Anorectic Action Research Articles

A PEGylated analog of the gut hormone oxyntomodulin with long-lasting antihyperglycemic, insulinotropic and anorexigenic activity

Peptide agonists of the glucagon-like peptide 1 (GLP-1) receptor (GLP1R) are rapidly gaining favor as antidiabetic agents, since in addition to increasing glucose-dependent insulin secretion, they also cause weight loss. Oxyntomodulin (OXM), a natural peptide with sequence homology to both glucagon and GLP-1, has glucose-lowering activity in rodents and anorectic activity in rodents and humans, but its clinical utility is limited by a short circulatory half-life due to rapid renal clearance and degradation by dipeptidyl peptidase IV (DPP-IV). Here, we describe the development of a novel DPP-IV-resistant, long-acting GLP1R agonist, based on derivatization of a suitably chosen OXM analog with high molecular weight polyethylene glycol (PEG) (‘PEGylation’). PEG-OXM exerts an anti-hyperglycemic effect in diet-induced obese (DIO) mice in a glucose-dependent manner, with a maximally efficacious dose of 0.1mg/kg, and reduces food intake and body weight with a minimally efficacious dose of 1mg/kg. If this pharmacology is recapitulated in patients with type 2 diabetes, these results indicate PEG-OXM as a potential novel once-weekly GLP-1 mimetic with both glucose-lowering activity and weight loss efficacy.

A role for PYY3-36 in GLP1-induced insulin secretion

A role for PYY3-36 in GLP1-induced insulin secretion

Important role of ventromedial hypothalamic carnitine palmitoyltransferase-1a in the control of food intake

Carnitine palmitoyltransferase-1 (CPT-1) liver isoform, or CPT-1a, is implicated in CNS control of food intake. However, the exact brain nucleus site(s) in mediating this action of CPT-1a has not been identified. In this report, we assess the role of CPT-1a in hypothalamic ventromedial nucleus (VMN). We stereotaxically injected an adenoviral vector containing CPT-1a coding sequence into the VMN of rats to induce overexpression and activation of CPT-1a. The VMN-selective activation of CPT-1a induced an orexigenic effect, suggesting CPT-1a in the VMN is involved in the central control of feeding. Intracerebroventricular administration of etomoxir, a CPT-1 inhibitor, decreases food intake. Importantly, in the animals with VMN overexpression of a CPT-1a mutant that antagonizes the CPT-1 inhibition by etomoxir, the anorectic response to etomoxir was attenuated. This suggests that VMN is involved in mediating the anorectic effect of central inhibition of CPT-1a. In contrast, arcuate nucleus (Arc) overexpression of the mutant did not alter etomoxir-induced inhibition of food intake, suggesting that Arc CPT-1a does not play significant roles in this anorectic action. Furthermore, in the VMN, CPT-1a appears to act downstream of hypothalamic malonyl-CoA action of feeding. Finally, we show that in the VMN CPT-1 activity was altered in concert with fasting and refeeding states, supporting a physiological role of CPT-1a in mediating the control of feeding. All together, CPT-1a in the hypothalamic VMN appears to play an important role in central control of food intake. VMN-selective modulation of CPT-1a activity may therefore be a promising strategy in controlling food intake and maintaining normal body weight.

Leptin resistance is a secondary consequence of the obesity in ciliopathy mutant mice

Although primary cilia are well established as important sensory and signaling structures, their function in most tissues remains unknown. Obesity is a feature associated with some syndromes of cilia dysfunction, such as Bardet-Biedl syndrome (BBS) and Alström syndrome, as well as in several cilia mutant mouse models. Recent data indicate that obesity in BBS mutant mice is due to defects in leptin receptor trafficking and leptin resistance. Furthermore, induction of cilia loss in leptin-responsive proopiomelanocortin neurons results in obesity, implicating cilia on hypothalamic neurons in regulating feeding behavior. Here, we directly test the importance of the cilium as a mediator of the leptin response. In contrast to the current dogma, a longitudinal study of conditional Ift88 cilia mutant mice under different states of adiposity indicates that leptin resistance is present only when mutants are obese. Our studies show that caloric restriction leads to an altered anticipatory feeding behavior that temporarily abrogates the anorectic actions of leptin despite normalized circulating leptin levels. Interestingly, preobese Bbs4 mutant mice responded to the anorectic effects of leptin and did not display other phenotypes associated with defective leptin signaling. Furthermore, thermoregulation and activity measurements in cilia mutant mice are inconsistent with phenotypes previously observed in leptin deficient ob/ob mice. Collectively, these data indicate that cilia are not directly involved in leptin responses and that a defect in the leptin signaling axis is not the initiating event leading to hyperphagia and obesity associated with cilia dysfunction.

