Functional and 123I-MIBG scintigraphy assessment of cardiac adrenergic dysfunction in diabetes

OBJECTIVES

To assess the agreement between clinical cardiovascular adrenergic function and cardiac adrenergic innervation in type 2 diabetes patients (T2D).

METHODS

Thirty-three patients with T2D were investigated bimodally through (1) a standardized clinical cardiovascular adrenergic assessment, evaluating adequacy of blood pressure responses to the Valsalva maneuver and (2) 123I-meta-iodobenzylguanidine (MIBG) scintigraphy assessing myocardial adrenergic innervation measured as early and delayed heart heart/mediastinum (H/M) ratio, and washout rate (WR).

RESULTS

T2D patients had significantly lower early and delayed H/M-ratios, and lower WR, compared to laboratory specific reference values. Thirteen patients had an abnormal adrenergic composite autonomic severity score (CASS > 0). Patients with abnormal CASS scores had significantly higher early H/M ratios (1.76 [1.66-1.88] vs. 1.57 [1.49-1.63], p < 0.001), higher delayed H/M ratios (1.64 [1.51:1.73] vs. 1.51 [1.40:1.61] (p = 0.02)), and lower WR (-0.13(0.10) vs -0.05(0.07), p = 0.01). Lower Total Recovery and shorter Pressure Recovery Time responses from the Valsalva maneuver was significantly correlated to lower H/M early (r = 0.55, p = 0.001 and r = 0.5, p = 0.003, respectively) and lower WR for Total Recovery (r = -0.44, p = 0.01).

CONCLUSION

The present study found impairment of sympathetic innervation in T2D patients based on parameters derived from MIBG cardiac scintigraphy (low early H/M, delayed H/M, and WR). These results confirm prior studies. We found a mechanistically inverted relationship with favourable adrenergic cardiovascular responses being significantly associated unfavourable MIBG indices for H/M early and delayed. This paradoxical relationship needs to be further explored but could indicate adrenergic hypersensitivity in cardiac sympathetic denervated T2D patients.

Cholinergic changes in Lewy body disease: implications for presentation, progression and subtypes

Cholinergic degeneration is significant in Lewy body disease, including Parkinson's disease, dementia with Lewy bodies, and isolated REM sleep behavior disorder. Extensive research has demonstrated cholinergic alterations in the central nervous system of these disorders. More recently, studies have revealed cholinergic denervation in organs that receive parasympathetic denervation. This enables a comprehensive review of cholinergic changes in Lewy body disease, encompassing both central and peripheral regions, various disease stages, and diagnostic categories. Across studies, brain regions affected in Lewy body dementia show equal or greater levels of cholinergic impairment compared to the brain regions affected in Lewy body disease without dementia. This observation suggests a continuum of cholinergic alterations between these disorders. Patients without dementia exhibit relative sparing of limbic regions, whereas occipital and superior temporal regions appear to be affected to a similar extent in patients with and without dementia. This implies that posterior cholinergic cell groups in the basal forebrain are affected in the early stages of Lewy body disorders, while more anterior regions are typically affected later in the disease progression. The topographical changes observed in patients affected by comorbid Alzheimer pathology may reflect a combination of changes seen in pure forms of Lewy body disease and those seen in Alzheimer's disease. This suggests that Alzheimer co-pathology is important to understand cholinergic degeneration in Lewy body disease. Thalamic cholinergic innervation is more affected in Lewy body patients with dementia compared to those without dementia, and this may contribute to the distinct clinical presentations observed in these groups. In patients with Alzheimer's disease, the thalamus is variably affected, suggesting a different sequential involvement of cholinergic cell groups in Alzheimer's disease compared to Lewy body disease. Patients with isolated REM sleep behavior disorder demonstrate cholinergic denervation in abdominal organs that receive parasympathetic innervation from the dorsal motor nucleus of the vagus, similar to patients who experienced this sleep disorder in their prodrome. This implies that REM sleep behavior disorder is important for understanding peripheral cholinergic changes in both prodromal and manifest phases of Lewy body disease. In conclusion, cholinergic changes in Lewy body disease carry implications for understanding phenotypes and the influence of Alzheimer co-pathology, delineating subtypes and pathological spreading routes, and for developing tailored treatments targeting the cholinergic system.

Impaired cholinergic integrity of the colon and pancreas in dementia with Lewy bodies

Dementia with Lewy bodies is characterized by a high burden of autonomic dysfunction and Lewy pathology in peripheral organs and components of the sympathetic and parasympathetic nervous system. Parasympathetic terminals may be quantified with 18F-fluoroetoxybenzovesamicol, a PET tracer that binds to the vesicular acetylcholine transporter in cholinergic presynaptic terminals. Parasympathetic imaging may be useful for diagnostics, improving our understanding of autonomic dysfunction and for clarifying the spatiotemporal relationship of neuronal degeneration in prodromal disease. Therefore, we aimed to investigate the cholinergic parasympathetic integrity in peripheral organs and central autonomic regions of subjects with dementia with Lewy bodies and its association with subjective and objective measures of autonomic dysfunction. We hypothesized that organs with known parasympathetic innervation, especially the pancreas and colon, would have impaired cholinergic integrity. To achieve these aims, we conducted a cross-sectional comparison study including 23 newly diagnosed non-diabetic subjects with dementia with Lewy bodies (74 ± 6 years, 83% male) and 21 elderly control subjects (74 ± 6 years, 67% male). We obtained whole-body images to quantify PET uptake in peripheral organs and brain images to quantify PET uptake in regions of the brainstem and hypothalamus. Autonomic dysfunction was assessed with questionnaires and measurements of orthostatic blood pressure. Subjects with dementia with Lewy bodies displayed reduced cholinergic tracer uptake in the pancreas (32% reduction, P = 0.0003) and colon (19% reduction, P = 0.0048), but not in organs with little or no parasympathetic innervation. Tracer uptake in a region of the medulla oblongata overlapping the dorsal motor nucleus of the vagus correlated with autonomic symptoms (rs = -0.54, P = 0.0077) and changes in orthostatic blood pressure (rs = 0.76, P < 0.0001). Tracer uptake in the pedunculopontine region correlated with autonomic symptoms (rs = -0.52, P = 0.0104) and a measure of non-motor symptoms (rs = -0.47, P = 0.0230). In conclusion, our findings provide the first imaging-based evidence of impaired cholinergic integrity of the pancreas and colon in dementia with Lewy bodies. The observed changes may reflect parasympathetic denervation, implying that this process is initiated well before the point of diagnosis. The findings also support that cholinergic denervation in the brainstem contributes to dysautonomia.

Severe cholinergic terminal loss in newly diagnosed dementia with Lewy bodies

Cholinergic changes play a fundamental role in the natural history of dementia with Lewy bodies and Lewy body disease in general. Despite important achievements in the field of cholinergic research, significant challenges remain. We conducted a study with four main objectives: (i) to examine the integrity of cholinergic terminals in newly diagnosed dementia with Lewy bodies; (ii) to disentangle the cholinergic contribution to dementia by comparing cholinergic changes in Lewy body patients with and without dementia; (iii) to investigate the in vivo relationship between cholinergic terminal loss and atrophy of cholinergic cell clusters in the basal forebrain at different stages of Lewy body disease; and (iv) to test whether any asymmetrical degeneration in cholinergic terminals would correlate with motor dysfunction and hypometabolism. To achieve these objectives, we conducted a comparative cross-sectional study of 25 newly diagnosed dementia with Lewy bodies patients (age 74 ± 5 years, 84% male), 15 healthy control subjects (age 75 ± 6 years, 67% male) and 15 Parkinson's disease patients without dementia (age 70 ± 7 years, 60% male). All participants underwent 18F-fluoroetoxybenzovesamicol PET and high-resolution structural MRI. In addition, we collected clinical 18F-fluorodeoxyglucose PET images. Brain images were normalized to standard space and regional tracer uptake and volumetric indices of basal forebrain degeneration were extracted. Patients with dementia showed spatially distinct reductions in cholinergic terminals across the cerebral cortex, limbic system, thalamus and brainstem. Also, cholinergic terminal binding in cortical and limbic regions correlated quantitatively and spatially with atrophy of the basal forebrain. In contrast, patients without dementia showed decreased cholinergic terminal binding in the cerebral cortex despite preserved basal forebrain volumes. In patients with dementia, cholinergic terminal reductions were most severe in limbic regions and least severe in occipital regions compared to those without dementia. Interhemispheric asymmetry of cholinergic terminals correlated with asymmetry of brain metabolism and lateralized motor function. In conclusion, this study provides robust evidence for severe cholinergic terminal loss in newly diagnosed dementia with Lewy bodies, which correlates with structural imaging measures of cholinergic basal forebrain degeneration. In patients without dementia, our findings suggest that loss of cholinergic terminal function occurs 'before' neuronal cell degeneration. Moreover, the study supports that degeneration of the cholinergic system is important for brain metabolism and may be linked with degeneration in other transmitter systems. Our findings have implications for understanding how cholinergic system pathology contributes to the clinical features of Lewy body disease, changes in brain metabolism and disease progression patterns.

