Depot-related and thiazolidinedione-responsive expression of uncoupling protein 2 (UCP2) in human adipocytes

Uncoupling protein 2 (UCP2) is a recently described homologue of the uncoupling protein of brown adipocytes (UCP1), which is expressed at high levels in human white adipose tissue. Studies were undertaken (1) to establish whether the expression of UCP2 mRNA varies in a depot-related manner in isolated human adipocytes, (2) to determine whether thiazolidinedione exposure influences the expression of UCP2 mRNA in cultured human preadipocytes, and (3) to determine whether human UCP2 is targeted to mitochondria when transfected into mammalian cells. Abdominal subcutaneous and omental adipose tissue biopsies were obtained from adult patients undergoing elective intra-abdominal surgical procedures. A competitive reverse transcriptase-polymerase chain reaction (RT-PCR) was used to quantify UCP2 mRNA expression in human omental and subcutaneous adipocytes, and in cultured human preadipocyes differentiated in vitro using the thiazolidinedione, BRL49653. Chinese hamster ovary cells were transfected with a vector expressing human UCP2, and its cellular localization was determined by confocal immunfluorescence microscopy. Adipocytes isolated from human omentum consistently expressed more UCP2 mRNA than did subcutaneous adipocytes from the same subjects (mean fold difference 2.92 +/- 0.44 P