Inhibition of glucose transport in PC12 cells by the atypical antipsychotic drugs risperidone and clozapine, and structural analogs of clozapine

Interaction of amisulpride with GLUT1 at the blood-brain barrier. Relevance to Alzheimer's disease

Blood-brain barrier (BBB) dysfunction may be involved in the increased sensitivity of Alzheimer's disease (AD) patients to antipsychotics, including amisulpride. Studies indicate that antipsychotics interact with facilitated glucose transporters (GLUT), including GLUT1, and that GLUT1 BBB expression decreases in AD. We tested the hypotheses that amisulpride (charge: +1) interacts with GLUT1, and that BBB transport of amisulpride is compromised in AD. GLUT1 substrates, GLUT1 inhibitors and GLUT-interacting antipsychotics were identified by literature review and their physicochemical characteristics summarised. Interactions between amisulpride and GLUT1 were studied using in silico approaches and the human cerebral endothelial cell line, hCMEC/D3. Brain distribution of [3H]amisulpride was determined using in situ perfusion in wild type (WT) and 5xFamilial AD (5xFAD) mice. With transmission electron microscopy (TEM) we investigated brain capillary degeneration in WT mice, 5xFAD mice and human samples. Western blots determined BBB transporter expression in mouse and human. Literature review revealed that, although D-glucose has no charge, charged molecules can interact with GLUT1. GLUT1 substrates are smaller (184.95±6.45g/mol) than inhibitors (325.50±14.40g/mol) and GLUT-interacting antipsychotics (369.38±16.04). Molecular docking showed beta-D-glucose (free energy binding: -15.39kcal/mol) and amisulpride (-29.04kcal/mol) interact with GLUT1. Amisulpride did not affect [14C]D-glucose hCMEC/D3 accumulation. [3H]amisulpride uptake into the brain (except supernatant) of 5xFAD mice compared to WT remained unchanged. TEM revealed brain capillary degeneration in human AD. There was no difference in GLUT1 or P-glycoprotein BBB expression between WT and 5xFAD mice. In contrast, caudate P-glycoprotein, but not GLUT1, expression was decreased in human AD capillaries versus controls. This study provides new details about the BBB transport of amisulpride, evidence that amisulpride interacts with GLUT1 and that BBB transporter expression is altered in AD. This suggests that antipsychotics could potentially exacerbate the cerebral hypometabolism in AD. Further research into the mechanism of amisulpride transport by GLUT1 is important for improving antipsychotics safety.

Insight into mitochondrial dysfunction mediated by clozapine-induced inhibition of PGRMC1 in PC12 cells

Clozapine is usually considered as the last resort for treatment-resistant schizophrenia (TRS). However, it shows limited efficacy in cognition improvement. Moreover, the metabolic side effects induced by clozapine can aggravate cognitive impairment, which is closely related to its neurotoxicity. Nevertheless, the mechanisms underlying clozapine's neurotoxicity remain largely elusive. In this study, PC12 cells were simultaneously treated with different concentrations (0μM, 10μM, 20μM, 40μM and 80μM) of clozapine and AG205 which functions as a blocking reagent of progesterone receptor membrane component 1 (PGRMC1). In addition, we examined the effect of PGRMC1 in clozapine-induced neurotoxicity through overexpressing or downregulating PGRMC1. Molecular docking and surface plasmon resonance (SPR) analysis indicated that clozapine and AG205 inhibited the binding of endogenous progesterone to PGRMC1. The results showed that high concentration of clozapine and AG205 induced a significant increase in cytotoxicity, reactive oxygen species (ROS) accumulation and mitochondrial membrane potential (MMP) collapse, all of which were worsened as concentration increases, while overexpression of PGRMC1 reverted the above toxic effect of clozapine on PC12 cells. Furthermore, clozapine and AG205 also downregulated the expression of PGRMC1, glucagon-like peptide-1 receptor (GLP-1R) and mitofusin2 (Mfn2). Interestingly, overexpression of PGRMC1 could revert these effects. Our data suggest that overexpression of PGRMC1 in PC12 cells prevents and restores clozapine-induced oxidative and mitochondrial damage. We propose PGRMC1 activation as a promising therapeutic strategy for clozapine-induced neurotoxicity to facilitate the relief of neuronal damage.

Schizophrenia: a disorder of broken brain bioenergetics

A substantial and diverse body of literature suggests that the pathophysiology of schizophrenia is related to deficits of bioenergetic function. While antipsychotics are an effective therapy for the management of positive psychotic symptoms, they are not efficacious for the complete schizophrenia symptom profile, such as the negative and cognitive symptoms. In this review, we discuss the relationship between dysfunction of various metabolic pathways across different brain regions in relation to schizophrenia. We contend that several bioenergetic subprocesses are affected across the brain and such deficits are a core feature of the illness. We provide an overview of central perturbations of insulin signaling, glycolysis, pentose-phosphate pathway, tricarboxylic acid cycle, and oxidative phosphorylation in schizophrenia. Importantly, we discuss pharmacologic and nonpharmacologic interventions that target these pathways and how such interventions may be exploited to improve the symptoms of schizophrenia.

Imipramine Accelerates Nonalcoholic Fatty Liver Disease, Renal Impairment, Diabetic Retinopathy, Insulin Resistance, and Urinary Chromium Loss in Obese Mice

Imipramine is a tricyclic antidepressant that has been approved for treating depression and anxiety in patients and animals and that has relatively mild side effects. However, the mechanisms of imipramine-associated disruption to metabolism and negative hepatic, renal, and retinal effects are not well defined. In this study, we evaluated C57BL6/J mice subjected to a high-fat diet (HFD) to study imipramine’s influences on obesity, fatty liver scores, glucose homeostasis, hepatic damage, distribution of chromium, and retinal/renal impairments. Obese mice receiving imipramine treatment had higher body, epididymal fat pad, and liver weights; higher serum triglyceride, aspartate and alanine aminotransferase, creatinine, blood urea nitrogen, renal antioxidant enzyme, and hepatic triglyceride levels; higher daily food efficiency; and higher expression levels of a marker of fatty acid regulation in the liver compared with the controls also fed an HFD. Furthermore, the obese mice that received imipramine treatment exhibited insulin resistance, worse glucose intolerance, decreased glucose transporter 4 expression and Akt phosphorylation levels, and increased chromium loss through urine. In addition, the treatment group exhibited considerably greater liver damage and higher fatty liver scores, paralleling the increases in patatin-like phospholipid domain containing protein 3 and the mRNA levels of sterol regulatory element-binding protein 1 and fatty acid-binding protein 4. Retinal injury worsened in imipramine-treated mice; decreases in retinal cell layer organization and retinal thickness and increases in nuclear factor κB and inducible nitric oxide synthase levels were observed. We conclude that administration of imipramine may result in the exacerbation of nonalcoholic fatty liver disease, diabetes, diabetic retinopathy, and kidney injury.

Doxepin Exacerbates Renal Damage, Glucose Intolerance, Nonalcoholic Fatty Liver Disease, and Urinary Chromium Loss in Obese Mice

Doxepin is commonly prescribed for depression and anxiety treatment. Doxepin-related disruptions to metabolism and renal/hepatic adverse effects remain unclear; thus, the underlying mechanism of action warrants further research. Here, we investigated how doxepin affects lipid change, glucose homeostasis, chromium (Cr) distribution, renal impairment, liver damage, and fatty liver scores in C57BL6/J mice subjected to a high-fat diet and 5 mg/kg/day doxepin treatment for eight weeks. We noted that the treated mice had higher body, kidney, liver, retroperitoneal, and epididymal white adipose tissue weights; serum and liver triglyceride, alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, and creatinine levels; daily food efficiency; and liver lipid regulation marker expression. They also demonstrated exacerbated insulin resistance and glucose intolerance with lower Akt phosphorylation, GLUT4 expression, and renal damage as well as higher reactive oxygen species and interleukin 1 and lower catalase, superoxide dismutase, and glutathione peroxidase levels. The treated mice had a net-negative Cr balance due to increased urinary excretion, leading to Cr mobilization, delaying hyperglycemia recovery. Furthermore, they had considerably increased fatty liver scores, paralleling increases in adiponectin, FASN, PNPLA3, FABP4 mRNA, and SREBP1 mRNA levels. In conclusion, doxepin administration potentially worsens renal injury, nonalcoholic fatty liver disease, and diabetes.

