Cerebrospinal fluid correlates of depression in Huntington's disease

Why Woody got the blues: The neurobiology of depression in Huntington's disease

Huntington's disease (HD) is an extraordinary disorder that usually strikes when individuals are in the prime of their lives, as was the case for the influential 20th century musician Woody Guthrie. HD demonstrates the exceptionally fine line between life and death in such 'genetic diseases', as the only difference between those who suffer horribly and die slowly of this disease is often just a handful of extra tandem repeats (beyond the normal polymorphic range) in a genome that constitutes over 3 billion paired nucleotides of DNA. Furthermore, HD presents as a complex and heterogenous combination of psychiatric, cognitive and motor symptoms, so can appear as an unholy trinity of 'three disorders in one'. The autosomal dominant nature of the disorder is also extremely challenging for affected families, as a 'flip of a coin' dictates which children inherit the mutation from their affected parent, and the gene-negative family members bear the burden of caring for the other half of the family that is affected. In this review, we will focus on one of the earliest, and most devastating, symptoms associated with HD, depression, which has been reported to affect approximately half of gene-positive HD family members. We will discuss the pathogenesis of HD, and depressive symptoms in particular, including molecular and cellular mechanisms, and potential genetic and environmental modifiers. This expanding understanding of HD pathogenesis may not only lead to novel therapeutic options for HD families, but may also provide insights into depression in the wider population, which has the greatest burden of disease of any disorder and an enormous unmet need for new therapies.

A Critical Evaluation of Wet Biomarkers for Huntington's Disease: Current Status and Ways Forward

There is an unmet clinical need for objective biomarkers to monitor disease progression and treatment response in Huntington's disease (HD). The aim of this review is, therefore, to provide practical advice for biomarker discovery and to summarise studies on biofluid markers for HD. A PubMed search was performed to review literature with regard to candidate saliva, urine, blood and cerebrospinal fluid biomarkers for HD. Information has been organised into tables to allow a pragmatic approach to the discussion of the evidence and generation of practical recommendations for future studies. Many of the markers published converge on metabolic and inflammatory pathways, although changes in other analytes representing antioxidant and growth factor pathways have also been found. The most promising markers reflect neuronal and glial degeneration, particularly neurofilament light chain. International collaboration to standardise assays and study protocols, as well as to recruit sufficiently large cohorts, will facilitate future biomarker discovery and development.

Platelet-derived extracellular vesicles in Huntington's disease

The production and release of extracellular vesicles (EV) is a property shared by all eukaryotic cells and a phenomenon frequently exacerbated in pathological conditions. The protein cargo of EV, their cell type signature and availability in bodily fluids make them particularly appealing as biomarkers. We recently demonstrated that platelets, among all types of blood cells, contain the highest concentrations of the mutant huntingtin protein (mHtt)-the genetic product of Huntington's disease (HD), a neurodegenerative disorder which manifests in adulthood with a complex combination of motor, cognitive and psychiatric deficits. Herein, we used a cohort of 59 HD patients at all stages of the disease, including individuals in pre-manifest stages, and 54 healthy age- and sex-matched controls, to evaluate the potential of EV derived from platelets as a biomarker. We found that platelets of pre-manifest and manifest HD patients do not release more EV even if they are activated. Importantly, mHtt was not found within EV derived from platelets, despite them containing high levels of this protein. Correlation analyses also failed to reveal an association between the number of platelet-derived EV and the age of the patients, the number of CAG repeats, the Unified Huntington Disease Rating Scale total motor score, the Total Functional Capacity score or the Burden of Disease score. Our data would, therefore, suggest that EV derived from platelets with HD is not a valuable biomarker in HD.

Biofluid Biomarkers in Huntington's Disease

Huntington's disease (HD) is a chronic progressive neurodegenerative condition where new markers of disease progression are needed. So far no disease-modifying interventions have been found, and few interventions have been proven to alleviate symptoms. This may be partially explained by the lack of reliable indicators of disease severity, progression, and phenotype.Biofluid biomarkers may bring advantages in addition to clinical measures, such as reliability, reproducibility, price, accuracy, and direct quantification of pathobiological processes at the molecular level; and in addition to empowering clinical trials, they have the potential to generate useful hypotheses for new drug development.In this chapter we review biofluid biomarker reports in HD, emphasizing those we feel are likely to be closest to clinical applicability.

