Mice lacking δ-opioid receptors resist the development of diet-induced obesity

Current perspectives on brain circuits involved in food addiction-like behaviors

There is an emerging view that the increased availability of energy-dense foods in our society is contributing to excessive food consumption which could lead to food addiction-like behavior. Particularly, compulsive eating patterns are predominant in people suffering from eating disorders (binge-eating disorder, bulimia and anorexia nervosa) and obesity. Phenotypically, the behavioral pattern exhibits a close resemblance to individuals suffering from other forms of addiction (drug, sex, gambling). Growing body of evidence in neuroscience research is showing that excessive consumption of energy-dense foods alters the brain circuits implicated in reward, decision-making, control, habit formation, and emotions that are central to drug addiction. Here, we review the current understanding of the circuits of food addiction-like behaviors and highlight the future possibility of exploring those circuits to combat obesity and eating disorders.

Effects of bariatric surgery and dietary interventions for obesity on brain neurotransmitter systems and metabolism: A systematic review of positron emission tomography (PET) and single-photon emission computed tomography (SPECT) studies

This systematic review collates studies of dietary or bariatric surgery interventions for obesity using positron emission tomography and single-photon emission computed tomography. Of 604 publications identified, 22 met inclusion criteria. Twelve studies assessed bariatric surgery (seven gastric bypass, five gastric bypass/sleeve gastrectomy), and ten dietary interventions (six low-calorie diet, three very low-calorie diet, one prolonged fasting). Thirteen studies examined neurotransmitter systems (six used tracers for dopamine DRD2/3 receptors: two each for 11 C-raclopride, 18 F-fallypride, 123 I-IBZM; one for dopamine transporter, 123 I-FP-CIT; one used tracer for serotonin 5-HT2A receptor, 18 F-altanserin; two used tracers for serotonin transporter, 11 C-DASB or 123 I-FP-CIT; two used tracer for μ-opioid receptor, 11 C-carfentanil; one used tracer for noradrenaline transporter, 11 C-MRB); seven studies assessed glucose uptake using 18 F-fluorodeoxyglucose; four studies assessed regional cerebral blood flow using 15 O-H2 O (one study also used arterial spin labeling); and two studies measured fatty acid uptake using 18 F-FTHA and one using 11 C-palmitate. The review summarizes findings and correlations with clinical outcomes, eating behavior, and mechanistic mediators. The small number of studies using each tracer and intervention, lack of dietary intervention control groups in any surgical studies, heterogeneity in time since intervention and degree of weight loss, and small sample sizes hindered the drawing of robust conclusions across studies.

Effects of Combined Therapy of Olanzapine and Samidorphan on Safety and Metabolic Parameters in Schizophrenia Patients: A Meta-Analysis

Purpose

This meta-analysis intended to evaluate the safety and metabolic effects of the combination of olanzapine (OLZ) and samidorphan (SAM) in the treatment of schizophrenia (SCZ) patients.

Patients and Methods

We searched for the English and Chinese databases for randomized controlled trials (RCTs) on the OLZ combined with SAM for SCZ. The English databases included PubMed, Web of Science, EMbase, and Cochrane Library, however, Chinese databases included Chinese Biology Medicine (CBM), VIP, Wanfang, and China National Knowledge Infrastructure (CNKI). All database searches were due by May 31, 2023. Using Review Manager 5.4 software, a meta-analysis was conducted following a literature review and data extraction.

Results

This study included five RCTs involving 1781 patients. Regarding safety, the meta-analysis revealed that the probability of weight gain was reduced in the OLZ and SAM group than in the OLZ group (RR = 0.83, 95% CI (0.69, 0.99), P < 0.05). Statistically, the incidence of severe adverse safety events, dry mouth, headache, drowsiness, death, and suicidal perception events was insignificant (P > 0.05); in terms of metabolism, compared with the OLZ group, the OLZ plus SAM group reduced total cholesterol (TC) levels (MD = -3.58, 95% CI (-6.81, -0.34), P < 0.05). However, it had no significant effect on metabolic indices, including low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, glucose, and insulin index (P > 0.05).

Conclusion

In patients with SCZ, treatment with the combination of OLZ and SAM decreased the incidence of weight gain adverse events and TC levels; nevertheless, it did not affect other adverse events or metabolic parameters. These findings provide clinicians with evidence-based guidance and support for drug selection. However, it is crucial to confirm these findings through further high-quality research.

Combining samidorphan with olanzapine to mitigate weight gain as a side effect in schizophrenia treatment

Purpose

This article analyzes clinical trials that provide evidence for the positive effects of using samidorphan to mitigate undesirable weight gain in patients diagnosed with schizophrenia who are undergoing treatment with olanzapine.

Views

Weight gain is a prevalent and problematic side effect of antipsychotic drug therapy, particularly in patients with schizophrenia. To address this issue, extensive research is being conducted to explore new drug therapies that can effectively counteract psychotic symptoms while minimizing the occurrence of unwanted side effects. One promising approach involves the addition of weight-loss substances to existing medications. Studies have indicated that opioid receptor antagonists, such as samidorphan, have the potential to facilitate weight loss. Consequently, a novel therapy combining samidorphan and olanzapine has been developed and is discussed in detail in this article.

Conclusions

The combination of samidorphan and olanzapine has demonstrated its ability to effectively reduce weight gain in patients with schizophrenia, without compromising the drug's primary function of alleviating psychotic symptoms. Moreover, the inclusion of samidorphan in the treatment regimen may contribute to a lower risk of cardiovascular events, though it is worth noting that it could also lead to an increase in digestive side effects. Despite this potential drawback, the introduction of this innovative therapy represents a significant advancement in the management of obesity among individuals with schizophrenia.

Hepatic levels of S-adenosylmethionine regulate the adaptive response to fasting

There has been an intense focus to uncover the molecular mechanisms by which fasting triggers the adaptive cellular responses in the major organs of the body. Here, we show that in mice, hepatic S-adenosylmethionine (SAMe)-the principal methyl donor-acts as a metabolic sensor of nutrition to fine-tune the catabolic-fasting response by modulating phosphatidylethanolamine N-methyltransferase (PEMT) activity, endoplasmic reticulum-mitochondria contacts, β-oxidation, and ATP production in the liver, together with FGF21-mediated lipolysis and thermogenesis in adipose tissues. Notably, we show that glucagon induces the expression of the hepatic SAMe-synthesizing enzyme methionine adenosyltransferase α1 (MAT1A), which translocates to mitochondria-associated membranes. This leads to the production of this metabolite at these sites, which acts as a brake to prevent excessive β-oxidation and mitochondrial ATP synthesis and thereby endoplasmic reticulum stress and liver injury. This work provides important insights into the previously undescribed function of SAMe as a new arm of the metabolic adaptation to fasting.

Reduction in Multiple Cardiometabolic Risk Factors With Combined Olanzapine/Samidorphan Compared With Olanzapine: Post Hoc Analyses From a 24-Week Phase 3 Study

BACKGROUND AND HYPOTHESES

Weight gain and adverse cardiometabolic effects often limit the clinical utility of olanzapine. In ENLIGHTEN-2, combining olanzapine with the opioid receptor antagonist samidorphan (OLZ/SAM) mitigated olanzapine-associated weight gain. These analyses tested the hypothesis that OLZ/SAM would be associated with reduced adverse cardiometabolic effects compared with olanzapine.

STUDY DESIGN

This phase 3 double-blind study randomized adults with schizophrenia to OLZ/SAM or olanzapine for 24 weeks. Post hoc analyses assessed changes from baseline to week 24 in cardiometabolic risk parameters, including body mass index (BMI), risk of developing obesity (BMI ≥30 kg/m2) or metabolic syndrome, waist circumference, along with mean and potentially clinically significant changes in blood pressure, glucose, and lipids.

RESULTS

After 24 weeks' treatment, compared with olanzapine, OLZ/SAM was associated with smaller least-squares mean (LSM) changes from baseline in systolic blood pressure (LSM difference, -2.63 mm Hg; 95% CI: -4.78, -0.47), diastolic blood pressure (LSM difference, -0.75 mm Hg; 95% CI: -2.31, 0.80), and BMI (LSM difference, -0.65 kg/m2; 95% CI: -1.01, -0.28). OLZ/SAM treatment was also associated with reduced risk of shifting from normal blood pressure to stage 1/2 hypertension (odds ratio [OR], 0.48; 95% CI: 0.24, 0.96), becoming obese (OR, 0.52; 95% CI: 0.32, 0.82), and developing metabolic syndrome (OR, 0.55; 95% CI: 0.31, 0.99) compared with olanzapine. No treatment group differences were noted for risk of hyperglycemia or hyperlipidemia.

