Protection of palmitic acid-mediated lipotoxicity by arachidonic acid via channeling of palmitic acid into triglycerides in C2C12

Hyae Cheon,Young Cho

doi:10.1186/1423-0127-21-13

Abstract

BackgroundExcessive saturated fatty acids have been considered to be one of major contributing factors for the dysfunction of skeletal muscle cells as well as pancreatic beta cells, leading to the pathogenesis of type 2 diabetes.ResultsPA induced cell death in a dose dependent manner up to 1.5 mM, but AA protected substantially lipotoxicity caused by PA at even low concentration of 62 μM, at which monounsaturated fatty acids including palmitoleic acid (POA) and oleic acid (OA) did not protect as much as AA did. Induction of cell death by PA was resulted from mitochondrial membrane potential loss, and AA effectively blocked the progression of apoptosis. Furthermore, AA rescued significantly PA-impaired glucose uptake and -signal transduction of Akt in response to insulin.Based on the observations that polyunsaturated AA generated competently cellular droplets at low concentration within the cytosol of myotubes compared with other monounsaturated fatty acids, and AA-driven lipid droplets were also enhanced in the presence of PA, we hypothesized that incorporation of harmful PA into inert triglyceride (TG) may be responsible for the protective effects of AA against PA-induced lipotoxicity. To address this assumption, C2C12 myotubes were incubated with fluorescent probed-PA analogue 4, 4-difluoro-5, 7-dimethyl-4-boro-3a,4a-diaza-s-indacene-3-hexadecanoic acid (BODIPY FL C16) in the presence of AA and their subsequent lipid profiles were analyzed. The analyses of lipids on thin layer chromatograpy (TLC) showed that fluorescent PA analogue was rapidly channeled into AA-driven TG droplets.ConclusionTaken together, it is proposed that AA diverts PA into inert TG, therefore reducing the availability of harmful PA into intracellular target molecules.

Highlights

Excessive saturated fatty acids have been considered to be one of major contributing factors for the dysfunction of skeletal muscle cells as well as pancreatic beta cells, leading to the pathogenesis of type 2 diabetes
Dulbecco's Modified Eagle's Medium (DMEM), Dulbecco’s phosphate buffered saline (D-PBS), fetal bovine serum and antibiotics were purchased from Gibco (Grand Island, NY, USA). 5, 5’, 6, 6’tetrachloro-1, 1’, 3, 3’-tetraethylbenzimidazolcarbocyanine iodide (JC-1) and BODIPY FL C16 fatty acid were from Molecular Probes (Leiden, The Netherlands). 2-[1,2-3H]deoxy-D-glucose was from Amersham Biosciences
Cytotoxic activity of PA and protection of arachidonic acid (AA) from PA-caused cytotoxicity in C2C12 As a preliminary test, myotubes were exposed to PA at different concentrations to understand the titration effects of PA on cell death

Summary

Introduction

Excessive saturated fatty acids have been considered to be one of major contributing factors for the dysfunction of skeletal muscle cells as well as pancreatic beta cells, leading to the pathogenesis of type 2 diabetes. Type 2 diabetes is a clinical disease characterized by disruption in the metabolism of glucose and lipids, and consequential failure in the production of insulin as well as insulin resistance [1,2]. These dysfunctions are ascribed partly to a reduced disposal of blood glucose by peripheral tissues such as fat and muscle tissue. Clinical trial of multiple lipid-lowering drugs and supplements provides patients with new strategies to reduce lipid levels [6]

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