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

Aims/hypothesis. Thiazolidinediones, a new class of insulin sensitizers, up -regulate the expression of uncoupling protein 2 in rodent adipocytes. It i s not known, however, whether thiazolidinediones influence uncoupling prote in 2 expression in human adipocytes, We therefore investigated the effect o f these drugs on uncoupling protein 2 expression in the recently immortaliz ed human PAZ6 adipocyte cell line, Methods. Immortalized human PAZ6 preadipocytes were differentiated into adi pocytes 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 unc oupling protein 2 and of five adipocyte differentiation markers. Results. When cells were differentiated 15 days in the presence of thiazoli dinediones, uncoupling protein 2 expression was 2.1-fold higher than in the absence of the drugs. The expression of five adipocyte differentiation mar kers was, however, also increased by thiazolidinediones, Short-term incubat ion for 4 and 24 h with thiazolidinediones increased uncoupling protein 2 e xpression 1.35-fold and 2.3-fold, respectively. The expression of adipocyte markers studied in parallel was also augmented. Conclusion/interpretation. Thiazolidine diones rapidly increase the express ion of uncoupling protein 2 in human PAZ6 adipocytes but the increase of un coupling 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 reflect s a general increase in adipocyte differentiation rather than a specific au gmentation of uncoupling protein 2 gene expression.