Objective: To explore clinical phenotype and characteristics of Parkinson disease (PD) at different ages at onset in recently diagnosed patients with untreated PD. Methods: We have analyzed baseline data from the Parkinson9s Progression Markers Initiative database. Four hundred twenty-two patients with a diagnosis of PD confirmed by DaTSCAN imaging were divided into 4 groups according to age at onset (onset younger than 50 years, 50–59 years, 60–69 years, and 70 years or older) and investigated for differences in side, type and localization of symptoms, occurrence/severity of motor and nonmotor features, nigrostriatal function, and CSF biomarkers. Results: Older age at onset was associated with a more severe motor and nonmotor phenotype, a greater dopaminergic dysfunction on DaTSCAN, and reduction of CSF α-synuclein and total tau. The most common presentation was the combination of 2 or 3 motor symptoms (bradykinesia, resting tremor, and rigidity) with rigidity being more common in the young-onset group. In about 80% of the patients with localized onset, the arm was the most affected part of the body, with no difference across subgroups. Conclusions: Although the presentation of PD symptoms is similar across age subgroups, the severity of motor and nonmotor features, the impairment of striatal binding, and the levels of CSF biomarkers increase with age at onset. The variability of imaging and nonimaging biomarkers in patients with PD at different ages could hamper the results of future clinical trials.

Objective To investigate whether diabetes mellitus is associated with Parkinson-like pathology in people without Parkinson disease and to evaluate the effect of diabetes mellitus on markers of Parkinson pathology and clinical progression in drug-naive patients with early-stage Parkinson disease. Methods We compared 25 patients with Parkinson disease and diabetes mellitus to 25 without diabetes mellitus, and 14 patients with diabetes mellitus and no Parkinson disease to 14 healthy controls (people with no diabetes mellitus or Parkinson disease). The clinical diagnosis of diabetes mellitus was confirmed by 2 consecutive fasting measurements of serum glucose levels >126 mL/dL. Over a 36-month follow-up period, we then investigated in the population with Parkinson disease whether the presence of diabetes mellitus was associated with faster motor progression or cognitive decline. Results The presence of diabetes mellitus was associated with higher motor scores (p < 0.01), lower striatal dopamine transporter binding (p < 0.05), and higher tau CSF levels (p < 0.05) in patients with Parkinson disease. In patients with diabetes but without Parkinson disease, the presence of diabetes mellitus was associated with lower striatal dopamine transporter binding (p < 0.05) and higher tau (p < 0.05) and α-synuclein (p < 0.05) CSF levels compared to healthy controls. At the Cox survival analysis in the population of patients with Parkinson disease, the presence of diabetes mellitus was associated with faster motor progression (hazard ratio = 4.521, 95% confidence interval = 1.468–13.926; p < 0.01) and cognitive decline (hazard ratio = 9.314, 95% confidence interval = 1.164–74.519; p < 0.05). Conclusions Diabetes mellitus may predispose toward a Parkinson-like pathology, and when present in patients with Parkinson disease, can induce a more aggressive phenotype.

Currently, no reliable predictors of cognitive impairment in Parkinson's disease exist. We hypothesized that microstructural changes at grey matter T1-weighted MRI and diffusion tensor imaging in the cholinergic system nuclei and associated limbic pathways underlie cognitive impairment in Parkinson's disease. We performed a cross-sectional comparison between patients with Parkinson's disease with and without cognitive impairment. We also performed a longitudinal 36-month follow-up study of cognitively intact Parkinson's disease patients, comparing patients who remained cognitively intact to those who developed cognitive impairment. Patients with Parkinson's disease with cognitive impairment showed lower grey matter volume and increased mean diffusivity in the nucleus basalis of Meynert, compared to patients with Parkinson's disease without cognitive impairment. These results were confirmed both with region of interest and voxel-based analyses, and after partial volume correction. Lower grey matter volume and increased mean diffusivity in the nucleus basalis of Meynert was predictive for developing cognitive impairment in cognitively intact patients with Parkinson's disease, independent of other clinical and non-clinical markers of the disease. Structural and microstructural alterations in entorhinal cortex, amygdala, hippocampus, insula, and thalamus were not predictive for developing cognitive impairment in Parkinson's disease. Our findings provide evidence that degeneration of the nucleus basalis of Meynert precedes and predicts the onset of cognitive impairment, and might be used in a clinical setting as a reliable biomarker to stratify patients at higher risk of cognitive decline.

