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Objective: Reported rates of hypoglycemia in patients with type 2 diabetes mellitus are lower with glimepiride as compared to glyburide. The aim of this study was to determine whether physiologic differences in counterregulatory neuroendocrine and metabolic mechanisms during hypoglycemia provide a basis for the observed clinical differences between glimepiride and glyburide., Research Design and Methods: Non-diabetic volunteers (age 38±2years, BMI 26±1kg/m(2)) were studied in a single-blind fashion during separate 2day randomized protocols consisting of 2h hyperinsulinemic (9pmol/kg/min) euglycemic (4.9±0.1mmol) and hypoglycemic (2.9±0.1mmol/L) clamps. Individuals received biologically equivalent doses of glimepiride (4mg) or glyburide (10mg) 1h prior to each glucose clamp (n=11) as well as a control group of placebo studies. Glucose kinetics were calculated using D-Glucose-6-6d2., Results: Insulin and C-peptide levels were increased (p<0.05) during euglycemia in both sulfonylurea groups as compared to placebo. However, despite equivalent hypoglycemia, insulin and C-peptide levels were higher (p<0.05) only after glyburide. Glucagon responses and endogenous glucose production (EGP) were decreased (p<0.05) during hypoglycemia following glyburide administration as compared to glimepiride. Glyburide reduced (p<0.05) norepinephrine responses during euglycemic clamps. In addition combined epinephrine and norepinephrine responses during hypoglycemia were reduced (p<0.05) following glyburide as compared to placebo. Leptin levels fell by a greater amount (p<0.05) during hypoglycemia with both sulfonylureas as compared to placebo., Conclusions: In summary, glimepiride and glyburide can both similarly increase insulin and C-peptide levels during hyperinsulinemic euglycemia. However, during moderate hyperinsulinemic hypoglycemia (2.9mmol/L) glyburide resulted in increased C-peptide and insulin, but blunted glucagon, sympathetic nervous system and EGP responses. We conclude that glyburide can acutely reduce key neuroendocrine and metabolic counterregulatory defenses during hypoglycemia in healthy individuals., (Copyright © 2015. Published by Elsevier Inc.)

Conversion of amyloid fibrils by many peptides/proteins involves cytotoxic helix-rich oligomers. However, their toxicity and biophysical studies remain largely unknown due to their highly dynamic nature. To address this, we chose two helical peptides (melittin, Mel and pancreatic polypeptide, PP) and studied their aggregation and toxicity. Mel converted its random coil structure to oligomeric helical structure upon binding to heparin; however, PP remained as helix after oligomerization. Interestingly, similar to Parkinson's associated α-synuclein (AS) oligomers, Mel and PP also showed tinctorial properties, higher hydrophobic surface exposure, cellular toxicity and membrane pore formation after oligomerization in the presence of heparin. We suggest that helix-rich oligomers with exposed hydrophobic surface are highly cytotoxic to cells irrespective of their disease association. Moreover as Mel and PP (in the presence of heparin) instantly self-assemble into stable helix-rich amyloidogenic oligomers; they could be represented as models for understanding the biophysical and cytotoxic properties of helix-rich intermediates in detail.

Introduction: Pancreatic polypeptide (PP) is a hormone secreted by islet cells of the ventral pancreas. It has been proposed that a blunted PP response to a mixed meal can distinguish diabetes mellitus (DM) secondary to pancreatic disease from other types of DM. We performed a proof of concept study to determine if PP response to a mixed meal discriminates DM secondary to pancreatic cancer (PaCDM) from type 2 DM (T2DM)., Methods: We studied 18 subjects with new onset DM (PaCDM (n = 9) and T2DM (n = 9); matched for age and gender). Serum PP levels were measured at 0, 30, and 60 min following a mixed meal. Increases in PP levels from baseline were compared using the Wilcoxon test., Results: In PaCDM the PP increase following a mixed meal was less than T2DM at 30 min (median 60.0%, IQR, 33.0-119.8 vs. 134.5%, IQR, 117.5-265.9; p = 0.03), but statistically similar at 60 min (median 55.8%, interquartile range (IQR) 23.7-121.5 vs. 100.0%, IQR, 47.7-202.5; p = 0.17). In PaCDM subjects, the PP increase over baseline was smaller in those with a tumor located in the pancreatic head (n = 6) compared to the body/tail (n = 3) at 30 min (41.3% vs. 158.7%, p = 0.02) and at 60 min (37.4% vs. 167.4%,p = 0.04)., Conclusions: Subjects with PaCDM have a blunted PP response to a mixed meal compared to T2DM. However, the blunted PP response is only observed in those PaC subjects with a tumor located in the head of the pancreas. Confirmation in larger studies may suggest this could be used to aid screening for sporadic PaC., (Copyright © 2015 IAP and EPC. Published by Elsevier B.V. All rights reserved.)

Context: Inflammation in the pancreas can cause β-cell stress, leading to diabetes development. Access to human pancreas tissues via the Network for Pancreatic Organ Donors with Diabetes (nPOD) has allowed characterization of pathways leading to this inflammation., Objective: 12-Lipoxygenase (12-LO) induces inflammation and has been implicated in diabetes development. Our goal was to determine expression of 12-LO in human islets from control, autoantibody-positive, type 1 diabetic, and type 2 diabetic nPOD pancreas donors., Design: Pancreas tissues from nPOD donors were examined by immunohistochemistry and immunofluorescence for islet expression of 12-LO in different subsets of islet cells., Participants: Donor pancreas samples were obtained from nPOD based on disease status (control, n = 7; autoantibody-positive, n = 8; type 1 diabetic, n = 17; or type 2 diabetic donors, n = 15)., Main Outcome Measure: Determination of 12-LO expression within human islets served as the main outcome measure, including distinguishing which types of islet cells expressed 12-LO., Results: Islets from control participants (nondiabetic) lacked islet expression of 12-LO. Of donors in the other groups, 25% to 37% expressed islet 12-LO with a clear inverse relation between the numbers of β-cells and 12-LO(+) cells within islets of 12-LO(+) cases. 12-LO expression was not seen within macrophages, endothelial cells, α-cells, or β-cells, but only within cells expressing low levels of pancreatic polypeptide (PP) and increased levels of vimentin., Conclusions: 12-LO expression colocalizes within a specific type of islet PP(+) cell under prediabetic and diabetic conditions. The costaining of PP and vimentin suggests that 12-LO participates in the process leading to β-cell dedifferentiation in the islet.

Background: Plasma levels of pancreatic polypeptide (PP) rise upon food intake. Although other pancreatic islet hormones, such as insulin and glucagon, have been extensively investigated, PP secretion and actions are still poorly understood., Methods: The release of PP upon glucose stimulation and the effects of PP on glucagon and insulin secretion were analyzed in isolated pancreatic islets. Expression of PP receptor (PPYR1) was investigated by immunoblotting, quantitative RT-PCR on sorted pancreatic islet cells, and immunohistochemistry., Results: In isolated mouse pancreatic islets, glucose stimulation increased PP release, while insulin secretion was up and glucagon release was down. Direct exposure of islets to PP inhibited glucagon release. In mouse islets, PPYR1 protein was observed by immunoblotting and quantitative RT-PCR revealed PPYR1 expression in the FACS-enriched glucagon alpha-cell fraction. Immunohistochemistry on pancreatic sections showed the presence of PPYR1 in alpha-cells of both mouse and human islets, while the receptor was absent in other islet cell types and exocrine pancreas., Conclusions: Glucose stimulates PP secretion and PP inhibits glucagon release in mouse pancreatic islets. PP receptors are present in alpha-cells of mouse and human pancreatic islets., General Significance: These data demonstrate glucose-regulated secretion of PP and its effects on glucagon release through PPYR1 receptors expressed by alpha-cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Reduced beta cell mass in pancreatic islets (PI) of Goto-Kakizaki (GK) rats is frequently observed in this diabetic model, but knowledge on delta cells is scarce. Aiming to compare delta cell physiology/pathology of GK to Wistar rats, we found that delta cell number increased over time as did somatostatin mRNA and delta cells distribution in PI is different in GK rats. Subtle changes in 6-week-old GK rats were found. With maturation and aging of GK rats, disturbed cytoarchitecture occurred with irregular beta cells accompanied by delta cell hyperplasia and loss of pancreatic polypeptide (PPY) positivity. Unlike the constant glucose-stimulation index for insulin PI release in Wistar rats, this index declined with GK age, whereas for somatostatin it increased with age. A decrease of GK rat PPY serum levels was found. GK rat body weight decreased with increasing hyperglycemia. Somatostatin analog octreotide completely blocked insulin secretion, impaired proliferation at low autocrine insulin, and decreased PPY secretion and mitochondrial DNA in INS-1E cells. In conclusion, in GK rats PI, significant local delta cell hyperplasia and suspected paracrine effect of somatostatin diminish beta cell viability and contribute to the deterioration of beta cell mass. Altered PPY-secreting cells distribution amends another component of GK PI's pathophysiology.

