Hyperglycemia impairs glucagon‐like peptide‐1 receptor (GLP‐1R) signaling in multiple cell types and thereby potentially attenuates the therapeutic effects of GLP‐1R agonists. We hypothesized that the downregulation of GLP‐1R by hyperglycemia might reduce the renal‐protective effects of GLP‐1R agonists in diabetic nephropathy (DN). In this study, we examined the effects of high glucose on the expression of GLP‐1R and its signaling pathways in the HBZY‐1 rat mesangial cell line. We found that high glucose reduced GLP‐1R messenger RNA (mRNA) levels in HBZY‐1 cells and in the renal cortex in db/db mice comparing with control groups. In consistence, GLP‐1R agonist exendin‐4 induced CREB phosphorylation was attenuated by high glucose but not low glucose treatment, which is paralleled with abrogated anti‐inflammatory functions in HBZY‐1 cells linked with nuclear factor‐κB (NF‐κB) activation. In consistence, GLP‐1R inhibition aggravated the high glucose‐induced activation of NF‐κB and MCP‐1 protein levels in cultured HBZY‐1 cells while overexpression of GLP‐1R opposite effects. We further proved that metformin restored high glucose‐inhibited GLP‐1R mRNA expression and decreased high glucose evoked inflammation in HBZY‐1 cells. On the basis of these findings, we conclude that high glucose lowers GLP‐1R expression and leads to inflammatory responses in mesangial cells, which can be reversed by metformin. These data support the rationale of combinative therapy of metformin with GLP‐1R agonists in DN.

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Background:Astragalus mongholicus polysaccharides (APS) have anti-inflammatory, antioxidant and immunomodulatory effects. Recent studies have demonstrated the epigenetic regulation of N6-methyladenosine (m6A) in the development of inflammation. However, the effect of APS on m6A modification is unclear. Here, for the first time, we investigate the mechanism of m6A modification in APS regulation of THP-1 macrophage inflammation.Methods: We treated LPS-induced THP-1 macrophages with APS at different concentrations and times, and detected IL-6 mRNA and protein levels by quantitative real-time PCR (qRT-PCR) and western blot, respectively. The m6A modification level was detected by m6A quantification kit. The proteins that regulate m6A modification were screened by western blot. Wilms’ tumor 1-associating protein (WTAP) was overexpressed in APS-treated THP-1 macrophages and the m6A modification level and IL-6 expressions were detected.Results: These findings confirmed that APS significantly abolished LPS-induced IL-6 levels in THP-1 macrophages. Meanwhile, APS reduced m6A modification levels and WTAP gene expression in THP-1 macrophages. Further overexpression of WTAP can significantly reverse APS-induced m6A modification level and IL-6 expression. Mechanistically, APS regulates IL-6 expression through WTAP-mediated p65 nuclear translocation.Conclusion: Overall, our study suggested that WTAP mediates the anti-inflammatory effect of APS by regulating m6A modification levels in THP-1 macrophages. This study reveals a new dimension of APS regulation of inflammation at the epigenetic level.

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Intestinal epithelial cells are critical for nutrient absorption and defending against pathogen infection. Deoxynivalenol (Don), the most common mycotoxin, contaminates cereals and food throughout the world, causes serious damage to mammal intestinal mucosa, and appears as intestinal epithelial cell apoptosis and proliferation inhibition. Our previous study has found that milk-derived exosome ameliorates Don-induced intestinal damage, but the mechanism is still not fully understood. In this study, we demonstrated that Don downregulated the expression of miR-221/222 in intestinal epithelial cells, and exosome treatment reversed the inhibitory effect of Don on miR-221/222. Through immunofluorescence and flow cytometry analysis, we identified that miR-221/222 ameliorates Don-induced apoptosis and proliferation inhibition in intestinal epithelial cells. Through bioinformatics analyses and RNA immunoprecipitation analysis, we identified Phosphatase and tensin homolog (PTEN) is the target of miR-221/222. Through the PTEN interfering experiment, we found Don-induced apoptosis and proliferation inhibition relied on PTEN. Finally, through adenovirus to overexpress miR-221/222 in mice intestinal epithelial cells specifically, our results showed that miR-221/222 ameliorated Don-induced apoptosis and proliferation inhibition in intestinal epithelial cells by targeting PTEN. This study not only expands our understanding of how miR-221/222 and the host gene PTEN regulate intestinal epithelial cells defending against Don-induced damage, but also provides a new way to protect the development of the intestine.