Late-life methionine restriction attenuates neuroinflammation in Alzheimer's disease mice via FGF21 activation in a metabolism-independent manner.

INTRODUCTION

Aging worsens Alzheimer's disease (AD) peripheral metabolism and central pathology, yet few interventions are effective when started late. Methionine restriction (MR) induces the hepatokine FGF21 and may protect brain function, but its efficacy and mechanisms when started late are unclear.

METHODS

Fourteen-month-old male APP/PS1 mice received 17 weeks of MR (0.17% methionine); behavioral, histological, and molecular assays were performed and hippocampal FGFR1 was knocked down by adeno-associated virus.

RESULTS

Late-life MR improved peripheral glucose/lipid profiles, reduced Aβ deposition, preserved synaptic markers, and suppressed neuroinflammation. MR-induced hepatic FGF21 and brain FGFR1-AMPKα signaling to inhibit NFκB; hippocampal FGFR1 knockdown abolished MR's neuroprotective effects while leaving peripheral metabolic changes intact.

DISCUSSION: Even when initiated in late life, MR robustly reduces AD pathology via the hepatic FGF21-brain FGFR1 axis, independent of peripheral metabolic changes. These preclinical findings position MR and FGF21-FGFR1 axis as actionable late-life intervention targets with potential for clinical translation.