Investigation of thymol effect on learning and memory impairment induced by intrahippocampal injection of amyloid beta peptide in high fat diet- fed rats
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Obesity and consumption of a high fat diet (HFD) are known to increase the risk of Alzheimer’s disease (AD). In the present study, we have examined the protective and therapeutic effects of thymol (main monoterpene phenol found in thyme essential oil) on a HFD-fed rat model of AD. Fourty adult male Wistar rats were randomly assigned to 5 groups:(n = 8 rats/group): group 1, control, consumed an ordinary diet, group 2 consumed a HFD for 8 weeks, then received phosphate-buffered saline (PBS) via intrahippocampal (IHP) injection, group 3 consumed HFD for 8 weeks, then received beta-amyloid (Aβ)1–42 via IHP injections to induce AD, group 4 consumed HFD for 8 weeks, then received Aβ1–42, and was treated by thymol (30 mg/kg in sunflower oil) daily for 4 weeks, and group 5 consumed HFD for 8 week, then received Aβ1–42 after what sunflower oil was administered by oral gavage daily for 4 weeks. Biochemical tests showed an impaired lipid profile and higher glucose levels upon consumption of HFD, which was ameliorated by thymol treatment. In behavioral results, spatial memory in group 3 was significantly impaired, but groups treated with thymol showed better spatial memory compared to group 3 (p ≤ 0.01). In histological results, formation of Aβ plaque in hippocampus of group 3 increased significantly compared to group 1 and group 2 (p ≤ 0.05), but group 4 showed decreased Aβ plaques compared to group 3 (p ≤ 0.01). In conclusion, thymol decreased the effects of Aβ on memory and could be considered as neuroprotective.
KeywordsAlzheimer's disease Abeta High fat diet Memory Thymol
This study has been performed in the Laboratory Complex of the Science and Research Branch of Azad University and in the Neurophysiology Research Center of Hamadan University of Medical Sciences. The project has been partly supported by grant number 9312186882 of the Hamadan University of Medical Sciences.
Compliance with ethical standards
Conflict of interests
All authors declare to have no conflict of interests.
- Aman S, Moin S, Owanis M, Siddiqui MU (2013) Antioxidant activity of thymol: protective role in AAPH-induced hemolysis in diabetic erythrocytes. IJPSI 2(3):55–60Google Scholar
- Angelov, Ivan, Villanueva, D, Stateva, Roumiana P, Reglero, Guillermo, Ibañez, Elena & Fornari, Tiziana (2013) Extraction of Thymol from different varieties of thyme plants using green solventsGoogle Scholar
- Esmaeili A, Khodadadi A (2012) Antioxidant activity of a solution of thymol in ethanol. Zahedan J Res Med Sci 14(7):14–18Google Scholar
- Ghahremanitamadon, Fatemeh, Shahidi, Siamak, Zargooshnia, Somayeh, Nikkhah, Ali, Ranjbar, Akram, & Soleimani, Asl Sara. (2014). Protective effects of Borago officinalis extract on amyloid β-peptide (25–35)-induced memory impairment in male rats: a behavioral study. BioMed research international, 2014Google Scholar
- Komatsu T, Chiba T, Yamaza H, Yamashita K, Shimada A, Hoshiyama Y, Henmi T, Ohtani H, Higami Y, de Cabo R, Ingram DK, Shimokawa I (2008) Manipulation of caloric content but not diet composition, attenuates the deficit in learning and memory of senescence-accelerated mouse strain P8. Exp Gerontol 43(4):339–346CrossRefPubMedGoogle Scholar
- Kulshreshtha A, Piplani P (2016) Current pharmacotherapy and putative disease-modifying therapy for Alzheimer’s disease. Neurol Sci:1–33Google Scholar
- Li, Hongyan, Qin, Tingting, Li, Min, Ma, Shiping (2016) Thymol improves high-fat diet-induced cognitive deficits in mice via ameliorating brain insulin resistance and upregulating NRF2/HO-1 pathway. Metabolic Brain Disease, 1–9Google Scholar
- Paxinos G, Watson C (2005) The rat brain in stereotaxic coordinates. Burlington MA Elsevier Inc.Google Scholar
- Vargas-Robles H (2015) Rios, Amelia, Arellano-Mendoza, Monica, Escalante, Bruno a, & Schnoor, Michael (2015) antioxidative diet supplementation reverses high-fat diet-induced increases of cardiovascular risk factors in mice . doi: 10.1155/2015/467471 Oxidative medicine and cellular longevity Google Scholar