GLP-1 neurons in the nucleus of the solitary tract project directly to the ventral tegmental area and nucleus accumbens to control for food intake

Review Article: GLP-1 Receptor Agonists and Glucagon/GIP/GLP-1 Receptor Dual or Triple Agonists-Mechanism of Action and Emerging Therapeutic Landscape in MASLD

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) is primarily managed through diet and lifestyle modifications. However, these behavioural interventions alone may not achieve disease regression or remission, and maintaining long-term adherence is challenging. Incretin mimetics and other gastrointestinal hormones targeting the pleiotropic pathophysiological pathways underlying MASLD have now emerged as promising disease-modifying therapies.

AIMS

This is a comprehensive review summarising the role of glucagon-like peptide-1 (GLP-1) receptor agonists and glucagon/glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor dual or triple agonists in the treatment of metabolic dysfunction-associated steatohepatitis (MASH).

METHODS

Only clinical trials with endpoints assessed by liver histology were included for a robust evaluation of therapeutic efficacy.

RESULTS

Recent evidence from phase 2 clinical trials for MASH demonstrated that pharmacological agents based on GLP-1 receptor agonism are effective in improving disease activity. Additionally, tirzepatide and survodutide showed potential clinical benefits in reducing fibrosis. Other cardiometabolic benefits observed include weight loss and improvements in glycaemic control and lipid profile. Adherence to treatment may be limited by gastrointestinal side effects, though they were found to be generally mild to moderate in severity. An interim analysis of the semaglutide phase 3 trial confirmed its efficacy in improving steatohepatitis and demonstrated its potential to improve fibrosis.

CONCLUSIONS

GLP-1 receptor agonists, alone or in combination with GIP and/or glucagon receptor agonists, represent promising, effective pharmacotherapies for the treatment of MASLD/MASH. Larger and longer-duration clinical trials are needed to further evaluate the efficacy and safety of GIP receptor and glucagon receptor agonism.

Mechanisms of GLP-1 Receptor Agonist-Induced Weight Loss: A Review of Central and Peripheral Pathways in Appetite and Energy Regulation

Glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) have become central in managing obesity and type 2 diabetes, primarily through appetite suppression and metabolic regulation. This review explores the mechanisms underlying GLP-1 RA-induced weight loss, focusing on central and peripheral pathways. Centrally, GLP-1 RAs modulate brain regions controlling appetite, influencing neurotransmitter and peptide release to regulate hunger and energy expenditure. Peripherally, GLP-1 RAs improve glycemic control by enhancing insulin secretion, reducing glucagon release, delaying gastric emptying, and regulating gut hormones. They also reduce triglycerides and low-density lipoprotein cholesterol, mitigate adipose tissue inflammation, and minimize ectopic fat deposition, promoting overall metabolic health. Emerging dual and triple co-agonists, targeting GLP-1 alongside glucose-dependent insulinotropic polypeptide, and glucagon pathways, may enhance weight loss and metabolic flexibility. Understanding these mechanisms is crucial as the therapeutic landscape evolves, offering clinicians and researchers insights to optimize the efficacy of current and future obesity treatments.

Dopaminergic Pathways in Neuroplasticity After Stroke and Vagus Nerve Stimulation

Stroke remains a significant cause of disability worldwide. In addition to multidisciplinary rehabilitation approaches, various forms of technology, including vagus nerve stimulation, have emerged to facilitate neuroplasticity and, thereby, improve functional status after stroke. Vagus nerve stimulation was recently approved by the Food and Drug Administration, but questions remain regarding its mechanism of action. Here, a potential role for dopaminergic signaling is considered. This review first examines evidence that dopamine is important to neuroplasticity after stroke. Next, 2 different dopaminergic pathways are considered as potential mechanisms underlying vagus nerve stimulation-related benefits after stroke: direct modulation of brain dopaminergic pathways, and engagement of systemic dopaminergic pathways such as those found in the gut-brain axis. A contribution of dopamine signaling to vagus nerve stimulation efficacy could have therapeutic implications that extend to a precision medicine approach to stroke rehabilitation.

Mechanistic and translational insights from preclinical cocaine choice procedures on the economic substitutability of cocaine and nondrug reinforcers

Substance use disorders are increasingly being conceptualized as behavioral misallocation disorders; however, the neurobiological determinants of this behavioral misallocation are poorly understood. Cocaine use disorder (CUD) develops as a result of behavior being disproportionally directed towards the procurement and use of cocaine at the expense of behaviors maintained by more adaptive, nondrug reinforcers (i.e., job, family). Preclinical cocaine-vs-nondrug reinforcer choice procedures are uniquely positioned to 1) elucidate the biological mechanisms of drug and nondrug reinforcement and 2) inform the development of effective pharmacological and behavioral CUD therapies. Accordingly, this review addresses the existing preclinical literature regarding the economic substitutability and mesolimbic dopaminergic mechanisms underlying cocaine self-administration in the context of three different concurrently available nondrug reinforcers: food, social interaction, and electric foot shock (a negative reinforcer). The manuscript focuses on how the existing cocaine-vs-nondrug reinforcer choice literature guides future research directions to facilitate advances in understanding of CUD from both a neuroscience and translational research perspective.

Blood phosphatidylethanol measurements indicate GLP-1 receptor stimulation causes delayed decreases in alcohol consumption

BACKGROUND

The investigation of glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1RA) as a potential treatment for individuals with alcohol use disorder (AUD) and obesity is currently underway. In this secondary analysis of a randomized placebo-controlled trial, we included AUD patients with comorbid obesity and assessed the effect of the GLP-1RA exenatide versus placebo on alcohol consumption as measured by the alcohol biomarker phosphatidylethanol (PEth).

METHODS

Thirty AUD patients (9 females, 21 males), with an average age of 53 years and a body mass index (BMI) of at least 30 kg/m2, were included in this secondary analysis. Blood samples for PEth were collected at baseline and at weeks 4, 12, 20, and 26. The effect of time and treatment on PEth levels was analyzed using a baseline-adjusted linear mixed model.

RESULTS

A significant interaction between time and treatment was observed at Week 26, with PEth levels reduced by -0.9 μmol/L in the exenatide group compared to placebo (95% CI [-1.6 to -0.1], p = 0.03). However, the difference in PEth blood levels between the exenatide and placebo groups was not significant at earlier time points.

CONCLUSION

This secondary analysis indicates that exenatide has a delayed yet significant impact on alcohol consumption in individuals with AUD and obesity, as assessed by PEth levels. These findings warrant further investigation, which is currently underway (NCT05895643).

The Influence of the Sympathetic Nervous System on Cardiometabolic Health in Response to Weight Gain or Weight Loss

Alterations in sympathetic nervous activity are evident in response to changes in body weight. Sympathetic nervous activity and sympathetic responses to weight change are regionalized, with alterations in end organ function dependent on the changes occurring in the brain regulatory pathways invoked and in the effector organs engaged. The obesity-induced activation of the sympathetic nervous system likely contributes to the initiation and worsening of cardiometabolic risk factors, including elevated blood pressure, cardiac dysfunction, dyslipidaemia, increased fasting blood glucose, insulin resistance, and non-alcoholic steatohepatitis. Unintended weight loss, as occurs in cachexia, is driven, at least in part, by the activation of sympathetic nervous-stimulated thermogenesis. The complexity of sympathetic nervous regulation renders the use of global measures of sympathetic activity problematic and the development of targeted therapies difficult, but these are not without promise or precedent. Knowledge of the central and peripheral pathways involved in sympathetic nervous regulation has opened up opportunities for pharmacological, surgical, and device-based approaches to mitigating the burden of disease development and progression. In this narrative review, we elaborate on sympathetic activity in response to changes in body weight, the brain pathways involved, and the cardiovascular and metabolic risks associated with perturbations in regional sympathetic activity.

Therapeutic Potential of the Novel GLP-1 Receptor Agonist Semaglutide in Alcohol Use Disorder

Alcohol use disorder (AUD) is a prevalent neuropsychiatric disorder with serious health and social consequences. However, few licensed and successful pharmacotherapies exist for heterogeneous and complex disorders such as AUD, and these are poorly utilized. Preclinical and clinical findings suggest that the glucagon-like peptide-1 (GLP-1) system, a gut-brain peptide, is involved in the neurobiology of addictive behaviors. Additionally, the GLP-1 receptor (GLP-1R) has become a promising target for the treatment of AUD. Semaglutide, a novel GLP-1R agonist, has received clinical approval to treat type 2 diabetes in both subcutaneous and oral dosage forms. Studies have shown that it significantly reduces alcohol consumption and relapse of alcohol addiction in rats, suggesting its potential effectiveness for treating alcohol abuse in humans, particularly in overweight patients with AUDs. However, the use of semaglutide is associated with potential risks, such as gallbladder disease and clinical complications associated with delayed gastric emptying. This review evaluates the safety of semaglutide to inform its wider clinical application. Further extensive and in-depth studies on semaglutide are needed to reveal additional valuable clinical benefits.