Involvement of Prolactin‐Releasing Peptide in the Activation of Oxytocin Neurones in Response to Food Intake

Food intake activates neurones expressing prolactin-releasing peptide (PrRP) in the medulla oblongata and oxytocin neurones in the hypothalamus. Both PrRP and oxytocin have been shown to have an anorexic action. In the present study, we investigated whether the activation of oxytocin neurones following food intake is mediated by PrRP. We first examined the expression of PrRP receptors (also known as GPR10) in rats. Immunoreactivity of PrRP receptors was observed in oxytocin neurones and in vasopressin neurones in the paraventricular and supraoptic nuclei of the hypothalamus and in the bed nucleus of the stria terminalis. Application of PrRP to isolated supraoptic nuclei facilitated the release of oxytocin and vasopressin. In mice, re-feeding increased the expression of Fos protein in oxytocin neurones of the hypothalamus and bed nucleus of the stria terminalis. The increased expression of Fos protein in oxytocin neurones following re-feeding or i.p. administration of cholecystokinin octapeptide (CCK), a peripheral satiety factor, was impaired in PrRP-deficient mice. CCK-induced oxytocin increase in plasma was also impaired in PrRP-deficient mice. Furthermore, oxytocin receptor-deficient mice showed an increased meal size, as reported in PrRP-deficient mice and in CCKA receptor-deficient mice. These findings suggest that PrRP mediates, at least in part, the activation of oxytocin neurones in response to food intake, and that the CCK–PrRP–oxytocin pathway plays an important role in the control of the termination of each meal.

Metabolic effect of short term administration of Hoodia gordonii, an herbal appetite suppressant

Hoodia gordonii (family: Apocynaceae) is used traditionally by the Khoi-San tribes to control hunger. It has become extremely popular and has triggered commercial interest due to its appetite suppressant property. The present study was undertaken to investigate the appetite regulatory mechanism and associated metabolic changes induced by the herb. Effect of organic solvent extract of H. gordonii on food intake and body weight of male Sprague Dawley rats was monitored at three different doses 50, 100 and 150mg/kg body weight, given orally for five days. Subsequently, the dose of 100mg/kg body weight was selected for further studies on the regulatory hormones and biochemical variables. Dose-dependent reduction in food intake (12–26%) was observed at a dose of 100 and 150mg/kg body weight (p<0.05). Appetite suppression persisted for 6h and food intake was restored within 24h after stopping of the treatment. There was an increase in liver glycogen stores, activity of mitochondrial CPT-1 and thyroid hormones in treated animals. The circulating levels of NPY and IGF-1 were decreased with marginal increase in leptin and CCK, in case of treated rats. There was no change in blood glucose and insulin levels were not affected significantly. The hormonal and metabolic changes due to treatment with the H. gordonii extract may be responsible for its anorectic activity.

The role of nesfatin-1 in metabolism regulation: an overview / Rola nesfatyny-1 w regulacji metabolizmu: artykuł przeglądowy