CONCLUSIONS

OLZ/SAM treatment was associated with lower risk of worsening cardiometabolic risk factors related to obesity, hypertension, and metabolic syndrome relative to olanzapine. NCT02694328, https://clinicaltrials.gov/ct2/show/NCT02694328.

Regulation of body weight and food intake by AGRP neurons during opioid dependence and abstinence in mice

Dysregulation of body weight maintenance and opioid dependence are often treated as independent disorders. Here, we assessed the effects of both acute and long-term administration of morphine with and without chemogenetic activation of agouti-related peptide (AGRP)-expressing neurons in the arcuate nucleus (ARCAGRP neurons) to elucidate whether morphine and neuronal activation affect feeding behavior and body weight. First, we characterized interactions of opioids and energy deficit in wild-type mice. We observed that opioid administration attenuated both fasting-induced refeeding and ghrelin-stimulated feeding. Moreover, antagonism of opioid receptors blocked fasting-induced refeeding behavior. Next, we interfaced chemogenetics with opioid dependence. For chemogenetic experiments of ARCAGRP neurons, we conducted a priori behavioral qualification and post-mortem FOS immunostaining verification of arcuate activation following ARCAGRP chemogenetic activation. We administered clozapine during short-term and long-term morphine administration paradigms to determine the effects of dependence on food intake and body weight. We found that morphine occluded feeding behavior characteristic of chemogenetic activation of ARCAGRP neurons. Notably, activation of ARCAGRP neurons attenuated opioid-induced weight loss but did not evoke weight gain during opioid dependence. Consistent with these findings, we observed that morphine administration did not block fasting-induced activation of the ARC. Together, these results highlight the strength of opioidergic effects on body weight maintenance and demonstrate the utility of ARCAGRP neuron manipulations as a lever to influence energy balance throughout the development of opioid dependence.

Samidorphan for the treatment of weight gain associated with olanzapine in patients with schizophrenia and bipolar disorder

INTRODUCTION

Olanzapine (OLZ) is one of the most effective antipsychotic agents, however, its clinical utility has been limited by weight gain. Samidorphan (SAM) is aμ-opioid receptor antagonist and it can reduce the weight gain associated with OLZ. A combination of OLZ and SAM (OLZ/SAM) has been developed to provide the antipsychotic efficacy of OLZ, while mitigating OLZ-associated weight gain.

AREAS COVERED

A comprehensive literature search was conducted in PubMed. Key search terms included SAM and weight gain associated with OLZ. The pharmacological action, clinical efficacy, and safety of SAM were reviewed.

EXPERT OPINION

OLZ can lead to weight gain. SAM is a new drug that acts as an opioid receptor antagonist that can decrease weight gain. SAM mitigates OLZ-associated weight gain while preserving the antipsychotic efficacy of OLZ. Clinical trials have confirmed that OLZ/SAM significantly improved psychotic symptoms, and resulted in significantly less weight gain than OLZ. OLZ/SAM was well tolerated. Therefore, it is a potential new treatment option for schizophrenia.

Olanzapine/Samidorphan: A New Combination Treatment for Schizophrenia and Bipolar I Disorder Intended to Reduce Weight Gain

Olanzapine is a second-generation antipsychotic with established efficacy in several psychiatric disease states, but its use is limited because of weight gain and metabolic side effects. Samidorphan is a novel opioid antagonist that binds to mu-opioid, kappa-opioid, and delta-opioid receptors and is hypothesized to reduce cravings for high-calorie foods thus attenuating antipsychotic-induced weight gain. The combination product olanzapine/samidorphan was approved by the US Food and Drug Administration in June 2021 for the treatment of schizophrenia and bipolar I disorder; this article reviews the pharmacological properties of oral olanzapine/samidorphan and its clinical efficacy and tolerability with a focus on mitigation of olanzapine-induced weight gain in these patient populations. In clinical trials, the combination of olanzapine/samidorphan was associated with significantly less weight gain and smaller increases in waist circumference as compared with olanzapine monotherapy. Olanzapine/samidorphan demonstrated similar efficacy as olanzapine monotherapy and was well tolerated. Weight gain and metabolic side effects associated with olanzapine monotherapy can result in tolerability issues and potentially medication nonadherence. Olanzapine/samidorphan is an effective treatment for schizophrenia and bipolar I disorder with less weight gain than olanzapine monotherapy.

Olanzapine and samidorphan combination treatment: A systematic review

INTRODUCTION

The overarching aim of this review is to synthesize the efficacy, tolerability, and weight-mitigation effects of the olanzapine/samidorphan (OLZ/SAM) combination treatment in adults with schizophrenia and bipolar disorder-I.

METHODS

A systematic search of PubMed, Web of Science, Embase, and The Cochrane Library was conducted on August 15th, 2021. Studies were included if they investigated the use of OLZ/SAM treatment in patients with schizophrenia or bipolar disorder-I, and reported the clinical outcomes: efficacy, change in weight or waist circumference, tolerability, pharmacokinetics, or change in metabolic parameters. A narrative synthesis was undertaken of the data.

RESULTS

Eight studies met the inclusion criteria. All identified studies were conducted in adults with schizophrenia. Compared to OLZ-monotherapy, OLZ/SAM was associated with decreased odds of developing clinically significant (>10%) weight gain (OR=0.50, 95% CI:0.31,0.80; p= 0.003) and increase in waist circumference (risk difference = -17.1% 95% CI:-26.3,-7.8) from baseline measurements respectively. In another study, OLZ was 2.7 times more associated with clinically significant weight gain as compared to OLZ/SAM (OR=2.73, 95% CI:1.11, 6.67; p = 0.023). The clinical efficacy of OLZ/SAM remained similar to OLZ with improved tolerability in both short- and long-term studies with no significantly altered pharmacokinetic properties of the constituent agents.

CONCLUSION

OLZ/SAM-treatment is associated with mitigated weight-gain liability when compared to OLZ-monotherapy in adults with schizophrenia. Additional studies are needed to ascertain patient acceptability, appropriate selection and sequencing of OLZ/SAM in the treatment algorithms for adults with schizophrenia (and BD-I), as well as to determine cost-effectiveness and long-term metabolic effects.

Kappa-Opioid Receptor Blockade Ameliorates Obesity Caused by Estrogen Withdrawal via Promotion of Energy Expenditure through mTOR Pathway

Weight gain is a hallmark of decreased estradiol (E2) levels because of menopause or following surgical ovariectomy (OVX) at younger ages. Of note, this weight gain tends to be around the abdomen, which is frequently associated with impaired metabolic homeostasis and greater cardiovascular risk in both rodents and humans. However, the molecular underpinnings and the neuronal basis for these effects remain to be elucidated. The aim of this study is to elucidate whether the kappa-opioid receptor (k-OR) system is involved in mediating body weight changes associated with E2 withdrawal. Here, we document that body weight gain induced by OVX occurs, at least partially, in a k-OR dependent manner, by modulation of energy expenditure independently of food intake as assessed in Oprk1−/−global KO mice. These effects were also observed following central pharmacological blockade of the k-OR system using the k-OR-selective antagonist PF-04455242 in wild type mice, in which we also observed a decrease in OVX-induced weight gain associated with increased UCP1 positive immunostaining in brown adipose tissue (BAT) and browning of white adipose tissue (WAT). Remarkably, the hypothalamic mTOR pathway plays an important role in regulating weight gain and adiposity in OVX mice. These findings will help to define new therapies to manage metabolic disorders associated with low/null E2 levels based on the modulation of central k-OR signaling.

Opioid antagonism mitigates antipsychotic-associated weight gain: focus on olanzapine

BACKGROUND

The endogenous opioid system affects metabolism, including weight regulation. Evidence from preclinical and clinical studies provides a rationale for targeting this system to mitigate weight-related side effects of antipsychotics. This review describes the role of the opioid system in regulating weight and metabolism, examines the effects of opioid receptor antagonism on those functions, and explores the use of opioid antagonists to mitigate antipsychotic-associated weight gain and/or metabolic effects.

METHODS

A PubMed literature search was conducted to identify representative opioid antagonists and associated preclinical and clinical studies examining their potential for the regulation of weight and metabolism.

