Vibrotherapy restores the basic gene activity disturbed by chronic muscle disuse

Muscle atrophy (mass loss) is a common problem in aging, neuromuscular diseases, or in reduced gravity. Using a laboratory model of chronic body disuse in the 60-day bed rest (BR) test, the global gene expression profile was analyzed for the first time in conjunction with proteomic analysis to map molecular adaptations in unused soleus muscle (control group, CTR). The same analyzes were performed in response to BR test and conventional resistance exercise (RE) preventing the chronic unloading effects or conventional resistance exercise with additional vibration mechanosignals (RVE). After the BR test:

• 235 genes were differentially activated in CTR,
  206 – in RE,
  51 – in RVE;
• most changes in gene expression and protein profile were related to the functions of contractile structures and to key metabolic pathways such as glycolysis, oxidative phosphorylation, the Krebs cycle, and fat metabolism;
• new genes in human soleus muscle have been identified that were related solely to mechanical vibration signalling – PANK2 and DENND2C.

Prepared on the basis of:

Vibration mechanosignals superimposed to resistive exercise result in baseline skeletal muscle transcriptome profiles following chronic disuse in bed rest. Salanova M, Gambara G, Moriggi M, et al. Sci Rep. 2015;5:17027.

Study population

Gene expression analysis was performed on 12 healthy men, randomly assigned to 3 equal groups (n = 4): CTR, RE or RVE.

Test procedure

In RE appropriate resistance exercises (5 – 10 min; 3/ week) were performed on a specially constructed device. RVE underwent the same procedure as RE but additionally vibrations were delivered (see below).

24 samples of soleus muscle were biopsied – 2 from each patient (2 days before start and 2 days before the end of the BR test). Biopsy samples were immediately frozen in liquid nitrogen and stored at -80 °C for further procedures.

RNA was isolated from biopsy homogenates using the RNeasy Micro Kit (Qiagen). Complementary DNA (cDNA) libraries were generated from total RNA with an input concentration of 40-120 ng using the Ambion WT Expression Kit (Life Technologies) according to the manufacturer’s instructions. Complementary RNA libraries were then constructed in which the differentially expressed genes were detected using GeneChip “HuGene 1.0 ST v1” microarrays (Affymetrix) offering coverage of the entire transcriptome, in this case considered to be 28869 genes. Validation of microarrays results was performed by protein composition analysis using mass spectrometry and immunoblotting.

Use of vibration in the study

The RVE protocol assumed a short series (5 – 10 min; 3/ week) of resistance exercises enriched with the administration of vibrations. Whole body vibrations (24-26 Hz; 3.5-4 mm; 8.7-10.2 g) were administered to both feet by a vibrating platform in the supine position.

Results

A decrease in the expression of numerous specific genes was observed after the BR test in the CTR. These genes were coding for enzymes related to the contractile functions or energetic functions (such as anaerobic glycolysis, oxidative phosphorylation, Krebs cycle, fat metabolism). Using the DNA microarray technology and analyzing the expression (activity) of nearly 30,000 genes in CTR after the BR test, 235 genes were identified which showed different expression compared to before the test. The activity of the remaining genes did not change. In RE – similarly, however in RVE only 51 genes were found to be expressed differentially. Among them the main genes that turned out to be regulated only by mechanical vibration signals are PANK2 (essential in the synthesis of coenzyme A) and DENND2C (associated with numerous physiological functions of the cell, including cytoskeleton organization).

Comment

Conventional methods to counteract chronic musculoskeletal system unloading effects by short series of resistance exercise turned out to be effective in preventing gene expression changes only partially. On the other hand, the enrichment of resistance exercise with whole-body vibrations (focused mainly on the soleus muscle) resulted in almost complete prevention of changes in genetic activity observed in both CTR or RE. Performed gene analysis allowed to identify genes related to the response to mechanical signals of vibrations in the human calf soleus muscle. The RVE procedure effectively reduced the key morphological and biochemical disadvantages of the BR test on muscles, which was possible by regulating defined genetic activity. Moreover, vibrations significantly improved the effectiveness of resistance exercise in enhancing the metabolism of energy substrates. It seems that results discussed here have clinical potential to optimize counteracting chronic unload-induced muscle atrophy protocols in rehabilitation, geriatrics, and long-term space missions.

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