Brain-derived neurotrophic factor in patients with Huntington's disease

Use of Curcumin, a Natural Polyphenol for Targeting Molecular Pathways in Treating Age-Related Neurodegenerative Diseases

Progressive accumulation of misfolded amyloid proteins in intracellular and extracellular spaces is one of the principal reasons for synaptic damage and impairment of neuronal communication in several neurodegenerative diseases. Effective treatments for these diseases are still lacking but remain the focus of much active investigation. Despite testing several synthesized compounds, small molecules, and drugs over the past few decades, very few of them can inhibit aggregation of amyloid proteins and lessen their neurotoxic effects. Recently, the natural polyphenol curcumin (Cur) has been shown to be a promising anti-amyloid, anti-inflammatory and neuroprotective agent for several neurodegenerative diseases. Because of its pleotropic actions on the central nervous system, including preferential binding to amyloid proteins, Cur is being touted as a promising treatment for age-related brain diseases. Here, we focus on molecular targeting of Cur to reduce amyloid burden, rescue neuronal damage, and restore normal cognitive and sensory motor functions in different animal models of neurodegenerative diseases. We specifically highlight Cur as a potential treatment for Alzheimer's, Parkinson's, Huntington's, and prion diseases. In addition, we discuss the major issues and limitations of using Cur for treating these diseases, along with ways of circumventing those shortcomings. Finally, we provide specific recommendations for optimal dosing with Cur for treating neurological diseases.

New directions in therapeutics for Huntington disease

Huntington disease (HD) is an autosomal dominantly inherited neurodegenerative disease that affects motor, cognitive and psychiatric functions, and ultimately leads to death. The pathology of the disease is based on an expansion of CAG repeats in exon 1 of the huntingtin gene on chromosome 4, which produces a mutant huntingtin protein (mHtt). This protein is involved in neurotoxicity and brain atrophy, and can form β-sheets and abnormal mHtt aggregates. Currently, there are no approved effective treatments for HD, although tetrabenazine (Xenazine™) and deutetrabenazine (AUSTEDO™) have been approved for treatment of the motor symptom chorea in HD. This literature review aims to address the latest research on promising therapeutics based on influencing the hypothesized pathological mechanisms.

Measuring and Validating the Levels of Brain-Derived Neurotrophic Factor in Human Serum

Brain-derived neurotrophic factor (BDNF) secreted by neurons is a significant component of synaptic plasticity. In humans, it is also present in blood platelets where it accumulates following its biosynthesis in megakaryocytes. BDNF levels are thus readily detectable in human serum and it has been abundantly speculated that they may somehow serve as an indicator of brain function. However, there is a great deal of uncertainty with regard to the range of BDNF levels that can be considered normal, how stable these values are over time and even whether BDNF levels can be reliably measured in serum. Using monoclonal antibodies and a sandwich ELISA, this study reports on BDNF levels in the serum of 259 volunteers with a mean value of 32.69 ± 8.33 ng/ml (SD). The mean value for the same cohort after 12 months was not significantly different (N = 226, 32.97 ± 8.36 ng/ml SD, p = 0.19). Power analysis of these values indicates that relatively large cohorts are necessary to identify significant differences, requiring a group size of 60 to detect a 20% change. The levels determined by ELISA could be validated by Western blot analyses using a BDNF monoclonal antibody. While no association was observed with gender, a weak, positive correlation was found with age. The overall conclusions are that BDNF levels can be reliably measured in human serum, that these levels are quite stable over one year, and that comparisons between two populations may only be meaningful if cohorts of sufficient sizes are assembled.

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.

Human Neural Stem Cell Transplantation Rescues Functional Deficits in R6/2 and Q140 Huntington's Disease Mice

Huntington's disease (HD) is an inherited neurodegenerative disorder with no disease-modifying treatment. Expansion of the glutamine-encoding repeat in the Huntingtin (HTT) gene causes broad effects that are a challenge for single treatment strategies. Strategies based on human stem cells offer a promising option. We evaluated efficacy of transplanting a good manufacturing practice (GMP)-grade human embryonic stem cell-derived neural stem cell (hNSC) line into striatum of HD modeled mice. In HD fragment model R6/2 mice, transplants improve motor deficits, rescue synaptic alterations, and are contacted by nerve terminals from mouse cells. Furthermore, implanted hNSCs are electrophysiologically active. hNSCs also improved motor and late-stage cognitive impairment in a second HD model, Q140 knockin mice. Disease-modifying activity is suggested by the reduction of aberrant accumulation of mutant HTT protein and expression of brain-derived neurotrophic factor (BDNF) in both models. These findings hold promise for future development of stem cell-based therapies.

Modulation of nuclear REST by alternative splicing: a potential therapeutic target for Huntington's disease

Huntington's disease (HD) is caused by a genetically mutated huntingtin (mHtt) protein with expanded polyQ stretch, which impairs cytosolic sequestration of the repressor element-1 silencing transcription factor (REST), resulting in excessive nuclear REST and subsequent repression of neuronal genes. We recently demonstrated that REST undergoes extensive, context-dependent alternative splicing, of which exon-3 skipping (∆E3 )-a common event in human and nonhuman primates-causes loss of a motif critical for REST nuclear targeting. This study aimed to determine whether ∆E3 can be targeted to reduce nuclear REST and rescue neuronal gene expression in mouse striatal-derived, mHtt-expressing STHdhQ111/Q111 cells-a well-established cellular model of HD. We designed two morpholino antisense oligos (ASOs) targeting the splice sites of Rest E3 and examined their effects on ∆E3 , nuclear Rest accumulation and Rest-controlled gene expression in STHdhQ111/Q111 cells. We found that (1) the ASOs treatment significantly induced ∆E3 , reduced nuclear Rest, and rescued transcription and/or mis-splicing of specific neuronal genes (e.g. Syn1 and Stmn2) in STHdhQ111/Q111 cells; and (2) the ASOs-induced transcriptional regulation was dependent on ∆E3 induction and mimicked by siRNA-mediated knock-down of Rest expression. Our findings demonstrate modulation of nuclear REST by ∆E3 and its potential as a new therapeutic target for HD and provide new insights into environmental regulation of genome function and pathogenesis of HD. As ∆E3 is modulated by cellular signalling and linked to various types of cancer, we anticipate that ∆E3 contributes to environmentally tuned REST function and may have a broad range of clinical implications.

Effect of Clotting Duration and Temperature on BDNF Measurement in Human Serum

Brain-derived neurothrophic factor (BDNF) is a neurotrophin expressed in different tissues and cells, including neurons, endothelial cells, leukocytes, megakaryocytes and platelets. Modifications of BDNF in plasma and/or in serum are associated with neurodegenerative and psychiatric disorders, cardiovascular diseases, metabolic syndrome and with mortality risk. Indeed, changes in blood levels of BDNF may reflect those of its tissue of origin and/or promote pathological dysfunctions. The measurement of BDNF amount in plasma or in serum has been characterized with particular attention in the impact of different anti-coagulants, clotting duration, temperature (≤21 °C) and delay in blood sample centrifugation as well as in stability of storage. However, the influences of normothermic conditions (37 °C) and of clotting duration on BDNF levels in human serum have not been investigated yet. Here, we showed that time and temperature during serum preparation could be taken into consideration to assess the association and/or impact of BDNF levels in the occurrence of pathological conditions.

