Indeed, ER, stress-induced pharmacologically by using tunicamycin, thapsigargin or brefeldin A was able to block leptin-induced hypothalamic STAT3 phosphorylation and to augment appetite and body weight gain in mice, whereas chemical chaperones, 4-phenyl butyric acid and tauroursodeoxycholic acid, which have the ability to reduce ER stress, acted as leptin-sensitising agents, thus providing the basis for potential novel treatments of obesity [85,86,87]. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.