Dual inhibition of classical protein kinase C-α and protein kinase C-β isoforms protects against experimental murine diabetic nephropathy

Endothelial NOX5 Obliterates the Reno-Protective Effect of Nox4 Deletion by Promoting Renal Fibrosis via Activation of EMT and ROS-Sensitive Pathways in Diabetes

Chronic hyperglycemia induces intrarenal oxidative stress due to the excessive production of reactive oxygen species (ROS), leading to a cascade of events that contribute to the development and progression of diabetic kidney disease (DKD). NOX5, a pro-oxidant NADPH oxidase isoform, has been identified as a significant contributor to renal ROS in humans. Elevated levels of renal ROS contribute to endothelial cell dysfunction and associated inflammation, causing increased endothelial permeability, which can disrupt the renal ecosystem, leading to progressive albuminuria and renal fibrosis in DKD. This study specifically examines the contribution of endothelial cell-specific human NOX5 expression in renal pathology in a transgenic mouse model of DKD. This study additionally compares NOX5 with the previously characterized NADPH oxidase, NOX4, in terms of their relative roles in DKD. Regardless of NOX4 pathway, this study found that endothelial cell-specific expression of NOX5 exacerbates renal injury, albuminuria and fibrosis. This is attributed to the activation of the endothelial mesenchymal transition (EMT) pathway via enhanced ROS formation and the modulation of redox-sensitive factors. These findings underscore the potential therapeutic significance of NOX5 inhibition in human DKD. The study proposes that inhibiting NOX5 could be a promising approach for mitigating the progression of DKD and strengthens the case for the development of NOX5-specific inhibitors as a potential therapeutic intervention.

Pathomechanisms of Diabetic Kidney Disease

The worldwide occurrence of diabetic kidney disease (DKD) is swiftly rising, primarily attributed to the growing population of individuals affected by type 2 diabetes. This surge has been transformed into a substantial global concern, placing additional strain on healthcare systems already grappling with significant demands. The pathogenesis of DKD is intricate, originating with hyperglycemia, which triggers various mechanisms and pathways: metabolic, hemodynamic, inflammatory, and fibrotic which ultimately lead to renal damage. Within each pathway, several mediators contribute to the development of renal structural and functional changes. Some of these mediators, such as inflammatory cytokines, reactive oxygen species, and transforming growth factor β are shared among the different pathways, leading to significant overlap and interaction between them. While current treatment options for DKD have shown advancement over previous strategies, their effectiveness remains somewhat constrained as patients still experience residual risk of disease progression. Therefore, a comprehensive grasp of the molecular mechanisms underlying the onset and progression of DKD is imperative for the continued creation of novel and groundbreaking therapies for this condition. In this review, we discuss the current achievements in fundamental research, with a particular emphasis on individual factors and recent developments in DKD treatment.

A protein kinase C α and β inhibitor blunts hyperphagia to halt renal function decline and reduces adiposity in a rat model of obesity-driven type 2 diabetes

Type 2 diabetes (T2D) and its complications can have debilitating, sometimes fatal consequences for afflicted individuals. The disease can be difficult to control, and therapeutic strategies to prevent T2D-induced tissue and organ damage are needed. Here we describe the results of administering a potent and selective inhibitor of Protein Kinase C (PKC) family members PKCα and PKCβ, Cmpd 1, in the ZSF1 obese rat model of hyperphagia-induced, obesity-driven T2D. Although our initial intent was to evaluate the effect of PKCα/β inhibition on renal damage in this model setting, Cmpd 1 unexpectedly caused a marked reduction in the hyperphagic response of ZSF1 obese animals. This halted renal function decline but did so indirectly and indistinguishably from a pair feeding comparator group. However, above and beyond this food intake effect, Cmpd 1 lowered overall animal body weights, reduced liver vacuolation, and reduced inguinal adipose tissue (iWAT) mass, inflammation, and adipocyte size. Taken together, Cmpd 1 had strong effects on multiple disease parameters in this obesity-driven rodent model of T2D. Further evaluation for potential translation of PKCα/β inhibition to T2D and obesity in humans is warranted.

Potential implications of protein kinase Cα in pathophysiological conditions and therapeutic interventions

PKCα is a molecule with many functions that play an important role in cell survival and death to maintain cellular homeostasis. Alteration in the normal functioning of PKCα is responsible for the complicated etiology of many pathologies, including cancer, cardiovascular diseases, kidney complications, neurodegenerative diseases, diabetics, and many others. Several studies have been carried out over the years on this kinase's function, and regulation in normal physiology and pathological conditions. A lot of data with antithetical results have therefore accumulated over time to create a complex framework of physiological implications connected to the PKCα function that needs comprehensive elucidation. In light of this information, we critically analyze the multiple roles played by PKCα in basic cellular processes and their molecular mechanism during various pathological conditions. This review further discusses the current approaches to manipulating PKCα signaling amplitude in the patient's favour and proposed PKCα as a therapeutic target to reverse pathological states.

Single Nucleotide Polymorphisms of the RAC1 Gene as Novel Susceptibility Markers for Neuropathy and Microvascular Complications in Type 2 Diabetes

Single nucleotide polymorphisms (SNP) in the RAC1 (Rac family small GTPase 1) gene have recently been linked to type 2 diabetes (T2D) and hyperglycemia due to their contribution to impaired redox homeostasis. The present study was designed to determine whether the common SNPs of the RAC1 gene are associated with diabetic complications such as neuropathy (DN), retinopathy (DR), nephropathy, angiopathy of the lower extremities (DA), and diabetic foot syndrome. A total of 1470 DNA samples from T2D patients were genotyped for six common SNPs by the MassArray Analyzer-4 system. The genotype rs7784465-T/C of RAC1 was associated with an increased risk of DR (p = 0.016) and DA (p = 0.03) in males, as well as with DR in females (p = 0.01). Furthermore, the SNP rs836478 showed an association with DR (p = 0.005) and DN (p = 0.025) in males, whereas the SNP rs10238136 was associated with DA in females (p = 0.002). In total, three RAC1 haplotypes showed significant associations (FDR < 0.05) with T2D complications in a sex-specific manner. The study's findings demonstrate, for the first time, that the RAC1 gene's polymorphisms represent novel and sex-specific markers of neuropathy and microvascular complications in type 2 diabetes, and that the gene could be a new target for the pharmacological inhibition of oxidative stress as a means of preventing diabetic complications.

Independent of Renox, NOX5 Promotes Renal Inflammation and Fibrosis in Diabetes by Activating ROS-Sensitive Pathways

Excessive production of renal reactive oxygen species (ROS) plays a major role in diabetic kidney disease (DKD). Here, we provide key findings demonstrating the predominant pathological role of the pro-oxidant enzyme NADPH oxidase 5 (NOX5) in DKD, independent of the previously characterized NOX4 pathway. In patients with diabetes, we found increased expression of renal NOX5 in association with enhanced ROS formation and upregulation of ROS-sensitive factors early growth response 1 (EGR-1), protein kinase C-α (PKC-α), and a key metabolic gene involved in redox balance, thioredoxin-interacting protein (TXNIP). In preclinical models of DKD, overexpression of NOX5 in Nox4-deficient mice enhances kidney damage by increasing albuminuria and augmenting renal fibrosis and inflammation via enhanced ROS formation and the modulation of EGR1, TXNIP, ERK1/2, PKC-α, and PKC-ε. In addition, the only first-in-class NOX inhibitor, GKT137831, appears to be ineffective in the presence of NOX5 expression in diabetes. In vitro, silencing of NOX5 in human mesangial cells attenuated upregulation of EGR1, PKC-α, and TXNIP induced by high glucose levels, as well as markers of inflammation (TLR4 and MCP-1) and fibrosis (CTGF and collagens I and III) via reduction in ROS formation. Collectively, these findings identify NOX5 as a superior target in human DKD compared with other NOX isoforms such as NOX4, which may have been overinterpreted in previous rodent studies.

