Summary Background Blood biomarkers of neuronal damage could facilitate clinical management of and therapeutic development for Huntington's disease. We investigated whether neurofilament light ...protein NfL (also known as NF-L) in blood is a potential prognostic marker of neurodegeneration in patients with Huntington's disease. Methods We did a retrospective analysis of healthy controls and carriers of CAG expansion mutations in HTT participating in the 3-year international TRACK-HD study. We studied associations between NfL concentrations in plasma and clinical and MRI neuroimaging findings, namely cognitive function, motor function, and brain volume (global and regional). We used random effects models to analyse cross-sectional associations at each study visit and to assess changes from baseline, with and without adjustment for age and CAG repeat count. In an independent London-based cohort of 37 participants (23 HTT mutation carriers and 14 controls), we further assessed whether concentrations of NfL in plasma correlated with those in CSF. Findings Baseline and follow-up plasma samples were available from 97 controls and 201 individuals carrying HTT mutations. Mean concentrations of NfL in plasma at baseline were significantly higher in HTT mutation carriers than in controls (3·63 SD 0·54 log pg/mL vs 2·68 0·52 log pg/mL, p<0·0001) and the difference increased from one disease stage to the next. At any given timepoint, NfL concentrations in plasma correlated with clinical and MRI findings. In longitudinal analyses, baseline NfL concentration in plasma also correlated significantly with subsequent decline in cognition (symbol-digit modality test r =–0·374, p<0·0001; Stroop word reading r =–0·248, p=0·0033), total functional capacity ( r =–0·289, p=0·0264), and brain atrophy (caudate r =0·178, p=0·0087; whole-brain r =0·602, p<0·0001; grey matter r =0·518, p<0·0001; white matter r =0·588, p<0·0001; and ventricular expansion r =–0·589, p<0·0001). All changes except Stroop word reading and total functional capacity remained significant after adjustment for age and CAG repeat count. In 104 individuals with premanifest Huntington's disease, NfL concentration in plasma at baseline was associated with subsequent clinical onset during the 3-year follow-up period (hazard ratio 3·29 per log pg/mL, 95% CI 1·48–7·34, p=0·0036). Concentrations of NfL in CSF and plasma were correlated in mutation carriers ( r =0·868, p<0·0001). Interpretation NfL in plasma shows promise as a potential prognostic blood biomarker of disease onset and progression in Huntington's disease. Funding Medical Research Council, GlaxoSmithKline, CHDI Foundation, Swedish Research Council, European Research Council, Wallenberg Foundation, and Wolfson Foundation.
Summary Background TRACK-HD is a multinational prospective observational study of Huntington's disease (HD) that examines clinical and biological findings of disease progression in individuals with ...premanifest HD (preHD) and early-stage HD. We aimed to describe phenotypic changes in these participants over 36 months and identify baseline predictors of progression. Methods Individuals without HD but carrying the mutant huntingtin gene (classed as preHD-A if ≥10·8 years and preHD-B if <10·8 years from predicted onset), participants with early HD (classed as HD1 if they had a total functional capacity score of 11–13 and HD2 if they had a score of 7–10), and healthy control individuals were assessed at four study sites in the Netherlands, the UK, France, and Canada. We measured 36-month change for 3T MRI, clinical, cognitive, quantitative motor, and neuropsychiatric assessments and examined their prognostic value. We also assessed the relation between disease progression and the combined effect of CAG repeat length and age. All participants were analysed according to their baseline subgroups. Longitudinal results were analysed using a combination of repeated-measure weighted least squares models and, when examining risk of new diagnosis, survival analysis. Findings At baseline, 366 participants were enrolled between Jan 17, and Aug 26, 2008, and of these 298 completed 36-month follow-up: 97 controls, 58 participants with preHD-A, 46 with preHD-B, 66 with HD1, and 31 with HD2. In the preHD-B group, several quantitative motor and cognitive tasks showed significantly increased rates of decline at 36 months, compared with controls, whereas few had at 24 months. Of the cognitive measures, the