GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
l-Ornithine stimulates growth hormone release in a manner dependent on the ghrelin system.
Ho. Yee Yin YY; Nakato. Junya J; Mizushige. Takafumi T; Kanamoto. Ryuhei R; Tanida. Mamoru M; Akiduki. Saori S; Ohinata. Kousaku K
Key Findings
- Intraduodenal l‑ornithine raises GH levels in rats.
- The GH boost is blocked by the ghrelin‑receptor antagonist [d‑Lys³]‑GHRP‑6, indicating a ghrelin‑mediated mechanism.
- l‑Ornithine increases ghrelin mRNA in the duodenum, and the effect is stopped by propranolol, a β‑adrenergic blocker.
Practical Outcomes
- For biohackers, the data suggest that oral l‑ornithine might have the potential to raise growth hormone via the ghrelin pathway, but the study used direct duodenal delivery in rats, so real‑world dosing and effectiveness are unclear. It highlights that combining l‑ornithine with strategies that support ghrelin release (e.g., fasting, certain amino acids) could be worth experimenting, while being aware that beta‑adrenergic activity may also play a role. Caution is advised until human studies confirm these effects.
Summary
In rats, giving l‑ornithine straight into the duodenum makes the body release more growth hormone, and it does this by triggering the ghrelin system. The effect disappears when a ghrelin‑receptor blocker (GHRP‑6) is used, showing that l‑ornithine works through ghrelin, not by binding the receptor itself. The study also links this pathway to the sympathetic nervous system via beta‑adrenergic signals.
Abstract
We found that intraduodenal administration of l-ornithine (l-Orn) stimulates growth hormone (GH) secretion in Wistar rats, and then investigated its mechanism. GH-releasing activity after intraduodenal administration of l-Orn was blocked by [d-Lys<sup>3</sup>]-GHRP-6, an antagonist of the ghrelin receptor; however, l-Orn (100 μM) has no affinity for the ghrelin receptor, suggesting that the GH-releasing activity of l-Orn is mediated via ghrelin release and activation of the ghrelin receptor. Intraduodenally administered l-Orn increased ghrelin mRNA expression in the duodenum but not in the stomach or hypothalamus. In addition, l-Orn-induced GH-releasing activity was inhibited by propranolol, an antagonist of β-adrenergic receptor, which is known to be coupled to ghrelin release. In conclusion, intraduodenally administered l-Orn stimulates GH secretion through the sympathetic nervous and ghrelin systems.
Study Information
pubmed
2017
2017-05-17T00:00:00.000Z
10.1039/c7fo00309a
7
30