Diabetes and Kidney Disease: Role of Oxidative Stress

TXNIP deficiency attenuates renal fibrosis by modulating mTORC1/TFEB-mediated autophagy in diabetic kidney disease

Thioredoxin-interacting protein (TXNIP) is an important regulatory protein for thioredoxin (TRX) that elicits the generation of reactive oxygen species (ROS) by inhibiting the redox function of TRX. Abundant evidence suggests that TXNIP is involved in the fibrotic process of diabetic kidney disease (DKD). However, the potential mechanism of TXNIP in DKD is not yet well understood. In this study, we found that TXNIP knockout suppressed renal fibrosis and activation of mammalian target of rapamycin complex 1 (mTORC1) and restored transcription factor EB (TFEB) and autophagy activation in diabetic kidneys. Simultaneously, TXNIP interference inhibited epithelial-to-mesenchymal transformation (EMT), collagen I and fibronectin expression, and mTORC1 activation, increased TFEB nuclear translocation, and promoted autophagy restoration in HK-2 cells exposed to high glucose (HG). Rapamycin, an inhibitor of mTORC1, increased TFEB nuclear translocation and autophagy in HK-2 cells under HG conditions. Moreover, the TFEB activators, curcumin analog C1 and trehalose, effectively restored HG-induced autophagy, and abrogated HG-induced EMT and collagen I and fibronectin expression in HK-2 cells. Taken together, these findings suggest that TXNIP deficiency ameliorates renal fibrosis by regulating mTORC1/TFEB-mediated autophagy in diabetic kidney diseases.

Abdelaziz M, Sakr HI, Ahmed OM. Bone marrow-derived mesenchymal stem cells reduce CCl4-induced kidney injury and fibrosis in male Wistar rats

AIM

This study explores the possible therapeutic role of rats and mice bone marrow-derived mesenchymal stem cells (BM-MSCs) on renal damage and toxicity brought on by carbon tetrachloride (CCl4) in Wistar rats.

METHODS

Following an intraperitoneal injection of CCl4 (0.5 mL/kg b.w. twice weekly) for eight weeks, male Wistar rats were intravenously treated with rats and mice BM-MSCs (1 × 106 cells in 0.2 mL Dulbecco's Modified Eagle Medium (DMEM)/rat/week) a week for four weeks. Kidney functions were evaluated and kidney samples were examined using hematoxylin and eosin (H&E), Masson's trichrome (MT) staining techniques, and electron microscopy analysis. Kidney cyclooxygenase-2 (COX-2), protein 53 (p53), and tumor necrosis factor-α (TNF-α) were detected by immunohistochemical staining techniques. Additionally, bioindicators of oxidative stress and antioxidant defense systems were identified in kidney tissue.

RESULTS

In CCl4-injected rats, serum creatinine, urea, and uric acid levels significantly increased, as did renal lipid peroxidation (LPO), while superoxide dismutase, glutathione peroxidase (GPx), glutathione (GSH) transferase, and GSH levels significantly dropped in the kidneys. Histologically, the kidneys displayed a wide range of structural abnormalities, such as glomerular shrinkage, tubular dilations, inflammatory leukocytic infiltration, fibroblast proliferation, and elevated collagen content. Inflammatory cytokines like COX-2 and TNF-α as well as the pro-apoptotic mediator p53 were considerably upregulated. Treatment of BM-MSCs from mice and rats with CCl4-injected rats considerably reduced the previously noted abnormalities.

CONCLUSIONS

By boosting antioxidant defense and reducing apoptosis and inflammation, BM-MSCs from mice and rats were able to enhance kidney function and histological integrity in rats that had received CCl4 injections.

TAK-242 improves sepsis-associated acute kidney injury in rats by inhibiting the TLR4/NF-κB signaling pathway

OBJECTIVE

This study was designed to observe the effect of toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) pathway activity on sepsis-associated acute kidney injury (SA-AKI), thereby providing new considerations for the prevention and treatment of SA-AKI.

METHODS

The rats were divided into Sham, cecal ligation and puncture (CLP), CLP + vehicle, and CLP + TAK-242 groups. Except the Sham group, a model of CLP-induced sepsis was established in other groups. After 24 h, the indicators related to kidney injury in blood samples were detected. The pathological changes in the kidneys were observed by hematoxylin-eosin staining, and tubular damage was scored. Oxidative stress-related factors, mitochondrial dysfunction-related indicators in each group were measured; the levels of inflammatory factors in serum and kidney tissue of rats were examined. Finally, the expression of proteins related to the TLR4/NF-κB signaling pathway was observed by western blot.

RESULTS

Compared with the CLP + vehicle and CLP + TAK-242 groups, the CLP + TAK-242 group reduced blood urea nitrogen (BUN), creatinine (Cr), cystatin-C (Cys-C), reactive oxygen species (ROS), malondialdehyde (MDA), and inflammatory factors levels (p < 0.01), as well as increased superoxide dismutase (SOD) activity of CLP rats (p < 0.01). Additionally, TAK-242 treatment improved the condition of CLP rats that had glomerular and tubular injuries and mitochondrial disorders (p < 0.01). Further mechanism research revealed that TAK-242 can inhibit the TLR4/NF-κB signaling pathway activated by CLP (p < 0.01). Above indicators after TAK-242 treatment were close to those of the Sham group.

CONCLUSION

TAK-242 can improve oxidative stress, mitochondrial dysfunction, and inflammatory response by inhibiting the activity of TLR4/NF-κB signaling pathway, thereby preventing rats from SA-AKI.

Advances in Traditional Chinese Medicine research in diabetic kidney disease treatment

CONTEXT

Diabetic kidney disease (DKD) is a prominent complication arising from diabetic microangiopathy, and its prevalence and renal impact have placed it as the primary cause of end-stage renal disease. Traditional Chinese Medicine (TCM) has the distinct advantage of multifaceted and multilevel therapeutic attributes that show efficacy in improving clinical symptoms, reducing proteinuria, protecting renal function, and slowing DKD progression. Over recent decades, extensive research has explored the mechanisms of TCM for preventing and managing DKD, with substantial studies that endorse the therapeutic benefits of TCM compounds and single agents in the medical intervention of DKD.

OBJECTIVE

This review lays the foundation for future evidence-based research efforts and provide a reference point for DKD investigation.

METHODS

The relevant literature published in Chinese and English up to 30 June 2023, was sourced from PubMed, Cochrane Library, VIP Database for Chinese Technical Periodicals (VIP), Wanfang Data, CNKI, and China Biology Medicine disc (CBM). The process involved examining and summarizing research on TCM laboratory tests and clinical randomized controlled trials for DKD treatment.

RESULTS AND CONCLUSIONS

The TCM intervention has shown the potential to inhibit the expression of inflammatory cytokines and various growth factors, lower blood glucose levels, and significantly affect insulin resistance, lipid metabolism, and improved renal function. Furthermore, the efficacy of TCM can be optimized by tailoring personalized treatment regimens based on the unique profiles of individual patients. We anticipate further rigorous and comprehensive clinical and foundational investigations into the mechanisms underlying the role of TCM in treating DKD.

Research progress on the role of extracellular vesicles in the pathogenesis of diabetic kidney disease

Diabetic kidney disease (DKD) is a serious complication of diabetes mellitus (DM) and has become the main cause of end-stage renal disease worldwide. In recent years, with the increasing incidence of DM, the pathogenesis of DKD has received increasing attention. The pathogenesis of DKD is diverse and complex. Extracellular vesicles (EVs) contain cell-derived membrane proteins, nucleic acids (such as DNA and RNA) and other important cellular components and are involved in intercellular information and substance transmission. In recent years, an increasing number of studies have confirmed that EVs play an important role in the development of DKD. The purpose of this paper is to explain the potential diagnostic value of EVs in DKD, analyze the mechanism by which EVs participate in intercellular communication, and explore whether EVs may become drug carriers for targeted therapy to provide a reference for promoting the implementation and application of exosome therapy strategies in clinical practice.

Metformin attenuates PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway in proximal renal tubular epithelial cells

The harmful effects of PM2.5 on human health, including an increased risk of chronic kidney disease (CKD), have raised a lot of attention, but the underlying mechanisms are unclear. We used the Shanghai Meteorological and Environmental Animal Exposure System (Shanghai-METAS) to simulate the inhalation of PM2.5 in the real environment and established an animal model by exposing C57BL/6 mice to filtered air (FA) and Particulate Matter (PM2.5) for 8 weeks. PM2.5 impaired the renal function of the mice, and the renal tubules underwent destructive changes. Analysis of NHANES data showed a correlation between reduced kidney function and higher blood levels of PM2.5 components, polychlorinated biphenyls (PCBs) and dioxins, which are Aryl hydrocarbon Receptor (AhR) ligands. PM2.5 exposure induced higher levels of AhR and CYP1A1 and oxidative stress as evidenced by the higher levels of ROS, MDA, and GSSG in kidneys of mice. PM2.5 exposure led to AhR overexpression and nuclear translocation in proximal renal tubular epithelial cells. Inhibition of AhR reduced CYP1A1 expression and PM2.5-increased levels of ROS, MDA and GSSG. Our study suggested metformin can mitigate PM2.5-induced oxidative stress by inhibiting the AhR/CYP1A1 pathway. These findings illuminated the role of AhR/CYP1A1 pathway in PM2.5-induced kidney injury and the protective effect of metformin on PM2.5-induced cellular damage, offering new insights for air pollution-related renal diseases.

