Clozapine, but not haloperidol, increases neuropeptide Y neuronal expression in the rat hypothalamus

The role of hypothalamic endoplasmic reticulum stress in schizophrenia and antipsychotic-induced weight gain: A narrative review

Schizophrenia (SCZ) is a serious mental illness that affects 1% of people worldwide. SCZ is associated with a higher risk of developing metabolic disorders such as obesity. Antipsychotics are the main treatment for SCZ, but their side effects include significant weight gain/obesity. Despite extensive research, the underlying mechanisms by which SCZ and antipsychotic treatment induce weight gain/obesity remain unclear. Hypothalamic endoplasmic reticulum (ER) stress is one of the most important pathways that modulates inflammation, neuronal function, and energy balance. This review aimed to investigate the role of hypothalamic ER stress in SCZ and antipsychotic-induced weight gain/obesity. Preliminary evidence indicates that SCZ is associated with reduced dopamine D2 receptor (DRD2) signaling, which significantly regulates the ER stress pathway, suggesting the importance of ER stress in SCZ and its related metabolic disorders. Antipsychotics such as olanzapine activate ER stress in hypothalamic neurons. These effects may induce decreased proopiomelanocortin (POMC) processing, increased neuropeptide Y (NPY) and agouti-related protein (AgRP) expression, autophagy, and leptin and insulin resistance, resulting in hyperphagia, decreased energy expenditure, and central inflammation, thereby causing weight gain. By activating ER stress, antipsychotics such as olanzapine activate hypothalamic astrocytes and Toll-like receptor 4 signaling, thereby causing inflammation and weight gain/obesity. Moreover, evidence suggests that antipsychotic-induced ER stress may be related to their antagonistic effects on neurotransmitter receptors such as DRD2 and the histamine H1 receptor. Taken together, ER stress inhibitors could be a potential effective intervention against SCZ and antipsychotic-induced weight gain and inflammation.

Clozapine's multiple cellular mechanisms: What do we know after more than fifty years? A systematic review and critical assessment of translational mechanisms relevant for innovative strategies in treatment-resistant schizophrenia

Almost fifty years after its first introduction into clinical care, clozapine remains the only evidence-based pharmacological option for treatment-resistant schizophrenia (TRS), which affects approximately 30% of patients with schizophrenia. Despite the long-time experience with clozapine, the specific mechanism of action (MOA) responsible for its superior efficacy among antipsychotics is still elusive, both at the receptor and intracellular signaling level. This systematic review is aimed at critically assessing the role and specific relevance of clozapine's multimodal actions, dissecting those mechanisms that under a translational perspective could shed light on molecular targets worth to be considered for further innovative antipsychotic development. In vivo and in vitro preclinical findings, supported by innovative techniques and methods, together with pharmacogenomic and in vivo functional studies, point to multiple and possibly overlapping MOAs. To better explore this crucial issue, the specific affinity for 5-HT₂R, D1R, α_2c, and muscarinic receptors, the relatively low occupancy at dopamine D2R, the interaction with receptor dimers, as well as the potential confounder effects resulting in biased ligand action, and lastly, the role of the moiety responsible for lipophilic and alkaline features of clozapine are highlighted. Finally, the role of transcription and protein changes at the synaptic level, and the possibility that clozapine can directly impact synaptic architecture are addressed. Although clozapine's exact MOAs that contribute to its unique efficacy and some of its severe adverse effects have not been fully understood, relevant information can be gleaned from recent mechanistic understandings that may help design much needed additional therapeutic strategies for TRS.

Association between neuropeptide Y gene polymorphism and antipsychotics effect

OBJECTIVE

The pathogenesis of schizophrenia is associated with neuropeptide Y (NPY) gene polymorphism to explore the relationship between rs16141, rs16145, and rs5573 polymorphisms in the NPY gene and antipsychotics response in the Chinese population.

METHODS

The unrelated 228 Chinese Han patients with schizophrenia were enrolled in the present study. Genotypisation within NPY gene was performed using the KASP genotyping assays. Before treatment and on the weekends of the 2nd, 4th, and 8th weeks after treatment, the medication status of the patients was recorded and the positive and negative syndrome scale (PANSS) was used to evaluate the clinical effect. A reduction in total PANSS scores ≥50% were classified as good responders, while others were poor responders. We evaluated the association between NPY gene and antipsychotic efficacy by comparing allele and genotype distribution, correlation analysis, linkage imbalance, and five genetic models between the two groups.

