Vitamin D is a steroid hormone with numerous actions in the organism. There are strong evidences that relate vitamin D deficiency with liver lipid metabolism disturbances, but the mechanism of this action is still unknown. In our previous work we postulated the localization and accumulation of vitamin D receptor (VDR) in membrane of the lipid droplets (LDs) in hepatocytes. In this study, we applied the transmission electron microscopy (TEM) to confirm this hypothesis by using a long-term (6 months) high sucrose intake rat model that was previously found to be appropriate for research of the hepatic lipid accumulation. In addition to the VDR, we also found key vitamin D metabolizing enzymes, 1α-hydroxylase and CYP 24 associated with the membrane of the LDs. A light-microscopy data revealed significant increase in expression of VDR and CYP 24 in liver of high-sucrose treated rats, in comparison to controlones. According to the best of our knowledge, this is a first study confirming the presence of the VDR in the membrane of the LDs in general and also in particular in LDs of the hepatocytes that were accumulated as a consequence of the prolonged high sucrose intake. Moreover, we found association of main vitamin D metabolizing enzymes with LD membrane. These results provide a new insight in the possible relation of vitamin D signalling system with LD morphology and function and with the lipid metabolism in general.

中文翻译：

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大鼠脂肪肝脂质滴中维生素D受体和代谢酶的超微结构表征。

维生素D是类固醇激素，在生物体内具有多种作用。有强有力的证据将维生素D缺乏与肝脂质代谢紊乱联系起来，但是这种作用的机制仍是未知的。在我们以前的工作中，我们推测了维生素D受体（VDR）在肝细胞脂质滴（LDs）膜中的定位和积累。在这项研究中，我们使用透射电子显微镜（TEM）通过使用长期（6个月）高蔗糖摄入大鼠模型来证实这一假说，该模型先前被发现适合研究肝脂质蓄积。除了VDR，我们还发现了与LDs膜相关的关键维生素D代谢酶，1α-羟化酶和CYP 24。光学显微镜数据显示，与对照组相比，高蔗糖处理的大鼠肝脏中VDR和CYP 24的表达显着增加。据我们所知，这是第一个证实VDR普遍存在于LDs膜中，尤其是长期摄入高蔗糖而积累的肝细胞LDs中的研究。此外，我们发现主要的维生素D代谢酶与LD膜相关。这些结果为维生素D信号系统与LD形态和功能以及一般脂代谢的可能关系提供了新的见解。这是第一个证实VDR普遍存在于LDs膜中，尤其是由于长期高蔗糖摄入而积累的肝细胞LDs中VDR的研究。此外，我们发现主要的维生素D代谢酶与LD膜相关。这些结果为维生素D信号系统与LD形态和功能以及一般脂代谢的可能关系提供了新的见解。这是第一个证实VDR普遍存在于LDs膜中，尤其是由于长期高蔗糖摄入而积累的肝细胞LDs中VDR的研究。此外，我们发现主要的维生素D代谢酶与LD膜相关。这些结果为维生素D信号系统与LD形态和功能以及一般脂代谢的可能关系提供了新的见解。