The Gut-Brain Axis as a Driver of Neuroinflammation: A Non-Amyloid Pathogenesis Framework for Alzheimer’s

Background

Even though the traditional Amyloid Cascade Hypothesis identifies the deposition of Amyloid-beta as the primary cause of Alzheimer’s disease (AD), several clinical trials targeting amyloid therapies suggests that may signify a late-stage symptom rather than a key driver. Emerging research studies show that AD is not merely a central nervous system disorder, but a systemic multi-organ disorder. Precisely, the Microbiota-Gut-Brain Axis (MGBA) has grown as a compelling regulator of neuroinflammation, recognizing it as an important factor in the pathogenesis and early-stage progression of AD.

Method

Using PRISMA 2020 guidelines, a meta-synthetic methodology was followed. Through a systematic search, clinical data from high-impact literature (2022-2025) were evaluated. We selected 25 studies for synthesis and theoretical modeling of the gut-brain inflammatory axis. The focus of the review was on studies linking Dysbiosis to Microglial Activation, explicitly the role of microbial metabolites such as Lipopolysaccharides (LPS) and Short-Chain Fatty Acids (SCFAs) in lowering microglial phenotypes.

Results

The neuroinflammatory pathways are activated by Dysbiosis through the gut-brain axis. This influence AD pathogenesis through inflammatory mediators. As a result, SCFA bacteria which normally protects the brain are reduced in AD patients. Also, the inflammatory theory of neurodegeneration is supported by the raised levels of inflammatory biomarkers such as , , and , perceived in AD. Furthermore, consistent correlation between the increased microglial activation and LPS, the pro-inflammatory toxic byproduct of bad gut bacteria which destroys healthy neurons exists. These toxins release pro-inflammatory cytokines which make microglia into a hyper-aggressive state and in turn this accelerates the formation of Amyloid plaques and Tau tangles.

Conclusion

The neuroinflammation can be reduced by targeting the gut microbiome to restore balance before cognitive decline happens. It offers a scalable, low-cost strategy for preventing AD, especially in areas where advanced neuroimage is not easily accessible. While this framework is promising, it is also necessary to study the role of significant factors such as genetic predispositions and environmental influences in the development of AD. Future research is required to fully understand the complex interactions within the gut-brain axis and its implications in the treatment of AD.

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