Mouse study: brain cells active post-workout

A mouse study published in Neuron found that a set of hypothalamic brain cells stayed active after exercise ended, and that shutting down those cells blocked the usual gains in endurance from training. The work was led by researchers at the University of Pennsylvania and The Jackson Laboratory and was described in a May 15 ScienceDaily release. The experiments were done in mice, not people. The paper says the cells are steroidogenic factor-1, or SF1, neurons in the ventromedial hypothalamus. ### Which brain cells did the researchers focus on? The Neuron paper identified SF1-expressing neurons in the ventromedial hypothalamus as the key cell group tracked during and after treadmill running in mice. The authors reported that these neurons were activated by exercise and that repeated training increased their post-exercise activity. PubMed’s summary of the paper said exercise training increased both the intrinsic excitability of the neurons and the density of excitatory synapses on them. (cell.com) J. Nicholas Betley of Penn and Erik Bloss of JAX were named by their institutions as senior authors on the work. In institutional summaries, the researchers said they were studying more immediate effects of exercise in the brain, rather than only the longer-term cognitive effects already associated with physical activity. ### How long did the cells stay active after the mice stopped running? (cell.com) ScienceDaily and JAX said the SF1 neurons remained active for about an hour after a run. That post-run window became a central part of the study because the researchers found the activity was not limited to the exercise period itself. Nature’s news coverage of the paper said the number of connections between those neurons increased as mice exercised more. (jax.org) JAX said animals that exercised had about twice as many connections between the neurons as animals that did not, according to the team’s experiments. ### What happened when the researchers blocked those neurons? The mouse experiments showed that blocking SF1 neuron output prevented the endurance and metabolic improvements that normally follow exercise training. (jax.org) PubMed’s summary said inhibition of SF1 neuron output blocked endurance gains and metabolic improvements resulting from training. (nature.com) JAX said that when the team turned off the neurons for 15 minutes after each training session, mice stopped improving their endurance even though they continued the same daily treadmill regimen for three weeks. ScienceDaily likewise said the animals still exercised normally, but their stamina did not improve when those cells were blocked. ### Did activating the neurons change performance? (pubmed.ncbi.nlm.nih.gov) The Neuron paper reported that stimulating SF1 neurons after training enhanced endurance in mice. Cell Press’s summary said SF1 neural activity was required for mice to achieve endurance benefits and that post-training stimulation enhanced those gains. JAX said mice receiving a post-exercise boost to those neurons ran longer distances and reached higher maximum speeds by the end of the training period than control animals. (jax.org) That finding, like the rest of the paper, came from mouse experiments. ### Does this study show the same thing happens in humans? The May 15 ScienceDaily release described mouse experiments and did not report human trial results. (cell.com) The Neuron paper summary available through Cell Press and PubMed also described the findings in mice. Nature’s coverage said the work adds to evidence that the central nervous system helps drive physical adaptation to exercise, but the published experiments were in mice. (jax.org) Any extension to human training or treatment remains a next research step rather than a reported result in this study. ### What comes next from here? A Neuron commentary published alongside the paper said the findings suggest a path for studying exercise-mimetic therapies by targeting the neural circuits involved in adaptation. (sciencedaily.com) Penn’s February 20 research note also said the work could open the door to exercise-mimicking approaches, though it did not report a human study or a clinical timeline. The current milestone is the Neuron publication itself: “Exercise-induced activation of ventromedial hypothalamic steroidogenic factor-1 neurons is required for endurance gains in mice.” The next reported step in the source material is further work by Betley, Bloss and colleagues on downstream signals linking those neurons to muscle and metabolic changes. (nature.com) (cell.com 1) (cell.com 2)