A cumulative effect of reduced energy intake, increased oxygen consumption, and/or increased lipid oxidation could explain the fat loss associated with sprint interval exercise training (SIT). This study assessed the effects of acute sprint interval exercise (SIE) on energy intake, subjective appetite, appetite-related peptides, oxygen consumption, and respiratory exchange ratio over 2 days. Eight men (25 ± 3 years, 79.6 ± 9.7 kg, body fat 13% ± 6%; mean ± SD) completed 2 experimental treatments: SIE and recovery (SIEx) and nonexercise control. Each 34-h treatment consisted of 2 consecutive 10-h test days. Between 0800-1800 h, participants remained in the laboratory for 8 breath-by-breath gas collections, 3 buffet-type meals, 14 appetite ratings, and 4 blood samples for appetite-related peptides. Treatment comparisons were made using 2-way repeated measures ANOVA or t tests. An immediate, albeit short-lived (<1 h), postexercise suppression of appetite and increase in peptide YY (PYY) were observed (P < 0.001). However, overall hunger and motivation to eat were greater during SIEx (P < 0.02) without affecting energy intake. Total 34-h oxygen consumption was greater during SIEx (P = 0.04), elicited by the 1491-kJ (22%) greater energy expenditure over the first 24 h (P = 0.01). Despite its effects on oxygen consumption, appetite, and PYY, acute SIE did not affect energy intake. Consequently, if these dietary responses to SIE are sustained with regular SIT, augmentations in oxygen consumption and/or a substrate shift toward increased fat use postexercise are most likely responsible for the observed body fat loss with this type of exercise training.

Structural characterization of the human Y4 receptor (hY4R) interaction with human pancreatic polypeptide (hPP) is crucial, not only for understanding its biological function but also for testing treatment strategies for obesity that target this interaction. Here, the interaction of receptor mutants with pancreatic polypeptide analogs was studied through double-cycle mutagenesis. To guide mutagenesis and interpret results, a three-dimensional comparative model of the hY4R-hPP complex was constructed based on all available class A G protein-coupled receptor crystal structures and refined using experimental data. Our study reveals that residues of the hPP and the hY4R form a complex network consisting of ionic interactions, hydrophobic interactions, and hydrogen binding. Residues Tyr(2.64), Asp(2.68), Asn(6.55), Asn(7.32), and Phe(7.35) of Y4R are found to be important in receptor activation by hPP. Specifically, Tyr(2.64) interacts with Tyr(27) of hPP through hydrophobic contacts. Asn(7.32) is affected by modifications on position Arg(33) of hPP, suggesting a hydrogen bond between these two residues. Likewise, we find that Phe(7.35) is affected by modifications of hPP at positions 33 and 36, indicating interactions between these three amino acids. Taken together, we demonstrate that the top of transmembrane helix 2 (TM2) and the top of transmembrane helices 6 and 7 (TM6-TM7) form the core of the peptide binding pocket. These findings will contribute to the rational design of ligands that bind the receptor more effectively to produce an enhanced agonistic or antagonistic effect.

Y-receptors control energy homeostasis, but the role of Npy6 receptors (Npy6r) is largely unknown. Young Npy6r-deficient (Npy6r(-/-)) mice have reduced body weight, lean mass, and adiposity, while older and high-fat-fed Npy6r(-/-) mice have low lean mass with increased adiposity. Npy6r(-/-) mice showed reduced hypothalamic growth hormone releasing hormone (Ghrh) expression and serum insulin-like growth factor-1 (IGF-1) levels relative to WT. This is likely due to impaired vasoactive intestinal peptide (VIP) signaling in the suprachiasmatic nucleus (SCN), where we found Npy6r coexpressed in VIP neurons. Peripheral administration of pancreatic polypeptide (PP) increased Fos expression in the SCN, increased energy expenditure, and reduced food intake in WT, but not Npy6r(-/-), mice. Moreover, intraperitoneal (i.p.) PP injection increased hypothalamic Ghrh mRNA expression and serum IGF-1 levels in WT, but not Npy6r(-/-), mice, an effect blocked by intracerebroventricular (i.c.v.) Vasoactive Intestinal Peptide (VPAC) receptors antagonism. Thus, PP-initiated signaling through Npy6r in VIP neurons regulates the growth hormone axis and body composition., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The skin and skin secretion of Chinese toad Bufo gargarizans have long been used in traditional Chinese medicine. However, the exact types and location of bioactive substances in Bufo gargarizans skin still have not been fully elucidated. The aim of the study was to investigate the distribution and density of six types of gastrointestinal (GI) hormone immunoreactive (IR) cells in the skin and parotoids of Bufo gargarizans. Immunohistochemistry was used for qualitative and semiquantitative analysis of GI hormone presence in the dorsal and ventral skin, and parotoids of eight adult Chinese toads. Six types of IR cells were found: serotonin (5-HT), glucagon (GLU), gastrin (GAS), somatostatin (SS), pancreatic polypeptide (PP) and neuropeptide Y(NPY) IR cells. They were mainly present in the epidermis and skin glands. 5-HT-IR cells were distributed in all layers of epidermis and glands, with higher density in the glands. Glucagon was prominently expressed in the epidermis and the bottle-shaped glands of parotoids; however, it was not present in the granular glands of skin and parotoids. The distributions of GAS and SS-IR cells were similar since they were present mainly in mucous, granular and bottle-shaped glands, while these cell types were absent in the differentiated glands of parotoids. PP-IR cells were predominant in the granular glands and the bottle-shaped glands. The expression of NPY was high in epidermal stratum granulosum and mucous glands of the dorsal skin, the bottle-shaped glands and differentiated glands of parotoids, while NPY-IR was rarely seen in the granular glands of ventral skin, and not present in the granular glands of dorsal skin and parotoids. The expression of several types of GI hormones in the skin and parotoids of Bufo gargarizans varies depending on tissue and type of glands.

Background: Previous research indicated that coeliac disease (CD) is associated with type 1 diabetes mellitus (T1DM). However, the gut-brain axis peptide hormones secretion has not been evaluated so far in patients with CD prior to treatment initiation or under treatment, irrespective of patients having concomitant T1DM or not. The aim of the study was therefore to evaluate these gut hormones at the preprandial levels of patients with CD before and under treatment., Methods: Of forty-seven CD children, 12 untreated (UCD), 22 treated with gluten-free diet (TCD) and 13 treated CD with coexisting T1DM (DCD), and 18 healthy controls (HC) were enrolled. Preprandial glucagon-like-peptide-1 (GLP-1), glucose-dependent-insulinotropic-polypeptide (GIP), active amylin, acylated ghrelin (AG), leptin, pancreatic polypeptide (PP) and peptide-tyrosine-tyrosine (PYY) were determined with hormone-map-array technology., Results: We found in patients with CD compared with HC that the concentration of (i) GLP-1 was reduced remarkably in all patients with CD (P = 0.008), (ii) GIP was lower in patients with UCD (P = 0.008), (iii) amylin was remarkably reduced (P < 0.01) in all patients with CD, (iv) AG was significantly decreased in patients with DCD (P < 0.01), while (v) leptin, PP and PYY were not significantly different. GIP, GLP-1 and amylin levels correlated positively with insulin concentrations (P < 0.001, P = 0.004 and P < 0.01, respectively) in all patients. Amylin and GIP levels were strongly associated with triglycerides concentrations (P < 0.001, for both peptides) in children with CD., Conclusions: Our study revealed a different secretion pattern of gut-brain axis hormones in children with CD compared with HC. The alterations in the axis were more pronounced in children with both CD and T1DM., (© 2013 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd.)