RESULTS

The mu opioid receptor (MOR), delta opioid receptor (DOR), and kappa opioid receptor (KOR) types have overlapping but distinct patterns of central and peripheral expression, and each contributes to the regulation of body weight and metabolism. Three representative opioid antagonists (eg, naltrexone, samidorphan, and LY255582) were identified for illustration. These opioid antagonists differed in their receptor binding and pharmacokinetic profiles, including oral bioavailability, systemic clearance, and half-life, and were associated with varying effects on food intake, energy utilization, and metabolic dysregulation.

CONCLUSIONS

Preclinical and clinical data suggest that antagonism of the endogenous opioid system is a mechanism to address antipsychotic-associated weight gain and metabolic dysregulation. However, evidence suggests that the differing roles of MOR, DOR, and KOR in metabolism, together with the differences in receptor binding, pharmacokinetic, and functional activity profiles of the opioid receptor antagonists discussed in this review, likely contribute to their differential pharmacodynamic effects and clinical outcomes observed regarding antipsychotic-associated weight gain.

Angiocrine polyamine production regulates adiposity

Reciprocal interactions between endothelial cells (ECs) and adipocytes are fundamental to maintain white adipose tissue (WAT) homeostasis, as illustrated by the activation of angiogenesis upon WAT expansion, a process that is impaired in obesity. However, the molecular mechanisms underlying the crosstalk between ECs and adipocytes remain poorly understood. Here, we show that local production of polyamines in ECs stimulates adipocyte lipolysis and regulates WAT homeostasis in mice. We promote enhanced cell-autonomous angiogenesis by deleting Pten in the murine endothelium. Endothelial Pten loss leads to a WAT-selective phenotype, characterized by reduced body weight and adiposity in pathophysiological conditions. This phenotype stems from enhanced fatty acid β-oxidation in ECs concomitant with a paracrine lipolytic action on adipocytes, accounting for reduced adiposity. Combined analysis of murine models, isolated ECs and human specimens reveals that WAT lipolysis is mediated by mTORC1-dependent production of polyamines by ECs. Our results indicate that angiocrine metabolic signals are important for WAT homeostasis and organismal metabolism.

In vivo Characterization of the Opioid Receptor-Binding Profiles of Samidorphan and Naltrexone in Rats: Comparisons at Clinically Relevant Concentrations

INTRODUCTION

The atypical antipsychotic olanzapine is approved for the treatment of schizophrenia and bipolar I disorder; however, weight gain and metabolic dysregulation associated with olanzapine therapy have limited its clinical utility. In clinical studies, treatment with the combination of olanzapine and the opioid receptor antagonist samidorphan (OLZ/SAM) mitigated olanzapine-associated weight gain while providing antipsychotic efficacy similar to that of olanzapine. Although samidorphan is structurally similar to the opioid receptor antagonist naltrexone, the two differ in their pharmacokinetics and in vitro binding affinities to mu, delta, and kappa opioid receptors (MOR, DOR, and KOR, respectively). The objective of this series of nonclinical studies was to compare the in vivo binding profiles of samidorphan and naltrexone and their receptor occupancies at MOR, DOR, and KOR in rat brains.

METHODS

Male rats were injected with samidorphan or naltrexone to obtain total and unbound plasma and brain concentrations representing levels observed in humans at clinically relevant oral doses. Subsequently, samidorphan and naltrexone brain receptor occupancy at MOR, DOR, and KOR was measured using ultra-performance liquid chromatography and high-resolution accurate-mass mass spectrometry.

RESULTS

A dose-dependent increase in samidorphan occupancy was observed at MOR, DOR, and KOR (EC₅₀: 5.1, 54.7, and 42.9 nM, respectively). Occupancy of naltrexone at MOR (EC₅₀: 15.5 nM) and KOR was dose dependent; minimal DOR occupancy was detected. At the clinically relevant unbound brain concentration of 23.1 nM, samidorphan bound to MOR, DOR, and KOR with 93.2%, 36.1%, and 41.9% occupancy, respectively. At 33.5 nM, naltrexone bound to MOR and KOR with 79.4% and 9.4% occupancy, respectively, with no binding at DOR.

DISCUSSION

At clinically relevant concentrations, samidorphan occupied MOR, DOR, and KOR, whereas naltrexone occupied only MOR and KOR. The binding profile of samidorphan differs from that of naltrexone, with potential clinical implications.

An Evidence-Based Review of OLZ/SAM for Treatment of Adults with Schizophrenia or Bipolar I Disorder

Olanzapine effectively treats schizophrenia and bipolar I disorder (BD-I); however, its use is limited by the risk of significant weight gain and metabolic effects. OLZ/SAM, a combination of olanzapine and samidorphan, was recently approved in the United States for the treatment of adults with schizophrenia or BD-I. OLZ/SAM provides the efficacy of olanzapine while mitigating olanzapine-associated weight gain through opioid-receptor blockade. Here, we summarize OLZ/SAM clinical data characterizing pharmacokinetics, antipsychotic efficacy, weight mitigation efficacy, safety, and long-term treatment effects. In an acute exacerbation of schizophrenia, OLZ/SAM and olanzapine provided similar symptom improvements versus placebo at week 4. In stable outpatients with schizophrenia, OLZ/SAM treatment resulted in significantly less weight gain, reducing the risk for clinically significant weight gain and waist circumference increases of ≥5 cm by half, compared with olanzapine at week 24. Based on open-label extension studies, OLZ/SAM is safe and well tolerated for up to 3.5 years of treatment, while maintaining schizophrenia symptom control and stabilizing weight. The olanzapine component of OLZ/SAM was bioequivalent to branded olanzapine (Zyprexa); adjunctive OLZ/SAM had no clinically significant effects on lithium or valproate pharmacokinetics. Additionally, OLZ/SAM had no clinically relevant effect on electrocardiogram parameters in a dedicated thorough QT study. Overall, safety and tolerability findings from clinical studies with OLZ/SAM indicate a similar safety profile to that of olanzapine, with the exception of less weight gain. As OLZ/SAM contains the opioid antagonist samidorphan, it is contraindicated in patients using opioids and in those undergoing acute opioid withdrawal. Clinical trial results from more than 1600 subjects support the use of OLZ/SAM as a new treatment option for patients with schizophrenia or BD-I.

A phase 3, multicenter study to assess the 1-year safety and tolerability of a combination of olanzapine and samidorphan in patients with schizophrenia: Results from the ENLIGHTEN-2 long-term extension

AIM

A combination of olanzapine and samidorphan (OLZ/SAM) is in development for the treatment of patients with schizophrenia or bipolar I disorder and is intended to provide the efficacy of olanzapine while mitigating olanzapine-associated weight gain. This 52-week open-label extension (NCT02873208; ENLIGHTEN-2-EXT) assessed the long-term safety and tolerability of OLZ/SAM in patients with schizophrenia.

METHODS

Patients completing the 24-week randomized, double-blind, phase 3 ENLIGHTEN-2 study (NCT02694328) comparing weight change from baseline to week 24 with OLZ/SAM versus olanzapine were eligible to enroll in the 52-week ENLIGHTEN-2-EXT study. Assessments included adverse events (AEs; each visit), weight/waist circumference (every other week for the first 8 weeks, then every 4 weeks thereafter), metabolic laboratory parameters (weeks 4, 12, 24, 36, and 52), Positive and Negative Syndrome Scale (PANSS) scores (weeks 2, 4, 8, 12, 24, 36, and 52), and Clinical Global Impression-Severity (CGI-S) scores (weeks 2 and 4, then every 4 weeks thereafter through week 48, and at week 52). Analyses were based on observed results using descriptive statistics. Baseline was relative to the first OLZ/SAM dose in the extension study.

RESULTS

In total, 265 patients were enrolled and received at least 1 dose of OLZ/SAM; 167 (63.0%) completed the 52-week extension study. Common AEs (≥5%) were weight decreased (n = 23; 8.7%), extra dose administered (n = 21; 7.9%), headache (n = 18; 6.8%), and weight increased (n = 16; 6.0%). At week 52, the mean (SD) change from baseline for weight and waist circumference was -0.03 (6.17) kg and - 0.35 (6.12) cm, respectively. Changes in fasting lipid and glycemic parameters were generally small and remained stable over 52 weeks. During the extension, PANSS total scores remained stable, and at week 52, 81.3% of patients had CGI-S scores of 3 or less, reflecting mild illness severity.

