Optimizing the structure of repurposed metformin can improve anti-cholinesterase and anti-amyloidogenic effects

Alzheimer's disease (AD) and diabetes mellitus (DM) share common pathological features, including insulin resistance, oxidative stress, and inflammation, suggesting AD may be considered a brain-specific form of DM. Metformin, a widely used antidiabetic drug, has shown neuroprotective effects potentially beneficial in AD by modulating insulin signaling, reducing inflammation, and inhibiting beta-amyloid (Aβ) aggregation. However, its hydrophilic nature limits brain permeability, prompting the synthesis of metformin derivatives to enhance pharmacokinetic properties. This study investigates a series of sulfonamide derivatives of metformin for their cholinesterase (ChE) inhibition using human acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), anti-Aβ aggregation using thioflavin T fluorescence assay in vitro, and antioxidative properties in human umbilical endothelial cells (HUVEC) and astrocytes. In vitro assays revealed that studied derivatives exhibit selective inhibitory activity against BChE over AChE. Additionally, certain derivatives demonstrated a synergistic effect with donepezil in AChE inhibition. The derivatives effectively inhibited also Aβ aggregation at both early and late stages, which may reduce Aβ plaque formation. Furthermore, the antioxidative properties of these derivatives were validated in cell-based assays, showing protective effects against oxidative stress in HUVEC and astrocytes. Thus, these findings suggest that metformin derivatives could serve as a dual-action therapy for AD by targeting both cholinergic and amyloidogenic pathways while providing antioxidative support. Future studies may focus on refining these compounds to optimize therapeutic potential in AD treatment, presenting a promising approach for repurposing antidiabetic drugs to address neurodegenerative disease mechanisms.