The GH secretagogue KP-102 stimulated eating in fed rats but not in fasted or stressed rats, and somatostatin blocked this effect, revealing complex appetite regulation by GH peptides.
State-dependent effectKP-102 only stimulated eating in fed rats — fasting, stress, and brain somatostatin all eliminated its appetite effect
What the researchers found
KP-102 stimulated food intake in freely-fed but not fasted or stressed rats, and central somatostatin administration blocked this effect, demonstrating state-dependent appetite modulation by GH secretagogues.
Why it matters
Understanding that GH peptides only stimulate appetite under certain conditions helps predict their effects in different patient populations and reveals how the brain integrates hunger signals with metabolic status.
How the study worked
Animal study in rats. KP-102-induced food intake was measured under normal feeding, 24-hour fasting, and post-restraint stress conditions. Somatostatin was administered intracerebroventricularly to test its blocking effect.
What this study cannot tell us
Rat study with limited translational certainty to humans. Single stress model used. The mechanism by which fasting or stress blocks KP-102's appetite effect was not determined.
How to read the evidence
Preliminary animal evidence showing clear state-dependent effects, but mechanism not elucidated and human relevance uncertain.
When this study was published
Published in 1998. These findings were later understood in the context of ghrelin receptor signaling, as KP-102 acts on what was later identified as the ghrelin receptor.
The bigger picture
GH secretagogues' appetite effects are mediated through the same system as ghrelin (the hunger hormone, discovered later). Understanding how this system responds to different states helps explain why appetite regulation is so complex and context-dependent.
Questions still open
- Why does fasting eliminate KP-102's appetite-stimulating effect?
- Does stress-induced appetite suppression override GH secretagogue signaling in humans too?
- Is the somatostatin pathway a therapeutic target for appetite disorders?
Common questions
Why would a growth hormone peptide affect appetite?
Why didn't it work in fasting rats?
Read the original research
The growth hormone secretagogue KP-102-induced stimulation of food intake is modified by fasting, restraint stress, and somatostatin in rats.
Neuroscience letters, 255(1), 9-12
Citation
Shibasaki, T; Yamauchi, N; Takeuchi, K; Ishii, S; Sugihara, H; Wakabayashi, I. (1998). The growth hormone secretagogue KP-102-induced stimulation of food intake is modified by fasting, restraint stress, and somatostatin in rats.. Neuroscience letters, 255(1), 9-12.