Effects Of Trans-fatty Acids On Learning And Memory In Mice And The Related Mechanisms

ObjectiveAs an unsaturated fatty acids with at least one unsaturated,nonconjugated double bond in the trans(rather than the typical cis)configuration,trans-fatty acids(TFA)[1],are widely used in food industry.Kinds of food(fried foods,desserts,fries and so on)using TFA to enhance the palatability of baked goods and sweets,because of their long shelf life,stability and semisolidity.Large numbers of studies had shown that trans-fatty acids consumption effect human growth and development,and also related to lots of disease:cardiovascular disease like atherosclerosis(AS),coronary heart disease(CHD);type 2 diabetes,cancer and so on.Trans-fatty acids has a certain degree of neurotoxicity,it could pass through the blood-brain barrier,deposited in nerve cells in hippocampus,striatum,frontal cortex etc..Studies had shown that excessive intake of trans-fatty acids also has some relationship with Alzheimer's disease(AD)characterized by progressive aggravation of memory impairment and cognitive deficit.However,the effects of trans-fatty acids on cognitive deficit and the exact mechanisms are not yet clearly known.Therefore,all animals were treated with trans-fatty acids by gavage for 12 weeks.The effects of trans-fatty acids on learning and memory were detected by Morris water maze;the pathomorphology changes of hippocampus in mice brain were observed by hematoxylin-eosin staining(H&E).The activities of superoxide dismutase(SOD),glutathione peroxidase(GSH-Px),catalase(CAT)and the content of lipid peroxidation-derived aldehyde malondialdehyde(MDA)in the brain tissue of mice were determined by biochemical kit;The activities of Na+/K+-ATPase,Ca2+/Mg2+-ATPase,acetylcholinesterase(AchE)and nitric oxide synthase(NOS)in the brain tissue of mice were detected by biochemical kit;the contents of amino acid neurotransmitters including glutamic acid(Glu),glycine(Gly),aspartic acid(Asp),y-aminobutyric acid(GABA)and taurine(Tau)were determined by high efficiency liquid chromatography.Investigate the effects of trans-fatty acids on cognitive deficit and the roles oxidative stress and neurotransmitters in brain of mice play.Methods1.Animals experimentAfter 7 days' acclimation,56 male Kunming mice(weight:18-22g)were randomly divided into four groups(n=14),including control group,low-dose trans-fatty acids group,medium-dose trans-fatty acids group,high-dose trans-fatty acids group.Low,medium,high-dose trans-fatty acids exposure group were treated with 25 mg/kg,50 mg/kg,100 mg/kg of trans-fatty acids respectively,control group received an equal volume of corn oil.All animals were treated by gavage with a volume of 0.1 ml/10g,once a day,6 days a week,for 12 weeks.The weight of mice was weighed and recorded every week to adjust the dosage.2.Cognitive function determination in rats treated with trans-fatty acidsAt the end of the experiment,12 mice in each group were picked up randomly to investigate the Morris water maze(MWM)test for consecutively six days.The cognitive function of the mice was evaluated comprehensively by positioning navigation experiment and space exploration experiment.Escape latency and swimming distance were used to evaluate the learning capacity;times of crossing the platform were used to evaluate the memory of mice.3.Histopathological observation of the mice brainThe paraffin sections of each mouse were prepared.The morphological changes of hippocampus were detected by hematoxylin-eosin staining(H&E).4.Oxidative stress related indexes determinationThe activities of SOD,GSH-Px and CAT,the content of MDA in the brain tissues of mice were measured according to the instructions of relevant kits.5.The activity of ATPase in the brain tissue of miceThe activity of Na+/K+-ATPase and Ca2+/Mg2+-ATPase in the brain tissue of mice were detected by kit according to the relevant instructions.6.The activity of AchE and NOS in the brain tissue of miceThe changes of AchE and NOS activity in brain tissue were detected according to the instructions of the relevant kits.7.Detection of amino acid neurotransmitters in the brain tissue of miceHigh performance liquid chromatography-diode array detection was used to detect the content of Glu,Gly,Asp,GABA and Tau in the brain tissue of mice.Results1.Effect of trans-fatty acids on general growth and development of miceMice in control group and low-dose,medium-dose and high-dose trans-fatty acids exposure groups were generally in good conditions.The body weight gain of mice in each experimental group increased slowly,but there were no significant difference between them(p>0.05).2.Effect of trans-fatty acids on cognitive function in miceThe Morris water maze data showed that escape latency and swimming distance of mice in each experimental group decreased with the increasing of the training time.Compared with the control group,mice in low-dose,medium-dose and high-dose trans-fatty acids exposure groups showed no significant difference in escape latency,swimming distance,average swimming speed,times crossing the platform and other indicators(p>0.05).3.Effect of trans-fatty acids on morphological changes in mice hippocampusMorphological observation in mice hippocampus show:Compared with the control group,the neuronal lines in hippocampus exposed to low-dose,medium-dose and high-dose trans-fatty acids seemed thin and blurred.Neuron numbers in CA3,CA2 of hippocampus were decreased under high-power microscope.4.Effect of trans-fatty acids on activities of SOD,GSH-Px,CAT and MDA content in brain tissue of miceCompared with the control group,the low,medium and high-dose trans-fatty acids group hold a decreased activity of SOD,GSH-Px,CAT activity and a increased level of MDA content(p<0.05).5.Effect of trans-fatty acids on Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities in brain tissue of miceCompared with the control group,the activities of Na+/K+-ATPase and Ca2+/Mg2+-ATPase in the brain tissue of mice in low-dose,medium-dose and high-dose trans-fatty acids group reduced respectively(p<0.05).6.Effect of trans-fatty acids on AchE and NOS activities in brain tissue of miceCompared with the control group,the activities of AchE in the brain tissue of mice treated with low-dose and medium-dose trans-fatty acids were decreased significantly(p<0.05).In the brain tissue of mice,the activity of NOS in the high dose trans-fatty acid group was higher than that in the control group(p<0.05).The NOS activity of the low and medium dose trans-fatty acids was higher than that of the control group,but there was no significant difference(p>0.05).7.Effect of trans-fatty acids on amino acid neurotransmitters content in brain tissue of miceCompared with the control group,the contents of Glu,Gly,Asp,GABA and Tau in the brain tissue of the low and medium dose trans-fatty acids were increased(p<0.05).The contents of Glu,Gly,Asp,GABA and Tau in the high dose trans-fatty acid group were also increased(p>0.05).Compared with the control group,the ratio of Glu/GABA in the brain tissue of mice exposed to low-dose and medium-dose of trans-fatty acids increased(p<0.05),respectively;the ratio of Glu/GABA in the brain tissue of mice exposed to high-dose trans-fatty acids group increased(p>0.05).Conclusion1.The brain is a trans-fatty acids toxicity sensitive target organ,trans-fatty acids exposure can lead to mice hippocampus morphological changes.2.Trans-fatty acids can result in mouse brain tissue damage of oxidative system.3.Trans-fatty acids have an impact on the activities of AchE and NOS.4.Trans-fatty acids are excitatory neurotoxicity and can influence the activities of ATPase.