Recent advances in the pharmacotherapeutic management of diabetic kidney disease

INTRODUCTION

Diabetic kidney disease (DKD) remains a major cause of morbidity and mortality in diabetes and is a key cause of end-stage kidney disease (ESKD) worldwide. Major clinical advances have been confirmed in large trials demonstrating renoprotection, adding to the benefits of existing intensive glucose and blood pressure control therapies. Furthermore, there are exciting new treatments predominantly at an experimental and early clinical phase which appear promising.

AREAS COVERED

The authors review DKD in the context of existing and emerging therapies affording cardiorenal benefits including SGLT2 inhibitors and GLP-1 receptor agonists. They explore novel therapies demonstrating potential including a newly developed mineralocorticoid receptor antagonist and endothelin receptor blockade, while evaluating the utility of DPP4 inhibitors in current clinical practice. They also consider the recent evidence of emerging therapies targeting metabolic pathways with enzyme inhibitors, anti-fibrotic agents, and agents modulating transcription factors.

EXPERT OPINION

Significant improvements have been made in the management of DKD with SGLT2i and GLP-1 agonists providing impressive renoprotection, with novel progress in renin-angiotensin-aldosterone system (RAAS) blockade with finerenone. There is also great potential for several new experimental therapies. These advances provide us with optimism that the outlook of this devastating condition will continue to improve.

Podocyte Endocytosis in Regulating the Glomerular Filtration Barrier

Endocytosis is a mechanism that internalizes and recycles plasma membrane components and transmembrane receptors via vesicle formation, which is mediated by clathrin-dependent and clathrin-independent signaling pathways. Podocytes are specialized, terminally differentiated epithelial cells in the kidney, located on the outermost layer of the glomerulus. These cells play an important role in maintaining the integrity of the glomerular filtration barrier in conjunction with the adjacent basement membrane and endothelial cell layers within the glomerulus. An intact podocyte endocytic machinery appears to be necessary for maintaining podocyte function. De novo pathologic human genetic mutations and loss-of-function studies of critical podocyte endocytosis genes in genetically engineered mouse models suggest that this pathway contributes to the pathophysiology of development and progression of proteinuria in chronic kidney disease. Here, we review the mechanism of cellular endocytosis and its regulation in podocyte injury in the context of glomerular diseases. A thorough understanding of podocyte endocytosis may shed novel insights into its biological function in maintaining a functioning filter and offer potential targeted therapeutic strategies for proteinuric glomerular diseases.

The role of protein kinase C in diabetic microvascular complications

Protein kinase C (PKC) is a family of serine/threonine protein kinases, the activation of which plays an important role in the development of diabetic microvascular complications. The activation of PKC under high-glucose conditions stimulates redox reactions and leads to an accumulation of redox stress. As a result, various types of cells in the microvasculature are influenced, leading to changes in blood flow, microvascular permeability, extracellular matrix accumulation, basement thickening and angiogenesis. Structural and functional disorders further exacerbate diabetic microvascular complications. Here, we review the roles of PKC in the development of diabetic microvascular complications, presenting evidence from experiments and clinical trials.

Systems biology and machine learning approaches identify drug targets in diabetic nephropathy

Diabetic nephropathy (DN), the leading cause of end-stage renal disease, has become a massive global health burden. Despite considerable efforts, the underlying mechanisms have not yet been comprehensively understood. In this study, a systematic approach was utilized to identify the microRNA signature in DN and to introduce novel drug targets (DTs) in DN. Using microarray profiling followed by qPCR confirmation, 13 and 6 differentially expressed (DE) microRNAs were identified in the kidney cortex and medulla, respectively. The microRNA-target interaction networks for each anatomical compartment were constructed and central nodes were identified. Moreover, enrichment analysis was performed to identify key signaling pathways. To develop a strategy for DT prediction, the human proteome was annotated with 65 biochemical characteristics and 23 network topology parameters. Furthermore, all proteins targeted by at least one FDA-approved drug were identified. Next, mGMDH-AFS, a high-performance machine learning algorithm capable of tolerating massive imbalanced size of the classes, was developed to classify DT and non-DT proteins. The sensitivity, specificity, accuracy, and precision of the proposed method were 90%, 86%, 88%, and 89%, respectively. Moreover, it significantly outperformed the state-of-the-art (P-value ≤ 0.05) and showed very good diagnostic accuracy and high agreement between predicted and observed class labels. The cortex and medulla networks were then analyzed with this validated machine to identify potential DTs. Among the high-rank DT candidates are Egfr, Prkce, clic5, Kit, and Agtr1a which is a current well-known target in DN. In conclusion, a combination of experimental and computational approaches was exploited to provide a holistic insight into the disorder for introducing novel therapeutic targets.

Vaccination Against Receptor for Advanced Glycation End Products Attenuates the Progression of Diabetic Kidney Disease

Effective treatment of diabetic kidney disease (DKD) remains a large unmet medical need. Within the disease's complicated pathogenic mechanism, activation of the advanced glycation end products (AGEs)-receptor for AGE (RAGE) axis plays a pivotal role in the development and progression of DKD. To provide a new therapeutic strategy against DKD progression, we developed a vaccine against RAGE. Three rounds of immunization of mice with the RAGE vaccine successfully induced antigen-specific serum IgG antibody titers and elevated antibody titers were sustained for at least 38 weeks. In addition, RAGE vaccination significantly attenuated the increase in urinary albumin excretion in streptozotocin-induced diabetic mice (type 1 diabetes model) and leptin-receptor-deficient db/db mice (type 2 diabetes model). In microscopic analyses, RAGE vaccination suppressed glomerular hypertrophy and mesangial expansion in both diabetic models and significantly reduced glomerular basement membrane thickness in streptozotocin-induced diabetic mice. Results of an in vitro study indicated that the serum IgG antibody elicited by RAGE vaccination suppressed the expression of AGE-induced vascular cell adhesion molecule 1 and intracellular adhesion molecule 1 in endothelial cells. Thus, our newly developed RAGE vaccine attenuated the progression of DKD in mice and is a promising potential therapeutic strategy for patients with DKD.

Vascular Permeability: Regulation Pathways and Role in Kidney Diseases

BACKGROUND

Vascular permeability (VP) is a fundamental aspect of vascular biology. A growing number of studies have revealed that many signalling pathways govern VP in both physiological and pathophysiological conditions. Furthermore, emerging evidence identifies VP alteration as a pivotal pathogenic factor in acute kidney injury, chronic kidney disease, diabetic kidney disease, and other proteinuric diseases. Therefore, perceiving the connections between these pathways and the aetiology of kidney disease is an important task as such knowledge may trigger the development of novel therapeutic or preventive medical approaches. In this regard, the discussion summarizing VP-regulating pathways and associating them with kidney diseases is highly warranted.

SUMMARY

Major pathways of VP regulation comprise angiogenic factors including vascular endothelial growth factor/VEGFR, angiopoietin/Tie, and class 3 semaphorin/neuropilin and inflammatory factors including histamine, platelet-activating factor, and leukocyte extravasation. These pathways mainly act on vascular endothelial cadherin to modulate adherens junctions of endothelial cells (ECs), thereby augmenting VP via the paracellular pathway. Elevated VP in diverse kidney diseases involves EC apoptosis, imbalanced regulatory factors, and many other pathophysiological events, which in turn exacerbates renal structural and functional disorders. Measures improving VP effectively ameliorate the diseased kidney in terms of tissue injury, endothelial dysfunction, kidney function, and long-term prognosis. Key Messages: (1) Angiogenic factors, inflammatory factors, and adhesion molecules represent major pathways that regulate VP. (2) Vascular hyperpermeability links various pathophysiological processes and plays detrimental roles in multiple kidney diseases.

