@article {9323, title = {Association of Mitochondrial DNA Copy Number With Brain MRI Markers and Cognitive Function: A Meta-analysis of Community-Based Cohorts.}, journal = {Neurology}, year = {2023}, month = {2023 Mar 16}, abstract = {

BACKGROUND AND OBJECTIVES: Previous studies suggest lower mitochondrial DNA (mtDNA) copy number (CN) is associated with neurodegenerative diseases. However, whether mtDNA CN in whole blood is related to endophenotypes of Alzheimer{\textquoteright}s disease (AD) and AD related dementia (AD/ADRD) needs further investigation. We assessed the association of mtDNA CN with cognitive function and MRI measures in community-based samples of middle-aged to older adults.

METHODS: We included dementia-free participants from nine diverse community-based cohorts with whole-genome sequencing in the Trans-Omics for Precision Medicine (TOPMed) program. Circulating mtDNA CN was estimated as twice the ratio of the average coverage of mtDNA to nuclear DNA. Brain MRI markers included total brain, hippocampal, and white matter hyperintensity volumes. General cognitive function was derived from distinct cognitive domains. We performed cohort-specific association analyses of mtDNA CN with AD/ADRD endophenotypes assessed within {\textpm}5 years (i.e., cross-sectional analyses) or 5 to 20 years after blood draw (i.e., prospective analyses) adjusting for potential confounders. We further explored associations stratified by sex and age (<60 vs. >=60 years). Fixed-effects or sample size-weighted meta-analyses were performed to combine results. Finally, we performed Mendelian randomization (MR) analyses to assess causality.

RESULTS: We included up to 19,152 participants (mean age 59 years, 57\% women). Higher mtDNA CN was cross-sectionally associated with better general cognitive function (Beta=0.04; 95\% CI 0.02, 0.06) independent of age, sex, batch effects, race/ethnicity, time between blood draw and cognitive evaluation, cohort-specific variables, and education. Additional adjustment for blood cell counts or cardiometabolic traits led to slightly attenuated results. We observed similar significant associations with cognition in prospective analyses, although of reduced magnitude. We found no significant associations between mtDNA CN and brain MRI measures in meta-analyses. MR analyses did not reveal a causal relation between mtDNA CN in blood and cognition.

DISCUSSION: Higher mtDNA CN in blood is associated with better current and future general cognitive function in large and diverse communities across the US. Although MR analyses did not support a causal role, additional research is needed to assess causality. Circulating mtDNA CN could serve nevertheless as a biomarker of current and future cognitive function in the community.

}, issn = {1526-632X}, doi = {10.1212/WNL.0000000000207157}, author = {Zhang, Yuankai and Liu, Xue and Wiggins, Kerri L and Kurniansyah, Nuzulul and Guo, Xiuqing and Rodrigue, Amanda L and Zhao, Wei and Yanek, Lisa R and Ratliff, Scott M and Pitsillides, Achilleas and Aguirre Pati{\~n}o, Juan Sebastian and Sofer, Tamar and Arking, Dan E and Austin, Thomas R and Beiser, Alexa S and Blangero, John and Boerwinkle, Eric and Bressler, Jan and Curran, Joanne E and Hou, Lifang and Hughes, Timothy M and Kardia, Sharon L and Launer, Lenore and Levy, Daniel and Mosley, Tom H and Nasrallah, Ilya M and Rich, Stephen S and Rotter, Jerome I and Seshadri, Sudha and Tarraf, Wassim and Gonz{\'a}lez, Kevin A and Ramachandran, Vasan and Yaffe, Kristine and Nyquist, Paul A and Psaty, Bruce M and DeCarli, Charles S and Smith, Jennifer A and Glahn, David C and Gonz{\'a}lez, Hector M and Bis, Joshua C and Fornage, Myriam and Heckbert, Susan R and Fitzpatrick, Annette L and Liu, Chunyu and Satizabal, Claudia L} }