Histone deacetylases: Regulation of vascular homeostasis via endothelial cells and vascular smooth muscle cells and the role in vascular pathogenesis

Histone deacetylases (HDACs) are proteases that play a key role in chromosome structural modification and gene expression regulation, and the involvement of HDACs in cancer, the nervous system, and the metabolic and immune system has been well reviewed. Our understanding of the function of HDACs in the vascular system has recently progressed, and a significant variety of HDAC inhibitors have been shown to be effective in the treatment of vascular diseases. However, few reviews have focused on the role of HDACs in the vascular system. In this study, the role of HDACs in the regulation of the vascular system mainly involving endothelial cells and vascular smooth muscle cells was discussed based on recent updates, and the role of HDACs in different vascular pathogenesis was summarized as well. Furthermore, the therapeutic effects and prospects of HDAC inhibitors were also addressed in this review.

Beyond hemoglobin: Critical role of 2,3-bisphosphoglycerate mutase in kidney function and injury

AIM

2,3-bisphosphoglycerate mutase (BPGM) is traditionally recognized for its role in modulating oxygen affinity to hemoglobin in erythrocytes. Recent transcriptomic analyses, however, have indicated a significant upregulation of BPGM in acutely injured murine and human kidneys, suggesting a potential renal function for this enzyme. Here we aim to explore the physiological role of BPGM in the kidney.

METHODS

A tubular-specific, doxycycline-inducible Bpgm-knockout mouse model was generated. Histological, immunofluorescence, and proteomic analyses were conducted to examine the localization of BPGM expression and the impact of its knockout on kidney structure and function. In vitro studies were performed to investigate the metabolic consequences of Bpgm knockdown under osmotic stress.

RESULTS

BPGM expression was localized to the distal nephron and was absent in proximal tubules. Inducible knockout of Bpgm resulted in rapid kidney injury within 4 days, characterized by proximal tubular damage and tubulointerstitial fibrosis. Proteomic analyses revealed involvement of BPGM in key metabolic pathways, including glycolysis, oxidative stress response, and inflammation. In vitro, Bpgm knockdown led to enhanced glycolysis, decreased reactive oxygen species elimination capacity under osmotic stress, and increased apoptosis. Furthermore, interactions between nephron segments and immune cells in the kidney suggested a mechanism for propagating stress signals from distal to proximal tubules.

CONCLUSION

BPGM fulfills critical functions beyond the erythrocyte in maintaining glucose metabolism in the distal nephron. Its absence leads to metabolic imbalances, increased oxidative stress, inflammation, and ultimately kidney injury.

The Traditional Chinese Medicine in Treating Diabetic Nephropathy: A Bibliometric Analysis

Background

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus, causing a serious economic burden worldwide. Traditional Chinese Medicine (TCM) is playing an increasingly important role in the treatment of DN. The purpose of this study was to comprehend the main themes and developments in relevant research throughout the last 11 years.

Methods

We looked for publications in the Web of Science Core Collection database (WOS) and the Chinese National Knowledge Infrastructure (CNKI) between 2013 and 2024. CiteSpace 6.3.R1 software was used to analyze the co-authorship of countries/regions, organizations, and co-occurrence of keywords. In addition, burst detection was applied to predict research hotspots and future trends.

Results

A total of 530 articles were included. The overall trend of published articles is increasing. China is the country with the highest number of publications and the highest impact. The research institutions are relatively scattered, with Beijing University of Traditional Chinese Medicine having the highest number of publications. The cooperation among institutions is mainly between universities of traditional Chinese medicine and their affiliated hospitals, and the cross-regional cooperation is not common. The research hotspots are the efficacy of TCM on DN and its mechanism of action, the exploration of TCM and formulas related to the treatment of DN, and the identification and typing of DN in TCM. The research frontiers lie in the control of oxidative stress and the effects of TCM on gut microbiota. In addition, the use of network pharmacology to explore the targets of Chinese herbal formulas for the treatment of this disease has also become popular.

Conclusion

TCM provides more possibilities for the treatment of DN. Researchers can refer to the research hotspots and trends in this paper for future research direction, on the one hand, they can focus on the study of the clinical efficacy of TCM and its improvement of renal function, on the other hand, they can also start from the pharmacological mechanism of TCM for the treatment of DN. Among them, improving oxidative stress in human body and regulating gut microbiota are the directions that can be studied.

Association of dietary antioxidant indices with kidney function indicators in patients with type 2 diabetes: a cross-sectional study

This cross-sectional study investigated the relationship between dietary antioxidant indices and kidney function indicators in 240 outpatient adults with type 2 diabetes. Dietary intake was assessed using three 24-h dietary recalls. Dietary total antioxidant capacity (DTAC), dietary antioxidant index (DAI), and dietary antioxidant quality score (DAQS) were obtained. Indicators of kidney function, including serum creatinine, urea, blood urea nitrogen (BUN), and glomerular filtration rate (GFR), were extracted from medical records. After adjustment, the highest DAI tertile had lower serum creatinine (0.98 ± 0.27 vs 1.03 ± 0.32 mg/dL, P < 0.001), reduced urea (30.97 ± 8.75 vs 34.07 ± 14.45 mg/dL, P = 0.005), and higher GFR (85.16 ± 29.43 vs 74.16 ± 22.18 ml/min per 1·73 m2, P < 0.001) compared to the lowest tertile. The results of logistic regression analysis indicated a borderline significant inverse association of serum urea > 20 mg/dl with DTAC (odds ratio (OR):0.28; 95% CI: 0.07-1.09; Ptrend = 0.06). Multivariable linear regression analysis revealed a significant aligned correlation between DAQs and GFR (β: 0.20; P-value: 0.005) and a marginally significant direct relationship between DAI and GFR (β: 0.14; P-value: 0.06). However, no significant association was observed for DTAC with GFR (β:-0.02; P-value: 0.80). Diets with higher antioxidant capacity may be linked to improved kidney function in type 2 diabetes but our results did not support this strongly.

Metformin and vitamin D combination therapy ameliorates type 2 diabetes mellitus-induced renal injury in male Wistar rats

Diabetic kidney disease is a major microvascular diabetes mellitus (DM) complication clinically associated with a gradual renal function decline. Although metformin is a common drug for managing DM, however, monotherapy treatment with any antidiabetic drug will necessitate dosage increment since type 2 DM (T2DM) deteriorates over time due to the increasing pancreatic β-cell dysfunction and will eventually require a combination therapy approach with another antidiabetic medication. Vitamin D is a food supplement that has been proven to have antidiabetic and reno-protective activities. Hence, we explore the combination of vitamin D and metformin on T2DM-induced renal dysfunction. Thirty male Wistar rats were randomized into five (5) groups: control, diabetes untreated, diabetics treated with metformin, vitamin D, and vitamin D + metformin. Vitamin D and metformin significantly reversed DM-induced hyperglycemia, electrolyte imbalance, and dyslipidemia. Also, vitamin D and metformin reversed T2DM-induced increase in serum creatinine and urea and renal lactate, LDH, and oxido-inflammatory response. These observed alterations were accompanied by an increase in proton pump activities and modulation of Nrf2/Nf-κB and XO/UA signaling. This study revealed that vitamin D and/or metformin ameliorated T2DM-induced renal injury.

Significance of Programmed Cell Death Pathways in Neurodegenerative Diseases

Programmed cell death (PCD) is a form of cell death distinct from accidental cell death (ACD) and is also referred to as regulated cell death (RCD). Typically, PCD signaling events are precisely regulated by various biomolecules in both spatial and temporal contexts to promote neuronal development, establish neural architecture, and shape the central nervous system (CNS), although the role of PCD extends beyond the CNS. Abnormalities in PCD signaling cascades contribute to the irreversible loss of neuronal cells and function, leading to the onset and progression of neurodegenerative diseases. In this review, we summarize the molecular processes and features of different modalities of PCD, including apoptosis, necroptosis, pyroptosis, ferroptosis, cuproptosis, and other novel forms of PCD, and their effects on the pathogenesis of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), multiple sclerosis (MS), traumatic brain injury (TBI), and stroke. Additionally, we examine the key factors involved in these PCD signaling pathways and discuss the potential for their development as therapeutic targets and strategies. Therefore, therapeutic strategies targeting the inhibition or facilitation of PCD signaling pathways offer a promising approach for clinical applications in treating neurodegenerative diseases.

The Use of Kidney Biomarkers, Nephrin and KIM-1, for the Detection of Early Glomerular and Tubular Damage in Patients with Acromegaly: A Case-Control Pilot Study

BACKGROUND

Acromegaly is a rare disorder caused by excessive growth hormone (GH) secreted from a pituitary tumor. High levels of GH and insulin growth factor-1 can lead to renal hypertrophy, as well as to diabetes mellitus and hypertension, which negatively impact kidney function. It is believed that high GH may also be involved in the onset of diabetic nephropathy, the main cause of end-stage kidney disease in developed countries.

MATERIAL AND METHODS

This case-control study was conducted on 23 acromegalic patients and on a control group represented by 21 healthy subjects. The following parameters were determined for all the subjects: serum creatinine, serum urea, estimated glomerular filtration rate (eGFR), urinary albumin/creatinine ratio (UACR), nephrin and kidney injury molecule 1 (KIM-1).

