Glucagon-like Peptide-1 (GLP-1) Receptor Agonists and Neuroinflammation: Implications for Neurodegenerative Disease Treatment

Katherine O. Kopp, Elliot J. Glotfelty, Yazhou Li, Nigel H. Greig; Pharmacological Research, 2022, 106550, DOI:10.1016/j.phrs.2022.106550. Abstract: Chronic, excessive neuroinflammation is a key feature of neurodegenerative diseases such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). However, neuroinflammatory pathways have yet to be effectively targeted in clinical treatments for such diseases. Interestingly, increased inflammation and neurodegenerative disease risk have been associated with type 2 diabetes mellitus (T2DM) and insulin resistance (IR), suggesting that treatments that mitigate T2DM pathology may be successful in treating neuroinflammatory and neurodegenerative pathology as well. Glucagon-like peptide-1 (GLP-1) is an incretin hormone that promotes healthy insulin signaling, regulates blood sugar levels, and suppresses appetite. Consequently, numerous GLP-1 receptor (GLP-1R) stimulating drugs have been developed and approved by the US Food and Drug Administration (FDA) and related global regulatory authorities for the treatment of T2DM. Furthermore, GLP-1R stimulating drugs have been associated with anti-inflammatory, neurotrophic, and neuroprotective properties in neurodegenerative disorder preclinical models, and hence hold promise for repurposing as a treatment for neurodegenerative diseases. In this review, we discuss incretin signaling, neuroinflammatory pathways, and the intersections between neuroinflammation, brain IR, and neurodegenerative diseases, with a focus on AD and PD. We additionally overview current FDA-approved incretin receptor stimulating drugs and agents in development, including unimolecular single, dual, and triple receptor agonists, and highlight those in clinical trials for neurodegenerative disease treatment. We propose that repurposing already-approved GLP-1R agonists for the treatment of neurodegenerative diseases may be a safe, efficacious, and cost-effective strategy for ameliorating AD and PD pathology by quelling neuroinflammation. 

 FRDA is a heritable neurodegenerative movement disorder fueled and exacerbated by neuroinflammation 290, 291, 292, which could make it a candidate for GLP-1R agonist treatment. Exenatide treatment was found to re-elevate reduced levels of frataxin, a critical mitochondrial protein, in FRDA patients, which can enhance mitochondrial health and function and could, by extension, reduce neuroinflammation and neurodegeneration characteristic of the disease [293]—again, providing a potentially fruitful area of future basic and clinical research. Similarly, studies by Meissner and colleagues [178] demonstrated the presence of impaired insulin/IGF-1 and IR in vulnerable brain regions of multiple system atrophy patients and a related transgenic mouse model, and their mitigation in the latter by exendin-4, likewise suggesting a promising area of future research.

Decreased mitochondrial respiration in cardiac fibers isolated from a mouse model of Friedreich’s ataxia

Peter Vitiello, Paul Pierce, Shirley/Xiu Wang, Alec Cooper, Aristides Rivera, Jared Ailts, Holly Van Remmen, Jacob Brown; Free Radical Biology and Medicine,Volume 192, Supplement 1, 2022, Page 75, doi:10.1016/j.freeradbiomed.2022.10.308.

Characterization of human mitochondrial aconitase and its interaction with frataxin

Santiago Mansilla, Verónica Tórtora, Florencia Pignataro, Santiago Sastre, Ignacio Castro, María Laura Chiribao, Carlos Robello, Ari Zeida, Javier Santos, Laura Castro; Free Radical Biology and Medicine, Volume 192, Supplement 1, 2022, Pages 86-87, doi:10.1016/j.freeradbiomed.2022.10.151.

RNA as a Major-Groove Ligand: RNA-RNA and RNA-DNA Triplexes Formed by GAA and UUC or TTC Sequences

Zhang J, Fakharzadeh A, Roland C, Sagui C.; ACS Omega. 2022 Nov;7(43):38728-38743. DOI: 10.1021/acsomega.2c04358. PMID: 36340174; PMCID: PMC9631886. 

