No abstract available.
Glucagon-Like Peptide 1* ; Thyroid Neoplasms* ; Glucagon-Like Peptide-1 Receptor

No abstract available.
Glucagon-Like Peptide 1* ; Thyroid Neoplasms* ; Glucagon-Like Peptide-1 Receptor

At present, surgery has become one of the treatments for type 2 diabetes, but it is still unclear about the therapeutic mechanism. Many experiments has proved that the anatomical and physiological structure has been altered leading to significant changes related to the secretion of gastrointestinal hormones and neuropeptides. These molecular are related to the metabolism of glucose, functions of islet cells and sensitivity of insulin. Intensive studies of glucagon-like peptide-1 (GLP-1) play an important role in the surgical treatment of diabetes and now it has gained increasing recognition. However, GLP-1 must be combined with GLP-1 receptor (GLP-1R) to execute its function. In this paper we reviewed the role of GLP-1 and its receptor in the mechanism of metabolic surgery.
Diabetes Mellitus, Type 2 ; surgery ; Glucagon-Like Peptide 1 ; Glucagon-Like Peptide-1 Receptor ; Humans ; Receptors, Glucagon

The prevalence of type 2 diabetes (T2D) is increasing worldwide. Patients with T2D suffer from various diabetes-related complications. Since there are many patients with T2D that cannot be controlled by previously developed drugs, it has been necessary to develop new drugs, one of which is a glucagon-like peptide-1 (GLP-1) based therapy. GLP-1 has been shown to ameliorate diabetes-related conditions by augmenting pancreatic β-cell insulin secretion and having the low risk of causing hypoglycemia. Because of a very short half-life of GLP-1, many researches have been focused on the development of GLP-1 receptor (GLP-1R) agonists with long half-lives such as exenatide and dulaglutide. Now GLP-1R agonists have a variety of dosing-cycle forms to meet the needs of various patients. In this article, we review the physiological features of GLP-1, the effects of GLP-1 on T2D, the features of several GLP-1R agonists, and the therapeutic effect on T2D.
Diabetes Complications ; Glucagon-Like Peptide 1* ; Glucagon-Like Peptide-1 Receptor* ; Half-Life ; Humans ; Hypoglycemia ; Insulin ; Prevalence

Recent advances in incretin biology have led to the development of a new class of oral anti-diabetic drugs. To date, there are two known incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), of which the former is a more important therapeutic target for type 2 diabetes. GLP-1 is secreted by intestinal L-cells in response to oral nutrient intake, and it stimulates insulin secretion and suppresses glucagon secretion in a glucose-dependent manner. However, both GLP-1 and GIP are rapidly degraded by dipeptidyl peptidase-4 (DPP-4), a multifunctional type II transmembrane glycoprotein. Thus, several DPP-4 inhibitors with different pharmacologic features are now available and can be used either as monotherapy or in combination with other anti-diabetic agents for the treatment of type 2 diabetes. In both therapeutic regimens, DPP-4 inhibitors have been shown to reduce hemoglobin A1c levels by approximately 0.5-0.8%. In clinical trials, DPP-4 inhibitors were generally well-tolerated, posed a low risk of hypoglycemia, and did not increase body weight. Despite some reports of a possible increased risk of pancreatitis with GLP-1 receptor agonists and DPP-4 inhibitors, no causal associations have been found. Recent randomized controlled clinical trials have shown that DPP-4 inhibitors did not increase or decrease the rates of major adverse cardiovascular events in patients with type 2 diabetes at high risk of cardiovascular disease, even though this class of anti-diabetic agents had various salutary effects in many studies involving animals or healthy and diabetic humans. Additional studies will be required to resolve these disparate conclusions.
Animals ; Biology ; Body Weight ; Cardiovascular Diseases ; Glucagon ; Glucagon-Like Peptide 1 ; Glucagon-Like Peptide-1 Receptor ; Glycoproteins ; Humans ; Hypoglycemia ; Incretins ; Insulin ; Pancreatitis

