Serum zonulin levels are increased in Alzheimer’s disease but not in vascular dementia
Elisa Boschetti, Giacomo Caio, Carlo Cervellati, Anna Costanzini, Valentina Rosta, Fabio Caputo, Roberto De Giorgio, Giovanni Zuliani
Abstract
BACKGROUND: Zonulin is involved in the integrity and functioning of both intestinal-epithelial barrier and blood-brain barrier (BBB) by regulating tight junction molecular assembly. AIM: Since changes in microbiota and BBB may play a role in neurodegenerative disorders, we aimed to determine whether serum zonulin levels change in older patients affected by different types of dementia or mild cognitive impairment (MCI). METHODS: We evaluated serum zonulin levels in patients with late-onset AD (LOAD), vascular dementia (VAD), MIXED (AD + VAD) dementia, amnestic MCI, and in healthy controls. RESULTS: Compared with controls, serum zonulin increased in LOAD, MIXED dementia, and aMCI but not in VAD, independent of potential confounders (ANCOVA p = 0.01; LOAD vs controls, p = 0.01; MIXED vs. controls, p = 0.003; aMCI vs. controls, p = 0.04). Notably, aMCI converting to dementia showed significantly higher levels of zonulin compared with stable aMCI (p = 0.04). Serum zonulin inversely correlated with the standardized Mini-Mental State Examination (MMSE) score (p < 0.05), regardless of potential confounders. DISCUSSION: We found increased serum zonulin levels in patients with aMCI, LOAD and MIXED dementia, but not in VAD; moreover, zonulin levels were higher in aMCI converting to AD compared with stable ones. CONCLUSIONS: Our findings suggest that a dysregulation of intestinal-epithelial barrier and/or BBB may be an early specific event in AD-related neurodegeneration.