Sa1725 A Novel Rat Cachexia Model With Possible Ghrelin Resistance Made by Inoculation of a Gastric 85as2 Cancer Cell Line: A Traditional Japanese Medicine Rikkunshito Ameliorates Cachexia Symptoms by Potentiation of Ghrelin Receptor-Mediated Signaling

Abstract

Aims: Gastric cancer patients have high frequency of weight loss and anorexia, causing highest tendency of cachexia. Cancer cachexia (CC) is a multifactorial syndrome characterized by anorexia, low fat-free mass (FFM) and weight loss. We established a novel rat CC model by inoculation of a gastric cancer 85AS2 cell line. To improve gastrointestinal-related anorexia and weight loss, treatment with an orexygenic peptide ghrelin has been tested in clinical trials. However, plasma ghrelin levels in CC patients are relatively high possibly due to compensatory mechanisms. We evaluated the effects of ghrelin or a traditional Japanese medicine rikkunshito (RKT), effective for the treatment of gastrointestinal disorders, on the CC symptoms. We postulate that RKT has other mechanisms in addition to elevate ghrelin concentrations (Takeda et al., Gastroenterology (2008)). Accordingly we further investigated the effects of RKT on the ghrelin-mediated cellular signaling. Methods: To establish CC models, 85As2 cell lines derived from gastric MKN-45 cancer cells was inoculated subcutaneously into nude rats. We evaluated the effects of single intraperitoneal ghrelin or oral RKT administration for 7 days after the onset of CC rats. Further, the effects of RKT on ghrelin receptor activity was investigated with cells stably expressing ghrelin receptors; ghrelininduced increases in intracellular Ca2+ concentrations ([Ca2+]i) was measured with Ca2+ imaging asssay. Ghrelin receptor binding assay was also performed with radiolabelled ghrelin in the ghrelin receptor-expressing cells. Results: 85As2-inoculated rats showed significant weight loss, anorexia, low FFM (including loss of skeletal muscle) and fat mass were observed with 100% efficacy. Increased acute phase proteins and decreased albumin levels were observed in the plasma of all CC rats. Ghrelin administration significantly increased food intake in non-tumor-bearing rats but not in 85As2-induced CC rats; higher plasma ghrelin levels were detected in all CC rats. Although ghrelin failed to improve the CC symptoms, RKT significantly ameliorated anorexia, weight loss and decreased FFM. In ghrelin receptorexpressed cells, RKT enhanced ghrelin-induced [Ca2+]i in a concentration-dependent manner. We screened 43 compounds contained in RKT, and 2 (atractylodin and atractylodinol) showed marked increases in ghrelin receptor binding capacity. We finally found atractylodin potentiated the ghrelin-induced increase in [Ca2+]i as well as RKT. Conclusions: We established the novel CC model by using 85As2 cells and this model showed ghrelin resistance. The ameliorative effects of CC symptoms by RKT may be due to enhanced ghrelin receptor activity. RKT as well as atractylodin may contribute to the development of novel therapeutics for CC patients even ghrelin concentrations in plasma were higher.