Survival of Huntington’s disease patients in Serbia: longer survival in female patients

Association between sex and Huntington's disease: an updated review on symptomatology and prognosis of neurodegenerative disorders

Huntington's disease is a rare autosomal dominant disorder presenting with chorea, rigidity, hypo-/akinesia, cognitive decline, and psychiatric disturbances. Numerous risk factors have been defined in the onset of this disease. However, the number of CAG repeats in the genes are the most crucial factor rendering patients susceptible to the disease. Studies have shown significant differences in onset and disease presentation among the sexes, which prompts analysis of the impact of different sexes on disease etiology and progression. This article therefore discusses the evidence-based role of sex in aspects of symptomatology, pathogenesis, biomarkers, progression, and prognosis of Huntington's disease, with a secondary review of sex-linked differences in Alzheimer's and Parkinson's disease.

Gene-dosage- and sex-dependent differences in the prodromal-Like phase of the F344tgHD rat model for Huntington disease

In Huntington disease (HD) the prodromal phase has been increasingly investigated and is currently in focus for early interventional treatments. Also, the influence of sex on disease progression and severity in patients is under discussion, as a sex-specific impact has been reported in transgenic rodent models for HD. To this end, we have been studying these aspects in Sprague Dawley rats transgenic for HD. Here, we took up on the congenic F344tgHD rat model, expressing a fragmented Htt construct with 51 CAG repeats on an inbred F344 rat background and characterized potential sexual dimorphism and gene-dosage effects in rats during the pre-symptomatic phase (1-8 months of age). Our study comprises a longitudinal phenotyping of motor function, emotion and sensorimotor gating, as well as screening of metabolic parameters with classical and automated assays in combination with investigation of molecular HD hallmarks (striatal cell number and volume estimation, appearance of HTT aggregates). Differences between sexes became apparent during middle age, particularly in the motor and sensorimotor domains. Female individuals were generally more active, demonstrated different gait characteristics than males and less anxiolytic-like behavior. Alterations in both the time course and affected behavioral domains varied between male and female F344tgHD rats. First subtle behavioral anomalies were detected in transgenic F344tgHD rats prior to striatal MSN cell loss, revealing a prodromal-like phase in this model. Our findings demonstrate that the congenic F344tgHD rat model shows high face-validity, closely resembling the human disease's temporal progression, while having a relatively low number of CAG repeats, a slowly progressing pathology with a prodromal-like phase and a comparatively subtle phenotype. By differentiating the sexes regarding HD-related changes and characterizing the prodromal-like phase in this model, these findings provide a foundation for future treatment studies.

Huntington's disease: Mortality and risk factors in an Australian cohort

INTRODUCTION

There has not been any examination of the risk factors associated with mortality in Huntington's Disease (HD) in an Australian cohort.

METHOD

This retrospective study included inpatients admitted to a specialist neuropsychiatry service in Melbourne, Australia. HD status was based on genetic testing. Risk factors included age of onset, CAG repeat length and neuroimaging. Mortality data was acquired through the Australian Institute of Health and Welfare National Death Index.

RESULTS

The cohort included 83 participants, with 44 (53%) deceased. The median age of death was 59 years and median survival was 18.8 years from onset age (median 41.0 years). CAG repeat length (median 44.0, IQR 42.5, 47.0) was inversely correlated with age of onset (r = -0.73) and age at death (r = -0.80) but was not correlated with mortality status. There was no difference in functional and cognitive assessments, nor brain volumes, in the alive group compared to the deceased group. There were more people who were alive who had a positive family history of a psychiatric condition (p = 0.006) or dementia (p = 0.009). Standardised mortality ratios demonstrated a 5.9× increased risk of death for those with HD compared to the general population.

CONCLUSIONS

This is the first study to examine risk factors of mortality in HD in an Australian cohort. Median survival in our cohort is consistent with previous studies in HD, and markedly reduced compared to the general Australian population. CAG repeat length was not associated with mortality suggesting that non-genetic factors contribute to mortality status and warrant further investigation.