Abstract The hypothalamus synthesizes molecules involved in the regulation of feeding behaviour. Nesfatin- 1 is a recently discovered substance expressed in both the brain and peripheral tissues and exerts a strong anorectic action. Nesfatin-1-immunoreactive cell bodies are distributed in arcuate (ARC), paraventricular (PVN) and supraoptic (SON) nuclei, where the peptide has been found to be co-expressed with pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART), oxytocin (OX) and vasopressin (VP). More detailed studies have shown a wide distribution of nesfatin-1-positive neurons in several brain areas, such as the forebrain, hindbrain, brainstem and spinal cord. Moreover, nesfatin-1 has been also expressed in peripheral tissues, colocalizing with ghrelin in the gastric mucosa and insulin in β-cells of the endocrine pancreas and adipose tissue. Functional studies have revealed that exogenous nesfatin-1 administered into the brain ventricles, subcutaneously or intraperitoneally, was able to decrease both food intake in the dark phase as well as body weight gain in a dose-dependent manner. In addition, recent findings suggest the involvement of nesfatin-1 in the control of insulin secretion as well as immune and stress-related responses. However, since there is still a deficiency of data concerning the nesfatin-1 receptor, the possible implementation of nesfatin-1 analogs during human metabolic disorders requires further study.

Pregnane glycosides interfere with steroidogenic enzymes to down‐regulate corticosteroid production in human adrenocortical H295R cells

A group of bioactive steroidal glycosides (pregnanes) with anorectic activity in animals was isolated from several genera of milkweeds including Hoodia and Asclepias. In this study, we investigated the effects, structure-activity relationships, and mechanism of action of pregnane glycosides on steroidogenesis in human adrenocortical H295R cells. Administration of pregnane glycosides for 24 h suppressed the basal and forskolin-stimulated release of androstenedione, corticosterone, and cortisone from H295R cells. The conversion of progesterone to 11-deoxycorticosterone and 17-hydroxyprogesterone to either androstenedione or 11-deoxycortisol was most strongly affected, with 12-cinnamoyl-, benzoyl-, and tigloyl-containing pregnanes showing the highest activity. Incubation of pregnane glycosides for 24 h had no effect on mRNA transcripts of CYP11A1, CYP21A1, CYP11B1 cytochrome enzymes and steroidogenic acute regulatory protein (StaR) protein, yet resulted in twofold decrease in HSD3B1 mRNA levels. At the same time, pregnane glycosides had no effect on the CYP1, 2, or 3 drug and steroid metabolism enzymes and showed weak Na(+) /K(+) ATPase and glucocorticoid receptor binding. Taken together, these data suggest that pregnane glycosides specifically suppress steroidogenesis through strong inhibition of 11β-hydroxylase and steroid 17-alpha-monooxygenase, and weak inhibition of cytochrome P450 side chain cleavage enzyme and 21β-hydroxylase, but not 3β-hydroxysteroid dehydrogenase/isomerase.

Reversal of Diet-Induced Obesity Increases Insulin Transport into Cerebrospinal Fluid and Restores Sensitivity to the Anorexic Action of Central Insulin in Male Rats

Diet-induced obesity (DIO) reduces the ability of centrally administered insulin to reduce feeding behavior and also reduces the transport of insulin from the periphery to the central nervous system (CNS). The current study was designed to determine whether reversal of high-fat DIO restores the anorexic efficacy of central insulin and whether this is accompanied by restoration of the compromised insulin transport. Adult male Long-Evans rats were initially maintained on either a low-fat chow diet (LFD) or a high-fat diet (HFD). After 22 weeks, half of the animals on the HFD were changed to the LFD, whereas the other half continued on the HFD for an additional 8 weeks, such that there were 3 groups: 1) a LFD control group (Con; n = 18), 2) a HFD-fed, DIO group (n = 17), and 3) a HFD to LFD, DIO-reversal group (DIO-rev; n = 18). The DIO reversal resulted in a significant reduction of body weight and epididymal fat weight relative to the DIO group. Acute central insulin administration (8 mU) reduced food intake and caused weight loss in Con and DIO-rev but not DIO rats. Fasting cerebrospinal fluid insulin was higher in DIO than Con animals. However, after a peripheral bolus injection of insulin, cerebrospinal fluid insulin increased in Con and DIO-rev rats but not in the DIO group. These data provide support for previous reports that DIO inhibits both the central effects of insulin and insulin's transport to the CNS. Importantly, DIO-rev restored sensitivity to the effects of central insulin on food intake and insulin transport into the CNS.

First Report of Fusarium oxysporum Causing Wilt on Hoodia gordonii in South Africa.