There has been great interest in the extent of β-cell regeneration after pancreatic duct ligation (PDL) and whether α- to β-cell conversion might account for β-cell regeneration after near-complete β-cell loss. To assess these questions, we established a PDL-model in adult male rats after almost complete beta-cell depletion achieved by giving a single high dose of streptozocin (STZ) in the fasted state. Because of the resultant severe diabetes, rats were given islet cell transplants to allow long-term follow-up. Although animals were followed up to 10 months, there was no meaningful β-cell regeneration, be it through replication, neogenesis, or α- to β-cell conversion. In contrast, the acinar cell compartment underwent massive changes with first severe acinar degeneration upon PDL injury followed by the appearance of pancreatic adipocytes, and finally near-complete reappearance of acini. We conclude that β-cells and acinar cells, although originating from the same precursors during development, have very distinct regenerative potentials in our PDL model in adult rats.

Xenin-25 (Xen) is a 25-amino acid neurotensin-related peptide that activates neurotensin receptor-1 (NTSR1). We previously showed that Xen increases the effect of glucose-dependent insulinotropic polypeptide (GIP) on insulin release 1) in hyperglycemic mice via a cholinergic relay in the periphery independent from the central nervous system and 2) in humans with normal or impaired glucose tolerance, but not type 2 diabetes mellitus (T2DM). Since this blunted response to Xen defines a novel defect in T2DM, it is important to understand how Xen regulates islet physiology. On separate visits, subjects received intravenous graded glucose infusions with vehicle, GIP, Xen, or GIP plus Xen. The pancreatic polypeptide response was used as an indirect measure of cholinergic input to islets. The graded glucose infusion itself had little effect on the pancreatic polypeptide response whereas administration of Xen equally increased the pancreatic polypeptide response in humans with normal glucose tolerance, impaired glucose tolerance, and T2DM. The pancreatic polypeptide response to Xen was similarly amplified by GIP in all 3 groups. Antibody staining of human pancreas showed that NTSR1 is not detectable on islet endocrine cells, sympathetic neurons, blood vessels, or endothelial cells but is expressed at high levels on PGP9.5-positive axons in the exocrine tissue and at low levels on ductal epithelial cells. PGP9.5 positive nerve fibers contacting beta cells in the islet periphery were also observed. Thus, a neural relay, potentially involving muscarinic acetylcholine receptors, indirectly increases the effects of Xen on pancreatic polypeptide release in humans., (© 2013.)

Context: In obese patients with type 2 diabetes (T2DM), Roux-en-Y-gastric-bypass (RYGB) and sleeve gastrectomy (SLG) improve glycemic control., Objective: The objective of this study was to investigate the mechanisms of surgery-induced T2DM improvement and role of gastrointestinal hormones. PATIENTS, SETTING, AND INTERVENTION: In 35 patients with T2DM, we performed a mixed-meal test before and 15 days and 1 year after surgery (23 RYGB and 12 SLG)., Main Outcome Measures: Insulin sensitivity, β-cell function, and amylin, ghrelin, PYY, pancreatic polypeptide (PP), glucagon, and glucagon-like peptide-1 (GLP-1) responses to the meal were measured., Results: T2DM remission occurred in 13 patients undergoing RYGB and in 7 patients undergoing SLG. Similarly in the RYGB and SLG groups, β-cell glucose sensitivity improved both early and long term (P < .005), whereas insulin sensitivity improved long term only (P < .006), in proportion to body mass index changes (P < .001). Early after RYGB, glucagon and GLP-1 responses to the meal increased, whereas the PP response decreased. At 1 year, PYY was increased, and PP, amylin, ghrelin, and GLP-1 were reduced. After SLG, hormonal responses were similar to those with RYGB except that PP was increased, whereas amylin was unchanged. In remitters, fasting GLP-1 was higher (P = .04), but its meal response was flat compared with that of nonremitters; postsurgery, however, the GLP-1 response was higher. Other hormone responses were similar between the 2 groups. In logistic regression, presurgery β-cell glucose sensitivity (positive, P < .0001) and meal-stimulated GLP-1 response (negative, P = .004) were the only predictors of remission., Conclusions: RYGB and SLG have a similar impact on diabetes remission, of which baseline β-cell glucose sensitivity and a restored GLP-1 response are the chief determinants. Other hormonal responses are the consequences of the altered gastrointestinal anatomy.

peripheral nervous system. Considering the structure and evolutionary origin, neuropeptide Y (NPY) is a peptide of the same family as peptide YY (PYY) and pancreatic polypeptide (PP). These proteins were discovered relatively recently, however, knowledge about them is deepened. They are 36-amino acid peptide acting through G-protein coupled receptors, Y1, Y2, Y3, Y4, Y5 and Y6. The diverse structure C-terminus of the peptide and protein binding to receptors affect the biological activity and the physiological effects on the digestive system, blood vessels, and the center of hunger and satiety in the hypothalamus. Peptides have anorexic properties, they regulate appetite and food intake mainly through the intestinal cerebrospinal axis and the hypothalamus. These substances represent an important potential target of new drugs in the long-term treatment and prevention of obesity. Furthermore, neuropeptide Y affects many processes depending on the central nervous system modifies ethanol consumption, affect circadian rhythms, memory processes, anxiety behavior. Peripherally NPY affects smooth muscle contraction of the blood vessels, blood pressure, and atherogenic processes. Conducted more thorough research trying to define the role and participation of various neuropeptides in the development of diseases of the pancreas and the gastrointestinal tract, cardiovascular system and use it for diagnosis.

Rectal neuroendocrine tumors (NETs) are currently divided into L-cell and non-L-cell types. In the World Health Organization 2010 classification, L-cell tumors are defined as borderline, whereas non-L-cell tumors are considered to represent malignancies. To establish differential diagnostic criteria and therapeutic strategy, we investigated the pathologic features of rectal NETs associated with lymph node metastasis and the clinicopathologic significance of the L-cell phenotype. We analyzed 284 patients with rectal NETs. Factors, including T stage, mitosis, histologic pattern, lymphatic invasion, tumor border, and lymph node metastasis, were retrospectively evaluated. We also evaluated tumor immunoreactivity for L-cell markers, including glucagon-like peptide 1, pancreatic peptide, and peptide YY, in 240 cases. L-cell immunoreactivity was detected in 189 of 240 NETs (79%). Of the factors evaluated, only age and the frequency of lymphatic invasion were significantly different between patients with L-cell and non-L-cell tumors. Of the 284 patients, 18 (6.3%) had lymph node metastases. Lymphatic invasion and T stage were independent risk factors for lymph node metastasis. Subgroup analysis based on tumor size showed lymph node metastasis in 0%, 4%, 24%, and 100% of patients with NETs with a size of <5, 5 to 9, 10 to 14, and ≥ 15 mm, respectively. Depth of tumor invasion, lymphatic invasion, and mitosis were correlated with tumor size (P<0.0001). In conclusion, L-cell phenotype alone does not guarantee favorable biological characteristics. The clinical management of rectal NETs should depend on tumor size. Careful pathologic examination of lymphatic invasion is necessary.

Background: Satiety is centrally and peripherally mediated by gastrointestinal peptides and the vagal nerve. We aimed to investigate whether intragastric balloon treatment affects satiety through effects on fasting and meal-stimulated cholecystokinin (CCK) and pancreatic polypeptide (PP) secretion., Methods: Patients referred for obesity treatment were randomised to 13 weeks of sham treatment followed by 13 weeks of balloon treatment (group 1; sham/balloon) or to twice a 13-week period of balloon treatment (group 2; balloon/balloon). Blood samples were taken for fasting and meal-stimulated CCK and PP levels at the start (T0) and after 13 (T1) and 26 (T2) weeks. Patients filled out visual analogue scales (VAS) to assess satiety., Results: Forty-two patients (35 females, body weight 125.1 kg, BMI 43.3 kg/m(2)) participated. In group 1, basal CCK levels decreased but meal-stimulated response remained unchanged after 13 weeks of sham treatment. In group 2, basal and meal-stimulated CCK levels decreased after 13 weeks of balloon treatment. At the end of the second 13-week period, when group 1 had their first balloon treatment, they duplicated the initial 13-week results of group 2, whereas group 2 continued their balloon treatment and reduced meal-stimulated CCK release. Both groups showed reduced meal-stimulated PP secretions at T1 and T2 compared to T0. Changes in diet composition and VAS scores were similar. Improvements in glucose homeostasis partly explained the PP results., Conclusions: The reduced CCK and PP secretion after balloon positioning was unexpected and may reflect delayed gastric emptying induced by the balloon. Improved glucose metabolism partly explained the reduced PP secretion. Satiety and weight loss were not adversely influenced by these hormonal changes.

