Dysregulated mTOR signaling in Alzheimer's disease: Linking pathogenic mechanisms to emerging therapeutic strategies

Alzheimer's disease (AD) is a complex neurodegenerative disorder characterized by progressive cognitive decline and multifaceted pathogenic mechanisms (including amyloid-β [Aβ] plaques, tau neurofibrillary tangles, synaptic dysfunction, and neuroinflammation). Importantly, no effective disease-modifying treatment is currently available for AD. Emerging evidence implicates dysregulated mammalian target of rapamycin (mTOR) signaling as a key contributor to AD pathogenesis. This review analyzes how aberrant mTOR signaling influences major aspects of AD pathology, including Aβ production and clearance, tau protein hyperphosphorylation, autophagy dysfunction, synaptic plasticity impairments, neuroinflammation, and oxidative stress. Notably, hyperactivated mTOR accelerates AD progression through multiple mechanisms. It promotes Aβ accumulation and tau pathology, suppresses autophagic clearance of toxic aggregates, and disrupts neuronal homeostasis, thereby exacerbating cognitive decline. Consequently, mTOR has gained attention as a therapeutic target. This review evaluates the therapeutic potential of various mTOR-targeted interventions, such as the mTORC1 inhibitor rapamycin and its analogues (rapalogs), second-generation ATP-competitive mTOR inhibitors, and certain natural compounds and traditional Chinese medicine approaches. These strategies have demonstrated promise in mitigating AD-related pathology by enhancing autophagy, reducing Aβ/tau burden, and preserving synaptic and cognitive function in preclinical studies. However, the clinical translation of mTOR-targeted therapies faces key challenges, including poor blood-brain barrier penetration of many mTOR inhibitors, potential systemic side effects, and limited clinical validation to date. Further research is needed to optimize brain delivery, dosing regimens, and target specificity to fully realize the therapeutic potential of mTOR modulation in AD.