Effect Of Electroacupuncture At Tinggong And Yifeng On Aging Of Auditory Cortex In Guinea Pigs With Age-related Hearing Loss By D-galactose Through SIRT1/PGC-1α Pathway

Objective:To investigate the role of SIRT1/PGC-1αpathway in the auditory cortex aging of guinea pigs with age-related hearing loss and whether the electroacupuncture at Tinggong and Yifeng can delay the aging process of the auditory cortex in the aged guinea pigs induced by D-galactose through the regulation of SIRT1/PGC-1αpathway.Methods:1.Animal grouping.There were four groups.The elderly group was composed of ten 18-month-old guinea pigs.Thirty 4-month-old guinea pigs with no history of noise and normal acoustic pinna reflex were randomly divided into three groups including the control group（n=10）,D-galactose group（model group,n=10）,and D-galactose and electroacupuncture group（electroacupuncture group,n=10）.2.Animal modeling.The guinea pigs in model group and electroacupuncture group had been subcutaneously injected with D-galactose(300mg·kg^-1·d^-1)for 6 weeks.Besides,the guinea pigs in Electroacupuncture group were electroacupunctured at Tinggong and Yifeng for 15 minutes once a day for 6 weeks.3.Audiometry.After 6 weeks,the ABR thresholds and ABR waveⅢlatency at 110 dB SPL were detected respectively in guinea pigs of each group.4.Real-time quantitative PCR（RT-qPCR）.The total RNA was extracted from the auditory cortex of each group,and the expressions of SIRT1 and PGC-1αwere tested at mRNA level respectively by RT-qPCR.5.Western Blot.The total protein was extracted,and the expressions of SIRT1 and PGC-1αwere tested in auditory cortex of all guinea pigs at protein level respectively by Western Blot.6.Statistical methods.Data was expressed as mean？±standard deviation（？±s）,and analyzed by One-Way ANOVA test using SPSS17.0 software.P<0.05means statistical significance.Results:1.The changes in weight.There was no statistic difference in the weight of the guinea pigs in the control group,model group and electroacupuncture group before and after the experiment（P>0.05）.2.The average latent period of the third wave of ABR.The average latent period of the third wave of ABR of control group,model group,electroacupuncture group and elderly group were 2.89±0.09 ms,3.43±0.09ms,3.02±0.08 ms and 3.49±0.10 ms respectively when stimulus intensity was 110 dB SPL.There was a significant increase in the average latent period of the third wave of ABR in the model group and elderly group（P<0.001,compared with the control group）,and decrease in the electroacupuncture group（P<0.001,compared with the model group）.3.The threshold of ABR.The ABR thresholds in the control group,model group,electroacupuncture group,and elderly groups were（35.75±4.66）,（74.5±5.59）,（44.4±7.92）and（76.5±7.8）dB SPL respectively.There was a significant difference in the thresholds of ABR of the model group and elderly group in comparison with the control group,and the same change between electroacupuncture group and model group（P<0.01）.There was no significant difference between the elderly group and model group（P>0.05）.4.The mRNA expression of SIRT1 and PGC-1αin auditory cortex.The fold change of SIRT1 mRNA in auditory cortex of control group,model group,electroacupuncture group and elderly group were 1.00±0.00,0.52±0.05,0.87±0.05 and 0.55±0.07,respectively.Moreover,the fold change of PGC-1αmRNA in auditory cortex of control group,model group,electroacupuncture group and elderly group was 1.00±0.00,0.56±0.08,0.89±0.04 and 0.56±0.12,respectively.There was a significant down-regulation of SIRT1 and PGC-1αin the model group and elderly group（P<0.05,compared with the control group）,and up-regulation in the electroacupuncture group（P<0.05,compared with the model group and elderly group）.Furthermore,there was no statistic difference between the elderly group and model group（P>0.05）.5.The protein expression of SIRT1and PGC-1αin auditory cortex.The average gray value of SIRT1 protein in auditory cortex was 1.32±0.06,0.67±0.02,1.19±0.03 and 0.64±0.02respectively in control group,model group,electroacupuncture group and elderly group.In addition,the average gray values of PGC-1αprotein in auditory cortex was 1.52±0.04,0.68±0.04,1.08±0.07 and 0.67±0.03respectively in control group,model group,electroacupuncture group and elderly group.The expression of SIRT1 and PGC-1αprotein declined in the model group and elderly group（P<0.001,compared with the control group）,and increased in the electroacupuncture group（P<0.001,compared with the model group and elderly group）,and there was no significant difference between the elderly group and model group（P>0.05）.Conclusions:1.A age-related hearing loss model in guinea pig can be successfully established by continuous subcutaneous injection of D-galactose(300mg·kg^-1·d^-1)for 6 weeks.2.SIRT1/PGC-1αpathway may play a role in aging process of the auditory cortexin of guinea pigs with age-related hearing loss induced by D-galactose.3.The aging of the auditory cortex in guinea pigs may be related to the decrease of antioxidant capacity due to the down-regulation of SIRT1 and PGC-1α.4.Eelectroacupuncture at Tinggong and Yifeng may increase the antioxidant capacity,and result in delaying the aging process of auditory cortex by activating SIRT1/PGC-1αpathway in guinea pigs with age-related hearing loss.