Dopamine Transporter Imaging, Current Status of a Potential Biomarker: A Comprehensive Review

Mitochondrial Parkinsonism: A Practical Guide to Genes and Clinical Diagnosis

BACKGROUND

Primary mitochondrial diseases (PMDs) are the most common inborn errors of energy metabolism, with a combined prevalence of 1 in 4300. They can result from mutations in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA). These disorders are multisystemic and mainly affect high energy-demanding tissues, such as muscle and the central nervous system (CNS). Among many clinical features of CNS involvement, parkinsonism is one of the most common movement disorders in PMDs.

METHODS

This review provides a pragmatic educational overview of the most recent advances in the field of mitochondrial parkinsonism, from pathophysiology and genetic etiologies to phenotype and diagnosis.

RESULTS

mtDNA maintenance and mitochondrial dynamics alterations represent the principal mechanisms underlying mitochondrial parkinsonism. It can be present in isolation, alongside other movement disorders or, more commonly, as part of a multisystemic phenotype. Mutations in several nuclear-encoded genes (ie, POLG, TWNK, SPG7, and OPA1) and, more rarely, mtDNA mutations, are responsible for mitochondrial parkinsonism. Progressive external opthalmoplegia and optic atrophy may guide genetic etiology identification.

CONCLUSION

A comprehensive deep-phenotyping approach is needed to reach a diagnosis of mitochondrial parkinsonism, which lacks distinctive clinical features and exemplifies the intricate genotype-phenotype interplay of PMDs.

Unraveling olfactory subtypes in Parkinson's disease and their effect on the natural history of the disease

BACKGROUND

Hyposmia in Parkinson's disease (PD) had been studied before but had not been detailed by its temporal progression. This study observed how each olfactory subtype evolved in terms of motor symptoms, cardiac sympathetic innervation, and cognition.

METHODS

Two hundred and three early PD patients were classified as normosmia, hyposmia-converter (hypo-converter), and hyposmia. Their presynaptic monoamine availability at the time of diagnosis was assessed by positron emission tomography imaging using 18F-N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane and compared across the subtypes. Motor symptoms were evaluated in all patients, cardiac denervation was examined in 183 patients, and cognition in 195 patients were assessed using a neuropsychological battery. The domains were re-assessed 2-4 times, and the longitudinal data were analyzed to discern the natural course of each subtype.

RESULTS

Twenty-nine (14.3%) patients belonged to the normosmia group, 34 (16.7%) to the hypo-converter group, and the rest to the hyposmia (69.0%) group. 85.7% of the total population became hyposmic during an average 3 years of follow-up. The baseline motor symptoms, cardiac denervation, and cognition were comparable across the olfactory subtypes. Across the subtypes, a decline in the presynaptic monoamine densities of the caudate, especially the ventral-anterior subdivisions, correlated inversely with olfaction dysfunction. Over time, motor and cardiac denervation burdens worsened regardless of olfactory subtypes, but hypo-converters experienced faster cognitive deterioration than the other two groups.

CONCLUSIONS

The results suggest that the olfactory subtypes have differential significance along the disease course, which might reflect the involvement of different neuro-biochemical circuitries.

Preclinical evaluation of [18F]FP-CIT, the radiotracer targeting dopamine transporter for diagnosing Parkinson's disease: pharmacokinetic and efficacy analysis

BACKGROUND

N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane (FP-CIT), the representative cocaine derivative used in dopamine transporter imaging, is a promising biomarker, as it reflects the severity of Parkinson's disease (PD). 123I- and 18F-labeled FP-CIT has been used for PD diagnosis. However, preclinical studies evaluating [18F]FP-CIT as a potential diagnostic biomarker are scarce. Among translational research advancements from bench to bedside, translating preclinical findings into clinical practice is one-directional. The aim of this study is to employ a circular approach, beginning back from the preclinical stage, progressing to the supplementation of [18F]FP-CIT, and subsequently returning to clinical application. We investigated the pharmacokinetic properties of [18F]FP-CIT and its efficacy for PD diagnosis using murine models.

