cDNA array reveals increased expression of glucose-dependent insulinotropic polypeptide following chronic clozapine treatment: role in atypical antipsychotic drug-induced adverse metabolic effects

Tirzepatide prevents neurodegeneration through multiple molecular pathways

BACKGROUND

Several evidence demonstrated that glucagon-like peptide 1 receptor agonists (GLP1-RAs) reduce the risk of dementia in type 2 diabetes patients by improving memory, learning, and overcoming cognitive impairment. In this study, we elucidated the molecular processes underlying the protective effect of Tirzepatide (TIR), a dual glucose-dependent insulinotropic polypeptide receptor agonist (GIP-RA)/ GLP-1RA, against learning and memory disorders.

METHODS

We investigated the effects of TIR on markers of neuronal growth (CREB and BDNF), apoptosis (BAX/Bcl2 ratio) differentiation (pAkt, MAP2, GAP43, and AGBL4), and insulin resistance (GLUT1, GLUT4, GLUT3 and SORBS1) in a neuroblastoma cell line (SHSY5Y) exposed to normal and high glucose concentration. The potential role on DNA methylation of genes involved in neuroprotection and epigenetic modulators of neuronal growth (miRNA 34a), apoptosis (miRNA 212), and differentiation (miRNA 29c) was also investigated. The cell proliferation was detected by measuring Ki-67 through flow cytometry. The data were analysed by SPSS IBM Version 23 or GraphPad Prism 7.0 software and expressed as the means ± SEM. Differences between the mean values were considered significant at a p-value of < 0.05. GraphPad Prism software was used for drawing figures.

RESULTS

For the first time, it was highlighted: (a) the role of TIR in the activation of the pAkt/CREB/BDNF pathway and the downstream signaling cascade; (b) TIR efficacy in neuroprotection; (c) TIR counteracting of hyperglycemia and insulin resistance-related effects at the neuronal level.

CONCLUSIONS

We demonstrated that TIR can ameliorate high glucose-induced neurodegeneration and overcome neuronal insulin resistance. Thus, this study provides new insight into the potential role of TIR in improving diabetes-related neuropathy.

Targeting glucose-dependent insulinotropic polypeptide receptor for neurodegenerative disorders

INTRODUCTION

Incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1) exert pleiotropic effects on endocrine pancreas and nervous system. Expression of GIP and GIP receptor (GIPR) in neurons, their roles in neurogenesis, synaptic plasticity, neurotransmission, and neuromodulation uniquely position GIPR for therapeutic applications in neurodegenerative disorders. GIP analogs acting as GIPR agonists attenuate neurobehavioral and neuropathological sequelae of neurodegenerative disorders in preclinical models, e.g. Alzheimer's disease (AD), Parkinson's disease (PD), and cerebrovascular disorders. Modulation of GIPR signaling offers an unprecedented approach for disease modification by arresting neuronal viability decline, enabling neuronal regeneration, and reducing neuroinflammation. Growth-promoting effects of GIP signaling and broad-based neuroprotection highlight the therapeutic potential of GIPR agonists. Areas covered: This review focuses on the role of GIPR-mediated signaling in the central nervous system in neurophysiological and neuropathological conditions. In context of neurodegeneration, the article summarizes potential of targeting GIPR signaling for neurodegenerative conditions such as AD, PD, traumatic brain injury, and cerebrovascular disorders. Expert opinion: GIPR represents a validated therapeutic target for neurodegenerative disorders. GIPR agonists impart symptomatic improvements, slowed neurodegeneration, and enhanced neuronal regenerative capacity in preclinical models. Modulation of GIPR signaling is potentially a viable therapeutic approach for disease modification in neurodegenerative disorders.

Anorectic response to the trichothecene T-2 toxin correspond to plasma elevations of the satiety hormone glucose-dependent insulinotropic polypeptide and peptide YY3-36

T-2 toxin, a potent type A trichothecene mycotoxin, is produced by various Fusarium species and can negatively impact animal and human health. Although anorexia induction is a common hallmark of T-2 toxin-induced toxicity, the underlying mechanisms for this adverse effect are not fully understood. The goal of this study was to determine the roles of two gut satiety hormones, glucose-dependent insulinotropic polypeptide (GIP) and Peptide YY_3-36 (PYY_3-36) in anorexia induction by T-2 toxin. Elevations of plasma GIP and PYY_3-36 markedly corresponded to anorexia induction following oral exposure to T-2 toxin using a nocturnal mouse anorexia model. Direct administration of exogenous GIP and PYY_3-36 similarly induced anorectic responses. Furthermore, the GIP receptor antagonist Pro3GIP dose-dependently attenuated both GIP- and T-2 toxin-induced anorectic responses. Pretreatment with NPY2 receptor antagonist JNJ-31020028 induced a dose-dependent attenuation of both PYY_3-36- and T-2 toxin-induced anorectic responses. To summarize, these findings suggest that both GIP and PYY_3-36 might be critical mediators of anorexia induction by T-2 toxin.

