Of the manuscript: relationship between serum Zonulin level and sarcopenia in Parkinson's disease

This study aimed to evaluate serum zonulin levels, an intestinal permeability marker, in Parkinson's disease (PD) patients and explore its relationships with sarcopenia, motor subtypes, clinical features, and age- and sex-matched controls.

This observational cross-sectional study evaluated 119 participants (64 with PD, 55 controls). Demographic data, along with disease duration, comorbidities, and motor subtypes, were documented. Handgrip strength and skeletal muscle mass index (SMMI) were used to assess sarcopenia, with SMMI determined by bioelectrical impedance analysis and adjusted for BMI using Turkish-specific cut-offs. Serum zonulin levels were assessed via ELISA.

Compared to controls, zonulin levels were generally increased in PD patients; however, the difference was statistically insignificant (p = 0.289). Zonulin levels, though, varied notably across PD motor subtypes, with mixed-type showing the highest median levels (p = 0.004). The PD group had a significantly higher sarcopenia prevalence (73.4%) than the control group (53.7%), and longer disease duration was associated with sarcopenia (p = 0.014). There was no significant difference in zonulin levels between sarcopenic and non-sarcopenic individuals.

Zonulin serum levels seem to differ based on PD motor subtype, which implies that gut permeability might influence phenotypic expression. The connection between sarcopenia, common in PD and related to disease duration, and its direct association with zonulin remains unclear. Future research should investigate gut-muscle-brain connections in longitudinal designs and evaluate whether interventions targeting intestinal permeability are associated with, rather than directly modifying, clinical outcomes in PD.