Mitochondrial function-associated genes underlie cortical atrophy in prodromal synucleinopathies

Isolated rapid eye movement sleep behaviour disorder (iRBD) is a sleep disorder characterized by the loss of rapid eye movement sleep muscle atonia and the appearance of abnormal movements and vocalizations during rapid eye movement sleep. It is a strong marker of incipient synucleinopathy such as dementia with Lewy bodies and Parkinson's disease. Patients with iRBD already show brain changes that are reminiscent of manifest synucleinopathies including brain atrophy. However, the mechanisms underlying the development of this atrophy remain poorly understood. In this study, we performed cutting-edge imaging transcriptomics and comprehensive spatial mapping analyses in a multicentric cohort of 171 polysomnography-confirmed iRBD patients [67.7 ± 6.6 (49-87) years; 83% men] and 238 healthy controls [66.6 ± 7.9 (41-88) years; 77% men] with T1-weighted MRI to investigate the gene expression and connectivity patterns associated with changes in cortical thickness and surface area in iRBD. Partial least squares regression was performed to identify the gene expression patterns underlying cortical changes in iRBD. Gene set enrichment analysis and virtual histology were then done to assess the biological processes, cellular components, human disease gene terms, and cell types enriched in these gene expression patterns. We then used structural and functional neighbourhood analyses to assess whether the atrophy patterns in iRBD were constrained by the brain's structural and functional connectome. Moreover, we used comprehensive spatial mapping analyses to assess the specific neurotransmitter systems, functional networks, cytoarchitectonic classes, and cognitive brain systems associated with cortical changes in iRBD. All comparisons were tested against null models that preserved spatial autocorrelation between brain regions and compared to Alzheimer's disease to assess the specificity of findings to synucleinopathies. We found that genes involved in mitochondrial function and macroautophagy were the strongest contributors to the cortical thinning occurring in iRBD. Moreover, we demonstrated that cortical thinning was constrained by the brain's structural and functional connectome and that it mapped onto specific networks involved in motor and planning functions. In contrast with cortical thickness, changes in cortical surface area were related to distinct genes, namely genes involved in the inflammatory response, and to different spatial mapping patterns. The gene expression and connectivity patterns associated with iRBD were all distinct from those observed in Alzheimer's disease. In summary, this study demonstrates that the development of brain atrophy in synucleinopathies is constrained by specific genes and networks.

Thyroid [123I]MIBG uptake in Parkinson’s disease and diabetes mellitus

Thyroid [¹²³I]MIBG uptake is proposed as a tool for differentiating between Parkinson's disease (PD) and diabetes mellitus (DM) on [¹²³I]MIBG scintigraphies since both patient groups show decreased cardiac uptake. One study compared thyroid [¹²³I]MIBG uptake in DM and PD patients and reported reduced [¹²³I]MIBG uptake only in the PD group. Here, we investigated thyroid [¹²³I]MIBG uptake in patients with PD and DM and found severely reduced thyroid [¹²³I]MIBG uptake in DM. Larger studies are needed to substantiate whether DM patients are more or less likely to exhibit decreased thyroid MIBG uptake compared to controls and PD patients.

Dopaminergic Dysfunction Is More Symmetric in Dementia with Lewy Bodies Compared to Parkinson's Disease

BACKGROUND

The α-syn Origin site and Connectome model (SOC) proposes that α-synucleinopathies can be divided into two categories: the asymmetrical brain-first, and more symmetrical body-first Lewy body disease. We have hypothesized that most patients with dementia with Lewy bodies (DLB) belong to the body-first subtype, whereas patients with Parkinson's disease (PD) more often belong to the brain-first subtype.

OBJECTIVE

To compare asymmetry of striatal dopaminergic dysfunction in DLB and PD patients using [18F]-FE-PE2I positron emission tomography (PET).

METHODS

We analyzed [18F]-FE-PE2I PET data from 29 DLB patients and 76 PD patients who were identified retrospectively during a 5-year period at Dept. of Neurology, Aarhus University Hospital. Additionally, imaging data from 34 healthy controls was used for age-correction and visual comparison.

RESULTS

PD patients showed significantly more asymmetry in specific binding ratios between the most and least affected putamen (p < 0.0001) and caudate (p = 0.003) compared to DLB patients. PD patients also had more severe degeneration in the putamen compared to the caudate in comparison to DLB patients (p < 0.0001) who had a more universal pattern of striatal degeneration.

CONCLUSION

Patients with DLB show significantly more symmetric striatal degeneration on average compared to PD patients. These results support the hypothesis that DLB patients may be more likely to conform to the body-first subtype characterized by a symmetrical spread of pathology, whereas PD patients may be more likely to conform to the brain-first subtype with more lateralized initial propagation of pathology.

Disruption of Sleep Microarchitecture Is a Sensitive and Early Marker of Parkinson's Disease

BACKGROUND

Although sleep disturbances are highly prevalent in patients with Parkinson's disease, sleep macroarchitecture metrics show only minor changes.

OBJECTIVE

To assess alterations of the cyclic alternating pattern (CAP) as a critical feature of sleep microarchitecture in patients with prodromal, recent, and established Parkinson's disease.

METHODS

We evaluated overnight polysomnography for classic sleep macroarchitecture and CAP metrics in 68 patients at various disease stages and compared results to 22 age- and sex-matched controls.

RESULTS

Already at the prodromal stage, patients showed a significantly reduced CAP rate as a central characteristic of sleep microarchitecture. Temporal characteristics of CAP showed a gradual change over disease stages and correlated with motor performance. In contrast, the sleep macroarchitecture metrics did not differ between groups.

CONCLUSION

Data suggest that alterations of sleep microarchitecture are an early and more sensitive characteristic of Parkinson's disease than changes in sleep macroarchitecture.

[18F]FEOBV positron emission tomography may not be a suitable method to measure parasympathetic denervation in patients with Parkinson's disease

INTRODUCTION

The peripheral autonomic nervous system may be involved years before onset of motor symptoms in some patients with Parkinson's disease (PD). Specific imaging techniques to quantify the cholinergic nervous system in peripheral organs are an unmet need. We tested the hypothesis that patients with PD display decreased [¹⁸F]FEOBV uptake in peripheral organs - a sign of parasympathetic denervation.

METHODS

We included 15 PD patients and 15 age- and sex matched healthy controls for a 70 min whole-body dynamic positron emission tomography (PET) acquisition. Compartmental modelling was used for tracer kinetic analyses of adrenal gland, pancreas, myocardium, spleen, renal cortex, muscle and colon. Standard uptake values (SUV) at 60-70 min post injection were also extracted for these organs. Additionally, SUVs were also determined in the total colon, prostate, parotid and submandibular glands.

RESULTS

We found no statistically significant difference of [¹⁸F]FEOBV binding parameters in any organs between patients with PD and healthy controls, although trends were observed. The pancreas SUV showed a 14% reduction in patients (P = 0.021, not statistically significant after multiple comparison correction). We observed a trend towards lower SUVs in the pancreas, colon, adrenal gland, and myocardium of PD patients with versus without probable REM sleep behavior disorder.

CONCLUSION

[¹⁸F]FEOBV PET may not be a sensitive marker for parasympathetic degeneration in patients with PD.

Detection of companion galaxies around hot dust-obscured hyper-luminous galaxy W0410-0913

The phase transition between galaxies and quasars is often identified with the rare population of hyper-luminous, hot dust-obscured galaxies. Galaxy formation models predict these systems to grow via mergers, that can deliver large amounts of gas toward their centers, induce intense bursts of star formation and feed their supermassive black holes. Here we report the detection of 24 galaxies emitting Lyman-α emission on projected physical scales of about 400 kpc around the hyper-luminous hot dust-obscured galaxy W0410-0913, at redshift z = 3.631, using Very Large Telescope observations. While this indicates that W0410-0913 evolves in a very dense environment, we do not find clear signs of mergers that could sustain its growth. Data suggest that if mergers occurred, as models expect, these would involve less massive satellites, with only a moderate impact on the internal interstellar medium of W0410-0913, which is sustained by a rotationally-supported fast-rotating molecular disk, as Atacama Large Millimeter Array observations suggest.

Lyman-alpha emission is one of the observational probes for the high-redshift universe. Here, the authors show several Lyman-alpha emitting companion galaxies around the hot dust-obscured galaxy W0410-091 suggesting that the galaxy evolves in a very dense environment.

Imaging progressive peripheral and central dysfunction in isolated REM sleep behaviour disorder after 3 years of follow-up

INTRODUCTION

Most patients with isolated rapid eye movement sleep behaviour disorder (iRBD) convert to Parkinson's disease (PD), dementia with Lewy bodies, or multiple system atrophy within 15 years of diagnosis. Furthermore, iRBD patients develop non-motor symptoms similar to those of manifest PD patients and display dysfunction of the sympathetic and parasympathetic nervous system, comparable to that seen in PD. However, progression rates of autonomic dysfunction in iRBD have not been studied with objective measures in detail, which is the aim of this study.

