Huntington's disease: A generalized membrane defect

Huntington's disease, a progressively degenerative neurological disorder inherited as an autosomal dominant trait, results in selective neuronal loss in the basal ganglia and other areas of the brain. Based on research in our laboratory employing electron spin resonance, analytical, enzymatic, biochemical and morphological techniques to study erythrocyte membranes, which are completely outside the central nervous system, we have suggested that Huntington's disease is associated with a generalized membrane defect involving a protein and probably manifested at the external membrane surface. Other workers have subsequently obtained biophysical, biochemical, and morphological results on extraneural tissue in Huntington's disease including erythrocytes, lymphocytes, platelets,and cultured skin fibroblasts that supports this hypothesis. This review will summarize and evaluate the current knowledge of the involvement of a membrane defect in the etiology and pathogenesis of Huntington's disease.     

Evidence for a membrane surface defect in erythrocytes in Huntington's disease

Electron spin resonance studies of erythrocyte membranes from patients with Huntington's disease and normal controls have been performed. Intact erythrocytes in each case were either untreated or subjected to proteolysis with the membrane impermeable enzymes, pronase, chymotrypsin, or trypsin. Membrane ghosts were prepared from untreated and protease-treated intact cells and spin labeled with protein- or lipid-specific spin probes. Comparison of the resulting electron spin resonance spectra confirmed our previous findings that in untreated samples the relevant parameter of the protein-specific spin label was increased in Huntington's disease (P < 0.02) suggesting an altered physical state of membrane proteins in this disorder, while no difference in erythrocyte lipid fluidity could be discerned. No significant difference in the physical state of membrane proteins in Huntington's disease and control as judged as spin labeling methods could be detemined in membrane ghosts prepared from protease-treated intact cells. These results, together with the known specificity of the proteases used in this study, suggest that a molecular defect in Huntington's disease erythrocytes is manifested in an exterior part of a membrane protein and supports our hypothesis that Huntington's disease is associated with a generalized cell membrane defect.     

Cerebrospinal fluid homocarnosine in Huntington's disease

The concentration of homocarnosine (γ-aminobutyryl-L-histidine) in the cerebrospinal fluid (CSF) of ten patients with Huntington's disease (HD) and 24 control subjects was determined by high-performance cation exchange chromatography. The mean CSF homocarnosine level was significantly lower in HD patients (0.86 ± 0.16 nmo1/m1) than in controls (1.69 ± 0.18 nmo1/m1).     

Sodium-independent glutamic acid binding in cultured fibroblasts from patients with Huntington's disease

Glutamic acid, in the absence of sodium, binds to a single population of binding sites in the fibroblast membrane with a dissociation constant (K_d) in the nanomolar range, similar to those obtained in human and rat cortices. The density of binding sites (B_max) in fibroblast membranes from patients with Huntington's disease was only 54% of that in control membranes.     

Glucosamine dependence of Huntington's chorea fibroblasts in culture

Huntington's chorea is an autosomal dominant disease of the nervous system. Fibroblasts of one such case obtained from the Genetic Mutant Repository have a normal growth rate when compared with an age, sex and passage number matched human fibroblast cell line obtained from the same source. However, when the culture medium is depleted of nutrients and non-essential amino-acids added either individually or in combination, the Huntington's chorea fibroblasts show a dependence for glucosamine in the culture medium for cell survival and replicative capacity. Glutamine cannot be used in place of glucosamine. In fact, there is a further increment of cell morphology and number deterioration by Huntington's chorea but not normal fibroblasts when glutamine is added to depleted cultures.     

Effect of isoniazid on cerebrospinal fluid and plasma GABA levels in Huntington's disease

During a double-blind placebo controlled trial, γ-aminobutyric acid (GABA) was measured in cerebrospinal fluid (CSF) and plasma obtained from patients with Huntington's Disease prior to the start of the trial, at the end of the placebo period and following treatment with isoniazid. The results showed that the GABA concentrations in CSF tripled following treatment with isoniazid although no significant change occurred in plasma GABA levels. This finding in humans indirectly confirms reports of a similar increase of brain GABA content in experimental animals following isoniazid treatment and provides additional evidence that CSF GABA measurements reflect brain GABA activity.     

