Rejuvenation of the aged neuromuscular junction by exercise

Sarcopenia and Ageing

Musculoskeletal ageing is a major health challenge as muscles and bones constitute around 55-60% of body weight. Ageing muscles will result in sarcopenia that is characterized by progressive and generalized loss of skeletal muscle mass and strength with a risk of adverse outcomes. In recent years, a few consensus panels provide new definitions for sarcopenia. It was officially recognized as a disease in 2016 with an ICD-10-CM disease code, M62.84, in the International Classification of Diseases (ICD). With the new definitions, there are many studies emerging to investigate the pathogenesis of sarcopenia, exploring new interventions to treat sarcopenia and evaluating the efficacy of combination treatments for sarcopenia. The scope of this chapter is to summarize and appraise the evidence in terms of (1) clinical signs, symptoms, screening, and diagnosis, (2) pathogenesis of sarcopenia with emphasis on mitochondrial dysfunction, intramuscular fat infiltration and neuromuscular junction deterioration, and (3) current treatments with regard to physical exercises and nutritional supplement.

Evaluation of Sarcopenia Using Biomarkers of the Neuromuscular Junction in Parkinson's Disease

Patients with Parkinson's disease (PD) present with an advanced form of age-related muscle loss or sarcopenia. However, the search for a biomarker to accurately predict muscle loss in PD remains elusive. We evaluated the biomarkers of neuromuscular junction (NMJ) stability, including c-terminal agrin fragment-22 (CAF22), brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF) as predictors of muscle wasting and physical capacity in PD. Male, 63-78 years patients of PD, were investigated for physical capacity, handgrip strength (HGS), and circulating biomarkers at the diagnosis and follow-up during rehabilitation 6 months apart. Patients with PD presented with elevated CAF22 and reduced BDNF and GDNF levels, which were partially restored to normal levels with rehabilitation. All three biomarkers showed significant dynamic associations with HGS and indexes of sarcopenia. Logistic regression revealed that the combination of biomarkers levels into a cumulative risk score enhanced the diagnostic accuracy of sarcopenia. In brief, measurements of plasma BDNF, GDNF, and CAF22 may be helpful in timely diagnosis and/or evaluation of sarcopenia.

Structural and Functional Changes in the Coupling of Fascial Tissue, Skeletal Muscle, and Nerves During Aging

Aging is a one-way process associated with profound structural and functional changes in the organism. Indeed, the neuromuscular system undergoes a wide remodeling, which involves muscles, fascia, and the central and peripheral nervous systems. As a result, intrinsic features of tissues, as well as their functional and structural coupling, are affected and a decline in overall physical performance occurs. Evidence from the scientific literature demonstrates that senescence is associated with increased stiffness and reduced elasticity of fascia, as well as loss of skeletal muscle mass, strength, and regenerative potential. The interaction between muscular and fascial structures is also weakened. As for the nervous system, aging leads to motor cortex atrophy, reduced motor cortical excitability, and plasticity, thus leading to accumulation of denervated muscle fibers. As a result, the magnitude of force generated by the neuromuscular apparatus, its transmission along the myofascial chain, joint mobility, and movement coordination are impaired. In this review, we summarize the evidence about the deleterious effect of aging on skeletal muscle, fascial tissue, and the nervous system. In particular, we address the structural and functional changes occurring within and between these tissues and discuss the effect of inflammation in aging. From the clinical perspective, this article outlines promising approaches for analyzing the composition and the viscoelastic properties of skeletal muscle, such as ultrasonography and elastography, which could be applied for a better understanding of musculoskeletal modifications occurring with aging. Moreover, we describe the use of tissue manipulation techniques, such as massage, traction, mobilization as well as acupuncture, dry needling, and nerve block, to enhance fascial repair.