title: Seasonal changes in the expression of energy metabolism-related genes in white adipose tissue and skeletal muscle in female Japanese black bears.
abstract: Bears undergo annual cycles in body mass: rapid fattening in autumn (i.e., hyperphagia), and mass loss in winter (i.e., hibernation). To investigate how Japanese black bears (Ursus thibetanus japonicus) adapt to such extreme physiological conditions, we analyzed changes in the mRNA expression of energy metabolism-related genes in white adipose tissues and skeletal muscle throughout three physiological stages: normal activity (June), hyperphagia (November), and hibernation (March). During hyperphagia, quantitative real-time polymerase chain reaction analysis revealed the upregulation of de novo lipogenesis-related genes (e.g., fatty acid synthase and diacylglycerol O-acyltransferase 2) in white adipose tissue, although the bears had been maintained with a constant amount of food. In contrast, during the hibernation period, we observed a downregulation of genes involved in glycolysis (e.g., glucose transporter 4) and lipogenesis (e.g., acetyl-CoA carboxylase 1) and an upregulation of genes in fatty acid catabolism (e.g., carnitine palmitoyltransferase 1A) in both tissue types. In white adipose tissues, we observed upregulation of genes involved in glyceroneogenesis, including pyruvate carboxylase and phosphoenolpyruvate carboxykinase 1, suggesting that white adipose tissue plays a role in the recycling of circulating free fatty acids via re-esterification. In addition, the downregulation of genes involved in amino acid catabolism (e.g., alanine aminotransferase) and the TCA cycle (e.g., pyruvate carboxylase) indicated a role of skeletal muscle in muscle protein sparing and pyruvate recycling via the Cori cycle. These examples of coordinated transcriptional regulation would contribute to rapid mass gain during the pre-hibernation period and to energy preservation and efficient energy production during the hibernation period.
authors.affiliation: Laboratory of Wildlife Biology and Medicine, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan. Electronic address: shimozuru@vetmed.hokudai.ac.jp.
authors.forename: Michito
authors.initials: M
authors.lastname: Shimozuru
authors.affiliation: Laboratory of Wildlife Biology and Medicine, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Nagashima
authors.affiliation: Laboratory of Wildlife Biology and Medicine, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Tanaka
authors.affiliation: Laboratory of Wildlife Biology and Medicine, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Tsubota
mesh_terms: D052436:Adipose Tissue, White / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D004734:Energy Metabolism / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D006605:Hibernation / Q000235:genetics; D006963:Hyperphagia / Q000235:genetics / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D012621:Seasons; D001503:Ursidae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology
keywords: Bear; Gene expression; Hibernation; Hyperphagia; Metabolism; Ursus