Multiple clinical features of Huntington's disease correlate with mutant HTT gene CAG repeat lengths and neurodegeneration

Huntington's disease (HD) is a fatal neurodegenerative disease caused by mutant HTT gene expansions of CAG triplet repeat numbers that are inherited in an autosomal dominant manner. HD patients display multiple clinical features that are correlated with HTT CAG repeat numbers that include age of disease onset, motor dysfunction, cognitive deficits, compromised daily living capacity, and brain neurodegeneration. It is important to understand the significant relationships of the multiple HD clinical deficits correlated with the number of mutant HTT CAG expansions that are the genetic basis for HD disabilities. Therefore, this review highlights the significant correlations of the HD clinical features of age of onset, motor and cognitive disabilities, decline in living capabilities, weight loss, risk of death, and brain neurodegeneration with respect to their associations with CAG repeat lengths of the HTT gene. Quantitative HTT gene expression patterns analyzed in normal adult human brain regions demonstrated its distribution in areas known to undergo neurodegeneration in HD, as well as in other brain regions. Future investigation of the relationships of the spectrum of clinical HD features with mutant HTT molecular mechanisms will be important to gain understanding of how mutant CAG expansions of the HTT gene result in the devastating disabilities of HD patients.

Age at Death and Causes of Death in Patients with Huntington Disease in Norway in 1986-2015

BACKGROUND

The literature offers discrepant findings regarding age at death in individuals with Huntington disease (HD).

OBJECTIVE

To study the age at death and causes of death in males and females with a diagnosis of HD in Norway.

METHODS

Registry study of deaths in 1986-2015 using data from two national registries: the Norwegian Cause of Death Registry (NCDR) and the registry of the Centre for Rare Disorders (CRD), Oslo University Hospital.

RESULTS

Mean age at death for individuals with HD was found to be 63.9 years (NCDR) and 61.7 years (CRD), compared to a mean of 76.9 years in the general population (NCDR). There were no significant gender differences for age at death in individuals with HD. The significant increase in age at death within the general population from 1986 to 2015 was not observed in individuals with HD. In 73.5% of individuals with HD, the underlying cause of death was HD, followed by cardiovascular diseases, cancer and respiratory diseases. The most common immediate cause of death was respiratory diseases (44.2%). Suicide was a more common cause of death in the population with HD (2.3%) compared to the general population (1.3%).

CONCLUSION

The age at death of individuals with HD was stable over a period of 30 years and 13.3 years lower than in the general population. Longer life expectancy for females from the general population was not found in females with HD. Suicide was more common among individuals with HD compared to the general population.

Risk factors for the onset and progression of Huntington disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by chorea, behavioural and psychiatric manifestations, and dementia, caused by a CAG triplet repeat expansion in the huntingtin gene. Systematic review of the literature was conducted to determine the risk factors for the onset and progression of HD. Multiple databases were searched, using terms specific to Huntington disease and to studies of aetiology, risk, prevention and genetics, limited to studies on human subjects published in English or French between 1950 and 2010. Two reviewers independently screened the abstracts and identified potentially relevant articles for full-text review using predetermined inclusion criteria. Three major categories of risk factors for onset of HD were identified: CAG repeat length in the huntingtin gene, CAG instability, and genetic modifiers. Of these, CAG repeat length in the huntingtin gene is the most important risk factor. For the progression of HD: genetic, demographic, past medical/clinical and environmental risk factors have been studied. Of these factors, genetic factors appear to play the most important role in the progression of HD. Among the potential risk factors, CAG repeat length in the mutant allele was found to be a relatively consistent and significant risk factor for the progression of HD, especially in motor, cognitive, and other neurological symptom deterioration. In addition, there were many consistent results in the literature indicating that a higher number of CAG repeats was associated with shorter survival, faster institutionalization, and earlier percutaneous endoscopic gastrostomy.

