The Primary Study Of Simvastatin Ameliorates Olanzapine-induced Weight Gain And Metabolic Imbalance Through Mediating In The Activity Of Brown Adipose Tissue In Rats

Background:Olanzapine is one of commonly used second generation antipsychotic drugs(SGAs)and now widely used for the treatment of schizophrenia.Olanzapine works on5-HT receptor and DA receptor in brain,which has good curative effects on the positive,negative symptoms and treatment-resistant schizophrenia.However,long-term use of olanzapine triggers a series of diseases including obesity,insulin resistance,high cholesterol and high blood sugar,etc.These side effects have serious influence on the patient's quality of life and may make these patients lose faith in the therapeutic effect of olanzapine.Over the years,researchers have been looking for the mechanism of olanzapine-induced side effects.It has reported that olanzapine can reduce the activity of thermogenesis and morphology in brown adipose tissue.Brown adipose tissue(BAT)is one of the important organs on body energy metabolism to maintain the body normal temperature.Mammals have more brown fat in the period of infant than the adult life.Uncoupling protein 1(UCP1)in the Mitochondrial membrane of cells brown adipocytes can alter chemical energy into heat energy.Thus,UCP1 is the biomarkers of BAT and mediating the UCP1 expression level may threat some metabolic disorders such as obesity and hyperlipidemia.Moreover,PGC-1?,PPAR?,PRDM16,POMC and TH are related to thermgenesis in BAT.Recently,brown fat is a famous potential therapeutic targets and improve the activity of thermogenesis in it could take improvement of energy metabolism in the body.Statins such as simvastatin,as first-line lipid-lowering drugs improve the symptoms of hyperlipidemia and control weight in patients.But it has few researches to report that simvastatin ameliorates olanzapine-induced abnormal energy metabolism and weight gain through thermogenesis by BAT.Therefore,the co-treatment of simvastatin and olanzapine acting on BAT is worth studying.Objective:To test effects of simvastatin ameliorating olanzapine-induced abnormal energy metabolism and weight gain through mediating thermogenesis of BAT.Methods:1.Female Sprague Dawley rats were treated orally with either olanzapine(3.0 mg/kg/day,t.i.d.)in 14 days.Body weight,food intake and anal temperature were measured once every 2 days throughout the experiment period.2.Female Sprague Dawley rats were treated orally with either olanzapine(3.0 mg/kg/day,t.i.d.),simvastatin(10 mg/kg/day),olanzapine plus simvastatin(O+S),or vehicle(control)for 35 days.Body weight,food intake and anal temperature were measured once every 2 days throughout the experiment period.3.At 30 th day,we did the open field tests.Every rat was placed in the center of a black rectangular area(50*50 cm2,50 cm high).The behavior of the rats was recorded from the top by a video camera for 25 min.Locomotor activity was analyzed by Noldus observer.4.At the 20 th day and end of the experiment,plasma was assayed for total cholesterol,triglycerides,and glucose.At the end of the experiment,rats were sacrificed by ether anesthesia.Perirenal,inguinal and periovarian white adipose tissue(WAT),interscapular brown adipose tissue(BAT)and brain were dissected,weight and frozen in liquid nitrogen.These tissue samples were stored at-80 ? until assay.Oil red O staining frozen sections of BAT were performed.5.RT-q PCR tested expression m RNA of UCP1,PGC-1?,PPAR? and PRDM16 in BAT and expression of POMC m RNA in the hypothalamus and TH m RNA in the brainstem.West blotting tested expression protein level of UCP1 and PGC-1?.Results:1.Simvastatin prevent olanzapine-induced body weight and food intake in rats.During the first 2 weeks,olanzapine increased weight gain(79.5±4.5 g vs.99.5±5.7 g,p<0.05)and food intake(40.2±3.6 g vs.33.5±2.5 g,p<0.05)compared by the control group.The olanzapine-only group had a slightly lower temperature but not significantly lower than the control group in the duration of first 14 days.During the last35 days,The final body weight gain of O+S co-treatment had significantly decreased compared to the olanzapine-only group(205.0±11.1 g vs.233.5±10.6 g,p<0.05).Simvastatin did not affect food intake.The co-treatment