 Friedreich's ataxia is associated with noncanonical nucleic acid structures that emerge when GAA:TTC repeats in the first intron of the FXN gene expand beyond a critical number of repeats. Specifically, the noncanonical repeats are associated with both triplexes and R-loops. Here, we present an in silico investigation of all possible triplexes that form by attaching a third RNA strand to an RNA:RNA or DNA:DNA duplex, complementing previous DNA-based triplex studies. For both new triplexes results are similar. For a pyridimine UUC+ third strand, the parallel orientation is stable while its antiparallel counterpart is unstable. For a neutral GAA third strand, the parallel conformation is stable. A protonated GA+A third strand is stable in both parallel and antiparallel orientations. We have also investigated Na+ and Mg2+ ion distributions around the triplexes. The presence of Mg2+ ions helps stabilize neutral, antiparallel GAA triplexes. These results (along with previous DNA-based studies) allow for the emergence of a complete picture of the stability and structural characteristics of triplexes based on the GAA and TTC/UUC sequences, thereby contributing to the field of trinucleotide repeats and the associated unusual structures that trigger expansion.

Phenotype and management of neurologic intronic repeat disorders (NIRDs)

Finsterer J.; Rev Neurol (Paris). 2022 Nov 9:S0035-3787(22)00793-7. doi: 10.1016/j.neurol.2022.09.004. Epub ahead of print. PMID: 36371266. 

During recent years an increasing number of neurologic disorders due to expanded tri-, tetra-, penta-, or hexa-nucleotide repeat motifs in introns of various genes have been described (neurologic intronic repeat disorders (NIRDs)). The repeat may be pathogenic in the heterozygous or homozygous form. Repeat lengths vary considerably and can be stable or unstable during transmission to the next generation. The most well-known NIRDs are Friedreich ataxia, spinocerebellar ataxia types-10, -31, and -36, CANVAS, C9Orf72 familial amyotrophic lateral sclerosis (fALS), and myotonic dystrophy-2 (MD2). Phenotypically, NIRDs manifest as mono-organ (e.g. spinocerebellar ataxia type 31) or multi-organ disease (e.g. Friedreich ataxia, myotonic dystrophy-2). A number of other more rare NIRDs have been recently detected. This review aims at summarising and discussing previous findings and recent advances concerning the etiology, pathophysiology, clinical presentation, and therapeutic management of the most common NIRDs.

Blood Transcript Biomarkers Selected by Machine Learning Algorithm Classify Neurodegenerative Diseases including Alzheimer’s Disease

Huseby, C.J.; Delvaux, E.; Brokaw, D.L.; Coleman, P.D.; Biomolecules 2022, 12, 1592. doi:10.3390/biom12111592 

A blood-based screen to distinguish and classify neurodegenerative diseases is especially interesting having low cost, minimal invasiveness, and accessibility to almost any world clinic. In this study, we set out to discover a small set of blood transcripts that can be used to distinguish healthy individuals from those with Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, Friedreich’s ataxia, or frontotemporal dementia. Using existing public datasets, we developed a machine learning algorithm for application on transcripts present in blood and discovered small sets of transcripts that distinguish a number of neurodegenerative diseases with high sensitivity and specificity. We validated the usefulness of blood RNA transcriptomics for the classification of neurodegenerative diseases. Information about features selected for the classification can direct the development of possible treatment strategies.

Prediction of the disease course in Friedreich ataxia

Christian Hohenfeld, Ulrich Terstiege, Imis Dogan, Paola Giunti, Michael H. Parkinson, Caterina Mariotti, Lorenzo Nanetti, Mario Fichera, Alexandra Durr, Claire Ewenczyk, Sylvia Boesch, Wolfgang Nachbauer, Thomas Klopstock, Claudia Stendel, Francisco Javier Rodríguez de Rivera Garrido, Ludger Schöls, Stefanie N. Hayer, Thomas Klockgether, Ilaria Giordano, Claire Didszun, Myriam Rai, Massimo Pandolfo, Holger Rauhut, Jörg B. Schulz & Kathrin Reetz. Sci Rep 12, 19173 (2022). doi:10.1038/s41598-022-23666-z 