Brain-derived neurotrophic factor and airway fibrosis in asthma

Airway remodeling in asthma driven by inflammation involves proliferation of epithelial cells and airway smooth muscle (ASM), as well as enhanced extracellular matrix (ECM) generation and deposition, i.e., fibrosis. Accordingly, understanding profibrotic mechanisms is important for developing novel therapeutic strategies in asthma. Recent studies, including our own, have suggested a role for locally produced growth factors such as brain-derived neurotrophic factor (BDNF) in mediating and modulating inflammation effects. In this study, we explored the profibrotic influence of BDNF in the context of asthma by examining expression, activity, and deposition of ECM proteins in primary ASM cells isolated from asthmatic vs. nonasthmatic patients. Basal BDNF expression and secretion, and levels of the high-affinity BDNF receptor TrkB, were higher in asthmatic ASM. Exogenous BDNF significantly increased ECM production and deposition, especially of collagen-1 and collagen-3 (less so fibronectin) and the activity of matrix metalloproteinases (MMP-2, MMP-9). Exposure to the proinflammatory cytokine TNFα significantly increased BDNF secretion, particularly in asthmatic ASM, whereas no significant changes were observed with IL-13. Chelation of BDNF using TrkB-Fc reversed TNFα-induced increase in ECM deposition. Conditioned media from asthmatic ASM enhanced ECM generation in nonasthmatic ASM, which was blunted by BDNF chelation. Inflammation-induced changes in MMP-2, MMP-9, and tissue inhibitor metalloproteinases (TIMP-1, TIMP-2) were reversed in the presence of TrkB-Fc. These novel data suggest ASM as an inflammation-sensitive source of BDNF within human airways, with autocrine effects on fibrosis relevant to asthma.

Rehabilitation training in neural restitution

Over the last decade, neural transplantation has emerged as one of the more promising, albeit highly experimental, potential therapeutics in neurodegenerative disease. Preclinical studies in rat lesion models of Huntington's disease (HD) and Parkinson's disease (PD) have shown that transplanted precursor neuronal tissue from a fetus into the lesioned striatum can survive, integrate, and reconnect circuitry. Importantly, specific training on behavioral tasks that target striatal function is required to encourage functional integration of the graft to the host tissue. Indeed, "learning to use the graft" is a concept recently adopted in preclinical studies to account for unpredicted profiles of recovery posttransplantation and is an emerging strategy for improving graft functionality. Clinical transplant studies in HD and PD have resulted in mixed outcomes. Small sample sizes and nonstandardized experimental procedures from trial to trial may explain some of this variability. However, it is becoming increasingly apparent that simply replacing the lost neurons may not be sufficient to ensure the optimal graft effects. The knowledge gained from preclinical grafting and training studies suggests that lifestyle factors, including physical activity and specific cognitive and/or motor training, may be required to drive the functional integration of grafted cells and to facilitate the development of compensatory neural networks. The clear implications of preclinical studies are that physical activity and cognitive training strategies are likely to be crucial components of clinical cell replacement therapies in the future. In this chapter, we evaluate the role of general activity in mediating the physical ability of cells to survive, sprout, and extend processes following transplantation in the adult mammalian brain, and we consider the impact of general and specific activity at the behavioral level on functional integration at the cellular and physiological level. We then highlight specific research questions related to timing, intensity, and specificity of training in preclinical models and synthesize the current state of knowledge in clinical populations to inform the development of a strategy for neural transplantation rehabilitation training.

Regenerative medicine in Huntington's disease: Strengths and weaknesses of preclinical studies

Huntington's disease (HD) is an inherited neurodegenerative disorder, characterized by impairment in motor, cognitive and psychiatric domains. Currently, there is no specific therapy to act on the onset or progression of HD. The marked neuronal death observed in HD is a main argument in favour of stem cells (SCs) transplantation as a promising therapeutic perspective to replace the population of lost neurons and restore the functionality of the damaged circuitry. The availability of rodent models of HD encourages the investigation of the restorative potential of SCs transplantation longitudinally. However, the results of preclinical studies on SCs therapy in HD are so far largely inconsistent; this hampers the individuation of the more appropriate model and precludes the comparative analysis of transplant efficacy on behavioural end points. Thus, this review will describe the state of the art of in vivo research on SCs therapy in HD, analysing in a translational perspective the strengths and weaknesses of animal studies investigating the therapeutic potential of cell transplantation on HD progression.

Plasma Brain-Derived Neurotrophic Factor and Psychopathology in Attempted Suicide

BACKGROUND/AIMS

Increasing evidence suggests a link between brain-derived neurotrophic factor (BDNF) and suicidal behaviour (SB). Furthermore, decreased peripheral BDNF levels have been associated with clinical symptoms in various psychiatric disorders as well as with personality dimensions in healthy individuals. However, the relationship between BDNF and psychopathology is poorly investigated regarding SB.

METHODS

Plasma BDNF concentrations were analysed in 61 recent suicide attempters. Clinical symptoms were evaluated using the Comprehensive Psychopathological Rating Scale. Personality dimensions were assessed using the Marke-Nyman Temperament Scale.

RESULTS

Plasma BDNF correlated positively and significantly with the personality dimension Solidity but not with the other personality dimensions or with clinical symptoms.

CONCLUSION

BDNF plays an important role in the regulation of neuroplasticity and neurogenesis in humans. Our results indicate that lower BDNF concentrations are associated with higher levels of impulsiveness and changeability (low scores on the Solidity scale). Furthermore, low plasma BDNF levels may be proposed as a trait marker rather than a state marker for attempted suicide.

miRNAs as biomarkers of neurodegenerative disorders

Neurodegenerative diseases (NDDs) are the result of progressive deterioration of neurons, ultimately leading to disabilities. There is no effective cure for NDDs at present; ongoing therapies are mainly aimed at treating the most bothersome symptoms. Since early treatment is crucial in NDDs, there is an urgent need for specific and sensitive biomarkers that can aid in early diagnosis of these disorders. Recently, altered expression of miRNAs has been implicated in several neurological disorders, including NDDs. miRNA expression has been extensively investigated in the cells, tissues and body fluids of patients with different types of NDDs. The aim of this review is to provide a comprehensive overview of miRNAs as biomarkers and therapeutic targets for NDDs.