Tea Drinking Alleviates Diabetic Symptoms via Upregulating Renal Water Reabsorption Proteins and Downregulating Renal Gluconeogenic Enzymes in db/db Mice

SCOPE

Tea, made from the plant Camellia sinensis, is known to have anti-diabetes effects and different mechanisms of action are proposed. Kidney is a vital organ in managing water reabsorption and glucose metabolism, and is greatly influenced by diabetes. The present study investigates the effects of tea administration on water reabsorption and gluconeogenesis in the kidney of diabetic mice.

METHODS AND RESULTS

Db/db mice are given tea infusion as drinking fluid when they begin to exhibit hyperglycemia. It is found that green tea or black tea infusion potently elevates renal proteins vital for water reabsorption, including protein kinase C-α, aquaporin 2, and urea transporter-A1, as well as increases trafficking of these proteins to apical plasma membrane where they exert water reabsorption function. The treatment also downregulates renal gluconeogenic enzymes, including glucose-6-phosphatase-α and phosphoenolpyruvate carboxykinase. Associated with these biochemical changes are the rectified polyuria, polydipsia, polyphagia, and hyperglycemia, all symptoms of diabetes.

CONCLUSIONS

For the first time, the present study demonstrates that tea has robust effects in enhancing kidney water reabsorption proteins and downregulating gluconeogenic enzymes in db/db mice. It remains to be investigated whether such beneficial effects of tea occur in humans.

SNPs in PRKCA-HIF1A-GLUT1 are associated with diabetic kidney disease in a Chinese Han population with type 2 diabetes

OBJECTIVE

To explore the relationship between SNPs in PRKCA-HIF1A-GLUT1 and diabetic kidney disease in Chinese Han people.

MATERIALS AND METHODS

A total of 2552 participants from Shanghai Diabetes Institute Inpatient Database of Shanghai Jiao Tong University Affiliated Sixth People's Hospital were involved in the stage 1 cross-sectional population. A total of 6015 subjects from the Hong Kong Diabetes Register were included for validation. Genotyping of participants was conducted by the MassARRAY Compact Analyzer (Agena Bioscience). The data were analysed by plink, SAS, Haploview.

RESULTS

We identified variants associated with diabetic kidney disease in stage 1. Rs1681851 (P = .0105, OR = 1.331) in GLUT1 as well as rs2301108 (P = .0085, OR = 1.289) and rs79865957 (P = .0204, OR = 1.263) in HIF1A were significantly associated with diabetic kidney disease. Regarding DKD-related traits, rs1681851 was associated with plasma creatinine levels (P = .0169, β = 4.822) and eGFR (P = .0457, β = -6.956). Moreover, the results showed the interactions between PRKCA-GLUT1 in the occurrence of DKD. We further sought validation of the 17 SNPs in a prospective cohort and found that rs900836 and rs844501 were associated with the percentage change in eGFR slope. We performed a meta-analysis of case-control analysis data from the Hong Kong samples together with the stage 1 data from Shanghai. Rs9894851 showed significant correlation with the serum creatinine level as well as eGFR and no SNP showed association with DKD after meta-analysis.

CONCLUSIONS

Our results suggest potential association between SNPs in PRKCA-HIF1A-GLUT1 and diabetic kidney disease in Chinese Han people.

The effect of total lignans from Fructus Arctii on Streptozotocin-induced diabetic retinopathy in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Arctii is the dried ripe fruit of Arctium lappa L. (family Asteraceae). It is a well-known Chinese Materia Medica that was included in the Chinese pharmacopoeia because of its traditional therapeutic actions, such as heat removal, detoxification, and elimination of swelling. Since ancient times Fructus Arctii has been used extensively in a number of classical drug formulas to treat type 2 diabetes mellitus. Modern pharmacological studies have shown that certain components of Fructus Arctii have multiple physiological activities on type 2 diabetes and its complications.

AIM OF THE STUDY

We have reported the inhibitory effect of total lignans from Fructus Arctii (TLFA) on aldose reductase, the key enzyme in the polyol pathway, which is considered to be closely related to the onset of diabetic retinopathy (DR). The present study aimed to observe the preventive and therapeutic effects of TLFA on DR in Streptozotocin (STZ)-induced DR rats.

MATERIALS AND METHODS

TLFA was prepared from Fructus Arctii and its content was determined using UV spectrophotometry. The DR model was induced by STZ in Wistar rats. For DR prevention, the animals were gavaged once daily for 9 weeks with TLFA (1.38, 0.69, and 0.35 g/kg/day) as soon as they were confirmed as diabetes models. Pathological changes to retinal tissues and the expression of vascular endothelial growth factor (VEGF) and protein kinase C (PKC) in the retina were detected after TLFA treatment. The effects of TLFA on blood glucose levels and body weight were also observed. For DR treatment, the animals were gavaged once daily for 12 weeks with TLFA (1.38 and 0.69 g/kg/day) at 3 months after they were confirmed as diabetes models. The therapeutic effect was studied using quantitative detection of blood-retina barrier (BRB) breakdown via an Evans Blue leakage assay.

RESULTS

For DR prevention, after 9 weeks of TLFA administration, histopathological examination of retinal tissue showed that TLFA improved the lesions in the retina. Changes to retinal microstructures such as capillaries, ganglion cells, bipolar cells, and the membrane disk examined by electron microscopy further confirmed that TLFA has a preventive effect on retinopathy. Terminal deoxynucleotidyl Transferase-mediated dUTP nick end labeling (TUNEL) detection showed that TLFA could inhibit retinal cell apoptosis in the diabetic rats, and fasting blood glucose (FBG) levels of rats in the TLFA-treated groups decreased during the experiment. For DR treatment, after 3 months of administration, the amount of dye leakage in the TLFA-administered groups was reduced by more than 50% compared with that in the model group, which indicated that TLFA has a therapeutic effect on middle and late DR. Messenger RNA (mRNA) expression of VEGF and PKCβ2 in the retina detected by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (FQ-RT-PCR) showed that TLFA could inhibit the expression of them, which was consistent with the results of immunohistochemistry (IHC).

CONCLUSION

TLFA has a preventive and therapeutic effect on DR. Its mechanism of action on DR is related to inhibiting PKC activation and blocking VEGF elevation.

Protein kinase C beta deficiency increases glucose-mediated peritoneal damage via M1 macrophage polarization and up-regulation of mesothelial protein kinase C alpha

BACKGROUND

Peritoneal membrane (PM) damage during peritoneal dialysis (PD) is mediated largely by high glucose (HG)-induced pro-inflammatory and neo-angiogenic processes, resulting in PM fibrosis and ultrafiltration failure. We recently demonstrated a crucial role for protein kinase C (PKC) isoform α in mesothelial cells.

METHODS

In this study we investigate the role of PKCβ in PM damage in vitro using primary mouse peritoneal macrophages (MPMΦ), human macrophages (HMΦ) and immortalized mouse peritoneal mesothelial cells (MPMCs), as well as in vivo using a chronic PD mouse model.

RESULTS

We demonstrate that PKCβ is the predominant classical PKC isoform expressed in primary MPMΦ and its expression is up-regulated in vitro under HG conditions. After in vitro lipopolysaccharides stimulation PKCβ-/- MPMΦ demonstrates increased levels of interleukin 6 (IL-6), tumour necrosis factor α, and monocyte chemoattractant protein-1 and drastically decrease IL-10 release compared with wild-type (WT) cells. In vivo, catheter-delivered treatment with HG PD fluid for 5 weeks induces PKCβ up-regulation in omentum of WT mice and results in inflammatory response and PM damage characterized by fibrosis and neo-angiogenesis. In comparison to WT mice, all pathological changes are strongly aggravated in PKCβ-/- animals. Underlying molecular mechanisms involve a pro-inflammatory M1 polarization shift of MPMΦ and up-regulation of PKCα in MPMCs of PKCβ-/- mice. Finally, we demonstrate PKCβ involvement in HG-induced polarization processes in HMΦ.

