6-n-propylthiouracil taste disruption and TAS2R38 nontasting form in Parkinson's disease

Background: The few studies that evaluated taste function in Parkinson's disease (PD) showed inconsistent results. The inherited ability to taste the bitter compound of 6-n-propylthiouracil has been considered to be a paradigm of general taste perception. 6-n-propylthiouracil taste perception is mediated by the TAS2R38 receptor, and reduced 6-n-propylthiouracil sensitivity has been associated with several diseases not typically related to taste function. Objectives: We evaluated the 6-n-propylthiouracil taste perception and the TAS2R38 gene as genetic risk factors for the development of idiopathic PD in PD patients and healthy controls (HC). Methods: The 6-n-propylthiouracil taste perception was assessed by testing the responsiveness, and the ability to recognize, 6-n-propylthiouracil and sodium chloride. The participants were classified for 6-n-propylthiouracil taster status and genotyped for the TAS2R38 gene. Results: A significant increase in the frequency of participants classified as 6-n-propylthiouracil nontasters and a reduced ability to recognize bitter taste quality of 6-n-propylthiouracil were found in PD patients when compared with healthy controls. The results also showed that only 5% of PD patients had the homozygous genotype for the dominant tasting variant of TAS2R38, whereas most of them carried the recessive nontaster form and a high number had a rare variant. Conclusions: Our results show that 6-n-propylthiouracil taster status and TAS2R38 locus are associated with PD. The 6-n-propylthiouracil test may therefore represent a novel, simple way to identify increased vulnerability to PD. Moreover, the presence of the nontasting form of TAS2R38 in PD may further substantiate that disease-associated taste disruption may represent a risk factor associated with the disease. © 2018 International Parkinson and Movement Disorder Society

Poor self-awareness of levodopa-induced dyskinesias in Parkinson's disease: Clinical features and mechanisms

Objectives: To study the factors and possible mechanisms associated with decreased self-awareness of levodopa-induced dyskinesias (LIDs) in patients with Parkinson's disease (PD). Methods: We enrolled 30 PD patients with LIDs. Patients were video-recorded in an "on" phase while experiencing LIDs. LIDs were objectively rated by means of the Unified Dyskinesias Rating Scale (UDyRS) by two movement disorders specialists while examining the patients. Patients were asked to rate the body site and the severity of their LIDs according to the 5-point UDyRS. Patients then rated their own LIDs while watching the video recording of themselves. Lastly, the patients rated the LIDs of other reference PD patients on a video recording. The same reference video recordings were shown to 15 healthy individuals matched for age, gender and education. Results: Seven of the 30 PD patients investigated were subjectively unaware of the presence of their LIDs. The majority of patients, however, recognized their LIDs when watching video recording of themselves. Patients displayed a specific poor self-awareness of trunk LIDs, in both the subjective evaluation and in the video recording-based subjective evaluation. By contrast PD patients correctly recognized LIDs in video recordings of reference PD patients. Poor self-awareness correlated with predominance of motor symptoms on the left body side. Conclusions: Poor self-awareness of LIDs is present in a proportion of PD patients as a form of anosognosia. The poor self-awareness of LIDs in the trunk is likely to be due to a complex interplay involving both anosognosic mechanisms and deficits in proprioceptive axial kinesthesia. (C) 2013 Published by Elsevier Ltd

GBA ‐Related Parkinson's Disease: Dissection of Genotype–Phenotype Correlates in a Large Italian Cohort

Background Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD). The impact of different variants on the PD clinical spectrum is still unclear. Objectives We determined the frequency of GBA ‐related PD in Italy and correlated GBA variants with motor and nonmotor features and their occurrence over time. Methods Sanger sequencing of the whole GBA gene was performed. Variants were classified as mild, severe, complex, and risk. β‐glucocerebrosidase activity was measured. The Kaplan‐Meier method and Cox proportional hazard regression models were performed. Results Among 874 patients with PD, 36 variants were detected in 14.3%, including 20.4% early onset. Patients with GBA‐PD had earlier and more frequent occurrence of several nonmotor symptoms. Patients with severe and complex GBA‐PD had the highest burden of symptoms and a higher risk of hallucinations and cognitive impairment. Complex GBA‐PD had the lowest β‐glucocerebrosidase activity. Conclusions GBA‐PD is highly prevalent in Italy. Different types of mutations underlie distinct phenotypic profiles