RESULTS

Biodistribution, metabolite and excretion analyses were performed in mice and PD models were induced in rats using 6-hydroxydopamine (6-OHDA). The targeting efficiency of [18F]FP-CIT for the dopamine receptor was assessed through animal PET/CT imaging. Subsequently, correlation analysis was conducted between animal PET/CT imaging results and immunohistochemistry (IHC) targeting tyrosine hydroxylase. Rapid circulation was confirmed after [18F]FP-CIT injection. [18F]FP-CIT reached the highest uptake of 23.50 ± 12.46%ID/g in the striatum 1 min after injection, and it was rapidly excreted within 60 min. The major metabolic organs of [18F]FP-CIT were confirmed to be the intestines, liver, and kidneys. Its uptake in the intestine was approximately 5% ID/g. The uptake in the liver gradually increased, with excretion beginning after reaching a maximum after 60 min. The kidneys exhibited rapid elimination after 10 min. In the excretion study, rapid elimination was verified, with 21.46 ± 9.53% of the compound excreted within a 6 h period. Additionally, the efficacy of [18F]FP-CIT PET was demonstrated in the PD model, with a high correlation with IHC for both the absolute value (R = 0.803, p = 0.0017) and the ratio value (R = 0.973, p = 0.0011).

CONCLUSIONS

This study fills the gap regarding insufficient preclinical studies on [18F]FP-CIT, including its ADME, metabolites, and efficiency. The pharmacological results, including accurate diagnosis, rapid circulation, and [18F]FP-CIT excretion, provide complementary evidence that [18F]FP-CIT can be used safely and efficiently to diagnose PD in clinics, although it is already used in clinics.

Teaghrelin protected dopaminergic neurons in MPTP-induced Parkinson's disease animal model by promoting PINK1/Parkin-mediated mitophagy and AMPK/SIRT1/PGC1-α-mediated mitochondrial biogenesis

Mitochondrial dysfunction, a common cellular hallmark in both familial and sporadic forms of Parkinson's disease (PD), is assumed to play a significant role in pathologic development and progression of the disease. Teaghrelin, a unique bioactive compound in some oolong tea varieties, has been demonstrated to protect SH-SY5Y cells against 1-methyl-4-phenylpyridinium induced neurotoxicity by binding to the ghrelin receptor to activate the AMPK/SIRT1/PGC-1α pathway. In this study, an animal model was established using a neurotoxin, 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP), a byproduct of a prohibited drug, to evaluate the oral efficacy of teaghrelin on PD by monitoring motor dysfunction of mice in open field, pole, and bean walking tests. The results showed that MPTP-induced motor dysfunction of mice was significantly attenuated by teaghrelin supplementation. Tyrosine hydroxylase and dopamine transporter protein were found reduced in the striatum and midbrain of MPTP-treated mice, and significantly mitigated by teaghrelin supplementation. Furthermore, teaghrelin administration enhanced mitophagy and mitochondria biogenesis, which maintained cell homeostasis and prevented the accumulation of αSyn and apoptosis-related proteins. It seemed that teaghrelin protected dopaminergic neurons in MPTP-treated mice by increasing PINK1/Parkin-mediated mitophagy and AMPK/SIRT1/PGC-1α-mediated mitochondria biogenesis, highlighting its potential therapeutic role in maintaining dopaminergic neurons function in PD. Mitochondrial dysfunction, a common cellular hallmark in both familial and sporadic forms of Parkinson's disease (PD), is assumed to play a significant role in pathologic development and progression of the disease. Teaghrelin, a unique bioactive compound in some oolong tea varieties, has been demonstrated to protect SH-SY5Y cells against 1-methyl-4-phenylpyridinium induced neurotoxicity by binding to the ghrelin receptor to activate the AMPK/SIRT1/PGC-1α pathway. In this study, an animal model was established using a neurotoxin, 1-methyl-4phenyl-1,2,3,6-tetrahydropyridine (MPTP), a byproduct of a prohibited drug, to evaluate the oral efficacy of teaghrelin on PD by monitoring motor dysfunction of mice in open field, pole, and bean walking tests. The results showed that MPTP-induced motor dysfunction of mice was significantly attenuated by teaghrelin supplementation. Tyrosine hydroxylase and dopamine transporter protein were found reduced in the striatum and midbrain of MPTP-treated mice, and significantly mitigated by teaghrelin supplementation. Furthermore, teaghrelin administration enhanced mitophagy and mitochondria biogenesis, which maintained cell homeostasis and prevented the accumulation of αSyn and apoptosis-related proteins. It seemed that teaghrelin protected dopaminergic neurons in MPTP-treated mice by increasing PINK1/Parkin-mediated mitophagy and AMPK/SIRT1/PGC-1α-mediated mitochondria biogenesis, highlighting its potential therapeutic role in maintaining dopaminergic neurons function in PD.

