Octanoic acid-rich diet alleviates breast cancer-induced bone pain via the acyl-ghrelin/NPY pathway.

BACKGROUND: Breast cancer is a common malignant tumor that has a high tendency to metastasis to the bone, leading to cancer-induced bone pain (CIBP). Ghrelin can not only stimulate appetite and regulate energy balance, but also alleviate CIBP by inducing NPY expression. Octanoic acid (OA), a type of medium chain fatty acids, provides an energy substrate and promotes acylation of ghrelin. However, it remains to be elucidated whether an OA-rich diet can alleviate CIBP by activating the acyl-ghrelin/NPY pathway. METHODS: First, thirty-six Sprague-Dawley rats were randomly divided into the sham, CIBP, CIBP + OA (20), CIBP + OA (40), CIBP + OA (60) and CIBP + OA (80) groups to investigate the effects of diets with different ratios of OA on CIBP and the acyl-ghrelin/NPY pathway. Next, a ghrelin O-acyltransferase (GOAT) inhibitor was exogenously administered to investigate whether an OA-rich diet alleviated CIBP through increasing the level of acyl-ghrelin and activating the acyl-ghrelin/NPY pathway. RESULTS: An OA-rich diet significantly alleviated nociceptive behaviors and increased the levels of acyl-ghrelin and NPY in a dose-dependent manner in cancer-bearing rats. With the exogenous administration of the GOAT inhibitor, the beneficial effects of an OA-rich diet on the acyl-ghrelin/NPY pathway and its pain-relieving effects were attenuated. CONCLUSIONS: An OA-rich diet could alleviate CIBP through increasing the level of acyl-ghrelin and activating the acylghrelin/ NPY pathway.