Bupropion increases activation in nucleus accumbens during anticipation of monetary reward

Efficacy of opioid antagonist in patients with binge eating behavior: A systemic review and meta-analysis

BACKGROUND

Binge eating (BE) involves consuming unusually large amounts of food within a short period and feeling a loss of control. Neurobiological mechanisms underlying BE involve dysregulation of reward and inhibitory control systems, with the endogenous opioid system playing a key role. Opioid antagonists and the combination therapies with bupropion may have potential to reduce BE by affecting the reward system, but evidence regarding their effectiveness remains inconclusive. This meta-analysis reviewed randomized controlled trials (RCTs) exploring the effects of opioid antagonists on BE frequency, BE severity, body weight, and mood.

METHODS

We systematically searched PubMed, Embase, Cochrane CENTRAL, Web of Science, and ClinicalTrials.gov to identify RCTs published before May 14, 2023,. The primary outcomes were BE severity and frequency. The secondary outcomes were percentage change in body weight and depressive symptoms.

RESULTS

Eight RCTs were included in our analysis. Opioid antagonists significantly reduced BE frequency (standard difference in means [SMD] = -0.624, 95 % confidence interval [CI] = -1.181 to -0.067, p = 0.028) and changes in body weight percentage (SMD = -0.981, 95 % CI = -1.657 to -0.305, p = 0.004), with a moderate-to-large effect size. Conversely, opioid antagonists didn't significantly improve BE severity (Hedges' g = -0.210, 95 % CI = -0.431 to 0.011, p = 0.063) or depressive symptoms (Hedges' g = -0.190, 95 % CI = -0.434 to 0.053, p = 0.125). Meta-regression analysis revealed that the dosage of naltrexone served as a moderator in reducing BE frequency and body weight percentage.

CONCLUSION

The present meta-analysis indicated that opioid antagonists effectively alleviate BE frequency and reduce percentage loss in body weight.

Novel multi-modal methodology to investigate placebo response in major depressive disorder

The neurobiological mechanisms underlying the placebo phenomenon in patients with major depressive disorder (MDD) remain largely unknown. The progressive rise in rates of placebo responses within clinical trials over the past two decades may impede the detection of a true signal and thus present a major obstacle in new treatment development. Understanding the mechanisms would have several important implications, including (1) identifying biomarkers of placebo responders (thereby identifying those individuals who could benefit therapeutically from such interventions), (2) opening new avenues for manipulating such mechanisms to maximize symptom reduction, and (3) refining treatments with approaches that decrease (in clinical trials) or increase (in clinical practice) the placebo response. Here we investigated the research question: is the dopaminergic system one of the neurobiological underpinnings of the placebo response within MDD? Inspired by preclinical and clinical findings that have implicated dopamine in the occurrence, prediction, and expectation of reward, we hypothesized that dopaminergic activity in the mesolimbic system is a critical mediator of placebo response in MDD. To test this hypothesis, we designed a double-blind, placebo-controlled, sequential parallel comparison design clinical trial aimed at maximizing placebo antidepressant response. We integrated behavioral, imaging, and hemodynamic probes of mesocorticolimbic dopaminergic pathways within the context of manipulations of psychological constructs previously linked to placebo responses (e.g., expectation of improvement). The aim of this manuscript is to present the rationale of the study design and to demonstrate how a cross-modal methodology may be utilized to investigate the role of reward circuitry in placebo response in MDD.

A randomized placebo controlled trial demonstrates the effect of dl-methylephedrine on brain functions is weaker than that of pseudoephedrine

Intellectual drug doping in athletics by using stimulants that affect central nervous system functions has been diversified. Stimulants are regulated by the World Anti-Doping Agency according to their levels of urinary concentration. Positron emission tomography could evaluate how stimulants affect central nervous system functions. We aimed to evaluate the effect of stimulants on brain function by examining the difference in brain dopamine transporter occupancy by PET after administration of dl-methylephedrine or pseudoephedrine at the clinical maximum daily dose. Four PET scans without and with drug administration (placebo, dl-methylephedrine 150 mg and pseudoephedrine 240 mg) were performed. The concentrations of dl-methylephedrine and pseudoephedrine in plasma and urine were measured. DAT occupancies in the striatum with placebo, dl-methylephedrine and pseudoephedrine were calculated by PET images. The urinary concentration of dl-methylephedrine (12.7 µg/mL) exceeded the prohibited concentration (10 µg/mL), but the DAT occupancy with dl-methylephedrine (6.1%) did not differ (p = 0.92) from that with placebo (6.2%). By contrast, although the urinary concentration of pseudoephedrine (144.8 µg/mL) was below the prohibited concentration (150 μg/mL), DAT occupancy with pseudoephedrine was 18.4%, which was higher than that with placebo (p = 0.009). At the maximum clinical dose, dl-methylephedrine was shown to have weaker effects on brain function than pseudoephedrine.

