Analysis of changes in triacylglycerol ratios in mouse liver and plasma in response to a liver X receptor agonist

An LC-MS method was developed for the analysis of triacylglycerols (TAG) in mouse liver extracts and plasma samples. C57 Mice were treated with two LXR agonists that have been shown to upregulate TAGs, T0901317 (T1317) or Org 264693 and compared to vehicle dosed animals. The dose used was 30 mg kg⁻¹, once daily, with three different dose regimes; 24 H, 48 H and 5 day. The TAG ratios measured were C52:2/C54:3 and C52:3/C54:4, which corresponded to a decrease in the palmitate and an increase in oleate composition of the TAGs. A significant change in the C52:2/C54:3 ratio was observed with all dose regimes and a good correlation was obtained between liver and plasma samples. In a separate study, the same compounds were dosed to LXR α and LXR β knock-out (KO) mice at 30 mg kg⁻¹, once daily, for 5 days. The LXR β KO mice showed similar TAG ratio changes to the C57 mice, whereas the LXR α KO mice showed no change in TAG ratios versus vehicle dosed animals. Measurements of lipid liability in response to an LXR agonist are typically made by measuring total liver TAG levels, which here, only showed a significant effect after the 48 H and 5 day dose regimes. By using a ratio measurement analysis could be performed on plasma samples, greatly simplifying the sample preparation procedure, without the requirement for either calibration curves or an internal standard.