RESULTS

Patients with acromegaly showed higher levels of UACR and lower levels of eGFR as compared to healthy subjects. No significant correlations were found between clinical or biochemical parameters associated with acromegaly and nephrin or KIM-1.

CONCLUSIONS

There was no glomerular or proximal tubular damage at the time of the study, as proven by the normal levels of the biomarkers nephrin and KIM-1. Studies including more patients with uncontrolled disease are needed to clarify the utility of nephrin and KIM-1 for the detection of early kidney involvement in acromegalic patients.

Advanced glycation end products and reactive oxygen species: uncovering the potential role of ferroptosis in diabetic complications

Advanced glycation end products (AGEs) are a diverse range of compounds that are formed when free amino groups of proteins, lipids, and nucleic acids are carbonylated by reactive carbonyl species or glycosylated by reducing sugars. Hyperglycemia in patients with diabetes can cause an overabundance of AGEs. Excess AGEs are generally acknowledged as major contributing factors to the development of diabetic complications because of their ability to break down the extracellular matrix directly and initiate intracellular signaling pathways by binding to the receptor for advanced glycation end products (RAGE). Inflammation and oxidative stress are the two most well-defined pathophysiological states induced by the AGE-RAGE interaction. In addition to oxidative stress, AGEs can also inhibit antioxidative systems and disturb iron homeostasis, all of which may induce ferroptosis. Ferroptosis is a newly identified contributor to diabetic complications. This review outlines the formation of AGEs in individuals with diabetes, explores the oxidative damage resulting from downstream reactions of the AGE-RAGE axis, and proposes a novel connection between AGEs and the ferroptosis pathway. This study introduces the concept of a vicious cycle involving AGEs, oxidative stress, and ferroptosis in the development of diabetic complications.

Natural polysaccharides as promising reno-protective agents for the treatment of various kidney injury

Renal injury, a prevalent clinical outcome with multifactorial etiology, imposes a substantial burden on society. Currently, there remains a lack of effective management and treatments. Extensive research has emphasized the diverse biological effects of natural polysaccharides, which exhibit promising potential for mitigating renal damage. This review commences with the pathogenesis of four common renal diseases and the shared mechanisms underlying renal injury. The renoprotective roles of polysaccharides in vivo and in vitro are summarized in the following five aspects: anti-oxidative stress effects, anti-apoptotic effects, anti-inflammatory effects, anti-fibrotic effects, and gut modulatory effects. Furthermore, we explore the structure-activity relationship and bioavailability of polysaccharides in relation to renal injury, as well as investigate their utility as biomaterials for alleviating renal injury. The clinical experiments of polysaccharides applied to patients with chronic kidney disease are also reviewed. Broadly, this review provides a comprehensive perspective on the research direction of natural polysaccharides in the context of renal injury, with the primary aim to serve as a reference for the clinical development of polysaccharides as pharmaceuticals and prebiotics for the treatment of kidney diseases.

PDK4-mediated Nrf2 inactivation contributes to oxidative stress and diabetic kidney injury

Diabetic kidney disease (DKD) is often featured with redox dyshomeostatis. Pyruvate dehydrogenase kinase 4 (PDK4) is the hub for DKD development. However, the mechanism by which PDK4 mediates DKD is poorly understood. The current work aimed to elucidate the relationship between PDK4 and DKD from the perspective of redox manipulation. Oxidative stress was observed in the human proximal tubular cell line (HK-2 cells) treated with a high concentration of glucose and palmitic acid (HGL). The mechanistic study showed that PDK4 could upregulate Kelch-like ECH-associated protein 1 (Keap1) in HGL-treated HK-2 cells through the suppression of autophagy, resulting in the depletion of nuclear factor erythroid 2-related factor 2 (Nrf2), the master regulator of redox homeostasis. At the cellular level, pharmacological inhibition or genetic knockdown of PDK4 could boost Nrf2, followed by the increase of a plethora of antioxidant enzymes and ferroptosis-suppression enzymes. Meanwhile, the inhibition or knockdown of PDK4 remodeled iron metabolism, further mitigating oxidative stress and lipid peroxidation. The same trend was observed in the DKD mice model. The current work highlighted the role of PDK4 in the development of DKD and suggested that PDK4 might be a promising target for the management of DKD.

Furanodienone induces apoptosis via regulating the PRDX1/MAPKs/p53/caspases signaling axis through NOX4-derived mitochondrial ROS in colorectal cancer cells

Furanodienone, a biologically active constituent of sesquiterpenes isolated from Rhizome Curcumae, has been reported to induce apoptosis in human colorectal cancer (CRC) cells by promoting the generation of reactive oxygen species (ROS). However, the source of ROS and how it manipulates apoptosis in CRC cells remains to be elucidated. Herein, we assessed the potential role of the well-known sources of intracellular ROS-mitochondrial electron transport chain and the nicotinamide adenine dinucleotide phosphate oxidases (NOXs), on furanodienone-induced cell death. The results indicated that furanodienone substantially increased the levels of mitochondrial ROS, which were subsequently eliminated by the general NOX inhibitor. Specifically, the nuclear factor kappa-B (NF-κB) translocation triggered a significant rise in the expression of NOX4, an isoform of the NOXs family, upon furanodienone treatment. Nevertheless, the specific NOX4 inhibitor GLX351322 attenuated cell apoptosis and mitochondrial ROS production. As a result, ROS burst induced by furanodienone suppressed the expression of peroxiredoxin1 (PRDX1), a redox signaling protein overexpressed in CRC cells, through a nuclear factor-erythroid-2-related factor 2 (Nrf2)-dependent pathway, thus amplifying the mitogen-activated protein kinases (MAPKs)/p53-mediated apoptotic signaling by increasing the p-p38, p-JNK levels, as well as the cleaved caspases -3, -8 and -9. In vivo experiments further confirmed the anti-proliferative impact of PRDX1 following furanodienone treatment. In summary, the study demonstrated that furanodienone-induced apoptosis in CRC cells is initiated by mitochondrial ROS derived from NOX4, which targeted the PRDX1 and activated the downstream MAPKs/p53-mediated caspase-dependent signaling pathway. Our findings may provide novel insights into the development of adjuvant drugs for CRC treatment and therapeutic applications.

The main molecular mechanisms of ferroptosis and its role in chronic kidney disease

The term ferroptosis, coined in 2012, has been widely applied in various disease research fields. Ferroptosis is a newly regulated form of cell death distinct from apoptosis, necrosis, and autophagy, the mechanisms of which have been extensively studied. Chronic kidney disease, characterized by renal dysfunction, is a common disease severely affecting human health, with its occurrence and development influenced by multiple factors and leading to dysfunction in multiple systems. It often lacks obvious clinical symptoms in the early stages, and thus, diagnosis is typically made in the later stages, complicating treatment. While research on ferroptosis and acute kidney injury has made continuous progress, studies on the association between ferroptosis and chronic kidney disease remain limited. This review aims to summarize chronic kidney disease, investigate the mechanism and regulation of ferroptosis, and attempt to elucidate the role of ferroptosis in the occurrence and development of chronic kidney disease.

Role of GDF-15 in diabetic nephropathy: mechanisms, diagnosis, and therapeutic potential

PURPOSE

Growth differentiation factor 15 (GDF-15) is a cytokine involved in regulating homeostasis, and its expression is up-regulated in response to injury, stress, and inflammation. This study explored the role of GDF-15 in diabetic nephropathy (DN), a severe complication of diabetes mellitus, and its potential as a biomarker for disease progression.

METHODS

As a member of the transforming growth factor-β superfamily, GDF-15 exhibits its renal protective functions primarily through its anti-inflammatory effects and the up-regulation of other renal protective factors. This study evaluated the association between circulating GDF-15 levels and DN progression, examining the underlying mechanisms.

RESULTS

Circulating GDF-15 levels are closely linked to the development and progression of DN. While existing research has yielded some consistent conclusions, a comprehensive understanding of the role of GDF-15 in DN pathogenesis is needed to identify new therapeutic targets and strategies.

CONCLUSION

GDF-15 has the potential to be a prognostic and diagnostic biomarker for DN. It is crucial to establish appropriate reference ranges and explore their clinical utility in routine practice for validating the role of GDF-15 in DN management. Further interventional studies are required to confirm its clinical value in diagnosing and predicting the progression of DN.

Gut microbiota-derived indole-3-propionic acid alleviates diabetic kidney disease through its mitochondrial protective effect via reducing ubiquitination mediated-degradation of SIRT1

INTRODUCTION

Gut microbes and their metabolites play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, which one and how specific gut-derived metabolites affect the progression of DKD remain largely unknown.

OBJECTIVES

This study aimed to investigate the potential roles of indole-3-propionic acid (IPA), a microbial metabolite of tryptophan, in DKD.

METHODS

Metagenomic sequencing was performed to analyze the microbiome structure in DKD. Metabolomics screening and validation were conducted to identify characteristic metabolites associated with DKD. The protective effect of IPA on DKD glomerular endothelial cells (GECs) was assessed through in vivo and in vitro experiments. Further validation via western blot, immunoprecipitation, gene knockout, and site-directed mutation elucidated the mechanism of IPA on mitochondrial injury.