RESULTS

No significant associations were found in the rs16141, rs16145, and rs5573 of NPY and antipsychotic treatment response (all p > 0.05). There was no significant relationship between the three SNPs polymorphisms in the NPY gene and the changes of positive, negative and general psychopathology subscales scores at each stage (all p > 0.05). The distribution of genotype and allele frequencies of locus rs16141 was not statistically difference between good responders and poor responders (genotype: χ2 =4.088, p=0.043, p-correction = 0.129; allele: χ² = 4.088, p = 0.027, p-correction = 0.081). The allele distribution of rs5573 was significantly different between groups, yet the difference was disappeared after correcting (χ² = 4.136, p = 0.042, p-correction =0.126). The distribution frequencies of TA/TG and GG haplotypes constituted by rs16141 and rs5573 showed no statistical difference between the two groups (p > 0.05). In recessive inheritance mode, NPYrs5573 was found to be associated with antipsychotic drug response (G/G vs. A/A +A/G: p = 0.028, AIC = 197.2, BIC = 210.9).

CONCLUSIONS

This study didn't found association between polymorphisms in the NPY gene locus (rs16141, rs16145, and rs5573) and the response to antipsychotics after Bonferroni correction. The polymorphism of NPY gene and the efficacy of antipsychotic drugs in patients with schizophrenia need further study.

Effect of liraglutide on neural and peripheral markers of metabolic function during antipsychotic treatment in rats

BACKGROUND

Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that prevents metabolic side effects of the antipsychotic drugs (APDs) olanzapine and clozapine through unknown mechanisms.

AIM

This study aimed to investigate the effect of chronic APD and liraglutide co-treatment on key neural and peripheral metabolic signals, and acute liraglutide co-treatment on clozapine-induced hyperglycaemia.

METHODS

In study 1, rats were administered olanzapine (2 mg/kg), clozapine (12 mg/kg), liraglutide (0.2 mg/kg), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle for six weeks. Feeding efficiency was examined weekly. Examination of brain tissue (dorsal vagal complex (DVC) and mediobasal hypothalamus (MBH)), plasma metabolic hormones and peripheral (liver and kidney) cellular metabolism and oxidative stress was conducted. In study 2, rats were administered a single dose of clozapine (12 mg/kg), liraglutide (0.4 mg/kg), clozapine + liraglutide co-treatment or vehicle. Glucose tolerance and plasma hormone levels were assessed.

RESULTS

Liraglutide co-treatment prevented the time-dependent increase in feeding efficiency caused by olanzapine, which plateaued by six weeks. There was no effect of chronic treatment on melanocortinergic, GABAergic, glutamatergic or endocannabionoid markers in the MBH or DVC. Peripheral hormones and cellular metabolic markers were unaltered by chronic APD treatment. Acute liraglutide co-treatment was unable to prevent clozapine-induced hyperglycaemia, but it did alter catecholamine levels.

CONCLUSION

The unexpected lack of change to central and peripheral markers following chronic treatment, despite the presence of weight gain, may reflect adaptive mechanisms. Further studies examining alterations across different time points are required to continue to elucidate the mechanisms underlying the benefits of liraglutide on APD-induced metabolic side effects.

A Focused Review of the Metabolic Side-Effects of Clozapine

The second generation antipsychotic drug clozapine represents the most effective pharmacotherapy for treatment-resistant psychosis. It is also associated with low rates of extrapyramidal symptoms and hyperprolactinemia compared to other antipsychotic drugs. However, clozapine tends to be underutilized in clinical practice due to a number of disabling and serious side-effects. These are characterized by a constellation of metabolic side-effects which include dysregulation of glucose, insulin, plasma lipids and body fat. Many patients treated with clozapine go on to develop metabolic syndrome at a higher rate than the general population, which predisposes them for Type 2 diabetes mellitus and cardiovascular disease. Treatments for the metabolic side-effects of clozapine vary in their efficacy. There is also a lack of knowledge about the underlying physiology of how clozapine exerts its metabolic effects in humans. In the current review, we focus on key studies which describe how clozapine affects each of the main symptoms of the metabolic syndrome, and cover some of the treatment options. The clinical data are then discussed in the context of preclinical studies that have been conducted to identify the key biological substrates involved, in order to provide a better integrated overview. Suggestions are provided about key areas for future research to better understand how clozapine causes metabolic dysregulation.

Effect of lurasidone versus olanzapine on cardiometabolic parameters in unmedicated patients with schizophrenia: a randomized controlled trial

OBJECTIVE

Patients with schizophrenia are at higher risk of cardiovascular morbidity and mortality than healthy individuals. This study was conducted to compare the effect of lurasidone and olanzapine on cardiometabolic parameters in unmedicated patients with schizophrenia.

