Lychee seed extract protects against neuronal injury and improves cognitive function in rats with type II diabetes mellitus with cognitive impairment

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Abstract

Lychee seed is a traditional Chinese medicine and has many beneficial effects such as modulation of blood sugar and lipids, antioxidation, antivirus and antitumor. Studies have indicated that type II diabetes mellitus (T2DM) and Alzheimer's disease (AD) share common biological mechanisms including insulin resistance, impaired glucose metabolism, β-amyloid (Aβ) formation, oxidative stress and presence of advanced glycation end products (AGEs). The present study investigated the effects of lychee seed extract (LSE) on neuroprotection, cognitive function improvement and possible underlying mechanisms in a rat model of T2DM with cognitive impairment. We analyzed the chemical profile of LSE using a UHPLC-SPD chromatogram and evaluated its effect on the improvement of spatial learning and memory of rats by a Morris water maze. The levels of glucose, insulin, Aβ, AGEs, Tau protein and acetylcholinesterase in the blood and/or hippocampus of rats were determined by blood-glucose meter, radioimmunoassay, chemical chromatometry, enzyme-linked immunosorbent assay (ELISA) and immunohistochemical analysis, respectively. Results demonstrated that LSE consists of eight major and around 20 minor ingredients, and it remarkably prevents neuronal injury and improves cognitive functions in T2DM rats. The levels of glucose, insulin, Aβ, AGEs and Tau protein were significantly increased in the blood and/or hippocampus of T2DM rats, while LSE remarkably decreased their levels compared to vehicle treatment (P<0.01). The possible mechanisms may be associated with IR improvement and decreased formations of Aβ, AGEs and Tau protein in the hippocampus of T2DM rats. LSE may be developed as the agent for the treatment of T2DM and/or AD clinically.

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Combination of high-fat diet-fed and low-dose streptozotocin-treated rat: a model for type 2 diabetes and pharmacological screening.

K. SRINIVASAN, B Viswanad, Lydia Asrat … (2005)

The objective of the present study was to develop a rat model that replicates the natural history and metabolic characteristics of human type 2 diabetes and is also suitable for pharmacological screening. Male Sprague-Dawley rats (160-180 g) were divided into two groups and fed with commercially available normal pellet diet (NPD) (12% calories as fat) or in-house prepared high-fat diet (HFD) (58% calories as fat), respectively, for a period of 2 weeks. The HFD-fed rats exhibited significant increase in body weight, basal plasma glucose (PGL), insulin (PI), triglycerides (PTG) and total cholesterol (PTC) levels as compared to NPD-fed control rats. Besides, the HFD rats showed significant reduction in glucose disappearance rate (K-value) on intravenous insulin glucose tolerance test (IVIGTT). Hyperinsulinemia together with reduced glucose disappearance rate (K-value) suggested that the feeding of HFD-induced insulin resistance in rats. After 2 weeks of dietary manipulation, a subset of the rats from both groups was injected intraperitoneally with low dose of streptozotocin (STZ) (35 mg kg(-1)). Insulin-resistant HFD-fed rats developed frank hyperglycemia upon STZ injection that, however, caused only mild elevation in PGL in NPD-fed rats. Though there was significant reduction in PI level after STZ injection in HFD rats, the reduction observed was only to a level that was comparable with NPD-fed control rats. In addition, the levels of PTG and PTC were further accentuated after STZ treatment in HFD-fed rats. In contrast, STZ (35 mg kg(-1), i.p.) failed to significantly alter PI, PTG and PTC levels in NPD-fed rats. Thus, these fat-fed/STZ-treated rats simulate natural disease progression and metabolic characteristics typical of individuals at increased risk of developing type 2 diabetes because of insulin resistance and obesity. Further, the fat-fed/STZ-treated rats were found to be sensitive for glucose lowering effects of insulin sensitizing (pioglitazone) as well as insulinotropic (glipizide) agents. Besides, the effect of pioglitazone and glipizide on the plasma lipid parameters (PTG and PTC) was shown in these diabetic rats. The present study represents that the combination of HFD-fed and low-dose STZ-treated rat serves as an alternative animal model for type 2 diabetes simulating the human syndrome that is also suitable for testing anti-diabetic agents for the treatment of type 2 diabetes.

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Alzheimer disease therapy--moving from amyloid-β to tau.

