Fig. 3. GP2 treatment inhibits the intestinal FXR signalling pathway and improves intestinal L-cell function via accumulation of fecal TβMCA.

a, b mRNA expression of the target genes in the ileum (a) and liver (a, b) (n = 7–8). c Gene expression of the target genes in the ileum (n = 7–8). d Individual taurine-conjugated bile acid levels were detected in the feces of HFD-fed mice (n = 3). e BSH enzymatic activity in the feces of HFD-fed mice treated with or without GP2 (200 mg/kg). The ratio of CDCA-d5 to TCDCA-d5 was used to represent the enzymatic activity of BSH (n = 4). f BSH enzymatic activity in the feces of HFD-fed mice treated with different concentrations of GP2 in vitro. The ratio of CDCA-d5 to TCDCA-d5 was used to represent the enzymatic activity of BSH (n = 3). g GLP-1 concentration in the supernatants of STC-1 cells were measured after incubation with DMSO or TβMCA for 24 h, and the TGR5 agonist INT-777 (10 μM) was used as a positive control (n = 4). h Gene expression of the target genes in STC-1 cells treated with 300 μM TβMCA for 12 h (n = 4). i Quantitation of the extracellular acidification rate (ECAR) by the seahorse assay. STC-1 cells were incubated with DMSO or TβMCA for 24 h and then successively injected with glucose (10 mM), oligomycin (1 μM), 2-deoxyglucose (100 mM) and rotenone (1 μM)/antimycin A (1 μM) for the seahorse flux assay at the indicated time. j–l Eight-week-old male WT or intestinal specific FXR KO (FXR^−/−) mice were fed a high-fat diet for 5 weeks, and then treated with or without GP2-200 mg/kg/d for 2 weeks (n = 5–6). Intestinal Fxr mRNA levels (j) and pro-glucagon protein levels (k, l) from WT mice and FXR^−/− mice after GP2 treatment were detected. The results are shown as the mean ± s.e.m., *P < 0.05, **P < 0.01, ***P < 0.001 compared with vehicle or DMSO.