vasoactive-intestinal-peptide and Diabetes-Mellitus--Type-2

Owing to the increasing prevalence of type 2 diabetes, the development of novel hypoglycemic drugs has become a research hotspot, with the ultimate goal of developing therapeutic drugs that stimulate glucose-induced insulin secretion without inducing hypoglycemia. Vasoactive intestinal peptide (VIP), a 28-amino-acid peptide, can stimulate glucose-dependent insulin secretion, particularly by binding to VPAC2 receptors. VIP also promotes islet β-cell proliferation through the forkhead box M1 pathway, but the specific molecular mechanism remains to be studied. The clinical application of VIP is limited because of its short half-life and wide distribution in the human body. Based on the binding properties of VIP and VPAC2 receptors, VPAC2-selective agonists have been developed to serve as novel hypoglycemic drugs. This review summarizes the physiological significance of VIP in glucose homeostasis and the potential therapeutic value of VPAC2-selective agonists in type 2 diabetes.

Topics: Diabetes Mellitus, Type 2; Glucose; Humans; Hypoglycemic Agents; Insulin Secretion; Receptors, Vasoactive Intestinal Peptide, Type II; Vasoactive Intestinal Peptide

Topics: Aged; Diabetes Mellitus, Type 2; Glucagon; Humans; Male; Multiple Endocrine Neoplasia Type 1; Neuroendocrine Tumors; Pancreatectomy; Pancreatic Neoplasms; Splenectomy; Treatment Outcome; Vasoactive Intestinal Peptide

Gut hormones represent a niche subset of pharmacologically active agents that are rapidly gaining importance in medicine. Due to their exceptional specificity for their receptors, these hormones along with their analogues have attracted considerable pharmaceutical interest for the treatment of human disorders including type 2 diabetes. With the recent advances in the structural biology, a significant amount of structural information for these hormones is now available. This Minireview presents an overview of the structural aspects of these hormones, which have roles in physiological processes such as insulin secretion, as well as a discussion on the relevant structural modifications used to improve these hormones for the treatment of type 2 diabetes.

Topics: Diabetes Mellitus, Type 2; Gastric Inhibitory Polypeptide; Gastrointestinal Hormones; Glucagon; Glucagon-Like Peptide 1; Humans; Pituitary Adenylate Cyclase-Activating Polypeptide; Vasoactive Intestinal Peptide

Type 2 diabetes (T2D) is characterized by chronic insulin resistance and a progressive decline in beta-cell function. Although rigorous glucose control can reduce morbidity and mortality associated with diabetes, achieving optimal long-term glycemic control remains to be accomplished in many diabetic patients. As beta-cell mass and function inevitably decline in T2D, exogenous insulin administration is almost unavoidable as a final outcome despite the use of oral antihyperglycemic agents in many diabetic patients. Pancreatic islet cell death, but not the defect in new islet formation or beta-cell replication, has been blamed for the decrease in beta-cell mass observed in T2D patients. Thus, therapeutic approaches designed to protect islet cells from apoptosis could significantly improve the management of T2D, because of its potential to reverse diabetes not just ameliorate glycemia. Therefore, an ideal beta-cell-preserving agent is expected to protect beta cells from apoptosis and stimulate postprandial insulin secretion along with increasing beta-cell replication and/or islet neogenesis. One such potential agent, the islet endocrine neuropeptide vasoactive intestinal peptide (VIP) strongly stimulates postprandial insulin secretion. Because of its broad spectrum of biological functions such as acting as a potent anti-inflammatory factor through suppression of Th1 immune response, and induction of immune tolerance via regulatory T cells, VIP has emerged as a promising therapeutic agent for the treatment of many autoimmune diseases including diabetes.