Phosphoproteomics of Acute Cell Stressors Targeting Exercise Signaling Networks Reveal Drug Interactions Regulating Protein Secretion

Exercise engages signaling networks to control the release of circulating factors beneficial to health. However, the nature of these networks remains undefined. Using high-throughput phosphoproteomics, we quantify 20,249 phosphorylation sites in skeletal muscle-like myotube cells and monitor their responses to a panel of cell stressors targeting aspects of exercise signaling in vivo. Integrating these in-depth phosphoproteomes with the phosphoproteome of acute aerobic exercise in human skeletal muscle suggests that co-administration of β-adrenergic and calcium agonists would activate complementary signaling relevant to this exercise context. The phosphoproteome of cells treated with this combination reveals a surprising divergence in signaling from the individual treatments. Remarkably, only the combination treatment promotes multisite phosphorylation of SERBP1, a regulator of Serpine1 mRNA stability, a pro-fibrotic secreted protein. Secretome analysis reveals that the combined treatments decrease secretion of SERPINE1 and other deleterious factors. This study provides a framework for dissecting phosphorylation-based signaling relevant to acute exercise.

Direct effects of antipsychotic drugs on insulin, energy sensing and inflammatory pathways in hypothalamic mouse neurons

INTRODUCTION

Second-generation antipsychotics cause serious metabolic side effects, but the mechanisms behind these effects remain largely unknown. However, emerging evidence supports that antipsychotics may act upon the hypothalamus, the primary brain region understood to regulate energy homeostasis. We have recently reported that the antipsychotics olanzapine, clozapine, and aripiprazole can directly act on hypothalamic rat neurons (rHypoE-19) to impair insulin, energy sensing, and modulate inflammatory pathways. In the current paper, we sought to replicate these findings to a mouse neuronal model.

METHODS

The mouse hypothalamic neuronal cell line, mHypoE-46, was treated with olanzapine, clozapine, or aripiprazole. Western blots were used to measure the energy sensing protein AMPK, components of the insulin signalling pathway (AKT, GSK3β), and components of the MAPK pathway (ERK1/2, JNK, p38), the latter linked to inflammation. RT-qPCR was used to measure mRNA expression of the inflammatory mediators IL-6, IL-10, and BDNF, well as putative receptors in the mHypoE-46 (current) and the rHypoE-19 (previously studied) cell lines.

RESULTS

In the mHypoE-46 neurons, olanzapine and aripiprazole increased AMPK phosphorylation, while clozapine and aripiprazole inhibited insulin-induced phosphorylation of AKT. Clozapine increased JNK and aripiprazole decreased ERK1/2 phosphorylation. Olanzapine also decreased IL-6 mRNA expression, while olanzapine and clozapine increased IL-10 mRNA expression. The rHypoE-19 neurons expressed the H₁, 5 H T_2A, and M₃ receptors, while the mHypoE-46 neurons expressed the 5 H T_2A, D₂, and M₃ receptors. Neither cell line expressed the 5 H T_2C receptor.

CONCLUSION

Similar to observed effects of these agents in rat neurons, induction of AMPK by aripiprazole and olanzapine suggests impaired energy sensing, while suppression of insulin-induced pAKT by clozapine and aripiprazole suggests impaired insulin signalling, seen across both rodent derived hypothalamic cell lines. Conversely, olanzapine-induced suppression of pro-inflammatory IL-6, alongside olanzapine and clozapine-induced IL-10, demonstrate anti-inflammatory effects, which do not corroborate with our prior observations in the rat neuronal line. The different findings between cell lines could be explained by differential expression of neurotransmitters receptors and/or reflect genetic heterogeneity across the rat and mouse lines. However, overall, our findings support direct effects of antipsychotics to impact insulin, energy sensing, and inflammatory pathways in hypothalamic rodent neurons.

Second-Generation Antipsychotics and Dysregulation of Glucose Metabolism: Beyond Weight Gain

Second-generation antipsychotics (SGAs) are the cornerstone of treatment for schizophrenia because of their high clinical efficacy. However, SGA treatment is associated with severe metabolic alterations and body weight gain, which can increase the risk of type 2 diabetes and cardiovascular disease, and greatly accelerate mortality. Several underlying mechanisms have been proposed for antipsychotic-induced weight gain (AIWG), but some studies suggest that metabolic changes in insulin-sensitive tissues can be triggered before the onset of AIWG. In this review, we give an outlook on current research about the metabolic disturbances provoked by SGAs, with a particular focus on whole-body glucose homeostasis disturbances induced independently of AIWG, lipid dysregulation or adipose tissue disturbances. Specifically, we discuss the mechanistic insights gleamed from cellular and preclinical animal studies that have reported on the impact of SGAs on insulin signaling, endogenous glucose production, glucose uptake and insulin secretion in the liver, skeletal muscle and the endocrine pancreas. Finally, we discuss some of the genetic and epigenetic changes that might explain the different susceptibilities of SGA-treated patients to the metabolic side-effects of antipsychotics.

Antipsychotics differentially regulate insulin, energy sensing, and inflammation pathways in hypothalamic rat neurons

INTRODUCTION

Second generation antipsychotic (AP)s remain the gold-standard treatment for schizophrenia and are widely used on- and off-label for other psychiatric illnesses. However, these agents cause serious metabolic side-effects. The hypothalamus is the primary brain region responsible for whole body energy regulation, and disruptions in energy sensing (e.g. insulin signaling) and inflammation in this brain region have been implicated in the development of insulin resistance and obesity. To elucidate mechanisms by which APs may be causing metabolic dysregulation, we explored whether these agents can directly impact energy sensing and inflammation in hypothalamic neurons.

METHODS

The rat hypothalamic neuronal cell line, rHypoE-19, was treated with olanzapine (0.25-100 uM), clozapine (2.5-100 uM) or aripiprazole (5-20 uM). Western blots measured the energy sensing protein AMPK, components of the insulin signaling pathway (AKT, GSK3β), and components of the MAPK pathway (ERK1/2, JNK, p38). Quantitative real-time PCR was performed to determine changes in the mRNA expression of interleukin (IL)-6, IL-10 and brain derived neurotrophic factor (BDNF).

RESULTS

Olanzapine (100 uM) and clozapine (100, 20 uM) significantly increased pERK1/2 and pJNK protein expression, while aripiprazole (20 uM) only increased pJNK. Clozapine (100 uM) and aripiprazole (5 and 20 uM) significantly increased AMPK phosphorylation (an orexigenic energy sensor), and inhibited insulin-induced phosphorylation of AKT. Olanzapine (100 uM) treatment caused a significant increase in IL-6 while aripiprazole (20 uM) significantly decreased IL-10. Olanzapine (100 uM) and aripiprazole (20 uM) increased BDNF expression.

CONCLUSIONS

We demonstrate that antipsychotics can directly regulate insulin, energy sensing, and inflammatory pathways in hypothalamic neurons. Increased MAPK activation by all antipsychotics, alongside olanzapine-associated increases in IL-6, and aripiprazole-associated decreases in IL-10, suggests induction of pro-inflammatory pathways. Clozapine and aripiprazole inhibition of insulin-stimulated pAKT and increases in AMPK phosphorylation (an orexigenic energy sensor) suggests impaired insulin action and energy sensing. Conversely, olanzapine and aripiprazole increased BDNF, which would be expected to be metabolically beneficial. Overall, our findings suggest differential effects of antipsychotics on hypothalamic neuroinflammation and energy sensing.