symbol digit modality test was especially sensitive (adjusted mean loss 4·11 points 95% CI 1·49–6·73 greater than controls; p=0·003). Among psychiatric indicators, apathy ratings specifically showed significant increases (0·34 points 95% CI 0·02–0·66 greater than controls; p=0·038). There was little evidence of reliable change in non-imaging measures in the preHD-A group, with the exception of the speeded tapping inter-tap interval (0·01 s 95% CI 0·01–0·02 longer than controls; p=0·0001). Several baseline imaging, quantitative motor, and cognitive measures had prognostic value, independent of age and CAG repeat length, for predicting subsequent clinical diagnosis in preHD. Of these, grey-matter volume and inter-tap interval were particularly sensitive (p=0·013 and 0·002, respectively). Longitudinal change in these two measures was also greater in participants with preHD who received a diagnosis of HD during the study compared with those who did not, after controlling for CAG repeat length and age-related risk (p=0·006 and 0·0003, respectively). In early HD, imaging, quantitative motor, and cognitive measures were predictive of decline in total functional capacity and tracked longitudinal change; also, neuropsychiatric changes consistent with frontostriatal pathological abnormalities were associated with this loss of functional capacity (problem behaviours assessment composite behaviour score p<0·0001). Age and CAG repeat length explained variance in longitudinal change of multimodal measures, with the effect more prominent in preHD. Interpretation We have shown changes in several outcome measures in individuals with preHD over 36 months. These findings further our understanding of HD progression and have implications for clinical trial design. Funding CHDI Foundation.
Summary Background TRACK-HD is a prospective observational study of Huntington's disease (HD) that examines disease progression in premanifest individuals carrying the mutant HTT gene and those with ...early stage disease. We report 12-month longitudinal changes, building on baseline findings. Methods We did a 12-month follow-up of patients recruited from the four TRACK-HD study sites in Canada, France, the Netherlands, and the UK. Participants were premanifest individuals (preHD) carrying the mutant HTT gene, patients with early HD, and controls matched by age and sex with the combined preHD and early HD groups. Data were collected by use of 3T MRI and clinical, cognitive, quantitative motor, oculomotor, and neuropsychiatric measures. Statistical analysis assessed annualised change with the use of linear regression models to estimate differences between groups. Findings 116 preHD individuals, 114 early HD patients, and 115 people in the control group completed follow-up. Four preHD individuals, nine early HD patients, and eight people in the control group did not complete the follow-up. A further nine participants, who completed follow-up assessments, were unable to undergo MRI. After adjustment for demographics, annualised rates of generalised and regional brain atrophy were higher in preHD and early HD groups than in controls. Whole-brain atrophy rates were 0·20% (95% CI 0·05–0·34; p=0·0071) per year higher in preHD participants and 0·60% (0·44–0·76; p<0·0001) in early HD patients, and caudate atrophy rates were 1·37% (0·99–1·75; p<0·0001) per year higher in preHD and 2·86% (2·34–3·39; p<0·0001) in early HD. Voxel-based morphometry revealed grey-matter and white-matter atrophy, even in subjects furthest from predicted disease onset. Quantitative imaging showed statistically significant associations with disease burden, an indicator of disease pathology, and total functional capacity, a widely-used clinical measure of disease severity. Relative to controls, decline in cognition and quantitative motor function was detectable in both pre- and early HD, as was deterioration in oculomotor function in early HD. Interpretation Quantitative imaging showed the greatest differentiation across the spectrum of disease and functional measures of decline were sensitive in early HD, with cognitive and quantitative motor impairment also detectable in preHD. We show longitudinal change over 12 months in generalised and regional brain volume, cognition, and quantitative motor tasks in individuals many years from predicted disease onset and show the feasibility of obtaining quantifiable endpoints for future trials. Funding CHDI/HighQ Foundation Inc.
