title: Individuals with higher metabolic rates have lower levels of reactive oxygen species in vivo.
abstract: There is increasing interest in the effect of energy metabolism on oxidative stress, but much ambiguity over the relationship between the rate of oxygen consumption and the generation of reactive oxygen species (ROS). Production of ROS (such as hydrogen peroxide, H2O2) in the mitochondria is primarily inferred indirectly from measurements in vitro, which may not reflect actual ROS production in living animals. Here, we measured in vivo H2O2 content using the recently developed MitoB probe that becomes concentrated in the mitochondria of living organisms, where it is converted by H2O2 into an alternative form termed MitoP; the ratio of MitoP/MitoB indicates the level of mitochondrial H2O2 in vivo. Using the brown trout Salmo trutta, we tested whether this measurement of in vivo H2O2 content over a 24 h-period was related to interindividual variation in standard metabolic rate (SMR). We showed that the H2O2 content varied up to 26-fold among fish of the same age and under identical environmental conditions and nutritional states. Interindividual variation in H2O2 content was unrelated to mitochondrial density but was significantly associated with SMR: fish with a higher mass-independent SMR had a lower level of H2O2. The mechanism underlying this observed relationship between SMR and in vivo H2O2 content requires further investigation, but may implicate mitochondrial uncoupling which can simultaneously increase SMR but reduce ROS production. To our knowledge, this is the first study in living organisms to show that individuals with higher oxygen consumption rates can actually have lower levels of H2O2.
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK salin.karine@gmail.com.
authors.forename: Karine
authors.initials: K
authors.lastname: Salin
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Sonya K
authors.initials: SK
authors.lastname: Auer
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Agata M
authors.initials: AM
authors.lastname: Rudolf
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Graeme J
authors.initials: GJ
authors.lastname: Anderson
authors.affiliation: School of Chemistry, University of Glasgow, Glasgow, UK.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Cairns
authors.affiliation: Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK.
authors.forename: William
authors.initials: W
authors.lastname: Mullen
authors.affiliation: School of Chemistry, University of Glasgow, Glasgow, UK.
authors.forename: Richard C
authors.identifier: http://orcid.org/0000-0003-1033-5405
authors.initials: RC
authors.lastname: Hartley
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Colin
authors.initials: C
authors.lastname: Selman
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
authors.forename: Neil B
authors.initials: NB
authors.lastname: Metcalfe
mesh_terms: D000818:Animals; D001481:Basal Metabolism / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D010101:Oxygen Consumption; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014337:Trout / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide
keywords: MitoP/MitoB ratio; fish; inter-individual variation; oxidative stress; oxygen consumption