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Immunogold labelling of vitamin D receptor and ultrastructural characterisation of metabolizing enzymes in lipid droplets in the rat liver

Vitamin D is a secosteroid with multiple actions throughout the body, usually obtained from diet, dietary supplements and exposure to sun lights. Its actions are mediated via its nuclear receptor, the vitamin D receptor (VDR). There are hard evidences that correlate vitamin D deficiency with liver lipid metabolism disturbances, but the mechanism of this action is still unknown. In our previous work, we localized the accumulation of VDR in membrane of the lipid droplets (LDs) in hepatocytes. In this study, we applied the transmission electron microscopy (TEM) by using a long-term (6 months) high sucrose intake rat model for research of the hepatic lipid accumulation. In addition to the VDR, vitamin D metabolizing enzymes 1α-hydroxylase and CYP 24 were found to be 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 controls. 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.

hepatic steatosis, lipid droplets, vitamin D, VDR, 1α-hydroxylase, CYP 24

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