CONCLUSIONS

PKCβ as the dominant PKC isoform in MPMΦ is up-regulated by HG PD fluid and exerts anti-inflammatory effects during PD through regulation of MPMΦ M1/M2 polarization and control of the dominant mesothelial PKC isoform α.

Klotho inhibits PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy

Diabetic nephropathy (DN) is a progressive disease, the main pathogeny of which is podocyte injury. As a calcium-dependent serine/threonine protein kinase involved in podocyte injury, protein kinase C isoform α (PKCα) was reported to regulate the phosphorylation of p66SHC. However, the role of PKCα/p66SHC in DN remains unknown. Klotho, an anti-aging protein with critical roles in protecting kidney, is expressed predominantly in the kidney and secreted in the blood. Nonetheless, the mechanism underlying amelioration of podocyte injury by Klotho in DN remains unclear. Our data showed that Klotho was decreased in STZ-treated mice and was further declined in diabetic KL ± mice. As expected, Klotho deficiency aggravated diabetes-induced proteinuria and podocyte injury, accompanied by the activation of PKCα and p66SHC. In contrast, overexpression of Klotho partially ameliorated PKCα/p66SHC-mediated podocyte injury and proteinuria. In addition, in vitro experiments showed that activation of PKCα and subsequently increased intracellular reactive oxygen species (ROS) was involved in podocytic apoptosis induced by high glucose (HG), which could be partially reversed by Klotho. Hence, we conclude that Klotho might inhibit PKCα/p66SHC-mediated podocyte injury in diabetic nephropathy.

Skin Autofluorescence Is Associated with Diabetic Peripheral Neuropathy in Chinese Patients with Type 2 Diabetes: A Cross-Sectional Study

Background: Diabetic peripheral neuropathy (DPN) affects nearly 50% of the diabetic population. Advanced glycation end products, measured through skin autofluorescence (SAF), play an important role in the diagnosis and prevention of DPN. To date, however, no relevant study has discussed the relationship between SAF and the Chinese population. Objective: We conducted this study to evaluate the association between DPN and SAF among the Chinese population. Methods: In this cross-sectional study, we recruited a total of 820 patients with type 2 diabetes. All of the patients underwent SAF measurements and a nerve conduction study (NCS). Post-SAF characterization, the patients were divided into three groups according to the first and third quartiles of their SAF values (AU) (SAF ≤ 2.2; 2.2 < SAF ≤ 2.7; SAF > 2.7). Based on the results of the NCS, patients were divided into two groups: DPN and non-DPN. Results: When compared with the non-DPN group (n = 275) with the DNP group. The latter had higher SAF values (2.72 ± 0.55 AU vs. 2.17 ± 0.71 AU, P < 0.01). There were significant differences in age, the percentage of DPN, and NCS parameters, including motor nerve conduction velocity, sensory nerve conduction velocity, distal latency, and sensory nerve action potential among the three SAF groups (p < 0.05). The SAF value was positively associated with DPN (r = 0.11, p < 0.01). After adjusting for all potential confounders, the SAF values were still associated with an increased risk of DPN (odds ratio 5.15; 95% confidence interval [1.48-4.53]) (p < 0.01). A receiver operating characteristic analysis indicated that an SAF value >2.57 ng/mL predicts a threefold increased risk of DPN (p < 0.01). Conclusions: SAF is an independent risk factor for DPN, which might be of potential value for screening DPN in Chinese patients with type 2 diabetes.

Inhibition of Sodium Glucose Cotransporter 2 Attenuates the Dysregulation of Kelch-Like 3 and NaCl Cotransporter in Obese Diabetic Mice

BACKGROUND

Mechanisms underlying the frequent association between salt-sensitive hypertension and type 2 diabetes remain obscure. We previously found that protein kinase C (PKC) activation phosphorylates Kelch-like 3 (KLHL3), an E3 ubiquitin ligase component, at serine 433. We investigated whether impaired KLHL3 activity results in increased renal salt reabsorption via NaCl cotransporter (NCC).

METHODS

We used the db/db diabetes mouse model to explore KLHL3's role in renal salt handling in type 2 diabetes and evaluated mechanisms of KLHL3 dysregulation in cultured cells.

RESULTS

We observed PKC activity in the db/db mouse kidney and phosphorylation of serine 433 in KLHL3 (KLHL3^S433-P). This modification prevents binding of with-no-lysine (WNK) kinases; however, total KLHL3 levels were decreased, indicating severely impaired KLHL3 activity. This resulted in WNK accumulation, activating NCC in distal convoluted tubules. Ipragliflozin, a sodium glucose cotransporter 2 (SGLT2) inhibitor, lowered PKC activity in distal convoluted tubule cells and reduced KLHL3^S433-P and NCC levels, whereas the thiazolidinedione pioglitazone did not, although the two agents similarly reduced in blood glucose levels. We found that, in human embryonic kidney cells expressing KLHL3 and distal convoluted tubule cells, cellular glucose accumulation increased KLHL3^S433-P levels through PKC. Finally, the effect of PKC inhibition in the kidney of db/db mice confirmed PKC's causal role in KLHL3^S433-P and NCC induction.

CONCLUSIONS

Dysregulation of KLHL3 is involved in the pathophysiology of type 2 diabetes. These data offer a rationale for use of thiazide in individuals with diabetes and provide insights into the mechanism for cardiorenal protective effects of SGLT2 inhibitors.

Effects of total flavonoids from Oxytropis falcata Bunge on the SOCS/JAK/STAT inflammatory signaling pathway in the kidneys of diabetic nephropathy model mice

To investigate the effects of total flavonoids from Oxytropis falcata Bunge on the inflammatory signaling pathway suppressor of cytokine signaling (SOCS)/Janus kinase (JAK)/signal transducer and activator of transcription (STAT) in diabetic nephropathy KK-Ay mice. KK-Ay mice were used to establish a diabetic nephropathy model. The general condition of the mice treated with different concentrations of total flavonoids from O. falcata was monitored, respectively. Body weight, blood glucose, 24-h urinary albumin (UAlb), serum creatinine (Cre), blood urea nitrogen (BUN), and uric acid (UA) levels were measured at different time points. Hematoxylin and eosin staining quantitative reverse transcription-polymerase chain reaction and western blotting were used to detect changes in renal tissues and glomerular mesangial cells. Four weeks after model establishment, body weight, blood glucose, and 24 h UAlb significantly increased in KK-Ay mice compared with that in control C57BL/6j mice ( P < 0.05). Compared with non-treated model mice, mice treated with total flavonoids from O. falcata for 4 weeks had significantly decreased serum Cre, BUN, and UA; monocyte chemoattractant protein-1(MCP-1), nuclear factor(NF)-κB, interleukin(IL)-6, and transforming growth factor(TGF)-β1, JAK 1, STAT 3 and STAT 4 mRNA levels; and p-JAK2 and p-STAT1 protein levels and significantly increased SOCS-1 and SOCS-3 protein levels in the kidneys. The treatment effects were dose-dependent and same to in vitro. Our results reflected that total flavonoids from O. falcata relieved renal tissue inflammation in diabetic mice by reducing blood glucose levels and inhibiting JAK/STAT signaling, thereby protecting against the development of diabetic nephropathy.

