Olanzapine affects locomotor activity and meal size in male rats

The effect of olanzapine on spatial memory impairment, depressive-like behavior, pain perception, and BDNF and synaptophysin expression following childhood chronic unpredictable mild stress in adult male and female rats

Chronic unpredictable mild stress (CUMS) method has been introduced as a rodent model of depression. On the other hand, olanzapine, as an antipsychotic, can induce antidepressant and antipsychotic effects. Also, olanzapine may improve cognitive functions. Both CUMS and olanzapine can also affect the expression level of brain-derived neurotrophic factor (BDNF) and synaptophysin, the molecular factors involved in synaptic function, and learning and memory. In this study, we investigated the effect of olanzapine on locomotor activity (using open field test), pain threshold (using hot plate), depressive-like behavior (using forced swim test), spatial learning and memory (using Morris water maze), and BDNF and synaptophysin hippocampal expression (using real-time PCR) in both male and female CUMS rats. CUMS was performed for three consecutive weeks. Olanzapine was also injected intraperitoneally at the dose of 5 mg/kg. Our data showed that olanzapine can reverse the effects of CUMS on behavioral functions and BDNF and synaptophysin expression levels in the hippocampus of both males and females. It was also shown that olanzapine effects on spatial memory, pain perception, and BDNF and synaptophysin level were stronger in females than males. In conclusion, we suggested that the therapeutic effects of olanzapine in CUMS rats may be closely related to the function of BDNF and synaptophysin. Also, the therapeutic effects of olanzapine may be stronger in females. Therefore, and for the first time, we showed that there may be a sex difference in the effects of olanzapine on behavioral and molecular changes following CUMS.

Allyl isothiocyanate, a TRPA1 agonist, protects against olanzapine-induced hypothalamic and hepatic metabolic aberrations in female mice

Olanzapine, a widely prescribed atypical antipsychotic, poses a great risk to the patient's health by fabricating a plethora of severe metabolic and cardiovascular adverse effects eventually reducing life expectancy and patient compliance. Its heterogenous receptor binding profile has made it difficult to point out a specific cause or treatment for the related side effects. Growing body of evidence suggest that transient receptor potential (TRP) channel subfamily Ankyrin 1 (TRPA1) has pivotal role in pathogenesis of type 2 diabetes and obesity. With this background, we aimed to investigate the role of pharmacological manipulations of TRPA1 channels in antipsychotic (olanzapine)-induced metabolic alterations in female mice using allyl isothiocyanate (AITC) and HC-030031 (TRPA1 agonist and antagonist, respectively). It was found that after 6 weeks of treatment, AITC prevented olanzapine-induced alterations in body weight and adiposity; serum, and liver inflammatory markers; glucose and lipid metabolism; and hypothalamic appetite regulation, nutrient sensing, inflammatory and TRPA1 channel signaling regulating genes. Furthermore, several of these effects were absent in the presence of HC-030031 (TRPA1 antagonist) indicating protective role of TRPA1 agonism in attenuating olanzapine-induced metabolic alterations. Supplementary in-depth studies are required to study TRPA1 channel effect on other aspects of olanzapine-induced metabolic alterations.

Intranasal administration of olanzapine has beneficial outcome in a rat activity-based anorexia model

The atypical antipsychotic drug olanzapine is prescribed despite clinical studies on olanzapine treatment showing mixed results on treatment efficacy in anorexia nervosa. We investigated the effect of systemic and intranasal administration of olanzapine in the activity-based anorexia (ABA) model. Rats were habituated to a running wheel and exposed to the ABA model while treated with olanzapine. During ABA rats had 1.5 h of daily access to food and ad libitum access to a running wheel for seven consecutive days. Olanzapine was administered via an osmotic minipump (1, 2.75, and 7.5 mg/kg) or intranasally 2 h before dark onset (1 and 2.75 mg/kg). We monitored body weight, food intake, wheel revolutions, body temperature, and adipose tissue. We found 2.75 and 7.5 mg/kg systemic olanzapine decreased wheel revolutions during ABA. Relative adipose tissue mass was increased in the 7.5 mg/kg olanzapine-treated group while body weight, food intake, and body temperature were unaltered by the systemic olanzapine. 1 and 2.75 mg/kg intranasal olanzapine diminished wheel revolutions and body temperature during the first 2 h after administration. The intranasal olanzapine-treated rats had a higher body weight at the end of ABA. We find that olanzapine has beneficial outcomes in the ABA via two administration routes by acting mainly on running wheel activity. Intranasal olanzapine showed a rapid effect in the first hours after administration in reducing locomotor activity. We recommend further exploring intranasal administration of olanzapine in anorectic patients to assist them in coping with restlessness.