Improvements in body composition, anthropometric measurements and lipid profile following discontinuation of clozapine

BACKGROUND

Metabolic syndrome (obesity, glucose intolerance, insulin resistance and dyslipidaemia) is a well-known adverse effect of most antipsychotics. It is particularly common in patients treated with olanzapine and clozapine. Currently, the mechanisms underlying its development are not completely understood.

CASE REPORT

We present a case of improved body composition (reduced amount of total body fat and visceral adipose tissue), anthropometric measurements (body weight, waist, abdominal and hip circumferences) and lipid profile in a 31-year-old man with schizophrenia following discontinuation of clozapine. During a combined treatment with clozapine, flupentixol and ziprasidone, a routine laboratory test revealed a severe dyslipidaemia (triglycerides > 1800 mg/dL; > 20.3 mmol/L), despite previous lipid-lowering therapy. This abnormality completely recovered after clozapine has been discontinued.

CONCLUSIONS

Clozapine may cause severe, but reversible metabolic abnormalities, including obesity and hypertriglyceridaemia. Atypical antipsychotic-related lipid abnormalities may have a very rapid onset, occur in relatively young patients, with severe lipid derangements and have potential serious complications. This case confirms how important is to monitor metabolic parameters in patients taking antipsychotics. Discontinuation or switching to another antipsychotic medication may improve components of the metabolic syndrome.

Antipsychotic drug-associated gene-miRNA interaction in T-lymphocytes

Antipsychotic drugs (APDs) can have a profound effect on the human body that extends well beyond our understanding of their neuropsychopharmacology. Some of these effects manifest themselves in peripheral blood lymphocytes, and in some cases, particularly in clozapine treatment, result in serious complications. To better understand the molecular biology of APD action in lymphocytes, we investigated the influence of chlorpromazine, haloperidol and clozapine in vitro, by microarray-based gene and microRNA (miRNA) expression analysis. JM-Jurkat T-lymphocytes were cultured in the presence of the APDs or vehicle alone over 2 wk to model the early effects of APDs on expression. Interestingly both haloperidol and clozapine appear to regulate the expression of a large number of genes. Functional analysis of APD-associated differential expression revealed changes in genes related to oxidative stress, metabolic disease and surprisingly also implicated pathways and biological processes associated with neurological disease consistent with current understanding of the activity of APDs. We also identified miRNA-mRNA interaction associated with metabolic pathways and cell death/survival, all which could have relevance to known side effects of APDs. These results indicate that APDs have a significant effect on expression in peripheral tissue that relate to both known mechanisms as well as poorly characterized side effects.

A gene expression and systems pathway analysis of the effects of clozapine compared to haloperidol in the mouse brain implicates susceptibility genes for schizophrenia

Clozapine has markedly superior clinical properties compared to other antipsychotic drugs but the side effects of agranulocytosis, weight gain and diabetes limit its use. The reason why clozapine is more effective is not well understood. We studied messenger RNA (mRNA) gene expression in the mouse brain to identify pathways changed by clozapine compared to those changed by haloperidol so that we could identify which changes were specific to clozapine. Data interpretation was performed using an over-representation analysis (ORA) of gene ontology (GO), pathways and gene-by-gene differences. Clozapine significantly changed gene expression in pathways related to neuronal growth and differentiation to a greater extent than haloperidol; including the microtubule-associated protein kinase (MAPK) signalling and GO terms related to axonogenesis and neuroblast proliferation. Several genes implicated genetically or functionally in schizophrenia such as frizzled homolog 3 (FZD3), U2AF homology motif kinase 1 (UHMK1), pericentriolar material 1 (PCM1) and brain-derived neurotrophic factor (BDNF) were changed by clozapine but not by haloperidol. Furthermore, when compared to untreated controls clozapine specifically regulated transcripts related to the glutamate system, microtubule function, presynaptic proteins and pathways associated with synaptic transmission such as clathrin cage assembly. Compared to untreated controls haloperidol modulated expression of neurotoxic and apoptotic responses such as NF-kappa B and caspase pathways, whilst clozapine did not. Pathways involving lipid and carbohydrate metabolism and appetite regulation were also more affected by clozapine than by haloperidol.

