Hypothesis: Amelioration of obesity-induced cognitive dysfunction via a lorcaserin-betahistine combination treatment

The prolonged exposure to obesogenic diets disrupts the mesocortical dopaminergic input to the prefrontal cortex (PFC). This leads to suboptimal dopamine levels in this brain region, which affects cognition and control of food intake. Treatments that restore mesocortical dopaminergic neurotransmission may improve obesity‐associated cognitive dysfunction and modulate food intake to induce weight loss. Given the complexity and multifactorial nature of obesity, combination treatments would likely achieve sizeable and sustained body weight loss and improve obesity‐linked outcomes, such as cognitive dysfunction. Given this background, we hypothesize that concomitant activation of serotonin 5‐HT2C and histamine H1 receptors, coupled with antagonism of histamine H3 receptors, synergistically modulates mesocortical dopamine neurotransmission and ameliorates obesity‐induced cognitive dysfunction. We propose to test the hypothesis in a diet‐induced obesity (DIO) rat model by treating animals with the 5‐HT2C agonist lorcaserin and the H1 agonist and H3 antagonist betahistine. Consistent with our hypothesis, both lorcaserin and betahistine have been shown to reduce body weight in humans with obesity and animals. Both drugs have been demonstrated to improve cognitive functions by influencing dopaminergic signaling in the PFC. The proposed combination treatment addresses the paucity of studies on obesity treatments that improve cognitive function. This research may also help identify a potential targetable mechanism connecting obesity and neurocognitive outcomes.

Orexin, serotonin, and energy balance

The lateral hypothalamus is critical for the control of ingestive behavior and spontaneous physical activity (SPA), as lesion or stimulation of this region alters these behaviors. Evidence points to lateral hypothalamic orexin neurons as modulators of feeding and SPA. These neurons affect a broad range of systems, and project to multiple brain regions such as the dorsal raphe nucleus, which contains serotoninergic neurons (DRN) important to energy homeostasis. Physical activity is comprised of intentional exercise and SPA. These are opposite ends of a continuum of physical activity intensity and structure. Non‐goal‐oriented behaviors, such as fidgeting, standing, and ambulating, constitute SPA in humans, and reflect a propensity for activity separate from intentional activity, such as high‐intensity voluntary exercise. In animals, SPA is activity not influenced by rewards such as food or a running wheel. Spontaneous physical activity in humans and animals burns calories and could theoretically be manipulated pharmacologically to expend calories and protect against obesity. The DRN neurons receive orexin inputs, and project heavily onto cortical and subcortical areas involved in movement, feeding and energy expenditure (EE). This review discusses the function of hypothalamic orexin in energy‐homeostasis, the interaction with DRN serotonin neurons, and the role of this orexin‐serotonin axis in regulating food intake, SPA, and EE. In addition, we discuss possible brain areas involved in orexin–serotonin cross‐talk; the role of serotonin receptors, transporters and uptake‐inhibitors in the pathogenesis and treatment of obesity; animal models of obesity with impaired serotonin‐function; single‐nucleotide polymorphisms in the serotonin system and obesity; and future directions in the orexin–serotonin field.

This article is categorized under:

Metabolic Diseases > Molecular and Cellular Physiology

Serotonin and Dopamine Mimic Glucose-Induced Reinforcement in C. elegans: Potential Role of NSM Neurons and the Serotonin Subtype 4 Receptor

Food produces powerful reinforcement that can lead to overconsumption and likely contributes to the obesity epidemic. The present studies examined molecular mechanisms mediating food-induced reinforcement in the model system C. elegans. After a 1-h training session during which food (bacteria) is paired with the odorant butanone, odor preference for butanone robustly increased. Glucose mimicked this effect of bacteria. Glucose-induced odor preference was enhanced similarly by prior food withdrawal or blocking glucose metabolism in the presence of food. Food- and glucose-induced odor preference was mimicked by serotonin signaling through the serotonin type-4 (5-HT4) receptor. Dopamine (thought to act primarily through a D1-like receptor) facilitated, whereas the D2 agonist bromocriptine blocked, food- and glucose-induced odor preference. Furthermore, prior food withdrawal similarly influenced reward produced by serotonin, dopamine, or food, implying post-synaptic enhancement of sensitivity to serotonin and dopamine. These results suggest that glucose metabolism plays a key role in mediating both food-induced reinforcement and enhancement of that reinforcement by prior food withdrawal and implicate serotonergic signaling through 5-HT4 receptor in the re-enforcing properties of food.

