Glucagon-like peptide-1 receptor expression and its functions are regulated by androgen

Abstract

Glucagon-like peptide-1 receptor (GLP-1R) is an important pharmacological target for type 2 diabetes mellitus because it maintains glucose homeostasis and promotes β cell proliferation. Androgen is suggested not only to regulate hypothalamic-pituitary-gonadal axis but also to affect metabolism. In this study, Glp1r mRNA was found widely expressed in normal male mice and its levels were positively correlated with the serum testosterone (T) concentrations. Using mouse insulinoma 6 (MIN6) cells, which highly express GLP-1R, we observed GLP-1R was upregulated both at transcriptional and protein levels induced by dihydrotestosterone (DHT) and was downregulated by androgen receptor inhibitor ARN-509 or small interfering RNA (siRNA) targeting Glp1r mRNA. In normal C57BL/6 mice and db/db mice, Glp1r mRNA levels in the pancreases increased in the DHT treatment group and decreased in the ARN-509 treatment group. And the increased GLP-1R expression had insulinotropic function both in vitro and in vivo. Further analysis showed that the androgen receptor (Ar) located in the cytosol of MIN6 cells and translocated to the nucleus after DHT treatment. In addition, we found that there was an Ar motif in the promoter region of the Glp1r gene. Further studies revealed that the translocated DHT/Ar complex from the cytosol to the nucleus bound to the Ar motif of the Glp1r gene and upregulated gene transcription. Taken together, the widely expressed GLP-1R was positively regulated by androgen under physiological condition and in diabetic models at the transcriptional level.