Refining the clinical diagnosis of Parkinson's disease

Our ability to define, understand, and classify Parkinson's disease (PD) has undergone significant changes since the disorder was first described in 1817. Clinical features and neuropathologic signatures can now be supplemented by in-vivo interrogation of genetic and biological substrates of disease, offering great opportunity for further refining the diagnosis of PD. In this mini-review, we discuss the historical perspectives which shaped our thinking surrounding the definition and diagnosis of PD. We highlight the clinical, genetic, pathologic and biologic diversity which underpins the condition, and proceed to discuss how recent developments in our ability to define biologic and pathologic substrates of disease might impact PD definition, diagnosis, individualised prognostication, and personalised clinical care. We argue that Parkinson's 'disease', as currently diagnosed in the clinic, is actually a syndrome. It is the outward manifestation of any array of potential dysfunctional biologic processes, neuropathological changes, and disease aetiologies, which culminate in common outward clinical features which we term PD; each person has their own unique disease, which we can now define with increasing precision. This is an exciting time in PD research and clinical care. Our ability to refine the clinical diagnosis of PD, incorporating in-vivo assessments of disease biology, neuropathology, and neurogenetics may well herald the era of biologically-based, precision medicine approaches PD management. With this however comes a number of challenges, including how to integrate these technologies into clinical practice in a way which is acceptable to patients, promotes meaningful changes to care, and minimises health economic impact.

Synthesis and initial evaluation of radioiodine-labelled deuterated tropane derivatives targeting dopamine transporter

The dopamine transporter (DAT) is closely related to a variety of neurological disorders including Parkinson's disease (PD) and other neurodegenerative diseases. In vivo imaging of DAT with radio-labelled tracers has become a powerful technique in related disorders. The radioiodine-labelled tropane derivative [123I]FP-CIT ([123I]1a) is widely used in clinical single photon emission computed tomography (SPECT) imaging as a DAT imaging agent. To develop more metabolically stable DAT radioligands for accurate imaging, this work compared two novel deuterated tropane derivatives ([131I]1c-d) with non-deuterated tropane derivatives ([131I]1a-b). [131I]1a-d were obtained in high radiochemical purity (RCP) above 99 % with molar activities of 7.0-10.0 GBq/μmol. The [131I]1a and [131I]1c exhibited relatively higher affinity to DAT (Ki: 2.0-3.12 nM) than [131I]1b and [131I]1d. Biodistribution results showed that [131I]1c consistently exhibited a higher ratio of the target to non-target (striatum/cerebellum) than [131I]1a. Furthermore, metabolism studies indicated that the in vivo metabolic stability of [131I]1c was superior to that of [131I]1a. Ex vivo autoradiography showed that [131I]1c selectively localized on DAT-rich striatal regions and the specific signal could be blocked by DAT inhibitor. These results indicated that [131I]1c might be a potential probe for DAT SPECT imaging in the brain.

The Formation and Function of the VTA Dopamine System

The midbrain dopamine system is a sophisticated hub that integrates diverse inputs to control multiple physiological functions, including locomotion, motivation, cognition, reward, as well as maternal and reproductive behaviors. Dopamine is a neurotransmitter that binds to G-protein-coupled receptors. Dopamine also works together with other neurotransmitters and various neuropeptides to maintain the balance of synaptic functions. The dysfunction of the dopamine system leads to several conditions, including Parkinson's disease, Huntington's disease, major depression, schizophrenia, and drug addiction. The ventral tegmental area (VTA) has been identified as an important relay nucleus that modulates homeostatic plasticity in the midbrain dopamine system. Due to the complexity of synaptic transmissions and input-output connections in the VTA, the structure and function of this crucial brain region are still not fully understood. In this review article, we mainly focus on the cell types, neurotransmitters, neuropeptides, ion channels, receptors, and neural circuits of the VTA dopamine system, with the hope of obtaining new insight into the formation and function of this vital brain region.

