ABSTRACT
PURPOSE: Duodenal-jejunal bypass (DJB) has a definite hypoglycemic effect; however, the intrinsic mechanisms remain unclear. The purpose of this study was to determine whether DJB may cause changes in the gut microbiota and metabolite of portal venous blood and to explore the effects of DJB on blood glucose metabolism. METHODS: T2DM was induced in rats with a high-fat diet and a low dose of streptozotocin, which were randomly divided into two groups: Sham operation and DJB. RESULTS: DJB significantly improved several diabetic parameters. 16S rRNA analyses showed that the compositions of the gut microbiota were significantly different between the two groups. The results of metabolomics showed that DJB could significantly regulate the metabolites, among which diaminopimelic acid and isovaleric acid had a significant down-regulation in the DJB group. Transcriptomic analysis showed that DJB can regulate the expression of hepatic genes related to abnormal glucose metabolism, such as Ltc4s, Alox15, Ggt1, Gpat3, and Cyp2c24. Correlation analyses showed that diaminopimelic acid was positively associated with Allobaculum, Serratia, and Turicibacter. There was a significant correlation between diaminopimelic acid and Gpat3, and its Spearman correlation coefficient was the highest among metabolite-DEG pairs (ρ=0.97). DISCUSSIONS: These results suggest an important cue of the relation between the diaminopimelic acid, Gpat3, and gut microbiome in the mechanism by which DJB can improve glucose metabolism.
Subject(s)
Diabetes Mellitus, Type 2 , Obesity, Morbid , Rats , Animals , Diaminopimelic Acid/metabolism , Multiomics , RNA, Ribosomal, 16S , Obesity, Morbid/surgery , Jejunum/surgery , Jejunum/metabolism , Duodenum/surgery , Blood Glucose/metabolism , Glucose/metabolismABSTRACT
The aim of the present study was to clarify the mechanism of how METTL3 regulated pancreatic ductal adenocarcinoma (PDAC) progression by m6A modification of its downstream target mRNA and signaling pathway. Immunoblotting and qRT-PCR assays was employed to determine the expression levels of METTL3. In situ fluorescence hybridization was conducted to localize the cellular distribution of METTL3 and DEAD-box helicase 23 (DDX23). CCK8, colony formation, EDU incorporation, TUNEL, wound healing and Transwell assays were carried out accordingly to study the viability, proliferation, apoptosis, and mobility of cells under different treatments in vitro. Xenograft and animal lung metastasis experiments were also conducted to study the functional role of METTL3 or DDX23 on tumor growth and lung metastasis in vivo. MeRIP-qPCR and bioinformatical analyses were used to obtain the potential direct targets of METTL3. It was shown that m6A methyltransferase METTL3 was upregulated in PDAC tissues with gemcitabine resistance, and its knockdown sensitized pancreatic cancer cells to chemotherapy. Furthermore, silencing METTL3 remarkably reduced pancreatic cancer cell proliferation, migration, and invasion both in vitro and in vivo. Mechanistically, validation experiments confirmed that DDX23 mRNA was a direct target of METTL3 in YTHDF1-dependent manner. Additionally, DDX23 silence resulted in the suppression of pancreatic cancer cell malignancy and PIAK/Akt signaling inactivation. Strikingly, rescuse experiments demonstrated the inhibitive effects of METTL3 silence on cell phenotypes and gemcitabine resistance were partially reversed by forcibly expressed DDX23. In summary, METTL3 promotes PDAC progression and gemcitabine resistance by modifying DDX23 mRNA m6A methylation and enhancing PI3K/Akt signaling activation. Our findings establish a potential tumor promotive and chemo-resistant role for METTL3/DDX23 axis in PDAC.
Subject(s)
Carcinoma, Pancreatic Ductal , Lung Neoplasms , Pancreatic Neoplasms , Animals , Humans , Gemcitabine , Methylation , Adenosine/pharmacology , Adenosine/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Methyltransferases/genetics , Methyltransferases/metabolism , Carcinoma, Pancreatic Ductal/drug therapy , Carcinoma, Pancreatic Ductal/genetics , Pancreatic Neoplasms/drug therapy , Pancreatic Neoplasms/genetics , Pancreatic Neoplasms/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , Pancreatic NeoplasmsABSTRACT
Spermine synthase (SMS) is an enzyme participating in polyamine synthesis; however, its function and role in pancreatic cancer remains elusive. Here we report that SMS is upregulated in pancreatic cancer and predicts a worse overall survival and significantly promotes the proliferation and migration of pancreatic cancer cells. Excessive SMS reduces the accumulation of spermidine by converting spermidine into spermine, which activates the phosphorylation of serine/threonine kinase (AKT) and epithelial-mesenchymal transition (EMT) signaling pathway, thereby inhibiting pancreatic cancer cell proliferation and invasion. Moreover, SMS was identified as the direct target of both methyltransferase like 3 (METTL3) and insulin like growth factor 2 mRNA binding protein 3 (IGF2BP3), which directly bind to the m6A modification sites of SMS and inhibit mRNA degradation. Knockdown of METTL3 or IGF2BP3 significantly reduced the SMS protein expression and inhibited the migration of pancreatic cancer. We propose a novel regulatory mechanism in which the METTL3-IGF2BP3 axis mediates the mRNA degradation of SMS in an m6A-dependent manner to regulate spermine/spermidine conversion, which regulates AKT phosphorylation and EMT activation, thereby inducing tumor progression and migration in pancreatic cancer.
