Gut–brain axis dysfunction in Parkinson’s disease: a meta-analysis of microbiome dysbiosis and intestinal barrier markers

Parkinson's disease is associated with reproducible alterations in gut microbiota composition and evidence of intestinal barrier dysfunction. A meta-analysis included 33 studies with 1,588 Parkinson's disease patients and 1,449 healthy controls. The research demonstrated decreased levels of short-chain fatty acid-producing bacteria (Prevotellaceae, Faecalibacterium, and Lachnospiraceae) and increased levels of other species (Akkermansia, Bifidobacteriaceae, and Christensenellaceae). Elevated fecal calprotectin and zonulin levels indicate low-grade intestinal inflammation and impaired intestinal epithelial integrity. Patients with the gut-first disease phenotype showed potentially more pronounced microbiota alterations compared to those with the brain-first phenotype, although this observation is currently based on a limited number of studies. The findings support a biologically plausible role for gut-related mechanisms in disease pathophysiology.