NAD+ Intermediates: The Biology and Therapeutic Potential of NMN and NR

Jun Yoshino, Joseph A. Baur, Shin-ichiro Imai,  Cell Metabolism, Available online 14 December 2017, ISSN 1550-4131, doi:10.1016/j.cmet.2017.11.002.

Research on the biology of NAD+ has been gaining momentum, providing many critical insights into the pathogenesis of age-associated functional decline and diseases. In particular, two key NAD+ intermediates, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), have been extensively studied over the past several years. Supplementing these NAD+ intermediates has shown preventive and therapeutic effects, ameliorating age-associated pathophysiologies and disease conditions. Although the pharmacokinetics and metabolic fates of NMN and NR are still under intensive investigation, these NAD+ intermediates can exhibit distinct behavior, and their fates appear to depend on the tissue distribution and expression levels of NAD+ biosynthetic enzymes, nucleotidases, and presumptive transporters for each. A comprehensive concept that connects NAD+ metabolism to the control of aging and longevity in mammals has been proposed, and the stage is now set to test whether these exciting preclinical results can be translated to improve human health.

Friedreich and dominant ataxias: quantitative differences in cerebellar dysfunction measurements

Tanguy Melac A, Mariotti C, Filipovic Pierucci A on behalf of the EFACTS group, et al; J Neurol Neurosurg Psychiatry Published Online First: 26 December 2017. doi: 10.1136/jnnp-2017-316964

Cerebellar dysfunction, as measured with the CCFS and SARA scales, was more severe in FRDA than in patients with SCA, but with lower progression indexes, within the limits of these types of indexes. Ceiling effects may occur at late stages, for both scales. The CCFS scale is rater-independent and could be used in a multicentre context, as it is simple, rapid and fully automated.

The International Rare Diseases Research Consortium: Policies and Guidelines to maximize impact

Hanns Lochmüller, Josep Torrent i Farnell, Yann Le Cam, Anneliene H Jonker, Lilian PL Lau, Gareth Baynam, Petra Kaufmann, Hugh JS Dawkins, Paul Lasko, Christopher P Austin, Kym M Boycott & on behalf of the IRDiRC Consortium Assembly; European Journal of Human Genetics 25, 1293–1302 (2017) doi:10.1038/s41431-017-0008-z

The IRDiRC Policies and Guidelines are the first, detailed agreement of major public and private funding organizations worldwide to govern rare disease research, and may serve as a template for other areas of international research collaboration. While it is too early to assess their full impact on research productivity and patient benefit, the IRDiRC Policies and Guidelines have already contributed significantly to improving transparency and collaboration in rare disease research.

Exploring patient and family involvement in the lifecycle of an orphan drug: a scoping review

Andrea Young, Devidas Menon, Jackie Street, Walla Al-Hertani and Tania Stafinski; Orphanet Journal of Rare Diseases 201712:188 doi:10.1186/s13023-017-0738-6

Patients and their families have become more active in healthcare systems and research. The value of patient involvement is particularly relevant in the area of rare diseases, where patients face delayed diagnoses and limited access to effective therapies due to the high level of uncertainty in market approval and reimbursement decisions. It has been suggested that patient involvement may help to reduce some of these uncertainties. This review explored existing and proposed roles for patients, families, and patient organizations at each stage of the lifecycle of therapies for rare diseases (i.e., orphan drug lifecycle).

Early VGLUT1-specific parallel fiber synaptic deficits and dysregulated cerebellar circuit in the KIKO mouse model of Friedreich ataxia

Hong Lin, Jordi Magrane, Elisia M. Clark, Sarah M. Halawani, Nathan Warren, Amy Rattelle, David R. Lynch; Disease Models & Mechanisms 2017 10: 1529-1538; doi: 10.1242/dmm.030049

