Lower Circulating Gas6 Levels Are Associated with Bulbar Phenotype and Faster Disease Progression in Amyotrophic Lateral Sclerosis Patients

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that primarily affects the motor neurons in the brain and spinal cord. While the exact cause of ALS is not fully understood, a combination of genetic and environmental factors is believed to contribute to its development. Growth arrest-specific 6 (Gas6), a vitamin K-dependent protein, has been recognized to enhance oligodendrocytes and neurons' survival and is associated with different kinds of (neuro)inflammatory conditions. Therefore, we aimed to determine a possible implication of Gas6 in ALS phenotype and progression by evaluating the value of circulating Gas6 and its soluble receptors (sAxl, sMer, sTyro-3) in ALS patients. We conducted a prospective observational study including 65 ALS patients and measured the circulating serum levels of Gas6, sAxl, sMer, soluble Tyro-3 (sTyro-3), and neurofilaments (NfLs). In our ALS cohort, lower serum levels of Gas6 and concomitantly higher levels of NfLs were associated with a more aggressive disease, expressed with bulbar phenotype (p-value for Gas6 = 0.03) and faster progression (p-value for Gas6 = 0.03). Also, serum Gas6 was able to distinguish (area under the curve, cut-off 13.70 ng/mL, sensitivity 69.57%, specificity 72.72%) between fast and slow progressors. Due to its neuroprotective properties, our data suggest that Gas6 could be an intriguing biomarker in ALS patients.