Linking inflammation, metabolic dysfunction, and neurodegeneration: a comprehensive review of TLR2 pathways in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder increasingly recognized as a systemic inflammatory condition with significant neurological effects. Growing evidence shows that chronic low-grade inflammation (CLGI), insulin resistance, and metabolic imbalance contribute to cognitive decline and the development of neurodegenerative diseases like Alzheimer's and Parkinson's. Toll-like receptor 2 (TLR2), a critical pattern-recognition receptor of the innate immune system, has emerged as an essential molecular link between metabolic dysfunction and neuroinflammation and neuronal damage. This review summarizes current experimental, clinical, and translational evidence on the role of TLR2 in T2DM-related inflammation, mitochondrial dysfunction, lipid imbalance, insulin resistance, and blood-brain barrier (BBB) issues. We explore how ongoing TLR2 activation by internal danger signals and metabolic stressors maintains systemic inflammation and fuels neuroimmune responses via microglial activation and cytokine release, thereby accelerating neurodegenerative processes. Additionally, we discuss new therapeutic strategies targeting TLR2 signaling, including drugs, dietary supplements, and the repurposing of antidiabetic medications with neuroprotective effects. By combining immunometabolic and neurodegenerative pathways, this review highlights TLR2 as a promising target for preventing or reducing diabetes-related cognitive decline neurodegeneration.