Interleukin-6 and amyotrophic lateral sclerosis

Abstract

Background: IL-6 is an inflammatory cytokine that is a possible factor in progression of the disease. We have investigated venous blood levels of IL-6 in controls and ALS patients in relation to clinical staging and respiratory function.

Methods: We studied 82 patients with ALS and 43 age and gender-matched healthy control subjects. Blood was drawn at the same time of day in the mornings to avoid diurnal variation. IL-6 levels were estimated according to a fixed protocol. Clinical measures included ALSFRS-R, vital capacity, and mean bilateral phrenic nerve CMAP amplitude. A multi-regression data analysis was used in addition to conventional statistical methods.

Results: IL-6 levels were positively correlated with increasing age in the control group. In ALS patients mean IL-6 levels were raised but the levels were markedly variable from case to case and did not reach significance (p 0.1). In addition to age effects reduction in phrenic nerve CMAP amplitude was correlated with increased IL-6 levels (p 0.026).

Conclusions: IL-6 levels were physiologically influenced by aging in controls and by respiratory dysfunction in ALS. There was marked variability in levels from case to case, which might be related to respiratory factors, which cause pulmonary inflammation.

Keywords: Amyotrophic lateral sclerosis; Biomarker; Interleukin-6; Respiratory function; Respiratory insufficiency.