METHODS

Twenty-two iRBD patients were included at baseline and 14 participated in follow-up after 3 years. Colonic transit time (CTT) was examined using radio opaque markers, colonic volume was defined on abdominal computed tomography (CT) scans, Iodine-123-metaiodobenzylguanidine ([123I]MIBG) scintigraphy was performed to assess cardiac sympathetic innervation, and 3,4-dihydroxy-6-(18F) fluoro-l-phenylalanine ([18F]FDOPA) positron emission tomography (PET) scan determined nigrostriatal dopamine storage capacity. All examinations were performed at baseline and after 3 years.

RESULTS

iRBD patients displayed increased CTT (p = 0.001) and colonic volume (p = 0.01) at follow-up compared to baseline. Furthermore, [123I]MIBG uptake and [18F]FDOPA uptake showed progressive reductions at follow-up (p = 0.02 and p = 0.002, respectively). No correlations were seen between changes in intestinal or cardiac measurements and dopaminergic function.

CONCLUSION

Using objective markers, the present study documented that intestinal dysfunction and cardiac sympathetic degeneration worsen in the majority of iRBD patients over a 3-year period. The absent correlation between these markers and nigrostriatal dopaminergic dysfunction suggests that progressive gastrointestinal and cardiac dysfunction in iRBD is caused mainly by non-dopaminergic mechanisms.

Alpha-Synuclein Strain Variability in Body-First and Brain-First Synucleinopathies

Pathogenic alpha-synuclein (asyn) aggregates are a defining feature of neurodegenerative synucleinopathies, which include Parkinson's disease, Lewy body dementia, pure autonomic failure and multiple system atrophy. Early accurate differentiation between these synucleinopathies is challenging due to the highly heterogeneous clinical profile at early prodromal disease stages. Therefore, diagnosis is often made in late disease stages when a patient presents with a broad range of motor and non-motor symptoms easing the differentiation. Increasing data suggest the clinical heterogeneity seen in patients is explained by the presence of distinct asyn strains, which exhibit variable morphologies and pathological functions. Recently, asyn seed amplification assays (PMCA and RT-QuIC) and conformation-specific ligand assays have made promising progress in differentiating between synucleinopathies in prodromal and advanced disease stages. Importantly, the cellular environment is known to impact strain morphology. And, asyn aggregate pathology can propagate trans-synaptically along the brain-body axis, affecting multiple organs and propagating through multiple cell types. Here, we present our hypothesis that the changing cellular environments, an asyn seed may encounter during its brain-to-body or body-to-brain propagation, may influence the structure and thereby the function of the aggregate strains developing within the different cells. Additionally, we aim to review strain characteristics of the different synucleinopathies in clinical and preclinical studies. Future preclinical animal models of synucleinopathies should investigate if asyn strain morphology is altered during brain-to-body and body-to-brain spreading using these seeding amplification and conformation-specific assays. Such findings would greatly deepen our understanding of synucleinopathies and the potential link between strain and phenotypic variability, which may enable specific diagnosis of different synucleinopathies in the prodromal phase, creating a large therapeutic window with potential future applications in clinical trials and personalized therapeutics.

Brain atrophy in prodromal synucleinopathy is shaped by structural connectivity and gene expression

Isolated REM sleep behaviour disorder (iRBD) is a synucleinopathy characterized by abnormal behaviours and vocalizations during REM sleep. Most iRBD patients develop dementia with Lewy bodies, Parkinson's disease, or multiple system atrophy over time. Patients with iRBD exhibit brain atrophy patterns that are reminiscent of those observed in overt synucleinopathies. However, the mechanisms linking brain atrophy to the underlying alpha-synuclein pathophysiology are poorly understood. Our objective was to investigate how the prion-like and regional vulnerability hypotheses of alpha-synuclein might explain brain atrophy in iRBD. Using a multicentric cohort of 182 polysomnography-confirmed iRBD patients who underwent T1-weighted MRI, we performed vertex-based cortical surface and deformation-based morphometry analyses to quantify brain atrophy in patients (67.8 years, 84% men) and 261 healthy controls (66.2 years, 75%) and investigated the morphological correlates of motor and cognitive functioning in iRBD. Next, we applied the agent-based Susceptible-Infected-Removed model (i.e., a computational model that simulates in silico the spread of pathologic alpha-synuclein based on structural connectivity and gene expression) and tested if it recreated atrophy in iRBD by statistically comparing simulated regional brain atrophy to the atrophy observed in patients. The impact of SNCA and GBA gene expression and brain connectivity was then evaluated by comparing the model fit to the one obtained in null models where either gene expression or connectivity was randomized. The results showed that iRBD patients present with cortical thinning and tissue deformation, which correlated with motor and cognitive functioning. Next, we found that the computational model recreated cortical thinning (r = 0.51, p = 0.0007) and tissue deformation (r = 0.52, p = 0.0005) in patients, and that the connectome's architecture along with SNCA and GBA gene expression contributed to shaping atrophy in iRBD. We further demonstrated that the full agent-based model performed better than network measures or gene expression alone in recreating the atrophy pattern in iRBD. In summary, atrophy in iRBD is extensive, correlates with motor and cognitive function, and can be recreated using the dynamics of agent-based modelling, structural connectivity, and gene expression. These findings support the concepts that both prion-like spread and regional susceptibility account for the atrophy observed in prodromal synucleinopathies. Therefore, the agent-based Susceptible-Infected-Removed model may be a useful tool for testing hypotheses underlying neurodegenerative diseases and new therapies aimed at slowing or stopping the spread of alpha-synuclein pathology.

A non-coding RNA balancing act: miR-346-induced DNA damage is limited by the long non-coding RNA NORAD in prostate cancer

BACKGROUND

miR-346 was identified as an activator of Androgen Receptor (AR) signalling that associates with DNA damage response (DDR)-linked transcripts in prostate cancer (PC). We sought to delineate the impact of miR-346 on DNA damage, and its potential as a therapeutic agent.

METHODS

RNA-IP, RNA-seq, RNA-ISH, DNA fibre assays, in vivo xenograft studies and bioinformatics approaches were used alongside a novel method for amplification-free, single nucleotide-resolution genome-wide mapping of DNA breaks (INDUCE-seq).

RESULTS

miR-346 induces rapid and extensive DNA damage in PC cells - the first report of microRNA-induced DNA damage. Mechanistically, this is achieved through transcriptional hyperactivation, R-loop formation and replication stress, leading to checkpoint activation and cell cycle arrest. miR-346 also interacts with genome-protective lncRNA NORAD to disrupt its interaction with PUM2, leading to PUM2 stabilisation and its increased turnover of DNA damage response (DDR) transcripts. Confirming clinical relevance, NORAD expression and activity strongly correlate with poor PC clinical outcomes and increased DDR in biopsy RNA-seq studies. In contrast, miR-346 is associated with improved PC survival. INDUCE-seq reveals that miR-346-induced DSBs occur preferentially at binding sites of the most highly-transcriptionally active transcription factors in PC cells, including c-Myc, FOXA1, HOXB13, NKX3.1, and importantly, AR, resulting in target transcript downregulation. Further, RNA-seq reveals widespread miR-346 and shNORAD dysregulation of DNA damage, replication and cell cycle processes. NORAD drives target-directed miR decay (TDMD) of miR-346 as a novel genome protection mechanism: NORAD silencing increases mature miR-346 levels by several thousand-fold, and WT but not TDMD-mutant NORAD rescues miR-346-induced DNA damage. Importantly, miR-346 sensitises PC cells to DNA-damaging drugs including PARP inhibitor and chemotherapy, and induces tumour regression as a monotherapy in vivo, indicating that targeting miR-346:NORAD balance is a valid therapeutic strategy.

CONCLUSIONS

A balancing act between miR-346 and NORAD regulates DNA damage and repair in PC. miR-346 may be particularly effective as a therapeutic in the context of decreased NORAD observed in advanced PC, and in transcriptionally-hyperactive cancer cells.

Clinical and imaging evidence of brain-first and body-first Parkinson's disease

Braak's hypothesis has been extremely influential over the last two decades. However, neuropathological and clinical evidence suggest that the model does not conform to all patients with Parkinson's disease (PD). To resolve this controversy, a new model was recently proposed; in brain-first PD, the initial α-synuclein pathology arise inside the central nervous system, likely rostral to the substantia nigra pars compacta, and spread via interconnected structures - eventually affecting the autonomic nervous system; in body-first PD, the initial pathological α-synuclein originates in the enteric nervous system with subsequent caudo-rostral propagation to the autonomic and central nervous system. By using REM-sleep behavior disorder (RBD) as a clinical identifier to distinguish between body-first PD (RBD-positive at motor symptom onset) and brain-first PD (RBD-negative at motor symptom onset), we explored the literature to evaluate clinical and imaging differences between these proposed subtypes. Body-first PD patients display: 1) a larger burden of autonomic symptoms - in particular orthostatic hypotension and constipation, 2) more frequent pathological α-synuclein in peripheral tissues, 3) more brainstem and autonomic nervous system involvement in imaging studies, 4) more symmetric striatal dopaminergic loss and motor symptoms, and 5) slightly more olfactory dysfunction. In contrast, only minor cortical metabolic alterations emerge before motor symptoms in body-first. Brain-first PD is characterized by the opposite clinical and imaging patterns. Patients with pathological LRRK2 genetic variants mostly resemble a brain-first PD profile whereas patients with GBA variants typically conform to a body-first profile. SNCA-variant carriers are equally distributed between both subtypes. Overall, the literature indicates that body-first and brain-first PD might be two distinguishable entities on some clinical and imaging markers.

