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Metabolism and Physiology
Session Title: Cardiac Metabolism, Energetics, and Function

Abstract 15613: Plin2 Protects Against Palmitate-mediated Lipotoxicity in a Cardiomyoblast Cell Line

Originally publishedCirculation. 2016;134:A15613

    Introduction: We have previously shown that palmitate causes ER stress in primary cardiomyocytes and this is associated with a diffuse lipid staining histology. This is in contrast to oleate which is non-toxic and leads to the formation of abundant, clearly delineated lipid droplets (LDs).

    Hypothesis: The aberrant lipid histology led us to hypothesize that perhaps there is an impairment in LD formation in palmitate treated cells, which leads to accumulation of lipids in the ER and consequent ER stress.

    Methods: To test this hypothesis we treated H9C2s (a cardiomyoblast cell line) with either 300μM Oleate or palmitate for 8 hours. Treated cells were then subjected to Western analysis for assessment of Plin2 expression; (iii) Cellular sub-fractionation to identify differential lipid distribution; (iv) Propidium iodide exclusion assays for viability analyses; And finally (v) thin layer chromatography (TLC) to determine differential lipid profiles.

    Results: We found that palmitate resulted in significantly less LD abundance despite equivalent fatty acid uptake rates. In accordance with the paucity of LDs, we found that Plin2, a key LD binding protein, was induced in a time dependent fashion by oleate but not palmitate. Next we showed that palmitate pre-treatment caused lipids to accumulate in the ER, while oleate pre-treatment led to preferential lipid accumulation in LDs. Next assessed lipid profiles by TLC in cells treated with oleate or palmitate. Interestingly, we found that palmitate led to greater diacylglyceride (DAG) and less triacylglyceride levels (TAG) than oleate. This is of interest because DAG has more lipotoxic potential than the neutral inert TAG. Finally we tested the possibility that the lack of Plin2 may be the cause of palmitate-mediated toxicity by impairing LD formation. To test this, we evaluated the effect of overexpressing Plin2 in palmitate treated cells. We found that overexpressing Plin2 protected against palmitate mediated cell death.

    Conclusions: We show that palmitate lacks the capacity to induce Plin2, which may be the cause for the poor LD formation in these cells. In turn, the paucity of LDs in palmitate treated cells leads to accumulation of lipids in the ER and consequent ER stress.

    Footnotes

    Author Disclosures: A. Akoumi: None. T. Haffar: None. N. Bousette: None.

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