Cerebrospinal fluid amyloid beta and glial fibrillary acidic protein concentrations in Huntington’s disease

Introduction Huntingtons disease (HD) is a genetic incurable lethal disease. Biomarkers are needed for objective assessment of disease progression. Evidence supports both complex protein aggregation and astrocyte activation in HD. This study assesses the 42 amino acid long amyloid beta (A{beta}42) and glial fibrillary acidic protein (GFAP) as potential biomarkers in the cerebrospinal fluid (CSF) of HD mutation carriers. Methods CSF was obtained from manifest HD patients (ManHD), premanifest HD-gene-expansion carriers (PreHD) and gene-negative controls (controls). Disease Burden Score (DBS) and Total Functional Capacity (TFC) were calculated. Protein concentrations were measured by enzyme-linked immunosorbent assays (ELISA) and intergroup differences were analysed using Mann-Whitney U test. Spearman correlations were calculated to assess disease stage association. Age-adjustment was included in the statistical tests. Results The study enrolled 27 ManHD and 13 PreHD subjects. The number of controls differed in the analysis of A{beta}42 and GFAP (n = 19, and 8 respectively). A{beta}42 levels were higher in ManHD (mean 741 ng/l, SD 361) compared with PreHD (mean 468 ng/l, SD 184) (p= 0.025). Likewise GFAP concentration was higher in ManHD (mean 435 ng/l, SD 255) compared with both PreHD (mean 266 ng/l, SD 92.4)(p = 0.040) and controls (mean 208 ng/l, SD 83.7)(p = 0.011). GFAP correlated with DBS (r = 0.361, p = 0.028), TFC (r = -0.463, p = 0.005), and 5-year risk of onset in PreHD (r = 0.694, p = 0.008). In contrast, there was no correlation between A{beta}42 concentration and DBS, TFC or 5-year risk of onset. Conclusion CSF A{beta}42 levels did not correlate with disease stage suggesting no A{beta}aggregation in HD. GFAP is a potential biomarker in HD with association to disease stage. Validation in larger HD cohorts and potential correlations with clinical phenotype would be of interest.