TGF-β and Diabetic Nephropathy: Lessons Learned Over the Past 20 Years

Exercise training improves diabetic renal injury by reducing fetuin-A, oxidative stress and inflammation in type 2 diabetic rats

Background

Diabetic kidney disease (DKD) stands as a primary contributor to end-stage renal disease, associated with heightened mortality in cardiovascular diseases. This study aimed to explore the impact of an eight-week high-intensity interval training (HIIT) on renal injury in diabetic rats.

Methods

Twenty-eight male Wistar rats were randomly allocated into four groups: healthy control (CTL), diabetic control (DC), exercise (EX), and diabetes-exercise (D + EX). Induction of diabetes in the DC and D + EX groups occurred through a two-month high-fat diet followed by a single dose of 35 mg/kg streptozotocin (STZ). Rats in the EX and D + EX groups underwent 4-10 intervals of HIIT (80-100% Vmax) over 8 weeks. Subsequently, pathological and biochemical parameters were assessed in the serum and kidney tissue of the experimental groups.

Results

In the DC group, diabetes led to elevated kidney damage, glomerulosclerosis, fasting blood glucose (FBG), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) index, animal weight, kidney dysfunction, albuminuria, and glomerular filtration rate. Additionally, serum and kidney levels of fetuin-A increased, along with kidney levels of KIM-1. Mechanistically, diabetes induction resulted in kidney inflammation by elevating levels of tumor necrosis factor-alpha (TNF-α), transforming growth factor beta (TGF-β), and interleukin 6 (IL-6), while reducing IL-10 levels and increasing the IL-6/IL-10 ratio. Furthermore, diabetes triggered renal oxidative stress, evidenced by increased Malondialdehyde (MDA) levels and decreased levels of glutathione peroxidase (GPx), catalase, and superoxide dismutase (SOD). HIIT mitigated the adverse effects of diabetes in the D + EX group compared to the DC group.

Conclusion

Our findings suggest that HIIT ameliorates type 2 diabetes (T2D)-induced kidney damage by mitigating inflammation, lowering serum levels of fetuin-A, and bolstering antioxidant defenses. This study highlights the potential of HIIT as a time-efficient intervention for diabetic nephropathy.

Apabetalone Downregulates Fibrotic, Inflammatory and Calcific Processes in Renal Mesangial Cells and Patients with Renal Impairment

Epigenetic mechanisms are implicated in transcriptional programs driving chronic kidney disease (CKD). Apabetalone is an orally available inhibitor of bromodomain and extraterminal (BET) proteins, which are epigenetic readers that modulate gene expression. In the phase 3 BETonMACE trial, apabetalone reduced risk of major adverse cardiac events (MACE) by 50% in the CKD subpopulation, indicating favorable effects along the kidney-heart axis. Activation of human renal mesangial cells (HRMCs) to a contractile phenotype that overproduces extracellular matrix (ECM) and inflammatory cytokines, and promotes calcification, frequently accompanies CKD to drive pathology. Here, we show apabetalone downregulated HRMC activation with TGF-β1 stimulation by suppressing TGF-β1-induced α-smooth muscle actin (α-SMA) expression, α-SMA assembly into stress fibers, enhanced contraction, collagen overproduction, and expression of key drivers of fibrosis, inflammation, or calcification including thrombospondin, fibronectin, periostin, SPARC, interleukin 6, and alkaline phosphatase. Lipopolysaccharide-stimulated expression of inflammatory genes IL6, IL1B, and PTGS2 was also suppressed. Transcriptomics confirmed apabetalone affected gene sets of ECM remodeling and integrins. Clinical translation of in vitro results was indicated in CKD patients where a single dose of apabetalone reduced plasma levels of key pro-fibrotic and inflammatory markers, and indicated inhibition of TGF-β1 signaling. While plasma proteins cannot be traced to the kidney alone, anti-fibrotic and anti-inflammatory effects of apabetalone identified in this study are consistent with the observed decrease in cardiovascular risk in CKD patients.

Nano-Technological Approaches for Targeting Kidney Diseases With Focus on Diabetic Nephropathy: Recent Progress, and Future Perspectives

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide. With the rising prevalence of diabetes, the occurrence of DN is likely to hit pandemic proportions. The current treatment strategies employed for DN focus on the management of blood pressure, glycemia, and cholesterol while neglecting DN’s molecular progression mechanism. For many theranostic uses, nano-technological techniques have evolved in biomedical studies. Several nanotechnologically based theranostics have been devised that can be tagged with targeting moieties for both drug administration and/or imaging systems and are being studied to identify various clinical conditions. The molecular mechanisms involved in DN are discussed in this review to assist in understanding its onset and progression pattern. We have also discussed emerging strategies for establishing a nanomedicine-based platform for DN-targeted drug delivery to increase drug’s efficacy and safety, as well as their reported applications.