Traditionally the San people of southern Africa used Hoodia species as an appetite suppressant and various medicinal purposes (1). Hoodia gordonii (Masson) Sweet ex Decne therefore became a commercially sought-after species due to the claim of its anorectic activity. During 2004, extensive wilting was observed on H. gordonii in commercial plantings near Kakamas and Pofadder (northern Cape, South Africa). The wilting gradually increased, which caused stems to rot at the base and shrivel up, causing plants to collapse and die. Affected plants exhibited discoloration in the stems' vascular tissues. Vascular tissue excised from stems and excisions of roots were surface sterilized for 3 min in 70% ethanol followed by 3 min in 1% NaOCl, rinsed with sterile water and plated onto Van Wyks Agar, a Fusarium-selective medium (3). Isolates were grown on potato dextrose agar (PDA) and carnation leaf agar (CLA) for 14 days at 25°C. The morphological features were examined (2); identification was based on colony and sporodochia color as well as conidial morphology from single-spore colonies. The conidial morphology includes the presence or absence of macro- and microconidia and chlamydospores as well as the shape, number of septa, and basal cell of the macroconidia. The shape, characteristics, and phialides of the microconidia was also included in this analysis. To confirm pathogenicity, 18 1-year-old H. gordonii plants, 18 H. pilifera (L.f.) Plowes subsp. annulata (N.E.Br.) Bruyns plants, and 18 carnation seedlings were planted into autoclaved soil amended with 1% finely grounded oats inoculated with isolate CBS 132482 (PREM 11783), while control plants were planted in sterile soil. After 30 days, tissue was dissected from each stem, surface sterilized, rinsed, and plated on CLA and PDA for recovery of fungi. Control plants and carnations remained healthy and no fungi were recovered. All Hoodia plants displayed wilt symptoms and F. oxysporum were reisolated from the infected plants. DNA was extracted from the representative isolate (CBS 132482) and a fragment of the translation elongation factor 1-alpha (EF-1α) gene was amplified using primers EF-1/EF-2 by the polymerase chain reaction assay (4). After the isolate was sequenced and aligned, BLAST analysis of the 603-bp fragment (GenBank Accession No. JX003858) showed a 100% homology with F. oxysporum (GenBank Accession No. GU226828). The beta tubulin gene sequenced (GenBank Accession No. JX003859) was amplified using the primers Bt-2a/Bt-2b. BLAST searches with the resulting 311-bp fragment showed a 99.4% homology with several isolates of F. oxysporum in the GenBank database (JQ265753; FR828825; DQ092480). The fungus had a specific host preference because it did not infect carnations as well as previously tested plants, which included beans, pumpkin, tomato, and watermelon. To our knowledge, this is the first report of F. oxysporum causing wilt in H. gordonii in South Africa.

The anorectic effect of GLP-1 in rats is nutrient dependent.

GLP-1-induced insulin secretion from the β-cell is dependent upon glucose availability. The purpose of the current study was to determine whether CNS GLP-1 signaling is also glucose-dependent. We found that fasting blunted the ability of 3rd cerebroventricularly (i3vt)-administered GLP-1 to reduce food intake. However, fasted animals maintained the anorexic response to melanotan II, a melanocortin receptor agonist, indicating a specific effect of fasting on GLP-1 action. We also found that i3vt administration of leptin, which is also decreased with fasting, was not able to potentiate GLP-1 action in fasted animals. However, we did find that CNS glucose sensing is important in GLP-1 action. Specifically, we found that i3vt injection of 2DG, a drug that blocks cellular glucose utilization, and AICAR which activates AMPK, both blocked GLP-1-induced reductions in food intake. To examine the role of glucokinase, an important CNS glucose sensor, we studied glucokinase-heterozygous knockout mice, but found that they responded normally to peripherally administered GLP-1 and exendin-4. Interestingly, oral, but not i3vt or IP glucose potentiated GLP-1′s anorectic action. Thus, CNS and peripheral fuel sensing are both important in GLP-1-induced reductions in food intake.