METHODS

The present study was a randomized open-label, parallel design, active-controlled clinical trial. After recruitment and randomization of 101 patients, a baseline assessment was done by PANSS, SOFAS, lipid profile, fasting blood glucose, HbA_1c, serum insulin and serum hs-CRP. HOMA-IR, atherogenic index, coronary risk index and cardiovascular risk indices were calculated as derived parameters. Patients received either lurasidone 80 mg or olanzapine 10 mg as monotherapy and followed up after 6 weeks.

RESULTS

There was a significant increase in fasting blood glucose (p < 0.001), HbA_1c (p < 0.001) and serum insulin (p < 0.001) after 6 weeks of therapy in both the treatment groups but the difference between the groups was not significant (FBS, p = 0.209; HbA1c, p = 0.209; serum insulin, p = 0.720). Olanzapine showed worsening of lipid profile (p < 0.001) while the same improved with lurasidone (p < 0.001) and the difference between the groups was found to be significant (p < 0.001). Serum HDL level decreased in both the treatment groups (olanzapine, p < 0.001; lurasidone, p < 0.001) but the difference between the groups was not significant (p = 0.333). There was an increase in hs-CRP levels in both the treatment groups (olanzapine, p < 0.001; lurasidone, p < 0.001) with no significant difference between them (p = 0.467). Atherogenic index, coronary risk index and cardiovascular risk index increased significantly in the olanzapine group as compared with the lurasidone group (p < 0.001).

CONCLUSION

Lurasidone showed a favourable effect on lipid profile and cardiovascular risk indices over olanzapine. However, long-term studies are needed to establish and generalize the findings.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03304457.

Sex-dependent alterations of dopamine receptor and glucose transporter density in rat hypothalamus under long-term clozapine and haloperidol medication

OBJECTIVE

Sex-dependent disturbances of peripheral glucose metabolism are known complications of antipsychotic drug treatment. The influence of long-term clozapine and haloperidol medication on hypothalamus, maintaining aspects of internal body homeostasis, has not yet been completely clarified.

METHODS

After puberty, male and female Sprague Dawley rats were fed orally with ground pellets containing haloperidol (1 mg/kgBW/day) or clozapine (20 mg/kgBW/day) for 12 weeks. The hypothalamic protein expression of dopamine receptors D2R and D4R, melanocortin receptor MC4R, and glucose transporters Glut1 and Glut3 was examined. Glucose, glycogen, lactate, and pyruvate levels were determined, also malondialdehyde equivalents as markers of oxidative stress.

RESULTS

D2R expression was increased in the male haloperidol and clozapine group but decreased in females medicated with clozapine. D4R expression was upregulated under clozapine medication. While females showed increased Glut1, Glut3 was elevated in both male and female clozapine-medicated animals. We found no changes of hypothalamic malondialdehyde, glycogen, and MC4R. Hypothalamic lactate was elevated in the female clozapine group.

CONCLUSION

Clozapine sex-dependently affects the expression of D2R, Glut1, and Glut3. The upregulation of the glucose transporters indicates glucose deprivation in the endothelial cells and consequently in astrocytes and neurons. Increased hypothalamic lactate in females under clozapine points to enhanced glycolysis with a higher glucose demand to produce the required energy. Haloperidol did not change the expression of the glucose transporters and upregulated D2R only in males.

Progress in Genetic Polymorphisms Related to Lipid Disturbances Induced by Atypical Antipsychotic Drugs

Metabolic side effects such as weight gain and disturbed lipid metabolism are often observed in the treatment of atypical antipsychotic drugs (AAPDs), which contribute to an excessive prevalence of metabolic syndrome among schizophrenic patients. Great individual differences are observed but the underlying mechanisms are still uncertain. Research on pharmacogenomics indicates that gene polymorphisms involved in the pathways controlling food intake and lipid metabolism may play a significant role. In this review, relevant genes (HTR2C, DRD2, LEP, NPY, MC4R, BDNF, MC4R, CNR1, INSIG2, ADRA2A) and genetic polymorphisms related to metabolic side effects of AAPDs especially dyslipidemia were summarized. Apart from clinical studies, in vitro and in vivo evidence is also analyzed to support related theories. The association of central and peripheral mechanisms is emphasized, enabling the possibility of using peripheral gene expression to predict the central status. Novel methodological development of pharmacogenomics is in urgent need, so as to provide references for individualized medication and further to shed some light on the mechanisms underlying AAPD-induced lipid disturbances.

