Comment on “Microbiota Composition and Metabolism Are Associated With Gut Function in Parkinson's Disease”

Abstract

I would like to comment on the recently published article titled "Microbiota Composition and Metabolism Are Associated With Gut Function in Parkinson's Disease" in Movement Disorders. Cirstea et al 1 analyzed the correlation between intestinal symptoms, intestinal flora, and serum metabolomics in patients with Parkinson's disease (PD) based on large samples and came up with novel findings. The researchers evaluated 300 participants in detail, including daily dietary intake and intestinal complications. However, I have some concerns. First, it was declared in the Results section that p-cresol (HMDB0001858) and phenylacetylglutamine (HMDB0006344) were both significantly positively correlated with constipation severity among patients (Fig. 3E). Nevertheless, the result of phenylacetylglutamine cannot be found in Figure 3E, and there are 2 plots of different correlations between p-cresol and constipation severity among patients with PD. Second, as shown in the Discussion section, nearly half of controls (43 of 103) were spouses of the PD patients. In other words, within the cohort composed of pairs of couples, the diet-driven heterogeneity in gut microbiota between the patient and the control might be negligible because couples share more of their gut microbiota than individuals from different households. 2 However, an individual's dietary pattern might be a confounding factor for analysis of gut microbiota for the rest of the 147 patients and the other healthy controls. Notably, several studies 2-4 assessing the relationship between gut microbiota and PD included merely couples-based populations to reduce the interfering effect of different dietary patterns. Therefore, we hope that the authors will make a further subgroup analysis to validate their findings in different patient cohorts. To sum up, the present study is interesting and inspiring research in which more detailed information should be analyzed and available to readers so as to be more helpful in a deep understanding of intestinal symptoms, intestinal flora, and serum metabolomics in PD patients.