RESULTS

Alterations in gut microbial community structure and dysregulated tryptophan metabolism were evident in DKD mice. Serum IPA levels were significantly reduced in DKD patients and correlated with fasting blood glucose, HbA1c, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR). IPA supplementation ameliorated albuminuria, bolstered the integrity of the glomerular filtration barrier, and mitigated mitochondrial impairments in GECs. Mechanistically, IPA hindered SIRT1 phosphorylation-mediated ubiquitin-proteasome degradation, restoring SIRT1's role in promoting PGC-1α deacetylation and nuclear translocation, thereby upregulating genes associated with mitochondrial biosynthesis and antioxidant defense.

CONCLUSION

Our findings underscore the potential of the microbial metabolite IPA to attenuate DKD progression, offering novel insights and potential therapeutic strategies for its management.

Phenylsulfate-induced oxidative stress and mitochondrial dysfunction in podocytes are ameliorated by Astragaloside IV activation of the SIRT1/PGC1α /Nrf1 signaling pathway

Astragaloside IV (AS-IV) exhibits diverse biological activities. Despite this, the detailed molecular mechanisms by which AS-IV ameliorates diabetic nephropathy (DN) and shields podocytes from oxidative stress (OS) and mitochondrial dysfunction remain poorly understood. In this study, we used biochemical assays, histopathological analysis, Doppler ultrasound, transmission electron microscopy，flow cytometry, fluorescence staining, and Western blotting and other methods. AS-IV was administered to db/db mice for in vivo experimentation. Our findings indicated that AS-IV treatment significantly reduced diabetes-associated markers, proteinuria, and kidney damage. It also diminished ROS levels in the kidney, enhanced the expression of endogenous antioxidant enzymes, and improved mitochondrial health. Phenyl sulfate (PS), a protein-bound uremic solute of enteric origin, has been closely linked with DN and represents a promising avenue for further research. In vitro, PS exposure induced OS and mitochondrial dysfunction in podocytes, increasing ROS levels while decreasing antioxidant enzyme activity (Catalase, Heme Oxygenase-1, Superoxide Dismutase, and Glutathione Peroxidase). ROS inhibitors (N-acetyl-L-cysteine, NAC) as the positive control group can significantly reduce the levels of ROS and restore antioxidant enzymes protein levels. Additionally, PS reduced markers associated with mitochondrial biosynthesis and function (SIRT1, PGC1α, Nrf1, and TFAM). These adverse effects were partially reversed by AS-IV treatment. However, co-treatment with AS-IV and the SIRT1 inhibitor EX527 failed to restore these indicators. Overall, our study demonstrates that AS-IV effectively attenuates DN and mitigates PS-induced OS and mitochondrial dysfunction in podocytes via the SIRT1/PGC1α/Nrf1 pathway.

The role of PI3K/Akt signaling pathway in chronic kidney disease

Chronic kidney disease (CKD), including chronic glomerulonephritis, IgA nephropathy and diabetic nephropathy, are common chronic diseases characterized by structural damage and functional decline of the kidneys. The current treatment of CKD is symptom relief. Several studies have reported that the phosphatidylinositol 3 kinases (PI3K)/protein kinase B (Akt) signaling pathway is a pathway closely related to the pathological process of CKD. It can ameliorate kidney damage by inhibiting this signal pathway which is involved with inflammation, oxidative stress, cell apoptosis, epithelial mesenchymal transformation (EMT) and autophagy. This review highlights the role of activating or inhibiting the PI3K/Akt signaling pathway in CKD-induced inflammatory response, apoptosis, autophagy and EMT. We also summarize the latest evidence on treating CKD by targeting the PI3K/Akt pathway, discuss the shortcomings and deficiencies of PI3K/Akt research in the field of CKD, and identify potential challenges in developing these clinical therapeutic CKD strategies, and provide appropriate solutions.

Aerobic training increases renal antioxidant defence and reduces angiotensin II levels, mitigating the high mortality in SHR-STZ model

OBJECTVE

The purpose of the research was to investigate the effects of aerobic training on renal function, oxidative stress, intrarenal renin-angiotensin system, and mortality of hypertensive and diabetic (SHR-STZ) rats.

MATERIALS AND METHODS

Blood pressure, creatinine, urea levels, urinary glucose, urine volume, and protein excretion were reduced in trained SHR-STZ rats.

RESULTS

Aerobic training not only attenuated oxidative stress but also elevated the activity of antioxidant enzymes in the kid'ney of SHR-STZ rats. Training increased intrarenal levels of angiotensin-converting enzymes (ACE and ACE2) as well as the neprilysin (NEP) activity, along with decreased intrarenal angiotensin II (Ang II) levels. Aerobic training significantly improved the survival of STZ-SHR rats.

CONCLUSION

The protective role of aerobic training was associated with improvements in the renal antioxidative capacity, reduced urinary protein excretion along with reduced intrarenal Ang II and increased NEP activity. These findings might reflect a better survival under the combined pathological conditions, hypertension, and diabetes.

Tirzepatide alleviates oxidative stress and inflammation in diabetic nephropathy via IL-17 signaling pathway

Oxidative stress (OS) and inflammation play essential roles in the development of diabetic nephropathy (DN). Tirzepatide (TZP) has a protective effect in diabetes. However, its underlying mechanism in DN remains unclear. DN model mice were induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg), followed by administration of different doses of TZP (3 and 10 nmol/kg) via intraperitoneal injection for 8 weeks. The effects of TZP on DN were evaluated by detecting DN-related biochemical indicators, kidney histopathology, apoptosis, OS, and inflammation levels. Additionally, to further reveal the potential mechanism, we investigated the role of TZP in modulating the IL-17 pathway. TZP reduced serum creatinine (sCR), blood urea nitrogen (BUN), and advanced glycosylation end products (AGEs) levels, while simultaneously promoting insulin secretion in diabetic mice. Additionally, TZP attenuated tubular and glomerular injury and reduced renal apoptosis levels. Further studies found that TZP increased the levels of SOD and CAT, and decreased MDA. Meanwhile, TZP also reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in both mouse serum and kidney homogenates. TZP effectively inhibited the IL-17 pathway, and subsequent intervention with an IL-17 pathway agonist (IL-17A) reversed the suppressive effects of TZP on OS and inflammation. TZP can improve DN by inhibiting OS and inflammation through the suppression of the IL-17 pathway.

Molecular mechanisms and therapeutic potential of natural flavonoids in diabetic nephropathy: Modulation of intracellular developmental signaling pathways

Recognized as a common microvascular complication of diabetes mellitus (DM), diabetic nephropathy (DN) is the principal cause of chronic end-stage renal disease (ESRD). Patients with diabetes have an approximately 25% risk of developing progressive renal disease. The underlying principles of DN control targets the dual outcomes of blood glucose regulation through sodium glucose cotransporter 2 (SGLT 2) blockade and hypertension management through renin-angiotensin-aldosterone inhibition. However, these treatments are ineffective in halting disease progression to kidney failure and cardiovascular comorbidities. Recently, the dysregulation of subcellular signaling pathways has been increasingly implicated in DN pathogenesis. Natural compounds are emerging as effective and side-effect-free therapeutic agents that target intracellular pathways. This narrative review synthesizes recent insights into the dysregulation of maintenance pathways in DN, drawing from animal and human studies. To compile this review, articles reporting DN signaling pathways and their treatment with natural flavonoids were collected from PubMed, Cochrane Library Web of Science, Google Scholar and EMBASE databases since 2000. As therapeutic interventions are frequently based on the results of clinical trials, a brief analysis of data from current phase II and III clinical trials on DN is discussed.

Modified Citrus Pectin (MCP) Confers a Renoprotective Effect on Early-Stage Nephropathy in Type-2 Diabetic Mice

Diabetic nephropathy (DN) is a significant global health concern with a high morbidity rate. Accumulating evidence reveals that Galectin-3 (Gal-3), a β-galactoside-binding lectin, is a biomarker in kidney diseases. Our study aimed to assess the advantageous impacts of modified citrus pectin (MCP) as an alternative therapeutic strategy for the initial and ongoing progression of DN in mice with type 2 diabetes mellitus (T2DM). The animal model has been split into four groups: control group, T2DM group (mice received intraperitoneal injections of nicotinamide (NA) and streptozotocin (STZ), T2DM+MCP group (mice received 100 mg/kg/day MCP following T2DM induction), and MCP group (mice received 100 mg/kg/day). After 4 weeks, kidney weight, blood glucose level, serum kidney function tests, histopathological structure alterations, oxidative stress, inflammation, apoptosis, and fibrosis parameters were determined in renal tissues. Our findings demonstrated that MCP treatment reduced blood glucose levels, renal histological damage, and restored kidney weight and kidney function tests. Additionally, MCP reduced malondialdehyde level and restored glutathione level, and catalase activity. MCP demonstrated a notable reduction in inflammatory and apoptosis mediators TNF-α, iNOS, TGF-βRII and caspase-3. Overall, MCP could alleviate renal injury in an experimental model of DN by suppressing renal oxidative stress, inflammation, fibrosis, and apoptosis mediators.

