Receptor occupancy-based analysis of the contributions of various receptors to antipsychotics-induced weight gain and diabetes mellitus

Metformin for atypical antipsychotic-induced weight gain and glucose metabolism dysregulation: review of the literature and clinical suggestions

Individuals receiving certain atypical antipsychotic medications are at risk of gaining weight and developing metabolic problems. There are no established drug treatments to prevent or counter these problems. However, the antihyperglycaemic agent metformin appears promising in some recent studies and we review the literature that evaluates metformin for limiting or reversing atypical antipsychotic drug-induced weight gain and glucose metabolism dysregulation. These studies suggest that metformin is beneficial if started early in antipsychotic drug treatment. Metformin has also been shown to prevent or delay the onset of type 2 diabetes mellitus in high-risk individuals from the general population. Based on these findings, we identify antipsychotic drug-treated patients who might benefit from metformin therapy and offer clinical guidelines for its use. Further long-term studies are needed to extend our observations and improve this strategy.

The role of histaminergic H1 and H3 receptors in food intake: a mechanism for atypical antipsychotic-induced weight gain?

Atypical antipsychotics such as olanzapine and clozapine are effective at treating the multiple domains of schizophrenia, with a low risk of extra-pyramidal side-effects. However a major downfall to their use is metabolic side-effects particularly weight gain/obesity, which occurs by unknown mechanisms. The present paper explores the potential candidature of histaminergic neurotransmission in the mechanisms of atypical antipsychotic-induced weight gain, with a focus on the histaminergic H1 and H3 receptors. Olanzapine and clozapine have a high affinity for the H1 receptor, and meta-analyses show a strong correlation between risk of weight gain and H1 receptor affinity. In addition, olanzapine treatment decreases H1 receptor binding and mRNA expression in the rat hypothalamus. Furthermore, a complex role is emerging for the histamine H3 receptor in the control of hunger. The H3 receptor is a pre-synaptic autoreceptor that inhibits the synthesis and release of histamine, and a heteroreceptor that inhibits other neurotransmitters such as serotonin (5-HT), noradrenaline (NA) and acetylcholine (ACh), which are also implicated in the regulation of food intake. Thus, the H3 receptor is in a prime position to regulate food intake, both through its control of histamine and its influence on other feeding pathways. We proposed that a mechanism for atypical antipsychotic-induced weight gain may be partly through the H3 receptor, as a drug-induced decrease in H1 receptor activity may decrease histamine tone through the H3 autoreceptors, compounding the weight gain problem. In addition, atypical antipsychotics may affect food intake by influencing 5-HT, NA and ACh release via interactions with the H3 heteroreceptor.

Acetyl-coenzyme A carboxylase alpha gene variations may be associated with the direct effects of some antipsychotics on triglyceride levels

Acetyl-coenzyme A carboxylase alpha (ACACA) single-nucleotide polymorphism (SNP) (rs2229416) was significantly associated with hypertriglyceridemia, during exploration of antipsychotic direct effects on lipids. Neuropeptide Y (NPY) gene (rs1468271) and ACACB gene (rs2241220) SNPs were significantly associated with severe hypercholesterolemia. In the same sample (173 patients on olanzapine, quetiapine, chlorpromazine or mirtazapine [increasing the risk of hyperlipidemia] and 184 controls taking other antipsychotics), three (rs1266175, rs12453407 and rs9906543) of eight additional ACACA SNPs were significantly associated with hypertriglyceridemia in those taking drugs of interest, but not in controls. Five other ACACA SNPs, three additional NPY SNPs, and seven additional ACACB SNPs were not significant.

Management of schizophrenia with obesity, metabolic, and endocrinological disorders

People with schizophrenia have an increased prevalence of overweight/obesity, type 2 diabetes mellitus, dyslipidemia, and metabolic syndrome, which increases the risk for cardiovascular diseases and mortality. Part of this increased risk is attributable to the use of antipsychotic medications, especially second-generation antipsychotics. Antipsychotic drugs differ in their potential to induce weight gain, with clozapine and olanzapine exhibiting the highest weight gain liability; evidence for differing effects of antipsychotics on glucose and lipid metabolism is less convincing. Individuals with schizophrenia may develop hyperprolactinemia, with or without clinical symptoms, after starting antipsychotic medications. This effect is particularly frequent with first-generation antipsychotics and with the second-generation antipsychotic risperidone and paliperidone. Psychiatrists should be aware of metabolic and endocrine side effects of antipsychotics and should make every effort to prevent or minimize them to improve the patients' compliance and quality of life.

