Exogenous Addition of 25‐Hydroxycholesterol Reduces Level of Very Long‐Chain Fatty Acids in X‐Linked Adrenoleukodystrophy

X‐Linked adrenoleukodystrophy (X‐ALD) is a severe metabolic disorder characterized by the accumulation of very long‐chain fatty acids (VLCFAs). Recently, we demonstrated that levels of 25‐hydroxycholesterol (25‐HC) and cholesterol 25‐hydroxylase (CH25H) were found to be elevated in X‐ALD. Herein, we report that the exogenous addition of 25‐HC significantly reduces C26:0 levels in X‐ALD patient‐derived fibroblasts and oligodendrocytes differentiated from induced pluripotent stem cells (iPSCs) derived from X‐ALD patients. Moreover, 25‐HC treatment was found to down‐regulate the expression of ELOVL1, a key enzyme for the synthesis of C26. In addition, activation of liver X receptor (LXR), a molecular target of endogenous 25‐HC, also reduced C26:0 level. The reduction of C26:0 levels by 25‐HC treatment might result, at least partially, from the decrease of ELOVL1 expression as well as the activation of LXR. Our findings could provide a better understanding of the role of 25‐HC in X‐ALD and useful information to find therapeutic agents to treat X‐ALD.