GBA1 and Parkinson disease: Ambroxol treatment resulted in a significant elevation of glucosylceramidase protein levels in control [median increase 30% of untreated cells (IQR 15–40%), Mann-Whitney U-test P = 0.0085], Gaucher disease [median increase 100% of untreated (IQR 87–200% increase), P = 0.004], Parkinson’s disease with GBA mutations [median increase 50% of untreated (IQR 40–130%), P = 0.04] and non-manifesting carrier fibroblasts [median increase 35% of untreated cells (IQR 25–40% increase), P = 0.008] on western blotting (Fig. 5).