Interventions for the management of obesity in people with bipolar disorder

BACKGROUND

Bipolar disorder is one of the most common serious mental illnesses, affecting approximately 60 million people worldwide. Characterised by extreme alterations in mood, cognition, and behaviour, bipolar disorder can have a significant negative impact on the functioning and quality of life of the affected individual. Compared with the general population, the prevalence of comorbid obesity is significantly higher in bipolar disorder. Approximately 68% of treatment seeking bipolar patients are overweight or obese. Clinicians are aware that obesity has the potential to contribute to other physical health conditions in people with bipolar disorder, including diabetes, hypertension, metabolic syndrome, cardiovascular disease, and coronary heart disease. Cardiovascular disease is the leading cause of premature death in bipolar disorder, happening a decade or more earlier than in the general population. Contributing factors include illness-related factors (mood-related factors, i.e. mania or depression), treatment-related factors (weight implications and other side effects of medications), and lifestyle factors (physical inactivity, poor diet, smoking, substance abuse). Approaches to the management of obesity in individuals with bipolar disorder are diverse and include non-pharmacological interventions (i.e. dietary, exercise, behavioural, or multi-component), pharmacological interventions (i.e. weight loss drugs or medication switching), and bariatric surgery.

OBJECTIVES

To assess the effectiveness of interventions for the management of obesity in people with bipolar disorder.

SEARCH METHODS

We searched the Cochrane Common Mental Disorders Controlled Trials Register (CCMDCTR) and the Cochrane Central Register for Controlled Trials (CENTRAL) to February 2019. We ran additional searches via Ovid databases including MEDLINE, Embase, and PsycInfo to May 2020. We searched the World Health Organization (WHO) trials portal (International Clinical Trials Registry Platform (ICTRP)) and ClinicalTrials.gov. We also checked the reference lists of all papers brought to full-text stage and all relevant systematic reviews.

SELECTION CRITERIA

Randomised controlled trials (RCTs), randomised at the level of the individual or cluster, and cross-over designs of interventions for management of obesity, in which at least 80% of study participants had a clinical diagnosis of bipolar disorder and comorbid obesity (body mass index (BMI) ≥ 30 kg/m²), were eligible for inclusion. No exclusions were based on type of bipolar disorder, stage of illness, age, or gender. We included non-pharmacological interventions comprising dietary, exercise, behavioural, and multi-component interventions; pharmacological interventions consisting of weight loss medications and medication switching interventions; and surgical interventions such as gastric bypass, gastric bands, biliopancreatic diversion, and vertical banded gastroplasty. Comparators included the following approaches: dietary intervention versus inactive comparator; exercise intervention versus inactive comparator; behavioural intervention versus inactive comparator; multi-component lifestyle intervention versus inactive comparator; medication switching intervention versus inactive comparator; weight loss medication intervention versus inactive comparator; and surgical intervention versus inactive comparator. Primary outcomes of interest were changes in body mass, patient-reported adverse events, and quality of life.

DATA COLLECTION AND ANALYSIS

Four review authors were involved in the process of selecting studies. Two review authors independently screened the titles and abstracts of studies identified in the search. Studies brought to the full-text stage were then screened by another two review authors working independently. However, none of the full-text studies met the inclusion criteria. Had we included studies, we would have assessed their methodological quality by using the criteria recommended in the Cochrane Handbook for Systematic Reviews of Interventions. We intended to combine dichotomous data using risk ratios (RRs), and continuous data using mean differences (MDs). For each outcome, we intended to calculate overall effect size with 95% confidence intervals (CIs).

MAIN RESULTS

None of the studies that were screened met the inclusion criteria.