Role of H3K4 demethylases in complex neurodevelopmental diseases

Significant neurological disorders can result from subtle perturbations of gene regulation that are often linked to epigenetic regulation. Proteins that regulate the methylation of lysine 4 of histone H3 (H3K4) and play a central role in epigenetic regulation, and mutations in genes encoding these enzymes have been identified in both autism and Rett syndrome. The H3K4 demethylases remove methyl groups from lysine 4 leading to loss of RNA polymerase binding and transcriptional repression. When these proteins are mutated, brain development is altered. Currently, little is known regarding how these gene regulators function at the genomic level. In this article, we will discuss findings that link H3K4 demethylases to neurodevelopment and neurological disease.

The role of leptin in antipsychotic-induced weight gain: genetic and non-genetic factors

Schizophrenia is a chronic and disabling mental illness affecting millions of people worldwide. A greater proportion of people with schizophrenia tends to be overweight. Antipsychotic medications have been considered the primary risk factor for obesity in schizophrenia, although the mechanisms by which they increase weight and produce metabolic disturbances are unclear. Several lines of research indicate that leptin could be a good candidate involved in pathways linking antipsychotic treatment and weight gain. Leptin is a circulating hormone released by adipocytes in response to increased fat deposition to regulate body weight, acting through receptors in the hypothalamus. In this work, we reviewed preclinical, clinical, and genetic data in order to infer the potential role played by leptin in antipsychotic-induced weight gain considering two main hypotheses: (1) leptin is an epiphenomenon of weight gain; (2) leptin is a consequence of antipsychotic-induced "leptin-resistance status," causing weight gain.

GIP-Dependent Expression of Hypothalamic Genes

GIP (glucose dependent insulinotrophic polypeptide), originally identified as an incretin peptide synthesized in the gut, has recently been identified, along with its receptors (GIPR), in the brain. Our objective was to investigate the role of GIP in hypothalamic gene expression of biomarkers linked to regulating energy balance and feeding behavior related neurocircuitry. Rats with lateral cerebroventricular cannulas were administered 10 μg GIP or 10 μl artificial cerebrospinal fluid (aCSF) daily for 4 days, after which whole hypothalami were collected. Real time Taqman™ RT-PCR was used to quantitatively compare the mRNA expression levels of a set of genes in the hypothalamus. Administration of GIP resulted in up-regulation of hypothalamic mRNA levels of AVP (46.9±4.5 %), CART (25.9±2.7 %), CREB1 (38.5±4.5 %), GABRD (67.1±11 %), JAK2 (22.1±3.6 %), MAPK1 (33.8±7.8 %), NPY (25.3±5.3 %), OXT (49.1±5.1 %), STAT3 (21.6±3.8 %), and TH (33.9±8.5 %). In a second experiment the same set of genes was evaluated in GIPR-/- and GIPR+/? mice to determine the effect of lack of GIP stimulation on gene expression. In GIPR-/- mice expressions of the following genes were down-regulated: AVP (27.1±7.5 %), CART (28.3±3.7 %), OXT (25.2±5.8 %), PTGES (23.9±4.5 %), and STAT3 (8.8±2.3 %). These results suggest that AVP, CART, OXT and STAT3 may be involved in energy balance-related hypothalamic circuits affected by GIP.

Association between the GIPR gene and the insulin level after glucose loading in schizophrenia patients treated with olanzapine

Several studies have shown increased rates of hyperglycemia and diabetes in schizophrenic patients treated with olanzapine. However, the underlying mechanism is poorly understood. Glucose-dependent insulinotropic polypeptide (GIP) is known to affect insulin secretion by pancreatic β cells. Recently, a meta-analysis study reported an association between a GIP receptor (GIPR) gene polymorphism (rs10423928) and insulin secretion measured by an oral glucose tolerance test (OGTT). We assessed the influence of this GIPR gene polymorphism on glucose metabolism in 60 schizophrenic patients treated with olanzapine and 103 healthy controls. The GIPR gene polymorphism was determined using TaqMan methods. We performed repeated-measures analysis of variance (ANOVA) and one-way ANOVA for the glucose and insulin levels during OGTTs in four groups divided by the GIPR gene polymorphism and cohort (schizophrenia or control). We found significant effects of the GIPR gene and cohort on the insulin levels at 30 min. Our findings suggest that schizophrenic patients with the A allele of GIPR rs10423928 are at risk of developing hyperinsulinemia when treated with antipsychotics.