Objective: The purpose of this study was to compare postprandial satiety regulating hormone responses (pancreatic polypeptide (PP) and peptide tyrosine tyrosine (PYY)) and visual analog scale- (VAS) assessed perceived appetite and satiety between liquid high-protein (HP) and high-carbohydrate (HC) meals in obese women during acute (24-h) caloric restriction., Design: Eleven obese premenopausal women completed two conditions in random order in which they consumed 1500 calories as six 250-calorie HP meals or six 250-calorie HC meals over a 12-h period. Blood samples were taken at baseline and every 20 min thereafter and analyzed for PP and PYY concentrations. At these same points, perceived hunger and fullness were assessed with a VAS. The incremental area under the curve (iAUC) was used to compare postprandial responses., Results: The 12-h PP and PYY iAUC were greater (P≤0.05) during the HP condition (PP: 4727±1306 pg/ml×12 h, PYY: 1373±357 pg/ml×12 h) compared with the HC condition (PP: 2300±528 pg/ml×12 h, PYY: 754±246 pg/ml×12 h). Perceived hunger and fullness were not different between conditions (P>0.05). The greatest changes in PYY and perceived fullness occurred after the morning meals during both conditions., Conclusions: These data suggest that in obese women during acute caloric restriction before weight loss, i) liquid HP meals, compared with HC meals, result in greater postprandial PP and PYY concentrations, an effect not associated with differential appetite or satiety responses, and ii) meal-induced changes in PYY and satiety are greatest during the morning period, regardless of dietary macronutrient composition.

Recent investigation of the factors and pathways that are involved in regulation of pancreatic secretory function (PSF) has led to development of a pancreatic vagovagal reflex model. This model consists of three elements, including pancreatic vagal afferents, the dorsal motor nucleus of the vagus (DMV) and pancreatic vagal efferents. The DMV has been recognized as a major component of this model and so this review focuses on the role of this nucleus in regulation of PSF. Classically, the control of the PSF has been viewed as being dependent on gastrointestinal hormones and vagovagal reflex pathways. However, recent studies have suggested that these two mechanisms act synergistically to mediate pancreatic secretion. The DMV is the major source of vagal motor output to the pancreas, and this output is modulated by various neurotransmitters and synaptic inputs from other central autonomic regulatory circuits, including the nucleus of the solitary tract. Endogenously occurring excitatory (glutamate) and inhibitory amino acids (GABA) have a marked influence on DMV vagal output to the pancreas. In addition, a variety of neurotransmitters and receptors for gastrointestinal peptides and hormones have been localized in the DMV, emphasizing the direct and indirect involvement of this nucleus in control of PSF.

The vesicular monoamine transporter, type 2 (VMAT2) is responsible for sequestering monoamine neurotransmitters into exocytic vesicles in neurons, enterochromaffin-like cells of the stomach and cells arising from the common myeloid progenitor. VMAT2 is also present in the pancreas and is expressed by insulin producing β cells, but not by glucagon or somatostatin expressing islet cells. Positron emission tomography (PET) targeting of VMAT2 is currently being evaluated as a non-invasive tool to measure β cell mass (BCM) in living humans. In recent trials, PET measurements of VMAT2 in the pancreas overestimated BCM in type 1 diabetes (T1D) patients predicted to have little to no BCM by metabolic measures. Recently, tissue immunohistochemistry studies suggested that VMAT2 staining may also co-localize with pancreatic polypeptide (PP) staining cells in pancreas tissue, but these studies were not quantitative. In this report, we evaluated VMAT2 specificity for β cells in sub-regions of the human pancreas using antibodies targeting VMAT2, insulin and PP by double-label immunofluorescence. Immunostaining for VMAT2 and insulin demonstrated 89 ± 8% overlap in the body and tail of the pancreas. However, 44 ± 12% and 53 ± 15% of VMAT2 cells co-stained with PP- and insulin-staining cells, respectively in the pancreatic head. Significant co-staining for VMAT2 and PP cells in the head of the pancreas may partly explain the apparent overestimation of BCM in T1D by PET. Specific targeting of the pancreatic body and tail using VMAT2 PET scanning may reflect BCM more accurately.

Circulating agents cause intestinal secretion or changes in motility with decreased intestinal transit time, resulting in secretory-type diarrhea. Secretory diarrhea as opposed to osmotic diarrhea is characterized by large-volume, watery stools, often more than 1 L per day; by persistence of diarrhea when patients fast; and by the fact that on analysis of stool-water, measured osmolarity is identical to that calculated from the electrolytes present. Although sodium plays the main role in water and electrolyte absorption, chloride is the major ion involved in secretion., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objective: The aim of our study was to evaluate the effect of a lifestyle intervention program on β-cell function and to explore the role of gastrointestinal peptides in subjects with T2D., Methods: Subjects with T2D (n=74) received 24 weeks of intervention: 12 weeks of slimming diet (-500 kcal/day) and the subsequent 12 weeks of diet were combined with aerobic exercise. All subjects were examined at weeks 0, 12 and 24. β-cell function was assessed during standard meal tests. Insulin secretory rate (ISR) was calculated by C-peptide deconvolution, and β-cell function was quantified with a mathematical model. Plasma concentrations of gastrointestinal peptides were measured in a fasting state and during hyperinsulinemia induced by hyperinsulinemic isoglycemic clamp., Results: Mean weight loss was 5.03±4.38 kg (p<0.001) in weeks 0-12. Weight did not change significantly in weeks 12-24. Both insulin secretion at the reference level and glucose sensitivity increased in weeks 0-12 (by 33%±54% and by 26%±53%, respectively, p<0.001) and remained unchanged in weeks 12-24. Both fasting and hyperinsulinemic plasma concentrations of pancreatic polypeptide (PP) decreased in weeks 0-12 (p<0.05 for both) and did not change significantly in weeks 12-24. Changes in insulin secretion at the reference level correlated negatively with plasma concentrations of PP during hyperinsulinemia (r=-0.36; p<0.001). Changes in glucose sensitivity correlated negatively with changes in plasma concentrations of PP, both in fasting and during hyperinsulinemia (r=-0.2; p=0.01 for both). The correlations remained significant after adjustment for changes in body-mass-index., Conclusions: After diet-induced weight loss, β-cell function improved in T2D subjects and remained unchanged after the addition of exercise. We demonstrate for the first time that these changes are associated with a decrease in PP secretion., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Background and Aims: In the pancreas, peptide YY (PYY) is expressed by a subpopulation of nonbeta cells in the islets of Langerhans. We investigated the function of these cells in the pancreas of adult mice., Methods: We generated mice in which administration of diphtheria toxin (DT) led to specific ablation of PYY-expressing cells. We investigated the effects of loss of PYY cells on glucose homeostasis., Results: Loss of PYY cells in adult mice resulted in severe hyperglycemia, which was associated with significant loss of pancreatic insulin and disruption of islet morphology. In vitro administration of DT to isolated islets significantly reduced numbers of PYY-expressing cells and levels of insulin. Administration of either pancreatic polypeptide (a strong agonist of the receptor Y(4)) or PYY(3-36) (a selective agonist of the receptor Y(2)) did not restore loss of pancreatic insulin following administration of DT. However, a long-acting PYY analogue reduced the loss of insulin, and administration of this analogue reduced the hyperglycemia and insulin loss induced by streptozotocin in mice., Conclusions: PYY appears to regulate beta cell function and survival via the receptor Y(1/2). These findings might be developed to treat and prevent loss of beta cells in patients with diabetes mellitus., (Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.)

