[Effects of metabolic surgery on islet function in Asian patients with type 2 diabetes].

Type 2 diabetes is a high-profile global public health problem, particularly in Asia. The young age of onset, low body mass index, and early appearance of pancreatic islet dysfunction are characteristics of Asian patients with T2DM. Metabolic surgery has become the standard treatment for T2DM patients and can significantly improve T2DM through a variety of mechanisms including modulation of energy homeostasis and reduction of body fat mass. Indeed, restoration of islet function also plays an integral role in the remission of T2DM. After metabolic surgery, islet function in Asian T2DM patients has improved significantly, with proven short-term and long-term effects. In addition, islet function is an important criterion and reference for patient selection prior to metabolic surgery. The mechanism of islet function improvement after metabolic surgery is not clear, but postoperative anatomical changes in the gastrointestinal tract leading to a number of hormonal changes seem to be the potential cause, including glucagon-like peptide-1, gastric inhibitory polypeptide, peptide YY, ghrelin, and cholecystokinin. The authors analyzed the current retrospective and prospective studies on the effect of metabolic surgery on the islet function of Asian T2DM patients with a low BMI and its mechanism, summarized the clinical evidence that metabolic surgery improved islet function in Asian T2DM patients with a low BMI, and discussed its underlying mechanism. It is of great significance for realizing personalized and precise treatment of metabolic surgery and further improving its clinical benefits.

The Neuropeptide Y Y2 Receptor Is Coexpressed with Nppb in Primary Afferent Neurons and Y2 Activation Reduces Histaminergic and IL-31-Induced Itch.

Itch stimuli are detected by specialized primary afferents that convey the signal to the spinal cord, but how itch transmission is regulated is still not completely known. Here, we investigated the roles of the neuropeptide Y (NPY)/Y2 receptor system on scratch behavior. The inhibitory Y2 receptor is expressed on mouse primary afferents, and intrathecal administration of the Y2 agonist peptide YY (PYY)3-36 reduced scratch episode frequency and duration induced by compound 48/80, an effect that could be reversed by intrathecal preadministration of the Y2 antagonist BIIE0246. Also, scratch episode duration induced by histamine could be reduced by PYY3-36 In contrast, scratch behavior induced by α-methyl-5HT, protease-activated receptor-2-activating peptide SLIGRL, chloroquine, topical dust mite extract, or mechanical itch induced by von Frey filaments was unaffected by stimulation of Y2 Primary afferent neurons expressing the Npy2r gene were found to coexpress itch-associated markers such as natriuretic peptide precursor b, oncostatin M receptor, and interleukin (IL) 31 receptor A. Accordingly, intrathecal PYY3-36 reduced the scratch behavior induced by IL-31. Our findings imply that the NPY/Y2 system reduces histaminergic and IL-31-associated itch through presynaptic inhibition of a subpopulation of itch-associated primary afferents. SIGNIFICANCE STATEMENT: The spinal neuropeptide Y system dampens scratching behavior induced by histaminergic compounds and interleukin 31, a cytokine involved in atopic dermatitis, through interactions with the Y2 receptor. The Y2 receptor is expressed by primary afferent neurons that are rich in itch-associated neurotransmitters and receptors such as somatostatin, natriuretic peptide precursor b, and interleukin 31 receptors.

Half-Life Extending Modifications of Peptide YY3-36 Direct Receptor-Mediated Internalization.

Peptide YY3-36 (PYY3-36) is an endogenous ligand of the neuropeptide Y2 receptor (Y2R), on which it acts to reduce food intake. Chemically modified PYY3-36 analogues with extended half-lives are potential therapeutics for the treatment of obesity. Here we show that the common half-life extending strategies PEGylation and lipidation not only control PYY3-36's pharmacokinetics but also affect central aspects of its pharmacodynamics. PEGylation of PYY3-36 inhibited endocytosis by increasing receptor dissociation rates (koff), which reduced arrestin-3 (Arr3) activity. This is the first link between Arr3 recruitment and Y2R residence time. C16-lipidation of PYY3-36 had a negligible impact on Y2R signaling, binding, and endocytosis. In contrast, C18acid-lipidation minimized endocytosis, which indicated a decreased internalization through non-arrestin-related mechanisms. We propose a temporal model that connects the properties and position of the half-life extender with receptor Gi versus Arr3 signaling bias. We believe that this will be important for future design of peptide therapeutics.

