White matter protection in ageing through innovative nutrients

人脑白质——尤其是髓磷脂——是高级认知的主要神经解剖学基础。脑老化伴随着白质萎缩和髓磷脂损失（Peters, 2009）。中枢神经系统（CNS）中负责髓鞘形成的细胞，即少突胶质细胞，在衰老过程中增殖和分化谱发生改变，从而导致髓鞘形成缺陷（Wang and Yang, 2014）。我们已经证明，诸如omega-3多不饱和脂肪酸（PUFA）这样的营养素，无论是单独使用还是在多营养素制剂中，都对中枢神经系统具有显著的神经保护潜力（Huang et al . 2007; Ward et al . 2010; Pallier et al . 2015）。在以前的研究中，我们观察到少突胶质细胞的显著保护作用。在目前的建议中，我们的目的是研究选定的营养物质对少突胶质细胞及其产生髓磷脂的能力的影响。这将最终使识别和开发支持白质完整性和促进健康大脑衰老的营养素组合成为可能。研究表明，特定的脂质（如棕榈酸或棕榈酰磷脂酰胆碱）在系统性治疗脱髓鞘疾病（如多发性硬化症）时具有治疗潜力（Ho et al., 2012）。我们将探索这一概念，并开发一种适用于普通人群的大脑保护方法，以防止白质老化。健康人的脑髓磷脂在中年开始分解，因此有充足的机会采用营养为基础的方法来改变这一过程的进程（Bartzokis et al . 2010）。我们将分析选定营养素在以下方面的影响：1)原代小鼠少突胶质祖细胞（OPC）培养（表征对OPC和髓磷脂合成能力的内在影响），2)少突胶质细胞-神经元共培养（表征对髓鞘形成的影响），以及3)器官型切片（进行电生理研究，从而评估改善髓磷脂的功能影响）。脂质约占髓鞘的70%，因此测试的营养物质将优先考虑脂质，如PUFA，简单或复杂的磷脂，神经酰胺，神经节苷脂和硫脂。营养素将在基础条件下进行测试，并使用模拟自然因素的刺激进行测试，这些自然因素会产生少突胶质细胞应激，加速大脑老化并促进神经变性，即缺血（氧-葡萄糖剥夺），炎症（脂多糖）和兴奋毒性（例如谷氨酸和各种谷氨酸受体配体）（Schmitz et al 2012）。将通过免疫细胞化学和western blot检测髓磷脂蛋白，脂质组学质谱检测髓磷脂，电生理记录功能结果来评估效果。所选择的对少突胶质细胞和髓磷脂有积极作用的营养素最终将在老年大鼠（12-15个月）诱导中枢神经系统脱髓鞘模型中进行体内测试。

The human brain white matter - in particular the myelin - is a major neuroanatomical substrate of higher cognition. Brain ageing is accompanied by white matter shrinkage and myelin loss (Peters, 2009). The cells responsible for myelination in the central nervous system (CNS), i.e. oligodendrocytes, have an altered proliferation and differentiation profile in ageing, and this leads to myelination deficits (Wang and Yang, 2014). We have shown that nutrients such as omega-3 polyunsaturated fatty acids (PUFA) have significant neuroprotective potential in the CNS, either on their own or in multi-nutrient preparations (Huang et al 2007; Ward et al 2010; Pallier et al 2015). In previous studies we observed significant protection of oligodendrocytes. In the present proposal, we aim to study the impact of selected nutrients specifically on oligodendrocytes and their capacity to produce myelin. This will ultimately enable the identification and development of combinations of nutrients which support white matter integrity and promote healthy brain ageing. It has been shown that specific lipids (e.g. palmitic acid or palmitoyl-phosphatidylcholine) have therapeutic potential when systemically administered in demyelinating disorders, e.g. multiple sclerosis (Ho et al., 2012). We will explore this concept and develop a brain protective approach applicable in the general population, to prevent white matter ageing. In healthy individuals brain myelin breakdown starts in middle-age, therefore there is ample opportunity for nutrient-based approaches to alter the course of this process (Bartzokis et al 2010). We will analyse the effects of selected nutrients in: i) primary mouse oligodendrocyte progenitor cell (OPC) cultures (to characterize intrinsic effects on OPC and the myelin synthesis capacity), ii) oligodendrocyte-neuronal co-cultures (to characterize the effects on myelin sheath formation), and iii) organotypic slices (to carry out electrophysiological studies, hence assess the functional impact of improved myelin). Lipids constitute around 70% of the myelin sheath, therefore the nutrients tested will be with priority lipids, such as PUFA, and simple or complex phospholipids, ceramides, gangliosides and sulfatides. Nutrients will be tested under basal conditions and also using stimuli which mimic natural factors which create oligodendrocyte stress, accelerate brain ageing and promote neurodegeneration, i.e. ischaemia (oxygen-glucose deprivation), inflammation (lipopolysaccharide) and excitotoxicity (e.g. glutamate and various glutamate receptor ligands) (Schmitz et al 2012).The effects will be assessed by immunocytochemistry and western blot for myelin proteins, lipidomic mass spectrometry for myelin lipids, and electrophysiological recordings for functional outcome. The selected nutrients with positive effects on oligodendrocytes and myelin will ultimately be tested in vivo in a model of induced CNS demyelination in aged rats (12-15 months).