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.

Olanzapine-induced weight gain in the rat: role of 5-HT2C and histamine H1 receptors

INTRODUCTION

Substantial increases in body weight can be induced by several antipsychotic drugs, most notably olanzapine and clozapine. Antagonism at certain receptors, particularly 5-HT2C and histamine H1 receptors, is implicated in this effect.

MATERIALS AND METHODS

We have investigated the contribution of effects at these receptors to olanzapine-induced weight gain occurring over 5 days following daily intraperitoneal drug injections in groups of eight female rats.

RESULTS

Olanzapine (2 mg/kg) and the 5-HT2C antagonist SB 243213 (1 mg/kg), but not the histamine H1 antagonist mepyramine (1 mg/kg), produced significant increases in percentage body weight above vehicle; olanzapine showed a significantly greater effect than SB 243213. Haloperidol (0.1 mg/kg) alone or with mepyramine had no significant effects on weight gain, while with SB 243213 and with both SB 243213 and mepyramine, it showed olanzapine-like increases in weight.

CONCLUSION

These results suggest that 5-HT2C receptor antagonism or inverse agonism, in the presence of D2 receptor antagonism, may contribute to olanzapine-induced weight gain.

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.

A psychiatric-cardiac case: analysis for education and clinical practice

Psychiatric patients are now known to have disproportionately high cardiovascular disease mortality rates. Today's nurse needs more knowledge to manage the care of the psychiatric-cardiac patient. This paper uses a case scenario to cite essential components of care. Psychiatric-cardiac events are explained using a conceptual model. The model provides the nurse with a template for identifying needs and mapping the changes observed through therapy. The paper serves as an organizing tool for clinical practice and a case presentation for continued education of nurses.

An exploration of the effect of modafinil on olanzapine associated weight gain in normal human subjects

BACKGROUND

Weight gain has been associated with many second generation antipsychotics (SGAs). A variety of theories have been put forward as to the etiology of SGA-associated weight gain. Modafinil possesses pharmacologic effects that could influence the weight gain associated with SGAs. The objective of this trial was to determine the effect of modafinil on olanzapine-associated weight gain.

METHODS

This study was a 3-week, randomized, double-blind, placebo-controlled trial. All subjects received olanzapine titrated to 10 mg/day. Concurrently, subjects were randomized to receive modafinil titrated to 200 mg/day or placebo. Weight and feeding lab assessments were conducted at baseline and endpoint.

RESULTS

Fifty subjects were enrolled in the study with 20 subjects per group completing the trial. The primary outcome variable was change in the body mass index (BMI) over the 3 weeks of the trial. Increases in BMI were observed in both groups. However, analysis of covariance, controlled for baseline BMI, revealed that the olanzapine/placebo group had a greater increase in BMI at end point compared with the olanzapine/modafinil group (.89 +/- .59 vs. .47 +/- .50 kg/m(2), p < .05). When controlled for gender, the comparison showed a significant difference between groups at week 1 but not at weeks 2 or 3.

CONCLUSIONS

The results of this trial should not be extrapolated to clinical practice at this time. These data do serve to support further evaluation in a patient population to determine if the weight modifying effect of modafinil can be demonstrated over a longer period of time.

Association between the insulin-induced gene 2 (INSIG2) and weight gain in a German sample of antipsychotic-treated schizophrenic patients: perturbation of SREBP-controlled lipogenesis in drug-related metabolic adverse effects?

Atypical antipsychotics are nowadays the most widely used drugs to treat schizophrenia and other psychosis. Unfortunately, some of them can cause major metabolic adverse effects, such as weight gain, dyslipidemia and type 2 diabetes. The underlying lipogenic mechanisms of the antipsychotic drugs are not known, but several studies have focused on a central effect in the hypothalamic control of appetite regulation and energy expenditure. In a functional convergent genomic approach we recently used a cellular model and demonstrated that orexigenic antipsychotics that induce weight gain activate the expression of lipid biosynthesis genes controlled by the sterol regulatory element-binding protein (SREBP) transcription factors. We therefore hypothesized that the major genes involved in the SREBP activation of fatty acids and cholesterol production (SREBF1, SREBF2, SCAP, INSIG1 and INSIG2) would be strong candidate genes for interindividual variation in drug-induced weight gain. We genotyped a total of 44 HapMap-selected tagging single nucleotide polymorphisms in a sample of 160 German patients with schizophrenia that had been monitored with respect to changes in body mass index during antipsychotic drug treatment. We found a strong association (P=0.0003-0.00007) between three markers localized within or near the INSIG2 gene (rs17587100, rs10490624 and rs17047764) and antipsychotic-related weight gain. Our finding is supported by the recent involvement of the INSIG2 gene in obesity in the general population and implicates SREBP-controlled lipogenesis in drug-induced metabolic adverse effects.

