Huertas, Jesus RRuiz-Ojeda, Francisco JavierPlaza-Diaz, JulioNordsborg, Nikolai BMartin-Albo, JesusRueda-Robles, AscensionCasuso, Rafael A2023-01-252023-01-252019-08-09Huertas JR, Ruiz-Ojeda FJ, Plaza-Díaz J, Nordsborg NB, Martín-Albo J, Rueda-Robles A, et al. Human muscular mitochondrial fusion in athletes during exercise. FASEB J. 2019 Nov;33(11):12087-120980892-6638http://hdl.handle.net/10668/14383The main objective of this work was to investigate whether mitochondrial fusion occurs in the skeletal muscle of well-trained athletes in response to high-intensity exercise. Well-trained swimmers (n = 9) performed a duration-matched sprint interval training (SIT) and high-intensity high-volume training (HIHVT) session on separate days. Muscle samples from triceps brachii were taken before, immediately after, and 3 h after the training sessions. Transmission electron microscopy (TEM) was applied to assess mitochondrial morphology. Moreover, expression of genes coding for regulators of mitochondrial fusion and fission were assessed by real-time quantitative PCR. In addition, mitofusin (MFN)2 and optic atrophy 1 (OPA1) were quantified by Western blot analysis. TEM analyses showed that mitochondrial morphology remained altered for 3 h after HIHVT, whereas SIT-induced changes were only evident immediately after exercise. Only SIT increased MFN1 and MFN2 mRNA expression, whereas SIT and HIHVT both increased MFN2 protein content 3 h after exercise. Notably, only HIHVT increased OPA1 protein content. Mitochondrial morphologic changes that suggest fusion occurs in well-adapted athletes during exercise. However, HIHVT appears as a more robust inducer of mitochondrial fusion events than SIT. Indeed, SIT induces a rapid and transient change in mitochondrial morphology.-Huertas, J. R., Ruiz-Ojeda, F. J., Plaza-Díaz, J., Nordsborg, N. B., Martín-Albo, J., Rueda-Robles, A., Casuso, R. A. Human muscular mitochondrial fusion in athletes during exercise.enmitochondrial fissionmitofusin 2physical activityskeletal muscleAthletesCross-Over StudiesExerciseGTP PhosphohydrolasesGene ExpressionHigh-Intensity Interval TrainingHumansMaleMicroscopy, Electron, TransmissionMitochondria, MuscleMitochondrial DynamicsMitochondrial Membrane Transport ProteinsMitochondrial ProteinsMuscle, SkeletalSwimmingYoung Adultresearch article31398297Restricted Access10.1096/fj.201900365RR1530-6860https://faseb.onlinelibrary.wiley.com/doi/pdfdirect/10.1096/fj.201900365RR