AUTHORS' CONCLUSIONS

None of the studies that were assessed met the inclusion criteria of this review. Therefore we were unable to determine the effectiveness of interventions for the management of obesity in individuals with bipolar disorder. Given the extent and impact of the problem and the absence of evidence, this review highlights the need for research in this area. We suggest the need for RCTs that will focus only on populations with bipolar disorder and comorbid obesity. We identified several ongoing studies that may be included in the update of this review.

Increasing motor neuron excitability to treat weakness in sepsis

OBJECTIVE

Weakness induced by critical illness (intensive care unit acquired weakness) is a major cause of disability in patients and is currently untreatable. We recently identified a defect in repetitive firing of lower motor neurons as a novel contributor to intensive care unit acquired weakness. To develop therapy for intensive care unit acquired weakness, it was necessary to determine the mechanism underlying the defect in repetitive firing.

METHODS

Both computer simulation and in vivo dynamic voltage clamp of spinal motor neurons in septic rats were employed to explore potential mechanisms underlying defective repetitive firing.

RESULTS

Our results suggest alteration in subthreshold voltage-activated currents might be the mechanism underlying defective repetitive firing. It has been shown previously that pharmacologic activation of serotonin receptors on motor neurons increases motor neuron excitability, in part by enhancing subthreshold voltage-activated inward currents. Administration of a U.S. Food and Drug Administration-approved serotonin agonist (lorcaserin) to septic rats greatly improved repetitive firing and motor unit force generation.

INTERPRETATION

Our findings suggest activation of serotonin receptors with lorcaserin may provide the first ever therapy for intensive care unit acquired weakness in patients. Ann Neurol 2017;82:961-971.

Combination Varenicline and Lorcaserin for Tobacco Dependence Treatment and Weight Gain Prevention in Overweight and Obese Smokers: A Pilot Study

INTRODUCTION

Post-cessation weight gain (PCWG) is a major barrier to maintaining abstinence, especially in weight-concerned smokers. Varenicline is the most effective medication for smoking cessation but has minimal impact on PCWG. Lorcaserin is an FDA-approved medication for weight management in overweight or obese patients which also provides a noticeable benefit in treating drug dependence. We hypothesized that combining varenicline with lorcaserin may help prevent PCWG. We conducted an open-label, single arm, Phase II clinical pilot study to obtain preliminary data on the safety and effectiveness of combination varenicline and lorcaserin in preventing PCWG in overweight and obese smokers.

METHODS

Twenty overweight or obese (body mass index 27-40 kg/m2) cigarette smokers were enrolled. The primary outcomes were weight and waist circumference (WC) changes at 12 and 26 weeks in smokers meeting criteria for prolonged smoking abstinence. All participants received open-label varenicline (1 mg twice a day) and lorcaserin (10 mg twice a day) for 12 weeks with follow-up at 26 weeks.

RESULTS

Ten subjects met criteria for prolonged smoking abstinence at 12 weeks (50%) and 6 at 26 weeks (30%). Among those achieving prolonged smoking abstinence at 12 weeks, WC was +0.2 ± 6.0 cm (90% CI; -2.9, +3.4) and weight gain was +1.1 ± 3.9 kg (90% CI; -0.9, +3.1).

CONCLUSIONS

Weight gain and WC increases following prolonged smoking abstinence may be reduced among overweight and obese smokers using combination varenicline and lorcaserin. This combinatory treatment warrants further research in the obese and weight-concerned smoking population.

IMPLICATIONS

This is the first published prospective pilot study to evaluate lorcaserin for use in reducing PCWG in overweight and obese smokers. When combined with varenicline, lorcaserin minimized PCWG and increases in WC. In addition to the benefit on PCWG reduction, lorcaserin may be a potential new pharmacological treatment for smoking cessation and warrants further larger studies.

