Diet-induced obesity regulates the galanin-mediated signaling cascade in the adipose tissue of mice.

Galanin is a neuropeptide that regulates the food intake, neurogenesis, memory, and gut secretion. This study was conducted to evaluate the high-fat diet (HFD)-induced regulation of the galanin receptors (GalRs) and the associated signaling molecules in the adipose tissues of mice. Twenty C57BL/6J mice were given either an HFD or a normal diet for 12 wk. The results of the semiquantitative RT-PCR analyses indicated that the HFD upregulated the expression of GalR1, GalR2, GalR3, resistance to audiogenic seizures, peroxisome proliferator-activated receptorgamma2, adipocyte protein 2, and protein kinase Cdelta and downregulated the expression of peroxisome proliferative activated receptor gamma coactivator 1alpha and uncoupling protein 1 in the adipose tissues. The immunoblot results showed that the protein levels of peroxisome proliferator-activated receptorgamma2 and adipocyte protein 2, and the phosphorylation of c-Raf and extracellular signal-regulated kinase 1/2 were increased, while the phosphorylation of cyclic adenosine monophosphate-responsive element-binding protein, which regulates peroxisome proliferative activated receptor gamma coactivator 1alpha and uncoupling protein 1, was decreased in the epididymal adipose tissues of the HFD-fed mice. These results suggest the possible association of the galanin-mediated signaling pathways in the manifestation of the HFD-induced activation of adipogenesis along with the suppression of thermogenesis in the adipose tissues of mice.