GHRL and obesity due to melanocortin 4 receptor deficiency: Several studies have shown that GHSR antagonists improve glucose tolerance associated with obesity by enhancing insulin secretion [261,287], and it was more recently demonstrated that ghrelin inhibition with the GHSR antagonist GHRP-6 could reverse diabetic symptoms also in a genetic mouse model of maturity-onset diabetes of the young, type 3 (MODY3) caused by mutations of the HNF1-alpha homeobox gene [288].