Superoxide dismutase 1 mutation in a cellular model of amyotrophic lateral sclerosis shifts energy generation from oxidative phosphorylation to glycolysis Scott P. Allen, Sandeep Rajan, Lynn Duffy, Heather Mortiboys, Adrian Higginbottom, Andrew J. Grierson, Pamela J. Shaw * Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Sheffield, UK article info Article history: Received 11 June 2013 Received in revised form 13 October 2013 Accepted 24 November 2013 Available online 3 December 2013 Keywords: ALS SOD1 Mitochondria Metabolism abstract Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder involving the progressive degeneration of motor neurons in the brain and spinal cord. Mitochondrial dysfunction plays a key role in ALS disease progression and has been observed in several ALS cellular and animal models. Here, we show that fibroblasts isolated from ALS cases with a Cu/Zn superoxide dismutase (SOD1) I113T mutation recapitulate these mitochondrial defects. Using a novel technique, which measures mitochondrial respiration and glycolytic flux simultaneously in living cells, we have shown that SOD1 mutation causes a reduction in mitochondrial respiration and an increase in glycolytic flux. This causes a reduction in adenosine triphosphate produced by oxidative phosphorylation and an increase in adenosine triphos- phate produced by glycolysis. Switching the energy source from glucose to galactose caused uncoupling of mitochondria with increased proton leak in SOD1 I113T fibroblasts. Assessment of the contribution of fatty acid oxidation to total respiration, suggested that fatty acid oxidation is reduced in SOD1 ALS fi- broblasts, an effect which can be mimicked by starving the control cells of glucose. These results highlight the importance of understanding the interplay between the major metabolic pathways, which has the potential to lead to strategies to correct the metabolic dysregulation observed in ALS cases. Ó 2014 Elsevier Inc. All rights reserved. 1. Introduction Amyotrophic lateral sclerosis (ALS) or motor neuron disease is an adult onset neurodegenerative disorder characterized by pro- gressive degeneration of motor neurons in the motor cortex, brain stem, and spinal cord. This results in denervation, which is destructive for the muscle leading to progressive weakness and atrophy. Disease progression is rapid, with typical survival only 2e3 years post-diagnosis. The leading therapeutic agent riluzole, offers only a modest extension of life expectancy by approximately 3 months (Lacomblez et al., 1996a, 1996b) and to date there is no known neuroprotective therapy of major impact for this devas- tating disease. Approximately 5%e10% of ALS cases have a genetic cause and are termed familial ALS (FALS). Mutations have been identified in approximately 70% of FALS cases with mutations in C9ORF72, TARDBP , FUS, and SOD1 underlying the most common genetic sub- types (DeJesus-Hernandez et al., 2011; Kwiatkowski et al., 2009; Renton et al., 2011; Rosen, 1993; Vance et al., 2009). Sporadic ALS (SALS) accounts for 90%e95% of all cases with the cause of disease being unknown. However, genome wide association studies have linked several loci such as ELP3, UNC13A, and C9ORF72 with increased susceptibility to sporadic ALS (DeJesus-Hernandez et al., 2011; Renton et al., 2011; Simpson et al., 2009; van Es et al., 2009). Expanded GGGGCC repeats in C9ORF72 have been shown to account for 40%e50% of FALS and approximately 7% of SALS cases (Cooper-Knock et al., 2012; Majounie et al., 2012). However, the functional impact of the expanded repeat and the function of the C9ORF72 protein in health and disease have yet to be determined. Although SALS and FALS are clinically indistinguishable, there is a great deal of evidence to suggest that they share multiple patho- physiological mechanisms including protein aggregation, excito- toxicity, axonal transport defects, dysregulation of RNA metabolism, mitochondrial dysfunction, metabolic dysregulation, and oxidative stress (Dupuis et al., 2011; Ferraiuolo et al., 2011). Mutation of Cu/Zn superoxide dismutase (SOD1) is responsible for around 20% of FALS cases (Rosen, 1993). It is a generally accepted * Corresponding author at: Director Sheffield Institute for Translational Neuro- science (SITraN), University of Sheffield, 385A Glossop Road, Sheffield S102HQ, UK. Tel.: þ44 114 2222295; fax: þ44 114 2222291. E-mail address: pamela.shaw@sheffield.ac.uk (P.J. Shaw). Contents lists available at ScienceDirect Neurobiology of Aging journal homepage: www.elsevier.com/locate/neuaging 0197-4580/$ e see front matter Ó 2014 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.neurobiolaging.2013.11.025 Neurobiology of Aging 35 (2014) 1499e1509