Correlation of Body Mass Index and Exercise on Telomere Length and Mitochondrial <scp>DNA</scp> Copy Number in Saliva Samples

Mitochondrial DNA (mtDNA) copy number and telomere length are widely recognized as biomarkers of cellular aging and metabolic health. This study aimed to investigate the relationships between BMI, exercise modality, mtDNA copy number, and telomere length using saliva samples from Iranian adults. Participants (n = 96) were categorized into four groups: endurance athletes, strength athletes, overweight/obese individuals (BMI > 25), and healthy controls (BMI 18-25). Saliva samples were collected for DNA extraction, and mtDNA copy number and telomere length were quantified using real-time PCR. Statistical analyses included Kruskal-Wallis and Dunnett's post hoc tests, as well as linear regression to assess correlations among variables. The results indicated that endurance athletes exhibited a significantly higher mtDNA copy number compared to controls and strength athletes, reflecting enhanced mitochondrial biogenesis from aerobic training. No significant differences in telomere length were observed among groups. While BMI showed no significant correlation with telomere length or mtDNA copy number overall, a significant negative correlation between mtDNA copy number and BMI was found exclusively in endurance athletes. Additionally, a strong positive correlation between mtDNA copy number and telomere length was observed in all groups except strength athletes. No significant differences were found between saliva and blood samples for either biomarker, and women demonstrated longer telomeres than men. This study highlights the positive impact of endurance exercise on mitochondrial biogenesis while revealing complex relationships between BMI, exercise modality, and cellular aging biomarkers. These findings offer insights into exercise-specific effects on cellular aging.