Effects Of Trans Fatty Acids On Nervous System In Rats And The Related Mechanisms

ObjectiveTrans fatty acid(TFA)is the general name of unsaturated fats with at least one double bond in the trans configuration.Catalytic hydrogenation of oils and fats is the main source of TFAs.TFAs are widely used in packaged and fried foods,because they can add crispy taste and have a longer storage life.Recent studies suggest that dietary TFAs from partially hydrogenated oils may be responsible for many diseases,particularly a positive association between TFAs intake and the risk of coronary heart disease.A number of epidemiologic research and animal studies have provided evidences that intake of TFAs increases the risk of nervous system impairment.TFAs may have desirable effects on neurons implicated in learning and memory.However,the mechanisms of these effects on nervous system are not yet clearly known.Wistar rats were administered with TFAs.The activities of antioxidant enzyme,adenosine triphosphatase(ATPase),acetylcholinesterase(AChE)and nitric oxide synthase(NOS)and the contents of essential elements in rats,brain were determined;The morphological changes and apoptosis of hippocampus of rats were observed,to investigate and discuss the effects of TFAs on nervous system injuries in rats.Methods 1.Animal grouping and exposure48 male Wistar rats were randomly divided into four groups of 12 rats in each,including control group,TFAs groups with low(L-TFA),medium(M-TFA)and high(H-TFA)dosages.In control group,only corn oil was applied.And rats in TFAs groups received different dosages of TFAs with 50 mg/kg,100 mg/kg,and 150 mg/kg,respectively.All solutions above were administrated via oral gavage every day for 12 weeks.Two rats selected from each group were perfused by 4%paraformaldehyde after the administration stage.Their brains were quickly removed and fixed in 4%paraformaldehyde to make paraffin section for hematoxylin-eosin(HE)staining and TUNEL test.The other rats were killed by decapitation.Brains were quickly removed and isolated cortex and hippocampus.Blood was immediately collected,and was centrifuged at 3,000 g for 5 min at 4 ? to collect serum.All samples were saved in the temperature of-80? for the use of bioassays.2.General growth and development status of ratsThe eating situation,athletic ability and behavior changes of rats were observed everyday.Rats were weighed every week.The brain were seperated and weighed for calculating the coefficient of brain tissue.3.Determination of antioxidant system in cortex of ratsThe content of Malondialdehyde(MDA),the activities of Superoxide dismutase(SOD)and Glutathione peroxidase(GSH-Px)were measured immediately following the kit instructions,to investigate the effect of TFAs on antioxidant system in cortex of rats.4.Determination of antioxidant system in serum of ratsThe content of MDA,the activities of SOD and GSH-Px were measured immediately following the kit instructions,to investigate the effect of TFAs on antioxidant system in serum of rats.5.Determination of the activities of ATPase in cortex of ratsThe activities of Na+K+-ATPase,Mgt+-ATPase and Ca2+-ATPase were tested following the kit instructions,to investigate the effect of TFAs on ATPase activities in cortex of rats.6.Determination of the activities of acetylcholinesterase(AChE)and nitric oxide(NOS)in cortex of ratsThe activities of AChE and NOS were tested following the kit instructions,to investigate the effect of TFAs.7.Determination of the contents of some essential elements in brain of ratsThe samples were digested by the microwave digestion system and tested by flame atomic absorption spectrophotometry.8.Histopathological observation of rat hippocampusThe paraffin sections were prepared and stained by Hematoxylin-eosin.Sections were observed under microscope to observe the morphological changes of hippocampus of rats.9.Determination of apoptosis in hippocampus of ratsThe paraffin sections were operated following the in situ cell death detection kit,POD(Roche)as described by the manufacturer.The sections were then visualized using a microscope.The expression of Bcl-2 and Bax mRNA were analyzed by RT-PCR to investigate the effect of TFAs on apoptosis in hippocampus of rats.Results1.Effects of TFAs on general growth and development status of ratsAfter 12 weeks of exposure,rats in control group were in good condition with smooth and shiny fur,and maintained good response and athletic ability.The rats in TFA groups appeared poor diet,poor spirit,fluffy and dull fur.Tthe body weight of all rats increased over time.Starting from the 3rd week,it was shown a significant decline(P<0.05)in body weight gain in high-dose TFA group.The brain coefficient showed a significant increase in high-dose TFA group,as compared to the control group.2.Effects of TFAs on antioxidant system in cortex of ratsExposure to TFAs raised the level of MDA and decreased activities of GSH-Px and SOD in cortex,as compared to the control rats.The activity of GSH-Px in medium-and high-dose TFA groups and the activity of SOD in all TFA groups were significantly decreased(P<0.05),while the level of MDA in the TFA groups showed a significant increase(P<0.05).3.Effects of TFAs on antioxidant system in serum of ratsExposure to TFAs raised the level of MDA and decreased activities of GSH-Px and SOD in serum,as compared to the control rats.The activity of GSH-Px and SOD in medium-and high-dose TFA groups were significantly decreased(P<0.05),while the level of MDA in all TFA groups showed a significant increase(P<0.05).4.Effects of TFAs on the activities of ATPase in cortex of ratsTFAs caused a reduction of Na+K+-ATPase,Mg2+-ATPase,and Ca2+-ATPase in rat cortex,as compared to those activities in the control rats.The activities ofNa+K+-ATPase and Ca2+-ATPase were significantly reduced in the TFA groups(P<0.05).Besides,administration of TFAs caused a significant reduction of Mg2+-ATPase in the medium-and high-dose TFA groups(P<0.05).5.Effects of TFAs on the activities of AChE and NOS in cortex of ratsCompared to the control group,NOS activities in medium-,and high-dose TFA groups showed an apparent increase(P<0.05).Significant decreases in AChE activity were observed in all TFA groups(P<0.05),as compared to the activity in control group.6.Effects of TFAs on the contents of essential elements in brain of ratsThere were significantly lower levels of Mg and Fe in all TFA groups(P<0.05).Zn levels were significantly lower in the medium-and high-dose TFA groups(P<0.05).However,TFAs had no apparent effect on Ca and Cu contents(P>0.05).7.Effects of TFAs on histopathologic injury in hippocampus of ratsCompared to control group,the neuronal lines of hippocampal c-type structure in low-,medium-,and high-dose TFA groups seemed thinner and more blurred.Neuron numbers in hippocampus were decreased with loose and disordered arrangement in TFA groups.Some neural cells appeared karyopyknosis and trachychromatic cytoplasm.8.Effects of TFAs on apoptosis in hippocampus of ratsIn the study,compared to the control group,the positive cells in TFA groups were not apparently increased.There were no significant differences in the expressions of Bcl-2 and Bax mRNA among the groups(P>0.05).ConclusionsTFAs intake could effect the activities of antioxidant system,ATPase,NOS and AChE,lead to the imbalance of essential elements levels;and TFAs intake may cause the morphological changes of hippocampus of rats.But in this study,the effect of TFAs on apoptosis of hippocampal cells was not observed.