Vitamin D is a fat-soluble secosteroid that exerts its effects by binding to the vitamin D receptor (VDR), through which it directly and indirectly modulates the expression of hundreds to thousands of genes. While originally known for its role in regulating calcium homeostasis and metabolism, vitamin D is now associated with many other health conditions, including Parkinson's disease (PD). A high prevalence of vitamin D deficiency has been noted in PD for at least the past two decades. These findings, along with the discovery that the VDR and 1α-hydroxylase, the enzyme that converts vitamin D to its active form, are highly expressed in the substantia nigra, led to the hypothesis that inadequate levels of circulating vitamin D may lead to dysfunction or cell death within the substantia nigra. Studies investigating the relationship between vitamin D status and PD, however, have been inconsistent. Two prospective studies examined the association between mid-life vitamin D levels and risk of PD and produced conflicting results-one demonstrated an increased risk for PD with lower mid-life vitamin D levels, and the other showed no association between vitamin D and PD risk. One of the most consistent findings in the literature is the inverse association between serum vitamin D level and motor symptom severity in cross-sectional studies. While these data suggest that vitamin D may modify the disease, another likely explanation is confounding due to limited mobility. Fall risk has been associated with vitamin D in PD, but more study is needed to determine if supplementation decreases falls, which has been demonstrated in the general population. The association between vitamin D and non-motor symptoms is less clear. There is some evidence that vitamin D is associated with verbal fluency and verbal memory in PD. Studies in PD have also shown associations between vitamin D status and mood, orthostatic hypotension and olfactory impairment in PD. While more research is needed, given the numerous potential benefits and limited risks, vitamin D level assessment in PD patients and supplementation for those with deficiency and insufficiency seems justified.

中文翻译：

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维生素 D 与帕金森病症状之间关系的综述。

维生素 D 是一种脂溶性类固醇，通过与维生素 D 受体 (VDR) 结合发挥作用，通过该受体直接或间接调节数百至数千个基因的表达。维生素 D 最初因其调节钙稳态和新陈代谢的作用而闻名，但现在它与许多其他健康状况有关，包括帕金森病 (PD)。至少在过去二十年里，帕金森病中维生素 D 缺乏症的患病率很高。这些发现，加上 VDR 和 1α-羟化酶（将维生素 D 转化为其活性形式的酶）在黑质中高度表达的发现，导致了这样的假设：循环维生素 D 水平不足可能会导致功能障碍或黑质内的细胞死亡。然而，关于维生素 D 状态与帕金森病之间关系的研究并不一致。两项前瞻性研究考察了中年维生素 D 水平与 PD 风险之间的关联，但得出了相互矛盾的结果 - 一项研究表明中年维生素 D 水平较低会增加患 PD 的风险，而另一项研究则表明维生素 D 与 PD 风险之间没有关联。文献中最一致的发现之一是横断面研究中血清维生素 D 水平与运动症状严重程度之间的负相关。虽然这些数据表明维生素 D 可能会改善这种疾病，但另一种可能的解释是由于活动能力有限而令人困惑。跌倒风险与 PD 中的维生素 D 相关，但需要更多的研究来确定补充剂是否可以减少跌倒，这一点已在普通人群中得到证实。维生素 D 与非运动症状之间的关联尚不清楚。有一些证据表明维生素 D 与帕金森病患者的语言流畅性和语言记忆有关。帕金森病的研究还表明维生素 D 状态与帕金森病的情绪、直立性低血压和嗅觉障碍之间存在关联。虽然还需要更多的研究，但考虑到维生素 D 具有众多的潜在益处和有限的风险，对帕金森病患者进行维生素 D 水平评估以及对维生素 D 缺乏和不足的患者进行补充似乎是合理的。