Insulin receptor signaling regulates the formation of dendritic spine and the development excitatory synapse in hippocampal neurons through activation of the Rac1 and PI3K/Akt/mTOR signaling pathways ( Lee et al., 2011).

Proliferator-activated receptor Оі co-activator-1О± and mitochondrial biogenesis have important roles in the formation and maintenance of hippocampal dendritic spines and synapses ( Cheng et al., 2012). Some studies have detected the associations between metabolism and neuroplasticity at the cellular level and the systems level, where mitochondrial function, activation of insulin receptor, and expression of surface glucose transporter-3 (GLUT3) have all been linked with synaptic mechanisms for learning and memory.

There is a close relationship between diabetes and AD. The roles of epigallocatechin-3-gallate (EGCG) in diabetes and AD were studied by some scientists, thus we also summarize the protection of EGCG in SZT injection-induced models. This article will review the relationship between diabetes and AD and the STZ-induced models. Streptozotocin (STZ)-treated rodents have become a reliable model to investigate the mechanisms and therapy of diabetes and AD. Diabetes and AD are always the research focus and aporia of scientists. More than 99% of AD patients represent the so-called sporadic form, which is involved with various etiopathogenic mechanisms, such as brain trauma, inflammation, impairment of brain glucose metabolism, DM, and the gene dose of apolipoprotein E type 4 allele ( Corder et al., 1993 Iqbal and Grundke-Iqbal, 2010).Дiabetes has been clinically considered as a risk factor of AD. Familial AD constitutes no more than 1% of all AD patients, and the pathomechanism of most familial AD is related with the mutations of the proteins, such as Presenilin 1 (PS1), Presenilin 2 (PS2), and AОІ precursor protein (APP) ( Bird, 2008). AD is divided into early onset familial AD and late-onset sporadic AD. The major pathological hallmarks are amyloid-ОІ(AОІ) plaques and intracellular neurofibrillary tangles (NFT) and other molecular and biochemical abnormalities, including cell loss, impaired cellular metabolism, increased oxidative stress, and mitochondrial dysfunction ( Mattson, 2004). AD is characteristically marked by progressive decline of cognitive functions and loss of learning and memory. Metabolic impairments of such disease are a substantial cause of severe biochemical, molecular, and functional complications in many organs, consequently leading to progressive damage to the whole body.ДЄlzheimerвЂ™s disease (AD) is the most common one of neurodegenerative diseases and the main cause for dementia. GDM is more similar to type 2 and attacks about 7% of pregnancies, usually remits after delivery, and composes a major risk factor for the development of type 2 diabetes later in life ( Sacks et al., 2011). Type 2 diabetes mellitus, formerly known as non-IDDM, is caused by a combination of inadequate insulin secretion and insulin resistance ( Reaven, 1988). Type 1 diabetes mellitus, namely insulin-dependent DM (IDDM), is ordinarily caused by the autoimmune damage of pancreatic islet ОІ-cells, resulting in the pancreas unable to synthetise and secrete insulin ( Castano and Eisenbarth, 1990). This review highlights the link between diabetes and AD and recent studies on STZ injection-induced models, and also discusses the protection of EGCG to clarify its treatment in STZ-induced diabetes and AD.Дiabetes mellitus (DM) is a prevalent chronic endocrine diseases characterized by increased serum glucose concentrations, which is classified as type 1, type 2, gestational DM (GDM) and some other distinctive types. The protective roles of tea polyphenols epigallocatechin-3-gallate (EGCG) on both two diseases were researched by some scientists. A model generated by intracerebroventricular STZ (icv-STZ) also shows numerous aspects of sporadic AD. Streptozotocin (STZ) is a toxin for pancreatic ОІ-cell, which can construct a model of insulin deficient diabetes through intraperitoneal or intravenous injection.

3Henan Key Laboratory of Tea Biology, Xinyang Normal University, Xinyang, ChinaДiabetes mellitus is considered as a risk factor of AlzheimerвЂ™s disease (AD), the front runner of neurodegenerative disorders.

2Institute for Conservation and Utilization of Agro-bioresources in Dabie Mountains, Xinyang Normal University, Xinyang, China.

1College of Life Sciences, Xinyang Normal University, Xinyang, China.

Jin-Jing Jia 1,2,3вЂ , Xian-Si Zeng 1,2,3*вЂ , Xin-Qiang Song 1, Peng-Peng Zhang 1 and Lei Chen 1*

Alzheimer type 3 diabetes