Characterizing changing brain structure in neurodegeneration is fundamental to understanding long-term effects of pathology and ultimately providing therapeutic targets. It is well established that ...Huntington’s disease (HD) gene carriers undergo progressive brain changes during the course of disease, yet the long-term trajectory of cortical atrophy is not well defined. Given that genetic therapies currently tested in HD are primarily expected to target the cortex, understanding atrophy across this region is essential.
Capitalizing on a unique longitudinal dataset with a minimum of 3 and maximum of 7 brain scans from 49 HD gene carriers and 49 age-matched control subjects, we implemented a novel dynamical systems approach to infer patterns of regional neurodegeneration over 10 years. We use Bayesian hierarchical modeling to map participant- and group-level trajectories of atrophy spatially and temporally, additionally relating atrophy to the genetic marker of HD (CAG-repeat length) and motor and cognitive symptoms.
We show, for the first time, that neurodegenerative changes exhibit complex temporal dynamics with substantial regional variation around the point of clinical diagnosis. Although widespread group differences were seen across the cortex, the occipital and parietal regions undergo the greatest rate of cortical atrophy. We have established links between atrophy and genetic markers of HD while demonstrating that specific cortical changes predict decline in motor and cognitive performance.
HD gene carriers display regional variability in the spatial pattern of cortical atrophy, which relates to genetic factors and motor and cognitive symptoms. Our findings indicate a complex pattern of neuronal loss, which enables greater characterization of HD progression.
Huntington disease (HD) can be seen as a model neurodegenerative disorder, in that it is caused by a single genetic mutation and is amenable to predictive genetic testing, with estimation of years to ...predicted onset, enabling the entire range of disease natural history to be studied. Structural neuroimaging biomarkers show that progressive regional brain atrophy begins many years before the emergence of diagnosable signs and symptoms of HD, and continues steadily during the symptomatic or 'manifest' period. The continued development of functional, neurochemical and other biomarkers raises hopes that these biomarkers might be useful for future trials of disease-modifying therapeutics to delay the onset and slow the progression of HD. Such advances could herald a new era of personalized preventive therapeutics. We describe the natural history of HD, including the timing of emergence of motor, cognitive and emotional impairments, and the techniques that are used to assess these features. Building on this information, we review recent progress in the development of biomarkers for HD, and potential future roles of these biomarkers in clinical trials.
ObjectivesCognitive flexibility, which is key for adaptive decision-making, engages prefrontal cortex (PFC)-striatal circuitry and is impaired in both manifest and premanifest Huntington’s disease ...(pre-HD). The aim of this study was to examine cognitive flexibility in a far from onset pre-HD cohort to determine whether an early impairment exists and if so, whether fronto-striatal circuits were associated with this deficit.MethodsIn the present study, we examined performance of 51 pre-HD participants (mean age=29.22 (SD=5.71) years) from the HD Young Adult Study cohort and 53 controls matched for age, sex and IQ, on the Cambridge Neuropsychological Test Automated Battery (CANTAB) Intra-Extra Dimensional Set-Shift (IED) task. This cohort is unique as it is the furthest from disease onset comprehensively studied to date (mean years=23.89 (SD=5.96) years). The IED task measures visual discrimination learning, cognitive flexibility and specifically attentional set-shifting. We used resting-state functional MRI to examine whether the functional connectivity between specific fronto-striatal circuits was dysfunctional in pre-HD, compared with controls, and whether these circuits were associated with performance on the critical extradimensional shift stage.ResultsOur results demonstrated that the CANTAB IED task detects a mild early impairment in cognitive flexibility in a pre-HD group far from onset. Attentional set-shifting was significantly related to functional connectivity between the ventrolateral PFC and ventral striatum in healthy controls and to functional connectivity between the dorsolateral PFC and caudate in pre-HD participants.ConclusionWe postulate that this incipient impairment of cognitive flexibility may be associated with intrinsically abnormal functional connectivity of fronto-striatal circuitry in pre-HD.
