Ginsenoside compound K increases glucagon-like peptide-1 release and L-cell abundance in db/db mice through TGR5/YAP signaling

Abstract

Background: Incretin impairment refers to L-cell-derived glucagon-like peptide-1 (GLP-1) deficiency, commonly observed in patients with type 2 diabetes mellitus (T2DM). Promoting the enteroendocrine L-cell population to elevate GLP-1 secretory capacity represents a potential therapeutic strategy for T2DM. It has been established that ginsenoside compound K (CK) could stimulate GLP-1 secretion; however, the underlying mechanisms remain elusive.

Methods: CK was intragastrically administered to male db/db mice for 4 weeks that subsequently underwent oral glucose tolerance testing. Serum samples were collected to measure the GLP-1 secretion, insulin level, inflammatory factors, and bile acid (BA) profiles. Ileum epithelial injury was detected by Hematoxylin and Eosin (H&E) and Masson staining. Gene markers associated with L-cell differentiation were evaluated by RT-PCR, and L-cells were labeled by Gcg via immunofluorescence assays. TGR5 and YAP expression was analyzed by immunoblotting and immunofluorescence assays.

Results: Compound K attenuated hyperglycemia and inflammation in db/db mice and upregulated TGR5 expression by increasing lithocholic acid (LCA) and deoxycholic acid (DCA) levels in response to ileum epithelium injury. Meanwhile, fibrosis was alleviated, and the crypt architecture was restored, with increased L-cell abundance and serum GLP-1 levels. The upregulation in genes associated with L-cell differentiation promoted transformation into L-cells. Further mechanistic analyses showed that the effects of CK on the L-cell population required YAP activation, which triggered actin cytoskeleton dynamics.

Conclusions: Our results indicate that TGR5 could modulate the abundance of L-cells to enhance GLP-1 release through YAP-driven intestinal regeneration in db/db mice. Accordingly, CK has huge prospects for application to alleviate incretin impairment in T2DM.

Keywords: Enteroendocrine cells; GLP-1; Ginsenoside CK; Secondary bile acids; TGR5.