Hyperbaric oxygen exposure alleviate metabolic side-effects of olanzapine treatment and is associated with Langerhans islet proliferation in rats

Introduction: Olanzapine (OLZ) is one of the second-generation antipsychotics drugs (APDs) used to treat several psychiatric illnesses. Olanzapine treatment is often associated with many metabolic side effects in a dose dependent manner such as obesity, dyslipidemia and insulin resistance, induction of type II diabetes and acute pancreatitis in some patients. Methods: Hyperbaric Oxygen therapy (HBOT) was investigated as a tool to mitigate olanzapine metabolic side effects in rats. Thirty-six female Sprague Dawley (SD) rats were divided into 4 groups; rats on olanzapine treatment either exposed to hyperbaric oxygen therapy (HBOOLZ) or left without exposure (OLZ) then non-treated rats that either exposed to hyperbaric oxygen therapy or left without exposure (control). Rats received Hyperbaric Oxygen therapy for 35 days at 2.4 atmospheres absolute (ATA) for 2.5 h daily followed by intraperitoneal injection of olanzapine at 10 mg/kg or placebo. Results: Rats on either hyperbaric oxygen therapy or olanzapine had a significant loss in body weight. Olanzapine treatment showed a decrease in serum insulin level, triglyceride, highdensity lipoprotein (HDL) cholesterol, and lipase level but an increase in fasting blood sugar (FBS), insulin resistance index (HOMA-IR) and amylase, while rats' exposure to hyperbaric oxygen therapy reversed these effects. The Pancreatic Langerhans islets were up-regulated in both hyperbaric oxygen therapy and olanzapine treatments but the combination (HBOOLZ) doubled these islets number. Discussion: This study advocated that hyperbaric oxygen therapy can be an alternative approach to control or reverse many metabolic disorders (MDs) associatedwith olanzapine treatment. In addition, it seems that hyperbaric oxygen therapy positively affect the pancreatic Langerhans cells activity and architecture.

Chronic Oral Olanzapine Treatment but not Haloperidol Decreases [3H] MK-801 Binding in the Rat Brain Independent of Dietary Conditions

Haloperidol and olanzapine are first and second-generation antipsychotic (neuroleptic) medications approved to treat schizophrenia. Glutamate signaling is known to play an important role in the manifestation of schizophrenia symptoms, as phencyclidine, a non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist, replicates and exasperates these symptoms. While initial reports show that neuroleptic treatments can impact aspects of NMDAR expression, there is little attention on the interaction between neuroleptics and dietary conditions. Thus, we examined the impact of chronic haloperidol and olanzapine treatment under both normal and high-fat dietary conditions on NMDAR expression. Adult male rats were treated for 28-days with either oral vehicle, haloperidol (1.5mg/kg), or olanzapine (10mg/kg), and fed either a standard control diet or a high-fat diet. In-vitro receptor autoradiography binding was performed using [³H] MK-801 as a measure of NMDAR expression. Results showed that olanzapine, irrespective of the diet, significantly decreased [³H] MK-801 binding within the cingulate cortex, substantia nigra, insular cortex, piriform cortex, ectorhinal cortex and perirhinal cortex, the forelimb region of the somatosensory cortex, and all quadrants of the caudate-putamen. In contrast, haloperidol treatment did not impact [³H] MK-801 binding, and we also report no effect of diet on [³H] MK-801 binding. These data suggest that the effects seen in olanzapine treatment are not mediated by diet, nor does a 28-day chronic high-fat diet alter [³H] MK-801 binding. Furthermore, these data also importantly support that combined consumption of a high-fat diet and pharmacological treatments are not immediately detrimental to NMDARs and contribute to the expansive literature of precision medicine.

Chronic neuroleptic treatment combined with a high fat diet elevated [3H] flunitrazepam binding in the cerebellum

Clinical and preclinical studies have shown dysfunctions in genetic expression and neurotransmission of γ-Aminobutyric acid (GABA), GABA_A receptor subunits, and GABA-synthesizing enzymes GAD₆₇ and GAD₆₅ in schizophrenia. It is well documented that there is significant weight gain after chronic neuroleptic treatment in humans. While there are limited studies on the effects of diet on GABA signaling directly, a change in diet has been used clinically as an adjunct to treatment for schizophrenic relief. In this study, rats chronically consumed either a chow diet (CD) or a 60% high-fat diet (HFD) and drank from bottles that contained one of the following solutions: water, haloperidol (1.5 mg/kg), or olanzapine (10 mg/kg) for four weeks. Rats were then euthanized and their brains were processed for GABA_A in-vitro receptor autoradiography using [³H] flunitrazepam. A chronic HFD treatment yielded significantly increased [³H] flunitrazepam binding in the rat cerebellum independent of neuroleptic treatment. The desynchronization between the prefrontal cortex and the cerebellum is associated with major cognitive and motor dysfunctions commonly found in schizophrenic symptomatology, such as slowed reaction time, motor dyscoordination, and prefrontal activations related to speech fluency and cognitive alertness. These data support the notion that there is a dietary effect on GABA signaling within the cerebellum, as well as the importance of considering nutritional intervention methods as an adjunct treatment for patients chronically treated with neuroleptics. Finally, we indicate that future studies involving the analysis of individual patient's genetic profiles will further assist towards a precision medicine approach to the treatment of schizophrenia.

