Divergent Effect of Central Incretin Receptors Inhibition in a Rat Model of Sporadic Alzheimer's Disease.

The incretin system is an emerging new field that might provide valuable contributions to the research of both the pathophysiology and therapeutic strategies in the treatment of diabetes, obesity, and neurodegenerative disorders. This study aimed to explore the roles of central glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) on cell metabolism and energy in the brain, as well as on the levels of these incretins, insulin, and glucose via inhibition of the central incretin receptors following intracerebroventricular administration of the respective antagonists in healthy rats and a streptozotocin-induced rat model of sporadic Alzheimer's disease (sAD). Chemical ablation of the central GIP receptor (GIPR) or GLP-1 receptor (GLP-1R) in healthy and diseased animals indicated a region-dependent role of incretins in brain cell energy and metabolism and central incretin-dependent modulation of peripheral hormone secretion, markedly after GIPR inhibition, as well as a dysregulation of the GLP-1 system in experimental sAD.

GLP2-GLP2R signal affects the viability and EGFR-TKIs sensitivity of PC9 and HCC827 cells.

BACKGROUND: The resistance to epidermal growth factor receptor (EGFR)- tyrosine kinase inhibitors (TKIs) therapy is currently the major clinical challenge in the treatment of lung cancer. This study aims to reveal the role of glucagon-like peptide (GLP) 2 and GLP-2 receptor (GLP2R) signaling on the EGFR-TKIs and cisplatin resistance of lung cancer cells. METHODS: The common differentially expressed genes in PC9 and HCC827 cells that were individually resistant to one of the three EGFR-TKIs (dacomitinib, osimertinib and afatinib) were screened. The data were from GSE168043 and GSE163913. The expression of GLP2R in drug-resistant cells was detected by western blot. The effect of GLP2R expression down- or up-regulation on resistance to dacomitinib, osimertinib, afatinib or cisplatin was measured by CCK-8 and flow cytometry assays. The long-acting analog of GLP-2, teduglutide, treated the parental cells. RESULTS: A total of 143 common differentially expressed genes were identified. Compared with the parent cells, the GLP2R expression in drug-resistant cell lines was significantly up-regulated. The exogenous expression of GLP2R in parental cells enhanced cell viability, while knockdown of GLP2R levels in drug-resistant cell lines inhibited cell viability. In addition, teduglutide treatment also enhanced the viability of lung cancer cells. CONCLUSION: GLP2-GLP2R signal may change the sensitivity of cells to EGFR-TKIs and cisplatin. The development of GLP-2 or GLP2R inhibitors may be beneficial to the clinical treatment of lung cancer.

The early history of GIP 1969-2000: From enterogastrone to major metabolic hormone.

This paper describes the early history of Gastric Inhibitory Polypeptide, better referred to simply as GIP, from its isolation by purification from a crude preparation of CCK-PZ (cholecystokinin/pancreozymin) to its recognition as a key player in the pathogenesis of obesity and other metabolic disorders far removed from the enterogastrone properties by which it was originally identified. Augmentation of glucose mediated insulin release, the incretin effect, was discovered soon after GIP was first isolated and only much later was its important role in the pathogenesis of obesity, through mechanism other than insulin secretion, appreciated. Immunoassay - the only method by which the concentration of GIP was measured in plasma until quite recently - was found to be flawed and to depend upon which specific epitope of the hormone an assay detected. This was especially true if it was an amino-acid sequence specific to porcine rather than human GIP. A further confounder was the discovery that much of the GIP measured by immunoassay was its biological antagonist produced by cleavage of its two N-terminal amino-acids in the circulation by the same dipeptidyl-peptidase as de-activates GLP-1. Potential use of synthetic agonistic and antagonistic GIP analogues in therapeutics was barely alluded to before year 2000.

The effect of body mass index on glucagon-like peptide receptor gene expression in the post mortem brain from individuals with mood and psychotic disorders.

There is an increasing interest in the putative role of glucagon-like peptide 1 receptor (GLP-1R) agonists as novel therapeutic agents for mental disorders. Herein, we investigated the expressions of GLP-1R and GLP-2R genes, and its relationship with body mass index (BMI), in the post-mortem brain tissue of patients with mood (MD) and psychotic disorders. Brain samples were localized to the dorsolateral prefrontal cortex (dlPFC) (n = 459) and hippocampus (n = 378). After adjustment for age, sex, ethnicity, post-mortem interval (PMI) and BMI, we observed significant differences, between healthy controls and MD subjects, in GLP-1R and GLP-2R gene expression in the dlPFC (ß = 1.504, p = 0.004; and ß = 1.305, p = 0.011, respectively); whereas in the hippocampus, only GLP-1R expression was significantly associated with MD (ß = -1.28, p = 0.029). No significant differences were found in relation to schizophrenia. In addition, we observed a moderating effect of MD diagnosis on the associations between BMI, GLP-1R and GLP-2R expression values in the dlPFC (ß = -0.05, p = 0.003; and ß = -0.04, p = 0.004, respectively). There was a similar moderating effect for GLP-1R in the hippocampus (ß = 0.043, 95% CI 0.003; 0.08 p = 0.03), but in an opposite direction than observed in the dlPFC. This is the first evidence of abnormal gene expression of GLP-1R and GLP-2R in postmortem brain of individuals with MD, providing a rationale for further inquiry and proof of principle interventional studies.

Association of incretin receptors genetic polymorphisms with type 2 diabetes mellitus in Egyptian patients.

BACKGROUND: Incretins have opened a new era in type 2 diabetes mellitus (T2DM) pathogenesis. The present study aimed to assess whether there is an association between GIPR rs2302382, GIPR rs1800437 and GLP-1R rs367543060 polymorphisms with T2DM or not and also to determine the effect of these polymorphisms on gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) levels. METHODS: One hundred and fifty T2DM patients and 150 healthy controls were included in the study. Polymorphisms of GIPR rs1800437, GIPR rs2302382 and GLP-1R rs367543060 were genotyped using restriction fragment length polymorphism (RFLP)-polymerase chain reaction (PCR), multiplex allele-specific PCR and RFLP-PCR respectively. GIP and GLP levels were measured by an enzyme-linked immunosorbent assay. RESULTS: We found a significant association of both the homozygous AA and the minor allele A of GIPR rs2302382 with T2DM. The frequency of haplotype C(rs2302382) G(rs1800437) was significantly higher in controls than in diabetics; odds ratio (95% confidence interval): 1.99 (1.44-2.75) (p < 0.001), whereas the haplotype A(rs2302382) C(rs1800437) was significantly higher in patients than controls. We did not find any association of GLP-1R rs367543060 polymorphism with T2DM. We found a significant increase in serum total GIP and a significant decrease of GLP-1 levels in T2DM patients. CONCLUSIONS: We reveal for the first time an association between the GIPR rs2302382 polymorphism and T2DM in Egyptians. Yet, there was no significant association of GIPR rs1800437 or GLP-1R rs367543060 with T2DM risk. The haplotype A (rs2302382) C (rs1800437) was associated with an increased risk of T2DM. Furthermore, there was a significant increase of GIP and a significant decrease of GLP-1 levels when diabetic patients were compared with controls. An important finding was that there was a relationship between both GIPR rs2302382 and rs1800437 variants and their cognate ligand levels.