Targeted biochemical profiling of brain from Huntington's disease patients reveals novel metabolic pathways of interest

Huntington's disease (HD) is a devastating, progressive neurodegenerative disease with a distinct phenotype characterized by chorea and dystonia, incoordination, cognitive decline and behavioral difficulties. The precise mechanisms of HD progression are poorly understood; however, it is known that there is an expansion of the trinucleotide cytosine-adenine-guanine (CAG) repeat in the Huntingtin gene. Herein DI/LC-MS/MS was used to accurately identify and quantify 185 metabolites in post mortem frontal lobe and striatum from HD patients and healthy control cases. The findings link changes in energy metabolism and phospholipid metabolism to HD pathology and also demonstrate significant reductions in neurotransmitters. Further investigation into the oxidation of fatty acids and phospholipid metabolism in pre-clinical models of HD are clearly warranted for the identification of potential therapies. Additionally, panels of 5 metabolite biomarkers were identified in both the frontal lobe (AUC?=?0.962 (95% CI: 0.85–1.00) and striatum (AUC?=?0.988 (95% CI: 0.899–1.00). This could have clinical utility in more accessible biomatrices such as blood serum for the early detection of those entering the prodromal phase of the disease, when treatment is believed to be most effective. Further evaluation of these biomarker panels in human cohorts is justified to determine their clinical efficacy.     

Characterization of subventricular zone-derived progenitor cells from mild and late symptomatic YAC128 mouse model of Huntington's disease

Huntington's disease (HD) is caused by an expansion of CAG repeats in the HTT gene, leading to expression of mutant huntingtin (mHTT) and selective striatal neuronal loss, frequently associated with mitochondrial dysfunction and decreased support of brain-derived neurotrophic factor (BDNF). New neurons derived from the subventricular zone (SVZ) are apparently not able to rescue HD pathological features. Thus, we analyzed proliferation, migration and differentiation of adult SVZ-derived neural stem/progenitor cells (NSPC) from mild (6 month-old (mo)) and late (10 mo) symptomatic HD YAC128 mice expressing full-length (FL)-mHTT versus age-matched wild-type (WT) mice. SVZ cells derived from 6 mo YAC128 mice exhibited higher migratory capacity and a higher number of MAP2 + and synaptophysin + cells, compared to WT cells; MAP2 labeling was enhanced after exposure to BDNF. However, BDNF-evoked neuronal differentiation was not observed in 10 mo YAC128 SVZ-derived cells. Interestingly, 6 mo YAC128 SVZ-derived cells showed increased intracellular Ca²⁺ levels in response to KCl, which was potentiated by BDNF, evidencing the presence of differentiated neurons. In contrast, KCl depolarization-induced intracellular Ca²⁺ increase in 10 mo YAC128 SVZ-derived cells was shown to be increased only in BDNF-treated YAC128 SVZ-derived cells, suggestive of decreased differentiation capacity. In addition, BDNF-untreated NSPC from 10 mo YAC128 mice exhibited lower mitochondrial membrane potential and increased mitochondrial Ca²⁺ accumulation, in relation with NSPC from 6 mo YAC128 mice. Data evidence age-dependent reduced migration and decreased acquisition of a neuronal phenotype, accompanied by decreased mitochondrial membrane potential in SVZ-derived cells from YAC128 mice through HD symptomatic phases.     

Implant‐supported overdenture in an elderly patient with Huntington’s disease

doi:10.1111/j.1741‐2358.2009.00343.x
Implant‐supported overdenture in an elderly patient with Huntington’s disease Huntington’s disease is a hereditary, progressive, neuro‐degenerative disorder characterised by increasingly severe motor impairment, cognitive decline and behavioural manifestations leading to functional disability. Dyskinesia and hyperkinesia of the tongue and the peri‐oral musculature make it impossible for the patient to wear a conventional complete denture, despite an adequate alveolar ridge. The present paper reports on a patient with Huntington’s disease who was rehabilitated with a mandibular overdenture supported by two endosteal implants. One year follow‐up examination showed that the prosthesis was stable and there was considerable improvement in the patient’s masticatory function.     

