Opposite Roles of Co-enzyme Q10 and Formaldehyde in Neurodegenerative Diseases

Most of neurodegenerative diseases (NDD) have no cure. The common etiology of neurodegenerations is unclear. Air pollutant-gaseous formaldehyde is notoriously known to induce demyelination and cognitive impairments. Unexpectedly, an amount of formaldehyde has been detected in the brains. Multiple factors can induce the generation and accumulation of endogenous formaldehyde. Excessive formaldehyde can induce oxidative stress to generate H2O2; in turn, H2O2 promote formaldehyde production. Clinical investigations have shown that an abnormal high level of formaldehyde but low level of coenzyme Q10 (coQ10) was observed in patients with NDD. Further studies have proven that excessive formaldehyde directly inactivates coQ10, reduces the ATP generation, enhances oxidative stress, initiates inflammation storm, induces demyelination; subsequently, it results in neurodegeneration. Although the low water solubility of coQ10 limits its clinical application, nanomicellar water-soluble coQ10 exhibits positive therapeutical effects. Hence, nanopackage of coQ10 may be a promising strategy for treating NDD.

Stereopsis and ocular alignment in Parkinson's disease patients with and without freezing of gait symptoms

BACKGROUND

Parkinson's disease patients are classically described by having motor disorder symptoms. Freezing of gait is one of these motor symptoms that presents in some of these patients. Even though freezing of gait is classically considered as motor dysfunction, it is now widely accepted that deficits in other sensory systems, for example visual system, may lead or contribute to freezing of gait. The purpose of this study is to characterise some of the binocular vision functions in freezing of gait patients, non-freezing of gait Parkinson's disease patients and age-matched healthy controls.

METHODS

Binocular vision measurements included local and global stereopsis using different clinical stereo tests, along with fixation disparity and fixation disparity curves. The fixation disparity measures were primarily an assessment of the vergence motor system, and the clinical stereo tests assess the combined effects of motor and sensory aspects of binocular vision. Twenty-two freezing of gait patients, 25 non-freezing of gait patients, and 25 aged-matched healthy controls completed all of the measurements in this study.

RESULTS

The freezing of gait group had worse stereopsis than the non-freezing of gait group, and the non-freezing of gait group had worse stereopsis than the healthy controls. The impairment of global stereopsis was more common than local stereopsis in Parkinson's disease patient groups. The reduction in stereopsis among Parkinson's disease patients was not associated with fixation disparity.

CONCLUSIONS

Results from this study clearly indicate that the freezing of gait patients group has a greater loss in stereopsis than the other two groups, especially for the global tests. Whether these impairments are contributing to the freezing of gait or just associated with freezing of gait is uncertain.

Gait in Parkinson's disease: A visuo-cognitive challenge

Vision and cognition have both been related to gait impairment in Parkinson's disease (PD) through separate strands of research. The cumulative and interactive effect of both (which we term visuo-cognition) has not been previously investigated and little is known about the influence of cognition on vision with respect to gait. Understanding the role of vision, cognition and visuo-cognition in gait in PD is critical for data interpretation and to infer and test underlying mechanisms. The purpose of this comprehensive narrative review was to examine the interdependent and interactive role of cognition and vision in gait in PD and older adults. Evidence from a broad range of research disciplines was reviewed and summarised. A key finding was that attention appears to play a pivotal role in mediating gait, cognition and vision, and should be considered emphatically in future research in this field.

Reduction of negative afterimage duration in Parkinson's disease patients: a possible role for dopaminergic deficiency in the retinal Interplexiform cell layer

Dopaminergic deficiency may affect Parkinson's disease patients (PD) in the central as well as the peripheral tissues. In the retina, the neuromodulatory role of the dopaminergic Interplexiform cell layer (IP) plays a major role in the retinal light adaptation and may account for the duration of the negative afterimage. Here we present results showing a significant reduction of negative afterimage duration in PD patients. This supports the hypothesis that the retinal dopaminergic system may be the main cause for the long duration of negative afterimage. We suggest that the observed reduction of afterimage duration is due to possible dopaminergic deficiency in patients with Parkinson's disease.

Effect of optical flow versus attentional strategy on gait in Parkinson's Disease: a study with a portable optical stimulating device

Background

Several studies have demonstrated the capability of PD subjects to improve gait if appropriate visual cues are provided. Possible explanations referred to attentional factors and to the presence of optic flow on peripheral vision. The aim of the present study was to evaluate separately these two mechanisms in a group of fifteen subjects with Parkinson's Disease at different stages and in a group of ten age-matched controls.

Methods

A microprocessor-controlled portable device implementing two different optical stimulation modalities has been used: bilateral continuous optic flow and unilateral reciprocal optical stimulus that is synchronized to the swing phase of gait. The latter allowed for the implementation of an attentional strategy.

Results

Results showed that mild PD subjects (H&Y<= 2) are responsive to forward oriented optic flow which produces an increment of gait cadence (+ 7.8%) and velocity (+ 8.1%) (p < 0.05), while PD subjects at more advanced stages (H&Y>2) tend to be more responsive to the attentional strategy, through an increase of stride length (+ 19.8%) and a compensatory decrease of cadence (- 16.2%).

