Different exercise modalities have distinct effects on the transcriptome profile in the male rat femoral diaphysis

Mechanical loading is a key determinant of bone mass, geometry and strength and is essential to maintain optimal skeletal health. We hypothesized that spontaneous low-impact exercise would affect global gene transcript levels in cortical bone of growing rats. We used RNA-Seq to analyse the transcriptome of the femoral mid-diaphysis in pre-pubertal male rats that were assigned to one of three exercise groups for 15 days: control (CON); bipedal stance (BPS); and wheel exercise (WEX). RNA-seq analysis identified 808 and 324 differentially expressed transcripts in the BPS and WEX animals, respectively. In WEX animals, the up-regulated transcripts were enriched for gene ontology terms associated with bone metabolism. Both BPS and WEX animals showed changes in transcripts that were enriched for muscle-related processes. However, in WEX these transcripts were down-regulated while in BPS such transcripts were up-regulated. Importantly, we observed that the exercise mode had diametrically opposite effects on transcripts for multiple genes within the integrin-linked kinase (ILK) and Ca2+ signalling pathways such that they were up-regulated in BPS and down-regulated in WEX. The findings are important for our understanding of possible ways in which different exercise regimens might affect bone when normal activities apply mechanical stimuli during post-natal growth and development. Overall design: 24 weanling (21 day old) male Sprague-Dawley rats were assigned to three exercise groups .After the 15 day trial period, total RNA was extracted from the femoral diaphysis and mRNA profiles were analysed using RNA-seq