Management of Chemotherapy-Induced Nausea and Vomiting in Pediatric Patients

Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life and is perceived by patients as a major adverse effect of the treatment. This review summarizes the safety and efficacy of current antiemetic agents for the prevention of CINV in children. Information on antiemetic prophylaxis for CINV in children was obtained from a literature review of current peer-reviewed articles and recent international guidelines. The literature review and the international antiemetic guidelines provide recommendations for use of specific antiemetics in children based on the emetogenicity of the chemotherapy. 5-Hydroxytryptamine-3 (5-HT₃) receptor antagonists have been safe and effective in the prevention of acute emesis with a few patients experiencing mild headache. No adequate studies have been conducted to date for specific recommendations for the prevention of delayed nausea and vomiting in children. The neurokinin (NK)-₁ receptor antagonist aprepitant has been approved by the US FDA for use in children of a specific age and weight. No studies for the NK₁ receptor antagonists netupitant and rolapitant in children have been conducted. Olanzapine, an antipsychotic, has been shown to be safe and effective in preventing nausea and emesis in adult patients receiving chemotherapy. Its use in children has been limited to children with poor control of CINV; more studies are necessary in this population. In conclusion, practitioners should follow international antiemetic guidelines to provide patients with the specific antiemetics in the recommended dose for the highest possible quality of care.

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

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

Pharmacological Management of the Obese Patient

Being obese goes beyond moral failure or a character flaw. Obesity has the defining characteristics of a chronic disease for which there is no cure. Treatment may require lifelong treatment which may include pharmacotherapy. Experience with long term use of obesity drugs is limited but evidence suggests that pharmacotherapy can improve patient outcomes and patient outlook. With current obesity drugs, weight loss is usually modest but clinically significant satisfying the FDA threshold for drug effectiveness. This weight loss is associated with clinically significant improvements in many obesity co morbidities and risk factors and could eliminate some risk factors with continued use. When used in conjunction with a comprehensive program for weight management, obesity drugs can reduce appetite or hunger, increase satiety, provide improved control over aberrant eating behaviors and modify food seeking behaviors. Pharmacotherapy can enhance weight loss and compliance during the periods of weight loss and in maintaining that weight loss, increasing physical activity and may enhance a focus on making life long changes.

This article will discuss mechanisms of action of obesity drugs, theories of altered body defense of body weight, Food and Drug Administration (FDA) approved obesity drugs, and off-label use of FDA approved drugs. The value of over-the counter (OTC) medications and diet supplements, as well as fat substitutes in the treatment of obesity drugs will be explored. Obesity drugs awaiting FDA approval and compounds under development will be reviewed. The section on approaches to drug management will include clinical considerations for; who should receive pharmacotherapy and when, length of treatment and drug discontinuation, weight regain and the role of pharmacotherapy.

Lorcaserin: A novel antiobesity drug

Obesity is a major co-morbidity with hypertension and diabetes mellitus. There are few drugs for treatment of obesity like orlistat and recentlty approved drug lorcaserin. Lorcaserin has serotonergic properties and acts as an anorectic. It may cause serious side effects, including serotonin syndrome, particularly when taken with certain medicines that increase serotonin levels or activate serotonin receptors. Although, mainstay and first line of approach of treatment will always remain in having low calorie diet and increase in physical activity. Lorcaserin has come as a new hope to achieve success in treating obese patients but still a long road with further extensive research to be undertaken in the treatment of obesity.

Olanzapine for the prevention and treatment of chronic nausea and chemotherapy-induced nausea and vomiting

Olanzapine is an atypical antipsychotic agent of the thiobenzodiazepine class. It blocks multiple neurotransmitter receptors including dopaminergic at D1, D2, D3, D4 brain receptors, serotonergic at 5-HT2a, 5-HT2c, 5-HT3, 5-HT6 receptors, catecholamines at alpha1 adrenergic receptors, acetylcholine at muscarinic receptors, and histamine at H1 receptors. Olanzapine has five times the affinity for 5-HT2 receptors than D2 receptors and has been used to treat schizophrenia and delirium. Olanzapine's activity at multiple receptors, particularly at the D2, 5-HT2c, and 5-HT3 receptors which appear to be involved in nausea and emesis, has prompted its use in the treatment of nausea and vomiting refractory to standard antiemetics. Case reports and formal clinical trials have demonstrated its efficacy in the treatment of chronic nausea, the prevention of chemotherapy-induced nausea and emesis, and the treatment of breakthrough chemotherapy-induced nausea and emesis. Phase II and phase III clinical trials have demonstrated that there is a significant improvement in nausea when olanzapine is added to guideline directed prophylactic antiemetic agents 5-HT3 receptor antagonists and tachykinin NK1 receptor antagonists in patients receiving moderately or highly emetogenic chemotherapy Common side effects of olanzapine when used over a period of months include weight gain as well as an association with the onset of diabetes mellitus, but these effects have not been seen with short term use of daily doses of less than one week.

