Background: Endoplasmic reticulum(ER) stress is associated with multiple pathological processes of intestinal diseases. Despite a critical role of mechanistic target of rapamycin complex 1(m TORC1) in regulating cellular stress response, the crosstalk between m TORC1 and ER stress signaling and its contribution to the intestinal barrier function is unknown.Results: In the present study, we showed that intestinal epithelial cells(IEC-6) incubated with tunicamycin led to caspase-3-dependent apoptotic cell death. The induction of cell death was accompanied by activation of unfolded protein response as evidenced by increased protein levels for Bi P, p-IRE1α, p-e IF2α, p-JNK, and CHOP. Further study demonstrated that tunicamycin-induced cell death was enhanced by rapamycin, a specific inhibitor of m TORC1.Consistently, tunicamycin decreased transepithelial electrical resistance(TEER) and increased permeability of the cells. These effects of tunicamycin were exacerbated by m TORC1 inhibitor.Conclusions: Taken together, the data presented here identified a previously unknown crosstalk between an unfold protein response and m TORC1 signaling in the intestinal epithelium. This feed-back loop regulation on ER stress signaling by m TORC1 is critical for cell survival and intestinal permeability in epithelial cells.
Endoplasmic reticulum(ER)stress has been associated with the dysfunction of intestinal barrier in humans and animals.We have previously shown that oral administration of glycine to suckling-piglets improves ER stress-related intestinal mucosal barrier impairment and jejunal epithelial apoptosis.However,the underlying mechanism remains unknown.In this study,the protective effect and the mechanism of glycine on apoptosis and dysfunction in intestinal barrier induced by brefeldin A(BFA),an ER stress inducer,was explored in porcine intestinal epithelial cells(IPEC-1).The results showed that BFA treatment led to enhanced apoptosis and upregulation of proteins involved in ER stress signaling,including inositol-requiring enzyme 1a(IRE1a),activating transcription factor 6a(ATF6a),c-Jun N-terminal kinase(JNK),and C/EBP-homologous protein(CHOP).In addition,BFA induced a dysfunction in intestinal epithelial barrier,as evidenced by the increased paracellular permeability,decreased transepithelial electrical resistance(TEER),and reduced abundance of tight junction proteins(occludin,claudin-1,zonula occludens[ZO]-1,and ZO-2).These alterations triggered by BFA were significantly abolished by glycine treatment(P<0.05),indicating a protective effect of glycine on barrier function impaired by ER stress.Importantly,we found that the regulatory effect of glycine on intestinal permeability,proteins implicated in ER stress and apoptosis,as well as the morphological alterations of the ER were reversed by rapamycin.In summary,our results indicated that glycine alleviates ER stress-induced apoptosis and intestinal barrier dysfunction in IPEC-1 cells in a mammalian target of rapamycin complex 1(mTORC1)-dependent manner.The data provides in vitro evidence and a mechanism for the protective effect of glycine against the disruption of intestinal barrier integrity induced by ER stress.
Background: Excessive white fat accumulation in humans and other animals is associated with the development of multiple metabolic diseases. It is unknown whether dietary L-arginine supplementation reduces lipid deposition in high fat diet-fed Nile tilapia(Oreochromis niloticus).Results: In the present study, we found that dietary supplementation with 1% or 2% arginine decreased the deposition and concentration of fats in the liver;the concentrations of triglycerides, low-density lipoprotein, total cholesterol, and high-density lipoprotein in the serum;and the diameter of adipocytes in intraperitoneal adipose tissue. Compared with the un-supplementation control group, the hepatic activities of alanine aminotransferase,aspartate aminotransferase, and lactate dehydrogenase, and hepatic concentration of malondialdehyde were reduced but these for catalase and superoxide dismutase were enhanced by dietary supplementation with 2% arginine. Arginine supplementation reduced the total amounts of monounsaturated fatty acids, while increasing the total amounts of n-3 and n-6 polyunsaturated fatty acids in the liver. These effects of arginine were associated with reductions in mRNA levels for genes related to lipogenesis(sterol regulatory element-binding protein-1, acetyl-CoA carboxylase α, stearoyl-CoA desaturase, and fatty acid synthase) but increases in mRNA levels for genes involved in fatty acid β-oxidation(carnitine palmitoyltransferase 1α and peroxisome proliferator-activated receptor α). In addition, hepatic mRNA levels for Δ4 fatty acyl desaturase 2 and elongase 5 of very long-chain fatty acids were enhanced by arginine supplementation.Conclusion: These results revealed that dietary L-arginine supplementation to tilapia reduced high fat diet-induced fat deposition and fatty acid composition in the liver by regulating the expression of genes for lipid metabolism.
