INS and obesity due to melanocortin 4 receptor deficiency: Because current studies indicate the occurrence of metabolic disturbances in the brain in depression, type II diabetes, and obesity, the aim of the present study was to determine whether there are changes in selected markers characterizing glucose metabolism and whether they are accompanied by disturbances in insulin, GLP-1, and their receptors levels in an animal model of depression and in rats fed with a high-fat diet.