Inflammatory mediators as biomarkers in brain disorders

Neurodegenerative diseases such as Alzheimer, Parkinson, amyotrophic lateral sclerosis, and Huntington are incurable and debilitating conditions that result in progressive death of the neurons. The definite diagnosis of a neurodegenerative disorder is disadvantaged by the difficulty in obtaining biopsies and thereby to validate the clinical diagnosis with pathological results. Biomarkers are valuable indicators for detecting different phases of a disease such as prevention, early onset, treatment, progression, and monitoring the effect of pharmacological responses to a therapeutic intervention. Inflammation occurs in neurodegenerative diseases, and identification and validation of molecules involved in this process could be a strategy for finding new biomarkers. The ideal inflammatory biomarker needs to be easily measurable, must be reproducible, not subject to wide variation in the population, and unaffected by external factors. Our review summarizes the most important inflammation biomarkers currently available, whose specificity could be utilized for identifying and monitoring distinctive phases of different neurodegenerative diseases.

Hypothalamic-pituitary-adrenal axis functioning in Huntington's disease and its association with depressive symptoms and suicidality

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis has been reported in Huntington's disease (HD). In non-HD populations, alterations in HPA axis activity have been associated with depression and suicidality. The present study aims to compare HPA axis activity between HD mutation carriers and controls, and examine its association with depressive symptoms and suicidality. To this end, salivary cortisol concentrations at seven time points, as well as depressive symptoms and suicidality, were assessed in 49 pre-motor, 102 motor symptomatic mutation carriers and 55 controls, at baseline and follow-up combined. Differences in parameters of HPA axis activity between these three groups, and their associations with depressive symptoms and suicidality in HD mutation carriers, were analysed using multilevel regression analyses. There were no differences in parameters of HPA axis activity between mutation carriers and controls, whereas pre-motor symptomatic mutation carriers had a significantly higher area under the curve to the increase (AUCi ) compared to motor symptomatic mutation carriers. In the entire HD cohort, HPA axis activity was not associated with depressive symptoms or suicidality. After stratifying mutation carriers into pre-motor, early and advanced disease stages, β values differed between these groups. Remarkably, a higher AUCi was significantly associated with depressive symptoms in pre-motor and early disease stage mutation carriers, with a reverse nonsignificant association in advanced disease stage mutation carriers. The lower AUCi in motor symptomatic mutation carriers and the varying associations with depressive symptoms and suicidality in pre-motor, early and advanced disease stages could possibly be explained by exhaustion of the HPA axis after prolonged stress-induced HPA axis hyperactivity and deserves further longitudinal study.

Cortisol and depression in pre-diagnosed and early stage Huntington's disease

Hypothalamic-pituitary-adrenal (HPA) axis dysfunction and depression have both been shown to occur in Huntington's disease (HD) gene carriers prior to diagnosis (pre-HD) and in diagnosed HD patients. However, the relationship between HPA axis dysfunction and the severity of depressive symptomatology in pre-HD and early-HD has not been systematically examined, despite morning hypercortisolism being a characteristic feature of some subtypes of idiopathic depression. The aim of this study was to investigate whether HPA axis function is related to levels of depression in pre-HD and early-HD. To assess HPA axis function we obtained salivary cortisol concentrations from 20 controls, 20 pre-HD, and 17 early-HD participants at four time points over a 24h period. Depression symptoms were assessed using the Inventory of Depressive Symptomatology - Self-Report. Of the participants who were found not to be depressed, the early-HD group had significantly lower morning cortisol levels relative to pre-HD and controls. In contrast, the early-HD group with at least mild or greater levels of depression symptoms had a comparable cortisol concentration to pre-HD and controls. The results suggest that early-HD may be associated with hypocortisolism. However when depressed, a hyperactive HPA axis response may still be induced in early-HD and lead to cortisol levels that are similar to pre-HD and controls. Our study reveals that cortisol levels in HD may be modified by the presence or absence of depressive symptomatology. Depression may be an important factor for understanding how the HPA axis is affected in HD, particularly in the morning.

