Targeted Metabolomics Reveals a Protective Role for Basal PPARα in Cholestasis Induced by α-Naphthylisothiocyanate

Abstract

α-Naphthylisothiocyanate (ANIT) is an experimental agent used to induce intrahepatic cholestasis. The Ppara-null mouse line is widely employed to explore the physiological and pathological roles of PPARα. However, little is known about how PPARα influences the hepatotoxicity of ANIT. In the present study, wild-type and Ppara-null mice were orally treated with ANIT to induce cholestasis. The serum metabolome of wild-type mice segregated from that of the Ppara-null mice, driven by changes of bile acid (BA) metabolites. Alkaline phosphatase and total BAs were elevated preferentially in Ppara-null mice, which correlated with changes in Cyp7a1, Cyp8b1, Mrp3, Cyp3a11, Cyp2b10, Ugt1a2, and Ugt1a5 genes and showed cross-talk between basal PPARα and potentially adaptive pathways. Il6, Tnfa, and target genes in the STAT3 pathway ( Socs3, Fga, Fgb, and Fgg) were up-regulated in Ppara-null mice but not in wild-type mice. The JNK pathway was activated in both mouse lines, while NF-κB and STAT3 were activated only in Ppara-null mice. These data suggest protection against cholestasis by basal PPARα involves regulation of BA metabolism and inhibition of NF-κB/STAT3 signaling. Considering studies on the protective effects of both basal and activated PPARα, caution should be exercised when one attempts to draw conclusions in which the PPARα is modified by genetic manipulation, fasting, or activation in pharmacological and toxicological studies.

Metabolomic and Lipidomic Biomarkers for Premalignant Liver Disease Diagnosis and Therapy

“…A metabolomic investigation has also been reported, whereby regulation of BA metabolism by the nuclear receptor PPARα and inhibition of NF-κB/STAT3 signaling protected against cholestasis induced by ANIT [95]. Furthermore, a lipidomic study of ANIT-induced intrahepatic cholestasis uncovered the role of the aryl hydrocarbon receptor (AHR) in regulating expression of choline kinase (CHK) in mice.…”

PPARα-independent action against metabolic syndrome development by fibrates is mediated by inhibition of STAT3 signalling

“…[42] In mice treated with ANIT, the liver inflammation was lower in wild-type compared with that in Ppara-null mice, also suggesting the protective function of basal PPARa. [30] In mice fed a diet enriched with hydrogenated coconut oil, hyperinsulinaemia was observed in wild-type mice, but not in Ppara-null mice. [27] In Ppara-null mice treated with HFD, the insulin sensitivity, blood pressure and intimal lesion were all improved.…”

“…In Ppara ‐null mice and wild‐type (C57BL/6N) mice treated with cholic acid, the bile acid homeostasis was disrupted in Ppara ‐null mice, indicating the protective role of basal PPARα . In mice treated with ANIT, the liver inflammation was lower in wild‐type compared with that in Ppara ‐null mice, also suggesting the protective function of basal PPARα . In mice fed a diet enriched with hydrogenated coconut oil, hyperinsulinaemia was observed in wild‐type mice, but not in Ppara ‐null mice .…”

“…The samples from eight groups (WT‐Con/KO‐Con, WT‐MFD/KO‐MFD, WT‐MFD‐G/KO‐MFD‐G, WT‐MFD‐F/KO‐MFD‐F) for qPCR were determined in the same run on one 384‐well plate. The procedures of Western blot analysis also followed a previous study by our group …”

“…The procedures of Western blot analysis also followed a previous study by our group. [30] STAT3 knockdown in 3T3-L1 adipogenic stem cells 3T3-L1 adipogenic stem cells were cultured in high-glucose (4.5 g/l) DMEM containing 10% fetal bovine serum (FBS) and penicillin/streptomycin (both at 100 U/ml) at 37°C with 5% CO 2 . To induce differentiation, the cells were cultured for 2 days after confluence and then treated with culture medium supplemented with 1.0 lM dexamethasone, 0.5 mmol/l 3-isobutyl-1-methylxanthine and 5.0 lg/ml insulin for 48 h. The cells were cultured in DMEM/10% FBS supplemented with 5.0 lg/ml insulin for additional 6 days.…”