374-P: Oleate Prevents Palmitate-Induced Abnormalities in Insulin Signaling in Human Cardiac Progenitor Cells

Abstract

Myocardial ectopic lipid deposition has been associated with insulin resistance and cardiovascular risk. Palmitate, one of the most abundant saturated fatty acids, has been shown to impair insulin signaling in multiple cell types. Human cardiac progenitor cells (CPC) represent a compartment of multipotent stem cells essential for constant tissue repair and renewal in the adult heart. In this study, the ability of palmitate to impair insulin signaling, and the modulatory effects of oleate, a mono-unsaturated fatty acid, on palmitate-induced abnormalities were investigated in human CPC isolated from control subjects undergoing cardiac surgery. Human CPC express insulin receptor (IR), as assessed by quantitative RT-PCR and immunoblotting. Specifically, in human CPC both IR isoforms, A (IR-A) and B (IR-B), were identified, and IR-A was more expressed than IR-B. Exposure of human CPC to 100 nM insulin for 15 minutes resulted in increased Akt and p44/p42 MAPK phosphorylation (p<0.05), evidenced by immunoblotting. Treatment of human CPC with 0.25 mM palmitate for 24 h impaired the ability of insulin, added for the last 15 minutes, to phosphorylate both Akt and p44/p42 MAPK (p<0.05), without no effect on total Akt and p44/p42 MAPK protein levels. Interestingly, palmitate was able to increase both IR-A and IR-B mRNA levels (p<0.05), and to reduce IR protein expression (p<0.05). Co-incubation of palmitate with 0.1 mM oleate prevented the ability of palmitate to reduce insulin-induced Akt phosphorylation (p<0.05), but did not rescue the impaired p44/p42 MAPK phosphorylation. In addition, co-treatment with oleate also prevented both palmitate-induced upregulation of IR-A and IR-B mRNA (p<0.05), and downregulation of IR protein levels (p<0.05). In conclusion, oleate prevents some of the palmitate-induced impairments in insulin signaling in human CPC, thus contributing to cardiac protection from lipotoxicity-induced metabolic alterations. Disclosure R. Doria: None. F. Giorgino: Consultant; Self; AstraZeneca, Boehringer Ingelheim International GmbH, Lilly Diabetes, Novo Nordisk, Roche Diabetes Care, Sanofi, Research Support; Self; Lilly Diabetes, Roche Diabetes Care. C. Caccioppoli: None. R. Schipani: None. V. Genchi: None. A. Leonardini: None. A. Natalicchio: Speaker’s Bureau; Self; AstraZeneca, Boehringer Ingelheim International GmbH, Lilly Diabetes, Sanofi. S. Perrini: None. A. Cignarelli: None. L. Laviola: Advisory Panel; Self; A. Menarini Diagnostics, Abbott, AstraZeneca, Lilly Diabetes, Novo Nordisk Inc., Roche Diabetes Care, Sanofi-Aventis, Speaker’s Bureau; Self; Boehringer Ingelheim International GmbH, Medtronic.