Selenium restores synaptic deficits by modulating NMDA receptors and selenoprotein K in an Alzheimer's disease model.

AIMS Strong evidence has implicated synaptic failure as a direct contributor to cognitive decline in Alzheimer's disease (AD), and selenium (Se) supplementation has demonstrated potential for AD treatment. However, the exact roles of Se and related selenoproteins in mitigating synaptic deficits remain unclear. RESULTS Our data show that selenomethionine (Se-Met), as the major organic form of Se in vivo, structurally restored synapses, dendrites and spines, leading to improved synaptic plasticity and cognitive function in triple transgenic AD (3×Tg-AD) mice. Furthermore, we found that Se-Met ameliorated synaptic deficits by inhibiting extrasynaptic N-methyl-D-aspartate acid receptors (NMDARs) and stimulating synaptic NMDARs, thereby modulating calcium ion (Ca2+) influx. We observed that a decrease in selenoprotein K (SELENOK) levels was closely related to AD and a similar disequilibrium was found between synaptic and extrasynaptic NMDARs in SELENOK knockout mice and AD mice. Se-Met treatment upregulated SELENOK levels and restored the balance between synaptic and extrasynaptic NMDAR expression in AD mice. INNOVATION These findings establish a key signaling pathway linking SELENOK and NMDARs with synaptic plasticity regulated by Se-Met, and thereby provides insight into mechanisms by which Se compounds mediate synaptic deficits in AD. CONCLUSION Our study demonstrates that Se-Met restores synaptic deficits through modulating Ca2+ influx mediated by synaptic and extrasynaptic NMDARs in 3×Tg-AD mice, and suggests a potentially functional interaction between SELENOK and NMDARs.