A Glimpse of the Mechanisms Related to Renal Fibrosis in Diabetic Nephropathy

Diabetic nephropathy (DN) is a common kidney disease in people with diabetes, which is also a serious microvascular complication of diabetes and the main cause of end-stage renal disease (ESRD) in developed and developing countries. Renal fibrosis is a finally pathological change in DN. Nevertheless, the relevant mechanism of cause to renal fibrosis in DN is still complex. In this review, we summarized that the role of cell growth factors, epithelial-mesenchymal transition (EMT) in the renal fibrosis of DN, we also highlighted the miRNA and inflammatory cells, such as macrophage, T lymphocyte, and mastocyte modulate the progression of DN. In addition, there are certain other mechanisms that may yet be conclusively defined. Recent studies demonstrated that some of the new signaling pathways or molecules, such as Notch, Wnt, mTOR, Epac-Rap-1 pathway, may play a pivotal role in the modulation of ECM accumulation and renal fibrosis in DN. This review aims to elucidate the mechanism of renal fibrosis in DN and has provided new insights into possible therapeutic interventions to inhibit renal fibrosis and delay the development of DN.

Niclosamide ethanolamine improves kidney injury in db/db mice

AIMS

Early diabetic kidney disease (DKD) is characterized by renal hypertrophy and albuminuria. The mTOR signal pathway is closely related to DKD. This study was performed to determine the renal protection of niclosamide ethanolamine salt (NEN) which was identified as mTOR inhibitor.

METHODS

Type 2 diabetes (T2D) db/db mice were used and divided into db/db and db/db + NEN groups. Lean wild type mice served as T2D-control. NEN treatment lasted for 12 weeks. The kidney morphological changes, urine indices, blood glucose and metabolic symptoms were evaluated. In addition, the effects of NEN on kidney mitochondria and mTOR/4E-BP pathway were also measured.

RESULTS

NEN could prevent diabetic kidney hypertrophy and alleviate glomerular mesangial expansion, attenuate GBM and TBM thickening in db/db mice. It also restored podocyte dysfunction, reduced urinary albumin, NAG, NGAL, and TGF-β1 excretion. Specifically, it could uncouple kidney mitochondria and significantly inhibit renal cortical activation of mTOR/4E-BP1 pathway.

CONCLUSIONS

This study demonstrated that NEN could improve kidney injury in db/db mice and has the potential to translate to future clinical studies.

Niclosamide ethanolamine improves diabetes and diabetic kidney disease in mice

Diabetes and its renal complications are major medical challenges worldwide. There are no effective drugs currently available for treating diabetes and diabetic kidney disease (DKD), especially in type 1 diabetes (T1D). Evidence has suggested that niclosamide ethanolamine salt (NEN) could improve diabetic symptoms in mice of type 2 diabetes (T2D). However, its role in T1D and DKD has not been studied to date. Here we report that NEN could protect against diabetes in streptozotocin (STZ) induced T1D mice. It increased serum insulin levels, corrected the unbalanced ratio of α-cells to β-cells, and induced islet morphologic changes under diabetic conditions. In addition, NEN could impede the progression of DKD in T1D. Specifically, it reduced urinary albumin levels, NAG, NGAL and TGF-β1 excretion, ameliorated renal hypertrophy, alleviated podocyte dysfunction, and suppressed the renal cortical activation of mTOR/4E-BP1 signaling pathway. Moreover, it is hepatoprotective and does not exhibit heart toxicity. Therefore, these findings open up a completely novel therapy for diabetes and DKD.

Comparison of retinal vascular geometry in obese and non-obese children

Purpose

Childhood obesity is associated with adult cardiometabolic disease. We postulate that the underlying microvascular dysfunction begins in childhood. We thus aimed to compare retinal vascular parameters between obese and non-obese children.

Methods

This was a cross-sectional study involving 166 children aged 6 to 12 years old in Malaysia. Ocular examination, biometry, retinal photography, blood pressure and body mass index measurement were performed. Participants were divided into two groups; obese and non-obese. Retinal vascular parameters were measured using validated software.

Results

Mean age was 9.58 years. Approximately 51.2% were obese. Obese children had significantly narrower retinal arteriolar caliber (F_(1,159) = 6.862, p = 0.010), lower arteriovenous ratio (F_(1,159) = 17.412, p < 0.001), higher venular fractal dimension (F_(1,159) = 4.313, p = 0.039) and higher venular curvature tortuosity (F_(1,158) = 5.166, p = 0.024) than non-obese children, after adjustment for age, gender, blood pressure and axial length.

Conclusions

Obese children have abnormal retinal vascular geometry. These findings suggest that childhood obesity is characterized by early microvascular abnormalities that precede development of overt disease. Further research is warranted to determine if these parameters represent viable biomarkers for risk stratification in obesity.

RNA-sequencing reveals genome-wide long non-coding RNAs profiling associated with early development of diabetic nephropathy

Background

Diabetic nephropathy (DN) seriously threatens the lives of patients, and the mechanism of DN remains largely unknown because of the complex regulation between long non-coding RNA (lncRNA) and protein-coding genes. In early development of diabetic nephropathy (DN), pathogenesis remains largely unknown.

Results

We used RNA-sequencing to profile protein-coding and lncRNA gene transcriptome of mouse kidney proximal tubular cells during early stage of DN at various time points. Over 7000 protein-coding and lncRNA genes were differentially expressed, and most of them were time-specific. Nearly 40% of lncRNA genes overlapped with functional element signals using CHIP-Seq data from ENCODE database. Disease progression was characterized by lncRNA expression patterns, rather than protein-coding genes, indicating that the lncRNA genes are potential biomarkers for DN. For gene ontologies related to kidney, enrichment was observed in protein-coding genes co-expressed with neighboring lncRNA genes. Based on protein-coding and lncRNA gene profiles, clustering analysis reveals dynamic expression patterns for kidney, suggesting that they are highly correlated during disease progression. To evaluate translation of mouse model to human conditions, we experimentally validated orthologous genes in human cells in vitro diabetic model. In mouse model, most gene expression patterns were repeated in human cell lines.

Conclusions

These results define dynamic transcriptome and novel functional roles for lncRNAs in diabetic kidney cells; these roles may result in lncRNA-based diagnosis and therapies for DN.

Effect of diacerein on renal function and inflammatory cytokines in participants with type 2 diabetes mellitus and chronic kidney disease: A randomized controlled trial

Diacerein seems to improve metabolic control and reduce inflammatory marker levels in individuals with type 2 diabetes mellitus (Type 2 DM), but for participants with chronic kidney disease (CKD) its effect is unknown. This study aimed to evaluate the effect of diacerein vs. placebo on urinary albumin/creatinine ratio (ACR), glomerular filtration rate (GFR), and inflammatory cytokines in type 2 DM participants with CKD. Blood pressure (BP) and metabolic control were secondary outcomes. This randomized, placebo-controlled, parallel trial of adjuvant treatment of type 2 DM with diacerein enrolled seventy-two participants with CKD, aged 30–80 years, with glycated hemoglobin levels from 53–97 mmol/mol (7.0–11.0%), receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and antidiabetic agents. Participants randomized to diacerein or placebo were followed-up up to 90 days. Both groups had a marked reduction in ACR, but there was no effect on glomerular filtration rate. While the diacerein group had reduced TNF-α levels at the 75th percentile with a borderline significance (P = 0.05), there were no changes in the IL levels at the 75^th percentile.

Diacerein prevented the increase in blood glucose to the level observed in the placebo group (P = 0.04), improving metabolic control by 74%, reducing 24-hour diastolic BP, nighttime systolic and diastolic BP compared to the placebo group. In conclusion, among patients with type 2 DM and CKD, diacerein does not have an effect on ACR or GFR, but slows metabolic control deterioration and is associated with lower nighttime systolic and diastolic blood pressure.