Atypical antipsychotics-induced metabolic syndrome and nonalcoholic fatty liver disease: a critical review

The atypical antipsychotics (AAPs) have been used as first-line drugs in psychiatric practice for a wide range of psychotic disorders, including schizophrenia and bipolar mania. While effectively exerting therapeutic effects on positive and negative symptoms, as well as cognitive impairments in schizophrenia patients, these drugs are less likely to induce extrapyramidal symptoms compared to typical antipsychotics. However, the increasing application of them has raised questions on their tolerability and adverse effects over the endocrine, metabolic, and cardiovascular axes. Specifically, AAPs are associated to different extents, with weight gain, metabolic syndrome (MetS), and nonalcoholic fatty liver disease (NAFLD). This article summarized clinical evidence showing the metabolic side effects of AAPs in patients with schizophrenia, and experimental evidence of AAPs-induced metabolic side effects observed in animals and cell culture studies. In addition, it discussed potential mechanisms involved in the APPs-induced MetS and NAFLD.

Current Views on Dopaminergic Drugs Affecting Glucose Homeostasis

BACKGROUND

For more than three decades, it has been known that manipulation of dopaminergic system could affect glucose homesotasis in experimental animals. The notion that glucose homeostasis in human might be influenced by dopaminergic drugs has attracted a great deal of attention in the past two decades. In spite of rapid advancements in revealing involvement of dopaminergic neurotransmission in insulin release, glucose up-take and pancreatic beta cell function in general through centrally and peripherally controlled mechanisms, there are discrepancies among observations on experimental animals and human subjects.

CONCLUSION

With the expansion of pharmacotherapy in psychotic conditions, depression and endocrine abnormalities along with a sharp increase in prevalence of type two diabetes and disturbances of glucose homeostasis as a major risk factor for many cardiovascular complications and associated mortalities; it seems a critical analysis of recent investigations on drugs which act as agonists or antagonists of dopaminergic receptors in various tissues and organs may provide better insight into how safe and efficient these medicines could be prescribed. Furthermore, the other main objective of present review is to compare clinical data on significance of changes in blood glucose and insulin levels during short term and after long term treatment with these agents. This in turn would be beneficial for determining adequate strategies to combat or to avoid adverse effects associated with dopaminergic drug therapy.

Antipsychotics and glucose metabolism: how brain and body collide

Since the serendipitous discovery of the first antipsychotic (AP) drug in the 1950s, APs remain the cornerstone of treatment for schizophrenia. A shift over the past two decades away from first-generation, conventional APs to so-called "atypical" (or 2nd/3rd generation) APs parallels acknowledgment of serious metabolic side-effects associated in particular with these newer agents. As will be reviewed, AP drugs and type 2 diabetes are now inextricably linked, contributing to the three- to fivefold increased risk of type 2 diabetes observed in schizophrenia. However, this association is not straightforward. Biological and lifestyle-related illness factors contribute to the association between type 2 diabetes and metabolic disease independently of AP treatment. In addition, APs have a well-established weight gain propensity which could also account for elevated risk of insulin resistance and type 2 diabetes. However, compelling preclinical and clinical evidence now suggests that these drugs can rapidly and directly influence pathways of glucose metabolism independently of weight gain and even in absence of psychiatric illness. Mechanisms of these direct effects remain poorly elucidated but may involve central and peripheral antagonism of neurotransmitters implicated not only in the therapeutic effects of APs but also in glucose homeostasis, possibly via effects on the autonomic nervous system. The clinical relevance of studying "direct" effects of these drugs on glucose metabolism is underscored by the widespread use of these medications, both on and off label, for a growing number of mental illnesses, extending safety concerns well beyond schizophrenia.

Clozapine-induced Insulin-resistant Hyperglycemia in a Diabetic Patient

Clozapine is superior to all other antipsychotics in treatment-resistant schizophrenia. However, metabolic side effects are common while treating patients with clozapine. Administering clozapine in a patient who already is diabetic involves careful weighing of risks and benefits. Here, we report our experience of starting clozapine in a known diabetic patient. Clozapine was started in a patient with treatment-resistant psychosis in view of suicidal risk. Her diabetes mellitus was under good control with oral medications. After initiation of clozapine, blood sugars increased several fold within few days. Blood glucose continued to increase even with high doses of insulin and insulin infusion. Finally, blood sugars came under control only after discontinuation of clozapine. Precautionary measures while initiating clozapine in a diabetic patient are suggested - close monitoring of blood sugar during the initial few days and intensive intervention if blood sugar levels increase. Discontinuation of clozapine should also be kept in mind as a last resort.

Metabolic Syndrome and Antipsychotics: The Role of Mitochondrial Fission/Fusion Imbalance

Second-generation antipsychotics (SGAs) are known to increase cardiovascular risk through several physiological mechanisms, including insulin resistance, hepatic steatosis, hyperphagia, and accelerated weight gain. There are limited prophylactic interventions to prevent these side effects of SGAs, in part because the molecular mechanisms underlying SGAs toxicity are not yet completely elucidated. In this perspective article, we introduce an innovative approach to study the metabolic side effects of antipsychotics through the alterations of the mitochondrial dynamics, which leads to an imbalance in mitochondrial fusion/fission ratio and to an inefficient mitochondrial phenotype of muscle cells. We believe that this approach may offer a valuable path to explain SGAs-induced alterations in metabolic homeostasis.

Olanzapine and aripiprazole differentially affect glucose uptake and energy metabolism in human mononuclear blood cells

The use of antipsychotics carries the risk of metabolic side effects, such as weight gain and new onset type-2 diabetes mellitus. The mechanisms of the observed metabolic alterations are not fully understood. We compared the effects of two atypical antipsychotics, one known to favor weight gain (olanzapine), the other not (aripiprazole), on glucose metabolism. Primary human peripheral blood mononuclear cells (PBMC) were isolated and stimulated with olanzapine or aripiprazole for 72 h. Cellular glucose uptake was analyzed in vitro by 18F-FDG uptake. Further measurements comprised mRNA expression of glucose transporter (GLUT) 1 and 3, GLUT1 protein expression, DNA methylation of GLUT1 promoter region, and proteins involved in downstream glucometabolic processes. We observed a 2-fold increase in glucose uptake after stimulation with aripiprazole. In contrast, olanzapine stimulation decreased glucose uptake by 40%, accompanied by downregulation of the cellular energy sensor AMP activated protein kinase (AMPK). GLUT1 protein expression increased, GLUT1 mRNA expression decreased, and GLUT1 promoter was hypermethylated with both antipsychotics. Pyruvat-dehydrogenase (PDH) complex activity decreased with olanzapine only. Our findings suggest that the atypical antipsychotics olanzapine and aripiprazole differentially affect energy metabolism in PBMC. The observed decrease in glucose uptake in olanzapine stimulated PBMC, accompanied by decreased PDH point to a worsening in cellular energy metabolism not compensated by AMKP upregulation. In contrast, aripiprazole stimulation lead to increased glucose uptake, while not affecting PDH complex expression. The observed differences may be involved in the different metabolic profiles observed in aripiprazole and olanzapine treated patients.

The Role of Inhaled Loxapine in the Treatment of Acute Agitation in Patients with Psychiatric Disorders: A Clinical Review

Loxapine is a first generation antipsychotic, belonging to the dibenzoxazepine class. Recently, loxapine has been reformulated at a lower dose, producing an inhaled powder that can be directly administered to the lungs to treat the agitation associated with psychiatric disorders, such as schizophrenia and bipolar disorder. Thus, the aim of this narrative and clinical mini-review was to evaluate the efficacy and tolerability of inhaled loxapine in the treatment of acute agitation in patients with psychiatric disorders. The efficacy of inhaled loxapine has been evaluated in one Phase II trial on patients with schizophrenia, and in two Phase III trials in patients with schizophrenia and bipolar disorder. Moreover, there are two published case series on patients with borderline personality disorder and dual diagnosis patients. Inhaled loxapine has proven to be effective and generally well tolerated when administered to agitated patients with schizophrenia and bipolar disorder. Two case series have suggested that inhaled loxapine may also be useful to treat agitation in patients with borderline personality disorder and with dual diagnosis, but further studies are needed to clarify this point. However, the administration of inhaled loxapine requires at least some kind of patient collaboration, and is not recommended in the treatment of severe agitation in totally uncooperative patients. Moreover, the drug-related risk of bronchospasm must always be kept in mind when planning to use inhaled loxapine, leading to a careful patient assessment prior to, and after, administration. Also, the higher costs of inhaled loxapine, when compared to oral and intramuscular medications, should be taken into account when selecting it for the treatment of agitation.