Here, we report early cerebellar VGLUT1 (SLC17A7)-specific parallel fiber (PF) synaptic deficits and dysregulated cerebellar circuit in the frataxin knock-in/knockout (KIKO) FRDA mouse model. At asymptomatic ages, VGLUT1 levels in cerebellar homogenates are significantly decreased, whereas VGLUT2 (SLC17A6) levels are significantly increased, in KIKO mice compared with age-matched controls. Additionally, GAD65 (GAD2) levels are significantly increased, while GAD67 (GAD1) levels remain unaltered. This suggests early VGLUT1-specific synaptic input deficits, and dysregulation of VGLUT2 and GAD65 synaptic inputs, in the cerebellum of asymptomatic KIKO mice. Immunohistochemistry and electron microscopy further show specific reductions of VGLUT1-containing PF presynaptic terminals in the cerebellar molecular layer, demonstrating PF synaptic input deficiency in asymptomatic and symptomatic KIKO mice. Moreover, the parvalbumin levels in cerebellar homogenates and Purkinje neurons are significantly reduced, but preserved in other interneurons of the cerebellar molecular layer, suggesting specific parvalbumin dysregulation in Purkinje neurons of these mice. Furthermore, a moderate loss of large principal neurons is observed in the dentate nucleus of asymptomatic KIKO mice, mimicking that of FRDA patients. Our findings thus identify early VGLUT1-specific PF synaptic input deficits and dysregulated cerebellar circuit as potential mediators of cerebellar dysfunction in KIKO mice, reflecting developmental features of FRDA in this mouse model.

Liquid Chromatography-High Resolution Mass Spectrometry Analysis of Platelet Frataxin as a Protein Biomarker for the Rare Disease Friedreich’s Ataxia

Lili Guo, Qingqing Wang, Liwei Weng, Lauren A. Hauser, Cassandra J. Strawser, Agostinho G. Rocha, Andrew Dancis, Clementina A Mesaros, David R. Lynch, and Ian Alexander Blair; Anal. Chem., Just Accepted Manuscript DOI: 10.1021/acs.analchem.7b04590 Publication Date (Web): December 22, 2017

Frataxin is undetectable in serum or plasma, and whole blood cannot be used because it is present in long-lived erythrocytes. Therefore, an assay was developed for analyzing frataxin in platelets, which have a half-life of 10-days. The assay is based on stable isotope dilution immunopurification two-dimensional nano-ultrahigh performance liquid chromatography/parallel reaction monitoring/mass spectrometry. The lower limit of quantification was 0.078 pg frataxin/μg protein and the assay had 100% sensitivity and specificity for discriminating between controls and FA cases. The mean levels of control and FA platelet frataxin were 9.4 2.6 pg/g protein and 2.4 0.6 pg/g protein, respectively. The assay should make it possible to rigorously monitor the effects of therapeutic interventions on frataxin expression in this devastating disease.

Somatic instability of the expanded GAA repeats in Friedreich’s ataxia

Ashlee Long, Jill S. Napierala, Urszula Polak, Lauren Hauser, Arnulf H. Koeppen, David R. Lynch, Marek Napierala; PLoS ONE 12(12): e0189990. Doi:10.1371/journal.pone.0189990

Friedreich’s ataxia (FRDA) is a genetic neurodegenerative disorder caused by transcriptional silencing of the frataxin gene (FXN) due to expansions of GAA repeats in intron 1. FRDA manifests with multiple symptoms, which may include ataxia, cardiomyopathy and diabetes mellitus. Expanded GAA tracts are genetically unstable, exhibiting both expansions and contractions. GAA length correlates with severity of FRDA symptoms and inversely with age of onset. Thus, tissue-specific somatic instability of long GAA repeats may be implicated in the development of symptoms and disease progression. Herein, we determined the extent of somatic instability of the GAA repeats in heart, cerebral cortex, spinal cord, cerebellar cortex, and pancreatic tissues from 15 FRDA patients. Results demonstrate differences in the lengths of the expanded GAAs among different tissues, with significantly longer GAA tracts detected in heart and pancreas than in other tissues. The expansion bias detected in heart and pancreas may contribute to disease onset and progression, making the mechanism of somatic instability an important target for therapy. Additionally, we detected significant differences in GAA tract lengths between lymphocytes and fibroblast pairs derived from 16 FRDA patients, with longer GAA tracts present in the lymphocytes. This result urges caution in direct comparisons of data obtained in these frequently used FRDA models. Furthermore, we conducted a longitudinal analysis of the GAA repeat length in lymphocytes collected over a span of 7–9 years and demonstrated progressive expansions of the GAAs with maximum gain of approximately 9 repeats per year. Continuous GAA expansions throughout the patient’s lifespan, as observed in FRDA lymphocytes, should be considered in clinical trial designs and data interpretation.