Emerging therapeutic potential for peptide YY for obesity-diabetes.

The vast majority of research to date on the gut hormone Peptide YY (PYY) has focused on appetite suppression and body weight regulation effects. These biological actions are believed to occur through interaction of PYY with hypothalamic Y2 receptors. However, more recent studies have added additional knowledge to understanding of the physiological, and potential therapeutic, roles of PYY beyond obesity alone. Thus, PYY has now been shown to impart improvements in pancreatic beta-cell survival and function, with obvious benefits for diabetes. This effect has been linked mainly to binding and activation of Y1 receptors by PYY, but more evidence is still required in this regard. Given the potential therapeutic promise of PYY-derived compounds, and complexity of receptor interactions, it is important to fully understand the complete biological action profile of PYY. Therefore, the current review aims to compile, evaluate and summarise current knowledge on PYY, with particular emphasis on obesity and diabetes treatment, and the importance of specific Y receptor interactions for this.

Antiobesity and emetic effects of a short-length peptide YY analog and its PEGylated and alkylated derivatives.

Neuropeptide Y2 receptor (Y2R) agonism is an important anorectic signal and a target of antiobesity drug discovery. Recently, we synthesized a short-length Y2R agonist, PYY-1119 (4-imidazolecarbonyl-[d-Hyp24,Iva25,Pya(4)26,Cha27,36,γMeLeu28,Lys30,Aib31]PYY(23-36), 1) as an antiobesity drug candidate. Compound 1 induced marked body weight loss in diet-induced obese (DIO) mice; however, 1 also induced severe vomiting in dogs at a lower dose than the minimum effective dose administered to DIO mice. The rapid absorption of 1 after subcutaneous administration caused the severe vomiting. Polyethylene glycol (PEG)- and alkyl-modified derivatives of 1 were synthesized to develop Y2R agonists with improved pharmacokinetic profiles, i.e., lower maximum plasma concentration (Cmax) and longer time at maximum concentration (Tmax). Compounds 5 and 10, modified with 20 kDa PEG at the N-terminus and eicosanedioic acid at the Lys30 side chain of 1, respectively, showed high Y2R binding affinity and induced significant body weight reduction upon once-daily administration to DIO mice. Compounds 5 and 10, with their relatively low Cmax and long Tmax, partially attenuated emesis in dogs compared with 1. These results indicate that optimization of pharmacokinetic properties of Y2R agonists is an effective strategy to alleviate emesis induced by Y2R agonism.

Bariatric surgery - time to replace with GLP-1?

Obesity with a body mass index (BMI) over 30 kg/m2 represents a significant risk for increased morbidity and mortality, with reduced life expectancy of about 10 years. Until now, surgical treatment has been the only effective longterm intervention. The currently standardized method of bariatric surgery, gastric bypass, means that many gastrointestinal peptide hormones are activated, yielding net reductions in appetite and food intake. Among the most important gut peptide hormones in this perspective is glucagon-like peptide-1 (GLP-1), which rises sharply after gastric bypass. Consistent with outcomes of this surgery, GLP-1 suppresses appetite and reduces food intake. This implies that GLP-1 has the potential to achieve a similar therapeutic outcome as gastric bypass. GLP-1 analogs, which are used for the treatment of type 2 diabetes mellitus, also lead to significant weight loss. Altered hormonal profiles after gastric bypass therefore indicate a logical connection between gut peptide hormone levels, weight loss and glucose homeostasis. Furthermore, combinations of GLP-1 with other gut hormones such as peptide YY (PYY) and cholecystokinin (CCK) may be able to reinforce GLP-1 driven reduction in appetite and food intake. Pharmacological intenvention in obesity by use of GLP-1 analogs (exenatide, liraglutide, albiglutide, dulaglutide, lixisenatide, taspoglutide) and inhibitors of dipeptidyl peptidase-IV (DPP-IV) degradation that inactivate GLP-1 (sitagliptin, vildagliptin), leading to reduced appetite and weight with positive effects on metabolic control, are realistically achievable. This may be regarded as a low-risk therapeutic alternative to surgery for reducing obesity-related risk factors in the obese with lower BMIs.

