Ghrelin and the Gastrointestinal Tract

Ghrelin is an important hormone that is secreted by the ghrelin cells of the gastrointestinal tract.

Some of the roles of ghrelin in the gastrointestinal tract include:

• Ghrelin helps promote the proliferation of intestinal cells and also inhibits programmed cell death (apoptosis) during states of inflammation and oxidative stress.
• Ghrelin has also been shown to suppress the mechanisms that promote inflammation within the gut and to augment anti-inflammatory mechanisms. Ghrelin therefore provides a potential therapy for inflammatory gastrointestinal diseases such as colitis, ischemia, reperfusion, injury and sepsis. Therapeutic doses of ghrelin have been shown beneficial in animal models of these conditions.
• Ghrelin also helps in the regeneration of the mucosal lining of the gut and stomach after mucosal injury.
• Ghrelin also promotes the motility and movement of the gastrointestinal tract.
• Ghrelin has also been implicated in increasing the risk of gastrointestinal cancer and pancreatic cancer.
• Ghrelin is one of the main hormones to stimulate hunger. Ghrelin levels increase before meals and decrease after meals, a mechanism that has its roots in the hypothalamus. If the lateral hypothalamus is removed (as seen in animal studies), feeding becomes less frequent leading to severe weight loss and death. If the ventromedial hypothalamus is removed, feeding increases leading to weight gain and severe obesity.
• A hormone that counteracts the effects of ghrelin is leptin, which is produced by the fat or adipose tissue in the body. Leptin induces satiation or a feeling of fullness after a meal. When the leptin level is high, hunger is decreased. Since ghrelin increases hunger, several weight loss procedures aim to reduce the ghrelin level in order to increase satiation, even with a small meal.
• If ghrelin is injected into the peripheral bloodstream, it can stimulate the hypothalamic neurons and therefore stimulate food intake.