A murine model of atypical antipsychotic-induced weight gain and metabolic dysregulation

In comparison with conventional, first-generation antipsychotics (e.g., haloperidol), the administration of atypical antipsychotics (AAPs) has been associated with a higher risk of metabolic derangements, including body weight increase, dysregulation of glucose homeostasis, fat accumulation, and even liability to develop type II diabetes. Since this is a serious clinical problem that may be further exacerbated in overweight schizophrenics, establishing animal models of AAP-induced adverse effects may contribute to clarifying the mechanisms underlying these effects. Here we present three basic protocols by which this problem has been modeled. The three protocols differ in many aspects (routes of administration, extent of the chronic treatment, diets, and dosage regimen), and the pros and cons of each procedure are systematically detailed throughout. It should be noted that several factors (e.g., species, sex, duration, and class of AAPs) could restrict the feasibility of these models, as well as their correspondence to the clinical condition.

Cocainomics: new insights into the molecular basis of cocaine addiction

Until recently, knowledge of the impact of abused drugs on gene and protein expression in the brain was limited to less than 100 targets. With the advent of high-throughput genomic and proteomic techniques, investigators are now able to evaluate changes across the entire genome and across thousands of proteins in defined brain regions and generate expression profiles of vulnerable neuroanatomical substrates in rodent and nonhuman primate drug abuse models and in human post-mortem brain tissue from drug abuse victims. The availability of gene and protein expression profiles will continue to expand our understanding of the short- and long-term consequences of drug addiction and other addictive disorders and may provide new approaches or new targets for pharmacotherapeutic intervention. This review summarizes several important genomic and proteomic studies of cocaine abuse/addiction from rodent, nonhuman primate, and human postmortem studies of cocaine abuse and explores how these studies have advanced our understanding of addiction.

30 days of continuous olanzapine infusion determines energy imbalance, glucose intolerance, insulin resistance, and dyslipidemia in mice

The aim of this study was to model in mice the association between metabolic syndrome and the administration of atypical antipsychotic (AAP). Two dosages (4 and 8 mg/kg per day) of olanzapine (OL) were infused in 36 female mice for 30 days by osmotic mini-pumps. This study was also designed to further extend the implications raised in other experiments by our model of AAP-induced metabolic dysregulation. Through the use of the osmotic mini-pumps, this model is aimed to circumvent the shorter (than in humans) half-life of AAPs in rodents and to chronically administer OL by a reliable and less disturbing method. Indirect calorimetry was used to evaluate metabolic rate (MR) and respiratory exchange ratio together with weight and caloric intake. Serum insulin, leptin, and glucose tolerance (oral glucose tolerance test) were assessed. Pancreatic beta cells insulin levels, periuterine and liver fat content were also analyzed. Olanzapine-infused mice exhibited a reduction of overall MR (kilojoule per hour) and resting MR and respiratory exchange ratio, with periuterine fat significantly enlarged. All metabolic alterations were detected at the highest dose, with major effects found on weight gain and hyperphagia. Impaired glucose metabolism, associated with hyperinsulinemia and hyperleptinemia were found. Insulin resistance was evidenced by the raise of HOMA-IR index. Increased insulin and lipid storage were detected at pancreatic and hepatic levels respectively. These findings illustrate the development of a cluster of risk factors (metabolic syndrome) and, for the first time, a decrease of energy expenditure (MR) due to chronic OL infusion.