Trial registration: Brazilian Clinical Trials Registry (Registro Brasileiro de Ensaios Clinicos; ReBeC) U1111-1156-0255

NADPH Oxidase Nox5 Accelerates Renal Injury in Diabetic Nephropathy

NADPH oxidase-derived excessive production of reactive oxygen species (ROS) in the kidney plays a key role in mediating renal injury in diabetes. Pathological changes in diabetes include mesangial expansion and accumulation of extracellular matrix (ECM) leading to glomerulosclerosis. There is a paucity of data about the role of the Nox5 isoform of NADPH oxidase in animal models of diabetic nephropathy since Nox5 is absent in the mouse genome. Thus, we examined the role of Nox5 in human diabetic nephropathy in human mesangial cells and in an inducible human Nox5 transgenic mouse exposed to streptozotocin-induced diabetes. In human kidney biopsies, Nox5 was identified to be expressed in glomeruli, which appeared to be increased in diabetes. Colocalization demonstrated Nox5 expression in mesangial cells. In vitro, silencing of Nox5 in human mesangial cells was associated with attenuation of the hyperglycemia and TGF-β1-induced enhanced ROS production, increased expression of profibrotic and proinflammatory mediators, and increased TRPC6, PKC-α, and PKC-β expression. In vivo, vascular smooth muscle cell/mesangial cell-specific overexpression of Nox5 in a mouse model of diabetic nephropathy showed enhanced glomerular ROS production, accelerated glomerulosclerosis, mesangial expansion, and ECM protein (collagen IV and fibronectin) accumulation as well as increased macrophage infiltration and expression of the proinflammatory chemokine MCP-1. Collectively, this study provides evidence of a role for Nox5 and its derived ROS in promoting progression of diabetic nephropathy.

High Glucose Stimulates Mineralocorticoid Receptor Transcriptional Activity Through the Protein Kinase C β Signaling

Activation of mineralocorticoid receptor (MR) is shown in resistant hypertension including diabetes mellitus. Although protein kinase C (PKC) signaling is involved in the pathogenesis of diabetic complications, an association between PKC and MR is not known. Activation of PKCα and PKCβ by TPA (12-O-Tetradecanoylphorbol 13-acetate) increased MR proteins and its transcriptional activities in HEK293-MR cells. In contrast, a high glucose condition resulted in PKCβ but not PKCα activation, which is associated with elevation of MR protein levels and MR transcriptional activities. Reduction of endogenous PKCβ by siRNA decreased those levels. Interestingly, high glucose did not affect MR mRNA levels, but rather decreased ubiquitination of MR proteins. In db/db mice kidneys, levels of phosphorylated PKCβ2, MR and Sgk-1 proteins were elevated, and the administration of PKC inhibitor reversed these changes compared to db/+ mice. These data suggest that high glucose stimulates PKCβ signaling, which leads to MR stabilization and its transcriptional activities.

Rapid Action of Aldosterone on Protein Levels of Sodium-Hydrogen Exchangers and Protein Kinase C Beta Isoforms in Rat Kidney

Previous in vitro studies demonstrated that aldosterone rapidly activates sodium-hydrogen exchangers 1 and 3 (NHE 1 and 3). In vitro investigations revealed that protein kinase C (PKC) regulates NHE properties. We previously demonstrated that aldosterone rapidly enhances PKCα protein abundance in the rat kidney. There are no reports of renal PKCβ (I and II) protein levels related to the regulation by aldosterone. There are also no in vivo data regarding the rapid effects of aldosterone on renal protein levels of NHE (1 and 3) and PKCβ (I and II), simultaneously. In the current study, rats received normal saline solution or aldosterone (150 μg/kg BW, i.p.). After 30 minutes, abundance and immunoreactivity of these proteins were determined by Western blot analysis and immunohistochemistry, respectively. Aldosterone increased NHE1 and NHE3 protein abundance to 152% and 134%, respectively (P < 0.05). PKCβI protein level was enhanced by 30%, whereas PKCβII declined slightly. Aldosterone increased NHE protein expression mostly in the medulla. PKCβI immunostaining intensity was increased in the glomeruli, renal vasculature, and thin limb of the loop of Henle, while PKCβII was reduced. This is the first in vivo study to simultaneously demonstrate that aldosterone rapidly elevates PKCβI and NHE (1 and 3) protein abundance in the rat kidney. Aldosterone-induced NHE (1 and 3) protein levels may be related to PKCβI activation.

The anti-ALS drug riluzole attenuates pericyte loss in the diabetic retinopathy of streptozotocin-treated mice

Loss of pericytes, considered an early hallmark of diabetic retinopathy, is thought to involve abnormal activation of protein kinase C (PKC). We previously showed that the anti-amyotrophic lateral sclerosis (ALS) drug riluzole functions as a PKC inhibitor. Here, we examined the effects of riluzole on pathological changes in diabetic retinopathy. Pathological endpoints examined in vivo included the number of pericytes and integrity of retinal vessels in streptozotocin (STZ)-induced diabetic mice. In addition, PKC activation and the induction of monocyte chemotactic protein (MCP1) were assessed in diabetic mice and in human retinal pericytes exposed to advanced glycation end product (AGE) or modified low-density lipoprotein (mLDL). The diameter of retinal vessels and the number of pericytes were severely reduced, and the levels of MCP1 and PKC were increased in STZ-induced diabetic mice. Administration of riluzole reversed all of these changes. Furthermore, the increased expression of MCP1 in AGE- or mLDL-treated cultured retinal pericytes was inhibited by treatment with riluzole or the PKC inhibitor GF109203X. In silico modeling showed that riluzole fits well within the catalytic pocket of PKC. Taken together, our results demonstrate that riluzole attenuates both MCP1 induction and pericyte loss in diabetic retinopathy, likely through its direct inhibitory effect on PKC.

Drug discovery in focal and segmental glomerulosclerosis

Despite the high medical burden experienced by patients with focal segmental glomerulosclerosis, the etiology of the condition remains largely unknown. Focal segmental glomerulosclerosis is highly heterogeneous in clinical and morphologic manifestations. While this presents challenges for the development of new treatments, research investments over the last 2 decades have yielded a surfeit of potential avenues for therapeutic intervention. The development of many of those ideas and concepts into new therapies, however, has been very disappointing. Here, we describe some of the factors that have potentially contributed to the poor translational performance from this research investment, including the confidence we ascribe to a target, the conduct of experimental studies, and the availability of selective reagents to test hypotheses. We will discuss the significance of genetic and systems traits as well as other methods for reducing bias. We will analyze the limitations of a successful drug development. We will use specific examples hoping that these will guide a consensus for investment and drive greater translational quality. We hope that this substrate will serve to exemplify the tremendous opportunity for intervention as well as facilitate greater collaborative effort between industry, academia, and private foundations in promoting appropriate validation of these targets. Only then will we have achieved our goal for curative therapies for this devastating disease.

Podocyte-specific Nox4 deletion affords renoprotection in a mouse model of diabetic nephropathy

AIMS/HYPOTHESIS

Changes in podocyte morphology and function are associated with albuminuria and progression of diabetic nephropathy. NADPH oxidase 4 (NOX4) is the main source of reactive oxygen species (ROS) in the kidney and Nox4 is upregulated in podocytes in response to high glucose. We assessed the role of NOX4-derived ROS in podocytes in vivo in a model of diabetic nephropathy using a podocyte-specific NOX4-deficient mouse, with a major focus on the development of albuminuria and ultra-glomerular structural damage.

METHODS

Streptozotocin-induced diabetes-associated changes in renal structure and function were studied in male floxedNox4 and podocyte-specific, NOX4 knockout (podNox4KO) mice. We assessed albuminuria, glomerular extracellular matrix accumulation and glomerulosclerosis, and markers of ROS and inflammation, as well as glomerular basement membrane thickness, effacement of podocytes and expression of the podocyte-specific protein nephrin.

