title: The Preventive Effects of 8 Weeks of Resistance Training on Glucose Tolerance and Muscle Fiber Type Composition in Zucker Rats.
abstract: BACKGROUND
  We investigated the therapeutic effects of resistance training on Zucker rats before and after the onset of diabetes to understand the importance of the timing of exercise intervention. We assessed whether 8 weeks of resistance training ameliorated impaired glucose tolerance and altered muscle fiber type composition in Zucker rats.
  
  
  METHODS
  Five-week-old male Zucker rats were divided into Zucker lean control (ZLC-Con), non-exercised Zucker diabetic fatty (ZDF-Con), and exercised Zucker diabetic fatty (ZDF-Ex) groups. The ZDF-Ex rats climbed a ladder three times a week for 8 weeks. Intraperitoneal glucose tolerance tests (IPGTT) were performed on the 1st and 8th weeks of training, and grip strength was measured during the last week. We also measured glucose transporter 4 (GLUT4) expression by Western blot and immunofluorescence. Moreover, immunohistochemistry was performed to assess muscle fiber type composition.
  
  
  RESULTS
  Fasting glucose levels and area under the curve responses to IPGTTs gradually increased as diabetes progressed in the ZDF-Con rats but decreased in the ZDF-Ex rats. Grip strength decreased in the ZDF-Con rats. However, resistance training did not improve grip strength in the ZDF-Ex rats. GLUT4 expression in the ZLC-Con and the ZDF-Con rats did not differ, but it increased in the ZDF-Ex rats. The proportions of myosin heavy chain I and II were lower and higher, respectively, in the ZDF-Con rats compared to the ZLC-Con rats. Muscle fiber type composition did not change in the ZDF-Ex rats.
  
  
  CONCLUSIONS
  Our results suggest that regular resistance training initiated at the onset of diabetes can improve glucose tolerance and GLUT4 expression without changing muscle morphology in Zucker rats.
authors.affiliation: Health and Exercise Science Laboratory, Institute of Sports Science, Seoul National University College of Education, Seoul, Korea.
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Health and Exercise Science Laboratory, Institute of Sports Science, Seoul National University College of Education, Seoul, Korea.
authors.forename: Mi Jung
authors.initials: MJ
authors.lastname: Choi
authors.affiliation: Health and Exercise Science Laboratory, Institute of Sports Science, Seoul National University College of Education, Seoul, Korea.
authors.forename: Byunghun
authors.initials: B
authors.lastname: So
authors.affiliation: Health and Exercise Science Laboratory, Institute of Sports Science, Seoul National University College of Education, Seoul, Korea.
authors.forename: Hee-Jae
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Laboratory of Developmental Biology and Genomics, BK21 Program for Veterinary Science, Institute for Veterinary Science, Seoul National University College of Veterinary Medicine, Seoul, Korea. ; Korea Mouse Phenotyping Center (KMPC), Seoul, Korea.
authors.forename: Je Kyung
authors.initials: JK
authors.lastname: Seong
authors.affiliation: Health and Exercise Science Laboratory, Institute of Sports Science, Seoul National University College of Education, Seoul, Korea. ; Institute on Aging, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Wook
authors.initials: W
authors.lastname: Song
keywords: Diabetes mellitus, type 2; Glucose tolerance; Muscle fiber type; Rats, Zucker; Resistance training