Pioglitazone ameliorates ischemia/reperfusion-induced acute kidney injury via oxidative stress attenuation and NLRP3 inflammasome

Acute kidney injury (AKI) induced by renal ischemia/reperfusion injury (IRI) is a severe clinical condition. ROS accumulation, antioxidant pathways deficiency, and inflammation are involved in IRI. Pioglitazone (Pio) exerts anti-inflammatory and antioxidant effects. The aim of this study was to explore the protective effects of pioglitazone against IRI-induced AKI. Pathogen-free Sprague-Dawley (SD) rats were arbitrarily divided into four groups: Sham operation group Control (CON) group, CON + Pio group, I/R + Saline group, and I/R + Pio group. In addition, HK-2 cells were subjected to hypoxia and reoxygenation to develop an H/R model for investigation of the protective mechanism of Pio. Pretreatment with pioglitazone in the model rats reduced urea nitrogen and creatinine levels, histopathological scores, and cytotoxicity after IRI. Pioglitazone treatment significantly attenuated renal cell apoptosis, decreased cytotoxicity, increased Bcl-2 expression, and downregulated Bax expression. Besides, the levels of ROS and inflammatory factors, including NLRP3, ASC, pro-IL-1β, pro-caspase-1, cleaved-caspase-1, TNF-α, IL-6, and IL-1β, in I/R rats and H/R cells were normalized by the pioglitazone treatment. Pioglitazone improved IRI-induced AKI by attenuating oxidative stress and NLRP3 inflammasome activation. Therefore, pioglitazone has the potential to serve as a novel agent for renal IRI treatment and prevention.

Advances of Iron and Ferroptosis in Diabetic Kidney Disease

Diabetes mellitus presents a significant threat to human health because it disrupts energy metabolism and gives rise to various complications, including diabetic kidney disease (DKD). Metabolic adaptations occurring in the kidney in response to diabetes contribute to the pathogenesis of DKD. Iron metabolism and ferroptosis, a recently defined form of cell death resulting from iron-dependent excessive accumulation of lipid peroxides, have emerged as crucial players in the progression of DKD. In this comprehensive review, we highlight the profound impact of adaptive and maladaptive responses regulating iron metabolism on the progression of kidney damage in diabetes. We summarize the current understanding of iron homeostasis and ferroptosis in DKD. Finally, we propose that precise manipulation of iron metabolism and ferroptosis may serve as potential strategies for kidney management in diabetes.

Proteomics coupled transcriptomics reveals Slc34a1 and Slc34a3 downregulation as potential features of nephrotoxin-induced acute kidney injury

Acute kidney injury (AKI) stands as a prevalent and economically burdensome condition worldwide, yet its complex molecular mechanisms remain incompletely understood. To address this gap, our study employs a multifaceted approach, combining mass spectrometry and RNA sequencing technologies, to elucidate the intricate molecular landscape underlying nephrotoxin-induced AKI in mice by cisplatin- and LPS-induced. By examining the protein and RNA expression profiles, we aimed to uncover novel insights into the pathogenesis of AKI and identify potential diagnostic and therapeutic targets. Our results demonstrate significant down-regulation of Slc34a1 and Slc34a3, shedding light on their crucial roles in AKI pathology and highlighting their promise as actionable targets for diagnosis and treatment. This comprehensive analysis not only enhances our understanding of AKI pathophysiology but also offers valuable avenues for the development of targeted interventions to mitigate its clinical impact. SIGNIFICANCE: Nephrotoxicity acute kidney injury (AKI) is a common clinical condition whose pathogenesis is the process by which some drugs, chemicals or other factors cause damage to the kidneys, resulting in impaired kidney function. Although it has been proved that different nephrotoxic substances can affect the kidney through different pathways, whether they have a commonality has not been registered. Here, we combined transcriptomics and proteomics to study the molecular mechanism of LPS and cisplatin-induced nephrotoxic acute kidney injury finding that the down-regulation of Slc34a1 and Slc34a3 may be a critical link in nephrotoxic acute kidney injury, which can be used as a marker for its early diagnosis.

Hormonal regulation in diabetes: Special emphasis on sex hormones and metabolic traits

Diabetes constitutes a significant global public health challenge that is rapidly reaching epidemic proportions. Among the non-communicable diseases, the incidence of diabetes is rising at an alarming rate. The International Diabetes Federation has documented a 9.09% prevalence of diabetes among individuals aged between 20 and 79 years. The interplay of gonadal hormones and gender differences is critical in regulating insulin sensitivity and glucose tolerance, and this dynamic is particularly crucial because of the escalating incidence of diabetes. Variations in insulin sensitivity are observed across genders, levels of adiposity, and age groups. Both estrogen and testosterone are seen to influence glucose metabolism and insulin sensitivity. This chapter surveys the present knowledge of sex differences, sex hormones, and chromosomes on insulin imbalance and diabetes development. It further highlights the influence of metabolic traits in diabetes and changes in sex hormones during diabetic pregnancy. Notably, even stressful lifestyles have been acknowledged to induce hormonal imbalances. Furthermore, it discusses the potential of hormonal therapy to help stabilize sex hormones in diabetic individuals and focuses on the most recent research investigating the correlation between sex hormones and diabetes.

The impact of chitooligosaccharides with a certain degree of polymerization on diabetic nephropathic mice and high glucose-damaged HK-2 cells

Diabetic nephropathy (DN) is a primary diabetic complication ascribed to the pathological changes in renal microvessels. This study investigated the nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch ECH associating protein (Keap1)/antioxidant response element (ARE) signaling pathway impact of chitooligosaccharides (COS) with a certain degree of polymerization (DP) on DN mouse models and high glucose-damaged human kidney 2 (HK-2) cells. The findings indicated that COS effectively reduced the renal function indexes (uric acid [UA], urinary albumin excretion rate [UAER], urine albumin-to-creatinine ratio [UACR], blood urea nitrogen [BUN], and creatinine [Cre]) of DN mice. It increased (p < .05) the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) antioxidant enzyme activity in the serum and kidneys, and decreased (p < .05) the malondialdehyde (MDA) content. The mechanistic investigation showed that COS significantly increased (p < .05) Nrf2 and downstream target gene (GCLM, GCLC, HO-1, and NQO-1) expression, and substantially decreased (p < .05) Keap1 expression. The protein level was consistent with the messenger RNA (mRNA) level in in vitro and in vivo models. The docking data indicated that COS and Keap1 protein binding included six hydrogen bond formation processes (Gly364, Arg415, Arg483, His436, Ser431, and Arg380). The COS intervention mechanism may be related to the Nrf2/Keap1/ARE antioxidant pathway. Therefore, it provides a scientific basis for COS application in developing special medical food for DN patients.

Study on the mechanisms by which pumpkin polysaccharides regulate abnormal glucose and lipid metabolism in diabetic mice under oxidative stress

Pumpkin polysaccharide (PPe-H) can perform physiological functions through its antioxidative and hypoglycemic effects; however, the mechanisms through which PPe-H regulates abnormal glucose and lipid metabolism caused by oxidative stress injury remain unclear. In the present study, streptozotocin was used to generate an acute diabetic mouse model, and the effects of PPe-H on glucose and lipid metabolism impaired by oxidative stress in diabetic mice were studied. PPe-H significantly reduced blood glucose levels and enhanced the oral glucose tolerance of diabetic mice under stress injury (p < 0.05). The analysis of liver antioxidant enzymes showed that PPe-H significantly enhanced the activities of SOD and CAT (p < 0.05), increased the GSH level, and decreased the level of MDA (p < 0.05). Transcriptomic and metabolomic analyses of the liver tissues of mice revealed characteristic differences in the genetic and metabolic levels of the samples, which showed that PPe-H treatment may play a positive role in regulating the metabolism of methionine, cysteine, glycerol phospholipid, and linoleic acid. These results indicated that PPe-H alleviated the symptoms of hyperglycemia by regulating metabolites related to oxidative stress and glycolipid metabolism in diabetic mice.

Association of KLOTHO gene variants with metabolic and renal function parameters in Mexican patients living with type 2 diabetes

Objective

Type 2 diabetes (T2D) and high blood pressure are the main causes of chronic kidney disease (CKD) in adulthood. Both metabolic and oxidative stresses driven by hyperglycemia as well as genetic factors have been suggested as pathogenic causes of renal failure. Some single nucleotide variants (SNVs) on gene coding KLOTHO (KL) have been implicated in several clinical scenarios including hypertension, diabetes, and cardiovascular disease. The aim of this study was to analyze the association of rs1207568 (-395G > A), rs953614 (+ 1062T > G) and rs564481 (+ 1818 C > T) SNVs with metabolic and renal function parameters in Mexican patients living with type 2 diabetes.

Methods

A cross-sectional study was conducted in 637 Mexican patients with T2D, and/or hypertension without previous diagnosis of CKD. Anthropometric, metabolic, and renal function parameters were determined. Patients were genotyped for rs1207568, rs953614 and rs564481 SNVs and associations under a dominant genetic model were analyzed by logistic regression.

Results

For rs9536314, G-allele showed to be protective for hypo-HDL-C, albuminuria, and CKD. Carriers of minor allele of rs564481 had low odds for high glucose levels. No differences in genotype nor allele frequencies between the patients and the reference population were observed.

Conclusion

In Mexican patients living with type 2 diabetes, KL variant rs9536314 was found associated with low odds of hypo-HDL cholesterol, albuminuria and presence of CKD. Meanwhile the consensus of soluble KLOTHO measurement is reached, genetic variants in the KL gene could be considered as genetic markers for CKD susceptibility in patients at high-risk of vascular complications.

