Recent advances in biomarkers for Parkinson's disease focusing on biochemicals, omics and neuroimaging

Parkinson's disease (PD) is one of the most common neurodegenerative disorders, involving progressive loss of the nigro-striatal dopaminergic neurons. Cardinal symptoms including tremors, muscle rigidity, drooping posture, drooping, walking difficulty, and autonomic symptoms appear when a significant number of nigrostriatal dopaminergic neurons have already been destroyed. Hence, reliable biomarkers are needed for early and accurate diagnosis to measure disease progression and response to therapy. We review the current status of protein and small molecule biomarkers involved in oxidative stress, protein aggregation and inflammation etc. which are present in cerebrospinal fluid, human blood, urine or saliva. In recent years, advances in genomics, proteomics, metabolomics, and functional brain imaging techniques have led to new insights into the pathoetiology of PD. Further studies in the novel discovery of PD biomarkers will provide avenues to treat PD patients more effectively with few or no side effects.