1959-P: Upregulation of PYY, GLP-1, and NTS by Intermittent Hypoxia in Enteroendocrine Cells

The patients with sleep apnea syndrome (SAS) are exposed to intermittent hypoxia (IH) during sleep. Although accumulating evidence indicates a strong relationship between SAS and obesity, we previously demonstrated that IH up-regulates the mRNA levels of anorexigenic peptides POMC and CART via GATA transcription factors in human neuronal cells (Int. J. Biochem. Cell Biol. 95, 100, 2018). Appetite is regulated not only by the central nervous system but also by gastrointestinal peptides. Here, we investigated the effect of IH on the appetite-inhibiting gut hormone expression using in vitro IH system. Human and mouse enteroendocrine cells, Caco-2 and STC-1, were exposed to IH [64 cycles of 5 min hypoxia (1% O₂) and 10 min normoxia (21% O₂)] or normoxia for 24 hours. Real-time RT-PCR revealed that IH significantly increased the mRNA levels of PYY, GLP-1, and neurotensin (NTS) in both Caco-2 and STC-1. ELISA showed that the concentrations of PYY, GLP-1, and NTS in the culture medium were significantly increased by IH. To determine whether the IH-induced increases in PYY, GLP-1, and NTS in enteroendocrine cells were caused by transcriptional activation, reporter plasmids for PYY, GCG, which encodes a preprotein, part of which is cleaved into GLP-1, and NTS were transfected into Caco-2, and the luciferase activity was measured after the IH treatment. The promoter activities of PYY, GCG and NTS were not increased by IH. We then searched targeted miRNA and found that PYY, GLP-1 and NTS mRNAs have potential target sequences for miR-96, -527, and -2116. We measured the levels of the miRNAs and found that the levels of the miRNAs were not decreased by IH. Furthermore, the mRNA levels of PYY, GLP-1, and NTS were significantly up-regulated even in normoxia by trichostatin A and were significantly decreased even in IH by 5-azacytidine, suggesting that IH increases PYY, GLP-1, and NTS mRNAs via alterations in the chromatin structure in enteroendocrine cells. IH might have an anorexigenic influence on the enteric nervous system.