Metformin improves memory via AMPK/mTOR-dependent route in a rat model of Alzheimer’s disease

Document Type : Original Article


1 Cellular and Molecular Research Center, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran

2 Department of Physiology, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran

3 Neuroscience Research Center, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran


Objective(s): Metformin, as an insulin sensitizer, is a familiar antidiabetic drug. Increasing evidence points to metformin’s protective effects against Alzheimer’s disease (AD). However, the mechanism is not well understood. The present study evaluated whether inhibiting AMPK and activating mTOR could stop metformin from improving memory in rats with streptozotocin (STZ) -induced Alzheimer’s disease.
Materials and Methods: Twelve-week-old Wistar rats, were injected 3 mg/kg STZ intracerebroventricularly on days 1 and 3 to develop the animal model. Metformin was applied orally at 100 mg/kg (17 days). Forty-five min before the retrieval phase, dorsomorphin (DM; AMPK inhibitor, 2 M) and MHY (mTOR activator, 0.1 M) were administered. Morris Water Maze (MWM) and shuttle box were utilized to measure spatial and passive avoidance memory, respectively. Congo red staining was used to identify cortical amyloid deposition.
Results: The findings exhibited a considerable enhancement in spatial learning and memory in the metformin treatment group (P≤0.05). Injection of DM and MHY alone could not significantly change MWM and passive avoidance. Additionally, co-administration of DM and MHY increased escape latency (P≤0.001) and reduced the total time spent in the target quadrant (TTS) (P≤0.05) compared to the STZ+MET group during retrieval of MWM. Also, co-injection of DM and MHY increased step-through latency (STL) and decreased time spent in the dark compartment (TDC) compared to the STZ+MET group (P≤0.001).
Conclusion: Metformin appears to have a therapeutic impact by activating AMPK and inactivating mTOR. As a result, it could be used as an Alzheimer’s treatment strategy.