Neural Circuitry-Related Biomarkers for Drug Development in Psychiatry: An Industry Perspective

Drug development in psychiatry has been hampered by the lack of reliable ways to determine the neurobiological effects of the assets tested, difficulties in identifying patient subsets more amenable to benefit from a given asset, and issues with executing trials in a manner that would convincingly provide answers. An emerging idea in many companies is to validate tools to address changes in neural circuits by pharmacological tools as a key piece in quantifying the effects of our drugs. Here, we review past, present, and emerging approaches to capture the outcome of the modulation of brain circuits. The field is now ripe for implementing these approaches in drug development.

Neurogenetics and Epigenetics of Loneliness

Loneliness, an established risk factor for both, mental and physical morbidity, is a mounting public health concern. However, the neurobiological mechanisms underlying loneliness-related morbidity are not yet well defined. Here we examined the role of genes and associated DNA risk polymorphic variants that are implicated in loneliness via genetic and epigenetic mechanisms and may thus point to specific therapeutic targets. Searches were conducted on PubMed, Medline, and EMBASE databases using specific Medical Subject Headings terms such as loneliness and genes, neuro- and epigenetics, addiction, affective disorders, alcohol, anti-reward, anxiety, depression, dopamine, cancer, cardiovascular, cognitive, hypodopaminergia, medical, motivation, (neuro)psychopathology, social isolation, and reward deficiency. The narrative literature review yielded recursive collections of scientific and clinical evidence, which were subsequently condensed and summarized in the following key areas: (1) Genetic Antecedents: Exploration of multiple genes mediating reward, stress, immunity and other important vital functions; (2) Genes and Mental Health: Examination of genes linked to personality traits and mental illnesses providing insights into the intricate network of interaction converging on the experience of loneliness; (3) Epigenetic Effects: Inquiry into instances of loneliness and social isolation that are driven by epigenetic methylations associated with negative childhood experiences; and (4) Neural Correlates: Analysis of loneliness-related affective states and cognitions with a focus on hypodopaminergic reward deficiency arising in the context of early life stress, eg, maternal separation, underscoring the importance of parental support early in life. Identification of the individual contributions by various (epi)genetic factors presents opportunities for the creation of innovative preventive, diagnostic, and therapeutic approaches for individuals who cope with persistent feelings of loneliness. The clinical facets and therapeutic prospects associated with the current understanding of loneliness, are discussed emphasizing the relevance of genes and DNA risk polymorphic variants in the context of loneliness-related morbidity.

The human cerebellum in reward anticipation and reward outcome processing: An activation likelihood estimation meta-analysis

The cerebellum generates internal prediction models and actively compares anticipated and actual outcomes in order to reach a desired end state. In this process, reward can serve as a reinforcer that shapes internal prediction models, enabling context-appropriate behavior. While the involvement of the cerebellum in reward processing has been established in animals, there is no detailed account of which cerebellar regions are involved in reward anticipation and reward outcome processing in humans. To this end, an activation likelihood estimation meta-analysis of functional neuroimaging studies was performed to investigate cerebellar functional activity patterns associated with reward anticipation and reward outcome processing in healthy adults. Results showed that reward anticipation (k=31) was associated with regional activity in the bilateral anterior lobe, bilateral lobule VI, left Crus I and the posterior vermis, while reward outcome (k=16) was associated with regional activity in the declive and left lobule VI. The findings of this meta-analysis show distinct involvement of the cerebellum in reward anticipation and reward outcome processing as part of a predictive coding routine.

Hazardous or harmful alcohol use and reward processing in people with HIV

The intersecting epidemics of HIV and hazardous or harmful alcohol use (HAU) can have significant detrimental consequences. Both HIV and HAU have independent negative influences on executive function. Dysfunction in reward processing may play a role in these co-occurring epidemics. In this cross-sectional case-control study, we investigated the association of HAU with reward processing amongst people with HIV (PWH). We investigated the function of the ventral-striatal reward system using a functional MRI (fMRI) monetary incentive delay (MID) task in a sample of 60 South African adults (mean age 32.7 years): 42 living with HIV and on ART (21 with harmful alcohol use [HIV + HAU], 21 without [HIV-HAU]) and 18 healthy controls, matched for age, gender, and resident community. Education significantly influenced task performance, with those with a secondary level of education demonstrating a greater increase in reaction time (p = 0.048) and accuracy (p = 0.002) than those without. There were no significant differences in reward anticipation in the ventral striatum (VS) between HIV + HAU, HIV-HAU, and healthy controls when controlling for level of education. There were also no significant differences in reward outcome in the orbitofrontal cortex (OFC) between HIV + HAU, HIV-HAU, and healthy controls when controlling for level of education. In a sample of South African adults, we did not demonstrate significant differences in reward anticipation in the VS and reward outcome in the OFC in PWH, with and without HAU, and controls. Factors, such as task performance, education, and depression may have influenced our results. Further studies are needed to better delineate the potential links between HIV, HAU, and depression and reward system function.

