Peptide YY

PYY3-36 infused systemically or directly into the VTA attenuates fentanyl seeking in male rats

More effective treatments for fentanyl use disorder are urgently needed. An emerging literature indicates that glucagon-like peptide-1 receptor (GLP-1R) agonists attenuate voluntary opioid taking and seeking in rodents. However, GLP-1R agonists produce adverse malaise-like effects that may limit patient compliance. Recently, we developed a dual agonist of GLP-1Rs and neuropeptide Y2 receptors (Y2Rs) that attenuates fentanyl taking and seeking at doses that do not produce malaise-like effects in opioid-experienced rats. Whether activating Y2Rs alone is sufficient to reduce opioid taking and seeking, however, is not known. Here, we investigated the efficacy of the Y2R ligand PYY3-36 to reduce fentanyl self-administration and the reinstatement of fentanyl-seeking behavior, a model of relapse in humans. Male rats were allowed to self-administer fentanyl (2.5 μg/kg, i.v.) for 21 days on a fixed-ratio 5 (FR5) schedule of reinforcement. Rats were then pretreated with vehicle or PYY3-36 (50 μg/kg s.c.; 0.1 and 1.0 μg/100 nL intra-VTA) prior to fentanyl self-administration test sessions. There were no effects of systemic or intra-VTA PYY3-36 on intravenous fentanyl self-administration. Opioid taking was then extinguished. Prior to subsequent reinstatement test sessions, rats were pretreated with vehicle or PYY3-36 (50 μg/kg s.c.; 0.1 and 1.0 μg/100 nL intra-VTA). Both systemic and intra-VTA administration of PYY3-36 attenuated fentanyl reinstatement in male rats at doses that did not affect food intake or produce adverse malaise-like effects. These findings indicate that Y2R agonism alone is sufficient to decrease fentanyl-seeking behavior during abstinence in opioid-experienced rats and further support strategies aimed at targeting Y2Rs for treating opioid use disorders.

Hypertension Related to Obesity: Pathogenesis, Characteristics and Factors for Control

The World Health Organization (WHO) refers to obesity as abnormal or excessive fat accumulation that presents a health risk. Obesity was first designated as a disease in 2012 and since then the cost and the burden of the disease have witnessed a worrisome increase. Obesity and hypertension are closely interrelated as abdominal obesity interferes with the endocrine and immune systems and carries a greater risk for insulin resistance, diabetes, hypertension, and cardiovascular disease. Many factors are at the interplay between obesity and hypertension. They include hemodynamic alterations, oxidative stress, renal injury, hyperinsulinemia, and insulin resistance, sleep apnea syndrome and the leptin-melanocortin pathway. Genetics, epigenetics, and mitochondrial factors also play a major role. The measurement of blood pressure in obese patients requires an adapted cuff and the search for other secondary causes is necessary at higher thresholds than the general population. Lifestyle modifications such as diet and exercise are often not enough to control obesity, and so far, bariatric surgery constitutes the most reliable method to achieve weight loss. Nonetheless, the emergence of new agents such as Semaglutide and Tirzepatide offers promising alternatives. Finally, several molecular pathways are actively being explored, and they should significantly extend the treatment options available.

A novel approach to treating opioid use disorders: Dual agonists of glucagon-like peptide-1 receptors and neuropeptide Y2 receptors

The widespread misuse of opioids and opioid use disorder (OUD) together constitute a major public health crisis in the United States. The greatest challenge for successfully treating OUD is preventing relapse. Unfortunately, there are few FDA-approved medications to treat OUD and, while effective, these pharmacotherapies are limited by high relapse rates. Thus, there is a critical need for conceptually new approaches to developing novel medications to treat OUD. Here, we review an emerging preclinical literature that suggests that glucagon-like peptide-1 receptor (GLP-1R) agonists could be re-purposed for treating OUD. Potential limitations of this approach are also discussed along with an alternative strategy that involves simultaneously targeting and activating GLP-1Rs and neuropeptide Y2 receptors (Y2Rs) in the brain using a novel monomeric dual agonist peptide. Recent studies indicate that this combinatorial pharmacotherapy approach attenuates voluntary fentanyl taking and seeking in rats without producing adverse effects associated with GLP-1R agonist monotherapy alone. While future studies are required to comprehensively determine the behavioral effects of GLP-1R agonists and dual agonists of GLP-1Rs and Y2Rs in rodent models of OUD, these provocative preclinical findings highlight a potential new GLP-1R-based approach to preventing relapse in humans with OUD.

