title: The effects of mitochondrial DNA deletion and copy number variations on different exercise intensities in highly trained swimmers.
abstract: It has been suggested that heavy exercise might increase oxidative stress, causing mitochondrial DNA (mtDNA) mutations as well as DNA mutations and changes in the mtDNA copy number in cells. mtDNA4977 deletion is one of the most common deletions seen on mitochondria. We hypothesize association between exercise induced oxidative stress and mtDNA damage in peripheral blood lymphocytes (PBLs) of highly trained swimmers. Therefore we studied the mtDNA4977 deletion level, mtDNA copy number and their relationship with cellular ATP and oxidative stress status in PBLs of swimmers. 8 highly trained and 8 normal trained swimmers and 8 non-athlete subjects were included in the study. The mtDNA4977 deletion and amount of mtDNA were measured using RT-PCR method whereas dichlorohydrofluoroscein (DCF) assay method was used to assess cellular oxidative stress and ATP levels were measured using bioluminescence method. Even though an increase in mtDNA4977 deletion was found in all study groups, the difference was not statistically significant (p=0.98). The mtDNA copy numbers were found to be surprisingly high in highly trained swimmers compared to normal trained swimmers and non-athlete subjects by 4.03 fold (p= 0.0002) and 5.58 fold (p=0.0003), respectively. No significant differences were found between groups by means of intracellular ATP levels (p=0.406) and oxidative stress (p=0.430).  No correlation was found between mtDNA copy number and intracellular ATP content of the PBLs (p=0.703). Our results suggest that heavy training does not have a specific effect on mtDNA4977 deletion but it may be affecting mitochondrial copy numbers which may act as a compensatory mechanism related to ATP levels in blood.
authors.affiliation: Department of Medical Biology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey. obaykara@istanbul.edu.tr.
authors.forename: O
authors.initials: O
authors.lastname: Baykara
authors.affiliation: Department of Physical Education, Education Faculty, Uludag University, Bursa, Turkey.
authors.forename: S K
authors.initials: SK
authors.lastname: Sahin
authors.affiliation: Department of Medical Biology, Medical Faculty, Bezmialem Vakif University, Istanbul, Turkey.
authors.forename: F
authors.initials: F
authors.lastname: Akbas
authors.affiliation: Department of Medical Biology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: M
authors.initials: M
authors.lastname: Guven
authors.affiliation: Department of Medical Biology, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: I
authors.initials: I
authors.lastname: Onaran
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000293:Adolescent; D056352:Athletes; D056915:DNA Copy Number Variations; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism*; D015444:Exercise; D006801:Humans; D008163:Luminescent Measurements; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress / Q000235:genetics; D010991:Plethysmography; D060888:Real-Time Polymerase Chain Reaction; D012129:Respiratory Function Tests; D017384:Sequence Deletion; D013550:Swimming
chemical_list: D004272:DNA, Mitochondrial; D000255:Adenosine Triphosphate