RESULTS

Podocyte-specific Nox4 deletion in streptozotocin-induced diabetic mice attenuated albuminuria in association with reduced vascular endothelial growth factor (VEGF) expression and prevention of the diabetes-induced reduction in nephrin expression. In addition, podocyte-specific Nox4 deletion reduced glomerular accumulation of collagen IV and fibronectin, glomerulosclerosis and mesangial expansion, as well as glomerular basement membrane thickness. Furthermore, diabetes-induced increases in renal ROS, glomerular monocyte chemoattractant protein-1 (MCP-1) and protein kinase C alpha (PKC-α) were attenuated in podocyte-specific NOX4-deficient mice.

CONCLUSIONS/INTERPRETATION

Collectively, this study shows the deleterious effect of Nox4 expression in podocytes by promoting podocytopathy in association with albuminuria and extracellular matrix accumulation in experimental diabetes, emphasising the role of NOX4 as a target for new renoprotective agents.

Human Neutrophil Elastase Induce Interleukin-10 Expression in Peripheral Blood Mononuclear Cells through Protein Kinase C Theta/Delta and Phospholipase Pathways

Objective

Neutrophils have an important role in the rapid innate immune response, and the release or active secretion of elastase from neutrophils is linked to various inflammatory responses. Purpose of this study was to determine how the human neutrophil elastase affects the interleukin-10 (IL-10) response in peripheral blood mononuclear cells (PBMC).

Materials and Methods

In this prospective study, changes in IL-10 messenger RNA (mRNA) and protein expression levels in monocytes derived from human PBMCs were investigated after stimulation with human neutrophil elastase (HNE). A set of inhibitors was used for examining the pathways for IL-10 production induced by HNE.

Results

Reverse transcription polymerase chain reaction (RT-PCR) showed that stimulation with HNE upregulated IL-10 mRNA expression by monocytes, while the enzyme-linked immunosorbent assay (ELISA) revealed an increase of IL-10 protein level in the culture medium. A phospholipase C inhibitor (U73122) partially blunt- ed the induction of IL-10 mRNA expression by HNE, while IL-10 mRNA expression was significantly reduced by a protein kinase C (PKC) inhibitor (Rottlerin). A calcium chelator (3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester: TMB-8) inhibited the response of IL-10 mRNA to stimulation by HNE. In addition, pretreatment with a broad-spectrum PKC inhibitor (Ro-318425) partly blocked the response to HNE. Finally, an inhibitor of PKC theta/delta abolished the increased level of IL-10 mRNA expression.

Conclusion

These results indicate that HNE mainly upregulates IL-10 mRNA ex- pression and protein production in moncytes via a novel PKC theta/delta, although partially via the conventional PKC pathway.

Influence of protein kinase C (PKC) on the prognosis of diabetic nephropathy patients

AIMS

To investigate the association between protein kinase C (PKC) and the prognosis of patients with diabetic nephropathy (DN).

METHODS

92 patients with DN who had received treatments with angiotensin converting enzyme inhibitor (ACEI) or angiotensin-receptor blockade (ARB) were collected. The clinicopathologic characteristics were recorded and a 4-year follow-up with the final result of impaired renal functions (eGFR < 40 mL/min) was conducted. The expression of PKC was detected by immunohistochemical assay. Kaplan-Meier and Cox regression analysis were performed to estimate the effects of PKC on DN prognosis.

RESULTS

According to immunohistochemical analysis, there were 54 cases with positive expression of PKC (positive rate 58.7%). Meanwhile, during the follow-up, the urine protein, mean serum creatinine and eGFR in patients with positive PKC were all higher than those in negative expression group (P < 0.05). The expression of PKC was influenced by age (P < 0.001), course of disease (P < 0.001), blood pressure (P = 0.002), blood glucose (P < 0.001), HbA1c (P = 0.002), renal functions of patients before (P = 0.011) and after (P = 0.041) the biopsy. Besides, the Kaplan-Meier curve revealed that patients with positive PKC expression had shorter survival time than those with negative PKC expression (P < 0.001). Cox regression analysis indicated that HbA1c (P = 0.009), renal functions of patients after the biopsy (P = 0.002) and PKC (P = 0.028) were important factors in the prognosis of DN and they might be independent prognostic markers.

CONCLUSION

The expression of PKC is relatively higher in DN patients than in healthy controls. And PKC may be a valuable prognostic marker for patients with DN.

NADPH oxidase 5 and renal disease

PURPOSE OF REVIEW

To highlight the latest novel developments in renal NADPH oxidase 5 (Nox5) biology, with an emphasis not only on diabetic nephropathy but also on many of the other renal disease contexts in which oxidative stress is implicated.

RECENT FINDINGS

Nox-derived reactive oxygen species have been shown to contribute to a wide variety of renal diseases, particularly in the settings of chronic renal disease such as diabetic nephropathy. Although much emphasis has been placed on the role of NADPH oxidase 4 in this setting, a growing body of work continues to uncover the key roles for other Nox family members, not only in diabetic kidney disease, but also in a diverse array of renal pathological conditions. The most recently identified member of the Nox family, Nox5, has for the most part been overlooked in renal disease, partly owing to its absence from the rodent genome. New evidence suggests that Nox5 may be a contributing factor in glomerulopathies and altered tubular physiology. Furthermore, Nox5 appears to harbor a significant number of single-nucleotide polymorphisms that alter its enzymatic activity.

SUMMARY

Given the unique structure and expression pattern of Nox5, it may prove to be an attractive therapeutic target in the treatment of renal disease.

Novel Therapies for Diabetic Kidney Disease: Storied Past and Forward Paths

IN BRIEF Current therapeutic approaches are only moderately efficacious at preventing the progression of diabetic kidney disease (DKD). As the number of people with DKD continues to rise worldwide, there is an urgent need for novel therapies. A better understanding of the root causes and molecular mechanisms of DKD pathogenesis has enabled the identification of numerous new therapeutic targets, including advanced glycation end products, reactive oxygen species, protein kinase C, and serum amyloid A. Although experimental studies have illustrated the potential of such approaches, challenges in clinical translation remain a barrier in therapeutic development. Advances in preclinical safety and efficacy evaluations and improved delivery systems may aid in clinical translation of novel DKD therapies.

Different localization and expression of protein kinase C-beta in kidney cortex of diabetic nephropathy mice and its role in telmisartan treatment

AIM

This study aims to investigate the localization and expression of protein kinase C-beta I and beta II in kidney cortex of diabetic nephropathy mice and their roles in telmisartan treatment.

METHODS

18 mice were randomly divided into three groups: normal group, diabetic nephropathy group and telmisartan-treated group. The localization and expression of protein kinase C-beta I and beta II were measured with confocal immunofluorescence laser scanning microscopy, immunohistochemistry and western blotting. The expression of transforming growth factor-beta 1 and vascular endothelial growth factor in glomeruli was detected by immunohistochemistry.

RESULTS

Compared to the normal mice, the expression and localization of protein kinase C-beta I and beta II are differed in diabetic nephropathy mice, with increased expression of protein kinase C-beta I but decreased level of protein kinase C-beta II. Meanwhile, the expression of transforming growth factor-beta 1 and vascular endothelial growth factor showed increase in the glomeruli of diabetic nephropathy, compared to the controls. Also, protein kinase C-beta I exhibited a positive correlation to transforming growth factor-beta 1 (r = 0.649, P = 0.030), but no correlation to vascular endothelial growth factor (r = 0.387, P = 0.079). Telmisartan treatment exercised significant beneficial role in diabetic nephropathy, which is associated with protein kinase C-beta I, but not beta II.

CONCLUSIONS

The expression and localization of protein kinase C-beta I and beta II differ in the diabetic nephropathy, and such difference is associated with the pathogeneses of diabetic nephropathy.