The regional distribution and relative frequency of peptide YY (PYY)-, pancreatic polypeptide (PP)-, and glucagon-like peptide 1 (GLP-1)-immunoreactive (IR) cells were determined immunohistochemically in the gastrointestinal tract at seven ontogenetic stages in pre- and postnatal cattle. Different frequencies of PYY-, PP-, and GLP-1-IR cells were found in the intestines at all stages; they were not found in the esophagus and stomach. The frequencies varied depending on the intestinal segment and the developmental stage. The frequencies of PYY- and PP-IR cells were lower in the small intestine and increased from ileum to rectum, whereas GLP-1-IR cells were more numerous in duodenum and jejunum, decreased in ileum and cecum, and increased again in colon and rectum. The frequencies also varied according to pre- and postnatal stages. All three cell types were most numerous in fetus, and decreased in calf and adult groups, indicating that the frequencies of these three types of endocrine cells decrease with postnatal development. The results suggest that these changes vary depending on feeding habits and adaptation of growth, secretion, and motility of intestine at different ontogenetic stages of cattle., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The purpose of this study was to examine the effects of electroacupuncture at Zusanli on the immunohistochemical density of enteroendocrine cells related to gastrointestinal function. The authors investigated the histochemical changes of mucous substances and immunohistochemical density of gastrin, serotonin, calcitonin gene-related peptide (CGRP), insulin, and pancreatic polypeptide (PP) secreting cells in rats. Staining density of mucous substances and the enteroendocrine cells of the gastrointestinal tract was observed with histochemical and immunohistochemical methods. Stainless steel needles with a diameter of 0.25 mm were inserted into Zusanli (St36, 5mm below the head of the fibula under the knee joint, and 2mm lateral to the anterior tubercle of the tibia) and connected to an electrical stimulator. The electroacupuncture (EA) stimulation was delivered for 30 minutes at 10 mA, 2 Hz in EA stimulation (2EA group) or 4 Hz in EA stimulation (4EA group) in each experimental group. In 4EA stimulation at the Zusanli, staining density of Alcian blue-periodic acid-Schiff on mucous substances of the stomach body was stronger than those of the 2EA and control groups. Periodic acid-Schiff staining density of pyloric mucosa in the 4EA group was stronger than that of the 2EA and control groups. The immunohistochemical staining density of gastrin, serotonin, and CGRP-secreting cells of pylorus in the 2EA and 4EA groups was stronger than that of the control group. Immunohistochemical staining density of insulin and PP secreting cells of islets of the pancreas in the 2EA and 4EA groups was stronger than that of the control group. These results suggest that EA stimulus at St36 has the potential to influence gastric mucous substances and enteroendocrine cells (gastrin, serotonin, CGRP, insulin, and PP) that subsequently modulate digestive functions., (Copyright © 2012. Published by Elsevier B.V.)

Purpose: It has now been established that exercise performed under various environmental conditions may affect acute energy intake and appetite-related hormones. The exact mechanism linking acute energy intake and exercise remains unknown, although indirect evidence suggests a possible role for hydration status. Therefore, the purpose of this study was to investigate the interaction of exercise and hydration status on subsequent energy intake and appetite-related hormones., Methods: In a randomized, counterbalanced design, 10 physically active males completed three experimental trials in a fasted state: exercise when hydrated (0%-1% of body mass), exercise when dehydrated (-1% to -2% of body mass), and a hydrated resting control. Exercise consisted of treadmill running for 45 min at 70% VO2peak. Participants were then given access to a buffet-style breakfast from which they could consume ad libitum. Blood was sampled regularly during trials for appetite-related hormones., Results: There were no significant differences in total energy intake between trials (P = 0.491); however, relative energy intake was significantly higher in the control (4839 ± 415 kJ, P < 0.001) compared to hydrated (1749 ± 403 kJ) and dehydrated exercise (1656 ± 413 kJ) conditions. Exercise performed in a dehydrated state resulted in significantly lower concentrations of ghrelin compared with control (P = 0.045) and hydrated exercise conditions (P = 0.014)., Conclusions: Exercise significantly decreased relative energy intake compared with resting control; however, energy intake (relative and total) was no different between the exercise conditions (dehydrated vs hydrated). Despite similar energy intake between trials, exercise in a dehydrated state resulted in a significantly lower concentration of ghrelin, a hormone responsible for stimulating appetite.

Complex mechanisms have evolved that control feeding and energy homeostasis in mammals. Centrally, particularly in the hypothalamus, numerous neurotransmitters have been identified that regulate appetite and energy homeostasis. On the other hand, hormones released from the gut signal states of hunger and satiety to the brain. From the large number of players involved in this interplay, peptides from the neuropeptide Y (NPY) family are unique, with the predominantly neuronally expressed NPY being one of the most strongly stimulating agents for food intake while its two other closely related family members peptide YY (PYY) and pancreatic polypeptide (PP) released from the gut induce satiety. Another major player in this circuitry is ghrelin, which is released from the stomach and is the only known hormone that signals hunger to the brain. It is doing this by stimulating hypothalamic NPY production and release, subsequently leading to increased appetite and feeding behaviour. Deregulation of these processes can lead to either the development of obesity or the other extreme, anorexia. The aim of this review is to summarize the recent literature on NPY and ghrelin and its involvement in anorexia nervosa.

The present study included 104 patients with gastric disorders associated with Helicobacter pylori infection. Thirty of them presented with chronic atrophic gastritis (CAG), 30 with gastric ulcer (GU), 20 with adenomatous gastric polyps (AGP), and 24 with gastric cancer (GC). The control group was comprised of 12 practically healthy subjects. We elucidated the role of vascular endothelial growth factor (VEGF) and endocrine cells of gastric mucosa producing glucagon (GC) and pancreatic polypeptide (PPP) in the patients with GAG, GU, AGP and GC prior to and after the surgical intervention and following eradication therapy. It was shown that GAG, AGP, and GC were associated with the persistence of Helicobacter pylori infection and accompanied by hyperplasia of GC and PPP-secreting endocrine cells of gastric mucosa. GU was characterized by hypolasia of VEGF-secreting epithelial cells of the stomach and GC and PPP-secreting endocrine cells of gastric mucosa. The levels of VEGF, GC and PPP that directly or indirectly realize their pathological properties through H. pylori, Bcl-2, and proapoptotic protein BAX proved to be of high prognostic value as regards the evolvement and clinical course of gastric disorders associated with Helicobacter pylori infection. The study demonstrated that adequate eradication therapy in patients with H. pylori-associated diseases of the stomach significantly reduces the number of gastric cells secreting VEGF and has practically no effect on the amount of GC and PPP-producing endocrine cells of gastric mucosa.

The control of food intake consists of neural and hormonal signals between the gut and central nervous system (CNS). Gut hormones such as CCK, PYY and PP signal to important areas in the CNS involved in appetite regulation to terminate a meal. These hormones can act directly via the circulation and activate their respective receptors in the hypothalamus and brainstem. In addition, gut vagal afferents also exist, providing an alternative pathway through which gut hormones can communicate with higher centres through the brainstem. Animal and human studies have demonstrated that peripheral administration of certain gut hormones reduces food intake and leads to weight loss. Gut hormones are therefore potential targets in the development of novel treatments for obesity and analogue therapies are currently under investigation.

Context: The global prevalence of diabetes mellitus, and in particular type 2 diabetes mellitus is increasing at an alarming rate. Risk factors for development of diabetes include obesity and advancing age., Objectives: The distribution of insulin, glucagon, somatostatin and pancreatic polypeptide in the pancreatic islets has been investigated in young and elderly type 2 Zucker diabetic fatty (ZDF) rats and age-matched Zucker lean (ZL) controls., Methods: Experiments were performed in male animals aged either 9-13 weeks or 30-34 weeks. Immunohistochemistry was used to label insulin, glucagon, somatostatin and pancreatic polypeptide in islet cells., Results: The percentage of insulin-positive cells was unaltered in young but decreased in elderly ZDF (35.5 ± 2.5%) rats compared to ZL controls (57.9 ± 1.8%). The percentage of glucagon-positive cells was increased in young ZDF (58.7 ± 3.4%) compared to ZL controls (23.4 ± 2.1%). However, in elderly rats the percentage of glucagon-positive cells declined in ZDF rats and was no longer different from ZL controls. The percentage of somatostatin-positive cells was unaltered in young and elderly ZDF rats compared to ZL controls. The percentage of pancreatic polypeptide-positive cells was unaltered in young but increased in elderly ZDF (22.0 ± 2.5%) rats compared to ZL controls (13.8 ± 1.8%)., Conclusions: The distribution of pancreatic hormones is altered to varying extents in the ZDF rat and during the normal aging process.

