In male rats, the ability of central insulin to suppress glucose production is impaired by olanzapine, whereas glucose uptake is left intact.

BACKGROUND: Insulin receptors are widely expressed in the brain and may represent a crossroad between metabolic and cognitive disorders. Although antipsychotics, such as olanzapine, are the cornerstone treatment for schizophrenia, they are associated with high rates of type 2 diabetes and lack efficacy for illness-related cognitive deficits. Historically, this risk of diabetes was attributed to the weight gain propensity of antipsychotics, but recent work suggests antipsychotics can have weight-independent diabetogenic effects involving unknown brain-mediated mechanisms. Here, we examined whether antipsychotics disrupt central insulin action, hypothesizing that olanzapine would impair the well-established ability of central insulin to supress hepatic glucose production. METHODS: Pancreatic euglycemic clamps were used to measure glucose kinetics alongside a central infusion of insulin or vehicle into the third ventricle. Male rats were pretreated with olanzapine or vehicle per our established model of acute olanzapine-induced peripheral insulin resistance. Groups included (central-peripheral) vehicle-vehicle (n = 11), insulin-vehicle (n = 10), insulin-olanzapine (n = 10) and vehicle-olanzapine (n = 8). RESULTS: There were no differences in peripheral glucose or insulin levels. Unexpectedly, we showed that central insulin increased glucose uptake, and this effect was not perturbed by olanzapine. We replicated suppression of glucose production by insulin (clamp relative to basal: 77.9% ± 13.1%, all p < 0.05), an effect abolished by olanzapine (insulin-olanzapine: 7.7% ± 14%). LIMITATIONS: This study used only male rats and an acute dose of olanzapine. CONCLUSION: To our knowledge, this is the first study suggesting olanzapine may impair central insulin sensing, elucidating a potential mechanism of antipsychotic-induced diabetes and opening avenues of investigation related to domains of schizophrenia psychopathology.

Acute effects of single-dose olanzapine on metabolic, endocrine, and inflammatory markers in healthy controls.

Atypical antipsychotics may "directly" influence glucose homeostasis, increasing risk of type 2 diabetes independently of changes in adiposity. Animal models suggest direct effects after even a single dose of certain atypical antipsychotics on glucose dysregulation. Here, we investigated effects of a single-dose olanzapine (OLA) on glucose metabolism in healthy volunteers, thereby minimizing confounding effects of the illness of schizophrenia and adiposity. In a randomized double-blind crossover design, 15 subjects were administered 10 mg of OLA or placebo at 7:00 A.M. on separate study dates. A frequently sampled intravenous glucose tolerance test was initiated 4.25 hours later to assess changes in glucose homeostasis, including an index of insulin sensitivity, disposition index, glucose effectiveness, and acute insulin response to glucose. We also examined effects on cortisol, prolactin, fasting free fatty acids (FFAs), insulin-mediated suppression of FFAs, and adipocytokines (leptin, adiponectin, C-reactive protein, interleukin 6, and tumor necrosis factor α). Complete data for both visits were analyzed for 12 subjects. Olanzapine treatment significantly decreased glucose effectiveness (P = 0.041) and raised fasting glucose over 4.25 hours (P = 0.03) as compared to placebo. Olanzapine was associated with lower serum cortisol (P = 0.003), lower fasting FFA (P = 0.042), and increased prolactin levels (P < 0.0001). We therefore suggest that a single dose of OLA may invoke early changes in some parameters of glucose and lipid metabolism, as well as endocrine indices.

Acutely administered antipsychotic drugs are highly selective for dopamine D2 over D3 receptors.

We showed previously, using [(3)H]-(+)-4-propyl-9-hydroxynaphthoxazine ([(3)H]-(+)-PHNO) autoradiography, that several antipsychotic drugs do not occupy dopamine D3 receptors at clinically-relevant doses in rat. This is an unexpected finding considering the near-equivalent in vitro affinity of these drugs for D2 and D3 receptors. The purpose of the current study was to address two possible methodological limitations of our previous report, namely that (1) [(3)H]-(+)-PHNO may have been administered at non-tracer dose, potentially causing underestimate of D3 receptor occupancy, and (2) antipsychotic drugs were administered chronically, potentially causing increased D3 receptor expression not accounted for in the vehicle-treated control group. We found that decreasing [(3)H]-(+)-PHNO dose from 5.6nmol/kg (our previous dose) to 0.6nmol/kg caused a >60% increase in [(3)H]-(+)-PHNO binding to D3 receptors in cerebellar lobes 9 and 10, indicating that our previous study was indeed conducted under non-tracer dose conditions. However, neither reducing [(3)H]-(+)-PHNO dose further to 0.3nmol/kg (a tracer dose), nor administering antipsychotics acutely affected antipsychotic receptor occupancy. At clinically-relevant levels of D2 occupancy (57-82% inhibition of striatal binding), neither olanzapine nor haloperidol occupied D3 receptors, while clozapine occupied D3 receptors at levels similar to our previous report (33%). Risperidone moderately occupied D3 receptors (40%), but at a dose occupying >90% of D2 receptors and therefore of questionable clinical relevance. These findings demonstrate that the lack of antipsychotic occupancy of D3 receptors is not attributable to limitations of our previous study. These results suggest that D3 receptor blockade is not necessary for the therapeutic effects of the antipsychotic drugs examined.