A phenotypic Caenorhabditis elegans screen identifies a selective suppressor of antipsychotic-induced hyperphagia

Antipsychotic (AP) drugs are used to treat psychiatric disorders but are associated with significant weight gain and metabolic disease. Increased food intake (hyperphagia) appears to be a driving force by which APs induce weight gain but the mechanisms are poorly understood. Here we report that administration of APs to C. elegans induces hyperphagia by a mechanism that is genetically distinct from basal food intake. We exploit this finding to screen for adjuvant drugs that suppress AP-induced hyperphagia in C. elegans and mice. In mice AP-induced hyperphagia is associated with a unique hypothalamic gene expression signature that is abrogated by adjuvant drug treatment. Genetic analysis of this signature using C. elegans identifies two transcription factors, nhr-25/Nr5a2 and nfyb-1/NFYB to be required for AP-induced hyperphagia. Our study reveals that AP-induced hyperphagia can be selectively suppressed without affecting basal food intake allowing for novel drug discovery strategies to combat AP-induced metabolic side effects.

Association Study of Arcuate Nucleus Neuropeptide Y Neuron Receptor Gene Variation And Serum Npy Levels in Clozapine Treated Patients With Schizophrenia

Background

Antipsychotic-induced weight gain (AIWG) leads to metabolic consequences and comorbidity, social stigmatization and nonadherence in patients with schizophrenia. Neuropeptide Y (NPY) has an important role in appetite and body weight regulation. Associations between AIWG and serum NPY levels, and genetic polymorphisms (SNPs) associated with its serum levels have been little studied in these patients.

Subjects and methods

Associations between serum NPY concentration and other metabolic and inflammatory markers, and 215 SNPs in 21 genes (NPY gene, NPY receptor genes and genes encoding arcuate nucleus NPY neuron receptors) were studied in 180 patients with schizophrenia on clozapine treatment.

Results

The serum levels of NPY correlated with levels of resistin (r = 0.31, P < 0.001) and age (r = 0.22, P = 0.003). In the general linear univariate model the best-fitting model with explanatory factors age, serum resistin level, serum insulin level, BMI and gender explained 18.0% (P < 0.001) of the variance of serum NPY. Genetic risk score (GRSNPY) analysis found twelve significant (P < 0.05) serum NPY concentration related SNPs among α7 nicotinic acetylcholine receptor gene CHRNA7, insulin receptor gene INSR, leptin receptor gene LEPR, glucocorticoid receptor (GR) gene NR3C1, and NPY gene. However, after permutation test of gene score the predictive value of GRSNPY remained non-significant (P = 0.078).

Conclusions

Serum NPY level does not seem to be a feasible biomarker of AIWG. Serum NPY level alterations are not significantly associated with the candidate gene polymorphisms studied.

Investigation of molecular serum profiles associated with predisposition to antipsychotic-induced weight gain

OBJECTIVES

Metabolic disturbances are major adverse side effects in the treatment of schizophrenia patients with antipsychotics. A substantial proportion of patients discontinue treatment with second-generation antipsychotics due to weight gain. The objective of this study was to investigate molecular factors predisposing patients to the development of such metabolic disturbances.

METHODS

We investigated whether serum molecules measured before treatment initiation were associated with subsequent weight gain following a 6-week treatment with antipsychotics. The concentrations of 191 molecules were measured longitudinally in serum from 77 schizophrenia patients using multiplex immunoassays.

RESULTS

This showed that the levels of 10 serum molecules at T0 were significantly associated with ΔBMI, which included interleukin-6 receptor, epidermal growth factor and thyroid stimulating hormone.

CONCLUSIONS

Our results suggest that patients who experience antipsychotic-induced weight gain have specific molecular alterations already prior to treatment. Further studies are required to validate and evaluate current findings in the context of response and side-effect development. This may ultimately lead to molecular tests that can aid in the selection of antipsychotic treatments.

Association study of the HTR2C, leptin and adiponectin genes and serum marker analyses in clozapine treated long-term patients with schizophrenia

Clozapine treatment is associated with weight gain and cardio-metabolic consequences among patients with schizophrenia. Polymorphisms of leptin, serotonin receptor HTR2C and adiponectin genes have been associated with antipsychotic-induced weight gain and metabolic comorbidity. However, the results of the studies so far are inconclusive. The aim of the present study was first to test for a possible role of serum leptin and adiponectin levels as a marker of weight gain in association with inflammatory cytokines/adipokines (IL-6, IL-1Ra, hs-CRP and adipsin), and second to study associations between SNPs LEP rs7799039 (-2548 A/G), ADIPOQ rs1501299 and HTR2C rs1414334 and weight gain and levels of leptin and adiponectin, in 190 patients with schizophrenia on clozapine treatment, with retrospectively assessed weight change and cross-sectionally measured cytokine levels. A strong association was found between serum levels of leptin and weight gain and cytokines/adipokines related to metabolic comorbidity, especially among female patients (in women leptin vs. weight gain, IL-6 and IL-1Ra, P<0.001; in men leptin vs. weight gain, P=0.026, leptin vs. IL-1Ra, P<0.001). In male patients low adiponectin level was a more specific marker of clozapine-induced weight gain (P=0.037). The results of the present study do not support a major role of SNPs LEP rs7799039, ADIPOQ rs1501299 and HTR2C rs1414334 in the regulation of weight gain or association of serum levels of leptin and adiponectin and corresponding studied SNPs in patients with schizophrenia on clozapine treatment.