Examining Weight Suppression, Leptin Levels, Glucagon-Like Peptide 1 Response, and Reward-Related Constructs in Severity and Maintenance of Bulimic Syndromes: Protocol and Sample Characteristics for a Cross-Sectional and Longitudinal Study

BACKGROUND

Bulimia nervosa and related syndromes (BN-S) characterized by binge eating vary considerably in illness severity and course. Using the Research Domain Criteria framework of the National Institute of Mental Health, we developed a model positing that the same set of physiological consequences of weight suppression (WS; defined as the difference between the highest and current adult body weight) contribute to binge-eating severity and maintenance by (1) increasing the drive or motivation to consume food (reward valuation effort [RVE]) and (2) decreasing the ability for food consumption to lead to a state of satiation or satisfaction (reward satiation).

OBJECTIVE

Our funded project aimed to test concurrent associations among WS, physiological factors (leptin concentrations and postprandial glucagon-like peptide 1 [GLP-1] response), behavioral indicators of RVE (breakpoint on progressive ratio tasks) and reward satiation (ad-lib test meal intake), self-report of these core constructs, and binge-eating severity in BN-S (aim 1); test prospective associations to determine whether WS predicts BN-S maintenance in longitudinal models and whether posited mediators also predict BN-S maintenance (aim 2); and determine whether associations between WS and BN-S severity and maintenance are mediated by alterations in leptin levels, GLP-1 response, RVE, and reward satiation (aim 3).

METHODS

We aimed to recruit a sample of 320 women with BN-S or noneating disorder controls, with BMI from 16 kg/m2 to 35 kg/m2, for our study. The study included diagnostic interviews; questionnaires; height, weight, and percentage of body fat measurements; weight history; fasting leptin level; postprandial GLP-1 and insulin responses to a fixed meal; and ad-lib meal and progressive ratio tasks to behaviorally measure reward satiation and RVE, respectively, at baseline, with at least 78.1% (250/320) of the participants providing data at 6- and 12-month follow-up visits. Data will be analyzed using structural equation models to test posited pathways.

RESULTS

Data collection began in November 2016 and ended in April 2023, pausing in-person data collection from March 2020 to February 2021 due to the COVID-19 pandemic. Of 399 eligible women enrolled, 290 (72.7%) provided clinical, behavioral, and biological data at baseline, and 249 (62.4%) provided follow-up data. Measures demonstrated strong psychometric properties.

CONCLUSIONS

We seek to identify biobehavioral predictors to inform treatments that target key factors influencing the severity and course of binge eating. These data, supported solely through federal funding, can inform questions emerging from recent interest and controversy surrounding the use of GLP-1 agonists for binge eating.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

RR1-10.2196/66554.

The neurobiology of overeating

Food intake serves to maintain energy homeostasis; however, overeating can result in obesity, which is associated with serious health complications. In this review, we explore the intricate relationship between overeating, obesity, and the underlying neurobiological mechanisms. We review the homeostatic and hedonic feeding systems, highlighting the role of the hypothalamus and reward systems in controlling food intake and energy balance. Dysregulation in both these systems leads to overeating, as seen in genetic syndromes and environmental models affecting appetite regulation when consuming highly palatable food. The concept of "food addiction" is examined, drawing parallels to drug addiction. We discuss the cellular substrate for addiction-related behavior and current pharmacological obesity treatments-in particular, GLP-1 receptor agonists-showcasing synaptic plasticity in the context of overeating and palatable food exposure. A comprehensive model integrating insights from addiction research is proposed to guide effective interventions for maladaptive feeding behaviors. Ultimately, unraveling the neurobiological basis of overeating holds promise for addressing the pressing public health issue of obesity.

Targeting central pathway of Glucose-Dependent Insulinotropic Polypeptide, Glucagon and Glucagon-like Peptide-1 for metabolic regulation in obesity and type 2 diabetes

Obesity and type 2 diabetes are significant public health challenges that greatly impact global well-being. The development of effective therapeutic strategies has become more and more concentrated on the central nervous system and metabolic regulation. The primary pharmaceutical interventions for the treatment of obesity and uncontrolled hyperglycemia are now generally considered to be incretin-based anti-diabetic treatments, particularly glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide receptor agonists. This is a result of their substantial influence on the central nervous system and the consequent effects on energy balance and glucose regulation. It is increasingly crucial to understand the neural pathways of these pharmaceuticals. The purpose of this review is to compile and present the most recent central pathways regarding glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide and glucagon receptors, with a particular emphasis on central metabolic regulation.

PACAP Signaling Network in the Nucleus Accumbens Core Regulates Reinstatement Behavior in Rat

Cocaine use disorder (CUD) lacks FDA-approved treatments, partly due to the difficulty of creating therapeutics that target behavior-related neural circuits without disrupting signaling throughout the brain. Recent evidence highlights the therapeutic potential of targeting gut-brain axis components, such as GLP-1 receptors, to modulate neural circuits with minimal central nervous system disruption. Like GLP-1, pituitary adenylate cyclase polypeptide (PACAP) is a component of the gut-brain axis that regulates behavior through a network spanning the gut and brain. Here, we investigated the potential existence and function of an endogenous PACAP signaling network within the nucleus accumbens core (NAcc), which is a structure that integrates emotional, cognitive, and reward processes underlying behavior. We found that PACAP and its receptor, PAC1R, are endogenously expressed in the rat NAcc and that PACAP mRNA is present in medial prefrontal cortical projections to the NAcc. Behaviorally, intra-NAcc infusions of PACAP (100 pm) did not induce seeking behavior but blocked cocaine-primed reinstatement (10 mg/kg, IP). Intra-NAcc PACAP also inhibited reinstatement driven by co-infusion of the D1 receptor agonist (SKF 81297, 3 µg) but not the D2 receptor agonist (sumanirole, 10 ng). These findings are significant since D1 and D2 receptor activities in the NAcc govern distinct behavioral mechanisms indicating precise actions of PACAP even within the NAcc. Future research should examine whether NAcc PACAP signaling can be selectively engaged by peripheral gut-brain axis mechanisms, potentially unveiling novel therapeutic approaches for CUD and related disorders.

Metabolic factors modulate effort-based decision-making in major depressive disorder

BACKGROUND

Abnormalities in effort-based decision-making have been consistently reported in major depressive disorder (MDD). Evidence indicates that metabolic factors, such as insulin resistance and dyslipidemia, which are highly prevalent in MDD, are independently associated with reward disturbances. Herein, we investigate the moderating effect of metabolic factors on effort-based decision-making in individuals with MDD.

METHODS

Forty-nine adults with MDD completed the Effort Expenditure for Rewards Task (EEfRT). Anthropometric and laboratorial parameters were assessed in all participants. We conducted a factor analysis to identify combinations of correlated metabolic variables, and reduce the number of comparisons.

RESULTS

Proxy markers of elevated insulin resistance (OR: 0.816, p < 0.001) and hyperglycemia (OR: 0.898, p = 0.021) were associated with a lower willingness to exert physical effort for rewards in the EEfRT. In contrast, elevated HDL (OR: 1.165, p = 0.004), and elevated non-HDL cholesterol and triglycerides (OR: 1.184, p < 0.001) were associated with increased frequency of hard task choices. These associations were independent of age, sex, depressive symptoms severity and medication use. Computational modeling revealed that the insulin resistance (β = 0.275, p = 0.035) and cholesterol factors (β = 0.565, p < 0.001) were independently associated with increased effort discounting.

LIMITATIONS

Post-hoc analysis using a relatively small sample of convenience.

CONCLUSIONS

Metabolic factors significantly and independently modulated effort-based decision-making in patients with MDD. These results have implications for our understanding of reward disturbances in MDD, and offer insights for further mechanistic investigations.

