Kidney microRNA Expression Pattern in Type 2 Diabetic Nephropathy in BTBR Ob/Ob Mice

Mannan-Binding Lectin Is Associated with Inflammation and Kidney Damage in a Mouse Model of Type 2 Diabetes

Autoreactivity of the complement system may escalate the development of diabetic nephropathy. We used the BTBR OB mouse model of type 2 diabetes to investigate the role of the complement factor mannan-binding lectin (MBL) in diabetic nephropathy. Female BTBR OB mice (n = 30) and BTBR non-diabetic WT mice (n = 30) were included. Plasma samples (weeks 12 and 21) and urine samples (week 19) were analyzed for MBL, C3, C3-fragments, SAA3, and markers for renal function. Renal tissue sections were analyzed for fibrosis, inflammation, and complement deposition. The renal cortex was analyzed for gene expression (complement, inflammation, and fibrosis), and isolated glomerular cells were investigated for MBL protein. Human vascular endothelial cells cultured under normo- and hyperglycemic conditions were analyzed by flow cytometry. We found that the OB mice had elevated plasma and urine concentrations of MBL-C (p < 0.0001 and p < 0.001, respectively) and higher plasma C3 levels (p < 0.001) compared to WT mice. Renal cryosections from OB mice showed increased MBL-C and C4 deposition in the glomeruli and increased macrophage infiltration (p = 0.002). Isolated glomeruli revealed significantly higher MBL protein levels (p < 0.001) compared to the OB and WT mice, and no renal MBL expression was detected. We report that chronic inflammation plays an important role in the development of DN through the binding of MBL to hyperglycemia-exposed renal cells.

miR-802-5p is a key regulator in diabetic kidney disease

Background

Diabetic kidney disease has substantial burden and limited therapeutic options. An inadequate understanding of the complex gene regulatory circuits underlying this disorder contributes to the insufficiency of current treatment strategies. MicroRNAs (miRNAs) play a crucial role as regulators of functionally related gene networks. Previously, mmu-mir-802-5p was identified as the sole dysregulated miRNA in both the kidney cortex and medulla of diabetic mice. This study aims to investigate the role of miR-802-5p in diabetic kidney disease.

Materials and Methods

The validated and predicted targets of miR-802-5p were identified using miRTarBase and TargetScan databases, respectively. The functional role of this miRNA was inferred using gene ontology enrichment analysis. The expression of miR-802-5p and its selected targets were assessed by qPCR. The expression of the angiotensin receptor (Agtr1a) was measured by ELISA.

Results

miR-802-5p exhibited dysregulation in both the kidney cortex and medulla of diabetic mice, with two- and four-fold over-expressions, respectively. Functional enrichment analysis of the validated and predicted targets of miR-802-5p revealed its involvement in the renin-angiotensin pathway, inflammation, and kidney development. Differential expression was observed in the Pten transcript and Agtr1a protein among the examined gene targets.

Conclusion

These findings suggest that miR-802-5p is a critical regulator of diabetic nephropathy in the cortex and medulla compartments, contributing to disease pathogenesis through the renin-angiotensin axis and inflammatory pathways.

Role of microRNAs in programmed cell death in renal diseases: A review

MicroRNAs (miRNAs) regulate gene expression involving kidney morphogenesis and cell proliferation, apoptosis, differentiation, migration, invasion, immune evasion, and extracellular matrix remodeling. Programmed cell death (PCD) is mediated and regulated by specific genes and a wealth of miRNAs, which participate in various pathological processes. Dysregulation of miRNAs can disrupt renal development and induce the onset and progression of various renal diseases. An in-depth understanding of how miRNAs regulate renal development and diseases is indispensable to comprehending how they can be used in new diagnostic and therapeutic approaches. However, the mechanisms are still insufficiently investigated. Hence, we review the current roles of miRNA-related signaling pathways and recent advances in PCD research and aim to display the potential crosstalk between miRNAs and PCD. The prospects of miRNAs as novel biomarkers and therapeutic targets are also described, which might provide some novel ideas for further studies.

