R1441G but not G2019S mutation enhances LRRK2 mediated Rab10 phosphorylation in human peripheral blood neutrophils.

Heterozygous gain-of-kinase function variants in LRRK2 (leucine-rich repeat kinase 2) cause 1-2% of all cases of Parkinson's disease (PD) albeit with incomplete and age-dependent penetrance. All pathogenic LRRK2 mutations reside within the two catalytic domains of LRRK2-either in its kinase domain (e.g. G2019S) with modest effect or its ROC-COR GTPase domain (e.g. R1441G/H) with large effect on LRRK2 kinase activity. We have previously reported assays to interrogate LRRK2 kinase pathway activity in human bio-samples measuring phosphorylation of its endogenous substrate Rab10, that mirrors LRRK2 kinase activation status. Here, we isolated neutrophils from fresh peripheral blood from 101 participants including 42 LRRK2 mutation carriers (21 with the G2019S and 21 with the R1441G mutations), 27 patients with idiopathic PD, and 32 controls. Using a dual approach, LRRK2 dependent Rab10 phosphorylation at Threonine 73 (pRab10Thr73) was measured by quantitative multiplexed immunoblotting for pRab10Thr73/total Rab10 as well as targeted mass-spectrometry for absolute pRab10Thr73 occupancy. We found a significant over fourfold increase in pRab10Thr73 phosphorylation in carriers of the LRRK2 R1441G mutation irrespective of clinical disease status. The effect of the LRRK2 G2019S mutation did not reach statistical significance. Furthermore, we show that LRRK2 phosphorylation at Serine 935 is not a marker for LRRK2 kinase activity in human neutrophils. When analysing pRab10Thr73 phosphorylation in post-mortem brain samples, we observed overall high variability irrespective of clinical and LRRK2 mutation status and attributed this mainly to the adverse effect of the peri- and post-mortem period on the stability of posttranslational modifications such as protein phosphorylation. Overall, in vivo LRRK2 dependent pRab10Thr73 phosphorylation in human peripheral blood neutrophils is a specific, robust and promising biomarker for significant LRRK2 kinase hyperactivation, as with the LRRK2 R1441G mutation. Additional readouts and/or assays may be needed to increase sensitivity to detect modest LRRK2 kinase activation, as with the LRRK2 G2019S mutation. Our assays could be useful for patient stratification and target engagement studies for LRRK2 kinase inhibitors.

Relationship between the MDS-UPDRS and Quality of Life: A large multicenter study of 3206 patients.

BACKGROUND: The relationship between Health-Related Quality of Life (HRQoL) and MDS-UPDRS has not been fully studied so far. The aim of this study was to evaluate the relationship between all MDS-UPDRS components and HRQoL in a representative international cohort of PD patients. METHODS: We collected demographic and disease-related data as well as MDS-UPDRS and PDQ8 scales. Data were analyzed using correlations between PDQ8 and all MDS-UPDRS items, subsequently two hierarchical multiple regressions were performed, first between the scores of the MDS-UPDRS Parts and PDQ8 and second between individual items from those Parts demonstrating significant relationship to PDQ8 scores in the first regression. LASSO regression analyses were performed to evaluate the relationship between PDQ8 and all individual MDS-UPDRS items. RESULTS: A total of 3206 PD patients were included in the study. In the first regression analysis, PDQ8 was significantly related to MDS-UPDRS parts I and II, but not to III and IV. In the second regression model, significant contributions to PDQ8 were found for Part I items Fatigue, Pain, Depressed mood, Apathy; and Part II items Dressing, Doing hobbies, Freezing, Speech and Tremor. In the LASSO analysis, six Part I, seven Part II, three Part III and one Part IV items contributed to PDQ8 scores. The five items most significantly related to the model were Depressed mood, Dressing, Apathy, Pain and Fatigue. CONCLUSIONS: This is so far the largest study related to HRQoL issues in PD. Restrictions in activities of daily living and non-motor symptoms significantly contribute to HRQoL in PD.

Differences in MDS-UPDRS Scores Based on Hoehn and Yahr Stage and Disease Duration.