An endogenous GLP-1 circuit engages VTA GABA neurons to regulate mesolimbic dopamine neurons and attenuate cocaine seeking

Recent studies show that systemic administration of a glucagon-like peptide-1 receptor (GLP-1R) agonist is sufficient to attenuate cocaine seeking. However, the neural mechanisms mediating these effects and the role of endogenous central GLP-1 signaling in cocaine seeking remain unknown. Here, we show that voluntary cocaine taking decreased plasma GLP-1 levels in rats and that chemogenetic activation of GLP-1-producing neurons in the nucleus tractus solitarius that project to the ventral tegmental area (VTA) decreased cocaine seeking. Single-nuclei transcriptomics and FISH studies revealed that GLP-1Rs are expressed primarily on GABA neurons in the VTA. Using in vivo fiber photometry, we found that the efficacy of a systemic GLP-1R agonist to attenuate cocaine seeking was associated with increased activity of VTA GABA neurons and decreased activity of VTA dopamine neurons. Together, these findings suggest that targeting central GLP-1 circuits may be an effective strategy toward reducing cocaine relapse and highlight a functional role of GABAergic GLP-1R-expressing midbrain neurons in drug seeking.

Use of semaglutide in a 54-year-old patient with cocaine abuse and weight loss: a case report

CONTEXT

This case report is interesting because it highlights a direction for the treatment of comorbid obesity and cocaine use disorder, which is an increasing clinical condition from an epidemiological point of view, and allows us to identify the possibility of a new strategy to address the problem of substance craving, particularly for cocaine.

CASE PRESENTATION

This case report discusses the efficacy of semaglutide in a 54-year-old Caucasian patient with a history of cocaine abuse and obesity. Subcutaneous semaglutide was administered, as per guidelines, with a progressive weekly increase for a total of 12 weeks. The patient was monitored with respect to clinical parameters, as well as psychodiagnostic ones. The patient demonstrated significant weight loss and a marked reduction in cocaine craving.

CONCLUSION

The action of semaglutide on the hunger and reward centers offers a new approach to the treatment of patients with obesity and concomitant substance use disorders. By targeting glucagon-like peptide-1 receptors involved in both metabolic regulation and reward processing, semaglutide could potentially reduce both food intake and drug craving, thereby improving outcomes for these patients. The findings suggest that semaglutide may be a promising therapeutic option for the management of substance abuse in patients with comorbid obesity.

Integration of Glucagon-Like Peptide 1 Receptor Actions Through the Central Amygdala

Understanding the detailed mechanism of action of glucagon-like peptide 1 receptor (GLP-1R) agonists on distinct topographic and genetically defined brain circuits is critical for improving the efficacy and mitigating adverse side effects of these compounds. In this mini-review, we propose that the central nucleus of the amygdala (CeA) is a critical mediator of GLP-1R agonist-driven hypophagia. Here, we review the extant literature demonstrating CeA activation via GLP-1R agonists across multiple species and through multiple routes of administration. The precise role of GLP-1Rs within the CeA is unclear but the site-specific GLP-1Rs may mediate distinct behavioral and physiological hallmarks of GLP-1R agonists on food intake. Thus, we propose important novel directions and methods to test the role of the CeA in mediating GLP-1R actions.

Novel neural pathways targeted by GLP-1R agonists and bariatric surgery

The glucagon-like peptide 1 receptor (GLP-1R) agonist semaglutide has revolutionized the treatment of obesity, with other gut hormone-based drugs lined up that show even greater weight-lowering ability in obese patients. Nevertheless, bariatric surgery remains the mainstay treatment for severe obesity and achieves unparalleled weight loss that generally stands the test of time. While their underlying mechanisms of action remain incompletely understood, it is clear that the common denominator between GLP-1R agonists and bariatric surgery is that they suppress food intake by targeting the brain. In this Review, we highlight recent preclinical studies using contemporary neuroscientific techniques that provide novel concepts in the neural control of food intake and body weight with reference to endogenous GLP-1, GLP-1R agonists, and bariatric surgery. We start in the periphery with vagal, intestinofugal, and spinal sensory nerves and then progress through the brainstem up to the hypothalamus and finish at non-canonical brain feeding centers such as the zona incerta and lateral septum. Further defining the commonalities and differences between GLP-1R agonists and bariatric surgery in terms of how they target the brain may not only help bridge the gap between pharmacological and surgical interventions for weight loss but also provide a neural basis for their combined use when each individually fails.

Effect of acute treatment with the glucagon-like peptide-1 receptor agonist, liraglutide, and estrus phase on cue- and drug-induced fentanyl seeking in female rats

Opioid use disorder (OUD) is a crisis in the USA. Despite advances with medications for OUD, overdose deaths have continued to rise and are largely driven by fentanyl. We have previously found that male rats readily self-administer fentanyl, with evident individual differences in fentanyl taking, seeking, and reinstatement behaviors. We also have shown that acute treatment with the glucagon-like peptide-1 receptor (GLP-1R) agonist, liraglutide, can reduce fentanyl seeking behavior in male rats. However, given that females are significantly more vulnerable to drug-related cues, drug cravings, and to the development of OUD compared to males, it is imperative that we investigate the biological risk factors on fentanyl use disorder. Further, preclinical models report that females in estrus have increased fentanyl intake, more rapid development of OUD, and enhanced relapse vulnerability compared to those in a non-estrus phase. Thus, we aimed here to understand the effect of estrus phase on our model of OUD and on the effectiveness of acute liraglutide treatment. Herein, we show that female rats readily self-administer fentanyl (1.85 μg/infusion) intravenously, with marked individual differences in fentanyl taking behavior. Additionally, rats in the estrus phase exhibited greater fentanyl intake compared with those in a non-estrus phase, greater cue-induced fentanyl seeking, and greater drug-induced reinstatement of fentanyl seeking. Finally, acute liraglutide treatment (0.3 mg/kg s.c.) reduced cue-induced fentanyl seeking and blocked drug-induced reinstatement of fentanyl seeking, particularly when tested in estrus. Overall, these data support the broad effectiveness of acute GLP-1R agonists as a promising non-opioid treatment for OUD.

Development and validation of the Food Noise Questionnaire

OBJECTIVE

Food noise has received attention in the media, although no validated questionnaires exist to measure it. This study developed and tested the reliability and validity of the Food Noise Questionnaire (FNQ).

METHODS

Participants (N = 400) successfully completed, the FNQ and a demographic questionnaire and self-reported weight and height. A subsample (n = 150) completed the FNQ 7 days later for test-retest reliability, and this subsample's first FNQ data were subjected to exploratory factor analysis. The remaining subsample (n = 250) completed two preoccupation with food questionnaires to test convergent validity, along with mood, anxiety, and stress questionnaires to test for discriminant validity. Confirmatory factor analysis was conducted using this subsample's FNQ data.

RESULTS

Data from 396 participants were analyzed (4 participants did not complete all FNQ items). The FNQ had excellent internal consistency reliability (Cronbach α = 0.93) and high test-retest reliability (r = 0.79; p < 0.001; mean [SD] = 7.4 [1.0] days between administration). Factor analyses found that the five FNQ items loaded onto a single factor, with good fit indices (χ2[5] = 52.87, p < 0.001; root mean square error of approximation [RMSEA] = 0.20; comparative fit index [CFI] = 0.95; standardized root mean squared residual [SRMR] = 0.03). The FNQ showed good convergent (all r > 0.78; p < 0.001) and discriminant (all r < 0.39; p < 0.001) validity.

CONCLUSIONS

The FNQ provides a psychometrically reliable and valid measure of food noise, although further research is needed to evaluate its clinical utility.

Glucagon-Like Peptide-1 Links Ingestion, Homeostasis, and the Heart

Glucagon-like peptide-1 (GLP-1), a hormone released from enteroendocrine cells in the distal small and large intestines in response to nutrients and other stimuli, not only controls eating and insulin release, but is also involved in drinking control as well as renal and cardiovascular functions. Moreover, GLP-1 functions as a central nervous system peptide transmitter, produced by preproglucagon (PPG) neurons in the hindbrain. Intestinal GLP-1 inhibits eating by activating vagal sensory neurons directly, via GLP-1 receptors (GLP-1Rs), but presumably also indirectly, by triggering the release of serotonin from enterochromaffin cells. GLP-1 enhances glucose-dependent insulin release via a vago-vagal reflex and by direct action on beta cells. Finally, intestinal GLP-1 acts on the kidneys to modulate electrolyte and water movements, and on the heart, where it provides numerous benefits, including anti-inflammatory, antiatherogenic, and vasodilatory effects, as well as protection against ischemia/reperfusion injury and arrhythmias. Hindbrain PPG neurons receive multiple inputs and project to many GLP-1R-expressing brain areas involved in reward, autonomic functions, and stress. PPG neuron-derived GLP-1 is involved in the termination of large meals and is implicated in the inhibition of water intake. This review details GLP-1's roles in these interconnected systems, highlighting recent findings and unresolved issues, and integrating them to discuss the physiological and pathological relevance of endogenous GLP-1 in coordinating these functions. As eating poses significant threats to metabolic, fluid, and immune homeostasis, the body needs mechanisms to mitigate these challenges while sustaining essential nutrient intake. Endogenous GLP-1 plays a crucial role in this "ingestive homeostasis."