Associations between plasma clozapine/N-desmethylclozapine ratio, insulin resistance and cognitive performance in patients with co-morbid obesity and ultra-treatment resistant schizophrenia.

Clozapine (CLZ), the sole antipsychotic with superior efficacy for ultra-treatment resistant schizophrenia (TRS), is limited by adverse effects, including metabolic dysregulation. Clozapine's main metabolite, N-desmethylclozapine (NDMC), has potent 5-HT2C antagonist properties which may explain this metabolic dysfunction, thus the CLZ:NDMC ratio is of particular interest. High insulin resistance states could be associated with CYP1A2 induction and lower CLZ:NDMC ratios. Additionally, lower CLZ:NDMC ratios have been associated with better cognitive, but worse metabolic functioning. This study investigated associations between metabolic and cognitive parameters with the CLZ/NDMC ratio. Primary outcomes included relationships between the CLZ:NDMC ratio to the homeostatic model assessment for insulin resistance (HOMA-IR) and Brief Assessment of Cognition in Schizophrenia (BACS) composite z-scores. Secondary outcomes assessed relationships between CLZ:NDMC ratios to fasting insulin, BMI, weight, fasting glucose, and BACS digit sequencing z-scores. 38 patients who were overweight or obese with schizophrenia or schizoaffective disorder completed fasting bloodwork, anthropometric, psychopathological, and cognitive assessments. Multivariate regressions found a statistically significant inverse association between the CLZ/NDMC ratio and HOMA-IR (B = - 1.028, SE B = .473, ß = - 0.348 p = 0.037), which may have been driven by fasting insulin levels (B = - 27.124, SE B = 12.081, ß = - 0.351 p = 0.031). The CLZ/NDMC ratio may predict insulin resistance/metabolic comorbidity among patients with TRS receiving clozapine.

Metformin for early comorbid glucose dysregulation and schizophrenia spectrum disorders: a pilot double-blind randomized clinical trial.

Patients with schizophrenia have exceedingly high rates of metabolic comorbidity including type 2 diabetes and lose 15-20 years of life due to cardiovascular diseases, with early accrual of cardiometabolic disease. In this study, thirty overweight or obese (Body Mass Index (BMI) > 25) participants under 40 years old with schizophrenia spectrum disorders and early comorbid prediabetes or type 2 diabetes receiving antipsychotic medications were randomized, in a double-blind fashion, to metformin 1500 mg/day or placebo (2:1 ratio; n = 21 metformin and n = 9 placebo) for 4 months. The primary outcome measures were improvements in glucose homeostasis (HbA1c, fasting glucose) and insulin resistance (Matsuda index-derived from oral glucose tolerance tests and homeostatic model of insulin resistance (HOMA-IR)). Secondary outcome measures included changes in weight, MRI measures of fat mass and distribution, symptom severity, cognition, and hippocampal volume. Twenty-two patients (n = 14 metformin; n = 8 placebo) completed the trial. The metformin group had a significant decrease over time in the HOMA-IR (p = 0.043) and fasting blood glucose (p = 0.007) vs. placebo. There were no differences between treatment groups in the Matsuda index, HbA1c, which could suggest liver-specific effects of metformin. There were no between group differences in other secondary outcome measures, while weight loss in the metformin arm correlated significantly with decreases in subcutaneous, but not visceral or hepatic adipose tissue. Our results show that metformin improved dysglycemia and insulin sensitivity, independent of weight loss, in a young population with prediabetes/diabetes and psychosis spectrum illness, that is at extremely high risk of early cardiovascular mortality. Trial Registration: This protocol was registered with clinicaltrials.gov (NCT02167620).

The clozapine to norclozapine ratio: a narrative review of the clinical utility to minimize metabolic risk and enhance clozapine efficacy.

