Regulation of podocyte survival and endoplasmic reticulum stress by fatty acids

Abstract

Apoptosis of podocytes is considered critical in the pathogenesis of diabetic nephropathy (DN). Free fatty acids (FFAs) are critically involved in the pathogenesis of diabetes mellitus type 2, in particular the regulation of pancreatic beta-cells survival. The objectives of this study were to elucidate the role of palmitic acid, palmitoleic, and oleic acid in the regulation of podocyte cell death and endoplasmic reticulum (ER) stress. We show that palmitic acid increases podocyte cell death, both apoptosis and necrosis of podocytes in a dose and time-dependent fashion. Palmitic acid induces podocyte ER stress leading to an unfolded protein response (UPR) as reflected by the induction of the ER chaperon immunoglobulin heavy chain binding protein (BiP) and proapoptotic C/EBP (CCAAT/enhancer binding protein) homologous protein (CHOP) transcription factor. Of note, the monounsaturated palmitoleic and oleic acid can attenuate the palmitic acid-induced upregulation of CHOP, thereby preventing cell death. Similarly, gene silencing of CHOP protects against palmitic acid induced podocyte apoptosis. Our results offer a rationale for interventional studies aimed at testing whether dietary shifting of the FFA balance towards unsaturated FFAs can delay the progression of DN.