Phentermine/topiramate for the treatment of obesity

OBJECTIVE

To review the pharmacology, efficacy, and safety of phentermine/topiramate (PHEN/TPM) in the management of obese patients.

DATA SOURCES

MEDLINE (1966-July 2012) was searched using the terms weight loss, obesity, phentermine and topiramate, phentermine, topiramate, Qnexa, Qsymia, and VI-0521. Additionally, the new drug application and prescribing information for PHEN/TPM were retrieved.

STUDY SELECTION/DATA EXTRACTION

All studies considering the pharmacology, efficacy, and safety of PHEN/TPM were reviewed with a focus on efficacy and safety data from Phase 3 trials.

DATA SYNTHESIS

In 3 Phase 3 trials (EQUIP, CONQUER, and SEQUEL), treatment with PHEN/TPM consistently demonstrated statistically significant weight loss compared with placebo. After 56 weeks of treatment, percent weight loss achieved with PHEN/TPM was 10.6%, 8.4%, and 5.1% with 15/92 mg, 7.5/46 mg, and 3.75/23 mg, respectively (p < 0.0001). The 52-week extension study (SEQUEL) showed maintained weight loss over 2 years with 9.3% and 10.5% weight loss from baseline for 7.5/46 mg and 15/92 mg PHEN/TPM (p < 0.0001). A significantly higher proportion of patients achieved greater than 5%, 10%, or 15% weight loss with PHEN/TPM compared with placebo. Significant reductions in waist circumference, fasting triglycerides, and fasting glucoses were also attributable to PHEN/TPM. The drug was generally well tolerated in clinical trials. Adverse reactions occurring in 5% or more of study subjects included paresthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth.

CONCLUSIONS

PHEN/TPM is a new, once-daily, controlled-release, combination weight-loss product approved as an adjunct to diet and exercise for chronic weight management of obese or overweight patients with weight-related comorbidities. PHEN/TPM is modestly effective and a viable option for patients interested in losing weight, although long-term safety data are lacking.

Role of the gastroenterologist in managing obesity

Obesity has become a major public health problem as a consequence of its prevalence, negative impact on morbidity, mortality and quality of life and its associated direct and indirect healthcare costs. The etiology of obesity is multifactorial and reflects complex interactions of genetic, neurohumoral, environmental, behavioral and possibly, microbial factors. Available treatments for obesity include diet and exercise, behavioral modification, medications and surgery. Gastroenterologists are becoming increasingly involved in the care of obese patients. Although much of this care has historically centered on the preoperative and postoperative care of the bariatric patient, gastroenterologists are also evaluating and managing a variety of gastrointestinal symptoms and disorders that occur more commonly among obese individuals and are increasingly involved in the primary treatment of obesity. In this review, the gastrointestinal symptoms and disorders that are associated with obesity will be reviewed, the gastrointestinal contribution to the pathogenesis of obesity will be described and the current treatment options of obesity and where the gastroenterologist typically plays a role in the management will be discussed.

Reducing the risk of obesity: defining the role of weight loss drugs

The prevalence of obesity has increased dramatically in the past 20 years. As a public health concern, obesity is associated with a health care resource burden that is quickly approaching that associated with tobacco use. Although lifestyle intervention (diet and exercise) remains the mainstay of treatment of obesity, its effectiveness is limited by poor long-term adherence. Drug therapy has historically been unsuccessful in producing sustained weight loss. Many older weight loss drugs have adverse benefit-to-risk profiles. This review provides an overview of nonpharmacologic interventions for weight loss. The safety and efficacy of older weight loss drugs, as well as current data related to lorcaserin, phentermine/topiramate, and naltrexone-bupropion, are evaluated. Although associated with modest weight loss and some improvement in adverse obesity-related metabolic effects, none of these drugs has been demonstrated to reduce mortality. In addition, the long-term safety of these drugs remains largely unknown. Bariatric surgery is an option for patients with morbid obesity who have failed conventional treatment.

