Metabolomic Analyses of Lipid and Aqueous Liver Extracts in TCDD-Treated Mice.
Kent, M.N.1, Reo, N.V.1,
Jahns, G.J.2, DelRaso, N.3,
Boverhof, D.R.4,Burgoon, L.D.4,6,
of Biochemistry & Molecular Biology, Boonshoft School of Medicine,
Wright St University, Dayton, OH
Thin layer chromatography (TLC), 13C, 31P, and 1H NMR (14.1 T), and high pressure liquid chromatography (HPLC) were used to assess the hepatic aqueous and lipid metabolite changes in C57BL/6 mice treated with 30 ug/kg TCDD by gavage as part of a more comprehensive toxicogenomic analysis. TCDD induced a significant increase in liver weight with marked cytoplasmic vacuolization accompanied by individual cell apoptosis and foci of mixed populations of inflammatory cells consisting mainly of mononuclear cells and some neutrophils. Oil Red O staining indicated vacuolization was due to lipid accumulation and TLC lipid analysis revealed a 2.5-fold increase in triglycerides. Principal Component Analysis (PCA) of 13C, 31P, and 1H NMR clearly demonstrates significant temporal changes in aqueous and lipid metabolites at 168 hrs as a result of TCDD treat. 31P NMR phospholipid (PL) analysis showed an increase in phosphatidylcholine 24%, while phosphatidylethanolamine and cardiolipin each decreased 16%. PCA of 13C lipid spectra clearly shows significant changes in hepatic lipid composition relative to vehicle with (1) cholesterol levels were unaffected, (2) triacylglycerides were increased 3.5-fold (20.8 ± 1.9 vs. 6.0 ± 0.3 umol/g liver), and (3) omega-3 fatty acids were decreased by 22%. Moreover, composition of the lipids also changed during the time course. HPLC analysis of lipid extracts identified >3-fold increases in 16:0, 18:1n9, 18:2n6, 18:3n3, 20:2n, 20:3n6, 20:3n9 and 22:5n3 fatty acids. Consequently, in addition to eliciting changes in transcription, TCDD also induces dramatic alterations in hepatic aqueous molecules and lipids. Funded by RO1 ES013927.