Recently there was a very interesting series in three parts in the online magazine Slate.com concerning the use of mice and rats as surrogates for humans in animal studies. Anyone who has worked with mice in the lab is aware of the conditions that they are generally kept in – they live in small cages with limited opportunity for exercise and have an unlimited food supply. The inevitable consequence of this is that the majority of lab mice and rats are overweight – if not obese. What does this mean for their ability to serve as appropriate controls? As detailed in an article in PNAS last year, laboratory rodents “metabolically morbid”. They are overweight, insulin-resistant, have premature cardiovascular disease, are prone to infection and cancer and appear to be more likely to develop degenerative neurological disorders. Overall, when you think about it, they aren’t very representative of healthy humans at all. This has major implications for medical research. Laboratory mice as currently bred are cheap, reproduce rapidly and are easily manipulated genetically. Any changes to feeding regimens and exercise availability are going to significantly increase costs associated with their use so there is a trade off between practicality and the unquantified effect that using these obese animals may be having on the results of our experiments. It must be pointed out, however, that most research on mice uses animals that are young and have not had time to become particularly overweight such that this would not apply to all mouse models. It’s a fascinating topic and the sheer number of citations that the PNAS article has accrued already indicates that others recognize that this is a potentially serious issue. Comments are welcome,
I was sure you were talking about the human species when you stated: "They live in small cages with limited opportunity for exercise and have an unlimited food supply."
How is that different from society currently? We live in small places, never work out, AND eat unlimited food.
Great article. I need to change my screen saver to remind myself of my own metabolic morbidity in front of the computer. Unfortunately these mice don't seem such an inappropriate model…
In an eerie parallel the NYT had an article earlier this week on truckers, people who are trapped in a truck cabin for most of the day and typically eat a steady high fat and carbohydrate diet, they site their obesity rates at over 85%! Even more shocking they describe a blood pressure screeing day where 21% of participants were sent directly to the emergency room with one having an MI in route!
With US adult and child obesity rates up over 30% and 15% respectively I wonder if the physiology in these mice is of utility in this large and growing portion of our population.