Fisiopatología de la ataxia de Friedreich: Transporte y degeneración axonal

Muñoz Lasso, DC. (2017). Fisiopatología de la ataxia de Friedreich: Transporte y degeneración axonal [Tesis doctoral no publicada]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/92842

Friedreich ataxia (FRDA) is a recessive human disease of central and peripheral nervous system that affects children and young adults. FRDA is a peripheral neuropathy characterized by a initial degeneration of the large neurons of the dorsal root ganglia (DRG) or proprioceptive neurons. Most of the patients with FRDA have a homozygous guanine-adenine-adenine (GAA) expansion within the first intron of the gen that codifies for a small mitochondrial protein, frataxin (FXN). This mutation leads to a reduction of frataxin expression in all human cells, which produces changes in both the cell and mitochondrial physiology, resulting in a dysfunction of the mitochondrial energetic metabolism linked to the increase of oxidative stress and calcium dyshomeostasis. These cellular proceses are tightly related with the regulation of the actin and microtubule cytoskeletons and with vesicle trafficking. Here, we show how the absence of frataxin in the mouse models YG8R and YG8sR affects the axonal cytoskeleton of adult sensory neurons. Changes of actin and microtubule cytoskeletons and the failure of Ca 2+ signaling induce alterations of dynamics growth cones of sensory neurons, which in turn produce a reduction of their capacity to grow and regenerate their axons. This study shows how these events can lead to the neurodegeneration in Friedreich's ataxia.

Development of an iron-selective antioxidant probe with protective effects on neuronal function

García-Beltrán O, Mena NP, Aguirre P, Barriga-González G, Galdámez A, Nagles E, et al. (2017). PLoS ONE 12(12): e0189043. doi:10.1371/journal.pone.0189043

ron accumulation, oxidative stress and calcium signaling dysregulation are common pathognomonic signs of several neurodegenerative diseases, including Parkinson´s and Alzheimer’s diseases, Friedreich ataxia and Huntington’s disease. Given their therapeutic potential, the identification of multifunctional compounds that suppress these damaging features is highly desirable. Here, we report the synthesis and characterization of N-(1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)-2-(7-hydroxy-2-oxo-2H-chromen-4-yl)acetamide, named CT51, which exhibited potent free radical neutralizing activity both in vitro and in cells. CT51 bound Fe2+ with high selectivity and Fe3+ with somewhat lower affinity. Cyclic voltammetric analysis revealed irreversible binding of Fe3+ to CT51, an important finding since stopping Fe2+/Fe3+ cycling in cells should prevent hydroxyl radical production resulting from the Fenton-Haber-Weiss cycle. When added to human neuroblastoma cells, CT51 freely permeated the cell membrane and distributed to both mitochondria and cytoplasm. Intracellularly, CT51 bound iron reversibly and protected against lipid peroxidation. Treatment of primary hippocampal neurons with CT51 reduced the sustained calcium release induced by an agonist of ryanodine receptor-calcium channels. These protective properties of CT51 on cellular function highlight its possible therapeutic use in diseases with significant oxidative, iron and calcium dysregulation.

Health-related quality of life among adults with diverse rare disorders

Kathleen R. Bogart and Veronica L. Irvin; Orphanet Journal of Rare Diseases 201712:177 doi:10.1186/s13023-017-0730-1

Twenty-five to 30 million Americans live with a rare disease (RD) and share challenges unique to RD. The majority of research on RDs has focused on etiology, treatment and care, while the limited health-related quality of life (HRQL) research has been restricted to single RDs, small samples, or non-validated measures. This study reports HRQL among adults with diverse RDs, and compares their scores to those of the U.S. population and people with common chronic health conditions.