Effects Of Testosterone Propionate On Mitochondrial Biogenesis And Mitochondrial Dynamics In Hippocampal CA1 Region Of Brain Aging

Human growth is a process of gradual aging and eventually death.With the increase of age,various life activities of the body gradually weaken and the redox balance is broken,which leads to an increase in oxidative stress in the body,an increase in the production of reactive oxygen species(ROS)and a decrease in the antioxidant capacity.Studies have shown that the occurrence of aging and aging-related neurodegenerative diseases is closely related to mitochondrial dysfunction.As the main site of energy ATP synthesis,mitochondria is also the main source of ROS production and the target of attack.Mitochondrial biogenesis is an important process for cells to form new mitochondria and then maintain mitochondrial function,which is closely related to mitochondrial energy metabolism.Mitochondrial dynamics is a dynamic equilibrium process of mitochondrial division and fusion,and it is one of the mechanisms of mitochondrial self-repair defects.Recent studies have found that it is an important endogenous antioxidant transcription factornuclear factor erythroid 2-related factor 2(Nrf2)to regulate oxidative stress,it may also participate in the regulation of mitochondrial function.Based on the fact that during the aging process,there is a decline in testosterone levels and mitochondrial dysfunction in aged males and the fact that supplementation with testosterone can improve brain functional activity in aged male rats,it is speculated that the improvement of testosterone on the brain function of aged rats is related to the regulation of mitochondrial biogenesis and mitochondrial dynamic balance during aging.Therefore,in this study,Nrf2 wild and Nrf2 knockout aged male mice and gonadectomy adult male mice were selected as experimental subjects.The hippocampal CA1 region,which is closely related to learning and memory,was selected.The changes of mitochondrial biogenesis and mitochondrial dynamics-related factors expression is analyzed and the mechanism of androgen to improve brain function of aged males during aging is explored.Objective: To observe the changes of mitochondrial biogenesis and mitochondrial dynamics-related factors expression in hippocampal CA1 region of aged male mice and castrated adult male mice by testosterone propionate supplementation and explore the role of Nrf2 in this process.Methods: Nrf2 wild(WT)and Nrf2 knockout(KO)mice were divided into two periods: old and adult.The mice in the aging period included adult control,aged control and aged with TP supplementation group.The mice in the adult period included normal control group,castrated group and castrated with TP supplementation group.The TP group was injected subcutaneously at the back of 1 mg / Kg daily for 7 weeks.Hematoxylin and eosin(HE)staining was used to observe the cellular status of the pyramidal cell layer in the hippocampal CA1 region.The level of malondialdehyde(MDA)is measured by spectrophotometry,which is the end product of lipid peroxide.Real-time quantitative PCR was used to analyze mRNA expression levels of mitochondrial biogenesis and mitochondrial dynamics related factors.The protein content changes of TFAM,DRP1,and MFN1 were analyzed by immunoblotting.Result:1.HE staining in hippocampal CA1 areaCompared with the adult control group,the number of pyramidal cell nuclei in the hippocampal CA1 region of the aged control group increased and the KO aged control group increased more significantly than the WT aged control group.Compared with the WT aged control group,the number of contractions of the WT aged with TP supplementation group decreased.There was no significant difference in the number of nuclear contractions in the pyramidal cell layer of the hippocampal CA1 region between the KO aged with TP supplementation group and the KO aged control group.2.MDACompared with the adult control group,the MDA level in the hippocampal CA1 area of the aged control group increased,and the KO aged control group increased more significantly than the WT aged control group.Compared with the WT aged control group,the MDA level of the WT aged with TP supplementation group decreased.There was no significant change in MDA levels between the KO aged with TP supplementation group and the KO aged control group.Compared with the WT normal control group and the KO normal control group,respectively,the MDA level in the castrated group increased.Compared with the WT castrated group,the MDA level in the WT castrated with TP supplementation group significantly decreased and reach the level of the WT normal control group,the MDA levels in the KO castrated with TP supplementation group were lower than those in the KO castration group,but still higher than those in the KO normal control group.3.The changes in mRNA levels of mitochondrial biogenesis mitochondrial dynamics related factors.1)The changes in mRNA levels of mitochondrial biogenesisCompared with the adult control group,the mRNA levels of PGC-1?,NRF1,NRF2,and TFAM in the hippocampal CA1 area of the aged control group were reduced.Except for PGC1?,the mRNA levels of NRF1,NRF2,and TFAM in the KO aged control group were more significantly lower than those in the WT aged control group.Compared with the WT aged control group,the mRNA levels of PGC-1?,NRF1,NRF2,and TFAM in the hippocampal CA1 area of the WT aged with TP supplementation group increased,but did not reach the level of the WT adult control group.There was no significant difference in the mRNA levels of PGC-1?,NRF1,NRF2,and TFAM in the hippocampal CA1 region between the KO aged with TP supplementation group and the KO aged control group.Compared with the normal control group of two genotypes,castration reduced the mRNA levels of PGC-1?,NRF1,NRF2,and TFAM in the hippocampal CA1 region and supplementation with TP reversed the above observation indicators to the level of the normal control group.2)The changes in mRNA levels of mitochondrial dynamics related factors.Compared with the adult control group,the mRNA levels of DRP1,Fis1,MFN1,MFN2,and OPA1 in hippocampal CA1 area of the aged control group were reduced.The mRNA levels of DRP1,Fis1,MFN1,MFN2,and OPA1 in the KO aged control group were significantly lower than those in the WT aged control group.Compared with the WT aged control group,the mRNA levels of DRP1,Fis1,MFN1,MFN2,and OPA1 in the hippocampal CA1 area of the WT aged with TP supplementation group increased,but did not reach the level of the WT adult control group.There was no significant difference in the mRNA levels of DRP1,Fis1,MFN1,MFN2,OPA1 in the hippocampal CA1 region between the KO aged with TP supplementation group and the KO aged control group.Compared with normal control group of two genotypes,castration increased the mRNA levels of DRP1 and Fis1 in the hippocampal CA1 region and reduced the mRNA levels of MFN1,MFN2,and OPA1 in the hippocampal CA1 region.But supplementation with TP reversed the above observation indicators to the level of the normal control group.4.Western blotCompared with the adult control group,the protein levels of TFAM,DRP1,and MFN1 in the hippocampal CA1 area of the aged control group were reduced.Compared with the WT aged control group,the protein levels of TFAM,DRP1 and MFN1 in the hippocampal CA1 area of the WT aged with TP supplementation group increased,but did not reach the level of the WT adult control group.There was no significant difference in the protein levels of TFAM,DRP1 and MFN1 in the hippocampal CA1 region between the KO aged with TP supplementation group and the KO aged control group.Compared with normal control group of two genotypes,castration reduced the protein levels of TFAM and MFN1 and increased the protein expression levels of DRP1 in the hippocampal CA1 region.But supplementation with TP reversed the above observation indicators to the level of the normal control group.Conclusion:1.Supplementation of testosterone propionate can promote mitochondrial biogenesis and stabilize mitochondrial dynamic balance in the hippocampal CA1 region during aging.This effect depends on the presence of the transcription factor Nrf2.2.Knockout of Nrf2 aggravates mitochondrial biogenesis and mitochondrial dynamic damage in hippocampal CA1 region during aging.3.The changes of androgen levels affected Mitochondrial biogenesis and mitochondrial dynamics.