Liver X receptor (LXR) agonism has theoretical potential for treating NAFLD/NASH, but synthetic agonists induce hyperlipidemia in preclinical models. Desmosterol, which is converted by & UDelta... Show moreLiver X receptor (LXR) agonism has theoretical potential for treating NAFLD/NASH, but synthetic agonists induce hyperlipidemia in preclinical models. Desmosterol, which is converted by & UDelta;24-dehydrocholesterol reductase (DHCR24) into cholesterol, is a potent endogenous LXR agonist with anti-inflammatory properties. We aimed to investigate the effects of DHCR24 inhibition on NAFLD/NASH development. Here, by using APOE*3-Leiden. CETP mice, a well-established translational model that develops diet-induced human-like NAFLD/NASH characteristics, we report that SH42, a published DHCR24 inhibitor, markedly increases desmosterol levels in liver and plasma, reduces hepatic lipid content and the steatosis score, and decreases plasma fatty acid and cholesteryl ester concentrations. Flow cytometry showed that SH42 decreases liver inflammation by preventing Kupffer cell activation and monocyte infiltration. LXRa deficiency completely abolishes these beneficial effects of SH42. Together, the inhibition of DHCR24 by SH42 prevents diet-induced hepatic steatosis and inflammation in a strictly LXRa-dependent manner without causing hyperlipidemia. Finally, we also showed that SH42 treatment decreased liver collagen content and plasma alanine transaminase levels in an established NAFLD model. In conclusion, we anticipate that pharmacological DHCR24 inhibition may represent a novel therapeutic strategy for treatment of NAFLD/NASH. Show less
During the last decade, the understanding of the biological functions of cholesterol biosynthesis intermediates has changed significantly. Particularly, the enzyme sterol dehydrocholesterol... Show moreDuring the last decade, the understanding of the biological functions of cholesterol biosynthesis intermediates has changed significantly. Particularly, the enzyme sterol dehydrocholesterol reductase 24 (DHCR24) has taken center stage as a potential drug target. Inhibition of DHCR24 leads to accumulation of the endogenous, biologically active metabolite cholesta-5,24-dien-3 beta-ol (desmosterol). Desmosterol is an endogenous agonist of the liver X receptor (LXR). LXR is a master regulator of lipid metabolism and, as such, is involved in numerous pathophysiological processes such as inflammation, atherosclerosis, cancer, diabetes mellitus (DM), multiple sclerosis (MS), nonalcoholic steatohepatitis (NASH), and the progression of viral infections. Up to now, selective pharmacological targeting of LXR without activating the sterol-response element binding proteins (SREBP) and thereby boosting endogenous lipid biosynthesis has not been achieved. In turn, no selective LXR receptor agonists leveraging its beneficial activation have yet reached the clinic. Therefore, using potent and selective inhibitors of DHCR24 leading to an accumulation of endogenous desmosterol is a promising alternative strategy for the selective activation of LXR. Here we summarize the present landscape of novel lead structures for targeting DHCR24, covering steroidal enzyme inhibitors (e.g., 20,25-diazacholesterol, SH42) as well as non-steroidal scaffolds (e.g., amiodarone, triparanol). Further, we explain the molecular mechanisms of DHCR24 inhibition/LXR activation, discuss possible therapeutic applications, and underpin why DHCR24 is an upcoming promising drug target. Show less
