Type 3 Diabetes: A Molecular Link Between Cerebral Insulin Resistance and Neurodegeneration via AGE–RAGE Signaling

Type 3 diabetes, a term that underscores the pathological connection between Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD), emphasizes the role of cerebral insulin resistance and metabolic dysfunction in neuron degeneration. Cerebral insulin resistance impairs Akt signaling, leading to the suppression of GSK-3β activity, enhancement of tau hyperphosphorylation and neurofibrillary tangle formation. Concurrent impaired GLUT-3/4 translocation, mitochondrial function, and amyloid-β clearance exacerbate oxidative stress and plaque deposition. Collectively, these disruptions compromise synaptic plasticity and cognition, accelerating AD progression. Moreover, activation of AGE-RAGE-NF-κB signaling amplifies neuroinflammation, further aggravating tau and Aβ pathology. This interaction activates downstream MAPK, ERK1/2, and JNK/STAT pathways, which in turn stimulate transcription factors such as NF-κB, TGF-β, HIF-1α, and AP-1. The resulting cascade promotes oxidative stress, neuroinflammation, and PI3K/Akt/IRS-1 signaling impairment. Together, these interconnected pathways accelerate neuronal loss and cognitive decline. Emerging evidence indicates that natural bioactive compounds offer therapeutic benefits in AD by attenuating AGE-RAGE-mediated oxidative stress, neuroinflammation, and cerebral insulin resistance, thereby reducing amyloid-β accumulation and tau hyperphosphorylation. This review highlights the AGE-RAGE axis as a critical molecular mediator connecting T2DM and AD, orchestrating neuroinflammation, mitochondrial dysfunction, and tau hyperphosphorylation. Therapeutic strategies aimed at inhibiting AGE formation or blocking RAGE activation represent promising approaches to attenuate cognitive decline associated with Type 3 diabetes.