Bezafibrate as treatment option in patients with mitochondrial complex I deficiency. B. M. Haberberger1,2, P. Freisinger3, V. Strecker4, M. Steger4, H. Heide4, B. F. Müller5, T. Beckhaus5, K. Heim2, U. Ahting6, B. Rolinski6, J. Mayr7, A. Rötig8, W. Sperl7, M. Zeviani9, I. Wittig4, T. Meitinger1,2, H. Prokisch1,2 1) Institute of Human Genetics, Technical University Munich, Germany; 2) Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg, Germany; 3) Department of Paediatrics, Klinikum Reutlingen, Germany; 4) Molekulare Bioenergetik, Zentrum der Biologischen Chemie, Goethe-University Frankfurt, Germany; 5) Institute for Pharmaceutical Chemistry, Cluster of Excellence "Macromolecular Complexes", Goethe-University Frankfurt , Germany; 6) Department of Clinical Chemistry, Städtisches Klinikum München GmbH, Munich, Germany; 7) Department of Pediatrics, Paracelsus Medical University Salzburg, Salzburg, Austria; 8) Institut National de la Santé et de la Recherche Médicale (INSERM), Paris, France; 9) Unit of Child Neurology, Neurological Institute Carlo Besta-IRCCS Foundation, Milan, Italy.

   Faulty energy supply due to defective oxidative phosphorylation is the biochemical signature of the genetically heterogeneous group of mitochondrial disorders. A majority of them affect the respiratory chain complexes and the cellular ATP production. In spite of rapid progress in finding the molecular cause, in most instances no curative therapeutic options are available. Bastin et al. (2008) and Wenz at al. (2011) provided evidence from in vitro studies and mouse models that activation of the PPAR/PGC-1-alpha pathway with bezafibrate could be a new therapeutic approach. Djouadi et al. (2010) showed in a clinical study, that bezafibrate increased the resting activity of -oxidation enzymes in patients with inherited -oxidation disorders leading to a significant improvement in the condition of the patients. In order to verify this effect, we collected 32 fibroblast cell lines from patients with isolated complex I (CI) deficiency and a defined molecular diagnosis. The CI activity in fibroblasts ranged from 10% to 80% in comparison to control cell lines. After bezafibrate treatment we found no improvement in cell lines with mtDNA mutation (n=4); but in all cell lines with nuclear mutations an increase (15-140%) of CI activity was found. The largest effect was observed in a homogeneous group of missense mutations in the same gene, ACAD9. Analysis of genome-wide expression levels, confirmed increased expression of genes involved in lipid and fatty acid metabolism as well as transport, but provided no evidence of upregulation of genes coding for respiratory chain complex subunits (n=10). Raised CI activity was combined by a larger amount of CI assembled in supercomplexes visualized by 2D-BN/SDS-PAGE experiments (n=8). We further examined the consequences of bezafibrate treatment on protein level to get a clearer picture of the involved mechanisms. Enriched mitochondrial fractions from untreated and bezafibrate treated controls and patients with mutations in ACAD9 gene were analyzed by 2D-DIGE (n=5) and significant changes (p<0.05) were identified by MALDI-MS and ESI-MS. We detected reduced levels of proteins involved in metabolic pathways and stability of complexes compared to healthy controls. Proteomics data confirmed increased expression of proteins involved in lipid and fatty acid metabolism upon bezafibrate treatments. These results support bezafibrate as a promising treatment option for specific subgroups of patients with CI deficiency.