Effects of risperidone treatment on the expression of hypothalamic neuropeptide in appetite regulation in Wistar rats.

Although the use of atypical antipsychotic drugs has been successful in the treatment of schizophrenia, they can cause some complications in the long-term use, including weight gain. Patients using these drugs tend to disrupt treatment primarily due to side effects. The atypical antipsychotic mechanism of action regulates a number of highly disrupted neurotransmitter pathways in the brains of psychotic patients but may also cause impairment of neurohormonal pathways in different brain areas. In this study, we investigated the circulating levels of hypothalamic neurohormones, which are related to appetite regulation; neuropeptide Y (NPY); alpha melanocyte stimulating hormone (α-MSH); cocaine and amphetamine regulated transcript (CART); agouti-related peptide (AgRP); and leptin in male Wistar rats, which were treated with risperidone, a serotonin antagonist, for four weeks. Alterations in the mRNA expression levels of these candidate genes in the hypothalamus were also analyzed. We hypothesized that risperidone treatment might alter both hypothalamic and circulating levels of neuropeptides through serotonergic antagonism, resulting in weight gain. Gene expression studies revealed that the mRNA expression levels of proopiomelanocortin (POMC), AgRP, and NPY decreased as well as their plasma levels, except for NPY. Unexpectedly, CART mRNA levels increased when their plasma levels decreased. Because POMC neurons express the serotonin receptor (5HT2C), the serotonergic antagonism of risperidone on POMC neurons may cause an increase in appetite and thus increase food consumption even in a short-term trial in rats.

Weight gain in risperidone therapy: investigation of peripheral hypothalamic neurohormone levels in psychotic patients.

The use of antipsychotic drugs has started a new era in the treatment of psychotic disorders. Nevertheless, they cause complications in the long-term treatment, which is mainly weight gain. In this study, we investigated circulating levels of hypothalamic neuropeptides, which are related to appetite regulation, neuropeptide Y (NPY), α-melanocyte-stimulating hormone (α-MSH), cocaine- and amphetamine-regulated transcript (CART), and leptin, in first-attack psychotic patients who were treated with an atypical antipsychotic drug, risperidone, for 4 weeks. We used a case-control association design to compare the neuropeptides in the control group versus before and after treatment of the patient group. Samples were obtained from psychotic patients who were admitted to the Psychiatry Outpatient Clinics, Gulhane School of Medicine, Ankara, Turkey. When compared with the control group, NPY and α-MSH plasma levels of psychotic patients were severely reduced, and the CART levels were substantially increased when they were first diagnosed (before treatment). However, the patients' body mass index and circulating leptin levels were markedly high after the treatment. Circulating levels of those neurohormones were not significantly changed between before and after treatment of the patients. These data demonstrate that peripheral α-MSH and NPY, although reflecting only secretion from peripheral organs, nevertheless, may provide an insight into the patients sympathetic tone and also suggest change of their appetite regulation. α-Melanocyte-stimulating hormone, NPY, and CART plasma levels may be used as a predictor of weight gain in the early treatment of the patients along with the leptin levels.

The investigation of leptin and hypothalamic neuropeptides role in first attack psychotic male patients: olanzapine monotherapy.

The mechanism underlying the weight gain due to treatment with olanzapine and other second generation antipsychotics has not been fully understood. To examine olanzapine's weight gain effects, we accepted first attack psychotic patients with no medication (pre-treatment) (n=22) and the healthy control group (n=26) in this study. After patients diagnosis, they were hospitalized and then treated for four weeks with olanzapine (post-treatment). We used case-control association design to test body mass index (BMI) and biochemical changes in each group. We also investigated peripheral leptin and neuropeptides/hormones namely, pro-opiomelanocortin (POMC), cocaine and amphetaime regulated transcript (CART), and neuropeptide Y (NPY) levels. These neuropeptides which are synthesized/secreted from arcuate nucleus of hypothalamus affect food intake and therefore, body weight. After 4 weeks of olanzapine treatment; BMI (body mass index), waist circumference, blood triglyceride, total cholesterol, and very low density lipoprotein (VLDL) levels were increased significantly in patients compared to their pre-treatment baseline. In pre-treatment, patients' NPY levels were significantly lower while α-MSH, the anorexigenic product of POMC levels were significantly higher vs. control. Both leptin and NPY levels were significantly increased in patients after the treatment but the NPY levels were also significantly lower in post-treatment vs. the control group. The CART levels did not change after the treatment. We may presume that the antagonist effect of olanzapine on the serotonin (5HT2CR and 5HT1BR) receptors of the arcuate hypothalamic neurons may be a basis for a deregulation of the neurohormones secretion.

Obese carboxypeptidase E knockout mice exhibit multiple defects in peptide hormone processing contributing to low bone mineral density.

Carboxypeptidase E (CPE) is a prohormone/proneuropeptide processing enzyme, and mice bearing CPE mutations exhibit an obese and diabetic phenotype. Studies on CPE knockout (KO) mice revealed poor prohormone processing, resulting in deficiencies in peptide hormones/neuropeptides such as insulin, gonadotropin-releasing hormone, and cocaine- and amphetamine-regulated transcript (CART). Here, we show that CPE KO mice, an obese animal model, have low bone mineral density (BMD) accompanied by elevated plasma CTX-1 (carboxy-terminal collagen crosslinks), and osteocalcin, indicators of increased bone turnover. Receptor activator for NF-kappaB ligand (RANKL) expression was elevated approximately 2-fold relative to osteoprotegerin in the femur of KO animals, suggesting increased osteoclastic activity in the KO mice. In the hypothalamus, mature CART, a peptide involved in eating behavior and implicated in bone metabolism, was undetectable. The melanocortin and neuropeptide Y (NPY) systems in the hypothalamus have also been implicated in bone remodeling, since MC4R KO and NPY KO mice have increased BMD. However, reduction of alpha-MSH, the primary ligand of MC4R by up to 94% and the lack of detectable NPY in the hypothalamus of CPE KO do not recapitulate the single-gene KO phenotypes. This study highlights the complex physiological interplay between peptides involved in energy metabolism and bone formation and furthermore suggests the possibility that patients, bearing CPE and CART mutations leading to inactive forms of these molecules, may be at a higher risk of developing osteoporosis.