Farnesoid X Receptor (FXR) Interacts with Camp Response Element Binding Protein (CREB) to Modulate Glucagon-Like Peptide-1 (7-36) Amide (GLP-1) Secretion by Intestinal L Cell

Cell Physiol Biochem. 2018;47(4):1442-1452. doi: 10.1159/000490836. Epub 2018 Jun 21.


Background/aims: Type II diabetes is a complex, chronic, and progressive disease. Glucagon-like peptide-1 (7-6) amide (GLP-1) is a gut hormone released from the L cells which stimulates insulin secretion, and promotes insulin gene expression and β-cell growth and differentiation. Elevated levels of hormone secreted by L cells are an important reason for diabetes improvement. GLP-1 secretion has been reported to be regulated by farnesoid X receptor (FXR), a transcriptional sensor for bile acids which also acts on glucose metabolism. Herein, we attempted to evaluate the effect of FXR on GLP-1 secretion in mouse enteroendocrine L cell lines, STC-1 and GLUTag, and to investigate the underlying mechanism.

Methods: ELISA and Western blot assays were employed to examine the levels of GLP-1 and FXR, and the effect of FXR on GLP-1 secretion; online database, including BioGRID and KEGG were used to identify the potential interactions between FXR and proteins and involved pathways; GST pull-down and Co-Immunoprecipitation (Co-IP) assays were performed to validate FXR-CREB interaction; Luciferase reporter gene assays were used for CREB transcriptional activity determination.

Results: FXR inversely regulated GLP-1 secretion in the mouse enteroendocrine L cell lines, GLUTag and STC-1. A total of 24 nonredundant human proteins were shown to be related to FXR by BioGRID; KEGG pathway analysis showed that FXR was related to glucagon signaling pathway, particularly with the transcriptional activators CREB, PGC1α, Sirt1 and CBP. CREB could positively regulate GLP-1 secretion in GLUTag and STC-1 cells. FXR combined with CREB to inhibit its transcriptional activity, thus inhibiting proprotein convertase subtilisin/ kexin type 1 (PCSK1) protein level and GLP-1 secretion.

Conclusion: In the present study, we demonstrated a negative regulation of GLP-1 secretion by FXR in L cell lines, GLUTag and STC-1; FXR exerts its function in L cells through interacting with CREB, a crucial transcriptional regulator of cAMP-CREB signaling pathway, to inhibit its transcriptional activity. Targeting FXR to rescue GLP-1 secretion may be a promising strategy for type II diabetes.

Keywords: Farnesoid X receptor (FXR); Glucagon signaling pathway; Glucagon-like peptide-1 (7-36) amide (GLP-1); L cell; Type II diabetes.

MeSH terms

  • Animals
  • CREB-Binding Protein / genetics
  • CREB-Binding Protein / metabolism*
  • Diabetes Mellitus, Type 2 / genetics
  • Diabetes Mellitus, Type 2 / metabolism
  • Diabetes Mellitus, Type 2 / pathology
  • Enteroendocrine Cells / metabolism*
  • Enteroendocrine Cells / pathology
  • Glucagon-Like Peptide 1 / metabolism*
  • L Cells
  • Mice
  • Peptide Fragments / metabolism*
  • Receptors, Cytoplasmic and Nuclear / genetics
  • Receptors, Cytoplasmic and Nuclear / metabolism*


  • Peptide Fragments
  • Receptors, Cytoplasmic and Nuclear
  • farnesoid X-activated receptor
  • glucagon-like peptide 1 (7-36)amide
  • Glucagon-Like Peptide 1
  • CREB-Binding Protein
  • Crebbp protein, mouse