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Induction of PCK1 Expression by Palmitate in HepG2 Cells: Involvement of Multiple Pathways
Author(s) -
Mamedova Laman K,
Bradford Barry J
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.331.7
Subject(s) - gluconeogenesis , palmitic acid , chemistry , medicine , endocrinology , signal transduction , lipid metabolism , biochemistry , fatty acid , metabolism , biology
Type 2 diabetes is associated with enhanced gluconeogenesis. Saturated fatty acids alter hepatic metabolism, and at least 3 inflammatory pathways are proposed to mediate such effects. Fatty acids may act by 1) binding and activating Toll‐like receptor 4 (TLR4), 2) causing oxidative stress, and/or 3) promoting synthesis of lipids such as diacylglycerols (DAG) and ceramides (CER). We tested the roles of these pathways in mediating palmitate effects on expression of PCK1 , a rate‐controlling gluconeogenic enzyme. HepG2 cells were incubated in DMEM ± 1 mM palmitate for 24 h. Specific pathways were blocked with a peptide antagonist of TLR4 (1 μM), myriocin (1 μM; CER synthesis inhibitor), or vitamin E (50 μM; antioxidant). Treatment effects were declared at P < 0.05. No treatments affected cell viability at 24 h. Palmitate increased PCK1 mRNA by 4‐fold. Myriocin and vitamin E prevented the induction of PCK1 by palmitate, and the TLR4 antagonist decreased PCK1 abundance with or without palmitate. Palmitate induced a 3.6‐fold increase in cellular DAG, but did not alter CER content. All pathway blockades decreased CER content, especially without palmitate. In contrast, only myriocin and vitamin E decreased DAG content, and only in palmitate‐treated cells. Results demonstrated that inhibiting any one of these pathways was sufficient to prevent the induction of PCK1 expression, and multiple pathways also altered CER and DAG content.