Age-Related Expression Dynamics of Uncoupling Protein 1 in Adipose Tissues of ICR Outbred Mice during Postnatal Ontogenesis

Mitochondrial uncoupling protein (UCP1) facilitates adaptive non-shivering thermogenesis in brown and beige adipocytes due to uncoupling of mitochondrial respiration and oxidative phosphorylation (ATP synthesis). The presence of UCP1-expressing adipocytes in fat depots is known to promote metabolic health and provide protection against metabolic disorders, thus stimulating interest in studying the age-related dynamics of UCP1 expression. The available data are scarce and were mainly obtained on obesity-prone C57Bl/6J mice, referring to either early or late ontogenesis. In our study, UCP1 expression in adipose tissues of outbred male ICR mice was studied for the first time in the period from weaning to old age. Interscapular brown adipose tissue (BAT), as well as inguinal and perigonadal white adipose tissues (IWAT and GWAT, respectively), were sampled from mice aged 20 days, 1.5, 6, and 18 months. UCP1 expression levels were assessed by Western blotting. In IWAT, relative UCP1 expression decreased 2-fold between the ages of 20 days and 1.5 months, and was undetectable at later stages. In GWAT, UCP1 expression was only detected in 30% of the tissue samples from mice aged between 1.5 and 6 months, with its level being 10-fold lower compared to IWAT depots. In BAT, no statistically significant changes in UCP1 expression were revealed. The physiological role of the UCP1-expressing cell population in GWAT, as well as a possible relationship between UCP1 expression time course and decline rate during the growth and maturation of reproductive function and the activation of lipogenesis in IWAT, are discussed.