Factors contributing to clinical picture and progression of Huntington's disease

Mitochondria in Huntington's disease: implications in pathogenesis and mitochondrial-targeted therapeutic strategies

Huntington's disease is a genetic disease caused by expanded CAG repeats on exon 1 of the huntingtin gene located on chromosome 4. Compelling evidence implicates impaired mitochondrial energetics, altered mitochondrial biogenesis and quality control, disturbed mitochondrial trafficking, oxidative stress and mitochondrial calcium dyshomeostasis in the pathogenesis of the disorder. Unfortunately, conventional mitochondrial-targeted molecules, such as cysteamine, creatine, coenzyme Q10, or triheptanoin, yielded negative or inconclusive results. However, future therapeutic strategies, aiming to restore mitochondrial biogenesis, improving the fission/fusion balance, and improving mitochondrial trafficking, could prove useful tools in improving the phenotype of Huntington's disease and, used in combination with genome-editing methods, could lead to a cure for the disease.

Disease Burden of Huntington's Disease (HD) on People Living with HD and Care Partners in Canada

Background:

Huntington’s disease (HD) has been shown to reduce health-related quality of life (HRQoL) and affect healthcare resource utilization (HRU) among patients and care partners internationally but has not been studied specifically in the Canadian context.

Objective:

To characterize the burden of HD on individuals with HD and care partners of individuals with HD in Canada.

Methods:

An online survey was distributed (September 14–November 23, 2020) through patient organizations to collect data on demographic and clinical characteristics, as well as: HRQoL, measured using the 36-Item Short-Form Health Survey (SF-36v1); HRU, measured using the Client Service Receipt Inventory (CSRI); and care partner burden, measured using the Caregiver Strain Index (CSI) and Huntington’s Disease Quality of Life Battery for Carers (HDQoL-C). Descriptive statistics were used to report data and compare subgroups.

Results:

A total of 62 adult individuals with HD (or their proxies) and 48 care partners met defined eligibility criteria. The mean [standard deviation] age was 51.2 [13.8] and 58.1 [13.9] years for individuals with HD and care partner respondents, respectively. For individuals with HD, the greatest HRQoL burden (i.e., lowest score) was for the SF-36v1 Role –Physical scale (46.8 [42.9]). HRU was higher for some services (e.g., general practitioner visits) for respondents who had experienced motor onset transition. Among care partners, 55.3% experienced high strain, as indicated by the CSI. The HDQoL-C showed the greatest HRQoL burden in feelings about life (45.1 [17.9]).

Conclusion:

This study quantified the substantial burden on individuals with HD and care partners in Canada, addressing a critical knowledge gap that can affect the availability of and access to healthcare services.

Sex Differences in Huntington's Disease: Evaluating the Enroll-HD Database

BACKGROUND

Identifying sex-related differences is critical for enhancing our understanding of factors that may impact prognosis and advance treatments in Huntington's disease (HD).

OBJECTIVES

To investigate if sex-related differences exist in clinical HD.

METHODS

Longitudinal study of the Enroll-HD database. Manifest HD patients were included in the analysis (N = 8401). Linear mixed models were used to assess motor, behavioral, and cognitive functioning over a series of four annual visits, and compared male and female HD gene carriers.

RESULTS

HD patients showed significant sex-dependent differences in motor, cognitive, and behavioral symptoms. Both sexes had worsened motor symptoms over the course of four visits, but there was a significant disparity between sexes, with females consistently presenting with more symptoms than males. For behavioral symptoms, specifically depressive symptoms, females had significantly more depressive symptoms, although self-reported symptoms in both sexes became less severe throughout time.

CONCLUSIONS

Our analyses suggest that women have worse symptoms than men during the course of HD.

18F-FDG PET/CT: an unexpected case of Huntington's disease

Background

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.

Case presentation

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.

Conclusions

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.

Deutetrabenazine in the treatment of Huntington's disease

Deutetrabenazine (DTBZ) is a US FDA-approved treatment for chorea in Huntington's disease. The substitution of deuterium for hydrogen at specific positions imparts a longer half-life on DTBZ, allowing for less-frequent daily dosing. As a reversible vesicular monoamine transporter Type 2 inhibitor, DTBZ depletes monoamines at presynaptic nerve terminals. DTBZ significantly improved chorea in Huntington's disease patients compared with placebo. This effect continued in an ongoing open-label extension study in the cohort who switched from tetrabenazine to DTBZ. Whereas there are currently no head-to-head studies to adequately compare safety profiles between tetrabenazine and DTBZ, an indirect comparison study suggested that the tolerability profile of DTBZ was similar to placebo. In fact, there are currently no direct comparisons between vesicular monoamine transporter Type 2 inhibitors in humans. This review will explore DTBZ's pharmacological properties, drug interactions, administration and efficacy.