Mitochondrial Genome Characterization In Male World-class Elite Endurance Athletes

PURPOSE: This study aimed to assess the role of the mitochondrial genome in male world-class elite endurance athletes (EEA), part of the GENATHLETE cohort. METHODS: We isolated DNA from whole blood samples of 153 World-Class male EEA aged 16 – 48 years of European descent. We amplified the mitochondrial DNA (mtDNA) by long-range PCR, tagged with Nextera libraries and sequenced on a MiqSeq Instrument. The subjects were deemed elite endurance athletes based on participation in international and world championship events, including biathlon, cross-country skiing, cycling, and running, plus having a maximal aerobic capacity (VO2max) of 75.0 mL/kg/min or greater. We used MITOMAP to characterize mtDNA haplogroups and the Eupedia database to query haplogroup distribution in individuals with European ancestry. The Cambridge Reference Sequence database was used to compare EEA and identify informative mtDNA variants, which we defined as occurring in 50% or more of the EEA and not present in the reference genome. We also assessed mtDNA copy with a gene-specific assay using Digital Droplet PCR. RESULTS: We found 12 major haplogroups among the 153 EEA (Percent of EEA with haplogroup: H = 46.4%; I = 1.3%; J = 7.8%; K = 5.2%; L = 0.7%, N = 0.7%, R = 2.0%; T = 11.1%; U = 16.3%, V = 3.3%, W = 2.0%, and X = 3.3%). This EEA haplogroup distribution was similar to that reported across the literature in populations of European ancestry (Mean difference across haplogroups: 0.4% ± 0.03%). We identified 26 informative mtDNA variants, where 20 were in protein coding regions of the mitochondrial genome (mtND2, mtCO1, mtATP6, mtND4, mtND5, and mtCYB genes), five in ribosomal RNA regions (mtRNR1 and mtRNR2 genes), and 1 in the hypervariable region (mtHV2 gene). Of these 26 informative variants, 16 were non-haplogroup markers in mtND2 (1 site), mtCO1 (1 site), mtCYB (12 sites), and mtRNR2 (2 sites) genes. We did not find that mtDNA copy numbers differed by haplogroups in EEA (p = 0.18). CONCLUSION: Haplogroup distribution among EEA was comparable to the general population of European descent. However, 16 non-haplogroup markers originating in protein coding and ribosomal regions of the mitochondrial genome may have significant relevance to EEA status and exceptionally high VO2max.