CONCLUSIONS

OLZ/SAM was generally well tolerated over 52 weeks. Weight, waist circumference, metabolic laboratory parameters, and schizophrenia symptoms remained stable throughout the study.

Population Pharmacokinetics of Olanzapine and Samidorphan When Administered in Combination in Healthy Subjects and Patients With Schizophrenia

A combination of olanzapine and samidorphan was recently approved by the US Food and Drug Administration for the treatment of patients with schizophrenia or bipolar I disorder. Population pharmacokinetic models for olanzapine and samidorphan were developed using data from 11 clinical studies in healthy subjects or patients with schizophrenia. A 2‐compartment disposition model with first‐order absorption and elimination and a lag time for absorption adequately described concentration‐time profiles of both olanzapine and samidorphan. Age, sex, race, smoking status, and body weight were identified as covariates that impacted the pharmacokinetics of olanzapine. A moderate effect of body weight on samidorphan pharmacokinetics was identified by the model but was not considered clinically meaningful. The effects of food, hepatic or renal impairment, and coadministration with rifampin on the pharmacokinetics of olanzapine and samidorphan, as estimated by the population pharmacokinetic analysis, were consistent with findings from dedicated clinical studies designed to evaluate these specific covariates of interest. Food intake did not have a clinically relevant effect on the pharmacokinetics of olanzapine or samidorphan. Consistent with the known metabolic pathways for olanzapine (primarily via uridine 5′‐diphospho‐glucuronosyltransferase–mediated direct glucuronidation and cytochrome P450 [CYP]‐mediated oxidation) and for samidorphan (predominantly mediated by CYP3A4), coadministration of olanzapine and samidorphan with rifampin, a strong inducer of CYP3A4 and an inducer of uridine 5′‐diphospho‐glucuronosyltransferase enzymes, significantly decreased the systemic exposure of both olanzapine and samidorphan. Severe renal impairment or moderate hepatic impairment resulted in a modest increase in olanzapine and samidorphan exposure.

Effects of Olanzapine Combined With Samidorphan on Weight Gain in Schizophrenia: A 24-Week Phase 3 Study

OBJECTIVE

A combination of olanzapine and the opioid receptor antagonist samidorphan is under development for the treatment of schizophrenia and bipolar I disorder. The single-tablet combination treatment is intended to provide the efficacy of olanzapine while mitigating olanzapine-associated weight gain. In this phase 3 double-blind trial, the authors evaluated the weight profile of combined olanzapine/samidorphan compared with olanzapine in patients with schizophrenia.

METHODS

Adults (ages 18‒55 years) with schizophrenia were randomly assigned to receive either combination treatment with olanzapine and samidorphan or olanzapine treatment for 24 weeks. Primary endpoints were percent change from baseline in body weight and proportion of patients with ≥10% weight gain at week 24. The key secondary endpoint was the proportion of patients with ≥7% weight gain. Waist circumference and fasting metabolic laboratory parameters were also measured.

RESULTS

Of 561 patients who underwent randomization (olanzapine/samidorphan combination, N=280; olanzapine, N=281), 538 had at least one postbaseline weight assessment. At week 24, the least squares mean percent weight change from baseline was 4.21% (SE=0.68) in the olanzapine/samidorphan group and 6.59% (SE=0.67) in the olanzapine group (the difference of -2.38% [SE=0.76] was significant). Significantly fewer patients in the olanzapine/samidorphan combination group compared with the olanzapine group had weight gain ≥10% (17.8% and 29.8%, respectively; number needed to treat [NNT]=7.29; odds ratio=0.50) and weight gain ≥7% (27.5% and 42.7%, respectively; NNT=6.29; odds ratio=0.50). Increases in waist circumference were smaller in the olanzapine/samidorphan combination group compared with the olanzapine group. Schizophrenia symptom improvement was similar between treatment groups. Adverse events (in ≥10% of the groups) in the olanzapine/samidorphan and olanzapine groups included weight gain (24.8% and 36.2%), somnolence (21.2% and 18.1%), dry mouth (12.8% and 8.0%), and increased appetite (10.9% and 12.3%). Metabolic changes were small and similar between treatments.

CONCLUSIONS

Olanzapine/samidorphan combination treatment was associated with significantly less weight gain and smaller increases in waist circumference than olanzapine and was well tolerated. The antipsychotic efficacy of the combination treatment was similar to that of olanzapine monotherapy.

FBNTI, a DOR-Selective Antagonist That Allosterically Activates MOR within a MOR-DOR Heteromer

This report describes the unique pharmacological profile of FBNTI, a potent DOR antagonist that acts as a MOR agonist via an allosteric mechanism. Binding of FBNTI to opioid receptors expressed in HEK 293 cells revealed a 190-fold greater affinity for DOR (K_i = 0.84 nM) over MOR (K_i = 160 nM). In mice, intrathecal FBNTI produced potent antinociception (ED₅₀ = 46.9 pmol/mouse), which was antagonized by selective MOR antagonists (CTOP, β-FNA). Autoantagonism of the MOR agonism by FBNTI was observed above the ED₇₅ dose, suggesting antagonism of activated MOR. That FBNTI is devoid of agonism in DOR knockout mice is consistent with allosteric activation of the MOR protomer via FBNTI bound to within a MOR-DOR heteromer. This proposed mechanism is supported by calcium mobilization assays, which indicate that FBNTI selectively activates the MOR-DOR heteromer and functionally antagonizes the MOR protomer at >ED₇₅. The unprecedented mode of MOR activation by FBNTI may be responsible for the lack of tolerance after intrathecal (i.t.) administration. FBNTI was highly effective upon topical administration to the ipsolateral hind paw in the Hargreaves assay (EC₅₀ = 0.17 ± 0.08 μM) and without significant contralateral activity, suggesting a lack of systemic exposure.

Neuroimaging of Sex/Gender Differences in Obesity: A Review of Structure, Function, and Neurotransmission

While the global prevalence of obesity has risen among both men and women over the past 40 years, obesity has consistently been more prevalent among women relative to men. Neuroimaging studies have highlighted several potential mechanisms underlying an individual’s propensity to become obese, including sex/gender differences. Obesity has been associated with structural, functional, and chemical alterations throughout the brain. Whereas changes in somatosensory regions appear to be associated with obesity in men, reward regions appear to have greater involvement in obesity among women than men. Sex/gender differences have also been observed in the neural response to taste among people with obesity. A more thorough understanding of these neural and behavioral differences will allow for more tailored interventions, including diet suggestions, for the prevention and treatment of obesity.

Genetic contributions to the etiology of anorexia nervosa: New perspectives in molecular diagnosis and treatment

Background

Anorexia nervosa is a multifactorial eating disorder that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Long‐term effects include organ failure, disability, and in extreme cases, even death.

Methods

Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

Results

Anorexia nervosa often has a familial background and shows strong heritability. Various genetic studies along with genome‐wide association studies have identified several genetic loci involved in molecular pathways that might lead to anorexia.

Conclusion

Anorexia nervosa is an eating disorder with a strong genetic component that contributes to its etiology. Various genetic approaches might help in the molecular diagnosis of this disease and in devising novel therapeutic options.

Anorexia nervosa is a multifactorial eating disorder with a strong genetic component that manifests with self‐starvation, extreme anxiety, hyperactivity, and amenorrhea. Through a literature search, here we summarize what is known about the molecular etiology of anorexia nervosa and propose genetic testing for this condition.

The Role of Prenatal Melatonin in the Regulation of Childhood Obesity

There is a growing awareness that pregnancy can set the foundations for an array of diverse medical conditions in the offspring, including obesity. A wide assortment of factors, including genetic, epigenetic, lifestyle, and diet can influence foetal outcomes. This article reviews the role of melatonin in the prenatal modulation of offspring obesity. A growing number of studies show that many prenatal risk factors for poor foetal metabolic outcomes, including gestational diabetes and night-shift work, are associated with a decrease in pineal gland-derived melatonin and associated alterations in the circadian rhythm. An important aspect of circadian melatonin’s effects is mediated via the circadian gene, BMAL1, including in the regulation of mitochondrial metabolism and the mitochondrial melatoninergic pathway. Alterations in the regulation of mitochondrial metabolic shifts between glycolysis and oxidative phosphorylation in immune and glia cells seem crucial to a host of human medical conditions, including in the development of obesity and the association of obesity with the risk of other medical conditions. The gut microbiome is another important hub in the pathoetiology and pathophysiology of many medical conditions, with negative consequences mediated by a decrease in the short-chain fatty acid, butyrate. The effects of butyrate are partly mediated via an increase in the melatoninergic pathway, indicating interactions of the gut microbiome with melatonin. Some of the effects of melatonin seem mediated via the alpha 7 nicotinic receptor, whilst both melatonin and butyrate may regulate obesity through the opioidergic system. Oxytocin, a recently recognized inhibitor of obesity, may also be acting via the opioidergic system. The early developmental regulation of these processes and factors by melatonin are crucial to the development of obesity and many diverse comorbidities.

