Previous studies have implicated the orexigenic hormone ghrelin as a mediator of exercise endurance and the feeding response post-exercise. Specifically, plasma ghrelin levels nearly double in mice when they are submitted to an hour-long bout of high-intensity interval exercise (HIIE) using treadmills. Also, GHSR (ghrelin receptor)-null mice exhibit decreased food intake following HIIE and a diminished running distance (time until exhaustion) during a longer, step-wise exercise endurance protocol. To investigate whether ghrelin-responsive mediobasal hypothalamus (MBH) neurons mediate these effects, we stereotaxically delivered the inhibitory DREADD virus AAV2-hSyn-DIO-hM4(Gi)-mCherry to the MBH of Ghsr-IRES-Cre mice, which express Cre-recombinase directed by the Ghsr promoter. We found that chemogenetic inhibition of GHSR-expressing MBH neurons [upon delivery of clozapine-N-oxide (CNO)] 1) suppressed food intake following HIIE by 31.3%, 2) reduced maximum running distance by 20.7%-22.7% and raised blood glucose and blood lactate levels by 18.4%-51.5% and 24.6%-39.2%, respectively, during an exercise endurance protocol, 3) reduced food intake following ghrelin administration by 57.2%, but 4) did not affect glucose tolerance. Further, HIIE increased MBH Ghsr expression. These results indicate that activation of ghrelin-responsive MBH neurons is required for the normal feeding response to HIIE and the usual amount of running exhibited during an exercise endurance protocol.
Omprakash Singh, Sean B. Ogden, Salil Varshney, Kripa Shankar, Deepali Gupta, Subhojit Paul, Sherri Osborne-Lawrence, Corine P. Richard, Nathan P. Metzger, Connor Lawrence, Luis León-Mercado, Jeffrey M. Zigman