Niemann-Pick disease type C (NP-C) is a devastating, neurovisceral lysosomal storage disorder which is characterised by variable manifestation of visceral signs, progressive neuropsychiatric deterioration and premature death, caused by mutations in the NPC1 and NPC2 genes. Due to the complexity of diagnosis and the availability of an approved therapy in the EU, improved detection of NP-C may have a huge impact on future disease management. At the cellular level dysfunction or deficiency of either the NPC1 or NPC2 protein leads to a complex intracellular endosomal/lysosomal trafficking defect, and organ specific patterns of sphingolipid accumulation. Lysosphingolipids have been shown to be excellent biomarkers of sphingolipidosis in several enzyme deficient lysosomal storage disorders. Additionally, in a recent study the lysosphingolipids, lysosphingomyelin (SPC) and glucosylsphingosine (GlcSph), appeared to be elevated in the plasma of three adult NP-C patients. In order to investigate the clinical utility of SPC and GlcSph as diagnostic markers, an in-depth fit for purpose biomarker assay validation for measurement of these biomarkers in plasma by liquid chromatography-tandem mass spectrometry was performed. Plasma SPC and GlcSph are stable and can be measured accurately, precisely and reproducibly. In a retrospective analysis of 57 NP-C patients and 70 control subjects, median plasma SPC and GlcSph were significantly elevated in NP-C by 2.8-fold and 1.4-fold respectively. For miglustat-naïve NP-C patients, aged 2–50 years, the area under the ROC curve was 0.999 for SPC and 0.776 for GlcSph. Plasma GlcSph did not correlate with SPC levels in NP-C patients. The data indicate excellent potential for the use of lysosphingomyelin in NP-C diagnosis, where it could be used to identify NP-C patients for confirmatory genetic testing.

The biogenic amine serotonin (5-HT) is a multi-faceted hormone that is synthesized from dietary tryptophan with the rate limiting step being catalyzed by the enzyme tryptophan hydroxylase (TPH). The therapeutic potential of peripheral 5-HT synthesis inhibitors has been demonstrated in a number of clinical and pre-clinical studies in diseases including carcinoid syndrome, lung fibrosis, ulcerative colitis and obesity. Due to the long half-life of 5-HT in blood and lung, changes in steady-state levels are slow to manifest themselves. Here, the administration of stable isotope labeled tryptophan (heavy “h-Trp”) and resultant in vivo conversion to h-5-HT is used to monitor 5-HT synthesis in rats. Dose responses for the blockade of h-5-HT appearance in blood with the TPH inhibitors L-para-chlorophenylalanine (30 and 100 mg/kg) and telotristat etiprate (6, 20 and 60 mg/kg), demonstrated that the method enables robust quantification of pharmacodynamic effects on a short time-scale, opening the possibility for rapid screening of TPH1 inhibitors in vivo. In the bleomycin-induced lung fibrosis rat model, the mechanism of lung 5-HT increase was investigated using a combination of synthesis and steady state 5-HT measurement. Elevated 5-HT synthesis measured in the injured lungs was an early predictor of disease induced increases in total 5-HT.

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene coding for α-galactosidase A (α-GalA). The deleterious mutations lead to accumulation of α-GalA substrates, including globotriaosylceramide (Gb3) and globotriaosylsphingosine. Progressive glycolipid storage results in cellular dysfunction, leading to organ damage and clinical disease, i.e. neuropathic pain, impaired renal function and cardiomyopathy. Many Fabry patients are treated by bi-weekly intravenous infusions of replacement enzyme. While the only available oral therapy is an α-GalA chaperone, which is indicated for a limited number of patients with specific ‘amenable’ mutations. Lucerastat is an orally bioavailable inhibitor of glucosylceramide synthase (GCS) that is in late stage clinical development for Fabry disease. Here we investigated the ability of lucerastat to lower Gb3, globotriaosylsphingosine and lysosomal staining in cultured fibroblasts from 15 different Fabry patients. Patients’ cells included 13 different pathogenic variants, with 13 cell lines harboring GLA mutations associated with the classic disease phenotype. Lucerastat dose dependently reduced Gb3 in all cell lines. For 13 cell lines the Gb3 data could be fit to an IC50 curve, giving a median IC50 [interquartile range (IQR)] = 11 μM (8.2–18); the median percent reduction (IQR) in Gb3 was 77% (70–83). Lucerastat treatment also dose dependently reduced LysoTracker Red staining of acidic compartments. Lucerastat’s effects in the cell lines were compared to those with current treatments—agalsidase alfa and migalastat. Consequently, the GCS inhibitor lucerastat provides a viable mechanism to reduce Gb3 accumulation and lysosome volume, suitable for all Fabry patients regardless of genotype.