Microfluidic flow injection analysis system for the electrochemical detection of dopamine using diazonium-grafted copper nanoparticles on multi-walled carbon nanotube-modified surfaces

In this proof-of-concept study, a microfluidic flow injection analysis (FIA) system was developed using multi-walled carbon nanotube-modified screen-printed carbon electrodes (CNTSPEs) that were modified with copper nanoparticles (CuNPs) following the electrodeposition of the diazonium salt of 4-aminothiophenol to form 4-thiophenol-conjugated CuNPs (CuNPs-CNTSPE). Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) were used to characterize the size of CuNPs, morphology and elemental analysis of CuNPs-CNTSPE, respectively. Using electrochemical impedance spectroscopy (EIS), the charge-transfer resistance (Rct) of CuNPs-CNTSPE was found to be 20-fold lower than that of CNTSPE. The CuNPs-CNTSPE displayed an oxidation peak for dopamine at -0.08 V which is ∼80 mV lower than the one detected using CNTSPE. The modified electrode was used in microfluidic flow injection analysis and offline systems for sensitive detection of dopamine (DA). The pH, flow rate, loop volume, concentration, and type of surfactant were all optimized for on-chip detection. Under the optimal conditions, using phosphate electrolyte solution (pH 6) containing 0.05% (w/v) Tween 20® as the carrier at a flow rate of 0.6 mL min-1 and a loop volume of 50 μL, the calibration curve was linear from 1.5 to 500 nM with a limit of detection of 0.33 nM. This technique was used for the successful detection of DA in real samples with recovery ranging from 96.5% to 103.8%. The microfluidic FIA system described here has the potential to be used as an electrochemical point-of-care device for rapid DA detection with high sensitivity and reproducibility.

Advances in iPSC Technology in Neural Disease Modeling, Drug Screening, and Therapy

Neurodegenerative disorders (NDs) including Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease are all incurable and can only be managed with drugs for the associated symptoms. Animal models of human illnesses help to advance our understanding of the pathogenic processes of diseases. Understanding the pathogenesis as well as drug screening using appropriate disease models of neurodegenerative diseases (NDs) are vital for identifying novel therapies. Human-derived induced pluripotent stem cell (iPSC) models can be an efficient model to create disease in a dish and thereby can proceed with drug screening and identifying appropriate drugs. This technology has many benefits, including efficient reprogramming and regeneration potential, multidirectional differentiation, and the lack of ethical concerns, which open up new avenues for studying neurological illnesses in greater depth. The review mainly focuses on the use of iPSC technology in neuronal disease modeling, drug screening, and cell therapy.

Therapeutic Effects of Geranium Oil in MPTP-Induced Parkinsonian Mouse Model

Parkinson's disease (PD) is an incurable neurodegenerative disease characterized by motor and non-motor disabilities resulting from neuronal cell death in the substantia nigra and striatum. Microglial activation and oxidative stress are two of the primary mechanisms driving that neuronal death. Here, we evaluated the effects of geranium oil on 1-methyl-4-phenyl-1,2,3,6-tetra-hydropyridine (MPTP) mouse model for PD, on microglial activation, and oxidative stress. We demonstrate that oral treatment with geranium oil improved motor performance in this model. The therapeutic effects of geranium oil were observed as a significant increase in rotarod latency and distance among the mice treated with geranium oil, as compared to vehicle-treated MPTP mice. Geranium oil also prevented dopaminergic neuron death in the substantia nigra of the treated mice. These therapeutic effects can be partially attributed to the antioxidant and anti-inflammatory properties of geranium oil, which were observed as attenuated accumulation of reactive oxygen species and inhibition of the secretion of proinflammatory cytokines from geranium oil-treated activated microglial cells. A repeated-dose oral toxicity study showed that geranium oil is not toxic to mice. In light of that finding and since geranium oil is defined by the FDA as generally recognized as safe (GRAS), we do not foresee any toxicity problems in the future and suggest that geranium oil may be a safe and effective oral treatment for PD. Since the MPTP model is only one of the preclinical models for PD, further studies are needed to confirm that geranium oil can be used to prevent or treat PD.

How should we be using biomarkers in trials of disease modification in Parkinson's disease?