Anorexia Induction by the Trichothecene Deoxynivalenol (Vomitoxin) Is Mediated by the Release of the Gut Satiety Hormone Peptide YY

Consumption of deoxynivalenol (DON), a trichothecene mycotoxin known to commonly contaminate grain-based foods, suppresses growth of experimental animals, thus raising concerns over its potential to adversely affect young children. Although this growth impairment is believed to result from anorexia, the initiating mechanisms for appetite suppression remain unknown. Here, we tested the hypothesis that DON induces the release of satiety hormones and that this response corresponds to the toxin's anorectic action. Acute ip exposure to DON had no effect on plasma glucagon-like peptide-1, leptin, amylin, pancreatic polypeptide, gastric inhibitory peptide, or ghrelin; however, the toxin was found to robustly elevate peptide YY (PYY) and cholecystokinin (CCK). Specifically, ip exposure to DON at 1 and 5mg/kg bw induced PYY by up to 2.5-fold and CCK by up to 4.1-fold. These responses peaked within 15-120 min and lasted up to 120 min (CCK) and 240 min (PPY), corresponding with depressed rates of food intake. Direct administration of exogenous PYY or CCK similarly caused reduced food intake. Food intake experiments using the NPY2 receptor antagonist BIIE0246 and the CCK1A receptor antagonist devazepide, individually, suggested that PYY mediated DON-induced anorexia but CCK did not. Orolingual exposure to DON induced plasma PYY and CCK elevation and anorexia comparable with that observed for ip exposure. Taken together, these findings suggest that PYY might be one critical mediator of DON-induced anorexia and, ultimately, growth suppression.

Our evolving understanding of the interaction between leptin and dopamine system to regulate ingestive behaviors

Dopamine (DA) has been with us scientifically for a long time. Dopamine's function as a neurotransmitter was first recognized in 1958, a finding that eventually led to Arvid Carlsson being awarded the Nobel Prize in 2000. Among its numerous identified physiological roles, dopaminergic signaling is well known to regulate ingestive behaviors [1]. This is not surprising. Eating food is a pleasurable act and the DA projections from the ventral tegmental area (VTA) to the nucleus accumbens (NAc) clearly play a role in many aspects of reward that shape behavior. Consequently, a number of investigators have hypothesized a role for the DA system to interact with key peripheral signals that regulate food intake such as leptin [2,3] and ghrelin [4]. Literally thousands of papers have focused on the hypothalamic pathways mediating the anorectic effect of leptin. However, leptin receptors are also expressed in the VTA, and leptin decreases the firing rate of DA neurons and decreases feeding behavior independently of hypothalamic mechanisms [2,3]. In this issue, Billes and colleagues report that the systemic injection of DA receptor 2 antagonists before leptin treatment blunts the anorexigenic action of leptin [5]. Supporting those pharmacological findings, the administration of leptin to mice lacking DA receptor 2 showed an attenuated effect of leptin on feeding [5]. Conversely, DA receptor blockade had no effect on the acute hypophagic effect of melanocortin receptor agonists or the increased food intake caused by exogenous ghrelin administration [5]. This work lays another important brick in the foundation that leptin and the DA system have important interactions that are critical for the regulation of food intake and points the finger squarely at the D2 receptor as a key component of this interaction. This leaves open several interesting questions. First, which neuronal population is responsible for the interaction between leptin and DA receptor 2. Since both leptin and DA receptors are located within the VTA and different hypothalamic nuclei, other methodologies will need to be applied to give us clues as to the key neuroanatomical locations that mediate these effects. This question remains important since a previous study reported that DA receptor 2-deficient mice showed an increased response to central leptin administration [6]. Therefore, it is plausible to hypothesize that the manipulation of DA receptor 2 in specific neuronal populations might differentially affect leptin's actions. A second important question concerns the molecular pathway mediating the interaction between leptin and D2R. It could be hypothesized that the long isoform of the leptin receptor heterodimerizes with D2R. Interestingly, such heterodimers have been identified for ghrelin receptor (GHS-R1a) and D2R, and preventing such heterodimers alters the DRD2 signal transduction [7]. Answering this question could identify potential new downstream targets modulating the anorectic action of leptin. Finally, a key question concerns the possibility that leptin's actions on the DA system impact not only ingestive behaviors but have an important role in a wide range of other behaviors. For example, the dopaminergic system plays an important role as a mediator of the actions of ghrelin on food intake [4], spatial memories [8], and locomotor activity [9]. The findings of Billes et al. highlight the relevance of the dopaminergic system as a physiological mediator of feeding behavior and as a regulator of leptin's actions. Given that this interaction is independent of the melanocortin system it highlights the need to continue to explore new pathways that may underlie leptin's effects on energy balance, reproduction and peripheral fuel utilization. Revealing such pathways allows for new insights that can provide for better understanding of how dysregulation of body weight can occur and novel therapeutic strategies to make it easier for individuals to sustain meaningful weight loss.

