Interactive effect of exercise training and mild hypoxia on muscle morphology and glucoes tolerance

Autor: Ming-Chieh Wu, 吳明杰
Rok vydání: 2011
Druh dokumentu: 學位論文 ; thesis
Popis: 99
Study I: The main purpose of this study was to determine, whether variations in fiber type composition and capillary density are involved with AMPK-PGC-1α signaling pathway and MEF2A protein levels, over the period of a training program. For this study, weight-matched SD rats were categorized into sedentary and trained groups (trained for 1, 7 and 14 days, n=10 in each group). Training consisted of swimming exercise for 90 min/day. Citrate synthase (CS) activity, GLUT4 and MEF2A protein levels were significantly greater in plantaris muscle of 7-day trained group compared to the sedentary group, while, no change in soleus muscle. Fiber type transformation from type IIb-to-IIa in plantaris was evidenced following the last bout of training program. However, no significant differences in AMPKα Thr172 phosphorylation and PGC-1α protein levels in both muscles. Our results suggest that the increased of MEF2A protein expression may play an essential role in fiber type transformation in trained rat muscles. Study II: It is unknown whether hypoxia training can effectively suppress overweight and hyperinsulinemia for the genetically obese animals. In this study, both lean and obese Zucker rats were randomly assigned into the following groups: control (CON, N=7), exercise training (EX, N=7), hypoxia (HYP, N=7), and exercise training with hypoxia recovery (EX+HYP, N=7). During a 6-week training period, rats underwent swimming progressively from 30 to 180 min/day and recovered under hypoxia (14% oxygen for 8 h/day). Obese Zucker rats exhibited substantially greater fasted insulin and exaggerated glucose and insulin responses following an oral glucose challenge compared with lean rats. At the beginning of the Week 6, body weight, fasting glucose, fasting insulin, area under curve of glucose and insulin in the EX+HYP group were significantly lower than those in the CON group for the obese rats. Only GAUC in the EX group was significantly lower than that in the CON group. At the end of the Week 6, capillaries to fiber ratio (C/F), capillary density (CD), and type IIa fiber proportion of plantaris muscle in the EX group were significantly greater than those in the CON group (P < 0.05), but no additive effect of hypoxia on exercise training was observed. Our data demonstrate that exercise training with prolonged hypoxia recovery provides strong metabolic benefits for the obese Zucker rats. This advantage was closely associated with effective weight reduction but less associated with alterations in skeletal muscle properties.
Databáze: Networked Digital Library of Theses & Dissertations
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