Therapeutic potential of brain-derived neurotrophic factor (BDNF) and a small molecular mimics of BDNF for traumatic brain injury

Traumatic brain injury (TBI) is a major health problem worldwide. Following primary mechanical insults, a cascade of secondary injuries often leads to further neural tissue loss. Thus far there is no cure to rescue the damaged neural tissue. Current therapeutic strategies primarily target the secondary injuries focusing on neuroprotection and neuroregeneration. The neurotrophin brain-derived neurotrophic factor (BDNF) has significant effect in both aspects, promoting neuronal survival, synaptic plasticity and neurogenesis. Recently, the flavonoid 7,8-dihydroxyflavone (7,8-DHF), a small TrkB agonist that mimics BDNF function, has shown similar effects as BDNF in promoting neuronal survival and regeneration following TBI. Compared to BDNF, 7,8-DHF has a longer half-life and much smaller molecular size, capable of penetrating the blood-brain barrier, which makes it possible for non-invasive clinical application. In this review, we summarize functions of the BDNF/TrkB signaling pathway and studies examining the potential of BDNF and 7,8-DHF as a therapy for TBI.

Psychoactive drugs influence brain-derived neurotrophic factor and neurotrophin 4/5 levels in the serum of colorectal cancer patients

Previous studies have reported the association between brain-derived neurotrophic factor (BDNF) and tumor development in numerous cancers. However, the accurate implication of the two specific ligands of tropomyosin kinase B receptor, BDNF and neurotrophic factor 4 (NT4/5), has not been studied in colorectal cancer (CRC) patients. The present study investigated the significance of serum BDNF and the NT4/5 in association with the intake of psychoactive drugs in CRC patients. Soluble BDNF and NT4 in the serum were assessed by ELISA. Although no correlation of BDNF and NT4 with the CRC stage was identified, a positive correlation was found between NT4 and the intake of psychoactive drugs (P=0.0457). For BDNF, a correlation was found in particular with the intake of benzodiazepine (P=0.0221). As BDNF and NT4/5 are implicated in the response of psychoactive treatments applied to manage depression, which frequently occurs in cancer patients, they cannot be used as prognostic or diagnostic markers for CRC in these patients. However, high expression of BDNF and NT4 was significantly associated with better survival. Therefore, these NTs may be used as markers for monitoring depression or predicting survival in CRC patients.

Clinical trial perspective for adult and juvenile Huntington's disease using genetically-engineered mesenchymal stem cells

Progress to date from our group and others indicate that using genetically-engineered mesenchymal stem cells (MSC) to secrete brain-derived neurotrophic factor (BDNF) supports our plan to submit an Investigational New Drug application to the Food and Drug Administration for the future planned Phase 1 safety and tolerability trial of MSC/BDNF in patients with Huntington's disease (HD). There are also potential applications of this approach beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), spinocerebellar ataxia (SCA), Alzheimer's disease, and some forms of Parkinson's disease. The MSC/BDNF product could also be considered for studies of regeneration in traumatic brain injury, spinal cord and peripheral nerve injury. This work also provides a platform for our future gene editing studies, since we will again use MSCs to deliver the needed molecules into the central nervous system.

Downregulation of the PHLDA1 gene in IMR-32 neuroblastoma cells increases levels of Aurora A, TRKB and affects proteins involved in apoptosis and autophagy pathways

We have recently shown that mRNA and protein of PHLDA1 (pleckstrin-homology-like domain family A, member  1) were by far the most upregulated molecules upon treatment of IMR-32 cells with the anti-GD2 ganglioside monoclonal antibody 14G2a. Hence, we decided to study functions of PHLDA1 using human neuroblastoma IMR-32 cells as a model. Here, we show that constitutive expression of mRNA and protein of the PHLDA1 gene in IMR-32 cells was inversely correlated with transcript of the AURKA gene and Aurora A oncoprotein. Next, we silenced PHLDA1 expression in IMR-32 cells using an shRNA interference method. We report that IMR-32 cells with stable downregulation of PHLDA1 showed enhanced cellular ATP levels and an increase in mitochondrial membrane potential, as compared to control and non-transduced cells. We demonstrated that downregulation of PHLDA1 leads to a significant increase in expression of Aurora A and TRKB that are markers of poor prognosis in neuroblastoma. Also, we measured an increase in Aurora A and Akt kinases phosphorylation in the cells. Most importantly, PHLDA1-silenced cells were less susceptible to apoptosis than control cells, as shown by the lower expression of cleaved caspase-3 and PARP as well as a decreased activity of caspase-3 and -7. Our study negatively correlates expression of PHLDA1 and Aurora A in IMR-32 cells and sheds new light on functions of PHLDA1 in the neuroblastoma tumor cells, suggesting its role as a pro-apoptotic protein. Additionally, our results show possible links of the protein to regulation of features of mitochondria and formation of autophagosomes.

Engineered BDNF producing cells as a potential treatment for neurologic disease

INTRODUCTION

Brain-derived neurotrophic factor (BDNF) has been implicated in wide range of neurological diseases and injury. This neurotrophic factor is vital for neuronal health, survival, and synaptic connectivity. Many therapies focus on the restoration or enhancement of BDNF following injury or disease progression.

AREAS COVERED

The present review will focus on the mechanisms in which BDNF exerts its beneficial functioning, current BDNF therapies, issues and potential solutions for delivery of neurotrophic factors to the central nervous system, and other disease indications that may benefit from overexpression or restoration of BDNF.

EXPERT OPINION

Due to the role of BDNF in neuronal development, maturation, and health, BDNF is implicated in numerous neurological diseases making it a prime therapeutic agent. Numerous studies have shown the therapeutic potential of BDNF in a number of neurodegenerative disease models and in acute CNS injury, however clinical translation has fallen short due to issues in delivering this molecule. The use of MSC as a delivery platform for BDNF holds great promise for clinical advancement of neurotrophic factor restoration. The ease with which MSC can be engineered opens the door to the possibility of using this cell-based delivery system to advance a BDNF therapy to the clinic.

Neural and mesenchymal stem cells in animal models of Huntington's disease: past experiences and future challenges

Huntington's disease (HD) is an inherited disease that causes progressive nerve cell degeneration. It is triggered by a mutation in the HTT gene that strongly influences functional abilities and usually results in movement, cognitive and psychiatric disorders. HD is incurable, although treatments are available to help manage symptoms and to delay the physical, mental and behavioral declines associated with the condition. Stem cells are the essential building blocks of life, and play a crucial role in the genesis and development of all higher organisms. Ablative surgical procedures and fetal tissue cell transplantation, which are still experimental, demonstrate low rates of recovery in HD patients. Due to neuronal cell death caused by accumulation of the mutated huntingtin (mHTT) protein, it is unlikely that such brain damage can be treated solely by drug-based therapies. Stem cell-based therapies are important in order to reconstruct damaged brain areas in HD patients. These therapies have a dual role: stem cell paracrine action, stimulating local cell survival, and brain tissue regeneration through the production of new neurons from the intrinsic and likely from donor stem cells. This review summarizes current knowledge on neural stem/progenitor cell and mesenchymal stem cell transplantation, which has been carried out in several animal models of HD, discussing cell distribution, survival and differentiation after transplantation, as well as functional recovery and anatomic improvements associated with these approaches. We also discuss the usefulness of this information for future preclinical and clinical studies in HD.

