Zhao Yan, Dong Xinyi, Chen Bingyu, Zhang Yizhou, Meng Sijia, Guo Fangzhen, Guo Xiaojing, Zhu Jialei, Wang Haoyue, Cui Huixian, Li Sha
Department of Anatomy, Hebei Medical University, Shijiazhuang, China.
School of Nursing, Hebei Medical University, Shijiazhuang, China.
Front Aging Neurosci. 2022 Jul 22;14:934070. doi: 10.3389/fnagi.2022.934070. eCollection 2022.
Circulating methionine components have been reported to be associated with Alzheimer's disease (AD) and mild cognitive impairment (MCI), although outcomes are not always consistent.
Database searching was conducted using PubMed, Embase, Cochrane Library, and Web of Science from inception to 26 December 2021. In this study, two reviewers independently identified eligible articles and extracted the data. We used Joanna Briggs Institute (JBI) Critical Appraisal tools to assess the overall quality of the included studies. STATA software was employed to perform meta-analysis evaluating the standardized mean difference (SMD) with its 95% confidence intervals (CIs) using random-effects models. Evidence quality was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria.
Totally, 30 observational studies were eligible for inclusion. Compared with cognitively normal controls, patients with AD had increased homocysteine (Hcy) levels in the blood [standardized mean difference (SMD) = 0.59, 95% confidence interval [CI]: 0.36-0.82, = 0.000], plasma (SMD = 0.39, 95% CI: 0.23-0.55, = 0.000), and serum (SMD = 1.56, 95% CI: 0.59-2.95, = 0.002). Patients with MCI were not significantly different from controls (SMD = 0.26, 95% CI: -0.07-0.58, = 0.127). Patients with AD or MCI did not significantly differ from controls of blood vitamin B levels, AD (SMD = -0.05, 95% CI: -0.19-0.08, = 0.440), or MCI (SMD = 0.01, 95% CI: -0.16-0.17, = 0.94). Some cohort studies have suggested that higher Hcy, methionine, and -adenosylmethionine levels may accelerate cognitive decline in patients with MCI or AD, and vitamin B deficiency is a risk factor for the disease; however, the results of other studies were inconsistent. According to the GRADE system, all these outcomes scored very low to low quality, and no high-quality evidence was found.
Only Hcy levels in the plasma and serum were found to be inversely related to the risk of AD. However, due to the low quality of supporting these results, high-quality studies are needed to verify these findings.
http://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022308961.
尽管研究结果并不总是一致，但已有报道称循环蛋氨酸成分与阿尔茨海默病（AD）和轻度认知障碍（MCI）有关。
使用PubMed、Embase、Cochrane图书馆和Web of Science从建库至2021年12月26日进行数据库检索。在本研究中，两名评审员独立识别符合条件的文章并提取数据。我们使用乔安娜·布里格斯研究所（JBI）的批判性评价工具来评估纳入研究的整体质量。采用STATA软件进行荟萃分析，使用随机效应模型评估标准化平均差（SMD）及其95%置信区间（CI）。使用推荐分级评估、制定和评价（GRADE）标准评估证据质量。
总共30项观察性研究符合纳入标准。与认知正常对照组相比，AD患者血液中的同型半胱氨酸（Hcy）水平升高[标准化平均差（SMD）=0.59，95%置信区间[CI]：0.36 - 0.82，P = 0.000]，血浆中（SMD = 0.39，95% CI：0.23 - 0.55，P = 0.000），以及血清中（SMD = 1.56，95% CI：0.59 - 2.95，P = 0.002）。MCI患者与对照组无显著差异（SMD = 0.26，95% CI： - 0.07 - 0.58，P = 0.127）。AD或MCI患者与血液维生素B水平的对照组无显著差异，AD组（SMD = - 0.05，95% CI： - 0.19 - 0.08，P = 0.440），或MCI组（SMD = 0.01，95% CI： - 0.16 - 0.17，P = 0.94）。一些队列研究表明，较高的Hcy、蛋氨酸和S-腺苷甲硫氨酸水平可能会加速MCI或AD患者的认知衰退，维生素B缺乏是该疾病的一个危险因素；然而，其他研究结果并不一致。根据GRADE系统，所有这些结果的质量评分为极低到低质量，未发现高质量证据。
仅发现血浆和血清中的Hcy水平与AD风险呈负相关。然而，由于支持这些结果的证据质量较低，需要高质量研究来验证这些发现。
