Screening of the Key Genes and Signalling Pathways for Diabetic Nephropathy Using Bioinformatics Analysis.

Background: This study aimed to identify biological markers for diabetic nephropathy (DN) and explore their underlying mechanisms. Methods: Four datasets, GSE30528, GSE47183, GSE104948, and GSE96804, were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified using the "limma" package, and the "RobustRankAggreg" package was used to screen the overlapping DEGs. The hub genes were identified using cytoHubba of Cytoscape. Logistic regression analysis was used to further analyse the hub genes, followed by receiver operating characteristic (ROC) curve analysis to predict the diagnostic effectiveness of the hub genes. Correlation analysis and enrichment analysis of the hub genes were performed to identify the potential functions of the hub genes involved in DN. Results: In total, 55 DEGs, including 38 upregulated and 17 downregulated genes, were identified from the three datasets. Four hub genes (FN1, CD44, C1QB, and C1QA) were screened out by the "UpSetR" package, and FN1 was identified as a key gene for DN by logistic regression analysis. Correlation analysis and enrichment analysis showed that FN1 was positively correlated with four genes (COL6A3, COL1A2, THBS2, and CD44) and with the development of DN through the extracellular matrix (ECM)-receptor interaction pathway. Conclusions: We identified four candidate genes: FN1, C1QA, C1QB, and CD44. On further investigating the biological functions of FN1, we showed that FN1 was positively correlated with THBS2, COL1A2, COL6A3, and CD44 and involved in the development of DN through the ECM-receptor interaction pathway. THBS2, COL1A2, COL6A3, and CD44 may be novel biomarkers and target therapeutic candidates for DN.

PPARγ alleviates peritoneal fibrosis progression along with promoting GLUT1 expression and suppressing peritoneal mesothelial cell proliferation.

OBJECTIVE: Peritoneal fibrosis (PF) is commonly induced by bioincompatible dialysate exposure during peritoneal dialysis, but the underlying mechanisms remain elusive. This study aimed to investigate the roles of peroxisome proliferator-activated receptor gamma (PPARγ) in PF pathogenesis. METHODS: Rat and cellular PF models were established by high glucose dialysate and lipopolysaccharide treatments. Serum creatinine, urea nitrogen, and glucose contents were detected by ELISA. Histological evaluation was done through H&E and Masson staining. GLUT1, PPARγ, and other protein expression were measured by qRT-PCR, western blotting, and IHC. PPARγ and GLUT1 subcellular distribution were detected using confocal microscopy. Cell proliferation was assessed by MTT and Edu staining. RESULTS: Serum creatinine, urea nitrogen and glucose, and PPARγ and GLUT1 expression in rat PF model were reduced by PPARγ agonists Rosiglitazone or 15d-PGJ2 and elevated by antagonist GW9662. Rosiglitazone or 15d-PGJ2 repressed and GW9662 aggravated peritoneal fibrosis in rat PF model. PPARγ and GLUT1 were mainly localized in nucleus and cytosols of peritoneal mesothelial cells, respectively, which were reduced in cellular PF model, enhanced by Rosiglitazone or 15d-PGJ2, and repressed by GW9662. TGF-ß and a-SMA expression was elevated in cellular PF model, which was inhibited by Rosiglitazone or 15d-PGJ2 and promoted by GW9662. PPARγ silencing reduced GLUT1, elevated a-SMA and TGF-b expression, and promoted peritoneal mesothelial cell proliferation, which were oppositely changed by PPARγ overexpression. CONCLUSION: PPARγ inhibited high glucose-induced peritoneal fibrosis progression through elevating GLUT1 expression and repressing peritoneal mesothelial cell proliferation.

Lipopolysaccharide-induced inflammation in human peritoneal mesothelial cells is controlled by ERK1/2-CDK5-PPARγ axis.

BACKGROUND: Peritonitis is a common complication in which the peritoneum becomes inflamed. Peroxisome proliferator-activated receptor (PPAR)γ agonists and extracellular signal-regulated kinases 1/2 (ERK1/2) inactivation have been found to restore damage caused by lipopolysaccharide-induced (LPS) inflammation. This study aimed to investigate the association between PPARγ and ERK1/2 in LPS-induced inflammation in peritonitis. METHODS: Human peritoneal mesothelial cells were maintained in Dulbecco's Modified Eagle Medium and treated with LPS under a series of different concentrations and treatment times. Cellular interleukins-1ßeta (IL-1ß), cellular interleukins-6 (IL-6), cellular interleukins-12 (IL-12) were measured by enzyme-linked immunosorbent assay (ELISA) assay. Expression or activation of cyclin-dependent kinase (CDK)5, ERK1/2, and PPARγ was detected using quantitative real-time PCR and/or western blot. RESULTS: LPS induced dose- and time-dependent increments in the cellular IL-1ß, IL-6, and IL-12 contents, cyclin-dependent kinase 5 (CDK5) expression, and PPARγSer273 phosphorylation. Treatment with 1 µg/mL LPS for 12 hours was the optimal experimental design for inflammation stimulation. The concentration of LPS over 1 µg/mL or treatment more than 12 hours reduced the inflammatory status. LPS stimulation also activated ERK1/2 and increased its interaction with CDK5. Further, ERK1/2 inhibition by AZD0364 prevented IL-1ß, IL-6, IL-12, and CDK5 expression, as well as activation of ERK1/2 and phosphorylation of PPARγ, induced by LPS. Knockdown of CDK5 using its siRNA caused similar changes as AZD0364, minus ERK1/2 inactivation. CONCLUSIONS: Our results suggested that LPS-induced inflammation in human peritoneal mesothelial cells can be partly suppressed by inhibiting the ERK1/2/CDK5/PPARγ axis.