Ipamorelin. "Ipamorelin" by Ed (Edgar181) - Own work. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Ipamorelin.

Ipamorelin is a synthetic peptide that binds selectively to the growth hormone secretagogue receptor (GHS-R). It contains the artificial amino acids 2-aminoisobutyric acid (i.e. 2-methylalanine or Aib) and 2-naphthylalanine (2-Nal)¹. These differentiate it from the peptide growth hormone releasing protein-1 (GHRP-1), on which it was based¹. It has been found to have an efficacy and potency in releasing growth hormone comparable to that of GHRP-6 in in vitro and animal trials¹. Ipamorelin was found to have lower potency, but higher efficacy, that GHRP-2 in a swine pharmacokinetic study¹. Unlike the peptides GHRP-2 and -6, ipamorelin appears not to be associated with the release of adrenocorticotropic hormone (ACTH) or cortisol¹.

Appetite and the Gastrointestinal System

Ipamorelin is known as a ghrelin mimetic. Like this natural molecule, it increases appetite and gut motility². A study incorporating a rat model of postoperative decreases in these found that repeated 0.01-1mg/kg doses of ipamorelin significantly increased food intake, fecal output and body weight in the first 48 hours after an experimental surgery².

Ipamorelin and Diabetes

Ghrelin has been found to elicit significant increases in the pancreatic insulin production of both normal and diabetic rats³. Therefore, ipamorelin may have similar effects. A study induced diabetes (via strepozocin administration) in rats. Pancreatic tissue samples were then taken from diabetic and control rats and incubated with a range of ipamorelin doses. This resulted in a moderately significant increase in the insulin secretion from the preparations taken from both groups of rats⁴. Ipamorelin-associated insulin release was successfully inhibited by drugs that block alpha- and beta-adrenergic receptors and calcium channels in both 'normal' and 'diabetic' samples⁴. This implies the mechanism by which ipamorelin stimulates the release of insulin⁴. Interestingly, alpha-adrenergic and calcium channel blockers fail to inhibit insulin release stimulated by ghrelin in diabetic rats³. Ipamorelin-mediated insulin release was also significantly blocked by atropine, an acetylcholine receptor antagonist⁴.

Ipamorelin and Interactions 

Growth hormone has been found to counteract the negative effects of repeated steroid treatments on nitrogen balance in the body⁵. These effects may lead to increased risks of liver damage. A rat study found that ipamorelin significantly reduced prednisolone-mediated urea synthesis, although to a lesser extent than growth hormone⁵.

References:

1. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.

2. Venkova K, Mann W, Nelson R, Greenwood-Van Meerveld B. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. J Pharmacol Exp Ther. 2009;329(3):1110-1116.

3. Adeghate E, Ponery AS. Ghrelin stimulates insulin secretion from the pancreas of normal and diabetic rats. J Neuroendocrinol. 2002;14(7):555-560.

4. Adeghate E, Ponery AS. Mechanism of ipamorelin-evoked insulin release from the pancreas of normal and diabetic rats. Neuro Endocrinol Lett. 2004;25(6):403-406.

5. Aagaard NK, Grofte T, Greisen J, et al. Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats. Growth Horm IGF Res. 2009;19(5):426-431.