Selective molecular responses of rat white adipose tissue according to the fasting stage

Prolonged fasting-induced changes in rat white adipose tissue (epidydimal) transcriptome White adipose tissue is a central place to energy storage and a major endocrine organ. However, adipose molecular mechanisms have been poorly studied during prolonged fasting. To fill this gap, the aim of this study was to decipher transcriptomic regulations in rat adipose tissue during phase 2 (lipid mobilization) and phase 3 (protein catabolism) of prolonged fasting compared to the fed state. We describe a regulatory transcriptional program in epididymal adipose tissue in line with lipogenesis repression during both phases, and that would favor lipolysis during phase 2 and repress it during phase 3. Such regulations notably involve selective (i.e. phase-dependent) changes in gene expression levels of lipases, lipid droplet-associated factors, and the proteins involved in cAMP-dependent and cAMP-independent regulation of lipolysis. The mRNA levels of adipose-secreted factors were globally consistent with the repression of insulin signalling during prolonged fasting. Regulations of leptin and adiponectin levels could be related to their respective role in triggering refeeding during late fasting and controlling lipid metabolism. Specific responses reflecting adipose tissue inflammation, increased fibrinolysis and a possible protein catabolism-related energy saving mechanism were also recorded during phase 3. These data thus provide a comprehensive molecular basis of adipose tissue responses according to the fasting stage. We analyzed epididymal white adipose tissue (epiWAT) from 12 male Sprague Dawley rats randomly divided into 3 groups (4 fed, 4 fasted until phase 2 of fasting [P2], and 4 fasted until phase 3 of fasting [P3]) using the Affymetrix Rat Gene 1.0 ST platform. Array data was processed by Affymetrix GCOS v1.4 and Expression Console v1.1. No techinical replicates were performed.