Does semaglutide reduce alcohol intake in Danish patients with alcohol use disorder and comorbid obesity? Trial protocol of a randomised, double-blinded, placebo-controlled clinical trial (the SEMALCO trial)

INTRODUCTION

Alcohol use disorder (AUD) is a massive burden for the individual, relatives and society. Despite this, the treatment gap is wide compared with other mental health disorders. Treatment options are sparse, with only three Food and Drug Administration (FDA)-approved pharmacotherapies. Glucagon-like peptide-1 (GLP-1) receptor agonists have shown promising effects in reducing alcohol consumption in preclinical experiments, and clinical trials are in high demand to investigate these potentially beneficial effects in patients diagnosed with AUD.

METHODS AND ANALYSIS

The effects of the once-weekly GLP-1 receptor agonist semaglutide will be investigated in a 26-week, randomised, placebo-controlled, double-blinded clinical trial. 108 patients diagnosed with AUD and comorbid obesity (body mass index (BMI)≥30 kg/m2)) will be randomised to treatment with either semaglutide or placebo in combination with cognitive behavioural therapy. A subgroup of the patients will have structural, functional and neurochemical brain imaging performed at baseline and after 26 weeks of treatment. The primary endpoint is the reduction in heavy drinking days, defined as days with excess consumption of 48/60 g of alcohol per day (women and men, respectively). Secondary endpoints include changes from baseline to week 26 in alcohol consumption, smoking status, quality of life, fibrosis-4 score, plasma concentration of phosphatidylethanol, brain gamma-aminobutyric acid (GABA) levels, alcohol cue reactivity, functional connectivity and white matter tract integrity.

STATUS

Recruitment started in June 2023.

ETHICS AND DISSEMINATION

The study is approved by the Ethics Committee of the Capital Region of Denmark, the Danish Board of Health and the Danish Data Protection Agency. All patients will sign the written consent form before being included in the trial. Results will be disseminated through peer-reviewed publications and conference presentations. After the results are published, all de-identified data will be available in the Mendeley database.

TRIAL REGISTRATION NUMBER

NCT05895643.

Are glucagon-like peptide-1 receptor agonists anti-consummatory drugs?

Incretin-based treatments, such as glucagon-like peptide-1 receptor (GLP-1R) agonists (eg liraglutide and semaglutide), have rapidly transformed obesity treatment. The well-documented weight loss effect from these agents is considered to be primarily a result of their actions on food intake, but frequent anecdotal reports from varied sources have suggested that they might also broadly affect consummatory behavior, including alcohol and drugs of abuse, suggesting a potential modulatory effect on reward behavior. Herein, we critically review the extant literature on the behavioral effects of GLP-1R agonists in humans, including their impact on feeding behavior, alcohol/drug intake, and overall reward response. We also consider the physiological and neurobiological underpinnings of GLP-1 actions, with a focus on its distinct central and peripheral roles, as well as its relationships with the broader energy homeostasis network. We conclude with a discussion on the implications of this line of research on how behavior is conceptualized, and the potential future directions for research.

GLP-1 receptor agonist exenatide uncouples food intake from hedonic and anticipatory regulation in non-human primates: insights from an operant meal schedule paradigm

Glucagon-like peptide 1 (GLP-1), a neuroendocrine signal of energy balance and satiety, has a major role in regulating food intake behaviour. Here we investigated the effects of the GLP-1 agonist exenatide on palatability-driven feeding regulation in adult male rhesus macaques (n = 5) using a novel operant food intake paradigm with four meal schedule conditions where two types of pellets with different palatability values were offered as meal in all combinations in two consecutive daily feeding sessions (S1 and S2). In control conditions, a strong, palatability-driven anticipatory effect was found in S1, followed by a complementary positive contrast effect in S2. After acute subcutaneous treatment with 1 µg/kg dose of exenatide 1 h before S1, food intake decreased to the same very low level in all meal schedule conditions in S1, completely erasing the previously observed anticipatory effect. Conversely, exenatide induced hypoglycaemia in an anticipatory meal schedule dependent pattern. Interestingly, the previously observed positive contrast effect was spared in S2, with a weaker residual effect specifically on the consumption of the more palatable pellet type. To conclude, the food intake reducing effects of exenatide may temporally evolve from strong anorectic to weak anhedonic modulations, where hedonic experience and anticipation during the early anorectic phase is conserved but uncoupled from food intake behaviour.

Glucagon-like peptide-1 receptor agonist-based agents and weight loss composition: Filling the gaps

Excess adiposity is at the root of type 2 diabetes (T2D). Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have emerged as first-line treatments for T2D based on significant weight loss results. The composition of weight loss using most diets consists of <25% fat-free mass (FFM) loss, with the remainder from fat stores. Higher amounts of weight loss (achieved with metabolic bariatric surgery) result in greater reductions in FFM. Our aim was to assess the impact that GLP-1RA-based treatments have on FFM. We analysed studies that reported changes in FFM with the following agents: exenatide, liraglutide, semaglutide, and the dual incretin receptor agonist tirzepatide. We performed an analysis of various weight loss interventions to provide a reference for expected changes in FFM. We evaluated studies using dual-energy X-ray absorptiometry (DXA) for measuring FFM (a crude surrogate for skeletal muscle). In evaluating the composition of weight loss, the percentage lost as fat-free mass (%FFML) was equal to ΔFFM/total weight change. The %FFML using GLP-1RA-based agents was between 20% and 40%. In the 28 clinical trials evaluated, the proportion of FFM loss was highly variable, but the majority reported %FFML exceeding 25%. Our review was limited to small substudies and the use of DXA, which does not measure skeletal muscle mass directly. Since FFM contains a variable amount of muscle (approximately 55%), this indirect measure may explain the heterogeneity in the data. Assessing quantity and quality of skeletal muscle using advanced imaging (magnetic resonance imaging) with functional testing will help fill the gaps in our current understanding.

Hunting for heroes: Brain neurons mediating GLP-1R agonists in obesity treatment

Glucagon-like peptide 1 (GLP-1) receptor agonists (GLP-1RAs) have proven to be highly effective in reducing obesity across species and ages, gaining unmet popularity in clinical treatments against obesity. Although extensive research efforts have been made to explore how the brain regulates body weight homeostasis including the effect brought up by GLP-1 and its synthetic analogs GLP-1RAs, the identity of neurons and neural pathways that are responsible for the observed anti-obesity effect of GLP-1RAs remain largely elusive. Excitingly, three recent high-profile studies presented compelling evidence that each argues for the importance of GLP-1Rs in the dorsomedial hypothalamus, hindbrain, or lateral septum, respectively, in mediating the anti-obesity effect of GLP-1RAs. While these studies clearly illustrated the contributions of each of these distinct brain regions involved in GLP-1RAs in body weight regulation, the presented results also suggest the complexity of the involved brain neural network. This commentary briefly introduces these studies and highlights key knowledge gaps that require further investigation.

Neurolipidomics in schizophrenia: A not so well-oiled machine

Most patients with schizophrenia (SCZ) do not exhibit violent behaviors and are more likely to be victims rather than perpetrators of violent acts. However, a subgroup of forensic detainees with SCZ exhibit tendencies to engage in criminal violations. Although numerous models have been proposed, ranging from substance use, serotonin transporter gene, and cognitive dysfunction, the molecular underpinnings of violence in SCZ patients remains elusive. Lithium and clozapine have established anti-aggression properties and recent studies have linked low cholesterol levels and ultraviolet (UV) radiation with human aggression, while vitamin D3 reduces violent behaviors. A recent study found that vitamin D3, omega-3 fatty acids, magnesium, and zinc lower aggression in forensic population. In this review article, we take a closer look at aryl hydrocarbon receptor (AhR) and the dysfunctional lipidome in neuronal membranes, with emphasis on cholesterol and vitamin D3 depletion, as sources of aggressive behavior. We also discuss modalities to increase the fluidity of neuronal double layer via membrane lipid replacement (MLR) and natural or synthetic compounds. This article is part of the Special Issue on "Personality Disorders".

