Objective: To assess correlations between gastrointestinal symptoms and dopamine transporter (DAT) changes in striatal and extrastriatal areas in Parkinson´s disease (PD) patients.

Background: Gastrointestinal symptoms (GIS) are common in PD, but their neurophysiological correlates are not well understood. We recently reported that functional gastrointestinal symptoms were not associated with asymmetry per se but might be associated with lower left striatal DAT binding.¹

Method: 90 PD patients, who underwent DAT ¹²³I-FP-CIT SPECT imaging in the university hospitals of Helsinki and Turku in years 2015-2019, were assessed using the MDS Unified Parkinson´s Disease Rating Scale part III, Rome III, and Wexner constipation score. DAT binding was calculated from striatal subregions using region-to-occipital cortex ratio. Voxelwise analysis was used to assess the relationship between GIS and striatal DAT and extrastriatal serotonin transporter (SERT) binding.

We used independent sample T-test, Mann-Whitney U and Chi-Square test to investigate group differences. Linear regression was used with the regions of interest SBR as the dependent variable and, sex, age, UPDRS III total score and IBS or Wexner as the independent variable.  General linear model implemented in Statistical Parametric Mapping software version 12 was used to investigate the relationship of ¹²³I-FP-CIT binding between DAT and each GIS.

Results: Irritable bowel syndrome (IBS) criteria were fulfilled in 17 patients (Table 1) and this was linked to higher ¹²³I-FP-CIT binding in the right posterior putamen and adjacent areas as compared to patients without IBS (Figure 1). No other significant associations between gastrointestinal symptoms and DAT binding were found.

Conclusion: These findings suggest that PD patients with IBS may have higher DAT binding in the right hemisphere instead of lower binding in the left hemisphere. This finding implicates alterations of brain neurotransmitter physiology in the gastrointestinal symptoms of PD patients.

References: 1. Murtomäki K, Mertsalmi T, Jaakkola E, et al. Gastrointestinal Symptoms and Dopamine Transporter Asymmetry in Early Parkinson’s Disease. Mov Disord. Published online March 11, 2022:mds.28986.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/dopamine-transporter-in-the-brain-is-linked-to-irritable-bowel-syndrome-in-parkinsons-disease/