Complement factor H levels are decreased and correlated with serum C-reactive protein in late-onset Alzheimer's disease

Abstract Alzheimer’s disease (AD) is the most common cause of dementia. Despite numerous studies on the subject, the pathologies for AD are still unclear and there is still no ideal biomarker for diagnosis. The present study aimed to investigate clinical significance of human complement factor H (CFH) in patients with late-onset AD. Methods: The present prospective study included 187 late-onset AD patients who went to our hospital from January 2015 to December 2017. One hundred patients with mild cognitive impairment (MCI) and 80 healthy individuals who were age and gender matched to AD patients were enrolled as controls. Demographic data such as age, gender, and education duration were recorded. Blood samples were collected and serum levels of C-reactive protein (CRP), CFH, and brain-derived neurotrophic factor (BDNF) were determined by Enzyme-linked immunosorbent assay (ELISA). The mini-mental state examination (MMSE) score was measured for all patients. Results: No significant difference was found in age, gender, and education duration for all participants. The MMSE scores showed AD patients had lower MMES scores than the other two groups. All factors of CFH, CRP, and BDNF were dramatically decreased in AD patients compared with the MCI and the ealthy control. Levels of CFH were found to be positively correlated with levels of CRP; however, no significant correlation was found between CFH and BDNF, nor CFH and MMSE. Conclusion: CFH was decreased in late-onset AD patients, and serum levels of CFH was correlated with serum levels of CRP, but not MMSE and BDNF. These results may provide more clinical evidences for the role of CFH in AD patients.

摘要
阿尔茨海默病（Alzheimer’s disease, AD）是最常见的痴呆病因。尽管针对该疾病已开展大量研究，但其病理机制仍未明确，且目前尚无理想的诊断生物标志物。本研究旨在探讨人补体因子H（complement factor H, CFH）在晚发型阿尔茨海默病患者中的临床意义。
方法：本前瞻性研究纳入2015年1月至2017年12月于我院就诊的187例晚发型AD患者。另选取100例轻度认知障碍（mild cognitive impairment, MCI）患者及80例年龄、性别与AD患者匹配的健康个体作为对照。记录所有受试者的年龄、性别、受教育时长等人口学资料。采集血液样本，采用酶联免疫吸附试验（Enzyme-linked immunosorbent assay, ELISA）检测血清C反应蛋白（C-reactive protein, CRP）、CFH及脑源性神经营养因子（brain-derived neurotrophic factor, BDNF）水平。对所有受试者进行简易精神状态检查表（mini-mental state examination, MMSE）评分。
结果：所有受试者的年龄、性别及受教育时长均无显著差异。MMSE评分结果显示，AD患者的评分显著低于另外两组。与MCI患者及健康对照相比，AD患者的CFH、CRP及BDNF水平均显著降低。研究发现CFH水平与CRP水平呈正相关，但CFH与BDNF、CFH与MMSE之间均未发现显著相关性。
结论：晚发型AD患者体内CFH水平降低，且血清CFH水平与血清CRP水平相关，但与MMSE评分及BDNF水平无关。本研究结果可为CFH在AD患者中的作用提供更多临床证据。