The ameliorative potential of metformin against aluminum-induced neurotoxicity: Insights from in vitro studies

Abstract

Alzheimer's disease (AD) is increasingly recognized as a metabolic disorder, often referred to as type 3 diabetes, due to its strong association with insulin resistance. Chronic exposure to aluminum, a known neurotoxin, has been identified as a significant risk factor in the development and progression of AD. This study explores the potential of metformin, a common anti-diabetic drug, to mitigate aluminum-induced neurotoxicity in an in vitro model of AD. Our findings reveal that metformin significantly reduces oxidative stress markers such as malonaldehyde, carbonyl groups, and reactive oxygen species while enhancing antioxidant defenses. Metformin modulates critical signaling pathways, including glycogen synthase kinase 3 beta (GSK3-β)/RAC-alpha serine/threonine protein kinase (RAC-alpha serine/threonine protein kinase (Akt1)/protein phosphatase 2A (PP2A) and Wnt/β-catenin, decreasing Tau protein levels and promoting neurogenesis. These results suggest that metformin may offer a novel therapeutic approach for AD, particularly in cases where aluminum exposure is a contributing factor.

Keywords: Alzheimer's disease; GSK3‐β; Wnt signaling; aluminum; metformin.

FIGURE 1

Exposure of the cells and the procedure of the assay. Differentiation medium 1: DMEM F12 + 1% FBS + 1% antibiotics + 10 μM retinoic acid; differentiation medium 2: DMEM F12 + 1% FBS + 1% antibiotic s + 10 μM retinoic acid + BDNF (2.5 ng/mL). AD, Alzheimer's disease; BDNF, brain‐derived neurotrophic factor; DMEM, Dulbecco's modified eagle medium; FBS, fetal bovine serum.

FIGURE 2

Cell viability at different concentrations of aluminum. Values are given as mean ± SD. *p < 0.001 represents a significant difference between control and individual treatment. SD. ^# p < 0.001 represents a significant difference between control and individual treatment.

FIGURE 3

Cell viability at different concentrations of metformin. Values are given as mean ± SD. ^# p < 0.001 represents a significant difference between control and individual treatment.

FIGURE 4

Intracellular reactive oxygen species (ROS) levels of the study groups. The amount of intracellular ROS produced by the control cells was assumed to be 100%, and the amount of ROS produced by the other cells was calculated as % compared with the control. (a) Significant from the control group, (b) significant from the Met group, (c) significant from the Al group, (d) significant from the AD group, (e) significant from the AD‐Al group. ^# p < 0.001, n = 3. ROS, reactive oxygen species.

FIGURE 5

Cellular antioxidants and oxidants levels in the study groups. (A) Glutathione (GSH), (B) protein carbonyl, (C) malondialdehyde (MDA), and (D) total antioxidant capacity (TAOC) levels. (a) Significant from the control group, (b) significant from the met group, (c) significant from the Al group, (d) significant from the AD group, (e) significant from the AD‐Al group. ^# p < 0.001, n = 3.

FIGURE 6

GSK3‐β, TAU, PPP1CA, and PP2A levels in the study groups. (A) Glycogen synthase kinase‐beta (GSK3‐β), (B) serine/threonine protein phosphatase; PP1, alpha catalytic unit (PPP1CA), (C) protein phosphatase 2A (PP2A), (D) Tau, (E) RAC‐alpha serine/threonine protein kinase (Akt1) levels. (a) Significant from the control group, (b) significant from the met group, (c) significant from the Al group, (d) significant from the AD group, and (e) significant from the AD‐Al group. *p < 0.05, **p < 0.001, n = 3.

FIGURE 7

Alterations in the Wnt/β‐catenin pathway in the study groups. (A) Wnt levels. (B) β‐catenin levels. (a) Significant from the control group, (b) significant from the Metgroup, (c) significant from the Al group, (d) significant from the AD group, and (e) significant from the AD‐Al group. *p < 0.05, ^# p < 0.001, n = 3.