The impact of urinary albumin-creatinine ratio and glomerular filtration rate on long-term mortality in patients with heart failure: The National Health and Nutrition Examination Survey 1999-2018

BACKGROUND AND AIMS

The urinary albumin‒creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) are important markers of renal dysfunction, but few studies have simultaneously examined their impact on long-term mortality in patients with heart failure (HF).

METHODS AND RESULTS

This study included patients with HF from the National Health and Nutrition Survey from 1999 to 2018. The fully adjusted Cox proportional risk model was adopted, and propensity score matching (PSM) was also used for risk adjustment. Among 988 patients, a median follow-up of 7.75 years was recorded. A higher UACR corresponded to a higher risk of cardiovascular death (P < 0.001 for trend). No statistically significant difference was found in the trend of eGFR risk stratification on the risk of cardiovascular death (P = 0.09 for trend). After PSM, the results showed that when grouped by UACR, the high-risk group had a higher risk of cardiovascular death regardless of a cutoff value of 30 or 300 mg/g (all P < 0.05). When grouped by eGFR, regardless of a cutoff value of 45 or 30 mL/min/1.73 m2, compared to the low-risk group, the high-risk group did not have a statistically significant increase in cardiovascular death (P = 0.086 and P = 0.093, respectively). The subgroup analysis of the main outcome showed an interaction between the UACR and eGFR (P = 0.044).

CONCLUSIONS

Both the UACR and eGFR are markers for predicting the progression of HF, but the UACR may be a more important indicator than the eGFR, and they synergistically and complementarily reflect the long-term cardiovascular risk of HF patients.

Advancements in diabetic kidney disease management: integrating innovative therapies and targeted drug development

Diabetic kidney disease (DKD) is a leading cause of chronic kidney disease and affects approximately 40% of individuals with diabetes . Cases of DKD continue to rise globally as the prevalence of diabetes mellitus increases, with an estimated 415 million people living with diabetes in 2015 and a projected 642 million by 2040. DKD is associated with significant morbidity and mortality, representing 34% and 36% of all chronic kidney disease deaths in men and women, respectively. Common comorbidities including hypertension and ageing-related nephron loss further complicate disease diagnosis and progression. The progression of DKD involves several mechanisms including glomerular endothelial cell dysfunction, inflammation, and fibrosis. Targeting these mechanisms has formed the basis of several therapeutic agents. Renin-angiotensin-aldosterone system (RAAS) blockers, specifically angiotensin receptor blockers (ARBs), demonstrate significant reductions in macroalbuminuria. Sodium-glucose transporter type 2 (SGLT-2) inhibitors demonstrate kidney protection independent of diabetes control while also decreasing the incidence of cardiovascular events. Emerging agents including glucagon-like peptide 1 (GLP-1) agonists, anti-inflammatory agents like bardoxolone, and mineralocorticoid receptor antagonists show promise in mitigating DKD progression. Many novel therapies including monoclonal antibodies CSL346, lixudebart, and tozorakimab; mesenchymal stem/stromal cell infusion; and cannabinoid-1 receptor inverse agonism via INV-202 are currently in clinical trials and present opportunities for further drug development.

Osthole ameliorates early diabetic kidney damage by suppressing oxidative stress, inflammation and inhibiting TGF-β1/Smads signaling pathway

BACKGROUND

Osthole is a natural active ingredient extracted from the traditional Chinese medicine Cnidium monnieri. It has been demonstrated to have anti-inflammatory, anti-fibrotic, and anti-hyperglycemic properties. However, its effect on diabetic kidney disease (DKD) remains uncertain. This study aims to assess the preventive and therapeutic effects of osthole on DKD and investigate its underlying mechanisms.

METHODS

A streptozotocin/high-fat and high-sucrose diet induced Type 2 diabetic rat model was established. Metformin served as the positive drug control. Diabetic rats were treated with metformin or three different doses of osthole for 8 weeks. Throughout the treatment period, the progression of DKD was assessed by monitoring increases in urinary protein, serum creatinine, urea nitrogen, and uric acid, along with scrutinizing kidney pathology. Enzyme-linked immunosorbent assay (ELISA) was employed to detect inflammatory factors and oxidative stress levels. At the same time, immunohistochemical staining was utilized to evaluate changes in alpha-smooth muscle actin, fibronectin, E-cadherin, and apoptosis. The alterations in TGF-β1/Smads signaling pathway were ascertained through western blot and immunofluorescence. Furthermore, we constructed a high glucose-stimulated HBZY-1 cells model to uncover its molecular protective mechanism.

RESULTS

Osthole significantly reduced fasting blood glucose, insulin resistance, serum creatinine, uric acid, blood urea nitrogen, urinary protein excretion, and glomerular mesangial matrix deposition in diabetic rats. Additionally, significant improvements were observed in inflammation, oxidative stress, apoptosis, and fibrosis levels. The increase of ROS, apoptosis and hypertrophy in HBZY-1 cells induced by high glucose was reduced by osthole. Immunofluorescence and western blot results demonstrated that osthole down-regulated the TGF-β1/Smads signaling pathway and related protein expression.

CONCLUSION

Our findings indicate that osthole exhibits potential preventive and therapeutic effects on DKD. It deserves further investigation as a promising drug for preventing and treating DKD.

Combined use of Panax notoginseng and leech provides new insights into renal fibrosis: Restoration of mitochondrial kinetic imbalance

In this study, we aimed to investigate the protective effects of Panax notoginseng and leech (PL) on renal fibrosis and explore the mechanisms underlying their actions. For this study, we created an adenine-induced renal fibrosis model in SD rats to investigate the protective effect of PL on renal fibrosis and explore its underlying mechanism. Initially, we assessed the renal function in RF rats and found that Scr, BUN, and urine protein content decreased after PL treatment, indicating the protective effect of PL on renal function. Histological analysis using HE and Masson staining revealed that PL reduced inflammatory cell infiltration and decreased collagen fiber deposition in renal tissue. Subsequently, we analyzed the levels of α-SMA, Col-IV, and FN, which are the main components of the extracellular matrix (ECM), using IHC, RT-qPCR, and WB. The results demonstrated that PL was effective in reducing the accumulation of ECM, with PL1-2 showing the highest effectiveness. To further understand the underlying mechanisms, we conducted UPLC-MS/MS analysis on the incoming components of the PL1-2 group. The results revealed several associations between the differential components and antioxidant and mitochondrial functions. This was further confirmed by enzyme-linked immunosorbent assay and biochemical indexes, which showed that PL1-2 ameliorated oxidative stress by reducing ROS and MDA production and increasing GSH and SOD levels. Additionally, transmission electron microscopy results indicated that PL1-2 promoted partial recovery of mitochondrial morphology and cristae. Finally, using RT-qPCR and WB, an increase in the expression of mitochondrial fusion proteins Mfn1, Mfn2, and Opa1 after PL1-2 treatment was observed, coupled with a decline in the expression and phosphorylation of mitochondrial cleavage proteins Fis and Drp1. These findings collectively demonstrate that PL1-2 ameliorates renal fibrosis by reducing oxidative stress and restoring mitochondrial balance.

Coenzyme Q10 eyedrops conjugated with vitamin E TPGS alleviate neurodegeneration and mitochondrial dysfunction in the diabetic mouse retina

Diabetic retinopathy (DR) is a leading cause of blindness and vision impairment worldwide and represents one of the most common complications among diabetic patients. Current treatment modalities for DR, including laser photocoagulation, intravitreal injection of corticosteroid, and anti-vascular endothelial growth factor (VEGF) agents, target primarily vascular lesions. However, these approaches are invasive and have several limitations, such as potential loss of visual function, retinal scars and cataract formation, and increased risk of ocular hypertension, vitreous hemorrhage, retinal detachment, and intraocular inflammation. Recent studies have suggested mitochondrial dysfunction as a pivotal factor leading to both the vascular and neural damage in DR. Given that Coenzyme Q10 (CoQ10) is a proven mitochondrial stabilizer with antioxidative properties, this study investigated the effect of CoQ10 eyedrops [in conjunction with vitamin E d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS)] on DR-induced neurodegeneration using a type 2 diabetes mouse model (C57BLKsJ-db/db mice). Utilizing a comprehensive electroretinography protocol, supported by immunohistochemistry, our results revealed that topical application of CoQ10 eyedrops conjugated with vitamin E TPGS produced a neuroprotective effect against diabetic-induced neurodegeneration by preserving the function and histology of various retinal neural cell types. Compared to the control group, mice treated with CoQ10 exhibited thicker outer and inner nuclear layers, higher densities of photoreceptor, cone cell, and rod-bipolar cell dendritic boutons, and reduced glial reactivity and microglial cell density. Additionally, the CoQ10 treatment significantly alleviated retinal levels of MMP-9 and enhanced mitochondrial function. These findings provide further insight into the role of mitochondrial dysfunction in the development of DR and suggest CoQ10 eyedrops, conjugated with vitamin E TPGS, as a potential complementary therapy for DR-related neuropathy.

