Sox9 transcriptionally regulates Wnt signaling in intestinal epithelial stem cells in hypomethylated crypts in the diabetic state.

BACKGROUND: Distinctive structures called crypts harbor intestinal epithelial stem cells (IESCs) which generate progenitor and terminally differentiated cells in the intestinal epithelium. Mammalian IESCs and their daughter cells require the participation of DNA methylation and the transcription factor Sox9 for proliferation and differentiation. However, the association between Sox9 and DNA methylation in this process remains elusive. METHODS: The DNA methylation of small intestinal epithelial crypts in db/db mice was detected via combining methylated DNA immunoprecipitation with microarray hybridization. DNA methylation of Sox9 promoter in crypts and IESCs was validated using bisulfite sequence analysis. The target sequence of the transcription factor Sox9 in IESCs was investigated via chromatin immunoprecipitation (ChIP) combined with deep sequencing (ChIP-seq). RESULTS: Increased Sox9 expression is accompanied by the loss of methylation in its promoter in IESCs. Sox9 targets the enhancers of the Wnt signaling pathway-related genes. Sox9 predominantly acts as a transcriptional activator at proximal enhancers of Wnt4, Tab2, Sox4, and Fzd8, but also functions as a potential transcriptional inhibitor at a distant enhancer of Cdk1. Lack of Sox9 transcriptional activation in specific repressors of the Wnt signaling pathway leads to the loss of intrinsic inhibitory action and ultimately produces overactivation of this pathway in db/db mice. CONCLUSIONS: Our study sheds light on the connections among DNA methylation, transcription factor modulation, and Wnt signaling in IESCs in the diabetic state. Hypomethylation in the Sox9 promoter is correlated to increased Sox9 expression in db/db IESCs. Although there is increased expression of Sox9 in db/db IESCs, the loss of Sox9 transcriptional activation in specific repressors of the Wnt signaling pathway might result in abnormalities in this pathway.

Metformin depresses overactivated Notch1/Hes1 signaling in colorectal cancer patients with type 2 diabetes mellitus.

The function of metformin in colorectal cancer (CRC) patients with diabetes mellitus (DM) remains a controversial topic because studies are increasingly focusing on epidemiologic features. We examined Notch1/Hes1 signaling in CRC with DM (DM-CRC) and investigated alterations in signaling caused by metformin treatment. For this purpose, information on pathological characteristics was collected from each patient. The proliferation of epithelium labeled with proliferating cell nuclear antigen and the differentiation of goblet cells were investigated using immunohistochemistry and periodic acid-Schiff staining, respectively. The factors involved in Notch1/Hes1 signaling were detected using qRT-PCR and western blot. In our study, we found that lymphatic metastasis, pTNM staging, and the carcinoembryonic antigen level were significantly different between groups. The depth of crypts and the rate of proliferating cell nuclear antigen-positive cells were distinctly higher in DM-CRC and patients who were managed with insulin. Moreover, the goblet cell differentiation rate was decreased in DM-CRC. The expression of Dll1, Notch1, Math1, and RBP-Jκ was increased in DM-CRC, whereas the expression of Dll4 and Hes1 was decreased in this group in normal tissue. In CRC tissue, the expression of Dll1 and Notch1 was clearly higher than that in DM-CRC. Furthermore, the trend in these changes was aggravated with insulin management and alleviated with metformin treatment. In conclusion, the abnormal cell proliferation and differentiation observed in DM-CRC are correlated with overactivated Notch1/Hes1 signaling, which is potentially relieved by metformin treatment.

Overexpression of miR-429 impairs intestinal barrier function in diabetic mice by down-regulating occludin expression.

Diabetes mellitus (DM) is a group of metabolic diseases characterised by insulin deficiency/resistance and hyperglycaemia. We previously reported the presence of an impaired tight junction and decreased expression of occludin (Ocln) and zonula occludens-1 (ZO-1) in the intestinal epithelial cells (IECs) of type 1 DM mice, but the exact mechanism remains unclear. In this study, we investigated the role of microRNAs (miRNAs) in impairing the tight junction in IECs of DM mice. Using an integrated comparative miRNA microarray, miR-429 was found to be up-regulated in IECs of type 1 DM mice. Then, miR-429 was confirmed to directly target the 3'-UTR of Ocln, although it did not target ZO-1. Moreover, miR-429 down-regulated the Ocln expression in IEC-6 cells in vitro. Finally, exogenous agomiRNA-429 was shown to down-regulate Ocln and induce intestinal barrier dysfunction in normal mice, while exogenous antagomiRNA-429 up-regulated Ocln in vivo and improved intestinal barrier function in DM mice. In conclusion, increased miR-429 could down-regulate the expression of Ocln by targeting the Ocln 3'-UTR, which impaired intestinal barrier function in DM mice.

MEK/ERK pathway activation by insulin receptor isoform alteration is associated with the abnormal proliferation and differentiation of intestinal epithelial cells in diabetic mice.

