The diagnosis and natural history of Huntington disease

Metabolomic Footprint of Disrupted Energetics and Amino Acid Metabolism in Neurodegenerative Diseases: Perspectives for Early Diagnosis and Monitoring of Therapy

The prevalence of neurodegenerative diseases (NDs) is increasing due to the aging population and improved longevity. They are characterized by a range of pathological hallmarks, including protein aggregation, mitochondrial dysfunction, and oxidative stress. The aim of this review is to summarize the alterations in brain energy and amino acid metabolism in Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD). Based on our findings, we proposed a group of selected metabolites related to disturbed energy or mitochondrial metabolism as potential indicators or predictors of disease. We also discussed the hidden challenges of metabolomics studies in NDs and proposed future directions in this field. We concluded that biochemical parameters of brain energy metabolism disruption (obtained with metabolomics) may have potential application as a diagnostic tool for the diagnosis, prediction, and monitoring of the effectiveness of therapies for NDs. However, more studies are needed to determine the sensitivity of the proposed candidates. We suggested that the most valuable biomarkers for NDs studies could be groups of metabolites combined with other neuroimaging or molecular techniques. To attain clinically applicable results, the integration of metabolomics with other “omic” techniques might be required.

The Repeatable Battery for the Assessment of Neuropsychological Status, While Useful for Measuring Cognitive Changes in Manifest Huntington Disease, May Show Limited Utility in Premanifest Disease

BACKGROUND

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is a brief, standardized neuropsychological test that assesses several areas of cognitive function. Recent studies, although sparse, have examined the use of the RBANS to detect cognitive deficits in individuals with manifest Huntington disease (HD); however, no studies have investigated its utility to detect cognitive deficits in individuals with premanifest HD (PreHD), where cognitive symptoms are thought to be more subtle.

OBJECTIVE

To assess cognitive deficits in individuals with HD, particularly in individuals with PreHD, using an easily administered, brief but comprehensive, neuropsychological test.

METHOD

We administered the RBANS to 31 individuals with HD, 29 individuals with PreHD, and 22 healthy controls (HC) at an academic HD clinical research center and collected RBANS Total, Index, and subtest scores for group comparisons.

RESULTS

The HD group had significantly lower RBANS Total, Index, and subtest scores than the HC. The PreHD group had significantly lower RBANS Total scores and Coding subtest scores than the HC, but no other significant group differences were identified.

CONCLUSION

Our results substantiate previous findings of significant impairment on the RBANS in individuals with HD. In addition, we are the first to demonstrate that, although the RBANS can identify deficits in psychomotor speed and information processing in individuals with PreHD, it does not appear to have the ability to detect impairment in any additional cognitive domains in individuals with PreHD.

Function of exosomes in neurological disorders and brain tumors

Exosomes are a subtype of extracellular vesicles released from different cell types including those in the nervous system, and are enriched in a variety of bioactive molecules such as RNAs, proteins and lipids. Numerous studies have indicated that exosomes play a critical role in many physiological and pathological activities by facilitating intercellular communication and modulating cells' responses to external environments. Particularly in the central nervous system, exosomes have been implicated to play a role in many neurological disorders such as abnormal neuronal development, neurodegenerative diseases, epilepsy, mental disorders, stroke, brain injury and brain cancer. Since exosomes recapitulate the characteristics of the parental cells and have the capacity to cross the blood-brain barrier, their cargo can serve as potential biomarkers for early diagnosis and clinical assessment of disease treatment. In this review, we describe the latest findings and current knowledge of the roles exosomes play in various neurological disorders and brain cancer, as well as their application as promising biomarkers. The potential use of exosomes to deliver therapeutic molecules to treat diseases of the central nervous system is also discussed.

Extracellular vesicles in the diagnosis and treatment of central nervous system diseases

