Human muscular mitochondrial fusion in athletes during exercise

Abstract

ABSTRACT: The 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. TEManalyses showed thatmitochondrialmorphology remained altered for 3 h afterHIHVT,whereas SIT-induced changes were only evident immediately after exercise. Only SIT increased MFN1 and MFN2 mRNA expression, whereas SIT and HIHVT both increasedMFN2 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 mitochondrialmorphology.—Huertas, J. R., Ruiz-Ojeda, F. J., Plaza-D´ıaz, J., Nordsborg, N. B.,Mart´ın-Albo, J., Rueda-Robles, A., Casuso, R. A. Human muscular mitochondrial fusion in athletes during exercise. FASEB J. 33, 12087–12098 (2019). www.fasebj.org