Eicosapentaenoic acid (20:5 n-3) increases fatty acid and glucose uptake in cultured human skeletal muscle cells

Vigdis Aas,Merethe H Rokling-Andersen,Eili Tranheim Kase,G Hege Thoresen,Arild C Rustan

doi:10.1194/jlr.m500300-jlr200

Vigdis Aas, Merethe H Rokling-Andersen + Show 3 more

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https://doi.org/10.1194/jlr.m500300-jlr200

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Abstract

This study was conducted to evaluate the chronic effects of eicosapentaenoic acid (EPA) on fatty acid and glucose metabolism in human skeletal muscle cells. Uptake of [14C]oleate was increased >2-fold after preincubation of myotubes with 0.6 mM EPA for 24 h, and incorporation into various lipid classes showed that cellular triacylgycerol (TAG) and phospholipids were increased 2- to 3-fold compared with control cells. After exposure to oleic acid (OA), TAG was increased 2-fold. Insulin (100 nM) further increased the incorporation of [14C]oleate into all lipid classes for EPA-treated myotubes. Fatty acid beta-oxidation was unchanged, and complete oxidation (CO2) decreased in EPA-treated cells. Basal glucose transport and oxidation (CO2) were increased 2-fold after EPA, and insulin (100 nM) stimulated glucose transport and oxidation similarly in control and EPA-treated myotubes, whereas these responses to insulin were abolished after OA treatment. Lower concentrations of EPA (0.1 mM) also increased fatty acid and glucose uptake. CD36/FAT (fatty acid transporter) mRNA expression was increased after EPA and OA treatment compared with control cells. Moreover, GLUT1 expression was increased 2.5-fold by EPA, whereas GLUT4 expression was unchanged, and activities of the mitogen-activated protein kinase p38 and extracellular signal-regulated kinase were decreased after treatment with OA compared with EPA. Together, our data show that chronic exposure of myotubes to EPA promotes increased uptake and oxidation of glucose despite a markedly increased fatty acid uptake and synthesis of complex lipids.

Highlights

This study was conducted to evaluate the chronic effects of eicosapentaenoic acid (EPA) on fatty acid and glucose metabolism in human skeletal muscle cells
oleic acid (OA) compared with EPA and the bovine serum albumin (BSA) control decreased the phosphorylation of both the extracellular signal-regulated kinase (ERK) and p38 mitogenactivated protein kinases (Fig. 6)
The present study shows that pretreatment of differentiated human myotubes with EPA promotes increased uptake and metabolism of [14C]oleate to cellular lipids, and the increased oleate uptake was not accompanied by increased [14C]oleate oxidation

Summary

EXPERIMENTAL PROCEDURES

Bovine serum albumin (essentially fatty acid-free), cytochalasin B, 2-deoxy-D-glucose, extracellular matrix gel, glycogen (rabbit liver), L-carnitine, and OA were purchased from SigmaAldrich (St. Louis, MO). L-Glutamine, 0.05% trypsin/EDTA, penicillin/streptomycin, fetal calf serum (FCS), and minimum essential medium a (aMEM) were purchased from Gibco (Paisley, UK). After 1–2 weeks at z80% confluence, growth medium was replaced by aMEM with 2% FCS, 50 U/ml penicillin, 50 mg/ml streptomycin, and 1.25 mg/ml amphotericin B to induce the differentiation of myoblasts into multinucleated myotubes. On day 7, differentiated myotubes were pretreated with 0.6 mM fatty acids, either OA or EPA, in aMEM with 2% FCS for 24 h. Myotubes were incubated on six-well plates for 4 h in aMEM with [1-14C]OA (0.5 mCi/ml, 0.6 mM) and 0.24 mM fatty acid-free albumin (BSA) with or without 100 nM insulin to study insulinmediated or basal cellular oleate distribution, respectively. Accession Number b-Actin Diacylglycerol acyltransferase-1 CD36/FAT (fatty acid transporter) Glucose transporter GLUT1 Glucose transporter GLUT4

F: ACC GAG CGC GGC TAC A R: TCC TTA ATG TCA CGC ACG ATT T F

RESULTS

DISCUSSION