Conclusion

Although stated with caution due to the limited number of considered subjects, a possible descriptive model explaining the above findings is proposed, which correlates the different responsiveness to visual stimulation strategies with the progression of pathology and the consequent changes on the activation levels of the involved motor and associative areas.

Independent patterns of damage within magno-, parvo- and koniocellular pathways in Parkinson's disease

Sensory deficits have been documented in Parkinson's disease, in particular within the visual domain. However, ageing factors related to the brain and to neural and non-neural ocular structures could explain some of the previously reported results, in particular the claimed impairment within the koniocellular pathway. This study addressed visual impairment attributable to the magno- (luminance), parvo- (red-green) and koniocellular (blue-yellow) pathways in a population of Parkinson's disease patients. To avoid potentially confounding factors, all subjects underwent a full neurophthalmological assessment which led to exclusion of subjects with increased intraocular pressure, diabetes even in the absence of retinopathy, and ocular abnormalities (from a total of 72 patients' eyes, 12 were excluded). Both parvo- and koniocellular pathways were studied by means of contrast sensitivity (CS) measurements along protan, tritan and deutan axes and also by fitting chromatic discrimination ellipses using eight measured contrast axes. Magnocellular function was assessed, using stimuli that induce a frequency doubling illusion, in 17 locations in the fovea and periphery. Achromatic (luminance modulation) thresholds were significantly higher in Parkinson's disease both in foveal and peripheral locations. A significant impairment was observed along protan and deutan axes, but only marginally along the tritan axis. These results were corroborated by a significant elongation of chromatic discrimination ellipses in our Parkinson's disease group. Correlation analysis showed that achromatic and chromatic CS measures were independent, which implies that multiple visual pathways are affected independently in Parkinson's disease. Magnocellular impairment was significantly correlated with age and disease stage, in contrast to the measured chromatic deficits. We conclude that in Parkinson's disease, independent damage occurs in the early magno- and parvocellular pathways. Furthermore, traditional koniocellular probing strategies in Parkinson's disease may be confounded by ageing factors, which may reconcile the previously reported controversial findings concerning chromatic impairment in Parkinson's disease.

Visual object recognition deficits in early Parkinson's disease

The nature of the visual perception deficits in Parkinson's disease (PD) has remained unclear. The present study explored whether there emerge deficits in the different stages of visual object recognition in early PD. Twenty-eight patients and 14 healthy controls were studied. A set of reaction time tasks were applied to measure the different stages of object recognition. The results indicate some selective problems in both basic perceptual and semantic visual processing at an early stage of cognitive deterioration in PD.

Microprocessor-controlled optical stimulating device to improve the gait of patients with Parkinson's disease

Different types of visual cue for subjects with Parkinson's disease (PD) produced an improvement in gait and helped some of them prevent or overcome freezing episodes. The paper describes a portable gait-enabling device (optical stimulating glasses (OSGs) that provides, in the peripheral field of view, different types of continuous optic flow (backward or forward) and intermittent stimuli synchronised with external events. The OSGs are a programmable, stand-alone, augmented reality system that can be interfaced with a PC for program set-up. It consists of a pair of non-corrective glasses, equipped with two matrixes of 70 micro light emitting diodes, one on each side, controlled by a microprocessor. Two foot-switches are used to synchronise optical stimulation with specific gait events. A pilot study was carried out on three PD patients and three controls, with different types of optic flow during walking along a fixed path. The continuous optic flow in the forward direction produced an increase in gait velocity in the PD patients (up to + 11% in average), whereas the controls had small variations. The stimulation synchronised with the swing phase, associated with an attentional strategy, produced a remarkable increase in stride length for all subjects. After prolonged testing, the device has shown good applicability and technical functionality, it is easily wearable and transportable, and it does not interfere with gait.

Visual processing of rapidly presented stimuli is normalized in Parkinson’s disease when proximal stimulus strength is enhanced

Deficient perception and cognition in Parkinson's disease (PD) has been attributed to slow information processing, but an alternative explanation may be reduced signal strength. In 18 nondemented individuals with PD and 15 healthy adults, we enhanced the contrast level of rapidly flashed masked letters. The PD group required significantly higher contrast to reach criterion (80% accuracy). Normal motion detection in these participants indicated no gross, general dysfunction of the dorsal visual processing stream. These results suggest that putatively slowed processing in PD may be an artifact of reduced signal strength arising from depletion of dopamine in retina or cortical visual areas.

Motor impairment influences Farnsworth-Munsell 100 Hue test error scores in Parkinson's disease patients

Farnsworth-Munsell 100 Hue test (FMT) error scores and peg insertion abilities significantly differ between Parkinson's disease (PD) patients and controls. Both tasks ask for performance of voluntary movements. The objective of this study was to demonstrate a relation between FMT error scores and peg insertion outcomes. We successively performed both tasks in 28 previously untreated PD patients. The FMT error score was significantly (p=0.016) lower in patients with better peg insertion outcome. A significant (Spearman R=0.47, p=0.012) correlation between peg insertion results and the FMT error scores appeared. Motor impairment influences FMT error scores in PD patients.