In previous studies, we have reported the abnormal proliferation and differentiation of intestinal epithelial cells (IECs) in diabetes mellitus (DM) mice. The insulin receptor (IR) and its downstream mitogen-activated protein kinase kinase (MAPKK also known as MEK)/extracellular-regulated protein kinase (ERK) pathway is a classic pathway associated with cell proliferation and differentiation. The purpose of the present study is to investigate the role of the MEK/ERK pathway in abnormal proliferation and differentiation of IECs in DM mice. DM mouse models were induced by intraperitoneal injection of streptozotocin. The expression levels of the IR and its isoforms in IECs of DM mice and in IEC-6 cells were investigated. To ensure that the downstream pathways were monitored, QPCR and Western blotting were performed to detect the expression levels of MEK1/2, ERK1/2, PI3K, and Akt. Moreover, siRNA for IR-A and U0126, a specific inhibitor of MEK, were used to further investigate the relationship between the IR/MEK/ERK pathway and abnormal proliferation and differentiation of IECs in DM mice. In DM mice, excessive proliferation, disturbed differentiation, and a high ratio of IR-A/IR-B were detected in IECs. The expression levels of MEK1, MEK2, and ERK1/2 and their phosphorylated proteins in DM mice were significantly higher than those in the control group (P < 0.05), which could be offset by using siRNA for IR-A. The abnormal proliferation and differentiation of IECs in DM mice were normalized after the in vivo administration of U0126. The abnormal proliferation and differentiation of IECs in DM mice are associated with high IR-A/IR-B ratio and increased IR/MEK/ERK pathway activity.

Knockdown of linc-POU3F3 suppresses the proliferation, apoptosis, and migration resistance of colorectal cancer.

Long intergenic noncoding RNAs (lincRNAs) play important roles in regulating the biological functions and underlying molecular mechanisms of colorectal cancer (CRC). Here, we investigated the association of linc-POU3F3 and prognosis in CRC. We demonstrated that linc-POU3F3 was overexpressed in CRC tissues and positively correlated with tumor grade and N stage. Inhibition of linc-POU3F3 resulted in inhibition of cell proliferation and G1 cell cycle arrest, which was mediated by cyclin D1, CDK4, p18, Rb, and phosphorylated Rb. Inhibition of linc-POU3F3 induced apoptosis, and suppressed migration and invasion in LOVO and SW480 cell lines. This inhibition also increased the expressions of epithelial markers and decreased the expressions of mesenchymal markers, thus inhibiting the cancer epithelial-mesenchymal transition. The decreased migration and invasion following linc-POU3F3 knockdown were mediated by an increased BMP signal. Furthermore, autophagy was enhanced by linc-POU3F3 knockdown, suggesting the involvement of autophagy in the induced apoptosis. Collectively, linc-POU3F3 might be crucial in pro-proliferation, anti-apoptosis, and metastasis in LOVO and SW480 cells by regulating the cell cycle, intrinsic apoptosis, BMP signaling and autophagy. Thus, linc-POU3F3 is a potential therapeutic target and novel molecular biomarker for CRC.

DNA Methylation Dynamics During Differentiation, Proliferation, and Tumorigenesis in the Intestinal Tract.

DNA methylation, an epigenetic control mechanism in mammals, is widely present in the intestinal tract during the differentiation and proliferation of epithelial cells. Cells in stem cell pools or villi have different patterns of DNA methylation. The process of DNA methylation is dynamic and occurs at many relevant regulatory elements during the rapid transition of stem cells into fully mature, differentiated epithelial cells. Changes in DNA methylation patterns most often take place in enhancer and promoter regions and are associated with transcription factor binding. During differentiation, enhancer regions associated with genes important to enterocyte differentiation are demethylated, activating gene expression. Abnormal patterns of DNA methylation during differentiation and proliferation in the intestinal tract can lead to the formation of aberrant crypt foci and destroy the barrier and absorptive functions of the intestinal epithelium. Accumulation of these epigenetic changes may even result in tumorigenesis. In the current review, we discuss recent findings on the association between DNA methylation and cell differentiation and proliferation in the small intestine and highlight the possible links between dysregulation of this process and tumorigenesis.

Relative risk factors associated with the development of fundic gland polyps.

OBJECTIVES: The prevalence of fundic gland polyps (FGPs) is increasing. Some researchers consider this increase to be associated strongly with the long-term use of proton-pump inhibitors (PPIs); however, not all researchers share this belief. There are minimal data on the development of FGPs in China. Therefore, we aimed to investigate the prevalence of FGPs and risk factors associated with the development of this disease. MATERIALS AND METHODS: We studied 10 904 consecutive patients who underwent gastroduodenal endoscopies at our digestive endoscopy center between February 2011 and January 2013. Information on sex, age, Helicobacter pylori infection, PPIs intake, and the pathological results of the polyps were collected in the FGPs group and in the control group. The use of PPIs, sex, and H. pylori infection were statistically evaluated as dichotomous variables using a χ-test; age was evaluated as a continuous variable using a t-test. Finally, these factors were evaluated using a multiple logistic regression analysis. RESULTS: Gastric polyps were found in 759 (7.0%) patients, and 213 (2.0%) of these patients had FGPs. FGPs accounted for 28.1% of the gastric polyps. In the FGPs group, the percentage of H. pylori infection was 66.8% and the percentage of PPIs intake for at least 12 months was 23.1%. In the control group, the percentage of H. pylori infection was 77.4% and the percentage of PPIs intake for at least 12 months was 2.3%. The difference in the long-term use of PPIs was statistically significant between these two groups [χ=33.98, P<0.05, odds ratio (OR)=12.83, 95% confidence interval (CI): 4.47-36.80]. The results of the logistic regression were as follows: long-term use of PPIs (P<0.01, OR=14.11, 95% CI: 4.15-47.93); age (P<0.01, OR=1.69, 95% CI: 1.31-2.18). The P-values for sex and H. pylori infection were higher than 0.05. CONCLUSION: Age and the long-term use of PPIs were risk factors for the presence of FGPs; the long-term use of PPIs was a particularly strong risk factor.