Efeito do polimorfismo -174 G/C da região promotora do gene IL-6, índices plasmáticos de IL-6 e força muscular de mulheres idosas

Abstract

The present study investigates the effect of -174 G/C promoter polymorphism of the interleukin-6 (IL-6) gene on the plasmatic levels of IL-6 and muscular strength, as well as the association between doses of IL-6 and the muscular strength of elderly women. The sample consisted of 199 institutionalized and community-living elderly patients (73.0 ± 7.8 years) in the city of Belo Horizonte, Brazil. The -174 G/C polymorphism in the promoter of the human IL-6 gene was determined by direct sequencing of a polymerase chain reaction product. The plasmatic concentrations of IL-6 were measured using the ELISA method. The muscular strength of the articulation of the knee was assessed using the Biodex System 3 Pro® isokinetic dynamometer. The covariance analysis (ANCOVA) was applied to investigate the effect of the polymorphism on the IL-6 levels and muscular strength, while the Pearson correlation index was used to assess the relation between the plasmatic levels of IL-6 and muscular strength. The -174 G/C promoter polymorphism affected the plasmatic levels of IL-6 in elderly women (p<0.01) due to the fact that the homozygotes for the G allele presented high levels of IL-6 (GG 3.85 pg/ml; GC+CC 2.13 pg/ml). This polymorphism did not directly influence the muscular strength of the elderly patients (p>0.05). No association was found between the plasmatic levels of IL-6 and the muscular strength of the knee extensors (r=0.087; p=0.306) and knee flexors (r=-0.011; p=0.894). The results of this study support previous reports which defend that the -174 G/C promoter polymorphism contributed to the individual variability of the IL-6 plasmatic levels in elderly women. This polymorphism did not influence the muscular strength of the elderly patients.