N-Acetyl-seryl-aspartyl-lysyl-proline is a potential biomarker of renal function in normoalbuminuric diabetic patients with eGFR ≥ 30 ml/min/1.73 m2

Epigenetic modification in diabetic kidney disease

Diabetic kidney disease (DKD) is a common microangiopathy in diabetic patients and the main cause of death in diabetic patients. The main manifestations of DKD are proteinuria and decreased renal filtration capacity. The glomerular filtration rate and urinary albumin level are two of the most important hallmarks of the progression of DKD. The classical treatment of DKD is controlling blood glucose and blood pressure. However, the commonly used clinical therapeutic strategies and the existing biomarkers only partially slow the progression of DKD and roughly predict disease progression. Therefore, novel therapeutic methods, targets and biomarkers are urgently needed to meet clinical requirements. In recent years, increasing attention has been given to the role of epigenetic modification in the pathogenesis of DKD. Epigenetic variation mainly includes DNA methylation, histone modification and changes in the noncoding RNA expression profile, which are deeply involved in DKD-related inflammation, oxidative stress, hemodynamics, and the activation of abnormal signaling pathways. Since DKD is reversible at certain disease stages, it is valuable to identify abnormal epigenetic modifications as early diagnosis and treatment targets to prevent the progression of end-stage renal disease (ESRD). Because the current understanding of the epigenetic mechanism of DKD is not comprehensive, the purpose of this review is to summarize the role of epigenetic modification in the occurrence and development of DKD and evaluate the value of epigenetic therapies in DKD.

NLRP3-mediated pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN) is the main cause of end-stage renal disease (ESRD), which is characterized by a series of abnormal changes such as glomerulosclerosis, podocyte loss, renal tubular atrophy and excessive deposition of extracellular matrix. Simultaneously, the occurrence of inflammatory reaction can promote the aggravation of DN-induced kidney injury. The most important processes in the canonical inflammasome pathway are inflammasome activation and membrane pore formation mediated by gasdermin family. Converging studies shows that pyroptosis can occur in renal intrinsic cells and participate in the development of DN, and its activation mechanism involves a variety of signaling pathways. Meanwhile, the activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome can not only lead to the occurrence of inflammatory response, but also induce pyroptosis. In addition, a number of drugs targeting pyroptosis-associated proteins have been shown to have potential for treating DN. Consequently, the pathogenesis of pyroptosis and several possible activation pathways of NLRP3 inflammasome were reviewed, and the potential drugs used to treat pyroptosis in DN were summarized in this review. Although relevant studies are still not thorough and comprehensive, these findings still have certain reference value for the understanding, treatment and prognosis of DN.

Protective factors as biomarkers and targets for prevention and treatment of diabetic nephropathy: From current human evidence to future possibilities

Although hyperglycemia, high blood pressure and aging increase the risk of developing kidney complications, some diabetes patients exposed to these risk factors do not develop kidney disease, suggesting the presence of endogenous protective factors. There is a growing need to understand these factors determining protection of the kidney in order to improve the design of preventive strategies and to enhance the processes responsible for renoprotection. The aim of this review was to present the existing molecular and epidemiological data on factors showing protective effects in diabetic kidney disease, and to summarize the evidence regarding their potential in the area of future clinical diagnostics, therapeutics and early preventive strategies. These include transcriptomic and proteomic studies regarding the anti-inflammatory, anti-fibrotic and regenerative factors that were associated with slower progression of renal function loss. Another focus is the new evidence regarding the evaluation of alterations in the regulatory epigenome and its involvement in the risk of diabetic kidney disease. Further effort is required to validate and extend these findings, and to define their potential for clinical implementation in the future.

CD-1db/db mice: A novel type 2 diabetic mouse model with progressive kidney fibrosis

Aims/Introduction

To establish novel therapies to combat diabetic kidney disease, a human disease‐relevant animal model is essential. However, a type 2 diabetic mouse model presenting progressive kidney fibrosis has not yet been established. Kidneys of streptozotocin‐induced diabetic CD‐1 mice showed severe fibrosis compared with other backgrounds of mice associated with the suppression of antifibrotic peptide N‐acetyl‐seryl‐aspartyl‐lysyl‐proline. The BKS background (BKS^db/db) is often utilized for diabetic kidney disease research; the kidney fibrosis in the BKS^db/db phenotype is minimal.

Materials and Methods

We generated CD‐1^db/db mice by backcrossing the db gene into the CD‐1 background, and analyzed phenotypic differences compared with BKS^db/db and CD‐1^db/m mice.

Results

Male CD‐1^db/db mice appeared to have elevated blood glucose levels compared with those of BKS^db/db mice. Fasting insulin levels declined in CD‐1^db/db mice. Plasma cystatin C levels tended to be elevated in CD‐1^db/db mice from 16 to 24 weeks‐of‐age. Male CD‐1^db/db mice showed significantly progressive kidney and heart fibrosis from 16 to 24 weeks‐of‐age when compared with that of age‐matched BKS^db/db mice. The gene expression profile showed fibrogenic program‐associated genes in male CD‐1^db/db mice. Male CD‐1^db/db mice displayed significantly lower urine antifibrotic peptide N‐acetyl‐seryl‐aspartyl‐lysyl‐proline when compared to that of BKS^db/db at 24 weeks‐of‐age. The gene expression of prolyl oligopeptidase, the enzyme essential for antifibrotic peptide N‐acetyl‐seryl‐aspartyl‐lysyl‐proline production from thymosin β4, was significantly lower in the CD‐1 mice. Thymosin β4 levels were also lower in CD‐1 mice.

Conclusions

These results suggest that CD‐1^db/db mice are a novel type 2 diabetic mouse model with progressive kidney and heart fibrosis.

N-acetyl-seryl-aspartyl-lysyl-proline is a valuable endogenous antifibrotic peptide for kidney fibrosis in diabetes: An update and translational aspects

N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) is an endogenous peptide that has been confirmed to show excellent organ-protective effects. Even though originally discovered as a modulator of hemotopoietic stem cells, during the recent two decades, AcSDKP has been recognized as valuable antifibrotic peptide. The antifibrotic mechanism of AcSDKP is not yet clear; we have established that AcSDKP could target endothelial-mesenchymal transition program through the induction of the endothelial fibroblast growth factor receptor signaling pathway. Also, recent reports suggested the clinical significance of AcSDKP. The aim of this review was to update recent advances of the mechanistic action of AcSDKP and discuss translational research aspects.