title: Metabolic depression during warm torpor in the Golden spiny mouse (Acomys russatus) does not affect mitochondrial respiration and hydrogen peroxide release.
abstract: Small mammals actively decrease metabolism during daily torpor and hibernation to save energy. Recently, depression of mitochondrial substrate oxidation in isolated liver mitochondria was observed and associated to hypothermic/hypometabolic states in Djungarian hamsters, mice and hibernators. We aimed to clarify whether hypothermia or hypometabolism causes mitochondrial depression during torpor by studying the Golden spiny mouse (Acomys russatus), a desert rodent which performs daily torpor at high ambient temperatures of 32°C. Notably, metabolic rate but not body temperature is significantly decreased under these conditions. In isolated liver, heart, skeletal muscle or kidney mitochondria we found no depression of respiration. Moderate cold exposure lowered torpor body temperature but had minor effects on minimal metabolic rate in torpor. Neither decreased body temperature nor metabolic rate impacted mitochondrial respiration. Measurements of mitochondrial proton leak kinetics and determination of P/O ratio revealed no differences in mitochondrial efficiency. Hydrogen peroxide release from mitochondria was not affected. We conclude that interspecies differences of mitochondrial depression during torpor do not support a general relationship between mitochondrial respiration, body temperature and metabolic rate. In Golden spiny mice, reduction of metabolic rate at mild temperatures is not triggered by depression of substrate oxidation as found in liver mitochondria from other cold-exposed rodents.
authors.affiliation: Philipps-Universität Marburg, Faculty of Biology, Department of Animal Physiology, Karl-von-Frisch-Strasse 8, 35043 Marburg, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Grimpo
authors.forename: Maria
authors.initials: M
authors.lastname: Kutschke
authors.forename: Anja
authors.initials: A
authors.lastname: Kastl
authors.forename: Carola W
authors.initials: CW
authors.lastname: Meyer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Heldmaier
authors.forename: Cornelia
authors.initials: C
authors.lastname: Exner
authors.forename: Martin
authors.initials: M
authors.lastname: Jastroch
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001481:Basal Metabolism; D001831:Body Temperature; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism; D008930:Mitochondria, Liver / Q000378:metabolism*; D051189:Murinae / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D010101:Oxygen Consumption; D064348:Torpor
chemical_list: D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide
keywords: ADP; ATP; Acomys russatus; Daily torpor; FCCP; Hypometabolism; Hypothermia; MR; Mitochondrial respiration; RCR; RET; ROS; T(a); T(b); TPMP; adenosine-diphosphate; adenosine-triphosphate; ambient temperature; body temperature; carbonyl cyanide-p-trifluoromethoxyphenylhydrazone; metabolic rate, measured as oxygen consumption; reactive oxygen species; respiratory control ratio; reverse electron transfer; triphenylmethylphosphonium