Diabetic kidney disease (DKD) is the most common microvascular complication of type 2 diabetes mellitus (2-DM). Currently, urine and kidney biopsy specimens are the major clinical resources for DKD diagnosis. Our study proposes to evaluate the diagnostic value of blood in monitoring the onset of DKD and distinguishing its status in the clinic. This study recruited 1,513 participants including healthy adults and patients diagnosed with 2-DM, early-stage DKD (DKD-E), and advanced-stage DKD (DKD-A) from 4 independent medical centers. One discovery and four testing cohorts were established. Sera were collected and subjected to training proteomics and large-scale metabolomics. Deep profiling of serum proteomes and metabolomes revealed several insights. First, the training proteomics revealed that the combination of α₂-macroglobulin, cathepsin D, and CD324 could serve as a surrogate protein biomarker for monitoring DKD progression. Second, metabolomics demonstrated that galactose metabolism and glycerolipid metabolism are the major disturbed metabolic pathways in DKD, and serum metabolite glycerol-3-galactoside could be used as an independent marker to predict DKD. Third, integrating proteomics and metabolomics increased the diagnostic and predictive stability and accuracy for distinguishing DKD status. Serum integrative omics provide stable and accurate biomarkers for early warning and diagnosis of DKD. Our study provides a rich and open-access data resource for optimizing DKD management.

Background: Targeting the gut microbiota may become a new therapeutic to prevent and delay the progression of chronic kidney disease (CKD). Nonetheless, the causal relationship between specific intestinal flora and CKD is still unclear. Materials and Method: To identify genetically predicted microbiota, we used summary data from genome-wide association studies on gut microbiota in 18340 participants from 24 cohorts. Furthermore, we genetically predicted the causal relationship between 211 gut microbiotas and six phenotypes (outcomes) (CKD, estimated glomerular filtration rate (eGFR), urine albumin to creatinine ratio (UACR), dialysis, rapid progress to CKD, and rapid decline of eGFR). Four Mendelian randomization (MR) methods, including inverse variance weighted (IVW), MR-Egger, weighted median, and weighted mode were used to investigate the casual relationship between gut microbiotas and various outcomes. The result of IVW was deemed as the primary result. Then, Cochrane’s Q test, MR-Egger, and MR-PRESSO Global test were used to detect heterogeneity and pleiotropy. The leave-one method was used for testing the stability of MR results and Bonferroni-corrected was used to test the strength of the causal relationship between exposure and outcome. Results: Through the MR analysis of 211 microbiotas and six clinical phenotypes, a total of 36 intestinal microflora were found to be associated with various outcomes. Among them, Class Bacteroidia (=−0.005, 95% CI: −0.001 to −0.008, p = 0.002) has a strong causality with lower eGFR after the Bonferroni-corrected test, whereas phylum Actinobacteria (OR = 1.0009, 95%CI: 1.0003–1.0015, p = 0.0024) has a strong causal relationship with dialysis. The Cochrane’s Q test reveals that there is no significant heterogeneity between various single nucleotide polymorphisms. In addition, no significant level of pleiotropy was found according to MR-Egger and MR-PRESSO Global tests. Conclusions: Through the two-sample MR analysis, we identified the specific intestinal flora that has a causal relationship with the incidence and progression of CKD at the level of gene prediction, which may provide helpful biomarkers for early disease diagnosis and potential therapeutic targets for CKD.

Renal fibrosis is a pathologic feature of chronic kidney disease, which can lead to end-stage kidney disease. Myeloid fibroblasts play a central role in the pathogenesis of renal fibrosis. However, the molecular mechanisms pertaining to myeloid fibroblast activation remain to be elucidated. In the present study, we examine the role of signal transducer and activator of transcription 6 (STAT6) in myeloid fibroblast activation, macrophage polarization, and renal fibrosis development in a mouse model of folic acid nephropathy. STAT6 is activated in the kidney with folic acid nephropathy. Compared with folic-acid-treated wild-type mice, STAT6 knockout mice had markedly reduced myeloid fibroblasts and myofibroblasts in the kidney with folic acid nephropathy. Furthermore, STAT6 knockout mice exhibited significantly less CD206 and PDGFR-β dual-positive fibroblast accumulation and M2 macrophage polarization in the kidney with folic acid nephropathy. Consistent with these findings, STAT6 knockout mice produced less extracellular matrix protein, exhibited less severe interstitial fibrosis, and preserved kidney function in folic acid nephropathy. Taken together, these results have shown that STAT6 plays a critical role in myeloid fibroblasts activation, M2 macrophage polarization, extracellular matrix protein production, and renal fibrosis development in folic acid nephropathy. Therefore, targeting STAT6 may provide a novel therapeutic strategy for fibrotic kidney disease.

Introduction: The effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors on renal outcomes in patients with chronic kidney disease (CKD) were initially demonstrated in recent trials. However, the magnitude of renal benefits for CKD patients with different baseline features and underlying diseases remains unclear.Method: We systematically searched the Embase, PubMed, Web of Science, and Cochrane library databases from inception to April 15, 2021 to identify eligible trials. The primary outcome was a composite of worsening kidney function, end-stage kidney disease (ESKD), or renal death. Efficacy and safety outcomes were stratified by baseline features, such as type 2 diabetes, heart failure, atherosclerotic cardiovascular disease, proteinuria, and renal function.Results: A total of nine studies were included. These studies included 25,749 patients with estimated glomerular filtration rate (eGFR)300 mg/g. SGLT2 inhibitors reduced the risk of the primary renal outcome by 30% in patients with eGFR 300 mg/g (HR 0.57, [95% CI 0.48–0.67], I² = 16.59%). A similar benefit was observed in CKD patients with type 2 diabetes. SGLT2 inhibitors had no clear effects on renal outcomes in patients with eGFR 300 mg/g). SGLT2 inhibitors did not significantly reduce the risk of major renal outcomes in CKD patients with heart failure (eGFR 300 mg/g: HR 0.66, [95% CI 0.41–1.07], I² = 0.00%). SGLT2 inhibitors showed consistent renal benefits across different levels of eGFR (P interaction = 0.48).Conclusion: SGLT2 inhibitors significantly reduced the risk of the primary outcome in CKD patients. However, for patients with different features and underlying diseases, there exists differences in the renal protective effect.

Proteinuric chronic kidney disease (CKD) remains a major health problem worldwide. While it is well established that the progression of primary glomerular disease induces tubulointerstitial lesions, how tubular injury triggers glomerular damage is poorly understood. We hypothesized that injured tubules secrete mediators that adversely affect glomerular health. To test this, we used conditional knockout mice with tubule-specific ablation of β-catenin (Ksp-β-cat ^–/– ) and subjected them to chronic angiotensin II (Ang II) infusion or Adriamycin. Compared with control mice, Ksp-β-cat ^–/– mice were dramatically protected from proteinuria and glomerular damage. MMP-7, a downstream target of β-catenin, was upregulated in treated control mice, but this induction was blunted in the Ksp-β-cat ^–/– littermates. Incubation of isolated glomeruli with MMP-7 ex vivo led to nephrin depletion and impaired glomerular permeability. Furthermore, MMP-7 specifically and directly degraded nephrin in cultured glomeruli or cell-free systems, and this effect was dependent on its proteolytic activity. In vivo, expression or infusion of exogenous MMP-7 caused proteinuria, and genetic ablation of MMP-7 protected mice from Ang II–induced proteinuria and glomerular injury. Collectively, these results demonstrate that β-catenin–driven MMP-7 release from renal tubules promotes glomerular injury via direct degradation of the key slit diaphragm protein nephrin.