A novel dual agonist of glucagon-like peptide-1 receptors and neuropeptide Y2 receptors attenuates fentanyl taking and seeking in male rats

There has been a dramatic increase in illicit fentanyl use in the United States over the last decade. In 2018, more than 31,000 overdose deaths involved fentanyl or fentanyl analogs, highlighting an urgent need to identify effective treatments for fentanyl use disorder. An emerging literature shows that glucagon-like peptide-1 receptor (GLP-1R) agonists attenuate the reinforcing efficacy of drugs of abuse. However, the effects of GLP-1R agonists on fentanyl-mediated behaviors are unknown. The first goal of this study was to determine if the GLP-1R agonist exendin-4 reduced fentanyl self-administration and the reinstatement of fentanyl-seeking behavior, an animal model of relapse, in rats. We found that systemic exendin-4 attenuated fentanyl taking and seeking at doses that also produced malaise-like effects in rats. To overcome these adverse effects and enhance the clinical potential of GLP-1R agonists, we recently developed a novel dual agonist of GLP-1Rs and neuropeptide Y2 receptors (Y2Rs), GEP44, that does not produce nausea-like behavior in drug-naïve rats or emesis in drug-naïve shrews. The second goal of this study was to determine if GEP44 reduced fentanyl self-administration and reinstatement with fewer adverse effects compared to exendin-4 alone. In contrast to exendin-4, GEP44 attenuated opioid taking and seeking at a dose that did not suppress food intake or produce adverse malaise-like effects in fentanyl-experienced rats. Taken together, these findings indicate a novel role for GLP-1Rs and Y2Rs in fentanyl reinforcement and highlight a potential new therapeutic approach to treating opioid use disorders.

Peptide YY3-36 concentration in acute- and long-term recovered anorexia nervosa

Purpose

The gut–brain axis could be a possible key factor in the pathophysiology of anorexia nervosa. The neuropeptide peptide YY_3–36, secreted by endocrine L cells of the gastrointestinal tract, is a known regulator of appetite and food intake. The objective of this study was to investigate peptide YY_3–36 plasma concentrations at different stages of anorexia nervosa in a combined cross-sectional and longitudinal design to differentiate between effects of acute undernutrition and more enduring characteristics.

Methods

We measured fasting plasma peptide YY_3–36 concentrations in young patients with acute anorexia nervosa (n = 47) and long-term recovered patients (n = 35) cross-sectionally in comparison to healthy control participants (n = 58), and longitudinally over the course of inpatient treatment. Physical activity was controlled as it may modulate peptide YY secretion.

Results

There was no group difference in peptide YY_3–36 concentration among young acutely underweight anorexia nervosa patients, long-term recovered anorexia nervosa patients, and healthy control participants. Longitudinally, there was no change in peptide YY_3–36 concentration after short-term weight rehabilitation. For acute anorexia nervosa patients at admission to treatment, there was a negative correlation between peptide YY_3–36 concentration and body mass index.

Conclusions

The current study provides additional evidence for a normal basal PYY_3–36 concentration in AN. Future studies should study multiple appetite-regulating peptides and their complex interplay and also use research designs including a food challenge.

Electronic supplementary material

The online version of this article (10.1007/s00394-020-02210-7) contains supplementary material, which is available to authorized users.

Neuroendocrinology of reward in anorexia nervosa and bulimia nervosa: Beyond leptin and ghrelin

The pathophysiology of anorexia nervosa (AN) and bulimia nervosa (BN) are still poorly understood, but psychobiological models have proposed a key role for disturbances in the neuroendocrines that signal hunger and satiety and maintain energy homeostasis. Mounting evidence suggests that many neuroendocrines involved in the regulation of homeostasis and body weight also play integral roles in food reward valuation and learning via their interactions with the mesolimbic dopamine system. Neuroimaging data have associated altered brain reward responses in this system with the dietary restriction and binge eating and purging characteristic of AN and BN. Thus, neuroendocrine dysfunction may contribute to or perpetuate eating disorder symptoms via effects on reward circuitry. This narrative review focuses on reward-related neuroendocrines that are altered in eating disorder populations, including peptide YY, insulin, stress and gonadal hormones, and orexins. We provide an overview of the animal and human literature implicating these neuroendocrines in dopaminergic reward processes and discuss their potential relevance to eating disorder symptomatology and treatment.