Troxerutin affects nephropathy signaling events in the kidney of type-1 diabetic male rats

Objective

Nephropathy is known to be the leading cause of kidney failure in diabetic patients. Troxerutin, as a flavonoid component, could provide a novel protective strategy in the prevention of diabetic nephropathy. A large number of reports on the salutary effects of troxerutin inspired us to investigate its effect on the nephropathy signaling events (i.e., expression of TGF-β, miRNA192, and SIP1) in type-1 induced diabetic rats.

Materials and Methods

50 male Wistar rats were divided into 5 groups including control group, sham group treated with troxerutin for 4 weeks, diabetic group induced by streptozotocin (STZ) injection, DI group including insulin-treated diabetic animals and DT group treated with troxerutin. Ultimately, rat kidneys were extracted, and the level of miR-192 (using qPCR), transforming growth factor-beta (TGF-β), and smad interacting protein 1 (SIP1) using an ELISA kit, was measured.

Results

The level of TGF-β and miRNA192 significantly increased in the diabetic group. However, their expression levels decreased following the administration of troxerutin and insulin (p<0.05) compared to control group. SIP1 was down-regulated in the diabetic group, whereas a spike in the expression levels was observed after troxerutin administration compared to control and troxerutin groups (p<0.05). However, no significant difference was found in the effects of insulin and troxerutin on the level of miR-192, SIP1, and TGF- β.

Conclusion

According to the previous literatures, during the progression of nephropathy, TGF-β represses SIP1 (the repression region in the collagen gene) by increasing the expression of miR-192. Ultimately, in this study, diabetes led to up-regulation of TGF-β while troxerutin proved to have a protective effect on the kidney by increasing SIP and lowering miR-192 levels.

TGF-β1 is involved in senescence-related pathways in glomerular endothelial cells via p16 translocation and p21 induction

p16 inhibits cyclin-dependent kinases and regulates senescence-mediated arrest as well as p21. Nuclear p16 promotes G1 cell cycle arrest and cellular senescence. In various glomerular diseases, nuclear p16 expression is associated with disease progression. Therefore, the location of p16 is important. However, the mechanism of p16 trafficking between the nucleus and cytoplasm is yet to be fully investigated. TGF-β1, a major cytokine involved in the development of kidney diseases, can upregulate p21 expression. However, the relationship between TGF-β1 and p16 is poorly understood. Here, we report the role of podocyte TGF-β1 in regulating the p16 behavior in glomerular endothelial cells. We analyzed podocyte-specific TGF-β1 overexpression mice. Although p16 was found in the nuclei of glomerular endothelial cells and led to endothelial cellular senescence, the expression of p16 did not increase in glomeruli. In cultured endothelial cells, TGF-β1 induced nuclear translocation of p16 without increasing its expression. Among human glomerular diseases, p16 was detected in the nuclei of glomerular endothelial cells. In summary, we demonstrated the novel role of podocyte TGF-β1 in managing p16 behavior and cellular senescence in glomeruli, which has clinical relevance for the progression of human glomerular diseases.

The 100 top-cited articles in diabetic kidney disease: a bibliometric analysis

Background

Tremendous scientific researches have been conducted in the field of diabetic kidney disease (DKD), while few bibliometric analyses have been performed. We aim to identify 100 top-cited published articles about DKD and analyze their main characteristics quantitatively.

Methods

Web of Science was searched with the term ‘diabetic kidney disease’ OR ‘diabetic nephropathy’ to identify the top 100 most cited articles. For articles meeting the predefined criteria, the following data were extracted and analyzed: citation ranking, publication year, publication journal, journal impact factor, country and institution, authors, study type, and keywords.

Results

The highest number of citations was 4753 times. The median average citations per year was 21.8 (IQR, 16.6–33.0). Most articles focused on the pathogenesis and treatment. These articles were published in 25 different journals and the Journal of the American Society of Nephrology published the greatest number (20%). Forty-three articles (43%) originated from the United States. The University of Groningen was the leading institute, contributing five top-cited articles. The most frequent first author was de Zeeuw (n = 4), followed by Parving (n = 3). There was no correlation between the average citations and the number of authors, the number of institutes, or the number of funds, respectively. Experimental animal study was the research type most frequently conducted (n = 30), followed by observational study (n = 24). Keyword analysis revealed transforming growth factor-β, oxidative stress, proteinuria, and renin–angiotensin–aldosterone system interruption are classic research topics. Sodium-glucose cotransporter 2 inhibitors, glucagon-like peptide 1 receptor agonists, and anti-inflammatory agents are the emerging trends of DKD.

Conclusions

This bibliometric analysis helps in identifying the milestones, inadequacies, classic hotspots, and emerging trends of DKD. Pathogenesis and treatment are core themes in DKD research, while high-quality articles on the prediction and biomarker are insufficient. New analyzing metrics are needed to assess the actual impact of these top-cited articles on clinical practice.

