Neuromuscular Electrical Stimulation Induces Skeletal Muscle Fiber Remodeling and Specific Gene Expression Profile in Healthy Elderly

Abstract

Skeletal muscle aging is a multifactorial process strictly related to progressive weakness. One of the results that were focused on was the fiber phenotype modification and their loss. The physiological muscle recruitment to contraction, basically prosecuted under volitional control, can also be engaged by means of Neuromuscular Electrical Stimulation (NMES). Knowing that the NMES is effective in improving muscle strength in active healthy elderly, the aim was to investigate which physiological modifications were able to produce in the Vastus lateralis muscle and the pathways involved. It was found that NMES increased the cross sectional area and the isometric strength of type II myofibers together with the activated myogenic pathway in order to shift glycolytic toward the oxidative phenotype II myofibers, at a molecular level and with an increase of maximal voluntary contraction (MVC) at a functional level. Using the TaqMan low density array on 48 different genes, we found that NMES specific gene regulation highlighted: (i) increased protein synthesis with respect to protein degradation; (ii) the activation of an apoptotic pathway involved in the differentiation process; (iii) increased regeneration signals; (iv) oxidative enzyme regulation. These pathways were validated via confirmatory RT-PCR for genes involved in the regeneration process as well as Myosin isoforms. We also investigated the oxidative stress status analyzing superoxide anion levels, the protein expression of two different superoxide dismutase and the activity of both catalase and superoxide anion dismutase, being two main antioxidant enzymes. In conclusion, data demonstrates that NMES is effective in producing physiological adaptation on Vastus Lateralis of active healthy elderly as well as providing new insights for further research on elderly who experienced muscle detriment for periodic or permanent immobility.

Muscle Hypertrophy and Architectural Changes in Response to Eight-Week Neuromuscular Electrical Stimulation Training in Healthy Older People

“…As a matter of fact, our NMES loading with intensities corresponding to the individual’s pain threshold has already proved effective in improving various muscle parameters in previous studies including both quadriceps and lumbar multifidus muscles [ 23 , 24 , 55 ]. Altogether, our results extend previous findings of cellular and molecular studies on the hypertrophic effects of NMES training in the elderly muscle [ 71 , 73 , 74 , 75 ] by the mean of the non-invasive method of muscle ultrasound.…”

Neuromuscular electrical stimulation in early rehabilitation of patients with postoperative complications after cardiovascular surgery

“…[ 15 ] This is not surprising, since NMES provides an additional activation of those muscle fibers that are not involved in the voluntary muscle contraction. [ 16 ] As a result of NMES, a number of adaptation processes occur in skeletal muscles, [ 17 ] and in the function of the nervous system. [ 18 ] To maximize the effect of NMES, sufficiently intense exposure regimes [ 19 ] and/or a long course of stimulation (at least 4 weeks for athletes) are required.…”

Molecular and neural adaptations to neuromuscular electrical stimulation; Implications for ageing muscle

“…The distribution and classification of muscle fibres in humans is based on the content of three predominantly identified myosin heavy chain (MHC) isoforms, consisting of type 1, 2A and 2X ( Schiaffino and Reggiani, 2011 ). An upregulation of MHC-2A and a downregulation of MHC-I expression have been reported in the elderly received eight weeks NMES ( Mancinelli et al, 2019 ). The variability of the plasticity of MHC following NMES may be attributed to variations in stimulation levels ( Minetto et al, 2013 ) and/or variability in the non-selective order of MU recruitment ( Gregory and Bickel, 2005 ).…”