Abstract
BackgroundPrevious research has described a neuroprotective effect of IGF-I, supporting neuronal survival, axon growth and proliferation of muscle cells. Therefore, the association between IGF-I concentration, muscle histology and electrophysiological markers in a cohort of patients with sarcopenia dares investigation.MethodsMeasurement of serum concentrations of IGF-I and binding partners, electromyographic measurements with the MUNIX (Motor Unit Number Index) method and muscle biopsies were performed in 31 patients with acute hip fracture older age 60 years. Molecular markers for denervation (neural cell adhesion molecule NCAM) and proliferation markers (Ki67) were assessed by immunofluorescence staining of muscle biopsy tissue. Skeletal muscle mass by bioelectrical impedance analysis and hand-grip strength were measured to assess sarcopenia status according to EWGSOP2 criteria.ResultsThirty-one patients (20 women) with a mean age of 80.6 ± 7.4 years were included. Concentrations of IGF-I and its binding partners were significantly associated with sarcopenia (ß = − 0.360; p = 0.047) and MUNIX (ß = 0.512; p = 0.005). Further, expression of NCAM (ß = 0.380; p = 0.039) and Ki67 (ß = 0.424; p = 0.022) showed significant associations to IGF-I concentrations.ConclusionsThe findings suggest a pathogenetic role of IGF-I in sarcopenia based on muscle denervation.
Highlights
Previous research has described a neuroprotective effect of Insulin-like growth factor 1 (IGF-I), supporting neuronal survival, axon growth and proliferation of muscle cells
Since IGF-I is a key growth factor in muscle tissue and in the peripheral and central nervous system by promoting neuronal survival, this study focuses on the association of IGF-I concentrations and number of motor units measured by Motor unit number index (MUNIX), and expression of neural cell adhesion molecule (NCAM) and Ki67 in patients with sarcopenia
The groups differed significantly in maximal handgrip strength (p = 0.030) and the severity of sarcopenia represented by z-score sarcopenia (p = 0.040), showing that men were more affected by sarcopenia than women
Summary
Previous research has described a neuroprotective effect of IGF-I, supporting neuronal survival, axon growth and proliferation of muscle cells. Histological evaluation of muscle tissue usually includes measurement of expression of the usually used histological marker for denervated myofibers neural cell adhesion molecule (NCAM) It is unclear whether the reinnervation capacity is reduced in patients with sarcopenia and what specific role IGF-I plays in that regard. IGF-I production can be detected in the skeletal muscle itself [14] as a response to GH, testosterone or muscle stretch [15] It promotes hypertrophic effects in skeletal muscle via proliferation of satellite cells, stimulation of protein synthesis [15] and myoblast proliferation and differentiation [16]. GH secretion and subsequent IGF-I production is markedly reduced while aging [15] with poor muscle strength and poor physical performance [19, 20] Another important function of IGF-I is its growth promoting effect on the peripheral and central nervous system. It has been considered and tested as a potential therapeutic drug in neurodegenerative diseases like amyotrophic lateral sclerosis [24,25,26]
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