Topics: Diabetes Mellitus; Diabetes Mellitus, Type 2; Humans; Insulin-Secreting Cells; Pituitary Adenylate Cyclase-Activating Polypeptide; Vasoactive Intestinal Peptide

Topics: Cholecystokinin; Diabetes Mellitus, Type 2; Digestive System Physiological Phenomena; Gastric Inhibitory Polypeptide; Gastrins; Gastrointestinal Hormones; Glucagon; Glucagon-Like Peptides; Humans; Insulin; Motilin; Neurotensin; Obesity; Pancreatic Polypeptide; Pentagastrin; Secretin; Somatostatin; Vasoactive Intestinal Peptide

Acarbose, an alpha-glucosidase inhibitor, unexpectedly reduced the incidence of hypertension and cardiovascular endpoints in the STOP-NIDDM study. Based on the growing evidence of a link between vasoregulatory peptides and metabolic traits, we hypothesized that changes of the Glycemic Index by acarbose may modulate vasoregulatory peptide levels via regulation of postprandial metabolism.. Subjects with type 2 diabetes and with metabolic syndrome were treated with acarbose (12 weeks, 300mg/d) in a double-blind, placebo-controlled, cross-over intervention. Changes in fasting and postprandial levels of midregional pro-atrial natriuretic peptide (MR-proANP), C-terminal pro-endothelin-1 (CT-proET-1) and midregional pro-adrenomedullin (MR-proADM), WNT1 Inducible Signaling Pathway Protein 1 (WISP1) as well as fasting and postprandial glucose/insulin levels in the liquid meal test were assessed.. Acarbose strongly decreased postprandial insulin concentrations in subjects with metabolic syndrome (P=0.004), and postprandial glucose excursions in both groups. Postprandial MR-proANP and CT-proET-1 levels increased after acarbose treatment (P<0.01 and P<0.05, respectively) in subjects with metabolic syndrome only. No effect of acarbose treatment on MR-prADM was observed in both groups. All three peptides were correlated with each over, but neither with insulin sensitivity in euglycemic clamps, nor with adiponectin levels. WISP1 decreased after acarbose treatment in subjects with metabolic syndrome.. Plasma MR- proANP and CT-proET-1 concentrations, but not MR-prADM concentrations, were affected by treatment with acarbose over 12 weeks. Our findings provide new possible mechanisms of acarbose action in diabetes and metabolic syndrome.

Topics: Acarbose; Cardiotonic Agents; Cross-Over Studies; Diabetes Mellitus, Type 2; Double-Blind Method; Extracellular Matrix Proteins; Female; Humans; Insulin; Male; Metabolic Syndrome; Middle Aged; Vasoactive Intestinal Peptide

The central pacemaker of the mammalian biological timing system is located within the suprachiasmatic nucleus (SCN) in the anterior hypothalamus. Together with the peripheral clocks, this central brain clock ensures a timely, up-to-date and proper behaviour for an individual throughout the day-night cycle. A mismatch between the central and peripheral clocks results in a disturbance of daily rhythms in physiology and behaviour. It is known that the number of rhythmically expressed genes is reduced in peripheral tissue of individuals with type 2 diabetes mellitus. However, it is not known whether the central SCN clock is also affected in the pathogenesis of type 2 diabetes. In the current study, we compared the profiles of the SCN neurons and glial cells between type 2 diabetic and control individuals.. We collected post-mortem hypothalamic tissues from 28 type 2 diabetic individuals and 12 non-diabetic control individuals. We performed immunohistochemical analysis for three SCN neuropeptides, arginine vasopressin (AVP), vasoactive intestinal polypeptide (VIP) and neurotensin (NT), and for two proteins expressed in glial cells, ionised calcium-binding adapter molecule 1 (IBA1, a marker of microglia) and glial fibrillary acidic protein (GFAP, a marker of astroglial cells).. The numbers of AVP immunoreactive (AVP-ir) and VIP-ir neurons and GFAP-ir astroglial cells in the SCN of type 2 diabetic individuals were significantly decreased compared with the numbers in the SCN of the control individuals. In addition, the relative intensity of AVP immunoreactivity was reduced in the individuals with type 2 diabetes. The number of NT-ir neurons and IBA1-ir microglial cells in the SCN was similar in the two groups.. Our data show that type 2 diabetes differentially affects the numbers of AVP- and VIP-expressing neurons and GFAP-ir astroglial cells in the SCN, each of which could affect the daily rhythmicity of the SCN biological clock machinery. Therefore, for effectively treating type 2 diabetes, lifestyle changes and/or medication to normalise central biological clock functioning might be helpful.