Potential role of glucagon-like peptide-1 (GLP-1) receptor agonists in substance use disorder: A systematic review of randomized trials

BACKGROUND

Increasing evidence suggests that GLP-1 receptor agonists (GLP-1RA) have a potential use in addiction treatment. Few studies have assessed the impact of GLP-1RA on substance use disorder (SUD), particularly in humans. The study aimed to do systematic review of clinical trials to assess GLP-1RA's effect on reducing SUD in patients.

METHODS

The scientific literature was reviewed using the MEDLINE, Scopus and Cochrane Library databases, following PRISMA guidelines. Studies including patients with a diagnosis of SU who were treated with GLP-1RA were selected. The primary outcome was GLP-1RA's therapeutic effect on SUD, and the secondary outcomes were therapeutic effects of GLP-1RA on weight, BMI and HbA1c.

RESULTS

1218 studies were retrieved, resulting in 507 papers after title and abstract screening. Following full-text review, only 5 articles met inclusion criteria. We incorporated a total of 630 participants utilizing Exenatide (n=3) and Dulaglutide (n=2) as GLP-1RAs. Therapeutic effect of GLP-1RA on SUD was assessed in 5 studies, with 3 demonstrating a significant decrease in SUD (alcohol and nicotine). GLP-1RA's impact on body weight, BMI, and HbA1c, was reported in 3 studies. These revealed a notable reduction in these parameters among the GLP-1RA treated group.

CONCLUSION

This review will give an overview of current new findings in human studies; we suggest that the effects of GLP-1RA in SUD is a possible new option of therapy in addiction medicine.

Semaglutide and smoking cessation in individuals with type 2 diabetes mellitus: there is no smoke without fire!

Tobacco use represents the leading preventable risk factor for premature deaths worldwide. A meta-analysis of 74 epidemiological studies, including 3.2 million individuals with type 2 diabetes mellitus (T2DM) from 33 countries, reported a pooled prevalence of smoking of 20.8% among individuals with T2DM. Cigarette smoking further aggravates existing deleterious vascular effects of T2DM. Namely, chronic hyperglycemia and exposure to cigarette smoke cause additive injurious effect on the endothelium, leading to an acceleration of vascular complications seen in persons with T2DM and tobacco use disorders (TUD). In a recent study, Wang and colleagues found that semaglutide use was associated with a significantly lower risk for medical encounters for TUD, when compared to other antidiabetic drug classes; indeed, this effect was strongest compared with insulins and weakest compared with other glucagon-like peptide-1 receptor agonists. Semaglutide was associated with reduced smoking cessation medication prescriptions and counseling. Similar findings were observed irrespective of the presence of obesity. Therefore, semaglutide use might be useful in terms of smoking cessation among individuals with T2DM, thus offering an additional benefit for this constantly growing population. However, those interesting findings should be confirmed through dedicated, large-scale randomized controlled trials.

From Mammals to Insects: Exploring the Genetic and Neural Basis of Eating Behavior

Obesity and anorexia are life-threatening diseases that are still poorly understood at the genetic and neuronal levels. Patients suffering from these conditions experience disrupted regulation of food consumption, leading to extreme weight gain or loss and, in severe situations, death from metabolic dysfunction. Despite the development of various behavioral and pharmacological interventions, current treatments often yield limited and short-lived success. To address this, a deeper understanding of the genetic and neural mechanisms underlying food perception and appetite regulation is essential for identifying new drug targets and developing more effective treatment methods. This review summarizes the progress of past research in understanding the genetic and neural mechanisms controlling food consumption and appetite regulation, focusing on two key model organisms: the fruit fly Drosophila melanogaster and the mouse Mus musculus. These studies investigate how the brain senses energy and nutrient deficiency, how sensory signals trigger appetitive behaviors, and how food intake is regulated through interconnected neural circuits in the brain.

Gut Hormones: Possible Mediators of Addictive Disorders?

BACKGROUND

Alcohol and drug dependence are major health and economic burdens to society. One of the major challenges to reducing this burden will be to develop more effective and better tolerated medications that target alternative mechanisms in the brain. While the dopamine system has been well characterized for mediating the reward value of drugs, there is evidence that the endocrine system also conveys signals to the same neural systems using gut hormones.

SUMMARY

These gut hormones, produced in the stomach and intestine and that regulate food intake, have also been shown to control the use of other substances, such as alcohol and drugs of abuse. Examples of such hormones are ghrelin and glucagon-like peptide-1, which exert their effects on dopamine transmission in parts of the brain known to be involved in some of the core features of addiction, such as reward sensitivity.

KEY MESSAGES

This raises the possibility that gut hormone systems may play a pivotal role in addictive disorders. This review will briefly outline emerging evidence that the ghrelin and glucagon-like peptide-1 hormones are contrasting mediators of alcohol and drug use and may present a promising alternative target for treatment intervention in addictive disorders.

GLP-1 programs the neurovascular landscape

Readily available nutrient-rich foods exploit our inherent drive to overconsume, creating an environment of overnutrition. This transformative setting has led to persistent health issues, such as obesity and metabolic syndrome. The development of glucagon-like peptide-1 receptor (GLP-1R) agonists reveals our ability to pharmacologically manage weight and address metabolic conditions. Obesity is directly linked to chronic low-grade inflammation, connecting our metabolic environment to neurodegenerative diseases. GLP-1R agonism in curbing obesity, achieved by impacting appetite and addressing associated metabolic defects, is revealing additional benefits extending beyond weight loss. Whether GLP-1R agonism directly impacts brain health or does so indirectly through improved metabolic health remains to be elucidated. In exploring the intricate connection between obesity and neurological conditions, recent literature suggests that GLP-1R agonism may have the capacity to shape the neurovascular landscape. Thus, GLP-1R agonism emerges as a promising strategy for addressing the complex interplay between metabolic health and cognitive well-being.

GLP-1, GIP, and Glucagon Agonists for Obesity Treatment: A Hunger Perspective

For centuries, increasingly sophisticated methods and approaches have been brought to bear to promote weight loss. Second only to the Holy Grail of research on aging, the idea of finding a single and simple way to lose weight has long preoccupied the minds of laymen and scientists alike. The effects of obesity are far-reaching and not to be minimized; the need for more effective treatments is obvious. Is there a single silver bullet that addresses this issue without effort on the part of the individual? The answer to this question has been one of the most elusive and sought-after in modern history. Now and then, a miraculous discovery propagates the illusion that a simple solution is possible. Now there are designer drugs that seem to accomplish the task: we can lose weight without effort using mono, dual, and triple agonists of receptors for glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon. There are, however, fundamental biological principles that raise intriguing questions about these therapies beyond the currently reported side-effects. This perspective reflects upon these issues from the angle of complex goal-oriented behaviors, and systemic and cellular metabolism associated with satiety and hunger.

Neural processing of sweet taste in reward regions is reduced following bariatric surgery

OBJECTIVE

Bariatric surgery reduces sweet-liking, but mechanisms remain unclear. We examined related brain responses.

METHODS

A total of 24 nondiabetic bariatric surgery and 21 control participants with normal weight to overweight were recruited for an observational controlled cohort study. They underwent sucrose taste testing outside the scanner followed by stimulation with 0.40M and 0.10M sucrose compared with water during functional magnetic resonance imaging. A total of 21 bariatric participants repeated these procedures after surgery.

RESULTS

Perceived sweet intensity was not different among the control, presurgery, or postsurgery groups. Bariatric participants' preferred sweet concentration decreased after surgery (0.52M to 0.29M; p = 0.008). Brain reward system (ventral tegmental area, ventral striatum, and orbitofrontal cortex) region of interest analysis showed that 0.40M sucrose activation  (but not 0.10M) decreased after surgery. Sensory region (primary somatosensory and primary taste cortex) 0.40M sucrose activation was unchanged by surgery and did not differ between control and bariatric participants. Primary taste cortex activation to 0.10M sucrose solution was greater in postsurgical bariatric participants compared with control participants.

