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Article Title

THE EFFECTS OF DETRAINING ON GENE EXPRESSION PROFILES IN RAT SOLEUS MUSCLE AFTER ACUTE EXERCISE.

Abstract

Aerobic exercise training promotes gene expression for physiological changes that must occur with enhanced physical activity. Cessation of activity (detraining) theoretically reverses these adaptations, but it is unknown whether global gene expression profiles return to pre-training levels. PURPOSE: To compare gene expression profiles in the soleus muscle 24 hrs after an acute exercise bout in detrained, sedentary, and exercised rats. METHODS: Female Sprague-Dawley rats (n=8/group) were placed in one of three groups: voluntary exercise (EX) for 8 wks, sedentary (SED) for 8 wks, or a detraining model (DETR) in which animals ran voluntarily for 4 wks and were then sedentary for 4 wks. All animals were forced to run on a wheel for a total of 1 hour at 20 m/min and then killed 24 hrs later, when body and soleus muscle masses were recorded for each rat. Total mRNA extraction, conversion to cDNA, and microarray analyses were performed on the soleus muscle samples by Georgetown University to examine gene expression profiles. RESULTS: Body mass of EX rats was ~10% lower when compared to SED and DETR rats (p<0.05); however, absolute soleus mass was >10% higher in SED than in EX and DETR groups (p<0.05). There was 9% lower relative soleus mass (mg muscle/ g body mass) in DETR vs. both EX and SED rats. Genes that exhibited a ≥2-fold difference in expression between groups from microarray analysis were identified, and using this criteria, we found differences in 289 known genes between SED and EX rats, 56 between SED and DETR rats, and 460 between EX and DETR rats (p<0.05). CONCLUSION: Although the fewest differences in gene expression occurred between SED and DETR groups, microarray results showed that some training-induced adaptations persisted after 4 wks of detraining, suggesting that there is residual genetic benefit from previous exercising periods. Angiogenic gene expression will be confirmed using quantitative PCR, and capillary density will be quantified to further characterize physiological effects of detraining on skeletal muscle.

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