Modulation of Fatty Acid-Related Genes in the Response of H9c2 Cardiac Cells to Palmitate and n-3 Polyunsaturated Fatty Acids.

Silvia Cetrullo,Flavio Flamigni,Rosa Maria Borzì,Carla Pignatti,Stefania D’Adamo,Veronica Panichi

doi:10.3390/cells9030537

Abstract

While high levels of saturated fatty acids are associated with impairment of cardiovascular functions, n-3 polyunsaturated fatty acids (PUFAs) have been shown to exert protective effects. However the molecular mechanisms underlying this evidence are not completely understood. In the present study we have used rat H9c2 ventricular cardiomyoblasts as a cellular model of lipotoxicity to highlight the effects of palmitate, a saturated fatty acid, on genetic and epigenetic modulation of fatty acid metabolism and fate, and the ability of PUFAs, eicosapentaenoic acid, and docosahexaenoic acid, to contrast the actions that may contribute to cardiac dysfunction and remodeling. Treatment with a high dose of palmitate provoked mitochondrial depolarization, apoptosis, and hypertrophy of cardiomyoblasts. Palmitate also enhanced the mRNA levels of sterol regulatory element-binding proteins (SREBPs), a family of master transcription factors for lipogenesis, and it favored the expression of genes encoding key enzymes that metabolically activate palmitate and commit it to biosynthetic pathways. Moreover, miR-33a, a highly conserved microRNA embedded in an intronic sequence of the SREBP2 gene, was co-expressed with the SREBP2 messenger, while its target carnitine palmitoyltransferase-1b was down-regulated. Manipulation of the levels of miR-33a and SREBPs allowed us to understand their involvement in cell death and hypertrophy. The simultaneous addition of PUFAs prevented the effects of palmitate and protected H9c2 cells. These results may have implications for the control of cardiac metabolism and dysfunction, particularly in relation to dietary habits and the quality of fatty acid intake.

Highlights

It is noteworthy that high-lipid diets have a negative impact on health state, increasing evidence supports the view that fatty acids (FAs), derived from different foods, do not have the same biological effects
In the present study we describe some effects of palmitate on genetic and epigenetic regulation of key factors controlling FA metabolism and fate in H9c2 cells, and the ability of long-chain n-3 polyunsaturated fatty acids (PUFAs), eicosapentaenoicacid acid (EPA) and DHA, to contrast these actions that may contribute to cardiac dysfunction and remodeling
It should be noted that the n-3 PUFAs alone did not modify significantly cell viability, caspase activity and mitochondrial potential at the same concentrationthat protected from palmitate

Summary

Introduction

It is noteworthy that high-lipid diets have a negative impact on health state, increasing evidence supports the view that fatty acids (FAs), derived from different foods, do not have the same biological effects. High levels of saturated FAs, such as palmitic acid (C16:0) and stearic acid (C18:0), have been shown to favor cell death, hypertrophy and insulin resistance in a variety of cell types, including cardiac cells, both in vivo and in vitro [2,3,4]. Cells 2020, 9, 537 the cytotoxicity and dysfunction of cells treated with high concentrations of palmitate, implicating in particular the metabolic fate of this compound. A hypothesis relies on the de novo synthesis of ceramide [5]; other postulated mechanisms of lipotoxicity include accumulation of diacylglycerol (DAG) and other metabolic intermediates, due to the inability of the cell to handle high concentrations of palmitate [6,7]. FAs can have other relevant fates in cells following their activation to acyl-CoA, such as glycerophospholipid and sphingolipid synthesis or, even in a non-adipose tissue like cardiac muscle, triglyceride (TG)

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