Glucagon-like peptide-1 (GLP-1) is a member of the proglucagon incretin family, and GLP-1 receptor agonists (RAs) have been introduced as a new class of antidiabetic medications in the past decade. The benefits of GLP-1 RAs are derived from their pleiotropic effects, which include glucose-dependent insulin secretion, suppressed glucagon secretion, and reduced appetite. Moreover, GLP-1 RAs also exert beneficial roles on multiple organ systems in which the GLP-1 receptors exist, including the cardiovascular system. Cardiovascular effects of GLP-1 RAs have been of great interest since the burden from cardiovascular diseases (CVD) has been unbearably increasing in a diabetic population worldwide, despite strict glycemic control and advanced therapeutic techniques to treat CVD. Preclinical studies have already demonstrated the beneficial effects of GLP-1 on myocardium and vascular endothelium, and many clinical studies evaluating changes in surrogate markers of CVD have suggested potential benefits from the use of GLP-1 RAs. Data from numerous clinical trials primarily evaluating the antihyperglycemic effects of multiple GLP-1 RAs have also revealed that changes in most CVD risk markers reported as secondary outcomes have been in favor of GLP-1 RAs treatment. However, to date, there is only one randomized clinical trial of GLP-1 RAs (the ELIXA study) evaluating major cardiovascular events as their primary outcomes, and in this study, a neutral cardiovascular effect of lixisenatide was observed in high-risk diabetic subjects. Therefore, the results of ongoing CVD outcome trials with the use of GLP-1 RAs should be awaited to elucidate the translation of benefits previously seen in CVD risk marker studies into large clinical trials with primary cardiovascular outcomes.
Appetite ; Biomarkers ; Cardiovascular Diseases ; Cardiovascular System ; Endothelium, Vascular ; Glucagon ; Glucagon-Like Peptide 1* ; Glucagon-Like Peptide-1 Receptor* ; Humans ; Incretins ; Insulin ; Myocardium ; Proglucagon

New therapeutics for type 2 diabetes using incretin hormone were introduced recently. Incretin-based therapies consist of two types: GLP-1 agonists mainly acting on the GLP-1 receptor and dipeptidyl peptidase 4 inhibitors (DPP-4 inhibitors). The former is resistant to DPP-4 and injectable. The latter is oral medications raising endogenous GLP-1 by inhibiting the degrading enzyme DPP-4. The incretin based therapies are promising and more commonly used due to their action and safety profile. Stimulation of insulin secretion by these drugs occurs in a glucose-dependent manner. Incretin based therapies have low risk for hypoglycemia. The subsequent review outlines evidence from selected clinical trials of the currently available GLP-1 agonists, exenatide and liraglutide, and DPP-4 inhibitors, sitagliptin and vildagliptin.
Adamantane ; Dipeptidyl-Peptidase IV Inhibitors ; Glucagon-Like Peptide 1 ; Hypoglycemia ; Incretins ; Insulin ; Nitriles ; Peptides ; Pyrazines ; Pyrrolidines ; Receptors, Glucagon ; Triazoles ; Venoms ; Glucagon-Like Peptide-1 Receptor ; Liraglutide ; Sitagliptin Phosphate

It is well known that both insulin resistance and decreased insulin secretory capacity are important factors in the pathogenesis of type 2 diabetes mellitus (T2DM). In addition to genetic factors, obesity and lipotoxicity can increase the risk of T2DM. Glucagon-like peptide 1 (GLP-1) receptor agonists are novel antidiabetic drugs with multiple effects. They can stimulate glucose-dependent insulin secretion, inhibit postprandial glucagon release, delay gastric emptying, and induce pancreatic β-cell proliferation. They can also reduce the weight of patients with T2DM and relieve lipotoxicity at the cellular level. Many intracellular targets of GLP-1 have been found, but more remain to be identified. Elucidating these targets could be a basis for developing new potential drugs. My colleagues and I have investigated new targets of GLP-1, with a particular focus on pancreatic β-cell lines and hepatic cell lines. Herein, I summarize the recent work from my laboratory, with profound gratitude for receiving the prestigious 2016 Namgok Award.
Awards and Prizes ; Diabetes Mellitus ; Diabetes Mellitus, Type 2 ; Gastric Emptying ; Glucagon ; Glucagon-Like Peptide 1* ; Glucagon-Like Peptide-1 Receptor ; Hepatocytes* ; Humans ; Hypoglycemic Agents ; Insulin ; Insulin Resistance ; Obesity