The role of incretins in glucose homeostasis and diabetes treatment

Incretins are gut hormones that are secreted from enteroendocrine cells into the blood within minutes after eating. One of their many physiological roles is to regulate the amount of insulin that is secreted after eating. In this manner, as well as others to be described in this review, their final common raison d'être is to aid in disposal of the products of digestion. There are two incretins, known as glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1), that share many common actions in the pancreas but have distinct actions outside of the pancreas. Both incretins are rapidly deactivated by an enzyme called dipeptidyl peptidase 4 (DPP4). A lack of secretion of incretins or an increase in their clearance are not pathogenic factors in diabetes. However, in type 2 diabetes (T2DM), GIP no longer modulates glucose-dependent insulin secretion, even at supraphysiological (pharmacological) plasma levels, and therefore GIP incompetence is detrimental to beta-cell function, especially after eating. GLP-1, on the other hand, is still insulinotropic in T2DM, and this has led to the development of compounds that activate the GLP-1 receptor with a view to improving insulin secretion. Since 2005, two new classes of drugs based on incretin action have been approved for lowering blood glucose levels in T2DM: an incretin mimetic (exenatide, which is a potent long-acting agonist of the GLP-1 receptor) and an incretin enhancer (sitagliptin, which is a DPP4 inhibitor). Exenatide is injected subcutaneously twice daily and its use leads to lower blood glucose and higher insulin levels, especially in the fed state. There is glucose-dependency to its insulin secretory capacity, making it unlikely to cause low blood sugars (hypoglycemia). DPP4 inhibitors are orally active and they increase endogenous blood levels of active incretins, thus leading to prolonged incretin action. The elevated levels of GLP-1 are thought to be the mechanism underlying their blood glucose-lowering effects.

Coregulation of genes in the mouse brain following treatment with clozapine, haloperidol, or olanzapine implicates altered potassium channel subunit expression in the mechanism of antipsychotic drug action

BACKGROUND

Antipsychotic drugs are the most effective treatment for the psychotic symptoms of schizophrenia, yet their mechanism of action remains largely unknown.

OBJECTIVES

Earlier studies have shown gene expression changes in rodent brains after treatment with antipsychotic drugs. We aimed to further characterize these changes using whole-genome transcript profiling to explore coregulation of genes after multiple antipsychotic drug treatment studies.

METHODS

This study involved transcript profile analysis after 7-day treatment of inbred C57BL/6 mice with conventional (haloperidol) or atypical (clozapine or olanzapine) antipsychotic drugs. Microarray analysis was undertaken using whole-brain mRNA on Affymetrix 430v2 arrays, with quantitative reverse transcriptase-PCR used to confirm gene expression changes. Western blotting was also used to explore translation of gene dysregulation to protein changes and to explore anatomical specificity of such changes.

MAIN RESULTS

Thirteen genes showed verified regulation by multiple antipsychotic drugs - three genes significantly upregulated and 10 genes significantly downregulated by treatment. These genes encode proteins that function in various biological processes including neurogenesis, cell adhesion, and four genes are involved in voltage-gated ion channels: neural precursor cell developmentally downregulated gene 4 (Nedd4), Kv channel interacting protein 3 (KChip3), potassium voltage-gated channel, shaker-related subfamily, alpha1 (Kcna1) encoding Kv1.1 protein and beta1 (Kcnab1) encoding Kvbeta1 protein. The translation of these gene expression changes to protein dysregulation for Kv1.1, KCHIP3, and NEDD4 was confirmed by western blot, with regional protein analyses undertaken for Kv1.1 and KCHIP3.

CONCLUSION

These results suggest that transcriptional regulation of ion channels, crucial for neurotransmission, may play a role in mediating antipsychotic drug effects.

Impact of atypical antipsychotic therapy on leptin, ghrelin, and adiponectin

BACKGROUND

Many adverse effects of atypical antipsychotic treatment are associated with antagonism of monoamine receptors; however, data indicate that important metabolic effects, such as hypertriglyceridemia and impairment in glucose/insulin homeostasis, may not be related to these mechanisms, leading investigators to explore alternative hypotheses. Promising candidates include a possible impact of antipsychotics on peptide hormonal regulators of metabolic control such as leptin, ghrelin, and adiponectin. The purpose of this review is to summarize recent data on changes in these hormones during atypical antipsychotic treatment.

METHODS

A Medline search was performed for papers published from January 1999 to January 2007 using key words antipsychotic, atypical antipsychotic, and individual atypical antipsychotic drug names cross-referenced with leptin, ghrelin, and adiponectin.