Activation of Kappa Opioid Receptor Regulates the Hypothermic Response to Calorie Restriction and Limits Body Weight Loss

Mammals maintain a nearly constant core body temperature (T_b) by balancing heat production and heat dissipation. This comes at a high metabolic cost that is sustainable if adequate calorie intake is maintained. When nutrients are scarce or experimentally reduced such as during calorie restriction (CR), endotherms can reduce energy expenditure by lowering T_b [1-6]. This adaptive response conserves energy, limiting the loss of body weight due to low calorie intake [7-10]. Here we show that this response is regulated by the kappa opioid receptor (KOR). CR is associated with increased hypothalamic levels of the endogenous opioid Leu-enkephalin, which is derived from the KOR agonist precursor dynorphin [11]. Pharmacological inhibition of KOR, but not of the delta or the mu opioid receptor subtypes, fully blocked CR-induced hypothermia and increased weight loss during CR independent of calorie intake. Similar results were seen with DIO mice subjected to CR. In contrast, inhibiting KOR did not change T_b in animals fed ad libitum (AL). Chemogenetic inhibition of KOR neurons in the hypothalamic preoptic area reduced the CR-induced hypothermia, whereas chemogenetic activation of prodynorphin-expressing neurons in the arcuate or the parabrachial nucleus lowered T_b. These data indicate that KOR signaling is a pivotal regulator of energy homeostasis and can affect body weight during dieting by modulating T_b and energy expenditure.

Samidorphan mitigates olanzapine-induced weight gain and metabolic dysfunction in rats and non-human primates

BACKGROUND

Olanzapine, regarded as one of the most efficacious antipsychotic medications for the treatment of schizophrenia, is associated with a high risk of weight gain and metabolic dysfunction. ALKS 3831, a clinical candidate for treatment of schizophrenia, is a combination of olanzapine and samidorphan, an opioid receptor antagonist. The addition of samidorphan is intended to mitigate weight gain and the metabolic dysregulation associated with the use of olanzapine.

METHODS

Non-clinical studies were conducted to assess the metabolic effects of olanzapine and samidorphan alone and in combination at clinically relevant exposure levels.

RESULTS

Chronic olanzapine administration in male and female rats shifted body composition by increasing adipose mass, which was accompanied by an increase in the rate of weight gain in female rats. Co-administration of samidorphan normalized body composition in both sexes and attenuated weight gain in female rats. In hyperinsulinemic euglycemic clamp experiments conducted prior to measurable changes in weight and/or body composition, olanzapine decreased hepatic insulin sensitivity and glucose uptake in muscle while increasing uptake in adipose tissue. Samidorphan appeared to normalize glucose utilization in both tissues, but did not restore hepatic insulin sensitivity. In subsequent studies, samidorphan normalized olanzapine-induced decreases in whole-body glucose clearance following bolus insulin administration. Results from experiments in female monkeys paralleled the effects in rats.

CONCLUSIONS

Olanzapine administration increased weight gain and adiposity, both of which were attenuated by samidorphan. Furthermore, the combination of olanzapine and samidorphan prevented olanzapine-induced insulin insensitivity. Collectively, these data indicate that samidorphan mitigates several metabolic abnormalities associated with olanzapine in both the presence and the absence of weight gain.

Central nicotine induces browning through hypothalamic κ opioid receptor

Increased body weight is a major factor that interferes with smoking cessation. Nicotine, the main bioactive compound in tobacco, has been demonstrated to have an impact on energy balance, since it affects both feeding and energy expenditure at the central level. Among the central actions of nicotine on body weight, much attention has been focused on its effect on brown adipose tissue (BAT) thermogenesis, though its effect on browning of white adipose tissue (WAT) is unclear. Here, we show that nicotine induces the browning of WAT through a central mechanism and that this effect is dependent on the κ opioid receptor (KOR), specifically in the lateral hypothalamic area (LHA). Consistent with these findings, smokers show higher levels of uncoupling protein 1 (UCP1) expression in WAT, which correlates with smoking status. These data demonstrate that central nicotine-induced modulation of WAT browning may be a target against human obesity.

Nicotine reduces food intake and increases energy expenditure in brown adipose tissue. Here the authors show that nicotine also induces white adipose tissue browning via central kappa opioid receptor action.

Effect of hepatic and renal impairment on the pharmacokinetics of olanzapine and samidorphan given in combination as a bilayer tablet

Background

A combination of olanzapine and samidorphan (OLZ/SAM) is in development to provide the established antipsychotic efficacy of olanzapine while mitigating olanzapine-induced weight gain.

Methods

Two multicenter, open-label, parallel-cohort studies were performed to evaluate the effect of moderate hepatic impairment (Child-Pugh score 7–9 [class B]; study 1) and severe renal impairment (estimated glomerular filtration rate: 15–29 mL/min/1.73 m²; study 2) on the pharmacokinetics, safety, and tolerability of a single dose of OLZ/SAM 5/10 mg.

Results

There was a 1.67-fold increase in area under the plasma concentration-time curve from time 0 to infinity (AUC_0-∞) and a 2.17-fold increase in maximum plasma concentration (C_max) of olanzapine, and a 1.52-fold increase in AUC_0-∞ and a 1.63-fold increase in C_max of samidorphan, in subjects with moderate hepatic impairment compared with healthy control subjects. Compared with healthy control subjects, subjects with severe renal impairment had a 33% and 56% reduction in clearance, a 1.51- and 2.31-fold increase in AUC_0-∞, and a 1.32- and 1.37-fold increase in C_max of olanzapine and samidorphan, respectively.

Conclusion

OLZ/SAM 5/10 mg was generally well tolerated under the conditions of the studies, with a safety profile consistent with that observed in other clinical studies of OLZ/SAM.

Hypothalamic dopamine signaling regulates brown fat thermogenesis

Dopamine signaling is a crucial part of the brain reward system and can affect feeding behavior. Dopamine receptors are also expressed in the hypothalamus, which is known to control energy metabolism in peripheral tissues. Here we show that pharmacological or chemogenetic stimulation of dopamine receptor 2 (D2R) expressing cells in the lateral hypothalamic area (LHA) and the zona incerta (ZI) decreases body weight and stimulates brown fat activity in rodents in a feeding-independent manner. LHA/ZI D2R stimulation requires an intact sympathetic nervous system and orexin system to exert its action and involves inhibition of PI3K in the LHA/ZI. We further demonstrate that, as early as 3 months after onset of treatment, patients treated with the D2R agonist cabergoline experience an increase in energy expenditure that persists for one year, leading to total body weight and fat loss through a prolactin-independent mechanism. Our results may provide a mechanistic explanation for how clinically used D2R agonists act in the CNS to regulate energy balance.

Endogenous opioid modulation of food intake and body weight: Implications for opioid influences upon motivation and addiction

This review is part of a special issue dedicated to Opioid addiction, and examines the influential role of opioid peptides, opioid receptors and opiate drugs in mediating food intake and body weight control in rodents. This review postulates that opioid mediation of food intake was an example of "positive addictive" properties that provide motivational drives to maintain opioid-seeking behavior and that are not subject to the "negative addictive" properties associated with tolerance, dependence and withdrawal. Data demonstrate that opiate and opioid peptide agonists stimulate food intake through homeostatic activation of sensory, metabolic and energy-related In contrast, general, and particularly mu-selective, opioid receptor antagonists typically block these homeostatically-driven ingestive behaviors. Intake of palatable and hedonic food stimuli is inhibited by general, and particularly mu-selective, opioid receptor antagonists. The selectivity of specific opioid agonists to elicit food intake was confirmed through the use of opioid receptor antagonists and molecular knockdown (antisense) techniques incapacitating specific exons of opioid receptor genes. Further extensive evidence demonstrated that homeostatic and hedonic ingestive situations correspondingly altered the levels and expression of opioid peptides and opioid receptors. Opioid mediation of food intake was controlled by a distributed brain network intimately related to both the appetitive-consummatory sites implicated in food intake as well as sites intimately involved in reward and reinforcement. This emergent system appears to sustain the "positive addictive" properties providing motivational drives to maintain opioid-seeking behavior.