LRP10 genetic variants in familial Parkinson's disease and dementia with Lewy bodies: a genome-wide linkage and sequencing study

Background: Most patients with Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies do not carry mutations in known disease-causing genes. The aim of this study was to identify a novel gene implicated in the development of these disorders. Methods: Our study was done in three stages. First, we did genome-wide linkage analysis of an Italian family with dominantly inherited Parkinson's disease to identify the disease locus. Second, we sequenced the candidate gene in an international multicentre series of unrelated probands who were diagnosed either clinically or pathologically with Parkinson's disease, Parkinson's disease dementia, or dementia with Lewy bodies. As a control, we used gene sequencing data from individuals with abdominal aortic aneurysms (who were not examined neurologically). Third, we enrolled an independent series of patients diagnosed clinically with Parkinson's disease and controls with no signs or family history of Parkinson's disease, Parkinson's disease dementia, or dementia with Lewy bodies from centres in Portugal, Sardinia, and Taiwan, and screened them for specific variants. We also did mRNA and brain pathology studies in three patients from the international multicentre series carrying disease-associated variants, and we did functional protein studies in in-vitro models, including neurons from induced pluripotent stem-like cells. Findings: Molecular studies were done between Jan 1, 2008, and Dec 31, 2017. In the initial kindred of ten affected Italian individuals (mean age of disease onset 59·8 years [SD 8·7]), we detected significant linkage of Parkinson's disease to chromosome 14 and nominated LRP10 as the disease-causing gene. Among the international series of 660 probands, we identified eight individuals (four with Parkinson's disease, two with Parkinson's disease dementia, and two with dementia with Lewy bodies) who carried different, rare, potentially pathogenic LRP10 variants; one carrier was found among 645 controls with abdominal aortic aneurysms. In the independent series, two of these eight variants were detected in three additional Parkinson's disease probands (two from Sardinia and one from Taiwan) but in none of the controls. Of the 11 probands from the international and independent cohorts with LRP10 variants, ten had a positive family history of disease and DNA was available from ten affected relatives (in seven of these families). The LRP10 variants were present in nine of these ten relatives, providing independent—albeit limited—evidence of co-segregation with disease. Post-mortem studies in three patients carrying distinct LRP10 variants showed severe Lewy body pathology. Of nine variants identified in total (one in the initial family and eight in stage 2), three severely affected LRP10 expression and mRNA stability (1424+5delG, 1424+5G→A, and Ala212Serfs*17, shown by cDNA analysis), four affected protein stability (Tyr307Asn, Gly603Arg, Arg235Cys, and Pro699Ser, shown by cycloheximide-chase experiments), and two affected protein localisation (Asn517del and Arg533Leu; shown by immunocytochemistry), pointing to loss of LRP10 function as a common pathogenic mechanism. Interpretation: Our findings implicate LRP10 gene defects in the development of inherited forms of α-synucleinopathies. Future elucidation of the function of the LRP10 protein and pathways could offer novel insights into mechanisms, biomarkers, and therapeutic targets. Funding: Stichting ParkinsonFonds, Dorpmans-Wigmans Stichting, Erasmus Medical Center, ZonMw—Memorabel programme, EU Joint Programme Neurodegenerative Disease Research (JPND), Parkinson's UK, Avtal om Läkarutbildning och Forskning (ALF) and Parkinsonfonden (Sweden), Lijf and Leven foundation, and cross-border grant of Alzheimer Netherlands–Ligue Européene Contre la Maladie d'Alzheimer (LECMA)