Recent evidence and potential mechanisms underlying weight gain and insulin resistance due to atypical antipsychotics

OBJECTIVE

Atypical antipsychotics (AAPs) promote obesity and insulin resistance. In this regard, the main objective of this study was to present potential mechanisms and evidence concerning side effects of atypical antipsychotics in humans and rodents.

METHOD

A systematic review of the literature was performed using the MEDLINE database. We checked the references of selected articles, review articles, and books on the subject.

RESULTS

This review provides consistent results concerning the side effects of olanzapine (OL) and clozapine (CLZ), whereas we found conflicting results related to other AAPs. Most studies involving humans describe the effects on body weight, adiposity, lipid profile, and blood glucose levels. However, it seems difficult to identify an animal model replicating the wide range of changes observed in humans. Animal lineage, route of administration, dose, and duration of treatment should be carefully chosen for the replication of the findings in humans.

CONCLUSIONS

Patients undergoing treatment with AAPs are at higher risk of developing adverse metabolic changes. This increased risk must be taken into account when making decisions about treatment. The influence of AAPs on multiple systems is certainly the cause of such effects. Specifically, muscarinic and histaminergic pathways seem to play important roles.

Pharmacological mechanisms underlying the association of antipsychotics with metabolic disorders

Obesity and metabolic syndrome in association with an increased risk of cardiovascular disease and type II diabetes are significant problems that contribute to lower life expectancy of patients with schizophrenia. Understanding the pharmacological mechanisms of the current antipsychotic treatment is clearly the key to the improvement of pharmacotherapy, to avoid or to mitigate the metabolic adverse effects.

Association of a functional polymorphism in neuropeptide Y with antipsychotic-induced weight gain in schizophrenia patients

Significant body weight gain (BWG) is a serious adverse effect of a number of antipsychotic drugs. Previous studies have demonstrated an influence of clozapine, but not haloperidol, on neuropeptide Y (NPY) expression in the hypothalamus. Because NPY is a potent orexigenic peptide stimulating food intake, and genetic variation of the gene has been shown to influence development of obesity, we investigated the impact of NPY polymorphisms on antipsychotic-induced BWG.We analyzed 5 polymorphisms in the NPY gene (rs10551063, rs16147, rs5573, rs5574, and rs16475) in schizophrenia subjects (n = 226), treated mostly with clozapine and olanzapine for up to 14 weeks. Association was tested using analysis of covariance with change (%) from baseline weight as the dependent variable and duration of treatment and baseline body weight as covariates.In patients of European ancestry who received either clozapine or olanzapine, significant genotypic and allelic association of rs16147 with weight change was observed (P(corrected) = 0.012 and 0.018, respectively). Carriers of the C allele gained significantly more weight compared with individuals with TT genotype (CC + CT vs TT; 5.82% ± 5.6% vs 2.25% ± 4.8%; P= 0.001). Similarly, 2 other polymorphisms (rs5573 and rs5574) were also significantly associated with weight change (P(corrected) = 0.018 and 0.03). In addition, we observed a significant gene-gene interaction between the rs16147 in NPY and rs806378 in cannabinoid receptor 1 (P(corrected) = 0.011).Our observation of association of NPY polymorphisms gives further evidence for a genetic influence on antipsychotic-induced BWG and suggests a role of NPY gene in influencing this complex adverse effect.

Alterations to melanocortinergic, GABAergic and cannabinoid neurotransmission associated with olanzapine-induced weight gain

Background/Aim

Second generation antipsychotics (SGAs) are used to treat schizophrenia but can cause serious metabolic side-effects, such as obesity and diabetes. This study examined the effects of low to high doses of olanzapine on appetite/metabolic regulatory signals in the hypothalamus and brainstem to elucidate the mechanisms underlying olanzapine-induced obesity.