Association of adipokines with metabolic disorders in patients with schizophrenia: Results of comparative study with mental healthy cohort

AIM

The role of adipose tissue hormones, adipokines, in formation of metabolic disorders in schizophrenia is not fully understood. The aim was to investigate the association of leptin and adiponectin plasma levels with metabolic parameters in antipsychotic treated patients with schizophrenia and in the group of age, gender and body mass index matched mental healthy persons.

METHODS

One hundred patients with diagnosis of schizophrenia, who took antipsychotic medication, and equal number of control subjects, were enrolled for cross-sectional evaluation. Fasting blood plasma levels of glucose, lipids, insulin, adiponectin, leptin concentrations and insulin resistance HOMA index were determined.

RESULTS

In both groups plasma leptin concentration positively correlated with body mass index, insulin plasma level and HOMA index, while adiponectin level had negative correlations with adiposity measures and positive associations with high density lipoprotein cholesterol content. At the same time, in schizophrenia group, but not in control subjects, leptin level positively associated with cholesterol and triglycerides concentrations and adiponectin negatively correlated with plasma insulin content, HOMA index and triglycerides levels. After controlling for confounders significant correlations remained for leptin concentration with HOMA index and plasma triglycerides level in schizophrenic patients and for adiponectin concentration with plasma high density lipoprotein cholesterol concentrations in both studied groups.

CONCLUSIONS

Both adipokines associate with metabolic parameters in antipsychotic treated patients with schizophrenia. Leptin can play more specific role in pathogenesis of metabolic syndrome in schizophrenic persons than in mental healthy subjects.

Diabetes mellitus and severe mental illness: mechanisms and clinical implications

The prevalence of diabetes mellitus is twofold to threefold higher in people with severe mental illness (SMI) than in the general population, with diabetes mellitus affecting ∼12% of people receiving antipsychotics. The consequences of diabetes mellitus are more severe and frequent in people with SMI than in those without these conditions, with increased rates of microvascular and macrovascular complications, acute metabolic dysregulation and deaths related to diabetes mellitus. Multiple complex mechanisms underlie the association between diabetes mellitus and SMI; these mechanisms include genetic, environmental and disease-specific factors, and treatment-specific factors. Although antipsychotics are the mainstay of treatment in SMI, a causative link, albeit of uncertain magnitude, seems to exist between antipsychotics and diabetes mellitus. The principles of managing diabetes mellitus in people with SMI are similar to those for the general population and should follow currently established treatment algorithms. Lifestyle interventions are needed to reduce incident diabetes mellitus. In addition, improved uptake of opportunities to screen for this disease will reduce the high prevalence of undiagnosed diabetes mellitus. Currently, people with SMI receive poorer treatment for diabetes mellitus than the general population. Thus, health-care professionals in primary care, diabetes mellitus services and mental health teams have a responsibility to ensure that patients with SMI are not disadvantaged.

Antipsychotics-induced metabolic alterations: focus on adipose tissue and molecular mechanisms

The use of antipsychotic drugs for the treatment of mood disorders and psychosis has increased dramatically over the last decade. Despite its consumption being associated with beneficial neuropsychiatric effects in patients, atypical antipsychotics (which are the most frequently prescribed antipsychotics) use is accompanied by some secondary adverse metabolic effects such as weight gain, dyslipidemia and glucose intolerance. The molecular mechanisms underlying these adverse effects are not fully understood but have been suggested to involve a dysregulation of adipose tissue homeostasis. As such, the aim of this paper is to review and discuss the role of adipose tissue in the development of secondary adverse metabolic effects induced by atypical antipsychotics. Data analyzed in this article suggest that atypical antipsychotics may increase adipose tissue (particularly visceral adipose tissue) lipogenesis, differentiation/hyperplasia, pro-inflammatory mediator secretion and insulin resistance and decrease adipose tissue lipolysis. Consequently, patients receiving antipsychotic medication could be at risk of developing obesity, type 2 diabetes and cardiovascular disease. A better knowledge of the impact of these drugs on adipose tissue homeostasis may unveil strategies to develop novel antipsychotic drugs with less adverse metabolic effects and to develop adjuvant therapies (e.g. behavioral and nutritional therapies) to neuropsychiatric patients receiving antipsychotic medication.

Blood levels of glucose and insulin and insulin resistance in patients with schizophrenia on clozapine monotherapy

OBJECTIVE

We tested the hypothesis that fasting blood glucose and insulin levels are higher in schizophrenic subjects on clozapine monotherapy compared with healthy controls and they correlate with anthropometric measurements, laboratory tests and body composition.

METHODS

Data for 24 subjects with schizophrenia treated with clozapine and 24 age- and sex-matched healthy volunteers was analyzed.

RESULTS

Patients taking clozapine had higher fasting levels of glucose (103.5±31.6 vs. 87.8±11.7mg/dL, z=-2.03, p=0.04), there was no difference for insulin concentrations and markers of insulin resistance. In the clozapine group glucose levels correlated with clozapine dose (R=-0.43, p=0.03), while insulin levels correlated with weight (R=0.66, p<0.001), body mass index (R=0.54, p=0.007), abdominal (R=0.53, p=0.007) and waist (R=0.43, p=0.04) circumference, total body fat (R=0.51, p=0.01), and uric acid levels (R=0.50, p=0.01). In the clozapine group insulin levels were lower in subjects with body mass index <25kg/m(2) (7.0±3.3 vs. 13.4±8.8μU/mL, p=0.04) and in subjects without abdominal obesity (6.3±2.4 vs. 13.3±8.6μU/mL, p=0.03).

CONCLUSIONS

We found higher blood glucose levels in subjects taking clozapine and no differences in blood insulin levels between subjects with schizophrenia and controls. Associations between blood insulin levels and abdominal/waist circumferences support the role of abdominal obesity as an important risk factor of insulin resistance.

Second-generation antipsychotics cause a rapid switch to fat oxidation that is required for survival in C57BL/6J mice

Some second-generation antipsychotics (SGAs) increase insulin resistance and fat oxidation, but counter intuitively they do not activate lipolysis. This seems unsustainable for meeting energy demands. Here, we measured dose-dependent effects of SGAs on rates of oxygen consumption (VO2), respiratory exchange ratio (RER), and physical activity in C57BL/6J mice. The role of H1-histamine receptors and consequences of blocking fat oxidation were also examined. Olanzapine, risperidone, and clozapine (2.5-10mg/kg) elicited rapid drops in dark-cycle RER (~0.7) within minutes, whereas aripiprazole exerted only modest changes. Higher doses of olanzapine decreased VO2, and this was associated with accumulation of glucose in plasma. Clozapine and risperidone also lowered VO2, in contrast to aripiprazole, whereas all decreased physical activity. Astemizole and terfenadine had no significant effects on RER, VO2, or physical activity. The VO2 and RER effects appear independent of sedation/physical activity or H1-receptors. CPT-1 inhibitors can enhance muscle glucose utilization and prevent fat oxidation. However, after etomoxir (2 × 30 mg/kg), a low dose of olanzapine that did not significantly affect VO2 by itself caused precipitous drops in VO2 and body temperature, leading to death within hours or a moribund state requiring euthanasia. One 30 mg/kg dose of either etomoxir or 2-tetradecylglycidate followed by olanzapine, risperidone, or clozapine, but not aripiprazole, dramatically lowered VO2 and body temperature. Thus, mice treated with some SGAs shift their fuel utilization to mostly fat but are unable to either switch back to glucose or meet their energy demands when either higher doses are used or when fat oxidation is blocked.