Clinical monitoring and management of the metabolic syndrome in patients receiving atypical antipsychotic medications

Individuals with major mental illness are a high-risk group for cardio-metabolic derangements due to genetic predisposition, developmental and environmental stressors, and lifestyle. This risk is compounded when they receive antipsychotic medications. Guidelines for screening, monitoring, and managing these patients for metabolic problems have been in place for several years. Despite this, recent reports document that this population continues to receive poor care in this regard. In this article, we review the metabolic profile of atypical antipsychotic medications and offer guidelines to reduce the metabolic complications of these agents.

Efficacy and safety of bifeprunox in patients with an acute exacerbation of schizophrenia: results from a randomized, double-blind, placebo-controlled, multicenter, dose-finding study

RATIONALE

Bifeprunox is a partial dopamine agonist with a unique receptor-binding profile and potential antipsychotic properties.

OBJECTIVES

The current study evaluated the efficacy and safety of bifeprunox in patients with an acute exacerbation of schizophrenia.

MATERIALS AND METHODS

In this 6-week, double-blind, placebo-controlled study, 589 patients were randomly assigned to once-daily treatment with bifeprunox 5, 10, or 20 mg, placebo, or risperidone 6 mg. Efficacy was assessed by changes in symptom rating scales [Positive and Negative Syndrome Scale (PANSS) total and subscale scores; PANSS-derived BPRS scores; Clinical Global Impression--Severity (CGI--S) and Clinical Global Impression--Improvement (CGI--I) scores]. Safety and tolerability were assessed by monitoring adverse events, extrapyramidal symptoms (EPS), laboratory values, electrocardiograms, prolactin levels, and weight.

RESULTS

Compared with placebo, bifeprunox 20 mg produced a statistically significantly greater reduction from baseline to last assessment in the primary efficacy variable (PANSS total score; effect size = -0.339), as well as most secondary efficacy measures. No statistically significant differences in efficacy were seen with lower doses of bifeprunox. The most common treatment-emergent adverse events (TEAEs) noted with bifeprunox were gastrointestinal; no clear dose-related trend in the incidence of any TEAE was observed in the bifeprunox groups. Compared to placebo, treatment with bifeprunox led to small but statistically significant decreases in weight and prolactin levels. EPS were comparable between bifeprunox and placebo. The active reference in this study, risperidone 6 mg, showed statistically significant differences from placebo for the primary efficacy parameter (effect size = -0.628) and all secondary efficacy parameters.

CONCLUSIONS

These data suggest that 20 mg of bifeprunox may be efficacious in improving symptoms in patients with an acute exacerbation of schizophrenia. Bifeprunox appeared to be safe and well tolerated by patients in this 6-week study.

Increased expression of lipid biosynthesis genes in peripheral blood cells of olanzapine-treated patients

Recent in-vitro studies show that antipsychotic drugs increase lipid biosynthesis through changes in gene expression. Based on these finding we compared the expression of two central lipid biosynthesis genes, fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD), in whole blood of olanzapine-treated and unmedicated patients. Patients with psychotic disorders were consecutively selected from an ongoing, naturalistic study, and divided into two groups according to the following criteria: (1) strict monotherapy with olanzapine (n=19) or (2) no current medication (n=19). The groups were matched on gender, race and body mass index. Blood lipid levels were examined, and gene expression in whole blood was assessed with quantitative real-time PCR. Expression of FASN (p=0.003) and SCD (p=0.002) was significantly up-regulated in olanzapine-treated compared to unmedicated patients. Transcriptional activation of lipid biosynthesis genes in peripheral blood cells of olanzapine-treated patients suggests a direct lipogenic action of antipsychotic drugs, which may be related to metabolic adverse effects.