Characteristics, pathophysiology and clinical management of weight loss in Huntington’s disease

SUMMARY Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by a CAG repeat expansion in the HTT gene. Clinically, the disease is characterized by motor impairment, cognitive deterioration and behavioral disturbances. Unintended weight loss is also a hallmark of the disease and frequently leads to general weakening and a decline in the quality of life of HD patients. Moreover, a higher BMI has been associated with a slower rate of disease progression. In this review, the authors first delineate the characteristics of weight loss in both HD patients and genetic models of the disease. Subsequently, they discuss the pathophysiological processes underlying weight loss in HD and highlight the implications for management and care of HD patients with, or at risk of, unintended weight loss.

The relationship between cortisol and verbal memory in the early stages of Huntington's disease

Hypothalamic pituitary adrenal (HPA) axis hyperactivity has been linked to learning and memory difficulties in a range of neurodegenerative and neuropsychiatric conditions. In Huntington's disease (HD), both declines in learning and memory and HPA axis dysfunction are present early in the disease. However, the relationship between specific learning and memory deficits and HPA axis functioning in HD has not been examined. The aim of this study was to investigate cortisol levels in relation to verbal learning and memory in pre-diagnosed (pre-HD) participants and patients at the early stages of diagnosed HD (early-HD). Cortisol concentration was assayed in saliva samples from 57 participants (17 early-HD, 20 pre-HD, and 20 controls) at four time-points across a 24-h period. Verbal memory was assessed using the California Verbal Learning Test-Second Edition (CVLT-II). We focused statistical analyses on the late evening cortisol concentration, and examined cortisol levels and verbal memory function in relation to diagnostic group (control, pre-HD, early-HD), and in a separate set of analyses combining pre-HD and early-HD (and excluding controls) we also examined cortisol and verbal memory performance in relation to the severity of HD-related motor signs. Of these two classification approaches, HD motor sign severity was more strongly associated with high evening cortisol levels and both reduced information encoding and memory retrieval. Separately, there was also a trend of higher cortisol levels in pre-HD. The findings suggest hypercortisolism and the underlying pathological changes may begin many years before a clinical diagnosis is made, but the memory decline associated with HPA axis disturbance may only become detectable once motor signs become pronounced.

Paraventricular nucleus neuropeptide expression in Huntington's disease patients

Neuroendocrine, metabolic and autonomic nervous system dysfunctions are prevalent among patients with Huntington's disease (HD) and may underlie symptoms such as depression, weight loss and autonomic failure. Using post-mortem paraffin-embedded tissue, we assessed the integrity of the major neuropeptide populations in the paraventricular nucleus (PVN)-the hypothalamic neuroendocrine and autonomic integration center-in HD patients. The number corticotropin-releasing hormone, cocaine- and amphetamine-regulated transcript, arginine vasopressin and oxytocin immunoreactive (ir) neurons did not differ between HD patients and control subjects. However, the significant positive correlation between arginine vasopressin and oxytocin ir neurons in control subjects (P = 0.036) was absent in patients. Corticotropin-releasing hormone mRNA levels were 68% higher in HD patients (P = 0.046). Thyrotropin-releasing hormone mRNA levels did not differ between HD patients and control subjects, although a negative correlation with disease duration was present in the former (P = 0.036). These findings indicate that the PVN is largely unaffected in HD patients. However, our findings suggest that hypothalamic-pituitary-thyroid axis activity may alter during the course of the disease and that autonomic nervous system dysfunction might partly arise from an imbalance between arginine vasopressin and oxytocin neurons in the PVN.