A method for reproducible measurements of serum BDNF: comparison of the performance of six commercial assays

Brain-Derived Neurotrophic Factor (BDNF) has attracted increasing interest as potential biomarker to support the diagnosis or monitor the efficacy of therapies in brain disorders. Circulating BDNF can be measured in serum, plasma or whole blood. However, the use of BDNF as biomarker is limited by the poor reproducibility of results, likely due to the variety of methods used for sample collection and BDNF analysis. To overcome these limitations, using sera from 40 healthy adults, we compared the performance of five ELISA kits (Aviscera-Bioscience, Biosensis, Millipore-ChemiKine^TM, Promega-Emax^®, R&D-System-Quantikine^®) and one multiplexing assay (Millipore-Milliplex^®). All kits showed 100% sample recovery and comparable range. However, they exhibited very different inter-assay variations from 5% to 20%. Inter-assay variations were higher than those declared by the manufacturers with only one exception which also had the best overall performance. Dot-blot analysis revealed that two kits selectively recognize mature BDNF, while the others reacted with both pro-BDNF and mature BDNF. In conclusion, we identified two assays to obtain reliable measurements of human serum BDNF, suitable for future clinical applications.

Modelling the natural history of Huntington's disease progression

BACKGROUND

The lack of reliable biomarkers to track disease progression is a major problem in clinical research of chronic neurological disorders. Using Huntington's disease (HD) as an example, we describe a novel approach to model HD and show that the progression of a neurological disorder can be predicted for individual patients.

METHODS

Starting with an initial cohort of 343 patients with HD that we have followed since 1995, we used data from 68 patients that satisfied our filtering criteria to model disease progression, based on the Unified Huntington's Disease Rating Scale (UHDRS), a measure that is routinely used in HD clinics worldwide.

RESULTS

Our model was validated by: (A) extrapolating our equation to model the age of disease onset, (B) testing it on a second patient data set by loosening our filtering criteria, (C) cross-validating with a repeated random subsampling approach and (D) holdout validating with the latest clinical assessment data from the same cohort of patients. With UHDRS scores from the past four clinical visits (over a minimum span of 2 years), our model predicts disease progression of individual patients over the next 2 years with an accuracy of 89-91%. We have also provided evidence that patients with similar baseline clinical profiles can exhibit very different trajectories of disease progression.

CONCLUSIONS

This new model therefore has important implications for HD research, most obviously in the development of potential disease-modifying therapies. We believe that a similar approach can also be adapted to model disease progression in other chronic neurological disorders.

Primary cilia and autophagic dysfunction in Huntington's disease

Huntington's disease (HD) is an inherited, neurodegenerative disorder caused by a single-gene mutation: a CAG expansion in the huntingtin (HTT) gene that results in production of a mutated protein, mutant HTT, with a polyglutamine tail (polyQ-HTT). Although the molecular pathways of polyQ-HTT toxicity are not fully understood, because protein misfolding and aggregation are central features of HD, it has long been suspected that cellular housekeeping processes such as autophagy might be important to disease pathology. Indeed, multiple lines of research have identified abnormal autophagy in HD, characterized generally by increased autophagic induction and inefficient clearance of substrates. To date, the origin of autophagic dysfunction in HD remains unclear and the search for actors involved continues. To that end, recent studies have suggested a bidirectional relationship between autophagy and primary cilia, signaling organelles of most mammalian cells. Interestingly, primary cilia structure is defective in HD, suggesting a potential link between autophagic dysfunction, primary cilia and HD pathogenesis. In addition, because polyQ-HTT also accumulates in primary cilia, the possibility exists that primary cilia might play additional roles in HD: perhaps by disrupting signaling pathways or acting as a reservoir for secretion and propagation of toxic, misfolded polyQ-HTT fragments. Here, we review recent research suggesting potential links between autophagy, primary cilia and HD and speculate on possible pathogenic mechanisms and future directions for the field.

MicroRNA-124 slows down the progression of Huntington's disease by promoting neurogenesis in the striatum

MicroRNA-124 contributes to neurogenesis through regulating its targets, but its expression both in the brain of Huntington's disease mouse models and patients is decreased. However, the effects of microRNA-124 on the progression of Huntington's disease have not been reported. Results from this study showed that microRNA-124 increased the latency to fall for each R6/2 Huntington's disease transgenic mouse in the rotarod test. 5-Bromo-2'-deoxyuridine (BrdU) staining of the striatum shows an increase in neurogenesis. In addition, brain-derived neurotrophic factor and peroxisome proliferator-activated receptor gamma coactivator 1-alpha protein levels in the striatum were increased and SRY-related HMG box transcription factor 9 protein level was decreased. These findings suggest that microRNA-124 slows down the progression of Huntington's disease possibly through its important role in neuronal differentiation and survival.

Brain-Derived Neurotrophic Factor (BDNF) in Traumatic Brain Injury-Related Mortality: Interrelationships Between Genetics and Acute Systemic and Central Nervous System BDNF Profiles

BACKGROUND

Older adults have higher mortality rates after severe traumatic brain injury (TBI) compared to younger adults. Brain-derived neurotrophic factor (BDNF) signaling is altered in aging and is important to TBI given its role in neuronal survival/plasticity and autonomic function. Following experimental TBI, acute BDNF administration has not been efficacious. Clinically, genetic variation in BDNF (reduced signaling alleles: rs6265, Met-carriers; rs7124442, C-carriers) can be protective against acute mortality. Postacutely, these genotypes carry lower mortality risk in older adults and greater mortality risk among younger adults.

OBJECTIVE

Investigate BDNF levels in mortality/outcome following severe TBI in the context of age and genetic risk.

METHODS

Cerebrospinal fluid (CSF) and serum BDNF were assessed prospectively during the first week following severe TBI (n = 203) and in controls (n = 10). Age, BDNF genotype, and BDNF levels were assessed as mortality/outcome predictors.

RESULTS

CSF BDNF levels tended to be higher post-TBI (P = .061) versus controls and were associated with time until death (P = .042). In contrast, serum BDNF levels were reduced post-TBI versus controls (P < .0001). Both gene * BDNF serum and gene * age interactions were mortality predictors post-TBI in the same multivariate model. CSF and serum BDNF tended to be negatively correlated post-TBI (P = .07).

CONCLUSIONS

BDNF levels predicted mortality, in addition to gene * age interactions, suggesting levels capture additional mortality risk. Higher CSF BDNF post-TBI may be detrimental due to injury and age-related increases in pro-apoptotic BDNF target receptors. Negative CSF and serum BDNF correlations post-TBI suggest blood-brain barrier transit alterations. Understanding BDNF signaling in neuronal survival, plasticity, and autonomic function may inform treatment.