Atypical antipsychotics such as risperidone, but not paliperidone, worsen vascular endothelial function via upregulation of adhesion molecules VCAM-1, ICAM-1, and E-selectin in diabetic rats

Schizophrenia doubles the odds of diabetes, and atypical antipsychotics (AAPs) also increase risk of diabetes. Indeed, little is known about the effects of AAPs on vascular dysfunctions associated with diabetes. This study aimed to determine the effects of risperidone (RISP) and paliperidone (PALI) on the vascular function of diabetic rats. Diabetes was induced by feeding with a high-fat diet followed by the administration of streptozotocin (35 mg·(kg body mass)−1, by intraperitoneal injection). Rats received RISP or PALI (1.25 mg·kg−1·d−1, per os) for 3 weeks. Endothelium-dependent relaxation, systolic blood pressure, lipid profile, insulin resistance, and adhesion molecules, vascular cell-adhesion-molecule-1 (VCAM-1), intracellular-adhesion-molecule-1 (ICAM-1), and E-selectin were investigated. RISP significantly worsened the impaired endothelium-dependent relaxation of diabetic aortic rings with upregulation of the adhesion molecules VCAM-1, ICAM-1, and E-selectin, and proinflammatory cytokines MPC-1 and TNF-α. RISP augmented the metabolic dysfunctions and reduced insulin sensitivity in the insulin tolerance test as well as HOMA–IR. PALI produced insignificant effects on vascular and metabolic aberrations. Our results suggest that RISP, but not PALI, aggravates the metabolic abnormalities and vascular dysfunction associated with diabetes, which may be mediated by upregulation of VCAM-1, ICAM-1, and E-selectin. Nevertheless, future investigation for the possible mechanisms underlying the difference noticed between the 2 AAPs is warranted.

Metabolic effects of adjunctive aripiprazole in clozapine-treated patients with schizophrenia

OBJECTIVE

This study examined the effects of adjunctive aripiprazole therapy on metabolism in clozapine-treated patients with schizophrenia.

METHOD

In an 8-week randomized, double-blind, placebo-controlled study, subjects received either aripiprazole (15 mg/day) or placebo. At baseline and week 8, metabolic parameters were assessed by the frequently sampled intravenous glucose tolerance test, nuclear magnetic resonance spectroscopy and whole-body dual-energy X-ray absorptiometry (DXA).

RESULTS

Thirty subjects completed the study (16 in the aripiprazole group and 14 in the placebo group). Glucose effectiveness measured by the frequently sampled intravenous glucose tolerance test improved significantly in the aripiprazole group (0.003 ± 0.006 vs. -0.005 ± 0.007/min, P = 0.010). The aripiprazole group showed significant reductions in both plasma low-density lipoprotein (LDL) levels (-15.1 ± 19.8 vs. 4.4 ± 22.5 mg/dl, P = 0.019) and LDL particle numbers (-376 ± 632 vs. -36 ± 301 nm, P = 0.035). Further, there was a significant reduction in the lean mass (-1125 ± 1620 vs. 607 ± 1578 g, P = 0.011) measured by whole-body DXA scan in the aripiprazole group. All values were expressed as mean ± standard deviation, aripiprazole vs. placebo.

CONCLUSION

Adjunctive therapy with aripiprazole may have some metabolic benefits in clozapine-treated patients with schizophrenia.

The relationship between bipolar disorder and type 2 diabetes: more than just co-morbid disorders

Type 2 diabetes mellitus (T2DM) rates are three times higher in patients with bipolar disorder (BD), compared to the general population. This is a major contributing factor to the elevated risk of cardiovascular mortality, the leading cause of death in bipolar patients. There may be shared pathophysiology linking the two disorders, including hypothalamic-pituitary-adrenal and mitochondrial dysfunction, common genetic links, and epigenetic interactions. Life-style, phenomenology of bipolar symptoms, and adverse effects of pharmacotherapy may be contributing factors. Patients with BD and T2DM have a more severe course of illness and are more refractory to treatment. Control of their diabetes is poorer when compared to diabetics without BD, and an existing disparity in medical care may be partly responsible. Glucose abnormalities in bipolar patients need to be screened for and treated. Metformin appears to have the best benefit/risk ratio, and the dipeptidyl peptidase-4 inhibitors and glucagon-like peptide-1 receptor agonists and analogues also appear promising, although these agents have not been specifically studied in populations with mood disorders. Physicians need to be aware of the increased risk for T2DM and cardiovascular disease in bipolar patients, and appropriate prevention, screening, case finding, and treatment is recommended.

Metabolomic analysis of biochemical changes in the plasma and urine of first-episode neuroleptic-naïve schizophrenia patients after treatment with risperidone

Early findings propose that impaired neurotransmission in the brain plays a key role in the pathophysiology of schizophrenia. Recent advances in understanding its multiple etiologies and pathogenetic mechanisms provide more speculative hypotheses focused on even broader somatic systems. Using a targeted tandem mass spectrometry (MS/MS)-based metabolomic platform, we compared metabolic signatures consisting of monoamine and amino acid neurotransmitter (NT) metabolites in plasma/urine simultaneously between first-episode neuroleptic-naïve schizophrenia patients (FENNS) and healthy controls before and after a 6-week risperidone monotherapy, which suggest that the patient NT profiles are restoring during treatment. To detect and identify potential biomarkers associated with schizophrenia and risperidone treatment, we also performed a combined ultraperformance liquid chromatography-mass spectrometry (UPLC-MS) and 1H nuclear magnetic resonance (NMR)-based metabolomic profiling of the same samples, indicating a further deviation of the patients' global metabolic profile from that of controls. The NTs and their metabolites together with the 32 identified biomarkers underpin that metabolic pathways including NT metabolism, amino acid metabolism, glucose metabolism, lipid metabolism, energy metabolism, antioxidant defense system, bowel microflora and endocrine system are disturbed in FENNS. Among them, pregnanediol, citrate and α-ketoglutarate (α-KG) were significantly associated with symptomatology of schizophrenia after Bonferroni correction and may be useful biomarkers for monitoring therapeutic efficacy. These findings promise to yield valuable insights into the pathophysiology of schizophrenia and may advance the approach to treatment, diagnosis and disease prevention of schizophrenia and related syndromes.

Effects of aripiprazole and clozapine on the treatment of glycolytic carbon in PC12 cells

Aripiprazole is the only atypical antipsychotic drug known to cause the phosphorylation of AMP-activated protein kinase (AMPK) in PC12 cells. However, the molecular mechanisms underlying this phosphorylation in aripiprazole-treated PC12 cells have not yet been clarified. Here, using PC12 cells, we show that these cells incubated for 24 h with aripiprazole at 50 μM and 25 mM glucose underwent a decrease in their NAD⁺/NADH ratio. Aripiprazole suppressed cytochrome c oxidase (COX) activity but enhanced the activities of pyruvate dehydrogenase (PDH), citrate synthase and Complex I. The changes in enzyme activities coincided well with those in NADH, NAD⁺, and NAD⁺/NADH ratio. However, the bioenergetic peril judged by the lowered COX activity might not be accompanied by excessive occurrence of apoptotic cell death in aripiprazole-treated cells, because the mitochondrial membrane potential was not decreased, but rather increased. On the other hand, when PC12 cells were incubated for 24 h with clozapine at 50 μM and 25 mM glucose, the NAD⁺/NADH ratio did not change. Also, the COX activity was decreased; and the PDH activity was enhanced. These results suggest that aripiprazole-treated PC12 cells responded to the bioenergetic peril more effectively than the clozapine-treated ones to return the ATP biosynthesis back toward its ordinary level. This finding might be related to the fact that aripiprazole alone causes phosphorylation of AMPK in PC12 cells.

Does endoplasmic reticulum stress participate in APD-induced hepatic metabolic dysregulation?