PYY3-36: Beyond food intake

The gastrointestinal hormone peptide tyrosine tyrosine 3-36 (PYY(3-36)) has attained broad recognition with respect to its involvement in energy homeostasis and the control of food intake. It is mainly secreted by distal intestinal enteroendocrine L-cells in response to eating and exerts neurally mediated, paracrine and endocrine effects on various target organs. In addition to its gastrointestinal effects, PYY(3-36) has long been known to inhibit food intake. Recent closer examination of the effects of PYY(3-36) revealed that this gut-derived peptide also influences a wide spectrum of behavioral and cognitive functions that are pivotal for basic processes of perception and judgment, including central information processing, salience learning, working memory, and behavioral responding to novelty. Here, we review the effects of PYY(3-36) that go beyond food intake and provide a conceptual framework suggesting that several apparently unrelated behavioral actions of PYY(3-36) may actually reflect different manifestations of modulating the central dopamine system.

Interactions between adiponectin, visfatin, and omentin in subcutaneous and visceral adipose tissues and serum, and correlations with clinical and peripheral metabolic factors

Adiponectin, visfatin, and omentin are adipokines involved in insulin sensitivity. This study aimed to determine interactions between these adipokines in subcutaneous and visceral fat and in serum, and their associations with clinical factors. Adiponectin was present at the highest levels in subcutaneous and visceral fat and serum. Subcutaneous adiponectin showed positive correlations with serum adiponectin and the quantitative insulin sensitivity check index (QUICKI). Serum adiponectin correlated positively with QUICKI and serum omentin-1 but negatively with body weight, BMI, and homeostasis model assessment of insulin resistance (HOMA-IR). Subcutaneous omentin correlated positively with QUICKI but negatively with waist and hip circumferences. Serum omentin-1 correlated positively with QUICKI but negatively with body weight, BMI, waist and hip circumferences, weight gain, and HOMA-IR. Serum visfatin correlated positively with serum omentin-1 and negatively with weight gain. Serum peptide YY (PYY) levels were correlated positively with subcutaneous visfatin but negatively with visceral visfatin. Positive correlations were observed between subcutaneous expression of adiponectin, visfatin, and omentin and visceral expression of these genes. Multiple linear regression analysis showed that serum adiponectin was associated with BMI and QUICKI. Serum omentin-1 could be predicted from BMI, QUICKI, and weight gain. Weight gain, serum adiponectin, omentin-1, and DBP could be used to predict serum visfatin. In conclusion, adiponectin and omentin from subcutaneous fat displayed correlations with decreased obesity and increased insulin sensitivity while visfatin showed an association with serum PYY and weight gain. The expressions of these adipokines were correlated within each type of fat but not between different fat depots.

Gut-Brain Endocrine Axes in Weight Regulation and Obesity Pharmacotherapy

In recent years, the obesity epidemic has developed into a major health crisis both in the United States as well as throughout the developed world. With current treatments limited to expensive, high-risk surgery and minimally efficacious pharmacotherapy, new therapeutic options are urgently needed to combat this alarming trend. This review focuses on the endogenous gut-brain signaling axes that regulate appetite under physiological conditions, and discusses their clinical relevance by summarizing the clinical and preclinical studies that have investigated manipulation of these pathways to treat obesity.

The Y2 receptor agonist PYY(3-36) increases the behavioural response to novelty and acute dopaminergic drug challenge in mice