BACKGROUND: Glucagon-like peptide-1 (GLP-1) is an incretin hormone produced by cleavage of proglucagon in intestinal L-cells. In the pancreas, GLP-1 stimulates post-prandial insulin secretion, promotes insulin biosynthesis, and improves insulin sensitivity. Because of its insulinotropic activity, GLP-1 has been considered a good candidate drug for treatment of diabetes mellitus. However, clinical use of GLP-1 has been limited by its short half-life, as a result of rapid degradation by dipeptidyl peptidase-IV (DPP-IV). METHODS: We designed a novel GLP-1 analog, Xenopus GLP-1 (xGLP)-E4. The Ala residue in the second position of xGLP was replaced with a Ser residue to increase the half-life in the body. The C-terminal tail of exendin-4 was added to enhance the binding affinity for the GLP-1 receptor (GLP1R). The potency of GLP-1 and its analogs was determined by luciferase assay. The stability of GLP1R agonists was evaluated by determining the activity of agonists that had been preincubated in the presence of fetal bovine serum, which contains innate DPP-IV activity. The effects of xGLP-E4 on insulin secretion and beta-cell growth were investigated using insulin enzyme-linked immunosorbent assay and cell counting. RESULTS: xGLP-E4 exhibited improved stability against DPP-IV activity and increased potency to GLP1R, compared with GLP-1. An increase in glucose-dependent insulin secretion was observed in xGLP-E4-treated pancreatic beta-cells. The effect of xGLP-E4 on beta-cell growth was greater than that of GLP-1. CONCLUSION: We developed a novel GLP-1 analog, xGLP-E4, that shows prolonged longevity and improved efficacy. This analog is a potential candidate for treatment of type 2 diabetes.
Cell Count ; Diabetes Mellitus ; Enzyme-Linked Immunosorbent Assay ; Glucagon-Like Peptide 1* ; Half-Life ; Incretins ; Insulin Resistance ; Insulin* ; Longevity ; Luciferases ; Pancreas ; Proglucagon ; Xenopus ; Glucagon-Like Peptide-1 Receptor

BACKGROUND: Incretin-based therapies are rapidly becoming one of the main glycemic control strategies in diabetes. Considering the large numbers of papillary thyroid carcinomas (PTCs) and possible effects of glucagon-like peptide-1 (GLP-1) on cell proliferation, the expression of GLP-1 receptor (GLP-1R) in PTC is likely to have clinical significance. We performed this study to evaluate the expression of GLP-1R in PTC and the clinical meaning of GLP-1R expression in PTC. METHODS: Fifty-six cases of PTC, four cases of medullary thyroid cancer (MTC), seven cases of nodular hyperplasia and 56 normal thyroid tissue samples were selected for immunostaining for GLP-1R. Clinical parameters were obtained by retrospective review of medical records. RESULTS: Immunohistochemical staining for GLP-1R showed immunoreactivity in 18 of 56 cases of PTC (32.1%). All four cases of MTC exhibited cytoplasmic GLP-1R expression. Nodular hyperplasia exhibited immunoreactivity in two of seven cases (28.6%). All normal thyroid follicular cells showed negative immunoreactivity. In univariable and multivariable analyses, tumor multifocality was negatively correlated with GLP-1R expression. Extrathyroidal extension showed positive association with GLP-1R expression that was almost significant. Sex, age, tumor size, and lymph node metastasis were not significantly associated with GLP-1R expression. CONCLUSION: Some parts of PTC tissues express GLP-1R, and GLP-1R expression in PTC was negatively correlated with tumor multifocality. The long-term influence of pharmacologically increased GLP-1 on thyroid follicular cells and development and progression of tumors originating from thyroid follicular cells should be investigated.
Cell Proliferation ; Cytoplasm ; Glucagon-Like Peptide 1* ; Hyperplasia ; Lymph Nodes ; Medical Records ; Neoplasm Metastasis ; Retrospective Studies ; Thyroid Gland ; Thyroid Neoplasms* ; Glucagon-Like Peptide-1 Receptor