Inhaled PYY(3-36) dry-powder formulation for appetite suppression.

OBJECTIVE: Peptide YY3-36 [PYY(3-36)] has shown efficacy in appetite suppression when dosed by injection modalities (intraperitoneal (IP)/subcutaneous). Transitioning to needle-free delivery, towards inhalation, often utilizes systemic pharmacokinetics as a key endpoint to compare different delivery methods and doses. Systemic pharmacokinetics were evaluated for PYY3-36 when delivered by IP, subcutaneous, and inhalation, the systemic pharmacokinetics were then used to select doses in an appetite suppression pharmacodynamic study. METHODS: Dry-powder formulations were manufactured by spray drying and delivered to mice via nose only inhalation. The systemic plasma, lung tissue, and bronchoalveolar lavage fluid pharmacokinetics of different inhalation doses of PYY(3-36) were compared to IP and subcutaneous efficacious doses. Based on these pharmacokinetic data, inhalation doses of 70:30 PYY(3-36):Dextran T10 were evaluated in a mouse model of appetite suppression and compared to IP and subcutaneous data. RESULTS: Inhalation pharmacokinetic studies showed that plasma exposure was similar for a 2 × higher inhalation dose when compared to subcutaneous and IP delivery. Inhalation doses of 0.22 and 0.65 mg/kg were for efficacy studies. The results showed a dose-dependent (not dose proportional) decrease in food consumption over 4 h, which is similar to IP and subcutaneous delivery routes. CONCLUSIONS: The pharmacokinetic and pharmacodynamics results substantiate the ability of pharmacokinetic data to inform pharmacodynamics dose selection for inhalation delivery of the peptide PYY(3-36). Additionally, engineered PYY(3-36):Dextran T10 particles delivered to the respiratory tract show promise as a non-invasive therapeutic for appetite suppression.

Physiological adaptations following Roux-en-Y gastric bypass and the identification of targets for bariatric mimetic pharmacotherapy.

The present opinion article provides an overview of the key improvements in metabolic and cardiovascular health following Roux-en-Y Gastric Bypass (RYGB). Some clinically important long-term complications of RYGB are also briefly described to contextualise the potential value of finding selective non-surgical means of replicating only the beneficial aspects of RYGB. Three biological responses linked to changes in gastrointestinal tract structure and function post-RYGB, that are implicated in the clinical efficacy of RYGB and that have actual or potential applications as non-surgical mimetic based approaches are addressed. These are (1) exaggerated post-prandial gut hormone responses; (2) local increases in undiluted bile in the gut lumen and augmented circulating bile acid and FGF19 concentrations and (3) compositional changes in the gut microbiota.

A Hamster Model of Diet-Induced Obesity for Preclinical Evaluation of Anti-Obesity, Anti-Diabetic and Lipid Modulating Agents.