Hypothyroidism reduces ObRb–STAT3 leptin signalling in the hypothalamus and pituitary of rats associated with resistance to leptin acute anorectic action

Leptin has been shown to regulate the hypothalamus-pituitary-thyroid axis, acting primarily through the STAT3 pathway triggered through the binding of leptin to the long-chain isoform of the leptin receptor, ObRb. We previously demonstrated that although hyperthyroid rats presented leptin effects on TSH secretion, those effects were abolished in hypothyroid rats. We addressed the hypothesis that changes in the STAT3 pathway might explain the lack of TSH response to leptin in hypothyroidism by evaluating the protein content of components of leptin signalling via the STAT3 pathway in the hypothalamus and pituitary of hypothyroid (0·03% methimazole in the drinking water/21 days) and hyperthyroid (thyroxine 5 μg/100 g body weight /5 days) rats. Hypothyroid rats exhibited decreased ObRb and phosphorylated STAT3 (pSTAT3) protein in the hypothalamus, and in the pituitary gland they exhibited decreased ObRb, total STAT3, pSTAT3 and SOCS3 (P<0·05). Except for a modest decrease in pituitary STAT3, no other alterations were observed in hyperthyroid rats. Moreover, unlike euthyroid rats, the hypothyroid rats did not exhibit a reduction in food ingestion after a single injection of leptin (0·5 mg/kg body weight). Therefore, hypothyroidism decreased ObRb-STAT3 signalling in the hypothalamus and pituitary gland, which likely contributes to the loss of leptin action on food intake and TSH secretion, as previously observed in hypothyroid rats.

Hypothalamic CB1 Cannabinoid Receptors Regulate Energy Balance in Mice

Cannabinoid type 1 (CB(1)) receptor activation is generally considered a powerful orexigenic signal and inhibition of the endocannabinoid system is beneficial for the treatment of obesity and related metabolic diseases. The hypothalamus plays a critical role in regulating energy balance by modulating both food intake and energy expenditure. Although CB(1) receptor signaling has been implicated in the modulation of both these mechanisms, a complete understanding of its role in the hypothalamus is still lacking. Here we combined a genetic approach with the use of adeno-associated viral vectors to delete the CB(1) receptor gene in the adult mouse hypothalamus and assessed the impact of such manipulation on the regulation of energy balance. Viral-mediated deletion of the CB(1) receptor gene in the hypothalamus led to the generation of Hyp-CB(1)-KO mice, which displayed an approximately 60% decrease in hypothalamic CB(1) receptor mRNA levels. Hyp-CB(1)-KO mice maintained on a normocaloric, standard diet showed decreased body weight gain over time, which was associated with increased energy expenditure and elevated β(3)-adrenergic receptor and uncoupling protein-1 mRNA levels in the brown adipose tissue but, surprisingly, not to changes in food intake. Additionally, Hyp-CB(1)-KO mice were insensitive to the anorectic action of the hormone leptin (5 mg/kg) and displayed a time-dependent hypophagic response to the CB(1) inverse agonist rimonabant (3 mg/kg). Altogether these findings suggest that hypothalamic CB(1) receptor signaling is a key determinant of energy expenditure under basal conditions and reveal its specific role in conveying the effects of leptin and pharmacological CB1 receptor antagonism on food intake.