Hemispace differences in the visual perception of size in left hemiParkinson's disease

The visual perception of size in different regions of external space was studied in Parkinson's disease (PD). A group of patients with worse left-sided symptoms (LPD) was compared with a group with worse right-sided symptoms (RPD) and with a group of age-matched controls on judgements of the relative height or width of two rectangles presented in different regions of external space. The relevant dimension of one rectangle (the 'standard') was held constant, while that of the other (the 'variable') was varied in a method of constant stimuli. The point of subjective equality (PSE) of rectangle width or height was obtained by probit analysis as the mean of the resulting psychometric function. When the standard was in left space, the PSE of the LPD group occurred when the variable was smaller, and when the standard was in right space, when the variable was larger. Similarly, when the standard rectangle was presented in upper space, and the variable in lower space, the PSE occurred when the variable was smaller, an effect which was similar in both left and right spaces. In all these experiments, the PSEs for both the controls and the RPD group did not differ significantly, and were close to a physical match, and the slopes of the psychometric functions were steeper in the controls than the patients, though not significantly so. The data suggest that objects appear smaller in the left and upper visual spaces in LPD, probably because of right hemisphere impairment.

Coenzyme Q10 supplementation provides mild symptomatic benefit in patients with Parkinson's disease

Features of Parkinson's disease (PD) include oxidative stress, nigral mitochondrial complex I deficiency and visual dysfunction, all of which are also associated with coenzyme Q(10) (CoQ(10)) deficiency. The objective of this monocenter, parallel group, placebo controlled, double-blind trial was to determine the symptomatic response of daily oral application of 360 mg CoQ(10) lasting 4 weeks on scored PD symptoms and visual function, measured with the Farnsworth-Munsell 100 Hue test (FMT), in 28 treated and stable PD patients. CoQ(10) supplementation provided a significant (P=0.01) mild symptomatic benefit on PD symptoms and a significantly (F((1,24))=8.48, P=0.008) better improvement of FMT performance compared with placebo. Our results indicate a moderate beneficial effect of oral CoQ(10) supplementation in PD patients.

Drug treatment of non-motor symptoms in Parkinson's disease

Non-motor symptoms may considerably reduce parkinsonian quality of life, particularly in advanced stages of the disease. Autonomic features, such as seborrhoea, hyperhidrosis, orthostatic hypotension, excessive salivation, bladder dysfunction and GI disturbances, and neuropsychiatric symptoms, such as depression, sleep disorders, psychosis and dementia, appear in the course of Parkinson's disease. Pharmacotherapy of these non-motor symptoms complicates long-term antiparkinsonian combination drug therapy due to possible drug interactions, side effects and changes in metabolism. Moreover, antiparkinsonian compounds themselves contribute to the onset of these non-motor symptoms to a considerable extent. This complicates differentiation between the disease process itself and drug-related effects, thus influencing therapeutic options, which are often limited because of comorbidity and polypharmacy. Therefore, standardised recommendations are questionable, since drug tolerability and response differ between patients. Nevertheless, this review tries to provide a survey of possible therapeutic options for the treatment of the symptoms of Parkinson's disease other the dopamine-sensitive motor features.

Progress of visual dysfunction in Parkinson's disease

Studies on progression of Parkinson's disease (PD) mainly focus on the nigrostriatal dopaminergic decline, but not on the visual system. We determined progression of (i) disturbed color vision, assessed with the Farnsworth-Munsell 100 Hue test (FMT) and (ii) intensity of PD in 18 patients. Significant differences occurred between (i) initial FMT error scores and follow-up results 3 years later (P=0.002) and analogously (ii) scored intensity of PD (P=0.002). A relation between computed differences of FMT error scores and rated activities of daily living appeared. Deterioration of color vision progresses in PD.

A model of the Parkinsonian visual system: support for the dark adaptation hypothesis

Considerable evidence suggests that some visual abnormalities in Parkinson's disease are mediated by disruption of dopaminergic processes in the retina. Since dopamine is thought to be involved in the process of dark adaptation, and some of these abnormalities are similar to the changes which accompany dark adaptation in normal subjects, it has been proposed that the parkinsonian retina behaves as though inappropriately dark-adapted. In Parkinson's disease, the apparent contrast of peripherally viewed medium and high spatial frequency gratings is reduced. In our first experiment, normal subjects were dark-adapted, and were required to match the apparent contrast of a peripherally viewed grating to that of a foveally viewed grating. The results showed an interaction between spatial frequency and dark adaptation, reflecting a greater reduction in the apparent contrast of peripheral high spatial frequency gratings. In a second experiment, no effect of dark adaptation was found on the apparent spatial frequency of a peripherally viewed grating required to match that of a foveally viewed grating. The first experiment supports the dark adaptation hypothesis of parkinsonian vision, and the second suggests that the changes in apparent contrast are mediated by different amounts of change in contrast gain in central and peripheral vision, rather than by differential changes in receptive field size.