Tendency to engage in voluntary exercise is heritable in mice according to a new study published in Proceedings of the Royal Society.
US Scientists found that mice that exhibited high running levels, which were then selected for breeding, also produced offspring that were high runners, suggesting this was an inherited characteristic. 'High-runners' ran two and a half to three times more revolutions per day compared to control mice, as measured by the distance voluntarily run in wheels attached to cages.
'Our findings have implications for human health', said Professor Theodore Garland Jr, a biologist at the University of California-Riverside, whose laboratory conducted the research. 'Down the road people could be treated pharmacologically for low activity levels through drugs that targeted specific genes that promote activity. Pharmacological interventions in the future could make it more pleasurable for people to engage in voluntary exercise'.
Professor Garland Jr and his team began the investigation with a colony of mice possessing similar levels of genetic variation to the wild mouse population. Mice were then randomly divided into four groups and subsequently bred over 43 generations for high running, by selecting the highest running males and females from every generation to be the parents of the next generation. At the same time, four groups of mice were bred with no selection imposed to act as a control.
The researchers also found that high running female and male mice evolved differently. Females increased their daily running distance almost entirely by speed, whereas males increased their speed but also ran for a greater length of time per day. The authors suggested that gender specific limitations may explain this disparity.
'It shows that there are many ways to skin a cat: different ways in which a species may evolve a similar adaptive characteristic - running activity, in this case' said Professor Douglas Futuyma, an expert in ecology and evolution based at Stony Brook University, New York.
'It would be fascinating to know, and challenging to find out, if any one of these different responses is adaptively better than others'.
Interestingly, no significant difference was found between the four 'high runner' breeding groups, in terms of the number of revolutions per day. But there were significant differences found between the different control groups. The authors propose that the 'high running' trait became fixed at equivalent levels in the selected groups, but that the control groups were able to randomly diverge genetically.
The team are also starting to uncover the physiological basis for the difference in response between the sexes. According to the publication, the authors believe that this may be due to differences in maximal oxygen consumption and neurochemical levels, involving the endocannabinoid system.
This investigation was unusual because evolutionary studies do not often use mammals because of their long generation times and high upkeep. However, this research originally began in 1993 and highlights the time and effort needed to complete such mammal based studies.