Gastric Emptying Time and Volume of the Small Intestine as Objective Markers in Patients With Symptoms of Diabetic Enteropathy

Background/Aims

Patients with diabetes mellitus (DM) often suffer from gastrointestinal (GI) symptoms, but these correlate poorly to established objective GI motility measures. Our aim is to perform a detailed evaluation of potential measures of gastric and small intestinal motility in patients with DM type 1 and severe GI symptoms.

Methods

Twenty patients with DM and 20 healthy controls (HCs) were included. GI motility was examined with a 3-dimensional-Transit capsule, while organ volumes were determined by CT scans.

Results

Patients with DM and HCs did not differ with regard to median gastric contraction frequency (DM 3.0 contractions/minute [interquartile range {IQR}, 2.9-3.0]; HCs 2.9 [IQR, 2.8-3.1]; P = 0.725), amplitude of gastric contractions (DM 9 mm [IQR, 8-11]; HCs 11 mm (IQR, 9-12); P = 0.151) or fasting volume of the stomach wall (DM 149 cm3 [IQR, 112-187]; HCs 132 cm3 [IQR, 107-154]; P = 0.121). Median gastric emptying time was prolonged in patients (DM 3.3 hours [IQR, 2.6-4.6]; HCs 2.4 hours [IQR, 1.8-2.7]; P = 0.002). No difference was found in small intestinal transit time (DM 5 hours [IQR, 3.7-5.6]; HCs 4.8 hours [IQR, 3.9-6.0]; P = 0.883). However, patients with DM had significantly larger volume of the small intestinal wall (DM 623 cm3 [IQR, 487-766]; HCs 478 cm3 [IQR, 393-589]; P = 0.003). Among patients, 13 (68%) had small intestinal wall volume and 9 (50%) had gastric emptying time above the upper 95% percentile of HCs.

Conclusion

In our study, gastric emptying time and volume of the small intestinal wall appeared to be the best objective measures in patients with DM type 1 and symptoms and gastroenteropathy.

Asymmetric Dopaminergic Dysfunction in Brain-First versus Body-First Parkinson's Disease Subtypes

BACKGROUND

We have hypothesized that Parkinson's disease (PD) comprises two subtypes. Brain-first, where pathogenic α-synuclein initially forms unilaterally in one hemisphere leading to asymmetric nigrostriatal degeneration, and body-first with initial enteric pathology, which spreads through overlapping vagal innervation leading to more symmetric brainstem involvement and hence more symmetric nigrostriatal degeneration. Isolated REM sleep behaviour disorder has been identified as a strong marker of the body-first type.

OBJECTIVE

To analyse striatal asymmetry in [18F]FDOPA PET and [123I]FP-CIT DaT SPECT data from iRBD patients, de novo PD patients with RBD (PD +RBD) and de novo PD patients without RBD (PD - RBD). These groups were defined as prodromal body-first, de novo body-first, and de novo brain-first, respectively.

METHODS

We included [18F]FDOPA PET scans from 21 iRBD patients, 11 de novo PD +RBD, 22 de novo PD - RBD, and 18 controls subjects. Also, [123I]FP-CIT DaT SPECT data from iRBD and de novo PD patients with unknown RBD status from the PPPMI dataset was analysed. Lowest putamen specific binding ratio and putamen asymmetry index (AI) was defined.

RESULTS

Nigrostriatal degeneration was significantly more symmetric in patients with RBD versus patients without RBD or with unknown RBD status in both FDOPA (p = 0.001) and DaT SPECT (p = 0.001) datasets.

CONCLUSION

iRBD subjects and de novo PD +RBD patients present with significantly more symmetric nigrostriatal dopaminergic degeneration compared to de novo PD - RBD patients. The results support the hypothesis that body-first PD is characterized by more symmetric distribution most likely due to more symmetric propagation of pathogenic α-synuclein compared to brain-first PD.

Regional locus coeruleus degeneration is uncoupled from noradrenergic terminal loss in Parkinson's disease

Previous studies have reported substantial involvement of the noradrenergic system in Parkinson's disease. Neuromelanin-sensitive MRI sequences and PET tracers have become available to visualize the cell bodies in the locus coeruleus and the density of noradrenergic terminal transporters. Combining these methods, we investigated the relationship of neurodegeneration in these distinct compartments in Parkinson's disease. We examined 93 subjects (40 healthy controls and 53 Parkinson's disease patients) with neuromelanin-sensitive turbo spin-echo MRI and calculated locus coeruleus-to-pons signal contrasts. Voxels with the highest intensities were extracted from published locus coeruleus coordinates transformed to individual MRI. To also investigate a potential spatial pattern of locus coeruleus degeneration, we extracted the highest signal intensities from the rostral, middle, and caudal third of the locus coeruleus. Additionally, a study-specific probabilistic map of the locus coeruleus was created and used to extract mean MRI contrast from the entire locus coeruleus and each rostro-caudal subdivision. Locus coeruleus volumes were measured using manual segmentations. A subset of 73 subjects had 11C-MeNER PET to determine noradrenaline transporter density, and distribution volume ratios of noradrenaline transporter-rich regions were computed. Parkinson's disease patients showed reduced locus coeruleus MRI contrast independently of the selected method (voxel approaches: p < 0.0001, p < 0.001; probabilistic map: p < 0.05), specifically on the clinically-defined most affected side (p < 0.05), and reduced locus coeruleus volume (p < 0.0001). Reduced MRI contrast was confined to the middle and caudal locus coeruleus (voxel approach-rostral: p = 0.48, middle: p < 0.0001, and caudal: p < 0.05; probabilistic map-rostral: p = 0.90, middle: p < 0.01, and caudal: p < 0.05). The noradrenaline transporter density was lower in Parkinson's disease patients in all examined regions (group effect p < 0.0001). No significant correlation was observed between locus coeruleus MRI contrast and noradrenaline transporter density. In contrast, the individual ratios of noradrenaline transporter density and locus coeruleus MRI contrast were lower in Parkinson's disease patients in all examined regions (group effect p < 0.001). Our multimodal imaging approach revealed pronounced noradrenergic terminal loss relative to cellular locus coeruleus degeneration in Parkinson's disease; the latter followed a distinct spatial pattern with the middle-caudal portion being more affected than the rostral part. The data shed first light on the interaction between the axonal and cell body compartments and their differential susceptibility to neurodegeneration in Parkinson's disease, which may eventually direct research toward potential novel treatment approaches.

Vagus Nerve Cross-Sectional Area in Patients With Parkinson's Disease-An Ultrasound Case-Control Study

Background: Vagal parasympathetic neurons are prone to degeneration in Parkinson's disease (PD). High-resolution ultrasound can precisely estimate the cross-sectional (CSA) area of peripheral nerves. Here, we tested the hypothesis that vagus CSA is reduced in PD. Methods: We included 56 healthy controls (HCs) and 63 patients with PD. Using a high-end ultrasound system equipped with a high-frequency transducer, five images were obtained of each nerve. The hypoechoic neuronal tissue was delineated offline with dedicated software and the CSA extracted. Results: In the initial PD vs. HC comparison, no statistically significant differences were observed in mean left vagus CSA (HC: 1.97 mm2, PD: 1.89 mm2, P = 0.36) nor in mean right vagus CSA (HC: 2.37 mm2, PD: 2.23 mm2, P = 0.17). The right vagus CSA was significantly larger than the left vagus CSA in both groups (P < 0.0001). Females were overrepresented in the HC group and presented with generally smaller vagus CSAs. Consequently, sex-adjusted CSA was significantly smaller for the right vagus nerve of the PD group (P = 0.041), but not for the left. Conclusion: A small but significant reduction in sex-adjusted right vagus CSA was observed in patients with PD. The left vagus CSA was not significantly reduced in patients with PD. Ultrasound may not be a suitable method to detecting vagal axonal loss in individual patients.

Microsleep disturbances are associated with noradrenergic dysfunction in Parkinson's disease

STUDY OBJECTIVES

Parkinson's disease (PD) commonly involves degeneration of sleep-wake regulating brainstem nuclei; likewise, sleep-wake disturbances are highly prevalent in PD patients. As polysomnography macroparameters typically show only minor changes in PD, we investigated sleep microstructure, particularly cyclic alternating pattern (CAP), and its relation to alterations of the noradrenergic system in these patients.

METHODS

We analysed 27 PD patients and 13 healthy control (HC) subjects who underwent over-night polysomnography and 11C-MeNER positron emission tomography for evaluation of noradrenaline transporter density. Sleep macroparameters as well as CAP metrics were evaluated according to the consensus statement from 2001. Statistical analysis comprised group comparisons and correlation analysis of CAP metrics with clinical characteristics of PD patients as well as noradrenaline transporter density.