Topics: Arginine Vasopressin; Circadian Rhythm; Diabetes Mellitus, Type 2; Humans; Life Style; Microglia; Neuroglia; Neurons; Neuropeptides; Neurophysins; Protein Precursors; Suprachiasmatic Nucleus; Vasoactive Intestinal Peptide; Vasopressins

Type 2 diabetes mellitus (T2DM) is characterised by insulin resistance, glucose intolerance and beta cell loss leading to hyperglycemia. Vasoactive intestinal peptide (VIP) has been regarded as a novel therapeutic agent for the treatment of T2DM because of its insulinotropic and anti-inflammatory properties. Despite these beneficial properties, VIP is extremely sensitive to peptidases (DPP-4) requiring constant infusion or multiple injections to observe any therapeutic benefit. Thus, we constructed an HIV-based lentiviral vector encoding human VIP (LentiVIP) to test the therapeutic efficacy of VIP peptide in a diet-induced obesity (DIO) animal model of T2DM. VIP gene expression was shown by immunocytochemistry (ICC) and VIP peptide secretion was confirmed by ELISA both in HepG2 liver and MIN6 pancreatic beta cell lines. Functional properties of VIP were demonstrated by cAMP production assay and glucose-stimulated insulin secretion test (GSIS). Intraperitoneal (IP) delivery of LentiVIP vectors into mice significantly increased serum VIP concentrations compared to control mice. Most importantly, LentiVIP delivery in DIO animal model of T2DM resulted in improved insulin sensitivity, glucose tolerance and protection against STZ-induced diabetes in addition to reduction in serum triglyceride/cholesterol levels. Collectively, these data suggest LentiVIP delivery should be evaluated as an experimental therapeutic approach for the treatment of T2DM.

Topics: Animals; Blood Glucose; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diet, High-Fat; Disease Models, Animal; Gene Transfer Techniques; Glucose; Glucose Intolerance; Hep G2 Cells; Humans; Insulin; Insulin Resistance; Insulin-Secreting Cells; Lentivirus; Mice; Mice, Inbred C57BL; Obesity; Vasoactive Intestinal Peptide

As a potential protein therapeutic for type 2 diabetes mellitus (T2DM), BAY 55-9837 is limited by poor stability and a very short half-life in vivo. The purpose of this study was to construct a novel nanostructured biomaterial by conjugating BAY 55-9837 to chitosan-decorated selenium nanoparticles (CS-SeNPs) to prolong the in vivo half-life of BAY 55-9837 by reducing its renal clearance rate.. BAY 55-9837-loaded CS-SeNPs (BAY-CS-SeNPs) were prepared, and their surface morphology, particle size, zeta potential, and structure were characterized. The stability, protein-loading rate, and in vitro release of BAY 55-9837 from CS-SeNPs were also quantified. Additionally, a sensitive high-performance liquid chromatography (HPLC) assay was developed for the quantification of BAY 55-9837 in mouse plasma. Thereafter, mice were injected via the tail vein with either BAY 55-9837 or BAY-CS-SeNPs, and the plasma concentration of BAY 55-9837 was determined via our validated HPLC method at different time intervals postinjection. Relevant in vivo pharmacokinetic parameters (half-life, area under the curve from time 0 to last sampling point, observed clearance) were then calculated and analyzed.. BAY-CS-SeNPs were successfully synthesized, with diameters of approximately 200 nm. BAY-CS-SeNPs displayed good stability with a high protein-loading rate, and the release process of BAY 55-9837 from the CS-SeNPs lasted for over 70 hours, with the cumulative release reaching 78.9%. Moreover, the conjugation of CS-SeNPs to BAY 55-9837 significantly reduced its renal clearance to a rate of 1.56 mL/h and extended its half-life to 20.81 hours.. In summary, our work provides a simple method for reducing the renal clearance rate and extending the half-life of BAY 55-9837 in vivo by utilizing CS-SeNPs as nanocarriers.