 We explored whether disease severity of Friedreich ataxia can be predicted using data from clinical examinations. From the database of the European Friedreich Ataxia Consortium for Translational Studies (EFACTS) data from up to five examinations of 602 patients with genetically confirmed FRDA was included. Clinical instruments and important symptoms of FRDA were identified as targets for prediction, while variables such as genetics, age of disease onset and first symptom of the disease were used as predictors. We used modelling techniques including generalised linear models, support-vector-machines and decision trees. The scale for rating and assessment of ataxia (SARA) and the activities of daily living (ADL) could be predicted with predictive errors quantified by root-mean-squared-errors (RMSE) of 6.49 and 5.83, respectively. Also, we were able to achieve reasonable performance for loss of ambulation (ROC-AUC score of 0.83). However, predictions for the SCA functional assessment (SCAFI) and presence of cardiological symptoms were difficult. In conclusion, we demonstrate that some clinical features of FRDA can be predicted with reasonable error; being a first step towards future clinical applications of predictive modelling. In contrast, targets where predictions were difficult raise the question whether there are yet unknown variables driving the clinical phenotype of FRDA.

C-Path and EFACTS Announce Data Sharing Agreement Making RDCA-DAP the Largest Worldwide Database for Friedreich’s Ataxia

TUCSON, Ariz., Nov. 10, 2022 — Critical Path Institute (C-Path) and the European Friedreich’s Ataxia Consortium for Translational Studies (EFACTS) today announced a data sharing agreement to incorporate patient data into C-Path’s Rare Disease Cures Accelerator-Data and Analytics Platform (RDCA-DAP®) solidifying RDCA-DAP as the largest worldwide database for Friedreich’s ataxia. 

 “The Friedreich’s Ataxia Research Alliance (FARA) partnered with C-Path to create a database that could integrate data from natural history studies and clinical trials, FA Integrated Clinical Database (FA-ICD), and we are really excited that this data is now part of RDCA-DAP and that our EFACTS partners are also contributing such informative data,” said FARA CEO Jennifer Farmer, M.S. “The collaboration with EFACTS goes beyond the contribution of this important data as EFACTS concomitantly joins the steering committee of the C-Path’s taskforce for FA and will inform new research. We look forward to the new insights and clinical trial tools that will be derived from having such a robust database shared with the research community.”

Frataxin deficiency alters gene expression in Friedreich ataxia derived IPSC-neurons and cardiomyocytes

Angulo, M. B., Bertalovitz, A., Argenziano, M. A., Yang, J., Patel, A., Zesiewicz, T., & McDonald, T. V. (2022). Molecular Genetics & Genomic Medicine, 00, e2093. doi:10.1002/mgg3.2093 

 RNA-seq and differential gene expression enrichment analyses demonstrated that frataxin deficiency affected the expression of glycolytic pathway genes in neurons and extracellular matrix pathway genes in cardiomyocytes. Genes in these pathways were differentially expressed when compared to a control and restored to control levels when FRDA cells were supplemented with frataxin.

Clinical management guidelines for Friedreich ataxia: best practice in rare diseases

Corben, L.A., Collins, V., Milne, S. et al. Orphanet J Rare Dis 17, 415 (2022). doi:10.1186/s13023-022-02568-3 

Individuals with Friedreich ataxia (FRDA) can find it difficult to access specialized clinical care. To facilitate best practice in delivering healthcare for FRDA, clinical management guidelines (CMGs) were developed in 2014. However, the lack of high-certainty evidence and the inadequacy of accepted metrics to measure health status continues to present challenges in FRDA and other rare diseases. To overcome these challenges, the Grading of Recommendations Assessment and Evaluation (GRADE) framework for rare diseases developed by the RARE-Bestpractices Working Group was adopted to update the clinical guidelines for FRDA. This approach incorporates additional strategies to the GRADE framework to support the strength of recommendations, such as review of literature in similar conditions, the systematic collection of expert opinion and patient perceptions, and use of natural history data.