Background/Objectives: Telomeres and the enzyme telomerase play essential roles in cellular aging and cardiovascular health. Physical activity is thought to influence telomere dynamics via upregulation of the hTERT gene, which encodes the catalytic subunit of telomerase. However, data on this relationship in middle-aged endurance athletes remain limited. This study aimed to investigate the association between long-term endurance training, cardiac structural adaptations, and hTERT gene expression in middle-aged elite athletes. Methods: A total of 38 middle-aged elite runners and 37 age-matched sedentary controls were enrolled. Echocardiographic assessments, VO₂peak measurements, and hTERT gene expression analysis using RT-PCR were conducted. Left ventricular mass (LVM), wall thicknesses, and cardiac volumes were compared, and correlations with hTERT expression were analyzed. Results: Athletes demonstrated significantly higher VO₂peak and echocardiographic parameters including LVEDD, LV mass, and wall thicknesses (p < 0.05). hTERT gene expression was 2.06-fold higher in athletes compared to controls. Significant positive correlations were observed between hTERT expression and VO₂peak, LVM, LV wall thicknesses, and right ventricular parameters. Conclusions: These findings suggest that regular aerobic exercise may contribute to both improved cardiovascular performance and cellular longevity by enhancing telomerase-related mechanisms.

Background/Objectives: Telomeres and telomerase play crucial roles in cellular aging and genome stability. Emerging evidence indicates that alterations in telomerase activity and telomerase reverse transcriptase (hTERT) gene expression may be involved in cardiovascular pathophysiology. However, data on telomerase regulation in patients with stable coronary artery disease (CAD) are limited. This study aimed to compare serum telomerase concentration and hTERT gene expression levels between patients with stable CAD and healthy controls. Methods: A total of 52 patients diagnosed with stable CAD and 50 age-matched healthy controls were enrolled prospectively. Telomerase concentrations were measured in serum samples using the ELISA method, and hTERT mRNA expression was measured in blood samples using RT-PCR. Results: Serum telomerase levels were significantly higher in patients with stable CAD compared with controls (p < 0.05). Similarly, hTERT gene expression was upregulated in the patient group (p < 0.05). Multivariable analysis showed that increased log-transformed telomerase levels (AOR: 2.12, 95% CI: 1.14–5.13, p = 0.024) and hTERT expression (AOR: 1.79, 95% CI: 1.09–3.27, p = 0.037) were independently associated with coronary vessel involvement in stable CAD. These findings indicate an increase in both telomerase level and hTERT transcriptional activity in stable CAD. Conclusions: Increased telomerase level and hTERT expression may reflect a compensatory response to chronic vascular stress and are associated with disease severity in stable CAD.