Expression of cellular inhibitor of apoptosis protein-2 in human subcutaneous and omental adipose tissue.

Abstract

In the current study, we addressed the question if there is depot-specific expression of cellular inhibitor of apoptosis protein-2 (cIAP2) already in childhood and if the relative expression changes with age in parallel with increasing risk of developing visceral adiposity. Paired samples of human omental (OM) and subcutaneous (SC) adipose tissue were obtained from 23 patients (12 children and 11 adults). mRNA level of cIAP2 was determined using reverse transcription-polymerase chain reaction (RT-PCR) and protein expression confirmed by Western blotting. Apoptosis indices were determined by terminal deoxynucleotidyl transferase-mediated dUTP-fluorescein nick-end labelling (TUNEL). cIAP2 mRNA was 1.51-fold higher in OM compared with SC adipose tissue (OM>SC in 20 of 23 subjects; P<0.001). Western blots were in agreement with mRNA expression (OM>SC in nine of 10 subjects, P<0.01). Subgroup analyses showed depot difference in both children (P<0.01) and adults (P<0.05). Contrary to the hypothesis, depot-specific difference in mRNA expression of cIAP2 was significantly higher in children compared with adults (P<0.05). We were unable to demonstrate any difference in the basal apoptosis rate between adipocytes from the two depots. There was no significant association between cIAP2 mRNA expression and BMI or sex. The results demonstrated for the first time that depot-specific difference in cIAP2 expression is consistent in children and adults. This suggests that the higher expression of cIAP2 in OM than in SC adipose tissue may be due to inherent properties of cells from the two depots. The more pronounced depot-specific difference in children than in adults may reflect a net gain in visceral adipose tissue during growth.