RESULTS

The bulk of the published work focused on changes in body weight and serum leptin, with far less data on ghrelin, and adiponectin, and nonweight metabolic changes. Leptin changes were directly related to a medication's weight gain liability, with no added antipsychotic effects on leptin signaling. Conflicting results emerged for the other markers, but all three long-term studies on ghrelin showed increased levels in patients on atypical antipsychotics with weight gain liabilities.

CONCLUSIONS

Leptin increases during antipsychotic treatment are a result of weight gain rather than a direct impact of atypical antipsychotics on leptin physiology. Preliminary long-term data show increased ghrelin levels, but this finding must be replicated. The association with antipsychotic effects on glucose and lipid metabolism and these hormones remains virtually unstudied. Future research should indicate whether ghrelin and other peptide hormones may be useful predictors of weight gain or metabolic changes in patients on antipsychotics.

Chronic clozapine treatment in female rats does not induce weight gain or metabolic abnormalities but enhances adiposity: implications for animal models of antipsychotic-induced weight gain

The ability of clozapine to induce weight gain in female rats was investigated in three studies with progressively lowered doses of clozapine. In an initial preliminary high dose study, clozapine at 6 and 12 mg/kg (i.p., b.i.d.) was found to induce weight loss. In a subsequent intermediate dose study, we obtained no evidence for clozapine-induced weight gain despite using identical procedures and doses of clozapine (1-4 mg/kg, i.p., b.i.d.) with which we have observed olanzapine-induced weight gain, hyperphagia, enhanced adiposity and metabolic changes [Cooper G, Pickavance L, Wilding J, Halford J, Goudie A (2005). A parametric analysis of olanzapine-induced weight gain in female rats. Psychopharmacology; 181: 80-89.]. Instead, clozapine induced weight loss without alteration in food intake and muscle mass or changes in levels of glucose, insulin, leptin and prolactin. However, these intermediate doses of clozapine enhanced visceral adiposity and elevated levels of adiponectin. In a final study, low doses of clozapine (0.25-0.5 mg/kg, i.p, b.i.d.) induced weight loss. These data demonstrate that clozapine-induced weight gain can be much more difficult to observe in female rats than olanzapine-induced weight gain. Moreover, these findings contrast with clinical findings with clozapine, which induces substantial weight gain in humans. Clozapine-induced enhanced adiposity appears to be easier to observe in rats than weight gain. These findings, along with other preclinical studies, suggest that enhanced adiposity can be observed in the absence of antipsychotic-induced weight gain and hyperphagia, possibly reflecting a direct drug effect on adipocyte function independent of drug-induced hyperphagia [e.g. Minet-Ringuet J, Even P, Valet P, Carpene C, Visentin V, Prevot D, Daviaud D, Quignard-Boulange A, Tome D, de Beaurepaire R (2007). Alterations of lipid metabolism and gene expression in rat adipocytes during chronic olanzapine treatment. Molecular Psychiatry; 12: 562-571.]. These and other findings which show that the results of studies of antipsychotic treatment in animals do not always mimic clinical findings have important implications for the use of animal models of antipsychotic-induced weight gain. With regard to weight gain the results obtained appear to depend critically on the experimental procedures used and the specific drugs studied. Thus such models are not without limitations. However, they do consistently demonstrate the ability of various antipsychotics to enhance adiposity.

Pharmacogenetics and pharmacogenomics of schizophrenia: a review of last decade of research

The last decade of research into the pharmacogenetics of antipsychotics has seen the development of genetic tests to determine the patients' metabolic status and the first attempts at personalization of antipsychotic treatment. The most significant results are the association between drug metabolic polymorphisms, mainly in cytochrome P450 genes, with variations in drug metabolic rates and side effects. Patients with genetically determined CYP2D6 poor metabolizer (PMs) status may require lower doses of antipsychotic. Alternatively, CYP2D6 ultrarapid matabolizers (UMs) will need increased drug dosage to obtain therapeutic response. Additionally, polymorphisms in dopamine and serotonin receptor genes are repeatedly found associated with response phenotypes, probably reflecting the strong affinities that most antipsychotics display for these receptors. In particular, there is important evidence suggesting association between dopamine 2 receptor (D2) polymorphisms (Taq I and -141-C Ins/Del) and a dopamine 3 receptor (D3) polymorphism (Ser9Gly) with antipsychotic response and drug-induced tardive dyskinesia. Additionally, there is accumulating evidence indicating the influence of a 5-HT2C polymorphism (-759-T/C) in antipsychotic-induced weight gain. Application of this knowledge to clinical practice is slowly gathering pace, with pretreatment determination of individual's drug metabolic rates, via CYP genotyping, leading the field. Genetic determination of patients' metabolic status is expected to bring clinical benefits by helping to adjust therapeutic doses and reduce adverse reactions. Genetic tests for the pretreatment prediction of antipsychotic response, although still in its infancy, have obvious implications for the selection and improvement of antipsychotic treatment. These developments can be considered as successes, but the objectives of bringing pharmacogenetic and pharmacogenomic research in psychiatric clinical practice are far from being realized. Further development of genetic tests is required before the concept of tailored treatment can be applied to psychopharmatherapy. This review aims to summarize the key findings from the last decade of research in the field. Current knowledge on genetic prediction of drug metabolic status, general response and drug-induced side effects will be reviewed and future pharmacogenomic and epigenetic research will be discussed.