Survival of Korean Huntington's Disease Patients

OBJECTIVE

The survival of Huntington's disease (HD) patients is reported to be 15-20 years. However, most studies on the survival of HD have been conducted in patients without genetic confirmation with the possible inclusion of non-HD patients, and all studies have been conducted in Western countries. The survival of patients with HD in East Asia, where its prevalence is 10-50-fold lower compared with Western populations, has not yet been reported.

METHODS

Forty-seven genetically confirmed Korean HD patients from independent families were included in this retrospective medical record review study.

RESULTS

The mean age at onset among the 47 patients was 46.1 ± 14.0 years. At the time of data collection, 25 patients had died, and these patients had a mean age at death of 57.8 ± 13.7 years. The Kaplan-Meier estimate of the median survival from onset in the 47 patients was 14.5 years (95% confidence interval: 12.3-16.6). None of the following factors were associated with the survival time in the univariate Cox regression analysis: gender, age at onset, normal CAG repeat size, mutant CAG repeat size, and the absence or presence of non-motor symptoms at onset.

CONCLUSION

This is the first Asian study on survival in HD patients. Survival in Korean HD patients may be shorter than that reported for Western populations, or at least is in the lower range of expected survival. A larger longitudinal observation study is needed to confirm the results found in this study.

Genistein improves sensorimotor gating: Mechanisms related to its neuroprotective effects on the striatum

Huntington's disease (HD) is a neurodegenerative disorder, characterized by selective atrophy in the striatum, particularly the medium spiny GABAergic efferent neurons. This results in striatal sensorimotor gating deficits. Systemic administration of 3-nitropropionic acid (3-NPA) produces selective lesions mimicking those of HD. Males were found to be more susceptible to 3-NPA-induced neurotoxicity than females, suggesting neuroprotective effects of estrogens. Phytoestrogens, including genistein, are good estrogenic alternatives that keep their beneficial effects on non-reproductive organs and lack the potential hazardous side effects. The current study was designed to investigate the potential beneficial effects of genistein in 3-NPA-induced HD in ovariectomized rats. Results showed that 3-NPA (20 mg/kg) administration caused significant disruption of the rats' locomotor activity and prepulse inhibition. In addition, it decreased striatal ATP levels and increased oxidative stress, inflammatory and apoptotic markers with striatal focal hemorrhage and gliosis. Pretreatment with 17β-estradiol (2.5 mg/kg) or genistein (20 mg/kg) led to a significant improvement of behavioral parameters, increased ATP production, decreased oxidative stress, attenuated inflammation and apoptosis. Therefore, this study suggests potential neuroprotective effects of genistein in ovariectomized rats challenged with 3-NPA.

Deletion of the huntingtin proline-rich region does not significantly affect normal huntingtin function in mice

The N-terminus of Huntingtin, the protein encoded by the Huntington's disease gene, contains a stretch of polyglutamine residues that is expanded in Huntington's disease. The polyglutamine stretch is flanked by two conserved protein domains in vertebrates: an N1-17 domain, and a proline-rich region (PRR). The PRR can modulate the structure of the adjacent polyglutamine stretch, and is a binding site for several interacting proteins. To determine the role of the PRR in Huntingtin function, we have generated a knock-in allele of the mouse Huntington's disease gene homolog that expresses full-length normal huntingtin lacking the PRR. Mice that are homozygous for the huntingtin PRR deletion are born at the normal Mendelian frequency, suggesting that the PRR is not required for essential huntingtin functions during embryonic development. Moreover, adult homozygous mutants did not exhibit any significant differences from wild-type controls in general motor function and motor learning. However, 18 month-old male, but not female, homozygous PRR deletion mutants exhibited deficits in the Morris water task, suggesting that age-dependent spatial learning and memory may be affected in a sex-specific fashion by the huntingtin PRR deletion.

