Ghrelin Relieves Cancer Bone Pain by Triggering Hypothalamic NPY Production Through AMPK-mTOR | Research

The takeaway

Ghrelin administration alleviated cancer-induced bone pain in rats by activating the AMPK-mTOR pathway in the hypothalamus to increase NPY production, which exerted pain relief through Y1 and Y2 receptors.

Ghrelin → NPY pain relief
A novel non-opioid pathway where ghrelin stimulates hypothalamic NPY production through AMPK-mTOR to alleviate cancer bone pain

What the researchers found

Ghrelin activated the hypothalamic AMPK-mTOR pathway to induce NPY production, alleviating cancer-induced bone pain in rats. NPY's antinociceptive effect was mediated through Y1 and Y2 receptors and reversed by GHS-R1α antagonism.

Why it matters

Cancer bone pain is often inadequately controlled with existing analgesics. Discovering that ghrelin and NPY — naturally occurring peptides — can modulate this specific type of pain through a defined brain pathway opens entirely new therapeutic approaches.

The numbers in context

CIBP mouse model with exogenous NPY administration and NPY receptor antagonist testing. AMPK-mTOR pathway confirmed as mediator.

How the study worked

Cancer-induced bone pain model established in rats. Intracerebroventricular administration of NPY, NPY receptor antagonists (Y1R, Y2R), and ghrelin. Measured body weight, food intake, behavioral pain indicators, and hypothalamic ghrelin, NPY, and AMPK-mTOR pathway markers.

Who was studied

Cancer-induced bone pain model mice

What this study cannot tell us

Animal study using an intracerebroventricular injection route, which isn't practical for clinical use. The short-term nature of NPY's pain relief may limit standalone therapeutic utility. Translation from rat brain to human brain pain processing is uncertain.

How to read the evidence

Preliminary evidence from a single animal study with intracerebroventricular peptide administration. The mechanistic pathway is well-characterized but has no human clinical data.

When this study was published

Published in 2024; represents emerging research on peptide-mediated cancer pain management.

The bigger picture

Cancer pain management remains a major unmet need, with opioids carrying addiction risks and limited efficacy for bone pain. Peptide-based approaches targeting the brain's own pain regulation systems could provide alternatives or complementary therapies with potentially fewer side effects than opioids.

Questions still open

Could systemic ghrelin administration (rather than brain injection) provide enough hypothalamic NPY stimulation to relieve cancer bone pain?
Would ghrelin agonists already in clinical development for other indications show pain-relieving effects in cancer patients?
How does this ghrelin-NPY pain pathway interact with opioid-based pain management?

Common questions

What is cancer-induced bone pain and why is it so hard to treat?

When cancer spreads to bones, it causes severe, persistent pain that is often poorly controlled by standard painkillers. Bone metastasis pain involves complex mechanisms including nerve damage, inflammation, and bone destruction, making it one of the most challenging types of cancer pain to manage.

Could ghrelin be used as a pain medication?

Not yet — this study used direct brain injection, which isn't practical for patients. However, ghrelin and ghrelin-like drugs are already being studied for other conditions (appetite, muscle wasting). If the pain-relieving effects can be achieved with systemic administration, it could open a new approach to cancer pain management.

Read the original research

Ghrelin Induces the Production of Hypothalamic NPY Through the AMPK-mTOR Pathway to Alleviate Cancer-induced Bone Pain.

In vivo (Athens, Greece), 38(3), 1133-1142

View on PubMed ↗Publisher’s paper ↗

Citation

Xu, Longjie; Hou, Lili; Cao, Chun; Li, Xiaohua. (2024). Ghrelin Induces the Production of Hypothalamic NPY Through the AMPK-mTOR Pathway to Alleviate Cancer-induced Bone Pain.. In vivo (Athens, Greece), 38(3), 1133-1142. https://doi.org/10.21873/invivo.13548