INS and Impaired glucose tolerance: It was reported that ghrelin could inhibit glucose-stimulated insulin secretion in a dose-dependent manner in vitro [27]; intravenous ghrelin injection decreased plasma insulin and increased plasma glucose levels, likely by inhibition of insulin secretion [27]; ablation of ghrelin, GHSR, or GOAT enhanced insulin release and attenuated impaired glucose tolerance in high fat diet-induced and leptin-deficient obese mice models [28].