Relationship between mitochondrial DNA polymorphism and the individual differences in aerobic performance

This study focused on the mitochondrial DNA (mtDNA) as the genetic factor m ost likely to bring about the individual difference in endurance capacity o r its trainability. Platelets contain mtDNA but no nuclear DNA, whereas rho (0)-HeLa cells have nuclear DNA but no mtDNA. The oxidative capacity of mi tochondria in the cultured cells, which were fused rho (0)-HeLa cell with p latelets obtained from individual subjects (the so-called "cybrids"), refle cts the individual mtDNA polymorphism in the gene-coding region. The purpos e of this study was to investigate the relationship between the oxidative c apacity of cybrids and the individual difference in endurance capacity, or its trainability. Forty-one sedentary young males took part in an 8-week en durance training program. They were determined by using their (V) over dot O-2max as an index of endurance capacity on an ergocycle before and after t he endurance training program. The relations between (V) over dot O-2max be fore endurance training or the change of it by endurance training and the o xidative capacity of cybrids were investigated. There was no relation betwe en them, and two groups were drawn from all subjects, based on one standard division of their initial (V) over dot O-2max: the higper pre-(V) over dot O-2max group (n=6) and the lower pre-(V) over dot O-2max group (n=5) (51.8 +/- 3.5 ml/min/kg vs. 33.3 +/- 3.8 ml/min/kg, p<0.01). No significant diff erence was found between the O-2 consumption of the cybrids in the higher i nitial (V) over dot O-2max group and that in the lower initial (V) over dot O-2max group (16.3 +/- 4.9 vs. 15.9 +/- 2.0 nmol O-2/min/10(7) cells, NS). Furthermore, neither the cytochrome c oxidase (COX) activity nor the compl ex I+III activity of cybrids showed a significant difference between the tw o groups. The oxidative capacity of cybrids between the high trainability g roup (n=6) (<Delta>(V) over dot O-2max 12.1 +/- 1.6 ml/min/kg) and the low trainability group (n=9) ((V) over dot O-2max 2.3 +/- 0.5ml/min/kg) was als o similar. Thus the mtDNA polymorphism is very unlikely to relate to the in dividual difference in endurance capacity or its trainability in young sede ntary healthy subjects.