Main Subjects

1. Chen XQ, Mobley WC. Alzheimer disease pathogenesis: ]nsights from molecular and cellular biology studies of oligomeric aβ and tau species. Front Neurosci 2019; 13: 1-21.
2. Chen F, Dong RR, Zhong KL, Ghosh A, Tang SS, Long Y, et al. Antidiabetic drugs restore abnormal transport of amyloid-β across the blood-brain barrier and memory impairment in db/db mice. Neuropharmacology 2016; 101:123-136.
3. De Felice FG, Vieira MN, Bomfim TR, Decker H, Velasco PT, Lambert MP, et al. Protection of synapses against Alzheimer’s-linked toxins: insulin signaling prevents the pathogenic binding of Abeta oligomers. Proc Natl Acad Sci U S A 2009; 106:1971-1976.
4. Zanni R, Garcia-Domenech R, Galvez-Llompart M, Galvez J. Alzheimer: A decade of drug design. Why molecular topology can be an extra edge? Curr Neuropharmacol 2018; 16:849-864.
5. Markowicz-Piasecka M, Sikora J, Szydłowska A, Skupień A, Mikiciuk-Olasik E, Huttunen KM. Metformin - a future therapy for neurodegenerative diseases: theme: drug discovery, development and delivery in alzheimer’s disease guest editor: Davide brambilla. Pharm Res 2017; 34:2614-2627.
6. Gupta A, Bisht B, Dey CS. Peripheral insulin-sensitizer drug metformin ameliorates neuronal insulin resistance and Alzheimer’s-like changes. Neuropharmacology 2011; 60:910-920.
7. Alagiakrishnan K, Sankaralingam S, Ghosh M, Mereu L, Senior P. Antidiabetic drugs and their potential role in treating mild cognitive impairment and Alzheimer’s disease. Discov Med 2013; 16:277-286.
8. Peixoto CA, Oliveira WH, Araújo S, Nunes AKS. AMPK activation: Role in the signaling pathways of neuroinflammation and neurodegeneration. Exp Neurol 2017; 298:31-41.
9. Caberlotto L, Lauria M, Nguyen TP, Scotti M. The central role of AMP-kinase and energy homeostasis impairment in Alzheimer’s disease: a multifactor network analysis. PLoS One 2013; 8:e78919.
10. Salminen A, Kaarniranta K, Haapasalo A, Soininen H, Hiltunen M. AMP-activated protein kinase: A potential player in Alzheimer’s disease. J Neurochem 2011; 118:460-474.
11. Assefa BT, Tafere GG, Wondafrash DZ, Gidey MT. The  bewildering effect of AMPK activators in Alzheimer’s disease: Review of the current evidence. Biomed Res Int 2020; 9895121: 1-18.
12. Liao FF, Xu H. Insulin signaling in sporadic Alzheimer’s disease. Sci Signal 2009; 2: 1-6.
13. Wang Y, Zhang Y, Feng X, Tian H, Fu X, Gu W, et al. Metformin inhibits mTOR and c-Myc by decreasing YAP protein expression in OSCC cells. Oncology Reports 2021; 45:1249-1260.
14. Mueed Z, Tandon P, Maurya SK, Deval R, Kamal MA, Poddar NK. Tau and mTOR: The hotspots for multifarious diseases in Alzheimer’s development. Frontiers in neuroscience 2019; 12:1-14.
15. Maiese K. Novel nervous and multi-system regenerative therapeutic strategies for diabetes mellitus with mTOR. Neural Regen Res 2016; 11:372-385.
16. Kuhla A, Brichmann E, Ruhlmann C, Thiele R, Meuth L, Vollmar B. Metformin therapy aggravates neurodegenerative processes in ApoE-/- mice. J Alzheimers Dis 2019; 68:1415-1427.
17. Zhao M, Cheng X, Lin X, Han Y, Zhou Y, Zhao T, et al. Metformin administration prevents memory impairment induced by hypobaric hypoxia in rats. Behav Brain Res 2019; 363:30-37.
18. Paxinos G, Watson C. The rat brain in stereotaxic coordinates: Hard cover edition: Elsevier; 2006.
19. Rashtiani S, Goudarzi I, Jafari A, Rohampour K. Adenosine monophosphate activated protein kinase (AMPK) is essential for the memory improving effect of adiponectin. Neurosci Lett 2021; 749:1-7.
20. Mostafa DK, Ismail CA, Ghareeb DA. Differential metformin dose-dependent effects on cognition in rats: Role of Akt. Psychopharmacology (Berl) 2016; 233:2513-2524.
21. Kouhestani S, Jafari A, Babaei P. Kaempferol attenuates cognitive deficit via regulating oxidative stress and neuroinflammation in an ovariectomized rat model of sporadic dementia. Neural Regen Res 2018; 13:1827-1832.
22. Afshar S, Shahidi S, Rohani AH, Komaki A, Asl SS. The effect of NAD-299 and TCB-2 on learning and memory, hippocampal BDNF levels and amyloid plaques in Streptozotocin-induced memory deficits in male rats. Psychopharmacology (Berl) 2018; 235:2809-2822.
23. Farr SA, Roesler E, Niehoff ML, Roby DA, McKee A, Morley JE. Metformin improves learning and memory in the SAMP8 mouse model of Alzheimer’s disease. J Alzheimers Dis 2019; 68:1699-1710.
24. Zhao M, Li XW, Chen Z, Hao F, Tao SX, Yu HY, et al. Neuro-protective role of metformin in patients with acute stroke and type 2 diabetes mellitus via AMPK/mammalian target of rapamycin (mTOR) signaling pathway and oxidative stress. Med Sci Monit 2019; 25:2186-2194.
25. Ou Z, Kong X, Sun X, He X, Zhang L, Gong Z, et al. Metformin treatment prevents amyloid plaque deposition and memory impairment in APP/PS1 mice. Brain Behav Immun 2018; 69:351-363.
26. Cai Z, Chen G, He W, Xiao M, Yan LJ. Activation of mTOR: A culprit of Alzheimer’s disease? Neuropsychiatr Dis Treat 2015; 11:1015-1030.
27. Yang L, Jiang Y, Shi L, Zhong D, Li Y, Li J, et al. AMPK: Potential therapeutic target for alzheimer’s disease. Curr Protein Pept Sci 2020; 21:66-77.
28. Kickstein E, Krauss S, Thornhill P, Rutschow D, Zeller R, Sharkey J, et al. Biguanide metformin acts on tau phosphorylation via mTOR/protein phosphatase 2A (PP2A) signaling. Proc Natl Acad Sci U S A 2010; 107:21830-21835.
29. Chiang MC, Cheng YC, Chen SJ, Yen CH, Huang RN. Metformin activation of AMPK-dependent pathways is neuroprotective in human neural stem cells against Amyloid-beta-induced mitochondrial dysfunction. Exp Cell Res 2016; 347:322-331.
30. Inoki K, Kim J, Guan K-L. AMPK and mTOR in cellular energy homeostasis and drug targets. Annu Rev Pharmacol Toxicol 2012; 52:381-400.
31. Arsikin K, Kravic-Stevovic T, Jovanovic M, Ristic B, Tovilovic G, Zogovic N, et al. Autophagy-dependent and -independent involvement of AMP-activated protein kinase in 6-hydroxydopamine toxicity to SH-SY5Y neuroblastoma cells. Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease 2012; 1822:1826-1836.
32. Markowicz-Piasecka M, Sikora J, Szydlowska A, Skupien A, Mikiciuk-Olasik E, Huttunen KM. Metformin - a future therapy for neurodegenerative diseases: Theme: drug discovery, development and delivery in alzheimer’s disease guest editor: Davide brambilla. Pharm Res 2017; 34:2614-2627.