Ghrelin, the endogenous ligand for the growth hormone (GH) secretagogue (GHS) receptor, is secreted by the stomach and circulates in the blood at measurable concentrations. Ghrelin regulates GH release and plays a role in the regulation of food intake (FI) and energy balance.
In parallel with the data using exogenous administration of ghrelin of GHRP-2, there is data suggesting that circulating ghrelin could be implicated in meal-to-meal regulation. Ghrelin levels increase in anticipation of a meal and are suppressed by good ingestion.
We have seen that synthetic Growth Hormone-Releasing Peptite-2 (GHRP-2) increases food intake (FI) in lean healthy men. Here we are analyzing a study to discover if the same effect occurs in overweight subjects and how the dose effects the stimulatory effect.
A total of 19 subjects, 10 lean and 9 obese, received a randomized subcutaneous injection of GHRP-2 at high dose , low dose or a placebo. Blood for hormone assays was collected intravenously. Hunger and fullness were rated on visual analog scales before and after a fixed breakfast and again after a buffet lunch. Before lunch, subjects were instructed to eat as much as they wanted.
It was found that GHRP-2 infusion significantly increased FI in a dose-dependent manner.
However, lean and obese subjects did not differ in terms of hunger feelings, fullness, desire to eat, or appetite score at baseline before the infusion started.
Subjects in the high dose group reported more hunger and a greater appetite compared to both the low dose and placebo group. All subjects reported the same level of fullness after each meal.
The dual stimulatory effect of GHRP-2 on FI is dose dependent. Obese individuals retain their ability to respond to GHRP-2 both in terms of FI and human GH release.
The data gained confirms that subcutaneous infusion of GHRP-2 potently stimulates short-term FI in healthy human lean and obese subjects. This effect is dose dependent and of similar magnitude in obese women and lean men. However, additional studies are needed to investigate lean-obese differences as a function of age, gender, duration, severity, and stage of obesity.