Glucagon-like Peptide-1 Receptor Gene Research Articles

Glucose intolerance but normal satiety in mice with a null mutation in the glucagon-like peptide 1 receptor gene.

Glucagon-like peptide 1 (GLP1) is postulated to regulate blood glucose and satiety, but the biological importance of GLP1 as an incretin and neuropeptide remains controversal. The regulation of nutrient-induced insulin secretion is dependent on the secretion of incretins, gut-derived peptides that potentiate insulin secretion from the pancreatic islets. To ascertain the relative physiological importance of GLP1 as a regulator of feeding behavior and insulin secretion, we have generated mice with a targeted disruption of the GLP1 receptor gene (GLP1R). These GLP1R-/- mice are viable, develop normally but exhibit increased levels of blood glucose following oral glucose challenge in association with diminished levels of circulating insulin. It is surprising that they also exhibit abnormal levels of blood glucose following intraperitoneal glucose challenge. Intracerebroventricular administration of GLP1 inhibited feeding in wild-type mice but not in GLP1R-/- mice; however, no evidence for abnormal body weight or feeding behavior was observed in GLP1R-/- mice. These observations demonstrate that GLP1 plays a central role in the regulation of glycemia; however, disruption of GLP1/GLP1R signaling in the central nervous system is not associated with perturbation of feeding behavior or obesity in vivo.

A population association study of four candidate genes (hexokinase II, glucagon-like peptide-1 receptor, fatty acid binding protein-2, and apolipoprotein C-II) with type 2 diabetes and impaired glucose tolerance in Japanese subjects.

In order to define the major genetic factor(s) for the development of Type 2 (non-insulin-dependent) diabetes mellitus in Japanese subjects, a population association study of candidate genes involved in either glucose or lipid metabolism was carried out using microsatellite DNA polymorphisms. Each polymorphic locus near the four candidate genes, hexokinase II (HKII), glucagon-like peptide-1 receptor (GLP1R), fatty acid binding protein-2 (FABP-2), and apolipoprotein C-II (apoC-II) genes, were amplified by polymerase chain reaction (PCR) using 32P-labelled primers and each subject was genotyped for the association study. The HKII, GLP1R, FABP-2, and apoC-II polymorphisms exhibited 18, 10, 7, and 10 alleles, respectively. While polymorphism information contents (PICs) of these polymorphisms were relatively high, allele frequencies in these polymorphisms did not differ among subjects with Type 2 diabetes, impaired glucose tolerance (IGT) and non-diabetic controls. These results suggest that the HKII, GLP1R, FABP-2, and apoC-II genes are not the major inherited factors for the development of Type 2 diabetes or IGT in Japanese subjects, although minor contribution cannot be ruled out.

Cloning of the human GLP-1 receptor gene and partial characterization of the promotor

Cloning of the human GLP-1 receptor gene and partial characterization of the promotor

Expression of the glucagon-like peptide-1 receptor gene in rat brain.

Evidence that glucagon-like peptide-1 (GLP-1) (7-36) amide functions as a novel neuropeptide prompted us to study the gene expression of its receptor in rat brain. Northern blot analysis showed transcripts of similar size in RINm5F cells, hypothalamus, and brain-stem. First-strand cDNA was prepared by using RNA from hypothalamus, brainstem, and R1Nm5F cells and subsequently amplified by PCR. Southern blot analysis of the PCR products showed a major 1.4-kb band in all these preparations. PCR products amplified from hypothalamus were cloned, and the nucleotide sequence of one strand was identical to that described in rat pancreatic islets. In situ hybridization studies showed specific labeling in both neurons and glia of the thalamus, hypothalamus, hippocampus, primary olfactory cortex, choroid plexus, and pituitary gland. In the hypothalamus, ventromedial nuclei cells were highly labeled. These findings indicate that GLP-1 receptors are actually synthesized in rat brain. In addition, the colocalization of GLP-1 receptors, glucokinase, and GLUT-2 in the same areas supports the idea that these cells play an important role in glucose sensing in the brain.

Localization of a (CA)n repeat in glucagon-like peptide-1 receptor gene (Glp1r) to proximal mouse chromosome 17 and its linkage to other markers.

Localization of a (CA)n repeat in glucagon-like peptide-1 receptor gene (Glp1r) to proximal mouse chromosome 17 and its linkage to other markers.