This study was conducted to evaluate the effect of flavor on reproductive performance and fecal microbiota of sows during late gestation and lactation.A total of 20 healthy Yorkshire sows were fed a corn-soybean basal diet unsupplemented or supplemented with 0.1%flavor compound from d 90 of gestation to 25 d post-farrowing,and then the piglets were weaned.The reproductive performance and the fecal microbiota of sows were analyzed.Compared with the controls,flavor supplementation in maternal diets increased(P<0.05)weaning litter weight,litter weight gain,weaning body weight,and average daily gain of piglets.There was a trend of increase in the average daily feed intake of sows(P=0.09)by maternal dietary flavor addition.The backfat thickness and litter size were not affected by flavor supplementation(P>0.05).The 16S rRNA analysis showed that flavor supplementation signifi-cantly increased the abundance of Phascolarctobacterium(P<0.05),but significantly decreased genera Terrisporobacter,Alloprevotella,Clostridium_sensu_stricto_1,and Escherichia-shigella(P<0.05).Spearman correlation analysis showed that Phascolarctobacterum was positively correlated with the average daily feed intake of sows(P<0.05),the litter weight gain and average daily gain of piglets(P<0.05).In contrast,Clostridium_sensu_stricto_1 and unclassified_f__Lachnospiraceae were negatively correlated with the litter weight gain and average daily gain of piglets(P<0.05).Taken together,dietary flavor sup-plementation improved the reproductive performance of the sows,which was associated with enhanced beneficial microbiota and decreased potentially pathogenic bacteria in the sows.
Renjie WangNing LiuYuchen YangYan LeiJirong LyuZhaolai DaiIn Ho KimJu LiZhenlong WuDefa Li
In this study,we sought to investigate the expression of the transcription factor E2F1 in chicken pulmonary arterial smooth muscle cells upon hypoxia exposure,as well as the role that E2F1 played in the regulation of cell proliferation.Isolated chicken pulmonary arterial smooth muscle cells were subjected to hypoxia or normoxia for indicated time points.Cell viability,DNA synthesis,cell cycle profile,and expression of E2F1 were analyzed.The results showed that hypoxia promoted cell proliferation and DNA synthesis which was accompanied by an increased S phase entry and upregulation of E2F1 at mRNA and protein levels.Using siRNA technology,we demonstrated that gene inactivation of endogenous E2F1 abolished hypoxia-induced cell proliferation,DNA synthesis,and S phase entry compared with negative siRNA transfected cells.These results suggest that hypoxia-induced proliferation is mediated by inducing E2F1 in chicken pulmonary arterial smooth muscle cells.
Protein is quantitatively the most expensive nutrient in swine diets. Hence it is imperative to understand the physiological roles played by amino acids in growth, development, lactation, reproduction, and health of pigs to improve their protein nutrition and reduce the costs of pork production. Due to incomplete knowledge of amino acid biochemistry and nutrition, it was traditionally assumed that neonatal, post-weaning, growing-finishing, and gestating pigs could synthesize sufficient amounts of all "nutritionally nonessential amino acids" (NEAA) to support maximum production performance. Therefore, over the past 50 years, much emphasis has been placed on dietary requirements of nutritionally essential amino acids as building blocks for tissue proteins. However, a large body of literature shows that NEAA, particularly glutamine, glutamate, arginine and proline regulate physiological functions via cell signaling pathways, such as mammalian target of rapamycin, AMP-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and NEAA-derived gaseous molecules (e.g., nitric oxide, carbon monoxide, and hydrogen sulfide). Available evidence shows that under current feeding programs, only 70% and 55% of dietary amino acids are deposited as tissue proteins in 14-day-old sow-reared piglets and in 30-day-old pigs weaned at 21 days of age, respectively. Therefore, there is an urgent need to understand the roles and dietary requirements of NEAA in swine nutrition. This review highlights the basic biochemistry and physiology of absorption and utilization of amino acids in young pigs to enhance the efficacy of utilization of dietary protein and to minimize excretion of nitrogenous wastes from the body.