Hypothalamic dysfunction and neuroendocrine and metabolic alterations in Huntington's disease: clinical consequences and therapeutic implications

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by cognitive, psychiatric, behavioural and motor disturbances. Although the course of HD is also frequently complicated by unintended weight loss, sleep disturbances and autonomic nervous system dysfunction, the aetiology of these signs and symptoms remains largely unknown. In recent years, many novel findings from both animal and human studies have emerged that indicate considerable hypothalamic, endocrine and metabolic alterations in HD. However, a comprehensive overview of these findings is lacking and their precise clinical significance is far from clear. Therefore, in this review we attempt to put these recent developments in the field into perspective by integrating them with previous findings in a comprehensible manner, and by discussing their clinical relevance, with a special focus on body weight, sleep and autonomic functions in HD, which will also allow for the identification of future lines of research in this area.

New directions in the development of antidepressants: the interface of neurobiology and psychiatry

There have been considerable advances in neurobiology in recent years that are providing new directions for the development of novel classes of antidepressants. For example, the finding that corticotropin-releasing factor (CRF) is hypersecreted in depressed patients and mediates certain symptoms of depression has led to the development of specific antagonists of the CRF(1) receptor. These are expected to prove highly effective for the treatment of mood and anxiety disorders. Another related avenue of research is based on evidence that cortisol is integral to the pathophysiology of major depression with psychotic features. One alternative for treating this subtype of affective disorder is, therefore, to block the action of glucocorticoids using a receptor antagonist such as mifepristone. These are just two of the many new directions that will likely lead to the development of antidepressants in the near future.

An overview of psychiatric symptoms in Huntington's disease

Huntington's disease (HD) is an inherited autosomal dominant disorder characterized by neurologic, cognitive, and psychiatric symptomatology. Psychiatric symptoms in HD are often amenable to treatment, and relief of these symptoms may provide significant improvement in quality of life. This review will briefly describe neurologic, neuropsychologic and brain imaging data, and then review psychiatric syndromes seen in HD and their treatment.

Depression and Huntington's disease: prevalence, clinical manifestations, etiology, and treatment

In order to determine the extent to which depression complicates Huntington's disease (HD), we have analyzed the existing literature on depression in HD in order to report the prevalence, clinical manifestations, and treatment of HD depression. By means of MEDLINE literature searches and reviews of HD articles' bibliographies, we identified for our analysis 16 HD depression studies. Our results indicate that the prevalence of depression is 30% for all HD patients. Clinical manifestations of HD depression include a marked increased risk for suicide. The etiology of HD depression is unclear, but may be due to a number of factors, such as dysfunction in the caudate nucleus, dysfunction in the ventral striatum, and various genetic factors that are discussed in this review. Case reports and case series support the efficacy of standard antidepressant interventions in resolving symptoms of depression. Efficacious treatments reported in the literature include tricyclic antidepressants, monoamine oxidase inhibitors, selective serotonin reuptake inhibitors, and electroconvulsive therapy. In this study, the successful anecdotal treatment of seven consecutive HD depressed patients with sertraline suggests that sertraline may be a safe and efficacious treatment of HD depression.

Cellular localization of corticotropin releasing factor receptors in the adult mouse cerebellum

Corticotropin releasing factor is a 41 amino acid peptide that is present in afferent systems that project to the cerebellum. In the adult, this peptide modulates the activity of Purkinje cells by enhancing their responsiveness to excitatory amino acids. Two different types of corticotropin releasing factor receptors, designated type 1 and type 2, have been identified. The purpose of this study is to use immunohistochemistry to identify which corticotropin releasing factor receptors are present in the cerebellum of the adult mouse and to determine their cellular distribution. Receptor type 1 immunostaining is present throughout all lobules of the cerebellar cortex. Distinct labeling is present over the somas of most, if not all, Purkinje cells as well as the primary dendrites of Purkinje cells located at the base of vermal folia. In vermal lobules V, VI, VIII and IX numerous glial fibrillary acidic protein immunoreactive processes, oriented radially in the molecular layer, also are immunoreactive for receptor type 1. In the granule cell layer, scattered type 1 immunoreactive puncta are present throughout most cerebellar lobules. Receptor type 2 immunoreactive puncta are present throughout the molecular layer in all lobules. In addition, scattered basket and/or stellate cells, identified with a GABA antibody, are immunopositive for the type 2 receptor. In the Purkinje cell layer, the type 2 receptor immunolabeling is confined to the basal pole of the Purkinje cell including the initial axonal segment. In the granule cell layer, labeling is present over large cell bodies, and their initial axonal segments. These are likely to be Golgi cells, based on their co-staining with GABA. Finally, numerous elongated processes within the white matter, which are likely to be axons, also are type 2 immunoreactive. These data indicate that both types of corticotropin releasing factor receptor are present in the mouse cerebellum. However, the unique distribution of the two types of receptor strongly suggests a differential role for corticotropin releasing factor in modulating the activity of neurons, axons and glial cells via cell-specific ligand-receptor interactions.

