reach satisfaction.

This reduced sensitivity correlated with a reduction in one type of receptor (D2) for the neurotransmitter dopamine, a reduction seen in drug-addicted animals and people. When researchers used a virus to artificially reduce those receptors, only animals that had previously been exposed to the cafeteria diet showed overeating behavior and reduced reward, suggesting an environmental role also contributes to “food addiction.” It also makes a convincing argument to stay out of the cafeteria.

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A very cool study, but another paper published this week, by scientists from England, Australia and The Netherlands in PLoS Biology, shone a harsh spotlight on the elephant in the room of animal research. Scientific publications are almost always about laboratory or clinical successes, trials or experiments that produced an effect – even if it isn’t always the effect that was expected at the outset. But wherefore the negative results, those experiments where after the dust has settled from statistical analysis, nothing really happened? Only rarely are such non-effects published, a practice that led Emily Sena and colleagues to hypothesize a “publication bias” in animal studies looking at stroke interventions.

Reviewing 16 review studies (papers that aggregate dozens to hundreds of individual research findings), the authors found that only 1 out of 50 papers in those review studies reported negative results. Anyone who has worked in a lab knows that far fewer than 98 percent of all experiments show an effect, leading the authors to believe that many negative results go unreported. That’s kind of a big deal. For one, animal studies that didn’t work may be needlessly replicated by scientists who didn’t realize they’d already been tried out, wasting time, money, and laboratory animals’ lives. For two, when that research is translated from animals to humans, researchers may overestimate the efficacy of those interventions – a potential explanation for why the jump from lab rat to patient is so often unsuccessful. Obviously, if this is a problem for stroke interventions, one can imagine it affecting biomedical research of all stripes. But until more journals are willing to publish negative results and scientists willing to check their ego and publish those experimental duds, it’s an issue that’s not going away.

A lengthier analysis of this paper and similar efforts to self-police science is recommended reading at Respectful Insolence.

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Much has been written this week about the potentially landmark legal decision to revoke the patents held by a private company on BRCA-1 and BRCA-2, genes that signal a predisposition to breast or uterine cancer. I got the most information on the case from Genomics Law Report, a blog run by lawyer Daniel Vorhaus – particularly this post on the legal nitty-gritty and what happens next. Deborah Shelton of the Chicago Tribune (my former newsroom cubicle neighbor) also had a more accessible write-up in today’s paper.

Who says scientists don’t have a sense of humor? Check out this roundup by Nature News of the best science-related April Fool’s gags, including the new journal pictured above (I chuckled at “Evolution: Why Won’t It Stop?”).

University of Chicago internal medicine resident Shantanu Nundy is currently in rural Uganda working at a clinic for pregnant mothers, and he’s blogging about it here. Nundy, who apparently does not sleep, also wrote a book called Stay Healthy at Every Age: What Your Doctor Wants You to Know that is due to be released soon.

Finally, don’t get your medical information from twitter. Save it for Justin Bieber news.

About Rob Mitchum (526 Articles)
Rob Mitchum is communications manager at the Computation Institute, a joint initiative between The University of Chicago and Argonne National Laboratory.
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