Salivary Biomarkers for Parkinson’s Disease: A Systematic Review with Meta-Analysis

Abstract

Parkinson’s Disease (PD) is a common neurodegenerative disease which manifests with motor features, such as bradykinesia, resting tremor, rigidity, and postural instability. Using the non-invasive technique of saliva collection, we designed a systematic review to answer the question “Are salivary biomarkers reliable for the diagnosis of Parkinson’s Disease?”. Following inclusion and exclusion criteria, 30 studies were included in this systematic review (according to the PRISMA statement guidelines). Mostly proteins were reported as potential biomarkers in saliva. Based on meta-analysis, in PD patients, salivary levels of total alpha-synuclein were significantly decreased, and those of oligomeric alpha-synuclein were significantly increased. Also, according to pooled AUC, heme oxygenase-1 demonstrated significant predictive value for saliva-based PD diagnosis. In conclusion, some potential biomarkers, especially alpha-synuclein, can be altered in the saliva of PD patients, which could be reliably useful for early diagnosis of this neurodegenerative disease differentiating other synucleopathies.

Neuroinflammation: A Critical Factor in Neurodegenerative Disorders

“…One of the main proteins in the CNS, alpha-synuclein, misfolds and aggregates due to the incapacity of the dopaminergic neurons to manage oxidative stress, which leads to the accumulation of alpha-synuclein, gaining a toxic function at the same time. The overexpression of alpha-synuclein increases the levels of oxidative stress and changes the structure of the mitochondria, which decreases the amount of ATP produced and increases the generation of free radicals, followed by the accumulation of alphasynuclein [31,32].…”