The recent validation of the α-synuclein seed amplification assay as a biomarker with high sensitivity and specificity for the diagnosis of Parkinson's disease has formed the backbone for a proposed staging system for incorporation in Parkinson's disease clinical studies and trials. The routine use of this biomarker should greatly aid in the accuracy of diagnosis during recruitment of Parkinson's disease patients into trials (as distinct from patients with non-Parkinson's disease parkinsonism or non-Parkinson's disease tremors). There remain, however, further challenges in the pursuit of biomarkers for clinical trials of disease modifying agents in Parkinson's disease, namely: optimizing the distinction between different α-synucleinopathies; the selection of subgroups most likely to benefit from a candidate disease modifying agent; a sensitive means of confirming target engagement; and the early prediction of longer-term clinical benefit. For example, levels of CSF proteins such as the lysosomal enzyme β-glucocerebrosidase may assist in prognostication or allow enrichment of appropriate patients into disease modifying trials of agents with this enzyme as the target; the presence of coexisting Alzheimer's disease-like pathology (detectable through CSF levels of amyloid-β42 and tau) can predict subsequent cognitive decline; imaging techniques such as free-water or neuromelanin MRI may objectively track decline in Parkinson's disease even in its later stages. The exploitation of additional biomarkers to the α-synuclein seed amplification assay will, therefore, greatly add to our ability to plan trials and assess the disease modifying properties of interventions. The choice of which biomarker(s) to use in the context of disease modifying clinical trials will depend on the intervention, the stage (at risk, premotor, motor, complex) of the population recruited and the aims of the trial. The progress already made lends hope that panels of fluid biomarkers in tandem with structural or functional imaging may provide sensitive and objective methods of confirming that an intervention is modifying a key pathophysiological process of Parkinson's disease. However, correlation with clinical progression does not necessarily equate to causation, and the ongoing validation of quantitative biomarkers will depend on insightful clinical-genetic-pathophysiological comparisons incorporating longitudinal biomarker changes from those at genetic risk with evidence of onset of the pathophysiology and those at each stage of manifest clinical Parkinson's disease.

Association between regular physical activity and biomarker changes in early Parkinson's disease patients

INTRODUCTION

Physical activity benefits patients with Parkinson's disease (PD) and is assumed to possess disease-modifying potential. PD-related biomarkers, such as dopamine transporter (DAT) imaging and cerebrospinal fluid (CSF) α-synuclein (α-syn) and amyloid β (Aβ), correlate with disease severity and, to some extent, reflect disease progression and pathology. However, the association between regular physical activity and PD biomarker changes remains unknown. This study aimed to investigate the association between physical activity and longitudinal trajectories of PD biomarkers.

METHODS

This retrospective study included 444 patients with a median follow-up time of 5 years from the Parkinson's Progression Markers Initiative cohort. Data collection included physical activity as scaled by the Physical Activity Scale for the Elderly questionnaire, dopamine transporter imaging, CSF assessment, and serum biomarkers. We analyzed the data using a linear mixed regression model.

RESULTS

Regular physical activity was associated with a slower decline of DAT uptake in the caudate (β = 0.063, p = 0.011) and the putamen (β = 0.062, p = 0.023). No association was detected between regular physical activity and CSF, as well as serum biomarkers.

CONCLUSION

Regular physical activity is associated with favorable PD biomarker progression, indicating a potential disease-modifying effect.

Association between regular physical activity and biomarker changes in early Parkinson's disease patients

INTRODUCTION

Physical activity benefits patients with Parkinson's disease (PD) and is assumed to possess disease-modifying potential. PD-related biomarkers, such as dopamine transporter (DAT) imaging and cerebrospinal fluid (CSF) α-synuclein (α-syn) and amyloid β (Aβ), correlate with disease severity and, to some extent, reflect disease progression and pathology. However, the association between regular physical activity and PD biomarker changes remains unknown. This study aimed to investigate the association between physical activity and longitudinal trajectories of PD biomarkers.

METHODS

This retrospective study included 444 patients with a median follow-up time of 5 years from the Parkinson's Progression Markers Initiative cohort. Data collection included physical activity as scaled by the Physical Activity Scale for the Elderly questionnaire, dopamine transporter imaging, CSF assessment, and serum biomarkers. We analyzed the data using a linear mixed regression model.

