Neuropeptide Alterations in Parkinson’s Disease: A Meta-analysis
Victor Ghosh1, Muneeb Ahmad Muneer2, Vinay Suresh3, Savvy Aujla4, Abhinav Khare5, Poorvikha S6, Tirth Dave7
1Andhra Medical College, 2Allama Iqbal Medical College, 3King George Medical University, 4Government Medical College Amritsar, 5All India Institute of Medical Sciences Gorakhpur, 6St John's Medical College, 7Bukovinian State Medical University
Objective:

To analyze the levels of neuropeptides in CSF of patients with Parkinson’s disease (PD) compared to healthy individuals.

Background:
Neuropeptides are bioactive molecules that play an essential role in maintaining the normal physiological conditions of the body. Growing evidence suggests that neuropeptide dysregulation in cerebrospinal fluid influences the pathophysiology of PD. In this study, we aim to analyze substance P-like-immunoreactivity (SPLI) and somatostatin-like-immunoreactivity (SLI) levels in the CSF of PD patients compared to healthy controls.
Design/Methods:

We systematically searched MEDLINE (PubMed), EMBASE, ScienceDirect, and Scopus using specific search strategies comprising terms related to PD, SLI, and SPLI from the date of database inception to March 2024. Following PRISMA guidelines, our screening and extraction included studies investigating neuropeptide concentrations in Parkinson's patients' cerebrospinal fluid (CSF). Utilizing the 'meta' R package, particularly the 'metacont' tool, we analyzed mean concentration levels and standard differences via the random effects model. Data pooling utilized inverse variance weighting, with I² and tau² assessing heterogeneity. The primary outcome was the mean difference in CSF neuropeptide levels between Parkinson's patients and controls, considering reported units separately.


Results:

Substance P-like-immunoreactivity showed a significant mean difference of -0.77 fmol/mL  (95% CI: -1.48 to -0.06, I² = 0%) in 4 studies (106 PD, 60 controls). Somatostatin like-immunoreactivity showed a mean difference of -5.86 fmol/mL (95% CI: -11.95 to 0.22, I² = 75%) in 5 studies (87 PD, 76 controls), a difference of 8.30 pg/mL  (95% CI: -44.23 to 60.84, I² = 92%) in 2 studies (26 PD, 37 controls), and a difference of -9.19 pmol/L (95% CI: -16.77 to -1.61, I² = 52%) in 2 studies (44 PD, 49 controls). 


Conclusions:
Substance P-like-immunoreactivity significantly decreases in the CSF of PD patients, while somatostatin-like-immunoreactivity shows no significant alterations. Further investigations are necessary to validate and expand upon these significant findings. 
10.1212/WNL.0000000000210353
Disclaimer: Abstracts were not reviewed by Neurology® and do not reflect the views of Neurology® editors or staff.