The comparative effectiveness of antidepressants for youths with major depressive disorder: a nationwide population-based study in Taiwan

Background:

Guidelines recommend fluoxetine as a first-line medication for youths diagnosed with major depressive disorder (MDD). However, little is known about the long-term effectiveness of different antidepressants in juveniles in the real world. This study aimed to compare the effectiveness of antidepressants in youths with MDD.

Methods:

Youths (<20 years old) with a diagnosis of MDD who were new users of antidepressants were selected from a nationwide population-based cohort in Taiwan between 1997 and 2013. We divided a total of 16,981 users (39.9% male; mean age: 16.6 years) into 10 different antidepressant groups (fluoxetine, sertraline, paroxetine, venlafaxine, citalopram, escitalopram, bupropion, fluvoxamine, mirtazapine and moclobemide). Regarding treatment outcomes (hospitalisation and medication discontinuation), Cox proportional hazards regression models were applied to estimate the hazards of such outcomes.

Results:

Compared with the youths treated with fluoxetine, the bupropion-treated group demonstrated lower rates of hospitalisation and discontinuation. Mirtazapine-treated group demonstrated a higher hospitalisation risk mainly when administered for single depressive episodes. Furthermore, patients treated with sertraline and fluvoxamine had higher discontinuation rates. Among the younger teenage subgroups (< 16 years), significantly higher rates of discontinuation were observed in those treated with sertraline, escitalopram and fluvoxamine. Among the older teenage subgroups (⩾ 16 years), bupropion was superior to fluoxetine in preventing hospitalisation and discontinuation.

Conclusion:

We concluded that bupropion might surpass fluoxetine with regard to hospitalisation prevention and drug therapy maintenance among youths with MDD, while mirtazapine users demonstrated a higher hospitalisation risk. Our findings might serve as a reference for clinicians in future studies.

The Timing of Clinical Effects of Bupropion Misuse Via Insufflation Reported to a Regional Poison Center

BACKGROUND

Bupropion is an antidepressant medication with expanding indications including smoking cessation, weight loss, attention-deficit/hyperactivity disorder, seasonal affective disorder, and amphetamine dependence. Despite its increasing popularity among providers, it has a well-known narrow therapeutic window that can lead to delayed onset of symptoms with extended-release formulations and devastating consequences in overdose. We have noticed some patients misusing bupropion via insufflation, which added a layer of complexity with regards to the therapeutic application of the drug. This route of use created difficult decisions regarding clinical monitoring in these patients.

OBJECTIVES

To determine if prolonged observation is required after insufflation of bupropion and to further describe effects from this route of use.

METHODS

This is a retrospective observational study reviewing all the cases of insufflated bupropion use reported to a single poison center without any other coingestants.

RESULTS

The majority (85.7%) of patients had mild or moderate effects, and seizures occurred in 19.6% of cases; and the vast majority of patients were symptomatic by the time of the initial call to the poison center. We did not encounter any delayed effects after this route of use.

CONCLUSIONS

This report describes the clinical effects reported, and the timing of these effects, after insufflation of bupropion.

Diets and drugs for weight loss and health in obesity - An update

Numerous combinations of diets and pharmacological agents, including lifestyle changes, have been launched to treat obesity. There are still ambiguities regarding the efficacies of different approaches despite many clinical trials and the use of animal models to study physiological mechanisms in weight management and obesity comorbidities, Here, we present an update on promising diets and pharmacological aids. Literature published after the year 2005 was searched in PubMed, Medline and Google scholar. Among recommended diets are low-fat (LF) and low-carbohydrate (LC) diets, in addition to the Mediterranean diet and the intermittent fasting approach, all of which presumably being optimized by adequate contents of dietary fibers. A basic point for weight loss is to adopt a diet that creates a permanently negative and acceptable energy balance, and prolonged dietary adherence is a crucial factor. As for pharmacological aids, obese patients with type 2 diabetes or insulin resistance seem to benefit from LC diet combined with a GLP-1 agonist, e.g. semaglutide, which may improve glycemic control, stimulate satiety, and suppress appetite. The lipase inhibitor orlistat is still used to maintain a low-fat approach, which may be favorable e.g. in hypercholesterolemia. The bupropion-naltrexone-combination appears promising for interruption of the vicious cycle of addictive over-eating. Successful weight loss seems to improve almost all biomarkers of obesity comorbidities. Until more support for specific strategies is available, clinicians should recommend an adapted lifestyle, and when necessary, a drug combination tailored to individual needs and comorbidities. Different diets may change hormonal secretion, gut-brain signaling, and influence hunger, satiety and energy expenditure. Further research is needed to clarify mechanisms and how such knowledge can be used in weight management.

