Currently clinicians diagnose individuals with Parkinson disease (PD) based on their clinical symptoms. This occurs at later stages of the disease when the brain cells that control movement have already been killed due to the accumulation of abnormal clumps of a protein known as alpha-synuclein (aSyn). As a result, researchers have been trying to develop a test that can diagnose the disease earlier, when treatments might be more effective.
Several studies have shown that the presence of aSyn protein in the colon can be used to distinguish patients with PD. However, a new study led by UHN Researcher Dr. Lili-Naz Hazrati, which looked at the expression of aSyn in patients with and without PD, has raised serious concerns about these findings.
Dr. Hazrati and her team developed a staining technique that detects clumps of aSyn with greater sensitivity than those currently used. They used this technique to evaluate the levels of aSyn in patients with PD and compared the results to those of patients without any symptoms of the disease. Their analysis showed that even though tissues from patients with PD were more likely to express aSyn, patients without any symptoms for PD also had aSyn protein clumps present in their colons.
Explains Dr. Hazrati, "Our study provides strong evidence that levels of aSyn in the colon are not indicative of Parkinson disease. However, because levels of the protein are higher in individuals with PD, it remains to be determined if aSyn could be utilized as a biomarker when combined with other clinical tests."
This work was supported by Parkinson Society Canada and the Toronto General & Western Hospital Foundation.
Colonic mucosal α-synuclein lacks specificity as a biomarker for Parkinson disease. Visanji NP, Marras C, Kern DS, Al Dakheel A, Gao A, Liu LW, Lang AE, Hazrati LN. Neurology. 2015 Jan 14. [Pubmed abstract]