In vitro activity: Rosiglitazone is an insulin-sensitising agent of the thiazolidinedione class of oral antihyperglycaemic drugs. Rosiglitazone exhibits insulin-sensitising activity 60- to 200-fold higher than that of troglitazone, englitazone, or piogliazone in rodent models of insulin ressitance. Rosiglitazone reduces hyperglycaemia by improving insulin sensitivity in adipose tissue, the liver and skeletal muscle tissue. Such insulin sensitisation may be partly attributable to the effects of Rosiglitazone on the expression of molecules involved in the insulin signalling cascade. In adipose tissue, Rosiglitazone-mediated PPARγ stimulation promotes adipocyte differentiation. Rosiglitazone may also promote the uptake of free fatty acids in adipose tissue, thus reducing systemic free fatty acid levels. The insulin sensitivity of the liver and peripheral tissues may be modulated indirectly by Rosiglitazone-mediated changes in levels of fatty acid or adipocyte-derived factors, such as adiponectin and TNFα. Rosiglitazone may also be involved in modulating the expression of adiponectin receptors in some tissues, which may be relevant to some aspects of insulin sensitization.

Kinase Assay: cDNA encoding amino acids 174-475 of PPARγ1 is amplified via polymerase chain reaction and inserted into bacterial expression vector pGEX-2T. GST-PPARγ LBD is expressed in BL21(DE3)plysS cells and extracts. For saturation binding analysis, bacterial extracts (100 μg of protein) are incubated at 4°C for 3 h in buffer containing 10 mM Tris (pH 8.0), 50 mM KCl, 10 mM dithiothreitol with [3H]-BRL49653 (specific activity, 40 Ci/mmol) in the presence or absence of unlabeled Rosiglitazone. Bound is separated from free radioactivity by elution through 1-mL Sephadex G-25 desalting columns. Bound radioactivity eluted in the column void volume and is quantitated by liquid scintillation counting.

Cell Assay: C3H10T1/2 cells are grown in a 24-well plate in DME medium supplemented with 10% fetal calf serum. Medium and compound (Rosiglitazone) are exchanged every 3 days. Cells are stained at day 7 with Oil Red O and photographed