Preliminary Findings on Proline-Rich Protein 14 as a Diagnostic Biomarker for Parkinson's Disease

Assessment of the Relationship Between Amino Acid Status and Parkinson's Disease: A Comprehensive Review and Meta-analysis

BACKGROUND

Parkinson's disease (PD) is characterized by the inability of dopamine production from amino acids. Therefore, changes in amino acid profile in PD patients are very critical for understanding disease development. Determination of amino acid levels in PD patients with a cumulative approach may enlighten the disease pathophysiology.

METHODS

A systematic search was performed until February 2023, resulting in 733 articles in PubMed, Web of Science and Scopus databases to evaluate the serum amino acid profile of PD patients. Relevant articles in English with mean/standard deviation values of serum amino acid levels of patients and their healthy controls were included in the meta-analysis.

RESULTS

Our results suggest that valine, proline, ornithine and homocysteine levels were increased, while aspartate, citrulline, lysine and serine levels were significantly decreased in PD patients compared to healthy controls. Homocysteine showed positive correlations with glutamate and ornithine levels. We also analyzed the disease stage parameters: Unified Parkinson's Disease Rating Scale III (UPDRS III) score, Hoehn-Yahr Stage Score, disease duration and levodopa equivalent daily dose (LEDD) of patients. It was observed that LEDD has a negative correlation with arginine levels in patients. UPDRS III score is negatively correlated with phenylalanine levels, and it also tends to show a negative correlation with tyrosine levels. Disease duration tends to be negatively correlated with citrulline levels in PD patients.

CONCLUSION

This cumulative analysis shows evidence of the relation between the mechanisms underlying amino acid metabolism in PD, which may have a great impact on disease development and new therapeutic strategies.

Bidirectional regulation effect of rhubarb as laxative and astringent by metabolomics studies

ETHNOPHARMACOLOGICAL RELEVANCE

Rhubarb, a prominent traditional Chinese medicine, has been employed as a potent laxative for centuries and garnered particular popularity among the youth owing to its notable efficacy in weight management. Historical records indicated that rhubarb initially exhibited robust laxative properties, but extended and consistent usage may lead to an astringent response in the later stage of long-term use. In contrast, steamed pieces of rhubarb (SR), preparing through the process of steaming with wine, have demonstrated a gentle laxative effect with no reported adverse effects.

AIM OF THE STUDY

Our study was designed to explore the intricate mechanisms underlying laxative and astringent properties of rhubarb through metabolomics research.

MATERIALS AND METHODS

In this investigation, we employed a serum metabolomics approach utilizing the UPLC-Q-Extractive-Orbitrap-MS method to delve into the contrasting laxative and astringent effects of rhubarb, as well as to unravel the mechanisms of underpinning its bidirectional regulatory influence. To commence, we assessed alterations in Evacuation Index (EI) values, intestinal hormone levels, and colon histopathology in mice to gauge rhubarb's laxative and astringent effects. Subsequently, metabolomics methodology was employed for cluster analysis through Principal Component Analysis (PCA) and biomarker identification via Orthogonal Partial Least Squares-Discriminant Analysis (OPLS-DA). Then, we delved into the distinctions in characteristic biomarkers, metabolic pathways, their association with pathological changes, and correlation heatmap for biomarkers between raw pieces of rhubarb (RR) and SR to gain insights into the potential mechanisms behind rhubarb's bidirectional regulatory effects.

