Evaluation of the Relationship Between Zonulin and Claudin-5 Levels, Markers of Endothelial Permeability, and Essential Tremor: An Observational Case-Control Study

Essential tremor (ET) is a chronic, progressive movement disorder characterized by symmetrical kinetic and postural tremors. Zonulin and Claudins are key proteins involved in intestinal permeability, with Claudin-5 specifically found in the blood–brain barrier (BBB). Although hypotheses about ET’s pathophysiology exist, significant gaps remain. Recent studies suggest that neuroinflammation and the gut-brain axis may play a role in ET. This study investigates whether Zonulin and Claudin-5, molecules involved in the integrity of the BBB and intestinal endothelial tight junctions, are associated with ET. ET patients diagnosed and followed for at least one year were included in this study. The control group consisted of volunteers without neurological disorders. A total of 80 ET patients and 32 healthy controls were included. Serum Zonulin and Claudin-5 levels were measured from venous blood samples. The mean age of participants was 57.2 ± 14.8 years, with 43.8% male. No significant differences were observed in Zonulin levels between the ET and control groups. However, Claudin-5 levels were significantly lower in the ET group (p < 0.001) compared to controls. Claudin-5 is an important marker of endothelial and epithelial dysfunction in the BBB. The low serum Claudin-5 levels in the ET group may be related to impaired BBB permeability.