The main disadvantages of peptide pharmaceuticals are their rapid degradation and excretion, their low hydrophilicity, and low shelf lifes. These bottlenecks can be circumvented by acylation with fatty acids (lipidation) or polyethylene glycol (PEGylation). Here, we describe the modification of a human pancreatic polypeptide analogue specific for the human (h)Y(2) and hY(4) receptor with PEGs of different size and palmitic acid. Receptor specificity was demonstrated by competitive binding studies. Modifications had only a small influence on binding affinities and no influence on secondary structure. Both modifications improved pharmacokinetic properties of the hPP analogue in vivo and in vitro, however, lipidation showed a greater resistance to degradation and excretion than PEGylation. Furthermore, the lipidated peptide is taken up and degraded solely by the liver but not the kidneys. Lipidation resulted in prolonged action of the hPP analogue in respect of reducing food intake in mice after subcutaneous administration. Therefore, the lipidated hPP analogue could constitute a potential new therapeutic agent against obesity.

NPY, PYY and PP constitute the so-called NPY hormone family, which exert its biological functions in humans through YRs (Y₁, Y₂, Y₄ and Y₅). Systematic modulation of YR function became important as this multireceptor/multiligand system is known to mediate various essential physiological key functions and is involved in a variety of major human diseases such as epilepsy, obesity and cancer. As several YRs have been found to be overexpressed on different types of malignant tumors they emerge as promising target in modern drug development. Here, we summarize the current understanding of YRs function and the molecular mechanisms of ligand binding and trafficking. We further address recent advances in YR-based drug design, the development of promising future drug candidates and novel approaches in YR-targeted tumor diagnostics and therapy opportunities., (Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.)

Peptide YY (PYY) and pancreatic polypeptide (PP) are two appetite suppressing hormones, released post-prandially from the ileum and pancreas, respectively. PYY(3-36) , the major circulating form of the peptide, is considered to reduce food intake in humans and rodents via high affinity binding to the auto-inhibitory neuropeptide Y receptor Y2R, whereas PP is considered to act through the Y4R. Current evidence indicates the anorexigenic effects of both peptides occur via signalling in the brainstem and arcuate nucleus (ARC) of the hypothalamus. Manganese-enhanced magnetic resonance imaging (MEMRI) has previously been used to track hypothalamic neuronal activity in vivo in response to both nutritional interventions and gut hormone treatment. In the present study, we used MEMRI to demonstrate that s.c. administration of PP results in a significant reduction in signal intensity (SI) in the ARC, ventromedial hypothalamus and paraventricular nucleus of fasted mice. Subcutaneous delivery of PYY(3-36) resulted in a nonsignificant trend towards decreased SI in the hypothalamus of fasted mice. We found no SI change in the area postrema of the brainstem after s.c. injection of either peptide. These differences in hypothalamic SI profile between PP and PYY(3-36) occurred despite both peptides producing a comparable reduction in food intake. These results suggest that separate central pathways control the anorexigenic response for PP and PYY(3-36) , possibly via a differential effect of Y4 receptor versus Y2 receptor signalling. In addition, we performed a series of MEMRI scans at 0-2, 2-4 and 4-6 h post-injection of PYY(3-36) and a potent analogue of the peptide; PYY(3-36) (LT). We recorded a significant reduction in the ARC SI 2-4 h after PYY(3-36) (LT) injection compared to both saline and PYY(3-36) in fasted mice. The physiological differences between PYY(3-36) and its analogue were also observed in the long-term effects on food intake, with PYY(3-36) (LT) producing a more sustained anorexigenic effect. These data suggest that MEMRI can be used to investigate the long-term effects of gut peptide delivery on activity within the hypothalamus and brainstem., (© 2011 The Authors. Journal of Neuroendocrinology © 2011 Blackwell Publishing Ltd.)

Non-specific binding of Y receptor agonists to intact CHO cells, and to CHO cell or rat brain particulates, is much greater for human neuropeptide Y (hNPY) compared to porcine peptide Y (pPYY), and especially relative to human pancreatic polypeptide (hPP). This binding of hNPY is reduced by alkali cations in preference to non-ionic chaotrope urea, while the much lower non-specific binding of pPYY is more sensitive to urea. The difference could mainly be due to the 10-16 stretch in 36-residue Y agonists (residues 8-14 in N-terminally clipped 34-peptides), located in the sector that contains all acidic residues of physiological Y agonists. Anionic pairs containing aspartate in the 10-16 zone could be principally responsible for non-specific attachments, but may also aid the receptor site binding. Two such pairs are found in hNPY, one in pPYY, and none in hPP. The hydroxyl amino acid residue at position 13 in mammalian PYY and PP molecules could lower conformational plasticity and the non-selective binding via intrachain hydrogen bonding. The acidity of this tract could also be important in agonist selectivity of the Y receptor subtypes. The differences point to an evolutionary reduction of promiscuous protein binding from NPY to PP, and should also be important for Y agonist selectivity within NPY receptor group, and correlate with partial agonism and out-of group cross-reactivity with other receptors., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Objectives: To investigate the immunolocalization of the pancreatic polypeptide (PP)-fold peptide family, important regulatory factors for food intake, in the gastrointestinal tract of Suncus murinus, and to discuss the relation with the obesity-resistance, visceral fat accumulation-resistance phenomenon in Suncus murinus., Methods: The gastrointestinal tract of adult Suncus murinus, except for the stomach and pylorus, was divided into five sections (S1, corresponding to the duodenum, S2, S3 and S4, corresponding to the jejunum and ileum, and S5, corresponding to the colon and rectum in other mammals), to investigate the PP family and their receptor-producing cells by means of immunohistochemistry., Results: NPY, PYY, Y1 and Y4-immunoreactive cells were distributed widely throughout the gastrointestinal tract, moreover, the PP family and their receptor-immunoreactive cells were predominantly distributed at the end of the gastrointestinal tract, the rectum., Conclusion: In this study, we investigated the distribution of the PP family and their receptor-producing cells in the gastrointestinal tract of Suncus murinus in detail for the first time. It was presumed that the wide distribution of Y4 in the gastrointestinal tract may be related to (associated with) the phenomenon of natural obesity-resistance, visceral fat accumulation-resistance in aging Suncus murinus.

Background: Assays for assessing human islet cell quality, which provide results before transplantation, would be beneficial to improve the outcomes for islet transplantation therapy. Parameters such as percent β-cell apoptosis and cell composition are found to vary markedly between different islet preparations and may serve as markers of islet quality. We have developed fluorescence-based assays using laser scanning cytometry for assessing β-cell apoptosis and islet cell composition on serial sections of intact isolated islets., Methods: Isolated human islets were fixed in formalin and embedded in paraffin. Serial sections were immunostained for the pancreatic hormones and acinar and ductal cell markers. DNA fragmentation was used to label apoptotic cells. Stained cells were quantified using an iCys laser scanning cytometer., Results: Islet preparations from 102 human pancreatic islet isolations were analyzed. For the whole set of islet preparations, we found a mean islet cell composition of 54.5%±1.2% insulin-positive, 33.9%±1.2% glucagon, 12.1%±0.7% somatostatin, and 1.5%±0.2% pancreatic polypeptide-positive cells. The apoptotic β cells were 2.85%±0.4% with a range of 0.27% to 18.3%. The percentage of apoptotic β cells correlated well (P<0.0001, n=59) with results obtained in vivo by transplantation of the corresponding islets in diabetic NODscid mice., Conclusions: The analysis of whole, nondissociated islets for cell composition and β-cell apoptosis using laser scanning cytometry gives reliable and reproducible results and could be performed both before islet transplantation and on preserved cell blocks at any time in future. Thus, they can be a powerful tool for islet quality assessment.

The regional distribution and frequency of the pancreatic endocrine cells in the ddN mouse were studied using specific antisera against insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP). In the pancreatic islets, most of insulin-immunoreactive (IR) cells were located in the central region, and glucagon-, somatostatin and hPP-IR cells were located in the peripheral region regardless of the lobe. In the splenic part, glucagon-IR cells were also located in the central regions, and more numerous somatostatin-IR cells were detected in the central regions as compared with the duo-denal part. hPP-IR cells were restricted to the peripheral regions in both lobes but more numerous cells were detected in the duodenal portion. In the exocrine parenchyma of the splenic lobe, only insulin- and glucagon-IR cells were detected but all four kinds of IR cells were observed in the duodenal portion. In addition, insulin and hPP-IR cells were also demonstrated in the pancreatic duct regions. In conclusion, some strain-dependent characteristic distributional patterns of pancreatic endocrine cells were found in the ddN mouse with somewhat different distributional patterns between the two pancreatic lobes.