Xanthine oxidoreductase inhibition ameliorates high glucose-induced glomerular endothelial injury by activating AMPK through the purine salvage pathway

Xanthine oxidoreductase (XOR) contributes to reactive oxygen species production. We investigated the cytoprotective mechanisms of XOR inhibition against high glucose (HG)-induced glomerular endothelial injury, which involves activation of the AMP-activated protein kinase (AMPK). Human glomerular endothelial cells (GECs) exposed to HG were subjected to febuxostat treatment for 48 h and the expressions of AMPK and its associated signaling pathways were evaluated. HG-treated GECs were increased xanthine oxidase/xanthine dehydrogenase levels and decreased intracellular AMP/ATP ratio, and these effects were reversed by febuxostat treatment. Febuxostat enhanced the phosphorylation of AMPK, the activation of peroxisome proliferator-activated receptor (PPAR)-gamma coactivator (PGC)-1α and PPAR-α and suppressed the phosphorylation of forkhead box O (FoxO)3a in HG-treated GECs. Febuxostat also decreased nicotinamide adenine dinucleotide phosphate oxidase (Nox)1, Nox2, and Nox4 expressions; enhanced superoxide dismutase activity; and decreased malondialdehyde levels in HG-treated GECs. The knockdown of AMPK inhibited PGC-1α-FoxO3a signaling and negated the antioxidant effects of febuxostat in HG-treated GECs. Despite febuxostat administration, the knockdown of hypoxanthine phosphoribosyl transferase 1 (HPRT1) also inhibited AMPK-PGC-1α-FoxO3a in HG-treated GECs. XOR inhibition alleviates oxidative stress by activating AMPK-PGC-1α-FoxO3a signaling through the HPRT1-dependent purine salvage pathway in GECs exposed to HG conditions.

Diabetes and Renal Complications: An Overview on Pathophysiology, Biomarkers and Therapeutic Interventions

Diabetic kidney disease (DKD) is a major microvascular complication of both type 1 and type 2 diabetes. DKD is characterised by injury to both glomerular and tubular compartments, leading to kidney dysfunction over time. It is one of the most common causes of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Persistent high blood glucose levels can damage the small blood vessels in the kidneys, impairing their ability to filter waste and fluids from the blood effectively. Other factors like high blood pressure (hypertension), genetics, and lifestyle habits can also contribute to the development and progression of DKD. The key features of renal complications of diabetes include morphological and functional alterations to renal glomeruli and tubules leading to mesangial expansion, glomerulosclerosis, homogenous thickening of the glomerular basement membrane (GBM), albuminuria, tubulointerstitial fibrosis and progressive decline in renal function. In advanced stages, DKD may require treatments such as dialysis or kidney transplant to sustain life. Therefore, early detection and proactive management of diabetes and its complications are crucial in preventing DKD and preserving kidney function.

SGLT2 inhibition to target kidney aging

Anti-aging therapy is the latest frontier in the world of medical science, especially for widespread diseases such as chronic kidney disease (CKD). Both renal aging and CKD are characterized by increased cellular senescence, inflammation and oxidative stress. A variety of cellular signalling mechanisms are involved in these processes, which provide new potential targets for therapeutic strategies aimed at counteracting the onset and progression of CKD. At the same time, sodium-glucose co-transporter 2 inhibitors (SGLT2is) continuously demonstrate large beneficial effects at all stages of the cardiorenal metabolic continuum. The broad-spectrum benefits of SGLT2is have led to changes in several treatment guidelines and to growing scientific interest in the underlying working principles. Multiple mechanisms have been studied to explain these great renal benefits, but many things remain to be solved. With this in mind, we provide an overview of the experimental evidence for the effects of SGLT2is on the molecular pathway's ability to modulate senescence, aging and parenchymal damage, especially at the kidney level. We propose to shed some light on the role of SGLT2is in kidney care by focusing on their potential to reduce the progression of kidney disease across the spectrum of aging and dysregulation of senescence.

tRF3-IleAAT reduced extracellular matrix synthesis in diabetic kidney disease mice by targeting ZNF281 and inhibiting ferroptosis

It is well established that the synthesis of extracellular matrix (ECM) in mesangial cells is a major determinant of diabetic kidney disease (DKD). Elucidating the major players in ECM synthesis may be helpful to provide promising candidates for protecting against DKD progression. tRF3-IleAAT is a tRNA-derived fragment (tRF) produced by nucleases at tRNA-specific sites, which is differentially expressed in the sera of patients with diabetes mellitus and DKD. In this study we investigated the potential roles of tRFs in DKD. Db/db mice at 12 weeks were adapted as a DKD model. The mice displayed marked renal dysfunction accompanied by significantly reduced expression of tRF3-IleAAT and increased ferroptosis and ECM synthesis in the kidney tissues. The reduced expression of tRF3-IleAAT was also observed in high glucose-treated mouse glomerular mesangial cells. We administered ferrostatin-1 (1 mg/kg, once every two days, i.p.) to the mice from the age of 12 weeks for 8 weeks, and found that inhibition of the onset of ferroptosis significantly improved renal function, attenuated renal fibrosis and reduced collagen deposition. Overexpression of tRF3-IleAAT by a single injection of AAV carrying tRF3-IleAAT via caudal vein significantly inhibited ferroptosis and ECM synthesis in DKD model mice. Furthermore, we found that the expression of zinc finger protein 281 (ZNF281), a downstream target gene of tRF3-IleAAT, was significantly elevated in DKD models but negatively regulated by tRF3-IleAAT. In high glucose-treated mesangial cells, knockdown of ZNF281 exerted an inhibitory effect on ferroptosis and ECM synthesis. We demonstrated the targeted binding of tRF3-IleAAT to the 3'UTR of ZNF281. In conclusion, tRF3-IleAAT inhibits ferroptosis by targeting ZNF281, resulting in the mitigation of ECM synthesis in DKD models, suggesting that tRF3-IleAAT may be an attractive therapeutic target for DKD.

Serotonin regulation of mitochondria in kidney diseases

Serotonin, while conventionally recognized as a neurotransmitter in the CNS, has recently gained attention for its role in the kidney. Specifically, serotonin is not only synthesized in the kidney, but it also regulates glomerular function, vascular resistance, and mitochondrial homeostasis. Because of serotonin's importance to mitochondrial health, this review is focused on the role of serotonin and its receptors in mitochondrial function in the context of acute kidney injury, chronic kidney disease, and diabetic kidney disease, all of which are characterized by mitochondrial dysfunction and none of which has approved pharmacological treatments. Evidence indicates that activation of certain serotonin receptors can stimulate mitochondrial biogenesis (MB) and restore mitochondrial homeostasis, resulting in improved renal function. Serotonin receptor agonists that induce MB are therefore of interest as potential therapeutic strategies for renal injury and disease. SIGNIFICANCE STATEMENT: Mitochondrial dysfunction is associated with many human renal diseases such as acute kidney injury, chronic kidney disease, and diabetic kidney disease, which are associated with increased morbidity and mortality. Unfortunately, none of these pathologies has an FDA-approved pharmacological intervention, underscoring the urgency of identifying new therapeutics for such disorders. Studies show that induction of mitochondrial biogenesis via serotonin (5-hydroxytryptamine, 5-HT) receptors reduces kidney injury markers, restores mitochondrial and renal function after kidney injury, and decreases mortality, suggesting that targeting 5-HT receptors may be a promising therapeutic avenue for mitochondrial dysfunction in kidney diseases. While numerous reviews describe the importance of mitochondria and mitochondrial quality control mechanisms in kidney disease, the relevance of 5-HT receptor-mediated mitochondrial metabolic modulation in the kidney has yet to be thoroughly explored.

Epigallocatechin-3-gallate attenuates arsenic-induced fibrogenic changes in human kidney epithelial cells through reversal of epigenetic aberrations and antioxidant activities

Renal fibrosis is a pathogenic intermediate stage of chronic kidney disease (CKD). Nephrotoxicants including arsenic can cause kidney fibrosis through induction of oxidative stress and epigenetic aberrations. Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, is known to have antioxidant and epigenetic modulation properties. Whether EGCG, through its antioxidant and epigenetic modulating activities, can attenuate fibrogenesis is not known. Therefore, the objective of this study was to determine whether EGCG can attenuate arsenic-induced acute injury and long-term exposure associated fibrogenicity in kidney epithelial cells. To address this question, two human kidney epithelial cell lines Caki-1 and HK-2 exposed to arsenic for both acute and long-term durations were treated with EGCG. The protective effect of EGCG on arsenic-induced cytotoxicity and fibrogenicity were evaluated by measuring the cell growth, reactive oxygen species (ROS) production, genes expression, and epigenetic changes in histone marks. Results revealed that EGCG has a protective effect in arsenic-induced acute cytotoxicity in these cells. EGCG scavenges the increased levels of ROS in arsenic exposed cells. Aberrant expression of fibrogenic genes in arsenic exposed cells were restored by EGCG. Abrogation of arsenic-induced fibrogenic changes was also associated with EGCG-mediated restoration of arsenic-induced aberrant expression of epigenetic regulatory proteins and histone marks. Novel findings of this study suggest that EGCG, through its antioxidant and epigenetic modulation capacities, has protective effects against arsenic-induced cytotoxicity and fibrogenic changes in kidney epithelial cells.