Identification of a butyrophenone analog as a potential atypical antipsychotic agent: 4-[4-(4-chlorophenyl)-1,4-diazepan-1-yl]-1-(4-fluorophenyl)butan-1-one

The synthesis and exploration of novel butyrophenones have led to the identification of a diazepane analogue of haloperidol, 4-[4-(4-chlorophenyl)-1,4-diazepan-1-yl]-1-(4-fluorophenyl)butan-1-one (compound 13) with an interesting multireceptor binding profile. Compound 13 was evaluated for its binding affinities at DA subtype receptors, 5HT subtype receptors, H-1, M-1 receptors and at NET, DAT, and SERT transporters. At each of these receptors, compound 13 was equipotent or better than several of the standards currently in use. In in vivo mouse and rat models to evaluate its efficacy and propensity to elicit catalepsy and hence EPS in humans, compound 13 showed similar efficacy as clozapine and did not produce catalepsy at five times its ED(50) value.

Weight change in Parkinson and Alzheimer patients taking atypical antipsychotic drugs

Atypical antipsychotics (AA) are generally associated with weight gain. We determined body mass index (BMI) change in Parkinson's disease (PD) before and after taking AA and compared against PD controls and Alzheimer's disease (AD) patients on AA. In 66 consecutive PD subjects started on AA who had accurate weights for more than 6 months before and after initiation of AA, we compared weight change before and after AA use, against a control group of sixty-one sex-matched PD subjects, and against twenty-eight AD subjects taking AA. A linear regression model was created to compare weight changes. Fifty-nine PD subjects had complete data, quetiapine (n=53) and clozapine (n=6). The mean BMI change in the period before starting AA was 0.00 kg/m(2)/month over 1.95+/-1.41 years. After starting AA, subjects lost 0.03 kg/m(2)/month (95% CI 0.62-1.21, P<0.0001), comparing PD before AA to the same PD patients after AA. In 61 PD controls, the mean BMI loss was 0.01 kg/m(2)/month (95% CI 0.15-0.94, P=0.007) comparing PD on AA vs. PD controls. The BMI for 28 AD subjects on AA increased 0.01 kg/m(2)/month (95% CI 0.26-0.83, P<0.0001), comparing PD on AA vs. AD on AA. The weight loss seen in the PD/AA group, compared to AD, suggest uniquely altered weight homeostasis in PD.

Short- and long-term effects of antipsychotic drug treatment on weight gain and H1 receptor expression

The present study investigated body weight gain, food intake, open-field activity and brain histamine H1 receptor mRNA and protein expression in rats treated with three types of antipsychotics. Rats were divided into eight groups and treated with aripiprazole (2.25mg/kg/day), olanzapine (1.5mg/kg/day), haloperidol (0.3mg/kg/day) or vehicle (as control) for 1 or 12 weeks. Administration of olanzapine for 1 week led to a threefold increase in body weight gain and a 35% increase in fat deposits compared to controls (p<0.05). In the 12-week olanzapine treatment group, accumulative food intake was significantly higher in the first 7 weeks of treatment compared to controls (p<0.018), while body weight gain was significantly greater in the first 8 weeks compared to controls (p<0.045). Using in situ hybridization, we found that olanzapine treatment, but not aripiprazole or haloperidol treatment, significantly reduced H1 receptor mRNA expression in the arcuate hypothalamic nucleus (Arc: -18%, p=0.006, 1 week; -20%, p=0.008, 12 weeks) and ventromedial hypothalamic nucleus (VMH: -22%, p=0.006, 1 week; -19%, p=0.042, 12 weeks) compared to controls. The quantitative autoradiography data showed a reduction in VMH H1 receptor binding density after 1 (-12%, p=0.040) and 12 (-10%, p=0.094) weeks of olanzapine treatment. There were significant negative correlations between the levels of H1 receptor mRNA expression, and body weight gain and energy efficiency in the Arc and VMH after 1- and 12-week antipsychotic treatments in all groups. In addition, H1 receptor mRNA expression in the Arc showed a significant negative correlation with food intake and fat mass in all groups. Furthermore, there were negative correlations between H1 receptor binding density in the VMH and total fat mass and body weight gain after 1 week of antipsychotic treatment. The present study suggests that downregulated VMH and Arc H1 receptor expression may be a key factor contributing to olanzapine-induced obesity.

