Assessment of genotoxicity in rats treated with the antidiabetic agent, pioglitazone

Pioglitazone (PIO), a member of the thiazolidinedione class of antidiabetic agents, specifically targets insulin resistance. Drugs of this class act as ligands for the gamma subtype of the peroxisome proliferator-activated receptor. Although troglitazone, another drug in this class, displayed unacceptable hepatotoxicity, PIO was approved for human use by the U.S. Food and Drug Administration. To our knowledge, there are no published reports on the genotoxicity of PIO; however, the package insert indicates that it has minimal genotoxicity. In this study, we used the comet assay to investigate the DNA damage in the peripheral blood and liver cells of rats treated with PIO. Sixteen male Sprague-Dawley rats were randomly distributed into four groups, and dosed daily for 14 days by oral gavage with 0, 10, 20, and 40 mg/kg/day PIO. A dose-dependent increase in DNA damage, as assessed by % tail DNA, was observed in both hepatocytes and blood lymphocytes of the PIO-treated groups, with significant increases detected between the rats treated with all the doses of PIO and the control, and between the rats treated with different PIO doses (P < 0.005 to P < 0.0001). Treating nuclei from the exposed animals with an enzyme cocktail containing Fpg and Endonuclease III prior to performing the comet assay increased the level of DNA damage, which reflects oxidized purine and pyrimidine. Taken together, our data indicate that PIO is able to dose-dependently induce DNA damage in both the liver and blood lymphocytes of rats, which is partially due to the generation of oxidative lesions

Genotoxicity in rats treated with the antidiabetic agent, rosiglitazone

Rosiglitazone (RSG), a member of the thiazolidinedione class of antidiabetic agents, improves glycemic control by increasing insulin sensitivity. The therapeutic mode of action of RSG involves its activity as a highly selective and potent agonist for peroxisome proliferator-activated receptor-gamma. Although other drugs in this class have displayed unacceptable hepatotoxicity, RSG was approved for human use. The package insert indicates that RSG has minimal genotoxicity, but information on the genotoxicity of RSG is not available in the published literature. In this study, we used the single cell gel electrophoresis (SCGE)/Comet assay to investigate the DNA damage in peripheral blood and liver cells of rats treated with RSG. Sixteen male Sprague-Dawley rats were randomly distributed into four groups, and dosed daily by oral gavage with 0.0, 0.5, 1.0, and 2.0 mg/kg/day RSG. The rats dosed with 2.0 mg/kg/day RSG received an similar to 10-times the area under the curve concentration of the maximum recommended human daily dose. After 14 days of treatment, the rats were euthanized, and peripheral blood and liver were collected and. processed for the Comet assay. A dose-dependent increase in DNA damage (as assessed by % tail DNA and Olive Tail Moment) was observed in the hepatocytes of RSG-treated groups, with significant increases detected between rats treated with all the doses of RSG and the control, and between rats treated with different RSG doses (P < 0.05 - P < 0.0001). In contrast, DNA damage was detected in peripheral blood lymphocytes only in rats treated with the higher RSG doses (1.0 and 2 mg/kg/day). Taken together, the data indicate that RSG is able to induce primary DNA damage in rats, with greater damage being detected in liver cells than lymphocytes