AIM: Unlike rats and mice, hamsters develop hypercholesterolemia, and hypertriglyceridemia when fed a cholesterol-rich diet. Because hyperlipidemia is a hallmark of human obesity, we aimed to develop and characterize a novel diet-induced obesity (DIO) and hypercholesterolemia Golden Syrian hamster model. METHODS AND RESULTS: Hamsters fed a highly palatable fat- and sugar-rich diet (HPFS) for 12 weeks showed significant body weight gain, body fat accumulation and impaired glucose tolerance. Cholesterol supplementation to the diet evoked additional hypercholesterolemia. Chronic treatment with the GLP-1 analogue, liraglutide (0.2 mg/kg, SC, BID, 27 days), normalized body weight and glucose tolerance, and lowered blood lipids in the DIO-hamster. The dipeptidyl peptidase-4 (DPP-4) inhibitor, linagliptin (3.0 mg/kg, PO, QD) also improved glucose tolerance. Treatment with peptide YY3-36 (PYY3-36, 1.0 mg/kg/day) or neuromedin U (NMU, 1.5 mg/kg/day), continuously infused via a subcutaneous osmotic minipump for 14 days, reduced body weight and energy intake and changed food preference from HPFS diet towards chow. Co-treatment with liraglutide and PYY3-36 evoked a pronounced synergistic decrease in body weight and food intake with no lower plateau established. Treatment with the cholesterol uptake inhibitor ezetimibe (10 mg/kg, PO, QD) for 14 days lowered plasma total cholesterol with a more marked reduction of LDL levels, as compared to HDL, indicating additional sensitivity to cholesterol modulating drugs in the hyperlipidemic DIO-hamster. In conclusion, the features of combined obesity, impaired glucose tolerance and hypercholesterolemia in the DIO-hamster make this animal model useful for preclinical evaluation of novel anti-obesity, anti-diabetic and lipid modulating agents.

Nanocarrier for Oral Peptide Delivery Produced by Polyelectrolyte Complexation in Nanoconfinement.

The hydrophilic peptide YY (PYY) is a promising hormone-based antiobesity drug. We present a new concept for the delivery of PYY from pH-responsive chitosan-based nanocarriers. To overcome the drawbacks while retaining the merits of the polyelectrolyte complex (PEC) method, we propose a one-pot approach for the encapsulation of a hydrophilic peptide drug in cross-linked PEC nanocarriers. First, the hydrophilic peptide is encapsulated via polyelectrolyte complexation within water-in-oil miniemulsion droplets. In a second step, the PEC surface is reinforced by controlled interfacial cross-linking. PYY is efficiently encapsulated and released upon pH change. Such nanocarriers are promising candidates for the fight against obesity and, in general, for the oral delivery of protein drugs.

Can Bayliss and Starling gut hormones cure a worldwide pandemic?

Bayliss and Starling first coined the term 'hormone' with reference to secretin, a substance they found that was produced by the gut, but released into the blood stream to act at a distance. The intestine is now known as the largest endocrine organ in the body, and it produces numerous hormones with a wide range of functions. These include controlling appetite and energy homeostasis. Obesity is one of the greatest health threats facing the world today. At present, the only successful treatment is surgery. Bariatric procedures such as the Roux-en-Y bypass work by elevating gut hormones that induce satiety. Significant research has gone into producing versions of these hormones that can be delivered therapeutically to treat obesity. This review looks at the role of gut hormones in obesity, and the development of gut hormone-derived obesity treatments.

The role of peptide YY in gastrointestinal diseases and disorders (review).

Peptide YY (PYY) is affected in several gastrointestinal diseases and disorders. Changes in PYY appear to be an adaptive response to alterations in pathophysiological conditions caused by the disease. This applies to gastrointestinal diseases/disorders such as irritable bowel syndrome, inflammatory bowel disease, celiac disease, systemic sclerosis, and post-intestinal resection. By contrast, the changes in PYY in chronic idiopathic slow transit constipation (CST) seem to be of a primary nature, and may be one etiological factor of the disease. Abnormalities in PYY seem to contribute to the development of symptoms present in irritable bowel syndrome, inflammatory bowel disease, gastroenteropathy in long-standing diabetes and CST. The changes in PYY could, however, be favorable in some gastrointestinal disorders such as celiac disease, systemic sclerosis and post-intestinal resection state. Investigating changes in PYY in gastrointestinal diseases/disorders could be beneficial in clinical practice, where a receptor agonist or an antagonist can be used as a drug, depending on the condition. Similar to other neuroendocrine peptides/amines of the gut, PYY has broad physiological/pharmacological effects: it can bind to and activate several receptors with independent actions. Thus, in order to use PYY as a drug, receptor-specific agonists or antagonists need to be developed.

