Nobiletin protects enteric nerves and ameliorates disordered bowel motility in diet-induced obese mice via increasing Trem2 expression

Nobiletin can regulate lipid metabolism and protect the central nervous system. However, its role in the enteric nervous system (ENS) of obese subjects is still unclear. To investigate the ENS protective effects and mechanism of nobiletin in obese mice, male C57BL/6 mice were fed a chow diet and a high-fat diet (HFD) for 8 weeks. The identified obese and control mice were grouped and administered vehicle, nobiletin 40 mg/kg, 100 mg/kg or 200 mg/kg daily for 4 weeks. The major indexes of obesity, intestinal transit rate, PGP9.5, nNOS, TNF-α, IL-1β, IL-6, IL-10, Bcl2 and Bax were measured. The full-length transcriptome was used to analyze differentially expressed genes (DEGs) in the colon. The results indicated that nobiletin effectively improved major indexes of obesity and bowel motility function, suppressed the expression of TNF-α, IL-1β, IL-6 and Bax, and upregulated the expression of IL-10, Bcl2, PGP9.5 and nNOS. Based on full-length transcriptome sequencing, nobiletin regulated lipid metabolism and inflammation via the PPAR and NOD-like receptor signaling pathways. Trem2 expression was significantly reduced in obese mice. However, Trem2 expression was significantly increased after nobiletin treatment in obese mice. The enrichment analysis showed that Trem2 plays an important role in enteric neuroinflammation. In conclusion, nobiletin regulates lipid metabolism and inflammation in obese mice. Trem2 is a potential target of nobiletin for ENS protection in obese mice.