An update on Huntington's disease: from the gene to the clinic

PURPOSE OF REVIEW

This review highlights the recent advances in Huntington's disease, with a particular focus on development of disease biomarkers for use in therapeutic trials in the premotor phase of the disease, as well as the growing literature regarding pathophysiological mechanisms and their relevance to potential therapeutic targets.

RECENT FINDINGS

There have been continued advances in the development of disease biomarkers, and promising neuroprotection trials are beginning to emerge in the premotor stage of Huntington's disease. Deeper understanding of the pathophysiological mechanisms is being translated into potential therapeutic strategies.

SUMMARY

The premotor stage of Huntington's disease provides an ideal time to trial disease-modifying therapy, but reliable biomarkers are required for monitoring disease progression, and this remains an area of intense research. Our understanding of the underlying pathophysiological mechanisms continues to expand, and a number of promising therapeutic strategies are emerging, including strategies to silence mutant huntingtin expression.

Developing stem cell therapies for juvenile and adult-onset Huntington's disease

Stem cell therapies have been explored as a new avenue for the treatment of neurologic disease and damage within the CNS in part due to their native ability to mimic repair mechanisms in the brain. Mesenchymal stem cells have been of particular clinical interest due to their ability to release beneficial neurotrophic factors and their ability to foster a neuroprotective microenviroment. While early stem cell transplantation therapies have been fraught with technical and political concerns as well as limited clinical benefits, mesenchymal stem cell therapies have been shown to be clinically beneficial and derivable from nonembryonic, adult sources. The focus of this review will be on emerging and extant stem cell therapies for juvenile and adult-onset Huntington's disease.

Decreased cortical thickness in drug naïve first episode schizophrenia: in relation to serum levels of BDNF

This study was to examine cortical thickness in drug naïve, first episode schizophrenia patients, and to explore its relationship with serum levels of brain-derived neurotrophic factor (BDNF). Forty-five drug naive schizophrenia patients and 28 healthy controls were enrolled in the study. Freesurfer was used to parcellate cortical regions, and vertex-wise group analysis was used for whole brain cortical thickness. The clusters for the brain regions that demonstrated group differences were extracted, and the mean values of thickness were calculated. Serum levels of BDNF were measured using enzyme-linked immunosorbent assay (ELISA). After controlling for age and gender, significantly thinner cortical thickness was found in left insula and superior temporal gyrus in the patient group compared with the healthy control group (HC group) (p's < 0.001). Lower serum levels of BDNF were also found in the patient group compared with the HC group (p = 0.001). Correlation analysis showed a significant positive relationship between thickness of left insula and serum levels of BDNF within the HC group (r = 0.396, p = 0.037) but there was no such relationship within the patient group (r = 0.035, p = 0.819). Cortical thinning is present in drug naïve, first episode schizophrenia patients, indicating neurodevelopmental abnormalities at the onset of schizophrenia. Left insula might be an imaging biomarker in detecting the impaired protective role of neurotrophic factor for the brain development in schizophrenia.

Challenges of Huntington's disease and quest for therapeutic biomarkers

Huntington's disease (HD) is the most common inherited neurodegenerative disorder among polyglutamine (polyQ) diseases caused by cytosine-adenine-guanine repeat expansion in exon 1 of the huntingtin gene whose translation results in polyQ stretch in the N-terminus of the huntingtin protein (HD protein). This mutation significantly affects huntingtin conformation, proteolysis, PTMs, as well as its ability to bind interacting proteins. As a consequence, a variety of cellular mechanisms such as transcription, mitochondrial energy metabolism, axonal transport, neuronal vulnerability to oxidative stress, neurotransmission, and immune response are altered and involved in the pathogenesis of HD. Promising candidate molecular biomarkers of HD have emerged from proteomic studies. Recent analyses focused on HD protein itself, its PTM, and interacting proteins, which are of great importance for disease course. Furthermore, brain, body fluids, and immune system are intensively studied in order to search for additional proteins with a view to their use as a biomarker(s) or set of biomarkers in clinical trials in HD translational research.

Evaluation of current pharmacological treatment options in the management of Rett syndrome: from the present to future therapeutic alternatives

Neurodevelopmental disorders are a large family of conditions of genetic or environmental origin that are characterized by deficiencies in cognitive and behavioral functions. The therapeutic management of individuals with these disorders is typically complex and is limited to the treatment of specific symptoms that characterize each disorder. The neurodevelopmental disorder Rett syndrome (RTT) is the leading cause of severe intellectual disability in females. Mutations in the gene encoding the transcriptional regulator methyl-CpG-binding protein 2 (MECP2), located on the X chromosome, have been confirmed in more than 95% of individuals meeting diagnostic criteria for classical RTT. RTT is characterized by an uneventful early infancy followed by stagnation and regression of growth, motor, language, and social skills later in development. This review will discuss the genetics, pathology, and symptoms that distinguish RTT from other neurodevelopmental disorders associated with intellectual disability. Because great progress has been made in the basic and clinical science of RTT, the goal of this review is to provide a thorough assessment of current pharmacotherapeutic options to treat the symptoms associated with this disorder. Furthermore, we will highlight recent discoveries made with novel pharmacological interventions in experimental preclinical phases, and which have reversed pathological phenotypes in mouse and cell culture models of RTT and may result in clinical trials.

Alterations in DNA methylation of Fkbp5 as a determinant of blood-brain correlation of glucocorticoid exposure

BACKGROUND

Epigenetic studies that utilize peripheral tissues to identify molecular substrates of neuropsychiatric disorders rely on the assumption that disease-relevant, cellular alterations that occur in the brain are mirrored and detectable in peripheral tissues such as blood. We sought to test this assumption by using a mouse model of Cushing's disease and asking whether epigenetic changes induced by glucocorticoids can be correlated between these tissue types.

METHODS

Mice were treated with different doses of glucocorticoids in their drinking water for four weeks to assess gene expression and DNA methylation (DNAm) changes in the stress response gene Fkbp5.

RESULTS

Significant linear relationships were observed between DNAm and four-week mean plasma corticosterone levels for both blood (R(2)=0.68, P=7.1×10(-10)) and brain (R(2)=0.33, P=0.001). Further, degree of methylation change in blood correlated significantly with both methylation (R(2)=0.49, P=2.7×10(-5)) and expression (R(2)=0.43, P=3.5×10(-5)) changes in hippocampus, with the notable observation that methylation changes occurred at different intronic regions between blood and brain tissues.

CONCLUSION

Although our findings are limited to several intronic CpGs in a single gene, our results demonstrate that DNA from blood can be used to assess dynamic, glucocorticoid-induced changes occurring in the brain. However, for such correlation analyses to be effective, tissue-specific locations of these epigenetic changes may need to be considered when investigating brain-relevant changes in peripheral tissues.

