[LRP16 gene causes insulin resistance in C2-C12 cells by inhibiting the IRS-1 signaling and the transcriptional activity of peroxisome proliferator actived receptor γ].

OBJECTIVE: To explore the effect of LRP (leukemia related protein) 16 on insulin resistance in C2-C12 cells and explore its molecular mechanism.

METHODS: Lipidosome transfection and lentivirus mediated siRNA (small interfering RNA) technology were used to establish LRP 16 overexpression and underexpression cell lines and their corresponding control cell lines. And 2-deoxy-[(3)H]-glucose was used to measure the effect of LRP 16 on insulin-stimulated glucose uptake. The effects of LRP16 on the phosphorylation of IRS (insulin receptor substrate)-1, Akt and the expressions of PI3K (p85), PPAR (peroxisome proliferator actived receptor) γ and GLUT-4 were detected by Western blot. Luciferase was used to study the effect of LRP16 on the transcriptional activity of PPARγ.

RESULTS: Insulin-stimulated glucose uptake decreased to 46% of the control when LRP16 was over-expressed [(4700 ± 97) vs. (10200 ± 347), P < 0.01]. And the insulin-stimulated glucose uptake was 1.73 fold of control when the expression of LRP16 was suppressed in C2-C12 cells [(17600 ± 466) vs (10200 ± 91), P < 0.05]. The overexpression of LRP16 attenuated the insulin-induced tyrosine phosphorylation of IRS-1, the phosphorylation of Akt and the expressions of PI3K (p85), PPARγ and GLUT-4. But it promoted the insulin-induced phosphorylation of IRS-1 at Ser307 in C2-C12 cells. LRP16 decreased the transcriptional activity of PPARγ in a dose-dependent manner. The transcriptional activity of PPARγ decreased to 43% and 27% of the control when the doses of pcDNA3.1-16 were 0.4 µg and 0.5 µg [(76 ± 11) vs (33 ± 9), P < 0.01] and 27% [(21 ± 9) vs (76 ± 11), P < 0.01].

CONCLUSION: LRP16 gene causes insulin resistance in C2-C12 cells by inhibiting the IRS-1 signaling and the transcriptional activity of PPARγ.