Assessment of early renal damage in diabetic rhesus monkeys

The objectives of the study were to improve the model system of diabetic nephropathy in nonhuman primates and assess the early renal damage. Diabetes was induced in monkeys by streptozotocin, and the animals were administered exogenous insulin to control blood glucose (BG). Animals were divided into four groups, including the normal group (N = 3), group A (streptozotocin diabetic model with control of BG < 10 mmol/L, N = 3), group B (streptozotocin diabetic model with control of BG between 15 and 20 mmol/L, N = 4), and group C (streptozotocin diabetic model with control of BG between 15 and 20 mmol/L and high-sodium and high-fat diet, N = 4). The following parameters were evaluated: (1) blood biochemistry and routine urinalysis, (2) color Doppler ultrasound, (3) angiography, (4) renal biopsy, and (5) renal fibrosis-related gene expression levels. Animals in group C developed progressive histologic changes with typical diabetic nephropathy resembling diabetic nephropathy in human patients and exhibited accelerated development of diabetic nephropathy compared with other nonhuman primate models. Significant changes in the expression of the Smad2/3 gene and eNOS in renal tissue were also observed in the early stage of diabetic nephropathy. In conclusion, our model is an excellent model of diabetic nephropathy for understanding the pathogenesis of diabetic nephropathy.

Novel effective drugs for diabetic kidney disease? or not?

INTRODUCTION

Diabetes mellitus is increasingly common worldwide and is expected to affect 592 million people by 2035. The kidney is often involved. A key goal in treating diabetes is to reduce the risk of development of kidney disease and, if kidney disease is already present, to delay the progression to end-stage renal disease (ESRD). This represents a social and ethical issue, as a significant proportion of patients reaching ESRD in developing countries do not have access to renal replacement therapy.

AREAS COVERED

The present review focuses on novel therapeutic approaches for diabetic nephropathy (DN), implemented on the basis of recent insights on its pathophysiology, which might complement the effects of single inhibition of the renin-angiotensin-aldosterone system (RAAS), the cornerstone of renoprotective interventions in diabetes, along with glycemic and blood pressure control.

EXPERT OPINION

Although a plethora of new treatment options has arisen from experimental studies, the number of novel renoprotective molecules successfully implemented in clinical practice over the last two decades is disappointingly low. Thus, new investigational strategies and diagnostic tools - including the appropriate choice of relevant renal end points and the study of urinary proteome of patients - will be as important as new therapeutic interventions to fight DN. Finally, in spite of huge financial interests in replacing the less expensive ACE inhibitors and angiotensin II receptor blockers with newer drugs, any future therapeutic approach has to be tested on top of - rather than instead of - optimal RAAS blockade.

Nox-4 deletion reduces oxidative stress and injury by PKC-α-associated mechanisms in diabetic nephropathy

Current treatments for diabetic nephropathy (DN) only result in slowing its progression, thus highlighting a need to identify novel targets. Increased production of reactive oxygen species (ROS) is considered a key downstream pathway of end-organ injury with increasing data implicating both mitochondrial and cytosolic sources of ROS. The enzyme, NADPH oxidase, generates ROS in the kidney and has been implicated in the activation of protein kinase C (PKC), in the pathogenesis of DN, but the link between PKC and Nox-derived ROS has not been evaluated in detail in vivo. In this study, global deletion of a NADPH-oxidase isoform, Nox4, was examined in mice with streptozotocin-induced diabetes (C57Bl6/J) in order to evaluate the effects of Nox4 deletion, not only on renal structure and function but also on the PKC pathway and downstream events. Nox4 deletion attenuated diabetes-associated increases in albuminuria, glomerulosclerosis, and extracellular matrix accumulation. Lack of Nox4 resulted in a decrease in diabetes-induced renal cortical ROS derived from the mitochondria and the cytosol, urinary isoprostanes, and PKC activity. Immunostaining of renal cortex revealed that major isoforms of PKC, PKC-α and PKC-β1, were increased with diabetes and normalized by Nox4 deletion. Downregulation of the PKC pathway was observed in tandem with reduced expression of vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β1 and restoration of the podocyte slit pore protein nephrin. This study suggests that deletion of Nox4 may alleviate renal injury via PKC-dependent mechanisms, further strengthening the view that Nox4 is a suitable target for renoprotection in diabetes.

Therapeutic strategies of diabetic nephropathy: recent progress and future perspectives

Diabetic nephropathy (DN) is one of the most common complications of diabetes with high mortality rates worldwide. The treatment of DN has posed a formidable challenge to the scientific community. Simple control of risk factors has been insufficient to cope with the progression of DN. During the process of anti-DN drug discovery, multiple pathogeneses such as oxidative stress, inflammation and fibrosis should all be considered. In this review, the pathogenesis of DN is summarized. The major context focuses on a few small molecules toward the pathogenesis available in animal models and clinical trials for the treatment of DN. The perspectives of novel anti-DN agents and the future directions for the prevention of DN are discussed.

Novel therapies for diabetic kidney disease

The number of people diagnosed with diabetes is rising throughout the world, which in turn drives upward the global frequency of diabetic kidney disease (DKD). Individuals with DKD are at an increased risk for premature death, cardiovascular disease, and other severe illnesses that result in frequent hospitalizations and increased health-care utilization. Current treatments concentrate on controlling hyperglycemia and hypertension with the specific use of renin-angiotensin system inhibitors. Although such measures reduce the risk of progressive kidney disease, DKD remains the leading cause of ESRD and the major risk amplifier for death in this population. Therefore, novel therapeutic approaches are urgently needed. Ideas for novel targets for therapy are founded on recent advances in understanding DKD mechanisms that are based on experimental models and human observations. The purpose of this review is to describe the epidemiology and present knowledge of DKD pathophysiology as the basis for novel therapies including inhibitors of Janus kinases (JAK), protein kinase C, fibrosis, advanced glycation end products treatments, and endothelin.

Role of protein kinase C in podocytes and development of glomerular damage in diabetic nephropathy

The early glomerular changes in diabetes include a podocyte phenotype with loss of slit diaphragm proteins, changes in the actin cytoskeleton and foot process architecture. This review focuses on the role of the protein kinase C (PKC) family in podocytes and points out the differential roles of classical, novel, and atypical PKCs in podocytes. Some PKC isoforms are indispensable for proper glomerular development and slit diaphragm maintenance, whereas others might be harmful when activated in the diabetic milieu. Therefore, some might be interesting treatment targets in the early phase of diabetes.

New insight into the molecular drug target of diabetic nephropathy

Diabetic nephropathy (DN) lowered quality of life and shortened life expectancy amongst those affected. Evidence indicates interaction between advanced glycation end products (AGEs), activated protein kinase C (PKC) and angiotensin II exacerbate the progression of DN. Inhibitors of angiotensin-converting enzyme (ACEIs), renin angiotensin aldosterone system (RAAS), AGEs, and PKC have been tested for slowing down the progression of DN. The exact molecular drug targets that lead to the amelioration of renal injury in DN are not well understood. This review summarizes the potential therapeutic targets, based on putative mechanism in the progression of the disease.

Diabetic nephropathy: diagnosis and treatment

Nephropathy remains a major cause of morbidity and a key determinant of mortality in patients with type 1 or type 2 diabetes mellitus. Research is ongoing to identify biomarkers that in addition to albuminuria and glomerular filtration rate assist in the prediction and monitoring of renal disease in diabetes mellitus. Current strategies to treat this condition focus on intensification of glycaemic control and excellent control of blood pressure using regimens based on blockade of the renin-angiotensin system. Other approaches to control blood pressure and afford renoprotection are under active clinical investigation, including renal denervation and endothelin receptor antagonism. With increasing understanding of the underlying pathophysiological processes implicated in diabetic nephropathy, new specific renoprotective treatment strategies are anticipated to become available over the next few years.