Mitochondrial dynamics signaling is shifted toward fusion in muscles of very old hip-fractured patients: Results from the Sarcopenia in HIp FracTure (SHIFT) exploratory study

Background: Mitochondrial quality control (MQC) is crucial for maintaining mitochondrial fitness. We investigated MQC signaling in muscle of old hip-fractured patients. Methods: Twenty-three patients, enrolled in the Sarcopenia in Hip FracTure (SHIFT) study, were categorized into old (OL; n = 8) and very old groups (VOL; n = 15) using 85 years as the cut-off. The expression of a set of MQC signaling proteins was assayed in vastus lateralis muscle biopsies. Results: The content of lysosome-associated membrane protein 2, microtubule-associated protein 1 light chain 3B, optic atrophy protein 1, fission protein 1 (Fis1), peroxisome proliferator-activated receptor-gamma coactivator-1 alpha, and forkhead box 03 was unvaried between groups. Conversely, the protein expression of mitofusin 2 (Mfn2) as well as the fusion index (Mfn2/Fis1) was increased in VOL patients. Conclusions: Muscle mitochondrial dynamics appear to be shifted toward fusion in very advanced age. Whether this phenomenon represents an adaptation to cope with age-dependent mitochondrial dysfunction warrants further investigation. (C) 2017 Elsevier Inc. All rights reserved.