Huntington's disease

Huntington's disease is a genetically inherited degenerative neuropsychiatric disorder, characterized by motor alterations, including involuntary movements such as chorea, dementia and psychiatric disturbances. In this article, the authors review the clinical features of the disease. They also analyze some genetic and pathophysiologic aspects, that can help to improve our understanding of this disorder involving the basal ganglia.

A study of psychiatric morbidity in patients with Huntington's disease, their relatives, and controls. Admissions to psychiatric hospitals in Denmark from 1969 to 1991

Psychiatric morbidity among 74 non-affected first-degree relatives and 93 non-affected second-degree relatives of patients with Huntington's disease (HD) was compared with that of 37 patients with HD and with matched control groups. Due to specific age criteria, the first-degree relatives were at decreased risk and the second-degree relatives at negligible risk of being carriers of the gene for HD. Information on admissions to departments of psychiatry and diagnoses at discharge were obtained for all subjects from a nationwide central register. Psychiatric morbidity was no greater among relatives than among controls, whereas HD patients had significantly more admissions and psychiatric diagnoses than relatives. Growing up with a risk of developing HD does not itself increase the risk of developing psychiatric illness resulting in hospital admission. Severe psychiatric disorders in HD patients were thus most likely to be aetiologically related to the disease process, possibly through a genetic mechanism.

A Study of Elderly Suicide Attempters Admitted to an Inpatient Psychiatric Unit

The authors distinguish demographic and clinical characteristics of elderly suicide attempters admitted to an inpatient psychiatric unit within 4 weeks of a suicide attempt. Of 560 patients admitted, 28 (5%) were recent attempters, 32 (6%) had a past history of suicide attempt, and 500 (89%) were nonattempters. Of the 28 recent attempters, 21 (75%) were diagnosed with a mood disorder, 4 (14%) with an organic mental disorder, and 3 (11%) with other mental disorders. Among the nonattempters, the distribution among the three diagnostic categories was 188 (38%), 251 (50%), and 61 (12%), respectively. Of 166 patients with a diagnosis of major depression, 18 (11%) were recent attempters, 14 (8%) were past attempters, and 134 (71%) were nonattempters. Recent attempts were significantly associated with alcohol abuse. This study confirms earlier reports of high rates of major depression in elderly attempters.

Huntington's disease as a model for mood disorders. Clues from neuropathology and neurochemistry

Huntington's disease (HD) is an inherited neuropsychiatric degenerative process characterized by movement disorder, dementia, and, often, affective disorder (AfD) (seen in 38% of patients). Depression in HD is not just an understandable reaction to fatal illness: 10% of HD patients develop mania; AfD can occur 20 yr before neurological signs; and mood disorders are not randomly distributed, but occur in a subset of HD families. This evidence suggests that AfD in HD relates to brain pathophysiology. With its clear neuropathology, HD is proposed as one model for biological underpinnings of idiopathic AfD. There is striking atrophy and neuronal loss in HD neostriatum, particularly caudate. Caudate has rich connections to the limbic system. It is hypothesized that AfD in HD relates to dysfunction of the part of the neostriatum damaged earliest, dorsal medial caudate. Preliminary studies on neuropathological differences between HD patients with and without AfD are discussed. HD neurochemistry is reviewed, emphasizing the excitotoxin hypothesis, which involves dysfunction of the glutamate neurotransmitter system in HD (especially the NMDA receptor, which contains a channel with a phencyclidine (PCP) binding site). Based on the HD model, it is suggested that the glutamate system (particularly NMDA receptors) be examined in idiopathic AfD.