Association between aberrant biochemical indicators levels and respiratory musclesdysfunction in patients with amyotrophic lateral sclerosis (ALS). Preliminary data.

Background: respiratory failure due to muscular weakness is the main cause of death in amyotrophic lateral sclerosis (ALS). It has been suggested that, in ALS, serum levels of some biochemical indicators of iron homeostasis and energy metabolism, such as ferritin and uric acid, are altered and are associated with overall survival. Indeed, excessive iron causes oxidative stress and damage of cellular membranes, while uric acid is a natural antioxidant. We hypothesized that these substances could be related to indices of respiratory and muscle function. Methods: in 15 ALS patients, respiratory and muscle function were evaluated by sitting forced vital capacity (FVC), sniff nasal inspiratory pressure (SNIP), maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP) and peak cough flow (PCF). In addition, serum ferritin and uric acid were determined. Results: we obtained the following results: FVC 1.72±1.0 L (54.7±25.1 % of predicted), SNIP 32.8±27.7 cmH2O, MIP 33.2±13.3 cmH2O, MEP 33.2±23.7 cmH2O, PCF 262.8±114.1 L/min, ferritin 279.9±243 ng/ml, and uric acid 5.1±2.3 mg/dl. SNIP and PCF were positively correlated to uric acid (ρ. 76, p=0.0009, and ρ. 53, p=0.04, respectively) and negatively to ferritin (ρ= -.64, p=0.009, and ρ= -.65, p=0.01). FVC (% of predicted) was only correlated to uric acid (ρ=. 62, p=0.005). Conclusions: in ALS, biomarkers of oxidative stress appear to be related to the strength of respiratory muscles, which supports their possible role as prognostic markers. SNIP better than FVC may reflect the association between respiratory and metabolic impairment in patients with this disease