Interscapular white adipose tissue: An interesting depot for browning research in rodents

Interscapular brown adipose tissue is surrounded by a white fat depot, the interscapular WAT (isWAT), which has received little attention. Here, we have characterized isWAT and the impact of chronic intake of a very high-fat diet, the cafeteria diet, on isWAT browning capacity. The effect of high-fat diets on WAT browning is controversial, however, some groups have described increased WAT UCP1 expression, probably to counteract increased adiposity. We analyzed mRNA expression of key brown/brite markers and lipid metabolism genes, and of selected proteins in isWAT of control, cafeteria-obese and post-cafeteria rats. Morphological/immunohistochemical characterization was also performed. Results present isWAT as a depot with a molecular profile close to that of browning-prone white fat depots (inguinal and retroperitoneal), which also shares key features with BAT, including UCP1 expression (mRNA/protein). The cafeteria diet intake induced mRNA expression of browning/thermogenic genes, which was restored after the diet was withdrawn, and increased expression of key genes involved in lipid catabolism in isWAT. Moreover, basal mRNA expression of brown/brite markers was greater than in other white depots and higher UCP1 protein levels were observed compared to the browning-prone retroperitoneal depot. Thus, isWAT appears as an interesting depot to be taken into consideration for lipid research and to better characterize browning regulation.