👤 Eili Tranheim Kase

Liver X Receptor (LXR) modulators have shown potential as drugs since they target genes affecting metabolism and fatty acid synthesis. LXR antagonists are of particular interest since they are able to reduce the synthesis of complex fatty acids and glucose uptake. Based on molecular modeling, five new cholesterol mimics were synthesized, where four contained a hydroxyl group in the 22-S-position. The new compounds were screened in vitro against several genes affecting lipid metabolism. The compound that performed best in vitro was a dimethylamide derivative of 22(S)-hydroxycholesterol and it was chosen for in vivo testing. However, the blood plasma analysis from the in vivo tests revealed a concentration lower than needed to give any response, indicating either rapid metabolism or low bioavailability. Show less

Four new mimics of 22-S-hydroxycholesterol (22SHC) were synthesized and evaluated using molecular modeling and tested in human muscle cells (primary myotubes) and hepatocytes (HepG2 cells). The new compounds (9, 12, 15a and 15b) showed good interrelationship between docking scores, to both LXRα and LXRβ, and in vitro results. The LXR agonist T0901317 increased the expressions of genes involved in lipogenesis (SCD1, FAS) and cholesterol efflux (ABCA1), but only 22SHC counteracted the up-regulation of SCD1 and FAS by T0901317. Compound 9 and 12 decreased the expression of SCD1, while 9 also decreased the expression of FAS. Compounds 15a showed a significant antagonistic effect on ABCA1 expression, but neither 15a nor 15b were able to counteract the effect of T0901317 on all genes examined. Lipogenesis was increased after T0901317 treatment and only 22SHC significantly counteracted this effect. Treatment with 22SHC and compound 12 reduced lipogenesis compared to control. An increased glucose uptake was observed for all compounds, except for 15b. In summary, the new synthetic 22SHC mimics showed antagonistic effects similar to that of 22SHC, but the new substances were less potent. The sulfonamide 12 showed similar effects to 22SHC and the best effect on gene expression of the new mimics, however, it was not able to reduce the effect of T0901317 as observed for 22SHC. Show less

X-linked adrenoleukodystrophy (X-ALD) is a rare neurodegenerative disorder characterized by the accumulation of very-long-chain fatty acids resulting from a beta-oxidation defect. Oxidative stress and inflammation are also key components of the pathogenesis. X-ALD is caused by mutations in the ABCDI gene, which encodes for a peroxisomal half ABC transporter predicted to participate in the entry of VLCFA-CoA into the peroxisome, the unique site of their beta-oxidation. Two homologous peroxisomal ABC transporters, ABCD2 and ABCD3 have been proven to compensate for ABCD1 deficiency when overexpressed. Pharmacological induction of these target genes could therefore represent an alternative therapy for X-ALD patients. Since LXR activation was shown to repress ABCD2 expression, we investigated the effects of LXR antagonists in different cell lines. Cells were treated with GSK(17) (a LXR antagonist recently discovered from the GlaxoSmithKline compound collection), 22(S)-hydroxycholesterol (22S-HC, another LXR antagonist) and 22R-HC (an endogenous LXR agonist). We observed up-regulation of ABCD2,ABCD3 and CTNNB1 (the gene encoding for beta-catenin, which was recently demonstrated to induce ABCD2 expression) in human HepG2 hepatoma cells and in X-ALD skin fibroblasts treated with LXR antagonists. Interestingly, induction in X-ALD fibroblasts was concomitant with a decrease in oxidative stress. Rats treated with 22S-HC showed hepatic induction of the 3 genes of interest. In human, we show by multiple tissue expression array that expression of ABCD2 appears to be inversely correlated with NR1H3 (LXRalpha) expression. Altogether, antagonists of LXR that are currently developed in the context of dyslipidemia may find another indication with X-ALD. Show less