RESULTS

Regular physical activity was associated with a slower decline of DAT uptake in the caudate (β = 0.063, p = 0.011) and the putamen (β = 0.062, p = 0.023). No association was detected between regular physical activity and CSF, as well as serum biomarkers.

CONCLUSION

Regular physical activity is associated with favorable PD biomarker progression, indicating a potential disease-modifying effect.

Reduced Striatal Dopamine Transporter Availability and Heightened Response to Natural and Pharmacological Stimulation in CCK-1R-Deficient Obese Rats

Alterations in dopamine neurotransmission are associated with obesity and food preferences. Otsuka Long-Evans Tokushima Fatty (OLETF) rats that lack functional cholecystokinin receptor type-1 (CCK-1R), due to a natural mutation, exhibit impaired satiation, are hyperphagic, and become obese. In addition, compared to lean control Long-Evans Tokushima (LETO) rats, OLETF rats have pronounced avidity for over-consuming palatable sweet solutions, have greater dopamine release to psychostimulants, reduced dopamine 2 receptor (D2R) binding, and exhibit increased sensitivity to sucrose reward. This supports altered dopamine function in this strain and its general preference for palatable solutions such as sucrose. In this study, we examined the relationship between OLETF's hyperphagic behavior and striatal dopamine signaling by investigating basal and amphetamine stimulated motor activity in prediabetic OLETF rats before and after access to sucrose solution (0.3 M) compared to non-mutant control LETO rats, as well as availability of dopamine transporter (DAT) using autoradiography. In the sucrose tests, one group of OLETF rats received ad libitum access to sucrose while the other group received an amount of sucrose equal to that consumed by the LETO. OLETFs with ad libitum access consumed significantly more sucrose than LETOs. Sucrose exerted a biphasic effect on basal activity in both strains, i.e., reduced activity for 1 week followed by increased activity in weeks 2 and 3. Basal locomotor activity was reduced (-17%) in OLETFs prior to sucrose, compared to LETOs. Withdrawal of sucrose resulted in increased locomotor activity in both strains. The magnitude of this effect was greater in OLETFs and the activity was increased in restricted compared to ad-libitum-access OLETFs. Sucrose access augmented AMPH-responses in both strains with a greater sensitization to AMPH during week 1, an effect that was a function of the amount of sucrose consumed. One week of sucrose withdrawal sensitized AMPH-induced ambulatory activity in both strains. In OLETF with restricted access to sucrose, withdrawal resulted in no further sensitization to AMPH. DAT availability in the nucleus accumbens shell was significantly reduced in OLETF compared with aged-matched LETO. Together, these findings show that OLETF rats have reduced basal DA transmission and a heightened response to natural and pharmacological stimulation.

Outcome Measures for Disease-Modifying Trials in Parkinson's Disease: Consensus Paper by the EJS ACT-PD Multi-Arm Multi-Stage Trial Initiative

BACKGROUND

Multi-arm, multi-stage (MAMS) platform trials can accelerate the identification of disease-modifying treatments for Parkinson's disease (PD) but there is no current consensus on the optimal outcome measures (OM) for this approach.

OBJECTIVE

To provide an up-to-date inventory of OM for disease-modifying PD trials, and a framework for future selection of OM for such trials.

METHODS

As part of the Edmond J Safra Accelerating Clinical Trials in Parkinson Disease (EJS ACT-PD) initiative, an expert group with Patient and Public Involvement and Engagement (PPIE) representatives' input reviewed and evaluated available evidence on OM for potential use in trials to delay progression of PD. Each OM was ranked based on aspects such as validity, sensitivity to change, participant burden and practicality for a multi-site trial. Review of evidence and expert opinion led to the present inventory.

RESULTS

An extensive inventory of OM was created, divided into: general, motor and non-motor scales, diaries and fluctuation questionnaires, cognitive, disability and health-related quality of life, capability, quantitative motor, wearable and digital, combined, resource use, imaging and wet biomarkers, and milestone-based. A framework for evaluation of OM is presented to update the inventory in the future. PPIE input highlighted the need for OM which reflect their experience of disease progression and are applicable to diverse populations and disease stages.

CONCLUSION

We present a range of OM, classified according to a transparent framework, to aid selection of OM for disease-modifying PD trials, whilst allowing for inclusion or re-classification of relevant OM as new evidence emerges.