Postconditioning with curaglutide, a novel GLP-1 analog, protects against heart ischemia-reperfusion injury in an isolated rat heart

AimGLP-1(7–36)amide (GLP-1) is an intestinal hormone with effects on glucose metabolism and feeding behavior, including insulinotropic, insulinomimetic, glucagonostatic and anorectic actions. In experimental settings, GLP-1 has also been shown to diminish infarct size following heart ischemia-reperfusion. GLP-1 analogs with extended half-lives are continuously being developed against type 2 diabetes mellitus. Of these, only exendin-4 (exenatide, registered as Byetta) has been shown to mimic the infarct size-limiting effect of GLP-1 in a clinically relevant application as a postconditioning agent. The aim of this work was to test, in a postconditioning mode, a novel, proteolysis-resistant GLP-1 analog N-Ac-GLP-1(7–34)amide, herein termed curaglutide, for its cardioprotective ability. MethodGlobal ischemia (35min)-reperfusion (120min) was applied in isolated, retrogradely perfused rat hearts. Peptides were present for 15min at the onset of reperfusion. Cardiac function parameters (beats per minute, left ventricle developed and diastolic pressures, rate-pressure product) were measured. Infarct size was determined by 2,3,5-tripehyltetrazolium chloride staining and planimetry. ResultsCuraglutide did not affect any of the functional heart parameters when administered without preceding ischemia. Curaglutide 0.3nM diminished significantly the postischemic hypercontracture, with no significant effect on the left ventricle developed pressure or rate-pressure product. Infarct size was reduced by curaglutide postconditioning from 24.8% (SEM 2.8, N=14) to 11.4% (SEM 3.2, N=8; P<0.05). These effects of curaglutide on postischemic hypercontracture and infarct size were similar in magnitude to corresponding effects of GLP-1 receptor agonist exendin-4. The cardioprotective effects of both agents were abolished in the presence of a GLP-1 receptor antagonist exendin(9–39). ConclusionCuraglutide is a new, proteolysis-resistant GLP-1 analog with a beneficial effect on reperfusion-injury in an isolated rat heart. Curaglutide was here shown to act through GLP-1 receptors. Based on the present results, more extensive experimental studies in vivo, comparing dose–response characteristics and efficacy of curaglutide and exendin-4 appear warranted.

PEGylation of Neuromedin U yields a promising candidate for the treatment of obesity and diabetes

Neuromedin U (NMU) is an endogenous peptide, whose role in the regulation of feeding and energy homeostasis is well documented. Two NMU receptors have been identified: NMUR1, expressed primarily in the periphery, and NMUR2, expressed predominantly in the brain. We recently demonstrated that acute peripheral administration of NMU exerts potent but acute anorectic activity and can improve glucose homeostasis, with both actions mediated by NMUR1. Here, we describe the development of a metabolically stable analog of NMU, based on derivatization of the native peptide with high molecular weight poly(ethylene) glycol (PEG) (‘PEGylation’). PEG size, site of attachment, and conjugation chemistry were optimized, to yield an analog which displays robust and long-lasting anorectic activity and significant glucose-lowering activity in vivo. Studies in NMU receptor-deficient mice showed that PEG-NMU displays an expanded pharmacological profile, with the ability to engage NMUR2 in addition to NMUR1. In light of these data, PEGylated derivatives of NMU represent promising candidates for the treatment of obesity and diabetes.

POMC‐GLP‐2R signaling and action in the control of feeding behavior and gastric motility