Blockade of the orexin 1 receptors in the nucleus accumbens' shell reversed the reduction effect of olanzapine on motivation for positive reinforcers

Effort-based choice of high reward requires one to decide how much effort to expend for a certain amount of reward. Orexin is a crucial neuropeptide in the physiological aspect especially a variety of affective and cognitive processes. The nucleus accumbens (NAc) is a region of the neural system that serves effort-related high reward choices andthe Orexin 1 receptor (OX1R) is distributed extensively throughout the nucleus accumbens shell (AcbS). Olanzapine (OLZ), a typical antipsychotic drug, has a high affinity to D2 as an antagonist, and also partial agonistic-like action at D2 receptors has been reported. We examined the interaction of OLZ with the orexinergic receptor 1 in AcbS on effort- related high reward choice when two goal arms were different in the amount of accessible reward. The animals had to pass the barrier for receiving a high reward in one arm (HRA) or obtain a low reward in the other arm without any cost. Before surgery, all animals were selecting the HRA on almost every trial.During test days, the rats received local injections of either DMSO 20% /0.5 µl, as vehicle or SB334867 (30, 100, 300 nM/0.5 µl), as selective OX1R antagonist, within the AcbS. Other group received OLZ (32 µM/0.5 µl DMSO20%) / vehicle alone or 5 min after administration of SB334867 (300 nM/0.5 µl). The results showed that administration of OLZ in the AcbS alters rat's preference for high reward. On the other hand, blocked of the OX1R (300 nM/0.5 µl) in this region could reverse the effect of OLZ, however, administration of the OX1R antagonists alone in the AcbS led to decreasing rat's preference for high reward. This result indicates that the orexin-1 antagonist might affect some effects of antipsychotic drugs.

Zona incerta neurons projecting to the ventral tegmental area promote action initiation towards feeding

KEY POINTS

The zona incerta (ZI) and ventral tegmental area (VTA) are brain areas that are both implicated in feeding behaviour. The ZI projects to the VTA, although it has not yet been investigated whether this projection regulates feeding. We experimentally (in)activated the ZI to VTA projection by using dual viral vector technology, and studied the effects on feeding microstructure, the willingness to work for food, general activity and body temperature. Activity of the ZI to VTA projection promotes feeding by facilitating action initiation towards food, as reflected in meal frequency and the willingness to work for food reward, without affecting general activity or directly modulating body temperature. We show for the first time that activity of the ZI to VTA projection promotes feeding, which improves the understanding of the neurobiology of feeding behaviour and body weight regulation.

ABSTRACT

Both the zona incerta (ZI) and the ventral tegmental area (VTA) have been implicated in feeding behaviour. The ZI provides prominent input to the VTA, although it has not yet been investigated whether this projection regulates feeding. Therefore, we investigated the role of ZI to VTA projection neurons in the regulation of several aspects of feeding behaviour. We determined the effects of (in)activation of ZI to VTA projection neurons on feeding microstructure, food-motivated behaviour under a progressive ratio schedule of reinforcement, locomotor activity and core body temperature. To activate or inactivate ZI neurons projecting to the VTA, we used a combination of canine adenovirus-2 in the VTA, as well as Cre-dependent designer receptors exclusively activated by designer drugs (DREADD) or tetanus toxin (TetTox) light chain in the ZI. TetTox-mediated inactivation of ZI to VTA projection neurons reduced food-motivated behaviour and feeding by reducing meal frequency. Conversely, DREADD-mediated chemogenetic activation of ZI to VTA projection neurons promoted food-motivated behaviour and feeding. (In)activation of ZI to VTA projection neurons did not affect locomotor activity or directly regulate core body temperature. Taken together, ZI neurons projecting to the VTA exert bidirectional control overfeeding behaviour. More specifically, activity of ZI to VTA projection neurons facilitate action initiation towards feeding, as reflected in both food-motivated behaviour and meal initiation, without affecting general activity.

GABAergic function in the lateral hypothalamus regulates feeding behavior: Possible mediation via orexin

Aim

The lateral hypothalamus (LH) is known as the hunger center, but the mechanisms through which the LH regulates food intake are unclear. Since GABA neurons are reported to project to the LH, the present study investigated the role of GABAergic function in the LH in the regulation of feeding behavior.

Methods

GABA levels in the LH were measured by in vivo microdialysis. Food intake after drug injection into the LH was measured every 1 hour for 4 hours. The mRNA levels were measured using RT‐PCR.

Results

Food intake significantly increased GABA levels in the LH, suggesting that food intake stimulates GABAergic function in the LH. Injection of the GABA_A receptor agonist muscimol into the LH significantly inhibited food intake, whereas injection of the GABA_A receptor antagonist bicuculline into the LH did not significantly affect food intake. The inhibitory effect of muscimol injected into the LH was blocked by co‐administration of bicuculline. These results indicate that the stimulation of GABA_A receptors in the LH inhibits food intake. We next examined whether the stimulation of GABA_A receptors affects hypothalamic neuropeptides that are known to regulate feeding behavior. The injection of muscimol significantly decreased preproorexin mRNA in the hypothalamus.

Conclusion

These results indicate that food intake activates GABAergic function in the LH, which terminates feeding behavior by stimulating GABA_A receptors. Moreover, it is suggested that the stimulation of GABA_A receptors in the LH reduces food intake through inhibition of orexin neurons.

We investigated whether GABAergic function in the lateral hypothalamus (LH) regulates feeding behavior. We showed that food intake increased GABA levels in the LH in in vivo microdialysis and that the GABA_A receptor agonist muscimol injected into the LH decreased food intake. These results suggest that food intake activates GABA neurons projecting to the LH, and it terminates feeding behavior through GABA_A receptors.