RESULTS

PD patients and HC subjects were comparable in demographic characteristics (age, sex, body mass index) and polysomnography macroparameters. CAP rate as well as A index differed significantly between groups, with PD patients having a lower CAP rate (46.7 ± 6.6% versus 38.0 ± 11.6%, p = 0.015) and lower A index (49.0 ± 8.7/hour versus 40.1 ± 15.4/hour, p = 0.042). In PD patients, both CAP metrics correlated significantly with diminished noradrenaline transporter density in arousal prompting brainstem nuclei (locus coeruleus, raphe nuclei) as well as arousal propagating brain structures like thalamus and bitemporal cortex.

CONCLUSIONS

Sleep microstructure is more severely altered than sleep macrostructure in PD patients and is associated with widespread dysfunction of the noradrenergic arousal system.

Preserved noradrenergic function in Parkinson's disease patients with rest tremor

Noradrenergic neurotransmission may play an important role in tremor modulation through its innervation of key structures of the central tremor circuits. Here, Parkinson's disease (PD) patients with (PD^T+) or without (PD^T-) rest tremor had ¹¹C-methylreboxetine(¹¹C-MeNER) positron emission tomography (PET) to test the hypothesis that noradrenaline terminal function was relatively preserved in PD^T+ compared to PD^T-.

METHODS

Sixty-five PD patients and 28 healthy controls (HC) were scanned with ¹¹C-MeNER PET. Patients were categorized as PD^T+ if subscores in UPDRS-III item 3 or MDS-UPDRS-III item 17 was ≥2; remaining were categorized as PD^T-. Simplified reference tissue model 2 distribution volume ratios (DVR) for ¹¹C-MeNER were calculated for thalamus, dorsal and median raphe, locus coeruleus (LC) and red nucleus using time activity curves (TACs) obtained from volumes of interest (VOI). Data were statistically interrogated with a general linear mixed model using 'region', and 'group' as factors and the interaction of 'region x group' was examined.

RESULTS

Tremor positive PD patients had a significantly higher mean ¹¹C-MeNER DVR compared to PD^T- in LC and thalamus. The PD^T+ mean LC DVR was similar to that of HC. PD^T+ mean ¹¹C-MeNER DVRs were significantly lower than HC in the dorsal raphe while the PD^T- group showed significantly lower mean ¹¹C-MeNER DVR across all regions compared to HC.

CONCLUSION

While both PD ^T+ and PD ^T- groups showed a significant loss of noradrenaline terminal function compared to controls, noradrenergic neurons were relatively preserved in PD^T+ in LC and thalamus. The greater loss of noradrenergic transporters in PD^T- in LC and thalamus compared with PD^T+ is in line with earlier in-vitro studies and could potentially contribute to their tremor negative phenotype.

Brain-first versus body-first Parkinson’s disease: a multimodal imaging case-control study

Parkinson’s disease is characterized by the presence of abnormal, intraneuronal α-synuclein aggregates, which may propagate from cell-to-cell in a prion-like manner. However, it remains uncertain where the initial α-synuclein aggregates originate. We have hypothesized that Parkinson’s disease comprises two subtypes. A brain-first (top-down) type, where α-synuclein pathology initially arises in the brain with secondary spreading to the peripheral autonomic nervous system; and a body-first (bottom-up) type, where the pathology originates in the enteric or peripheral autonomic nervous system and then spreads to the brain. We also hypothesized that isolated REM sleep behaviour disorder (iRBD) is a prodromal phenotype for the body-first type. Using multimodal imaging, we tested the hypothesis by quantifying neuronal dysfunction in structures corresponding to Braak stages I, II and III involvement in three distinct patient groups. We included 37 consecutive de novo patients with Parkinson’s disease into this case-control PET study. Patients with Parkinson’s disease were divided into 24 RBD-negative (PDRBD−) and 13 RBD-positive cases (PDRBD+) and a comparator group of 22 iRBD patients. We used 11C-donepezil PET/CT to assess cholinergic (parasympathetic) innervation, 123I-metaiodobenzylguanidine (MIBG) scintigraphy to measure cardiac sympathetic innervation, neuromelanin-sensitive MRI to measure the integrity of locus coeruleus pigmented neurons, and 18F-dihydroxyphenylalanine (FDOPA) PET to assess putaminal dopamine storage capacity. Colon volume and transit times were assessed with CT scans and radiopaque markers. Imaging data from the three groups were interrogated with ANOVA and Kruskal-Wallis tests corrected for multiple comparisons. The PDRBD− and PDRBD+ groups showed similar marked reductions in putaminal FDOPA-specific uptake, whereas two-thirds of iRBD patients had normal scans (P &lt; 10−13, ANOVA). When compared to the PDRBD− patients, the PDRBD+ and iRBD patients showed reduced mean MIBG heart:mediastinum ratios (P &lt; 10−5, ANOVA) and colon 11C-donepezil standard uptake values (P = 0.008, ANOVA). The PDRBD+ group trended towards a reduced mean MRI locus coeruleus: pons ratio compared to PDRBD− (P = 0.07, t-test). In comparison to the other groups, the PDRBD+ group also had enlarged colon volumes (P &lt; 0.001, ANOVA) and delayed colonic transit times (P = 0.01, Kruskal-Wallis). The combined iRBD and PDRBD+ patient data were compatible with a body-first trajectory, characterized by initial loss of cardiac MIBG signal and 11C-colonic donepezil signal followed by loss of putaminal FDOPA uptake. In contrast, the PDRBD− data were compatible with a brain-first trajectory, characterized by primary loss of putaminal FDOPA uptake followed by a secondary loss of cardiac MIBG signal and 11C-donepezil signal. These findings support the existence of brain-first and body-first subtypes of Parkinson’s disease.

Normative values for gastric motility assessed with the 3D-transit electromagnetic tracking system

BACKGROUND

The Motilis 3D-Transit system allows ambulatory description of transit patterns throughout the gastrointestinal tract and offers an alternative method for studying gastric motility. We aimed to establish normative values for gastric motility assessed with the method.

METHOD

A total of 132 healthy volunteers ingested the 3D-Transit capsule for assessment of gastrointestinal transit times. Recordings from 125 subjects were used for definition of normative values. Forty-six subjects were studied on two consecutive days. Recordings were reanalyzed using newly developed software providing information on gastric emptying (GE) as well as contraction frequency and movement during gastric contractions.

RESULTS

The median GE time was 2.7 hours (range 0.1-21.2). In 89% of subjects, the capsule passed the pylorus within a postingestion period of 6 hours. The median frequency of gastric contractions was 3.1 per minute (range 2.6-3.8). The frequency was higher in women (3.2, range 2.7-3.8) than in men (3.0, range 2.6-3.5) and increased with age (0.004 per year) (P < .05). The median amplitudes were 35° (range 4-85) when based on rotation of the capsule and 11 mm (range 6-31) when based on capsule change in position. The rotation amplitude was higher in women and decreased with increasing BMI (P < .05). The position amplitude was also higher in women and increased with the amount of calories in the test meal, but decreased with increasing BMI and age (P < .05). Day-to-day variation (P > .05) was considerable while inter-rater variability was small.

CONCLUSION AND INFERENCES

We have established normative values for gastric motility assessed with the 3D-Transit system.

A Screening-Based Method for Identifying Patients with REM Sleep Behaviour Disorder in a Danish Community Setting

Isolated REM sleep behaviour disorder (iRBD) is a predictive marker of prodromal Lewy body disease. iRBD prevalence in the general population is around 1%, but it remains under-diagnosed, even though symptoms are alleviated by medication. We developed a population screening strategy and identified 16 iRBD patients by conducting telephone interviews and polysomnography examinations. We compared our population-screened cohort with sleep-center referred patients and found higher MoCA scores and lower MDS-UPDRS-III scores in our patients. In conclusion, screening can be used to identify iRBD patients in a cost-effective manner with the benefit of identifying patients at a very early disease stage.

In vivo positron emission tomography imaging of decreased parasympathetic innervation in the gut of vagotomized patients

BACKGROUND

Parasympathetic neuropathy is a key feature in many common disorders, including diabetes, neurological disorders, and cancers, but few objective methods exist for assessing damage to the parasympathetic nervous system, particularly in the gastrointestinal system. This study aimed to validate the use of ¹¹ C-donepezil positron emission tomography (PET) to assess parasympathetic integrity in a group of vagotomized patients.

METHODS

Sixteen healthy controls and 12 patients, vagotomized due to esophagectomy, underwent ¹¹ C-donepezil PET, measurement of colonic transit time, quantification of plasma pancreatic polypeptide (PP), and assessment of subjective long-term symptoms.

KEY RESULTS

Vagotomized patients had significantly decreased PET signal in the small intestine and colon compared with healthy controls (5.7 [4.4-7.9] vs 7.4 [4.5-11.3], P = .01 and 1.4 [1.1-2.1] vs 1.6 [1.4-2.4], P < .01, respectively). Vagotomized patients also displayed a significantly increased colonic transit time (2.9 ± 0.9 h vs 1.9 ± 0.8 h), P < .01 and increased volumes of the small intestine and colon (715 ccm [544-1177] vs 443 ccm [307-613], P < .01 and 971 ccm [713-1389] vs 711 ccm [486-1394], P = .01, respectively). Patients and controls did not differ in PP ratio levels after sham feeding, but PP ratio at 10 minutes. after sham feeding and PET signal intensity in the small intestine was positively correlated (P = .03).