BACKGROUND: The Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) is a newly developed tool to assess Parkinson's disease (PD). Changes in scores on the scale over the course of PD, including increasing disease duration and Hoehn and Yahr (HY) stages, have not been described. The objectives of this study were to analyze MDS-UPDRS scores on Parts I through IV and their differences based on HY stage and disease duration in a large cohort of patients with PD. METHODS: For this cross-sectional study, demographic data and MDS-UPDRS scores were collected, including HY stage. Subscores on MDS-UPDRS Parts I through IV were analyzed using 1-way analyses of variance for each HY stage and in 5-year increments of disease duration. Part III (motor assessment) scores were analyzed separately for on and off states. RESULTS: The mean age of the 3206 patients was 65.8 ± 10.6 years, 53.3% were men, the mean disease duration was 11.5 ± 4.6 years, and the median HY stage was 2 (range, 0-5); 2156 patients were examined in an on state and 987 were examined in an off state. Scores for all MDS-UPDRS parts increased significantly through HY stages 1 through 5, with an average increase of 3.8, 7.7, 14.6, and 2.0 points consecutively for parts I through IV, respectively. For the 5-year increments of disease duration, MDS-UPDRS subscores increased by an average of 1.6, 3.3, 4.2, and 1.4 points consecutively for parts I through IV, respectively. This increase was significant only during the first 15 years of disease for all 4 parts, including part III scores evaluated in both on and off states. CONCLUSIONS: MDS-UPDRS scores for all 4 parts increase significantly with every HY stage and also with 5-year increments of disease duration in the first 15 years of the disease.

Expanded and independent validation of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS).

The Movement Disorder Society-UPDRS (MDS-UPDRS) was published in 2008, showing satisfactory clinimetric results and has been proposed as the official benchmark scale for Parkinson's disease. The present study, based on the official MDS-UPDRS Spanish version, performed the first independent testing of the scale and adds information on its clinimetric properties. The cross-culturally adapted MDS-UPDRS Spanish version showed a comparative fit index ≥ 0.90 for each part (I-IV) relative to the English-language version and was accepted as the Official MDS-UPDRS Spanish version. Data from this scale, applied with other assessments to Spanish-speaking Parkinson's disease patients in five countries, were analyzed for an independent and complementary clinimetric evaluation. In total, 435 patients were included. Missing data were negligible and moderate floor effect (30 %) was found for Part IV. Cronbach's α index ranged between 0.79 and 0.93 and only five items did not reach the 0.30 threshold value of item-total correlation. Test-retest reliability was adequate with only two sub-scores of the item 3.17, Rest tremor amplitude, reaching κ values lower than 0.60. The intraclass correlation coefficient was higher than 0.85 for the total score of each part. Correlation of the MDS-UPDRS parts with other measures for related constructs was high (≥ 0.60) and the standard error of measurement lower than one-third baseline standard deviation for all subscales. Results confirm those of the original study and add information on scale reliability, construct validity, and precision. The MDS-UPDRS Spanish version shows satisfactory clinimetric characteristics.

The MDS-UPDRS Part II (motor experiences of daily living) resulted useful for assessment of disability in Parkinson's disease.

OBJECTIVE: To evaluate the motor experiences of daily living section of the Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS M-EDL) for assessing disability in PD patients; to determine the association between disability and quality of life; and to identify cut-off score ranges for no, mild, moderate and severe disability with this measure. METHODS: International, observational, cross-sectional study of 435 PD patients, assessed with: MDS-UPDRS, Hoehn and Yahr staging, Rapid Assessment of Disability Scale, Clinical Impression of Severity Index for PD, Parkinson's Disease Questionnaire-8 and EQ-5D. Descriptive statistics, Spearman's rank correlation coefficients, Kruskal-Wallis test for group comparisons, ordinal logistic regression analysis for setting cut-off values and a step-wise multiple linear regression model were calculated. RESULTS: MDS-UPDRS M-EDL correlated 0.70-0.80 with other disability measures, and -0.46 to 0.74 with quality of life scales. Scores significantly increased with higher disease duration and severity (p < 0.001). Cut-off values for the M-EDL were: 0-2 points, no disability; 3-16, mild; 17-31, moderate; and 32 points or more, severe. Linear regression analysis identified the MDS-UPDRS nM-EDL section as the main determinant of M-EDL, followed by the rest of MDS-UPDRS sections (explained variance: 59%). CONCLUSIONS: MDS-UPDRS M-EDL proved to be useful for assessing disability in PD.