Key Laboratory of Basic Pharmacology of Ministry of Education, Zunyi Medical University, Guizhou Province, China.
Behav Neurol. 2021 Apr 7;2021:6683318. doi: 10.1155/2021/6683318. eCollection 2021.
Excessive or insufficient intake of methionine (Met) causes neuronal dysfunction, neurodegeneration, cerebrovascular dysfunction, vascular leakage, and short-term memory loss, which result in the occurrence of Alzheimer's disease- (AD-) like symptoms.
To determine the relationship between high methionine diets (HMD) induced AD-like symptoms and 5-methylcytosine (5-mC) level.
C57BL/6J mice were randomly divided into two groups: the control group (Maintain diets) and the model group (2% HMD). Mice were fed with 2% HMD for 9 weeks. Animals were weighed and food intake was recorded weekly. Open field test, nesting ability test, Y maze test, new object recognition test, and Morris water maze test were used to detect the motor, learning, and memory ability. Hematoxylin-eosin (HE) staining was used to observe the damage of cells in hippocampus and cortex. Immunofluorescence (IF) staining was used to detect the expression and distribution of amyloid- 1-40 (A ), amyloid- 1-42 (A ), and 5-methylcytosine (5-mC) in hippocampus and cortex. Western blotting (WB) was used to determine the expression of A and DNA methyltransferases- (DNMTs-) related proteins in the cortex. Enzyme-linked immunosorbent assay (ELISA) was performed to detect homocysteine (Hcy) level (ELISA).
Feeding of HMD decreased the body weight and food intake of mice. Behavioral testing revealed that HMD caused learning, memory, and motor ability impairment in the mice. HE staining results showed that HMD feeding caused damage of hippocampal and cortical neurons, along with disordered cell arrangement, and loss of neurons. Furthermore, HMD increased the contents of A , A , and 5-mC in the hippocampus and cortex. WB results showed that HMD increased the expression of A production-related proteins, such as amyloid precursor protein (APP) and beta-secretase 1 (BACE1), and decreased the expression of A metabolism-related protein in the cortex, including insulin-degrading enzyme (IDE) and neprilysin (NEP). Additionally, the decreased expression of DNA methyltransferase1 (DNMT1) was observed in HMD-treated mice, but there was no significant change of DNMT3a level. ELISA results showed that HMD increased the levels of Hcy in serum.
Our result suggested that the HMD can cause neurotoxicity, leading to AD-like symptoms in mice, which may be related to 5-mC elevated.
蛋氨酸（Met）摄入过多或过少会导致神经元功能障碍、神经退行性变、脑血管功能障碍、血管渗漏和短期记忆丧失，从而导致阿尔茨海默病样症状的发生。
确定高蛋氨酸饮食（HMD）诱导的类似 AD 症状与 5-甲基胞嘧啶（5-mC）水平之间的关系。
将 C57BL/6J 小鼠随机分为两组：对照组（维持饮食）和模型组（2% HMD）。用 2% HMD 喂养小鼠 9 周。每周记录体重和食物摄入量。使用旷场试验、筑巢能力试验、Y 迷宫试验、新物体识别试验和 Morris 水迷宫试验检测运动、学习和记忆能力。用苏木精-伊红（HE）染色观察海马和皮质细胞损伤。免疫荧光（IF）染色检测海马和皮质中淀粉样蛋白-1-40（A ）、淀粉样蛋白-1-42（A ）和 5-甲基胞嘧啶（5-mC）的表达和分布。Western blot（WB）检测皮质中 A 和 DNA 甲基转移酶（DNMTs）相关蛋白的表达。酶联免疫吸附试验（ELISA）检测同型半胱氨酸（Hcy）水平（ELISA）。
HMD 喂养降低了小鼠的体重和食物摄入量。行为测试显示，HMD 导致小鼠学习、记忆和运动能力受损。HE 染色结果显示，HMD 喂养导致海马和皮质神经元损伤，细胞排列紊乱，神经元丢失。此外，HMD 增加了海马和皮质中 A 、A 和 5-mC 的含量。WB 结果显示，HMD 增加了 A 产生相关蛋白，如淀粉样前体蛋白（APP）和β-分泌酶 1（BACE1）的表达，降低了皮质中 A 代谢相关蛋白的表达，包括胰岛素降解酶（IDE）和 Neprilysin（NEP）。此外，在 HMD 处理的小鼠中观察到 DNA 甲基转移酶 1（DNMT1）的表达降低，但 DNMT3a 水平没有显著变化。ELISA 结果显示，HMD 增加了血清中 Hcy 的水平。
我们的结果表明，HMD 可引起神经毒性，导致小鼠出现类似 AD 的症状，这可能与 5-mC 升高有关。
