Effect of thiazolidinediones on expression of UCP2 and adipocyte markers in human PAZ6 adipocytes

Abstract

Aims/hypothesis. Thiazolidinediones, a new class of insulin sensitizers, up-regulate the expression of uncoupling protein 2 in rodent adipocytes. It is not known, however, whether thiazolidinediones influence uncoupling protein 2 expression in human adipocytes. We therefore investigated the effect of these drugs on uncoupling protein 2 expression in the recently immortalized human PAZ6 adipocyte cell line. Methods. Immortalized human PAZ6 preadipocytes were differentiated into adipocytes in the presence or absence of thiazolidinediones. The effect of the drugs on uncoupling protein 2 expression and adipocyte differentiation was measured by reverse transcription-polymerase chain reaction of mRNA of uncoupling protein 2 and of five adipocyte differentiation markers. Results. When cells were differentiated 15 days in the presence of thiazolidinediones, uncoupling protein 2 expression was 2.1-fold higher than in the absence of the drugs. The expression of five adipocyte differentiation markers was, however, also increased by thiazolidinediones. Short-term incubation for 4 and 24 h with thiazolidinediones increased uncoupling protein 2 expression 1.35-fold and 2.3-fold, respectively. The expression of adipocyte markers studied in parallel was also augmented. Conclusion/interpretation. Thiazolidinediones rapidly increase the expression of uncoupling protein 2 in human PAZ6 adipocytes but the increase of uncoupling protein 2 expression is always associated with an augmentation of the expression of all adipocyte markers studied in parallel. This indicates that the effect of thiazolidinediones on uncoupling protein 2 mRNA reflects a general increase in adipocyte differentiation rather than a specific augmentation of uncoupling protein 2 gene expression.