Friday, November 25, 2011

Those Lab Mice

Derek Lowe, a chemist who has done research in the pharmaceutical industry, recently had an interesting blogpost on the problems with research done on lab mice.

Because Lowe has done research with Big Pharma (including diabetes research), he provides a different point of view from the common "Big Pharma is evil and doesn't want to cure diseases" point of view found in many patient blogs. I think it's important to look at both sides of any issue, and Lowe often points out the difficulties of various chemical approaches to solving some drug problem. Most of them are over my head, but this one was interesting.

He links to another blog that has a series on mouse models, for those who are interested.

Many of the comments on Lowe's post are from other researchers, and it's interesting to see that unlike the popular press, the researchers are cautious about using mouse results. Even different strains of mice can show different results with the same drug.

One interesting comment was that when you put a human tumor into a mouse and some drug cures the tumor in that mouse it's possible that the drug simply kills human cells and hence would be dangerous in humans.

I think most of us understand that mouse studies often don't pan out to be human treatments. They are only suggestive. If only the popular press could show some restraint, patients wouldn't be told over and over again that some new cure was on the way, only to be disappointed when they never hear about it again.

Association and Causation

I recently read a great cat annecdote in Temple Grandin's book Animals Make Us Human.

According to Grandin, someone's cat loved watching the water swirl around when a toilet was flushed. The cat couldn't figure out how to flush itself, but it had noticed that when there was paper in the toilet, it was more apt to be flushed.

So the cat tore up toilet paper and threw it in the toilet and waited expectantly.

This is a perfect example of the difference between association and cause. The cat correctly noted that toilet paper was
associated with toilet flushing. But the cat incorrectly decided that toilet paper caused toilet flushing.

Of course, flushing didn't cause toilet paper any more than toilet paper caused flushing. It was a third factor, pulling the handle on the toilet, that caused the flushing.

Many of our scientific interpretations are like the cat's. If we see a fat person eating more than a thin person, most people conclude that overeating causes obesity. But perhaps obesity causes increased appetite, or perhaps a third factor that no one has discovered yet causes both obesity and increased appetite.

Whenever we see research that shows that two factors are associated, we should think of this cat story. Does the research provide any evidence that one factor caused the other, or is the researcher simply thinking like the cat because of a preconceived notion?

Gary Taubes is challenging the catlike assumption that because fat people tend to eat a lot and not exercise much, it's their behavior that is causing their obesity. Instead, he says it's insulin that is making the body store fat instead of burning it, and the resulting energy deficit makes the person want to eat more and exercise less.

The blogosphere is filled with people debating this theory. I won't go through it all here.

My point here is simply that we should keep this graphic cat story in mind as we evaluate evidence. Surely we humans can be smarter than a cat!