Progressive axonal transport and synaptic protein changes correlate with behavioral and neuropathological abnormalities in the heterozygous Q175 KI mouse model of Huntington's disease

A long-term goal of modeling Huntington's disease (HD) is to recapitulate the cardinal features of the disease in mice that express both mutant and wild-type (WT) huntingtin (Htt), as HD commonly manifests as a heterozygous condition in humans, and loss of WT Htt is associated with loss-of-function. In a new heterozygous Q175 knock-in (KI) mouse model, we performed an extensive evaluation of motor and cognitive functional deficits, neuropathological and biochemical changes and levels of proteins involved in synaptic function, the cytoskeleton and axonal transport, at 1-16 months of age. Motor deficits were apparent at 6 months of age in Q175 KI mice and at that time, postmortem striatal gamma-aminobutyric acid (GABA) levels were elevated and mutant Htt inclusions were present throughout the brain. From 6 months of age, levels of proteins associated with synaptic function, including SNAP-25, Rab3A and PSD-95, and with axonal transport and microtubules, including KIF3A, dynein and dynactin, were altered in the striatum, motor cortex, prefrontal cortex and hippocampus of Q175 KI mice, compared with WT levels. At 12-16 months of age, Q175 KI mice displayed motor and cognitive deficits, which were paralleled at postmortem by striatal atrophy, cortical thinning, degeneration of medium spiny neurons, dense mutant Htt inclusion formation, decreased striatal dopamine levels and loss of striatal brain-derived neurotrophic factor (BDNF). Data from this study indicate that the heterozygous Q175 KI mouse represents a realistic model for HD and also provides new insights into the specific and progressive synaptic, cytoskeletal and axonal transport protein abnormalities that may accompany the disease.

Plasma brain derived neurotrophic factor (BDNF) and response to ketamine in treatment-resistant depression

Ketamine produces rapid antidepressant effects in treatment-resistant depression (TRD), but the magnitude of response varies considerably between individual patients. Brain-derived neurotrophic factor (BDNF) has been investigated as a biomarker of treatment response in depression and has been implicated in the mechanism of action of ketamine. We evaluated plasma BDNF and associations with symptoms in 22 patients with TRD enrolled in a randomized controlled trial of ketamine compared to an anaesthetic control (midazolam). Ketamine significantly increased plasma BDNF levels in responders compared to non-responders 240 min post-infusion, and Montgomery-Åsberg Depression Rating Scale (MADRS) scores were negatively correlated with BDNF (r=-0.701, p = 0.008). Plasma BDNF levels at 240 min post-infusion were highly negatively associated with MADRS scores at 240 min (r = -0.897, p=.002), 24 h (r = -0.791, p = 0.038), 48 h (r = -0.944, p = 0.001) and 72 h (r = -0.977, p = 0.010). No associations with BDNF were found for patients receiving midazolam. These data support plasma BDNF as a peripheral biomarker relevant to ketamine antidepressant response.

Huntington's disease

Changes in the level and activity of brain-derived neurotrophic factor (BDNF) have been described in a number of neurodegenerative disorders since early 1990s. However, only in Huntington disease (HD) gain- and loss-of-function experiments have mechanistically linked these abnormalities with the genetic defect.In this chapter we will describe how huntingtin protein, whose mutation causes HD, is involved in the physiological control of BDNF synthesis and transport in neurons and how both processes are simultaneously disrupted in HD. We will describe the underlying molecular mechanisms and discuss pre-clinical data concerning the impact of the experimental manipulation of BDNF levels on HD progression. These studies have revealed that a major loss of BDNF protein in the brain of HD patients may contribute to the clinical manifestations of the disease. The experimental strategies under investigation to increase brain BDNF levels in animal models of HD will also be described, with a view to ultimately improving the clinical treatment of this condition.

Neuroprotective effects of psychotropic drugs in Huntington's disease

Psychotropics (antipsychotics, mood stabilizers, antidepressants, anxiolytics, etc.) are commonly prescribed to treat Huntington’s disease (HD). In HD preclinical models, while no psychotropic has convincingly affected huntingtin gene, HD modifying gene, or huntingtin protein expression, psychotropic neuroprotective effects include upregulated huntingtin autophagy (lithium), histone acetylation (lithium, valproate, lamotrigine), miR-222 (lithium-plus-valproate), mitochondrial protection (haloperidol, trifluoperazine, imipramine, desipramine, nortriptyline, maprotiline, trazodone, sertraline, venlafaxine, melatonin), neurogenesis (lithium, valproate, fluoxetine, sertraline), and BDNF (lithium, valproate, sertraline) and downregulated AP-1 DNA binding (lithium), p53 (lithium), huntingtin aggregation (antipsychotics, lithium), and apoptosis (trifluoperazine, loxapine, lithium, desipramine, nortriptyline, maprotiline, cyproheptadine, melatonin). In HD live mouse models, delayed disease onset (nortriptyline, melatonin), striatal preservation (haloperidol, tetrabenazine, lithium, sertraline), memory preservation (imipramine, trazodone, fluoxetine, sertraline, venlafaxine), motor improvement (tetrabenazine, lithium, valproate, imipramine, nortriptyline, trazodone, sertraline, venlafaxine), and extended survival (lithium, valproate, sertraline, melatonin) have been documented. Upregulated CREB binding protein (CBP; valproate, dextromethorphan) and downregulated histone deacetylase (HDAC; valproate) await demonstration in HD models. Most preclinical findings await replication and their limitations are reviewed. The most promising findings involve replicated striatal neuroprotection and phenotypic disease modification in transgenic mice for tetrabenazine and for sertraline. Clinical data consist of an uncontrolled lithium case series (n = 3) suggesting non-progression and a primarily negative double-blind, placebo-controlled clinical trial of lamotrigine.

Transplantation of umbilical cord-derived mesenchymal stem cells into the striata of R6/2 mice: behavioral and neuropathological analysis

Introduction

Huntington’s disease (HD) is an autosomal dominant disorder caused by an expanded CAG repeat on the short arm of chromosome 4 resulting in cognitive decline, motor dysfunction, and death, typically occurring 15 to 20 years after the onset of motor symptoms. Neuropathologically, HD is characterized by a specific loss of medium spiny neurons in the caudate and the putamen, as well as subsequent neuronal loss in the cerebral cortex. The transgenic R6/2 mouse model of HD carries the N-terminal fragment of the human HD gene (145 to 155 repeats) and rapidly develops some of the behavioral characteristics that are analogous to the human form of the disease. Mesenchymal stem cells (MSCs) have shown the ability to slow the onset of behavioral and neuropathological deficits following intrastriatal transplantation in rodent models of HD. Use of MSCs derived from umbilical cord (UC) offers an attractive strategy for transplantation as these cells are isolated from a noncontroversial and inexhaustible source and can be harvested at a low cost. Because UC MSCs represent an intermediate link between adult and embryonic tissue, they may hold more pluripotent properties than adult stem cells derived from other sources.

