基于端粒-端粒酶系统维生素D3对轻度认知功能障碍改善作用机制的研究

With the acceleration of aging process in human society，aging and cognitive delcline in older people have become major research focuses in nutrition fields. Mild cognitive impairment（MCI）refers to the clinical condition between normal aging and dementia，which is the critical period to delay or prevent progression to AD. It has been reported that vitamin D3 may affect the length and stability of telomere through genomic and non-genomic activities, which is associated with cell apoptosis and dementia. Our previous research has suggested that vitamin D3 supplementation could improve cognitive function in older people, which was associated with significantly reducing the levels of peripheral inammatory cytokines. However, whether vitamin D3 can improve MCI through mediating neurocyte apoptosis and telomere stability remains unclear. In this study，the relationship among vitamin D3 and telomere stability and neurocytes apoptosis and cognitive function will be confirmed in vivo and in vitro at molecular level. Health effects of vitamin D3 on the impovement of MCI in older people via mediating telomere stability will be determined by the randomized control trial. On the basis of above hypothesis，the research will explore the molecular mechanisms of vitamin D3 modulating neurocytes apoptosis and cognitive function by regulating telomere/telomerase system. This study will open new paths for delaying cognitive decline，preventing and treating dementing disorders.

随着社会老龄化进程加速,延缓衰老和认知减退成为营养科学领域关注热点。轻度认知功能障碍（mild cognitive impairment, MCI）是介于正常衰老和痴呆之间的一种认知功能损害状态，是阿尔茨海默病(Alzheimer’s disease，AD)预防关键期。文献报道：端粒缩短可触发神经元凋亡，与AD发生显著相关；维生素D3可通过基因组和非基因组活化途径影响端粒稳定性，我们前期研究结果显示：补充维生素D3可降低外周血炎性因子水平改善老年认知，但维生素D3能否通过调节端粒途径改善认知尚不清楚。本研究拟采用细胞和动物实验探讨维生素D3通过调节端粒长度和端粒酶活性对神经细胞凋亡及改善认知的作用机制；通过人群随机对照试验研究确定维生素D3基于端粒-端粒酶系统改善MCI。基于上述研究确定维生素D3通过调节端粒-端粒酶系统影响神经元凋亡进而改善认知，为维生素D3防治老年性痴呆开辟新途径。

采用细胞和动物实验探讨维生素D3通过调节端粒长度和端粒酶活性对改善认知的作用机制；随机对照试验研究确定维生素D3基于端粒-端粒酶系统改善轻度认知障碍（mild cognitive impairment，MCI）。. 一、细胞试验. B6-Tg（Prp-hAPP/hPS1）双转基因子代新生小鼠海马神经干细胞（NSCs）体外纯化培养，不同剂量1,25-(OH)2-VitD3处理，Almar Blue检测细胞活力，Brdu 掺入法检测增殖，诱导分化后用细胞免疫荧光法检测分化多能性， qPCR 法检测端粒长度，结果提示：高剂量（50nmol/L）1,25-(OH)2-VitD3促进子代新生鼠海马神经元产生和 NSCs 增殖，提高神经元分化潜力，降低新生鼠海马NSCs端粒长度，出生后促进子代小鼠海马神经发育，高剂量1,25-(OH)2-VitD3补充通过减轻氧化损伤、提高抗氧化能力，减轻端粒磨损，促进增殖分化。. 二、动物实验 . 采用APP/PS1双转基因AD小鼠模型，分为正常对照组和维生素D3不同干预剂量组，评估认知功能，测定脑组织基因组DNA氧化损伤，端粒区DNA中8-氧鸟嘌呤（8-OHdG）含量及端粒长度，结果显示：维生素D3补充延缓认知减退(P<0.05)，脑组织基因组和端粒区DNA氧化损伤程度降低(P<0.05)，神经元端粒长度缩短减缓(P<0.05)，减轻端粒磨损。提示维生素D3在延缓认知减退中的保护作用。. 三、人群研究 . 病例对照研究：183例MCI及183例认知正常老年人。分析外周血氧化应激-端粒相关指标与MCI发生风险之间关联。MCI老年人血清25-OH-VitD3和1,25-(OH)2-VitD3水平小于认知正常老年人；外周血白细胞端粒长度（leukocyte telomere length，LTL）与老年人MCI发生风险相关联；且较长LTL可能是MCI发生的保护因素。.2. 随机、双盲、安慰剂对照试验：社区老年人中随机筛选并随机分配维生素D3组（91例）和安慰剂组（90例）。维生素D3组每日口服400IU维生素D3，12个月后可显著改善老年MCI人群的认知功能，同时外周血氧化应激指标水平降低，LTL增加，P16INK4amRNA降低；提示补充维生素D3可能是通过调节氧化应激-端粒系统进而改善MCI老年人认知功能。