Background: Proghrelin, produced by the ghrelin (A-like) cells of the gastric mucosa, gives rise to cleavage products, including desacyl ghrelin, acyl ghrelin and obestatin. The products are thought to be secreted concomitantly. In an earlier study we found acyl ghrelin and obestatin, but not desacyl ghrelin, to suppress the release of hormones from isolated islets of mouse and rat pancreas., Results: Using isolated mouse pancreatic islets to study the suppression of the spontaneous secretion of pancreatic polypeptide (PP) by acyl ghrelin and obestatin, we determined the EC(50) values for the two peptides. For acyl ghrelin it was 2 x 10(-13)M (ranging from 1.7 to 2.8 x 10(-13)M), for obestatin it was 10(-13)M (ranging from 0.3 to 1.1 x 10(-13)M). The Hill coefficient (i.e. the midpoint slope) for the acyl ghrelin dose-response curve was 0.30 (ranging from 0.21 to 0.35); the corresponding value for obestatin was 0.35 (ranging from 0.21 to 0.35). The PP-releasing effect of acyl ghrelin, but not that of obestatin, was counteracted by desacyl ghrelin. The acyl ghrelin dose-response curve was shifted to the right in a parallel manner by increasing concentrations of desacyl ghrelin. A Schild plot was constructed with a slope of 0.78, giving an apparent pA(2) value of 14., Conclusions: The results favour the view that acyl ghrelin and obestatin suppress spontaneous PP secretion at physiologically relevant concentrations and that they act on separate receptors. However, we conclude also that desacyl ghrelin acts as a competitive, surmountable (and quite potent) inhibitor of acyl ghrelin. In view of the allegedly high circulating concentrations of desacyl ghrelin it is to be expected that the effect of acyl ghrelin - but not that of obestatin - will be impaired, in fact probably severely blunted by desacyl ghrelin, thereby compromising the functional significance of circulating acyl ghrelin. In addition, we suggest that isolated pancreatic islets are well suited for studies of receptors to acyl ghrelin and obestatin, and that suppression of PP secretion represents a convenient way to measure the effect of both these peptides., (Copyright 2010 Elsevier B.V. All rights reserved.)

A 14-year-old female spayed Golden Retriever was presented to the University of Florida's Veterinary Medical Center with history of lymphoplasmacytic gastroenteritis, intermittent vomiting, watery diarrhea, and weight loss for over a year. CBC, biochemical profile, and urinalysis were within reference intervals. Abdominal ultrasonographic examination revealed mesenteric and jejunal lymphadenopathy and hyperechoic hepatic nodules. Cytologic examination of the enlarged lymph nodes revealed loosely cohesive cells with moderate nuclear pleomorphism and rare punctate eosinophilic cytoplasmic granules. The cytologic interpretation was metastatic neuroendocrine neoplasia. On surgical exploration, a mass was detected in the right lobe of the pancreas. Histologic evaluation determined the mass to be an islet cell tumor. Approximately 98% of cells were positive by immunolabeling for pancreatic polypeptide (PP), and only rare cells were positive for insulin or somatostatin. All cells were negative for glucagon, gastrin, vasoactive intestinal polypeptide, protein gene product 9.5, synaptophysin, and chromogranins A and B. Pancreatic tumors that primarily produce PP are rare in dogs, and this is the first report of both the cytologic and histologic features of an islet cell tumor predominantly secreting PP. Clinical signs for these tumors are typically absent or nonspecific; signs may include watery diarrhea, as noted in this dog, although the diarrhea may have resulted from lymphoplasmacytic gastroenteritis. Additional case studies are needed to further characterize the cytomorphologic features and clinical presentation of PP-secreting islet cell tumor, or polypeptidoma, in dogs., (©2010 American Society for Veterinary Clinical Pathology.)

We previously reported that Reg IV is associated with neuroendocrine (NE) differentiation in gastric cancers. The aim was to examine which NE hormone products are related to Reg IV-positive NE cells and their roles in gastric cancers. In the present study, we performed immunohistochemical analysis in a tissue microarray (TMA) of a consecutive series of 630 cases with ten different antibodies, including chromogranin A, synaptophysin and neural cell adhesion molecule (NCAM) as NE differentiation markers, and gastrin, serotonin, calcitonin, gastrin-releasing peptide (GRP), pancreatic polypeptide (PP), somatostatin and glucagon as NE hormones. In 630 cases, we identified 205 (33%) with NE differentiation and 147 (23%) positive for Reg IV. Reg IV-positive cases showed NE differentiation more frequently than Reg IV-negative cases (P < 0.0001). In 205 cases with NE differentiation, Reg IV-positive cases expressed serotonin (P= 0.0032) and somatostatin (P= 0.036) more frequently than Reg IV-negative cases. Double immunofluorescence staining revealed co-expression of Reg IV with gastrin, serotonin and PP. These results indicate that Reg IV might be a mediating factor of several NE hormones.

Background: To understand the role of islet amyloid polypeptide (IAPP) in type 2 diabetes and pancreatic cancer (PC), we investigated the patterns of its expression and its ratio to insulin, glucagon, somatostatin and pancreatic polypeptide cells by morphometry in tissues from these two diseases in comparison to the normal pancreas., Materials and Methods: Pancreatic tissues from 11 donors (five without pancreatic disease and six with type 2 diabetes) and 11 surgical specimens from PC patients obtained from the cancer area (zone A) and the adjacent tumor-free area (zone B) were examined immunohistochemically. The size of islets, the number on beta-, alpha-, delta- pp- and IAPP-expressing cells and their ratios in the islets of these tissues were determined., Results: In the normal pancreas, only 50% of the beta-cells while alpha- and delta-cells co-expressed IAPP only sporadically. In tissues from diabetics as well as in zone A, the number of the beta-cells and the IAPP-expressing cells was reduced significantly, while the number of alpha- and delta-cells was increased. In zone B, however, significantly more beta-cell and IAPP-expressing cells and a significantly lower number of alpha-cells were found compared to those in zone A. Significant differences were also found between the specimens from type 2 diabetics and pancreatic cancer relative to the ratios of IAPP/beta-cell, IAPP/alpha-cells and beta-cell/delta-cells., Conclusion: The morphometric data show a decrease rather than an increase in the number of IAPP-expressing cells in PC. Differences in abnormalities in type-2 diabetics and in zone B of PC tissue strongly argue against the role of type 2 diabetes in PC. Rather, the development of diabetes in subjects prone to pancreatic cancer could be a red flag for malignancy.

Neuropeptide Y (NPY), Peptide YY (PYY) and pancreatic polypeptides (PPs) belong to the same peptide family called the Y or NPY family. Central and peripheral injections of these peptides are implicated in the regulation of food intake at the level of the hypothalamus (central effects; increased food intake) and dorsal vagal complex (DVC) (peripheral effects; decreased food intake). The DVC of the brainstem is a satiety reflex key region, which includes the nucleus tractus solitarius (NTS), area postrema (AP) and dorso motor nucleus of the vagus (DMX). NPY binding sites were quantified on serial DVC sections using in vitro receptor autoradiography in two feeding adaptation models: fasting and inflammatory anorexia. Receptor autoradiography revealed that Y(1), Y(2), Y(4) and Y(5) receptor subtypes are present in all nuclei of the DVC. Additionally, we also observed significant amount of specific labelling remaining even after having blocked all known NPY receptor subtypes targeted by radioligands such as [(125)I][Leu(31), Pro(34)]PYY, [(125)I]PYY3-36 and [(125)I]hPP. This binding is referred as an atypical NPY site. Lipopolysaccharide (LPS) injection and food deprivation (24-48h) did not induce any change in the expression of NPY Y(1), Y(2,) Y(4) and Y(5) receptors at the level of the NTS and DMX. However, a significant decrease in [(125)I]PYY3-36/Y(2) and [(125)I]hPP/Y(4)- and Y(5)-insensitive binding sites (residual or atypical site) was observed in the AP. Together, these data could suggest that residual or atypical NPY binding site in the AP is modulated by food deprivation and may be physiologically relevant and implicated in feeding behaviors., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Obesity is one of the greatest public health challenges of the 21st century with 1.6 billion adults currently classified as being overweight and 400 million as obese. Obesity is causally associated with type 2 diabetes, hypertension, cardiovascular disease, obstructive sleep apnoea and certain forms of cancer and is now one of the leading causes of mortality and morbidity worldwide. The gastrointestinal tract is the largest endocrine organ in the body producing hormones that have important sensing and signaling roles in regulating body weight and energy expenditure. The last decade has witnessed a marked increase in our understanding of the role of gut hormones in energy homeostasis. Consequently, strategies aimed at modulating circulating gut hormone concentrations or targeting their receptors are being developed as potential pharmacotherapies for obesity. This review summarizes the current knowledge regarding the mechanisms, sites of action and effects of the anorectic gut hormones peptide tyrosine-tyrosine (PYY), pancreatic polypeptide (PP), oxyntomodulin, and amylin and of the unique orexigenic hormone, ghrelin., (2009 Elsevier Ireland Ltd. All rights reserved.)

