Differential Modulation of WNT/β-Catenin Pathway-Associated Molecular Responses by Palmitate and Oleate in Lipid-Loaded HepG2 Cells.

Abstract

Background: Palmitate (PA) and oleate (OA), the predominant saturated and monounsaturated fatty acids, respectively, may differentially influence hepatic signaling. However, their individual and combined effects on WNT/β-catenin-related responses in HepG2 cells remain incompletely characterized.

Methods: Human HepG2 cells were exposed to PA, OA, or a combined PA/OA treatment for 24 h. Cell viability was determined via MTT assay, while intracellular lipid droplet (LD) accumulation was evaluated using Oil Red O staining. Transcriptional alterations of canonical WNT/β-catenin cascade genes (WNT, CTNNB1, GSK-3β, TCF, LEF, Axin1, and Axin2) were analyzed by RT-qPCR. Protein expression levels of WNT, β-catenin, and Glypican-3 (GPC3) were evaluated to assess pathway activation.

Results: Both fatty acids induced dose-dependent cytotoxicity and intracellular lipid accumulation, with the combined PA/OA treatment provoking the highest LD content. At the molecular level, palmitate predominantly activated the canonical cascade, significantly upregulating WNT, CTNNB1, TCF, and Axin2 mRNA, alongside elevated WNT, β-catenin, and GPC3 protein levels. Conversely, oleate selectively upregulated LEF and GSK-3β without coordinated canonical cascade activation, maintaining lower WNT and GPC3 protein expressions. Interestingly, co-treatment with PA/OA yielded intermediate molecular responses, partially attenuating palmitate-induced activation of WNT and Axin2, and facilitating a partial recovery of Axin1 expression.

Conclusion: PA and OA differentially modulated WNT/β-catenin pathway-associated responses in lipid-loaded HepG2 cells. PA elicited a broader response involving WNT, CTNNB1, TCF, Axin2, WNT, and β-catenin, whereas OA produced a more selective response. Their combination partially attenuated PA-associated changes, highlighting fatty acid composition as a potential determinant of cellular responses to lipotoxic stress.