Methods

Mesenchymal stem cells, isolated from the UC of day 15 gestation pups, were transplanted intrastriatally into 5-week-old R6/2 mice at either a low-passage (3 to 8) or high-passage (40 to 50). Mice were tested behaviorally for 6 weeks using the rotarod task, the Morris water maze, and the limb-clasping response. Following behavioral testing, tissue sections were analyzed for UC MSC survival, the immune response to the transplanted cells, and neuropathological changes.

Results

Following transplantation of UC MSCs, R6/2 mice did not display a reduction in motor deficits but there appeared to be transient sparing in a spatial memory task when compared to untreated R6/2 mice. However, R6/2 mice receiving either low- or high-passage UC MSCs displayed significantly less neuropathological deficits, relative to untreated R6/2 mice.

Conclusions

The results from this study demonstrate that UC MSCs hold promise for reducing the neuropathological deficits observed in the R6/2 rodent model of HD.

In vitro and in vivo models of Huntington's disease show alterations in the endocannabinoid system

In this study, we analyzed the components of the endocannabinoid system (ECS) in R6/2 mice, a widely used model of Huntington's disease (HD). We measured the endogenous content of N-arachidonoylethanolamine and 2-arachidonoylglycerol and the activity of their biosynthetic enzymes (N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D and diacylglycerol lipase, respectively) and hydrolytic enzymes [fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase, respectively] and of their target receptors (type 1 cannabinoid receptor, type 2 cannabinoid receptor, and transient receptor potential vanilloid-1) in the brains of wild-type and R6/2 mice of different ages, as well as in the striatum and cortex of 12-week-old animals. In addition, we measured FAAH activity in lymphocytes of R6/2 mice. In the whole brains of 12-week-old R6/2 mice, we found reductions in N-acyl-phosphatidylethanolamine-hydrolyzing phospholipase D activity, diacylglycerol lipase activity and cannabinoid receptor binding, mostly associated with changes in the striatum but not in the cortex, as well as an increase in 2-arachidonoylglycerol content as compared with wild-type littermates, without any other change in ECS elements. Then, our analysis was extended to HD43 cells, an inducible cellular model of HD derived from rat ST14A cells. In both induced and noninduced conditions, we demonstrated a fully functional ECS. Overall, our data suggest that the ECS is differently affected in mouse and human HD, and that HD43 cells are suitable for high-throughput screening of FAAH-oriented drugs affecting HD progression.

TrkB receptor signalling: implications in neurodegenerative, psychiatric and proliferative disorders

The Trk family of receptors play a wide variety of roles in physiological and disease processes in both neuronal and non-neuronal tissues. Amongst these the TrkB receptor in particular has attracted major attention due to its critical role in signalling for brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT3) and neurotrophin-4 (NT4). TrkB signalling is indispensable for the survival, development and synaptic plasticity of several subtypes of neurons in the nervous system. Substantial evidence has emerged over the last decade about the involvement of aberrant TrkB signalling and its compromise in various neuropsychiatric and degenerative conditions. Unusual changes in TrkB signalling pathway have also been observed and implicated in a range of cancers. Variations in TrkB pathway have been observed in obesity and hyperphagia related disorders as well. Both BDNF and TrkB have been shown to play critical roles in the survival of retinal ganglion cells in the retina. The ability to specifically modulate TrkB signalling can be critical in various pathological scenarios associated with this pathway. In this review, we discuss the mechanisms underlying TrkB signalling, disease implications and explore plausible ameliorative or preventive approaches.

Neuroprotective effects of PPAR-γ agonist rosiglitazone in N171-82Q mouse model of Huntington's disease

Huntington's disease (HD) is a devastating genetic neurodegenerative disease caused by CAG trinucleotide expansion in the exon-1 region of the huntingtin gene. Currently, no cure is available. It is becoming increasingly apparent that mutant Huntingtin (HTT) impairs metabolic homeostasis and causes transcriptional dysregulation. The peroxisome proliferator-activated receptor gamma (PPAR-γ) is a transcriptional factor that plays a key role in regulating genes involved in energy metabolism; recent studies demonstrated that PPAR-γ activation prevented mitochondrial depolarization in cells expressing mutant HTT and attenuated neurodegeneration in various models of neurodegenerative diseases. PPAR-γ-coactivator 1α (PGC-1 α) transcription activity is also impaired by mutant HTT. We now report that the PPAR-γ agonist, rosiglitazone (RSG), significantly attenuated mutant HTT-induced toxicity in striatal cells and that the protective effect of RSG is mediated by activation of PPAR-γ. Moreover, chronic administration of RSG (10 mg/kg/day, i.p) significantly improved motor function and attenuated hyperglycemia in N171-82Q HD mice. RSG administration rescued brain derived neurotrophic factor(BDNF) deficiency in the cerebral cortex, and prevented loss of orexin-A-immunopositive neurons in the hypothalamus of N171-82Q HD mice. RSG also prevented PGC-1α reduction and increased Sirt6 protein levels in HD mouse brain. Our results suggest that modifying the PPAR-γ pathway plays a beneficial role in rescuing motor function as well as glucose metabolic abnormalities in HD.

Brain-derived neurotrophic factor and its relation to leptin in obese children before and after weight loss

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) is a regulator of energy homeostasis and food intake through hypothalamic signaling. Currently, data regarding BDNF in children with obesity are lacking. We evaluated serum BDNF concentrations in obese children, both before and after lifestyle intervention, in reference to those of lean children.

METHODS

A total of 90 (24 normal weight; 66 obese) children were studied utilizing a cross-sectional clinical outpatient study design. In addition, longitudinal data analysis was performed in 30 obese children participating in a lifestyle intervention for one year.

RESULTS

Fasting serum BDNF concentrations were higher in obese vs. normal weight children (BDNF 20.3±1.0 vs. 12.5±1.7 ng/mL, respectively, mean±SEM, p<0.001) and correlated significantly to BMI standard deviation score (r=0.426, p<0.001), and leptin (r=0.414, p<0.01). BDNF concentrations were not regulated in response to food, 60 min after ingestion of a liquid test meal. After one year lifestyle intervention, delta BDNF correlated significantly to delta leptin (r=0.475, p<0.01), but not to changes of insulin resistance index HOMA-IR, systolic and diastolic blood pressure, HDL, LDL, and triglycerides. In a multiple stepwise linear regression adjusted for pubertal stage, age, sex, and BMI, delta BDNF correlated significantly (p<0.05) to delta leptin and delta triceps skinfold and in tendency to delta subscapularis skinfold thickness (p=0.050).

CONCLUSIONS

Our results in children do not indicate a significant relationship between BDNF and insulin resistance or cardiovascular risk factors. However, the correlation between changes of BDNF and changes of leptin suggests a relationship between BDNF and fat mass.