Metabolic side effects caused by certain antipsychotic drugs (APDs), in particular clozapine and olanzapine, are now clinically well-documented. However, the potential mechanisms implicated in the metabolic disturbances of these drugs on peripheral tissues remain obscure. Here, we investigated the effects of five frequently prescribed APDs on the Sterol Regulatory Element Binding Protein (SREBP) transcription factor pathways which control lipogenesis and cholesterogenesis, using the Immortalized Human Hepatocyte cell model (IHH). First, clozapine, haloperidol, olanzapine and risperidone activated, at different levels, SREBP-1 activity reflected by an increased expression of SREBP-1 target genes involved in fatty acid biosynthesis (SREBP-1, FAS and/or SCD1) resulting in an accumulation of intracellular lipids. Second, clozapine and haloperidol also stimulated the SREBP-2 pathway associated with an increase in HMGCoAR expression. In contrast, quetiapine did not affect either the SREBP-1 or -2 pathways, but induced a slight accumulation of intracellular lipids. Interestingly, clozapine, haloperidol and olanzapine induced Endoplasmic Reticulum (ER) stress and, more precisely, initiation of the ER stress-activated eIF2α kinase (PERK) branch of the Unfolded Protein Response (UPR). Furthermore, treatment with thapsigargin, which increases intracellular calcium release, induced both ER stress and SREBP-1 and -2 pathway activation, whereas Ca(2+) chelation by BAPTA completely reversed the lipogenic effects and ER stress induction produced by clozapine. Based on these results, we propose that certain APDs induce ER stress via changes in Ca(2+) homeostasis in hepatocytes. This phenomenon potentially underlies a part of their known undesirable hepatic metabolic side effects. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

Differential effects of various typical and atypical antipsychotics on plasma glucose and insulin levels in the mouse: evidence for the involvement of sympathetic regulation

Atypical antipsychotic treatment has been associated with serious metabolic adverse events, such as glucose dysregulation and development of type 2 diabetes. As part of our studies on possible underlying mechanisms, we investigated the acute effects of various typical and atypical antipsychotics on plasma glucose and insulin in FVB/N mice, a strain that showed a more pronounced hyperglycemic response to clozapine than C57BL/6 and CD-1 mice. Acute administration of high doses of clozapine, olanzapine, quetiapine, perphenazine, or chlorpromazine significantly increased plasma glucose by 100%-140% above basal levels without significant effects on insulin levels. In contrast, risperidone reduced plasma glucose (-30%) and markedly enhanced plasma insulin levels. Doses of ziprasidone that gave 50-fold higher free plasma concentrations than therapeutic plasma levels, as well as high doses of aripiprazole and haloperidol, did not significantly alter either glucose or insulin levels. Clozapine- and olanzapine-induced hyperglycemia occurred at free plasma concentrations that were within, or one order of magnitude above, the range of therapeutic plasma levels. Pretreatment with either the ganglionic blocker hexamethonium, or the alpha(2) adrenergic receptor antagonist yohimbine, blocked the clozapine- and chlorpromazine-induced increase in glucose levels. Taken together, these results suggest that typical and atypical antipsychotics with known metabolic liability produce acute hyperglycemia in mice and that this effect is likely driven by activation of the sympathetic autonomic nervous system via a central mechanism.

Atypical antipsychotics and diabetes mellitus

Recently, increasing attention has been drawn to the potential diabetogenic effect of novel antipsychotics. Until now, large prospective studies examining the relationship between atypical antipsychotics and impaired glucose metabolism have been lacking. However, the case reports and retrospective studies that we review here suggest an increased risk of developing diabetes mellitus (DM) in patients treated with atypical antipsychotics compared to schizophrenic patients treated with conventional antipsychotics or those without treatment. Although most atypical antipsychotic agents might have a diabetogenic potential, the risk of developing DM might be higher in patients treated with either clozapine or olanzapine than with risperidone, whereas data on quetiapine and ziprasidone is presently limited and needs further attention. Possible mechanisms include the induction of peripheral insulin resistance and the direct influence on pancreatic beta-cell function by 5-HT1A/2A/2C receptor antagonism, by inhibitory effects via alpha 2-adrenergic receptors or by toxic effects. On the other hand, atypical antipsychotics might not be an independent risk factor for the development of DM, but hasten the onset of DM in patients bearing other risk factors. It is suggested that schizophrenic patients should be monitored for the occurrence of glucose metabolism abnormalities before starting atypical antipsychotics, and at a 3-month interval at least during therapy.

How can antipsychotics cause Diabetes Mellitus? Insights based on receptor-binding profiles, humoral factors and transporter proteins

The prevalence of Diabetes Mellitus (DM) is becoming a serious public health problem. The use of atypical antipsychotics has been associated with disruption of the glucose metabolism and therefore with causing DM. The underlying mechanisms are unknown, but knowledge of the differences between the pharmacological features of various antipsychotics combined with their diabetogenic profile might help us to understand those mechanisms. This article describes how the binding of various essential receptors or transporters in essential body tissues, adipose tissue, pancreatic tissue and liver and skeletal muscle tissue can cause disruption of the glucose metabolism. With such knowledge in mind one can try to explain the differences between the diabetogenic propensities of various antipsychotics. It is well known that clozapine and olanzapine cause weight gain and DM, whereas aripiprazole and ziprasidone have much less disruptive clinical profiles. The most significant risk factor for adiposity seems to be strong blocking of histaminergic receptors. An agonistic activity on serotonergic-1a receptors, with a very low affinity for muscarinergic-3 receptors, might protect against the development of DM. More data will become available which may help to solve the puzzle.

Engineered GPCRs as tools to modulate signal transduction

Different families of G-protein-coupled receptors (GPCRs) have been engineered to provide exclusive control over the activation of these receptors and thus to understand better the consequences of their signaling in vitro and in vivo. These engineered receptors, named RASSLs (receptors activated solely by synthetic ligands) and DREADDs (designer receptors exclusively activated by designer drugs), are insensitive to their endogenous ligands but can be activated by synthetic drug-like compounds. Currently, the existing RASSLs and DREADDs cover the Gi, Gq, and Gs signaling pathways. These modified GPCRs can be utilized as ideal tools to study GPCR functions selectively in specific cellular populations.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

Atypical antipsychotic drugs induce derangements in glucose homeostasis by acutely increasing glucagon secretion and hepatic glucose output in the rat

AIMS/HYPOTHESIS

Use of the second-generation antipsychotic drugs (SGAs) results in the development of obesity and a type 2 diabetes-like syndrome. We hypothesised that, in addition to the insulin resistance associated with the obesity, the SGAs might have acute effects on glucose metabolism that could contribute to the derangements in glucose metabolism.

METHODS

We investigated the effects of therapeutically relevant levels of three different antipsychotic medications (haloperidol, quetiapine and clozapine) on glucose tolerance, measures of insulin resistance and hepatic glucose production, and on insulin and glucagon secretion in rats.

RESULTS

We found that these drugs induce impaired glucose tolerance in rats that is associated with increased insulin secretion (clozapine>quetiapine>haloperidol) but is independent of weight gain. However, Akt/protein kinase B activation is normal, and at these levels of drug there was no effect on insulin action in fat cells or soleus muscle, and no effect on insulin sensitivity as evaluated by insulin tolerance tests. We show that clozapine induces increased glucose levels following pyruvate and glycerol challenges, indicating an increase in hepatic glucose output (HGO). Increased HGO would in turn increase insulin release and would explain the apparent phenotype mimicking insulin resistance. We provide evidence that this effect could at least in part be mediated by a stimulation of glucagon secretion.

CONCLUSIONS/INTERPRETATION

Our findings indicate that SGAs can cause acute derangements in glucose metabolism that are not caused by a direct induction of insulin resistance but act via an increase in glucagon secretion and thus stimulation of hepatic glucose production.

[Diabetes mellitus associated with atypical antipsychotic medications: case report and review of the literature]

Since the introduction of atypical antipsychotic medications, starting with clozapine in 1990, many studies have associated these drugs with the development of diabetes among other metabolic disorders, as well as with the onset of the disease as ketoacidosis. We report the case of a 28-year-old patient with schizophrenia who was admitted with diabetic acidosis 1 month after the beginning of clozapine therapy. No weight gain was reported and the patient maintains satisfactory glycemia levels with no treatment required after discontinuation of the drug. The literature on this subject and cases reported so far are reviewed, including the association of other atypical antipsychotic drugs also involved in endocrine disorders. The objective of this report is to raise the awareness of physicians treating psychiatric patients to the possibility of new-onset diabetes during therapy with atypical antipsychotic drugs and to emphasize the necessity for increased vigilance and close metabolic follow-up of these patients.

Effects of clozapine administration on body weight, glucose tolerance, blood glucose concentrations, plasma lipids, and insulin in male C57BL/6 mice: A parallel controlled study

BACKGROUND

Clozapine has been associated with metabolic adverse events (AEs) (eg, elevated body weight, blood glucose concentrations, cholesterol, triglycerides [TG]), all of which have deleterious effects on health and medication compliance. However, little focus has been directed toward finding a suitable experimental model to study the metabolic AEs associated with clozapine.

