Lipid remodeling and an altered membrane-associated proteome may drive the differential effects of EPA and DHA treatment on skeletal muscle glucose uptake and protein accretion

Abstract

24In striated muscle, EPA and DHA have differential effects on the metabolism of glucose and 25 differential effects on the metabolism of protein. We have shown that, despite similar incorporation, 26 treatment of C 2 C 12 myotubes (CM) with EPA but not DHA improves glucose uptake and protein 27 accretion. We hypothesized that these differential effects of EPA and DHA may be due to divergent 28 shifts in lipidomic profiles leading to altered proteomic profiles. We therefore carried out an 29 assessment on the impact of treating CM with EPA and DHA on lipidomic and proteomic profiles. 30 FAME analysis revealed that both EPA and DHA led to similar but substantial changes in fatty acid 31 profiles with the exception of arachidonic acid, which was decreased only by DHA, and DPA, which 32 was increased only by EPA treatment. Global lipidomic analysis showed that EPA and DHA induced 33 large alterations in the cellular lipid profiles and in particular, the phospholipid classes. Subsequent 34 targeted analysis confirmed that the most differentially regulated species were phosphatidylcholines 35 and phosphatidylethanolamines containing long chain fatty acids with 5 (EPA treatment) or 6 (DHA 36 treatment) double bonds. As these are typically membrane associated lipid species we hypothesized 37 that these treatments differentially altered the membrane-associated proteome. SILAC based 38 proteomics of the membrane fraction revealed significant divergence in the effects of EPA and DHA 39 on the membrane associated proteome. We conclude that the EPA specific increase in polyunsaturated 40 long chain fatty acids in the phospholipid fraction is associated with an altered membrane associated 41 proteome and these may be critical events in the metabolic remodelling induced by EPA treatment. 42

Human skeletal muscle metabolic responses to 6 days of high‐fat overfeeding are associated with dietary n‐3PUFA content and muscle oxidative capacity

“…However, membrane lipid composition changes are likely to influence the muscle responsiveness to nutritional and/ or contractile stimuli, and therefore are important in determining the cellular and metabolic outcomes induced by HFEE (Casares et al, 2019). It is worth noting that in the present study, EPA was elevated in the muscle phospholipid fraction in the HF-FO group, and although AA was unchanged, these changes in lipid composition appear to drive metabolic benefits in skeletal muscle cells (Jeromson et al, 2018).…”

Potential Roles of n-3 PUFAs during Skeletal Muscle Growth and Regeneration

“…The potential positive effects of n-3 PUFA’s on myogenesis may relate to their capacity to alter the cell membrane lipid composition, which in turn, changes the profile of membrane bound proteins of lipid rafts [ 79 , 80 ]. These changes impact membrane fluidity and assist in myoblast fusion during myotube formation [ 81 ], allowing for n-3 PUFAs to simultaneously modulate several signalling pathways.…”

“…This could indicate that anabolic kinase efficiency is increased, suggesting less protein is required to elicit post translational modifications (e.g., phosphorylation) and that these posttranslational modifications occur at a faster rate with n-3 PUFA supplementation. This may be due to the increased incorporation of unsaturated fatty acids into membrane phospholipids thereby changing their composition and altering the activities of proteins that are associated with stimulating MPS tethered to cell membrane [ 79 , 80 ].…”

“…Activation of the mechanistic target of rapamycin (mTOR) and its downstream signalling targets the 70 kDa ribosomal protein S6 kinase-1 (p70S6K1) and eIF4E-binding protein 1 (4E-BP1) are involved in the regulation of translation initiation responses that are required for skeletal muscle growth, hypertrophy, and also have a role in myogenesis [ 121 ]. In isolation, n-3 PUFAs do not appear to have any effect on mTOR signalling pathway in fully formed C2C12 cells [ 80 ]. However, EPA exclusively augments leucine induced MPS in fully differentiated C2C12 myotubes and increases the phosphorylation of p70S6K1, with no changes in the phosphorylation of any of the other anabolic mTOR pathway members [ 122 ].…”

The impact of exercise and nutrition on the regulation of skeletal muscle mass

“…) and, potentially, lipidomic (Jeromson et al . ) technologies to study skeletal muscle plasticity following exercise and feeding in both older and young adults would no doubt address this important gap in our understanding (Figure ).…”