But the scientists now guessed it might also be the bridge between estrogen and the impulse to be physically active, an idea they substantiated by using high-tech genetic mapping techniques refined by one of the study’s authors, Jessica Tollkuhn, an assistant professor at Cold Spring Harbor Laboratory School of Biological Sciences in Cold Spring Harbor, N.Y. This gene, melanocortin-4, or Mc4r, previously had been linked in people to food intake and regulation of body weight. Next, the researchers examined the activity of a number of genes in the animals’ brains, noting that one, in particular, enthusiastically pumped out extra proteins when the animals’ brains were bathed in estrogen but became almost quiet when estrogen was absent.
Almost immediately, the animals without estrogen became noticeably more sedentary than the other females, confirming that estrogen somehow affects physical activity. To investigate that possibility, the scientists first gathered a crowd of healthy adult female mice and chemically blocked estrogen uptake in some of them, while tracking how much all of the animals moved. She and her collaborators wondered if estrogen might somehow shape genetic activity in the brain, which would then activate brain cells in ways that could set in motion, well, motion itself. In the intervening decades, researchers began to speculate that estrogen must play a driving role in this behaviour, with subsequent studies indicating that female lab animals’ daily skitterings typically would surge and wane in tandem with their estrogen levels.īut how could estrogen, which primarily controls ovulation and other aspects of reproduction, influence physical activity? That physiological puzzle recently drew the attention of Holly Ingraham, the Herzstein Endowed Professor of Physiology at the University of California, San Francisco, who has a longstanding research interest in women’s physiology and metabolism. This behaviour makes evolutionary sense, since female animals presumably need to be on the hunt then for a mate. The results also underscore how the brain and internal biological processes work together to play an unexpected and substantial role in whether the body gets up and moves or remains mostly still.įor close to a century, since a famous 1924 study involving rats, scientists have known that female mammals tend to be most physically active just before they ovulate, when they are also most sexually receptive. But the findings may open intriguing avenues of inquiry into why women so often become inactive after menopause, when estrogen fades. While humans share many of the same relevant hormones, genes and neurons, we are not mice and cannot yet say whether our brains and physiological systems work the same way. The study, which was published recently in Nature, involved mice.