Introduction: Clozapine remains the most effective antipsychotic for treatment-refractory schizophrenia. However, ~40% of the patients respond insufficiently to clozapine. Clozapine's effects, both beneficial and adverse, have been proposed to be partially attributable to its main metabolite, N-desmethylclozapine (NDMC). However, the relation of the clozapine to norclozapine ratio (CLZ:NDMC; optimally defined as ~2) to clinical response and metabolic outcomes is not clear.Areas covered: This narrative review comprehensively examines the clinical utility of the CLZ:NDMC ratio to reduce metabolic risk and increase treatment efficacy. The association of the CLZ:NDMC ratio with changes in psychopathology, cognitive functioning, and cardiometabolic burden will be explored, as well as adjunctive treatments and their effects.Expert opinion: The literature suggests a positive association between the CLZ:NDMC ratio and better cardiometabolic outcomes. Conversely, the CLZ:NDMC ratio appears inversely associated with better cognitive functioning but less consistently with other psychiatric domains. The CLZ:NDMC ratio may be useful for predicting and monitoring cardiometabolic adverse effects and optimizing potential cognitive benefits of clozapine. Future studies are required to replicate these findings, which if substantiated, would encourage examination of adjunctive treatments aiming to alter the CLZ:NDMC ratio to best meet the needs of the individual patient, thereby broadening clozapine's clinical utility.

Effects of acute olanzapine exposure on central insulin-mediated regulation of whole body fuel selection and feeding.

The use of antipsychotics is associated with severe disruptions in whole body glucose and lipid metabolism which may in part occur through the central nervous system and impaired insulin action at the brain. Here we investigated whether olanzapine treatment might also affect the ability of central insulin treatment to regulate food intake and fuel preference in the light and dark cycle. Male Sprague-Dawley rats were treated with olanzapine (or vehicle solution; 3 mg/kg, subcutaneous) and a simultaneous acute intracerebral ventricular (ICV) infusion of insulin (or vehicle; 3 µL at 10mU; ICV) at the beginning of the 12-h light and dark cycles. Olanzapine treatment reduced RER in the dark and light phases (most consistently in the 4-hours post-treatment), while ICV insulin reduced average RER predominantly in the dark phase, but also at the end of the light cycle. The RER lowering effect of ICV-insulin during the light cycle was absent in the group co-administered olanzapine. The reduction in RER during the dark phase was mirrored by decreased food intake with ICV insulin, but not olanzapine treated rats. The reduction in food intake by ICV-insulin was abolished in rats co-administered olanzapine suggesting rapid induction of central insulin resistance. A combination of ICV-insulin and olanzapine similarly reduced RER in the dark phase, independent of changes in food intake. Olanzapine treatment, alone or in combination with ICV-insulin, significantly reduced VCO2 at regular intervals in the dark phase (specifically 3 h post-treatment), while VO2 was not significantly altered by either treatment. Finally, heat production was increased by olanzapine treatment in the light phase, though this effect was not consistent. The findings confirm that acute olanzapine treatment directly reduces RER and suggest that treatment with this drug may also override central insulin-mediated reductions in food intake at the hypothalamus (while still independently favoring fatty acid oxidation). Acute central insulin similarly reduces RER, but in contrast to olanzapine, this may represent a physiologically appropriate response to reduction in food intake.

Antipsychotics, Metabolic Adverse Effects, and Cognitive Function in Schizophrenia.

Cognitive impairment is a core symptom domain of schizophrenia. The effect of antipsychotics, the cornerstone of treatment in schizophrenia, on this domain is not fully clear. There is some evidence suggesting that antipsychotics may partially improve cognitive function, and that this improvement may vary depending on the specific cognitive domain. However, this research is confounded by various factors, such as age, duration/stage of illness, medication adherence, and extrapyramidal side effects that complicate the relationship between antipsychotics and cognitive improvement. Furthermore, antipsychotics-particularly the second generation, or "atypical" antipsychotics-can induce serious metabolic side effects, such as obesity, dyslipidemia and type 2 diabetes, illnesses which themselves have been linked to impairments in cognition. Thus, the inter-relationships between cognition and metabolic side effects are complex, and this review aims to examine them in the context of schizophrenia and antipsychotic treatment. The review also speculates on potential mechanisms underlying cognitive functioning and metabolic risk in schizophrenia. We conclude that the available literature examining the inter-section of antipsychotics, cognition, and metabolic effects in schizophrenia is sparse, but suggests a relationship between metabolic comorbidity and worse cognitive function in patients with schizophrenia. Further research is required to determine if there is a causal connection between the well-recognized metabolic adverse effects of antipsychotics and cognitive deficits over the course of the illness of schizophrenia, as well as, to determine underlying mechanisms. In addition, findings from this review highlight the importance of monitoring metabolic disturbances in parallel with cognition, as well as, the importance of interventions to minimize metabolic abnormalities for both physical and cognitive health.

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.

Metformin attenuates olanzapine-induced hepatic, but not peripheral insulin resistance.