Comparison of weight gain in treatments for Tourette syndrome: tetrabenazine versus neuroleptic drugs

Weight gain occurs with most neuroleptic drugs used to treat tics. Tetrabenazine, a vesicular monoamine transporter type 2 inhibitor, inhibits dopamine release. It is used to treat a variety of hyperkinetic movement disorders, including tics. Weight gain over time was compared in a group of pediatric tic patients taking only tetrabenazine with an age-matched group of tic patients taking only neuroleptic drugs. Age in the tetrabenazine group (n = 36, 32 males) at initial therapy was 13.4 (SD 3.3) years. They were monitored for 25.2 (SD 12.3) months. The average dose of tetrabenazine (all visits) was 54.4 (SD 26.6) mg/d. In the neuroleptic group (n = 41, 33 males), the age at therapy onset was 12.3 +/- 4.0 years. They were monitored for 18.9 (SD 14.8) months. Weight increase was 0.8 lb/mo in the tetrabenazine group compared with 1.7 lb/mo in the neuroleptic group (P = .006). Most patients who switched from a neuroleptic drug to tetrabenazine subsequently lost weight. Although the study was not designed to compare efficacy, this tended to be greater with tetrabenazine than with neuroleptic drugs.

Identifying optimal biologic doses of everolimus (RAD001) in patients with cancer based on the modeling of preclinical and clinical pharmacokinetic and pharmacodynamic data

PURPOSE

To use preclinical and clinical pharmacokinetic (PK)/pharmacodynamic (PD) modeling to predict optimal clinical regimens of everolimus, a novel oral mammalian target of rapamycin (mTOR) inhibitor, to carry forward to expanded phase I with tumor biopsy studies in cancer patients.

PATIENTS AND METHODS

Inhibition of S6 kinase 1 (S6K1), a molecular marker of mTOR signaling, was selected for PD analysis in peripheral blood mononuclear cells (PBMCs) in a phase I clinical trial. PK and PD were measured up to 11 days after the fourth weekly dose. A PK/PD model was used to describe the relationship between everolimus concentrations and S6K1 inhibition in PBMCs of cancer patients and in PBMCs and tumors of everolimus-treated CA20948 pancreatic tumor-bearing rats.

RESULTS

Time- and dose-dependent S6K1 inhibition was demonstrated in human PBMCs. In the rat model, a relationship was shown between S6K1 inhibition in tumors or PBMCs and antitumor effect. This allowed development of a direct-link PK/PD model that predicted PBMC S6K1 inhibition-time profiles in patients. Comparison of rat and human profiles simulated by the model suggested that a weekly 20- to 30-mg dose of everolimus would be associated with an antitumor effect in an everolimus-sensitive tumor and that daily administration would exert a greater effect than weekly administration at higher doses.

CONCLUSION

A direct-link PK/PD model predicting the time course of S6K1 inhibition during weekly and daily everolimus administration allowed extrapolation from preclinical studies and first clinical results to select optimal doses and regimens of everolimus to explore in future clinical trials.

Synergistic impairment of glucose homeostasis in ob/ob mice lacking functional serotonin 2C receptors

To investigate how serotonin and leptin interact in the regulation of energy balance and glucose homeostasis, we generated a genetic mouse model, the OB2C mouse, which lacks functional serotonin 2C receptors and the adipocyte hormone leptin. The OB2C mice exhibited a dramatic diabetes phenotype, evidenced by a synergistic increase in serum glucose levels and water intake. The severity of the animals' diabetes phenotype would not have been predicted from the phenotypic characterization of mice bearing mutations of either the leptin (OB mutant mice) or the serotonin 2C receptor gene (2C mutant mice). The synergistic impairment in glucose homeostasis developed at an age when OB2C mice did not differ in body weight from OB mice, suggesting that this impairment was not an indirect consequence of increased adiposity. We also demonstrated that the improvement in glucose tolerance in wild-type mice treated with the serotonin releaser and reuptake inhibitor fenfluramine was blunted in 2C mutant mice. These pharmacological and genetic findings provide evidence that the serotonin 2C receptor has direct effects on glucose homeostasis.

