Sebastian Michels

Background: Amyotrophic lateral sclerdosis (ALS) and spinal muscular atrophy (SMA) are motor neuron diseases associated with distinct metabolic alterations. ALS patients feature an increased resting energy expenditure (REE) causing weight loss and cachexia. In SMA, a disturbed utilization of free fatty acids has been described. These metabolic alterations negatively affect prognosis in both diseases. The objective of this study was to further characterize these changes to identify potential therapeutic targets.Methods: Between 11/2020 and 08/2022, 112 ALS patients, 77 SMA patients, and 50 controls were recruited in the Department of Neurology of Ulm University. Standardized blood and urinary samples were collected to analyze fat and ketone metabolism.Results: Ketone body levels were higher in ALS and SMA compared to controls. In both diseases, patients with higher BMI featured higher ketone bodies and free fatty acids compared to those with lower BMI, while in controls we found the opposite phenomenon. In SMA, more severe disease types were associated with higher ketone body levels. Compared to ALS, SMA patients featured higher ketone body and free fatty acid levels.Conclusions: Our data suggest that already during early disease stages, ALS patients produce ketone bodies to compensate for the energy deficit. In SMA, on the other hand, the persistence of ketogenesis may indicate an upregulation of all available metabolic pathways for energy production due to the disturbance of fatty acid utilization. Therefore, the application of additional sources of energy, such as ketone bodies, might constitute a promising therapeutic option in both diseases.

Nuclear clearance and cytoplasmic aggregation of the RNA-binding protein TDP-43 are observed in many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS) and fronto- temporal dementia (FTD). Although TDP-43 dysregulation of splicing has emerged as a key event in these diseases, TDP-43 can also regulate polyadenylation; yet, this has not been adequately studied. Here, we applied the dynamic analysis of polyadenylation from RNA-seq (DaPars) tool to ALS/FTD transcriptome datasets, and report extensive alternative polyadenylation (APA) upon TDP-43 alteration in ALS/FTD cell models and postmortem ALS/FTD neuronal nuclei. Importantly, many identified APA genes highlight pathways implicated in ALS/FTD pathogenesis. To determine the functional significance of APA elicited by TDP-43 nuclear depletion, we examined microtubule affinity regulating kinase 3 (MARK3). Nuclear loss of TDP-43 yielded increased expression of MARK3 transcripts with longer 3’UTRs, resulting in greater transcript stability and elevated MARK3 protein levels, which promotes increased neuronal tau S262 phosphorylation. Our findings define changes in polyadenylation site selection as a previously unrecognized feature of TDP-43-driven disease pathology in ALS/FTD and highlight a potentially novel mechanistic link between TDP-43 dysfunction and tau regulation.

Alternative polyadenylation (APA) plays an essential role in brain development; however, current transcriptome-wide association studies (TWAS) largely overlook APA in nominating susceptibility genes. Here, we performed a 3′ untranslated region (3′UTR) APA TWAS (3′aTWAS) for 11 brain disorders by combining their genome-wide association studies data with 17,300 RNA-seq samples across 2,937 individuals. We identified 354 3′aTWAS-significant genes, including known APA-linked risk genes, such as SNCA in Parkinson’s disease. Among these 354 genes, ~57% are not significant in traditional expression- and splicing-TWAS studies, since APA may regulate the translation, localization and protein-protein interaction of the target genes independent of mRNA level expression or splicing. Furthermore, we discovered ATXN3 as a 3′aTWAS-significant gene for amyotrophic lateral sclerosis, and its modulation substantially impacted pathological hallmarks of amyotrophic lateral sclerosis in vitro. Together, 3′aTWAS is a powerful strategy to nominate important APA-linked brain disorder susceptibility genes, most of which are largely overlooked by conventional expression and splicing analyses.

