Abstract P198: Associations Between Plasma Proteome and Leukocyte Mitochondrial DNA Copy Number: The Atherosclerosis Risk in Communities Study (ARIC)

Introduction: The number of copies of the mitochondrial genome, termed mitochondrial DNA copy number (MTCN), is a proxy for mitochondrial function and varies by cell. Critically, lower MTCN has been associated with aging and chronic diseases such as dementia and cancer. We conducted a large-scale proteomics analysis of leukocyte MTCN (L-MTCN) to elucidate pathways modulated by L-MTCN that may be involved in diseases of aging. Hypothesis: We hypothesize that L-MTCN is significantly associated to plasma proteins that have been implicated in biological pathways of L-MTCN and related diseases. Methods: Based on whole genome sequencing (WGS) data measured in samples collected in ARIC visits 1, 2, and 3 (i.e., baseline for the current study), L-MTCN was calculated as (2 * coverage of the mitochondrial genome) / coverage of the autosome, using the median coverage of 1000 base pair bins overlapping the mitochondrial genome (16 total) and the median coverage of ~142,000 higher quality autosomal bins. Only samples with read lengths of 150 or 151 were included in subsequent analyses, and L-MTCN estimates were inverse normalized within read length group and WGS group before being merged together. This normalized L-MTCN was then analyzed as a predictor for an association with 4,870 plasma proteins measured by SOMAscan v4 in ARIC visit 3 in race-specific generalized linear models, adjusting for the following covariates at baseline: WGS sample visit, age, gender, field center, smoking status, and a measure of kidney function. Bonferroni correction was applied to account for the number of proteins tested in 5,007 White participants (p≤1x10 -5 ). Associations were tested for replication in 1,178 Black participants and considered significant if protein estimates had the same direction of association as Whites at p-value ≤ 2.2x10 -4 . Results: Among White participants, 230 proteins were significantly associated with L-MTCN. Of these proteins S100A9, GP1Bα, EGFR, THBS2, and FCGR3B were significantly replicated among Black participants. Strongest associations with L-MTCN were seen with GP1Bα (Estimate: 0.121) and S100A9 (Estimate: -0.191). Biologically S100A9 is a calgranulin and together with S100A8 forms calprotectin, which have roles mediating inflammatory processes. GP1Bα helps mediate platelet activation and forms the glycoprotein Ib-IX-V complex which acts as a platelet surface receptor for von Willebrand factor facilitating platelet adhesion. Conclusion: This large proteomics analysis identified 230 plasma proteins significantly associated with L-MTCN. Some of the proteins have been connected to inflammatory diseases, cardiovascular disease, and cancer in the literature. These results provide insight into proteins involved in biological pathways related to L-MTCN.