Evaluation of chemically diverse 5-HT₂c receptor agonists on behaviours motivated by food and nicotine and on side effect profiles

RATIONALE

Selective 5-HT2C receptor agonists, such as lorcaserin, are being developed for the treatment of obesity. Studies suggest that they may also have therapeutic potential for addictive behaviours including nicotine dependence, although few drugs of this class have been evaluated.

OBJECTIVES

The primary aim was to evaluate the highly selective 5-HT2C agonist, CP-809101, against food-motivated (operant FR5 and progressive ratio schedules, palatability-induced feeding) and nicotine-motivated (intravenous self-administration, drug discrimination) behaviours in rats and to compare with equivalent findings for the structurally distinct 5-HT2C receptor agonists lorcaserin and Ro 60-0175. The secondary aims were to evaluate the side effect profiles of lorcaserin and CP-809101 and to determine the plasma levels of lorcaserin at a dose (1 mg/kg) that reduces both food and nicotine reinforcement for comparison to plasma concentrations reported in human trials.

RESULTS

CP-809101 (0.3-3 mg/kg SC) reduced responding for both nicotine and food and blocked the discriminative stimulus properties of nicotine in a similar manner to lorcaserin and Ro 60-0175. Behaviours such as hypolocomotion, chewing and ptosis became evident following both CP-809101 and lorcaserin administration at higher doses. Plasma levels of lorcaserin were of similar range to those reported in obesity trials.

CONCLUSIONS

These studies support the utility of 5-HT2C agonists as a therapeutic approach to treat nicotine dependence. Plasma exposure levels after acute lorcaserin treatment suggest that equivalent dosages could be used to evaluate these drugs in obesity and smoking cessation trials. Finally, there may be differences in the side effect profiles between lorcaserin and CP-809101, raising the possibility for tolerability differences amongst 5-HT2C agonists.

Serotonin and the regulation of mammalian energy balance

Maintenance of energy balance requires regulation of the amount and timing of food intake. Decades of experiments utilizing pharmacological and later genetic manipulations have demonstrated the importance of serotonin signaling in this regulation. Much progress has been made in recent years in understanding how central nervous system (CNS) serotonin systems acting through a diverse array of serotonin receptors impact feeding behavior and metabolism. Particular attention has been paid to mechanisms through which serotonin impacts energy balance pathways within the hypothalamus. How upstream factors relevant to energy balance regulate the release of hypothalamic serotonin is less clear, but work addressing this issue is underway. Generally, investigation into the central serotonergic regulation of energy balance has had a predominantly “hypothalamocentric” focus, yet non-hypothalamic structures that have been implicated in energy balance regulation also receive serotonergic innervation and express multiple subtypes of serotonin receptors. Moreover, there is a growing appreciation of the diverse mechanisms through which peripheral serotonin impacts energy balance regulation. Clearly, the serotonergic regulation of energy balance is a field characterized by both rapid advances and by an extensive and diverse set of central and peripheral mechanisms yet to be delineated.

Was it worth the weight? - Drug review on two new weight loss agents: lorcaserin (Belviq®) and phentermine/topiramate ER (QsymiaTM)

The prevalence of obesity in the United States (U.S.) is currently at 34%. This article will review two of the newer weight loss agents: lorcaserin and phentermine/topiramate. Mechanism of action, dosing, adverse events, and drug interactions will be discussed.

5-HT2 ligands in the treatment of anxiety and depression

INTRODUCTION

One third of depressed patients do not respond adequately to conventional antidepressants including the selective serotonin reuptake inhibitors (SSRIs). Therefore, multi-target drugs or augmentation strategies have been developed for the management of SSRIs-resistant patients. In this context, the 5-HT(2) receptor subtypes represent promising targets but their precise roles have yet to be determined.