The gastrointestinal hormone PYY(3-36) is a preferential Y2 neuropeptide Y (NPY) receptor agonist. Recent evidence indicates that PYY(3-36) acts on central dopaminergic pathways, but its influence on dopamine-dependent behaviours remains largely unknown. We therefore explored the effects of peripheral PYY(3-36) treatment on the behavioural responses to novelty and to dopamine-activating drugs in mice. In addition, we examined whether PYY(3-36) administration may activate distinct dopamine and γ-aminobutyric acid (GABA) cell populations in the mesoaccumbal and nigrostriatal pathways. We found that i.p. PYY(3-36) injection led to a dose-dependent increase in novel object exploration. The effective dose of PYY(3-36) (1 μg/100 g body weight) also potentiated the locomotor reaction to the indirect dopamine receptor agonist amphetamine and increased stereotyped climbing/leaning responses following administration of the direct dopamine receptor agonist apomorphine. PYY(3-36) administration did not affect activity of midbrain dopaminergic cells as evaluated by double immuno-enzyme staining of the neuronal early gene product c-Fos with tyrosine hydroxylase. PYY(3-36) did, however, lead to a marked increase in the number of cells co-expressing c-Fos with glutamic acid decarboxylase in the nucleus accumbens and caudate putamen, indicating activation of GABAergic cells in dorsal and ventral striatal areas. Our results support the hypothesis that acute administration of the preferential Y2 receptor agonist PYY(3-36) modulates dopamine-dependent behaviours. These effects do not seem to involve direct activation of midbrain dopamine cells but instead are associated with neuronal activation in the major input areas of the mesoaccumbal and nigrostriatal pathways.

The role of gastrointestinal hormones in hepatic lipid metabolism

Hepatocellular accumulation of free fatty acids (FFAs) in the form of triglycerides constitutes the metabolic basis for the development of nonalcoholic fatty liver disease (NAFLD). Recent data demonstrate that excess FFA hepatocyte storage is likely to lead to lipotoxicity and hepatocyte apoptosis. Hence, FFA-mediated hepatocyte injury is a key contributor to the pathogenesis of nonalcoholic steatohepatitis (NASH). Nonalcoholic steatohepatitis, obesity, type 2 diabetes, essential hypertension, and other common medical problems together comprise metabolic syndrome. Evidence suggests that peptide hormones from the L cells of the distal small intestine, which comprise the core of the enteroendocrine system (EES), play two key roles, serving either as incretins, or as mediators of appetite and satiety in the central nervous system. Recent data related to glucagon-like peptide-1 (GLP-1) and other known L-cell hormones have accumulated due to the increasing frequency of bariatric surgery, which increase delivery of bile salts to the hindgut. Bile acids are a key stimulus for the TGR5 receptor of the L cells. Enhanced bile-salt flow and subsequent EES stimulation may be central to elimination of hepatic steatosis following bariatric surgery. Although GLP-1 is a clinically relevant pharmacological analogue that drives pancreatic β-cell insulin output, GLP-1 analogues also have independent benefits via their effects on hepatocellular FFA metabolism. The authors also discuss recent data regarding the role of the major peptides released by the EES, which promote satiety and modulate energy homeostasis and utilization, as well as those that control fat absorption and intestinal permeability. Taken together, elucidating novel functions for EES-related peptides and pharmacologic development of peptide analogues offer potential far-ranging treatment for obesity-related human disease.

Peripheral activation of the Y2-receptor promotes secretion of GLP-1 and improves glucose tolerance

The effect of peptide tyrosine-tyrosine (PYY) on feeding is well established but currently its role in glucose homeostasis is poorly defined. Here we show in mice, that intraperitoneal (ip) injection of PYY3-36 or Y2R agonist improves nutrient-stimulated glucose tolerance and enhances insulin secretion; an effect blocked by peripheral, but not central, Y2R antagonist administration. Studies on isolated mouse islets revealed no direct effect of PYY3-36 on insulin secretion. Bariatric surgery in mice, enterogastric anastomosis (EGA), improved glucose tolerance in wild-type mice and increased circulating PYY and active GLP-1. In contrast, in Pyy-null mice, post-operative glucose tolerance and active GLP-1 levels were similar in EGA and sham-operated groups. PYY3-36 ip increased hepato-portal active GLP-1 plasma levels, an effect blocked by ip Y2R antagonist. Collectively, these data suggest that PYY3-36 therefore acting via peripheral Y2R increases hepato-portal active GLP-1 plasma levels and improves nutrient-stimulated glucose tolerance.