Mitigation of Olanzapine-Induced Weight Gain With Samidorphan, an Opioid Antagonist: A Randomized Double-Blind Phase 2 Study in Patients With Schizophrenia

OBJECTIVE

Preclinical evidence and data from a proof-of-concept study in healthy volunteers suggest that samidorphan, an opioid antagonist, mitigates weight gain associated with olanzapine. This study prospectively compared combination therapy of olanzapine plus either samidorphan or placebo for the treatment of schizophrenia.

METHODS

This was an international, multicenter, randomized phase 2 study of olanzapine plus samidorphan in patients with schizophrenia. The study had a 1-week open-label olanzapine lead-in period followed by a 12-week double-blind treatment phase in which patients were randomly assigned in a 1:1:1:1 ratio to receive olanzapine plus placebo (N=75) or olanzapine plus 5 mg (N=80), 10 mg (N=86), or 20 mg (N=68) of samidorphan. The primary aims were to confirm that the antipsychotic efficacy of olanzapine plus samidorphan was comparable to olanzapine plus placebo, to assess the effect of combining olanzapine with samidorphan on olanzapine-induced weight gain, and to assess the overall safety and tolerability of olanzapine plus samidorphan.

RESULTS

Antipsychotic efficacy, as assessed by total score on the Positive and Negative Syndrome Scale (PANSS), was equivalent across all treatment groups. Treatment with olanzapine plus samidorphan resulted in a statistically significant lower weight gain (37% lower weight gain compared with olanzapine plus placebo). The least square mean percent change from baseline in body weight was 4.1% (2.9 kg) for the olanzapine plus placebo group and 2.6% (1.9 kg) for the olanzapine plus samidorphan group (2.8% [2.1 kg] for the 5 mg group, 2.1% [1.5 kg] for the 10 mg group, and 2.9% [2.2 kg] for the 20 mg group). Adverse events reported at a frequency ≥5% in any of the olanzapine plus samidorphan groups and occurring at a rate ≥2 times greater than in the olanzapine plus placebo group were somnolence, sedation, dizziness, and constipation. Other safety measures were comparable between the olanzapine plus samidorphan groups and the olanzapine plus placebo group.

CONCLUSIONS

The antipsychotic efficacy of olanzapine plus samidorphan was equivalent to that of olanzapine plus placebo, and olanzapine plus samidorphan was associated with clinically meaningful and statistically significant mitigation of weight gain compared with olanzapine plus placebo. Olanzapine plus samidorphan was generally well tolerated, with a safety profile similar to olanzapine plus placebo.

Exciting advances in GPCR-based drugs discovery for treating metabolic disease and future perspectives

INTRODUCTION

Current pharmacological therapies that target single receptors have limited efficacy for the treatment of diabetes and obesity. Novel approaches with hybrid peptides that activate more than one receptor at once to generate beneficial effects through synergistic effects have shown promising results. Several unimolecular dual and tri-agonists, mainly associated with GPCR like GLP-1/GCG/GIP receptors, have shown exceptional efficacy in preclinical models, and are currently being evaluated in clinical trials to investigate their safety and beneficial effects in humans. Areas covered: Herein, the authors review the development of drugs used in the treatment of metabolic disease, from single agonists to the new generation of tri-agonist peptides and compile the latest knowledge available on GPCR-based drug discovery. The authors also provide the reader with their expert perspectives on this exciting area of drug development. Expert opinion: The co-agonists that have been clinically tested so far have been well tolerated and reduce body weight as well as fasting glucose levels in patients with Type 2 Diabetes Mellitus to a higher degree than single agonists alone. The promising data collected so far now warrant large scale randomized clinical trials to assess whether a unimolecular polypharmacy-based approach could translate into safe and efficacious treatments for obesity and its comorbidities.

p53 in AgRP neurons is required for protection against diet-induced obesity via JNK1

p53 is a well-known tumor suppressor that has emerged as an important player in energy balance. However, its metabolic role in the hypothalamus remains unknown. Herein, we show that mice lacking p53 in agouti-related peptide (AgRP), but not proopiomelanocortin (POMC) or steroidogenic factor-1 (SF1) neurons, are more prone to develop diet-induced obesity and show reduced brown adipose tissue (BAT) thermogenic activity. AgRP-specific ablation of p53 resulted in increased hypothalamic c-Jun N-terminal kinase (JNK) activity before the mice developed obesity, and central inhibition of JNK reversed the obese phenotype of these mice. The overexpression of p53 in the ARC or specifically in AgRP neurons of obese mice decreased body weight and stimulated BAT thermogenesis, resulting in body weight loss. Finally, p53 in AgRP neurons regulates the ghrelin-induced food intake and body weight. Overall, our findings provide evidence that p53 in AgRP neurons is required for normal adaptations against diet-induced obesity.

Emerging studies suggest that p53 is an important regulator of energy metabolism, yet there is little known about the metabolic function of this tumor suppressor in the hypothalamus. Here, authors illustrate that p53, specifically in AgRP neurons, is required for adaptation to diet-induced obesity.

Delta Opioid Receptors and Cardioprotection

The opioid receptor family, with associated endogenous ligands, has numerous roles throughout the body. Moreover, the delta opioid receptor (DORs) has various integrated roles within the physiological systems, including the cardiovascular system. While DORs are important modulators of cardiovascular autonomic balance, they are well-established contributors to cardioprotective mechanisms. Both endogenous and exogenous opioids acting upon DORs have roles in myocardial hibernation and protection against ischaemia-reperfusion (I-R) injury. Downstream signalling mechanisms governing protective responses alternate, depending on the timing and duration of DOR activation. The following review describes models and mechanisms of DOR-mediated cardioprotection, the impact of co-morbidities and challenges for clinical translation.

Role of DOR in neuronal plasticity changes promoted by food-seeking behaviour

Several lines of evidence support that food overconsumption may be related to the role of the endogenous opioid system in the control of food palatability. The opioid system, and particularly the delta opioid receptor (DOR), plays a crucial role in the regulation of food rewarding properties. In our study, we used operant conditioning maintained by chocolate-flavoured pellets to investigate the role of DOR in the motivation for palatable food and the structural plasticity changes promoted by this behaviour. For this purpose, we evaluated the specific role of this receptor in the behavioural and neuroplastic changes induced by palatable food in the prefrontal cortex (PFC), hippocampus (HCP) and nucleus accumbens (NAc) in constitutive knockout (KO) mice deficient in DOR. Mutant mice and their wild-type littermates were trained to obtain chocolate-flavoured pellets on fixed ratio 1 (FR1), FR5 and progressive ratio (PR) schedule of reinforcement. No significant differences between genotypes were revealed on operant behaviour acquisition in FR1. DOR knockout mice displayed lower number of active lever-presses than wild-type mice on FR5, and a similar decrease was revealed in DOR KO mice in the breaking point during the PR. This operant training to obtain palatable food increased dendritic spine density in the PFC, HCP and NAc shell of wild-type, but these plasticity changes were abolished in DOR KO mice. Our results support the hypothesis that DOR regulates the reinforcing effects and motivation for palatable food through neuroplastic changes in specific brain reward areas.

Novel and ultra-rare damaging variants in neuropeptide signaling are associated with disordered eating behaviors

Objective

Eating disorders develop through a combination of genetic vulnerability and environmental stress, however the genetic basis of this risk is unknown.

Methods

To understand the genetic basis of this risk, we performed whole exome sequencing on 93 unrelated individuals with eating disorders (38 restricted-eating and 55 binge-eating) to identify novel damaging variants. Candidate genes with an excessive burden of predicted damaging variants were then prioritized based upon an unbiased, data-driven bioinformatic analysis. One top candidate pathway was empirically tested for therapeutic potential in a mouse model of binge-like eating.

Results

An excessive burden of novel damaging variants was identified in 186 genes in the restricted-eating group and 245 genes in the binge-eating group. This list is significantly enriched (OR = 4.6, p<0.0001) for genes involved in neuropeptide/neurotrophic pathways implicated in appetite regulation, including neurotensin-, glucagon-like peptide 1- and BDNF-signaling. Administration of the glucagon-like peptide 1 receptor agonist exendin-4 significantly reduced food intake in a mouse model of ‘binge-like’ eating.

