Association Of Klotho Protein And Klotho MRNA Expression With Cognitive Impairment In The Elderly

Objective:The purpose of this study was to investigate the changes of Klotho protein and m RNA expression in peripheral blood of patients with Alzheimer’s disease(AD)and Mild Cognitive Impairment(MCI).At the same time,whether the carrying status of APOE(?)4 allele affects the expression levels of Klotho protein and m RNA was analyzed to provide a theoretical basis for the study of the pathogenesis of cognitive dysfunction in the elderly.Methods:A case-control study was conducted.According to the American psychiatric association’s diagnostic and statistical manual of mental disorders fourth edition of the AD and MCI diagnostic criteria for diagnosis,and the inclusion and exclusion criteria were strictly followed during the screening of cases.From February 2021 to April 2022,40 patients(22 males and 18 females)aged≥60 years old diagnosed with AD with an average age of 77.47±7.33 years old,40 patients(20 males and 20 females)with MCI with an average age of 74.13±6.22 years old and 80 healthy controls(40 males and 40 females)were collected in the Geriatrics Department of our hospital with an average age of 74.88±6.79 years old.First by ELISA method to detect the plasma Klotho protein levels,and then use the q RT-PCR method to detect Klotho m RNA expression of relative quantity,finally using Sanger sequencing for genotyping.Results:(1)The expression level of Klotho protein in MCI group(1.51±0.70)ng/m L was lower than that in control group 1.83(1.27,2.47)ng/m L(Z=2.204,P=0.028),but there was no significant difference between AD group and control group,or between AD group and MCI group(Z=1.803,P>0.05;Z=0.347,P>0.05).(2)The m RNA expression level of Klotho in AD group 0.57(0.34,0.83)and MCI group(0.59±0.27)was lower than that in control group 1.00(0.61,1.66±)(Z=3.998,P=0.001;Z=4.528,P=0.001),but there was no significant difference in Klotho m RNA expression level between AD group and MCI group(Z=0.507,P>0.05).(3)The frequency of APOE(?)4 allele in AD group(42.5%)was higher than that in control group(18.75%),the difference was statistically significant(χ~2=7.692,P=0.019).There was no significant difference in the frequency of APOE(?)4allele between MCI group(32.5%)and AD group(42.5%)(χ~2=0.853,P>0.05).There was no significant difference in the frequency of APOE(?)4 allele between MCI group(32.5%)and control group(18.75%)(χ~2=2.818,P>0.05).(4)According to whether APOEε4allele was carried or not,there was no significant difference in Klotho protein and m RNA expression levels between individuals withε4 allele and individuals withoutε4 allele in AD group(Z=-0.944,P>0.05;Z=-0.752,P>0.05),MCI group(Z=-0.764,P>0.05;Z=-0.765,P>0.05)and control group(Z=-0.912,P>0.05;Z=-0.955,P>0.05).(5)Multivariate Logistic regression analysis showed that carrying APOEε4 allele(OR=0.874,95%CI:0.782-0.978)was a risk factor for cognitive impairment(P<0.05),and Klotho protein(OR=0.874,95%CI:0.782～0.978)and Klotho m RNA(OR=0.874,95%CI:0.782～0.978)were protective factors for cognitive impairment(P<0.05).(6)Spearman rank correlation analysis showed that:The expression level of Klotho m RNA was positively correlated with MMSE score in the three groups(r_s=0.304,P=0.001),but no correlation was found between the expression level of Klotho protein and MMSE score or Klotho m RNA expression level in the three groups(P>0.05).(7)ROC curve analysis showed that the areas under the curve of Klotho protein,Klotho m RNA and their combination for AD diagnosis were 0.598(95%CI:0.490-0.705,P>0.05),0.717(95%CI:0.620-0.815,P<0.05)and 0.731(95%CI:0.631-0.831,P<0.05),and the areas under the curve for the diagnosis of MCI were 0.627(95%CI:0.524-0.730,P<0.05),0.764(95%CI:0.681-0.847,P<0.05),and 0.812(95%CI:0.738-0.887,P<0.05),respectively.Conclusion:(1)KLOTHO gene is associated with cognitive impairment in the elderly,and the decreased expression level of KLOTHO gene in peripheral blood may promote the development of AD and MCI.(2)Increased expression levels of Klotho protein and m RNA had a protective effect on cognitive function.(3)Carriers of the APOE 4 allele had a higher risk of cognitive impairment than those without the APOE 4 allele.(4)It was not found that whether or not carrying APOE(?)4 allele will affected Klotho protein and Klotho m RNA expression levels.(5)The plasma Klotho protein level and Klotho m RNA expression level have certain predictive value for the diagnosis of AD and MCI,and the combination of the two has the best diagnostic efficacy for AD and MCI.