Study Of The Serum Levels Of Polyunsaturated Fatty Acids And The Expression Of Metabolic Enzymes In A Rat Valproate-induced Autism Model

Background and PurposeAutism is a neurodevelopmental disorder and the etiology of autism is not known.The study revealed that decreased level of serum PUFAs in patients with autism is associated with abnormal neurobehavior.As the important constituent of neuronal cell membranes,PUFAs are crucial for proper functioning of cell membranes,particularly in the brain.?5-desaturase,?6-desaturase and Elovl2 are important metabolic enzymes in the synthesis of PUFAs,and their functional status directly affects the synthesis of PUFAs.To investigate whether the decreased level of serum PUFAs in patients with autism is associated with the expression of related liver metabolic enzymes,we selected rats that were exposed to valproic acid(VPA)on embryonic day 12.5(E12.5)as the model of autism.We observed and analyzed the serum levels of PUFAs and the expression of related liver metabolic enzymes,including ?5-desaturase,?6-desaturase and Elovl2,in VPA-exposed and control rats on postnatal day 35(PND35)and conducted sex dimorphic analysis.We try to discuss whether the decreased level of serum PUFAs affects the change of neurobehavior,and attempt to reveal its mechanism.MethodsWe used Wistar rats with intraperitoneal injection of VPA on E12.5 as rats model of autism.On PND7-35,we evaluated the development and behavior in VPA and control rats,including body weight,eye opening score,vestibular sense,pain threshold and swimming ability.We used Morris water maze test to evaluate the learning and memory ability of rats.We utilized open field test to evaluate the locomotor activity of rats.We utilized 3-chambered social test to evaluate the social interaction of rats.We utilized GC-MS to analyze the serum levels of PUFAs of rats on PND35.We utilized Western Blot method to analyze the expression of ?5-desaturase,?6-desaturase and Elovl2 in liver and the expression of caspase-3,Bcl-2 and Bax in hippocampus of rats on PND35.We utilized Nissl staining to observe the neuronal morphological characteristics of hippocampal CA1 and analyzed the number of surviving neurons.We utilized Immunohistochemistry to observe the neuronal developmental status of hippocampal CA1.ResultsDevelopmental evaluation: VPA rats were significant developmental delay,compared to control rats.Behavioral evaluation: The pain threshold of VPA rats was significant higher than control rats(P < 0.05).The pain threshold of VPA rats showed sex dimorphism,that is,males was significant higher than females.Both rats in Morris water maze test showed certain learning and memory abilities.Escape latency and the number of times crossed the center of 3rd quadrant in VPA rats was significant lower than control rats.Escape latency and the number of times crossed the center of 3rd quadrant in VPA rats was significant lower than control rats(P < 0.05),while the distance spontaneously traveled and duration were significant higher than control rats(P < 0.05),which showed sex difference,that is,VPA males were significant higher than VPA females(P < 0.05).In sociability test,compared to control rats,the time and frequency in exploring stranger rat No.1 were significant lower(P < 0.05),while the time and frequency in exploring the empty cage were significant increased(P < 0.05),which showed impaired social interaction in VPA rats.In social preference test,compared to control rats,the time and frequency in exploring stranger rat No.1 were significant increased(P < 0.05),while the time and frequency in exploring stranger rat No.2 were significant decreased(P < 0.05),which showed that the VPA rats had less exploring to novelty.The level of serum PUFAs: The levels of the thirteen examined types of FFAs,n-3PUFAs,n-6PUFAs,total PUFAs and total FFAs in serum samples from the VPA males were significantly lower than those from the control males(P < 0.05),in which the level of serum C14:0,C16:1n-7,C20:5n-3,C22:5n-3,C22:6n-3,total PUFAs and total FFAs in VPA females were significantly lower than those from the control females(P < 0.05).Western blot results: The expression of ?5-desaturase,?6-desaturase and Elovl2 in VPA rats was significantly lower than those from the control rats(P < 0.05),and VPA males were significantly lower than those from the VPA females(P < 0.05).The expression of ?5-desaturase and ?6-desaturase in control males was significantly lower than those from the control females(P < 0.05).Compared to control rats,the expression of caspase-3 and Bax of VPA rats was significant up-regulated(P < 0.05),and the expression of Bcl-2 was significant down-regulated(P < 0.05).And the expression of caspase-3 showed sex difference,that is,females were significant higher males in VPA group(P < 0.05).VPA rats indicated neuronal injury of hippocampal CA1,that is,the neuronal survival rate,NeuN positive cell number and IOD of hippocampal CA1 were significantly lower than those from the controls(P < 0.05),and VPA males were significantly lower than those from the VPA females(P < 0.05).ConclusionsPrenatal exposure to VPA on day 12.5 of gestation had long-term and gender-specific effects on development and postnatal behavior in rats.Prenatal exposure to VPA on day 12.5 of gestation had long-term and gender-specific effects on the expression of PUFAs liver metabolic enzymes and apoptosis-related proteins and hippocampal neuronal survival rate in rats.VPA rats showed autism-like behavioral changes,such as learning disorder,hyperactivity and impaired social interaction.In the meantime VPA rats indicated the levels of serum PUFAs and related liver metabolic enzymes were significantly reduced,and the abnormal expression of apoptosis-related proteins and hippocampal neuronal injury were observed,which showed sex dimorphism.