Functional Correlates of Striatal Dopamine Transporter Cerebrospinal Fluid Levels in Alzheimer's Disease: A Preliminary 18F-FDG PET/CT Study

The aim of our study was to investigate regional glucose metabolism with 18F-FDG positron emission tomography/computed tomography in a population of patients with Alzheimer's disease (AD) in relation to cerebrospinal (CSF) levels of striatal dopamine transporter (DAT). All patients underwent lumbar puncture and received a biomarker-based diagnosis of AD. Differences in regional brain glucose metabolism were assessed by Statistical Parametric Mapping version 12 with the use of age, gender, and MMSE as covariates in the analysis. A positive correlation between CSF DAT levels and glucose metabolism at the level of two brain areas involved in the pathophysiological process of Alzheimer's disease, the substantia nigra and the posterior cingulate gyrus, has been highlighted. Results indicate that patients with higher CSF DAT levels have a better metabolic pattern in two key zones, suggesting less advanced disease status in patients with more conserved dopaminergic systems.

FMR1 deletion in rats induces hyperactivity with no changes in striatal dopamine transporter availability

Autism Spectrum Disorder (ASD) is a pervasive neurodevelopmental disorder emerging in early life characterized by impairments in social interaction, poor verbal and non-verbal communication, and repetitive patterns of behaviors. Among the best-known genetic risk factors for ASD, there are mutations causing the loss of the Fragile X Messenger Ribonucleoprotein 1 (FMRP) leading to Fragile X syndrome (FXS), a common form of inherited intellectual disability and the leading monogenic cause of ASD. Being a pivotal regulator of motor activity, motivation, attention, and reward processing, dopaminergic neurotransmission has a key role in several neuropsychiatric disorders, including ASD. Fmr1 ^Δexon 8 rats have been validated as a genetic model of ASD based on FMR1 deletion, and they are also a rat model of FXS. Here, we performed behavioral, biochemical and in vivo SPECT neuroimaging experiments to investigate whether Fmr1 ^Δexon 8 rats display ASD-like repetitive behaviors associated with changes in striatal dopamine transporter (DAT) availability assessed through in vivo SPECT neuroimaging. At the behavioral level, Fmr1 ^Δexon 8 rats displayed hyperactivity in the open field test in the absence of repetitive behaviors in the hole board test. However, these behavioral alterations were not associated with changes in striatal DAT availability as assessed by non-invasive in vivo SPECT and Western blot analyses.

Molecular Imaging in Nanomedical Research 2.0

Over the last two decades, imaging techniques have become irreplaceable tools in nanotechnology: electron microscopy techniques are routinely used to observe the structural features of newly manufactured nanoconstructs, while light and electron microscopy, magnetic resonance imaging, optical imaging, positron emission tomography, and ultrasound imaging allow dynamic monitoring of the biodistribution, targeting and clearance of nanoparticulates in living systems, either for the whole organism or at the level of single cells, tissues and organs [...]

Gait abnormalities and non-motor symptoms predict abnormal dopaminergic imaging in presumed drug-induced Parkinsonism

Drug-induced parkinsonism (DIP) can be clinically indistinguishable from degenerative parkinsonism, and bedside assessments are needed to differentiate between these conditions. We examined 34 U.S. Veterans with DIP using ¹²³I-FP-CIT (DAT-SPECT) to identify underlying nigrostriatal degeneration. Participants were 94% male with mean age of 64.5 ± 7.1 years. DAT-SPECT was abnormal in 12/34 (35%). Comparing normal and abnormal imaging groups, there were no differences in age, sex, race/ethnicity, psychiatric diagnosis, motor severity, or RBD Screening Questionnaire scores. Those with underlying neurodegeneration reported significantly more non-motor symptoms (NMS), worse olfactory function on the University of Pennsylvania Smell Identification Test, and greater turning duration/steps on the instrumented Timed Up and Go. Area under the curve (AUC) combining poor olfaction and total NMS burden was 0.84 (CI 0.71-0.97), while AUC for turn steps was 0.91 (CI 0.81-1.00). Gait impairment, hyposmia, and NMS may be useful alone and in combination to identify DIP patients with underlying dopaminergic degeneration.