Concentrações séricas diminuídas de IGF-I e IGFBP-3, atrofia muscular e alterações no desempenho neuromuscular contribuem para a fraqueza muscular em indivíduos hemiparéticos crônicos

Abstract

Muscle weakness is characterized as a significant cause of reduced physical capacity and functionality, this limitation is due to the decreased ability to produce voluntary contraction of the muscle groups in the affected hemisphere. It is a consequence of morphological and functional changes related to neural and muscular aspects. The aim of this study was to evaluate the neuromuscular performance, muscle volume and Growth Factor Insulin-like I (IGF-I) serum concentration (SC) and its Binding Protein, IGFBP-3, in subjects with chronic hemiparesis. For such, a cross-sectional study was designed. Fourteen subjects with chronic hemiparesis were evaluated for functionality performed by assessment tools Berg Balance Scale Test, Timed Up Go Adapted, Walk test 10 meters, Functional Reach Test, Fugl- Meyer Assessment, Barthel Index, Assessment of Quality of Life, Medical Outcomes Study- 36 Health Status Measurement. The subjects were allocated in the hemiparetic group (HG, 12 men). Healthy subjects (control group, CG) were paired for age, gender, height and body mass index with HG. Rectus femoris (RF), vastus medialis (VM), vastus intermedius (VI), vastus lateralis (VL), biceps femoris (BF) and semitendinosus / semimembranosus (SS) muscle volume was measured. The SC IGF-I and IGFBP-3 was quantified by ELISA. The peak torque (PT), work and power during concentric and eccentric contractions of knee extensors and flexors were evaluated using an isokinetic dynamometer at 60°/s, synchronously to record muscle activation RF, VM, VL, BF and semitendinosus (ST). For parametric data, the unpaired t test and ANOVA two-way followed by Tukey test were applied to identify statistical differences between groups and factors (dominance and condition; paretic limb: PL, non-paretic limb: NPL and control group CG). For nonparametric data was used the Mann Whitney U test followed by Bonferroni adjustment. The significance level of 5% was considered. The HG presented functional levels and CSs of IGF-I and IGFBP-3 reduced compared to the CG. The HG showed selective muscle atrophy of VM, VI, BF and SS, and also altered muscle activation between agonist and antagonist against the CG. There was a significant decrease in PT, work and power of the knee extensors and flexors for concentric and eccentric actions in the PL and NPL compared to the CG. In conclusion, hemiparetic group show weakness in the PL due to changes in neuromuscular performance, including decreased PT, power and work, and also due to changes in the agonist and antagonist muscle recruitment. These neural changes are accompanied by selective atrophy of quadriceps and hamstrings muscles and CSs decrease in IGF-I and IGFBP-3 serum concentrations.