Reward processing as a common diathesis for chronic pain and depression

Pain disorders and psychiatric illness are strongly comorbid, particularly in the context of Major Depressive Disorder (MDD). While these disorders account for a significant amount of global disability, the mechanisms of their overlap remain unclear. Understanding these mechanisms is of vital importance to developing prevention strategies and interventions that target both disorders. Of note, brain reward processing may be relevant to explaining how the comorbidity arises, given pain disorders and MDD can result in maladaptive reward responsivity that limits reward learning, appetitive approach behaviours and consummatory response. In this review, we discuss this research and explore the possibility of reward processing deficits as a common diathesis to explain the manifestation of pain disorders and MDD. Specifically, we hypothesize that contextual physical or psychological events (e.g. surgery, divorce) in the presence of a reward impairment diathesis worsens symptoms and results in a negative feedback loop that increases the chronicity and probability of developing the other disorder. We also highlight the implications for treatment and provide a framework for future research.

Clinical effects of intravenous bupropion misuse reported to a regional poison center

Bupropion is an antidepressant medication with expanding indications including smoking cessation, weight loss, attention-deficit/hyperactivity disorder, seasonal affective disorder, and amphetamine dependence. Despite its increasing popularity among providers, it has a well-known narrow therapeutic window which can lead to delayed onset of symptoms with extended-release formulations and devastating consequences in overdose. We have noticed some patients misusing bupropion via intravenous use and had difficulty guiding decisions regarding clinical monitoring in these patients. As this route entirely changes the kinetics of bupropion, this has caused concern within our group. We reviewed all the cases of intravenous bupropion use reported to a single poison center without any other coingestants. The majority (66.7%) of patients had moderate effects and one patient had a seizure. No deaths were reported. All patients were symptomatic by the time of initial call to the poison center if they had any reported symptoms due to bupropion. This case series describes the clinical effects reported, and the timing of these effects, after intravenous bupropion use.

Thalamic shape abnormalities in patients with multiple sclerosis-related fatigue

Thalamus plays an important role in the pathogenesis of multiple sclerosis-related fatigue (MSrF). However, the thalamus is a heterogeneous structure and the specific thalamic subregions that are involved in this condition are unclear. Here, we used thalamic shape analysis for the detailed localization of thalamic abnormalities in MSrF. Using the Modified Fatigue Impact Scale, we measured fatigue in 42 patients with relapsing-remitting multiple sclerosis (MS). The thalamic shape was extracted from T1w images using an automated pipeline. We investigated the association of thalamic surface deviations with the severity of global fatigue and its cognitive, physical and psychosocial subdomains. Cognitive fatigue was correlated with an inward deformity of the left anteromedial thalamic surface, but no other localized shape deviation was observed in correlation with global, physical or psychosocial fatigue. Our findings indicate that the left anteromedial thalamic subregions are implicated in cognitive fatigue, possibly through their role in reward processing and cognitive and executive functions.

Reward-related neural correlates in adolescents with excess body weight

The functional and connectivity reward processing in adults with excessive body weight is well documented, though is relatively less researched during adolescence. Given that reward and inhibition may be highly malleable during adolescence, it is unknown how impulsive behaviors, potentially stemming from impaired inhibitory control and heightened sensitivity to rewarding cues, relate to increases in body weight in adolescents. Adolescents (N = 76; mean age = 14.10 years, SD = 1.92) with varied body mass index (BMI) performed a child-friendly monetary incentive delay task during functional magnetic resonance imaging, to study reward processing during the anticipation of rewards (cue) and reactions to feedback about rewards (feedback). Our results show that adolescents with greater BMI z-score show neural activation and ventral striatum connectivity alterations in networks implicated in reward, salience detection, and inhibitory control. These bottom-up reward and top-down inhibitory control networks, as well as interactions between these networks were prevalent during the anticipation period (when the cue is presented) as well as when receiving feedback about whether one has received a reward. Specifically, our results were mainly driven by failure to receive a reward in the feedback period, and the anticipation of a potential reward in the anticipation period. Overall, we provide evidence for heightened reward salience as well as inhibitory control deficits that, in combination, may contribute to the impulsive behaviors that lead to higher BMI in adolescents.