Extracellular vesicles, including exosomes and microvesicles, play a fundamental role in the activity of the nervous system, participating in signal transmission between neurons and providing the interaction of central nervous system with all body systems. In many neurodegenerative diseases, neurons pack toxic substances into vesicles and release them into the extracellular space, which leads to the spread of misfolded neurotoxic proteins. The contents of neuron-derived extracellular vesicles may indicate pathological changes in the central nervous system, and the analysis of extracellular vesicle molecular content contributes to the development of non-invasive methods for the diagnosis of many central nervous system diseases. Extracellular vesicles of neuronal origin can be isolated from various biological fluids due to their ability to cross the blood-brain barrier. Today, the diagnostic potential of almost all toxic proteins involved in nervous system disease pathogenesis, specifically α-synuclein, tau protein, superoxide dismutase 1, FUS, leucine-rich repeat kinase 2, as well as some synaptic proteins, has been well evidenced. Special attention is paid to extracellular RNAs mostly associated with extracellular vesicles, which are important in the onset and development of many neurodegenerative diseases. Depending on parental cell type, extracellular vesicles may have different therapeutic properties, including neuroprotective, regenerative, and anti-inflammatory. Due to nano size, biosafety, ability to cross the blood-brain barrier, possibility of targeted delivery and the lack of an immune response, extracellular vesicles are a promising vehicle for the delivery of therapeutic substances for the treatment of neurodegenerative diseases and drug delivery to the brain. This review describes modern approaches of diagnosis and treatment of central nervous system diseases using extracellular vesicles.

How different aspects of motor dysfunction influence day-to-day function in huntington's disease

PURPOSE

This study examined the relationships between different aspects of motor dysfunction (chorea, dystonia, rigidity, incoordination, oculomotor dysfunction, dysarthria, and gait difficulties) and functional status in persons with Huntington's disease.

METHODS

A total of 527 persons with Huntington's disease completed the Unified Huntington's Disease Rating Scale motor, total functional capacity, and functional assessments.

RESULTS

Confirmatory factor analysis indicated that a 4-factor model provided a better model fit than the existing 5-factor model. Exploratory factor analysis identified the following 4 factors from the motor scale: dystonia, chorea, rigidity, and a general motor factor. Regression indicated that dystonia (β = -0.47 and -0.79) and rigidity (β = -0.28 and -0.59) had strong associations with function, whereas chorea had modest correlations (β = -0.16 and -0.15).

CONCLUSIONS

Dystonia and rigidity have stronger relationships with functional status than chorea in persons with Huntington's disease. The findings underscore the need for further research regarding the effects of dystonia and rigidity on functioning. © 2019 International Parkinson and Movement Disorder Society.

p62/SQSTM1 - steering the cell through health and disease

SQSTM1 (also known as p62) is a multifunctional stress-inducible scaffold protein involved in diverse cellular processes. Its functions are tightly regulated through an extensive pattern of post-translational modifications, and include the isolation of cargos degraded by autophagy, induction of the antioxidant response by the Keap1-Nrf2 system, as well as the regulation of endosomal trafficking, apoptosis and inflammation. Accordingly, malfunction of SQSTM1 is associated with a wide range of diseases, including bone and muscle disorders, neurodegenerative and metabolic diseases, and multiple forms of cancer. In this Review, we summarize current knowledge regarding regulation, post-translational modifications and functions of SQSTM1, as well as how they are dysregulated in various pathogenic contexts.

Understanding patient-reported outcome measures in Huntington disease: at what point is cognitive impairment related to poor measurement reliability?

PURPOSE

Symptom progression in Huntington disease (HD) is associated with cognitive decline which may interfere with the self-report of symptoms. Unfortunately, data to support or refute the psychometric reliability of patient-reported outcomes (PROs) as HD progresses are limited. This is problematic given that PROs are increasingly recognized as important measures of efficacy for new treatments.

METHODS

We examined PRO data from the HDQLIFE Measurement System (Speech Difficulties; Swallowing Difficulties; Chorea) in 509 individuals with premanifest, early-stage, or late-stage HD. Clinician-administered assessments of motor functioning (items from the UHDRS) and standardized objective assessments of cognition (Stroop, Symbol Digit Modalities) were also collected. We examined item bias using differential item functioning (DIF) across HD stage (premanifest, early-, late-) and relative to cognitive performance. We also examined the correlations between self-report and clinician ratings. Regression models that considered total cognitive ability were utilized to determine psychometric reliability of the PROs.

RESULTS

Most PRO items were free from DIF for both staging and cognition. There were modest correlations between PROs and clinician report (ranged from - 0.40 to - 0.60). Modeling analyses indicated that psychometric reliability breaks down with poorer cognition and more progressed disease stage; split-half reliability was compromised (i.e., split-half reliability < 0.80) when scores were < 136 for Chorea, < 109 for Speech Difficulties, and < 179 for Swallowing Difficulties.

CONCLUSIONS

Results indicate that the psychometric reliability of PROs can be compromised as HD symptoms progress and cognition declines. Clinicians should consider PROs in conjunction with other types of assessments when total cognition scores exceed critical thresholds.