Background and purpose: Respiratory insufficiency is a common symptom during the course of amyotrophic lateral sclerosis (ALS). The diagnostic workup may be challenging and includes a wide array of diagnostic measures. In this study, the aim was to analyze the relationship between hypercapnia‐associated symptoms, blood gas parameters and pulmonary function tests.Methods: In total, 109 patients (56 women, 53 men, 62.4 ± 11.9 years) with definite, possible or probable ALS according to El Escorial criteria were included. All patients received either arterial blood gas analysis, nocturnal capnometry or both. Pulmonary function was assessed by spirometry and peak cough flow. Clinical symptoms potentially indicating hypercapnia were assessed using 17 dichotomous (yes/no) items.Results: Of 109 ALS patients, 40 had hypercapnia. The highest accuracy and specificity for predicting hypercapnia was observed for dyspnea at rest (Youden's index 17%, 95% confidence interval [CI] 2%–34%; sensitivity 23%, 95% CI 9%–38%; specificity 95%, 95% CI 88%–100%). Daytime fatigue yielded the highest sensitivity of 58% (95% CI 40%–76%). Logistic regression for all assessed symptoms combined yielded an area under the receiver operating charteristic curve of 0.8 (95% CI 0.7–0.9). Compared to the clinical symptoms, forced vital capacity and peak cough flow showed higher sensitivity (70% and 87%, respectively) but lacked specificity (33% and 20%).Conclusion: Evaluation of the presence of hypercapnic symptoms can be utilized to predict incipient respiratory insufficiency and should complement pulmonary function tests. Further studies are needed to validate specific questionnaires in this regard. No single hypercapnia‐associated symptom or pulmonary function test on its own seems sufficient to safely predict hypercapnia.

Background and Objectives Nodo-paranodopathies are peripheral neuropathies with dysfunction of the node of Ranvier. Affected patients who are seropositive for antibodies against adhesion molecules like contactin-1 and neurofascin show distinct clinical features and a disruption of the paranodal complex. An axoglial dysjunction is also a characteristic finding of diabetic neuropathy. Here, we aim to investigate a possible association of antibody-mediated nodo-paranodopathy and diabetes mellitus (DM). Methods We retrospectively analyzed clinical data of 227 patients with chronic inflammatory demyelinating polyradiculoneuropathy and Guillain-Barré syndrome from multiple centers in Germany who had undergone diagnostic testing for antiparanodal antibodies targeting neurofascin-155, pan-neurofascin, contactin-1–associated protein 1, and contactin-1. To study possible direct pathogenic effects of antiparanodal antibodies, we performed immunofluorescence binding assays on human pancreatic tissue sections. Results The frequency of DM was 33.3% in seropositive patients and thus higher compared with seronegative patients (14.1%, OR = 3.04, 95% CI = 1.31–6.80). The relative risk of DM in seropositive patients was 3.4-fold higher compared with the general German population. Seropositive patients with DM most frequently harbored anti–contactin-1 antibodies and had higher antibody titers than seropositive patients without DM. The diagnosis of DM preceded the onset of neuropathy in seropositive patients. No immunoreactivity of antiparanodal antibodies against pancreatic tissue was detected. Discussion We report an association of nodo-paranodopathy and DM. Our results suggest that DM may be a potential risk factor for predisposing to developing nodo-paranodopathy and argue against DM being induced by the autoantibodies. Our findings set the basis for further research investigating underlying immunopathogenetic connections.

Huntington’s disease (HD) is a rare, genetic neurodegenerative disorder often presenting with emotional, cognitive and behavioral abnormalities before manifestation of disease defining motor symptoms. Cognitive impairment is a frequent clinical feature caused by different dementia subtypes. Imaging cortical and subcortical glucose metabolism via 18F-FDG PET/CT can help to discriminate the underlying disease. The patient is a 54-year old man presenting with progressive cognitive impairment and mild orofacial dyskinesia. 18F-FDG PET/CT of the brain revealed a severe bilateral hypometabolism in the striatum. Following imaging Huntington’s disease was suspected and a molecular genetic testing confirmed the diagnosis. Huntington’s disease is a rare but important differential diagnosis of cognitive impairment, especially before motor symptoms are manifest. 18F-FDG PET is capable to show early striatal dysfunction in HD even when structural imaging is normal. We conclude that, in cases with negative family history the HD characteristic metabolic pattern can lead to the diagnosis when no other dementia-suspected changes are present.