Ghrelin

What is that

Ghrelin is a hormone discovered in 1999 by a group of Japanese researchers. We are talking about a protein, a 28 amino acid acylated peptide produced mainly by the stomach.

Ghrelin increases the search and the intake of food (oressizing properties) and decreases the consumption of energy (reducing physical activity).

High levels of ghrelin are therefore related to an increase in body weight, especially as regards fat mass. All this despite its ability to stimulate the release of GH through the activation of the GH-secretagogue receptor (GH-segretagogue receptor type 1 = GHS-R) has long been known.

Influence of Food

Considering the biological or drying role of ghrelin, it is obvious that plasma levels of this hormone are normally maximum in fasting, while they reach minimum values ​​after food intake and hyperalimentation. In one study, plasma levels of ghrelin were shown to be significantly higher than that of ghrelin. norm in a group of bulimic girls; this finding could explain, at least in part, the hyperphagia crises to which sufferers of this eating disorder are subject. The concentrations of ghrelin in the blood of obese people appear lower than those of normal weight individuals.

Gastric ghrelin production covers about 50-70% of circulating levels, but this percentage is subject to compensatory productions by the pancreas, intestine, kidney, lung and hypothalamus.

The suppression of ghrelin release does not appear to be related to the simple distension of the gastric walls, but rather to the arrival of specific nutrients in the stomach. Sleep restriction is associated with a significant reduction in leptin (the satiety hormone produced by adipose tissue) and with an increase in ghrelin (appetite hormone).

Therapeutic Applications

For what has been said, blocking or neutralizing the action of ghrelin would seem a reasonable approach to deal with chronic obesity states (in this sense a possible anti-obesity vaccine was thought of); the administration of a synthetic analogue of graelin would instead be useful for stimulating the "appetite in the presence of eating disorders such as anorexia.

However, remember that ghrelin is only one of the many substances involved in the intertwined network of chemical and nervous mediators, which presides over the control of appetite. Among these substances we remember:

• leptin, insulin, Peptide YY (PYY), CCK (Cholecystokinin), CART (cocaine -anphetamine-regulated-transcript), Urocortina, Pro-opiomelacortina (POMC), a-MSH (Melanocyte Stimulating Hormone) (decrease appetite, anorectic ).
• endocannabinoids (β-Endorphins, Dinorphins, Enkephalins), NPY, MCH, ghrelin (increase appetite, orexigens).