DNA methylation enzymes in the kidneys of male and female BTBR ob/ob mice

Diabetic kidney disease (DKD) is the leading cause of the end-stage renal disease. Recent studies have shown that epigenetic modifications contribute to alterations in gene expression and the development of DKD. This study aimed to show an expression profile of key DNA (de)methylation enzymes (DNMT, TET proteins) and their differences between sexes under obesity and diabetic condition. Male and female black and tan brachyury (BTBR) ob/ob mice and their corresponding wild-type littermates (BTBR WT) were studied until 16 weeks of age. Metabolic parameters, kidney morphophysiology and the expression of fibrotic markers and epigenetic enzymes were studied in whole kidney tissue or specifically in the glomerulus. The results showed sexual dimorphism in the development of metabolic disease and in kidney morphophysiology. Female mice have a different profile of DNMTs expression in both WT and obese/diabetic condition. Furthermore, metabolic condition negatively modulated the glomerular expression of TET1 and TET3 only in females. To our knowledge, this is the first study that shows a kidney profile of the expression of key (de)methylation enzymes, DNMTs and TETs, in the BTBR ob/ob experimental model of DKD and its association with sex. The knowledge of this epigenetic profile may help future research to understand the pathophysiology of DKD in males and females.

Targeting inflammation to treat diabetic kidney disease: the road to 2030

Diabetic kidney disease (DKD) is one of the fastest growing causes of chronic kidney disease and associated morbidity and mortality. Preclinical research has demonstrated the involvement of inflammation in its pathogenesis and in the progression of kidney damage, supporting clinical trials designed to explore anti-inflammatory strategies. However, the recent success of sodium-glucose cotransporter-2 inhibitors and the nonsteroidal mineralocorticoid receptor antagonist finerenone has changed both guidelines and standard of care, rendering obsolete older studies directly targeting inflammatory mediators and the clinical development was discontinued for most anti-inflammatory drugs undergoing clinical trials for DKD in 2016. Given the contribution of inflammation to the pathogenesis of DKD, we review the impact on kidney inflammation of the current standard of care, therapies undergoing clinical trials, or repositioned drugs for DKD. Moreover, we review recent advances in the molecular regulation of inflammation in DKD and discuss potential novel therapeutic strategies with clinical relevance. Finally, we provide a road map for future research aimed at integrating the growing knowledge on inflammation and DKD into clinical practice to foster improvement of patient outcomes.

The Effect of Allograft Inflammatory Factor-1 on Inflammation, Oxidative Stress, and Autophagy via miR-34a/ATG4B Pathway in Diabetic Kidney Disease

Increasing evidence suggests that disorders of inflammation, oxidative stress, and autophagy contribute to the pathogenesis of diabetic kidney disease (DKD). This study attempted to clarify the effect of allograft inflammatory factor-1 (AIF-1), miR-34a, and ATG4B on inflammation, oxidative stress, and autophagy in DKD both in vitro and in vivo experiments. In vivo, it was found that the levels of AIF-1, miR-34a, oxidative stress, and inflammatory factors were significantly increased in blood and urine samples of DKD patients and mouse models and correlated with the level of urinary protein. In vitro, it was also found that the expressions of AIF-1, miR-34a, ROS, and inflammatory factors were increased, while ATG4B and other autophagy related proteins were decreased in human renal glomerular endothelial cells (HRGECs) cultured with high concentration glucose medium (30 mmol/L). When AIF-1 gene was overexpressed, the levels of miR-34a, ROS, and inflammatory factors were significantly upregulated, and autophagy-related proteins such as ATG4B were downregulated, while downregulation of AIF-1 gene had the opposite effect. In addition, miR-34a inhibited the expression of ATG4B and autophagy-related proteins and increased the levels of ROS and inflammation. Furthermore, the result of luciferase reporter assay suggested that ATG4B was the target gene of miR-34a. When ATG4B gene was overexpressed, the level of autophagy was upregulated, and inflammatory factors were downregulated. Conversely, when ATG4B gene was inhibited, the level of autophagy was downregulated, and inflammatory factors were upregulated. Then, autophagy inducers inhibited the levels of inflammation and ROS, whereas autophagy inhibitors had the opposite function in HRGECs induced by glucose (30 mmol/L). In conclusion, the above data suggested that AIF-1 regulated the levels of inflammation, oxidative stress, and autophagy in HRGECs via miR-34a/ATG4B pathway to contribute to the pathogenesis of diabetic kidney disease.