Roman high and low avoidance rats differ in their response to chronic olanzapine treatment at the level of body weight regulation, glucose homeostasis, and cortico-mesolimbic gene expression

Olanzapine, an antipsychotic agent mainly used for treating schizophrenia, is frequently associated with body weight gain and diabetes mellitus. Nonetheless, studies have shown that not every individual is equally susceptible to olanzapine's weight-gaining effect. Therefore, Roman high and low avoidance rat strains were examined on their responsiveness to olanzapine treatment. The Roman high avoidance rat shares many behavioral and physiological characteristics with human schizophrenia, such as increased central dopaminergic sensitivity, whereas the Roman low avoidance rat has been shown to be prone to diet-induced obesity and insulin resistance. The data revealed that only the Roman high avoidance rats are susceptible to olanzapine-induced weight gain and attenuated glucose tolerance. Here it is suggested that the specific olanzapine-induced weight gain in Roman high avoidance rats could be related to augmented dopaminergic sensitivity at baseline through increased expression of prefrontal cortex dopamine receptor D1 mRNA and nucleus accumbens dopamine receptor D2 mRNA expression. Regression analyses revealed that olanzapine-induced weight gain in the Roman high avoidance rat is above all related to increased prolactin levels, whereas changes in glucose homeostasis is best explained by differences in central dopaminergic receptor expressions between strains and treatment. Our data indicates that individual differences in dopaminergic receptor expression in the cortico-mesolimbic system are related to susceptibility to olanzapine-induced weight gain.

Oral haloperidol or olanzapine intake produces distinct and region-specific increase in cannabinoid receptor levels that is prevented by high fat diet

Clinical studies show higher levels of cannabinoid CB1 receptors (CB1R) in the brain of schizophrenic patients while preclinical studies report a significant functional interaction between dopamine D2 receptors and CB1Rs as well as an upregulation of CB1Rs after antipsychotic treatment. These findings prompted us to study the effects of chronic oral intake of a first and a second generation antipsychotic, haloperidol and olanzapine, on the levels and distribution of CB1Rs in the rat brain. Rats consumed either regular chow or high-fat food and drank water, haloperidol drinking solution (1.5mg/kg), or olanzapine drinking solution (10mg/kg) for four weeks. Motor and cognitive functions were tested at the end of treatment week 3 and upon drug discontinuation. Two days after drug discontinuation, rats were euthanized and brains were processed for in vitro receptor autoradiography. In chow-fed animals, haloperidol and olanzapine increased CB1R levels in the basal ganglia and the hippocampus, in a similar, but not identical pattern. In addition, olanzapine had unique effects in CB1R upregulation in higher order cognitive areas, in the secondary somatosensory cortex, in the visual and auditory cortices and the geniculate nuclei, as well as in the hypothalamus. High fat food consumption prevented antipsychotic-induced increase in CB1R levels in all regions examined, with one exception, the globus pallidus, in which they were higher in haloperidol-treated rats. The results point towards the hypothesis that increased CB1R levels could be a confounding effect of antipsychotic medication in schizophrenia that is circumveneted by high fat feeding.

Prevention of the adverse effects of olanzapine on lipid metabolism with the antiepileptic zonisamide

BACKGROUND

Atypical antipsychotic drugs, particularly olanzapine, represent a mainstay in the treatment of psychoses; however, their use is commonly associated with weight gain and diabetes. The aim of this study was to determine whether combined administration of olanzapine and zonisamide can be used to prevent olanzapine-induced metabolic disturbances.

METHODS AND RESULTS

These experiments involved female Sprague Dawley rats (n = 6-8/group) that were administered olanzapine, either acutely (6 mg/kg, s. c) or via continuous osmotic minipump infusion (6 mg/kg/day for 6 or 14 days), in combination with zonisamide (26 mg/kg/day,i.p.). Continuous infusion of olanzapine induced accumulation of adipose tissue and an associated reduction in stimulated lipolysis and reduced protein expression of CGI-58, a critical co-activator of ATGL. Olanzapine treatment caused a preferential shift toward carbohydrate oxidation (or reduced fat oxidation), elevated blood triglycerides and a reduction in locomotor activity. Olanzapine had a direct effect on glucose regulation, causing rapid hyperglycemia, and a reduction in glucose tolerance and insulin sensitivity. Continuous administration of olanzapine caused significant hyperinsulinemia and a significant reduction in insulin sensitivity. Zonisamide did not affect the impact of olanzapine on glucose homeostasis. On the other hand, co-administration of olanzapine with zonisamide completely ameliorated olanzapine-mediated shifts in lipid metabolism resulting in a normalization of olanzapine-induced weight gain.

CONCLUSION

These data collectively show an impact of olanzapine on body weight and lipid metabolism, which is ameliorated by co-administration with zonisamide. These findings suggest that a combined olanzapine and zonisamide approach might reduce weight gain, but will not provide protection against olanzapine-induced glucose intolerance.

Does activation of midbrain dopamine neurons promote or reduce feeding?

BACKGROUND

Dopamine (DA) signalling in the brain is necessary for feeding behaviour, and alterations in the DA system have been linked to obesity. However, the precise role of DA in the control of food intake remains debated. On the one hand, food reward and motivation are associated with enhanced DA activity. On the other hand, psychostimulant drugs that increase DA signalling suppress food intake. This poses the questions of how endogenous DA neuronal activity regulates feeding, and whether enhancing DA neuronal activity would either promote or reduce food intake.