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A BS TRACT: Background: Venglustat is a brain-penetrant, small molecule inhibitor of glucosylceramide synthase used in clinical testing for treatment of Parkinson's disease (PD). Despite beneficial effects in certain cellular and rodent models, patients with PD with mutations in GBA, the gene for lysosomal glucocerebrosidase, experienced worsening of their motor function under venglustat treatment (NCT02906020, MOVES-PD, phase 2 trial). Objective: The objective of this study was to evaluate venglustat in mouse models of PD with overexpression of wild-type α-synuclein. Methods: Mice overexpressing α-synuclein (Thy1-aSyn line 61) or Gba-mutated mice with viral vector-induced overexpression of α-synuclein in the substantia nigra were administered venglustat as food admixture. Motor and cognitive performance, α-synuclein-related pathology, and microgliosis were compared with untreated controls. Results: Venglustat worsened motor function in Thy1-aSyn transgenics on the challenging beam and the pole test. Although venglustat did not alter the cognitive deficit in the Y-maze test, it alleviated anxiety-related behavior in the novel object recognition test. Venglustat reduced soluble and membrane-bound α-synuclein in the striatum and phosphorylated α-synuclein in limbic brain regions. Although venglustat reversed the loss of parvalbumin immunoreactivity in the basolateral amygdala, it tended to increase microgliosis and phosphorylated α-synuclein in the substantia nigra. Furthermore, venglustat also partially worsened motor performance and tended to increase neurofilament light chain in the cerebrospinal fluid in the Gbadeficient model with nigral α-synuclein overexpression and neurodegeneration. Conclusions: Venglustat treatment in two mouse models of α-synuclein overexpression showed that glucosylceramide synthase inhibition had differential detrimental or beneficial effects on behavior and neuropathology possibly related to brain region-specific effects.

Adduction between acrylamide and cysteine residues is a post-translational modification associated with proteins separated by gel electrophoresis. In the present article, three model peptides containing 2-4 cysteine residues were reduced with dithiothreitol, incubated with acrylamide monomers and examined by on-line liquid chromatography coupled to electrospray tandem mass spectrometry. Each of the solutions examined in this work revealed the presence of four distinct components: the free peptide, two different peptide-acrylamide 1:1 adducts involving two cysteine residues at different positions within the same sequence, and the peptide-acrylamide 1:2 adducts. The use of liquid chromatography allowed the separation of components which differed only by the site of complexation of acrylamide, while the application of tandem mass spectrometry furnished reliable sequencing information permitting the identification of most cysteine residues involved in such complexation.

Background: Fabry disease (FD) is a lysosomal storage disorder caused by mutations in the GLA gene coding for α-galactosidase A (α-GalA). These mutations lead to the accumulation of α-GalA substrates, including globotriaosylceramide (Gb3). As a consequence of lipid storage, Fabry patients can suffer from neuropathic pain, impaired kidney function and cardiomyopathy. Existing treatments for FD either require biweekly intravenous infusions of replacement enzyme, or are effective in a limited number of patients with specific "amenable" mutations. Substrate reduction therapy with lucerastat, an orally-available small molecule inhibitor of glucosylceramide synthase (GCS) 1 is an alternative mechanism to reduce Gb3 accumulation, that would be suitable for all FD patients. Methods: Fabry patient-derived fibroblasts with the genotypes R301G (residual -GalA activity; 20%) R220X (<3%) and W162X (<1%) were obtained from the Coriell Institute and cultured for 9 days in the presence of 9 concentrations in duplicate of either lucerastat, migalastat or agalsidase alfa. Lysosomes were stained using LysoTracker® Red DND-99 and area was quantified. Sphingolipids were extracted with methanol and quantified with LC-MS/MS. Fabry mice (Gla-/0 and Gla-/-, n = 5 or 6 for each gender) were treated from 5 weeks of age with lucerastat (1200 mg/kg/day food admix) or normal food for 20 weeks. Mice were sacrificed and sphingolipids were quantified in various organs. Results: In Fabry patient-derived fibroblasts, lucerastat dose-dependently inhibited GCS, reducing glucosylceramide and increasing sphingomyelin, while ceramide remained unchanged. The downstream consequence of GCS inhibition was reduction of Gb3 and lysosome staining, including in cells from patients with no residual α-GalA activity. In Fabry mice, lucerastat treatment reduced lipid storage in two major organs affected by FD: mean Gb3 in the kidneys (-33%, p <0.001) and α-galactoseterminated glycosphingolipids in the dorsal root ganglia (-48%, p <0.05). In the liver of the Fabry mice, mean glucosylceramide (GlcCer (24:0)) was reduced (-59%, p <0.001) in addition to Gb3 (24:1) (-37%, p <0.05), demonstrating substrate reduction through GCS inhibition. Conclusion: Lucerastat, a GCS inhibitor, reduces Gb3 in the absence of residual -GalA activity both in vitro and in vivo. Lucerastat has potential to provide an oral substrate reduction therapy for all Fabry patients independent of genotype. A 12-week exploratory clinical study with lucerastat in Fabry patients has been completed, and a pivotal clinical efficacy study in Fabry patients is being designed. Support: References: 1. Guérard (2017) Orphanet J. Rare Dis.