Non-linkage of the glucagon-like peptide 1 receptor gene with maturity onset diabetes of the young

Glucagon-like peptide-1 (GLP-1) is a hormone derived from the preproglucagon molecule that is secreted by intestinal L cells and stimulates insulin secretion from betacells. The GLP-1 receptor is a candidate gene for diabetes mellitus, as mutations may induce the impaired insulin response that is a characteristic feature of NIDDM. To study the relationship between the GLP-1 receptor gene and NIDDM, linkage of a microsatellite polymorphism flanking the GLP-1 receptor gene with diabetes was investigated in three Caucasian families with MODY and in the nuclear families of 12 NIDDM probands. A cumulative LOD score −8.50 excludes linkage in these MODY pedigrees. A LOD score of −1.24 in the NIDDM nuclear pedigrees makes linkage improbable. Mutations in or near the GLP-1 receptor gene are unlikely to be the major cause of the inherited predisposition to NIDDM in Caucasian pedigrees, but we cannot exclude a role for this locus in a polygenic model or a major role in some pedigrees.

Non-linkage of the glucagon-like peptide 1 receptor gene with maturity onset diabetes of the young

Glucagon-like peptide-1 (GLP-1) is a hormone derived from the preproglucagon molecule that is secreted by intestinal L cells and stimulates insulin secretion from beta cells. The GLP-1 receptor is a candidate gene for diabetes mellitus, as mutations may induce the impaired insulin response that is a characteristic feature of NIDDM. To study the relationship between the GLP-1 receptor gene and NIDDM, linkage of a microsatellite polymorphism flanking the GLP-1 receptor gene with diabetes was investigated in three Caucasian families with MODY and in the nuclear families of 12 NIDDM probands. A cumulative LOD score -8.50 excludes linkage in these MODY pedigrees. A LOD score of -1.24 in the NIDDM nuclear pedigrees makes linkage improbable. Mutations in or near the GLP-1 receptor gene are unlikely to be the major cause of the inherited predisposition to NIDDM in Caucasian pedigrees, but we cannot exclude a role for this locus in a polygenic model or a major role in some pedigrees.

Human glucagon-like peptide-1 receptor gene in NIDDM. Identification and use of simple sequence repeat polymorphisms in genetic analysis.

Glucagon-like polypeptides, GLP-1-(7-36)-amide and GLP-1-(7-37), are important regulators of insulin synthesis and secretion by islet beta-cells. The hypothesis to be tested in this study was that defects in the islet beta-cell GLP-1 receptor gene contribute to the impaired glucose-regulated insulin secretion of non-insulin-dependent diabetes mellitus (NIDDM). Human islet GLP-1 receptor genomic clones were isolated, and two highly polymorphic simple sequence repeat regions (GLP-1R-CA1 and GLP-1R-CA3) were identified. Polymerase chain reaction assays were developed to define alleles. For GLP-1R-CA1, 14 alleles were observed in African-Americans (heterozygosity [het] = 0.78) and 6 alleles in Caucasians (het = 0.67). For GLP-1R-CA3, 16 alleles were observed in African Americans (het = 0.89) and 8 alleles in Caucasians (het = 0.83). By genotyping all members of the 40 reference Centre d'Etude du Polymorphisme Humain pedigrees at GLP-1R-CA3, the human GLP-1 receptor gene was uniquely placed on chromosome 6p between GLO1 and D6S19, 20.4 cM from human leukocyte antigen. To assess the possible role of the GLP-1 receptor gene in determining the genetic susceptibility to NIDDM, allelic frequencies of GLP-1R-CA1 and GLP-1R-CA3 were compared between African-American NIDDM patients (n = 95) and control subjects (n = 93). The frequencies did not differ between the two groups at either GLP-1R-CA1 or GLP-1R-CA3. The GLP-1 receptor gene simple-sequence repeat polymorphisms were used for linkage analysis in Utah Mormon pedigrees (n = 16) with NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Human glucagon-like peptide-1 receptor gene in NIDDM. Identification and use of simple sequence repeat polymorphisms in genetic analysis

Human glucagon-like peptide-1 receptor gene in NIDDM. Identification and use of simple sequence repeat polymorphisms in genetic analysis

Divergent tissue-specific and developmental expression of receptors for glucagon and glucagon-like peptide-1 in the mouse

