Tu1834 Orexins Exert a PRO-Apoptotic Effect on Digestive Human Neuroendocrine Tumors (NET) in an Ex-Vivo Culture Model of Tissue Slices

Abstract

Background:We have recently demonstrated that the presentation of primary cilia on gastric endocrine cells is regulated by food intake. A cilia-deficient mousemodel resulted in increased gastrin mRNA and hypergastrinemia, suggesting the presence of cilia is tightly linked to gastrin production. It has been shown in different organs that cilia dysfunction results in loss of sensory signaling, and obesity is characteristic of two ciliopathies, Bardet-Biedl syndrome and Alstrom. Therefore we tested the hypothesis that antral cilia can discriminate between standard and high fat diets. Methods: We analyzed C57BL/6J mice (wild type) fed with standard (Control, Lab Diet 5L0D) or High Fat (Research Diets Inc., D12492) chow. Mice were starved overnight and then allowed free access to food for 0.5, 1, 1.5, 2, 4 h and overnight (16 h). The amount of food ingested and emptied was determined by weighing the stomachs at time of euthanasia. Gastric acidity was measured by titration of gastric content and gastrin levels by ELISA. Cilia were visualized by immunohistochemistry for acetylated-tubulin then the number of cilia per gland (cpg) was quantified by morphometric analysis. Results: In mice fed Control chow (n=8), the maximum amount of food ingested was achieved by 1 h, gastric contents decreased by 4 h, and gastric acidity peaked at 2 h. The number of antral cilia decreased 45% over 1.5 h and then recovered by 4 h (Fig. 1A). Maximum circulating gastrin levels (3.5 fold increase) occurred by 2 h (Fig.1B). The stomach content, gastric acidity, gastrin levels, and cilia numbers did not change after 4 h of food intake. When mice were fed High Fat chow (n=6), the maximum amount of food ingested was achieved by 1 h and did not decrease for the entire 16 h of the experiment. Gastric acidity increased with High Fat intake, but in contrast with Control chow, remained elevated. The number of antral cilia varied slightly by 2 h then decreased only after 4 h (Fig.1A). Plasma gastrin levels increased 2 fold with High Fat during the first hour (Fig. 1B). However, gastrin levels did not increase further and did not reach the same level than with Control chow. Gastrin levels inversely correlated with antral cilia numbers with both chow diets. The number of cilia in the corpus was not different between the two diets. Conclusion: A high fat diet sensed by cilia on antral endocrine cells regulates gastrin release and thus the gastric response to food intake including acid secretion.