Turning back the clock

Figure 1 from a recent paper by Melov et al. (2007) studying gene expression profiles in older adults following resistance training. This figure is not particularly useful, and I included because it looks cool (hmmmm). Don't worry though, the results are actually pretty interesting. Melov et al. were interested in how resistance training alters gene expression profiles in skeletal muscle, and whether any of these changes were consistent with a reversal of age-related muscular impairments. They used microarray technology to map the transcription profiles in skeletal muscle of older adults (~70yo) before and after 6 months of full-body resistance training. Perhaps unsurprisingly, a bunch of genes are differentially expressed when older untrained adults are compared to sedentary younger adults, including some associated with mitochondrial function (see also Zahn et al., 2006). However, after 6 months of resistance training (which resulted in significant strength gains), the gene expression profile for older adults was markedly different. A subset of the genes that showed an age-related difference also showed a change in expression due to exercise. Notably, those genes that were expressed at a level lower than young adults were upregulated while those genes that were expressed at a level higher than young adults were downregulated. As the authors put it, the transcriptional signature of aging was reversed back to that of younger levels. Now, I don't have a good sense of how to interpret expression levels, and the authors tended to plot their data on relative scales, so I can't assess the magnitude of these results, but it's an interesting application of gene profiling technology. Unfortunately, there was no individual level correlation of strength gains with changes in gene expression profile (in those genes significantly associated with age and exercise), although this may be a power issue (I guess people aren't jumping for the chance to get repeated muscle biopsies with a 5mm diameter needle!?).

Melov S, Tarnopolsky MA, Beckman K, Felkey K, Hubbard A (2007) Resistance Exercise Reverses Aging in Human Skeletal Muscle. PLoS ONE 2(5): e465 doi:10.1371/journal.pone.0000465

Zahn JM, Sonu R, Vogel H, Crane E, Mazan-Mamczarz K, et al. (2006) Transcriptional Profiling of Aging in Human Muscle Reveals a Common Aging Signature. PLoS Genet 2(7): e115 doi:10.1371/journal.pgen.0020115