As one of microvascular complication of diabetes, DN is the main cause of ESRD. Existing treatments are not sufficient to control disease progression. New treatment strategies were needed. High-throughput omics data have been widely used to study mechanisms of disease and predict possible therapeutic targets. Current research aboout DN published on the public platform are mostly generated from a single-cohort study. Therefore, an integrated analysis of the data is needed. We performed differential expression analysis and WGCNA with gene expression profiles. GO analysis of combined gene list mainly included neutrophil activation, regulation of immune effector process, positive regulation of cytokine production and neutrophil mediated immunity. KEGG pathway analysis mostly included phagosome, complement and coagulation cascades, cell adhesion molecules (CAMs), ECM-receptor interaction, focal adhesion and AGE-RAGE signaling pathway in diabetic complications. The results supported that immune and inflammatory response may involve in DN. Cytokine release and extracellular matrix deposition may be subsequent events and continue with development of disease. Next, PPI network was established and the 20 hub genes were identificated from it. We also analysed one miRNA profiles to construct mRNA-miRNA network. The network suggested miR-766-3p/TGFBI, miR-1238-5p/ZNF652 and miR-1237-3p/SH2B3 axis. Because epigenetic modifications are considered an important factor during the long course of DN, 15 genes (ANXA1, C3, CXCL1, CXCL8, FCER1G, FN1, HLA-E, ITGAV, ITGB2, KNG1, LYN, P2RY13, P2RY14, RHOA and VWF) were verified methylation difference. But the degree of change is not attainable from GSE121820. Futhermore, correlation analysis with clinical data demonstrated the disease-promoting effect of SYK, CXCL1, LYN, VWF, ANXA1, C3, HLA-E, RHOA and SERPING1, which were up regulated in DN tubule samples. On the contrary, EGF and KNG1 was proved protective effect in DN, which were down regulated in DN tubule samples.
So far, there have been some reports about target genes and DN. Spleen tyrosine kinase (SYK) was reported to mediate high glucose induced TGF-β1 increasement and IL-1β secretion (23, 24). In two animal experiments, C-X-C motif chemokine ligand 1 (CXCL1) stimulated in DN pathogenic environment may served as proinflmmatory mediator (25, 26). In addition, VWF was reported to involve in intrarenal thrombosis leading to deterioration of renal function (27). Purvis et al. observed higher circulating plasma levels of ANXA1 in T1D and T2D patients, whereas exogenous supplement of ANXA1 improves insulin resistance and keeps off the progression of subsequent microvascular complications in mice (28, 29). Previous studies have demonstrated that statins prevent from DN by reducing Ras homolog family member A (RhoA) protein activation (30–33). Another study reported that activation of RhoA/ROCK may regulate NF-κB signaling pathway (34). In addition, sinomenine, kaempferol, catalpol and rutin have been shown a protective effects through RhoA/ROCK signaling pathway (35–38). EGF was considered as urine biomakers in two researches (39, 40). Recently, a newest report about cytosine methylation differences in kidney tubule samples supported this viewpoint (41). Besides, one large-scale linkage study revealed polymorphisms in kininogen 1 (KNG1) associated with DN in European populations (42).
Results is consistent with knowledge that complement system participates in DN. The development of diabetes intimately linked to low-grade inflammation (43). High levels of inflammatory markers such as c-reactive protein and adiponectin proved this viewpoint (44, 45). Inflammation might promote the occurrence and development of diabetic complications such as DN. But it is still poorly understood about underlying mechanisms of initiation of low-grade inflammation. More and more research evidence proved innate immune system are closely involved in diabetes (46). Simultaneously, roles for pattern recognition receptors (PRRs) have been discussed in related with DN (47, 48). Complement system is not only involved in innate immune defence but also considered as an important proinflammaton factor. Several studies pointed out that the complement system is involved in the pathogenesis of DN and might be a therapeutic target (49–51). Significant difference of complement system components level in both plasma and urine were found between patients sufferd from DN and kidney exempted patients. In addition, Li et al highlighted the relatively more important impact of C3a, C5a and sC5b-9 in the development of DN (52). Sun et al demonstrated more severe kidney damage in renal histopathology assessment was associated with deposition of C1q and C3c (53). Futhermore, a large-scale cohort study substantiated high plasms levels of C3 are more prone to kidney damage in individuals from the general population (54). Another research indicted that serum levels of C3 may help to differentiate non‑diabetic renal disease from DN in patients with T2DM (55). Blockade of C3a and C5a receptors in the T1DM model indicated a potential protective effect on renal fibrosis by improving endothelial to myofibroblast transition through the Wnt/β-catenin signalling pathway (56). Similarly, blockade of C3a receptors in rats with T2DM improved renal morphology and function by inhibiting cytokine release and TGFβ/Smad3 signalling (57). However, the best approach targeting the complement system to prevent the development of DN still needs to be explored. Therefore 10 potential small molecule compounds have been identified by Connectivity Map database in our study.