CONCLUSIONS

Bariatric surgery reduces the reward system response to sweet taste in women with obesity without affecting activity in sensory regions, which is consistent with reduced drive to consume sweet foods.

The GLP-1 receptor agonist exendin-4 reduces taurine and glycine in nucleus accumbens of male rats, an effect tentatively involving the nucleus tractus solitarius

The physiological effects of glucagon-like peptide-1 (GLP-1) are mainly centered on its ability to decrease blood glucose levels and facilitate satiety. Additional physiological functions have been identified by means of GLP-1 agonists such as exenatide (exendin-4; Ex4). In particular, Ex4 reduces the intake of natural and artificial rewards, effects that to some extent involve activation of GLP-1 receptors in the nucleus tractus solitarius (NTS). Although Ex4 acts in the brain, the neurochemical mechanisms underlying this activation are not fully elucidated. Investigating Ex4-induced neurochemical alterations in the nucleus accumbens (NAc) would be valuable for understanding its impact on reward-related behaviors. The aim of the present exploratory in vivo microdialysis study was therefore to study how Ex4, administered either systemically or locally into the NTS, influences classical neurotransmitters like dopamine, serotonin, noradrenaline, glutamate and GABA as well as additional players such as glycine, taurine and serine in NAc of male rats. We showed that Ex4 reduced extracellular levels of serine, taurine and glycine, where the latter two declines appear to involve activation of GLP-1R in the NTS. Besides, after systemic Ex4 injection the metabolites DOPAC, HVA, and 5HIAA are elevated. Where the increase in metabolites related to dopamine, but not serotonin, involves GLP-1 receptors in other areas than the NTS. Although the descriptive nature of the present data does not provide causality, it may however serve as an indication of mechanisms underlying how Ex4 may modulate reward-related behaviors.

Association of Semaglutide With Tobacco Use Disorder in Patients With Type 2 Diabetes : Target Trial Emulation Using Real-World Data

BACKGROUND

Reports of reduced desire to smoke in patients treated with semaglutide, a glucagon-like peptide receptor agonist (GLP-1RA) medication for type 2 diabetes mellitus (T2DM) and obesity, have raised interest about its potential benefit for tobacco use disorders (TUDs).

OBJECTIVE

To examine the association of semaglutide with TUD-related health care measures in patients with comorbid T2DM and TUD.

DESIGN

Emulation target trial based on a nationwide population-based database of patient electronic health records.

SETTING

United States, 1 December 2017 to 31 March 2023.

PARTICIPANTS

Seven target trials were emulated among eligible patients with comorbid T2DM and TUD by comparing the new use of semaglutide versus 7 other antidiabetes medications (insulins, metformin, dipeptidyl-peptidase-4 inhibitors, sodium-glucose cotransporter-2 inhibitors, sulfonylureas, thiazolidinediones, and other GLP-1RAs).

MEASUREMENTS

The TUD-related health care measures (medical encounter for diagnosis of TUD, smoking cessation medication prescriptions, and smoking cessation counseling) that occurred within a 12-month follow-up were examined using Cox proportional hazards and Kaplan-Meier survival analyses.

RESULTS

The study compared 222 942 new users of antidiabetes medications including 5967 of semaglutide. Semaglutide was associated with a significantly lower risk for medical encounters for TUD diagnosis compared with other antidiabetes medications, and was strongest compared with insulins (hazard ratio [HR], 0.68 [95% CI, 0.63 to 0.74]) and weakest but statistically significant compared with other GLP-1RAs (HR, 0.88 [CI, 0.81 to 0.96]). Semaglutide was associated with reduced smoking cessation medication prescriptions and counseling. Similar findings were observed in patients with and without a diagnosis of obesity. For most of the group comparisons, the differences occurred within 30 days of prescription initiation.

LIMITATION

Documentation bias, residual confounding, missing data on current smoking behavior, body mass index, and medication adherence.

CONCLUSION

Semaglutide was associated with lower risks for TUD-related health care measures in patients with comorbid T2DM and TUD compared with other antidiabetes medications including other GLP-1Ras, primarily within 30 days of prescription. These findings suggest the need for clinical trials to evaluate semaglutide's potential for TUD treatment.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Populations of Hindbrain Glucagon-Like Peptide 1 (GLP1) Neurons That Innervate the Hypothalamic PVH, Thalamic PVT, or Limbic Forebrain BST Have Axon Collaterals That Reach All Central Regions Innervated by GLP1 Neurons

Neurons in the caudal nucleus of the solitary tract (cNTS) and intermediate reticular nucleus (IRt) that express the glucagon gene (Gcg) give rise to glucagon-like peptide 1 (GLP1)-immunopositive axons in the spinal cord and many subcortical brain regions. Central GLP1 receptor signaling contributes to motivated behavior and stress responses in rats and mice, in which hindbrain GLP1 neurons are activated to express c-Fos in a metabolic state-dependent manner. The present study examined whether GLP1 inputs to distinct brain regions arise from distinct subsets of Gcg-expressing neurons, and mapped the distribution of axon collaterals arising from projection-defined GLP1 neural populations. Using our Gcg-Cre knock-in rat model, Cre-dependent adeno-associated virus (AAV) tracing was conducted in adult male and female rats to compare axonal projections of IRt versus cNTS GLP1 neurons. Overlapping projections were observed in all brain regions that receive GLP1 input, with the caveat that cNTS injections produced Cre-dependent labeling of some IRt neurons, and vice versa. In additional experiments, specific diencephalic or limbic forebrain nuclei were microinjected with Cre-dependent retrograde AAVs (AAVrg) that expressed reporters to fully label the axon collaterals of transduced GLP1 neurons. AAVrg injected into each forebrain site labeled Gcg-expressing neurons in both the cNTS and IRt. The collective axon collaterals of labeled neurons entered the spinal cord and every brain region previously reported to contain GLP1-positive axons. These results indicate that the axons of GLP1 neural populations that innervate the thalamic paraventricular nucleus, paraventricular nucleus of the hypothalamus, and/or bed nucleus of the stria terminalis collectively innervate all central regions that receive GLP1 axonal input.

Molecular Mechanisms behind Obesity and Their Potential Exploitation in Current and Future Therapy

Obesity is a chronic disease caused primarily by the imbalance between the amount of calories supplied to the body and energy expenditure. Not only does it deteriorate the quality of life, but most importantly it increases the risk of cardiovascular diseases and the development of type 2 diabetes mellitus, leading to reduced life expectancy. In this review, we would like to present the molecular pathomechanisms underlying obesity, which constitute the target points for the action of anti-obesity medications. These include the central nervous system, brain-gut-microbiome axis, gastrointestinal motility, and energy expenditure. A significant part of this article is dedicated to incretin-based drugs such as GLP-1 receptor agonists (e.g., liraglutide and semaglutide), as well as the brand new dual GLP-1 and GIP receptor agonist tirzepatide, all of which have become "block-buster" drugs due to their effectiveness in reducing body weight and beneficial effects on the patient's metabolic profile. Finally, this review article highlights newly designed molecules with the potential for future obesity management that are the subject of ongoing clinical trials.

The emerging role of glucagon-like peptide 1 in binge eating

Binge eating is a central component of two clinical eating disorders: binge eating disorder and bulimia nervosa. However, the large treatment gap highlights the need to identify other strategies to decrease binge eating. Novel pharmacotherapies may be one such approach. Glucagon-like peptide-1 (GLP-1) is an intestinal and brain-derived neuroendocrine signal with a critical role in promoting glycemic control through its incretin effect. Additionally, the energy balance effects of GLP-1 are well-established; activation of the GLP-1 receptor (GLP-1R) reduces food intake and body weight. Aligned with these beneficial metabolic effects, there are GLP-1R agonists that are currently used for the treatment of diabetes and obesity. A growing body of literature suggests that GLP-1 may also play an important role in binge eating. Dysregulation of the endogenous GLP-1 system is associated with binge eating in non-human animal models, and GLP-1R agonists may be a promising approach to suppress the overconsumption that occurs during binge eating. Here, we briefly discuss the role of GLP-1 in normal energy intake and reward and then review the emerging evidence suggesting that disruptions to GLP-1 signaling are associated with binge eating. We also consider the potential utility of GLP-1-based pharmacotherapies for reducing binge eating behavior.