Methodology/Results

Levels of pro-opiomelanocortin (POMC), neuropeptide Y (NPY) and glutamic acid decarboxylase (GAD₆₅, enzyme for GABA synthesis) mRNA expression, and cannabinoid CB1 receptor (CB1R) binding density (using [³H]SR-141716A) were examined in the arcuate nucleus (Arc) and dorsal vagal complex (DVC) of female Sprague Dawley rats following 0.25, 0.5, 1.0 or 2.0 mg/kg olanzapine or vehicle (3×/day, 14-days). Consistent with its weight gain liability, olanzapine significantly decreased anorexigenic POMC and increased orexigenic NPY mRNA expression in a dose-sensitive manner in the Arc. GAD₆₅ mRNA expression increased and CB1R binding density decreased in the Arc and DVC. Alterations to neurotransmission signals in the brain significantly correlated with body weight and adiposity. The minimum dosage threshold required to induce weight gain in the rat was 0.5 mg/kg olanzapine.

Conclusions

Olanzapine-induced weight gain is associated with reduced appetite-inhibiting POMC and increased NPY. This study also supports a role for the CB1R and GABA in the mechanisms underlying weight gain side-effects, possibly by altering POMC transmission. Metabolic dysfunction can be modelled in the female rat using low, clinically-comparable olanzapine doses when administered in-line with the half-life of the drug.

Atypical antipsychotic-induced weight gain: insights into mechanisms of action

Prescriptions for second-generation antipsychotics (SGAs) have surpassed those for first-generation agents in the treatment of schizophrenia and bipolar disorder. While SGAs have the benefit of a much reduced risk of causing movement disorders, they have been associated with weight gain and metabolic effects. These adverse reactions are not uncommon, and threaten to have a significant impact on the patient's health over the long-term treatment that the patient requires. Currently, the aetiology of these effects is not known. This article reviews the data exploring the weight gain phenomenon. The literature was reviewed from searches of PubMed and the references of major articles in the field. The SGAs present a heterogeneous risk for weight gain. In addition, different individuals receiving the same drug can exhibit substantially different weight changes. This pattern suggests that a group of factors are associated with the weight gain phenomenon rather than a single mechanism. Coupled with the genetic profile that the patient brings to the treatment, the risk for SGA-induced weight gain will be different for different drugs and different individuals. Targets for exploration of the weight gain phenomenon include receptor interactions involving serotonin, histamine, dopamine, adrenergic, cannabinoid and muscarinic receptors. The association of SGA-induced weight gain and the role of orexigenic and anorexigenic peptides are reviewed. Also, a brief discussion of genetic factors associated with SGA-induced weight gain is presented, including that of the serotonin 5-HT(2C) receptor gene (HTR2C) and the cannabinoid 1 receptor gene (CNR1). The most promising data associated with SGA-induced weight gain include investigations of the histamine H(1), 5-HT(2A), 5-HT(2C), muscarinic M(3) and adrenergic receptors. In addition, work in the genetic area promises to result in a better understanding of the variation in risk associated with different individuals.

Olanzapine-induced hyperphagia and weight gain associate with orexigenic hypothalamic neuropeptide signaling without concomitant AMPK phosphorylation

The success of antipsychotic drug treatment in patients with schizophrenia is limited by the propensity of these drugs to induce hyperphagia, weight gain and other metabolic disturbances, particularly evident for olanzapine and clozapine. However, the molecular mechanisms involved in antipsychotic-induced hyperphagia remain unclear. Here, we investigate the effect of olanzapine administration on the regulation of hypothalamic mechanisms controlling food intake, namely neuropeptide expression and AMP-activated protein kinase (AMPK) phosphorylation in rats. Our results show that subchronic exposure to olanzapine upregulates neuropeptide Y (NPY) and agouti related protein (AgRP) and downregulates proopiomelanocortin (POMC) in the arcuate nucleus of the hypothalamus (ARC). This effect was evident both in rats fed ad libitum and in pair-fed rats. Of note, despite weight gain and increased expression of orexigenic neuropeptides, subchronic administration of olanzapine decreased AMPK phosphorylation levels. This reduction in AMPK was not observed after acute administration of either olanzapine or clozapine. Overall, our data suggest that olanzapine-induced hyperphagia is mediated through appropriate changes in hypothalamic neuropeptides, and that this effect does not require concomitant AMPK activation. Our data shed new light on the hypothalamic mechanism underlying antipsychotic-induced hyperphagia and weight gain, and provide the basis for alternative targets to control energy balance.