Sex Differences in Circadian Dysfunction in the BACHD Mouse Model of Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder that affects men and women in equal numbers, but some epidemiological studies indicate there may be sex differences in disease progression. One of the early symptoms of HD is disruptions in the circadian timing system, but it is currently unknown whether sex is a factor in these alterations. Since sex differences in HD could provide important insights to understand cellular and molecular mechanism(s) and designing early intervention strategies, we used the bacterial artificial chromosome transgenic mouse model of HD (BACHD) to examine whether sex differences in circadian behavioral rhythms are detectable in an animal model of the disease. Similar to BACHD males, BACHD females display circadian disruptions at both 3 and 6 months of age; however, deficits to BACHD female mouse activity levels, rhythm precision, and behavioral fragmentation are either delayed or less severe relative to males. These sex differences are associated with a smaller suprachiasmatic nucleus (SCN) in BACHD male mice at age of symptom onset (3 months), but are not associated with sex-specific differences in SCN daytime electrical activity deficits, or peptide expression (arginine vasopressin, vasoactive intestinal peptide) within the SCN. Notably, BACHD females exhibited delayed motor coordination deficits, as measured using rotarod and challenge beam. These findings suggest a sex specific factor plays a role both in non-motor and motor symptom progression for the BACHD mouse.

The HTT CAG-Expansion Mutation Determines Age at Death but Not Disease Duration in Huntington Disease

Huntington disease (HD) is caused by an expanded HTT CAG repeat that leads in a length-dependent, completely dominant manner to onset of a characteristic movement disorder. HD also displays early mortality, so we tested whether the expanded CAG repeat exerts a dominant influence on age at death and on the duration of clinical disease. We found that, as with clinical onset, HD age at death is determined by expanded CAG-repeat length and has no contribution from the normal CAG allele. Surprisingly, disease duration is independent of the mutation's length. It is also unaffected by a strong genetic modifier of HD motor onset. These findings suggest two parsimonious alternatives. (1) HD pathogenesis is driven by mutant huntingtin, but before or near motor onset, sufficient CAG-driven damage occurs to permit CAG-independent processes and then lead to eventual death. In this scenario, some pathological changes and their clinical correlates could still worsen in a CAG-driven manner after disease onset, but these CAG-related progressive changes do not themselves determine duration. Alternatively, (2) HD pathogenesis is driven by mutant huntingtin acting in a CAG-dependent manner with different time courses in multiple cell types, and the cellular targets that lead to motor onset and death are different and independent. In this scenario, processes driven by HTT CAG length lead directly to death but not via the striatal pathology associated with motor manifestations. Each scenario has important ramifications for the design and testing of potential therapeutics, especially those aimed at preventing or delaying characteristic motor manifestations.

The group 2 metabotropic glutamate receptor agonist LY379268 rescues neuronal, neurochemical and motor abnormalities in R6/2 Huntington's disease mice

Excitotoxic injury to striatum by dysfunctional cortical input or aberrant glutamate uptake may contribute to Huntington's disease (HD) pathogenesis. Since corticostriatal terminals possess mGluR2/3 autoreceptors, whose activation dampens glutamate release, we tested the ability of the mGluR2/3 agonist LY379268 to improve the phenotype in R6/2 HD mice with 120-125 CAG repeats. Daily subcutaneous injection of a maximum tolerated dose (MTD) of LY379268 (20mg/kg) had no evident adverse effects in WT mice, and diverse benefits in R6/2 mice, both in a cohort of mice tested behaviorally until the end of R6/2 lifespan and in a cohort sacrificed at 10weeks of age for blinded histological analysis. MTD LY379268 yielded a significant 11% increase in R6/2 survival, an improvement on rotarod, normalization and/or improvement in locomotor parameters measured in open field (activity, speed, acceleration, endurance, and gait), a rescue of a 15-20% cortical and striatal neuron loss, normalization of SP striatal neuron neurochemistry, and to a lesser extent enkephalinergic striatal neuron neurochemistry. Deficits were greater in male than female R6/2 mice, and drug benefit tended to be greater in males. The improvements in SP striatal neurons, which facilitate movement, are consistent with the improved movement in LY379268-treated R6/2 mice. Our data indicate that mGluR2/3 agonists may be particularly useful for ameliorating the morphological, neurochemical and motor defects observed in HD.