Examining the Potential Applicability of Orexigenic and Anorexigenic Peptides in Veterinary Medicine for the Management of Obesity in Companion Animals

This review article comprehensively explores the role of orexigenic and anorexigenic peptides in the management of obesity in companion animals, with a focus on clinical applications. Obesity in domestic animals, particularly dogs and cats, is prevalent, with significant implications for their health and well-being. Factors contributing to obesity include overfeeding, poor-quality diet, lack of physical activity, and genetic predispositions. Despite the seriousness of this condition, it is often underestimated, with societal perceptions sometimes reinforcing unhealthy behaviors. Understanding the regulation of food intake and identifying factors affecting the function of food intake-related proteins are crucial in combating obesity. Dysregulations in these proteins, whether due to genetic mutations, enzymatic dysfunctions, or receptor abnormalities, can have profound health consequences. Molecular biology techniques play a pivotal role in elucidating these mechanisms, offering insights into potential therapeutic interventions. The review categorizes food intake-related proteins into anorexigenic peptides (inhibitors of food intake) and orexigenic peptides (enhancers of food intake). It thoroughly examines current research on regulating energy balance in companion animals, emphasizing the clinical application of various peptides, including ghrelin, phoenixin (PNX), asprosin, glucagon-like peptide 1 (GLP-1), leptin, and nesfatin-1, in veterinary obesity management. This comprehensive review aims to provide valuable insights into the complex interplay between peptides, energy balance regulation, and obesity in companion animals. It underscores the importance of targeted interventions and highlights the potential of peptide-based therapies in improving the health outcomes of obese pets.

An endogenous GLP-1 circuit engages VTA GABA neurons to regulate mesolimbic dopamine neurons and attenuate cocaine seeking

Recent studies show that systemic administration of a glucagon-like peptide-1 receptor (GLP-1R) agonist is sufficient to attenuate the reinstatement of cocaine-seeking behavior, an animal model of relapse. However, the neural mechanisms mediating these effects and the role of endogenous central GLP-1 signaling in cocaine seeking remain unknown. Here, we show that voluntary cocaine taking decreased plasma GLP-1 levels in rats and that chemogenetic activation of GLP-1-producing neurons in the nucleus tractus solitarius (NTS) that project to the ventral tegmental area (VTA) decreased cocaine reinstatement. Single nuclei transcriptomics and FISH studies revealed GLP-1Rs are expressed primarily on GABA neurons in the VTA. Using in vivo fiber photometry, we found that the efficacy of a systemic GLP-1R agonist to attenuate cocaine seeking was associated with increased activity of VTA GABA neurons and decreased activity of VTA dopamine neurons. Together, these findings suggest that targeting central GLP-1 circuits may be an effective strategy toward reducing cocaine relapse and highlight a novel functional role of GABAergic GLP-1R-expressing midbrain neurons in drug seeking.

The interplay between leptin, glucocorticoids, and GLP1 regulates food intake and feeding behaviour

Nutritional, endocrine, and neurological signals converge in multiple brain centres to control feeding behaviour and food intake as part of the allostatic regulation of energy balance. Among the several neuroendocrine systems involved, the leptin, glucocorticoid, and glucagon-like peptide 1 (GLP1) systems have been extensively researched. Leptin is at the top hierarchical level since its complete absence is sufficient to trigger severe hyperphagia. Glucocorticoids are key regulators of the energy balance adaptation to stress and their sustained excess leads to excessive adiposity and metabolic perturbations. GLP1 participates in metabolic adaptation to food intake, regulating insulin secretion and satiety by parallel central and peripheral signalling systems. Herein, we review the brain and peripheral targets of these three hormone systems that integrate to regulate food intake, feeding behaviour, and metabolic homeostasis. We examine the functional relationships between leptin, glucocorticoids, and GLP1 at the central and peripheral levels, including the cross-regulation of their circulating levels and their cooperative or antagonistic actions at different brain centres. The pathophysiological roles of these neuroendocrine systems in dysregulated intake are explored in the two extremes of body adiposity - obesity and lipodystrophy - and eating behaviour disorders.

Neurocircuitry underlying the actions of glucagon-like peptide 1 and peptide YY3-36 in the suppression of food, drug-seeking, and anxiogenesis

Obesity is a critical health condition worldwide that increases the risks of comorbid chronic diseases, but it can be managed with weight loss. However, conventional interventions relying on diet and exercise are inadequate for achieving and maintaining weight loss, thus there is significant market interest for pharmaceutical anti-obesity agents. For decades, receptor agonists for the gut peptide glucagon-like peptide 1 (GLP-1) featured prominently in anti-obesity medications by suppressing appetite and food reward to elicit rapid weight loss. As the neurocircuitry underlying food motivation overlaps with that for drugs of abuse, GLP-1 receptor agonism has also been shown to decrease substance use and relapse, thus its therapeutic potential may extend beyond weight management to treat addictions. However, as prolonged use of anti-obesity drugs may increase the risk of mood-related disorders like anxiety and depression, and individuals taking GLP-1-based medication commonly report feeling demotivated, the long-term safety of such drugs is an ongoing concern. Interestingly, current research now focuses on dual agonist approaches that include GLP-1 receptor agonism to enable synergistic effects on weight loss or associated functions. GLP-1 is secreted from the same intestinal cells as the anorectic gut peptide, Peptide YY3-36 (PYY3-36), thus this review assessed the therapeutic potential and underlying neural circuits targeted by PYY3-36 when administered independently or in combination with GLP-1 to curb the appetite for food or drugs of abuse like opiates, alcohol, and nicotine. Additionally, we also reviewed animal and human studies to assess the impact, if any, for GLP-1 and/or PYY3-36 on mood-related behaviors in relation to anxiety and depression. As dual agonists targeting GLP-1 and PYY3-36 may produce synergistic effects, they can be effective at lower doses and offer an alternative approach for therapeutic benefits while mitigating undesirable side effects.

Associations of semaglutide with incidence and recurrence of alcohol use disorder in real-world population

Alcohol use disorders are among the top causes of the global burden of disease, yet therapeutic interventions are limited. Reduced desire to drink in patients treated with semaglutide has raised interest regarding its potential therapeutic benefits for alcohol use disorders. In this retrospective cohort study of electronic health records of 83,825 patients with obesity, we show that semaglutide compared with other anti-obesity medications is associated with a 50%-56% lower risk for both the incidence and recurrence of alcohol use disorder for a 12-month follow-up period. Consistent reductions were seen for patients stratified by gender, age group, race and in patients with and without type 2 diabetes. Similar findings are replicated in the study population with 598,803 patients with type 2 diabetes. These findings provide evidence of the potential benefit of semaglutide in AUD in real-world populations and call for further randomized clinicl trials.

CCK-sensitive C fibers activate NTS leptin receptor-expressing neurons via NMDA receptors

The hormone leptin reduces food intake through actions in the peripheral and central nervous systems, including in the hindbrain nucleus of the solitary tract (NTS). The NTS receives viscerosensory information via vagal afferents, including information from the gastrointestinal tract, which is then relayed to other central nervous system (CNS) sites critical for control of food intake. Leptin receptors (lepRs) are expressed by a subpopulation of NTS neurons, and knockdown of these receptors increases both food intake and body weight. Recently, we demonstrated that leptin increases vagal activation of lepR-expressing neurons via increased NMDA receptor (NMDAR) currents, thereby potentiating vagally evoked firing. Furthermore, chemogenetic activation of these neurons was recently shown to inhibit food intake. However, the vagal inputs these neurons receive had not been characterized. Here we performed whole cell recordings in brain slices taken from lepRCre × floxedTdTomato mice and found that lepR neurons of the NTS are directly activated by monosynaptic inputs from C-type afferents sensitive to the transient receptor potential vanilloid type 1 (TRPV1) agonist capsaicin. CCK administered onto NTS slices stimulated spontaneous glutamate release onto lepR neurons and induced action potential firing, an effect mediated by CCKR1. Interestingly, NMDAR activation contributed to the current carried by spontaneous excitatory postsynaptic currents (EPSCs) and enhanced CCK-induced firing. Peripheral CCK also increased c-fos expression in these neurons, suggesting they are activated by CCK-sensitive vagal afferents in vivo. Our results indicate that the majority of NTS lepR neurons receive direct inputs from CCK-sensitive C vagal-type afferents, with both peripheral and central CCK capable of activating these neurons and NMDARs able to potentiate these effects.

