Endometriosis is a gynecological disorder characterized by the growth of endometrial tissue in areas outside the uterus. Previous studies in our laboratory demonstrated that endometriosis animals have increased mesenteric adipose tissue (MAT), inflammation, and implanted endometrial vesicles, which are all decreased by voluntary exercise. Interestingly, the levels of Uncoupling Protein 1 (UCP-1), a mitochondrial protein, are known to be increased by exercise promoting thermogenesis, and decreasing inflammation in rodents. However, the possible role of UCP-1 in endometriosis is still unclear. Our aim was to study the effects of exercise on UCP-1 in MAT near the endometrial implants in an endometriosis rat model. Hypothesis: UCP-1 increases due to exercise decreasing the MAT and thus beneficially impacts the endometrial vesicles. Methods: Endometriosis was induced by implanting uterine tissue on the intestinal mesentery in young adult female Sprague Dawley rats where the control group only received sutures. Exercise rats had access to a running wheel after induction: ENDO-EX or SHAM-EX, while non-exercised animals didn’t (ENDO and SHAM; n=10=11/group). After sixty days of intervention, animals were sacrificed and UCP-1 immunofluorescent staining was performed on collected MAT near the vesicles (ENDO, n=3; ENDO-EX, n=3; SHAM, n=4; SHAM-EX, n=4). Results: The vesicles from ENDO-EX animals had significantly decreased average weight (p<0.05) and smaller average total area (p<0.01) compared with the ENDO group. UCP-1 staining shows a trend to increase in exercise groups when compared to non-exercise groups. Interestingly, there is a moderate negative correlation between UCP-1 expression and vesicle size (r=-.69). Conclusions: Exercise is related to increasing the UCP-1 pathways in MAT that may be associated with decreasing the size of the endometrial vesicle implants. Supported by R15AT009915 and HRD-2008186. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.