Therapeutic Strategies for Huntington's Disease

Huntington's disease (HD) is a devastating autosomal dominant neurodegenerative disease, caused by expansion of the CAG repeat in the huntingtin (HTT) gene and characterized pathologically by the loss of pyramidal neurons in several cortical areas, of striatal medium spiny neurons, and of hypothalamic neurons. Clinically, a distinguishing feature of the disease is uncontrolled involuntary movements (chorea, dyskensias) accompanied by progressive cognitive, motor, and psychiatric impairment. This review focuses on the current state of therapeutic development for the treatment of HD, including the preclinical and clinical development of small molecules and molecular therapies.

Stably BDNF-GFP expressing embryonic stem cells exhibit a BDNF release-dependent enhancement of neuronal differentiation

Brain-derived neurotrophic factor (BDNF) is known to be a crucial regulator of neuronal survival and synaptic plasticity in the mammalian brain. Furthermore, BDNF positively influences differentiation of embryonic neural precursors as well as of neural stem cells from adult neurogenic niches. To study the impact of cell-released BDNF on neural differentiation of embryonic stem cells (ESCs), which represent an attractive source for cell transplantation studies, we have generated BDNF-GFP overexpressing mouse ESC clones by knock-in technology. After neural differentiation in vitro, we observed that BDNF-GFP overexpressing ESC clones gave rise to an increased number of neurons as compared to control ESCs. Neurons derived from BDNF-GFP expressing ESCs harbored a more complex dendritic morphology and differentiated to a higher extent into the GABAergic lineage than controls. Moreover, we show that ESC-derived neurons released BDNF-GFP in an activity-dependent manner and displayed similar electrophysiological properties as cortical neurons. Thus, our study describes the generation of stably BDNF-GFP overexpressing ESCs which are ideally suited to investigate the ameliorating effects of BDNF in cell transplantation studies for various neuropathological conditions.

Circadian and sleep disorder in Huntington's disease

Huntington's disease is a progressive neurological disorder that starts insidiously with motor, cognitive or psychiatric disturbance, and progresses through a distressing range of symptoms to end with a devastating loss of function, both motor and executive. There is a growing awareness that, in addition to cognitive and psychiatric symptoms, there are other important non-motor symptoms in HD, including sleep and circadian abnormalities. It is not clear if sleep-wake changes are caused directly by HD gene-related pathology, or if they are simply a consequence of having a neurodegenerative disease. From a patient point of view, the answer is irrelevant, since sleep and circadian disturbances are deleterious to good daily living, even in neurologically normal people. The assumption should be that, at the very least, sleep and/or circadian disturbance in HD patients will contribute to their symptoms. At worst, they may contribute to the progressive decline in HD. Here I review the state of our understanding of sleep and circadian abnormalities in HD. I also outline a set of simple rules that can be followed to improve the chances of a good night's sleep, since preventing any 'preventable' symptoms is the a logical first step in treating disease. The long-term impact of sleep disruption in HD is unknown. There have been no large-scale systematic studies of in sleep in HD. Furthermore, there has never been a study of the efficacy of pharmaceuticals that are typically used to treat sleep deficits in HD patients. Thus treatment of sleep disturbance in HD is necessarily empirical. A better understanding of the relationship between sleep/circadian abnormalities and HD pathology is needed, if treatment of this aspect of HD is to be optimized.

A study of molecular changes relating to energy metabolism and cellular stress in people with Huntington's disease: looking for biomarkers

Huntington's disease (HD) is a neurodegenerative disorder characterized by a progressive motor and cognitive decline and the development of psychiatric symptoms. The origin of molecular and biochemical disturbances in HD is a mutation in the HTT gene, which is autosomally dominantly inherited. The altered huntingtin protein is ubiquitously expressed in the CNS, as well as in peripheral tissues. In this study we measured the metabolism changes in gene transcription in blood of HD gene carriers (premanifest and manifest combined) versus 28 healthy controls. The comparison revealed statistically significant Global Pattern Recognition Fold Change (FC) for 6 mRNA transcripts, reflecting an increase of: MAOB (FC = 3.07; p = 0.0005) which encodes an outer mitochondrial membrane-bound enzyme called monoamine oxidase type B; TGM2 (FC = 1.8; p = 0.02) encoding a transglutaminase 2 that mediates cellular stress; SLC2A4 (FC = 1.64; p = 0.02) solute carrier family 2 (facilitated glucose transporter) member 4; branched chain ketoacid dehydrogenase kinase (BCKDK) (FC = 1.34; p = 0.02); decrease of LDHA (FC = -1.16; p = 0.03) lactate dehydrogenase A; and brain-derived neurotrophic factor (BDNF) (FC = -2,11; p = 0.03). These distinguished changes coincided with HD progress. The analyses of gene transcription levels in sub-cohorts confirmed these changes and also revealed 28 statistically significant FCs of gene transcripts involved in ATP production and BCAA metabolism.

Downregulation of genes involved in metabolism and oxidative stress in the peripheral leukocytes of Huntington's disease patients

BACKGROUND

Huntington's disease (HD) is caused by expanded CAG repeats encoding a polyglutamine tract in the huntingtin (HTT) protein. A number of differentially-expressed protein molecules have been identified in striatum of HD animal models. Here we examined if the expression changes could be visualized in the peripheral leukocytes of HD patients and pre-symptomatic HD (PreHD) carriers.

METHODS AND FINDINGS

The expression levels of 17 candidate genes that differentially expressed in striatum between transgenic HD and wild-type mice in literature were measured in the peripheral leukocytes of 4 PreHD carriers, 16 HD patients and 20 healthy controls. Four genes majorly involved in metabolism and oxidative stress response, including AHCY1, ACO2, OXCT1 and CAP1, demonstrated consistent downregulation in peripheral leukocytes of both PreHD carriers and HD patients, while UCP2 was only down-regulated in HD patients.

CONCLUSION

These results provide potential peripheral biomarkers to indicate disease onset in preclinical stage, and to monitor the efficacy of early treatment. Further studies of a large series of preHD carriers and symptomatic HD patients will be warranted to verify the findings and examine if these markers correlate with clinical features.

Role of experience, training, and plasticity in the functional efficacy of striatal transplants

Cell-based treatments of neurodegenerative diseases have been tested clinically with partial success. In the context of Huntington's disease (HD), experimental studies show that the grafted embryonic striatal cells survive, integrate within the host brain, and reverse some functional deficits. Importantly, once transplanted, the grafted striatal neurons retain a significant level of cellular, morphological, and functional plasticity which allows the experimental modification of their character through the manipulation of environmental cues or learning protocols. Using embryonic striatal grafts in the rodent model of HD as the principal example, this chapter summarizes seminal experiments that demonstrate that environmental factors, training, and activity can tap into mechanisms that influence the development of the grafted cells and can change the profile of graft-mediated behavioral recovery. Although currently there is limited understanding of the biological rationale behind the recovery, we put forward experimental data indicating that striatal grafts can express experience-dependent physiological plasticity at the synaptic as well as at the systemic functional level.