Abstract Previous studies have shown activation of the immune system and altered immune response in Huntington's disease (HD) gene carriers. Here, we hypothesized that peripheral and central immune ...responses could be concurrent pathophysiological events and represent a global innate immune response to the toxic effects of mutant huntingtin in HD gene carriers. We sought to investigate our hypothesis using 11 CPK11195 PET as a translocator protein (TSPO) marker of central microglial activation, together with assessment of peripheral plasma cytokine levels in a cohort of premanifest HD gene carriers who were more than a decade from predicted symptomatic conversion. Data were also compared to those from a group of healthy controls matched for age and gender. We found significantly increased peripheral plasma IL-1β levels in premanifest HD gene carriers compared to the group of normal controls ( P = 0.018). Premanifest HD gene carriers had increased TSPO levels in cortical, basal ganglia and thalamic brain regions ( P < 0.001). Increased microglial activation in somatosensory cortex correlated with higher plasma levels of IL-1β ( rs = 0.87, P = 0.013), IL-6 (rs = 0.85, P = 0.013), IL-8 ( rs = 0.68, P = 0.045) and TNF-α ( rs = 0.79; P = 0.013). Our findings provide first in vivo evidence for an association between peripheral and central immune responses in premanifest HD gene carriers, and provide further supporting evidence for the role of immune dysfunction in the pathogenesis of HD.
Huntington's disease is the most frequent autosomal dominant neurodegenerative disorder; however, no disease-modifying interventions are available for patients with this disease. The molecular ...pathogenesis of Huntington's disease is complex, with toxicity that arises from full-length expanded huntingtin and N-terminal fragments of huntingtin, which are both prone to misfolding due to proteolysis; aberrant intron-1 splicing of the HTT gene; and somatic expansion of the CAG repeat in the HTT gene. Potential interventions for Huntington's disease include therapies targeting huntingtin DNA and RNA, clearance of huntingtin protein, DNA repair pathways, and other treatment strategies targeting inflammation and cell replacement. The early termination of trials of the antisense oligonucleotide tominersen suggest that it is time to reflect on lessons learned, where the field stands now, and the challenges and opportunities for the future.
The longitudinal dynamics of the most promising biofluid biomarker candidates for Huntington's disease (HD)-mutant huntingtin (mHTT) and neurofilament light (NfL)-are incompletely defined. ...Characterizing changes in these candidates during disease progression could increase our understanding of disease pathophysiology and help the identification of effective therapies. In an 80-participant cohort over 24 months, mHTT in cerebrospinal fluid (CSF), as well as NfL in CSF and blood, had distinct longitudinal trajectories in HD mutation carriers compared with controls. Baseline analyte values predicted clinical disease status, subsequent clinical progression, and brain atrophy, better than did the rate of change in analytes. Overall, NfL was a stronger monitoring and prognostic biomarker for HD than mHTT. Nonetheless, mHTT has prognostic value and might be a valuable pharmacodynamic marker for huntingtin-lowering trials.
Variability in neurodegenerative disease progression poses great challenges for the evaluation of potential treatments. Identifying the persons who will experience significant progression in the ...short term is key for the implementation of trials with smaller sample sizes. We apply here disease course mapping to forecast biomarker progression for individual carriers of the pathological CAG repeat expansions responsible for Huntington disease. We used data from two longitudinal studies (TRACK-HD and TRACK-ON) to synchronize temporal progression of 15 clinical and imaging biomarkers from 290 participants with Huntington disease. We used then the resulting HD COURSE MAP to forecast clinical endpoints from the baseline data of 11,510 participants from ENROLL-HD, an external validation cohort. We used such forecasts to select participants at risk for progression and compute the power of trials for such an enriched population. HD COURSE MAP forecasts biomarkers 5 years after the baseline measures with a maximum mean absolute error of 10 points for the total motor score and 2.15 for the total functional capacity. This allowed reducing sample sizes in trial up to 50% including participants with a higher risk for progression ensuring a more homogeneous group of participants.
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