These findings demonstrate that insulin acting via ghrelin cell–expressed IRs mediates obesity-associated declines in plasma ghrelin, while also limiting ghrelin secretion in standard chow–fed mice, albeit to a lesser degree (presumably, due to lower insulin levels in standard chow–fed versus high-fat diet–fed mice) (58). The gene discussed is GHRL; the disease is obesity due to melanocortin 4 receptor deficiency.