METHODS

Here, we used designer receptors exclusively activated by designer drugs (DREADD) technology to determine the effects of enhancing DA neuronal activity on feeding behaviour. We chemogenetically activated selective midbrain DA neuronal subpopulations and assessed the effects on feeding microstructure in rats.

RESULTS

Treatment with the psychostimulant drug amphetamine or the selective DA reuptake inhibitor GBR 12909 significantly suppressed food intake. Selective chemogenetic activation of DA neurons in the ventral tegmental area (VTA) was found to reduce meal size, but had less impact on total food intake. Targeting distinct VTA neuronal pathways revealed that specific activation of the mesolimbic pathway towards nucleus accumbens (NAc) resulted in smaller and shorter meals. In addition, the meal frequency was increased, rendering total food intake unaffected. The disrupted feeding patterns following activation of VTA DA neurons or VTA to NAc projection neurons were accompanied by locomotor hyperactivity. Activation of VTA neurons projecting towards prefrontal cortex or amygdala, or of DA neurons in the substantia nigra, did not affect feeding behaviour.

CONCLUSIONS

Chemogenetic activation of VTA DA neurons or VTA to NAc pathway disrupts feeding patterns. Increased activity of mesolimbic DA neurons appears to both promote and reduce food intake, by facilitating both the initiation and cessation of feeding behaviour.

Ameliorative Effect of Curcumin on Olanzapine-induced Obesity in Sprague-Dawley Rats

OBJECTIVE

To evaluate the effect of curcumin on olanzapine-induced obesity in rats.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were used for experiments. The animals were divided into six groups, namely, normal control, olanzapine control, betahistine (10 mg/kg), and curcumin 50, 100, and 200 mg/kg treated groups. Except the normal control group, all other animals were administered with olanzapine 4 mg/kg intraperitoneally to induce obesity. The drugs were administered once daily, per oral for 28 days. During the experiment, body weight changes and behavior alterations were monitored at regular intervals. At the end of the experiment, blood sample was collected from all the experimental animals for biochemical analysis. Part of the liver and kidney tissues was harvested from the sacrificed animals and preserved in neutral formalin for histopathological studies.

RESULTS

Curcumin showed a significant reduction in olanzapine-induced body weight gain on the rats and improved the locomotor effects. The effect of curcumin on olanzapine-induced body weight gain is not comparable with that of betahistine.

CONCLUSION

This study has shown metabolic alteration effect of curcumin on olanzapine, an antipsychotic drug, treated SD rats.

SUMMARY

Olanzapine is an atypical antipsychotic drug used for the treatment of schizophrenia and bipolar disorder. Obesity is an adverse effect of olanzapine, and the present study was made an attempt to study the effect of curcumin on olanzapine-induced obesity in rats. In this present study, curcumin significantly reduced olanzapine-induced body weight gain in rats. Abbreviations Used: 5HT: 5-hydroxytryptamine, ALP: Alkaline phosphatase, ALT: Alanine transaminase, ANOVA: Analysis of variance, AST: Aspartate transaminase, CMC: Carboxymethyl cellulose, D: Dopamine, H and E: Hematoxylin and Eosin stain, H: Histamine, HDL-C: Highdensity lipoprotein cholesterol, IP: Intraperitoneal, MAO: Monoamine oxidase, NaOH: Sodium hydroxide, SD rats: Sprague Dawley rats, TCs: Total cholesterols, TG: Triglyceride.

Olanzapine-depot administration induces time-dependent changes in adipose tissue endocrine function in rats

OBJECTIVE

Metabolic adverse effects of atypical antipsychotics (AAP) contribute significantly to increased risk of cardiovascular morbidity and mortality in patients suffering from schizophrenia. Extensive preclinical research has addressed this issue over the past years, though mechanisms underlying these adverse effects of AAP are still not understood completely. Recently, attention is drawn towards the role of adipose tissue metabolism and neurohormonal regulations.

METHODS

The aim of this study was to evaluate the time-dependent effects of olanzapine depot administration at clinically relevant dosing on the regulation of energy homeostasis, glucose and lipid metabolism, gastrointestinal and adipose tissue-derived hormones involved in energy balance regulations in female Sprague-Dawley rats. The study lasted 8 weeks and the markers were assayed at day 8, 15, 29, 43 and 57.

RESULTS

The results indicate that in the absence of hyperphagia, olanzapine chronic exposure induced weight gain from the beginning of the study. In the later time-point, increased adiposity was also observed. In the initial phase of the study, lipid profile was altered by an early increase in triglyceride level and highly elevated leptin level was observed. Clear bi-phasic time-dependent effect of olanzapine on leptin serum concentration was demonstrated. Olanzapine treatment did not lead to changes in serum levels of ghrelin, FGF-21 and pro-inflammatory markers IL-1a, IL-6 and TNF-α at any time-point of the study.

CONCLUSION

This study provides data suggesting early alteration in adipose tissue endocrine function as a factor involved in mechanisms underlying metabolic adverse effects of antipsychotics.

Atypical antipsychotics and effects on feeding: from mice to men

RATIONALE

So-called atypical antipsychotics (AAPs) are associated with varying levels of weight gain and associated metabolic disturbances, which in patients with serious mental illness (SMI) have been linked to non-compliance and poor functional outcomes. Mechanisms underlying AAP-induced metabolic abnormalities are only partially understood. Antipsychotic-induced weight gain may occur as a result of increases in food intake and/or changes in feeding.