of simvastatin and olanzapine reversed the increase in feeding efficiency compared to the olanzapine group(p>0.05).2.The effect of simvastatin on olanzapine-induced lipid and glucose in rats.Plasma Glucose(7.74±0.13 mmol/L vs.7.39±0.11 mmol/L,p<0.05),triglyceride(1.02±0.06 mmol/L vs.0.73±0.02 mmol/L,p<0.01)and total cholesterol(2.40±0.04 mmol/L vs.2.28±0.03 mmol/L,p<0.05)levels were markedly elevated in olanzapine-only group compared to the control group in the early two weeks.In the later five weeks,simvastatin-only group reduced plasma lipid significantly,O+S co-treatment significantly ameliorated triglyceride(0.84±0.03 mmol/L vs.1.27±0.04 mmol/L,p<0.01),total cholesterol(2.22 ± 0.10 mmol/L vs.2.45 ± 0.03mmol/L,p<0.05)and glucose(7.47±0.03 mmol/L vs.7.95±0.18 mmol/L,p<0.01)compared to the olanzapine-only group.3.The effect of simvastatin on olanzapine-induced locomotor activity in rats.The olanzapine-only group had significantly less distance moved(4091.3 ±336.5 cm vs.4998.3±157.6 cm,p<0.05)and velocity(2.7±0.1 cm/s vs.3.3±0.1 cm/s,p<0.05)than the control but the simvastatin-only group showed no significant effect compared to the control.The total distance moved and velocity of O+S co-treatment group was lower than the control,but there was no significance between them.In addition,O+S co-treatment group showed slightly more distance moved and velocity than the olanzapine-only group.4.The physiological,morphological and molecular biochemistry evidence in the brown adipose tissue treated by olanzapine and/or simvastatin.It was interesting that the O+S co-treatment group of rats' body temperature had a tendency to increase temperature compared with olanzapine-only group(p>0.05).The olanzapine group had the biggest lipid droplets in the four subgroups,while O+S co-treatment group had size of lipid droplets similar to the control group.There was a significant decrease of UCP1 and PGC-1? m RNA level expression in the olanzapine-only group compared with controls which could be reversed by co-treatment with simvastatin(p<0.05).Compared to the olanzapine-only group,there was also a significant rise in UCP1 m RNA expression(144%±14% vs.56%±11%,p<0.01)and PGC-1? m RNA expression(103%±13% vs.56%±11%,p<0.05)in the O+S co-treatment group.The m RNA expression of PPAR? of the olanzapine group had a significant decrease by ~45% compared with the control group(p<0.05).The total cholesterol was negative correlation with UCP1 protien level.It was negative correlation between TG and the protein level of UCP1(r=-0.484,p<0.01).O+S co-treatment reversed the decrease of PPAR? compared with treatment with olanzapine(75%±14% vs.45%±6%,p<0.05).Furthermore,in comparison with the control group,simvastatin only treatment significantly increased by ~41% m RNA expression of PRDM16(p<0.05).Consistently,compared with controls,olanzapine treatment also dramatically decreased the UCP1 and PGC-1? protein levels in the BAT(p<0.05).O+S co-treatment increased UCP1 expression compared with olanzapine(86%±6% vs.71%±5%,p<0.05).5.The effect of expression of POMC m RNA in the hypothalamus and TH m RNA in the brainstem mediated by olanzapine and/or simvastatin.Olanzapine-only treatment induced a decline of the hypothalamic POMC m RNA expression compared with controls(p<0.05).Moreover,the simvastatin-only group had a significantly higher POMC m RNA expression than the control group(p<0.01).Similar results were also observed in the m RNA expression of TH in the brainstem.Conclusion:The study suggested that olanzapine significantly induced body weight gain and caused hyperlipidemia and hyperglycemia and abnormal energy metabolism in a rat model.Although simvastatin had no effect on food intake,it could improve olanzapine-induced energy metabolic imbalance and control body weight gain through increasing feeding efficiency and mediating UCP1 expression level of BAT.Moreover,simvastatin could ameliorate olanzapine-induced high levels of lipid and glucose.The hypolipidemic effect of simvastatin may be one pathway to activate the function of BAT.These findings support a potential mechanism of simvastatin preventing olanzapine-induced weight gain through mediation of energy expenditure,which provides pharmacological strategies to tackle the adverse effect of SGAs.