AREAS COVERED

The aim of this review is to shed some light on the preclinical evidence supporting the use of 5-HT(2A) and/or 5-HT(2C) receptor antagonists such as antipsychotics, as potential effective adjuncts in SSRIs-resistant depression. This review synthesizes the current literature about the behavioral, electrophysiological and neurochemical effects of 5-HT(2) receptors ligands on the monoaminergic systems but also on adult hippocampal neurogenesis.

EXPERT OPINION

Although studies support the hypothesis that the inactivation of 5-HT(2A) and/or 5-HT(2C) receptors might be of interest to reinforce different facets of the therapeutic activity of SSRIs, this pharmacological strategy remains debatable notably because of the lack of chronic data in relevant animal models. Conversely, emerging evidence suggests that the activation of 5-HT(2B) receptor is required for antidepressant-like activity, opening the way to new therapeutic approaches. However, the potential risks related to the enhancement of monoaminergic neurotransmissions could represent a major concern.

Drug treatment of obesity in cardiovascular disease

Obesity is a significant health problem worldwide and is associated with a number of co-morbidities including type 2 diabetes mellitus, hypertension, dyslipidemia, obstructive sleep apnea, and cardiovascular disease. A number of different pathophysiologic mechanisms including increased inflammation, oxidative stress, and insulin resistance have been associated with initiation and progression of atherosclerotic disease in obese individuals. Lifestyle modifications have provided modest results in weight reduction and the focus of interest has now shifted towards drug development to treat severely obese individuals with a body mass index (BMI) >30 kg/m(2) or those with a BMI >27 kg/m(2) who have additional co-morbidities. Different regimens focusing on dietary absorption or acting centrally to control hunger and food intake have been developed. However, their weight loss effect is, in most cases, modest and this effect is lost once the medication is discontinued. In addition, long-term use of these drugs is limited by significant side effects and lack of long-term safety and efficacy data. Orlistat is the only US FDA-approved medication for long-term use. A number of new medications are currently under investigation in phase III trials with promising preliminary results. This review comments on available anti-obesity pharmacologic regimens, their weight-loss benefit, and their impact on cardiovascular risk factors.

Effects of the 5-HT2C receptor agonist Ro60-0175 and the 5-HT2A receptor antagonist M100907 on nicotine self-administration and reinstatement

The reinforcing effects of nicotine are mediated in part by brain dopamine systems. Serotonin, acting via 5-HT(2A) and 5-HT(2C) receptors, modulates dopamine function. In these experiments we examined the effects of the 5-HT(2C) receptor agonist Ro60-0175 and the 5-HT(2A) receptor antagonist (M100907, volinanserin) on nicotine self-administration and reinstatement of nicotine-seeking. Male Long-Evans rats self-administered nicotine (0.03 mg/kg/infusion, IV) on either a FR5 or a progressive ratio schedule of reinforcement. Ro60-0175 reduced responding for nicotine on both schedules. While Ro60-0175 also reduced responding for food reinforcement, response rates under drug treatment were several-fold higher than in animals responding for nicotine. M100907 did not alter responding for nicotine, or food, on either schedule. In tests of reinstatement of nicotine-seeking, rats were first trained to lever press for IV infusions of nicotine; each infusion was also accompanied by a compound cue consisting of a light and tone. This response was then extinguished over multiple sessions. Injecting rats with a nicotine prime (0.15 mg/kg) reinstated responding; reinstatement was also observed when responses were accompanied by the nicotine associated cue. Ro60-0175 attenuated reinstatement of responding induced by nicotine and by the cue. The effects of Ro60-0175 on both forms of reinstatement were blocked by the 5-HT(2C) receptor antagonist SB242084. M100907 also reduced reinstatement induced by either the nicotine prime or by the nicotine associated cue. The results indicate that 5-HT(2C) and 5-HT(2A) receptors may be potential targets for therapies to treat some aspects of nicotine dependence.