A comparison of the effects of olanzapine and risperidone versus placebo on ghrelin plasma levels

To thoroughly investigate the phenomenon of atypical antipsychotic-associated weight gain, a feeding laboratory paradigm was developed that included obtaining plasma levels of the orexigenic peptide ghrelin that is associated with appetite and eating. This study is a randomized, double-blind, parallel group trial comparing the effects of a 2-week exposure to olanzapine, risperidone, or placebo on plasma ghrelin area under the plasma-time curve (AUC) in 28 healthy human subjects. Subjects were randomized to receive olanzapine, risperidone, or placebo and titrated over 4 days to 10 mg/d or 4 mg/d, respectively. The mean dose at end point was 8.6 + 1.8 mg/d for the olanzapine group and 2.8 + 0.8 mg/d for the risperidone group. Weight changes were significantly different between groups at end point (F2,44 = 10.193; P = 0.0001). The olanzapine group demonstrated a significant increase in weight at end point (2.25 + 1.84 kg) compared with placebo (0.13 + 1.05 kg; P = 0.007). Because of the small subject number, the comparisons between olanzapine and risperidone and risperidone and placebo did not reach statistical significance, although olanzapine's mean weight gain was numerically greater than that of risperidone (2.25 + 1.84 kg vs 1.10 + 0.99 kg) and risperidone's mean weight gain was numerically larger than placebo (1.10 + 0.99 kg vs 0.13 + 1.05 kg). The baseline adjusted Bonferroni corrected contrast of end point ghrelin AUC demonstrated a significant difference between groups (F2,24 = 4.40; P = 0.024), and the post hoc analysis revealed a significant decrease in ghrelin AUC for the olanzapine group in comparison with the risperidone group (P = 0.021) but not between risperidone and placebo or olanzapine and placebo. Ghrelin AUC values did not change significantly from baseline to end point in either of the other 2 groups. The difference between groups approached but did not reach significance (F2,23 = 3.299; P = 0.055) when body mass index change was included as a covariate, suggesting that the difference in ghrelin AUC change followed the change in body weight. Sedation associated with both active drugs (P = 0.006) and "stuffy nose" associated with risperidone (P = 0.020) were the only statistically different adverse reactions when compared with placebo. Thus, a human feeding laboratory paradigm using a brief exposure to atypical antipsychotics functions as a method to investigate pharmacologically induced weight gain and its association with changes in the orexigenic peptide ghrelin. This rejects the hypothesis that ghrelin levels are elevated by the antipsychotic and that this is a potential cause of the weight gain phenomenon.

Atypical antipsychotic-induced metabolic side effects: insights from receptor-binding profiles

Atypical antipsychotic drugs offer several notable benefits over typical antipsychotics, including greater improvement in negative symptoms, cognitive function, prevention of deterioration, and quality of life, and fewer extrapyramidal symptoms (EPS). However, concerns about EPS have been replaced by concerns about other side effects, such as weight gain, glucose dysregulation and dyslipidemia. These side effects are associated with potential long-term cardiovascular health risks, decreased medication adherence, and may eventually lead to clinical deterioration. Despite a greater understanding of the biochemical effects of these drugs in recent years, the pharmacological mechanisms underlying their various therapeutic properties and related side effects remain unclear. Besides dopamine D(2) receptor antagonism, a characteristic feature of all atypical antipsychotic drugs, these agents also bind to a range of non-dopaminergic targets, including serotonin, glutamate, histamine, alpha-adrenergic and muscarinic receptors. This review examines the potential contribution of different receptors to metabolic side effects associated with atypical antipsychotic treatment for all seven agents currently marketed in the United States (risperidone, olanzapine, quetiapine, ziprasidone, aripiprazole, paliperidone and clozapine) and another agent (bifeprunox) in clinical development at the time of this publication.

Olanzapine treatment decreases the density of muscarinic M2 receptors in the dorsal vagal complex of rats

In this study, we investigated the effects of antipsychotic drugs, olanzapine and haloperidol, on the density of the muscarinic M2 receptors in the dorsal vagal complex (DVC) and hypoglossal nucleus (HN). Female Sprague Dawley rats were treated with olanzapine, haloperidol or vehicle (control) for 1 (short-term) or 12 weeks (long-term). Quantitative autoradiography was used to investigate the M2 receptor density in the DVC and HN using a muscarinic antagonist [(3)H] AF-DX384. Olanzapine, but not haloperidol, treatment induced a significant decrease in the binding density of M2 receptors in the DVC compared to control groups. Although the HN showed a higher density of [(3)H] AF-DX384 binding than the DVC, treatment with both olanzapine and haloperidol did not induce any significant changes in [(3)H] AF-DX384 binding in the HN. These results suggest that olanzapine-induced body weight gain may be associated with functional changes in the muscarinic neurotransmission in the DVC.

