Is physical fitness associated with leucocyte telomere length in youth with type 1 diabetes?

Background: In type 1 diabetes, telomere length (TL) may predict complications and could be influenced by glycaemic control and physical activity, but its relationship with physical fitness in youths remains unexplored. The aim of the study was to assess the association between physical fitness and TL in youth with type 1 diabetes, both at baseline and one year later. Methods: Eighty-three children and adolescents (aged 6–18 years; 44.6% girls) with type 1 diabetes from the Diactive-1 Cohort Study were involved in this study. Physical fitness was assessed using spirometry on a cycloergometer (i.e., peak oxygen consumption), dynamometry, and maximal isometric strength (one-repetition maximum [1RM]), and muscle power. Leucocyte TL was assessed using multiplex monochrome real-time quantitative polymerase chain reaction. Results: Positive cross-sectional associations were identified between 1RM (unstandardized beta coefficient [B] = 0.042, 95% bias corrected and accelerated [BCa] confidence interval [CI] 0.012–0.069), muscle power (B = 0.056, 95% BCa CI 0.02–0.250), and overall physical fitness (B = 0.043, 95% BCa CI 0.015–0.071) with TL independent of maturation, glycated haemoglobin, and diabetes duration. However, no associations were observed one year later. Conclusion: Higher levels of fitness, particularly muscle strength, may play a role in telomere dynamics in youth with type 1 diabetes, suggesting that strength training exercise could be beneficial. Impact: This is the first study to examine cross-sectional and longitudinal perspectives on the correlation among muscle strength, peak oxygen consumption [VO_2peak] and telomere length in youths with type 1 diabetes. Higher physical fitness levels, as assessed by measures such as one-repetition maximum, muscle power, and overall physical fitness, are positively associated with telomere length in youths with type 1 diabetes. Understanding this link could improve management strategies, prioritizing muscle strength training for better long-term health in type 1 diabetes.