Preadipocyte differentiation in vitro: identification of a highly active adipogenic agent

A highly active adipogenic agent was identified in an in vitro adipose conversion system. This agent, ADD 4743 (or ADD), was synthesized by Takeda Chemical Industries (Osaka) as a 3-hydroxy derivative of an oral antidiabetic agent, ciglitazone, and has been presumed to be an active metabolite of the latter substance. When ST 13 mouse preadipose cells were treated with micromolar concentrations of ADD they rapidly and uniformly converted into lipid-accumulating adipocytelike cells within 8-11 days after cell seeding. The degree of adipose conversion and lipid accumulation induced by ADD far exceeded those of the previously known inducing agents such as indomethacin plus insulin. The highly potent adipogenic activity of ADD was confirmed with two other preadipose cell lines (3T3 L1 and RMT rat preadipose cells). In addition to adipogenic activity, ADD inhibited cell proliferation of preadipose cells specifically. Activity of ADD induced lipid accumulation and growth inhibition of ST 13 cells, exhibiting very similar dose-response relationships. Cell proliferation or triacylglycerol content of nonadipocytic mesenchymal cells or epithelial cells were not affected by ADD. These observations strongly suggest that ADD-induced growth inhibition is not due to the nonspecific toxicity of the drug but is tightly associated with the adipocytic character of the treated cells. The present observation provides evidence that ADD would be a powerful agent in studies that involve preadipocyte differentiation.