OBJECTIVE

The aim of this study was to assess the effects of clozapine administration for 28 days on body weight, glucose tolerance, blood glucose concentrations, plasma lipids, and insulin in C57BL/6 mice.

METHODS

C57BL/6 mice were grouped and treated with clozapine 2 or 10 mg/kg or vehicle intraperitoneally QD for 28 days. Body weight was assessed on days 0 (baseline), 7, 14, 21, and 28, and glucose tolerance, blood glucose concentrations, insulin (calculated by insulin resistance index [IRI]), and plasma lipids (including total cholesterol, TG, high-density lipoprotein cholesterol [HDL-C], and low-density lipoprotein cholesterol) were assessed on day 29.

RESULTS

Sixty 10-week-old, male C57BL/6 mice were included in the study and were divided into 3 groups (20 mice per group). The body weight significantly decreased in the clozapine 10-mg-treated group on days 14, 21, and 28 compared with the vehicle group (mean [SD] body weight: 21.61 [1.05] vs 22.79 [1.11], 22.53 [1.05] vs 24.17 [1.24], and 22.21 [1.07] vs 24.99 [1.39] g, respectively; all, P < 0.05). In the clozapine 10-mg/kg group, blood glucose concentrations significantly increased 0, 30, 60, and 120 minutes after glucose administration compared with the vehicle group (mean [SD]: 6.67 [1.25], 25.34 [5.85], 12.68 [3.39], and 7.52 [1.45] mmol/L, respectively, vs 4.61 [0.78], 21.54 [6.55], 11.46 [3.46], and 6.55 [1.42] mmol/L, respectively; all P < 0.05). The clozapine 10-mg/kg group also had significant increases in plasma insulin concentrations compared with the vehicle group (12.70 [5.27] vs 7.62 [4.54] μIU/mL; P < 0.05) and IRI (3.01 [1.26] vs 1.51 [0.96]; P < 0.05). Plasma HDL-C concentration also significantly decreased in the clozapine 10-mg/kg group compared with the vehicle group (1.23 [0.25] vs 1.47 [0.16]; P < 0.05).

CONCLUSION

Clozapine 10 mg/kg was associated with significant decreases in body weight and significant increases in fasting blood glucose and glucose tolerance in these male C57BL/6 mice.

Effects of haloperidol, clozapine and olanzapine on the survival of human neuronal and immune cells in vitro

Cytotoxic effects on neuronal as well as on immune cells have been reported for both typical and atypical antipsychotic drugs. We evaluated the effects of different concentrations of a typical (haloperidol) and two atypical (clozapine, olanzapine) antipsychotics on the survival of human neuronal (SH-SY5Y cells) and immune cells (U937 cells) by determining the metabolic activity after 24 h of incubation by the modified tetrazolium method. The dopaminergic neuroblastoma SH-SY5Y and the lymphoma U-937 cell line are well established models for in vitro investigations. To further elucidate possible mechanisms of action we also determined the ATP content in the cultured cells. After experimental treatment, significant effects were detected by Kruskal Wallis test for all treatment conditions. Post-hoc tests (Dunn's method) showed that haloperidol and clozapine at the two highest concentrations (25 and 50 microg/ml) caused a significant decrease of metabolic activity in both cell systems, which was also detectable after treatment with clozapine at a concentration of 12.5 microg/ml in U937 cells. In contrast, olanzapine induced a significant increase in metabolic activity of SH-SY5Y cells at all concentrations except for the concentration of 3.1 microg/ml, whereas the metabolic activity in U937 cells was increased at concentrations of 1.6 and 6.25 microg/ml. For the determination of ATP content, the LD(50) values of the metabolic activity were used, except for olanzapine for which no distinct LD(50) value was available. Significant changes were detected for all treatments and post-hoc tests revealed that haloperidol caused a significant decrease compared to the control condition in both cell systems. These findings suggest that antipsychotic substances of different classes exert differential metabolic effects in both neuronal and immune cell systems.

Acute administration of clozapine concurrently increases blood glucose and circulating plasma ghrelin levels in rats

OBJECTIVE

Among antipsychotics, clozapine ranks highest in terms of the risk for weight gain and developing diabetes. However, the mechanism by which clozapine induces weight gain and diabetes remains unclear. The aim of this study was to determine the mechanism of clozapine-induced weight gain and hyperglycemia, and to clarify whether clozapine-induced hyperglycemia results from impairment of the system regulating appetite.

METHODS

Circulatory glucose, insulin, leptin and ghrelin levels were analyzed after acute administration of clozapine in rats. Clozapine (10 mg/kg) or a vehicle was injected intraperitoneally and blood samples were collected at 0, 15, 30, and 60 min after the injection. Clozapine (5, 10 or 20 mg/kg) or the vehicle was given, and blood samples were collected at 30 min after the injection. Since clozapine has receptor affinity for multiple neurotransmitters, selective antagonists of it, including dopamine, serotonin, alpha-adrenergic, muscarine and histamine were administered to clarify the pathway of clozapine-induced blood glucose and changes in plasma ghrelin.

RESULTS

Clozapine administration increased the blood glucose level at all time points (p<0.05) compared to controls. Plasma ghrelin was elevated at 30 min (p=0.0124) and 60 min (p=0.00152). Blood glucose was increased in rats given 5 (p=0.0344), 10 (p<0.0001), or 20 mg/kg (p<0.0001) clozapine, while plasma ghrelin was increased in rats treated with 10 mg/kg (p=0.0009) or 20 mg/kg (p=0.0059) clozapine. Blood glucose was increased in rats treated with a selective alpha1-adrenergic receptor antagonist (p<0.0001), while plasma ghrelin was significantly increased in rats given a selective alpha1- (p=0.025) or alpha2-adrenergic receptor antagonist (p=0.0003).

CONCLUSIONS

Clozapine impairs glucose metabolism and the appetite-regulation system. Clozapine increases blood glucose independent of insulin. The antagonistic action of alpha-adrenergic receptors is one of the mechanisms that induces both hyperglycemia and elevation of ghrelin.

Central nervous system drug disposition: the relationship between in situ brain permeability and brain free fraction

The dispositions of 50 marketed central nervous system (CNS) drugs into the brain have been examined in terms of their rat in situ (P) and in vitro apparent membrane permeability (P(app)) alongside lipophilicity and free fraction in rat brain tissue. The inter-relationship between these parameters highlights that both permeability and brain tissue binding influence the uptake of drugs into the CNS. Hydrophilic compounds characterized by low brain tissue binding display a strong correlation (R(2) = 0.82) between P and P(app), whereas the uptake of more lipophilic compounds seems to be influenced by both P(app) and brain free fraction. A nonlinear relationship is observed between logP(oct) and P over the 6 orders of magnitude range in lipophilicity studied. These findings corroborate recent reports in the literature that brain penetration is a function of both rate and extent of drug uptake into the CNS.

Atypical antipsychotic drugs directly impair insulin action in adipocytes: effects on glucose transport, lipogenesis, and antilipolysis

Treatment with second-generation antipsychotics (SGAs) has been associated with weight gain and the development of diabetes mellitus, although the mechanisms are unknown. We tested the hypothesis that SGAs exert direct cellular effects on insulin action and substrate metabolism in adipocytes. We utilized two cultured cell models including 3T3-L1 adipocytes and primary cultured rat adipocytes, and tested for effects of SGAs risperidone (RISP), clozapine (CLZ), olanzapine (OLZ), and quetiapine (QUE), together with conventional antipsychotic drugs butyrophenone (BUTY), and trifluoperazine (TFP), over a wide concentration range from 1 to 500 microM. The effects of antipsychotic drugs on basal and insulin-stimulated rates of glucose transport were studied at 3 h, 15 h, and 3 days. Both CLZ and OLZ (but not RISP) at doses as low as 5 microM were able to significantly decrease the maximal insulin-stimulated glucose transport rate by approximately 40% in 3T3-L1 cells, whereas CLZ and RISP reduced insulin-stimulated glucose transport rates in primary cultured rat adipocytes by approximately 50-70%. Conventional drugs (BUTY and TFP) did not affect glucose transport rates. Regarding intracellular glucose metabolism, both SGAs (OLZ, QUE, RISP) and conventional drugs (BUTY and TFP) increased basal and/or insulin-stimulated glucose oxidation rates, whereas rates of lipogenesis were increased by CLZ, OLZ, QUE, and BUTY. Finally, rates of lipolysis in response to isoproterenol were reduced by the SGAs (CLZ, OLZ, QUE, RISP), but not by BUTY or TFP. These experiments demonstrate that antipsychotic drugs can differentially affect insulin action and metabolism through direct cellular effects in adipocytes. However, only SGAs were able to impair the insulin-responsive glucose transport system and to impair lipolysis in adipocytes. Thus, SGAs directly induce insulin resistance and alter lipogenesis and lipolysis in favor of progressive lipid accumulation and adipocyte enlargement. These effects of SGAs on adipocytes could explain, in part, the association of SGAs with weight gain and diabetes.

