Leukocyte telomere dynamic change in patients with mild to moderate covid-19 during three weeks of follow-up: Relation with therapy

Background: A three-year COVID-19 pandemic revealed a spectrum of disease severity and clinical manifestations. The most intriguing part of this phenomenon lays in inter-individual variability in COVID-19 course among patients, which is attributable to patient's age, comorbidities and general health status. Focus of this follow-up study was to assess leukocyte telomere length change in mild-to-moderate COVID-19 patients and concomitant influence of inflammation, oxidative stress (OS), pulmonary involvement and implemented therapy on the course of the disease. Methods: Routine biochemical/haematological parameters, markers of OS (prooxidants and antioxidants), vitamin D, IgM and IgG antibodies level and relative length of leukocyte telomeres (rLTL) were measured at three timepoints (at diagnosis, after 14 and 21 days from the disease onset) in blood samples of 31 consecutive COVID-19 patients, with a mild (n = 16) and moderate (n = 15) form of the disease, treated on an outpatient basis. Results: Although the patients had reduced rLTL at baseline (median: 0.592; 25th - 75th percentiles: 0.518­ 0.724), it significantly increased during the follow-up (median: 0.773; 25th - 75th percentiles: 0.615-0.923; P<0.01). The rate of telomere attrition was associated with the extent of OS and pulmonary involvement. During follow-up, the burden of OS was reduced, while antioxidant defence mechanisms were recovered. The use of antibiotics and N-acetylcysteine-propolis supplementation was associated with telomere lengthening. Conclusions: Results of this study revealed significant interaction between OS, inflammation and leukocyte telomere length attrition in COVID-19. Our data suggest that rRTL can be a biomarker that enables more precise therapy decision and accurate patient status estimation.