Astrocyte adenosine deaminase loss increases motor neuron toxicity in amyotrophic lateral sclerosis.

As clinical evidence supports a negative impact of dysfunctional energy metabolism on the disease progression in amyotrophic lateral sclerosis, it is vital to understand how the energy metabolic pathways are altered and whether they can be restored to slow disease progression. Possible approaches include increasing or rerouting catabolism of alternative fuel sources to supplement the glycolytic and mitochondrial pathways such as glycogen, ketone bodies and nucleosides. To analyse the basis of the catabolic defect in amyotrophic lateral sclerosis we used a novel phenotypic metabolic array. We profiled fibroblasts and induced neuronal progenitor-derived human induced astrocytes from C9orf72 amyotrophic lateral sclerosis patients compared to normal controls, measuring the rates of production of reduced nicotinamide adenine dinucleotides from 91 potential energy substrates. This approach shows for the first time that C9orf72 human induced astrocytes and fibroblasts have an adenosine to inosine deamination defect caused by reduction of adenosine deaminase, which is also observed in induced astrocytes from sporadic patients. Patient-derived induced astrocyte lines were more susceptible to adenosine-induced toxicity, which could be mimicked by inhibiting adenosine deaminase in control lines. Furthermore, adenosine deaminase inhibition in control induced astrocytes led to increased motor neuron toxicity in co-cultures, similar to the levels observed with patient derived induced astrocytes. Bypassing metabolically the adenosine deaminase defect by inosine supplementation was beneficial bioenergetically in vitro, increasing glycolytic energy output and leading to an increase in motor neuron survival in co-cultures with induced astrocytes. Inosine supplementation, in combination with modulation of the level of adenosine deaminase may represent a beneficial therapeutic approach to evaluate in patients with amyotrophic lateral sclerosis.

Cerebrospinal fluid macrophage biomarkers in amyotrophic lateral sclerosis.

OBJECTIVE: The neurodegenerative disease, amyotrophic lateral sclerosis (ALS), is a heterogeneous clinical syndrome involving multiple molecular pathways. The development of biomarkers for use in therapeutic trials is a priority. We sought to use a high-throughput proteomic method to identify novel biomarkers in individual cerebrospinal fluid (CSF) samples. METHODS: Liquid chromatography/tandem mass spectrometry with label-free quantification was used to identify CSF proteins using samples from a well-characterized longitudinal cohort comprising patients with ALS (n = 43), the upper motor neuron variant, primary lateral sclerosis (PLS; n = 6), and cross-sectional healthy (n = 20) and disease controls (Parkinsons' disease, n = 20; ALS mimic disorders, n = 12). RESULTS: Three macrophage-derived chitinases showed increased abundance in ALS: chitotriosidase (CHIT1), chitinase-3-like protein 1 (CHI3L1), and chitinase-3-like protein 2 (CHI3L2). Elevated CHI3L1 was common to ALS and PLS, whereas CHIT1 and CHI3L2 levels differed. Chitinase levels correlated with disease progression rate (CHIT1, r = 0.56, p < 0.001; CHI3L1, r = 0.31; p = 0.028; CHI3L2, r = 0.29, p = 0.044). CHIT1, CHI3L1, and CHI3L2 levels correlated with phosphorylated neurofilament heavy chain (pNFH; r = 0.62, p < 0.001; r = 0.49, p < 0.001; r = 0.41, p < 0.001). CHI3L1 levels, but not CHIT1 or CHI3L2, increased over time in those with low initial levels (gradient = 0.005 log abundance units/month, p = 0.001). High CHIT1 was associated with shortened survival (hazard ratio [HR] 2.84; p = 0.009). Inclusion of pNFH in survival models left only an association of pNFH and survival (HR 1.26; p = 0.019). INTERPRETATION: Neuroinflammatory mechanisms have been consistently implicated through various experimental paradigms. These results support a key role for macrophage activity in ALS pathogenesis, offering novel target engagement and pharmacodynamic biomarkers for neuroinflammation-focused ALS therapy. Ann Neurol 2018;83:258-268.

A risk stratifying tool to facilitate safe late-stage percutaneous endoscopic gastrostomy in ALS.

BACKGROUND: The safety of percutaneous endoscopic gastrostomy (PEG) insertion in amyotrophic lateral sclerosis (ALS) patients with significant respiratory compromise has been questioned. OBJECTIVES: To review the characteristics of an ALS clinic patient cohort undergoing PEG, and the introduction of a risk stratification tool with procedural adaptations for higher-risk individuals. METHODS: Patients undergoing PEG insertion were analysed (n = 107). Cases stratified as higher-risk underwent insertion in a semi-recumbent position, minimising sedation, with the option of nasal non-invasive ventilation. RESULTS: All underwent successful PEG. One-third had pre-procedure FVC ≤50% (mean, 64 ± 22%). Of those who underwent PEG insertion after introduction of risk stratification (n = 58), 39 (67%) met criteria for being higher risk, 16 (41%) of whom had FVC ≤50% (p = 0.005). High-risk patients received lower sedative doses vs. the low-risk group (midazolam 2.1 ± 1.1 vs.2.8 ± 0.95mg, p = 0.021; fentanyl 42 ± 16 vs. 60 ± 21µg, p = 0.015). Four deaths occurred within one month of insertion (attributable to the natural disease course). CONCLUSIONS: Risk stratification identified a greater number of patients with evidence of respiratory compromise than using the sole criterion of FVC ≤50%. A modified PEG procedure enabled safe insertion despite respiratory compromise, in those who might not have tolerated attempted insertion by alternative means such as radiologically-inserted gastrostomy.