Predictors of survival in a Huntington's disease population from southern Italy

BACKGROUND

The primary aim of the present study was to determine the survival rates and identify predictors of disease duration in a cohort of Huntington's disease (HD) patients from Southern Italy.

METHODS

All medical records of HD patients followed between 1977 and 2008 at the Department of Neurological Sciences of Federico II University in Naples were retrospectively reviewed and 135 patients were enrolled in the analysis. At the time of data collection, 41 patients were deceased (19 males and 22 females) with a mean ± SD age at death of 56.6 ± 14.9 years (range 18-83).

RESULTS

The median survival time was 20 years (95% CI: 18.3-21.7). Cox regression analysis showed that the number of CAG in the expanded allele (HR 1.09 for 1 point triplet increase, p=0.002) and age of onset (HR 1.05 for 1 point year increase, p=0.002) were independent and significant predictors of lower survival rates.

CONCLUSIONS

We believe that these findings are important for a better understanding of the natural history of the disease and may be relevant in designing future therapeutic trials.

Sex differences in the injured brain

Observations obtained in human and in experimental models clearly demonstrate sex differences in degenerative events occurring in the central nervous system. The present review focuses on potential factors that may contribute to these sex-dimorphic features; in particular, morphological organization of the central nervous system and functional influence by neuroactive steroids, genes, and immune system are considered.

Long-term disability and prognosis in dentatorubral-pallidoluysian atrophy: a correlation with CAG repeat length

Dentatorubral-pallidoluysian atrophy (DRPLA) is a rare autosomal dominant neurodegenerative disorder caused by CAG repeat expansion. Previous studies demonstrated that the onset of DRPLA is closely associated with CAG repeat length. However, the natural history of DRPLA has not yet been evaluated. We here retrospectively investigated the factors that determine the disease milestones and prognosis in 183 Japanese patients genetically diagnosed with DRPLA. We determined the age at onset, age at which each of the subsequent clinical manifestations appeared, age at becoming wheelchair-bound, and age at death. Kaplan-Meier analysis revealed that the patients with CAG repeats larger than the median length of 65 repeats developed each of the clinical features of DRPLA at a younger age than those with <65 repeats. The patients became wheelchair-bound at a median age of 33 years (n = 61; range, 3-77 years) and died at a median age of 49 years (n = 23; range, 18-80 years). The ages at becoming wheelchair-bound and at death strongly correlated with the expanded CAG repeat length. Moreover, the patients with >or=65 CAG repeats showed a more severe long-term disability and a poorer prognosis. In contrast, the rate of progression after the onset did not correlate with CAG repeat length. The CAG repeat length may have a considerable effect on not only the disease onset but also the disease milestones and prognosis in DRPLA patients. These effects of CAG repeat length may be relevant in designing future clinical therapeutic trials.

Sex-specific therapeutic strategies based on neuroactive steroids: In search for innovative tools for neuroprotection

Different pathologies of the central and peripheral nervous system show sex differences in their incidence, symptomatology and/or neurodegenerative outcome. These include Parkinson's disease, Alzheimer's disease, Huntington's disease, multiple sclerosis, traumatic brain injury, stroke, autism, schizophrenia, depression, anxiety disorders, eating disorders and peripheral neuropathy. These sex differences reveal the need for sex-specific neuroprotective strategies. This review article and other manuscripts published in this issue of Hormones and Behavior analyze possible sex-specific therapeutic strategies based on neuroactive steroids. In particular in our introductory article, the possibility that sex differences in the levels or in the action of neuroactive steroids may represent causative factors for sex differences in the incidence or manifestation of pathologies of the nervous system is considered.