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Mariniello, Katia, Min, Yoeju and Ghebremeskel, Kebreab (2018) Phosphorylation of protein kinase B, the key enzyme in insulin signalling cascade, is enhanced in linoleic and arachidonic acid treated HT29 and HepG2 cells. Nutrition. ISSN 0899-9007
Objective: Defects in insulin signalling pathway have been implicated in the pathogenesis of impaired glucose uptake, insulin resistance and type II diabetes. However, the specific defects that precipitate these abnormalities are yet to be fully elucidated. The plasma membrane embedded insulin receptor transmembrane protein, after binding to insulin, initiates a cascade of phosphorylation which leads to the activation of protein kinase B (AKT) and subsequently to initiation of some metabolic actions of insulin. The activities of this receptor, insulin binding and tyrosine kinase activation, is dependent on its plasma lipid environment. There are scarcity of published data on the influence of omega-3 and -6 polyunsaturated fatty acids on insulin response. Moreover, the findings of the published investigations, most of which have used omega-3 and -6 PUFA blend, have been inconclusive. Hence, a need for well- thought-out further research. The aim was to elucidate the effect of treatments with LNA, ARA, ALA, DHA, and EPA on cell membrane composition and consequently on insulin signalling pathway, specifically AKT phosphorylation.
Research Methods and Procedures: Human colon adenocarcinoma (HT29) and liver hepatocellular (HepG2) cells were treated with or without 40 µM of linoleic (LNA), arachidonic (ARA), alpha-linolenic (ALA), eicosapentaenoic (EPA) or docosahexaenoic (DHA) for 48 hours. Fatty acids composition of phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) from the treated cells by capillary gas liquid chromatograph. Cells were incubated for 30 minutes with or without human insulin (50ng/ml) and the phosphorylation of AKT assessed with the use of western blotting.
Results: The fatty acids were incorporated in PtdCho and PtdEtn of both cell lines; but, the level of incorporation was higher in HT29. Phosphorylation of AKT increased when HT29 was treated with LNA (P<0.05) and ARA (P<0.01), but not with ALA, EPA or DHA. A similar but non-significant increase in AKT phosphorylation was observed in LNA and ARA treated HepG2 cells. Conclusion: The finding of this investigation demonstrates, plasma membrane lipid bilayer enrichment with LNA or ARA treatment enhances insulin action by AKT activation.
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