CONCLUSIONS AND INFERENCES

We found significantly decreased ¹¹ C-donepezil signal in the intestine of vagotomized patients, supporting that ¹¹ C-donepezil PET is a valid measure of intestinal parasympathetic denervation.

Normative values for region-specific colonic and gastrointestinal transit times in 111 healthy volunteers using the 3D-Transit electromagnet tracking system: Influence of age, gender, and body mass index

BACKGROUND

The 3D-Transit electromagnet tracking system (Motilis Medica, SA, Lausanne, Switzerland) is an emerging tool for the ambulatory assessment of gastrointestinal (GI) transit and motility. Using this tool, we aimed to derive normative values for region-specific colonic and GI transit times and to assess the influence of age, gender, and body mass index (BMI).

METHODS

Regional and total colonic transit times (CTT), gastric emptying (GET), small intestinal (SITT), and whole gut (WGTT) transit times were extracted from 111 healthy volunteers from the United Kingdom and Denmark (58 female; median age: 40 years [range: 21-88]). The effects of age, gender, and BMI were assessed using standard statistical methods.

KEY RESULTS

The ascending, transverse, descending, and rectosigmoid colon transit times accounted for 32%, 34%, 17%, and 17% of total CTT in females, and 33%, 25%, 14%, and 28% of total CTT in males. CTT and WGTT were seen to cluster at intervals separated by approximately 24 hours, providing further evidence of the non-continuous nature of these measurements. Increasing age was associated with longer CTT (P = .021), WGTT (P < .001) ascending (P = .004), transverse (P < .001), and total right (P < .001) colon transit times, but shorter rectosigmoid (P = .004) transit time. Female gender was significantly associated with longer transverse (P = .049) and descending (P < .001) colon transit times, but shorter rectosigmoid (P < .001) transit time. Increasing BMI was significantly associated with shorter WGTT (P = .012).

CONCLUSIONS AND INFERENCES

For the first time, normative reference values for region-specific colonic transit have been presented. Age, gender, and BMI were seen to have an effect on transit times.

Enteric cholinergic neuropathy in patients with diabetes: Non-invasive assessment with positron emission tomography

BACKGROUND

¹¹ C-Donepezil positron emission tomography (PET) allows non-invasive assessment of cholinergic innervation of visceral organs. We aimed to compare cholinergic innervation in the gut in patients with diabetes mellitus (DM) and in healthy controls (HC).

METHODS

¹¹ C-Donepezil PET and computed tomography (CT) were performed in 19 patients with type 1 DM and gastrointestinal symptoms and in 19 age- and sex-matched HC in a cross-sectional design.

KEY RESULTS

All patients had severe gastrointestinal symptoms when assessed by standard questionnaires. DM patients had significantly increased volume of the small intestinal wall (DM: median 557 cm³ [interquartile range [IQR] 446-697] vs HC median: 448 cm³ [IQR; 341-518; P < .01]), and the ¹¹ C Donepezil PET uptake was reduced in patients (DM: median 7.08 standardized uptake value [SUV] [IQR; 5.94-8.43] vs HC: median 9.18 SUV [IQR; 8.57-10.11; P < .01]). A similar pattern was found in colon (DM: median volume 1064 cm³ [IQR; 882-1312] vs HC: median 939 cm³ [IQR; 785-1081; P = .13] and DM: median 1.22 SUV (IQR; 1.08-1.36) vs HC: median 1.42 SUV (IQR; 1.32-1.53; P = .03). Furthermore, patients had significantly reduced pancreatic volume (DM: median 53 cm³ [IQR; 41-69] vs HC: median 98 cm³ [IQR;82-110; P < .01]) and reduced PET uptake of the pancreas (DM: median 13.14 SUV [IQR;9.58-15.82] vs HC: median 21.46 SUV [IQR;18.97-24.06; P < .01]) as well as the adrenal gland (DM: median 7.62 SUV [IQR;7.61;15.82] vs HC: median 15.51 SUV [IQR;12.22;19.49; P = .03]).

CONCLUSION AND INFERENCES

Assessed with ¹¹ C-Donepezil PET/CT, patients with DM and severe bowel symptoms have reduced cholinergic innervation of the gut indicative of parasympathetic denervation.

Cardiac 11C-Donepezil Binding Increases With Age in Healthy Humans: Potentially Signifying Sigma-1 Receptor Upregulation

BACKGROUND

Donepezil may have cardioprotective properties, but the mechanism is unclear. Using positron-emission tomography (PET), we explored 11C-donepezil uptake in the heart of humans in relation to age. The results are discussed in the context of the cardioprotective property of donepezil.

METHODS

We included data from 57 patients with cardiac 11C-donepezil PET scans. Linear regression analyses were performed to explore the correlation between cardiac 11C-donepezil standardized uptake value (SUV) and age. Subgroup analyses were performed for healthy controls, patients with prodromal or diagnosed Parkinson disease (PD), males, and females.

RESULTS

In the total group of 57 patients, linear regression analysis revealed a significant positive correlation between cardiac 11C-donepezil uptake and age ( r2 = .63, P < .0001). The average increase was ≈1.25 SUV per decade and a 2-fold increase in SUV from age 30 to 65 years. Subgroup analyses also showed significant correlations: healthy control patients alone (n = 28, r2 = .73, P < .0001), prodromal or diagnosed PD (n = 29, r2 = .28, P = .03), male patients (n = 34, r2 = .49, P < .0001), and female patients (n = 23, r2 = .82, P < .0001). No other organs showed increased 11C-donepezil binding with age.

CONCLUSIONS

11C-donepezil SUV increases robustly with age in the normal human heart. We speculate that the increased donepezil binding is caused primarily by sigma-1 receptor upregulation. If our interpretation is correct, it shows that sigma-1 receptors are dynamically regulated and may represent an overlooked target for pharmacological intervention studies.

Imaging the Autonomic Nervous System in Parkinson's Disease

PURPOSE OF REVIEW

Patients with Parkinson's disease (PD) often display gastrointestinal and genitourinary autonomic symptoms years or even decades prior to diagnosis. These symptoms are thought to be caused in part by pathological α-synuclein inclusions in the peripheral autonomic and enteric nervous systems. It has been proposed that the initial α-synuclein aggregation may in some PD patients originate in peripheral nerve terminals and then spread centripetally to the spinal cord and brainstem. In vivo imaging methods can directly quantify the degeneration of the autonomic nervous system as well as the functional consequences such as perturbed motility. Here, we review the methodological principles of these imaging techniques and the major findings in patients with PD and atypical parkinsonism.

RECENT FINDINGS

Loss of sympathetic and parasympathetic nerve terminals in PD can be visualized using radiotracer imaging, including ¹²³I-MIBG scintigraphy, and ¹⁸F-dopamine and ¹¹C-donepezil PET. Recently, ultrasonographical studies disclosed reduced diameter of the vagal nerves in PD patients. Radiological and radioisotope techniques have demonstrated dysmotility and prolonged transit time throughout all subdivisions of the gastrointestinal tract in PD. The prevalence of objective dysfunction as measured with these imaging methods is often considerably higher compared to the prevalence of subjective symptoms experienced by the patients. Degeneration of the autonomic nervous system may play a key role in the pathogenesis of PD. In vivo imaging techniques provide powerful and noninvasive tools to quantify the degree and extent of this degeneration and its functional consequences.

Pancreatic Polypeptide in Parkinson's Disease: A Potential Marker of Parasympathetic Denervation

BACKGROUND AND OBJECTIVES

Parkinson's disease (PD) patients experience several non-motor symptoms from the gastrointestinal tract that may partly be caused by parasympathetic deficiency. The pancreas is densely innervated by the vagus nerve, which mediates early meal-induced secretion of pancreatic polypeptide (PP). Early secretion after sham feeding has been validated as a marker of vagal integrity. Thus, the aim was to evaluate the ratio of increased PP plasma levels after sham feeding in PD and correlate findings with gastrointestinal transit time (GITT).

METHODS

Twenty-five PD patients and 17 controls were included. PP, insulin, and blood glucose levels were measured before, during, and after sham feeding with white bread and chocolate spread. GITT was measured using radiopaque markers. Furthermore, faeces samples were analyzed for pancreatic elastase enzyme as a marker of exocrine pancreatic function.

RESULTS

PD patients showed significantly lower PP ratio levels after sham feeding, which was most pronounced at 10 minutes. No significant association was seen between attenuated PP response and GITT in PD patients. No between-group differences were seen in glucose or insulin levels over time, but PD patients showed generally lower insulin levels compared to controls. No difference was found in faeces pancreatic elastase.

CONCLUSIONS

Early-to-moderate stage PD patients demonstrated significantly decreased PP response after sham feeding suggestive of vagal denervation.

Gastrointestinal transit time and heart rate variability in patients with mild acquired brain injury

Background

Constipation is suspected to occur frequently after acquired brain injury (ABI). In patients with ABI, heart rate variability (HRV) is reduced suggesting autonomic dysfunction. Autonomic dysfunction may be associated with prolonged gastrointestinal transit time (GITT). The primary aim of this study was to investigate if GITT is prolonged in patients with ABI. Secondarily, HRV and its correlation with GITT was investigated.