RESULTS

Our findings revealed that RR exhibited a laxative effect in the early stage and transitioned to an astringent effect in the later stage, as indicated by the EI values. In contrast, SR consistently demonstrated a mild laxative effect. Biochemical indexes and histopathological assessments unveiled that RR triggered its astringent effect by inhibiting secretion of motilin (MTL), promoting secretion of vasoactive intestinal peptide (VIP) and epinephrine (EPI), and inducing onset of inflammation. Furthermore, serum metabolomics analysis identified 59 discriminative biomarkers modulated by RR and SR. Through comprehensive analysis, we elucidated the in vivo transformation relationships among multiple endogenous metabolites. Notably, our results underscored the down-regulation of certain phosphatidylcholines (PCs), amino acids, acylcarnitines, and up-regulation of lysophosphatidylcholines (LysoPCs) played pivotal roles in the onset of gut dysfunction, intestinal inflammation, gut barrier damage, and gastrointestinal motility disorder upon prolonging RR administration, ultimately contributing to its astringent effect. Additionally, our correlation analysis elucidated that anthraquinones, stilbenes, and phenylbutanones were the pharmacodynamic material basis responsible for inducing the astringent effect of RR.

CONCLUSION

This study provides valuable insights into the bidirectional regulatory effects of rhubarb and sheds light on its underlying mechanisms through a comprehensive metabolomics approach.

Shared Genetic Architecture between Parkinson's Disease and Brain Structural Phenotypes

BACKGROUND

Patients with Parkinson's disease (PD) have consistently demonstrated brain structure abnormalities, indicating the presence of shared etiological and pathological processes between PD and brain structures; however, the genetic relationship remains poorly understood.

OBJECTIVE

The aim of this study was to investigate the extent of shared genetic architecture between PD and brain structural phenotypes (BSPs) and to identify shared genomic loci.

METHODS

We used the summary statistics from genome-wide association studies to conduct MiXeR and conditional/conjunctional false discovery rate analyses to investigate the shared genetic signatures between PD and BSPs. Subsequent expression quantitative trait loci mapping in the human brain and enrichment analyses were also performed.

RESULTS

MiXeR analysis identified genetic overlap between PD and various BSPs, including total cortical surface area, average cortical thickness, and specific brain volumetric structures. Further analysis using conditional false discovery rate (FDR) identified 21 novel PD risk loci on associations with BSPs at conditional FDR < 0.01, and the conjunctional FDR analysis demonstrated that PD shared several genomic loci with certain BSPs at conjunctional FDR < 0.05. Among the shared loci, 16 credible mapped genes showed high expression in the brain tissues and were primarily associated with immune function-related biological processes.

CONCLUSIONS

We confirmed the polygenic overlap with mixed directions of allelic effects between PD and BSPs and identified multiple shared genomic loci and risk genes, which are likely related to immune-related biological processes. These findings provide insight into the complex genetic architecture associated with PD. © 2023 International Parkinson and Movement Disorder Society.

Increased PRR14 and VCAM-1 level in serum of patients with Parkinson's disease

Background

Regarding the complexity of Parkinson's disease (PD), the identification of reliable biomarkers is of great significance for improving the accuracy of diagnosis and monitoring disease progression. Recently, some studies suggested that serum proline-rich protein 14 (PRR14), vascular cell adhesion molecule-1 (VCAM-1), and soluble CD163 (sCD163) factors may be associated with PD, even as potential biomarkers. However, the role of these serum factors is still unclear.

Objectives

This study aimed to explore the alterations of serum PRR14, VCAM-1, and sCD163 levels during PD progression, and their association with disease-related variables of PD.

Methods

We performed the assessment of scale tests and the detection of serum samples in patients with PD (n = 100) and healthy controls (HCs, n = 100). Furthermore, we investigated the association between serum factors and sex, cognitive impairments, H&Y (Hohn and Yahr), age at onset (AAO), and other variables in patients with PD.

Results

Patients with PD exhibited increased PRR14 and VCAM-1 serum levels compared with HCs. No significant differences were found in serum levels of sCD163. Subgroup analysis uncovered increased VCAM-1 in the female and male subgroups (PD and HCs). Among patients with PD, decreased PRR14 and increased VCAM-1 were associated with severer cognitive impairments and severer PD (H&Y), respectively. Bivariate correlation analysis revealed that there was a positive correlation between VCAM-1 and AAO.

Conclusions

Increased serum levels of PRR14 and VCAM-1 suggest that inflammation and defective autophagy may play vital roles in the pathogenesis of PD. However, the potential mechanisms remain to be elucidated.