Abstract

Background: Short-chain fatty acids (SCFAs) are metabolites produced by the gut microbiota after fiber fermentation. Some SCFAs, such as acetate, propionate, and butyrate, have been recognized as essential for human health, especially for the brain; however, the cellular mechanisms activated by these molecules in food-intake-related organs, such as the olfactory bulb, remain unclear. Objective: This study evaluates the effects of acetic acid (AA) and sodium butyrate on the physiology of Ca2+ metabolism in olfactory bulb cells (OBCs). Methods: Primary OBC cultures of the postnatal rat (P7-21) were made, and Ca2+ imaging experiments were performed to record the intracellular Ca2+ responses (iCaR) elicited by the application of AA and sodium butyrate (100 nM–1 mM). Immunocytochemical analyses were performed to identify GFAP+ cells and GPR41 and GPR43 receptors in OBCs. Endpoint RT-PCR analyses were made to identify GPR41 and GPR43 transcripts in OBCs. Results: Fewer than 10% of the OBCs tested responded to the application of AA and sodium butyrate with iCaR. Pharmacological studies (20 µM 2-aminoethyl diphenylborinate (2-APB); 10 nM GLPG0974, 120 nM AR420626) showed that iCaR were independent of inositol triphosphate (IP3)-signaling pathways and that OBCs expressed both GPR41 and GPR43 receptors. Endpoint RT-PCR studies performed in both olfactory bulbs and primary OBC cultures confirmed the expression of the GPR41 receptor. Conclusions: This study shows that AA and butyrate induce intracellular Ca2+ responses activated by GPR41 and GPR43 receptors in a discrete cellular population of the rat olfactory bulb.

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