title: Rapid induction of REDD1 expression by endurance exercise in rat skeletal muscle.
abstract: An acute bout of exercise induces repression of protein synthesis in skeletal muscle due in part to reduced signaling through the mammalian target of rapamycin complex 1 (mTORC1). Previous studies have shown that upregulated expression of regulated in DNA damage and development (REDD) 1 and 2 is an important mechanism in the regulation of mTORC1 activity in response to a variety of stresses. This study investigated whether induction of REDD1/2 expression occurs in rat skeletal muscle in response to a burst of endurance exercise. In addition, we determined if ingestion of glucose or branched chain amino acids (BCAA) before exercise changes the expression of REDD1/2 in muscle. Rats ran on a motor-driven treadmill at a speed of 28 mmin(-1) for 90 min, and then the gastrocnemius muscle was removed and analyzed for phosphorylation of the eukaryotic initiation factor (eIF) 4E binding protein 1 (4E-BP1) and expression of REDD1/2. Exercise repressed the mTORC1-signaling pathway regardless of the ingestion of nutrients before the exercise, as shown by dephosphorylation of 4E-BP1. In addition, exercise induced the expression of REDD1 mRNA (∼8-fold) and protein (∼3-fold). Exercise-induced expression of REDD1 was not affected by the ingestion of glucose or BCAA. Expression of REDD2 mRNA was not altered by either exercise or nutrients. These findings indicated that enhanced expression of REDD1 may be an important mechanism that could partially explain the downregulation of mTORC1 signaling, and subsequent inhibition of protein synthesis in skeletal muscle during exercise.
authors.affiliation: Department of Nutrition, Shigakkan University, 55 Nadakayama, Yokone-machi, Ohbu 474-0011, Japan. tamuraka@sgk.ac.jp
authors.forename: Taro
authors.initials: T
authors.lastname: Murakami
authors.forename: Kazuya
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Mariko
authors.initials: M
authors.lastname: Yoshinaga
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002352:Carrier Proteins / Q000378:metabolism; D003345:Corticosterone / Q000097:blood; D015536:Down-Regulation; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010805:Physical Conditioning, Animal / Q000502:physiology*; D010807:Physical Endurance; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000096:biosynthesis* / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics
chemical_list: D000597:Amino Acids, Branched-Chain; D001786:Blood Glucose; D002352:Carrier Proteins; C000632146:Ddit4 protein, rat; C496187:Ddit4l2 protein, rat; C499526:Eif4ebp1 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D014157:Transcription Factors; C546845:mTOR protein, rat; D058570:TOR Serine-Threonine Kinases; D003345:Corticosterone