Molecular profiling of antipsychotic drug function: convergent mechanisms in the pathology and treatment of psychiatric disorders

Despite great progress in antipsychotic drug research, the molecular mechanisms by which these drugs work have remained elusive. High-throughput gene profiling methods have advanced this field by allowing the simultaneous investigation of hundreds to thousands of genes. However, different methodologies, choice of brain region, and drugs studied have made comparisons across different studies difficult. Because of the complexity of gene expression changes caused by drugs, teasing out the most relevant expression differences is a challenging task. One approach is to focus on gene expression changes that converge on the same systems that were previously deemed important to the pathology of psychiatric disorders. From the microarray studies performed on human postmortem brain samples from schizophrenics, the systems most implicated to be dysfunctional are synaptic machinery, oligodendrocyte/myelin function, and mitochondrial/ubiquitin metabolism. Drugs may act directly or indirectly to compensate for underlying pathological deficits in schizophrenia or via other mechanisms that converge on these pathways. Side effects, consisting of motor and metabolic dysfunction (which occur with typical and atypical drugs, respectively), also may be mediated by gene expression changes that have been reported in these studies. This article surveys both the convergent antipsychotic mechanisms and the genes that may be responsible for other effects elicited by antipsychotic drugs.

Immunohistochemical distribution of glucose-dependent insulinotropic polypeptide in the adult rat brain

We have previously demonstrated that glucose-dependent insulinotropic polypeptide (GIP; gastric inhibitory polypeptide) is present in the adult rat hippocampus. This finding leads to the conclusion that all members of the secretin-glucagon family of gastrointestinal regulatory polypeptides can be found in the brain. To investigate the localization of GIP-producing cells, we used immunohistochemistry on sections of the adult rat brain. High levels of GIP immunoreactivity were observed in the olfactory bulb, hippocampus, and Purkinje cells in the cerebellum. Moreover, a moderate but distinct GIP immunoreactivity was observed in the cerebral cortex, amygdala, substantia nigra, and lateral septal nucleus as well as in several nuclei in the thalamus, hypothalamus, and brainstem. GIP immunoreactivity was frequently found to colocalize with the neuronal marker NeuN but never with the glial marker glial fibrillary acidic protein. Thus, GIP appears to be mainly neuronal to its distribution. This widespread distribution of GIP-immunoreactive cells suggests the involvement of GIP in various neuronal functions and suggests that GIP may act as a neurotransmitter or neuromodulator. This is the first characterization of the anatomical distribution of GIP-immunoreactive cells in the rat brain providing an anatomical framework for future investigations regarding the functions of GIP in the central nervous system.

Assessment of genome and proteome profiles in cocaine abuse

Until recently, knowledge of the impact of abuse drugs on gene and protein expression in the brain was limited to less than 100 targets. With the advent of high-throughput genomic and proteomic techniques investigators are now able to evaluate changes across the entire genome and across thousands of proteins in defined brain regions and generate expression profiles of vulnerable neuroanatomical substrates in rodent and non-human primate drug abuse models and in human post-mortem brain tissue from drug abuse victims. The availability of gene and protein expression profiles will continue to expand our understanding of the short- and long-term consequences of drug addiction and other addictive disorders and may provide new approaches or new targets for pharmacotherapeutic intervention. This chapter will review gene expression data from rodent, non-human primate and human post-mortem studies of cocaine abuse and will provide a preliminary proteomic profile of human cocaine abuse and explore how these studies have advanced our understanding of addiction.