Impaired trunk stability in individuals at high risk for Parkinson's disease

Background

The search for disease-modifying treatments for Parkinson''s disease advances, however necessary markers for early detection of the disease are still lacking. There is compelling evidence that changes of postural stability occur at very early clinical stages of Parkinson''s disease, making it tempting to speculate that changes in sway performance may even occur at a prodromal stage, and may have the potential to serve as a prodromal marker for the disease.

Methodology/Principal Findings

Balance performance was tested in 20 individuals with an increased risk of Parkinson''s disease, 12 Parkinson''s disease patients and 14 controls using a cross-sectional approach. All individuals were 50 years or older. Investigated groups were similar with respect to age, gender, and height. An accelerometer at the centre of mass at the lower spine quantified sway during quiet semitandem stance with eyes open and closed, as well as with and without foam. With increasing task difficulty, individuals with an increased risk of Parkinson''s disease showed an increased variability of trunk acceleration and a decrease of smoothness of sway, compared to both other groups. These differences reached significance in the most challenging condition, i.e. the eyes closed with foam condition.

Conclusions/Significance

Individuals with an increased risk of Parkinson''s disease have subtle signs of a balance deficit under most challenging conditions. This preliminary finding should motivate further studies on sway performance in individuals with an increased risk of Parkinson''s disease, to evaluate the potential of this symptom to serve as a biological marker for prodromal Parkinson''s disease.     

Molecular heterogeneity in McArdle's disease

Biopsies were taken from a group of eleven patients with McArdle's disease, a congenital deficiency in muscle glycogen phosphorylase. The biopsies were screened by Western and Northern blotting for phosphorylase protein, phosphotrylase-bound pyridoxal-5′-phosphate (the cofactor of the enzyme) and for phosphorylase mRNA. Of the eleven patients, three expressed phosphorylase mRNA at near normal levels and at the expected size. One of these patients also expressed low levels of phosphorylase protein that correlated with a small amount of measurable phosphorylase activity. These data support the contention of molecular heterogeneity in the presentation of this phenotype.     

Plasma amine oxidases in Wilson's disease

Plasma Mono- and Diamine-Oxidase activities (MAO and DAO), two copper containing enzymes, were estimated in 5 patients with Wilson's disease, without treatment and during D-Penicillamine treatment. Ceruloplasmin and “free” copper plasma levels were simultaneously measured. MAO was elevated in all cases, while DAO was within normal limits.D-Penicillamine administration did not result in significant reductions of these enzyme activities. It is likely that alterations of copper metabolism induced by Wilson's disease and by D-Penicillamine administration do not affect the activity of MAO or DAO. The increase in MAO activity in Wilson's disease probably results from the hepatic fibrosis.     

Early defect of transforming growth factor β1 formation in Huntington’s disease

A defective expression or activity of neurotrophic factors, such as brain‐ and glial‐derived neurotrophic factors, contributes to neuronal damage in Huntington’s disease (HD). Here, we focused on transforming growth factor‐β (TGF‐β₁), a pleiotropic cytokine with an established role in mechanisms of neuroprotection. Asymptomatic HD patients showed a reduction in TGF‐β₁ levels in the peripheral blood, which was related to trinucleotide mutation length and glucose hypometabolism in the caudate nucleus. Immunohistochemical analysis in post‐mortem brain tissues showed that TGF‐β₁ was reduced in cortical neurons of asymptomatic and symptomatic HD patients. Both YAC128 and R6/2 HD mutant mice showed a reduced expression of TGF‐β₁ in the cerebral cortex, localized in neurons, but not in astrocytes. We examined the pharmacological regulation of TGF‐β₁ formation in asymptomatic R6/2 mice, where blood TGF‐β₁ levels were also reduced. In these R6/2 mice, both the mGlu2/3 metabotropic glutamate receptor agonist, LY379268, and riluzole failed to increase TGF‐β₁ formation in the cerebral cortex and corpus striatum, suggesting that a defect in the regulation of TGF‐β₁ production is associated with HD. Accordingly, reduced TGF‐β₁ mRNA and protein levels were found in cultured astrocytes transfected with mutated exon 1 of the human huntingtin gene, and in striatal knock‐in cell lines expressing full‐length huntingtin with an expanded glutamine repeat. Taken together, our data suggest that serum TGF‐β₁ levels are potential biomarkers of HD development during the asymptomatic phase of the disease, and raise the possibility that strategies aimed at rescuing TGF‐β₁ levels in the brain may influence the progression of HD.     

