Abstract

Background

Oxidative stress and maladaptive neuroimmune activation contribute to cognitive decline in Alzheimer's disease (AD) and represent therapeutic targets beyond amyloid-centered approaches.

Objective

To determine whether oral D-methionine (D-Met), a redox-active amino acid, reduces amyloid pathology and lipid peroxidation and confers disease-modifying benefits in AD models.

Methods

Male and female APP/PS1 and APPNL−Fmice with advanced AD pathology received oral D-Met or vehicle. Behavioral assessments included locomotor activity and hippocampal-dependent spatial learning and memory. Amyloid burden, lipid peroxidation, peripheral metabolic, and inflammatory markers, and hippocampal microglial phenotypes were evaluated.

Results

D-Met did not alter locomotor or exploratory behavior but improved spatial memory recall in both sexes of APP/PS1 mice and in female APPNL−F mice. APPNL−F males exhibited improved Morris water maze learning. Amyloid pathology was region-specifically reduced, including decreased hippocampal plaque size in male APPNL−F mice, reduced cortical plaque size in female APP/PS1 mice, and lower soluble amyloid-β (Aβ)42 in male APP/PS1 mice. Lipid peroxidation was reduced only in female APPNL−F mice. D-Met induced pronounced sex-dependent peripheral effects, increasing adiposity and pro-inflammatory adipose signaling in males, while reducing perigonadal white adipose tissue IL-6 expression in female APPNL−F mice. In the hippocampus, D-Met decreased microglial activation, with female APPNL−Fmice showing reduced Iba1 and disease-associated microglial markers and increased Axl expression.

Conclusions

Short-term D-Met acts as a metabolic and redox modulator with amyloid-lowering effects mediated by improved microglial function. Therapeutic efficacy is strongly sex- and model-dependent, with the greatest benefit observed in female APPNL−F mice.

Download

Share

COinS