Lifelong physical exercise delays age-associated skeletal muscle decline.

Aging is usually accompanied by a significant reduction in muscle mass and force. To determine the relative contribution of inactivity and aging per se to this decay, we compared muscle function and structure in (a) male participants belonging to a group of well-trained seniors (average of 70 years) who exercised regularly in their previous 30 years and (b) age-matched healthy sedentary seniors with (c) active young men (average of 27 years). The results collected show that relative to their sedentary cohorts, muscle from senior sportsmen have: (a) greater maximal isometric force and function, (b) better preserved fiber morphology and ultrastructure of intracellular organelles involved in Ca(2+) handling and ATP production, (c) preserved muscle fibers size resulting from fiber rescue by reinnervation, and (d) lowered expression of genes related to autophagy and reactive oxygen species detoxification. All together, our results indicate that: (a) skeletal muscle of senior sportsmen is actually more similar to that of adults than to that of age-matched sedentaries and (b) signaling pathways controlling muscle mass and metabolism are differently modulated in senior sportsmen to guarantee maintenance of skeletal muscle structure, function, bioenergetic characteristics, and phenotype. Thus, regular physical activity is a good strategy to attenuate age-related general decay of muscle structure and function (ClinicalTrials.gov: NCT01679977).

Effects of 8 weeks of vibration training at different frequencies (1 or 15 Hz) in senior sportsmen on torque and force development and of 1 year of training on muscle fibers.

OBJECTIVE: To examine the effects of 8 weeks of vibration training at different frequencies (1 and 15 Hz) on maximal isometric torque and force development in senior sportsmen, and of 1 year of heavy-resistance and vibration trainings on muscle fibers. METHODS: Seven healthy senior sportsmen (mean age: 69.0 +/- 5.4 years) performed an 8 weeks of strength training of knee extensors. Vibrations were applied vertically to the axis of movement during training. One leg of each subject was trained at a frequency of 1 Hz, while the other leg was trained at 15 Hz. Measures of isometric peak torque (at knee-angles of 60, 90 and 120 degrees ) and force development were recorded before and after training. Four sportsmen continued a year-long heavy-resistance training adding every second week a session of vibration training. After training, muscle biopsies were harvested from their quadriceps muscles and used for structural analyses. Morphometry of muscle fibers was performed by light microscopy. Immunohistochemistry using anti-MHCemb and anti-N-CAM antibodies was performed to measure potential muscle damage. Data from muscle morphometry were compared to that of a series of vastus lateralis biopsies harvested from 12 young sportsmen and four healthy elderly. RESULTS: Our results showed a significant increase in isometric peak torque at both 1 and 15 Hz vibration frequency in all three measured angles of the knee. There was no significant difference between the two frequencies, but we could find a higher increase in percentage of maximum power after the 1 Hz training. The results of force development showed a slight increase at the 1 Hz training in measured time frames from 0 to 50 and 200 ms, without statistical significance. A trend to significance was found at the 1 Hz training at the time window up to 200 ms. The 15 Hz training showed no significant changes of force development. Muscle biopsies show that the muscles of these well trained senior sportsmen contain muscle fibers which are 35% larger than those of sedentary elderly and, unexpectedly, 10% larger than those of young sportsmen. Despite 1 year of heavy resistance and vibration training, no evidence of muscle damage or denervation/reinnervation could be observed by light microscopy analyses, ATPase histochemistry and immunohistochemistry using anti-N-CAM or anti-MHC-emb antibodies. DISCUSSION: Integration of vibration to conventional strength training in elderly sportsmen induces similar improvement of isometric peak torque and force development independently from the vibration frequency after 8 weeks of training, and long-term results in the surprising evidence of hypertrophic muscle fibers larger than those of young active sportsmen. The observation that the vibration training with low frequency is safe opens the possibility to test these rehabilitation procedures in sedentary elderly.

Global histone acetylation and deacetylation in yeast.

Histone acetyltransferases and deacetylases can be targeted to promoters to activate or repress genes. For example, the histone acetyltransferase GCN5 is part of a yeast multiprotein complex that is recruited by the DNA-binding activator protein GCN4 (refs 1-3). The histone deacetylase RPD3 complex is recruited to DNA by the repressor UME6 (refs 4, 5); similar mechanisms exist in other eukaryotes. However, deletion of RPD3 also increases expression of the PHO5 gene that is repressed by nucleosomes, and regulated by GCN5 (ref. 10) but not by UME6. We have determined whether acetylation and deacetylation are promoter specific at PHO5, by using antibodies against acetylated lysine residues and chromatin immunoprecipitation to examine the acetylation state of a 4.25-kilobase region surrounding the PHO5 gene. Here we show that this region is acetylated extensively by ESA1 and GCN5 and deacetylated by HDA1 and RPD3, and that widespread histone modification affects three separate chromosomal regions examined, which total 22kb. Our data indicate that targeted modification occurs in a background of global acetylation and deacetylation that not only reduces basal transcription, but also allows a rapid return to the initial state of acetylation when targeting is removed.

Site-specific in vivo cleavages by DNA topoisomerase I in the regulatory regions of the 35 S rRNA in Saccharomyces cerevisiae are transcription independent.

Eukaryotic type I DNA topoisomerase controls DNA topology by transiently breaking and resealing one strand of DNA at a time. During transcription and replication its action reduces the torsional stress derived from these activities. The association of DNA topoisomerase I with the nucleolus has been reported and this enzyme was shown to be involved in yeast rDNA metabolism. Here, we have investigated the in vivo presence of DNA topoisomerase I cleavage sites in the non-transcribed spacer of the rDNA cluster. We show a specific profile of highly localized cleavage in relevant areas of this region. The sites are detected in the promoter and in the enhancer regions of the 35 S gene. The analysis of mutants in which transcription is prevented and/or reduced, namely a strain lacking the 43 kDa subunit of RNA polymerase I, a second one that does note transcribe, lacking a subunit of the core factor and another member of the RNA polymerase I transcription factors lacking one of the UAF component which transcribes at very low level, show that DNA topoisomerase I cleavage sites are not related to transcription by RNA polymerase I. These findings point to a role for DNA topoisomerase I that is additional to the commonly recognized function in removing the transcription-induced topological stress.

DNA protein-interactions at the Saccharomyces cerevisiae 35 S rRNA promoter and in its surrounding region.

This study represents a detailed analysis of the structural context of the RNA polymerase I promoter of Saccharomyces cerevisiae. We determined the presence of regularly spaced nucleosomes in the non-transcribed spacer (NTS) and found that five of them have well defined positions. We show that this nucleosome positioning is restricted to the region between the 35 S and 5 S rRNA promoters, beyond which a more delocalized chromatin structure is evident. A more refined analysis detects the DNA-protein interactions on the RNA polymerase I promoter at nucleotide resolution and provides the first in vivo footprints, attributable to factors like REB1, CF, UAF and an additional protection that seems to be sensitive to the topological context. Moreover, when this analysis is extended to different growth media (YPD versus YNB), some of these protections show a growth condition dependent behaviour.