Shedding pounds after going under the knife: metabolic insights from cutting the gut

Losing weight can pose a challenge, but how to avoid putting those pounds back on can be a real struggle. A major health problem for obese people is that diseases linked to obesity, such as type 2 diabetes and cardiovascular disease, put their lives at risk, even in young individuals. Although bariatric surgery-a surgical method to reduce or modify the gastrointestinal tract-was originally envisioned for the most severe cases of obesity, evidence suggests that the benefit of this procedure may not be limited to the staggering weight loss it causes. Endogenous factors released from the gut, and modified after surgery, may explain why bariatric surgery can be beneficial for obesity-related diseases and why operated individuals successfully maintain the weight loss. In 'Bedside to Bench,' Rachel Larder and Stephen O'Rahilly peruse a human study with dieters who regained weight despite a successful diet. Appetite-regulating hormones in the gut may be responsible for this relapse in the long term. In 'Bench to Bedside,' Keval Chandarana and Rachel Batterham examine how two different methods of bariatric surgery highlight the relevance of gut-derived hormones not only in inducing sustained weight loss but also in improving glucose homeostasis. These insights may open new avenues to bypass the surgery and obtain the same results with targeted drugs.

Role of Y(2) receptors in the regulation of gastric tone in rats

We set out to determine the effect of peptide YY(3-36) (PYY(3-36)) on the gastric muscle tone in conscious rats by measuring intragastric pressure (IGP) during intragastric nutrient drink infusion. After an overnight fast, a chronically implanted gastric fistula was connected to a custom-made nutrient drink infusion system and a catheter to measure IGP. IGP was measured before and during the infusion of a nutrient drink (Nutridrink; 0.5 ml/min) until 10 ml was infused. Rats were treated with PYY(3-36) (0, 33, and 100 pmol·kg(-1)·min(-1)) in combination with a subcutaneous injection of the Y(2) receptor antagonists JNJ31020028 (10 mg/kg) or BIIE0246 (2 mg/kg). Experiments were also performed after subdiaphragmatic vagotomy and after pretreatment with 3 ml of nutrient drink (to mimic a fed state). IGP was compared as the average IGP during nutrient infusion, represented as means ± SE and compared using ANOVA. PYY(3-36) dose dependently increased the IGP during nutrient infusion (4.7 ± 0.3, 5.7 ± 0.5 and 7.3 ± 0.7 mmHg; P < 0.01) while JNJ31020028 and BIIE0246 could block this increase [4.4 ± 0.5 (P < 0.001) and 4.8 ± 0.4 (P < 0.05) mmHg, respectively]. Also in vagotomized rats, PYY(3-36) was able to significantly increase the IGP during, an effect attenuated by JNJ31020028. BIIE0246 and JNJ31020028 were not able to decrease the IGP when no PYY(3-36) was administered. PYY(3-36) increased gastric tone through an Y(2) receptor-mediated mechanism that does not involve the vagus nerve. Y(2) receptor antagonists were not able to decrease gastric tone without exogenous administration of PYY(3-36), indicating that Y(2) receptors do not play a crucial role in the determination of gastric tone in physiological conditions.

Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, and peptide YY in healthy males

Resistance (muscle strengthening) exercise is a key component of exercise recommendations for weight control, yet very little is known about the effects of resistance exercise on appetite. We investigated the effects of resistance and aerobic exercise on hunger and circulating levels of the gut hormones acylated ghrelin and peptide YY (PYY). Eleven healthy male students: age 21.1 +/- 0.3 yr, body mass index 23.1 +/- 0.4 kg/m(2), maximum oxygen uptake 62.1 +/- 1.8 ml.kg(-1).min(-1) (means +/- SE) undertook three, 8-h trials, 1) resistance exercise: a 90-min free weight lifting session followed by a 6.5-h rest period, 2) aerobic exercise: a 60-min run followed by a 7-h rest period, 3) control: an 8-h rest, in a randomized crossover design. Meals were provided 2 and 5 h into each trial. Hunger ratings and plasma concentrations of acylated ghrelin and PYY were measured throughout. Two-way ANOVA revealed significant (P < 0.05) interaction effects for hunger, acylated ghrelin, and PYY, indicating suppressed hunger and acylated ghrelin during aerobic and resistance exercise and increased PYY during aerobic exercise. A significant trial effect was observed for PYY, indicating higher concentrations on the aerobic exercise trial than the other trials (8 h area under the curve: control 1,411 +/- 110, resistance 1,381 +/- 97, aerobic 1,750 +/- 170 pg/ml 8 h). These findings suggest ghrelin and PYY may regulate appetite during and after exercise, but further research is required to establish whether exercise-induced changes in ghrelin and PYY influence subsequent food intake.