Reductive stress in young healthy individuals at risk of Alzheimer disease

Oxidative stress is a hallmark of Alzheimer disease (AD) but this has not been studied in young healthy persons at risk of the disease. Carrying an Apo ε4 allele is the major genetic risk factor for AD. We have observed that lymphocytes from young, healthy persons carrying at least one Apo ε4 allele suffer from reductive rather than oxidative stress, i.e., lower oxidized glutathione and P-p38 levels and higher expression of enzymes involved in antioxidant defense, such as glutamylcysteinyl ligase and glutathione peroxidase. In contrast, in the full-blown disease, the situation is reversed and oxidative stress occurs, probably because of the exhaustion of the antioxidant mechanisms just mentioned. These results provide insights into the early events of the progression of the disease that may allow us to find biomarkers of AD at its very early stages.     

Identifying individuals at risk for fracture in Guatemala

Introduction

The FRAX calculator combines a set of clinical risk factors with country-specific incidence rates to determine the ten-year absolute risk of major osteoporotic fracture. However, regional or country-specific databases from Central American countries are not available. We compared the use of various FRAX databases and the Pluijm algorithm in determining risk of fracture.

Methods

We collected clinical risk factor data needed for the FRAX calculator and Pluijm algorithm of Hispanic women in Guatemala and calculated the FRAX absolute risk measures of major osteoporotic fracture and hip fracture. Subjects were postmenopausal women greater than age 40 with no history of using medication that affect bone. A random sample of 204 women in 34 different regions women in Guatemala City was visited in their homes to complete the surveys. The Pluijm risk score and FRAX risk score using the US Hispanic, Spain, and Mexican databases were calculated.

Results

We used the US NOF guidelines for treatment which suggest a treatment threshold for patients with a 10-year hip fracture probability ≥3% or a 10-year major osteoporotic fracture risk ≥20%. The number of patients meeting the suggested threshold limits for treatment using the Spain and Mexico calculators were identical. There was 100% conformity in threshold limits for both hip and major osteoporotic fracture risk. The mean conformity for any fracture risk between US Hispanic and the other two databases was 97.5%. Conformity was 99.0% based on major osteoporotic fracture and 97.5% based on risk of hip fracture. The Pluijm evaluation shows conformity of 87.2% and 83.3%, respectively, when compared to the US Hispanic and Spain/Mexico FRAX thresholds for risk of fracture.

Discussion

Although the different FRAX databases provide variations in the absolute risk of fracture, the overall conformity to treatment thresholds amongst the US Hispanic, Spain, and Mexico databases show the database used would have little effect as to the decision to treat. The Pluijm tool conforms to the FRAX thresholds and can be used as well. It does not matter which country-specific calculator or assessment tool is used, as there are a similar number of patients that would meet the intervention threshold.     

Management of altered metabolic activity in Drosophila model of Huntington’s disease by curcumin

Huntington’s disease (HD) is a devastating polyglutamine disorder characterized by extensive neurodegeneration and metabolic abnormalities at systemic, cellular and intracellular levels. Metabolic alterations in HD manifest as abnormal body weight, dysregulated biomolecule levels, impaired adipocyte functions, and defective energy state which exacerbate disease progression and pose acute threat to the health of challenged individuals in form of insulin resistance, cardiovascular disease, and energy crisis. To colossally mitigate disease symptoms, we tested the efficacy of curcumin in Drosophila model of HD. Curcumin is the bioactive component of turmeric (Curcuma longa Linn), well-known for its ability to modulate metabolic activities. We found that curcumin effectively managed abnormal body weight, dysregulated lipid content, and carbohydrate level in HD flies. In addition, curcumin administration lowered elevated reactive-oxygen-species levels in adult adipose tissue of diseased flies, and improved survival and locomotor function in HD flies at advanced disease stage. Altogether, these findings clearly suggest that curcumin efficiently attenuates metabolic derangements in HD flies and can prove beneficial in alleviating the complexities associated with HD.