My brain made me do it, and my gut didn't help.

Decisions about what, when and how much to eat are made by the brain, though these choices can be strongly influenced by the hedonic and rewarding properties of sweet or fatty foods. The rumbling before and the fullness after eating tells us that the gut also has an important role in the initiation and termination of feeding. Gut-derived peptides continually convey homeostatic information to the brain to guide feeding. These circulating signals can also modify the pleasure and reward associated with food.

Translational studies on PYY as a novel target in obesity.

The obesity epidemic has a direct impact on every aspect of health. Current strategies to treat obesity are limited and there is a need to pioneer novel solutions. Anorectic gut hormones, physiologically secreted post-prandially to mediate satiety, have recently emerged as potential therapeutic targets in obesity. Peptide tyrosine tyrosine (PYY) is one such anorectic gut hormone, secreted from entero-endocrine L cells, which acts on neuropeptide Y (NPY) receptors within the central appetite circuit. Since the first intravenous administration of PYY to man nearly a decade ago, a number of translational studies and clinical trials have ensued with a view to developing this peptide as a treatment for obesity. This review reports on the current state of play of this on-going research.

Bench-to-bedside review: the gut as an endocrine organ in the critically ill.

In health, hormones secreted from the gastrointestinal tract have an important role in regulating gastrointestinal motility, glucose metabolism and immune function. Recent studies in the critically ill have established that the secretion of a number of these hormones is abnormal, which probably contributes to disordered gastrointestinal and metabolic function. Furthermore, manipulation of endogenous secretion, physiological replacement and supra-physiological treatment (pharmacological dosing) of these hormones are likely to be novel therapeutic targets in this group. Fasting ghrelin concentrations are reduced in the early phase of critical illness, and exogenous ghrelin is a potential therapy that could be used to accelerate gastric emptying and/or stimulate appetite. Motilin agonists, such as erythromycin, are effective gastrokinetic drugs in the critically ill. Cholecystokinin and peptide YY concentrations are elevated in both the fasting and postprandial states, and are likely to contribute to slow gastric emptying. Accordingly, there is a rationale for the therapeutic use of their antagonists. So-called incretin therapies (glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide) warrant evaluation in the management of hyperglycaemia in the critically ill. Exogenous glucagon-like peptide-2 (or its analogues) may be a potential therapy because of its intestinotropic properties.

Peptide hormone isoforms: N-terminally branched PYY3-36 isoforms give improved lipid and fat-cell metabolism in diet-induced obese mice.

The prevalence of obesity is increasing with an alarming rate worldwide and there is a need for efficacious satiety drugs. PYY3-36 has been shown to play a role in hypothalamic appetite regulation and novel analogs targeting the Y2 receptor have potential as drugs for the treatment of obesity. We have designed a series of novel PYY3-36 isoforms, by first adding the dipeptide Ile-Lys N-terminal to the N(α) of Ser-13 in PYY13-36 and then anchoring the N-terminal segment, e.g. PYY3-12, to the new Lys N(ε)-amine. We hypothesized that such modifications would alter the folding of PYY, due to changes in the turn motif, which could change the binding mode to the Y receptor sub-types and possibly also alter metabolic stability. In structure-affinity/activity relationship experiments, one series of PYY isoforms displayed equipotency towards the Y receptors. However, an increased Y2 receptor potency for the second series of PYY isoforms resulted in enhanced Y receptor selectivity compared to PYY3-36. Additionally, acute as well as chronic mice studies showed body-weight-lowering effects for one of the PYY isoforms, which was also reflected in a reduction of circulating leptin levels. Interestingly, while the stability and pharmacokinetic profile of PYY3-36 and the N-terminally modified PYY3-36 analogue were identical, only mice treated with the branched analogue showed marked increases in adiponectin levels as well as reductions in non-esterified free fatty acids and triglycerides.