Conclusions

These findings implicate ultra-rare and novel damaging variants in neuropeptide/neurotropic factor signaling pathways in the development of eating disorder behaviors and identify glucagon-like peptide 1-receptor agonists as a potential treatment for binge eating.

Genome-wide association analysis and functional annotation of positional candidate genes for feed conversion efficiency and growth rate in pigs

Feed conversion efficiency is a measure of how well an animal converts feed into live weight and it is typically expressed as feed conversion ratio (FCR). FCR and related traits like growth rate (e.g. days to 110 kg—D110) are of high interest for animal breeders, farmers and society due to implications on animal performance, feeding costs and environmental sustainability. The objective of this study was to identify genomic regions associated with FCR and D110 in pigs. A total of 952 terminal line boars, showing an individual variation in FCR, were genotyped using 60K SNP-Chips. Markers were tested for associations with estimated breeding values (EBV) for FCR and D110. For FCR, the largest number of associated SNPs was located on chromosomes 4 (30 SNPs), 1 (25 SNPs), X (15 SNPs) and 6 (12 SNPs). The most prominent genomic regions for D110 were identified on chromosomes 15 (10 SNPs), 1 and 4 (both 9 SNPs). The most significantly associated SNPs for FCR and D110 mapped 129.8 Kb from METTL11B (chromosome 4) and 32Kb from MBD5 (chromosome 15), respectively. A list of positional genes, closest to significantly associated SNPs, was used to identify enriched pathways and biological functions related to the QTL for both traits. A number of candidate genes were significantly overrepresented in pathways of immune cell trafficking, lymphoid tissue structure, organ morphology, endocrine system function, lipid metabolism, and energy production. After resequencing the coding region of selected positional and functional candidate genes, six SNPs were genotyped in a subset of boars. SNPs in PRKDC, SELL, NR2E1 and AKRIC3 showed significant associations with EBVs for FCR/D110. The study revealed a number of chromosomal regions and candidate genes affecting FCR/D110 and pointed to corresponding biological pathways related to lipid metabolism, olfactory reception, and also immunological status.

Hypothalamic kappa opioid receptor mediates both diet-induced and melanin concentrating hormone-induced liver damage through inflammation and endoplasmic reticulum stress

The opioid system is widely known to modulate the brain reward system and thus affect the behavior of humans and other animals, including feeding. We hypothesized that the hypothalamic opioid system might also control energy metabolism in peripheral tissues. Mice lacking the kappa opioid receptor (κOR) and adenoviral vectors overexpressing or silencing κOR were stereotaxically delivered in the lateral hypothalamic area (LHA) of rats. Vagal denervation was performed to assess its effect on liver metabolism. Endoplasmic reticulum (ER) stress was inhibited by pharmacological (tauroursodeoxycholic acid) and genetic (overexpression of the chaperone glucose-regulated protein 78 kDa) approaches. The peripheral effects on lipid metabolism were assessed by histological techniques and western blot. We show that in the LHA κOR directly controls hepatic lipid metabolism through the parasympathetic nervous system, independent of changes in food intake and body weight. κOR colocalizes with melanin concentrating hormone receptor 1 (MCH-R1) in the LHA, and genetic disruption of κOR reduced melanin concentrating hormone-induced liver steatosis. The functional relevance of these findings was given by the fact that silencing of κOR in the LHA attenuated both methionine choline-deficient, diet-induced and choline-deficient, high-fat diet-induced ER stress, inflammation, steatohepatitis, and fibrosis, whereas overexpression of κOR in this area promoted liver steatosis. Overexpression of glucose-regulated protein 78 kDa in the liver abolished hypothalamic κOR-induced steatosis by reducing hepatic ER stress.

CONCLUSIONS

This study reveals a novel hypothalamic-parasympathetic circuit modulating hepatic function through inflammation and ER stress independent of changes in food intake or body weight; these findings might have implications for the clinical use of opioid receptor antagonists. (Hepatology 2016;64:1086-1104).

Association between obesity and asthma - epidemiology, pathophysiology and clinical profile

Obesity is a risk factor for asthma, and obese asthmatics have lower disease control and increased symptom severity. Several putative links have been proposed, including genetics, mechanical restriction of the chest and the intake of corticosteroids. The most consistent evidence, however, comes from studies of cytokines produced by the adipose tissue called adipokines. Adipokine imbalance is associated with both proinflammatory status and asthma. Although reverse causation has been proposed, it is now acknowledged that obesity precedes asthma symptoms. Nevertheless, prenatal origins of both conditions complicate the search for causality. There is a confirmed role of neuro-immune cross-talk mediating obesity-induced asthma, with leptin playing a key role in these processes. Obesity-induced asthma is now considered a distinct asthma phenotype. In fact, it is one of the most important determinants of asthma phenotypes. Two main subphenotypes have been distinguished. The first phenotype, which affects adult women, is characterised by later onset and is more likely to be non-atopic. The childhood obesity-induced asthma phenotype is characterised by primary and predominantly atopic asthma. In obesity-induced asthma, the immune responses are shifted towards T helper (Th) 1 polarisation rather than the typical atopic Th2 immunological profile. Moreover, obese asthmatics might respond differently to environmental triggers. The high cost of treatment of obesity-related asthma, and the burden it causes for the patients and their families call for urgent intervention. Phenotype-specific approaches seem to be crucial for the success of prevention and treatment.

Endogenous opioids and feeding behavior: A decade of further progress (2004-2014). A Festschrift to Dr. Abba Kastin

Functional elucidation of the endogenous opioid system temporally paralleled the creation and growth of the journal, Peptides, under the leadership of its founding editor, Dr. Abba Kastin. He was prescient in publishing annual and uninterrupted reviews on Endogenous Opiates and Behavior that served as a microcosm for the journal under his stewardship. This author published a 2004 review, "Endogenous opioids and feeding behavior: a thirty-year historical perspective", summarizing research in this field between 1974 and 2003. The present review "closes the circle" by reviewing the last 10 years (2004-2014) of research examining the role of endogenous opioids and feeding behavior. The review summarizes effects upon ingestive behavior following administration of opioid receptor agonists, in opioid receptor knockout animals, following administration of general opioid receptor antagonists, following administration of selective mu, delta, kappa and ORL-1 receptor antagonists, and evaluating opioid peptide and opioid receptor changes in different food intake models.

Acute but not chronic activation of brain glucagon-like peptide-1 receptors enhances glucose-stimulated insulin secretion in mice

AIM

To investigate the role of brain glucagon-like peptide-1 (GLP-1) in pancreatic β-cell function.

METHODS

To determine the role of brain GLP-1 receptor (GLP-1R) on β-cell function, we administered intracerebroventricular (i.c.v.) infusions of GLP-1 or the specific GLP-1 antagonist exendin-9 (Ex-9), in both an acute and a chronic setting.

RESULTS

We observed that acute i.c.v. GLP-1 infusion potentiates glucose-stimulated insulin secretion (GSIS) and improves glucose tolerance, whereas central GLP-1R blockade with Ex-9 impaired glucose excursion after a glucose load. Sustained activation of central nervous system GLP-1R, however, did not produce any effect on either GSIS or glucose tolerance. Similarly, ex vivo GSIS performed in islets from mice chronically infused with i.c.v. GLP-1 resulted in no differences compared with controls. In addition, in mice fed a high-fat diet we observed that acute i.c.v. GLP-1 infusion improved glucose tolerance without changes in GSIS, while chronic GLP-1R activation had no effect on glucose homeostasis.

CONCLUSIONS

Our results indicate that, under non-clamped conditions, brain GLP-1 plays a functional neuroendocrine role in the acute regulation of glucose homeostasis in both lean and obese rodents.

