Clinical and laboratory features of ALS

Abstract

Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. There is heterogeneity of the clinical features of ALS including site of onset and rate of progression. Previously, ALS was considered to be a disease of the motor system. However, there is evidence that ALS patients can have cognitive impairment. Some patients meet the diagnostic criteria for Frontotemporal dementia (FTD). It is now thought that FTD and ALS are related neurodegenerative disorders, which fall on the same disease spectrum. A reliable biomarker is needed to monitor the progression of the disease and assess the effects of potential therapies. Sequential Window Acquisition of all theoretical fragment-ion spectra analysis (SWATHTM) is a reliable and powerful proteomic approach to investigate the biomarker proteins in complex samples such as blood. Method: The aim of the first study is to evaluate the utility of neurofilament levels as blood or cerebrospinal fluid (CSF) biomarker in patients with ALS by using a systematic search of Pubmed, Embase and Scopus databases. Meta-analysis of the data was performed. The aim of the second study is to screen for cognitive and behavioural impairment in people with ALS and controls with neuromuscular disease and to correlate these with clinical features. 108 people with ALS and 60 controls were recruited and assessed with the Addenbrooke’s cognitive examination-III (ACE-III), the Frontal assessment battery (FAB), and the executive function component of the Edinburgh cognitive and behavioural ALS screen (ECAS). The Amyotrophic lateral sclerosis-Frontotemporal dementia questionnaire (ALS-FTD-Q) and the Motor Neuron Disease Behavioural instrument (MiND-B) were administered to the caregivers of people with ALS. Longitudinal studies of cognition were performed in 37 ALS patients. The aim of the third study is to search for plasma biomarkers in ALS patients compared to healthy controls by using SWATH™ quantification analysis and to compare proteomic analysis of ALS patients with and without cognitive impairment (CI). 42 patients with ALS and 18 healthy controls were recruited. Western blot analysis was used to confirm the results of analysis and in an independent set of samples. Ingenuity pathway analysis (IPA) was performed. Results: The systematic review found that levels of NF heavy chain and light chains were significantly elevated in the CSF of ALS patients compared to healthy controls/controls without parenchymal central nervous system (CNS) involvement and ALS mimic disease patients. NF light chain level in CSF was higher in ALS patients than in neurological patients with CNS involvement (SMD=1.352, P=0.001). NF light chain concentration in blood was higher in ALS patients than in healthy controls/controls without CNS involvement (SMD=1.448, P<0.0001). NF heavy chain levels in CSF were negatively correlated disease duration and ALSFRS-R (r=-0.447, P<0.0001; r=-0.279, P=0.011). NF light chain levels in CSF were negatively correlated with disease duration (r=-0.486, P<0.0001). In the patient cohort, the frequencies of cognitive impairment based on the ACE-III and FAB were 30.0% and 14.0%, in ALS and 11.7% and 3.3% in controls, respectively. In ALS, the frequencies of behavioural impairment based on ALS-FTD-Q and MiND-B were 32.1% and 39.4 %, respectively. ALS participants with cognitive impairment measured with ACE-III had significantly shorter survival time than those without. ALS participants with behavioural impairment measured with ALS-FTD-Q had worse prognosis than those without. No significant difference was found between the first two serial cognitive tests based on ACE-III and FAB by using a generalized estimating equation. Between ALS and controls, there were significant differences in the expression of 30 proteins. Of these, plasma gelsolin concentration was 1.2 fold higher in controls than ALS patients (P=0.006). Between controls and ALS with CI, there was significant difference in expression of 32 proteins. The clusterin level was 1.2 fold downregulated in patients with CI compared with controls (P=0.03). The observed changes in levels of gelsolin, clusterin, CD5L and ficolin 3 were validated by using western blot. Pathway analysis showed that the LXR/RXR pathway, complement pathway and coagulation pathway are regulated in ALS. Conclusions: The results of the first study shows that NF heavy and light chain levels have potential to be used as markers of neural degeneration in ALS, but are not specific for the disease, and are more likely to be used as measures of disease progression. The results of second study indicate that there is a greater frequency of cognitive impairment in people with ALS than in patients with other neuromuscular diseases. The cognitive and behavioural tests are potential biomarkers of the prognosis of ALS. The results of cognitive tests are stable over 6 months and possibly longer. The results of the third study illustrate that clusterin, gelsolin and ficolin 3 are novel potential biomarkers to differentiate the ALS patients from healthy controls. Abnormalities in the LXR/RXR pathway suggest that lipid metabolism is involved in ALS. There are widespread changes in immune function and coagulation in ALS.