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Influence of Calcium Propionate on Regulating Physical Activity
The short-chain fatty acid propionate is a commonly used food preservative and mold inhibitor and is produced endogenously by the gut microbiota. Although generally recognized as safe, it's possible contribution to neurodevelopmental disorders and mixed results related to diabetes and obesity metabolism have called the safety of the compound into question. While there is a strong indication supporting the involvement of short chain fatty acids (SCFAs) in exercise performance, it is currently unknown if calcium propionate (CaP) consumption will influence mechanisms driving voluntary physical activity levels. As such, the primary purpose of this dissertation was to determine the following: (1a) whether prenatal dietary calcium propionate affected voluntary wheel running; (1b) to determine the mechanisms by which calcium propionate alters voluntary wheel running. Secondary outcomes were to determine whether a 0.3% CaP diet would: (2a) alter fecal and circulating SCFAs; (2b) alter dopaminergic signaling in the nucleus accumbens; or (2c) alter GPR43/41 expression in the muscle. Methods consisted of wheel running, diet and drug interventions, gas-chromatography-mass spectrometry, and western blotting. Our results indicated that a 0.3% CaP diet did not significantly alter body composition or wheel running. Drug treatments utilizing a SCFA receptor antagonist did not reveal any differences in wheel running. Furthermore, no significant differences were detected in plasma or fecal propionate concentrations. These results indicate that the 0.3% CaP diet was insufficient at increasing systemic propionate to levels high enough to elicit changes on behavior or body composition. The CaP diet did not significantly alter DRD1 or TH protein expression in males or females; however, the treatment did significantly increase ERK ½ abundance in the nucleus accumbens of male mice and lower GPR43 receptor abundance in the gastrocnemius muscle of female mice. The alteration in muscle was most likely due to down regulation of receptor density after prolonged agonist exposure, in which case, the results would weakly support that a 0.3% CaP diet was sufficient at altering muscle physiology. However, changes in muscle did not coincide with changes in wheel running. These results would support that propionate as a food additive at 0.3% does have effects on muscle and brain physiology but these effects did not translate to measurable changes on body composition, physical activity levels or dopamine signaling. The electronic version of this dissertation is accessible from https://hdl.handle.net/1969.1/198468
Doctor of Philosophy Texas A&M University 2022 https://hdl.handle.net/1969.1/198468