Angiotensin-converting enzyme 2 (ACE2), a carboxypeptidase that is highly homologous to ACE, acts as a negative regulator for the renin-angiotensin system (RAS). Pancreatic RAS is thought to play important endocrine and exocrine roles in hormone secretion. Further exploration of this system is likely to offer new insights into the pathogenesis of pancreatic diseases such as diabetes mellitus. This study investigated the expression of ACE2 in rat pancreatic exocrine and endocrine tissue. Reverse transcription-polymerase chain reaction, immunoblotting and immunohistochemistry showed that ACE2 mRNA and protein were expressed in the pancreas. Immunoelectron microscopy demonstrated that ACE2 was expressed in both endocrine and exocrine pancreatic tissues. In the endocrine tissue, ACE2 was localized on the secretory granules. Double immunofluorescence labelling showed that ACE2 was co-localized with both insulin and somatostatin, while it was rarely co-localized with glucagon and pancreatic polypeptide. These findings suggest that ACE2 might play an important role in glucose homeostasis.

Childhood obesity is a global epidemic and associated with an increased risk of hypertension, diabetes mellitus, and coronary heart disease, in addition to psychological disorders. Interventions such as bariatric surgery are highly invasive and lifestyle modifications are often unsuccessful because of disturbed perceptions of satiety. New signaling peptides discovered in recent years that are produced in peripheral tissues such as the gut, adipose tissue, and pancreas communicate with brain centers of energy homeostasis, such as the hypothalamus and hindbrain. This review discusses the major known gut- and adipose tissue-derived hormones involved in the regulation of food intake and energy homeostasis and their serum levels in childhood obesity before and after weight loss as well as their relationship to consequences of obesity. Since most of the changes of gastrointestinal hormones and adipokines normalize in weight loss, pharmacological interventions based on these hormones will likely not solve the obesity epidemic in childhood. However, a better understanding of the pathways of body weight- and food intake-regulating gut- and adipose tissue-derived hormones will help to find new strategies to treat obesity and its consequences.

Peptide libraries have proven to be useful in applications such as substrate profiling, drug candidate screening and identifying protein-protein interaction partners. However, issues of fidelity, peptide length, and purity have been encountered when peptide libraries are chemically synthesized. Biochemically produced libraries, on the other hand, circumvent many of these issues due to the fidelity of the protein synthesis machinery. Using thioredoxin as an expression partner, a stably folded peptide scaffold (avian pancreatic polypeptide) and a compatible cleavage site for human rhinovirus 3C protease, we report a method that allows robust expression of a genetically encoded peptide library, which yields peptides of high purity. In addition, we report the use of methodological synchronization, an experimental design created for the production of a library, from initial cloning to peptide characterization, within a 5-week period of time. Total peptide yields ranged from 0.8% to 16%, which corresponds to 2-70 mg of pure peptide. Additionally, no correlation was observed between the ability to be expressed or overall yield of peptide-fusions and the intrinsic chemical characteristics of the peptides, indicating that this system can be used for a wide variety of peptide sequences with a range of chemical characteristics.

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) are structurally related peptides that have numerous functions in both neural and endocrine signaling. These effects are mediated by the NPY receptor family and five members of this family have been cloned in mammals. To better characterize these receptor subtypes, we cloned and expressed the Y1, Y2, Y4 and Y5 receptor subtypes from the rabbit. Comparison of these sequences with human orthologs revealed that the Y1, Y2 and Y5 receptors have generally strong amino-acid sequence conservation, with 91-96% identity, while Y4 receptor showed relatively weak similarity with 82% identity, as with other species. Particularly in the transmembrane regions, Y1, Y2, and Y5 receptor subtypes showed remarkable conservation, with 98-99% amino acid identity. Competitive binding studies by NPY-family peptides and analogs showed that Y1, Y2 and Y5 receptors had similar pharmacological profiles between the respective rabbit and human receptor subtypes. Interestingly, all the tested peptides had a greater affinity for rabbit Y4 receptor than human Y4 receptor. These results suggest that rabbit and human Y1, Y2 and Y5 receptor subtypes are well conserved, whereas Y4 receptors are less well conserved.

Despite a considerable sequence identity of the three mammalian hormones of the neuropeptide Y family, namely neuropeptide Y, peptide YY and pancreatic polypeptide, their structure in solution is described to be different. A so-called pancreatic polypeptide-fold has been identified for pancreatic polypeptide, whereas the structure of the N-terminal segment of neuropeptide Y is unknown. This element is important for the binding of neuropeptide Y to two of its relevant receptors, Y(1) and Y(5), but not to the Y(2) receptor subtype. In this study now, three doubly fluorescent-labeled analogs of neuropeptide Y have been synthesized that still bind to the Y(5) receptor with high affinity to investigate the conformation in solution and, for the first time, to probe the conformational changes upon binding of the ligand to its receptor in cell membrane preparations. The results obtained from the fluorescence resonance energy transfer investigations clearly show considerable differences in transfer efficiency that depend both on the solvent as well as on the peptide concentration. However, the studies do not support a pancreatic polypeptide-like folding of neuropeptide Y in the presence of membranes that express the human Y(5) receptor subtype.

Some 80-90% of gastrinomas are located in the gastrinoma triangle, which includes the duodenum, the pancreatic head, and the hepatoduodenal ligament. The natural history of the tumors depends on their origin. Duodenal gastrinomas are much less aggressive than pancreatic primaries and infrequently develop liver metastases. The reason therefore is unclear. The transcription factor pancreatic-duodenal homeobox 1 (Pdx1) is important in differentiation and development of the pancreas and duodenum. In embryonic development, Sonic hedgehog (Shh) expression establishes a sharp molecular boundary, which allows for the proper patterning of the duodenal and pancreatic epithelium. Pancreatic polypeptide (PP) is expressed in pancreatic islets and is known to be expressed in pancreatic endocrine tumors. This study aims to clarify the expression pattern of Pdx1, Shh, and PP in duodenal and pancreatic gastrinomas. Tissue from 15 patients with duodenal and from 11 patients with pancreatic gastrinomas that underwent surgery between 1987 and 2007 at our institution because of a gastrinoma were evaluated by immunohistochemistry (IHC). Furthermore, tissue from lymph node metastases from two patients with a so far undetected primary gastrinoma was analyzed. IHC revealed strong Pdx1 expression in pancreatic gastrinomas, but not in duodenal gastrinomas. By contrast, there was no Shh expression detectable in pancreatic gastrinomas, but found in all duodenal gastrinomas. This pattern was also true for associated metastases. Shh expression combined with absence of Pdx1 expression in lymph node metastases from patients with an unknown location of the primary suggests a so far undetected duodenal gastrinoma. We show for the first time that only pancreatic, but not duodenal gastrinomas express Pdx1. Moreover, only duodenal gastrinomas express Shh, suggesting a different genetic background of these two tumors. Whereas the expression of Pdx1 in pancreatic gastrinomas might suggest their endocrine origin from islets, duodenal gastrinomas develop from a Pdx1 negative cell cluster. The expression pattern of Pdx1, Shh, and PP in resected metastases can help to locate an otherwise undetected primary gastrinoma.

We used immunofluorescence double staining method to investigate the cellular localization of glucagon and pancreatic polypeptide (PP) in rat pancreatic islets. The results showed that both A-cells (glucagon-secreting cells) and PP-cells (PP-secreting cells) were located in the periphery of the islets. However, A-cells and PP-cells had a different regional distribution. Most of A-cells were located in the splenic lobe but a few of them were in the duodenal lobe of the pancreas. In contrast, the majority of PP-cells were found in the duodenal lobe and a few of them were in the splenic lobe of the pancreas. Furthermore, we found that 67.74% A-cells had PP immunoreactivity, 70.92% PP-cells contained glucagon immunoreactivity with immunofluorescence double staining. Our data support the concept of a common precursor stem cell for pancreatic hormone-producing cells.