Methods

We included 25 patients with ABI (18 men, median age: 61.3 years, range [30.7-74.5]). GITT was assessed using radio-opaque markers and HRV was calculated from 24-hour electrocardiograms. Medical records were reviewed for important covariates, including primary diagnosis, time since injury, functional independence measure, and use of medication. The GITT assessed in patients was compared to a control group of 25 healthy subjects (18 men, median age: 61.5 years, range [34.0-70.9]).

Results

In ABI patients, the mean GITT was significantly longer than in healthy controls (2.68 days, 95% CI [2.16-3.19] versus (1.92 days, 95% CI [1.62-2.22], p = 0.011)). No correlation was found between HRV and GITT.

Conclusion

Patients with mild to moderate ABI have prolonged GITT unrelated to the HRV.

Gastric emptying in Parkinson's disease - A mini-review

Patients with Parkinson's disease (PD) experience a range of non-motor symptoms, including constipation and other gastrointestinal problems. These symptoms are sometimes present in the prodromal disease phase. An improved understanding of the underlying pathophysiology is needed considering that PD has been hypothesized to originate in the gut. Delayed gastric emptying time (GET) is often listed as a prevalent gastrointestinal symptom in PD, but the true prevalence is controversial. The aim of this short review was to investigate if GET in PD is dependent on the applied measuring methodology. A systemic search of Pubmed identified 15 relevant studies, including six using gold standard method gastric scintigraphy and nine using ¹³C-octanoate breath tests. Overall, gastric scintigraphy studies showed a non-significant GET delay (standardized mean difference (SMD) 0.42) in PD patients. After exclusion of one outlier study, GET was significantly increased (SMD 0.59). In contrast, highly significant GET delay (SMD 1.70) was seen in breath test studies. A limitation of the meta-analyses was reuse of the same control group in some studies. In summary, the marked GET delay observed in breath test studies is not confirmed by gold standard gastric scintigraphy studies. This discrepancy can perhaps be explained by breath test being an indirect GET measure, depending not only on mechanic stomach emptying but also intestinal absorption and liver metabolism. Thus, multi-modality studies under standardized conditions are needed to elucidate the prevalence and severity of gastric dysmotility in PD, along with contributions from other factors including intestinal absorption and permeability.

In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study

BACKGROUND

Accumulating evidence suggests that α-synuclein aggregates-a defining pathology of Parkinson's disease-display cell-to-cell transmission. α-synuclein aggregation is hypothesised to start in autonomic nerve terminals years before the appearance of motor symptoms, and subsequently spread via autonomic nerves to the spinal cord and brainstem. To assess this hypothesis, we investigated sympathetic, parasympathetic, noradrenergic, and dopaminergic innervation in patients with idiopathic rapid eye movement (REM) sleep behaviour disorder, a prodromal phenotype of Parkinson's disease.

METHODS

In this prospective, case-control study, we recruited patients with idiopathic REM sleep behaviour disorder, confirmed by polysomnography, without clinical signs of parkinsonism or dementia, via advertisement and through sleep clinics in Denmark. We used ¹¹C-donepezil PET and CT to assess cholinergic (parasympathetic) gut innervation, ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy to measure cardiac sympathetic innervation, neuromelanin-sensitive MRI to measure integrity of pigmented neurons of the locus coeruleus, ¹¹C-methylreboxetine (MeNER) PET to assess noradrenergic nerve terminals originating in the locus coeruleus, and ¹⁸F-dihydroxyphenylalanine (DOPA) PET to assess nigrostriatal dopamine storage capacity. For each imaging modality, we compared patients with idiopathic REM sleep behaviour disorder with previously published reference data of controls without neurological disorders or cognitive impairment and with symptomatic patients with Parkinson's disease. We assessed imaging data using one-way ANOVA corrected for multiple comparisons.

FINDINGS

Between June 3, 2016, and Dec 19, 2017, we recruited 22 consecutive patients with idiopathic REM sleep behaviour disorder to the study. Compared with controls, patients with idiopathic REM sleep behaviour disorder had decreased colonic ¹¹C-donepezil uptake (-0·322, 95% CI -0·112 to -0·531; p=0·0020), ¹²³I-MIBG heart:mediastinum ratio (-0·508, -0·353 to -0·664; p<0·0001), neuromelanin-sensitive MRI locus coeruleus:pons ratio (-0·059, -0·019 to -0·099; p=0·0028), and putaminal ¹⁸F-DOPA uptake (Ki; -0·0023, -0·0009 to -0·0037; p=0·0013). No between-group differences were detected between idiopathic REM sleep behaviour disorder and Parkinson's disease groups with respect to ¹¹C-donepezil (p=0·39), ¹²³I-MIBG (p>0·99), neuromelanin-sensitive MRI (p=0·96), and ¹¹C-MeNER (p=0·56). By contrast, 15 (71%) of 21 patients with idiopathic REM sleep behaviour disorder had ¹⁸F-DOPA Ki values within normal limits, whereas all patients with Parkinson's disease had significantly decreased ¹⁸F-DOPA Ki values when compared with patients with idiopathic REM sleep behaviour disorder (p<0·0001).

INTERPRETATION

Patients with idiopathic REM sleep behaviour disorder had fully developed pathology in the peripheral autonomic nervous system and the locus coeruleus, equal to that in diagnosed Parkinson's disease. These patients also showed noradrenergic thalamic denervation, but most had normal putaminal dopaminergic storage capacity. This caudorostral gradient of dysfunction supports the hypothesis that α-synuclein pathology in Parkinson's disease initially targets peripheral autonomic nerves and then spreads rostrally to the brainstem.

FUNDING

Lundbeck Foundation, Jascha Foundation, and the Swiss National Foundation.

Gastrointestinal Transit Time in Parkinson's Disease Using a Magnetic Tracking System

BACKGROUND

Symptoms from the gastrointestinal tract are highly prevalent in Parkinson's disease (PD), but knowledge of the underlying pathology is incomplete and valid objective markers on regional gastrointestinal function are limited.

OBJECTIVE

The aims were to evaluate gastrointestinal transit time and motility in PD patients and controls.

METHODS

Twenty-two PD patients and 15 controls were included. Gastric-, small intestinal-, and caecum-ascending colonic transit times as well as colonic motility, defined as mass- and fast movements, were performed using the ambulatory 3D-Transit system. Gastrointestinal transit time with radio opaque markers, gastric emptying scintigraphy, and subjective non-motor symptoms were also evaluated.

RESULTS

Using the 3D-Transit system, the patient group displayed significantly longer small intestinal- and caecum-ascending transit times (p = 0.030 and p = 0.0063). No between-group difference was seen in gastric transit time (p = 0.91). Time to first mass- and fast colonic movement were significantly increased in PD (p = 0.023 and p = 0.006). Radio opaque marker gastrointestinal transit time was significantly increased in the patient group (p < 0.0001), whereas no difference was seen in scintigraphic gastric emptying time (p = 0.68). Prevalence of constipation symptoms on the NMSQuest was 41% in PD and 7% in controls.

CONCLUSIONS

Significantly increased small intestinal- and caecum-ascending 3D-Transit times were detected in PD patients. Also, time to first propagating colonic movement was increased. Radio opaque marker gastrointestinal transit time was significantly delayed, but no difference was seen in gastric transit time and gastric emptying time. The present findings highlight widespread intestinal involvement in PD increasing throughout the gastrointestinal tract.

Objective Colonic Dysfunction is Far more Prevalent than Subjective Constipation in Parkinson's Disease: A Colon Transit and Volume Study

BACKGROUND

Gastrointestinal function has received increased interest in the context of Parkinson's disease (PD). Constipation is among the most frequent non-motor symptoms, but our understanding of the underlying pathology is limited. Subjective constipation correlates poorly with objective markers.

OBJECTIVE

The aims were to evaluate colonic transit time and volume in PD and to correlate these measures with subjective symptoms and gastric emptying.

METHODS

Thirty-two PD patients and 26 controls were included. Colonic transit time, computed tomography-based volume estimation, and gastric emptying were performed as objective markers of gastrointestinal function. Subjective gastrointestinal symptoms were evaluated by three different questionnaires.

RESULTS

Seventy-nine percent of PD patients displayed prolonged colonic transit time (p < 0.0001) and 66% of patients had significantly increased colonic volume (p = 0.0002). Particularly the transverse and rectosigmoid segments were affected. There was no difference in gastric emptying time between groups. The prevalence of subjective constipation in PD patients was significantly lower and ranged from 3% to 38% depending on the type of questionnaire.

CONCLUSIONS

Significantly delayed colonic transit time and increased volume were frequent findings in PD patients, and objective dysfunction was considerably more prevalent than subjective constipation symptoms. Also, the prevalence of subjective constipation varied widely depending upon which questionnaire was employed. These findings highlight the need for more research on how to define constipation in PD and also the need for improved understanding of the relationship between subjective symptoms and objective dysfunction.