Diamond-Like Carbon Depositing on the Surface of Polylactide Membrane for Prevention of Adhesion Formation During Tendon Repair

Post-traumatic peritendinous adhesion presents a significant challenge in clinical medicine. This study proposes the use of diamond-like carbon (DLC) deposited on polylactic acid (PLA) membranes as a biophysical mechanism for anti-adhesion barrier to encase ruptured tendons in tendon-injured rats. The results indicate that PLA/DLC composite membrane exhibits more efficient anti-adhesion effect than PLA membrane, with histological score decreasing from 3.12 ± 0.27 to 2.20 ± 0.22 and anti-adhesion effectiveness increasing from 21.61% to 44.72%. Mechanistically, the abundant C=O bond functional groups on the surface of DLC can reduce reactive oxygen species level effectively; thus, the phosphorylation of NF-κB and M1 polarization of macrophages are inhibited. Consequently, excessive inflammatory response augmented by M1 macrophage-originated cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) is largely reduced. For biocompatibility evaluation, PLA/DLC membrane is slowly absorbed within tissue and displays prolonged barrier effects compared to traditional PLA membranes. Further studies show the DLC depositing decelerates the release of degradation product lactic acid and its induction of macrophage M2 polarization by interfering esterase and PLA ester bonds, which further delays the fibrosis process. It was found that the PLA/DLC membrane possess an efficient biophysical mechanism for treatment of peritendinous adhesion.

Application and design considerations of ROS-based nanomaterials in diabetic kidney disease

Diabetic nephropathy (DKD) is a common chronic complication of diabetes mellitus and an important cause of cardiovascular-related death. Oxidative stress is a key mechanism leading to diabetic nephropathy. However, the current main therapeutic approach remains combination therapy and lacks specific therapies targeting oxidative stress. With the development of nanotechnology targeting ROS, therapeutic fluids regarding their treatment of diabetic nephropathy have attracted attention. In this review, we provide a brief overview of various ROS-based nanomaterials for DKD, including ROS-scavenging nanomaterials, ROS-associated nanodelivery materials, and ROS-responsive nanomaterials. In addition, we summarize and discuss key factors that should be considered when designing ROS-based nanomaterials, such as biosafety, efficacy, targeting, and detection and monitoring of ROS.

GKT137831 in combination with adipose-derived stem cells alleviates high glucose-induced inflammaging and improves diabetic wound healing

Adipose-derived stem cells (ADSCs) have been proven to promote healing in diabetic wounds, which are one of the most serious chronic refractory wounds. However, reactive oxygen species (ROS) induced by high glucose (HG) lead to oxidative stress and aging in ADSCs, which limits the therapeutic effect of ADSCs. In this study, we investigated the role of GKT137831, a NOX1/4 inhibitor that can reduce ROS production, in protecting ADSCs from hyperglycemia and in diabetic wound healing. In vitro, ROS levels and NOX4 expression were increased after HG treatment of ADSCs, while the oxidative stress marker malondialdehyde was increased; mitochondrial membrane potential was decreased; inflammatory aging-related indicators such as p16, p21, matrix metalloproteinase-1 (MMP1), MMP3, interleukin-6, and β-galactosidase were increased; and migration was weakened. In vivo, we constructed a diabetic mouse wound model and found that the combination of ADSCs and GKT137831 synergistically promoted the 21-day wound healing rate, increased the expression of collagen and hydroxyproline, increased the number of blood vessels and the expression of CD31, and reduced the expression of interleukin-6, MMP1, MMP3, and p21. These results suggest that GKT137831 could protect ADSCs from oxidative stress and aging induced by HG and enhance the therapeutic effect of ADSCs on diabetic wounds.

Oxidative Stress: A Culprit in the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the principal culprit behind chronic kidney disease (CKD), ultimately developing end-stage renal disease (ESRD) and necessitating costly dialysis or kidney transplantation. The limited therapeutic efficiency among individuals with DKD is a result of our finite understanding of its pathogenesis. DKD is the result of complex interactions between various factors. Oxidative stress is a fundamental factor that can establish a link between hyperglycemia and the vascular complications frequently encountered in diabetes, particularly DKD. It is crucial to recognize the essential and integral role of oxidative stress in the development of diabetic vascular complications, particularly DKD. Hyperglycemia is the primary culprit that can trigger an upsurge in the production of reactive oxygen species (ROS), ultimately sparking oxidative stress. The main endogenous sources of ROS include mitochondrial ROS production, NADPH oxidases (Nox), uncoupled endothelial nitric oxide synthase (eNOS), xanthine oxidase (XO), cytochrome P450 (CYP450), and lipoxygenase. Under persistent high glucose levels, immune cells, the complement system, advanced glycation end products (AGEs), protein kinase C (PKC), polyol pathway, and the hexosamine pathway are activated. Consequently, the oxidant-antioxidant balance within the body is disrupted, which triggers a series of reactions in various downstream pathways, including phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), transforming growth factor beta/p38-mitogen-activated protein kinase (TGF-β/p38-MAPK), nuclear factor kappa B (NF-κB), adenosine monophosphate-activated protein kinase (AMPK), and the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling. The disease might persist even if strict glucose control is achieved, which can be attributed to epigenetic modifications. The treatment of DKD remains an unresolved issue. Therefore, reducing ROS is an intriguing therapeutic target. The clinical trials have shown that bardoxolone methyl, a nuclear factor erythroid 2-related factor 2 (Nrf2) activator, blood glucose-lowering drugs, such as sodium-glucose cotransporter 2 inhibitors, and glucagon-like peptide-1 receptor agonists can effectively slow down the progression of DKD by reducing oxidative stress. Other antioxidants, including vitamins, lipoic acid, Nox inhibitors, epigenetic regulators, and complement inhibitors, present a promising therapeutic option for the treatment of DKD. In this review, we conduct a thorough assessment of both preclinical studies and current findings from clinical studies that focus on targeted interventions aimed at manipulating these pathways. We aim to provide a comprehensive overview of the current state of research in this area and identify key areas for future exploration.

Icariin alleviates renal inflammation and tubulointerstitial fibrosis via Nrf2-mediated attenuation of mitochondrial damage

Tubulointerstitial fibrosis is an inevitable consequence of all progressive chronic kidney disease (CKD) and contributes to a substantial health burden worldwide. Icariin, an active flavonoid glycoside obtained from Epimedium species, exerts potential antifibrotic effect. The study aimed to explore the protective effects of icariin against tubulointerstitial fibrosis in unilateral ureteral obstruction (UUO)-induced CKD mice and TGF-β1-treated HK-2 cells, and furthermore, to elucidate the underlying mechanisms. The results demonstrated that icariin significantly improved renal function, alleviated tubular injuries, and reduced fibrotic lesions in UUO mice. Furthermore, icariin suppressed renal inflammation, reduced oxidative stress as evidenced by elevated superoxide dismutase activity and decreased malondialdehyde level. Additionally, TOMM20 immunofluorescence staining and transmission electron microscope revealed that mitochondrial mass and morphology of tubular epithelial cells in UUO mice was restored by icariin. In HK-2 cells treated with TGF-β1, icariin markedly decreased profibrotic proteins expression, inhibited inflammatory factors, and protected mitochondria along with preserving mitochondrial morphology, reducing reactive oxygen species (ROS) and mitochondrial ROS (mtROS) overproduction, and preserving membrane potential. Further investigations demonstrated that icariin could activate nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway both in vivo and in vitro, whereas inhibition of Nrf2 by ML385 counteracted the protective effects of icariin on TGF-β1-induced HK-2 cells. In conclusion, icariin protects against renal inflammation and tubulointerstitial fibrosis at least partly through Nrf2-mediated attenuation of mitochondrial dysfunction, which suggests that icariin could be developed as a promising therapeutic candidate for the treatment of CKD.

Enhanced Drug Carriage Efficiency of Curcumin-Loaded PLGA Nanoparticles in Combating Diabetic Nephropathy via Mitigation of Renal Apoptosis

Objectives

The Curcuma-derived diferuloylmethane compound CUR, loaded on Poly (lactide-co-glycolic) acid (PLGA) nanoparticles was utilized to combat DN-induced renal apoptosis by selectively targeting and modulating Bcl2.

Methods

Upon in silico molecular docking and screening study CUR was selected as the core phytocompound for nanoparticle formulation. PLGA-nano-encapsulated-curcumin (NCUR) were synthesized following standard solvent displacement method. The NCUR were characterized for shape, size and other physico-chemical properties by Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and Fourier-Transform Infrared (FTIR) Spectroscopy studies. For in vivo validation of nephro-protective effects, Mus musculus were pre-treated with CUR at a dose of 50 mg/kg b.w. and NCUR at a dose of 25 mg/kg b.w. (dose 1), 12.5 mg/kg b.w (dose 2) followed by alloxan administration (100 mg/kg b.w) and serum glucose levels, histopathology and immunofluorescence study were conducted.

Results

The in silico study revealed a strong affinity of CUR towards Bcl2 (dock score -10.94 Kcal/mol). The synthesized NCUR were of even shape, devoid of cracks and holes with mean size of ~80 nm having -7.53 mV zeta potential. Dose 1 efficiently improved serum glucose levels, tissue-specific expression of Bcl2 and reduced glomerular space and glomerular sclerosis in comparison to hyperglycaemic group.

Conclusion

This study essentially validates the potential of NCUR to inhibit DN by reducing blood glucose level and mitigating glomerular apoptosis by selectively promoting Bcl2 protein expression in kidney tissue.