Figure 3. Metformin suppresses POMC protein levels through phosphorylation of AMPK and subsequently LXRα in vitro.

The rat pituitary adenoma GH3 cells were treated with metformin by using the indicated concentrations and treatment times, and total cell lysates were used for western blotting. (a and b) Metformin upregulated AMPK phosphorylation and downregulated POMC expression. (c) Total cell lysates were used for immunoprecipitation with anti-phopho-Thr antibody and western blotting with anti-LXRα antibody. (d) Reduced POMC after metformin treatment was restored when two siRNAs (#1 and #2) targeting AMPK were transfected in GH3 cells. (e) After metformin treatment, knockdown of LXRα by using two siRNAs (#1 and #2) targeting LXRα (upper) restored POMC expression, although p-AMPK was still enhanced (lower). A representative data from 3 independent experiments. Full-length blots are presented in Supplementary Figure S8.