OBJECTIVE

In this review, we examine the available human and preclinical literature addressing AAP-related changes in feeding behavior, to determine whether changes in appetite and perturbations in regulation of food intake could be contributing factors to antipsychotic-induced weight gain.

RESULTS

In general, human studies point to disruption by AAPs of feeding behaviors and food consumption. In rodents, increases in cumulative food intake are mainly observed in females; however, changes in feeding microstructure or motivational aspects of food intake appear to occur independent of sex.

CONCLUSIONS

The findings from this review indicate that the varying levels of AAP-related weight gain reflect changes in both appetite and feeding behaviors, which differ by type of AAP. However, inconsistencies exist among the studies (both human and rodent) that may reflect considerable differences in study design and methodology. Future studies examining underlying mechanisms of antipsychotic-induced weight gain are recommended in order to develop strategies addressing the serious metabolic side effect of AAPs.

Effect of long-term olanzapine treatment on meal-induced insulin sensitization and on gastrointestinal peptides in female Sprague-Dawley rats

Meal-induced insulin sensitization (MIS), an endogenous adaptive mechanism is activated post-prandially. Reduced MIS leads to diabetes, but its activation improves insulin sensitivity. MIS is preserved to single olanzapine administration, therefore we aimed to investigate the chronic effect of olanzapine on fasted-state insulin sensitivity and on MIS in female Sprague-Dawley rats. Daily food and water intake, stool and urine production and body weight were determined. The MIS was characterized by a rapid insulin sensitivity test. Fasting hepatic and peripheral insulin sensitivity were determined by a hyperinsulinaemic euglycaemic glucose clamping supplemented with radiotracer technique. Fasted and post-prandial blood samples were obtained for plasma insulin, leptin, ghrelin, amylin, GLP-1, GIP, PYY and PP determination. Adiposity was characterized by weighing intra-abdominal and inguinal fat pads. Olanzapine caused hepatic insulin resistance and a reduced metabolic clearance rate of insulin, but the MIS retained its function. Body weight and adiposity were enhanced, but olanzapine failed to increase food intake. Fasting insulin and leptin were elevated and the post-prandial reduction in ghrelin level was inhibited by olanzapine.The MIS remained functionally intact after long-term olanzapine treatment. Altered insulin, leptin and ghrelin levels indicate olanzapine-induced metabolic derangements. Pharmacological activation of MIS could potentially be exploited to treat or prevent olanzapine-induced insulin resistance.

Olanzapine reduced brown adipose tissue thermogenesis and locomotor activity in female rats

Excessive weight gain has been identified as a serious metabolic side-effect of second-generation antipsychotics (SGAs), including olanzapine. While hyperphagia has been suggested to be the main contributor for this side-effect in the short term, reduced energy expenditure, in particular thermogenesis and locomotor activity, has been considered to contribute to the maintenance of heavy weight under long-term SGA treatments. Recent studies have identified metabolically active brown adipose tissues (BAT) in adult humans, suggesting potential clinical significance for the involvement of BAT thermogenesis in SGA-induced weight gain. However, to date there has been little research elucidating the central neuronal pathways affecting BAT thermogenesis or the morphological changes of the BAT. The present study aimed to investigate the role of BAT thermogenesis and locomotor activity in olanzapine-induced weight gain during the prolonged time courses of olanzapine treatment in an established female rat model. Although short- to mid-term olanzapine treatment had no effect on BAT temperature, we observed that long-term olanzapine treatment (from day 18 to 34) induced a significant reduction in BAT temperature, with an acute effect being observed between 45 and 150 min post-treatment in the long-term cohort. Additionally, in the long-term olanzapine group, the reduced BAT temperature was accompanied by decreased UCP1 and PGC-1α expressions in the BAT. Moreover, TH mRNA expressions in both hypothalamus and brainstem were also downregulated after mid- to long-term olanzapine treatment. Further, olanzapine led to reduced percentage of brown adipocytes in BAT during mid- to long-term treatments. Finally, locomotor activity was reduced throughout the three treatment cohorts. In summary, our results suggest that the reduction of BAT thermogenesis plays an important role during the long-term of olanzapine-induced weight gain, which was accompanied by an earlier onset of BAT adipocyte morphological changes and biochemical changes in the hypothalamus and the brainstem, while locomotor activity contributes to the entire olanzapine treatment courses.

Hypothalamic ghrelin signalling mediates olanzapine-induced hyperphagia and weight gain in female rats

Excessive weight gain is a major metabolic side effect of second-generation antipsychotics (SGAs) in the treatment of schizophrenia. Ghrelin is an orexigenic hormone secreted mainly from the stomach, which can induce weight gain and hyperphagia through regulating neuropeptides at the hypothalamus. Accumulating evidence implicates a relationship between ghrelin signalling and SGA-induced hyperphagia and weight gain. We report that olanzapine (a SGA with high weight gain liability) potently and time-dependently up-regulate ghrelin and ghrelin signalling, leading to hyperphagia and weight gain in female Sprague-Dawley rats, an action reversed by i.c.v. injection of a ghrelin receptor (GHS-R1a) antagonist. These findings indicate a crucial role of ghrelin signalling in hyperphagia induced by olanzapine, supporting the notion that GHS-R1a antagonist may be useful for pharmacological treatment of SGA-induced weight gain resulted from hyperphagia.