MicroRNAs in diabetic nephropathy: From molecular mechanisms to new therapeutic targets of treatment

Despite considerable investigation in diabetic nephropathy (DN) pathogenesis and possible treatments, current therapies still do not provide competent prevention from disease progression to end-stage renal disease (ESRD) in most patients. Therefore, investigating exact molecular mechanisms and important mediators underlying DN may help design better therapeutic approaches for proper treatment. MicroRNAs (MiRNAs) are a class of small non-coding RNAs that play a crucial role in post-transcriptional regulation of many gene expression within the cells and present an excellent opportunity for new therapeutic approaches because their profile is often changed during many diseases, including DN. This review discusses the most important signaling pathways involved in DN and changes in miRNAs profile in each signaling pathway. We also suggest possible approaches for miRNA derived interventions for designing better treatment of DN.

Anti-inflammatory cytokines IL-27, IL-10, IL-1Ra and TGF-β in subjects with increasing grades of glucose intolerence (DM-LTB-2)

Anti-inflammatory cytokines act as double edged swords- they can dampen inflammation but can also suppress immunity. The role played by these cytokines in latent TB infected (LTBI) subjects, with various grades of glucose intolerance was studied. Both serum levels and recall-secretion of IL-27, IL-10, IL-1Ra and TGF-β in Normal Glucose Tolerance (NGT), Pre-Diabetes (PDM), Newly diagnosed Diabetes (NDM) and Known Diabetes (KDM) subjects, both with and without LTBI (n = 382), were quantified by ELISA. All the subjects were screened for LTBI by QuantiFERON-TB Gold test. Serum levels of IL-27, IL-10 and IL-1Ra were significantly elevated in the LTB^-PDM, compared to LTB^-NGT group. Increased IL-27 and IL-10 levels and decreased levels of TGF-β were seen in the LTB^-NDM, compared to LTB^-NGT group. Decreased serum levels of IL-27 and increased levels of IL-1Ra and TGF-β were seen in the LTB^-KDM, compared to LTB^-NGT group. TB antigens induced the secretion of IL-1Ra in LTB⁺ subjects in the NGT, PDM and NDM groups, but not in the KDM group. Co-morbidity with LTBI brought about (diabetic) stage-specific modulation, in these cytokine levels. Major defects in the circulating levels and recall secretion of anti-inflammatory cytokines, as seen in LTB⁺KDM subjects, could fuel DM-TB synergy.

Upregulation of miRNA-1228-3p alleviates TGF-β-induced fibrosis in renal tubular epithelial cells

BACKGROUND

Chronic kidney disease (CKD) has become a major public health issue, which can lead to renal fibrosis regardless of the initial injury. It has been previously reported that miRNA-1228-3p was correlate with the progression of kidney fibrosis. However, the mechanism by which miRNA-1228-3p regulates renal fibrosis remains unclear.

METHODS

Renal tubular epithelial cells (HK-2) were treated with TGF-β1 (10 ng/ml) in an in vitro model of renal fibrosis. Gene and protein expressions in HK-2 cells were measured by Western-blot and RT-qPCR, respectively. The relation between miRNA-1228-3p and its target gene was investigated by dual luciferase report analysis.

RESULTS

Upregulation of miRNA-1228-3p significantly inhibited TGF-β1-induced fibrosis of HK-2 cells in vitro by targeting GDF11. In addition, miRNA-1228-3p exhibited anti-fibrosis effect through inhibition of the smad2/smad4 signaling pathway.

CONCLUSION

Upregulation of miRNA-1228-3p markedly inhibited the progression of renal fibrosis in vitro, indicating that miRNA-1228-3p may serve as a potential novel target for the treatment of renal fibrosis.

Renal protective effect of pinitol in experimental diabetes

Pinitol is a natural antidiabetic agent shown to prevent or ameliorate metabolic and overall vascular and neural function. In the present study we have evaluated the potential benefits of pinitol on renal function of streptozotocin (STZ)-induced diabetic rats. Both euglycemic or 8-week or 16-week diabetic rats were treated with either saline (1 ml/kg/12h; p.o) or pinitol (20 mg/kg/12h; p.o). The renal function was evaluated by using metabolic cages, renal hemodynamic and tubular parameters measurements. Histological examination and evaluation of the protein expression of renal markers such as nephrin, TGFβ and pERK were also performed. Pinitol decreased by 50% the increased urinary albumin/creatinine ratio in both 8-week and 16 week diabetic rats. In addition, the glomerular volume of 16-week rats increased by 55% and this increase was blunted by pinitol. Remarkably, pressure-natriuresis was completely blunted in both 8 and 16-week diabetic rats but this impairment was prevented by pinitol in both treatment regimens. Pinitol ameliorated renal lesions and also prevented the decrease in nephrin expression and the increase of pERK and TGFβ expression in both diabetic groups. Natriuresis due to high renal perfusion pressure increased 7-fold in control animals but was blocked in 16-week diabetic rats and remarkably pinitol partially restored pressure natriuresis (3-fold increase in sodium excretion during pressure natriuresis). Pinitol prevents and ameliorates albuminuria, glomerular expansion, impairment of pressure-natriuresis, renal structural alterations and changes of renal markers and has the potential to be tested for the prevention of diabetic kidney disease.