Proglucagon mRNA transcripts are transcribed in the pancreas, bowel, and brain, after which posttranslational processing results in the liberation of a different profile of biologically active peptides in each tissue. The receptors for two of these peptides, glucagon and glucagon-like peptide-1 (GLP-1), have recently been identified, but only limited information is available concerning the tissue- and age-specific distribution of these receptors in vivo. We have investigated the expression of these receptors in the mouse using a combination of Northern blot analysis and reverse transcription-polymerase chain reaction. DNA sequence analysis of a partial mouse glucagon receptor cDNA demonstrated a high degree of sequence conservation across rodent species. Glucagon receptor mRNA transcripts were detectable by Northern blotting in poly(A)+ RNA from liver and kidney. Reverse transcription-polymerase chain reaction also detected glucagon receptor mRNA transcripts in both fetal and adult pancreas and lung, jejunum, and ileum, but not in the large intestine. In contrast, mRNA transcripts for the GLP-1 receptor were detected in both small and large intestine as well as in pancreas, liver, lung, and kidney. Both glucagon and GLP-1 receptor mRNA transcripts were identified in different regions of the fetal and adult mouse brain, but the relative levels of GLP-1 receptor mRNA transcripts were much greater in the central nervous system. Furthermore, regulation of the GLP-1 receptor (but not the glucagon receptor) gene in the brain resembled the pattern of region-specific gene expression recently defined for the mouse proglucagon gene. Taken together, these studies define novel sites for both glucagon and GLP-1 receptor gene expression in the mouse and suggest that different regulatory mechanisms have evolved for tissue-specific and developmental control of receptor gene expression.

Divergent tissue-specific and developmental expression of receptors for glucagon and glucagon-like peptide-1 in the mouse.

Proglucagon mRNA transcripts are transcribed in the pancreas, bowel, and brain, after which posttranslational processing results in the liberation of a different profile of biologically active peptides in each tissue. The receptors for two of these peptides, glucagon and glucagon-like peptide-1 (GLP-1), have recently been identified, but only limited information is available concerning the tissue- and age-specific distribution of these receptors in vivo. We have investigated the expression of these receptors in the mouse using a combination of Northern blot analysis and reverse transcription-polymerase chain reaction. DNA sequence analysis of a partial mouse glucagon receptor cDNA demonstrated a high degree of sequence conservation across rodent species. Glucagon receptor mRNA transcripts were detectable by Northern blotting in poly(A)+ RNA from liver and kidney. Reverse transcription-polymerase chain reaction also detected glucagon receptor mRNA transcripts in both fetal and adult pancreas and lung, jejunum, and ileum, but not in the large intestine. In contrast, mRNA transcripts for the GLP-1 receptor were detected in both small and large intestine as well as in pancreas, liver, lung, and kidney. Both glucagon and GLP-1 receptor mRNA transcripts were identified in different regions of the fetal and adult mouse brain, but the relative levels of GLP-1 receptor mRNA transcripts were much greater in the central nervous system. Furthermore, regulation of the GLP-1 receptor (but not the glucagon receptor) gene in the brain resembled the pattern of region-specific gene expression recently defined for the mouse proglucagon gene. Taken together, these studies define novel sites for both glucagon and GLP-1 receptor gene expression in the mouse and suggest that different regulatory mechanisms have evolved for tissue-specific and developmental control of receptor gene expression.

Human Glucagon-Like Peptide-1 Receptor Gene: Localization to Chromosome Band 6p21 by Fluorescence In Situ Hybridization and Linkage of a Highly Polymorphic Simple Tandem Repeat DNA Polymorphism to Other Markers on Chromosome 6

Glucagon-like peptide-1 is a fragment of proglucagon secreted by intestinal L-cells. It has potent glucose-dependent insulin secretory effects and also suppresses gastric acid secretion in the stomach. The biological actions of GLP-1 are mediated by the GLP-1 receptor, the structure of which has recently been determined. Defects in insulin secretion are a common feature of NIDDM and as such the GLP-1 receptor is a candidate for contributing to the development of this clinically and genetically heterogeneous disorder. As a first step in determining the role of the GLP-1 receptor in the development of NIDDM, we have isolated the human GLP-1 receptor gene and mapped it to chromosome 6, band p21.1, using the technique of fluorescence in situ hybridization. We also identified a simple tandem repeat DNA polymorphism in the human GLP-1 receptor gene of the form (TG)n. This DNA polymorphism has 14 alleles and a heterozygosity of > 0.8. We have used this DNA polymorphism to localize the GLP-1 receptor gene within the genetic map of the short arm of chromosome 6. This DNA polymorphism will facilitate genetic studies of the contribution of the GLP-1 receptor gene to impaired beta-cell function and NIDDM.

Human glucagon-like peptide-1 receptor gene. Localization to chromosome band 6p21 by fluorescence in situ hybridization and linkage of a highly polymorphic simple tandem repeat DNA polymorphism to other markers on chromosome 6

Human glucagon-like peptide-1 receptor gene. Localization to chromosome band 6p21 by fluorescence in situ hybridization and linkage of a highly polymorphic simple tandem repeat DNA polymorphism to other markers on chromosome 6