Differential expression of genes for uncoupling proteins 1, 2 and 3 in brown and white adipose tissue depots during rat development

The different expression patterns of genes for uncoupling proteins (UCPs) 1 , 2 and 3 (ucp1, ucp2 and ucp3) were studied in interscapular brown adipose tissue (BAT) and in four white adipose tissue (WAT) depots (epididymal, in guinal, mesenteric and retroperitoneal) in male rats of different ages (18 days-12 months). UCP mRNA expression levels were determined by Northern blo tting. In BAT, there were high levels of expression of UCP1 and UCP3 mRNA, but no detectable levels of UCP2 mRNA. Both ucp1 and ucp3 followed a simila r expression pattern with age, with high levels in suckling rats which decr eased to 50% or less in rats just under 2 months old, declining thereafter until 5 months and then recovering with age. However, an additional peak of expression was observed for ucp3 at the age of 3 months. In WAT, ucp1 expr ession was rare: occasional expression was found for UCP1 mRNA in the retro peritoneal depot in suckling rats and in the epididymal and inguinal depots in suckling and mature adult rats. ucp2 and ucp3 had different development al expression patterns, but these were similar for each gene in the differe nt depots studied. UCP3 mRNA was highly expressed in rats soon after birth, it decreased until 3 months, and increased thereafter, except for the mese nteric WAT where ucp3 expression decreased until 7 months before recovering . The fact that changes with age of both ucp1 and ucp3 expression have a si milar profile in BAT, which is also similar to the ucp3 and also ucp1 profi les in some WAT depots, might reflect a common regulatory pattern for the e xpression of these genes, and also a common function. In contrast to ucp1 a nd ucp3, ucp2 had a peak of expression at about 2 months, and lower express ion at 3 months, suggesting different regulation and probably a different r ole for this UCP.