Alpha-synuclein in gastric and colonic mucosa in Parkinson's disease: Limited role as a biomarker.

BACKGROUND: Gastric and colonic alpha-synuclein immunoreactivity has been reported in patients with Parkinson's disease (PD). However, enteric alpha-synuclein also has been reported in healthy individuals.

OBJECTIVES: We aimed to investigate the utility of alpha-synuclein immunoreactivity from gastric and colonic mucosal tissues obtained by routine endoscopy to detect PD, and to correlate the pathological burden of alpha-synuclein with motor and nonmotor features of PD.

METHODS: We recruited 104 study subjects, consisting of 38 patients with PD, 13 patients with probable multiple system atrophy (MSA), and 53 healthy controls. Gastric and colonic mucosal tissues obtained by endoscopic gastroduodenoscopy and colonoscopy were assessed using alpha-synuclein immunohistochemistry. Detailed motor and nonmotor features of PD were correlated with enteric alpha-synuclein immunoreactivity.

RESULTS: No difference was seen in the enteric α-SYN immunoreactivity among patients with PD (31.6% for stomach and 10.4% for colon), patients with MSA (40.0% for stomach and 8.0% for colon), and healthy controls (33.3% for stomach and 18.5% for colon). The frequency of positive alpha-synuclein immunoreactivity was higher in gastric biopsy tissues than in colonic biopsy tissues in all of the study groups (P < 0.05). No significant correlation was found between the presence of alpha-synuclein immunoreactivity and the motor and nonmotor features of PD.

CONCLUSIONS: The presence of alpha-synuclein immunoreactivity in gastric and colonic mucosa was detected in a similar manner in patients with PD, patients with MSA, and controls, thus suggesting a limited role of enteric mucosal alpha-synuclein as a diagnostic biomarker for PD. Future studies are warranted to detect pathological alpha-synuclein strains.