Involvement of Endogenous Enkephalins and β-Endorphin in Feeding and Diet-Induced Obesity

Studies implicate opioid transmission in hedonic and metabolic control of feeding, although roles for specific endogenous opioid peptides have barely been addressed. Here, we studied palatable liquid consumption in proenkephalin knockout (PENK KO) and β-endorphin-deficient (BEND KO) mice, and how the body weight of these mice changed during consumption of an energy-dense highly palatable 'cafeteria diet'. When given access to sucrose solution, PENK KOs exhibited fewer bouts of licking than wild types, even though the length of bouts was similar to that of wild types, a pattern that suggests diminished food motivation. Conversely, BEND KOs did not differ from wild types in the number of licking bouts, even though these bouts were shorter in length, suggesting that they experienced the sucrose as being less palatable. In addition, licking responses in BEND, but not PENK, KO mice were insensitive to shifts in sucrose concentration or hunger. PENK, but not BEND, KOs exhibited lower baseline body weights compared with wild types on chow diet and attenuated weight gain when fed cafeteria diet. Based on this and related findings, we suggest endogenous enkephalins primarily set a background motivational tone regulating feeding behavior, whereas β-endorphin underlies orosensory reward in high need states or when the stimulus is especially valuable. Overall, these studies emphasize complex interplays between endogenous opioid peptides targeting μ-receptors, such as enkephalins and endorphins, underlying the regulation of feeding and body weight that might explain the poor efficacy of drugs that generally target μ-opioid receptors in the long-term control of appetite and body weight.

Cognitive and autonomic determinants of energy homeostasis in obesity

Obesity ensues from an imbalance between energy intake and expenditure that results from gene-environment interactions, which favour a positive energy balance. A society that promotes unhealthy food and encourages sedentary lifestyle (that is, an obesogenic environment) has become a major contributory factor in excess fat deposition in individuals predisposed to obesity. Energy homeostasis relies upon control of energy intake as well as expenditure, which is in part determined by the themogenesis of brown adipose tissue and mediated by the sympathetic nervous system. Several areas of the brain that constitute cognitive and autonomic brain systems, which in turn form networks involved in the control of appetite and thermogenesis, also contribute to energy homeostasis. These networks include the dopamine mesolimbic circuit, as well as the opioid, endocannabinoid and melanocortin systems. The activity of these networks is modulated by peripheral factors such as hormones derived from adipose tissue and the gut, which access the brain via the circulation and neuronal signalling pathways to inform the central nervous system about energy balance and nutritional status. In this Review, I focus on the determinants of energy homeostasis that have emerged as prominent factors relevant to obesity.

The use of animal models to decipher physiological and neurobiological alterations of anorexia nervosa patients

Extensive studies were performed to decipher the mechanisms regulating feeding due to the worldwide obesity pandemy and its complications. The data obtained might be adapted to another disorder related to alteration of food intake, the restrictive anorexia nervosa. This multifactorial disease with a complex and unknown etiology is considered as an awful eating disorder since the chronic refusal to eat leads to severe, and sometimes, irreversible complications for the whole organism, until death. There is an urgent need to better understand the different aspects of the disease to develop novel approaches complementary to the usual psychological therapies. For this purpose, the use of pertinent animal models becomes a necessity. We present here the various rodent models described in the literature that might be used to dissect central and peripheral mechanisms involved in the adaptation to deficient energy supplies and/or the maintenance of physiological alterations on the long term. Data obtained from the spontaneous or engineered genetic models permit to better apprehend the implication of one signaling system (hormone, neuropeptide, neurotransmitter) in the development of several symptoms observed in anorexia nervosa. As example, mutations in the ghrelin, serotonin, dopamine pathways lead to alterations that mimic the phenotype, but compensatory mechanisms often occur rendering necessary the use of more selective gene strategies. Until now, environmental animal models based on one or several inducing factors like diet restriction, stress, or physical activity mimicked more extensively central and peripheral alterations decribed in anorexia nervosa. They bring significant data on feeding behavior, energy expenditure, and central circuit alterations. Animal models are described and criticized on the basis of the criteria of validity for anorexia nervosa.

Genetics and Epigenetics of Eating Disorders

Eating disorders (EDs) are serious psychiatric conditions influenced by biological, psychological, and sociocultural factors. A better understanding of the genetics of these complex traits and the development of more sophisticated molecular biology tools have advanced our understanding of the etiology of EDs. The aim of this review is to critically evaluate the literature on the genetic research conducted on three major EDs: anorexia nervosa (AN), bulimia nervosa (BN), and binge eating disorder (BED). We will first review the diagnostic criteria, clinical features, prevalence, and prognosis of AN, BN, and BED, followed by a review of family, twin, and adoption studies. We then review the history of genetic studies of EDs covering linkage analysis, candidate gene association studies, genome-wide association studies, and the study of rare variants in EDs. Our review also incorporates a translational perspective by covering animal models of ED-related phenotypes. Finally, we review the nascent field of epigenetics of EDs and a look forward to future directions for ED genetic research.

Negative regulators of brown adipose tissue (BAT)-mediated thermogenesis

Brown adipose tissue (BAT) is specialized for energy expenditure, a process called adaptive thermogenesis. PET-CT scans recently demonstrated the existence of metabolically active BAT in adult humans, which revitalized our interest in BAT. Increasing the amount and/or activity of BAT holds tremendous promise for the treatment of obesity and its associated diseases. PGC1α is the master regulator of UCP1-mediated thermogenesis in BAT. A number of proteins have been identified to influence thermogenesis either positively or negatively through regulating the expression or transcriptional activity of PGC1α. Therefore, BAT activation can be achieved by either inducing the expression of positive regulators of PGC1α or by inhibiting the repressors of the PGC1α/UCP1 pathway. Here, we review the most important negative regulators of PGC1α/UCP1 signaling and their mechanism of action in BAT-mediated thermogenesis.

GLP-1 agonism stimulates brown adipose tissue thermogenesis and browning through hypothalamic AMPK

GLP-1 receptor (GLP-1R) is widely located throughout the brain, but the precise molecular mechanisms mediating the actions of GLP-1 and its long-acting analogs on adipose tissue as well as the brain areas responsible for these interactions remain largely unknown. We found that central injection of a clinically used GLP-1R agonist, liraglutide, in mice stimulates brown adipose tissue (BAT) thermogenesis and adipocyte browning independent of nutrient intake. The mechanism controlling these actions is located in the hypothalamic ventromedial nucleus (VMH), and the activation of AMPK in this area is sufficient to blunt both central liraglutide-induced thermogenesis and adipocyte browning. The decreased body weight caused by the central injection of liraglutide in other hypothalamic sites was sufficiently explained by the suppression of food intake. In a longitudinal study involving obese type 2 diabetic patients treated for 1 year with GLP-1R agonists, both exenatide and liraglutide increased energy expenditure. Although the results do not exclude the possibility that extrahypothalamic areas are also modulating the effects of GLP-1R agonists, the data indicate that long-acting GLP-1R agonists influence body weight by regulating either food intake or energy expenditure through various hypothalamic sites and that these mechanisms might be clinically relevant.

Expression of energy metabolism related genes in the gastric tissue of obese individuals with non-alcoholic fatty liver disease

Background

Stomach is an integral part of the energy balance regulating circuit. Studies exploring the effects of cross-system changes in the energy homeostasis in stomach tissue are scarce. The proximity of the stomach to liver - the most common secondary target affected by obesity – suggests that these two organs are exposed to each other’s local secretion. Therefore, we aimed at expression profiling of energy metabolism associated genes in the gastric tissue of obese non-alcoholic fatty liver disease (NAFLD) patients.

Methods

A total of 24 patients with histologically-proven NAFLD were included. In the gastric tissue, gene expression profiling of 84 energy metabolism associated genes was carried out.

Results

The accumulation of the fat in the liver parenchyma is accompanied by downregulation of genes encoding for carboxypeptidase E (CPE) and Interleukin 1B (IL1B) in the gastric mucosa of same patient. In patients with high grade hepatic steatosis, Interleukin 1 beta encoding gene with anorexigenic function, IL1B was downregulated. The levels expression of 21 genes, including ADRA2B, CNR1 and LEP were significantly altered in the gastric tissue of NAFLD patients with hepatic inflammation. There were also indications of an increase in the opioid signaling within gastric mucosa that may results in a shift to proinflammatory environment within this organ and contribute to systemic inflammation and the pathogenic processes in hepatic parenchyma.

Conclusions

We have shown differential expression of energy metabolism associated genes in the gastric tissue of obese NAFLD patients. Importantly, these gene expression profiles are associated with changes in the hepatic parenchyma as reflected in increased scores for hepatic steatosis, inflammation, fibrosis and NASH. This study suggests the complex interplay of multiple organs in the pathogenesis of obesity-related complications such as NAFLD and provides further evidence supporting an important role for gastric tissue in promoting obesity-related complications.