Weight gain, schizophrenia and antipsychotics: new findings from animal model and pharmacogenomic studies

Excess body weight is one of the most common physical health problems among patients with schizophrenia that increases the risk for many medical problems, including type 2 diabetes mellitus, coronary heart disease, osteoarthritis, and hypertension, and accounts in part for 20% shorter life expectancy than in general population. Among patients with severe mental illness, obesity can be attributed to an unhealthy lifestyle, personal genetic profile, as well as the effects of psychotropic medications, above all antipsychotic drugs. Novel "atypical" antipsychotic drugs represent a substantial improvement on older "typical" drugs. However, clinical experience has shown that some, but not all, of these drugs can induce substantial weight gain. Animal models of antipsychotic-related weight gain and animal transgenic models of knockout or overexpressed genes of antipsychotic receptors have been largely evaluated by scientific community for changes in obesity-related gene expression or phenotypes. Moreover, pharmacogenomic approaches have allowed to detect more than 300 possible candidate genes for antipsychotics-induced body weight gain. In this paper, we summarize current thinking on: (1) the role of polymorphisms in several candidate genes, (2) the possible roles of various neurotransmitters and neuropeptides in this adverse drug reaction, and (3) the state of development of animal models in this matter. We also outline major areas for future research.

Metabolic side effects of antipsychotic drug treatment--pharmacological mechanisms

Obesity and metabolic syndrome, with increased risk of eventual cardiovascular disease and type II diabetes, are significant problems for patients receiving antipsychotic drugs and are likely contribute to their decreased life expectancy. Several drug-related mechanisms may contribute to these problems, including effects both influencing food intake and on glucose and lipid metabolism. The metabolic consequences of different antipsychotic drugs vary substantially; these variations reflect differences in receptor pharmacology and provide clues as to the underlying pharmacological mechanisms. The two drugs with the greatest effects on body weight, olanzapine and clozapine, also have high affinity for the 5-HT2C and histamine H1 receptors, which implicate these receptors in antipsychotic-induced weight gain, while peripheral M3 muscarinic receptor antagonism as well as central 5-HT2C effects may contribute to obesity-independent diabetes. Other receptor mechanisms may have additive or synergistic effects; dopamine D2 receptor antagonism can enhance 5-HT2C-mediated effects on food intake, as well as influencing lipid and glucose metabolism via disinhibition of prolactin secretion. Pharmacogenetic associations of drug-induced weight gain with 5-HT2C receptor and leptin gene polymorphisms, among others, have provided further clues. Elevated leptin secretion in the absence of a decrease in food intake indicates drug-induced leptin insensitivity in the hypothalamus. The minimal weight gain seen with ziprasidone and aripiprazole may reflect their having further pharmacological effects that protect against changes in food intake and related metabolic factors. Understanding the pharmacology of metabolic consequences of current antipsychotic drug treatment is clearly the key to developing improved pharmacotherapies that avoid these problematic and limiting adverse effects.

Obesity, serious mental illness and antipsychotic drugs

The prevalence of overweight and obesity is higher in people with mental illness than in the general population. Body weight is tightly regulated by a complex system involving the cortex and limbic system, the hypothalamus and the gastrointestinal tract. While there are justifiable concerns about the weight gain associated with antipsychotic medication, it is too simplistic to ascribe all obesity in people with serious mental illness (SMI) to their drug treatment. The development of obesity in SMI results from the complex interaction of the genotype and environment of the person with mental illness, the mental illness itself and antipsychotic medication. There are dysfunctional reward mechanisms in SMI that may contribute to poor food choices and overeating. While it is clear that antipsychotics have profound effects to stimulate appetite, no one receptor interaction provides an adequate explanation for this effect, and many mechanisms are likely to be involved. The complexity of the system regulating body weight allows us to start to understand why some individuals appear much more prone to weight gain and obesity than others.

Hyperphagia and increased meal size are responsible for weight gain in rats treated sub-chronically with olanzapine

RATIONALE

Atypical antipsychotic-induced weight gain is a significant impediment in the treatment of schizophrenia.

OBJECTIVES

In a putative model of antipsychotic drug-induced weight gain, we investigated the effects of sub-chronic olanzapine on body weight, meal patterns, the expression of genes encoding for hypothalamic feeding-related neuropeptides and the contribution of hyperphagia to olanzapine-induced weight gain in rats.

MATERIALS AND METHODS

In experiment 1, female rats received either olanzapine (1 mg/kg, p.o.) or vehicle, twice daily for 7 days, while meal patterns were recorded. At the end of the treatment regimen, we measured the levels of hypothalamic messenger RNAs (mRNAs) encoding neuropeptide-Y (NPY), hypocretin/orexin (HCRT), melanin concentrating hormone and pro-opiomelanocortin. NPY and HCRT mRNA levels were also assessed in a separate cohort of female rats treated acutely with olanzapine (1 mg/kg, p.o.). In experiment 2, we investigated the effect of a pair-feeding paradigm on sub-chronic (1 mg/kg, p.o.) olanzapine-induced weight gain.