Post-mortem and neuroimaging studies suggest that the serotonergic system, which originates from the brainstem raphe nuclei, is disrupted in Parkinson’s disease. This could contribute to the occurrence of non-motor symptoms and tremor, which are only partially explained by dopamine loss. However, the level of involvement of the serotonergic raphe nuclei in early Parkinson’s disease is still debated. 123I-FP-CIT single photon emission computed tomography is a marker of dopamine and serotonin transporter availability. While 123I-FP-CIT binds primarily to dopamine transporters in the striatum, its binding in the brainstem raphe nuclei reflects serotonin transporter availability. We interrogated baseline single photon emission computed tomography scans of subjects recruited by the Parkinson’s Progression Markers Initiative to determine: (i) the integrity of the brainstem raphe nuclei in early Parkinson’s disease; and (ii) whether raphe serotonin transporter levels correlate with severity of tremor and symptoms of fatigue, depression, and sleep disturbance. Three hundred and forty-five patients with early drug-naïve Parkinson’s disease, 185 healthy controls, and 56 subjects with possible Parkinson’s disease without evidence of dopaminergic deficit were included. In the Parkinson’s disease cohort, 37 patients had a tremulous, 106 patients had a pure akinetic-rigid, and 202 had a mixed phenotype. Patients with Parkinson’s disease had significantly lower serotonin transporter availability in the brainstem raphe nuclei compared to controls ( P < 0.01) and subjects without evidence of dopaminergic deficit ( P < 0.05). However, only 13% of patients with Parkinson’s disease individually had reduced signals. Raphe serotonin transporter availability over the entire Parkinson’s disease cohort were associated with rest tremor amplitude (β = −0.106, P < 0.05), rest tremor constancy (β = −0.109, P < 0.05), and index of rest tremor severity (β = −0.104, P < 0.05). The tremulous Parkinson’s disease subgroup had significantly lower raphe serotonin transporter availability but less severe striatal dopaminergic deficits compared to akinetic-rigid patients with no resting tremor ( P < 0.05). In tremulous patients, raphe serotonin transporter availability was also associated with rest tremor constancy (β = −0.380, P < 0.05) and index of rest tremor severity (β = −0.322, P < 0.05). There was no association between raphe serotonin transporter availability and fatigue, depression, excessive daytime sleepiness, or rapid eye movement sleep behaviour disorder in early Parkinson’s disease. We conclude that the raphe nuclei are affected in a subgroup of early drug-naïve Parkinson’s disease patients and that reduced raphe serotonin transporter availability is associated with the severity of resting tremor but not non-motor symptoms. * Abbreviations : 123I-FP-CIT : 123-ioflupane-fluoropropyl-carbomethoxy-3-beta-4-iodophenyltropane SPECT : single photon emission computed tomography SWEDD : subjects without evidence of dopaminergic deficit

The type 2 ryanodine receptor (RyR2) is a Ca²⁺ release channel on the endoplasmic reticulum (ER) of several types of cells, including cardiomyocytes and pancreatic β cells. In cardiomyocytes, RyR2-dependent Ca²⁺ release is critical for excitation-contraction coupling; however, a functional role for RyR2 in β cell insulin secretion and diabetes mellitus remains controversial. Here, we took advantage of rare RyR2 mutations that were identified in patients with a genetic form of exercise-induced sudden death (catecholaminergic polymorphic ventricular tachycardia [CPVT]). As these mutations result in a “leaky” RyR2 channel, we exploited them to assess RyR2 channel function in β cell dynamics. We discovered that CPVT patients with mutant leaky RyR2 present with glucose intolerance, which was heretofore unappreciated. In mice, transgenic expression of CPVT-associated RyR2 resulted in impaired glucose homeostasis, and an in-depth evaluation of pancreatic islets and β cells from these animals revealed intracellular Ca²⁺ leak via oxidized and nitrosylated RyR2 channels, activated ER stress response, mitochondrial dysfunction, and decreased fuel-stimulated insulin release. Additionally, we verified the effects of the pharmacological inhibition of intracellular Ca²⁺ leak in CPVT-associated RyR2-expressing mice, in human islets from diabetic patients, and in an established murine model of type 2 diabetes mellitus. Taken together, our data indicate that RyR2 channels play a crucial role in the regulation of insulin secretion and glucose homeostasis.

Alzheimer's disease (AD) is a devastating and progressive neurodegenerative disease for which there is no cure. Mild cognitive impairment (MCI) is considered a prodromal stage of the disease. Molecular imaging with positron emission tomography (PET) allows for the in vivo visualisation and tracking of pathophysiological changes in AD and MCI. PET is a very promising methodology for differential diagnosis and novel targets of PET imaging might also serve as biomarkers for disease‐modifying therapeutic interventions. This review provides an overview of the current status and applications of in vivo molecular imaging of AD pathology, specifically amyloid, tau, and microglial activation. PET imaging studies were included and evaluated as potential biomarkers and for monitoring disease progression. Although the majority of radiotracers showed the ability to discriminate AD and MCI patients from healthy controls, they had various limitations that prevent the recommendation of a single technique or tracer as an optimal biomarker. Newer research examining amyloid, tau, and microglial PET imaging in combination suggest an alternative approach in studying the disease process.