Abstract:

The aim of this study was to investigate the effect of oleic acid (OA) treatment on the secretion of ghrelin and its related mechanisms. MGN3-1 cells (gastric starvation tumor cells) were treated with OA and GPR120 inhibitor (AH-7614), respectively, and the following experiments were performed: 1) Determine the processing conditions for OA and group them together; 2) the amount of acylated starvation hormone (AG) was detected in the supernatant of the cells by ELISA; RT-qPCR was used to detect the gene expression of ghrelin, GOAT (growth hormone-releasing peptide O-acyltransferase), GPR120 (long-chain fatty acid receptor), and ACCα (acetyl-coenzyme A carboxylase) in the cells of each group; Western blot was used to detect the protein expression of GPR120, PKC, and IP3R; and flow cytometry was used to detect the intracellular Ca²⁺ concentration. The results showed that: 1) The low, medium and high concentrations of OA were determined to be 20, 40 and 60 μmol·L^-1, respectively, and the treatment time was 8 h. 2) The treatment of high concentration of OA highly significantly down-regulated cellular ghrelin and GOAT gene expression and decreased AG secretion (P < 0.01), significantly increased Ca²⁺ concentration (P < 0.01), significantly or highly significantly up-regulated gene expression of GPR120 and ACCα and protein expression of GPR120, IP3R and PKC (P < 0.01 or P < 0.05); AH-7614 treatment significantly or highly up-regulated the gene expression of GOAT and ghrelin and protein expression of IP3R, elevated AG secretion levels, and down-regulated GPR120 and ACCα gene expression and protein expression of GPR120 and PKC(P < 0.01 or P < 0.05); in contrast to the AH-7614 group, treatment with AH-7614 followed by OA resulted in significant or highly significant reduction in AG secretion levels and ghrelin and GOAT gene expression levels(P < 0.01 or P < 0.05), and a certain degree of up-regulation of the expression of GPR120 and ACCα genes as well as of the protein expression of GPR120, IP3R and PKC. In conclusion, the results suggest that OA treatment reduced ghrelin secretion in MGN3-1 cells. The possible mechanism is that OA treatment inhibition of GOAT activity through activation of GPR120 and its downstream PKC/IP3R/Ca²⁺signaling pathway on the one hand, and activating fatty acid β-oxidation through up-regulation of ACCα expression on the other hand, the two pathways synergistically inhibit GOAT activity, resulting in decreased cellular ghrelin secretion and reduced AG production.

Key words: oleic acid (OA), ghrelin, MGN3-1 cells, secretion, mechanism