Effect Of Conjugated Linoleic Acid On Insulin Resistance Liver Cells

As was proved by the current research, the effect of conjugated linoleic acid (CLA) on insulin resistance may be isomer specific, the effect and mechanism of trans10, cis12-conjugated linoleic acid (t10, c12-CLA) and cis9, trans11-conjugated linoleic acid (c9, t11-CLA) on insulin resistance Chang liver cells was studied in the present paper.A reliable insulin resistance cell model was established by using Chang liver cells with high concentration insulin. The glucose consumption of Chang liver cells was measured by the method of glucose oxidizes peroxides (GOD-POD). As a result, the glucose consumption of Chang liver cells which were incubated with1%FBS and100nmol/L insulin significantly decreased, indicating a successful insulin resistant cell model. The model keeps stable in36h and cells morphocytology keeps the same before and after establishing insulin resistance cell model.To determine whether t10, c12-CLA and c9, t11-CLA have any effects on the cell viability of insulin resistance Chang liver cells in the concentrations of1,2,5and10μmol/L, cell viability was measured by MTT assay. As a result, there were not any significant differences between CLA isomer treated groups and control group in MTT OD value, indicating that t10, c12-CLA and c9, t11-CLA did not affect cells viability of insulin resistance Chang liver cells at these concentrations.In the present study, we incubated insulin resistance Chang liver cells with1,2,5and10μmol/L t10, c12-CLA or c9, t11-CLA for12h, respectively. As a result, t10, c12-CLA, but not c9, t11-CLA were found to enhance glucose consumption of insulin resistance cells in a dose-dependent way. Two μmol/L t10,c12-CLA for12h incubation significantly improved glucose consumption of insulin resistance cells by17.29(P<0.001). The most optimal incubation time is12h, the glucose consumption significantly increased4.82%(P<0.01) compared with control.In order to study the mechanism, we incubated insulin resistance Chang liver cells with t10, c12-CLA for12h, scraped the cells for further western blot analysis (the protein level of phospho-protein kinase B, p-PKB/p-Akt). As a result, p-Akt was markly higher in groups treated for12h with1μmol/L and2μmol/L t10, c12-CLA than in the group treated with insulin alone. In order to give more evidence to the hypothesis that phosphoinositide3-kinase/protein kinase B (PI3K/Akt) signaling pathway maybe involves in the beneficial effect of t10, c12-CLA on improving insulin resistance, experiments were performed by using a type of PI3K inhibitor, LY294002. We incubated insulin resistance Chang liver cells with t10, c12-CLA and LY294002. As a result, LY294002inhibited the beneficial effect of t10, c12-CLA on increasing glucose consumption of insulin resistance cells, indicating PI3K/Akt signaling pathway involved in the effect of t10, c12-CLA on modifying glucose uptake and utilization in insulin resistance Chang liver cells.