GPR43 Suppresses Intestinal Tumor Growth by Modification of the Mammalian Target of Rapamycin Complex 1 Activity in Apc Min/+ Mice

Objective: G protein-coupled receptor 43 (GPR43), a receptor for short-chain fatty acids, plays a role in suppressing tumor growth; however, the detailed underlying mechanism needs to be comprehensively elucidated. In this study, we investigated the role of GPR43 in inhibiting tumor growth using Apc^Min/+, a murine model of intestinal tumors. Materials and Methods: Using GPR43^−/− Apc^Min/+ and GPR43^+/− Apc^Min/+ mice, the number of tumors was analyzed at the end of the experimental period. Immunohistochemistry, quantitative polymerase chain reaction, and Western blotting were performed to analyze cellular proliferation and proliferation-associated signal pathways. Results: Our results revealed that GPR43 deficiency resulted in increased tumor numbers in Apc^Min/+ mice. Ki67 was highly expressed in GPR43^−/− mice ( p > 0.05). Increased expression levels of proinflammatory cytokines, including interleukin-6 and tumor necrosis factor-α, and amino acid transporters were not observed in GPR43-deficient mice compared to GPR43-sufficient mice. Furthermore, GPR43-deficient tumor tissues showed enhanced mammalian target of rapamycin-mediated phosphorylated ribosomal protein S6 kinase beta-1 ( p > 0.05) and phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 ( p > 0.05), but not Akt (protein kinase B) phosphorylation ( p = 0.7088). Conclusion: Collectively, GPR43 affords protection against tumor growth at least partly through inhibition of the mammalian target of rapamycin complex 1 pathway.