RESULTS

In experiment 1, sub-chronic olanzapine increased body weight, food intake and meal size. Hypothalamic neuropeptide mRNA levels were unchanged after both acute and sub-chronic olanzapine treatment. In experiment 2, the restriction of food intake to the level of vehicle-treated controls abolished the sub-chronic olanzapine-induced increase in body weight.

CONCLUSIONS

Hyperphagia mediated by drug-induced impairments in satiety (as evidenced by increased meal size) is a key requirement for olanzapine-induced weight gain in this paradigm. However, olanzapine-induced hyperphagia and weight gain may not be mediated via alterations in the expression of the feeding-related hypothalamic neuropeptides examined in this study.

Drug-induced hyperphagia: what can we learn from psychiatric medications?

This brief review examines hyperphagia and associated weight gain as undesirable side effects of psychiatric medications; exploring the scope of the problem, proposed mechanisms, and potential interventions. Mechanisms of action appear to include drug-mediated effects on hypothalamic appetite pathways that have been implicated in other etiologies of obesity. There is great individual variation in response to these medications as well as variation in the degree of weight gain within drug classes. Gene polymorphisms may be a key factor in determining individual variations in response. Better understanding of the underlying mechanisms can guide useful interventions. Medication selection and dosing appear to be important strategies to minimize adverse weight gain.

Pharmacological management of atypical antipsychotic-induced weight gain

Excessive bodyweight gain was reported during the 1950s as an adverse effect of typical antipsychotic drug treatment, but the magnitude of bodyweight gain was found to be higher with the atypical antipsychotic drugs that were introduced after 1990. Clozapine and olanzapine produce the greatest bodyweight gain, ziprasidone and aripiprazole have a neutral influence, and quetiapine and risperidone cause an intermediate effect. In the CATIE study, the percentage of patients with bodyweight gain of >7% compared with baseline differed significantly between the antipsychotic drugs, i.e. 30%, 16%, 14%, 12% and 7% for olanzapine, quetiapine, risperidone, perphenazine (a typical antipsychotic) and ziprasidone, respectively (p<0.001). Appetite stimulation is probably a key cause of bodyweight gain, but genetic polymorphisms modify the bodyweight response during treatment with atypical antipsychotics. In addition to nutritional advice, programmed physical activity, cognitive-behavioural training and atypical antipsychotic switching, pharmacological adjunctive treatments have been assessed to counteract excessive bodyweight gain. In some clinical trials, nizatidine, amantadine, reboxetine, topiramate, sibutramine and metformin proved effective in preventing or reversing atypical antipsychotic-induced bodyweight gain; however, the results are inconclusive since few randomized, placebo-controlled clinical trials have been conducted. Indeed, most studies were short-term trials without adequate statistical power and, in the case of metformin, nizatidine and sibutramine, the results are contradictory. The tolerability profile of these agents is adequate. More studies are needed before formal recommendations on the use of these drugs can be made. Meanwhile, clinicians are advised to use any of these adjunctive treatments according to their individual pharmacological and tolerability profiles, and the patient's personal and family history of bodyweight gain and metabolic dysfunction.

The 5-HT2C receptor and antipsychoticinduced weight gain - mechanisms and genetics

The mechanisms underlying weight gain resulting from antipsychotic drugs are not fully understood, although antagonism of the 5-HT2C receptor is likely to contribute. Animal studies indicate that the drugs most likely to cause weight gain, clozapine and olanzapine, have direct effects on the NPY-containing neurons of the hypothalamus; these neurons mediate the effects of the circulating anorexigenic hormone leptin on the control of food intake. The substantial differences between individuals in the extent of antipsychotic-induced weight gain suggest that genetic factors may be important. We have been studying pharmacogenetic correlates and find that a common 5-HT2C receptor promoter region polymorphisms demonstrates strong associations with weight gain in two first episode psychotic samples. In both series, we have found further association of antipsychotic drug-induced weight gain with a common and functional polymorphism of the gene for leptin. Along with initial BMI, these two pharmacogenetic factors account for almost 30% of the variance in drug-induced weight gain. Interestingly, the 5-HT2C polymorphism appears to determine levels of circulating leptin, providing a potential mechanism underlying the genetic association of the 5-HT2C receptor with weight gain. We have undertaken functional studies of haplotypes of the 5-HT2C promoter region and find the allele associated with protection from weight gain results in reduced promoter activity. These findings demonstrate the value of pharmacogenetics in determining liability to a major side effect of antipsychotic treatment, and indicate both the molecular and physiological mechanisms underlying this side effect.