Imaging Parkinson's disease below the neck

Parkinson's disease is a systemic disorder with widespread and early α-synuclein pathology in the autonomic and enteric nervous systems, which is present throughout the gastrointestinal canal prior to diagnosis. Gastrointestinal and genitourinary autonomic symptoms often predate clinical diagnosis by several years. It has been hypothesized that progressive α-synuclein aggregation is initiated in hyperbranched, non-myelinated neuron terminals, and may subsequently spread via retrograde axonal transport. This would explain why autonomic nerves are so prone to formation of α-synuclein pathology. However, the hypothesis remains unproven and in vivo imaging methods of peripheral organs may be essential to study this important research field. The loss of sympathetic and parasympathetic nerve terminal function in Parkinson's disease has been demonstrated using radiotracers such as 123I-meta-iodobenzylguanidin, 18F-dopamine, and 11C-donepezil. Other radiotracer and radiological imaging methods have shown highly prevalent dysfunction of pharyngeal and esophageal motility, gastric emptying, colonic transit time, and anorectal function. Here, we summarize the methodology and main findings of radio-isotope and radiological modalities for imaging peripheral pathology in Parkinson's disease.

In Vivo cortical tau in Parkinson's disease using 18F-AV-1451 positron emission tomography

BACKGROUND

Alzheimer's disease copathology is common in PD at autopsy. In non-PD subjects with mild cognitive impairment, tau depositions can be detected using 18F-AV-1451 PET. We hypothesized that 18F-AV-1451 PET would show tau aggregation in PD with mild cognitive impairment and correlate with cognitive dysfunction.

OBJECTIVES

To describe tau aggregation in PD patients.

METHODS

Twenty-six PD patients and 23 controls had 18F-AV-1451 PET and neuropsychological assessment to detect mild cognitive impairment.

RESULTS

Nine PD patients (35%) were identified with mild cognitive impairment. Regional analyses showed no significant differences between groups. Voxel-wise analyses showed no correlation with cognitive domain z-scores within patients. One patient with mild cognitive impairment was estimated Braak tau stage 5; all other patients were stage 0.

CONCLUSION

Our results indicate that tau pathology, as detected by 18F-AV-1451, is uncommon in PD with mild cognitive impairment and shows no significant correlation with cognitive dysfunction at this stage. © 2017 International Parkinson and Movement Disorder Society.

Decreased intestinal acetylcholinesterase in early Parkinson disease

Objective:

To investigate systemic levels of acetylcholinesterase in early Parkinson disease (PD) with 11C-donepezil PET, a potential marker of parasympathetic innervation.

Methods:

This was a cross-sectional study with 19 patients with early-stage PD (disease duration 1.5 ± 0.6 years) and 16 age-matched controls who had clinical assessments, olfaction tests, and 11C-donepezil PET to measure acetylcholinesterase density in peripheral organs.

Results:

The patients with PD showed significantly reduced 11C-donepezil uptake in the small intestine (−14%, p = 0.018), colon (−22%, p < 0.001), and kidneys (−14%, p = 0.028). No difference in myocardial or pancreatic acetylcholinesterase levels was seen.

Conclusion:

We found significantly decreased 11C-donepezil signal in the intestine and kidneys of patients with early PD, suggesting that parasympathetic denervation is present early in the disease course.

Constipation in parkinson's disease: Subjective symptoms, objective markers, and new perspectives

Constipation is among the first nonmotor symptoms to develop in the prodromal phase of PD. Pathological alpha-synuclein deposition is present throughout the gastrointestinal tract up to 20 years preceding diagnosis. Nevertheless, constipation in the context of PD remains ill defined and poorly understood. In this review, we summarize current knowledge of subjective symptoms and objective measures of constipation in PD. More than 10 different definitions of constipation have been used in the PD literature, making generalizations difficult. When pooling results from the most homogeneous studies in PD, a median constipation prevalence of 40% to 50% emerges, but with large variation across individual studies. Also, constipation prevalence tends to increase with disease progression. A similar prevalence is observed among patients with idiopathic rapid eye movement sleep behavior disorder. Interestingly, we detected a correlation between constipation prevalence in PD patients and healthy control groups in individual studies, raising concerns about how various constipation questionnaires are implemented across study populations. More than 80% of PD patients exhibit prolonged colonic transit time, and the same is probably true for de novo PD patients. Thus, the prevalence of objective colonic dysfunction exceeds the prevalence of subjective constipation. Colonic transit time measures are simple, widely available, and hold promise as a useful biomarker in manifest PD. More research is needed to elucidate the role of gastrointestinal dysfunction in disease progression of PD. Moreover, colonic transit measures may have utility as a more accurate risk factor for predicting PD in the prodromal phase. © 2016 International Parkinson and Movement Disorder Society.

Cholinergic PET imaging in infections and inflammation using 11C-donepezil and 18F-FEOBV

INTRODUCTION

Immune cells utilize acetylcholine as a paracrine-signaling molecule. Many white blood cells express components of the cholinergic signaling pathway, and these are up-regulated when immune cells are activated. However, in vivo molecular imaging of cholinergic signaling in the context of inflammation has not previously been investigated.

METHODS

We performed positron emission tomography (PET) using the glucose analogue 18F-FDG, and 11C-donepezil and 18F-FEOBV, markers of acetylcholinesterase and the vesicular acetylcholine transporter, respectively. Mice were inoculated subcutaneously with Staphylococcus aureus, and PET scanned at 24, 72, 120, and 144 h post-inoculation. Four pigs with post-operative abscesses were also imaged. Finally, we present initial data from human patients with infections, inflammation, and renal and lung cancer.

RESULTS

In mice, the FDG uptake in abscesses peaked at 24 h and remained stable. The 11C-donepezil and 18F-FEOBV uptake displayed progressive increase, and at 120-144 h was nearly at the FDG level. Moderate 11C-donepezil and slightly lower 18F-FEOBV uptake were seen in pig abscesses. PCR analyses suggested that the 11C-donepezil signal in inflammatory cells is derived from both acetylcholinesterase and sigma-1 receptors. In humans, very high 11C-donepezil uptake was seen in a lobar pneumonia and in peri-tumoral inflammation surrounding a non-small cell lung carcinoma, markedly superseding the 18F-FDG uptake in the inflammation. In a renal clear cell carcinoma no 11C-donepezil uptake was seen.

DISCUSSION

The time course of cholinergic tracer accumulation in murine abscesses was considerably different from 18F-FDG, demonstrating in the 11C-donepezil and 18F-FEOBV image distinct aspects of immune modulation. Preliminary data in humans strongly suggest that 11C-donepezil can exhibit more intense accumulation than 18F-FDG at sites of chronic inflammation. Cholinergic PET imaging may therefore have potential applications for basic research into cholinergic mechanisms of immune modulation, but also clinical applications for diagnosing infections, inflammatory disorders, and cancer inflammation.

In vivo imaging of neuromelanin in Parkinson's disease using 18F-AV-1451 PET

The tau tangle ligand (18)F-AV-1451 ((18)F-T807) binds to neuromelanin in the midbrain, and may therefore be a measure of the pigmented dopaminergic neuronal count in the substantia nigra. Parkinson's disease is characterized by progressive loss of dopaminergic neurons. Extrapolation of post-mortem data predicts that a ∼30% decline of nigral dopamine neurons is necessary to cause motor symptoms in Parkinson's disease. Putamen dopamine terminal loss at disease onset most likely exceeds that of the nigral cell bodies and has been estimated to be of the order of 50-70%. We investigated the utility of (18)F-AV-1451 positron emission tomography to visualize the concentration of nigral neuromelanin in Parkinson's disease and correlated the findings to dopamine transporter density, measured by (123)I-FP-CIT single photon emission computed tomography. A total of 17 patients with idiopathic Parkinson's disease and 16 age- and sex-matched control subjects had (18)F-AV-1451 positron emission tomography using a Siemens high-resolution research tomograph. Twelve patients with Parkinson's disease also received a standardized (123)I-FP-CIT single photon emission computed tomography scan at our imaging facility. Many of the patients with Parkinson's disease displayed visually apparent decreased (18)F-AV-1451 signal in the midbrain. On quantitation, patients showed a 30% mean decrease in total nigral (18)F-AV-1451 volume of distribution compared with controls (P = 0.004), but there was an overlap of the individual ranges. We saw no significant correlation between symptom dominant side and contralateral nigral volume of distribution. There was no correlation between nigral (18)F-AV-1451 volume of distribution and age or time since diagnosis. In the subset of 12 patients, who also had a (123)I-FP-CIT scan, the mean total striatal dopamine transporter signal was decreased by 45% and the mean total (18)F-AV-1451 substantia nigra volume of distribution was decreased by 33% after median disease duration of 4.7 years (0.5-12.4 years). (18)F-AV-1451 positron emission tomography may be the first radiotracer to reflect the loss of pigmented neurons in the substantia nigra of parkinsonian patients. The magnitude of the nigral signal loss was smaller than the decrease in striatal dopamine transporter signal measured by dopamine transporter single photon emission computed tomography. These findings suggest a more severe loss of striatal nerve terminal function compared with neuronal cell bodies, in accordance with the post-mortem literature.