Antipsychotics (APs) are linked to diabetes, even without weight gain. Whether anti-diabetic drugs are efficacious in reversing the direct effects of APs on glucose pathways is largely undetermined. We tested two metformin (Met) doses to prevent impairments seen following a dose of olanzapine (Ola) (3 mg/kg); glucokinetics were measured using the hyperinsulinemic-euglycemic clamp (HIEC). Met (150 mg/kg; n=13, or 400 mg/kg; n=11) or vehicle (Veh) (n=11) was administered through gavage preceding an overnight fast, followed by a second dose prior to the HIEC. Eleven additional animals were gavaged with Veh and received a Veh injection during the HIEC (Veh/Veh); all others received Ola. Basal glucose was similar across treatment groups. The Met 400 group had significantly greater glucose appearance (Ra) in the basal period (i.e., before Ola, or hyperinsulinemia) vs other groups. During hyperinsulinemia, glucose infusion rate (GINF) to maintain euglycemia (reflective of whole-body insulin sensitivity) was higher in Veh/Veh vs other groups. Met 150/Ola animals demonstrated increased GINF relative to Veh/Ola during early time points of the HIEC. Glucose utilization during hyperinsulinemia, relative to basal conditions, was significantly higher in Veh/Veh vs other groups. The change in hepatic glucose production (HGP) from basal to hyperinsulinemia demonstrated significantly greater decreases in Veh/Veh and Met 150/Ola groups vs Veh/Ola. Given the increase in basal Ra with Met 400, we measured serum lactate (substrate for HGP), finding increased levels in Met 400 vs Veh and Met 150. In conclusion, Met attenuates hepatic insulin resistance observed with acute Ola administration, but fails to improve peripheral insulin resistance. Use of supra-therapeutic doses of Met may mask metabolic benefits by increasing lactate.

Atypical antipsychotics and diabetic ketoacidosis: a review.

RATIONALE: Atypical antipsychotics have been linked to weight gain and type 2 diabetes, but are also associated with diabetic ketoacidosis (DKA), which can occur more acutely and in the absence of weight gain. OBJECTIVES: Our aim was to review current case reports of DKA in the context of atypical antipsychotic treatment to better understand (a) the scope of the problem, (b) its relationship to different atypical agents, (c) risk factors, (d) long-term outcome, and (e) putative mechanisms of action. METHOD: Searches in PubMed/Medline, as well as the University of Toronto's Scholar Portal, were performed for all relevant articles/abstracts in English. RESULTS: Sixty reports, yielding 69 cases, affirm that DKA is a rare but serious risk with almost all atypical antipsychotics; however, liability seems to vary between agents, at least partially mirroring risk of weight gain. Mean age of onset was 36.9 years (range 12-80), with 68 % of cases occurring in males, and 41 % in individuals of African American or African Caribbean descent. Over one third of cases present with either no weight gain or weight loss, and 61 % of these require ongoing treatment for glycemic control. Death occurred in 7.25 % of cases. CONCLUSION: While the underlying mechanisms are not well understood, antipsychotic-related DKA can occur soon after treatment onset and in the absence of weight gain. Although rare, clinicians must remain vigilant given its acute onset and potential lethality.

A Canadian multicenter trial assessing memory and executive functions in patients with schizophrenia spectrum disorders treated with olanzapine.

Serial verbal learning task (explicit long-term memory) and verbal fluency (generation of a response) are tests that are usually severely impaired in schizophrenia. Despite the growing literature supporting the clinical efficacy of olanzapine, psychiatrists still question its cognitive consequences. This study assessed the efficacy of olanzapine on neurocognitive functioning. Patients (N = 134) meeting diagnostic criteria for schizophrenia, schizophreniform, or schizoaffective disorders began an 8-week, open-label olanzapine treatment at a dose of 5 mg/d, which was increased to 10 mg/d after 1 week. Daily dosage was subsequently adjusted between 5 and 20 mg/d based on individual clinical status. All previous antipsychotics were tapered and discontinued during the first 2 weeks of the study. Neuropsychologic assessments were carried out at baseline and at 4 and 8 weeks. Explicit long-term memory was assessed with the Rey Auditory-Verbal Learning Test: the average immediate recall score significantly improved (P < 0.001), as did the delayed recall score (P < 0.001). The average total score on category fluency improved from 34.6 words at baseline to 37.6 words at end point (P < 0.0001). Time on both Trail A and B making tasks significantly decreased (P < 0.0001). Lack of a control arm makes it impossible to exclude a practice effect as an explanation for the enhanced cognitive performance, although the Word List Recall test represents one of the better resources to avoid a practice effect. After switching to olanzapine, there was a statistically significant improvement of cognitive function in the 3 main domains tested and no significant worsening of any memory or executive function measure.