Topics: Animals; Chitosan; Diabetes Mellitus, Type 2; Drug Carriers; Drug Stability; Half-Life; Mice; Nanoparticles; Particle Size; Peptide Fragments; Selenium; Vasoactive Intestinal Peptide

Obesity and type 2 diabetes are increasing in prevalence at an alarming rate in developed and developing nations and over 50% of patients with prolonged stages of disease experience forms of autonomic neuropathy. These patients have symptoms indicating disrupted enteric nervous system function including gastric discomfort, gastroparesis and intestinal dysmotility. Previous assessments have examined enteric neuronal injury within either type 1 diabetic or transgenic type 2 diabetic context. This study aims to assess damage to myenteric neurons within the duodenum of high-fat diet ingesting mice experiencing symptoms of type 2 diabetes, as this disease context is most parallel to the human condition and disrupted duodenal motility underlies negative gastrointestinal symptoms. Mice fed a high-fat diet developed symptoms of obesity and diabetes by 4 weeks. After 8 weeks, the total number of duodenal myenteric neurons and the synaptophysin density index were reduced and transmission electron microscopy showed axonal swelling and loss of neurofilaments and microtubules, suggesting compromised neuronal health. High-fat diet ingestion correlated with a loss of neurons expressing VIP and nNOS but did not affect the expression of ChAT, substance P, calbindin and CGRP. These results correlate high-fat diet ingestion, obesity and type 2 diabetes symptoms with a loss of duodenal neurons, biasing towards those with inhibitory nature. This pathology may underlie dysmotility and other negative GI symptoms experienced by human type 2 diabetic and obese patients.

Topics: Animals; Diabetes Mellitus, Type 2; Diet, High-Fat; Duodenum; Mice; Mice, Inbred C57BL; Mice, Obese; Myenteric Plexus; Neurons; Nitric Oxide Synthase; Obesity; Substance P; Vasoactive Intestinal Peptide

VPAC2 receptor is a potential target for the treatment of type 2 diabetes and may also convey neuroprotective effects. The aim of this study was to determine the potential efficacy of the VPAC2 receptor agonist Bay 55-9837 against stroke in type-2 diabetic Goto-Kakizaki (GK) rats. GK rats were treated intravenously once daily for 7 days with 0.25 or 0.025 nmol/kg Bay 55-9837 or vehicle before inducing stroke by transient middle cerebral artery occlusion. Treatments were then continued for 7 further days. The glycemic effects of Bay 55-9837 were assessed by measuring fasting blood glucose and oral glucose tolerance. The severity of stroke was measured by assessing ischemic volume. The results show that Bay 55-9837 is not effective in lowering fasting glycemia and does not facilitate glucose disposal. The highest dose of Bay 55-9837 (0.25 nmol/kg) led to increased mortality and brain hemorrhage when compared to control. The lower dose of Bay 55-9837 (0.025 nmol/kg) did not increase mortality rate but caused a threefold increase of the ischemic lesion size with signs of brain hemorrhages as compared to control. In conclusion, Bay 55-9837 did not show antidiabetic or antistroke efficacy in the type 2 diabetic GK rat. Contrarily, Bay 55-9837 treatment led to increased mortality and worsening of the severity of stroke.

Topics: Animals; Blood Glucose; Cell Count; Diabetes Mellitus, Type 2; Disease Progression; Glucose Tolerance Test; Immunohistochemistry; Infarction, Middle Cerebral Artery; Intracranial Hemorrhages; Male; Middle Cerebral Artery; Neurons; Peptide Fragments; Rats; Receptors, Vasoactive Intestinal Peptide, Type II; Stroke; Vasoactive Intestinal Peptide

Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) activate two shared receptors, VPAC1 and VPAC2. Activation of VPAC1 has been implicated in elevating glucose output, whereas activation of VPAC2 may be involved in insulin secretion. A hypothesis that a VPAC2-selective agonist would enhance glucose disposal by stimulating insulin secretion without causing increased hepatic glucose production was tested using a novel selective agonist of VPAC2. This agonist, BAY 55-9837, was generated through site-directed mutagenesis based on sequence alignments of PACAP, VIP, and related analogs. The peptide bound to VPAC2 with a dissociation constant (K(d)) of 0.65 nmol/l and displayed >100-fold selectivity over VPAC1. BAY 55-9837 stimulated glucose-dependent insulin secretion in isolated rat and human pancreatic islets, increased insulin synthesis in purified rat islets, and caused a dose-dependent increase in plasma insulin levels in fasted rats, with a half-maximal stimulatory concentration of 3 pmol/kg. Continuous intravenous or subcutaneous infusion of the peptide reduced the glucose area under the curve following an intraperitoneal glucose tolerance test. The peptide had effects on intestinal water retention and mean arterial blood pressure in rats, but only at much higher doses. BAY 55-9837 may be a useful therapy for the treatment of type 2 diabetes.

Topics: Amino Acid Sequence; Animals; Blood Pressure; Cells, Cultured; Diabetes Mellitus, Type 2; Diarrhea; Glucose; Heart Rate; Hormones; Humans; Injections, Intravenous; Injections, Subcutaneous; Insulin; Insulin Secretion; Islets of Langerhans; Molecular Sequence Data; Peptide Fragments; Rats; Rats, Wistar; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; Receptors, Pituitary Hormone; Receptors, Vasoactive Intestinal Peptide; Receptors, Vasoactive Intestinal Peptide, Type II; Receptors, Vasoactive Intestinal Polypeptide, Type I; Vasoactive Intestinal Peptide

Serum levels of gastrin, somatostatin and vasoactive intestinal polypeptide were evaluated in 105 noninsulin dependent diabetics (25 of them had a pyloric dysfunction). The serum levels were determined by RIA and blood was taken before and after the test meal. The basal gastrin level was significantly higher in patients with the pyloric dysfunction (p < 0.001). 45 minutes later the serum levels of vasoactive intestinal polypeptide and somatostatin were significantly higher in diabetics with the pyloric dysfunction (p < 0.001). The serum levels of gastrin, somatostatin and vasoactive intestinal polypeptide were impaired in diabetics with the pyloric dysfunction and might be associated with its pathogenesis.

Topics: Diabetes Mellitus, Type 2; Eating; Female; Gastric Emptying; Gastrins; Gastrointestinal Motility; Humans; Male; Middle Aged; Pylorus; Somatostatin; Vasoactive Intestinal Peptide

Basal and postprandial levels of gastrin, somatostatin, vasoactive intestinal polypeptide (VIP) and pancreatic polypeptide (PP) were followed up in 105 patients with non insulin dependent diabetes mellitus (20 with autonomic neuropathy only, 35 with peripheric neuropathy only, 30 with autonomic and peripheric neuropathy simultaneously and 20 without any sign of neuropathy) and in the control group of 40 individuals. Serum levels of gastrin, somatostatin, VIP and PP are determined by a RIA (used kits of Prof. SR Bloom, Hammersmith Hospital, London). The results of investigation showed significantly higher basal and postprandial levels of gastrin and VIP in patients with autonomic neuropathy in comparison with the group without neuropathy and with the control group (p < 0.001). The serum levels of somatostatin did not differ significantly between the groups of diabetics with and without neuropathy. Basal level of PP was significantly lower and postprandial PP levels remained low in patients with autonomic neuropathy in comparison with the group without neuropathy (p < 0.001). We postulate that basal and postprandial gastrin and VIP levels raised secondary to partial vagotomy in diabetics with autonomic neuropathy. Measuring PP serum levels in diabetics after a protein rich meal can be useful to check vagus nerve function in the gastrointestinal tract in order to detect autonomic neuropathy.

Topics: Adult; Autonomic Nervous System Diseases; Diabetes Mellitus, Type 2; Diabetic Neuropathies; Female; Gastrins; Gastrointestinal Hormones; Humans; Male; Middle Aged; Pancreatic Polypeptide; Somatostatin; Vasoactive Intestinal Peptide