Insulin counter-regulatory factors, fibrinogen and C-reactive protein during olanzapine administration: effects of the antidiabetic metformin

In this study, the Authors assessed some insulin counter-regulatory factors, fibrinogen and C-reactive protein after olanzapine administration, and the effect of metformin on these variables, 37 patients with chronic schizophrenia were given olanzapine (10 mg/day for 14 weeks). Nineteen patients received metformin (850-2550 mg/day) and 18 received placebo in a randomized, double-blind protocol. The following variables were quantified before and after olanzapine: cortisol, leptin, tumor necrosis factor-alpha, glucagon, growth hormone, fibrinogen and C-reactive protein. Results were correlated with the changes in body weight and the insulin resistance index. We have reported elsewhere that metformin did not prevent olanzapine-induced weight gain, and the insulin resistance index significantly decreased after metformin and placebo; Baptista T, et al. Can J Psychiatry 2006; 51: 192-196. Cortisol, tumor necrosis factor-alpha and fibrinogen levels significantly decreased in both groups. Glucagon significantly increased after metformin (P=0.03). Leptin tended to increase after placebo (P=0.1) and displayed a small nonsignificant reduction after metformin. The C-reactive protein did not change significantly in any group. Contrarily to most published studies, olanzapine was associated with decreased insulin resistance. Decrements in cortisol, fibrinogen and tumor necrosis factor-alpha levels point to an improvement in the metabolic profile. The trend for leptin to increase after placebo, but not after metformin in spite of similar weight gain suggests a beneficial effect of this antidiabetic agent.

Acute effects of atypical antipsychotics on whole-body insulin resistance in rats: implications for adverse metabolic effects

Although it is generally accepted that atypical antipsychotics differ in their risk for diabetic side effects, the underlying pharmacological mechanisms are unknown. Studies on the mechanisms of antipsychotic-induced hyperglycemia or insulin resistance are often confounded by the concomitant weight gain and dyslipidemia, known diabetic risk factors. To investigate whether antipsychotics can acutely cause metabolic effects before any change in body composition, we studied the effects of four atypical antipsychotics on whole-body insulin resistance. Using the hyperinsulinemic, euglycemic clamp technique in conscious rats, insulin and somatostatin were infused at a constant rate to provide constant hyperinsulinemia and to suppress pancreatic insulin secretion. Glucose was infused at a variable rate, adjusted to maintain euglycemia. At steady state, animals were administered vehicle (V) or antipsychotic and the glucose infusion rate was monitored as an index of insulin sensitivity. Clamp experiments using radiotracers and studies on glucose uptake into isolated skeletal muscle were conducted to differentiate between effects on hepatic glucose production (HGP) and on peripheral glucose uptake. Olanzapine (OLAN) and clozapine (CLOZ) acutely impaired whole-body insulin sensitivity in a dose-dependent manner (P<0.001 vs V), whereas ziprasidone and risperidone had no effect. CLOZ also induced profound insulin resistance after dosing 10 mg/kg/day for 5 days (P<0.05 vs V). Tracer studies indicated that acute changes mainly reflect increased HGP, consistent with the lack of effect on glucose uptake. OLAN and CLOZ can thus rapidly induce marked insulin resistance, which could contribute to the hyperglycemia and ketoacidosis reported for patients receiving those therapies.

Clozapine-induced alteration of glucose homeostasis in the rat: the contribution of hypothalamic-pituitary-adrenal axis activation

BACKGROUND/AIMS

To our knowledge, a suitable animal model to investigate how atypical antipsychotics may induce diabetes in patients has not received much attention.

METHODS

We investigated the effects of acute as well as subchronic administration of clozapine on food intake, body weight gain, glucose tolerance and insulin secretion in response to glucose in Sprague-Dawley rats. We then evaluated the effects of clozapine on corticosterone secretion and 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) and phosphoenolpyruvate carboxykinase (PEPCK) expression in the liver. We investigated the in vitro effects of clozapine on glucose uptake and development of differentiated myotubes in skeletal muscle cell (C2C12) cultures.

RESULTS

Clozapine administration caused hyperglycemia (p < 0.05) in female rats. In male rats, the increase of plasma glucose levels after clozapine injection was not statistically significant. The increase of plasma insulin concentrations and the intraperitoneal glucose tolerance test results proved that clozapine reduced insulin sensitivity in female rats. These endocrine and metabolic effects of clozapine were not related to changes in feeding behavior of fat accumulation. We observed a stimulatory effect of clozapine on corticosterone (p < 0.01) secretion in both female and male rats. Chronic clozapine administration upregulated PEPCK and 11beta-HSD-1 expression in rat liver. Clozapine did not inhibit basal and insulin-induced glucose transport in murine myotubes but it was able to antagonize the stimulatory effect of alpha-methyl-5-hydroxytryptamine on glucose uptake.

CONCLUSION

Clozapine induces sex-related alterations of glucose homeostasis and insulin sensitivity in rodents. We discussed the possible contribution of clozapine-induced activation of HPA and clozapine antagonistic activity at peripheral 5-HT(2A) receptors to the observed metabolic alterations.

The atypical antipsychotic clozapine impairs insulin secretion by inhibiting glucose metabolism and distal steps in rat pancreatic islets

AIMS/HYPOTHESIS

Diabetogenic effects of some atypical antipsychotic drugs have been reported, although the mechanisms are not fully understood. We investigated the long-term effects of culturing isolated rat pancreatic islets with atypical antipsychotic clozapine.

METHODS

Glucose- and non-glucose-stimulated insulin secretion, glucose metabolism and intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured in islets cultured with or without clozapine.

RESULTS

Although acute incubation or 3-day culture with clozapine did not affect glucose-stimulated insulin secretion, clozapine suppressed glucose-stimulated insulin secretion by 53.2% at 1.0 micromol/l (therapeutic concentration) after 7 days of culture. Islet glucose oxidation and [Ca(2+)](i) elevation by high glucose were not affected after 3 days of culture, but clozapine significantly inhibited islet glucose oxidation, ATP production, and [Ca(2+)](i) elevation by high glucose after 7 days of culture. Moreover, 7 days of culture with clozapine inhibited insulin secretion stimulated by: (1) membrane depolarisation induced by high K(+); (2) protein kinase C activation; and (3) mastoparan at 16.7 mmol/l glucose under stringent Ca(2+)-free conditions. Elevation of [Ca(2+)](i) by high K(+)-induced membrane depolarisation was similar in control and clozapine-treated islets. Clozapine, a muscarinic blocker, acutely inhibited carbachol-induced insulin secretion, as did atropine, whereas after 7 days of culture atropine did not have the inhibitory effect shown by clozapine after 7 days. The impairment of glucose-stimulated insulin secretion recovered 3 days after the removal of clozapine treatment.

CONCLUSIONS/INTERPRETATION

The present study demonstrated that the atypical antipsychotic drug clozapine directly impaired insulin secretion via multiple sites including glucose metabolism and the distal step in insulin exocytosis in a long-term culture condition. These mechanisms may be involved in the form of diabetes mellitus associated with atypical antipsychotic drugs.