UNCOUPLING PROTEIN GENE - QUANTIFICATION OF EXPRESSION LEVELS IN ADIPOSE TISSUES OF OBESE AND NONOBESE HUMANS

The mitochondrial uncoupling protein (UCP), which is exclusively expre ssed in brown adipose tissue, regulates energy expenditure in rodents but its importance in the energy homeostasis of adult humans is uncert ain. To study associations of UCP gene expression with human obesity, we determined, by a competitive reverse transcription-polymer ase chai n reaction assay, UCP mRNA expression levels in intra- and extraperito neal adipose tissues of 79 obese subjects and 17 lean controls. UCP mR NA and internal standard RNA were reverse transcribed and coamplified in one reaction in which tile same primers were used. The signal inten sities of UCP mRNA products were compared with the signal intensities of standard RNA products to quantify UCP mRNA abundance. UCP mRNA was detected in all intra- and extraperitoneal adipose tissues studied. In both obese and non-obese subjects, UCP mRNA abundance was highest in the intraperitoneal than in tile extraperitoneal tissue (P < 0.001). C ompared to lean controls, morbidly obese subjects showed a significant ly lower age- and gender-adjusted UCP mRNA expression level in the int raperitoneal adipose tissue (3.467 +/- 2.483 vs. 6.917 +/- 4.292 amol/ fmol beta-actin mRNA; mean +/- SD, P < 0.002), while UCP mRNA abundanc e in extraperitoneal adipose tissue did not differ between obese and n onobese subjects. These data are consistent with reduced energy expend iture in obesity, but it remains to be determined whether tile associa tion of decreased intraperitoneal UCP mRNA expression with obesity sta tus reflects a causal contribution of brown adipose tissue function to the pathogenesis of obesity.