NPY Y2 receptor agonist PYY(3-36) inhibits diarrhea by reducing intestinal fluid secretion and slowing colonic transit in mice.

Peptide YY (PYY)(3-36), a neuropeptide Y (NPY) Y2 receptor agonist, is a powerful inhibitor of intestinal secretion. Based on this anti-secretory effect, NPY Y2 receptor agonists may be useful as novel anti-diarrheal agents, but anti-diarrheal efficacy has yet to be determined. We therefore examined the anti-diarrheal efficacy of PYY(3-36) and a selective Y2 receptor agonist, N-acetyl-[Leu28, Leu31]-NPY(24-36), in experimental mouse models of diarrhea. Intraperitoneal administration of PYY(3-36) (0.01-1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) significantly inhibited diarrhea (increase in wet fecal weight and diarrhea score) induced by dimethyl-prostaglandin E2, 5-hydroxytryptamine, and castor oil. Anti-diarrheal activities of PYY(3-36) and N-acetyl-[Leu28, Leu31]-NPY(24-36) were comparable to the effects of loperamide (1mg/kg), a widely used anti-diarrheal drug. To clarify the anti-diarrheal mechanisms of NPY Y2 receptor agonists, we investigated the effects of PYY(3-36) and N-acetyl-[Leu28, Leu31]-NPY(24-36) on intestinal fluid secretion and colonic transit. PYY(3-36) (1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) significantly reduced dimethyl-prostaglandin E2-induced intestinal fluid accumulation in conscious mice, suggesting that NPY Y2 receptor agonists inhibit diarrhea, at least in part, by reducing intestinal secretion. In addition, PYY(3-36) (0.01-1mg/kg) and N-acetyl-[Leu28, Leu31]-NPY(24-36) (10mg/kg) potently inhibited normal fecal output, suggesting that NPY Y2 receptor activation inhibits colonic motor function and NPY Y2 receptor agonists inhibit diarrhea partly by slowing colonic transit. These results indicate that NPY Y2 receptor agonists inhibit diarrhea in mice by not only reducing intestinal fluid secretion, but also slowing colonic transit, and illustrate the therapeutic potential of NPY Y2 receptor agonists as effective treatments for diarrhea.

Therapeutic potential of gut peptides.

A great deal of research interest is directed toward understanding the control of appetite and regulation of metabolism. It seems as if an epidemic of obesity is sweeping the world, and type II diabetes (T2DM) is following in its wake. The regulation of energy homeostasis is an area that straddles neurobiology, classical endocrinology and metabolism. It is currently one of the most exciting and rapidly advancing topics in medical research, and is also one of the most frustrating areas. The availability of highly palatable, calorie-dense food, together with the low requirement for physical activity in our modern environment, are major factors contributing to the obesity epidemic. If energy intake exceeds energy use, the excess calories are stored as body fat. Knowledge of the homeostatic system that controls body weight has increased dramatically over the last years and has revealed new potential targets for the treatment of obesity. One therapeutic approach is the development of agents based on the gastrointestinal hormones that control food intake and appetite. This review discusses several gut hormones and ligands for their receptors as potential anti-obesity treatments.

Obesity treatment: novel peripheral targets.

Our knowledge of the complex mechanisms underlying energy homeostasis has expanded enormously in recent years. Food intake and body weight are tightly regulated by the hypothalamus, brainstem and reward circuits, on the basis both of cognitive inputs and of diverse humoral and neuronal signals of nutritional status. Several gut hormones, including cholecystokinin, glucagon-like peptide-1, peptide YY, oxyntomodulin, amylin, pancreatic polypeptide and ghrelin, have been shown to play an important role in regulating short-term food intake. These hormones therefore represent potential targets in the development of novel anti-obesity drugs. This review focuses on the role of gut hormones in short- and long-term regulation of food intake, and on the current state of development of gut hormone-based obesity therapies.