Betaine Ameliorates Hyperosmotic Stress-Induced Apoptosis and Autophagy of Porcine Intestinal Epithelium In Vivo and Vitro.

Abstract

Background: Hyperosmotic stress resulting from lumen contents is a big challenge to the normal function of the intestinal epithelium. Betaine is a potent organic osmolyte, but it is mostly studied in kidney. The purpose of this study was to gain insight into the osmoprotectant role of betaine in intestinal epithelium of piglets and intestinal porcine epithelial cells (IPEC-J2 cells) under hyperosmotic condition.Results: The result showed that the osmolarity of intestinal chyme was much higher than that of plasma (P < 0.05), indicating a natural hyperosmotic environment of intestinal lumen and subsequently leading to hyperosmotic stress to intestinal epithelium. Meanwhile, hyperosmolarity corresponding to intestinal environment was simulated by 150 mmol/L NaCl in vitro and caused a significant decrease of cell viability (P < 0.05). It was found that betaine could remarkably decrease hyperosmolarity-induced reactive oxygen species (ROS) of intestinal epithelium in vivo and vitro (P < 0.05) with the significant restoration of cell shrinkage (P < 0.05). Furthermore, since hyperosmolarity caused mitochondrial-related apoptosis with the remarkable increase of cleaved Caspase3, cleaved PARP-1, cytoplasm cytochrome c as well as obvious decrease of Bcl-2 in protein level (P < 0.05), betaine prevented mitochondria from membrane collapse and alleviated apoptosis (P < 0.05) in vivo and vitro. Meanwhile, it was also confirmed that betaine reduced hyperosmotic stress-induced apoptotic incidence in IPEC-J2 cells via fluorescence microscope and flow cytometry (P < 0.05). In addition, betaine supplementation significantly suppressed hyperosmotic stress-induced elevated expression of LC3 II and reduced expression of p62 (P < 0.05). indicating that betaine ameliorated autophagy of porcine intestinal epithelium caused by hyperosmolarity in vivo and vitro. Autophagic flux determined by mRFP-GFP-LC3B system in IPEC-J2 cells was in agreement with the result of western blotting as well (P < 0.05). Conclusions: Betaine could alleviate hyperosmotic stress-induced cell shrinkage, ROS accumulation as well as ameliorate subsequently apoptosis and autophagy in small intestinal epithelium of piglets and IPEC-J2 cells.