Gabriel Gold, E Giacobini (2013)

Disease-modifying treatments for Alzheimer disease (AD) have focused mainly on reducing levels of amyloid-β (Aβ) in the brain. Some compounds have achieved this goal, but none has produced clinically meaningful results. Several methodological issues relating to clinical trials of these agents might explain this failure; an additional consideration is that the amyloid cascade hypothesis--which places amyloid plaques at the heart of AD pathogenesis--does not fully integrate a large body of data relevant to the emergence of clinical AD. Importantly, amyloid deposition is not strongly correlated with cognition in multivariate analyses, unlike hyperphosphorylated tau, neurofibrillary tangles, and synaptic and neuronal loss, which are closely associated with memory deficits. Targeting tau pathology, therefore, might be more clinically effective than Aβ-directed therapies. Furthermore, numerous immunization studies in animal models indicate that reduction of intracellular levels of tau and phosphorylated tau is possible, and is associated with improved cognitive performance. Several tau-related vaccines are in advanced preclinical stages and will soon enter clinical trials. In this article, we present a critical analysis of the failure of Aβ-directed therapies, discuss limitations of the amyloid cascade hypothesis, and suggest the potential value of tau-targeted therapy for AD.

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Therapeutic strategies for Alzheimer's disease in clinical trials.

Justyna Godyń, Jakub Jończyk, Dawid Panek … (2016)

Alzheimer's disease (AD) is considered to be the most common cause of dementia and is an incurable, progressive neurodegenerative disorder. Current treatment of the disease, essentially symptomatic, is based on three cholinesterase inhibitors and memantine, affecting the glutamatergic system. Since 2003, no new drugs have been approved for treatment of AD. This article presents current directions in the search for novel, potentially effective agents for the treatment of AD, as well as selected promising treatment strategies. These include agents acting upon the beta-amyloid, such as vaccines, antibodies and inhibitors or modulators of γ- and β-secretase; agents directed against the tau protein as well as compounds acting as antagonists of neurotransmitter systems (serotoninergic 5-HT6 and histaminergic H3). Ongoing clinical trials with Aβ antibodies (solanezumab, gantenerumab, crenezumab) seem to be promising, while vaccines against the tau protein (AADvac1 and ACI-35) are now in early-stage trials. Interesting results have also been achieved in trials involving small molecules such as inhibitors of β-secretase (MK-8931, E2609), a combination of 5-HT6 antagonist (idalopirdine) with donepezil, inhibition of advanced glycation end product receptors by azeliragon or modulation of the acetylcholine response of α-7 nicotinic acetylcholine receptors by encenicline. Development of new effective drugs acting upon the central nervous system is usually a difficult and time-consuming process, and in the case of AD to-date clinical trials have had a very high failure rate. Most phase II clinical trials ending with a positive outcome do not succeed in phase III, often due to serious adverse effects or lack of therapeutic efficacy.

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Author and article information

Journal

Journal ID (nlm-ta): Int J Mol Med

Journal ID (iso-abbrev): Int. J. Mol. Med

Journal ID (publisher-id): IJMM

Title: International Journal of Molecular Medicine

Publisher: D.A. Spandidos

ISSN (Print): 1107-3756

ISSN (Electronic): 1791-244X

Publication date (Print): January 2018

Publication date (Electronic): 09 November 2017

Publication date PMC-release: 09 November 2017

Volume: 41

Issue: 1

Pages: 251-263

Affiliations

[1 ]Laboratory of Chinese Materia Medica, Department of Pharmacology, School of Pharmacy

[2 ]Pharmacy Intravenous Admixture Services, Affiliated Hospital of Traditional Chinese Medicine

[3 ]Department of Human Anatomy, School of Preclinical Medicine, Southwest Medical University, Luzhou, Sichuan 646000

[4 ]Chengdu Analytical Applications Center, Shimadzu (China) Co., Ltd., Chengdu, Sichuan 610063

[5 ]Laboratory of Cancer Pharmacology, Department of Pharmacology, School of Pharmacy, Southwest Medical University, Luzhou, Sichuan 646000, P.R. China

Author notes

Correspondence to: Professor Shousong Cao, Laboratory of Cancer Pharmacology, Department of Pharmacology, School of Pharmacy, Southwest Medical University, 3-319 Zhongshan Road, Luzhou, Sichuan 646000, P.R. China, E-mail: shousongc@ 123456gmail.com

Professor Dalian Qin, Laboratory of Chinese Materia Medica, Department of Pharmacology, School of Pharmacy, Southwest Medical University, 3-319 Zhongshan Road, Luzhou, Sichuan 646000, P.R. China, E-mail: dalianqin@ 123456lzmc.edu.cn

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Publisher ID: ijmm-41-01-0251

DOI: 10.3892/ijmm.2017.3245

PMC ID: 5746317

PubMed ID: 29138799

SO-VID: fef8e511-686d-48f7-b30f-bedd8b70c5cc

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This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Lychee seed extract protects against neuronal injury and improves cognitive function in rats with type II diabetes mellitus with cognitive impairment

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Alternative approaches to Alzheimer's Disease

Most cited references 54

Combination of high-fat diet-fed and low-dose streptozotocin-treated rat: a model for type 2 diabetes and pharmacological screening.

Alzheimer disease therapy--moving from amyloid-β to tau.

Therapeutic strategies for Alzheimer's disease in clinical trials.

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