Modelling olanzapine-induced weight gain in rats

The second-generation antipsychotic drug olanzapine has become a widely prescribed drug in the treatment of schizophrenia and bipolar disorder. Unfortunately, its therapeutic benefits are partly outweighed by significant weight gain and other metabolic side effects, which increase the risk for diabetes and cardiovascular disease. Because olanzapine remains superior to other antipsychotic drugs that show less weight gain liability, insight into the mechanisms responsible for olanzapine-induced weight gain is crucial if it is to be effectively addressed. Over the past few decades, several groups have investigated the effects of olanzapine on energy balance using rat models. Unfortunately, results from different studies have not always been consistent and it remains to be determined which paradigms should be used in order to model olanzapine-induced weight gain most accurately. This review summarizes the effects of olanzapine on energy balance observed in different rat models and discusses some of the factors that appear to contribute to the inconsistencies in observed effects. In addition it compares the effects reported in rats with clinical findings to determine the predictive validity of different paradigms.

Second generation antipsychotic-induced type 2 diabetes: a role for the muscarinic M3 receptor

Second generation antipsychotics (SGAs) are widely prescribed to treat various disorders, most notably schizophrenia and bipolar disorder; however, SGAs can cause abnormal glucose metabolism that can lead to insulin-resistance and type 2 diabetes mellitus side-effects by largely unknown mechanisms. This review explores the potential candidature of the acetylcholine (ACh) muscarinic M3 receptor (M3R) as a prime mechanistic and possible therapeutic target of interest in SGA-induced insulin dysregulation. Studies have identified that SGA binding affinity to the M3R is a predictor of diabetes risk; indeed, olanzapine and clozapine, SGAs with the highest clinical incidence of diabetes side-effects, are potent M3R antagonists. Pancreatic M3Rs regulate the glucose-stimulated cholinergic pathway of insulin secretion; their activation on β-cells stimulates insulin secretion, while M3R blockade decreases insulin secretion. Genetic modification of M3Rs causes robust alterations in insulin levels and glucose tolerance in mice. Olanzapine alters M3R density in discrete nuclei of the hypothalamus and caudal brainstem, regions that regulate glucose homeostasis and insulin secretion through vagal innervation of the pancreas. Furthermore, studies have demonstrated a dynamic sensitivity of hypothalamic and brainstem M3Rs to altered glucometabolic status of the body. Therefore, the M3R is in a prime position to influence glucose homeostasis through direct effects on pancreatic β-cells and by potentially altering signalling in the hypothalamus and brainstem. SGA-induced insulin dysregulation may be partly due to blockade of central and peripheral M3Rs, causing an initial disruption to insulin secretion and glucose homeostasis that can progressively lead to insulin resistance and diabetes during chronic treatment.

Olanzapine-induced changes in glucose metabolism are independent of the melanin-concentrating hormone system

Atypical antipsychotic drugs such as Olanzapine (Ola) induce weight gain and metabolic changes associated with the development of type 2 diabetes. The mechanisms underlying these undesired side-effects are currently unknown. Chagnon et al. showed that the common allele rs7973796 of the prepro-melanin-concentrating hormone (PMCH) gene is associated with a greater body mass index in Ola-treated schizophrenic patients. As PMCH encodes for the orexigenic neuropeptide melanin-concentrating hormone (MCH), it was hypothesized that MCH is involved in Ola-induced metabolic changes. We have recently reported that the intragastric infusion of Ola results in hyperglycaemia and insulin resistance in male rats. In order to test in vivo the possible involvement of the PMCH gene in the pathogenesis of Ola side-effects, we administered Ola intragastrically in wild-type (WT) and PMCH knock-out (KO) rats. Our results show that glucose and corticosterone levels, as well as endogenous glucose production, are elevated by the infusion of Ola in both WT and KO animals. Thus, the lack of MCH does not seem to affect the acute effects of Ola on glucose metabolism. On the other hand, these effects might be obliterated by compensatory changes in other hypothalamic systems. In addition, possible modulatory effects of the MCH KO on the long term effects of Ola, i.e. increased adiposity, body weight gain, have not been investigated yet.

The role of ghrelin signalling in second-generation antipsychotic-induced weight gain

Based on clinical and animal studies, this review suggests a tri-phasic effect of second-generation antipsychotics (SGAs) on circulating ghrelin levels: an initial increase exerted by the acute effect of SGAs; followed by a secondary decrease possibly due to the negative feedback from the SGA-induced body weight gain or hyperphagia; and a final re-increase to reach the new equilibrium. Moreover, the results can also vary depending on individual SGAs, other hormonal states, dietary choices, and other confounding factors including medical history, co-treatments, age, gender, and ghrelin measurement techniques. Interestingly, rats treated with olanzapine, an SGA with high weight gain liabilities, are associated with increased hypothalamic ghrelin receptor (GHS-R1a) levels. In addition, expressions of downstream ghrelin signalling parameters at the hypothalamus, including neuropeptide Y (NPY)/agouti-related peptide (AgRP) and proopiomelanocortin (POMC) are also altered under SGA treatments. Thus, understanding the role of ghrelin signalling in antipsychotic drug-induced weight gain should offer potential novel pharmacological targets for tackling the obesity side-effect of SGAs and its associated metabolic syndrome.

