The Study Of MRS Differences At Different Regions Of Bilateral Hippocampal In Process Of Brain Aging

Objective: To evaluate the metabolism changes with aging brain in thedifferent regions of the bilateral hippocampal using proton magnetic resonancespectroscopy(1H-MRS), and to further investigate the correlations betweenmetabolites, metabolite concentrations ratio and age. By exploring theregulation of normal aging in the different regions of the bilateral hippocampal,to lay the foundation for the early diagnosis and treatment of hippocampalrelated diseases.Methods: Brain conventional MRI, MRS were employed in a total of121right-handed healthy volunteers (62male and59female, age range20~89years, average age48.5±16.5).They were stratified into three age groups,youth (age range20~44years), middle-aged (age range45~59years) andelderly group (age range60~89years), with about forty subjects for each.After selecting the regions of interest artificially,the required parametersNAA,Cho,Cr,NAA/Cr,Cho/Cr were measured by the machine automatically.The SPSS13.0statistics software was used for the statistical inference. The ttest(two-sample/group t-test)was used to compare each statistical indexbetween right and left, male and female.The ANOVA (least significantdifference, LSD)was used to compare each statistical index among differentage groups. Statistical significance was designated at P<0.05. Finally, Pearsoncorrelation analysis was used to further investigate the correlations betweenthe concentrations of NAA, Cho, Cr and age in different parts of thehippocampus.Results:1Concentration of NAA was negatively correlated with age in bilateralhippocampal head, body (body1area, body2area), and tail (P＜0.05).Concentrations of Cho, Cr had no significant linear correlation with age in bilateral hippocampal head, body (body1area,body2area), and tail (P>0.05).2Age effect on metabolite concentrations:The concentration of NAA was significantly different between elderlygroup and youth group (P1-3＜0.05), as well as between elderly group andmiddle-aged group (P2-3＜0.05) in the bilateral hippocampal head, body(body1area,2area), tail. In the elderly group was significantly lower than thatof in youth and middle-aged groups,but there is no significantly differencebetween youth and middle-aged group(P>0.05). The concentrations of Cho,Cr had no significant statistical difference among the three age groups of thebilateral hippocampal head (P>0.05). The concentration ratios of NAA/Crwas significantly different in bilateral hippocampal head between the elderlygroup and youth group(P1-3＜0.05), between elderly group and middle-agedgroup(P2-3<0.05),at the same time,the elderly group was lower than the youthand middle-aged groups, but there was no statistical difference between youthand middle-aged group(P>0.05).Only in bilateral hippocampal body1area,lefthippocampal body2area, left hippocampal tail,we found significantlydifference on the ratio of NAA/Cr between the elderly group and youth group(P1-3<0.05).The concentrations of Cho,Cr,and the concentration ratio ofCho/Cr had no statistical significance among the three age groups in thehippocampal head,body(body1area,body2area),and tail(P＞0.05).3Gender effect on metabolite concentrations: No significant gender effectswere found in the concentrations of NAA, Cho, Cr and the concentrationratios of NAA/Cr, Cho/Cr (P>0.05).4Laterality differences on metabolite concentrations:In hippocampal head, there was no significant laterality differences wasfound in the concentrations of NAA, Cho, Cr,and the concentration ratios ofNAA/Cr, Cho/Cr (P＞0.05).In hippocampal body1area, there was significant laterality differenceswas found in the concentrations of NAA,Cho,Cr(P<0.05), the right was higherthan the left; While in hippocampal body1area, there is no significantlaterality differences was found in the concentration ratios of NAA/Cr, Cho/Cr (P>0.05);In hippocampal body2area, there was significant laterality differenceswas found in the concentrations of NAA,Cho,Cr(P<0.05), the right higherthan the left; while in hippocampal body2area, there was no significantlaterality differences was found in the concentration ratios of NAA/Cr,Cho/Cr(P>0.05);In hippocampal tail, there was significant laterality differences was foundin the concentrations of NAA, Cho, Cr(P <0.05), and the right higher than theleft; While in hippocampal tail, there was no significant laterality differenceswas found in the concentration ratios of NAA/Cr, Cho/Cr (P>0.05).Conclusion:1It was completely feasible to evaluate that whether there was a rule wefound that each part of the hippocampal’s metabolic substances had changedalong with the age.2The concentration of NAA was significantly decrease in elderly group,while there were no changes between young and middle aged groups in everypart of the hippocampus.The result showed that there was significantdifference between the concentration of NAA and the concentration ratio ofNAA/Cr,so it proved that the result of the concentration ratio of NAA/Cr isthe outcome of the interaction of the concentrations of NAA,Cr.So I thoughtwhen observed changes in neurons and axons the concentration of NAA wasmore accurate than the concentration ratio of NAA/Cr.In same region of thehippocampus,We found the concentrations of Cho,Cr had no differencesamong the different age groups.3The concentration of NAA decreased with the increasing age in thehippocampal head, body(body1area, body2area) and tail; But there were nolinear relationships between Cho,Cr and ages.4The concentrations of NAA, Cho, Cr, and the concentration ratios ofNAA/Cr,Cho/Cr had no gender differences in every parts of the bilateralhippocampal.5Hippocampal body (body1area, body2area), tail showed significant laterality differences in the concentrations of NAA, Cho, Cr, and the right washigher than the left; Hippocampal body(body1area, body2area), tail had nosignificant laterality differences in the concentration ratios of NAA/Cr,Cho/Cr;The concentrations of NAA,Cho,Cr,and the concentration ratios ofNAA/Cr, Cho/Cr had no significant laterality differences in the hippocampalhead.