Pharmacokinetics/Pharmacodynamics Analysis of the Relationship between the in Vivo Micturition Pressure and Receptor Occupancy of (R)-Oxybutynin and Its Metabolite in Rats

To elucidate the relationships between the pharmacokinetics and pharmacological effects of oxybutynin ((R/S)-OXY), the micturition pressure and the plasma concentration profiles of (R)-OXY and (R)-N-desethyloxybutynin ((R)-DEOB), a pharmacologically active metabolite, after administration by three different routes (i.v., p.o. and transdermal) in rats were measured and analyzed using an inhibitory effect E(max) model with their in vitro pharmacological effects. The plasma exposure ratios of (R)-DEOB to (R)-OXY calculated from the AUCs were somewhat different among the routes administered. (R)-OXY and (R)-DEOB equally inhibited the acetylcholine-induced contractions in vitro. The micturition pressure, measured using the cystometric method in vivo, exhibited saturation against the dose administered. The inhibitory effect E(max) model well described the relationship between the micturition pressure and the receptor occupancy calculated from the plasma concentrations and pA(2) values and resulted in an extremely small receptor occupancy (0.206%) to exhibit half of the maximum effect. The estimated receptor occupancy profiles suggested a sufficient and long-lasting receptor occupation after transdermal administration of (R/S)-OXY, while the receptor occupancy diminished rapidly after the i.v. and p.o. administration. These data indicate that transdermal administration of (R/S)-OXY would be useful to achieve suitable pharmacological effects without excess plasma concentrations.

Genetics of antipsychotic treatment emergent weight gain in schizophrenia

Classic and modern antipsychotics can induce substantial weight gain causing diabetes, lipid abnormalities and psychological distress. Treatment emergent weight gain varies within the broad class of antipsychotics; however, an individual's propensity to develop weight gain largely depends on genetic factors. The first part of this review highlights current ideas and concepts related to antipsychotic-induced weight gain, including principles on energy homeostasis. The second part summarizes genetic findings emphasizing studies published after 2003 as prior studies have been reviewed in detail elsewhere. Candidate gene studies have produced significant findings in the 5-hydroxytryptamin 2C (5HT2C) and adrenergic alpha2a (ADRalpha2a) receptor genes, as well as in the leptin, guanine nucleotide binding protein (GNB3) and synaptomal-associated protein 25kDa (SNAP25) genes. Results from genome-wide association and linkage studies point to several chromosomal regions (e.g., 12q24) and some specific genes (e.g., promelanin concentrating hormone [PMCH], polycyctic kidney and hepatic disease 1 [PKHD1], peptidylglycine alpha-amidating monooxygenase [PAM]). However, more efforts are needed before risk prediction and personalized medicine can be made available for antipsychotic-induced weight gain.

Antipsychotic induced metabolic abnormalities: An interaction study with various PPAR modulators in mice

Abnormalities in glucose and lipid regulation have been reported in schizophrenia during antipsychotic medications. The objectives of the present study were to evaluate the effect of various peroxisome proliferator-activated receptor modulators viz. glimepiride, rosiglitazone and fenofibrate on chlorpromazine, clozapine and ziprasidone induced hyperglycemia and hyperlipidemia in mice. Male Swiss albino mice were orally treated with chlorpromazine, clozapine and ziprasidone concurrently with the antidiabetic medications for 7 days. Plasma glucose, insulin and triglyceride levels were determined at the end of the study. Chlorpromazine and clozapine elevated the glucose and triglyceride levels in normal mice, with no effect on insulin but ziprasidone increased the basal triglyceride and insulin levels and did not have any effect on glucose. Glimepiride and rosiglitazone showed beneficial glucose and triglyceride lowering effects in chlorpromazine and clozapine animals and no effect on insulin levels. Fenofibrate significantly reduced the glucose levels only in animals treated with clozapine, and exhibited significant reduction of triglyceride levels in chlorpromazine, clozapine and ziprasidone treated animals. All three antidiabetic/hypolipidemic agents lowered triglyceride and insulin levels in ziprasidone treated animals. The results of the present studies suggest that hyperglycemia, hyperinsulinemia and hypertriglyceridemia induced by various antipsychotics may involve diverse mechanisms.