The snacking rat as model of human obesity: effects of a free-choice high-fat high-sugar diet on meal patterns

OBJECTIVES

Rats subjected to a free-choice high-fat high-sugar (fcHFHS) diet persistently overeat, exhibit increased food-motivated behavior and become overtly obese. Conversely, several studies using a non-choice (nc) high-energy diet showed only an initial increase in food intake with unaltered or reduced food-motivated behavior. This raises the question of the importance of choice in the persistence of hyperphagia in rats on a fcHFHS diet.

SUBJECTS

Meal patterns, food intake and body weight gain were studied in male Wistar rats on free-choice diets with fat and/or sugar and in rats on nc diets with fat and sugar (custom made with ingredients similar to the fcHFHS diet).

RESULTS

Rats on a ncHFHS diet initially overconsumed, but reduced intake thereafter, whereas rats on a fcHFHS diet remained hyperphagic. Because half of the sugar intake in the fcHFHS group occurred during the inactive period, we next determined whether sugar intake during the light phase was a necessary requirement for hyperphagia, by restricting access to liquid sugar to either the light or dark period with unlimited access to fat and chow. Results showed that hyperphagia occurred irrespective of the timing of sugar intake. Meal pattern analysis revealed consumption of larger but fewer meals in the ncHFHS group, as well as the fcHF group. Interestingly, meal number was increased in all rats drinking liquid sugar (whether on a fcHFHS or a fcHS diet), whereas a compensatory decrease in meal size was only observed in the fcHS group, but not the fcHFHS group.

CONCLUSION

We hereby show the importance of choice in the observation of fcHFHS diet-induced hyperphagia, which results in increases in meal number due to sugar drinking without any compensatory decrease in meal size. We thus provide a novel dietary model in rats that mimics important features of human overconsumption that have been ignored in rodent models of obesity.

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

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

Intermittent treatment with olanzapine causes sensitization of the metabolic side-effects in rats

The second generation antipsychotic drugs are effective treatments for psychotic disorders. Many of these compounds, including the drug olanzapine, have been associated with metabolic side-effects, including weight gain, impaired glucose tolerance and insulin resistance, which increase the risk of developing cardiometabolic disorders. Rodent models of olanzapine-induced metabolic side-effects have been used to study the physiology of these effects, but only at a single time point after drug treatment. The purpose of the present study was to examine longitudinal changes with chronic antipsychotic drug treatment. Adult female rats were treated with either olanzapine (15 mg/kg) or vehicle for five consecutive days each week, followed by a 48 h washout period. Animals were then challenged with either olanzapine (15 mg/kg) or vehicle, and fasting glucose and insulin values were recorded, as well as glucose clearance in the glucose tolerance test. Treatment with olanzapine was continued for 10 weeks, with weekly tests of metabolic indices. Rats treated acutely with olanzapine showed both glucose dysregulation and insulin resistance; for the group treated during the week with olanzapine, these effects did not change by the end of ten weeks of treatment. However, in the group of animals challenged only once per week with olanzapine, the metabolic side-effects markedly intensified with the passage of time, whereby glucose intolerance and insulin resistance increased significantly compared to both baseline values and all other treatment groups. This previously unreported sensitization phenomenon represents a novel finding that may have clinical implications for patients receiving intermittent antipsychotic drug dosing or with variable adherence to treatment.

Olanzapine treatment and metabolic dysfunction: a dose response study in female Sprague Dawley rats

Second generation antipsychotics are commonly prescribed for the treatment of schizophrenia, however some can induce metabolic dysfunction side-effects such as weight gain, obesity and diabetes. Clinical reports suggest olanzapine alters satiety signals, although findings appear conflicting. Previous animal model studies have utilised a range of olanzapine dosages, however the dosage that better mimics the human scenario of olanzapine-induced weight gain is unclear. Female Sprague-Dawley rats were treated orally, three times daily with olanzapine (0.25mg/kg, 0.5mg/kg, 1.0mg/kg, 2.0mg/kg), self-administered in a sweet cookie dough pellet at eight-hourly intervals) or vehicle (n=12/group) for 14-days. Olanzapine orally self-administered in multiple doses (eight-hourly intervals) may circumvent a drop in plasma drug concentration and ensure the maintenance of a consistently high olanzapine level in the rat. Olanzapine increased body weight (0.5mg/kg, 1.0mg/kg, 2.0mg/kg), food intake (2.0mg/kg) and feeding efficiency (0.5-2.0mg/kg), with no effect on water intake. Subcutaneous inguinal (1.0mg/kg, 2.0mg/kg) and intra-abdominal perirenal fat were increased (2.0mg/kg), but not interscapula brown adipose tissue. Olanzapine increased circulating ghrelin and cholecystokinin, but had no effect on peptide YY((3-36)). Olanzapine decreased insulin (0.25-2.0mg/kg) and locomotor activity in the open field arena (0.5-2.0mg/kg). A low dosage of 0.25mg/kg olanzapine had no effect on most parameters measured. Olanzapine-induced weight gain is associated with hyperphagia, enhanced feeding efficiency and adiposity, decreased locomotor activity and altered satiety signaling. The animal model used in the present study of self-administered oral olanzapine treatment (t.i.d.) at a dosage range of 0.5-2.0mg/kg (but not 0.25mg/kg) mimics aspects of the clinic.