Tissue distribution of messenger ribonucleic acid encoding the rat glucagon-like peptide-1 receptor.

TLDR

GLP‑1 regulates postprandial insulin secretion and promotes insulin‑independent glucose disposal, indicating the presence of extrapancreatic GLP‑1 receptors. The study sought to map the tissue distribution of GLP‑1 receptor mRNA in rats. RNAse protection assays, RT‑PCR, and in situ hybridization were used to detect GLP‑1 receptor transcripts. GLP‑1 receptor mRNA was found in pancreatic islets, lung, stomach, kidney, hypothalamus, and heart, but not in adipose, liver, or skeletal muscle, suggesting structural variants in kidney and heart and that extrapancreatic GLP‑1 actions may involve additional receptor forms.

Abstract

The incretin hormone glucagon-like peptide-1 (GLP-1) is an important regulator of postprandial insulin secretion. In addition to its insulinotropic actions on pancreatic beta-cells, GLP-1 enhances glucose disposal by insulin-independent mechanisms, suggesting that GLP-1 receptors are located on extrapancreatic tissues. In this study, we examined the tissue distribution of GLP-1 receptor (GLP-lR) messenger RNA (mRNA) in rat by RNAse protection, RT-PCR, and in situ hybridization. We identified GLP-1R mRNA in the lung, pancreatic islets, stomach, and kidney by the RNAse protection assay. RT-PCR analysis also detected GLP-1R mRNA in the hypothalamus and heart. In situ hybridization experiments identified receptor mRNA in the gastric pits of the stomach, large nucleated cells in the lung, crypts of the duodenum, and pancreatic islets. No localized specific grains were found in kidney, skeletal muscle, heart, liver, or adipocytes. These results indicate that sequences corresponding to the cloned rat islet GLP-1 receptor are expressed in the pancreatic islets, lung, hypothalamus, stomach, heart, and kidney but not in adipose, liver, and skeletal muscle. Further, the GLP-1 receptor expressed in the kidney and heart may be structural variants of the known receptor. Therefore, the observed extrapancreatic actions of GLP-1 may not be strictly confined to interactions with the defined GLP-1 receptor.