Glucagon‐like peptides (GLP‐1/2) are released in response to food intake. Central infusion of GLP‐2 suppresses food intake and gastric motility, and this is supposedly mediated through its receptor (GLP‐2R) action in the brain. However, the physiological relevance of GLP‐2R in the brain is unknown. Thus, our aims were to determine if GLP‐2R in POMC neurons regulates feeding behavior and gastric motility. [1] We generated mice with Glp2r deletion in POMC neurons, which showed late‐onset obesity, higher food intake, increased meal frequency, and accelerated gastric emptying using 13C‐octanoic acid breath test. For liquid meal, half‐excretion time was 29.0 ± 4.5 and 51.2 ± 4.5 min; and lag phase 17.8 ± 3.0 and 31.5 ± 3.0 min for the KO and WT mice, respectively. [2] We generated POMC‐specific p110α knockout mice and POMC‐specific FoxO1‐GFP over‐expression mice to define cellular mechanisms underlying GLP‐2‐initiated anorexic action. Using immunoprecipitation, we found that GLP‐2R interacted with p85α in hippocampal neurons. GLP‐2 acutely induced GLP‐2R translocation from membrane to cytoplasm, and enhanced Akt phosphorylation in a PI3K‐dependent manner. Moreover, GLP‐2 (at 20 nM for 30 min) induced nuclear exclusion of FoxO1‐GFP in POMC neurons, and this effect was abolished in POMC‐specific p110α KO mice, suggesting that GLP‐2 may disinhibit expression of FoxO1‐targeted genes in POMC neurons. Furthermore, GLP‐2 differentially modulated excitation of functionally‐segregated POMC neurons in a PI3K‐dependent manner. In conclusion, Glp2r deletion in POMC neurons impairs feeding behavior and gastric motility; and GLP‐2 acutely activates the PI3K signaling pathway in POMC neurons to modulate neuronal excitation and gene expression. Therefore, CNS GLP‐2R plays an important, physiological role in the control of food intake and gastric emptying.

Food intake in lean and obese mice after peripheral administration of glucagon-like peptide 2

We investigated the potential anorectic action of peripherally administered glucagon-like peptide 2 (GLP2) in lean and diet-induced obese (DIO) mice. Mice, fasted for 16 h, were injected i.p. with native GLP2 or [Gly2]GLP2, stable analog of GLP2, before or after GLP2 (3-33), a GLP2 receptor (GLP2R) antagonist, or exendin (9-39), a GLP1R antagonist. Food intake was measured at intervals 1, 2, 4, 8, and 24 h postinjection. In addition, we tested in lean mice the influence of [Gly2]GLP2 on gastric emptying and the effects of GLP1 alone or in combination with [Gly2]GLP2 on food intake. [Gly2]GLP2 dose dependently and significantly inhibited food intake in lean and DIO mice. The reduction of food intake occurred in the first hour postinjection and it was sustained until 4 h postinjection in lean mice while it was sustained until 2 h postinjection in DIO mice. GLP2 significantly inhibited food intake in both lean and DIO mice but only in the first hour postinjection. The efficiency of [Gly2]GLP2 or GLP2 in suppressing food intake was significantly weaker in DIO mice compared with lean animals. The [Gly2]GLP2 anorectic actions were blocked by the GLP2R antagonist GLP2 (3-33) or by the GLP1R antagonist exendin (9-39). The coadministration of [Gly2]GLP2 and GLP1 did not cause additive effects. [Gly2]GLP2 decreased the gastric emptying rate. Results suggest that GLP2 can reduce food intake in mice in the short term, likely acting at a peripheral level. DIO mice are less sensitive to the anorectic effect of the peptide.

Roles of Oxytocin Neurones in the Control of Stress, Energy Metabolism, and Social Behaviour

Oxytocin neurones are activated by stressful stimuli, food intake and social attachment. Activation of oxytocin neurones in response to stressful stimuli or food intake is mediated, at least in part, by noradrenaline/prolactin-releasing peptide (PrRP) neurones in the nucleus tractus solitarius, whereas oxytocin neurones are activated after social stimuli via medial amygdala neurones. Activation of oxytocin neurones induces the release of oxytocin not only from their axon terminals, but also from their dendrites. Oxytocin acts locally where released or diffuses and acts on remote oxytocin receptors widely distributed within the brain, resulting in anxiolytic, anorexic and pro-social actions. The action sites of oxytocin appear to be multiple. Oxytocin shows anxiolytic actions, at least in part, via serotoninergic neurones in the median raphe nucleus, has anorexic actions via pro-opiomelanocortin neurones in the nucleus tractus solitarius and facilitates social recognition via the medial amygdala. Stress, obesity and social isolation are major risk factors for mortality in humans. Thus, the oxytocin-oxytocin receptor system is a therapeutic target for the promotion of human health.