Dopamine neuron activity evoked by sucrose and sucrose-predictive cues is augmented by peripheral and central manipulations of glucose availability

Food deprivation drives eating through multiple signals and circuits. Decreased glucose availability (i.e., cytoglucopenia) drives eating and also increases the value of sucrose. Ventral tegmental area (VTA) dopamine neurons (DANs) contribute to the evaluation of taste stimuli, but their role in integrating glucoprivic signals remains unknown. We monitored VTA DAN activity via Cre-dependent expression of a calcium indicator with in vivo fibre photometry. In ad libitum fed rats, intraoral sucrose evoked a phasic increase in DAN activity. To manipulate glucose availability, we administered (intraperitoneal, lateral or fourth ventricular) the antiglycolytic agent 5-thio-D-glucose (5TG), which significantly augmented the phasic DAN activity to sucrose. 5TG failed to alter DAN activity to water or saccharin, suggesting the response was selective for caloric stimuli. 5TG enhancement of sucrose-evoked DAN activity was stronger after fourth ventricular administration, suggesting a critical node of action within the hindbrain. As 5TG also increases blood glucose, in a separate study, we used peripheral insulin, which stimulates eating, to decrease blood glucose-which was associated with increased DAN activity to intraoral sucrose. DAN activity developed to a cue predictive of intraoral sucrose. While 5TG augmented cue-evoked DAN activity, its action was most potent when delivered to the lateral ventricle. Together, the studies point to central glucose availability as a key modulator of phasic DAN activity to food and food-cues. As glucose sensing neurons are known to populate the hypothalamus and brainstem, results suggest differential modulation of cue-evoked and sucrose-evoked DAN activity.

Metformin and the Liver: Unlocking the Full Therapeutic Potential

Metformin is a highly effective medication for managing type 2 diabetes mellitus. Recent studies have shown that it has significant therapeutic benefits in various organ systems, particularly the liver. Although the effects of metformin on metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis are still being debated, it has positive effects on cirrhosis and anti-tumoral properties, which can help prevent the development of hepatocellular carcinoma. Furthermore, it has been proven to improve insulin resistance and dyslipidaemia, commonly associated with liver diseases. While more studies are needed to fully determine the safety and effectiveness of metformin use in liver diseases, the results are highly promising. Indeed, metformin has a terrific potential for extending its full therapeutic properties beyond its traditional use in managing diabetes.

Mechanisms of probiotic modulation of ovarian sex hormone production and metabolism: a review

Sex hormones play a pivotal role in the growth and development of the skeletal, neurological, and reproductive systems. In women, the dysregulation of sex hormones can result in various health complications such as acne, hirsutism, and irregular menstruation. One of the most prevalent diseases associated with excess androgens is polycystic ovary syndrome with a hyperandrogenic phenotype. Probiotics have shown the potential to enhance the secretion of ovarian sex hormones. However, the underlying mechanism of action remains unclear. Furthermore, comprehensive reviews detailing how probiotics modulate ovarian sex hormones are scarce. This review seeks to shed light on the potential mechanisms through which probiotics influence the production of ovarian sex hormones. The role of probiotics across various biological axes, including the gut-ovarian, gut-brain-ovarian, gut-liver-ovarian, gut-pancreas-ovarian, and gut-fat-ovarian axes, with a focus on the direct impact of probiotics on the ovaries via the gut and their effects on brain gonadotropins is discussed. It is also proposed herein that probiotics can significantly influence the onset, progression, and complications of ovarian sex hormone abnormalities. In addition, this review provides a theoretical basis for the therapeutic application of probiotics in managing sex hormone-related health conditions.

Acute and Chronic Exposure to Linagliptin, a Selective Inhibitor of Dipeptidyl Peptidase-4 (DPP-4), Has an Effect on Dopamine, Serotonin and Noradrenaline Level in the Striatum and Hippocampus of Rats

Linagliptin is a selective dipeptidyl peptidase-4 (DPP-4) inhibitor that indirectly elevates the glucagon-like peptide-1 (GLP-1) level. The aim of the present study was to check whether linagliptin has an influence on neurotransmission in rat brain. Rats were acutely and chronically exposed to linagliptin (10 and 20 mg/kg, intraperitoneally (i.p.)). Twenty-four hours later, the striatum and hippocampus were selected for further studies. In neurochemical experiments, using high-performance liquid chromatography with electrochemical detection (HPLC-ED), the concentrations of three major neurotransmitters-dopamine, serotonin and noradrenaline-and their metabolites were measured. The analysis of mRNA expression of dopamine (D1 and D2), serotonin (5-HT-1 and 5-HT-2) and noradrenaline (α1 and α2a) receptors was also investigated using real-time quantitative reverse transcription polymerase chain reaction (RQ-PCR) in the same brain areas. Linagliptin has the ability to influence the dopaminergic system. In the striatum, the elevation of dopamine and its metabolites was observed after repeated administration of that linagliptin, and in the hippocampus, a reduction in dopamine metabolism was demonstrated. Acute linagliptin exposure increases the serotonin level in both areas, while after chronic linagliptin administration a tendency for the mRNA expression of serotoninergic receptors (5-HT1A and 5-HT2A) to increase was observed. A single instance of exposure to linagliptin significantly modified the noradrenaline level in the striatum and intensified noradrenaline turnover in the hippocampus. The recognition of the interactions in the brain between DPP-4 inhibitors and neurotransmitters and/or receptors is a crucial step for finding novel discoveries in the pharmacology of DPP-4 inhibitors and raises hope for further applications of DPP-4 inhibitors in clinical practices.

Acupuncture for obesity and related diseases: Insight for regulating neural circuit

Obesity is defined as abnormal or excessive fat accumulation that may impair health. Obesity is associated with numerous pathological changes including insulin resistance, fatty liver, hyperlipidemias, and other obesity-related diseases. These comorbidities comprise a significant public health threat. Existing anti-obesity drugs have been limited by side effects that include depression, suicidal thoughts, cardiovascular complications and stroke. Acupuncture treatment has been shown to be effective for treating obesity and obesity-related conditions, while avoiding side effects. However, the mechanisms of acupuncture in treating obesity-related diseases, especially its effect on neural circuits, are not well understood. A growing body of research has studied acupuncture's effects on the endocrine system and other mechanisms related to the regulation of neural circuits. In this article, recent research that was relevant to the use of acupuncture to treat obesity and obesity-related diseases through the neuroendocrine system, as well as some neural circuits involved, was summarized. Based on this, acupuncture's potential ability to regulate neural circuits and its mechanisms of action in the endocrine system were reviewed, leading to a deeper mechanistic understanding of acupuncture's effects and providing insight and direction for future research about obesity. Please cite this article as: Jiang LY, Tian J, Yang YN, Jia SH, Shu Q. Acupuncture for obesity and related diseases: insight for regulating neural circuit. J Integr Med. 2024; 22(2): 93-101.

Review article: Pharmacologic management of obesity - updates on approved medications, indications and risks

BACKGROUND

Obesity has reached epidemic proportions, with >40% of the US population affected. Although traditionally managed by lifestyle modification, and less frequently by bariatric therapies, there are significant pharmacological advancements.

AIMS

To conduct a narrative review of the neurohormonal and physiological understanding of weight gain and obesity, and the development, clinical testing, indications, expected clinical outcomes, and associated risks of current FDA-approved and upcoming anti-obesity medications (AOMs).

METHODS

We conducted a comprehensive review in PubMed for articles on pathophysiology and complications of obesity, including terms 'neurohormonal', 'obesity', 'incretin', and 'weight loss'. Next, we searched for clinical trial data of all FDA-approved AOMs, including both the generic and trade names of orlistat, phentermine/topiramate, bupropion/naltrexone, liraglutide, and semaglutide. Additional searches were conducted for tirzepatide and retatrutide - medications expecting regulatory approval. Searches included combinations of terms related to mechanism of action, indications, side effects, risks, and future directions.

RESULTS

We reviewed the pathophysiology of obesity, including specific role of incretins and glucagon. Clinical data supporting the use of various FDA-approved medications for weight loss are presented, including placebo-controlled or, when available, head-to-head trials. Beneficial metabolic effects, including impact on liver disease, adverse effects and risks of medications are discussed, including altered gastrointestinal motility and risk for periprocedural aspiration.

CONCLUSION

AOMs have established efficacy and effectiveness for weight loss even beyond 52 weeks. Further pharmacological options, such as dual and triple incretins, are probable forthcoming additions to clinical practice for combating obesity and its metabolic consequences such as metabolic dysfunction-associated steatotic liver disease.