Associations of Mitochondrial DNA Alterations with Alzheimer's Disease Related Brain Health

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ABSTRACT Dementia is a major global health challenge that lacks effective treatment and early diagnosis tools. Alzheimer’s disease (AD) comprises 70% of all dementia syndromes. The Lancet Commission recently urged a life-course model of AD prevention, providing impetus for the development of scalable early biomarkers. Mitochondria play a critical bioenergetic role in maintaining physiologic homeostasis, particularly for high energy demand organs, like the brain. Mitochondrial DNA (mtDNA) copy number (mtDNA-CN), a quantitative indicator of mitochondrial function, is strongly associated with AD in older adults. Growing evidence also implicates mtDNA mutation load, or mtDNA heteroplasmy (mtDNA-Het), in AD. Despite the accumulating evidence for a key role of these blood indicators in cognitive decline and AD in older adults, there is a paucity of research examining their relationships in midlife, a critical time when preventive interventions may be most effective. Moreover, the relationships between these mtDNA alterations and early emerging AD-related neurobiological substrates is unclear. While cardiovascular disease (CVD) risk factors have also been associated with mtDNA alterations, the temporal associations are not fully discerned. Whether mtDNA alterations could mediate the well-known but less well understood associations of heart and brain health is unknown. Our central hypothesis is that mtDNA alterations are associated with cognitive decline and AD-related neurobiological substrates in midlife and mediate the associations of early life CVD risk factors with midlife brain health. To test this hypothesis, we will leverage life- long measures of CVD risk factors and two midlife measures of cognitive function in the full Bogalusa Heart Study (BHS) cohort (N=1,298; 850 whites and 448 Blacks), along with AD-related neurobiological substrates from brain magnetic resonance imaging (MRI) and photon emission tomography (PET) scans available in a large subsample at midlife (N=700). Within the BHS, we further propose measurement of mtDNA alterations at two midlife time-points. Our well-powered validation effort will be conducted among diverse participants from the Trans-Omics for Precision Medicine program (N=3,724) with existing data. These resources will allow us to examine the prospective and temporal associations of mtDNA alterations with cognitive decline (Aim 1) and neurobiological substrates in midlife (Aim 2); and assess prospective and temporal associations of early life CVD risk factors with mtDNA and investigate mediating effects of mtDNA on associations of childhood CVD risk factors with midlife brain health (Aim 3). Our work could have broad impacts on population-wide and targeted efforts to curb dementia, informing drug development and risk stratification. The K99 training will allow me to conduct the first study examining prospective associations of midlife mtDNA with cognitive decline. Mentored by a team of experts in epidemiology, genomics, and neurobiological aging and led by my primary mentor Dr. Kelly, this award will undoubtedly accelerate my career independence in multi-omics research of brain aging.