Acute clozapine exposure in vivo induces lipid accumulation and marked sequential changes in the expression of SREBP, PPAR, and LXR target genes in rat liver.

BACKGROUND: Several antipsychotic drugs (APDs) have high propensity to induce weight gain and dyslipidemia in patients, with clozapine and olanzapine as the most potent drugs. These lipid-related effects have been attributed to drug-mediated blockade or antagonism of histamine H1 and serotonin 5-HT2 receptors as well as activation of hypothalamic AMP-activated protein kinase. We recently showed that APDs activate lipid biosynthesis in cultured liver cells through stimulation of the sterol regulatory element-binding protein (SREBP) transcription factors. OBJECTIVE: The objective of the study was to search for clozapine-related lipogenic effects in peripheral tissues in vivo using rat liver as target organ. MATERIALS AND METHODS: Adult female Sprague-Dawley rats were administered single intraperitoneal injections of clozapine (25 and 50 mg/kg). Hepatic lipid levels were measured during a 48-h time course. Real-time quantitative PCR was used to analyze expression of genes involved in lipid biosynthesis, oxidation, efflux, and lipolysis. RESULTS: We identified an initial up-regulation of central lipogenic SREBP target genes, followed by a marked and sustained down-regulation. We also observed a sequential transcriptional response for fatty acid beta-oxidation and cholesterol efflux genes, normally controlled by the peroxisome proliferator activated receptor alpha and liver X receptor alpha transcription factors, and also down-regulation of genes encoding major lipases. The transcriptional responses were associated with a significant accumulation of triacylglycerol, phospholipids, and cholesterol in the liver. CONCLUSION: These results demonstrate that acute clozapine exposure affects SREBP-regulated lipid biosynthesis as well as other lipid homeostasis pathways. We suggest that such drug-induced effects on lipid metabolism in peripheral tissues are relevant for the metabolic adverse effects associated with clozapine and possibly other APDs.

Acute effects of orexigenic antipsychotic drugs on lipid and carbohydrate metabolism in rat.

OBJECTIVE: This study aims to investigate whether orexigenic antipsychotic drugs may induce dyslipidemia and glucose disturbances in female rats through direct perturbation of metabolically active peripheral tissues, independent of prior weight gain. METHODS: In the current study, we examined whether a single intraperitoneal injection of clozapine or olanzapine induced metabolic disturbances in adult female outbred Sprague-Dawley rats. Serum glucose and lipid parameters were measured during time-course experiments up to 48 h. Real-time quantitative PCR was used to measure specific transcriptional alterations in lipid and carbohydrate metabolism in adipose tissue depots or in the liver. RESULTS: Our results demonstrated that acute administration of clozapine or olanzapine induced a rapid, robust elevation of free fatty acids and glucose in serum, followed by hepatic accumulation of lipids evident after 12-24 h. These metabolic disturbances were associated with biphasic patterns of gluconeogenic and lipid-related gene expression in the liver and in white adipose tissue depots. CONCLUSION: Our results support that clozapine and olanzapine are associated with primary effects on carbohydrate and lipid metabolism associated with transcriptional changes in metabolically active peripheral tissues prior to the development of drug-induced weight gain.

Lipogenic effects of psychotropic drugs: focus on the SREBP system.

Antipsychotics, antidepressants and mood stabilizers are psychotropic drugs widely used in the treatment of psychiatric disorders, such as schizophrenia, bipolar disorder and major depressive disorder. Such drugs have been used since the early 1950s, and it is now well established that they target neurotransmitter receptors and/or transporters located on central nervous system (CNS) neurons. However, their mechanism of action is still not fully understood, and there is large inter-individual variation in therapeutic response. Psychotropic drugs are also associated with numerous adverse effects, of which weight gain and metabolic disturbances have gained increased focus during the last decade. Based on studies in cultured cells, we have demonstrated that several psychotropic drugs upregulate the expression of genes involved in cellular fatty acid and cholesterol biosynthesis, controlled by the SREBP transcription factors. Lipogenic effects were also observed in vivo, in rat liver and in lymphocytes from drug-treated patients. These results provide new insight into the molecular mechanisms of psychotropic drug action and could be relevant both for their therapeutic action and metabolic adverse effects.