Changes In Different Chain Lengths Of Saturated Fatty Acids In Elderly Brain And Its Impact On Aβ Metabolism In SH-SY5Y Cell

Background:In recent years, many investigations show that the composition of fatty acids in dietary and the composition and content of fatty acids in brain and serum were associated to the ability of brain cognitive and the incidence of Alzheimers’disease, but there is no clear consensus conclusion about composition characteristics of the unsaturated fatty acid in aging brain, this research needed to be more elucidated.Alzheimer’s disease (AD) is the most common types of senile dementia, β-amyloid (Aβ) is a key factor to the pathogenesis of AD. The recent studies have shown that high saturated fat diet is a risk factor for AD, Nerveless, there is no research report in domestic and abroad demonstrate whether different carbon chain length of saturated fatty acids have different effects on Aβ metabolism.Objective:This experiment discuss the changes in different chain lengths of saturated fatty acids in elderly brain and the impacts of different chain lengths of saturated fatty acid on Aβ metabolism in SH-SY5Y. its aim to provide experimental basis that aim to clarify the mechanism of elderly brain related neurodegenerative disease.Methods:Part Ⅰ:This experiment uses 22 months and 3 months old male SD rats as the subjects, the gas chromatographic method is applied to analyze the unsaturated fatty acid composition and content of the young and old rat’s cerebral cortex.Part Ⅱ:The SH-SY5Y cells were randomly divided into 4 groups, the control group (Control group), C16:0 group, C20:0 group and C26:0 group, it observes the cell morphology by fluorescent inverted microscope and uses ELISA method to measure Aβ content in cell culture, cell as APP, ADAM 10, BACE1, PS1, NEP was determined by semi-quantitative RT-PCR method, which cell were all gene expression of A(3 metabolism related factors. Finally, it uses fluorescent probe DCFH-DA method to detect intracellular reactive oxygen species (ROS) level.Result:Part I:Gas chromatographic analysis results show that the cortex of elderly group and young group contains 16 kinds of fatty acids; this experiment takes quantitative analysis on fatty acids through peak area normalization method, its purpose to comparing the saturated fatty acid content in young group’s cerebral cortex to elder one. In elderly group, the result shows that saturated fatty acid using C18:0 content significantly decreased, saturated fatty acid C20:0, C24:0 levels were significantly higher, C20:0 level also has the rising trend, which all above compared with young group.Part Ⅱ:1. The purpose of the experiment was to explore the effects of Aβ metabolism in SH-SY5Y cell, Which had selected three kinds of fatty acids C16:0, C20:0, C26:0 as experimental subjects, it was equal to carry out this experiment under the condition of physiological concentration had been reached by 10μmol/L and 15μmol/L, what has been dicussed above that based on comprehensive experiment determined by MTT, cell morphological observation and LDH experimental results.2. Secretory volume of Aμ cell, When fatty acid concentration was 10μmol/L, Aβ40 secretion in group of C26:0 was significantly higher than that in the control group; there was a increased trend of Aβ40 secretion in group of C20:0 compared to control group. When the concentration reached by 15μmol/L, Aβ40 secretion in group of C26:0 was slight higher than control group.3. The relative expression amount of APP mRNA:The relative expression amount of APP mRNA in group of C26:0 is significantly higher than that in control groupand C20:0 group when concentration reached by 15μmol/L. The relative expression amount of ADAM10:The relative expression amount of ADAM10 in group of C16:0was significantly lower than that in control group, and was lower significantly than other groups of C20:0, C26:0 when concentration reached by 10μmol/L. The relative expression amount of BACE1:the relative expression amount of BACE1 mRNA in group of C26:0 was higher significantly than control groupand group of C16:0, and had an increasing trend compare to group of C20:0when concentration reached by 10μmol/L. The relative expression amount of PS1:this experiment showed that the relative expression amount of PS1 mRNA in group of C16:0, C20:0 and C26:0 was higher significantly than that in control group. The research result also showed that the relative expression amount of PS1 mRNA in group of C20:0 is higher significantly than what in control groupand group of C26:0 when concentration reached by 15μmol/L. The relative expression amount of NEP: there was no statistical sense to difference of relative expression amount of NEP mRNA in every group when concentration was at 10μmol/L and 15μmol/L.4. there was no statistical sense to difference of level of ROS in control group and group of C16:0. it illuminated that level of ROS in group of C20:0 and C26:0 was higher significantly than that in control group and group C16:0 and level of ROS in group of C26:0 was higher significantly than that in group of C20:0 when concentration reached by 10μmol/L and 15μmol/L.Conclusion:1.The composition of elderly rats’cortex saturated fatty acid is different from young rats’, although the aging brain’s C18:0 reduce, but the longer chain saturated fatty acid C20:0 and C24:0 increase.2.In three kinds of saturated fatty acids C16:0, C20:0 and C26:0, saturated fatty acids with longer carbon chain would not only contribute greatly to promote the secretion of Aβ, but also enhance the expression effect of APP, BACE1 and PS1 mRNA, however, what has been mentioned substance would not affect the expression of NEP mRNA.3.The metabolic mechanism of Aβ is influenced by saturated fatty acids, the affected reason may be related to the production of ROS increased.