Great Expectations: A Critical Review of and Suggestions for the Study of Reward Processing as a Cause and Predictor of Depression

Both human and animal studies support the relationship between depression and reward processing abnormalities, giving rise to the expectation that neural signals of these processes may serve as biomarkers or mechanistic treatment targets. Given the great promise of this research line, we scrutinized those findings and the theoretical claims that underlie them. To achieve this, we applied the framework provided by classical work on causality as well as contemporary approaches to prediction. We identified a number of conceptual, practical, and analytical challenges to this line of research and used a preregistered meta-analysis to quantify the longitudinal associations between reward processing abnormalities and depression. We also investigated the impact of measurement error on reported data. We found that reward processing abnormalities do not reach levels that would be useful for clinical prediction, yet the available evidence does not preclude a possible causal role in depression.

Lithium modulates striatal reward anticipation and prediction error coding in healthy volunteers

Lithium is one of the most effective mood-stabilizing medications in bipolar disorder. This study was designed to test whether lithium administration may stabilize mood via effects on reward processing. It was hypothesized that lithium administration would modulate reward processing in the striatum and affect both anticipation and outcome computations. Thirty-seven healthy human participants (18 males, 33 with suitable fMRI data) received 11 (±1) days of lithium carbonate or placebo intervention (double-blind), after which they completed the monetary incentive delay task while fMRI data were collected. The monetary incentive delay task is a robust task with excellent test-retest reliability and is well suited to investigate different phases of reward processing within the caudate and nucleus accumbens. To test for correlations with prediction error signals a Rescorla-Wagner reinforcement-learning model was applied. Lithium administration enhanced activity in the caudate during reward anticipation compared to placebo. In contrast, lithium administration reduced caudate and nucleus accumbens activity during reward outcome. This latter effect seems related to learning as reward prediction errors showed a positive correlation with caudate and nucleus accumbens activity during placebo, which was absent after lithium administration. Lithium differentially modulates the anticipation relative to the learning of rewards. This suggests that lithium might reverse dampened reward anticipation while reducing overactive reward updating in patients with bipolar disorder. This specific effect of lithium suggests that a targeted modulation of reward learning may be a viable approach for novel interventions in bipolar disorder.

Using pharmacological manipulations to study the role of dopamine in human reward functioning: A review of studies in healthy adults

Dopamine (DA) plays a key role in reward processing and is implicated in psychological disorders such as depression, substance use, and schizophrenia. The role of DA in reward processing is an area of highly active research. One approach to this question is drug challenge studies with drugs known to alter DA function. These studies provide good experimental control and can be performed in parallel in laboratory animals and humans. This review aimed to summarize results of studies using pharmacological manipulations of DA in healthy adults. 'Reward' is a complex process, so we separated 'phases' of reward, including anticipation, evaluation of cost and benefits of upcoming reward, execution of actions to obtain reward, pleasure in response to receiving a reward, and reward learning. Results indicated that i) DAergic drugs have different effects on different phases of reward; ii) the relationship between DA and reward functioning appears unlikely to be linear; iii) our ability to detect the effects of DAergic drugs varies depending on whether subjective, behavioral, imaging measures are used.

Association between Chronic Pain and Alterations in the Mesolimbic Dopaminergic System

Chronic pain (pain lasting for >3 months) decreases patient quality of life and even occupational abilities. It can be controlled by treatment, but often persists even after management. To properly control pain, its underlying mechanisms must be determined. This review outlines the role of the mesolimbic dopaminergic system in chronic pain. The mesolimbic system, a neural circuit, delivers dopamine from the ventral tegmental area to neural structures such as the nucleus accumbens, prefrontal cortex, anterior cingulate cortex, and amygdala. It controls executive, affective, and motivational functions. Chronic pain patients suffer from low dopamine production and delivery in this system. The volumes of structures constituting the mesolimbic system are known to be decreased in such patients. Studies on administration of dopaminergic drugs to control chronic pain, with a focus on increasing low dopamine levels in the mesolimbic system, show that it is effective in patients with Parkinson's disease, restless legs syndrome, fibromyalgia, dry mouth syndrome, lumbar radicular pain, and chronic back pain. However, very few studies have confirmed these effects, and dopaminergic drugs are not commonly used to treat the various diseases causing chronic pain. Thus, further studies are required to determine the effectiveness of such treatment for chronic pain.